Lecture FourLecture Four

Air Pollution ControlAir Pollution Control

LearningObjectivesfor Today

Educational ObjectivesEducational Objectives

Control of Motor Vehicle emissions

Control of Stationary Sources

Integrated Pollution Control

ObjectivesTo prevent and minimize the release of substances that are potentially harmful to polluting to the environment

PrinciplesReformulate the product

1048700To develop a nonless polluting productprocessModify the process

1048700To change the process to control by-product formation or to incorporate non-polluting raw materials

Change the equipment 1048700To make the equipment more efficient or allow it to use by-products from another process

Recover resources1048700To recycle by-products for own use or use by others

Waste Minimization for Air Pollution Control

o1048700Replace chemical process with mechanical ones produce more manageable emissionso1048700Replace organic solvent-based inks paints and coasting with water-based ones reduces VOC emissionso1048700Replace halogenated compounds with non-halogenated compounds reduce the impacts on stratospheric ozone

Waste Minimization for Air Pollution Control

o1048700Replace toxic substances such as mercury cadmium and lead with other less toxic substances reduce emissions as particulate matter or as vaporized metalso1048700Improve technology to minimum producing pollutants from the process stream or to return useful products to the processo1048700Install improved process-monitoring equipment to make it possible to improve and continuously maintain optimum process conditions this improves all-round efficiency and so reduces emissions

Vehicle pollution control

Air Pollution Control of Mobile Sources

Type of engine1048700Gasoline engine1048700Diesel engine1048700Jet engine

Effect of design and operating variables on emissions10487001 Air-to-fuel ratio 8 Combustion chamber deposit buildup10487002 Load or power level 9 Surface temperature10487003 Speed 10 Surface-to-volume ratio10487004 Spark timing 11 Combustion chamber design10487005 Exhaust back pressure 12 Stroke-to-bore ratio10487006 Valve overlap 13 Displacement per cylinder10487007 Intake manifold pressure 14 Compression ratio

Two-stroke enginesTwo-stroke engines

A two-stroke engine with an expansion pipe illustrating the effect of the reflected pressure wave on the fuel charge

Air Pollution Control of Mobile Sources

Air-to-fuel Ratioo1048700AF ratio of 146 is the stoichiometric mixture for complete combustiono1048700At lower ratios CO and hydrocarbon emission increaseo1048700At higher ratios of ~155 NOx emission increaseso1048700At very high ratios (lean mixtures) the NOx emission begins to decrease

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

LearningObjectivesfor Today

Educational ObjectivesEducational Objectives

Control of Motor Vehicle emissions

Control of Stationary Sources

Integrated Pollution Control

ObjectivesTo prevent and minimize the release of substances that are potentially harmful to polluting to the environment

PrinciplesReformulate the product

1048700To develop a nonless polluting productprocessModify the process

1048700To change the process to control by-product formation or to incorporate non-polluting raw materials

Change the equipment 1048700To make the equipment more efficient or allow it to use by-products from another process

Recover resources1048700To recycle by-products for own use or use by others

Waste Minimization for Air Pollution Control

o1048700Replace chemical process with mechanical ones produce more manageable emissionso1048700Replace organic solvent-based inks paints and coasting with water-based ones reduces VOC emissionso1048700Replace halogenated compounds with non-halogenated compounds reduce the impacts on stratospheric ozone

Waste Minimization for Air Pollution Control

o1048700Replace toxic substances such as mercury cadmium and lead with other less toxic substances reduce emissions as particulate matter or as vaporized metalso1048700Improve technology to minimum producing pollutants from the process stream or to return useful products to the processo1048700Install improved process-monitoring equipment to make it possible to improve and continuously maintain optimum process conditions this improves all-round efficiency and so reduces emissions

Vehicle pollution control

Air Pollution Control of Mobile Sources

Type of engine1048700Gasoline engine1048700Diesel engine1048700Jet engine

Effect of design and operating variables on emissions10487001 Air-to-fuel ratio 8 Combustion chamber deposit buildup10487002 Load or power level 9 Surface temperature10487003 Speed 10 Surface-to-volume ratio10487004 Spark timing 11 Combustion chamber design10487005 Exhaust back pressure 12 Stroke-to-bore ratio10487006 Valve overlap 13 Displacement per cylinder10487007 Intake manifold pressure 14 Compression ratio

Two-stroke enginesTwo-stroke engines

A two-stroke engine with an expansion pipe illustrating the effect of the reflected pressure wave on the fuel charge

Air Pollution Control of Mobile Sources

Air-to-fuel Ratioo1048700AF ratio of 146 is the stoichiometric mixture for complete combustiono1048700At lower ratios CO and hydrocarbon emission increaseo1048700At higher ratios of ~155 NOx emission increaseso1048700At very high ratios (lean mixtures) the NOx emission begins to decrease

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Integrated Pollution Control

ObjectivesTo prevent and minimize the release of substances that are potentially harmful to polluting to the environment

PrinciplesReformulate the product

1048700To develop a nonless polluting productprocessModify the process

1048700To change the process to control by-product formation or to incorporate non-polluting raw materials

Change the equipment 1048700To make the equipment more efficient or allow it to use by-products from another process

Recover resources1048700To recycle by-products for own use or use by others

Waste Minimization for Air Pollution Control

o1048700Replace chemical process with mechanical ones produce more manageable emissionso1048700Replace organic solvent-based inks paints and coasting with water-based ones reduces VOC emissionso1048700Replace halogenated compounds with non-halogenated compounds reduce the impacts on stratospheric ozone

Waste Minimization for Air Pollution Control

o1048700Replace toxic substances such as mercury cadmium and lead with other less toxic substances reduce emissions as particulate matter or as vaporized metalso1048700Improve technology to minimum producing pollutants from the process stream or to return useful products to the processo1048700Install improved process-monitoring equipment to make it possible to improve and continuously maintain optimum process conditions this improves all-round efficiency and so reduces emissions

Vehicle pollution control

Air Pollution Control of Mobile Sources

Type of engine1048700Gasoline engine1048700Diesel engine1048700Jet engine

Effect of design and operating variables on emissions10487001 Air-to-fuel ratio 8 Combustion chamber deposit buildup10487002 Load or power level 9 Surface temperature10487003 Speed 10 Surface-to-volume ratio10487004 Spark timing 11 Combustion chamber design10487005 Exhaust back pressure 12 Stroke-to-bore ratio10487006 Valve overlap 13 Displacement per cylinder10487007 Intake manifold pressure 14 Compression ratio

Two-stroke enginesTwo-stroke engines

A two-stroke engine with an expansion pipe illustrating the effect of the reflected pressure wave on the fuel charge

Air Pollution Control of Mobile Sources

Air-to-fuel Ratioo1048700AF ratio of 146 is the stoichiometric mixture for complete combustiono1048700At lower ratios CO and hydrocarbon emission increaseo1048700At higher ratios of ~155 NOx emission increaseso1048700At very high ratios (lean mixtures) the NOx emission begins to decrease

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

PrinciplesReformulate the product

1048700To develop a nonless polluting productprocessModify the process

1048700To change the process to control by-product formation or to incorporate non-polluting raw materials

Change the equipment 1048700To make the equipment more efficient or allow it to use by-products from another process

Recover resources1048700To recycle by-products for own use or use by others

Waste Minimization for Air Pollution Control

o1048700Replace chemical process with mechanical ones produce more manageable emissionso1048700Replace organic solvent-based inks paints and coasting with water-based ones reduces VOC emissionso1048700Replace halogenated compounds with non-halogenated compounds reduce the impacts on stratospheric ozone

Waste Minimization for Air Pollution Control

o1048700Replace toxic substances such as mercury cadmium and lead with other less toxic substances reduce emissions as particulate matter or as vaporized metalso1048700Improve technology to minimum producing pollutants from the process stream or to return useful products to the processo1048700Install improved process-monitoring equipment to make it possible to improve and continuously maintain optimum process conditions this improves all-round efficiency and so reduces emissions

Vehicle pollution control

Air Pollution Control of Mobile Sources

Type of engine1048700Gasoline engine1048700Diesel engine1048700Jet engine

Effect of design and operating variables on emissions10487001 Air-to-fuel ratio 8 Combustion chamber deposit buildup10487002 Load or power level 9 Surface temperature10487003 Speed 10 Surface-to-volume ratio10487004 Spark timing 11 Combustion chamber design10487005 Exhaust back pressure 12 Stroke-to-bore ratio10487006 Valve overlap 13 Displacement per cylinder10487007 Intake manifold pressure 14 Compression ratio

Two-stroke enginesTwo-stroke engines

A two-stroke engine with an expansion pipe illustrating the effect of the reflected pressure wave on the fuel charge

Air Pollution Control of Mobile Sources

Air-to-fuel Ratioo1048700AF ratio of 146 is the stoichiometric mixture for complete combustiono1048700At lower ratios CO and hydrocarbon emission increaseo1048700At higher ratios of ~155 NOx emission increaseso1048700At very high ratios (lean mixtures) the NOx emission begins to decrease

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Waste Minimization for Air Pollution Control

o1048700Replace chemical process with mechanical ones produce more manageable emissionso1048700Replace organic solvent-based inks paints and coasting with water-based ones reduces VOC emissionso1048700Replace halogenated compounds with non-halogenated compounds reduce the impacts on stratospheric ozone

Waste Minimization for Air Pollution Control

o1048700Replace toxic substances such as mercury cadmium and lead with other less toxic substances reduce emissions as particulate matter or as vaporized metalso1048700Improve technology to minimum producing pollutants from the process stream or to return useful products to the processo1048700Install improved process-monitoring equipment to make it possible to improve and continuously maintain optimum process conditions this improves all-round efficiency and so reduces emissions

Vehicle pollution control

Air Pollution Control of Mobile Sources

Type of engine1048700Gasoline engine1048700Diesel engine1048700Jet engine

Effect of design and operating variables on emissions10487001 Air-to-fuel ratio 8 Combustion chamber deposit buildup10487002 Load or power level 9 Surface temperature10487003 Speed 10 Surface-to-volume ratio10487004 Spark timing 11 Combustion chamber design10487005 Exhaust back pressure 12 Stroke-to-bore ratio10487006 Valve overlap 13 Displacement per cylinder10487007 Intake manifold pressure 14 Compression ratio

Two-stroke enginesTwo-stroke engines

A two-stroke engine with an expansion pipe illustrating the effect of the reflected pressure wave on the fuel charge

Air Pollution Control of Mobile Sources

Air-to-fuel Ratioo1048700AF ratio of 146 is the stoichiometric mixture for complete combustiono1048700At lower ratios CO and hydrocarbon emission increaseo1048700At higher ratios of ~155 NOx emission increaseso1048700At very high ratios (lean mixtures) the NOx emission begins to decrease

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Waste Minimization for Air Pollution Control

o1048700Replace toxic substances such as mercury cadmium and lead with other less toxic substances reduce emissions as particulate matter or as vaporized metalso1048700Improve technology to minimum producing pollutants from the process stream or to return useful products to the processo1048700Install improved process-monitoring equipment to make it possible to improve and continuously maintain optimum process conditions this improves all-round efficiency and so reduces emissions

Vehicle pollution control

Air Pollution Control of Mobile Sources

Type of engine1048700Gasoline engine1048700Diesel engine1048700Jet engine

Effect of design and operating variables on emissions10487001 Air-to-fuel ratio 8 Combustion chamber deposit buildup10487002 Load or power level 9 Surface temperature10487003 Speed 10 Surface-to-volume ratio10487004 Spark timing 11 Combustion chamber design10487005 Exhaust back pressure 12 Stroke-to-bore ratio10487006 Valve overlap 13 Displacement per cylinder10487007 Intake manifold pressure 14 Compression ratio

Two-stroke enginesTwo-stroke engines

A two-stroke engine with an expansion pipe illustrating the effect of the reflected pressure wave on the fuel charge

Air Pollution Control of Mobile Sources

Air-to-fuel Ratioo1048700AF ratio of 146 is the stoichiometric mixture for complete combustiono1048700At lower ratios CO and hydrocarbon emission increaseo1048700At higher ratios of ~155 NOx emission increaseso1048700At very high ratios (lean mixtures) the NOx emission begins to decrease

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Vehicle pollution control

Air Pollution Control of Mobile Sources

Type of engine1048700Gasoline engine1048700Diesel engine1048700Jet engine

Effect of design and operating variables on emissions10487001 Air-to-fuel ratio 8 Combustion chamber deposit buildup10487002 Load or power level 9 Surface temperature10487003 Speed 10 Surface-to-volume ratio10487004 Spark timing 11 Combustion chamber design10487005 Exhaust back pressure 12 Stroke-to-bore ratio10487006 Valve overlap 13 Displacement per cylinder10487007 Intake manifold pressure 14 Compression ratio

Two-stroke enginesTwo-stroke engines

A two-stroke engine with an expansion pipe illustrating the effect of the reflected pressure wave on the fuel charge

Air Pollution Control of Mobile Sources

Air-to-fuel Ratioo1048700AF ratio of 146 is the stoichiometric mixture for complete combustiono1048700At lower ratios CO and hydrocarbon emission increaseo1048700At higher ratios of ~155 NOx emission increaseso1048700At very high ratios (lean mixtures) the NOx emission begins to decrease

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Air Pollution Control of Mobile Sources

Type of engine1048700Gasoline engine1048700Diesel engine1048700Jet engine

Effect of design and operating variables on emissions10487001 Air-to-fuel ratio 8 Combustion chamber deposit buildup10487002 Load or power level 9 Surface temperature10487003 Speed 10 Surface-to-volume ratio10487004 Spark timing 11 Combustion chamber design10487005 Exhaust back pressure 12 Stroke-to-bore ratio10487006 Valve overlap 13 Displacement per cylinder10487007 Intake manifold pressure 14 Compression ratio

Two-stroke enginesTwo-stroke engines

A two-stroke engine with an expansion pipe illustrating the effect of the reflected pressure wave on the fuel charge

Air Pollution Control of Mobile Sources

Air-to-fuel Ratioo1048700AF ratio of 146 is the stoichiometric mixture for complete combustiono1048700At lower ratios CO and hydrocarbon emission increaseo1048700At higher ratios of ~155 NOx emission increaseso1048700At very high ratios (lean mixtures) the NOx emission begins to decrease

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Two-stroke enginesTwo-stroke engines

A two-stroke engine with an expansion pipe illustrating the effect of the reflected pressure wave on the fuel charge

Air Pollution Control of Mobile Sources

Air-to-fuel Ratioo1048700AF ratio of 146 is the stoichiometric mixture for complete combustiono1048700At lower ratios CO and hydrocarbon emission increaseo1048700At higher ratios of ~155 NOx emission increaseso1048700At very high ratios (lean mixtures) the NOx emission begins to decrease

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Air Pollution Control of Mobile Sources

Air-to-fuel Ratioo1048700AF ratio of 146 is the stoichiometric mixture for complete combustiono1048700At lower ratios CO and hydrocarbon emission increaseo1048700At higher ratios of ~155 NOx emission increaseso1048700At very high ratios (lean mixtures) the NOx emission begins to decrease

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Internal combustion engine Combustion chemistry

C8H18 + 125 O2 + 47 N2 8CO2 + 47 N2+ 9 H2O

For complete combustion Air-fuel (AF) ratio = 151

CO is produced from incomplete combustion HCs are produced when the flame front approaches relatively cool walls of the cylinder NOx is produced from N2 + O2 2 NO

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Internal combustion engine combustion cycle

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Petrol and diesel engine Air-fuel ratio higher ratio for diesel Compression ratio High for diesel

CO HC NOx PM

Petrol High High Low Low

Diesel Low Low High High

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Emissions Emissions

Spark ignition four- stroke internal combustion engines Exhaust gases ldquoblow byrdquo gases Evaporative losses

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Exhaust emissionsExhaust emissions

Account for 90 to 92 of total motor vehicle emissions

Include unburnedpartially burned HCs Carbon monoxide Nitrogen oxides

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Evaporative emissionsEvaporative emissions Diurnal emissions-fuel tank cools at night

and heats up during the day Hot soak-evaporation of residual fuel on

shutting the engine off Operating losses-when engine is running Refueling losses

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Crankcase ventilationCrankcase ventilation Used to control ldquoblow byrdquo gases Crankcase purged with air Crankcase gases returned to combustion

chamber

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Crankcase ventilationCrankcase ventilation

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Evaporative emissionsEvaporative emissions Collect HCs on activated carbon Collected HCs are desorbed and burned Control systems are less efficient on high

volatilitylow molecular weight fuels

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Evaporative emissions controlEvaporative emissions control

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Exhaust gas recirculationExhaust gas recirculation

Exhaust gases used to absorb heat and decrease combustion chamber temperatures Reduces NOx production

Effectiveness depends on the amount of exhaust gas used 10 exhaust gases -reduces NOx by 30 to

50

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Exhaust gas recirculationExhaust gas recirculation

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

CO and HCs control Modify engine design

to improve combustion

Use of catalytic converters

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Control of NOx emission Generally more

difficult to control mainly to decrease combustion temperature Retardation of spark Decreased

compression ratio exhaust has

recirculation

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Control technologies New control technologies

dual and three-way catalytic converter (NOx -gtN2)

Alternative fuels

Conventional gasoline contains a mixture of paraffinic and aromatic HC compounds

Octane rating When combustion is too rapid a sharp metallic noise called knock is produced Component that reduces the knock has the octane quality

Historically lead alkyls have been added to boost octane ratings

In unlead gasoline aromatic HCs are added

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Control technologies Reformulated gasolines and oxygenated additives

oxygenated additives such as MTBE ETBE methanol ethanol (to boost the octane rating due to reducing aromatics)

- Alcohol fuels Alcohol-gasoline blend

- Compressed and liquefied gases Natural gas (mainly contains methane) Liquefied petroleum gas (largely propane) limited supply and higher exhaust reactivity

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Control of diesel vehicle pollution in Hong Kong

Euro III standard for vehicles of 1995 and onwards

Existing ones Taxies LPG Light buses 80 switched to LPG or

electricity Heavy duty traps andor catalytic converters

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Stationary sources control Tall stacks Fuel-use changes Fugitive emission containment Pollution prevention

Substitution Process equipment changes Plant operating practices Maintenance Process changes Energy conservation

ldquoEnd of the piperdquo control (see next pages)

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Control efficiency penetrationControl efficiency penetration

00

11

00

11

00

1100

1

1

cQ

cQefficiencypnPenetratio

cQ

cQ

cQ

cQcQefficiencyControl

Q0 c0 Q1 c1

Control device

If we have more than one control device in series

ηoverall = 1-(1-η1)(1-η2)(1-η3)(1-η4)

Poverall = p1p2p3p4

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Cleaning performanceCleaning performance Can be quantified

Where

E = collection efficiency

A = concentration of influent

B = concentration of out-fluent

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Generalized fractional Generalized fractional collection efficiency curvecollection efficiency curve

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Fractional collection Fractional collection efficiencies of dust collectorsefficiencies of dust collectors

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Particle collection systemsParticle collection systems Cyclones Filtrationbaghouses Electrostatic precipitation Scrubbers

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Cyclone collectors

In general collection efficiency increases with increased particle size and density dust loading and collector size

Multiple tubes collectors can be used to increase collection efficiency

Cyclones are often used to control relatively large particles and often are used in series as pre-cleaners for more efficient collectors

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Filtration Fabric filters are commonly

used to control particle emissions where dust loading are higher particle sizes are small and high collection efficiencies are needed

Limitations include high capital costs flammability hazards for some dusts high space requirements flue gas temperature limited to 285 C and sensitivity to gas moisture

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

The basic principle of baghouse operation involves the removal of dust from dust-laden gas by passing the dirty gas through a filtration medium

The cleaned gas emerges from one side of the medium while the dust is collected on the other side Periodically the collected dust is removed from the fabric

A fabric filter ldquobaghouserdquo system includes the bag cleaning system dust collection hoppers and dust removal system

Principle of filtrationPrinciple of filtration

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Electrostatic precipitator High collection efficiencies for all particle sizes

low operating and power requirements But high capital costs and space requirement

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Electrostatic precipitatorsElectrostatic precipitators

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Wet ScrubbersWet Scrubbersndash In wet scrubbing processes liquid or

solid particles are removed from a gas stream by transferring them to a liquid

ndash Most wet scrubbing systems operate with particulate collection efficiencies over 95 percent

ndash Wet scrubbing can effectively remove fine particles in the range from 01 μm to 20 μm

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Wet scrubbers Open spray Tower

Venturi Scrubber

Almost exclusively used to remove fine particles

Capital costs are low but operating costs are high (energy and disposal of waste liquid)

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Control of gas-phase emissionsControl of gas-phase emissions

Incineration (Thermal oxidation) Adsorption Absorption Condensation Biological treatment

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Control of gas-phase emissions

More complex technologically than control of particles Control techniques for a specific gas pollutant needs to be developed Combustion Adsorption Absorption

Combustion Direct flame incinerators

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Control of gas-phase emissions

Thermal incineration Additional fuel

needed

Catalytic incineration

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Control of gas-phase emissions Adsorption

Gas pollutant being adsorbed by the surfaces of solids such as molecular sieve activated carbons etc

Absorption Absorbed by liquids

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP

Emissions and pollution control in China and Lights Power in Hong Kong in 1990 - 2004

00

500

1000

1500

2000

Year

To

tal E

mis

sio

n (

kilo

ton

ne

)

0

5000

10000

15000

20000

25000

30000

35000

Lo

ca

l E

lec

tric

ity

Sa

les

(G

Wh

)

Low NOx burners

at Castle Peak

Nuclearat Daya Bay

Natural Gasat Black Point

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

Total Emission Reduction1990 ndash 2004

NOX 80

SO2 35

PM 68

Electricity over 65Sales

= Total NOX

= Total SO2

= Total PM

= Electricity Sales

Source Dr Jennie Ng CLP