NOX AND SOX EMISSION CONTROL

ABSTRACT

Ship’s SOX emissions forms 60% of total SOX Emissions.

We are polluting our environment by our choice of fuel.

Emission control in the angle of MARPOL and the technologies for reduction are taken into account.

POLLUTANTS

Air pollutants can also be of primary or secondary nature.

Primary is emitted directly to atmosphere. Secondary is formed by reactions between primary

pollutants. The major pollutants are

1. Oxides of nitrogen

2. Oxides of sulphur

3. Particulate matter

CHEMISTRY OF FORMATION

N2+O2 2NO

2NO+O2 2NO2

S+O2 SO2

SO2+NO2 NO+SO3

2NO+O2 2NO2

NO2+SUNLIGHT NO+O

O+O2 O3

HAZARDS

Corrosion Climate change Photochemical smog SO2 irritates the eyes, nose and lungs

SO2 causes acid rain

NO2 causes pulmonary edema

MARPOL LEGISLATION

Annex VI- Regulations for the prevention of air pollution from ships

Came to force on 19th May 2005 For every ship with 400 gross tonnage and

above and for fixed and floating drilling rig Certificate- “International air pollution

prevention certificate” Validity- period not exceeding five years

MAJOR REGULATIONS There are 19 Regulations but the following

Regulations impact Vessel operation :

Regulation 12 – Ozone Depleting Substances Regulation 13 – NOx emissions Regulation 14 – Sulphur Oxide emissions Regulation 15 – VOC emissions Regulation 16 – Shipboard Incinerators Regulation 18 – Fuel Oil Quality control

Emission standards are referred to a Tier I, II,III

Tier I came into force on 19th May 2005. The revised Annex VI enters into force on 1st

July 2010. Tier II,III are more stringent than Tier I . Tier II standards are expected to be met by

combustion process optimization. Tier III standards are expected to require

dedicated NOx emission control technologies.

REGULATION 13

Deals with control of NOX emissions. All engines with power more than 130KW and

built on or after 1/1/2000 Doesn’t apply to engines used in emergency. Emissions must be limited to, 17.0 g/kWh when n <130 rpm; 45.0 x n-0.2 g/kWh when n is 130 or more but

less than 2000 rpm; 9.8 g/kWh when n is 2000 rpm or more

SOX CONTROL

Sulphur content of fuel shall not exceed 4.5%. SOX emission ECA include Baltic and North sea

area. Sulphur content shall not exceed 1.5% in ECA. Total emission must be less than 6 g SOX/kWh

in ECA

FUEL OIL QUALITY

Fuel oil shall be free from inorganic acid. Bunker delivery note must be maintained. Bunker delivery note must kept for 3 years. Fuel oil sulphur content must never exceed

4.5%. Parties of 1997 protocol must maintain a

register of local suppliers of fuel oil.

EMISSION MEASUREMENT

For Attaining Interim Certificate of Compliance.

Engines combined into engine groups by manufacturer

Engine from this group selected for emission testing

EXHAUST GAS MONITORING TECHNIQUES

Exhaust Gas Monitoring Equipments

ExtractiveExtractive

Systems SystemsNon-Extractive Non-Extractive

SystemsSystems

UV UV AnalysersAnalysersChemi-

luminescence

Infrared Infrared

AnalysersAnalysers

Ultra-Violet Ultra-Violet

AnalysersAnalysers

Extractive Systems Permanently installed Requires additional equipment to process the

exhaust gas sample. Advantages Able to be remotely located in a controlled environment Easier to operate, calibrate and maintain. Can be set up to monitor exhaust gas emissions from more

than one engine.

Disadvantage High Cost

NON-EXTRACTIVE SYSTEMS

Predominately use infrared or ultra-violet techniques.

Measure the exhaust gas emissions without extracting the exhaust gas from the uptake system.

Advantages More portable Provides more rapid responses.

Disadvantages Difficult to calibrate.

CHEMILUMINESCENCE HCD (Heated Chemiluminescence Detector). Accepted standard for laboratory and test cell

measurement of NOx. Was the only available NOx detector available

during the development of the IMO Technical code.

Needs to have a continuous supply of clean dry air else damage to the analyser components will result.

NO determination with detection limits down to 1 ppb.

ULTRA-VIOLET ANALYSERS

Particularly useful for measuring SO2 .

Used in extractive and non-extractive systems. Not suitable for the measurement of NOx.

REDUCING SOX EMISSIONS

2 Possibilities :- Burning fuels with lower sulphur content Treating the engine exhaust gases

At Present limits on sulphur content of marine fuel

Globally – 4.5% SECA – 1% from 1st july,2010

SOX emission control areas (SECA) North Sea, English Channel and the Baltic Sea.

TECHNIQUES FOR REDUCING SOX EMISSIONS

3 possibilities to reduce SO2 emissions from combustion processes:

1) REMOVAL OF SULPHUR BEFORE COMBUSTION

2) REMOVAL OF SULPHUR DURING COMBUSTION

3) REMOVAL OF SOX AFTER COMBUSTION ( I.E. FLUE GAS DESULPHURISATION )

REMOVAL OF SULPHUR BEFORE COMBUSTION

Process used : Hydrotreating or Hydrodesulphurisation Treatment of the oil with hydrogen gas obtained e.g. during

catalytic reforming. Sulphur compounds are reduced by conversion to hydrogen

sulphide (H2S) in the presence of a catalyst.

H2S washed from the product gas stream by an amine wash H2S is recovered in highly concentrated form Converted to elemental sulphur via the Claus-Process Feedstock is mixed with hydrogen-rich make-up and recycled

gas and reacted at temperatures of 300 - 380 °C.

Removal of sulphur from heavier oils such as marine fuel oil often requires pressures of up to 200 bar.

Catalysts employed : cobalt, molybdenum or nickel finely distributed on alumina extrudates.

CLAUS PROCESS

Most significant Gas desulphurizing process Recovers elemental sulphur from gaseous

hydrogen sulphide The overall main reaction equation is:

2 H2S + O2 → S2 + 2 H2O

REMOVAL OF SULPHUR DURING COMBUSTION

Experimental Stage The combustible compound is mixed with an

admixture of water soluble and water insoluble sulphur sorbent.

Such admixtures, remarkably, produces a reduction in the SOX level far greater than would be expected based on the activity of each sorbent alone.

REMOVAL OF SOX AFTER COMBUSTION

THE THE SEAWATERSEAWATER SCRUBBER SCRUBBER

SPRAY SPRAY DRYDRY

SYSTEMSYSTEM

WELLMAN-LORD WELLMAN-LORD PROCESSPROCESS

LIMESTONELIMESTONE/GYPSUM /GYPSUM SYSTEMSYSTEM

FLUEFLUE GASGAS

DESULPHURISATION DESULPHURISATION (FGD)(FGD)

LIMESTONE/GYPSUM SYSTEM

Most widely used process Principle Suspension of crushed limestone in water is

sprayed into the flue gases. SO2 reacts with calcium ions to form calcium

sulphite slurry Aeration of the slurry with compressed air

oxidizes calcium sulphite to calcium sulphate After removal of the water, the calcium

sulphate can be disposed off

Advantage : SO2 reduction around 90 %

Disadvantages : limestone has to be stored onboard large quantities of gypsum waste is produced

SPRAY DRY SYSTEM A slurry of slaked lime is used as an alkaline

sorbent The slurry is injected into the flue gases in a

fine spray. The flue gases are simultaneously cooled by

the evaporation of water The SO2 present reacts with the drying sorbent

to form a solid reaction product, with no wastewater.

WELLMAN-LORD PROCESS Hot flue gases are passed through a pre-scrubber Ash, hydrogen chloride, hydrogen fluoride and SO3 are

removed. the gases are then cooled and fed into an absorption tower SO2 reacts with a saturated sodium sulphite solution to form

sodium bisulphite. The sodium bisulphate is regenerated after a drying step to

sodium sulphite again. The released and clean SO2 - may then be liquefied or

converted to elemental sulphur or sulphuric acid. The sorbent is regenerated during the combustion process and

is continuously recycled, but the products (sulphur compounds) have to be stored.

THE SEAWATER THE SEAWATER SCRUBBER Krystallon Sea-Water Scrubber Removes 90-95 % of SO2 In addition removes 80 % of the particulates

and 10-20% of hydrocarbons. Advantages♦ no limestone has to be stored on board, ♦ no waste (gypsum) is produced, which has to

be deposited on land, ♦ the seawater already contains substantial

amounts of sulphate and nitrate ♦reduction of engine noise and a reduction of

the diesel smell. .

Uses Cyclone Technology The system needs only a little extra space Aeration of the effluent is necessary high degree of recirculation

FeaturesFeatures

WorkingWorking

Water in contact with hot exhaust gas Exhaust gas is channelled through a concentric

duct into a shallow water tank. Mixing baffles break up large gas flow into

smaller bubbles SOx in exhaust gas is dissolves in seawater Larger particles (greater than 2.5 micron)

captured in the water. Fine particles (smaller than 2.5 micron) may

pass through without capture.

Pumped through a set of large cyclones Designed to separate some of the heavy

particles, as well as light particles in a two-stage system.

Fed to a settling tank for collection of soot and oil.

Runs with no ongoing maintenance Cleaned recirculated water is maintained at

extremely low concentrations of hydrocarbons, making it safe for discharge to sea.

OPERATIONAL CONCERNS AROUND THE CHANGE TO

LOW SULPHUR FUELS REDUCED FUEL VISCOSITY FUEL ACIDITY IGNITION AND COMBUSTION QUALITY FUEL LUBRICITY

REDUCED FUEL VISCOSITY

MGO and MDO fuels have a lower inherent viscosity than heavy fuel oil which can :

Effect Diesel Engines Effect Steam Boilers

Effect On Diesel Engines

Changes in fuel atomisation Adversely affects power output and engine

starting performance. Solution Recommended : Use fuel coolers to

control fuel viscosity

Effect On Steam Boilers

Affects fuel flow setting (for a given pressure) at the burners

Can lead to “Over Firing” Increased risk of flame failures and flame

impingement on boiler tube plates. Solution Recommended : Change the nozzle Or the air/fuel ratio settings

FUEL ACIDITYFUEL ACIDITY Does not present a problem for steam boilers But has a significant effect on diesel engines Engine lube oils are formulated with alkaline

additives to neutralise the acidic, sulphur, by-products of combustion.

IF amount of sulphur in the fuel is reduced, THE amount of alkaline additives should be reduced.

Too much alkalinity causes build-up of deposits that will affect the lubricating film

Solution Recommended : Oil with a lower Base Number (BN).

IGNITION AND IGNITION AND COMBUSTION QUALITYCOMBUSTION QUALITY

Effect On Diesel Engines Effect On Steam Boilers

Effect On Diesel Engines

Poor combustion and ignition may lead to increased fouling of the engine

Fouling is so excessive that moving parts such as exhaust valves are inhibited by the soot, leading to broken/bent valves

Excessive fouling of the scavenge air receiver combined with late ignition or prolonged combustion may lead to a buildup of soot deposit and the risk of fire.

Effect On Steam Boilers

Leads to starting failures and more frequent flame failures

May lead to increased soot formation and consequent fouling of the boiler and exhaust system.

Solution Recomended: Follow detailed advice given by manufactures on procedures to follow when switching fuel qualities.

FUEL LUBRICITYFUEL LUBRICITY

Ultra Low Sulphur Diesel (ULSD) contains <15ppm sulphur.

Inherent lubricity of such diesel is reduced which in turn increases wear on fuel pumps and injectors.

Solution : Lubricity additives are commonly added at source to such fuels to reduce these problems

ENGINE EXHAUST DEPENDS ENGINE EXHAUST DEPENDS UPONUPON

ENGINE TYPE ( i.e LOW,MEDIUM AND HIGH SPEED)

ENGINE SETTING ( i.e LOAD,SPEED AND FUEL INJECTION TIMING)

FUEL USED

FACTORS AFFECTING FACTORS AFFECTING NOx FORMATIONSNOx FORMATIONS

SPEED OF ENGINE MAXIMUM TEMPERATURE INSIDE CYLINDER COMPRESSION RATIO/PEAK PRESSURE AMOUNT OF SCAVENGE AIR

NOxNOx REDUCTIONREDUCTION TECHNIQUESTECHNIQUES

PRE-TREATMENT

INTERNAL MEASURE(PRIMARY

METHODS)

AFTER TREATMENT(SECONDARY METHODS)

NOxNOx REDUCTIONREDUCTION TECHNIQUESTECHNIQUES

PRE-TREATMENT

INTERNAL MEASURE(PRIMARY

METHODS)

AFTER TREATMENT(SECONDARY METHODS)

ALTERNATIVE FUELSALTERNATIVE FUELS

METHANOL LIQUIFIED PETROLEUM GAS

METHANOLMETHANOL

50% REDUCTION NO SULPHUR BAD IGNITION QUALITY CORROSIVE EXPENSIVE FUEL

LIQUIFIED PETROLEUM GASLIQUIFIED PETROLEUM GAS

BUTANE(C4H10)+PROPANE(C3H8)

LOW ENERGY DENSITY SO MORE FUEL CONSUMPTION

NON-CORROSIVE NON-TOXIC

WATER ADDITION TO FUELWATER ADDITION TO FUEL

UNDER RESEARCH WITH 30% OF WATER IN FUEL

30% REDUCTION IN NOx EMISSION EFFECT ON ENGINE COMPONENTS IS

NOT KNOWN DECREASE MAXIMUM TEMPERATURE

INSIDE CYLINDER HIGH SPECIFIC HEAT

NOxNOx REDUCTIONREDUCTION TECHNIQUESTECHNIQUES

PRE-TREATMENT

INTERNAL MEASURE(PRIMARY

METHODS)

AFTER TREATMENT(SECONDARY METHODS)

MODIFICATIONS IN MODIFICATIONS IN COMBUSTION PROCESSCOMBUSTION PROCESS

INJECTION TIMING RETARDATION INCREASE IN INJECTION PRESSURE OPTIMIZATION OF INDUCTION SWIRL MODIFICATION OF INJECTOR

SPECIFICATION CHANGE IN NUMBER OF INJECTORS

INJECTION TIMING INJECTION TIMING RETARDATIONRETARDATION

REDUCE MAXIMUM COMBUSTION TEMPERATURE & PRESSURE

REDUCTION UPTO 30% OF NOx EMISSION

INCREASE IN SFC BY 5% MORE EFFECTIVE FOR MEDIUM/HIGH

SPEED ENGINES

INCREASE IN INJECTION INCREASE IN INJECTION PRESSUREPRESSURE

COMBINED WITH OTHER TECHNIQUES PROVIDES BETTER ATOMIZATION

OPTIMIZATION OF OPTIMIZATION OF INDUCTION SWIRLINDUCTION SWIRL

COMBINED WITH OTHER NOx REDUCTION TECHNIQUES

HELPS IN GOOD COMBUSTION NO ADDITIONAL COST

INJECTOR SPECIFICATIONSINJECTOR SPECIFICATIONS

INJECTION PRESSURE NUMBER AND ANGLE OF HOLES SIZE OF HOLES

CHANGE IN NUMBER OF CHANGE IN NUMBER OF INJECTORINJECTOR

COMBUSTION PROCESS CAN BE CONTROLLED BETTER

REDUCE MAXIMUM COMBUSTION TEMPERATURE

ADDITIONAL COST OF FUEL INJECTOR AND PIPING

INCREASE IN MAINTENANCE COST 30% REDUCTION IS ACHIEVABLE

SCAVENGE/CHARGE AIR SCAVENGE/CHARGE AIR COOLINGCOOLING

14% REDUCTION IS POSSIBLE BY LOWERING CHARGE AIR TEMP. FROM 40oC to 25oC

REDUCE COMBUSTION TEMPERATURE SUITABLE FOR MEDIUM AND HIGH

SPEED ENGINES COOLING AIR TOO MUCH COULD LEND

TO COMBUSTION PROBLEMS

WATER INJECTIONWATER INJECTION

DURING COMBUSTION THROUGH SPECIAL INJECTOR

REDUCES THE BULK TEMPERATURE OF COMBUSTION

40% REDUCTION IN NOx EMISSION IS ACHIEVED

WATER INJECTION WATER INJECTION LIMITATIONSLIMITATIONS

NEED OF SEPARATE PUMP FOR FUEL AND WATER

COST FACTOR CORROSION

NOxNOx REDUCTIONREDUCTION TECHNIQUESTECHNIQUES

PRE-TREATMENT

INTERNAL MEASURE(PRIMARY

METHODS)

AFTER TREATMENT(SECONDARY METHODS)

WHAT IS SCR?WHAT IS SCR?

SELECTIVE CATALYST REDUCTION IS THE PROCESS OF REDUCING NOx COMPOUNDS WITH AMMONIA INTO NITROGEN AND WATER VAPOURS IN PRESENCE OF CATALYST.

SCR SYSTEM COMPONENTSSCR SYSTEM COMPONENTS

REDUCTANT STORAGE TANK PUMP VAPORIZER (NOT IN CASE OF

ANHYDROUS AMMONIA) MIXER INJECTION NOZZELS CATALYST CHAMBER

WORKING OF SCR SYSTEMWORKING OF SCR SYSTEM

AFTER TREATMENT TECHNIQUE REDUCTANT(AMMONIA) IS INJECTED

AND MIXED INTO EXHAUST PASS THIS MIXTURE THROUGH

CATALYST CHAMBER TEMPERATURE OF CATALYST

CHAMBER SHOULD BE 450K-720K

REACTIONS INVOLVEDREACTIONS INVOLVED

REDUCTANTS USEDREDUCTANTS USED

ANHYDROUS AMMONIA AQUEOUS AMMONIA UREA

CATALYST USEDCATALYST USED

BASE METAL OXIDES SUCH AS (VANADIUM AND TUNGSTEN)

TITANIUM OXIDE ZEOLITE (HIGH TEMPERATURE

DURABILITY)

EXHAUST GAS EXHAUST GAS RECIRCULATIONRECIRCULATION

REDUCES LOCAL COMBUSTION TEMPERATURE.

HIGH SPECIFIC HEAT OF EXHAUST GAS AND WATER VAPOUR.

DECREASES OXYGEN CONCENTRATION.

BUBBLE BATH SCRUBBERBUBBLE BATH SCRUBBER

EMISSION TRADE

Credit based system This system was proposed by the swedish ship

owners association. Large combustion installations are capped by

their maximum annual emissions. Installation that emits less than its allocated

credits can trade the difference in theemissions market.

HOW IT WORKS? Emission reductions become a tradable

commodity, which can be bought and sold like any other product in the market.

Each ship will be allocated points depending on its yearly emissions in tons.

Trading can be made anonymously through an emissions market.

CONCLUSION

Emission control is a necessity to make shipping transport viable.

CSR and Green marketing are the new buzz words.

One time investment and high returns. Decrease in peak temperature can limit NOX

emission. Limit SOX by removing sulphur prior

combustion.

REFERENCES

Reduction of NOx and SOx in an emission a snapshot of prospects and benefits for ships in the northern European SECA area.

www.imo.org MARPOL consolidated edition 2006 Exhaust emissions from ship engines - significance,

regulations, control technologies by Laurie Goldsworthy www.dieselnet.com

THANK YOUTHANK YOU