Furnace and boiler

7/29/2019 Furnace and boiler

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Welcome to Training Programon

OPERATION OF FURNACES &BOILERS


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MIND

SPIRIT

? YOUR EXPECTATIONS


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Type of furnaces / boilers in refinery

Heater nomenclature

Associated equipments(Burners, APH, Soot blowers etc.)

Fuel System

Combustion

Q & A

Presentation Session 1


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Types of furnaces

1. Natural draft furnaces (FCC, DHDS, Small furnacesin AU-I/II of JR, NSU, GR)

2. Balanced draft furnaces (All furnaces and boilers of

PDRP, AU-I/II/III/IV/V, new DCU and Russian Boilers

of BR, )3. Forced draft furnaces (New DHDT JR and Boiler-IV

BR)

4. Induced draft (VBU, JR)


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Furnace

Convection

Natural Draft Furnace System

Oil

Radiation

Vertical firing

Old system

Hut type furnace

Horizontal firing

History Hut, Verticalcylindrical/ box type,balanced draft

Atomizing steam


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Furnace

APH

Induced Draft

Fan

Damper

Balanced draft Furnace System

Oil FD fan


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Boiler Economiser

APH

Induced Draft

Fan

Damper

Boiler System (balanced draft)

Oil FD fan


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Boiler Economiser

APH

Boiler System (forced draft)

Oil FD fan


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Furnace

APH in top of

convection bank

Forced draft Furnace System

Oil FD fan


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Furnace

Induced Draft

Fan

Damper

Induced draft Furnace System

Oil

Atomizing steam


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Heater Nomenclature
http://localhost/var/www/apps/conversion/tmp/scratch_6/2.%20heater%20nomenclature1.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_6/2.%20heater%20nomenclature1.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_6/2.%20heater%20nomenclature1.pdf


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BURNERS


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Types of burners

1. Pressure atomized oil burners in Russian boilers2. Steam atomized oil burners in Boiler-IV and process

heaters

3. Mixed burners (Oil & Gas)


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Burners

Burners convert fuel oil into millions of small

dropletsprocess called atomization

High surface to volume ratio in oil to facilitate

evaporation and combustion

3 basic types of burners are pressure jet, air orsteam blast burners and Rotary Cup

TURNDOWN ratio is the relationship between the maximum

and minimum fuel input without affecting the excess air level

is called Turn-Down Ratio.

For example, a burner whose maximum input is 250,000

Kcals and minimum rate is 50,000 Kcals, has a Turn-Down

Ratio of 5 to 1.


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Energy Efficiency Measures

Replace old, oversized burnerandinefficient burners with modern, efficientand properly sized burner.

Consider variable firing rates and/or dual

fuel capabilities allowing you to choose low

cost fuel at any time.

Potential efficiency improvement-up to 5%


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DCU


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Vacuum Unit


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FCC


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APHs

Ai h t


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Air pre-heaters

Type Recuperative and regenerative

Recuperative Shell and tube type (all balance draft

furnaces and boilers)

Regenerative rotating metal element (Boiler-IV &

CO-Boiler)


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SOOT BLOWERS

S t Bl


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Soot Blowers

Motor driven (retractable / fixed)

Pneumatic driven (retractable / fixed)

Shot cleaning (old system)

F el S stem


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Fuel System

Fuel oil tank, pump, heater, back pressure control

Ensure water free oil

Minimum ash and metal content

Catalyst particles not desired

Heat up to desired temperature for attaining desired

viscosity

Fuel gas system

Ensure condensate free fuel gas

Steady fuel gas pressure

Oil


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Oil

The oil used in refinery is a blended fuel

consisting of residue from FCC, DCU and

AGO.

The important properties of oil are viscosity atburner tip, water content, density, specific

gravity, Calorific value, Sulphur, metal and

ash content.


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COMBUSTION


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What is COMBUSTION ?


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Oil Combustion

Stoichiometric ortheoreticalair is idealamount of air required for burning 1 kg of

fuel

1 kg of fuel oil requires ~14.1 kg of air forcomplete combustion

C + O2 CO 2 + 8084 Kcals/kg of Carbon

2C + O2 2 CO + 2430 Kcals/kg of Carbon2H 2 + O2 2H2O + 28,922 Kcals/kg of Hydrogen

S + O2 SO2 + 2,224 Kcals/kg of Sulphur

Combustion products


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Combustion products

CO2, H2O, SO2

CO is undesirable loss of fuel

Water vapour carries away heat as water is in

vapour form i.e. latent heat loss

Gas fuel more hydrogen more latent heat loss

Stoichiometric Air requirement


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The furnace oil quality is as under:

Constituents % weight

Carbon 85.9

Hydrogen 12

Oxygen 0.7

Nitrogen 0.5

Sulphur 0.5

H2O 0.35

Ash 0.05



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Basis : 100 Kg of furnace oil

C + O2 = CO2

12 + 32 = 44

12 Kg of carbon requires 32 Kg of Oxygen to

form 44 Kg of CO2

1 Kg of Carbon requires 32/12 = 2.67 Kg of

Oxygen

85.9 Kg of C + (85.9 x 2.67) O2 = 315.25 Kgof CO2



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2H2 + O2 = 2H2O

4 + 32 = 36

4 Kg of hydrogen requires 32 Kg of Oxygen to

form 36 Kg of H2O

1 Kg of hydrogen requires 32/4 = 8 Kg of

Oxygen

12 Kg of H2 + (12 x 8) O2 = 108 Kg of H2O



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S + O2 = SO2

32 + 32 = 64

1 Kg of sulphur requires 32 Kg of Oxygen to

form 64 Kg of SO2

0.5 Kg S + (0.5 x 1) O2 = 1Kg of SO2



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Total oxygen required = (229.35+96+.5)=325.85 Kg

Oxygen already present in fuel = 0.7 Kg

Additional oxygen required = 325.85 - .7 = 325.15 Kg

Theoretical quantity of dry air required = 325.15/0.23

= 1413.69 Kg

Theoretical air required per Kg of fuel = 1413/100

= 14.13 Kg of air

Theoretical CO2 content in fuel gas


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Theoretical CO2 content in fuel gas

Nitrogen in flue gas (QTY air O2) = 1413.69 325.15

= 1088.54 Kg

Moles of CO2 = 315.25/44=7.16

Moles of Nitrogen = 1088.54/28=38.87

Moles of SO2 = 1/64 = 0.016

Total moles = 46.06

Theor % CO2 by volume = (7.16/40.06)*100=15.5%

Flue gas components with excess air


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Flue gas components with excess air

% CO2 measured in flue gas = 10% by volume

Excess air = [(Theoretical CO2%/actual CO2%)-1]x100

= 55%

Theoretical air for 100 Kg of fuel burnt = 1413.69 Kg

Supply with 55% excess air = 1413.69 x 1.55

= 2191.22 Kg

Excess air quantity = 2191.22 1413.69 = 777.53 Kg

Oxygen = 777.53 x .23 = 178.83 Kg

Nitrogen = 777.53 178.83 = 598.7 Kg

Final components of flue gas with 55% excess air


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CO2 = 315.25 Kg = (315.25/44) = 7.16 moles

SO2 = 1 Kg = 1/64 = 0.016 moles

Oxygen = 178.83 Kg = 178.83 /32 = 5.59 moles

Nitrogen = 1687.24 Kg = 1687.24 / 28 = 60.25 moles

Total moles = 73.016

Theor %CO2 by volume = (7.16/73.016)x100=9.8%

Theor % O2 by volume = (5.59/73.016)x100=7.6%

3 T f C b ti


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3 Ts of Combustion

TIME

Sufficient time for complete combustion

TURBULENCE

Intimate mixing of fuel and air (primary air, secondary

air, tertiary air and angle of contract of air with fuel)

TEMPERATURE

Temperature high enough to ignite and maintain

ignition of fuel (viscosity of oil at burner tip 15-20 CST,

heating of oil)

What are the various types


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What are the various typesof combustion?

There are three types of combustion: -- Perfect -- Complete -- Incomplete

Perfect Combustionis achieved when all the fuel is burned using only the

theoretical amount of air, but perfect combustion cannot be achieved in aboiler.

Complete Combustion is achieved when all the fuel is burned using theminimal amount of air above the theoretical amount of air needed to burnthe fuel. Complete combustion is always our goal. With completecombustion, the fuel is burned at the highest combustion efficiency with

low pollution.

Incomplete Combustion occurs when all the fuel is not burned, whichresults in the formation of soot and smoke.

Critical success factor of combustion


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Critical success factor of combustion

Atomization

Mixing of oil and air (oil pressure drop and air

pressure drop)

A i i


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AtomizationOil as a liquidmust be converted to oil as gas

(vapour) before it can mix with air and begin to burn

Oil is passed to burner through atomizer which

converts liquid oil into millions of tiny droplets 10-50

micron size

Tremendous increase in the ratio of surface to mass

permitting substantially instantaneous heat absorption

by droplets to change physical state from oil to gas in

micro second

A i i


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AtomizationAtomization with the help ofsteam, air or high

pressure gas

Pressure atomization TPS old Russian boilers

Mechanical atomization Swirl chamber and rotary

cup

F f i i


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Factors of atomizationOil temperature at burner tip for attaining 15-20 CST

Dry atomizing steam

Delta P between steam and fuel about 2 Kg/Cm2

Cleanliness of burner

Impurities in oil like water, catalyst particles and metal

contents etc.

What the Nozzle Does


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What the Nozzle Does

Atomizing speeds up the vaporization process

One litre of oil becomes 15 billion droplets at 7kg/cm2

with size 0.0002 inch 0.010 inch

Metering deliver a fixed amount of atomized fuel to the

combustion chamber

Patterning

uniform spray

pattern and spray angle

What Affects Droplet Size?


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What Affects Droplet Size?

Higher Flow Rate Nozzles usually producelarger droplets

Wider Spray Angles produce smaller droplets

High Viscosity fuel produces larger droplets inthe spray

Heating Fuel reduces its viscosity and produces

smaller droplets.

Increasing Fuel Pressure reduces droplet size.


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Spray at 10 psi pressure Spray at 100-psi pressure

Spray at 300-psi pressure

Effects of Viscosity


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On Nozzle Performance

The nozzle orifice is polished to

a glasslike finish Dont ruin it with


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a glasslike finish. Don t ruin it witha wire or pin, or by bumping it with a

wrench. This can cause streaks in thespray.

Dont blow into the nozzle. While


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this may seem to be the handiest and

quickest way to clean a nozzle, yourun the risk of contaminating it instead.

Make sure the fuel tank is clean.W t d l d i th t k


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Water and sludge in the tank can

clog lines, filter or nozzles.


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Thank YouThank You

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Furnace and boiler