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BOILER EFFICIENCY

BOILER EFFICIENCY. Steam Output. Radiation Loss. Second Pass. Heat Input. ESP. Furnace. Heat Input is Pulverised Coal Heat Output is Superheated Steam. Efficiency Calculations. Standard Applied :- ASME Standard PTC 4.1 Calculation Method :- Loss Method

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BOILER EFFICIENCY

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  1. BOILER EFFICIENCY Steam Output Radiation Loss Second Pass Heat Input ESP Furnace Heat Input is Pulverised Coal Heat Output is Superheated Steam

  2. Efficiency Calculations Standard Applied :- ASME Standard PTC 4.1 Calculation Method :- Loss Method Losses calculated as percentage of INPUT as 100%

  3. Losses in Boilers Second Pass Heat Input Furnace ESP 1) Loss due to dry flue gas = 4.928%   

  4. Losses in Boilers Contd. Second Pass Heat Input ESP Furnace 2) Loss due to Unburnt Carbon   = 0.331%

  5. Losses in Boilers Contd. Second Pass Heat Input ESP Furnace 3) Due to Sen. Heat of Bottom Ash      =  0.071% 4) Due to Sen. Heat of Fly Ash      =  0.102%

  6. Losses in Boilers Contd. Second Pass Heat Input ESP Furnace 5)Radiation Losses                  = 0.200%

  7. Losses Related to Coal & Ambient Air Quality 6) Loss due to moisture in Fuel =  1.263% 7) Loss due to Hydrogen in Fuel =  5.537% 8) Loss due to Moisture in Air    =  0.074% 9) Unaccounted Losses   = 1.327%   Total Losses                     = 13.83%

  8. Data required for Boiler Efficiency Calculations Unit load MW FW Flow at Econ inlet T/hr Wet bulb Temp 0C Dry bulb Temp 0C Barometric Pressure mmHg Total Coal Flow T/hr Unburnt C in BA % Unburnt C in FA % Radiation & Unaccounted Losses % % Fly ash to Total Ash % % Bottom ash to Total ash %

  9. Data required……….2 Proximate Analysis of Coal Air Dry As fired Moisture % % Ash % % Volatile Matter % % Fixed Carbon % % Gross Cal. Value Kcal/kg Kcal/kg Ave FG O2 APH in Ave FG O2 APH Out Ave FG CO2 APH in Ave FG CO2 APH Out Ave FG CO APH in Ave FG CO APH Out Ave. FG Temp APH in Ave. FG Temp APH Out Air to APH in Air APH out Total Primary Flow Total Air Flow L Total Air Flow R Design Ambient / Ref air Temp

  10. Calculations Ultimate Analysis As fired Basis 1. Carbon = (Fixed Carbon AD+0.9(Vol Matter AD-14)) *GCV AF/GCV AD 2. Sulphur = 0.4 * GCV AF/GCV AD 3. Hydrogen = Vol.Matter AD*(7.35/(Vol Matter AD+10)- 0.013)* GCV AF/GCV AD 4. Moisture = Moisture AF 5. Nitrogen = (2.1-0.012 * Vol.Matter AD)* GCV AF/GCV AD 6. Oxygen = 100-(Carbon+Hydrogen+Nitrogen+Ash AD+Moisture AD)* GCV AF/GCV AD 7. Ash = Ash AF and 8. Gross Cal. Value=GCV AF

  11. Calculations ….. Losses Dry Gas Loss = Sensible heat of dry gas*100/(GCV AF*4.186) % Carbon in fuel % Sulfur in fuel % Carbon in ash / kg of fuel kg/kg coal Specific Heat of Gas kg/kg C Avg. Flue gas temp - APH Out 0C Unburned C in Ash = Pfa/100*Cfa + Pba/100*Cba % C in Ash / Kg of coal =A/100*Cash/(100-Cash) kg Total air Flow = A+B Thr Ratio SA Flow to Total Air Flow - Fsa/Fta % Ratio PA Flow to Total Air Flow = Fpa/Fta % Weighted Temp Air In = Tsai*Rsa+Tpai*Rpa 0CWeighted Temp Air Out = Tsao*Rsa+Tpao*Rpa 0C  Avg. Flue Gas CO2 -APH Out % Gross CV kcal/kg Weight of Dry Gas = (Ca+S/2.67-100*U)/(12*CO2out) kg/kg coal Sensible Heat Dry Gas = Wd*30.6(Tgo-Trai) kJ/kg

  12. CONTROLLABLE LOSSES 1 FOLLOWING LOSSES CAN BE CONTROLLED 1. LOSS DUE TO DRY FLUE GAS THE DESIGNER GIVES THIS LOSS AT THE FLUE GAS APH OUTLET TEMP OF 1400C ANY INCREASE IN THE FGT MORE THAN 1400C WILL BE RESULTING IN MORE LOSSES. THIS TEMP HAS TO BE CONTROLLED BY PROPER CLEANING OF THE FURNACE

  13. CONTROLLABLE LOSSES 2a LOSSES DUE TO THE UNBURNT COAL IN BOTTOM AND FLY ASH. LOSS DUE TO UNBURNT IN BOTTOM ASH THE DESIGNER GIVES THIS %AGE AS MAX 4.8 % ANY INCREASE IN THIS PERCENTAGE BEYOND THIS WILL RESULT IN MORE LOSSES IF UNBURNT IN BOTTOM ASH IS MORE, THE CULPRIT IS THE COAL MILL, CHECK THE FINENESS OF PULVERISED COAL. CHECK THE % RETENTION ON 50 MESH. IT SHALL NOT EXCEED 1%.

  14. CONTROLLABLE LOSSES 2b CHECK THE UNBURNT IN FLY ASH SAMPLE TAKEN FROM THE FIRST HOPPER OF ESP/BF AS PER THE DESIGNER IT SHALL NOT EXCEED 0.8%. IF UNBURNT IN FLY ASH EXCEEDS 0.8% IT INDICATES INCOMPLETE COMBUSTION DUE TO LESS AMOUNT OF AIR CHECK FOR O2 % AT THE APH FG INLET FOR 2.8%, INCREASE IF NECESSORY TO 3.2%. AGAIN CHECK FOR UNBURNTS IN FLY ASH. SIMULTANIOUSLY CHECK FOR AIR LEAKAGES/INGRESS IN THE SECOND PASS

  15. Losses Calculations • Assumptions:- • Fly Ash is 80% of Total Ash. • Bottom Ash is 20% of Total Ash • Sulphur is 0.4% in Coal

  16. DATA REQUIRED Fuel Properties Proximate Analysis of Coal Air Dry BasisAs Fired basis Moisture %Moisture % Ash %Ash % Volatile Matter %Volatile Matter % Fixed Carbon %Fixed Carbon % Gross Cal. Value %Gross Cal. Value %

  17. Data Required contd. Unit load MW FW Flow at Econ inlet T/hr Wet bulb Temp 0C Dry BulbTemp 0C Barometric Pressure Total Coal Flow T/hr Unburnt Carbon in BA % Unburnt Carbon in FA %

  18. Data Required Contd. ** Ave FG O2 APH in ** Ave FG CO2 APH in ** Ave FG CO APH in ** Ave FG O2 APH Out ** Ave FG CO2 APH Out ** Ave FG CO APH Out ** Air to APH in Temp ** Air APH out Temp ** Total Air Flow L ** Total Air Flow R ** Ave. FG Temp APH in ** Ave. FG Temp APH Out ** Total Primary Air Flow

  19. GCV Calculations for Coal Calculations of GCV As fired Basis Coal sample is taken as received basis, heated for calculation of A) Total Moisture content = TM% Air Dry Basis The sample is air dried for removal of surface moisture and burned completely for A) Inherent moisture content = M % B) Ash percentage = A %

  20. GCV Calculations for Coal Contd. 1) Useful Heat Value = 8900 – 138(A%+M%) kcal/kg 2) Gross Calorific Value = (UHV + 3645 – 75.4 M%)/1.466 (Air Dry Basis) Kcal/kg 3) Ash % (As fired basis) = [A %] (100 - TM%)/(100 – M%) % 4) Gross Calorific Value = [GCVAD] (100 - TM%)/(100 – M%) (As fired Basis) Kcal/kg 5) Net Calorific Value = [GCV] – 10.02M% Kcal/kg

  21. Calculations Weight of Dry Gas = (Ca+S/2.67-100*U)/(12*CO2out) Ca = % Carbon in fuel (Ultimate Analysis as Fired) S = % Sulfur in fuel (Ultimate Analysis as Fired) A = % of Ash in fuel (Ultimate Analysis as Fired) Unburned C in Ash = Pfa/100*Cfa + Pba/100*Cba U = Carbon in ash / kg of fuel=A/100*Cash/(100-Cash) CO2 Out = Avg. CO2 Flue Gas -APH Out Sensible Heat Dry Gas = Wd*30.6(Tgo-Trai)

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