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Published byFrances Romaine Modified over 2 years ago

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

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

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

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

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

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

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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%

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Data required for Boiler Efficiency Calculations Unit loadMW FW Flow at Econ inletT/hr Wet bulb Temp 0 C Dry bulb Temp 0 C Barometric PressuremmHg Total Coal FlowT/hr Unburnt C in BA% Unburnt C in FA% Radiation & Unaccounted Losses% % Fly ash to Total Ash% % Bottom ash to Total ash%

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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 inAve FG CO2 APH Out Ave FG CO APH inAve FG CO APH Out Ave. FG Temp APH inAve. FG Temp APH Out Air to APH in Air APH out Total Primary Flow Total Air Flow LTotal Air Flow R Design Ambient / Ref air Temp

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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) )* GCV AF/GCV AD 4. Moisture = Moisture AF 5. Nitrogen = ( * 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

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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 0 CWeighted Temp Air Out = Tsao*Rsa+Tpao*Rpa 0 C Avg. Flue Gas CO2 -APH Out % Gross CV kcal/kg Weight of Dry Gas = (Ca+S/ *U)/(12*CO2out) kg/kg coal Sensible Heat Dry Gas = Wd*30.6(Tgo-Trai) kJ/kg

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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 C ANY INCREASE IN THE FGT MORE THAN C WILL BE RESULTING IN MORE LOSSES. THIS TEMP HAS TO BE CONTROLLED BY PROPER CLEANING OF THE FURNACE

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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%.

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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

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Losses Calculations Assumptions:- 1.Fly Ash is 80% of Total Ash. 2.Bottom Ash is 20% of Total Ash 3.Sulphur is 0.4% in Coal

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

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

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Data Required Contd. Ave FG O 2 APH in Ave FG CO 2 APH in Ave FG CO APH in Ave FG O 2 APH Out Ave FG CO 2 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

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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 = T M % 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 %

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

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Calculations Weight of Dry Gas = (Ca+S/ *U)/(12*CO 2 out) 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) CO 2 Out = Avg. CO 2 Flue Gas -APH Out Sensible Heat Dry Gas = Wd*30.6(Tgo-Trai)

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