Heat Input

Radiation Loss

Steam Output

BOILER EFFICIENCY

Heat Input is Pulverised Coal

Heat Output is Superheated Steam

Furnace

Second Pass

ESP

Efficiency Calculations

Standard Applied :- ASME Standard PTC 4.1

Calculation Method :- Loss Method

Losses calculated as percentage of INPUT as 100%

Losses in Boilers

1) Loss due to dry flue gas = 4.928%    

Furnace

Second Pass

ESPHeat Input

Losses in Boilers Contd.

2) Loss due to Unburnt Carbon   = 0.331%

Furnace

Second Pass

ESPHeat Input

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

Losses in Boilers Contd.

Furnace

Second Pass

ESP

5) Radiation Losses                  = 0.200%

Heat Input

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%

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 %

Data required……….2Proximate 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

CalculationsUltimate 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

Calculations ….. LossesDry 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

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

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%.

CONTROLLABLE LOSSES 2bCHECK 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

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

DATA REQUIREDFuel Properties

Proximate Analysis of Coal

Air Dry Basis As Fired basis

Moisture % Moisture %

Ash % Ash %

Volatile Matter % Volatile Matter %

Fixed Carbon % Fixed Carbon %

Gross Cal. Value % Gross Cal. Value %

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 %

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

GCV Calculations for CoalCalculations 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 %

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

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)