Efficiency and Performance of Power Plant

PRESENTATION BY

S.VISWANATHAN

DEPUTY DIRECTORNATIONAL POWER TRAINING

INSTITUTE (SR)

NEYVELI

ANNUAL FUEL CONSUMPTION IN A TYPICAL

COAL FIRED 210 MW UNIT

PLANT LOAD FACTOR 83.1%

L.D.O. 180 K.L.

H.F.O. 1180 KL

TOTAL OIL 1360 KL

COAL 1053220 T

SPECIFIC OIL CONSUMPTION 0.89 ML/KWHR

SPECIFIC COALCONSUMPTION

0.69 KG/KWHR

PLANT HEAT RATE 2479 KCAL/KWHR

COST OF GENERATION IN THERMAL POWER PLANTS

COST/KWHR FUEL

OPERATIONALEXPENCESREPAIRS & MAINT.

FIXED COST

SL.NO. ELEMENT COST/KWHR %1 FUEL 105.48 80.1

2 OPERATIONAL EXPENCES 1.13 0.863 REPAIR & MAINT. 5.12 4.124 TOTAL RUNNING COST 112.01 85.15 FIXED COST 19.61 14.96 GRAND TOTAL 131.62 100

COST OF INEFFICIENCYThr Turbine

heat rateKcal/kWh 2000 2000 2000

E BoilerEfficiency % 86 87 88

Change % -1 0 1

Phr Plant heatrate

Kcal/kWh 2325.58 2298.85 2272.73 2479

For 210 MW with 83% PLF

UgUnitsGeneratedPer Year

Kwhr1526.8 68 *106

1526.868 *106

1526.868 *106

1526.868

*106

Kc KcalrequiredPer YearUg*Phr

Kcal 3550.855813953*109

3510.041379310*109

3470.154545455*109

3785.105772*109

With a Coal of 3600Kcal/KgQc Coal

requiredPer yearKc/3600/1000

T/Yr 986349 975011 963932 1051418

Taking coal cost Rs1400 per tonneCc Cost of

CoalQc*1400

Rs 138,08,88,372

136,50,16,092

134,95,04,545

147,1985,578

Change inCoalrequired

T/Yr 11337 0 -11080 76407

Change incost ofCoal

Rs 1,58,72,280 0 1,55,

11,54610,69,69,486

PLANT OPTIMISATION• OBJECTIVE

– A POWER PLANT MEETS IT’S INSTRUCTED LOAD THROUGHOUT IT’S LIFE AT MINIMUM COST

• REQUIREMENT– ESTABLISH THE BESTWAY WITHIN CLOSE

LIMITS TO OPERATE AND MAINTAIN THE STATION AND ENSURE THE LIMITS ARE ADHERED TO.

PLANT OPTIMISATION• RANGE OF DECISIONS TO BE OPTIMISED

– WHAT IS THE BEST PLANT DESIGN?– WHAT IS THE BEST FUEL TO BURN?– HOW MANY STAFF ARE REQUIRED?

PLANT OPTIMISATION—. HOW SHOULD A COMPLETE STATION BE OPERATED AT STEADY LOAD?

— HOW SHOULD A INDIVIDUAL BOILER OR TURBINE BE OPERATED AT STEADY LOAD?

— HOW SHOULD A INDIVIDUAL BOILER OR TURBINE BE OPERATED AT TRANSIENT LOAD?

— HOW FREQUIENTLY SHOULD A PLANT BE CLEANED?

— HOW FREQUIENTLY SHOULD A PLANT BE SERVICED?

—CAN PLANT MODIFICATIONS OR OTHER EXPENDITURE BE JUSTIFIED BY IMPROVED PERFORMANCE?

PLANT OPTIMISATION• DECISIONS AFFECTING PLANT OPTIMISATION

– UNCONTROLLABLE

– SHORTTERM

• DECISIONS UNDER CONTINUOUS CONTROL

– MEDIUMTERM • DECISIONS MADE AT INTERVALS OF HOURS OR

DAYS

– LONGTERM• DECISIONS MADE INTERVALS OF WEEKS OR

MONTHS

DECISIONS AFFECTING PLANT OPTIMISATION

UNCONTROLLABLE

– PLANT DESIGN

– FUEL QUALITY

– LOAD


SHORTTERM -DECISIONS UNDER CONTINUOUS CONTROL

– OPERATING PARAMETERS Viz..STEAM PRESSURE,TEMPERATURE,AIR FLOW ETC.

– LOADING OF AUXILLIARIES


MEDIUMTERM -DECISIONS MADE AT INTERVALS OF HOURS OR DAYS

– SOOT BLOWING

– CONDENSER CLEANING

– MILL CLASSIFIER VANES ADJUSTMENTS


• LONGTERM- DECISIONS MADE INTERVALS OF WEEKS OR MONTHS

–SERVICING OF PLANT

–REPLACEMENT OF WORNOUT PARTS

–PLANT MODIFICATIONS

REQUIREMENT FOR EFFICIENCY AND PERFORMANCE

MONITORING

• KNOWLEDGE ON VARIOUS FACTORS INFLUENCING PERFORMANCE

• COLLECTION OF SAMPLES• MEASUREMENT OF VARIOUS PARAMETERS• CALCULATION AND OBTAINING RESULTS• INTERPRETATION OF RESULTS• OPTIMISATION AND IMPLEMENTATION

KEY AREAS OF BOILER PERFORMANCE

• CONVERSION EFFICIENCY-BOILER EFFICIENCY

-AUXILIRY POWER

• BOILER AS PART OF SYSTEM-EFFECT OF BOILER PARAMETERS

-SPECIFIC OIL CONSUMPTION

• LONG TERM CAPABILITY-CAPACITY REDUCTION

LOSSES ENCOUNTERED IN BOILER

• CONTROLLABLE– COMBUSTIBLE IN ASH LOSS– DRY GAS LOSS– CO IN FLUE GAS– MILL REJECTS LOSS

• UN CONTROLLABLE– MOISTURE IN FUEL– HYDROGEN IN FUEL– AIR MOISTURE– SENSIBLE HEAT IN ASH– RADIATION AND UNACCOUNTED

AREAS CONTRIBUTING TO VARIOUS LOSSES IN A

BOILER• COMBUSTION IN BOILER• AIRHEATER PERFORMANCE• MILL PLANT PERFORMANCE• FANS• WATER LOSSES

FACTORS AFFECTING PERFORMANCE OF COMBUSTION

• SURFACE CONTACT AREA OF FUEL WITH AIR• AIR-FUEL RATIO• RETENTION TIME• COMBUSTION CHAMBER TEMPERATURE• TURBULANCE IN COMBUSTION CHAMBER• REMOVAL OF PRODUCTS OF COMBUSTION

CARBON LOSS

• HEAT LOSS DUE TO UNBURNT CARBON LEAVING THE BOILER ALONG WITH EITHER BOTTOM ASH OR FLY ASH

FACTORS AFFECTING CARBON LOSS

1 AIR DISTRIBUTION– DISTRIBUTION– EXCESS AIR

2 PARTICLE SIZE– MILL FINENESS -200– MILL FINENESS +50

3 COAL QUALITY– VOLATILE MATTER

4 COMBUSTION– TIME– TEMPERATURE– TURBULANCE

AIR DISTRIBUTION

SY.AIR

SY.AIR

SY.AIR

SY.AIR

SY.AIR

FUEL

FUEL

FUEL

FUEL

GOOD AIR DISTRIBUTION

AIR DISTRIBUTION

• EXCESS AIR– AIR SUPPLIED IN ADDITION TO

STOCHIOMETRIC AIR FOR COMPLETE COMBUSTION OF FUEL

• OPTIMUM EXCESS AIR DEPENDS ON

– FUEL QUALITY– FIRING SYSTEM DESIGN

AIR DISTRIBUTION

• EXCESS AIR LESS THAN OPTIMUM RESULTS– INCREASED CARBON IN ASH

PARTICLE SIZE• COARSER THE FUEL PARTICLE

MORE THE CARBON LOSS• MAINTAIN OPTIMUM FUEL SIZE BY

PERIODICALLY MONITORING P.F.SIZE

• OPTIMUM FINENESS FOR H.V.SUB BITUMINOUS COAL– 100% THROUGH 50 MESH– 90% THROUGH 100 MESH– 70% THROUGH 200 MESH

VOLATILE MATTER• LOWER THAN DESIGNED VALUE

NEEDS MORE TIME FOR COMPLETE COMBUSTION WHICH FURNACE CAN NOT PROVIDE

• LEADS TO INCREASED COMBUSTIBLES IN ASH

• REMEDY– BLENDING OF COAL

COMBUSTION• TIME

– SUFFICIENT RETENTION TIME MUST BE ALLOWED FOR THE FUEL TO STAY INSIDE THE FURNACE TO COMPLETE COMBUSTION

– TIME REQUIRED/AVAILABLE DEPENDS• FUEL TYPE,QUALITY,SIZE• FURNACE SIZE• VELOCITY

– DRAUGHT

COMBUSTION• TEMPERATURE

– EFFECTS THERMAL DIFFUSION OF REACTING MOLECULES DUE TO INCREASED VELOCITY OF MOLECULES WITH INCREASE IN TEMPERATURE

– INFLUENCE THE RATE OF REACTION• FACTORS AFFECTING TEMPERATURE

– HEAT ABSORBED BY FURNACE– HEAT ABSORBED BY REACTANTS TO

BRING THEM TO IGNITION TEMPERATURE

– HEAT ABSORBED BY NITROGEN IN AIR

COMBUSTION• TURBULANCE

– MECHANICAL AGITATION OF REACTANTS TO BRING THEM INTO PHYSICAL CONTACT

– REQUIREMENT IS MORE AT FINAL STAGE OF COMBUSTION

– LESSER THE TURBULANCE MORE CARBON LOSS

– DEPENDS• WIND BOX TO FURNACE DIFF.PR.IN

CORNER FIRED BOILERS• TERTIARY AIR IN WALL FIRED BOILERS

DRY FLUE GAS LOSS

• HEAT CARRIED AWAY BY THE DRY CONSTITUENTS OF FLUE GAS THROUGH THE CHIMNEY

DRY FLUE GAS LOSSHEAT CARRIED AWAYBY DRY FLUE GAS SHD = WD*CP*(TG - TA) Kcal/Kgf

WHERE

WD WEIGHT OF DRY FLUE GAS Kgm/KgfCP SPECIFIC HEAT OF DRY FLUE GAS Kcal/Kgm0CTG GAS TEMPERATURE AT AIR HEATER OUTLET 0CTA AMBIENT TEMPERATURE 0C

DRY FLUEGAS LOSS = (SHD/C.V.)*100 %

WHERE

SHD - HEAT CARRIED AWAY BY DRY FLUE GAS Kcal/KgfC.V. - CALORIFIC VALUE OF FUEL Kcal/Kgf

CALCULATION OF DRY FLUE GAS WEIGHT

C+O2 CO2 ; i.e. 12+32=44

44 Kg OF C02 CONTAINS 12 Kg OF C

1 Kg OF CO2 CONTAINS 12/44 = 3/11 Kg OF C

2C+O2 2CO ; i.e. 24+32=56

56 Kg OF CO CONTAINS 24 Kg OF C

1 Kg OF CO CONTAINS 24/56 = 3/7 Kg OF C

TOTAL DRY FLUE GAS = Kg CARBON * DRY F.G/Kg.'C' BURNT

DRY F.G/Kg.'C' BURNT = TOTAL DRY FLUE GAS/Kg.'C' IN F.G.


WHEN DRY F.G.CONTAINS CO2% OF CARBON-DI-OXIDEAND CO% OF CARBON MONOXIDE BY WEIGHT

Kg OF CARBON IN F.G = 3/11 CO2 + 3/7 CO

WHEN CO2% AND CO% IN FLUE GAS AREMEASURED IN VOLUME BASIS

Kg OF CARBON IN F.G = 3/11(44CO2%)+3/7(28CO%) = 12(CO2%+ CO%)

DRY F.G./Kg 'C' BURNT = TOTAL DRY F.G/ Kg. OF'C' IN F.G

= 100/12(CO2%+CO%)Kg.mol

CARBON BURNT = C/100 - UWhereC-% OF CARBON IN FUELU- CARBON IN ASH Kg/Kg OF FUEL



DRY FLUE GAS = 100 (C/100)-U /12(CO2%+CO%) Kgmol/Kg.fuel

IF SIGNIFICANT AMOUNT OF SULPHUR IS PRESENT ANDSO2 IS ALSO TAKEN INTO ACCOUNT THE CARBONEQUIVALENT OF SULPHUR WILL BE ADDED AS

S*12/32 = S/2.67 WHERE 'S' IS % SULPHUR IN FUEL

DRY FLUE GAS=100 (C/100)+(S/267)-U /12(CO2%+CO%) Kgmol/Kg.fuel

=C+(S/2.67)-100U/12(CO2%+CO%) Kgmol/Kg.fuel


C CARBON % 36.92H HYDROGEN % 2.60S SULPHUR % 0.28OX OXYGEN % 7.51U UNBURNT CARBON/Kg

OF FUELKg 0.001

QSA STOCHIOMETRIC AIR2.6664*(C-100*U)+7.937*H+S-Ox

Kg/Kg fuel 4.8051

O2 OXYGEN IN FLUE GAS % 6EA EXCESS AIR

(O2/21-O2)*100% 40

QXA Wt. OF EXCESS AIRQSA* EA/100

Kg/Kg fuel 1.9220

MWA MOL.WT.OF AIR Kg/ Kgmol 28.966

MEA MOLS OF EXCESS AIRQXA/ MWA

Kgmol/Kgfuel

0.0664

MO2 MOLS OF O2 INEXCESS AIRMEA*20.95/100

Kgmol/Kgfuel

0.0139

MDG DRY GAS WT. PER KgOF FUELMO2/ O2 *100

Kgmol/Kgfuel

0.2317

CALCULATION OF DRY FLUE GAS WEIGHT WITH O2 DRY

CALCULATION OF DRY FLUE GAS WEIGHT WITH O2 DRY

C CARBON % 36.92H HYDROGEN % 2.60S SULPHUR % 0.28OX OXYGEN % 7.51U UNBURNT

CARBON/Kg OF FUELKg 0.001

QSA STOCHIOMETRIC AIR2.6664*(C-100*U)+7.937*H+S-Ox

Kg/Kg fuel 4.8051

O2 OXYGEN IN FLUEGAS

% 6

EA EXCESS AIR(O2/21-O2)*100

% 40

QXA Wt. OF EXCESS AIRQSA* EA/100

Kg/Kg fuel 1.9220

MWA MOL.WT.OF AIR Kg/ Kgmol 28.966MEA MOLS OF EXCESS AIR

QXA/ MWA

Kgmol/Kgfuel

0.0664

MO2 MOLS OF O2 INEXCESS AIRMEA*20.95/100

Kgmol/Kgfuel

0.0139

MDG DRY GAS WT. PER KgOF FUELMO2/ O2 *100

Kgmol/Kgfuel

0.2317

O2 MEASUREMENT• DRY BASIS

– MEASURED THROUGH ORSAT APPARATUS

• WET BASIS– MEASURED THROUGH ONLINE

ANALYSERS LIKE ZIRCONIA PROBE• DIFFERENCE BETWEEN WET AND

DRY O2% IN FLUE GAS COAL FIRED BOILERS - 0.2% OIL/GAS FIRED BOILERS - 0.6% to1.0%

FACTORS AFFECTING DRY FLUEGAS LOSS

• COAL QUALITY– MOISTURE– CARBON– CALORIFIC VALUE

• AIR INLET TEMPERTATURE– AMBIENT TEMPERTURE– SCAPH

• FLUE GAS QUANTITY– EXCESS AIR– AH LEAKAGE

FACTORS AFFECTING DRY FLUEGAS LOSS

• FLUEGAS OUTLET TEMPERTATURE– AIR HEATER LEAKAGE– AH ENTERING AIR TEMPERATURE– AH ENTERING GAS TEMPERATURE

• BOILER LOAD• FW TEMPERATURE• X RATIO OF AH• TEMPERING AIR• AIR INGRESS

COAL QUALITY• VARIATION IN COAL QUALITY

VARIES AIR REQUIREMENT AND HENCE DRY FLUE GAS WEIGHT

• VARIATION IN CALORIFIC VALUE VARIES THE %LOSS CALCULATION– UN CONTROLLABLE FACTORS

• EFFECTS ARE NEED TO BE DETERMINED BEFORE ANALYSING CONTROLLABLE FACTORS

AIR INLET TEMPERTATURE• AMBIENT TEMPERTURE

– INCREASE IN AMBIENT TEMPERATURE BRING DOWN HEAT CARRIED AWAY BY DRYGAS

– AFFECT AIR HEATER PERFORMANCE– UNCONTRLLABLE

• SCAPH– CONTINUOUS SERVICE OF SCAPH

INCREASE TA BUT AT THE SAME INCREASE TG ALSODUE TO A.H.PERFORMANCE DETORIATION

– INCREASED LOSSES DUE TO STEAM CONSUMPTION IN SCAPH

FLUE GAS QUANTITY• EXCESS AIR

– MORE THAN OPTIMUM INCREASES WD AND SO DRY GAS LOSS

– LESS THAN OPTIMUM INCREASES CARBON LOSS

– OPTIMUM EXCESS AIR IS DETERMINED THROUGH FIELD TESTS

– OPTIMUM EXCESS AIR CAN BE MAINTAINED THROUGH F.G. ANALYSIS

INCREASE OF EXCESS OXYGEN %0 1 2 3 4 5

10

20

30

40

50

60M

ON

ET

OR

Y L

OSS

/ D

AY

IN

Rs.T

HO

US A

ND

S

LOSS DUE TO HIGH EXCESS OXYGEN

1% INCREASE IN EXCESS OXYGEN WILL LEAD TO AN ANNUAL LOSS OF

Rs. 38.23 LAKHS FOR A210 MW UNIT

FLUE GAS QUANTITY• AH LEAKAGE

– INCREASE DRY GAS WEIGHT– DECREASE A.H. GAS OUTLET

TEMPERATURE– INCREASE DRY GAS LOSS AND

DECREASE A.H. PERFORMANCE

FLUEGAS OUTLET TEMPERTATURE

• AH ENTERING AIR TEMPERATURE– FOR EVERY 30C RISE IN AIR INLET

TEMPERATURE GAS OUTLET TEMPERATURE RISES BY 20C

• AH ENTERING GAS TEMPERATURE– FOR EVERY 30C RISE IN GAS INLET

TEMPERATURE GAS OUTLET TEMPERATURE RISES BY 10C

INCREASE IN A.H. OUTLET TEMP 0C0 5 10 15 20

MO

NIT

OR

Y L

OSS

PE

R D

AY

IN

Rs.T

HO

USA

ND

S

LOSS DUE TO HIGH F.G. TEMP.AT A.H. OUTLET

INCREASE IN

F.G.TEMP. AT

A.H. OUTLET

BY 100C

WILL LEAD TO

AN ANNUAL

LOSS OF

Rs.1CRORE

FOR A 210 MW

UNIT

50

45

40

35

30

25

20

15

10

5

AIR HEATER PERFORMANCE

• GAS OUTLET TEMPERATURE LOWER THAN OPTIMUM– LEADS TO COLD

END CORROSION• LOSS OF HEAT

TRANSFER ELEMENTS

• GAS OUTLET TEMPERATURE HIGHER THAN OPTIMUM– MORE DRY GAS LOSS– RISE OF 220C ABOVE

OPTIMUM REDUCE BOILER EFFICIENCY BY 1%

– 20C RISE ABOVE OPTIMUM RESULTS LOSS OF 600Kcal HEAT IN 1 TONNE OF F.G.

FACTORS AFFECTING A.H. GAS OUTLET TEMPERATURE

• LOWER THAN OPTIMUM– LIGHTING AND

FIRING COLD BOILER

• USE SCAPH– AIR LEAKAGE

• SEALS CONDITON• DIFF. PR. BETWEEN

AIR AND F.G

• HIGHER THAN OPTIMUM– QTY. OF AIR PASSING THROUGH

A.H.• TEMPERING AIR• SETTING INFILTRATION• BYPASS DAMPERS PASSING

– TEMP.OF GAS ENTERING A.H• DEPOSITS ON BOILER HEAT TRANSFER

AREAS• DELAYED/SY.COMBUSTION• FEED WATER TEMP

– FOULED / CORRODED ELEMENTS– DEFECTIVE BAFFLES– QTY.OFGAS PASSING THROUGH A.H.

AIR HEATER PERFORMANCE TESTS

• REQUIREMENTS– CHECKING ACTUAL PERFORMANCE

AGAINST MANUFACTURER’S GUARANTEE– COMPARISON WITH A STANDARD OF

OPERATION – COMPARING PERFORMANCE WHEN FIRING

DIFFERENT FUELS– DETERMINING THE EFFECTS OF CHANGES

TO EQUIPMENT– DETERMINING CORRECTIONS TO A.H.

EXITGAS TEMP. CAUSED BY VARIATIONS IN INLET TEMP. IN AN EFFICIENCY TEST OF A BOILER

AIR HEATER PERFORMANCE TESTS

• PERFORMANCE ITEMS DETERMINED– GAS SIDE EFFICIENCY– AIR LEAKAGE– X-RATIO– GAS AND AIR TEMPERATURE

CORRECTIONS– GAS AND AIRPRESSURE LOSS

DATA REQUIRED FOR A.H. PERFORMANCE TESTS

• TEMP.OF AIR ENTERING• TEMP.OF AIR LEAVING• TEMP.OF GAS ENTERING• TEMP.OF GAS LEAVING• QTY. OF AIR ENTERING• QTY. OF HEATED AIR LEAVING• AIR SIDE INLET AND OUTLET STATIC PRESSURE• AIR SIDE INLET AND OUTLET VELOCITY PRESSURE• GAS SIDE INLET AND OUTLET STATIC PRESSURE• GAS SIDE INLET AND OUTLET VELOCITY PRESSURE• GAS ANALYSIS OF F.G.ENTERING AND LEAVING A.H• HUMIDITY OF INLET AIR

DATA REQUIRED FOR A.H. PERFORMANCE TESTS

• QTY. OF GAS ENTERING A.H.• QTY. OF GAS LEAVING A.H.• QTY. OF FUEL MEASURED OR COMPUTED• ULTIMATE ANALYSIS OF COAL• QTY. OF ATOMISING STEAM IF BURNING OIL

AIR HEATER CALCULATIONS

GAS SIDE EFFICIENCY

G = {(tG14-tG15(NL))/(tG14-tA8)}*100

WHERE tG14 - MEASURED GAS TEMP. ENTERING A.H. tA8 - MEASURED AIR TEMP. ENTERING A.H tG15(NL) - CALCULATED GAS TEMP LEAVING A.H. CORRECTED FOR NO AIR LEAKAGE

HEAT BALANCE FOR LEAKING AIR IN AIR HEATER

HEAT GAINED BY LEAKING AIR=HEAT LOST BY F.G

HEAT GAINED BY LEAKING AIR=HEAT REQUIRED TO RISE TEMP. OF LEAKING AIR (tA8) TO GAS OUTLET TEMP.( tG15)

=A (L)*CpA*(tG15- tA8)

WHERE A (L) - % AIR LEAKING CpA - Sp.HEAT OF AIR

HEAT BALANCE FOR LEAKING AIR IN AIR HEATER

HEAT LOST BY F.G =HEAT LOST TO BRING DOWN THE GAS TEMP. FROM IF THERE IS NO LEAK (tG15(NL)) TO ACTUAL GAS TEMP. ( tG15)

=100*CpG*( tG15(NL) - tG15 )WHERE CpG - Sp.HEAT OF F.G.

100*CpG*( tG15(NL) - tG15 ) = A (L)*CpA*(tG15- tA8)

tG15(NL) = [{A (L)*CpA*(tG15- tA8)}/ 100*CPg ] + tG15

AIR HEATER LEAKAGE

A(L) =[WET AIR LEAKAGE/WET GAS ENTERING A.H]*100

=[{WG15-WG14}/WG14]*100

BY EMPRICAL APPROXIMATION

A(L) =90*{%CO2 ENTERING A.H.-%CO2 LEAVING A.H.}/ %CO2 LEAVING A.H.

EFFECT OF VARIOUS PARAMETERS ON A.H. GAS SIDE

EFFICIENCY• AIR INLET TEMP.IN ALL CASES 300C

CASE

GASINLETTEMP.

0C

GASOUTLET

TEMP.0C

LEAKAGE%

EFFICIENCY%

IDEAL 400 140 13 66.5

1 400 155 13 62.2

2 400 140 20 64.6

3 400 155 20 59.7

4 430 165 20 59.8

EFFECT OF COMPONENT ON DRY GASLOSS / EFFICIENCY

Gcv Gross calorific valueof fuel

Kcal/kg 3689.10 3689.10 3689.10

C Carbon in fuel % 36.92 36.92 36.92S Sulphur in fuel % 0.28 0.28 0.28U Unburnt carbon/kg

fuelKg 0.0066 0.0066 0.0066

CO2 Carbon di oxide influe gas

% 13 12 13

Wd Dry gas wt. Per kgof fuel

Kgmol/kg 0.2331 0.2525 0.2331

Sp.ht Specific heat Kcal/kgmol/0c

7.31 7.31 7.31

Tg Gas temperatureleaving boiler

0C 155 155 165

Ta Ambienttemperature

0C 35 35 35

DT Tg-Ta 0C 120 120 130L1 Dry gas loss % 5.54 6.00 6.00Change in loss for1% CO2 % -0.46100C -0.46

EFFECTS OF TRAMP AIR TO BOILER

• NOT CONTRIBUTING TO COMBUSTION

• OFTEN IT IS COLD• INCREASE GAS VELOCITY

THROUGH E.S.P• BYPASSING A.H. INCREASED GAS

OUTLET TEMPERATURE

SOURCES OF AIR INGRESS• ASH HOPPER SEALS• ASH HOPPER DOOR LEFT OPEN• DEFECTIVE EXPANSION JOINTS• DUCT OPENINGS UNCOVERED• BOILER ROOF SEALS DEFECTIVE• ATTEMPERATING AIR DAMPERS

PASSING• A.H.AIR BYPASSING DAMPERS PASSING• SUCTION MILLING PLANT• WORN SHAFT SEAL ON EXHAUSTERS

X RATIO HEAT CAPACITY OF AIR PASSING THROUGH A.H.X RATIO = -------------------------------------------------------------------------- HEAT CAPACITY OF GAS PASSING THROUGH A.H.

WA9*CpA*(tA9 - tA8) = WG14*CpG*(tG14 - tG15(NL))

WA9*CpA (tG14 - tG15(NL))X RATIO = ------------- = ------------------ WG14*CpG (tA9 - tA8)

CpA / CpG = 0.95

INDICATION OF AIR BY PASSING A.HEFFECT OF BYPASSING AIR ON F.G. TEMP.LEAVING A.H

EFFECT OF AIR BYPASSING AH ON X RATIO AND GAS TEMP.

Qg Gas quantity enteringA.H.

T/hr 700 700 700

Qa Air quantity leaving A.H. T/hr 500 475 525Xr X ratio Qa*95/Qg 0.68 0.64 0.71Tgi Gas temp. entering A.H. 0C 330 330 330Tai Air temp. entering A.H. 0C 35 35 35Tao Air temp. leaving A.H. 0C 310 311 309Tgo Gas temp. leaving A.H.

without leakageTgi-[ Xr*( Tao- Tai )]

0C 143.39 152.08 134.78

VARIATION 8.69 - 8.62Aef A.H.Efficiency % 63 60 66

CALCULATING AIR INGRESS %

Qg Gas quantity at A.H.inlet T/hr 700Qaf Air quantity based on excess

air at A.H.inletT/hr 650

Xr A.H.Xratio 0.7Qa Air quantity leaving A.H.

Xr*Qg/0.95T/hr 515.79

Qat Tempering air quantity frommill heat balance

T/hr 100

Qi Air ingress quantityQaf-Qat-Qa

T/hr 34.21

% Air ingress 5.26

MILL PERFORMANCE FACTORS

• P.F. FINENESS– CARBON LOSS– MILL POWER CONSUMPTION

• COAL-AIR RATIO• MILL REJECTS

EFFECTS OF P.F.FINENESS• TOO COARSE

– WEAR IN COAL PIPE– SLOWER IGNITION– POOR FIREBALL MIXING– UNSTABLE FLAME FRONT AT LOW LOADS– HIGH CARBON LOSS

• TOO FINE– INCREASED WEAR OF PULVERISER– DECREASED PULVERISER OUTPUT– INCREASED POWER CONSUMPTION

• 1% CHANGE IN FINENESS EQUALS APPROXIMATELY 1.5% IN CAPACITY

PROCEDURE FOR CHECKING COAL FINENESS

• PERIODICALLY COLLECT COAL SAMPLE FROM ALL PIPE LINES OF A MILL IN TWO PLANES USING STANDARD PROBE

• BEFORE COLLECTING SAMPLE ENSURE– MILL IS RUNNING AT

MORE THAN 75% LOAD– MILL IS RUNNING AT A

STEADY LOAD FOR 30 MINUTES

– NO LOAD CHANGE TAKES PLACE DURING SAMPLE COLLECTION


• MIX ALL THE SAMPLES COLLECTED FROM A MILL HOMOGENEOUSLY

• TAKE REQUIRED MASS OF SAMPLE BY CONING AND QUARTERING

• CONDUCT SIEVE ANALYSIS ON THE SAMPLE

• OPTIMUM FINENESS– 100% THROUGH 50 MESH– 90% THROUGH 100 MESH– 70% THROUGH 200 MESH


• DEPENDING ON THE RESULT ADJUST THE CLASSIFIER VANES

• TO INCREASE FINENESS– MOVE THE VANES TOWARDS CLOSED POSITION

• TO DECREASE FINENESS– MOVE THE VANES TOWARDS OPEN POSITION

• AFTER ADJUSTING RECHECK FINENESS• IF NECESSARY

– ADJUST RING TO ROLL CLEARANCE– ADJUST PRESSURE SPRING– REPLACE GRINDING ELMENTS

EFFECTS OF COAL AIR RATIO• HIGH AIR FLOW

– AFFECTS COAL CLASSIFICATION– REDUCES DISCHARGE OF PYRITES– INCREASES COAL PIPE EROSION – AFFECTS IGNITION POINT– MORE P.A. FAN POWER

CONSUMPTION• LOW AIR FLOW

– INCREASES COAL PIPE SPILLAGE – CAUSES DRIFTING IN COAL PIPE AND

ULTIMATE COAL PIPE CHOKING

CLEAN AIR FLOW TEST

• DETERMINES– WHETHER THERE IS ENOUGH AIR TO

TRANSPORT THE COAL– AIR FLOW DISTRIBUTION IN COAL PIPES– COAL PIPE OBSTRUCTION

• METHOD

P IS MEASURED BY PITOT TUBE INCOAL PIPE AT 0.935R, 0.791R, 0.612R, AND0.354R WHERE 'R' IS THE RADIUS OF PIPEIN INCHES

CLEAN AIR FLOW TEST PV 0.5 AIR VELOCITY = 18.275 [ ----------------------------- ] Ft/s 1.326 Pb +0.0735 PS { ------------------} 460+TWHERE

PV - PITOT TUBE DIFF.PR.IN INCHES OF WC.Pb - BAROMETRIC PRESSURE IN INCHES OF Hg.PS - STATIC PRESSURE IN INCHES OF WC.T - TEMPERATURE IN 0F PV 0.5 AIR VELOCITY = 5.5702 [ ---------------------------------------- ] M/s 18.7113 Pb / 25.4 + PS /345.34 ( -------------------------- ) 273.3 + TWHERE

PV - PITOT TUBE DIFF.PR.IN mm. OF WC.Pb - BAROMETRIC PRESSURE IN mm OF Hg.PS - STATIC PRESSURE IN mm OF WC.T - TEMPERATURE IN 0C

CLEAN AIR FLOW TESTAIR FLOW = 0.32725*D2*V* lbs/min

D - DIA. OF PIPE IN INCHESV - AIR VELOCITY ft/s -AIR DENSITY

DESIRED RESULTS

MEASURED AIR FLOW BETWEEN 135% AND 160% OFSTANDARD AIR FLOW

MEASURED AIR VELOCITIES ARE WITHIN 5% OFAVERAGE VELOCITIES

CAUSES OF MILL REJECTS• LOW AIR VELOCITY

– LOW AIR FLOW– AIR BYPASSING

• HIGH RE CIRCULATION RATIO– WEAR OF GRINDING ELEMENTS– IMPROPER SETTING OF GRINDING

ELEMENTS– IMPROPER SPRING COMPRESSION– OPERATING MILL WITH HIGHER FINENESS– HIGH MOISTURE COAL/LOW MILL OUTLET

TEMPERATURE

CAUSES OF MILL REJECTS• OVER FEEDING EXCEEDING MILL

CAPACITY– MALFUNCTIONING OF FEEDER OR FEEDER

HINGE GATE– HIGH RPM OF FEEDER– REDUCTION IN MILL CAPACITY

• EFFECTS OF REJECTS– REDUCTION IN BOILER EFFICIENCY– DETORIARATION OF DUST GUARD SEAL– OIL CONTAMINATION RESULTING DAMAGE

TO MILL DRIVE COMPONENTS

MILL PLANT REQUIREMENTS• MUST BE ABLE TO HANDLE DESIGN QUANTITY

COAL AND PRODUCE AN ACCEPTABLE PRODUCT EVEN WITH WORN OUT COMPONENTS

• P.F.MUST BE WITHIN DESIRED GRINDING RANGE AT ALL STABLE LOADS

• WET COAL UPTO DESIGN WETNESS MUST BE ADEQUATELY DRIED WHILE FULL OUTPUT IS MAINTAINED

• AT NO TIME MUST IT BE NECESSARY TO OPERATE THE MILLING PLANT IN AN UNSAFE CONDITION

DRYING CAPACITYWf = AO*(TI-TO)*4.043*10-04/MC*(1+)WHERE

Wf - COAL THROUGHPUT Kg/sAO - AIR FLOW AT MILL OUTLET Kg/s - LEAKAGE FACTOR =(AO-AI)/AIAI - AIR FLOW AT MILL INLET Kg/sTI - AIR TEMPERATURE AT MILL INLET 0CTO - COAL-AIR TEMP. AT MILL OUTLET 0CMC - TOTAL MOISTURE FRACTION OF COAL

MILL PLANT CONSTRAINTS• GRINDING LIMIT

– GRINDABLITY INDEX– MILL MOTOR CAPACITY

• P.F.FALL OUT LIMIT– MIN. VEL. OF COAL-AIR 18 TO 20Kg/s

• EROSION LIMIT– 1.5 TIMES OF FALL OUT LIMIT

• FLAMMABLITY– SAFE AIR/FUEL RATIO 5:1

• FLAME STABLITY– MINIMUM THROUGHPUT NOT LESS THAN 50%

• ATTEMPERATION– MINIMUM AIR TEMP. CONSTANT

MILL OPERATING WINDOWBASIC DATACOAL TYPE - BITUMINOUSTOTAL MOISTURE - 24% MAXM; 14% NOMINALCOAL FLOW -12Kg/s(MAX.);10.3Kg/s NOMINALGRADING - 94% < 150 µmHOT AIR TO MILL TEMP. -2950C(MAX); 2000C(MIN)AIR FLOW TO MILL - 30.2Kg/sSEAL AIR FLOW TO MILL - 0.5Kg/s at 150CRATED P.A. FAN POWER - 406kw at 42.7Kg/s FLOWMINIMUM AIR FLOW - 21Kg/sEROSION LIMIT - 33 Kg/sAIR-FUEL MIXTURE TEMP. -700C

MILL OPERATING WINDOWLIMITING VALUESMAX.COAL THROUGHPUT-12Kg/s at 94% 150 mSTABLITY 0.5*12=6 Kg/s COAL FLOWEXPLOSION LIMIT AT 5:1 AIR/FUEL RATIO

FAN POWER Wf +Wa =12 + 30.2 + 5 =42.7 Kg/s

FALL OUT - MIN. AIR FLOW -21 Kg/sEROSION LIMIT - 33 Kg/sFOR DRYING LIMITAT 2900C AIR TEMP. & 24% MOISTURE = (30.7-30.2)/30.2 =0.017Wf = AO*(TI-TO)*4.043*10-04/MC*(1+) = AO*(290-70)*4.043*10-04/(0.24*1.017) = 0.36*AOAO = 2.7 WfAIR/FUEL RATIO = 2.7: 1

AT 2000C AIR TEMP. & 14% MOISTUREAIR/FUEL RATIO = 4.6: 1

COSTS OF WATER• RAW WATER COSTS• PUMPING • PRETREATMENT• DEMINERALISATION• BOILER CHEMICALS• HEAT• PUMPING OUT WASTE WATER

SOURCES OF WATER LOSSES

• BOILER– BLOW DOWN– SOOT BLOWING INCLUDING DRAINAGE– SAMPLERS– PASSING DRAINS OR VENTS– ATOMISING STEAM FOR OIL BURNERS– DRAINS FROM OIL HEATERS– DRAIN DURING START UP– BOILER EMPTYING OPERATIONS

SOURCES OF WATER LOSSES

• FEED SYSTEM– PUMP GLANDS– DRAIN VESSEL OVER FLOW/DRAINS– START UP-DRAINAGE VENTING

• WATER TREATMENT PLANT– REGENERATION LOSSES– LEAKS IN PIPE LINES– PUMP GLANDS– DE SLUDGING

SOOT BLOWING LOSSSTEAM FLOW RATE = 4500 Kg/HrSTEAM FLOW/BLOWER = 4500*84/3600 = 105 KgENTHALPY OF STEAMAT 25Kg/cm2 PR.& 3500C = 745 Kcal/Kg

HEAT LOSS WITHSTEAM / BLOWER = 105*745 = 74025 KcalNUMBER OF BLOWERS = 56TOTAL HEAT LOSS FORONE BLOWING CYCLE = 74025*56 = 41,45,400 Kcal

WATER LOSS FOR ONE BLOWING CYCLE = 5.88 TONNES

STEAM LOSS FROM TUBE PUNCTURES

DIA.OF HOLEIN mm

STEAM LEAK RATE Kg/HrAT

7Kg/cm2 21Kg/cm2

1.5 6.5 153 25 60

4.5 57 1356 100 240

25 1615 3801

6 0 1 2 3 4 50102030405060708090

100

INCREASED D.M.WATER MAKE UP %

MO

NIT

OR

Y

LO

SS/D

AY

IN R

s.TH

OU

SAN

DS

LOSS DUE TO HIGH WATER MAKE UP

1% INCREASE IN MAKE UP WATER LEADS TO AN ANNUAL LOSS OF Rs 55.83 LAKHS FOR A210MW UNIT

EFFECT OF THERMAL INSULATION

TEMP.DIFF.BETWEENSURFACE & AMBIENT

0C

HEAT LOSSKcal/m2/Hr

40 600

100 1410

150 2170

225 5430

Conditions causing Poor Performance of Boiler

• Non-Optimum Reheat or Superheat steam temperatures.

• Higher than design economizer exit gas temperature or furnace exit gas temperature caused by poor combustion.

• Higher than design Re heater or Super heater De-Superheating spray flows.


• Fly ash Unburned Carbon or Loss on Ignition greater than 5% for Eastern Bituminous Coals or greater than 1% for Western or Lignite Coals.

• High Bottom Ash Loss on Ignition.• Non-Optimum utilization or distribution

of primary air, secondary air and over fire air, if applicable.


• Increased auxiliary horsepower consumption by coal pulverizers and fans

• Reductions in capacity factors due to excessive furnace or convection pass slagging or fouling.

• Excessive boiler setting air in-leakage.• Excessive air heater leakage. • Increased cycle losses with increased

sootblowing due to non-optimum combustion.


• Excessive pulverizer spillage on vertical spindle, roll and race and ball bearing type pulverizers. Reductions in capacity factors due to pulverizer or fan capacity limitations.

• Reductions in capacity factors due to Superheater or Reheater tube overheating and/or coal-ash corrosion.

Requirements For Achieving Optimum Conditions

• Furnace exit must be oxidizing, preferably 3% excess O2.

• Minimal air in-leakage between the furnace exit and economizer exit.

• Pulverizer fineness of >75% passing 200 Mesh and <0.3% remaining on 50 Mesh.

• Secondary (combustion) air balanced to within ±5% between burners


• Optimum windbox to furnace differential, typically 4" w.c. at full load.

• Optimum Pulverizer Primary Air to Fuel Ratio. In most cases, air to fuel ratio of 1.8 to 1 on roll and race and ball bearing type pulverizers, and 1.4 to 1 on attrition and ball tube pulverizers.


• Fuel balanced between each pulverizers fuel lines to within ±10% deviation from the mean.

• Pulverized coal line dirty airflow balanced between each pulverizers fuel lines within ±5%.

• Pulverized coal line clean air velocities balanced to ±2% of the mean.


• Coal line minimum velocities of 3300 Fpm.

• Burner mechanical tolerances with ±¼" (circular burners), burner buckets stroked and synchronized to within ±2° (tangentially fired).

• Primary airflow metered and controlled to ±3% accuracy.

BOILERHEAT INPUT LOSSES

USEFUL OUTPUT HEAT IN STEAM

EFFICIENCY = = HEAT INPUT) (HEATOUTPUT / *100

HEAT OUTPUT = HEAT INPUT - LOSSES

EFFICIENCY = =[(HEAT INPUT - LOSSES)/ HEAT INPUT]*100

= (1- LOSSES/ HEAT INPUT )*100

= 100-%LOSSES

HEAT INPUTHi=Qc*Hc*1000

WHEREHi - HEAT INPUT Kcal/Hr

Hc - CALORIFICVALUE OF FUEL Kcal/KgQC - COAL FLOW T/Hr

HEAT OUTPUTHo =[{(Qs*Hs)-(Qf*Hf)}+{Qr*(Hro-Hri)}]*100 Kcal/Hr

WHERE

Qs - MAIN STEAM FLOW T/HrHs - MAIN STEAM ENTHALPY Kcal/KgQf - FEED WATER FLOW T/HrHf - FEED WATER ENTHALPY Kcal/KgQr - R.H STEAM FLOW T/HrHro - H.R.H STEAM ENTHALPY Kcal/KgHri - C.R.H STEAM ENTHALPY Kcal/Kg

Ho - HEAT OUTPUT Kcal/Hr

BOILER EFFICIENCYCALCULATION DIRECT METHOD

Qs - MAIN STEAM FLOW T/Hr 600MAIN STEAM PRESSURE Kg/cm2 140MAIN STEAM TEMPERATURE 0C 540

Hs - MAIN STEAM ENTHALPY Kcal/Kg 819.97 Qr - R.H STEAM FLOW T/Hr 563

C.R.H. STEAM PRESSURE Kg/cm2 40C.R.H. STEAM TEMPERATURE 0C 330

Hri - C.R.H. STEAM ENTHALPY Kcal/Kg 727.18H.R.H. STEAM PRESSURE Kg/cm2 38

H.R.H. STEAM TEMPERATURE 0C 540Hro - H.R.H. STEAM ENTHALPY Kcal/Kg 845.15


Qf - FEED WATER FLOW T/Hr 610F.W. PRESSURE Kg/cm2 160

F.W TEMPERATURE 0C 540Hf - FEED WATER ENTHALPY Kcal/Kg 237.3Ho - HEAT OUTPUT Kcal/Hr 41,36,63,800

[{(Qs*Hs)-(Qf*Hf)}+{Qr*(Hro-Hri)}]*1000

QC - COAL FLOW T/Hr 110Hc - CALORIFICVALUE OF FUEL Kcal/Kg 4300Hi - HEAT INPUT Kcal/Hr 47,30,00,000

Qc*Hc*1000

EFFICIENCY = Ho/Hi =87.46 %


• ACCURATE MEASUREMENT OF FUEL QUANTITY,HEATING VALUE, FEEDWATER AND STEAM QUANTITIES AND OTHER PARAMETERS ARE REQUIRED

• ANY ERROR IN MEASUREMENT OF THE ABOVE WILL MAGNIFY THE END RESULT BY FOUR OR FIVE TIMES

BOILER EFFICIENCYCALCULATION INDIRECT/LOSSES METHOD

• MORE INFORMATIVE• INDIVIDUAL LOSSES ARE

ESTABLISHED FOR COMPARISON• MEASUREMENTS WILL BE SIMPLE• AS TOTAL LOSSES ARE ONLY 10 TO

20% OF HEAT INPUT ANY ERROR IN SAMPLING AND ANALYSIS AFFECT THEEND RESULT ONLY MARGINALLY

LOSSES CALCULATED• COMBUSTIBLE IN ASH/CARBON LOSS• DRY GAS LOSS• LOSS DUE TO MOISTURE IN FUEL• LOSS DUE TO HYDROGEN IN FUEL• LOSS DUE TO MOISTURE IN AIR• LOSS DUE TO SENSIBLE HEAT OF

BOTTOM ASH• LOSS DUE TO SENSIBLE HEAT OF FLY

ASH• MILL REJECTS LOSS• RADIATION LOSS

REQUIREMENTS FOR CALCULATING LOSSES

• FUEL ANALYSIS– PROXIMATE– ULTIMATE– CALORIFIC VALUE

• FLUE GAS ANALYSIS• ASH ANALYSIS FOR CARBON

– BOTTOM ASH – FLY ASH

• AMBIENT AIR TEMPERATURE• A.H.GAS OUTLET TEMPERATURE• RATE OF MILL REJECTS

COMBUSTIBLE IN ASH/CARBON LOSSASH IN COAL A%FLY ASH DISTRIBUTION DF%

BOTTOM ASH DISTRIBUTION DB%

FLY ASH COMBUSTIBLES CF%FLY ASH COMBUSTIBLES UF=A*DF*CF/{100*100*(100-CF)}

Kg/Kgf

BOTTOM ASHCOMBUSTIBLES CB%BOTTOM ASH COMBUSTIBLES UB=A*DB*CB/{100*100*(100-CB)}

Kg/KgfTOTAL COMBUSTIBLES U = ( UF+UB ) Kg/Kgf

CALORIFIC VALUE OF COMBUTIBLES = 8077.8 Kcal/KgGROSS CALORIFIC VALUE OF COAL = GCV Kcal/Kg

CARBON LOSS = U*8077.8*100/GCV %

40 851.3

0.004515

10.2

0.00680.0113

4267.00

2.14

DRY GAS LOSSCARBON IN COAL C%SULPHUR IN COAL S%

TOTAL COMBUSTIBLES Ukg/KgfSp. HEAT OF GAS Cp KJ/Kg mol 0C

F.G.TEMP. AT A.H. OUTLET Tg0CAMBIENT TEMP. Ta0C

CO2 IN F.G.AT A.H. OUTLET CO2%GROSS CALORIFIC VALUE OF COAL GCV Kcal/KgWEIGHT OF DRY GAS Wd {(C+S/2.67)-100U}/12CO2 Kgmol/Kgf

SENSIBLE HEAT OF DRY GAS SH KJ/Kg

=Wd*Cp*(Tg-Ta) KJ/Kg

DRY GAS LOSS {SH/ (4.186*GCV)}*100 %

42.520.42

0.011332.00

156.0028.0014.20

4267.00

0.244

999.42

5.60

LOSS DUE TO MOISTURE IN FUELMOISTURE IN FUEL M%

F.G.TEMP. AT A.H. OUTLET Tg 0C AMBIENT TEMP. Ta 0C GROSS CALORIFIC VALUE OF COAL GCV Kcal/KgSENSIBLE HEAT OF WATER VAPOUR SW KJ/Kg

SW=1.88*(Tg-25)+2442+4.2*(25-Ta) KJ/Kg

LOSS DUE TO MOISTURE=SW*M/(4.186*GCV) %

10.4156.00

28.004267.00

2675.68

1.56

LOSS DUE TO HYDROGEN IN FUEL

HYDROGEN IN FUEL H %

LOSS DUE TO H2 IN FUEL 9*H*SW/(4.186*GCV) %

3.2

4.31

LOSS DUE TO MOISTURE IN AIRCARBON IN FUEL C %

HYDROGEN IN FUEL H % SULPHUR IN FUEL S %

OXYGEN IN FUEL O %GROSS CALORIFIC VALUE OF COAL GCV Kcal/Kg

AMBIENT TEMPERATURE (DRY ) Ta 0 CAMBIENT TEMPERATURE (WET) TW 0 C

WEIGHT OF MOISTURE (FROM CHART) MWV Kg/Kg AIRSTOCHIOMETRIC AIR SA

SA= (2.66C+8H+S-O)/23.2 Kg/KgfO2 AT A.H. OUTLET O2 %

TOTAL AIR INCL.EXCESS AIR EA = 21/(21-O2) Kg/Kg SATOTAL MOISTURE IN AIR=MA=SA*EA* MWV Kg/KgfF.G.TEMP. AT A.H. OUTLET Tg 0C

LOSS DUE TO MOISTURE IN AIR

=MA*1.88*(Tg-Ta)*100/(4.186*GCV) %

42.523.2

0.426.5

426728

0.028

5.725.81.38

0.22156

0.3

LOSS DUE TO SENSIBLE HEAT OF BOTTOM ASH

TEMP.OF BOTTOM ASH ABOVE AMBIENT TB 0CSP. HEAT OF BOTTOM ASH CPB Kcal/Kg0C

ASH IN COAL A %BOTTOM ASH DISTRIBUTION DB%

GROSS CALORIFIC VALUE OF COAL GCV Kcal/Kg


=A*DB*CPB*TB*100/(100*100*GCV) %

7000.2540.0

15

4267

0.25


TEMPERATURE OF FLY ASH Tg 0 C SPECIFIC HEAT OF FLY ASH CPF Kcal/Kg 0C DISTRIBUTION OF FLY ASH DF % LOSS DUE TO SENSIBLE HEAT OF FLY ASH =A*DF*CPF*(Tg-Ta)*100/(100*100*GCV) %

1560.285

0.2

LOSS DUE TO MILL REJECTSRATE OF MILL REJECTS WRE Kg/Hr FLOAT OF MILL REJECTS F % CALORIFIC VALUE OF MILL REJECTS CVR Kcal/Kg CVR = F*GCV/100 DESIGN FUEL FLOW WFD Kg/Hr

GROSS C.V. OF DESIGN FUEL GCVD Kcal/KgACTUAL FUEL FLOW WFA Kg/Hr WFA = WFD* GCVD / GCV WEIGHT OF MILL REJECTS WR Kg/Kgf WR = WRE/WFA Kg/Kgf HEAT LOSS DUE TO MILL REJECTS

= WR*CVR*100/GCV %

505

213.35900004500

94910

0.0005

0.0025

RADIATION AND UNACCOUNTED LOSSES

PREDICTED AS 0.21 %

ABSTRACT OF BOILER LOSSESCARBON LOSS 2.14 %DRY GAS LOSS 5.60 % LOSS DUE TO MOISTURE 1.56 %LOSS DUE TO H2 IN FUEL 4.31 %LOSS DUE TO MOISTURE IN AIR 0.30 %LOSS DUE TO S.H OF BOTTOM ASH 0.25 %LOSS DUE TO S.H OF FLY ASH 0.20 %LOSS DUE TO MILL REJECTS 0.0025%RADIATION LOSSES 0.21 %TOTAL LOSSES 14.57 %

BOILER EFFICIENCY

EFFICIENCY = 100-TOTAL LOSSES = 100-14.57 = 85.43 %

QUICK ESTIMATION OF BOILER PERFORMANCE PARAMETERS

1.THEORITICAL DRY AIR REQUIREMENT

Th. Dry Air [ WTA ] Kg./Mkcal. Coal –1360 Oil - 1325 Gas –13002.QUALITY &COMPOSITION OF FUEL

Higher Heating Value Kcal/Kg =

[83.052*FC+57.992*VM-14.178*ASH-43.611*MOISTURE+797.746]

3.EXCESS AIR O2EAi ( % ) = _____________ *100 *K1

21 - O2

K1 =1.0 for coal, 0.9 for oil, 0.92 for gas


4.O2 0N DRY BASIS

O2 on Dry basis % = O2 on Wet basis / K2

K2 =0.9 for coal, 0.87 for oil, 0.81 for gas

5.AIR & GAS QUANTITY

Air Quantity WAI [ Kg./s ] = WTA*HHV*{1+(EAi / 100)}*1.02*WF*10-6

WF =Fuel Quantity Kg/s

Wet gas Quantity at any section can be calculated from excess air levelcalculated from the fluegas O2 % in that section.

Gas Quantity WGI [ Kg./s ] = WF *[WTA*HHV*{1+(EAi/100)}*1.02* 10-6 – (Ash/100) +1]


6.AIR LEAKAGE AT AIR HEATER

Air Heater leakage AHL % = (O2O - O2I ) / (21 - O2O )*K3 K3 = 91 for coal; 94 for oil; 95 for gas

7.AIR HEATER X RATIO

XR = (TGI - TGO -AHL ) / (TAO - TAI )

TGI Gas Temp. AH inlet; TGO Gas Temp. AH outlet;

TAO AirTemp. AH outlet; TAI Air Temp. AH inlet;

8.AIR BYPASSING AIR HEATER %OF AIR IN FURNACE

AHBY = [ 1 - {(XR*WGI ) / (K4*WAI)}]*100

K4 = 0.95 for coal; 0.93 for oil; 0.92 for gas

SPECIFIC OIL CONSUMPTION• NUMBER OF TRIPS / START UPS• START UP TIME

– BRINGING MILLS QUICKLY– SYSTEMATIC START UPS

• IGNITION SUPPORT– UNIT LOADS– LOW VOLATILE COALS– AIR DISTRIBUTION

• FLAME SENSING DEVICES

CAPACITY REDUCTION IN BOILER• FUEL INPUT

– LOW C.V. FUEL– MILLING CAPACITY

• GRINDING CAPACITY• DRYING CAPACITY• CARRYING CAPACITY• DRIVE CAPACITY

• DRAUGHT SYSTEM– ID FAN LIMITATIONS

• PRESSURE DROPS HIGH– A.H.CHOKING– CHIMNEY BACK PRESSUREHIGH

CAPACITY REDUCTION IN BOILER• HIGH VOLUME

– A.H.LEAKAGE– DUCT LEAKAGES– HIGH GAS TEMPERATURES

• WORN OUT IMPELLERS

• METAL TEMPERATURES HIGH– HIGH SPRAY REQUIREMENTS– FOULING OF SURFACES

Date post:	30-Oct-2014
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Efficiency and Performance of Power Plant

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