Efficiency and Performance of Power Plant
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Transcript of 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
DECISIONS AFFECTING PLANT OPTIMISATION
SHORTTERM -DECISIONS UNDER CONTINUOUS CONTROL
– OPERATING PARAMETERS Viz..STEAM PRESSURE,TEMPERATURE,AIR FLOW ETC.
– LOADING OF AUXILLIARIES
DECISIONS AFFECTING PLANT OPTIMISATION
MEDIUMTERM -DECISIONS MADE AT INTERVALS OF HOURS OR DAYS
– SOOT BLOWING
– CONDENSER CLEANING
– MILL CLASSIFIER VANES ADJUSTMENTS
DECISIONS AFFECTING PLANT OPTIMISATION
• 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.
CALCULATION OF DRY FLUE GAS WEIGHT
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
CALCULATION OF DRY FLUE GAS WEIGHT
CALCULATION OF DRY FLUE GAS WEIGHT
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
CALCULATION OF DRY FLUE GAS WEIGHT
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
PROCEDURE FOR CHECKING COAL FINENESS
• 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
PROCEDURE FOR CHECKING COAL FINENESS
• 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.
Conditions causing Poor Performance of Boiler
• 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.
Conditions causing Poor Performance of Boiler
• 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.
Conditions causing Poor Performance of Boiler
• 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
Requirements For Achieving Optimum Conditions
• 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.
Requirements For Achieving Optimum Conditions
• 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.
Requirements For Achieving Optimum Conditions
• 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
BOILER EFFICIENCYCALCULATION DIRECT METHOD
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 %
BOILER EFFICIENCYCALCULATION DIRECT METHOD
• 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
LOSS DUE TO SENSIBLE HEAT OF BOTTOM ASH
=A*DB*CPB*TB*100/(100*100*GCV) %
7000.2540.0
15
4267
0.25
LOSS DUE TO SENSIBLE HEAT OF BOTTOM ASH
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
QUICK ESTIMATION OF BOILER PERFORMANCE PARAMETERS
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]
QUICK ESTIMATION OF BOILER PERFORMANCE PARAMETERS
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