Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
UtilityUnitsinIndia‐ ASummary
Unit Rating, MW No. Contracted No. Commissioned200 24 4800 22 4400210 116 24360 114 23940250 58 14500 52 13000270 37 9990 15 4050500 85 42500 82 41000525 7 3675 4 2100600 21 12600 12 7200660 72 47520 42 27720700 3 2100 3 2100800 30 24000 9 7200
TOTAL 453 186045 355 132710
OTSC 660‐800MW BHEL 55 LMB 18
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Current Trends in Power Sector
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Trend in unit sizes in India & Cycle parameters
Unit Size SHO Pressure (kg/cm2(a))
SHO/RHO Temperature
(Deg.C)
Year of Introduction
60 / 70 MW 96 540 1965
110 / 120 MW 139 540/540 1966
200 / 210 MW 137 / 156 540/540 1972
250 MW 156 540/540 1991
500 MW 179179
540/540 540/568
19791985
600 MW 179 540/568 2008
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Trend in unit sizes & Cycle parameters
Unit Size SHO Pressure (kg/cm2(a)
SHO/RHO Temperature
(Deg.C)
Year of Introduction
SC Units660 MW 256 540/568 2005660 MW 256 568/596 2008700 MW 256 568/596 2010
800 MW 256 568/596 2008
USC UNITS
660 MW 279 603/603 2015
800 MW 281 603/603 2016AUSC 800MW 316 713/723 Under Devpt
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
New Boiler Designs
Boilers for higher steam parameters – 270 ata/600/600
degC
Boilers for new fuels- Imported coals , Blended coals
Separate OFA/AA ports for Nox reduction
Boilers with 100% DeNoX system
Boilers with 100% FGD system
ESPs to be designed for 30mg/Nm3
AUSC Designs-300bar/700/700 degCNew Products
Sonic Tube Leak Detection System
Smart soot blowing system
Boilers suitable for Flexible operation
New Technologies & Products
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Sr. No. TPPs (Units) Installation Period
NOx Emission Requirement Deadline
1 Before Dec. 31, 2003 600 mg/Nm3 Within 2 year from notification
2 Between Jan 01, 2004 to Dec 31, 2016 300 mg/Nm3 Within 2 year from
notification
3 From Jan 01, 2017 100 mg/Nm3 Must meet upon completion
Latest NOx Emission LevelsAs per Ministry of Environment, Forest and Climate Change (MOEF & CC) Gazette dtd. 07.12.15, Latest NOx emission limits for Thermal Power Plants are:
This limit can only be achieved through Selective Catalytic Reduction (SCR) System.
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
CPCB Guidelines for Power Plants
Power Generation Capacity Stack Height/Limit in Meters
500 MW and above 275200 MW/210 MW and above to less than 500 MW
220
Less than 200 MW/210 MW H = 14 x (Q)0.3, where Q is emission rate of SO2 in kg/hr. and H Stack height in metres
MOEF approves EC based on space provision of FGD in overall plant layout of ThermalPower Units:
1. 500 MW and above capacity
2. Stations with 1500 MW+ capacity
3. Plants of smaller capacity in Sensitive Areas
Old SO2 Emission Standards
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
New SO2 Emission Standards
TPPs (Units) Installed Standards
Before 31 Dec 2003600 mg/Nm3 Units < 500 MW
200 mg/Nm3 Units ≥ 500 MW
After 2003 butBefore 31 Dec 2016
600 mg/Nm3 Units < 500 MW
200 mg/Nm3 Units ≥ 500 MW
After 1 Jan 2017 100 mg/Nm3 All Units
New Guidelines* for Thermal Power Plants
*As per MOEFCC Gazette Notification dated 7th December 2015
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Design Aspects of AirPreheaters
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
AirheatersinBoilers
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
HeatBalanceforSteamProcess
Steam Process
Energy InputFeed Water
Energy InputAir & Fuel
EnergyLossFlueGas
EnergyLossBlow DownWater
EnergyLossDue to PipingFriction LossEquipment etc.
Steam @ PressureP1
P1
Usefull EnergyOutput
Energy Output = Energy Input - Losses
Steam Process
Energy InputFeed Water
Energy InputAir & Fuel
EnergyLossFlueGas
EnergyLossBlow DownWater
EnergyLossDue to PipingFriction LossEquipment etc.
Steam @ PressureP1
P1
Useful EnergyOutput
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boiler efficiency = Heat Output / Heat Input
Heat Output =Heat Input –Losses +Credits
Boiler efficiency =100‐%Losses +%Credits
BoilerEfficiency
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boiler Heat Balnce
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
boiler T
482.8 Mkcal/hr 420 Mkcal/hr 180.6 Mkcal/hr 172 Mkcal/hr
200 MW120.7 t/h4000 kcal/kg
87.0 %
37.4%
35.6 %
43.0 %2000 kcal/kwhr
2299 kcal/kwhr
2414 kcal/kwhr
auxpower 10 MW
PLANT EFFICIENCY & HEAT RATE
210
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Airheaters have been successfully employed torecover heat from flue gas at lower temperaturelevels than is possible with economizer.
The heat rejected to chimney can be reduced to agreat extent thus increasing the efficiency of boiler
For every 20° C drop in flue gas exit temperature,the boiler efficiency increases by about 1%.
AirheatersinBoilers
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
In addition to increase in boiler efficiency, the otheradvantages are
Stability of combustion by use of hot air
Burning poor quality fuel efficiently
Intensified Combustion permits faster load variation
In case of PC fired boilers,hot air can be used for dryingthe coal and for transporting the pulversied coal toburners
Being a nonpressure part, it does not warrant shutdownof units due to corrosion of heat transfer surface
Airheaters inBoilers
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Why Boiler Efficiency is important ?
Utilities are interested in generating power in the mosteconomical way .This is possible if they address thefollowing aspects in power plant operation.
‐Reduced/Optimised Fuel Consumption
‐Reductioninpowerconsumptionofpowerplantauxiliaries
Airheaters inBoilers
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
MajorLossesinBoiler
• Dry Gas Loss =0.24 Wg ( tg - ta ) • Fuel Moisture Loss=Wc ( 595.4 + 0.46 tg ‐ tf ) • Fuel Hydrogen Loss= Wh ( 595.4 + 0.46 tg ‐ ta ) • Air Moisture Loss=0.46 Wa ( tg ‐ ta ) • Unburnt Carbon Loss• Radiation Loss• Sensible Heat Loss in Ash• Other Minor Losses
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boiler Efficiency can be improved in the following waysin case of Steam generators
‐Reduced Exit Gas Temp. at AH outlet
‐ReductioninExcessair
‐ReductioninCarbonloss
Airheaters inBoilers
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
In 1970s Indian Bituminous coal fired boilers weredesigned for APH outlet gas temp of 145‐150°C.
In 1980s they were designed for APH outlet gastemp of 135‐140°C.
With good operating experience of 200/210MW/500MW boilers, utilities stared adopting from1990 onwards APH outlet gas temp of 125°C toimprove the boiler efficiency
For every 20° C drop in flue gas exit temp,the boilerefficiency increases by about 1%.
Airheaters inBoilers
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Tender Conditions for Efficiency Calculation Values and RemarksExcess air at economizer outlet at 105% & 100% TMCR load 20 % (minimum)
Corrected flue gas temperature at air preheater outlet (at 105% & 100% TMCR)
125 0 C or as predicted by the Bidder whichever is higher
Unburnt fuel at all efficiency load at 105% & 100% TMCR load 1 % (minimum)
Ambient air condition:27 degree Celsius temperature (Dry bulb) and 60% relative humidity. The reference air temperature for the Steam Generator efficiency guarantee/ testing shall be taken as the temperature of air (i.e. 27 degree Celsius) entering APH.
Dry air heat credit that is air temperature rise across PA& FD fan shall not be considered as per this clause
The guaranteed steam generator efficiency shall be without any heat credit.
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Project For every 0.1% shortfall Year
APPDCL/Krishnapatnam2x800MW 6.20 Crores 2008
NTPC/Nabinagar 3x660MW 3.36 Crores 2012
NTPC/Tanda 2x660MW 8.48 Crores 2012
NUPPL/Ghatampur3x660MW 6.27 Crores 2016
EvaluationFactorsforBoilerEfficiency
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Project For every 1 KW increase Year
APPDCL/Krishnapatnam2x800MW 1.70 Lakhs 2008
NTPC/Nabinagar 3x660MW0.76 Lakhs
2012
NTPC/Tanda 2x660MW1.66 Lakhs
2012
NUPPL/Ghatampur3x660MW
1.94 Lakhs2016
EvaluationFactorsforAuxiliaryPower
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
GHATAMPUR660PerformanceGuaranteeLoadingSl. No. Performance Loading
1 Boiler Efficiency @ 100% TMCR (Quoted %)
58.30(88.50)
33.85(88.63)
-(88.81)
65.82(88.46)
2 BMCR Steam Flow(Quoted TPH)
-(2100.0)
-(2100.0)
-(2100.0)
-(2100.0)
3Total Power Consumptionfor all boilers(Quoted KW/Boiler)
53.76(14,307)
75.30(14,678)
-(13,381)
7.84(13,516)
4 Desuperheating spray water Flow (Quoted TPH)
-(0.0)
-(0.0)
-(0.0)
-(0.0)
Total Technical Loading (in INR Cr) 112 109 - 74
(INRCr)
Tender opened on 11-05-2016
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
2x 660 MW NTPC TANDA SG PACKAGE - TENDER OPENING TECHNICAL GUARANTEES (TENDER OPENED ON 14.12.12)EXCHANGE
RATE 1 USD 1 EURO 1 JAP YEN 1 GBP55.02 71.72 0.6571 88.38
SL.NO DESCRIPTION UNIT BHEL L&T DOOSAN THERMAX BASE
AS READ OUT
1 SG EFFICIENCY @ 105% TMCR PERCENTAGE 85.36% 85.40% 85.32% 85.28% 85.40%
2 SG EFFICIENCY @ 100% TMCR PERCENTAGE 85.40% 85.38% 85.31% 85.27% 85.40%
3 FEED WATER PRESSURE AT ECONOMISER INLET KG/CM2 291.00 289.00 293.70 286.00 286.00
4 REHEATER ATTEMPERATION SPRAY WATER FLOW TONNE/HR 0.00 0.00 0.00 0.00 0.00
5 AUXILIARY POWER CONSUMPTION KW 13046.00 12330.00 12372.00 12960.00 12330.00
LOADING IN RS CRS EVALUATION FACTOR IN USD
1 SG EFFICIENCY @ 105% TMCR 404,520 1.78 0.00 3.56 5.34
2 SG EFFICIENCY @ 100% TMCR 1,541,027 0.00 3.39 15.26 22.04
3 FEED WATER PRESSURE AT ECONOMISER INLET 107,227 5.90 3.54 9.09 0.00
4 REHEATER ATTEMPERATION SPRAY WATER FLOW 173,212 0.00 0.00 0.00 0.00
5 AUXILIARY POWER CONSUMPTION 3,026 23.84 0.00 1.40 20.98
Net Technical Loading for the Project crs. 31.52 6.93 29.31 48.36
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Design Aspects of Boilers&
Auxiliaries
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
BasicDataForBoilerDesign
BoilerParamters
FuelData
SiteConditions
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
SHO Flow,Pressure,Temp
RH Flow,Pressure,Temp at RHI & RHO
FeedWater Temp at Economiser Inlet
BoilerParameters
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
BoilerEfficiency
This is influenced by coal properties,ambient temp. & relative humidity, Boilerexit gas temp.
Determines the heat input to the boiler
Forms the basis for air & gas weightcalculations, quantity of coal fired
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
BoilerParametersdefineheatdutyoftheboiler
Heatfired,Mkcal/h =SH+RHheatduty÷ Boilerefficiency
Fuelqtyt/h=HeatFired÷ HHV
Airquantity=kg.ofair/kg.offuelxQty.ofcoalfired
Gasquantity =Fuel+air‐ ash
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
NormallyspecifiedCoalPropertiesProximateAnalysis
UltimateAnalysis
CalorificValue
AshConstituents
AshFusionTemperatures
HardGroveIndex
YGPIndex
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
CoalAnalysis‐TypicalIndianCoalsProximateAnalysis
Unit Design Coal
Worst Coal Best Coal
Fixed carbon % 22.0 20.0 25.0
Volatile matter % 21.0 19.5 23.0
Moisture % 15.0 16.5 14.0
Ash % 42.0 44.0 38.0
Total % 100.0 100.0 100.0
HHV Kcal/kg 3300 3000 3600
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
CoalAnalysis‐TypicalIndianCoalsUltimate Analysis
Unit Design Coal Worst Coal Best Coal
Carbon % 33.73 30.90 38.26
Hydrogen % 2.35 2.09 2.49
Oxygen(difference) % 5.48 5.00 5.96
sulphur % 0.37 0.36 0.38
Nitrogen % 0.75 0.85 0.57
Moisture % 15.00 16.50 14.00
Ash % 42.00 44.00 38.00
HARD GROVE INDEX 55 54 56
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
AshCharacteristics‐TypicalIndianCoalsDesign Worst Best
Initial Deformation Temp. Deg.C 1150 1100 1200
Hemispherical Temp. Deg.C 1400 1400 1400
Fusion Temp. Deg.C 1400 1400 1400
AshAnalysis:A – SiO2 % 60.08 61.40 60.30A – Al2O3 % 29.50 28.50 29.80B – Fe2O3 % 4.10 3.90 4.70B – CaO % 1.70 1.93 1.57B – MgO % 0.75 0.92 0.59B – Na2O + K2O % 0.65 0.85 0.53A – TiO2 % 1.70 1.60 1.80
- P2O5 % 0.80 1.10 0.13- SO3 % 0.27 0.31 0.25
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
ProblemsAssociatedWithIndianCoals
InconsistentCoalProperties
PresenceOfExtraneousMattersInCoal
HighQuantumOfAshWithHighPercentageOfQuartz
HighlyAbrasiveNatureOfCoalAsh
DueToLowSulphurContent‐ ExtremelyHighElectricalResistivityOfAsh
LowHeatingValueOfTheCoal
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Coals vary widely in their properties‐mine to mine and seam to seam
Coal firing therefore presents a varyingset of demands before the boiler designer
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
AshAnalysis
Providesindicatorsto
Slagging/fouling/depositionpotential
Erosionpotential
Corrosionpotential
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boilerdesign
CoalPropertiesinfluence
Thesizingoftheboilerheattransfersurfaces
Thefluegasvelocities
Thesizeofboilerauxiliaries
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Specifyingwiderangeofcoalpropertieshavethefollowingimplications:
If pulverising/firing equipment is oversized, turndown is limited and auxiliary power consumptionwill go up.
If furnace is oversized, attaining rated SH, RH outlettemperature becomes difficult.
If pulverisers and airheaters are oversized to handleoccasionally high moisture coals, there will beexcessive tempering air and higher gas outlettemperature when handling normal moisture coals.
EffectOfFuelOnBoilerDesign
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
BoilerauxiliariesDesignCriteria
Airheaters shall be sized for optimum gas temperaturewhile firing design coal for better boiler efficiency andsufficient hot air temperature shall be available for milldrying while firing highmoisture coal.
Sufficient margins shall be provided on volume and headwhile selecting FD/ID/PA fans so that no capacitylimitation will be experienced.
ESP to be sized to meet pollution norms with higher SCA.
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Indian Utilities often tend to specify wide range of coalproperties HHV from 3000 to 4500 kcal/kg,%M from 10%to 20% and % ash from 25% to 45% thinking that thiswill prevent fuel related problems.
This results in larger size mills and more no of mills andbigger size APH.
If pulverisers and airheaters are oversized to handleoccasionally high moisture coals, there will be excessivetempering air and higher gas outlet temperature whenhandling normal moisture coals .
FactorsaffectingAPHDesignspecifictoIndianCoals
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
HowmuchheatcanbeextractedbyAirPre‐Heaters
It is well known Economizer Pick‐up is limited by saturationtemperature
Air Pre‐Heaters can extract any amount of heat– Points to be remembered
• Proper sizing during design stage• The layout constraint• Cost consideration• Low temperature corrosion – Less applicable to Indian coal
fired boilers
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
SizingofAPHSizing of APH during boiler design stage is very important
– Maximum possible heat recovery to be targeted during design
– A good practice to keep space of at least one basket addition in future
– Many units suffer for want of space for additional recovery
– Present day fuel changes due to non availability of design fuel results in
high APH inlet temperature
• Fouling characteristic of fuel
• LRSB operation frequency
• Limitation in economizer absorption
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Gastemperatureenteringairheater
Gasquantityenteringairheater
Airquantityleavingairheater
Desiredpressuredroponair/gasside
Gastemperatureleavingairheater
DataforAirheaterSelection
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Recuperative(Tubularairheater)
Regenerative(Ljungstrom/Rothemuhle)
TypesofAirheaters
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
ChoiceofAirheaters
ForsmallcapacityofIndustrialboilers,generallytubularairheatersareusedduetocosteconomicsandlayoutconsiderations
Astheboilersizeincreases,heattransferarearequiredintheairheateralsoincreases.Ifthepressuredroponairandgassideistobekeptminimumtolimitthefancapacityandoperationcost,RAPHarebestsuited.
Forhighcapacityutilityboilers,RAPHsareusedduetocompactness,capitalcost&operatingcost
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
TubularAirPre‐heater
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Trisector Airheater Arrangement
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
1.PRIMARY AIR IN
1
2
34
5
6
2.SECONDARY AIR IN3.PRIMARY AIR OUT4.SECONDARY AIR OUT
5.GAS IN
6.GAS OUT
404
RegenerativeTrisectorAirheater
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
AIR
INAIR
OUT
OUT
GAS
GAS
IN
Regenerative Bisector Airheater
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boiler Technology Trends& Design Aspects of APH
GEECO International Seminar 18th July2019
Rotary airheaterAssembly of heating element
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
RAPHTypesandArrangementsMajorityofRAPHsoperationinIndiaareofTri‐sectordesign(Ljungstromtype)inPCfired210/250/600MWboilers.
Incaseof500MW,majorityoftheRAPHsoperationinIndiaareofBisectordesigneventhoughthereareunitswithTri‐sectorAHsalso.Incaseof660/700/800MW,thereisamixofboth.ButthetrendnowinsupercriticalboilersistowardsTri‐sectorRAPH
TheseRAPHsaredesignedwithrotordiametersrangingfrom2mto20m(7’to67’)Theductsandheatingsurfacearrangementsarepositionedforverticalflow.
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
210MWBoiler– TypicalArrangement
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
500MWBoiler– TypicalArrangement
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
RefListofRAPH–SubcriticalCoalFired
Project Typical Size Year
200/210 MW27VI7227VI80
Tri‐sector
250 MW 27.5VI 2000 Tri‐sector
500 MW30VI 200027.5VI2000
Bisector SecondaryBisector Primary
500 MW 31.5VI2000 Tri‐sector
600 MW 32.5VI2000 Tri‐sector
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
NTPC/BARH2x660MW
This image cannot currently be displayed.
GeneralArrangementofSteamGenerator– Plan
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
APPDCL/Krishnapatnam2x800MW
This image cannot currently be displayed.
Design Aspects of Airheater & Technology Trends
GEECO International Seminar 18th July2019
Plan View of Boiler Arrangement
OTSC Boilers for Cleaner EnvironmentGEECO International Seminar 18th July2019
Customer Prayagraj Power Generation Company Limited
Project PRAYAGRAJ STPP, PHASE‐I, 3x660 MW, BARA
Parameters at SHO / RHO
Steam Flow 2095.4/1706.9 t/h.
Pressure 255/54.33 kg/cm2 (g)
Temperature 568 / 596 oC
Fuel Coal
Major Auxiliaries
Mill 7 Nos. Bowl Mill
Airheater 2 Nos. Tri‐Sector AHs
FD Fan 2 Nos. Axial Reaction
PA Fan 2 Nos. Axial Reaction
ID Fan 2 Nos. Axial Reaction
Dust Collector Customer Scope
PPGCL/PRAYAGRAJSTPP,3x660MW,BARA
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
RefListofRAPH–SupercriticalCoalFired
Typical Size Year
660 MW33VI8033.5VI80
Trisector
660 MW31.5VI 70(82)28.5VI58(70)
Bisector SecondaryBisector Primary
700 MW 34VI88 Tri‐sector800 MW 34VI76(88) Tri‐sector
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
SCHEME OF AIR & GAS DUCTS / CIRCUITS
ColdPASystem
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
BisectorPrimaryandSecondarySystem
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
HotPrimaryAirSystem
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Indian Coal Imported CoalUnitSize MW 250 250Moisture % 10 8Ash % 40 8HHV Kcal/kg 3700 6230AirTempEnteringPri/Sec
Deg C 35/29 35/33
GasTempEntering Deg C 353 337
GasTempLeaving Deg C 134 136
RAPHSIZE 2x27.5VI2000(T)
2x27VI2000(T)
NoofMills 6nos 883 5nos 803
EffectofFuelonAirheaterDesign
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
IndianCoal IndianCoalUnitSize MW 660 660Moisture % 19 10Ash % 32 31HHV Kcal/kg 3250 4200
AirTempEnteringPri/Sec
Deg C 35/30 33/28
GasTempEntering Deg C 342 337GasTempLeaving Deg C 125 126
RAPHSIZE 2x33.5VI2000(T)
2x33VI1600(1900)(T)
NoofMills8nos 1103 7nos 1103
EffectofFuelonAirheaterDesign
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Airheater Heat Balance
Heat Drop by Gas = Heat Gained by air
Wg x Cpg x (Tgin – Tgout) = Wair x Cpairout x (Tairout – Tairin)
Heat Transfer across Airheater Q= U A (LMTD) X F
Heat Capacity Ratio = Wg x Cpg / Wair x Cpairout (Also known as X ratio)
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
FactorsAffectingAPHPerformance
EnteringAir/GasTemperature
GasFlow
HeatCapacityRatio(HCR)(XRatio)
PressureDrop
AirheaterLeakage
Ashquantity
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Factors Affecting APH Thermal PerformanceEntering Air Temp If the entering air temp increase by 10°C ,the exit
gas temp will increase by 10xGas side effy/100 Entering Gas Temp If the entering gas temp increase by 10°C ,the exit gas temp
will increase by 10x(1-Gas side effy/100)
Pressure Drop Across Air Heater The air and gas side pressure drops will change
approximately in proportion to the square of air and gas weights
Air Heater Leakage Pressure Differntials, Seal settings affects leakage
Boiler Technology Trends& Design Aspects of APH
GEECO Inernational Seminar 18th July2019
Factors Affecting APH Thermal PerformanceX ratio of APH Mass flow of air x Avg Sp. heat of air / Mass flow of
FG x Avg Sp. heat of FG A decrease in the X-ratio results in an increase in
the exit-gas temperature• A 10 to 12% change in this ratio may alter exit-gas
temperature by as much as 15 to 20°C.
Factors that affect the X-ratio• Tempering air• Overall boiler-system infiltration• Air pre-heater bypass for cold-end protection.
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Effect of Ash on Airheater Performance in a 500MW (Typical)
Qty of Ash at AH outlet =350000x.4x.8=112,000kg/h
Heat in the ash at Airheater outlet = 112000x.20x125= 2.8 x106 kcal/h
ΔT in the gas at Airheater outlet= 2.8 x 106 /2200 x103 x.25
=5°C
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Air pre-heater leakage Higher the leakage higher the loss
Low moisture coal than design Need higher quantity of tempering air This bypasses the APH – Increase exit gas temperature
High excess air Blockage in air pre-heater Corrosion of APH elements Soot blowing frequency High ambient temperature Boiler operation with high overload Slagging & fouling of boiler heat transfer surface Low feed water temperature at boiler inlet
Factors Affecting APH Thermal Performance
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boiler designed for Imported Coal
HHV 6230 kcal/kg
Moisture 8 %
Ash 8 %
HGI‐55
Performance Guarantee furnished based on Design Coal
Coal now Fired
HHV 5152 kcal/kg
Moisture 24.5 %
Ash 2 % ,HGI‐ 41
Major Difference
HHV is less by 20%
Moisture High
HGI Low
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
This high moisture coal is imported from Indonesia
It is possible to achieve the rated output
Due to high moisture and Low HGI all the 5 mills have to be inservice
Due to high volatile matter, MOT is kept low 60‐65Deg C
Airheater pressure drops are very high
PerformanceFeedBack(ImportedCoal)
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
AIRHEATER
2 Numbers Tri sector Regenerative 27.0 VI(T) 80
Primary sector opening 50 Deg.
Airheater performance @ 250 MW
Description Predicted for DC Actual
Total Primary Air, t/h Thro’ AH Tempering Air
19553142
227~ 160~ 67
Pressure drop PA side , mmwc
17 173/208
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
SCRSYSTEMS
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Typical 800MW Sliding Pressure Supercritical with Selective Catalytic Reduction system
Unit Mwe: 800
Max. Continuous Rating: 2415 t/h
SH Outlet Press: 250 bar
SH Outlet Temp: 569°C
RH Outlet Temp: 569°C
Fuel: Australian Bituminous
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
NOxReduction/SCR
Boiler
SCR
2 次空気2 次空気
Low Nox Combustion &In Furnace NOx Reduction
Harmful NO is decomposed into harmless N2 and H2O by catalytic action
4NO + 4NH3 + O2 → 4N2 + 6H2O
catalytic action
SCR
Total NOx Reduction TechnologyCombustion Control + SCR
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
1)ECO bypass line ObjectTo Keep the main Flue gas
temperature above MOT.
2) Key point - Sufficient Gas mixing (Temp & NOx);
Main flue gas + ECO bypass gas- After Gas mixing ,Gas rectification for
AIG (Ammonia injection grid)
Boiler
ECO SCR
ECObypassLine
Minimum Continuous Operating Temperature (MOT):
Temperature at which the SCR can be operated in which no ABS (Ammonia Bisulfate) will
accumulate on the catalyst. Continuous operation of the SCR
must be above MOT.Catalyst
Micro-pore
Active site
Plugging with ABS
Fig: Catalyst detail
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
FGDSYSTEMS
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
FGDSystemsSO2 being acidic in nature, needs removal by a reaction using suitable alkaline substance like limestone, quicklime, hydrated lime or sea water
Three types of FGD Systems Available
– Dry/Semi Dry CaO + H2O Ca (OH)2H2O + SO2 + Ca(OH)2 CaSO3 + 2H2O
– Sea Water BasedSO2 + H2O + ½ O2 SO4
2- + 2H+HCO3- + H+ CO2 + H2O
– Wet Limestone BasedCaCO3 + 2H2O + SO2 + ½O2 CaSO4.2H2O + CO2
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Wet Limestone (WLS) FGD System SchematicComponents of FGDSystem
Supporting Systems
• Absorber•Limestone Handling system•Limestone slurry preparation
system•Gypsum Dewatering system•Gypsum Handling system•Boost-up Fan•Gas-Gas Heater•Process Water system•Oxidation Air Blower•Pumps•Tanks / Sumps
•Ducting• Piping• Capacity Enhancement ofEffluent treatment plant
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
Connecting FGD system to Main Plant (Typical Arrangement)
Clean GasFrom FGD
Flue Gas from ESP
Bypass arrangement
Electrostatic Precipitator
Stack
Sample Scheme-referenceFGD
System
Boiler Technology Trends & Design Aspects of APH
GEECO International Seminar 18th July 2019
R.Kumar
Consultant/Boilers & Boiler Systems
Mail Id:[email protected]