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



Current Trends in Power Sector



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



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



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



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.





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



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



Design Aspects of AirPreheaters



AirheatersinBoilers



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 efficiency = Heat Output / Heat Input

Heat Output =Heat Input –Losses +Credits

Boiler efficiency =100‐%Losses +%Credits

BoilerEfficiency



Boiler Heat Balnce



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



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



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



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




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 Efficiency can be improved in the following waysin case of Steam generators

‐Reduced Exit Gas Temp. at AH outlet

‐ReductioninExcessair

‐ReductioninCarbonloss




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%.




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.



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



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



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



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



Design Aspects of Boilers&

Auxiliaries



BasicDataForBoilerDesign

BoilerParamters

FuelData

SiteConditions



SHO Flow,Pressure,Temp

RH Flow,Pressure,Temp at RHI & RHO

FeedWater Temp at Economiser Inlet

BoilerParameters



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



BoilerParametersdefineheatdutyoftheboiler

Heatfired,Mkcal/h =SH+RHheatduty÷ Boilerefficiency

Fuelqtyt/h=HeatFired÷ HHV

Airquantity=kg.ofair/kg.offuelxQty.ofcoalfired

Gasquantity =Fuel+air‐ ash



NormallyspecifiedCoalPropertiesProximateAnalysis

UltimateAnalysis

CalorificValue

AshConstituents

AshFusionTemperatures

HardGroveIndex

YGPIndex



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



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



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



ProblemsAssociatedWithIndianCoals

InconsistentCoalProperties

PresenceOfExtraneousMattersInCoal

HighQuantumOfAshWithHighPercentageOfQuartz

HighlyAbrasiveNatureOfCoalAsh

DueToLowSulphurContent‐ ExtremelyHighElectricalResistivityOfAsh

LowHeatingValueOfTheCoal



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



AshAnalysis

Providesindicatorsto

Slagging/fouling/depositionpotential

Erosionpotential

Corrosionpotential



Boilerdesign

CoalPropertiesinfluence

Thesizingoftheboilerheattransfersurfaces

Thefluegasvelocities

Thesizeofboilerauxiliaries



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



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.



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



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



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



Gastemperatureenteringairheater

Gasquantityenteringairheater

Airquantityleavingairheater

Desiredpressuredroponair/gasside

Gastemperatureleavingairheater

DataforAirheaterSelection



Recuperative(Tubularairheater)

Regenerative(Ljungstrom/Rothemuhle)

TypesofAirheaters



ChoiceofAirheaters

ForsmallcapacityofIndustrialboilers,generallytubularairheatersareusedduetocosteconomicsandlayoutconsiderations

Astheboilersizeincreases,heattransferarearequiredintheairheateralsoincreases.Ifthepressuredroponairandgassideistobekeptminimumtolimitthefancapacityandoperationcost,RAPHarebestsuited.

Forhighcapacityutilityboilers,RAPHsareusedduetocompactness,capitalcost&operatingcost



TubularAirPre‐heater



Trisector Airheater Arrangement



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



AIR

INAIR

OUT

OUT

GAS

GAS

IN

Regenerative Bisector Airheater



Boiler Technology Trends& Design Aspects of APH

GEECO International Seminar 18th July2019

Rotary airheaterAssembly of heating element



RAPHTypesandArrangementsMajorityofRAPHsoperationinIndiaareofTri‐sectordesign(Ljungstromtype)inPCfired210/250/600MWboilers.

Incaseof500MW,majorityoftheRAPHsoperationinIndiaareofBisectordesigneventhoughthereareunitswithTri‐sectorAHsalso.Incaseof660/700/800MW,thereisamixofboth.ButthetrendnowinsupercriticalboilersistowardsTri‐sectorRAPH

TheseRAPHsaredesignedwithrotordiametersrangingfrom2mto20m(7’to67’)Theductsandheatingsurfacearrangementsarepositionedforverticalflow.



210MWBoiler– TypicalArrangement



500MWBoiler– TypicalArrangement



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



NTPC/BARH2x660MW

This image cannot currently be displayed.

GeneralArrangementofSteamGenerator– Plan



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



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



SCHEME OF AIR & GAS DUCTS / CIRCUITS

ColdPASystem



BisectorPrimaryandSecondarySystem



HotPrimaryAirSystem



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



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



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)



FactorsAffectingAPHPerformance

EnteringAir/GasTemperature

GasFlow

HeatCapacityRatio(HCR)(XRatio)

PressureDrop

AirheaterLeakage

Ashquantity



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.



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



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 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



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)



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



SCRSYSTEMS



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





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



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



FGDSYSTEMS



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



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



Connecting FGD system to Main Plant (Typical Arrangement)

Clean GasFrom FGD

Flue Gas from ESP

Bypass arrangement

Electrostatic Precipitator

Stack

Sample Scheme-referenceFGD

System



R.Kumar

Consultant/Boilers & Boiler Systems

Mail Id:[email protected]

Documents

GEECO International Seminar 18th July 2019