Onlineefficiencyanddiagnostics

ofacoalfiredBoiler

Name: Kota. Bhanu Prakash, B Tech (Mech), MBA(Fin) , MTech (IIT Delhi)

Computational Fluid Dynamics, Multiphase dynamics Heat exchangers, Turbo machinery Steam generators design, Heat transfer and Radiation 500MW Boiler Computational fluid Dynamics

Job profile: 1988, :` Hindustan Aeronautics limited (design of Aero engines) 1989 -2010: NTPC

Commissioning of coal fired units of capacities 210 MW,500MW, Performance testing of the boilers, turbines and associated auxiliaries, Environment Management systems

2010 : Steag Energy Services

System Technologies, Engineering thermal power plants, O&M Currently: Chief Executive Officer for a Steag O&M Company

Seite 3

STEAG SteagistheGermany'sfifthlargestproducerofelectricity,

Operates15powerplantsat11sitesthroughoutGermany,

Installedgeneratingcapacityofabout8,600MW;eightofthesepowerplantsusehardcoalasprimaryenergysource.

SteagO&MCompanyisaJVof

SteagEnergyServices,India

And

HindujaEnergyIndia

SOMCcurrentlyoperatesthe2X520MWcoalfiredunitsinVishakapatnam

Powerplantefficiency

750MW–Walsum10PowerPlant

EfficiencyandHeatrate

Efficiency: [Electricaloutput/Fuelinput]A500MWcoalfiredpowerplantconsumes300T/hrofcoal(CV4000Kcal/Kg)willhaveanefficiency[500X10^6(W]X3600S)/[300X10^3(Kg)*4000*4180J)]=35.85%Inpowerplantterminology,UnitHeatrateisdefinedastheratioofTurbineheatrateandBoilerefficiency.

SubcriticalandSupercritical

•  Subcriticalsteamcycles(Pressure<criticalpressure225bar)haveunitheat

ratesintheorderof2400Kcal/Kwh

•  Highertheheatrate,pooreristhecycleinefficiencybecausecoal

consumptionishigh.

•  Supercriticalcyclesbecauseofhighersteamparametershaveabetter

cycleefficiencythansubcriticalunits

Rankine Cycle

Tuesday, 8 December 15 Fußzeilentext 8

Lossesinthecycle

1.  Boilerefficiency

2.  Turbineheatrate

3.  Oxygeninfluegas

4.  Condenservacuum

5.  Demineralizedmakeupconsumption

6.  Secondaryfuelconsumption

7.  Auxiliarypower

AnalysisofOperatingparametersonPlantefficiency

Effectsof pressure, Superheating, Reheating

Effectsof Condenservacuum Regeneration

AdvancementsinHeatrate

Cycleefficiencies

IfaplantcanoperateideallybetweenthetemperaturelimitsT5andT1,thereis6%lossincycleefficiencybetweenCarnotandRankinecycles

Accurate unit heat rate

•  The obstacles to calculating an accurate heat rate for a coal-fired

unit using this method are:

•  The difficulty in accurately assessing the quantity of coal

•  The inaccuracies of the as-received coal

•  Uncertainty associated with measurements made over long periods of

time.

•  The use of an average heating value for a fuel whose heating value

may vary widely with different fuel suppliers.

Tuesday, 8 December 15 Fußzeilentext 13

Actualversusdesignedheatrate

CostofHeatratedeviation

•  Ifaplant’stargetheatrateis2300Kcal/KWhandtheactualvalueis2350Kcal/kWh,whatistheincreaseinannualfuelcost?

•  ChangeinAnnualFuelCost(Rs/yr)=HRD/BE×FC×PLF×UGC×TWhere:

•  HRDHeatRateDeviation(netunitorturbinecycleheatrate)

•  BE BoilerEfficiency=0.88

•  FC FuelCost/1,000,Kcal

•  PLF UnitCapacityFactor=0.85

•  UGCUnitGrossCapacity=500,000kW

•  T= 8760hr/year

•  ForaHRDof50Kcal/Kwhthecostis86.5MillionINRfora500MWunit

•  [@fuelcostis3600Rs/1000Kg]

Boilerlosses•  FoulingofBoilerheatingsurfaces:Affectsheattransfer•  Airingress:Disturbsfurnacedraft,fluegasvelocities,dilutes

combustion•  HighlevelsofunburntsinAsh:inefficientcombustion,loss

offuelvalue•  Poorcoalcalorificvalue:highfuelrequirement,hugewaste

handling•  Impropercombustion:metaltemperatureexcursions,

secondaryfires•  Boilerscales:InternaltubescalesaffectsHeattransfer,

leadstotubefails•  Suboptimizedequipmentoperation:Equipmentoperation

belowdesign•  Poordesign:inadequatemargins,qualityofmaterial,

resistancepaths•  Poorinsulation:heatradiationloss•  Highpressuredrops:heavyloadondraftsystemleadingto

increasedpower

and Environmental Research Center (EERC) have developed anash behavior prediction tool to assess slagging and fouling incoal-fired boilers called AshProSM. The development of thistool combines EERC's coal ash behavior expertise and RMTSmartBurn®'s expertise in combustion, CFD modeling andboiler operation. AshProSM integrates ash behavior modelsincluding ash formation, transport, deposition, and growth withboiler CFD simulations [3]. A unique advantage of AshProSM isthat it can be used to evaluate the localized slagging and foulingproblems that are related to actual operating conditions. There-fore, it can be used to identify the major causes of ash depositionso that measures to reduce the problem can be implemented.

2. Ash behavior models and the integration with CFD

simulations

The inorganic coal components undergo complex physicaland chemical transformations during combustion to producevapors, liquids, and solid phases in the flame. The abundanceand chemical characteristics of these phases depend on howthe inorganic species are associated in the fuel and oncombustion conditions. The partitioning of the inorganiccomponents into the various phases during combustion andgas cooling involves a continuum of complex interrelatedchemical reactions and physical transformations. The

Fig. 2. Deposit thickness (mm) on furnace rear wall close to corner 3 SOFA and furnace wall picture at a similar location.

Fig. 3. Ash impaction (kg/m2–s), deposit thickness (mm), temperature (K), deposit strength (Pa) on the furnace walls.

1036 Z. Ma et al. / Fuel Processing Technology 88 (2007) 1035–1043

Challenges

Airpreheater

IssueswithAirHeater

Thepoorperformanceofairpreheater:higherunitheatrate,deteriorationinboilerefficiency.ThemainproblemofairpreheateristheleakageofairtothefluegassideThehigherashcontentinIndiancoalalsoaddstotheproblemsassociatedwithairpreheater.Airpreheatersaredesignedtomeetperformancerequirementswithconsiderationofhighlyinfluencingparametersviz.heattransfer,leakageandpressuredrop.

SealleaksanderosioninAPH

2

PERFORMANCE IMPROVEMENT IN REGENERATIVE AIR PREHEATERS

SEAL LEAKAGES

Air leaks across radial and by-pass seals to flue gas

side .Leakages are measured by comparing oxygen

content of the flue gas entering and leaving

airpreheater .

This calculated leakage includes leakages through

radial seals on hot and cold end sides together and is

measured as percent of air flow.. Flue gas leakage

across bypass seals is not accounted for.O2 content

does not vary as gases bypass air heater totally and

leave APH without transferring heat to heating

elements and in turn air stream, which result in

increased flue gas temperature at outlet and increased

loading on Electro static precipitators. Similarly air

bypassing APH is not getting heated reducing air

outlet temperature. Heat loss occurred reduces boiler

efficiency. Leakages can be as high as 15 to 20 percent.

And are difficult to measure.

Utmost care needs to be taken while setting bypass

seals. Flexible seals are developed to reduce leakages

through radial seals. Modified `T` bars along with

flexible seals are also developed to reduce leakages

across bypass seals.

High flue gas velocity on outboard side causes heavy

erosion of heating elements at outer baskets.

Comparatively less erosion is observed on inboard side

baskets. Non-uniform distribution of flue gas entering

APH from economizer is the main reason. If coarse fly

ash from economizer hoppers is not evacuated

regularly, heap of ash forms in these hoppers. The

heaps not only affect flue gas distribution but also spill

over to APH causing erosion. Non uniform distribution

of gas also causes erosion of ‘T’ bars, rotor angle,

bypass seals and rear side duct plates from economizer

to APH along with expansion joints.

)9.20()(*100

2

22

outOinOoutOLeakages

��

Erosion pattern

on out board

side of APH

2

PERFORMANCE IMPROVEMENT IN REGENERATIVE AIR PREHEATERS

SEAL LEAKAGES

Air leaks across radial and by-pass seals to flue gas

side .Leakages are measured by comparing oxygen

content of the flue gas entering and leaving

airpreheater .

This calculated leakage includes leakages through

radial seals on hot and cold end sides together and is

measured as percent of air flow.. Flue gas leakage

across bypass seals is not accounted for.O2 content

does not vary as gases bypass air heater totally and

leave APH without transferring heat to heating

elements and in turn air stream, which result in

increased flue gas temperature at outlet and increased

loading on Electro static precipitators. Similarly air

bypassing APH is not getting heated reducing air

outlet temperature. Heat loss occurred reduces boiler

efficiency. Leakages can be as high as 15 to 20 percent.

And are difficult to measure.

Utmost care needs to be taken while setting bypass

seals. Flexible seals are developed to reduce leakages

through radial seals. Modified `T` bars along with

flexible seals are also developed to reduce leakages

across bypass seals.

High flue gas velocity on outboard side causes heavy

erosion of heating elements at outer baskets.

Comparatively less erosion is observed on inboard side

baskets. Non-uniform distribution of flue gas entering

APH from economizer is the main reason. If coarse fly

ash from economizer hoppers is not evacuated

regularly, heap of ash forms in these hoppers. The

heaps not only affect flue gas distribution but also spill

over to APH causing erosion. Non uniform distribution

of gas also causes erosion of ‘T’ bars, rotor angle,

bypass seals and rear side duct plates from economizer

to APH along with expansion joints.

)9.20()(*100

2

22

outOinOoutOLeakages

��

Erosion pattern

on out board

side of APH

Onlineefficiencyanddiagnostics

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Condenser

25

26

Air flue gas system 27

Ebsilonmodelling-offline

Improvements in Power Plant Efficiency

•  There are a number of specific improvements in power for example: •  Cleaning tubes and boilers •  maintaining instrumentation •  restoring seals •  removing deposits on turbine blades •  condenser maintenance programs •  decreasing excess oxygen to the boiler •  Instaling variable speed drives for motors •  waste heat utilization for feed water heating

•  Installing a online performance diagnostic software

Tuesday, 8 December 15 Fußzeilentext 29

Wecancontribute

•  SteagO&MCompanycanhelpyou….

•  InOperatingandMaintainingthepowerplants•  Efficiencytestingofthepowerplants•  OrganizingtheO&Msystems•  EnergyAuditingofthepowerplants•  Commissioningofthepowerplants•  OwnersEngineeringofpowerplants•  Supplyonlineefficiencymonitoringsystems•  Benchmarkingofoperationsforreducingthecostofgeneration

THANKYOUK . BHANUPRAKASH@STEAG . I N