SESSION 1 – PART 1

Main Steam Flow at Superheater outlet. Auxiliary Steam Consumptions before stop valve. Main Steam Pressure at superheater outlet. Main Steam Temperature at superheater outlet. Feed Water Temperature at Economiser Inlet.

Main Steam Flow at Superheater outlet. Auxiliary Steam Consumptions before stop valve. Main Steam Pressure at superheater outlet. Main Steam Temperature at superheater outlet. Feed Water Temperature at Economiser Inlet.

Steam flow at reheater outlet. Steam pressure at reheater inlet. Steam pressure at reheater outlet. Steam Temperature reheater outlet. Feed Water Temperature at Economiser Inlet.

The heat to be transferred to steam would changeas per HP heater water outlet temperature

If there are long term instances for HP heater –out of service- same to be specified.

Steam coil preheating requirement Soot blower steam requirement. Drum coil preheating. Furnace coil preheating. Furnace oil heat tracing Steam atomization. Deaerator steam requirement Ejector steam requirement HP / LP gland sealing - generally taken care of

turbine maker.

TAKE CARE OF THE PRESSURE DROPBETWEEN BOILER TERMINAL POINT TO THEFARTHEST TURBINE INCASE CROSS OVERPIPING / COMMON STEAM HEATER SYSTEM ISCONSIDERED.

Pr drop for ID<152 Delta P = 122.364 x 10^6 x F^1.85 x V x TEL / ID^4.97

Pr drop for ID>152 Delta P = 89.254 x 10^6 x {1 + (91.44/ID) } F^2 x V x TEL / ID^5

V - Specific volume, m3/kgTEL - total equivalent length, mF - flow in a circuit , kg/s

ID - inside diameter of tube / pipe , mm

DARCY'S EQUATION Pr drop: (3.36E-6 x FF x F^2 x EL x SP.V / (ID^5) )

Tube ID inchDarcy friction factor(FF) noFlow(F) lb/hEquivalent length(EL) ftSpecific volume(SP.V) cft/lbPressure drop psi

Di mm Friction Factor

12.7 0.02819.05 0.02525.4 0.02338.1 0.02150.8 0.0263.5 0.01876.2 0.018101.6 0.017127 0.016203.2 0.014254 0.013

length metre No off ID

entry no 20exit no 40squeeze bend no 75180 bend no 5090 short rad bend (R<3d) no 3290 std radius ( r = 3d) no 2690 long rad bend ( R>3d) no 2045 short rad bend ( r<3d) no 1545 long rad bend ( R >3d) no 12reducer no 120expander no 100Tee - entering run no 60Tee- entering branch no 90

Generally 5 – 10 deg C drop is expected in mainsteam line.

Selection and proper application of insulation isimportant to ensure not much temperature isdropped across the steam piping.

Stepped over insulation and sagged insulation arecauses for temperature drop.

HP turbine exhaust pressure – IP turbine inlet pressure

Generally the reheater pressure drop isdesigned for 50 % of allowable totalpressure drop

Fuels to be fired Fuel ultimate analysis. (Element Constituents.)

such as – C,H,N,O,S etc., As fired fuel moisture Calorific value of fuel – as fired Ambient temperature Relative humidity Type of combustion system Boiler exit gas temperature as dictated by flue

gas composition

Boiler Heat Output / Duty =Steam Flow x (Main Steam Enthalpy – Feed Water Enthalpy)

Presenter

Presentation Notes

The above is a typical calculation of heat output from the boiler.

If the HP Heater is out then the Boiler heat output has toincrease by 9.6% since the Feed Water temperature is lower.

Importance of GCV

Ways of Reporting

Air Dried Basis As Received Basis As Sampled Basis As Fired Basis Bone dry basis Dry mineral matter free basis

• Samples received at lab are left opento lab ambient conditions (UsuallyStandardized Temp and relativehumidity) for equilibrium moisture.

• Data reported on the air dried samplebasis is called air dried basis (ADB).

• This refers to data reported on thebasis of as received moisture.

• Such samples are received at lab inproperly packed containers.

• At plant conditions, the samples may bedelivered to lab just as sampledimmediately.

• This is very much required to know theheat content in coal as received fromsuppliers.

• Surface moisture burden is usuallydeducted as per PO.

Has relevance to boiler performance. The coal gets dried at yard, on handling, on

crushing & screening before it reaches boilerterminal point.

The moisture / ash / volatile matter / fired carboncan change considerably from receipt to firing.

Data expressed on moisture removedbasis is called dry basis.

It is also called as “Bone Dry” basis.

• The mineral matter converts to ash oncombustion.

• Some of the minerals may also leave asvapor form.

• Data expressed on DMMF basis is usefulfor coal rank classification.

Calorific value is the heat produced by thecombustion of a unit quantity of coal in a bombcalorimeter with oxygen under a specified set ofconditions

Calorific value is expressed as GCV or HHV Alternately expressed as LCV or LHV In GCV all the vapor produced in combustion

process is full condensed. The latent heat isadded to GCV and thus GCV is higher to LCV

Net calorific value informs that the water isremoved as vapor with the combustion products.

In Bomb calorimeter, the fuel is burnt with oxygen andthe heat is absorbed by water

Correction to be given for formation of Nitric acid &Sulphuric acid

The oxidation of nitrogen and formation of nitric aciddoes not occur in actual combustion equipment. This isan exothermic reaction

Only 5% sulphur-dioxide is oxidised to SO3 in actualcombustor. In bomb calorimeter all the SO2 is burnt toSO3 as sulphur oxygen is available and higher pressure

Heat is liberated additionally when SO2 is oxidised toSO3 and in formation of Sulphuric acid

For a reaction carried out in a calorimeter, the heatevolved by a reaction is absorbed by the calorimeterand its contents.

qrxn = – qcalorimeter

qcalorimeter = mass x specific heat x △T By measuring the temperature change that occurs in a

calorimeter, and using the specific heat and mass ofthe contents, the heat evolved (or absorbed) by areaction can be determined and the enthalpy changecalculated.

(100 – MAFR)AS FIRED GCV = x GCVADB

(100 – MADB)MAFR - Moisture as fired (To be done by plant

lab).MADB - Moisture air dried basisGCVADB - GCV air dried basis (from Lab report)

At LAB, the fuel sample is powdered and dried. Portion of fuel moisture thus gone. The fuel GCV is thus called GCV on air dried basis.

DIFFERENCE BETWEEN AIR DRIED BASIS GCV & AS FIRED GCV

(100 – MAR)AS RECD GCV = x GCVADB

(100 – MADB)MAR - Moisture as recd (To be done by plant lab).MADB - Moisture air dried basisGCVADB - GCV air dried basis (from Lab report)

At LAB, the fuel sample is powdered and dried. Portion of fuel moisture thus gone. The fuel GCV is thus called GCV on air dried basis.

DIFFERENCE BETWEEN AIR DRIED BASIS GCV & AS RECEIVED GCV

As fired GCV is used for boiler efficiency calculation.

As sampled basis is used for paying the vendor.

Air dried basis / bone dry basis is used for knowing the trend of GCV.

EfficiencyEfficiency

Wh t F l (F il) E t St When we convert Fuel (Fossil) Energy to Steam,there are losses

Efficiency = Heat liberated by Fuel – Lossesy yHeat liberated by fuel

Loss 1Loss 1--Heat lost through unburned carbon particles Heat lost through unburned carbon particles in the ash removed from the boilerin the ash removed from the boilerin the ash removed from the boilerin the ash removed from the boiler

D di th b ti h i th Depending upon the combustion mechanism theunburned carbon particles are found in the ash.

The fuel size, the combustor design, fuel moisture/ fixed carbon / ash / volatile matter govern thisloss.

Measured as LOI ( loss on ignition or GCV of ash)( g ) LOI is the weight loss of the ash sample when

reburning is done at lab furnace.reburning is done at lab furnace.

Loss 1Loss 1: Heat lost through unburned carbon particles in : Heat lost through unburned carbon particles in boiler ashboiler ashbo e asbo e as

LOI is different from heat lost through ash

Heat lost though unburnt cannot be calculated on LOI basisHeat lost though unburnt cannot be calculated on LOI basisfor high GCV ash such as the case of Petcoke ash

Fly ash collected per day = 60 Tons

Petcoke consumption per day = 230 tonsCalorific value of fly ash = 2500 kcal/kgCalorific value of carbon = 8050 kcal/kg

Fuel GCV = 8010 kcal/kg

HLS1-1, unburnt carbon loss in fly ash

= 100 x 60 x 2500 / (230 x 8010)

= 8.14%

Loss 2Loss 2: Heat lost towards sensible heat of ash in : Heat lost towards sensible heat of ash in fuelfuelfuelfuel

Depending upon the boiler arrangement the ash Depending upon the boiler arrangement the ashcollection rate and ash temperatures vary atvarious ash hoppersvarious ash hoppers.

Some of the heat given by the fuel is used up forl tti th h t hi h t t th thletting the ash at higher temperature than thetemperature at which it came into the combustor.

Loss 2Loss 2: Heat lost towards sensible heat in ash: Heat lost towards sensible heat in ash

Fly ash is let out of system at 140 deg C Bed ash is let out at 200 deg C in case a cooler is used.g

Loss 3Loss 3: Heat lost though heating up at atmospheric : Heat lost though heating up at atmospheric moisturemoisturemoisturemoisture

The water vapor prevalent in atmospheric air also The water vapor prevalent in atmospheric air alsogets inside the furnace when the fan suppliescombustion aircombustion air.

Naturally, a part of the heat has to be given forh ti th t f t h iheating the water vapor from atmospherictemperature to boiler exit temperature.

Loss 3Loss 3: Heat lost through heating up of : Heat lost through heating up of atmospheric moistureatmospheric moistureatmospheric moistureatmospheric moisture

Loss 4Loss 4

Heat lost through the evaporation of fuel moisture and themoisture formed during combustion due to fuel constituentsmoisture formed during combustion due to fuel constituentssuch as hydrogen and hydrocarbons (Methane / Ethane)

There is always some moisture in fuel In agro fuels such There is always some moisture in fuel. In agro fuels suchas bagasse, wood it could be as much as 50%

Part of the heat from the fuel is used up for evaporation of Part of the heat from the fuel is used up for evaporation offuel moisture and the water vapor formed duringcombustion of hydrogen, hydrocarbons.combustion of hydrogen, hydrocarbons.

Depending on the exit temperature, the water vaporleaves the boiler at superheated condition.leaves the boiler at superheated condition.

Loss 4Loss 4: Heat lost through evaporation of fuel : Heat lost through evaporation of fuel moisture & moisture formed during combustionmoisture & moisture formed during combustion

As fired moist re is a ke parameter in this loss As fired moisture is a key parameter in this loss Manipulation of H2 content can vary the loss

Since the heat lost through the flue gas throughair moisture are separately estimated, the leftout components is the heat through the dry fluegas.

By designing the boiler for low exit gasy g g gtemperature the loss can be kept minimum.

Further the lower the excess air percentage Further, the lower the excess air percentage,the loss will be lower.

Loss 6: Radiation heat lost to surroundingLoss 6: Radiation heat lost to surrounding

Radiation losses occur due to heat flow from theh t i l t d / i l t d f f th b ilhot insulated / uninsulated surface of the boilerand accessories.

A portion of the heat from fuel goes for this . Thecondition of boiler insulation will decide this.Heat loss is unavoidable, but it can minimized,by choosing to apply insulation in the propermanner to the required thickness.

Standard radiation heat loss chart is available toestimate the heat lost surrounding. The % losscan be about 0.5%.

Loss 6: Radiation heat lost to surroundingLoss 6: Radiation heat lost to surrounding

Boiler Thermal EfficiencyBoiler Thermal Efficiency

Heat loss due to limestone addition in a boilerHeat loss due to limestone addition in a boiler

CaCO3 to Co2 & CaO‐ heat required kcal/kg 436.6CaCO3 to Co2 & CaO heat required kcal/kg 436.6

MgCO3 to CO2 & MgO ‐ heat required kcal/kg 284.8

SO2 to CaSO4‐ heat given by reaction kcal/kg 3620.48

Calcination needs heat input. Sulfation gives heat. In addition there is moisture added by limestone In addition there is moisture added by limestone

which adds to additional heat loss

Heat loss due to limestone addition 

CaCO3 to Co2 & CaO‐ heat required kcal/kg 436.6MgCO3 to CO2 & MgO ‐ heat required kcal/kg 284.8MgCO3 to CO2 & MgO  heat required kcal/kg 284.8

SO2 to CaSO4‐ heat given by reaction kcal/kg 3620.48

Fuel fed kg/h = 100Fuel fed kg/h = 100Moisture fed in limestone kg/h = 1.8Dry Lime stone fed kg/h = 15Fraction of CaCo3 in limestone kg/kg = 0.75F ti f M C 3 i li t k /k 0 15Fraction of MgCo3 in limestone kg/kg = 0.15Inerts in limestone kg/kg = 0.4GCV of fuel kcal/kg = 7900Heat loss due to calcination of CaCo3 &  Kcal/kg of fuel = ( 15 / 100 )  x  ( 0.75 x 436.6) + (0.15 x 284.8)MgCO3

= 55.5255Sulfur content in fuel kg/kg = 0.007% SOX capture % = 80% p %Heat gain from sulfation reaction kcal/kg of fuel fired = 0.007 x ( 80 / 100 ) x 3620.48

= 20.27Sensible heat addition to limestone Kcal/kg = ( 15 / 100 ) x 0 24 x 100Sensible heat addition to limestone Kcal/kg = ( 15 /  100 ) x 0.24 x 100

Kcal/kg = 3.6Moisture heat loss = (M / F )x [595.4+(Cp1 x Te) ‐Ta] x 100 / GCV

= 10.61Efficiency loss due to limestone feeding % = 100*(55.5255 + 3.6 + 10.61 ‐ 20.27 )/7900

= 0.63

Fuel Firing RateFuel Firing Rate

LOSS 1: HEAT LOST THROUGH UNBURNED CARBON PARTICLES IN THE ASHPARTICLES IN THE ASH

SmallerSmaller thethe fuelfuel sizesize moremore surfacesurface areaarea isis exposedexposed SmallerSmaller thethe fuelfuel size,size, moremore surfacesurface areaarea isis exposedexposedforforOO22 reactionreaction..HH titi fifi thth ff llll ll CBFCCBFC HoweverHowever optimumoptimum finesfines areare therethere forfor allall coalcoal.. CBFCCBFCacceptsaccepts moremore finesfines asas comparedcompared toto BFBCBFBC.. PFPF alsoalso

dd ll ifi difi d f lf l iineedsneeds onlyonly specifiedspecified fuelfuel sizesize..

LOSS 1: HEAT LOST THROUGH UNBURNED CARBON PARTICLES IN THE ASHPARTICLES IN THE ASH

ThreeThree ‘T’s,‘T’s, namely,namely, Time,Time, TemperatureTemperature andandTurbulenceTurbulence areare thethe factorsfactors forfor aa completecompletecombustioncombustion..

TheThe threethree factorsfactors varyvary withwith thethe combustioncombustionyytechnologytechnology..

FBCFBC TechnologyTechnology withwith underbedunderbed fuelfuel feedingfeedingFBCFBC TechnologyTechnology withwith underbedunderbed fuelfuel feedingfeedingarrangementarrangement ensuresensures threethree ‘T’S‘T’S areare availableavailable..

LOSS 1: HEAT LOST THROUGH UNBURNED CARBON PARTICLES IN THE ASHPARTICLES IN THE ASH

OverfedOverfed FBCFBC boilersboilers certainlycertainly fallfall behindbehind inin thisthisrespect,respect, asas thethe residenceresidence timetime forfor thethe fuelfuel toto staystayp ,p , yywithinwithin thethe bedbed isis lessless..

CFBCCFBC technologytechnology withwith hothot cyclonecyclone // coldcold cyclonecyclone //CFBCCFBC technologytechnology withwith hothot cyclonecyclone // coldcold cyclonecyclone //UU beambeam separatorseparator ++ CycloneCyclone provideprovide adequateadequateresidenceresidence timetime forfor betterbetter combustioncombustion unlessunless &&residenceresidence timetime forfor betterbetter combustioncombustion unlessunless &&untiluntil thethe sizesize ofof thethe fuelfuel // ashash isis belowbelow thethe cutcut offoff..

TIP FOR CFBC

PoorPoor cyclonecyclone efficiencyefficiency cancan affectaffect thethe boilerboiler outputoutputduedue toto lessless particleparticle inventoryinventory..pp yy

ParticleParticle sizesize distributiondistribution atat ESPESP firstfirst fieldfield ashashhopperhopper shouldshould bebe monitoredmonitored inin CFBCCFBC InIn casecase thethehopperhopper shouldshould bebe monitoredmonitored inin CFBCCFBC.. InIn casecase thethepercentagepercentage ofof 100100 micronsmicrons andand aboveabove isis seen,seen, ititimpliesimplies deteriorationdeterioration inin CFBCCFBC performanceperformanceimpliesimplies deteriorationdeterioration inin CFBCCFBC performanceperformance..

TIP FOR AFBC

InAFBC Bed temperature should beminimum 850 degC Bed temperature should beminimum 850 degC. Shallow bed leads to high elutriation loss. Denser bed leads to high elutriation loss.

TIP FOR PF

In PF boiler High PA leads to more loss High PA leads to more loss. Unbalance in fuel piping leads to unburnt loss of

bcarbon. Too lessO2 leads to poor combustion.

TIP FOR TRAVELING GRATETIP FOR TRAVELING GRATE

In travagrate boiler

Grit refiring would help. Proper secondary air turbulence will reduce loss. Particle size control helps – more fines more loss.p

LOSS 2: HEAT LOST TOWARDS SENSIBLE HEAT OF ASH IN FUELHEAT OF ASH IN FUEL

If it is practical, all the ash should be removed from theflue gas at dust collector before chimney. Depending onthe boiler configurations, ash hoppers are to be providedwherever the gas takes a turn.

Ash coolers are used to recover the heat from the ashparticularly where the ash is removed from the furnace.

TIPS FOR CFBC / AFBCTIPS FOR CFBC / AFBC

Stripper coolers separate finer particles and recycleto furnace alone with hot air.

fluidized bed HX with condensate heating systemcan be usedcan be used.

Rotary ash coolers are widely used by Chinese,where only condensate is used for heat recoverywhere only condensate is used for heat recoveryfrom ash.

LOSS 3: HEAT LOST THROUGH THE EVAPORATION OF FUEL MOISTURE & THE MOISTURE FORMEDOF FUEL MOISTURE & THE MOISTURE FORMED DURING COMBUSTION

The main factor is the fuel moisture. Closed sheds to prevente a acto s t e ue o stu e C osed s eds to p e e trainwater entry into fuel storage yard would keep the lossminimum.

Solar drying of fuel would help in achieving overall economy.Flue gas drying is being adopted in the case of bagasse.

LOSS 4: HEAT LOST THROUGH HEATING UP ATMOSPHERIC MOISTUREATMOSPHERIC MOISTURE

As explained earlier the loss is because of theAs explained earlier, the loss is because of themoisture in ambient.

One has to ensure the air is not drawn from closed One has to ensure the air is not drawn from closedrooms where the air is saturated with water vaporsuch as paper mills or near cooling towersuch as paper mills, or near cooling tower.

LOSS 5LOSS 5: RADIATION HEAT LOST TO SURROUNDING: RADIATION HEAT LOST TO SURROUNDING

THE BOILER MUST BE COMPLETELY INSULATED WITHPROPER INSULATIONMATERIALS.

HAND MADE MATTRESSES DO NOT HAVE UNIFORMDENSITY.

RESIN BONDED MATTRESSES WOULD GIVE BETTERINSULATIONOFTHE BOILER.

IT IS IMPORTANT TO PERIODICALLY CHECK AND REPLACETHE INSULATIONASANDWHENNECESSARY.

ALL VALVES AND CONDENSATE PIPING SHOULD BE ALL VALVES AND CONDENSATE PIPING SHOULD BEINSULATED.

LOSS 5: RADIATION HEAT LOST TO SURROUNDING

Some boiler companies maintain that the insulation of airbox & valves are not their practice. 

LOSS 6: HEAT LOST THROUGH THE DRY FLUE GAS AT THE END OF HEAT RECOVERY DEVICE OF BOILEREND OF HEAT RECOVERY DEVICE OF BOILER

Excess air is a must to complete the combustion. Thecombustor design and fuel quality govern excess air

d f l brequired for complete combustion.

Each combustion technology dictates a set of parameters tob h k d d t b i t i d tbe checked and to be maintained to ensure propercombustion and to keep the excess air minimum.

LOSS 6: HEAT LOST THROUGH THE DRY FLUE GAS AT THE END OF HEAT RECOVERY DEVICE OF BOILEREND OF HEAT RECOVERY DEVICE OF BOILER

In the case of solid fuel fired boilers, inadequate airwill lead to black smoke and unburnt fuel in ash.

It is necessary to strike a balance between theunburnt in ash and the excess air based on theunburnt in ash and the excess air based on thecombustion technology.

The flue gas composition is decided by the fuel and The flue gas composition is decided by the fuel andexcess air. Hence, it is customary to spell out theCO2 or O2 level in flue gas to be maintained to setCO2 or O2 level in flue gas to be maintained to setthe excess air.

LOSS 6: HEAT LOST THROUGH THE DRY FLUE GAS AT THE END OF HEAT RECOVERY DEVICE OF BOILEREND OF HEAT RECOVERY DEVICE OF BOILER

In addition to excess air, Boiler outlet gas temperature willdecide the amount of heat lost to chimney.

Boilers are designed with heat recovery devices such asEconomizer, air heater or feed water heater to bring downthe gas temperature to 140 degC to 170 degC.

h h b bl l d h f Chimney has to be suitably lined with refractory to protectagainst corrosion. Corrosion occurs due to Sulfur‐di‐oxidecondensation Sulfur‐di‐oxide is produced due to sulfurcondensation. Sulfur‐di‐oxide is produced due to sulfurcontent in fuel.

Otherwise also the water vapor in flue gas which is due toOtherwise also the water vapor in flue gas, which is due tofuel moisture / air moisture also condense and lead tocorrosion of steel.

LOSS 6: HEAT LOST THROUGH THE DRY FLUE GAS AT THE END OF HEAT RECOVERY DEVICE OF BOILEREND OF HEAT RECOVERY DEVICE OF BOILER

All i hi h h i h h k d i h Allowing high exhaust temperature with choked air heater,fouled economizer leads to poor efficiency of the boiler.depositsdeposits.

Honey combing of ash accumulations is seen in agro wastefired boilers.fired boilers.

BLOW DOWN

Blow down loss is not listed in the estimation of boiler efficiency forBlow down loss is not listed in the estimation of boiler efficiency, forreason the amount of blow down is governed by the feed water andthe boiler water quality.

Continuous blow down helps to maintain a steady value of boilerwaterTDS, silica and the loss will be minimum in the process.

Intermittent blow down would lead to a higher heat loss since therate is uncontrolled.

BLOW DOWN HEAT LOSS ‐ TYPICAL

CASE STUDY‐ PLANT WITH SEVERAL BOILERS

• COMPARETHEASHOF DIFFERENT BOILERS• COMPARETHEASHOF DIFFERENT BOILERS.• COMPARETHEASH FOR DIFFERENTCOALS.• COMPARETHEASH FOR DIFFERENT PERIODS• COMPARETHEASH FOR DIFFERENT PERIODS.• COMPARETHEASH FOR DIFFERENTOPERATORS

GCV ANALYSIS & REPORTINGGCV ANALYSIS & REPORTING

The GCV of the fuel was reported on ADB forpayment purpose. Tonnage was taken as perp y p p g pactual.

As sampled moisture was never reportedAs sampled moisture was never reported. The lab reported the GCV on air dried basis. The

purchase department was unaware of the totalpurchase department was unaware of the totalmoisture and ended up in losing crores of rupees.

SAMPLING PROCEDURES & DELAYSAMPLING PROCEDURES & DELAY

Taking samples was a very slow process. There wasconsiderable time delay in sampling.y p g

Codes specify better sampling procedures on lineto avoid error in handling the samplesto avoid error in handling the samples.

Low relative humidity, higher ambienttemperature wind are the factors for dryingtemperature, wind are the factors for drying.Mixing process (at the time of quarter coning)drives out the surface moisturedrives out the surface moisture.

DIRECT FEEDING OF WET COAL TO BOILERDIRECT FEEDING OF WET COAL TO BOILER

Direct feeding of wet coal can result in more loss. Wet coal is to be stocked in yard for psychrometric Wet coal is to be stocked in yard for psychrometric

drying. An efficiency difference of 0 85% due to direct feed An efficiency difference of 0.85% due to direct feed

of 12%moisture coal means 255 tons of coal can besaved per month The plant consumed about 1000saved per month. The plant consumed about 1000tons a day.

BELT WEIGHERBELT WEIGHER

Empty running of belts cause errors in belt weigherreading.g

Installation in inclined conveyor length is notpreferred as the belt tends to lift off due to beltpreferred as the belt tends to lift off due to belttensioning arrangement.

YARD MANAGEMENTYARD MANAGEMENT

Mi i t diff t f l ff t th b ti tMixing two different fuels affects the combustion to someextent. Manually rpm regulation is not practical when theGCV aries d e to improper f el miGCV varies due to improper fuel mix.

Separate hoppers are req ired for deciding the proportionSeparate hoppers are required for deciding the proportion.Regulated hopper feed is required. Multi fuel operatingsystems need multi bunker systemsystems need multi bunker system.

USE OF SHEDSUSE OF SHEDS

Loss of volatile matter from yard at high temperature. Astudy needs to be conducted for thisstudy needs to be conducted for this.

Depending on the surface exposed and by the nature ofDepending on the surface exposed and by the nature ofcoal, the extent varies. In the yard management rake wisecoal should be consumed We can avoid loss of GCVcoal should be consumed. We can avoid loss of GCV.

Sheds prove useful Temporary covers are also usable forSheds prove useful. Temporary covers are also usable forless coal consumers. Lignites are very sensitive to this.

CALIBRATION OF DRAG CHAIN FEEDERSCALIBRATION OF DRAG CHAIN FEEDERS

Drag chain feeders have gate setting for controlling thef l d h Thi h ld b f lfuel depth. This should be set perfectly.Calibration is required for records and to calculate the fuelf dfeed rates.Drag chain feeder discharge rates are practically linear

i hwith rpm.Non uniform feed result in poor combustion.

CALIBRATION OF DRAG CHAIN FEEDERSCALIBRATION OF DRAG CHAIN FEEDERS

RPM SETTINGS FOR FUEL FEED‐ AFBC BOILERS

There is a tendency to vary the rpm of feeders as per bedtemperature indicationtemperature indication.This is not a correct way. When the air flow is distributed,the fuel flow should set equally at all feedersthe fuel flow should set equally at all feeders.

CALIBRATION OF BELT FEEDERSCALIBRATION OF BELT FEEDERS

BELT FEEDERS AT PF BOILERS ARE TO HANDLECOAL PARTICLES OF 50 MM AND BELOWCOAL PARTICLES OF 50 MM AND BELOW.THE FRONT WINDOW OPENING CONFIGURATIONDECIDES THE FUEL FLOWDECIDES THE FUEL FLOW.

IMPROPER / INTERRUPTED FLOW IN TO FEEDERIMPROPER / INTERRUPTED FLOW IN TO FEEDER

UNBALANCED FLOW TO PF BURNERSUNBALANCED FLOW TO PF BURNERS

OFFSET HOPPER INLETS ENSURE INLETS ENSURE SMOOTH FLOW OF COAL

UNBALANCED FLOW TO PF BURNERS‐ EFFECT OF ADJUSTMENT OF GATESADJUSTMENT OF GATES

IMPROPERIMPROPER CONDITIONCONDITION OFOF MILLSMILLS LEADLEAD TOTO UNBALANCEUNBALANCE ATATELEVATIONSELEVATIONS‐‐ RPMRPM OFOF FEEDERSFEEDERS ATAT DIFFERENTDIFFERENT LEVELSLEVELS VARYVARY DUEDUETOTO THISTHIS WORNWORN OUTOUT BALLSBALLS SPRINGSPRING SETTINGSSETTINGS RINGRINGTOTO THISTHIS.. WORNWORN OUTOUT BALLSBALLS –– SPRINGSPRING SETTINGSSETTINGS –– RINGRINGCLEARANCECLEARANCE LEADLEAD TOTO POORPOOR OUTPUTOUTPUT..

Setting the auto combustion control parameters.

This is the trend of O2, steam flow, steam pressure & fuel feeder rpm (feeder no 6 & feeder no 1) in 90 TPH boiler. The cyclic pattern of O2 to repeat within a short span of 3 minutes. This cycle comes short because the feeder rpm is increased by 66% over the lowest rpm by the combustion control. When two feeders are on auto the net fuel flow variation is 22%. This fuel addition when dumped in two locations in the compartments may lead to poor combustion. Reducing the gain would help to remove such a cycle.

LOI feed back to boiler operators –in an hour after the shiftcommencescommences

• The plant laboratory is busy with routine tests requiredThe plant laboratory is busy with routine tests requiredfor the company product. Time delay between test andth i t t ti l d t i tthe interpretations lead to no improvement.

• An express laboratory for the analysis of LOI of ESPash.

• Some plants consume 1000 tons of coal a day. LOIp yshould be the interest of the operators.