Coal handling plant


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Coal handling plant

  2. 2. CONTENTSL.No. TOPIC PAGE No. 1 2 Abstract . 2 2 Introduction 3 2 Working of Coal Handling Plant 4 4 Availability of Coal in India 5 5 Transportation of Coal 6 5 CHP Auxiliary And Equipments 7 6 Operational Cycle. 8 7 Measures before Transporting Coal 9 7 Problems in coal handling plant 10 8 Dust management in thermal power plant 1
  3. 3. ABSTRACTMany thermal power plants use coal as their fuel.To handle the coal, each power station is equipped with a coalhandling plant. The coal has to be sized, processed, and handled which should be done effectively and efficiently.While working in the coal handling plant the major factor which reduces staff efficiency is the working environmenti.e., dust etc.. Generally all systems used in power station coal handling plants are wet dust suppression systems.INTRODUCTIONCoal Handling Plant (CHP) is a plant which handles the coal from its receipt to transporting it to Boiler and store inBunkers. It also processes the raw coal to make it suitable for Boiler Opeartion.Coal Handling Plant (CHP):-Extent of work: - In brief we can say that receipt of coal from coal mines, weighing of coal, crushing it to requiredsize and transferring the quanta of coal to various coal mill bunkers. This is the responsibility and duty of the CHP andits staff.Receipt of Coal:-Normally Thermal Power Station receives the coal by three modes of transportation.1. By Railway (80-90% of the requirement is fulfilled by this way)2. By Road ( if required 5-10% of the requirement is fulfilled by this way )3. By Arial ropewaysGeneral Working of a Coal Handling Plant :-As mentioned above, coal is brought to power station by either of three means of coal transportation. This coal is firstconveyed to primary crusher with the help of different combination of conveyor belts and its rate of feeding iscontrolled by Electro-magnetic vibrating feeders. Conveyor belt before the crusher is provided with hanging magnetsto separate ferrous materials. Stones are picked up manually. In primary crusher, coal is first crushed to 100 mm size.This coal is again conveyed to secondary/final crusher on belt system. Here vibrating screens are used to feedcrushers, which bypasses coal of size more than 25 mm. In final crushers, coal is further crushed to required 25 mmsize. This sized coal is then send to bunkering belt and with the help of coal trippers. This sized coal is finally fed tocoal bunkers. This cycle is called coal bunkering.In case bunkers are full, then available coal is stored in stock yardwith the help of stacking belts /automatic stacker cum reclaimer. This cycle is called stacking.In emergency when coalis not available in plant by railways/ropeways, then this stacked coal is diverted to the coal bunkers by reclaimimgconv. belts. This cycle is called reclaiming. The coal stored in bunkers is further send to coal mill for pulverizationand combustion in boiler furnace. 2
  4. 4. GENARAL LAYOUT OF COAL HANDLING PLANT(CHP)Availability of Coal In India :- 3
  5. 5. Mostly E and F grade coal used in India. Blending Is Done To get Average D Grade.e C.V. % Ash + Moisture ( K Cal / Kg. ) > 6200 19.57 5601-6200 19.57 - 23.97 4941-5600 23.92 - 28.69 4201-5940 28.69 - 34.05 3361-4200 34.06 - 40.14 2401-3360 40.14 - 47.10 TRANSPORTATION OF COAL:- Coal is brought to the power station by three modes of transportation : 1.Roadways 2.Railways 3.Ropeways 1. Roadways :Coal is carried in trucks and a truck can carry about 8-10 tons of coal. But due to low capacity, low unloading rate and time consuming, this mode is not in much use for large thermal power stations. 2. Railways :coal is brought by railway wagons. One rack consists of 58 wagons. Each wagon contains 58 MT of coal. Locos bring the wagons from the marshalling yard and place them on wagon tippler. These wagons are then 4
  6. 6. unloaded with the help of wagon tippler. If these wagons are not unloaded in stipulated time period (generally 7 hrs.),demurrage charges are lavied by railway department.3. Ropeways :This mode of coal transportation is used where coal mines are located near the power stations. Coal isbrought by hanging buckets/trolleys travelling on track ropes, which are pulled by a haulage rope with a drivingmechanism. The payload of each bucket varies from 1 to 3 tons. Automatic loading and unloading mechanisms areprovided at loading and unloading stations. Rate of unloading varies from 75 to 275 MT/Hr depending on the type ofropeways used. This type of coal transportation is very economical compared to road or rail transportation and givesassured supply of coal, being the MSEB property. The only disadvantage of this system is long time for maintenanceworks.Coal HanndlingPlantAuxilaries:-Major auxiliaries of CHP:-1. Wagon Tipplers2. Vibrating Feeders3. Conveyor Belts4. Coal Crushers5. Trippers6. Electromagnetic Separators7. Dust extraction systems8. Gas Extractor  Wagon Tipplers:- These are the giant machines having gear boxes and motor assembly and are used to unload the coal wagons into coal hoppers in very less time (e.g. 20 wagons/hr. or more).  Vibrating Feeders:- These are electromagnetic vibrating feeders or sometimes in the form of dragging chains which are provided below the coal hoppers. This equipment is used for controlled removal of coal from coal hoppers.  Conveyor Belts:- These are the synthetic rubber belts which move on metallic rollers called idlers and are used for shifting of coal from one place to other places.  Coal Crushers:- We receive the coal in the form of odd shaped lumps. These lumps are to be crushed to required size. These lumps are crushed by coal crushers.  Trippers:- These are the motorized or manually operated machines and are used for feeding the coal to different coal bunkers as per their requirement. 5
  7. 7.  Electromagnetic Separators:- Electromagnets are used for removing of Iron and magnetic impurities from the coal.  Dust Extraction System:- This system is provided in CHP for suppression of coal dust in coal handling plant.  Gas Extractors:- Gas extractors are provided at the bunker level to remove all types of poisonous and non poisonous gases from the working area.Operational Cycles:-1. Normal Bunkering cycle.2. Stacking cycle.3. Reclaiming Cycle.  Normal Bunkering Cycle:- Shifting of coal received from coal wagons directly to coal bunkers is normal bunkering cycle.  Stacking Cycle:- When there is no coal requirement at coal bunkers even then CHP has to unload the received coal which is stacked at open ground called yard. This is stacking cycle.  Reclaiming Cycle:- when coal wagons are not available the requirement of coal bunkers is fulfilled from the stacked coal this is reclaiming cycle. Precautionary Measures before Transporting Coal  Weighing of Coal:- Weighing of coal is carried out at wagon tippler. Weight of loaded wagon is taken; after unloading the coal, weight of empty wagon is taken the difference of the two will give the weight of the coal (normally 55-60 metric ton of coal come in each wagon).  Payment of Coal:- Payment of coal is made to the coalmines as per the weighing of coal carried out at their premises. However, if any dispute arises regarding weighing of coal same is to be settled by the committee of both the parties.  Stone shells:- Sometimes stone shells are received along with coal same has to be removed from the coal before bunkering and is done sometimes manually or by different type of machines. If quantum of stone shells is beyond minimum limit the cost of the coal is recovered from the coal mines 6
  8. 8. against the quantity of stone shells received from them.  Chemical Analysis of Coal:- Sample of coal is randomly collected from each rake by concerned MSEB (Maharashtra State Electricity Board) staff and detailed chemical analysis, calculation of calorific value is carried out and is confirmed whether it is as per agreement with the coal mines or not.General Problems faced in Coal Handling Plant :1. DesignProblems :-Coal received in power station is having cal. Value much less and ash percentage more thanthe rated values recommended by manufacturer. Hence the systems in coal handling plant get overloaded resulting inlow bunkering.2. Rainy Season Problems :Chute choke ups, Coal yard -Slurry Formation Transfer chutes gets choked up due towet or muddy coal. Slurry formed in coal yard may cause problems with electro-magnetic feeders at input points,frequent choke-ups at transfer chutes etc.3. Other Misc. Problems: • Snapping of belts /ropes : Conv. belts and ropeway ropes get damaged or brokenbecause of jerks and overloading problems due to various reasons. Repairing and replacement of these belts and ropesrequire more time for maint.• Derailment of coal wagons :De-railment of wagons result in obstacle in unloading of balance wagons in line.This results in lower bunkering and may attract demurrage charges from railway department.• Oversized coal/Muddy Coal :Oversized / muddy coal may cause damage to the belt system, frequent choke-upsof transfer chutes and damages to the crusher rings.DUSTMANAGEMENTATCOALHANDLINGPLANTOFA THERMALPOWERPLANT :-INTRODUCTION :- Coalfirethermal powerplantsare keysto power productionin thecountry.Theyplayvitalrolein power generationand distribution, and constitute 64.75%oftotalpower productionin India. Sincecoal is thebasicrawmaterialusedinsuch power plant,so they areequippedwithalargecoalhandling plant (CHP)wherecoaltransportedfrom coalminesare storedandprocessedbeforesendingto boilerand steamgenerationsection.ACHPmayalsobecalled a"coalhandling andpreparation plant"(CHPP).At this plant, major ergonomic concern is of dust particleswhich become airbornewhile coalstorage andprocessing. CHPrequirevery largeareaforcoal storageandprocessing, thereforelargescaledust generation occursatsuchplant.Peopleworkinghere becomevictimofPneumoconiosis whichisan occupational lung diseaseandarestrictive lung diseasecausedby theinhalation ofdust. Thus ergonomic design ofCHPisnecessary forbetterment ofworkersandauthority concern.SinceCHPrequire largeamount ofwaterfordustsuppression, therefore innovative methodshave to be designin order to minimizeuseofwater.Sincemany thermal power plant in India facing acute shortage of water, thereforeefficient methodofdustsuppressionand prevention ishighlyrecommendedwhichusesleast amountofwater.Thefollowing 7
  9. 9. paperdiscusses design ofadustcollectorwhichdischarges dustin concentrated form in order to reduce water consumption. ApartfromDustCollector, typical nozzledesign isalsoproposed which utilizes elegant divergingwaterspray fordustpreventionminimizing waterwastage.Dustsuppression playsvitalrolein improving performanceofworkers andtheirhealth, henceergonomic design ofCHPisveryimportant issue discussed at industry level, especially at ThermalPowerPlant. LayoutofaTypicalCoalFiredThermalPowerPlant The abovediagram typically outline a coal fire thermal power plantwhere coaltransported fromcoalminesthroughcoalvesselscalledwagonTripleris unloadedandcoalsiloisformed.Asclearlyoutlinethemajorregionofdustgenerationwhileperforming above operations results in large scale airborne particles which mustbe suppressed. We clearlydefinetheregionforwhichergonomicdesignshouldbeproposed.Thedustparticlesemanatingfromcoal are typicallyis of size 1 to 100 microns. A typicalNTPC plantrequires 4.4 cubic meters per megawatt per hour.DESIGNPROPOSALSFORDUST CONTROLATFIVEDIFFERENTSTAGESOF ATYPICALCHPOFA THERMALPOWER PLANT:- Design proposalsfor preventing and suppressingdustatCHPusingefficientmethods. Theabovefigureclearlydepictsthedesignproposal forpreventingandsuppressingdustat CHPusing efficient methods 8
  10. 10. and implementing cutting edge technology.Thegivendesignproposaltargetsfive differentstageswheredustgenerationisquitelarge.  STAGE1 Atthisstage,coaltransportedfromcoal minesis broughtatCHPusingWagonTriplerandunloadedtoreclaimer.Largeamountofdustisgeneratedandin order toprevent dust, moisture addition is mostefficienttechniqueaswaterisverypowerfulbinding solvent. Directlyadding moistureto coal prevents dustfrombecoming airborne.Herediverging nozzles areusedformoistureaddition.Divergingnozzlewillallowoptimumproportionateofwatertobeadded withcoal.Sinceitisnecessarytoknow exactlywhatamountofwatertobeaddedastoomuchwaterwill causemudandmakecoalheavier,ontheotherhand, toolittlewaterwillbeineffectiveindustcontrol.  STAGE2Here(reclaimerstage)coalisunloadedfromwagon Triplertobereclaimed. Theareawherereclaiming is done isquitelargeandhencewateraddition willbe futile.Alsowindplaydevastating roleinincreasing dust. Thuswind is themajorfactor.Sowindspeedi s c o n t r o l l e d inorderto preventdusttobecomeairborne.windshieldnetorwindbreakforest isprovidedinordertoreduce dust generation.  STAGE3Reclaimerpiles upthe coalatalargestorageareaand formsastackerorcoalpile.Whiledoing this,large amountofdustisgenerated. Alsocoalstackerisa constantsourceofairbornedustparticles.Therefore itisnecessary tosuppressdustgeneration.Atthis stagesurface compaction methodis usedtosuppress dust using 6-12% water solution of verygood binding substancewhichbindsthecoaldust and preventitfrom becomingairborne.Moisture additionisdoneatthisstageusingwelldesigned spraywhich allowscontrolledflow ofsolution overcoalpilein ordertoproperlysuppressdustwithoutaffectingthe qualityofcoal.  STAGE4Thisstageismajorareaofconcern becausedust particlesizeis aslow as1-10microns.Thereforethis stagerequiresasuitable,innovative andefficient technique of dust suppression. Since moisture additionisfutileexercise,thereforewedevelopwet dustcollectorwhichcanreducedustconcentrationaslowas1%intheconcernedarea.Dustcollectoris veryelegantdevicewhich discharges dustinconcentratedformreducingwaterconsumption.Even for suppressing1mm thick dust layer, we require largeamountofwater, but dust collectorwith minimumuseofwater,suppresses largeamountof dust. Thefollowingsectiondiscussesdesign ofwet centrifugaldust collectorwithautomatic discharg for suppressingdustat thisstage.Hereprocessedcoal istransferredfromcoalstackthrough conveyortorelaysection,hencelargeamountofdustisgenerated whichcanbe suppressedusingdustcollector.  STAGE5 9
  11. 11. Laststageisunloadingofcoalfromrelay section and transfer totheboilersection.Atthisstage,usual methodofmoistureaddition issufficientsincesmall amount of dust generates which can easily be suppressusingproperamountofmoistureaddition. Atthisstagealso,diverging nozzles ofoptimum diameterare used forproperwater spray.DESIGNOFAWETCENTRIFUGALDUST COLLECTOR :- Centrifugal collectors usecyclonicactiontoseparate dustparticlesfrom thegasstream.Inatypical cyclone, the dustgasstream enters atan angleandis spunrapidly.The centrifugalforce created bythe circular flowthrows the dust particles toward the wall ofthecyclone. Afterstrikingthe wall,these particlesfallintoahopperlocatedunderneath. Themostcommon typesofcentrifugal orinertial collectorsinusetodayare: 1) Single-cycloneseparators 2) CycloneMultiple-separators 3) SecondaryAir FlowSeparatorsAtypicalwet centrifugaldustcollectorusesscrubbing effect ofwatertosuppressdust.Waterisverygoodbinding substancefordust and therefore it is used as scrubbingelement.Thisdeviceappliestheprincipleoffilmformationoverthedustlayerandconfines dust particles leavingfreshairtoescape..Thepowerratingofmotorvariesasperrequirement. This deviceuses theprinciple of dynamicprecipitation techniqueinwhichveryhigh suction pressuresuck the dusty air and allow to centrifuge through it. Centrifugal actionseparates dustfromfreshairandfreshairisallowedtoescape fromotherendofdustcollector.The dust collector has a small tank full of water whichhastwovalves. Thesetwosprings loadedvalvesareoperatedtoallow passageofconcentrated dust andautomatic filling of fresh water usingsensors.Thesesensorssensetheconcentrationlevel ofdustinthecontainerand whenit goesbeyond 90%,itopensthedischargevalve.Thisremains open untiltotaldischarge ofconcentrated dust occurs fromthetank.Atthesametime,itopens inletvalveto allowfreshwaterto fillup.The dust collector uses automatic discharge technique andhencesavetimeformanualoperationsfordischarging andrefilling.Alsodischargeis recycledin order to haveminimumwaterwastage. Thiscentrifugaldustcollectorisvery efficientand requires minimum amount of water since it discharges dustin concentratedform. Taking atypicalcaseof aNTPC plantwhichuses 4.4cubic meterpermegawattperhour,assuming powerproductionof 1000MW, totalwaterconsumptionwill be4400 millioncubicmeterwater. Thisishuge amountofwaterwhich 10
  12. 12. isutilizedatsuchplant.But withtheabovementionedtechniques, if implemented properlycansavelargeamountofwaterandhence reducechancesofacutewater shortage.RESULTSANDDISCUSSION :-Awetcentrifugal dustcollectorwithautomatic discharge can reduceairborne dust particlesandminimizewaterwastage.Alsoothermethods ofdust collectionreducedustandwaterwastageasdiscussed earlier.Thishasgreatimpactnotonly atworkplace butalsoinenvironment. Properimplementation of dustsuppressionandpreventionmethodsreduces healthhazards ofworkers,employeesandpeople residingnearby.Sincecurrentsituationdemands eco- friendlymethodsofdustsuppression withoutmuch waterwastage,abovementionedergonomic designs arenoteworthy. 11
  13. 13. PRESENTED BY ROHIT KUMAR :- 111MN0521 JITEN KUMAR PAL :- 111MN0522 M. SHIVA SAI :- 111MN0523 N.SHASHANK :- 111MN0524 0