p o t e n t l a l l yh a z a r d o u s The main deveLopmentof cokernakingtook place ln t h e m t h u s a v o i d i n g i h e to combustlonls onry pollulion. heat consequent The its Lrse In Englancland Germany, most lmportantly process and the ba ance partialLy the utillzed dlring lhe blast lurnace facilitaied iron melling at hLgher for energy gas galnfully utilized waste flue heat ln temperatures.Cokemaklngbegan with the crlarcoal generation. pile.The methodol coke productionwas initiallythe same as lor the production of charcoal, stockpillng oi coal n round heaps, igniling the plles, and lhen Sesa Goa Lld., in India has a 280,000TPA coke covering wilh sides with clay. This laid the iounda- pant in Goa, India.The coke pant comprising84 lion for beehivecokemaking GraduallyinnovatLve ovens are oi nonrecoverytype (2745 wldth, 10760 advances led to the deve opmenl oi the beehive, Length),21 ovens connecledio a slack The ovens reverberaioryand byproductovens, culminatlnglnto with lop charging and are operatingsatisiactorilyto coke oven with byproduclsa centuryago regenerative produce high qualiiy mei coke slnce 1999 Over ihe have the USA years severalln-ho!se modilications/innovations Slot ovens were evoved in Pitlsburghln lllve edgF. corpe md'nlal_ ils chem cals Io been rnlroduced primarllydue to the need to recover coa and coke oven gas ior lighting.In facl the coal The sesa coke plani ls presenty being retroitled wilh chemicalswere lhe man productsthen wlth coKe compactedchargingdeveopedby Vecon of Germany. as a byproduct oi coal carbonization. By prodllci Thls slate-of-the-artcoal compactionfacilly capable recoverycoke ovens remaineddom nant cokemaklng of obtaining a stable coal cake wlth bulk density > cokemaklnglecrlnology 1.1 t/m3 will be commissioned soon With this roule reachingsiate-oJ-1he-art in lhe lale 70. significantanrountoi cheaper seml soit coal will flnd way into Sesa coal blend and would brlng down the gasesevolvedduringthe met coke productioncost signiiicantly ln byproductcokemaking, in lhe carbonizaton are cooled, and various primarychemi- Continua developmenl at Sesa has resulled ph!rizaiion cals llke ammonia,lar and benzol are recoveled- latest deveLopmentoi Sesa In situ Desu compacleo Puriiied coke oven gas is used al various locations (SlD) technoLogycustomjzed wrtrl only capable of ls not technology The SID ovens, charging. of coke plant, flrlng such as n lhe steel hrri in the rehealing iurnaces etc. The coking ls carried out in reducing SOx emissions by 65 75% 1% The less lhan slot ovens.whlch are also designatedas convenllonal process restrict burnng loss lo ot capacity ln the coke ovens. This has been the lraditionalmethod of added advantage ls the reduclion Llnlt. externaldesulphurizaUon cokemaking n the lntegrated iron and sleel works to I the SOx emission long,3 minimize 18 meter iurther Eiforls are on to Byproductovens are 12 lo Ls chamdesulphurlzatLon Several external wide level where level to a meier tall and 400 10 600 mm the sharpened has furiher and a slngle The SID baltery wilh. dispensed bers are grouped to lorm one -Ihe culling eclge oi SER cokemaking technology baitery nray cons st uP 10 85 ovens ienrle:Iu-.s o' SER-SlDCorenakirg aro given'n Until recently,the value oi these byproduclsexceeoed sa Table 1. that oi lhe coke. However,the advent ol petroleum Inslalledon a reflning has driven the price oi these chemicals to A 30 l/W power plant is also being go on stream In the such a low level that ioday ihe byproducl plant ol BOO basis and ls expected to coke ovens is no more lhan a major pollutingsource last quaner ot 2006. The block ilow diagram ol Sesa Energy Recovery ln lhe integratedsieel plant. Coke productionwith cogenerationof electrLcpower Nonrecovery CokemakinE is depicted in Figure 1 In the nonrecoverycokemakingprobess,volaliles son between Conventional Slot Ovens & evolved during coal carbonizalion,are not recovered Cotnpa Energy BecoverY Ovens as by-productsbul are combusledcompletelyin pres- Sesa ence oi controlledquantityoi air and the heal of lhe Comparisonoi conveniionalbyproductrecoverysloi coKe oven volatiles oi evolving gases is utillzed for coking the oven battery and Sesa enelgy recovery coal consideraiions, ihe design coal mass into coke and thus no external heating is baitery underlying quality, emlsslon coke resultant required.The higher level of heat imporianllyis used qlralty usage & is presented in the 10 break lrp ihe potenliallypollutinghydrocarbonsInto levels wiih cost conslderations lhat the Sesa shows paragraphs cleariy the constituentcombusliblecompoLlndsand to burn following )
Tablel Salient features of Sesa Cokemaking
Oven Desiqn Refractory CoalCharging Heat Recovery Emissions SPM SOx
Simple, studier HighAlumina Compacted, Veoondesign Highest;hot foundationair re-circulalion < 50 mg/Nm3 < 450 mg/Nm3 < 115/50 mg/Nm3 (ln-situ desulf Genl/Gen2) < 75 mg/Nm3 Nil Absenl Low due lo simple design & alumina bricks
NOx @
H/C Operation& Maintenance cost Coalqualityusage StandardN4odule ECO Friendliness
Wide flexibility,up to 60% semi soft coals 300,000TPA Veryhighlevel
:igurel Block Flow OiagramSesa EnergyRecoveryCoke Ovenswith HeatRecoverypower plant
(up ro 60ol" somi sofr coars)
Flow
E'iagrarn
Steel & Metallurgy
of SESA
'
, 1
Energy
Recovery
Metacoke
Production
rId slot pressureeffects. lt is worthwhileio elaboratethis has a distinctedgeoverconvenlional technology ooinl in qrealerdetailsas lo whv Sesa ovensofier ovens. greaterrl-exrbrliiy lo'aw malerialbase {widercoal Design Considerctions qualityspectrum). Sesa Ovens due to its semicirculardome are height,less ovensotferedby compet- Sesa ovensoperatewith very low bed slurdierthan nonrecovery and thus ovens to slot The seleclionof Iiteclayalumlna than a meler,as compared ino technoloqies. side walls pressllre on swelling reiracloryb akworklhal has evolvedafterellensive problemsencountered by aboul pressure is lower The sidewall siie trials has a potentialto improvesigniJicanlly is negligible. for Sesa ovens as comparedto than times 6.5 batteries oven to coke longevityof ovenscompaled sloi ovens which are designedto coke conventional calegoryas wellas convenlional in nonrecovery Table 2
Designconsideralionsconvenlionalvis-a_vis SESACokemaking Sesa Ovens Simple Ovenswiderthanialler Few brickshapes SlightlyNegative Slighily Positive Internallyby partialcombuslionol ExternallybY combustionoi evoMnggases gas CO/BF/mixed Radialion& HeatTransferDirection& Mode Horizontal& IndirectconductionVertical& Direct lrom top. Indirect: convection kom the bottom/sole Conduclion Not suscePtible Susceptible
Parameter Design Shape Brickwork OperalingPressure HeatSupply
ConventionalSlol Ovens Complicated Ovenstallerthanwider Larqenumberof brickshapes
pressure.In case of Sesa psi oven batteries.The otherparamelersol companson tolerate1.0/1.5 wall to less than 0 2 parameter amounts this Ovens are presentedin Table 2. of mei coalthai they psi.Thereare certaincategories The basicchangesin the Sesa designconsistsof qiveexcellenlcokebui theyexerlwallpressuremore improvementin oven lefractorymaterials,closer ihan the permissibledesignedlimit which means conirolof combustionconditionslhroughcontrolled conventional ot ovensare deprivedof the possibility level and at primaryair inpui to, sub-stoichiometric procluclng for characterized coals using lhese underflues/soleflues as secondaryair and tertlary excellentmet coke. Moreovernowall pressure'no air in the commonheade/flue to ensurecomplete siickersi combustionwithoutexcessivelydilutingthe heat in to give The byproductcokeovensare characterized the flue. highercoke yield as lhere is no burningloss HowCoal Quality Usage & Coke Chatacteristtcs ever,burningloss of - 37" is partiallycompensated producehighqualitycokeas long by increasecolresponding Bothlhe processes electricpowergeneration' as appropriaiecoal blendsare used, thoughSesa Table3 illustrates meritsand demeritsrelaledto coal cokeovensproducesuperiorqualityof cokefor the blend usageand resultantcoke qualityoi the two sameblendin termsof coldand hot strengthproper technologies. lies becauseof highercokinqiemperature,longer rankcoals Envi ronmen tal Consi dention s soakingtimeabilityto use lowvolalile_high recoveryovens,Sesa in the blend and greaterpresenceol pyrolytic Likeany olher nonrecovery/heat pressure whichmeans operaiesunderslightnegative calbon. is no genThere from the oven doors. Sesa Ovensbeingmuchwiderthan slot ovens,the no leakages coke ovens unlikeconventional swellingpressureis releasedfrom lhe lop whichin erationoi etfluentsgas puriiication in the byproduct on whereincokeoven caseof narrowslotovensis exerleddangerously effluents quantilies generates huge plants recovery the heatingwalls and thus free from any wall
Table3 vis--a-visSESACokemaking Conventional Coal & CokeQuality Parametel CoalQualityUsage CokeQualaty CokeYield Temperalure Carbonization
ConventionalSlot Ovens Rest cted to thatlrom Lowercompared sesa cokeovens Higherthan Sesacokeovens by 3-5% -Max achievabletemperaturelower thanSesaovens
Sesa Ovens Wideflexibility nrgnercorr|Parcu LUu rdt
fromconventionalovens Lowerdueto bumingloss. Canbe limitedto 3% bY properProcesscontrol Maxachievable higherthanin temperature Byproductslot ovens
oven.battery.requireslarge investmentin that needeffluenttreatment/BOD Plant. Solidwastes Byproduct pioviding^polutioncontol equipmentsto make it "r" t t"rfv uu""nt u" tf'ere is no processiniir 6ruds compalible
ffff;#iilil;i;i'lt'
g*!i"i*
t ,,Lt"r"dse environmentallv
oP*ation o,f ovens Sesa ovensare operatedat sufficientlyhightem peraSimplicityoJ operationand absenceof complicated ' i*"" to-flu"nt "ti""ions of PAH whiah are fully the cokeplanbased neaiing;egimecharacterislic.of ano combusted brokendowninto its components
between-surr::: version, charsins Incompacted s_ap i"1y".;t;:i.::i"fr"Tli,:TT;j?:tl"ffitd;#:: dc oven of the bottom of coal cake and tess.manpower' grsning ot airanJ"Jpsiifi! sionilicantlv thusavoids milimerers consideations cost anj blo;ng upof theoven;in" nvJ.uri"regime fh" Jh"rgi"g oicoal cake does ;ot involve leveling
Capitalcost oI Sesa coke oven batteryis significantly
Table 4 Environmental Considerations Conventional vis-a-vis SESA Cokemaking
ConvenlionalSlot Ovens Higherlorlowcapacities LandRequkement riendly -vironnrentunf Environmental to make investment Large pollution control for Investment comPliant environmentallv devr@s in SludgeGeneration Solidwaste bv prcducts Excessivegeneration Efttuents Present Emissions Present /Pushing Fugitive Charging Present Carcinogens exceptPoven Noncompliant USEPAregulalion
Parameter
and fugitiveemissionsthereof Flat bed hot coke ca/quenchingcar inbuiltin the Sesa technologyminimizespushingemissionsas coke glidesin to the hot coke car on incandescent level and there is no fall of coke from a the same to 7 melersas in case of tall ovens' heightof up High tevelof superiorityol Sesa coke ovens as comoa;ed to slot oven battedeswhich operateunder in Table4 positivepressureis highlighted
Sesa Ovens Lowerfor lowcapacities Environmentfriendly investment Noadditional No solidwaste Noetlluents Absent Absent Absent Compliant
lower comDaredto that of conventionalbyproduct recoverycoke oven battery for the given coke capacity.This is mainlydue to simpledesign,fewer shapesof refractorybdcks, no complexgas networK and absenceof byproductrecoveryfacilities-Needless to mentioninstallationlime is almost60% ot cokeoven& byproduct that requiredfor conventional complex. While initialinvestmentfor Sesa EnergyRecovery
Table 5 Cost ConsiderationsConventionalvis-a-vis SESACokemaking
Parameter Capitalcosl Operatlng cost Construction Commssronng Products Co product Byproduct
ivlanpower N,4ainiainabilily
ConventionalSlot Ovens Capitalintensive
High Highenergyrequrrement servicesrequired l\,4ore Longerperiod Slow IVlut ple-products CokeOvengas Primarycoalchemcalslike crudetat,benzolrequitesf!rther processing unlessusedas fueL, ammonumsulphateas byproducts Skilled Only hot Tralntenance
Sesa Ovens Lowinveslment Lowenergyrequirernent Lessseruces required Shortperiod ast Two:Coke& power Steam/eleclricity Nil
Notso skilled
down Easyby cooling
the heatingchambers HealingFlues'linking of inslalled coke CokeOvensis aroundRs 5000/ionne gas in case of slol firing is burned the under capacty,subjeclto site condtions,extenlof rnecha- where as mennoned ation and convection nizatlonand automalionelc., the same lor compa- ovenswhileby rad ovens. facilitiesis to the tune alrovetor energyrecovery rabe capaciiycokeproduclion of Fls 10000. Thus selectionln favourof Sesa Treatmentoi productsof carbonzallon/ lechnologyotfersmarkedadvanlagein coklng,particually raw coke oven gas that Involves Cokemaking investmenl costl coolingin byproductrecoveryovensas a lechnologi lowerat lessthan ca necessity. Energyrecoveryovenson the other Operatingcosi is alsosignliicantly involvingseveral Rs 200 per tonneof coke for Sesa cokemaking handdo not requileunil operauons, slages. of utilitiessuchas electric- puriflcation tacilltiesas consumptlon ily ls 4 to 5 time lower (7 as aganst -33 kwh for The coolingof raw COG al around 800 deg C in lessman- the hydraulic ovens),no steamrequiremenl, conventional ln the down mainsand subsequently tactors slreambyproductgas cleaningplantto 35 deg C or power requirement. Table 5 enumerales for lowercost oi ihe Sesaovens. responsible belowleadsio a loss of over 30% oi heat nputlor byproduct ihroughconventional Enetgy Elliciency met cokeproduclion generally shown n not This is coke ovens. recovery batchpro.essand The cokingis a hightemperature as given sha4^yoagrar compdrisor oalance " o l o r . o s ' o ' F a v i n g L'e'eal ooo' sre s u c h p r o c e s s ea 1o 67 heat is equivalent This loss oi ln Fig 2. thermalefficiencies.In orderto examineenergyconol iwice the consumption which is sumplionil is possibleio dlvidethe processintolhree kwh/i oi energy oven coke slot oven distinctparts ior conventionalbyproductrecovery electricityin conventional comp!exl ' reac- The heai balanceof byproducirecoverycoke oven Cokingchamber-wherecarbonization proper tionstakep ace.The reactlonsare themallyneutral/ shownin Figure2 ls for ihe cokeovenbattery gas the raw slightlyexothermic;they requirereactantto lle at that is silenton heat lost in cooling This While therrnaletficiencyis apparentlyis 80%, the in orderthaltheymayproceed. highlemperature heat throughthe actualefficiencyis below50% for coke ovenswlh is achievedmainlyby transferring reiractorywallsof the cokingchambersin slot oven dry cokequenchlngfacilitieswheresensibleheatoi ovensheatlransferls raw gas is not recoveredas waste heat recovery while in case of nonrecovery and systemwhichis seldomdone.The themal efficiency irom the underflues achievedby conduction is greaterlhan gasesundergorng combu$lon of Sesaenergyrecoverycokemaking tadiation& convection
Figure2 HeatBalanceConventionalvis a-vis SESACokemaking
Combustion of Evolvng gas
LJnder FiringGas Heatof Reaction 2479
8653 2oo tt"rt ot errn-off 987
MJ / tonneof caalcharge F l u eG a s 352
Coke 1311
151 Raw COG 829
SuafaceLoss 1324 Coke 1214
Conventional Byproduct CokeOven
COFG 7463
SESAEnergyRecovery CokeOven
85%, il sensibe heat is extracledfor steam/power tradethroughCleanDevelopment (CDM) lvlechanism generation and 70"k il heal lost in the stackgas whichis expected to rakeUS $ 5-10bilionovera periodot time. Waste heat recoveryirom the flue afterboileris accountedfor. Carbon Credits & Sesa Enetgy Recovery Coke gas generatedlrom Sesa EnergyRecoveryCoke Ovensqualifiesthe requirement ot Kyotoprotoco. gone aheadfor regislrationof its waste Amonggrowingconcernand increasingawareness Sesa has on the need for pollulionconirol,the concepl oi heat recoverybasedon powerplantwhichis under on BOO basisas CDN4project. carboncreditscame into vogueas a part oi Kyoto construction Proiocol.Carboncreditsare certificatesissuedto Possibility of intrcduction of Sesa coke ovens in countriesthat reduceemissionof GHG (greenhouse ISE Addrcssing Gas Balance gases)whichcauseglobalwarming.Indiais signa- Havingestablished supe ority by analyzingdifferent tory to lhis presligiolsinternational agreement. lechno-commerdaF iinancial factorsenumerated in the Carboncreditsare soldin globalmarketto the coun- lorgoingparagraphs wiih illustrations selectionfor the tries that meet their emissionlargets and provide best availabletechnology(BAT)undoubtedly zeroed financialincentives. to SesaCokemaking withcompacted charging-HowOne creditis equivalentto one tonneof CO, emis, ever, two factors, namely gas balanceof the sionsreducedand are availablefor establishments integraledsteelplant(lSP)and landrequkement for engagedin developing needs10be addressed. renewable energy,wasteheai coke plantinstallalion uiilizationthat ollsetthe use of fossilfuel. In coun- The SesaEnergyRecoveryCokemaking technology trieslike Indja,GHG emissionis much.below the has a potentialfor ils iniroduction in ISP wherecontarget fixed by Kyoto Protocol and so they are ventionalbyproductcoke ovensare due for rebuildexcludedfrom reductionof GHG emission.On the ing, the existingcoke productioncapacityis to be conhary they are entilledto sell surpluscreditslo enhanced,or new steelmaking capacityis contemdevelopedcounlries. India is considereoas rne plated.This also presupposesstrlct environmental largestbeneiiciary, about317" of lhe world carbon complrance norms, Steâ&#x201A;Źl & Metallu.gy
,
,
)
Figure3 EnergyDistdbutionr TypicalISP
Powerplant 2%
Others 4%
CC & Platemills 7% Sinterplant 100/o
B.F 470/"
S M S& Rollingmills 140/.
CokeOvens 16% plant. lt needsto be and is being recognizedthat Gas Balance of ISP plant is not a fuel gas (coke oven gas) technology coke Sesacokemaking In orderto incorporate producerbut its core functionis to producehigh it is quality as part ot ISP to meet BF coke requirements met cokefor blastfurnaceiron making-The considerednecessaryto analyzeenergyconsump- specificenergyconsumptionin ihe integratedsteel of energy plantsis rangingfromoverB to as lowas 4.5-5Gcal/ tion ot the lSP. A typicaldistribution pafternin ditferentprocessesof steel- tonneof crudesleel {tcs) . consumption makingof the ISP up lo the salablefinishedsteel The bestoperaledlSPsin IndialikeBhilaiSteelPlant productsfrom coke,sinterand hot metalproduclion of Steel Authorityof India and Tala Steel have through blast furnaceroute depictedin Figuie 3 reportedspecificenergyconsumptionless than 7 shows that conventionalbyproduct recovery Gcal^cs. In the primaryzone of ISP coke, sinter accounttor a sizableamountof 16%of and blast furnace accountsfor 70-75"/.oi lolal cokemaking overallenergyconsumPtion. per tonneo{ crudesleel. energyconsumption The coke oven and byproductplant is not only for A shop-wisedistribution of totalenergyconsumption productionof high-grademet coke but also to of typical ISP with facilitieslike BOF , continuous producecokeovengas (COG),a highcalorificvalue casting,hot stripmilland coldrollingmillsetc shown gaseousfuel,is requiredto meetthe energyrequrre- in Figure 4 also gives the breakupof type of ments of down stream units ol steelmakingand energy:gaseousfuel and electrical/ steam. rollingmills is the commonbeliefof lSPs nuriured The gaseousfuel (CO,BF and LD gas)accountsfor overlhe years. for steelmaking 327"of specificenergyconsumption Recognizing the importanceof energy,introduction and downstream rollingmills,out of whichlesslhan of energyreductionmeasurescouplednewtechnolo- half or about 15% of total energyconsumptionis in contribuledby CO gas. The enerqycontribuledby gies/innovations; lhe specificenergyconsumption lhe lSPs is constantlywitnessinga downwardtrend. CO gas amountsto 0.212Gcal/tcsor around4% of in ISP The energyrequirement This opportunity ofiersto changethe mindsetof the energyconsumption of does not callfor inslallation the role ol coke of lhis order certainly makers in lSPs towards decision stoor & Motâ&#x201A;Źrlursylmmi.
E::lhl
Figure4 Area wise Ene.gyconsumptionin IntegratedSteel plant
l I
I
r _ cc
I
HStu
I CRM
- r _ ] , MM
high capital-intensive conventionalBR coKeovens The SesaEnergyBecoveryCokemaking Technology characterized by their poor thermalefliciency.The with coal compactjonis a state-of-the-art technology alteanative is coal gasificatjon or naturalgas to meel lhat ofiersimmensepotentialfor usingcheaperseml the gaseousfuejof 3OO0+ calorificvaluerequirement sott coalsthat go in blendformulaljonfor produciion for enrichingthe BF and LD gas for reheating of high qualitycoke cosl competitively. lurnacesof the rollingmills,sinierplantetc. The recentdevelopment of in-situdesulphurization Lancl Bequircment surpassesthe contemporarycompetjtivecoke It is commonlybelievedthat Sesaovensbeingmuch production lechnologies by nonrecovery methodsand widerwouldoccupysignificanily morespacefor their is ideallysuitedfor environmentally consciouslsps. installaiion.This statementappearsto be in order Sesa cokemakingtechnologyhas a potentialfor its unlessanalyzedjn depth.Coalreceipt,coal prepara_ introduction in the integrated kon & Sieelplanrswhere tion,cokehandlingfacilitieshavesamelandrequire, convenijonal byproductcoke ovens are due for ment for both the technologjes.The land required rebuildingor the existingcokeproduclioncapacityis tor widerovensoffsetthe spacerequired for byproduct to be enhanced. Coke oven gas (COG),a high gas purificalion plant and downstream chemical calorificgas thai is presenty being used to meet processingunits,and BOD plant. lhe energyrequirements of downstreamunjtsof steel The preliminary studylor one of our prospective lSp maKngmay swilchoverto the use oI naturalgas or customersptanningto sel up a state-of_the_art steel to someextentgasesfromthe coalgasitiersdepend_ plantof 2.5 I\,,1T crudesteelcapacitiesconfirmedthat ing on the specificlocalconditions. land/spaceearmarkedfor 7 meter tall coke oven batterywith byproduclplant is adequatefor setting With simple& robustoven design,simplicityoi up a coke ptant based on Sesa cokemaking operanon,aosenceto complicaiedheatingsystem as in conventional batleries, environmenuriendliness, technology withprovisionfor futureexpansron. significanicapitalcost advantageand alsothe tower Havingaddressedall the faclors for selectionof operating comparedto conventional byproduct recov_ appropnate technology for metcokeproduction of high ery coke ovenswho would deny that Sesa Energy qualitysiageis set for the introduciion of cokeplants Recovery CokemakingTechnologyis all set to basedon SesaEnergyRecoverytechnology. challengethe convenlionalcokemakingif lsp gas Conclusion balanceand lanorequirement ts addressedin proper lncreasingly stringent environmental regulations wortd_ perspective?What is requiredis changejn mind wide have made il imperativefor any fulurecapital set and out-of-boxthing and the process in this investmenlin cokemaking 10take ihesefacrorsrnro dkectionhas startedl consideraiion ihai has swungthe thinkingjn favour Summingup, can the questionpui up in the tile oi of the more environment-friendly energy recovery the paper be answeredaffirmatively?Technology cokemaktng processes. oplionis available,cokemakers to decide. r stsot a meiarurgyEEllEdEEtilil!\
J