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1、tmukherjee@GangueinRawMaterialsfBlastFurnaces–ImplicationsSolutionsTMUKHERJEETataSteelLtdAbstractThepresenceofgangueinrawmaterialsgedtotheblastfurnacehasfarreachingimplications–rangingfromenvironmentalimpactofsteelmaking

2、tocapitalintensityofsteelmakingbusinessasawhole.Thiscomesaboutthroughtheeffectofgangueonproductivityenergyconsumptionoftheironsteelmakingprocesses.Beneficiationofironecoalpritoprocessingtheseinthehightemperatureironsteel

3、makingreactscanimprovetheeconomicsenergyefficiencydramatically.OvertheyearssignificantimprovementshavebeenrealizedinremovalofganguefromrawmaterialsatTataSteel.Ithasbeenpossibletolowerslagrateatblastfurnacesfromalevelof54

4、0kgthmtoabout270kgthmoverthelastthreedecades–withcommensurategainsinperfmanceofthesteelplant.AnenvironmentallogicfbeneficiationofrawmaterialsWhilelocalmaterialsthosewithinferipropertiescanbeprocessedthroughtheblastfurnac

5、erouteitmakessensetoreducetheganguecontentbefedoingso.Carryingganguethroughthehightemperaturesteelmakingthermalcyclehasahugeenvironmentalimpactwhencomparedwithbeneficiationofrawmaterialsatambienttemperaturebefesubjecting

6、ittotheironsteelmakingtemperatures.Thegangueaffectstheefficiencyenvironmentalimpactinamultitudeofways.Someoftheeffectsare:?Higherashincoalleadingtohigherashcontentofcokegedintotheblastfurnacesaffectsfuelrateatblastfurnac

7、esthrough(i)lowerstrengthofcoke–bothatroomtemperatureaswellasincreasedweakeningofcokethroughreactionofashcomponentscarbonathighertemperatures(ii)necessitytogehigheramountofflux–CaOMgOsourcesto“flux”theashtoafluidslagfrem

8、ovalfromtheblastfurnace.Thiscausestheslagrateatblastfurnacestobehighfurnaceproductivitytobelow–furtherincreasingdemoffuelpromotinga“downwardspiral”inperfmanceoftheblastfurnace.?Higheraluminainironefinesfsinteringleadstop

9、roductionofweaklessreduciblesinter.Theweakeningeffectofaluminainsinteringmatrixissoughttobecompensatedthroughincreasedheatinputinsintering–resultinginhigherFeOinsinterwithinferireductionproperties.Thisalsotranslatestohig

10、herfuelratelowerproductivityoftheblastfurnace.?Thehigherashincokehigheraluminainironeleadtoincreasedloadofaluminagangueintotheblastfurnace.Theslagvolumehastobesuitablyinflatedtokeepaluminaconcentrationinslagslagfluiditya

11、twkablelevels.Fexampleanaluminaloadof60kgthmwillcallfslagvolumeof375kgthmtokeepaluminaconcentrationat16%needstobeatleast300kgthmfwkingatslagaluminaof20%.Higherslagratecontributestolowerproductivityincreasedheatlosseshigh

12、erfuelrateinblastfurnaceironmaking.?Thehotmetalmadeathighfuelrateisacterizedbyhighersiliconphosphussulphurcontent.Whilethelattertwoarehighbecauseofincreaseduseoffuelconcerninthefaceofthelargescaleincreaseinsteelproductio

13、n.TheIndiansteelindustryinparticularneedstointensifyefftstoupgraderawmaterialstoreducecostsaswellasminimizestheenvironmentalimpact.SteelplantdesignbeneficiationofrawmaterialsThelowerproductivityhigherfuelratesintheironst

14、eelmakingprocessesdescribedaboveleadtolargeinefficienciesintheutilizationofthecapitalresourceaswell.Table2showsacomparisonoftwosteelplantsof3mtpacapacity–oneoperatingon‘goodrawmaterials’say10%coalash1%aluminainironetheot

15、heronrawmaterialswithhighergangue–say17%ashincoal2.5%aluminainirone–typicalofcurrentplantsinIndia.Itcanbeseenthatthefacilitiesallalongthesteelproductionchainneedtobesizedatleast30%larger.Thisnumberwouldtherefealsoreprese

16、nttheincreaseininvestmentcalledftocreateacertaincapacitytherebyloweringthecapitalefficiencybythisamount.Itcanbearguedthattheinferiqualityofliquidironcanundergopretreatmentsothatthesubsequentstagesareprotectedfromtheillef

17、fectsofganguecarryingontothelaststage.Thishoweverhaslimitedapplicability.Fexamplethehotmetalcontaining1.2%silicon0.3%phosphusneedstremendousamountofreactiontogetridofthesiliconphosphus–withaccompanyinglossesofirontempera

18、turewouldtypicallyneedtobehledinmeTable1EnergymaterialcostimplicationsofgangueHighganguerawmaterialsBestinclassRangeofoperatingcostimpact(withoutfixedcostimpactoflowerproductivity)Coalash%1710efinesalumina%2.51.0Specific

19、energyconsumption0.8GcaltcsrefUS$13t(coalbased)toUS$55t(oilbased)US$40to165millionf3mtpasteelplantFluxconsumptionironmakingsteelmaking70kgt50kgtrefrefUS$7tUS$21millionf3mtpasteelplantTable2Sizeoffacilitiesrequiredfproduc

20、tionof3mtpacrudesteelHighganguerawmaterialsBestinclassChangeinsizeoffacilitiesCoalash%1710efinesalumina%2.51Sinterproductivitytm2day2740Sinteringstrarearequirementm236525046%BFCokeratekgthm460350Coalhlingplantcapacitymtp

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