外文翻译中英文冲天炉炼铁Word文件下载.docx

外文翻译中英文冲天炉炼铁Word文件下载.docx

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冲天炉炼铁

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指导教师:

J.E.Rehder,President,MetkemProcessesLtd,Toronto,Canada

ITiswellknownthatironcanbemadebyheatingpelletsofmixedironoreandcarbon..Thereareconsiderableattractionstothisprocedureincludingtheuseoforefinesordusts,low-costreductioncarbonandpossibilityofoperatingeconomicallyatmoderateratesof50,000to300,000ton/year.Variousattemptshave,therefore,beenmadetofindacommerciallysuccessfulroute.Outlinedherearetheproblemandasolutionthatisworkingverywellatpilotplantscale.

Metallurgy

Thebasicprocedureistomakeacompactoffinelydividedironoxidewithenoughcarbontocompletelyreducetheoxidetometal,andthentoheatthiscompactuntilreactioniscomplete.Twocourseofaction,whichhavedifferentresults,arepossible.

Oneistoheattheore-carboncompactstosomewhatbelowtheirfusionpoint,tomakeaproductofsolidstatereducedironmixedwithgangueandcarbonash.Thiscanbedoneinarotarykiln,onatravelinggrateorinaverticalshaftfurnace,andconsiderabledevelopmentworkhasbeendoneonthefirsttwomethods.Theproductcanbeusedasblastfurnacefeedorcanbemeltedandrefinedtosteelinanarcfurnace.However,itisnowclearthatuseofreducedpelletsasblastfurnacefeeddoesnotgivethebesteconomics,andmeltingrefiningofsteelmustcontendwiththeaddedslagvolumeandsulfurbroughtinwiththereductioncarbon.

Theothercourseistoheatore-carbonpelletstoandthroughthefusionpointsofironandgangue,toproducehotmetalandmoltenslag.Thiscanandhasbeendoneinanarcfurnaceandinaninductionfurnace,butthemosteconomicalwayisinafuelfiredshaftfurnace.Thebestknownsuchfurnaceisacupola,suchasisusedinironfoundries.Whenore-carbonpelletsarechargedtoacupolathatisbeingoperatedundertherightconditions,hotmetalandslagarereadilyproducedandtappedwithexcellentrecovery.Thishasbeensuccessfullydoneduringadevelopmentprogram,andatonestagealeanorethatproduced2tonofslag/tonofhotmetalwas

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satisfactorilyhandled.Scrapironorsteelisreadilyincorporatedinthecharge.Thehotmetalproducedcanbeuseddirectlyinanironfoundryorconvertedtosteel.

Thecupola

Atthispointacleardistinctionmustbemadebetweenacupolaandablastfurnace.Oneisnotasmallorlargeversionoftheothersincethemodesofoperationandinternalconditionsarequitedifferent.Innormalpracticethecupolaisoperatedsolelyasaheatgeneratortomeltsolidchargematerial,whetheriron,bronzeorstone,anditdoesthiswiththehighestthermalefficiencyofanywidely-usedfuel-firedmeltingfurnace.Fuelcokeisburnedunderconditiontocreatethemaximumcarbondioxidecontentconsistentwithlowoxidationlossesofironandalloys.Thisisnormally11to13%andmeansthatmorethanintheblastfurnace.Thetopgasisleanbutisampleinheatcontenttorecuperativelyheatcombustionairtothemoderatedegreerequired.

Whenore-carbonpelletsarechargedtoacupola,aconsiderableamountsofcarbonmonoxideisgeneratedfromthereductionreactionsandenrichesthetopgas.Thetopgasalsoishigherinvolumeduetothecombustionoftheincreasedamountofcoketosupplylargeheatofreaction.Thenetresultis70,000to80,000cuftoftopgas/tonofhotmetalcontaining25to30%carbonmonoxide,whichgivesasurplusafterblastheatingofabout5MMBtu/tonofhotmetal.

Stockcolumnheightisrelativelylow,20to50ft,andresidencetimeis1.0to1.5hr.Blowingrateincfm/spftofshaftcrosssectionisaboutdoublethatintheblastfurnace,butpressureislowerduetotheshorterstockcolumnandahigherpermeability.Productionratesof4to5tonofhotmetal/sqft/dayappearpractical.Atthisstageitisnotknownhowlargethecupolacanbeeffectiveinthismanner.Thelargestexistingironmeltingcupolais12.5ftIDwhichcouldrepresent600tonofhotmetal/dayassmelter,butthereisevidenceofadead-manandsomequestionastowhetherthecupolamodeofcombustioncanbemaintainedinthisorlargercupolas.

Duetolowerblastpressurethecupolaoperatedasasmeltercanbetappedcontinuouslythroughasiphonifdesired.Thecupolaisalsoreadilyexternallywatercooledinthehightemperaturezone,andiseasilyshutdownforrepairaftera3to

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5-weekcampaign.Theseandotherfactorsindicatethatforexample,600tonofhotmetal/daywouldbemorepracticallyobtainedfromtwo8.8–ftdiacupolasthanfrom

oneof12.5ftdia.

Hotblastandoxygenenrichment

Useofhotblastsavescokeinlinearproportiontoairtemperatureandalsoincreasesproductionrate,butinironmeltingpracticeabout1200F（649C）isthemaximumused.Thisisprimarilyduetothecostofhighertemperatureairheatingequipment,butateveryhighairtemperaturethereisevidenceoflowercombustionefficiencytuyeres.Themaximumeconomicalairtemperatureforthesmeltingmodeofoperationisnotpresentlyknown.

Oxygenenrichmentofcombustionairiseffectiveindecreasingcokeconsumptioninironmeltingandinsmelting.Theeconomy,ofcourse,dependonlocalpricesofoxygenandofcoke.

Bothhotblastandoxygenenrichmentareeffectivethroughincreaseinflame（i.e,maximumbed）temperature,andthisissubjecttodifferentconstraintsinthecupolaandintheblastfurnace.Theproductionofincreasedreducinggasbyusingtuyereinjectedfuelisuselessinthecupola,sincetheobjectiveisacombinationofmaximumbedtemperaturewithmaximumheatproduction.

Agglomeration

Strengthrequirementofore-carboncompactsforacupolaaremuchlessseverethanforblastfurnacepellets,sincethestockcolumnisshorterandinmanycasesthecompactscanbemadeatthecupolasitesothathandlingisminimal.

Pelletizing,extrusionandbriquettinghaveallbeenused,andbindersarecarbonates,silicatesorasphalt.Theprincipallimitationisthatthecompacts,ofcourse,cannotbeheatedforhardeningabovetheignitiontemperatureofthecontainedcarbon,unlessautoclaved.Thereareseveralsystemsavailableandthesewillnotbereviewedhere.

Economicsanduses

Thereisnoquestionthatsmeltingofore-carboncompactsinacupolaisnotexpectedtobeeconomicallycompetitivewiththeblastfurnace,ortooperateinor

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nearitsproductionratesandsizeranges.However,theredoesseemtobeaplaceformoderatetonnagesinsuitablesupplysituations.

Ore-supply

Supplyofironorefinescanbeaneconomicproblemsincetheironoreindustryisorganizedtoprovidepelletsorlumporeinlargequantity,andobtaining150,000ton/yearofcleanconcentrateforexamplecouldencounterhighfreightcosts.Millwastes,suchasblastfurnacedustandmillscale,can,however,bereadilyhandledandareinreasonablequantity.Thereisbasisforthinkingthatsuchwastescanbeturnedintohotmetalatlowercapitalandoperatingcostinthecupola,thanbyprocessingoverasinterstrandandthroughablastfurnace.Anaddedfactorhereisthatvolatileelements,suchaszinc,shouldbemorereadilyhandledinthecupolathanintheblastfurnace.

Coke

Itisessentialtotheeconomyofcupolaoperationtousecokeofreasonablelargelumpsize,thisbeingoneofseveraldifferencesfromblastfurnaceoperation.Ifacupolaisusedtosmeltmillwastesinornearasteelplant,theeconomiccourseistousetheoversizecokefromthecokeplantprimaryscreenorgrizzly,sincethisavoidsthecostofcrushingtoblastfurnacesize,andtheproductionofhotmetal/tonofcokeishigherthanfromablastfurnace.

Ifthecupolaisusedseparatelyfromasteelplantandsuchcokeisnotavailable,foundrycokemustbeusedbutatconsiderablyhigherprice.Lumpanthracitecanbeusedtoreplaceaportionofthecokecharge,andbriquettedcalcinedpetroleumcokeisanexcellentcupolafuel.

Reductioncarbon

Thedesirablepropertiesofthecarbontobemixedwiththeorearehighfixedcarboncontent,goodreactivity,andlowsulfurashandvolatilemattercontents.Thesecanbemetbyaconsiderablevarietyofrelativelylowcostcarbons,andthisisaprinciplereasonforgoodeconomicsinsmeltingore-carboncompactsinthecupola.Thetotalfixedcarbonrequired/tonofhotmetalwillbeintheorderof1250to15001b,but40to45%ofthisdoesnotrequiretobecokedorcokeable.

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Uses

Therearethreeareaswherecupolamodesmeltingcanbeeconomicallyinteresting.Thesearetreatingmilloxidewastes,providinghotmetalfordirectuseinironfoundriesandforministeelmillsbasedonsmalloxygenvessels.

Processingofmillwastesisimmediatelyinterestingbecauseofthereadysupplyofrawmaterials,thereisactivityinmorethanonelocationindevelopingthisroute.Thecostadvantagewill,ofcourse,varywithlocalconditions,suchaswhetheranexistingsinterplantisoverloaded,wornoutorrequiringextensivenewairpollutioncontrol.

Hotmetalformediumsizeandlargeironfoundriescanshoweverygoodeconomicsfromironore,themainuncertainlyatthepresenttimebeingtheavailabilityandcostofironorefines.Thisdependsonlocationandontheinterestofironoresuppliersinsuchamarket.Therewouldappeartobeopportunityforaconsiderableindependentbusinessinthemanufactureandsaleofore-carbonpelletsorcompacts.

Operationofaministeelmilloranoxygenvesselsuppliedbyhotmetalfromacupolacanbeeconomicdependingonlocalprices.Afeasibilitystudyona300,000ton/yearmillusinga35-tonves