石油焦基本知识汇总Word文档格式.docx
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石油焦基本知识汇总Word文档格式.docx
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Theresidueremainingwhenallofthecokeisburnedoff.Itismostlymetalsandsilica.
Calcineablecoke
Petroleumcokethatqualifiestobecalcined,i.e.,generallynonshotandlowinmetalsthatwillqualifyforanodegrade.Calcineablecokeisgenerallyreferredtoastheavailablesupplytocalciners.Alsoknownasgreencoke(seesame).
Calcinedcoke
Petroleumcokeorgreencoke(seesame)thathasbeenprocessedinacalciner(seesame)
Calciner
Alargerotarykiln(similartoacementkiln)thatdrivesoffthemoistureandvolatilityofgreenorcalcineablecoke(seeeach)sothatthecokecanbeusedforaluminumanodes,ortitaniumdioxideapplications.Thekilnreceivesthecokeatthehigherendwherethecokeflowsdownhillasthekilnrotates.Atthesametimeheatedaircounterflowsuphillfromthelowerend,drivingoffthemoistureandvolatilematerial
Carbonrejection
Crudeoilcontainsawidevarietyofhydrocarbonmolecules,rangingfromasinglecarbonatom(methane)toverylongchainmolecules.Thelightermoleculesthatmakeupgasoline,jetanddieselcontainalowerratioofcarbontohydrogenthantheheaviermolecules.Inordertoconverttheheaviermoleculestolighterproducts,theheaviermoleculesmustnotonlybecracked,buttheexcesscarbonmustberemovedtoreducethecarbontohydrogenratioofthecrackedmaterial.
CirculatingFluidizedBed(CFB)Boiler
Atypeofboilerwherethesolidfuelisfluidizedinaverticalfurnace.Theadvantageforthepetcokeindustryisthat100%veryhighsulfurcokecanbeburned.Thesulfurisremovedbyadditionoflimestoneinthebedwhichformsaneasilyremovablecalciumsulfateash.
Coker
Arefineryprocessingunitthatconvertstheresidualoilfromthecrudeunitvacuumoratmosphericcolumnintogasoilthatcanbemadeintolightproducts(gasoline,jetanddiesel),weak(i.e.,lowenergycontent)fuelgasandpetcoke.Thereare3types:
Delayed,Fluid,andFlexi(seeeach).Theseareallbasicallycarbonrejectionschemes(seesame).
Delayedcoker
Atypeofcokerwhoseprocessconsistsofheatingtheresidualoilfeedtoitsthermalcrackingtemperatureinamultiparallelpassfurnace.Thiscracksthelongchainheavycarbonandhydrogenmoleculesoftheresidualoilintocokergasoilandpetcoke.Bothareinaliquefiedforminthemixtureasitleavesthefurnaceandentersthecokedrum.
Inthedrum,thecokergasoilvaporizesandseparatesfromthemixture.Itisdirectedtoafractionationcolumnwhereitisseparatedintothedesirableboilingpointfractions.Theliquidcokesolidifiesinthedrumasitcoolsandthevelocityslowsdown.
Afterthedrumisfullofthesolidifiedcoke,thehotmixturefromthefurnaceisswitchedtoaseconddrum.Whiletheseconddrumisfilling,thefulldrumissteamedtofurtherreducehydrocarboncontentofthepetcoke,andthenwaterquenchedtocoolit.Thetopandbottomheadsofthefullcokedrumareremoved,andthesolidpetcokeisthencutfromthecokedrumwithahighpressurewaternozzle,whereitfallsintoapitforreclamationtostorage.
Largercokershaveseveralpairsoftandemdrums.
Demurrage
Contractsforrailcars,trucksandmarineshipsalwaysincludeaspecifiedtimelimitthattherespectivevehicleorshipwilltaketounloadorload.Thepenaltyfordelayingbeyondthetimeallowedisalsospecifiedineachcontract.Uponcompletionoftheactualloadorunload,thevehicleorshipownerpresentsthecustomerwithademurragebillspecifyingthetimedelaybeyondtheallowance,reasonsforitandthe$penalty.
Drymetricorshortton
Aunitofmeasureforbillingpetcokeweight,whichreferstothegrosscokeweightadjustedforexcludingthecontainedmoisturecontent.Togetthismeasure,thecokemustbetestedformoisturecontent(seesame).Calcineablecoke(Seesame)isfrequentlymeasuredintheseunits.AlsoseeWetmetricton.
Energycontent
TheenergycontentofcoalandcokeisusuallyspecifiedineitherBTU/lborKcal/kg.Itismeasuredinacalorimeterthatliterallyignitesthetestsampleandmeasuresthetemperatureriseofthewaterbathsurroundingit.
Flexicoker
Theflexicokeraddsathirdvessel,agasifier,tothefluidcokertogasifythepurgecokeintoaweakfuelgas.Cokeismadein3areas:
purgecokefromtheheater,andbothlargerandsmallerrecoveredcokefinesfromtheweakgasscrubbers.Itisa“flexible”cokerinthatthegasifiercanberuntomakeeithermorecokeormoreweakfuelgas.
FluidCoker
Afluidcokerproducesmorelightproductyieldandlesscokebutthecokeishigherinmetalsandharderthanadelayedcoker.Theprocessisacontinuousfluidizedbedconsistingofareactorandaburnervessel.Feedissprayedontoseedpelletsofcokeinthereactorwhereitiscoked.Purgecokeisdrawnofftheburnervessel.
Fuelgradecoke
Petcokethatcompeteswithsteamcoalasfuelforafurnace,boilerorcementkiln.Ifthecokecontainslowmetals,itmayqualifyasanodegrade(seesame).Thechoiceofwhetheracokermakesfuelgradevsanodegradeisdictatedsolelybythecrudeslateandthemetalscontenttherein.
Greencoke
Usuallyreferstocalcineablecoke,i.e,potentialanodequalitycokethatstillcontainsmoistureandvolatilematerial,i.e,beforecalcining.
HargroveGrindabilityIndex(HGI)
Ameasureoftherelativehardnessofthecokeintermsofresistancetogrinding.AnHGIbelow35usuallymeansaveryhardcokerequiringconsiderablegrindingbeforeitcanbeproperlysizedtomeetburnernozzlespecificationsforthepulverizedfeedtothefurnacewherethecokewillbeburned.AnHGIabove65isusuallyrecognizedasasoftcokethatwillgrindveryeasily.
LossonIgnition(LOI)
Cokethatisaddedtocoalinafurnaceoriginallydesignedforcoal,maynotfullyburninthefurnace.Somecokeparticlesescapetheflameenvelopeandarecaughtbytheprecipitatorsorbaghouses.ThisLOIresultsinreducedfurnaceefficiencyandsomecarboncontaminationofthefluegasashrecovered.
Metalscontent
Thedistillationprocessesoftheatmosphericandvacuumcolumnsresultinalmostallofthemetalscontentofthecrudetoconcentrateintheresidualoil(thecokerfeed),andthenfurtherconcentratedinthecoker.Generallymetalsarenotaproblemtofuelgradecokebuyers,otherthanvanadiumtosome.Howeveranodegradecokebuyerspreferlowmetalsasthemetalstendtoreducetheefficiencyoftheanodeinthealuminumsmeltingprocess
Moisturecontent
Petcokeascutfromacokercontainsroughlyfrom7-10%moisturewhichthecokepickedupfromthesteamingandquenchoperations.Itismeasuredbyheatinga100gsampleofgroundcoke,untilthemoistureisgone,andthenreweighing.SeeWetmetrictonsandDryMetrictons.
NeedleCoke
Aspecialqualitycokeproducedfromaromaticfeedstocks.Ithasacrystallinestructurewithmoreunidirectionalpores.Itisusedforhighqualitygraphiteanodessuchasforelectricarcfurnacesinthesteelindustry.
Shotcoke
Duetomechanismsnotwellunderstood,thecokefromsomecrudesformsintosmall,tight,nonattachedclustersthatlooklikepellets,marblesorBB’s.Itusuallyisaveryhardcoke,i.e.,lowHGI(seesame).Suchcokeislessdesirabletotheendusersbecauseofdifficultiesinhandlingandgrinding.Itisalsolessdesirableforcalcineablecokebecausetheshottendsto“pop”inthekilnreducingthethermalstability.
Spongecoke
Mostdelayedcokeisinaformthatresemblesasponge,i.e,sortofbubblylooking.
Sulfurcontent
Sulfurincrudenaturallydistributesitselfthroughouttherangeofthecrude’shydrocarbonmolecules.However,theresidualoilandcokeusuallyattractadisproportionatelyhigherSulfurpercent.Also,asmostlowsulfurcrudesbecomeextinct,refinerieswillrunhighersulfurcrudestherebyincreasingthecokesulfur.
VolatilityorVCM
Petcokefromacokercontainsasmallamount(<
10%)oflighthydrocarbonstrappedintheporesofthecoke.Theamountofsuchvolatilityisgenerallyrelatedtothehowhardthecokerfurnaceisdriven:
hotterfurnaceoutlettemperaturesresultinmorehydrocarbonsdrivenoffandthereforelowervolatility.
Wetmetricton
Fuelgradecokeistypicallysoldinthesebillingunitswhichisatastandard8%moisture.Ifthecoketestsforahigher%,thebillingweightisadjustedaccordingly.
2石油焦
石油焦(Petroleumcoke)是原油经蒸馏将轻重质油分离后,重质油再经热裂的过程,转化而成的产品,从外观上看,焦碳为形状不规则,大小不一的黑色块状(或顆粒),有金属光泽,焦碳的颗粒具多孔隙结构,主要的元素组成为碳,占有80wt%以上,其余的为氢、氧、氮、硫和金属元素。
石油焦具有其特有的物理、化学性质及机械性质,本身是发热部份的不挥发性碳,挥发物和矿物杂质(硫、金属化合物、水、灰等)這些指标決定焦炭的化学性质。
2.1石油焦分类及性质
石油焦的形态随制程、操作条件及进料性质的不同而有所差异。
从石油焦工场所生产的石油焦均称为生焦(greencokes),含一些未碳化的碳烃化合物的挥发份,生焦就可当做燃料级的石油焦,如果要做炼铝的阳极或炼钢用的电极,则需再经高温锻烧,使其完成碳化,降低挥发份至最少程度。
大部份石油焦工场所生产的焦外观为黑褐色多孔固体不规则块状,此种焦又称为海绵焦(spongecoke)。
第二种品质较佳的石油焦叫做针状焦(needlecoke)与海绵焦比,由于其具较低的电阻及热膨胀系数,因此更适合做电极。
有时另一种坚硬石油焦亦会产生,称之为球状焦(shotcoke)。
这种焦形如弹丸,表面积少,不易焦化,故用途不多。
石油焦具有其特有的物理、化学性质及机械性质,本身是发热部份的不挥发性碳,挥发物和矿物杂质(硫、金属化合物、水、灰等)这些指针决定焦炭的化学性质。
物理性质中孔隙度及密度,决定焦炭的反应能力和热物理性质。
机械性质有硬度、耐磨性、强度及其它机械特性,颗粒组成及其它加工和运输、堆放、贮存等性质影响的情形
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