油氣儲(chǔ)運(yùn)專(zhuān)業(yè)設(shè)計(jì)文獻(xiàn)翻譯(附原文)原油的加工工藝本科畢業(yè)論文

PAGEPAGE11PetroleumRefiningProcessesDesulphurisationSulphuroccursincrudeoilscombinedinavarietyofways,fromthesimplestcompoundH2Stocomplexringstructures.H2SisproducedduringdistillationofthecrudeoilbydecompositionofhigherboilingsulphurcompoundsandappearsintheLPGfromwhichitmustberemovedbecauseofitspoisonousandcorrosivenature.Thisisdonebycountercurrentwashingwithanamine(e.g.diethanolamine),theH2Sbeingremovedforsulphurrecoverybyheatingtheaminesolutioninaseparatevesselthusregeneratingtheamineforrecycletothewashingstage.MercaptanscanbeconsideredderivativesofH2S,inwhichonehydrogenatomisreplacebyacarbon/hydrogengroup,andsharesomeofitsunpleasantpropertiesofbadsmellandcorrosivity.Thosemercaptansboilingbelowabout80℃arereadilydissolvedinalkalinesolutionsTheUOPMeroxprocessusescausticsodatoextractthemercaptanswhicharethenoxidisedwithairtodisulphidesandthecausticsodaregeneratedforfurtheruse.Theoxidationstepisassistedbyametalcomplexcatalystdissolvedinthecausticsoda.Theprocesscanberepresentedasfollow:4C2H5SH+4NaOH=4C2H5SNa+2H2O+2H2O+O22C2H5S—SC2H5+4NaOHThedisulphidesarenotsolubleincausticsodaandformanoillayerwhichcanberemoved.Mercaptansinfractionboilingbetween80℃and250℃cannotbeoxidisedtodisulphidesintheMeroxsolutionwithair.Thedisulphides,whicharenon-corrosiveandhavelittlesmell,remaindissolvedintheoilsothatnoactualdesulphurisationhasbeenachivedbuttheproductshavebeen“sweetenedAsthecutstakenfromcrudeoilincreaseinboilingpointitisfoundthatthesulphurincreases.Inthe250-350℃rangewhichisusedforbothdieselfuelanddomesticcentral-heatingfuelthesulphurcontentisabout1percentweightfrommostMiddleEastcrudes.WhenthismaterialisburntthesulphurisoxidisedtoSO2which,beingeasilyoxidisedtosulphuricacid,causesatmosphericpollutionandcorrosionofmetals.Thesulphurcannotbetreatedbythemethodspreviouslyoutlinedasitismainlycombinedwithcarbonandhydrogeninformsmuchmorecomplicatedthanthesimplemercaptans.Thesecomplexcompoundshavetobebrokendowntogetatthesulphurwhichisdonebypassingtheoiltogetherwithhydrogenathightemperature(320-420℃)andhighpressure(25-70bar),overacatalystcontainingcobaltandmolybdenumoxidesonanaluminabase,madeintheformofsmallpelletsorextrudates.Thereactioniseasierandthecatalystlifebetterwhentheratioofhydrogentofeedisseveraltimeshigherthanthatnecessarytocompletethereactionchemically.UndertheseconditionsthesulphurcompoundsdecomposeandthesulphurcombineswiththehydrogentogiveHThisprocessofdesulphurisation,alsocalled“hydrofining”,iseffectiveinattackingallformsofsulphurcompounds,andcanbeusedtotreatanypartofcrudeoil.Inprincipletheequipmentusedforallfeedsisbasicallysimlarandwillcontainmeansforcarryingoutthefollowingsteps:1Supplythefeedandhydrogentothereactoratthecorrecttemperatureandpressure.2Coolthereactorproducttocondensetheoilandallowtheseparationoftheexcesshydrogensothatitcanberecycledtothereactor.3RemovetheH2Sandsmallquantity(2-3percent)oflow-boilinghydrocarbonsproductedinthereaction.Apumptakesthefeedandraisesittotherepuiredpressureandpassesitthroughtubesinafurnacewhereitisheatedtotherequiredtemperaturebeforebeingmixedwiththehydrogenandpassingintothereactor.Thereactorproductiscooled,partiallybythefreshfeedinaheatexchangertosavefuel,andpartiallybywaterinanotherheatexchanger.Excesshydrogenisseparatedfromthecondensedoilinadrumandrecirculatedbacktothereactorbyacompressortogetherwithfreshhydrogentoreplacetheamountconsumedinthereaction.TheliquidfromthedrumispassedintoadistillationcolumnwheretheH2Sandlow-boilingbreakdownproductsareremovedandthedesulphurisedoiltakenfromthebottomofthecolumn.Muchofthecrudeoilboilingabove350℃isusedtomakeheavyfueloilforpower-stations,shipsandlargeindustrialplantsandcanhaveasulphurcontentof2.5-4percentweightfrommostMiddleEastcrudes.BuringthismaterialreleasesSO2andveryhighchimneyshavetobeused(anumberinthe500-600footrangehavebeenbuilt,oneof800feetintheUSA)sothattheSO2canbedisperedwidelyintheatmospherethusavoidinglocalisedpollution.Theidealsolutionwouldbetodesulphuriseallpartsofthecrudeoil.Unfortunately,althoughthedesulphurisationofdistillatesboilinguptoabout550℃cabberelativelyeasilyaccomplished,thetreatmentofheavycrude-oilresiduesposesmanydifficultproblems.Withincreasingboiling-pointthedifficultyofdesulphurisationincreasesandalsotheproportionofmoleculescontainingsulphurbecomeshigInarefinerywheredesulphurisationisusedextensivelytheproductionofH2Scaneasilyreach100tonnesperday.AlthoughtheH2ScouldbeburnttoSO2andventedfromallstacks,itisveryundesirablebecauseoftheatmosphericpollutioncausedandadditionalplantisinstslledtorecoverthesulphur.TheH2SisburnttoSO2withtheoxygensupplylimitedsothataboutone-thirtoftheH2Sburns.Thisgivesamixtureoftwo-thirdsH2Sandone-thirdSO2whichwillcombinetoformsulphurandwater:2H2S+SO2=3S+2H2OThesulphuriscollectedandisusuallysoldtochemicalcompaniesmainlyforthemanufactureofsulphuricacid.ThermalCrackingWhenhydrocarbonsareheatedtotemperaturesexceedingabout450℃theybegintodecompose.Thelargemoleculesbreakingor“cracking”intosmallerones.Paraffinsarethemosteasilycrackedfollowedbynaphthenes,aromaticsbeingextremelyrefractory.Atonetimethermal-crackingprocesseswerewidelyusedtoimprovetheoctanenumberofnaphthasortoproducegasolineandgasoilfromheavyfractions.Thequalityofthegasolinefromthethermalcrackingofnaphthaisnothighenoughforpresentmotorgasolinesandtheprocesshasfallenoutofuse.Theproductsfromheavyoilcrackingrequirementsandwhileatpresenttheprocessislittleuseditcouldbeofinterestshouldconversionofheavydistillates(upto550℃)togasoilsberequired.OnethermalAnotherthermal-crackingprocesspresentlyemployedisDelayedCoking,whichisnormallyappliedtoatmosphericorvacuumresiduesfromlowsulphurcrudesfortheproductionofelectrodegradecoke(usedmostlyinaluminiumproduction).Theresidueisheatedtoabout500℃andpassedtothebottomofalargedrumwherethecrackingreactionproceedswhichbreaksdownthehigh-boilingmaterials,ThelowerboilingmaterialsformedvaporiseatthehightemperatureinthedrumandpassoutofthetoptothefractionationsysteCatalyticCrackingThermalcrackingofheavydistillatesforgasolineproductionisnotselectiveandproducessubstantialquantitiesofgasandfueloiltogetherwiththegasoline,whichisalsonotofverygoodquality.Aboutthirtyyearsagoitwasfoundthatfuller’searthandsimillarmaterialscouldactascrackingcatalystsandgiveagoodyieldofhighoctanenumbergasline(catalyticcracking).Unfortunately,thefuller’searthbecamequicklycoveredincarbonandnolongeractedasacatalystwasreturnedtoitspreviousactivityandthustooperatetheprocesscontinuouslyitwasnecessarytodevisemethodsofalternativelyusingandregeneratingthecatalystcontinuouslyonalargescale.Oneofthemostsuccessfulmethodsofachievingthisdependsontheuseoffluidisation.Whenagasispassedupthroughabedoffinepowerthebehaviourofthepowerdependsonthevelocityofthegas.Ifitishigh(about1m/sec.)theparticlesaremovedaboutbythegasandthebedofpoweractslikeafluidandcanbetransported,finditsownlevel,ect.justlikealiquid.Byusingthisproperty,thecatalyst,inpowerform,canbecirculatedcontinuouslybetweenareactionstageandaregenerationstage.Thereactorandregeneratorvesselsareeachdesignedsothattheupwardvapourvelocityissufficienttofluidisethecatalyst.Theoilfeed(normallyboiling350-550℃)meetshot(620-740℃)regeneratedcatalyst,whichissubstantiallyfreeofcarbon,andthevaporisedoilandcatalystpassthroughatransferlinetothereactor,wherethecatalystformsafluidisedbed.Thecrackingreactionproceedsassoonascatalystmeetstheoilandiscompletedwithinthereactorat480-540℃,depositingcarbononthecatalyst.Thespentcatalystissteamstrippedtoremoveentrainedhydrocarbonsandreturnedtotheregeneratorwhereairisusedtoburnthecarbonfromthecatalyst.Theoilproductsleavethereactor,viacyclonestoreducecatalystentrainment,andareseparatedintofuelgasC3Thecatalystlosesactivityasaresultofhydrothermaldeactivationandtheaccumulationofmetalsfromthefeed,whichcancontainupto1p.p.m.ofvanadiumplusnickel.Catalystactivityismaintainedbycontinuoussdditionooffreshcatalystandwithdrawalofequilibriumcatalysttomaintainaconstantinventory.Inadditiontostraight-runandvacuumgasoils,cokergasoil,etc.thefeedtoacatalyticcrackercanincludeatmosphericresidueprovidedthemetalscontentislowenough.TheKelloggheavyoilcracking(HOC)processisdesignedforhighmetalscontentatmosphericresidue.Greatimprovementhavebeenmadeinthemanufactureofcatalystswhichnowincorporatemolecularsievematerials(zeolite)andhaveaveryhighactivity.Ithasbeenfoundthatthelongresidencetimeofthevapoursinthereactorgivesrisetosecondaryreactionswhichreducetheselectivityoftheconversiontogasolineandproducemoregasandcoke.Newdesignsdispesewiththefluidbedinthereactorandcarryoutthereactioninthetransferline;theoilandcatalystarequicklyseparatedattheendofthetransferline,forinstanceinacyclone,andthecatalystdropsintoastripperaspreviouslytotheremoveentrainedhydrocarbonsbeforetransfertotheregenerator.ThisiscalledShortContactTime(SCT)crackingandhasmarkedlyimprovedtheyieldofgasolineobtainableintheprocess.HydrocrackingAshydrocarbonsincreaseinthenumberofcarbonatomstheycontain,sothereisadecreaseintheratioofthenumberofhydrogenatomspercarbonatom,e.g.methane,CH4,hasaratioof4;pentane,C5H12,hasaratioof2.4;decane,C10H22,hasaratioof2.2.Ifwewishtoproducelow-boilinghydrocarbons(e.g.gasolinecontaining5-10carbonatoms)fromhighboilinghydrocarbonscontainingsay20carbonatomswemustfindsomemeansofincreasingtheratioofhydrogentocarbon.Inthermalcrackingolefines(whichhavealowerhydrogen/carbonratiothanparaffins)areproducedandalsocarboneliminatedbydepositioninthecatalyst.Thealternativeapproachistoaddhydrogenandthisisdoneinthehydrocrackingprocessbycrackingataveryhighpressureinhydrogen.Thisprocess,whichisveryflexibleandcanproducehighyieldsofeithergasolineorgasoilfromwaxdistillaate,orgasolinefromgasoil,operatesatpressuresof150-170barandtemperaturesofaround430℃.Reactorscapableofwithstandingthesesevereconditionsmaybe150-200mmthickandposemanydifficultengineeringproblemsindesignandconstruction.Hydrogenrequirementsforhydrocrackingareveryhigh,uptoabout300m3permWhendesignedtoproducegasoilahydrocrackerwilluseonereactorandthebasic-flowdiagramappearsverysimilartoahydrofiner,buttworeactorscontainingdifferentcatalystareusedwhengasolineproductionisrequired.Unreactedfeedisrecycledtothereactorsothatcompleteconversionofthefeedtolowerboilingproductsmaybeachieved.Itwillbeappreciatedthatthesevereoperatingconditionsrequiredinthisprocessnecessitatehigh-dutyequipmenttowithstandthehightemperaturesandpressures,largegascompressorsandpumps,andahydrogenproductionunitwhichmakesthecapitalcostveryhigh.CatalyticReformingCatalyticreformingisnowoneofthemostimportantprocessesfortheproductionofmotorgasolinestakingstraight-runmaterialsintheboilingrangeofabout70-190℃asfeedandraisingtheoctanenumberfromabout40to95-100Themainreactionstakingplaceare:DehydrogenationofnaphthenestoaromaticsCH2CH3CHsCH2CHCH2CHCH3+3H2CH2CH2CH2CHCH2CH2aparaffinisomerisationnhexane2methylpentanebnaphtheneisomerisationCH3CH2CH2CHCH2CH2CH2CH2CH2CH2CH2CH2Thecyclohexanecanthendehydrogenatebyreaction(1)Dehydrocyclisationnheptanemethylcyclohexane+H2Thestraight-chainparaffincancyclisetothenaphthenewithproductionofhydrogenandthenaphthenethendehydrogenatetoanaromaticbyreaction(1)HydrocrackingC10H22+H2C6H14+C4H10Hydrocrackinginvolvesthebreakingofacarbonchaintogivetwosmallermolecules.Paraffinsareproducedbecauseoftheadditionofhydrogentotheolefinicfragmentsresultingfromthecracking.Allfourreactionsresultinanincreaseinoctanenumberasinthefirstthreereactionsaromaticsareproducedwhichhavemuchgreateroctanenumbersthanthecorrespondingparaffinsandnapthenes,andinthefourthreactionlowoctanenumberlong-chainparaffinsaredestroyed.Thecatalystsoriginallydevelopedconsistedofplatinium(about0.3-0.75percentweight)onhighlypurifiedalumina.Inthepastfewyearsnewcatalystshavebeendevelopedstillusingplatinumasamajorcomponentbutalsoaddingothermetassuchasrtheniumwhichimprovethelifeofthecatalystundersevereoperatingconditions.Thereactionsarecarriedoutattemperaturesintheregion490-540℃andpressure10-30bar.Thereareothersidereactionswhichtendtodeactivatethecatclystbythefoemationofcarbononit.Thesereactionscanbereducedbyahighpressureofhydrogenwhichismaintainedbyacombinationofunitoperatingpressureandrecycleofhydrogenwiththefeed.However,yieldsofreformatearehigheratlowerpressureswhilstahighrecycleofDehydrogenationofnaphtheneswhichoccursinthefirstthreereactionsisahighlyendothermicprocss(absorbsheat)anditisnecessarytodividethecatalystintoanumberofseparatereactorsbecausethetemperaturedropssomuchasthereactionproceedsthatitsratebecomestooslowandtheproductshavetobereheatedtoenablethereactiontobecompleted.Catalyticreformingisavaluablesourceofhydrogenwhichisusedmainlyindesulphurisationunits.Theprocessisalsousedfortheproductionofaromatics(e.g.benzene,toluene,xvlenes)foruseaspetrochemicalfeedstocks.Inordertomaintainthecatalystatahighlevelofactivitythefeedstockmustbecarefullypurified;itispreferabletomaintainlevelsofsulphurandwaterbelowabouttwopartspermillionandeliminatetracesoflead.Itisnecessarytoburncarbonoffthecatelystperiodically.Thisisnormallydonebyshuttingdowntheplant.However,thereareversionsoftheprocessinwhicheachreactoristakenoffstreaminturnforregenerationbyinterchangingwithaswingreactor.Inanothercasesmallamountsofcatalystcanberemovedfrom,andreturnedto,thereactorscontinuouslyafterregenerationorreactivationstepsinwhichthedistributionofmetalsonthecatalystareadjustedtomaintainthecatalystinthemostactivestate.原油的加工工藝脫硫原油中含有硫，它從最簡(jiǎn)單的混合物H2S到復(fù)雜的環(huán)狀結(jié)構(gòu)等多種形式與原油混合在一起。原油蒸餾過(guò)程中，分解較高沸點(diǎn)的硫化物產(chǎn)生H2S,并進(jìn)入石油液化氣里。由于H2S有毒性和腐蝕性，故石油液化氣里的H2S必須除去。用一種胺溶液（例如二乙醇胺）進(jìn)行逆流洗滌除去H2S；然后在一個(gè)單獨(dú)的容器里加熱吸收H2S的胺溶液脫除H2S回收硫，并將胺溶劑再生循環(huán)用作逆流洗滌。硫醇可以看作是H2S的衍生物，硫化氫中一個(gè)氫原子被一個(gè)碳?xì)鋱F(tuán)替代了。硫醇也有H2S的臭味和腐蝕性這樣一些令人不愉快的性質(zhì)。那些沸點(diǎn)在80℃以下的硫醇極易溶解于堿性溶液，不過(guò)溫度在80℃以上時(shí)，其可溶性就迅速降低。因此，在生產(chǎn)石油液化氣和輕質(zhì)汽油時(shí)采用苛性鈉溶液進(jìn)行逆流洗滌以除去硫醇。UOPMerox硫醇氧化法使用苛性鈉萃取硫醇，然后硫醇用空氣氧化后生成二硫化物，苛性鈉再生后循環(huán)使用。氧化這一步由一種溶于苛性鈉的金屬絡(luò)合物作催化劑。這個(gè)流程可以用以下方程表示：4C2H5SH+4NaOH=4C2H5SNa+2H2O+2H2O+O22C2H5S—SC2H5+4NaOH二硫化物不能溶于苛性鈉，而形成一層可以除去的油層。沸點(diǎn)在80℃和250℃之間餾分里的硫醇不能萃取，但是在Merox溶液里能用空氣氧化生成二硫化物。這些二硫化物無(wú)腐蝕作用而且?guī)缀鯖](méi)有氣味；它們依然溶于油中，所以并未達(dá)到脫硫的目的，不過(guò)，產(chǎn)品已經(jīng)“去臭隨著原油中蒸餾出來(lái)的餾分沸點(diǎn)的增高，會(huì)發(fā)現(xiàn)含硫量也在增多。生產(chǎn)柴油和家庭供暖系統(tǒng)燃料油的沸點(diǎn)在250℃到350℃之間，在這個(gè)沸點(diǎn)范圍內(nèi)，中東產(chǎn)的原油含硫量大約為1%重量。這種油料燃燒時(shí)，硫就氧化成SO2，而SO2又極易氧化成硫酸，會(huì)引起大氣污染和金屬腐蝕。由于硫主要與碳和氫結(jié)合，其結(jié)構(gòu)比簡(jiǎn)單硫醇復(fù)雜得多，它就不能用上面介紹的方法處理。這些復(fù)雜的化合物必須經(jīng)過(guò)裂解才能得到硫，其方法如下：在高溫（320℃至420℃之間）及高壓（25至70巴之間）條件下，使原油連同氫氣一起通過(guò)以鋁礬土為載體的氧化鈷和氧化鉬的催化劑（制成小球或壓制物）。當(dāng)氫氣與進(jìn)料的比例超過(guò)所需要的比例幾倍的時(shí)候，這一反應(yīng)就比較容易，催化劑的壽命也較長(zhǎng)。在這些條件下，硫化物就分解；硫與氫氣化合生成為H2S。幾乎所有的硫化物均可用這一方法分解而不影響所余的碳?xì)浠衔铩＿@種脫硫工藝，也稱(chēng)為“加氫精制”，在處理各種結(jié)構(gòu)的硫化物方面是有效的，而且也可用來(lái)處理原油的任一餾分。原則上，處理各種原料的設(shè)備都基本相似，它將包括完成下列各步驟：在合適的溫度和壓力下，為反應(yīng)塔提供進(jìn)料和氫氣。冷卻反應(yīng)塔出口產(chǎn)品使油品冷凝，并讓過(guò)量的氫氣分離出來(lái)以供反應(yīng)塔循環(huán)使用。除去H2S和少量的（2~3%）在反應(yīng)過(guò)程中產(chǎn)生的低沸點(diǎn)碳?xì)浠衔?。用泵輸送原料并使之增高到所要求的壓力后，通過(guò)管道送進(jìn)加熱爐，原料在加熱爐加熱到所要求的溫度，然后與氫氣混合在一起進(jìn)入反應(yīng)塔。出反應(yīng)塔的高溫產(chǎn)品，一部分由熱交換器中新鮮的原料冷卻以節(jié)省燃料，一部分由另一個(gè)熱交換器里的水冷卻。過(guò)量的氫氣在一個(gè)臥罐里從冷凝油中分離出來(lái)，然后由一臺(tái)壓縮機(jī)將它再循環(huán)回到反應(yīng)塔里與新加進(jìn)的氫氣一起補(bǔ)充反應(yīng)中消耗掉的部分。臥罐中出來(lái)的液體被送入一個(gè)蒸餾塔（汽提塔）；在蒸餾塔里除去H2S和低沸點(diǎn)的裂解產(chǎn)品，并在塔底取得脫去硫的產(chǎn)品油。沸點(diǎn)超過(guò)350℃的許多原油用作生產(chǎn)發(fā)電廠、船只和大型工廠所需的重燃料油。絕大多數(shù)的中東原油含硫量為2.5%~4%（重量），燃燒這種原油會(huì)釋放出H2S，所以必須建造很高的煙囪（美國(guó)以建造了若干個(gè)高度在500到600英尺，其中一個(gè)高達(dá)800影馳的煙囪），這樣H2S會(huì)飄散在高空，可以避免局部地區(qū)的污染，但會(huì)造成大氣嚴(yán)重污染。理想的解決方法是脫去原油各個(gè)餾分的硫。遺憾的是盡管沸點(diǎn)高達(dá)550℃左右的蒸餾物的脫硫相對(duì)說(shuō)來(lái)容易達(dá)到，但是，處理重質(zhì)原油的殘?jiān)蜕杏性S多困難。脫硫工藝的困難隨沸點(diǎn)的增高而增大，而且，含硫分子的比例也會(huì)增高（可能到達(dá)50%），也就是說(shuō)，呈現(xiàn)出來(lái)的高比例分子必須分解。油中微量金屬往往會(huì)使最有效的脫硫催化劑失去活性，因此，必須使用高壓（高達(dá)170巴）。所有這些因素結(jié)果都會(huì)造成燃料油脫硫的成本增高。再者，近來(lái)世界范圍的原油供應(yīng)形勢(shì)的發(fā)展非常強(qiáng)調(diào)對(duì)能源的保護(hù)。因此，只有在不能采用別的方法減少污染時(shí)，才能最后采用染料精加工工藝。在廣泛采用脫硫工藝的煉廠里，要達(dá)到日產(chǎn)100噸的H2S是容易的。盡管H2S燃燒能生產(chǎn)SO2并從高煙囪里排放掉，但這樣處理并不理想，因?yàn)檫@樣造成環(huán)境污染。因此，需要安裝一個(gè)裝置來(lái)回收硫。H2S在氧氣供應(yīng)不足的情況下燃燒生成SO2，大約只有三分之一的H2S的燃燒，結(jié)果形成三分之二的H2S和三分之一的SO2的混合物；H2S和SO2將化合成硫和水：2H2S+SO2=3S+2H2O硫收集起來(lái)后通常出售給化學(xué)公司主要用于生產(chǎn)硫酸。熱裂化碳?xì)浠衔锛訜岬?50℃以上就開(kāi)始分解，結(jié)果大的分子分裂或“裂化”成較小的分子。石蠟最容易裂化，其次是石腦油，而芳香烴特別難于裂化。過(guò)去有個(gè)時(shí)期曾廣泛采用熱裂化來(lái)改進(jìn)石腦油中的辛烷值，或者以重餾分來(lái)生產(chǎn)汽油和柴油。石腦油熱裂化所生產(chǎn)的汽油質(zhì)量不夠高，故不能用作現(xiàn)代的車(chē)用汽油，所以上述工藝已被淘汰。重油裂化產(chǎn)品要求完全加氫以滿(mǎn)足現(xiàn)代質(zhì)量要求。盡管這一加氫工藝目前極少采用。不過(guò)，如果需要把重餾分（溫度高達(dá)550℃）變成粗柴油，那么人們可能還會(huì)對(duì)這一工藝感興趣的。當(dāng)今通用的一種熱裂化工藝稱(chēng)為“減粘裂化當(dāng)今采用的另一種熱裂化工藝稱(chēng)為“延遲焦化”，這一工藝通常用來(lái)處理低硫原油的常壓或真空蒸餾殘?jiān)?，以生產(chǎn)電極焦（主要用于制鋁工業(yè)）。殘?jiān)图訜岬?00℃左右，進(jìn)入一個(gè)大焦化塔的底部，在塔底部高沸點(diǎn)原料進(jìn)行裂化反應(yīng)，焦化塔里形成的低沸點(diǎn)原料在高溫下氣化，經(jīng)塔頂部進(jìn)入分餾系統(tǒng)在這里分餾成石油氣、汽油和粗柴油，而塔中留下一堆多孔的焦。焦化塔結(jié)滿(mǎn)焦后，把進(jìn)料送入另一個(gè)焦化塔，將結(jié)滿(mǎn)焦的塔通入蒸汽、以除去焦炭。這時(shí)，另一塔內(nèi)的進(jìn)料裂化結(jié)焦又滿(mǎn)了。正如在裂化工藝中那樣，液態(tài)產(chǎn)品要進(jìn)行加氫處理以便當(dāng)作石腦油或柴油之用。催化裂化熱裂化重餾分生產(chǎn)汽油不太適宜，它能產(chǎn)生大量的石油氣和燃料油，并伴有汽油，汽油的質(zhì)量亦不是太好。大約三十年前就發(fā)現(xiàn)：漂白土（硅藻）以及相似的材料能起到裂化催化劑的作用，而且還能生產(chǎn)出高辛烷值的汽油（催化裂化）。遺憾的是，漂白土很容易被焦炭覆蓋失去催化劑的作用。不過(guò)焦炭燒掉后，催化劑又回復(fù)其先前所具有的活性。因此，為了使這一工藝流程能持續(xù)進(jìn)行，就必須設(shè)計(jì)出能大規(guī)模地、持續(xù)不斷地，交替使用的再生催化劑的方法。達(dá)到這一目的最成功的方法之一就是采用流化技術(shù)。當(dāng)空氣往上吹經(jīng)過(guò)細(xì)粉末層時(shí)，粉末的狀態(tài)取決于空氣的速度。如果速度高（大約10米/秒以上，粉末就似一片飛塵往上吹；可是速度中等時(shí)（大約1米/秒），粉塵就被空氣帶動(dòng)四處轉(zhuǎn)動(dòng)，粉末層就起到流體的作用，而且能流動(dòng)，像流體一樣保持水平狀態(tài)，等等。通過(guò)利用這一特性，粉末狀的催化劑就能在反應(yīng)和再生兩個(gè)階段之間持續(xù)流通。反應(yīng)塔和再生塔都分別進(jìn)行設(shè)計(jì)，以便上升氣流的速度大得足以輸送催化劑。原料油（正常沸點(diǎn)在350℃到550℃之間）與熱的（沸點(diǎn)在620℃與740℃之間）再生催化劑相遇，再生催化劑上沒(méi)有焦炭。汽化了的油同催化劑一道經(jīng)輸送管進(jìn)入反應(yīng)塔，在反應(yīng)塔里催化劑形成流化層。催化劑遇到油，裂化反應(yīng)就開(kāi)始就在反應(yīng)塔里溫度在480℃至540℃之間完成這一反應(yīng)，之后催化劑被積焦。這種失效的催化劑用蒸汽解吸，除去夾帶在催化劑中的碳?xì)浠衔?，并使催化劑回到再生塔里，在這里空氣把催化劑表面的焦炭燒掉。石油產(chǎn)品經(jīng)旋風(fēng)分離器分離催化劑后離開(kāi)反應(yīng)塔以減少催化劑的流失，然后分離成燃料氣、C3/C4、汽油和粗柴油。汽油的辛烷值可高達(dá)95。由于水蒸汽減活作用以及進(jìn)料中的金屬積聚（進(jìn)料中釩和鎳的含量高達(dá)1ppm），催化劑會(huì)失去活性。通過(guò)不斷加進(jìn)新鮮催化劑和回收平衡催化劑以維持總量不變來(lái)保持催化劑的活性。除了直餾粗柴油和減壓粗柴油以及焦化粗柴油外，假若金屬含量十分低的話(huà)，輸送到催化裂化裝置的進(jìn)料還可以包括常壓殘?jiān)?。凱洛克重油裂化（HOC）工藝就是為金屬含量高的常壓殘?jiān)驮O(shè)計(jì)的工藝。目前，在生產(chǎn)與分子篩（沸石）混合的、并具有很高活性的催化劑方面，已有很大改進(jìn)。業(yè)已發(fā)現(xiàn)，蒸汽在反應(yīng)塔里長(zhǎng)時(shí)間阻滯會(huì)引起副反應(yīng)，這就會(huì)降低生產(chǎn)汽油的選擇性，并產(chǎn)生更多的氣體和焦炭。新設(shè)計(jì)省略了反應(yīng)塔的流化層，而在輸送管道里進(jìn)行反應(yīng)；油和催化劑迅速在輸送管道的末端分離（例如，在旋風(fēng)分離器內(nèi)）。催化劑在輸送到再生塔之前，像先前一樣進(jìn)入汽提塔