化工专业英语

Unit8

CoalconversionprocessCoalconsistsprimarilyofcarbon,hydrogen,andoxygen,andcontainslesseramountsofnitrogenandsulfurandvaryingamountsofmoistureandmineralmatter.Themodeofformationofcoal,thevariationinplantcomposition,themicrostructure,andthevarietyofmineralmatterindicatethatthereisamixtureofmaterialsincoal.Thenatureoftheorganicspeciespresentdependsonthedegreeofbiochemicalchangeoftheoriginalplantmaterial,onthehistoricpressuresandtemperaturesaftertheinitialbiochemicaldegradation,andonthefinelydividedmineralmatterdepositedeitheratthesametimeastheplantmaterialorlater.煤主要由碳、氢、氧组成并含有少量的氮、硫及含量不一的水份和矿物质。煤的构成方式、成煤植物成分的变化、微观结构以及所含矿物质的多样性均说明煤是由多种物质组成的混合体。各种有机物质的性质取决于最初植物成分生化变化的程度、最初生物降解后长期各种压力和温度的影响、与植物成分同期沉积或后期沉积的细微的矿物质的作用。Deposition沉积物sedimentTheprincipaltypesoforganiccompoundshaveresultedfromtheformationandcondensationofpolynuclearandheterocyclicringcompoundscontainingcarbon,hydrogen,nitrogen,oxygen,andsulfur.Thefractionofcarboninaromaticringstructuresincreaseswithrank.主要类型的有机化合物是含碳、氢、氮、氧和硫的多核化合物与杂环化合物构成与缩合的产物。芳环结构中碳的含量随着煤化程度的增加而增加。PolynuclearAromaticHydrocarbons（PAH）多环芳烃polycyclicaromatichydrocarbonsMonocyclicBicyclicNearlyallcoalisusedincombustionandcoking.Atleast80%isburneddirectlyinboilersforgenerationofelectricityorsteamforindustrialpurposes.Smallamountsareusedfortransportation,spaceheating,firingofceramicproducts,etc.Therestisessentiallypyrolyzedtoproducecoke,coalgas,ammonia,coaltar,andlightoilproductsfromwhichmanychemicalsareproduced.Combustiblegasesandchemicalintermediatesarealsoproducedbythegasificationofcoal,anddifferentcarbonproductsareproducedbyvariousheattreatments.Asmallamountofcoalisusedinmiscellaneous各种各样的applicationssuchasfillers,pigments,foundrymaterial,andwaterfiltration.几乎所有的煤都用于燃烧和炼焦。至少80%的煤直接在锅炉中燃烧用于工业发电或产生蒸汽。少量的煤用于运输、供热和烧制陶器。其余基本通过热裂解产生焦碳、煤气、氨、煤焦油和轻油等产品由此可生成其他很多化工产品。煤气化过程产生许多可燃气体和化学中间体不同的热处理会生成不同的含碳产品。也有少部分的煤被广泛用作填料、颜料、铸造材料和水过滤材料等方面。Thereisnodoubtabouttheswitchfromoiltocoalasasourceoforganicchemicals;theonlyuncertaintyconcernsthetime-scaleandrateatwhichithappens.Coal-conversionprocessesunderdevelopmentaredirectedtowardsproducingeithergaseousorliquidfeedstockswhichapproximateincompositiontopetroleum-derivedfeedstocks.Theycanthenbeutilizeddirectlyinexistingpetrochemicalplantsandprocesses.从以石油作为有机化学品的来源到以煤为有机化学品的来源这种转变是无可置疑的。但是唯一无法确定的是这种转变需要的时间与发生的速度。

研制中的煤转化工艺目的是为了生产出气体原料或液体原料。这些原料与石油衍生物原料的成分近似可直接应用于当今的石化工厂及其工艺中。Gaseousproduct气体产物Toachievethis,however,twoproblemsmustbeovercome,whichareaconsequenceofthedifferingnaturesofcoalandoil.Firstly,theH:Cratiosaredifferentforcoalandforpetroleum-derivedliquidfeedstocks.Secondly,significantamountsofheteroatomsarepresentincoal,particularlysulphurwhichmayreachlevelsashighas3%.Thesulphurhastoberemovedfortworeasons:(ⅰ)oncombustionitwillformtheatmospheric(大气的)pollutantSO2,and(ⅱ)itisapotent（强烈的）catalystpoison,andmostofthedownstreampetrochemicalprocessesarecatalytic.However,itsremovalfromcoalisdifficultanditisthereforeremovedfromtheconversionproductsinstead.但由于煤和石油性质不同，为达到这个目的有两个问题必须解决。首先煤和从石油中提取的液态原料中的氢/碳比不同。其次煤包含众多的杂环原子尤其是硫原子比例高达3%。基于以下两方面原因煤必须脱硫,1:燃烧时会生成大气污染物SO2；2：它是一种很强的催化剂毒物而大部分下游石油化工工艺都需用催化剂。但从煤中脱硫很困难，因此需要从煤转化产品中脱硫。CoalProcessingtoSyntheticFuelsandOtherProductsTheprimaryapproachestocoalprocessingorcoalconversionarethermaldecomposition,includingpyrolysisorcarbonization,gasification,andliquefactionbyhydrogenation.Thehydrogenationofcoalisnotcurrentlypracticedcommercially.HighTemperatureCarbonization.Hightemperaturesandlongprocessingtimesareusedincarbonizingcokingcoalsincokeovensorgasretorts.Besidesmetallurgical（冶金的）orgascoketheproductsincludefuelgas,crudetar,lightoils(benzene,tolueneandxylene,referredtoasBTX,andsolventnaphtha),andammoniagas.煤制备合成燃料及其它产品煤加工转化的主要方法是热分解，包括高温分解或干馏、气化及加氢液化。煤的加氢目前还没有实现商业化。高温碳化。在焦炉或干馏炉中在高温下长时间进行煤的碳化和焦化。除了冶金焦炭和气化焦之外，焦化的主要产品包括燃料气、粗焦油、轻油（苯、甲苯、二甲苯，也就是BTX，和溶剂石脑油和氨气）Metallurgy冶金Mostcoalchemicalsareobtainedfromhightemperaturetarwithanaverageyieldover5%ofthecoalwhichiscarbonized.Theyieldsincokingareabout70%oftheweightoffeedcoal.Tarsobtainedfromverticalgasretortshaveamuchmoreuniformchemicalcompositionthanthosefromcokeovens.Twoormorecoalsareusuallyblended（配煤）.Theconditionsofcarbonizationvarydependingonthecoalsusedandaffectthetarcomposition.Coal-tarchemicalsincludephenols,cresols,xylenes,benzene,toluene,naphthanlene,andanthracene.大部分煤基化学品是从高温煤焦油中获取，碳化过程中平均5%的煤生成焦油。焦的产率大约是进料煤的70%。从立式干馏炉制备的焦油比焦炉中的焦油有更均匀的化学成分。通常两种或更多中的煤配合使用。碳化的条件因煤种而异，因此焦油的组成也不同。煤焦油化学品包括苯酚、甲酚、苯、甲苯、二甲苯、萘和蒽。vertical竖直的horizontal水平的

Thelargestconsumerofcokeistheironandsteelindustry.Cokeisalsousedtomakecalciumcarbide,fromwhichacetylene乙炔ismade.Synthesisgasformethanolandammoniaproductionisalsomadefromgasificationofcoke.LowTemperatureCarbonization.Lowertemperaturecarbonizationoflumpcoalatca700℃primarilyusedforproductionofsolidsmokelessfuel,givesaquantitativelyandqualitativelydifferentyieldofsolid,liquid,andgaseousproductsthandoesthehightemperatureprocesses.Althoughanumberoflowtemperatureprocesseshavebeenstudied,onlyafewhavebeenusedcommercially.Thesehavebeenlimitedinthetypesofcoalthatareacceptable,andtheby-productsarelessvaluablethanthoseobtainedfromhightemperatureprocessing.焦化的最大消费者是炼铁和炼钢工业。焦还没用于制造电石用于制备乙炔。焦的气化所得合成气可用于制备甲醇和合成氨。低温碳化在大约700度下低温碳化块煤主要用于制备固体无烟燃料，得到了与高温加工量和性质截然不同的固体、液体和气体产物。虽然研究了很多低温碳化过程，但是仅有很少的实现商业化。由于可接受的煤种很有限，同时副产物没有高温碳化产物的价值高。Liquefactionofcoal,viahydrogenation,isquiteanoldprocesswhichwasoperatedcommerciallyinGermanyduringWorldWarIIwhenexternalfuelsupplieswerecutoff.Tensofmillionsoftonnesofgasolinewereproducedinthiswayduringthisperiod.Interestingly,Germanyistodayplayingaleadingpartinthedevelopmentofmoreefficientprocesses.FortheresultingliquidstobesuitablechemicalfeedstocktheH:Cratiomustbeimprovedinfavorofmorehydrogen.Clearlythiscanbeachievedintwoways—eitherbyaddinghydrogenorbyremovingcarbon.液化。煤的加氢液化是一个非常古老的工艺，早在第二次世界大战期间，德国由于缺乏外部的燃料供给，就已经进行商业化操作了。在这个时期，约通过该法生产了几千万吨汽油。有趣的是现在德国在开发更有效的工艺上走在了前列。对于生成的液体可以作为合适的化学品原料的话，H：C比必须改善以有更多的氢。很明显这个可以通过加氢或脱炭实现。LiquefactionAlthoughmanyofthenewprocessesareonlyatthepilot-plantstage（中试阶段）ofdevelopment,theirsuperiorityovertheoldmethodsisduetoincreasedsophisticationofthechemicalengineeringemployedplusimprovementsinthecatalystsavailable.Thebasicproblems,however,remainthesame—poorselectivityinproducingthedesiredfractionsandarelativelyhighrateofconsumptionofhydrogen.虽然很多新工艺仍处于发展的初级阶段，但是，同老方法相比，它们由于提高可用催化剂的性能和增加了所用化工工程的精确性，因而这种方法更具优势。但是基本问题仍然是一样的——对生产目标产品的选择性较低，而氢的用量相对较高。Thefundamentalprocessesinvolvedarepyrolysis,solventextractionandhydrogenation.Differencesbetweenthetechniquesbeingdevelopedlieinhowthesefundamentalprocessesarecombined.Notethatintheaboveprocessesthemainproductisahighlycarbonaceous（含碳的）solidmaterialknownaschar.Thisiseitherburnttoprovideprocessheatorreactedwithwaterandoxygentoproducehydrogen.液化所涉及的基本过程有热解，溶剂萃取和加氢。研发的各种工艺间的差异在于这些基本过程的结合方式。请注意，在上述过程中的主要产品是一种高含碳的固体材料，即焦炭。焦炭可以用于燃烧来提供热量，或与水和氧反应产生氢气。Theliquidsproducedbycoalliquefactionaresimilartofractionsobtainedbydistillationofcrudeoil(althoughtheyaremuchricherinaromatics),andthereforerequirefurthertreatment,e.g.cracking,beforebeingusedforsynthesis.煤液化的液相产品与粗油蒸馏获得的产品组分相似（尽管其芳香族化合物的含量更高），因此，在其用于合成前，必须经过进一步处理，即裂解。Anumberofgasifiersareeitheravailablecommerciallyorinvariousstagesofdevelopment.Thesearedescribedasfixedbed,fluidizedbed,andentrainedorrotatingbed.气化。气化炉较多，有的已经商业化，有的还处于研发的不同阶段。这些气化炉可分为固定床、流化床和夹带床或旋转床。Thefixedbedinvolvesanupwardflowofreactiongasthrougharelativelystationarybedofhotcoal.Thegasvelocityisslowenoughtoavoidblowingthecoaloutofthebed.Thefluidizedbedoperateathighergasvelocitiesthanthefixedbedandutilizessomewhatsmallerparticles.固定床是让一股向上流动的反应气流经一个相对固定的热煤床层。气体流速很慢从而避免将煤带出床层。流化床则在一个气速比固定床高的操作条件下进行，并且使用较细颗粒的物料。Gasification.Theentrainedbedoperateswithparallelflowsofreactiongasandfinelypulverizedcoalparticlestominimizereactiontimeandmaximizethroughputofproduct.夹带床采用反应气和细粉煤颗粒并行流动的操作方式，从而获得最小的反应时间和最大的产品吞吐量。Therotatingbedissimilartoakiln,whichoperateswiththecoalenteringattheupperpartoftheinclinedkiln.Rotationavoidsclinkingandexposesfreshsurfacestoenhancecompletionofthereaction.旋转床则类似于一个窑，煤从这个倾斜的窑的上部进入。旋转避免了碎裂和新鲜表面的暴露，从而强化了热解反应的完成。SurfaceGasificationtechnology.Gasificationofcoalforfuelgasandchemicalintermediateproductionhasbeendevelopedcommerciallyandimprovementsintechnologyarebeingstudiedinanumberoffacilities.IntheUnitedStates,thepurposeofanumberofprogramshasshiftedfromproductionofasubstitutenaturalgas(methane)toelectricpowergenerationthroughtheintegratedgasification-combined-cycle(IGCC)plants.Theinterestinthisuseofcoalresultsfromthelowemissionlevelsthatcanbeachievedandthepotentialforhigherpowergenerationefficiency.表面气化技术。煤气化用于燃料气和化学品中间体的生产已经商业化，且很多机构正在进行技术改进的研究。在美国，一些项目的目标从代用天然气（甲烷）的生产向利用整体煤气化联合循环（IGCC）技术发电转移。人们之所以对这种煤炭利用技术感兴趣，是因为它存在低排放水平和高发电效率的潜力。Futurelargegasificationplants,intendedtoproduceca7X106m3standardofmethaneperdayareexpectedtobesitednearacoalfieldhavinganadequatewatersupply.Itischeapertotransportenergyintheformofgasthroughapipelinethancoalbyeitherrailorpipeline.Theprocesschosenisexpectedtoutilizeavailablecoalinthemosteconomicalmanner.未来可日产7X106m3标准甲烷的大型气化厂，其理想的位置是在具有充足水源的煤田附近。能源通过管道以气相形式输送要比通过铁路或管线输送煤要便宜。选择的工艺最好是采用最经济的方式利用不同的煤。UndergroundCoalGasification(UCG).Undergroundcoalgasificationisintendedtogasifyacoalseaminsitu,convertingthecoalintogasandleavingtheashunderground.Thisapproachavoidstheneedforminingandreactorsgasification.UCGispresentlyconsideredmostinterestingfordeepcoalorsteeplyslopingseams.Thisapproachinvolvesdrillingholestoprovideairoroxygenforgasificationandremovalofproductgasesandliquids.地下煤气化（UCG）。地下煤气化是为了在原位将煤层气化，使煤转化为气，同时将灰留于地下。这种方法无需开采和反应器气化。对深层煤和极度倾斜煤层，UCG是目前人们最感兴趣的技术。这种方法需要钻孔以输入气化所需的空气或氧气并输出生成的气体和液体产品。Alowcalorificvaluegas,whichincludesnitrogenfromair,couldbeproducedforboilerorturbineuseinelectricpowerproduction,oranintermediatecalorificvaluegascontainingnonitrogenforanindustrialfuelgas,orsynthesesgasforchemicalandmethaneproductioncouldbeprovided.Thisapproachisstillnoncommercialinpartbecauseitisnoteconomicallycompetitive.地下煤气化可以产出供锅炉和发电的汽轮机所用的含有氮气的（源自空气）低热值气体，也可以生产供工业燃料气所需的不含氮的中等热值的气体，或是供化学品和甲烷生产所需的合成气。由于在经济上不具备竞争力，这种方法目前仍没有实现商业化。AlthoughmanyenvironmentalandsafetyproblemscanbeavoidedusingUCG.thereissomeconcernaboutgroundwatercontaminationasaresultoftheprocess.Thechemistryofundergroundgasificationhasmuchincommonwithsurfacegasification,however,manyoftheparameters参数cannotbecontrolledbecausethereactionoccursinaremotesite.HeatenergytodrivethegasificationcomesprimarilyfromcarboncombustiontoproduceCOandthenCO2.虽然UCG技术可以避免许多环境和安全问题，但是该工艺对地下水的污染还是需要注意的。虽然地下气化化学和地表气化有许多相同之处，然而，由于其反应发生在远程地点，因而许多参数无法控制。气化反应所需的热能主要来自于碳燃烧生成CO和CO2的反应。Becausemanycoalseamsarealsoaquifers含水层thereisaconsiderableamountofwaterintrusion,whichleadstosteamgenerationattheexpenseofthereactionenergy.Asaresulttherateofairoroxygenpassagethroughtheinjectionwellsandseamareadjustedtomaintainalowlevelofmoistureintheproductgas.ThesteamisbeneficialforchargasificationandsomeisconsumedinthewatergasshiftreactiontoproduceH2andCO,fromH20andCO2.SomeH2reactswithCtoproduceCH4,whichenhancesthecalorificvalueofthegas.由于许多煤层同时也是含水层，因此有大量水入侵，从而导致反应热的消耗和蒸汽的生成。因此，必须调整空气或氧气通过注入井和煤层的速率，以维持产品气中的水分在一个较低的水平。蒸汽对于焦炭的气化是有好处的，其中部分蒸汽用于从H20和CO2向H2和CO转变的水煤气变换反应。一些氢气和C发生反应产生甲烷，从而增加气体的热值。GasificationofcoalusingsteamandoxygenindifferentgasifiersprovidesvaryingproportionsofCOandH2.Operationsatincreasingpressuresincreasetheformationofmethane.BecausemixturesofCOandH2areusedasthestartofchemicalsynthesisandmethaneisnotwantedorneededforchemicalprocesses,theconditionsfavoringitsformationareavoided.Theproductgasesmaythenbepassedovercatalyststoobtainspecificproducts.Iron-basedcatalystsareusedtoproducehydrocarbonsintheFischer-Tropschprocess,orzineorcoppercatalystsareusedtomakemethylalcohol.煤气化制备液体燃料和化学品。在不同的气化炉中采用蒸汽和氧气进行煤气化所产生的一氧化碳和氢气的比值是不同的。操作压力的增大可以促进甲烷的形成。由于一氧化碳和氢气的混合物才是化学合成的初始底物，而甲烷是该化学过程不需要的，因此，需要避开有利于甲烷形成的条件。产品气将被通过催化剂以生产特定的产品。在FT工艺中用铁基催化剂可生产烃类，锌或铜催化剂则用于甲醇的生产。LiquidFuelsandChemicalsfromGasificationofCoal.TheFischer-Tropschprocesshasnotbeeneconomicalincompetitivemarkets.TheSouthAfricanSasolplanthasoperatedsuccessfullyusingthemodificationoftheFischer-Tropschprocess.Theoriginalplantwasdesignedtoproduce227,000t/yofgasoline,dieseloil,solvents,andchemicalsfrom907,000metrictonsofnoncakinghighashsub-bituminouscoal.ThesuccessoftheSasolprojectisattributedtotheavailabilityofcheapcoalandthereliabilityoftheselectedcomponents.Fischer-Tropsch工艺在竞争市场中不具备经济优势。南非Sasol厂应用改良的Fischer-Tropsch工艺却取得了成功。该厂的设计生产能力是：每年利用907,000吨不粘高灰次烟煤来生产227,000t汽油、柴油、溶剂和化学品。Sasol项目的成功归功于便宜煤的使用以及所选组分的可靠性。Avarietyofpilotplantsusingfluid-bedgasifiershavebeenbuiltintheUnitedStates,Germanyandelsewhere.TheWinklerprocessistheonlyonethathasbeenusedonalargescale.ItwasdevelopedinGermanyinthe1920stomakesynthesisgasatatmosphericpressure.Planswerebeingmadetodevelopapressurizedversion.在美国、德国以及其他地方建立了各种应用流化床气化炉的工厂。Winkler工艺是唯一以大规模进行运作的工艺。在常压下进行合成气生产的工艺始于1920s的德国。并制订了加压工艺的发展计划。Pressurized加压的AtmosphericpressureTheuseofbiotechnologytoprocesscoaltomakegaseousandliquidfuelsisanemergingfield.Bacteriaandenzymeshavebeenstudiedtoestablishthetechnicalfeasibilityofconversion.TheearliestworkwasdoneonmicrobialdecompositionofGermanhardcoals.Reactorshavebeendesignedtouseavarietyofbacteriaandfungitobreakdownthelargemolecularstructureintosmallerunitsthatmaybeusefulasintermediates(solubilization)orasliquidandgaseousfuels(conversion).煤的生物处理。利用生物技术处理煤来生产气体和液体燃料是一个新兴的领域。人们对细菌和酶进行研究以建立这种转化的技术可行性。最早的工作是对德国的硬煤进行微生物