Unit-10-What-Is-Chemical-Engineering

Unit10WhatIsChemicalEngineering?什么是化学工程学Inawidersense,engineeringmaybedefinedasascientificpresentationofthetechniquesandfacilitiesusedinaparticularindustry.Forexample,mechanicalengineeringreferstothetechniquesandfacilitiesemployedtomakemachines.Itispredominantlybasedonmechanicalforceswhichareusedtochangetheappearanceand/orphysicalpropertiesofthematerialsbeingworked,whiletheirchemicalpropertiesareleftunchanged.Chemicalengineeringencompassesthechemicalprocessingofrawmaterials,basedonchemicalandphysico-chemicalphenomenaofhighcomplexity.广义来讲，工程学可以定义为对某种工业所用技术和设备的科学表达。例如，机械工程学涉及的是制造机器的工业所用技术和设备。它优先讨论的是机械力，这种作用力可以改变所加工对象的外表或物理性质而不改变其化学性质。化学工程学包括原材料的化学过程，以更为复杂的化学和物理化学现象为基础。Thus,chemicalengineeringisthatbranchofengineeringwhichisconcernedwiththestudyofthedesign,manufacture,andoperationofplantandmachineryinindustrialchemicalprocesses.因此，化学工程学是工程学的一个分支，它涉及工业化化学过程中工厂和机器的设计、制造、和操作的研究。Chemicalengineeringisaboveallbasedonthechemicalsciences,suchasphysicalchemistry,chemicalthermodynamics,andchemicalkinetics.Indoingso,however,itdoesnotsimplycopytheirfindings,butadaptsthemtobulkchemicalprocessing.Theprincipalobjectivesthatsetchemicalengineeringapartfromchemistryasapurescience,is“tofindthemosteconomicalrouteofoperationandtodesigncommercialequipmentandaccessoriesthatsuititbestofall”.Therefore,chemicalengineeringisinconceivablewithoutclosetieswitheconomics,physics,mathematics,cybernetics,appliedmechanics,andothertechnicalsciences.前述化学工程学都是以化学科学为基础的，如物理化学，化学热力学和化学动力学。然而这样做的时候，它并不是仅仅简单地照搬结论，而是要把这些知识运用于大批量生产的化学加工过程。把化学工程学与纯化学区分开来的首要目的是“找到最经济的生产路线并设计商业化的设备和辅助设备尽可能地适应它。”因此如果没有与经济学，物理学，数学，控制论，应用机械以及其它技术的联系就不能想象化学工程会是什么样的。Initsearlydays,chemicalengineeringwaslargelyadescriptivescience.Manyoftheearlytextbooksandmanualsonchemicalengineeringwereencyclopediasofthecommercialproductionprocessesknownatthetime.Progressinscienceandindustryhasboughtwithitanimpressiveincreaseinthenumberofchemicalmanufactures.Today,petroleumforexampleservesasthesourcematerialfortheproductionofabout80thousandchemicals.Theexpansionofthechemicalprocessindustriesontheonehandandadvancesinthechemicalandtechnicalsciencesontheotherhavemadeitpossibletolaytheoreticalfoundationsforchemicalprocessing.早期的化学工程学以描述性为主。许多早期的有关化学工程的教科书和手册都是那个时候已知的商品生产过程的百科全书。科学和工业的发展使化学品的制造数量迅速增加。举例来说，今天石油已经成为八万多种化学产品生产的原材料。一方面是化学加工工业扩张的要求，另一方面是化学和技术水平的发展为化学工艺建立理论基础提供了可能。Asthechemicalprocessindustriesforgedahead,newdata,newrelationshipsandnewgeneralizationswereaddedtothesubject-matterofchemicalengineering.Manybranchesintheirownrighthaveseparatedfromthemainstreamofchemicalengineering,suchasprocessandplantdesign,automation,chemicalprocesssimulationandmodeling,etc.随着化学加工工业的发展，新的数据，新的关系和新的综论不断添加到化学工程学的目录中。然后又从主干上分出许多的分支，如工艺和工厂设计，自动化，化工工艺模拟和模型，等等。1.ABriefHistoricalOutlineHistorically,chemicalengineeringisinseparablefromthechemicalprocessindustries.Initsearlydayschemicalengineeringwhichcameintobeingwiththeadventofearlychemicaltradeswasapurelydescriptivedivisionofappliedchemistry.1．简要的历史轮廓从历史上来说，化学工程学与化学加工工业密不可分。在早期，化学工程学随着早期化学产品交易的发展而出现，是应用化学的纯描述性的分支。ThemanufactureofbasicchemicalproductsonEuropeappearstohavebeguninthe15thcenturywhensmall,specializedbusinesseswerefirstsetuptoturnoutacids,alkalis,salts,pharmaceuticalpreparations,andsomeorganiccompounds.在欧洲，基础化学产品的制造出现在15世纪。一些小的、专门的企业开始创立，生产酸、碱、盐、药物中间体和一些有机化合物。Foralltherhetoricofnineteenth-centuryacademicchemistsinBritainurgingthepriorityofthestudyofpurechemistryoverapplied,theirstudentswhobecameworkschemistswerelittlemorethanqualitativeandquantitativeanalysts.Beforethe1880sthiswasequallytrueofGermanchemicalfirms,whoremainedcontenttoretainacademicconsultantswhopursuedresearchwithintheuniversityandwhowouldoccasionallyprovidethematerialformanufacturinginnovation.Bythe1880s,however,industrialistswerebeginningtorecognizethatthescalingupofconsultants’laboratorypreparations,andsyntheseswasadistinctlydifferentactivityfromlaboratoryinvestigation.Theybegantorefertothisscalingproblemanditssolutionas“chemicalengineering”—possiblybecausethemechanicalengineerswhohadalreadybeenintroducedintoworkstowhoseemedbestabletounderstandtheprocessinvolved.Theacademicdichotomyofheadandhanddiedslowly.由于十九世纪英国的学院化学家强调纯化学的研究高于应用化学，他们的要成为工业化学家的学生也只是定性和定量分析者。在19世纪80年代以前，德国的化学公司也是这样。他们愿意聘请那些在大学里进行研究的人作顾问，这些人偶尔为制造的革新提供一些意见。然而到了80年代，工业家们开始认识到要把顾问们在实验室的准备和合成工作进行放大是一个与实验室研究截然不同的活动。他们开始把这个放大的问题以及解决的方法交给“化学工程师”—这可能是受到已经进入工厂的机械工程师的表现的启发。由于机械工程师熟悉所涉及的加工工艺，是维修日益复杂化的工业生产中的蒸气机和高压泵的最合适的人选。学院研究中头和手两分的现象逐渐消亡。Unitoperation.InBritainwhenin1881therewasanattempttonamethenewSocietyofChemicalindustryasthe“SocietyofChemicalengineers”,thesuggestionwasturneddown.Ontheotherhand,asaresultofgrowingpressurefromtheindustrialsectorthecurriculaoftechnicalinstitutionsbegantoreflect,atlast,theneedforchemicalengineersratherthancompetentanalysts.Nolongerwasmeredescriptionofexistingindustrialprocessestosuffice.Insteadtheexpectationwasthattheprocessesgenerictovariousspecificindustrieswouldbeanalyzed,thusmakingroomfortheintroductionofthermodynamicperspectives,aswellasthosebeingopenedupbuythenewphysicalchemistryofkinetics,