化工前沿知识讲座幻灯片

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1、Unit6Chlor-AlkaliandRelatedProcessesByZhaoYa-qiDepartmentofChemicalEngineeringContents1.Lime-BasedProducts2.Soda-Ash3.ElectrolyticProcessesforChlorine/CausticSoda4.TheUsesofChlorineandSodiumHydroxideGuidingquestionsListsomemajorproductsinthechlor-alkaliprocesses.

2、DescribebrieflytheSolvayammoniasodaprocess.Outlinethemainstepsinmarkingsulfuricacid.Pointoutthemajorusesofsomemainproductsdescribedinthetext.PreludeHistoricallythebulkchemicalindustry(大化工)wasbuiltonchlor-alkaliandrelatedprocesses.Thesegmentisnormallytakentoinclud

3、etheproductionofchlorinegas,causticsoda(sodiumhydroxide),soda-ash(derivativesofsodiumcarbonateinvariousforms)and,forconvenience,lime-basedproducts.Soda-ashandsodiumhydroxidehavecompetedwitheachotherasthemajorsourceofalkalieversinceviableprocesseswerediscoveredfor

4、both.Thepeculiareconomicsofelectrolyticprocessesmeanthatyouhavetomakechlorineandcausticsodatogetherinafixedratiowhatevertherelativedemandforthetwototallydifferenttypesofproduct,andthiscausesswingsinthepriceofcausticsodawhichcanrendersoda-ashmoreorlessfavorableasa

5、nalkali.Bothchlorine/causticsodaandsoda-ashproductionaredependentoncheapreadilyavailablesuppliesofrawmaterials.Chlorine/causticsodarequiresareadysupplyofcheapbrineandelectricity,soda-ashrequiresbrine,limestoneandlotsofenergy.Soda-ashplantsareonlyprofitableiftheir

6、rawmaterialsdonothavetobetransportedfar.Theavailabilityofsuchsuppliesisamajorfactorinthelocationofmanyofthechemicalindustry’sgreatcomplexes.Oneofthekeyrawmaterialsislime.Limestoneconsistsmostlyofcalciumcarbonate(CaCO3)laiddownovergeologicaltimebyvariousmarineorga

7、nisms.High-qualitylimestonesareoftengoodenoughtobeuseddirectlyascalciumcarbonateinfurtherreactions.LimestoneisusuallyminedinvastoLine-BasedProductspen-castquarries,manyofwhichwillalsocarryoutsomeprocessingofthematerials.Thetwokeyrawproductsderivedfromlimestoneare

8、quicklime(CaO)andslakedlime(Ca(OH)2).Quicklimeismanufacturedbythethermaldecomposition(1200~1500℃)oflimestoneaccordingtotheequation:CaCO3→CaO+CO2Lime-BasedProdu