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RetrofittingofadistillerybasedonprocesssynthesisZhaolinGu*,ZhonghuaTao,NanXu,YunLiDepartmentofEnvironmentalScienceandTechnology,SchooloftheBuiltEnvironmentandCivilEngineering,Xi’anJiaoTongUniversity,No.28,XianWestRoad,710049Xi’an,PRChinaReceived10January2006;accepted15July2006Availableonline18September2006AbstractThisworkpointsoutsomeimproperheatexchangersettingsandretrofitmodificationsbytheprocessintegrationtechnology,study-ingthecaseofthefivecolumnalcoholdistillationsection,whichisbroadlyusedinnewdistilleriesinChina.Intherectificationgrandcompositecurve,thereisamassofsecondaryvaporwiththetemperatureofabout80C,belowthepinch.SomeofitisusedastheheatsourcefortheLiBr–H2Oabsorptionrefrigeratorthroughthesingleeffectrefrigeratingcycle,andtherefore,thispartofthesecondaryvaporischangedintoliquidwithoutcondensationandcooling.Atthesametime,thelowtemperaturecoolingwaterisgeneratedfromtherefrigeratingcycle,anditcanbeusedintheothersections,exceptthedistillation,likethefermentationandcoolingtheendproduct.Theothersecondaryvaporisupgradedbytheheatpumptoreplacethepartialheatingsteam.Aftertheaboveretrofittingforthedistillerywiththeannualyieldof49,416kl,247.1t/hlowtemperaturecoolingwatercanbeobtainedtoreplacethedeepwellwatercompletely;theamountofheatingsteamandrecycledcoolingwater,respectively,isdecreasedby8.257t/hand205.9t/h,butthepowerconsumptionisraisedby445.6kWfordrivingtheheatpumpcompressor.Bythermoeconomicanalysis,thefollowingperformanceoftheretrofittingcasecanbeachieved:anoverallinvestmentof7,476,900¥RMB,savingsof7,452,100¥RMB/yearintheoperatingcostandsavingsof187.5¥RMB/tintheproductioncost,thepaybackperiodwillbe1.01years.2006ElsevierLtd.Allrightsreserved.Keywords:Alcoholdistillation;Energysaving;Watersaving;Processintegration1.IntroductionAlcoholalwaysplaysanimportantroleinmanyindus-tries,suchasfood,chemicalengineering,electronics,med-icine,spice,cosmeticsandsoon.Forsustainabledevelopmentofthedomesticeconomy,Chinaispromotingmobileethanolgasolineasanalternativetofueloil.Etha-nolgasolineisthefuelfortheignitionofinternalcombus-tionengines,whichismadefromanhydrousalcohol.Addingsomeadditivesintoanhydrousalcoholmakesfuelalcohol,andthen,themixtureisthemobileethanolofwhichthefuelalcoholandthegasolineisintheratioof10–100[1,2].However,now,thecostoffuelethanolishigherthanthecostofgasoline,mainlybecauseofthehighcostofanhydrousalcohol.So,retrofittingtosavetheman-ufacturingcostisreallyimportant[3,4].Inthetraditionalalcoholproductionprocess,thecon-sumptionofsteamandcoolingwaterintherectificationsectionis60–70%oftheconsumptionofthewholeprocess.Mostoftheheatislostandtakenawaybythecoolingwaterandthewasteliquid,andanamountofthewastewaterisdischargedatthesametime[4].So,reducingtheconsumptionofenergyandthelowtemperaturecoolingwatermakesforreducedcostandthedevelopmentofclearproduction.Thealcoholmanufacturingprocess,aninte-gratedheatexchangersnetworkwithmulti-columns,isusuallyanalyzedbysomesystemicanalyticmethods[5],andthepinchtechnologyisespeciallycredible[6,7].Fica-rellaandLaforgia[8]presentedapinchtechnologyanalysisofadistillery,aimingatoptimizationoftheheatexchang-ersnetworkformaximumenergyrecoveryandapplicationofacombinedcogenerationpowerplantandheatpump.0196-8904/$-seefrontmatter2006ElsevierLtd.Allrightsreserved.doi:10.1016/j.enconman.2006.07.006*Correspondingauthor.Tel./fax:[phone].E-mailaddress:[e-mail](Z.Gu).(2007)335–343Whenemployingheatpumpsandrefrigeratingsystems,whichareputforwardonthebasisofthepinchtechnology,intherectification,theperformanceofthemselvesshouldbetakenintoaccount[9].Inaddition,thevariableratiooftheelectricalpricetothesteampriceindifferentplacesshouldalsobeconsidered,sothermoeconomicsanalysisisindispensable[10,11].Performingahighlyefficientclearproductionisthedevelopmentaldirectionofthepresentdesignandretrofit-tingofalcoholproduction[12],butitisnotenoughforadistilleryonlytotakeintoaccountthedistillationsection.Inprocessintegration,othersectionsinadditiontothedis-tillationmightbeconsidered,suchasfermentation,dregstreatment,endalcoholstorageandsoon.Thesesectionsalsoinvolvealargenumberofusagesofcoolingwaterandheatexchangers[13].Therefore,theheatexchangernetwork(HEN)[14]andwaterconsumption[15]involvingthemulti-columnisalsoacomplextask.Thisworkintroducespinchtechnologyintothecasestudyofthefivecolumndistillationsection,whichisbroadlyusedinnewdistilleriesinChina,andanalyzestheutilizationstateofenergyandwateroftheexistingsys-tem.Itthenpointsouttheimproperheatexchangersset-tingsandputsforwardpreliminaryretrofittingprojects.Byanalyzingtheprocessgrandcompositecurve,thefol-lowingretrofittingisdecided:usingthesecondaryalcoholvaporbelowthepinchtoproducecoolingwaterwiththetemperatureofabout17C,whichisusedinthenon-distil-lationsectionslikefermentationandendproductcooling;thenusingheatpumpstoreplacepartialheatingsteam.Attheend,theoptimizedretrofittingprojectsareanalyzedbythermoeconomictheory.2.BriefsoftheexistingfivecolumndistillationflowsheetAbasicmanufacturing