06 Introduction To Heat Exchanger Network Synthesis.ppt

6 introhensynthesis designandanalysisii c danielr lewin 1 054402designandanalysisii lecture6 introductiontoheatexchangernetworksynthesisdanielr lewindepartmentofchemicalengineeringtechnion haifa israel 6 introhensynthesis designandanalysisii c danielr lewin 2 schedule introductiontohensynthesis unit1 introduction capitalvs energywhatisanoptimalhendesignasimpleexample classexercise1 settingenergytargetsunit2 thepinchandmerdesigntheheatrecoverypinchhenrepresentationclassexercise2unit3 theproblemtableclassexercises3and4 6 introhensynthesis designandanalysisii c danielr lewin 3 schedule advancedhensynthesis unit4 loopsandsplitsminimumnumberofunitsbyloopbreakingclassexercise5streamsplitdesignsclassexercise6unit5 thresholdproblemsclassexercise7 6 introhensynthesis designandanalysisii c danielr lewin 4 schedule heatandpowerintegration unit6 dataextractionclassexercise8unit7 heatintegrationindesigngrandcompositecurveheat integrateddistillationheatenginesheatpumps 6 introhensynthesis designandanalysisii c danielr lewin 5 partone objectives thefirstpartofthisthree partunitonhensynthesisservesasanintroductiontothesubject andcovers the pinch thedesignofhentomeetmaximumenergyrecovery mer targetstheuseoftheproblemtabletosystematicallycomputemertargetsinstructionalobjectives givendataonhotandcoldstreams youshouldbeableto computethepinchtemperaturescomputemertargetsdesignasimplehentomeetthemertargets 6 introhensynthesis designandanalysisii c danielr lewin 6 ashortbibliography earlypioneers rudd wisconsin 1968 hohmann usc 1971 centralfigure linnhoff ici umist 1978 currently president linnhoff marchrecommendedtexts seider seaderandlewin 1999 processdesignprinciples wileyandsons nylinnhoffetal 1982 auserguideonprocessintegrationfortheefficientuseofenergy i chem e londonmostup to datereview gundersen t andnaess l 1988 thesynthesisofcostoptimalheatexchangernetworks anindustrialreviewofthestateoftheart comp chem eng 12 6 503 530 6 introhensynthesis designandanalysisii c danielr lewin 7 unit1 introduction capitalvs energy thedesignofheatexchangernetworksdealswiththefollowingproblem given nhhotstreams withgivenheatcapacityflowrate eachhavingtobecooledfromsupplytemperaturethstotargetstht nccoldstreams withgivenheatcapacityflowrate eachhavingtobeheatedfromsupplytemperaturetcstotargetstct design anoptimumnetworkofheatexchangers connectingbetweenthehotandcoldstreamsandbetweenthestreamsandcold hotutilities furnace hot oil steam coolingwaterorrefrigerant dependingontherequireddutytemperature whatisoptimal impliesatrade offbetweencapitalcosts costofequipment andenergycosts costofutilities 6 introhensynthesis designandanalysisii c danielr lewin 8 example networkforminimalenergycost networkforminimalequipmentcost 6 introhensynthesis designandanalysisii c danielr lewin 9 numericalexample designb area 13 3 designa area 20 4 a q u tlm 6 introhensynthesis designandanalysisii c danielr lewin 10 somedefinitions ts streamsupplytemperature oc tt streamtargettemperature oc h streamenthalpy mw cp mw oc heatcapacityflowrate mw oc streamflowratespecificheatcapacity 6 introhensynthesis designandanalysisii c danielr lewin 11 whichofthetwocounter currentheatexchangersillustratedbelowviolates t 20of i e tmin 20of clearly exchangeraviolatesthe tminconstraint dtmin example tmin lowestpermissibletemperaturedifference 6 introhensynthesis designandanalysisii c danielr lewin 12 definitions cont d 6 introhensynthesis designandanalysisii c danielr lewin 13 utilities steam 150oc cw 25ocdesignanetworkofsteamheaters watercoolersandexchangersfortheprocessstreams wherepossible useexchangersinpreferencetoutilities tmin 10oc classexercise1 6 introhensynthesis designandanalysisii c danielr lewin 14 settingenergytargets summaryofproposeddesign are60kwofsteamnecessary 6 introhensynthesis designandanalysisii c danielr lewin 15 thetemperature enthalpydiagram onehotstream twohotstreams 6 introhensynthesis designandanalysisii c danielr lewin 16 thetemperature enthalpydiagram correlationbetween tmin qhminandqcminmorein moreout qhmin x qcmin x 6 introhensynthesis designandanalysisii c danielr lewin 17 thecompositecurve hotcompositecurve 6 introhensynthesis designandanalysisii c danielr lewin 18 thecompositecurve cont d coldcompositecurve 6 introhensynthesis designandanalysisii c danielr lewin 19 thecompositecurve cont d method manipulatehotandcoldcompositecurvesuntilrequired tminissatisfied thisdefineshotandcoldpinchtemperatures 6 introhensynthesis designandanalysisii c danielr lewin 20 unit2 thepinch the pinch separatesthehenproblemintotwoparts heatsink abovethepinch whereatleastqhminutilitymustbeusedheatsource belowthepinch whereatleastqcminutilitymustbeused x x 6 introhensynthesis designandanalysisii c danielr lewin 21 significanceofthepinch donottransferheatacrosspinchdonotusecoldutilitiesabovethepinchdonotusehotutilitiesbelowthepinch summaryofmodifieddesign 6 introhensynthesis designandanalysisii c danielr lewin 22 henrepresentation whereisthepinch 6 introhensynthesis designandanalysisii c danielr lewin 23 henrepresentationwiththepinch thepinchdividesthehenintotwoparts thelefthandside abovethepinch therighthandside belowthepinch atthepinch allhotstreamsarehotterthanallcoldstreamsby tmin 6 introhensynthesis designandanalysisii c danielr lewin 24 classexercise2 forthisnetwork drawthegridrepresentationgivenpinchtemperaturesat480oc 460oc andmertargets qhmin 40 qcmin 106 redrawthenetworkseparatingthesectionsaboveandbelowthepinch whyisqh qhmin 6 introhensynthesis designandanalysisii c danielr lewin 25 classexercise2 solution 6 introhensynthesis designandanalysisii c danielr lewin 26 classexercise2 solution cont d thiscanbefixedbyreducingthecoolingdutyby10units andeliminatetheexcess10unitsofheatingbelowthepinch 6 introhensynthesis designandanalysisii c danielr lewin 27 designformaximumenergyrecovery mer step1 mertargeting pinchat90o hot and80o cold energytargets totalhotutilities 20kwtotalcoldutilities 60kw example 6 introhensynthesis designandanalysisii c danielr lewin 28 designformer cont d step2 dividetheproblematthepinch 6 introhensynthesis designandanalysisii c danielr lewin 29 designformer cont d step3 designhot end startingatthepinch pairupexchangersaccordingtocp constraints immediatelyabovethepinch pairupstreamssuchthat cphot cpcold thisensuresthatth tc tmin 6 introhensynthesis designandanalysisii c danielr lewin 30 designformer cont d step3 cont d completehot enddesign byticking offstreams 90 240 addheatingutilitiesasneeded mertarget qhmin 20kw 20 6 introhensynthesis designandanalysisii c danielr lewin 31 designformer cont d step4 designcold end startingatthepinch pairupexchangersaccordingtocp constraints immediatelyabovethepinch pairupstreamssuchthat cphot cpcold thisensuresthatth tc tmin 6 introhensynthesis designandanalysisii c danielr lewin 32 designformer cont d step4 cont d completecold enddesign byticking offstreams addcoolingutilitiesasneeded mertarget qcmin 60kw 30 90 60 35o 6 introhensynthesis designandanalysisii c danielr lewin 33 designformer cont d completeddesign notethatthisdesignmeetsthemertargets qhmin 20kwandqcmin 60kw 6 introhensynthesis designandanalysisii c danielr lewin 34 designformer cont d designformer summary mertargeting definepinchtemperatures qhminandqcmindivideproblematthepinchdesignhot end startingatthepinch pairupexchangersaccordingtocp constraints immediatelyabovethepinch pairupstreamssuchthat cphot cpcold tickoff streamsinordertominimizecosts addheatingutilitiesasneeded uptoqhmin donotusecoldutilitiesabovethepinch designcold end startingatthepinch pairupexchangersaccordingtocp constraints immediatelybelowthepinch pairupstreamssuchthat cphot cpcold tickoff streamsinordertominimizecosts addheatingutilitiesasneeded uptoqcmin donotusehotutilitiesbelowthepinch done 6 introhensynthesis designandanalysisii c danielr lewin 35 classexercise3 designanetworkofsteamheaters watercoolersandexchangersfortheprocessstreams wherepossible useexchangersinpreferencetoutilities tmin 10oc utilities steam 150oc cw 25oc qhmin 48 qcmin 6 54 120 43oc 6 100 8 40 6 introhensynthesis designandanalysisii c danielr lewin 36 unit3 theproblemtable tmin 10of example step1 temperatureintervals subtract tminfromhottemperatures temperatureintervals 250 f 240 f 235 f 180 f 150 f 120 f 6 introhensynthesis designandanalysisii c danielr lewin 37 unit3 theproblemtable cont d step2 intervalheatbalancesforeachinterval compute hi ti ti 1 cphot cpcold 6 introhensynthesis designandan