Kraft Foods relies on industrial heat pump for sustainable operations
Result•Annualoperatingsavingsof$267,407
•14,000,000gallonsofwatersavedannually
•Wasteheatrecoveryof7.0MMBtuh(2.1MW)
•6.51coefficientofperformance(summer)
•4.23coefficientofperformance(winter)
•Ammoniarefrigerantwith0ODP&0GWP
•15%higherefficiencythancomparabletechnologies
•Designfor+20yearsservicewithoutcostlymaintenance
ApplicationInnovativeammoniaheatpumpplantusingheatextractedfromrefrigerationforenergysavingheatingandcoolingsystem.
CustomerKraftFoodsplantinDavenport,Iowa.
ChallengeTheKraftFoodsplantinDavenport,Iowa,madesignificantinvestmentsinenergyconservation.Withafocusonenergysavings,theplantinstalledhighefficiencyboilersandinvestedtocaptureandrecoverboilerstackheat.
Yet,likemanyfoodprocessingplants,KraftFoodswaspayingforelectricalenergytoremoveheatfromtheirrefrigeratedspaceswithanammoniarefrigerationsystemandrejectingthatheattotheatmosphere.Also,theywerepayingfornaturalgastoaddheattohotwaterusedforthehygieniccleaningoftheplant.
“The heat pump automatically responds to varying operating conditions for the ammonia and hot water. There is very little input needed from the operators. Maintenance requirements are really no different than what is already required for existingcompressors, vessels and heat exchangers.Between the boiler stack gas heat recovery and the heat pump, we no longer use the conventional hot water heaters on a daily basis.”
DonStroud,InfrastructureProgramManager,Kraft Foods
Iftherejectedheatcouldbecapturedandusedtoprovidewaterheating,substantialenergywouldbesaved.Thehighestpressuresandtemperaturesintherefrigerationsystem(compressordischargegas)providedthebestsourceforheattobetransferredtothesanitationclean-upwater.But,asammoniarefrigerationpractitionerswhohaveemployed“heatreclaim”practiceshavenoted,ammoniaattypicalcondensingpressures,whilepossessinglargequantitiesofheatenergy,condensesatfairlylowtemperatures[75-95°F(24-35°C)].Thetransferofthisenergytocitywater,throughconventionalheatexchangers,tocreate145-185°F(63-85°C)washdownwater,isonlyeffectiveforlimitedpre-heatingofthecoldwatersupply.
Iftherefrigerationsystemcompressordischargegas,atfairlyhighpressures[180psig(13.2atm)]couldbefeddirectlyintothesuctionofa“heatpump”compressorandcompressedtoevenhigherpressures[i.e.450-800psig(32-55atm)],condensingthishigherpressureammoniawithcoldwaterinaheatexchangerwouldcapturemuchlargerquantitiesofheatenergythanheatreclaimandelevatethecoldwatersupplyfrom60°F(15°C)uptothe145°F(63°C)requiredforwashdown.
Therequirementoftheplanttohavethewashdownwaterclassifiedasapotablesupplypresentedanotherchallenge,aslocalcodesprohibitpotablewatertobeindirectheatexchangewithammonia.Usingsuchanammoniaheatpumpsystemwouldrequireasecondaryloop,therebyloweringtheefficiencyofheattransfer.
Giventheneedforsustainableprojectstoclearthesameinternalrateofreturnhurdleasnon-sustainableprojects,thechallengewastodefineandjustifytheproject.Theprojectcostswouldincludetappingintotheammoniarefrigerationsystem,addingandinstallingacustomammoniaheatpumpsystemandemployingtheelectricalenergytooperatethehighpressureammoniaheatpumpsystem.
SolutionTheammoniaheatpumpsystemdelivershotwaterat145°Fusingheatextractedfromrefrigerationandfeatures Vilter™singlescrewcompressors.Theinherenthighpressurecapabilityofthesinglescrewcompressorallowsforfullacceptanceofthehighestoperatingdischargepressurefromthehostsystem,eveninexcessof180psig,withouttheriskofrotordeflectionandexcessivebearingthrustloads,whichcanresultinaccelerateddegradation,orthelossofefficiencyduetoover-compression.
Withthelower60°F(15.6°C)incomingcoldwatertemperatureduringwinter,theestimatedheatingcapacityoftheheatpumpduringwinterconditionswasestimatedat5.738MMBtuh(1,682kW),providing135GPM(30.7m3/h)ofcontinuous145°F(62.8°C)hotwaterflow.Theheatpumpwasestimatedtoprovideanaverageyear-roundheatingcapacityof7.013MMBtuh(2,056kW),heating170GPM(38.6m3/h)from62.5°F(16.9°C)to145°F(62.8°C).
Sincecommissioning,theplantisheating170gallonsperminuteofwater.Andthishotwaterisdeliveredfarmoreefficientlythanfromtheirnaturalgashotwaterheater.Theammoniaheatpumpsolutionhascutheatenergycostbyover$250,000eachyearandsavesfourteenmilliongallonsofwaterperyearbecauseofthereducedloadontheevaporativecondensers.
Byusingammonia,Emerson’scompressortechnologysolutionoffersarefrigerantwithagoodenvironmentalprofile(non-ozonedepletingandzeroglobalwarmingimpact),delivershighertemperaturesandprovidessuperiorperformancebenefitsfromitsconsumedresourcesthancompetingtechnologies.Also,thebalancedradialandaxialforcedesignofthesinglescrewcompressorlowersstressontheunit’sbearings,resultinginlowoperatingandmaintenancecostswhiledeliveringaperformanceunachievablewithanyothertypeofcompressor.
ResourcesLearnmoreaboutindustrialheatpumpsystems,featuringViltersinglescrewcompressorsatEmersonClimate.com/IndustrialHeatPumps
2012VM-19R1(09/12)EmersonandVilteraretrademarksofEmersonElectricCo.oroneofitsaffiliatedcompanies.OSCARMAYERisatrademarkofKraftFoodsCompanyintheU.S.and/orothercountries.©2012EmersonClimateTechnologies,Inc.Allrightsreserved.PrintedintheUSA.
