SustainableProcessDesignandLife-cycleAssessment(LCA)ofHydrogenProductionusingNaturalGas

Abstract

Thegoalofreachingnetzeroby2050hasbeenestablishedtoaddressexistingenvironmentalconcerns.Hydrogenisanticipatedtoplayakeyroleinachievingtheenergytransitionsinceitcanbeutilizedasvarioustypesoffuelstogeneratedifferentkindsofenergy.Itismainlyproducedbysteammethanereforming(SMR)technologyusingnaturalgasinthepresent,althoughthisusesalotofsteamandthermalenergy,bothofwhichhaveahighCO2cost. Todevelopenvironmentallyadvancedhydrogenproductionprocesses,otherreactions,includingauto-thermalreforming(ATR)andpartialoxidation(POX),havebeensuggestedinthisresearch.Additionally,electricheatersreplacedtheconventionalfurnacesintheSMRandATRprocesses,andtheOrganicRankineCycle(ORC)convertedleftoverheattoelectricity.Finally,thecarboncaptureunithasbeenintegratedintoeachprocessforthesakeofcarbonreduction.TheprocessesaredescribedinthereportbyIEAGHGandsimulatedthroughAspenHYSYS®.Then,theenvironmentaleffectswerequantifiedfromprocessdatausingSimaPro®aspartofthelife-cycleassessmentprocess,specificallytheglobalwarmingpotential(GWP).TheassessmentsfollowedIPCC2013GWP100amethodwithEcoinvent3database. TheSMRprocesshada77.6%largeremissionwithane-furnacethanthebasecasebecausethereactorisincapableofburningallthemethanebyitselfandtheoff-gaswasassumedtobereleaseddirectlytotheair.Eventhecarboncapturecannotdroptill10.44GWPofthebasescenariosincetheCH4accountingratiowasfartoohigh.So,itneededanadditionalfurnaceafterthePSAunit,whichcandecreasetheemissionto2.62GWPand-1.51GWPwiththecarboncapture.Otherwise,ATRreactorcanutilizethemethaneforcombustionreactions,resultingin11.01GWP,whichisalowervaluethantheSMRelectrificationcaseandtheATRbasecase.Also,mostoftheemissionwasconsistofCO2,whichcanbecapturedbytheunit,sothattheelectrificationandcarboncapturecasehadarelativelylowemissionof4.66kg.Lastly,POXhasbenefitedfromtheprocessrenovation,asithastheabilitytodirectlyburnmethaneinthereactor.Itimpliesthattheoff-gasdidnotcontainCH4andthattheCO2wascapturedbythemonoethanolamine(MEA).TheprocesswiththeORCsystemhad11.03GWP,whichis0.29lowerthanthebasecase,andthecarboncapturereduceditsvalueto2.55GWP.Inconclusion,theSMRprocesswithanelectricheateristheworstoption,sothatitneedsanadditionalburner.ThePOXprocesswithORCandcarboncaptureisoneoftheenvironment-friendlyscenarios,evenwithoutafurnace.