Molten carbonate fuel cell - Wikipedia

MCFCs are high-temperature fuel cells that use an electrolyte composed of a molten carbonate salt mixture suspended in a porous, chemically inert ceramic matrix ... Moltencarbonatefuelcell FromWikipedia,thefreeencyclopedia Jumptonavigation Jumptosearch Schemeofamolten-carbonatefuelcell Molten-carbonatefuelcells(MCFCs)arehigh-temperaturefuelcellsthatoperateattemperaturesof600 °Candabove. Moltencarbonatefuelcells(MCFCs)weredevelopedfornaturalgas,biogas(producedasaresultofanaerobicdigestionorbiomassgasification),andcoal-basedpowerplantsforelectricalutility,industrial,andmilitaryapplications.MCFCsarehigh-temperaturefuelcellsthatuseanelectrolytecomposedofamoltencarbonatesaltmixturesuspendedinaporous,chemicallyinertceramicmatrixofbeta-aluminasolidelectrolyte(BASE).Sincetheyoperateatextremelyhightemperaturesof650 °C(roughly1,200 °F)andabove,non-precious[dubious–discuss]metalscanbeusedascatalystsattheanodeandcathode,reducingcosts.[1] ImprovedefficiencyisanotherreasonMCFCsoffersignificantcostreductionsoverphosphoricacidfuelcells(PAFCs).Moltencarbonatefuelcellscanreachefficienciesapproaching60%,considerablyhigherthanthe37–42%efficienciesofaphosphoricacidfuelcellplant.Whenthewasteheatiscapturedandused,overallfuelefficienciescanbeashighas85%.[1] Unlikealkaline,phosphoricacid,andpolymerelectrolytemembranefuelcells,MCFCsdon'trequireanexternalreformertoconvertmoreenergy-densefuelstohydrogen.DuetothehightemperaturesatwhichMCFCsoperate,thesefuelsareconvertedtohydrogenwithinthefuelcellitselfbyaprocesscalledinternalreforming,whichalsoreducescost.[1] Moltencarbonatefuelcellsarenotpronetopoisoningbycarbonmonoxideorcarbondioxide—theycanevenusecarbonoxidesasfuel—makingthemmoreattractiveforfuelingwithgasesmadefromcoal.Becausetheyaremoreresistanttoimpuritiesthanotherfuelcelltypes,scientistsbelievethattheycouldevenbecapableofinternalreformingofcoal,assumingtheycanbemaderesistanttoimpuritiessuchassulfurandparticulatesthatresultfromconvertingcoal,adirtierfossilfuelsourcethanmanyothers,intohydrogen.Alternatively,becauseMCFCsrequireCO2bedeliveredtothecathodealongwiththeoxidizer,theycanbeusedtoelectrochemicallyseparatecarbondioxidefromthefluegasofotherfossilfuelpowerplantsforsequestration. TheprimarydisadvantageofcurrentMCFCtechnologyisdurability.Thehightemperaturesatwhichthesecellsoperateandthecorrosiveelectrolyteusedacceleratecomponentbreakdownandcorrosion,decreasingcelllife.Scientistsarecurrentlyexploringcorrosion-resistantmaterialsforcomponentsaswellasfuelcelldesignsthatincreasecelllifewithoutdecreasingperformance.[1] Contents 1Operation 1.1Background 1.2Reactions[5] 1.3Materials 1.3.1Anode 1.3.2Cathode 1.3.3Electrolyte 2MTUfuelcell 3Seealso 4References 5Sources 6Externallinks Operation[edit] Background[edit] MoltencarbonateFCsarearecentlydevelopedtypeoffuelcellthattargetssmallandlargeenergydistribution/generationsystemssincetheirpowerproductionisinthe0.3-3MWrange.[2]Theoperatingpressureisbetween1-8atmwhilethetemperaturesarebetween600and700 °C.[3]DuetotheproductionofCO2duringreformingofthefossilfuel(methane,naturalgas),MCFCsarenotacompletelygreentechnology,butarepromisingduetotheirreliabilityandefficiency(sufficientheatforco-generationwithelectricity).CurrentMCFCefficienciesrangefrom60to70%.[4] Reactions[5][edit] InternalReformer: C H 4 + H 2 O = 3 H 2 + C O {\displaystyleCH_{4}+H_{2}O=3H_{2}+CO} Anode: H 2 + C O 3 2 − = H 2 O + C O 2 + 2 e − {\displaystyleH_{2}+CO_{3}^{2-}=H_{2}O+CO_{2}+2e^{-}} Cathode: 1 2 O 2 + C O 2 + 2 e − = C O 3 2 − {\displaystyle{\frac{1}{2}}O_{2}+CO_{2}+2e^{-}=CO_{3}^{2-}} Cell: H 2 + 1 2 O 2 = H 2 O {\displaystyleH_{2}+{\frac{1}{2}}O_{2}=H_{2}O} NernstEquation: E = E o + R T 2 F l o g P H 2 P O 2 1 2 P H 2 O + R T 2 F l o g P C O 2 , c a t h o d e P C O 2 , a n o d e {\displaystyleE=E^{o}+{\frac{RT}{2F}}log{\frac{P_{H_{2}}P_{O_{2}}^{\frac{1}{2}}}{P_{H_{2}O}}}+{\frac{RT}{2F}}log{\frac{P_{CO_{2},cathode}}{P_{CO_{2},anode}}}} Materials[edit] DuetothehighoperatingtemperaturesofMCFC's,thematerialsneedtobeverycarefullyselectedtosurvivetheconditionspresentwithinthecell.Thefollowingsectionscoverthevariousmaterialspresentinthefuelcellandrecentdevelopmentsinresearch. Anode[edit] Theanodematerialtypicallyconsistsofaporous(3-6μm,45-70%materialporosity)Nibasedalloy.NiisalloyedwitheitherChromiumorAluminuminthe2-10%range.ThesealloyingelementsallowforformationofLiCrO2/LiAlO2atthegrainboundaries,whichincreasesthematerials'creepresistanceandpreventssinteringoftheanodeatthehighoperatingtemperaturesofthefuelcell.[6]RecentresearchhaslookedatusingnanoNiandotherNialloystoincreasetheperformanceanddecreasetheoperatingtemperatureofthefuelcell.[7]Areductioninoperatingtemperaturewouldextendthelifetimeofthefuelcell(i.e.decreasecorrosionrate)andallowforuseofcheapercomponentmaterials.Atthesametime,adecreaseintemperaturewoulddecreaseionicconductivityoftheelectrolyteandthus,theanodematerialsneedtocompensateforthisperformancedecline(e.g.byincreasingpowerdensity).OtherresearchershavelookedintoenhancingcreepresistancebyusingaNi3AlalloyanodetoreducemasstransportofNiintheanodewheninoperation.[8] Cathode[edit] Ontheothersideofthecell,thecathodematerialiscomposedofeitherLithiummetatitanateorofaporousNithatisconvertedtoalithiatednickeloxide(lithiumisintercalatedwithintheNiOcrystalstructure).Theporesizewithinthecathodeisintherangeof7-15μmwith60-70%ofthematerialbeingporous.[9]TheprimaryissuewiththecathodematerialisdissolutionofNiOsinceitreactswithCO2whenthecathodeisincontactwiththecarbonateelectrolyte.ThisdissolutionleadstoprecipitationofNimetalintheelectrolyteandsinceitiselectricallyconductive,thefuelcellcangetshortcircuited.Therefore,currentstudieshavelookedintotheadditionofMgOtotheNiOcathodetolimitthisdissolution.[10]MagnesiumoxideservestoreducethesolubilityofNi2+inthecathodeanddecreasesprecipitationintheelectrolyte.Alternatively,replacementoftheconventionalcathodematerialwithaLiFeO2-LiCoO2-NiOalloyhasshownpromisingperformanceresultsandalmostcompletelyavoidstheproblemofNidissolutionofthecathode.[10] Electrolyte[edit] MCFC'susealiquidelectrolyte(moltencarbonate)whichconsistsofasodium(Na)andpotassium(K)carbonate.Thiselectrolyteissupportedbyaceramic(LiAlO2)matrixtocontaintheliquidbetweentheelectrodes.Thehightemperaturesofthefuelcellisrequiredtoproducesufficientionicconductivityofcarbonatethroughthiselectrolyte.[3]CommonMCFCelectrolytescontain62%Li2CO3and38%K2CO3.[11]AgreaterfractionofLicarbonateisusedduetoitshigherionicconductivitybutislimitedto62%duetoitslowergassolubilityandionicdiffusivityofoxygen.Inaddition,Li2CO3isaverycorrosiveelectrolyteandthisratioofcarbonatesprovidesthelowestcorrosionrate.Duetotheseissues,recentstudieshavedelvedintoreplacingthepotassiumcarbonatewithasodiumcarbonate.[12]ALi/Naelectrolytehasshowntohavebetterperformance(higherconductivity)andimprovesthestabilityofthecathodewhencomparedtoaLi/Kelectrolyte(Li/Kismorebasic).Inaddition,scientistshavealsolookedintomodifyingthematrixoftheelectrolytetopreventissuessuchasphasechanges(γ-LiAlO2toα-LiAlO2)inthematerialduringcelloperation.Thephasechangeaccompaniesavolumedecreaseintheelectrolytewhichleadstolowerionicconductivity.Throughvariousstudies,ithasbeenfoundthatanaluminadopedα-LiAlO2matrixwouldimprovethephasestabilitywhilemaintainingthefuelcell'sperformance.[12] MTUfuelcell[edit] TheGermancompanyMTUFriedrichshafenpresentedanMCFCattheHannoverFairin2006.Theunitweighs2tonnesandcanproduce240 kWofelectricpowerfromvariousgaseousfuels,includingbiogas.Iffueledbyfuelsthatcontaincarbonsuchasnaturalgas,theexhaustwillcontainCO2butwillbereducedbyupto50%comparedtodieselenginesrunningonmarinebunkerfuel.[13]Theexhausttemperatureis400 °C,hotenoughtobeusedformanyindustrialprocesses.Anotherpossibilityistomakemoreelectricpowerviaasteamturbine.Dependingonfeedgastype,theelectricefficiencyisbetween12%and19%.Asteamturbinecanincreasetheefficiencybyupto24%.Theunitcanbeusedforcogeneration. Seealso[edit] Energyportal Glossaryoffuelcellterms Hydrogentechnologies References[edit] ^abcd "TypesofFuelCells".OfficeofEnergyEfficiencyandRenewableEnergy,UnitedStatesDepartmentofEnergy.Retrieved2016-03-18. ^"TypesofFuelCells-FuelCellEnergy".www.fuelcellenergy.com.Archivedfromtheoriginalon2013-08-25.Retrieved2015-11-02. ^ab"NFCRCTutorial:MoltenCarbonateFuelCell(MCFC)".www.nfcrc.uci.edu.Archivedfromtheoriginalon2018-10-08.Retrieved2015-11-02. ^"TypesofFuelCells|DepartmentofEnergy".energy.gov.Retrieved2015-11-02. ^"HighTemperatureFuelCells"(PDF).UniversityofBabylon.Retrieved1November2015. ^Boden,Andreas(2007)."TheanodeandtheelectrolyteintheMCFC"(PDF).DivaPortal.Retrieved1November2015. ^Nguyen,HoangVietPhuc;Othman,MohdRoslee;Seo,Dongho;Yoon,SungPil;Ham,HyungChul;Nam,SukWoo;Han,Jonghee;Kim,Jinsoo(2014-08-04)."NanoNilayeredanodeforenhancedMCFCperformanceatreducedoperatingtemperature".InternationalJournalofHydrogenEnergy.39(23):12285–12290.doi:10.1016/j.ijhydene.2014.03.253. ^Kim,Yun-Sung;Lim,Jun-Heok;Chun,Hai-Soo(2006-01-01)."CreepmechanismofporousMCFCNianodesstrengthenedbyNi3Al".AIChEJournal.52(1):359–365.doi:10.1002/aic.10630.ISSN 1547-5905. ^Wijayasinghe,Athula(2004)."DevelopmentandCharacterisationofCathodeMaterialsfortheMoltenCarbonateFuelCell"(PDF).Retrieved2November2015. ^abAntolini,Ermete(December2011)."Thestabilityofmoltencarbonatefuelcellelectrodes:Areviewofrecentimprovements".AppliedEnergy.88(12):4274–4293.doi:10.1016/j.apenergy.2011.07.009. ^Fang,Baizeng;Liu,Xinyu;Wang,Xindong;Duan,Shuzhen(1998-01-15)."ThemechanismofsurfacemodificationofaMCFCanode".JournalofElectroanalyticalChemistry.441(1–2):65–68.doi:10.1016/S0022-0728(97)00202-7. ^abKulkarni,A.;Giddey,S.(2012-06-08)."Materialsissuesandrecentdevelopmentsinmoltencarbonatefuelcells".JournalofSolidStateElectrochemistry.16(10):3123–3146.doi:10.1007/s10008-012-1771-y.ISSN 1432-8488. ^MCFCemission Sources[edit] https://web.archive.org/web/20060927032111/http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_types.html#molten Externallinks[edit] LLNL:TheCarbon/AirFuelCellConversionofCoal-DerivedCarbons DoD MTU240kWfuelcellpresentedontheHannoverFair2006 LoganEnergyLimitedintegrate,installandoperateallfuelcelltechnologies [1]moltencarbonatefuelcellsdistributedgenerationchallenge [2]presentationtoFourthAnnualConferenceonCarbonCaptureandSequestration vteFuelcellsByelectrolyte Alkalinefuelcell Moltencarbonatefuelcell Phosphoricacidfuelcell Proton-exchangemembranefuelcell Solidoxidefuelcell Byfuel Direct-ethanolfuelcell Directmethanolfuelcell Formicacidfuelcell Reformedmethanolfuelcell Directcarbonfuelcell Zinc-airbattery Metalhydridefuelcell Directborohydridefuelcell Biofuelcells Enzymaticbiofuelcell Microbialfuelcell Others Blueenergy Electro-galvanicfuelcell Flowbattery Photoelectrochemicalcell Regenerativefuelcell Solidoxideelectrolysercell Unitizedregenerativefuelcell Proton-exchangemembrane Membraneelectrodeassembly MembranelessFuelCells Protonicceramicfuelcell Hydrogen Economy Storage Station Vehicle Glossary Retrievedfrom"https://en.wikipedia.org/w/index.php?title=Molten_carbonate_fuel_cell&oldid=1090011400" Categories:FuelcellsHiddencategories:AllaccuracydisputesArticleswithdisputedstatementsfromOctober2014 Navigationmenu Personaltools NotloggedinTalkContributionsCreateaccountLogin Namespaces ArticleTalk English Views ReadEditViewhistory More Search Navigation MainpageContentsCurrenteventsRandomarticleAboutWikipediaContactusDonate Contribute HelpLearntoeditCommunityportalRecentchangesUploadfile Tools WhatlinkshereRelatedchangesUploadfileSpecialpagesPermanentlinkPageinformationCitethispageWikidataitem Print/export DownloadasPDFPrintableversion Languages DeutschFrançais한국어ItalianoNederlands日本語PolskiRomânăSuomiTürkçe Editlinks