国际天然气联盟-低碳气体技术导论 Introduction to Low Carbon Gas Technologies 2024

IntroductiontoLowCarbonGasTechnologies

Contents

OVERVIEWPage3

Part1:DECARBONISATIONPage6

BiomethaneproductionthroughanaerobicdigestionPage6

PyrogasificationPage8

HydrothermalgasificationPage9

E-methanePage10

SolarphotocatalyticprocessesPage11

Part2:DIVERSIFICATIONPage12

MethanereformationPage13

-MethanereformingprocessforpureH2productionPage13

WaterelectrolysisPage14

ThermalgasificationPage14

MethanepyrolysisPage15

SolarphotocatalyticprocessesPage15

BiologicalproductionPage16

GeologicalextractionPage17

Part3:INNOVATION

Page18

ACKNOWLEDGEMENTS

Page19

Frontcoverimage:iS/artisteer

02IntroductiontoLowCarbonGasTechnologies

Overview

Attheendof2023,morethan140countrieshadamid-century

carbon-neutralitypledge.Meetingthesecommitmentswillrequirea

dramaticandrapidchangeintheentireglobalenergysystem,onewhichtheflexibilityandinnovationofthegasindustryiswellplacedtodeliver.

Reducingemissionsinlinewiththe2015ParisAgreementonClimateChangewillrequire,asaminimum,therampingupofthreekeyareas:

1

Decarbonisation:improvingenergyefficiency,andreducingemissionsandmethaneleaks.

2

Diversification:usingnaturalgaswithlow-carbonandrenewablealternatives,suchasbiomethane,e-methaneandhydrogen.

3

Innovation:supportingtheindustry,bothfromalegislative,regulatoryandinvestmentperspectivetocontinuouslyinnovateitsproductsandservicesrenderedtomarkets,consumersandusers.

Organicgrowth:

Amodernbiofuelgasplant.

Photo:iS/VadymTerelyuk

IntroductiontoLowCarbonGasTechnologies03

Overview

AlignedtoIGU’ssupportoftheParisAgreement’sNationallyDeterminedContributionstoreduceGHG

emissionsanditscommitmenttosignificantlydecarbonisetheglobalenergysystem,this“IntroductiontoLowCarbonGasTechnologies”providesabriefguideonkeylow-carbonandrenewablegastechnologiesthatarecurrentlyavailablefordeploymenttorampupthegasindustry’seffortstowardsdeepdecarbonisation.

Naturalgasanditsevolvingtechnologiessupporttherenewableenergysupplybyovercomingintermittencyandinstability.Existingnaturalgasinfrastructurewillalsoenablecost-effectiveandmorerapiddeploymentoflow-carbonandrenewablegases-criticalfordeepdecarbonisationoftheglobaleconomy.Together,theycanenablenet-zeropathways,energysecurityandaccessissues.

Futureenergymix:

Therearearangeof

optionsonthehorizon.

Image:iS/sharfsinn

04IntroductiontoLowCarbonGasTechnologies

Overview

I.

Thefirstsectionofthereportwillreviewthemainfivelow-CO2gastechnologiesaimingtodecarbonisethemethanemoleculesupplychain.Theseare:

1

Anaerobicdigestion:biomethanebasedonwetbiomass.

2

Pyrogasification:syntheticmethaneobtainedfromthermo-chemicalprocesswastesrichincarbon.

3

4

Hydrothermalgasification:syntheticmethanebasedonliquidbiomasstreatmentathightemperatures.

5

E-methane:syntheticmethaneusingcarbondioxideasfeedstock.Solarphotocatalyticprocesses.

Thesecondsectionofthereportwillprovideanoverviewofhydrogenproduction

technologiesasenergycarriers.Currently,thereisalimitednumberofsuchtechnologiesinwidespreadoperation,andthesemustberampedupbyordersofmagnitudetobe

consistentwiththeworld’scurrentclimatetargets.Onlythencanweensurethattheprioritiesofenergysecurityandenergytransitiondonotundermineeachother.

Thecurrentenergy-carryinghydrogenproductiontechnologiesare:

Methanereformation:extractinghydrogenfrommethanemoleculesandremovingCO2.

Waterelectrolysis:usingrenewableelectricitytoproducehydrogenfromwater.

Thermalgasification:extractinghydrogenfromsolidmaterialwithhighheat.

Methanepyrolysis:extractinghydrogenfrommethaneusingaprocessthatdoesnotproduceCO2.

Solarphotocatalytic:usingdedicatedsolarenergyinstallationstoproducerenewablehydrogen.

Biologicalproductionofhydrogen:throughfermentationandphotolysisofbiomass.

Geologicalextractionofnaturalhydrogen.

2.

4

6

3

7

2

5

1

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I.Decarbonisation

1Biomethaneproductionthroughanaerobicdigestion

Feedstocksproduction,storageandphysicalpretreatment

Production

Digestate

valorisation

Biogas/Biomethanevalorisation

Anaerobicdigestion

Biogas

Combinedheat

andpowerplant

(CHP)

Digestate

Collect

feedstocks

Digestatestorage

Fertilizer

Storage

Biogasupgrading

Biofuel

Spreading

Naturalgasgridinjection

Agriculturalwastes

Other

biowastes

Electricity

Biomethane

Manure

Heat

Anaerobicdigestionisaprocessthroughwhichbacteriabreakdownorganicmatterintheabsenceofoxygen.

Thisprocessreleasesenergy-richbiogas,whichisrelativelyhighinmethane(CH4)contentandcanbe

capturedandusedasfuel.Itcanbeenhancedeitherbyinjectinghydrogen(H2)inthereactororbyusingalightelectricalcurrenttoimprovetheCH4/CO2-ratio.

Thereisawiderangeofpotentialorganicmatterinputsthatcanbeusedasfeedstock,suchasfoodandfeedindustrywastes,manureandslurry,greenwastes,intermediatecropsandsewagesludge.

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Biomethaneisconsideredcarbon-neutral

Biomethaneproductioncapturesmethane,astrong

greenhousegas,fromitsbiorawmaterial,andturnsitinto

usefulfuel.Thisprocessstopsmethanefromescapingintotheatmosphere,whereitwouldcontributetoglobalwarming.

Biomethane,madefrombiogas,canbeusedjustlikenaturalgas.

Iteasilyusestheexistinggassystemswithoutneedinganychanges,makingitacost-effectiveandsimplewaytosupportdecarbonisation.

CO2fromtheatmosphereiscapturedbyorganicwasteusedtoproduce

biomethane.ItscombustionproducesbiogenicCO2emissions.

Compensationeffect:almostnoimpactongreenhousegasemissions.

0

CarbonNeutral

%

1.CollectionOrganicwasteiscollectedand

transportedtothemethanisationsite.

fermentation

processwhichproduces

digestateandbiogas.

Digestate

Isusedandanaturalfertiliser.

Biogas

Arenewablefuelto

generateheat(hotwaterandsteam)and

electricity(CHP)onsite.

Organicwaste

goesthroughananaerobic

2.Anaerobicdigestion

RGGO=1MWhgreengasinjected

4.EndusesBiogasispurifiedtobeinjectedinto3.Upgrade

thegasgridforindustrialanddomesticuses,suchasheatingandcooking.

Thesefeedstocksarecollectedandtransportedtothefacility(methanisationsite),wheretheyareturnedintobiogas.

Thebiogascanthenbedirectlyusedtoproduceelectricityandheat,oritcanbepurifiedintoBiomethane,whichisaone-for-onereplacementfornaturalgas.

Biomethanecanbeinjectedintotheexistinggasgridforindustrialanddomesticuses,suchasheatingorcooking,andformobilitypurposes.Itisimportanttorememberthattheefficiencyofbiomethaneproductionisheavilydependentonthesourcematerial.

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2Pyrogasification

Pyrogasificationisathermochemicalprocessthatconsistsofheatingwasteintheabsenceofoxygentoproducearenewablemethane.Ithastwomainsources:

IDrybiomass:woodwaste,residuesfromwastemanagement,andmostorganicwaste.

IISolidrecoveredfuels(SRF)areproducedfromhouseholdrecyclingwasteandgeneralindustrialandcommercialwaste.

Oncecollected,thewasteisheatedtoveryhightemperatures(800to1,500degreesCelsius)inthepresenceofasmallamountofoxygen,convertingthewasteintosyntheticgas(syngas).Syngasisrichincarbonmonoxide,hydrogen,carbondioxideandmethaneandmustbepurified.

SyngasfromSRFcontainsmorepollutantsthansyngasfromcleanbiomass,suchasfromplants.Further

challengesarefoundinconventionalinorganicgasremovalprocesses,whichmustbeadaptedbeforebeinguseable.

Developmentisalsonecessarytopurifythesyngasaccordingtoitsfutureusage,includinginmakingammonia,methanolorotherindustrialchemicalsandfuels.

Pyro-gasificationprocess

Stepaimingtoincreasethecarbon

conversion

intomethane

Stepaiming

atconvertingbiomassintoasyntheticgas(<<syngas>>)richinCO,H2,CO2andCH4

Stepdesignedtoremove

undesirablecompoundssuchastarsorinorganicsulfur

StepdesignedtoadjustthebioSNGqualityaccordingto

itsusage

CO+3H2>>CH4+H2OCO2+4H2>>CH4+2H2O

Hightemperatureheatapplied

Renewable

carbon

feedstock

Catalytic

methanation

Syngas

purification

Gas

upgrading

Removingimpurities

BioSNG

Fieldwork:Biogasfromcorn.Photo:iS/Jan-Otto

08IntroductiontoLowCarbonGasTechnologies

Decarbonisation

3Hydrothermalgasification

Hydrothermalgasificationrequiresthepresenceofwatertoconvertwetorliquidorganicwasteintosyngas,throughaprocesswhichsubjectsthewastetohighpressureandtemperatures.

Theproducedsyngasisarenewablegas,composedofmethane,hydrogenandcarbondioxide.However,thecompositionofthissyngasvaries,accordingtothecharacteristicsoftheinputs.

Theprocesscreatesgreengasesusingliquidorganicwaste,whichisotherwisedifficulttodisposeof,suchasdigestatesfromanaerobicdigestion,sewagesludgefromindustrialormunicipalwastewatertreatmentplants,macroandmicro-algae,liquidandsolidfarmingwaste,foodindustryresiduesandby-products.

Thehydrothermalgasificationconsistsofthefollowing:

-Liquidorganicwasteispumpedathighpressure(260-300bars).

-Thematterthenpassesthroughaheatexchanger,whichseparatesphosphorus,potassium,calciumandmetalswhichareextractedandrecovered.

Hydrothermalgasificationisgasificationinhotcompressedwaterwhichuseswaterinasupercriticalstate

HydrothermalreactorSyngasabovethe

watersupercritical

point(221bar,374oC)

Non-catalytic600-700oC

S

Syngas

Separation

Catalytic380-420oC

CH4

Liquidorganicwaste

Productionofsyngas,CH4,H2,orchemicals

●Rawsyngascanbevalorisedeitherdirectlyforheatand/orelectricityproduction,orpurifiedtocleanCH4orH2,orconvertedintochemicals.

CH4contentreaches50-60%incatalyticconversion,andupto90%whenH2isco-injectedinthegasifier.H2concentrationcanachieve50-75%insyngas.

Source:2020.LeCadreE.MertensJ.EmergingSustainableTechnologies

P,K,Ca

metalsrecovery

Heat

exchanger

Waterand

NH4+

260-300bar

Purification

Pump

CO2

H2

Theprocessispossibleatbothhigherandlowertemperatures(aslongasacatalystisused).Therearepositivesandnegativesforboth,ashighertemperaturesrequiremoreenergy,andtheuseofapreciousmetalcatalystatlowertemperaturesiscostlyandhasafinitelifespan.

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Theresultingsyngasisthenpurifiedtoextractunwantedcarbondioxide,leavingmethaneandhydrogen.Thisrawsyngashasthepotentialtobeuseddirectlyforheatandelectricityproduction.Alternatively,the

hydrogencanbeusedtoconvertsomeofthecarbondioxideintoadditionalmethanethroughamethanationstep,afterwhichtheresultinggascanbetreatedsoitisreadytoinjectintothegastransmissionsystem.

Methanecontentreaches50-60%incatalyticconversionandevenupto90%whenadditionalhydrogenisalsoinjectedintothegasifier.Theprocessproducesmethaneorhydrogenefficiently.

4E-methane

Methanationcanalsobeusedtocombinecarbonmonoxide(CO)orcarbondioxide(CO2)withhydrogentoproducee-methane,inaprocessthatalsoproducesheat.Methanationisaprocessthroughwhich

hydrogenisconvertedintomethane,whichcanbeusedintheexistingnaturalgasinfrastructure.

Carbondioxidecanbeobtainedfrommanysources,suchasmethanisationplants(biogenicCO2)orfrom

industrialproductionandcapturefromtheatmosphere,supportingthedevelopmentofawiderangeofnewtechnologiesthatmayhavethepotentialtoreducegreenhousegasemissions.

CO2canbeusedasbuildingblocksforhighadded-valuefuelslikemethane

SOURCEofCO2

Atmosphere

Cleaning

Capture(iflowconcentration)

OR

Industry

SOURCEofHYDROGEN

elabityle}Electrolyser

Plants

Algae,Cynobacteria,

CO2

CO2

Minerals

Bacteria

CO2

C2}2

+

CO2

VALORISATION

PHOTOSYNTHESISBiological

ENHANCEDOILRECOVERY

CARBONATIONFOODINDUSTRY

POLYMERISATIONChemical

MINERALISATIONChemical

FERMENTATIONBiological

HYDROGENATIONChemical

Co-Electrolysis

MARKETS

Decarbonisedrenewable

electricity

requiredforallprocessestobe

sustainable

Thiscouldbesyntheticnaturalgas(=syntheticmethane)

10IntroductiontoLowCarbonGasTechnologies

Decarbonisation

5Solarphotocatalyticprocesses

Artificialphotosynthesis(AP),alsoknownassolarphotocatalyticprocess,hasthepotentialtoproducesyntheticmethane.ThisprocessdecreasesorremovestheneedforusingelectricalpowerandGHG

emissions,aswellasbiomass,intheproductionoflow-CO2methane.

Artificialphotosynthesisseekstoreplicatethenaturalphotosynthesisprocess.Itwidelyusessemi-conductorsasthephotocatalyst,anditoftensplitstheprocessintotwosteps:

IProductionofhydrogenbysplittingwaterthroughthemethodofphotocatalysis.

IICarbondioxideproduction,anditssubsequentreactionswithhydrogen,toformlightweighthydrocarbons,byusingdifferentapproaches.

OxygenEvolution

Reaction(OER)

h

O2

Greenhydrogenmarket

CO2

H2O

bH2b

(photo)-electrocatalysis

HydrogenEvolution

Reaction(HER)

Greensyntheticmolecules

(CH4,CH3OH,COOH,CxHy,...)

Conversion:PhotovoltaicpowersupplysystemsPhoto:iS

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2.Diversification

Hydrogenissettoplayagrowingroleintheenergysector,withseveralemergingtechnologiesaimingtoconvertvariousinputsintohydrogen,whichcanthenbeutilisedwithinthepowerandheatingindustries,andasfeedstockinthechemicalindustry.

Thegraphbelowillustrateshydrogenproductiontechnologiesandtheirpotentialenergysources:

Hydrogen

Inadditiontothesetechnologies,geologicalH2isemergingasapotentialsource.

Mostexistinghydrogenmarketsareveryspecific,consistingmainlyofindustrialuseandsupplyinginputsintoammoniaandmethanolproduction,actingalsoasareducingagentforthepetrochemical,chemical,steelandfoodindustries.

Presentusesofhydrogenasanenergycarrierremainlimited,andoftenexperimentalandpilot;however,

globalplanstoexpandthemaresignificant.Thereareseveraltechnologyadvancementprioritiestoaddressfortheseplanstomaterialise:

-Loweringcostsandgrowingtheircommercialtrackrecord.

-Storageandtransportationtechnologies,infrastructure,andstandards.

-Certificationdevelopment.

-End-userequipmentconversiontosupporthydrogenasfuel.

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1Methanereformation

I

Methane(CH4)canbeutilisedtocreatepurehydrogenusingthefollowingprocessofsteammethanereformation:

II

Byusingheat,steamandmethanereacttogetherwithacatalysttoformcarbonmonoxideandhydrogen;thisisanenergy-intensiveprocess.

Inthewater-gasshiftreaction,carbonmonoxideiscombinedwithmoresteam,

producinghydrogenandcarbondioxide.Thecarbondioxidecanthenbecapturedthroughcarboncapturetechnologies,asitisinacontrolledenvironment.

Ifcarboncaptureandsequestrationarenotutilisedduringthisprocess,therewillbecarbonemissions

associatedwithit.However,whencarboncaptureandsequestrationareaddedtotheprocess,thehydrogenproducedisconsideredlowcarbon,alsocalled“bluehydrogen”.

MethanereformingprocessforpureH2production

Thisprocessconsistsoffourstages:

IPretreatmentunittopre-formfeedstockandtoeliminatesulphurcompounds.

IIReformingsteptoproducesyngasusingeithersteammethanereforming,partial

oxidisationorautothermalreforming.Itispossibletocombinethesetechnologies.IIIShiftreactor(s)toconvertsyngasand(increaseH2contentanddecreaseCO).

IVThepurificationunitseparatesthehydrogenfromtheproductstream.CO2canbecapturedthroughcarboncapturetechnologies.

1

Pretreatment

2

SteamMethaneReforming

Partial

Oxidation

AutothermalReforming

Steam

Heat

3

Water-GasShiftConversion

4

CO2

NaturalGas,HeavyOil,Naphtha,LPG

O2

Steam

O2

CO2

Purification

Hydrogen

Catalysts:

-TherelativecatalyticactivityofmetalsintheSMRreaction:Ru>Rh>Ir>Ni>Pt>Pd

PartialOxidation

CH4+1/2O2>>CO+2H2H=36kJ/mol

-Conventionaliron-chromiumforhightemperatureWGSandcopperalloysforlowtemperatureWGS

AutothermalReforming

CH4+H2O>>CO+3H2CH4+1/2O2>>CO+2H2

Water-GasShift

CO+H2O>>H2+CO2H=41kJ/mol

SteamMethaneReforming

CH4+H2O>>CO+3H2H=206kJ/mol

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2Waterelectrolysis

Waterelectrolysisisawayofproducinghydrogenthatuseselectricitytosplitwaterintohydrogenand

oxygen.Whentheelectricityusedintheprocessisrenewableornuclear,therearenoGHGemissionsproducedintheprocess,andthiscanbereferredtoasrenewable,“green”and“pink”hydrogen,respectively.

Anelectricalcircuitiscreatedbycombininganelectrolyteandtwoelectrodestoformanelectrolyticcell.Thesechargedelectrodesthensplitthewater,withtheresultingnegativelychargedelectrodeattractingthepositivelychargedhydrogenionsand,conversely,thepositiveelectrodeattractingthenegativelychargedoxygenions

formingseparatebubblesofoxygenorhydrogenthatcanthenbecollected.

Therearefivemaintechnologiesusedtoperformwaterelectrolysis,whichdifferintermsofthematerialsusedfortheelectrodesandplates:

I

II

III

Alkalineelectrolysis

PEM(Protonexchangemembrane)electrolysis

SOEC(Solidoxideelectrolysis)

IVPCEC(Photoelectrochemical)

VAEM(Anionexchangemembrane)

Eachofthesefivetechnologieshasbenefitsanddrawbacks,rangingfromcost,efficiency,anddurability.

Thisiswhyfurtherresearchtoimproveperformanceandviabilityofwaterelectrolysisiscurrentlyongoing.

3Thermalgasification

Thermalgasificationisaprocessthatuses

solidorganicmatter(suchascoal,biomass-basedfeedstocks,SRFsandfractionsofnon-recyclableplastics)andconvertsthemintosyngasusing

hightemperatures(rangingfrom700-1500°C).Thereactionoccursunderstoichiometric

conditions(meaningallreactantsarecontrolledandfullyused),turningsolidresiduesinto

syngas.

Thesyngasisthenpurifiedtoremoveorganic

pollutants(suchaslightandheavytars)and

inorganicpollutants(suchashydrogensulphide,ammonia,andhydrochloricacid).Thisisthen

followedbythegas-watershiftreaction,which

meansthatthecarbonmonoxideproducedcan

beconvertedintoadditionalhydrogenandcarbondioxide.

Thegasesproducedarecollected,andhydrogenisextractedfromtheothergasesproduced(mainlycarbondioxide,carbonmonoxideandmethane)togivethehydrogenapurityofover99.9%.

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4Methanepyrolysis

Methanepyrolysisusesmethaneasfeedstockand,byapplyingenergytobreakthechemicalbondbetweencarbonandhydrogen,itproduceshydrogengasandasolidcarbonproduct.

Theprocessrequireslessenergythanelectrolysis,anditsGHGfootprintislowduetotheabsenceofemissions.

Usingnaturalgasasfeedstockalsoprovidesthebenefitofaccesstotheexistinginfrastructure.Therearedifferentwaysofgeneratingtheheatformethanepyrolysis:

IPlasmapyrolysis:electriccurrentsareusedtocreateahotplasmawhichbreaksdownthemethaneintohydrogenandcarbon.

IIThermalpyrolysis:hotbathsofmoltensaltsormetalsareusedtobreakdownthemethaneintohydrogenandcarbon.

IIICatalyticpyrolysis:methaneispassedthroughafluidisedbedcontainingacatalystwhichbreaksdownthemethanewithincreasedefficiency.

IVMicrowaveassistedpyrolysis:microwavesareusedwithacatalysttobreakthemethanemoleculeintohydrogenandcarbon.

5Solarphotocatalyticprocesses

SolarphotocatalyticprocessesavoidanyGHGemissionsastheyrelyexclusivelyonsolarpower:

aphotocatalyticinstallationwhichcouldbefurtherenhancedbytheadditionofsolarPVpanels.Inthis

process,aphoto-absorber(typicallyasemi-conductor)absorbslight,leadingtotheseparationofpositiveandnegativecharges.Thereductioncreateshydrogen,andoxidationproducesoxygen,hydrogen,and

e-charges,makingthemavailableforredoxreactions(transferofelectrons)toproducehydrogenfromwater.Thisbasicconceptisutilisedinseveraltechnologies:

I

Photocatalysed(PC)watersplitting:thissystemisthesimplestoneand

consists,typically,ofaphotocatalystimmersedinasolution,atthesurfaceof

whichthereactionstakeplace.Oxygenandhydrogenmustbefurtherseparated.

II

Photo-ElectroChemical(PEC)watersplitting:thissystemisbasedontheprincipleofelectrolysiswheretheanodeand/orcathodeareimplementedwithphotocatalysts.Thedifference,comparedtophotocatalysedwater

splitting,isthatthissystemiselectro-assisted,allowingthecurrenttobeincreasedforhigheryields.

III

Photo-ElectroChemical(PV-EC)watersplitting:thislastsystemisoftenassociatedwithPCandPECprocessesandconsistsofanelectrolyser

equippedwithanintegratedhighlyefficientmultijunctionIII-VPVcell.

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6Biologicalproduction

Therearetwomainbiologicalprocessesthatcanbeusedtoproducehydrogen:fermentationandbiophotolysis.

Thefermentationprocessharnessesmacro-nutrients(longmolecules)frombiomass,whicharebrokendown

intohydrogen,andshortmoleculessuchasalcohols,simplesugars,andvolatilefattyacids.Variousfermentationtechnologiesarelistedbelow,anditshouldbenotedthatphotofermentationandMECmustbecoupledwith

thefirststepofdarkfermentationinatwo-stepprocess.

IDarkfermentation(fermentationwithoutlight),wherethesubstrateusedisacomplexorganicmatter.Large-scalebacteriacanperformdarkfermentation.

IIPhoto-fermentation(fermentationassistedbylight),wherethesubstrateusedissmallorganicacids.

IIIMECfermentation(assistedbyalowelectricalcurrent),wherethesubstrateusedisasimplecarbonsourcesuchasC2toC6(volatilefattyacids,singlesugarandalcohols).

WhileBiophotolysisproduceshydrogenfromlightandwater,cyanobacteriaandgreenalgaecansplitwaterintohydrogenandoxygenusingtheirhydrogenaseornitrogenaseenzymesystem.

Macro-nutrientsfrombiomass

Carbohydrates,

proteins,

lipids

Image:iS

(alcohols,simple

sugars,volatile

fattyacids)

Bacteria

H2+shortmolecules

16IntroductiontoLowCarbonGasTechnologies

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7Geologicalextraction

TherearetwomainwaysofproducingH2throughgeologicalextraction:

Naturalhydrogenproduction(“white”hydrogen)

H2ismainlyproducedthroughnaturalwater-rockreactions,suchasserpentinisation,wherewater

reactswithiron-richmineralswithintheEarth’s

crust.Thishydrogenper