20120904 150120 Proefschrift Meerman

7/29/2019 20120904 150120 Proefschrift Meerman

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Perspectivesongasificationsystemstoproduce

energycarriersandotherchemicalswithlowCO2

emissions

Technoeconomicsystemanalysisoncurrentand

advancedflexiblethermochemicalconversion

offossilfuelsandbiomass

HansMeerman


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Perspectivesongasificationsystemstoproduceenergycarriersandotherchemicalswith

lowCO2emissions:Technoeconomicsystemanalysisoncurrentandadvancedflexible

thermochemicalconversionoffossilfuelsandbiomass

HansMeerman,UtrechtUniversity,FacultyofGeosciences,DepartmentofInnovation,

EnvironmentalandEnergySciences,CopernicusInstitute,GroupEnergy&Resources.

ISBN: 9789039358375

Coverdesign: UitgeverBoxpress

Printing: UitgeverBoxpress

Copyright:

2012,

Hans

Meerman


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Perspectivesongasificationsystemstoproduceenergy

carriersandotherchemicalswithlowCO2emissions

Technoeconomicsystemanalysisoncurrentandadvancedflexiblethermochemicalconversionoffossilfuelsandbiomass

Perspectiefopvergassingssystemenvoorhetproducerenvan

energiedragersenanderechemicalinmetlageCO2emissies

Technoeconomischesysteemanalysevanhuidigeentoekomstigeflexibelethermochemischeomzettingvanfossielebrandstoffenenbiomassa

(meteensamenvattinginhetNederlands)

Proefschrift

terverkrijgingvandegraadvandoctoraandeUniversiteitUtrecht

opgezagvanderectormagnificus,prof.dr.G.J.vanderZwaan,

ingevolgehetbesluitvanhetcollegevoorpromoties

inhetopenbaarteverdedigenop

vrijdag7september2012desmiddagste12.45uur

door

JohannesCornelisMeerman

geborenop3augustus1981teHellevoetsluis


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Promotoren: Prof.dr.A.P.C.Faaij

Prof.dr.W.C.Turkenburg

Copromotor: Dr.C.A.Ramrez

Thisthesishasbeenmadepossiblewiththefinancialsupportof

NWOAgentschapNLandtheEOSresearchprogrammeCapTech.


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Voormijnouders


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WedonotinherittheEarthfromourancestors,weborrowitfromourchildrennativeAmericanproverb


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Contents

1 Introduction 11

1.1 Background........................................................................................................12

Energy........................................................................................................................12

Climatechange..........................................................................................................13

CO2emissions............................................................................................................13

1.2 Mitigationstrategies..........................................................................................14

Sectors.......................................................................................................................15

Biomassandbiofuels.................................................................................................16

Carbondioxidecapture,transportandstorage........................................................16

1.3 Integratedgasificationpolygenerationfacilities..............................................19

Processdescription....................................................................................................21

Performance..............................................................................................................21Flexibility....................................................................................................................22

1.4 Summarising......................................................................................................23

1.5 Thesisobjectiveandoutline..............................................................................24

2 Performanceofsimulatedflexibleintegratedgasification

polygenerationfacilities.PartA:Atechnicalenergeticassessment 272.1 Introduction.......................................................................................................29

2.1.1 General......................................................................................................30

2.1.2 Objectives..................................................................................................31

2.2 Commodities......................................................................................................322.2.1 Feedstocks.................................................................................................32

2.2.2 Endproducts.............................................................................................32

2.2.3 Byproducts...............................................................................................32

2.3 Processdescription............................................................................................33

2.3.1 Plantflexibility...........................................................................................33

2.3.2 Pretreatment...........................................................................................33

2.3.3 Pressurisingandfeeding...........................................................................35

2.3.4 Airseparationunit(ASU)..........................................................................36

2.3.5 Gasifier......................................................................................................36

2.3.6 Gascleanupandsyngascompositionoptimising......................................382.3.7 Syngasconversion.....................................................................................41

2.4 Methodology:AspenPlusflowsheetmodel.......................................................45

2.4.1 Modelledcomponents..............................................................................45

2.4.2 Parameters................................................................................................47

2.5 Casestudies.......................................................................................................49

2.6 Results................................................................................................................51

2.6.1 Referencecases........................................................................................53

2.7 Discussion..........................................................................................................66

2.7.1 Modelvalidation.......................................................................................66

2.7.2 Fuelflexibility............................................................................................66


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2.7.3 Modelassumptions...................................................................................67

2.8 Conclusion..........................................................................................................67

2.9 Acknowledgements...........................................................................................70

2.10 Supportinginformation.....................................................................................71

3 Performanceofsimulatedflexibleintegratedgasification

polygenerationfacilities.PartB:Economicevaluation. 833.1 Introduction.......................................................................................................84

3.2 Methodology.....................................................................................................85

3.2.1 TechnicaldataandAspenPlusprocessmodel..........................................86

3.2.2 Casestudies...............................................................................................88

3.2.3 Scenarios...................................................................................................90

3.2.4 TotalCapitalInvestment...........................................................................92

3.2.5 Economicmodel........................................................................................93

3.3

EconomicData

...................................................................................................

94

3.3.1 Commodityprices.....................................................................................94

3.3.2 Capitalcostsdata......................................................................................98

3.4 Results..............................................................................................................104

3.4.1 StaticIGPGfacilities...............................................................................104

3.4.2 Variationoffeedstock.............................................................................107

3.4.3 Variationofproduction...........................................................................114

3.4.4 Retrofit....................................................................................................115

3.4.5 Sensitivityanalysis...................................................................................116

3.5 Discussion&Conclusions.................................................................................118

3.6

Acknowledgement

...........................................................................................

120

3.7 Supplementarydata........................................................................................121

3.7.1 Commoditypriceprojectionsinliterature..............................................121

3.7.2 DetailedtechnicalandeconomicdataofthestaticIGPGfacilities.......123

4 Technicalandeconomicprospectsofcoal andbiomassfiredIGPG

facilitiesequippedwithCCSovertime. 1274.1 Introduction.....................................................................................................128

4.2 Integratedpolygenerationgasificationfacilities............................................129

4.2.1 Processdescription.................................................................................129

4.3

Configurations..................................................................................................

130

4.4 Economicanalysis............................................................................................135

4.5 Results..............................................................................................................138

4.5.1 Sensitivity................................................................................................142

4.6 Discussion........................................................................................................142

4.7 Conclusions......................................................................................................143

4.8 Acknowledgement...........................................................................................144

4.9 Supportinginformation...................................................................................145

4.9.1 ProductionandCO2avoidancecostsformula.........................................145

4.9.2 Capitalcostbreakdown...........................................................................146

4.9.3 Detailedmass,energyandeconomicresults..........................................147


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5 FuturetechnologicalandeconomicperformanceofIGCCandFT

productionfacilitieswithandwithoutCO2capture:combining

componentbasedlearningcurveandbottomupanalysis. 1555.1 Introduction.....................................................................................................157

5.2 Methodology...................................................................................................164

5.2.1 Gasificationtechnology...........................................................................164

5.2.2 Costandperformanceprojectionswithexperiencecurves...................165

5.2.3 Costandperformanceprojectionsbymeansofabottomupanalysis..171

5.2.4 Comparisonofexperiencecurvebasedwiththebottomupanalysis....172

5.3 Dataforthecurrentsituationandfutureprojections.....................................174

5.3.1 Currentcostsandefficiencies.................................................................174

5.3.2 Progressratiosandinstalledcapacities..................................................175

5.4 Resultsoftheexperiencecurveanalysis.........................................................183

5.4.1 EfficiencydevelopmentofIGCC..............................................................183

5.4.2 CapitalcostsofIGCC...............................................................................1845.4.3 TrendsintheCOEandCO2mitigationcostsforIGCC.............................186

5.4.4 FTliquidsproduction..............................................................................189

5.5 Discussion........................................................................................................192

5.6 Conclusion........................................................................................................194

5.7 Supportinginformation...................................................................................197

6 TechnoeconomicassessmentofCO2captureatsteammethane

reformingfacilitiesusingcommerciallyavailabletechnology 2036.1 Introduction.....................................................................................................204

6.2 Background......................................................................................................2056.2.1 Steammethanereforming......................................................................206

6.2.2 Carbondioxidecaptureandstorage.......................................................206

6.3 Approach..........................................................................................................208

6.3.1 CO2capturelocation...............................................................................208

6.3.2 Solventselection.....................................................................................209

6.3.3 CO2captureunitconfiguration...............................................................211

6.3.4 OptimisationofCO2captureconfigurationconditions...........................212

6.3.5 Overviewoftechnicalparameters..........................................................215

6.3.6 TechnoeconomicperformanceofCO2captureatSMR.........................215

6.4 Technoeconomicresults.................................................................................2176.4.1 CO2captureunitperformancecasestudies............................................217

6.4.2 EffectloadfactoronCO2captureunitperformance..............................220

6.4.3 Sensitivityanalysis...................................................................................221

6.4.4 Utilityimport...........................................................................................222

6.4.5 Conclusion...............................................................................................223

6.4.6 Acknowledgements.................................................................................225

7 Summary,conclusionsandrecommendations 2277.1 Background......................................................................................................228

7.2 Objectiveandresearchquestions...................................................................229


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7.3 Methodology...................................................................................................230

7.4 Summaryoftheresults....................................................................................232

7.5 Mainfindingsandconclusions.........................................................................238

7.6 Finalremarksandrecommendationsforfurtherresearch.............................241

Samenvatting,conclusiesenaanbevelingen 245

Appendix:TechnicaldescriptionofIGPGfacilities 2679.1 Feedstock.........................................................................................................268

9.2 Feedstockpretreatment.................................................................................268

9.2.1 Feedstockprocessingandfeeding..........................................................269

9.3 Airseparation..................................................................................................270

9.3.1 Iontransportmembraneseparation......................................................271

9.3.2 Chemicallooping.....................................................................................272

9.3.3 (Vacuum)pressureswingabsorption.....................................................2729.4 Gasifier.............................................................................................................272

9.4.1 Supercriticalwatergasifier(SCWG)........................................................273

9.4.2 Highpressuregasification.......................................................................273

9.5 GasCleaning....................................................................................................274

9.5.1 Hotgascleaning......................................................................................275

9.6 Watergasshift.................................................................................................278

9.6.1 Sorptionenhancedwatergasshift.........................................................278

9.6.2 Advancedwatergasshift........................................................................279

9.7 CO2compressor...............................................................................................279

9.7.1 Shockwavecompression........................................................................2809.7.2 Electrolyticcompression.........................................................................281

9.8 Electricityproduction.......................................................................................281

9.8.1 Syngascombustion.................................................................................281

9.8.2 Steamturbinesandheatrecoverysteamgenerators.............................283

9.9 FTsynthesis.....................................................................................................284

9.10 Availability........................................................................................................284

References 287

Dankwoord 305

CurriculumVitae 307

Nomenclature 309


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11

1 Introduction


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Chapter1

12

1.1 BackgroundEnergyOurmodernsocietyrequiresaccesstoabundant,affordable,reliableandenvironmentally

sound sources of energy. As population and living standards are increasing, so is ourenergydemand(seeFigure1.1).In2009,globalprimaryenergydemandexceeded500EJ,

representingadoublinginabout35years.About80%ofthisdemandiscoveredbyfossil

fuels.[1,2,3]

In its Energy Technology Perspectives 2010 report, the International Energy

Agency (IEA) presented a business as usual scenario projecting an increase of the global

energy demand to over 750 EJ in 2035.[2]

Similar trends are forecasted by other

studies.[1,2,4,5,6,7,8]

Most of these studies indicate that fossil fuels will continue to play an

importantroleformanydecadestocome.

Figure1.1GlobalhistoricenergydemandandfutureprojectionoftheIEAbusinessasusual

scenario.[2,3]

Unfortunately,theuseoffossilfuelshasseveral importantdrawbacks.First,mostofthe

conventionaloilandgasreservesarelocatedinafewworldregions.Consequently,many

countriesaredependentonfewothercountriesfortheir energysupplies.

[2,4,9,10]

Second,keeping up extraction from easily recoverable fossil fuel sources to the everincreasing

demandforfossilfuelsprovesdifficult,causingimpactsonthepriceoffossilfuels.[2]

Third,

the combustion of fossil fuels is responsible for the largest share of anthropogenic

greenhousegas(GHG)emissionsintotheatmosphere.[11]

Andlastbutnotleast,duetothe

depletionofeasilyrecoverablefossilfuelsources,extractionofunconventionalfossilfuel

sources,suchastarsandsandshalegas,andextractioninenvironmentallysensitiveareas

areexpectedtoincrease,resultinginhigherGHGemissionsandincreasedrisksofsevere

environmentaldamage.[5,12]

0

100

200

300

400

500

600

700

800

1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 2035

G

lobalenergydemand(EJ/yr)

Year

Otherrenewables Hydro Nuclear NG Oil Coal

Historicdemand Projecteddemand


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Introduction

13

ClimatechangeEmissionsofGHGarelinkedtoglobalwarming

1,withCO2beingresponsibleformorethan

50% of the direct radiative forcing ofGHG.[11]

In 1992, theUnitedNations Framework

Convention on Climate Change (UNFCCC) was established with the goal of achieving

stabilisationof

atmospheric

greenhouse

gas

concentrations

at

alevel

that

would

prevent

dangerousanthropogenicinterferencewiththeclimatesystem.[13]

By2005,averageglobal

temperatures were already about 0.8C higher than preindustrial levels (see Figure

1.2).[11]

The4th

AssessmentReportof the InternationalPanelonClimateChange (IPCC)

projects thatascenario focussingoneconomicdevelopmentand relianceon fossil fuels

(A1fossilintensive:A1FI)couldresultinanincreaseintheaveragetemperatureonEarth

of 2.96.9C above preindustrial values (with a best estimate of 4.5C) by 2100.[2]

A

temperature change of thismagnitudewould be unprecedented in human history and

probablyresult indetrimental impactsonclimate,biodiversity, foodproductionandsea

levelrise.Thesamereportalsoprojectsthat inascenariowhichassumesstrongpolicies

to mitigate GHG emissions, the increase in average temperatures could be limited to

1.63.4C, with a best estimate of 2.3C.[11]

In 2009 and 2010, the Conference of the

Parties(COP)totheUNFCCCagreedthattheincreaseinglobalmeantemperatureshould

bekeptbelow2C,comparedtopreindustriallevels.[14,15]

Figure1.2Historicclimatechangeandprojectedclimatechangeunder

differentGHGmitigationpolicies.[11]

CO2emissionsKeeping the increase in global mean temperature to less than 2C means that the

atmosphericCO2concentrationneeds tostabilisemostprobablyat350400ppm(v)CO2

(445490

ppm(v)

CO2

equivalent).

11]

The

current

proven

reserves

of

fossil

fuels

contain

around800Gtcarbon,[1]

whichcouldresultinalmost3000GtofCO2emissions.Thisvalue

isroughlythesameamountofCO2currentlypresentintheatmosphere.Maintainingthe

increaseinglobalmeantemperaturebelow2Cimpliesthatonly10001625GtCO2canbe

emittedbetween20002100,thesocalledcarbonbudget.[16,17]

Between2000and2010,

already330GtCO2wereemitted,leavingroomforonly6701295GtofanthropogenicCO2

emissionsinthecomingdecades.WithoutadditionalCO2abatementpolicies,thisvalueis

expectedtobereachedwithinafewdecades.[2,4,6,16]

Keepingwithintheindicatedcarbon

1Formore informationonclimatechangeand itseffectswerefertothe4

thassessment

reportof

the

IPCC.[11]


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Chapter1

14

budgetwillrequirereductionsinCO2emissionsofmostlikely5080%in2050comparedto

the2000level.[11,15,18]

1.2 MitigationstrategiesThere

are

several

routes

to

reduce

global

CO2

emissions.

The

most

obvious

one

is

to

consume less primary energy. This, however, has proved to be difficult in the past.

Keepingtheglobalenergydemandconstantwithanincreasingpopulationandincreasing

average standard of living is already a daunting challenge, as indicated by several

studies.[2,4,5,6,7]

Nevertheless,thereisalargepotentialtoincreasetheefficiencyofenergy

conversionprocessesthatneedstobetargeted.Thesecondoptionistousefossilenergy

sourceswhichare less carbonintensiveor to switch to renewableenergy sources.This

includes switching from fossil fuels to renewable and nuclear energy sources, but also

fromcoaltonaturalgas.Inthescenariosfrome.g.,theIEA,IPCC,BP,Greenpeace,WWF,

and in the Global Energy Assessment (GEA), an increased utilisation of renewables is

projected

but

at

various

degrees

depending

on,

among

others,

assumptions

related

to

technologicalimprovementsintheenergysystemandclimatepolicies.Athirdoptionisto

reduce the CO2 emitted by the use of fossil fuels (and biomass) using carbon dioxide

capture,transportandstorage(CCS)technologies.Allstudiesjustmentionedprojectthat

noneofthethreeoptionsbythemselvescanreachthe2Ctarget,andthataportfolioof

mitigationoptionshastobe implemented inordertomeettheGHGemissionmitigation

targets(seee.g.,Figure1.3).[2,4,5,6,7,8,19]

Figure1.3ContributionofdifferentCO2mitigationstrategiesintheIEABluemapscenario,aiming

atstabilisingatmosphericGHGemissionsat450ppm(v)CO2eq.[4]

CCS(19%)

Renewables(17%)

Nuclear(6%)

Powergenerationefficiency

andfuelswitching(5%)

Endusefuelswitching

(15%)

Endusefuelandelectricity

efficiency(38%)0

10

20

30

40

50

60

2010 2015 2020 2025 2030 2035 2040 2045 2050

GlobalCO2emissions(GtCO2/yr)

Year


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Introduction

15

SectorsAlmost 85% of the 29 Gt CO2 emitted by the combustion of fossil fuels in 2009, were

producedbythepower,transportandindustrysectorscombined(seeFigure1.4).[20]

Each

sector has its own unique characteristics and challenges and, therefore, needs specific

strategiestomitigateGHGemissions.

Figure1.4GlobaldirectannualCO2emissionsbysectorin2009.[20]

Thepowersectorconsumed190EJofprimaryenergyin2009ofwhichalmost50%came

from coal and another 25% from natural gas and oil.[2]

Most CO2 emissions from this

sector stem from large, stationary sources, making this sector suitable for endofpipe

solutions, such as CCS. Literature studies indicate that the most costeffective CO2

mitigation options for the short to mid term are fuel switching (cofiring biomass in

coalfired power plants or replacing coalfired power plants by natural gasfired power

plants)andapplyingCCS.[2,4,5,6,7]

Thetransportsector consumed almost100 EJ of primary energy in 2009, of which more

than 90% came from oil.[2]

The CO2 emissions from this sector originate from numerous

small, mobile sources, making endofpipe solutions unattractive.[34]

Therefore,

decarbonisingthissectorisonlyrealisticviadecarbonisingthefuel.Amainobstacleinany

transition towards a new transportation fuel is the large interdependence between car,

fuel and infrastructure, making any transition difficult and expensive if the currentinfrastructure and car park cannot be used.

[21] The current infrastructure is designed for

liquidswithahighenergydensity,likeliquefiedpetroleumgas(LPG),gasoline,dieseland

FischerTropsch liquids (FTliquids are a mixture of linear hydrocarbons of different

length).LiteratureindicatesthatapromisingCO2mitigationoptionfortheshortertomid

term is replacing conventional diesel and gasoline with liquid 2nd

generation biofuels.

When producing these fuels, CCS can be applied to reduce GHG emissions even

further.[21,22,23,24,25]

Theindustrysectorconsumedalmost90EJofprimaryenergyin2009ofwhich40%came

fromcoal,28%fromnaturalgasand20%fromoil.Almost75%ofthedirectCO2emissions

Other

2.9GtCO210%

Industry

5.9GtCO220%

Electiricty

andheat

11.8GtCO241%

Transport

6.5GtCO222%

Residential

1.9GtCO27%


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Chapter1

16

from this sector originate mainly from the production of iron and steel, cement and

chemicals.[4]

These emissions come from large, stationary sources, making the industry

sectorsuitableforCCS.FormoreinformationonCO2mitigationstrategiesintheindustry

sector,werefertoKuramochi.[26]

BiomassandbiofuelsSustainable biomass is an attractive CO2 mitigation strategy as it can be converted into

carbonneutralbuildingblocksforthechemicalindustryorintohighenergydensityliquids

forthetransportsector.[7]

Biomass istheonlyrenewablecarbonsourceforthechemical

industryandisconsideredakeyalternativeforthetransportsectorintheshortterm.[2,4,7]

In2009,10%oftheglobalprimaryenergydemand(about50EJ)wassuppliedbybiomass,

ofwhich1112EJwasbeingused inmodernapplications, likepowerplantsandbiofuels

facilities.[7,27,28]

For comparison, in the same year the total energy demand of the power

and transport sectors combined was almost 300 EJ.[2]

The deployment potential for

sustainablebiomass isuncertain,butconsiderable.Scenarioandmodelanalyses indicatethatthetechnicalpotentialofbiomassenergyresourcesmayrangebetween50500EJ/yr

in 2050[7,28,29,30]

and the deployment potential could be in the order of 100300 EJ/yr in

2050, depending on policies and market conditions.[7]

These high deployment levels of

biomass require the implementation of sustainability criteria to prevent, among others,

competitionwithfoodorfeedsupplies,depletionofwatersources,lossofbiodiversityor

excessiveGHGemissionsdueto(indirect)landusechange.[7,28]

In general, a distinction is made between 1st

and 2nd

generation biofuels. Examples of

1st

generation biofuels are vegetable oils, ethanol from corn and sugarcane and biogas

fromorganicwaste,while2nd

generationbiofuelsincludeFTliquidsorethanolfromwood,

grassesorresiduesfromtheforestandagriculturalsectors.[7]FTdieselhastheadvantage

that it is almost similar to conventional diesel, allowing the use of the existing

infrastructure and car park. Advantages of 2nd

generation biofuels over 1st

generation

biofuelsaretheuseofnonfood/feedsourcesasfeedstockandhigherenergyyieldsand

(potential) savings in GHG emissions on a hectare basis.[28,31]

Finally, biomass crops

(including trees) for 2nd

generation biofuels can be cultivated on marginal or degraded

land, not only further reducing the competition with food supplies, but also offering an

opportunitytorestoredegradedland.[32,33]

Carbondioxidecapture,transportandstorageCarbondioxidecapture,transportandstorage(CCS)isthegeneraltermforprocessesthat

preventtheemissionofCO2bylongtermisolationoftheCO2fromtheatmosphere.[34,35]

It

allowstheuseoffossilfuelsbutwithsignificantlylowerCO2emissions.ForthisreasonCCS

canbeseenasatransitionalmitigationoption.Itincreasestheavailabletimetotransform

thecurrentfossilfuelbasedenergy infrastructure intoan infrastructurebasedmainlyon

renewable sources. Moreover, when CCS is applied in combination with conversion of

sustainably produced biomass, it can result in negative emissions, i.e., extracting and

isolating CO2fromtheatmosphere andthusextending thecarbon budget.Thepotential

deploymentofCCSdependsheavilyontechnological improvementsandclimatepolicies.

The IPCC special report on CCS indicates that the economic potential of CCS could be

2202200 Gt CO2 avoided cumulative by 2100, while the IEA Energy Technology


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Introduction

17

Perspectivesprojectsashareofabout19% in2050,equivalentto18GtCO2emissionsa

year.[4,34]

TheEuropeanCommissionsEnergyRoadmap2050estimatesthat,dependingon

the scenario, CCS could account for 1932% of the total mitigated CO2 emissions in the

powersector.[36]

Althoughtotalmitigationcostsareuncertain, ithasbeenprojectedthat

largescaledeploymentofCCScouldreduceglobalmitigationcostsbyupto40%asmoreexpensive CO2 mitigation options can be postponed or even avoided.[34,37,38,39,40]

FurthermoreapplyingCCSatbiomassfeedstockscouldresultinanadditionalreductionin

globalmitigationcostsofabout40%relativetotheoptionofusingCCSatfossilfeedstocks

only.[38,39]

However,tofullyrealisethispotentialrequiresthatdeploymentofCCStakesoff

this decade. In 2011, there were only 8 operational integrated commercial scale CCS

demonstrationprojectsintheworld[41]

and,accordingtotheIEATechnologyroadmapon

CCS, the number of projects needs to increase to around 100 projects by 2020 and to

almost3500by2050ifthefullcontributionofCCStoprojectedmitigationeffortsistobe

realised(seeFigure1.5).[37]

Figure1.5RoadmapforglobaldeploymentofCCSuptill2050accordingtotheIEATechnology

roadmaponcarboncaptureandstorage.[37]

TheCCSchainiscomposedofthreesteps:capture,transportandstorage.DuringtheCO2

capturestep,CO2isextractedfromindustrialandenergyrelatedsourcese.g.,naturalgas,

fluegasandsyngas.ThisCO2issubsequentlypurified,driedandcompressed.Thisstepis

generally the most expensive part of the CCS chain due to the high capital costs of the

equipmentandtheenergyuseinvolved.Exceptionsaresomespecificindustrialprocesses,likeammoniaorethyleneoxideproduction,whichalreadyproduceahighlyconcentrated

CO2gasstream.ThisreducestheCO2capturesteptodryingandcompressionoftheCO2.

Inthetransportstep,theCO2ismovedfromtheemissionsourcetothestoragelocation.

CO2 transport by pipeline is already applied in various settings, including enhanced oil

recovery (EOR) and enhanced natural gas recovery (EGR). CO2 is transported in

supercritical phase to improve economics. In this phase CO2 behaves like a liquid with a

liquidlikedensity,whiletheviscosityandcompressibilityshowagasphasebehaviour.The

storage phase consists of the longterm isolation of CO2 from the atmosphere via

0

2

4

6

8

10

12

0

1000

2000

3000

4000

2010 2015 2020 2025 2030 2035 2040 2045 2050

CO2captured(GtCO2

/yr)

Numberofprojects

Year

OECDNorthAmerica

OECDEurope

OECDPacific

China&India

Other

CO2captured (world)


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Chapter1

18

mineralisation or by injection of the CO2 into underground geological locations, such as

depletedgasoroilfieldsorsalineaquifers.[5]

CO2 capture is often divided into four categories: postcombustion capture,

precombustioncapture,oxyfuelcombustioncaptureandcaptureatindustrialprocesses.

PostcombustioncaptureinvolvestheextractionofCO2fromfluegaseswhichareproduced by combusting fossil fuels or biomass with air. The flue gas is at

atmospheric pressure and has a low CO2 concentration, resulting in a low CO2

partialpressure.Duetothislowpartialpressure,captureiscurrentlyachievedby

chemicalabsorptionusingsolvents.Theregenerationofthesesolventsinvolvesa

temperatureswing,whichrequireslargeamountsofenergy.Anadvantageisthat

it can be applied at existing power plants (retrofit). Moreover, the CO2 capture

processdoesnot interferewithnormaloperations,meaningthattheavailability

ofthefacilityisnotaffected.

Precombustioncapture isthe extraction of CO2 from anenergyrichgas streamprior to combustion. This prevents N2 dilution and, if the facility operates at

elevated pressure, allows the removal of the CO2 at this elevated pressure.

BecauseofthehighpartialpressureofCO2,physicalsolventscanbeusedinstead

ofchemicalsolventstocapturetheCO2.Asregenerationofphysicalsolventscan

be achieved by pressure swing instead of temperature swing, this results in a

lower energy consumption in the capture process and thus (in principle) lower

CO2capturecosts.

OxyfuelcombustioncaptureentailstheextractionofCO2fromfluegasconsistingmainlyofCO2andsteamasthefossilfuelorbiomassiscombustedwith(almost)

pure O2. Removal of the steam by condensation results in a CO2 purity of

8098%.[34]

In this process high temperatures in the combustion process can be

reached resulting, in principle, in more efficient Brayton (for gas turbines) or

Carnot (for boilers) cycles. Currently, metallurgical constrains prevent the

utilisation of these high temperatures. Therefore, CO2 or steam needs to be

recycledtoreducetheoperatingtemperature.Amaindrawbackofthisoptionis

theneedfor(currentlyexpensive)pureO2.

For capture from industrial processes generally one of the above describedoptions is applied, depending on the process conditions. In some industrial

processes (e.g., ammonia production and natural gas processing) CO2 is already

extracted as part of the industrial process. Applying CCS at these sources,therefore,significantlyreducestheadditionalcostsforCO2separation.Formore

information on the possibilities and potential of CO2 capture at industrial

processes,werefertoKuramochi.[26]

There are three main approaches to separate CO2 from other gases, namely using

sorbents,membranesorcryogenics.[34,35]

SeparationbysorptionmeansbringingthegasstreamcontainingCO2inclosecontactwith

asorbent(orsolventwheninliquidphase).TheCO2isabsorbedintooradsorbedontothe

sorbent. To release the CO2, the sorbent is regenerated. This is commonly done by

increasingthetemperatureforchemicalsorbentsordecreasingthepressureforphysical


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Introduction

19

sorbents. The main disadvantage of this process is the high energy consumption in the

regenerationstep,especiallywhenchemicalsolventsareused.[34,35]

Cryogenic separation involves cooling the gas stream containing the CO2 to below the

boilingtemperatureofCO2.ImpuritiescaneasilyberemovedfromtheliquidCO2.Priortocooling, the gas stream is dried to prevent ice formation in the heat exchangers. After

compression,theCO2isreadyfortransport.Anadvantageofthistechniqueisthataliquid

CO2streamisproduced,whichisbeneficialforcertaintransportoptions,suchastransport

by ship. The main disadvantage is that the entire gas stream needs to be cooled down,

resulting in bulky equipment and a high energy consumption when separating CO2 from

dilutedstreams.[34,35]

MembraneseparationinvolvespassingthegasstreamcontainingCO2alonga(polymeric,

metallicorceramic)materialwhichisselectivelypermeableforonlyCO2orpermeablefor

all other relevant gases except CO2. As only the permeable gases pass through the

membrane,thisresultsinapureCO2stream.Thedrivingforceisthedifferenceinpartial

pressure across the membrane, making high pressure streams more suitable than low

pressure streams for membrane separation. The advantage of this technique is the low

energyconsumptionwhenapressurisedgasstreamisavailable.Althoughthisprocesscan

also be applied at low pressure streams, it requires creating a vacuum,which drastically

increases energy consumption. Furthermore, reliable and affordable CO2 selective

membranes are currently not commercially available and CO2 removal by membrane

separationhasnotyetbeentestedinlargescaleindustrialfacilities.[34,35]

1.3 Integratedgasificationpoly-generationfacilitiesA key technology which can play a role in the development of a sustainable energy

infrastructure is the production of fuels and other chemicals via gasification. Interest in

gasification has increased significantly in the last few decades, resulting in an installed

syngascapacityofaround70GWthin2010.Projectionsfromtheindustryindicatethatthis

capacity could almost double by 2016 (Figure 1.6).[42]

Gasification technology (partly

combinedwithCCS)isseenasaninterestingoptionforCO2mitigation.IntheBlueenergy

scenariooftheIEA,forinstance,installedgasificationcapacityisprojectedtoexceed1500

GWth syngas in 2050[27]

and the World Energy Technology Outlook 2050 H2case scenario

projectsthatmorethan900GWthsyngasisneededforhydrogenproductionalone.[43]


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Chapter1

20

Figure1.6Worldwideinstalledsyngascapacity(GWth)accordingtoChildress.

[42,44,45,46]

The main reason behind the increasing interest in gasification is its ability to convert

carbonaceous feedstocks, like coal, stranded natural gas and biomass, into high value

products, e.g., electricity, transportation fuels and other chemicals.[42]

Gasification offers

additional benefits over the conventional production of energy carriers and chemicals,

namely:

Theabilitytouseavarietyofcarbonaceousfeedstockswithoutbeingdependentonaspecificfeedstock;

[47]

Theabilitytoproduceavarietyofproducts(electricity,fuels,fertilizersandotherchemicals)fromthesyngas,allowingflexibleproductionandoutput;[47]

Lowerspecificemissionsof,amongothers,NOx,sulphurcompounds,particulatematter and heavy metals compared to conventional PC power plants and

refineries;[47]

Facilitating the more energy efficient precombustion CO2 capture instead ofpostcombustion CO2 capture, as the syngas has a high pressure and a high

concentrationofCO2;

The conversion of sustainable biomass feedstocks into carbon neutraltransportationfuelswhichcanbeusedinthecurrenttransportinfrastructure;

[2]

The conversion of sustainable biomass feedstocks into carbon neutral rawmaterialsforthechemicalindustry.[48]

Gasificationfacilitiesalsohavesomedisadvantages.Forelectricityproduction,integrated

gasification combined cycle (IGCC) facilities are more complex and expensive than

conventional natural gas combined cycle (NGCC) and pulverised coal (PC) power plants.

Whenconsideringproductionoftransportationfuelsandotherchemicals,theuseofcoal

as feedstock in the absence of CCS can double specific CO2 emissions compared to

producing the chemical in conventional refineries using natural gas or crude oil.[22,23,24]

Lastly,thecommercialexperiencewithgasificationfacilitiesisstilllimited.This,combined

withthecomplexoperationofthefacilities,hindersitsdeployment.

0

20

40

60

80

100

120

140

1970 1980 1990 2000 2010

Installedsyngascapcity(GWth)

Year

1999forecast 2004forecast

2007forecast 2010forecastOperationalcapacity


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Introduction

21

ProcessdescriptionAn integrated gasification polygeneration (IGPG) facility consists of various key

processes. A schematic overview is given in Figure 1.7. First, a solid carbonaceous

feedstock is fed into an entrained flow (EF) gasifier. The high operating temperature

(>1500C)ofthistypeofgasifierbreaksthefeedstockdownintosyngas,consistingmainlyofCO,CO2,H2andH2O.Therequiredtemperatureisobtainedbycombustingpartofthe

feedstock insidethegasifier.Asubstoichiometricamountof(almost)pureO2,produced

inanairseparationunit(ASU)functionsasoxidant.PureO2isusedtopreventN2dilution

of the syngas, increasing the overall conversion efficiency and reducing the size of

downstream equipment.[47,49,50]

Prior to the gas cleaning, the syngas is quenched to

prevent fouling of the cooling equipment. In the gas cleaning sector, impurities like

halogen gases and solid particles are removed using filters and wet scrubbers. Acidic

compoundsareremovedintheacidgasremovalsection(AGR).

Dependingonthedesiredproduction,theH2:COrationeedstobeadjusted.Thisisdoneina watergas shift (WGS)reactorwhich canbe locatedupstream or downstream theAGR

unit. After cleaning, the syngas can be converted into the final product. To improve

economics and the overall conversion efficiency, steam is generated at various locations

throughoutthefacilityandusedforelectricityproduction.

KeycharacteristicofanIGPGfacilityisthatCO2needstobeextractedfromthesyngasto

improve the conversion efficiency of the downstream chemical or transportation fuel

conversion reactors. Using that concentrated CO2 for CCS purposes results in low CO2

removalcosts,makingIGPGfacilitiesinterestingearlyoptionsforCCSimplementation.

Figure1.7SimplifiedprocesslayoutofaflexibleIGPGfacilitywithCO2captureusing

stateofthearttechnology.Waste,heatandrecyclestreamsarenotdisplayed.

PerformanceDespite the many advantages of gasification facilities, the current globally installed

gasificationcapacityisrelativelylow.Amainreasonisthehighcapitalcostsofgasification

facilities, resulting in high production costs.[51]

Literature studies indicate that an IGCC

without CO2 capture can produce electricity for 5094 /MWh with an efficiency of

4045%HHV.[52,53]

If CCS is applied, the production costs are projected to increase to

64132 /MWh and efficiency could drop by as much as 11%pt, depending on the

technologyusedforgasification,CO2extractionandturbine;theseresultsaresimilarfora

Feedstock

ASU

Pre treatment GasifierGas

Cleanup

Power

production

FTliquids

production

H2production

AGR

MeOH

production

Urea

production

CO2compression

Claus/

SCOT

FTfuel

MeOH

Urea

LiquidS

H2

O2

O2

N2

CO2

H2S

Scompounds

Syngas

CO2


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Chapter1

22

conventional PC plant, both with and without CCS.[52,53]

A recent study by the European

Technology Platform for Zero Emission Fossil Fuel Power Plants (ZEP) reported the

production costs of electricity of different types of Nth

of a kind power plants, namely

pulverised coal (PC), integrated gasification combined cycle (IGCC) and natural gas

combined cycle (NGCC), both with and without CCS. Production costs of electricityproductionwithoutapplyingCCSare48/MWhforPCand72/MWhforNGCC.IfCCSis

applied,theproductioncostsofIGCC2andPCaresimilar(6675/MWhvs.6773/MWh

respectively), while NGCCCCS results in significant higher electricity production costs

(104/MWh).AstudybytheNationalEnergyTechnologyLaboratory(NETL)foundsimilar

results for coal, but much lower production costs of electricity for NGCC mainly due to

lowernaturalgasprices.[53,54]

Furthermore, model studies indicate that FTliquids can be produced from coal in

commercialscaleplantsfor617/GJ.[22,23,24,25,55,56]

Thelowerrangesaremainlyaresultof

low coal prices (in the range of 1 /GJ). For comparison,oilderived transportation fuels

canbeproducedfor13/GJifcrudeoilpriceare72/bbl(whichwastheaveragecrude

oilpricein2011).[65]

Asmentionedbefore,CO2needstobeextractedfromthesyngasto

enablehighefficiencies intheconversionreactors.Thisresults inCO2avoidancecostsas

low as 17 /t CO2.[57]

IGPG facilities can also use biomass. However, literature studies

suggest that production costs of electricity and FTliquids could double due to higher

feedstockcosts,lowerefficienciesandsmallerscaleinstallations.[22,23,24]

Thecombineduse

of coal and biomass in gasificationfacilities equipped with CCS hasbeen investigated by

the Princeton Environmental Institute, but only for dedicated gasifiers for each type of

feedstock.[23,24,25,57]

They conclude that CCS can be applied at integrated gasification

facilities producing FTliquids (IGFT) at relative low costs. The cofeeding of biomass

results in higher production costs compared to a coalfired IGFT, mainly due to higher

capital and feedstock costs. Their studies also indicate that applying CCS at a coalfired

IGFT facility has the same effect to mitigating CO2 emissions as replacing about 40% of

thecoalbybiomassatanIGFTfacilitywithoutCCS.[57]

Inthemidtolongterm,significantcostsreductionsareexpectedforgasificationfacilities

due to technological learning. Studies by the NETL estimate that novel technologies and

improved operating experience could decrease production costs of electricity in an IGCC

by 33% and reduce the CO2 avoidance costs to 13 /t CO2.[58,59]

Production costs of

FTliquids without CCS could potentially drop to 9 /GJ, equivalent to an oil price of

50/bbl.

FlexibilityThementionedstudiesassumenoflexibilityinfeedstockorproduction.However,market

conditions can change considerably in the operational lifetime of a largescale IGPG

facility.Examplesaretheemergingmarketofbiomasspelletsforenergy,thedevelopment

oftheCO2creditspriceandthemarketofnonoilbasedtransportationfuelsaswellasthe

mature markets of coal and crude oil which has experienced strong price fluctuations in

2 In this study the reference plants is always a PC power plant, therefore data for IGCC

withoutCCSarenotreported.


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Introduction

23

thelastyears(seeFigure1.8).[60,61,62,63,64,65]

Besideslongtermuncertainties,therearealso

shortterm variations, such as the daily variation in the electricity price,[66]

which can

impacttheeconomicsof IGPG facilities,especiallyas largescalestorageofelectricity is

currentlyeconomicallynotfeasible.

Figure1.8Historicpricesofprimaryenergycarriers(left)anddistributionofhistoricelectricityprices(right).[60,61,64,65,66]

AsIGPGfacilitiescanhandleavarietyoffeedstocksandcanproducemultipleproducts,

thesefacilitiesallowreactiontoandexploitationoffluctuations inmarketconditions.An

example is exploiting the daily electricity variation existing in North WestEurope by

producing electricity during peak hours and transportation fuels or chemicals during

offpeak hours. Flexibility of the facility does, however, come with thedisadvantage of

highercapitalinvestmentandO&Mcostsand,dependingonthetypeofflexibility,lower

efficiencies compared to nonflexible IGPG facilities. Currently, a detailed analysis of

whether the advantages of flexibility offset the disadvantages has not been performed

yet, despite the fact that flexibility is mentioned to be a strong argument in favour of

IGPG

facilities.[44,67]

1.4 SummarisingThere are significant potentials for both biomass and CCS to reduce GHG emissions.

However,thecurrentcapacityofbothCO2mitigationoptionsislow.Asstatedpreviously,

biomass for modern applications only comprises 2% of our global primary energy

demand[7,27,28]

and CCS is only being applied in eight commercialscale projects.[41]

Important reasons for the lowpenetration forbiomassare thecurrentlyhigh feedstock

prices,theuncertaintyregardingavailabilityduetotheimmaturityofthebiomassforthe

energymarket,[7]

resulting in relatively smallscalebiomassfed conversion facilities.For

CCS,important

reasons

are

the

high

costs

to

avoid

CO2

emissions

relative

to

the

current

CO2creditpriceorCO2taxandtheuncertaintyinfutureclimatepolicy.

Gasification can play an important role to increase the deployment of both mitigation

options.Theinstalledgasificationcapacityis,however,onlyaround70GWth.Animportant

cause is the high production costs. Although technological innovation resulting in large

reductionsincapitalcostsandimprovementinoverallefficiencyareforeseeninthenear

future, achieving this improved performance requires that the installed gasification

capacityincreasessignificantly.

0

5

10

15

2000 2002 2004 2006 2008 2010

2008

/GJ

Year

EUBrentCrudeOilBiomasspelletsNorthernAppalachia

0%

5%

10%

15%

20%

0 50 100 150 200

Occurence(%)

Electricityprice(2008/MWh)

Nominalprice

Dayprice

Nightprice

Priceat50%occurence


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Chapter1

24

Flexibility might facilitate the deployment of gasification facilities for two main reasons.

First, the ability of IGPG facilities to be feedstock flexible allows the construction of

biomassfed facilities at coalfed scale, and thereby takes advantage of economies of

scale,butwithouttheriskimposedbyaninadequatesupplyofbiomass.Second,flexibility

lowers the investment risk as both feedstock and production can be altered during theoperationallifetimeofthefacility.Anadditionaladvantageofgasificationfacilitiesisthat

CO2 is often removed when chemicals are produced. This should allow the

implementation of CCS at relatively low costs. Currently, there is a need for better

understanding what the possibilities and limitations of flexibility at gasification facilities

areandunderwhich(economic)conditionsflexiblefacilitiesaremoreadvantageousthan

theirstaticcounterparts.Theseaspectsareatthecoreofthisthesis.

A promising (natural gasfired) gasification application for the deployment of CCS in the

shorttermissteammethanereforming(SMR)atindustrialfacilities.CO2avoidancecosts

at SMR facilities are projected to be lower compared to the avoidance costs at power

plants due to the presence of a pressurised CO2 rich gas stream and the possible

availability of waste heat streams, as SMR facilities are generally located inside large

industrial complexes, like refineries. Although literature studies on applying CCS at SMR

facilities have been performed, the impact of applying CCS at existing facilities (retrofit)

andtheeffectofusingwasteheatontheCO2avoidancecostsatSMRfacilitieshavenot

yetbeenstudied.

1.5 ThesisobjectiveandoutlineThe main objective of this thesis is to determine the technoeconomic potential of

commercialscalegasificationsystemsproducingenergycarriersandotherchemicalswith

low CO2 emissions and to assess how and when flexibility improves the overall

performanceofthesegasificationsystems.

Thethreemainresearchquestionsare:

RQ.I Whatistheimpactofflexibleoperationofstateoftheartgasificationfacilitieson the technical and economic performance of integrated gasification

polygenerationfacilities?

RQ.II What is the potential improvement intechnicaland economic performanceofintegratedgasificationfacilitiesinthecomingdecades?

RQ.III WhataretheCO2avoidancecostsofgasificationfacilities,includingSMR,intheshorttolongterm?

Furthermore, literature indicates that performance of IGPG facilities can improve in the

future.[58,59]

However,therateofthisimprovementandthedriversbehinditisstillpoorly

understood.Inthisthesistheimprovementpotentialisanalysedusingtwoapproaches:

A bottomup analysis, giving insights into the extent of the potential costreductions and how they can be realised. This approach involves identifying

promising technologies, determining their current status and potential


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Introduction

25

development in the future and designing new process layouts of gasification

facilitieswhichtakeoptimaladvantageofnewtechnologies;

Atopdownanalysismakinguseofanaloguelearningcurvestudies,givesinsightsintohowcost reductionscoulddevelopover time.Thisapproachcombines the

required

growth

in

installed

capacity

with

scenario

projections

on

the

deploymentofgasificationfacilities.

Bycomparingthetwoapproachesamorerobustpredictionisobtainedonhow,whenand

towhatextentproductioncostsingasificationfacilitiescandecreaseinthefuture.

Table 1.1 gives an overview of the chapters of this thesis in which these research

questionsareaddressed.

Table1.1Structureofthethesis.RQ.I RQ.II RQ.III

Chapter2:Performanceofsimulatedflexibleintegratedgasificationpolygenerationfacilities.PartA:Atechnical

energeticassessment

Chapter3:Performanceofsimulatedflexibleintegratedgasificationpolygenerationfacilities.PartB:Economic

evaluation

Chapter4:Technicalandeconomicprospectsofcoal andbiomassfiredIGPGfacilitiesequippedwithCCSovertime

Chapter5:FuturetechnologicalandeconomicperformanceofIGCC

and

FT

production

facilities

with

and

without

CO2capture:

combiningcomponentbasedlearningcurveandbottomup

analysis

Chapter6:TechnoeconomicassessmentofCO2 captureatsteammethanereformingfacilitiesusingcommercially

availabletechnology

Chapter 2 aims to determine the technical impacts of flexibility in largescale IGPGfacilities.ThechapterprovidesanoverviewofthemajorcomponentsinanIGPGfacility.

For each component the possibilities, limitations and effects of flexible operation is

investigated.Thisinformationisusedtodevelopacomponentbasedcomputersimulation

model.Thismodelyieldsthemassandenergybalancesneededtodeterminethetechnical

performance of IGPG facilities and the impact flexibility has on overall IGPG facility

performance. The chapter also investigates the impact on the CO2 fraction that can be

captured in a flexible IGPG facility. The flexibility comprises both feedstock (biomass

pellets, torrefiedbiomasspelletsandcoal)andproduct (electricity, FTliquids,methanol

andurea).


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Chapter1

26

Chapter3 focuses on the impact of flexibility on the economics of IGPG facilities. Theresults of the technical model developed in Chapter 2 are combined with an economic

model to calculate production costs using the net present value (NPV) method. The

resulting production costs are used to identify under which conditions flexible IGPG

facilities

are

economically

more

attractive

than

static

IG

PG

facilities.

The

chapter

also

investigates the effect a CO2 credit price has on the profitability of the use of biomass

versuscoalasfeedstockandonventingCO2versusapplyingCCS.

Chapter 4 assesses the potential improvement in overall performance of static IGPGfacilitiesproducingelectricityortransportationfuels,withorwithoutCCSfromeithercoal

or biomass using a bottomup analysis. For each component, possible improvements in

existing technologies, as well as advanced alternative technologies are identified. The

improvementsandadvancedtechnologiesarecategorizedinthreedifferenttimeperiods

basedontheirexpectedcommercialisationperiod.Foreachtimeperiod,aprocesslayout

ofthe IGPG facility ismadeusingthetechnologiesavailable forthattimeperiod.These

processlayouts

are

used

in

the

technical

and

economic

models

developed

in

Chapters

2

and3.Thisresultsininsightsintothepotentialreductioninproductioncostsandintothe

extentthedifferentimprovementscouldpotentiallycontributetothatreduction.

Chapter5aimstoassessthepotentialimprovementinoverallperformanceofstaticIGPGfacilitiesproducingelectricityortransportationfuel,withorwithoutCCSfromeithercoal

orbiomassusingatopdownapproach.Learningcurveanalysis isapplied inthischapter

basedoncurrentandprojectedinstalledcapacitiesofmajorIGPGcomponents.Basedon

theseresults,productioncostsforelectricityandFTliquidsarecalculated,aswellasthe

impactonCO2emissions,uptill2050.TheresultsarecomparedwiththeresultsofChapter

4.

Chapter6aimstodeterminetheoptimalstateoftheartCO2capturesystemformodernsteam methane reforming (SMR) facilities using process simulations. A stepbystep

methodologyisdevelopedtoidentifytheoptimalCO2capturesystemforanSMRfacility,

withtheaimofreducingtheenergypenaltyandminimisingCO2avoidancecosts,without

compromisingH2purityorSMRavailability.Thechapterassessesthe locationoftheCO2

captureunitwithintheSMRprocess,theCO2capturesolventandthedimensionsofthe

absorberandregenerator.

Chapter7summarisestheobjectives,approachandkeyfindingsofthisthesis.Besidesthemainconclusions,recommendationsforfurtherresearcharegiven.


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27

2 Performanceofsimulatedflexibleintegratedgasificationpolygenerationfacilities.PartA:A

technical-energeticassessment

HansMeerman,AndreaRamrez,WimTurkenburg&AndrFaaij

RenewableandSustainableEnergyReviews15(2011)256387

DOI:http://dx.doi.org/10.1016/j.rser.2011.03.018

AbstractThis article investigates technical possibilities and performances of flexible integrated

gasification polygeneration (IGPG) facilities equipped with CO2 capture for the near

future.These facilitiescanproduceelectricityduringpeakhours,whileswitching to the

productionofchemicalsduringoffpeakhours.

SeveralsimulationswereperformedtoinvestigatetheinfluenceofsubstitutingfeedstockandproductiononIGPGfacilityoutput,loadandefficiency.Thesesimulationsweredone

usingadetailedAspenPlussimulationmodelofaShellentrainedflowgasifiercombined

with conversion facilities. In this model carbonrich feedstocks (oil residues, coal and

biomass)wereconvertedtoavarietyofproducts(H2,electricity,FTliquids,methanoland

urea) using stateoftheart technology. The size of the gasifier was limited to the

equivalentof2000MWthIl#6coalinput.

Overallefficiencyofthesimulatednonflexibleconfigurationstoconvertpurecoalorpure

woodpelletstoelectricity (40%HHVvs.38%HHV),FTliquids (60%HHVvs.55%HHV),methanol

(53%HHVvs.

49%HHV)

or

urea

(51%HHV

vs.

47%HHV)

are

in

good

agreement

with

the

literature.

Using torrefiedwoodpellets instead ofpurewoodpellets reduces thepenaltydrop in

efficiency compared to coal.Moreover, torrefiedwood pellets have superior energetic

density,handlingandfeedingcomparedtowoodpellets.

Inthisanalysis,theH2:COratioofthesweetsyngaswasfixedtomatchFTliquidscriterion.

Asaresult,overallCO2captureratesarelow,around5665%,dependingonthefeedstock

used. Still, especially with FTliquids and methanol production, CO2 emissions at the

facility are significantly reduced; less than 20% of the carbon feedstock entering the

facility is emitted with the flue gas. Applying biomass and CO2 capture shows great

opportunitiesto

produce

CO2

neutral

electricity

or

chemicals.

When

the

biomass

fraction

exceeds 40% on an energy basis, production is CO2neutral, independent of what is

produced.

Biomasscanbecofedup till50%onanenergybasis.Higher fractionscausesignificant

fouling on cooling equipment. A small partload penalty is observed during the

substitutionofcoalbybiomass.Whenchangingfrompurecoaltopurewoodpellets,the

powercasesuffersa2.5%efficiencydrop,whileallthreechemicalcaseshaveanefficiency

dropoflessthan1%.Atthesametimetotaloutputisreducedto6769%,mainlybecause

ofthelowerenergydensityofbiomass.Byoverdimensioningthegasifierandgascleanup

andoptimisation

section

this

drop

can

be

eliminated.


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Chapter2

28

The syngas can be tailored to the desired composition regardless of the used feedstock.

Therefore,thechemicalconversionsectionsonlyhavetocopewithareductioninsyngas

flowandnotwithachangeinsyngascomposition.Alteringproductionbetweenchemicals

and electricity is possible, although the load of the conversion sections should remain

between 40% and 100% to prevent operational problems. This gives a high degree offlexibility.

Complete substitution between chemical and power production while using the same

feedstockispossibleforthemethanolandureacases.TheFTliquidscaseisrestrictedto

60100% load of the chemical conversion section to prevent that the gas turbine load is

reducedbelow40%.

TheeconomicaspectsofflexibleIGPGfacilitiesareaddressedinpartB.


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Performanceoffacilities.PartA:Atechnicalenergeticassessment

29

2.1 IntroductionIn 2008 global fossil fuel consumption was around 410 EJ. About 40% of this camefrom

crude oil.[68,69]

These fossil fuels power the economies of today. However, their use has

several drawbacks. Fossil fuel resources are finite and their consumption results in large

CO2 emissions (unless carbon capture and storage is applied) as well as otherenvironmental effects. Moreover, their consumption may result in high import

dependence which may threaten supply security, for example in the European Union.

Lastly, largescale implementation of solar and wind power socalled intermittent

renewables requires largescale backup electricity generation capacity. The output of

backup facilities must be easily adjustable in case solar and wind electricity production

changes.[70]

Also, the operating hours of these backup facilities will be relatively low

comparedtobasepowerplants.

A technology that can partly help to overcome these drawbacks is gasification. Through

gasification (renewable) biomass, coal and oil residues can be converted into syngas,which can subsequently be converted into electricity, transportation fuels and other

chemicals(Figure2.1).Naturalgascanbeconvertedintosyngasusingreforming.

Figure2.1Conversionofcarbonrichfeedstockstodifferentproducts.

ToreduceCO2emissions,CO2canbeextractedfromprocessandfluegases,compressed

to30110bar,transportedandstoredinundergroundfields(generallyknownasCCS).In

this way, electricity and hydrogen can be produced with minimal CO2 emissions. CCS at

IGPGfacilitiescanbeaccomplishedatreducedcosts.[24,71]

Thereasonforthis istwofold.

First,thechemicalconversionprocessesalreadyrequireremovalofCO2fromthesyngas.

Second, the higher partial pressure of the CO2 makes precombustion capture using

physical solvents possible. This lowers the energy requirements for the CO2 capture and

subsequent compression. By combining gasification and CCS it is possible to drastically

reduce global CO2 emissions without drastic changes to the current infrastructure.Furthermore, cofeeding biomass allows the production and use of liquid hydrocarbon

transportation fuels with no net CO2 emissions.[22,72]

At large biomass fractions even net

negativeCO2emissionscanbeachieved.

Anattractivefeatureofgasificationis itspotentialflexibility.Especiallythefollowingtwo

combinations of flexible integrated gasification polygeneration (IGPG) facilities are

interesting:

(1) Coal substitution by biomass can facilitate the use of biomass as feedstockwithoutbeingdependentonaconstantbiomasssupply.

Coal

Biomass

Heavyoil

Gas

Electricity

Hydrogen

FTliquids

Methanol

Urea

Syngas


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Chapter2

30

(2) Chemicalplantsproducingmidloadelectricitycanreducetheneedofdedicatednatural gas fired midload power plants. Midload plants are operated when

electricitydemandexceedsthebase load.As intermittentrenewableselectricity

generation capacity is everincreasing, midload power plants will increasingly

havetoactasbackuppowerplantsfortheseintermittentrenewables.ThismaycreateopportunitiesforflexiblelargescaleIGPGfacilities.

Multifeedstock polygeneration (XtY)3 system integration has seen a lot of attention in

literature. A brief overview of studies highlighting results relevant for this study is given

below.

2.1.1 GeneralCummerandBrown investigated themajorancillary components, i.e. pretreatmentand

gas cleaning, in integrated gasification combined cycle (IGCC) facilities.[73]

They

investigated whether components specifically designed for coal could also handle

biomass. They also determined the stage of development of ancillary equipment forbiomass fired IGCC. Their conclusion is that most of the ancillary equipment is not yet

commerciallyavailable.

2.1.1.1 Electricity productionElectricity production using coalfired IGCC combined with CCS has received quite some

attention. A recent study by NETL indicates that, based on stateoftheart (SOTA) Shell

gasificationtechnology,a636MWeIGCCcanachieveanoverallefficiencyof41%HHV,while

emitting750kgCO2/MWh.EquippedwithCO2capture,plantefficiencywouldatpresent

dropto32%HHVandCO2emissionsto90kgCO2/MWh.[74]

Similarvaluesarepresentedby

the IEAGHG with 40%HHV efficiency for Shell IGCC without CO2 capture and 32%HHV with

CO2capture.[49,50]

2.1.1.2 Fischer-Tropsch fuels productionAlthough there is some variation in final efficiency among the literature, reported XtL

conversion efficiencies lay between 46%HHV and 56%HHV. Boerrigter calculated an overall

conversion efficiency of 56%HHV for a noncapture CtL facility.[75]

Larson et al., calculated

an overall conversion efficiency for a noncapture CtL facility of 49%HHV (33% FT + 17%

power). Introducing CO2 capture and compression lowers the power output by 3%pt.

Converting a mixture of switch grass and coal to FTliquids with CO2 capture could be

performed with an overall conversion efficiency of 47%HHV.[76]

This efficiency was

confirmedbyastudyofHamelincketal.TheycalculatedthatbiomasscanbeconvertedtoFTliquidswithCO2captureat46%HHVefficiency(33%FT+13%power).

[77]

2.1.1.3 Methanol productionA CtM studybased onthe liquid phase methanol (LPMeOH

TM) demonstration process at

the Eastman Chemical Company in Kingsport was performed by Heydorn and Diamond

3 Facilities or systems where feedstocks are gasified and converted into products are

referred to as XtY systems. The X is often substituted if a specific feedstock is used:

biomass(BtY),torrefiedbiomass(TtY)orcoal(CtY).TheYisoftensubstitutedifaspecific

outputisproduced:electricity(XtP),FTliquids(XtL),methanol(XtM)orurea(XtU).


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31

showing a CtM efficiency of 60%HHV assuming a gasification efficiency of 80%HHV and a

syngasenergytoelectricityefficiencyof40%HHV.[78]

TwodifferentCtMconfigurationswere

analysed by Larson and Tingjin.[79]

They calculated an efficiency of 47%HHV for

oncethroughand63%HHVforsyngasrecycle.ABtMefficiencywascalculatedbyWilliams

et al., at 61%HHV.

[80]

Hamelinck and Faaij calculated a BtM efficiency of 51%HHV using afluidisedbedsystem.[81]

2.1.1.4 Urea productionUreasynthesisviagasificationhasreceived little interest in open literature.Neelisetal.,

found an energy consumption of 21 GJLHV/t urea, resulting in a CtU energy conversion

efficiencyof44%LHV.[82]

2.1.2 ObjectivesAll these studies do not investigate variation in feedstock or production during the

operationofthefacility.ArecentstudyfromIEAGHGhasmadeafirstassessmentofthe

flexibility between hydrogen and electricity production, but only at two different

production ratios.[49]

To our knowledge that is the only study which investigated the

possibilities of flexible IGPGfacilities andthe impact offlexibility on overallefficiencies.

Thisstudyaimstofillthisgap.Theobjectivesofthisstudyaretherefore:

First,to identify which bottlenecks occurwhen altering feedstock or productionandhowthesebottleneckscanberesolved;

Second,toanalysesystembehaviourandchangesintheoverallefficiencyandintheenergy,massandcarbonbalanceswhenalteringfeedstockorproduction;

Third, to analyse the effect of flexibility on the CO2 balance and emissions andcomparethebalanceandemissionswiththosefromdedicatedXtYfacilities.

In this study the focus is on the performance of SOTA commercial technologies relevant

for XtY systems. To study these systems, an AspenPlus flowsheet process model of a

flexibleIGPGfacilitywasbuildtogenerateenergyandmassbalancesfordifferentIGPG

facilities.Toallowaccuratemodelling,dataonthetechnicalbottlenecksasminimal load

constraintsandpartloadbehaviourofthevariouscomponentswerecollected.

Thestructureof this article is asfollows: Section 2describes the commodities, including

the different feedstock characteristics. In Section 3 the different components, including

feedstock pretreatment, syngas cleaning and syngas conversion, and their operating

conditions are described. Section 4 gives the process model and plant configurations. In

Section 5 the case studies are defined. Section 6 gives the simulation results, including

overallperformanceandtheeffectofflexibilityonoverallIGPGperformance.InSection7

a discussion of the results and used assumptions is given. Finally, Section 8 contains the

conclusions.

In this study, units are in SIunits and heating values are in higher heating value (HHV),

unlessstatedotherwise.


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2.2 Commodities2.2.1 FeedstocksFor this study three representative solid carboncontaining feedstocks were selected.

Eucalyptuspellets(EP),torrefiedwoodpellets(TOPS)andIllinois#6coal.Theirpropertiesare given in Table 2.1. Short rotation trees, of which Eucalyptus is one of them, is a

potentiallyimportantbiomasssource.[83,84,85]

Thebiomassisdirectlypelletisedortorrefied

andthenpelletisedasthisdrasticallyimprovesbiomassproperties,likeheatingvalueand

moisture content (Table 2.2). This results, among others, to a more efficient

transportation and handling of the biomass.[22,84,86,87]

Illinois #6 coal is a Bituminous coal

typeoftenusedinandcommonlyusedasreferencecoal.[74,79,88,89]

Table2.1Feedstockparametersusedinthisstudy.

Composition Unit(1)

EP[90]

TOPS[90]

Il#6coal[74]

Heatingvalue MJHHV/kga.r. 17.29 20.51 27.14Moisture wt%a.r. 10.00 5.00 11.12

VolatileMatter wt%dry 86.60 75.90 44.50

FixedCarbon wt%dry 12.83 24.10 44.59

Ash wt%dry 0.50 1.34 10.91

C wt%d.a.f. 49.77 54.63 80.50

H wt%d.a.f. 5.80 5.67 5.68

O wt%d.a.f. 44.20 39.45 8.70

N wt%d.a.f. 0.14 0.22 1.58

S wt%d.a.f. 0.03 0.02 3.17

Cl wt%d.a.f. 0.06 0.01 0.37

(1) The composition is on as received (a.r.), moisture free (dry) or moisture and ash free (d.a.f.)

basis.

2.2.2 End-productsSyngas can be converted into a wide variety of endproducts. The main endproducts

evaluated in this study are electricity, FTliquids, methanol and urea. An important

intermediateproductishydrogen.

2.2.3 By-products

TwoimportantbyproductsofXtYfacilitiesareslagandelementalsulphur.Slagisaninertglasslike material consisting mainly of minerals. It is formed as the ash in the feedstock

meltsand issubsequentlyquenched.Slag is,amongothers,usedasconcreteadditiveor

road surface coating compound.[91]

The amount and quality of the slag depends on the

used feedstock. Coal generally produces more slag than woody biomass. Almost all

sulphur inthefeedstock isrecoveredaselementalsulphur.Itisused inawidevarietyof

processes, including vulcanisation, bleaching and the production of fertilizers and

viscose.[92]

Coalgenerallycontainsmoresulphurthanbiomass.


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33

2.3 ProcessdescriptionIn this section a technical description and partload performance of the different

components used in a flexible IGPG facility is presented. For all components only

commercial available technologies were investigated. The key processesare displayed in

Figure2.2.

Figure2.2SimplifiedprocesslayoutofaflexibleIGPGfacilityusingSOTAcommerciallyavailable

technology.Waste,heatandrecyclestreamsarenotdisplayed.

2.3.1 PlantflexibilityA flexible IGPG facility must be designed to cope with alterations in feedstock, syngas

flowandheatstreams.Amongothers, itmustbeabletoadjusttheH2:COratio.Physical

limitationsrestricttheflexibilityoftheconversionprocesses.Forexample,separatorsare

usually unable to operate properly below 40% volume load.[93,94]

Also, gas turbines havedifficulties maintaining the desired flue gas exit temperature below this load.

[95] In the

subsequent paragraphs the load restrictions and partload behaviour of the various

componentsarediscussed.

2.3.2 Pre-treatmentThe gasifier has several minimal requirements concerning the feedstock (see 2.3.5). To

fulfil these requirements, the feedstock, especially biomass, needs pretreatment, like

pelletisingandtorrefactioncombinedwithpelletising.Theeffectsofthesetechniquesare

giveninTable2.2.Forcomparisontheaveragecoalcharacteristicsarealsogiven.

The pretreatment can be performed at the harvesting, central gathering or factory

location.[22,86]

Itcanalsobedividedovertheselocations.Inthisstudyitwasassumedthat

thebiomassisalreadytorrefiedorpelletisedwhenarrivingattheIGPGfacility.Themost

importantpretreatmenttechniquesaredescribedbelow.

Prepared

feedstock

ASU

GasifierGas

Cleanup

Power

production

FTliquids

production

H2production

AGR

MeOH

production

Urea

production

CO2compression

Claus/

SCOT

FTfuel

MeOH

Urea

LiquidS

H2

O2

O2

N2

CO2

H2S

ScompoundsCO2

Sweet

WGSSour

WGS


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Table2.2Overviewofchemicalpropertiesofdifferentfueltypes.

PropertyIl.#6coal

79

(Bituminous)

Fresh

Wood[90]

Wood

pellets[96]

TOPS

[97]

Heatingvalue(MJHHV/kga.r.) 27 1011 1820 2024

Massdensityofbulkmaterial(kg/m3) 600 350 500650 850

Energydensityofbulkmaterial(GJ/m3) 1617[97] 34 913 1721

Moisturecontent(wt%) 11 50 610 15

C/Hratio(wt)1

1316 ~8 ~8 91087

C/Oratio(wt)2

710 1 1 1287

Flammability3

o ++ +++ ++98

Hydrophobicity + +

(1) GasifyingafeedstockwithahigherC/HratioresultsinmoreCOandlessH2.

(2) AlowerC/Oratioresultsinalowerheatingvalue(HHV)ofthefuel.Inagasifieritalsoresultsin

lowerexternalO2consumption.

(3) Theflammabilityofcoalwassetonaverage.Woodiseasiertocombust,butitshighmoisture

contentlowersflammabilityslightly.Duringpelletisation,thismoistureisremoved.TOPShasa

lowmoisturecontent,butduringthetorrefactionprocessitlostmostofitsvolatilecompounds,therebyloweringitsflammability.

2.3.2.1 TorrefactionTorrefaction transforms biomass into a brittle, moisturepoor, hydrophobic solid with an

increased energy density compared to the original biomass.[86,99]

In short: the biomass

becomes more coallike. Another benefit is better storage properties as deterioration is

muchslowerthanrawbiomass.Thetorrefactionprocessconsistsoffourstages:heating,

drying,torrefactionandcooling.Duringthetorrefactionstage,thebiomassisheatedina

moving bed reactor to 200300C for several minutes. H2O, CO2 and other volatile

compounds evaporate, resulting in an increased C/O ratio of the solid product. Besides

thissolid,alowcaloricgasisproduced.Onaverage,thebiomasswilllose30%ofitsmass

and 510% of its energy, depending on the biomass used and the original moisture

content.Thelowcaloricgasiscombustedandusedasheatingsource.Additionalbiomass

is combusted to supply the remaining heat demand, resulting in an almost completely

selfsufficientsystem.[86,99]

Torrefactionisabatchprocessrequiringstoragewhenapplied

inacontinuousprocess,suchasanIGPGfacility.Storagealsofitstopartloadoperation

of the facility. The torrefaction process is operated at full load, regardless of the IGPG

facility load. When the storage bins are filled, the torrefaction process is shutdown. It is

restartedwhenthefeedstockinthestoragebinscomesbelowacertainthresholdvalue.

2.3.2.2 PelletisingPelletising increases the energy density of biomass feedstocks. This, among others,

reduces transportation costs. During pelletising the biomass is highly compressed. If the

biomass is torrefied, pelletising is mandatory except if the torrefied product is used

immediately. When using raw biomass, the pelletising process consists of four stages:

dryingandgrinding,steamconditioning(tosoftenthefibres),pressurisationandcooling.

Topreventpelletdisintegration,glueisneeded.Whenpelletisingat150Cthelignininthe

biomass which softens above 100C is used as glue.[86]

The energy density of the

biomassincreasesbyaboutafactorof2(Table2.2).Electricityconsumptionofpelletising

is90160MJe/tinput.[86]


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Combiningtorrefactionwithpelletisingresultsinafactor3increaseinbulkenergydensity

comparedtorawbiomass(Table2.2)andahalvingoftheelectricityconsumptionofthe

pelletising process. It isbest topelletisethe biomassdirectly after the torrefaction step.

This reduces the pelletising process to pressurisation and cooling only. Like torrefaction,

pelletisingisabatchprocess.Therefore,thesamepartloadbehaviourapplies.

2.3.2.3 SizingSizing reduces the particle size of solid feedstocks, making transporting and feeding the

feedstock more efficient and easier. It also improves drying, torrefaction and pelletising.

ShellEFgasifiers demand particles smallerthan 0.1 mm for coaland smaller than 1mm

forbiomass.Biomassparticlescanbelargerastheyaremorereactivethancoal.[100]

Hard

brittlefeedstocks(TOPS,coal)aregroundusingcrushers.Morefibrousfeedstocks(rawor

pelletisedbiomass)aregroundusingahammermill.Grindingbiomassto1mmandcoalto

0.1mmrequiresanenergyconsumptionof0.010.02kWe/kWth grindingbiomassto0.1

mm would require 0.08 kWe/kWth.[100]

Sizing has good partload behaviour. By reducing

the speed of the conveyer belt and the sizing equipment, partload operation can be

achievedwithoutlowerefficiencies.

2.3.2.4 DryingThehighmoisturecontentinrawbiomassmakesitunsuitableforgasification freshwood

hasatypicalmoisturecontentofaround50wt%.[90]

Dryingispreferredbeforepelletising

or long distance transport. Active drying of biomass below 10 wt% moisture is not

practical as drying efficiency drops dramatically below that value.[101]

Heat demand

depends among others on initial and final moisture content, particle size and

hydrophobicity of the feedstock. This heat can be supplied by waste heat of other

processes.Dryinghasgoodpartloadbehaviour.Justlikesizingthespeedoftheconveyerbeltandtheamountofheataddedtothefeedstockcanbereduced.Inthisstudythecoal

was dried to 2.5 wt% using waste heat of the IGPG facility. Biomass did not receive

furtherdryingasitsmoisturecontentwasalreadybelow10wt%.

2.3.3 PressurisingandfeedingPrevious research indicated that pressurised gasifiers have significant advantages over

atmospheric gasifiers. The most important advantages are smaller downstream

equipmentandhavingagasstreamatelevatedpressure.[77]

Asmostchemicalconversion

processes and the gas turbine operate at higher pressure, the latter advantage

significantly lowers compression requirements. However, using pressurised gasifiers alsorequires pressurised feeding. For solid feedstocks, the pressurising and feeding systems

dependontheparticledensityandsize.Coal isusuallyfedbya lockhoppersystemwith

pneumaticfeed.Fresh(orpelletised)biomassneedsadifferentfeedingsystemasitistoo

fibrous. This can lead to blockage of the lockhopper feeding system. Due to the larger

particle size of biomass, a hydraulic piston system with screw feeding can be used. The

torrefaction process destroys the fibres, allowing TOPS to use both feeding systems.

However,screwfeedingismoreefficientthanpneumaticfeeding.[100]

Asbothsystemsare

batch systems, they are equipped with pressurised storage bins, allowing homogeneous

and continuous feeding. As pressurising agent, CO2 was used. Energy consumption

dependsontheusedprocessandisneededforCO2compressionandthehydraulicpiston


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36

feedersystem.Inthisstudyseparatefeedingsystemforthebiomassandcoalwereused.

Partloadoperationonlyaffectsthefrequencyatwhichthestoragebinsarerefilled.The

effectoffeedingthedifferentfeedstocksisgiveninTable2.3.[100]

Table2.3Feedstockpressurisationcharacteristics.[100]

Il.#6coal(1)

TOPS(1)

EP(1)

CO2consumption Nm3

CO2/tfeedstock 3.7 0.2 0.2

ofwhich:togasifier 2.1 0.1 0.1

toatmosphere 1.6 0.1 0.1

Electricalconsumption kWh/tfeedstock 46.7 42.5 42.5

(1) Basedonalockhoppersystemwithpneumaticfeedingforcoalandahydraulicpistonsystem

withscrewfeedingforbiomass.

2.3.4 Airseparationunit(ASU)The use of pure oxygen (95%) instead of air leads to a lower syngas volume and higher

syngas energy density. There are three different air separation techniques available toextractoxygenfromair:(vacuum)pressureswingadsorption,membraneseparation,and

cryogenicseparation.[102]

Largescalemembraneseparationshowshighpotentialbutisstill

in the demonstration phase. Of the other options, cryogenic separation is currently the

most economical option when high purity (>95%) and throughput (>2.5 t/h) are

required.[103,104]

Energy savings can be accomplished by integrating the ASU with thegas

turbine. An integrated ASU receives (part of) its air already partly compressed from the

gas turbine. Although this increases efficiency, plant flexibility and reliab

20120904 150120 Proefschrift Meerman

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