Thermochemical Fuel Reforming for Ice

7/31/2019 Thermochemical Fuel Reforming for Ice

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Arnold SchwarzeneggerGovernor

THERMOCHEMICAL FUELREFORMING FOR

RECIPROCATING INTERNALCOMBUSTION ENGINES

PIER

FINALP

ROJECTREPOR

T

Prepared For:

California Energy CommissionPublic Interest Energy Research Program

Prepared By:Gas Technology Institute

January 2011CEC-500-2009-011


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DISCLAIMER

This report was prepared as the result of work sponsored by the California Energy Commission. It does not necessarily represent the views of theEnergy Commission, its employees or the State of California. The Energy Commission, the State of California, its employees, contractors andsubcontractors make no warrant, express or implied, and assume no legal liability for the information in this report; nor does any party representthat the uses of this information will not infringe upon privately owned rights. This report has not been approved or disapproved by the CaliforniaEnergy Commission nor has the California Energy Commission passed upon the accuracy or adequacy of the information in this report.

Prepared By:Gas Technology InstituteProject Manager: John PratapasDes Plaines, IL 60018Commission Contract No. 500-02-014

Prepared For:Public Interest Energy Research (PIER) Program

California Energy Commission

Jennifer Allen

Contract Manager

Arthur Soinski, Ph.D.Program Area Lead

Environmentally Preferred Advanced Generation

Kenneth Koyama

Office Manager

Energy Generation And Research Office

Laurie ten Hope

Deputy Director

ENERGY RESEARCH AND DEVELOPMENT DIVISION

Melissa Jones

Executive Director


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i

Acknowledgements

ThisreportdescribesresearchsponsoredbytheElectricPowerResearchInstitute(EPRI),

CaliforniaEnergyCommission,UtilizationTechnologyDevelopmentNFP,andtheGas

TechnologyInstitute.

JohnM.Pratapas,GasTechnologyInstituteProjectManager

PrincipalInvestigators:

Dr.AleksandrKozlov,GasTechnologyInstitute

MarkKhinkis,GasTechnologyInstitute

Dr.GregoryAronchik,GasTechnologyInstitute

Dr.DanielMather,DigitalEngines,LLC

AntonKozlovsky,DigitalEngines,LLC

EPRIProjectManager:

D.Thimsen

Pleasecitethisreportasfollows:

Pratapas,John.2009.ThermochemicalFuelReformingForReciprocatingInternalCombustion

Engines.CaliforniaEnergyCommission,PIEREnvironmentallyPreferredAdvanced

Generation.CEC5002009011.


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Preface

TheCaliforniaEnergyCommissionsPublicInterestEnergyResearch(PIER)Programsupports

publicinterestenergyresearchanddevelopmentthatwillhelpimprovethequalityoflifein

Californiabybringingenvironmentallysafe,affordable,andreliableenergyservicesand

productstothemarketplace.

ThePIERProgram,conductspublicinterestresearch,development,anddemonstration(RD&D)

projectstobenefitCalifornia.

ThePIERProgramstrivestoconductthemostpromisingpublicinterestenergyresearchby

partneringwithRD&Dentities,includingindividuals,businesses,utilities,andpublicor

privateresearchinstitutions.

PIERfundingeffortsarefocusedonthefollowingRD&Dprogramareas:

BuildingsEndUseEnergyEfficiency

EnergyInnovationsSmallGrants

EnergyRelatedEnvironmentalResearch

EnvironmentallyPreferredAdvancedGeneration

EnergySystemsIntegration

Industrial/Agricultural/WaterEndUseEnergyEfficiency

RenewableEnergyTechnologies

Transportation

ThermochemicalFuelReformingforReciprocatingInternalCombustionEnginesisthefinalreportfor

theThermochemicalFuelReformingforReciprocatingInternalCombustionEnginesproject

(contractNumber50002014,workauthorizationnumber124)conductedbytheElectricPower

ResearchInstituteandGasTechnologyInstitute.Theinformationfromthisprojectcontributes

totheEnvironmentallyPreferredAdvancedGenerationProgram.

FormoreinformationaboutthePIERProgram,pleasevisittheEnergyCommissionswebsiteat

www.energy.ca.gov/researchorcontacttheEnergyCommissionat9166544878.


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Table of Contents

Acknowledgements.................................................................................................................................... iPrefaceiiiTableofContents...................................................................................................................................... iv1.0 IntroductionandBackground.....................................................................................................5 ivListofFigures.......................................................................................................................................... viiListofTables.............................................................................................................................................. ixAbstract...................................................................................................................................................... xiExecutiveSummary................................................................................................................................... 1Acronym.................................................................................................................................................... 71

Definition................................................................................................................................................... 711.0 IntroductionandBackground.....................................................................................................5

1.1. InternalCombustionEngineHeatRecoveryTechnologies................................................ 5

1.1.1. CombinedCooling,Heating,andPower(CCHP)........................................................... 6

1.1.2. TurboCompounding........................................................................................................... 6

1.1.3. RankineBottomingCycles.................................................................................................. 8

1.1.4. ThermochemicalRecuperation(TCR)................................................................................ 9

1.2. ProjectObjectives.................................................................................................................... 111.2.1. DesignandLaboratoryEvaluationandValidationof3to5kWeResearchScale

RecuperativeReformingReactor..................................................................................... 11

1.2.2. ReformateFueledInternalCombustionEnginePerformance.................................... 11

1.3. TechnicalApproach............................................................................................................... 12

1.4. ReportOrganization............................................................................................................... 12

2.0 SummaryofPreviousGTIThermochemicalFuelReformingInvestigations....................13

2.1. HydrogenEnrichedFuelfromThermochemicalFuelReforming................................... 13

2.1.1. Hydrogen(H2)EnrichedCombustion............................................................................. 132.1.2. TCFRSystemforSupplyingHydrogentoFuelBlend.................................................. 15

2.1.3. EngineAnalysis.................................................................................................................. 16

2.1.4. PerformanceGoals/CriteriaforDesignofTCRS........................................................... 18

2.1.5. EngineSimulationofTCRReformedFuel..................................................................... 18

2.1.6. BiogasandLandfillGas..................................................................................................... 23


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2.1.7. Summaryof1kWeLaboratoryScaleTCFRTests.......................................................... 25

2.2. TCFRRICECostEstimation.................................................................................................. 30

2.2.1. Approach............................................................................................................................. 30

2.2.2. KeyAssumptions............................................................................................................... 30

2.2.3. TCRSystemCost................................................................................................................ 32

3.0 SummaryofThermochemicalFuelReformingTechnologyandScaleUpApproach......35

3.1. ThermochemicalFuelReformingTechnologyStatusSummary..................................... 35

3.2. PerformanceGoals/CriteriaforDesignofTCRSystem.................................................... 39

3.3. ConceptualDesignofRecuperativeReformer................................................................... 40

4.0 LaboratoryScaleTestingofRecuperativeReformingforSimulatedExhaustfrom

CumminsQSK19GNaturalGasFueledReciprocatingEngine........................................... 43

4.1. LaboratoryStudiesofRecuperativeReformingReactor.................................................. 43

4.2. RecuperativeReformer.......................................................................................................... 46

4.3. TestPlan................................................................................................................................... 48

4.4. AnalysisofExperimentalData............................................................................................. 49

4.4.1. Catalyticreformingtestresults........................................................................................ 49

5.0 Operationof50kWeResearchEnginewithReformedFuelfromTCRTestRig...............55

5.1. GoalandObjectives................................................................................................................ 55

5.2. TestPlan................................................................................................................................... 55

5.2.1.Test

Matrix

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

57

5.2.2. TestProcedures................................................................................................................... 58

5.2.3. EngineDASMeasurementsandMethods...................................................................... 59

5.2.4. DataAnalysisProcedure................................................................................................... 60

5.2.5. QualityAssuranceProcedures......................................................................................... 60

5.2.6. DataResults(July1718,2007andJuly29,2007)........................................................... 60

5.3. ComputerSimulationofHCCIwithReformulatedFuel.................................................. 67

5.4. Conclusions............................................................................................................................. 68

6.0 ConclusionsandRecommendations........................................................................................ 696.1. CommercializationPotential................................................................................................. 69

6.2. Recommendations.................................................................................................................. 70

6.3. BenefitstoCalifornia.............................................................................................................. 70

7.0 Glossary........................................................................................................................................ 71


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AppendixA: ConceptualDesignoftheRecuperativeReformerfortheCummins1400kW

QSK60GEngine........................................................................................................................................ 73

AppendixB: BillofMaterialsforTCRSRICEQSK60G.................................................................... 76

AppendixC: PreliminaryAnalysisofTCRforLandfillGasandBiogasApplications................77

AppendixD:PhotographsofReformedFuelDeliverySystemComponentsforHCCIResearchEngineTests............................................................................................................................................ 833


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List of Figures

Figure1. Energybalanceofleanburngasengineattypicaloperatingconditions......................... 5

Figure2. ConceptualschematicflowdiagramofaCCHPsystem.................................................... 6

Figure3. Potentialnetturbocompressorpoweravailable.................................................................. 7

Figure4. Typicalturbocompoundingconfiguration(indistributedgeneration

applicationsthepowertrainisanelectricgenerator)............................................................... 8

Figure5. Thermochemicalrecuperationsystemschematic.............................................................. 10

Figure6. SchematicofasimplifiedTCFRsystem.............................................................................. 15

Figure7. SchematicoftheCumminsQSK60GgasengineequippedwiththeTCRsystem........17

Figure8. ProcessflowdiagramoftheCumminsQSK60Ggasengineequippedwiththe

TCRsystem....................................................................................................................................... 19

Figure9. Normalizedsystemefficiencyversusexcessairratio()fornaturalgasand

TCRreformedfuel........................................................................................................................... 20

Figure10a. ComparisonofnormalizedsystemefficiencyversusnormalizedNOx

emissionsfornaturalgasandTCRreformedfuel...................................................................... 21

Figure11. NormalizedUHCemissionsversusexcessairratio()fornaturalgasand

TCRreformedfuel........................................................................................................................... 22

Figure12. Turbochargerexhaustoutlettemperatureasafunctionofexcessairratio()...........22

Figure13. Laboratorysetuplowtemperaturemethanereforming(recuperative

reformingforreciprocatingengine)............................................................................................. 26

Figure14. CH4conversionsversustemperatureforprereformingcatalyst.................................. 26

Figure15. SchematicoftheGTIRRexperimentaltestunit.............................................................. 27

Figure16. GTIlaboratoryscalerecuperativereformertestcell....................................................... 28

Figure17. TCRSsystemassemblyandcomponentsforcostestimation........................................ 32

Figure18. SimplifiedflowdiagramforCumminsQSK19Gleanburnenginewithout

TCR.................................................................................................................................................... 37

Figure19. SankeydiagramofQSK19GleanburnenginewithoutTCR......................................... 37

Figure20. SimplifiedflowdiagramofCumminsQSK19Gleanburnenginewith

recuperativereformerafterturbocharger.................................................................................... 38

Figure21. SankeydiagramforQSK19leanburnenginewithsteam/naturalgasreforming(reformerafterturbocharger)...................................................................................... 39

Figure22. ConceptualdesignofthermochemicalrecuperationsystemforQSK19G

engine................................................................................................................................................ 41

Figure23. ConceptualdesignofrecuperativereformerforQSK19Gengine................................. 41

Figure24. Schematicoflaboratorysetupfor250SCFHTCRtestrig.............................................. 44


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Figure25. Photographoflaboratorysetupfor250SCFHTCRtestrig........................................... 45

Figure26. DrawingofeclipserecuperatorsinstalledonTCRtestrig............................................. 46

Figure27. Eclipserecuperator(recuperativereformer)withcatalyticinsertsinstalled...............46

Figure28. PhotographsofcatalyticinsertsevaluatedinTCRtestrig............................................. 47

Figure29. Photographofanindividualnickeloxidecatalystdisc.................................................. 48

Figure30. Equilibriumcompositionfornaturalgas/steamreforming(steam/carbon=2)............50

Figure31.Methaneconversionratebyequilibrium.......................................................................... 51

Figure32. Reformingprocesscompletenessvs.spacevelocity(atstandard)................................ 52

Figure33.Measuredhydrogenvolumeconcentrationinreformedfuelcomparedto

equilibriumpredictions.................................................................................................................. 53

Figure34: SimplifiedFlowDiagramoftheReformedFuelDeliverySystem................................ 56

Figure35. HCCIH2/Naturalgasenginetestbenchsetupforflowcontrolanddata

measurement/acquisitionsystem.................................................................................................. 56

Figure36. Enginemapoftestpointscompleted................................................................................ 67

Figure37. SimulatedandtheexperimentalpressureforthelastrunconditionofTable

25........................................................................................................................................................ 68

FigureA1. Alternativereformertubedesigns................................................................................... 74

FigureA2. Recuperativereformerfor60literengine....................................................................... 75

FigureC1. FlowdiagramforlandfillgasleanburnQSK19engine................................................ 79

FigureC2. SankeydiagramforlandfillgasleanburnQSK19engine............................................ 80

FigureC3. FlowdiagramforlandfillgasleanburnQSK19enginewithTCR.............................. 81

FigureD 1. Fuelcompressorwithfilter.............................................................................................. 83

FigureD2.Cooler/condenser(blackverticaltube)............................................................................ 83

FigureD3.Reformedfuelline(yellow)connectiontotheengine................................................... 84

FigureD4. Naturalgaslinewithflowcontroller,pressuregauge,andvalves............................ 84

FigureD5. ComparisonofflamesgeneratedbysupplementalburnerforTCRtesting

(a)combustingofneatnaturalgasand(b)combustingreformedfuelfromTCRtestrig ...........85

FigureD6. Absorbertube(intheforeground)forsulfurremovalfromnaturalgassuppliedtoTCRtestrig............................................................................................................................................... 85


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List of Tables

Table1. AdvantagesanddisadvantagesofH2enrichednaturalgascombustion........................ 13

Table2. ThermodynamicequilibriumcalculationforsimplifiedTCRFsystem............................ 16

Table3. SpecificationofCumminsQSK60Gleanburngasengine................................................. 16

Table4. USDOEARESgoals................................................................................................................ 17

Table5. CompositionsofnaturalgasandHYSYScalculatedreformedfuel(mol%)..................19

Table6. Reformedbiogasfuelproperties Table7. Reformedlandfillgasproperties...........23

Table8. Engineperformanceandemissionscomparisonlandfillgas............................................ 24

Table9. Engineperformanceandemissionscomparisonbiogas.................................................... 24

Table10. Experimentaltestconditions................................................................................................ 29

Table11. Experimentalreformateflow(testconditionsinTable10).............................................. 30

Table12. TCRScostestimatesforCumminsQSK60Ggeneratorset............................................... 33Table13. Referencenaturalgascompositionforengine/reformermodeling................................ 35

Table14. QSK19leanburnenginecharacteristicswithoutTCR(ratedspeed1800rpm)............36

Table15. PreliminaryTestPlanMatrix................................................................................................ 49

Table16. Hydrogencontent(%volume,drybasis)inreformedfuel............................................. 53

Table17. OperatingconditionsforHCCItestengine........................................................................ 57

Table18. Predictedcompositionsandreformedfuelflowratesofreformedfuelat

differentreformertemperatures(steamtocarbon=2)................................................................ 58

Table19. ProposedtestmatrixfortheHCCIenginewithreformedfuel....................................... 58

Table20. Datatakenonlinenaturalgas.............................................................................................. 61

Table21. Dataat2.0bar,2.4%hydrogen............................................................................................. 62

Table22. Dataat2.0bar,15%hydrogen.............................................................................................. 63

Table23. Dataat2.0bar,7.5%hydrogeninreformedfuel............................................................... 64

Table24. Dataat2.0bar,25%hydrogeninreformedfuel................................................................ 65

Table25. Dataat2.5bar......................................................................................................................... 66

TableA1. Temperatureandpressuredropsforalternativecatalysts............................................ 74

TableC1. Engineparametersfornaturalgasandlandfillgasengines.......................................... 78

TableC2. Heatbalance(modeling)..................................................................................................... 79

TableC3. ParametersofengineandTCR........................................................................................... 80

TableC4. PredictedparametersofenginewithTCR....................................................................... 81

TableC5. Predictedparametersatcharacteristicpointsinsystemflowdiagram........................ 82


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TableC6. HeatbalanceofenginewithTCR(HYSYSmodeling).................................................... 82


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Abstract

Thermochemicalrecuperationmaybeconsideredasanalternativetocombinedheatandpower

asameasuretoincreasetheefficiencyofanengine.Exhaustheatfromaninternalcombustion

engine,alongwithacatalyst,isusedtoreformfuelsuchasnaturalgasintoafuelstreamwitha

significantconcentrationofhydrogenandahighercaloricvalue.Thistechniqueofrecyclingthe

engineexhaustheatandconvertingittochemicalenergyinthefuelstreamcanreduceengine

fueluse.Inaddition,thecombustionofhydrogenenhancedfuelallowstheenginetooperateat

anairtofuelratiothatresultsinverylowproductionofnitrogenoxides.

IncludedinthisreportisasummaryofpriorresearchanddevelopmentbytheGasTechnology

Instituteonthetechnologyofthermochemicalrecuperationforreciprocatinggasenginesused

indistributedgeneration;apreliminaryconceptualdesignofarecuperativereformerfora

commerciallyavailable331kilowattenginegeneratingsetofferedbyCummins,Inc.; a

descriptionoflaboratoryscaleexperiments;updatedperformancepredictions;andtheresults

fromoperatinga50kilowattresearchengineonthermochemicallyreformedfuelversusnaturalgas.Projectresultssupportrecommendationsforthescaleup(anincreaseaccordingtoafixed

ratio)andcontinueddevelopment,demonstration,andcommercializationofthermochemical

fuelreformingforreciprocatinginternalcombustionengines.

Athermochemicalfuelreformingsystemcouldreasonablyresultinfuelsavingsofabout$1.1

millionperyearbythefifthyearofcommercialization.ThisaddressestheCaliforniaEnergy

Commissionsgoalsofenhancingenergyefficiency,diversifyingelectricitysuppliesby

investinginrenewableandothercleanenergytechnologies,strengtheningCaliforniasenergy

infrastructure.

Keywords: Thermochemicalfuelreforming,thermochemicalrecuperation,recuperative

reformingreactor,distributedgeneration,combinedheatandpower,hydrogenenhanced

combustion,naturalgas,biogas,reciprocatinginternalcombustionengine


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ProjectObjectives

Developadetailedengineeringdesignofarecuperativereformingreactortoconvert

naturalgasandyieldhydrogeninamountscorrespondingtofuelflowandexhaust

conditionsfora50kilowattgasengineinthelaboratory.

Operatea50kilowattlaboratoryscaleengineonreformedfuelproducedfromathermochemicalrecuperationlaboratorytestrig.Thistestingwillconfirmsatisfactory

operationwithingenerallyaccepteddesignparametersforreciprocatinginternal

combustionengines,anddocumentfuelsavingsandemissions(andemission

reductions)ofnitrogenoxides,carbonmonoxide,andvolatileorganiccompounds.

Developthebasisforanengineeringdesigntoscaleup(increaseaccordingtoafixed

ratio)thelaboratoryscalethermochemicalrecuperationtechnologyinsubsequent

developmentanddemonstrationprojects.

ProjectOutcomes

Thisprojectresultedinscaleupofarecuperative,catalyticreformingreactorfromanaturalgasflowrateof50tomorethan250standardcubicfeetperhour.A

commerciallyavailabletubeandshelldesignedgastogasrecuperatorwasmodified

toincludeprovisionsforaddingthecatalystinsidethetubeswherethenaturalgasand

steammixtureflow.HeattransferandprocessmodelsdevelopedbyGasTechnology

Instituteprovidedpredictionsofperformanceoftherecuperativereformer.These

predictionswereconfirmedexperimentallyonthelaboratoryunit.

Thescaleduprecuperativereformerwasoperatedatexhaustgastemperaturesand

conditionssimulatingtheCumminsQSK19Gleanburnengineandproducedenough

reformedfueltooperatea50kilowattresearchengine.Engineperformanceand

emissionsoftheengineoperatedonreformedfuelweremeasuredandcomparedtooperationoftheengineonpipelinequalitynaturalgas.

Theresearchteampreparedapreliminaryconceptualdesignofarecuperativereformer

fortheCumminsQSK19Gengineconfigurationevaluatedinthisproject.Thisdesign

providesaperspectiveonitspotentialphysicalsizeandoperatingtemperaturesand

flowratesatthecurrentstateofdevelopmentforthermochemicalfuelreforming.

Conclusions

Thetestingofthelaboratoryscalerecuperativereformingreactorattemperaturesthat

simulatedexhaustfromreciprocatingengine(operatedunderleanburnconditionson

naturalgas)suggeststhatanickelrhodiumreformingcatalystprovidedthehighestconversionofnaturalgas/steammixtureatsteamtocarbonratioof2.Theresidence

times(timespentinsidethesystem)requiredtoachievedifferentlevelsofreforming

(measuredbyhydrogenyield)couldbeexperimentallydeterminedforusein

developingadesignmodelofthermochemicalrecuperation.

The50kilowattlaboratoryscaleengine(configuredforhomogeneouscharge

compressionignition[aformofinternalcombustioninwhichwellmixedfueland


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oxidizerarecompressedtothepointofautoignition]insteadofsparkignition[the

initiationofthecombustionprocessoftheairfuelmixtureisignitedwithinthe

combustionchamberbyasparkfromasparkplug]configuration)wasoperatedon

reformedfuelproducedinthelaboratorythermochemicalrecuperatortestrigand

providedsufficientdatatocomparekeyperformanceparametersandemissionsversus

conventionalengineoperation(alsowithhomogeneouschargecompressionignitionandoperatedonpipelinenaturalgas).Testingsuggestedthatthethermochemical

recuperationtestrig,ascurrentlyoperated,wouldnotproducesufficientreformedfuel

toenableoperationofthetestengineinasparkignitionconfiguration.Itwasnotwithin

thescopeofthetasktooptimizetheenginesoperationonreformedfuel.Nevertheless,

thedataobtainedfromtestingsupportsthetechnicalfeasibilitythatthermochemical

recuperationonareciprocatingenginecouldbeusedtoincreaseoverallsystem

efficiency.Thelimitedtestingsuggestedthatforthehomogeneouschargecompression

ignitionconfiguration,theengineefficiency(brakethermal)onreformedfuelwas

comparabletothealreadyhighbaselineefficiencyonnaturalgas.Engineoperationwith

homogeneouschargecompressionignitiononreformedfuelresultedinlowerhydrocarbonemissionscomparedtotheemissionsforthesameengineoperatedwith

unreformednaturalgas.Becauseoftheextremelyleancombustionassociatedwith

homogeneouschargecompressionignition,thebaselinenitrogenoxidesemissionson

naturalgaswerealreadyverylow.Insomecasesthereformedfuelresultedinslightly

highernitrogenoxides.Furtheroptimizationbetweennitrogenoxidesandcarbon

monoxidetradeoffiswarranted.

Theresearchteamdevelopedaconceptualdesignofatubularrecuperativereformerfor

theCumminsQSK19Greciprocatinginternalcombustionengine.Thisdesignprovides

anindicationoftheoveralldimensionsoftherecuperativereformerforthe331kilowatt

engine.

Recommendations

Basedupontheresultsoftheworkreportedinthisproject,theresearchteam

recommendsdevelopmentofathermochemicalrecuperationsystemforreciprocating

internalcombustionenginesbecontinued.

Becauseoftheextensiveamountofthermochemicalrecuperationprocessmodeling

performedtodatethatisbasedupontheCumminsQSK19engineconfigurations(thatis

leanburnandstoichiometric,naturalgasandbiogas),theresearchteamrecommends

continuingthermochemicalrecuperationdevelopmentanddemonstrationwith

Cummins.

BenefitstoCalifornia

ThisprojectaddressesthePublicInterestEnergyResearchProgramsgoalsofenhancing

energyefficiency,diversifyingelectricitysuppliesbyinvestinginrenewableandother

cleanenergytechnologies,strengtheningCaliforniasenergyinfrastructuretoprovide

forreliability,andcontinuingCaliforniasenvironmentalstewardship.


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Athermochemicalfuelreformingsystemcouldreasonablyresultina5%reductionin

overallsystemheatratecomparedtothecurrentlyavailableenginegeneratorset. Ata

5%reductioninfuelpurchaseandanassumedCaliforniamarketpenetrationrateof

about50megawattsbythefifthyearofcommercialization,theprojectedfuelsavingsare

estimatedatabout$1.1millionperyear(atapriceof$7permillionBritishthermalunits

fornaturalgas).

Becausethermochemicalfuelreformingproduceshydrogenenrichedfuelthathasbeen

documentedtoextendthelimitsofareciprocatinginternalcombustionengineto

operateinleancombustionmode,onecouldpotentiallyusethermochemical

recuperationforsignificantreductionofnitrogenoxideswithoutexacerbatingemissions

ofcarbonmonoxideandunburnedhydrocarbons.

Preliminarymodelinganalysessuggestthatthermochemicalfuelreformingcanalsobe

appliedtoincreaseefficiencyandreduceemissionsfromenginesfueledwithbiogasor

landfillgas.ThissupportsattainmentoftheCaliforniaEnergyCommissionPublic

InterestEnergyResearchgoalofdiversifyingelectricitysuppliesbyinvestingin

renewableandothercleanenergytechnology.

TheCaliforniaAirResourcesBoard2007emissionlimitsfordistributedgeneration

couldprecludeafuturemarketforreciprocatinginternalcombustionenginesystems

unlesstheycandemonstratethecapabilitytocosteffectivelymeettheselimits.

Thermochemicalfuelreformingmayprovideameansforcontinueduseofreciprocating

internalcombustionenginesasprimemoversfordistributedgenerationinSouthern

California.

Increasingelectricpowergenerationefficiencyandminimizingthecostofcomplying

withtheCaliforniaAirResourcesBoard2007emissionslimitsfordistributedgeneration

will

contribute

to

a

more

cost

competitive

California

economy.


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1.0 Introduction and Background

1.1. Internal Combustion Engine Heat Recovery Technologies

Thenatural

gas

fired

reciprocating

engine

has

been

the

prime

mover

of

choice

for

the

majority

ofrecentdistributedgeneration(DG)installationsinthe1,000kilowattelectric(kWe)to10,000

kWeoutputrange.Reciprocatingenginesalsodriveasignificantshareoftheexistingcapacity

ofcompressorsfornaturalgastransmission.

Regulatorscontinuetoreducetheallowableemissionofoxidesofnitrogen(NOx)fromgas

engines.InCalifornia,Texas,NewJersey,andinotherserioustosevereozonenonattainment

areas,singledigitpartspermillionNOxlimitsareleadingtoincreasedinstallationsofselective

catalyticreduction(SCR)atsignificantcost.Thisishavingasubstantialimpactontheoperating

economicsofDG.Whilecombinedheatandpower(CHP)canincreasefuelutilization

efficienciestoaround80%,notallapplicationsfordistributedenergycantakeadvantageof

CHP.Therefore,aneedexiststoincreasetheefficiency,whilealsoloweringtheemissionsofnaturalgasreciprocatingenginesusedinDGandpipelinetransmissionsystems.

Figure1showsatypicalenergybalanceofthemodernnaturalgasreciprocatingengine. About

32%oftheenergyinput(higherheatingvalue)isavailableintheexhaustgasesfromtheengine.

Thetemperatureofthisexhaustcanbegreaterthan500C.Recoveringandutilizingthisenergy

wouldimproveefficiencyandreduceemissionsperunitoutput.Adescriptionofseveral

strategiesforutilizingthisexhaustheatisdescribedbelow.

Other7%

Exhaust Heat Losses32%

Aftercooler7%

In-Cylinder Heat Losses19%

Net Power35%

Figure 1. Energy balance of lean-burn gas engine at typical operating conditions

Source: Gas Technology Institute


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1.1.1. Combined Cooling, Heating, and Power (CCHP)1

CCHPisanintegratedsystemlocatedatornearabuildingorfacilitywheretheheatco

producedbytheelectric(orshaft)powergenerationequipmentprovidesheating,cooling,

and/ordehumidificationtoabuildingand/orindustrialprocesses.Aconceptualdiagramof

CCHPisshowninFigure2.ThemajorCHPcomponentsareprimemovertechnologies,heat

recoverytechnologies,andthermallyactivatedtechnologies.

Figure 2. Conceptual schematic flow diagram of a CCHP system


Key factors for CCHP financial attractiveness:

Coincidenceofelectricloadsandthermalloadsthemoreafacilityneedselectricityand

atthesametimeitneedsthermalenergy(heating,cooling,ordehumidification),the

greaterthedutycycleoftheCCHPinstallationandthemoreattractivethesavingsany

paybackassociatedwithCCHP.

SparkSpreadthe higherthedifferentialbetweenthecostofbuyingelectricpower

fromthegridandthecostofnaturalgas,themoreattractivethesavingsandpayback

associatedwithCCHP.

InstalledCostDifferentialthelowerthedifferentialbetweentheinstalledcostsofthe

CCHPsystemandthatofaconventionalheating/coolingsystem,themoreattractivethe

savingsandpaybackassociatedwithCCHP.

1.1.2. Turbo-Compounding

Turbocompoundingusesgasturbinetechnologytoconvertthermalenergytomechanical

powerwhichinturndrivesanelectricalgeneratortoproduceelectricalpower.Turbogenerator

technologyisusedtoextractpowerfromtheexhaustofareciprocatinginternalcombustionengine.Theexhaustexitstheenginecylindersathightemperatureandpressureandcarriesas

muchas3035%oftheenergyinthefuelouttoatmosphere.Theturbogeneratoractsasa

bottomingcycle fortheengineinafashionsimilartothatofasteamgeneratoronacombined

cyclegasturbineplant.

1.CombinedHeatandPowerResourceGuide,September2003,USDOE


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Turbocompressorscommonlyusedtoincreasespecificpoweroutputofaninternalcombustion

engineemployturbineswithoutputmatchedtothecompressorpowerrequiredtoachievethe

desiredincreaseinmassofair/fuelenteringthecylinder.Figure3showsanexampleofthe

powerthatmightbegeneratedbyanoptimizedexhaustturbinecomparedwiththecompressor

load2.Turbocompoundingtakesadvantageofthispowersurplus.Figure4providesa

conceptualdepictionofthecompleteelectricalturbocompoundingsystem.

BowmanPowerGroup(BPG)3hasidentifiedthreecoretechnologiesnecessarytosupportthe

useofturbogenerators:

Compact,simple,lowcostturbomachinery.

Highspeedelectricalgeneratorswhichareextremelyefficient(98%)andsmallenough

tocoupledirectlytotheshaftofturbomachinery.

Softwarecontrolledpowerelectronicstomanageelectricalpowerquality(power

conditioners).

Figure 3. Potential net turbocompressor poweravailable

Source: Caterpillar

2.DieselEngineWasteHeatRecoveryUtilizingElectricTurboCompoundTechnology,Ulrich

HopmannCaterpillarInc.,2002DieselEngineEmissionReductionConference.August2529,2002,San

Diego,California.

3.http://www.bowmanpower.co.uk/Turbocompounding.html11/21/08


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Figure 4. Typical turbo-compounding configuration(in distributed generation applications the powertrain is anelectric generator)

Source: Caterpillar

Initsimplementationofthesetechnologies,BPGclaimsthatpowerisboostedbyupto30%

andfueleconomyimprovedby10to15%.Theelectricalpowergeneratedcanbeusedto

powerelectricalloadsortodirectlydrivetheenginecrankshaft.BPGhasdevelopedsystemsto

covertherange25kWto165kW,withsystemsupto2,000kWeplannedforfuture

development.

1.1.3. Rankine Bottoming Cycles

SteamRankineBottomingCyclesoperatebestatrelativelyhighworkingtemperaturesand

pressures.Exhaustgastemperaturesfromreciprocatingenginesaregenerallynotsufficiently

highforeconomicalsteambasedbottomingcycles.However,byusingcertainorganicfluids,

typicallyrefrigerants,powercanbeeconomicallygeneratedusinglowerworkingpressuresand

temperatures.BottomingsystemsthatusethesefluidsarecommonlyreferredtoasOrganic

RankineCycles(ORC).Heatfromtheengineexhaustisusedtoraisethetemperatureofand

boilthepressurizedworkingfluidinanevaporator.Theresultingvaporflowsthrougha

turbinetoproduceworkbeforeitiscondensedatlowpressureinthecondenserandthen

repressurizedandrecycled.

SystemeconomicsofORCswillbeinfluencedbytheworkingtemperaturesandpressures,cost

ofthefluid,heatexchangerdesign,andrequirementsforintegratingthesystematthe

application.UTCPowerismarketingapackagedORCbrandedPureCyclesuitableforuse

withreciprocatinginternalcombustionengines4

.ThePureCyclesystememploysofftheshelfrefrigerationsystemcomponentsandusesarefrigerantastheworkingfluid.Thisbottoming

cyclecanincreasetheelectricaloutputofa3,000kWegasfiredICEgeneratorbyapproximately

200kW.ThereareseveralothervendorsofORCsystemsandfurtherdevelopmentsare

underway.

4.http://www.utcfuelcells.com/fs/com/bin/fs_com_Page/0,11491,0167,00.html9/26/08


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9

1.1.4. Thermochemical Recuperation5(TCR)

TCRsystems(employingengineexhaustgasrecuperation)offeraninnovativemeansforboth

increasingefficiencywhileloweringemissionsofreciprocatinginternalcombustionengines

(RICE)usedforpowergenerationandpipelinetransmission.TCRsystemsforreciprocating

enginescouldconceivablyincluderecoveryofwasteheatenergyfromtheenginecooling,

lubricating,andexhaustsystems.Availablewasteheatisthermochemicallyrecuperatedaschemicalenergyinthefuelstream.

AsimplifieddepictionofaTCRsystememployingsteammethanereformingisprovidedin

Figure5.Themajorequipmentitemsincludeheatexchangers,arecuperativereformingreactor,

andaheatrecoverysteamgenerator.Becauseoftherelativelylowtemperatureofenginewaste

heat,acatalyticreformingreactorisusedtoachievetargetconversions.Thesteamorproducts

ofcombustionprovideoxidantrequiredtosupportthereformingreactions.

ThemainreactionschemesoftheTCRreformingareasfollows:

( )0HH2mnnCOOHHC 29822mn >

+++

o

(1)

( )kJ/kmol206.2HH3COOHCH 298224 >++ o (2)

)kJ/kmol41.2-HHCOOHCO 298222 >++ o (3)

( ) 2mn HsCHC2

mn +

(4)

Reaction(1)isahighlyendothermicirreversiblereaction,whichincreasesthetotalfuel

gasvolume. Allhigherhydrocarbons(n>1)areconvertedtoC1components.

Reaction(2)isanendothermicinversemethanationreaction,whichisanequilibrium

reactionthatdeterminesthefinalcompositionofthereformedfuel.

Reaction(3)isanexothermicwatergasshift(WGS)reaction,whichisalsoan

equilibriumreactionthatdeterminesthefinalcompositionofthereformedfuel.

Reaction(4)isanirreversiblereactionthatoccursintheabsenceofsufficientsteamor

CO2toprovidesufficientlocaloxygentoconvertthecarbontoCO.

5.ThermochemicalRecuperationSystems(TCRS)forIncreasedEfficiencyandReducedEmissionsfrom

StationaryReciprocatingICEngines.NaturalGasTechnologiesIIIConferenceProceedings.GTIT05153.

Orlando,FL. February2005.


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10

ExhaustGas

ExhaustGas

ExhaustGas

Steam/Water

Water

NaturalGas

Steam/Natural Gas

Reformed Fuel

ReciprocatingInternal Combustion

Engine (RICE)

PumpFeed Water

ThermochemicalRecuperative

Reformer

HeatRecovery

SteamGenerator

Engine CoolingHeat Recovery

Cooler/Heater Steam

Oxidant

Figure 5. Thermochemical recuperation system schematicSource: Gas Technology Institute

Overall,thereformingreactionsareendothermic.InaTCRsystem,theheattodrivethe

reactionsisprovidedbyheattransferfromthehotengineexhaust.Powercycleefficiency

increasesbytheamountofexhaustheatthatcanbesuccessfullyincorporatedinthe

endothermicreactions.

ThethreemajorcontrolparametersfortheTCRreformingreactionsaresteam/carbonratio

(S/CR),reformertemperature,andreformerpressure. TheS/CRcontrolsH2yield;thus,thereis

aneedtofindanoptimumS/CRforreciprocatinginternalcombustionengineapplications.The

reformertemperaturecontrolsthereformingrateandfinalcomposition;thus,italsocontrolstheH2yield.Thereformerpressurealsocontrolsthereformingrateandcomposition;andthe

reformingrateisalmostproportionaltothepartialpressureofCH4(i.e.reformerpressure).The

reformertemperatureandpressurearecriticalparametersinsizingareformerasisthetypeof

catalyst.IntypicalICenginesystems,thetemperatureavailableforthereformerisrelatively

lowcomparedtoindustrialapplicationsandcaremustbetakentomaximizetheuseofthe

rejectedthermalenergyandtominimizethereformersizewhileachievingmaximumattainable

H2yield.

ResearchhasshownthatH2enhancedcombustioncansignificantlyreduceNOxemissionsfrom

sparkignitedenginesbyextendingtheleanlimit.6Mostofthepriorartforinsitu

hydrogenproductionforreciprocatingenginesinvolvesmixingsomefractionoftheexhaustgaseswithfueltosupportautothermalreformingreactions.Excessoxygenintheexhaustgases

ofleanburnenginesresultsinexothermicoxidationoffuelthusincreasingfuelconsumption.

6.Heywood,J.B.,Ivanic,Z., et.al.,EffectsofHydrogenEnhancementonEfficiencyandEmissionsof

LeanandEGRdilutedMixturesinaSparkIgnitedEngineSAEPaper2005010253,April2005.


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11

Thisfuelconsumptionpenaltyaffectsthepotentialoverallsystemefficiencyandeconomics.

TCRusesonlyexhaustheatrecuperationtosupporttheendothermicreformingreactions,

therebyofferingdirectimprovementinoverallsystemefficiencyplushydrogenenrichedfuel

forcombustion.Acriticalfactorforcommercialsuccessistheintegrationofthisrecuperation

andenergyconversionprocessinacosteffectiveandreliablepackagewiththeengine

generatorset.

1.2. Project Objectives

Theprojectobjectiveswereto:

Developadetailedengineeringdesignofarecuperativereformingreactorforlaboratory

validationofnaturalgasconversionandhydrogenyieldscorrespondingtofuelflow

andexhaustconditionsfora50kWegasengine.

Operatea50kWelaboratoryscaleengineonreformedfuelproducedfroma

thermochemicalrecuperationlaboratorytestrigtoconfirmsatisfactoryoperationwithin

generallyaccepteddesignparametersforreciprocatinginternalcombustionengines.ThistestingwilldocumentfuelsavingsandNOx,CO,andVOCemissionsandemission

reduction.

DeveloptheengineeringdesignbasistoscaleupTCRtechnologyinasubsequent

developmentanddemonstrationproject.

1.2.1. Design and Laboratory Evaluation and Validation of 3 to 5 kWe ResearchScale Recuperative Reforming Reactor

Apreliminarythermochemicalfuelreformer(TCFR)systemanalysisatanominal331kWe

naturalgasfueled,sparkignitedinternalcombustionenginewasprepared.Byextrapolating

theresultsfornaturalgas,ananalysisofthepotentialbenefitsofusingTCFRforagenericbiogasfuelcomposedof50%methaneand50%carbondioxidewasalsobecompleted.Usinga

conceptualfullscaledesignofarecuperativereformerforthestudyengine,specificationswere

preparedforfabricatingarecuperativereformingreactorscaledandsizedforgasflows

equivalenttoa3to5kWeengine.ThisisthereactorthatwastestedintheGTIlaboratory.

Adetailedengineeringdesignofarecuperativereformingreactorcorrespondingtofuelflow

andexhaustconditionsfora3to5kWegasenginewasprepared.Thisreactorwasusedfor

laboratoryvalidationofnaturalgasconversionandhydrogenyields.Testingwasconductedto

evaluatetheperformanceoftherecuperativereformingreactoraskeyengineandprocess

parametersarevaried.Forexample,itwasimportanttomeasuretheeffectofchangesin

exhaustgastemperaturesasafunctionofengineloads.Thetestingalsoincludedvariationofprocessvariablessuchasthesteamtomethaneratioforreforming.

1.2.2. Reformate-Fueled Internal Combustion Engine Performance

Afuelblendthatsimulatesthecompositionofproductsfromtherecuperativereformerwas

usedtofuela50kWeresearchengine.Hydrogenwassuppliedfrombottlesandasteam

generatorwasusedtomatchthewatercontentinthecooledreformedfuelfromtheTCFR


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12

process.Themaximumtemperatureofsimulatedreformedfuelneededtosatisfythe

specificationsfortheengine.Testingwasconductedtomeasuretheeffectoftheblendedfuel

compositiononengineperformanceandemissions.

1.3. Technical Approach

TheresearchinthisprojectisbuildinguponpriorlaboratoryscaleR&DperformedbyGTIandsupportedbytheUtilizationTechnologyDevelopment(UTD)andtheGasResearchInstitute.

ResultsofthisworkaresummarizedinElectricPowerResearchInstituteinterimreport1012774

ThermochemicalFuelReformerDevelopmentProjectHigherEfficiencyandLowerEmissions

forReciprocatingEnginesUsedinDistributedGenerationApplications.

CumminsandUTDprovidedmatchfundingfortheprojectreviewedinthisreport.Cummins

wasparticularlyinterestedinasystemanalysisofTCRfortheirQSK19engineandpreparation

ofaconceptualdesignofarecuperativereformerforthatengine.

Thesequenceofactivitiestomeetobjectivenumberoneabove(developdetailedengineering

designofrecuperativereformer),canreasonablybesummarizedasfollows:

1. DesignandfabricatelaboratoryscaleexperimentaltestrigforTCRtests.

2. Developtestplan,conducttesting,andanalyzedata.

3. Usedataobtainedtodeveloporvalidateanalyticaltoolsforsystemanalysisand

designofrecuperativereformers.

AfterassemblingaworkingTCRtestrig,theprojectteamconfirmedwhetheritwouldbe

possibletosupplysufficientreformedfueltotheGTIsinglecylinderengine(configuredatthe

timeforHomogenousChargeCompressionIgnitioncombustion)toenablecomparisons

betweenoperationandperformanceonnaturalgasversusreformedfuel.Therewasnot

sufficientbudgetavailabletoreconfiguretheenginetooperatewithsparkignition.

ThefinaltaskwastouseresultsandexperienceobtainedforsystemanalysisofTCRand

prepareaconceptualdesignofrecuperativereformerfortheQSK19Gengine.

1.4. Report Organization

Followingthisintroduction,Section3summarizespreviousR&DworkatGTIwithTCRfor

reciprocatinginternalcombustionengines. Section4isasummaryofTCFRtechnology

developmentandscaleupapproach. Section5reviewsthelaboratoryscalesetupand

experimentsrunontheTCRtestrigoperatedtosimulateexhaustgasconditionsfora

reciprocatingenginefueledwithnaturalgas.Section6reportsontheexperimentalsetupand

resultsfromoperatinganominal50kWeresearchengineonreformedfuelproducedintheTCR

testrig.Thelastsectionofthereportincludesconclusions,recommendationsandprojected

benefitsfromcontinueddevelopment,demonstrationandcommercializationofTCRforthe

QSK19GenginefordistributedgenerationapplicationsinCalifornia. AppendixAincludesthe

conceptualdesignforaTCFRsizedtothe1,400kWegenset.AppendixBincludesaBillof

MaterialsandcostestimatesfortheTCFRsizedtothe1,400kWegenset. AppendixCisthe

preliminaryanalysisofTCRforlandfillgasandbiogasapplications. AppendixDincludes

photographsofthereformedfuelconditioninganddeliverysystemforthe50kWeenginetests.


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2.0 Summary of Previous GTI Thermochemical FuelReforming Investigations

ThecurrentprojectisacontinuationofpreviousworkundertakenatGTIandreported

elsewhere.Thepreviousworkconsistedofthermochemicalfuelreformerprocessdesign,a

preliminarydesignofacompletesystemfora1,400kWenginegenerator,preliminaryperformanceandcostestimatesforacompletesystem,andlabscaleinvestigationsofcatalyst

performanceinthisapplication.WorkbyothersandthepreviousGTIworkisabstractedbelow.

2.1. Hydrogen-Enriched Fuel from Thermochemical Fuel Reforming

2.1.1. Hydrogen (H2) Enriched Combustion

H2enrichedcombustionisaprovenwaytoextendtheleanlimitofnaturalgasengines.H2

offersmanyadvantagesasaprimaryfuelorinfuelgasmixture.Table1listsadvantagesand

disadvantagesofusingH2enrichednaturalgas.Higherpeakflametemperaturescanbe

mitigatedusingleanercombustionand/orexhaustgasrecovery.H2enrichedfuelcanbereadily

usedinsparkignitionengineswithsomemodificationsinthesystemssuchasfuelhandlingandairhandlingsystems.

Table 1. Advantages and disadvantages of H2-enriched natural gas combustion

Advantages Disadvantages

Increases flame speed Increases peak flame temperature

Improves combustion quality Increases fuel system cost

Increases engine performance

Reduces unburned hydrocarbon emissions

Increases methane number (MN)Widens flammability limits

Lowers minimum ignition energy

Improves EGR tolerance

Shortens quenching distance

Source: Gas Technology Insitute

Tunestal7,etal.usedasinglecylinder1.6liternaturalgasenginetoextendtheleanburnlimit

ofanaturalgasenginebyadditionofH2totheprimaryfuel.H2concentrationsusedinthe

studywere0,5,10,and15%byvolume.Theyoperatedtheengineatthreeoperatingpoints:

idle,partload(5barindicatedmeaneffectivepressure),andsimulatedturbocharging(13bar

indicatedmean

effective

pressure).

The

air

fuel

ratio

(A/F)

was

varied

between

stoichiometric

andtheleanlimit.TheresultsshowedthatH2enrichedcombustionincreasedtheburnrateand

extendedtheleanlimit.H2additionloweredHCemissionsandincreasedNOxemissionsfor

7.TunestlP.,ChristensenM.,EinewallP.,AndersonT.,andJohanssonB.,HydrogenAdditionfor

ImprovedLeanBurnCapabilityofSlowandFastBurningNaturalGasCombustionChambers,SAE

2002012686,2002.


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14

constantairexcessratio()andignitiontiming.Increasedburnrateallowedretardedignition

timing,whichresultedinlowerheatlossesandhigherefficiency.Retardedignitiontimingalso

ledtolowermaximumtemperatureandthuslowerNOxemissions.TheeffectofH2additionat

wideopenthrottlewasmostprominentclosetotheleanlimit.

Jensen8etal.

investigated

the

effect

ofadditional

producer

gas

on

the

combustion

process

and

theengineoutemissionsbyfuelinganaturallyaspiratedfourcylindergasenginewithnatural

gasandmixturesofnaturalgasandH2containingproducergas.Theproducergaswasa

syntheticgas(orsyngas)withthesamecompositionasafuelproducedbythermalgasification

ofbiomassinatwostagegasifier.Theproducergasconsistedof33.9%H2,19.1%CO,1.3%CH4,

14.9%CO2,and30.8%N2 involume.Themixtureswere75%naturalgasand25%producergas

(byvolume),and50%naturalgasand50%producergas(byvolume),respectively.Theresults

showedthattheNOxemissionswerenotaffectedbyadditionofproducergas.Thismightbe

dueto45.7%byvolumeofinertgasesintheproducergas.Unburnedhydrocarbons(UHC)

emissionsdecreasedupto50%onlyatexcessairratioabove=1.4.COemissionsdecreasedand

formaldehyde(CH2O)emissionwasdecreasedsignificantlywiththeadditionofproducergas.

AlthoughH2hasmanyadvantagesininternalcombustionengines,thesourceofH2hastobe

considered.SupplyingpureH2fromprocessplantstoengineinstallationshasassociated

transportation,storage,anddeliverysystemcosts.Extendedresearchanddevelopmenthas

beenconductedtoevaluatethemeansforonboardfuelreformingsystemsformobilefuel

cellapplications.Thesefuelreformingtechnologiesincludeautothermalreforming,partial

oxidationreforming,steamreforming,andexhaustgasrecoveryreformingbypartiallyorfully

reformingaprimaryfuel,usuallynaturalgas.

AndreattaandDibbleuseda1986Pontiacfourcylinderinlineturbochargedengine.Thiswas

convertedfromagasolinetoagaseousfuelenginetoinvestigatetheeffectofairreformed(or

autothermalreformed)fuelonsparkignitionengines.Theyusedcylinderbottlegasestoformulatethecompositionofairreformedfuel.TheH2inthereformedfuelallowedtheengine

torunleanerascomparedtonaturalgas,particularlyathigherfractionsofreformedfuel.With

fullyreformedfuel,theenginecouldrunatequivalenceratioof0.25(=4).Leanercombustion

reducedNOxemissionssignificantly.COandHCemissionswerenotsignificantlyaffectedby

thereformedfuelovertheequivalenceratiosstudied.However,therewasanexceptionnearthe

leanlimit,wherethepresenceofH2stabilizedcombustionandreducedCOandHCemissions

foragivenequivalenceratio.Enginepeakoutputandthermalefficiencywasdependenton

equivalenceratio,notthereformedfuelconcentration,exceptneartheleanlimit.

Sgaard9etal.usedasmallscaleadiabaticcatalyticreactorasasteamreformertoproduce

reformednaturalgas.Inthisapplication,therequiredthermalenergywasprovidedfrom

8.JensenT.K.,SchrammJ.,NarusawaK.,andHoriS.,HydrocarbonEmissionfromCombustionof

MixturesofNaturalGasandHydrogenContainingProducerGasinaSIEngine,SAE2001013532,

2001.

9.SgaardC.,SchrammJ.,andJensenT.K.,ReductionofUHCemissionsfromNaturalGasFiredSI

engineProductionandApplicationofSteamReformedNaturalGas,SAE2000012823,2000.


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15

externalsources.Theirmaingoalwastoreduceunburnedhydrocarbonemissionsandincrease

engineefficiencyusingreformednaturalgasinastationaryinternalcombustionengine.They

alsoperformedtheoreticalstudies,whichshowedapotentialforvaryingtheH2content

between8and30vol%.Thestudiesalsoshowedconsiderableincreaseinmethanenumberby

reformingnaturalgas.Ahighermethanenumberwillallowtheuseofhighercompressionratio

engines,whichwillleadtohigherengineBrakeMeanEffectivePressure(BMEP)andthermalefficiency.Thereformednaturalgascompositionwasalmostinsensitivetothenaturalgas

composition,i.e.thecontentofhigherhydrocarbons.Theuseofreformednaturalgasreduced

unburnedhydrocarbonsandCOemissionsandincreasedenginepowerandthermalefficiency.

However,NOemissionwasincreasedduetoimprovedcombustionquality(thus,higher

cylindertemperature).Theflamedevelopmentduration(startofignitionto10%fuelburn)and

rapidburnduration(10~90%fuelburn)weresignificantlyshortenedwiththeuseofthe

reformednaturalgasfuel.

2.1.2. TCFR System for Supplying Hydrogen to Fuel Blend10

QuantitativeevaluationsofthepotentialbenefitsofusingaTCFRsystemforsupplying

hydrogenforimprovingtheperformanceandreducingtheemissionsofreciprocatingengine

applicationsbeganwithasimpleenginecycleanalysis.Thethermodynamicequilibrium

analysisusedtheLagrangeUndeterminedMultiplierMethodforthesimplifiedpreliminary

designshowninFigure6.Preliminaryresultsindicatedthat,underidealizedconditions,overall

efficiency(netengineminuscombustionandexhaustlosses)ispredictedtoincreaseby

approximately18%19%.Thisiswhentheengineoperateswiththereformedfuelatthe

stoichiometricoperatingconditionsforthecasesconsideredinTable2.

TCRAir

Reformed Fuel

Gas Fuel

CoolingWater

Hot Water/Steam

W

ColdExhaust

ReformedFuel/Air

Steam

RICE

HotExhaust

Heat Exchanger

Gas Fuel/Steam

Generator

EGR

Heat Exchanger

Figure 6. Schematic of a simplified TCFR

system

10.TechnicalandEconomicFeasibilityofThermochemicallyRecuperatedReciprocatingInternalCombustion

Engine.FinalReport.GTIProject20013.NYSERDAReport7885.August2006.


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16


Thissimplified,idealizedmodelcouldnotresolvepredictionsofemissionsfromtheengine.In

ordertodeveloprealisticestimatesfortechnicalandeconomicfeasibilityemployingaTCFR

systemforefficiencygainandemissionsbenefits,acombinationofcommercialcodesforengine

andprocessmodelingwasemployed.RicardosWAVEv5.2wasusedtomodelthenaturalgas

engine,andtheHyprotechsHYSYS

modelwasusedfortheTCRreformerandtheheatrecoverysteamgeneratorsystem.ProjectparticipantCumminsrecommendeditsQSK60G

engineforthemodelingandprovidedthenecessaryinformationtoconstructaWAVEmodel.

Cumminsalsoprovidedactualtestdatasothemodelcouldbecalibrated.

Table 2. Thermodynamic equilibrium calculation for simplified TCRF system

Steam

/Carbon Ratio

Peak

Cylinder

Pressure

[atmospheric]

Adiabatic Flame

Temperature

[C]

Efficiency

Net

Engine(%)

Loss in

Combustion(%)

Loss in

Exhaust(%)

0 158.5 2877.4 ~ 53.15 ~ 16.93 ~ 29.93

1.68 116.8 2972.6 ~ 62.92 ~ 12.20 ~ 24.882.0 114.5 2925.6 ~ 63.21 ~ 12.04 ~ 24.75


2.1.3. Engine Analysis

KeyspecificationsoftheQSK60GenginearelistedinTable3below.Thematchinggeneration

setmodel1400GQKAhasanelectricalratingof1,400kWeat60Hz(1800rpm).Theengineis

watercooled,turbochargedwithanaftercooler.TheQSK60Gisleanburn,designedforspark

ignitednaturalgascombustion.TheQSKGseriesengineisalsotheCumminsplatformfortheir

AdvancedReciprocatingEngineSystem(ARES)collaborationwiththeU.S.Departmentof

Energy(DOE).TheARESprogramgoalsaresummarizedinTable4.

AschematicoftheCumminsQSK60GengineequippedwiththeTCRreformerisshownin

Figure7.ThisengineisnotacommercialversionofQSK60Gengines.Itwasbuiltandtestedby

CumminsforR&Dpurposes.

Table 3. Specification of Cummins QSK60G lean-burn gas engine

No. of Cylinders 16

Strokes per Cycle 4

Engine Type Spark Ignition, Lean Burn

No. of Intake Valves per Cylinder 2

No. of Exhaust Valves per Cylinder 2

Compression Ratio 11.4:1Displacement 60 liters

Bore/Stroke 158.75 mm/190 mm

Connecting Rod Length 320.96 mm

Piston Pin Offset None

TDC Combustion Chamber Volume 0.0003616 m3

Clearance Height 0.9 mm


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Spark Timing 18~20 bTDC

Turbocharger

No. of Turbocharger

Waste gate

Holset

2

None


Table 4. US DOE ARES goals

A Commercial Engine by 2010 with:

High Efficiency Fuel-to-electricity conversion efficiency of at least 50%

Environmental Superiority NOx < 0.1 g/hp-hr (natural gas)

Reduced Cost of Power Energy costs, including O&M, at least 10% less than

current state-of-the-art engines

Fuel Flexibility Adaptable to future firing with dual fuel capabilities, include further

adaptation to hydrogen

Reliability and Maintainability Equivalent to current state-of-the-art engines

Source: U.S. Department of Energy

AF

C1 AC

QSK60G GAS ENGINE

T1

AB

CV

AF EST

TP

NG

ES

MW

TCR R

HX 1

Steam

CD

CRF

HW/SWW

FWRW

WTS

ControlValve

CC

LTHT

WR

C2

CI

CO

HX 2

1

23 4 5 7

6

8

13

14

1516

9

19

10 11

12

17

18AB - AIR BOXAC - AFTERCOOLERAF - AIR FILTERCC - CONDENSATES C OLLECTORCD - CONDENSATESCI - COOLANT INC1 - COMPRESSOR 1CO - COOLANT OUTCRF - COOLED REFORMED FUELC2 - COMPRESSOR 2CV - CONTROL VALVEES - EXCESS STEAMEST - EXHAUST STACKFW - FEED WATERHRSG - HEAT RECOVERY STEAM GENERATORHRF - HOT REFORMED FUELHT - HIGH TEMPERATUREHX1 - HEAT EXCHANGER 1HX2 - HEAT EXCHANGER 2HW - HOT WATERLT - LOW TEMPERATURE

MW - MAKEUP WATERNG - NATURAL GAS

P - PUMPRW - RECYCLED WATERS - STEAMTCR R - TCR REFORMERT1 - TURBINE 1T2 - TURBINE 2TP - THROTTLE PLATEWR - WATER RESERVEWTS - WATER TREATMENT SYSTEMWW - WARM WATER

T2

HRSG

HRF

LEGEND

P

P

P

Figure 7. Schematic of the Cummins QSK60G gas engine equipped with the TCRsystem


Theenginesystemhastwobanks,theleftbank(LB)andrightbank(RB),andhasa

turbochargerinstalledineachbank.Intheanalyses,theTCRreformerislocatedjust

downstreamoftheturbochargers.Theseturbochargershavenowastegate.Aheatrecovery

steamgeneratorislocateddownstreamoftheTCRreformer.Thereformedfuelishotandhasa


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largequantityofwatervapor.Twoheatexchangersinseriesareusedtoreducethereformed

fueltemperature;watervaporiscondensedasthereformedfueliscooled.Thereformedfuel

temperatureiscontrolledtomaintainthemaximumenginemanifoldtemperaturebelow55C.

Justenoughsteamisgeneratedtosupplythereformer.

2.1.4. Performance Goals/Criteria for Design of TCRS Targetheatratereduction(fromthermochemicalreformersystem)of>10%.

Assumestartupon100%naturalgasandtransitiontoreformedfuel.

Intakemanifoldtemperaturenottoexceed55C.

ZerosupplementalfuelconsumedtosupportTCRreformingreactions.

Hydrogencontentofreformednaturalgasmixturedeliveredaheadofaircompressors

between2030%byvolume.

TCRtobeinstalleddownstreamofturbochargertoavoidpotentialneedtoredesign

turbochargers.

SteamtocarbonratioofRecuperativeReformernottoexceed2to1.

Exhaustgastemperaturedownstreamofturbochargersapproximately553Catfullload

Designfor8000hoursperyearcapacityfactor.

Theengineshallbecapableofachievingratedpoweratthefollowingconditions:

o Ambienttemperature:upto32C

o Altitude:upto1000meters

o Fuel:Pipelinequalitynaturalgas

o FuelminimumMN:75

o Inletrestriction:upto50mbar

o Exhaustrestriction:upto100mbar

o Relativehumidity:upto100%

o Jacketwaterinlettemperature:95C

Naturalgassupplysystempressurerangebetween0.25to3.9bar(g).

2.1.5. Engine Simulation of TCR Reformed Fuel

AsimplifiedprocessflowdiagramoftheTCRSanalyzedwiththeHYSYSmodelisprovidedin

Figure8.


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19

Air

Engine Exhaust

Natural Gas

Reformed Fuel

WaterSupply

ENGINECatalyst

PreHeat

Cool Exhaust

E-4

SteamP-18

Reformer Out

E-5

Reformer Feed

Condenser

CondensatePump

P-25

Hot Water

Exhaust

CoolingWater

Reformer Out C

Figure 8. Process flow diagram of the Cummins QSK60G gas engineequipped with the TCR system


Fortheconditionsreportedabove,theHYSYSmodelpredictedareformedfuelcomposition

fromtheTCFRreactorasreportedinTable5.Thiscompositionwasusedinthecalibrated

WAVEmodeltopredicttheCumminsQSK60Gengineperformanceandemissions.TheWAVE

modelwasadjustedtoaccountfortheshortenedcombustiondurationwiththeuseoftheH2

enrichedfuel.

Table 5. Compositions of natural gas and HYSYS-calculated reformed fuel (mol%)

Component Natural Gas Reformed Fuel

Methane 94.37 59.01

Ethane 2.82 0

Propane 0.42 0

i-Butane 0.05 0

n-Butane 0.06 0

i-Pentane 0.02 0

n-Pentane 0.02 0

n-Hexane 0.03 0Hydrogen 0 28.11

Water Vapor 0 3.67

Carbon Monoxide 0 0.13

Carbon Dioxide 0.94 8.25

Nitrogen 1.27 0.83

Total 100 100


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Source: Gas Technology InstituteAsimulationwasperformedat50%loadinordertopermitevaluationofabroadrangeofthe

excessairratio.Operationonnaturalgaswascomparedtoreformedfuelonlyatoneoperating

point,i.e.,anexperimentalpointavailablefromactualtestsbyCumminsonnaturalgas.For

thissimulation,theengineBMEPwasmaintainedat8.07barforbothnaturalgasandreformed

fuel,whichisthesameastheexperimentalBMEPatthisload.

ThevolumetriccalorificheatingvalueoftheTCRreformedfuelisapproximately22%lessthan

thatofthenaturalgas.Thisis,however,morethancompensatedforbytheincreasedvolume

producedbythereformingreactionssothatcalorificvalueenteringtheenginepermoleof

naturalgasconsumedactuallyincreases.Therefore,inadditiontoBrakeThermalEfficiency,

whichistheefficiencybasedonthefuelconsumedbytheengine,theconceptofsystemthermal

efficiencyneedstobeintroduced.Thesystemefficiencyisbasedonthefuelfedintothe

engine/TCRsystem(i.e.naturalgas).

AsshowninFigure9,thesystemefficiencyoftheengine/TCRsystemwasincreasedbyabout

8.5%relativetothenaturalgasengineat50%load.ThisefficiencyincreaseisdirectlyattributabletothereductionofthenaturalgasfuelconsumptionusingtheTCRreformer.

Naturalgasfuelconsumptionoftheengine/TCRsystemwasreducedbyabout8.5%relativeto

thenaturalgasenginewithouttheTCRsystem.Themaximumengineefficiencywasobserved

atexcessairratio=1.8.Aswasincreasedfurther,thesystemefficiencystartedtodecrease.

Figure 9. Normalized system efficiency versus excess air ratio

( ) for natural gas and TCR reformed fuel


Figure10ashowsthenormalizedsystemefficiencyversusthenormalizedNOxemissions.NOx

emissionslinearlydecreasedasthesystemefficiencyincreaseduptocertain(i.e.1.8inthis

1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.30.900

0.925

0.950

0.975

1.000

1.025

1.050

1.075

1.100

1.125

1.150

NormalizedSystemE

fficiency

Excess Air Ratio,

50% load @1800 rpmReformed FuelNatural Gas

Excess Air Ratio,


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21

case).Whenwasabove1.8,thesystemefficiencyincreasedrapidlyastheNOxemissions

increased.Thisfigureshowsthattheengine/TCRsystemcansimultaneouslyachievesignificant

improvementsinbothefficiencyandNOxemissionsbyoperatingtheengineinleaner

combustion.

Figure

10bshows

normalized

NOx

emissions

with

respect

to

.NOx

emissions

exponentially

decreasedaswasincreasedfrom1.4to2.2.Atthesame,thereformedfuelshowedhigher

NOxemissionsthanthenaturalgas.ThisisbecausetheH2enrichedcombustionincreased

cylindertemperaturecomparedtonaturalgas.However,theH2inthereformedfuelallowsthe

extensionoftheleanlimittoabove=2.Thisresultsinmorethan62%reductioninpredicted

NOxemissions.Asmentionedearlier,thereareotherstrategiestofurtherreduceNOx

emissionsthathavenotbeenexaminedyetinthisstudy.

Figure11showsnormalizedUHCemissionsforthetwodifferentfuelsasafunctionofexcess

airratio.BecausetheWAVEoverpredictedUHCemissionsat50%load,theexperimentdata

wasalsoincludedforcomparisoninthefigure.Predictedunburnedhydrocarbonemissionsincreasedabout41%.

Figure 10a. Comparison of normalizedsystem efficiency versus normalized NOxemissions for natural gas and TCRreformed fuel


Figure 10b. Normalized NOxemissions versus excess air

ratio ( ) for natural gas andTCR reformed fuel


1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.30

1

2

3

4

5

6

7

NormalizedNOxEmissions

Excess Air Ratio,

50% load @1800 rpmReformed FuelNatural Gas

0 1 2 3 4 5 6 70.98

1.00

1.02

1.04

1.06

1.08

1.10

1.12

NormalizedSystemE

fficiency

Normalized NOx Emissions

50% Load @ 1800 rpmReformed FuelNatural Gas

Leaner Combustion


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Figure 11. Normalized UHC emissions versus excess air ratio

( ) for natural gas and TCR reformed fuel


Figure 12. Turbocharger exhaust outlet temperature as a

function of excess air ratio ()


Turbochargerturbineouttemperature(i.e.theTCRreformerinlettemperature)isshownwith

respecttotheexcessairratio()inFigure12.Thepredictedturbineouttemperatureofthe

naturalgaswasslightlylowerthanthatofthepredictedreformedfuel.Thereformedfuel

maintaineda489C(912F)turbineouttemperatureevenat=2.2.Thishightemperaturegives

1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.30.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.002.25

2.50

2.75

3.00

NormalizedUHC

Emission

s

Excess Air Ratio,

50% load @1800 rpmReformed FuelNatural Gas (WAVE)Natural Gas (Experiment)

1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3450

475

500

525

550

575

600

625

650

675

700

725

750

TurbineOutTemperature

[degreeC]

Excess Air Ratio,

50% load @1800 rpmReformed FuelNatural Gas (WAVE)


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positiveresultstotheTCRreformer,whosereformingrateisalmostproportionaltoreformer

inlettemperature,atleastinthetemperaturerangesofinternalcombustionengines.

2.1.6. Biogas and Landfill Gas

Sincefuelreformingincreasesthemethanenumber(MN)ofafuel,itisbelievedthatthe

applicationofTCFRtoenginesusinglandfillgasorbiogascouldprovidecombustionandperformanceimprovements.ToquantifythesebenefitsfortheQSK60Gengine,calibrated

WAVEandHYSYSsimulationswereruntocalculatechangesinsystemefficiencyandengine

powerwithandwithoutthermochemicalrecuperationsystems.

Thesecomparisonsbeganbydefiningrepresentativecompositionsandheatingvaluesfor

landfillgasandbiogas.TheWAVEmodelwasrunfortheQSK60Gengine(calibratedfor

naturalgas)witheachofthesealternativefuelstocalculatebaselineestimatesofengine

efficiencyandperformance,aswellasengineexhaustcharacteristics.Theengineexhaustresults

wereusedintheHYSYSmodeltopredicttheproductgasesfromtherecuperativereformer.

TheWAVEmodelwasrunwiththehydrogenenrichednaturalgastopredictTCFRefficiency

andemissions.

ThereformedfuelpropertiesforbiogasandlandfillgaspredictedbyHYSYSmodelingare

listedinTables6and7,respectively.Inbothcases,thereformedfuelfromTCRScontained

about18%hydrogenbyvolume.

SomekeyfindingsfromtheWAVEmodelinganalysisforlandfillgaswithandwithoutTCRS

aresummarizedinTable8.ThebiogasandlandfillgasTCFRwasmodeledat50%loadwhile

holdingtorqueandexcessairratioconstantforreformedandunreformedcases.At50%load

andconstantexcessairratioof1.59,abouta0.77%decreaseinsystemheatratewaspredicted.

Undersimilarconditionsadecreaseinsystemheatrateofabout8.5%wascalculatedfornatural

gasfueling.However,theWAVEmodelingpredictedthattheNOxemissionsfuelingwithreformedlandfillgaswouldbeabout40%lowerthanfuelingwithrawlandfillgas.

Table 6. Reformed biogas fuel properties Table 7. Reformedlandfill gas properties

Source: Gas Technology Institute Source: Gas Technology Institute

Mole Fraction Type Value

Mole Fraction (CO) 0.0026

Mole Fraction (CO2) 0.3000

Mole Fraction (H2O) 0.0416

Mole Fraction (Hydrogen) 0.1865

Mole Fraction (Methane) 0.4632Mole Fraction (Nitrogen) 0.0046

Mole Fraction (Oxygen) 0.0015

Lower Calorific Value (kcal/kgmole) 99,800

Mole Fraction Type Value

Mole Fraction (CO) 0.0011

Mole Fraction (CO2) 0.0818

Mole Fraction (H2O) 0.0416

Mole Fraction (Hydrogen) 0.1786

Mole Fraction (Methane) 0.4326Mole Fraction (Nitrogen) 0.2402

Mole Fraction (Oxygen) 0.0241

Lower Calorific Value (kcal/kgmole) 93,400


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ComparableWAVEmodelingresultsforreformedbiogasaresummarizedinTable9.Inthis

case,useofTCFRresultsinabouta1.33%reductioninheatrateat50%loadandconstantexcess

airratio().ThemodeldoesnotpredictmuchchangeintheNOxemissionsatconstantexcess

airratio().

Table 8. Engine performance and emissions comparison-landfill gas

Parameter Units LandfillGas

Reformedlandfill Gas

Remark

1.59 1.59 ConstantBrake Thermal Efficiency % 32.9 32.8System Thermal Efficiency % 32.9 33.2 0.77%Brake Torque N-m 3862 3862 ConstantBrake Power kW 728 728Brake Specific FuelConsumption

kg/kWh 0.4618 0.5318

System Specific FuelConsumption

kg/kWh 0.4618 0.4582

Brake NOx g/kWh 3.077 1.944Exhaust NOx ppmv 311 189Exhaust CO ppmv 233 152Brake Specific UHC g/kWh 9.0 11.9Exhaust UHC ppmv 1290 1429


Table 9. Engine performance and emissions comparison-biogas

Parameter Units Biogas ReformedBiogas

Remark

1.59 1.59 Constant

Brake Thermal Efficiency % 32.7 32.5System Thermal Efficiency % 32.7 33.2 0.77%Brake Torque N-m 3865 3862 ConstantBrake Power kW 729 728Brake Specific FuelConsumption

kg/kWh 0.4618 0.5830

System Specific FuelConsumption

kg/kWh 0.5223 0.5142

Brake NOx g/kWh 1.370 1.357Exhaust NOx ppmv 131 129Exhaust CO ppmv 144 142Brake Specific UHC g/kWh 9.7 11.8

Exhaust UHC ppmv 1672 1792Source: Gas Technology Institute

LaboratoryStudiesofRecuperativeReformingReactors11

11.RecuperativeReformerforHighEfficiencyandUltraLowEmissionsDGwithReciprocatingEngines,Final

Report:August2004March2006.April2006.GTIProject20094


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2.1.7. Summary of 1kWe Laboratory-Scale TCFR Tests

Concurrentwiththeperformancemodelingdescribedabove,laboratoryinvestigationswere

beguntosupportthedesignoftherecuperativereformingreactor.Theobjectivewastodesign,

build,andtestalabscalethermochemicalrecuperativereformer(RR)forreciprocatinggas

engines.Therecuperativereformerwastestedonabenchundersimulatedgasengineoperating

conditionstomeasureandcompareheattransferandreformingefficienciesrelativetopredictedvalues.Targetswerederivedfromresultsofthetechnicalandeconomicfeasibility

studyofTCRforthe1,400kWereciprocatingengine.

ThepreliminaryconceptualRRdesignwasbasedonatubeandshellgeometryratherthan

plateandframe.Twoconceptualdesignsforrecuperativereformersforreciprocatingenginesin

the1,000kWeto1,500kWesizerangewereprepared.

Abenchscalerecuperativereformingreactor,scaledtoequivalentgasflowsfroma1kWe

engine,wasdesigned,fabricated,andtested.Usingsimulatedengineexhaustconditionsthat

werescaledfromthefullscalemodelingstudiesfortheCumminsQSK60Gengine,the

preliminarytestsconfirmedthetechnicalviabilityoftheRRconcept.Specifically,thetestingconfirmsthepotentialtoachieveatargethydrogenyieldofabout25%byvolumefroma

recuperativereformerrecoveringwasteheatfromengineexhaustandusingsteammethane

reformingatasteamtocarbonratioof2:1.

Laboratorytestresultswerethenusedtovalidateanengineeringdesigntoolforfuturescaleup

andlaboratorytestingofanimprovedRRforanaturalgasengines.Theimprovementswill

largelybedirectedtowardreducinglossesandimprovingheatrecovery.Thisistoleadtomore

efficientandcosteffectivedesignoftherecuperativereformer.

TheexperimentaldesigndepictedinFigure13wasusedtoconfirmthefundamentalfeasibility

oftherecuperativereformersubsystem.ThepreviousHYSYSprocesssimulationsofTCRappliedtotheCumminsQSK60Genginewerebasedonthewasteheatfromanengineexhaust,

downstreamoftheturbocharger.Thisresultsinalowtemperaturewastestream,around

550C.

Proofofreformingtestswerecompletedutilizingacommercialprereformingcatalyst.As

showninFigure14,theofftheshelfprereformingcatalystdataverifiesthatconversions

consistentwiththeprocesssimulationswereobtainableacrossawiderangeofspacevelocities.

Testresultsconfirmthatexhaustgasheatcanbeusedfromanengine,downstreamofa

turbocharger,atabout520C.Thewasteheatcanbeusedtoprereformnaturalgasandproduce

arawreformatewith10to15%H2.Whenthewateriscondensedoutat30C,afuelinputtothe

internalcombustionengineofabout25%H2results.


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Figure 13. Laboratory set-up low temperature methane reforming(recuperative reforming for reciprocating engine)


0

5

10

15

20

25

30

35

40

320 340 360 380 400 420 440 460 480 500 520 540 560

Average Bed Temperature, oC

CH4Conversion,

%

Test Conditions

Catalyst: C11-PR-3 (4.4 mm x 4.7 mm)Bed Diameter:0.93 in

Bed Height:6 in

Bed Volume:66.8 cm3

S/C:2.0

SV:4,314 hr-1

Figure 14. CH4 conversions versus temperature for pre-reformingcatalyst



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27

Furthertestingwasconductedusingthelaboratoryscaleunitshownbyschematicand

photographinFigures15and16,respectively.

Figure 15. Schematic of the GTI RR experimental test unit



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Figure 16. GTI laboratory-scale recuperative reformer test cell


ThetestunitrepresentstherecuperativereformerinaTCRSystem.Thetestunitshownin

Figure15schematiccontainstwosectionsacombustionchamberandareformingreactor.The

combustionchamberconsistsofaninsulated6inch316SStubewithinletconnectionsfor

naturalgas,deionizedwater,primaryair,andsecondaryair.Anaturalgasburnerfiresdownintoainchdiameter316SScoiledtubeheatexchangerwherenaturalgasandwaterare

heatedtosupplythereformerfeed.Thereformerfeedisamixtureofnaturalgasandsteam

correspondingtoasteamtocarbon(S/C)ratioof2.Thefeedispreheatedto245Cbeforeits

partialconversiontohydrogen,carbonmonoxide,carbondioxide,andwatervaporinthe

catalystbed.Thehotengineexhaustat550Craisesthereformercatalystbedtemperatureto

about380Cbyheattransfer.

Thetestunitwassizedtosimulatetheequivalentflowofa1kWeengine.Theprocess

conditionsareshowninTable10.TestconditionsarecomparabletothosesetintheHYSYS

processmodelingsimulationoftheRRforaCumminsQSK60Genginesystem.Thetopand

bottomofthereformingreactorwasfilledwithknitted316SSwiremeshtoenhancetheheatup

ofthecatalystbedbythehotsimulatedengineexhaustgasesviaheattransfer.Thereforming

reactorispackedwith18inchofC11PRprereformingcatalystsuppliedbySdChemie,Inc.

Theeffectivenessofthisprereformingcatalystwasdemonstratedpreviouslyinlabscale

reformingexperiments.Athermowellwiththreethermocoupleswasinstalledintothe

reformingreactortomeasurethegastemperaturesjustabovetheinlet,middle,andexitofthe

catalystbed.Inaddition,thermocoupleswerealsoinsertedtomeasuretheinletandoutlet


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temperaturesofthereformerflueandreformergas.Pressuredifferencesandpressureswere

alsomeasuredbypressuregauges.

Thetestresults,includingtemperaturesandpressuresatvariouslocationsintheunitduring

thetest,areshowninTable11.Aproductgasanalysiswascarriedoutusingagas

chromatographto

determine

natural

gas

conversion

in

the

recuperative

reformer.

The

results

in

Table11indicatethatthenaturalgasconversionlevelof7%inthereformeriscomparableto

thelevelpredictedbyHYSYSmodelsimulation.However,thedrypercentageofhydrogenin

theproductsofreformingwasonly69%ofwhatwasexpectedfromtheHYSYSsimulation(18

versus26%).Thiswasduetoalowerreformerbedtemperatureof324C(averageofthethree

thermocouplereadingsinthecatalystbed)comparedto382Cemployedforthesimulation

study.ThissuggestedthatfutureRRdesignconfigurationsneedtoaddresstheoptimizationof

heattransferintheRRsystemtoattainahigheranduniformtemperaturedistributioninthe

reformercatalystbedforhighernaturalgastohydrogenconversionlevels.Overall,thetest

successfullydemonstratedtheviabilityoftheRRconcept.

Table 10. Experimental test conditions

Length 49.53 cm Na tura l Ga s to Reforme r 6.0 SLPM

Diamete r 3.048 cm W ate r to Reforme r 9.15 g/m

V olume 361 cm3

Catalyst:

Type C11-P R Na tura l Ga s to Burne r 6.0 SLPM

S ize 4.7x4.7 mm Prima ry Air to Burner 16.9 SLPM

W eight 287.4 g Se condary Air 137.4 SLPM

Tota l 160.3 SLPM

Compone nt mol%

Me tha ne 90.7N2 4.65

Etha ne 3.35

CO2 0.92Propa ne 0.28

n-Butane 0.05

i -Butane 0.03

n-Pe nta ne 0.02

Tota l 100.00

Fee d Natural Gas Comp osition

Experimental Flue Gas Flows

Reforme r Reactor Expe rimental Reforme r Gas Flows



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Table 11. Experimental reformate flow (test conditions in Table 10)


2.2. TCFR RICE Cost Estimation

2.2.1. Approach

ThesimulationandmodelingresultsreviewedabovewereusedtorefinetheTCFRconceptual

designandtoprovideguidanceforapreliminaryengineeringdesignofaTCRRICEsystem.

ThepreliminarydesignwasbasedupontheuseofaCumminsQSK60Ggasenginegenerator

setproducing1,400kWelectricaloutput.Abillofmaterialswasgenerated.Thesimulation

modelswereusedtodefinethekeyperformanceandsizingparametersfornewcomponentsof

theTCFRsystem.Theseperformancespecificationswereusedtogeneratequotationsand

engineeringestimatesforthekeycomponents.Thecostofothercomponentsandmaterialsin

thebillofmaterialswereestimatedbaseduponcatalogpricesandengineeringestimates.An

economiccostmodelwasdevelopedusinganExcelspreadsheet.Theeconomicmodel

consideredfuelconsumptionsavings,TCRoperationandmaintenancecosts,TCR

manufacturingcosts,andinstallationcosts.Themodelcalculatedapaybackperiod.The

economicmodelwassetuptoalloweasychangesoftheinputassumptionssothatsensitivity

analysescouldbeconducted.

2.2.2. Key Assumptions

TheTCFRRICEsystemequipmentlayoutthatservedasthebasisforthecostanalysisisshown

inFigure17.ItwasassumedthattheTCFRsystemwouldbepackagedonaseparatemounting

platformtoalloweasyinstallation(onsite)nexttotheengineandgeneratorset.Theitems

withinthedashedlineboxoftheschematicarethosecomponentsthatmakeuptheTCFR

system.ThedesignoftherecuperativereformingreactorisgiveninAppendixA.


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Otherkeyassumptionsarelistedbelow:

Enginebrakeandelectricaloutput(i.e.generatorefficiency)fromCumminsbrochure

10/02CPGQSK60G/C.

Naturalgaslowerheatingvalue(LHV)of33.44MJ/Nm3.

QSK60GbrakethermalefficiencyasreportedbyAxelzurLoyeinpresentationreport

titledARESTechnologyDevelopmentforQSK60NaturalGasEnginedatedMarch15,

2005.

FuelcostisspotpriceattheHenryHubtakenfromNaturalGasWeeklyUpdatefor24

March2005www.eia.doe.gov.

Brakethermalefficiency=actualfuelconsumption(Btu/kWhr)dividedby3412

(Btu/kWhr).

ElectricitycostfromNewYorkStateEnergyResearchandDevelopmentAuthority2004.

Operationandmaintenancecostincludesmaintenancereserveforoverhaul.

Facilitiescapitalcostofmoneycalculationassumestotalgensetpurchasepricewith

TCRis$600,000(approx.$428/kWinstalledprice).

30Cmaximumreformategastemperaturehigherallowablereformategas

temperaturewilllowercostofcertainTCRcomponents.

91%availability.


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Recuperative Reformer Heat Recovery SteamGenerator

J/WRadiator

Radiator

Engine driven CACpump

Engine Driven J/WPump

Left Bank Compressors Right Bank Turbines

Left Bank TurbinesRight Bank Compressors

Fan

Fan

Air Filter

Fuel/Air Mixer

Charge Air Cooler

Expansion tank

Oil Cooler

J/WExpansion Tank

QuadTurbochargers

Control Valve

By-Pass Control Valve

Gas FlowMeter

SteamFlow Meter

Heat Exchanger

Gas/SteamMixer

SteamWater Pump,Electric Motor driven

Steamwater feedtank

Condenser

Make upwater

Regulated NaturalGas Supply

ThrottleValve

ExhaustOutlet

Thermal ChemicalRecuperator RICE System

Schematic21 April 2005

T1 T2 T3P1

T4

T5

P2

T6P3

Control Valve

Thermostat

Thermostat

Condenser Radiator

Condenser coolingwater pump,

electric motor driven

Condenserexpansion tank

Condensatereturn

Thermostat

Auto level controller

TCR Assembly

Cummins QSK60G

Gas Flow Meter

SulfurRemovalSystem

Water filter

Figure 17. TCRS system assembly and components for cost estimation

Source: Gas Technology Insti

Documents

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