development of an integrated gasifier–solid oxide fuel cell test system- a detailed system study...

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ARTICLE IN PRESSGModelPOWER-14231; No.of Pages13Journal of Power Sources xxx (2011) xxxxxx

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Journal of Power Sources

journa l homepage: www.e lsev ier .com

Develo xiddetaile

Ming Liu H.Ma Delft Universi etherb Federal Unive Brazil

a r t i c l

Article history:Received 16 DReceived in reAccepted 20 FAvailable onlin

Keywords:GasicationSolid oxide fueCombined heaExergy

ted gon isem inned hsiderith thnsitivhis wing ss clea

1. Introduction

Energy stainable begasicationThebiosyngenergy systcell types, stion becausfor differenin the biosyto removecalkali comptolerate, beferent typesremove thoare not cleacontaminanoptions for

The commany studifeasibility sstudies, and

CorresponE-mail add

gas. Colpanet al. [1] focusedon theeffects of gasication agents (air,enriched oxygen and steam) on SOFC performance and showed the

0378-7753/$ doi:10.1016/j.this article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.jpowsour.2011.02.065

ystems based on biomass fuels are considered as sus-cause they are practically carbon neutral. Biomasscan generate a mixture gas, which is called biosyngas.as after purication canbeutilized as a fuel in advancedems with gas turbines and/or fuel cells. Within the fuelolid oxide fuel cells (SOFCs) are being paid much atten-e of their advantages like high efciency and exibilityt fuels. To use hydrogen, carbonmonoxide andmethanengas for fuelling SOFCs, gas cleaning is necessary. This isontaminants likeparticulates, tars, sulphur compounds,ounds, andhalogencompounds to a level that SOFCs cancause these contaminantsmay poison the fuel cells. Dif-of gas cleaning technologies are generally suggested tose impurities. However, impurity constraints for SOFCsrly understood. General tolerance levels for SOFCs forts within the raw biosyngas and typical gas cleaningthose contaminants are given in Table 1.bination of biomass gasiers and SOFCs is a subject ofes. These studies can be divided into several topics liketudies, studies on gasication effects, complete systemstudies on safe SOFC operation when fed with biosyn-

ding author. Tel.: +31 15 2786987; fax: +31 15 2782460.ress: [email protected] (M. Liu).

highest electrical efciency (41.8%) with steam as the gasicationagent. Athanasiou et al. [2] studied the integration of solid oxidefuel cells (SOFCs) in biomass gasicationgas turbine systems forthe estimation of the overall electrical efciency. The effect of thelower heating value of biomass on system performance was ana-lyzed. As for gasierSOFC system studies, Aravind et al. [3] diddetailed modeling work on gasierSOFCgas turbine hybrid sys-tems. The results show that total (combined heat and power) CHPsystem efciency can be over 70%. Omosun et al. [4] employedtwo different gasiers and considered cold gas cleaning and hotgas cleaning processes for gasierSOFC systems. No signicantdifference in electrical efciency was found but a signicant devia-tion (26%) in total CHP efciency was observed. For safe operationof gasierSOFC systems, Mermelstein et al. [5] used benzene tomodel tar in biomass gasication. They investigated experimen-tally the impacts of steam and current density on carbon formationon Ni/YSZ and Ni/CGO SOFC anodes. Carbon formation and celldegradation was studied. However, the carbon deposition could bereduced by means of steam reforming of tar over the nickel anode,and partial oxidation of tar while operating the fuel cell under load.Aravind et al. [6] investigated the inuence of H2S, HCl and naph-thalene on SOFC Ni-GDC anodes. No signicant impact has beenobserved up to 9ppm H2S and HCl and 110ppm naphthalene inthis work. Ouweltjes et al. [7] presented the results of biosyngasutilization in solid oxide fuel cells with Ni-GDC anodes at 850 and

see front matter 2011 Elsevier B.V. All rights reserved.jpowsour.2011.02.065pment of an integrated gasiersolid od system studya,, P.V. Aravinda, T. Woudstraa, V.R.M. Cobasb, A.ty of Technology, Energy Technology Section, Leeghwaterstraat 44, 2628 CA Delft, The Nrsity of Itajuba, Department of Mechanical Engineering, Pinheirinhos 37500-903, MG,

e i n f o

ecember 2010vised form 29 January 2011ebruary 2011e xxx

l cellt and power

a b s t r a c t

A detailed system study on an integrabined heat and power (CHP) applicatithermodynamic calculations. The systkinds of gas cleaning systems, a combiperature gas cleaning system, are conmodel of the gasierSOFC system wof energy and exergy efciencies. A seworking parameters. The results of tCHP systems with different gas cleansystems with the high temperature gaexergy./ locate / jpowsour

e fuel cell test system: A

. Verkooijena

lands

asierSOFC test system which is being constructed for com-presented. The performance of the system is evaluated usingcludes a xed bed gasier and a 5kW SOFC CHP system. Twoigh and low temperature gas cleaning system and a high tem-ed to connect the gasier and the SOFC system. A completeese two gas cleaning systems is built and evaluated in termsity study is carried out to check system responses to differentork show that the electrical efciencies of the gasierSOFCystems are almost the same whereas the gasierSOFC CHPning system offers higher heat efciency for both energy and

2011 Elsevier B.V. All rights reserved.

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ARTICLE IN PRESSGModelPOWER-14231; No.of Pages132 M. Liu et al. / Journal of Power Sources xxx (2011) xxxxxx

Table 1SOFC tolerance on contaminants and typical gas cleaning options [15].

Contaminants SOFC tolerance Low temperature High temperature

Particles Few ppmw Bag lter, cyclone wet scrubber, wetor (W

Cyclone, ESP, bag lter, granular bed

Tars lter

Alkali comp les

H2S d carbHCl

920 C. Theoperatedwet al. [8] invover 10gNoperation ftheViking tand smoothperformancBesides theinto gasier

In this pnamic evaludevelopmeCell Technois being inter. Two tytemperaturgas cleaninThermodynperformancformance oproposed gand exergysystem respobtain suitafor improve

2. System

2.1. Gasie

A downgasifying ager with th10kW essentop sectionconical fuelder with agrate servessecond stagtion. The boport and anbiosyngas.avoid the foperation.

The gasiticulate levgas becausepass througsion furthefrom the gatar removareduced cosble gasica

ation

s cle

CombCTG

raturst paoes tobtt-bawithlike Ca wrticleed caompwatesynged cossibarougasll noent wer. Hdisp

Highhe hiosyncatalold wto arnpaompsyngsubsemoassinppli

FC Celectrostatic precipitatFew ppmw Wet scrubber, WESP,

ounds Few ppmw Removal as solid partic

Few ppmv Wet scrubber, activateFew ppmv Wet scrubber

investigations made clear that Ni-GDC anodes can beithin awide range of biosyngas compositions. Hofmannestigated the inuence of real biosyngaswith a tar levelm3 on SOFC Ni-GDC anodes reporting successful SOFCor 7h. Planar SOFC operation on real wood gas fromwo-stagexed-beddowndraft gasierwas investigatedoperation without carbon deposition and signicant

e degradation for 150h has also been reported in [9].se, several other studies [1014] provide more insightSOFC systems.aper, we present the results from detailed thermody-ations of a gasierSOFC test system which is under

nt. A small scale SOFC CHP system developed by Fuellogies Ltd. (FCT) based on tubular SOFCs from Siemensegrated with a commercial downdraft xed-bed gasi-pes of gas cleaning systems, a combined high and lowe gas cleaning system (CTGCS) and a high temperatureg system (HTGCS), were proposed for this integration.amic calculations were rst carried out to evaluate thee of the SOFC system fed by natural gas. Then the per-f the SOFC system fed by biosyngas puried using theas cleaning systems was evaluated in terms of energyefciencies. A sensitivity study was conducted to checkonses to changes in variousworking parameters and toble working conditions for safe system operation andd gasierSOFC system performance.

conguration

r

draft xed-bed reactor using air (double-stage) as theent is employed for the gasierSOFC system. This gasi-e thermal capacity of 50kW and the electric capacity oftially consists of four sections assembled together. Thehas two parts; an upper cylindrical fuel inlet part and astorage part. The second section has a mild steel cylin-primary stage for air feed. The third section above theas the reduction zone where biosyngas is formed. Thee of air supply is close to the upper part of the third sec-ttom section has an ash pit performing as an ignitionash removal section and the outlet of the production

Two vibrators are set on the rst and third sections toormation of bridges resulting in unstable gasication

inform[17].

2.2. Ga

2.2.1.The

tempeer rthen gcan becatalysthe targasesfed tolike paactivattrace csomethe bioactivatleast pgas atIn thisber, witreatmreformcan be

2.2.2.In t

raw bibasedusing cdowndenseoalkali cthe biowhichbents rAfter pthen su

2.3. SOthis article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.

er described above is used because of (1) lower par-els in the produced gas and (2) lower tar content in themost tars are destroyed by thermal cracking as theyh the hot reduction zone. The double stage air provi-r reduces tar content [16]. Low tar levels in biosyngassier will reduce the cleaning load of the downstreaml unit. Hence the tar cleaning unit can be built atts. The gasier works at ambient pressure and the sta-tion zone temperature is around 750850 C. Detailed

The SOFby Fuel Celemploys thatesat900desulphuriztor that puinto the stethe recycledESP) lter, rigid barrier lterCracking with catalysts (750900 C),or high temperature thermal(9001200 C) crackingRemoval as solid particles (800 C)

on, Sorbents (>300 C, e.g. ZnO)Sorbents (300600 C, e.g. Na2CO3)

and test results on this gasier are available elsewhere

aning system

ined high and low temperatureCS mentioned in this work has both high and lowe components. The biosyngas which leaves the gasi-sses a cyclone to eliminate large size particulates ando a ceramic lter by which particulate-free biosyngasained. Following these two units is a dolomite/nickelsed tar reformer working around 800 C, throughwhichin the biosyngas is almost completely decomposed intoO and H2 [18]. After the steam reforming the gas is

ater scrubber, which removes most of the impuritiess, alkalis, and halogens by cold water. After scrubbing,rbon is used to absorb sulphur-compounds and other

onents,whichmayhave escaped the scrubber. Althoughr vapor (around 2vol.% as indicated in the model) inas after scrubbing may deactivate a small part of thearbon, it is still necessary to ensure a sulphur-free orle sulphur containing biosyngas. The cleaned biosyn-nd room temperature then ows to the SOFC system.cleaning system, waste water, coming from the scrub-t contain large amounts of tars. The cost of waste waterill be much lower than for the system without the tarowever, the water should be further treated before itosed off [19,20].

temperaturegh temperature gas cleaning process as shown in Fig. 1,gas rst passes through a cyclone and a dolomite/nickelyst reactor working at 800 C. Then the hot gas is cooledater for producing hot water. The biosyngas is cooled

ound 450 C under which alkalis are expected to con-rticulates. Theparticulates togetherwith thecondensedounds are then removed by a primary-stage lter. Thenas passes through two units working around 450 C, inequent beds with sodium carbonate and zinc oxide sor-ve halide and sulphur compounds from the biosyngas.g through the second-stage lter, puried biosyngas ised to the downstream SOFC system.

HP systemjpowsour.2011.02.065

C CHP system is based on the Alpha unit developedl Technologies. The SOFC stack inside the Alpha unite tubular SOFCs developed by Siemens. The stack oper-1000 Candat close toatmosphericpressure.Generally,ed natural gas as fuel is compressed and fed to an ejec-lls a part of anode-off gas from a recirculation plenumam reformer. A part of the natural gas is reformed bysteam in the steam reformer. The rest of the gaswill be

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ARTICLE IN PRESSGModelPOWER-14231; No.of Pages13M. Liu et al. / Journal of Power Sources xxx (2011) xxxxxx 3

Fig. 1. Flow diagram of the high temperature gas cleaning system.

converted tohydrogenandcarbonmonoxideby internal reforming.Theother portionof the anode-off gas passes to thepost-combustoror after burner and reacts with the air from the cathode. A part oftheheat fromtheuegas leaving thepost-combustor is used topre-heat the air that goes to the cathode, and the remaining heat in theue gas is recovered by a heat exchanger for space heating and/ordomestic hot water production. The ow scheme of the Alpha unitis presented in Fig. 2. More details about this unit are available in[21].

3. Modeling

3.1. Gasier

The gasication section in the models built in computer pro-gram CyclecompositioGibbs energsidered to bclose to amassumed. Averted and iusually occuused as thefrom the Phconcentratimodel as ex

3.2. Anode recirculation

In the model a recirculation fan (NO.110 in base case, NO.117 incase 1 andfunctions otant compochamber ofgas whichthe reformisented in thby avoiding4.3.

3.3. Gas pro

The calcstem. Narefored b

xH2

2O

he cd wed. Ft andinanaccorSO

el ce

ailed[3,22kes tV, tted.raturstantll ow

mposTempo [22] is based on equilibrium calculations. Then of the produced gas is calculated by minimizing they. For the equilibrium calculations, the gasier is con-e working at a temperature of 800 C and a pressure

bient pressure, and a gas outlet temperature of 800 C ispart of the carbonwithin biomass, around5% is not con-s removed from the gasier representing the losses thatr in downdraft xed-bed gasiers. Eucalyptus wood isbiomass fuel for the gasier, and its composition takenyllis database [23] is given in Table 2. The methane

on was adjusted to t experimental data in the gasierplained elsewhere [3].

the syenergysteamdescrib

CxHy +

CO + H

In toxidizeassumoxidancontammainlygasie

3.4. Fu

Detwhererst tavoltagecalculatempebe confuel ce

Table 2Wood cothis article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.

Fig. 2. Flow scheme of the SOFC system.

Carbon (C)Hydrogen (HNitrogen (NOxygen (O)Sulphur (S)Chorine (Cl)Lower heatiNO.118 in cases 2 and 3) is employed to simulate thef the ejector in the Alpha unit. The ejector is an impor-nent as it (1) compensates pressure losses in the anodethe fuel cell stack, and (2) recirculates the anode-off

is steam rich and supplies sufcient steam to supportng taking place in external reformer. In all cases pre-is work, the anode recirculation fraction is determinedthe risk of carbon deposition as discussed in Section

cessing

ulations for the steam reformer and combustor ins are based on the minimization of the Gibbs freetural gas and other higher hydrocarbons would haveming described by Eq. (1) and water gas shift reactiony Eq. (2), which are considered to be in equilibrium.

O xCO + ((2x+ y)/2)H2 (1)

CO2 +H2 (2)

ombustor, the remaining fuel in the anode-off gas isith the cathode-off gas and equilibrium composition islue gas compositions, released heat, mass ows of fuel,ue gas can be calculated by the program. Since thets are not actually modeled, the gas cleaning system ismmodatedwith heat transfer and pressure drops in theFC CHP systems.

ll model

descriptions of the fuel cell model are available else-]. It is outlined for the case considered here. The modelhe inlet gas to the equilibrium conditions. Then, the cellhe current ow I and the electrical output power Pe areIt is supposed that the processes occur at a constante and pressure. Gas compositions are also supposed toin a cross-section, perpendicular to the direction of the. A set of equations were used in the fuel cell modeling

ition in the model.jpowsour.2011.02.065

Amount Unit

49.5 wt%) 5.75 wt%

) 0.14 wt%44 wt%0.03 wt%0.055 wt%

ng value (dry) 17,963 kJ kg1

Please cite 16/j.jpowsour.2011.02.065


and they are given below.

I = 2F UFm,a,inMa

(y0H2 + y0CO + 4y0CH4 ) (3)

Vrev,x = V0rev

ix = IA

Vx = ix V = Vrev,x Pe = V I

Here m,a,intheconcentMa is the mconstant (Cvoltage (V),ix is the cur( cm2),Vthe fuel cellPcell is the ois the efcie

3.5. Energy

ExergyExergy anahensively birreversibiliversibilitiesThermomeca referencepressure of0.03%, H2Ocies are calfuel. The neratio of thefuel input tciency, descheat divideis dened adivided by

Eele = Mbio

Eheat = Mb

CHP = MbioEa is the toting comprethe biomassheating val

Exergy ethe producdescribed bSystem totaexergy efc

Ex,heat = M

Fi

Mb

=M

the1), E(kJ k

stem

y areecifyoutput load of the fuel cell stack. Input and output variablessystem calculation and ow scheme of the whole system

ing are shown in Fig. 3.

atural gas fuelled SOFC CHP system (base case)

mplied model of the SOFC system based on the Alpha unitilt using Cycle-tempo and is shown in Fig. 4. Three heatgers are used here to represent the heat transfer within theystem. Some other assumptions are alsomade for themodel,) the system is under steady state operation, (2) processesiabatic, (3) fouling caused by the contaminants on the walltalyst is neglected, (4) heat exchangers are supposed to oper-counter ow and (5) pressure drop in all the equipmentsimated. These assumptions are also applied in the cases 13are described in Section 3.8.ural gas is the fuel for the Alpha unit, although several otherf gases could be used for the unit if there are appropriatecations [24]. Since detailed working conditions from exper-with the Alpha unit are not available, the input parametersn Table 3 are selected from and/or assumed based on otherystem calculations performed by Campanari [25] and per-ommunications [24]. Fresh fuel entering the ejector will beted to 700 C by heat exchange with ue gas in the heatger NO.104 in the model.this article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.10

+ RT2F

ln

(y1/2O2,C

yH2,a

yH2O,a P1/2

cell

)(4)

(5)

Req (6)

Vx (7)

DC/AC (8)

is the mass ow that goes to the anode (kg s1), y0iare

rationsat theanode inlet (i is a specieofH2,COandCH4),ole mass of the anode gas (kgmol1), F is the Faradaymol1), UF is the fuel utilization, Vrev,x is the reversibleV0rev is the standard reversible voltage for hydrogen (V),rent density (mAcm2), Req is the equivalent resistancex is the voltage loss (V), T is theworking temperature ofstack (K), R is the universal gas constant (Jmol1 K1),perating pressure of the fuel cell stack (Pa) and DC/ACncy of the DC/AC inverter.

and exergy efciency

calculations can be performed using Cycle-Tempo.lysis allows a system to be analyzed more compre-y determining where exergy is destroyed by internalties and by bringing out the causes of those irre-. Kinetic and potential exergy effects are neglected.hanical exergy and chemical exergy are calculatedwithenvironment, which is set at a temperature of 15 C, a101,325Pa with an air composition of Ar 0.91%, CO21.68%, N2 76.78%, and O2 20.60%. The energy efcien-culated based on the lower heating value (LHV) of thet AC electrical efciency, described by Eq. (9), is thenet produced electricity divided by the mass of the

o the gasier times the lower heating value. Heat ef-ribed by Eq. (10), is dened as the value of the producedd by the total fuel heating value. Total CHP efciencys the energy content of products, electricity and heat,the total fuel heating value described by Eq. (11).

Eele Eamass fuel LMVbiomass fuel

(9)

Eheat

iomass fuel LMVbiomass fuel(10)

Eheat + Eele Eamass fuel LHVbiomass fuel

(11)

al power consumption of auxiliary components includ-ssors and pumps (kW), Mbiomass fuel is the mass ow offuel fed to the system (kg s1), LHVbiomass fuel is the low

ue of the biomass fuel (kJ kg1).fciency is dened as the ratio between the exergy ofts and the fuel input exergy. Heat exergy efciency isy Eq. (12) and net electricity exergy is given by Eq. (13).l exergy efciency is the sum of heat and net electricityiency and is described by Eq. (14).

Ex,heat

biomass fuel Ex,biomass fuel(12)

Ex,ele =

Ex,CHP

Ex,a is(kJ kg

system

3.6. Sy

Theis to sppowerfor themodel

3.7. N

A siwas buexchanSOFC slike: (1are adand caate inare estwhich

Natkinds omodiimentsgiven iSOFC ssonal cpreheaexchang. 3. Flow scheme of the system performance modeling.

Ex,ele Ex,aiomass fuel Ex,biomass fuel

(13)

Ex,heat + Ex,ele Ex,abiomass fuel Ex,biomass fuel

(14)

total exergy loss caused by auxiliary componentsx,biomass fuel is the exergy of the biomass fuel fed to theg1).

modeling process

twoways to start the iteration in the program.Onewaythe biomass fuel mass ow, the other way is to set the

Please cite


304304 303303 302302

301301

203203202202

117117 116116

115115

111111

106106

105105

305 304303

H

302301

203

H202201

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Heat recovery by hot water production

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d by n

3.8. Biosyng

The owwhich is pushown in FFig. 6 beingis themethadded intodiscussed inheat from a3, the steamthe post-co

Table 3Parameters va

Parameters

Isentropic efblowers andMechanicalblowers andAir preheatiFuel cell exhFuel cell worDC/AC conveEquivalent cCell numberSingle cell acGlobal fuel uP/P air sideNatural gas:0.04%, C6H14113113

107107104104

103103

102102101101

104

H

103102101Natural gas

Fig. 4. Flow diagram of the SOFC CHP system fuellethis article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.

as fuelled SOFC CHP system

diagrams of SOFC CHP system fuelled by biosyngasried by the two types of gas cleaning systems are

igs. 57. The difference between the system shown inthe case 2 and the one shown in Fig. 7 being the case 3od used for steam generation. The generated steamwasthe biosyngas stream to prevent carbon formation asSection 4.3. In the case 2, the steam is generated usingcombustor fuelled by raw biosyngas, while in the caseis provided using heat from the ue gas which exits

mbustor of the Alpha unit itself. For the case 3, a heat

lue used in the SOFC CHP unit calculations.

Value

ciency for compressors,pumps

75%

efciency for compressors,pumps

98%

ng temperature 993Kaust gas temperature 1183Kking temperature 1243Krsion efciency 92%ell resistance 0.65 cm2

88tive area 370 cm2

tilization 80%/fuel side/combustor 0.02/0.03/0.03barCH4 81.29%, C2H6 2.87%, C3H8 0.38%, C4H10 0.15%, C5H120.05%, CO2 0.89%, N2 14.32%, O2 0.01%

exchanger iexchanger ipurpose. Ifthis requireThis systemcase 2. The

4. Results

4.1. Gasic

The inpugiven in Tagiven in Tabculation genfor carbon dwhile otherance [17], was the prodable agreem

Table 4Gas compositi

Component

CH4H2H2ON2CO2CO205205

114114

112112

110110

109109

108108

109

108

107A C

After burner

SOFCstack

atural gas (base case).jpowsour.2011.02.065

s required for the extra steam generation and the heats placed after the air preheater (NO.124 in Fig. 7) for thismodications can be made with the Alpha unit to fulllment, the case 3 described here may become available.gives a higher AC electrical efciency than that in the

explanations for this difference are given in Section 4.4.

ation

t composition of the biomass used for gasication isble 2 and the results from the model calculations arele 4. The biosyngas composition obtained from the cal-erallymatcheswellwith the experimental data, exceptioxide. CH4, H2, and COwas measured experimentally,gases were calculated based on mass and energy bal-hich may be the reason for this deviation. Generally,

uct compositions from the gasier model are in reason-ent with the experimental data and it is expected that

on comparison.

Model (vol.%) Experiment (vol.%)

1.35 0.8215.94 12179.72 911

40.66 404411.32 131617.04 1422

Please cite this article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.jpowsour.2011.02.065


506506

505505

504504

402402

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308308 307307

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Air preheater

Reformer SOFC

Cold water

Hot water

Air

Stack

Storage

Activated carbon

Scrubber

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Cyclone/ Filter

waterairbiomass

Gasifier

Input SOFC CHP Unit

Fig. 5. Flow diagram of the gasierCTGCSSOFC CHP system (case 1).

606606 604604 603603

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Eextra steam addition

Air

Filter/Storage

HCl

SulphurNa2CO3

ZnO

Filter/Cooling

Cyclone/Reformer

Stack Heat recovery

SOFC CHP unit

WaterAirBiomass

Gasifier

Input

Fig. 6. Flow diagram of the gasierHTGCSSOFC CHP system with external combustor for extra steam generation (case 2)

Please cite


501501

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For a sinior in termspowerdenTempo. The[26] and theat 900 C anvapor. Fuelference betwshowing a freasonably

4.3. Carbon

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Stack

Gasifier

Fig. 7. Flow diagram of the gasierHTGCSSOFC CHP system with internthis article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.

CO2 does not inuence system performance toomuch,tion model is considered acceptable and is used for thee evaluation of the gasierSOFC systems.

ll model validation

gle tubular SOFC, also developedby Siemens, the behav-of currentdensity to voltage and currentdensity to

sity is calculated using the fuel cell model in Cycle-results are compared with experimental results fromcomparison is shown in Fig. 8. The single cell isworkingd the inlet fuel consists of 89% hydrogen and 11%waterutilization is set to 85% in themodel. Themaximumdif-eenmodeling and experimental values is less than 4%,

airly good t and indicating the proposed model workswell to predict the performance of the tubular SOFC.

deposition

eposition can cause blocking of the gas pipes, systeme degradation and even anode damage. In the CHOhen gas composition lies below the carbon depositiono solid carbon exists, and if the gas composition liesurve, carbon formation will occur [3]. The possible sec-e carbon deposition may happen are analyzed basedynamic calculations using Factsage 5.4.1 [27] and theram indicating carbon deposition is shown in Fig. 9.se case, the gas composition of the natural gas is repre-oint A in the ternary diagram. It is located at the carbonregion of all carbon boundary lines of different working

temperaturcled anode-is far awaythe diagram

In the caical reactioplace at amof it is likelwith anodeambient pr

1000,2

0,4

0,6

0,8

1,0

Volta

ge (V

)

Fig. 8. Experim11% H2O119119

118118

117117116116115115

117

116

odied section for steam generation (case 3)jpowsour.2011.02.065

e levels in the diagram. Natural gas with a part of recy-off gas, represented by point B, in the steam reformerfrom the carbon boundary line at 600 C as indicated in.se 1, as the gas is cooled fast in the scrubber, the chem-ns causing carbon deposition are not expected to takebient temperature. Even if solid carbon is formed, mosty to get removed in the scrubber. The biosyngas mixed-off gas in the steam reformer working at 600 C andessure is in the carbon free region as point F is below

550500450400350300250200150

Pow

er d

ensit

y (w

cm-2 )

Current density (mA cm-2)

Modeling Experimental

0,5

1,0

1,5

2,0

2,5

3,0

3,5

ental and modeling data of a single cell at 900 C under 89% H2 and

Please cite


.9 0.1

0.2

0.3

0.4

C

F

970

Fig. 9. CHOF represents bgas in cases 2respectively, 4

the carbonIn the ca

800 to 450above the cais required.into gas macarbon depoff gaswill bpoint C furtis expected

It must bindicationssuch as kinet al. [28] fsteam to cation as indiare requiredeposition

4.4. System

The perfconversionCHP systemdeviation in0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0

A

B

E

C(D)this article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.

0.40.50.60.70.80.9mole fraction

H

ternary diagram indicating carbon deposition region (A represents the natural gas, B riosyngas with recycled anode-off gas in case 1, C represents biosyngas with steam addand 3, E represents raw biosyngas, 970 C is fuel cell stack working temperature, 800 C50 C is the biosyngas after cooling in cases 2 and 3, note: there is an overlap between po

formation boundary line at this temperature.ses 2 and 3, when the biosyngas is cooled down fromC, carbon formation may occur as point E is locatedrbonboundary line at 450 C; therefore, steamadditionAbout 17% steam (by volume of biosyngas) is addedinstream which makes the biosyngas escape from theosition region from point E to point C. Since the anode-ring steam rich gas to the steam reformer, thiswill dragher away from the carbon boundary, hence no carbonto be formed in the steam reformer.e noted is that thermodynamic calculations only giveregarding the carbon deposition while other factorsetics will also inuence it. For example, Mermelsteinound carbon deposition on SOFC anodes even with arbon ratio >1, which is not favourable for carbon forma-cated in thermodynamic calculations. Further studiesd to arrive at solid conclusions for preventing carbonin the gasierSOFC systems.

performance

ormance of the SOFC CHP systemwith regard to energyfor all the considered cases is given in Table 5. The SOFCfuelled by the natural gas presented here has a largerthe performance compared to that from literature [29].

This deviatance of plagas compousually de-efciency ociency chantheoreticalshows goodthermal efture; this mwork) of th100200 Can inuencAC electrici

Table 5SOFC CHP syst

Fuel input (kAC power ouHeat outputAuxiliary coGross electrNet AC electHeat efcienCHP efcien0.5

0.6

0.7

0.8

0.9

C

800C

600C

450Cjpowsour.2011.02.065

0.10.20.3 O

epresents the natural gas with recycled anode-off gas in base case,ed in cases 2 and 3, D represents biosyngas with recycled anode-offand 600 C is the temperature of raw biosyngas and steam reformer,ints C and D).

ion may arise from the assumptions related to the bal-nt (BOP), deviation in working conditions and naturalsition. Normally, electrical power of the Alpha unit israted by 3035% [21] caused by BOP, especially by poorf DC/AC inverter in real operations. The electrical ef-ges to 39.8% if the inverter efciency decreases from avalue of 92% to 75%, a typical value in operation. Thisagreement with the value from the literature [29]. Theciency appears to be higher than that from the litera-ay be caused by the lower temperature (100 C in thise exhaust ue gas, which is typically in the range ofin real operations. The adiabatic assumption also hase on the thermal efciency. Exergy efciencies for netty and heat are around 47.5% and 4.1%, respectively in

em energy conversion performance.

Base case Case 1 Case 2 Case 3

W) 9.12 18.43 18.43 18.43tput SOFC (kW) 4.65 4.61 4.25 4.59(kW) 3.48 6.24 8.18 7.69nsumption (kW) 0.16 0.35 0.27 0.28ical efciency (%) 50.9 25.0 23.0 24.9rical efciency (%) 49.2 23.1 21.6 23.3cy (%) 38.1 33.9 44.4 41.7cy (%) 87.4 57.0 66.0 65.0

Please cite


Ex NG =9.45 kW (100%)

Ex Ancilla

Ex Air=0.001 kW

Ex Inverter=0.4 kW(4.2%)

the calculatAround 62%thermodynthe externa

In the gbiomass fuehigher in thwere madethe base cascentration a1 while extthe cases 2in the cases3 which havtrical efcieIt is clearlythe HTGCSCTGCS, thisHTGCS. In ter SOFC syand HTGCSHowever, wgies and cothe gasierdifference bof steam gesplit streamcombustorows to thea lower elehigher therthe case 3 lneeded for

The exer24 are shofor heat excthe largestexergy. Thisities includgasicationprocess. Theicant due toand temperdrop in thegas cleaninhigh tempe

Table 6SOFC CHP system exergy performance.

Base case Case 1 Case 2 Case 3

xergyer ou

utputary coelectrelectxergyxergy

anin, theFor tergyeat

city eanc

stem

afelyly orciened. Fndwivelyhat tperistuyingFC sre coessaThisgeneystemted iundserfonots canthe

workscussystem

Inuel utilEx flue gas stack=0.29 kW (3.1%)

Ex CHP=4.88 kW (51.6%)

Ex HE, nodes=2.68 kW

Ex AC=4.65 kW (49.1%)

Ex Heat=0.39 kW (4.1%)

ry=0.16 kW(1.7%)

Ex Fuel cell stack =0.93 kW (9.84%) Ex Reformer loss =0.15 kW

Ex Combustor loss =0.5 kW

Fig. 10. Exergy ow diagram of base case.

ions, and the exergy ow diagram is plotted in Fig. 10.of the anode-off gas is recirculated, which makes it

amically unlikely that carbon deposition will occur inl reformer and in the anode as discussed in Section 4.3.asierSOFC systems (cases 13), for a mass ow ofl (0.00114kg s1), the gross AC electrical efciency ise case 1 than in the cases 2 and 3 (no modicationson the electrical efciency as previously explained fore). This can be explainedby the difference in steamcon-s the steam content of the fuel gas is lower in the casera steam addition for suppressing carbon deposition inand 3 reduces the electrical efciency. Parasitic power13 does not showmuch difference, but the cases 1 ande different gas cleaning systems give comparable elec-ncies which are slightly higher than that in the case 2.seen that thermal efciencies in the cases 2 and 3 withare almost 9% higher than that in the case 1 with theis because of the lower heat losses in the systems withhis regard, CTGCS is proposed for integration in a gasi-stem when electricity production is given importance,may be preferred when there is a high heat demand.hen considering thematurity of gas cleaning technolo-st effectiveness, CTGCS shall be initially preferred forSOFC systems. An interesting point is the performanceetween the cases 2 and 3 caused by different meansneration to avoid the risk of carbon formation. Since aof raw biosyngas fuel is used as the fuel for the extra

in the case 2 to produce steam from coldwater, less fuelSOFC system generating less electricity which causes

ctrical efciency. However, the case 2 has around 3%

Fuel eAC powHeat oAuxiliGrossNet ACHeat eCHP e

gas clesystemlosses.tem exmore helectriperform

4.5. Sy

To sto parttem efexploragent ais relatfound tsystemthe moand drand SOmoistube neccation.can beation sas poincompoSOFC phere issystemtions inhencether diSOFC s

4.5.1.Fuethis article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.

mal efciency than the case 3, this is mainly because iness heat can be recovered in the case 3 as more heat issteam generation in this case.gy ows in the gasierSOFC CHP systems, i.e. the caseswn in Figs. 1113, respectively (HE in the plot standshanger). It is found that the gasication process causesexergy loss, which is about 24% of the system inputexergy loss is mainly caused by the large irreversibil-

ing the heating of the cold fuel and air, combustion,, and carbon losses, which occur during the gasicationexergy losses of the gas cleaning process are not signif-the low content of impurities and also small pressureature drops. However, due to the larger temperaturecase 1 with the combined high and low temperatureg process compared to that in the cases 2 and 3 withrature gas cleaning technologies, the exergy loss of the

SOFC systemgas which ition that cafuel utilizawill result iseveral reanickel oxidments [32,1a safe workhigh fuel utof nickel ox[33] showsgas producNi-CGO anoof 6585% isystem of thinput (kW) 9.45 20.76 20.76 20.76tput SOFC (kW) 4.65 4.61 4.25 4.59(kW) 0.39 0.69 1.52 1.53nsumption (kW) 0.16 0.35 0.27 0.28icity exergy efciency (%) 49.1 22.2 20.4 22.1ricity exergy efciency (%) 47.5 20.5 19.2 20.7efciency (%) 4.1 3.3 7.3 7.4efciency (%) 51.6 23.9 26.5 28.1

g system is higher in the former case. For the SOFC CHPfuel cell stack causesonly a small part of the total exergyhe complete system, the case 3 shows the highest sys-efciency of 28.1% among three cases mainly becausewas recovered. However, no signicant difference inxergyefciency is found in these three cases. Theexergye of all the cases is summarized in Table 6.

performance responses to variation in parameters

operate the SOFC system using the biosyngas in ordercompletely replace natural gas, and to obtain high sys-cy, suitable off-design working conditions need to beor the xed-bed downdraft with air as the gasifyingoodas the fuel employedhere, the gasierperformancestable. During experimental work on the gasier, it ishemoisture content in thewoodhasa largeeffect on theformance. The wood was dried naturally and thereforere content depends heavily on the weather conditiontime. It can be expected that the gasication efciencyystem performance would drop if biomass with highntent was used, because then more biomass fuel will

ry to evaporate the additional moisture before gasi-decreases the fuel ows to the SOFC and less powerrated. Generally, for a gasication based power gener-, biomass moisture content should be below 1020%

n [30]. The level of contaminants like tars and sulphur-in the product biosyngas also has a great inuence onrmance. However the gas cleaning process describedactually modeled. It is expected that the gas cleaningreduce the contaminants to sufciently lowconcentra-biosyngas that they donot affect the SOFCperformance,ing parameters of the gas cleaning process are not fur-ed. In thiswork,we focus our sensitivity analysis on theand the system of case 1 is employed for this study.

nce of fuel utilizationization is one of the main operation parameters of the. It determines the composition of the anode exhaust

s recirculated and hence inuences the carbon forma-n occur in the downstream steam reformer. Moreover,tion usually cannot be more than 85%; higher valuesn a performance drop of the SOFC. This drop is due tosons such as gas composition changes or formation ofe [31]. For real biosyngas fuelled SOFCs, many experi-1] use low fuel utilization down to 20% in order to havejpowsour.2011.02.065

ing condition to protect the cell. In [11], it is found thatilization (75%) caused a SOFC performance loss becauseidation on Ni-GDC anode. On the contrary, literaturethat a fuel utilization of about 75% is possible with syn-ed from gasication in a commercial SOFC stack withdes [34]. Considering these, fuel utilization in the ranges selected for the sensitivity study in the gasierSOFCe case 1 employed here.

Please cite


Ex Biomass = 20.76 kW (100%)

Ex Clean biosyngas =12.22 kW (58.9%)

Ex AC electricity= 4.61 kW (22.2%)

Ex Ancillary =0.35 kW (1.7%)

Ex aux.=0.0043 kW

Ex aux.=0.0006 kW

Ex aux.=0.345 kW

Ex heat=0.69 kW (3.3%)

Ex Flue gas stack=0.77 kW (3.7%)

Ex Raw biosyngas =15.84 kW (76.4%)

Ex Gasifier loss =4.89 kW (23.6%)

Ex Gas cleaning loss =1.73 kW (8.3%)

Ex CHP=4.96 kW (23.9%)

Ex air=0.0034 kW

Ex Ashes =0.04 kW

Ex Impurities=1.86 kW

Ex Scrubber water =0.03 kW

Ex Combustor=0.57 kW

Ex Reformer=0.32 kWEx Fuel cell stack loss =0.94 kW (4.5%)

Ex HE.,nodes=4.6 kW

Ex inverter=0.4 kW (1.9%)

Fig. 11. Exergy ow diagram of case 1.

Fig. 14(a) reveals the relationship between variable fuel utiliza-tion and system energy conversion performance under a certainbiomass ow rate. Apparently, the electrical efciency increaseswith increawhen recircfuel utilizatheat can beincreasingciency is hi

efciency is less inuenced by the fuel utilization than the elec-trical efciency. It seems that the total CHP efciency reaches to amaximum value at around 80% in this case. The system exergy per-

ce ahe nn, thexergydoescy wsing fuel utilization because more power is producedulation rate is around60%, as shown inFig. 14(a).Higherion induces less fuel go to the combustor and hence lessrecovered. The total CHP efciency also increases withfuel utilization because the increase of electrical ef-gher than the decrease of heat efciency. The thermal

formanSince tlizatioheat ebut itefcienthis article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.

Fig. 12. Exergy ow diagram of cases a function of the fuel utilization is shown in Fig. 14(b).et AC power output increases with increasing fuel uti-net AC electricity exergy efciency increases too. Theefciency decreases with increasing fuel utilization,not have too much inuence on system CHP exergyhich is higher for higher fuel utilization. For all thejpowsour.2011.02.065

2.

Please cite


Fig. 13. Exergy ow diagram of case

calculations with regard to the inuence of fuel utilization, car-bon deposition-free operation conditions for the steam reformerand the fuel cell stack were carefully checked and adjusted in theprogramusing theCHO ternarydiagram, especially for the condi-

12

16

20

24

28

32

36

40

44a

b

Net AC Heat

ficie

ncy

(%)

Elec

trica

l and

hea

t effi

cienc

y (%

)

57,0

57,5

58,0

58,5

59,0

CHP

14

16

18

20

22

24

26

28

Exer

gy e

fficie

ncy

of n

et A

C an

d CH

P(%)

Fig. 14. (a) Efof fuel utilizat

tions of lowlevels but h

4.5.2. InueIn real o

controllableing other pthe changewhen varyiciency decrpolarizationperformanctrical efcie

is trstemch. TimilaCHP

ef

56,0

56,5 energyThe sytoo muhas a sthis article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.

8580757065Fuel utilization (%)

55,0

55,5

8580757065

Net AC

CHP

Fuel utilization (%)3,0

3,2

3,4

3,6

3,8

4,0

Heat

Hea

t exe

rgy

(%)

fect of fuel utilization on energy conversion efciency and (b) effection on system exergy efciency.

4.5.3. InueAnode r

not only prin the anodtemperaturwithin the

Since thlow and thsary to havrecirculationet AC electincreases. Tenergy andis also founexternal retion fractionfuel cell staciency. In ththe requireand for prethe anode r3.

er fuel utilization as these conditions have lower steamigher CO concentrations.

nce of current densityperation of the fuel cell stack, stack current is directly. Current density can be varied in the model when x-arameters as listed in Table 3. Fig. 15(a) demonstratess in electrical and thermal cogeneration efciencyng the current density. It is evident that electrical ef-eases with increasing current density due to increasedlosses. The decreased cell voltage degrades the stack

e under the constant fuel utilization. A decreased elec-ncy of the fuel cell stack means that more chemical

ansformed into heat; hencemore heat can be recovered.CHP efciency slightly decreases but it does not changehe exergy efciency of the system, shown in Fig. 15(b)r changing trend as energy conversion efciency.jpowsour.2011.02.065

nce of anode recirculationecirculation plays an important role in the system as itevents carbon formation in the external reformer ande chamber but it also inuences the anode fuel inlete which might have an impact on the thermal stressesfuel cell stack.e concentration of methane in the biosyngas is verye anode-off gas is rich in water vapor, it is not neces-e a higher anode recirculation ratio; the higher anoden dilutes the fresh fuel which decreases the fuel cellrical efciency although system heat efciency slightlyhe inuence of the anode recirculation on systemexergy efciency can be clearly seen from Fig. 16. Itd that the temperature of reformate gas exiting theformer increases with increasing the anode recircula-. Although it helps to reduce the thermal gradient of the

ck to some extent, it also reduces the systemnet AC ef-is regard, a loweranode recirculation ratiowhich fulllsment of steam for supporting the external reformingventing the carbon formation is desirable. In this work,ecirculation fraction is set around 62%which is in agree-

Please cite


14016

20

24

28

32

36

40

44a

b

59

60

Net AC Heat

Elec

trica

l and

hea

t effi

cienc

y (%

)

12018

19

20

21

22

23

24

25

26

27

28

Exer

gy e

fficie

ncy

of n

et A

C an

d CH

P(%)

Fig. 15. (a) Sysexergy perform

mentwith Cto carbon raof carbon d

5. Conclus

A commfuelled by nevaluated btems weresystem.

(1) Naturalmance,the gasiconversciency aexergyethan the

(2) No signobservetwo typbined hcase 1 oimportadescribedemand

55

36

40a

) 57,6

58,032030028026024022020018016052

53

54

55

56

57

58

CHP

effic

ienc

y (%

)

Current density (mAcm-2)

CHP

Hea

t exe

rgy

(%)

Net AC

CHP

2,6

2,8

3,0

3,2

3,4

3,6

3,8

4,0

Heat

16

20

24

28

32

b

Elec

trica

l and

hea

t effi

cienc

y (%

18

19

20

21

22

23

24

25

26

Exer

gy e

fficie

ncy

of n

et A

C an

d CH

P(%)this article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.1016/j.

Current density (mAcm-2)320300280260240220200180160140

2,4

temenergy conversion as a functionof current density and (b) systemance as a function of current density.

ampanariswork [25], and this valuemakes the oxygentio bigger than 2.0which is sufcient to prevent the riskeposition in practical operations [24].

ions and future work

ercial SOFC CHP system (Alpha unit from Siemens-FCT)atural gas and biosyngas from biomass gasicationwasy thermodynamic calculations. Two gas cleaning sys-proposed to integrate the gasier with the SOFC CHP

gas fuelled SOFC system has a better system perfor-especially with regard to electricity production, thaned-biosyngas fuelled SOFC systems. As of the energyion, the latter system offers comparable thermal ef-lthough the total CHP efciency is lower. However, thefciencies in thegasierSOFCsystemsaremuch lowernatural gas fuelled SOFC system.icant differences of the electrical efciency wered between SOFC systems fed by biosyngas with thees of gas cleaning systems (cases 1 and 2). The com-igh and low temperature gas cleaning system of theffers advantages when electricity production is givennce, while the high temperature gas cleaning systemd in the case 2 is preferred when there is a larger heat. If a modication can be properly made with the SOFC

5517

Fig. 16. (a) Inand (b) inuen

CHP syciency oin the to

(3) There ishigh temavoid crealisticelectric

(4) A sensitapproprfor high

Althougtions of theoutput forference is tpressure (off gas. Appa detailedfuture to rewould be hthe systemwhich hasCTGCS whiCHP systemmance ofcleaning syimentally s858075706560

Net AC Heat

Anode recirculation fraction (%)

CHP

effic

ienc

y (%

)

56,0

56,4

56,8

57,2

CHP

Hea

t exe

rgy

(%)

Net AC

CHP

3,2

3,6

4,0

4,4

4,8

5,2

Heatjpowsour.2011.02.065

858075706560Anode recirculation fraction (%)

2,8

uence of anode recirculation on system energy conversion efciencyce of anode recirculation on system exergy performance.

stem for steam generation, the net AC electrical ef-f the case 3 is increased without sacricing too muchtal CHP efciency.the possibility of carbon formation when the typicalperature gas cleaning technologies are employed. To

arbon formation, steam addition seems to be a moreoption for the system operation but it sacrices the

al efciency of the system.ivity studypresented in thiswork is helpful for selectingiate working conditions for safe system operations andsystem efciency.

h anode recirculation is analyzed to simulate the func-ejector, there might be a difference in net AC power

real system operations. The main reason for this dif-hat the fresh fuel needs to be pressurized to a higher3bar) to ensure the ejector entrain a part of the anode-arently, this process takes more parasitic power. Henceejector calculation is to be carried out in the nearne the system study presented here. These studieselpful for carrying out the experimental work with. For the experimental work, the SOFC CHP systembeen installed will be rst tested using natural gas. Ach is being built is to be used to integrate the SOFCwith the downdraft xed-bed gasier. The perfor-

the complete system including the gasier, the gasstem and the SOFC CHP unit will be evaluated exper-oon. The results from the experimental evaluations

Please cite 16/j.


will be used to validate the modeling results presented in thiswork.

References

[1] C.O. Colpan, F. Hamdullahpurb, I. Dincerc, Y. Yoo, Int. J. Hydrogen Energy 35(2009) 50015009.

[2] C. Athanasiou, E. Vakouftsi, F.A. Coutelieris, G. Marnellos, A. Zabaniotou, Chem.Eng. J. 149 (2009) 183190.

[3] P.V. Aravind, T. Woudstra, N. Woudstra, H. Spliethoff, J. Power Sources 190(2009) 461475.

[4] A.O. Omosun, A. Bauen, N.P. Brandon, C.S. Adjiman, D. Hart, J. Power Sources131 (2004) 96106.

[5] J. Mermelstein, M. Millan, N. Brandon, J. Power Sources 195 (2010) 16571666.

[6] P.V. Aravind, J.P. Ouweltjes, N. Woudstra, G. Rietveld, Electrochem. Solid-StateLett. 11 (2008) B24B28.

[7] J.P. Ouweltjes, P.V. Aravind, N. Woudstra, G. Rietveld, J. Fuel Cell Sci. Technol. 3(2006) 495498.

[8] Ph. Hofmann, K.D. Panopoulos, P.V. Aravind, M. Siedlecki, A. Schweiger, J.Karl, J.P. Ouweltjes, E. Kakaras, Int. J. Hydrogen Energy 34 (2009) 92039212.

[9] Ph. Hofmann, A. Schweiger, L. Fryda, K.D. Panopoulos, U. Hohenwarter, J.D.Bentzen, J.P. Ouweltjes, J. Ahrenfeldt, U. Henriksen, E. Kakaras, J. Power Sources173 (2007) 357366.

[10] L. Fryda, K.D. Panopoulos, E. Kakaras, Energy Convers. Manage. 49 (2008)281290.

[11] Ph. Hofmann, K.D. Panopoulos, L.E. Fryda, A. Schweiger, J.P. Ouweltjes, J. Karl,Int. J. Hydrogen Energy 33 (2008) 28342844.

[12] V. Alderucci, P.L. Antonucci, G. Maggio, N. Giordano, V. Antonucc, Int. J. Hydro-gen Energy 19 (1994) 369376.

[13] L. Fryda, K.D. Panopoulos, J. Karl, E. Kakaras, Energy 33 (2008) 292299.[14] R. Toonssen, N. Woudstra, A.H.M. Verkooijen, Proceedings of the 8th European

Solid Oxide Fuel Cell Forum, Luzerne, Switzerland, 2008.[15] R. Zevenhoven, P. Kilpinen, Helsinki Univ. Technol. (2001) 17179.[16] S.C. Bhattacharya, A.M.R. Siddique, H.L. Pham, Energy 24 (1999) 285296.[17] J.D. Martinez, MSc thesis (in Portuguese), Federal University of Itajuba, Brazil,

2009.[18] P.A. Smell, J.B. son Bredenberg, Fuel 69 (1990) 12191225.[19] A.V. Bridgwater, Fuel 74 (1995) 631653.[20] K.R. Cummer, R.C. Brown, Biomass Bioenergy 23 (2002) 113128.[21] Fuel Cell Technology Ltd., 5 kW SOFC Alpha Unit Operations Manual, 2005.[22] Cycle-Tempo 5.0, TU Delft, 2006, www.cycle-tempo.nl.[23] Phyllis, database for biomass and waste, http://www.ecn.nl/phyllis.[24] Personal communication with Dr. Wojtek Halliop.[25] S. Campanari, J. Power Sources 92 (2001) 2634.[26] S.C. Singhal, Solid State Ionics 135 (2000) 305313.[27] www.factsage.com.[28] J. Mermelstein, N. Brandon, M. Millan, Energy Fuels 23 (2009) 50425048.[29] G. Allen, Rural Energy Conf. (2004).[30] H. Morita, F. Yoshiba, N. Woudstra, K. Hemmes, H. Spliethoff, J. Power Sources

138 (2004) 3140.[31] P. Nehter, J. Power Sources 164 (2007) 252259.[32] Ph. Hofmann, K.D. Panopoulosb, P.V. Aravind,M. Siedlecki, A. Schweiger, J. Karl,

J.P. Ouweltjes, E. Kakaras, Int. J. Hydrogen Energy 34 (2009) 92039212.[33] L.P.L.M. Rabou, R.J.C. van Leijenhorst, J.H.O. Hazewinkel, ECN-E-08-086,

November, 2008.[34] A.D. Hawkes, D.J.L. Brett, N.P. Brandon, Int. J. Hydrogen Energy 34 (2009)

95589569.this article in press as: M. Liu, et al., J. Power Sources (2011), doi:10.10 jpowsour.2011.02.065

Development of an integrated gasifiersolid oxide fuel cell test system: A detailed system studyIntroductionSystem configurationGasifierGas cleaning systemCombined high and low temperatureHigh temperature

SOFC CHP system

ModelingGasifierAnode recirculationGas processingFuel cell modelEnergy and exergy efficiencySystem modeling processNatural gas fuelled SOFC CHP system (base case)Biosyngas fuelled SOFC CHP system

ResultsGasificationFuel cell model validationCarbon depositionSystem performanceSystem performance responses to variation in parametersInfluence of fuel utilizationInfluence of current densityInfluence of anode recirculation

Conclusions and future workReferences

development of an integrated gasifier–solid oxide fuel cell test system- a detailed system study...

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