MACRO-LEVEL MODELING OF PLANAR DIRECT INTERNAL REFORMING SOLID OXIDE FUEL CELLS CAN OZGUR COLPAN. Carleton University

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1 MACR-LEVEL MDELIG PLAAR DIRECT ITERAL RERMIG SLID XIDE UEL CELLS CA ZGUR CLPA Crleton Unversty tonl Reserch Councl Cnd-Insttute or Chemcl Process nd Envronmentl Technology June 6, ttw, Cnd

2 UTLIE Introducton SC perton o SCs Clsscton o SCs 0-D Model Model ncludng recrculton o depleted uel Cse study Crbon Deposton Problem Theory C-- Trngulr Dgrms Cse Study -D Trnsent Model et-up nd strt-up smultons Cse study Conclusons

3 Introducton SC gh temperture uel cell ( C) Applcton res: Sttonry power nd het generton Trnsportton pplctons Portble pplctons Advntges: o need or precous metl electroctlysts uel leblty (ydrogen, crbon monode, methne, hgher hydrocrbons, methnol, ethnol, lndll nd bomss-produced gses, mmon, hydrogen sulde) Internl reormng Good therml ntegrton wth other systems Dsdvntges: Degrdton due to crbon deposton nd sulphur posonng Chllenges wth constructon nd durblty

4 Introducton perton o SCs Anode Electrolyt e Cthod e e - e - e - e Lod e - e - e - e -

5 Introducton Clsscton o SCs Clsscton crter Temperture level Cell nd stck desgn Type o support low congurton uel reormng type Types Low temperture SC (LT-SC) (500 C 650 C) Intermedte temperture SC (IT-SC) (650 C 800 C) gh temperture SC (T-SC) (800 C C) Plnr SC (lt-plnr, rdl-plnr) Tubulr SC (Mcro-tubulr, tubulr) Segmented-n-Seres SC (or Integrted-plnr SC) Monolthc SC Sel-supportng (Anode-supported, cthode-supported, electrolytesupported) Eternl-supportng (Interconnect supported, porous substrte supported) Co-low Cross-low Counter-low Eternl reormng SC (ER-SC) Drect nternl reormng SC (DIR-SC) Indrect nternl reormng SC (IIR-SC)

6 C C 4 4 U r r U r b 3 ) )( ( ) ( b C C b C C U r r U b b 3 ) ( ADE ELECTRLYTE CATDE UEL CAEL AIR CAEL LAD e - e - 0-D Modelng - I [ ] 3 4 P P RT g K C C z r r ) )( ( ) ( ) ( / Δ ep [ ] ) )( ( ) ( ) ( / Δ ep C C z s s RT g K U r r U b c A I 3 ) ( Et gs composton: The ollowng utons re solved smultneously:

7 con ct ohm V V V V V j j C j j h h W h h 5 LV W C cell el, η V I W C P P RT T g V z z ln ) ( Δ L ρ R V k k k contct ohm c o s o s c ct ct ct RT RT V V V,,,, snh snh cs z s z s z c conc conc conc RT p p RT RT V V V ln ln ln z e s L RT D P 4 c z ce cs L RT P P P D P 4 0-D Modelng - II Cell voltge Power output Energy blnce Electrcl Ecency ernst Voltge hmc Polrzton Actvton Polrzton Concentrton Polrzton

8 Input Dt or Cse Study (0-D Model) Gs composton: % C 4, 40%, 0% C, 8% C, % Input Vlue Temperture o the et (T z ) 850 C Temperture derence between et nd nlet (ΔT) 00 C Pressure o the cell (P cell ) br Actve surce re (A) 00 cm Echnge current densty o node ( o ) 0.65 A/cm Echnge current densty o cthode ( oc ) 0.5 A/cm Eectve gseous dusvty through the node 0. cm /s Eectve gseous dusvty through the cthode 0.05 cm /s Thckness o node (L ) 500 μm Thckness o electrolyte (L e ) 0 μm Thckness o cthode (L c ) 50 μm

9 Results-I (0-D Model) Termnl voltge (V) r r0.3 r Current densty (A/cm ) Ar utlzton rto r0. r0.3 r Current densty (A/cm ) Power output [W] Current densty (A/cm ) r0.3 r0. r0. Electrcl ecency r0. r0.3 r Current densty (A/cm )

10 Results-II (0-D Model) Ar utlzton rto U U 0.85 U Current densty (A/cm ) Termnl voltge (V) U 0.65 U 0.85 U Current densty (A/cm ) Power output [W] U 0.85 U 0.75 U 0.65 Electrcl ecency U 0.85 U 0.75 U Current densty (A/cm ) Current densty (A/cm )

11 Crbon Deposton Problem When methne, butne, propne, JP-8, methnol, ethnol, etc. re ed drectly to the SC Crbon deposton rsk Cuses degrdton n the perormnce nd eventully the uel cell s brekdown. Mechnsms: C C C 4 C ( s ) C C C ( s ) ( s ) Soluton: Adjustng the S/C rto t the uel chnnel nlet. Send stem rom n eternl source Recrculte the depleted uel Source: Tkeguch et l., 00, J. Power Sources, :

12 Modelng o Crbon Deposton - Theory TERY Assume, C,, C, C 4 nd C (s) re n chemcl ulbrum. (CP- )6-6 Temperture, pressure, one mterl blnce constrnt nd three ulbrum constnt utons Rectons: Stem-reormng, wter-gs sht recton, crckng o methne Equtons: PC 4 α PC β PC δ P ε P ζ o Grn K(T ) ep RT α β δ ε ζ P K 3 δ ζ α ε K β ζ δ ε K 3 ζ α

13 Modelng o Crbon Deposton Soluton Methodology the prtl pressure o one o the gses Chnge the prtl pressure o the ed gs between 0 nd 0 Mke ntl guesses or the prtl pressures o other gses Solve the non-lner utons nd nd the prtl pressure o gses Clculte the C, nd tom rtos btn set o dt or C-- rtos

14 C-- Trngulr Dgrm Crbon deposton possblty t gven temperture nd pressure my be determned or ll possble vrtons o C-- systems usng ths dgrm. C Crbon deposton 400 K 00 K 00 K 000 K 900 K 800 K 800 K 900 K 000 K 00 K 00 K 400 K o Crbon deposton

15 Crbon ctvtes C 4 C C C Crbon Deposton - Actvty ( s ) C C C ( s ) ( s ) c5 c4 K K 5 4 ( ) C 4 ( C ) C α c Crbon ormton s observed α c < Crbon ormton s thermodynmclly mpossble c6 K 6 C

16 Crbon Deposton- Results Syngs Syngs: % C 4, 40%, 0% C, 8% C nd % r0. r0. r0.3 r0.4 r0.5 r0.6 r0.7 r0.8 C Crbon deposton Syngs LT-SC U 0.85 Crbon ctvty U 0.65 U 0.75 U 0.85 o Crbon deposton Recrculton rto r0. r0. r0.3 r0.4 r0.5 C Crbon deposton Syngs IT-SC U 0.85 Crbon ctvty U 0.65 U 0.75 U 0.85 o Crbon deposton Recrculton rto

17 Crbon Deposton- Results Syngs Mnmum recrculton rto LT-SC IT-SC T-SC Globl uel utlzton rto

18 Trnsent et Trnser Model In trnsent modelng o SC het-up strt-up shut-down nd lod chnge smultons my be crred out. Temperture nd current densty dstrbutons w.r.t tme re nvestgted. Results my be used s bss or thermomechncl nlyss. et-up nd strt-up tme re clculted Crucl or portble uel cells.

19 Trnsent et Trnser Model Approch etures o the developed -D trnsent model: The repet element o plnr, co-low, drect nternl reormng SC s tken. Sold structure s modeled n -D, wheres gs chnnels re modeled n -D. Reynolds number t the uel chnnel nlet, ecess r coecent re nput prmeters. uel utlzton rto, current densty nd temperture dstrbutons, power output nd electrcl ecency o the cell re output prmeters. S gs speces, C4,, C, C, nd t the uel chnnel nlet nd two gs speces nd re consdered. ully developed lmnr low condtons re ssumed n chnnels. Convecton n the rectngulr ducts nd surce-to-surce rdton eects, conducton het trnser t the secton where the nterconnects re n contct wth PE structure, ohmc, ctvton nd concentrton polrztons re consdered.

20 Trnsent et Trnser Model - Approch - The contnuty utons t the gs chnnels: electrochemcl recton rte rte uton or the stem-reormng chemcl ulbrum relton or wter gs sht recton - The energy blnce, boundry nd ntl condtons: cthode nterconnect r chnnel PE Reltons or the ohmc, ctvton nd concentrton polrztons uel chnnel node nterconnect

21 Trnsent et Trnser Model - umercl Soluton (,s) (,r3) (,r) (,r) (,r) (,p3) (,p) (,p) (,p) (,) Anode Interconnect uel chnnel PE Ar chnnel Cthode Interconnect (m,s) (m,r3) (m,r) (m,r) (m,r) (m,p3) (m,p) (m,p) (m,p) (m,) j L cell nte Derence Method ully mplct nte derent scheme (uncondtonlly stble ) T t,j,n T n, j T Δt n, j o( Δt) T,j,n T n,j T n,j ( Δ) T n,j o [( Δ) ] Boundry condtons re tken s second order ccurte The set o utons re lnerzed by usng the lggng propertes by one tme step method Guss elmnton method

22 Trnsent et Trnser Model Cse study Cell geometry Length o the cell [cm] Wdth o the sold prt [cm] Wdth o the gs prt [cm] Thckness o cthode nterconnect [cm] Thckness o r chnnel [cm] Thckness o cthode [cm] Thckness o electrolyte [cm] Thckness o node [cm] Thckness o uel chnnel [cm] Thckness o node nterconnect [cm] pertng prmeters Temperture t the uel chnnel nlet t stedy stte [ C] Temperture t the r chnnel nlet t stedy stte [ C] Pressure o the cell [br] Cell voltge [V] Ecess r coecent Reynolds number t the uel chnnel nlet Gs composton t the r chnnel nlet Gs composton t the uel chnnel nlet Ambent temperture [ C] %,79% 7.% C 4, 6.6%,.94% C, 4.6% C, 49.34%

23 Trnsent et Trnser Model Results (et-up) - et-up tme s ul to 3 mnutes 44 seconds. ¼ het-up tme ¾ het-up tme t the end o the het-up perod. ½ het-up tme

24 Trnsent et Trnser Model Results (strt-up) It s ound tht 55 mnutes 30 seconds s the tme needed or the system to operte t stedy stte ter the het-up perod ends. ¼ strt-up tme ¾ strt-up tme t the end o the strt-up perod. ½ strt-up tme

25 Trnsent et Trnser Model Results Gs composton Poston n the drecton [cm] Gs composton dstrbuton -ch4 -h -co -co -ho -o -n Current densty [A/cm ] Poston n the drecton [cm] Current densty dstrbuton

26 Conclusons The recrculton o the node et gs strem s tken nto ccount n the 0-D model to obtn ormulton vld or gs mtures contnng derent gs compostons. Recrculton rto should be kept s mnmum s possble to obtn better thermodynmc perormnce. gher opertng temperture nd globl uel utlzton rto s needed to operte the system t low recrculton rtos. or T-SC opertng t uel utlzton rto o 0.85, the mnmum recrculton rto s ound to be 0.4 nd 0.07 or the uel s methne nd the selected syngs, respectvely. A new trnsent, -D DIR-SC model hs been dscussed. et-up nd strt-up smultons o ths model re done. Temperture, current densty nd molr gs composton dstrbutons re clculted or derent tme steps. A uture study wll nclude optmzng the het-up nd strt-up tme, clcultng the temperture grdents whch re necessry to clculte the therml stresses wthn the components, nd nvestgtng the crbon deposton possblty n the cell.