Gas-phase reactions of methane and natural-gas with air and steam in non-catalytic regions of a solid-oxide fuel cell

Abstract This paper uses a large elementary reaction mechanism to study the homogeneous chemistry of methane and natural-gas mixed with air and steam. Temperatures and residence times are chosen to represent SOFC operating conditions, including within feed lines that may be at elevated temperature but without any electrochemical or catalytic interactions. Mole fractions of six major species (CH4, O2, H2O, H2, CO, and CO2) are presented as contour maps as functions of temperature, residence time, and initial fuel mixture compositions. In addition, deposit propensity is predicted by the sum of mole fractions of all species containing five or more carbon atoms, designated as C 5 + . Comparison with chemical equilibrium predictions shows that the homogeneous reactions are far from equilibrium. These results indicate that the composition of the fuel mixture entering the active SOFC region might be significantly different from that originally entering the fuel cell.

[1]  Andrew Dicks,et al.  Catalytic aspects of the steam reforming of hydrocarbons in internal reforming fuel cells , 1997 .

[2]  Michael Frenklach,et al.  Detailed Modeling of PAH Profiles in a Sooting Low-Pressure Acetylene Flame , 1987 .

[3]  T. Just,et al.  Kinetics of the cyclopentadiene decay and the recombination of cyclopentadienyl radicals with H‐atoms: Enthalpy of formation of the cyclopentadienyl radical , 2001 .

[4]  Ellen Ivers-Tiffée,et al.  Oxidation of H2, CO and methane in SOFCs with Ni/YSZ-cermet anodes , 2002 .

[5]  Anthony M. Dean,et al.  Importance of gas-phase kinetics within the anode channel of a solid-oxide fuel cell , 2004 .

[6]  Kevin Kendall,et al.  Effects of dilution on methane entering an SOFC anode , 2002 .

[7]  John W. Cotton,et al.  Fuel reforming and electrical performance studies in intermediate temperature ceria-gadolinia-based SOFCs , 2000 .

[8]  Scott A. Barnett,et al.  Operation of anode-supported solid oxide fuel cells on methane and natural gas , 2003 .

[9]  G. D. Byrne,et al.  VODE: a variable-coefficient ODE solver , 1989 .

[10]  Andrew Murray,et al.  Cell cycle: A snip separates sisters , 1999, Nature.

[11]  Frank A. Coutelieris,et al.  The importance of the fuel choice on the efficiency of a solid oxide fuel cell system , 2003 .

[12]  Scott A. Barnett,et al.  Operation of anode-supported solid oxide fuel cells on propane–air fuel mixtures , 2004 .

[13]  Anil V. Virkar,et al.  A High Performance, Anode-Supported Solid Oxide Fuel Cell Operating on Direct Alcohol , 2001 .

[14]  Raymond J. Gorte,et al.  An Examination of Carbonaceous Deposits in Direct-Utilization SOFC Anodes , 2004 .

[15]  S. A. Barnett,et al.  A direct-methane fuel cell with a ceria-based anode , 1999, Nature.

[16]  Ta-Jen Huang,et al.  Study of Ni-samaria-doped ceria anode for direct oxidation of methane in solid oxide fuel cells , 2003 .

[17]  M. H. Back,et al.  The thermal decomposition of methane. II. Secondary reactions, autocatalysis and carbon formation; non-Arrhenius behaviour in the reaction of CH3 with ethane , 1976 .

[18]  Raymond J. Gorte,et al.  Direct Oxidation of Liquid Fuels in a Solid Oxide Fuel Cell , 2001 .

[19]  Robert J. Kee,et al.  CHEMKIN-III: A FORTRAN chemical kinetics package for the analysis of gas-phase chemical and plasma kinetics , 1996 .

[20]  Philippe Dagaut,et al.  Experimental and modeling study of the oxidation of natural gas in a premixed flame, shock tube, and jet-stirred reactor , 2004 .

[21]  G. J. Saunders,et al.  Reactions of hydrocarbons in small tubular SOFCs , 2002 .

[22]  W. Corcoran,et al.  Pyrolysis, theory and industrial practice , 1983 .

[23]  P. Glarborg,et al.  Chemically Reacting Flow : Theory and Practice , 2003 .