Numerical analysis of an internal methane reforming solid oxide fuel cell with fuel recycling

The development of solid oxide fuel cell (SOFC) systems capable of direct internal reforming (DIR) of methane is being actively pursued. However, a major challenge with current state-of-the-art nickel-based anodes is their propensity to form deteriorous carbon deposits in DIR, unless excess steam is introduced in the fuel. Reduced fuel humidification levels are desirable from the viewpoints of cell performance, reliability and plant economics. This study explores the use of partial recycling of the anode exhaust as a mitigation strategy against carbon deposits at fuel steam-to-carbon ratios less than unity. Using a detailed computational fluid dynamics (CFD) model which couples momentum, heat, mass and charge transport with electrochemical and chemical reactions, the spatial extent of carbon deposition within a SOFC anode is analyzed by accounting for both the cracking and Boudouard reactions, for several fuel humidification and recycling conditions. At temperatures of approximately 1173K and for inlet fuel molar H2O/CH4 ratios between 0.5 and 1, 50% (mass%) fuel recycling is found to be an effective strategy against carbon deposition. For lower recycling levels at the same fuel compositions, or lower fuel humidification levels (regardless of the recycling level), fuel recycling reduces the risk of coking, but does not eliminate it. The analyses presented suggest that recycling of the anodic fuel stream could help extend the operational range of DIR-SOFCs to lower fuel humidification levels than typically considered, with reduced risks of carbon deposits, while reducing system cost and complexity in terms of steam production. For dry or weakly humidified fuels, additional mitigation strategies would be required.

[1]  Nigel P. Brandon,et al.  Recent Advances in Materials for Fuel Cells , 2003 .

[2]  John B. Young.  Thermofluid Modeling of Fuel Cells , 2007 .

[3]  Chunshan Song,et al.  Fuel processing for low-temperature and high-temperature fuel cells , 2002 .

[4]  Ayodeji Jeje,et al.  3D modeling of anode-supported planar SOFC with internal reforming of methane , 2007 .

[5]  L. Kershenbaum,et al.  Modelling of an indirect internal reforming solid oxide fuel cell , 2002 .

[6]  T. Inagaki,et al.  Direct Internal Steam Reforming at SOFC Anodes Composed of NiO – SDC Composite Particles , 2007 .

[7]  O. Deutschmann,et al.  Methane reforming kinetics within a Ni–YSZ SOFC anode support , 2005 .

[8]  R. Peters,et al.  Internal reforming of methane in solid oxide fuel cell systems , 2002 .

[9]  John P. Kopasz,et al.  Fuel processing for fuel cell systems in transportation and portable power applications , 2002 .

[10]  Robert J. Kee,et al.  Anode barrier layers for tubular solid-oxide fuel cells with methane fuel streams , 2006 .

[11]  S. Barnett,et al.  Direct operation of solid oxide fuel cells with methane fuel , 2005 .

[12]  Suttichai Assabumrungrat,et al.  Catalytic steam reforming of methane, methanol, and ethanol over Ni/YSZ : The possible use of these fuels in internal reforming SOFC , 2007 .

[13]  Yann Bultel,et al.  Modeling of a Solid Oxide Fuel Cell Fueled by Methane: Analysis of Carbon Deposition , 2007 .

[14]  U. Stimming,et al.  Recent anode advances in solid oxide fuel cells , 2007 .

[15]  Werner Lehnert,et al.  Modelling of gas transport phenomena in SOFC anodes , 2000 .

[16]  Alberto Traverso,et al.  Liquid fuel utilization in SOFC hybrid systems , 2009 .

[17]  A. Dicks.  Advances in catalysts for internal reforming in high temperature fuel cells , 1998 .

[18]  K. Kendall,et al.  SOFC system with integrated catalytic fuel processing , 2000 .

[19]  John T. S. Irvine,et al.  Improved Oxidation of Hydrocarbons with New Electrodes in High Temperature Fuel Cells , 2001 .

[20]  J. Armor,et al.  The multiple roles for catalysis in the production of H2 , 1999 .

[21]  G. Parrour,et al.  Gradual internal reforming of methane: A demonstration , 2006 .

[22]  Robert J. Kee,et al.  Solid Oxide Fuel Cells: Operating Principles, Current Challenges, and the Role of Syngas , 2008 .

[23]  G. Froment,et al.  Methane steam reforming, methanation and water‐gas shift: I. Intrinsic kinetics , 1989 .

[24]  Suk-In Hong,et al.  Internal carbon dioxide reforming by methane over Ni-YSZ-CeO2 catalyst electrode in electrochemical cell , 2002 .

[25]  R. Kikuchi,et al.  Internal Reforming of SOFCs Carbon Deposition on Fuel Electrode and Subsequent Deterioration of Cell , 2007 .

[26]  R. Hughes,et al.  The kinetics of methane steam reforming over a Ni/α-Al2O catalyst , 2001 .

[27]  D. A. G. Bruggeman.  Berechnung verschiedener physikalischer Konstanten von heterogenen Substanzen. I. Dielektrizitätskonstanten und Leitfähigkeiten der Mischkörper aus isotropen Substanzen , 1935 .

[28]  E. Iglesia,et al.  Isotopic and kinetic assessment of the mechanism of reactions of CH4 with CO2 or H2O to form synthesis gas and carbon on nickel catalysts , 2004 .

[29]  Olav Bolland,et al.  Finite-volume modeling and hybrid-cycle performance of planar and tubular solid oxide fuel cells , 2005 .

[30]  K. Kendall,et al.  High temperature solid oxide fuel cells : fundamentals, design and applicatons , 2003 .

[31]  Michael B. Pomfret,et al.  In situ studies of fuel oxidation in solid oxide fuel cells. , 2007, Analytical chemistry.

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

[33]  Kohei Ito,et al.  Performance analysis of planar-type unit SOFC considering current and temperature distributions , 2000 .

[34]  Zhiqiang Ren,et al.  Geometric optimization of a 10-cell modular planar solid oxide fuel cell stack manifold , 2013 .

[35]  I. Dincer,et al.  Thermodynamic modeling of direct internal reforming solid oxide fuel cells operating with syngas , 2007 .

[36]  E. Achenbach.  Three-dimensional and time-dependent simulation of a planar solid oxide fuel cell stack , 1994 .

[37]  R. Gorte,et al.  A study of steam reforming of hydrocarbon fuels on Pd/ceria , 2002 .

[38]  Bengt Sundén,et al.  Review on modeling development for multiscale chemical reactions coupled transport phenomena in solid oxide fuel cells , 2010 .

[39]  J. Guindet,et al.  Gradual Internal Methane Reforming in Intermediate‐Temperature Solid‐Oxide Fuel Cells , 1998 .

[40]  Yixiang Shi,et al.  Modeling of an anode-supported Ni–YSZ|Ni–ScSZ|ScSZ|LSM–ScSZ multiple layers SOFC cell: Part I. Experiments, model development and validation , 2007 .

[41]  Yann Bultel,et al.  Modeling of a SOFC fuelled by methane: From direct internal reforming to gradual internal reforming , 2007 .

[42]  F. Calise,et al.  Design and partial load exergy analysis of hybrid SOFC–GT power plant , 2006 .