Methane Diffusion and Carbon Deposition in Cermet Anode of Internal Reforming Solid Oxide Fuel Cell

Natural gas appears to be a fuel of great interest for solid oxide fuel cell (SOFC) systems. It mainly consists of methane, which can be converted into hydrogen by direct internal reforming (DIR) within the SOFC anode. However, a major limitation to DIR is carbon formation within the ceramic layers at intermediate temperatures. This paper proposes a model solution using the CFD-ACE software package to simulate the behavior of a tubular SOFC. A detailed thermodynamic analysis is carried out to predict the boundary of carbon formation for SOFCs fueled by methane. Thermodynamic equilibrium calculations that take into account Boudouard and methane cracking reactions allow us to investigate the occurrence of carbon formation. This possibility is discussed from the values of driving forces for carbon deposition defined as α=PCO2∕(KBPCO2) and β=PH22∕(KCPCH4), from the equilibrium constants KB and KC of the Boudouard and cracking reactions, and from the partial pressure Pi of species i. Simulations allow the calculation of the distributions of partial pressures for all the gas species (CH4, H2, CO, CO2, and H2O), current densities, and potentials of both electronic and ionic phases within the anode part (i.e., gas channel and Cermet anode). Finally, a mapping of α and β values enables us to predict the predominant zones where carbon formation is favorable (α or β<1) or unfavorable (α or β>1) according to the calculation based on thermodynamic equilibrium. With regard to the values of these different coefficients, we can say that a carbon formation can be supposed for temperature less than 800°C and for ratios xH2O∕xCH4 smaller than 1.

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Improve electrical conductivity of reduced La 2 Ni 0.9 Fe 0.1 O 4+δ as the anode of a solid oxide fuel cell by carbon deposition

International Journal of Hydrogen Energy ◽

10.1016/j.ijhydene.2015.06.026 ◽

2015 ◽

Vol 40 (31) ◽

pp. 9783-9789 ◽

Cited By ~ 23

Author(s):

Ping Li ◽

Yicheng Zhao ◽

Baolong Yu ◽

Jiang Li ◽

Yongdan Li

Keyword(s):

Electrical Conductivity ◽

Fuel Cell ◽

Solid Oxide Fuel Cell ◽

Carbon Deposition ◽

Solid Oxide ◽

Oxide Fuel

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Application of an Anode Model to Investigate Physical Parameters in an Internal Reforming Solid-Oxide Fuel Cell

Journal of Fuel Cell Science and Technology ◽

10.1115/1.1895925 ◽

2005 ◽

Vol 2 (2) ◽

pp. 136-140 ◽

Cited By ~ 8

Author(s):

Eric S. Greene ◽

Maria G. Medeiros ◽

Wilson K. S. Chiu

Keyword(s):

Fuel Cell ◽

Solid Oxide Fuel Cell ◽

Structural Parameters ◽

Porous Electrode ◽

Cell Voltage ◽

Solid Oxide ◽

Physical Parameters ◽

Oxide Fuel ◽

Internal Reforming ◽

Porous Anode

A one-dimensional model of chemical and mass transport phenomena in the porous anode of a solid-oxide fuel cell, in which there is internal reforming of methane, is presented. Macroscopically averaged porous electrode theory is used to model the mass transfer that occurs in the anode. Linear kinetics at a constant temperature are used to model the reforming and shift reactions. Correlations based on the Damkohler number are created to relate anode structural parameters and thickness to a nondimensional electrochemical conversion rate and cell voltage. It is shown how these can be applied in order to assist the design of an anode.

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