Lattice Boltzmann Simulation on Molten Carbonate Fuel Cell Performance

Abstract

Based on a model of a porous electrode, we make a detailed numerical simulation on molten carbonate fuel cell ͑MCFC͒ performance by using the lattice Boltzmann method ͑LBM͒. We apply Brinkman-Forchheimer-extended Darcy equations ͑gener-alized momentum equation͒ together with a reaction-diffusion equation with several reasonable assumptions and, to simulate more realistic physical conditions, we consider a curved boundary lying between the nodes of equal lattice space. As an attempt to assess the validity and efficiency of our model, two benchmark problems are investigated, including ͑i͒ the calculation of the dependence of generated current density on averaged gas velocity and the comparison between the result obtained by the LBM and by some other analytical solutions; ͑ii͒ the comparison between the result by the LBM calculation and the one by measuring experimentally the current density of test series in an overall range of H 2 concentration. An excellent agreement is found between the results from the LBM calculation and those from the experiment. In addition, the dependence of CO 2 removal rate on current density, the contributions of CO 2 concentration and O 2 concentration on cell performance, and the relations of cell voltage and power density with current density ͑load͒ are also studied.The molten carbonate fuel cell ͑MCFC͒ is an electrochemical power generator with potential applications for attaining very high electrical energy conversion efficiency while operating quietly with minimal polluting emissions. In such a cell, the cathode is NiO, the anode is Ni, and the electrolyte is a carbonate compound of alkaline metals ͑Li 2 CO 3 , K 2 CO 3 , etc.͒. Efficiency ranges from 60 to 80%, and operating temperature is about 650°C. Units with output up to 2 MW have been constructed, and designs exist for units up to 100 MW. Considerable research and development of MCFC have been carried out mainly in the United States, Japan, and Europe. A successful application of MCFC requires accurate prediction of unitcell performance and operation characteristics. Generally, MCFC operation can be characterized as fluid transport and transformation of species by an electrochemical reaction. Numerical computation is used to realize the quantizing prediction, emulation, and analysis of MCFC performance under a large range of operation and different transient conditions.Usually, numerical models for MCFC can be categorized into two classes: microscopic ͑porous-electrode models͒ and macroscopic ͑cell-performance models͒. 1,2 In this work, we focus on porous-electrode model. Note that two well-known porous-electrode models have been derived for MCFC. They are the thin-film model 3 and the agglomerate model. 4 Fontes et al. 5 presented a steady-state agglomerate model for a MCFC cathode, which takes into account the heterogeneous structure of a porous electrode. In their approach, the resulting model equations were solved by means of a finiteelement method, but their simulation results were limited to a small agglomerate. Two ye...

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