Full Cell Mathematical Model of a MCFC

Molten Carbonate Fuel Cells (MCFCs) are used in MW-scale power plants. Recently, they have also been explored for carbon capture. A recent MCFC experimental campaign for carbon capture applications has shown interesting results. It revealed that at carbon capture conditions a secondary reaction mechanism involving hydroxide ions starts to affect cell performance. This is important since part of the electricity produced will be used to transfer water instead of CO 2 , decreasing capture efficiency. Previously, the authors developed a dual-ion model for MCFCs to account for the observed loss of carbon capture efficiency at low-CO 2 cathode gas conditions. A more recent, deeper exploration of MCFC control parameters found that the split between the competing reaction paths depends not only on the cathode gas composition, but also on cathode diffusion resistance. Thus, in this work we increase the applicability range and reliability of the dual-ion electrochemical model by including the diffusion of reactants in the porous cathode along the axis perpendicular to the cell plane. This transport component can account for the shifting of carbonate and hydroxide contributions to the overall cell current as a function of cathode feed properties and for different current collector designs that determine the diffusion resistance term.

Section: Diffusion Modelmentioning

confidence: 99%

The Effects of Gas Diffusion in Molten Carbonate Fuel Cells Working as Carbon Capture Devices

Audasso

Bosio

Bove

et al. 2020

“…Some of them can be found in Ref. 8, but others are necessary to be measured experimentally. In Table I we have listed all these parameters and some data we measured experimentally.…”

Section: Computational Results and Discussionmentioning

confidence: 99%

“…Such behavior is expected because the activation polarization, observed in the low-temperature fuel cell at low current density, vanishes in a high-temperature cell. 8 Power density is defined as the product of the applied current density and the voltage. One sees from the figure that the power density curve against current density is a quasi-parabolic one, which increases initially with the current density, reaches a peak, and then decreases.…”

Section: A610mentioning

confidence: 99%

Lattice Boltzmann Simulation on Molten Carbonate Fuel Cell Performance

Liu

et al. 2006

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...

“…Assuming the equilibrium potentials in the anode reactions are zero, E eq,an,E2 = 0, E eq,an,E4 = 0 [29] then the equilibrium potential in the cathode equals the open circuit voltage of the cell E eq,ca = V OCV [30] where V OCV is the open circuit voltage of the cell. The temperature dependence of the anode exchange current density in Eq.…”

Section: Model Equationsmentioning

confidence: 99%

A Mathematical Model of a Molten Carbonate Direct Carbon Fuel Cell

Song

Xie

Zhang

et al. 2019

A one-dimensional (1D) homogeneous unit cell model was developed to study the performance of the molten carbonate direct carbon fuel cell (DCFC), which uses solid carbon as fuel and molten carbonate as electrolyte. It is the first unit cell model for the molten carbonate DCFC in which both 4-electron carbon oxidation and 2-electron CO oxidation reactions, as well as the reverse Boudouard reaction, are considered. The simulation results verify that, besides the relatively sluggish kinetics of the anodic reactions, cell performance is mainly limited by ohmic losses in the anode. Further modeling exploration reveals that a minimum effective electronic conductivity of around 0.56 S/cm is required to facilitate proper electrical conduction in the cathode to attain high DCFC performance. It was found that there are optimal volume fractions for the carbon fuel and liquid electrolyte in the anode. If the effective electronic conductivity of the cathode falls to 0.56 S/cm, optimal volume fractions also exist for the solid material and liquid electrolyte in the cathode. The detailed modeling analysis showed that performance improvement at high operating temperature was mainly attributed to improvement of anodic kinetics and reduction of ohmic loss in the electrolyte of electrodes and electrolyte matrix.