(729a) Kinetic Models for Direct Carbon Fuel Cell Anode | AIChE

(729a) Kinetic Models for Direct Carbon Fuel Cell Anode

Authors 

Parulekar, S. - Presenter, Illinois Institute of Technology
Peng, F., Illinois Institute of Technology
Li, Y., Illinois Institute of Technology
Selman, J. R., Illinois Institute of Technology



Direct carbon fuel cells (DCFCs), which use solid carbon as fuel and molten carbonate as electrolyte, have generated renewed attention recently because of their potentially high conversion efficiencies and convenience for CO2 capture and sequestration. Although the primary anodic reaction is believed to be a four-electron carbon oxidation reaction, to explain the performance of the DCFC in practice, it is also necessary to consider the two-electron carbon oxidation reaction as well as the dissociation equilibrium reaction of CO32- to O2-. A one-dimensional macro-homogeneous model of slurry-based carbon anode was developed taking into account diffusion of dissolved gases, multiple electrochemical and chemical reactions, and electronic and ionic conduction. The model describes detailed operation of the anode, expressed in terms of profiles of ionic and electronic currents, local potentials, and overvoltage, and rates of key reactions.  The result shows that the active zone is mostly located on the portion of the gas phase, while the concentrations of dissolved gas (CO2 and CO) nearest the anode current collector are at the highest. The concentrations of CO2 and CO are supersaturated in this model.

The analysis of the dimensionless resistances suggests the DCFC anode is mainly limited by the mass transfer losses and the sluggish kinetics of the anodic reactions. The effects of specific surface area, electrical conductivity of carbon, length of anode, and pore volume fraction on distributions of carbon efficiency, cell polarization and power density were studied in detail to optimize the design of DCFC. The maximum power density and optimal current density were identified for various model parameters.

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