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By Vinod Janardhanan

This booklet lays out a numerical framework for the distinct description of heterogeneous chemistry, electrochemistry and porous media delivery in solid-oxide gas cells (SOFC). Assuming hydrogen because the purely electrochemically lively species, a changed Butler-Volmer equation is used to version the electrochemical cost move.

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Additional info for A detailed approach to model transport, heterogeneous chemistry, and electrochemistry in solid-oxide fuel cells

Example text

64] the multi-step mechanism was evaluated only for 800°C. In work presented in this thesis, the mechanism have been extended to wider temperature ranges (500°C-1800°C) and is listed in the appendix. Though the mechanism is elementary like in nature it covers the global aspects of steam reforming, dry reforming, water-gas shift, reverse water-gas shift and C deposition. The reaction mechanism consists of 42 irreversible reactions among 6 gas-phase species and 12 surface adsorbed species. 1), and some of the activation energies are coverage dependent.

1), and some of the activation energies are coverage dependent. 24) Af ∆S = exp . 25) However, the mechanism has not been specifically validated for conditions where coking and bulk-phase Ni oxidation occur. Accurate prediction of surface carbon is essential for precise calculation of open circuit potentials for SOFCs operating on hydrocarbon fuels. Furthermore, the redox stability of Ni under SOFC operating conditions is also a major concern for long term stable operation of SOFCs. Therefore, work remains to be done in validating the mechanism for C deposition and incorporating steps that account for the redox state of the catalyst surface.

The net molar production rate s˙k of a gaseous species or a surface adsorbed species due to heterogeneous reaction can be written as Kg +K s +Kb Ns [Xk ]νki . 4) where k fi is the rate constant for the i’th reaction, µki and ki are the parameters modeling the coverage dependency of rate constant for the i’th reaction, and θk is the surface coverage of the kth species. 5) where p0 is the standard state pressure and K pi is the equilibrium constant calculated by K pi = exp ∆S i0 ∆Hi0 − . 5 follows from the definition of Kci and K pi as Kci = Kg +K s νki k=1 [Xk ] , Kg +K s νki [X ] k k=1 K pi = Kg 0 νki k=1 (pk /p ) Kg 0 νki k=1 (pk /p ) Kg +K s νki k=kg +1 θk Kg +K s νki k=kg +1 θk .

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