Modelling of non-catalytic gas–solid reactions – multicomponent non-equimolar counter diffusion of gaseous phase

Abstract

Mathematical modelling of non-catalytic gas–solid reactions was carried out based on the grain model in terms of non-equimolar counter diffusion of gaseous phase in the solid matrix. By justifying the model parameters, the model can be used for reactions involving volume change between gaseous products and gaseous reactants. The grain model was used in the present work. The model was used for studying the reduction of chromium oxide with methane in the formation of chromium carbide. By justifying the diffusion coefficient of reactant methane through the product layer around the grains, the simulation results showed a good fit with experimental data. A MATLAB m-file has been developed to simulate the gas–solid reactions under unsteady state condition in the gas phase and by considering mass transfer resistances in gas phase outside the solid and through the product layer around the grains for different orders of reaction. Transport equations were solved numerically by using finite volume technique in the implicit form. After parameter justification, the model was used for studying effect of different parameters on the conversion of the reaction. The model shows a good fit to experimental data and can be used for studying the sensitivity analysis for such reactions.