Evaluation of the application of different diffusion models for the methanation of CO/CO2 mixtures

Abstract

CO/CO2-Methanation can contribute to the storage of intermittently produced renewable energy. In order to be able to design this heterogenous catalytic process well with models, a solid diffusion model is necessary. Thus, the effects of diffusion model selection are simulated in this context under steady-state and unsteady-state conditions. Therefore, the dusty gas and the Wilke-Bosanquet model are compared with the binary friction model. The operation conditions are varied over a wide range to achieve general validity of conclusions. It is shown that all diffusion models lead to similar results for high Knudsen numbers and for steady-state conditions. Under unsteady-state conditions in porous catalyst pellets with low Knudsen numbers, however, the results differ and thus the binary friction model is recommended. Although the simulations were carried out with methanation as an example reaction, the results are transferable to comparable heterogeneously catalyzed gas phase reactions.