Theoretical calculations and CFD simulations of membrane reactor designs

Abstract

Membrane reactors are promising for enabling various reactions that are thermodynamically-limited. Yet research into their design is often performed on a case-by-case basis; also, no general but quantified analysis has been conducted on the selection and matching of suitable membranes for reactions. In this study, we first introduce two dimensionless numbers, – namely the Damköhler (Da) and Péclet (Pe) numbers. We then develop the relationship of equilibrium constant-conversion-DaPe in a general form for membrane reactors, which incorporates the parameters of the operating conditions and reaction stoichiometric coefficients. To exemplify the relationship, it is applied to the reactions of the dry reforming of methane and reverse water gas shift using theoretical calculations. Subsequently, an analysis of the compatibility of the reaction kinetics and permeation flux, as well as the effects of reactor geometry characteristics is performed by means of CFD simulations. Finally, we discuss the relationship of the stoichiometric coefficient and conversion enhancement. Beyond the contribution to conversion enhancement by the operating conditions, it is informed that the contribution of the stoichiometric coefficient should also be effectively leveraged in order to achieve higher conversion enhancement, especially for reactions that feature higher equilibrium constants. The relationships derived in this study deliver insights into the selection and matching of membranes for a given reaction prior to detailed designs being developed.