CFD modelling and simulation of a zeolite catalytic membrane reactor for low temperature water-gas shift reaction

Abstract

In this work, a catalytic membrane reactor is proposed to couple water-gas shift reaction with selective separation of H2 product to improve the overall conversion. A 3D isothermal CFD model of this catalytic membrane reactor is developed with COMSOL Multiphysics software. The effects of reaction temperature, pressure, sweep gas flow rate and reactor geometry on CO conversion and H2 recovery are analysized in details. Based on the results, the coupling mechanism of reaction, and H2 permeation is proposed. It is found that that the catalyst bed could be divided into active and less-active volume and reducing less-active volume helps improve the utilization efficiency of catalyst. As a conclusion, H2 permeation directly affects H2 mole fraction in near-membrane area, and the effect is spreaded to the rest part to boost the local reaction rate. However, the effect is neutralized by the improved H2 production and permeation affecting volume is mainly less-active volume while active volume is hardly to be affected. Our study indicates that H2 permeation tends to deplete H2 fraction in catalyst volume but the consequent improved reaction rate acts as a resistance and tends to move back to a new steady state.