Modelling and simulation of microchannel catalytic WGS reactor for an automotive fuel processor

Abstract

The water-gas shift (WGS) is one of the major steps for H2 production from gaseous, liquid and solid hydrocarbons. It is used to produce hydrogen for ammonia synthesis, to adjust the hydrogen-to-carbon monoxide ratio of synthesis gas, to detoxify gases. The WGS reactor is widely used as a part of fuel processors which produce hydrogen-rich stream from hydrocarbon-based fuels in a multi-step process. The WGS unit is placed downstream the fuel reformer in order to increase overall efficiency of hydrogen production and to lower CO content in reformate. Fuel processors stand for considerable option for fuelling PEM fuel cells for both portable and stationary applications. Micro-structured reactors are used with benefits of process miniaturization, intensification and higher heat and mass transfer rates compared with conventional reactors. Micro-structured reactor systems are essential for processes where potential for considerable heat transfer exists as well as for kinetic studies of highly exothermic reactions at near-isothermal conditions. Modelling and simulation of a microchannel reactor for the WGS reaction is presented. The mathematical models concern a single reaction channel with porous layer of catalyst deposited on the metallic wall of the microstructure unit. Simplified one-phase and more sophisticated two-phase models, with separate mass and energy balances for gas and solid phase at different levels of complexity, were developed. The models were implemented into gPROMS process modelling software. The models were used for an estimation of parameters in a kinetic expression using experimental data obtained with a new WGS catalyst. The simulations provide detailed information about the composition and temperature distribution in gas phase and solid catalyst inside the channel.