Hydrogen production in microchannel methanol steam reforming reactors

Abstract

Many attempts have been made to improve heat transfer for thermally integrated microchannel reforming reactors. However, the mechanisms for the effects of design factors on heat transfer characteristics are still not fully understood. This study relates to a thermochemical process for producing hydrogen by methanol steam reforming in a microchannel reactor. Computational fluid dynamics simulations are conducted to understand the consumption, generation, and exchange of thermal energy between endothermic and exothermic processes in the reactor. The effects of wall heat conduction properties and channel dimensions on heat transfer characteristics and reactor performance are investigated. A thermodynamic analysis is performed based on specific enthalpy to understand the evolution of thermal energy in the reactor. The results indicate that the thermal conductivity of the channel walls is fundamentally essential. Highly thermally-conductive solids are preferred for the channel walls. Wall materials with poor heat conduction properties degrade the reactor performance. Reaction heat flux profiles are considerably affected by channel dimensions. The peak reaction heat flux increases with the channel dimensions while maintaining the flow rates. The change in specific enthalpy is positive for the exothermic reaction and negative for the endothermic reaction. The change in specific sensible enthalpy is always positive. Design recommendations are made to improve thermal performance for the reactor.