Simulation of exhaust gas reforming of natural gas in a microchannel reactor

Abstract

The present work is aimed to conduct modeling and simulation of exhaust gas reforming of natural gas in a catalytic microchannel reactor. Natural gas, an alternative fuel that can be used in internal combustion engines in compressed form, is modeled as methane only and methane/propane mixtures. The multichannel reactor is composed of a cordierite block with parallel channels, each of which is washcoated with Rh/Al2O3 catalyst. Due to the low thermal conductivity of cordierite, heat transfer between the channels is neglected, and a single, adiabatic microchannel is considered as the modeling domain representing the behavior of the multichannel unit. Two dimensional continuity and conservation equations for the fluid and porous washcoat phases are solved by the finite volume method using the ANSYS Fluent platform. Effects of feed temperature, fuel compositions (i.e. molar inlet steam-to-carbon (H2O/C) and oxygen-to-carbon (O2/C) ratios) and presence of propane in natural gas on temperature and product distribution are investigated in the context of a parametric study. It is observed that temperature is well distributed along the channel and no notable hot spot formation is observed. Increasing feed temperature favors methane conversion and hydrogen production, but results in less uniform temperature distribution. Feeding higher amounts of steam increases hydrogen formation, but slightly dampens methane conversion. Increasing O2/C ratio at the inlet results in a proportional increase in methane conversion and temperature. Even though channel temperature is found to decrease, hydrogen production is favored upon using methane/propane mixture as the fuel.