Numerical investigation on the transient characteristics of hydrogen production from catalytic autothermal reforming of methane in a micro combustor with multiple cylinders

•A cube micro combustor with multiple cylinders is developed.•This paper studies the transient characteristics of autothermal reforming of methane.•Reaction time reaching steady state is less affected by mixture gas composition.•Reaction time reaching steady state decreases with increasing wall temperature.•Inlet velocity of mixture gas has a significant effect on methane conversion rate.

The transient characteristics of autothermal reforming of methane in a cube micro combustor with multiple cylinders are numerically investigated. The effects of mixture gas composition, catalytic wall temperature and inlet velocity of the mixture feed gas on autothermal reforming of methane are thoroughly discussed. The results demonstrate that the yield of hydrogen decreases and the time to steady state slightly decreases with the increasing of steam content at a constant O2/CH4 molar ratio, while the yield of hydrogen decreases and the time to steady state slightly increases with the increasing of oxygen content at a constant H2O/CH4 molar ratio. Methane conversion significantly increases with the increasing of catalytic wall temperature, meanwhile, the reaction time to steady state sharply decreases, which are 61 ms and 29 ms at 790 K and 1190 K, respectively. The flow velocity has a determined influence on autothermal reforming of methane. As the velocity decreases from 0.5 m/s to 0.05 m/s, methane conversion increases from 62.60% to 98.88% and the yield of hydrogen increases from 56.21% to 90.48%. Higher inlet velocity leads to short residence time, which may not be sufficient to complete the reaction.