Thermodynamic Study of the Humidity Ratio for Methane Reforming at Low Temperature in a Micro-Combustor

Abstract

To realize the stable combustion of methane in a micro-combustor it is necessary to investigate the influence of the humidity ratio on the reforming system for methane-wet air reforming.Thus,we studied the effects of the humidity ratio on carbon deposition,methane conversion,H2 production,and the reaction process under lean oxygen below 973 K and at 0.1 MPa theoretically with a constant air-methane ratio or feed gas flux using thermodynamic analysis.Results show that carbon deposition always decreases with a humidity ratio increase at a certain methane mass flow in the micro-combustor.In contrast,the methane conversion ratio decreased initially and then increased while the H2 yield always increased.The main product of methane conversion is CO2.The CO selectivity increases initially and then decreases while the CO2 selectivity always increases with an increase in the humidity ratio.Furthermore,the amount of consumed steam will finally increase to more than the amount of generated steam during the reaction process with an increase in the humidity ratio,which also leads to an increase for steam after the reaction.When the amount of steam is less than the air in the feed gas,a steam consumption-dominant system is always obtained upon varying the steam mass fraction before and after the reaction when the humidity ratio reaches 280 g·kg-1.Additionally,it is beneficial to reduce the carbon deposition and to promote reforming during the reaction process when the humidity ratio is higher than 350 g·kg-1.By meeting the humidity ratio conditions mentioned above a higher methane conversion ratio and H2 yield can be obtained under a constant air-methane ratio condition.