Homogeneous Combustion of Fuel Ultra-Lean Methane–Air Mixtures: Experimental Study and Simplified Reaction Mechanism

Abstract

The use of ventilation air methane (VAM) has attracted more and more attention in recent years. The experimental investigation on homogeneous combustion of fuel ultra-lean methane–air mixtures is carried out in reactors packed with and without a monolith. The experimental results show that the methane oxidation follows a consecutive reaction scheme. In the reaction process, although a little CH4 may be directly oxidized to CO2 at low temperatures, most CH4 is oxidized to CO as the intermediate product and then further oxidized to CO2 at high temperatures. The present experimental results also show that the presence of a monolith has an obvious effect on the combustion of methane. The methane combustion can be enhanced by both expanding the specific surface area and decreasing the diameter of the monolith channel. However, an extremely small diameter may lead to the quenching of combustion. Moreover, it is found that the effect of homogeneous combustion cannot be neglected for the catalytic flow reversal reactor (CFRR) at high temperatures. On the basis of the analysis of the present experimental data, a simplified two-step consecutive mechanism is developed and the kinetic parameters are determined to describe the methane combustion in an empty reactor and a reactor packed with a monolith. The present research is helpful for understanding the reaction mechanism for VAM use.