Design of a Porous Burner for the Oxidation of Methane in Mine Ventilation Air

One of the major greenhouse gas emissions from modern coal mines is the methane in the mine ventilation air (MVA). MVA emissions are characterised by very low methane concentrations (typically less than 1%) and high flow rates, with significant fluctuations in both concentration and flow. These attributes constitute the major technical barriers to the capture and use of the methane in MVA, and, consequently, a cost effective mitigation technique has yet to be proven. A porous burner, in which combustion is stabilised within the pores of a ceramic or metallic matrix, has the ability to burn lean fuel/air mixtures. Furthermore, the combustion process is comparatively stable against changes in fuel concentration and flow rate. In this paper we describe the design of a porous burner that will be used to assess the suitability of this technology for the oxidation of methane in MVA. The burner comprises a combustion chamber filled with a porous bed of alumina saddles, combined with an arrangement of external heat exchanger tubes for preheating the incoming fuel/air mixture. An even flow distribution is required for the burner to operate effectively with very lean fuel/air mixtures. The burner design was optimised using a computational fluid dynamics (CFD) model that was developed primarily to simulate the flow at the burner inlet.