Combustion characteristics of low-concentration coal mine methane in ceramic foam burner with embedded alumina pellets

Ceramic foam as a rigid matrix is difficult to be embedded with various shapes of heat exchange tubes. In this paper, a ceramic foam burner with embedded alumina pellets was designed, which can set different shapes of tubes by taking advantage of the discrete pellets. An experimental system was built to study the effects of the pellet diameter and pellet location on the combustion of low-concentration coal mine methane (LCM). Results indicate that the heat transfer features of 13-mm pellets are more similar to those of 10-PPI ceramic foam compared with 6-mm pellets and 9-mm pellets. When arranged in upper section of the burner, the 13-mm pellets preserve the combustion heat, which helps to move the flame stabilization position to the upstream of the burner. In addition, the start-up time in the burner with the upper 13-mm pellets is longer than that with the intermediate 13-mm pellets. The total NOx emissions of the studied burners are improved with the increasing inlet velocity, while the CO emissions first decrease and then increase. The HC emissions of the ceramic foam burner with embedded pellets are between those of the pellet burner and the ceramic foam burner.