Experimental study of a staged methane/air burner based on combustion in a porous inert medium

Further decreases in NOx. emissions from burner systems, in particular domestic heating systems, Stirling engines, gas and steam turbines, and so forth, are of enormous interest at present. Staged combustion in inert porous media offers a high potential to meet the operational and environmental requirements for those applications. A special experimental facility was built to study the behavior of staged combustion in porous inert media. The construction allows investigations of the effects of staging with pure methane or air by measuring the temperatures in the combustion region. In addition, the emissions of NOx COx and CH4 were measured in the flue gases to establish how the thermal heat load, the staged quantity and the air ratio affect them. For certain staged quantities and overall air ratios, the pollutant emissions lie in an optimal range. The results show that the NOx emissions can be decreased by approximately 30-40% for the same overall air ratio in comparison with the case without staging. Two different porous media used-an alumina fabric lamella structure and an SiC foam-show that the characteristics of the pollutant emissions are only slightly dependent on the porous medium. Another result is that in the staged mode, the combustion can be kept stable at higher primary air ratios.