Characteristics of ignition on the sand layer combustion

To gain further understanding of the combustion in a sand layer of fluidized bed, the characteristics of methane-air premixed gas combustion in a packed sand bed were studied according to the equivalence ratio and the sand temperature. CO₂ concentrations increased at > 950°C for equivalence ratios of 0.2:1-2.5:1. The sand temperature also increased after supplying the fuel at > 950°C. Thus, combustion in the sand started at > 950°C. The sand temperatures for stable combustion were the same for each equivalence ratio and combustion occurred without flammability limit. CO concentration increased significantly at ∼ 900°C. A simple numerical simulation showed that the residence time of the gas in the tube was closely equal to the reaction delay time, which strongly depends on the gas temperature. Thus, to start reactions including the CO generation probably depend on the temperature and residence time of the gas in sand layer. This is an abstract of a paper presented at the 30th International Symposium on Combustion (Chicago, IL 7/25-30/2004).