Abstract
High temperature air gasification of sludge was carried out in the entrained down flow gasifier. Sludge gasification performance, such as carbon conversion, gasification rate and cold gas efficiency, was evaluated compared with the performance of the woody biomass gasification. Dried sludge, sieved 60 mesh, was injected from the top of the gasifier with air, and the gasification experiment was conducted over 1300 K. Feeding rate of the sludge was controlled around 25 kg/h during the experiment, but the air ratio was changed as an operation parameter. Temperature profile in the gasifier was significantly different between the sludge and the wood. While the temperature at the bottom section of the gasifier was stable in the sludge gasification, the temperature gradually decreased at the bottom section in the woody biomass gasification due to the endothermic CO2 gasification reaction. Since the gasification rate of the sludge was slower than that of the woody biomass, the carbon conversion of the sludge was less than that of the wood, which was around 70 %, while 100 % of the carbon conversion was achieved in the woody biomass gasification. Tar components produced from the sludge were not able to decompose completely even in the high temperature gasification operation due to the slow sludge decomposition. Significant difference was also found in the collected ash and the high ash content sludge built huge slags on the gasifier wall during the high temperature gasification.
