Measurements of reduction of NO supplied with the primary air in grate combustion of biomass fuel.

摘要

This report is a preliminary study of reducing NO in diesel exhaust by using the exhaust gases as combustion air in a grate fired furnace using biomass fuel. The experiments were performed at the Section of Combustion Technology at the National Defence Research Institute in a small scale batch fired furnace. In the experiments the diesel exhaust was simulated by adding NO to the primary air supplied through the grate. Gas samples were continuously collected in the bed during the combustion of the fuel and the gas was analysed for NO, CO, CO2 and O2. Experiments performed without NO injection show that the concentration of NO formed by combustion increases with increasing bed region air ratio, from 27 ppm NO at a bed region air ratio of 0.5 to 109 ppm at an air ratio of 1.5. When 1000 ppm NO was added to the primary air the NO-concentration was reduced to 200 ppm at a bed region air ratio of 0.5. At an air ratio of 1.5 the reduced NO concentration was 700 ppm. The experiments with 2000 ppm NO added to primary air show similar results as those with 1000 ppm added. Four types of fuels were used: coniferous chips, birchwood chips, soft wood blocks and bark/wood pellets. No differences in NO reducing capability for the different fuels could be observed. The results of the preliminary test are promising and future experiments in a full scale continuously fired reactor are recommended. (2 refs., 26 figs., 6 tabs.).