Combined non-catalytic reduction of NOx and SO2 by ammonia liquor during staged fluidized-bed combustion

Emissions of NOx and SO2 were monitored in the presence of ammonia liquor i n a 0.09 m(2) and 2 m high stainless-steel fluidized-bed combustor. Experim ents were carried out at 2 m/s fluidizing velocity, 40% excess air, and 870 degrees C bed temperature. Ammonia liquor with 7% ammonia by weight was in jected into the freeboard of the combustor 52 cm above the distributor thro ugh a water-cooled injector. A 65 : 34 primary/secondary air ratio was main tained throughout the investigation. Approximately 70% of NO and 20% of SO2 was reduced at an NH3/NO molar ratio of 2 : 1, respectively. However, a hi gher reduction in SO2 emissions (62%) was achieved at a very high NH3/NO mo lar ratio of 7 : 1. These experiments showed that ammonia addition did have a significant effect in SO2 reduction if injected in an excess amount. The injection of ammonia liquor combined with staged combustion was found to b e very effective in reducing NOx emissions. A reduction of about 50% was ac hieved at an NH3/NO molar ratio of 0.6 : 1 which is also coupled with a ver y low level of ammonia in the flue.