The gas-phase reaction NO-NH3-O-2 was investigated in a tubular flow reactor at a pressure of 788 kPa and temperatures from 650 to 850 degrees C. Injection of ammonia into a 2MWthPFBC combustor was also attempted, and it was found that 55% of NO was converted to N-2 at 855 degrees C with an NH3/NO molar ratio of 2 and residence time of 1.4 s. In the combustor, the nitric oxide concentration could be reduced to less than 70 ppm, and leakage of ammonia was kept below 5 ppm at the full load. During the load change operation in the combustor, nitric oxide was decreased as the load became higher when the ammonia injection was controlled by the prediction method.