Study on emission control of NOx and N2O in a fly-ash recycle fluidized bed test rig

Experiments on NOx and N2O release characteristics and emission control were studied in a fly-ash recycle fluidized bed test rig. The total height of the fluidized bed is 4.4m. The fluidization section is 1.2m high with a cross-section 0.23m×0.23m. The freeboard is 3.0m high with a cross-section 0.460m×0.345m. The coal-fired weight of the test rig is 30 kg/h, and coal is fed by a screw feeder. Fine ash is collected by a cyclone and recycled to the bed surface through a J-valve, slag is then removed from the bottom. An oil-fired start-up burner is also used. Test fuels are Xuzhou bituminite and Henan anthracite from China with particle range of 0-8mm. When the bed temperature rises, NOx increases and N2O decreases. At the same temperature, N2O emission of bituminite is less than that of anthracite. While the secondary air ratio reached 15% under staged combustion, NOx emission decreased to 14% and N2O emission decreased to 24%. As the Ca/S molar ratio increases, NOx emission also increases while N2O emission decreases. Ammonia injection decreases NOx emission significantly, but it has no effect on the emission of N2O.