Power Equipment and System
YAO Xiangyu, JIANG Huiqing, WANG Ningze, LI Fangqin, ZENG Zhuoxiong, PAN Weiguo
Taking a coal-fired unit of a 600 ℃ ultra supercritical 650 MW power plant as the research object, combined with the overall plan of the coal-fired boiler of the 650-700 ℃ ultra supercritical power plant, the simulation study was conducted on the mixed combustion of NH3 and coal in the boiler by replacing part of the coal with NH3.The temperature and material distribution of NH3 in the furnace at different mixing ratios, as well as the effects of different mixing ratios and NH3 injection ways on NOx emissions were explored. Results show that as the NH3 mixing ratio increases, the flame temperature at the center of the furnace decreases significantly, the high-temperature area reduces, and the flame temperature inside the furnace shows an overall downward trend, this is mainly due to the lower theoretical flame temperature of NH3, which prolongs the low-temperature jet and causes the delay of ignition. At the NH3 nozzle position, the NH3 concentration reaches its peak. As combustion progresses, NH3 is basically consumed, and there will be no ammonia escape at the furnace outlet. Under air staged combustion, the low oxygen concentration in the main combustion zone of the furnace is conducive to the occurrence of NH3 reduction reaction. As the NH3 mixed fuel ratio increases, the NOx emission concentration at the furnace outlet decreases, which results from the reduction reaction between NH3 and NO in the furnace, inhibiting the generation of NO.When NH3 is sprayed into the furnace in different ways, the NOx concentration at the furnace outlet is lower when using the oil gun nozzle for injection. This is because the position of the oil gun nozzle is closer to the main combustion zone.