高温空气低燃气浓度燃烧过程的数值模拟研究

NUMERICAL SIMULATION OF HIGH TEMPERATURE AIR LOW FUEL GAS CONCENTRATION COMBUSTION

从工程实际出发,本文提出了高温空气低燃气浓度燃烧新技术,即充分利用烟气余热提高助燃空气温度,提高热能利用率;同时通过优化喷口结构,提高燃气射流速度,使燃气射流在同空气射流混合燃烧前卷吸大量炉内烟气,从而降低燃气射流中的可燃物浓度,进而降低氮氧化物的排放。通过数值模拟研究表明,通过燃气射流速度从24.56m/s提高到55.26m/s,可以降低NOx的排放;当围绕燃气喷口的六个圆形空气喷口改为两个矩形喷口时,燃气射流可从两侧卷吸更多的炉内烟气,形成低燃气浓度燃烧,从而大大降低了NOx的排放。

Prom the view of engineering application, a new technology of high temperature air low fuel gas concentration combustion is proposed in this paper. In this technology, the air temperature is preheated to very high temperature by the waste heat in exhaust gas, thus the rate of thermal energy utilization is increased. At the same time, the configuration of nozzle is optimized and the fuel gas jet velocity is raised so as to make the fuel gas jet entrain much more flue gas in furnace. Thus the combustible gas concentration in fuel gas is decreased so that NOx emission is reduced. The numerical simulation results showed that NOx emission reduced with the fuel gas jet velocity increasing from 24.56 m/s to 55.26 m/s. In addition, NOx emission reduced drastically if six circle air ports around fuel gas port were converted to two rectangle air ports because the fuel gas jet could entrain much more flue gas before ignition.