高温、痕迹氧气氛下NH_(3)-NO_(x)还原反应的机理模拟研究

Mechanism Simulation of NH_(3)-NO_(x)Reactions within Atmosphere of High Temperatureand Trace Oxygen in Pulverized Coal Fired Furnace

煤粉电站锅炉中利用空气分级创造还原区,在还原区中喷射氨气也可有效降低NO_(x)浓度,即分级火焰中喷氨脱硝技术。利用Chemkin软件,模拟还原区的高温、痕迹氧气氛下NH_(3)-NO_(x)的基元反应体系,并进行解析。研究结果表明:(1)基于4篇文献中喷氨脱硝的实验数据,Chemkin模拟结果与之有较好的符合;(2)随着O_(2)浓度的降低,NH_(3)-NO_(x)还原反应的温度区间由800~1150℃向800~1600℃倾斜;(3)在高温、痕迹氧气氛下,脱硝还原的3个关键反应是CO_(2)+H=CO+OH,OH+NH_(3)=NH_(2)+H_(2)O,NH_(2)+NO=NNH+OH。在高温缺氧的气氛下,CO_(2)引起了不分支链锁还原反应的启链作用。研究所获得的机理模型可用于火焰喷氨CFD模拟中。

The air staging technology is useful to form reduction zone in the pulverized-coal-fired boiler.The high temperature and trace oxygen occur in the reduction zone,where the ammonia injection has a certain effect on controlling NO_(x)emission,as named Reagent Injection in Staged Flame technology.The Chemkin software was used to investigate the elementary reaction system of NH_(3)-NO_(x).The research results include:1)the simulation results of Chemkin are in good agreement with the measured data in four reported literature.2)With the decrease of O_(2)concentration in flue-gas,the temperature window of NH_(3)-NO_(x)reduction reaction is inclined from 800-1150℃to 800-1600℃.3)There are three key reactions of high-temperature SNCR,e.g.CO_(2)+H=CO+OH,OH+NH_(3)=NH_(2)+H_(2)O,NH_(2)+NO=NNH+OH.Within lower oxygen atmosphere,CO_(2)plays an essential role to start the non-branching chain reactions in higher temperature.The obtained kinetic description could be used in the CFD modeling.