煤粉炉SNCR对SO3生成影响的数值模拟

Numerical simulation on formation of SO_3 during SNCR process in pulverized coal-fired boiler

基于详细化学反应机理,利用CHEMKIN-PRO软件中的平推流反应器研究了选择性非催化还原(SNCR)脱硝过程对SO_3生成作用,以及烟气中SO_2、NO、O_2和H_2O的体积浓度对SO_3生成量的影响。结果表明,氨的注入改变了SO_3生成机理和主要路径,明显促进烟气中SO_2向SO_3氧化。在NH_3的体积浓度为300μl·L^(-1)、SO_2的体积浓度为2000μl·L^(-1)、停留时间1.9 s内温度从1373 K降低至573 K时,生成的SO_3体积浓度大于10μl·L^(-1)。随着SO_2体积分数的降低,生成的SO_3体积浓度减小,但转化率有所增加;此外生成的SO_3体积浓度随O_2体积浓度、NO体积浓度和停留时间的增加而增加,随着H_2O体积浓度的增加而减小。燃用高硫煤时,SNCR对SO_3的生成作用必须给予重视。

A numerical investigation on the formation of SO3 during selective non-catalytic reduction （SNCR） process and the influences of the concentrations of SO2, NO, 02, and H20 were performed using the plug flow reactor of the CHEMKIN-PRO software with a detailed chemical kinetic mechanism. The simulation results showed that the presence of NH3 changed the formation mechanism and reaction pathway of SO3 and noticeably enhanced the formation of SO3. When the reaction temperature decreased from 1373 K to 573 K within 1.9 s residence time with inlet NH3 concentration being 300 μl·L-1 and inlet SO2 concentration being 2000 μl·L^-1, the formation concentration of SO3 was above 10 μl·L^-1. The SO3 concentration decreased while SO3/802 conversion ratio slightly increased with increasing inlet concentration of SO2. Meanwhile, SO3 concentration increased with increasing inlet concentrations of 02 and NO, and decreased with increasing H20 inlet concentration in the flue gas. Based on the study, the formation of SO3 during SNCR process should be paid attention when high sulfur coal was burned.