Abstract:

A numerical investigation on the formation of SO₃ during selective non-catalytic reduction (SNCR) process and the influences of the concentrations of SO₂, NO, O₂, and H₂O 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/SO₂ conversion ratio slightly increased with increasing inlet concentration of SO₂. Meanwhile, SO₃ concentration increased with increasing inlet concentrations of O₂ and NO, and decreased with increasing H₂O 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.

Key words: selective non-catalytic reduction, ammonia, sulfur dioxide, sulfur trioxide, plug flow reactor

摘要：

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SO₃生成作用，以及烟气中SO₂、NO、O₂和H₂O的体积浓度对SO₃生成量的影响。结果表明，氨的注入改变了SO₃生成机理和主要路径，明显促进烟气中SO₂向SO₃氧化。在NH₃的体积浓度为300 μl·L^-1、SO₂的体积浓度为2000 μl·L^-1、停留时间1.9 s内温度从1373 K降低至573 K时，生成的SO₃体积浓度大于10 μl·L^-1。随着SO₂体积分数的降低，生成的SO₃体积浓度减小，但转化率有所增加；此外生成的SO₃体积浓度随O₂体积浓度、NO体积浓度和停留时间的增加而增加，随着H₂O体积浓度的增加而减小。燃用高硫煤时，SNCR对SO₃的生成作用必须给予重视。

关键词: 选择性非催化还原, 氨, 二氧化硫, 三氧化硫, 平推流反应器