全烟道宽度SCR烟气混合器在对冲锅炉上的应用研究

Application Research of Full-width SCR Flue Mixer for Opposed Firing Boiler

某前后墙对冲燃烧锅炉SCR烟气脱硝系统配置的涡流盘型氨喷射系统的负荷适应性差,不同负荷下的局部氨逃逸峰值浓度过大,导致空气预热器硫酸氢铵堵塞严重。基于烟气强制混流机理,设计了含小分区格栅型氨喷射系统和全烟道宽度混合器的优化改造方案,并在该SCR系统上进行了应用。CFD模拟结果表明:在机组高、中和低负荷下,优化方案的顶层催化剂上部截面氨氮摩尔比分布相对标准偏差CV值分别为4.5%、3.8%和1.4%,高负荷下系统阻力仅增加130 Pa。改造工程现场测试结果显示,不同负荷下的SCR脱硝反应器出口NOx浓度分布CV值为10.5%、9.2%和7.9%,喷氨系统具有良好的全负荷适应性。

The ammonia injection with vortex mixer of SCR system in an opposed firing boiler has poor load adaptability and the concentration of ammonia escape is too high under different loads,causing serious ammonium hydrogen sulfate blockage of air preheater.Based on the forced mixing principle of flue gas,the optimization scheme of ammonia injection system with small partition grid and full flue-width mixer is designed and applied in the SCR system.CFD simulation results show that the CV values of NH3/NO molar ratio distribution in upstream section of top catalyst under high,medium and low load conditions are 4.5%,3.8% and 1.4% respectively,and the resistance of SCR denitrification unit increases by only 130 Pa at high load.The test results of reconstruction project show that the CV values of NOx concentration distribution at the outlet of SCR reactor under different loads are 10.5%,9.2% and 7.9%,respectively.The ammonia injection system has good full-load adaptability.