导流均流装置对烟气SCR脱硝系统的流场优化模拟

Numerical simulation on flue gas rectification method of SCR denitration reaction system

针对烟气进入SCR脱硝反应系统后,烟气速度及其组分(NOx、NH3)浓度的分布不均的问题,提出一种基于导流板的烟气整流方案。该方案的技术关键是在喷氨格栅至脱硝反应器进口间的烟道内加装烟气混合装置、导流板、折流板等整流装置。以国内典型的300 MW燃煤锅炉机组SCR烟气脱硝系统为研究对象,并采用数值模拟方法研究了采用该整流装置对脱硝反应系统入口烟气流场和NH3及NOx质量浓度均匀性的影响。结果表明,整流后的SCR脱硝反应系统内的速度场与浓度场均匀性得到显著提升。反应器中首层催化剂上游的速度相对标准偏差由现役典型方案的19.1%下降至9.85%,NOx质量浓度相对标准偏差从现役典型方案的22.82%下降至13.45%,NH3质量浓度相对标准偏差从现役典型方案的12.33%下降至7.28%。整流后SCR脱硝反应系统整体流动阻力下降314 Pa,整体流场优化效果显著。本研究可为电站燃煤锅炉SCR脱硝反应器的系统设计与喷氨优化改造提供参考。

The aim of this paper is to solve the problem of uneven distribution of flue gas velocity and component(NOxand NH3) concentration in SCR denitrification reactor. Therefore, a kind of flue gas rectification scheme based on diversion plate. The key technology is to install flue gas mixing device, diversion plate, baffle plate and other rectification devices in the flue between the ammonia injection gate and the denitration reactor entrance. Taking the typical SCR denitrification system of 300 MW coal-fired boiler unit as the research object, the effects of different schemes on the smoke flow field, NH3and NOxconcentration uniformity of denitrification reactor inlet were studied by numerical simulation method. The results show that the uniformity of velocity field and concentration field in the optimized SCR denitration reaction system is significantly improved. The relative standard deviation of velocity upstream of the first layer catalyst in the reactor decreased from 19.1% to 9.85%, the relative standard deviation of NOxconcentration decreased from^(2)2.82% to 13.45%, and the relative standard deviation of NH3concentration decreased from 12.33% to 7.28%.After rectification, the overall flow resistance of SCR denitration reaction system decreases by 314 Pa, and the overall flow field optimization effect is significant. This study can provide reference for the system design and ammonia injection optimization of SCR denitration reactor of coal-fired boiler in power station.