燃煤锅炉SCR烟气脱硝系统流场优化的数值模拟

Flow Field Optimization for SCR System of Coal-fired Power Plants

对某600 MW超临界燃煤机组SCR系统进行反应器内烟气流动均匀性和飞灰沉积的数值模拟.通过对比进入上层催化剂层烟气速度分布不均匀性,加入飞灰颗粒离散相后,开展烟道内导流板布置形式和导流板结构对SCR反应器内流场以及飞灰沉积的影响研究.结果表明:当SCR反应器入口导流板数目为13时,烟气通过上层催化剂层速度分布较其他3种工况均匀;导流板的弧形板后加装一段竖直直板可进一步引导烟气流动,减小回流作用,烟气进入上层催化剂层时速度更加均匀,综合考虑,弧-直型导流板为最优结构;数目13块的弧-直型导流板结构有利于改善SCR反应器壁面飞灰沉积情况;飞灰颗粒对SCR反应器内流场有一定影响,但改变较小,在实际运行中应进行相应吹灰处理.

A numerical study was carried out to evaluate the gas flow uniformity and fly ash deposition in the SCR reactor of a 600 MW supercritical coal-fired unit.The influence of deflector arrangement and structure on flow field and fly ash deposition in the reactor was studied through comparing the inhomogeneity of flue gas velocity distribution in the top catalyst layer after adding ash dispersed phase.Results show that when the number of deflectors installed at reactor inlet is thirteen,the flue gas velocity would be more uniformly distributed in the top catalyst layer than other three conditions;the deflector made up by an arc panel plus a vertical panel is comprehensively considered to be the most optimal structure,which helps to further guide the gas flow and reduce the refluxing effect,and therefore makes the gas velocity be more uniform in the top catalyst layer;agroup of thirteen deflectors in arc-straight shape are beneficial to the reduction of ash deposition upon the reactor wall;fly ash particles affect little on the internal field of SCR reactor,where soot blowing is generally required in actual operation.