SCR脱硝装置关键断面的流场试验及系统优化

选择性催化还原脱硝是NO X治理最佳技术,其脱硝效率、氨逃逸率与关键断面的流场状况密切相关。以某300 MW机组SCR脱硝装置为对象,在锅炉冷态通风条件下,对SCR反应器入口导流板出口、上层及中层催化剂床层上方0.5 m处3个断面进行流场测试,结果表明:沿烟气流动方向,3个断面A/B侧相对偏差系数分别为0.33/0.40、0.27/0.29、0.16/0.18,均呈现甲乙侧均匀,而前后墙差异大的特点。由于格栅、床层的整流作用,后续烟气流动的均匀性不断改善。通过建立全尺寸三维计算模型,CFD数值模拟优化结果显示,对非等距布置后墙的18个整流格栅逐渐加高,可使上层催化剂床层上方0.5 m处速度偏差从27.0%降到12.2%。

Flow Field Test and System Optimization of Key Sections in SCR Denitration Unit

Selective catalytic reduction(SCR)process is the best technology for NO X treatment in power industry,and the denitrification efficiency and ammonia escape rate are closely related to flow field conditions at critical sections.In this paper,based on a 300 MV SCR denitrification device,the flow fields of 3 sections were tested under the condition of cold ventilation of the boiler,such as the outlet of the guide plates located at the inlet of the SCR reactor and 0.5 m above the upper and middle catalyst beds.The results showed that the relative deviation coefficients for A and B sections were 0.33/0.40,0.27/0.29 and 0.16/0.18 respectively.Along the direction of the flue gas,the difference between front and back walls was great,while the difference between sides of part A and B was uniform.Due to the rectified action of grille and catalyst bed,the uniformity of the following flue gas flow was continuously improved.Based on the full size three-dimensional calculation mode,calculations of CFD numerical simulation optimization were carried out.The results showed that the speed deviation of the section at 0.5 m above the catalyst bed could be reduced from 27.0%to 12.2%after the height of the 18 rectifying gratings was increased with non equidistant layout of the back wall.