SCR脱硝超低排放工程改造流场优化
Flow field optimization of SCR DeNOx project for ultra-low emission retrofit
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摘要: 采用CFD数值模拟方法对某电厂400 MW机组烟气脱硝装置流场进行了诊断，分析了导致效率低、烟道积灰以及空预器磨损等问题的具体原因，之后对此脱硝装置流场进行优化。优化结果表明：在省煤器出口水平扩张段烟道增设导流板，消除了该区域的大范围涡流，有利于减轻烟道积灰，并使喷氨区域烟气速度分布均匀；将喷氨混合装置改成喷氨格栅+圆盘混合器型式，强化了氨氮混合，使首层催化剂入口氨浓度分布均匀性得到显著改善，有利于提高脱硝效率、降低氨逃逸率；在空预器上游烟道增设导流装置，提高了空预器烟气速度分布均匀性，有利于解决空预器磨损问题。通过流场优化后，提高了此脱硝装置脱硝效率，减轻和消除了烟道积灰及空预器磨损。Abstract: Flow field in the flue gas denitrification reactor of a 400 MW unit in a coal-fired power plant was diagnosed by numerical simulation. Possible reasons were detailed for the current issues such as low denitrification efficiency, dust deposition in ducts as well as abrasion of air preheaters. Then the flow filed of denitrification reactor could be optimized and the results demonstrated that installing guide plates in the horizontal expansion section at the economizer outlet could eliminate the large-scale eddies in the duct, which was beneficial to reduce the dust deposition in the duct and uniformly distribute the flue gas velocity profile in the AIG area. After changing the original ammonia-nitrogen mixer into AIG + disk mixer type, the ammonia-nitrogen mixing effect was enhanced, and the distribution uniformity of the ammonia concentration in the first catalyst layer inlet can be improved remarkably, which can improve the denitrification efficiency and reduce the ammonia escape rate. Installing guide plates upstream the air preheater could improve the uniformity of flue gas velocity distribution, which was helpful to solve the problem of air preheater abrasion. By optimizing the flow field, the efficiency of the denitrification reactor can be improved, and the dust deposition in the duct and the abrasion of the air preheater can be reduced and eliminated.
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