基于CFD模拟计算的SCR脱硝系统喷氨优化试验方法

Test Method for Ammonia Injection Optimization of SCR Denitrification System Based on CFD Simulation Calculation

提出了一种对脱硝系统进行计算流体力学(CFD)模拟计算、并引入示踪气体精准调节喷氨格栅阀门的方法。将SCR系统全尺度建模划分网格,对部分喷氨支管使用等量示踪气体替换原有烟气,数值模拟SCR反应器内气体湍流流动、多组分扩散,计算反应器出口断面各示踪气体的浓度分布,获得各喷氨支管喷出的氨气所对应的影响区域,精确指导试验人员调整每根喷氨支管的开度,调节喷氨流量,使反应器出口断面NOx浓度均匀分布。以某1000 MW机组塔式锅炉SCR入口烟道为实例进行验证,结果表明,该方法能够提高典型试验的效率和准确性,能有效指导现场喷氨优化试验。

In this paper,a method of simulation calculation with computational fluid dynamics(CFD)is presented to precisely adjust the ammonia injection grid valve by introducing tracer gases into the denitrification system.Through full-scale modeling of the SCR system,and by replacing the original flue gas with the equivalent tracer gases in some ammonia-spraying branches,numerical simulation is conducted for the turbulent flow and multi-component diffusion of the flue gas in the SCR reactor.Then the concentration distribution of tracer gases at the outlet section of the denitrification system are calculated and the corresponding influencing areas of the ammonia-spraying branches at the outlet can be obtained.In this way the operators can be instructed to accurately change the ammonia flow rate by adjusting the opening of each ammonia spray branch so as to make the NO_x concentration evenly-distributed at the outlet section of the reactor.Finally,the verification test is carried out on the inlet flue duct of the SCR system of the tower boiler of a 1000 MW unit.The test results show that this method can improve the efficiency and accuracy of typical tests,and therefore can effectively provide the guidelines for the field ammonia spraying optimization test.