廖立++杨鹏志

摘 要：SCR脱硝技术是火电站使用的较为成熟的脱硝方法。本文中，以SCR反应器出口NO浓度为研究目标，采用Langmuir吸附层模型和E-R反应机理建立反应模型，运用现场运行数据和辨识技术获得了模型特征参数，并假设NO反应速率指前因子KNO是一个随反应过程氨氮比变化的变量。通过电站实际运行中动态、稳态过程进行验证分析。仿真试验表明：1）辨识参数及对于KNO的的假设具有合理性，模型能够反应运行过程中NO出口浓度变化过程。2）反应温度，进口NO浓度，供氨量、烟气流速对于催化反应有着重要的影响。3）运行过程中，及时控制供氨量、保证氨氮比变化率是防止排放超标的有效手段。

关键词：烟气脱硝；建模与仿真；辨识；电站运行

Modeling and simulation of SCR reaction in a power plant

Liao Li， Yang Pengzhi

Key Laboratory of Low-grade Energy Utilization Technologies and Systems， Chongqing University， Ministry of Education， Chongqing 400044， PR China

Abstract： The SCR （selective catalytic reduction） technique is an advanced way to removal NOx from the flue gases in coal-fired power plants. Based on the Langmuir adsorption-desorption model and Eley-Rideal reaction mechanism， a dynamic mathematical model is established in this paper to focus on the nitrogen monoxide concentration at the outlet of the SCR reactor . In additional， identification technique is applied to obtain the exact value of certain kinetic parameters based on the data from a power plant and the assumption that the pre-exponential factor for the DeNOx reaction KNO is a variable which is affected by the NH3/NO concentration ratio at the inlet of the SCR reactor. The SCR model is tested in static state situation and dynamic state situation in different loads in the power plant .The result of simulation suggests that： A）these parameters gained from identification and the SCR model can suit the real SCR reaction in this power plant .B） Temperature， ammonia concentration， nitrogen monoxide concentration as well as gas velocity play crucial roles in SCR reaction .C）In the power plant， the amount of ammonia supply， the control of NH3/NO concentration ratio are effective methods to ensure the nitrogen monoxide concentration at the outlet of the SCR reactor stays in an appropriate range especially in the load up process or load down process.

Keywords： SCR； modeling and simulation； identification； power plant operation

對于该电厂，相比于温度和进口NO的影响，NH3的增加对于脱硫效率的提高较为缓慢，如图3（b）、图6。表3也可以看出，该厂需要的供氨量也很大，氨氮比偏高，在1.4以上，尤其是在负荷变化时，需要更大的氨量，其氨气逃逸量控制在0.015PPM-0.03PPM左右，符合排放标准。在实际运行中，升降负荷时，需提前增大供氨量，保持氨氮比变化率在0.01以内。并随时监视出口NO和NH3的排放量，防止排放超标（该厂出口浓度大于200mg/m3即为超标排放）。

（4）温度与NO共同扰动

选取机组某500MW时稳定状态时的参数值。 图7中，5s时刻，进口NO浓度突然升高至962mg/m3，出口NO的浓度相应的增大至68mg/m3 。 15s时刻，突然增加进口烟气温度至385℃，催化效应增加，出口NO浓度减小，直至25s处，保持温度385℃，进口NO浓度降至924 mg/m3。此时可见出口NO浓度减小至56 mg/m3。……