催化剂结构和磨损对SCR系统影响的数值模拟

发布时间：2019-05-09 00:42

【摘要】：我国的能源结构以煤炭为主。燃煤发电是我国最主要的煤炭消费途径,是煤炭能源转换的主要环节。燃煤发电带来的环境污染问题一直是环境治理的重点。燃煤烟气中的主要污染物是氮氧化物(NOx),氮氧化物对自然环境和人类健康都有极大的危害。国家为了严格控制氮氧化物的排放,要求燃煤电厂使用选择性催化还原(SCR)工艺脱除烟气中的氮氧化物。为了研究SCR工艺中催化剂的结构和磨损对催化还原系统的影响,本研究利用计算流体动力学(CFD)模拟SCR系统流场,并对模拟结果进行分析得到结论。根据SCR反应器实际情况,使用Gambit软件建立了多种满足模拟实验要求的三维模型,并根据计算要求进行网格划分。最终在Fluent软件中进行数值模拟,得到模拟数据和图表。选取了蜂窝式、波纹板式、平板式三种催化剂结构,研究其孔结构、孔径、安装距离等参数对SCR系统流场的影响。根据现场采集的催化剂磨损数据,模拟了催化剂磨损后对SCR系统流场的影响。数值模拟结果表明平板式催化剂气体通过性最佳,不易发生磨损的和积灰现象,蜂窝式催化剂气体通过性较差,波纹板式催化剂的气体通过性介于二者之间。催化剂的孔径越大气体通过性越好,单层催化剂的压力降越小。两层催化剂间距越大,越有利于气体混合。磨损后的催化剂会改变反应器内流场,使得催化剂失效速度加快。理想状态下应选择孔径大、压力降小、层间距大、耐磨性好的催化剂,但受催化反应效率限制还应在各项参数上做出取舍。
[Abstract]:China's energy structure is dominated by coal. Coal-fired power generation is the main way of coal consumption and the main link of coal energy conversion. The environmental pollution caused by coal-fired power generation has always been the focus of environmental control. The main pollutant in coal-fired flue gas is nitrogen oxide (NOx), which has great harm to natural environment and human health. In order to strictly control the emission of nitrogen oxides, coal-fired power plants are required to use selective catalytic reduction (SCR) process to remove nitrogen oxides from flue gas. In order to study the effect of catalyst structure and wear on the catalytic reduction system in SCR process, the computational fluid dynamics (CFD) (CFD) was used to simulate the flow field in SCR system, and the simulation results were analyzed. According to the actual situation of SCR reactor, a variety of three-dimensional models satisfying the requirements of simulation experiments were established by using Gambit software, and the meshes were divided according to the requirements of calculation. Finally, the numerical simulation is carried out in the Fluent software, and the simulated data and charts are obtained. Three kinds of catalyst structures, honeycomb, corrugated plate and flat plate, were selected to study the effects of pore structure, pore size and installation distance on the flow field of SCR system. Based on the field data of catalyst wear, the influence of catalyst wear on the flow field of SCR system was simulated. The numerical simulation results show that the gas passing ability of flat plate catalyst is the best, and the wear and ash accumulation are not easy to occur. The gas passing ability of honeycomb catalyst is poor, and the gas passing performance of corrugated plate catalyst is between the two. The larger the pore size of the catalyst is, the better the gas transmissibility is, and the smaller the pressure drop of the monolayer catalyst is. The larger the distance between the two catalysts, the more favorable the gas mixing. The worn catalyst can change the flow field in the reactor and accelerate the failure rate of the catalyst. Under the ideal condition, the catalyst with large pore size, small pressure drop, large layer spacing and good wear resistance should be chosen. However, due to the limitation of catalytic reaction efficiency, the choice should be made on various parameters.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X773;O643.36

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