SCR系统NO_x催化还原反应模拟仿真研究
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摘要
利用仿真软件AVL BOOST建立了针对选择性催化还原(SCR)反应过程的计算模型,对影响NO_x催化转化效率的因素进行了模拟仿真。通过小样试验测试了在不同温度、氨氮比、空速、热老化时间条件下NO_x转化效率,确定反应温度窗口宽度的变化情况。结果表明,试验与模拟的对比分析结果较为吻合,NO_x转化效率会随着温度升高而呈现先增高后降低的趋势;在合理控制氨泄漏的情况下,适当增加氨氮比可以提高NO_x转化效率;低温时,NO_x转化效率随着空速比的提高而减小;对催化剂进行快速热老化后,性能出现一定的衰减。反应温度窗口宽度介于240～500℃之间。
In order to simulate the influence factors of NO_x conversion efficiency, a computational model for the Selective Catalytic Reduction(SCR) reaction process is established by using the AVL BOOST. The conversion efficiency of NO_x under different temperature,ammonia-nitrogen ratio, air velocity and thermal aging time was tested by sample test, determining the change in the width of the reaction temperature window. The results show that the calculated value of the model is in good agreement with the test result. With the increase of the temperature, the efficiency of NO_x conversion will rise first and then decrease; In the case of reasonable control of ammonia leakage, the conversion efficiency of NO_x can be improved by increasing the ratio of ammonia-nitrogen appropriately; The conversion efficiency of NO_x decreases with the increase of air speed ratio at low temperature; After rapid thermal aging of the catalyst, there is a certain attenuation of performance. The reaction temperature window width is between 240～500 ℃.
In order to simulate the influence factors of NO_x conversion efficiency, a computational model for the Selective Catalytic Reduction(SCR) reaction process is established by using the AVL BOOST. The conversion efficiency of NO_x under different temperature,ammonia-nitrogen ratio, air velocity and thermal aging time was tested by sample test, determining the change in the width of the reaction temperature window. The results show that the calculated value of the model is in good agreement with the test result. With the increase of the temperature, the efficiency of NO_x conversion will rise first and then decrease; In the case of reasonable control of ammonia leakage, the conversion efficiency of NO_x can be improved by increasing the ratio of ammonia-nitrogen appropriately; The conversion efficiency of NO_x decreases with the increase of air speed ratio at low temperature; After rapid thermal aging of the catalyst, there is a certain attenuation of performance. The reaction temperature window width is between 240～500 ℃.
引文
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[2]Yun B K,Man Y K. Modeling the selective catalytic reduction of NOx,by ammonia over a Vanadia-based catalyst from heavy duty diesel exhaust gases[J]. Applied Thermal Engineering,2013,50(1):152-158.
[3]焦运景,纪晓静,纪丽伟.柴油机Urea-SCR系统NO_x转化效率影响因素研究[J].柴油机设计与制造,2015,21(2):16-19,40.
[4]Wurzenberuer J C, Wanker R. Multi-scale SCR modeling, 1D kinetic analysis and 3D system simulation[C]. SAE Paper.Detroit, Michigan, USA, 2005-01-0948.
[5]Cornclio A, Shukla A, Koukctsu S, et al. Simulation of ammonia SCR-catalytic converters:model development, calibration and application[C]. SAE Paper 2010-0l-1947.
[6]Christian W, Peter F, Patil M D, et al. Modeling of SCR DeNOx,Catalysts-Looking at the impact of substrate attributes[C].SAE Paper 2003-O1-0845.
[7]佟德辉,李国祥,陶建忠,等.氨基SCR催化反应的数值模拟及分析[J].内燃机学报,2008,260(4):335-340.
[8]苏庆运,冯廷智,郑贯宇,等.柴油机SCR催化转化器的数值模拟[J].内燃机学报,2017,35(01):53-59.
[9]贾思峰,管斌,刘柯,等.SCR反应物理化学过程模型及验证[J].车用发动机,2016(05):1-4,16.
[10]Kaviany M. Principles of heat transfer in porous media[M].Springer Science&Business Media, 2012.
[11]村田豊,德井贞仁,渡边聪一郎,等.关于提高尿素选择性催化还原系统氮氧化物净化率的研究—NH3吸附量控制及其在瞬态运行时的应用[J],国外内燃机,2009, 41(2). 32-36.