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Numerical analysis of mixing chamber non-uniformities and feed conditions for optimal performance of urea SCR
Reaction Chemistry & Engineering ( IF 3.4 ) Pub Date : 2020-09-10 , DOI: 10.1039/d0re00269k Risha Raju 1, 2, 3, 4 , Jishnu Chandran R 1, 2, 3, 4 , A. Salih 1, 2, 3, 4 , Kuruvilla Joseph 2, 3, 4, 5
Reaction Chemistry & Engineering ( IF 3.4 ) Pub Date : 2020-09-10 , DOI: 10.1039/d0re00269k Risha Raju 1, 2, 3, 4 , Jishnu Chandran R 1, 2, 3, 4 , A. Salih 1, 2, 3, 4 , Kuruvilla Joseph 2, 3, 4, 5
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The ammonia used for NOx reduction in urea SCR is formed from the decomposition of urea in the mixing chamber. The main challenges in urea SCR are the incomplete decomposition of urea to NH3 and its subsequent non-uniform distribution at the SCR inlet. A uniform profile at the SCR inlet without accounting for the non-uniformities from the mixing chamber may lead to an error in the system design. For symmetrical injection of urea inside the mixing chamber, the insufficient exhaust gas temperature and lower residence time of urea are two important factors that lead to the incomplete conversion of urea and the non-uniform distribution of ammonia at the SCR inlet. A CFD analysis of the mixing chamber with a symmetrical injection of urea is carried out to study these factors. The analysis showed that by simultaneously lowering the flow rate of urea and reducing the velocity of the exhaust gas, which is at a sufficiently high temperature, the NH3 generation is improved considerably. The CFD analysis was further extended to model the SCR with different inlet conditions. This analysis revealed that for SCR with non-uniform inlet conditions arising from the mixing chamber, the NOx reduction achieved is lower compared to that in the case of a uniform inlet profile for the SCR. The analysis shows that the radial variation in NOx reduction arising from the non-uniformities in the mixing chamber diminishes with a rise in the exhaust gas temperature. As compared to that with uniform inlet profiles, the NOx conversion in SCR with non-uniform inlet profiles exhibit a sharp rise with an increase in NO2 concentration.
中文翻译：
混合室不均匀性和进料条件的数值分析，以实现尿素SCR的最佳性能
用于尿素SCR中的NO x还原的氨是由混合室内的尿素分解形成的。尿素SCR的主要挑战是尿素不完全分解为NH 3以及随后在SCR入口处的不均匀分布。如果不考虑混合室的不均匀性，SCR入口处的轮廓要均匀，可能会导致系统设计错误。为了将尿素对称地喷射到混合室内，排气温度不足和尿素的停留时间短是导致尿素转化不完全和氨氮在SCR入口分布不均匀的两个重要因素。对混合室进行对称注入尿素的CFD分析，以研究这些因素。分析表明，通过同时降低尿素流量和降低排气温度（在足够高的温度下），NH 3一代大大改善。进一步扩展了CFD分析，以模拟不同进气条件下的SCR。该分析揭示，对于SCR与来自混合室所产生的非均匀的入口条件时，NO X在用于SCR均匀入口外形轮廓的情况下实现较低时相比减少。分析表明，由于混合室的不均匀性而导致的NO x还原的径向变化随着废气温度的升高而减小。与具有均匀入口轮廓的情况相比，具有不均匀入口轮廓的SCR中的NO x转化率随NO 2浓度的增加而急剧增加。
更新日期：2020-11-03
中文翻译：
混合室不均匀性和进料条件的数值分析，以实现尿素SCR的最佳性能
用于尿素SCR中的NO x还原的氨是由混合室内的尿素分解形成的。尿素SCR的主要挑战是尿素不完全分解为NH 3以及随后在SCR入口处的不均匀分布。如果不考虑混合室的不均匀性，SCR入口处的轮廓要均匀，可能会导致系统设计错误。为了将尿素对称地喷射到混合室内，排气温度不足和尿素的停留时间短是导致尿素转化不完全和氨氮在SCR入口分布不均匀的两个重要因素。对混合室进行对称注入尿素的CFD分析，以研究这些因素。分析表明，通过同时降低尿素流量和降低排气温度（在足够高的温度下），NH 3一代大大改善。进一步扩展了CFD分析，以模拟不同进气条件下的SCR。该分析揭示，对于SCR与来自混合室所产生的非均匀的入口条件时，NO X在用于SCR均匀入口外形轮廓的情况下实现较低时相比减少。分析表明，由于混合室的不均匀性而导致的NO x还原的径向变化随着废气温度的升高而减小。与具有均匀入口轮廓的情况相比，具有不均匀入口轮廓的SCR中的NO x转化率随NO 2浓度的增加而急剧增加。
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