Performance Optimization of High-pressure SCR System in a Marine Diesel Engine. Part II: Catalytic Reduction and Process
Performance Optimization of High-pressure SCR System in a Marine Diesel Engine. Part II: Catalytic Reduction and Process
复制标题
船用柴油机高压 SCR 系统的性能优化。
DOI：
10.1007/s11244-018-1088-x
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发表时间：
2018
影响因子：
3.6
通讯作者：
Yongming Feng
中科院分区：
文献类型：
--
作者：
Yuanqing Zhu;Rongpei Zhang;Song Zhou;Chunan Huang;Yongming Feng
高压SCR（HP-SCR）系统的工作过程是在高压排气流中进行的一种催化反应过程，包括尿素分解反应、NOx的催化还原反应和NH3的氧化反应。本文针对船用低速柴油机现有的排放条件，采用计算流体力学（CFD）耦合化学反应动力学、催化过程和系统工作性能的方法进行了相应的研究。在优化方案的基础上，确定了系统的浓度均匀性、线速度和总压损失。得到了NH3、NO和NO2的浓度分布，并对NOx还原反应的催化动力学进行了分析。优化方案下，催化剂迎风段NH3浓度和流动均匀性满足HP-SCR系统设计要求，SCR催化剂层压力损失约占总压力损失的40%。当NO、NO2和NH3同时存在于排气中时，标准SCR反应和快速SCR反应都是竞争性的，并且它们主要沿着第一层催化剂反应。最后，采用ISO 8717测试循环E3确定了HP-SCR系统后NOx排放的加权平均值为2.67 g/kWh，满足IMO Tier III的NOx限值要求。
The working process of high-pressure SCR (HP-SCR) system is a kind of catalytic reaction process in the high-pressure exhaust flow, which involves urea decomposition reaction, catalytic reduction reaction of NOxand oxidizing reaction of NH3. Based on existing exhaust conditions of marine low-speed diesel engines, computational fluid dynamics (CFD) coupled with the chemical reaction kinetics, the catalytic process, and the working performance of the HP-SCR system were correspondingly studied in this paper. With the optimized scheme of the HP-SCR system, concentration uniformity, linear velocity, and total pressure loss were determined. Likewise, the concentration distribution of NH3, NO, and NO2were obtained, and the catalytic kinetics of the NOxreduction reaction was analyzed. For the optimized scheme, the concentration of NH3and the flow uniformity of the catalyst upwind section was met with the design requirements of the HP-SCR system, and the pressure loss of the SCR catalyst layer occupied about 40% of the total pressure loss. With NO, NO2, and NH3existing together in the exhaust, both the standard SCR reaction and fast SCR reaction are competitive, and they mostly react along the first layer of catalyst. Finally, the weighted average value of the NOxemission behind the HP-SCR system was determined using the ISO8717 test cycle E3, and the value was 2.67 g/kWh, which met with the NOxlimited requirement of the IMO Tier III.