Optimization of uniformity of NH3 distribution and thermolysis of urea in the SCR marine process

doi:10.16085/j.issn.1000-6613.2017.02.047

Abstract

Abstract: The distribution process of NH₃ in the SCR marine mixing chamber was investigated by numerical simulation. The simulation model considered atomization,evaporation,and thermolysis of urea,and its interaction with gas turbulence. This model provides the detailed information of velocity field,temperature field,component field,and trajectories of the droplets. Production and distribution of NH₃ was affected by flue gas temperature,inlet turbulent intensity,and swirl mixing. It is found that,by increasing the flue gas temperature,inlet turbulent intensity or adding a swirl mixer,the evaporation and thermolysis of urea solution accelerated,and the distribution uniformity increased. However,if the swirl angle was too large,some drops would impact the wall of the pipe,which would decrease the NH₃ production. Comparing the cases of swirl angle with 15°,30ånd 45°,it is found that the 30°swirl mixer yielded the best performance,which decreased NH₃ distribution non-uniformity from 39.57% to 9.36%.

Key words: SCR, de-NO_x, NH₃ distribution uniformity, numerical simulation

摘要： 以某船型柴油机尾气选择性催化还原法（SCR）脱硝工艺为对象，采用数值模拟研究喷射管内氨气（NH₃）生成过程及分布均匀性。模型包括尿素液滴的雾化、蒸发、分解以及与流场的相间作用等。结果表明，模型可详细预测烟道内气体速度场、温度场、NH₃等气体组分场、液滴轨迹等，NH₃转化率及分布均匀性受到烟气温度、入口湍流强度、扰流器的影响。提高烟气温度、提高烟气入口湍流强度、增加扰流器，均促进NH₃生成并提高分布均匀性，但是，扰流器的旋片角度过大，会导致部分液滴冲击到管道壁面，不利于NH₃生成。对比扰流器旋片角度为15°、30°和45°的情况，发现旋片角度30°时对提高NH₃生成及分布最为有利，其出口NH₃分布不均匀性从无绕流器条件下的39.57%降低到9.36%。

关键词: 选择性催化还原, 脱硝, 氨分布均匀性, 数值模拟

CLC Number:

TK09

WANG Zheng, LIU Daoyin, LIU Meng, WU Qinrui, TAN Jing, CHEN Xiaoping. Optimization of uniformity of NH₃ distribution and thermolysis of urea in the SCR marine process[J]. Chemical Industry and Engineering Progree, 2017, 36(02): 742-749.

王铮, 刘道银, 刘猛, 吴勤瑞, 檀净, 陈晓平. 船舶SCR脱硝尿素喷射分解及氨气分布均匀性的优化[J]. 化工进展, 2017, 36(02): 742-749.

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Optimization of uniformity of NH₃ distribution and thermolysis of urea in the SCR marine process

船舶SCR脱硝尿素喷射分解及氨气分布均匀性的优化

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