分布式能源站天然气内燃机Urea-SCR系统模拟优化研究

doi:10.3969/j.issn.1674-1951.2021.05.007

摘要/Abstract

摘要：

为提高Urea-SCR系统的NO_x脱除率,以某分布式能源站9.7 MW天然气内燃机Urea-SCR系统为研究对象,通过建立三维数值模型,研究了不同喷射位置条件下反应器内静态混合器、多孔板对流场、NH₃转化率及NH₃摩尔分数分布的影响。模拟结果表明：喷射位置距离首层催化剂越远,首层催化剂截面NH₃转化率越高、NH₃摩尔分数分布越均匀;挡板式静态混合器会破坏首层催化剂入口速度分布的均匀性,不利于NH₃的转化及混合;入口渐扩段布置多孔板能够有效改善首层催化剂入口前流场的均匀性,提高NH₃的转化率,但不利于NH₃的混合。采取在备用层催化剂处布置多孔介质的措施,可获得较为理想的NH₃转化率及分布的均匀性。

关键词: 分布式能源站, 天然气内燃机, NO_x, Urea-SCR系统, 数值模拟, 多孔板, 混合器, NH₃转化率, 均匀性

Abstract:

In order to improve the NO_x removal rate of a Urea-SCR system, a three-dimensional numerical model of a 9.7 MW natural gas internal combustion engine's Urea-SCR system was established. The effects of the static mixer, porous plate in the reactor on flow field, NH₃ conversion rate and NH₃ mole fraction distribution were studied. Simulation results show that, the farther the injection location is from the first-layer catalyst, the higher the NH₃ conversion rate is and the more evenly the NH₃ distributes. A baffle static mixer will hamper the uniformity of flow velocity at the inlet of the first layer catalyst,which is not conducive to the transformation and mixing of NH₃. The porous plates arrangement in the diffuser can effectively improve the uniformity of the flow field in front of the inlet of the first layer catalyst and improve the conversion of NH₃.However,it is not conducive to the mixing of NH₃. Laying porous media on the standby layer of catalyst, an ideal conversion rate and decent NH₃ uniformity can be obtained.

Key words: distributed energy station, natural gas internal combustion engine, NO_x, Urea-SCR system, numerical simulation, porous plate, mixer, NH₃ conversion rate, uniformity

中图分类号:

TK402：X701

赵大周, 王明祥, 阮慧锋, 谷菁, 王明晓. 分布式能源站天然气内燃机Urea-SCR系统模拟优化研究[J]. 华电技术, 2021, 43(5): 45-52.

ZHAO Dazhou, WANG Mingxiang, RUAN Huifeng, GU Jing, WANG Mingxiao. Simulation and optimization for Urea-SCR system of the natural gas internal combustion engine in a distributed energy station[J]. Huadian Technology, 2021, 43(5): 45-52.

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反应式	指前因子/(s^-1)	活化能/(J·kmol^-1)
CO(NH₂)₂→NH₃+HCNO	4 900	2.30×10⁷
HCNO+H₂O→NH₃+CO₂	250 000	4.46×10⁷

项目	单位	参数
型号		瓦锡兰W20V34SG
额定功率	kW	9 780
转速	r/min	750
允许的排气背压	kPa	5
气缸数量	个	20

项目	单位	参数
内燃机负荷率	%	100	75	50
排烟温度	℃	377	406	431
NO_x质量浓度（干基、标态、5% O₂）	mg/m³	500	500	500
烟气量（湿）	kg/h	56 119	41 932	29 116

项目	单位	参数
喷射压力	MPa	7.5
尿素溶液初始温度	K	300
喷孔直径	mm	1
喷雾半锥角	（°）	15
粒径分布		Rosin-Rammler函数
喷嘴类型		实心锥

工况	是否有多孔板	是否有混合器
1	无	无
2	有	无
3	无	有
4	有	有