Simulation and optimization for Urea-SCR system of the natural gas internal combustion engine in a distributed energy station

doi:10.3969/j.issn.1674-1951.2021.05.007

Abstract

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

CLC Number:

TK402：X701

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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References 16

[1]	余莉. 浅析楼宇式天然气分布式供能系统的开发与设计[J]. 华电技术, 2018,40(5):73-74.
	YU li. A brief analysis on the development and design of building type distributed natural gas power supply system[J]. Huadian Technology, 2018,40(5):73-74.
[2]	固定式内燃机污染物综合排放标准:DB 11/1056—2013[S].
[3]	孙克勤. 火电厂烟气脱硝技术及工程应用[M]. 北京: 化学工业出版社, 2006.
[4]	王朝阳, 陈鸿伟, 王广涛, 等. 双变截面SCR脱硝系统导流板优化设计[J]. 环境工程学报, 2018,12(10) : 2818-2824.
	WANG Zhaoyang, CHEN Hongwei, WANG Guangtao, et al. Optimization design of deflector for SCR denitration system with double variable cross-section[J]. Chinese Journal of Environmental Engineering, 2018,12(10):2818-2824.
[5]	江婷, 胡永锋, 宋洪涛, 等. 楼宇型分布式能源系统SCR脱硝数值模拟研究[J]. 华电技术, 2019,41(3):1-7.
	JIANG Ting, HU Yongfeng, SONG Hongtao, et al. Numerical simulation research on SCR denitration in a building type distributed energy system[J]. Huadian Technology, 2019,41(3):1-7.
[6]	王卫群, 张磊, 黄治军, 等. 基于 CFD 模拟计算的 SCR 脱硝系统喷氨优化试验方法[J]. 中国电力, 2020,53(6) : 185-190.
	WANG Weiqun, ZHANG Lei, HUANG Zhijun, et al. Test method for ammonia injection optimization of SCR denitrification system based on CFD simulation calculation[J]. Electric Power, 2020,53(6) : 185-190.
[7]	谭理刚, 何利华, 寇传富, 等. 柴油机Urea-SCR系统喷射雾化的数值模拟[J]. 环境工程学报, 2014,8(4):1554-1560.
	TAN Ligang, HE Lihua, KOU Chuanfu, et al. Numerical simulation on spray atomization of diesel engine Urea-SCR system[J]. Chinese Journal of Environmental Engineering, 2014,8(4):1554-1560.
[8]	王谦, 张铎, 王静, 等. 车用柴油机 Urea-SCR 系统数值分析与参数优化[J]. 内燃机学报, 2013,31(4):343-348.
	WANG Qian, ZHANG Yi, WANG Jing, et al. Numerical analysis and parametric optimization on Urea-SCR system of vehicle diesel[J]. Transactions of CSICE, 2013,31(4):343-348.
[9]	陈贵升, 杨锐敏, 和志高, 等. 选择性催化还原混合器及整流器的设计与结构优化[J]. 内燃机工程, 2020,41(2):46-53.
	CHEN Guisheng, YANG Ruimin, HE Zhigao, et al. Design and structure optimization of selective catalytic reduction mixer and rectifier[J]. Chinese Internal Combustion Engineer Engineering, 2020,41(2):46-53.
[10]	王文晓, 朱智富, 赵英良, 等. 发电柴油机选择性催化还原系统尿素喷雾锥角的仿真及试验研究[J]. 内燃机工程, 2020,41(1):64-69.
	WANG Wenxiao, ZHU Zhifu, ZHAO Yingliang, et al. Simulation and experimental study on urea spray cone angle of selective catalytic reduction system for a generating set diesel engine[J]. Chinese Internal Combustion Engineer Engineering, 2020,41(1):64-69.
[11]	TAN Ligang, FENG Pengfei, YANG Shubao, et al. CFD studies on effects of SCR mixers on the performance of urea conversion and mixing of the reducing agent[J]. Chemical Engineering & Processing: Process Intensification, 2018,123:82-88.
[12]	ZHU Yuanqing, LI Tinghui, XIA Chong, et al. Simulation analysis on vaporizer/mixer performance of the high-pressure SCR system in a marine diesel[J]. Chemical Engineering & Processing: Process Intensification, 2018,148:1-9.
[13]	王铮, 刘道银, 刘猛, 等. 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(2):742-749.
	WANG Zheng, LIU Daoyin, LIU Meng, et al. Optimization of uniformity of NH₃ distribution and thermolysis of urea in the SCR marine process[J]. Chemical Industry and Engineering Progress, 2017,36(2):742-749.
[14]	KUHNKE D. Spray/wall-interaction modelling by dimensionless data analysis[M]. Aachen:Shaker Verlag GmbH, 2004.
[15]	CHOI C, SUNG Y, CHOI G M, et al. Numerical analysis of NO_x reduction for compact design in marine urea-SCR system[J]. International Journal of Naval Architecture and Ocean Engineering, 2015,7(6):1020-1034. doi: 10.1515/ijnaoe-2015-0071
[16]	YIM S D, KIM S J, BAIK J H, et al. Decomposition of urea into NH₃ for the SCR process[J]. Industrial & Engineering Chemistry Research, 2004,43(16):4856-4863. doi: 10.1021/ie034052j

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