Clean Coal Technology

2022, v.28;No.142(06) 159-167

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Flow field optimization of SCR-DeNO_x system in a 300 MW coal-fired power plant

HUANG Jun;LI Xinglei;RUAN Bin;LUO Sheng;LU Zhimin;YAO Shunchun;Guangzhou Zhujiang Electric Power Co.,Ltd.;School of Electric Power,South China University of Technology;Guangdong Province Key Laboratory of Efficient and Clean Energy Utilization;Guangdong Province Engineering Research Center of High Efficiency and Low Pollution Energy Conversion;

Abstract:

Under the requirements of ultra-low emission, the excessive injection of ammonia in the SCR DeNO_x reactor not only affects the economy, but has also causes a series of operation and maintenance problems such as air preheater blockage, electrostatic precipitator fouling, and bag paste. In order to improve the uniformity of SCR inlet flue gas velocity and ammonia-nitrogen molar ratio, the computational fluid dynamics simulation and optimization research of flue flow field on one side SCR reactor of an old 300 MW unit in a certain power plant were carried out. Using Fluent as the main tool and based on the analysis of the empty tower model and the original deflector arrangement, the SCR flue deflector structure was optimized, and a static mixer was arranged downstream of the ammonia injection grid to achieve uniform cross-sectional velocity and ammonia-nitrogen molar ratio in the first layer of catalyst. The relative standard deviation of the velocity of the empty tower scheme is 26.1%,and the relative standard deviation of the ammonia-nitrogen molar ratio is 24.8%,all of which can not meet the engineering design requirements. In the original scheme, six groups of deflectors are set at the gradual expansion and corner of SCR flue, and the uniformity of speed and concentration is greatly improved, the relative standard deviation of the speed is 13.9%,which can meet the engineering design requirements, while the relative standard deviation of the ammonia nitrogen molar ratio is 15.3%,which can not meet the design requirements of less than 10%. The flow deflector arranged in the optimized scheme eliminates the vortex and reflux of flue gas at the flue corner and gradual expansion. Meanwhile, the static mixer is installed to enhance mixing, so that the relative standard deviation of velocity is reduced to 11.4%,and the relative standard of ammonia-nitrogen molar ratio to 9.4%. The uniformity of the flow field in the SCR flue has been greatly improved and the speed and concentration uniformity meet the design requirements. At the same time, the pressure loss of the optimized scheme is 706 Pa, which meets the B-level design requirements. The results show that the reasonable arrangement of the baffle and static mixer can improve the uniformity of the flow field without causing excessive pressure loss. The present work has reference value for the optimization of the on-site SCR flow field retrofit.

Key Words: SCR-DeNO_x;flow field optimization;baffle;ammonia-nitrogen molar ratio;static mixer

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Foundation: 国家重点研发计划资助项目(2019YFE0109700);; 广州市科技计划重点资助项目(201904020017)

Authors: HUANG Jun;LI Xinglei;RUAN Bin;LUO Sheng;LU Zhimin;YAO Shunchun;Guangzhou Zhujiang Electric Power Co.,Ltd.;School of Electric Power,South China University of Technology;Guangdong Province Key Laboratory of Efficient and Clean Energy Utilization;Guangdong Province Engineering Research Center of High Efficiency and Low Pollution Energy Conversion;

DOI: 10.13226/j.issn.1006-6772.21061004

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