Experimental study on nitric oxide reduction by urea solution injection into low-oxygen zone of anthracite coal combustion flame

XU Yun; ZHU Zhixiang; DONG Yuehong; ZHANG Qian; XU Jingxin; ZHANG Zhongxiao; LI Zixiang; WU Xiaojiang

doi:10.13205/j.hjgc.202501018

Volume 43 Issue 1

Mar. 2025

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Article Navigation > ENVIRONMENTAL ENGINEERING > 2025 > 43(1): 167-174

LIU Yuxin, ZENG Lingwu, FANG Zheng, SUN Dezhi. COMPREHENSIVE PERFORMANCE EVALUATION OF URBAN WASTEWATER TREATMENT PLANTS IN THE UPPER AND MIDDLE REACHES OF THE YELLOW RIVER BASIN[J]. ENVIRONMENTAL ENGINEERING , 2024, 42(12): 34-42. doi: 10.13205/j.hjgc.202412005

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XU Yun, ZHU Zhixiang, DONG Yuehong, ZHANG Qian, XU Jingxin, ZHANG Zhongxiao, LI Zixiang, WU Xiaojiang. Experimental study on nitric oxide reduction by urea solution injection into low-oxygen zone of anthracite coal combustion flame[J]. ENVIRONMENTAL ENGINEERING , 2025, 43(1): 167-174. doi: 10.13205/j.hjgc.202501018

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Experimental study on nitric oxide reduction by urea solution injection into low-oxygen zone of anthracite coal combustion flame

doi: 10.13205/j.hjgc.202501018

1. Science and Technology Research Institute Co., Ltd., CHN Energy, Nanjing 210046, China;
2. School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Received Date: 2023-09-19
Accepted Date: 2024-03-12
Rev Recd Date: 2023-12-29

Available Online: 2025-03-21

Publish Date: 2025-03-21

Abstract

Abstract

Down-fired boilers are designed to burn low-volatile coal, of which the NO_x emission is much higher than that of conventional coal-fired boilers. With the proposal of ultra-low emission standards for thermal power units, the efficient and low-cost reduction of NO_x emission in down-fired boilers has become a key issue to be solved urgently. Experiments were conducted in a high-temperature drop tube furnace to investigate the effects of excess air ratio (λ), NH₃/NO_x molar ratio (NSR), temperature, etc. on the NO_x reduction characteristics during anthracite coal combustion by urea solution injection into the high-temperature fuel-rich zone. The experimental results indicated that air-staging combustion could lower approximately 30% of NO_x emissions when the excess air ratio was decreased from 1.05 to 0.75. NO_x emissions could be further lowered by urea solution injection into a high-temperature reduction zone based on air-staging combustion, and a lower excess air ratio and higher temperature were conducive to the NO_x reduction efficiency of urea solution. The optimal NH₃/NO_x molar ratio was 1.5 under 1400 ℃ or oxidizing atmosphere. However, the optimal NH₃/NO_x molar ratio was shifted to 2.0 under relatively lower temperatures and a reducing atmosphere. Urea solution injection into a high-temperature fuel-rich zone could reduce 34.27% of NO_x emissions and achieve a minimum NO_x emission of 438.30 mg/Nm³ under the optimal experimental conditions, i.e., temperature of 1400 ℃, excess air ratio of 0.75, NH₃/NO_x molar ratio of 1.5. Our findings verify the effectiveness of urea solution injection into the high-temperature fuel-rich zone in lowering NO_x emission in down-fired boilers burning anthracite coal.
- anthracite coal combustion,
- excess air ratio,
- NH₃/NO_x molar ratio,
- temperature,
- NO_x emission

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References

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