Xu, Qian; Shen, Meng; Shi, Kejian; Liu, Zhihui; Akkurt, Nevzat; Xiong, Yaxuan; Liu, Lin; Feng, Junxiao; Wang, Jiulong

To solve the problem of low efficiency of NOx emission reduction in self-reflux burners, this study is based on the concept of coordinated control of self-reflux burner structural and thermal parameters. After completing the structural design and optimization of thermal parameters, we continue to adjust the two key structural parameters: the nozzle axis distance and the length of the cylindrical section, to minimize NOx emissions. These are the two parameters that chiefly affect the mixing of flue gas and fuel gas. The results show that increasing nozzle axis distance can delay the mixing of gas and air and create a more uniform oxygen concentration field for the combustion process. The maximum combustion temperature is reduced from 1973.65 K to 1935.88 K and the volume fraction of NOx in the flue gas is reduced from 188.08×10−6 to 143.47×10−6. However, compared with the nozzle axis distance, the length of the cylindrical section of the burner has little effect on the mixing of the flow field. Under different cylindrical section lengths, the maximum combustion temperature does not change more than 3 K, and the volume fraction of NOx in the flue gas changes within 5×10−6.

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Xu, Qian; Akkurt, Nevzat; Yang, Gang; Zhu, Lidong; Shi, Kejian; Wang, Kang; Zou, Zhenwei; Liu, Zhihui; Wang, Jiulong; Du, Zhiwei

To optimize the structure of the burner, improve the combustion performance, and reduce the emission of NOx, a self-circulating low NOx combustion technology was used to design a new type of flue gas self-circulating low NOx burner. Based on previous research on the numerical model of combustion and the composition of mixed gas on combustion and NOx emissions, the effect of various factors on the ejection coefficient of the flue gas self-circulating structure was analyzed using the orthogonal test method, and the burner operating parameters, such as preheating temperature and excess air coefficient, were deeply studied through the three-dimensional finite element numerical model in this paper. The results show that the diameter ratio of the nozzle and the length of the cylindrical section of the flue gas self-circulating structure have great influence on its ejection and mixing ability. The optimal ejection coefficient was 0.4829. Overall, the amount of NOx emissions greatly increased from 6.23×10−6 (volume fraction) at the preheating temperature 973 K to 3.5×10−3 at preheating temperature 1573 K. When the excess air coefficient decreased from 1.2 to 1, the maximum combustion temperature decreased from 2036.3 K to 1954.22 K, and the NOx emissions decreased from 352.29×10−6 to 159.73×10−6.

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