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<p>Zhundong high-alkali coal occupies substantial reserve and excellent combustion performance while it encounters a serious phenomenon of ash slagging and fouling during the traditional thermal utilization process. The cyclone combustion with slag-tap furnace has the potential to reduce the tendency of ash slagging and fouling of high-alkali coal. However, the cyclone combustion in traditional air atmosphere has confronted with quite high-level of nitrogen oxides (NO<sub><i>x</i></sub>) emission. In this study, the oxy-fuel combustion of high-alkali coal in a cyclone boiler with slag-tap furnace was focused to propel the clean and safe utilization of Zhundong coal and achieve the visionary goal of carbon neutrality. The combustion and NO<sub><i>x</i></sub> generation characteristics of high-alkali coal in oxy-fuel atmosphere in a cyclone boiler were mainly elucidated in terms of gas atmosphere, total oxygen volume fraction, and air staging strategy via numerical simulation approach. The results demonstrated that the oxy-fuel atmosphere led to none thermal NO<sub><i>x</i></sub> generation. The NO concentration at the outlet of the cyclone in air and oxy-fuel atmosphere was 691.42 mg·m<sup>−3</sup> and 209.17 mg·m<sup>−3</sup> (approximately one third of that in air atmosphere), respectively. In comparison with air combustion, the NO conversion rate at the outlet of the cyclone and furnace was decreased by 69.28% and 20.81% respectively under oxy-fuel condition. An increase of the total oxygen volume fraction could effectively reduce the conversion rate of NO at the furnace outlet. Especially, when the total oxygen volume fraction was elevated from 30% to 40%, the conversion rate of NO at the cyclone and furnace outlet was decreased by 23.13% and 28.26%, respectively. An increase of over fire air (OFA) rate can significantly inhibit the generation of NO<sub><i>x</i></sub>. When the OFA rate was enhanced from 33.0% to 37.5%, the NO conversion rate at the cyclone and furnace outlet was diminished by 47.16% and 25.46%, respectively. The OFA rate was suggested being 37.5%, where the low emission of NO<sub><i>x</i></sub> and relatively economical OFA volume can be obtained. Moreover, the emission of NO<sub><i>x</i></sub> can be controlled by decreasing the excess oxygen coefficient. The optimal excess oxygen coefficient was selected to be 1.20, which obtained the lowest NO<sub><i>x</i></sub> emissions (814.79 mg·m<sup>−3</sup>) among all the studied conditions. The present study can offer novel insight into the oxy-fuel combustion of high-alkali coal in a cyclone boiler using slag-tap furnace.</p>

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Numerical Simulation on the NOx Generation Characteristics of Zhundong High-Alkali Coal under Oxy-Fuel Condition in a Cyclone Boiler with Slag-Tap Furnace

  • 期刊论文

  • 发表日期：

    2026年1月30日

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  • Yongting Wu,
  • Guowei Ma,
  • Chang’an Wang,
  • Liujun Chang,
  • Lin Zhao,
  • Tianlin Yuan,
  • Yingchao Nie,
  • Defu Che

摘要

Zhundong high-alkali coal occupies substantial reserve and excellent combustion performance while it encounters a serious phenomenon of ash slagging and fouling during the traditional thermal utilization process. The cyclone combustion with slag-tap furnace has the potential to reduce the tendency of ash slagging and fouling of high-alkali coal. However, the cyclone combustion in traditional air atmosphere has confronted with quite high-level of nitrogen oxides (NOx) emission. In this study, the oxy-fuel combustion of high-alkali coal in a cyclone boiler with slag-tap furnace was focused to propel the clean and safe utilization of Zhundong coal and achieve the visionary goal of carbon neutrality. The combustion and NOx generation characteristics of high-alkali coal in oxy-fuel atmosphere in a cyclone boiler were mainly elucidated in terms of gas atmosphere, total oxygen volume fraction, and air staging strategy via numerical simulation approach. The results demonstrated that the oxy-fuel atmosphere led to none thermal NOx generation. The NO concentration at the outlet of the cyclone in air and oxy-fuel atmosphere was 691.42 mg·m−3 and 209.17 mg·m−3 (approximately one third of that in air atmosphere), respectively. In comparison with air combustion, the NO conversion rate at the outlet of the cyclone and furnace was decreased by 69.28% and 20.81% respectively under oxy-fuel condition. An increase of the total oxygen volume fraction could effectively reduce the conversion rate of NO at the furnace outlet. Especially, when the total oxygen volume fraction was elevated from 30% to 40%, the conversion rate of NO at the cyclone and furnace outlet was decreased by 23.13% and 28.26%, respectively. An increase of over fire air (OFA) rate can significantly inhibit the generation of NOx. When the OFA rate was enhanced from 33.0% to 37.5%, the NO conversion rate at the cyclone and furnace outlet was diminished by 47.16% and 25.46%, respectively. The OFA rate was suggested being 37.5%, where the low emission of NOx and relatively economical OFA volume can be obtained. Moreover, the emission of NOx can be controlled by decreasing the excess oxygen coefficient. The optimal excess oxygen coefficient was selected to be 1.20, which obtained the lowest NOx emissions (814.79 mg·m−3) among all the studied conditions. The present study can offer novel insight into the oxy-fuel combustion of high-alkali coal in a cyclone boiler using slag-tap furnace.