Abstract: Nitrogen oxide (NO_x) pollutants emitted from coal combustion are attracting growing public concern. While the traditional technologies of reducing NO_x were mainly focused on terminal treatment, and the research on source treatment is limited. This paper proposes a new coal combustion strategy that significantly reduces NO_x emissions during coal combustion. This strategy has two important advantages in reducing NO_x emissions. First, by introducing iron-based catalyst at the source, which will catalyze the conversion of coke nitrogen to volatile nitrogen during the pyrolysis process, thereby greatly reducing the coke nitrogen content. The second is de-NO_x process by a redox reaction between NO_x and reducing agents (coke, HCN, NH₃, etc.) that occurred during coke combustion. Compared to direct combustion of coal, coke prepared by adding iron-based catalyst has 46.1% reduction in NO_x emissions. To determine the effect of iron-based additives on de-NO_x performance, demineralized coal (de-coal) was prepared to eliminate the effect of iron-based minerals in coal ash. The effects of iron compounds, additive dosages, and combustion temperatures on de-NO_x efficiency are systematically studied. The results revealed that the NO_x emission of the coke generated by pyrolysis of de-coal loaded with 3% (mass) Fe₂O₃ decreases to 27.3% at combustion temperature of 900 ℃. Two main reasons for lower NO_x emissions were deduced: (1) During the catalytic coal pyrolysis stage, the nitrogen content in the coke decreases with the release of volatile nitrogen. (2) Part of the NO_x emitted during the coke combustion was converted into N₂ for the catalytic effect of the Fe-based catalysts. It is of great practical value and scientific significance to the comprehensive treatment and the clean utilization process of coal.

Key words: NO_x, Coal combustion, Coal pyrolysis, Fe₂O₃ catalyst

摘要： Nitrogen oxide (NO_x) pollutants emitted from coal combustion are attracting growing public concern. While the traditional technologies of reducing NO_x were mainly focused on terminal treatment, and the research on source treatment is limited. This paper proposes a new coal combustion strategy that significantly reduces NO_x emissions during coal combustion. This strategy has two important advantages in reducing NO_x emissions. First, by introducing iron-based catalyst at the source, which will catalyze the conversion of coke nitrogen to volatile nitrogen during the pyrolysis process, thereby greatly reducing the coke nitrogen content. The second is de-NO_x process by a redox reaction between NO_x and reducing agents (coke, HCN, NH₃, etc.) that occurred during coke combustion. Compared to direct combustion of coal, coke prepared by adding iron-based catalyst has 46.1% reduction in NO_x emissions. To determine the effect of iron-based additives on de-NO_x performance, demineralized coal (de-coal) was prepared to eliminate the effect of iron-based minerals in coal ash. The effects of iron compounds, additive dosages, and combustion temperatures on de-NO_x efficiency are systematically studied. The results revealed that the NO_x emission of the coke generated by pyrolysis of de-coal loaded with 3% (mass) Fe₂O₃ decreases to 27.3% at combustion temperature of 900 ℃. Two main reasons for lower NO_x emissions were deduced: (1) During the catalytic coal pyrolysis stage, the nitrogen content in the coke decreases with the release of volatile nitrogen. (2) Part of the NO_x emitted during the coke combustion was converted into N₂ for the catalytic effect of the Fe-based catalysts. It is of great practical value and scientific significance to the comprehensive treatment and the clean utilization process of coal.

关键词: NO_x, Coal combustion, Coal pyrolysis, Fe₂O₃ catalyst