Abstract: NO reduction by coal char was investigated in a fixed bed reactor using a simulated flue gas. Two different operation modes(programmed temperature and constant temperature) were employed to explore the mechanism of NO removal by coal char and to study the effects of the variables on NO removal efficiency and selectivity including temperature, coal type, NO and oxygen concentrations in flue gas and space velocity. The results indicated that surface complexes formed by chemisorption of NO and O₂ on carbon active sites played the key role in reactions between C-NO and C-O₂. XLHT coal char showed both the highest rate of NO reduction and C-NO selectivity among the coal chars studied. NO reduction by XLHT coal char could reach 99% at 723 K. Under the experimental conditions in this work, an increase in temperature and/or oxygen concentration in flue gas enhanced NO reduction. However, C-NO selectivity decreased with the increasing O₂ concentration. Higher NO concentration in flue gas led to lower NO reduction but higher C-NO selectivity.

Key words: coal char, nitric oxide, reduction, selectivity

摘要： 选用3种不同煤焦，采用程序升温和恒温实验方法，在固定床上考察了不同实验条件下的NO转化率和C对NO选择性，分析了煤焦脱硝的机理和影响因素。实验结果表明：NO和O₂在煤焦表面发生化学吸附所形成的络合物在脱硝过程中起着关键作用，影响C-NO反应和C-O₂反应的竞争与协作关系。在所考察的煤焦中锡林浩特褐煤焦脱硝效果最好，当温度为723 K时烟道气中NO还原率可达99%；在温度623～923 K、O₂浓度0～5%范围内，提高温度和O₂浓度均有利于提高NO转化率，而降低O₂浓度有利于提高C对NO选择性；烟道气中NO浓度越高，其转化率越低，但C对NO选择性越高。

关键词: 煤焦, 氮氧化物, 还原, 选择性