煤粉再燃过程中NO均相与异相还原反应相对贡献的研究

Study on Relative Contributions of Homogeneous and Heterogeneous Reaction During NO Reduction in Pulverized Coal Reburning

利用固定床反应器分析各种因素对煤粉再燃NO还原过程均相与异相反应相对贡献的影响.在1 000℃和1 100℃下,利用模拟烟气对不同煤种的挥发分、煤焦、煤粉的再燃反应进行分析.结果表明:长广煤均相还原反应的贡献大于异相反应,但对于兖州煤和合山煤,异相还原反应的贡献大于均相反应,神木煤两者贡献相当.分析认为:除煤粉挥发分含量、焦的比表面积之外,煤灰中金属氧化物的含量,尤其是CaO的含量,是决定NO异相还原反应贡献大小的主要因素;而反应温度的升高,使NO均相和异相还原效率均提高,但并未改变异相和均相反应贡献的大小.

Effects of all the factors on relative contributions of homogeneous and heterogeneous reaction during NO reduction reaction in pulverized coal reburning were analyzed by use of a fixed bed reactor.Using simulative flue gas,the reburning reactions of volatile,char and pulverized coal of different coals were analyzed at 1 000℃ and 1 100℃ respectively.Results indicate that for Changguang coal,the contribution of homogeneous reaction is greater than that of heterogeneous reaction,while for Yanzhou coal and Heshan coal,the contribution of heterogeneous reaction is greater than that of homogeneous reaction,and for Shenmu coal, the effects of both are almost equivalent.Through analysis,it is considered that besides volatile content in pulverized coal and specific surface of char,the content of metal oxide in coal ash,especially CaO content is a main factor for determining the contribution of NO heterogeneous reduction.With the increase of reaction temperature,the reduction efficiencies of homogeneous and heterogeneous reaction increase,while the contributions of both reactions remain the same.