影响水煤浆再燃效果的主要因素研究

Influence of Coal Water Slurry Reburning on NOx Reduction

为了研究使用水煤浆作为再燃燃料在大型电站锅炉上的再燃脱硝效果和影响因素,在1台新建的670t/h的水煤浆锅炉上进行了再燃燃料量比在12.5%～25%、主燃区过量空气系数α_1在0.92～1.34、再燃区过量空气系数α_2在0.91～1.04之间变化的低NO_x燃烧调整试验,分析了再燃燃料量比、再燃区过量空气系数、主燃区过量空气系数、再燃区温度、烟气在再燃区停留时间和混合状况对脱硝率的影响。试验结果显示,相对于均等配风时锅炉的NO_x排放量788mg/m3,水煤浆再燃能够有效地降低NO_x的排放量,脱硝效果最高可以达到42.5%,说明大型电站锅炉上采用水煤浆再燃是一种有前景的脱硝方法,同时通过试验确定了再燃过量空气系数为0.95时的最佳再燃燃料比为16%,再燃燃料比为25%时,在实验工况范围内,最佳再燃区过量空气系数为0.91。

Coal water slurry can be used as rebuming fuel to reduce the NOx emission in large scale station boiler .In order to study the reburning effect and influence, experiments were done on a 670t/h CWS-fired boiler with reburning fuel fraction varying from 12.5% to 25%; rebuming zone excess air ratio varying from 0.91 to 1.04; primary combustion zone excess air ratio varying from 0.92 to 1.34. The influence on NOx reduction such as reburning fuel fraction, reburning zone excess air ratio, primary combustion zone excess air ratio in reburning zone as well as reburning zone temperature, flue residence time and mixing condition were all investigated. The normal NOx emission is 788 mg/m^3 in boiler and the highest NOx reduction ratio up to 42.5% when the CWS reburning is utilized. These results show that CWS used as reburning fuel on power station boiler is an excellent technology. At the same time, the optimal reburning fuel fraction was 16% with the reburning excess air ratio 0.95, and the optimal reburning zone excess air ratio was 0.91 with reburning fuel fraction 25% among our experiments.