混煤燃烧过程中的交互作用:掺混方式对混煤燃烧特性的影响

在沉降炉上开展了高、低挥发分煤不同配比(贫煤掺混烟煤比例0,25%,50%,75%,100%)下混煤燃烧特性实验,研究了"炉外"和"炉内"两种掺烧方式对混煤燃尽与NO_x排放特性的影响。结果表明,混煤燃烧过程中烟煤对贫煤存在促进和抑制两种作用,两者的竞争共同决定了混煤的燃尽特性。"炉外"掺烧方式下,掺烧烟煤比例较小时,促进大于抑制作用,有利于混煤燃尽;进一步提高烟煤掺烧的比例,抑制作用增加并大于促进作用,不利于混煤的燃尽;NO_x排放量随烟煤掺烧比例增加基本呈线性增加规律。掺烧烟煤比例控制在25%以内有利于提高混煤燃尽率;掺烧烟煤比例为75%时,混煤燃尽率显著降低。"炉内"掺烧方式下,混煤燃烧中的促进与抑制作用会同时减弱;掺烧大比例烟煤时,烟煤与贫煤混合越晚越有利于混煤燃尽;NO_x排放量随着烟煤延迟混合而逐渐降低。"炉内"掺烧烟煤且烟煤延迟送入炉内有利于混煤燃尽率,且NO_x的排放降低明显;而贫煤延迟送入炉内则会导致混煤燃尽率进一步降低,但NO_x排放降低程度低于前者。

Interaction of blended-coal combustion process：influence of coal blending methods on combustion characteristics

The experiment of the influence of out-furnace and in-furnace blending method on the combustion characteristics and NOx emissions were performed under high-volatile coal，low-volatile coal and their blended coal (lean coal blended with bituminous of 0，25%，50%，75%，100%) in this paper.The results show that the combustion of blended coal is impacted by two opposite effect：the promote function and the restrain function.The role of the two competition determines the characteristics of blended-coal combustion.Under the out-furnace coal blending method，the promote function is more obvious than the restrain function when the blending coal ratio is relatively small，which is in favour of the blended-coal burnout.As further increasing the bituminous ratio，the restrain function becomes strong gradually，and more obvious than the promote function，which is not in favour of the blended coal burnout.NOx emissions of blended coal is in consistence with linear NOx，and increase as increasing the blending ratios.Especially，the blended-coal burnout degree decreases significantly when the proportion of bituminous is more than 75%.The proportion of bituminous within 25% is beneficial to improve the coal burnout rate.The in-furnace method of blending coal weakens not only the promote function，but also the restrain function.The mixing of bituminous and lean coals is later at the large proportion of blending coal ratio，the burnout of blending coals is higher.NOx emissions of blended coal gradually decrease as increasing the delaying time.Bituminous are delayed to be mixing with lean coals at the in-furnace blending method，which is in favor of the burnout and NOx reducing，while lean coals are delayed to be mixing with bituminous，which is not in favor of the burnout，and NOx reducing is not obvious compared to the former.