再燃过程再燃煤粉燃料C释放特性的试验研究

EXPERIMENTAL INVESTIGATION ON FUEL-C RELEASE CHARACTERISTIC OF REBURN FUEL

再燃煤粉中 C 是重要的 NO 还原剂,也是煤中主要可燃质,其释放特性是影响 NO 还原效率及再燃煤粉燃尽的关键因素。在携带炉煤粉再燃试验过程中采集了不同实验条件下的煤焦样,对采集样品的元素构成进行了测定。对不同煤粉细度、再燃燃料比和再燃区氧量下再燃煤粉燃料 C 的释放规律进行了分析;以燃料 H 作为挥发分的示踪物,对挥发分 C 与煤焦 C 的释放时段进行了对比分析;研究了燃料C 释放与 NO 还原效率间的关系。试验与分析结果表明,在0.2s 以前,挥发分的释放与煤焦的氧化和气化是同步进行的,因而挥发分 C 的释放与煤焦 C 的释放也是同步进行的;0.4s 时,挥发分释放完全,以后,燃料 C 主要以煤焦 C 的形式释放;再燃燃料比与氧量的改变主要影响 0.2s 后煤焦 C的释放;煤粉细度对挥发分 C 与煤焦 C 的释放均有影响,对于一定量的煤粉,其煤焦的氧化与气化速率与煤粉粒径的平方成反比关系,细化再燃煤粉,不仅有利于煤粉的燃尽,还有利于提高 NO 的还原效率。

For rebuning with pulverized coal, the NO reduction rate and the burnout of reburn coal are strongly dependent on fuel-C release characteristic. Experiments of reburning with pulverized coal have been carried out on an entrained-flow reactor. The element compositions of chars collected under different coal particle sizes, reburn fuel fractions, reburn zone oxygen contents have been analyzed. The release characteristic of fuel-C, its impact on the NO reduction rate and burnout of reburn coal have been investigated. The experimental results indicate that when reaction time is less than 0.2s, the release of volatile and the oxidation and gasification of char take place simultaneously. The release of C after 0.2s is strongly dependent on reburn fuel fraction and oxygen content. Increased stoichiometric air leads to increased release of char-C and decreased NO reduction rate; Decreasing coal particle size leads to increased NO reduction rate and fuel C release rate.