煤粉燃烧火焰区域中碳烟的结构与行为

Structure and Behavior of Soot in Pulverized-Coal Flame

在25 kW的一维下行炉的煤粉燃烧火焰区域,通过两级稀释水冷等速取样系统和荷电低压撞击器(ELPI)颗粒分级系统收集碳烟颗粒,利用高分辨透射电镜(HRTEM)获取超细颗粒物中碳烟的纳米结构图像,通过纳米结构图像分析研究碳烟在火焰区域内的各种行为.结果表明,在火焰区域中形成的碳烟因其行为不同而呈现出多样化的纳米结构,包括同心圆洋葱状、胶囊状、碳纤维微晶状和碳包覆的金属氧化物等,这些纳米结构客观反映了碳烟在火焰区域内较高梯度的含氧条件和高温环境下,存在着复杂的反应机理,包括碳烟基本粒子的形成、粒子间的碰撞聚并、在碳烟形成演变过程中所发生的石墨化作用和氧化反应、以及碳烟和随同煤粉挥发分析出的有机键连接金属元素间的相互作用.

In this paper, the soot generated from a pilot-scale 25 kW down-fired combustor was extensively investigated by using a nitrogen-aspirated, water-cooling isokinetic probe with two-stage dilution. A 13-stage electric low pressure impactor （ELPI） was used to deposit particles, among which the last six stages were selected for the further analysis by the high-resolution transmission electron microscopy （ HRTEM）. The result indicates that different experiences of soot particles in coal flames cause different nanostructures of soot, which reflects the complex mechanisms of soot particles in high temperature oxidative ambiences, including the formation of primary particles, graphitization, oxidation and the interaction between soot and metals connected with organic compounds during coal devolatilization.