燃煤过程中颗粒物的形成机理研究进展

A REVIEW ON PARTICLE FORMATION MECHANISMS DURING COAL COMBUSTION

介绍了煤粉燃烧过程中颗粒物的形成机理 ,包括亚微米飞灰和残灰颗粒的主要形成途径 .亚微米颗粒主要来自无机物的气化 -凝结过程 ,在高温条件下无机矿物首先以氧化物、次氧化物或原子的形式气化 ,当温度降低时 ,无机蒸气通过均相成核、异相冷凝、凝并、团聚等过程形成细微颗粒 .残灰由残留在焦炭颗粒中的矿物转化而成 ,焦炭破碎和表面灰的聚合是决定残灰最终粒径分布的主要过程 ,除此之外 ,对于含外来矿物较多的煤种 ,矿物破碎对残灰颗粒的形成也有十分重要的影响 .最后对燃煤过程中颗粒物的形成机理研究提出了建议 .

Particle formation mechanisms during pulverized coal combustion have been introduced in this review, including the main processes that contribute to the formation of submicron particulates and residual ash particles. Vaporization-condensation is the major source of submicron particulates. Inorganic mineral matter vaporizes at higher temperatures in the form of oxides, sub-oxides or atoms firstly. Subsequently, the vapors may form a large number of fine particulates by nucleation, heterogeneous condensation, coagulation and agglomeration when the temperature decreases. Residual ash is formed by the transformation of minerals that remain after the carbon burns away and the particle size distribution is determined by char fragmentation and coalescence of surface ash droplets. In addition, the influence of the fragmentation of mineral particles on the residual ash particle size distribution becomes important if the coal contains significant amount of extraneous minerals. Finally, the future research ideal on the mechanisms of particle formation during pulverized coal combustion is proposed.