Abstract:

The Zhundong coal reserve in China is abundant and characterized by high sodium content. The present work investigated the chemical looping combustion (CLC) performance using the high sodium-based Zhundong coal as fuel, CO₂ as gasification agent and iron ore as oxygen carrier. The experiments were performed in a bubbling fluidized bed reactor. Effects of coal particle size, reaction temperature, fluidization velocity and coal char particle size on the escaping behavior of combustible gases during CLC process of coal or coal char were evaluated. Meanwhile, the effect of minerals in the coal on char gasification was investigated. The results indicated that in the CLC process using bubbling bed as reactor, segregation is present due to the large difference of fluidizing properties between oxygen carrier materials and coal. Volatile as well as char conversion are influenced in CLC process due to the presence of segregation. A high fluidization velocity remarkably enhances the mixing between oxygen carrier and solid coal/char particles and reduces the negative influence of segregation. Consequently, the combustible gases escaping is reduced and char gasification rate is increased. The minerals in coal char can maintain fast gasification rate of coal char.

Key words: fluidized-bed, coal combustion, chemical looping combustion, oxygen carrier, CO₂ capture

摘要：

我国准东煤储量丰富，钠含量高。以高钠准东煤为燃料，CO₂为气化介质，铁矿石为载氧体，基于鼓泡流化床反应器开展准东煤化学链燃烧特性的实验研究，考察了煤粒径、温度、流化风速和煤焦粒径对煤及煤焦化学链燃烧过程中可燃气体逃逸规律的影响；同时研究了煤中矿物质对煤焦气化过程的影响。结果表明，在基于鼓泡流化床实施的煤化学链燃烧过程中，由于煤颗粒和载氧体床料流化特性差异大，存在离析现象；离析影响煤化学链燃烧过程中挥发分和焦炭的转化；较高流化风速可显著增强载氧体与煤/焦炭颗粒的混合，有效改善离析对可燃气体转化的影响，降低可燃气体逃逸，并加快焦炭气化速率；煤焦中的矿物质能够维持煤焦较快的气化速率。

关键词: 流化床, 煤燃烧, 化学链燃烧, 载氧体, 二氧化碳捕集