Computer-Controlled Scanning Electron Microscopy Investigation on Ash Formation Characteristics of a Calcium-Rich Coal under O2/CO2 Environments

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• 作者：Tai Zhang ; Zhaohui LiuXiaohong Huang ; Qing Sun ; Chao Liu ; Junjie Li ; Chuguang Zheng
• 刊名：Energy & Fuels
• 出版年：2017
• 出版时间：January 19, 2017
• 年：2017
• 卷：31
• 期：1
• 页码：319-327
• 全文大小：649K
• ISSN：1520-5029

文摘

The present study aimed to address the influence of oxy-fuel combustion on ash formation characteristics on a particle-by-particle basis. A Chinese sub-bituminous coal rich in calcium was burned under air and O₂/CO₂ environments in a high-temperature drop-tube furnace (HDTF). Computer-controlled scanning electron microscopy (CCSEM) and CaO–Al₂O₃–SiO₂ ternary diagram analysis of the collected ashes were executed thereafter. The results showed that, although the change of the combustion environment has a slight effect on the bulk composition of the ashes, a significant effect on the statistics of individual ash composition and particle size distribution was observed. Distribution of Ca-related minerals for a 20% O₂/CO₂ atmosphere is relatively dispersed in comparison to that in other combustion environments, and more calcium is enriched in small particles that are assimilated into aluminosilicate to form sticking ash particles with an increase of the O₂ concentration. The higher CO₂ concentration also leads to an increasing yield of carbonate minerals. O₂/CO₂ combustion has insignificant effects on the coalescence of small particles (<2.5 μm); however, it inhibits the fragmentation of large particles (>10 μm), which causes the reduced generation of medium particles (>2.5 and <10 μm). The generation of medium particles obviously increases when the O₂ concentration is increased in O₂/CO₂ combustion. All of the results indicate that O₂/CO₂ environments can increase the slagging tendency of high-calcium-yield coal.