Limestone Decomposition in an O2/CO2/Steam Atmosphere Integrated with Coal Combustion

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• 作者：Zehua Li ; Yin Wang ; Zhiwei Li ; Meng Li ; Kai Xu ; Wenqiang Liu ; Guangqian Luo ; Hong Yao
• 刊名：Energy & Fuels
• 出版年：2016
• 出版时间：June 16, 2016
• 年：2016
• 卷：30
• 期：6
• 页码：5092-5100
• 全文大小：615K
• 年卷期：0
• ISSN：1520-5029

文摘

Ca looping is one of the most promising technologies for CO₂ capture. Calcined limestone can be used in the Ca-looping system. It is a low-cost approach to decompose limestone integrated with coal combustion in an O₂/CO₂/steam atmosphere. In this approach, coal combustion heat is continuously supplied for limestone decomposition. We aim to obtain high-purity CO₂ exhaust gas and high-reactivity CaO sorbent. High-purity CO₂ exhaust gas is then further compressed or used. High-reactivity sorbent is then used to capture CO₂ from the coal power plant. However, little research was found to investigate limestone decomposition behavior under oxy-steam combustion conditions. In this study, limestone and coal particles were mixed together and decomposed/combusted in a continuously operating fluidized bed reactor in an O₂/CO₂/steam atmosphere. The results show that increasing O₂ and steam supply reduces the emission of CO, H₂, and SO₂, which enhances the purity of CO₂ exhaust gas. Limestone decomposition conversion is also enhanced with the increase of O₂ and steam supply. Besides, most coal sulfur and ash react with small CaO sorbent particles, which flow out of the reactor and remain in the cyclone. The amount of coal sulfur and ash is very low in a large CaO sorbent particle and has little influence on sorbent reactivity. In situ coal combustion results in a high particle temperature and high limestone decomposition conversion in the fluidized bed but also results in sorbent sintering and a sorbent reactivity decrease. Fortunately, sorbent reactivity is improved by introducing steam into limestone decomposition and a coal combustion atmosphere.