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High-Efficiency CaO-Based Sorbent Modified by Aluminate Cement and Organic Fiber Through Wet Mixing Method

Li, Zehua, Ouyang, Juncheng, Luo, Guangqian, Yao, Hong
Industrial & engineering chemistry process design and development 2019 v.58 no.48 pp. 22040-22047
acetates, calcium, calcium carbonate, calcium hydroxide, calcium oxide, carbon dioxide, cellulose, cement, lint cotton, mixing, sorbents
CaO-based sorbents are usually used for high-temperature postcombustion CO₂ capture through cyclic carbonation–calcination reactions. However, the rapid decay of sorbent reactivity limits their application. In this study, three types of CO₂ sorbent precursors, namely Ca(CH₃COO)₂, Ca(OH)₂, and CaCO₃, are used to produce initial CaO-based sorbents. Then, the initial sorbents are mixed with aluminate cement and organic fibers at an appropriate ratio to synthesize high-efficiency sorbents. Our results show that the cyclic performance of the sorbent that decomposed from Ca(CH₃COO)₂ is better than that decomposed from Ca(OH)₂ and CaCO₃. It is mainly because the sorbent pore structure becomes much developed after Ca(CH₃COO)₂ decomposition. Furthermore, when mixed with aluminate cement, the CaO-based sorbent achieves a good performance for CO₂ capture because of the formation of the sorbent skeleton Ca₁₂Al₁₄O₃₃. For example, when the mass ratio of Ca(OH)₂ to aluminate cement is set as 1:1, CaO conversion achieves 56% even after 20 cycles. To further improve the composite sorbent pore structure and its performance, pore-forming method is also put forward by mixing an organic fiber (cotton fiber, palm fiber, or microcrystalline cellulose) with the composite sorbent before decomposition. The result shows that the sorbent pore-formed by cotton fiber achieves a good performance with CaO conversion of 80% after 20 cycles, whereas the CaO conversion of the sorbent pore-formed by palm fiber shows only a little enhancement. On the contrary, the reactivity and stability of the sorbent pore-formed by microcrystalline cellulose show a marked decline.