氧化钙基CO_2吸收剂活化方式研究进展

Research advance review over the activation methods for calcium oxide based sorbents for CO_2

基于煅烧/碳酸化反应的原理,利用氧化钙(CaO)基吸收剂捕集CO2工艺具有明显的技术优势和广阔的应用前景,被视为削减CO2排放的有效措施,然而高温烧结将明显降低吸收剂的CO2循环吸收效率。对CaO基吸收剂活化方式的研究现状进行综述,分析了人工合成、掺杂或负载、高温预处理、水/水蒸气水合4种主要活化方法的特点,并总结了最具应用潜力的CaO基吸收剂活化方式及研究趋势。结果表明,利用工业废弃物作为CO2吸收剂和采用碳酸化-煅烧再生-水蒸气活化3段反应耦合这两种活化方式具有明显优势。未来CaO基吸收剂活化方式的研究除考察CO2吸收容量外,吸收剂机械性能的评价也将作为后续活化方式的重点研究内容。

This paper intends to provide a research advance review over the activation methods for CaO based sorbents, which include the synthesis, addition of dopants and supports, thermal activation and water/steam hydration, with an analysis of the research trends included. The ability of CaO based sorbents to maintain stable reactivity over multiple carbonation/calcination cycles is considered as important factor to CO2 capture. Nevertheless, high temperature sintering tends to cause the morphological change of sorbents, including the pore pluggage and surface area reduction. It is just for the above reasons that have brought about the great need for improving the sorbent reactivity through the activation in recent years. Of all the above activation strategies, the sorbents obtained from the synthesis and addition of dopants and supports, the thermal activation tend to be much higher costly, so they are not sustainable for practical application. On the contrary, the activation methods including indust.rial waste usage （i. e., carbide slag） and water/steam hydration are likely tO be most promising ones for their sustaining and retaining the sorbent reactivity. Thus, it can be concluded that the mayenite （CaI2Al14033） is expected to be made from the carbide slag through calcination, which comes from the principal reason for its high stability in the carbonate looping process. In addition, hydration method mainly adopted in the carbonationcalcination - steam hydration can also effectively promote the sorbent reactivity. Besides, the hydration step can also be well integrated into the overall energy conversion process in an efficient and economical way. As has been broadly reported in science literatures, carbonate looping process can most conveniently be realized in circulating fluidized bed （CFB）. Under the CFB system, it is likely for the severe mechanical degradation of sorbent particle to occur due to the motion and collision and then CO2 capture efficiency decreases. Thus, from a practical standpoint of view, the future research of activation methods for CaO based sorbents should not only be focused on the sorbent reactivity, but great attention has to be paid to further investigations of the attributive behaviors of sorbent particles.