The purpose of this study is to examine the possibility of establishing a novel CO 2 absorption process with molten alkali carbonate using a bubble column reactor. In our previous study, a hot CO 2 recovery process using Li 4 SiO 4 suspended in molten Li 2 CO 3 -K 2 CO 3 was developed. In the process, molten alkali carbonate itself showed great potential for CO 2 absorption at high temperature. If a hot CO 2 absorption process were established using only molten alkali carbonate, it could make the system simpler and the operating temperature range could be extended without the limitation of reaction temperature of solid absorbent. In the study, molten Li 2 CO 3 , Na 2 CO 3 , K 2 CO 3 and its eutectic mixture were selected as CO 2 absorbent. A bubble column was chosen as the device for gas absorption at high temperature. First, the CO 2 absorption performance of each single molten alkali carbonate was investigated. The result showed that the molten Li 2 CO 3 had a great ability to absorb CO 2 at high temperature. Li 2 O was thought to be produced by decomposition of Li 2 CO 3 during the melting and purging process and a reaction of CO 2 with Li 2 O occurred during the absorption process. Further, the CO 2 absorption performance of eutectic mixture increased exponentially with increasing the ratio of Li 2 CO 3 in composition. Second, the possibility of establishing a CO 2 absorption process using molten Li 2 CO 3 was examined. The overall CO 2 absorption process in the bubble column was investigated and the experimental results showed that the mass transfer of CO 2 into molten Li 2 CO 3 was the rate-controlling step. The operational conditions of the bubble column were optimized. The superficial gas velocity was an important operational parameter that affected both the CO 2 absorption rate and total amount of CO 2 finally absorbed in the bubble column. The operating temperature also greatly affected the amount of absorbed CO 2 .
ASJC Scopus subject areas
- Chemical Engineering(all)