| Summary: | This study used the solvent monoethylamine (MEA)/CaCl<sub>2</sub>/H<sub>2</sub>O to investigate CO<sub>2</sub> absorption and CaCO<sub>3</sub> crystallization in a bubble column scrubber. The variables explored were pH, gas flow rate, gas concentration, the liquid flow rate of the solution to absorb CO<sub>2,</sub> and CaCO<sub>3</sub> crystallization. Under a continuous mode, the solution of CaCl<sub>2</sub> was fed continuously, and the pH dropped after CO<sub>2</sub> absorption. To maintain the set pH value, there was an automatic input of the MEA solvent into the bubble column. In addition to maintaining the pH, the solution could also absorb CO<sub>2</sub> and produce CaCO<sub>3</sub> crystals, which served two purposes. The results showed that there were mainly vaterite crystals. At different pH values, the lower the pH, the higher the precipitation rate of vaterite (F<sub>p</sub>), and vice versa. However, under different gas flow rates, the F<sub>p</sub> decreased as the pH value increased. Additionally, the process variables also affected the absorption rate (R<sub>A</sub>) and the overall mass-transfer coefficient (K<sub>G</sub>a) generally increased with increasing pH, gas concentration, and gas flow rate. However, it slowed down under operating conditions at high pH and high gas flow rate. Finally, correlation equations for R<sub>A</sub>, K<sub>G</sub>a, and F<sub>p</sub> were also obtained and discussed in the study.
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