Selective Absorption of HCl from a Gas Mixture with CO2 by Alkali Solution in a Rotor–Stator Reactor

• Published in: Industrial & engineering chemistry research Vol. 63; no. 4; pp. 2057 - 2062
• Main Authors: Xiao, Hao, Wu, Tianyang, Song, Yunhua, Chen, Jianming, Xiang, Yang, Yun, Jimmy, Shao, Lei
• Format: Journal Article
• Language: English
• Published: American Chemical Society 31.01.2024
• Subjects: General Research
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.3c03526

This study proposes the utilization of a rotor–stator reactor (RSR) to address the issue of excessive alkali consumption by CO2 in the treatment of off-gas containing HCl and CO2 in conventional columns. First, an investigation was conducted to explore the interaction between HCl absorption and CO2 absorption by alkali solution in the RSR. The results revealed that no discernible interaction between HCl and CO2 absorption occurred in the RSR under the typical concentrations of HCl and CO2 in off-gas. Subsequently, the absorption performances of HCl and CO2 by using different absorbents in the RSR were explored. It was observed that the absorption of HCl by both water and alkali solution in the RSR demonstrated negligible disparities. This may be attributed to the high liquid-side mass-transfer coefficient in the RSR, which mitigated the intensification effect of the reaction on the mass transfer of HCl. According to these findings, a selective absorption process for HCl from a gas mixture containing CO2 employing an alkali solution during a recycle operation in the RSR was implemented. This process facilitated the desorption of CO2 absorbed in the initial stage by lowering the final pH during the recycling operation, resulting in zero consumption of alkali by CO2. Although the process based on the packed column can selectively absorb HCl by intensification such as multiple columns in series, the smaller size of RSR will save the cost of equipment investment.