Post Combustion Carbon Dioxide Capture with Membrane-Solvent Hybrid Systems
Akan, Aytaç Perihan
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The main objective of this research is to investigate carbon dioxide (CO2) absorption performance of aqueous methyldiethanolamine (MDEA) and activated methyldiethanolamine (aMDEA) solvents in a module containing microporous polypropylene cross-flow hollow fiber membrane coated with fluorosiloxane on the outer surface of fibers; such a module was used for both absorption and stripping. To investigate CO2 absorption rate, removal rate and recovery rate, a number of lab-scale CO2 absorption-stripping experiments were conducted using these absorbents for different operating conditions, such as gas flow rate, liquid flow rate, concentration of the absorbent, type of stripping mode. The experimental results reveal that overall mass transfer coefficient through the membrane increases as aMDEA concentration increases from 80 vol % to 100 %. Due to an increase in absorbent concentration, high amount of reactive amine molecules diffuses to the gas/liquid contacting interface resulting in an increase in the chemical activity between CO2 and amines. Moreover, overall mass transfer coefficient increases with increasing gas velocity and concentration of amine, but it shows a decreasing trend with increasing the liquid flow rate because of the residence time of absorption solution in membrane contactor. The maximum 98.4 % of absorbed CO2 was recovered in case of absorbent concentration of 90 % and in minimum gas, liquid and sweep gas flow rate conditions. To obtain better results, lower sweep gas flow rate and humidified feed gas flow rate should be suggested to provide better regeneration of the solvent and higher recovery of the absorbed CO2 for future works.