The Ratio of Chemical and Physical CO2 Absorption Capacity in Triethanola mine and Methyl-diethanolamine Solution Systems

The present paper reports the ratio of real chemical (rCAC(C)) and physical (rCAC(P)) CO2 absorption capacity to total absorption capacity (CAC(T)) at absorption time t in 0.01-0.05 mol/L (M) triethanolamine (TEA) and methyl-diethanolamine (MDEA) aqueous solution systems; this is calculated based on the directly measured electrical conductivity (ECm) of the solutions during the absorption time. Although physical absorption becomes dominant in the initial absorption period, it does not reach its saturation state. Thereafter, the chemical absorption dominant period (CADP)-which is the time period where the ratio of rCAC(C) to CAC(T) exceeds 50%-is present in the MDEA and TEA solutions over 0.02 M. The CADP and its ratio to the overall absorption time were proportional to the amine concentrations of the solutions, and with the same amine concentrations, the MDEA system had a lower CADP ratio than the TEA system; specifically, the CADP ratios of the 0.04 M MDEA and TEA solutions were 23.2 and 36.4%, respectively, which is because the absorption rate of MDEA is relatively faster than that of TEA. Upon completion of chemical absorption, physical CO2 absorption resumed to reach the saturation state, and all the absorption reactions were terminated.

Automated summary

This study investigated the ratio of real chemical and physical CO2 absorption capacity to total absorption capacity in triethanolamine and methyl-diethanolamine aqueous solutions. Physical absorption dominated in the initial absorption period without reaching saturation. A period of chemical absorption dominance was observed, proportional to the amine concentration. Methyl-diethanolamine had a lower dominance ratio compared to triethanolamine, likely due to its faster absorption rate. Upon completion of chemical absorption, physical CO2 absorption resumed until saturation was reached.