Experimental and Theoretical Studies on Mass Transfer Performance for CO2 Absorption into Aqueous N,N-Dimethylethanolamine Solution in the Polytetrafluoroethylene Hollow-Fiber Membrane Contactor

N,N-Dimethylethanolamine (DMEA) is a promising absorbent due to the relative higher reaction rate and high capacity for CO2 capture. In this work, the CO2 absorption performance into aqueous DMEA solution using a polytetrafluoroethylene (PTFE) hollow-fiber membrane contactor (HFMC) was investigated experimentally and numerically. The CO2 absorption fluxes were determined under various important operating parameters, including liquid velocity, gas velocity, liquid feed temperature, CO2 partial pressure, and CO2 loading in liquid phase. In addition, a 2D steady-state mathematical model was established to predict the CO2 absorption flux in two operation modes, nonwetted and partially wetted modes, and was validated by using the CO2 absorption into water and aqueous MEA solution. The experimental and simulated results revealed that the CO2 absorption flux can be enhanced by increasing liquid velocity, liquid-phase temperature, and amine concentration in a moderate range. Also, the CO2 absorption flux will increase with the increasing gas velocity and CO2 partial pressure but decrease with increasing CO2 loading in the liquid phase. In addition, the membrane wetting can cause a severe deterioration in the CO2 absorption performance even with a slight membrane wetting. The CO2 absorption fluxes for CO2 absorption into DMEA solutions show the good agreement with or are closer to the simulated data with the membrane wetting of 10% under the same operational conditions, with the average absolute relative deviation (AARD) of 5.02%. Furthermore, the obtained radical and axial CO2 concentration profiles from the mathematical model were also discussed to further understand the CO2 absorption process.