Effects of activators on mass-transfer enhancement in a hollow fiber contactor using activated alkanolamine solutions

Abstract

In this work, CO 2 capture from a CO 2/N 2 mixture was investigated in a membrane gas absorption (MGA) process experimentally and theoretically. 2-Amino-2-methyl-1-propanol (AMP) and piperazine (PZ) as activators were added into methyldiethanolamine (MDEA) solution, respectively, to form two aqueous solutions of activated MDEA. The experiments of CO 2 absorption into the activated MDEA aqueous solutions were carried out in a hollow fiber module. The activated mechanisms which combined chemical reaction mechanisms and a shuttle mechanism were presented to explain the activation phenomena in the course of gas–liquid mass transfer. A mathematical model was developed to simulate the mass-transfer behavior of the MGA. Both experimental and simulation results show that, the activated MDEA solutions can maintain lower CO 2 concentration of gas outlet of the module with an increase of liquid CO 2-loading of liquid inlet as compared with the non-activated MDEA solution. The mass transfer can be effectively enhanced in MGA for CO 2 capture when a little amount activators are added into the MDEA solution. Activator PZ has an advantage over activator AMP in mass-transfer enhancement of MGA. The mass-transfer fluxes of the activated MDEA solutions are significantly higher than that of MDEA solution. Effects of operation conditions such as gas and liquid flow rates on mass-transfer enhancement are limited. The model simulation is validated with experimental data.