Insights into the interaction between typical amines and alkaline minerals for improved CO 2 absorption and mineralization

Abstract

Amine scrubbing is a mature technology to cut down CO2 emissions from human activities but suffers from a high energy consumption of solvent regeneration. The integrated CO2 absorption and mineralization (IAM) process can effectively reduce the energy consumption of amine regeneration by replacing traditional thermal regeneration with chemical regeneration via CO2 mineralization. However, a fundamental understanding of the interaction between typical amines and alkaline minerals was still lacking. In this paper, the effects of amine types on amine regeneration, alkaline metal leaching, and CaCO3 precipitation during the IAM process were explored by using five typical amines and Ca(OH)2/Mg(OH)2. Results showed very different regeneration kinetics and efficiencies were observed in five selected amine solutions, which displayed a decreased performance in the order TEA > MDEA > DEA > AMP > MEA. The regeneration performance was significantly affected by the dissolution of Ca(OH)2/Mg(OH)2 which was inversely proportional to the trend of their pKa values. TEA displayed the largest regeneration efficiency of about 95% by Ca(OH)2 and 83% by Mg(OH)2, which was much larger than other amines reported in the open literature, due to its lower pKa value than other selected amines. More interestingly, the particle size of CaCO3 produced from amine solutions was smaller than that from CaCl2 solution reported in the literature. There was a rough linear relationship between CaCO3 particle size and amine pKa values. TEA induced the formation of nano scaled CaCO3, which might be attributed to the adsorbing of TEA on the CaCO3 crystal and inhibiting the crystal growth. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.