Amine based solvent for CO2 absorption : from molecular structure to process

Abstract

Global warming is a well-known, worldwide concern, most probably caused by increasing concentrations of CO2 and other greenhouse gases in the earth’s atmosphere, due to human activities. Carbon Capture and Storage (CCS) offers the opportunity to reduce the CO2 emissions associated with the use of fossil fuels. Carbon dioxide capture with a regenerable solvent is considered a mature technology and already successfully applied as CO2 removal technology in industrial applications. In order to make this technology more economical for post-combustion capture, especially in the power-sector, solvents which require less energy and lead to lower solvent loss- and corrosion rates in this application are needed. In this thesis, the development of improved, energy efficient amine based solvents is targeted, through experimental (screening) work and by a further understanding of the role of molecular structure on the solvent absorption properties for amine-based solvents in a CO2 absorption process. Various molecular structural effects like carbon chain length, steric hindrance, functional groups and different configurations of cyclic amines have been investigated by quantum mechanical calculations. Furthermore, solvent screening experiments for CO2 absorption and regeneration were performed to identify above-mentioned molecular structural effects. 1,6 Hexamethylenediamine (HMDA) and 1,6 Hexanediamine, N,N' dimethyl (HMDA, N’N’) were identified as a potential solvent for CO2 absorption in this study. Solubility experiments for CO2 absorption were performed for 0.5, 1 and 2.5 mole/L aqueous solutions of HMDA at 20, 30 and 40°C. CO2 absorption kinetics for aqueous solutions of HMDA and HMDA, N,N’ were determined at concentrations ranging from 0.5 to 2.5 mole/L and temperatures from 10 to 30°C. Based on above experiments, new solvent formulations for CO2 recovery from flue gas were tested in a continuous flow pilot plant located at Shell Technology Centre, Amsterdam. The two most promising solvents tested in this study showed attractive properties for CO2 removal from flue gas and an almost 50% reduction in energy consumption, when compared to the commonly used MEA solvent. This work is expected to benefit the development of even better solvents for CO2 capture in the future.