Experiment and simulation for CO2 capture using low transition temperature mixtures as solvents

Abstract

CO2 capture and storage technology, which is used to control the rate of global warming, is the most promising and feasible solution to reduce the concentration of CO2 in the atmosphere. In this work, experiment and simulation of CO2 capture process using low transition temperature mixtures (LTTMs) as solvents are studied. First, LTTMs were synthesized by using levulinic acid as hydrogen bond donor (HBD) and tetraethylammonium chloride as hydrogen bond acceptor (HBA). The solubility of CO2 in LTTMs was measured and effects of the mole ratio of HBD to HBA on solubility were also examined. It demonstrated that the solubility of CO2 in LTTMs increased with the increasing pressure or the decreasing temperature. Henry’s constants and thermodynamic properties such as Gibbs energy, enthalpy and entropy of dissolution were deduced by correlating the solubility data. Second, in order to explain the absorption mechanism, σ-profiles were adopted to study the molecular interactions between HBD/HBA/LTTMs and CO2. The analysis for geometry, interaction energy, independent gradient model and atoms in molecules were performed to explain the interaction mechanisms between CO2 and HBD/HBA/LTTMs. Moreover, CO2 capture process with LTTMs as solvents was simulated using Aspen Plus software. The design variables of CO2 capture process were optimized using multi-objective generic algorithm, and the optimal operating parameters were obtained. At last, the dynamic controllability of CO2 capture process was studied and an effective control structure was proposed, which worked quite well for the disturbances in both feed flow rate and feed composition.