Design of Carbon Dioxide Capture Plant using Amine Based Ternary Deep Eutectic Solvents: DFT and Simulation

Abstract

The escalating levels of atmospheric carbon dioxide (CO2) and their profound impact on global climate patterns necessitate the advancement of effective carbon capture and storage (CCS) techniques. This thesis provides a review of CCS technologies, with a focus on the potential of amine-based deep eutectic solvents (DESs) for efficient CO2 absorption. The methodology adopted in this study includes the development of a comprehensive thermodynamic model that will be incorporated into a process simulation to simulate [Ch][Cl]:6MEA and [Ch][Cl]:6MEA mixed with water as a viscosity reducing ternary component. Ab-initio calculations for the DESs were performed using an implicit density functional theory (DFT) model based on COSMO continuum solvation effects. The methodology, adapted from ionic liquids using COSMO-RS, Aspen Plus, and Aspen Process Economic Analyzer, defined the solvents in Aspen Plus. This approach thermodynamically modeled the physiochemical properties and interactions of the DESs with CO2 using COSMO-RS, DFT, and experimental data from literature, followed by regression and input into Aspen Plus with the COSMO-SAC thermodynamic model for simulating postcombustion processes. The study investigated the effect of water on Henry’s law constant and reaction equilibrium, incorporating water's dielectric constant into the DFT calculations. Results indicated that adding 10% water by weight improved physical interactions and made the reaction more spontaneous, increasing the reaction enthalpy from -20.81 kJ/mol to -22.86 kJ/mol and 24.45 kJ/mol for [Ch][Cl]:6MEA – 5 wt.% and [Ch][Cl]:6MEA – 10 wt.%, respectively. Simulation results showed enhanced solubility with water addition, from 0.097 gCO2/gDES to 0.12 gCO2/gDES and 0.23 gCO2/gDES for [Ch][Cl]:6MEA – 5 wt.% and [Ch][Cl]:6MEA – 10 wt.%, respectively, at 1 bar and 313K. Desorption energy for [Ch][Cl]:6MEA – 10 wt.% (5.09 GJ/tCO2) was found to be lower than that for [Ch][Cl]:6MEA (6.23 GJ/tCO2) and the benchmark 30wt.% MEA (5.28 GJ/tCO2). Adding water reduced pumping costs and water circulation by reducing viscosity and increasing solubility, thus lowering coolant requirements. Economic analysis showed reduced column diameters and improved CAPEX. Sensitivity analysis on solvent prices indicated total annual costs (TAC) of 152.8 $/tCO2, 141.02 $/tCO2, 130.34 $/tCO2, and 110.40 $/tCO2 for [Ch][Cl]:6MEA, [Ch][Cl]:6MEA – 5 wt.%, [Ch][Cl]:6MEA – 10 wt.%, and 30 wt.% MEA, respectively. The best solvent was determined to be [Ch][Cl]:6MEA – 10 wt.%, where the capture cost is 18% higher compared to benchmark 30 wt.%MEA. Future works requires a more sophisticated approach for DFT that involves using transition state calculation and pilot plants testing to validate the absorption isotherms of the solvents and validate the solubility at the demonstrated process configuration.

Date of Award	20 Jul 2024
Original language	American English
Supervisor	Enas Nashef (Supervisor)