(154e) Experimental CO2 Capture Using Deep Eutectic Solvents and Modelling of CO2 Removal from Shale Gas

Carbon capture and storage (CCS) involves the capture of CO₂ from the emissions generated mainly due to the combustion of coal or natural gas and includes the further sequestration of the captured CO₂ in the particular geological formations. However, the overall cost during CCS is mostly in capturing CO₂ from emission sources. Therefore, it is required to make the capture process economical to allow the deployment of CCS.

Recently, Deep Eutectic Solvents (DESs) similar to that of Ionic Liquids have shown the ability to capture CO₂. They comprise of salt and another compound as hydrogen bond donor (HBD) resulting in a low melting point mixture. DESs usually have low melting temperatures due to the formation of their intermolecular hydrogen bonds. In particular, the highest CO2 absorption was observed for the tetra butyl ammonium bromide and methyl diethanol amine
(TBAB/4MDEA) system at 1 MPa and 303.15 K. Thermophysical properties of all synthesized DESs were estimated using the modified Lydersen−Joback−Reid method and Lee−Kesler mixing rule. Experimental CO2 solubility data were well fitted using the nonrandom two liquid and the Peng−Robinson thermodynamic models.

Present Work involves the experimental CO₂ solubility in different combinations of Deep Eutectic Solvents involving Choline Chloride and Tetra butyl ammonium bromide as Hydrogen Bond Acceptor while Di-ethanol amine, Methyl diethanol amine, ethylene glycol and di-ethylene glycol as Hydrogen Bond Donors. Decarbonization of Shale Gas is based on two very effective amine based DESs- Ethaline and Reline. We intend to present the Decarbonization (CO­₂ Removal) of Shale Gas using economical Deep Eutectic Solvents proved as a perfect substitute for Ionic Liquids. The experimentally calculated solubility results of CO₂, as well as CH₄ in the reline and ethaline along with the physicochemical properties of DESs, were employed for the modelling and simulation of CO2 removal studies. The VLE data of CO₂ in DESs and CH₄ in DESs were modelled using the Peng-Robinson equation of state and the calculated values are in good agreement with the experimental values. Furthermore, the process simulation was done to investigate the DES-based CO₂ removal from a model shale gas. The simulation results show higher shale gas recovery from DES process compared to conventional MDEA process. Also, the purity of shale gas was more in the DES-based CO₂ capture process than the MDEA process.

A real shale gas stream was subjected to the absorber and flash drums were used to recover the CO₂. The process flow sheet was designed from the results obtained from the experimental process. The enhance CO₂ solubility in the DESs is due to a decrease in viscosity and Vapor-liquid equilibria of CO₂ solubility in aqueous DESs is further modeled using the NRTL thermodynamic model. Kinetic modeling of CO₂ absorption in DESs was also studied and rate constants were evaluated.