Energy Efficiency Analysis of Hydrate and Ionic Liquid-Based Binary Gas Separation Processes

Hydrate-based CO2 separation is a novel carbon capture and storage (CCS) technology that can alleviate the global warming. The effects of the CO2 concentration, driving force, subcooling degree, and liquid–gas ratio on the energy consumption and separation efficiency of three hydrate-based separation processes were investigated in this study. The simulation results showed that an increase in the liquid/gas ratio corresponds to an increase in the CO2 concentration, resulting in lower energy consumption for single-stage hydrate-based separation. Higher driving forces and subcooling degrees negatively impact the CO2 separation efficiency and energy consumption reduction. The maximum CO2 molar ratio obtained by the two-stage hydrate method was 82%, whereas that obtained by the hybrid ionic liquid (IL)-hydrate method reached 89% with the minimum energy consumption for a 20 mol % CO2/N2 gas mixture. Furthermore, the energy consumption for hydrate-based gas separation (HBGS) with a two-stage hydrate-based separation process achieved the minimal energy consumption at a driving force of 1.0 MPa. Without an energy recovery device, the minimum energy consumption of the two-stage hydrate method was 1.54 kWh/kgCO2, and that of the hybrid IL-hydrate method was 0.82 kWh/kgCO2. The findings revealed that the HBGS technology demonstrates significant potential for CO2 separation and capture.