Post-combustion CO2 capture and separation in flue gas based on hydrate technology : A review

Hydrate-based CO2 separation technology is limited by complex formation conditions and low separation efficiency, makes it temporarily unable to realize commercial application. In this review, according to the superiority of additives in strengthening hydrate formation, the effects of different additives on the thermodynamics kinetics of hydrate formation were systematically summarized, and the strengthening mechanism was further elaborated from the perspectives of hydrate structure change and gas selectivity. Among them, quaternary ammonium salt is more environmentally friendly, and the separation factor reached 37 with TBAF, more than 90 mol% CO2 captured by the two-stage hydrate + membrane separation method. In addition, based on the characteristics of nanoparticles in enhancing heat and mass transfer, the impact of nanoparticles on the formation of CO2 hydrate was summarized, which provided a new idea for the research of additives. More importantly, the effects of experimental conditions and process flow on separation efficiency were also summarized. Energy analysis showed that the use of thermodynamic additives significantly reduced the investment cost of the system by more than 50%. However, higher hydrate formation heat leads to higher energy consumption, and the presence of kinetic additives improves significantly, emphasizing the urgency of developing more stable and lower formation heat thermodynamic additives and exploring the effect of mixed additives on commercial applications. At present, stirring methods were mostly used to strengthen hydrate formation with higher energy consumption. Future research should also strive to carry out experimental measurements under static conditions, and constantly optimize the reaction vessel and process.