CO 2 hydrate can be used as an alternate cooling substance in air-conditioning systems to minimize the use of traditional refrigerants, such as HFCs and HCFCs. A novel CO 2 hydrate-based refrigeration system with a function of cold energy storage was designed and investigated, using tetrahydrofuran (THF) as the thermodynamic promoter. Coefficient of performance (COP) of this system was calculated based on the simulation results. Effects of various operation parameters were also studied closely. The cold storage operation was then designed to investigate the energy storage ability of the current system. Results show that the system COP is 6.8, which is the major strength of this novel system. Because of the energy intensive process of CO 2 compression, the work imposed on elevating the gas pressure was considerable. A search for more appropriate additives or alternate guest substances should be conducted. In addition, compressor efficiency and pump efficiency are both critical for improving the energy efficiency. Enhanced refrigeration performance can also be realized at higher hydrate mass fraction. In addition, two different cold energy storage operation strategies were obtained. This research is of great significance to the in-depth development of hydrate-based refrigeration and cold energy storage system. The proposed system might contribute to minimizing the use of conventional coolants and realizing peak load shifting in the near future.

Carbon capture and storage (CCS) is regarded as the most efficient approach in handling the global warming crisis. MEA-based CO 2 capture is a well-developed chemical absorption method with a long period of industrial application. A novel hydrate-based gas separation (HBGS) method, with a wide range of advantages, has recently received special attention from researchers. In this study, two different CO 2 separation processes were simulated utilizing Aspen Plus software. The feasibility of both processes was validated, and the process energy consumption and exergy loss were also compared at the same flue gas condition. Some efforts have also been made to investigate the effects of different operation parameters on the process energy efficiency. Results show that the first law efficiency of the MEA-based CO 2 separation system is 88.19% and the second law efficiency of the system is 38.32%, while the corresponding values of the hydrate-based separation system are 74.15% and 38.85%, respectively. Cooling of the lean amine solution and the regeneration process occupy the largest portion of exergy loss in the MEA separation system. In the hydration separation, the flue gas compression and cooling are the major causes for exergy loss.

Hydrate-based gas separation (HBGS) is a novel carbon dioxide capture technology, which helps in the alleviation of the human-induced global warming crisis. However, hydrate formation for flue gases with relatively low CO2 concentration requires higher pressures or lower temperatures. The addition of thermodynamic and kinetic promoters seems to be the most efficient way of moderating the hydrate formation condition. In this research, a two-stage hydrate-based CO2 capture process was proposed and then simulated in Aspen HYSYS software to investigate the effect of two commonly used promoters tetrahydrofuran (THF) and tetra-n-butylammonium bromide (TBAB). These two promoters were then compared in terms of energy consumption, exergy loss, and environmental perspective. Sensitivity analysis was also carried out to study the effect of the split fraction of CO2. Results show that the energy consumed in the compression process is much more significant than that in the refrigeration process and the pumping process. Increasing the THF concentration from 1 to 3 mol % leads to a decrease of around 10% in the total electrical power consumption at the same formation condition. TBAB is recommended as an appropriate promoter compared with THF, considering the captured CO2 concentration, the flow rate of CO2, and effects on the environment. Exergy analysis results indicate that a considerable process exergy loss is caused by the clean gas outflows. In the sensitivity analysis, the split fraction of CO2 has a great impact on the concentration of the captured target gas and energy consumption per unit. Energy consumption results, exergy analysis, and sensitivity analysis in this study are of great value for research and development of HBGS technology for CO2 emission reduction.