Formation methods and applications of carbon dioxide hydrate: An overview
Qian Hu, Xin Xiao
Abstract
Continuous consumption of non-renewable energy and global warming brought by the emission of greenhouse gas induce great threats to sustainable development of humans. Fortunately, the studies of carbon dioxide hydrate provide a new perspective to effectively respond to above challenges. In the present study, the methods for the reinforcement of the formation of carbon dioxide hydrate are described from two aspects of thermodynamics and kinetics. The presence of thermodynamic additives could benefit for reducing the formation pressure of carbon dioxide hydrate while mechanical measurements, kinetic accelerators and external fields could play the positive roles in effectively improving associated kinetic parameters, which makes hydrate-based method more competitive than other carbon capture techniques due to higher efficiency and lower cost and energy consumption. Then the thermophysical properties including phase equilibrium data, dissociation enthalpy, thermal conductivity, thermal diffusivity, specific heat capacity and viscosity in the absence and presence of additives are also introduced briefly, which suggest that carbon dioxide hydrate possesses suitable phase temperature range required in air conditioning systems and large dissociation enthalpy, and good flow characteristics could be appeared for hydrate slurries. Finally, the application principle of hydrate-based method in carbon capture is explained and both separation efficiency and energy consumption are analyzed. In addition to carbon capture, the carbon storage technologies based on carbon dioxide hydrate are also described, and especially methane-carbon dioxide replacement technique is stressed due to the positive roles in both carbon dioxide storage and methane recovery. Considering air conditioning application, the studies on the carbon dioxide slurries as cold storage and transport media as well as alternative refrigerants are introduced. In addition, the existing problems of carbon dioxide hydrate are discussed, and the future development directions are pointed out.