The effect of CO2-air mixture compositions on the formation and dissociation of CO2 hydrate

The disposal of carbon dioxide to the marine and sea bed sediments as CO2 gas hydrate is an innovative technique for solving the global environment issue. Experiments on the formation and dissociation of gas hydrate have been carried out using a pressure vessel to investigate the effect of carbon dioxide concentration in the gas phase. From the experiment results, the following are clarified: (1) There is a strong relationship between the partial pressure of carbon dioxide, concentration, and the temperature of formation and dissociation of gas hydrate. Therefore, the use of this relation enables the estimation of equilibrium conditions of the gas mixture. (2) The initial formation rate varies from 0.1 to 0.5 ml/(min.g). In terms of average values, the initial formation rate increases as the carbon dioxide concentration of the initial gas mixture increases. (3) From the analysis of component gas of gas hydrate and space gas, it can be assumed that nitrogen and oxygen are also incorporated into the hydrate structure cage as guest molecules. Moreover, it can be seen that the carbon dioxide concentration in the initial space gas is higher than that in the space gas at the time of gas hydrate formation. Therefore, this hydrate technology applies to the concentration of carbon dioxide. In future, we will attempt to carry out tests on the formation and dissociation of CO2 hydrate under a low concentration of CO2, Furthermore, we will analyze the structure of gas hydrate using Raman spectroscopy to clarify that nitrogen and oxygen are incorporated into the gas hydrate cage as guest molecules.