CO2 Hydrate Dissociation Research Articles

Formation of Carbon Dioxide Hydrate in Soil and Soil Mineral Suspensions with Electrolytes

We have identified the effects of solid surface (soil, bentonite, kaolinite, nontronite, and pyrite) and electrolyte (NaCl, KCl, CaCl2, and MgCl2) types on the formation and dissociation of CO2 hydrate in this study. The hydrate formation experiments were conducted by injecting CO2 gas into the soil suspensions with and without electrolytes in a 50 mL pressurized vessel. The formation of CO2 hydrate in deionized water was faster than that in aqueous electrolyte solutions. The addition of soil suspensions accelerated the formation of CO2 hydrate in the electrolyte solutions. The hydrate formation times in the solid suspensions without electrolytes were very similar to that in the deionized water. We did not observe any significant differences between the hydrate dissociation in the solid suspension and that in the deionized water. The pHs of clay mineral suspensions decreased significantly after CO2 hydrate formation and dissociation experiments, while the pH of the soil suspension slightly decreased by less than pH 1 and that of pyrite slightly increased due to the dissolution of CO2 forming carbonic acid. The results obtained from this research could be indirectly applied to the fate of CO2 sequestered into geological formations as well as its storage as a form of CO2 hydrate.

The Effect of CO2‐Air Mixture Compositions on the Formation and Dissociation of CO2 Hydrate

Abstract: 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.

混合ガスにおける二酸化炭素濃度の影響 二酸化炭素ハイドレートの生成解離に関する基礎的研究 Ｉ

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 mixture gas. 2 The initial formation speed varies from 0.1 to 0.5 ml / (min. g). Considering, the average values of the initial formation speed, the initial formation speed increases as the carbon dioxide concentration of the initial mixture gas also 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 cage of hydrate structure as guest molecules. Moreover, it can be seen that the carbon dioxide concentration in the initial space gas is of higher level than the carbon dioxide concentration in the space gas at the time when the gas hydrate grew up. Therefore, this hydrate technology applies in the concentration of carbon dioxide. In the near 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 the Raman spectroscopy to clarify that nitrogen and oxygen are incorporated into the cage of gas hydrate structure as guest molecules.