Fundamental study of impurities influence on hydrate nuclaeation

It is important to elucidate the knowledge of hydrate nucleation for not only hydrate basic field but also engineering and industrial field。However the knowledge of hydrate nucleation is lacked due to the difficulty of formation of hydrate even under the suitable pressure and temperature conditions on the phase diagram experimentally.The objective of the present study is to elucidate the conditions which influence on hydrate nucleation。In this study，we used the liquid CO_2related to the ocean as a guest and measured the induction time under the various conditions of the surrounding water as a host(temperature，dissolved CO_2concentration，and initial H_2O cluster)We measured the time from putting liquid CO_2droplet into the pressure chamber(30 MPa，3~5℃)to forming the hydrate film.Relationship between dissolved CO_2concentration，water temperature in the chamber and induction time was evaluated respectively and following results were obtained。·The relation between CO_2concen…More tration and induction time wasn‘t confirmed.·There is the tendency that the lower temperature and the larger volume of putted liquid CO_2droplet cause the shorter the induction time.We putted liquid CO_2droplet and measured the induction time after the temperature and pressure history of a host water side have been changed，(Initial H_2O Cluster Have Been Changed)We obtained following results。·In the case of using the water that had previously left under the atmospheric pressure and low temperature，hydrate formation was hardly observed。·In the case of using the water that had previously frozen as ice and melted at atmospheric pressure，hydrate formation was not observed。·In the case of using the water that had previously frozen as ice and melted at hydrate formation pressure，hydrate formation was identified。In addition the ratio of melted water weight was changed.The lager quantity of melted water causes the shorter the induction time.From above knowledge，we elucidated that CO_2concentration hardly influence on hydrate nucleation in the range of CO_2concentration of this study and the condition of H_2O cluster of the host water side may influence on hydrate nucleation greatly.Less：Less

It is important to elucidate the knowledge of hydrate nucleation for not only hydrate basic field but also engineering and industrial field. However the knowledge of hydrate nucleation is lacked due to the difficulty of formation of hydrate even under the suitable pressure and temperature conditions on the phase diagram experimentally.The objective of the present study is to elucidate the conditions which influence on hydrate nucleation. In this study, we used the liquid CO_2 related to the ocean as a guest and measured the induction time under the various conditions of the surrounding water as a host (temperature, dissolved CO_2 concentration, and initial H_2O cluster)We measured the time from putting liquid CO_2 droplet into the pressure chamber (30MPa, 3〜5℃) to forming the hydrate film. Relationship between dissolved CO_2 concentration, water temperature in the chamber and induction time was evaluated respectively and following results were obtained.・The relation between CO_2 concen … More tration and induction time wasn't confirmed.・There is the tendency that the lower temperature and the larger volume of putted liquid CO_2 droplet cause the shorter the induction time.We putted liquid CO_2 droplet and measured the induction time after the temperature and pressure history of a host water side have been changed, (Initial H_2O cluster have been changed) We obtained following results.・In the case of using the water that had previously left under the atmospheric pressure and low temperature, hydrate formation was hardly observed.・In the case of using the water that had previously frozen as ice and melted at atmospheric pressure, hydrate formation was not observed.・In the case of using the water that had previously frozen as ice and melted at hydrate formation pressure, hydrate formation was identified. In addition the ratio of melted water weight was changed. The lager quantity of melted water causes the shorter the induction time.From above knowledge, we elucidated that CO_2 concentration hardly influence on hydrate nucleation in the range of CO_2 concentration of this study and the condition of H_2O cluster of the host water side may influence on hydrate nucleation greatly. Less