Discussion on Mechanism of Self-preservation Effect of Methane Hydrate

摘要

Recently-discovered self-preservation phenomenon of gas hydrate, slow dissociation rate at out of hydrate forming condition, has attracted much attention to utilize for the shipping of natural gas as hydrate form. It was reported that this phenomenon appears strongly in very limited temperature ranges at several Celsius below zero. The experiment conducted at the National Maritime Research Institute, however, did not show such conspicuous self-preservation in the same temperature ranges. Then the authors propose a new model of self preservation basing on the assumption that the dissociation probability of hydrogen bond near the freezing point of water has a meaningful value compared with the association probability and makes the ice strong by restoring the cracks in the ice layer surrounding hydrate mass. This model can well explain the self preservation phenomenon and its strong temperature dependence. The different experimental results were also explained by combining the above model and the size dependent nature of plastic deformation of ice.