Study on the characteristics of natural gas hydrate crystal structures during decomposition process

Abstract

Hydrate decomposition is inevitable in the process of hydrate formation, and has an important research significance. In order to study the crystal decomposition process, the formation and flow of hydrate particles in natural gas + pure water system were experimentally studied in a high-pressure visual autoclave. During the experiments, the high-speed digital camera was used to capture the micro-morphology and decomposition process of gas hydrate particles, and the high definition camera was used to capture the agglomeration state of nature gas hydrate at the visual window to connect macro-and micro-phenomena organically. By analyzing the data obtained from experiments, we find that the micro-morphology of hydrate particles can be roughly divided into two categories: planar flake particles and polyhedral solid particles. The planar flake particles are further refined into non-trunk snowflake particles and dendritic particles with trunk growth. When snowflake particles begin to decompose, they tend to decrease in area and have rounded edges. The decomposition time of dendritic particles is longer, and there is always trunk in the system. During the decomposition process, the number of particles gradually decreases to zero, but there will be a slightly increase. Meanwhile, it is found that the higher heating temperature and initial pressure will aggravate the fluctuation of particle number. Finally, according to the microscopic changes of hydrate particles in the decomposition process obtained by high-speed digital camera and other equipment, and based on the independent physical models of two types of hydrate particles, the physical model of hydrate particles decomposition is established.