Analysis of thermal stability of clathrate hydrate and increase of gas storage kinetics

Abstract

Clathrate hydrate is a kind of inclusion compound which is composed of water and small molecules such as methane, ethane, tetrahydrofuran, nitrogen, oxygen and etc. Water molecules comprise host framework of clathrate cages and small molecules are enclathrated within cages. To form such cage-like structures, low temperature and high pressure condition is essential. Lots of studies for application of clathrate hydrate to various fields have been preceded. The objective of this study can be divided into three one. First, how size of pore affects on phase equilibrium of $CO_2$ + $N_2$ hydrate system. Seconds, increase of gas storage rate of THF hydrate system by using thermal cycle. In the First study, we examined the role of porous silica gels as natural sandstone media contained in deep ocean methane hydrate. To secure the indispensable information needed for developing the $CH_4$-$CO_2$ swapping method, we must first determine various types of phase equilibrium data concerning three major guests of $CH_4$, $CO_2$, and $N_2$. Here, we adopted the saturated water in silica gel pores to substantially enhance active surface for contacting and encaging gas molecules and measured the three-phase hydrate (H)-water-rich liquid ($L_W$)-vapor (V) equilibria of $CO_2$+$N_2$ gas hydrates in 6.0, 15.0, 30.0nm silica gel pores to investigate the effect of geometrical constraints on the phase equilibrium patterns. As expected, the hydrate stability region is shifted to a higher pressure region depending on pore size when compared with those of bulk hydrates and we also confirmed that both the modeling and experimental data agrees well. The overall experimental results can be useful in the exploitation of natural gas hydrate in marine sediments and sequestration of carbon dioxide into the deep ocean In the second study, we had focused on how to increase gas storage rate by thermal cycles and investigated factors that affect storage kinetics. Thermal cycle means procedure th...