Hydrate Phase Equilibrium Of Methane In The Aqueous Solutions Of Salts And Methanol Medium

Methane hydrates is a huge and new energy in the 21st century. It plays a important role in energy , environmental protection chemical engineering , space-flight and bioengineering. The research and development of the various new techniques as well as the utilization about gas hydrates are the research hot-point and developing direction at present. However, phase equilibrium and kinetic of methane (gas) hydrates are the key of the mentioned above, and also core and soul. In this paper, we present the concept , the present situation of study and developmental trend about gas hydrates. Based on the previous research, we discuss the characteristics , conditions and affecting mechanics on phase equilibrium of methane hydrates and analysis the formation and structural characteristics about methane hydrates by using the theory and method of geochemistry , physical chemistry and mathematics and experimental way( eg. Raman spectra). We apply the mathematics method in the study resulting in the empirical equation on calculating phase equilibrium conditions of methane hydrates. Based on the present phase equilibrium on gas hydrates, we conclude the regulation and phenomenon of different anions, cations and charges in the different salts about methane hydrates so as to have a huge contribution for explore and exploit of gas hydrates.According to the phase equilibrium, formation and Raman spectra experiment for methane hydrates, it is concluded that the following results and understandings:The water activity has an effect on the phase equilibrium conditions of methane hydrates in the presence of the electrolytes; and the electrolytes again influence the water activity. The inhibiting effectiveness increase with increased electrolyte concentration. The water activity increase with increased cation ionic radius, which results in the decreased inhibiting effectiveness. The water activity decrease with increased nation ionic radius, which results in the increased inhibiting effectiveness. The water activity decrease with increased ionic charges, which results in the increased inhibiting effectiveness. We concluded that the formational and stableconditions of methane hydrates depend on the salt, pressure, temperature , chemical composition and present environment and so on. Improved the phase equilibrium theory. As mentioned above, we think that AlCl3,NaK NaBr and so on are all the better inhibitors. A empirical equation on the phase equilibrium of methane hydrates is gained by statistics analysis, which has a very good agreement with the experimental data. As the formational experiment shown, the inhibiting effectiveness of pure water , molecular sieve , 3.5 wt%NaCl, 10wt%NaCl and sediments are different. According to the relationship between pressure and temperature, it is concluded that the formation of methane hydrates is consisted of solution , nucleation and growth and so on. According to Raman spectra analysis, the vibrational spectra of hydrates were shown to change when they are incorporated into the hydrate lattice, both in terms of position and band shape. The frequency of the CH4 band in the hydrate provides a signature for a specific crystal structure, suggesting that the Raman technique can be used to identify the hydrate crystal structure. The frequency of CH4 in the small and large cavities are not influenced by the present environment of methane hydrates. At last, in term of the phase equilibrium, we analysis the present geological conditions for methane hydrates, and also predict the possible distributional future of the north slope of Hanhai, the northwest slope of Okinawa trough and the permafrost regions on the qinghai-tibet plateau in China.