메탄 하이드레이트 형성을 위한 제올라이트의 영향

Abstract

Methane hydrate is formed by physical binding between water molecules and gases such as methane, ethane, propane, or carbon dioxide, etc., which are captured in the cavities of water molecules under the specific temperature and pressure. More than 99% of naturally produced methane hydrate consists of methane, and is widely dispersed in the continental slope and continental Shelf of the Pacific and the Atlantic, the Antarctica, etc. The reserve of fossil fuel is 500 billion carbon ton and the reserve of methane is 360 million carbon ton. The reserve of gas hydrate is more than 1 trillion carbon ton, which is twice the fossil fuel. Therefore, natural gas hydrate as a kind of gas hydrate is expected to replace fossil fuel as new energy source of 21st century.

Also 1 m3 hydrate of pure methane can be decomposed to the maximum of 216 m3 methane at standard condition. If these characteristics of hydrate are reversely utilized, the natural gas is fixed into water in the form of hydrate solid. Therefore, the hydrate is considered to be a great way to transport and store natural gas in large quantity. Especially the transportation cost is known to be 18∼25% less than that of the liquefied transportation.

However, when natural gas hydrate is artificially formed, its reaction time may be too long and the gas consumption in water becomes relatively low, because the reaction rate between water and gas is low. Therefore, for the practical purpose in the application, the present investigation is focused on the rapid production of hydrates and on the increases of gas consumption by adding natural zeolite into pure water.

The results of the study show that the equilibrium pressure in natural zeolite is more lower than that in distilled water, and methane hydrate could be formed rapidly during pressurization, if the subcooling is maintained at 8K or above in distilled water and 6.5K or above in natural zeolite, respectively. Also, the amount of consumed gas volume in natural zeolite is more higher than in distilled water at the same experimental conditions. Also, when the natural zeolite of 0.01 wt% was added to distilled water, the amount of consumed gas was about four times higher than that in distilled water and the hydrate formation time decreased at the low subcooling temperature. Therefore, it is found that natural zeolite acts as a catalyst in hydrate formation.