The Gas Hydrates

Monday, September 21, 2009 by ShoXee

The GAS HYDRATES

A gas hydrate is a crystalline solid; its building blocks consist of a gas molecule surrounded by a cage of water molecules. Thus it is similar to ice, except that the crystalline structure is stabilized by the guest gas molecule within the cage of water molecules. Many gases have molecular sizes suitable to form hydrate, including such naturally occurring gases as carbon dioxide, hydrogen sulfide, and several low-carbon-number hydrocarbons, but most marine gas hydrates that have been analyzed are methane hydrates.

Gas Hydrates will be the coming future generation new source of energy.

Clathrate hydrates (or alternatively gas clathrates, gas hydrates, clathrates, hydrates etc) are a class of solids in which gas molecules occupy "cages" made up of hydrogen-bonded water molecules. These "cages" are unstable when empty, collapsing into conventional ice crystal structure, but they are stabilized by the inclusion of appropriately sized molecules within them. Most low molecular weight gases (including O2, H2, N2, CO2, CH4, H2S, Ar, Kr, and Xe), as well as some higher hydrocarbons and freons will form hydrate under certain pressure-temperature conditions. Clathrate hydrates are not chemical compounds. The formation and decomposition of clathrate hydrates are first order phase transitions, not chemical reactions.

Clathrates are believed to occur in large quantities on some outer planets, moons and trans-Neptunian objects, binding gas at fairly high temperatures. Clathrates have also been discovered in large quantity on Earth, e.g. in giant natural methane clathrate deposits on the deep ocean floor (e.g. in the northern headwall flank of the Storegga Slide, which is a part of the Norwegian continental shelf) and in permafrost regions (e.g. the Mallik gas hydrate field in the Mackenzie Delta of northwestern Canadian Arctic). Hydrocarbon clathrates are a problem for the petroleum industry, since their formation inside gas pipelines frequently leads to plug formation in the latter. Deep sea deposition of carbon dioxide clathrate to remove this greenhouse gas from the atmosphere has also been proposed.

Gas hydrates are created when water and gas combine to form a crystalline substance that looks like ice. This occurs when excess methane is present, and when temperature and pressure conditions are suitable. Gas hydrates are common in marine sediments along the margins of continents, where the methane originates from the decomposition of living things. Off the Oregon coast, the Juan de Fuca plate slides beneath the North American plate in a process called subduction. As subduction occurs, sediments are scraped off the Juan de Fuca plate and form ridges on the edge of the North American plate. This process leads to formation of gas hydrates.

Natural deposits

Worldwide distribution of confirmed or inferred offshore gas hydrate-bearing sediments.

Last edited by tahir ali (2009-09-06 09:30:39)