Clathrate hydrate

Gas hydrates are present in the solid Aggregatzustrand inclusion compounds ( clathrates ), consisting of various gases and water. Natural gas hydrates contain mainly the gases methane, carbon dioxide and hydrogen sulfide. Special forms, mainly containing a particular gas molecule are referred to as, for example, methane.

The most important factors that lead to the formation of natural gas hydrates, are pressure, temperature and high gas concentration ( free gas dissolved in the sediment or in the pore water) in the surrounding medium. High pressure, low temperature and correspondingly high gas concentrations, the gas molecules are "captured" in the sediment on the seabed or in the clathrate formation in a molecular lattice consisting of water molecules. This results in a cage made of a plurality of water molecules, in which a gas molecule is included. One cubic meter of gas hydrate contains about 164 m3 of the corresponding gas. Cladratbildung by the pore space of the sediment is filled, and there are resources in the rule as sediment Gashydratgemisch. The sediment is cemented by gas hydrate and solidified with what is on continental slopes for their stability is of great importance. The gas hydrate is lighter than water and is held in this way from the heavier sediment on the seabed. Free gas hydrate in the water column rises quickly to the top. On its way it decomposes and feeds the appropriate vacant greenhouse while in the water column and possibly directly into the atmosphere. In the sediment the gas hydrate is stable up to several hundred meters depth. Partly due to sedimentation processes on long time scales, the gas hydrates formed near the sediment surface may also be located at greater depths below a stable surface layer. In larger sediment depths of the gas hydrate is again unstable due to the heat flow of the earth.

The process of gas hydrate formation is to ensure that even the CO ₂ sequestration that CO2 may be deposited from power plants for a long time, for example, on the sea floor safe and so can not escape into the atmosphere. Under favorable conditions, the artificially introduced into deep layers of sediment CO2 can convert there in the solid hydrate and kept as stable.

Gas hydrates were first found in 1811 by Davy in the form of hydrochloride. They have long been considered a curiosity until it was discovered by 1930 that an ice-like substance natural gas pipelines stuffy in cold regions. For these substances it was methane hydrate, which had been formed with the water present in the natural gas under the pressure of the pipeline. This existing also in the transportation of petroleum problem is circumvented by certain chemicals, inhibitors, are transported with the passengers. They change necessary for the formation of gas hydrates conditions so that as few gas hydrates occur at the pressure prevailing in the pipeline temperatures and pressures. Still can increasingly make or jam gas hydrates in particular on valves and similar disorders.

Seismic surveys have recently suggested that the amount of methane hydrate deposits is very significant on the seabed. They might be a potentially important source of energy for our future, even if the lossless decomposition could prove to be quite difficult, since methane must not get in larger quantities in the atmosphere ( greenhouse gas). The total amount of greenhouse gases from fossil fuels should be less than the amount of greenhouse gases that could be released from the known gas hydrate occurrences. Both carbon dioxide and methane are known greenhouse gases. It is estimated that a total of more than 1,000 gigatons of carbon stored in different types of gas hydrates.

However, not only as an energy supplier to the gas hydrates are of particular interest. The stability of the sea bottom is ensured at specific locations through it. So it can at sudden temperature or pressure differentials and the associated destruction or destabilization of gas hydrate layer to a slipping of the seabed on continental slopes come ( Storegga ), in which a tsunami could form.

Gas hydrates could facilitate the transport of natural gas on ships. When transporting a storage temperature of -10 ° C would be necessary, as opposed to the storage temperature of liquid natural gas from -162 ° C

With regard to the current climate change gas hydrate should be examined from two points of view in the end:

• The use is not only because of possible accidents in the degradation controversial, but above all due to the fact that it is another fossil fuels, which would increase the potential of the anthropogenic CO2 emissions by a multiple.
• The increasing global warming also affects the hydrate in the sea, whose thawing would significantly speed up the heating additionally ( The greenhouse effect of methane is 30 times higher than that of carbon dioxide). The science currently believes that is to be expected with increased methane outlets in two to three hundred years.