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Specialists of the Siberian Branch of the Russian Academy of Sciences are working on what they call a non-cryogenic method of helium extraction straight from natural gas and right at the gas fields.
Helium is a valuable and safe nuclear fuel and its use reduces radioactive discharges from operating reactors. Helium is consumed in large volumes at launchings of space probes operating on liquid hydrogen, in explosion-prone technological processes, in metal smelting, cutting and welding, in underwater operations, medicine (especially in tomography), gas chromatography, fiber optics, powder metallurgy, etc. The demand for helium is expected to grow with broader uses of airships, superconducting materials and the growing number of technical operations in space.
Helium is not retained by Earth's gravitation (as very light and chemically inert) and inevitably escapes beyond its confines. That creates a threat of its deficit already at the present time. As we know, helium is extracted from rare natural gases whose deposits were discovered for the first time in the United States at the start of the 20th century. Since then the main share of the world production and consumption of helium has belonged to that country (about 85 percent).
Today US helium deposits have been nearly exhausted. And although according to expert assessments the Americans have considerable resources of gas concentrates, obtained earlier and stored in underground reservoirs, scientists and industrialists are concerned with the possibility of a future crisis when these accumulated resources run out. This could happen in the 20s - 50s of the 21st century.
Unfortunately, in Russia too the only significant production of helium in Orenburg can come to an end (the size of the local deposits of such natural gases is rapidly dwindling). Our only hope in this respect is Eastern Siberia with its long established helium-bearing gas-and-oil condensate deposits: Sobinskoye (Krasnoyarsk Territory), Boutobinskoye (Yakutia), and Kovytkinskoye (Irkutsk Region).
The physical method of helium extraction has been known for a long time: the gas is gradually cooling with the carbohydrate components being condensed in the form of droplets or liquid film and helium remaining in gaseous state. It freezes down as the final component at temperatures near absolute zero.
But how much energy will be required to cool down all of that gas to the level of condensation of its components? Would it be necessary to have a power station at every gas well? And such deposits in Eastern Siberia are located far from the local industrial centers with their powerful sources of electricity. In a word, the aforesaid classical method does not suit our country.
But a way out was found, say what you may. According to RAS Corresponding Member, Vasily Fomin,
this happened when integration project began to be developed at the RAS Siberian Branch. Its specialists set the task of finding a material which would absorb helium. This problem has been solved by geologists. They suggested using zeolite-alumosilicates which are used at gas fields for drainage (dewatering) of natural gas. Detailed studies revealed that such materials absorb helium well when it is cooled down to cryogenic temperatures. But their industrial uses are practically impossible.
But the suggested idea has still been used by experts of the RAS Siberian Branch. They recalled that this "sunny", or solar gas has a unique capacity of penetrating through the glass shells of microspheres (cenospheres) at ordinary temperatures. And scientists decided that helium can be absorbed from a stream of gas with the help of just these peculiar glass pellets, or globules.
But how can helium be extracted without previous considerable cooling? As Prof. V. Fomin explains, during preparations for transportation through a main pipeline, gas condensate passes through adsorption columns where it must be stripped of excessive "residues" of water and benzine hydrocarbons. Vapors of their fractions condense upon zeolites and the globules retain helium. From there helium cannot escape in an easy way: to extract it, a layer of globules has to be heated up, or pressure has to be reduced of the initial gas mixture. In this way one can obtain not pure helium, but its concentrate containing 80 percent of the gas. And then the gas can be cleaned of admixtures by means of adsorption or similar methods, getting the final product of the required purity.
The important task before scientists now is to coordinate all of these parameters with the technologies used in ordinary production processes. Let us say that the zeolites absorb moisture for a certain time and helium is also absorbed until the sorption capacity of the layer is exhausted. And that means that the given time intervals should coincide to ensure the optimal regime for the process.
Summing up the proposals of the experts of the RAS Siberian Branch, one comes to the conclusion that what we shall finally have at our disposal will be plants set up at gasfields for the production of gas mixtures highly enriched with helium.
Nauka v Sibiri (Science in Siberia), 2004
Prepared by Yaroslav RENKAS
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