Gas separation – Means within gas stream for conducting concentrate to collector
Patent
1989-11-17
1992-01-14
Spitzer, Robert
Gas separation
Means within gas stream for conducting concentrate to collector
55 58, 55 62, 55 66, 55 74, 55 75, B01D 5304
Patent
active
050806947
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a National Phase application of PCT/EP88/00440 filed May 19, 1988 and based upon German application P 37 16 899.1 filed May 20, 1987 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a method of helium recovery, according to a pressure swing adsorption process.
THE RELATED ART
EP 0 92 695 discloses a pressure swing adsorption process for the purification of helium. Reportedly therein helium with a purity of over 99.9% by volume can be recovered by using carbon molecular sieves starting with a mixture containing helium and consisting essentially of nitrogen, argon and oxygen, as well as smaller fractions of carbon dioxide and methane. However, the initial gas mixture in this process has already a content of 50 to 95% by volume helium. This process is not suitable for gas mixtures containing only up to 10% helium.
Furthermore, it is known from EP-A-0 112 640, that higher degrees of argon purity can be achieved, when the gas enriched in a first adsorption stage is again dissociated in a subsequent adsorption stage. According to this document, the adsorbers work also based on the known principle of the pressure swing adsorption process, for instance with four adsorbers in each stage and with carbon molecular sieves with a mean adsorption pore diameter of 0.3 nm. The waste gas of one can be recycled into the feed gas of a preceding stage.
Finally, from DE-A-3 132 758 and EP-A-0 071 553, it is known to use adsorbers filled with activated carbon as a prefiltering stage, in order to remove higher-molecular hydrocarbons, as well as other possible contaminants from a helium-containing gas mixture.
High purity helium is increasingly in demand for several applications, e.g. refrigeration plants for refrigeration, as a shielding gas during welding and in the chemical industry, as an inert gas in space technology as a respiration gas during diving, as a carrier gas in chromatography, in the detection of leakages, as a balloon-filling gas and for other purposes as well.
For these purposes, helium with a high degree of purity is required. In order to achieve these high purity levels from gas mixtures containing only low levels of helium, several process steps are necessary to first enrich such mixtures with helium and then to recover high purity helium from this helium-enriched gas mixture.
According to the state of the art, as known from the publication "Bureau of Mines, Preprint from Bulletin 675--Helium--, 1985 Edition, United States Department of Interior", pages 3 and 4, helium is recovered in multistep processes with a purity of 99.9% by volume from helium-containing natural gases. Helium-containing natural gases contain as main components nitrogen and methane, as well as up to 10% by vol. helium, besides lower proportions of various higher-molecular hydrocarbons and carbon dioxide.
Thereby, the natural gas is first cooled down to approximate -150.degree. C. in a cryogenation plant, whereby primarily the hydrocarbons are released by condensation. The co-produced gas mixture contains over 50% by vol. helium, as well as nitrogen, and lower proportions of other gases. This crude helium is then subjected to further dissociation in a pressure swing adsorption installation. Helium with a purity of over 99.9% by volume is recovered. The helium yield of a pressure swing plant oscillates around 60%, whereas the remaining and highly contaminated helium is present in the desorption gas. The desorption gas is subjected to further treatment. After compression, the desorption gas is cooled down to approximate -185.degree. C. in a second cryogenation plant, whereby the contaminants are eliminated by condensation. The remaining mixture of helium and nitrogen is recycled to the pressure swing plant and blended with the crude helium from the first cryogenation unit. Due to recycling, it is possible to recover a high proportion of the helium. One drawback of the process is that it requires two cryogenation plants plus a pressure swing
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Chemical Abstracts, vol. 92, No. 14 -Apr. 1980, 92:11309a (p. 127).
Bukowski Hans
D'Amico Joseph S.
Glessler Klaus
Knoblauch Karl
Pilarczyk Erwin
Bergwerksverband GmbH
Dubno Herbert
Spitzer Robert
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