Separation of xenon from gas mixtures

0001The invention relates to a method of separating xenon from a Gas mixture.

0002The narcotic effects of xenon have been known since the 40s. A mixture of about 80% xenon and 20% oxygen than is almost ideal anesthetic gas considered, the mostly in relation to today Anesthetic gases used on the basis of nitrous oxide numerous advantages Has. Because of the high cost of xenon xenon anesthesia are in clinical area practically not applied. In order to reduce these costs, were therefore eg in DE 44 11 533 C1 anesthesia machines with a Recovery plant for Xenon proposed. When in DE 44 11 533 C1 proposed recovery plant is the exhaled gas compressed according to a pre-cleaning and introduced into a pressure vessel, is what was added to a cooling device. Via the cooling device the pressure vessel is cooled so far that the be recovered xenon liquefies. The gaseous components in the pressure vessel discharged via a filter choke. When a sufficient amount of liquid xenon is present in the pressure vessel, this is in a further container pumped. This device has the disadvantage of high equipment cost for compressing the gas and the Cooling an entire container. In addition, the degree of transfer of the not xenon recovering satisfactorily.

0003DE 41 08 653 A1 describes a method for separating gases verdichteteter of different molecular weights by utilizing the reversal of the Bulk density in comparison to a liquid. It is a very general Separation principle described without suitable for the separation of gas mixtures to call.

0004It is the object of the invention to provide a simple and economical process for separating xenon from the expiratory gas a to provide anesthesia patients. is a further object of the invention therein, an economical recycling process for an anesthetic gas to Xenon base to create.

0005These objects are achieved by a method for separating xenon a xenon-containing anesthetic gas or exhaled xenon-containing Dissolved gas mixture, wherein the anesthetic gas or the gas mixture with a Liquid mixed and compacted so that xenon lower in a Phase separates.

0006When liquid is suitable, for example, water, ammonia, pentane or Heptane.

0007The principle and implementation of the method is generally described in DE 41 08 described 653 A1, which is hereby incorporated by reference.

0008In the process, the gas mixture with the liquid is applicable compressed that the xenon is already überbarotrop. The solubility of Xenon in the fluid must be greater than the solubility of the other Gas components. A supersaturation of the liquid with xenon is z. B. achieved by a further increase in pressure. in case of stress relaxation a pressure at which the xenon is a higher specific weight than the Liquid has (barotropic conditions), xenon separates into a lower phase.

0009The method may also be carried out so that at a temperature the xenon is preferably dissolved in the liquid, and by Temperature increase supersaturation is achieved.

0010If the liquid is water used, then the formation of xenon hydrate be exploited. The xenon hydrate is specifically heavier and falls out. The xenon-absorbed hydrate also usually xenon. If by Change of temperature or pressure melts the xenon-hydrate, the Xenon released. If barotropic conditions still exist, forms below the water phase, a phase with xenon.

0011The method is particularly suitable for separation of gas mixtures, containing xenon, nitrogen and oxygen. The Expirationsgas an anesthetic patients contains as main components Xenon, nitrogen, oxygen and carbon dioxide. To separate Carbon dioxide is the expiration gas through a filter or absorber (z. B. conducted with soda lime as an absorber mass) or a gas scrubber (z. B. liquor) subjected. Optionally, organic impurities in the Gas mixture are removed by activated carbon.

0012The to be separated, preferably pre-cleaned gas mixture is in a High-pressure vessel (autoclave) initiated the previously partially with the Separating liquid, preferably water, more preferably distilled Water was charged. The pressure is on the barotropy-limit pressure elevated. The temperature is selected so that xenon hydrate precipitates to the Floor sinks. dissociated by temperature increase and Druckemiedrigung the xenon hydrate. If one stays above the limit pressure, so is barotropy raised the water layer and separates Xenon (bottom) of oxygen and Nitrogen mixture (above).

0013The xenon-hydrate, by temperature and / or pressure change in Xenon and water vapor are cleaved. For example, you can by Draining a portion of the supernatant gas phase (light gas) pressure Lower bit; However, care must be taken that one still in the process remains above the barotropy-limit pressure.

0014The resulting in the dissociation of the hydrate moisture Xenon (Supercritical) Xenon can a dryer cartridge (z. B. Filter Cartridge Silica gel) directed and are then discharged for further use. If the recovered xenon directly fed back to the anesthesia machine is, there is no drying.

0015The barotropy-limit pressure is that pressure at which the density of the compressed xenon is the density of the separating liquid, eg. as equal the density of water. The confining pressure is a function of temperature and is when water is used for. B. at 37 ° C 79 bar. At the critical Point of xenon (16.6 ° C / 58.4 bar) and the point (50 ° C / 100 bar) is coated the water on the Xenon, ie it is at this Operating conditions already above the barotropic point.

0016To improve the separation of xenon and for the recovery of xenon with increased purity, the method in a cascade, ie in two or a plurality of series-connected separation stages, are carried out.

0017Fig. 1 shows schematically a continuous two-stage process with Recycling xenon-containing gas fractions, the xenon not as Main component.

0018From the container (1) from the upper gas phase (12) the gas mixture (5) taken consisting mainly light gas (oxygen, nitrogen), and Xenon is something, and supplied to the container (2). From the bottom Gas phase (13) of container (1) is removed from the gas mixture (6) besides xenon as the main component still contains some light gas, and the Container (3) is supplied. In the containers (2) and (3) the gases again separated barotropic. The heavy gas (7) (lower gas phase (13)) from the container (2) and the light gas (8) (upper gas phase (12)) from the Container (3) be recycled to the container (1), wherein the feed in the isolation liquid (11) (eg., water) takes place. The from the container (2) used gas (9) with light gas is usually discarded. Dating back to the Container (3) discharged gas (10) is the recovered, pure Xenon (Heavy gas). The recovered xenon, either in a Compressed gas containers are compacted or with suitable pressure again the Anesthetic machine to be supplied. If the recovered xenon after two Plates still not sufficiently pure, so the process can on three or more plates are extended.