Method for obtaining xenon using a molecular sieve

Abstract

The invention relates to a method (100) for obtaining xenon. A first feed flow (1) which contains xenon and sulfur hexafluoride is supplied to a rectification step (10), and a first resulting flow (2) is formed by means of the rectification step (10), said resulting flow containing xenon and being enriched with sulfur hexafluoride in comparison to the first feed flow (1), wherein at least one part of the first resulting flow (2) is subjected to an adsorption step (20) as a second feed flow (4), and a second subsequent flow (4) is formed by means of the adsorption step (10), said second subsequent flow containing xenon and being depleted of sulfur hexafluoride in comparison to the feed mixture (1). The invention likewise relates to a corresponding system.

Description

[0001] Description

[0002] METHOD USING A MOLECULAR SIEVE TO OBTAIN XENON

[0003] The invention relates to a method and a plant for producing xenon.

[0004] Background of the invention

[0005] The noble gases krypton and xenon, which occur in the air with a concentration of approximately 1 ppm krypton and 0.09 ppm xenon, can be obtained by converting significant amounts of air in air separation plants. The boiling points of krypton and xenon are 120 K and 165 K, respectively, well above the boiling points of nitrogen, oxygen, and the other noble gases. Therefore, krypton and xenon accumulate in the liquid oxygen in conventional double-column rectifiers, along with various hydrocarbons.

[0006] To extract krypton and xenon, a portion of the krypton- and xenon-enriched liquid oxygen can be taken from the main condenser and fed into a krypton enrichment column. The enrichment column then produces a so-called krypton-xenon concentrate, which contains approximately 1% krypton, 0.5% hydrocarbons, and 0.1% xenon. The main component is oxygen.

[0007] The concentrate obtained in the krypton enrichment column can be vaporized under supercritical pressure, heated to approximately 500 °C, and passed over a catalyst, where the hydrocarbons are decomposed into water vapor and carbon dioxide. Nitrous oxide can also be converted to nitrogen and oxygen on the catalyst. The water vapor and carbon dioxide can be removed from the concentrate by adsorption using molecular sieves. In a subsequent distillation column, the oxygen can be removed overhead, yielding a highly enriched krypton-xenon concentrate. In a subsequent krypton-xenon rectification, krypton and xenon can then be separated.

[0008] In the described extraction of krypton and xenon in

[0009] Cryogenic air separation plants are highly enriched in krypton and xenon. The disadvantage is that trace contaminants in the air are also enriched. These include, in particular, fluorocarbons and sulfur hexafluoride. Tetrafluoromethane, hexafluoroethane, and the aforementioned sulfur hexafluoride are particularly critical, as these compounds can pass through molecular sieve adsorbers. Sulfur hexafluoride accumulates along with xenon due to their similar boiling points (similar boiling points), and the other two components accumulate in the krypton.

[0010] These compounds are thermally very stable and are difficult to remove catalytically, or they degrade to undesirable byproducts. Sulfur hexafluoride has similar physical properties to xenon and is therefore difficult to separate. Sulfur hexafluoride therefore follows xenon in the air separation process.

[0011] EP 0 863 375 A1 discloses the purification of a krypton-xenon concentrate and / or krypton and / or xenon in a solid sorbent containing phyllosilicates, whereby fluorine- and / or chlorine-containing impurities, in particular fluorocarbons such as carbon tetrafluoride and / or sulfur hexafluoride, are removed from the krypton-xenon concentrate and / or the krypton and / or the xenon. These impurities are irreversibly bound by the sorbent through chemisorption. However, carbon dioxide is formed as a degradation product during the sorption reaction, and water vapor and oxygen are released from the sorbent. Therefore, subsequent adsorption steps are required to remove the carbon dioxide and water.

[0012] The present invention aims to improve corresponding processes for the production of xenon, in particular by an effective and cost-effective removal of sulfur hexafluoride from the process.

[0013] Disclosure of the invention

[0014] This object is achieved by a method and a plant having the features of the independent patent claims. Embodiments of the invention are specified in the dependent patent claims and the following description. The present invention provides a method for producing xenon, wherein a first feed stream containing xenon and sulfur hexafluoride is fed to a rectification step, wherein by means of the rectification step a first follow-up stream is formed which contains xenon and is enriched in sulfur hexafluoride compared to the first feed stream, wherein using at least a portion of the first follow-up stream a second feed stream is formed, wherein the second feed stream is subjected to an adsorption step, and wherein by means of the adsorption step a second follow-up stream is formed which contains xenon and is depleted in sulfur hexafluoride compared to the feed mixture.

[0015] As is common in technical jargon, the term "adsorption" in this application refers to physical adsorption (also called physisorption), i.e., a process based solely on physical processes. This excludes, in particular, chemical processes for sorption, such as chemisorption and getters. Getters and other chemisorbents differ from adsorbents in that they bind the adsorbed substances very tightly. Therefore, unlike adsorbents, they cannot be regenerated during the process but must be replaced after use.

[0016] The process proposed here comprises a (cryogenic) rectification separation, to which xenon containing sulfur hexafluoride (the "first feed stream") is fed, and in which the slightly lighter xenon is recovered as the overhead gas. In the rectification separation, a mixture of a few volume percent of sulfur hexafluoride in xenon is obtained as the bottoms liquid (using which the "first downstream stream" is formed).

[0017] For example, the content of sulfur hexafluoride in the first feed stream in the context of the present invention can be from 20 Vppm (millionths by volume) to 300 Vppm or from 50 Vppm to 150 Vppm, and in the bottoms liquid from 1 to 10 or from 2 to 4 percent by volume. The top gas can in particular contain less than 10 Vppm or less than 1 Vppm of sulfur hexafluoride. The first feed stream, the bottoms product and the top gas are in particular free or essentially free of other components such as in particular krypton and oxygen, i.e. they contain such other components at most 1 Vppm. However, the bottoms product does not have to be free of krypton and oxygen, since after the removal of sulfur hexafluoride it can be fed back upstream into the process.

[0018] To obtain pure xenon, the bottom liquid, or a portion of it, can be continuously withdrawn and discarded. Alternatively, the bottom liquid can be discontinuously drained and treated in the adsorption process. Both methods prevent the accumulation of sulfur hexafluoride in the circuit.

[0019] However, this results in a continuous loss of xenon, as the sump liquid also contains xenon. In principle, getters that completely absorb sulfur hexafluoride could be used for this purpose, but the required concentrations of sulfur hexafluoride are relatively high. Pure combustion of sulfur hexafluoride is not possible, as various degradation products (sulfur, fluorine, and oxygen species) would contaminate the xenon.

[0020] In this context, the present invention provides a possibility for increasing the xenon yield in pure xenon production or in the production of high-purity krypton and xenon, which proves to be significantly advantageous, particularly compared to the solution explained above with reference to EP 0 863 375 A1. By dispensing with chemisorption, which can also be used in principle, the solution proposed according to the invention can be implemented more simply in terms of construction and operation.

[0021] In a first variant of the invention, the adsorption step is carried out using an adsorbent on which xenon is retained more strongly than sulfur hexafluoride, with the second subsequent stream being formed during a desorption phase in which the adsorbent is purged using a purge gas stream. In this case, the adsorption step is carried out, in particular, using a molecular sieve whose pore size is selected such that xenon, but not the significantly larger sulfur hexafluoride, can enter it and is thus retained therein.

[0022] These embodiments therefore comprise the use of a particularly commercially available adsorbent whose pores are too small for the adsorption of the relatively large molecule sulfur hexafluoride, e.g. molecular sieve 5A. Xenon can be retained well in this adsorbent, whereby sulfur hexafluoride can pass through the adsorbent essentially without retention. The adsorbent fills with xenon until it breaks through at the outlet. As the stronger adsorbate, xenon completely ejects the very weakly adsorbing sulfur hexafluoride from its adsorption sites, i.e., in the event of a xenon breakthrough, the adsorbent is practically free of sulfur hexafluoride. The same would occur in the presence of nitrogen, oxygen, krypton or other weakly adsorbing gases: xenon accumulates in the adsorbent without these gases.

[0023] In corresponding embodiments of the invention, the purge gas stream can be provided during the desorption phase, in particular at a temperature in a temperature range of 0 to 200 °C, and the second feed stream can be supplied to the adsorption step in gaseous form and at a temperature in a temperature range of -100 to 30 °C or 0 to 20 °C. A temperature increase during the desorption phase can also be omitted. In this case, however, more purge gas (e.g., nitrogen) is required.

[0024] Within the scope of the present invention, it was surprisingly discovered that the temperature of the second feed stream is of secondary importance for the adsorption performance, but rather that the temperature of the adsorption bed at the beginning of the adsorption phase is crucial for the resulting temperature equilibrium. Therefore, according to one embodiment of the invention, pre-cooling of the bed, for example, to approximately 5 °C, is desirable in order to increase the adsorption capacity. In a corresponding embodiment of the invention, the adsorbent is therefore pre-cooled before an adsorption phase.

[0025] In corresponding embodiments of the invention, the adsorbent serves as a temporary storage medium for xenon gas, which can later be desorbed by means of a corresponding purge gas stream, in particular at higher temperatures and lower pressure. The purge gas stream can, for example, be an oxygen-rich crude krypton-xenon stream, which is used to feed the noble gas production. In this way, xenon can be fed back into the production process with almost no sulfur hexafluoride content. Such a stream can be fed into the process, in particular, upstream of a catalytic methane removal process or shortly thereafter, but in particular still upstream of existing molecular sieve adsorbers for carbon dioxide removal and drying, i.e. the desorption gas or the second downstream stream is fed into the warm part of the production plant, i.e. a part of a corresponding plant operated at temperatures above 0 °C.

[0026] In corresponding embodiments of the invention, it can therefore be provided that the purge gas stream contains predominantly nitrogen. (Alternatively, a purge gas stream containing krypton, xenon, and oxygen can be used.) In any case, the purge gas stream leaves the adsorber together with the desorbed xenon as a second downstream stream. The second downstream stream can, as also mentioned, be subjected to a krypton-xenon separation, with the first feed stream being formed using the krypton-xenon separation.

[0027] The adsorbent to be used can be either continuously flowed through by xenon contaminated with sulfur hexafluoride from the column sump or discontinuously. For example, xenon contaminated with sulfur hexafluoride can be slowly filled into a storage container and later withdrawn at a different flow rate and fed into the adsorbent, which retains xenon but allows sulfur hexafluoride to pass through. In corresponding embodiments of the present invention, xenon breakthrough at the end of the adsorption process can be analytically monitored during the adsorption step.

[0028] In embodiments of the invention, an auxiliary stream of poorly adsorbing gas (e.g. nitrogen) can be used during adsorption and desorption in order to maintain a measurable flow in the adsorber. The formation of the second feed stream and the formation of the purge gas stream can therefore comprise the metered addition of an auxiliary gas stream which contains at least one gas which adsorbs less well than xenon in the adsorption step, in particular nitrogen. In other words, nitrogen can be metered into the adsorber during both the adsorption phase and the desorption phase. This nitrogen passes into the second subsequent stream and can be separated from it again relatively easily in a rectification step, to which the second subsequent stream is returned.

[0029] The amount of the addition may be 0.5 times to 5 times the xenon flow, ie the first subsequent flow or a part used by it, or the auxiliary gas flow may be added to the first subsequent flow or to the part used to form the second feed stream in an amount which corresponds to 0.5 times to 5 times the first subsequent flow or the said part.

[0030] At low sulfur hexafluoride concentrations, on the order of 2%, the adsorber would experience virtually no discharge flow, as only sulfur hexafluoride would escape. This could create the risk of backmixing from downstream processes. This is avoided by the aforementioned dosing.

[0031] The desorption gas, i.e., the second downstream stream, can be transferred to a storage balloon, which absorbs all noble gas-rich residual gases generated during the fine purification process. The contents can then be recycled upstream into the process, optionally using a compressor or blower.

[0032] In general, within the scope of the present invention, the adsorption step can be carried out using adsorption vessels with a vessel diameter of, for example, 0.6 meters and a bed height of 1.5 meters, if necessary with a safety margin of 0.5 meters. By means of the aforementioned introduction of nitrogen, the second feed stream can be provided, for example, with 6 standard cubic meters per hour and a content of 33% xenon and the remainder nitrogen and sulfur hexafluoride. Its temperature can be, for example, 15 to 25 °C, in particular approx. 20 °C, and its pressure can be 1.3 to 1.7 bar absolute pressure, in particular approx. 1.5 bar absolute pressure. In this case, with a loading time of 4 hours, approx. 8 standard cubic meters of xenon can be stored. Regeneration can, for example, take place with 4 standard cubic meters of nitrogen per hour, i.e. with an unchanged amount of nitrogen, for example for approx. 10 hours.No heating of the nitrogen is required. A corresponding embodiment of the invention thus comprises passing a first amount of nitrogen, introduced via the auxiliary gas stream, over the adsorbent during the adsorption phase in a first time interval with the first feed stream, and passing a second amount of nitrogen, introduced via the auxiliary gas stream, over the adsorbent during the desorption phase in a second time interval with the purge gas stream. Advantageously, the first and second amounts of nitrogen differ by no more than 10% or are essentially identical.

[0033] In a specific design, the second feed stream is fed discontinuously to the adsorber. For example, a collection period of several months to one year in the column sump is followed by an adsorption phase of approximately one day. After the end of the adsorption phase, nitrogen is fed into the adsorber as a purge gas, and desorption begins. The desorption time is of the same order of magnitude but slightly longer than the adsorption time. This allows adsorption / desorption—in contrast to the illustration in the drawing—to be operated with a single vessel.

[0034] In a second variant of the present invention, the adsorption step can be carried out using an adsorbent that retains xenon less effectively than sulfur hexafluoride. In these embodiments, the second subsequent stream is formed by the non-adsorbing xenon during an adsorption phase.

[0035] In other words, it can also be provided that sulfur hexafluoride is retained on an adsorbent together with other well-adsorbing contaminants such as nitrous oxide and carbon dioxide, whereas xenon breaks through much earlier. Such a solution advantageously comprises a pair of adsorbers that adsorb alternately and are then thermally regenerated. The escaping xenon can, in particular, be condensed into a storage container until sulfur hexafluoride appears at the adsorber outlet. The more strongly adsorbing sulfur hexafluoride ejects xenon almost completely from its adsorption sites, meaning that the xenon loss is minimal at the end of the adsorption cycle. The breakthrough of sulfur hexafluoride is advantageously monitored analytically.As already explained in other words, the adsorption step can be carried out using a molecular sieve whose pore size is chosen such that sulfur hexafluoride can enter it.

[0036] In all variants of the invention, the adsorption process is preferably carried out discontinuously in only a single container (batch process), as already explained above and described in claim 14. Alternatively, the adsorbent can be accommodated in two or more adsorber containers, which are operated in the adsorption / desorption phase at different times from one another.

[0037] A plant for producing xenon is also subject of the present invention. This plant is designed to feed a first feed stream containing xenon and sulfur hexafluoride to a rectification step, to form a first downstream stream containing xenon and enriched in sulfur hexafluoride compared to the first feed stream by means of the rectification step, to form a second feed stream using at least a portion of the first downstream stream, to subject the second feed stream to an adsorption step, and to form a second downstream stream containing xenon and depleted in sulfur hexafluoride compared to the feed mixture by means of the adsorption step.

[0038] For the features and advantages of a corresponding system, reference is expressly made to the above explanations regarding the method according to the invention and its embodiments. The same applies to a system according to an embodiment of the invention that is designed to carry out a corresponding method and any embodiments thereof.

[0039] The invention is further explained below with reference to the accompanying drawings, in which embodiments of the invention are illustrated. Description of the figures

[0040] Figure 1 illustrates a method 100 for producing xenon according to one embodiment of the invention.

[0041] If subsequent process steps (e.g., a "rectification step") are explained, the corresponding explanations also apply to corresponding plant components (e.g., a "rectification column"), and vice versa. For the sake of clarity, repeated explanations are omitted, and the same reference symbols are used in some cases.

[0042] In the drawing, three rectification steps 110, 120, and 10 in the process 100 are shown extremely schematically as rectification columns, each with a bottom reboiler 111, 121, and 11 and a top condenser 112, 122, and 12. Each of the rectification steps 110, 120, and 10 also includes the associated heat exchangers, lines, valves, and vessels, even if these are not shown in Figure 1. The rectification steps 110, 120, and 10 can internally comprise more than one column, for example, two to five columns. They can be located at the same location; however, they are usually set up at least partially at different locations. An intermediate product is transported between them, for example in a gas cylinder or a liquid container. All of this is not shown in the simplified drawing.A first rectification step (C1), not shown in the drawing, is often directly integrated into a cryogenic air separation plant. Its product is usually stored in a liquid tank and transported from time to time by tanker to the location of the rectification step 110 (C2). Here, liquids from several C1 plants are generally collected and further processed. Since the quantities processed are becoming increasingly smaller, one C3 plant is often sufficient for a larger geographical area, for example a medium-sized European country, in which all C2 products are collectively processed. The rectification column 110 is operated as a separation device for oxygen and the rectification column 120 as a separation device for xenon and krypton.

[0043] In the rectification column 110, oxygen is separated overhead from a pre-cooled crude mixture 101, which may contain, for example, 5,000 ppm of krypton and xenon in oxygen, into an overhead stream 103, so that a bottoms stream 102 of the rectification column 110 essentially contains krypton and xenon with the impurities explained above. In contrast, a krypton-rich fraction and a xenon-rich fraction are formed in the rectification column 120, so that an overhead stream 105 essentially containing krypton and impurities and a bottoms stream 104 essentially containing xenon with, for example, approximately 100 ppm of sulfur hexafluoride can be withdrawn from the rectification column 120. The overhead stream 105 can be passed to a further purification stage, which is not separately illustrated here since it is not necessarily the subject of the invention.

[0044] The krypton- and xenon-containing raw mixture 101, which, as mentioned, still predominantly contains oxygen, can, for example, be a correspondingly concentrated raw mixture from an air separation plant, freed from at least hydrocarbons, nitrous oxide, and carbon dioxide. The raw mixture 101 can, for example, be passed through a deoxo stage and a dryer and pass through a heat exchanger (not shown here), in which it is cooled in countercurrent to a cold stream, for example, the oxygen stream or overhead stream 103 from the first rectification column 100. The feed does not have to be in the center of the rectification column 110.

[0045] The rectification columns illustrated in Figure 1 can be configured as packed columns or randomly arranged columns. The first rectification column 110 can, for example, be operated at a pressure in the range of 1.5 to 5 bar (abs.).

[0046] The top condenser of the rectification column 110 can, for example, be operated with a liquid cryogenic coolant. This is typically liquid nitrogen, liquid oxygen, liquid argon, or mixtures thereof.

[0047] The feed into the rectification column 120 does not necessarily have to be centered. The operating pressure of the rectification column 120 can be 0.5 to 4 bar lower than the pressure of the rectification column 110 explained above. Stream 104 can be used, in particular, to form a first feed stream 1, which has already been referred to frequently above. Stream 1 is fed to a rectification step 10 or the corresponding rectification column.

[0048] By means of the rectification step 10 or in a corresponding rectification column, a stream 2, referred to here as the first downstream stream, is formed using bottoms liquid. This stream contains xenon and is enriched in sulfur hexafluoride compared to the first feed stream 1. Furthermore, a pure xenon stream 3, which is essentially freed from sulfur hexafluoride in the rectification, is formed using overhead gas.

[0049] Part of the process 100 is an adsorption step 20, which in the example shown here is carried out using adsorber vessels 21, 22, each containing the same adsorption material, which are operated alternately, as is generally known from the field of adsorption technology and therefore not shown in detail here. A material stream 4, referred to here as the second feed stream, is fed to the adsorption step 2. This stream is formed using at least a portion of the first downstream stream 2. The second downstream stream 5 contains xenon and is depleted in sulfur hexafluoride compared to the second downstream stream 4. It can be recycled upstream into the process 100.

[0050] In embodiments of the first variant of the invention, the second subsequent stream 5 is formed during a desorption phase in which the adsorbent is purged using a purge gas stream 6. This is the case when the adsorption step 20 is carried out using a molecular sieve whose pore size is selected such that xenon, but not sulfur hexafluoride, can enter it. In this case, the purge gas stream 6 can contain krypton, xenon, and oxygen, and the second subsequent stream 5 can then comprise at least a portion of the purge gas stream 6. During an adsorption phase, in such embodiments, a sulfur hexafluoride-enriched material stream is formed as a third subsequent stream 7, which flows out of the respective adsorption material. This third subsequent stream 7 is removed from the process, for example by being discarded.The second downstream stream 5 is returned to the process, for example, by being introduced into a storage balloon 30. Further residual gases that still contain krypton or xenon in quantities worthy of processing can be introduced into this balloon. They can originate from any step of the overall plant 100, in particular from the third rectification step 10. The largely depressurized gas 31 from the balloon 30 is returned—if necessary by means of a blower—to the inlet of the rectification stage 110, in particular before a warm pretreatment at the inlet of the C2 stage. The corresponding amount of xenon is retained for product recovery.

[0051] However, according to the second variant of the invention, it is also possible to form the subsequent stream 5 during an adsorption phase, namely in embodiments in which the adsorption step 20 is carried out using an adsorbent on which xenon is retained less effectively than sulfur hexafluoride. The adsorption step 20 is carried out using a molecular sieve whose pore size is selected such that sulfur hexafluoride can enter it. In this case, a purge gas stream 6 is fed in during a desorption phase, which desorbs the sulfur hexafluoride and transfers it into a stream 7.

Claims

Patent claims 1. A process (100) for the production of xenon, wherein a first feed stream (1) containing xenon and sulfur hexafluoride is fed to a rectification step (10), wherein a first follower stream (2) containing xenon and enriched in sulfur hexafluoride compared to the first feed stream (1) is formed by means of the rectification step (10), wherein a second feed stream (4) is formed using at least a part of the first follower stream (2), wherein the second feed stream (4) is subjected to an adsorption step (20), and wherein a second follower stream (5) containing xenon and depleted in sulfur hexafluoride compared to the second feed stream (4) is formed by means of the adsorption step (20).

2. Method according to claim 1, wherein a third follower stream (7) is also formed by means of the adsorption step (20), which is enriched in sulfur hexafluoride compared to the second input stream (4).

3. The method of claim 2, wherein the third follower stream (7) is removed from the method.

4. Method (100) according to any of the preceding claims, wherein the adsorption step (20) is carried out using an adsorbent in which xenon is retained more strongly than sulfur hexafluoride, and wherein the second follower stream (5) is formed during a desorption phase in which the adsorbent is purged using a purge gas stream (6).

5. Method (100) according to claim 4, wherein the adsorption step (20) is carried out using a molecular sieve whose pore size is selected such that xenon, but not sulfur hexafluoride, can enter it.

6. Method (100) according to claim 4 or 5, wherein the purge gas stream (6) is provided during the desorption phase at a temperature in a temperature range of 50 to 200 °C, and wherein the second feed stream (4) is supplied to the adsorption step in gaseous form and at a temperature in a temperature range of -100 to 30 °C or -50 to 0 °C.

7. Method (100) according to any one of claims 4 to 6, wherein the adsorbent is pre-cooled before an adsorption phase.

8. Method (100) according to any one of claims 4 to 6, wherein the purge gas stream (6) contains predominantly nitrogen.

9. Method (100) according to one of the preceding claims, wherein the second follower stream (5) is subjected to a rectification step for krypton-xenon separation (C2 step 110) and the first input stream (1 ) is formed using the rectification step for krypton-xenon separation (30).

10. Method (100) according to any one of claims 4 to 9, wherein the formation of the second feed stream (4) and the formation of the purge gas stream (6) comprises the addition of an auxiliary gas stream containing at least one gas which adsorbs less readily than xenon in the adsorption step (20), in particular nitrogen.

11. Method (100) according to claim 8, wherein the auxiliary gas stream is added to the first subsequent stream (2) or to the part thereof used to form the second input stream (4) in an amount corresponding to 0.5 to 5 times the first subsequent stream (2) or of its part.

12. Method (100) according to any one of claims 1 to 3, wherein the adsorption step (20) is carried out using an adsorbent in which xenon is retained less strongly than sulfur hexafluoride.

13. Method (100) according to claim 12, wherein the adsorption step (20) is carried out using a molecular sieve whose pore size is selected such that sulfur hexafluoride can enter it.

14. Method (100) according to one of claims 4 to 11, wherein the adsorbent is contained in a single adsorber container (11), and the second feed stream (4) is collected at different times and the adsorber container is operated in the adsorption phase and desorption phase. Xenon production plant, which is configured to feed a first feed stream (1) containing xenon and sulfur hexafluoride to a rectification step (10), to form a first follower stream (2) containing xenon and enriched in sulfur hexafluoride compared to the first feed stream (1) by means of the rectification step (10), to form a second feed stream (4) using at least a part of the first follower stream (2), to subject the second feed stream to an adsorption step (20), and to form a second follower stream (5) containing xenon and depleted in sulfur hexafluoride compared to the feed mixture (1) by means of the adsorption step (10).

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