Argon separation plant and purification process

Abstract

The invention relates to a purification process and an installation for separating argon from a gas stream, comprising a treatment circuit (2) including, between a first end intended to be connected to a source of gas to be purified and a second end intended to be connected to a purified gas receiver, a first adsorption purification element (3) configured to lower the argon content in the gas stream below a first threshold, the treatment circuit (2) including, arranged in series downstream of the first purification element (3), a second purification element (4) including a cryogenic cooler (5) configured to cool the gas stream to a predetermined cryogenic temperature between 25K and 40K, and a filter (7) for collecting the argon solidified at the cryogenic temperature to lower the argon content in the gas stream below a second threshold lower than the first threshold. Abstract figure: Fig. 1

Description

Title of the invention: Argon separation installation and purification process

[0001] The invention relates to an argon separation installation and a purification process.

[0002] The invention relates more particularly to an installation for separating argon in a gas stream such as hydrogen, helium or neon comprising a treatment circuit including, between a first end intended to be connected to a source of gas to be purified and a second end intended to be connected to a receiver of purified gas, a first purification element by adsorption configured to lower the argon content in the gas stream below a first threshold, for example below 1 Oppm.

[0003] There is a growing demand for ultrapure gases (hydrogen, helium, or neon, for example). Electronic applications, such as the manufacture of components with increasingly fine electronic structures, require, for example, pure gases with a purity level reaching parts per billion (ppb) (see ppt, parts per trillion). Hydrogen (dihydrogen, h2) may be required with an argon purity level below 30 to 50 ppb.

[0004] A known solution for obtaining these ultrapure gases consists of carrying out purification by adsorption at cryogenic temperature, typically at the temperature of liquid nitrogen (77 K). Even though the adsorption capacities decrease with the partial pressure of the impurity to be trapped (i.e., the residual impurity level), the temperature effect makes the purification effective for most impurities.

[0005] For argon, at a certain level of partial pressure, the purification capacity can drop sharply to reach unusable values.

[0006] Operating adsorption at a lower temperature is a known solution, but does not avoid this effect of sudden drop in capacity.

[0007] The sublimation curve of argon shows that the pressure drops very rapidly with temperature to reach 30x109 bar at the critical temperature of hydrogen, on the order of 33K, that is to say the level of purity typically specified for one bar of hydrogen, or for a typical operating pressure of 10 bar an order of magnitude lower.

[0008] Cooling below the critical temperature of hydrogen is technically difficult to achieve because (partial) condensation of hydrogen is difficult to manage and requires a lot of energy, especially since a non-negligible amount of argon could dissolve in the liquid hydrogen phase thus generated.

[0009] One object of the present invention is to overcome all or part of the disadvantages of the prior art noted above.

[0010] To this end, the installation according to the invention, which also conforms to the generic definition given in the preamble above, is essentially characterized in that the treatment circuit comprises, arranged in series downstream of the first purification unit, a second purification unit comprising a cryogenic cooler configured to cool the gas stream to a determined cryogenic temperature between 25K and 40K, and a filter intended to collect the argon solidified at the cryogenic temperature to lower the argon content in the gas stream below a second threshold lower than the first threshold.

[0011] The present invention thus adds an additional purification module to separate the argon. This module is located downstream of a cryogenic adsorption purification that already partially removes the argon.

[0012] Furthermore, embodiments of the invention may include one or more of the following features: - the first purification unit comprises a temperature-modulated adsorption device (“TSA”) including one or more beds of adsorbents maintained at a cryogenic temperature, for example around 80K, - The first purification unit comprises a non-cryogenic temperature "PSA" adsorption device and a cooler for the purified gas at the outlet of the first purification unit. - the cryogenic cooler includes a cryo-cooler comprising a cold head in heat exchange with the gas flow and configured to provide cooling power at cryogenic temperature, the cryo-cooler being for example of the Joule Thomson, Gifford-McMahon, Stirling or pulsed gas tube type, - The treatment circuit includes a heat exchanger ensuring heat exchange between the gas to be purified and the cold head of the cryogenic cooler, - The heat exchanger ensuring heat exchange between the gas to be purified and the cold head of the cryogenic cooler includes a porous volume, for example a volume of metallic foam or a filter screen for capturing solidified argon, - The cryogenic cooler comprises two cold heads in heat exchange with the processing circuit, for example with two parallel sections of the processing circuit respectively - the filter is of the mechanical type and regenerable, for example by heating, particularly electrical heating and vacuum operation and / or by gas purging. - The filter is separate and located away from the heat exchanger, ensuring heat exchange between the gas to be purified and the cold head of the cooler. - the treatment circuit includes at least one regeneration line and a set of regeneration valve(s) configured to allow the circulation of a gas flow exiting the first purification unit into the filter for the purpose of its regeneration, - The treatment circuit comprises two parallel branches, each equipped with a filter and a set of valve(s) configured to allow alternating filtration of argon from the gas flow in one filter while the other filter is in a regeneration phase. - the treatment circuit includes a heat exchanger configured to ensure heat exchange between the gas flow exiting the filter and the gas flow upstream of its exchange with the cryogenic cooler.

[0013] The invention also relates to a method for purifying a gas stream to be purified comprising hydrogen, helium or neon, the method comprising a first step of purifying the gas stream by adsorption in which the argon content in the gas stream is lowered below a first threshold, for example below 1 Oppm, the method comprising a second purification step configured to lower the argon content in the gas stream below a second determined threshold, for example 50ppb, the second purification being carried out by cooling the gas stream with a cryogenic cooler to a determined cryogenic temperature between 25K and 40K to solidify all or part of the argon molecules and capture this solidified argon in a mechanical filter.

[0014] According to other possible features:

[0015] The invention may also relate to any alternative device or method comprising any combination of the above or below features within the scope of the claims.

[0016] Other features and advantages will become apparent from the following description, given with reference to the figures in which: Brief description of the figures

[0017] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings in which:

[0018] [Fig-1] is a schematic view that illustrates a first example of structure and the operation of an installation according to the invention,

[0019] [Fig.2] is a schematic view that illustrates a second example of the structure and operation of an installation according to the invention,

[0020] [Fig.3] is a schematic view which illustrates a third example of the structure and operation of an installation according to the invention. Detailed description

[0021] In all figures, the same references refer to the same elements.

[0022] In this detailed description, the following are examples. The fact that the description refers to one or more embodiments does not mean that the features apply only to a single embodiment. Simple features from different embodiments can also be combined and / or interchanged to provide other embodiments.

[0023] The illustrated installation 1 is designed for the purification of a gas such as hydrogen, helium, or neon, for example. This installation 1 ensures the separation of argon contained in a gas stream.

[0024] The installation 1 comprises a treatment circuit 2 having a first end intended to be connected to a source 13 of gas to be purified and a second end intended to be connected to a receiver 14 of purified gas. Between its ends, the treatment circuit 2 has a first adsorption purification element 3 configured to lower the argon content in the gas stream below a first threshold. This first threshold is, for example, less than 1000 ppm by mass.

[0025] This first purification element 3 comprises or is constituted, for example, by a temperature-swing adsorption device (TSA) comprising one or more beds 9 of adsorbents, arranged in series and / or in parallel, maintained at a cryogenic temperature, for example around 80 K, for example via heat exchange with a saturated liquid nitrogen bath. The gas stream to be purified is purified as it passes through the adsorption beds (argon binds to the adsorbent).

[0026] Such a purification organ 3 may, for example, be of the type of cryogenic purifier marketed under the name "ULTRAL" by the applicant.

[0027] As illustrated, the treatment circuit 2 comprises, arranged in series downstream of the first purification unit 3, a second purification unit 4. This second purification unit 4 comprises a cryogenic cooler 5 configured to cool the gas stream to a predetermined cryogenic temperature between 25K and 40K, and a filter 7 for collecting the argon solidified at the cryogenic temperature.

[0028] Typically, for hydrogen at a pressure of 10 bar, the minimum temperature reached can be on the order of 30 K (temperature at which the first liquid droplets appear). Installation 1 makes it possible to lower the temperature sufficiently. (typically below 35K) to achieve the correct level of purity in the gas to be purified, typically below 50ppb.

[0029] Indeed, at this temperature the argon solidifies and partially deposits on the walls of the piping of circuit 2 and of the exchanger 6. To retain all or almost all of the solidified argon, the filter 7 can be configured to ensure a determined filtration rate, for example by defining a filtration mesh smaller than a micrometer.

[0030] This makes it possible to lower the argon content in the gas stream below a second threshold that is lower than the first threshold. The second threshold is, for example, parts per million (ppb) and, for example, less than 50 ppb by mass.

[0031] The filter 7 is preferably of the mechanical type and regenerable, for example by electrical heating followed by vacuum pumping and / or gas purging. In particular, cleaning of the filter 7 can be carried out by one or more heating cycles (electric or other heater 15 and / or by gas circulation at ambient temperature). This regeneration is preferably carried out under the atmosphere of the gas to be purified and is preferably followed by vacuum pumping.

[0032] As illustrated, the filter 7 is preferably separate and distant from the heat exchanger 6 ensuring heat exchange between the gas to be purified and the cold head of the cooler 5.

[0033] As illustrated, the treatment circuit 2 comprises several parallel branches (two in this example), each equipped with a filter 7 and a set of valve(s) 8, 9 configured to allow alternating filtration of argon from the gas stream in a first filter 7 while the other filter 7 is in a regeneration phase. Thus, the filtration and regeneration phases can be alternated to provide a continuous flow of purified gas.

[0034] This alternating operation of the filters 7 in parallel allows a continuous operation when cleaning a filter 7 (for example heating and vacuum drawing).

[0035] As seen in [Fig. 1], the treatment circuit 2 may include at least one regeneration line 12 and a set of regeneration valve(s) 10 configured to allow the circulation of a gas flow exiting the first purification unit 3 into the filter(s) 7 for the purpose of regeneration.

[0036] Installation 1 allows the decoupling of the mechanical filtration function (storage of impurities at deep cryogenic temperature, in particular below 80K which are expelled out of the circuit in regeneration phase via a suitable conduit 16, for example via a pumping element 17).

[0037] The cryogenic cooler 5 comprises a cryo-cooler equipped with a cold head in heat exchange with the gas stream and configured to provide cooling power at the target cryogenic temperature. For example, the cryo- The cooler is a machine of the Joule-Thomson, Gifford-McMahon, Stirling type, or a pulsed gas tube, or even a reverse Brayton cycle type.

[0038] As illustrated, the treatment circuit 2 preferably includes a heat exchanger 6 ensuring heat exchange between the gas to be purified and the cold head of the cryogenic cooler 5, for example via a heat exchanger and / or a suitable arrangement of the treatment circuit 2 around the cold head of the cryogenic cooler 5.

[0039] It should be noted that, in addition to the downstream filter 7, the heat exchanger 6 ensuring heat exchange between the gas to be purified and the cold head of the cryogenic cooler 5 could include a porous volume, for example, a volume of metallic foam for capturing solidified argon. For this purpose, the heat exchanger 6 may have an increased surface area dedicated to this purpose for the solid deposition.

[0040] Furthermore, as illustrated, the treatment circuit 2 may advantageously include a heat exchanger 11 (for example, counter-current) configured to ensure heat exchange between the relatively cooler gas stream exiting the filter 7 and the relatively warmer gas stream exiting the first purification unit 3, before its exchange with the cryogenic cooler 5. This allows the transfer of cooling power to the gas stream that must be cooled by the cold head.

[0041] The embodiment of [Fig. 3] differs from that of [Fig. 2] in that the gas to be purified, supplied by the source 13, is purified in the first adsorption purification stage 3 at a cryogenic temperature (for example, at a temperature close to the liquefaction temperature of nitrogen) and then heated to a value close to ambient temperature to deliver the previously purified fluid at ambient temperature. Upon exiting, the fluid to be purified to an ultimate level of purity is brought back to a cryogenic temperature, for example, around 80 K, in a heat exchanger 18 cooled by a cold source, for example, a flow of liquid nitrogen, to then undergo the ultra-purification process described above.

[0042] In another possible embodiment not shown, the cryogenic cooler 5 could comprise two cold heads (belonging to the same cryogenic cooler 5 or to two separate cryogenic coolers) and in heat exchange with the treatment circuit 2, for example, with two parallel portions of the treatment circuit 2. For example, the two cold heads could cool the gas streams feeding two separate filters 7.

[0043] Note that the second purification unit 4 and all or part of the associated circuitry can be housed in a thermally insulated cold box which can be separate from the first purification unit 3.

[0044] Note that an additional argon adsorbent may be provided upstream of the filter(s) 7 to increase the autonomy of the installation.

Claims

Demands

1. Argon separation installation in a gas stream such as hydrogen, helium or neon comprising a treatment circuit (2) including, between a first end intended to be connected to a source of gas to be purified and a second end intended to be connected to a purified gas receiver, a first adsorption purification element (3) configured to lower the argon content in the gas stream below a first threshold, for example below 1 Oppm, characterized in that the treatment circuit (2) includes, arranged in series downstream of the first purification element (3), a second purification element (4) including a cryogenic cooler (5) configured to cool the gas stream to a determined cryogenic temperature between 25K and 40K,and a filter (7) for collecting the argon solidified at cryogenic temperature to lower the argon content in the gas stream below a second threshold lower than the first threshold.

2. Installation according to claim 1, characterized in that the first purification component (3) comprises a temperature-modulated adsorption device (“TSA”) comprising one or more beds (9) of adsorbents maintained at a cryogenic temperature, for example around 80K.

3. Installation according to claim 1 or 2, characterized in that the first purification element (3) comprises a non-cryogenic temperature “PSA” adsorption device and a cooler (18) for the purified gas at the outlet of the first purification element (3).

4. Installation according to any one of claims 1 to 3, characterized in that the cryogenic cooler (5) comprises a cryo-cooler including a cold head in heat exchange with the gas stream and configured to provide cooling power at cryogenic temperature, the cryo-cooler being for example of the Joule Thomson, Gifford-McMahon, Stirling or pulsed gas tube type.

5. Installation according to claim 4, characterized in that the treatment circuit (2) includes a heat exchanger (6) ensuring heat exchange between the gas to be purified and the cold head of the cryogenic cooler (5).

6. Installation according to claim 5, characterized in that the heat exchanger (6) ensuring heat exchange between the gas to be purified and the cold head of the cryogenic cooler (5) comprises a porous volume, for example a volume of metallic foam or a filter screen for capturing solidified argon.

7. Installation according to claim 5 or 6 characterized in that the filter (7) is separate and distant from the heat exchanger (6) ensuring heat exchange between the gas to be purified and the cold head of the cooler (5).

8. Installation according to any one of claims 4 to 7, characterized in that the cryogenic cooler (5) comprises two cold heads in heat exchange with the processing circuit (2), for example with respectively two parallel portions of the processing circuit (2).

9. Installation according to any one of claims 1 to 8, characterized in that the filter (7) is of the mechanical type and regenerable, for example by heating, in particular electrical and vacuum operation and / or by gas purging.

10. Installation according to any one of claims 1 to 9, characterized in that the treatment circuit (2) comprises at least one regeneration line (12) and a set of regeneration valve(s) (10) configured to permit the circulation of a flow of gas exiting the first purification unit (3) into the filter (7) for the purpose of its regeneration.

11. Installation according to any one of claims 1 to 10, characterized in that the treatment circuit (2) comprises two parallel branches each equipped with a filter (7) and a set of valve(s) (8, 9) configured to allow the alternation of argon filtration of the gas stream in a first filter (7) while the other filter (7) is in a regeneration phase.

12. Installation according to any one of claims 1 to 11, characterized in that the treatment circuit (2) includes a heat exchanger (11) configured to provide heat exchange between the gas flow exiting the filter (7) and the gas flow upstream of its exchange with the cryogenic cooler (5).

13. A process for purifying a gas stream to be purified comprising hydrogen, helium, or neon, the process comprising a first step of purifying the gas stream by adsorption in in which the argon content in the gas stream is lowered below a first threshold, for example below 1 Oppm, characterized in that the process includes a second purification step configured to lower the argon content in the gas stream below a second determined threshold, for example 50ppb, the second purification being carried out by cooling the gas stream with a cryogenic cooler (5) to a determined cryogenic temperature between 25K and 40K to solidify all or part of the argon molecules and capture this solidified argon in a mechanical filter (7).

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