System for purifying argon by cryogenic distillation

Abstract

The invention relates to a system for purifying argon by cryogenic distillation comprising a single column (K) equipped with a top condenser (C), a fluid inlet (1) located at the lower part of the column, a fluid outlet (3) located at the upper part of the column and N distillation sections, N ≥ 4, at least two uppermost sections (T1, T2) of the column being respectively equipped with a first liquid distributor (D1) and a second liquid distributor (D2) able to mix together the liquids falling onto the distributor, said distributors each being located above the corresponding section; at least two lowermost sections (T N‑1 ,T N ) of the column being respectively equipped with an (N-1)th and an Nth liquid distributor (D N‑1 ,D N ) able to mix together the liquids falling onto the distributor and arranged above the corresponding section; the first, second, (N-1)th and Nth distributors each being sized to accommodate the maximum height of the liquid head, the liquid head maximum height(s) of the first and second distributors exceeding the liquid head maximum height(s) of the (N-1)th and Nth distributors.

Description

Technical Field

[0001] This invention relates to a system for purifying argon gas by cryogenic distillation, and to a cryogenic distillation air separation unit comprising such a system. Background Technology

[0002] While the continued availability of renewable energy cannot be guaranteed, the use of renewable energy enhances the benefits provided by the cryogenic distillation air separation unit, whose energy consumption can be significantly reduced in some respects.

[0003] The minimum load for a conventional cryogenic distillation air separation unit is essentially limited by the compressor and the distillation column. In the case of a distillation column, this minimum load in the prior art is approximately 50% of the nominal load, which is sufficient for units equipped with a single air compressor, where the conventional minimum load is 60-70% of the nominal load.

[0004] However, if energy transfer allows for the parallel installation of 2-3 air compressors, the minimum load required for the distillation column can reach 25-30% of the nominal load. Summary of the Invention

[0005] The purpose of this invention is to reduce the minimum load on argon purification systems used in cryogenic distillation air separation units without significantly sacrificing efficiency. Complete argon purification via cryogenic methods requires more than 150 theoretical plates, making it practically very difficult. It is considered particularly important to ensure excellent surface distribution of the liquid along the entire length of the column.

[0006] The tower could be divided into 4-8 sections, with each section supplied with a high-performance distributor. The high-performance distributor is a surface distributor that ensures the flow rate is distributed evenly across all areas of the tower, maintaining a difference of no more than 2%, wherein these areas have the height of the filling element as a characteristic dimension when the load on the tower is at a set minimum and the deviation from the theoretical geometry is at the maximum of the manufacturing tolerance.

[0007] FR-A-3084736 describes an example of a simple eight-segment tower.

[0008] When aiming to reduce the minimum load on the column, a common practice is to increase the flexibility of each distributor to maintain high-quality distribution even under reduced load. For example, if the distributor is constructed of perforated slots, the cross-sectional area of ​​the perforations is reduced, ensuring that the liquid head height under reduced load remains significantly higher (typically 20-50 times higher) than the maximum difference in height between these holes, a difference stemming from construction. Consequently, the height of the distributor needs to be increased to accommodate the liquid head height under full load. In practice, for distributors in actual operation, some holes may be higher than others due to defects in distributor manufacturing, installation in the column, or the column's own verticality. This can create differences, leading to variations in the liquid head height above the holes, and consequently, variations in flow rates.

[0009] This invention is based on the observation that the effects of significant defects in distribution can be almost entirely compensated for by mixing liquids from two tower regions with different reflux ratios, and thus different compositions, or even by partial mixing of these liquids. In absolute terms, the more significant the difference in composition, the greater the compensatory effect of mixing these liquids.

[0010] Therefore, in the lower region of the argon purification tower, the oxygen content and, consequently, the differences (in absolute value) caused by potential partition defects remain significant, making the installation of a mixing distributor in this lower region highly effective in correcting the effects of partition defects. In contrast, in the upper part of the argon purification tower, multiple mixing distributors are required to achieve a comparable effect.

[0011] Therefore, the present invention includes installing a distributor capable of providing high-quality dispensing at the top of the argon purification tower, while the rest of the tower may be equipped with a more conventional mixing distributor for liquid dispensing, such as having a smaller height, or in any case allowing for a reduction in the total cost of the tower, for example due to the use of a simpler distributor.

[0012] The distributor that plays the most essential role in distributing the mass in the unit is located directly below the condenser at the very top of the tower, because this distributor is used to distribute the purest liquid.

[0013] The operation of purifying argon gas in a single column or in two columns connected in series is already known. This invention applies to both cases.

[0014] According to one aspect of the present invention, a system for purifying argon gas by cryogenic distillation is provided, the system comprising:

[0015] i) A single column equipped with a top condenser, a fluid inlet at the bottom of the column, a fluid outlet at the top of the column, and N distillation sections, where N ≥ 4. Each section is made of a stack of structured packing units of an alternating corrugated type, each unit comprising small packages of rectangular corrugated sheets. At least two uppermost sections of the column are respectively equipped with a first liquid distributor and a second liquid distributor, the second liquid distributor functioning to mix the liquids falling onto it. The first and second distributors are each located above their respective sections. At least two lowermost sections of the column are respectively equipped with a (N-1)th and an Nth liquid distributor, the liquid distributor functioning to mix the liquids falling onto it, and arranged above their respective sections.

[0016] ii) A first column and a second column, each equipped with a top condenser, a fluid inlet at the bottom of the first column, a fluid outlet at the top of the second column, and means for connecting the top of the first column and the bottom of the second column, thereby allowing liquid from the bottom of the second column to be fed to the top of the first column and allowing gas from the top of the first column to be fed to the second column, the first column and the second column comprising a total of N distillation sections, where N ≥ 4. Each section is made of a stack of structured packing units, wherein the structured packing is of an alternating corrugated type, and each unit contains small rectangular corrugated sheets; wherein at least two uppermost sections of the second tower are respectively equipped with a first liquid distributor and a second liquid distributor, the second liquid distributor being capable of mixing the liquids falling onto it, and the first and second distributors are each located above their respective sections; and at least two lowermost sections of the first tower are respectively equipped with a (N-1)th and an Nth liquid distributor, the liquid distributors being capable of mixing the liquids falling onto them, and are arranged above their respective sections.

[0017] The system is characterized by:

[0018] • The first, second, (N-1)th, and Nth distributors are each dimensioned to accommodate the maximum height of the liquid head, wherein the maximum height of one or more liquid heads in the first and second distributors exceeds the maximum height of one or more liquid heads in the (N-1)th and Nth distributors.

[0019] Therefore, the maximum height of one or more liquid heads in the first and second distributors exceeds the maximum height of one or more liquid heads in the (N-1)th and Nth distributors.

[0020] The dimensions of the first and second dispensers do not necessarily have to be designed for the same maximum liquid head height.

[0021] The dimensions of the (N-1)th and Nth distributors do not have to be designed for the same maximum liquid head height.

[0022] Based on other optional aspects:

[0023] • The system comprises: a single tower containing N sections, where N ≥ 8, each section being a stack of structured packing units of an alternating corrugated type, each unit comprising small packages of rectangular corrugated sheets, wherein at least three uppermost sections of the tower are respectively equipped with a first liquid distributor, a second liquid distributor, and a third liquid distributor, the second liquid distributor functioning to mix liquids falling onto it, the third liquid distributor functioning to mix liquids falling onto it; the first, second, and third distributors are each arranged above their respective sections, and...

[0024] • At least five lowermost sections of the tower are each equipped with a liquid distributor, which functions to mix the liquids falling onto the distributor and is arranged above the respective sections; the first, second, third, (N-4), (N-3), (N-2), (N-1), and Nth distributors are each sized to accommodate the maximum height of the liquid head, wherein the maximum height of the liquid head(s) of the first, second, and third distributors exceeds the maximum height of the liquid head(s) of the (N-4), (N-3), (N-2), (N-1), and Nth distributors.

[0025] • The dimensions of the (N-1)th and Nth distributors are designed to accommodate the maximum height of the liquid head, which is at least 30% smaller than the maximum height of the liquid head(s) of the first and second distributors.

[0026] • The dimensions of the (N-1)th and Nth distributors are designed to accommodate a maximum liquid head height greater than 50 mm.

[0027] • The first, second, and optional third dispensers are designed to accommodate a maximum liquid head height of 150-300 mm.

[0028] • The system comprises a single column containing N distillation sections, where N ≥ 8. Each section is made of a stack of structured packing units of an alternating corrugated type. Each unit comprises small packets of rectangular corrugated sheets. At least three uppermost sections of the column are equipped with a first liquid distributor, a second liquid distributor, and a third liquid distributor, respectively. The second liquid distributor functions to mix the liquids falling onto it, and the third liquid distributor functions to mix the liquids falling onto it. The first, second, and third distributors are each arranged above their respective sections.

[0029] • At least five lowermost sections of the tower are each equipped with a liquid distributor, which functions to mix the liquid falling onto the distributor and is arranged above the respective section; wherein the first, second, and third distributors each contain at least two rows of perforations for distributing liquid, with one row of perforations arranged above the other row of perforations, and

[0030] • The (N-4), (N-3), (N-2), (N-1), and Nth dispensers contain a single row of perforations for dispensing liquid.

[0031] Another aspect of the invention relates to an air separation unit comprising: a column suitable for operation at a first pressure and a column suitable for operation at a second pressure, wherein the second pressure is lower than the first pressure, the top of the column suitable for operation at the first pressure being thermally connected to the bottom of the column suitable for operation at the second pressure; a conduit for conveying purified air to the column suitable for operation at the first pressure; a conduit for conveying an oxygen-rich liquid from the column suitable for operation at the first pressure to the column suitable for operation at the second pressure; a conduit for conveying a nitrogen-rich liquid from the column suitable for operation at the first pressure to the column suitable for operation at the second pressure; a conduit for removing the oxygen-rich liquid from the column suitable for operation at the second pressure; a conduit for removing a nitrogen-rich fluid from the column suitable for operation at the second pressure; and a conduit connected to a midpoint on the column suitable for operation at the second pressure for removing an argon-rich fluid, and this conduit being connected to the purification system as described above.

[0032] The unit preferably includes at least two compressors or even at least three compressors connected in parallel to the piping for delivering purified air to the tower suitable for operation at the first pressure.

[0033] Another subject of the invention relates to a distillation method using a purification system as described above, wherein a feed stream containing argon and oxygen is fed into the purification system, and an oxygen-rich liquid and an argon-rich fluid are separated in the purification system, the argon-rich fluid containing up to 100 ppm of oxygen. Attached Figure Description

[0034] The invention will now be described in more detail with reference to the accompanying drawings.

[0035] [ Figure 1 This invention relates to an argon purification tower.

[0036] [ Figure 2 The separation unit is shown, which includes the argon purification tower of the present invention. Detailed Implementation

[0037] [ Figure 1 The diagram shows a column system comprising a single distillation column K. The distillation column K, equipped with a condenser C, contains N distillation sections T1, T2…T… N-1 T N Each segment is made of a stack of structured packing units, wherein the structured packing is of an interlaced corrugated type, and each unit contains small packets of rectangular corrugated sheets. Each segment T1, T2…T N-1 T N The column receives liquid from the distributor located just above the section, so there are N distributors, one for each section. This column can contain 150 theoretical plates, and the number of sections N is at least 4, for example, at least 8 sections.

[0038] [ Figure 1 The two sections T1 and T2 closest to the condenser C are equipped with liquid distributors D1 and D2 respectively. D2 can mix the liquid falling from section T1, which is located just above the liquid distributor D2.

[0039] The section T1 closest to the condenser C is equipped with a liquid distributor D1, which receives the liquid condensed in the condenser C and preferably distributes the liquid along the entire horizontal cross-section of the section T1.

[0040] At the base of this tower are the two lowest sections, T. N-1 T N and related liquid dispenser D N-1 D N Liquid dispenser D N-1 Used to receive liquid from the (N-2)th segment and deliver this mixed liquid to segment T. N-1 Liquid dispenser D NUsed to receive liquid from the (N-1)th segment, mix these liquids, and send them to the last segment, the Nth segment.

[0041] The diagram does not show segments from the third segment to the (N-2)th segment and their distributors.

[0042] The quality of liquid distribution achieved by a distributor located at the top of the tower is better than that achieved by a distributor located at the bottom of the tower.

[0043] One possible approach is to design the dimensions of the first, second, (N-1), and Nth distributors to accommodate the maximum height of the liquid head, where the maximum height of the liquid head in the first and second distributors exceeds the maximum height of the liquid head(s) in the (N-1)th and Nth distributors. If the amount of liquid delivered to the distributor fills to a position higher than the aforementioned maximum liquid head height, the distributor overflows, and the distributor cannot accommodate the excess liquid.

[0044] The first and second distributors can have the same maximum liquid head height or different maximum heights.

[0045] The (N-1)th and Nth distributors can have the same maximum liquid head height or different maximum heights.

[0046] A second possibility compatible with the first scheme is that for the first and second dispensers, each of them contains at least two rows of perforations for dispensing liquid, with one row of perforations arranged above the other row of perforations; and for the (N-1)th and Nth dispensers, they contain a single row of perforations for dispensing liquid.

[0047] When N equals at least 8, the dimensions of the first, second, third, (N-4), (N-3), (N-2), (N-1), and Nth distributors are each designed to accommodate the maximum height of the liquid head, wherein the maximum height of one or more liquid heads of the first, second, and third distributors exceeds the maximum height of one or more liquid heads of the (N-4), (N-3), (N-2), (N-1), and Nth distributors.

[0048] Another approach is that the first, second, and third dispensers each contain at least two rows of perforations for dispensing liquid, with one row of perforations arranged above the other row; and the (N-4), (N-3), (N-2), (N-1), and Nth dispensers each contain a single row of perforations for dispensing liquid.

[0049] In one example, the dimensions of the (N-1)th and Nth distributors are designed to accommodate the maximum height of the liquid head, which is at least 30% smaller than the maximum height of one or more liquid heads of the first and second distributors.

[0050] Alternatively, the dimensions of the (N-4), (N-3), (N-2), (N-1), and Nth distributors are designed to accommodate the maximum height of the liquid head, which is at least 30% smaller than the maximum height of one or more liquid heads of the first, second, and third distributors.

[0051] To ensure proper operation, the (N-1)th and Nth dispensers, or even the (N-4), (N-3), (N-2), (N-1)th and Nth dispensers, are designed to accommodate a maximum liquid head height greater than 50 mm.

[0052] Preferably, the first, second, and optional third dispensers are sized to accommodate a maximum liquid head height of 150-300 mm.

[0053] With reduced operations, the flow rate of the feed stream 1 fed to tower K, which includes at least a first and a second distributor, corresponds to 25-45% of the tower's nominal load. In this case, due to the improved structure, at least the first distributor ensures that the flow rate difference between regions of the horizontal cross-section of its feed section is less than 1%.

[0054] In contrast, distributors located at the bottom of the tower can have poorer performance; for example, at least one distributor located above one of the lower sections may provide a flow rate difference of more than 1% between the regions of its feed section's horizontal cross-section.

[0055] Preferably, all distributors from the second to the (N-1)th will mix the liquid received along at least one axis together and send at least 20% of the flow that falls on one area of ​​its horizontal cross-section to an area completely opposite to that area.

[0056] Preferably, the argon-rich fluid 3 contains up to 100 ppm of oxygen.

[0057] At least three lower sections are equipped with liquid dispensers D3, D4, and D5, which function to mix the liquids falling onto them. These dispensers are arranged above the respective sections and have a dispensing quality index below a second threshold, which is lower than the first threshold.

[0058] Each liquid dispenser D1, D 2… D N-2 D N-1 DN Preferably, it is of the type described in FR3077505, FR2655877, FR2860990, or FR2732616. The liquid dispenser may, for example, comprise an inverted U-shaped component having substantially vertical walls and a bottom, in which a plurality of parallel grooves are formed, each groove being covered by one of the shaped components, which are fixed to the bottom in a permanent fluid seal manner. Fins are attached to the sides of the shaped component, thereby forming lateral openings. The bottom may have perforations.

[0059] However, other types of allocators can also be used.

[0060] A feed stream 1 containing argon and oxygen is sent to the bottom of column K, where it is separated to form an argon-rich fluid 3 at the top of the column, which contains up to 100 ppm of oxygen; and an oxygen-rich liquid 5 at the bottom of the column.

[0061] Tower K is used as part of an air separation unit comprising a first distillation tower K1 operating at a first pressure and a second distillation tower K2 operating at a second pressure lower than the first pressure. The top of the first tower is thermally connected to the bottom of the second tower. Purified air 11 is supplied to the first distillation tower K1, and oxygen-rich liquid is supplied from the first tower to the second tower, as are nitrogen-rich liquids. The oxygen-rich fluid is withdrawn from the bottom of the second tower, and the nitrogen-rich fluid is withdrawn from the top of the second tower. A conduit connected to the midpoint of the second distillation tower K2 is used to withdraw argon-rich fluid from the second tower, and this conduit is connected to tower K.

[0062] The nominal load used for tower K is the normal flow rate during normal operation. This flow rate can be reduced. For example, if the air stream 11 is compressed by two compressors in parallel, the flow rate of stream 17 can be reduced by half, or even by two-thirds. If the air 11 passes through three compressors in parallel, the flow rate of stream 17 can be reduced by two-thirds, or even by three-quarters.

[0063] [ Figure 2 The air separation unit is shown, which includes two distillation columns K1 and K2, wherein the first distillation column K1 corresponds to […]. Figure 1 The lower part of column K is shown in the diagram, and the second distillation column K2 corresponds to the upper part of column K, so it includes the condenser C. N segments are distributed between the two distillation columns K1 and K2, where at least segments T1 and T2 are located just below the condenser in the second distillation column K2, and at least segment T... N-1 T NIt is the lowest section located at the bottom of the first distillation column K1.

[0064] Each segment has, for example, [ Figure 1 The relevant distributor shown in the diagram supplies an argon-rich feed stream to the bottom of the first distillation column K1, producing an oxygen-rich liquid 5. The top gas 15 of the first distillation column K1 is sent to the bottom of column K2, and the bottom liquid 12 from the second distillation column K2 is pumped from the second distillation column K2 to the top of the first distillation column K1 via pump P, without excluding the possibility of removing intermediate liquid or gas. Gas 15 is separated in the second distillation column K2 and becomes argon-rich as it rises in the second distillation column K2; at the top, after passing through sections T1 and T2, an argon-rich fluid 3 is obtained.

[0065] The type of allocator is determined according to [...] Figure 1 The same method is used to select the distributor, so that the distributor located at the top of the second distillation column K2 has a better distribution effect than the distributor located at the bottom of the first distillation column K1.

Claims

1. A system for purifying argon gas by cryogenic distillation, the system comprising: i. A single column (K) equipped with a top condenser (C), a fluid inlet at the bottom of the column, a fluid outlet at the top of the column, and N distillation sections, where N ≥ 4, each section being made of a stack of structured packing units of an alternating corrugated type, each unit comprising small packages of rectangular corrugated sheets; wherein at least two uppermost sections (T1, T2) of the column are respectively equipped with a first liquid distributor (D1) and a second liquid distributor (D2), the second liquid distributor functioning to mix the liquids falling onto it, the first liquid distributor and the second liquid distributor being located above the respective sections; wherein at least two lowermost sections (T1, T2) of the column are ... top condenser (C), a fluid inlet at the bottom of the column, a fluid outlet at the top of the column, and N distillation sections, where N ≥ 4, each section is made of a stack of structured packing units of an alternating corrugated type, each unit comprising small packages of rectangular corrugated sheets; wherein at least two uppermost sections (T1, T2) of the column are respectively equipped with a first liquid distributor (D1) and a second liquid distributor (D2) and a third liquid distributor (D2) and a fourth liquid distributor (D2) and a fifth liquid distributor (D2) and a fifth liquid distributor (D2) and a sixth liquid distributor (D2) and a fifth liquid distributor (D2) and a fifth liquid distributor (D2) and a sixth liquid distributor (D2) and a fifth liquid distributor (D2) and a fifth liquid distributor (D2) and a sixth liquid distributor (D2) and a fifth liquid distributor (D2) and a fifth liquid distributor (D2) and a sixth liquid distributor (D2) and a fifth liquid distributor (D2) and a sixth liquid distributor (D2) and a N-1 , T N ) respectively equipped with the (N-1)th and Nth liquid dispensers (D N-1 D N These liquid dispensers function to mix the liquids that fall onto them and are arranged above the corresponding sections. or ii. A first column (K1) and a second column (K2), each equipped with a top condenser (C), a fluid inlet located at the bottom of the first column, a fluid outlet located at the top of the second column, and means for connecting the top of the first column and the bottom of the second column, thereby allowing liquid from the bottom of the second column to be delivered to the top of the first column and allowing gas from the top of the first column to be delivered to the second column. The first and second columns comprise a total of N distillation sections, where N ≥ 4. Each section is made of a stack of structured packing units of an alternating corrugated type, each unit comprising small packages of rectangular corrugated sheets. At least two uppermost sections of the second column are respectively equipped with a first liquid distributor (D1) and a second liquid distributor (D2), the second liquid distributor functioning to mix liquids falling onto it. The first and second liquid distributors are each located above their respective sections. At least two lowermost sections of the first column are respectively equipped with the (N-1)th and Nth liquid distributors (D1 and D2). N-1 D N The liquid distributor functions to mix liquids falling onto it and is arranged above the corresponding sections. The system is characterized by: The first, second, (N-1)th and Nth liquid dispensers are each sized to accommodate the maximum height of the liquid head, wherein the maximum height of one or more liquid heads in the first and second liquid dispensers exceeds the maximum height of one or more liquid heads in the (N-1)th and Nth liquid dispensers.

2. The system according to claim 1, comprising: a single A tower (K) comprises N sections, where N ≥ 8, each section being a stack of structured packing units of an alternating corrugated type, each unit comprising small packets of rectangular corrugated sheets; wherein at least three uppermost sections (T1, T2) of the tower are respectively equipped with a first liquid distributor (D1) and a second liquid distributor (D2), the second liquid distributor functioning to mix the liquids falling onto it, and a third liquid distributor (D3), the third liquid distributor functioning to mix the liquids falling onto it; the first, second, and third liquid distributors are each arranged above their respective sections, and... The tower is provided with at least five lowermost sections, each equipped with a liquid distributor that mixes the liquids falling onto it and is arranged above the respective sections. The first, second, third, (N-4), (N-3), (N-2), (N-1), and Nth liquid distributors are each sized to accommodate the maximum height of the liquid head, wherein the maximum height of one or more liquid heads of the first, second, and third liquid distributors exceeds the maximum height of one or more liquid heads of the (N-4), (N-3), (N-2), (N-1), and Nth liquid distributors.

3. The system according to claim 1, wherein the (N-1)th and Nth liquid dispensers (D N-1 D N The dimensions are designed to accommodate the maximum height of the liquid head, which is at least 30% smaller than the maximum height of one or more liquid heads of the first and second liquid distributors.

4. The system according to claim 1, wherein the (N-1)th and Nth liquid dispensers (D N-1 D N The dimensions are designed to accommodate a liquid head height greater than 50mm.

5. The system according to claim 1, wherein the first, second and optionally third liquid dispensers are sized to accommodate a maximum liquid head height of 150-300 mm.

6. The system according to claim 1, wherein a single tower comprises N sections, where N ≥ 8, each section being made of a stack of structured packing units, the structured packing being of an interlaced corrugated type, each unit comprising small packages of rectangular corrugated sheets; wherein at least three uppermost sections (T1, T2) of the tower are respectively equipped with a first liquid distributor (D1) and a second liquid distributor (D2), the second liquid distributor being capable of mixing liquids falling onto it, and are equipped with a third liquid distributor (D3), the third liquid distributor being capable of mixing liquids falling onto it; the first, second, and third liquid distributors are each arranged above the corresponding section, and The tower has at least five lowermost sections each equipped with a liquid distributor, which functions to mix the liquid falling onto the distributor and is arranged above the respective section; wherein the first, second, and third liquid distributors each contain at least two rows of perforations for distributing liquid, with one row of perforations arranged above the other row of perforations, and... The (N-4), (N-3), (N-2), (N-1), and Nth liquid dispensers contain a single row of perforations for dispensing liquid.

7. An air separation unit, comprising: A column (31) suitable for operation at a first pressure and a column (32) suitable for operation at a second pressure, wherein the second pressure is lower than the first pressure; the top of the column suitable for operation at the first pressure is thermally connected to the bottom of the column suitable for operation at the second pressure; a conduit for supplying purified air to the column suitable for operation at the first pressure; a conduit for supplying oxygen-rich liquid from the column suitable for operation at the first pressure to the column suitable for operation at the second pressure; a conduit for supplying nitrogen-rich liquid from the column suitable for operation at the first pressure to the column suitable for operation at the second pressure; a conduit for removing oxygen-rich liquid from the column suitable for operation at the second pressure; a conduit for removing nitrogen-rich fluid from the column suitable for operation at the second pressure; and a conduit connected to an intermediate point on the column suitable for operation at the second pressure to remove argon-rich fluid, and this conduit is connected to the system according to any one of claims 1-4.

8. The unit according to claim 7, comprising at least two compressors, or even at least three compressors, connected in parallel to a conduit for delivering purified air (33) to the tower (31) suitable for operation at the first pressure.

9. A distillation method using the system according to any one of claims 1-6, wherein a feed stream containing argon and oxygen is fed into the system and separated in the system to form an oxygen-rich liquid (5) and an argon-rich fluid containing up to 100 ppm of oxygen.

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