Rotary valve optimized especially for a PSA type installation

Abstract

The object of the present invention relates to a rotary valve comprising at least one rotary valve flat seal (7, 8) defining chambers between the faces of a stator (9) and a rotor (6), characterized in that the rotary valve flat seal (7, 8) comprises at least one first lubrication seal (8) in contact with at least one second elastically deformable seal (7), and its application in a PSA (Pressure Swing Adsorption) type installation. Abstract figure: Fig. 1

Description

Title of the invention: Rotary valve optimized in particular for a PSA type installation

[0001] The subject of the present invention relates to a rotary valve comprising at least one rotary valve flat seal delimiting chambers between the faces of a stator and a rotor, characterized in that the rotary valve flat seal comprises at least one first lubrication seal in contact with at least one second elastically deformable seal, as well as its application in a PSA (“Pressure Swing Adsorption” type installation).

[0002] Rotary valves are widely used in industry to direct fluids from one or more process sources to one or more process destinations during repeatable cyclic process steps. This is particularly the case in the industry specializing in gas separation processes by pressure and / or temperature swing adsorption (also called "PSA"), or in regenerative catalytic processes, in the separation of liquids by concentration swing adsorption, in gas or liquid chromatography, in pneumatic or hydraulic sequential control systems, and in many other cyclic processes.

[0003] Document US5807423 thus discloses a rotary valve which comprises three components: - a first valve element, - a second valve element and - a drive means for causing relative rotation of the first and second valve elements.

[0004] The first and second valve members have smooth surfaces that are engaged and relatively rotatable about a common center of rotation to provide valve action between various ports incorporated in one of the valve members. The first valve member contains two circular arrays of through-openings, each of which is connected to a conduit. The second valve member contains a plurality of passages that provide communication between various openings of the first valve member and valve ports located in the second valve member. The second valve member also contains one or more passages that provide communication between two openings of one array of openings and one opening of the other array of openings.The rotary valve may be used to automate the operation of a gas or liquid adsorption system comprising two or more adsorption vessels, the number of vessels being equivalent to the total number of openings in either network. It is disclosed that the use of the valve in a system . adsorption eliminates the need for numerous valves required in conventional multi-vessel adsorption systems. However, this valve in practice requires lubrication means to ensure free rotation of the valve elements which are also subject to wear due to their respective friction.

[0005] Document CA2364881A discloses a valve for implementing a high-frequency pressure swing adsorption process, which comprises: - a stator comprising a number of functional compartments opening onto the valve faces of the stator, - a rotor rotatably coupled to the stator and comprising a number of apertures opening in the valve faces of the rotor, and - a self-regulating clearance valve seat positioned between the valve faces of the stator and rotor so as to regulate the gas flow rate between the stator and the rotor.

[0006] Each valve seal includes a sealing face disposed adjacent a respective one of the rotor valve faces and is pivotable relative to the respective rotor valve face to vary the gas flow rate as a function of the clearance distance between the sealing face and the respective rotor valve face. Each valve seal also includes a passageway that communicates with one of the functional compartments to vary the clearance distance in response to a pressure difference between the passageway and an approaching opening. In this manner, the valve seal maintains a smooth pressure transition profile as flow paths are switched between the functional compartments. It is disclosed that as a result, balance is maintained between the adsorbent material and the mass transfer front of the gas, and the efficiency of the gas separation process is improved.However, for its operation this valve requires perfect alignment of the axes of rotation of the stator with the rotor so that the self-regulating valve seat can operate efficiently. This valve therefore also requires lubrication means to ensure perfect alignment of the valve elements which are also subject to wear due to their respective friction.

[0007] Similarly, documents US2006283325, US2007028971, US2009107332, US2012285321 are additional illustrations of rotary valves. However, in all these documents, the rotary valves described are subject to mechanical constraints requiring significant maintenance to ensure their efficiency.

[0008] Document US2004 / 094216 discloses a rotary valve comprising a rotor having a rotor face rotatable about an axis perpendicular to the rotor face, wherein the rotor face has a plurality of openings, one or more of which are disposed at a selected radial distance from the axis, and wherein the rotor comprises at least one passage connected to at least one pair of the plurality of openings. The valve comprises a flexible orifice plate having a first side and a second side, the first side facing the rotor and engaging the rotor such that the flexible orifice plate is coaxially rotatable by the rotor and axially movable relative to the rotor, the flexible orifice plate having a plurality of orifices between the first and second sides, which orifices are aligned with the openings in the face of the rotor. The valve also includes a stator having a stator face disposed coaxially with the rotor and the flexible orifice plate, the second side of the flexible orifice plate being in sealable, sliding, rotatable contact with the stator face, the stator face having a plurality of openings, some of which are disposed at the selected radial distance from the axis, and in which the openings extend as passages through the stator. It is disclosed that the valve can be used in pressure- or temperature-swing adsorption systems.If this system is subject to mechanical constraints, it is reported, however, that a suitable material for the orifice plate may be polytetrafluoroethylene (PTFE), possibly loaded with carbon or bronze. Such a plate has self-lubricating properties that reduce friction between the parts in contact with it. However, on the one hand, depending on the pressures applied, such a plate may have limitations in terms of strength depending on its design. In addition, it is desirable not to use as many fluorocarbon compounds, for various reasons, including environmental ones, for industrial production of such parts.

[0009] The aim of the invention is therefore to overcome the drawbacks of the prior art and thus aims to propose a rotary valve having limited mechanical constraints requiring less maintenance compared to the state of the art while ensuring the same level, or even a higher level, of efficiency. Summary of the invention

[0010] To do this, a first aspect of the invention thus relates, in its broadest acceptance, to a rotary valve comprising: (a) a stator having a stator face and a plurality of openings disposed on the stator face and passing through said stator, (b) a rotor having a rotor face rotatable about an axis perpendicular to the rotor face in sealing and compressive contact with the stator face to form a rotary valve plane seal defining at least a first and a second chamber on the rotor face, said first and second chambers being arranged such that at least two stator openings are positioned to jointly and sequentially coincide respectively with said rotor face chambers, the stator further comprising a pressurized fluid inlet configured to coincide with only the first chamber, and the rotor comprises at least one orifice exhaust, the rotor being further configured to occupy an angular position in which the first chamber is in coincidence with the pressurized fluid inlet and the second chamber is in coincidence with the exhaust, characterized in that the rotary valve flat seal comprises at least a first lubrication seal in contact with at least a second elastically deformable seal.

[0011] Thus, thanks to the presence of the elastically deformable seal, the lubrication seal ensures perfect sealing of the rotor-stator assembly of the valve while limiting friction. The mechanical stresses between the rotor and the stator are therefore much lower than those of the state of the art, which therefore makes it possible to limit maintenance with the same level, or even a higher level of efficiency given that the lubrication and sealing are better controlled.

[0012] The "stator", also known as the "fixed barrel", is the functional stationary part of a rotary valve.

[0013] The "rotor," also known as the "moving barrel," is the functional rotating part of a rotary valve, as opposed to the stator.

[0014] By "rotary valve flat seal" is understood in the context of the present invention a sandwiched element of generally flattened shape in contact with both the face of the stator and the face of the rotor and ensuring a seal between the stator and the rotor.

[0015] By "coincide sequentially respectively with said chambers of the rotor face", it is understood that said at least two openings of the stator are placed in such a way that when the rotor rotates, these openings of the stator coincide with said chambers of the rotor face, and this one after the other therefore in a sequential manner.

[0016] By "exhaust", is understood in the context of the present invention an outlet towards the outside of the rotary valve, in particular of the assembly constituted by the rotor and the stator.

[0017] By "lubricating seal", in the context of the present invention is understood a seal whose properties limit friction.

[0018] By "elastically deformable joint", is understood in the context of the present invention a joint which has the property of regaining, at least partially, its shape or its volume, after having lost at least one of the two by compression or extension.

[0019] The present invention relates in particular to a rotary valve as described above, in which the stator and / or the rotor comprises at least one groove configured to at least partially accommodate the rotary valve flat seal. There are several advantages to such a groove. For example, such a groove makes it possible to fix the position of the seal rotary valve plane with respect to the rotor and / or stator.

[0020] In a particular embodiment, the stator and / or the rotor comprises at least one groove configured to at least partially accommodate said at least one second elastically deformable seal.

[0021] In a particular embodiment, the stator and / or the rotor comprises at least one groove configured to fully accommodate said at least one second elastically deformable seal.

[0022] Preferably, the elastically deformable seal of the rotary valve flat seal is received at least partially in a groove of the rotor face.

[0023] The advantage of a groove configured to at least partially accommodate said at least one second elastically deformable seal is to be able to increase the exposure of said at least one first lubrication seal, thus making it possible to promote lubrication.

[0024] In a particular embodiment, the stator and / or the rotor comprises at least one groove configured to accommodate: - completely said at least one second elastically deformable seal, and - partially said at least one first lubricating seal.

[0025] Such configurations in which said at least one second elastically deformable seal is partially or totally received in at least one groove allow greater exposure of said at least one first lubrication seal, which thus makes it possible to promote lubrication between the rotor and the stator.

[0026] In a particular embodiment, pressure is exerted on the stator and / or the rotor so as to exert pressure on the rotary valve flat seal and promote the reception of the latter in said at least one groove of said stator and / or rotor.

[0027] Advantageously, the rotor and the stator are held in compression against each other by means of a spring. This promotes, where appropriate, the reception of said rotary valve flat seal in said at least one groove of said stator and / or rotor.

[0028] In a particular embodiment, the rotor is accommodated by a fixed barrel having a leakage opening communicating with the second chamber. In this embodiment, the rotor is in contact with the stator and on the opposite side of the rotor, the latter is accommodated by a fixed barrel. This fixed barrel is distinguished from the stator in that it does not necessarily have a face (in contact with the rotor) with a plurality of openings passing through it as is the case with the stator.

[0029] In a particular embodiment, the lubrication seal is a seal made of a self-lubricating material. The advantage is that the seal and thus the valve gain in operating autonomy and require less maintenance than with a seal without self-lubricating material.

[0030] Advantageously, the lubricating seal comprises PTFE and / or graphite.

[0031] Preferably, the lubrication seal comprises PTFE. The configuration of the lubrication seal makes it possible to incorporate PTFE in a minimal quantity, but sufficient to ensure self-lubrication.

[0032] Preferably, the elastically deformable seal has a toric cross-section. The toric section will have the advantage of being able to deform relatively easily by conforming to the surface of the rotor or stator on which it is in contact and said at least one first lubricating seal. Furthermore, in the case where the elastically deformable seal is accommodated in a groove, such an toric seal allows effective anchoring of the seal in said groove.

[0033] Advantageously, the pressurizing opening is placed along the axis of rotation of the rotor. Thus, the opening can be configured to always be supplied with pressurized fluid.

[0034] In a particular embodiment, the rotary valve flat seal delimits at least one third chamber on the rotor face configured to allow pressure equalization between said at least two openings of the stator which coincide with said at least one third chamber. This is one of the advantages of the present invention: the rotary valve flat seal can be easily configured to define additional chambers if necessary. Thus, a pressure equalization chamber between at least two openings of the stator. Such pressure equalization may be of interest in particular in gas separation processes by pressure swing adsorption, in which a pressure equalization step may be required.

[0035] Advantageously, the plurality of openings passing through said stator form channels having at least one bend. This is indeed also one of the advantages of the present invention: being able to propose a stator having a fluid communication means (a channel) which is not necessarily parallel to the axis of rotation of the rotor, given that the rotary valve plane seal is limited to the stator-rotor contact interface.

[0036] In a particular embodiment, an even number of the plurality of openings passing through said stator has at least one end connectable upstream of an air purification device. Indeed, in gas separation processes by modulated adsorption, in particular in pressure, it is customary to couple the columns. Thus, this is enabled by the rotary valve according to the present invention.

[0037] In a particular embodiment, the second chamber communicates freely with the exterior of the rotary valve.

[0038] The subject of the present invention further relates to the use of a rotary valve as described above, in a PSA type installation.

[0039] Thus, the subject of the present invention also relates to an installation for the production of oxygen, said installation comprising at least one air compressor, one oxygen generator and one oxygen compressor, said oxygen generator applying the so-called PSA technology (Pressure Swing Adsorption) comprising tanks, each tank having two ends and a body at least partially filled with a molecular sieve (adsorbent), open at each of its ends to define between said ends a flow path through the molecular sieve, one of the ends, called the first end of each tank, being selectively connectable to a source of pressurized air or exhausted to allow a pressurization / depressurization cycle of said tank,each molecular sieve being capable of adsorbing nitrogen molecules and allowing oxygen to pass through under the effect of pressurization of the tank and releasing nitrogen molecules by desorption under the effect of exhausting the tank, in which the installation comprises, for the pressurization / depression of the tanks or at least part of the tanks, a rotary valve common to said tanks, this rotary valve interposed between the first end of each tank and at least one source of compressed air having for each tank to which it is connected at least two angular positions corresponding, one, called the pressurization position, to a position for supplying pressurized air to said tank, another, called the depressurization position, to a position for exhausting said tank, characterized in that the rotary valve conforms to the description above. FIGURES

[0040] Embodiments of the present invention will be described below, by way of non-limiting examples, with reference to the appended figures in which:

[0041] [Fig.l] [Fig.l] is an exploded perspective view of the rotary valve according to the present invention.

[0042] [Fig.2] [Fig.2] is a perspective view of the rotary valve according to [Fig.l] assembly.

[0043] [Fig.3] [Fig.3] is a top view representation of the rotary valve as presented in [Fig.l] showing an AA section.

[0044] [Fig.4] [Fig.4] is a sectional view along section AA of [Fig.2].

[0045] [Fig.5] [Fig.5] is a top view representation of the rotary valve as presented in [Fig.l] showing a section AB.

[0046] [Fig.6] [Fig.6] is a sectional view along section AB of [Fig.4].

[0047] [Fig.7] [Fig.7] is a schematic view of one embodiment of the installation according to the present invention employing in particular twelve reservoirs.

[0048] [Fig-8] [Fig.8] is a schematic view of another embodiment of the installation according to the present invention employing in particular twelve tanks.

[0049] With reference to [Fig.l], a rotary valve according to the present invention is shown in exploded perspective view, said rotary valve comprises a stator 9 having a stator face 9 and a rotor 6 having a rotor face 6. A distribution flange 10 is placed under the stator 9. A flat gasket 13 is placed between the stator 9 and the distribution flange 10. The rotary valve according to the present invention comprises a deformable elastic seal 7 superimposed on a lubrication seal 8 to form a flat rotary valve seal 7,8. The flat seal 7,8 is sandwiched between the stator face 9 and the rotor face 6. A spring 5 provides compression to the rotor 6. The spring 5 is here placed around an eccentric 4. An O-ring 12 ensures sealing between the eccentric 4 and a friction ring 3 placed above said eccentric 4. A lantern 11 surrounds and covers the assembly up to and including the flat seal 13.The distribution flange 10 is thus visible when the lantern is in place. A motor flange 2, comprising a centering ring 1 on its upper face, is placed in a central opening of the motor flange 2.

[0050] With reference to [Fig.2] which represents a perspective view of the rotary valve according to [Fig.l] assembled, a motor-reducer connection 14 can be seen in the center of the motor flange 2 according to [Fig.l], that is to say at the centering ring 1 according to [Fig.l]. Connections 15, for example for purification columns are visible at the base of the rotary valve, at the distribution flange 10 according to [Fig.l].

[0051] With reference to [Fig.3], there can be seen a section AA taken in a sectional view according to [Fig.4].

[0052] With reference to [Fig. 4], a rotary valve according to the present invention and in accordance with the exploded view according to [Fig. 1] in an angular configuration as shown in [Fig. 3], in which there can be seen from left to right a distribution flange 10, a flat seal 13, a stator 9, a lubrication seal 8, a deformable elastic seal 7, a rotor 6, a spring 5, an eccentric 4 provided with an O-ring 12 going around this eccentric 4, a friction ring 3, a motor flange 2, a centering ring 1 and a lantern 11 partially covering the distribution flange 10 up to the friction ring 3, said lantern 11 being sealed at its right end by the motor flange 2. In this representation, the rotary valve is shown for a fluid flow supplying two columns.Thus, an arrow representing the fluid (air inlet here) passes via a conduit in the center of the distribution flange 10 and the flat seal 13, then through a conduit in the center of the stator 9, then communicates at the interface between the rotor 6 and the stator 9 by splitting into two separate flows with two conduits placed towards the outside of the stator 9 close to its periphery, to pass to the . through the distribution flange 10 via angled conduits to the columns.

[0053] With reference to [Fig.5], there can be seen a section AB taken in a sectional view according to [Fig.6].

[0054] With reference to [Fig. 6], a rotary valve according to the present invention and in accordance with the exploded view according to [Fig. 1] in an angular configuration as shown in [Fig. 5], in which there can be seen from left to right a distribution flange 10, a flat seal 13, a stator 9, a lubrication seal 8, a deformable elastic seal 7, a rotor 6, a spring 5, an eccentric 4 provided with an O-ring 12 going around this eccentric 4, a friction ring 3, a motor flange 2, a centering ring 1 and a lantern 11 partially covering the distribution flange 10 up to the friction ring 3, said lantern 11 being sealed at its right end by the motor flange 2. In this representation, the rotary valve is shown for two exhausted fluid flows.Thus, two arrows representing the fluids from columns pass via conduits configured for this in the distribution flange 10, the stator 9, and cross the lantern 11 towards the atmosphere (here being a free exhaust).

[0055] Thus, Figures 3, 4, 5 and 6 make it possible to appreciate operating modes of the rotary valve according to the present invention, when the rotor 6 is rotated in two different positions (pressurizing the columns - Figures 3 and 4, and exhausting the fluid from the columns - Figures 5 and 6). Another figure (not provided here) could have represented the case where two columns are put into communication with each other only, allowing equalization of the pressures between these two columns. For example, this embodiment is possible with two columns placed next to each other, the rotary valve being provided with a flat rotary valve seal delimiting an intermediate chamber allowing only communication between these two columns.

[0056] With reference to [Fig.7], the installation shown comprises a source of compressed air 20 supplying a rotary valve 21 according to the present invention and twelve reservoirs 16.

[0057] Thus, the embodiment as shown in [Fig.7] presents, in addition to the rotary valve 21 according to the present invention, an optimized installation allowing an adjustable variation of the flow rate according to the direction of the fluid downstream of the reservoirs 16, as described below.

[0058] The reservoirs 16 each comprise a first end 17, a body 19 and a second end 18.

[0059] The rotary valve 21 supplies the twelve reservoirs 16 via their first end 17.

[0060] The second end 18 of each reservoir 16 opens into a line 22 for connecting the second ends 18 of the reservoirs 16 to each other via an interface 23 connection.

[0061] This connecting interface 23 defines two parallel pipes 24 over at least part of their length and each connecting the second end 18 of the tank 16 and the connecting line 22 between them.

[0062] Each pipe 24 has a non-return valve 25, the non-return valves 25 being reversed from one pipe to another.

[0063] Furthermore, each pipe 24 has at least one flow regulator 26 arranged in series with said non-return valve 24.

[0064] The connection line 22 is provided with at least one outlet 27 for evacuating the oxygen produced.

[0065] This installation with the interface 23 as shown makes it possible to control the fluid flows downstream of the reservoirs 16, which allows for production optimization, particularly in terms of consistency of the flow rate of fluid produced.

[0066] For reasons of ease of implementation of such an installation, it can be incorporated, at least partially, in a frame (not shown here) configured to be moved and installed easily in a room of limited size (such as a hospital room or a dedicated technical room).

[0067] Alternatively to this embodiment, it is possible to replace this connection interface with a connection interface connected to a second rotary valve, such as a rotary valve 21 according to the present invention.

[0068] With reference to [Fig.8], the installation shown, of a design very close to the installation according to [Fig.7], comprises a source of compressed air 20 supplying a rotary valve 21 according to the present invention and twelve reservoirs 16.

[0069] Thus, the embodiment as shown in [Fig.8] presents, in addition to the rotary valve 21 according to the present invention, an optimized installation allowing an adjustable variation of the flow rate according to the direction of the fluid downstream of the reservoirs 16, as described below.

[0070] The reservoirs 16 each comprise a first end 17, a body 19 and two second (outlet) ends 18.

[0071] The rotary valve 21 supplies the twelve reservoirs 16 via their first end 17.

[0072] The second ends 18 of each reservoir 16 open into a line 22 for connecting the second ends 18 of the reservoirs 16 to each other by a connecting interface 23A.

[0073] This connecting interface 23A defines two parallel pipes 24 over at least part of their length and each connecting the two second ends 18 of the tank 16 and the connecting line 22 between them.

[0074] Each pipe 24 has a non-return valve 25, the non-return valves 25 being reversed from one pipe to another.

[0075] Furthermore, each pipe 24 has at least one flow regulator 26 arranged in series with said non-return valve 24.

[0076] The connection line 22 is provided with at least one outlet 27 for evacuating the oxygen produced.

[0077] This installation with the interface 23A as shown makes it possible to control the fluid flows downstream of the reservoirs 16, which allows for production optimization, particularly in terms of consistency of the flow rate of fluid produced.

[0078] For reasons of ease of implementation of such an installation, it can be incorporated, at least partially, in a frame (not shown here) configured to be moved and installed easily in a room of limited size (such as a hospital room or a dedicated technical room).

[0079] Thus the installation according to [Fig.8] has valves 25 arranged in parallel instead of being in series as in [Fig.7].

[0080]

Claims

Claims

1. A rotary valve comprising: (a) a stator (9) having a stator face (9) and a plurality of openings disposed on the stator face (9) and passing through said stator (9), (b) a rotor (6) having a rotor face (6) rotatable about an axis perpendicular to the rotor face (6) in sealing and compressive contact with the stator face (9) to form a rotary valve planar seal (7,8) defining at least a first and a second chamber on the rotor face (6), said first and second chambers being arranged such that at least two openings of the stator (9) are arranged to coincide jointly and sequentially respectively with said chambers of the rotor face (6), the stator (9) further comprising a pressurized fluid inlet configured to coincide with only the first chamber, and the rotor (6) comprises at least one exhaust port,the rotor (6) being further configured to occupy an angular position in which the first chamber is in coincidence with the inlet of pressurized fluid and the second chamber is in coincidence with the exhaust, characterized in that the flat seal (7, 8) of the rotary valve comprises at least a first lubrication seal (8) in contact with at least a second elastically deformable seal (7).,

2. Rotary valve according to claim 1, characterized in that the stator and / or the rotor comprises at least one groove configured to at least partially accommodate the rotary valve flat seal (7,8).

3. Rotary valve according to claim 1 or 2, characterized in that the elastically deformable seal (7) of the rotary valve plane seal (7, 8) is accommodated at least partially in a groove of the rotor face (6).

4. Rotary valve according to any one of claims 1-3, characterized in that the rotor (6) and the stator (9) are held in compression against each other by means of a spring (5).

5. Rotary valve according to any one of claims 1-4, characterized in that the rotor (6) is accommodated by a fixed barrel (11) having a leakage opening communicating with the second chamber.

6. Rotary valve according to any one of claims 1-5, characterized in that the lubricating seal (8) is a seal made of a self-lubricating material.

7. Rotary valve according to claim 6, characterized in that the lubricating seal (8) comprises PTFE and / or graphite.

8. Rotary valve according to any one of claims 1-7, characterized in that the elastically deformable seal (7) is of toroidal cross-section.

9. Rotary valve according to any one of claims 1-8, characterized in that the pressurizing opening is placed along the axis of rotation of the rotor (6).

10. Rotary valve according to any one of claims 1-9, characterized in that the rotary valve flat seal (7,8) delimits at least one third chamber on the rotor face (6) configured to allow equalization of pressures between said at least two openings of the stator (9) which coincide with said at least one third chamber.

11. Rotary valve according to any one of claims 1-10, characterized in that the plurality of openings passing through said stator (9) form channels having at least one bend.

12. Rotary valve according to any one of claims 1-11, characterized in that an even number of the plurality of openings passing through said stator (9) has at least one end connectable upstream of an air purification device.

13. Rotary valve according to any one of claims 1-12, characterized in that the second chamber communicates freely with the exterior of the rotary valve.

14. Use of a rotary valve according to any one of the preceding claims, in a PSA type installation.

15. Installation for the production of oxygen, said installation comprising at least one air compressor, one oxygen generator and one oxygen compressor, said oxygen generator applying the so-called PSA technology comprising tanks (16), each tank (16) having two ends (17, 18) and a body (19) at least partially filled with a molecular sieve (adsorbent), open at each of its ends (17, 18) to define between said ends (17, 18) a flow path through the molecular sieve, one of the ends (17, 18) called the first end (17) of each tank (16) being selectively connectable to a source (20) of pressurized or exhausted air to allow a pressurization / depressurization cycle of said tank (16), each molecular sieve being capable of adsorbing nitrogen molecules and allowing oxygen to pass through under the effect of pressurization of the tank (16) and releasing the nitrogen molecules by desorption under the effect of exhausting the tank (16), in which the installation comprises, for the pressurization / depression of the tanks (16) or at least part of the tanks (16) a rotary valve (21) common to said tanks (16), this rotary valve (21) interposed between the first end (17) of each tank (16) and at least one source (20) of compressed air having for each tank (16) to which it is connected at least two angular positions corresponding one, called the pressurization position, to a position for supplying pressurized air to said tank (16), another, called the depressurization position, to a position for exhausting said tank (16), characterized in that the rotary valve (21) conforms to any one of claims 1 to 13.

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