Device for recycling at least part of a hydrogen-containing gas composition and fuel cell system

Abstract

The present invention relates to a device (1, 30) for recycling at least part of a gas composition containing hydrogen, wherein the device (1, 30) is a dry rotary pump comprising a first rotary shaft (13) and a second rotary shaft (14), the first rotary shaft (13) and the second rotary shaft (14) respectively driving a first piston (8) with claws and a second piston (9) with claws in rotation in a pumping chamber (2) comprising an inlet opening (11) and an outlet opening (10) for the gas composition, the first rotary shaft (13) and the second rotary shaft (14) being configured to be driven in rotation by a drive system (17, 18) located in a gear chamber (4); wherein the device (1, 30) comprises a first pair of seals (19) and a second pair of seals (20), each pair of seals comprising a first shaft seal (19a, 20a) and a second shaft seal (19b, 20b), the first and second rotary shafts (13, 14) being configured to be driven in rotation by a drive system (17, 18) located in a gear chamber (4); A pair of seals (19) is arranged around a first rotating shaft (13), and the second pair of seals (20) is arranged around a second rotating shaft (14) between a pumping chamber (2) and a gear chamber (4); wherein the device (1, 30) includes a pressure balancing chamber (25) fluidically connected to a gap (24) between first shaft seals (19a, 20a) and second shaft seals (19b, 20b) of the first pair of shaft seals (19) and the second pair of shaft seals (20) to regulate the pressure in the gap (24); wherein the gear chamber (4) is fluidically connected to the gap (24); and wherein the pumping chamber (2) is fluidically connected to the first shaft seal (19a) of the first pair of shaft seals (19) and the first shaft seal (20a) of the second pair of shaft seals (20) via a pulsation damping chamber (22). The invention also relates to a fuel cell system (40, 50, 60, 70, 80, 90) comprising the device for recirculation according to the invention.

Description

Technical Field

[0001] The present invention relates, in a first aspect, to the field of devices for recycling at least part of a gas composition, in particular to the field of devices for recycling at least part of a gas composition containing hydrogen. More particularly, the invention relates to the field of devices for recycling at least part of a gas composition containing hydrogen in a fuel cell, in particular a fuel cell for a motor vehicle. In a second aspect, the invention relates to a fuel cell system allowing recycling of at least part of a gas composition containing hydrogen. Background Art

[0002] In a fuel cell system, gaseous hydrogen and oxygen are necessary to produce electricity. To help remove the water generated by the reaction of hydrogen and oxygen in the fuel cell, the fuel cell is supplied with a gas having a flow rate greater than the gas that can be converted.

[0003] Therefore, the fuel cell exhausts a gas composition containing at least a portion of unreacted gaseous hydrogen that is not used in the fuel cell (referred to as hydrogen off-gas). In order to be able to use this hydrogen off-gas, the fuel cell system is equipped with a hydrogen recirculation loop to resupply the fuel cell with hydrogen off-gas. To this end, the hydrogen recirculation loop is usually equipped with a hydrogen recirculation device.

[0004] Known in the prior art are ejectors or Roots pumps as hydrogen recirculation devices. A Roots pump consists of a pump unit and a motor unit, including an electric drive motor. A rotating shaft extends from the electric motor of the motor unit to the pumping unit, and a pair of rotors are housed in a pumping chamber. When the two rotors are set to rotate by the motor-driven rotating shaft, hydrogen exhaust gas is drawn into the pumping chamber, then discharged from the pumping chamber and reintroduced into the fuel cell.

[0005] It is crucial that the pump dedicated to hydrogen recirculation be configured to prevent hydrogen exhaust gas drawn into the pumping chamber from penetrating into the motor unit, or to prevent the hydrogen concentration in the motor unit from reaching explosive levels. To this end, known prior art devices utilize shaft seals, typically positioned around the rotating shaft or shafts between the gear chamber and the motor. The shaft seals prevent gaseous hydrogen from escaping from the pumping chamber along the rotating shaft toward the motor, thereby preventing the hydrogen concentration in the motor unit from reaching explosive levels.

[0006] However, gaseous hydrogen can pass through the shaft seal. Consequently, some hydrogen can diffuse from the pumping chamber into the motor unit, potentially increasing the hydrogen concentration in the motor. To address this issue, hydrogen pumps have been proposed in which a gas flow is actively introduced into the motor unit to pass through the motor unit and transport any hydrogen that might have passed through the shaft seal.

[0007] Unfortunately, although these pumps can limit the risk of explosion due to an increase in the hydrogen concentration in the motor unit, they cannot ensure that water molecules contained in at least part of the gas composition to be recycled cannot enter the drive chamber and / or the motor unit of the pump. This contamination of the pump interior is problematic because it often leads to pump failure.

[0008] A hydrogen pump, in particular for hydrogen recirculation in fuel cells in the automotive sector, must also meet a number of supplementary requirements, namely (this list is not exhaustive):

[0009] -Meet the maximum external leakage of hydrogen of 10Ncm 3 / h standard;

[0010] - Ability to operate within a wide adjustment range that can extend up to a ratio of 1:20, in particular reaching a maximum speed of 12,000 rev / min;

[0011] - Must be able to operate over a wide range of ambient temperature and gas input, in particular from -40°C to 100°C;

[0012] - Due to the supply voltage of the fuel cell, it must be able to operate at a nominal voltage of 12 to 800 VCC, in particular a nominal voltage of 24 VCC, 48 VCC, 200 VCC, 400 VCC or 750 VCC, and must have a high efficiency; and

[0013] - Due to the sensitivity of the bipolar plates or membranes of fuel cells to substances such as lubricants, suitable substances must be used in the pumping chamber and motor unit.

[0014] Therefore, the main challenge lies in the different behavior of the fuel cell, such as different operating cycles and operating pressures, vehicle area temperatures, water flow rates, etc.

[0015] There is therefore a need for a pump that is robust and flexible, such that it satisfies a combination of all the requirements mentioned above and such that it circumvents the problems of the known systems mentioned above. Summary of the Invention

[0016] One object of the present invention is therefore to propose a device for recycling at least part of a gas composition containing hydrogen making it possible to overcome the above-mentioned limitations.

[0017] In a more specific manner and according to a first aspect, an object of the present invention is achieved by a device for recycling at least part of a gas composition containing hydrogen, wherein the device is a dry rotary pump, the dry rotary pump comprising a first rotary shaft and a second rotary shaft, the first rotary shaft and the second rotary shaft respectively driving a first piston with claws and a second piston with claws in rotation in a pumping chamber comprising an inlet opening and an outlet opening for the gas composition, the first rotary shaft and the second rotary shaft being configured to be driven in rotation by a drive system located in a gear chamber; the device comprising a first pair of seals and a second pair of seals, each pair of seals The device comprises a first shaft seal and a second shaft seal, wherein the first pair of seals is arranged around a first rotating axis and the second pair of seals is arranged around a second rotating axis between a pumping chamber and a gear chamber; the device comprises a pressure balancing chamber, which is fluidically connected to a gap between the first shaft seal and the second shaft seal of the first pair of shaft seals and the second pair of shaft seals to regulate the pressure in the gap; wherein the gear chamber is fluidically connected to the gap; and wherein the pumping chamber is fluidically connected to the first shaft seal of the first pair of shaft seals and the first shaft seal of the second pair of shaft seals via a pulsation damping chamber.

[0018] The device according to the invention balances the pressures acting on both sides of the shaft seal, which ensures the tightness of the pumping chamber relative to the gear chamber. Due to this pressure balance, the friction between the shaft seal and the rotating shaft around which they are mounted always remains constant, which makes it possible to avoid premature wear of the shaft seal and thus avoid contamination of the gear chamber with water molecules in gaseous or liquid form and / or contamination of the pumping chamber with lubricant molecules present in the gear chamber. In an advantageous manner, the first pair of seals is made of fluororubber (e.g. Viton TM ), which makes these seals resistant to oil, and a second pair of seals is made of polytetrafluoroethylene (PTFE), which makes these seals resistant to substances present in the process of generating electricity in fuel cells (such as water, hydrogen and nitrogen).

[0019] In a first preferred embodiment of the present invention, at least one shaft seal of the first pair of shaft seals, the second shaft seal of the first pair of shaft seals, the first shaft seal of the second pair of shaft seals, and the second shaft seal of the second pair of shaft seals is a lip seal. The use of lip seals allows for a particularly simple implementation of the device according to the present invention. Furthermore, the use of lip seals allows for maximum sealing because the pressure of the lip on the shaft self-regulates as a function of the pressure prevailing around the lip.

[0020] In a first preferred embodiment of the present invention, the fluid connection between the gap and the gear chamber is established via a pressure balancing channel provided in the first and / or second rotating shaft. This facilitates pressure balancing between the gap between the shaft seals of both pairs of seals and the gear chamber.

[0021] In another preferred embodiment of the present invention, the device comprises a lubricating fluid filter between the pressure balancing channel and the gear chamber. Due to the lubricating fluid filter, the lubricating fluid can be prevented from entering the pressure balancing channel and thereby diffusing into the pumping chamber.

[0022] In a preferred embodiment of the present invention, a regulating inlet is provided to control the pressure in the pressure balancing chamber from outside the device. Thus, a gas, such as air, nitrogen, helium, hydrogen, neon, argon, krypton, xenon, or a mixture of these gases, can be introduced into the pressure balancing chamber to regulate the pressure in the chamber from outside the device.

[0023] In another preferred embodiment of the present invention, the pulsation damping chamber is fluidically connected to the pressure equalization chamber via a membrane that is permeable to gaseous hydrogen but impermeable to water molecules in both liquid and gaseous form. The fluid connection between the pulsation damping chamber and the gap enables automatic pressure equalization of the pressures existing in the gap, the pulsation damping chamber, and the gear chamber. Therefore, in this embodiment, active pressure regulation in the gap is not required. Furthermore, the presence of the semipermeable membrane allows for the filtration of water molecules, reducing the risk of contamination of the gear chamber and / or contamination of the pumping chamber by the lubricating fluid of the gear chamber.

[0024] In another preferred embodiment of the present invention, the fluid connection between the pulsation damping chamber and the pumping chamber is at least partially labyrinthine. This allows the pulsations generated by the compression cycles in the pumping chamber to be effectively damped and balanced. This ensures that the pressure acting on the first shaft seal, acting on the first and second pairs of seals, remains substantially constant during use of the device.

[0025] In a preferred embodiment according to the invention, the pulsation damping chamber is fluidically connected to a drain outlet. This makes it possible to drain away condensate, in particular water, that forms in the pulsation damping chamber.

[0026] In another preferred embodiment of the present invention, the inlet opening of the pumping chamber is oriented to allow the liquid to drain under gravity. This is particularly advantageous for preventing the formation of a water reservoir within the pumping chamber when the device is in a stopped state. Such a water reservoir could freeze, preventing the device from restarting. Liquid drainage under gravity allows for a simple design, as it eliminates the need for additional "active" components.

[0027] In a further preferred embodiment of the present invention, the gear chamber and / or the pumping chamber are provided with a hydrogen-resistant material or are covered with a hydrogen-resistant material. This makes it possible to increase the service life of the device.

[0028] In a further preferred embodiment of the present invention, the device is configured as a fuel cell for a motor vehicle, in particular as:

[0029] -The maximum external leakage of hydrogen allowed is 10Ncm 3 / h;

[0030] - increasing the pressure of the pumped gas mixture at the inlet of the fuel cell to a pressure in the range of up to 15 bar, in particular to a pressure of 1.5 to 5 bar absolute;

[0031] -Can be driven with a ratio of 1:20 within a control range of up to 12,000 rpm;

[0032] - capable of operating within an ambient temperature range and capable of inputting at least part of the gas composition between -40°C and 100°C; and / or

[0033] - Capable of operating at a nominal voltage between 12 and 800 VCC, in particular a nominal voltage of 24 VCC, 48 VCC, 200 VCC, 400 VCC or 750 VCC.

[0034] According to a second aspect, the object of the present invention is achieved by a fuel cell system comprising a reservoir of a gas composition at least partially containing hydrogen, which reservoir is connected to an inlet of a fuel cell, wherein the system comprises a device for recirculation according to the invention, the outlet of the fuel cell being connected to the inlet opening of the device for recirculation, and the outlet opening of the device for recirculation being connected to the inlet of the fuel cell.

[0035] Thanks to such a system, the fuel cell can be supplied with the gas composition not only from the reservoir but also from a recirculation device. Thus, hydrogen not consumed in the fuel cell is reintroduced into the fuel cell, limiting hydrogen losses and thus increasing the efficiency of the system.

[0036] In a first preferred embodiment of this aspect of the invention, the system includes a water separator that is fluidically connected to the outlet of the fuel cell and to the inlet opening of the device for recycling. The water separator allows water to be extracted from the gas composition exiting the fuel cell before it is introduced into the device for recycling. This makes it possible to avoid the introduction of excessive water into the device for recycling.

[0037] In a second preferred embodiment of this aspect of the invention, the system includes a relief valve fluidly connected to the discharge outlet of the water separator. The relief valve allows water to be removed while preventing backflow. The valve preferably includes a sensor that allows the amount of water in the water separator to be measured. When a certain water level is reached, the relief valve is opened, allowing the water to be discharged.

[0038] In another preferred embodiment of this aspect of the invention, the regulated inlet of the recirculation device is fluidically connected to the reservoir. This allows the gas contained in the reservoir to be introduced into the recirculation device and to equalize the pressure acting on the shaft seal of the device. By equalizing the pressure, premature wear of the seal can be avoided.

[0039] In a further preferred embodiment of this aspect of the invention, the discharge outlet of the device for recirculation is fluidly connected to the discharge outlet of the water separator. This allows the removal of water that tends to accumulate in the device for recirculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The characteristics and advantages of the invention will appear in more detail in the following description, which gives examples of implementation by way of illustration and in a non-limiting manner, with reference to the 17 accompanying drawings, which show:

[0041] - Figure 1 shows a first cross-sectional view of an apparatus for recycling at least part of a hydrogen-containing gas composition according to a first preferred embodiment;

[0042] - Figure 1a Shown Figure 1 Details;

[0043] - Figure 2 shows a front view of the device according to a first preferred embodiment;

[0044] - Figure 3 showing a second cross-sectional view of the device according to the first preferred embodiment;

[0045] - Figure 4 shows a third cross-sectional view of the device according to the first preferred embodiment;

[0046] - Figure 5 Shown Figure 4 Details;

[0047] - Figure 6 shows a side view of the device according to a first preferred embodiment;

[0048] - Figure 7 shows a fourth cross-sectional view of the device according to the first preferred embodiment;

[0049] - Figure 8 Shown Figure 7 Details;

[0050] - Figure 9 represents a first cross-sectional view of an apparatus for recycling at least part of a hydrogen-containing gas composition according to a second preferred embodiment;

[0051] - Figure 10 Shown Figure 9 Details;

[0052] - Figure 11 showing a second cross-sectional view of the apparatus according to a second preferred embodiment;

[0053] - Figure 12 A fuel cell system according to a first embodiment of the present invention is diagrammatically illustrated;

[0054] - Figure 13 diagrammatically illustrates a fuel cell system according to a second embodiment of the present invention;

[0055] - Figure 14 diagrammatically illustrates a fuel cell system according to a third embodiment of the present invention;

[0056] - Figure 15 diagrammatically illustrates a fuel cell system according to a fourth embodiment of the present invention; and

[0057] - Figure 16 diagrammatically illustrates a fuel cell system according to a fifth embodiment of the present invention; and

[0058] - Figure 17 A fuel cell system according to a sixth embodiment of the present invention is diagrammatically illustrated. DETAILED DESCRIPTION

[0059] Figure 1 The apparatus 1 for recycling at least part of a hydrogen-containing gas composition according to a first preferred embodiment of the present invention is shown along line AA (reference Figure 2 ). The device 1 (here in the form of a dry claw pump) consists of a plurality of subunits that are detachably connected to one another, namely, in the illustrated construction, a pumping chamber 2 with a pumping chamber cover 3 and a gear chamber 4 with a gear chamber cover 5.

[0060] The pumping chamber 2 is arranged to receive two pistons 8 and 9 with claws (cf. Figure 3), the piston is driven to rotate by a first rotating shaft 13 and a second rotating shaft 14, which are supported by bearings 15 and 16 located in the gear chamber cover 5 and the gear chamber 4, respectively. The rotating shaft 13 of the piston 8 with claws represents the input shaft, while the shaft 14 of the piston 9 with claws forms the output shaft. The rotating shaft 13 is configured to be driven by an electric motor in a manner known to those skilled in the art and will not be described in detail here.

[0061] The second rotary shaft 14 of the claw piston 9 and its necessary synchronization with the first rotary shaft 13 of the claw piston 8 are driven by a drive system comprising two toothed wheels 17 and 18 meshing between two bearings 15 and 16. To ensure optimal driving of the toothed wheel 17 against the toothed wheel 18, the gear chamber 4 contains a lubricating fluid. For use of the device 1 for recycling hydrogen-containing compositions, it is advantageous to ensure that the lubricating fluid is suitable for this application. It is particularly advantageous to provide a lubricating fluid that is non-reactive with hydrogen and compatible with the materials used in the membranes of the fuel cell.

[0062] like Figure 3 As shown, pistons 8 and 9 are pistons with claws configured to roll or wrap relative to each other so that they effectively transport and compress the gas composition entering through inlet opening 11 and exiting through outlet opening 10. Inlet opening 11 is advantageously oriented in such a way that when the device 1 is as shown Figure 1 In the orientation shown, that is to say when it rests on the base 12 , the liquid present in the pumping chamber 2 can flow out of this chamber under the effect of gravity.

[0063] As mentioned above, it is important that the recirculation device 1 is configured in such a way as to prevent water, in liquid or gaseous form, from entering the gear chamber 4 and / or from contaminating the pumping chamber 2 with lubricating fluid. Indeed, some water could react with the lubricating fluid present in the gear chamber 4 and / or prevent optimal actuation of the toothed wheels 17 and 18 and / or the bearings 15 and 16, which could, in the long term, lead to malfunctions of the device 1. Furthermore, contamination of the pumping chamber 2 with some lubricating fluid could lead to a decrease in the performance of the fuel cell to which the device 1 is connected.

[0064] In order to separate the pumping chamber from the gear chamber of the claw pump, it is known in the prior art to use a rubber shaft seal positioned between the pumping chamber and the gear chamber. This generally prevents water contained in part of the gas composition supplied to the fuel cell from entering the gear chamber and prevents the lubricating fluid from contaminating the pumping chamber.

[0065] In a preferred embodiment, the shaft seal, which is generally positioned around the rotating shaft driving the piston with the claws, is of the lip type, so that the sealing lip contacts the rotating shaft and the elastic action of the lip achieves an optimal sealing. The shaft seal can be of different nature, mechanical seal type, labyrinth type or other.

[0066] As previously mentioned, the present invention aims to provide a device 1 for recycling hydrogen that can be used in the fuel cell sector, more specifically in the field of fuel cells for motor vehicles. In this application, the pressure of the composition containing hydrogen to be recycled can vary greatly, which means that the pressure exerted on the lip of the shaft seal can also vary greatly. Under high pressure, high frictional forces arise between the seal lip and the rotating shaft around which it rotates, which can lead to rapid wear of the lip. A worn lip no longer allows the necessary sealing to be achieved, and some gaseous or liquid water can enter the gear chamber, or some lubricating fluid can contaminate the pumping chamber.

[0067] To address this issue, as shown in various figures, the device 1 includes a first pair of seals 19, comprising a first shaft seal 19a and a second shaft seal 19b, positioned around the first rotating shaft 13, and a second pair of seals 20, comprising a first shaft seal 20a and a second shaft seal 20b, positioned around the second rotating shaft 14. As mentioned above, a shaft seal is a seal for the shaft. This means that the greater the pressure differential between the two sides of the seal, the tighter the lip presses against the rotating shaft around which the seal is positioned. This means that as the pressure differential increases, the friction between the seal lip and the shaft also increases. This increase can lead to premature wear and, potentially, rupture of the seal.

[0068] In order to prevent premature wear of the seals of the seal pair 19 and 20, the device 1 includes a pressure balancing system so that the pressure on both sides of the shaft seal can be balanced. Figure 4 and Figure 5 As shown, the device 1 includes a pressure balancing chamber 25, which is in fluid connection with the gap 24 existing between the first and second shaft seals of the seal pairs 19 and 20. The pressure in the pressure balancing chamber 25 can be adjusted by introducing gas from outside the device via a regulating inlet 29. This thus makes it possible to control the pressure in the pressure balancing chamber 25 and in the gap 22, thereby balancing the pressures acting on both sides of the shaft seals.

[0069] As can be seen from these figures, the pumping chamber 2 is also fluidically connected to a pulsation damping chamber 22 via an orifice 21. The pulsation damping chamber 22 itself is fluidically connected to the first shaft seal 19a of the seal pair 19 and the first shaft seal 20a of the seal pair 20. Thanks to the pulsation damping chamber 22, pressure pulsations generated during the pumping cycle of the pumping chamber 2 can be damped or even balanced, thereby ensuring that the pressure acting on the lips of the first shaft seals 19a and 20a remains essentially constant during the use of the device 1. This is important for ensuring optimal sealing. The fluid connection between the pulsation damping chamber 22 and the pumping chamber 2 advantageously takes the form of a labyrinth 23 with low gas flow, which makes it possible to effectively dampen or even balance the pressure pulsations.

[0070] Due to the fluid connection between the pulsation damping chamber 22 and the pumping chamber 2, water can accumulate in the pulsation damping chamber 22. In this case, it is advantageous to provide a discharge outlet 26 through which the water can be discharged (see also the discharge outlet 26). Figure 6 ). In addition, the water itself can be re-sucked by the circulation of the pumping chamber 2 through the connection hole 21. In addition, by regulating the inlet 29, a gas (for example air, nitrogen, helium, hydrogen, neon, argon, krypton, xenon or a mixture of these gases) can be introduced into the pressure equalization chamber 25 and thus into the gap 24, which makes it possible to easily equalize the pressure acting on the shaft seal.

[0071] In order to prevent premature wear of the seals 19a and 20a as well as the seals 19b and 20b, the second rotary shaft 14 comprises a pressure equalization channel 27 which connects the gap 24 to the gear chamber 4 (see Figure 7 and Figure 8 ). Thus, the pressure acting on both sides of the shaft seals 19b and 20b is balanced, which reduces the friction between the rotating shaft and these seals. To prevent the lubricating liquid from flowing back into the gap 24 through the channel 27, the second rotating shaft 14 includes a filter 28 at its end in the gear chamber, which allows the diffusion of gas but not liquid.

[0072] Figure 9 and Figure 10 The apparatus 30 for recycling at least part of the hydrogen-containing gas composition according to the second preferred embodiment of the present invention is shown along line AA (reference Figure 2 ). Here, we will omit the description of the elements of the device 30 that are similar to those of the device 1. In addition, in the drawings illustrating the two embodiments, similar elements are marked with the same reference numerals.

[0073] In device 30, pulsation damping chamber 22 is fluidically connected to pressure balancing chamber 25, and thus to gap 24. This enables automatic pressure balancing in pumping chamber 2, gap 24, and gear chamber 4. In this embodiment, there is no need to actively regulate the pressure in pressure balancing chamber 25. Due to the fluid connection between pumping chamber 2 and gap 24 via pulsation damping chamber 22, the pressures on both sides of shaft seals 19a and 20a of shaft seal pair 19 and 20 are automatically balanced.

[0074] Advantageously, the fluid connection between the pulsation damping chamber 22 and the pressure equalization chamber 25 is realized by a semipermeable membrane 31, through which gaseous hydrogen can diffuse, but which retains water in liquid or gaseous form and the lubricating fluid. In a manner similar to the device 1, the fluid connection between the pulsation damping chamber 22 and the pumping chamber 2 has at least partially the shape of a labyrinth 23, which makes it possible to effectively dampen and even equalize the pressure pulsations coming from the pumping chamber 2. In addition, Figure 10 30, the fluid connection between the pulsation damping chamber 22 and the gap 24 (and therefore the pressure balance chamber 25) is advantageously achieved by means of a first pair of calibrated holes 32, a second pair of calibrated holes 33 and a third pair of calibrated holes 34. The size of the calibrated holes 33 makes it possible to control the flow rate of the gas composition along the membrane 31. In a manner similar to that of the device 1, the discharge outlet 26 allows the drainage of water that tends to accumulate in the pulsation damping chamber 22. In the device 30, the discharge outlet 26 is configured to drain water that is pushed back through the calibrated holes 32 under the action of centrifugal forces. Finally, in this embodiment, a regulation inlet 29 is also provided for regulating the pressure of the pressure balance chamber 25 from outside the device.

[0075] The presence of the membrane 31 makes it possible to further reduce the risk of diffusion of water molecules in the gear chamber 4 and of the lubricating liquid in the pumping chamber 2. It is worth noting that, in a manner similar to that of the device 1, the pressure on both sides of the shaft seals of the seal pairs 19 and 20 is balanced, which makes it possible to limit their wear. In addition, as Figure 9 As shown, the second rotary shaft 14 of the device 30 also comprises, at one end thereof, a filter 28 which prevents the lubricating fluid present in the gear chamber from flowing back through the channel 27 .

[0076] Figure 12A fuel cell system 40 according to a first embodiment of the present invention is shown. The system 40 includes a hydrogen storage 41, a pressure regulator 42, a fuel cell 43 having an anode 43a, a membrane 43b, and a cathode 43c. The system 40 also includes a device 1 for recycling at least a portion of a hydrogen-containing gas composition according to a first embodiment of this aspect of the present invention. The outlet port 10 of the device 1 is connected to a pipe 44 that supplies gaseous hydrogen to the fuel cell 43, which allows unconsumed hydrogen to be reintroduced into the fuel cell. The outlet 43e of the fuel cell 43 is connected to a water separator 45 that allows most of the water contained in the gas composition leaving the fuel cell to be removed. This water is discharged through the discharge outlet 45a of the water separator 45 and through the overflow valve 46. Due to the action of the water separator 45, the gas composition from which most of the water has been removed is introduced into the device 1 through the inlet port 11 of the device 1. Therefore, the device 1 can compress the gas composition to the necessary pressure and reintroduce it into the pipe 44. In this embodiment, the regulated inlet 29 of the device 1 is connected to the duct 44 and therefore to the reservoir 41, which allows the pressure acting on both sides of the shaft seal (not shown here) of the device 1 to be equalized. Figure 12 As shown, the discharge outlet 26 is not used in this embodiment and is preferably closed.

[0077] Figure 13 A fuel cell system 50 according to a second embodiment of the present invention is shown. Figure 12 4 is comparable to the system 40 shown in FIG, except that in this embodiment the drain outlet 26 is connected to the outlet of the water separator 45. This allows the water that is intended to form in the device 1 to be drained away.

[0078] Figure 14 A fuel cell system 60 according to a third embodiment of the present invention is shown. This system 60 is similar to Figure 12 . The difference is that the system 60 includes a device 30 for recycling at least part of the hydrogen-containing gas composition according to a second embodiment of this aspect of the invention. As mentioned above, this embodiment of the recycling device provides a system for automatically balancing the pressure on both sides of the shaft seal (not shown here) acting on the device 30. Due to this automatic balancing system, it is not necessary to introduce gas through the regulating inlet 29 in order to balance the pressure acting on the shaft seal. Therefore, in Figure 14 In the embodiment of FIG. 4 , the regulating inlet 29 is not connected to the conduit 44. It should be noted that in this embodiment, a connection can also be provided between the regulating inlet 29 and the conduit 44 to allow gas to be introduced into the device 30 when necessary. This may be necessary, for example, if the automatic balancing device is not functioning as desired.

[0079] Figure 15 A fuel cell system 70 according to a fourth embodiment of the present invention is shown. Figure 14 60 in the embodiment, except that in this embodiment the drain outlet 26 is connected to the outlet of the water separator 45. This allows the water that is intended to form in the device 30 to be removed.

[0080] Figure 16 and Figure 17 The fuel cell systems 80 and 90 according to the fifth and sixth embodiments of the present invention are shown. In these embodiments, the exhaust outlet 26 is fluidically connected to the inlet openings 11 of the recirculation device 1 and 11 of the recirculation device 30, respectively. This makes it possible to remove water that may form inside the recirculation device and reintroduce it into the fuel cell 43 via the recirculation devices 1, 30 and the conduit 44.

[0081] Obviously, the present invention is susceptible to numerous variations. Although non-limiting embodiments have been described by way of example, it is understood that it is not possible to identify all possible variations in an exhaustive manner. Of course, equivalent devices can be substituted for the devices described without departing from the scope of the present invention. All such modifications form part of the common knowledge of those skilled in the art of pumps and circulators.

Claims

1. A device (1, 30) for recycling at least part of a hydrogen-containing gas composition, characterized in that The device (1, 30) is a dry rotary pump comprising a first rotary shaft (13) and a second rotary shaft (14), wherein the first rotary shaft (13) and the second rotary shaft (14) respectively drive a first piston (8) with a claw and a second piston (9) with a claw to rotate in a pumping chamber (2), wherein the pumping chamber (2) comprises an inlet hole (11) and an outlet hole (10) for a gas composition, and the first rotary shaft (13) and the second rotary shaft (14) are configured to be driven in rotation by a drive system (17, 18) located in a gear chamber (4); The device (1, 30) comprises a first pair of shaft seals (19) and a second pair of shaft seals (20), each pair of seals comprising a first shaft seal (19a, 20a) and a second shaft seal (19b, 20b), the first pair of shaft seals (19) being arranged around a first rotating shaft (13) and the second pair of shaft seals (20) being arranged around a second rotating shaft (14) between a pumping chamber (2) and a gear chamber (4); The device (1, 30) includes a pressure balance chamber (25) fluidly connected to a gap (24) between a first shaft seal (19a, 20a) and a second shaft seal (19b, 20b) of a first pair of shaft seals (19) and a second pair of shaft seals (20) to regulate the pressure in the gap (24); The gear chamber (4) is fluidically connected to the gap (24), wherein the fluid connection between the gap (24) and the gear chamber (4) is performed via a pressure equalization channel (27) provided in the first rotating shaft (13) and / or the second rotating shaft (14); and The pumping chamber (2) is fluidly connected to a first shaft seal (19a) of the first pair of shaft seals (19) and a first shaft seal (20a) of the second pair of shaft seals (20) via a pulsation damping chamber (22).

2. The device (1, 30) according to claim 1, wherein among the first shaft seal (19a) of the first pair of shaft seals (19), the second shaft seal (19b) of the first pair of shaft seals (19), the first shaft seal (20a) of the second pair of shaft seals (20), and the second shaft seal (20b) of the second pair of shaft seals (20), at least one shaft seal is a lip seal.

3. The device (1, 30) according to claim 1, comprising a lubricating fluid filter (28) between the pressure equalization channel (27) and the gear chamber (4).

4. The device (1, 30) according to any one of claims 1 to 3, wherein a regulating inlet (29) is provided in order to control the pressure in the pressure balance chamber (25) from outside the device.

5. The device (30) according to any one of claims 1 to 3, wherein the pulsation damping chamber (22) is fluidically connected to the pressure equalization chamber via a membrane (31) which is permeable to gaseous hydrogen but at least impermeable to water molecules in liquid and gaseous form.

6. The device (1, 30) according to any one of claims 1 to 3, wherein the fluid connection between the pulsation damping chamber (22) and the pumping chamber (2) at least partially has the form of a labyrinth.

7. The device (1, 30) according to any one of claims 1 to 3, wherein the pulsation damping chamber (22) is fluidically connected to the discharge outlet (26).

8. The device (1, 30) according to any one of claims 1 to 3, wherein the inlet opening (11) of the pumping chamber (2) is oriented in a manner allowing the liquid to be drained away under the effect of gravity.

9. The device (1, 30) according to any one of claims 1 to 3, wherein the gear chamber (4) and / or the pumping chamber (2) is provided as a hydrogen-resistant material or is covered with a hydrogen-resistant material.

10. The device (1, 30) according to any one of claims 1 to 3, wherein the device is configured to allow a maximum external leakage of hydrogen of 10 Ncm 3 / h.

11. The device (1, 30) according to any one of claims 1 to 3, being configured to be drivable within a control range of up to 12,000 rpm.

12. The apparatus (1, 30) according to any one of claims 1 to 3, configured to operate within an ambient temperature range and to input at least part of the gas composition between -40°C and 100°C.

13. The device (1, 30) according to any one of claims 1 to 3, configured to be capable of operating at a nominal voltage of 12 to 800 VCC.

14. The device (1, 30) of claim 13, being configured to operate at a nominal voltage of 24 VCC, 48 VCC, 200 VCC, 400 VCC or 750 VCC.

15. The device (1, 30) according to any one of claims 1 to 3, configured to increase the pressure of at least part of the hydrogen-containing gas composition at the inlet of the fuel cell to a pressure in the range of up to 15 bar.

16. The device (1, 30) according to any one of claims 1 to 3, configured to increase the pressure of at least part of the hydrogen-containing gas composition to a pressure in the range of 1.5 to 5 bar absolute at the inlet of the fuel cell.

17. A fuel cell system (40, 50, 60, 70), comprising a reservoir (41) of a gas composition at least partially containing hydrogen, the reservoir (41) being connected to an inlet (43d) of a fuel cell (43), characterized in that The system comprises a device for recycling (1, 30) according to any one of claims 1 to 16, the outlet (43e) of the fuel cell (43) being connected to the inlet hole (11) of the device for recycling (1, 30), and the outlet hole (10) of the device for recycling (1, 30) being connected to the inlet (43d) of the fuel cell (43).

18. The fuel cell system (40, 50, 60, 70, 80, 90) according to claim 17, comprising a water separator (45) which is fluidically connected to the outlet of the fuel cell (43) and to the inlet opening of the device (1, 30) for recirculation.

19. The fuel cell system (40, 50, 60, 70, 80, 90) according to claim 18, comprising a relief valve (46) fluidically connected to the discharge outlet (45a) of the water separator (45).

20. The fuel cell system (40, 50, 60, 70, 80, 90) according to any one of claims 17 to 19, wherein a regulating inlet (29) of the device (1, 30) for recirculation is in fluid connection with the reservoir (41).

21. The fuel cell system (40, 50, 60, 70, 80, 90) according to claim 18 or 19, wherein the outlet outlet (26) of the device (1, 30) for recirculation is fluidically connected to the outlet outlet (45a) of the water separator (45).

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