Electrochemical system and method of controlling such a system

Abstract

Electrochemical system and method of controlling such a system The present invention relates to an electrochemical system (10), comprising a fuel cell (20), the system (10) further comprising a cell anode recirculation circuit (30), and an anode purge circuit (40) comprising an electrochemical filter (35), comprising a filter cathode inlet (36), a filter cathode outlet (37) and a filter anode outlet (38), the electrochemical filter being adapted to deliver filtered hydrogen to the filter anode outlet (38).The system comprises a filter recirculation circuit (50), comprising a filter recirculation valve (51) configured to assume an open configuration, in which the recirculation valve connects the filter anode outlet to the filter cathode outlet and to assume a closed configuration, in which the filter recirculation valve separates the filter anode outlet from the filter cathode outlet. Figure for abstract: Figure 1.

Description

Title of the invention: Electrochemical system and method of controlling such a system

[0001] The present invention relates to an electrochemical system and a method of controlling such a system.

[0002] During operation of a fuel cell, not all of the supplied reactive gas, in particular hydrogen, is consumed. It is known to fluidically connect the fuel cell to a recirculation circuit in order to recycle the hydrogen leaving the fuel cell and circulate it again in the fuel cell.

[0003] WO2008019300A2 discloses a hydrogen pump with an exchange membrane protons, or electrochemical filter, for filtering a gas mixture containing hydrogen. WO2008049448A1 and US2007128478A1 each disclose a fuel cell supply system for filtering the hydrogen leaving the fuel cell, using a filter, before circulating it back into the cell.

[0004] These systems are however difficult to supply with electricity without risking rapid damage, particularly when the hydrogen supply is intermittent. Indeed, hydrogen pumps must be electrically supplied to operate, but risk being damaged if they are supplied with electricity in the presence of an insufficient quantity of hydrogen. Controlling the electrical supply according to the quantity of hydrogen requires knowing precisely the quantity of hydrogen circulating in the proton exchange membrane hydrogen pump, making control difficult and expensive.

[0005] The aim of the invention is then to propose an electrochemical system which is easy to use and which is less subject to deterioration.

[0006] For this purpose, the subject of the invention is an electrochemical system for generating electricity, the system comprising a fuel cell comprising a cell anode inlet, a cell cathode inlet, a cell anode outlet and a cell cathode outlet, gas containing hydrogen flowing from the cell anode inlet to the cell anode outlet, the system further comprising a cell anode recirculation circuit, connecting the cell anode outlet to the cell anode inlet and an anode purge circuit which is connected to the cell anode outlet, and which comprises a purge valve, the anode purge circuit comprising: - an electrochemical filter, of the proton exchange membrane hydrogen pump type, adapted to be electrically powered, the electrochemical filter comprising a filter cathode inlet, a filter cathode outlet filter and a filter anode outlet, the electrochemical filter being adapted to deliver filtered hydrogen to the filter anode outlet; - a first fluidic control device; and - a second fluidic control device;

[0007] in which: - the purge valve is configured to take an open configuration in which it connects the battery anode output and the filter cathode inlet; - the purge valve is configured to assume a closed configuration, in which it separates the filter anode outlet and the filter cathode inlet - the first fluidic control device is configured to take an open configuration, in which it connects the filter cathode output to the stack cathode output; - the first fluidic control device is configured to take a closed configuration, in which it separates the filter cathode output from the stack cathode output; - the second fluidic control device is configured to assume an open configuration, in which it connects the filter anode outlet to the cell anode inlet, the filtered hydrogen thus being delivered to the cell anode outlet; and - the second fluidic control device is configured to take a closed configuration, in which it separates the filter anode output from the cell anode inlet.

[0008] According to the invention, the system comprises a filter recirculation circuit, the filter recirculation circuit comprising a filter recirculation valve configured to assume an open configuration, in which the recirculation valve connects the filter anode outlet to the filter cathode inlet or to the filter cathode outlet and to assume a closed configuration, in which the filter recirculation valve separates the filter anode outlet from the filter cathode inlet or from the filter cathode outlet.

[0009] One idea underlying the invention is to provide the filter recirculation circuit between the anode outlet of the electrochemical filter and the cathode of the same electrochemical filter. In this case, the electrochemical filter is continuously supplied with hydrogen. Indeed, when the purge valve is open, the cathode of the electrochemical filter is supplied with gas containing hydrogen from the anode outlet of the fuel cell. When the filter recirculation valve is open, the filter remains supplied with hydrogen by the cell anode recirculation circuit, even when the purge valve is closed. Thus, there is no risk that the electrochemical filter chemical is damaged due to an insufficient amount of hydrogen at its cathode. It is therefore not necessary to stop the power supply to the filter when the purge valve is closed, which simplifies the use of the electrochemical system.

[0010] According to other advantageous aspects of the invention, the system comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0011] - the electrochemical filter is supplied electrically uninterruptedly with a constant voltage as long as a voltage across an electrochemical cell included in the electrochemical filter is less than or equal to a predetermined voltage threshold;

[0012] - the cell recirculation circuit further comprises a recirculation pump, and wherein the anode purge circuit is connected to the cell anode outlet by being connected to the cell recirculation circuit upstream of the recirculation pump;

[0013] - the first fluid control device is a first valve;

[0014] - the second fluid control device is a second valve;

[0015] - the filter recirculation valve is configured to take a configuration open, in which it connects the filter anode output to the filter cathode output and to assume a closed configuration, in which it separates the filter anode output from the filter cathode output; and

[0016] - the filter recirculation valve is configured to take a configuration open, in which it connects the filter anode output to the filter cathode input and to take a closed configuration, in which it separates the filter anode output from the filter cathode input.

[0017] The invention also relates to a method for controlling the system comprising at least the following steps: - opening then closing the purge valve; - measurement of pressure at the anode outlet of the filter; - measurement of pressure at the cathode outlet of the filter; - closing the second fluid control device and opening the filter recirculation valve when the pressure measured at the filter anode outlet is less than or equal to an anode pressure threshold; - opening of the second fluid control device and closing of the filter recirculation valve when the pressure measured at the anode outlet of the filter is strictly greater than the anode pressure threshold; - closing the first fluid control device when the pressure measured at the filter cathode outlet or a pressure measured at the filter cathode inlet is less than or equal to a cathode pressure threshold; and

[0018] opening of the first fluid control device when the pressure measured at the filter cathode output is strictly greater than the cathode pressure threshold.

[0019] According to other advantageous aspects of the invention, the method comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0020] - a step of stopping the power supply to the electrochemical filter if the voltage across an electrochemical cell included in the electrochemical filter is greater than a predetermined voltage threshold; and

[0021] - a step of stopping the power supply to the electrochemical filter if the voltage at the terminals of an electrochemical cell included in the electrochemical filter is greater than a predetermined voltage threshold and if the pressure measured at the cathode output of the filter is less than a safety pressure threshold, or if a pressure measured at the cathode input of the filter is less than the safety pressure threshold.

[0022] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0023] [Fig-1] [Fig.l] is a diagram of an electrochemical system according to a first mode of carrying out the invention;

[0024] [Fig.2] [Fig.2] is a block diagram of a method of controlling the system electrochemical of [Fig.l]; and

[0025] [Fig.3] [Fig.3] is a diagram of an electrochemical system according to a second embodiment of the invention.

[0026] [Fig.4] [Fig.4] is a diagram of an electrochemical system according to a third embodiment of the invention.

[0027] [Fig.l] represents a diagram of an electrochemical system 10. The electrochemical system 10 may be integrated into a vehicle, for example in order to provide electricity used to propel the vehicle. The electrochemical system 10 comprises a fuel cell 20 also called cell 20, a cell anode recirculation circuit 30, an anode purge circuit 40 and a filter recirculation circuit 50.

[0028] The fuel cell 20 generally comprises a stack of electrochemical cells, not shown. The fuel cell 20 also comprises a cell anode inlet 21, a cell anode outlet 22, a cell cathode inlet 23 and a cell cathode outlet 24. The cell anode inlet 21 is advantageously connected to a gas reservoir containing hydrogen, not shown. The cell cathode outlet 24 advantageously communicates with the outside of the system 10.

[0029] Gases circulate in the electrochemical system 10, more particularly in the fuel cell 20 and in the cell anode recirculation circuit 30.

[0030] When the system 10 is in operation, hydrogen enters the fuel cell 20 through the cell anode inlet 21 and air enters the fuel cell 20. fuel 20 through the cell cathode inlet 23. At the cell cathode outlet 24, oxygen-depleted air is present, mixed in particular with water in vapor form or in partially liquid form, and a cell anode outlet gas, essentially containing hydrogen and nitrogen, is present at the cell anode outlet, which then circulates in the cell anode recirculation circuit 30.

[0031] The cell anode recirculation circuit 30 connects the cell anode outlet 22 to the cell anode inlet 21. In a known manner, the cell anode recirculation circuit 30 has the main function of avoiding the discharge, to the outside, of hydrogen not consumed by the cell 20, by recirculating, to the cell anode inlet 21, the hydrogen not consumed by the cell 20 and which is therefore discharged at the cell anode outlet 22.In a known manner, the anode recirculation circuit 30 comprises a recirculation pump 44 which can be produced in the form of a motorized pump arranged in the cell anode recirculation circuit 30 or in the form of a venturi ejector generally arranged at the junction of the cell anode recirculation circuit 30 with a supply pipe of the cell anode inlet 22, a flow of fresh hydrogen circulating in this pipe causing the suction of gases into the cell anode recirculation circuit 30.

[0032] The anode purge circuit 40 is connected to the cell anode outlet 22, generally via the cell anode recirculation circuit 30, and comprises a purge valve 4L. Preferably, the anode purge circuit 40 is connected to the cell anode recirculation circuit 30 upstream of the recirculation pump 44. The anode purge circuit 40 makes it possible, when the purge valve 41 is open, to evacuate, from the cell anode recirculation circuit 30, undesirable anode effluents which appear at the anode of the cell 20, in particular nitrogen and water. Indeed, due to the anode recirculation by the cell anode recirculation circuit 30, the quantity of these undesirable anode effluents, other than hydrogen, tends to increase as the recirculation cycles progress.However, it is known that, when the purge valve 41 is opened to evacuate the elements which circulate in the cell anode recirculation circuit 30, not only the undesirable anode effluents such as water or nitrogen are evacuated, but also hydrogen which, in the general case, is then lost.

[0033] Preferably, the anode purge circuit 40 does not open directly outside the system 10 but is preferably connected to the cathode outlet of the cell 24 so that the undesirable anode effluents discharged by the anode purge circuit 40 are mixed with the cathode effluents from the cell 20, in particular in order to dilute these anode effluents before their discharge outside the system 10.

[0034] To limit the release, to the outside, of the hydrogen which is evacuated by the anode purge circuit 40, the anode purge circuit 40 comprises, within the framework of the invention, an electrochemical filter 35 of the hydrogen pump type with proton exchange membrane, downstream of the purge valve 41 in the anode purge circuit 40.

[0035] It will also be detailed that the anode purge circuit 40 advantageously comprises a first fluidic control device 42, between the cathodic output 37 of the electrochemical filter 35 and the cathodic output 24 of the cell 20, and / or a second fluidic control device 43, between the anode output 38 of the electrochemical filter 35 and the anode inlet 21 of the cell 20.

[0036] The electrochemical filter 35 comprises at least one electrochemical cell of the hydrogen pump type with a proton exchange membrane, and is advantageously a stack of at least two electrochemical cells of the hydrogen pump type with a proton exchange membrane which are arranged fluidically in parallel with each other but electrically in series. The electrochemical filter 35 comprises a cathode 35A, an anode 35B, a filter cathode inlet 36, connected to the cathode 35A, a filter cathode outlet 37, connected to the cathode 35A, and a filter anode outlet 38, connected to the anode 35B.

[0037] The electrochemical filter 35 is electrically connected to a power supply, not shown. The power supply is preferably a direct current power supply adapted to deliver a constant voltage to the electrochemical filter 35. The power supply powers the electrochemical filter 35 as long as a voltage across an electrochemical cell included in the electrochemical filter 35 is less than or equal to a predetermined voltage threshold.

[0038] According to a particularly advantageous aspect of the invention, the electrochemical filter 35 is equipped with a filter recirculation circuit 50 making it possible to return, to the cathode 35A of the electrochemical filter 35, the hydrogen which is transferred from the cathode to the anode 35B of the electrochemical filter 35 when the latter is electrically powered.

[0039] The purge valve 41 is configured to take an open configuration and a closed configuration. In the open configuration, the purge valve 41 fluidly connects the cell anode outlet 22, here via the anode purge circuit 40, to the filter cathode inlet 36. In the closed configuration, the purge valve 41 fluidly separates the cell anode outlet 22 from the filter cathode inlet 36. Conventionally, the purging of the cell anode recirculation circuit 30 is carried out discontinuously, so that the passage of the purge valve 41 from the closed configuration to the open configuration and then from the open configuration to the closed configuration advantageously takes place regularly. For example, the purge valve 41 passes from the closed configuration to the open configuration, remains in the open configuration for a duration ranging from 0.1 to 1 second, for example example of the order of 0.5 seconds, then changes from the open configuration to the closed configuration and remains in the closed configuration for 10 seconds. Alternatively, the purge valve remains in the closed configuration for 5 seconds, or 15 seconds, for example.

[0040] The first fluidic control device 42 is preferably a valve, as shown in [Fig. 1]. Alternatively not shown, the first fluidic control device may be another device, such as for example a non-return valve. The first fluidic control device 42 is configured to take an open configuration and a closed configuration. In the open configuration, the first fluidic control device 42 fluidly connects the filter cathode outlet 37 and the filter cathode outlet 24. In the closed configuration, the first fluidic control device 42 fluidly separates the filter cathode outlet 37 from the battery cathode outlet 24.The first fluidic control device 42 passes from the closed configuration to the open configuration when a pressure P37 of a gas at the cathode outlet of filter 37 is strictly greater than a first pressure threshold PI, called the cathode pressure threshold, and from the open configuration to the closed configuration when the pressure P37 of the gas at the cathode outlet of filter 37 is less than or equal to the first pressure threshold PL. This pressure threshold PI is preferably a relative pressure threshold with respect to the relative pressure at the cathode outlet of cell 24, for example of the order of a few millibars. In the case where the first fluidic control device 42 is produced in the form of a non-return valve, the latter is arranged to allow the circulation of fluid in a single direction: from the cathode outlet of filter 37 to the cathode outlet of cell 24.

[0041] The pressure P37 of the gas at the cathode outlet of filter 37 is, for example, measured by a pressure sensor 137.

[0042] As a non-limiting example, the value of the pressure threshold PI can be chosen between 1 and 3 bars absolute.

[0043] The second fluidic control device 43 is preferably a valve. Alternatively not shown, the second fluidic control device may be another device, such as for example a non-return valve. The second fluidic control device 43 is configured to take an open configuration and a closed configuration. In the open configuration, the first fluidic control device 43 fluidly connects the filter anode outlet 38 and the battery anode inlet 21 and, in the closed configuration, it fluidly separates the filter anode outlet 38 and the battery anode inlet 21. The second fluidic control device 43 switches from the closed configuration to the open configuration when a pressure P38 of a gas at the filter anode outlet 38 is strictly greater than a second pressure threshold P2, called the anode pressure threshold, and from the open configuration to the confi closed when the pressure P38 of the gas at the filter anode outlet 38 is less than or equal to the second pressure threshold P2. This pressure threshold P2 is preferably a relative pressure threshold with respect to the relative pressure at the cell anode inlet 21, for example of the order of a few millibars. In the case where the second fluid control device 43 is produced in the form of a non-return valve, the latter is arranged to allow the circulation of fluid in only one direction: from the filter anode outlet 38 to the cell anode inlet 37.

[0044] The pressure P38 of the gas at the anode outlet of filter 38 is for example measured by a pressure sensor 138.

[0045] The second pressure threshold P2 is for example chosen to be between a gas pressure at the anode outlet of cell 22 and a gas pressure at the anode inlet of cell 21.

[0046] By way of non-limiting example, the value of the pressure threshold P2 can be chosen between 1 and 3 bars absolute.

[0047] Generally, the filter anode outlet 38 is connected directly or indirectly to the cell anode inlet 21 so that the filtered hydrogen, which appears at the anode 35A of the electrochemical filter 35 when the latter is electrically powered, is recycled to the cell 20, thus avoiding releasing this hydrogen into the atmosphere. In the example illustrated in [Fig.l], the filter anode outlet 38 is connected indirectly to the cell anode inlet 21 because it is connected to the cell anode recirculation circuit 30, here upstream of the recirculation pump 44. In other words, in the example of [Fig.l], the recirculation pump 44 connects the second fluid control device 43, in addition to the cell anode outlet 22, to the cell anode inlet 21.The recirculation pump 44 advantageously serves to increase the pressure of the gases coming from the second fluidic control device 43 and from the cell anode outlet 22, such that this pressure is greater than or equal to the pressure of the gas at the cell anode inlet 21. This makes it possible in particular to avoid gas circulation in an undesired direction, for example from the cell anode inlet 21 to the cell anode outlet 22. Optionally, the recirculation pump 44 can be replaced by an ejector.

[0048] The filter recirculation circuit 50 fluidly connects the filter anode outlet 38 to the cathode 35A of the electrochemical filter 35. In the example of [Fig.l], the filter recirculation circuit 50 fluidly connects the filter anode outlet 38 to the cathode outlet 37 of the electrochemical filter 35. The filter recirculation circuit 50 comprises a filter recirculation valve 51 for interrupting or allowing the circulation of fluid in the filter recirculation circuit 50. The filter recirculation valve 51 is configured to assume an open configuration and to assume a closed configuration. In the open configuration, the recirculation valve of filter 51 fluidly connects the filter anode outlet 38 to the cathode 35A of the electrochemical filter 35, in this case to the filter cathode outlet 37. In the closed configuration, the filter recirculation valve 51 fluidly separates the filter anode outlet 38 from the cathode 35A of the electrochemical filter, in this case from the filter cathode outlet 37. The filter recirculation valve 51 switches from the closed configuration to the open configuration when the pressure P38 of the gas at the filter anode outlet 38 is less than or equal to the second pressure threshold P2. It switches from the open configuration to the closed configuration when the pressure P38 of the gas at the filter anode outlet 38 is strictly greater than the second pressure threshold P2.Preferably, to avoid a reversal of the direction of the fluids between the filter cathode outlet 37 and the cell anode outlet 22, the filter recirculation valve 51 is also closed when the valve 41 is open and / or a non-return valve can be provided between the purge valve 41 and the filter cathode inlet 36 which prevents the circulation of fluids from the filter cathode inlet 36 to the cell anode outlet 22. In both cases, this will prevent the reinjection of filtered hydrogen to the cell anode via the cell anode outlet 22, and this will force the filtered hydrogen to accumulate on the anode side 35B, which will promote the increase in its pressure and assist its reinjection towards the cell anode inlet 21.

[0049] A method of operation of the system 10 will now be explained, in connection with [Fig. 2]. As mentioned previously, hydrogen enters the fuel cell 20 through the cell anode inlet 21 and air enters the fuel cell 20 through the cell cathode inlet 23. A portion of the hydrogen and a portion of the oxygen in the air react as they pass through the fuel cell 20, thereby generating electricity. Furthermore, gas diffusion phenomena take place in the cell, resulting in particular in a mixing of nitrogen, initially present in the air, in the hydrogen circulating at the anode of the fuel cell 20. At the cathode outlet of the cell 24, oxygen-depleted air is present, mixed in particular with water in the form of vapor or in partially liquid form, and the anode outlet gas of the cell, essentially containing hydrogen and nitrogen, is present at the anode outlet of the cell.

[0050] As long as the purge valve 41 is in the closed configuration, the cell anode outlet gas flows directly from the cell anode outlet 22 to the recirculation pump 44 and is reinjected at the cell anode inlet 21.

[0051] During a step S201, the purge valve 41 switches to the open configuration, the cell anode outlet gas can then flow from the cell anode outlet 22 to the filter cathode inlet 36. As mentioned previously, the purge valve 41 remains in the open configuration for a determined duration, for example 0.5 seconds, before switching to the closed configuration.

[0052] The battery anode outlet gas enters the cathode 35A through the filter cathode inlet 36. The electrochemical filter 35 is electrically powered by a constant supply voltage, delivered by the power supply. The voltage delivered to the electrochemical filter 35 by the power supply is preferably determined as a function of the theoretical performance of the electrochemical system 10, in particular the quantity of hydrogen present in the battery anode outlet gas that the electrochemical filter 35 is theoretically caused to filter. More precisely, a theoretical current is calculated, linked to the pressure of the battery anode outlet gas, the quantity of hydrogen present in this gas and operating parameters of the electrochemical filter 35 such as for example the volume, the temperature, the number of electrochemical cells making up the electrochemical filter 35, etc. according to Faraday's law.The voltage delivered to the electrochemical filter 35 is then deduced from the calculation of the theoretical current.

[0053] The electrochemical filter 35 filters the cell anode outlet gas, by dissociating the hydrogen present in the cell anode outlet gas at the cathode 35A to form protons, which are then recombined at the anode 35B to form new hydrogen molecules, more precisely dihydrogen. The other components of the cell anode outlet gas, in particular nitrogen, remain on the cathode 35A side of the electrochemical filter and form the undesirable anode effluents. High purity filtered hydrogen is therefore formed at the anode 35B. As the filtration takes place, the pressure P38 at the filter anode outlet 38 increases.

[0054] A step S202 of the method of [Fig. 2] consists of measuring the pressure P38 in the filter anode outlet 38 and comparing it with the second pressure threshold P2. If the pressure P38 in the filter anode outlet 38 is less than or equal to the second pressure threshold P2, a step S203 is implemented, in which the second fluidic control device 43 switches to the closed configuration. A step S204, in which the filter recirculation valve 51 switches to the open configuration, is implemented, advantageously simultaneously with step S203. The hydrogen then flows from the filter anode outlet 38 to the filter cathode outlet 37 through the recirculation circuit 50 and returns to the cathode 35A through the filter cathode outlet 37. The hydrogen is then filtered again and then flows from the filter anode outlet 38 into the cell recirculation circuit 50.

[0055] If the pressure P38 in the filter anode outlet 38 is strictly greater than the second pressure threshold P2, a step S205 is implemented, in which the second fluidic control device 43 switches to the open configuration. A step S206 in which the filter recirculation valve 51 switches to the closed configuration is implemented, advantageously simultaneously with step S205. The hydrogen then flows from the anode outlet 38 to the cell anode inlet 21, via the recirculation pump 44, and cannot flow into the filter recirculation circuit 50.

[0056] A step S210 is then implemented, in which the pressure P37 at the filter cathode outlet 37 is measured and compared to the first pressure threshold PL If the pressure P37 at the filter cathode outlet 37 is less than or equal to the first pressure threshold PI, a step S211 is implemented, in which the first fluidic control device 42 switches to the closed configuration. The undesirable anode effluents, possibly mixed with the hydrogen which has been filtered by the electrochemical filter 35 if the filter recirculation valve 51 is in the open configuration, cannot then circulate to the cell cathode outlet 24.

[0057] If the pressure P37 at the cathode outlet of filter 37 is strictly greater than the first pressure threshold PI, a step S212 is implemented, in which the first fluidic control device 42 switches to the open configuration.

[0058] When the filter recirculation valve 51 is in the open configuration, the first fluidic control device 42 is maintained in the closed configuration, and vice versa. This makes it possible to prevent the hydrogen which has been filtered by the electrochemical filter 35 from circulating to the cell cathode outlet 24. Similarly, when the first fluidic control device 42 is in the open configuration, the second fluidic control device 43 is in the closed configuration.

[0059] Optionally, if the pressure P37 measured at the filter cathode outlet 37, or alternatively, if a pressure measured at the filter cathode inlet 36 is less than or equal to a third pressure threshold, called the safety pressure threshold, a voltage across each electrochemical cell of the electrochemical filter 35 is measured. The third pressure threshold is for example associated with an absence of cell anode outlet gas at the filter cathode inlet 36 or at the filter cathode outlet 37. This absence of cell anode outlet gas may be due to a leak, or to a shutdown of the fuel cell 20. The voltage measurement makes it possible in particular to verify that the voltage across the terminals of the electrochemical cells of the electrochemical filter 35 does not exceed a certain predetermined voltage threshold, associated with a malfunction of the electrochemical filter 35.For example, if the voltage across one of the electrochemical cells of the electrochemical filter 35 exceeds the voltage threshold, the power supply to the electrochemical filter 35 is stopped. This prevents damage to the electrochemical filter 35.

[0060] Alternatively, the voltage across each electrochemical cell can be measured and the electrochemical filter 35 stopped in the event of the voltage being too high, i.e. in the event of the predetermined voltage threshold being exceeded, independently of the value of the pressure P37 measured at the cathode output of the filter 37.

[0061] By way of non-limiting example, the value of the safety pressure threshold can be chosen between 1 and 1.1 bars absolute, for example equal to 1.05 bars absolute.

[0062] By way of non-limiting example, the value of the predetermined voltage threshold can be chosen between 0.1 and 0.5 Volts, for example equal to 0.3 Volts.

[0063] When the second gas circulates in the cell recirculation circuit 50, the second gas enters the cathode 35A via the filter cathode outlet 37. This makes it possible to homogenize the gas circulation within the cathode 35A and the operation of the electrochemical filter 35 over time. Indeed, in the absence of hydrogen arriving via the filter recirculation circuit 50, the cell anode outlet gas enters the cathode 35A via the filter cathode inlet 36, which is generally distant from the filter cathode outlet 37. The electrochemical cells of the electrochemical filter 35 have an inhomogeneous operation, causing the electrochemical cells closest to the filter cathode inlet 36 to age more quickly than the cells furthest away, which are themselves closer to the filter cathode outlet 37.The circulation of hydrogen through the cathode outlet of filter 37 thus makes it possible to homogenize the aging of the electrochemical cells of the electrochemical filter 35.

[0064] The arrangement of the recirculation circuit 50 may however be different, as described below.

[0065] In the electrochemical system 100 of the second embodiment of the invention shown in [Fig. 3], elements similar to those of the first embodiment bear the same references. If a reference is given in [Fig. 3] without being mentioned in the description, or mentioned in the description without being given in [Fig. 3], it designates the same element as that bearing the same reference in the first embodiment. In the following, we mainly describe what distinguishes the second embodiment from the first.

[0066] The electrochemical system 100 differs from the electrochemical system 10 by its filter recirculation circuit 150, which replaces the filter recirculation circuit 50. The recirculation circuit 150 fluidly connects the filter anode outlet 38 no longer to the filter cathode outlet 37 of the electrochemical filter 35, but to the filter cathode inlet 36. The filter recirculation circuit 150 also comprises a filter recirculation valve 151. The filter recirculation valve 151 is configured to assume an open configuration and to assume a closed configuration. In the open configuration, the filter recirculation valve 151 connects the filter anode outlet 38 to the filter cathode inlet 36. In the closed configuration, the filter recirculation valve 151 separates the filter anode outlet 38 from the filter cathode inlet 36.The filter recirculation valve 151 changes from the closed configuration to the open configuration when the gas pressure P38 at the . filter anode outlet 38 is less than or equal to the second pressure threshold P2, and changes from the open configuration to the closed configuration when the gas pressure at the filter anode outlet 38 is strictly greater than the second pressure threshold P2, in the same way as the filter recirculation valve 51 of the electrochemical system 10.

[0067] In the electrochemical system 200 of the third embodiment of the invention shown in [Fig. 4], elements similar to those of the first embodiment bear the same references. If a reference is given in [Fig. 4] without being mentioned in the description, or mentioned in the description without being given in [Fig. 4], it designates the same element as that bearing the same reference in the first embodiment. In the following, we mainly describe what distinguishes the third embodiment from the first.

[0068] The electrochemical system 200 differs from the electrochemical system 10 by its anode purge circuit 240, which replaces the anode purge circuit 40. The anode purge circuit 240 fluidly connects the filter anode outlet 38 to the cell anode inlet 21, here via a second fluidic control device 243, and is connected to the cell anode recirculation circuit 30 downstream of the recirculation pump 44, and no longer upstream. This makes it possible in particular to pressurize the hydrogen at the filter anode outlet 38 thanks to the second fluidic control device 243, without risking circulation of the hydrogen through the recirculation pump 44 to the cell anode outlet 22.

[0069] In a variant not shown, the filter anode output 38 is connected directly to the filter cathode output 37, preferably via the second fluidic control device 43, without being connected to the battery anode recirculation circuit 30.

[0070] According to a variant not shown, the pressure measurements carried out at the filter cathode inlet are carried out at the filter cathode outlet, and vice versa.

[0071] Whatever the embodiment, the cell recirculation circuit 30 makes it possible to reuse the hydrogen that has not reacted in the fuel cell 20 and therefore to save it. In addition, in the case where the electrochemical system 10 or 100 is on board a vehicle, it is advantageous to release as little hydrogen as possible into the air, in order to meet standards, such as for example the “GTR-13” standard (“United Nations global technical regulation (gtr) for Hydrogen and Fuel Cell Vehicles - Addendum 13: Global technical regulation No. 13”. The filter recirculation circuit 51, or 151, facilitates the use and control of the electrochemical system 10 or 100, by allowing a voltage supply to the filter as long as the voltage across an electrochemical cell included in the electrochemical filter 35 is less than or equal to the predetermined voltage threshold.The predetermined voltage threshold is designed as a safety threshold, which is advantageously not . not reached during the nominal operating conditions of the system 10. In particular, when the system 10 is operating nominally, the electrical supply to the filter 35 is maintained uninterruptedly between several successive openings of the purge valve 40, without damaging the electrochemical filter 35.

[0072] Any feature described for one embodiment or variation in the foregoing may be implemented for the other embodiments and variations described above, as long as technically feasible.

Claims

1. Claims An electrochemical system (10; 100; 200) for generating electricity, the system (10; 100; 200) comprising a fuel cell (20) comprising a cell anode inlet (21), a cell cathode inlet (23), a cell anode outlet (22) and a cell cathode outlet (24), hydrogen-containing gas flowing from the cell anode inlet (21) to the cell anode outlet (22), the system (10; 100; 200) further comprising a cell anode recirculation circuit (30), connecting the cell anode outlet (22) to the cell anode inlet (21) and an anode purge circuit (40; 240) which is connected to the cell anode outlet (22), and which comprises a purge valve (41), the anode purge circuit (40; 240) comprising: - an electrochemical filter (35), of the proton exchange membrane hydrogen pump type, adapted to be electrically powered, the electrochemical filter (35) comprising a filter cathode inlet (36), a filter cathode outlet (37) and a filter anode outlet (38), the electrochemical filter (35) being adapted to deliver filtered hydrogen to the filter anode outlet (38); - a first fluidic control device (42); and - a second fluidic control device (43; 243); in which: - the purge valve (41) is configured to take an open configuration in which it connects the battery anode outlet (22) and the filter cathode inlet (36); - the purge valve (41) is configured to take a closed configuration, in which it separates the filter anode outlet (22) and the filter cathode inlet (36); - the first fluidic control device (42) is configured to take an open configuration, in which it connects the filter cathode output (37) to the battery cathode output (24); - the first fluidic control device (42) is configured to take a closed configuration, in which it separates the filter cathode output (37) from the filter cathode output cell (24); - the second fluidic control device (43; 243) is configured to take an open configuration, in which it connects the filter anode outlet (38) to the cell anode inlet (21), the filtered hydrogen being delivered to the cell anode outlet (21); and - the second fluidic control device (43; 243) is configured to take a closed configuration, in which it separates the filter anode outlet (38) from the cell anode inlet (21); characterized in that the system (10; 100; 200) comprises a filter recirculation circuit (50; 150), the filter recirculation circuit (50; 150) comprising a filter recirculation valve (51; 151) configured to take an open configuration, in which the recirculation valve (51;151) connects the filter anode outlet (38) to the filter cathode inlet (36) or the filter cathode outlet (37) and to assume a closed configuration, wherein the filter recirculation valve (51; 151) separates the filter anode outlet (38) from the filter cathode inlet (36) or the filter cathode outlet (37).;

2. System (10; 100; 200) according to claim 1, wherein the electrochemical filter (35) is electrically supplied uninterruptedly with a constant voltage as long as a voltage across an electrochemical cell included in the electrochemical filter (35) is less than or equal to a predetermined voltage threshold.

3. A system (10; 100) according to any preceding claim, wherein the cell recirculation circuit (30) further comprises a recirculation pump (44), and wherein the anode purge circuit (40) is connected to the cell anode outlet (22) by being connected to the cell recirculation circuit (30) upstream of the recirculation pump (44).

4. System (10; 100) according to any one of the preceding claims, wherein the first fluidic control device (42) is a first valve.

5. System (10; 100) according to any one of the preceding claims, wherein the second fluid control device (43) is a second valve.

6. A system (10) according to any preceding claim, wherein the filter recirculation valve (51) is configured to assume an open configuration, in which it connects the filter anode outlet (38) to the filter cathode outlet (37) and to assume a closed configuration, in which it separates the filter anode outlet (38) from the filter cathode outlet (37).

7. System (100) according to any one of claims 1 to 5, wherein the filter recirculation valve (151) is configured to assume an open configuration, in which it connects the filter anode outlet (38) to the filter cathode inlet (36) and to assume a closed configuration, in which it separates the filter anode outlet (38) from the filter cathode inlet (36).

8. Method for controlling the system (10; 100; 200) of any one of the preceding claims comprising at least the following steps: - opening then closing (S201) the purge valve (41); - measuring (S202) a pressure (P38) at the filter anode outlet (38); - measuring (S210) a pressure (P37) at the filter cathode outlet (37); - closing (S203) the second fluidic control device (43) and opening (S204) the filter recirculation valve (51; 151) when the pressure (P38) measured at the filter anode outlet (38) is less than or equal to an anode pressure threshold (P2); - opening (S205) of the second fluid control device (43) and closing (S206) of the filter recirculation valve (51; 151) when the pressure (P38) measured at the anode outlet of the filter (38) is strictly greater than the anode pressure threshold (P2);- closing (S211) of the first fluidic control device (42) when the pressure (P37) measured at the filter cathode outlet (37) or a pressure measured at the filter cathode inlet (36) is less than or equal to a cathode pressure threshold (PI); and - opening (S212) of the first fluidic control device (42) when the pressure (P37) measured at the cathode outlet; filter (37) is strictly greater than the cathodic pressure threshold (PI).

9. A method according to claim 8, further comprising a step of stopping the power supply to the electrochemical filter (35) if the voltage across an electrochemical cell included in the electrochemical filter (35) is greater than a predetermined voltage threshold.

10. A method according to claim 8, further comprising a step of stopping the power supply to the electrochemical filter (35) if the voltage across an electrochemical cell included in the electrochemical filter (35) is greater than a predetermined voltage threshold and if the pressure (P37) measured at the cathode output of the filter (37) is less than a safety pressure threshold, or if a pressure measured at the cathode input of the filter (36) is less than the safety pressure threshold.

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