FR3047611A1 - COMBUSTIBLE MEMBRANE FUEL CELL GENERATOR AND METHOD FOR CONTROLLING THE SAME - Google Patents

Abstract

A proton exchange membrane fuel cell generator (1; 1 ') comprises a buffer compartment (50; 50') in fluid communication with the anode compartment (A) and configured to allow heat removal and hence condensation of water inside it. The generator may include a purge conduit (80) configured to purge the buffer compartment (50) and a purge valve (85) configured to plug the purge conduit (80).

Description

PROTON EXCHANGE MEMBRANE FUEL CELL GENERATOR AND METHOD OF CONTROLLING THE SAME

Field of the invention

The present invention relates to a proton exchange membrane fuel cell generator and a method of controlling the same.

Background of the invention

Figure 1 schematically shows in section a proton exchange membrane fuel cell generator (hereinafter referred to as a "generator" for convenience) 100 known.

Such a generator 100 comprises, in a housing (not shown), at least one proton exchange membrane fuel cell (hereinafter "fuel cell"). In order to simplify the understanding of the invention, only the case where the generator comprises a single fuel cell is described. It is however obvious that the generator 100, as well as the generator 1 according to the invention which will be described hereinafter, may comprise several fuel cells stacked one after the other, the manner of obtaining such a stack of batteries. fuel being well known.

The fuel cell comprises a first bipolar plate 10, a second bipolar plate 20, and a proton exchange membrane 30.

The proton exchange membrane 30 divides the fuel cell into anode compartment A and a cathode compartment C. Compartments A and C are passages in which a reagent in the liquid or gaseous state can circulate.

A first inlet duct 11 for the hydrogen-containing reducing feed intake RH and a first outlet duct 12 are in fluid communication with the anode compartment A.

Similarly, a second inlet duct 21 for the oxygen-containing oxidant inlet RO and a second outlet duct 22 are in fluid communication with the cathode compartment C.

The construction of bipolar plates 10 and 20 is well known in the field of proton exchange membrane fuel cells and is therefore not described in detail.

As is known, the generator 100 further comprises, on either side of the fuel cell, two collector plates 4 for collecting the electric current generated by the oxidation-reduction reaction between the reducing fuel RH and the oxidant RO , two insulating plates 3 for electrically insulating the collector plates 4 of the housing, and two end plates 2RH and 2RO, the end plate 2RH being located on the side of the anode compartment A (that is to say closer to the anode compartment A than the cathode compartment C), and the end plate 2RO is located on the side of the cathode compartment C (that is to say closer to the cathode compartment C than the anode compartment A).

At least one of the two terminal plates 2RH and 2RO exerts a compressive force (provided for example by an elastic element (not shown)) on the stack in order to hold in place the insulating plates 3, the collector plates 4, the plates bipolar 10 and 20, and the membrane 30.

In a manner known per se, the oxidation-reduction reaction between the reducing fuel RH and the oxidant RO produces water, and other reaction products PR. The reaction products PR and a large portion (1 ×) H 2 O of the water produced are discharged from the cathode compartment C through the second outlet pipe 22. However, a part of this water tends to be back-diffused, ie ie to diffuse through the proton exchange membrane 30 from the cathode compartment C to the anode compartment A. The presence of water in the anode compartment A tends to decrease the efficiency of the oxidation-reduction reaction, so that a part of the reducing fuel RH leaves the anode compartment A without having reacted, which reduces the efficiency of the fuel cell 100.

To remedy this drawback, a so-called "dead-end" command of the generator 100 has been proposed, in which the first output duct 12 is periodically obstructed by a shutter element 90, as shown in FIG. in this way, the reducing fuel RH is trapped in the cathode compartment C.

However, the water that retro-diffuses from the cathode compartment C to the anode compartment A then accumulates in a region 95 of the anode compartment A. When, in this region 95, the quantity of water becomes too great, an equilibrium RH and RO reagents are established in the fuel cell 100 and / or the proton exchange membrane 30 is "flooded" with water (a phenomenon known as "anode flooding"), which prevents the reaction to continue. It then becomes necessary to open the outlet duct 12 again to evacuate the water from the cathode compartment C. Part of the reducing fuel RH is then entrained with the water, which results in a loss of reducing fuel and therefore a decrease in the efficiency of the fuel cell.

There is therefore a need for a proton exchange membrane fuel cell generator and a control method for eliminating the reducing fuel losses and efficiency of the configurations just described and / or avoid or at least delay the "flooding" of the anode.

Object and summary of the invention

To meet this need, the present invention provides a proton exchange membrane fuel cell generator, comprising: a proton exchange membrane fuel cell comprising a first bipolar plate, a second bipolar plate, and a proton exchange membrane disposed between the first bipolar plate and the second bipolar plate and dividing the fuel cell into an anode compartment and a cathode compartment; a first inlet duct for the intake of reducing fuel containing hydrogen; a second inlet conduit for the oxygen-containing oxidant inlet; wherein the first input conduit is in fluid communication with the anode compartment, and the second input conduit is in fluid communication with the cathode compartment; the proton exchange membrane fuel cell generator further comprising a buffer compartment in fluid communication with the anode compartment and configured to allow heat removal and thereby condensation of water therein.

The buffer compartment in fluid communication with the anode compartment increases the volume of the anode compartment. This increase in volume tends to reduce the local concentration of water in the anode compartment, which tends to delay the occurrence of the phenomenon of "flooding" of the proton exchange membrane. In addition, the buffer compartment is configured so that at least a portion of the water that is admitted as vapor can condense there when the generator is in operation. This condensed water is thus subtracted from the anode compartment and is then no longer available to "drown" the proton exchange membrane, which further delays the occurrence of the phenomenon of "flooding". As the occurrence of the "flooding" phenomenon is delayed, the efficiency of the fuel cell generator is increased.

According to one possibility, the proton exchange membrane fuel cell generator further comprises a first output conduit in fluid communication with the anode compartment.

Usually, the proton exchange membrane fuel cell generator further comprises a second output conduit in fluid communication with the cathode compartment.

According to one possibility, the proton exchange membrane fuel cell generator further comprises a heat exchanger configured to cool the buffer compartment.

According to one possibility, the proton exchange membrane fuel cell generator further comprises: a purge conduit configured to purge the buffer compartment; and a purge valve configured to close the purge duct. The condensed water in the buffer compartment can then be recovered and reused to feed another system that requires water for operation.

According to one possibility, the proton exchange membrane fuel cell generator further comprises a cooling circuit configured to circulate at least a portion of the reducing fuel through the heat exchanger before said reducing fuel is admitted into the heat exchanger. anode compartment via the first inlet duct.

The reducing fuel is then preheated at least in part by heat exchange with the buffer compartment, which improves the efficiency of the fuel cell generator.

According to one possibility, the buffer compartment is in fluid communication with the anode compartment via the first output conduit.

According to one possibility, the proton exchange membrane fuel cell generator further comprises an end plate, and at least a portion of the buffer compartment is disposed in the thickness of the end plate.

This configuration reduces the volume occupied by the fuel cell generator, which is particularly beneficial when it is to be embarked on board an aircraft or a space vehicle. In addition, this configuration makes it possible to limit the number of pipe bends, and thus to limit the accumulation of reducing fuel and / or water in these bends. In addition, the fuel cell generator responds more quickly to a possible purge of the buffer compartment caused by the opening of the purge valve.

According to one possibility, the buffer compartment is in fluid communication with the anode compartment via a communication duct different from the first outlet duct, and the first outlet duct is configured to be closed at least during certain phases of operation of the generator.

According to one possibility, the buffer compartment is placed lower than the anode compartment. Naturally, the proton exchange membrane fuel cell generator is then configured such that water can flow by gravity from the anode compartment to the buffer compartment. With this configuration, the condensed water tends to accumulate, due to its higher density, in the lower part of the buffer compartment, this lower part being the furthest away from the proton exchange membrane. This further delays the occurrence of the phenomenon of "flooding" of the proton exchange membrane.

The present invention also relates to a method of controlling a proton exchange membrane fuel cell generator according to any of the possibilities which have just been described. This method comprises the steps of: introducing into the anode compartment hydrogen reducing fuel and in the cathode compartment of the oxygen-containing oxidant; cooling the buffer compartment so as to condense at least a portion of the water vapor contained in the buffer compartment.

As mentioned above, the "flooding" of the proton exchange membrane is delayed.

If the proton exchange membrane fuel cell generator is provided with the purge duct and the purge valve defined above, the method may further comprise a step in which the purge valve is opened so that at least a portion of the liquid water condensed in the buffer compartment is discharged via the purge duct.

As mentioned above, the water thus recovered can be reused.

According to one possibility, after opening the purge valve, the purge valve is closed so that some of the liquid water condensed in the buffer compartment remains in the buffer compartment.

Since the purge valve is closed so as to leave liquid water in the buffer compartment, the outlet products leaving the purge conduit do not contain reducing fuel. Thus, all the reducing fuel admitted into the fuel cell eventually react, resulting in better efficiency and reducing fuel economy; and the risk of explosion and / or fire of the output products is greatly reduced. On the other hand, it is not necessary to provide a pressure regulator for regulating the outlet pressure of the purge duct, even when the fuel cell generator is installed in an aircraft or space vehicle facing an external pressure. very weak.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and its advantages will appear better on reading the following detailed description of several embodiments, shown by way of non-limiting examples. The description refers to the accompanying drawings in which: - Figure 1 shows schematically in section a proton exchange membrane fuel cell generator of the state of the art; FIG. 2 represents the fuel cell generator of FIG. 1 operating in "dead-end" mode; - Figure 3 shows schematically in section a fuel cell generator membrane proton exchange according to a first embodiment of the invention; FIG. 4A schematically represents in section a proton exchange membrane fuel cell generator according to a second embodiment of the invention; FIG. 4B is a view of detail B of FIG. 4A.

Detailed description of the invention

FIG. 3 is a schematic sectional view of a proton exchange membrane fuel cell generator (hereinafter referred to as a "generator" for convenience) 1 according to a first embodiment of the invention.

The elements in common with the prior art generator 100 are designated by like reference numerals and are not described again in detail.

The generator 1 comprises a buffer compartment 50 in fluid communication with the anode compartment A, for example via the first outlet conduit 12. The buffer compartment 50 increases the volume of the anode compartment A. This increase in volume tends to reduce the local concentration of water in the anode compartment A, which tends to delay the occurrence of the "flooding" phenomenon of the proton exchange membrane 30. The buffer compartment 50 is configured to allow heat evacuation, i.e. when the buffer compartment 50 is placed in a medium whose temperature is lower than that of the interior of the buffer compartment 50, heat exchange occurs between the interior of the buffer compartment 50 and said medium.

Thus, at least a portion of the water which is admitted as steam into the buffer compartment 50 tends to condense inside thereof in the form of liquid water 56. This liquid water 56 does not is then more available to "drown" the proton exchange membrane 30, which further delays the occurrence of the phenomenon of "flooding".

The buffer compartment 50 can exchange heat with a volume of air located in the interior space of the aircraft or space vehicle in which the generator 1 is installed, this air volume having a temperature substantially lower than the operating temperature of the fuel cell, thereby condensing at least a portion of the water contained in the buffer compartment 50.

The generator 1 may further comprise a heat exchanger 60 configured to cool the buffer compartment 50.

In one example, the heat exchanger 60 comprises in particular cooling fins in order to promote the transfer of heat between the buffer compartment 50 and the volume of air.

In addition or alternatively, the generator 1 further comprises a cooling circuit 70 configured to circulate a cooling fluid through the heat exchanger 60. In a preferred example, at least a portion of the reducing fuel RH circulates in the cooling circuit 70 and passes through the exchanger 60 before being admitted into the anode compartment A via the first inlet duct 11. This part of the reducing fuel RH is then preheated, which improves the efficiency of the generator 1.

The buffer compartment 50 can be placed lower than the anode compartment A in the normal operating position. In the present embodiment, the vertical direction DV, shown in FIG. 3, is the direction connecting the first outlet duct to the first inlet duct, the upward direction being the direction from the first outlet duct to the first duct. 'Entrance. Thus, the first outlet duct 12 is located lower than the first inlet duct 11, that is to say at a lower altitude. On the other hand, the "bottom" part of an element is the lowest in this element along the vertical direction DV.

With this configuration, the condensed water tends to accumulate, because of its higher density, in the lower part of the buffer compartment 50, this lower part being the furthest away from the proton exchange membrane 30. This further delays the occurrence of the phenomenon of "flooding" of the proton exchange membrane 30.

In some embodiments, the generator 1 is provided to operate for a short period of time, so that the buffer compartment 50 can be provided with a volume sufficient to store all the water that has retro-diffused through the exchange membrane proton 30 and then will be condensed in the buffer compartment 50.

In other embodiments, the generator 1 further comprises a purge conduit 80 configured to purge the buffer compartment 50, and a purge valve 85 configured to close the purge conduit 80. By "purge" is meant that the purge duct 80 is able to let the fluid (s) contained (s) in the buffer compartment 50, as the purge valve 85 is open.

Thus, when the amount of water condensed in the buffer compartment 50 may cause "flooding" of the proton exchange membrane 30, it is sufficient to open the purge valve 85 to evacuate a portion of the condensed water and thus to further delay the occurrence of the phenomenon of "flooding" of the proton exchange membrane 30.

Preferably, the purge duct 80 opens into the buffer compartment 50 lower than the outlet duct 12, and more preferably still in a lower part of the buffer compartment 50. Thus, when the purge valve 85 is open, the duct purge 80 tends to evacuate first the liquid water 56 which has accumulated in the lower part of the buffer compartment 50.

A method of controlling the generator 1 will now be described.

The anode compartment A is supplied with reducing fuel RH, and in the cathode compartment C with the oxidant RO. The oxidation-reduction reaction occurs, as is known, and generates electricity, reaction products, and water. Part of the water produced by the backscattering reaction through the proton exchange membrane 30.

Buffer compartment 50 is cooled. As previously described, in this way at least a portion of the water vapor contained in buffer compartment 50 condenses as liquid water 56.

It will be noted that, in general, the generator 1 operates continuously, so that the introduction of reducing fuel and oxidant and the cooling of the buffer compartment 50 are carried out simultaneously and continuously over a significant period of time.

In some embodiments, the generator 1 is not provided with the purge conduit 80 and the purge valve 85, so that the condensed water simply accumulates in the buffer compartment 50 until the end of the process. planned operating period of the generator 1 (which, in the case of a spacecraft, is generally of the order of one hour, or even less).

In other embodiments, the generator 1 is provided with the purge duct 80 and the purge valve 85. In this case, the purge valve 85 is opened, for example periodically. Thus, at least part of the liquid water 56 contained in the buffer compartment 50 is evacuated via the purge duct 80.

Preferably in this case, after opening the purge valve 85, the purge valve 85 is closed again so that a portion of the liquid water 56 contained in the buffer compartment 50 remains in the buffer compartment 50. other words, the purge valve 85 is controlled so that it closes before the purge duct 80 begins to discharge a mixture of liquid water 56 and steam and / or reducing fuel RH. Thus, the purge pipe 80 does not expel RH reducing fuel, which greatly reduces the risk of explosion and / or fire at the bleed pipe 80. On the other hand, it is not necessary to provide a pressure regulator for regulating the pressure at the outlet of the purge duct 80, even when the generator 1 is installed in an aircraft or a space vehicle confronted with a very low external pressure. The liquid water 56 discharged via the purge duct 80 can simply be evacuated outside the aircraft or space vehicle. Alternatively, it can be recovered and reused to power another system that requires water for operation.

Various control laws can be used to control the opening and closing of the purge valve 85.

For example, a control unit (not shown) of the generator 1 can determine, from the operating parameters of the generator 1 (for example, the flow rate of reducing fuel RH and oxidant RO, the operating time of the generator 1, the operating temperature of the generator 1), a time interval between two successive openings of the purge valve 85 and an opening time of the purge valve 85, and controlling the opening and closing of the valve purge 85 accordingly.

In another example, a sensor (not shown) can detect the liquid water level 56 in the buffer compartment 50, and the control unit can control the opening of the bleed valve 85 when the liquid water level reaches a value determined in advance.

The purge valve 85 can then be an "on-off" solenoid valve whose opening is controlled by the control unit.

In another example, the opening of the purge valve 85 may be mechanically caused by a float (not shown), the float itself being driven by the rise of the liquid water level 56 in the buffer compartment 50.

The mode of operation of the generator 1 which has just been described is applicable to any type of reducing fuel RH and oxidant RO, provided that the oxidation-reduction reaction produces water in the form of steam.

In a particular example, the reducing fuel RH is dihydrogen (H2) and the oxidizing fuel is oxygen (O2) · The oxidation-reduction reaction between H2 and O2 can occur at a temperature of between 100 ° C and 200 ° C for example at a temperature of about 160 ° C. The oxidation-reduction reaction between H 2 and O 2 can occur at an absolute pressure close to atmospheric pressure, for example at an absolute pressure of between 0.6 bar and 1 bar. The generator 1 is generally installed in a medium whose temperature is less than or equal to 85 ° C., which makes it possible to cool the buffer compartment 50 and to condense at least part of the water that it contains. Other reducing fuels RH may be used, such as methanol (CH3OH). It is also possible that the RH fuel dissociates into hydrogen and other compounds in the vicinity of the anode.

Figures 4A and 4B show schematically in section a generator the according to a second embodiment of the invention.

In this embodiment, a buffer compartment 50 'is disposed at least in part, and preferably entirely, in the thickness of the end plate 2RH (remember that the terminal plate 2RH is located on the side of the anode compartment A), i.e. at least a portion, and preferably all, of the inner volume of the buffer compartment 50 'is included in the volume of the end plate 2RH.

This configuration makes it possible to limit the number of pipe elbows, and therefore to limit the accumulation of reducing fuel RH and / or water in these elbows. In addition, the generator 1 'responds more quickly to a possible purge of the buffer compartment 50' caused by the opening of the purge valve 85.

As in the first embodiment, the buffer compartment 50 'is preferably located lower than the anode compartment A as shown in Fig. 4A. The buffer compartment 50 'can be in fluid communication with the anode compartment A via the first outlet conduit 12. However, in order to further limit the number of pipe bends, it is preferable that the buffer compartment 50' is in fluid communication with the anode compartment A via a communication duct 14 distinct from the first outlet duct 12. In this case, the first outlet duct 12 may be closed, for example by a closure element 90, at least during certain operating phases of the generator 1 '.

The buffer compartment 50 'can exchange heat with a volume of air located in the interior space of the aircraft or spacecraft in which the generator 1' is installed, this volume of air having a temperature substantially below the temperature of operation of the fuel cell.

The generator may further comprise a heat exchanger 60 'configured to cool the buffer compartment 50'. This heat exchanger 60 'is generally integrated with the terminal plate 2RH.

In one example, the heat exchanger 60 'includes cooling fins in particular to promote heat transfer between the buffer compartment 50' and the volume of air.

In addition or alternatively, the generator 1 'further comprises a cooling circuit 70' configured to circulate a cooling fluid through the heat exchanger 60 '. The cooling circuit 70 'is preferably integrated with the end plate 2RH. As in the first embodiment, it can be provided that at least a portion of the reducing fuel RH circulates in the cooling circuit 70 'and passes through the exchanger 60' before being admitted into the anode compartment A via the first conduit 11.

The cooling circuit 70 'can also be configured to cool the generator Γ, which simplifies the design of the fuel cell Γ.

The generator 1 'may comprise a purge duct 80 and a purge valve 85 similar to those of the first embodiment.

The generator 1 'has the same operation and the same advantages as the generator 1, which are therefore not described in detail again. In addition, since the buffer compartment 50 'is disposed at least partly in the thickness of the end plate 2RH, the volume occupied by the generator 1' is reduced, which is particularly beneficial when it must be on board an aircraft or spacecraft.

Claims (9)

A proton exchange membrane fuel cell generator (1; 10, comprising: a fuel cell comprising a first bipolar plate (10), a second bipolar plate (20), and a proton exchange membrane (30) disposed between the first bipolar plate (10) and the second bipolar plate (20) and dividing the fuel cell (1; 10 into an anode compartment (A) and a cathode compartment (C); a first input conduit (11) for admitting reducing fuel (RH) containing hydrogen, a second inlet conduit (21) for oxygen-containing oxidant (RO) inlet, wherein the first inlet conduit ( 11) is in fluid communication with the anode compartment (A), and the second input conduit (21) is in fluid communication with the cathode compartment (C), the proton exchange membrane fuel cell generator (1; 10 being characterized in that it further comprises a buffer compartment (50; 500 in fluid communication with the anode compartment (A) and configured to allow heat removal and thereby water condensation therein. The proton exchange membrane fuel cell generator according to claim 1, further comprising a heat exchanger (60; 600 configured to cool the buffer compartment (50; The proton exchange membrane fuel cell generator according to claim 2, further comprising a cooling circuit (70; 700 configured to circulate at least a portion of the reducing fuel (RH) through the heat exchanger ( 60, 600 before said reducing fuel (RH) is admitted into the anode compartment (A) via the first inlet conduit (11). The proton exchange membrane fuel cell generator according to any one of claims 1 to 3, further comprising a terminal plate (2RH), and wherein at least a portion of the buffer compartment (50; the thickness of the end plate (2RH). The proton exchange membrane fuel cell generator according to any one of claims 1 to 4, wherein the buffer compartment (50; 500 is placed lower than the anode compartment (A). The proton exchange membrane fuel cell generator according to any one of claims 1 to 5, further comprising: a purge conduit (80) configured to purge the buffer compartment (50; 500; and a purge valve (85) configured to close the purge duct (80). 7. A method of controlling a proton exchange membrane fuel cell generator (1; 10) according to any one of claims 1 to 5, the method comprising the steps of: introducing into the anode compartment (A) fuel hydrogen-containing reductant (RH) and in the cathode compartment (C) of the oxygen-containing oxidant (RO), cooling the buffer compartment (50; 500) so as to condense at least a portion of the vapor water contained in the buffer compartment (50; 500- The method of claim 7, wherein the proton exchange membrane fuel cell generator (1; 10) further comprises: a purge conduit (80) configured to purge the buffer compartment (50; 500; and a valve purge valve (85) configured to close the purge duct (80), and wherein the purge valve (85) is opened so that at least a portion of the liquid water (56) is condensed in the buffer compartment ( 50, 500 is evacuated via the purge duct (80). A method according to claim 8, wherein after opening the purge valve (85), the purge valve (85) is closed so that a portion of the liquid water (56) condensed in the buffer compartment ( 50, 500 remains in the buffer compartment (50;