DE102014214420A1 - Redox fuel cell system and method of operating a redox fuel cell system - Google Patents

Abstract

The invention relates to a redox fuel cell system 10, comprising at least one redox fuel cell and at least one regenerator 60. The at least one redox fuel cell comprises an anode 20 and a cathode 30, which are separated by an ion-selective separator 40. The anode 20 has a supply 22 for a fuel. The at least one regenerator 60 serves to regenerate a nonvolatile catholyte solution L by an oxidizing agent. The cathode 30 and the regenerator 60 are connected by a fluid line system 100, 110 so that the catholyte solution L can circulate between the cathode 30 and the regenerator 60. The fluid conduit system 100, 110 includes at least one oxidant inlet 120, 120 ', 120 "through which the oxidant flows into the fluid conduit system 100, 110.

Description

The present application relates to a redox fuel cell system and a method of operating a redox fuel cell system.

Fuel cell systems for mobile applications such as motor vehicles are known in the art. In its simplest form, a fuel cell is an electrochemical energy converter that converts fuel and oxidant into reaction products, producing electricity and heat. For example, hydrogen is used as the fuel and air or oxygen as the oxidizing agent in such a fuel cell. The reaction product of the reaction in the fuel cell is, for example, water. The gases are fed into corresponding diffusion electrodes, which are separated by a solid or liquid electrolyte. The electrolyte transports charged ions between the two electrodes. In an indirect or redox fuel cell system, the oxidant (and / or fuel in some cases) does not react directly at the cathode (anode for fuel). Rather, a reduced form (oxidized form for fuel) of a redox couple reacts at a location spaced from the cathode (anode for fuel) to be oxidized (to be reduced for fuel). This oxidized form (reduced form for fuel) of the redox couple is then fed to the cathode (anode for fuel). From the WO 2014/001786 A1 , of the DE 10 2013 217 858 A1 as well as the EP 1 999 811 B1 Such redox fuel cells are known. Furthermore, from the WO2010 / 128333 A1 a regenerator is known in which by use of injectors, nebulizers or steam radiators intensive mixing in a small regenerator is to be achieved.

In such redox systems as well as in conventional systems, the problem arises that the fuel cell for the transport of the oxidant to the regenerator must provide relatively much power (see. DE 10 2013 217 858 A1 ). For example, with an electric power of a fuel cell stack of about 100 kW, an oxidation fluid delivery unit with a maximum consumption of about 30 kW during the starting phase may be required. As Oxidationsfluidfördereinheit a correspondingly heavy, large and expensive compressor is used. Further, the compressor considerably reduces the output of the redox fuel cell system. Particularly in the lower and middle performance range of the redox fuel cell system, the overall efficiency of the fuel cell system is reduced by the high consumption of the oxidation fluid delivery unit.

It is an object of the present application to reduce or remedy the aforementioned disadvantages. The object of the present invention is achieved by the subject matter of patent claim 1. The dependent claims represent advantageous embodiments.

The technology disclosed herein includes a redox fuel cell system having at least one redox fuel cell. The redox fuel cell comprises an anode and a cathode, which are separated in particular by an ion-selective separator. The anode has a supply for a fuel to the anode. In other words, during operation of the redox fuel cell system, the anode is in fluid communication with a fuel reservoir. Preferred fuels for the redox fuel cell system are: hydrogen, low molecular weight alcohol, biofuels, or liquefied natural gas. The cathode has, for example, a supply of catholyte solution to the cathode. The ion-selective separator can be designed, for example, as a proton exchange membrane (PEM). Preferably, a cation-selective polymer electrolyte membrane is used. Materials for such a membrane include Nafion ^®, Flemion ^® and Aciplex ^®. Preferred oxidizing agents are, for example, air, hydrogen and peroxides. As a redox couple, for example, a polyoxometalate (POM) and / or as a solvent of the catholyte solution, for example, water can be used. Several redox fuel cells can be combined to form a stack.

Further, the redox fuel cell system may include at least one regenerator for regenerating a non-volatile catholyte solution under operating conditions, wherein the cathode and the regenerator are fluidly coupled, in particular such that the catholyte solution may circulate between the cathode and the regenerator. The regenerator is preferably separate and spaced from the cathode.

A redox fuel cell system comprises the at least one redox fuel cell and the peripheral system components (BOP components) that can be used during operation of the at least one redox fuel cell. For example, in the description of the figures, a system with a fuel cell and a regenerator is shown in simplified form. If a system component is listed below in the singular, the majority should also be included. For example, a plurality of fuel cells may be fluidly coupled through a plurality of fluid systems having a plurality of regenerators.

• a) Kationen (z. B. H⁺-Protonen) und Elektronen werden an der Anode gebildet, die sich neben dem ionenselektiven Separator befindet;
• b) die Katholytlösung mit ihrem Redox-Paar wird im oxidierten Zustand zur Kathode befördert, die sich benachbart zum ionenselektiven Separator gegenüber der Anode befindet;
• c) die oxidierte Form der Katholytlösung wird beim Kontakt mit der Kathode und den Kationen (H⁺-Protonen) reduziert (d. h. Elektronenaufnahme);
• d) die Katholytlösung gelangt von der Kathode zum Regenerator, wo die reduzierte Form der Katholytlösung reoxidiert d. h. regeneriert wird;
• e) die regenerierte Katholytlösung kann dann wieder zur Kathode befördert werden.

The catholyte solution includes, for example, a solvent and a redox couple. The redox Couple is at least partially reducible at the cathode. The redox couple is at least partially regenerable on the regenerator after reduction at the cathode. In other words, after the reduction at the cathode, the redox couple is at least partially oxidized again on or in the regenerator to the original shape. In the context of the technology disclosed herein, a redox couple comprises at least two molecules which can be converted into each other by electron uptake or electron emission. In the case of the redox fuel cell disclosed here, the following reactions may take place, inter alia:

• a) Cations (eg, H ⁺ protons) and electrons are formed at the anode, which is adjacent to the ion-selective separator;
• b) the catholyte solution with its redox couple is transported in the oxidized state to the cathode, which is adjacent to the ion-selective separator with respect to the anode;
• c) the oxidized form of the catholyte solution is reduced on contact with the cathode and the cations (H ⁺ protons) (ie electron uptake);
• d) the catholyte solution passes from the cathode to the regenerator where the reduced form of the catholyte solution is reoxidized ie regenerated;
• e) the regenerated catholyte solution can then be returned to the cathode.

The circulating catholyte solution or its redox pairs can therefore be oxidized and reduced as desired. In the regenerator of the redox fuel cell system, specific catalytically active centers of the redox molecules of the catholyte solution can act as a catalyst for the reduction of the oxidizing agent. For hydrogen as the fuel, oxygen as the oxidant, and polyoxometalate as the redox couple, the reactions at the cathode and anode are shown in, for example, the article "Journal of Power Sources 201 (2012, pages 159-163, authors: R. Singh, AA Shah, A. Potter, B." Performance and analysis of a novel polymer electrolyte fuel cell using a solution based redox mediator ". Clarkson, A. Creeth, C. Downs, FC Walsh) has been published.

The redox fuel cell system includes means for providing an electrical circuit between the anode and the cathode and between respective terminals of the stack. For example, an electrical consumer is connected to such a circuit.

Among other things, the technology disclosed here is based on the idea of shifting part of the redox reaction into the fluid line system. This can happen, for example, by at least one oxidant inlet and / or by at least one atomization device which is / are arranged in the fluid line system. It can therefore be fed or introduced into the fluid conduit system oxidizing agent to allow regeneration there. It can thus be advantageous to reduce the size and weight of the regenerator and / or the Oxidationsfluidfördereinheit. Further preferred smaller oxidation fluid delivery units can be used.

Among other things, the technology disclosed here is based on the idea of replacing the operation of the oxidation fluid delivery unit, at least in the inefficient partial load range, with other devices which can have better efficiency, at least in a partial load range.

The redox fuel cell system may include at least one oxidant inlet. Through the oxidant inlet, the oxidant may flow into the fluid conduit system. In particular, the redox fuel cell system may have a supply line to the oxidant inlet, through which the oxidant can flow into the fluid line system.

In particular, the oxidant may flow through the at least one oxidant inlet directly into the fluid conduit system. In other words, the inflow of oxidant into the fluid line system is not equated with an indirect influx of oxidant into the fluid line system. In the case of indirect inflow, the oxidant flows directly into the regenerator, for example via a regenerator feed line, and then passes thereafter, i. H. through the regenerator outlet, into the fluid line system.

The term fluid conduit system or catholyte fluid conduit system comprises all pipeline elements of the catholyte fluid circuit or fluid circuit, which connect the other elements of the fuel cell system with each other. In other words, the abstract term "fluid conduit system" is to be distinguished from the components connected to the fluid conduit (s), such as the regenerator and the cathode. In the simplest embodiment, the fluid conduit system comprises a first fluid conduit connecting the cathode to the regenerator and a second fluid conduit connecting the regenerator to the cathode. However, the fluid line system may also have multiple branches. The term "fluid line system" thus includes all lines, which in turn form together with the components or elements connected to these lines the catholyte fluid circuit.

In addition to the regeneration in the regenerator thus further regeneration in the fluid conduit system is made possible. The through the at least one oxidant inlet into the In this case, oxidizing agent flowing in fluid line system preferably flows into the fluid line system as small oxidant bubbles. This can be made possible for example by turbulence. This results in a comparatively large contact area between the catholyte solution and the oxidizing agent, which can enable a comparatively good transfer of oxygen into the solution. The advantage here is the utilization of the fluid line length from the oxidant inlet to Oxidationsmittelauslass to allow the highest possible residence time of the oxidizing agent and thus the best possible carry. Thus, smaller regenerators and / or oxidation fluid delivery units can preferably be used. The comparatively small oxidation fluid delivery units may consume less energy. Furthermore, they can advantageously be operated at a better operating point. The redox fuel cell system can thus be made lighter, more efficient and smaller than previously known systems.

The at least one oxidant inlet may be provided in the first fluid line and / or in the second fluid line. In particular, an oxidant inlet in the first fluid line may cause a turbulent flow of catholyte solution and oxidant to flow into the regenerator. This incoming turbulent flow may cause better mixing of oxidant and catholyte solution in the regenerator itself.

Advantageously, the redox fuel cell system may include a catholyte separator downstream of the regenerator. The catholyte separator may be capable of separating the catholyte solution and the oxidizer. The regenerator and the catholyte separator preferably constitute a structural unit with a housing. Such a constructional unit of regenerator and catholyte separator is independent of the aforementioned basic idea of at least partially relocating the regeneration into the fluid line system. Preferably, however, the unit will also find use in combination with the regeneration technology disclosed herein.

The redox fuel cell system typically includes at least one main oxidation fluid delivery unit positioned upstream of the oxidant flow to the regenerator and feeding oxidant into the regenerator. Furthermore, at least one further oxidation fluid delivery unit may be provided, which is provided upstream of the at least one oxidant inlet. This further oxidation fluid delivery unit is suitable for supplying the at least one oxidant inlet with oxidizing agent. Preferably, each oxidant inlet can each be connected to a further oxidation fluid delivery unit. Furthermore, in each case a further oxidation fluid delivery unit can supply a plurality of oxidant inlets with oxidizing agent.

Preferably, the at least one further Oxidationsfluidfördereinheit promotes oxidizing agent to the at least one oxidant inlet with a differential pressure of 0 to 5 bar, further preferably from 0.1 to 2.0 bar, and particularly preferably from 0.4 to 1.0 bar which is is a differential pressure to atmospheric pressure. Such a further oxidation fluid delivery unit can be equipped with a correspondingly smaller drive unit, whereby preferably the parasitic consumption power can be reduced and the efficiency can be increased. Instead of a very large Hauptoxidationsfluidfördereinheit so more Oxidationsfluidfördereinheiten be provided, which in total preferably consume less power than the very large Hauptoxidationsfluidfördereinheit. The efficiency of the fuel cell can thus be further increased, especially in the partial load range. In low load operation it may be sufficient that only the further oxidation fluid delivery unit is activated. In such a low load range, it is thus possible to use the redox fuel cell system without operating the comparatively large oxidizing fluid conveying unit.

The oxidant supplied to the at least one oxidant inlet may also be provided by the main oxidation fluid delivery unit, which supplies oxidant to the regenerator. In other words, from the main air duct, i. H. the regenerator, oxidizer are diverted, which is then fed to the at least one oxidant inlet. The oxidizing agent may be, for example, air or oxygen. Preferably, the oxidant for the at least one oxidant inlet is tapped before or after the main oxidation fluid feed unit, which supplies the regenerator with oxidizing fluid. Preferably, the regenerator and the at least one oxidant inlet can be supplied with oxidant from a common oxidant stream. Advantageously, this common oxidant stream can be filtered with a common filter, for example an air filter. Furthermore, the oxidant, which is supplied to the at least one oxidant inlet, originate from the environment of the stack or from the housing.

The redox fuel cell system may include at least one nebulizer. The nebulizer may nebulise the catholyte solution within the fluid conduit system. Further preferably, the nebulizer may nebulize the catholyte solution within a container connected to the fluid conduit system fluidly connected. The nebulization or sputtering of catholyte solution leads to a surface enlargement of the catholyte solution or to aerosol particles. In the presence of oxidizing agent, due to the increase in surface area, an improved transfer of oxygen into the solution occurs. The container can also be designed as a storage container for catholyte solution. The aspect of the nebulizing device is not functionally connected to the at least one oxidant inlet. Thus, it is also conceivable to have a fuel cell system that has at least one nebulizing device but not at least one oxidant inlet.

The redox fuel cell system preferably comprises at least one bypass line. The bypass line may branch off from the first line upstream of the regenerator and open into the second fluid line downstream of the regenerator. Preferably, at least one oxidant inlet and / or at least one fogging device may be arranged in the bypass line. In the first and / or second fluid line further oxidant inlets and / or nebulization devices may be provided. Advantageously, the bypass in front of the catholyte separator open into the second fluid line. As a bypass is here understood a line of the fluid conduit system, which is arranged parallel to a further fluid conduit section of the fluid conduit system or parallel to an element of the fluid circuit.

Furthermore, at least two preferably different oxidant inlets and / or at least two preferably different atomization devices can be provided. Preferably, the oxidant inlets and / or nebulizers are arranged or connected in series and / or parallel to each other. For example, four oxidant inlets may be provided, with two oxidant inlets each connected in series to two pairs, the two pairs being arranged parallel to one another.

The redox fuel cell system preferably comprises at least one fluid flow regulator. The fluid flow regulator may be adapted to divide a stream of catholyte solution into several sub-streams. For example, the fluid flow regulator can divide an incoming fluid flow into two or three partial flows. The fluid flow regulator can be designed as a 3- or 4-way valve. The fluid flow regulator may preferably branch off a portion of the flow of catholyte solution from the first fluid conduit into a bypass conduit. Preferably, the distribution of the total volume flow to a plurality of partial flows can be controlled or regulated. Preferably, the division of the catholyte solution flow can be regulated as a function of the operating state and the load requirement. By controlling the distribution of the catholyte stream to different line sections, the flow rate of the catholyte solution and the introduction of oxidant can be influenced. Thus, depending on the load requirement, the parasitic power dissipation can be reduced by appropriately controlling the catholyte current. For example, in the low load range or in the lower load range of the fuel cell system, the main oxidation fluid delivery unit could be switched off. Also, at least in the low load range of the regenerator can be bypassed by a bypass circuit. The bypass circuit may then have lower flow resistances, which in turn may reduce the power requirements of the catholyte flow pumping device.

The at least one oxidant inlet and / or the at least one atomization device can be designed, for example, as a Venturi nozzle. A Venturi nozzle generally comprises a pipe section with a cross-sectional constriction, for example by two oppositely directed cones, which are united at the point of their smallest diameter. At this point or adjacent thereto, at least one opening is provided for the inlet of the oxidizing agent. With such a Venturi nozzle, for example, a particularly good distribution of oxidizing agent and catholyte solution can be achieved. In the nebulization device, a finely dispersed atomization can thus be achieved.

The at least one oxidant inlet may further comprise a porous material or holes which may additionally enhance bubble formation.

The at least one oxidant inlet can / can be designed, for example, as a jet pump or jet pump, in particular in such a way that the oxidizing agent is sucked in by the catholyte solution flowing in the fluid line system. In other words, the catholyte solution serves as a driving medium, which sucks the suction medium "oxidizing agent" in the jet pump. Particularly advantageously, at least part of the jet pump can be designed as a Venturi nozzle. Furthermore, the pump device and the at least one fluid flow regulator can be controlled such that the at least one jet pump can suck in oxidizing agent.

If the at least one oxidant inlet is designed as a jet pump, then preferably at least the further oxidation fluid delivery unit can be dispensed with. In other words, the jet pump then constitutes another oxidation fluid delivery unit. A jet pump is more robust and less expensive than the conventional oxidation fluid delivery units (eg, compressors). In addition, the redox fuel cell system can be operated more efficiently. For example, the jet pump in particular have a higher efficiency in the lower part load range than the Hauptoxidationsfluidfördereinheit. It can be provided, for example, that at least in the lower part-load range the main oxidation fluid delivery unit is switched off and only at least one jet pump is connected to the fluid line system or supplies the catholyte circuit with oxidizing agent. As a lower load range of the fuel cell system, a load range below the upper load range is generally considered here. For example, here a range of about 0% to 70%, preferably from about 0% to 50%, and more preferably from about 0% to 15% of the stack gross power and the maximum current density of the fuel cell system is assumed as the lower load range become. The upper load range would then be a range from about 70% to 100%, preferably from about 50% to 100%, and most preferably from about 85% to 100% of the stack gross horsepower or maximum current density of the fuel cell system.

The jet pump requires a certain flow rate of the catholyte solution for suction. The flow rate of the catholyte solution can be controlled or regulated, for example, via the pump device and / or via the fluid flow regulator. In this case, the energy consumption of the pump device may increase in some load ranges, which however is more than compensated by the efficiency gain in conveying the oxidant (eg omitting the (main) oxidation fluid delivery unit). In many load ranges, the pump can also be operated more efficiently.

For example, the redox fuel cell system may include at least two different jet pumps. The different jet pumps may, for example, be connected in series or parallel to one another, in particular in the bypass disclosed here. Different jet pumps are here, for example jet pumps with different delivery pressures at different propellant velocities. For example, they have different optimal operating points and different efficiency characteristics. The difference therefore relates to the jet pump parameters, which are taken into account for the application. Suitably, the fuel cell system is designed such that the flow of catholyte reaches the at least one jet pump at such a speed that oxidizing agent is sucked in efficiently. In order to prevent the catholyte solution from entering the oxidant supply line via the oxidant inlet at a pressure drop (eg, when shutting down the system), a valve (eg, a check valve) may be provided or integrated into the oxidant inlet.

Preferably, within the fluid conduit system, a recirculation circuit may be provided, in which catholyte solution is branched off downstream of a fluid conduit system section which then flows through a recirculation section and is recycled upstream of the fluid conduit system section, in particular in front of the catholyte separator and / or vessel. The recirculation section preferably comprises at least one oxidant inlet and / or at least one misting device. Thus, the residence time of regenerating mixture comprising catholyte solution and oxidizing agent in the fluid conduit system or in the recirculation circuit can be increased.

Instead of a pump device for the flow of catholyte, it is also possible to provide a plurality of pump devices which provide the required total pumping power. Further advantageously, the fuel cell system comprises at least one further pumping device, which in particular promotes a partial flow of the fluid system, preferably the partial fluid flow of the recirculation section. Advantageously, the at least one pumping device and / or the at least one further pumping device can be arranged directly upstream of the at least one oxidizing agent inlet and / or the at least one atomizing device. Thus, the catholyte solution flows through the oxidant inlet and / or through the relatively high pressure or relatively high velocity nebulizer.

The technology disclosed herein further includes a method of operating a redox fuel cell system. The method preferably comprises the steps of: providing a redox fuel cell system as disclosed herein; and direct introduction of oxidant into the fluid conduit system. The introduction of oxidizing agent can be carried out, for example, by at least one misting device and / or at least one oxidant inlet.

The introduction of oxidizing agent into the fluid line system can preferably take place by means of at least one jet pump, which conveys the oxidizing agent at least in a partial load range of the redox fuel cell system. In particular, in a part load range in which the main oxidation fluid delivery unit, z. As a compressor, a lower efficiency or higher power consumption than the at least one jet pump. The at least one jet pump can preferably promote the oxidizing agent at least in the lower part-load range of the redox fuel cell system. Advantageously, the oxidant supply without the operation of a Hauptoxidationsfluidfördereinheit exclusively via at least one jet pump and / or at least one other Oxidationsfluidfördereinheit carried out. The exclusive operation preferably takes place via the at least one jet pump and / or at least one further oxidation fluid delivery unit only in the lower part-load range.

The main oxidation fluid delivery unit may promote the oxidant, for example, in an upper part-load range of the redox fuel cell system. Preferably, the method further comprises the step of dividing the stream of catholyte solution into a plurality of partial streams, wherein at least one partial stream flows through at least one jet pump in such a way that oxidizing agent is sucked in. Furthermore, at least two different jet pumps can be flowed through by catholyte solution such that in each case oxidizing agent can be sucked in. The splitting of the stream of catholyte solution into a plurality of partial streams through the at least one fluid flow regulator can be effected, for example, as a function of the load of the fuel cell system. The load of the fuel cell system here is the driver's / vehicle's requested electrical power that the fuel cell system is to provide to the vehicle. If, for example, a load is requested from the lower part-load range, the control of the fuel cell system, for example, may find that sufficient regeneration can be provided by operating one or more jet pumps. The controller may then turn off the main oxidation fluid delivery unit and, via the at least one fluid flow regulator, switch the one or more jet pump (s) to the fluid circuit thereto, for example by activating a bypass circuit. In this case, the catholyte flow rate is then preferably controlled or regulated such that the jet pump (s) are operated efficiently.

Hereinafter, the disclosed technology will be explained with reference to Figs

1 to 8th schematically the basic structure of a redox fuel cell system; and

9 show the overall efficiency of the fuel cell system.

1 shows a redox fuel cell system 10 , By the feed 22 Fuel, in this case hydrogen, enters the anode 20 , The anode 20 is performed by the separator S, here as a proton exchange membrane PEM, from the cathode 30 separated. On the anode side, hydrogen is oxidized as in conventional fuel cells. The protons pass through the separator into the region of the cathode 30 , The cathode 30 is via a fluid line system 100 . 110 with the regenerator 60 connected. From the regenerator 60 exiting regenerated catholyte solution L _ox with an increased proportion of oxidized redox molecules passes through the second fluid line 110 to the cathode 30 , There, the catholyte solution L is at least partially reduced. At the same time she picks up the protons. The reduced catholyte solution L _red then passes through the first fluid line 100 into the regenerator R. In the regenerator R, the catholyte solution is regenerated. Ie. the redox molecules are again oxidized as much as possible and also release the protons. It creates a cycle, driven by the pumping device 80 in which at least parts of the catholyte solution L are continuously reduced and oxidized. The main oxidation fluid delivery unit 70 promotes oxidizing fluid, here oxygen or air, in the regenerator R. As a reaction product, water or water vapor leaves the regenerator R. Downstream of the regenerator R is the fluid collecting device 90 arranged. The fluid collecting device 90 is here as a capacitor 90 executed and separates water from the outflowing gases. Not shown is the at least one oxidant inlet 120 . 120 ' . 120 '' through which the oxidant enters the fluid line system 100 . 110 flows, which also comes to the regeneration in the fluid line system.

2 shows a redox fuel cell system 10 in which the main oxidation fluid delivery unit 70 directly via a supply line 72 with the regenerator 60 connected is. A second supply line 74 goes from the supply line 72 to an oxidant inlet 120 from. The oxidant inlet 120 is here in the first fluid line 100 of the fluid line system 100 . 110 between the cathode 30 and the regenerator 60 arranged. The pressurized oxidant thus flows from the Hauptoxidationsfluidfördereinheit 70 in the two supply lines 72 and 74 , Through the oxidant inlet 120 the oxidant enters the first fluid line 100 introduced or injected. Downstream of the oxidant inlet 120 A turbulent flow forms here, in which the oxidizing agent and the catholyte solution L mix well. It comes in this section of line 114 already for the partial regeneration of the catholyte solution L, in the regenerator 60 can be continued. The at least partially regenerated catholyte leaves the regenerator 60 and passes through a connector 112 in the catholyte separator 92 , In the catholyte separator 92 Excess oxidant and the resulting water during regeneration is separated from the catholyte solution. The regenerated catholyte solution L then flows through the second fluid line 110 into the cathode. The fluid circuit is driven here by a pump 80 that's here in the second fluid line 110 is arranged.

3 shows a redox fuel cell system 10 in which in the first fluid line 100 a fluid flow actuator or fluid flow regulator 130 is arranged. The fluid flow regulator 130 can be here as Valve 130 be configured, which divides the incoming total flow of catholyte in two sub-streams. A first partial flow flows through the downstream of the valve 130 arranged part 114 the first fluid line 100 , A second portion of the flow of catholyte solution flows through the bypass line 104 , The bypass line 104 here includes an oxidant inlet 120 ' that has a supply line 74 ' with another oxidizing fluid delivery unit 70 ' connected is. It can therefore be regenerated preferably in the bypass line catholyte. The bypass line 104 can in the connector 112 in front of the catholyte separator 92 lead. It is also possible to use all bypass lines without oxidant inlet 120 ' and without another Oxidationsfluidfördereinheit 70 ' provided. Instead of another oxidation fluid unit 70 ' may be the supply to the oxidant inlet 74 ' also in fluid communication with the main oxidation fluid delivery unit 70 be connected. Likewise, the oxidant inlet can be used as a jet pump 120 be executed. Then the further oxidation fluid unit 70 ' omitted. Instead of a pumping device 80 Here are two smaller pumping devices 80 ' provided that apply the required pump power.

The redox fuel cell system according to 4 also includes those related to 3 described bypass line 104 as well as the described fluid flow regulator 130 , Here are two oxidant inlets 120 ' . 120 '' provided, which are connected here in series, ie one behind the other. The two oxidant inlets are through the supply line 74 ' supplied by a common further Oxidationsfluidfördereinheit with oxidizing agent. There could also be two more oxidation fluid delivery units 70 ' be provided, each having an oxidant inlet 120 ' . 120 '' supply with oxidizing fluid. However, the two oxidant inlets are preferred 120 ' . 120 '' as jet pumps 120 ' . 120 '' designed. The further oxidation fluid delivery unit 70 ' then disappears. The jet pumps 120 ' . 120 '' are in particular designed differently and have different operating characteristics. Also, all oxidant inlets shown could be via a central main oxidation fluid delivery unit 70 be fed. Shown dashed is the oxidant inlet 120 as he already related 2 was explained. In this context, it should be noted that all configurations included in the 2 to 8th shown can also be combined with each other. For example, the configuration according to the 2 combine with one of the configurations according to the 3 to 8th , In front of the oxidant inlet 120 is another pumping device 82 arranged here directly into the regenerator 60 inflowing partial flow of catholyte solution promotes. The pumping device is immediately adjacent upstream of the oxidant inlet 120 arranged.

5 shows a configuration with a bypass line 104 in which two oxidizer inlets 120 ' . 120 '' are arranged parallel to each other. The supply lines 74 ' were omitted here. As in the 3 and 4 The oxidant inlets may be shown with a common or separate further oxidation fluid delivery unit (s). 70 ' or with the main oxidation conveyor unit 70 be connected. Particularly preferred in the embodiment according to the 5 as well as in the embodiments according to the other figures jet pumps used. In the embodiment shown here are two fluid flow controllers 130 . 130 ' provided, which are controlled such that the catholyte flow in the desired speed to the respective oxidant inlet 120 ' . 120 '' flows. This adaptation takes place as a function of the operating state of the fuel cell or of the fuel cell system (eg the load request by the driver).

6 shows a redox fuel cell system in which in the connector 112 between regenerator 60 and catholyte separator 92 an oxidant inlet 120 is provided. In the connector 112 also opens a recirculation section shown in dashed lines 160 , The recirculation section 160 branches downstream of the pumping device 80 Catholyte solution. In this branched partial flow is through the oxidant inlet 120 ' Oxidizing agent introduced for regeneration, which later through the catholyte separator 92 is disconnected. The pipe sections 160 . 112 . 110 form a recirculation circuit here. It may be upstream just before the oxidant inlet 120 another pump 82 be provided.

7 shows two further aspects of the technology disclosed herein. For one, here is a structural unit of regenerator 60 and catholyte separator 92 shown here in a housing 62 are arranged. By placing both components in a housing 62 a comparatively small and inexpensive construction is achieved. If such a structural unit used with a housing, so eliminates the connector 112 , The inflow of the bypass, as he, for example, in the 3 to 6 can be shown here above the separator 92 into the structural unit 62 respectively. The foam-like mixture comprising, for example, oxidizing agent and catholyte solution can be used in the catholyte separator 92 For example, be converted into two separate phases. These separate phases can then enter the container 150 flow, from which they then flow separately. Alternatively and / or additionally, the separate phases could also be separated by separate outputs 92 leave.

Another aspect presented here concerns the container 150 , The container 150 here represents a structural unit with the pumping device 80 which promotes the catholyte solution in the fluid circuit. The container 150 may, for example, as part of the pumping device 80 be executed. Furthermore, the container 150 serve as a reservoir. The reservoir can, for example, with an oxidant line 76 be equipped. From the container 150 can be sucked oxidant-free catholyte solution. By the residence time in the container 150 or by additional measures, for example, the oxidizing agent is largely separated. Also, the catholyte solution may be drained into the container, for example, when the system or vehicle is not operating. So it's possible that on the catholyte separator 92 is dispensed and the container 150 takes over this function with. From the regenerator 60 would then, for example, the mixture of catholyte and oxidizing agent and the reaction product water in the container 150 flow. Not shown here are the at least one oxidant inlet or jet pump 120 . 120 ' . 120 '' and / or the at least one fogging device 140 . 140 ' , In principle, all oxidant inlets disclosed herein are 120 . 120 ' . 120 '' and / or nebulizers 140 . 140 ' combined.

8th shows a redox fuel cell system 10 in which nebulizer devices 140 . 140 ' . 140 '' be used. The fogging devices 140 . 140 ' . 140 '' lead into the container here 150 , It is also possible that this nebulizing device within the fluid line (s) 100 . 110 . 112 is provided, wherein the diameter of the fluid line (s) is preferably increased in the nebulization section / are. The fogging devices 140 . 140 ' . 140 '' nebulize or atomize the catholyte solution L in the container 150 is injected. This forms aerosol particles, ie small mediator liquid droplets that can react with the oxidizing agent. Such fogging devices can be designed as simple injection nozzles or as Venturi nozzles. Particularly advantageous for these fogging devices 140 . 140 ' . 140 '' is that no other catholyte separator 92 must be used, which separates the oxidant from the catholyte. The droplets can not penetrate the liquid surface. In the embodiment of the container shown here 150 are the pumping device 80 and the container 150 run separately from each other. Shown dashed is another recirculation circuit, which in turn is optional. The recirculation section 160 branches catholyte solution from the container 150 from. The further pumping device 82 promotes the catholyte solution to another nebulization device 140 '' which sprays the catholyte solution. The container 150 and the recirculation section 160 form a recirculation circuit here.

9 schematically shows the efficiency of the fuel cell system for different current densities. The efficiency of the overall system is stated in each case. As a comparison value, the efficiency of a redox fuel cell system is shown in dotted lines, in which the oxidizing agent flows from the main oxidation fluid delivery unit into the regenerator. The regeneration takes place here only in the regenerator. Especially in the lower part load range, the system is inefficient due to the losses in the main oxidation fluid delivery unit. Dashed lines show the course according to the present invention with a jet pump 120 that in the first fluid line 100 is provided. The efficiency of this system is increased compared to the system without regeneration in the fluid line system. Shown as a solid line is a redox fuel cell system with a jet pump 120 , which is switched on only in the lower part load operation. The efficiency in the lower part-load operation is higher than in the other systems.

The foregoing description of the present invention is for illustrative purposes only, and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

LIST OF REFERENCE NUMBERS

10

Redox fuel cell

20

anode

22

supply

30

cathode

40

ion-selective separator

50

Device for providing an electrical circuit

60

regenerator

62

structural unit, housing

70

Main oxidizing fluid delivery unit

70 '

further oxidation fluid delivery unit

72

Regeneratorzuleitung

74

Supply line to Oxidationsmittelauslass

76

Outlet of the container

80, 80 '

pumping device

82

further pumping device

90

Fluid collection device

92

Catholyte separator

100, 110

Fluid line system, fluid circuit

100

first fluid line

102

joint

104

bypass line

110

second fluid line

114

Part of the first fluid line

120, 120 ', 120' '

Oxidant inlet

130, 130 '

Fluid flow regulator, fluid flow actuator, valve

140, 140 ', 140' '

Fogging device, atomizer

150

container

L

catholyte

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2014/001786 A1 [0002]
• DE 102013217858 A1 [0002, 0003]
• EP 1999811 B1 [0002]
• WO 2010/128333 A1 [0002]

Cited non-patent literature

• "Journal of Power Sources 201 (2012, pages 159-163, authors: R. Singh, AA Shah, A. Potter, B." Performance and analysis of a novel polymer electrolyte fuel cell using a solution based redox mediator ". Clarkson, A. Creeth, C. Downs, FC Walsh) [0009]

Claims (15)

Redox fuel cell system ( 10 ), comprising: - at least one redox fuel cell having an anode ( 20 ) and a cathode ( 30 ) separated by an ion-selective separator ( 40 ) are separated, wherein the anode ( 20 ) a feeder ( 22 ) for a fuel to the anode; and at least one regenerator ( 60 for the regeneration of a catholyte solution (L) by an oxidizing agent, wherein the cathode ( 30 ) and the regenerator ( 60 ) by a fluid line system ( 100 . 110 ) are connected so that the catholyte solution (L) between the cathode ( 30 ) and the regenerator ( 60 ) can circulate; characterized in that the fluid conduit system ( 100 . 110 ) at least one oxidant inlet ( 120 . 120 ' . 120 '' ), through which the oxidizing agent in the fluid line system ( 100 . 110 ) flows. Redox fuel cell system ( 10 ) according to claim 1, wherein the redox fuel cell system ( 10 ) at least one fogging device ( 140 . 140 ' . 140 '' ) containing the catholyte solution within the fluid conduit system ( 100 . 110 ) and / or in one with the fluid line system ( 100 . 110 ) fluid-connected containers ( 150 ) fogged. Redox fuel cell system ( 10 ) according to one of the preceding claims, wherein at least one bypass line ( 104 ) upstream of the regenerator ( 60 ) branches off and downstream of the regenerator ( 60 ), wherein at least one oxidant inlet ( 120 . 120 ' . 120 '' ) and / or at least one fogging device ( 140 . 140 ' . 140 '' ) in the bypass line ( 104 ) is / are arranged. Redox fuel cell system ( 10 ) according to any one of the preceding claims, wherein the oxidant inlet ( 120 . 120 ' . 120 '' ) and / or the fogging device ( 140 . 140 ' . 140 '' ) is designed as a Venturi nozzle / are. Redox fuel cell system ( 10 ) according to one of the preceding claims, wherein at least two oxidant inlets ( 120 . 120 ' . 120 '' ) are provided, which are each arranged in series and / or parallel to each other. Redox fuel cell system ( 10 ) according to any one of the preceding claims, wherein the oxidant inlet ( 120 . 120 ' . 120 '' ) as a jet pump ( 120 . 120 ' . 120 '' ), and wherein the jet pump ( 120 . 120 ' . 120 '' ) is designed and arranged such that oxidizing agent can be sucked into the fluid line system. Redox fuel cell system ( 10 ) according to claim 6, wherein the redox fuel cell system ( 10 ) at least two different jet pumps ( 120 . 120 ' . 120 '' ). Redox fuel cell system ( 10 ) according to one of the preceding claims, wherein the fuel cell ( 10 ) at least one fluid flow regulator ( 130 . 130 ' ), which is suitable for dividing a stream of catholyte solution into a plurality of partial streams. Redox fuel cell system ( 10 ) according to one of the preceding claims, wherein the redox fuel cell system ( 10 ) a main oxidation fluid delivery unit ( 70 ), which is suitable in the regenerator ( 60 ) To supply oxidizing agent, wherein a further oxidation fluid delivery unit ( 70 ' . 70 '' ) is provided, which is suitable, the at least one oxidant inlet ( 120 . 120 ' . 120 '' ) with oxidizing agent. Method for operating a redox fuel cell system ( 10 ), comprising the steps: - providing a redox fuel cell system ( 10 ) according to one of the preceding claims 1 to 9; and - introduction of oxidant into the fluid line system ( 100 . 110 ). The method of claim 10, wherein for introducing oxidant into the fluid line system ( 100 . 110 ) the at least one jet pump ( 120 . 120 ' . 120 '' ) the oxidizing agent at least in a partial load range of the redox fuel cell system ( 10 ) promotes. The method of claim 11, wherein the redox fuel cell system ( 10 ) a main oxidation fluid delivery unit ( 70 ), which is suitable in the regenerator ( 60 ) To supply oxidizing agent, wherein the at least one jet pump ( 120 . 120 ' . 120 '' ) promotes the oxidant at least in a lower part-load range of the redox fuel cell system, and wherein the main oxidation fluid feed unit ( 70 ' . 70 '' ) promotes the oxidizing agent in an upper part-load range of the redox fuel cell system. A method according to claim 11 or 12, wherein at least two different jet pumps ( 120 . 120 ' . 120 '' ) can be flowed through by catholyte so that oxidizing agent can be sucked. Method according to one of claims 11 to 13, comprising the step: - dividing the stream of catholyte solution into a plurality of substreams, wherein at least one substream comprises at least one jet pump ( 120 . 120 ' . 120 '' ) flows through in such a way that oxidizing agent is sucked. The method of 14, wherein dividing the flow of catholyte solution into a plurality of substreams by the at least one fluid flow regulator (15). 130 . 130 ' ) takes place as a function of the load of the fuel cell.

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