Fuel cell system for generating electrical energy

Abstract

The present invention relates to a fuel cell system (100) for generating electrical energy, comprising a fuel cell stack (110) with an anode section (120) and a cathode section (130), the anode section (120) having an anode supply section (122) for supplying an anode feed gas (AZG) and an anode discharge section (124) for discharging an anode exhaust gas (AAG), the anode discharge section (124) transitioning to an anode recirculation section (140) for recirculating the anode exhaust gas (AAG) to the anode supply section (122) as an anode recirculation gas (ARG), and the cathode section (130) for discharging a cathode feed gas (KZG). and a cathode discharge area (134) for discharging a cathode exhaust gas (KAG). An active cooling device (180) for cooling the anode recirculation gas (ARG) is arranged in the anode recirculation area (140). A water discharge section (128) for condensed water (KW) condensed in the active cooling device (180) is arranged downstream of the active cooling device (180). A mixing area (123) is arranged downstream of the water discharge section (128) for mixing the combustion gas (BRG) and the anode recirculation gas (ARG) and for supplying the ARG to the anode supply area (122) as an anode supply gas (AZG).

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system for producing electrical energy and to a method for recycling anode exhaust gas in such a fuel cell system. [Background technology]

[0002] It is known to use fuel cell systems for the production of electrical energy. To this end, such fuel cell systems typically comprise a fuel cell stack, in which a number of individual fuel cells, each having an anode region and a cathode region, are arranged in a stack. To produce electrical energy, fuel gases and usually ambient air are supplied to the fuel cell stack, where they can undergo chemical conversion while producing electrical energy.

[0003] In known fuel cell systems, hydrogen or natural gas is usually used as the fuel gas, and in addition, in order to improve the efficiency of fuel gas utilization, it is also known that a portion of the fuel gas that is not converted in the fuel cell stack during conversion is supplied again to the fuel cell stack for the next cycle as a recycle gas.

[0004] A drawback of known solutions is that recirculation can reduce efficiency during operation, especially when hydrogen is used as the fuel gas. When hydrogen is supplied to a fuel cell stack, it is converted in the anode region into a mixture of water and residual hydrogen that remains in the anode exhaust gas. When this mixture is recirculated, the water contained therein can significantly reduce the Nernst voltage. For a fuel cell stack, a decrease in Nernst voltage leads to a decrease in efficiency, which usually offsets the efficiency gains achieved by recirculation. In other words, when a fuel cell system is operated with hydrogen, recirculation does not lead to the desired increase in efficiency, or only to a reduced extent.

[0005] Although it is already known in principle that cooling of the anode exhaust gas during recirculation can be used to condense a portion of the water contained therein and to separate this condensed water, such designs are very complex and expensive. In particular, such designs rely on the use of an external cooling circuit that can deliver coolant to the recirculation piping via an external heat sink to induce condensation of the water vapor in the anode exhaust gas. The addition of an additional cooling circuit and the corresponding peripheral equipment undesirably increases the complexity and cost of the fuel cell system. Summary of the Invention [Problem to be solved by the invention]

[0006] Further fuel cell systems with anode recirculation piping are known from US 2008 / 187789 A1, US 2007 / 017368 A1, and WO 2021199103 A1. [Means for solving the problem]

[0007] The above-mentioned problem is solved by a fuel cell system having the features of claim 1 and a method having the features of claim 14. Further features and details of the invention will become apparent from the dependent claims, the detailed description and the drawings, whereby features and details described in the context of the fuel cell system according to the invention are naturally also relevant in the context of the method according to the invention and vice versa, so that cross-reference is always made or can be made to the disclosure of the individual inventive aspects.

[0008] According to the present invention, a fuel cell system for generating electrical energy is proposed. Such a fuel cell system includes a fuel cell stack having an anode section and a cathode section. The anode section includes an anode supply section for supplying an anode feed gas and an anode discharge section for discharging an anode exhaust gas. The anode supply section further transitions to an anode recirculation section for recirculating the anode exhaust gas to the anode supply section as anode recirculation gas. Similarly, the cathode section includes a cathode supply section for supplying a cathode feed gas and a cathode discharge section for discharging the cathode exhaust gas. The fuel cell system according to the present invention is characterized in that an active cooling device is arranged in the anode recirculation section for cooling the anode recirculation gas. A water discharge section is arranged downstream of the active cooling device for removing condensed water condensed in the active cooling device. Furthermore, a mixing section is arranged downstream of the water discharge section for mixing the combustion gas with the anode recirculation gas and for supplying the anode recirculation gas to the anode supply section as anode feed gas.

[0009] The central idea of the present invention is to ensure the recirculation of anode exhaust gas as anode recirculation gas. The recirculation of the anode recirculation gas is carried out in dry form, i.e., by passing it through an active cooling device. In this active cooling device, the temperature of the anode recirculation gas is lowered below the condensation temperature of water, i.e., below approximately 100°C, depending on the pressure conditions and the partial pressure, which depends on the gas composition. This leads to the condensation of water vapor contained in the anode recirculation gas and the appearance of liquid condensate.

[0010] A separator serving as a water discharge is provided downstream of the active cooling device, where the condensed components, and therefore the condensed water, are separated from the gaseous components of the anode recirculation gas. The liquid condensed water can then be removed from the system and, for example, discharged to the environment. The remaining anode recirculation gas, also referred to as dry anode recirculation gas, can be supplied to a mixing zone in this dry state. In this mixing zone, which may be configured, for example, as an ejector device, a mixing chamber, or similar, the combustion gas supplied from the combustion gas source and the anode recirculation gas are mixed. Depending on how much anode recirculation gas is available, the remaining required amount of combustion gas can be mixed accordingly. The mixture of combustion gas and anode recirculation gas is then supplied back to the anode zone of the fuel cell stack as anode feed gas.

[0011] The central idea of the present invention is that, in particular, an external cold air source and a separate external cold air circuit are not required for condensation of the condensate of the anode recirculation gas or the anode exhaust gas. Instead, an active cooling device is provided in the manner according to the present invention. The condensation process in this active cooling device, according to the present invention, takes place without the influence of an external cooling source, in particular without a cooling circuit external to the fuel cell system.

[0012] It should also be noted that in complex fuel cell systems, cooling circuits may of course be provided at other locations to allow the desired temperature regulation process to be carried out. In particular, in the case of a fuel cell system configured as an SOFC system, due to the expected extremely high temperatures, for example, a portion of the fuel cell stack may be configured with an external cooling device. However, in the present invention, such an external cooling source is not utilized for the condensation function of the anode recirculation gas or the anode exhaust gas.

[0013] According to the present invention, the integration of the condensation function with an active cooling device results in the desired condensation of condensed water in the anode recirculation gas. Accordingly, the dry anode recirculation gas is mixed with the combustion gas, realizing the correspondingly desired efficiency increase due to the recirculation without the penalty of the reduced Nernst voltage that occurs in the case of undried anode recirculation gas. Compared to known solutions, this drying step and the associated efficiency increase are realized without additional complex components during the operation of the fuel cell system.

[0014] In addition to the resulting increased efficiency, it is even possible to use a smaller ejector, since the unwanted condensate is separated and therefore a correspondingly smaller volumetric flow rate has to be mixed into the combustion gases.

[0015] In the solution of the fuel cell system according to the invention, an active cooling device replaces the use of a separate external cooling circuit. Within the scope of the present invention, an active cooling device refers to the active generation of cold air and thus the active generation of a heat sink. Thermally and / or electrically activated heat sinks are particularly contemplated. A thermally activated heat sink can be, for example, an absorption heat pump. Cold air generated by the use of an electric compressor and the corresponding pressure change through the refrigerant can also be used as an electrically activated cooling device. Naturally, other active cooling devices are also conceivable in principle, which generate the desired heat sink in situ without the need for a separate external cooling circuit.

[0016] A key advantage of the fuel cell system according to the present invention is that, through active cooling, a maximum recirculation rate of up to 100% of the anode exhaust gas as anode recirculation gas is possible. In other words, it is possible to configure the anode section as a so-called dead end, since 100% of the anode exhaust gas discharged there is fed back into the anode supply gas as anode recirculation gas. This further reduces the overall system complexity of the fuel cell system and, in particular, makes it possible to substantially completely avoid the costs of exhaust gas aftertreatment. In known solutions, the recovered exhaust gas of a fuel cell system must typically be aftertreated, for example, by an oxidation catalyst, in order to oxidize the residual combustion gases remaining in the anode exhaust gas and thereby properly combust it before the mixed exhaust gas is released into the environment. In the embodiment of the fuel cell system according to the present invention, a 100% feedback rate or recirculation rate of the anode exhaust gas is possible, so that release of the anode exhaust gas into the environment is not intended at all. Consequently, aftertreatment of the anode exhaust gas that is not released into the environment is also not required. Finally, it should be pointed out that the mixing section, for example in the form of an injector device, can also be operated with lower pressure on the primary side and can be constructed accordingly more compact and less expensive.

[0017] In the fuel cell system according to the present invention, the active cooling device is intended to comprise a thermally activated cooling device, in particular an absorption heat pump. The active cooling device is in heat-transfer contact with the cathode exhaust area and is configured for thermal activation by the heat contained in the cathode exhaust gas. As already explained in the introduction, a thermally activated cooling device is one possible embodiment of the active cooling device according to the present invention. In this embodiment, in addition to the above, heat provided by the fuel cell system itself is also used for thermal activation. When the individual gases are converted in the fuel cell stack, a large amount of heat is generated as a by-product. This heat generates the anode exhaust gas and the cathode exhaust gas accordingly. The heat present in the cathode exhaust gas can therefore be used, at least in part, for thermal activation of such a cooling device. A thermally activated cooling device means that the hot cathode exhaust gas is used as energy in such a thermally activated cooling device, is cooled in the process, and thus provides a heat sink. To utilize this thermal energy for cooling, thermally activated cooling devices are typically equipped with an absorption heat pump, which allows for the efficient generation of a heat sink for the anode exhaust gas of the anode recycle gas through the absorption and desorption processes. It is again clear that such active cooling devices do not require external energy or an external cooling circuit. Apart from a circulation pump, which may be required for the refrigerant between the absorption and desorption sections of such thermally activated cooling devices, no external energy input or, in particular, a supply of an externally cooled refrigerant is required.

[0018] Alternatively or additionally, in the fuel cell system according to the invention, the active cooling device can comprise an electrically operated cooling device. This can be intended as an addition or replacement to a thermally operated cooling device, in particular a cold air circuit machine that constitutes a conventional heat pump with a compressor. In this way, the direct injection of electrical energy at the active cooling device can provide the desired heat sink and, accordingly, the condensation function for the condensed water in the anode recirculation gas.

[0019] Further advantages can be realized in the fuel cell system according to the present invention if the anode recirculation section includes a condenser in heat-transfer contact with the cathode supply section. This serves to cool the anode recirculation gas by heating the cathode supply gas. A separate water outlet is then arranged downstream of the condenser and upstream of the active cooling device for discharging the condensed water condensed in the condenser. In other words, in this embodiment, two-stage cooling and therefore two-stage condensation are also possible. This means that the anode exhaust gas leaves the anode section at a high discharge temperature, is brought to the desired temperature in several steps, and is mixed with the combustion gas at this temperature as anode recirculation gas. Two cooling steps and two condensation steps are implemented here, whereby in the first step, the still-hot anode exhaust gas is cooled via ambient air, which can have different ambient air temperatures in different regions. As a result, in particularly high-temperature areas, the ambient air drawn in as cathode supply gas can have a temperature of 50°C or higher, which limits the cooling effect on the hot anode exhaust gas. Because the volumetric flow rate of air as cathode supply gas can be flexibly varied, albeit only to a limited extent, this cooling and condensation can be followed by an active cooling device according to the present invention, which can be designed to be smaller and more compact than conventional solutions, since the condenser already provides pre-condensation. The cooling waters flowing out of both water outlets can be discharged separately to the environment by appropriate separators at the water outlets, or they can be combined and discharged together.

[0020] In addition, it may be preferable for the cathode discharge area in the fuel cell system according to the present invention to be configured without a catalyst device and / or a burner. As already explained, the fuel cell system according to the present invention provides, in particular, for the complete recirculation of the anode exhaust gas as the anode recirculation gas. As a result, the anode exhaust gas is not discharged to the environment, and therefore post-treatment of any residual fuel present in this anode exhaust gas is also not necessary. Instead, only the cathode exhaust gas is discharged to the environment, which does not contain any fuel in a functional fuel cell. The omission of the catalyst device and / or the burner leads to a more compact, lightweight, and inexpensive design of the entire fuel cell system.

[0021] Additionally, it may be advantageous if the anode discharge zone and the anode recirculation zone in the fuel cell system according to the present invention are configured without a separate zone for the complete or substantially complete recirculation of the anode exhaust gas as the anode recirculation gas. As already explained, this is only possible with the use of an active cooling device, which offers another advantage, for example, the omission of the catalytic converter described in the previous paragraph. That is, no exhaust gas is generated on the anode side that must be discharged to the environment, and therefore no aftertreatment is required. By eliminating such a separate zone, the entire fuel cell system can be configured without such components, which makes it simpler, more cost-effective, and more compact.

[0022] It is also advantageous if a discharge valve for controlled release of at least one portion of the recirculated gas is arranged in the anode recirculation zone downstream of the active cooling device and downstream of the water discharge. While a preferably complete recirculation rate is intended for the anode exhaust gas in the fuel cell system according to the present invention, it is possible that such complete recirculation is undesirable under specific circumstances of the fuel cell system. To provide control flexibility, the discharge valve allows a portion of the recirculated gas to be discharged to the environment in a controlled manner, at least qualitatively, preferably quantitatively. Since the anode recirculated gas usually contains a residual amount of fuel, such a discharge valve can preferably be integrated with a catalytic device, so that, in this special case, the anode exhaust gas as the anode recirculated gas is catalytically post-treated and the residual fuel is thus oxidized. In particular, the discharge valve is intended and configured solely for controlled release of at least one portion of the recirculated gas. This prevents, in particular, any form of heat transfer and therefore no permanent division. If the hydrogen is at least substantially pure, such a release valve is not normally provided.

[0023] In a fuel cell system according to the invention, it may be advantageous if the anode discharge area has an anode discharge heat exchanger in heat transfer contact with the anode supply area for heat transfer from the anode exhaust gas to the anode supply gas. This allows for even greater efficiency in terms of temperature. In this way, in conjunction with various other possible heat exchangers, which will be described later, a heat exchange system with an active cooling device is created, which can also be called a temperature regulation system, allowing as much residual heat as possible in both the anode exhaust gas and the cathode exhaust gas to be reused and used for other functions, such as condensation or the supply and conditioning of the anode supply gas and the cathode supply gas. Accordingly, this embodiment offers the possibility of cooling the hot anode exhaust gas and utilizing its energy to heat the anode supply gas when it is supplied to the anode area. As a side effect, this leads to the anode exhaust gas reaching the active cooling device already pre-cooled, which allows the active cooling device to assume a correspondingly lower input temperature, resulting in a corresponding reduction in the required cooling power.

[0024] In the fuel cell system according to the present invention, it is also advantageous if the mixing section is configured as an ejector device, with a fuel supply of combustion gas at the primary connection of the ejector device and an anode recirculation section at the secondary connection of the ejector device. Using an ejector device instead of a conventional fan device for the mixing section offers many advantages. On the one hand, rotating components and, accordingly, wear parts are eliminated. On the other hand, mixing and delivery are preferably combined in a common component, so that a separate delivery device is not required in the anode supply section, especially when a combustion gas source with a high delivery pressure is available. Instead, it is sufficient to apply the appropriate combustion gas with the desired prepressure to the primary connection of the ejector device, and the corresponding suction action at the secondary connection of the ejector device draws in the dry anode recirculation gas for mixing. This results in an improved overall efficiency for the fuel cell system according to the present invention, and in particular improved wear resistance.

[0025] Another advantage of the fuel cell system according to the present invention is realized when the cathode supply section includes a cathode supply heat exchanger in heat transfer contact with the cathode discharge section for heat transfer from the cathode exhaust gas to the cathode supply gas. Preconditioning the cathode supply gas so that it enters the cathode section at as high a temperature as possible, and thus particularly close to the operating temperature of the fuel cell stack, similar to preheating the anode supply gas, further improves the efficiency of the fuel cell system during operation. Because the cathode exhaust gas is at a correspondingly high operating temperature as a result of the chemical reactions within the fuel cell stack, this high temperature can be utilized to partially release it into the cathode supply gas. This corresponds to preconditioning in the form of preheating the cathode exhaust gas to the cathode supply gas. Such recovery of the heat contained in the cathode exhaust gas further improves efficiency and avoids heat loss through the cathode exhaust gas.

[0026] It is also advantageous if a cathode exhaust heat exchanger for transferring heat from the cathode exhaust gas to the anode supply gas is arranged in the anode supply section, preferably downstream of the anode supply heat exchanger. This allows the heat contained in the cathode exhaust gas to be transferred to the anode supply gas, either additionally or alternatively. In addition, in combination with the anode supply heat exchanger, this allows for a correspondingly improved preheating function, or, in other words, for the anode supply gas to be heated to a higher temperature. As already mentioned, a fuel cell system according to the present invention can be equipped with a heat exchanger system at multiple locations throughout the heat exchange function. Naturally, the individual heat exchangers of this heat exchange system can be controlled via valves, which allows, in particular, for flexible activation or deactivation of various parts of such a heat exchange system depending on the operating situation. This allows for precise and flexible adaptation to various operating situations and always achieving the maximum temperature difference.

[0027] It may also be advantageous if a cathode supply heat exchanger is arranged in the cathode supply section of the fuel cell system according to the invention for heat transfer from the cathode exhaust gas to the cathode supply gas. This can be considered as an alternative or in addition to the other heat exchangers mentioned above, and it should be noted that valves are preferably capable of activating and deactivating the various heat exchangers. In this case, too, the residual heat of the cathode exhaust gas can be utilized by heat transfer to ensure preconditioning in the form of pre-temperature adjustment of the cathode supply gas, thereby further improving the operating efficiency of the fuel cell system.

[0028] In addition, in the fuel cell system according to the present invention, it may be preferable to arrange a control valve in the anode supply section upstream of the mixing section for controlling the volumetric flow rate of the combustion gas through the mixing section. This allows the amount and pressure of the fuel gas to be controlled in a controlled manner, particularly from a pressure-biased combustion gas source. Depending on the divided amount of the anode recirculation gas, a correspondingly adapted amount of combustion gas can be added, so that the desired composition and the desired volumetric flow rate of the anode supply gas are always actually provided in the anode section. Therefore, the control valve is preferably a quantitatively controllable control valve, in order to be able to adapt appropriately to various operating conditions of the fuel cell system.

[0029] In addition, in the fuel cell system according to the invention, it is preferred if the anode discharge area is configured without an external cooling circuit. As already explained, the central idea of the invention is to provide such a condensation function as efficiently as possible and without additional complexity. The configuration of the anode discharge area without an external cooling circuit represents precisely this reduced complexity, since the condensation function is at least partially ensured by the heat sink of the active cooling device.

[0030] It is also preferred in the fuel cell system according to the invention if a cathode mixing section, particularly in the form of an ejector device, is arranged in the cathode supply section. A secondary connection to such an ejector device is fluidly connected to a cathode recirculation section for the recirculation of a portion of the cathode exhaust gas as cathode recirculation gas. In combination with the recirculation to the anode section, this can also be called double recirculation. This allows the cathode exhaust gas and the residual oxygen contained therein to be fed back to the cathode section in a mixture with the cathode supply gas.

[0031] In principle, within the scope of the present invention, it may be desirable to provide for regenerative adsorption, in which case the water vapor is regeneratively separated, for example, by silica gel pads. In particular, regenerative separating elements, such as silica gel pads, are arranged in an active cooling device.

[0032] Another subject of the present invention is a method for the recirculation of anode exhaust gas as anode recycle gas in a fuel cell system according to the present invention, comprising the following steps: - cooling the anode recirculation gas below the boiling temperature of water by active cooling with an active cooling device; - the condensed water is separated from the anode recirculation gas; The dry recirculated gas is mixed with the combustion gas to provide the anode feed gas.

[0033] The application of the method of the invention in a fuel cell system according to the invention provides the same advantages as those detailed in relation to the fuel cell system according to the invention. [Brief explanation of the drawings]

[0034] Other advantages, features and specific features of the invention will become apparent from the following description of an embodiment of the invention, which is given with reference to the drawings, in which: FIG.

[0035] [Figure 1] 1 is an embodiment of a fuel cell system according to the present invention. [Figure 2] 3 is another embodiment of a fuel cell system according to the present invention. [Figure 3] 3 is another embodiment of a fuel cell system according to the present invention. [Figure 4a] 3 is another embodiment of a fuel cell system according to the present invention. [Figure 4b] 3 is another embodiment of a fuel cell system according to the present invention. [Figure 5] 3 is another embodiment of a fuel cell system according to the present invention. [Figure 6] 3 is another embodiment of a fuel cell system according to the present invention. [Figure 7] 3 is another embodiment of a fuel cell system according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] FIG. 1 shows a schematic diagram of a fuel cell system 100 having a fuel cell stack 110 with an anode section 120 and a cathode section 130. The anode section is supplied with an anode supply gas AZG via an anode supply section 122, and an anode exhaust gas AAG is discharged via an anode discharge section 124. Similarly, the cathode section 130 is supplied with a cathode supply gas KZG, here in the form of air LU, via a cathode supply section 132, and a cathode exhaust gas KAG is discharged via a cathode discharge section 134. As can be clearly seen in FIG. 1, the anode section here has a so-called dead-end configuration, since 100% of the anode exhaust gas AAG is directly recirculated, and thus completely, as anode recirculation gas ARG. This is solved in design by transitioning the anode discharge section 124 into the anode recirculation section 140. To provide the desired dryness for the recirculation of the anode exhaust gas AAG, an active cooling device 180 is arranged downstream of the anode recirculation section 140, which provides a heat sink for actively cooling the anode recirculation gas ARG at that point, and thus without any external cooling connections. This cooling function is configured as a condensation function, whereby the anode recirculation gas ARG is cooled to a temperature below the boiling point of water, for example below 100° Celsius, depending on the partial pressure. The cooled anode recirculation gas ARG is condensed with respect to its water content, and the liquid condensate KW is separated from the anode recirculation section 140 via a separator into the water discharge section 128. The dried anode recirculation gas ARG is supplied to an injector device, here serving as a mixing section 123, where it is mixed with the combustion gas BRG, and this mixture is supplied back to the anode section 120 as the anode feed gas AZG. As can be seen, a 100% feedback ratio allows for maximum efficiency in the utilization of the combustion gases BRG, including the anode exhaust gas AAG, and the reduction in Nernst voltage that would normally be caused by the water content of the anode recirculation gas ARG can now be avoided or at least reduced.The active cooling device 180 allows the resulting water to be at least partially condensed and separated at the water discharge 128 in a cost-effective and easy manner.

[0037] Figure 2 shows a development of the embodiment of Figure 1. Here, an expanded heat transfer system is provided that complements the active cooling device 180 and thus further increases the efficiency of the overall system. The individual components of this additional temperature regulation system can, of course, be freely combined with one another, as long as this makes technical sense.

[0038] For example, FIG. 2 shows an anode supply heat exchanger 121 that can ensure heat exchange from the hot anode exhaust gas AAG to the anode supply gas AZG to be heated. Accordingly, the anode supply gas AZG can be conditioned and preheated to ensure the desired high intake temperature for the anode section 120. Similarly, the anode exhaust gas AAG is precooled here, so that the cooling power required, particularly of the active cooling device 180, is further reduced in this manner. The design of the active cooling device 180 can be correspondingly more compact. To provide further precooling, particularly even partial condensation, a condenser 126 is additionally integrated in the cathode supply section 132. Heat exchange takes place there between the anode exhaust gas AAG and the air LU that is supplied as the cathode supply gas KZG. Air is drawn in from the surroundings and heated there by heat transfer from the anode exhaust gas AAG. In a similar manner, particularly in combination with the anode feed heat exchanger 121 already described, a first condensation step is already performed here, in which the anode exhaust gas AAG is cooled as anode recirculation gas ARG, i.e., to a temperature below 100° Celsius. Accordingly, at least a portion of the water is already condensed from the anode recirculation gas ARG and separated as condensed water KW via a separate water outlet 128. An active cooling device 180 is then arranged afterwards, which allows further cooling and thus more intensive drying of the anode recirculation gas. This three-stage cooling of the anode exhaust gas as anode recirculation gas ARG further strengthens the effect according to the invention.

[0039] FIG. 2 also shows additional details of the operation of the active cooling device 180, which in this example is configured as a thermally activated cooling device 180. The thermal activation is provided here by the fuel cell system itself, since the likewise hot cathode exhaust gas KAG is guided from the cathode discharge area 134 to the activation area of the active cooling device 180. As already mentioned, such a thermally activated cooling device 180 can be configured, for example, as an absorption heat pump, in which case the required thermal activation is provided by the high temperature of the cathode exhaust gas KAG. Since the cathode exhaust gas KAG also usually has a very high temperature and the cathode supply gas KZG can likewise be preconditioned to a high temperature, in the embodiment of FIG. 2 the overall temperature regulation system of the fuel cell system 100 further includes an air-to-heat exchanger 190. This makes it possible to use the hot cathode exhaust gas KAG in a first step for preconditioning the cathode supply gas KZG and subsequently use the remaining residual heat for thermal activation of the active cooling device. In the opposite direction, this means that two heating stages are now provided for the air LU supplied as cathode supply gas KZG, namely by the compensation device 126 and the above-mentioned air-to-heat exchanger 190.

[0040] FIG. 3 also shows a development of the embodiment of FIGS. 1 and 2. Here, additional components are added that can be used alone or in combination with other components of the temperature regulation system. One of these components is a cathode supply heat exchanger 131, which here serves as a heating stage for heating cathode supply gas 132. Additionally, a release valve 129 is provided, which provides additional flexibility based on a 100% feedback rate of the anode exhaust gas. In special situations where the amount of anode recirculation gas ARG is greater than required, such a release valve 129, which can also be called a discharge valve, provides the function of discharging part or all of the anode recirculation gas ARG.

[0041] 4a also shows another component of the temperature regulation system, here particularly relating to the additional temperature regulation of the anode supply gas AZG by the heated cathode exhaust gas KAG, for which a cathode exhaust heat exchanger 133 is arranged in the anode supply section 122 to ensure the above-mentioned heat transfer.

[0042] Figure 4b shows a fuel cell system 100 that otherwise corresponds to that of Figure 4a, except that in Figure 4b, the cathode exhaust heat exchanger 133 is arranged with its cold side downstream of the anode supply heat exchanger 121. That is, the hot anode exhaust gas AAG is guided through the hot side of the anode supply heat exchanger 121, so that the anode supply gas AZG is brought to a higher operating temperature. The cathode exhaust gas KAG is now guided through the hot side of the cathode exhaust heat exchanger 133, so that the anode supply gas AZG is heated first by the cathode exhaust gas KAG in the cathode exhaust heat exchanger 133 and then by the anode exhaust gas AAG in the anode supply heat exchanger 121. Conversely, in the embodiment shown in FIG. 4 a , the anode supply gas AZG is heated first by the anode exhaust gas AAG in the anode supply heat exchanger 121 and subsequently by the cathode exhaust gas KAG in the cathode exhaust heat exchanger 133 .

[0043] 5 also shows further components with which the fuel cell system 100 can be further developed. These are, on the one hand, a cathode recirculation fan 171 and a cathode dividing section 137, which allows a portion of the cathode exhaust gas KAG to be divided into a cathode recirculation section 170. This divided portion of the cathode exhaust gas KAG can then be supplied as cathode recirculation gas KRG to an ejector device, here the cathode mixing section 135, thereby ensuring cathode recirculation. In this way, a variable recirculation rate is possible at the cathode, and relatively high recirculation rates can be set during partial load operation. The variable cathode exhaust gas KAG is supplied to the catalytic device 136 in the manner already described several times.

[0044] 5 also shows a control valve 160 in the combustion gas supply for the combustion gas BRG, which is particularly configured to be quantitatively controllable so that different volumetric flow rates of the combustion gas BRG can be adjusted and different amounts of combustion gas actually mixed into the anode recirculation gas ARG for different operating conditions.

[0045] 6 shows further components that can further develop the fuel cell system 100. For example, in the embodiment of FIG. 6, the overall temperature regulation system of the fuel cell system 100 is additionally supplemented with another air-heat exchanger 192, which provides for the remaining heat of the cathode exhaust gas KAG to be used for preconditioning the cathode supply gas KZG in a separate step before it is released to the environment. This means that in the reverse direction, three heating stages are now provided for the air LU supplied as cathode supply gas KZG, namely by the condenser 126, the air-heat exchanger 192, and the air-heat exchanger 190.

[0046] FIG. 7 shows yet another alternative fuel cell system 100. Elements with the same reference numerals as in the previous embodiments correspond to each other and will not be described again. A discharge valve 195 is provided here, through which the anode exhaust gas AAG can be discharged from the anode recirculation zone 140. The dashed lines of the discharge valve 195 indicate possible alternative arrangements. The discharge valve 195 may be necessary when fuels such as hydrogen or ammonia contain impurities such as nitrogen or carbon dioxide to prevent the accumulation of non-condensable inert gases in the anode path. The discharge valve 195 can be opened periodically or continuously. An exhaust gas conversion device 194, for example, configured as an oxidation catalyst, is provided to chemically convert the anode exhaust gas. Additionally, an aftertreatment unit 193 is provided downstream of the air / heat exchanger 190. The aftertreatment unit 193 is particularly preferred when operating the fuel cell system 100 with ammonia, in which case a small amount of ammonia is reconverted before the exhaust gas is released to the atmosphere. To this end, the aftertreatment unit 193 may be configured as an ammonia slip catalyst (ASC) operating at temperatures between 200°C and 500°C, for example.

[0047] In this case, the individual components of the system, in particular consisting of a number of heat exchangers, can be freely combined with one another and, in particular, can be freely switchable via a control valve system in order to be able to adapt as flexibly as possible to the various operating conditions of the fuel cell system 100.

[0048] In this sense, further alternative features and feature combinations are explicitly proposed below.

[0049] For example, the components of the ejector device as the cathode mixing section 135 based on the embodiment of the fuel cell system 100 shown in FIG. 5 can be combined with the embodiment of the fuel cell system 100 shown in FIG. 6, which includes the components of another air-heat exchanger 192.

[0050] Furthermore, in an embodiment including the above-mentioned components of the ejector device as the cathode mixing section 135 shown in FIG. 5 and the components of another air-heat exchanger 192 shown in FIG. 6, the cooling device 180 can optionally be supported by a water cooling device available on the side of the system environment of the application of the fuel cell system 100.

[0051] Additionally, in an embodiment including the above-described components of the alternative air-to-heat exchanger 192 shown in FIG. 6, a fan may be utilized as the cathode mixing section 135 in place of the ejector device shown in FIG.

[0052] Alternatively, in an embodiment including the above-described components of another air-heat exchanger 192 shown in FIG. 6 and utilizing a fan as the cathode mixing section 135 instead of the ejector device shown in FIG. 5, the cooling device 180 can be supported by the above-described water cooling device, which may be available in the system environment of the application of the fuel cell system 100.

[0053] The above description of the various embodiments describes the present invention by way of example only. (Other possible items) (Item 1) A fuel cell system (100) for generating electrical energy, comprising a fuel cell stack (110) with an anode section (120) and a cathode section (130), the anode section (120) having an anode supply section (122) for supplying an anode supply gas (AZG) and an anode discharge section (124) for discharging an anode exhaust gas (AAG), the anode discharge section (124) transitioning to an anode recirculation section (140) for recirculating the anode exhaust gas (AAG) to the anode supply section (122) as an anode recirculation gas (ARG), the cathode section (130) for supplying a cathode supply gas (KZG), 1. A fuel cell system comprising a cathode supply section (132) and a cathode discharge section (134) for discharging a cathode exhaust gas (KAG), wherein an active cooling device (180) for cooling an anode recirculation gas (ARG) is disposed in the anode recirculation section (140), a water discharge section (128) for condensed water (KW) condensed in the active cooling device (180) is disposed downstream of the active cooling device (180), and a mixing section (123) is disposed downstream of the water discharge section (128) for mixing a combustion gas (BRG) and an anode recirculation gas (ARG) and supplying the ARG to the anode supply section (122) as an anode supply gas (AZG). (Item 2) Item 1, a fuel cell system according to item 1, wherein the active cooling device (180) comprises a thermally activated cooling device, in particular an absorption heat pump, and the active cooling device (180) is arranged in heat transfer contact with the cathode discharge area (134) for thermal activation by the heat contained in the cathode exhaust gas (KAG). (Item 3) 3. The fuel cell system (100) according to claim 1 or 2, wherein the active cooling device (180) comprises an electrically activated cooling device. (Item 4) 4. The fuel cell system (100) according to any one of items 1 to 3, wherein the anode recirculation zone (140) has a condenser (126) in heat transfer contact with the cathode supply zone (132) for cooling the anode recirculation gas (ARG) by heating the cathode supply gas (KZG), and a water discharge section (128) for discharging condensed water (KW) condensed in the condenser (126) is arranged downstream of the condenser (126) and upstream of the active cooling device (180). (Item 5) 5. The fuel cell system (100) according to any one of items 1 to 4, wherein the cathode discharge area (134) is configured without a catalytic device and / or a burner. (Item 6) 6. The fuel cell system (100) according to any one of items 1 to 5, wherein the anode discharge zone (124) and the anode recirculation zone (140) are configured without a separate zone for complete or substantially complete recirculation of the anode exhaust gas (AAG) as the anode recirculation gas (RZG). (Item 7) 7. The fuel cell system (100) according to any one of items 1 to 6, wherein a discharge valve (129) for controlled discharge of at least a portion of the recirculated gas (RZG) is arranged in the anode recirculation zone (140) downstream of the active cooling device (180) and downstream of the water discharge section (128). (Item 8) 8. The fuel cell system (100) according to any one of items 1 to 7, wherein the anode discharge zone (124) comprises an anode supply heat exchanger (121) in thermal conduction contact with the anode supply zone (122) for heat transfer from an anode exhaust gas (AAG) to an anode supply gas (AZG). (Item 9) 9. The fuel cell system (100) according to any one of items 1 to 8, wherein the mixing section (123) is configured as an ejector device, has a fuel supply of combustion gas (BRG) at a primary connection of the ejector device, and has the anode recirculation section (140) at a secondary connection of the ejector device. (Item 10) 10. The fuel cell system (100) according to any one of items 1 to 9, wherein the cathode supply section (132) comprises a cathode supply heat exchanger (131) in heat transfer contact with the cathode discharge section (134) for heat transfer from a cathode exhaust gas (KAG) to a cathode supply gas (KZG). (Item 11) 11. The fuel cell system (100) according to any one of items 1 to 10, wherein a cathode exhaust heat exchanger (133) for heat transfer from cathode exhaust gas (KAG) to anode supply gas (AZG) is arranged in the anode supply section (122), preferably downstream of the anode supply heat exchanger (121). (Item 12) 12. The fuel cell system (100) according to any one of items 1 to 11, wherein a control valve (160) is disposed in the anode supply zone (122) upstream of the mixing zone (123) for controlling the volumetric flow rate of the combustion gas (BRG) passing through the mixing zone (123). (Item 13) 13. The fuel cell system (100) of any one of items 1 to 12, wherein the anode discharge area (122) is configured without an external cooling circuit. (Item 14) 14. The fuel cell system (100) according to any one of items 1 to 13, wherein a cathode mixing section (135), in particular in the form of an ejector device, is arranged in the cathode supply section (132), at a secondary connection of which a cathode recirculation section (170) for the recirculation of a portion of the cathode exhaust gas (KZG) as cathode recirculation gas (KRG) is connected in fluid communication. (Item 15) A method for recycling an anode exhaust gas (AZG) as an anode recirculation gas (ARG) in a fuel cell system (100) having the fuel cell system according to any one of items 1 to 14, comprising the steps of: the active cooling by the active cooling device (180) cools the anode recirculation gas (ARG) below the boiling temperature of water; Separation of condensed water (KW) from anode recirculation gas (ARG); The dry anode recirculation gas (ARG) is mixed with the combustion gas (BRG) to form the anode feed gas (AZG); A method comprising: [Explanation of symbols]

[0054] 100 Fuel Cell System 110 Fuel Cell Stack 120 Anode Section 121 Anode supply heat exchanger 122 Anode Supply Area 123 Mixed area 124 Anode Discharge Area 126 Condenser 128 Water discharge part 129 Release valve 130 cathode area 131 Cathode supply heat exchanger 132 cathode supply area 133 Cathode exhaust heat exchanger 134 Cathode Discharge Area 135 Cathode Mixing Area 140 Anode Recirculation Zone 160 Control Valve 170 cathode recirculation zone 171 Cathode recirculation fan 180 Active Cooling Device 190 Air and Heat Exchanger 192 Air and heat exchangers 193 Aftertreatment Unit 194 Exhaust Gas Conversion Equipment 195 Release valve AZG Anode supply gas AAG Anode exhaust gas ARG Anode recirculation gas KZG cathode supply gas KAG cathode exhaust gas KRG cathode recirculation gas BRG Combustion Gas LU Air KW condensate

Claims

1. anode exhaust gas flowing through the anode supply section and the cathode exhaust gas flowing through the anode supply section; a cathode supply section for supplying the cathode supply gas and a cathode exhaust gas flowing through the cathode exhaust gas; an active cooling device for cooling the anode recirculation section; a water discharge port for condensed water condensed in the active cooling device; and a mixing section for mixing the combustion gas and the anode recirculation gas and for supplying the anode recirculation gas to the anode supply section; A fuel cell system, wherein the active cooling device comprises a thermally activated cooling device, in particular an absorption heat pump, and the active cooling device is arranged in heat transfer contact with the cathode exhaust area for thermal activation by the heat contained in the cathode exhaust gas.

2. 10. The fuel cell system of claim 1, wherein said active cooling system comprises an electrically activated cooling system.

3. 2. The fuel cell system of claim 1, wherein the anode recirculation zone has a condenser in heat transfer contact with the cathode supply zone for cooling the anode recirculation gas by heating the cathode supply gas, and a water discharge section for discharging condensed water condensed in the condenser is disposed downstream of the condenser and upstream of the active cooling device.

4. 10. The fuel cell system of claim 1, wherein the cathode exhaust area is configured without a catalytic device and / or a burner.

5. 10. The fuel cell system of claim 1, wherein the anode exhaust zone and the anode recirculation zone are configured without a separate zone for complete or substantially complete recirculation of the anode exhaust gas as the anode recirculation gas.

6. 2. The fuel cell system of claim 1, wherein a release valve for controlled release of at least a portion of the recirculated gas is disposed in the anode recirculation zone downstream of the active cooling device and downstream of the water release.

7. 10. The fuel cell system of claim 1, wherein the anode exhaust section includes an anode supply heat exchanger in heat conductive contact with the anode supply section for heat transfer from the anode exhaust gas to the anode supply gas.

8. 2. The fuel cell system of claim 1, wherein the mixing zone is configured as an ejector device having a fuel supply of combustion gas at a primary connection of the ejector device and the anode recirculation zone at a secondary connection of the ejector device.

9. 10. The fuel cell system of claim 1, wherein the cathode supply section comprises a cathode supply heat exchanger in heat transfer contact with the cathode discharge section for heat transfer from cathode exhaust gas to cathode supply gas.

10. 2. The fuel cell system of claim 1, wherein a cathode exhaust heat exchanger is disposed in the anode supply section, preferably downstream of the anode supply heat exchanger, for transferring heat from the cathode exhaust gas to the anode supply gas.

11. 10. The fuel cell system of claim 1, wherein a control valve is disposed in the anode supply section upstream of the mixing section for controlling a volumetric flow rate of combustion gases through the mixing section.

12. 10. The fuel cell system of claim 1, wherein the anode exhaust area is configured without an external cooling circuit.

13. 2. The fuel cell system according to claim 1, wherein a cathode mixing section, in particular in the form of an ejector device, is arranged in the cathode supply section, the secondary connection of which is connected in fluid communication with a cathode recirculation section for the recirculation of a portion of the cathode exhaust gas as cathode recirculation gas.

14. 14. A method for recycling an anode exhaust gas as an anode recirculation gas in a fuel cell system according to claim 1, comprising the steps of: the anode recirculation gas is cooled below the boiling temperature of water by active cooling by the active cooling device; Separating condensed water from the anode recycle gas; mixing the dry anode recirculation gas with the combustion gas to form the anode feed gas; A method comprising:

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