Fuel cell system for generating electrical energy

Abstract

The invention relates to a fuel cell system (100) for generating electrical energy, comprising a fuel cell stack (110) having an anode section (120) and a cathode section (130), the anode section (120) having an anode supply (122) for supplying an anode supply gas (AZG) and an anode discharge (124) for discharging an anode off-gas (AAG), the cathode section (130) has a cathode supply section (132) for supplying a cathode supply gas (KZG) and a cathode discharge section (134) for discharging a cathode exhaust gas (KAG), and wherein the anode discharge section (124) has a distribution section (125) for distributing the anode exhaust gas (AAG) to the anode circulation section (140) for circulation as an anode circulation gas (ARG) and to the anode exhaust gas section (150) for discharge as an anode exhaust gas (AUG) to the environment, a condenser device (126) in heat-transfer contact with the cathode supply (132) is provided in the anode discharge (124) or in the anode circulation (140) in order to cool the anode off-gas (AAG) or the anode circulation gas (ARG) by heating the cathode supply gas (KZG), a water outlet (128) is provided downstream of the condenser device (126) in order to discharge condensate water (KW) condensed in the condenser device (126), and the condenser device (126) is in heat-transfer contact with the cathode supply (132) in order to cool the anode off-gas (AAG) or the anode circulation gas (ARG) in order to cool the anode off-gas (AAG) or the anode circulation gas (ARG) in order to cool the anode off-gas (AAG) or the anode circulation gas (ARG). A mixing section (123) for mixing the anode recycle gas (ARG) with the fuel gas (BRG) and supplying the mixture as an anode supply gas (AZG) into the anode supply section (122) is provided downstream of the drain opening (128).

Description

Technical Field

[0001] The invention relates to a fuel cell system for generating electrical energy and to a method for circulating an anode exhaust gas in such a fuel cell system. Background Art

[0002] It is known that fuel cell systems are used to generate electrical energy. For this purpose, fuel cell systems are usually equipped with a fuel cell stack in which a plurality of individual fuel cells, each with an anode portion and a cathode portion, are arranged in a stack. To generate electrical energy, the fuel cell stack is supplied with fuel gas and usually also with ambient air, so that these gases can react chemically therein to generate electrical energy.

[0003] As the fuel gas, hydrogen or natural gas is usually used in known fuel cell systems. It is also known that a portion of the fuel gas that is not reacted during the reaction process in the fuel cell stack is sent back into the fuel cell stack as circulating gas for recirculation, thereby improving the efficiency of fuel gas use.

[0004] A disadvantage of the known solutions is that the circulation may reduce the operating efficiency, especially when hydrogen is used as the fuel gas. If hydrogen is fed into the fuel cell stack, the hydrogen reacts in the anode portion to form an anode exhaust gas mixture consisting of water and residual hydrogen. When the gas mixture is circulated, the water contained causes a significant reduction in the Nernst voltage. The reduction in the Nernst voltage of the fuel cell stack leads to a reduction in efficiency, which generally offsets the efficiency improvement caused by the circulation. In other words, the circulation does not achieve the desired efficiency improvement or has a limited improvement effect when the fuel cell system is operated with hydrogen.

[0005] Although it is already known in principle that a portion of the water contained in the anode exhaust gas can be condensed and separated by cooling the anode exhaust gas during circulation, the structure is extremely complex and costly. This is especially because an external cooling circuit must be used, which can use an external heat sink to feed a coolant into the circulation pipeline in order to achieve condensation of the water vapor in the anode exhaust gas. The addition of an additional cooling circuit and corresponding peripheral equipment leads to a disadvantageous increase in the complexity and cost of the fuel cell system. Summary of the invention

[0006] The object of the present invention is to at least partially eliminate the aforementioned disadvantages. In particular, the object of the present invention is to remove condensed water in a cost-effective and simple manner even when the fuel cell system is operated with hydrogen.

[0007] The above-mentioned object is achieved by a fuel cell system having the features of claim 1 and a method having the features of claim 12. Further features and details of the invention are derived from the dependent claims, the description and the figures. Here, the features and details described with respect to the fuel cell system according to the invention are of course also applicable in connection with the method according to the invention and vice versa, so that reference is always made or can be made to each other with respect to the disclosure of the individual inventive aspects.

[0008] According to the present invention, a fuel cell system for generating electric energy is proposed. It has a fuel cell stack with an anode part and a cathode part. The anode part is equipped with an anode supply part for supplying an anode supply gas and an anode discharge part for discharging an anode exhaust gas. Similarly, the cathode part is equipped with a cathode supply part for supplying a cathode supply gas and a cathode discharge part for discharging a cathode exhaust gas. A distribution part is provided in the anode discharge part, which allows the anode exhaust gas to be distributed to the anode circulation part for circulation as an anode circulation gas and to the anode exhaust part for discharging as an anode exhaust gas to the environment. The fuel cell system according to the present invention is characterized in that a condenser device in heat transfer contact with the cathode supply part is provided in the anode discharge part or in the anode circulation part. It is used to cool the anode exhaust gas or the anode circulation gas by heating the cathode supply gas. A drain port is provided downstream of the condenser device for discharging condensed water condensed in the condenser device. In addition, a mixing part is provided downstream of the drain port for mixing the anode circulation gas with the fuel gas and supplying it into the anode supply part as the anode supply gas.

[0009] The core idea of ​​the invention is to ensure the circulation of the anode exhaust gas. The circulation takes place in a distributed manner, so that a portion of the anode exhaust gas is circulated as anode circulation gas by means of the distribution unit. The remaining anode exhaust gas is discharged to the environment as anode exhaust gas. As will be explained below, the anode exhaust gas can also be reprocessed. In particular, the anode exhaust gas is combined with the cathode exhaust gas.

[0010] The circulation of the anode circulation gas takes place in a dry manner, i.e. by conducting it through a condenser device. In the condenser device, the temperature of the anode exhaust gas or anode circulation gas is brought to below the boiling point of water, i.e., depending on the pressure conditions and the partial pressure depending on the gas components, to below about 100° C. This has the effect that the water vapor contained in the anode circulation gas is condensed out and is present as liquid condensed water. It should be pointed out here that, depending on the positioning of the distributor, the condenser device can be arranged not only in the anode discharge section in front of the distributor, but also in the anode circulation section behind the distributor. In both cases, the advantages of the invention can be achieved.

[0011] A separator in the form of a drain outlet is provided downstream of the condenser device, in which the condensed components (i.e., condensed water) of the anode circulating gas can be separated from the gaseous components. Liquid condensed water can therefore be discharged from the system and, for example, discharged to the environment. The remaining anode circulating gas can also be referred to as dry anode circulating gas and is accordingly fed into a mixing section in a dry state. In a mixing section, which can be designed, for example, as an ejector device, a mixing chamber, or the like, the anode circulating gas is mixed with a fuel gas supplied by a fuel gas source. Depending on the amount of anode circulating gas available, the amount of fuel gas required to be supplemented can be mixed in accordingly. The mixed gas consisting of the fuel gas and the anode circulating gas is then fed back into the anode section of the fuel cell stack as an anode supply gas.

[0012] The core idea of ​​the present invention is now, in particular, that in order to condense the condensed water in the anode circulation gas or the anode exhaust gas, no external cold source and no separate external cold cycle are required. Instead, the condenser device is designed in a heat transfer contact with the cathode supply part in the manner of the present invention. Since this fuel cell system works with air as the cathode supply gas of the cathode part, air is sucked in from the surrounding environment. The suction can be achieved, for example, by means of a fan device. The sucked air therefore has an ambient temperature, which can be in the range of -20°C to 50°C or even higher depending on the temperature conditions. It is important here that the ambient air does not exceed the boiling point of water (usually 100°C) even in high-temperature application environments, such as in desert areas. In other words, even if the ambient temperature is very high, the supplied ambient air, as a heat sink, is sufficient as the coldest available temperature to provide cooling power for the anode exhaust gas or the anode circulation gas, so that it can be cooled to below the condensation temperature of water. As shown in the previous explanation, now only by supplying ambient air as the cathode supply gas, a cold source that can also be called a heat sink can be provided as a secondary function. The heat sink is used to extract sufficient heat energy from the anode exhaust gas circulating as the anode circulating exhaust gas in the condenser device so that the temperature of the anode exhaust gas or the anode circulating gas is reduced to below the boiling point of water. According to the present invention, the condensation process is carried out without the action of an external cooling source, especially without an external cooling cycle of the fuel cell system.

[0013] It should also be pointed out that in complex fuel cell systems, cooling circuits can of course be provided at other locations in order to be able to carry out the desired temperature regulation process. In particular, in the case of a fuel cell system designed as an SOFC system, very high temperatures are expected, so that, for example, parts of the fuel cell stack can be designed with external cooling. However, according to the invention, such existing external cooling sources are not used for the condensation function of the anode circulating gas and the anode exhaust gas.

[0014] According to the invention, the desired condensation of condensed water in the anode circulating gas or anode exhaust gas is achieved by integrating the condensation function into the cathode supply. As a result, the dried anode circulating gas is mixed into the fuel gas and the desired efficiency increase caused by the circulation is obtained accordingly, without the Nernst voltage reduction caused by the undried anode circulating gas. Compared to known solutions, this drying step and the corresponding efficiency increase can be achieved in the operation of the fuel cell system without the need for additional complex components, in particular only by means of a condenser device designed as a gas-gas heat exchanger.

[0015] In addition to the increased efficiency, in particular even smaller ejectors can therefore be used, since the undesired condensed water is separated off and the volume flow to be admixed into the fuel gas is correspondingly reduced.

[0016] It may be advantageous that in the fuel cell system of the present invention, the anode exhaust has an anode exhaust heat exchanger in heat transfer contact with the anode supply part to transfer heat from the anode exhaust gas to the anode supply gas. Here, a further efficiency improvement can be achieved in terms of temperature. In combination with other possible different heat exchangers to be explained below, a heat exchanger system is formed together with the condenser device, which can also be called a temperature control system, which allows as much waste heat as possible in the anode exhaust gas and the cathode exhaust gas to be reused and used for other functions, such as condensation and the supply and treatment of the anode supply gas and the cathode supply gas. Therefore, in this embodiment, it is possible to cool the high-temperature anode exhaust gas and use the energy to heat the anode supply gas when it is sent to the anode part. As a side effect, the anode exhaust gas arriving at the condenser device has therefore been precooled, so it can be assumed that there is a lower inlet temperature at the condenser device and the required condenser power is correspondingly lower. In other words, in this way, even with a smaller air flow and a smaller construction form and structural volume, the condenser device can be equipped with the desired condensation function.

[0017] Advantages may also be brought about when the mixing section is designed as an ejector device in the fuel cell system of the present invention, and the primary interface of the ejector device is connected to the fuel supply mechanism of the fuel gas, and the secondary interface of the ejector device is connected to the anode circulation section. As a mixing section, the use of an ejector device instead of a conventional fan device brings many advantages. On the one hand, the use of rotating parts and corresponding wearing parts is avoided. On the other hand, mixing and delivery are preferably integrated in the same component, so that a separate delivery device is no longer required in the anode supply section, especially when a fuel gas source with a high delivery pressure is used. On the contrary, it is only necessary to connect the corresponding fuel gas with the desired pre-pressure at the primary interface of the ejector device, and the corresponding suction effect at the secondary interface of the ejector device is sufficient to inhale the dry anode circulation gas for mixing. Therefore, the overall efficiency of the fuel cell system of the present invention is further improved and the wear resistance is especially improved.

[0018] It is also advantageous that in the fuel cell system of the present invention, the cathode exhaust portion has a catalyst device, which is connected to the anode exhaust portion fluidly and is provided for catalytic reprocessing of the anode exhaust and cathode exhaust gas. As already explained, a portion of the anode exhaust gas is separated from the anode circulating gas in the distributor and should be discharged to the environment. As also already explained, the anode exhaust gas has residual fuel gas components, such as hydrogen and ammonia. In order to ensure that no pure hydrogen enters the surrounding environment, catalytic reprocessing can occur in such a catalyst device. In order to provide a sufficient amount of oxygen for catalytic reprocessing, it is preferably provided to mix with the cathode exhaust gas before or in the catalyst device. The purpose of catalytic reprocessing is especially to reduce the fuel gas content in the anode exhaust to a minimum, or even completely deplete it. This improves safety and can further improve efficiency, especially when heat is generated in this way. This is particularly applicable when the heat generated at the catalyst device, for example, which is designed as an oxidation catalyst, is returned to the fuel cell system at other locations through a heat exchanger device. If the fuel cell system is operated with ammonia, it may be advantageous to provide an additional reprocessing unit, which also reacts the last residual ammonia.

[0019] Another advantage can be obtained when the cathode supply part in the fuel cell system of the present invention has a cathode supply heat exchanger that is in heat transfer contact with the cathode exhaust part to transfer heat from the cathode exhaust gas to the cathode supply gas. Similar to the preheating of the anode supply gas, the operating efficiency of the fuel cell system is further improved when the cathode supply gas is also pretreated and enters the cathode part at a temperature as high as possible and therefore in particular at a temperature close to the operating temperature of the fuel cell stack. Since the cathode exhaust gas has reached a correspondingly high exhaust temperature as a result of the chemical reaction in the fuel cell stack, the high temperature can be used here to partially output to the cathode supply gas. Therefore, this corresponds to a pretreatment in the form of preheating the cathode supply gas by the cathode exhaust gas. The recovery of the heat contained in the cathode exhaust gas further improves efficiency and avoids heat losses caused by the cathode exhaust gas. Preferably, the cathode supply heat exchanger is arranged upstream of the cathode part and directly in front of it, so it is arranged upstream of the catalyst device in the cathode exhaust part and after the condenser device in the cathode supply part.

[0020] In the fuel cell system of the present invention, it may be further advantageous to arrange the distribution portion at one of the following positions:

[0021] - upstream of the condenser unit,

[0022] - downstream of the condenser unit and downstream of the drain,

[0023] - downstream of the condenser unit and upstream of the drain.

[0024] The above three positions are different from each other and they are preferably not used at the same time. If the distribution occurs upstream of the condenser device, the subsequent condensation process and the condensate discharge only need to be carried out for the anode circulating gas that is actually circulated. However, it may also be advantageous to guide the entire anode exhaust gas through the condenser device, even through the drain, so that the post-distribution of the distribution section not only cools the entire anode exhaust gas, but also removes water. In particular, when a higher air pretreatment power is required than for the cathode supply gas, using the waste heat of the entire volume flow of the anode exhaust gas for the preheating may bring advantages, because not only the separated anode circulating gas, but all the anode exhaust gas is guided through the condenser device. Because in this case, a correspondingly large amount of condensed water will be produced, it is also advantageous that the distribution section is not only located between the condenser device and the drain, but is preferably arranged downstream of the drain. Therefore, the cathode supply gas can obtain the highest thermal efficiency, while separating more condensed water from the anode circulating gas, which will then be sent to the distribution section and later to the mixing section.

[0025] Advantages are also brought about when a cathode exhaust heat exchanger is arranged in the anode supply section, preferably downstream of the anode supply heat exchanger, in the fuel cell system of the present invention for transferring heat from the cathode exhaust gas to the anode supply gas. This allows the heat contained in the cathode exhaust gas to be transferred to the anode supply gas in addition or alternatively. This also allows, in combination with the anode supply heat exchanger, to further enhance the corresponding preheating function, or in other words to bring the anode supply gas to a higher temperature. As shown, in the fuel cell system of the present invention, a system consisting of multiple heat exchangers can now be equipped with a heat exchanger function at many locations. Obviously, the individual heat exchangers of the heat exchanger system can be controlled by valves, so that different parts of the heat exchanger system can be flexibly activated or deactivated, especially according to the operating conditions. It is therefore possible to respond to different operating conditions in a targeted and flexible manner and always achieve the highest temperature efficiency.

[0026] It may also be advantageous to provide a cathode supply heat exchanger in the cathode supply section in the fuel cell system according to the invention for heat transfer from the cathode exhaust gas to the cathode supply gas. It is also conceivable that it serves as an alternative or supplement to the other heat exchangers mentioned, it being noted that the valve preferably enables and disables different heat exchangers. It is also possible here to utilize the waste heat of the cathode exhaust gas by heat transfer in order to ensure pretreatment of the cathode supply gas in the form of pre-temperature control and thus further increase the operating efficiency of the fuel cell system.

[0027] It may also be advantageous if, in the fuel cell system according to the invention, a control valve for controlling the volume flow of the fuel gas flowing through the mixing section is provided in the anode supply section upstream of the mixing section. The amount and pressure of the fuel gas from the pressurized fuel gas source can thus be adjusted in a controlled manner, in particular. Depending on the amount of anode circulating gas distributed, a correspondingly adapted amount of fuel gas can now be mixed in, so that the anode section is always provided with the actually required anode supply gas composition and volume flow. The control valve is therefore preferably a quantitatively controllable control valve, so that it can react accordingly and flexibly to very different operating conditions of the fuel cell system.

[0028] It is also advantageous that in the fuel cell system of the invention the anode exhaust is designed without an external cooling circuit. As already explained, the core idea of ​​the invention is to provide the condensation function as efficiently as possible and without additional complexity. The design of the anode exhaust without an external cooling circuit is a manifestation of low complexity, since the condensation function is essentially realized only by a heat sink, which is provided by the ambient air supplied as cathode supply gas.

[0029] It is also advantageous if, in the fuel cell system according to the invention, a cathode mixing section, in particular in the form of an ejector device, is provided in the cathode supply section. The secondary interface of the ejector device is connected to the cathode circulation section in a fluidically connected manner for circulating a portion of the cathode exhaust gas as cathode circulation gas. This can also be referred to as a double circulation together with the circulation of the anode section. Thus, the cathode exhaust gas and the residual oxygen it contains can also be fed back to the cathode section as a mixture with the cathode supply gas.

[0030] Another subject matter of the present invention is a method for circulating anode exhaust gas as anode circulation gas in a fuel cell system according to the invention, comprising the following steps:

[0031] - distributing at least a portion of the anode exhaust gas as anode circulation gas to the anode circulation section,

[0032] - cooling the anode circulating gas to below the boiling point of water by heat transfer to the cathode supply gas,

[0033] - separating condensed water from the anode circulating gas,

[0034] - Mixing the dry anode circulating gas with the fuel gas to form the anode supply gas.

[0035] The use of the method according to the invention in the fuel cell system according to the invention brings about the same advantages as explained in detail with respect to the fuel cell system according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Further advantages, features and details of the invention are derived from the following description of an embodiment of the invention described in detail with reference to the drawings, which schematically show:

[0037] Figure 1 One embodiment of the fuel cell system of the present invention is shown.

[0038] Figure 2 Another embodiment of the fuel cell system of the present invention is shown.

[0039] Figure 3 Another embodiment of the fuel cell system of the present invention is shown.

[0040] Figure 4 Another embodiment of the fuel cell system of the present invention is shown.

[0041] Figure 5 Another embodiment of the fuel cell system of the present invention is shown.

[0042] Figure 6 Another embodiment of the fuel cell system of the present invention is shown. DETAILED DESCRIPTION

[0043] Figure 1 A fuel cell system 100 for generating electrical energy is schematically shown. A fuel cell stack 110 is schematically shown here, which has an anode part 120 and a cathode part 130. Obviously, a plurality of individual fuel cells are stacked in the fuel cell stack 110, which in turn have a plurality of individual anode parts 120 and cathode parts 130. For the sake of simplicity, the entire stack is shown here, including an anode supply part 122, an anode discharge part 124, a cathode supply part 132 and a cathode discharge part 134.

[0044] During operation of the fuel cell system 100, a fuel gas BRG is supplied from a fuel source not shown in detail. The fuel gas BRG is mixed with an anode circulation gas ARG to be explained in detail later to form an anode supply gas AZG, wherein an ejector device is used as the mixing unit 123. It is used to suck in the anode circulation gas ARG and mix it with the fuel gas BRG.

[0045] The anode supply gas AZG is now fed into the anode section 120 via the anode supply section 122 and can react there with the cathode supply gas KZG in the form of air LU. In this chemical reaction, in addition to the electrical energy generated during operation, which is the goal of the fuel cell system 100, heat is also generated, which causes the anode exhaust gas AAG and the cathode exhaust gas KAG to heat up. The high-temperature anode exhaust gas AAG is now fed into the distribution section 125, where it is divided into the anode circulation gas ARG that is fed into the anode circulation section 140 and the anode exhaust gas AUG that is fed into the anode exhaust section 150. The exhaust section can also be flexibly controlled here, so that in particular the volume ratio between the anode circulation gas ARG and the anode exhaust gas AUG can be adjusted.

[0046] While the still hot anode circulating gas ARG continues to be transported, it is now led through a condenser device 126, which has the function of exchanging heat with the supplied air LU. The air LU is taken from the environment and therefore has an ambient temperature, which is below the boiling point of water even in very hot ambient conditions. The anode exhaust gas AAG can therefore be cooled to below the boiling point as the anode circulating gas ARG, so that the contained moisture condenses and exists as condensed water KW in the anode circulating gas ARG that continues to be transported. The mixture consisting of condensed water KW and dry anode circulating gas ARG is led through a separator in the form of a drain 128, so that the condensed water KW is separated and can be discharged to the environment. The remaining dry anode circulating gas ARG is now sent to the ejector device as a mixing section 123, so that the remaining fuel in the anode circulating gas ARG is mixed with the new fuel gas BRG and is again sent to the anode section 120 as anode supply gas AZG.

[0047] The cathode exhaust gas KAG also has a correspondingly high temperature and is further processed before being discharged to the environment. Figure 1 In the simplest version, a catalyst device 136 is provided for aftertreatment, in which a mixture of cathode exhaust gas KAG and anode exhaust gas AUG is catalytically aftertreated together. The purpose of the catalytic aftertreatment is in particular to reduce the volume proportion of the residual fuel gas BRG in the anode exhaust gas AUG, so as to discharge the mixed gas consisting of the anode exhaust gas AUG and the cathode exhaust gas KAG into the environment as safely as possible.

[0048] Figure 2 Show Figure 1An improvement of an embodiment of the invention is provided, in which various additional components are added here by way of example, which can be used individually or in combination. One of the additional components is an anode supply heat exchanger 121. It allows the anode exhaust gas AAG to be precooled from the perspective of the anode exhaust gas, so that less cooling power is subsequently required at the condenser device 126. The precooling is achieved by transferring heat from the high-temperature anode exhaust gas AAG to the anode supply gas AZG to be pretreated, so that the precooling also has a positive effect on the anode supply gas, thereby further improving the operating efficiency of the fuel cell system 100.

[0049] Figure 2 Another additional component in the cathode supply section 132 is an air heat exchanger 190, which is located downstream of the condenser device 126 in the cathode supply section 132. Therefore, the cathode supply gas KZG, which has been heated by the condenser device 126, is further heated by the waste heat of the mixed gas obtained after the catalyst device 136, so that a higher inlet temperature of the cathode supply gas KZG at the cathode section 130 is achieved.

[0050] Figure 2 The Figure 1 The third difference is the position of the distributor 125. It is arranged after the drain 128 here, so that all the anode exhaust gas AAG undergoes the condensation function as well as the heat exchange function. This allows maximum heat recovery from the anode exhaust gas, but requires a correspondingly larger condenser device 126 in order to be able to draw in and process more air LU for cooling. Since the condensed water KW is now also completely separated from the entire dry anode exhaust gas AAG, only the dry anode exhaust gas is further transported as anode circulating gas ARG and anode exhaust gas AUG in the fuel cell system 100.

[0051] Figure 3 Additional components are also shown, which can further increase the efficiency of the fuel cell system 100. On the one hand, a cathode supply heat exchanger 131 is additionally provided here, which allows heat from the hot cathode exhaust gas KAG to be recovered into the cathode supply gas KZG. The cathode supply gas KZG thus receives heat input at three locations, namely the condenser device 126, the air heat exchanger 190 and finally the heat exchange in the cathode supply heat exchanger 131. Figure 3 1 shows a variant in which the distributor 125 is now arranged downstream of the condenser device 126 but upstream of the drain 128. This allows the heat recovered from the anode exhaust gas AAG to be transferred completely to the air LU in the condenser device 126. However, the drain 128 and the separation function only need to be provided for the anode circulating gas ARG that is actually required, so the separator of the drain 128 can be designed accordingly than in Figure 2 The version in is smaller.

[0052] Figure 4 Also shown are further subcomponents that can be used in the fuel cell system 100 according to the invention. Here, part of the heat of the cathode exhaust gas KAG is now used to further heat the anode supply gas AZG by arranging the cathode exhaust heat exchanger 133 in heat-transferring contact with the anode supply 122. In this possible embodiment, it is therefore provided that as much heat as possible is input into the anode supply gas AZG.

[0053] Figure 5 Other components that can improve the fuel cell system 100 are also shown. On the one hand, it is a cathode circulation fan 171 and a cathode distributor 137, which allow a portion of the cathode exhaust gas KAG to be distributed to the cathode circulation section 170. Therefore, this distributed portion of the cathode exhaust gas KAG can be fed as cathode circulation gas KRG into the ejector device as the cathode mixing section 135, so that the cathode circulation can be realized. Therefore, a variable circulation ratio at the cathode can be achieved, wherein a higher circulation rate can occur under partial load operation. The remaining cathode exhaust gas KAG is fed to the catalyst device 136 in the manner explained many times above.

[0054] Figure 5 The control valve 160 in the fuel gas supply mechanism of the fuel gas BRG is also shown. It is particularly designed to be quantitatively controllable, so different volume flows of the fuel gas BRG can occur, and different fuel gas quantities can be mixed with the anode circulating gas ARG as required for different operating conditions.

[0055] Figure 6 Another embodiment of the fuel cell system 100 of the present invention is shown, wherein most of the components shown correspond to Figure 5 Components. In this case, an aftertreatment unit 191 is additionally provided, which is arranged downstream of the air heat exchanger 190. The aftertreatment unit 191 is particularly advantageous when the fuel cell system 100 is operated with ammonia, in order to react traces of ammonia again before the exhaust gas is discharged to the environment. For this purpose, the aftertreatment unit 191 can be designed, for example, as an ammonia slip catalyst (ASC), which operates at a temperature of 200 to 500° C. It may also be advantageous to provide a purge valve and / or a bypass valve (in Figure 6 In order to discharge hydrogen and / or ammonia in the event of a leak, such valves can be provided in all embodiments.

[0056] The individual components, in particular components of a system of a plurality of heat exchangers, can be freely combined with one another and can be freely switched, in particular via a control valve system, in order to be able to respond as flexibly as possible to very different operating situations of the fuel cell system 100 .

[0057] Specifically, Figure 2Additional components of the illustrated embodiment of the fuel cell system 100 (i.e., the anode supply heat exchanger 121 and / or the air heat exchanger 190) may also be similarly positioned relative to the distribution portion 125, with Figure 1 , 3 , 4 or 5 are combined to supplement the system components of the fuel cell system 100 embodiments.

[0058] also, Figure 3 Additional components of the illustrated embodiment of the fuel cell system 100 (i.e., the cathode supply heat exchanger 131) may also be used with Figure 1 , 2 , 4 or 5 are combined to supplement the system components of the fuel cell system 100 embodiments.

[0059] in addition, Figure 4 Additional components of the illustrated embodiment of the fuel cell system 100 (i.e., the cathode exhaust heat exchanger 133) may also be used with Figure 1 , 2 , 3 or 5 are combined to supplement the system components of the fuel cell system 100 embodiments.

[0060] same, Figure 5 and or Figure 6 Additional components of the embodiment of the fuel cell system 100 shown, namely the cathode circulation section 170, the cathode circulation fan 171 and the cathode distribution section 137 and / or the reprocessing unit 191 and / or the control valve 160, may also be used with Figure 1 , 2 , 3 or 4 of the fuel cell system 100 are supplemented and combined.

[0061] The above explanations of the embodiments are only used as examples to describe the present invention.

[0062] Reference numerals list

[0063] 100 Fuel Cell Systems

[0064] 110 Fuel Cell Stack

[0065] 120 Anode

[0066] 121 Anode supply heat exchanger

[0067] 122 Anode Supply Department

[0068] 123 Mixing Section

[0069] 124 Anode discharge section

[0070] 125 Distribution Department

[0071] 126 Condenser device

[0072] 128 Drain

[0073] 130 cathode

[0074] 131 Cathode supply heat exchanger

[0075] 132 Cathode Supply Department

[0076] 133 Cathode exhaust heat exchanger

[0077] 134 cathode discharge part

[0078] 135 cathode mixing unit

[0079] 136 Catalytic converter

[0080] 137 Cathode distribution unit

[0081] 140 Anode circulation unit

[0082] 150 Anode exhaust

[0083] 160 Control valve

[0084] 170 Cathode circulation unit

[0085] 171 Cathode circulation fan

[0086] 190 Air Heat Exchanger

[0087] 191 Reprocessing Unit

[0088] AZG Anode supply gas

[0089] AAG Anode Exhaust Gas

[0090] AUG Anode Exhaust

[0091] ARG Anode circulation gas

[0092] KZG Cathode supply gas

[0093] KAG cathode exhaust gas

[0094] KRG cathode circulating gas

[0095] BRG Fuel Gas

[0096] LU Air

[0097] KW Condensate

Claims

1. A fuel cell system (100) for generating electric energy, comprising a fuel cell stack (110) having an anode section (120) and a cathode section (130), wherein the anode section (120) has 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), and the cathode section (130) has a cathode supply section (132) for supplying a cathode supply gas (KZG) and a cathode discharge section (134) for discharging a cathode exhaust gas (KAG), in, The anode discharge part (124) has a distribution part (125) for distributing the anode exhaust gas (AAG) to the anode circulation part (140) for circulation as anode circulation gas (ARG) and to the anode exhaust part (150) for discharge to the environment as anode exhaust gas (AUG). Its characteristics are: A condenser device (126) is provided in the anode discharge section (124) or in the anode circulation section (140) and is in heat transfer contact with the cathode supply section (132), for cooling the anode exhaust gas (AAG) or the anode circulation gas (ARG) by heating the cathode supply gas (KZG), wherein a drain port (128) is provided downstream of the condenser device (126) for discharging condensed water (KW) condensed in the condenser device (126), wherein a mixing section (123) is provided downstream of the drain port (128) for mixing the anode circulation gas (ARG) with the fuel gas (BRG) and supplying the mixed anode circulation gas (ARG) with the fuel gas (BRG) as the anode supply gas (AZG) into the anode supply section (122).

2. The fuel cell system (100) according to claim 1, characterized in that: The anode exhaust (124) has an anode supply heat exchanger (121) in heat transfer contact with the anode supply (122) for transferring heat from the anode exhaust gas (AAG) to the anode supply gas (AZG).

3. The fuel cell system (100) according to claim 1, characterized in that: The mixing section (123) is designed as an injector device, a primary interface of the injector device is connected to a fuel supply mechanism of a fuel gas (BRG), and a secondary interface of the injector device is connected to the anode circulation section (140).

4. The fuel cell system (100) according to one of the preceding claims, characterized in that The cathode exhaust portion (134) has a catalyst device (136) which is fluidically connected to the anode exhaust portion (150) for catalytically after-treating the anode exhaust gas (AUG) and cathode exhaust gas (KAG).

5. The fuel cell system (100) according to one of the preceding claims, characterized in that The cathode supply (132) has a cathode supply heat exchanger (131) in heat transfer contact with the cathode exhaust (134) for transferring heat from the cathode exhaust gas (KAG) to the cathode supply gas (KZG).

6. The fuel cell system (100) according to one of the preceding claims, characterized in that The distribution portion (125) is arranged at one of the following positions: - upstream of said condenser device (126), - downstream of the condenser device (126) and downstream of the drain (128), - downstream of said condenser device (126) and upstream of said drain outlet (128).

7. The fuel cell system (100) according to any one of the preceding claims, characterized in that In the anode supply section (122), a cathode exhaust heat exchanger (133) is preferably provided downstream of the anode supply heat exchanger (121) for transferring heat from the cathode exhaust gas (KAG) to the anode supply gas (AZG).

8. The fuel cell system (100) according to any one of the preceding claims, characterized in that A cathode supply heat exchanger (131) is provided in the cathode supply part (132) for transferring heat from the cathode exhaust gas (KAG) to the cathode supply gas (KZG).

9. The fuel cell system (100) according to any one of the preceding claims, characterized in that In the anode supply section (122), a control valve (160) is provided upstream of the mixing section (125) for controlling the volume flow of the fuel gas (BRG) flowing through the mixing section (125).

10. The fuel cell system (100) according to one of the preceding claims, characterized in that The anode exhaust (124) is designed without an external cooling circuit.

11. The fuel cell system (100) according to one of the preceding claims, characterized in that A cathode mixing section (135) is provided in the cathode supply section (132), in particular in the form of an ejector device, the secondary interface of which is fluidically connected to the cathode circulation section (170) for circulating a portion of the cathode exhaust gas (KAG) as cathode circulation gas (KRG).

12. A method for circulating anode exhaust gas (AAG) as anode circulation gas (ARG) in a fuel cell system (100) having the features of one of claims 1 to 11, comprising the following steps: - distributing at least a portion of the anode off-gas (AAG) as anode circulation gas (ARG) to the anode circulation unit (140), - cooling the anode circulation gas (ARG) to below the boiling point of water by heat transfer to the cathode supply gas (KZG), - separating condensed water (KW) from the anode circulation gas (ARG), - mixing the dried anode circulation gas (ARG) with the fuel gas (BRG) into the anode supply gas (AZG).

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