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 anode discharge (124) communicating to an anode circulation section (140), and the cathode circulation section (140) communicating to the anode circulation section (140). The anode circuit (140) has an anode supply (122) for circulating the anode off-gas (AAG) as an anode circuit gas (ARG) to the anode supply (122), and a cathode circuit (130) having a cathode supply (132) for supplying a cathode supply gas (KZG) and a cathode discharge (134) for discharging the cathode off-gas (KAG), an active cooling device (180) for cooling the anode circuit gas (ARG) being provided in the anode circuit (140), a drain opening (128) for discharging condensate water (KW) condensed in the active cooling device (180) is provided downstream of the active cooling device (180), and wherein a mixing section (123) is provided downstream of the drain opening (128) for mixing the anode recycle gas (ARG) with the fuel gas (BRG) and feeding the mixture as an anode supply gas (AZG) into the anode supply section (122).

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] In known fuel cell systems, hydrogen or natural gas is usually used as fuel gas. It is also known that a portion of the fuel gas that is not reacted during the reaction in the fuel cell stack is fed 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 part to form an anode exhaust gas mixture consisting of water and residual hydrogen. When the gas mixture is circulated, the water contained may cause 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 usually offsets the efficiency improvement caused by the circulation. In other words, the circulation does not achieve the desired efficiency improvement or the improvement effect is not obvious 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 15. 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 the disclosures of these inventive aspects are always made or can be referred to one another.

[0008] According to the present invention, a fuel cell system for generating electric energy is provided. This fuel cell system has a fuel cell stack with an anode portion and a cathode portion. The anode portion is equipped with an anode supply portion for supplying an anode supply gas and an anode discharge portion for discharging an anode exhaust gas. In addition, the anode supply portion leads to an anode circulation portion for circulating the anode exhaust gas as an anode circulation gas to the anode supply portion. The cathode portion also has a cathode supply portion for supplying a cathode supply gas and a cathode discharge portion for discharging the cathode exhaust gas. The fuel cell system of the present invention is characterized in that an active cooling device for cooling the anode circulation gas is provided in the anode circulation portion. A drain port for discharging condensed water condensed in the active cooling device is provided downstream of the active cooling device. In addition, a mixing portion is provided downstream of the drain port for mixing the anode circulation gas with the fuel gas and supplying it into the anode supply portion as the anode supply gas.

[0009] The core idea of ​​the invention is to ensure that the anode waste gas is circulated as anode circulation gas. The circulation of the anode circulation gas takes place in a dry manner, i.e. by passing it through an active cooling device. In the active cooling device, the temperature of the anode circulation gas is brought 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.

[0010] A separator is provided as a drain outlet downstream of the active cooling device, in which the condensed components (i.e., condensed water) of the anode circulating gas are separated from the gaseous components. Liquid condensed water can thus 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 the mixing section in a dry state. In the 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 the fuel gas supplied by the 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.

[0011] The core idea of ​​the invention is that, in order to condense the condensed water in the anode circulation gas or the anode exhaust gas, no external cooling source or a separate external cooling circuit is required. Instead, an active cooling device is provided in the manner of the invention. According to the invention, the condensation process in the active cooling device is carried out without the action of an external cooling source, in particular without an external cooling circuit of the fuel cell system.

[0012] 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 present invention, such existing external cooling sources are not used for the condensation function of the anode circulating gas and the anode exhaust gas.

[0013] According to the invention, the desired condensation of condensed water in the anode circulation gas is achieved by integrating a condensation function by means of an active cooling device. As a result, the dried anode circulation gas is mixed into the fuel gas and the desired efficiency increase due to the circulation is obtained accordingly, without a decrease in the Nernst voltage due to undried anode circulation gas. Compared to known solutions, this drying step can be realized in the operation of the fuel cell system and the corresponding efficiency increase can be achieved without the need for additional complex components.

[0014] 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.

[0015] In the fuel cell system solution of the present invention, a separate external cooling cycle is no longer required, but an active cooling device is used instead. Within the scope of the present invention, an active cooling device is a device that actively produces a cooling effect and thus actively forms a heat sink. In particular, thermally driven (activated) and / or electrically driven (activated) heat sinks are conceivable here. A thermally driven heat sink can be, for example, an absorption heat pump. Similarly, an electric compressor that produces a cooling effect by changing the pressure of the refrigerant can also be used as an electrically driven cooling device. In principle, other active cooling devices are obviously also conceivable, which produce the desired heat sink in situ without having to use a separate external cooling cycle.

[0016] Therefore, the fuel cell system according to the invention has significant advantages, especially because a maximum circulation rate of up to 100% of the anode exhaust gas as the anode circulation gas can be achieved by active cooling. In other words, the anode part can be designed as a so-called dead end, because the anode exhaust gas discharged thereby reaches 100% and is therefore all fed back to the anode supply gas as the anode circulation gas. This allows the overall system complexity of the fuel cell system to be further reduced and in particular the expenditure for exhaust gas reprocessing is also basically completely avoided. In known solutions, the collected fuel cell system exhaust gas usually has to be reprocessed, for example, by means of an oxidation catalyst, so that the residual fuel gas remaining in the anode exhaust gas is oxidized and thus purposefully burned, and then the mixed exhaust gas is discharged to the environment. Since the fuel cell system embodiment of the present invention can now achieve a 100% return rate (i.e., circulation rate) of the anode exhaust gas, it is no longer necessary to discharge the anode exhaust gas to the environment. Therefore, it is no longer necessary to reprocess the anode exhaust gas because it is no longer discharged to the environment. Finally, it should be pointed out that the mixing section, for example in the form of an ejector device, can also work at a lower pressure on the primary side and can therefore be designed to be smaller and less expensive.

[0017] Advantages can be brought when the active cooling device has a heat-driven cooling device, especially with an absorption heat pump, in the fuel cell system of the present invention. Here, the active cooling device is in heat transfer contact with the cathode discharge portion and is equipped for thermal drive (activation) by means of the heat contained in the cathode exhaust gas. As already explained in the introduction, the heat-driven cooling device is a possible embodiment of the active cooling device of the present invention. In addition, in this embodiment, the heat provided by the fuel cell system itself is used for thermal drive. In the case of these gas reactions in the fuel cell stack, a large amount of heat is generated as a byproduct. The generated heat heats the anode exhaust gas and the cathode exhaust gas accordingly. The heat present in the cathode exhaust gas can now be used at least partially for the thermal drive of this cooling device. The heat-driven cooling device therefore refers to the hot cathode exhaust gas being used as energy in the heat-driven cooling device, where it is cooled and a heat sink is formed in this way. In order to use this thermal energy for cooling, an absorption heat pump can usually be provided in the heat-driven cooling device, so that a heat sink for the anode exhaust gas as the anode circulation gas can be generated in a targeted manner through the absorption process and the desorption process. It can be clearly seen here again that this active cooling device does not require external energy at all and does not require an external cooling cycle. Apart from a possible circulation pump for the coolant between the absorption section and the desorption section of such a heat-driven cooling device, no external energy input and in particular no supply of externally cooled coolant is required.

[0018] Alternatively or additionally, it is conceivable that in the fuel cell system of the invention, the active cooling device has an electrically driven cooling device. It can be provided as a supplement or alternative to the thermally driven cooling device. In this case, it can be a cold cycle machine, which forms a conventional heat pump with the aid of a compressor. In this way, the desired heat sink can be provided directly in situ at the active cooling device by inputting electrical energy, and the condensation function for the condensed water in the anode circulation gas can be provided accordingly.

[0019] Further advantages can be obtained when the anode circulation part has a condensation device in heat transfer contact with the anode supply part in the fuel cell system of the invention. It is used to cool the anode circulation gas by heating the cathode supply gas. Therefore, a further drain is provided downstream of the condensation device and upstream of the active cooling device for discharging the condensed water condensed in the condensation device. In other words, in this embodiment, two-stage cooling and therefore two-stage condensation can now be performed. This therefore means that the anode exhaust gas leaves the anode part with a high discharge temperature and reaches the desired temperature through multiple steps, at which it is mixed with the fuel gas as anode circulation gas. Here, two cooling steps and two condensation steps are formed, so that in the first step, the still hot anode exhaust gas is cooled by the ambient air, wherein the ambient air in different regions can have different ambient air temperatures. In particular in high-temperature regions, the ambient air sucked in as cathode supply gas may therefore also have a temperature of 50° C. or higher, so that the cooling effect on the hot anode exhaust gas is limited. Since the volume flow of air as cathode supply gas can only be flexibly changed within a limited range, it is now possible to arrange the active cooling device of the present invention after this cooling and condensation process, and since the condensation device already provides pre-condensation, the active cooling device can be designed to be smaller and more compact compared to conventional solutions. The cooling water discharged from the two drains can be discharged to the environment separately through corresponding separators in the drains, or can also be merged and discharged together.

[0020] It may also be advantageous to design the cathode exhaust in the fuel cell system according to the invention without a catalyst device and / or a burner. As already explained, the fuel cell system according to the invention is used in particular for completely circulating the anode exhaust gas as anode circulation gas. The anode exhaust gas is therefore no longer discharged to the environment and any residual fuel in the anode exhaust gas does not therefore need to be processed. Instead, only the cathode exhaust gas that does not contain fuel in a properly functioning fuel cell is discharged to the environment. The omission of the catalyst device and / or the burner makes the entire fuel cell system smaller, lighter and cheaper.

[0021] Furthermore, when the anode discharge and anode circulation are designed without a distributor in the fuel cell system according to the invention, advantages may be obtained for achieving a complete or substantially complete circulation of the anode exhaust gas as anode circulation gas. As mentioned above, this is only possible by using an active cooling device and it leads to other advantages, such as the fact that the catalyst device can be omitted as described in the previous paragraph. Therefore, no exhaust gas is generated on the anode side that needs to be discharged to the environment and therefore no further treatment is required. Due to the omission of such a distributor, the entire system of the fuel cell system can now also be designed to be simpler, more economical and more compact without such a component.

[0022] Advantages are also brought about when a discharge valve is provided in the anode circulation section downstream of the active cooling device and downstream of the drain in the fuel cell system of the present invention, for the controllable discharge of at least a portion of the circulating gas. Since the full circulation rate of the anode exhaust gas is preferably stipulated in the fuel cell system of the present invention, in special cases, full recirculation may be undesirable for the fuel cell system. In order to provide regulatory flexibility, a portion of the circulating gas can be output to the environment at least in a qualitatively controlled manner, preferably in a quantitatively controlled manner, by means of a discharge valve. Since the anode circulating gas usually also contains residual fuel, a catalyst device can be preferably integrated in such a discharge valve so that the anode exhaust gas as the anode circulating gas is catalytically reprocessed for such special cases and the residual fuel is oxidized in this way. In particular, the discharge valve is only provided and designed for the controllable discharge of at least a portion of the circulating gas. In particular, heat transfer is not performed in any form, and a constant distribution is also provided. If the hydrogen is at least substantially pure, such a discharge valve is generally not provided.

[0023] It may be advantageous if the anode exhaust part in the fuel cell system according to the invention has an anode exhaust heat exchanger which is in heat transfer contact with the anode supply part for transferring heat from the anode exhaust gas to the anode supply gas. A further increase in efficiency can be achieved here in terms of temperature. In combination with other possible different heat exchangers which will be explained below, a heat exchanger system is thus formed together with the active cooling device, which can also be referred to as a temperature control system, which allows as much waste heat as possible in the anode exhaust gas and 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 cathode supply gas. In this embodiment, it is therefore possible to cool the hot anode exhaust gas and use this energy to heat the anode supply gas when it is transported to the anode part. As a side effect, the anode exhaust gas arriving at the active cooling device is thus already precooled, so that a lower inlet temperature at the active cooling device can be assumed accordingly and the required cooling power is correspondingly lower.

[0024] Advantages can 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 blower brings many advantages. On the one hand, the use of rotating parts and corresponding wear parts is avoided. On the other hand, mixing and delivery are preferably integrated in the same component, so 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 particularly improved.

[0025] Further advantages can be obtained when the cathode supply part in the fuel cell system of the present invention has a cathode supply heat exchanger in heat transfer contact with the cathode discharge 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. This therefore 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 also further improves the efficiency and avoids heat losses caused by the cathode exhaust gas.

[0026] Advantages are also brought about when a cathode exhaust heat exchanger is provided in the anode supply section, preferably downstream of the anode supply heat exchanger, in the fuel cell system according to the 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, a system consisting of a plurality of heat exchangers can now be equipped in the fuel cell system according to the invention at many locations via the heat exchanger function. 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, in particular depending on the operating conditions. It is thus possible to react purposefully and flexibly to different operating conditions and always achieve maximum temperature efficiency.

[0027] It may also be advantageous if, in the fuel cell system according to the invention, a cathode supply heat exchanger is provided in the cathode supply for transferring heat from the cathode exhaust gas to the cathode supply gas. It is also conceivable that it serves as an alternative or in addition to the other heat exchangers mentioned, wherein it should be noted that valves preferably enable and disable 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 preconditioning of the cathode supply gas in the form of pre-temperature conditioning and thus further increase the operating efficiency of the fuel cell system.

[0028] It may also be advantageous if a control valve for controlling the volume flow of fuel gas through the mixing section is arranged in the anode supply section in the fuel cell system according to the invention 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. Depending on the amount of anode circulating gas distributed, a correspondingly adapted amount of fuel gas can now be added 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 in order to be able to react accordingly and flexibly to very different operating states of the fuel cell system.

[0029] It is also advantageous that in the fuel cell system according to the invention the anode discharge 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 discharge without an external cooling circuit is a manifestation of low complexity, since the condensation function is at least partially ensured by the heat sink of the active cooling device.

[0030] It is also advantageous to provide a cathode mixing section, in particular in the form of an ejector device, in the cathode supply section in the fuel cell system according to the invention. The secondary interface fluid of the ejector device is connected to the cathode circulation section for circulating a part 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.

[0031] In principle, it is also advantageous within the scope of the invention to provide for regenerative adsorption. Here, the water in the form of water vapor is regeneratively separated, for which, for example, a silica gel pad can be provided. In particular, the regenerative separation element (such as a silica gel pad) is arranged in the active cooling device.

[0032] 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:

[0033] - cooling the anode circulation gas to below the boiling point of water by means of active cooling of the active cooling device,

[0034] - Separation of condensed water from the anode circulating gas,

[0035] - Mix the dried anode circulating gas with the fuel gas to form the anode supply gas.

[0036] 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

[0037] Further advantages, features and details of the invention are derived from the following detailed description of an embodiment of the invention with reference to the accompanying drawings. The drawings schematically show:

[0038] Figure 1 One embodiment of the fuel cell system of the present invention is shown.

[0039] Figure 2 Another embodiment of the fuel cell system of the present invention is shown.

[0040] Figure 3 Another embodiment of the fuel cell system of the present invention is shown.

[0041] Figure 4a Another embodiment of the fuel cell system of the present invention is shown.

[0042] Figure 4b Another embodiment of the fuel cell system of the present invention is shown.

[0043] Figure 5 Another embodiment of the fuel cell system of the present invention is shown.

[0044] Figure 6 Another embodiment of the fuel cell system of the present invention is shown.

[0045] Figure 7 Another embodiment of the fuel cell system of the present invention is shown. DETAILED DESCRIPTION

[0046] Figure 1 A fuel cell system 100 is schematically shown, which has a fuel cell stack 110 with an anode part 120 and a cathode part 130. The anode part is supplied with an anode supply gas AZG via an anode supply part 122, and an anode exhaust gas AAG is discharged via an anode discharge part 124. In the same way, the cathode part 130 is supplied with a cathode supply gas KZG, here in the form of air LU, via a cathode supply part 132, and a cathode exhaust gas KAG is discharged via a cathode discharge part 134. Figure 1As can be clearly seen in the figure, the anode part is designed as a so-called dead end, since the anode exhaust gas AAG is also circulated directly to a degree of up to 100% and therefore completely as anode circulation gas ARG. This is solved structurally in that the anode discharge part 124 leads to the anode circulation part 140. In order to carry out the required drying treatment of the circulating anode exhaust gas AAG, an active cooling device 180 is provided in the subsequent path of the anode circulation part 140, which actively provides a heat sink to cool the anode circulation gas ARG, so that no external cooling interface is required. The cooling function is designed as a condensation function, so that the anode circulation gas ARG is cooled to below the boiling point of water depending on the partial pressure, in simple terms, for example below 100°C. The cooled anode circulation gas ARG is therefore condensed with respect to the water content, and the now liquefied condensed water KW is separated from the anode circulation part 140 by a separator in the drain outlet 128. The dried anode circulating gas ARG is fed into the ejector device as the mixing section 123 and mixed with the fuel gas BRG therein, wherein the mixed gas is then fed back into the anode section 120 as the anode supply gas AZG. It can be seen that the maximum efficiency of the use of the fuel gas BRG can be achieved from the anode exhaust gas AAG by a 100% recirculation rate. Since the water contained therein can be at least partially condensed and discharged through the drain 128 in a low-cost and simple manner by means of the active cooling device 180, the problem of a decrease in the Nernst voltage caused by the water content in the anode circulating gas ARG can be avoided or at least alleviated.

[0047] Figure 2 Show Figure 1 An improvement of the embodiment of the invention is provided. A downstream heat transfer system is provided here to supplement the active cooling device 180 and thus further improve the overall system efficiency. These components of the additional temperature control system can obviously be freely combined with each other as long as it is technically reasonable.

[0048] Therefore Figure 2, an anode supply heat exchanger 121 is shown, which enables heat exchange between the high-temperature anode exhaust gas AAG and the anode supply gas AZG to be heated. Therefore, the anode supply gas AZG can be pretreated and preheated to reach the higher inlet temperature required for entering the anode part 120. In the same process, the anode exhaust gas AAG is precooled here, and the cooling power required at the active cooling device 180 is reduced again in this way. This allows the size of the active cooling device 180 to be correspondingly smaller. In order to provide further precooling, especially to provide partial condensation in advance, the condensation device 126 is also integrated into the cathode supply part 132 here. Thereby, heat exchange is achieved between the anode exhaust gas AAG and the air LU supplied as the cathode supply gas KZG. Therefore, air is sucked in from the surrounding environment and is heated by the high-temperature anode exhaust gas AAG here by heat transfer. Similarly, in particular in combination with the aforementioned anode supply heat exchanger 121, a first condensation step has already occurred here, and the anode exhaust gas AAG is therefore cooled to a temperature below 100° C. here as the anode circulating gas ARG. Thus, at least a portion of the water has already condensed from the anode circulating gas ARG and is discharged as condensed water KW via the separate drain 128. An active cooling device 180 is now provided downstream, which allows for even further cooling and thus even more intensive drying of the anode circulating gas. The effect of the invention is further intensified by cooling the anode exhaust gas as anode circulating gas ARG in three stages.

[0049] Figure 2 Also shown are additional details of the design of the drive (activation) method of the active cooling device 180. It is designed here as a heat-driven cooling device 180. The heat drive (activation) is provided here by the fuel cell system itself, because the high-temperature cathode exhaust gas KAG is also transported from the cathode discharge part 134 to the drive (activation) area of ​​the active cooling device 180. As mentioned above, such a heat-driven cooling device 180 can be designed as an absorption heat pump, wherein the required heat drive is provided here by the increased temperature of the cathode exhaust gas KAG. Because the cathode exhaust gas KAG usually also has a very high temperature and the cathode supply gas KZG can also be pretreated to reach an increased temperature, in Figure 2 In the embodiment of the invention, an air heat exchanger 190 is additionally provided in the overall temperature control system of the fuel cell system 100. This allows the high-temperature cathode exhaust gas KAG to be used for pre-treating the cathode supply gas KZG in a first step and the remaining waste heat to be used for thermal operation of the active cooling device. Conversely, the air LU supplied as cathode supply gas KZG passes through two heating stages here, which are respectively achieved by the condensation device 126 and the aforementioned air heat exchanger 190.

[0050] Figure 3 That's right too Figure 1 and Figure 2Improvements of the embodiment. Other additional components are also added here, which can be used alone or in combination with other components of the temperature control system. One of the components is a cathode supply heat exchanger 131, which is used here as a third heating stage to heat the cathode supply gas 132. In addition, a discharge valve 129 is provided here, which provides additional flexibility due to the 100% recirculation rate of the anode exhaust gas. In the special case that the amount of anode circulating gas ARG is greater than the required amount, this discharge valve 129 can now also be called a drain valve, which provides a discharge function for part or all of the anode circulating gas ARG.

[0051] Figure 4a Other components of the temperature control system are also shown, in particular the additional temperature control of the anode supply gas AZG with the heated cathode exhaust gas KAG. For this purpose, a cathode exhaust heat exchanger 133 is arranged in the anode supply 122 to ensure the heat transfer.

[0052] Figure 4b Shows that most of the corresponding Figure 4a The fuel cell system 100. Figure 4b In the embodiment, the cathode exhaust heat exchanger 133 is arranged with the cold side downstream of the anode supply heat exchanger 121. The high-temperature anode exhaust gas AAG is therefore conveyed through the hot side of the anode supply heat exchanger 121, thereby further bringing the anode supply gas AZG to operating temperature. The cathode exhaust gas KAG is guided through the hot side of the cathode exhaust heat exchanger 133, so that the anode supply gas AZG is first heated by the cathode exhaust gas KAG in the cathode exhaust heat exchanger 133 and then heated by the anode exhaust gas AAG in the anode supply heat exchanger 121. In contrast, in accordance with Figure 4a In the embodiment of the present invention, the anode supply gas AZG is first heated by the anode exhaust gas AAG in the anode supply heat exchanger 121 and then heated by the cathode exhaust gas KAG in the cathode exhaust heat exchanger 133.

[0053] exist Figure 5 Other components that can improve the fuel cell system 100 are also shown. On the one hand, it is the cathode circulation fan 171 and the cathode distribution part 137, which allow a part of the cathode exhaust gas KAG to be distributed to the cathode circulation part 170. Therefore, this distributed part of the cathode exhaust gas KAG can be sent to the ejector device as the cathode mixing part 135 as cathode circulation gas KRG, 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 sent to the catalyst device 136 in the manner explained many times above.

[0054] Figure 5The 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 that different fuel gas BRG volume flows 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 component that can improve the fuel cell system 100 is shown. Figure 6 In the embodiment of the invention, a further air heat exchanger 192 is additionally provided in the overall temperature control system of the fuel cell system 100, which uses the remaining heat in a further step of pre-treating the cathode supply gas KZG before the cathode exhaust gas KAG is discharged to the environment. Conversely, the air LU supplied as cathode supply gas KZG passes through three heating stages, which are respectively achieved by the condensation device 126, the air heat exchanger 192 and the air heat exchanger 190.

[0056] Figure 7 Another fuel cell system 100 is shown. Components with the same reference numerals as in the previous embodiment correspond thereto and are not described further. A discharge valve 195 is provided here, by which the anode exhaust gas AAG can be discharged from the anode circulation section 140. Another possible arrangement of the discharge valve 195 is indicated by a dotted line. When the fuel (such as hydrogen or ammonia) contains impurities (such as nitrogen or carbon dioxide), a discharge valve 195 may be required to prevent inert and non-condensable gases from being enriched in the anode path. The discharge valve 195 can be opened periodically, or the discharge can also be carried out continuously. For the chemical reaction of the anode exhaust gas, an exhaust gas reaction device 194 is provided, which is designed as an oxidation catalyst, for example. In addition, a post-processing unit 193 is additionally provided, which is arranged downstream of the air heat exchanger 190. The post-processing unit 193 is particularly advantageous when the fuel cell system 100 is operated with ammonia, so as to react trace amounts of ammonia again before the exhaust gas is discharged to the environment. For this purpose, aftertreatment unit 193 may be designed, for example, as an ammonia slip catalytic converter (ASC) which operates at a temperature of 200° C. to 500° C.

[0057] In particular, the individual components of the system, which consist 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 .

[0058] In this sense, further alternative features and feature combinations will be explicitly proposed below.

[0059] therefore, Figure 5 The components of the ejector device as the cathode mixing unit 135 in the embodiment of the fuel cell system 100 shown can also be connected with Figure 6The fuel cell system 100 embodiment is combined with the fuel cell system 100 embodiment, the latter including another component of the air heat exchanger 192.

[0060] In addition, in a Figure 5 The ejector device as the cathode mixing section 135 and Figure 6 In another embodiment of the component of the air heat exchanger 192, the cooling device 180 can be assisted by water cooling, which may be provided by the application system environment of the fuel cell system 100.

[0061] In addition, in a Figure 6 In another embodiment of the component of the air heat exchanger 192, a fan can be used as the cathode mixing part 135 instead. Figure 5 The ejector device.

[0062] Or, in a file that includes Figure 6 The fan is used as the cathode mixing part 135 instead of the component part of the air heat exchanger 192. Figure 5 In an embodiment of the ejector device, the cooling device 180 may be assisted by water cooling, which may be provided by the application system environment of the fuel cell system 100.

[0063] The above explanations of the embodiments are merely intended to describe the present invention by way of example.

[0064] Reference numerals list

[0065] 100 fuel cell systems

[0066] 110 fuel cell stack

[0067] 120 Anode

[0068] 121 Anode supply heat exchanger

[0069] 122 Anode Supply Department

[0070] 123 Mixing Department

[0071] 124 Anode discharge part

[0072] 126 Condensing device

[0073] 128 Drainage outlet

[0074] 129 discharge valve

[0075] 130 cathode part

[0076] 131 cathode supply heat exchanger

[0077] 132 Cathode supply unit

[0078] 133 cathode exhaust heat exchanger

[0079] 134 cathode discharge part

[0080] 135 cathode mixing unit

[0081] 140 Anode circulation unit

[0082] 160 control valve

[0083] 170 cathode circulation unit

[0084] 171 cathode circulation fan

[0085] 180 Active Cooling Device

[0086] 190 air heat exchanger

[0087] 192 air heat exchanger

[0088] 193 Reprocessing Unit

[0089] 194 Waste gas reaction device

[0090] 195 discharge valve

[0091] AZG anode supply gas

[0092] AAG anode exhaust gas

[0093] ARG anode circulating gas

[0094] KZG cathode supply gas

[0095] KAG cathode exhaust gas

[0096] KRG cathode circulating gas

[0097] BRG fuel gas

[0098] LU Air

[0099] 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), wherein: The anode discharge part (124) is connected to the anode circulation part (140) for circulating the anode exhaust gas (AAG) as the anode circulation gas (ARG) to the anode supply part (122), and the cathode part (130) has a cathode supply part (132) for supplying the cathode supply gas (KZG) and a cathode discharge part (134) for discharging the cathode exhaust gas (KAG). It is characterized in that An active cooling device (180) for cooling the anode circulating gas (ARG) is provided in the anode circulation section (140), wherein a drain port (128) is provided downstream of the active cooling device (180) for discharging condensed water (KW) condensed in the active cooling device (180), wherein a mixing section (123) is provided downstream of the drain port (128) for mixing the anode circulating gas (ARG) with the fuel gas (BRG) and supplying the mixed anode circulating 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 active cooling device (180) has a heat-driven cooling device, which in particular has an absorption heat pump, wherein the active cooling device (180) is arranged in heat-transfer contact with the cathode discharge part (134) for achieving thermal drive by means of the heat contained in the cathode exhaust gas (KAG).

3. The fuel cell system (100) according to any one of the preceding claims, characterized in that The active cooling device (180) has an electrically driven cooling device.

4. The fuel cell system (100) according to any one of the preceding claims, characterized in that The anode circulation section (140) has a condensing device (126) in heat transfer contact with the cathode supply section (132), and is used to cool the anode circulation gas (ARG) by heating the cathode supply gas (KZG), wherein a drain port (128) is provided downstream of the condensing device (126) and upstream of the active cooling device (180) for discharging condensed water (KW) condensed in the condensing device (126).

5. The fuel cell system (100) according to any one of the preceding claims, characterized in that The cathode exhaust (134) is designed without a catalyst device and / or a burner.

6. The fuel cell system (100) according to any one of the preceding claims, characterized in that The anode exhaust part (124) and the anode circulation part (140) are designed without a distribution part to achieve complete or substantially complete circulation of the anode exhaust gas (AAG) as anode circulation gas (RZG).

7. The fuel cell system (100) according to any one of the preceding claims, characterized in that In the anode circulation section (140), a discharge valve (129) is provided downstream of the active cooling device (180) and downstream of the drain port (128) for controllably discharging at least a portion of the circulating gas (RZG).

8. The fuel cell system (100) according to any one of the preceding claims, characterized in that The anode exhaust (124) has an anode supply heat exchanger (121) in heat transfer contact with the anode supply (122) to transfer heat from the anode exhaust gas (AAG) to the anode supply gas (AZG).

9. The fuel cell system (100) according to any one of the preceding claims, characterized in that The mixing section (123) is designed as an ejector device, wherein a fuel supply mechanism of a fuel gas (BRG) is in communication with a primary port of the ejector device, and the anode circulation section (140) is in communication with a secondary port of the ejector device.

10. The fuel cell system (100) according to any 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).

11. 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).

12. 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 (123) for controlling the volume flow of the fuel gas (BRG) flowing through the mixing section (123).

13. The fuel cell system (100) according to any one of the preceding claims, characterized in that The anode exhaust (122) is designed without an external cooling circuit.

14. The fuel cell system (100) according to any 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 (KZG) as cathode circulation gas (KRG).

15. A method for circulating anode exhaust gas (AZG) as anode circulation gas (ARG) in a fuel cell system (100) having the features of one of claims 1 to 14, comprising the following steps: - cooling the anode circulating gas (ARG) to below the boiling point of water by active cooling of the active cooling device (180), - separating condensed water (KW) from the anode circulating gas (ARG), - Mixing the dried anode circulating gas (ARG) with the fuel gas (BRG) to form the anode supply gas (AZG).

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