CN117321814A

CN117321814A - Circulation device for circulating anode off-gas as circulation gas in fuel cell system

Info

Publication number: CN117321814A
Application number: CN202280035141.XA
Authority: CN
Inventors: 拉斐尔·纽鲍尔; R·珀斯彻尔; 马利斯·霍费尔; 贝恩德·赖特尔; C·施勒克纳; 约尔格·马斯
Original assignee: AVL List GmbH
Current assignee: AVL List GmbH
Priority date: 2021-05-18
Filing date: 2022-05-17
Publication date: 2023-12-29
Also published as: AT525145A1; DE112022002638A5; WO2022241494A1; AT525145B1

Abstract

The invention relates to a circulation device (10) for circulating an anode exhaust gas (AAG) as a circulating gas (RG) from an anode portion (120) of a fuel cell stack (110) of a fuel cell system (100), comprising a circulation line (20) with a receiving portion (22) for connecting in fluid communication to an anode outlet (124) of the anode portion (120), wherein the circulation line (20) comprises a first partial circulation line (24), a second partial circulation line (26) and a distribution device (30) for distributing the circulating gas (RG) to the two partial circulation lines (24, 26), wherein the first partial circulation line (24) further comprises a first injector device (40) for connecting in fluid communication into an anode supply (122) of the anode portion (120), and the second partial circulation line (26) comprises a blower device (94) for connecting in fluid communication into the anode supply (122) upstream of the first injector device (40).

Description

Circulation device for circulating anode off-gas as circulation gas in fuel cell system

Technical Field

The present invention relates to a circulation device for circulating anode exhaust gas of a fuel cell system as a circulation gas, a fuel cell system having at least one such circulation device, and a method for distributing a circulation gas using such a circulation device.

Background

It is known that fuel cell systems have a circulation line for returning at least a portion of the anode exhaust gas from the anode section to the anode supply. This serves to send part of the unburned fuel contained in the anode off-gas into the fuel cell stack for reuse and thus to improve the fuel cell system operating efficiency. For reinfusion, two reinfusion possibilities are known in principle. First, an active return by means of a blower is known, which actively feeds the circulating gas into the anode supply. A passive solution is to use a so-called injector device which provides a suction function at the suction connection to the circulation line by means of the fuel at the drive connection and thus for sucking in the circulation gas.

A disadvantage of the known blower is that it is prone to heat generation. Since the anode exhaust gas generally has a high temperature of up to about 1000 ℃ during operation of the fuel cell system, the blower device must be designed to be heat-resistant accordingly. This results in high construction costs and correspondingly high costs for the heat-resistant material. Even in the case of advanced equipment, severe wear is assumed at the blowing devices of the known solutions because of the high temperature load.

The use of passive ejector devices in the known solutions results in high suction powers that have to be generated in the ejector device at high circulation rates and correspondingly high circulation gas flows. In order to be able to ensure a high suction power, a high primary pressure is required at the drive nipple of the ejector device. This results in a high energy cost that must be paid in the absence of a correspondingly high preload in order to be able to provide compression work to obtain a high primary pressure. Both the high primary pressure and the correspondingly high suction power also lead to very high flow rates in the ejector device, in particular at supersonic levels, which may occur. This results in high loads and correspondingly complex constructional requirements in the injector device.

Disclosure of Invention

The object of the invention is to at least partially eliminate the aforementioned disadvantages. The object of the invention is in particular to provide a reduced delivery pressure in a simple manner at low cost while reducing wear in the circulation by means of the blower.

The aforementioned object is achieved by a circulation device having the features of claim 1, a circulation device having the features of claim 16, a fuel cell system having the features of claim 17 and a method having the features of claim 20. Other features and details of the invention come from the dependent claims, the description and the figures. The features and details described in connection with the circulation device according to the invention are obviously applicable here also in connection with other circulation devices according to the invention, fuel cell systems and methods according to the invention, and vice versa, so that the disclosures on these inventive aspects are always cross-referenced or cross-referenced.

According to the present invention, the circulation device is used for circulating anode off-gas from the anode portion of the fuel cell stack of the fuel cell system as a circulation gas. For this purpose, the circulation device has a circulation line with a receiving portion for fluid communication with an anode exhaust connected to the anode portion. The circulation line is divided into a first partial circulation line and at least one second partial circulation line. A distribution device is also provided for distributing the recycle gas to the two partial recycle lines. The first part-cycle line is provided with first injector means for feeding in fluid communication to the anode supply of the anode section. The second partial circulation line has a blower means for adding in fluid communication to the anode supply upstream of the first injector means.

The circulation device according to the invention forms part of a fuel cell system, in particular as will be described in more detail below. The blower device is here added to the anode supply upstream of the first injector device in such a fuel cell system.

The core idea according to the invention is based on combining the transport possibility of the ejector means with the transport possibility of the blower means to realize a circulation function in the fuel cell system. The anode exhaust gas, optionally containing a residual amount of fuel, can now be fed via the receiving portion into the circulation line of the circulation device according to the invention. This can be done until a very high circulation rate is achieved, for example about 80% of the anode exhaust gas. This means that about 20% of the anode exhaust gas is led into the separate exhaust gas line, while the majority of the anode exhaust gas, in this case about 80% of the anode exhaust gas, is fed into the cycle as recycle gas.

In the known solutions with a single ejector device, a very high flow rate and/or a large circulating gas supply is/are added to the ejector device in this way, whereas in the design of the invention the distribution of the large flow can be performed by means of the distribution device. In the known solutions a large amount of circulating gas results in a correspondingly high suction power in the ejector device, whereas in the inventive combination the required suction power can be reduced.

It is to be noted here that the dispensing device allows the dispensing of these partial circulation lines in a fixedly set manner, in a switchable manner or even in a variable and in particular flexibly controllable manner. In the design according to the invention, it is thus now possible that a part of the circulating gas is not diverted to the first ejector, but to the blower device. If it is assumed that the distribution is 50:50, for example, half is fed to the first ejector means and the other half to the blower means at a high recycle gas recirculation. This allocation brings a number of advantages.

The advantages with regard to the ejector device are in particular that the suction connection of the ejector device is supplied with a significantly reduced amount of circulating gas. A correspondingly reduced suction power is also required at the suction connection of the ejector device due to the reduced amount. Since there is generally a nonlinear relationship between the primary pressure at the drive connection of the first injector device and the suction power at the suction connection associated therewith, a reduction in the required suction power results in a significantly stronger reduction in the corresponding required operating pressure. Thus if the circulating gas flow quantity at the suction connection is halved, for example by reducing the suction power from, for example, 60 mbar to 30 mbar, this results in a significantly stronger restriction of the required operating pressure at the drive connection, for example by a factor of up to 5, i.e. from about 5 bar to about 1 bar. The weakening effect on the primary pressure at the drive nipple thus exceeds the reduction of the suction power at the suction nipple.

In order to now also be able to achieve the desired high circulation rate, for example about 80%, with a reduced flow through the first ejector device, the desired circulating gas flow remaining is now guided to the blower device via the second partial circulation line in the design of the invention. The blower can now also send the circulating gas back into the anode supply. However, in comparison with prior art solutions using only a blower, the required flow quantity in the blower is correspondingly reduced by the fraction of the first injector device at high circulation rates, since at least a part of the desired circulation quantity is already fed into the anode supply via the injector device. Apart from the correspondingly reduced flow cross section, the reduced power required for the blower and the further constructional advantages, this results in a correspondingly reduced input heat, since a smaller flow quantity reaches the blower in the heated state.

In summary, a high circulation flow rate can be achieved with correspondingly high circulation rates in the design according to the invention, whereby, owing to the combination of the first ejector device and the blower device, a low primary pressure at the drive pipe connection of the first ejector device, a correspondingly subsonic operating mode at the suction pipe connection of the ejector device and a low-wear design of the blower device can still be used in combination with one another.

It is thus possible to provide a higher efficiency for the fuel cell system at a high circulation rate without having to take into account the high costs known hitherto with regard to high primary pressures at the injector device or high protection against wear at the blower device.

It may be advantageous in the circulation device according to the invention for the first part of the circulation device to open into the suction connection of the first ejector device and for the anode supply to open into the drive connection of the first ejector device. The drive nipple and the outlet of the first injector means thus form part of the anode supply flow path, while the suction nipple can be said to be a lateral supply of circulated circulating gas. The mixing of the gas fed in from the drive pipe connection with the circulating gas thus takes place in the first injector device. As already explained, the high circulation gas flow in the suction connection can also be minimized at high circulation rates, so that subsonic suction occurs correspondingly at the suction connection of the first ejector device. For this purpose, a significantly lower pressure is required on the primary side, i.e. at the drive pipe connection of the first injector device, so that the primary flow is no longer accelerated to supersonic speed. For this purpose, the ejector device can advantageously be designed as a jet pump device, in particular as a suction jet pump.

It is further advantageous if in the circulation device according to the invention a heat exchanger is arranged in the second partial circulation line, in particular downstream of the blower device and/or upstream of the first injector device, for heat exchange with the anode supply. In other words, the cold side of the heat exchanger is added to the anode supply downstream of the blower means and upstream of the first injector means. This has two advantageous effects. First, the waste heat in the circulating gas in the second partial circulating line can be further reduced by the heat exchanger, so that the heat load in the blower can be further reduced. The already explained wear advantages based on the temperature-induced wear reduction of the blower device are further enhanced. Secondly, the hot white is not lost due to the addition to the anode supply, but rather is used to preheat in particular the fuel or the mixture comprising fuel and recycle gas to reach the anode section correspondingly at a preheated temperature. The overall efficiency of the fuel cell system is further improved because unwanted heat loss from the system can be avoided.

It is also advantageous when in the circulation device according to the invention a condenser is provided in the second partial circulation line upstream of the blower device for condensing vaporous moisture from the circulating gas, wherein the condenser distributes condensate to the condensate line and the remaining circulating gas to the residual exhaust gas line. This allows a large amount of water vapor to be condensed from the circulating gas and accordingly to be fed separately after the condenser again in the condensate line. Both the condensate line and the residual exhaust gas line thus form part of the second partial circulation line. Furthermore, the pressure in the second part of the recycle gas line can be reduced further in this way. Such a condenser is combined in particular with an evaporator to finally convert the condensed condensate again into the vapor phase.

It is also advantageous if an evaporator for evaporating condensate is provided in the condensate line in the circulation device according to the preceding paragraph. This is combined in particular with a mixing device within the anode supply, into which the evaporated condensate can then in turn be fed for mixing with fuel, for example. The heat for the required evaporation energy can here originate from a separate exhaust gas line, so that the evaporator is designed as a heat exchanger in order to draw the required evaporation enthalpy as waste heat from the outgoing exhaust gas.

It is also advantageous if in the circulation device according to the invention a mixing device is provided in the condensate line, in particular downstream of the evaporator, for mixing with the fuel of the fuel source and/or for mixing with the circulating gas downstream of the blowing device. It is thus possible that the fuel and the evaporated condensate are mixed in the same mixing device with the recycle gas from the residual exhaust gas line and the blowing device. The mixture of the three components now subsequently allows the anode supply gas in the anode supply to be fed into the drive pipe connection of the first injector device. The blower device is also used in this case in particular for generating the desired primary pressure at the drive nipple of the first injector device.

It is also advantageous in the circulation device according to the invention to provide a second ejector device for addition in fluid communication to the anode supply in the second partial circulation line upstream of the blower device. It is thus possible to also use two or more stages of ejector devices, so that a finer distribution of these flows can be achieved. The advantage of the invention of reducing thermal wear in the blower and of creating subsonic conditions can also be better provided in this case, in particular for greater circulation gas flows.

Further advantages can be brought about when in the circulation device according to the invention the second partial circulation line opens into the drive pipe joint of the second spraying device. The second partial circulation line can be fed in gaseous form or, as will be explained later, for example feed the liquid condensate in the circulation gas into the second injection device. As a result of the pipe connection to the drive pipe, a pressure in the second partial circulation line is now provided as a primary pressure for the second injection device, which differs from the design of the first injection device. The suction line connection can be formed in various ways and can receive, for example, fuel or another part of the circulating gas. Preferred here is a design as will be described in more detail later also with reference to the condenser arrangement.

It is also advantageous if in the circulation device according to the invention a condenser device is provided in the second partial circulation line upstream of the second injection device for condensing the vaporous moisture from the circulating gas. The condenser means distributes condensate to the condensate line and the remaining residual recycle gas to the residual exhaust gas line. The condensate line and the residual exhaust gas line form part of this section of the second partial circulation line. The circulating gas which has not been distributed to the first spraying device in the distribution device now flows into the condenser device and can be cooled, for example, in the manner of being cooled by the inlet air as cathode supply gas, to a temperature below the condensate temperature of the condensable components of the circulating gas. For example, water is used here as a condensable component, so that cooling the recycle gas to below 100 ℃ causes the water to condense out. The condenser device preferably separates the liquid condensate from the remaining gaseous residual exhaust gas, so that the condensate can be conveyed further in the condensate line and the residual exhaust gas in the residual exhaust gas line. The condensate line is preferably connected here to the drive pipe connection of the second spraying device, and the gas line is connected to the suction pipe connection of the second spraying device. By adding a condensate line to the primary side, a further reduction of the work costs required for generating pressure at the drive pipe joint is caused. In particular, since the condensate is present in liquid form, the costs for forming the desired high pressure in the prescribed manner on the primary side are significantly lower than if the drive tube connection of the second injection device requires compression of the gaseous component.

In the circulation device according to the preceding paragraph, it may be advantageous to provide a compressor device in the condensate line for compressing the condensate. This compression causes an increase in the prescribed pressure at the drive pipe interface of the second injection device, where the compressor work is significantly lower than the compression of the gaseous component. In particular this is combined with an evaporator according to the next paragraph.

A further advantage can thus be brought about when an evaporator for evaporating condensate is arranged in the circulation device of the invention upstream of the second injection device and in particular downstream of the compressor device in the condensate line. This allows, in particular after the pressure has been increased by the compressor device, the liquid compressed condensate to continue to evaporate in the liquid state of the condensate and to be supplied to the second injection device in this way at a correspondingly produced high pressure on the primary side of the drive pipe connection. In this case, an intermediate pressure accumulator can also be provided in the case of an evaporator and/or compressor device in order to compensate or completely avoid the transfer of pressure pulses from the evaporator and/or compressor device to the drive line connection of the second injection device. In particular such an evaporator may be combined with heat transfer from one or more exhaust gas lines of the fuel cell system, whereby cooling of the anode exhaust gas, cooling of the cathode exhaust gas and/or cooling of the combined exhaust gas stream may be performed to provide heat for evaporation or at least auxiliary evaporation.

It may further be advantageous to provide a mixing device in the residual exhaust gas line in the circulation device of the invention for connection in fluid communication to a fuel source for mixing the residual circulation gas with the fuel. In other words, the fuel is fed from the fuel source in gaseous form to the recycle gas in the residual exhaust gas line, so that it is jointly fed into the system, preferably through the suction pipe connection of the second injection device. Since the fuel source can thus also be connected in fluid communication to the anode supply via the suction pipe connection of the second injection device, a separate compressor for fuel can be dispensed with in case of a low pressure in the fuel source. Instead, this may be sufficient to draw in the residual recycle gas in gaseous form together with the required fuel in the residual exhaust gas line under corresponding pressure conditions at the second injection device. The overall efficiency in the operation of the fuel cell system can be further improved in this way.

It may further be advantageous to provide in the circulation device of the invention a mixing device in the condensate line and in particular upstream of the compressor device and/or upstream of the evaporator for connection in fluid communication to a fuel source for mixing the condensate with the fuel. This is conceivable as an alternative or complement to the embodiment described in the preceding paragraph. It is possible here for the fuel to be fed even in liquid form, in particular when the mixing device is arranged upstream of the evaporator. It may therefore be possible to store and supply fuel in liquid form, so that the corresponding costs required for fuel supply may be further reduced. It is also possible here for the fuel from the fuel source to be fed into the fuel cell system in a low-pressure or even pressureless manner, since the required delivery work and/or compressor work is supplied in liquid form by the compressor device together with the fuel and condensate.

It may further be advantageous in the circulation device according to the invention for the mixing device to have a fuel supply with a regulating valve for changing the amount of fuel flow in the mixing device. This is in particular combined with a regulating valve according to the next paragraph. Such a regulating valve allows to change the fuel flow quantity in the mixing device at least once qualitatively, preferably quantitatively.

It is also advantageous if in the circulation device according to the invention a regulating valve is provided in the residual exhaust gas line for changing the flow quantity in the residual exhaust gas line. In particular in combination with the control valve of the preceding paragraph in the fuel supply, a defined control of these flow amounts can be carried out in this way, so that not only the flow amounts can be controlled in a defined manner, preferably quantitatively, but also the pressure to be present at the drive pipe connection and/or the suction pipe connection of the second injector device can be controlled.

Another subject of the invention is a circulation device for circulating anode exhaust gas from the anode part of a fuel cell stack of a fuel cell system as a circulation gas. In this embodiment, the circulation device has a circulation line with a receiving portion for fluid communication with an anode exhaust connected to the anode portion. A first injector device is provided in the circulation line for fluid communication addition to the fuel supply of the fuel source, and a blower device is provided downstream of the first injector device for fluid communication addition to the anode supply. This embodiment is a similar basic idea of the invention, i.e. that the ejector device is used in combination with the blower device. However, in this embodiment, no recirculation gas is required, since the desired suction function is not used to suck the recirculation gas in the first injector device, but rather to suck the fuel. For this purpose, the circulation line opens into the drive connection of the first injector device and in this way subsonic conditions are also formed at the suction connection for sucking fuel from the fuel source. The "mixing of fuel and recycle gas in the first injector means at subsonic speed" results in a mixture as anode supply gas, which is now fed into the anode section in the second stage by the blower means again as anode supply gas. In this embodiment, the change between the drive pipe connection and the suction pipe connection also results in the first ejector device avoiding supersonic conditions. Furthermore, the mixing of the hot recycle gas with the cold fuel results in a dual advantage being obtained. The mixing temperature occurs as a result of the mixing, with a consequent heating of the desired fuel on the one hand and a desired cooling of the hot recycle gas on the other hand. The mixing temperatures that occur are significantly lower than the temperature of the hot circulating gas itself, so that the thermal load and thermal damage in the downstream blower device are correspondingly minimized. In this design, it is also possible to integrate a heat exchanger in the anode supply downstream of the blower device, in order to be able to provide additional heat exchange for heating the anode supply gas and for achieving additional cooling of the recycle gas.

Another subject of the invention is a fuel cell system for generating an electric current from a fuel. In this regard, the fuel cell system has a fuel cell stack including an anode portion and a cathode portion. The anode portion has an anode supply portion for supplying an anode supply gas and an anode discharge portion for discharging an anode off-gas. The cathode portion has a cathode supply portion for supplying a cathode supply gas and a cathode discharge portion for discharging a cathode off-gas. Here, the fuel cell system is also equipped with the circulation device of the present invention. The fuel cell system of the invention thus brings about the same advantages as described in detail with respect to the circulation device of the invention.

The fuel cell stack preferably has a plurality of individual fuel cells in order to be able to provide the desired current generating capacity. Carbon-containing gases such as methane, ethane or natural gas or hydrogen are preferably used as fuel. Oxygen-containing inlet air is used in particular as cathode supply gas. It is apparent that other components and features may be preferably included in such fuel cell systems, such as reformers for preparing and reforming fuel, oxidation catalysts or heat exchanger devices for exhaust gas aftertreatment, in order to further increase thermal efficiency in the operation of the fuel cell system.

It may be advantageous in the fuel cell system according to the invention to provide mixing means in the anode supply upstream of the first injection means and downstream of the blowing means for mixing fuel from the fuel source with the circulating gas. Such a mixing device can also be used in combination with the already explained evaporation condensate feed possibilities. The fuel is preferably fed into the mixing device in gaseous form here, so that the blower device serves for mixing and also provides a mixed anode supply gas with the desired primary pressure required on the primary side of the first injector device.

It is further advantageous in the fuel cell system according to the invention that an exhaust gas distribution device is provided in the anode exhaust gas outlet for distributing the anode exhaust gas to the receiving portion of the circulation line and to the exhaust gas line separate therefrom. A separate exhaust gas line is used in particular for feeding the gas which is not circulated into the environment. In such a separate exhaust gas line, for example, a combination with the cathode exhaust gas can be carried out and further aftertreatment steps can be specified. So that for example an oxidation catalyst, another heat exchanger, etc. may be provided. It is also conceivable within the scope of the invention to exchange heat with the respective recycle gas part, in particular the second part recycle line.

Another subject of the invention is a method for distributing a circulating gas in a circulating device according to the invention in a fuel cell system according to the invention, having the following steps:

sensing the operating condition of the fuel cell system,

-distributing the recycle gas in a distribution device to the two partial recycle lines.

The method of the invention thus brings about the same advantages as described in detail in relation to the circulation device of the invention and the fuel cell system of the invention. The distribution rate is carried out in a controlled manner, in particular at a high circulation rate, i.e. for example 80% of the anode exhaust gas occurring as a result of the recirculation, and is preferably dependent on the operating conditions of the fuel cell system. For example, it may be distributed at 50:50, so that 50% of the recycle gas is distributed to the first part of the recycle line and another 50% of the recycle gas is distributed to the second part of the recycle line. In addition to the operating conditions of the fuel cell system, it is also preferable to consider the desired speed within the injection device and/or the pressure at the injection device interface.

Drawings

Other advantages, features and details of the invention come from the following description of embodiments of the invention described in detail with reference to the drawings, which schematically show:

figure 1 shows one embodiment of the fuel cell system of the present invention,

figure 2 shows another embodiment of the fuel cell system of the present invention,

figure 3 shows another embodiment of the fuel cell system of the present invention,

figure 4 shows another embodiment of the fuel cell system of the present invention,

figure 5 shows another embodiment of the fuel cell system of the present invention,

fig. 6 shows another embodiment of the fuel cell system of the present invention.

Detailed Description

Fig. 1 schematically shows a very simple design of a fuel cell system 100 of the present invention. Here, in the fuel cell stack 110, the anode supply gas AZG is sent into the anode portion 120 through the anode supply portion 122 and there reacts with the cathode supply gas KZG sent into the cathode portion 130 via the cathode supply portion 132. Here, the anode off-gas AAG discharged through the anode discharge portion 124 and the cathode off-gas KAG discharged through the cathode discharge portion 134 are generated. The anode exhaust gas AAG is in this embodiment divided in the exhaust gas distribution device 160 into the recycle gas RG of the recycle line 20 and the remaining residual exhaust gas in the separate exhaust line 170. The circulating gas RG is fed from the receiver 22 in the circulating line RG to the distributor device 30 and is distributed there, for example, to the two partial circulating lines 24 and 26 at a ratio of 50:50. Through the first partial circulation line 24, the part of the circulating gas RG supplied therein is sucked into the first ejector device 40 via the suction connection 44. To achieve the suction effect, a corresponding primary pressure is set at the drive nipple 42 of the first injector device 40. It is provided by the anode supply gas AZG arriving there, which is a mixture formed by the fuel BS and the recycle gas RG coming from the second partial recycle line 26.

The second flow of the recycle gas RG is first led in the second partial recycle line 26 through a heat exchanger 150 for cooling and at the same time transferring heat to the anode supply gas AZG. The cooled circulation gas RG is now actively fed and placed under pressure in the blower device 94, and is subsequently mixed in the mixing device 90 with the fuel BS from the fuel source 140 via the fuel supply 142 and supplied to the first injector device 40 on the primary side of the drive pipe connection 42.

Fig. 1 clearly shows a possible way of distributing the circulating gas RG to two different circulation systems, namely the first ejector device 40 in the first partial circulation line 24 and the blower device 94 in the second partial circulation line 26.

Fig. 2 shows another embodiment, which integrates a condenser 60 and an evaporator 80 into the embodiment of fig. 1. The condenser 60 is driven here by an air source 180, so that the cooling of the circulating gas RG leads to the condensation of condensate K. Condensate K is separately (here in condensate line 62) discharged and subsequently converted into a vapor phase again in evaporator 80 by compressor device 70 for mixing in mixing device 90. The residual exhaust gas is fed as circulating gas RG alone in the residual exhaust gas line 64 to the blower device 94, so that in the manner already described the desired pressure can be provided for mixing in the mixing device 90 and likewise for the primary pressure at the drive nipple 42 of the first injector device 40.

Fig. 3, 4 and 5 show further embodiments, in which the injector devices are divided into a first injector device 40 and a second injector device 50, which is arranged upstream of the blower device 94, in this case. With respect to fig. 3, 4 and 5, the multi-stage injector apparatus will be further explained below.

Fig. 3 schematically illustrates a fuel cell system 100 having a fuel cell stack 110. The fuel cell stack 110 is divided into an anode portion 120 and a cathode portion 130. Operation of the fuel cell system 100 requires a fuel BS, which is provided by a fuel source 140. Air provided by the air source 180 is also required. For operation of the fuel cell system 100, the fuel BS of the fuel source 140 is now supplied by the fuel supply 142 in the embodiment of fig. 3. Through steps in the anode supply 122, the fuel BS is now fed into the anode section 120 and reacts there in these fuel cells with the inlet air as cathode supply gas KZG provided via the cathode supply 132 and the cathode section 130. The reaction generates an electric current and an anode off-gas AAG and a cathode off-gas KAG.

Since the anode exhaust gas AAG contains different amounts of unused fuel BS depending on the operating conditions, in the embodiment of the fuel cell system 100, a part of the anode exhaust gas AAG present is distributed from the anode outlet 124 to the receptacle 22 by means of the exhaust gas distribution device 160. The divided portions are fed back as circulating gas RG into the circulation line 20 and finally distributed in the distribution device 30 to the first partial circulation line 24 and the second partial circulation line 26. The integration of the first partial circulation line 24 and the supply of the circulation gas RG to the suction line connection 44 of the first injection device 40 are in principle also present in the known solutions. In this case, a pressure is generated via the drive pipe connection 42 of the first injection device 40, which pressure results in a suction effect on the circulating gas RG from the first partial circulation line 24 at the suction pipe connection 44.

In the design of the fuel cell system 100 according to the invention, however, a part of the circulating gas RG is now distributed via the distribution device 30 to the second partial circulation line 26. This now results in a preheating of the fuel BS and a simultaneous cooling of the circulating gas RG flowing through it via the heat exchanger 150. The circulating gas RG precooled in this way reaches in this embodiment a condenser device 60, which obtains the cooling power required for the desired condensation from a separate cooling cycle or from the intake air of the air source 180 as shown in fig. 3.

Further reduction in the temperature of the recycle gas RG in the second part-cycle line 26 causes condensate K to be present, which is continued to be conveyed via condensate line 62. Since it is here a liquid condensate, it can be compressed to the desired pressure by means of the subsequent compressor device 70, which allows a significantly smaller compressor work than gaseous compression. Condensate K under pressure is then evaporated in the evaporator 80, wherein in the present embodiment the waste heat from the separate exhaust gas line 170 is utilized. The condensate K, which is still evaporated under pressure, is now located at the drive pipe connection 52 of the second spraying device 50 and can in this way provide a suction function at the suction pipe connection 54 of the second spraying device 50 as a result of the formation of negative pressure. The circulating gas RG in the residual exhaust gas line 64 remaining after the condenser device 60 is thus again sucked into the second injection device 50 via the suction line connection 54 and is then mixed with the supplied fuel BS in the mixing device 90 in the anode supply 122. Furthermore, in order to ensure a control option in this embodiment, the control valve 12 is also integrated into the residual exhaust gas line 64.

To further reprocess the anode exhaust gas AAG that is not circulated, the anode exhaust 124 feeds it via a separate exhaust line 170 to the catalyst device 172, and the cathode exhaust 134 also feeds the cathode exhaust gas KAG to the catalyst device. The cathode exhaust gas KAG is here led through a separate heat exchanger 150, which may supply heat to the reformer 126 to reform the anode supply gas AZG. Multiple heat transfers, here intake air to the air source 180 at the heat exchanger 150 and also for evaporation within the evaporator 80, are performed before all of the common exhaust gas can be expelled to the environment after the catalyst device 172.

Fig. 4 shows an alternative design of the solution shown in fig. 3. The basic components remain unchanged, but the fuel BS is added here at other points, i.e. in the circulation line 20 and, rather, in the second partial circulation line 26. The gaseous fuel BS can be fed here into the mixing device 90 of the residual exhaust gas line 64 by means of the fuel supply 142 in a manner which can be controlled by means of the control valve 12. The already explained suction function at the suction line connection 54 of the second injection device 50 can also be provided here for the suction of the gaseous fuel BS. The other components here operate in a similar or identical manner as explained with reference to fig. 3.

An embodiment is also shown in fig. 5, in which the addition of fuel BS is integrated into the second partial circulation line 26. Here, however, the fuel BS can even be added in liquid form to the liquid condensate K in the condensate line 62 and then be compressed together with the condensate by the compressor device 70 and evaporated by the evaporator 80. The other components of the fuel cell system 100 also function in a similar or identical manner as explained herein with reference to fig. 3.

In fig. 6, another embodiment of the circulation device 10 is added to the fuel cell system 100. The advantages of the invention are present here because the ejector device 40 is combined with the blower device 94 but without the distribution device 30. The injector device 40 and the blower device 94 are thus in line here, but the suction connection 44 of the first injector device 40 is connected to the fuel supply 142 here, so that subsonic conditions can also be provided in the first injector device 40 here. The whole is operated by a corresponding pressure in the circulation line 20 at the driving nipple 42.

The above explanation of the embodiments describes the present invention only in the scope of examples.

List of reference numerals

10. Circulation device

12. Regulating valve

20. Circulation pipeline

22. Receiving portion

24. First part circulation pipeline

26. Second part circulation pipeline

30. Dispensing device

40. First injector device

42. Driving pipe joint

44. Suction pipe joint

50. Second injector device

52. Driving pipe joint

54. Suction pipe joint

60. Condenser

62. Condensate line

64. Residual waste gas pipeline

70. Compressor device

80. Evaporator

90. Mixing device

92. Heat exchanger

94. Blower device

100. Fuel cell system

110. Fuel cell stack

120. Anode part

122. Anode supply part

124. Anode discharge portion

126. Reformer with a heat exchanger

130. Cathode part

132. Cathode supply part

134. Cathode discharge portion

140. Fuel source

142. Fuel supply part

150. Heat exchanger

160. Exhaust gas distribution device

170. Waste gas pipeline

172. Catalytic converter device

180. Air source

BS fuel

K condensate

RG cycle gas

AZG anode supply gas

AAG anode exhaust gas

KZG cathode supply gas

KAG cathode exhaust.

Claims

1. A circulation device (10) for circulating anode exhaust gas (AAG) as circulating gas (RG) from an anode portion (120) of a fuel cell stack (110) of a fuel cell system (100), having a circulation line (20) with a receiving portion (22) for being connected in fluid communication to an anode discharge portion (124) of the anode portion (120), wherein the circulation line (20) has a first partial circulation line (24), a second partial circulation line (26) and a distribution device (30) for distributing the circulating gas (RG) to the two partial circulation lines (24, 26),

it is characterized in that the method comprises the steps of,

the first partial circulation line (24) has a first injector device (40) for connecting in fluid communication into an anode supply (122) of the anode section (120), and the second partial circulation line (26) has a blower device (94) for connecting in fluid communication into the anode supply (122) upstream of the first injector device (40).

2. The circulation device (10) according to claim 1, characterized in that the first partial circulation line (24) opens into the suction connection (44) of the first ejector device (40), and the anode supply (122) opens into the drive connection (42) of the first ejector device (40).

3. The circulation device (10) according to one of the preceding claims, characterized in that a heat exchanger (150) is provided in the second partial circulation line (26) for exchanging heat with the anode supply (122), in particular downstream of the blower device (94) and/or upstream of the first injector device (40).

4. The circulation device (10) according to one of the preceding claims, characterized in that a condenser (60) is arranged in the second partial circulation line (26) upstream of the blowing device (94) for condensing steam-like moisture from the circulation gas (RG), wherein the condenser (60) distributes condensate (K) to the condensate line (62) and the remaining circulation gas (RG) to the residual exhaust gas line (64).

5. The circulation device (10) according to claim 4, characterized in that an evaporator (80) for evaporating the condensate (K) is provided in the condensate line (62).

6. The circulation device (10) according to claim 4 or 5, characterized in that a mixing device (90) is arranged in the condensate line (62), in particular downstream of the evaporator (80), for mixing with fuel (BS) from a fuel source (140) and/or for mixing with the circulation gas (RG) downstream of the blowing device (94).

7. The circulation device (10) according to one of the preceding claims, characterized in that a second ejector device (50) is provided in the second partial circulation line (26) upstream of the blower device (94) for the fluid-connected connection into the anode supply (122).

8. The circulation device (10) according to claim 7, characterized in that the second partial circulation line (26) opens into a drive pipe connection (52) of the second ejector device (50).

9. The circulation device (10) according to claim 7 or 8, characterized in that a condenser (60) is arranged in the second partial circulation line (26) upstream of the second ejector device (50) for condensing steam-like moisture from the circulation gas (RG), wherein the condenser (60) distributes condensate (K) into a condensate line (62) and the remaining circulation gas (RG) into a residual exhaust gas line (64).

10. The circulation device (10) according to claim 9, characterized in that a compressor device (70) is arranged in the condensate line (62) for compressing the condensate (K).

11. The circulation device (10) according to claim 9 or 10, characterized in that an evaporator (80) for evaporating the condensate (K) is provided in the condensate line (62) upstream of the second ejector device (50) and in particular downstream of the compressor device (70).

12. The circulation device (10) according to one of claims 9 to 11, characterized in that a mixing device (90) is provided in the residual exhaust gas line (64) for being connected in fluid communication to the fuel source (140) for mixing the residual circulation gas (RG) with the fuel (BS).

13. The circulation device (10) according to one of claims 9 to 12, characterized in that a mixing device (90) is provided in the condensate line (62), in particular upstream of the compressor device (70) and/or upstream of the evaporator (80), for connection in fluid communication to the fuel source (140) for mixing the condensate (K) with the fuel (BS).

14. The circulation device (10) according to one of claims 9 to 13, characterized in that the mixing device (90) has a fuel supply (142) with a regulating valve (12) for varying the flow quantity of fuel (BS) into the mixing device (90).

15. The circulation device (10) according to one of claims 9 to 14, characterized in that a regulating valve (12) is provided in the residual exhaust gas line (64) for changing the flow quantity in the residual exhaust gas line (64).

16. A circulation device (10) for circulating anode exhaust gas (AAG) as circulation gas (RG) from an anode part (120) of a fuel cell stack (110) of a fuel cell system (100), having a circulation line (20) with a receiving part (22) for being connected in fluid communication to an anode discharge part (124) of the anode part (120), wherein in the circulation line (20) first injector means (40) are provided for being added in fluid communication to a fuel supply part (142) of a fuel source (140), and downstream of the first injector means (40) blower means (94) are provided for being added in fluid communication to the anode supply part (122).

17. A fuel cell system (100) for generating electric current from a fuel (BS), having a fuel cell stack (110) with an anode part (120) and a cathode part (130), the anode part (120) having an anode supply (122) for supplying an anode supply gas (AZG) and an anode exhaust (124) for exhausting an anode exhaust gas (AAG), the cathode part (130) having a cathode supply (132) for supplying a cathode supply gas (KZG) and a cathode exhaust (134) for exhausting a cathode exhaust gas (KAG), wherein the fuel cell system (100) further comprises a circulation device (10) having the features of one of claims 1 to 16.

18. The fuel cell system (100) according to claim 17, characterized in that a mixing device (90) is provided in the anode supply (122) upstream of the first injector device (40) and downstream of the blower device (94) for mixing the circulating gas (RG) and the fuel (BS) from the fuel source (140).

19. The fuel cell system (100) according to claim 17 or 18, characterized in that an exhaust gas distribution device (160) is provided in the anode exhaust (122) for distributing the anode exhaust gas (AAG) to the receiving portion (22) of the circulation line (20) and to an exhaust gas line (170) separate therefrom.

20. A method for distributing a circulation gas (RG) in a circulation device (10) in a fuel cell system (100) having the features of one of claims 17 to 19, having the steps of:

sensing the operating condition of the fuel cell system (100),

-distributing the circulating gas (RG) in the distribution device (30) to the two partial circulation lines (24, 26).