DE102019111462A1 - Fuel cell system, stationary power plant and method for operating a fuel cell system - Google Patents

Abstract

The present invention relates to a fuel cell system (1) comprising at least one fuel cell stack (10) having an anode portion (11) and a cathode portion (12), a cathode supply portion (20) for supplying cathode gas (30) to the cathode portion (12), an anode supply portion (21) for supplying anode gas (31) to the anode portion (11), a cathode exhaust portion (22) for discharging cathode exhaust gas (32) from the cathode portion (12), an anode exhaust portion (23) for discharging anode exhaust gas (33) from the anode portion (11 wherein the cathode exhaust portion (22) and the anode exhaust portion (23) open into an exhaust gas burner (40) for at least partially burning the cathode exhaust gas (32) and the anode exhaust gas (33), and an exhaust gas exhaust portion (24) for discharging fuel cell exhaust gas (34) from the exhaust gas burner (40). Furthermore, the present invention relates to a stationary power plant (100) for generating electrical energy, comprising a fuel cell system (1) and a method for operating a fuel cell system (1) or a stationary power plant (100) with a fuel cell system (1), wherein the fuel cell system ( 1) generates electrical energy for a downstream electrical consumer network (101).

Description

The present invention relates to a fuel cell system comprising at least a fuel cell stack having an anode portion and a cathode portion, a cathode supply portion for supplying cathode gas to the cathode portion, an anode supply portion for supplying anode gas to the anode portion, a cathode exhaust portion for discharging cathode exhaust gas from the cathode portion, an anode exhaust portion for discharging Anode exhaust from the anode portion, wherein the cathode exhaust portion and the anode exhaust gas portion open into an exhaust gas burner for at least partially burning the cathode exhaust gas and the anode exhaust gas, and an Abgasabfuhrabschnitt for discharging fuel cell exhaust gas from the exhaust gas burner. Furthermore, the invention relates to a stationary power plant for generating electrical energy, comprising a fuel cell system. A further aspect of the present invention relates to a method for operating a fuel cell system or a stationary power plant with a fuel cell system, wherein the fuel cell system generates electrical energy for a downstream electrical consumer network.

In modern technology, fuel cell systems, often comprising one or more fuel cell stacks, each with a plurality of fuel cells, are used inter alia in stationary power plants for generating electrical energy for a downstream consumer network. A fuel cell system is in particular a particularly energy-efficient way to generate electricity. Solid oxide fuel cells (SOFC) in particular, which are operated at high temperatures, have proven to be particularly suitable for this use.

A power plant, which is used to power a downstream consumer network, must ensure that there is always a required electrical power available. There are different levels of regulation (primary, secondary, tertiary), which indicate within which time period (seconds, 5 minutes, 15 minutes) to respond to changes in the consumer network in order to ensure a frequency stability in the consumer network. Fuel cells, in particular SOFCs, are usually not suitable for increasing or reducing their power in such a short time. Also, such a fuel cell system can not be easily turned off and turned on again because the fuel cell system always needs a certain operating temperature.

From the prior art, for example the DE 10 2013 207 349 A1 , It is known, in a sudden collapse of the required electrical power in the consumer network to convert the released electrical power of a resistive load into heat. This heat can be used in various ways, for example, to keep the fuel cell system at an operating temperature. The disadvantage here, however, may be that this consumption of electrical power in the resistance load often can not be abruptly and thus can be performed only with a certain delay.

Object of the present invention is to at least partially take into account the problem described above, or at least to provide alternative solutions. In particular, it is an object of the present invention to provide a fuel cell system, a stationary power plant and a method for operating a fuel cell system, which in a particularly simple and cost-effective manner, a fuel cell system, a stationary power plant and a method for operating a fuel cell system in that In particular, a released electrical power can be consumed particularly quickly in order to enable operation of the fuel cell system with constant or at least substantially constant electrical output power.

The above object is solved by the claims. In particular, the above object is achieved by the fuel cell system according to the independent claim 1, by the stationary power plant according to the independent claim 9 and by the method according to the independent claim 10. Further advantages of the invention will become apparent from the dependent claims, the description and the drawings. In this case, features and details that are described in connection with the fuel cell system according to the invention apply, of course, also in connection with the stationary power plant according to the invention and the inventive method for operating a fuel cell system and in each case vice versa, so always with respect to the disclosure of the individual aspects of the invention always referenced or can be.

According to a first aspect of the present invention, the object is achieved by a fuel cell system comprising at least one fuel cell stack having an anode section and a cathode section, a cathode supply section for supplying cathode gas to the cathode section, an anode supply section for supplying anode gas to the anode section, a cathode exhaust section for Discharging cathode exhaust gas from the cathode portion, an anode exhaust gas portion for discharging anode exhaust gas from the anode portion, the cathode exhaust gas portion and the anode exhaust gas portion opening into an exhaust gas burner for at least partially burning the cathode exhaust gas and the anode exhaust gas, and an exhaust gas exhausting portion for exhausting fuel cell exhaust gas from the exhaust gas burner. A fuel cell system according to the invention is characterized in that the cathode feed section and / or the Abgasabfuhrabschnitt comprises a flow element for varying a flow resistance for the respective flowing gas and that a fan for conveying the fuel cell exhaust gas is provided.

A fuel cell system according to the invention has at least one fuel cell stack with an anode section and a cathode section. For generating electrical energy, a cathode gas, in particular an oxygen-containing gas such as, for example, air, is fed to the cathode section through an cathode feed section, and an anode gas, in particular a hydrogen-containing gas, is fed through an anode feed section to the anode section. In particular, the anode gas can also be specially treated, for example by a reformer as part of the fuel cell system. By means of such a reformer, natural gas, in particular the methane contained in the natural gas, can be treated by adding water and heat in such a way that a hydrogen-containing gas mixture is produced as anode gas , In the current-generating reaction in the fuel cell stack, oxygen ions mostly diffuse from the cathode section through an electrolyte to the anode section, where they react with the anode gas. Unused cathode gas is discharged as a cathode off-gas from the cathode portion through a cathode off-gas portion, accordingly, unused anode gas and the resulting reaction products are discharged as an anode off-gas from the anode portion through an anode off-gas portion. Downstream, both the cathode exhaust portion and the anode exhaust portion open into an exhaust gas combustor in which at least part of the cathode exhaust gas is burned together with the anode exhaust gas. This can for example provide a further purification of the entire exhaust gas of the fuel cell system, but also an additional thermal utilization of the cathode exhaust gas and the anode exhaust gas to increase the total energy efficiency. Subsequent to the exhaust gas burner, the fuel cell exhaust gas generated in the exhaust gas burner is discharged in a Abgasabfuhrabschnitt.

The operation of a fuel cell system according to the invention requires at least substantially constant or at least partially constant conditions. In particular, a rapid change in the electrical output power, both in terms of an increase and in terms of reduction, is not readily possible. In particular, a sudden drop in a demand for electrical power can turn out to be particularly problematic when using a fuel cell system according to the invention for generating the electrical energy.

It is therefore provided in a fuel cell system according to the invention, in particular to be consumed at least partially internally in the fuel cell system itself in a decrease in a need for electrical power released electric power. For this purpose, the cathode supply section and / or the exhaust gas discharge section have a flow element for varying a flow resistance for the respectively flowing gas and a fan for conveying the fuel cell exhaust gas. By the flow element, a flow resistance can be increased, wherein the fan for an at least partial compensation of this increase can be operated with increased power. This power increase is accompanied by an increased consumption of electrical energy, which is preferably provided directly or indirectly by the fuel cell system itself. An at least partial compensation of the electric power released when a demand for electrical power decreases can be provided in this way. A constant or at least substantially constant operation of the fuel cell system can thus be made possible in this way.

In other words, a flow element is arranged in the flow path, which is formed from Kathodenzuführabschnitt Kathodenenzuführabschnitt, cathode section, cathode exhaust gas section, exhaust gas burner and Abgasabfuhrabschnitt, through which a flow resistance in the entire flow path varies, in particular can be increased. This variation of the flow resistance can in particular be provided independently of whether the flow element is already arranged in the cathode feed section or only in the exhaust gas removal section. At the same time a fan is arranged, through which a promotion of the fuel cell exhaust gas can be provided. The fan may be formed in the context of the invention as an exhaust fan and arranged in Abgasufuhrabschnitt. Alternatively, this can also be designed as a cathode fan and arranged in the cathode feed section. In principle, it is also conceivable that both the Akthodenzuführabschnitt and Abgasufuhrabschnitt have a fan. As already described above, the cathode supply section, the cathode section, the Cathode exhaust portion, the exhaust gas burner and Abgasabfuhrabschnitt fluid communicating connected as a common flow path. The blower is thus also designed, in particular, for conveying the cathode gas in the cathode supply section and the cathode exhaust gas in the cathode exhaust gas section. For this task, the blower can be designed in particular as a suction fan. In other words, the blower in the exhaust gas discharge section generates a negative pressure that promotes both the fuel cell exhaust gas in the exhaust gas discharge section and the cathode exhaust gas in the cathode exhaust gas section and the cathode gas in the cathode supply section. Particularly preferably, the fan is arranged in the Abgasfuhrabschnitt. The arranging of the blower in the exhaust gas discharge section brings with it in particular the advantage that the gases in the flow path, in particular the cathode gas in the cathode supply section, the cathode exhaust gas in the cathode exhaust gas section and the fuel cell exhaust gas in the exhaust gas discharge section, are drawn or sucked through the flow path. Particularly good flow properties, in particular a prevention of congestion of the flowing gases and associated pressure peaks, can be provided in this way.

In addition, as described above, the blower can preferably be controlled in such a way that the variation of the flow resistance in the flow path generated by the flow element can be at least partially compensated. This compensation enables at least substantially unchanged operation of the fuel cell system, at least with regard to the gas system of the fuel cell system. Furthermore, it leads to an increased consumption of electrical energy in the fan. It can preferably be provided that the variation, in particular the increase, of the flow resistance through the flow element is carried out in such a way that the electrical energy increasingly required by the blower corresponds or at least essentially corresponds to that electrical energy which occurs when the demand for electrical power falls becomes free. In this way, an at least substantially constant operation of the fuel cell system can also be made possible with regard to the electrical power provided by the fuel cell system.

In summary, in a fuel cell system according to the invention, an internal consumption of the released electrical energy, which occurs when a load request is reduced, can be provided in a particularly simple, cost-effective and, in particular, timely manner. This can be made possible in particular by the interaction of the flow element and the blower of the fuel cell system according to the invention.

It is favorable if the cathode supply section and / or the exhaust gas removal section has the blower for conveying the fuel cell exhaust gas. The fan may be formed in the context of the invention as an exhaust fan and arranged in Abgasufuhrabschnitt. Alternatively, this can also be designed as a cathode fan and arranged in the cathode feed section. In principle, it is also conceivable that both the cathode supply section and the Abgasfuhrabschnitt have a fan.

A fuel cell system according to the invention can also be designed such that the flow element comprises at least one controllable throttle element in the cathode feed section. Such a controllable throttle element is a mechanically particularly simple way to realize a flow element. In particular, suitable controllable throttle elements can preferably also be used as the flow element in the sense of the invention, which are already present in the cathode supply section. By the possibility of driving the flow resistance in the flow path, in this embodiment, in particular in Kathodenzuführabschnitt be targeted and in particular reversible. A particularly need-based and - adjusted adjustment of the flow resistance of the entire flow path can be provided in this way. If the blower is arranged in the cathode feed section, the controllable throttle valve can advantageously be arranged upstream of the blower. It may also be favorable if two controllable throttle valves are provided in the cathode feed section, wherein a first throttle valve is arranged upstream and a second throttle valve is arranged downstream of the blower.

Alternatively or additionally, it may be provided in a fuel cell system according to the invention that the flow element comprises a controllable throttle element in Abgasabfuhrabschnitt, wherein the throttle element is arranged in particular downstream of the blower. In this case, it is thus advantageously provided that the fan is arranged in the exhaust gas section. Also in this embodiment, a controllable throttle element is a mechanically particularly simple way to realize a flow element. Furthermore, suitable controllable throttle elements may also be used as the flow element in the sense of the invention which are already present in the exhaust gas removal section. By the possibility of driving the flow resistance in the flow path, in this embodiment, in particular in Abgasabfuhrabschnitt be targeted and in particular reversible. A particularly needs-based and adapted adjustment of the flow resistance the entire flow path can also be provided in this way. Even if the fan is arranged in the cathode supply section, a controllable throttle element may advantageously be provided in the exhaust gas section.

Alternatively or additionally, a fuel cell system according to the invention may be designed such that the flow element comprises a controllable throttle element in the exhaust gas removal section, wherein the throttle element is arranged in particular upstream of the exhaust gas suction fan. In this case, the blower is designed in particular as an exhaust fan and arranged in the Abgasfuhrabschnitt. This embodiment of a fuel cell system according to the invention represents a further alternative or additional possibility to place the flow element according to the invention in the flow path. All the advantages described with respect to the flow element at other locations in the flow path can also be provided in this embodiment of a fuel cell system according to the invention.

In summary, one or more flow elements can be arranged in the flow path, in particular the cathode feed section and the exhaust gas discharge section. In this way, it is possible in particular to provide a particularly needs-based and adapted placement of the flow element and thereby also a particularly need-based and adapted influencing of the flow resistance.

Furthermore, it can be provided in a fuel cell system according to the invention that the Abgasabfuhrabschnitt is connected to a heat exchanger element in the Kathodenzuführabschnitt for delivering heat energy to the Kathodenzuführgas. The fuel cell exhaust gas, which is formed during the at least partial burning of the cathode exhaust gas with the anode exhaust gas in the exhaust gas burner, usually has a high temperature. By a heat exchanger element, the heat energy thus stored in the fuel cell exhaust gas can be at least partially transferred to the cathode gas. Heating elements for heating the cathode gas can be dispensed with in this way or at least made smaller. Overall, an energy efficiency of a fuel cell system according to the invention can thus be increased in this way.

In addition, alternatively or additionally, a fuel cell system according to the invention may further be designed such that the Abgasabfuhrabschnitt is connected to a reformer in the Anodeenzuführabschnitt for the provision of heat energy. In such a reformer, as already described above, the anode gas can be treated, for example by reforming natural gas, in particular the methane contained in natural gas, with the addition of water and heat such that a hydrogen-containing gas mixture is produced as anode gas. By connecting the Abgasabfuhrabschnitts with the reformer in Anodenzuführabschnitt necessary for conditioning heat energy can be provided at least partially by the hot fuel cell exhaust gas. Heating elements for heating the reformer can be omitted in this way, or at least made smaller. Overall, an energy efficiency of a fuel cell system according to the invention can thus also be increased in this way.

Furthermore, it can be provided in a fuel cell system according to the invention that the fuel cell system has an electrical connection element for direct and / or indirect supply of the fan with electrical energy of the fuel cell stack. In this way, in particular by the electrical connection element, it is particularly easy to ensure the provision of the electrical energy required by the fan through the fuel cell system itself. An inventive fuel cell system usually generates electrical energy in the form of direct current. In the case of a fan which likewise requires electrical energy in the form of direct current, the required electrical energy can thus be conducted directly to the fan by means of the electrical connection element according to the invention. In an alternative fan, which requires electrical energy in the form of alternating current, it may be advantageous to remove the electrical energy by the electrical connecting element for a DC-AC converter, as it is usually present for example when connected to a downstream consumer network. In particular, a reliable provision of the electrical energy required by the blower through the fuel cell system itself can thus be made possible by a suitably designed electrical connection element for all possible combinations of provided by the fuel cell system electrical energy form and the electric energy required by the blower.

According to a second aspect of the invention, the object is achieved by a stationary power plant for generating electrical energy, comprising a fuel cell system. A stationary power plant according to the invention is characterized in that the fuel cell system according to the first aspect of the invention is formed. All the advantages have been described in detail with respect to a fuel cell system according to the invention according to the first aspect of the invention can thus be provided by a stationary power plant according to the second aspect of the invention, the fuel cell system is formed according to the first aspect of the invention.

1. a) Erkennen eines Lastabfalls im nachgeschalteten Verbrauchernetz,
2. b) Erhöhen eines Strömungswiderstands durch das Strömungselement,
3. c) Erhöhen einer Pumpleistung des Gebläses zur zumindest teilweisen Kompensation des in Schritt b) erhöhten Strömungswiderstands durch wenigstens teilweises Zuleiten von durch das Brennstoffzellensystem erzeugter elektrischer Energie, welche durch den in Schritt a) erkannten Lastabfall frei wird.

According to a third aspect of the invention, the object is achieved by a method for operating a fuel cell system according to the first aspect of the invention or a stationary power plant with a fuel cell system according to the second aspect of the invention, wherein the fuel cell system generates electrical energy for a downstream electrical consumer network. A method according to the invention is characterized by the following steps:

1. a) detecting a load drop in the downstream consumer network,
2. b) increasing a flow resistance through the flow element,
3. c) increasing a pumping power of the blower for at least partial compensation of the increased flow resistance in step b) by at least partially supplying electrical energy generated by the fuel cell system, which is released by the load drop detected in step a).

An inventive method operates a fuel cell system according to the first aspect of the invention or a stationary power plant according to the second aspect of the invention. All the advantages, which have been described in detail in relation to a fuel cell system according to the invention according to the first aspect of the invention or in relation to a stationary power plant according to the second aspect of the invention, can thus also be provided by a method according to the third aspect of the invention, which for operating a fuel cell system according to the invention according to the first aspect of the invention or a stationary power plant according to the second aspect of the invention.

By a method according to the invention, a fuel cell system or a stationary power plant is operated with a fuel cell system. In particular, by the fuel cell system, directly or as a preferred primary power generator in the power plant, be electrical energy for a downstream electrical consumer network. Such a consumer network may be particularly preferably designed as a local, regional and / or supra-regional power grid.

Such a downstream electrical consumer network can sometimes be subject to large fluctuations in the demand for electrical energy, up to a complete load shedding, in which suddenly, in particular within a few minutes or even seconds, the demand for electrical energy is completely or at least substantially entirely zero , In order to be able to react to such fluctuations, a load drop in the downstream consumer network is detected in the first step a) of a method according to the invention. Detection in the sense of the invention comprises in particular the measures necessary for this, for example a preferably repeated measurement of the required requirement or an evaluation of these measurements. In other words, after performing step a) of a method according to the invention, the information is available that a load drop has occurred in the downstream consumer network.

In the next two steps b) and c) of a method according to the invention measures are taken to compensate for this load drop at least partially and at the same time continue to operate the fuel cell system, in particular the fuel cell stack of the fuel cell system unchanged. For this, in the next step b) of a method according to the invention, a flow resistance through the flow element of the fuel cell system is increased. Such an increased flow resistance would lead to a reduced supply of cathode gas to the cathode portion of the fuel cell stack. In order to compensate for this at least partially, in time or preferably at the same time, in step c) of a method according to the invention, a pumping power of the blower of the fuel cell system is increased. In this way, the supply of the fuel cell stack with cathode gas at least rudimentary, in particular sufficient, are kept constant. This increase in pump power is automatically accompanied by an increased demand for the fan of electrical energy. In order to serve this increased energy requirement of the blower, at least part of the electrical energy generated by the fuel cell system, which is released by the load drop detected in step a), is used for this purpose.

In this way, there are several advantages of a method according to the invention. Thus, by the at least partial compensation of the increased flow resistance in the flow path by the simultaneous increase in the pump power of the fan, the operation of the fuel cell system with regard to supply with cathode gas at least substantially continued without change. At the same time, the electrical energy generated by the fuel cell stack is at least partially consumed internally in the fuel cell system due to the increased demand of the blower. so that the reduced demand for electrical energy in the downstream consumer network can be at least partially compensated. This can be provided particularly fast by the use of the blower as a consumer of the released electrical energy and with no or only a slight time delay to the detected in step a) load drop. In other words, the fuel cell system, in particular the fuel cell stack, can be operated with an at least substantially constant generation rate of electrical energy, independently of a need for electrical energy in the downstream consumer network.

Furthermore, it can be provided in a method according to the invention that in step c) to increase the pump power, the entire or at least substantially all of the electrical energy released by the load drop detected in step a) is supplied to the fan. A complete or at least substantially complete compensation of the load drop detected in step a) by the increased consumption of electrical energy by the blower can be provided in this way.

Alternatively or additionally, a method according to the invention may also be designed such that in step c) the increased flow resistance in step b) is completely or at least substantially completely compensated by increasing the pumping capacity of the blower. In other words, even if the flow resistance in step b) has been increased by the flow element, the volume flow of cathode gas in the cathode supply section or fuel cell exhaust gas in the exhaust gas discharge section does not change or at least does not change significantly. An operation of the fuel cell system with respect to supply of cathode gas can be continued in this way without change or at least substantially without change.

In a particularly preferred embodiment of the method according to the invention, step a) comprises a continuous or at least substantially continuous monitoring of the downstream consumer network. In this way, fluctuations in the demand for electrical energy in the consumer network, in particular load drops up to a complete load shedding, can be detected particularly quickly and promptly. A compensation of the released electrical energy by a consumption in the fan can thus also be introduced very quickly and in a timely manner.

Also, a method according to the invention can be designed such that in step c) the released electrical energy is fed directly from the fuel cell stack to the blower as direct current. A direct supply of electrical energy in the sense of the invention comprises, in particular, a supply of direct current, without conversion to alternating current being carried out. Preferably, a suitably designed connecting element can be used for this purpose. In particular, in a blower that requires electrical energy in the form of direct current, this embodiment of a method according to the invention is advantageous, as a particularly simple supply of electrical energy to the fan can be provided.

Alternatively or additionally, it can further be provided in a method according to the invention that in step c) the released electrical energy of the fuel cell stack is converted into alternating current and then fed to the blower. This constitutes, within the meaning of the invention, an indirect delivery of the electrical energy to the fan. Here, too, a correspondingly designed connecting element can be used. In particular, in a blower that requires electrical energy in the form of alternating current, this embodiment of a method according to the invention is advantageous because a particularly simple supply of electrical energy to the fan can be provided. In particular, the electrical energy can also be taken from the downstream consumer network.

Particularly preferably, a method according to the invention can be further developed such that an increased waste heat of the blower generated by the increased pumping power is at least partially supplied to a heat consumer and / or a heat store. An increased pumping power in the blower is usually accompanied by an increased power loss in the blower. This often leads to an increase in the heat generated by the blower. By supplying this waste heat to a heat consumer, for example as a possible heat source for heating the fuel cell stack, and / or to a heat storage, for example for a later use of heat energy, a use of this waste heat can be provided. An energy efficiency in operating a fuel cell system can be increased in this way.

Further, measures improving the invention will become apparent from the following description of various embodiments of the invention, which are shown schematically in the figures. Elements with the same function and mode of action are in the 1 to 4 each provided with the same reference numerals.

• 1 eine Ansicht eines erfindungsgemäßen Kraftwerks;
• 2 eine erste Ausgestaltungsform eines Verbindungselement;
• 3 eine zweite Ausgestaltungsform eines Verbindungselement;
• 4 ein erfindungsgemäßes Verfahren;
• 5 eine Ansicht eines weiteren erfindungsgemäßen Kraftwerks.

Each show schematically:

• 1 a view of a power plant according to the invention;
• 2 a first embodiment of a connecting element;
• 3 a second embodiment of a connecting element;
• 4 a method according to the invention;
• 5 a view of another power plant according to the invention.

In 1 schematically is a power plant according to the invention 100 or a fuel cell system according to the invention 1 shown. Through such a power plant 100 or fuel cell system 1 may be a method according to the invention, which is exemplified in 4 is shown to be executed. The individual steps of the process a), b) and c) according to the invention are described in 4 each marked with capital letters. The two figures are therefore described below together, with the individual figures will be discussed separately.

An inventive stationary power plant 100 has as a central element of an inventive fuel cell system 1 on. The fuel cell system 1 generates electrical energy that a downstream consumer network 101 (not shown) is fed. 1 shows the essential components of such a fuel cell system 1 , In a fuel cell stack 10 the generation of electrical energy is made. This is indicated by the fuel cell stack 10 an anode section 11 and a cathode portion 12 on. The cathode section 12 is via a Kathodenzuführabschnitt 20 with cathode gas 30 , preferably an oxygen-containing gas such as air supplied. Analogously, the anode section 11 through an anode feed section 21 an anode gas 31 , preferably a hydrogen-containing gas supplied. For a purification of the anode gas 31 of sulfur components is in the anode feed section 21 a desulphurisation element 43 arranged. An anode gas delivery unit 45 , For example, a fan, provides a promotion of the anode gas 31 for sure. The anode gas 31 can also, as shown, in a reformer 42 be processed, for example, in which natural gas, in particular methane, is split together with water and under heat in a hydrogen-containing gas mixture. In the fuel cell stack 10 are the cathode section 12 and the anode section 11 separated by an electrolyte, which is usually continuous for oxygen ions. In the electricity generating reaction in the fuel cell stack 10 oxygen ions diffuse from the cathode section 12 through the electrolyte to the anode section 11 and react there with the anode gas 31 , Unused cathode gas 30 is called cathode exhaust gas 32 from the cathode section 12 through a cathode exhaust section 22 derived, corresponding to unused anode gas 31 and the resulting reaction products as anode exhaust gas 33 from the anode section 11 through an anode exhaust section 23 derived. Downstream open both the cathode exhaust gas section 22 and the anode exhaust section 23 in an exhaust gas burner 40 , Part of the anode exhaust 33 is further controlled by an anode exhaust gas recirculation section 44 in the anode delivery section 21 initiated. As a result, in particular unused anode gas 31 as part of the anode exhaust gas 33 be reused. Because the anode exhaust 33 by the reactions in the anode section 11 is heated, is in the anode removal section 21 a heat exchanger element 41 arranged to be in the anode feed section 21 passed anode gas 31 before entering the anode section 11 to heat or heat up. The reactions in the fuel cell stack 10 can be supported in this way. In the exhaust gas burner 40 becomes at least partially the cathode exhaust gas 32 together with the anode exhaust gas 33 burned. This can for example be a further purification of the entire exhaust gas of the fuel cell system 1 but also, for example, an additional thermal utilization of the cathode exhaust gas 32 and the anode exhaust gas 33 to increase total energy efficiency. Then to the exhaust gas burner 40 This will be in the exhaust gas burner 40 generated fuel cell exhaust 34 in a Abgasabfuhrabschnitt 24 dissipated. To the heat energy of the fuel cell exhaust gas 34 continue to use, is in the Abgasabfuhrabschnitt 24 both a heat exchanger element 41 of the cathode feed section 20 arranged, as well as the Abgasabfuhrabschnitt 24 with the reformer 42 connected. In this way, both the cathode gas 30 heated up, as well as the reformer 42 Heat energy to be supplied. Overall, in addition to other, not shown components of a fuel cell system according to the invention 1 , in particular the fuel cell stack 10 , the exhaust burner 40 and the reformer 42 in a hot cell 5 arranged. The for efficient operation of the fuel cell system 1 necessary high temperatures, often several hundred degrees Celsius, are particularly easy to deploy. Other possible elements of a fuel cell system 1 For example, a water supply and disposal, direct supply lines for providing cathode gas 30 and anode gas 31 for starting the exhaust gas burner 40 are not shown for clarity.

According to the invention, the illustrated fuel cell system 1 a fan 4 on, in the Abgasabführabschnitt 24 is arranged. The Arranging the fan 4 in the Abgasabfuhrabschnitt 24 brings here in particular the advantage that the gases in the flow path, in particular the cathode gas 30 in the cathode feed section 20 , the cathode exhaust 32 in the cathode exhaust section 22 and the fuel cell exhaust 34 in the Abgasabfuhrabschnitt 24 be pulled or sucked through the flow path. Particularly good flow properties, in particular avoiding congestion of the flowing gases and the associated pressure peaks, can be provided in this way. Furthermore, a fuel cell system according to the invention 1 at least one flow element 2 on, in the presentation as controllable throttle element 3 formed and at three possible arrangement positions, in Kathodenzuführabschnitt 20 and in the exhaust gas removal section 24 upstream and downstream of the blower 4 is shown. In other embodiments, only one or two flow elements may be used 2 be provided at each one of these arrangement positions.

An inventive method, as in 4 is shown is for operating an in 1 exemplified fuel cell system 1 intended. In particular, by the fuel cell system 1 electrical energy for a downstream electrical consumer network 101 generated. In a first step a), in 4 With A referred to, this electrical consumer network 101 monitored to detect a performance degradation. To be able to provide this as quickly and promptly as possible, step a) can preferably be carried out continuously or at least substantially continuously. A drop in performance may be particularly problematic because the operation of the fuel cell system 1 , in particular with regard to the electrical energy generated by it, essentially allows no rapid changes. Thus, at a load drop in the downstream electrical consumer network 101 electrical energy free. To compensate for this, preferably completely or at least substantially completely compensate, in step b) of a method according to the invention, in 4 With B denotes the flow element 2 controlled so that a flow resistance in the flow path is increased. Subsequently or preferably even simultaneously, in step c) of a method according to the invention, in 4 With C denotes a pumping power of the fan 4 increased in order to compensate for the increased flow resistance at least partially, preferably completely or at least substantially completely. An unchanged at least in terms of a gas supply operation of the fuel cell system 1 can be provided thereby. Essential to the invention is the increase in the pumping power of the blower 4 achieved by that the blower 4 at least part of this through the load drop in the consumer network 101 released electrical energy from the fuel cell stack 10 is generated, is supplied. Preferably, to increase the pumping power, all or at least substantially all of the released electrical energy is available to the fan 4 be supplied. In addition, also by the increase in the pump power also increased waste heat of the fan 4 be used, for example, by supplying this waste heat to a heat consumer and / or a heat storage. An overall energy efficiency of a fuel cell system according to the invention 1 or a power plant according to the invention 100 can be further increased.

In summary, in a fuel cell system according to the invention 1 or by an inventive method thus particularly simple, inexpensive and in particular temporally fast internal consumption of the released electrical energy, the case of a load drop in the downstream electrical consumer network 101 occurs. This can in particular by the interaction of the flow element 2 and the blower 4 the fuel cell system according to the invention 1 to be provided.

The 2 and 3 show two ways to the blower 4 electrical energy coming from the fuel cell stack 10 a fuel cell system according to the invention 1 or a power plant according to the invention 100 generated and by a load drop in the downstream electrical consumer network 101 is free to feed. For each a correspondingly trained electrical connection element 50 used. In the figures, only the essential components are shown, in particular the fuel cell stack 10 as well as the blower 4 , Furthermore, the downstream electrical consumer network 101 shown in the via an ac transformer 102 those from the fuel cell stack 10 generated electrical energy is fed. In 2 the case is shown that the blower 4 electrical energy in the form of direct current needed. Because the fuel cell stack 10 electrical energy already generated in the form of direct current can, by the appropriately designed electrical connection element 50 this electrical energy directly to the blower 4 be supplied. Alternatively, it may be preferable if the blower 4 electrical energy in the form of alternating current needed, the electrical connection element 50 the AC converter 102 be arranged downstream, see 3 , This can still be internal to the fuel cell system 1 but also already as part of the downstream consumer network 101 be realized. Overall, this represents an indirect one Supply line of the released by the load loss electrical energy.

In particular, can thus by an appropriately trained electrical connection element 50 for all sorts of combinations through the fuel cell system 1 provided electrical energy form and by the blower 4 required electrical energy form a safe supply of the blower 4 required electrical energy through the fuel cell system 1 even be made possible.

In 5 is schematically another power plant according to the invention 100 or a fuel cell system according to the invention 1 shown. The elements corresponding to those of the 1 shown power plant 100 correspond and have the same function will not be described again. That is, all those elements that are not described correspond to those 1 respectively. 2 , In contrast to the embodiment according to 1 is the fan 4 in the cathode feed section 20 arranged. Furthermore, this fuel cell system also has 1 at least one flow element 2 on, in the presentation as controllable throttle element 3 formed and at a possible arrangement position, in Kathodenzuführabschnitt 20 upstream of the blower 4 is arranged. In principle, the throttle element 3 also in the exhaust gas removal section 24 be arranged. In other embodiments, two flow elements can also be used 2 in the cathode feed section 20 upstream and downstream of the blower 4 or a flow element 2 downstream of the blower 4 in the cathode feed section 20 be arranged.

In addition to the illustrated embodiments, the invention allows for further design principles. Ie. the invention should not be considered limited to the embodiments explained with reference to the figures.

LIST OF REFERENCE NUMBERS

1

The fuel cell system

2

flow element

3

throttle element

4

fan

5

hot cell

10

fuel cell stack

11

anode section

12

cathode portion

20

Kathodenzuführabschnitt

21

Anodenzuführabschnitt

22

Cathode exhaust section

23

Anode exhaust section

24

Exhaust gas discharge section

30

cathode gas

31

anode gas

32

cathode exhaust

33

anode exhaust gas

34

fuel cell exhaust gas

40

exhaust gas burner

41

Heat exchanger element

42

reformer

43

desulfurizing

44

Anode exhaust gas recirculation section

45

Anode gas feed unit

50

connecting element

100

power plant

101

consumer network

102

AC converter

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102013207349 A1 [0004]

Claims (16)

A fuel cell system (1) comprising at least one fuel cell stack (10) having an anode portion (11) and a cathode portion (12), a cathode feed portion (20) for supplying cathode gas (30) to the cathode portion (12), an anode feed portion (21) for supplying anode gas (31) to the anode portion (11), a cathode exhaust portion (22) for discharging cathode exhaust gas (32) from the cathode portion (12), an anode exhaust portion (23) for discharging anode exhaust gas (33) from the anode portion (11), the cathode exhaust portion (22) and the anode exhaust gas portion (23) into an exhaust gas burner (40) for at least partially burning the cathode exhaust gas (32) and the anode exhaust gas (33) open, and an Abgasabfuhrabschnitt (24) for discharging fuel cell exhaust gas (34) from the exhaust gas burner (40) , characterized in that the cathode feed section (20) and / or the Abgasabfuhrabschnitt (24) has a flow element (2) for varying a flow resistance ands for the respective flowing gas, and that a fan (4) for conveying the fuel cell exhaust gas (34) is provided. Fuel cell system (1) after Claim 1 , characterized in that the Kathodenzuführabschnitt (20) and / or Abgasabfuhrabschnitt (24) comprises the blower (4) for conveying the fuel cell exhaust gas (34). Fuel cell system (1) after Claim 1 or 2 , characterized in that the flow element (2) comprises at least one controllable throttle element (3) in the Kathodenzuführabschnitt (20). Fuel cell system (1) according to one of Claims 1 to 3 , characterized in that the flow element (2) comprises a controllable throttle element (3) in Abgasabfuhrabschnitt (24), wherein the throttle element (3) in particular downstream of the blower (4) is arranged. Fuel cell system (1) according to one of the preceding claims, characterized in that the flow element (2) comprises a controllable throttle element (3) in Abgasabfuhrabschnitt (24), wherein the throttle element (3) is arranged in particular upstream of the blower (4). Fuel cell system (1) according to one of the preceding claims, characterized in that the Abgasabfuhrabschnitt (24) with a heat exchanger element (41) in the Kathodenzuführabschnitt (20) for emitting heat energy to the cathode gas (30) is connected. Fuel cell system (1) according to one of the preceding claims, characterized in that the Abgasabfuhrabschnitt (24) is connected to a reformer (42) in the Anodeenzuführabschnitt (21) for providing heat energy. Fuel cell system (1) according to one of the preceding claims, characterized in that the fuel cell system (1) has an electrical connection element (50) for direct and / or indirect supply of the fan (4) with electrical energy of the fuel cell stack (10). Stationary power plant (100) for generating electrical energy, comprising a fuel cell system (1), characterized in that the fuel cell system (1) is designed according to one of the preceding claims. Method for operating a fuel cell system (1) according to one of Claims 1 to 6 or a stationary power plant (100) with a fuel cell system (1) according to Claim 7 in which the fuel cell system (1) generates electrical energy for a downstream electrical consumer network (101), characterized by the following steps: a) detecting a load drop in the downstream consumer network (101), b) increasing a flow resistance through the flow element (2), c) Increasing a pumping power of the fan (4) for at least partially compensating the increased flow resistance in step b) by at least partially supplying electrical energy generated by the fuel cell system (1), which is released by the load drop detected in step a). Method according to Claim 10 , characterized in that in step c) for increasing the pump power, the entire or at least substantially all of the electrical energy released by the load drop detected in step a) is supplied to the blower (4). Method according to Claim 10 or 11 , characterized in that in step c) by increasing the pumping power of the blower (4) of the increased flow resistance in step b) is completely or at least substantially completely compensated. Method according to one of Claims 10 to 12 , characterized in that step a) comprises a continuous or at least substantially continuous monitoring of the downstream consumer network (101). Method according to one of Claims 10 to 13 , characterized in that in step c) the released electrical energy is supplied directly from the fuel cell stack (10) to the fan (4) as a direct current. Method according to one of Claims 10 to 14 , characterized in that in step c) the released electrical energy of the fuel cell stack (10) is converted into alternating current and then the blower (4) is supplied. Method according to one of Claims 10 to 15 , characterized in that an increased waste heat generated by the increased pumping power of the blower (4) is at least partially supplied to a heat consumer and / or a heat storage.

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