DE102008010202A1 - High temperature fuel cell system and method for generating electricity and heat by means of a high temperature fuel cell system - Google Patents

Abstract

In a high-temperature fuel cell system having a reformer (3) for converting a fuel into a hydrogen-rich anode gas, a fuel cell stack (4) for converting the hydrogen-rich anode gas while supplying a cathode gas to electricity and heat, and an afterburner (5) for post-burning one from the fuel cell stack exiting, hydrogen-depleted reformate under supply of the cathode gas, the efficiency can be increased by a separation reactor (2) for separating oxygen from air, wherein the oxygen separated during operation is at least partially used as a cathode gas.

Description

The The invention relates to a high-temperature fuel cell system with the features of the preamble of claim 1.

The The invention further relates to a method for generating electricity and Heat with Help a high-temperature fuel cell system with the steps the preamble of claim 8.

One High-temperature fuel cell system designed for operation with hydrocarbons is usually from the three main components reformer, fuel cell stack and Afterburner.

Of the Reformer converts a fuel into a hydrogen-rich anode gas around. Suitable fuels are z. As natural gas, biogas, LPG, vaporized Diesel, vaporized kerosene or other fossil fuels. For a reform by partial oxidation is added an oxidizing agent is needed. In the simplest case, atmospheric oxygen serves as an oxidizing agent.

in the Fuel cell stack is the hydrogen-rich anode gas under With the help of air as cathode gas is converted to electricity and heat.

The emerging from the fuel cell hydrogen-depleted reformate is then post-combusted in an afterburner with further supply of air, z. B. to comply with specified emission limits.

In all three main components release heat during operation, which are dissipated got to. The heat dissipation takes place by means of suitable devices for heat transfer. It is known these devices for heat transfer convective by a sufficiently large excess of air on the cathode side remove the fuel cell stack.

air contains mostly Nitrogen (about 78%). For this reason, the operation of conventional Fuel cell system with air in the fuel cell stack high nitrogen contents both on the anode side and on the cathode side arise as an inert gas, the performance of the fuel cell stack reduce.

moreover have to unnecessarily high due to the high nitrogen content in the air Gas flow rates be warmed up before entering the fuel cell to avoid damage to the fuel cell To avoid fuel cell. Warming up for power generation is not required Gas flow rates lowers the efficiency of the fuel cell system.

The Reforming the fuel with atmospheric oxygen (partial oxidation) reduced to a hydrogen-rich hydrogen / carbon monoxide mixture due to the nitrogen inert gas also the efficiency of the high-temperature fuel cell system.

Furthermore, the partial oxidation of hydrocarbons is carried out by a two-stage formal mechanism: In one stage, the fuel is totally oxidized with atmospheric oxygen to carbon dioxide (CO ₂ ) and water; in a second stage, the hydrocarbons are reformed with the previously formed water and CO ₂ . While the total oxidation is a highly exothermic reaction, the subsequent reforming with water and CO ₂ proceeds under significant heat absorption. This results in an inhomogeneous temperature profile, which leads to problems especially when using catalysts. Thus, in the inlet region of the catalyst, temperature peaks can occur which lead to thermal destruction of the catalyst material and / or of the catalyst support, while low temperatures present in the rear region lead to poor degrees of conversion and production selectivities of the reforming.

task The invention therefore is to provide an improved high-temperature fuel cell system, which avoids or reduces the disadvantages described above. The object of the present invention is also a method for generating electricity and heat with the aid of the high-temperature fuel cell system according to the invention provide.

The Task is solved by a high-temperature fuel cell system with the features of Claim 1.

The Task is further solved by a method having the features of claim 8.

advantageous Embodiments of the high-temperature fuel cell system according to the invention and the method of the invention in the subclaims, the description and the drawing.

The High-temperature fuel cell system according to the invention is in contrast to known fuel cell systems with pure Oxygen operated, which is separated from the air. With pure Oxygen means that the oxygen content is significantly higher as the proportion of other gases, for example, significantly higher than the nitrogen content.

By using pure oxygen For example, the high-temperature fuel cell system according to the invention is operated at a higher oxygen partial pressure on the cathode side of the fuel cell stack and at a higher fuel gas partial pressure on the anode side than in conventional high-temperature fuel cell systems. This leads to a higher efficiency compared to known high-temperature fuel cell systems.

The High-temperature fuel cell system according to the invention is also characterized by the fact that the amount of emitted harmful gases, especially of nitrogen oxides, compared to known high temperature fuel cell systems is reduced. Thus provide both the high-temperature fuel cell system according to the invention as well as the inventive method a positive contribution to environmental protection.

In the individual components of the high-temperature fuel cell system according to the invention is a homogeneous distribution of temperature, in contrast to known systems reached. This homogeneous temperature distribution leads to a longer service life and a higher one Efficiency of high-temperature fuel cell systems and to a simplified implementation of the method according to the invention. A uniform temperature range of reformer, fuel cell stack and afterburner allows In addition, a simple integration and compact design.

at the high-temperature fuel cell system according to the invention and the method of the invention is not an ignitable mixture before the entry of the fuel into the reformer from hydrocarbons and oxidizing agent. That on this If no ignitable mixture is present in front of the reaction zone, it acts have a positive impact on operational safety.

The Carbon dioxide from the exit gas of the afterburning can be after all easily separated by condensation of water vapor and sequestered.

In an advantageous embodiment the separation reactor has perovskite ceramic as an oxygen separation membrane on.

The perovskite oxygen separation membranes are mixed conducting, dense, oxidic ceramics capable of oxygen ion conduction and electron conduction. In the presence of an oxygen partial pressure gradient, oxygen ions O ² and O ² vacancies and electrons or electron holes simultaneously diffuse through the material in different directions in these materials. The diffusion takes place in accordance with the partial pressure gradient of the oxygen. The operating temperature of these materials is above 700 ° C and thus in a range in which both typical high-temperature fuel cells such. As SOFC (Solid Oxide Fuel Cell) or MCFC (Molten Carbonate Fuel Cell), as well as the partial oxidation of hydrocarbons are operated. During operation of the membrane, oxygen is absorbed on the feed side (air-facing side of the membrane) and, with electron uptake as an ion, enters the oxide material of the perovskite membrane. From the permeate side (air-remote side of the membrane), the oxygen ions can be released either as molecular oxygen in the gas phase, or hydrocarbons react directly with the lattice oxygen.

According to the invention, it is provided that in operation on the feed side of the separation reactor, a higher pressure is present as on the permeate side of the separation reactor. By this air-side overpressure In operation, a continuous oxygen flow on the permeate side reached the perovskite ceramics.

In a particular embodiment the reformer has a perovskite ceramic as oxygen separation membrane on. The perovskite ceramic can be used for the partial oxidation of Hydrocarbons are used with pure oxygen. On that way the nitrogen content in the anode gas is reduced.

Preferably The oxygen transferred by the perovskite ceramic reacts directly on an adjacent catalyst with the supplied hydrocarbons.

It However, it is also conceivable that the hydrocarbons as a carrier for the transferred Oxygen can be used, and that partial oxidation in this case takes place in a separate reactor.

Appropriately the oxygen separation in the reformer on the air side with overpressure, d. H. the pressure on the feed side is higher than the pressure on the permeate side the perovskite pottery. In this way, can be a continuous Oxygen flow on the permeate side of the perovskite ceramic produce.

Around Dissipate heat, the Formation of carbonaceous deposits to suppress and the reforming towards autothermal mode or endothermic To shift operation, the anode gas water or water vapor can be added.

In a particular embodiment, the Perovskite ceramic applied directly to the cathode of the fuel cell stack. This provides a high oxygen partial pressure difference between cathode and anode for electrochemical conversion. In this case, the fuel cell stack forms a unit with the separation reactor.

The invention is further provided that the post-combustion catalytic or non-catalytic he follows.

The The invention will be described with reference to one of the following figures embodiment explained in more detail.

It shows:

1 - A simplified representation of the high-temperature fuel cell system according to the invention together with a representation of the method according to the invention.

In 1 is a high-temperature fuel cell system according to the invention 1 shown in simplified form.

The high-temperature fuel cell system 1 has a separation reactor 2 , a reformer 3 , a fuel cell stack 4 and an afterburner 5 on.

The separation reactor 2 includes a perovskite ceramic 6 , which simultaneously conducts oxygen ions and electrons at high operating temperatures (> 700 ° C).

On a feed page 7 of the separation reactor 2 air is supplied. On a permeate side 8th oxygen is removed. The separation reactor 2 is on the air side (on the feed side 7 ) with a higher pressure than the permeate side (on the permeate side 8th ) operated. This overpressure leads to a continuous flow of oxygen on the permeate side 8th the perovskite pottery 6 ,

At an exit 9 of the separation reactor 2 nitrogen is removed, optionally with a small amount of oxygen.

From the permeate side 8th becomes pure oxygen 10 via a suitable outlet 11 a cathode 12 of the fuel cell stack 4 fed.

The reformer 3 has an air inlet 13 and one from the air inlet 13 separate inlet 14 on. About the inlet 14 becomes the reformer 3 water 15 and methane 16 fed.

The reformer 3 has a perovskite membrane 17 on. On the one side (feed side) of the perovskite membrane 17 gets air 18 supplied (feed side). On the other side (permeate side) of the perovskite membrane 17 becomes the water 15 and the methane 16 supplied (permeatseitig).

The reformer 3 converts fuel (methane 16 ) into a hydrogen-rich anode gas. The hydrogen-rich gas (anode gas 19 ) is in this case a mixture of methane, carbon monoxide, molecular hydrogen, carbon dioxide and water. The anode gas 19 will have an outlet 20 an anode 21 of the fuel cell stack 4 fed. For reforming of fuel with that through perovskite ceramics 17 separated oxygen has the reformer 3 a catalyst on.

The anode gas 19 will be between the reformer 3 and the fuel cell stack 4 additionally water and / or water vapor 22 fed.

The anode 21 is from the cathode 12 through a membrane 23 separated.

The fuel cell stack 4 is in this case an SOFC stack.

In the fuel cell stack 4 becomes the anode gas 19 with the extra water and / or water vapor 22 with the help of oxygen 10 converted into electricity and heat. From the fuel cell stack 4 enters a reformat 24 and at least partially the afterburner 5 fed.

The Reformat 24 is hydrogen depleted because in the conversion in the fuel cell stack 4 Hydrogen with oxygen (oxyhydrogen) has been converted into electricity and heat. The cathode side becomes oxygen 25 from the fuel cell stack 4 at least partially the afterburner 5 fed.

In the afterburner 5 becomes the hydrogen-depleted reformate 24 with the help of oxygen 25 afterburning in order to comply with emission limit values where appropriate.

From the afterburner 5 becomes a mixture after afterburning 26 removed from carbon dioxide and water.

In the present embodiment, the high-temperature fuel cell system 1 it is envisaged that the reformat 24 partly on the inlet 14 is returned (return 27 ).

It is further provided that the mixture 26 partly on the inlet 14 recycled will (return 28 ).

In addition, it is envisaged that the oxygen 25 from the cathode compartment of the fuel cell stack 4 is partially returned and the cathode side of the fuel cell stack 4 is fed back (feedback 29 ).

From an exit 30 the reformer 3 Nitrogen is vented with optionally a portion of oxygen as the residual gas (drain 31 ).

1

High-temperature fuel cell system

2

separating reactor

3

reformer

4

Fuel cell stack

5

afterburner

6

perovskite membrane

7

Feed

8th

permeate

9

output side

10

oxygen

11

outlet

12

cathode

13

air intake

14

inlet

15

water

16

methane

17

perovskite membrane

18

air

19

anode gas

20

outlet

21

anode

22

water

23

membrane

24

reformate

25

oxygen

26

mixture

27

return

28

return

29

return

30

outlet

31

drainage

State of the art

One simple high-temperature fuel cell system designed for operation is designed with hydrocarbons, usually consists of the three main components Reformer, fuel cell stack and afterburning. The reformer is required, fuel (eg, natural gas, bioliquid or LPG or vaporized diesel, Kerosene or other fossil fuels) in a hydrogen-rich To convert gas. For the partial oxidation reforming additionally becomes an oxidizing agent needed, in simplest case atmospheric oxygen. In the fuel cell stack takes place then the conversion of the hydrogen-rich anode gas with the help from cathode air to electricity and heat. The hydrogen-depleted from the fuel cell Reformat is then in an afterburner with further supply of Air afterburned to fulfill the corresponding Emission limits.

In all three main components release heat during operation, the dissipated must become. That is why they usually belong Facilities for heat transfer to such high temperature fuel cell systems. Especially in the conversion of the reformate in the fuel cell depending on the operating point different amounts of heat freely which usually dissipated convective are due to a sufficiently large excess of air on the cathode side.

disadvantage

Of the Operation of such fuel cell systems with air causes that in the fuel cell stack both on the anode and on the cathode side high nitrogen contents are present, as inert gas the efficiency reduce the fuel cell stack. In addition, unnecessarily high gas flow rates before entry be warmed up in the fuel cell, for damage to avoid the fuel cell.

If the reforming of the fuel to a hydrogen-rich hydrogen / carbon monoxide mixture with atmospheric oxygen (partial oxidation), also results in a reduction in efficiency by the nitrogen inert gas. Furthermore, the partial oxidation of hydrocarbons by a two-stage formal mechanism, wherein the fuel is first totally oxidized with atmospheric oxygen to carbon dioxide and water and then in a second step, the reforming of the hydrocarbons with the previously formed water and CO ₂ takes place. While the total oxidation is a highly exothermic reaction, the subsequent reforming with water and CO ₂ proceeds under significant heat absorption. This results in an inhomogeneous temperature profile, which leads to problems especially when using catalysts. Thus, in the inlet region of the catalyst, temperature peaks can occur which lead to thermal destruction of the catalyst material and / or of the catalyst support, while the low temperatures present in the rear region lead to poor degrees of conversion and product selectivities of the reforming.

Proposed measures

It is proposed to operate a high temperature fuel cell system with pure oxygen which is separated from air. This should be pe Rowskitische ceramics are used as oxygen separation membranes in conjunction with a reformer, a high-temperature fuel cell stack and post-combustion.

These perovskite oxygen separation membranes are mixed-conducting, dense, oxidic ceramics capable of oxygen-ion and electron conduction. Upon presentation of an oxygen partial pressure gradient, oxygen ions O ² and O ² vacancies and electron or electron holes in different directions simultaneously diffuse in these materials according to the partial pressure gradient of the oxygen through the material. The operating temperature of these materials is> 700 ° C and thus in a range in which both typical high-temperature fuel cells (eg SOFC, MCFC) and the partial oxidation of hydrocarbons are operated. During operation of the membrane, oxygen is adsorbed dissociatively on the feed side and enters the oxide material of the perovskite membrane with electron uptake as an ion. From the permeate side, the oxygen ions can either be released into the gas phase as molecular oxygen, or hydrocarbons react directly with the lattice oxygen.

For combining such separation membranes with high temperature fuel cell systems, a system interconnection according to 1 proposed.

• (1) Es handelt sich um ein Hochtemperaturbrennstoffzellen-System, bestehend aus Reformer, Brennstoffzelle und Nachverbrennung, das als Gesamtsystem ausschließlich mit kohlenwasserstoffhaltigen Brennstoffen einerseits sowie andererseits mit aus Luft mittels Perowskitmembranen abgetrennten Sauerstoff betrieben wird. Ergänzend kann eine Zugabe von Wasser in das Gesamtsystem vorgesehen werden. Dadurch kann a) ein höherer elektrischer Gesamtwirkungsgrad von Hochtemperaturbrennstoffzellen-Systemen bezogen auf den eingesetzten Brennstoff erzielt werden, b) die Menge an emittierten Schadgasen von Hochtemperaturbrennstoffzellen-Systemen (insbesondere Stickoxide) reduziert werden, c) eine Vergleichmäßigung der Temperaturverteilung in den Einzelkomponenten erreicht werden mit dem Effekt höherer Lebensdauer und vereinfachter Betriebsführung von Hochtemperaturbrennstoffzellen-Systemen, d) das Kohlendioxid aus dem Austrittsgas der Nachverbrennung durch Kondensation des Wasserdampfes leicht separiert und sequestriert werden.
• (2) Ein Reformer für Hochtemperaturbrennstoffzellen-Systeme zur Herstellung von geeignetem Brenngas, bestehend vorwiegend aus Wasserstoff und Kohlenmonoxid, wobei der Anteil an Wasserstoff und Kohlenmonoxid besonders erhöht wurde, dergestalt, dass a) perowskitische Keramiken als Sauerstoff-Trennmembranen in Verbindung mit einem Reformer zur partiellen Oxidation von Kohlenwasserstoffen mit reinem Sauerstoff eingesetzt werden, b) der von der perowskitischen Keramik übertragene Sauerstoff direkt am angrenzenden Katalysator mit den zugeführten Kohlenwasserstoffen abreagiert, c) die Kohlenwasserstoffe alternativ auch als Träger für den übertragenen Sauerstoff verwendet werden können; die partielle Oxidation kann dann in einem separaten Reaktor erfolgen, d) alternativ erfolgt die Sauerstoffabtrennung luftseitig mit Überdruck, um einen kontinuierlichen Sauerstoffstrom auf der Permeatseite der perowskitischen Keramik zu erreichen. e) Ergänzend kann dem Edukt Wasser bzw. Wasserdampf zugefügt werden, um Wärme abzuführen, die Bildung kohlenstoffhaltiger Ablagerungen zu unterdrücken und/oder die Reformierung in Richtung auto- oder endotherme Betriebsweise zu verschieben.
• (3) Ein Apparat zur Abtrennung von Sauerstoff aus Luft dergestalt, dass a) eine perowskitische Keramik bei hohen Betriebstemperaturen gleichzeitig Sauerstoffionen und Elektronen leitet und damit einen kontinuierlichen Sauerstoffstrom auf der Permeatseite erzeugt, b) die Sauerstoffabtrennung luftseitig mit Überdruck erfolgt, um einen kontinuierlichen Sauerstoffstrom für die Kathode der Hochtemperaturbrennstoffzelle zu erzeugen, c) die perowskitische Keramik alternativ direkt auf die Kathode der Hochtemperaturbrennstoffzelle aufgetragen werden kann, um eine möglichst hohe Sauerstoffpartialdruckdifferenz zwischen Kathode und Anode für die elektrochemische Umwandlung zur Verfügung zu stellen.
• (4) Ein Apparat zur Nachverbrennung nicht-umgesetzter Brenngasanteile dergestalt, dass a) mit dem Sauerstoff des Kathodenabgases ein vollständiger Brenngasumsatz erreicht wird, b) lediglich Wasser und Kohlendioxid als Reaktionsprodukt entstehen, woraus ein inertgasfreier Betrieb resultiert, c) ergänzend kann eine einfache Abtrennung des Kohlendioxides durch Auskondensieren des Wasseranteiles nachgeschaltet werden. Das dann verbleibende reine Kohlendioxid kann sequestriert werden, d) die Nachverbrennung kann sowohl katalytisch oder nichtkatalytisch erfolgen.

The invention is characterized by the following features:

• (1) It is a high-temperature fuel cell system consisting of reformer, fuel cell and afterburning, which is operated as a whole system exclusively with hydrocarbon fuels on the one hand and on the other hand with separated from air by means of Perowskitmembranen oxygen. In addition, an addition of water can be provided in the overall system. As a result, a) a higher overall electrical efficiency of high-temperature fuel cell systems based on the fuel used can be achieved, b) the amount of emitted noxious gases from high-temperature fuel cell systems (in particular nitrogen oxides) can be reduced, c) a homogenization of the temperature distribution in the individual components can be achieved the effect of longer life and simplified operation of high temperature fuel cell systems, d) the carbon dioxide from the exit gas of the post combustion by condensation of the water vapor easily separated and sequestered.
• (2) A reformer for high temperature fuel cell systems for producing suitable fuel gas consisting mainly of hydrogen and carbon monoxide, wherein the proportion of hydrogen and carbon monoxide has been particularly increased, such that a) perovskite ceramics as oxygen separation membranes in conjunction with a reformer for b) reacting the oxygen transferred by the perovskite ceramic directly on the adjacent catalyst with the supplied hydrocarbons, c) the hydrocarbons can alternatively also be used as carrier for the transferred oxygen; the partial oxidation can then take place in a separate reactor, d) alternatively, the oxygen separation takes place on the air side with overpressure in order to achieve a continuous flow of oxygen on the permeate side of the perovskite ceramic. e) In addition, water or steam can be added to the educt in order to dissipate heat, to suppress the formation of carbonaceous deposits and / or to postpone the reforming in the direction of auto or endothermic operation.
• (3) An apparatus for separating oxygen from air such that a) a perovskite ceramic simultaneously conducts oxygen ions and electrons at high operating temperatures and thus produces a continuous flow of oxygen on the permeate side; b) the oxygen separation is positive pressure on the air side to provide a continuous flow of oxygen c) the perovskite ceramic may alternatively be applied directly to the cathode of the high temperature fuel cell to provide the highest possible oxygen partial pressure difference between the cathode and the anode for electrochemical conversion.
• (4) An apparatus for afterburning unreacted fuel gas fractions such that a) complete combustion gas conversion is achieved with the oxygen of the cathode exhaust gas, b) only water and carbon dioxide are formed as the reaction product, resulting in inert gas-free operation, c) in addition, a simple separation the carbon dioxide are followed by condensation of the water content. The remaining pure carbon dioxide can then be sequestered, d) the post-combustion can take place both catalytically or non-catalytically.

advantages

• a) die Sauerstoffabtrennung bei den Betriebstemperaturen des Hochtemperaturbrennstoffzellen-Systems erfolgt,
• b) ein höherer Sauerstoffpartialdruck auf der Kathodenseite der Hochtemperaturbrennstoffzelle zu einem höheren elektrischen Brennstoffzellenwirkungsgrad führt,
• c) ein höherer Brenngaspartialdruck auf der Anodenseite der Hochtemperaturbrennstoffzelle zu einem höheren elektrischen Brennstoffzellenwirkungsgrad führt,
• d) ein vergleichsmäßiges Temperaturprofil im Reformer zu höherer Effizienz und verlängerter Lebensdauer führt,
• e) vor Eintritt des Reformers kein Gemisch aus Kohlenwasserstoff und Oxidationsmittel vorliegt. Dies erhöht die Betriebssicherheit, da kein zündfähiges Gemisch vor der eigentlichen Reaktionszone vorliegt,
• f) ein einheitlicher Temperaturbereich von Reformer, Stack und Nachverbrennung eine verbesserte Integration und kompaktere Bauweise ermöglicht,
• g) das Gesamtsystem einen höheren Gesamtwirkungsgrad und geringere Emissionen aufweist.

The proposed method for operating a high-temperature fuel cell system with nitrogen-free gases using perovskite ceramics as oxygen separation membranes has the advantages that

• a) the oxygen separation takes place at the operating temperatures of the high-temperature fuel cell system,
• b) higher oxygen partial pressure on the cathode side of the high temperature fuel cell results in higher fuel cell electrical efficiency,
• c) higher fuel gas partial pressure on the anode side of the high temperature fuel cell results in higher fuel cell electrical efficiency,
• d) a comparative temperature profile in the reformer leads to higher efficiency and longer life,
• e) before the onset of the reformer there is no mixture of hydrocarbon and oxidizing agent. This increases the operational safety, since no ignitable mixture is present before the actual reaction zone,
• f) a uniform temperature range of reformer, stack and afterburning enables improved integration and more compact design,
• g) the overall system has a higher overall efficiency and lower emissions.

Claims (14)

High-temperature fuel cell system with a) a reformer ( 3 ) for converting a fuel into a hydrogen-rich anode gas, b) a fuel cell stack ( 4 ) for converting the hydrogen-rich anode gas while supplying a cathode gas to electricity and heat, c) an afterburner ( 5 ) for post-combustion of a hydrogen-depleted reformate leaving the fuel cell stack while supplying the cathode gas, characterized by d) a separation reactor ( 2 ) for separating oxygen from air, wherein the oxygen separated during operation is at least partially used as cathode gas. High-temperature fuel cell system according to claim 1, characterized in that the separation reactor is a perovskite ceramic ( 6 ) as oxygen separation membranes. High-temperature fuel cell system according to claim 2, characterized in that the perovskite ceramic ( 6 ) directly on a cathode ( 12 ) of the fuel cell stack ( 4 ) is applied. High-temperature fuel cell system according to claim 2 or 3, characterized in that in operation on the input side ( 7 ) of the separation reactor ( 2 ) there is a higher pressure than on the output side ( 8th ) of the separation reactor ( 2 ). High-temperature fuel cell system according to one of the preceding claims, characterized in that the reformer ( 3 ) a perovskite ceramic ( 17 ) as oxygen separation membranes. High-temperature fuel cell system according to one of the preceding claims, characterized in that the educt ( 19 ) Water and / or water vapor ( 22 ) can be fed. High-temperature fuel cell system according to one of the preceding claims, characterized in that the afterburner ( 5 ) is formed, nachverbrennen catalytically or non-catalytically. Method for generating electricity and heat with the aid of a high-temperature fuel cell system ( 1 ) according to one of the preceding claims, comprising the steps of: a) converting the fuel into the hydrogen-rich anode gas in the reformer ( 3 ); b) converting the hydrogen-rich anode gas while supplying the cathode gas to electricity and heat in the fuel cell stack ( 4 ); c) afterburning of the fuel cell stack ( 4 ), hydrogen-depleted reformates ( 24 ) with supply of the cathode gas in the afterburner ( 5 characterized by the steps of: d) separating the oxygen from air in the separation reactor ( 2 ); e) At least partially using the separated oxygen as the cathode gas. A method according to claim 8, characterized in that the separation of the oxygen from the air in the separation reactor ( 2 ) with the help of a perovskite ceramic ( 6 ) takes place as an oxygen separation membrane. Process according to Claim 9, characterized in that the separation reactor ( 2 ) on the input side ( 7 ) with a higher pressure than on the output side ( 8th ) is operated. Method according to one of claims 8 to 10, characterized in that in the reformer ( 3 ) by means of a perovskite ceramic ( 17 ) Oxygen is separated from the air. Method according to claim 11, characterized in that that the separated oxygen on a catalyst with added hydrocarbons reacts to form the anode gas. Method according to one of claims 9 to 12, characterized in that the anode gas ( 19 ) Water and / or water vapor ( 22 ). Method according to one of claims 8 to 13, characterized the post-combustion takes place catalytically or non-catalytically.