EP2135315A2 - Fuel cell system with a recirculation strand - Google Patents

Fuel cell system with a recirculation strand

Info

Publication number
EP2135315A2
EP2135315A2 EP08734376A EP08734376A EP2135315A2 EP 2135315 A2 EP2135315 A2 EP 2135315A2 EP 08734376 A EP08734376 A EP 08734376A EP 08734376 A EP08734376 A EP 08734376A EP 2135315 A2 EP2135315 A2 EP 2135315A2
Authority
EP
European Patent Office
Prior art keywords
fuel cell
reformate
reformer
fuel
cell system
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP08734376A
Other languages
German (de)
French (fr)
Inventor
Norbert GÜNTHER
Andreas Reinert
Stefan Käding
Björn Erik MAI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Enerday GmbH
Staxera GmbH
Original Assignee
Enerday GmbH
Staxera GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Enerday GmbH, Staxera GmbH filed Critical Enerday GmbH
Publication of EP2135315A2 publication Critical patent/EP2135315A2/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H01M8/04097—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with recycling of the reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H01M8/04225—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells during start-up
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H01M8/04228—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells during shut-down
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04302—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during start-up
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04303—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during shut-down
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H01M2008/1293—Fuel cells with solid oxide electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • H01M8/04014—Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
    • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the invention relates to a fuel cell system with a reformer for generating a reformate of fuel and oxidant, a fuel cell for converting the reformate into depleted reformate and electrical energy, and a Rezirkulationsstrang for partially returning lead the depleted reformate to the reformer.
  • the invention relates to a method for operating a fuel cell system, comprising the steps of producing a reformate from fuel and oxidizing agent by means of a reformer; Converting the reformate into depleted reformate and electrical energy by means of a fuel cell; and partially returning the depleted reformate to the reformer in a recirculation strand.
  • Fuel cell systems serve in a well-known way the conversion of chemical energy into electrical energy. Fuel cell systems must be able to process common fuels in practice. Since hydrogen and oxygen are converted in a fuel cell, the fuel used must be prepared so that the gas supplied to the anode of the fuel cell has the highest possible proportion of hydrogen. On the cathode side, atmospheric oxygen is supplied to the fuel cell in most cases. For this purpose, fuel and an oxidizing agent, preferably air, are fed to a reformer. In the reformer then takes place a reaction of the fuel with the oxygen, wherein preferably the process of partial oxidation is carried out.
  • EP 1 557 896 A1 discloses a fuel cell system with the features of the preamble of claim 1. In this fuel cell system, a reformate gas is returned to a reformer, which leaves a fuel cell on the output side. However, this system has a complex structure.
  • the fuel cell system builds on the generic state of the art in that a conveyor is provided by means of which both the fuel and the depleted reformate of the recirculation lationsstranges the reformer can be fed.
  • a conveyor which supplies the reformer both the fuel and the depleted reformate, additional conveyors could be saved.
  • such a structure also allows a simplified control, since by increasing the delivery rate of the conveyor automatically the fuel delivery rate and the delivery rate of the depleted reformate is increased, so that when a flow rate change, not the individual strands must be coordinated with each other. The delivery rate of the recirculated depleted reformate is thus controlled via the delivery rate of the fuel supplied.
  • a flow control valve is provided upstream of the conveyor to control the supply of fuel and depleted reformate to the conveyor independently.
  • This structure makes it possible to set the ratio of fuel to recirculation flow by varying the two valve positions relative to each other and the variation of the speed of the conveyor.
  • this interconnection has the advantage that a high flexibility in the adjustment of the gas composition in the reformer can be achieved, whereby a high flexibility of the fuel cell system in response to load changes can be achieved. Since this ratio also has an influence on the temperature of the reformer, it can be operated by the setting in a desired temperature range.
  • the provision of separate control valves is also less expensive than providing separate conveyors in each strand.
  • the fuel cell system according to the invention can be further developed by providing a heat exchanger for cooling the depleted reformate in the recirculation train.
  • a heat exchanger for cooling the depleted reformate in the recirculation train.
  • components in the recirculation line such as, for example, the valve or the conveyor, would have to be designed for temperatures of up to 850 ° C., which greatly increases the system complexity and makes it difficult to locate such components at all.
  • high application temperatures lead to high wear on mechanical components.
  • an oxidant strand leads through the heat exchanger, which leads oxidizing agent to the reformer, to the fuel cell or to an afterburner.
  • a media stream already present in the fuel cell system can be used to cool the recycled, depleted reformate. Additional fans for cooling down the recirculation flow can thus be saved.
  • the invention provides a method of controlling such a fuel cell system.
  • this can advantageously be distinguished by closing the flow control valve in the recirculation line during the start or shutdown of the fuel cell system.
  • This measure makes it possible to deactivate the recirculation line for the start of the fuel cell system, to which insufficiently depleted reformate is available, or to shut down the fuel cell system, so that advantageous conditions can be created for these operating states.
  • FIG. 1 is a schematic representation of the fuel cell system according to the invention.
  • FIG. 1 shows a schematic representation of the fuel cell system 10 according to the invention.
  • the fuel cell system 10 comprises a reformer 12 to which fuel can be fed from a delivery device 14 and a deflated reformate which will be explained later.
  • a fan or all suitable types of pumps such as rotary vane pumps for gases, can be used.
  • a flow control valve 16 is provided upstream of the conveyor 14 and upstream of a recombining point 18 at which the recirculated depleted reformate is introduced.
  • the fuel is preferably a gas.
  • the reformer 12 is supplied by means of a reformer 20 Oxidizer.
  • the reformer 12 converts the materials supplied via the delivery device 14 and the reforming fan 20, preferably under partial oxidation, into a reformate which can be supplied to a fuel cell 22.
  • a fuel cell stack can also be provided.
  • the reformate is a hydrogen-containing gas which is converted in the fuel cell 22 into electric power, heat and depleted reformate by means of cathode air delivered by a fuel cell fan 24.
  • the output side of the fuel cell 22 discharged depleted reformate is divided into two strands.
  • a portion of the depleted anode exhaust gas is fed to a Nachbren- ner 26, which is associated with a Nachbrennerbläse 28.
  • the depleted reformate is reacted with air conveyed through the afterburner fan 28 to form a combustion exhaust gas which contains virtually no pollutants.
  • the other part of the depleted reformate is fed via a recirculation line 30. next passed through a heat exchanger 32 and a Reformatküh- ler. This heat exchanger 32 cools the recirculated depleted reformate to, for example, 150 ° C.
  • the recirculation flow can advantageously be cooled via the heat exchanger 32 by a medium flow which is already present in the fuel cell system 10.
  • Suitable media streams are, for example, the media streams taken in by the reformer fan 20, the fuel cell fan 24 and / or the afterburner fan 28.
  • the recirculation flow via a flow control valve 34 leads to flow control of the recirculation flow.
  • This recirculation flow is mixed with the fuel at the merging point 18 and fed to the conveyor 14.
  • the delivery device 14 simultaneously aspirates the fuel and the depleted reformate recycled via the recirculation line 30.
  • Flow control valves 16 and 34 and the conveyor 14 is realized with suitable control algorithms, which are stored in an electronic control unit.
  • This electronic control unit is preferably a microcontroller and at least with the conveyor 14, the
  • Flow control valve 16 the reforming fan 20, the fuel cell blower 24, the afterburner fan 28 and the flow control valve 34 is connected.
  • the fuel cell fan 24 and the afterburner fan 28 corresponding pumps for gas delivery may also be provided.

Abstract

The invention relates to a fuel cell system (10) comprising a reformer (12) for producing a reformate from fuel and an oxidation agent, a fuel cell (22) for converting said reformate into a depleted reformate and electric energy, and a recirculation strand (30) for partially guiding the depleted reformate back to the reformer (12). The invention is characterised in that a transport device (14) is provided, said device guiding the fuel as well as the depleted reformate of the recirculation stand (30) to the reformer (12). The invention also relates to a method for operating said type of fuel cell system (10).

Description

BrennstoffZeilensystem mit RezirkulationsstrangFuel line system with recirculation line
Die Erfindung betrifft ein BrennstoffZellensystem mit einem Reformer zum Erzeugen eines Reformats aus Brennstoff und Oxidationsmittel, einer Brennstoffzelle zum Umsetzen des Reformats in abgereichertes Reformat und elektrische Energie, und einem Rezirkulationsstrang zum teilweisen Zurück- führen des abgereicherten Reformats zum Reformer.The invention relates to a fuel cell system with a reformer for generating a reformate of fuel and oxidant, a fuel cell for converting the reformate into depleted reformate and electrical energy, and a Rezirkulationsstrang for partially returning lead the depleted reformate to the reformer.
Darüber hinaus betrifft die Erfindung ein Verfahren zum Betreiben eines Brennstoffzellensystems, mit den Schritten Erzeugen eines Reformats aus Brennstoff und Oxidationsmit- tel mittels eines Reformers; Umsetzen des Reformats in abgereichertes Reformat und elektrische Energie mittels einer Brennstoffzelle; und teilweises Zurückführen des abgereicherten Reformats zum Reformer in einem Rezirkulationsstrang.Furthermore, the invention relates to a method for operating a fuel cell system, comprising the steps of producing a reformate from fuel and oxidizing agent by means of a reformer; Converting the reformate into depleted reformate and electrical energy by means of a fuel cell; and partially returning the depleted reformate to the reformer in a recirculation strand.
Brennstoffzellensysteme dienen in allgemein bekannter Weise der Umwandlung von chemischer Energie in elektrische Energie. Brennstoffzellensysteme müssen in der Lage sein, in der Praxis übliche Brennstoffe zu verarbeiten. Da in einer Brennstoffzelle Wasserstoff und Sauerstoff umgesetzt werden, muss der verwendete Brennstoff so aufbereitet werden, dass das der Anode der Brennstoffzelle zugeführte Gas einen möglichst hohen Anteil an Wasserstoff besitzt. Kathodensei- tig wird in den meisten Fällen Luftsauerstoff an die Brenn- stoffzelle zugeführt. Zu diesem Zweck werden einem Reformer Brennstoff und ein Oxidationsmittel, vorzugsweise Luft, zugeführt. In dem Reformer erfolgt dann eine Umsetzung des Brennstoffs mit dem Sauerstoff, wobei vorzugsweise das Verfahren der partiellen Oxidation durchgeführt wird. EP 1 557 896 Al offenbart ein Brennstoffzellensystem mit den Merkmalen des Oberbegriffes des Anspruches 1. In diesem Brennstoffzellensystem wird zu einem Reformer ein Reformat- gas zurückgeführt, welches eine Brennstoffzelle ausgangs- seitig verlässt. Dieses System weist jedoch einen komplexen Aufbau auf .Fuel cell systems serve in a well-known way the conversion of chemical energy into electrical energy. Fuel cell systems must be able to process common fuels in practice. Since hydrogen and oxygen are converted in a fuel cell, the fuel used must be prepared so that the gas supplied to the anode of the fuel cell has the highest possible proportion of hydrogen. On the cathode side, atmospheric oxygen is supplied to the fuel cell in most cases. For this purpose, fuel and an oxidizing agent, preferably air, are fed to a reformer. In the reformer then takes place a reaction of the fuel with the oxygen, wherein preferably the process of partial oxidation is carried out. EP 1 557 896 A1 discloses a fuel cell system with the features of the preamble of claim 1. In this fuel cell system, a reformate gas is returned to a reformer, which leaves a fuel cell on the output side. However, this system has a complex structure.
Es ist daher die Aufgabe der vorliegenden Erfindung, eine Möglichkeit zu schaffen, ein Brennstoffzellensystem bereit- zustellen, welches relativ einfach aufgebaut ist und somit kostengünstig herstellbar ist.It is therefore the object of the present invention to provide a possibility to provide a fuel cell system which is of relatively simple construction and thus can be produced cost-effectively.
Diese Aufgabe wird durch die Merkmale der unabhängigen Ansprüche gelöst.This object is solved by the features of the independent claims.
Vorteilhafte Ausgestaltungen und Weiterbildungen der Erfindung ergeben sich aus den abhängigen Ansprüchen.Advantageous embodiments and modifications of the invention will become apparent from the dependent claims.
Das erfindungsgemäße Brennstoffzellensystem baut auf dem gattungsgemäßen Stand der Technik dadurch auf, dass eine Fördereinrichtung vorgesehen ist, mittels der sowohl der Brennstoff als auch das abgereicherte Reformat des Rezirku- lationsstranges dem Reformer zuführbar sind. Durch die Fördereinrichtung, welche dem Reformer sowohl den Brennstoff als auch das abgereicherte Reformat zuführt, könnten weitere Fördereinrichtungen eingespart werden. Darüber hinaus ermöglicht ein derartiger Aufbau auch eine vereinfachte Steuerung, da durch Erhöhung der Fördermenge der Fördereinrichtung automatisch die Brennstofffördermenge als auch die Fördermenge des abgereicherten Reformats erhöht wird, so dass bei einer Fördermengenänderung nicht die einzelnen Stränge zwangsläufig aufeinander abgestimmt werden müssen. Die Fördermenge des zurückgeführten abgereicherten Reformats ist somit über die Fördermenge des zugeführten Brenn- stoffs steuerbar. Darüber hinaus ist vorteilhaft, dass stromaufwärts der Fördereinrichtung jeweils ein Stromregelventil vorgesehen ist, um das Zuführen von Brennstoff und abgereichertem Reformat zu der Fördereinrichtung unabhängig voneinander zu steuern. Dieser Aufbau ermöglicht, dass durch die Variation der beiden Ventilstellungen zueinander und der Variation der Drehzahl der Fördereinrichtung das Verhältnis von Brennstoff zu Rezirkulationsstrom eingestellt werden kann. Somit bietet diese Verschaltung den Vorteil, dass eine hohe Flexibilität bei der Einstellung der GasZusammensetzung im Reformer erreicht werden kann, wodurch eine hohe Flexibilität des Brennstoffzellensystems bei der Reaktion auf Laständerungen erreicht werden kann. Da dieses Verhältnis auch einen Ein- fluss auf die Temperatur des Reformers hat, kann dieser durch die Einstellung auch in einem gewünschten Temperaturbereich betrieben werden. Ferner ist das Vorsehen von separaten Regelventilen auch, preiswerter als das Bereitstellen von separaten Fördereinrichtungen in jedem Strang.The fuel cell system according to the invention builds on the generic state of the art in that a conveyor is provided by means of which both the fuel and the depleted reformate of the recirculation lationsstranges the reformer can be fed. By the conveyor, which supplies the reformer both the fuel and the depleted reformate, additional conveyors could be saved. In addition, such a structure also allows a simplified control, since by increasing the delivery rate of the conveyor automatically the fuel delivery rate and the delivery rate of the depleted reformate is increased, so that when a flow rate change, not the individual strands must be coordinated with each other. The delivery rate of the recirculated depleted reformate is thus controlled via the delivery rate of the fuel supplied. Moreover, it is advantageous that in each case a flow control valve is provided upstream of the conveyor to control the supply of fuel and depleted reformate to the conveyor independently. This structure makes it possible to set the ratio of fuel to recirculation flow by varying the two valve positions relative to each other and the variation of the speed of the conveyor. Thus, this interconnection has the advantage that a high flexibility in the adjustment of the gas composition in the reformer can be achieved, whereby a high flexibility of the fuel cell system in response to load changes can be achieved. Since this ratio also has an influence on the temperature of the reformer, it can be operated by the setting in a desired temperature range. Furthermore, the provision of separate control valves is also less expensive than providing separate conveyors in each strand.
Ferner kann das erfindungsgemäße BrennstoffZellensystem dadurch weitergebildet sein, dass ein Wärmetauscher zum Kühlen des abgereicherten Reformats im Rezirkulationsstrang vorgesehen ist. Ohne diesen Wärmetauscher müssten Komponen- ten im Rezirkulationsstrang wie beispielsweise das Ventil oder die Fördereinrichtung auf Temperaturen von bis zu 8500C ausgelegt werden, was den Systemaufbau stark verteuert und schwierig macht, derartige Komponenten überhaupt ausfindig zu machen. Außerdem führen hohe Anwendungstempe- raturen zu hohem Verschleiß an mechanischen Bauteilen.Furthermore, the fuel cell system according to the invention can be further developed by providing a heat exchanger for cooling the depleted reformate in the recirculation train. Without this heat exchanger, components in the recirculation line, such as, for example, the valve or the conveyor, would have to be designed for temperatures of up to 850 ° C., which greatly increases the system complexity and makes it difficult to locate such components at all. In addition, high application temperatures lead to high wear on mechanical components.
Durch Kühlen des Rezirkulationsstroms kann dieser Problematik begegnet werden, so dass der Rezirkulationsstrom auf beispielsweise 1500C gekühlt wird, um zu ermöglichen, dass normale Komponenten verwendet werden können. Die normalen Komponenten können dann auf relativ moderaten Temperaturen betrieben werden.By cooling the recycle stream, this problem can be addressed so that the recycle stream is cooled to, for example, 150 ° C. to allow normal components to be used. The normal ones Components can then be operated at relatively moderate temperatures.
In diesem Zusammenhang kann vorteilhafterweise vorgesehen sein, dass durch den Wärmetauscher ein Oxidationsmit- telstrang führt, der Oxidationsmittel zum Reformer, zur Brennstoffzelle oder zu einem Nachbrenner führt. Somit kann ein bereits im Brennstoffzellensystem vorhandener Medienstrom dazu verwendet werden, das zurückgeführte abgerei- cherte Reformat zu kühlen. Zusätzliche Gebläse für das Herunterkühlen des Rezirkulationsstroms können somit eingespart werden.In this connection, it may be advantageously provided that an oxidant strand leads through the heat exchanger, which leads oxidizing agent to the reformer, to the fuel cell or to an afterburner. Thus, a media stream already present in the fuel cell system can be used to cool the recycled, depleted reformate. Additional fans for cooling down the recirculation flow can thus be saved.
Darüber hinaus stellt die Erfindung ein Verfahren zum Steu- ern solch eines Brennstoffzellensystems bereit.In addition, the invention provides a method of controlling such a fuel cell system.
Im Rahmen des Verfahren kann sich dieses vorteilhafterweise auszeichnen durch Schließen des Stromregelventils im Rezir- kulationsstrang während des Starts oder des Herunterfahrens des Brennstoffzellensystems . Durch diese Maßnahme können für den Start des Brennstoffzellensystems, zu dem ungenügend abgereichertes Reformat zur Verfügung steht, oder beim Herunterfahren des Brennstoffzellensystems der Rezirkulati- onsstrang deaktiviert werden, so dass für diese Betriebszu- stände vorteilhafte Bedingungen geschaffen werden können.Within the scope of the method, this can advantageously be distinguished by closing the flow control valve in the recirculation line during the start or shutdown of the fuel cell system. This measure makes it possible to deactivate the recirculation line for the start of the fuel cell system, to which insufficiently depleted reformate is available, or to shut down the fuel cell system, so that advantageous conditions can be created for these operating states.
Eine bevorzugte Ausführungsform der Erfindung wird nachfolgend anhand der Figur beispielhaft erläutert.A preferred embodiment of the invention will be explained by way of example with reference to the figure.
Es zeigt:It shows:
Figur 1 eine schematische Darstellung des erfindungsgemäßen Brennstoffzellensystems . Figur 1 zeigt eine schematische Darstellung des erfindungsgemäßen BrennstoffZeilensystems 10. Das Brennstoffzellen- system 10 umfasst einen Reformer 12, dem von einer Fördereinrichtung 14 Brennstoff und später erläutertes abge- reichertes Reformat zuführbar ist. Als Fördereinrichtung 14 kann ein Gebläse oder alle geeigneten Pumpentypen, wie beispielsweise Drehschieberpumpen für Gase, eingesetzt werden. Zur Steuerung der Zufuhr des Brennstoffs ist ein Stromregelventil 16 stromaufwärts der Fördereinrichtung 14 und stromaufwärts einer Zusammenführstelle 18, an der das rückgeführte abgereicherte Reformat eingeleitet wird, vorgesehen. Als Brennstoffarten kommen Diesel, Benzin, Biogas, Erdgas, und weitere aus dem Stand der Technik bekannten Brennstoffarten in Frage, wobei im vorliegenden Ausfüh- rungsbeispiel der Brennstoff vorzugsweise ein Gas ist. Weiterhin wird dem Reformer 12 mittels eines Reformergebläses 20 Oxidationsmittel zugeführt. Der Reformer 12 setzt die über die Fördereinrichtung 14 und das Reformergebläse 20 zugeführten Stoffe vorzugsweise unter partieller Oxidation in ein Reformat um, welches einer Brennstoffzelle 22 zuführbar ist. Alternativ zur Brennstoffzelle 22 kann auch ein Brennstoffzellenstapel vorgesehen sein. Bei dem Reformat handelt es sich um ein Wasserstoffhaltiges Gas, das in der Brennstoffzelle 22 mit Hilfe von durch ein Brennstoff- zellengebläse 24 geförderter Kathodenluft zu elektrischem Strom, Wärme und abgereichertem Reformat umgesetzt wird. Das ausgangsseitig von der Brennstoffzelle 22 abgeführte abgereicherte Reformat teil sich in zwei Stränge auf. Ein Teil des abgereicherten Anodenabgases wird einem Nachbren- ner 26 zugeführt, dem ein Nachbrennergebläse 28 zugeordnet ist. In dem Nachbrenner 26 erfolgt eine Umsetzung des abgereicherten Reformats mit durch das Nachbrennergebläse 28 geförderter Luft zu einem Verbrennungsabgas, das nahezu keine Schadstoffe enthält. Der andere Teil des abgereicher- ten Reformats wird über einen Rezirkulationsstrang 30 zu- nächst durch einen Wärmetauscher 32 bzw. einen Reformatküh- ler hindurchgeführt. Dieser Wärmetauscher 32 kühlt das zurückzuführende abgereicherte Reformat auf beispielsweise 1500C ab. Dabei kann der Rezirkulationsstrom in vorteilhaf- ter Weise über den Wärmetauscher 32 durch einen Medienstrom abgekühlt werden, der schon im BrennstoffZeilensystem 10 vorhanden ist. Als Medienströme kommen hier beispielsweise die vom Reformergebläse 20, vom Brennstoffzellengebläse 24 und/oder vom Nachbrennergebläse 28 angesaugten Medienströme in Frage. Alternativ ist auch möglich, ein Gebläse vorzusehen, welches die Wärmeenergie vom Wärmetauscher 32 abtransportiert. Anschließend führt der Rezirkulationsstrom über ein Stromregelventil 34 zur Durchflusssteuerung des Rezir- kulationsstroms . Dieser Rezirkulationsstrom wird an der Zu- sammenführstelle 18 mit dem Brennstoff gemischt und der Fördereinrichtung 14 zugeführt. Die Fördereinrichtung 14 saugt gleichzeitig den Brennstoff und das über den Rezirku- lationsstrang 30 zurückgeführte abgereicherte Reformat an. Durch eine derartige Rückführung kann ein höherer System- Wirkungsgrad erreicht werden, da die Energie des abgerei- cherten Reformats noch vollständiger umgesetzt wird, so dass im Vergleich zu Systemen ohne Rezirkulationsstrang 30 mit der gleichen Brennstoffmenge mehr elektrische Energie gewonnen werden kann, so dass sich der elektrische System- Wirkungsgrad erhöht. Die Einstellung bzw. Regelung derFigure 1 is a schematic representation of the fuel cell system according to the invention. FIG. 1 shows a schematic representation of the fuel cell system 10 according to the invention. The fuel cell system 10 comprises a reformer 12 to which fuel can be fed from a delivery device 14 and a deflated reformate which will be explained later. As a conveyor 14, a fan or all suitable types of pumps, such as rotary vane pumps for gases, can be used. To control the supply of fuel, a flow control valve 16 is provided upstream of the conveyor 14 and upstream of a recombining point 18 at which the recirculated depleted reformate is introduced. As fuel types come diesel, gasoline, biogas, natural gas, and other known from the prior art types of fuel in question, wherein in the present embodiment, the fuel is preferably a gas. Furthermore, the reformer 12 is supplied by means of a reformer 20 Oxidizer. The reformer 12 converts the materials supplied via the delivery device 14 and the reforming fan 20, preferably under partial oxidation, into a reformate which can be supplied to a fuel cell 22. As an alternative to the fuel cell 22, a fuel cell stack can also be provided. The reformate is a hydrogen-containing gas which is converted in the fuel cell 22 into electric power, heat and depleted reformate by means of cathode air delivered by a fuel cell fan 24. The output side of the fuel cell 22 discharged depleted reformate is divided into two strands. A portion of the depleted anode exhaust gas is fed to a Nachbren- ner 26, which is associated with a Nachbrennerbläse 28. In the afterburner 26, the depleted reformate is reacted with air conveyed through the afterburner fan 28 to form a combustion exhaust gas which contains virtually no pollutants. The other part of the depleted reformate is fed via a recirculation line 30. next passed through a heat exchanger 32 and a Reformatküh- ler. This heat exchanger 32 cools the recirculated depleted reformate to, for example, 150 ° C. In this case, the recirculation flow can advantageously be cooled via the heat exchanger 32 by a medium flow which is already present in the fuel cell system 10. Suitable media streams are, for example, the media streams taken in by the reformer fan 20, the fuel cell fan 24 and / or the afterburner fan 28. Alternatively, it is also possible to provide a fan which removes the heat energy from the heat exchanger 32. Subsequently, the recirculation flow via a flow control valve 34 leads to flow control of the recirculation flow. This recirculation flow is mixed with the fuel at the merging point 18 and fed to the conveyor 14. The delivery device 14 simultaneously aspirates the fuel and the depleted reformate recycled via the recirculation line 30. By virtue of such a recirculation, a higher system efficiency can be achieved, since the energy of the stripped reformate is converted even more completely, so that more electrical energy can be obtained in comparison to systems without recirculation line 30 with the same amount of fuel, so that the electrical system efficiency increased. The adjustment or regulation of
Stromregelventile 16 und 34 sowie der Fördereinrichtung 14 wird mit geeigneten Regelalgorithmen verwirklicht, die in einer elektronischen Steuereinheit abgelegt sind. Diese e- lektronische Steuereinheit ist vorzugsweise ein Mikrocont- roller und zumindest mit der Fördereinrichtung 14, demFlow control valves 16 and 34 and the conveyor 14 is realized with suitable control algorithms, which are stored in an electronic control unit. This electronic control unit is preferably a microcontroller and at least with the conveyor 14, the
Stromregelventil 16, dem Reformergebläse 20, dem Brennstoffzellengebläse 24, dem Nachbrennergebläse 28 sowie dem Stromregelventil 34 verbunden. Alternativ zum vorhergehend beschriebenen Ausführungsbeispiel können anstatt des Reformergebläses 20, des Brennstoffzellengebläses 24 und des Nachbrennergebläses 28 auch entsprechende Pumpen zur Gasförderung vorgesehen sein.Flow control valve 16, the reforming fan 20, the fuel cell blower 24, the afterburner fan 28 and the flow control valve 34 is connected. As an alternative to the previously described embodiment, instead of the reformer fan 20, the fuel cell fan 24 and the afterburner fan 28, corresponding pumps for gas delivery may also be provided.
Die in der vorstehenden Beschreibung, in den Zeichnungen sowie in den Ansprüchen offenbarten Merkmale der Erfindung können sowohl einzeln als auch in beliebiger Kombination für die Verwirklichung der Erfindung wesentlich sein. The features of the invention disclosed in the foregoing description, in the drawings and in the claims may be essential to the realization of the invention both individually and in any combination.
Bezugszeichenliste:LIST OF REFERENCE NUMBERS
10 Brennstoffzellensystem10 fuel cell system
12 Reformer12 reformers
14 Fördereinrichtung14 conveyor
16 Stromregelventil16 flow control valve
18 Zusammenführstelle 20 Reformergebläse18 merge point 20 reformer fan
22 Brennstoffzelle22 fuel cell
24 Brennstoffzellengebläse24 fuel cell blower
26 Nachbrenner26 afterburner
28 Nachbrennergebläse 30 Rezirkulationsstrang28 Afterburner fan 30 Recirculation line
32 Wärmetauscher32 heat exchangers
34 Stromregelventil 34 flow control valve

Claims

ANS PRÜCHE
1. Brennstoffzellensystem (10) mit einem Reformer (12) zum Erzeugen eines Reformats aus Brennstoff und Oxidations- mittel, einer Brennstoffzelle (22) zum Umsetzen des Reformats in abgereichertes Reformat und elektrische Energie, und einem Rezirkulationsstrang (30) zum teilweisen Zurück- führen des abgereicherten Reformats zum Reformer (12), dadurch gekennzeichnet, dass eine Fördereinrichtung (14) vorgesehen ist, mittels der sowohl der Brennstoff als auch das abgereicherte Reformat des Rezirkulationsstranges (30) dem Reformer (12) zuführbar sind.A fuel cell system (10) comprising a reformer (12) for generating a reformate of fuel and oxidant, a fuel cell (22) for converting the reformate into depleted reformate and electrical energy, and a recirculation strand (30) for partially recycling of the depleted reformate to the reformer (12), characterized in that a conveyor (14) is provided, by means of which both the fuel and the depleted reformate of the recirculation strand (30) are fed to the reformer (12).
2. Brennstoffzellensystem (10) gemäß Anspruch 1, dadurch gekennzeichnet, dass stromaufwärts der Fördereinrichtung2. Fuel cell system (10) according to claim 1, characterized in that upstream of the conveyor
(14) jeweils ein Stromregelventil (16, 34) vorgesehen ist, um das Zuführen von Brennstoff und abgereichertem Reformat zu der Fördereinrichtung (14) unabhängig voneinander zu steuern.(14) a respective flow control valve (16, 34) is provided to independently control the supply of fuel and depleted reformate to the conveyor (14).
3. Brennstoffzellensystem (10) gemäß einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass ein Wärme- tauscher (32) zum Kühlen des abgereicherten Reformats im Rezirkulationsstrang (30) vorgesehen ist.3. Fuel cell system (10) according to one of the preceding claims, characterized in that a heat exchanger (32) for cooling the depleted reformate in the recirculation line (30) is provided.
4. Brennstoffzellensystem (10) gemäß Anspruch 4, dadurch gekennzeichnet, dass durch den Wärmetauscher (32) ein Oxi- dationsmittelstrang führt, der Oxidationsmittel zum Reformer (12) , zur Brennstoffzelle (22) oder zu einem Nachbrenner (26) führt.4. Fuel cell system (10) according to claim 4, characterized in that through the heat exchanger (32) leads an oxidizing dationsmittelstrang, the oxidizing agent to the reformer (12), the fuel cell (22) or to an afterburner (26) leads.
5. Verfahren zum Betreiben eines Brennstoffzellensystems (10) , mit den Schritten-. Erzeugen eines Reformats aus Brennstoff und Oxidati- onsmittel mittels eines Reformers (12) ;5. A method of operating a fuel cell system (10), comprising the steps. Generating a reformate of fuel and Oxidati- onsmittel means of a reformer (12);
- Umsetzen des Reformats in abgereichertes Reformat und elektrische Energie mittels einer Brennstoffzelle (22) ; und- converting the reformate into depleted reformate and electrical energy by means of a fuel cell (22); and
teilweises Zurückführen des abgereicherten Reformats zum Reformer (12) in einem Rezirkulationsstrang (30) ,partially returning the depleted reformate to the reformer (12) in a recirculation line (30),
gekennzeichnet durch, Betreiben einer Fördereinrichtung (14) , um sowohl den Brennstoff als auch das abgereicherte Reformat des Rezirkulationsstranges (30) dem Reformer (12) zuzuführen.characterized by operating a conveyor (14) to supply both the fuel and the depleted reformate of the recirculation line (30) to the reformer (12).
6. Verfahren gemäß Anspruch 5, gekennzeichnet durch,6. The method according to claim 5, characterized by,
Steuern des Zuströmens von Brennstoff und Steuern des Zu- strömens von abgereichertem Reformat zu der Fördereinrich- tung (14) jeweils mittels eines Stromregelventils (16, 34) .Controlling the flow of fuel and controlling the flow of depleted reformate to the conveyor (14) by means of a flow control valve (16, 34), respectively.
7. Verfahren gemäß einem der Ansprüche 5 oder 6, gekennzeichnet durch, Kühlen des abgereicherten Reformats im Rezirkulationsstrang (30) mittels eines Wärmetauschers (32).7. The method according to any one of claims 5 or 6, characterized by, cooling the depleted reformate in the recirculation (30) by means of a heat exchanger (32).
8. Verfahren gemäß Anspruch 7, gekennzeichnet durch, Kühlen des abgereicherten Reformats im Rezirkulationsstrang (30) durch Führen von Oxidationsrαittel durch den Wärmetauscher (32) , welches dem Reformer (12) , der Brennstoffzelle (22) oder einem Nachbrenner (26) zugeführt wird.8. The method according to claim 7, characterized by, cooling the depleted reformate in the recirculation (30) by passing Oxidationsrαmittel through the heat exchanger (32) which is the reformer (12), the fuel cell (22) or an afterburner (26) is supplied ,
9. Verfahren gemäß Anspruch 6, gekennzeichnet durch,9. The method according to claim 6, characterized by,
Schließen des Stromregelventils (34) im Rezirkulationsstrang (30) während des Starts oder des Herunterfahrens des Brennstoffzellensystems (10) . Closing the flow control valve (34) in the recirculation line (30) during startup or shutdown of the fuel cell system (10).
EP08734376A 2007-03-16 2008-03-13 Fuel cell system with a recirculation strand Withdrawn EP2135315A2 (en)

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DE102007012762A DE102007012762A1 (en) 2007-03-16 2007-03-16 Fuel cell system with recirculation line
PCT/DE2008/000436 WO2008113327A2 (en) 2007-03-16 2008-03-13 Fuel cell system with a recirculation strand

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CN101669241A (en) 2010-03-10
KR101128923B1 (en) 2012-07-11
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BRPI0808975A2 (en) 2014-09-09
JP2010521785A (en) 2010-06-24
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AU2008228663A1 (en) 2008-09-25
CA2679689A1 (en) 2008-09-25

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