EP1312131A1 - High-temperature fuel cell power station having reduced carbon dioxide emissions - Google Patents

High-temperature fuel cell power station having reduced carbon dioxide emissions

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Publication number
EP1312131A1
EP1312131A1 EP01956382A EP01956382A EP1312131A1 EP 1312131 A1 EP1312131 A1 EP 1312131A1 EP 01956382 A EP01956382 A EP 01956382A EP 01956382 A EP01956382 A EP 01956382A EP 1312131 A1 EP1312131 A1 EP 1312131A1
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EP
European Patent Office
Prior art keywords
fuel cell
cell power
fuel
carbon
hydrogen
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EP01956382A
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German (de)
French (fr)
Inventor
Frank Thom
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Forschungszentrum Juelich GmbH
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Forschungszentrum Juelich GmbH
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Publication of EP1312131A1 publication Critical patent/EP1312131A1/en
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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
    • H01M8/06—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
    • H01M8/0625—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 in a modular combined reactor/fuel cell structure
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/22—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of gaseous or liquid organic compounds
    • C01B3/24—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of gaseous or liquid organic compounds of hydrocarbons
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/0266—Processes for making hydrogen or synthesis gas containing a decomposition step
    • C01B2203/0272—Processes for making hydrogen or synthesis gas containing a decomposition step containing a non-catalytic decomposition step
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/06—Integration with other chemical processes
    • C01B2203/066—Integration with other chemical processes with fuel cells
    • 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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

Definitions

  • the invention relates to a high-temperature fuel cell power plant and a method for the improved use of such.
  • So-called emission-free fuel cell power plants pump the resulting and then liquefied C0 2 into emptied underground oil or gas deposits. It should be kept there permanently.
  • the object of the invention is to provide a method for generating electricity / hydrogen in which a liquid or gaseous CO 2 production is almost completely avoided.
  • the object is achieved by a method for operating a high-temperature fuel cell power plant according to the main claim.
  • Advantageous procedures result from the claims referring back to them.
  • the inventive method according to claim 1 for operating a high-temperature fuel cell power plant is characterized in that a hydrocarbon-containing fuel is converted to solid carbon.
  • a fuel cell power plant by an electrochemical conversion of a fuel and an oxidizing agent with the help of a high temperature fuel cell, for. B.
  • the SOFC generates electricity.
  • typical Hydrocarbon fuels are natural gas with its main constituent methane or methanol.
  • a hydrocarbon-containing fuel is converted, for example, by endothermic decomposition reactions in accordance with:
  • the process according to the invention has the advantage that carbon is obtained from the hydrocarbon-containing fuel as solid carbon (graphite, soot), which can be removed from the system in a simple manner and thus does not arise as environmentally harmful CO or CO 2 .
  • the solid carbon can, for example, be separated from the gaseous hydrogen formed and removed from the system solely on the basis of the density differences due to gravity or also increasingly by means of filters.
  • more than 50%, in particular more than 90%, of the carbon from the fuel gas is converted into solid carbon.
  • Particularly suitable fuels are gaseous hydrocarbons, especially at room temperature (25 ° C) and normal pressure (1 bar) gaseous hydrocarbons (e.g. methane), since the conversion to solid carbon can take place via the decomposition reaction without prior conversion into the gas phase.
  • the reaction parameters e.g. equilibrium constant
  • the decomposition reaction of the carbon-containing fuel takes place before the conversion in the fuel cell.
  • the carbon is separated off before the fuel cell, and predominantly only hydrogen reaches the fuel cell.
  • Another advantage results from the use of the heat generated during the electrochemical conversion reaction in the high-temperature fuel cell for the mostly endothermic decomposition of the hydrocarbon-containing fuel.
  • the waste heat from the fuel cell can convectively take the place of the decomposition reaction, for example via an exhaust gas stream, or also by direct heat radiation or heat conduction.
  • the device for converting the fuel into solid carbon can be in direct contact with the fuel cell stack.
  • the waste heat is made permanently available in the continuous mode of operation typical of high-temperature fuel cell power plants, so that the apparatus for splitting the hydrocarbons can also advantageously be operated continuously. Is the heat extraction from the fuel cell z. B. by utilizing the heat radiation on the decomposition apparatus, it is possible to specifically cool the fuel cell by the endothermic decomposition reaction. A reduction in the amount of atmospheric oxygen down to the stoichiometric requirement is thus possible.
  • the amount of the hydrocarbon-containing fuel gas, in particular the methane is regulated in such a way that considerably more hydrogen is produced in the fuel decomposer than is electrochemically converted in the high-temperature fuel cell stack.
  • part of the hydrogen stream is withdrawn from the plant.
  • Fuel gas e.g. B. natural gas, is thus decomposed in excess.
  • An excess feed in the sense of the invention is present in particular if the amount of hydrogen drawn off is at least 20%, advantageously at least
  • FIG. 1 a simplified process flow diagram of a solid oxide high-temperature fuel cell system.
  • natural gas 1 is passed into a methane decomposer 3.
  • the amount of heat necessary for the endothermic reaction 2 to take place is transmitted convectively by the exhaust gas stream 4.
  • the hydrogen 5 emerging from the methane decomposer advantageously has the working temperature of the stack 6 (700 - 1000 ° C).
  • the methane decomposer 3 is designed so that the hydrogen contains negligible amounts of soot particles.
  • the resulting solid carbon is extracted from the methane decomposer 3 by a suitable conveyor 7.
  • Air 8 is compressed in a compressor 9 and also preheated in an air preheater 10 to the working temperature of the stack.
  • the electrochemical conversion of hydrogen and oxygen to water vapor takes place in the fuel cell stack. Electric current is generated 14.
  • the anode-side and cathode-side exhaust gas is burned in an afterburning chamber 11. Heat is extracted from the exhaust gas stream in the apparatus decomposer 3 and air preheater 10. The remaining amount of heat can be used to additionally heat out in a useful heat exchanger 12. Finally, an almost C0 2 -free exhaust gas 4 leaves the system.
  • a C0 2 -free exhaust gas in the sense of the invention is present in particular if the ratio of the emerging C0 2 mole stream to the natural gas mole stream used (here assumed as 100% methane) is less than 2%.
  • reaction 1 the electrochemical H 2 conversion (reaction 1) is combined with the methane decomposition reaction (reaction 2) in the process according to the invention.
  • Reaction 1 is exothermic and takes place in the high-temperature fuel cell, reaction 2, on the other hand, is endothermic and takes place with the addition of heat in a heat-resistant apparatus.
  • the equilibrium position of reaction 2 can be described by the following temperature-dependent equilibrium constant K p (Ulimann, 4th edition, 1977, vol. 14, gas generation from coal and hydrocarbons):
  • Fuel cell power plants have established themselves as processes for generating electricity and hydrogen.
  • the resulting C0 2 can so far only be liquefied using complex technology and then stored or deposited in deposits.
  • the method according to the invention opens up a way of using the technology of fuel cell power plants effectively and the problem of CO 2 emissions in a simple manner
  • the carbon produced can thus be used or sold specifically for downstream syntheses / processes.
  • Reference number for FIG. 1

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Sustainable Energy (AREA)
  • Sustainable Development (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Fuel Cell (AREA)
  • Hydrogen, Water And Hydrids (AREA)

Abstract

Fuel cell power stations have established themselves as methods for producing electricity, heat and hydrogen from fossil fuels. Up to now, the resulting CO2 can be liquefied and subsequently stored or deposited in beds only by using complicated techniques. According to the inventive method, the majority of the carbon, which is located inside the fuel that contains hydrocarbons, is converted into solid carbon before the actual electrochemical reaction inside the fuel cell. The solid carbon can then be easily passed out of the system and no longer presents any threat to the environment. The resulting carbon constitutes a valuable product, which can be utilized for other process steps or sold.

Description

B e s c h r e i b u n g Description
HOCHTEMPERATUR-BRENNSTOFFZELLENKRAFTWERK MIT VERMINDERTER KOHLENDIOXID-EMISSIONHIGH TEMPERATURE FUEL CELL POWER PLANT WITH REDUCED CARBON DIOXIDE EMISSION
Technisches GebietTechnical field
Die Erfindung betrifft ein Hochtemperatur-Brennstoffzellen-Kraftwerk sowie ein Verfahren zur verbesserten Nutzung eines solchen.The invention relates to a high-temperature fuel cell power plant and a method for the improved use of such.
Stand der TechnikState of the art
In einem Hochtemperatur-Brennstoffzellen-Kraftwerk wird neben der MCFC (Molten Carbonate Fuel Cell) auch die SOFC (Solid Oxide Fuel Cell) zur Stromerzeugung undIn a high-temperature fuel cell power plant, in addition to the MCFC (Molten Carbonate Fuel Cell), the SOFC (Solid Oxide Fuel Cell) for power generation and
10 WasserstoffProduktion eingesetzt (H.-E. Vollmer,10 hydrogen production used (H.-E. Vollmer,
C.-ü. Maier, C. Nölscher, T. Merklein, M. Poppinger; Innovative concepts for the coproduction of electricity and syngas with solid oxide fuel cells, Journal of Power Sources, Vol. 86, (2000), pp. 90-97). Als Brenn-C.-ü. Maier, C. Nölscher, T. Merklein, M. Poppinger; Innovative concepts for the coproduction of electricity and syngas with solid oxide fuel cells, Journal of Power Sources, Vol. 86, (2000), pp. 90-97). As a focal
15 stoff wird Erdgas verwendet. Typischerweise findet innerhalb oder außerhalb der Brennstoffzelle eine Reformierung des Methans mit Wasserdampf zu CO und Wasserstoff statt. Diese reagieren dann an der Anode elektrochemisch zu Wasser und C02. Das entstehende gasförmige15 natural gas is used. Typically, the methane is reformed with steam to CO and hydrogen inside or outside the fuel cell. These then react electrochemically to water and CO 2 at the anode. The resulting gaseous
20 C02 führt jedoch regelmäßig zu Umweltemissionen, da C02 zu den Treibhausgasen gezählt wird. Eine Reduktion des C02 aus einer gasförmigen Atmosphäre ist nur schwierig zu realisieren.20 C0 2 , however, regularly leads to environmental emissions, since C0 2 is one of the greenhouse gases. A reduction of the C0 2 from a gaseous atmosphere is difficult to achieve.
25 Fortschrittliche Verfahren verflüssigen vorher durch geeignete Vorrichtungen separiertes C02, um es separat zu lagern (E. Riensche, E. Achenbach, D. Froning, M. R. Heines, W. K. Heidug, A. Lokurlu, S. von Andrian; Clean combined-cycle SOFC power plant - cell modeling and process analysis; Journal of Power Sources, Vol. 86, (2000) , pp. 404-410) .25 Advanced processes liquefy previously separated C0 2 by suitable devices in order to store it separately (E. Riensche, E. Achenbach, D. Froning, MR Heines, WK Heidug, A. Lokurlu, S. von Andrian; Clean combined-cycle SOFC power plant - cell modeling and process analysis; Journal of Power Sources, Vol. 86, (2000), pp. 404-410).
Sogenannte emissionsfreie Brennstoffzellen-Kraftwerke pumpen das entstehende und anschließend verflüssigte C02 in entleerte unterirdische Erdöl- oder Erdgaslagerstätten. Dort soll es dauerhaft festgehalten werden.So-called emission-free fuel cell power plants pump the resulting and then liquefied C0 2 into emptied underground oil or gas deposits. It should be kept there permanently.
Aufgabe und LösungTask and solution
Die Aufgabe der Erfindung ist es, ein Verfahren zur Strom/Wasserstofferzeugung zur Verfügung zu stellen, bei welchem eine flüssige oder gasförmige C02-Produk- tion nahezu vollständig vermieden wird.The object of the invention is to provide a method for generating electricity / hydrogen in which a liquid or gaseous CO 2 production is almost completely avoided.
Die Aufgabe wird gelöst durch ein Verfahren zum Betreiben eines Hochtemperatur-Brennstoffzellen-Kraftwerks gemäß Hauptanspruch. Vorteilhafte Verfahrensweisen er- geben sich aus den darauf rückbezogenen Ansprüchen.The object is achieved by a method for operating a high-temperature fuel cell power plant according to the main claim. Advantageous procedures result from the claims referring back to them.
Darstellung der ErfindungPresentation of the invention
Das erfindungsgemäße Verfahren nach Anspruch 1 zum Betreiben eines Hochtemperatur-Brennstoffzellen-Kraft- werks ist dadurch gekennzeichnet, daß ein kohlenwasser- stoffhaltiger Brennstoff zu festem Kohlenstoff umgewandelt wird.The inventive method according to claim 1 for operating a high-temperature fuel cell power plant is characterized in that a hydrocarbon-containing fuel is converted to solid carbon.
In einem Brennstoffzellen-Kraftwerk wird durch eine elektrochemische Umwandlung eines Brennstoffs und eines Oxidations ittels mit Hilfe einer Hochtemperatur-Brennstoffzelle, z. B. der SOFC, Strom erzeugt. Typische Kohlenwasserstoff haltige Brennstoffe sind dabei Erdgas mit seinem Hauptbestandteil Methan oder auch Methanol. Eine Umwandlung eines kohlenwasserstoffhaltigen Brennstoffs erfolgt beispielsweise durch endotherme Zerset- zungsreaktionen gemäß:In a fuel cell power plant by an electrochemical conversion of a fuel and an oxidizing agent with the help of a high temperature fuel cell, for. B. the SOFC, generates electricity. typical Hydrocarbon fuels are natural gas with its main constituent methane or methanol. A hydrocarbon-containing fuel is converted, for example, by endothermic decomposition reactions in accordance with:
CH4 o C + 2H2 CH 4 o C + 2H 2
C2H6 <=> 2C + 3H2 Durch geeignete Wahl der Reaktionsparameter, wie z. B. die Temperatur, der Druck oder die Konzentration ein- zelner Reaktionspartner, können die Gleichgewichtsreaktionen derart zu einer Seite hin verschoben werden, daß es nahezu zu einer vollständigen Zersetzung kommt.C 2 H 6 <=> 2C + 3H 2 By suitable choice of the reaction parameters, such as. B. the temperature, the pressure or the concentration of individual reactants, the equilibrium reactions can be shifted to one side so that there is almost complete decomposition.
Diese Zersetzungsreaktionen setzen die Abwesenheit von Sauerstoff voraus, da sonst während dieser Reaktionen nachteilhaft Kohlenstoffoxide gebildet werden können.These decomposition reactions require the absence of oxygen, since otherwise carbon oxides can be formed disadvantageously during these reactions.
Das erfindungsgemäße Verfahren weist den Vorteil auf, daß aus dem kohlenwasserstoffhaltigen Brennstoff der Kohlenstoff als fester Kohlenstoff (Graphit, Ruß) anfällt, der auf einfache Weise aus dem System entfernt werden kann und somit nicht als umweltschädliches CO oder C02 anfällt. Der feste Kohlenstoff läßt sich beispielsweise allein aufgrund der Dichteunterschiede durch die Schwerkraft oder auch verstärkt durch Filter vom gebildeten gasförmigen Wasserstoff trennen und aus dem System entfernen.The process according to the invention has the advantage that carbon is obtained from the hydrocarbon-containing fuel as solid carbon (graphite, soot), which can be removed from the system in a simple manner and thus does not arise as environmentally harmful CO or CO 2 . The solid carbon can, for example, be separated from the gaseous hydrogen formed and removed from the system solely on the basis of the density differences due to gravity or also increasingly by means of filters.
In einer vorteilhaften Ausführungsform wird der Kohlen- stoff aus dem Brenngas zu über 50 %, insbesondere zu über 90 % in festen Kohlenstoff umgewandelt. Damit arbeitet dieses Verfahren zum Betreiben eines Brennstoffzellen-Kraftwerks nahezu C02-emissionsfrei . Besonders geeignete Brennstoffe sind gasförmige Kohlenwasserstoffe, insbesondere bei Raumtemperatur (25°C) und Normaldruck (1 bar) gasförmige Kohlenwasserstoffe (z. B. Methan), da hier die Umwandlung zu festem Kohlenstoff über die Zersetzungsreaktion ohne vorherige Umwandlung in die Gasphase erfolgen kann. Ferner sind die Reaktionsparameter (z. B. Gleichgewichtskonstante) für diese Reaktion sehr günstig.In an advantageous embodiment, more than 50%, in particular more than 90%, of the carbon from the fuel gas is converted into solid carbon. This means that this method of operating a fuel cell power plant works almost CO 2 -emission-free. Particularly suitable fuels are gaseous hydrocarbons, especially at room temperature (25 ° C) and normal pressure (1 bar) gaseous hydrocarbons (e.g. methane), since the conversion to solid carbon can take place via the decomposition reaction without prior conversion into the gas phase. Furthermore, the reaction parameters (e.g. equilibrium constant) are very favorable for this reaction.
In einem Ausführungsbeispiel der Erfindung findet die Zersetzungsreaktion des kohlenstoffhaltigen Brennstoffs vor der Umwandlung in der Brennstoffzelle statt. Dadurch wird der Kohlenstoff noch vor der Brennstoffzelle abgetrennt, und es gelangt überwiegend nur noch Wasserstoff in die Brennstoffzelle.In one embodiment of the invention, the decomposition reaction of the carbon-containing fuel takes place before the conversion in the fuel cell. As a result, the carbon is separated off before the fuel cell, and predominantly only hydrogen reaches the fuel cell.
Ein weiterer Vorteil ergibt sich aus der Nutzung der bei der elektrochemischen Umwandlungsreaktion in der Hochtemperatur-Brennstoffzelle entstehenden Wärme zur meist endothermen Zersetzung des kohlenwasserstoffhaltigen Brennstoffs. Die Abwärme der Brennstoffzelle kann dabei konvektiv, beispielsweise über einen Abgasstrom, oder auch durch direkte Wärmestrahlung oder Wärmelei- tung an die Stelle der Zersetzungsreaktion gelangen.Another advantage results from the use of the heat generated during the electrochemical conversion reaction in the high-temperature fuel cell for the mostly endothermic decomposition of the hydrocarbon-containing fuel. The waste heat from the fuel cell can convectively take the place of the decomposition reaction, for example via an exhaust gas stream, or also by direct heat radiation or heat conduction.
Dazu kann beispielsweise die Vorrichtung zur Umwandlung des Brennstoffs in festen Kohlenstoff in direktem Kontakt zum Brennstoffzellenstapel stehen. Die Abwärme wird bei der für Hochtemperatur-Brennstoffzellen-Kraft- werke typischen kontinuierlichen Fahrweise permanent zur Verfügung gestellt, so daß auch die Apparatur für die Spaltung der Kohlenwasserstoffe vorteilhaft kontinuierlich betrieben werden kann. Erfolgt die Wärmeauskopplung aus der Brennstoffzelle z. B. durch Ausnutzung der Wärmestrahlung auf den Zersetzungsapparat, so ist es möglich, die Brennstoffzelle gezielt durch die endotherme Zersetzungsreaktion zu kühlen. Eine Reduktion der Luftsauerstoffmenge bis auf den stöchiometrischen Bedarf ist somit möglich.For this purpose, for example, the device for converting the fuel into solid carbon can be in direct contact with the fuel cell stack. The waste heat is made permanently available in the continuous mode of operation typical of high-temperature fuel cell power plants, so that the apparatus for splitting the hydrocarbons can also advantageously be operated continuously. Is the heat extraction from the fuel cell z. B. by utilizing the heat radiation on the decomposition apparatus, it is possible to specifically cool the fuel cell by the endothermic decomposition reaction. A reduction in the amount of atmospheric oxygen down to the stoichiometric requirement is thus possible.
In einer vorteilhaften Ausgestaltung der Erfindung wird die Menge des kohlenwasserstoffhaltigen Brenngases, insbesondere des Methans, derart geregelt, daß in dem Brennstoffzersetzer wesentlich mehr Wasserstoff produziert wird, als in dem Hochtemperatur-Brennstoffzellen- stapel elektrochemisch umgesetzt wird. Somit ist es möglich, Wasserstoff zu produzieren und gleichzeitig die Brennstoffzelle effektiv zu kühlen. Dazu wird ein Teil des WasserstoffStroms der Anlage entzogen. Brenngas, z. B. Erdgas, wird somit im Überschuß zersetzt. Eine Überschußeinspeisung im Sinne der Erfindung liegt insbesondere dann vor, wenn die abgezogene Wasserstoff- menge mindestens 20%, vorteilhafterweise mindestensIn an advantageous embodiment of the invention, the amount of the hydrocarbon-containing fuel gas, in particular the methane, is regulated in such a way that considerably more hydrogen is produced in the fuel decomposer than is electrochemically converted in the high-temperature fuel cell stack. This makes it possible to produce hydrogen while effectively cooling the fuel cell. For this purpose, part of the hydrogen stream is withdrawn from the plant. Fuel gas, e.g. B. natural gas, is thus decomposed in excess. An excess feed in the sense of the invention is present in particular if the amount of hydrogen drawn off is at least 20%, advantageously at least
50%, der während der Zersetzung erzeugten Wasserstoffmenge beträgt.50% of the amount of hydrogen generated during the decomposition.
Beschreibung der ZeichnungenDescription of the drawings
Nachfolgend wird das Verfahren anhand eines vereinfachten Verfahrensfließbildes (Fig. 1) einer Festoxid- Hochtemperatur-BrennstoffZeilenanlage erläutert. Erdgas 1 wird nach einer Verdichtung 2 in einen Methan-Zerset- zer 3 geleitet. Die zum Ablaufen der endothermen Reaktion 2 notwendige Wärmemenge wird durch den Abgasstrom 4 konvektiv übertragen. Der aus dem Methan-Zersetzer austretende Wasserstoff 5 besitzt vorteilhafterweise die Arbeitstemperatur des Stacks 6 (700 - 1000 °C) . Ferner ist der Methan-Zersetzer 3 konstruktiv so gestaltet, daß der Wasserstoff vernachlässigbar geringe Mengen an Rußpartikeln enthält. Der entstehende feste Kohlenstoff wird dem Methan-Zersetzer 3 durch eine geeignete Fördereinrichtung 7 entzogen. Luft 8 wird in einem Verdichter 9 verdichtet und in einem Luftvorwärmer 10 ebenfalls auf die Arbeitstemperatur des Stacks vorgewärmt. Im Brennstoffzellenstapel läuft die elekt- rochemische Umsetzung von Wasserstoff und Sauerstoff zu Wasserdampf ab. Elektrischer Strom wird erzeugt 14. Das anodenseitige und kathodenseitige Abgas wird in einer Nachbrennkammer 11 verbrannt. Dem Abgasstrom wird in den Apparaten Zersetzer 3 und Luftvorwärmer 10 Wärme entzogen. Die restliche Wärmemenge kann dazu genutzt werden, um in einem Nutzwärmeübertrager 12 zusätzlich Wärme auszukoppeln. Schließlich verläßt ein nahezu C02- freies Abgas 4 die Anlage. Ein C02-freies Abgas im Sinne der Erfindung liegt insbesondere dann vor, wenn das Verhältnis von austretendem C02-Molenstrom zu eingesetztem Erdgas-Molenstrom (hier angenommen als 100% Methan) geringer als 2% ist.The process is explained below using a simplified process flow diagram (FIG. 1) of a solid oxide high-temperature fuel cell system. After compression 2, natural gas 1 is passed into a methane decomposer 3. The amount of heat necessary for the endothermic reaction 2 to take place is transmitted convectively by the exhaust gas stream 4. The hydrogen 5 emerging from the methane decomposer advantageously has the working temperature of the stack 6 (700 - 1000 ° C). Furthermore, the methane decomposer 3 is designed so that the hydrogen contains negligible amounts of soot particles. The resulting solid carbon is extracted from the methane decomposer 3 by a suitable conveyor 7. Air 8 is compressed in a compressor 9 and also preheated in an air preheater 10 to the working temperature of the stack. The electrochemical conversion of hydrogen and oxygen to water vapor takes place in the fuel cell stack. Electric current is generated 14. The anode-side and cathode-side exhaust gas is burned in an afterburning chamber 11. Heat is extracted from the exhaust gas stream in the apparatus decomposer 3 and air preheater 10. The remaining amount of heat can be used to additionally heat out in a useful heat exchanger 12. Finally, an almost C0 2 -free exhaust gas 4 leaves the system. A C0 2 -free exhaust gas in the sense of the invention is present in particular if the ratio of the emerging C0 2 mole stream to the natural gas mole stream used (here assumed as 100% methane) is less than 2%.
Ausführungsbeispieleembodiments
In einem Ausführungsbeispiel wird bei dem erfindungsgemäßen Verfahren die elektrochemische H2-Umsetzung (Reaktion 1) mit der Methanzersetzungsreaktion (Reaktion 2) kombiniert. Reaktion 1 ist exotherm und findet in der Hochtemperatur-Brennstoffzelle statt, Reaktion 2 hingegen ist endotherm und findet unter Wärmezufuhr in einem hitzebeständigen Apparat statt. Reaktion 1:In one exemplary embodiment, the electrochemical H 2 conversion (reaction 1) is combined with the methane decomposition reaction (reaction 2) in the process according to the invention. Reaction 1 is exothermic and takes place in the high-temperature fuel cell, reaction 2, on the other hand, is endothermic and takes place with the addition of heat in a heat-resistant apparatus. Response 1:
H2 + 0,5 02 <=> H20 ΔH 1000K = -248 kJ/mol Reaktion 2:H 2 + 0.5 0 2 <=> H 2 0 ΔH 1000K = -248 kJ / mol reaction 2:
CH4 => C + 2 H2 ΔH IOOOK - 90 kJ/molCH 4 => C + 2 H 2 ΔH IOOOK - 90 kJ / mol
Die Gleichgewichtslage der Reaktion 2 läßt sich durch folgende die temperaturabhängige Gleichgewichtskonstante Kp beschreiben (Ulimann, 4. Aufl., 1977, Bd. 14, Gaserzeugung aus Kohle und Kohlenwasserstoffen) :The equilibrium position of reaction 2 can be described by the following temperature-dependent equilibrium constant K p (Ulimann, 4th edition, 1977, vol. 14, gas generation from coal and hydrocarbons):
mit Temperatur/°C Kc = Kp/ [bar] = P with temperature / ° CK c = K p / [bar] = P
P(CH4)P (CH 4 )
700 7,8700 7.8
800 22,0800 22.0
900 52,7 1000 100900 52.7 1000 100
Brennstoffzellen-Kraftwerke haben sich als Verfahren zur Erzeugung von Strom und Wasserstoff etabliert. Das dabei anfallende C02 kann bislang nur durch aufwendige Technik verflüssigt und anschließend gespeichert oder in Lagerstätten deponiert werden. Das erfindungsgemäße Verfahren eröffnet demgegenüber einen Weg, die Technik der Brennstoffzellen-Kraftwerke weiterhin effektiv zu nutzen und das Problem der C02-Emission auf einfacheFuel cell power plants have established themselves as processes for generating electricity and hydrogen. The resulting C0 2 can so far only be liquefied using complex technology and then stored or deposited in deposits. In contrast, the method according to the invention opens up a way of using the technology of fuel cell power plants effectively and the problem of CO 2 emissions in a simple manner
Weise durch die Umwandlung zu festem Kohlenstoff deutlich zu verringern. Der produzierte Kohlenstoff kann somit gezielt für nachgeschaltete Synthesen/Prozesse verwendet oder veräußert werden. Bezugszeichen zu Figur 1Way to significantly reduce by converting to solid carbon. The carbon produced can thus be used or sold specifically for downstream syntheses / processes. Reference number for FIG. 1
Nummer BedeutungNumber meaning
1 Erdgas1 natural gas
2 Verdichter2 compressors
3 Methan-Zersetzer3 methane decomposer
4 Abgasleitung4 exhaust pipe
5 Wasserstoffleitung5 hydrogen line
6 SOFC-Brennstoffzellenstapel6 SOFC fuel cell stacks
7 Kohlenstoff-Fördereinrichtung7 carbon conveyor
8 Luft8 air
9 Verdichter9 compressors
10 Luftvorwärmer10 air preheaters
11 Nachbrennkammer11 afterburner
12 NutzwärmeÜberträger12 useful heat exchangers
13 Wasserstoffleitung13 hydrogen line
14 Strom 14 electricity

Claims

P a t e n t a n s p r ü c h e Patent claims
1. Verfahren zum Betreiben eines Hochtemperatur- Brennstoffzellen-Kraftwerks, dadurch gekennzeichnet, daß ein kohlenwasserstoffhaltiger Brennstoff zu- mindest teilweise in festen Kohlenstoff umgewandelt wird.1. A method for operating a high-temperature fuel cell power plant, characterized in that a hydrocarbon-containing fuel is at least partially converted into solid carbon.
2. Verfahren nach -vorhergehendem Anspruch, dadurch gekennzeichnet, daß ein gasförmiger kohlenwasserstoffhaltiger2. The method according to the preceding claim, characterized in that a gaseous hydrocarbon
Brennstoff eingesetzt wird.Fuel is used.
3. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die gasförmigen Brennstoffe bei Raumtemperatur (25 °C) und Normaldruck (1 bar) gasförmig sind.3. The method according to any one of the preceding claims, characterized in that the gaseous fuels are gaseous at room temperature (25 ° C) and normal pressure (1 bar).
4. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß eine kontinuierlich betriebene Methanzersetzungsreaktion stattfindet.4. The method according to any one of the preceding claims, characterized in that a continuously operated methane decomposition reaction takes place.
5. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Abwärme einer Brennstoffzelle zumindest teilweise der Methanzersetzungsreaktion zugeführt wird. 5. The method according to any one of the preceding claims, characterized in that the waste heat of a fuel cell is at least partially supplied to the methane decomposition reaction.
6. Verfahren nach vorhergehendem Anspruch, dadurch gekennzeichnet, daß die Wärmeübertragung durch Wärmestrahlung erfolgt.6. The method according to the preceding claim, characterized in that the heat transfer takes place by heat radiation.
7. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Methanzersetzung der Brennstoffzelle vorgeschaltet ist.7. The method according to any one of the preceding claims, characterized in that the methane decomposition is connected upstream of the fuel cell.
8. Verfahren nach einem der vorhergehenden Ansprüche, bei dem maximal 80% des durch Methanzersetzung erzeugten Wasserstoffs in der Brennstoffzelle umgesetzt wird, insbesondere nicht mehr als 50%.8. The method according to any one of the preceding claims, in which a maximum of 80% of the hydrogen generated by methane decomposition is converted in the fuel cell, in particular not more than 50%.
9. Vorrichtung zur Durchführung des Verfahrens nach einem der vorhergehenden Ansprüche, umfassend eine Vorrichtung zur Methanzersetzung und Mittel zur Abführung von festem Kohlenstoff. 9. Device for carrying out the method according to one of the preceding claims, comprising a device for methane decomposition and means for removing solid carbon.
EP01956382A 2000-08-23 2001-07-21 High-temperature fuel cell power station having reduced carbon dioxide emissions Withdrawn EP1312131A1 (en)

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DE10041262A DE10041262A1 (en) 2000-08-23 2000-08-23 Fuel cell power plant
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US6187465B1 (en) * 1997-11-07 2001-02-13 Terry R. Galloway Process and system for converting carbonaceous feedstocks into energy without greenhouse gas emissions
JP2000086201A (en) * 1998-07-14 2000-03-28 Agency Of Ind Science & Technol Production of hydrogen
AU2906401A (en) * 1999-12-21 2001-07-03 Bechtel Bwxt Idaho, Llc Hydrogen and elemental carbon production from natural gas and other hydrocarbons

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