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
  • H01M8/0662—Treatment of gaseous reactants or gaseous residues, e.g. cleaning
• • 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
  • H01M8/04186—Arrangements for control of reactant parameters, e.g. pressure or concentration of liquid-charged or electrolyte-charged 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
  • 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
  • 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
  • H01M8/04119—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
  • H01M8/04156—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying with product water removal
• • 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
  • H01M8/04186—Arrangements for control of reactant parameters, e.g. pressure or concentration of liquid-charged or electrolyte-charged reactants
  • H01M8/04194—Concentration measuring 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
  • H01M8/1009—Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
• • 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 method for regulating the fuel concentration in the anode liquid of a fuel cell with anode, membrane and cathode, in which an exhaust gas is produced on the anode on the one hand and on the cathode on the other hand.
• the invention also relates to a device with the necessary means for carrying out the method.
• the fuel is preferably, but not exclusively, methanol.
• Fuel cells are operated with liquid or gaseous fuels. If the fuel cell works with hydrogen, a hydrogen infrastructure or a reformer is required to generate the gaseous hydrogen from the liquid fuel.
• Liquid fuels are e.g. Gasoline or alcohol, such as ethanol or methanol.
• a so-called DMFC Direct Methanol Fuel Cell * works directly with liquid methanol as a fuel. The function and status of the DMFC are described in detail in “VIK reports *, No. 214 (Nov. 1999), pages 55 to 62.
• Fuel cell systems consist of a large number of individual fuel cell units, which together form a fuel cell stack, which in the technical field is also referred to as a fuel cell stack or simply as a “stack *”.
• a fuel cell stack which in the technical field is also referred to as a fuel cell stack or simply as a “stack *”.
• exhaust gases are produced in the fuel cell at the anode on the one hand and at the cathode on the other hand.
• the fuel methanol is mixed with water on the anode side and pumped through the stack using a metering pump.
• the metha- nol is partly consumed by the anode reaction and carbon dioxide is generated.
• Another part of the methanol is transported through the membrane to the cathode by permeation and electro-osmosis and directly oxidized to carbon dioxide on the catalyst of the cathode.
• the anode liquid with the gas / steam mixture is separated into gas and liquid after exiting the anode. As much more carbon dioxide as possible is removed from the liquid and then the liquid is returned to the anode by means of the pump. So that the methanol concentration of this liquid does not become too low, sufficient methanol must be added.
• the amount of methanol corresponding to the electric current can be calculated from the current flow, but the additional amount, which replaces the loss via electroosmosis and permeation, cannot be determined qualitatively, so that the anode liquid would have a concentration that is too low.
• the amount of methanol in the direct methanol fuel cell is calculated via the current flow and increased by a constant factor, for example 1.5 or 2.0. This compensates for the methanol losses, whereby it is accepted that the methanol concentration is not optimal for the current density. Since the methanol tends to doses must be metered in order to avoid undersupply and thus the risk of polarity reversal, the methanol loss is greater than necessary
• the object of the invention is therefore to specify a method with which the regulation of the fuel concentration in the anode liquid of a direct methanol fuel cell is improved, and to create an associated device.
• the fuel loss across the membrane is advantageously detected.
• a commercially available sensor is used to measure the concentration. after cooler and pressure regulator is attached.
• the single figure shows a schematic representation of a single unit, specifically a DMFC fuel cell, with the associated system components which are necessary for the operation of this fuel cell.
• FIG. 1 shows a methanol tank 1 with a subsequent metering pump 2 and a heater 3, via which the liquid methanol as fuel reaches the fuel cell unit 10.
• a cooler 4, a CO 2 separator 5, a unit 6 for rectification and a methanol sensor 7 are assigned to the anode part.
• Another metering pump 8 is used to feed methanol back into the fuel circuit.
• a compressor 14 for air On the cathode side there is a compressor 14 for air, a cooler or water separator 15 for the cathode liquid and a C0 2 sensor 16. Furthermore, a unit 25 for controlling the fuel cell unit 10 and optionally an electrical inverter 26 are provided for the operation of the system.
• the DMFC shown has primary and secondary fluid circuits.
• the methanol / water mixture is fed to the anode 11 and air to the cathode 13 of the fuel cell 10.
• the C0 2 is separated from the residual fuel and this is returned to the fuel circuit.
• the cathode exhaust gas is conducted via the cooler or water separator 15 in the exhaust gas-side fluid circuit.
• the CO 2 content which is a measure of the methanol loss via the membrane 12 of the fuel cell, is then measured in the exhaust gas.
• the measurement signal is fed back to the primary metering pump 2.
• the C0 2 sensor 16 in the figure is a commercially available sensor, which is advantageously installed in the gas stream after the cooler 15 and the existing pressure regulator. The Co 2 concentration is thus measured in molar.
• One mole of carbon dioxide also corresponds to one mole of methanol.
• the amount of air on the cathode side is known from the compressor power or can be determined by measuring the air flow.
• There is a certain systematic error in the amount of carbon dioxide determined with the sensor since a small proportion of the carbon dioxide that is generated at the anode by the electrochemical reaction can diffuse through the membrane to the cathode, so that the air used has a small and possibly also a little fluctuating carbon dioxide concentration. Since no additional electroosmosis is effective for the carbon dioxide, as is the case with methanol, this error can be tolerated.
• the metering of the methanol results from the flow and is to be calculated additively from the carbon dioxide concentration on the cathode side.
• MEA membrane-electrolyte-anode
• stack properties can then this rule base of the ⁇ Faraday current one hand and the leakage current on the other hand, an additional flow of methanol are added.
• the lambda for methanol is then increased to 1.05 to 1.5 as required.
• the additive use of the carbon dioxide concentration on the cathode side in the exhaust air is essential for controlling the fuel cell system. It is no longer absolutely necessary to measure the methanol concentration in the fuel cycle.
• the DMFC is equipped with a carbon dioxide sensor in the exhaust gas. Characteristic measurements were successfully carried out for verification.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Fuel Cell (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2000
  • 2000-08-16 DE DE10039959A patent/DE10039959A1/de not_active Ceased
• 2001
  • 2001-08-03 CA CA002419452A patent/CA2419452A1/en not_active Abandoned
  • 2001-08-03 JP JP2002520342A patent/JP2004507053A/ja not_active Withdrawn
  • 2001-08-03 WO PCT/DE2001/002976 patent/WO2002015314A1/de not_active Application Discontinuation
  • 2001-08-03 EP EP01962605A patent/EP1310007A1/de not_active Withdrawn
  • 2001-08-03 CN CN01814070A patent/CN1446385A/zh active Pending
• 2003
  • 2003-02-18 US US10/368,154 patent/US20030146094A1/en not_active Abandoned

Non-Patent Citations (1)

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