WO2004024299A1 - Device and method for separating almost pure hydrogen from a gas flow containing hydrogen - Google Patents

Device and method for separating almost pure hydrogen from a gas flow containing hydrogen Download PDF

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Publication number
WO2004024299A1
WO2004024299A1 PCT/DE2003/002902 DE0302902W WO2004024299A1 WO 2004024299 A1 WO2004024299 A1 WO 2004024299A1 DE 0302902 W DE0302902 W DE 0302902W WO 2004024299 A1 WO2004024299 A1 WO 2004024299A1
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Prior art keywords
hydrogen
separation module
gas stream
hydrogen separation
fuel cell
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PCT/DE2003/002902
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German (de)
French (fr)
Inventor
Arnold Lamm
Thomas Poschmann
Wolfgang Weger
Norbert Wiesheu
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Daimlerchrysler Ag
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Publication of WO2004024299A1 publication Critical patent/WO2004024299A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B01D53/225—Multiple stage diffusion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B01D53/229—Integrated processes (Diffusion and at least one other process, e.g. adsorption, absorption)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/75—Multi-step processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/08—Flat membrane modules
    • 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
    • C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
    • C01B3/12—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents by reaction of water vapour with carbon monoxide
    • C01B3/16—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents by reaction of water vapour with carbon monoxide using catalysts
    • 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
    • C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
    • C01B3/501—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by diffusion
    • 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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2317/00—Membrane module arrangements within a plant or an apparatus
    • B01D2317/02—Elements in series
    • 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
    • C01B2203/0283—Processes for making hydrogen or synthesis gas containing a CO-shift step, i.e. a water gas shift 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
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0405—Purification by membrane separation
    • 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
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0465—Composition of the impurity
    • C01B2203/047—Composition of the impurity the impurity being carbon monoxide
    • 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
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0465—Composition of the impurity
    • C01B2203/0475—Composition of the impurity the impurity being carbon dioxide
    • 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
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0465—Composition of the impurity
    • C01B2203/0495—Composition of the impurity the impurity being water
    • 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
    • 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
    • C01B2203/14—Details of the flowsheet
    • C01B2203/145—At least two purification steps in parallel
    • 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 device and a method for separating at least almost pure hydrogen from a hydrogen-containing gas stream according to the kind defined in the preambles of claims 1 and 9.
  • Fuel cells can be produced by hydrogen generation devices e.g. can be supplied with hydrogen by reforming hydrocarbons such as methanol, gasoline or diesel.
  • the product gas generated in a reforming process contains hydrogen, carbon monoxide, carbon dioxide and water vapor.
  • the carbon monoxide must be removed for use in the fuel cell, since this gas acts as a catalyst poison and leads to a loss in performance in the fuel cell.
  • membranes have been used for hydrogen separation, which can consist of different materials such as ceramic, glass, polymer or metal.
  • Metal membranes are characterized by high selectivity for hydrogen and high temperature stability, but have comparatively low permeation rates.
  • a large number of membrane cells each with a hydrogen-selective membrane, are used, in which the individual membranes either successively (in series) or side by side (in parallel) the hydrogen-containing reformate gas flows against them.
  • the membrane cells are stacked on top of each other to form a compact hydrogen separation module.
  • Such hydrogen separation modules or membrane modules are described, for example, by DE 198 60 253 Cl or DE 199 20 517 Cl.
  • the documents DE 692 01 942 T2, EP 0 570 185 A2 and EP 0 974 389 A2 each disclose methods and / or devices for generating an almost pure gas for permeation. These devices are constructed so that they can have two separate permeation stages. Immediately after the first permeation stage there is a second permeation stage on the high pressure side, so that the residual gas remaining after the first permeation stage has the desired gas component, e.g. Hydrogen, can be separated. By connecting two permeation stages in series, the yield of the desired pure gas is increased.
  • the desired gas component e.g. Hydrogen
  • the object of the present invention to provide a device and a method for separating virtually pure hydrogen from a hydrogen-containing gas stream, in particular a gas stream from a hydrogen generation device, for operating a fuel cell, with a hydrogen separation module, which allows the highest possible yield of hydrogen with the smallest possible hydrogen separation module.
  • a method according to the invention which is described by the features of the characterizing part of claim 9, also achieves the object of the invention mentioned above.
  • the invention provides for the use of a first hydrogen separation module, by means of which a first portion of hydrogen is separated from the hydrogen-containing gas. The remaining gas stream then arrives again in the at least one further hydrogen separation module. Since the residual gas flow after the first hydrogen separation module still contains at least a few percent of hydrogen, hydrogen is separated off again in the at least one further hydrogen separation module, the individual hydrogen streams being combined according to a further development of the invention according to the hydrogen separation modules.
  • the yield of hydrogen and thus the uti- lization or the efficiency of the hydrogen separation modules increases. Utilization or efficiency is understood to mean the ratio between the amount of hydrogen which is separated by the hydrogen separation module and the amount of hydrogen which is fed to the hydrogen separation module.
  • the cascading of the hydrogen separation modules described can be repeated as often as desired, with the residual gas, the so-called retentate, being passed from one hydrogen separation module into the subsequent hydrogen separation module.
  • the usual hydrogen content of a hydrogen-containing gas stream originating from a hydrogen generation device two to three of the hydrogen separation modules in the serial connection according to the invention are sufficient, particularly also from the point of view of a construction that is as compact as possible.
  • only two hydrogen separation modules will now be dealt with, which, however, is not intended to restrict the invention or the following explanations to exactly this number of hydrogen separation modules.
  • a water gas shift reactor is arranged upstream of the at least one further hydrogen separation module in the flow direction of the residual gas stream.
  • the water gas shift reaction which is known per se and is frequently used in the field of hydrogen generation devices, is used to remove the carbon monoxide present in the residual gas stream, the concentration of which has risen again due to the separation of a large part of the hydrogen contained in the hydrogen-containing gas stream. with water contained in the residual gas stream to convert to carbon dioxide and hydrogen.
  • the hydrogen additionally obtained in this way can then at least partially be separated off, together with the hydrogen still present in the residual gas stream, in the further hydrogen separation module, the total yield of hydrogen increases.
  • a particularly advantageous embodiment of the method according to the invention provides that a pressure of the hydrogen after the first hydrogen separation module is kept below 1.2 bar a (absolute pressure), while the pressure of the hydrogen after the at least one further hydrogen separation module is kept below 0.9 bar a is maintained, the pressure difference between the two hydrogen streams being compensated for by a hydrogen delivery device.
  • the pressure below 1.2 bar a or lower can be achieved, for example, by changing the operating parameters of the fuel cell and, in particular, by dispensing with a jet pump, which is used to return residual hydrogen after flowing through an anode compartment of the fuel cell into the area of the inflowing hydrogen frequently used can be achieved.
  • jet pumps of this type require a pressure of at least 1.3 to 1.5 bar a of the conveying gas stream, which in this case is the pressure from the hydrogen separator. tion module coming hydrogen flow.
  • a low pressure behind the hydrogen separation module can ideally be achieved. This lower pressure in the flow direction behind the hydrogen separation module compared to the prior art allows the utilization or the efficiency of the hydrogen separation module to be increased.
  • the increase in utilization by lowering the pressure level after the hydrogen separation module can be achieved with significantly less energy overall than a comparable increase in utilization by increasing the pressure in the hydrogen-containing gas flowing into the hydrogen separation module, the so-called feed gas.
  • This energy saving occurs particularly in systems in which the hydrogen-containing gas from an autothermal reforming of a hydrocarbon, e.g. Gasoline comes on, because in such systems, in addition to the water and the hydrocarbon, the compressible medium air must also be compressed.
  • a hydrogen delivery device is used after the hydrogen separation module on the hydrogen side, so that a pressure level of less than 0.9 bar a , in particular about 0.8 bar a , in the area between the further hydrogen separation module and the hydrogen delivery device bar a is reached.
  • the yield of hydrogen in the region of the at least one further hydrogen separation module can be increased again, the pressure difference to the hydrogen from the first hydrogen separation module, which are usually below 500 mbar can be compensated for by the hydrogen delivery device.
  • the hydrogen flow which flows to the fuel cell, is usually composed such that approx. 90% of the hydrogen comes from the area of the first hydrogen separation module and only approx. 10% of the hydrogen comes from the area of the further hydrogen separation module.
  • Lowering the pressure behind the least one further hydrogen separation module to a low level that is very favorable for the yield is therefore possible with a comparatively low use of energy. If, in parallel, the pressure downstream of the first hydrogen separation module is not, or at least not, reduced by using larger amounts of energy, there is the possibility of a very high yield of hydrogen with a comparatively low use of parasitic energy.
  • Figure 1 shows an inventive device for separating hydrogen from a hydrogen-containing gas stream.
  • FIG. 2 shows a structure of the device according to FIG. 2 as an integrated component
  • FIG. 3 shows a partial section of the component according to FIG. 3.
  • a device 1 according to the invention is shown in its principle.
  • a first hydrogen separation module 2 can be seen, to which a hydrogen-containing gas, a so-called feed gas, is fed via a line 3.
  • this feed gas can come from any source.
  • the feed gas comes from a hydrogen generation device 4, which is only indicated here.
  • the feed gas is obtained in a manner known per se from a starting material which has carbon and hydrogen, e.g. Gasoline, diesel, methanol or the like.
  • This starting material is converted together with water and optionally with air in a reformer and, if appropriate, in one or more downstream water gas shift stages to give the hydrogen-containing gas or reformate gas.
  • the reformate gas usually contains hydrogen, carbon dioxide, carbon monoxide and residues of water and the starting material.
  • the proportion of hydrogen in the feed gas is around 40% (autothermal reforming) to 65% (steam reforming).
  • the hydrogen generation device 4 is connected via the line 3 coming hydrogen-containing gas stream, a certain proportion of hydrogen, which, based on the available amount of hydrogen in the feed gas, forms the utilization or the efficiency of the first hydrogen separation module 2, is selectively separated from the feed gas.
  • the hydrogen obtained in this way is at least almost pure. It is fed via a line 5 to an anode compartment 6 of a fuel cell 7, which is not shown in its entirety.
  • the hydrogen is usually fed to the anode compartment 6 with an excess of approximately 20 to 50%, so that a gas stream remains after the anode compartment 6, which gas stream is returned in an anode circuit 8 via a conveying device 9 into the region of the hydrogen in front of the anode compartment 6 ,
  • the conveyor 9 is preferably designed as a diaphragm piston pump, but it can be designed in any manner.
  • the conveyor 9 is not a jet pump.
  • a pressure p x of less than 1.2 bar a can be achieved at the outlet of the hydrogen from the first hydrogen separation module 2, whereas the pressure there in the event that a jet pump would be used, should be at least 1.3 to 1.5 bar a due to the system, since otherwise the jet pump would not be able to maintain the volume flow in the anode circuit 8.
  • the 1 also shows a further hydrogen separation module 10, into which the residual gas stream, the so-called retentate, from the first water Substance separation module 2 flows.
  • this residual gas stream in addition to carbon monoxide, carbon dioxide, water and residues of the starting materials for hydrogen production in the hydrogen production device 4, there are still portions of hydrogen.
  • this proportion of hydrogen is approximately 10 to 20% of the hydrogen originally contained in the hydrogen-containing gas stream.
  • the further hydrogen separation module 10 whose surface area of the separation membranes, that is to say its active surface, ideally amounts to approximately 0.1 to 0.3 of the surface area of the separation membranes in the first hydrogen separation module 2, hydrogen is again separated from the residual gas stream.
  • This separated hydrogen is fed to the hydrogen flow from the first hydrogen separation module 2 via a hydrogen delivery device 12 and in the area of a junction 13 with this - and in the exemplary embodiment shown here with the hydrogen flow from the anode circuit 8 - combined to form a hydrogen flow, which then leads to the anode space 6 the fuel cell 7 flows.
  • the hydrogen delivery device 12 compensates for a pressure difference between the two gas flows and ensures a negative pressure P 2 in the region of the exit of the hydrogen from the further hydrogen separation module 10.
  • a low pressure P which in this case, for example, is of the order of 0, has an effect .8 bar a can have a positive effect on the utilization of the further hydrogen separation module 10. The overall utilization or the overall efficiency of the hydrogen separation thus increases.
  • the pressure p_ after the further hydrogen separation module 10 must therefore be raised to the pressure px after the first hydrogen separation module 2 by the hydrogen delivery device.
  • the energy expenditure for operating the hydrogen delivery device 12 is therefore limited within this low volume flow of hydrogen. This in turn has a positive effect on the overall efficiency of a fuel cell system comprising, for example, the device 1, the hydrogen generating device 4, the fuel cell 7 and also required auxiliary units, such as air supply and the like.
  • the hydrogen delivery device 12 can be designed as a diaphragm piston pump, but other delivery means are also conceivable.
  • the advantage in such a diaphragm piston pump lies in its efficiency, which is significantly better than that of a jet pump, and in the fact that no system-related minimum pressure, as for the delivery jet, has to be provided.
  • a very low pressure for example the 0.8 bar a or less mentioned above, can thus be achieved behind the further hydrogen separation module 10 by means of the membrane piston pump.
  • the diaphragm piston pump is robust and very inexpensive. It can also be built very compact, which makes it particularly interesting for use in mobile systems.
  • An alternative embodiment, not shown here, can nevertheless provide a jet pump as a hydrogen delivery device 12, which, however, is designed in such a way that its delivery jet has a significantly higher density and a significantly higher pressure than the hydrogen which it delivers from the area of the further hydrogen separation module 10 , Since the pressure and density of the medium which forms the delivery jet directly influences the result to be achieved by the jet pump, a low pressure of the hydrogen behind the further hydrogen separation module 10 can also be achieved in this way.
  • water in one Pressure of more than 5 bar a especially at about 10 bar a , can be used as a delivery jet.
  • the feed stream reaches, for example, a pump via a pump into the area of the hydrogen delivery device 12, which is then designed as a jet pump.
  • the delivery flow entrains the hydrogen coming from the further hydrogen separation module 10 and generates the desired low pressure in the area between the further hydrogen separation module 10 and the hydrogen delivery device 12 p 2 . If necessary, the water forming the delivery flow is then at least partially separated from the hydrogen-containing material flow in a separator.
  • the device 1 is operated, for example, with a hydrogen-containing gas stream from a hydrogen generation device 4, which works according to the principle of autothermal reforming, then typical concentrations of hydrogen in the feed gas of the order of about 40% achieved.
  • the hydrogen-containing gas stream or feed gas should have a pressure of approximately 10 bar a .
  • the device 1 is constructed such that the active area of the first hydrogen separation module 2 to the further hydrogen separation module 10 is approximately 3: 1. It is operated such that the pressure p x behind the first hydrogen separation module 2 is approximately 1.15 bar a . At a pressure p 2 of approximately 0.8 bar a downstream of the further hydrogen separation module 10, an overall efficiency in the size of 85% to 90% can be achieved. A single hydrogen separation module would only achieve about 80% efficiency under similar conditions for comparison.
  • the anode circuit 8 is just as little necessary for the functioning of the device 1 described in FIG. 1 as for the device 1 described in FIG. 2 However, as with all systems which supply almost pure hydrogen to the anode compartment 6 of the fuel cell 7, irrespective of the source of this hydrogen, it makes sense for the operation of the fuel cell 7.
  • a water gas shift reactor 14 is arranged in the region of the line 11.
  • This water gas shift reactor 14 can e.g. be designed as a high-temperature shift stage in which a water gas shift reaction takes place at temperatures of approximately 350-400 ° C., in which hydrogen and carbon dioxide are produced from water and carbon monoxide.
  • the advantage of such a water gas shift reactor 14 is firstly that the emission of toxic carbon monoxide is reduced by the water gas shift reactor 14.
  • hydrogen is again generated from the carbon monoxide and water present in the residual gas stream, so that a further hydrogen separation module 10 can be offered a higher hydrogen concentration in the residual gas stream.
  • the overall efficiency of the separation of the hydrogen can be determined Increase the hydrogen-containing gas flow by another 2-3% compared to a structure without water gas shift stage 14. This enables a total utilization of the hydrogen separation of over 90% to be achieved even with comparatively little hydrogen in the hydrogen-containing gas stream, e.g. approx. 40% with autothermal reforming. Utilizations of 95-98% can be achieved when used together with a feed gas stream with approx. 65% hydrogen originating from steam reforming.
  • FIG. 2 shows the device 1 in an embodiment with two hydrogen separation modules 2, 10 and a water gas shift reactor 14.
  • the same device 1 can be seen again in FIG. 3 in a partial section.
  • the two hydrogen separation modules 2 and 10 and the water gas shift reactor 14 are integrated in a single component in the construction according to FIGS. 2 and 3.
  • the hydrogen-containing gas stream or feed gas stream flowing in via line 3 first arrives in the first hydrogen separation module 2, in which a large part of the hydrogen in the hydrogen-containing gas stream is separated and through a collector 15, which is only partially shown here, into line 5 and to the junction 13 arrives.
  • the residual gas flow flows after the first hydrogen separation module 2 through the line 11 formed here as a channel into the water gas shift reactor 14.
  • the direction of flow in the water gas shift reactor 14 is approximately perpendicular to the main direction of flow in the first hydrogen separation module 2.
  • a section of the line 11 designed as a channel connects again, which feeds the residual gas stream, which has now been enriched again with hydrogen, to the further hydrogen separation module 10.
  • the flow direction is rotated again by 90 °, so that the further hydrogen separation module 10 has a main flow direction, which is rotated by 180 ° to the main flow direction of the first hydrogen separation module 2.
  • the further hydrogen separation module 10 also has a collector 16, from which the separated hydrogen can flow to the hydrogen delivery device 12. The remaining gas after the further hydrogen separation module 10 then leaves the component in countercurrent to the feed gas.
  • This structure of the two hydrogen separation modules 2, 10 and the water gas shift reactor 14 allows a very space-saving arrangement, which is very compact and, ultimately, can also be realized with comparatively little weight.
  • the flow guidance also ensures that all connections on the component are accessible from one side. This is very inexpensive, particularly when used under tight spatial conditions, as can often be found in mobile systems, during assembly and maintenance.
  • the device 1 and the method for separating hydrogen from a hydrogen-containing gas stream can in principle be used in all types of fuel cell systems, regardless of whether they are in a mobile system, such as a vehicle on land, on water or in the air, be used in a mobile emergency power supply facility or in a stationary system.
  • auxiliary power unit APU
  • the fuel cell system should not be provided - which would also be conceivable - for supplying the mobile system with drive energy, but for the provision of energy for auxiliary and auxiliary units, such as e.g. the vehicle electronics, an air conditioner, a communication device, a navigation device and the like.

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Abstract

The invention relates to a method and a device which are used to provide almost pure hydrogen from a gas flow containing hydrogen, especially from a the gas flow from a hydrogen generating device, for the operation of a fuel cell. Also, at least one hydrogen is used. According to the invention, at least one other hydrogen separation module is used on the residual gas side after the first hydrogen separation module in order to separate hydrogen from the residual gas flow. A water-gas auxiliary reactor is arranged upstream from the other module. The inventive method and/or device can be used, preferably, in an auxiliary power unit/APU based on a fuel cell and a hydrogen generating device in a mobile system, in especially a motor vehicle. However, the invention can also be used for other purposes.

Description

Vorrichtung und Verfahren zum Abtrennen von nahezu reinem Wasserstoff aus einem wasserstoffhaltigen Gasstrom Device and method for separating almost pure hydrogen from a hydrogen-containing gas stream
Die Erfindung betrifft eine Vorrichtung sowie ein Verfahren zum Abtrennen von zumindest nahezu reinem Wasserstoff aus einem wasserstoffhaltigen Gasstrom nach der in den Oberbegrif- fen der Ansprüche 1 und 9 näher definierten Art .The invention relates to a device and a method for separating at least almost pure hydrogen from a hydrogen-containing gas stream according to the kind defined in the preambles of claims 1 and 9.
Brennstoffzellen, insbesondere solche für mobile Anwendungen, können durch Wasserstofferzeugungseinrichtungen z.B. mittels Reformierung von Kohlenwasserstoffen wie zum Beispiel Metha- nol, Benzin oder Diesel mit Wasserstoff versorgt werden. Das in einem Reformierungsprozess entstandene Produktgas enthält neben Wasserstoff auch Kohlenmonoxid, Kohlendioxid und Wasserdampf. Insbesondere das Kohlenmonoxid muss für die Anwendung in der Brennstoffzelle entfernt werden, da dieses Gas als Katalysatorgift wirkt und zu einer Leistungseinbuße in der Brennstoffzelle führt.Fuel cells, especially those for mobile applications, can be produced by hydrogen generation devices e.g. can be supplied with hydrogen by reforming hydrocarbons such as methanol, gasoline or diesel. The product gas generated in a reforming process contains hydrogen, carbon monoxide, carbon dioxide and water vapor. In particular, the carbon monoxide must be removed for use in the fuel cell, since this gas acts as a catalyst poison and leads to a loss in performance in the fuel cell.
Für die Wasserstoffabtrennung werden seit langem Membranen eingesetzt, die aus verschiedenen Materialien wie zum Bei- spiel Keramik, Glas, Polymer oder Metall bestehen können. Metallmembranen zeichnen sich durch eine hohe Selektivität für Wasserstoff und eine hohe Temperaturstabilität aus, haben aber vergleichsweise niedrige Permeationsraten.For a long time, membranes have been used for hydrogen separation, which can consist of different materials such as ceramic, glass, polymer or metal. Metal membranes are characterized by high selectivity for hydrogen and high temperature stability, but have comparatively low permeation rates.
Um eine gewünschte Permeationsrate zu erreichen, verwendet man eine Vielzahl von Membranzellen mit jeweils einer wasserstoffselektiven Membran, bei denen die einzelnen Membranen entweder nacheinander (seriell) oder nebeneinander (parallel) vom wasserstoffhaltigen Reformatgas angeströmt werden. Die Membranzellen werden aufeinander gestapelt, um ein kompaktes Wasserstoffseparationsmodul zu bilden.In order to achieve a desired permeation rate, a large number of membrane cells, each with a hydrogen-selective membrane, are used, in which the individual membranes either successively (in series) or side by side (in parallel) the hydrogen-containing reformate gas flows against them. The membrane cells are stacked on top of each other to form a compact hydrogen separation module.
Derartige Wasserstoffseparationsmodule bzw. Membranmodule sind beispielsweise durch die DE 198 60 253 Cl oder die DE 199 20 517 Cl beschrieben.Such hydrogen separation modules or membrane modules are described, for example, by DE 198 60 253 Cl or DE 199 20 517 Cl.
Aus den Schriften DE 692 01 942 T2 , EP 0 570 185 A2 sowie EP 0 974 389 A2 , gehen jeweils Verfahren und/oder Vorrichtungen zur Erzeugung eines nahezu reinen Gases zur Permeation hervor. Diese Vorrichtungen sind dabei durchgehend so aufgebaut, dass sie über zwei getrennte Permeationsstufen verfügen kön- nen. Unmittelbar an die erste Permeationsstufe schließt sich dabei hochdruckseitig eine zweite Permeationsstufe an, so dass dem nach der ersten Permeationsstufe verbleibenden Restgas nochmals der gewünschte Gasbestandteil, z.B. Wasserstoff, abgeschieden werden kann. Durch das Hintereinanderschalten von zwei Permeationsstufen wird die Ausbeute an dem gewünschten reinen Gas erhöht .The documents DE 692 01 942 T2, EP 0 570 185 A2 and EP 0 974 389 A2 each disclose methods and / or devices for generating an almost pure gas for permeation. These devices are constructed so that they can have two separate permeation stages. Immediately after the first permeation stage there is a second permeation stage on the high pressure side, so that the residual gas remaining after the first permeation stage has the desired gas component, e.g. Hydrogen, can be separated. By connecting two permeation stages in series, the yield of the desired pure gas is increased.
Ausgehend von dem oben beschriebenen Stand der Technik ist es nun die Aufgabe der vorliegenden Erfindung eine Vorrichtung sowie eine Verfahren zum Abtrennen von nahezu reinem Wasserstoff aus einem wasserstoffhaltigen Gasstrom, insbesondere einem Gasstrom aus einer Wasserstofferzeugungseinrichtung, zum Betreiben einer Brennstoffzelle, mit einem Wasserstoffseparationsmodul zu schaffen, welche eine möglichst hohe Aus- beute an Wasserstoff bei möglichst kleinem Wasserstoffseparationsmodul erlaubt.Starting from the prior art described above, it is the object of the present invention to provide a device and a method for separating virtually pure hydrogen from a hydrogen-containing gas stream, in particular a gas stream from a hydrogen generation device, for operating a fuel cell, with a hydrogen separation module, which allows the highest possible yield of hydrogen with the smallest possible hydrogen separation module.
Erfindungsgemäß wird diese Aufgabe durch die im kennzeichnenden Teil des Anspruchs 1 genannten Merkmale gelöst . Ein er- findungsgemäßes Verfahren, welches durch die Merkmale des kennzeichnenden Teils des Anspruchs 9 beschrieben ist, löst die oben genannte Aufgabe der Erfindung ebenfalls. Die Erfindung sieht die Verwendung eines ersten Wasserstoffseparationsmoduls vor, durch welches ein erster Anteil an Wasserstoff aus dem wasserstoffhaltigen Gas abgetrennt wird. Der verbleibende Restgasstrom gelangt dann nochmals in das wenigstens eine weitere Wasserstoffseparationsmodul . Da der Restgastrom nach dem ersten Wasserstoffseparationsmodul immer noch einen Anteil von zumindest einigen Prozent an Wasserstoff aufweist, wird in dem wenigstens einen weiteren Wasser- stoffseparationsmodul nochmals Wasserstoff abgetrennt, wobei die einzelnen Wasserstoffströme gemäß einer Weiterbildung der Erfindung nach den Wasserstoffseparationsmodulen zusammengeführt werden. Die Ausbeute an Wasserstoff und damit die Uti- lisation bzw. der Wirkungsgrad der Wasserstoffseparationsmo- dule steigt damit an. Unter der Utilisation bzw. dem Wirkungsgrad ist dabei das Verhältnis zwischen der Menge an Wasserstoff, welcher durch das Wasserstoffseparationsmodul abgetrennt wird, und der Menge an Wasserstoff, welcher dem Wasserstoffseparationsmodul zugeführt wird, zu verstehen.According to the invention this object is achieved by the features mentioned in the characterizing part of claim 1. A method according to the invention, which is described by the features of the characterizing part of claim 9, also achieves the object of the invention mentioned above. The invention provides for the use of a first hydrogen separation module, by means of which a first portion of hydrogen is separated from the hydrogen-containing gas. The remaining gas stream then arrives again in the at least one further hydrogen separation module. Since the residual gas flow after the first hydrogen separation module still contains at least a few percent of hydrogen, hydrogen is separated off again in the at least one further hydrogen separation module, the individual hydrogen streams being combined according to a further development of the invention according to the hydrogen separation modules. The yield of hydrogen and thus the uti- lization or the efficiency of the hydrogen separation modules increases. Utilization or efficiency is understood to mean the ratio between the amount of hydrogen which is separated by the hydrogen separation module and the amount of hydrogen which is fed to the hydrogen separation module.
Diese beschriebene Kaskadierung der Wasserstoffseparationsmodule lässt sich im Prinzip beliebig oft wiederholen, wobei jeweils das Restgas, das sogenannte Retentat, aus dem einen Wasserstoffseparationsmodul in das nachfolgende Wasserstoff- separationsmodul geleitet wird. Bei dem üblichen Wasserstoff- gehalten eines aus einer Wasserstofferzeugungseinrichtung stammendem wasserstoffhaltigen Gasstroms sind, insbesondere auch unter dem Gesichtpunkt einer möglichst kompakten Bauweise zwei bis drei der Wasserstoffseparationsmodule in der er- findungsgemäßen seriellen Verschaltung ausreichend. Um die nachfolgenden Ausführungen und dass Ausführungsbeispiel leichter verständlich zu gestalten, wird nunmehr auf jeweils nur zwei Wasserstoffseparationsmodule eingegangen, was jedoch weder Erfindung noch die nachfolgenden Ausführungen auf genau diese Anzahl an Wasserstoffseparationsmodule einschränken soll . Um die Effizienz des Aufbaus noch weiter zu steigern, ist es vorgesehen, dass in Stfömungsrichtung des Restgasstroms vor dem wenigstens einen weiteren Wasserstoffseparationsmodul ein Wassergasshiftreaktor angeordnet ist.In principle, the cascading of the hydrogen separation modules described can be repeated as often as desired, with the residual gas, the so-called retentate, being passed from one hydrogen separation module into the subsequent hydrogen separation module. With the usual hydrogen content of a hydrogen-containing gas stream originating from a hydrogen generation device, two to three of the hydrogen separation modules in the serial connection according to the invention are sufficient, particularly also from the point of view of a construction that is as compact as possible. In order to make the following explanations and that the exemplary embodiment easier to understand, only two hydrogen separation modules will now be dealt with, which, however, is not intended to restrict the invention or the following explanations to exactly this number of hydrogen separation modules. In order to further increase the efficiency of the structure, it is provided that a water gas shift reactor is arranged upstream of the at least one further hydrogen separation module in the flow direction of the residual gas stream.
Mit diesem Wassergasshiftreaktor zwischen den kaskadierten Wasserstoffseparationsmodulen wird die an sich bekannte und im Bereich von Wasserstofferzeugungseinrichtungen ohnehin häufig genutzte Wassergasshiftreaktion verwendet, um das in dem Restgasstrom vorhandene Kohlenmonoxid, dessen Konzentration aufgrund der Separation eines großen Teils des in dem wasserstoffhaltigen Gasstrom enthaltenen Wasserstoffs nochmals angestiegen ist, mit in dem Restgasstrom enthaltenen Wasser zu Kohlendioxid und Wasserstoff umzusetzen. Der so zu- sätzlich gewonnene Wasserstoff kann zusammen mit dem in dem Restgasstrom noch vorhandenen Wasserstoff dann zumindest teilweise in dem weiteren Wasserstoffseparationsmodul abgetrennt werden, die Gesamtausbeute an Wasserstoff steigt an.With this water gas shift reactor between the cascaded hydrogen separation modules, the water gas shift reaction, which is known per se and is frequently used in the field of hydrogen generation devices, is used to remove the carbon monoxide present in the residual gas stream, the concentration of which has risen again due to the separation of a large part of the hydrogen contained in the hydrogen-containing gas stream. with water contained in the residual gas stream to convert to carbon dioxide and hydrogen. The hydrogen additionally obtained in this way can then at least partially be separated off, together with the hydrogen still present in the residual gas stream, in the further hydrogen separation module, the total yield of hydrogen increases.
Eine besonders vorteilhafte Ausbildung des erfindungsgemäßen Verfahrens sieht es vor, dass ein Druck des Wasserstoffs nach dem ersten Wasserstoffseparationsmodul unter 1,2 bara (absoluter Druck) gehalten wird, während der Druck des Wasserstoff nach dem wenigstens einen weiteren Wasserstoffseparationsmo- dul unter 0,9 bara gehalten wird, wobei die Druckdifferenz zwischen den beiden Wasserstoffströmen über eine Wasserstofffördereinrichtung ausgeglichen wird.A particularly advantageous embodiment of the method according to the invention provides that a pressure of the hydrogen after the first hydrogen separation module is kept below 1.2 bar a (absolute pressure), while the pressure of the hydrogen after the at least one further hydrogen separation module is kept below 0.9 bar a is maintained, the pressure difference between the two hydrogen streams being compensated for by a hydrogen delivery device.
Der Druck unterhalb von 1,2 bara oder niedriger kann bei- spielsweise durch veränderte Betriebsparameter der Brennstoffzelle und insbesondere durch den Verzicht auf eine Strahlpumpe, welche zur Rückführung -von Rest-Wasserstoff nach dem Durchströmen eines Anodenraums der Brennstoffzelle in den Bereich des einströmenden Wasserstoffs häufig eingesetzt wird, erreicht werden. Derartige Strahlpumpen benötigen prinzipbedingt einen Druck von zumindest 1,3 bis 1,5 bara des Fördergasstroms, welcher hier der aus dem Wasserstoffsepara- tionsmodul kommende Wasserstoffström ist. Durch den Verzicht auf eine derartige Strahlpumpe bzw. den Einsatz einer nach einem anderen Prinzip arbeitenden Pumpe, wie z.B. einer Membrankolbenpumpe, für den Anodenkreislauf kann also in idealer Weise ein niedriger Druck hinter dem Wasserstoffseparationsmodul erzielt werden. Durch diesen gegenüber dem Stand der Technik niedrigeren Druck in Strömungsrichtung hinter dem Wasserstoffseparationsmodul lässt sich die Utilisation bzw. der Wirkungsgrad des Wasserstoffseparationsmoduls steigern.The pressure below 1.2 bar a or lower can be achieved, for example, by changing the operating parameters of the fuel cell and, in particular, by dispensing with a jet pump, which is used to return residual hydrogen after flowing through an anode compartment of the fuel cell into the area of the inflowing hydrogen frequently used can be achieved. In principle, jet pumps of this type require a pressure of at least 1.3 to 1.5 bar a of the conveying gas stream, which in this case is the pressure from the hydrogen separator. tion module coming hydrogen flow. By dispensing with such a jet pump or by using a pump that works on a different principle, such as a diaphragm piston pump, for the anode circuit, a low pressure behind the hydrogen separation module can ideally be achieved. This lower pressure in the flow direction behind the hydrogen separation module compared to the prior art allows the utilization or the efficiency of the hydrogen separation module to be increased.
Die Steigerung der Utilisation durch die Senkung des Druckniveaus nach dem Wasserstoffseparationsmodul kann insgesamt mit deutlich weniger Energieeinsatz erreicht werden, als eine vergleichbare Steigerung der Utilisation durch eine Steige- rung des Drucks in dem in das Wasserstoffseparationsmodul einströmenden wasserstoffhaltigen Gas, dem sogenannten Feed- gas. Diese Energieeinsparung tritt insbesondere bei Systemen, bei welchen das wasserstoffhaltige Gas aus einer autothermen Reformierung eines Kohlenwasserstoffs, wie z.B. Benzin stammt, auf, da bei derartigen Systemen neben dem Wasser und dem Kohlenwasserstoff auch noch das kompressible Medium Luft verdichtet werden muss .The increase in utilization by lowering the pressure level after the hydrogen separation module can be achieved with significantly less energy overall than a comparable increase in utilization by increasing the pressure in the hydrogen-containing gas flowing into the hydrogen separation module, the so-called feed gas. This energy saving occurs particularly in systems in which the hydrogen-containing gas from an autothermal reforming of a hydrocarbon, e.g. Gasoline comes on, because in such systems, in addition to the water and the hydrocarbon, the compressible medium air must also be compressed.
In dem wenigsten einen weiteren Wasserstoffseparationsmodul wird gemäß einer sehr vorteilhaften Weiterbildung des erfindungsgemäßen Verfahrens wasserstoffseitig nach dem Wasserstoffseparationsmodul eine Wasserstofffördereinrichtung eingesetzt, so dass im Bereich zwischen dem weiteren Wasserstoffseparationsmodul und der Wasserstofffördereinrichtung ein Druckniveau kleiner als 0,9 bara, insbesondere ca. 0,8 bara erreicht wird.In at least one further hydrogen separation module, according to a very advantageous development of the method according to the invention, a hydrogen delivery device is used after the hydrogen separation module on the hydrogen side, so that a pressure level of less than 0.9 bar a , in particular about 0.8 bar a , in the area between the further hydrogen separation module and the hydrogen delivery device bar a is reached.
Durch diese weitere Absenkung des Druckniveaus lässt sich die Ausbeute an Wasserstoff im Bereich des wenigstens einen wei- teren Wasserstoffseparationsmoduls nochmals steigern, die Druckdifferenz zu dem Wasserstoff aus dem ersten Wasserstoffseparationsmodul, welche üblicherweise unter 500 mbar liegen wird, kann durch die Wasserstofffördereinrichtung ausgeglichen werden. Üblicherweise setzt sich der Wasserstoffström, welcher zu der Brennstoffzelle strömt so zusammen, dass ca. 90% des Wasserstoffs aus dem Bereich des ersten Wasserstoff- separationsmoduls und nur ca. 10% des Wasserstoff aus dem Bereich des weiteren Wasserstoffseparationsmoduls stammen. Den Druck hinter dem wenigsten einen weiteren Wasserstoffseparationsmodul auf ein für die Ausbeute sehr günstiges niedriges Niveau abzusenken ist also mit einem vergleichsweise geringen Einsatz an Energie möglich. Wird parallel dazu der Druck hinter dem ersten Wasserstoffseparationsmodul nicht oder zumindest nicht durch den Einsatz von größeren Mengen an Energie abgesenkt, so ergibt sich die Möglichkeit einer sehr hohen Ausbeute an Wasserstoff bei vergleichsweise geringem Einsatz an parasitärer Energie.As a result of this further lowering of the pressure level, the yield of hydrogen in the region of the at least one further hydrogen separation module can be increased again, the pressure difference to the hydrogen from the first hydrogen separation module, which are usually below 500 mbar can be compensated for by the hydrogen delivery device. The hydrogen flow, which flows to the fuel cell, is usually composed such that approx. 90% of the hydrogen comes from the area of the first hydrogen separation module and only approx. 10% of the hydrogen comes from the area of the further hydrogen separation module. Lowering the pressure behind the least one further hydrogen separation module to a low level that is very favorable for the yield is therefore possible with a comparatively low use of energy. If, in parallel, the pressure downstream of the first hydrogen separation module is not, or at least not, reduced by using larger amounts of energy, there is the possibility of a very high yield of hydrogen with a comparatively low use of parasitic energy.
Eine besonders vorteilhafte Verwendung für alle Ausgestaltungen der erfindungsgemäßen Vorrichtung und/oder des erfindungsgemäßen Verfahrens ist durch den Anspruch 14 näher be- schreiben.A particularly advantageous use for all configurations of the device according to the invention and / or the method according to the invention is described in more detail by claim 14.
Der hohe Wirkungsgrad bei der Wasserstoffabscheidung sowie die Möglichkeit eines sehr kompakten, integrieren Aufbaus, welcher mittels der Erfindung zu erzielen ist, prädestiniert die Erfindung geradezu für kleine Energieversorgungssysteme, wie z.B. Hilfsenergieerzeuger (Auxiliary Power Unit/APU), auf der Basis einer Brennstoffzelle, insbesondere mit einer integrierten Wasserstofferzeugungseinrichtung. Gerade hier spielen der Wirkungsgrad sowie die kompakte und leichte Bau- weise eine entscheidende Rolle. Da es nun einer der besonderen Vorteile der Erfindung ist, je Volumeneinheit sehr viel Wasserstoff abtrennen zu können, ist sie für den Einsatz in solchen APU-Systemen besonders geeignet.The high efficiency in the hydrogen separation and the possibility of a very compact, integrated structure, which can be achieved by means of the invention, predestines the invention for small energy supply systems, such as e.g. Auxiliary power unit (APU), based on a fuel cell, in particular with an integrated hydrogen generation device. Efficiency and the compact and lightweight design play a decisive role here. Since it is now one of the special advantages of the invention to be able to remove a large amount of hydrogen per unit volume, it is particularly suitable for use in such APU systems.
Weitere vorteilhafte Ausgestaltungen der Erfindung ergeben sich aus den restlichen Unteransprüchen sowie aus den nach- folgend anhand der Zeichnung näher dargestellten Ausführungs- beispielen.Further advantageous embodiments of the invention result from the remaining subclaims and from the following exemplary embodiments shown in more detail with reference to the drawing.
Dabei zeigen:Show:
Fig. 1 eine erfindungsgemäße Vorrichtung zum Abtrennen von Wasserstoff aus einem wasserstoffhaltigen Gasstrom;Figure 1 shows an inventive device for separating hydrogen from a hydrogen-containing gas stream.
Fig. 2 einen Aufbau der Vorrichtung gemäß Fig. 2 als ein in- tegriertes Bauteil; undFIG. 2 shows a structure of the device according to FIG. 2 as an integrated component; and
Fig. 3 einen Teilschnitt des Bauteils gemäß Fig. 3.3 shows a partial section of the component according to FIG. 3.
In Fig. 1 ist eine erfindungsgemäße Vorrichtung 1 in ihrem Prinzip dargestellt. Dabei ist ein erstes Wasserstoffseparationsmodul 2 erkennbar, welchem über eine Leitung 3 ein wasserstoffhaltiges Gas, ein sogenanntes Feedgas, zugeführt wird. Dieses Feedgas kann prinzipiell aus beliebigen Quellen stammen. Für die nachfolgend erläuterten Beispiele wird je- doch davon ausgegangen, dass das Feedgas aus einer hier nur angedeuteten Wasserstofferzeugungseinrichtung 4 stammt . In der Wasserstofferzeugungseinrichtung 4 wird das Feedgas in an sich bekannter Weise aus einem Ausgangstoff gewonnen, welcher Kohlenstoff und Wasserstoff aufweist, z.B. Benzin, Diesel, Methanol oder dergleichen. Dieser Ausgangsstoff wird zusammen mit Wasser und gegebenenfalls mit Luft in einem Reformer und gegebenenfalls in einer oder mehreren nachgeschalteten Wassergasshiftstufen zu dem wasserstoffhaltigen Gas bzw. Refor- matgas umgesetzt. Das Reformatgas enthält dabei üblicherweise Wasserstoff, Kohlendioxid, Kohlenmonoxid sowie Reste des Wassers und des Ausgangstoffes. Je nach eingesetztem Verfahren in dem Reformer liegt der Anteil an Wasserstoff in dem Feedgas bei ca. 40% (autotherme Reformierung) bis 65% (Dampfre- formierung) .In Fig. 1, a device 1 according to the invention is shown in its principle. A first hydrogen separation module 2 can be seen, to which a hydrogen-containing gas, a so-called feed gas, is fed via a line 3. In principle, this feed gas can come from any source. For the examples explained below, however, it is assumed that the feed gas comes from a hydrogen generation device 4, which is only indicated here. In the hydrogen generating device 4, the feed gas is obtained in a manner known per se from a starting material which has carbon and hydrogen, e.g. Gasoline, diesel, methanol or the like. This starting material is converted together with water and optionally with air in a reformer and, if appropriate, in one or more downstream water gas shift stages to give the hydrogen-containing gas or reformate gas. The reformate gas usually contains hydrogen, carbon dioxide, carbon monoxide and residues of water and the starting material. Depending on the process used in the reformer, the proportion of hydrogen in the feed gas is around 40% (autothermal reforming) to 65% (steam reforming).
Durch das erste Wasserstoffseparationsmodul 2 wird von dem über die Leitung 3 aus der Wasserstofferzeugungseinrichtung 4 kommenden wasserstoffhaltigen Gasstrom ein gewisser Anteil an Wasserstoff, welcher rückbezogen auf die verfügbare Wasserstoffmenge in dem Feedgas die Utilisation bzw. den Wirkungsgrad des ersten Wasserstoffseparationsmoduls 2 bildet, selek- tiv aus dem Feedgas abgetrennt . Der so gewonnene Wasserstoff ist zumindest nahezu rein. Er wird über eine Leitung 5 einem Anodenraum 6 einer Brennstoffzelle 7, welche in ihrer Gesamtheit nicht dargestellt ist, zugeführt. Der Wasserstoff wird dem Anodenraum 6 üblicherweise mit einem Überschuss von ca. 20 bis 50% zugeführt, so dass nach dem Anodenraum 6 ein Gasstrom übrig bleibt, welcher in einem Anodenkreislauf 8 über eine Fördereinrichtung 9 in den Bereich des Wasserstoffs vor dem Anodenraum 6 zurückgeführt wird. Die Fördereinrichtung 9 ist bevorzugt als Membrankolbenpumpe ausgebildet, sie kann jedoch in beliebiger Art und Weise ausgebildet sein.By means of the first hydrogen separation module 2, the hydrogen generation device 4 is connected via the line 3 coming hydrogen-containing gas stream, a certain proportion of hydrogen, which, based on the available amount of hydrogen in the feed gas, forms the utilization or the efficiency of the first hydrogen separation module 2, is selectively separated from the feed gas. The hydrogen obtained in this way is at least almost pure. It is fed via a line 5 to an anode compartment 6 of a fuel cell 7, which is not shown in its entirety. The hydrogen is usually fed to the anode compartment 6 with an excess of approximately 20 to 50%, so that a gas stream remains after the anode compartment 6, which gas stream is returned in an anode circuit 8 via a conveying device 9 into the region of the hydrogen in front of the anode compartment 6 , The conveyor 9 is preferably designed as a diaphragm piston pump, but it can be designed in any manner.
Sinnvoll ist es dabei, wenn es sich bei der Fördereinrichtung 9 nicht um eine Strahlpumpe handelt . Durch den Verzicht auf die an dieser Stelle üblicherweise eingesetzte Strahlpumpe kann am Austritt des Wasserstoffs aus dem ersten Wasserstoffseparationsmodul 2 ein Druck px von weniger als 1,2 bara erreicht werden, wogegen der Druck dort im Falle, dass eine Strahlpumpe Verwendung finden würde, systembedingt mindestens 1,3 bis 1,5 bara betragen müsste, da die Strahlpumpe ansons- ten den Volumenstrom im Anodenkreislauf 8 nicht aufrecht erhalten könnte .It is useful if the conveyor 9 is not a jet pump. By dispensing with the jet pump usually used at this point, a pressure p x of less than 1.2 bar a can be achieved at the outlet of the hydrogen from the first hydrogen separation module 2, whereas the pressure there in the event that a jet pump would be used, should be at least 1.3 to 1.5 bar a due to the system, since otherwise the jet pump would not be able to maintain the volume flow in the anode circuit 8.
Die Absenkung des Druckes pi beispielsweise von 1,3 bara auf 1,15 bara führt bei Beibehaltung der sonstigen Parameter z.B. bei einem Wasserstoffgehalt von 40% und einem Druck von 10 bara im Feedgas, bereits zu einer Steigerung des Wirkungsgrades des ersten Wasserstoffseparationsmoduls 2 um mehr als 2,5%.Lowering the pressure pi from 1.3 bar a to 1.15 bar a , for example, while maintaining the other parameters, for example with a hydrogen content of 40% and a pressure of 10 bar a in the feed gas, already leads to an increase in the efficiency of the first hydrogen separation module 2 by more than 2.5%.
In Fig. 1 ist darüber hinaus ein weiteres Wasserstoffseparationsmodul 10 zu erkennen, in welches über eine Leitung 11 der Restgastrom, das sogenannte Retentat, aus dem ersten Was- serstoffseparationsmodul 2 strömt. In diesem Restgasstrom sind neben Kohlenmonoxid, Kohlendioxid, Wasser und Resten der Ausgangstoffe der Wasserstofferzeugung in der Wasserstofferzeugungseinrichtung 4 immer noch Anteile an Wasserstoff ent- halten. Bei üblichen Wirkungsgraden von Wasserstoffseparati- onsmodulen liegt dieser Anteil an Wasserstoff bei ca. 10 bis 20% des ursprünglich in dem wasserstoffhaltigen Gasstrom enthaltenen Wasserstoffs. In dem weiteren Wasserstoffseparationsmodul 10, dessen Flächeninhalt der Separationsmembranen, also dessen aktive Fläche, in idealer Weise ca. 0,1 bis 0,3 des Flächeninhalts der Separationsmembranen in dem ersten Wasserstoffseparationsmodul 2 beträgt, wird aus dem Restgasstrom nochmals Wasserstoff abgetrennt. Dieser abgetrennte Wasserstoff wird über eine Wasserstofffördereinrichtung 12 dem Wasserstoffström aus dem ersten Wasserstoffseparationsmodul 2 zugeführt und im Bereich einer Zusammenführung 13 mit diesem -und im dem hier dargestellten Ausführungsbeispiel mit dem Wasserstoffström aus dem Anodenkreislauf 8- zu einem Wasserstoffström vereinigt, welcher dann zu dem Anodenraum 6 der Brennstoffzelle 7 strömt.1 also shows a further hydrogen separation module 10, into which the residual gas stream, the so-called retentate, from the first water Substance separation module 2 flows. In this residual gas stream, in addition to carbon monoxide, carbon dioxide, water and residues of the starting materials for hydrogen production in the hydrogen production device 4, there are still portions of hydrogen. With the usual degrees of efficiency of hydrogen separation modules, this proportion of hydrogen is approximately 10 to 20% of the hydrogen originally contained in the hydrogen-containing gas stream. In the further hydrogen separation module 10, whose surface area of the separation membranes, that is to say its active surface, ideally amounts to approximately 0.1 to 0.3 of the surface area of the separation membranes in the first hydrogen separation module 2, hydrogen is again separated from the residual gas stream. This separated hydrogen is fed to the hydrogen flow from the first hydrogen separation module 2 via a hydrogen delivery device 12 and in the area of a junction 13 with this - and in the exemplary embodiment shown here with the hydrogen flow from the anode circuit 8 - combined to form a hydrogen flow, which then leads to the anode space 6 the fuel cell 7 flows.
Die Wasserstofffördereinrichtung 12 gleicht dabei eine Druckdifferenz zwischen den beiden Gasströmen aus und sorgt für einen Unterdruck P2 im Bereich des Austritts des Wasserstoffs aus dem weiteren Wasserstoffseparationsmodul 10. Wie oben bereits beschreiben wirkt sich ein niedriger Druck P , welcher hier beispielsweise in der Größenordnung von 0,8 bara liegen kann, positiv auf die Utilisation des weiteren Wasserstoffseparationsmodul 10 aus. Die Gesamtutilisation bzw. der Gesamt- wirkungsrad der Wasserstoffabscheidung steigt damit an.The hydrogen delivery device 12 compensates for a pressure difference between the two gas flows and ensures a negative pressure P 2 in the region of the exit of the hydrogen from the further hydrogen separation module 10. As already described above, a low pressure P, which in this case, for example, is of the order of 0, has an effect .8 bar a can have a positive effect on the utilization of the further hydrogen separation module 10. The overall utilization or the overall efficiency of the hydrogen separation thus increases.
Der Druck p_ nach dem weiteren Wasserstoffseparationsmodul 10 muss also durch die Wasserstofffördereinrichtung auf den Druck px nach dem ersten Wasserstoffseparationsmodul 2 ange- hoben werden. Dabei werden von dem insgesamt der Brennstoffzelle 7 zugeführten Wasserstoffström ca. 80 bis 90% an dem ersten Wasserstoffseparationsmodul 2 und lediglich der Rest an dem weiteren Wasserstoffseparationsmodul 10 aus dem wasserstoffhaltigen Gasstrom abgetrennt. Der energetische Aufwand zum Betreiben der Wasserstofffördereinrichtung 12 hält sich also bei diesen geringen Volumenstrom des Wasserstoffs in Grenzen. Dies wirkt sich wiederum positiv auf den Gesamt- Wirkungsgrad eines z.B. die Vorrichtung 1, die Wasserstofferzeugungseinrichtung 4, die Brennstoffzelle 7 sowie benötigte Nebenaggregate, wie Luftversorgung und dergleichen, umfassenden Brennstoffzellensystems aus.The pressure p_ after the further hydrogen separation module 10 must therefore be raised to the pressure px after the first hydrogen separation module 2 by the hydrogen delivery device. Of the total hydrogen flow supplied to the fuel cell 7, about 80 to 90% of the first hydrogen separation module 2 and only the rest separated from the hydrogen-containing gas stream on the further hydrogen separation module 10. The energy expenditure for operating the hydrogen delivery device 12 is therefore limited within this low volume flow of hydrogen. This in turn has a positive effect on the overall efficiency of a fuel cell system comprising, for example, the device 1, the hydrogen generating device 4, the fuel cell 7 and also required auxiliary units, such as air supply and the like.
Die Wasserstofffördereinrichtung 12 kann gemäß dem hier dargestellten Ausführungsbeispiel, wie auch die Fördereinrichtung 9, als Membrankolbenpumpe ausgebildet sein, es sind jedoch auch andere Fördermittel denkbar. Der Vorteil in einer derartigen Membrankolbenpumpe liegt jedoch in ihrem gegenüber einer Strahlpumpe deutlich besseren Wirkungsgrad und darin, dass kein systembedingter Mindestdruck, wie für den Förderstrahl, vorgesehen werden muss . Durch die Membrankolbenpumpe lässt sich damit ein sehr niedriger Druck, z.B. die oben ge- nannten 0,8 bara oder weniger, hinter dem weitern Wasserstoffseparationsmodul 10 erzielen. Des weiteren ist es sehr günstig, dass die Membrankolbenpumpe robust und sehr kostengünstig ist . Sie kann außerdem sehr kompakt gebaut werden kann, was Sie insbesondere für den Einsatz in mobilen Syste- men interessant macht.According to the exemplary embodiment shown here, the hydrogen delivery device 12, like the delivery device 9, can be designed as a diaphragm piston pump, but other delivery means are also conceivable. The advantage in such a diaphragm piston pump, however, lies in its efficiency, which is significantly better than that of a jet pump, and in the fact that no system-related minimum pressure, as for the delivery jet, has to be provided. A very low pressure, for example the 0.8 bar a or less mentioned above, can thus be achieved behind the further hydrogen separation module 10 by means of the membrane piston pump. Furthermore, it is very favorable that the diaphragm piston pump is robust and very inexpensive. It can also be built very compact, which makes it particularly interesting for use in mobile systems.
Eine alternative, hier nicht dargestellte Ausgestaltung kann dennoch eine Strahlpumpe als Wasserstofffördereinrichtung 12 vorsehen, welche jedoch so ausgebildet ist, dass deren För- derstrahl eine deutlich höhere Dichte und einen deutlich höheren Druck aufweist als der von ihm aus dem Bereich des weiteren Wasserstoffseparationsmoduls 10 geförderte Wasserstoff. Da Druck und Dichte des Mediums, welches den Förderstrahl bildet, unmittelbar das durch die Strahlpumpe zu erzielenden Ergebnis beeinflusst, lässt sich auch so ein niedriger Druck des Wasserstoffs hinter dem weiteren Wasserstoffseparationsmodul 10 erreichen. Beispielsweise kann Wasser bei einem Druck von mehr als 5 bara, insbesondere bei ca. 10 bara, als Förderstrahl genutzt werden. Dadurch findet gleichzeitig die ohnehin erforderliche Befeuchtung und eine Kühlung eines Teil des zu dem Anodenraum strömenden Wasserstoffs durch die mit Wasser betriebene Strahlpumpe statt . Der Förderstrom gelangt z.B. aus einem Vorratsbehälter über einen Pumpe in den Bereich der dann als Strahlpumpe ausgebildeten Wasserstofffördereinrichtung 12. Der Förderstrom reißt den aus dem weiteren Wasserstoffseparationsmodul 10 kommenden Wasserstoff mit und erzeugt im Bereich zwischen dem weiteren Wasserstoffseparationsmodul 10 und der Wasserstofffördereinrichtung 12 den gewünschten niedrigen Druck p2. Falls erforderlich wird das den Förderstrom bildende Wasser danach in einem Abscheider zumindest teilweise wieder aus dem den Wasserstoff aufweisenden Stoffström abgeschieden.An alternative embodiment, not shown here, can nevertheless provide a jet pump as a hydrogen delivery device 12, which, however, is designed in such a way that its delivery jet has a significantly higher density and a significantly higher pressure than the hydrogen which it delivers from the area of the further hydrogen separation module 10 , Since the pressure and density of the medium which forms the delivery jet directly influences the result to be achieved by the jet pump, a low pressure of the hydrogen behind the further hydrogen separation module 10 can also be achieved in this way. For example, water in one Pressure of more than 5 bar a , especially at about 10 bar a , can be used as a delivery jet. As a result, the humidification and cooling of part of the hydrogen flowing to the anode compartment, which is required anyway, takes place simultaneously by means of the jet pump operated with water. The feed stream reaches, for example, a pump via a pump into the area of the hydrogen delivery device 12, which is then designed as a jet pump. The delivery flow entrains the hydrogen coming from the further hydrogen separation module 10 and generates the desired low pressure in the area between the further hydrogen separation module 10 and the hydrogen delivery device 12 p 2 . If necessary, the water forming the delivery flow is then at least partially separated from the hydrogen-containing material flow in a separator.
Wird die Vorrichtung 1 gemäß der in Fig. 1 dargestellten Ausführung beispielsweise mit einem wasserstoffhaltigen Gasstrom aus einer Wasserstofferzeugungseinrichtung 4 betrieben, wel- ehe nach dem Prinzip der autothermen Reformierung arbeitet, so werden im Feedgas typische Konzentrationen von Wasserstoff in der Größenordnung von ca. 40% erzielt. Das wasserstoffhaltigen Gasstrom bzw. Feedgas soll dabei einen Druck von ca. 10 bara aufweisen. Die Vorrichtung 1 ist so aufgebaut, dass die aktive Fläche des ersten Wasserstoffseparationsmodul 2 zum weiteren Wasserstoffseparationsmodul 10 ca. 3:1 beträgt. Sie wird so betrieben, dass der Druck px hinter dem ersten Wasserstoffseparationsmodul 2 ca. 1,15 bara beträgt. Bei einem Druck p2 von ca. 0,8 bara hinter dem weiteren Wasserstoffse- parationsmodul 10 kann so ein Gesamtwirkungsgrad in der Größe von 85% bis 90% erzielt werden. Ein einzelnes Wasserstoffseparationsmodul würde unter ähnlichen Bedingungen zum Vergleich nur etwa 80% Wirkungsgrad erreichen.If the device 1 according to the embodiment shown in FIG. 1 is operated, for example, with a hydrogen-containing gas stream from a hydrogen generation device 4, which works according to the principle of autothermal reforming, then typical concentrations of hydrogen in the feed gas of the order of about 40% achieved. The hydrogen-containing gas stream or feed gas should have a pressure of approximately 10 bar a . The device 1 is constructed such that the active area of the first hydrogen separation module 2 to the further hydrogen separation module 10 is approximately 3: 1. It is operated such that the pressure p x behind the first hydrogen separation module 2 is approximately 1.15 bar a . At a pressure p 2 of approximately 0.8 bar a downstream of the further hydrogen separation module 10, an overall efficiency in the size of 85% to 90% can be achieved. A single hydrogen separation module would only achieve about 80% efficiency under similar conditions for comparison.
Der Anodenkreislauf 8 ist dabei für die Funktionsweise der in Fig. 1 beschriebenen Vorrichtung 1 genau sowenig notwendig, wie bei der unten beschriebenen Vorrichtung 1 in Fig. 2. Er ist jedoch wie bei allen Systemen, welche dem Anodenraum 6 der Brennstoffzelle 7 nahezu reinen Wasserstoff zuführen, unabhängig aus welche Quelle dieser Wasserstoff stammt, für den Betrieb der Brennstoffzelle 7 sinnvoll.The anode circuit 8 is just as little necessary for the functioning of the device 1 described in FIG. 1 as for the device 1 described in FIG. 2 However, as with all systems which supply almost pure hydrogen to the anode compartment 6 of the fuel cell 7, irrespective of the source of this hydrogen, it makes sense for the operation of the fuel cell 7.
Außerdem ist im Bereich der Leitung 11 ein Wassergasshiftreaktor 14 angeordnet ist. Dieser Wassergasshiftreaktor 14 kann z.B. als Hochtemperaturshiftstufe ausgebildet sein, in welcher bei Temperaturen von ca. 350-400°C eine Wasser- gasshiftreaktion abläuft, bei der aus Wasser und Kohlenmonoxid Wasserstoff und Kohlendioxid entsteht . Der Vorteil eines derartigen Wassergasshiftreaktor 14 liegt nun zum einen darin, dass durch den Wassergasshiftreaktor 14 der Ausstoß an giftigem Kohlenmonoxid reduziert wird. Zum anderen wird aus dem im Restgasstrom vorhandenen Kohlenmonoxid und Wasser nochmals Wasserstoff erzeugt, so dass dem weiteren Wasserstoffseparationsmodul 10 eine höhere Wasserstoffkonzentration in dem Restgasstrom angeboten werden kann. In dem wasserstoffhaltigen Gasstrom ist vor dem ersten Wasserstoffsepara- tionsmodul 2, wenn dieser aus einer auf einer autothermen Reformierung mit einer nachfolgenden Hochtemperaturshiftstufe basierenden Wasserstofferzeugungseinrichtung 4 stammt ein Kohlenmonoxidgehalt von ca. 2,5% zu erwarten. Nachdem ersten Wasserstoffseparationsmodul 2 wird diese Konzentration auf- grund der sich wegen des abgetrennten Wasserstoffs verringernden Gasmenge des Restgasstroms gegenüber dem Wasserstoff- haltigen Gasstrom auf rund 5 bis 7% ansteigen. Durch den Wassergasshiftreaktor 14 wird dieser Kohlenmonoxidgehalt wieder auf ca. 2,5% gesenkt, wozu ein Teil des Kohlenmonoxids mit dem Wasser zu Kohlendioxid und Wasserstoff umgewandelt wird. Dieser Wasserstoff lässt sich zusammen mit dem ohnehin in dem Restgasstrom vorhanden Wasserstoff dann zu einem großen Teil in dem Wasserstoffseparationsmodul 10 aus dem Restgasstrom abtrennen.In addition, a water gas shift reactor 14 is arranged in the region of the line 11. This water gas shift reactor 14 can e.g. be designed as a high-temperature shift stage in which a water gas shift reaction takes place at temperatures of approximately 350-400 ° C., in which hydrogen and carbon dioxide are produced from water and carbon monoxide. The advantage of such a water gas shift reactor 14 is firstly that the emission of toxic carbon monoxide is reduced by the water gas shift reactor 14. On the other hand, hydrogen is again generated from the carbon monoxide and water present in the residual gas stream, so that a further hydrogen separation module 10 can be offered a higher hydrogen concentration in the residual gas stream. A carbon monoxide content of approx. 2.5% is to be expected in the hydrogen-containing gas stream upstream of the first hydrogen separation module 2 if this comes from a hydrogen generation device 4 based on an autothermal reforming with a subsequent high-temperature shift stage. After the first hydrogen separation module 2, this concentration will increase to around 5 to 7% due to the gas quantity of the residual gas stream which is reduced due to the separated hydrogen compared to the hydrogen-containing gas stream. This carbon monoxide content is reduced again to approximately 2.5% by the water gas shift reactor 14, for which purpose a portion of the carbon monoxide is converted with the water to carbon dioxide and hydrogen. This hydrogen can then be largely separated from the residual gas stream together with the hydrogen already present in the residual gas stream in the hydrogen separation module 10.
Durch den Einsatz des Wassergasshiftreaktors 14 lässt sich der Gesamtwirkungsgrad der Abtrennung des Wasserstoffs aus dem wasserstoffhaltigen Gasstrom gegenüber einem Aufbau ohne Wassergasshiftstufe 14 um nochmals 2-3% steigern. Damit kann eine Gesamtutilisation der Wasserstoffabtrennung von über 90% auch bei vergleichsweise wenig Wasserstoff in dem wasserstoffhaltigen Gasstrom, z.B. ca. 40% bei autothermer Refor-- mierung, realisiert werden. Bei Verwendung zusammen mit einem aus einer Dampfreformierung stammenden Feedgasstrom mit ca. 65% Wasserstoff lassen sich Utilisationen von 95-98% erreichen.By using the water gas shift reactor 14, the overall efficiency of the separation of the hydrogen can be determined Increase the hydrogen-containing gas flow by another 2-3% compared to a structure without water gas shift stage 14. This enables a total utilization of the hydrogen separation of over 90% to be achieved even with comparatively little hydrogen in the hydrogen-containing gas stream, e.g. approx. 40% with autothermal reforming. Utilizations of 95-98% can be achieved when used together with a feed gas stream with approx. 65% hydrogen originating from steam reforming.
Um die Verwendung der Wasserstoffseparationsmodule 2 und 10 zusammen mit der Wassergasshiftreaktor 14 möglichst effektiv zu gestalten, sollte auf eine Zwischenkühlung und/oder Erwärmung des Restgasstroms zwischen den Bauteilen 2, 14, 10 ver- ziehtet werden. Dies kann in günstiger Weise durch die Verwendung von Membranen in den Wasserstoffseparationsmodule 2, 10 erreicht werden, welche ähnliche Betriebstemperaturen wie der Wassergasshiftreaktor 14 benötigen oder zumindest tolerieren. Der Aufbau ist also prädestiniert für den Einsatz vom metallischen Membranen, mit ihrer hohen Selektivität, in denIn order to make the use of the hydrogen separation modules 2 and 10 together with the water gas shift reactor 14 as effective as possible, intermediate cooling and / or heating of the residual gas flow between the components 2, 14, 10 should be delayed. This can be achieved in a favorable manner by using membranes in the hydrogen separation modules 2, 10, which require or at least tolerate similar operating temperatures to the water gas shift reactor 14. The structure is therefore predestined for the use of metallic membranes, with their high selectivity, in the
Wasserstoffseparationsmodulen 2, 10, z.B. auf Basis von Palladium Legierungen.Hydrogen separation modules 2, 10, e.g. based on palladium alloys.
In Fig. 2 ist die Vorrichtung 1 in einer Ausgestaltung mit zwei Wasserstoffseparationsmodulen 2, 10 und einem Wassergasshiftreaktor 14 dargestellt. Dieselbe Vorrichtung 1 ist in Fig. 3 nochmals in einem Teilschnitt zu erkennen.2 shows the device 1 in an embodiment with two hydrogen separation modules 2, 10 and a water gas shift reactor 14. The same device 1 can be seen again in FIG. 3 in a partial section.
Die beiden Wasserstoffseparationsmodule 2 und 10 sowie der Wassergasshiftreaktor 14 sind bei dem Aufbau gemäß den Figuren 2 und 3 in einem einzigen Bauteil integriert. Der über die Leitung 3 einströmende wasserstoffhaltigen Gasstrom bzw. Feedgasstrom gelangt zuerst in das erste Wasserstoffseparationsmodul 2, in welchem ein großer Teil des Wasserstoffs in dem wasserstoffhaltigen Gasstrom abgetrennt wird und durch einen hier nur teilweise dargestellten Sammler 15 in die Leitung 5 und zu der Zusammenführung 13 gelangt. Der Restgastrom strömt nach dem ersten Wasserstoffseparationsmodul 2 durch die hier als Kanal ausgebildete Leitung 11 in den Wassergasshiftreaktor 14. Die Strömungsrichtung in dem Wassergas- shiftreaktor 14 ist dabei in etwa senkrecht zu der hauptsäch- liehen Strömungsrichtung in dem ersten Wasserstoffseparationsmodul 2 ausgebildet.The two hydrogen separation modules 2 and 10 and the water gas shift reactor 14 are integrated in a single component in the construction according to FIGS. 2 and 3. The hydrogen-containing gas stream or feed gas stream flowing in via line 3 first arrives in the first hydrogen separation module 2, in which a large part of the hydrogen in the hydrogen-containing gas stream is separated and through a collector 15, which is only partially shown here, into line 5 and to the junction 13 arrives. The residual gas flow flows after the first hydrogen separation module 2 through the line 11 formed here as a channel into the water gas shift reactor 14. The direction of flow in the water gas shift reactor 14 is approximately perpendicular to the main direction of flow in the first hydrogen separation module 2.
Nach dem Wassergasshiftreaktor 14 schließt sich erneut ein Abschnitt der als Kanal ausgebildeten Leitung 11 an, welcher den nun mit Wasserstoff wieder angereicherten Restgasstrom dem weiteren Wasserstoffseparationsmodul 10 zuführt. Auch hier wird die Strömungsrichtung nochmals um 90° gedreht, so dass das weitere Wasserstoffseparationsmodul 10 eine hauptsächliche Strömungsrichtung aufweist, welche um 180° gedreht zu der hauptsächlichen Strδmungsrichtung des ersten Wasserstoffseparationsmodul 2 verläuft. Auch das weitere Wasserstoffseparationsmodul 10 weist einen Sammler 16 auf, von welchem der abgetrennte Wasserstoff zu der Wasserstofffördereinrichtung 12 strömen kann. Das verbleibende Restgas nach dem weiteren Wasserstoffseparationsmodul 10 verlässt das Bauteil dann im Gegenstrom zum Feedgas .After the water gas shift reactor 14, a section of the line 11 designed as a channel connects again, which feeds the residual gas stream, which has now been enriched again with hydrogen, to the further hydrogen separation module 10. Here, too, the flow direction is rotated again by 90 °, so that the further hydrogen separation module 10 has a main flow direction, which is rotated by 180 ° to the main flow direction of the first hydrogen separation module 2. The further hydrogen separation module 10 also has a collector 16, from which the separated hydrogen can flow to the hydrogen delivery device 12. The remaining gas after the further hydrogen separation module 10 then leaves the component in countercurrent to the feed gas.
In Fig. 3 ist aus diesem Aufbau lediglich das erste Stück der als Kanal ausgebildeten Leitung 11 herausgeschnitten, so dass die Strömungswege in den jeweiligen Komponenten 2 und 14 leichter zu erkennen sind.In FIG. 3, only the first piece of the line 11 designed as a channel is cut out of this structure, so that the flow paths in the respective components 2 and 14 are easier to recognize.
Dieser Aufbau der beiden Wasserstoffseparationsmodule 2, 10 und des Wassergasshiftreaktors 14 erlaubt eine sehr platzspa- rende Anordnung, welche sehr kompakt und damit letztendlich auch mit vergleichsweise wenig Gewicht realisiert werden kann. Durch die Strömungsführung wird zusätzlich erreicht, dass alle Anschlüsse an dem Bauteil von einer Seite aus zugänglich sind. Die ist insbesondere beim Einsatz unter engen räumlichen Bedingungen, wie sie häufig in mobilen Systemen anzutreffen sind, bei der Montage und Wartung sehr günstig. Die Vorrichtung 1 sowie das Verfahren zum Abtrennen von Wasserstoff aus einem wasserstoffhaltigen Gasstrom können prinzipiell bei allen Arten von Brennstoffzellenanlagen Verwendung finden, unabhängig davon, ob diese in einem mobilen Sys- tem, wie z.B. ein Fahrzeug zu Land, zu Wasser oder in der Luft, in einer mobilen Notstromversorgungseinrichtung oder in einer stationären Anlage eingesetzt werden.This structure of the two hydrogen separation modules 2, 10 and the water gas shift reactor 14 allows a very space-saving arrangement, which is very compact and, ultimately, can also be realized with comparatively little weight. The flow guidance also ensures that all connections on the component are accessible from one side. This is very inexpensive, particularly when used under tight spatial conditions, as can often be found in mobile systems, during assembly and maintenance. The device 1 and the method for separating hydrogen from a hydrogen-containing gas stream can in principle be used in all types of fuel cell systems, regardless of whether they are in a mobile system, such as a vehicle on land, on water or in the air, be used in a mobile emergency power supply facility or in a stationary system.
Der bevorzugte Einsatzzweck einer derartigen, wirkungsgradop- timierten und kompakt zu bauenden Brennstoffzellenanlage liegt jedoch in der Verwendung als Hilfsenergieerzeuger (Auxiliary Power Unit/APU) in einem mobilen System. Die Brennstoffzellenanlage soll dabei nicht -was jedoch auch denkbar wäre - für die Versorgung des mobilen Systems mit Antriebs- energie vorgesehen sein, sondern für die unabhängig vom Antrieb ausgeführte Bereitstellung von Energie für Hilfs- und Nebenaggregate, wie z.B. die Fahrzeugelektronik, eine Klimaanlage, eine Kommunikationseinrichtung, eine Navigationseinrichtung und dergleichen. The preferred application of such an efficiency-optimized and compact fuel cell system is, however, for use as an auxiliary power unit (APU) in a mobile system. The fuel cell system should not be provided - which would also be conceivable - for supplying the mobile system with drive energy, but for the provision of energy for auxiliary and auxiliary units, such as e.g. the vehicle electronics, an air conditioner, a communication device, a navigation device and the like.

Claims

DaimlerChrysler AGPatentansprüche DaimlerChrysler AG patent claims
Vorrichtung zum Abtrennen von zumindest nahezu reinem Wasserstoff aus einem wasserstoffhaltigen Gasstrom, insbesondere einem Gasstrom aus einer Wasserstofferzeugungseinrichtung, zum Betreiben einer Brennstoffzelle, wobei ein erstes Wasserstoffseparationsmodul vorhanden ist, welches das wasserstoffhaltige Gas in einen zumindest nahezu reinem Wasserstoffgasstrom und einen Restgasstrom aufteilt, und wobei in Strömungsrichtung des Restgas- Stroms wenigstens ein weiteres Wasserstoffseparationsmodul angeordnet ist, welches den Restgasstrom erneut in zumindest nahezu reinen Wasserstoff und Restgas aufteilt d a d u r c h g e k e n n z e i c h n e t , dass in Strδmungsrichtung des Restgasstroms vor dem wenigstens einen weiteren Wasserstoffseparationsmodul (10) ein Wassergasshiftreaktor (14) angeordnet ist.Device for separating at least almost pure hydrogen from a hydrogen-containing gas stream, in particular a gas stream from a hydrogen generation device, for operating a fuel cell, wherein a first hydrogen separation module is present which divides the hydrogen-containing gas into an at least almost pure hydrogen gas stream and a residual gas stream, and in At least one further hydrogen separation module is arranged in the direction of flow of the residual gas flow, which again divides the residual gas flow into at least almost pure hydrogen and residual gas, characterized in that a water gas shift reactor (14) is arranged upstream of the at least one further hydrogen separation module (10) in the flow direction of the residual gas flow.
Vorrichtung nach Anspruch 1, d a d u r c h g e k e n n z e i c h n e t , dass das erste Wasserstoffseparationsmodul (2) , der Wassergasshiftreaktor (14) und das wenigstens eine weiteren Wasserstoffseparationsmodul (10) als ein integriertes Bauteil ausgebildet sind.Device according to Claim 1, so that the first hydrogen separation module (2), the water gas shift reactor (14) and the at least one further hydrogen separation module (10) are designed as an integrated component.
Vorrichtung nach Anspruch 1 oder 2, d a d u r c h g e k e n n z e i c h n e t , dass in Strδmungsrichtung des nahezu reinen Wasserstoffs nach dem wenigstens einen weiteren Wasserstoffseparati- onsmodul (10) eine Wasserstof ffördereinrichtung (12) angeordnet ist .Apparatus according to claim 1 or 2, characterized in that in the direction of flow of the almost pure hydrogen after the at least one further hydrogen separa- onsmodul (10) a hydrogen conveyor (12) is arranged.
4. Vorrichtung Anspruch 3 , d a d u r c h g e k e n n z e i c h n e t , dass die Wasserstof ffördereinrichtung (12) als Membrankolbenpumpe ausgebildet ist.4. The device of claim 3, so that the hydrogen delivery device (12) is designed as a diaphragm piston pump.
5. Vorrichtung nach Anspruch 3 oder 4, d a d u r c h g e k e n n z e i c h n e t , dass der Wasserstoff aus dem wenigsten einen weiteren Wasserstoffseparationsmodul (10) nach der Wasserstofffördereinrichtung (12) mit dem Wasserstoffgasstrom aus dem ersten Wasserstoffseparationsmodul (2) zusammengeführt ist .5. Apparatus according to claim 3 or 4, so that the hydrogen from the least one further hydrogen separation module (10) after the hydrogen delivery device (12) is brought together with the hydrogen gas flow from the first hydrogen separation module (2).
6. Vorrichtung nach Anspruch 5, d a d u r c h g e k e n n z e i c h n e t , dass in Strömungsrichtung der Wasserstoffgasströme nach der Zusammenführung (13) ein Anodenraum (6) der Brennstoffzelle (7) angeordnet ist, wobei das aus dem Anodenraum (6) der Brennstoffzelle (7) ausströmende Gas in einem Anodenkreislauf (8) in den Bereich des in den Anodenraum (6) einströmenden Wasserstoffgases zurückgeführt ist, wobei in dem Anodenkreislauf (8) eine Fördereinrichtung (9) vorgesehen ist.6. The device according to claim 5, characterized in that an anode space (6) of the fuel cell (7) is arranged in the flow direction of the hydrogen gas streams after the merging (13), wherein the gas flowing out of the anode space (6) of the fuel cell (7) in one Anode circuit (8) is returned to the area of the hydrogen gas flowing into the anode space (6), a conveyor device (9) being provided in the anode circuit (8).
7. Vorrichtung Anspruch 6, d a d u r c h g e k e n n z e i c h n e t , dass die Fördereinrichtung (9) in dem Anodenkreislauf (8) als Membrankolbenpumpe ausgebildet ist .7. The device of claim 6, so that the delivery device (9) in the anode circuit (8) is designed as a diaphragm piston pump.
8. Vorrichtung nach einem der Ansprüche 1 bis 7, d a d u r c h g e k e n n z e i c h n e t , dass die aktive Fläche des wenigstens einen weiteren Wasserstoffseparationsmodul (10) den 0,1 bis 0,3-fachen Flä- cheninhalt der aktiven Fläche des ersten Wasserstoffseparationsmoduls (2) aufweist.8. Device according to one of claims 1 to 7, characterized in that the active area of the at least one further hydrogen separation module (10) 0.1 to 0.3 times the area. Chen content of the active surface of the first hydrogen separation module (2).
9. Verfahren zum Abtrennen von zumindest nahezu reinem Wasserstoff aus einem wasserstoffhaltigen Gasstrom, insbesondere einem Gasstrom aus einer Wasserstofferzeugungseinrichtung, zum Betreiben einer Brennstoffzelle, wobei zuerst das wasserstoffhaltige Gas in einem ersten Wasserstoffseparationsmodul in einen zumindest nahezu reinem Wasserstoffgasstrom und einen Restgasstrom aufteilt wird, wonach der Restgasstrom in wenigstens einem weiteren Wasserstoffseparationsmodul erneut in zumindest nahezu reinen Wasserstoff und Restgas aufteilt wird, d a d u r c h g e k e n n z e i c h n e t , dass der Restgasstrom vor dem wenigstens einen weiteren Wasserstoffseparationsmodul (10) einer Wassergasshiftreaktion unterzogen wird.9.Method for separating at least almost pure hydrogen from a hydrogen-containing gas stream, in particular a gas stream from a hydrogen generation device, for operating a fuel cell, the hydrogen-containing gas first being divided into an at least almost pure hydrogen gas stream and a residual gas stream in a first hydrogen separation module, after which the Residual gas stream in at least one further hydrogen separation module is again divided into at least almost pure hydrogen and residual gas, characterized in that the residual gas stream is subjected to a water gas shift reaction before the at least one further hydrogen separation module (10).
10. Verfahren nach Anspruch 9, d a d u r c h g e k e n n z e i c h n e t , dass ein Druck (pi) des Wasserstoffs nach dem ersten Wasserstoffseparationsmodul (2) unter 1,2 bara (absoluter Druck) gehalten wird, während ein Druck (p2) des Wasserstoff nach dem wenigstens einen weiteren Wasserstoffseparationsmodul (10) unter 0,9 bara gehalten wird, wobei die Druckdifferenz zwischen den beiden Wasserstoffströmen ü- ber eine Wasserstofffördereinrichtung (12) ausgeglichen wird.10. The method according to claim 9, characterized in that a pressure (pi) of the hydrogen after the first hydrogen separation module (2) is kept below 1.2 bar a (absolute pressure), while a pressure (p 2 ) of the hydrogen after the at least one Another hydrogen separation module (10) is kept below 0.9 bar a , the pressure difference between the two hydrogen streams being compensated for by a hydrogen delivery device (12).
11. Verfahren nach Anspruch 9 oder 10, d a d u r c h g e k e n n z e i c h n e t , dass der Anteil an Wasserstoff, welcher in dem ersten Wasserstoffseparationsmodul (2) aus dem wasserstoffhaltigen Gasstrom abgetrennt wird mindestens 75%, insbesondere ca. 90%, des insgesamt aus dem wasserstoffhaltigen Gasstrom abgetrennten Wasserstoffs ausmacht . 11. The method according to claim 9 or 10, characterized in that the proportion of hydrogen which is separated from the hydrogen-containing gas stream in the first hydrogen separation module (2) makes up at least 75%, in particular approximately 90%, of the total hydrogen separated from the hydrogen-containing gas stream ,
2. Verwendung des Verfahrens und/oder der Vorrichtung nach einem der vorhergehenden Ansprüche für einen auf einer Brennstoffzelle basierten Hilfsenergieerzeuger (Auxiliary Power Unit/APU) in einem mobilen System, insbesondere einem Kraftfahrzeug, welches zumindest den größten Teil seiner zur Mobilität erforderlichen Antriebsenergie von einem weiteren Energieerzeuger, insbesondere einem Verbrennungsmotor, bezieht. 2. Use of the method and / or the device according to one of the preceding claims for an auxiliary power unit (APU) based on a fuel cell in a mobile system, in particular a motor vehicle, which has at least the largest part of its drive energy required for mobility by one further energy producers, in particular an internal combustion engine.
PCT/DE2003/002902 2002-09-09 2003-09-02 Device and method for separating almost pure hydrogen from a gas flow containing hydrogen WO2004024299A1 (en)

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