Membrane for the separation of hydrogen, methanol reformer using this membrane and process for its operation

0001The invention relates to a membrane for separation of Hydrogen from a gas mixture at a such a Equipped membrane methanol reformer and a A method for operating such a plant.

0002A known technique for preparing high purity hydrogen is therein, from appropriate starting materials by means of a corresponding chemical reaction, a hydrogen-containing gas mixture to produce and because of this the hydrogen via a separate Wasserstoffabtrennmembran, which is designed so that of the gas mixture components specifically only the hydrogen can diffuse through it. An important application are reforming systems for hydrogen production, eg plants for the steam reforming of methanol. By Reforming reaction of a suitable hydrocarbon, among for simplicity hereinafter also hydrocarbon derivatives to be understood, such as methanol, produced a hydrogen-containing reformate gas from which the hydrogen is separated by a hydrogen separation, which as essential element contains the Wasserstoffabtrennmembran. In Methanol reforming systems of this type, as described in the patents US 4,981,676 and US 5,229,102 are disclosed, is the Hydrogen separation in the reforming reactor stage characterized integrated that Wasserstoffabtrennmembran a the reforming reaction chamber limiting side wall of the reactor forms. Alternatively, the hydrogen separation as the reactor stage downstream, self-contained unit to be realized.

0003Recently, reforming plants are propagated for Hydrogen Production suggested for mobile use, especially for the production of hydrogen for the fuel cells of a fuel-cell vehicle. This has the Advantage that no expensive hydrogen storage in vehicles is required, but instead of starting material used for the reforming reaction hydrocarbon, in particular Methanol, is carried in liquid form, which considerably is less problematic. Especially for this purpose in motor vehicles, it is desirable, as rapidly as possible After starting the vehicle, and thus the hydrogen-providing Refomierungsanlage hydrogen by investing in To ask an amount sufficient to enable the A fuel cell system according to the required vehicle drive power quickly can provide.

0004Since most of the hydrogen-donating reforming reactions at run an opposite room temperature elevated temperature, such as eg the particularly important for use in vehicles steam reforming of methanol, it is already known, the Reforming reaction chamber at least during cold start phases heat. So has the method disclosed in the aforementioned US 4,981,676 Conditioning a gas burner assembly, in a suitable, supplied fuel / air mixture at an open flame on the Outer side of a cylindrical outer wall of the annular cylinder The reaction chamber is combusted, the radially inward from limited hollow cylinder designed Wasserstoffabtrennmembran becomes. Alternatively to burners with an open flame it is known the reaction chamber using a catalytic, flame free Combustion process or flow onto a outside generated the reactor, hot gas or liquid stream to heat. Another known technique is the Disposing an external heating system for the reactor, as in the patent US 5,674,301 discloses.

0005In the published patent application JP 06-345408 A is a methanol reforming reactor discloses the plate stack type in which a Hydrogen deduction layer bounded on both sides by a membrane plate is, on the opposite side in each case a reforming catalyst layer followed. At the reforming catalyst layer adjacent to which the hydrogen-trigger diaphragm plate opposite sides a combustion catalyst layer at. In this combustion catalyst layers may be carried out a catalytic combustion to the Reactor and in particular the reforming reaction chamber forming to heat reforming catalyst layers.

0006The invention is the technical problem of providing eienr Wasserstoffabtrennmembran, an equipped so Methanol reforming system and a method of operation for same with improved cold-start performance based, by a makes possible rapid reaching the operating temperature becomes.

0007The invention solves this problem by providing a Wasserstoffabtrennmembran with the features of claim 1, a Methanol reforming system with the features of claim 3 as well as an operating method thereof having the features of Claim 4. Characteristically, the Wasserstoffabtrennmembran at least one side with a catalyst layer provided for a predetermined catalytic combustion process. By flow onto the membrane on this page with the reactants of the catalytic combustion process in question may be under the action of the catalyst layer where this catalytic Verbrennungsproezß conduct which in this Way directly and immediately heats the Wasserstoffabtrennmembran. In a methanol reforming system according to claim 3 can consequently their hydrogen separation by means of direct, flameless heating of Wasserstoffabtrennmembran very quickly by the method according to claim 4 to operating temperature bring.

0008If the hydrogen separation integrated with the reactor stage is also characterized, the reaction chamber is heated indirectly.

0009In addition, as required immediate heating also the reaction chamber in one of the conventional ways appropriate be. While in the conventional approach, only the reaction space to heat directly, a loss of heat from the reaction chamber passing into the hydrogen separation reforming product gas during cold start phase characterized occurs that This first heat the still cold Wasserstoffabtrennmembran must, this heat loss can be by the ability of be inventive membrane, directly heated catalytically can advantageously avoid. This means the system brought total operating temperature more quickly, which particularly in mobile use in fuel cell powered motor vehicles is desirable. Especially with this application, it may be necessary, the hydrogen separation after a each plant shutdown initially cooled in a Hibernate to enable and activate from there again, which according to the invention very quickly and with relatively little can take place effort.

0010A further embodiment according to claim 2 Wasserstoffabtrennmembran is coated with a catalyst layer, the catalytic a Combustion process for hydrogen and / or methanol catalyzed. This is especially for hydrogen generating reforming plants and especially methanol reforming systems of Advantage, since in these, the hydrogen or methanol systemic is available and therefore no additional other fuel for the catalytic combustion process to heat the membrane must be provided.

0011An advantageous embodiment of the invention is in the Drawings and is described below. in this connection show:<dl tsize="7"><dt>Fig. 1</dt><dd>a schematic block diagram representation of the invention substantially A part for use in a suitable fuel-cell vehicle Methanol reformer in cold start mode and</dd><dt>FIG. 2</dt><dd>a view corresponding to Fig. 1, but in the warmed-up Operating condition.</dd></dl>

0012Fig. 1 shows schematically a plant for methanol reforming Obtaining hydrogen for a fuel cell system of a motor vehicle with their interest here components during operation during a cold start phase. The facility includes a central part of a reactor stage with a reaction chamber 1, the with a for catalysing steam reforming reaction filled methanol suitable catalyst pellet fill is. The reactor stage is connected upstream of an evaporator 2, the via a first supply line 3 liquid water and an second supply line 4 liquid methanol from each, not shown storage tank is supplied. The two liquids be in the evaporator 2 to a methanol / water vapor mixture 5 evaporated, the sufficiently high temperature in the reaction chamber 1 is initiated.

0013On the side of the reaction chamber 1 joins on one side a hydrogen separation stage 6, and on the other side a catalytic Burner 7 on, both to the reaction chamber 1 are integrated a common reforming reactor unit. The hydrogen separation 6 includes a hydrogen plenum 8 and a Wasserstoffabtrennmembran 9, which as a boundary wall of the reaction chamber 1 opposite the hydrogen plenum 8 acts. The Wasserstoffabtrennmembran 9 is constructed, that they of the present in the reaction chamber 1 gas constituents selectively diffuse only the hydrogen produced leaves. It consists to a suitable material, for example, of palladium or a palladium alloy. On the other Page is the reaction chamber 1 by means of a gas-impermeable, However, good heat conducting partition 10 from a boiler room 11 of the catalytic burner 7 separately. The evaporator has 2 to produce the methanol / water vapor mixture 5 a suitable Heater, such as an electric heating element or a burner, wherein in the latter case, this evaporator-side Burner with the adjacent to the reaction chamber 1 catalytic integrated burner 7 to a common burner unit may be, if desired.

0014The Wasserstoffabtrennmembran 9 is characteristically on its the hydrogen collecting chamber 8 facing side with a Catalyst layer 13 coated which a flameless combustion process of hydrogen and / or methanol with oxygen catalyzed. Here, the catalyst layer 13 of any For this purpose, the known materials, for example from Platinum, being applied so that by the hydrogen diffusion not appreciably affected by the membrane 9 through becomes. This is eg characterized realized that a also used hydrogen permeable catalyst material or the catalyst layer 13 with sufficiently low thickness and / or not the whole area, but as a porous layer or in structured form, leaving uncoated surface regions, for example, is applied as a grid pattern. With the help of Catalyst layer 13, the Wasserstoffabtrennmembran 9 directly are heated by the thus-coated side of the membrane with the corresponding combustion gas mixture, ie, a mixture of oxygen or an oxygen-containing gas on the one hand, hydrogen and / or methanol on the other hand, flows against becomes. If necessary, a both sides with such a Catalyst layer provided membrane used and this on both sides flows against the associated combustion gas mixture will. In addition, several membranes in sheet or From disk are combined to form a membrane module.

0015While the illustrated in Fig. 1 operating situation a Cold start phase is in the boiler room 11 of the catalytic burner 7 a suitable fuel supplied to B and there flameless catalytically burned. As fuel B can fluently in Vehicle entrained methanol or during a previous Operational phase produced hydrogen or any other Material used. On the output side of Brennerheizraums 11 the associated flue gas A1 is discharged. enters the combustion heat produced in the catalytic burner 7 via the heat conductive partition wall 10 into the reaction chamber 1 and heated there, the catalyst pellet fill a to Steam reforming of methanol sufficient operating temperature on. Simultaneously, a catalytically via an inlet line 12 combustible gas mixture of oxygen and one part Hydrogen and / or methanol on the other hand in the hydrogen plenum 8 introduced. This gas mixture combusts catalytically flameless, and thus on the catalyst layer corresponding to the 13 provided, facing the hydrogen plenum 8 Side of Wasserstoffabtrennmembran 9. The generated Daduchus Combustion heat directly heats the Wasserstoffabtrennmembran 9 on the operating temperature.

0016The evaporator 2 to the reaction space 1, the methanol / water vapor mixture 5 with this cold start operating phase yet relatively low rate to, with increasing the operating temperature the reactor stage can be increased, so that the supplied is mixture always completely reformed. From a temperature of about 100 ° C passes the resulting in the reaction chamber 1 Hydrogen by Wasserstoffabtrennmembran 9 in the Hydrogen collecting space 8, from which it via an outlet conduit 14 discharged and, for example, to a fuel cell system is forwarded. On the other hand prevents the Wasserstoffabtrennmembran 9 the passage of the other components of the reaction space 1 generated reforming product gas, in particular the as a fuel cell poison acting carbon monoxide, so that these Residual components R via an outlet conduit 15 with the reaction chamber 1 leave. Before reaching the necessary operating temperature the hydrogen may be burned in the catalytic burner 7 will.

0017The direct heating of the reaction chamber on the one hand and the hydrogen separation stage 6, in particular the Wasserstoffabtrennmembran 9, on the other hand reaches the reformer relatively quickly its operating temperature, typically within a few seconds. Once this is the case, the Plant switched to the operation shown in FIG. 2. The introduction the gas mixture of oxygen and hydrogen and / or methanol in the hydrogen plenum 8 for the purpose of catalytic Combustion at the Wasserstoffabtrennmembran is terminated so that then formed only of the reaction chamber 1 and selectively through the membrane 9 hindurchdiffundierte hydrogen collects the hydrogen plenum 8 and associated over the Outlet 14 is forwarded. Since the reactor stage now their And operates with their full potential has, in the evaporator 2 water and methanol can now also at a high rate, depending on the power demand, evaporated and preferably overheated as appropriate are mixture 5 to the reaction chamber 1 is supplied. Since the steam reforming is endothermic of methanol, the operation is the catalytic burner 7 maintained to the reaction chamber 1 on this lowest operating temperature to hold. To maintain the operating temperature of the Wasserstoffabtrennmembran 9 sufficient in this warmed-up mode the installation of heat transfer from the catalytic burner 7 and the overheated supplied into the reaction chamber methanol / steam mixture 5, which is favored by the fact that the Membrane 9 directly adjacent to the reaction chamber. 1

0018It is understood that a Wasserstoffabtrennmembran the invention Kind not only, as shown, in methanol reforming plants, especially for fuel cell powered vehicles, but also in other fields of application wherever can be usefully employed, where a need for a direct Heating of the membrane by means of a catalytic combustion process consists. In this part, the membrane, as described, a hydrogen separation integrated formed with the reactor stage be or alternatively in one of the reactor stage spatially separated Wasserabtrennstufe be used. By the catalytic combustion process to the diaphragm are not otherwise additional means for heating the same as for example, an electric heater required.