DE10222804C1 - Gas generation system to produce virtually pure hydrogen, for a fuel cell, has a hydrogen separation module with an integrated heat exchanger in its housing, working with a catalytic burner and a reforming stage - Google Patents

Abstract

Gas generation system has autothermal reforming stage(s), catalytic burner, a mixer and a hydrogen separation module (2). Hydrogen separation module is downstream of reforming stage (3) and upstream of additional oxygen feed channel at mixer (7). Burner (6) is upstream of mixer and downstream of heat exchanger. The heated educt channel, in thermal contact with heat exchanger (9), is upstream to the reformer stage. During a cold start, higher volumes of fuel and air are fed to the burner.

Description

The invention relates to a gas generating system for providing almost pure hydrogen, with at least one car Thermen Reformierungsstufe, a catalytic burner, a from the catalytic burner heated heat exchanger, a Mixer for at least two catalytic burners supplied substances and a hydrogen separation module with egg a housing.

From DE 197 55 815 C2 is a method for steam formation of a hydrocarbon or hydrocarbon derivative vats as well as a reforming plant operable with it a fuel cell operating method is known. The construction of the system described there besides evaporator and reform tion reactor a membrane module or hydrogen separation module on, by which from the hydrogen-containing reformate almost pure hydrogen is deposited. This hydrogen para tion module can, for example, via metallic membranes Palladium or the like.

From the above patent is also a Verfah ren known for starting such a system. This will be a Heating process carried out in which in a first operation phase with the reforming reactor and an evaporator in thermally conductive contact standing catalytic burner device heated to a temperature above the water boiling temperature becomes. For this purpose, the hydrocarbon and / or hydrogen un The supply of oxygen-containing gas is burned catalytically. Subsequently, in a second phase of operation the evaporator  Water and hydrocarbon are added, with respect to the Normal operation an increased water / hydrocarbon ratio is complied with. The emerging from the reforming reactor Mixture is after flowing through and heating the Mem branmoduls returned to the catalytic burner device leads.

The disadvantage of this cold starter process is certainly in it to see that a comparatively long time is needed before the membrane module, which only in the second phase of operation be exiting from the reforming reactor exhaust gases is heated, can be brought to operating temperature. except this is due to the use of a catalytic burner direction influencing the combustion processes to Reg ting the temperature comparatively expensive.

The system represented by the above mentioned DE-font also has the disadvantage that in the first operation phase of the heating process, although the catalytic burner tion and the reforming reactor are preheated, the heating However, the membrane module is carried out exclusively in the second phase of operation by the hot reformat or the hot gases from the reforming stage. When these hot fumes now hit the still cold membrane module, this can in the Exhaust gases contained auskon water in the region of the membrane module condense. The condensed water in the membrane However, the membrane module can damage them massively. Become further, as in the embodiment of the above Font shown, use several catalytic part burner det, if necessary, a division of the hot gas stream done, which in turn very expensive, complex and troublefree ge suitable for correspondingly high temperatures Ventileinrich required.

From US 4,820,594 is another starting method for a Gas generating system in a fuel cell system known. By the fuel used in the plant is in the  Starting phase of the gas generating system for the gas production system required thermal energy through a direct Ver combustion of this fuel in the range of at least individual Components of the gas generating system achieved. It is the fuel present in the fuel cell system anyway, which then in normal operation by the gas generating system in the hydrogen-containing reformate is reformed, for this di direct combustion for rapid heating of gas generation used.

In the case of such a gas generating system, however, there are several individual burner necessary, which designed accordingly Components of the system through the direct combustion of Heat the fuel. Furthermore, the heated compo nents in one for the heating by means of the burner ten be formed, so that an optimization of this Kom components in terms of space etc. or very difficult becomes possible.

For these reasons, it is therefore the task of the present Invention, a gas generating system for providing almost pure hydrogen with a hydrogen separation module too which feeds those fed into the gas generating system Energy, largely independent of the geometric Ausgestal tion of the components that are ideal for use. Furthermore, it is it is the object of the present invention, a method to specify for starting such a gas generating system.

According to the invention, this object is achieved in that in the Housing of the hydrogen separation module, a heat exchanger in tegriert, wherein the components of the gas generating system so are connected to each other via line elements that a in the autothermal reforming stage of several reactants produce tes product gas for distribution in almost pure hydrogen and a residual gas flows into the hydrogen separation module, wherein the residual gas flows to a mixing device in which it mixes with an oxygen-containing medium and in the ka  talytic burner arrives. Furthermore, by the Ver Connecting pipes achieved that exhaust gases of the catalytic Bren ners into the housing of the hydrogen separation module inte flow through grated heat exchanger, and that at least one Part of the educts for the autothermal reforming stage before the Entry into the autothermal reforming stage of the kata lytic burner to flow through heated heat exchanger.

This complex nested structure of the gas generating system has the advantage that the thermal energies zwi The gas streams are ideally exchanged with each other so that the best possible use of the registered thermal energy is enabled. It already allows the structure according to the invention in itself these advantages without For elaborate valves, as well as a controller for these Venti le would be necessary.

The procedural part of the above task is there solved by that the mixing device ge as start burner is used, in which in a first process step Fuel ignited together with the oxygen-containing medium is heated and the catalytic burner, after which the kata lytic burner sufficient for its launch temperature has reached is in a second step of the kata ignited lytic burner, wherein the hot exhaust gases, the What to heat the hydrogen separation module, and wherein in a third Process step of at least one of the educts by the heat the catalytic burner to the autothermal Refor is passed and this heated, after which in a fourth step after reaching a sufficient the temperature in the autothermal reforming stage and in the Hydrogen separation module the autothermal reforming stage ignited and operated exothermically, after which in a fifth Process step after the components have their Solltemperatu have reached the gas generating system through a changes tion of the composition of the added educts in the regulä operation is transferred.  

The method according to the invention makes it possible to start the Ga generating system, starting from a very low tempera ture, for example, the commonly occurring environment temperature between -10 ° C and + 25 ° C. The system will be there heated up very quickly, as the registered thermal energy gie ideally used by the system structure according to the invention that can. Furthermore, the structure is designed so that the Membrane module by the heat exchanger integrated in its housing scher is preheated to an elevated temperature before the au totherme reforming stage is ignited. This can sicherge be that there is no condensation of water in the area of the membranes of the hydrogen separation module comes, causing damage to the same by liquid water can be avoided.

In addition, the structure of the gas generating system with which he inventive method so that the gas streams without addi che valve device or the like by the individual Kom components, since during start-up and during the regular operation the same flow paths are used.

According to a very favorable development of the invention Procedure, it is provided that during the third Verfah First, only the oxygen-containing medium through the Heat exchanger of the catalytic burner into the autothermal Re Formierungsstufe, before which the heated air then the Fuel is supplied is given, after which the What serstoffseparationsmodul a predetermined temperature above the boiling temperature of water below that in the Wasserstoffsepara module has exceeded existing conditions Lich water through the heat exchanger of the catalytic burner is added to the autothermal reforming stage.

According to this embodiment of the invention is achieved that the start of the autothermal reforming stage during the two th process step exclusively with oxygen-containing  Medium and the fuel takes place. Depending on the used Brenn Substance is usually the amount of in the Abga sen / product gases of the reforming stage occurring water be relatively low, so that also the Auskon condensation of water in the area of the membranes of the water fabric separation module can be reduced. After the what serstoffseparationsmodul a predetermined temperature above the boiling temperature of water below that in the Wasserstoffsepara module has reached additional conditions Lich water through the heat exchanger of the catalytic burner placed in the autothermal reforming stage. This water as one of the educts for the autothermal reforming stage causes then a much better heat transfer from the area of Heat exchanger of the catalytic burner and out of the range the autothermal reforming stage in the following compo on the one hand and a start to the actual reform in the autothermal reforming stage, but still exothermic operating conditions, on the other hand. As a result of that However, this addition of water only takes place when the above ge called temperature of the hydrogen separation module achieved is, the risk of condensation of liquid water be minimized in the hydrogen separation module.

A particularly favorable use for such a gas generator system and / or a method for starting suchi gene gas generating system is in the production of almost Rei nem hydrogen for operating a fuel cell system. Especially in fuel cell systems, which in mobile Facilities, such as motor vehicles or the like operated It may be of particular advantage when gas generators systems are used, which is very compact let build and most of the fed into it use thermal energy ideally. Besides, here is a lot faster start of particular advantage, since just in suchi systems, for example in motor vehicles, regardless of their use as auxiliary power generators or as parts of a Traction system, cold start conditions occur very frequently  and the delays associated with them from the users Of such a motor vehicle very often perceive as disadvantageous to become.

Further advantageous embodiments of the gas generating system and the method for starting such gas generation stems arise from the remaining subclaims and the Ausfüh illustrated below with reference to a drawing approximately, for example.

It shows:

Fig. 1 shows a possible embodiments of a Gaserzeugungssy stems according to the invention;

Fig. 2 shows a possible embodiments of the mixing device of the gas generating system of FIG. 1.

In Fig. 1, a gas generating system 1 for generating near-pure hydrogen H _{2 is} shown. In the regular operation of the gas generating system 1 is from an oxygen-containing medium O ₂ , such as air, water H ₂ O and a koh hywasserstoffhaltigen compound C _n H _m or a mixture of hydrocarbon-containing compounds such. As gasoline, diesel or hydrocarbon derivatives, such as alcohols or derglei surfaces, produces a hydrogen-containing gas. From this hydrogen-containing gas is then separated by means of a Wasserstoffseparati onsmoduls 2 of almost pure hydrogen. For this purpose, the hydrogen separation module 2 , which is also referred to as Membranmo module 2 , membranes, which are selectively permeable to hydrogen H ₂ .

In the gas generating system 1 is thus from the above educts air O ₂ , water H ₂ O, and a kohlenwasserstoffhalti gene compound C _n H _m in an autothermal reforming stage 3 and a subsequent high temperature shift stage 4, the water-rich gas generated, which then in the membrane module 2 in the almost pure hydrogen H ₂ and a residual gas R, the so-called retentate, is divided. The hydrogen H ₂ can then be supplied to a fuel cell, for example. The residual gas is led abge via the line 5 from the membrane module 2 and, optionally together with other exhaust gases and / or optional additional fuel F, via later explained intermediate components fed to a catalytic burner 6 . In the catalytic burner 6 then takes place to a conversion of the usable contents of the residual gas R into thermal energy, including in the catalytic burner 6 except the residual gas R at least one oxygen-containing medium O ₂ or air is supplied via a mixing device 7 . In the catalytic burner 6 , these starting materials are then converted into thermal energy and the hot exhaust gases of the catalytic combustion in the region of the membrane module 2 , and here in particular in a housing 8 of the membrane module 2 , passed, which is designed as a heat exchanger so that the membrane module 2 can be heated by the hot exhaust gases of the catalytic burner 6 . The integration of the heat exchanger in the housing 8 of the membrane module 2 allows a very compact structure with favorable properties in terms of thermal losses, packaging and the like. Furthermore, the catalytic cal burner 6 heats the heat exchanger 9 .

The gas generating system 1 operates in normal operation, after passing through a cold start, which will be explained later, in such a way that air O _{2 is} added via line 10 as one of the educts for the autothermal reforming stage 3 . Via a heat exchanger 11 , this air O _{2 is} then preheated by a part of the residual heat in the out of the housing 8 of the membrane module 2 passing exhaust gases of the catalytic burner 6 . In the preheated air O ₂ , a portion of the water required as starting material H ₂ O is metered so that thus the temperature of the product gas for the high temperature turshiftstufe 4 is cooled in a heat exchanger 13 in the region of a metering point 12 that the temperature level of the product gas to Implementation in the high temperature shift stage 4 is as ideal as possible. After the heat exchanger 13 , the superheated mixture of water H ₂ O and air O _{2 reaches} the area of a further metering point 14 . Here, the remaining water required for autothermal reforming H ₂ O is added.

After flowing through the heat exchanger 9 , the then generally overheated mixture of air O ₂ and steam H ₂ O, the hydrocarbon-containing compound C _n H _{m is} supplied, for. B. atomized in the flow of the mixture. In the autothermal Re formation stage 3 , these starting materials are then reacted in a manner known per se ter in the hydrogen-containing product gas, which is also referred to as a reformate. After the above-described flow through the heat exchanger 13 and a Dar in succession cooling of the reformate to a high tem peraturshiftstufe 4 suitable temperature level, at the same time tiger heating of the reactants, the reformate flows into the Hochtem peraturshiftstufe 4 and leaves them as a hydrogen-rich gas to to flow into the membrane module 2 .

In the membrane module 2 , the separation of the hydrogen-rich reformate in hydrogen H ₂ and retentate or residual gas R, which is guided to the above-described heat exchanger 11 to be carried out to preheat with its residual heat, the air O ₂ for the auto-thermal reforming stage 3 . After flowing through the heat exchanger 11 , the retentate or residual gas passes through further optional devices, such as a pressure holding device 15 for maintaining the system pressure in the gas generating system 1 , in the region of the mixing device. 7 There, the residual gas R, as already mentioned, at least with the oxygen-containing medium or the air O ₂ and where appropriate mixed with an additional optional fuel F and fed to the catalytic burner 6 . The hot exhaust gases from the catalytic burner 6 then pass to the heat exchanger designed as a housing 8 of the membrane module 2 and then optionally via suitable exhaust gas purification devices and / or residual heat exchanger into the environment.

The additional optional fuel F can, for. B. the same koh hydrocarbon-containing compound C _n H _m , as for operating the autothermal reforming stage 2 , be. In addition to this anyway required hydrocarbon compound C _n H _m , the use of another fuel F, z. B. a lower boiling or already gaseous fuel conceivable bar. In particular, for the starting case, a short-chain hydrocarbon compound or a hydrogen-rich gas could be used for fast Anwär the system.

The mixing device 7 can, except for mixing the residual gas R with the air O ₂ , are used for the start of the gas generating system 1 as a starting burner.

As shown in Fig. 2, the mixing device 7 to an ignition device 16 , which may be formed, for example, as Glühker ze, spark plug or the like. If the mixing device 7 is now supplied with air O ₂ together with the fuel F in the start case, then this mixture can be ignited via the ignition device 16 . The mixture is then burned directly with a flame and, if appropriate, after a ge know line length, flow into the catalytic burner 6 and heat it to its starting temperature before there, the mixture of air O ₂ and fuel F is catalytically implemented.

After the catalytic burner 6 is heated and has reached a sufficient temperature for its start, the catalytic burner 6 itself is ignited. The hot exhaust gases of its catalytic combustion then heat the water stoffseparationsmodul 2 by flowing through the inte grated in his housing 8 heat exchanger. In the area of the water separation module or membrane module 2 auskondensierendes water will condense out only in the region of the heat exchanger, so that the membranes of the membrane module 2 itself does not come into contact with the condensed water. In a third process step, the educts or at least one of the educts, generally air O ₂ , then passed through the heat exchanger 9 of the catalytic burner 6 to the autothermal reforming stage 3 , which is heated with the flowing through hot air O ₂ . The hot air stream can then also heat the downstream Hochtemperaturshiftstu fe 4 and the membrane module 2 itself and can then be used after flowing back to the mixing device 7 for re-supply of preheated convertible radicals in the catalytic burner 6 .

Only after the autothermal reforming stage 3 has reached a suffi cient temperature for their start and also in the hydrogen separation module 2 is a sufficient temperature, the autothermal reforming stage 3 itself ignited, to which the hydrocarbon-containing compound C _n H _m will give added. During the starting phase, the autothermal Refor is mierungsstufe 3 then with the air O ₂ as oxygen-containing Me medium and the hydrocarbon-containing compound C _n H _m so be exaggerated that an exothermic operation is achieved by the choice of an air lambda λ of more than 0.3. Through this exothermic operation of the autothermal reforming stage 3 in the start case is achieved that the exhaust gases of the autothermal reforming stage 3, the following components, such as the high temperature turshiftstufe 4 and the membrane module 2 , heat faster. For this purpose, in addition, in the region of the catalytic burner 6, a higher amount of fuel F and air O ₂ or oxygen-containing medium are metered than for the normal operation of the catalytic burner 6 is provided. Although the catalytic burner 6 is then loaded during startup with higher temperatures, which lead to a faster aging of the catalytic active material, but this can be tolerated due to the generally very short start phases of derarti conditions gas generating system 1 for the purpose of faster start.

During the third process step can also be used to improve the heat transfer from the hot exhaust gases of the exothermally operated autothermal reforming stage 3 to the following components of water H ₂ O in the area of exo thermal reforming stage 3 and in the range of Wärmetau shear 9 of the catalytic burner 6 are injected, z. B. on the dosage 14th This water, which in regular loading operation over at least one of the metering points 12 , 14 , and ideally in cold start only via the dosage 14 to avoid un necessary cooling of the exhaust gases of the autothermal reforming stage 3 before flowing into the high temperature shift stage 4 to ver , injected as educt anyway improved during the start of the gas generating system 1, the heat transfer from the hot exhaust gases of the then exothermically operated autothermal Re formation stage 3 on the following components, so that the starting process can be shortened again.

After the components have reached their target temperatures, the gas generating system 1 can then be converted by a change in the composition of the reactants in the regular operation. This means, in particular, a change in the air lambda and the ratio S / C of water vapor (S / steam) to carbon C and the switching off of the ignition device 16 and the supply of fuel F to the mixing device 7 .

In addition, even before all other components have reached their setpoint temperatures, the heating of the membrane module 2 can be reduced, since this component generally reaches its required operating temperature be the first. Already in the water phase can then be separated from the gases flowing into the membrane module 2 hydrogen H ₂ .

All in all, this procedure is used to start the gas system using the already existing system maufbaus an ideal and very fast cold start possible.

Claims (12)

1. gas generating system for providing almost pure hydrogen, with at least one autothermal reforming stage, a catalytic burner, a heated catalytic converter from the heat exchanger, a Mischeinrich device for at least two the catalytic burner zugeführ te substances and a hydrogen separation module with a housing, characterized characterized in that in the housing ( 8 ) of the hydrogen separation module ( 2 ), a heat exchanger is integrated, that the hydrogen separation module ( 2 ) downstream with the autothermal reformer stage ( 3 ) and upstream with the additional Zuführlei device for oxygen-containing medium having Mischein direction ( 7 ), the catalytic burner ( 8 ) is connected downstream with the mixing device ( 7 ) and upstream with the integrated heat exchanger in the housing ( 8 ) and that a ducting to the heated from the catalytic burner ( 6 ) and in thermal contact therewith heat exchanger ( 9 ) leads, the upstream with the autothermal reformer ( 2 ) is connected ver. 2. Gas generating system according to claim 1, characterized in that between the autothermal reforming stage ( 3 ) and the hydrogen separation module ( 2 ) at least one shift stage, in particular a high-temperature shift stage ( 4 ), and in the flow direction of the product gas before a Wärmetau exchanger ( 13 ) for transmission of thermal energy of the product gas is arranged on at least one of the educts. 3. Gas generating system according to claim 1 or 2, characterized in that between the hydrogen separation module ( 2 ) and the mixing device ( 7 ), a heat exchanger ( 11 ) for transmitting thermal energy from the residual gas (R) is arranged on at least one of the educts. 4. Gas generating system according to claim 1, 2 or 3, characterized in that the mixing device ( 7 ) fuel (F) can be fed. 5. Gas generating system according to one of claims 1 to 4, characterized in that the mixing device ( 7 ) additionally has a Zündeinrich device ( 16 ). 6. A method for starting a gas generating system according to any one of the preceding claims, characterized in that
in a first method step, the mixing device ( 7 ) is used as a starting burner, wherein in this a fuel (F) is ignited together with the oxygen-containing Medi to (O ₂ ) and the catalytic burner ( 6 ),
, the catalytic burner (6) is ignited in a second method step, after the catalytically diagram burner has (6) reaches a sufficient temperature for a start, wherein the hot flue gas-separation module, the water (2) warm,
in a third process step, at least one of the educts is passed through the heat exchanger ( 9 ) of the catalytic burner ( 6 ) to the autothermal reforming stage ( 3 ) and heated,
in a fourth process step after reaching a sufficient temperature in the autothermal Refor mierungsstufe ( 3 ) and in the hydrogen separation module ( 2 ) the autothermal reforming stage ( 3 ) ignited and operated exothermic, and
in a fifth method step, after the components have reached their setpoint temperatures, the gasification system ( 1 ) is converted into regular operation by a change in the composition of the added educts. 7. The method according to claim 6, characterized in that the autothermal reforming stage ( 3 ) during the fourth process step with air (O ₂ ) as sauerstoffhal term medium and a hydrocarbon-containing compound (C _n H _m ) will operate, the exothermic operation by an air lambda (λ) of more than 0.3 is achieved. 8. The method according to claim 6 or 7, characterized in that during the cold start higher amounts of fuel (F) and oxygen-containing medium (O ₂ ) in the catalytic burner ( 6 ) are metered as in normal operation. 9. The method of claim 6, 7 or 8, characterized in that during the third process step, first only the oxygen-containing medium (O ₂ ) through the heat exchanger ( 9 ) of the catalytic burner ( 6 ) in the autothermal Refor mierungsstufe ( 3 ) is, wherein after the hydrogen separation module ( 2 ) above a predetermined temperature above the boiling point of water below the present in the water stoffseparationsmodul ( 2 ) conditions has additionally water (H ₂ O) through the Wärmetau shear ( 9 ) of the catalytic burner ( 6 ) in the autothermal reforming stage ( 3 ) is given. 10. The method according to any one of claims 6 to 9, characterized in that after reaching the operating temperature of the What hydrogen separation module ( 2 ) the heating of the water stoffseparationsmoduls ( 2 ) is reduced. 11. The method according to any one of claims 6 to 10, characterized in that for starting the gas generating system, a fuel (F) is used, which boils easier and / or light ter ter flammable than the fuel (C _n H _m ), which in Normal operation is used. 12. Use of a gas generating system and / or a method according to one of the above claims for He testify of nearly pure hydrogen (H ₂ ) for operating ei Nes fuel cell system.