DE19902926C2 - Reactor plant and operating procedure therefor - Google Patents

Description

The invention relates to a reactor plant for implementation a hydrocarbon or hydrocarbon derivative Input material according to the preamble of claim 1 and on a Process for operating such a system.

Plants and operating procedures for the implementation of reformie reaction processes that involve the formation of carbon mon oxide-associated pyrolysis reaction and the water gas shift react tion as sub-processes are of many types knows. More recently, their use in firing has increased Tissue cell vehicles are considered, being used as Mostly methanol is used. Common systems of this type just now for such a mobile application also include an evaporator fer, in which a feed / water mixture is prepared, as well as a one- or multi-stage reforming reactor for Um the feed / water / steam mixture supplied hydrogen-containing gas mixture. So z. B. in conventional Methanol reforming plants the metha prepared in the evaporator nol / water-steam mixture in a reforming reaction space passed and there using a CuO / ZnO catalyst  materials according to the steam reforming reaction in a water Substance-rich reformate gas converted, this reformie ration reaction process two parallel, in the reforming reaction includes sub-processes running on the one hand Methanol cleavage in synthesis gas, i.e. H. into a carbon monoxide / what mixture of hydrogen, by means of pyrolysis and secondly the implementation of the carbon monoxide formed with the water of the supplied Methanol / water vapor mixture according to the water gas shift reaction in carbon dioxide and hydrogen. The water generated by it Material can then be used as a fuel cell system, for example Fuel are supplied.

To increase the hydrogen yield and to reduce the Carbon monoxide content of the reformate gas generated is known this through a CO shift stage where the carbon monoxide about the water gas shift reaction with water to additional what hydrogen and carbon dioxide is implemented. Furthermore, it is known, the hydrogen contained in the reformate gas by means of egg selectively separate a suitable hydrogen separation membrane, why the separation membrane in the reforming reaction space itself or a downstream gas cleaning stage can. The vaporizer and the endothermic reforming freak reforming reactors are suitably heated, e.g. B. by an electric heater, a gas burner or a Catalytic burner device with one in the plant self-generated fuel can be fed. Plants and Operating methods of these types are e.g. B. in the patent document ten FR 1.417.757, FR 1.417.758 and US 4,981,676 and the Offen documents DE 44 23 587 A1 and EP 0 615 949 A2.

It is made of Dy especially for use in vehicle technology namik and space problems desirable, the components of the Reformer system to be as small and light as possible. At the same time, a high level of efficiency is sought, and it will be tries to get by with as few components as possible, especially in particular with as few regulation and control units as possible and  to be built-in housings with high heat capacity. The white There is also a desire for this mobile application after a good cold start behavior. When using the Refor matgases for fuel cells there is also the requirement that the carbon monoxide content is very low, typically below 50 ppm, should lie in to corresponding symptoms of intoxication to avoid the fuel cells.

Plants and operating procedures of the type mentioned at the beginning which the overall reform process from a pyrolysis reaction of the feed and a spatially separated water gas Shift reaction of the pyrolysis product gas with supplied water steam in a shift reactor downstream of the pyrolysis reactor exists, z. B. in the published documents DE 28 32 136 A1 and DE 33 06 693 A1. While there is a catalytic Pyrolysis reaction of methanol or another alkanol Temperatures between about 200 ° C and about 600 ° C described is in the patent DE 34 22 608 C2 a non- Catalytic pyrolysis of methanol proposed at over 850 ° C.

In the published patent application EP 0 486 174 A1 is hydrogen proposed implementation of a feedstock that partial oxidation of the feed with oxygen for synthesis gas generation and a downstream water gas Shift reaction of the synthesis gas comprises.

Apparently in one in laid-open specification JP 07-133101 (A) The stacker stacked reformer is equipped with a Vaporizer with a CO shift stage of a multi-stage reformie tion reactor in thermal contact. The entire stack of panels is also due to the hot combustion gases of a burner heatable, in which supplied fuel is non-catalytic is burned.

The invention is a technical problem of providing a reactor plant and an associated operating method of  type mentioned at the beginning, which is also suitable for mobile users suitable and lightweight, a compact Design, easy controllability and high water material yield with low carbon monoxide concentration and a enable good cold start capability.

The invention solves this problem by providing a Reactor system with the features of claim 1 or 2 and an operating method for this with the features of claim 7.

The plant according to the invention separates the reforming reaction process in the pyrolysis reaction and the water gas shift reaction as sub-processes carried out serially one after the other by a pyrolysis reactor to which the feedstock is used for pyrolyti shear cleavage is supplied, and a downstream Shift reactor contains the product gas of the pyrolysis reactor along with what was needed for the water gas shift reaction ser is supplied. The shift reactor can be used depending on the application case in a common unit with the pyrolysis reactor Connect the gate directly to it or as separate from it Unit be realized. By separating pyrolysis reac tion and water gas shift reaction can the respective compo nenten, d. H. the pyrolysis reactor and the shift reactor, optimal to carry out the respective sub-process of the entire refor Mation reaction process are designed. It shows, that a system constructed in this way, supplemented depending on the application through additional, optional system components, a simple rain reforming with high hydrogen yield with sufficient low carbon monoxide concentration and the system can be compact and lightweight.

The system of claim 1 further comprises a special one Evaporator for the feed, which is used as a heating medium internal catalytic burner unit as well an external heating device, e.g. B. an electric heater  tion, are assigned. The external heating device can especially for cold starts to be activated as quickly as possible vaporous feed for the pyrolysis reaction available to have.

The system according to claim 2 specifically has a pyrolysis reaction Tor assigned catalytic burner unit and an oxygen supply line through which an oxygen-containing gas in the Pyrolysis reactor can be passed. This line can do this open directly into the pyrolysis reactor or upstream of it, for example in the feed vaporizer. This oxygen Supply can serve especially in the event of a cold start in the Py rolysis reactor initially to partially oxidize the feedstock in order to with the heat of this exothermic reaction the plant faster to bring to operating temperature.

In a system developed according to claim 3 is in the Py rolysis reactor and / or in the shift reactor a respective What Integrated hydrogen separation membrane. So that in each Reactor formed hydrogen directly at the point of origin pulled what the reaction equilibrium in question further shifted in favor of hydrogen production and thereby to one complete conversion of the input material as possible and Lich contributes to a high hydrogen yield. In particular, lets the pyrolysis reactor is also made very small.

In a system developed according to claim 4, a Ver steamer to provide water vapor for the shift reactor from an internal catalytic burner unit and / or with heat from the pyrolysis reactor or the shift reactor heated, so that a further external heating of the same mostly can be omitted.

The purpose of the system quickly to operating temperature during a cold start to bring, is also the connection specified in claim 5 Line from the product gas outlet of the pyrolysis reactor to the associated  gene catalytic burner unit conducive to this connection power line at cold start initially at least partially ge is opened and thereby emerging from the pyrolysis reactor Product gas directly from the catalytic heating the pyrolysis reactor the burner unit is fed. In warm operation can then completely or in any case the connecting line as far as possible be closed.

According to an advantageous further-developed system structure, such as that of him is given by claim 6, the existing several ka analytical burner units connected in series.

The operating method according to claim 7 includes advantageous Cold start measures to quickly return the system to its normal loading bring operating temperature. One or more of the serve the following three measures. First, an external, e.g. B. electrical heating of the feed material evaporator is provided his. Second, in the pyrolysis reactor there can initially be a partial one Methanol oxidation can be carried out if this in addition to metha an oxygen-containing gas is also supplied. Third can the product gas of the pyrolysis via the corresponding connec cable, if present, directly into the catalytic burner nereinheit for the pyrolysis reactor are passed so that this can contribute very quickly to heating the pyrolysis reactor.

According to the method further developed according to claim 8, methanol is used as starting material in the pyrolysis reactor at a temperature above 350 ° C catalytically split into CO and H ₂ , and the carbon monoxide is then in the shift reactor with water by a catalytic cal low-temperature shift reaction at a temperature of at most 380 ° C or by a catalytic high-temperature shift reaction at a temperature of more than 380 ° C in CO ₂ and further hydrogen. It can be seen that a largely complete methanol conversion with high hydrogen yield and low CO concentration can be achieved in the product gas of the shift reactor using these process conditions.

An advantageous embodiment of the invention is in the Drawing shown and is described below.

The single figure shows a block diagram of a reactor plant for methanol conversion for hydrogen production.

The system shown is suitable for steam reforming nes hydrocarbon or hydrocarbon derivative, in particular of methanol, by pyrolysis of the feedstock and other closing water gas shift reaction of the pyrolysis product gas and ter supply of water vapor and can, for example, in one Fuel cell vehicle to be installed there for the Fuel cells need to provide hydrogen. The For the sake of simplicity, the system is described below without restriction of general use in methanol reforming wrote.

The system contains a methanol tank 1 , from which the methanol stored there can be fed to a methanol evaporator 3 via a pump 2 . Optionally, an oxygen supply line 4 also opens into the methanol evaporator 3 , as indicated by dotted lines. The evaporator outlet side is connected to the inlet side of a pyrolysis reactor 5 , which contains a suitable methane nolfission catalyst, for. B. platinum. In the pyrolysis reactor 5 , a first hydrogen separation membrane 6 is integrated, which forms a delimiting wall of the pyrolysis reaction space and to which on the opposite side of the pyrolysis reaction space adjoins a first hydrogen discharge space 7 , from which hydrogen can be drawn off via an outlet line 8 , which is in the pyrolysis reaction space generated and diffused selectively through the What serstoffabtrennmembran 6 into the hydrogen discharge space 7 .

Via a corresponding product gas line 9 , the product gas formed in the pyrolysis reactor 5 passes into a downstream shift reactor 10 . In the product gas line 9 opens a water vapor line 12 coming from egg nem water evaporator 11 , so that 5 water vapor can be added to the product gas of the pyrolysis reactor. The water required is removed from a water tank 13 and supplied to the water evaporator 11 via a pump 14 . In the shift reactor 10 , a second hydrogen separation membrane 15 is integrated, which forms a delimiting wall of the shift reaction space and separates it from a second hydrogen extraction space 16 , from which hydrogen can be drawn off via an outlet line 17, which can be removed from the shift reaction space through the second hydrogen separation membrane 15 diffuses into the second water extraction chamber 16 . The shift reaction space contains a suitable shift catalyst material for catalyzing the water gas shift reaction, e.g. B. a CuO / ZnO catalyst material on Al ₂ O _{3 support} . Optionally, the methanol evaporator 3 can also be heated by an electric heating device 24 , as indicated by dotted lines.

Furthermore, the system includes a three-unit catalytic burner device, of which a first burner unit 18 a with the water evaporator 11 , a second burner unit 18 b with the pyrolysis reactor 5 and a third burner unit 18 c with the methanol evaporator 3 is in thermal contact. The three catalytic burner units 18 a, 18 b, 18 c can be flowed through serially in the order mentioned by the residual gas emerging from the shift reactor 10 , for which purpose this can be fed into the first burner unit 18 a from the shift reactor outlet via a corresponding residual gas line 19 . The there unused residual gas fraction passes through a first Brennerver connecting line 20 a to the central burner unit 18 b, with the output of the third burner unit 18 c through a second connecting line burner 20 is connected b. The exhaust gas 23 emerging from the last burner unit 18 c is suitably discharged.

In addition, a connecting or bypass line 21 is optionally provided, as indicated by dots, which connects the pyrolysis reactor output directly to the input of the second burner unit 18 b that is in thermal contact with the pyrolysis reactor 5 . Furthermore, as also indicated by dots, a heat exchanger 22 is optionally provided in thermal contact with the shift reactor 10 , alternatively in thermal contact with the gas emerging from it, which in a manner not shown by the water stream flowing from the water tank 13 to the product gas line 9 can be streamed. The heat exchanger 22 can, depending on the application, replace the water evaporator 11 or be connected in series to it in the water flow path.

The mode of operation of the system shown is discussed in more detail below. Starting from a cold start, methanol is fed from the methanol tank 1 to the methanol evaporator 3 via the metering pump 2 . In the starting phase, this is also primarily heated by the electrical heating device 24 , if present, otherwise by the associated catalytic burner unit 18 c. The methanol, which has a low enthalpy of vaporization, is thereby evaporated and overheated to a temperature of over 350 ° C., preferably to a temperature between 400 ° C. and 480 ° C. The superheated, gaseous methanol then enters the pyrolysis reactor 5 , in which it is pyrolysed according to the reaction equation

CH ₃ OH ↔ CO + 2.H ₂

is split into carbon monoxide and hydrogen, the free enthalpy of this endothermic reaction being 129 kJ / mol. The heat required for this endothermic reaction is generated by the associated, second catalytic burner unit 18 b. To this end, in the starting phase is emerging from the pyrolysis reactor 5 product gas via the bypass line 21, if present, directly this burner unit 18 b to the combustion of the non reactor in the pyrolysis of 5 unreacted methanol and may not hindurchdiffundierten by the Wasserstoffabtrennmembran 6 hydrogen supplied. Possibly unconverted fuel in this burner unit 18 b can be used in the subsequent burner unit 18 c which is in thermal contact with the methanol evaporator 3 for heat generation.

Optionally, for even faster heating of the system for the starting process, an oxygen-containing gas, such as air, can be passed through the oxygen supply line 4 , if present, into the pyrolysis reactor 5 . More specifically, the oxygen-containing gas is fed upstream of the pyrolysis reactor 5 parallel to the methanol in the methanol evaporator 3 and mixed and heated there with it. Since the methanol cleavage catalyst, e.g. B. platinum, in the presence of oxygen also catalyzes the partial methane oxidation, this reactor then runs in the pyrolysis reactor instead of the methanol cleavage reaction, as long as the oxygen supply is maintained. The heat generated by the exothermic partial oxidation reaction can bring the pyrolysis reactor 5 to operating temperature in a very short time. At the same time, it already supplies hydrogen which, with increasing heating of the hydrogen separation membrane 6, is increasingly able to diffuse through it and is available, for example, for supplying fuel cells. With this operating mode, partial load operation of a connected fuel cell system and thus a corresponding motor vehicle drive is already possible if required.

In order to bring the shift reactor 10 and what the server steamer 11 largely to normal operating temperature even in the starting phase, provision can be made for not all of the product gas emerging from the pyro lysis reactor 5 via the bypass line 21 directly to the second burner unit 18 b, but at least some of it of which feed to the shift reactor 10 in order to heat it by this process gas heat transport and to implement gas-containing carbon monoxide in the supplied process with increasing heating via the water gas shift reaction. The product gas formed in the shift reactor 10 is then supplied to the first catalytic burner unit 18 a, which, in turn, causes the heating of the water evaporator 11 , except for the increasing heating of the hydrogen separation membrane 15 there through this selectively withdrawn hydrogen. This unused fuel can be used in the subsequent burner units 18 b, 18 c.

As soon as the various system components have essentially reached their normal operating temperature, the system is switched to normal operation. For this purpose, the possible supply of oxygen to the pyrolysis reactor 5 is stopped, and the electrical heating device 24 can be switched off in most applications. At the same time, the optional bypass line 21 is completely or at least largely closed.

When the oxygen supply is terminated, the partial methanol oxidation which may be activated in the pyrolysis reactor 5 is ended , and the methanol which is then supplied exclusively is cleaved catalytically into carbon monoxide and hydrogen. The hydrogen formed can be drawn off from the pyrolysis reaction space through the associated hydrogen separation membrane 6 , which shifts the equilibrium of the methanol cleavage reaction in favor of the products. A complete methanol conversion is achieved by even with a shorter residence time, so that a rela tively short run length of the reaction mixture and thus a relatively small volume of the pyrolysis reactor 5 are sufficient. To the fact that the pyrolysis reactor 5 can be built small, also contributes to the fact that it is operated in a relatively high temperature range of over 350 ° C, in which the conventional methanol cleavage catalysts have high activity. In addition, the permeability of the hydrogen vent membrane 6 at this temperature is turbereich higher than at low temperatures, so that more hydrogen can be selectively separated.

The product gas of the pyrolysis reactor 5 , in the normal operation of the system mainly carbon monoxide and possibly not separated ter hydrogen, is fed via the product gas line 9 to the shift actuator 10 , with evaporated and superheated water being supplied via the steam line 12 , which is prepared by the water evaporator 11 becomes. Alternatively or additionally, the water withdrawn from the water tank 13 via the pump 14 can be evaporated via the heat exchanger 22 by the gas mixture in the shift reactor 10 or by the residual gas emerging therefrom.

In the shift reactor 10 , the carbon monoxide then becomes catalytic via the water gas shift reaction

CO + H ₂ O ↔ CO ₂ + H ₂

implemented with water to carbon dioxide and further hydrogen, this reaction being endothermic with a free enthalpy of 3 kJ / mol. For the temperature in the shift reactor 10 , a low temperature range up to at most about 400 ° C, preferably less than 250 ° C, z. B. in the order of 200 ° C, egg nem high temperature range with shift reaction temperatures in the order of 400 ° C and more, preferably between 400 ° C and 480 ° C. For the low-temperature variants, it is normally sufficient to use only the water evaporator 11 or the heat exchanger 22 for steam preparation. For the high-temperature variant, both components are preferably seen before, in which case the water vapor from the water evaporator 11 can be overheated by the product or residual gas from the shift reactor 10 via the heat exchanger 22 .

The hydrogen additionally formed in the shift reactor 10 is selectively drawn off via the hydrogen discharge membrane 15 there, which in turn allows the reaction equilibrium of the water gas shift reaction to be shifted to the product side, which further improves the hydrogen yield. The light exiting the shift reactor 10 residual gas from unseparated hydrogen, unconverted carbon monoxide and water is successively seri the economic catalytic burner units 18 a, b 18, c 18, and supplied there catalytically burnt completely under heat.

It goes without saying that in addition to the example shown and here in addition to the variants mentioned above, further implementations of the invention possible are. The door is characteristic of each the entire reform process of the Koh hydrogen or hydrocarbon derivative in the pyrolyti cleavage reaction without the presence of water and the after switched water gas shift reaction. Obviously the Heat requirement of the overall endothermic reforming process entirely or at least largely internally through catalytic Incineration of the input material or the product obtained from it be covered. By using a respective water material separation membrane, the reaction equilibrium for both processes in favor of hydrogen production and thus a complete conversion of the input material  move fes. Possibly not split in the pyrolysis reactor Methanol can still in the shift reactor with what is there steam can be reformed, which with the help of the catalytic converter there door material is possible.

As is clear from the realizations mentioned, the Invention a steam reforming plant for Hydrogen Ge available, which is compact and light in weight can build, including in particular the shift of the reacti equilibria due to the separation membranes in the two reacts contributes gates, which results in a relatively short barrel length can be placed. The selected feed material can be filled constantly and with high hydrogen yield at high hydrogen Selectivity greater than 99.99999% for use in particular re convert into fuel cells. The separation of pyrolysis reac tion and water gas shift reaction and the self-regulating, largely internal heating of the system components with heat may allow a relatively simple regulation of the entire An location.

Claims (8)

1. Reactor system for the implementation of a hydrocarbon or hydrocarbon derivative feedstock by a reaction process which includes a pyrolysis reaction associated with the formation of carbon monoxide and the water gas shift reaction as subprocesses with

• - A pyrolysis reactor ( 5 ) to which the feedstock can be fed by a pyrolysis reaction for the purpose of cleavage, and
• - A downstream of the pyrolysis shift reactor ( 10 ), the koh lenmonoxidhaltige product gas from the pyrolysis reactor and water can be supplied for the implementation of the water gas shift reaction,

marked by

• - One of the pyrolysis reactor ( 5 ) upstream feed evaporator ( 3 ), to which an internal system-fed, catalytic burner unit ( 18 c) and an external heating device ( 24 ) are assigned.

2. Reactor system for the implementation of a hydrocarbon or hydrocarbon derivative feedstock by a reaction process which includes a pyrolysis reaction associated with the formation of carbon monoxide and the water gas shift reaction as subprocesses, in particular according to claim 1, with

• - A pyrolysis reactor ( 5 ), to which the feedstock can be fed by a pyrolysis reaction for the purpose of cleavage, and
• - A downstream of the pyrolysis shift reactor ( 10 ), the koh lenmonoxidhaltige product gas from the pyrolysis reactor and water can be supplied for the implementation of the water gas shift reaction,

characterized in that

• - The pyrolysis reactor ( 5 ) is assigned a heating, catalytic burner unit ( 18 b) and an oxygen supply line ( 4 ) for supplying an oxygen-containing gas to the pyrolysis reactor.

3. Reactor system according to claim 1 or 2, characterized in that in the pyrolysis reactor ( 5 ) and / or in the shift reactor ( 10 ) egg ne respective hydrogen separation membrane ( 6 , 15 ) is integrated. 4. Reactor system according to one of claims 1 to 3, characterized by a water evaporator ( 11 ) which is heated by a system-internally fed, most catalytic burner unit ( 18 a) and / or with heat from the shift reactor ( 10 ). 5. Reactor system according to one of claims 2 to 4, characterized by a controllable opening and closing connecting line ( 21 ) from the product gas outlet of the pyrolysis reactor ( 5 ) to the sen heating, catalytic burner unit ( 18 b). 6. Reactor plant according to one of claims 2 to 5, characterized in that the catalytic burner units ( 18 b, 18 c) are serially connected in series. 7. A method of operating a system according to claims 1 to 6 for implementing a hydrocarbon or hydrocarbon derivative feedstock, characterized in that when the system is cold started before the transition to normal operation when the system is warmed up, the external heating device ( 24 ) of the insert material Evaporator ( 3 ) activated and / or a partial oxi dation of the feed in the pyrolysis reactor ( 5 ) by supplying an oxygen-containing gas via the oxygen supply line ( 4 ) and / or at least part of the product gas of the pyrolysis reactor is carried out via the associated, this least partially kept open connecting line ( 21 ) is passed into the catalytic burner unit ( 18 b) which heats the pyrolysis reactor. 8. The method according to claim 7, characterized in that

• - In the pyrolysis reactor ( 5 ) supplied methanol at a temperature of over 350 ° C, preferably between 400 ° C and 480 ° C, is catalytically split into carbon monoxide and hydrogen and
• - In the shift reactor ( 10 ), the carbon monoxide contained in the supplied product gas of the pyrolysis reactor with supplied water by a low-temperature catalytic shift reaction at a temperature of at most 380 ° C, preferably at most 250 ° C, or by a high-temperature catalytic shift reaction at one temperature of more than 380 ° C, preferably between 400 ° C and 450 ° C, is converted to carbon dioxide and hydrogen.