DE10151393B4 - Reactor for a gas generating system and its use in a motor vehicle - Google Patents

Abstract

reactor (1) for a gas generating system for generating a hydrogen-containing gas for one Fuel cell, which is designed in plate construction, wherein through the plates first, second and third media spaces (2, 3, 5) are formed and in the first media spaces (2) endothermic reactions and in the third media rooms (5) exothermic reactions are feasible, being the media rooms (2, 3, 5) in thermally conductive contact each other, and wherein each of the first media spaces (2) between two third media rooms (5) is arranged and the media at least some of the third media rooms (5) about one of the second media rooms (3) supplied which are in each case between two of the third media spaces (5) is arranged, characterized in that the second media spaces (3) Nonwovens (4) or knitted fabrics have.

Description

The The invention relates to a reactor for a gas generating system the type defined in the preamble of claim 1 in more detail.

Numerous reactors for a comparable purpose as described by the preamble of claim 1 are known from the general state of the art. Many of these reactors are designed in plate construction, for example by the DE 199 20 786 A1 described reactor.

To the Entry of heat It is very common in the reactor for that Heat-requiring Reactions, such as steam reforming of water and a carbon and hydrogen-containing starting material for producing a hydrogen-containing gas with heat-generating Reactions, for example, a selective oxidation of in the resulting hydrogen-containing gas contained carbon monoxide, housed in a reactor, so that in the one reaction resulting heat to the expiration of the other reactions can be used. issues occur in such reactors, especially in the cold start phase on when for the heat-producing reaction still no starting material available or this is not the required quality in terms of dryness and temperature.

To solve this problem, separate cold start components are known, which may optionally also be thermally coupled to the reactor, as for example in the older DE 101 26 665 A1 is described.

at However, such reactors occur in the cold start case by the comparatively high thermal mass at the first contact of catalytically coated media rooms with hot gas streams to a condensation of moisture transported in these gas streams. The moisture sets as a liquid the catalytic centers and delays the start of the reactor further.

Become however, burners used to over whose exhaust gases preheat the reactor, This is due to the very high temperatures in these components to a reaction of the newly generated hydrogen or of other hydrocarbon-containing fuel residues in the media stream, so that a lot of water vapor forms in the exhaust gases. Here too Then arises the problem already mentioned above that the in be called Exhaust gases contained water vapor on the relatively cold walls of the Reactor can condense and arranged generally there Catalyst is added, so that the catalytic reaction or the Start of the catalytic reaction is further delayed.

The DE 199 48 221 C1 describes an evaporator / reformer / burner module for a gas generating system of a fuel cell system, which is constructed in the form of a multi-layer plate stack. In the module, a first evaporator layer, a first catalytic burner layer, a second evaporator layer, a second catalytic burner layer, a reformer layer for carrying out a usually endothermic reforming reaction and a third catalytic burner layer are arranged successively. During operation of the evaporator / reformer / burner module, recycled feedstocks are fed to the reformer layer in the evaporator layers, which in turn is connected to a separately formed gas purification system of the gas generating system.

From the DE 197 54 012 A1 a plate-stack reactor for a steam reforming plant of a fuel cell system is known. In the plate reactor, first alternately evaporator layers and first catalytic burner layers and then alternately first pre-reforming layers and CO oxidation layers are arranged. Subsequently, alternating CO shift layers and second pre-reforming layers and finally alternately second catalytic burner layers and main reforming layers are arranged. A channel having an evaporator-side header channel and a pre-reforming side header channel connects the evaporator layers to the first pre-reforming layers.

The JP 11 021 104 A discloses a plate reactor in which a first heating chamber, a first reforming chamber, a water gas shift reaction chamber, a second reforming chamber and a second heating chamber are sequentially arranged.

It is therefore an object of the invention, these disadvantages mentioned above to avoid and to create a reactor which with the smallest possible structure optimal heat utilization both in cold start as well as in stationary operation allows and which can be realized as a compact and lightweight component.

According to the invention this Task by a reactor having the features mentioned in claim 1 solved.

By the arrangement of the first media rooms, in which the endothermic reaction is feasible, each between two third media rooms, in which the exothermic reaction is feasible, it is achieved that the heat the one reaction to operate the other reaction in ideal Way can be used. Furthermore, the influx will increase the two third media rooms, in which the exothermic reaction is feasible, by the second media rooms reaches that entering in the region of the exothermic reaction Media stream already preheated and dried accordingly, so that the conditions for the reaction is ideal.

Of the inventive structure allows it to advantageously construct a reactor, which with ideal heat utilization represents a very compact component and due to its plate construction in terms of the required performance very easy to dimension is because the number of media rooms can be varied without changing the structure of the reactor itself have to.

According to the invention are in the second media rooms Fleeces or knitted fabrics arranged.

Droplet, which are in the media stream entering the second media spaces deposited in the field of nonwovens or wire mesh. In the event of the cold start is also the high thermal mass of the reactor exploited as a condenser in the second media rooms the moisture from the supplied Condense media stream. In addition to the sensible use of condensation heat for Heating the reactor is thereby prevented, moreover, that the Condensation in the third media spaces for the exothermic reaction takes place and where appropriate, inhibits the effectiveness of the catalyst.

Further advantageous embodiments of the invention will become apparent from the remaining dependent claims and the embodiment illustrated below with reference to the drawing.

The only attached Figure shows a reactor according to the invention in a highly schematic representation.

An illustrated in the single attached figure reactor 1 is designed in a plate design, with individual media spaces form between the plates in a conventional manner, which are indicated here in principle.

The structure of the reactor 1 is chosen so that in the first media rooms 2 in which an endothermic reaction is feasible, a media stream is introduced via a dosing and conveying device, not shown here. The media stream then flows through the first media spaces 2 , In the first media rooms 2 while the endothermic reaction takes place. In the embodiment shown here, in which the reactor 1 Part of a gas generating system for generating a hydrogen-containing gas for a fuel cell is in the first media spaces 2 steam reforming of a mixture of water and a hydrocarbon-containing compound, for example, a hydrocarbon derivative, take place. That in the first media rooms 2 produced reformate then passes, optionally via other known intervening elements, in the second media rooms 3 , in which the media flow ever a principle indicated nonwoven or knitted wire 4 flows through.

In the fleece or wire mesh 4 According to a first embodiment, droplets contained in the media stream are deposited and any moisture contained is optionally condensed out. This condensation of moisture in the area of the second media spaces 3 takes place in particular in the cold start case of such a reactor, if due to the very large thermal mass of the reactor 1 a corresponding temperature gradient between the possibly not yet reformed at this time media stream and the wire mesh 4 is present and the moisture condenses on the same. The resulting condensation enthalpy becomes the other areas of the reactor 1 fed and helps to heat this, so that by such an arrangement, the cold start behavior of the reactor 1 can be decisively improved.

After flowing through the second media rooms 3 the media stream enters third media rooms 5 , In these third media rooms 5 is then an exothermic reaction feasible, which may be a catalytic combustion or a selective oxidation in the embodiment shown here. The additive required for this selective oxidation, for example the selective oxidation of carbon monoxide to carbon dioxide, is generally an oxygen-containing medium, eg air, which thereby evacuates in a region between the second and the third media 3 and 5 the media stream is supplied, which here by the metering 6 for oxygen-containing medium (O ₂ ) is indicated.

Now to the heat utilization in the reactor 1 Ideally, the individual media streams are guided so that they are between the second media spaces 3 and the third media rooms 5 in which the exothermic reaction is feasible, in Counterflow while they are to the third media rooms 5 and the first media rooms 2 , in which the endothermic reaction is feasible, are conducted in cocurrent. From the beginning of the inflow of the media flow is thus the endothermic reaction, a very high temperature level available. The run length of the medium required for the endothermic reaction in the first media spaces 2 and the required space can therefore be minimized. In the second media rooms 3 on the other hand, in the cold start case, the area of the inflow is still quite cold, while the second media rooms 3 then heat up more in the course of the flow. The processes of condensation, drying and an optionally occurring catalytic reaction, which will be explained in more detail in the course of a second embodiment, can thus be carried out ideally. During normal operation, a comparatively high temperature prevails in the region of the inflow of the medium flow, so that condensed moisture can be evaporated again.

Such a reactor 1 therefore allows a very compact design and an ideal interconnection of the individual media rooms 2 . 3 . 5 to each other. Furthermore, as shown in the single appended figure, the structure is designed such that always two of the third media spaces 5 in which the exothermic reaction is practicable, are arranged to be one of the first media spaces 2 in which the endothermic reaction is feasible. In the field of third media rooms 5 resulting heat can thus through the plates of the plate assembly to the first media spaces 2 be forwarded and provide the energy required for the reaction occurring there. The inflow of the medium into the third media rooms 5 takes place through one of the second media rooms 3 , which is between two third media rooms 5 is arranged. Thus, before the entry of the media stream, generally from the first media rooms 2 originating Reformatstrom, the above-mentioned processes take place.

In a further embodiment of the construction, the nonwovens or wire knits 4 , which are in the second media rooms 3 may also be provided with a corresponding catalytic coating, so that it may also be in the range of the second media spaces 3 can come to a catalytic, heat-emitting reaction, which for heating the reactor 1 contributes. For this it may be useful, at the two optional dosing points 6 ' between the first media rooms 2 and the second media rooms 3 to meter in a further additive, in particular oxygen or air. After the start of this dosage may optionally be turned off again, as this reaction in particular for rapid warming of the reactor 1 makes sense in a cold start case.

When cold starting such a device is now due to the high thermal mass of the reactor 1 in the field of nonwovens or wire knits 4 in the second media rooms 3 first, droplet deposition and condensation of moisture contained in the media stream take place. The further a second media room 3 is passed through and the drier the gas, the better the conditions for the start of a reaction, which is favored by the catalyst. The resulting heat then spreads in the direction of the colder areas of the nonwovens or wire mesh 4 out, so that the condensed water can evaporate again. The reactor 1 is then available for the next cold start again in the above manner.

This is an ideal cold start in the area of nonwovens 4 can be done, these are at least partially from the rest of the reactor 1 thermally decoupled, so that heat generated in them is first used to start the scheduled reaction in them, and only then heated due to the heat of these reactions, the surrounding areas. Since such a decoupling for the benefit of condensation enthalpy is not necessarily desired, it may for example be designed so that the nonwovens or Drahtgestricke 4 in the region of the incoming gas thermally into the reactor 1 integrated and are thermally decoupled from the plates in the area of the outflowing gases. This is in the cold start case, a very rapid warming of the first flowed in the flow direction of the web or wire mesh 4 achieved without the heat too fast to the reactor 1 is derived. As soon as the reaction takes place in the region of the nonwoven or wire knitted fabric which is located further forward in the direction of flow 4 starts, there is so much heat that this is the reactor 1 or the third media rooms 5 can be made available. In this area can and must be dispensed with a thermal decoupling.

The further processes in the first and third media rooms 2 and 5 are known per se and should therefore not be explained in detail. You can example as to catalytic materials, which in particular in the case of the third media rooms 5 are applied as a coating on the plates, drain. For the first media rooms 2 On the other hand, pellets coated with the catalytic material, which can be introduced as a charge, are available.

To a discharge of catalytic material from the range of such beds, nonwovens or Drahtgestricke 4 or catalytically coated To prevent foams, appropriate filter elements may be provided. In a construction in which the first media rooms 2 with dumps and the second media rooms 3 With nonwovens or wire mesh or foams, in which optionally particles can be solved, are provided, can ideally a filter element before the entry of the media stream in the third media spaces 5 be provided.

by virtue of The possibility the reactor is very small, very compact and both in stationary operation as well as in the cold start case very effectively build, he is for applications predestined which are small, compact, lightweight, cheap and well working components need, For example, fuel cell systems in motor vehicles.

Claims (11)

Reactor ( 1 ) for a gas generating system for generating a hydrogen-containing gas for a fuel cell, which is designed in plate-like construction, wherein through the plates first, second and third media spaces ( 2 . 3 . 5 ) and in the first media rooms ( 2 ) endothermic reactions and in the third media spaces ( 5 ) exothermic reactions are feasible, the media spaces ( 2 . 3 . 5 ) are in heat-conducting contact with each other, and wherein each of the first media spaces ( 2 ) between two third media rooms ( 5 ) is arranged and the media at least to some of the third media spaces ( 5 ) via one of the second media rooms ( 3 ), which in each case between two of the third media spaces ( 5 ), characterized in that the second media spaces ( 3 ) Nonwovens ( 4 ) or knitted wire. Reactor according to claim 1, characterized in that the media streams in the first media spaces ( 2 ) in cocurrent to the media streams in the third media spaces ( 5 ) are feasible. Reactor according to claim 1 or 2, characterized in that the media streams in the second media spaces ( 3 ) in countercurrent to the media streams in the third media spaces ( 5 ) are feasible. Reactor according to claim 1, 2 or 3, characterized in that a device ( 6 ) to an additive for the exothermic reaction in an area between the second media spaces ( 3 ) and the third media rooms ( 5 ) is provided. Reactor according to one of claims 1 to 4, characterized in that the nonwovens ( 4 ) or wire knits are coated with a catalytically active material. Reactor according to claim 5, characterized in that a further device ( 6 ' ) for metering an additive in an area in front of the second media spaces ( 3 ) is provided. Reactor according to one of claims 1 to 6, characterized in that the nonwovens ( 4 ) or knitted wire are thermally decoupled from the plates further. Reactor according to one of claims 1 to 7, characterized in that the third media spaces ( 5 ) have a catalytic coating in the region of the plates. Reactor according to one of Claims 1 to 8, characterized that the exothermic reaction is a selective oxidation and the endothermic Reaction is a steam reforming. Reactor according to claim 4 or 6, characterized that the additive is an oxygen-containing medium, in particular Air is. Use of the reactor ( 1 ) according to one of claims 1 to 10 in a gas generating system for a fuel cell system in a motor vehicle.