EP1131826A2

EP1131826A2 - Recombiner for effectively removing hydrogen from air contaminated by accidents

Info

Publication number: EP1131826A2
Application number: EP99963296A
Authority: EP
Inventors: Peter BRÖCKERHOFF; Werner Von Lensa; Ernst Arndt Reinecke
Original assignee: Forschungszentrum Juelich GmbH
Current assignee: Forschungszentrum Juelich GmbH
Priority date: 1998-11-17
Filing date: 1999-11-12
Publication date: 2001-09-12
Also published as: WO2000030122A2; WO2000030122A3; DE19852954A1

Abstract

The invention relates to a recombiner for removing hydrogen from air contaminated by accidents, which comprises a housing (10) which defines a longitudinal direction for a through-flow and at both ends, in the longitudinal direction, has at least one opening. Said recombiner further comprises at least one catalyst element (11) arranged inside the housing (10). The aim of the invention is to solve the technical problem of reacting in a controlled and efficient manner and at a wide range of concentrations both small and large quantities of hydrogen with the atmospheric oxygen present in the containment vessels. To this end the at least one catalyst element (11) is configured in modular form and filled with a porous substrate which is coated with a catalytic material. The catalyst element (11) at least partly fills the cross-section of the housing (10).

Description

Recombiner for the effective removal of hydrogen from

Incident atmospheres

The invention relates to devices with which released or interference-generated hydrogen f from non-inertized rooms, for. B. Safety containers of pressure and non-inertized boiling water reactors, which in addition to hydrogen also contain water vapor, air, aerosols and other gases, can be effectively removed without reignition. The hydrogen can be present in the presence of atmospheric oxygen, e.g. B. by means of catalytic processes, recombined to water vapor within the device.

In the course of serious accidents, water-cooled nuclear reactors (LWR) generate large amounts of hydrogen as a result of the reduction in water vapor, which can get into the containment. Amounts the maximum hydrogen pressure both in boiling water reactors and about 20,000 m ³ _n betra- Due to the atmospheric oxygen in the containment containers, there is a risk of the formation of ignitable mixtures, the uncontrolled ignition of which, with subsequent detonation, causes heavy dynamic pressure on the containment walls. In addition, water vapor and hydrogen always lead to pressure and temperature increases in the accident atmosphere. This is significant especially in boiling water reactors, since the volumes m _n be their containers only about 20,000 to 70,000 m ³ compared _n ³ for pressurized water reactors. Increases in pressure and temperature lead to an additional static load on the containment walls. In addition, there is a risk of radiotoxic substances escaping in the event of leakages due to the excess pressure.

Preventive safety precautions consist in inerting the gas volumes with nitrogen, as has already been done in the case of boiling water reactors. Other countermeasures that have already been implemented are catalytic recombinerators. With the aid of them, the hydrogen produced is catalytically recombined both inside and outside the ignition limits, ie. H. converted into water vapor while generating heat. Hydrogen contents with concentrations within the ignition limits can also be burned off conventionally after spark ignition. However, the processes that occur are not controllable, so that the above-mentioned reactions which could endanger the system may occur.

Both thermal and catalytic recombiners have been developed to remove the hydrogen generated during normal operation and in the event of an accident, which recombine the hydrogen with the oxygen in the air in water vapor. Preference is given to catalytic systems that work passively, ie self-starting and without external energy supply, so that availability is guaranteed during an accident. is steady. There are two types of recombiner, both metallic plates or foils and highly porous granules, to which platinum or palladium is applied as a catalyst, being used as substrates. Several foils and granule packages - the granules are held together by wire nets to form flat packages - are arranged vertically and parallel to each other in one housing. The hydrogen / air mixture enters the bottom of the housing and the reaction begins on the catalytically coated surfaces. However, the mixture or the reaction products only flow over the surfaces of the foils or the granulate packs as a result of the thermal buoyancy that arises.

For this reason, only a small part of the total available catalytic surface is overflowed, particularly in the case of the granulate packages, and used to convert the hydrogen. Despite the large free surface of the recombiner, which uses porous granules as the substrate, the effectiveness is significantly lower than the other systems also developed, for which plates or foils are used. The fuel gas / air mixture does not reach all catalytic centers when the coated substrates flow over it, since the reaction only takes place on the package surfaces. The reaction is incomplete in both systems. In addition, the vertical arrangement of the foils or the granulate packages means that a large proportion of the cross section of the housing is freely flowed through and is therefore not used for recombination.

Another disadvantage is the fact that targeted premixing is not possible before entering the recombiners. The reactants oxygen and hydrogen are fed to the recombiners as they arise or exist locally. The maximum degradation rates or thermal outputs of existing systems are limited due to the overflow of the surfaces and the associated wrestle cross exchange. In addition, the possibility of storing heat is low.

The removal of the heat of reaction from the systems is also problematic. It occurs almost exclusively as a result of convection from the solid surfaces to the gases flowing past as well as heat radiation from neighboring structures. Excessive amounts of hydrogen can lead to overheating of the coated substrates, so that the ignition temperature is reached or exceeded and consequently homogeneous gas phase reactions with deflagration or detonation can occur. Another disadvantage is the additional heating of the surroundings.

The available systems provide the entry of the mixture containing the hydrogen on the underside. Due to the reaction on the catalytically active surfaces, there is a buoyancy, so that the depleted mixture emerges at the top. To increase the buoyancy, narrowing of the outer housing is therefore provided in the prior art. Another variant of the prior art, however, has a constant cross section over the entire height. In the upper area, however, the mixture is deflected by 90 °. It leaves the housing through an outlet grille. These systems are therefore preferably only suitable for vertical flow from bottom to top.

In the large safety containers, however, there will also be a downward flow on the outer walls, so that recombiners arranged there will also flow from top to bottom for at least a certain time and for longer periods due to the internal buoyancy and the resulting opposite flow directions can be blocked. In addition, there may be a reversal of the flow under certain operating conditions, so that in these cases and under these conditions, effective dismantling devices tion with improved start-up behavior are required.

The technical problem of the present invention is therefore to control both small and large amounts of hydrogen with the atmospheric oxygen present in the containment containers in a controlled and efficient manner in a wide concentration range.

The technical problem outlined above is solved by a recombiner for removing hydrogen from hazardous atmospheres with a housing which specifies a longitudinal direction for a flow and has at least one opening at both ends in the longitudinal direction and with at least one catalyst element which is arranged in the housing , solved, wherein the at least one catalyst element is modular and is filled with a porous substrate which is coated with a catalyst material, and wherein the at least one catalyst element essentially completely fills the cross section of the housing.

According to the invention, it has been recognized that the efficiency of the recombiner can be decisively improved by the fact that the gas mixture of the accident atmosphere flowing through the recombiner not only flows past the surfaces of the catalyst elements, but also has to flow through the catalyst elements, so that as large a proportion as possible of the catalyst elements acting surfaces within the catalyst module is flowed over by the gas mixture. Higher conversion rates are thus achieved, so that the gas mixture emerging from the recombiner is sufficiently emaciated to efficiently avoid uncontrolled combustion of the gas mixture outside the recombiner. It is therefore achieved by the present invention that the hydrogen in the containment of a pressurized water reactor is catalytically layered surfaces is implemented in a controlled manner, the risk of ignition of the hydrogen-rich mixture being largely avoided. In addition, the removal of the hydrogen is so effective that the high hydrogen concentrations which may be present at the beginning of the accident are quickly reduced to concentrations below the lower ignition limit and the risk of the explosion of large amounts of hydrogen can thus be avoided with certainty.

At least two catalytic converter modules are preferably provided, which are arranged next to one another and / or one above the other in the housing. At least one free flow channel can be provided between two catalyst modules arranged next to one another. Furthermore, at least one intermediate space is preferably provided between two catalyst modules arranged one above the other or two layers of several catalyst modules arranged one above the other, the catalyst modules being arranged symmetrically or asymmetrically in the housing. This variable arrangement of the catalyst modules, which is possible in the first place due to the modular properties of the catalyst elements, ensures that in addition to the flow through the catalyst modules, a free flow of the gas mixture through the recombiner is also possible. The free cross-section in the layers in which catalyst modules are arranged only makes up a small part of the total cross-section. Overall, however, an internal circulation is generated in this way, so that especially when the flow direction changes within the containment, the flow direction within the recombiner can also be reversed by the main flow direction of the gas mixture flow. The spaces between two catalyst modules or layers of catalyst modules also each serve to mix the gas mixture which enters the space from the catalyst modules through which flow has taken place. If several layers of catalyst modules are therefore arranged one above the other, each of which is separated by an intermediate space, a more uniform conversion of the hydrogen is achieved due to the mixing of the gas mixture in each intermediate space in the catalyst module through which flow subsequently flows.

In a further preferred embodiment of the present invention, plates or foils are provided which subdivide the housing of the recombiner in the longitudinal direction into flow channels, the flow channels being at least partially filled with catalyst modules. As a result, in addition to the catalyst modules, further surfaces are provided in the housing of the recombiner that are coated with a catalytic material. Furthermore, the formation of the flow channels serves to evenly form the flow distribution of the gas mixture through the recombiner. Finally, the additional surfaces of the plates and foils serve to absorb the heat generated by the recombination also within the recombiner and to dissipate it either to the openings of the housing arranged in the longitudinal direction or to the housing itself.

The porous catalytic substrate which is contained in the catalyst modules is preferably in the form of granules or as an arrangement of nets, strips and / or expanded metals. A combination of granules and an arrangement of nets, strips and / or expanded metals is also possible. The most uniform possible distribution of the catalytically active surface of the porous substrate is achieved. Furthermore, the flow resistance is set by the distribution of the catalytic substrate within the catalyst module in such a way that the flows of the gas mixture predetermined by the flow conditions in the containment are not prevented by the recombiner. The natural train through the The recombiner must therefore be sufficient to ensure a flow through the recombiner. Therefore, the flow resistance, which is built up by the catalyst modules within the housing of the recombiner, must not exceed an upper threshold.

Due to the increased efficiency of the conversion of hydrogen according to the invention, it is necessary to ensure sufficient heat dissipation within the recombiner. The plates or foils already arranged in the housing serve for this purpose. Furthermore, a combination of a coated, catalytically active substrate and an uncoated, non-catalytically active substrate can also be provided for this purpose in a catalyst module. The hydrogen is then reacted on the catalytically active substrate with the liberation of heat, the uncoated substrates being able to absorb the thermal energy and, if appropriate, to pass it on. For this purpose, the uncoated, non-catalytically active substrates are preferably in heat-conducting contact with external structures.

The modular structure of the catalytic converter elements of the present invention is reinforced in particular by the design of the catalytic converter module with a housing which is open at least on two sides in order to allow a flow through the catalytic converter module. On the one hand, the housing creates easily manageable units or modules, on the other hand, through a suitable arrangement of the catalyst modules with their housings, free flow channels can be formed in the housing of the recombiner. Furthermore, the size and shape of the catalyst modules can be very easily adapted to the relevant circumstances due to the design with a housing. In this case, the housing of the catalyst module is preferably completely filled with catalytic substrate, while in a further embodiment at least in the housing a flow channel is formed which is not filled with catalytic substrate. Like the housing of the recombiner, the housing of a catalyst module can also have plates or foils which subdivide the housing of the catalyst module in the longitudinal direction into flow channels. These flow channels are then at least partially filled with catalytic substrate. Here, too, the plates and foils serve to improve the flow and possibly better dissipate the heat generated by the recombination.

As has already been stated, it is necessary that a recombiner arranged in the containment can be flowed through in both directions. For this purpose, the housing of the recombiner is preferably designed such that it has an essentially identical cross section over the entire length. Therefore, there are no cross-sectional changes that would flow through the recombiner in one of the two directions.

In order to achieve a better conversion of the gas mixture by the recombiner, it is advantageous if the gas mixture is mixed sufficiently, that is to say that the oxygen and the hydrogen are in each case distributed as evenly as possible in the gas mixture. For this purpose, a calming and mixing zone is preferably provided on at least one of the two open ends within the housing of the recombiner before the inflowing gas mixture reaches the first catalyst module or the first layer of catalyst modules. The result is a more efficient and more even conversion of the hydrogen.

In a further preferred manner, the plates and foils arranged in the interior of the housing of the recombiner divide the calming and mixing zone into partial volumes. This serves to ensure that the entering gas mixture calmed more and can be aligned to the catalyst modules. On the other hand, the division of the volume ensures that the size of the partial volumes is so small that any ignition of the gas mixture which may occur when it emerges from the recombiner is prevented, since the free distances between the plates and foils are smaller than the size of the Detonation cells are.

Ignition of the gas mixture in the area of the calming and mixing zone upon entry and exit of the gas mixture is further prevented by the plates or foils being at least partially uncoated. This prevents further recombination and heating of the recombiner in the inlet and outlet area of the housing, and the uncoated areas can absorb and dissipate the heat present in the gas mixture.

The cooling devices, which are preferably arranged on at least one of the two open ends of the housing and which cool the incoming or outgoing gas mixture sufficiently to avoid exceeding the ignition temperature within the hydrogen-containing gas mixture, serve the same purpose.

To cool the recombiner itself, cooling devices are arranged in a more preferred manner within the housing of the recombiner in the volumes left free by the catalyst modules. These can be the free flow channels or the spaces between two catalyst modules or layers of catalyst modules arranged one above the other. The cooling devices are designed in particular in the form of radiation sheets or in the form of cooling tubes through which coolants flow.

Finally, ignition of the gas mixture is prevented by non-return locks, which on at least one of the Both open ends of the housing are provided. The non-return valves have openings with a size that allow the gas mixtures to enter and exit. Due to the heat dissipation by means of these barriers, however, the passage of the flame is prevented.

The size, shape, material selection and technical conception of the above-mentioned components as well as the components to be used according to the invention described in the exemplary embodiments are not subject to any special exceptional conditions, so that the selection criteria known in the field of application can be used without restriction. Further details, features and advantages of the subject matter of the invention result from the following description of the accompanying drawing, in which - by way of example - preferred embodiments of the recombiner according to the invention are shown. The drawing shows:

1 shows a safety container of a reactor system in a schematic representation, with recombiners from the prior art being shown in the right half and an inventive recombiner in the left half,

2 shows a first exemplary embodiment of a recombiner according to the invention,

3a, b the recombiner shown in Fig. 2 in cross section,

4a, b a second embodiment of a recombiner according to the invention in longitudinal section and in cross section, O 00/30122

12th

5 a-c a third embodiment of a recombiner according to the invention in longitudinal section and

Fig. 6 different configurations of the catalyst modules in cross section.

1 schematically represents a safety container of a reactor system. It shows the flow processes within the containment during an accident by way of example.

For the sake of simplification, the illustration of the reactor and other components which are arranged within the security container 1 has been omitted. In the lower area 2, after an accident, hydrogen reacts from the reaction of the water vapor with the fuel element casings. The mixture consisting of steam, air, hydrogen and aerosols rises due to the density differences - high temperature of the mixture and low density of the hydrogen - as shown by the dashed line 3a. As a result of the heat dissipation on the cooler outer walls, a downward movement occurs due to the higher density, as shown by arrow 3b.

On the right-hand side of FIG. 1, two recombiners 4a and 4b known from the prior art are likewise indicated schematically and by way of example, which are generally attached to the walls according to the prior art. They consist of a housing 10 'and catalytically active elements 11' which, in the case of the recombiner 4a, consist of plates or foils and in the case of the recombiner 4b, consist of granule packs.

As described above, all known systems are designed for a flow from bottom to top, as shown by arrow 5a. The indicated convection roller however, allows the conclusion that a flow in the direction of gravity is possible. The assumption of an upward flow indicated by the arrow 5a certainly applies in the event that the recombiners 4 are either in the upward flow or the gas mixture inside the containment is initially at rest and after the start of the reaction on the catalyst elements a flow against the gravity of the earth starts. But even in this case, a downward flow through the recombiners or circulation in them may occur after a certain time. However, the systems known from the prior art are not designed for this operation.

In the left half of FIG. 1, a recombiner 6 according to the invention, likewise consisting of housing 10 and catalyst modules 11, is shown, in which the inflow is possible both from above and from below. The cross section of the housing 10 is the same over the entire height. In addition, the catalytic catalyst modules 11 are arranged symmetrically or asymmetrically in the housing, so that internal circulations can also be generated in this way.

Coolers 7 are arranged at the inlet and outlet to absorb the heat of reaction or to cool the atmosphere. The heat absorbed by the coolers 7 is released through risers 8 to higher water basins. The cooled water flows back through the lines 9 into the cooler 7.

2 shows an exemplary embodiment of the recombiner 6 in greater detail. Catalytic catalyst modules 11 are arranged next to one another and one above the other in a housing 10. A continuous flow channel 13 is provided, which enables a flow in both directions. Between the catalyst modules 11 there are spaces 14 in which the emaciated gas can mix and cool. Further calming or mixing zones 15 are on the Einzw. Exit of the housing 10 is provided.

In the case of an upward flow, the mixture enters at the bottom, as shown by arrow 16. As a result of the exothermic reaction, the mixture in the flow channel 13 is heated and rises, as shown by the arrow 17. Above, the mixture, depleted and heated, leaves the recombiner 6, as shown by the arrow 18. The case of a downward flow is also indicated. Entry 19 and exit 20 are indicated by dashed lines.

The amount of heat released in a catalyst module 11 is either dissipated convectively from the other gases, as shown by the arrow 21, or dissipated through the recombiner wall 10 to the outer containment atmosphere 22 or to the atmosphere 23 flowing through the middle flow channel 13. This prevents additional heating and possibly overheating of the subsequent catalyst modules 11.

There are check valves 12 at the inlet and outlet which are intended to prevent the flame from spreading into the containment when the mixture is ignited. These barriers can be designed as nets, expanded metals or grids for dissipating the heat, the free distances between the wires, webs or bars are smaller than detonation cells. This means that they can also prevent detonations from escaping. 3a and 3b show two exemplary embodiments of the recombiner 6 described above, which show in cross section the outer wall 10, catalyst modules 11 and a flow channel 13 for cooling, which is shown here as a single and central channel. However, further, not symmetrically arranged flow channels are also conceivable, which support the formation of internal circulation flows in the case of a downward flow. The representations of the cross sections in Fig. 3 shows that the catalyst modules 11 are modular and on the other hand essentially fill the cross section of the housing 10, wherein only one flow channel 13 is formed, which only a small part of the cross section of the housing 10 occupies.

The catalyst modules 11 show in FIGS. 3a and 3b as porous substrates arrangements of granules on the left and nets or expanded metals on the right. Numerous modifications are possible for both, e.g. B. size (edge length, diameter, effective heights), materials (ceramic, metal), grain or wire diameter (granulate shape, porosity), arrangement of the individual layers to each other (rotation), layer thicknesses and catalyst materials and amounts. Combinations of nets and granules are also provided and have advantageous effects. The amount of the porous substrate is dimensioned so that there is no excessive pressure loss when flowing through the porous substrate, which prevents a flow due to natural draft. Furthermore, in order to avoid overheating and ignition, a combination of catalytically active elements with uncoated nets, expanded metals, granules or plates is also possible for the purpose of heat storage or dissipation. When using the aforementioned plates or foils, only one side can be coated. FIG. 4a shows a longitudinal section through a recombiner 6 modified in comparison to FIG. 2. In this embodiment, plates or foils 24 are arranged in parallel in the housing 10. At the inlet and outlet there are the non-return safeguards 12 described above. The catalyst modules 11 are arranged in the longitudinal direction in the middle of the housing. The different flow channels can be seen in the cross section shown in FIG. 4b. The previously described networks, expanded metals or granules come into consideration as catalytically active material. In FIG. 4b it can also be seen that the catalyst modules 11 completely fill the cross section of the housing 10.

To increase or better control sales, the plates or foils 24 can be coated over the entire length or only in sections with catalyst materials. The turnover is only in sectors. In the subsequent uncoated section, heat is stored and dissipated. This leads to cooling of the mixture flowing past and thus overheating in the next coated section is avoided. Another possibility is to use short plates or foils which are coated on one or both sides and between which there are empty spaces. The gas can mix and cool in the empty spaces between adjacent plate or film sections.

5a to c show three exemplary embodiments of the previously described recombiner 6. 5a shows a plurality of catalyst modules 11 lying next to one another, which are separated from one another by plates 24 and substantially completely fill the cross section of the housing 10. Between the individual catalyst modules 11 one above the other there are intermediate spaces 14 for swirling, mixing and cooling the atmosphere. In FIG. 5 b, individual zones lying one above the other and next to one another are not filled with porous substrate, so that they act as flow channels 13 and are freely flowed through and can contribute to cooling the catalyst modules 11. The width of the catalyst modules 11 and the free zones is dimensioned such that the buoyancy in the reaction zones does not completely hinder a downward flow through the free zones, the catalyst modules 11 of each layer essentially completely filling the cross section of the housing 10.

The embodiment shown in FIG. 5c alternately provides catalyst modules 11 and free flow channels 13 in each layer, in which the hydrogen-containing mixture is either converted or used for cooling. In the subsequent layer, catalyst modules 11 and flow channels 13 are arranged offset from the previous position. As in the other exemplary embodiments, calming and mixing zones are also provided in the intermediate spaces 14 between the individual modules 11. A great advantage of these arrangements is the flexibility and adaptability to the respective circumstances, i. H. The height, cross-section and number of modules can be freely selected.

The overview of FIG. 6 shows the arrangement of possible individual catalyst modules in a recombiner housing 10. Each catalyst module 11 has a separate housing 33. This arrangement offers the advantage that a hydrogen-rich containment atmosphere can flow in the free spaces between the housings 33 of the individual catalyst modules and between the housings 33 of the catalyst modules and the recombiner wall 10 and can dissipate part of the heat of reaction generated in the catalyst modules 11. The number and arrangement of the catalyst modules 11 are adapted to the circumstances, the catalyst modules 11 of a layer of catalyst modules 11 each having the cross section of the housing 10 essentially completely fill and the free spaces make up only a small part of the cross section.

In the entire cross section, the catalyst module 25 has either nets or granules, both coated with catalyst material.

A flow channel 34, arranged centrally in the example, is additionally provided for cooling the catalyst module 26.

In the catalyst module 27, the cross section is divided into smaller channels by means of inserted plates or foils 35, the cross sections of which are each filled with networks of the same or different wire diameters or mesh sizes.

In the catalyst module 28, both sides of the plates or foils 35 for hydrogen recombination are also coated with catalyst material at the edges of the individual cross sections.

The catalytic converter module 29 provides free flow channels 36, the cross sections of which are not filled with nets, for heat dissipation. This creates zones in which free convection can form and contribute to cooling. These zones make up only a small part of the total cross-section. The plates or foils 35 are coated only on the sides that are in contact with the catalyst elements.

In the catalyst module 30, porous granules are provided in all cross sections. Material, porosity and catalyst coating can be the same or vary in all channels. In the catalyst module 31, both sides of the plates or foils 35 are coated. The channels are filled with granules as before.

The catalyst module 32 again provides free flow channels 36 to create convection zones and thus heat dissipation. As described above, the porous granules in the catalyst elements can be the same or have different porosities. The plates or foils 35 are coated on one side only.

The symmetrical arrangement of the catalyst modules in the recombiner housing 10 is shown in FIG. 6. Also in FIGS. 5a and 5b, the asymmetrical position of one or more catalytic converter modules 11 in the housing 10 is also the case when the hydrogen-rich mixture flows downwards through the free gaps or through the catalytic converter modules 11 itself due to the pressure differences between the free cross sections and channels filled with porous catalytic converter elements Modules that lead to the cross exchange of the mixture strands, an internal circulation with upward flow through the catalyst module and thus a starting of the reaction possible.

To avoid heating up the containment atmosphere, the recombiners shown can be operated with upstream and downstream coolers 7, as shown in FIG. 1. Combinations with self-starting turbocompressor units are also conceivable, so that the flow is forced and their catalytic effectiveness is increased due to higher flow velocities and thus also higher heat and mass transfer coefficients. In this case, the recombiners no longer have to be arranged vertically. Your inclination to the vertical axis can be arbitrary. Reference numeral e

1 security container

2 lower area

3 flow gas mixture

4 recombiners

5 flow

6 recombiner

7 cooler

8 riser

9 Downpipe

10 housing

11 catalyst module

12 Non-return check

13 flow channel

14 space

15 calming and mixing zone

16 Upward flow

17 Upward flow

18 Upward flow

19 Downward flow

20 Downward flow

21 convection

22 Heat dissipation in a containment atmosphere

23 Heat dissipation in the containment atmosphere of the flow channel 13

24 plates or foils

25 to 32 catalyst module

33 housing of 11

34 flow channel

35 plates / foils

36 flow channel

Claims

Claims;

1. Recombiner for removing hydrogen from hazardous atmospheres with a housing (10) which specifies a longitudinal direction for a flow and has at least one opening at both ends in the longitudinal direction, and with at least one catalyst element (11) which is in the housing (10) is arranged,

characterized,

that the at least one catalyst element (11) is of modular design and is filled with a porous substrate which is coated with a catalyst material, and that the at least one catalyst element (11) essentially completely fills the cross section of the housing (10).

2. Recombiner according to claim 1, characterized in that at least two catalyst modules (11) are provided, which are arranged side by side and / or one above the other in the housing (10).

3. Recombiner according to claim 2, characterized in that between two catalyst modules (11) arranged next to one another at least one free flow channel

(13) is provided.

4. Recombiner according to claim 2 or 3, characterized in that between two stacked catalyst modules (11) at least one space

(14) is provided.

5. Recombiner according to one of claims 2 to 4, characterized in that the catalyst modules (11) are arranged symmetrically or asymmetrically in the housing (10).

6. Recombiner according to one of claims 1 to 5, characterized in that plates or foils (24) divide the housing (10) in the longitudinal direction into flow channels, the flow channels being at least partially filled with catalyst modules (11).

7. Recombiner according to one of claims 1 to 6, characterized in that the porous catalytic substrate is designed as granules or as an arrangement of networks, strips and / or expanded metals.

8. Recombiner according to one of claims 1 to 6, characterized in that the porous catalytic substrate is formed as a combination of a granulate and an arrangement of nets, strips and / or expanded metals.

9. recombiner according to one of claims 1 to 8, characterized in that in a catalyst module (11) a combination of a coated, catalytically active substrate, in particular plates or films, and an uncoated, non-catalytically active substrate, in particular plates or films, is provided.

10. Recombiner according to one of claims 1 to 9, characterized in that the catalyst module (11) has a housing (33).

11. Recombiner according to claim 10, characterized in that the housing (33) of the catalyst module (11) is arranged at a distance from the housing (10).

12. Recombiner according to claim 10 or 11, characterized in that the housing (33) of two catalyst modules (11) spaced apart from each other in the housing (10) of the recombiner (6) are arranged.

13. Recombiner according to one of claims 10 to 12, characterized in that the housing (33) of the catalyst module (11) is completely filled with catalytic substrate.

14. Recombiner according to one of claims 10 to 12, characterized in that at least one flow channel (34) is formed in the housing (33).

15. Recombiner according to one of claims 10 to 14, characterized in that plates or foils (35)

Subdivide the housing (33) in the longitudinal direction into flow channels (36), the flow channels (36) being at least partially filled with catalytic substrate.

16. Recombiner according to one of claims 1 to 15, characterized in that the housing (10) has a substantially same cross section over the entire length.

17. Recombiner according to one of claims 1 to 16, characterized in that a calming and mixing zone (15) is provided on at least one of the two open ends within the housing (10).

18. Recombiner according to claim 17, characterized in that arranged in the interior of the housing (10) divide the calming and mixing zone (15) into partial volumes.

19. Recombiner according to claim 18, characterized in that the plates or foils (24) in the region of the calming and mixing zone (15) are at least partially uncoated.

20. Recombiner according to one of claims 1 to 19, characterized in that cooling devices (7) are arranged on at least one of the two open ends of the housing (10).

21. Recombiner according to one of claims 1 to 20, characterized in that in the housing (10) of the catalyst modules (11) released volumnia cooling devices are arranged, in particular in the form of radiation plates or cooling tubes through which coolants flow.

22. Recombiner according to one of claims 1 to 21, characterized in that non-return locks (12) are provided on at least one of the two open ends of the housing (10).