Electrically heated metal foam component and reactor arrangement comprising electrically heated metal foam element

Abstract

The invention relates to an electrically heatable metal foam component, comprising a metal foam material having at least one contact section for electrical contact with the metal foam material, at least one transition section and at least one heat transfer section, wherein the transition section is arranged between the contact section and the heat transfer section, the metal foam material being densified in the contact section compared to the heat transfer section, and the metal foam material being densified in the transition section compared to the heat transfer section. The degree of densification varies from the degree of densification in the contact section to the metal foam material in the heat transfer section.

Description

Technical Field

[0001] The present invention relates to an electrically heated metal foam component (EHC) and a reactor arrangement comprising the electrically heated metal foam component. Background Art

[0002] In many chemical processes, it's necessary to supply energy to the reaction medium. This is done to reach the ignition point of exothermic reactions more quickly, or to meet the high energy requirements of endothermic processes. By supplying energy, the rate of a chemical reaction can be increased. The higher the temperature of the reaction system, the greater the likelihood that the reactants will overcome the activation energy barrier and react to produce the desired product.

[0003] The required energy can be supplied to the system in the form of heat. The transfer of heat to the reaction site in the reactor is always based on at least one of heat conduction, convection and radiation. Heat transfer in solids (such as reactor walls or reactor fillers) is mainly based on heat conduction. In a flowing medium, thermal energy is transferred by entrainment and movement of larger material aggregates. In a fluid, heat transfer by convection is superimposed on heat transfer by conduction. Heat transfer by radiation utilizes electromagnetic radiation and therefore does not require a transfer medium. It occurs in all heat transfer processes and increases with the increase of geometric surface area. The same transfer phenomenon also leads to the loss of unused energy or heat.

[0004] In the field of reaction engineering, heat supply to, for example, the reaction site is often achieved by preheating the medium before entering the chemical reactor or by externally heating the reactor's outer wall. However, known methods have limitations in explicitly transferring heat to the reaction site. In typical reactor arrangements, heat is transferred from the reactor wall to the reactor interior, but is also released into the surrounding environment. Furthermore, in reactor arrangements used for continuous processes, the reactor's packing can only store absorbed heat to a limited extent, as most of the heat is discharged from the reactor with the outflowing medium. To achieve the required temperature at the reaction site, heat losses must be compensated by increasing energy input. Therefore, for economic and ecological reasons, it is desirable to keep this heat loss as low as possible through appropriate measures and to continuously optimize heat input methods. Another difficulty with conventional reactor heating via the reactor wall is the uneven heat distribution along the reactor cross-section. The temperature of sections near the reactor wall can be significantly higher than that of sections further from the reactor wall. In particular, in fixed-bed reactors, heat sinks can occur in the central portion of the reactor, i.e., the section farthest from the reactor wall.

[0005] For many industrial processes, such as steam methane reforming (SMR), heating of the reactor unit is typically performed externally via an open flame. Since this external heating is indirect, i.e., heat is typically transferred via the reactor wall, this approach has significant inertia and the difficulties mentioned above regarding uneven heat distribution. While this inertia is tolerable for large-scale, continuous SMR processes, the open flame is typically fed by fossil fuels, producing combustion gases that often require additional post-processing and / or release greenhouse gases into the atmosphere. Therefore, there is a need to provide a system that can supply heat to the reactor in a uniform manner without the need for external heating via an open flame.

[0006] The obstacles mentioned above can be observed when supplying heat to many different types of reactors, such as reactor devices for exhaust gas treatment. Such reactor devices are installed downstream of exhaust gas generating devices, such as combustion chambers. Combustion chambers can be found in internal combustion engines, but also in many other applications, such as power plants. In the automotive field in particular, hybrid vehicles with electric and internal combustion engines are becoming increasingly popular. When a hybrid vehicle is propelled by the electric engine, the internal combustion engine can be turned off to save fuel. The internal combustion engine is started at any time to provide power to the drive system as long as necessary. In such vehicles, the internal combustion engine operates for a considerable period of time in cold conditions, generating a significant amount of unnecessary exhaust gas. Since the internal combustion engine does not run continuously, the exhaust gas treatment system located downstream of it cannot operate under ideal conditions. There are several concepts for supplying additional heat to the exhaust gas treatment system, however, they have the same disadvantages as those described above for the field of reaction engineering, and in addition, they are often not fast enough to ensure that the internal combustion engine reaches operating temperature almost instantly after starting. Summary of the Invention

[0007] The object of the present invention is therefore to provide a component for supplying heat in a direct, rapid and spatially defined manner, in particular inside a chemical reactor for treating fluids, which component at the same time has a long life and is easy to connect electrically.

[0008] This object is achieved by an electrically heatable metal foam component (EHC) according to claim 1. Furthermore, the object is achieved by a reactor arrangement comprising such an electrically heatable metal foam and a method for treating a fluid, wherein the fluid flows through such a reactor arrangement.

[0009] Specifically, the electrically heatable metal foam component (EHC) of the present invention includes a metal foam material, which has at least one contact section for electrical contact with the metal foam material, at least one transition section and at least one heat transfer section, wherein the transition section is arranged between the contact section and the heat transfer section, wherein in the contact section, the metal foam material is densified, in particular compressed, compared to the heat transfer section, and wherein in the transition section, the degree of densification, in particular the degree of compression, changes from the degree of densification in the contact section to the metal foam material in the heat transfer section.

[0010] By providing a contact section, a transition section and a fluid handling section, the metal foam material can be brought into electrical contact with an electrical energy source while ensuring a uniform distribution of the current throughout the electrically heatable metal foam. It has been found that direct electrical contact of the electrical energy source with an undensified (such as uncompressed) metal foam material leads to an uneven distribution of the current, in particular in the contact area, even if the contact is made across the entire thickness of the metal foam (e.g. by welded contact plates or contact tabs). The current takes the shortest path to the counter-pole contact point without using all available conductive paths, i.e. the struts of the metal foam material. This effect leads to higher local resistances (underutilization of the conductor cross section) and correspondingly higher temperatures, which place an additional strain on the mechanical load-bearing capacity of the material. In this context, the change in the degree of densification (in particular by compression) is preferably gradual.

[0011] Experiments have shown that during current coupling, the connection points of the undensified (e.g., uncompressed) foam are subjected to enormous stresses. Failure of the component (i.e., the individual metal struts) is most likely to occur here. Gradually, more and more of these metal struts become damaged until the current coupling into the metal foam material fails. This effect limits the service life of EHCs without contact sections. The design of the electrically heatable metal foam of the present invention allows the current to be coupled uniformly into the metal foam material at the contact section. The transition section then distributes the current in a uniform manner to the heat transfer section, especially when the degree of compression in the transition section varies gradually. As a result, a more uniform current distribution is achieved, especially in the contact area, and this design therefore suppresses the occurrence of locally higher resistances and correspondingly higher temperatures, which otherwise could lead to rapid failure of the metal foam struts. Therefore, the present invention provides a long service life of the EHC.

[0012] In the EHC of the present invention, the density of the metal foam is increased in the contact section, for example by compressing the cells of the metal foam material, particularly to the point where overlapping struts (which were originally (i.e., before compression) arranged spatially apart) are in direct contact with one another, thereby increasing the effective (utilized) conductor cross section. The series of contacts in the contact section and the gradual transition from the contact section via the transition section to the heat transfer section result in an EHC with uniform electrical conductivity and homogeneous heat generation over a large area. This results in a significantly longer service life for the EHC of the present invention. Densification can be achieved through additive processing, such as by filling the cells of the foam material with a conductive additive (e.g., in the form of a powder), plasma spraying, or treatment with a metal slurry.

[0013] Furthermore, the higher density of the contact sections also simplifies contacting (eg by resistance welding or screws). In the original (ie uncompressed) state of the foam, this can only be left to specialists.

[0014] According to a specific embodiment of the EHC of the present invention, the number of heat transfer sections disposed in the metal foam material is preferably half the number of transition sections and contact sections, wherein each heat transfer section transitions into two contact sections via two transition sections disposed at separate portions of the heat transfer section. This allows current to be coupled into and out of the heat transfer section, thereby allowing more than one heat transfer section to be connected in parallel or in series.

[0015] In a preferred embodiment, in an EHC according to the present invention, the length of the transition section is at least 0.3 times, and particularly at least 0.5 times, the thickness of the metal foam material at the location where the heat transfer section is adjacent to the transition section. More preferably, the length of the transition section is in the range of 1.0 to 5.0 times the thickness of the metal foam material at the location where the heat transfer section is adjacent to the transition section. Since the mechanical stability of the metal foam depends on the interconnected network of cells, compression is performed in a manner that ensures that the network and its connections remain intact. Step-wise compression may damage parts of the structure due to the shear forces that occur. By setting the transition section length to at least 0.5 times, and particularly 1.0 to 5.0 times, the thickness of the metal foam material at the location where the heat transfer section is adjacent to the transition section, a gradual (i.e., smooth) transition is provided while maintaining the mechanical stability of the metal foam material. In other words, when the transition section has the lengths indicated above, the material between the contact section and the heat transfer section is less likely to break.

[0016] In a preferred embodiment of the present invention, more than one heat transfer section is electrically connected via the transition section and the contact section. This allows for a more complex design and the EHC to be adapted to its intended use.

[0017] According to the present invention, it is particularly preferred to compress the metal foam material in the contact section so that its thickness is reduced by at least 60%, particularly at least 70%, at least 75%, or at least 85% compared to the thickness of the uncompressed metal foam material. There is no upper limit to the compression, and the metal foam material in the contact section can be compressed as much as possible. With such compression, the thermal load at the electrode contact point is significantly reduced. This results in significantly improved durability of the entire component. The minimum degree of compression can vary greatly, depending on the type of metal foam material (i.e., uncompressed metal foam material). Relatively dense metal foam materials (having a porosity of, for example, 60%, as defined below) can achieve the advantageous effects of the present invention with a compression equivalent to a thickness reduction of less than 60%. However, particularly for high porosities, such as greater than or equal to 70%, particularly preferably greater than or equal to 80%, very particularly preferably greater than or equal to 85%, even more preferably greater than or equal to 95%, and most preferably 97% or more, the degree of compression is, in particular, as indicated above. The porosity of a metal foam as referred to herein refers to the ratio of the metal volume to the void fraction volume and can be determined by image analysis as explained below.

[0018] According to the present invention, the thickness of the metal foam element, particularly the thickness of the metal foam, can vary widely. The thickness of the metal foam material in the heat transfer section is preferably in the range of 1.0 to 100 mm, particularly 1.5 to 75 mm, and even more preferably 1.5 to 50 mm. Preferably, the thickness is such that at least three pores, particularly at least five pores, and even more preferably at least seven pores are present in the thickness direction. In the case of sheet-like metal foam, the thickness direction is perpendicular to the sheet; in the case of coiled metal foam, the thickness is in the radial direction. If the metal foam material thickness exceeds the indicated values, the metal foam may be heated unevenly, which may negatively impact the service life of the EHC.

[0019] The EHC is preferably configured in the reactor such that the gas flow length through the metal foam is equal to or greater than the thickness of the metal foam element. Most preferably, the gas flow length is greater than the thickness of the metal foam element. For example, when the foam sheet is arranged such that fluid flow through the reactor is normal to the metal foam surface, the flow length is equal to the thickness of the metal foam. When the metal foam is arranged such that fluid flow is not normal to the metal foam surface, the flow length is correspondingly increased.

[0020] In a preferred embodiment of the present invention, the porosity of the metal foam material in the heat transfer section is greater than or equal to 70%, particularly preferably greater than or equal to 80%, and very particularly preferably greater than or equal to 85%, and most preferably it can be 95% or greater. By using such a highly porous metal foam material, the pressure drop across the metal foam material can be kept low, which can be advantageous for certain applications. Porosity here refers to the quotient of the volume of the pores in the metal foam and the total volume of the metal foam. It has been found that when such metal foams are used in electrically heatable metal foam components (EHCs), a porosity of less than 70% has a negative impact on mass transfer and pressure loss. The porosity is determined by image analysis of a cross-section of the metal foam. For this purpose, a cross-section of the metal foam is prepared and an image of it is recorded. To determine the porosity, the image surfaces with and without material (i.e., the material area and the pore area) are correlated. For example, a porosity of 50% means that the surface with and without material in the recorded image is of equal size. The higher the proportion of material-free surfaces in the recorded image, the higher the porosity of the metal foam.

[0021] Metal foams possess a variety of properties that allow for efficient, rapid, and targeted heat transfer to fluids through heatable metal foams. The foam structure includes irregular pores, which induce turbulence in the fluid passing through or along the metal foam surface. This turbulence supports heat transfer via convection, thereby heating the fluid more rapidly. Furthermore, the metal foam provides a large surface area, further facilitating heat transfer from the heated substrate (i.e., the metal foam) to the fluid. Furthermore, direct heat transfer to the reactor interior can be achieved through radiation. The heated metal foam can radiate heat directly within the reactor. Reactor fillers (such as catalyst particles), which can be located near the EHC, can receive thermal energy via radiation from the metal foam elements. This allows for the supply of radiant heat to the center of the reactor, something that is only very limited, if possible, with conventional reactor designs utilizing externally heated reactor walls. Furthermore, direct heat supply via electrically heated metal foam within the reactor assembly is significantly faster than typical indirect heat supply, such as via the reactor wall. Therefore, heat transfer can be initiated precisely when necessary, without the significant lead time required, for example, by indirect heat supply via the reactor wall. Because the metal foam is within the reactor assembly and arranged so that the fluid within the reactor assembly is in contact with the open pores of the metal foam, no indirect heat supply via the reactor wall is required. Avoiding the use of external flames to heat the reactor walls can further significantly reduce greenhouse gas emissions, provided, of course, that the metal foam elements are heated using electricity from sustainable energy sources.

[0022] Because the metal foam is preferably open-pore, at least in the heat transfer section, gaseous and liquid reactants can permeate throughout the metal foam and be directly heated. In this context, it should be noted that, according to one embodiment of the present invention, it is preferred for the reactor apparatus of the present invention that the metal foam material of the heat transfer section be arranged such that the fluid contacts the metal foam by flowing through the metal foam (i.e., the fluid passes through the open pores of the metal foam). A preferred way to achieve this is to arrange the metal foam within the flow path of the fluid within the reactor, such that the fluid is substantially unable to bypass the metal foam or metal foam elements.

[0023] According to another embodiment, in an EHC according to the present invention, the metal foam material, at least in its heat transfer section, has a tubular shape with a hollow interior along its axis. This provides a flow path within the tubular shape of the heat transfer section, i.e., fluid can flow through the hollow interior section without having to pass through the metal foam material. It may be desirable to direct the fluid through the metal foam material. In this case, the hollow interior section may be blocked by a material that is impermeable to the fluid, so that fluid entering the hollow section must penetrate the metal foam material to exit the heat transfer section. Alternatively, the EHC may be designed and arranged within the reactor device such that fluid must penetrate the metal foam material before reaching the hollow interior section and continuing to flow within the reactor device.

[0024] In another embodiment of the present invention, the metal foam material has a spiral shape, at least in its heat transfer section, wherein preferably, electrically insulating sections or gaps of insulating material are arranged between adjacent strips of the spiral. The electrically insulating material, or one or more electrically insulating sections, define an electrical path through the metal foam material. The spiral shape of the metal foam material increases its length and reduces its geometric and electrical cross-section, requiring current to travel a longer distance through the metal foam before exiting it, resulting in more uniform heating of the metal foam. This results in more uniform heat transfer compared to tubular or rod-shaped designs. Furthermore, by placing insulating material between adjacent strip sections of the spiral metal foam material, short circuits between the strip sections are avoided, although this can, in principle, also be achieved by providing sufficient gaps between adjacent strip sections. Furthermore, the spiral metal foam material can be mechanically stabilized by the insulating material. Furthermore, by filling the space between adjacent sections of the spiral metal foam material, an overall tubular shape can be created, which has the advantages described above, while also increasing the electrical path length and improving heat transfer capabilities. The insulating sections have a higher specific electrical resistance than the electrical resistance of the metal foam material itself. The insulating section preferably has 10 7 Ω·cm or higher, more preferably 10 8 Ω·cm or higher, even more preferably 10 9Specific resistance of Ω·cm or higher. As mentioned above, the insulating section can be a gap. In this case, the specific resistance is determined by the substance in the gap (ie, the fluid flowing therethrough).

[0025] The EHC of this embodiment of the invention may comprise more than one spiral metal foam segment, in particular two or more spiral metal foam segments. This further increases the temperature uniformity. It is particularly preferred that the two or more spiral heat transfer segments form a double helix, or a triple helix, or a quad helix, etc., depending on the number of spirally formed metal foam heat transfer segments, i.e., the strips of the spirals are arranged parallel to each other and the spirals rotate around a common longitudinal axis. The strips of the double helix (and higher-order spirals) can be separated from each other by arranging an electrically insulating material (such as ceramic, glass, polymer material, etc.) between the strips or by providing an air gap between them. As described above for a single spiral, in this way, short circuits between the strips can be reliably avoided and the mechanical strength can be improved.

[0026] Alternatively or in addition, in at least two heat transfer sections having a spiral shape, the two spiral sections are essentially wound around the same longitudinal axis, wherein one of the heat transfer sections has a smaller radius and is positioned within the cavity of the heat transfer section having a larger radius, i.e., one spirally wound heat transfer section is positioned within the other spirally wound heat transfer section.

[0027] Since the current is provided with a geometrically restricted cross-section, a single or multiple spiral strips result in a defined current flow. This is preferred for large cross-sections, since experiments have shown that the current always chooses the shortest path through the metal foam and may heat large partial areas poorly or not at all. The smaller the cross-section (also in terms of current density), the more uniform the flow of current in the cross-section. Therefore, the more strips there are, the more uniform the heat coupled into the reactor medium. The spiral is connected to the current-carrying conductor via an electrode. The electrode is positioned at the end of the spiral. If multiple spirals are used, the current can be collected at the end of one side via a common electrode. This corresponds to a parallel connection of the individual strips of the spiral. If the cross-section of the body through which the flow passes is too large, a series connection can also be established and the end of one strip of the spiral can be connected to the end of an adjacent strip.

[0028] Preferably, each of the at least two spiral-shaped heat transfer segments is electrically connected to one another via a contact area provided at each of the spiral heat transfer segments. This creates a long electrical path, improving the uniformity of heat transfer and the uniformity of the EHC of the present invention. The spiral heat transfer segments can be connected in a parallel circuit or in a series circuit. It has been found that connecting the spiral heat transfer segments in a series circuit is advantageous for EHCs in which the length of the heat transfer segment is less than 10 times, and particularly less than 5 times, its diameter. Below, a series circuit is explained with the EHC disposed within a reactor device through which a fluid flows, such that the EHC has an upstream end and a downstream end. In the series circuit, current is coupled to the upstream end of the first spiral heat transfer segment. At the downstream end of the first spiral heat transfer segment, an electrical connection is provided toward the downstream end of the second spiral heat transfer segment, allowing current to flow from the downstream end to the upstream end of the second heat transfer segment. Thus, current flows through the EHC in a serpentine manner. In contrast, in a parallel circuit, all upstream ends of the spirally wound heat transfer segments are coupled to the current source. Current flows through each spiral from the upstream end to the downstream end.It was found that parallel coupling is suitable for EHCs where the length of the heat transfer section is greater than 10 times its diameter.

[0029] According to another embodiment of the present invention, the EHC comprises at least one, in particular at least two, plate-shaped heat transfer sections. Such plate-shaped heat transfer sections can be arranged in the fluid flow so that the fluid flows over the surface of the metal foam material. This allows a particularly low pressure drop to be achieved. In addition, the large surface area of ​​the metal foam plate enables efficient heat transfer. In particular, the EHC of this embodiment has at least two plate-shaped heat transfer sections, wherein the plate-shaped heat transfer sections are arranged with a gap between the individual plates. The plates can be fixed in place by a frame. When arranged in the reactor device, the frame can be appropriately connected to the plates and the reactor wall in order to couple the current into the metal foam material of the plates. Parallel or series coupling of the metal foam plates can also be achieved here.

[0030] In another embodiment of the present invention, the EHC includes one or more fluid-impermeable portions. The fluid-impermeable portions are specifically designed to direct the flow of fluid through the metal foam material of the heat transfer section. As described above for the tubular design, such one or more fluid-impermeable portions can direct the fluid in a desired manner, for example through the metal foam material. Alternatively, the one or more fluid-impermeable portions can cover the upstream face of the metal foam plate so that at least a portion of the fluid flows over the plate surface without penetrating the metal foam material. The fluid-impermeable portion can be an electrically insulating portion as mentioned above. The terms electrically insulating and electrically isolating are used interchangeably herein.

[0031] In another preferred embodiment, the electrically heatable metal foam component further comprises a conductive strip connected to the contact section, so that current can be evenly coupled into the contact section and evenly distributed over the entire cross section of the metal foam material in the heat transfer section via the transition section.

[0032] According to another embodiment of the present invention, it is preferred that the metal foam material of the heat transfer section is arranged in such a way that the fluid comes into contact with the metal foam by flowing over the surface of the metal foam. This can preferably be achieved by arranging the metal foam element within the flow path of the fluid, without having to block the entire flow path. Thereby, gaps are formed between the metal foam material and the flow path-defining walls of the reactor device. Due to these gaps, at least a part of the fluid can flow around the metal foam element and experience a smaller pressure drop. The foam-like structure of the metal foam provides a rough and irregular surface, which causes turbulence in the fluid flowing over the metal foam surface. Thereby, heat transfer by convection is significantly increased, in particular when compared to a fluid flowing along a smooth or corrugated reactor wall or along the surface of a sheet-like reactor filler. According to this embodiment, one possibility is to arrange the metal foam inside the reactor wall, i.e. the wall of the reactor device of the present invention that defines the flow path of the fluid, wherein the metal foam forms an inner cladding of the wall of the reactor device.

[0033] According to another embodiment of the present invention, it is preferred that the fluid contacts the metal foam by flowing through the metal foam and over the surface of the metal foam. This can be considered a combination of the first and second embodiments of the present invention described in the previous paragraphs. Therefore, in this embodiment of the present invention, gaps are formed between the metal foam elements and the flow path defining walls of the reactor device. However, these gaps are narrow so that the pressure drop of the fluid flowing through the gaps is similar to the pressure drop of the fluid flowing through the metal foam. Alternatively, the gaps are formed only in a portion of the flow path of the fluid defined by one or more flow path defining walls of the reactor device.

[0034] Compared to widely used ceramic supports, metal catalyst supports show increased mechanical stability and higher thermal conductivity. Therefore, catalysts based on metal supports generally show faster initial activity. Metal honeycomb bodies and monoliths known in the prior art are generally made of metal sheets or metal foils. US7189271B2 describes a catalytic reactor comprising a plurality of stacked metal sheets arranged to define gas flow channels. The metal sheets are shaped in a manner that provides an increased heat transfer area. The temperature of the reactor can be raised to the required operating temperature by direct electrical heating, passing an electric current through the sheets forming the reactor. However, the geometric surface area of ​​metal sheets and metal foils is much smaller than the surface area of ​​the three-dimensional porous metal foam substrate. The combination of the relatively large geometric surface of the metal foam and the irregular shape of its pores improves the heat transfer between the reactants and the metal substrate by conduction and radiation, constituting a significant advantage over the prior art. In addition, since the irregular foam structure of the metal foam element used in the present invention causes turbulence in the fluid flowing over (surface) and / or flowing through the metal foam, heat transfer by convection can also be increased. In view of this, the surface area of ​​the metal foam (in mm 2 in units) and volume (in mm 3 The ratio of 2.0 mm is preferably at least 2.0 mm. 2 / mm 3 More preferably, the ratio is at least 3.0 mm 2 / mm 3 , even more preferably at least 5 mm 2 / mm 3 , even more preferably at least 8 mm 2 / mm 3 The surface area to volume ratio can be determined by performing X-ray phase contrast microtomography on the metal foam. The upper limit of the surface area to volume ratio is not particularly limited and can be as high as 50 mm 2 / mm 3 , or up to 30mm 2 / mm 3 , or up to 15mm 2 / mm 3 .

[0035] Two adjacent scans were collected and subsequently merged into a single volume of data for each sample. The X-ray beam energy in this setup was 102.5 KeV and the voxel size was 0.65 μm x 0.65 μm. A δ / β value of 2.5 was used for phase retrieval.

[0036] The term metallic foam can be used interchangeably with the term metal foam. As used herein, both terms refer to a preferably open, porous foam material of any metal or any metal alloy, which may optionally contain additional additives, such as carbides. Metal foam is characterized by having a large number of pores connected to each other, making the material permeable to gaseous and liquid fluids. Metal foam can be manufactured by several methods well known to those skilled in the art. Foams composed of pure metals (such as nickel, iron, copper, silver and some alloys) can be produced by electrodepositing the corresponding metal on an organic foam structure. Metal alloy foams can also be produced by a powder metallurgy process. Pure metal foam is coated with an alloy powder composed of metals in the desired proportion. A homogeneous alloy is then produced by sintering close to the melting point, wherein the structure of the previously used metal foam is retained. For example, the process is described in German patent application DE 10 2004 014076. However, the present invention is not limited to the specific process for manufacturing metal foam.

[0037] The heat distribution within the reactor arrangement of the present invention can be controlled by various factors. By controlling the design of the metal foam elements, the distribution of one or more of these elements throughout the reactor arrangement, and by selectively controlling the electrical heating of the metal foam, hotter / colder zones, zones of separate heating elements, temperature gradients, or, in particular, a homogeneously heated reactor can be specifically created within the reactor. The amount of heat generated depends on the size and number of metal foam elements introduced into the reactor, their spatial arrangement, the geometry of the metal foam, and other material parameters of the selected metal foam. The metal foam can have different metal compositions, densities / porosities, pore sizes, and strut thicknesses. The metal foam can be easily processed by stamping, compression, and combination with metal foil. However, there are many other possibilities for processing the metal foam, such as laser cutting, waterjet cutting, spark erosion, machining (particularly sawing, drilling, turning, or grinding), controlled crushing, twisting, rolling, pressing, folding, heat treatment, welding (particularly arc welding, separation welding, or treatment with a brazing lamp).

[0038] According to one aspect of the present invention, in addition to the metal foam, the metal element preferably also includes one or more electrically isolating portions. The isolating portion can be made of an isolating material, which can be any of ceramics, polymers, composites, such as a conductive material with an isolating surface, but can also be provided in the form of grooves or other interruptions in the metal foam, making the metal foam discontinuous. In the case of a discontinuous metal foam, the one or more electrically isolating portions can be filled with a fluid flowing through the reactor during operation. The isolating material includes a maximum electrical conductivity of 10 -7 S / cm, specific resistance of at least 10 7 Ωcm and / or any material having a dielectric strength of at least 10 kV / mm. Isolating materials include mechanically or physically deformable materials. Other suitable examples of insulating materials are glass wool or ceramic wool, fibers, soft-pastes, mats or insulating coated metal sheets / foils, ceramic fiber mats, aluminum silicate wool, Al2O3 coated steel sheets, and soft paste porcelain foils.

[0039] According to the present invention, it is preferred that the EHC further comprises an isolation section formed of one or more isolation materials as mentioned above. Such isolation section can be realized as an isolation portion of an isolation material, for example in the form of ceramic, polymer, composite, for example, a conductive material with an isolation surface, or a region of any gas, for example, air. The isolation material comprises a maximum conductivity of 10 -7 S / cm, specific resistance of at least 10 7 Ωcm and / or dielectric strength are any materials of at least 10kV / mm. The insulating material preferably comprises a material that can be mechanically or physically deformed. Other examples of insulating material are glass wool or ceramic wool, fiber, soft base, mat or insulating coated metal sheet / foil, ceramic fiber mat, aluminum silicate wool, Al2O3 steel plate and soft porcelain foil applied. Preferably, the isolated section is impermeable for the fluid in the reactor device. In the case of an insulating section that is impermeable to fluid, the fluid in the reactor device passes through the open pores of the metal foam, while avoiding the bypass by the insulating section. Thereby, it is possible to realize better heat transfer to the fluid in the reactor.

[0040] According to a preferred aspect of the present invention, the reactor device defines a flow path bounded by the walls of the reactor device. The flow path guides a fluid through the reactor device. The metal foam element is positioned within the flow path such that the fluid flowing through the reactor device also comes into contact with the metal foam of the metal foam element. According to the present invention, the metal foam element preferably fills the entire cross-section of at least one location in the flow path of the reactor device. As a result, the fluid flowing through the reactor device is forced to pass through the metal foam of the metal foam element, ensuring excellent heat exchange due to the high surface area of ​​the metal foam.

[0041] Preferably, the metal foam element has a portion that abuts a wall defining a flow path of the reactor device. This abutment achieves a certain sealing effect, preventing fluid from bypassing the reactor, particularly the flow path of the reactor as described above. The abutting portion can be made of metal foam. However, for reasons of workability and assembly, it can also be formed from a non-porous sealing member.

[0042] The metal foam element as used in the present invention has a downstream end and an upstream end. Preferably, the length of the metal foam element of the reactor device of the present invention is 0.5 mm or more, more preferably 5 mm or more, even more preferably 10 mm or more, even more preferably 100 mm or more. The upper limit of the length of the metal foam element is not particularly limited and can be the entire length of the reactor device. The length of the metal foam element is preferably 5000 mm or less, more preferably 4000 mm or less, even more preferably 3000 mm or less and even more preferably 2500 mm or less. As indicated above, the length of the metal foam element is the length from the downstream end to the upstream end measured along the flow path of the reactor device.

[0043] According to the present invention, at least a first metal foam element and a second metal foam element are preferably arranged within the reactor device. These at least first and second metal foam elements can be arranged in direct contact with each other, or can be arranged remotely from each other, i.e., with a gap between the metal foam elements. The at least first and second metal foam elements can be arranged such that a gap is formed between the metal foam elements, spanning from the upstream end of the first metal foam element to the downstream end of the second metal foam element. In this regard, preferably two or more, more preferably three or more, even more preferably five or more, even more preferably ten or more, and most preferably twenty or more metal foam elements are arranged within the reactor device such that a gap is formed between two metal foam elements arranged adjacent to each other in the direction of the flow path. The gap between the at least two metal foam elements can be filled with catalyst material, such as catalyst particles or catalyst-coated foam, for example, in the form of particles. Alternatively or additionally, the reactor device of the present invention further comprises an inlet between the upstream end of the first metal foam element and the downstream end of the second metal foam element, i.e., an inlet within the gap. The inlet can be a reactant inlet for feeding a reactant into the reactor assembly at a location between two metal foam elements, or a sensor inlet for inserting a sensor into the reactor assembly at a location between two metal foam elements or at the sensor inlet. Multiple inlets can also be provided, either at subsequent gaps between subsequent metal foam elements or within a single gap. This allows for more than one reactant to be fed into the reactor assembly at the gaps between adjacent metal foam elements, or for more than one sensor input to be obtained, or for a sensor input to be obtained in the gaps where reactants are fed into the reactor assembly.

[0044] Furthermore, according to the present invention, it is preferred to arrange two or more metal foam elements one after the other in the flow direction, wherein a gap is formed between the downstream end of a first metal foam element and the subsequent upstream end of the metal foam element. This can preferably be achieved by arranging the metal foam elements in a stack, with gaps between adjacent metal foam elements, so that when the fluid flows from the downstream end to the upstream end of the reactor device according to the present invention, the fluid can flow through the gaps.

[0045] According to the present invention, the metal foam element preferably further comprises one or more electrically isolating portions in addition to the metal foam. The isolating portions are preferably arranged within the metal foam to define an electrical path through the metal foam element. To achieve this, the isolating portions preferably define a path therebetween, which is filled with open-pore metal foam. The shape of the electrical path defined by the one or more isolating portions is not particularly limited and can be zigzag, spiral, meandering, etc., for providing a particularly long electrical path throughout the metal foam element. Further preferably, the metal foam element further comprises one or more fluid-impermeable portions in addition to the metal foam. These impermeable portions can be made of an electrically insulating material, such as those mentioned above.

[0046] One or more fluid-impermeable sections are preferably arranged within the metal foam to define a flow path through the metal foam element. To achieve this, the one or more fluid-impermeable sections may define a path therebetween, which is filled with open-pore metal foam. The shape of the flow path defined by the one or more fluid-impermeable sections is not particularly limited and may be zigzag, spiral, serpentine, etc., to provide particularly long flow paths throughout the metal foam element. According to the present invention, one or more electrically insulating sections may be the fluid-impermeable sections.

[0047] Preferably, the metal foam element further comprises (in addition to the metal foam) optional electrically isolating portions, optional fluid-impermeable portions, conductive strips and / or wires. Depending on the actual use of the reactor device according to the invention, these additional conductive strips and / or wires can be used to conduct the current to the desired portion of the metal foam element, so that heat is specifically provided in the portion where the conductive strips and / or wires guide the current. For some applications, it may be desirable to provide higher heat in the downstream section of the metal foam element, while for other applications it may be desirable to provide the greatest heat in the upstream section of the metal foam element. Further applications may require a particularly uniform distribution of heat throughout the metal foam. By using conductive strips and / or wires, this can be appropriately adapted to the desired application when required.

[0048] According to the present invention, when in a reactor device, the metal foam is preferably electrically connected to at least two electrodes so that when an electric current is conducted through the metal foam, the metal foam can be resistively heated. One of these electrodes can be a wall of the reactor device, for example a wall defining a flow path.

[0049] According to another preferred embodiment of the present invention, the reactor device comprises an induction heater for inductively heating the metal foam. This is an alternative to coupling current into the metal foam material via a cable and has the advantage that the metal foam material itself does not need to be wired. In this case, according to the present invention, the induction coil can be placed inside the reactor itself or attached to the outer wall of the reactor. In a second case, the reactor device can comprise a wall material with low electrical conductivity, such as ceramic, glass ceramic, glass, metallic glass, allowing the magnetic field to penetrate into the reactor filler. The reactor filler can be formed by a large number of shaped metal or alloy foam bodies, for example in the form of stacked plates, a single monolith, a series of monoliths or any other shape described for metal foam in this specification.

[0050] According to another preferred embodiment, the reactor device further comprises an electromagnetic wave generator for dielectrically heating the metal foam. Particularly preferably, the electromagnetic wave is a microwave.

[0051] Preferably, the reactor device of the invention is designed for a continuous flow of at least one fluid.

[0052] According to a preferred aspect of the present invention, the metal foam is contained in a reaction chamber of a reactor device, which is preferably a flow reactor, in particular a continuous flow reactor.

[0053] Preferably, in the reactor apparatus of the present invention, the catalyst is positioned near the metal foam element. This allows the desired amount of heat to be applied to the catalyst by radiation. In conventional reactor arrangements, the catalyst is heated via the reactor wall. However, heat transfer by radiation requires that electromagnetic waves reach the area to be heated. Therefore, heat transfer by radiation through the reactor wall is very limited.

[0054] Further preferably, the catalyst is positioned downstream of the metal foam element. With this arrangement, the catalyst can be heated by radiation, as mentioned above, while also providing heat from the metal foam element to the fluid before the fluid contacts the catalyst. To support heating of the catalyst positioned downstream of the metal foam element, the catalyst is preferably positioned adjacent to the metal foam element.

[0055] The catalyst arranged downstream of the metal foam element can be the only catalyst in the reactor arrangement. However, depending on the application, additional catalysts can also be provided in the reactor element, for example in the form of metal foam or in the form of catalytic particles within the metal foam, i.e., arranged within the pores of the metal foam, preferably on the struts of the metal foam. Thus, the catalyst can be introduced into the pores in the form of a washcoat by precipitation, chemical deposition, incipient wetness, physical vapor deposition, chemical vapor deposition, or the like.

[0056] To preheat the fluid before it undergoes a chemical reaction, for some applications, it is preferable to arrange the EHC upstream of the reaction chamber of the reactor device according to the present invention. For other applications, such as when heat is required at the reaction site, it is preferable to arrange a metal foam element within the reaction chamber, with the metal foam of the EHC being catalytically active or being a carrier of catalytic particles with catalytic activity to catalyze the chemical reaction at the reaction site.

[0057] According to a preferred embodiment, the metal foam includes a catalytically active material that can catalyze heterogeneous reactions and is particularly suitable for converting gaseous and / or liquid reactants. The catalytic material can be present in the form of catalytic particles deposited on the metal foam (i.e., on the outer and inner surfaces of the metal foam). Alternatively or additionally, the catalytic material can be part of the metal foam material itself, i.e., the metal foam material is catalytically active.

[0058] The metal foam preferably comprises at least one of the elements Ni, Fe, Cr, Al, Nb, Ta, Ti, Mo, Co, B, Zr, Mn, Si, La, W, Cu, Ag, Au, Pd, Pt, Zn, Sn, Bi, Ce, Mg, Ru, Rh, Ir, and / or Os. The metal foam particularly preferably comprises at least one of the elements Ni, Fe, Cr, and / or Al, and very particularly preferably comprises at least one of the elements Ni and / or Al. Several of these elements may be alloyed together to form components of the metal foam, or may be present as particles on the metal foam. Furthermore, these elements may be contained in particles within the metal foam. The metal foam particularly preferably comprises a nickel-iron-chromium-aluminum alloy and / or a nickel-chromium-aluminum alloy. The nickel-iron-chromium-aluminum alloy and / or the nickel-chromium-aluminum alloy may be doped with further elements to adjust and optimize the catalytic activity. Examples of such additional elements are elements selected from the group consisting of Ni, Fe, Cr, Al, Nb, Ta, Ti, Mo, Co, B, Zr, Mn, Si, La, W, Cu, Ag, Au, Pd, Pt, Zn, Sn, Bi, Ce, Mg, Ru, Rh, Ir and Os.

[0059] Very particularly preferably, the metal foam consists at least substantially of a nickel-iron-chromium-aluminum alloy and / or a nickel-chromium-aluminum alloy. This means that, apart from any doping of the nickel-iron-chromium-aluminum alloy and / or the nickel-chromium-aluminum alloy, the metal foam comprises only unavoidable contaminants and / or residues of brazing films that may have been used during production.

[0060] The metal foam preferably has pores with a unimodal or multimodal, in particular bimodal, distribution of pore diameters. According to a particularly preferred embodiment, the pores are distributed multimodally and spatially arranged within the metal foam such that the diameter of pores present in a first region of the metal foam is greater than the diameter of pores in a second, spatially separated region of the metal foam. Pores with different diameters can be used to influence the residence time of reactants and products within the metal foam. The formation of turbulence can also be influenced by pores of different size, type, or geometry, thereby influencing heat and mass transfer.

[0061] The metal foam material preferably has pores with diameters of 10 μm to 10,000 μm, preferably 50 μm to 5000 μm, very particularly preferably 300 μm to 3000 μm, and most preferably 1500-3000 μm. Pores with diameters less than 10 μm lead to deteriorated mass transfer properties. Better heat and mass transfer properties can be achieved using metal foam materials with pore diameters of 10 μm or greater. However, with pore diameters greater than 10,000 μm, the efficiency of reactors using such metal foams as catalyst supports and / or carriers decreases due to the reduced ratio of the catalytically active surface provided by the metal foam to the internal volume of the pores. In addition, pores of 10,000 μm or greater result in only minimal turbulence in the fluid flowing through the metal foam, resulting in reduced convective heat transfer compared to metal foams with pore diameters within the indicated range.

[0062] The metal foam porosity is preferably greater than or equal to 70%, particularly preferably greater than or equal to 80%, and very particularly preferably greater than or equal to 85%, and most preferably it can be 95% or more.The metal foam is therefore a metal foam of a highly porous material.

[0063] The metal foam preferably has a pillar thickness of 10 to 2000 μm, more preferably 20 to 1000 μm, and even more preferably 25 to 200 μm. If the pillar thickness is less than the indicated values, the metal foam has poor mechanical strength and may have a high electrical resistance. Applying an electric current may then lead to hot spots at the thinnest pillars, potentially causing the formation of necking and ultimately deteriorating the metal foam. If the pillar thickness is greater than the indicated values, the metal foam has a low electrical resistance, and heating by applying an electric current may require very high currents.

[0064] There are various possibilities for heating the metal foam of the metal foam element. In the reactor arrangement of the present invention, the metal foam is preferably electrically connected to at least two electrodes, such that when an electric current is conducted through the metal foam, the metal foam is resistively heated. In other words, the metal foam is preferably a heating element of a resistive heater.

[0065] According to an alternative, the reactor device of the present invention preferably comprises an induction heater for inductively heating the metal foam.Thereby, electrical energy can be supplied to the metal foam without the need for additional electrical contacts and / or wires connected to the metal foam.

[0066] In another preferred embodiment, it is preferred when the reactor device further comprises an electromagnetic wave generator for dielectric heating of the metal foam. More preferably, the electromagnetic wave is a microwave.

[0067] Preferably, the reactor device according to the present invention is designed for a continuous flow of at least one fluid.Even more preferably, the metal foam is contained within a reaction chamber of the reactor device.

[0068] It may also be preferred when the metal foam is arranged upstream of the reaction chamber of the reactor arrangement.

[0069] Furthermore, the catalyst particles are preferably disposed within the open pores of the metal foam. Heat supplied by the electrically heatable metal foam can then be used directly for the chemical reaction at the heat supply location. This prevents heat loss when the fluid flows through the downstream portion of the reactor element.

[0070] For some applications, it may be advantageous to arrange an additional catalyst downstream of the metal foam. Thus, the fluid is heated by the metal foam and subsequently reacts in the additional downstream catalyst. This can be particularly useful when, for example, the catalyst is incompatible with the material or structure of the metal foam.

[0071] The reactor device of the present invention has a defined flow path for a fluid, which flow path is delimited by the walls of the reactor device, wherein the flow path guides at least one fluid through the reactor device, and wherein an electrically heatable metal foam component (EHC) according to the present invention, i.e. as described generally above, in the embodiments mentioned herein and in the accompanying claims.

[0072] According to one embodiment, the reactor device according to the invention is arranged in a flow path such that it has a downstream end and an upstream end, wherein the flow path from the upstream end to the downstream end of the electrically heatable metal foam component passes through the metal foam material.

[0073] In another embodiment, the metal foam of the EHC is designed and arranged so that at least one fluid passes from the radially outer side of the metal foam material to the radially inner side of the metal foam material, or the metal foam component is designed and arranged so that at least one fluid passes from the radially inner side of the metal foam material to the radially outer side of the metal foam material.

[0074] In another preferred embodiment of the reactor device according to the invention, the wall of the reactor device defines a tubular flow path, and in the electrically heatable metal foam component, the metal foam material has a tubular shape at least in its heat transfer section, which is arranged essentially concentrically with the tubular flow path defined by the reactor wall.

[0075] According to another exemplary embodiment of the reactor device according to the present invention, the wall of the reactor device defines a tubular flow path, and in the electrically heatable metal foam component, the metal foam material has a helical shape, at least in its heat transfer section, which is arranged substantially concentrically with the tubular flow path defined by the reactor wall. Preferably, more than two, in particular more than three, in particular more than four, and in particular more than six, helically wound heat transfer sections of metal foam material are provided, wherein the individual heat transfer sections are arranged concentrically and their helical strips operate in parallel to form a double helix or higher, depending on the number of helical strips (i.e., heat transfer sections).

[0076] According to another embodiment, the reactor device of the invention is provided with an EHC comprising at least one heat transfer section having a plate shape, wherein the at least one plate-shaped heat transfer section is arranged substantially parallel to the flow direction of the flow path.

[0077] The EHC can be designed so that the fluid passes through or along the metal foam material in the radial or axial direction of the reactor. In the case of a design that allows the fluid to flow through or along the metal foam in the axial direction, the length of the EHC is preferably in the range of 1.0 mm to 500 mm, preferably 10 mm to 400 mm, and more preferably 20 to 300 mm. In the case of a design that allows the fluid to flow through or along the metal foam in the radial direction, the length of the EHC is preferably in the range of 5.0 mm to 5000 mm, more preferably 30 mm to 2000 mm, and even more preferably 50 mm to 1000 mm. The length of the EHC is the length from its downstream end to its upstream end when measured directly from the downstream end to the upstream end (i.e., not along the helical winding path of, for example, the heat transfer section).

[0078] According to one embodiment, in the reactor arrangement according to the invention, the metal foam is electrically connected to at least two electrodes, such that the metal foam can be resistively heated when an electric current is conducted through the metal foam.

[0079] According to an alternative embodiment, the reactor arrangement comprises an induction heater for inductively heating the metal foam.

[0080] According to yet another preferred embodiment, the reactor device further comprises an electromagnetic wave generator for dielectrically heating the metal foam. For example, the electromagnetic wave is a microwave.

[0081] Preferably, the reactor arrangement is designed for continuous flow of at least one fluid.

[0082] According to a preferred embodiment of the present invention, the metal foam of the heat transfer section of the EHC is housed within a reaction chamber of the reactor device.

[0083] According to another preferred embodiment of the present invention, the metal foam of the heat transfer section of the EHC is arranged upstream of the reaction chamber of the reactor device.

[0084] According to another embodiment, in the reactor arrangement according to the invention, the catalyst is arranged downstream of the metal foam.

[0085] The reactor arrangement according to the invention can be used for different processes. According to one exemplary embodiment, the reactor arrangement is used for treating exhaust gases of internal combustion engines, or for treating exhaust gases of industrial processes, or for supplying heat to industrial processes.

[0086] The present invention also relates to the use of a reactor assembly according to the invention for carrying out any method for chemical reactions (gas and liquid phase), industrial emissions control, and automotive emissions control. In a specific embodiment, the present invention relates to the use of a reactor assembly according to the invention for fixed-bed reactions, such as those carried out at elevated temperatures with high energy requirements. The reactor assembly according to the invention can be used to carry out endothermic as well as exothermic processes.

[0087] The following specific applications are described for situations in which the reactor device according to the present invention can be used. Steam reforming is a process that mainly produces hydrogen and synthesis gas (hydrogen and carbon monoxide) formed by the reaction of hydrocarbons (methane, ethane, propane or other gases in natural gas) and water. The SMR (steam methane reforming) process is an endothermic process, consuming 206kJ / mol of heat and having an efficiency of about 70%. On an industrial scale, the reaction is typically carried out in multiple reaction tubes up to 15 meters in length. These tubes are externally heated at 750-800°C in an open flame burner top combustion furnace, making SMR an energy and capital intensive process. The integration of the electrically heated metal foam element according to the present invention enhances the overall energy balance of the process by improving the uniformity of heat supply, heat utilization and heat distribution. In view of this, the reactor device according to the present invention is preferably at least a part of a steam methane reforming reactor. As described above, the electrically heated metal foam can supply heat directly at the desired reaction site, eliminating the need for indirect heating via the reactor wall. The present invention also allows the avoidance of external heating by an open flame as for conventional SMR processes. Therefore, the SMR process can be carried out without releasing combustion gases from an external burner. This is particularly useful for generating hydrogen from methane (e.g., from natural gas), whereby it is desired to release as few greenhouse gases as possible. When the carbon dioxide produced by the SMR process is released into the atmosphere, the hydrogen obtained by this process is often referred to as gray hydrogen, or when carbon capture technology is applied to capture and store the carbon dioxide, this hydrogen is referred to as blue hydrogen. In view of this, it is preferred to use the reactor device of the present invention to produce gray hydrogen or blue hydrogen by the SMR process, more preferably to produce blue hydrogen.

[0088] Another aspect of the present invention relates to the catalytic treatment of industrial and automotive exhaust gases containing pollutants such as NOx, CO or hydrocarbons. As increasingly stringent national and regional laws continue to reduce the amount of pollutants allowed to be discharged, exhaust gas treatment continues to receive attention. The conversion of pollutants generally requires elevated temperatures so that the catalyst can fully reduce the concentration of pollutants in the exhaust gas.

[0089] Furthermore, the present invention relates to a method for manufacturing an EHC as described herein. The method comprises the steps of providing a metal foam element and compressing segments of the metal foam element to obtain contact segments and transition segments. Compression can be achieved in different possible ways, such as rolling, calendering, stamping (in particular hot stamping), hydroforming, riveting, embossing, molding and deep drawing. Hot stamping refers to a stamping technique in which the metal foam material and / or the stamping tool are heated to a temperature above room temperature, in particular to a temperature value (in ° C) of at least 50% of the melting point of the metal foam material. For example, when the melting temperature of the metal foam is 750 ° C, 50% of this value corresponds to a temperature of 375 ° C.

[0090] The compression is preferably performed in such a way that the metal struts of the metal foam in the transition section do not break.

[0091] The method of manufacturing the EHC further comprises attaching a contact plate or contact tab to the contact segment, in particular by welding or brazing. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Hereinafter, the present invention will be further described with reference to the accompanying drawings and examples. These drawings and examples do not limit the present invention. The following are shown in the accompanying drawings:

[0093] Figure 1 A schematic diagram showing one embodiment for preparing an EHC according to the present invention.

[0094] Figure 2 A schematic diagram showing one embodiment for preparing an EHC according to the present invention.

[0095] Figure 3 Schematic diagram of one embodiment of an electrically heatable metal foam component according to the present invention.

[0096] Figure 4 Figure 3 Cross-sectional view of an embodiment.

[0097] Figure 5A Another embodiment of the EHC of the present invention is viewed from the upstream end of the reactor interior.

[0098] Figure 5B Observed from the downstream end of the reactor Figure 5A EHC.

[0099] Figure 6A Another embodiment of the EHC of the present invention is viewed from the upstream end of the reactor interior.

[0100] Figure 6B Observed from the downstream end of the reactor Figure 6A EHC.

[0101] Figure 7 Another embodiment of the EHC of the present invention is inside the reactor.

[0102] Figure 8 Graph showing the electrical resistance of a metal foam material depending on the degree of compression in the contact section. DETAILED DESCRIPTION

[0103] exist Figure 1, a process for producing an electrically heatable metal foam component (EHC) 10 according to the present invention is schematically shown. First, a metal foam material 12 having a substantially uniform thickness T1 is provided. Next, a section of the metal foam material 12 is compressed to a thickness T2 to form a contact section 14, while another section of the metal foam material 12 is not compressed. The uncompressed section of the metal foam material 12 is a heat transfer section 16. Between the heat transfer section 16 and the contact section 14, the degree of compression gradually changes, for example, between Figure 1 In the embodiment shown, the thickness decreases from an uncompressed thickness T1 at the heat transfer section 16 to a compressed thickness T2 at the contact section 14. The section where the degree of compression gradually changes is the transition section 18. Figure 1 The drawings are purely schematic and are not shown to scale with respect to the thickness and width of the contact section 14, the heat transfer section 16, or the transition section 18. However, as noted above, it is preferred that the length of the transition section 18 (i.e., the distance between the uncompressed metal foam in the heat transfer section 16 and the contact section 14) be at least 0.5 times, and preferably 1.0 to 5.0 times, the thickness of the metal foam material 12 at a location adjacent to the transition section 18 at the heat transfer section 16, to provide a gradual (i.e., smooth) transition while maintaining the mechanical stability of the metal foam material 12. That is, with the transition section 18 having the lengths noted above, the individual struts of the metal foam material 12 between the contact section 14 and the heat transfer section 16 are less likely to fracture.

[0104] An alternative embodiment for producing an electrically heatable metal foam component 10 is schematically shown in FIG. Figure 2 middle. Figure 2 Also not drawn to scale. First, a metal foam material is provided. The thickness of this initially provided metal foam material is not uniform. Instead, the thickness T3 at one portion is greater than the thickness T4 at another portion. The thickness gradually decreases from thickness T3 to thickness T4. Next, the metal foam material is compressed so that it also has a uniform thickness T4 at the portion that initially had thickness T3. Thus, the section with initial thickness T3 is compressed, while the section with initial thickness T4 remains uncompressed. The compressed section with initial thickness T3 forms the contact section 14, while the uncompressed section with initial thickness T4 forms the heat transfer section 16. In between, the section with gradual thickness change before compression forms the transition section 18 after compression.

[0105] Although Figure 1 and Figure 2The formation of the metal foam material having one contact section 14, one transition section 18, and one heat transfer section 16 is shown, but it should be understood that in the electrically heatable metal foam component 10, preferably, each heat transfer section 16 is provided with two contact sections 14 and two transition sections 18. For simplicity, only the formation of one contact section 14 and one transition section 18 is shown.

[0106] The degree of compression, i.e. Figure 1 The change from thickness T1 to thickness T2, and from thickness T3 to thickness T4, can vary significantly depending on the type of metal foam material 12, and in particular the density, i.e., the porosity, of the uncompressed metal foam material 12. A relatively dense metal foam material 12 (having a porosity of, for example, 60% as defined below) can achieve the advantageous effects of the present invention with a compression corresponding to a thickness reduction of less than 60%. However, particularly for high porosities, e.g., greater than or equal to 70%, particularly preferably greater than or equal to 80%, and very particularly preferably greater than or equal to 85%, and most preferably 95% or more, the degree of compression is particularly as described above, i.e., at least 60%, particularly at least 70%, at least 75%, or at least 85%.

[0107] Figure 3 A preferred embodiment of the present invention is shown wherein the metal foam material 12 is in the shape of a spiral. Figure 4 Shows Figure 3 sectional view of the metal foam material 12. Figure 3 and Figure 4 The spiral strip 26 of metal foam shown in FIG can be obtained, for example, by cutting a tubular-shaped metal foam body to provide a spiral cut 22 which is wound like the threads of a screw along the longitudinal axis 1. The longitudinal ends 20 of the spiral strip 26 of metal foam material 12 can only be Figure 3 . The width of the strip of metal foam material 12 is substantially uniform in the heat transfer section and gradually decreases towards these longitudinal ends 20 due to the compression of the metal foam material. Thus, a contact section 14 and a transition section 18 are provided on both sides of the heat transfer section 16. The metal foam material 12, in particular the heat transfer section 16, is wound around the radially inner section 19 in the longitudinal direction along the longitudinal axis l. The electric current coupled into the metal foam material at one contact section 14, for example by a connected cable (not shown in the drawings), passes through the adjacent transition section 18 and the heat transfer section 16, and travels towards the transition section 18 and the contact section 14 at the opposite longitudinal end. As shown from Figure 4In particular, it can be seen that due to the spiral cutouts 22, the path for the current is long, and the cross-section of the metal foam 12 is reduced, since the spiral cutouts 22 electrically isolate adjacent sections of the helically wound metal foam from each other. This results in more homogeneous heating. The cutouts 22 can be filled with an insulating material to increase mechanical stability and prevent short circuits between adjacent strut sections, for example, due to bending the helically wound metal foam 12. As an alternative to coupling current into the metal foam 12 via a cable, the metal foam 12 can also be heated by induction heating. In this case, according to the present invention, the induction coil can be placed inside the reactor itself or attached to the outer wall of the reactor. In the latter case, the reactor assembly can include a wall material with low electrical conductivity, such as ceramic, glass ceramic, glass, or metallic glass, to achieve magnetic permeability in the reactor filling. The reactor filling can be formed from a plurality of shaped metal or alloy foam bodies, such as stacked plates, a single monolith, a series of monoliths, or any other shape described for metal foam in this specification.

[0108] Although Figure 3 and Figure 4 An embodiment with a single cut is shown, but it is also possible to start with a tubular metal foam and make two helical cuts. This results in a double helix ( Figure 3 and Figure 4 (not shown). The cross-section of the metal foam 12 is further reduced by providing more than a single cut compared to a single cut. This may be advantageous for larger diameters of the spiral structure, as this reduces the cross-sectional area of ​​the metal foam, thereby providing more uniform heating. Multiple spiral strips of metal foam ( Figure 5A 26' and 26") in the figure can be connected to each other in the form of a parallel circuit or a series circuit. It has been found that parallel coupling is particularly suitable for EHCs with a heat transfer section length greater than 10 times its diameter. For EHCs with a length less than 10 times its diameter, a series circuit and the resulting serpentine current flow path may be advantageous. The circuits and connectors are not shown in the drawings.

[0109] Figure 5A and Figure 5B 1 shows an embodiment of an EHC 10 according to the present invention, specifically showing a longitudinal view of the EHC. The EHC 10 is arranged along the periphery of a reactor wall 24. The reactor wall 24 may have a circular cross section, or may be slightly elliptical, such as Figure 5A and Figure 5B shown. Figure 5A The upstream end of the EHC is shown, i.e. a longitudinal view from the upstream end to the downstream end. Figure 3 and Figure 4Similar to that shown in FIG, the metal foam material 12 is in a spiral shape, however, two spiral strips 26' and 26" of metal foam material are provided to form a double helix. In addition, a contact section 14 and a transition section 18 are provided on each of the two spiral strips 26' and 26", which are schematically shown in FIG. Figure 5A .like Figure 5A As shown. A first metal foam strip 26' begins at the contact section 14 and transitions into the heat transfer section 16 via the transition section 18. The first strip 26' is wound in a clockwise direction into the plane of the paper. It extends beyond the contact section 14 of the second strip 26". The second strip 26" also begins at the contact section 14 and transitions into the heat transfer section 16 via the transition section 18. The second strip 26" is wound in a clockwise direction into the plane of the paper and extends beyond the contact section 14 of the first strip 26'. The radially inner section at the upstream end of the EHC is provided with a fluid-impermeable section 28, for example in the form of a cover, Figure 5A Indicated in black in FIG. At the downstream end of the EHC 10 (shown in FIG. Figure 5B At the center, the contact section 14, the heat transfer section 16 and the transition section 18 cannot be seen because they are covered by another fluid-impermeable section 28. The fluid-impermeable section 28 covering the upstream end may cover only the upstream face or may extend into the empty radially inner section 19 of the EHC. The fluid flowing from the upstream end to the downstream end (not shown in the figure) is first Figure 5A The fluid-impermeable section 28 shown in FIG is blocked to prevent it from flowing directly into the radially inner section of the EHC 10. Instead, the fluid is forced to flow through the porous metal foam material 12 at the reactor wall. Since the metal foam material 12 at the downstream end of the EHC 10 is covered by the fluid-impermeable section 28, the fluid is further forced to flow into the radially inner section 19 of the EHC. The fluid is thereby forced to flow through the metal foam material. This can be beneficial for improving heat transfer efficiency or catalytic treatment of the fluid (the metal foam material itself is a catalyst or a carrier of a catalyst, i.e., catalytic particles are disposed in the pores of the metal foam material). When the fluid-impermeable section 28 at the upstream end also fills a portion of the radially inner section 19, the length of the fluid flow through the metal foam material can be increased. Although not shown in FIG. Figure 5A and Figure 5B , but they are electrically isolated or insulated by providing a gap between the EHC and the reactor wall 24, or by placing an electrically insulating material therebetween.

[0110] Figure 6A and 6B An embodiment of an EHC according to the present invention is shown, similar to Figure 5A and Figure 5BHowever, the metal foam has a tubular shape, ie does not have the spiral cutouts 22. For simplicity, the contact section 14 and the transition section 18 are not shown. Here, too, the fluid is forced to flow through the metal foam in the heat transfer section 16, such as described above for Figure 5A and Figure 5B As explained.

[0111] Another embodiment of an EHC according to the present invention is shown in Figure 7 In this embodiment, the metal foam material 12 of the EHC is provided in the form of three metal foam plates, which are arranged inside an elliptical reactor. It should be understood that the shape of the reactor can also have another shape, such as a circle or any other shape. In addition, the number of plates can vary and can be one or more, two or more, three or more, etc. The plates of the reactor are arranged at an angle of about 0° relative to the flow direction or the fluid flowing through the reactor. At two adjacent ends, the plates are connected to a frame 30, such as a metal frame. The contact section 14 and the transition section 18 are provided at each plate of the metal foam material 12, where the metal foam material is connected to the frame 30, but for simplicity, in Figure 7 . On one side, the metal frame 30 is not electrically connected to the reactor wall, i.e., is electrically insulated from the reactor wall, while on the other side, the frame 30 is electrically connected to the reactor wall. On the side where the frame 30 is not connected to the reactor wall, the frame can be connected to an electrical conductor (such as a cable) to transfer current to or from the EHC.

[0112] The EHC can be heated by coupling an electrical current into the plates of metal foam 12 via the reactor wall and frame 30. The current flows through the metal foam and thereby electrically heats the plates. Because the plates are oriented at approximately 0° relative to the flow direction of the fluid flowing through the reactor, the fluid flows over the surface of the metal foam plates and is thereby heated without entering the metal foam 12 itself.

[0113] The following describes an experiment used to determine the degree of compressibility of metal foam materials.

[0114] Electrodes were attached to the ends of each nickel-iron-chromium-aluminum alloy metal foam test strip. The metal foam had a pore size of 800 μm and a strut thickness of 55 μm. The porosity of the metal foam ranged from 5% to 15%. The aim was to find out whether compression at the electrode junction had a significant effect on the resistance. Some specimens were subjected to a special compression at the junction. The result was that the resistance decreased only at high compression. Figure 8 It will be appreciated that for this particular type of metal foam, the degree of compression should be at least 70% to reduce the observed electrical resistance.

[0115] Without being bound by theory, it is believed that this observation can be explained as follows. When current is coupled to only one strut at the surface, this strut or metal foam primarily bears the electrical resistance. The struts parallel to it are not used by the current because they are not in the direction of current flow. Cross-sections of the cell structure at different compression levels show that the cells arranged one above the other, forming the foam structure, collapse only at their center. This means that the cell structure deforms, but contact between the struts only occurs at higher compression levels. Therefore, all pre-compressions below a certain threshold level are ineffective in achieving current coupling at the electrode.

[0116] If the material is compressed in the fixed area by at least 70%, but preferably at least 85%, the thermal load at the contact point with the electrode is significantly reduced. This leads to a significant improvement in the durability of the entire component. Since the mechanical stability of the foam is given by the interconnected network of cells, compression must be carried out in a way that keeps the network and its connections intact, for example, in a gradual manner to provide the transition section 18. Step-by-step compression may damage parts of the structure due to the resulting shear forces.

[0117] The degree of compression depends on the heating element's material, mounting, shape, and deformation direction. Compression thus creates an 'expandable zone' (contact section) and a 'solid zone' (initial material, heat transfer section) around the mounting point, connected by a 'gradient zone' (transition section). The 'expandable zone' can be shaped using varying amounts of compression (0% to <100%) to improve the EHC's mechanical load capacity. The 'gradient zone' can be linear, i.e., along a rectangular area with steadily increasing compression, or a gradually increasing (sinusoidal) curve. The 'gradient zone' ensures a functional transition from the 'expandable zone' to the 'solid zone' and optimal, uniform coupling of electrical current by keeping all traces (struts) intact. In the 'expandable zone', the foam is in electrical contact. Forming the 'expandable zone' compresses the cell body to the point where several overlapping struts (previously spaced apart) now contact each other, thereby increasing the effective (utilized) conductor cross section. The series of contacts in the 'ductile zone' and the smooth transition from the 'gradient zone' to the 'solid zone' result in a heating element with uniform electrical conductivity and resulting homogeneous heat generation over a large area. This results in a significantly longer service life of the EHC.

[0118] The higher density of the 'ductile zone' also simplifies contacting (e.g. by resistance welding or screws). In the original state of the foam, this can only be reserved for experts.

[0119] Examples of spiral EHCs:

[0120] In the example, a reactor with a length of 900 mm and an inner diameter of 120 mm was used. The metal foam in the heat transfer section of the EHC had a wall thickness of 5 mm and a pore size of 1500 μm. A NiCrAl alloy was used. The inner diameter of the spiral heat transfer section was 80 mm and the outer diameter was 90 mm. The heating element was designed as a double helix. This means it has two circumferential foam strips, insulated from each other, electrically connected in parallel at their ends. Each strip has a contact section and a transition section at each end. The caps at the ends of the heating element are airtightly connected to the two circumferential spiral metal foam strips that form the double helix. The caps also serve as the positive pole of the circuit. The inlet of the helix (in the flow direction) is connected to the helix as a support ring, and at the same time, this closes a bypass to the fluid around the helix via a separately attached steel ring. In this configuration, the support ring is the negative pole. The EHC is connected to the reactor via the support ring. The total length of the helix is ​​290 mm. The helix is ​​electrically loaded with 5000 watts. Ambient air is used as the medium. The air mass flow rate at the reactor inlet was 100 kg / h at 20° C. The reactor outlet had a constant temperature of 83° C.

[0121] Several embodiments of the present invention are explained below: Embodiments 1 to 32 describe electrically heatable metal foam components (EHCs), Embodiments 33 to 48 describe reactor devices, and Embodiments 50 to 52 describe methods for treating fluids.

[0122] Embodiment 1. An electrically heatable metal foam component comprising a metal foam material, the metal foam material having at least one contact section for electrically contacting the metal foam material, at least one transition section, and at least one heat transfer section, wherein the transition section is arranged between the contact section and the heat transfer section, wherein in the contact section, the metal foam material is compressed compared to the heat transfer section, and wherein in the transition section, the degree of compression changes from the degree of compression in the contact section to the metal foam material in the heat transfer section.

[0123] Embodiment 2. An electrically heatable metal foam component according to embodiment 1, wherein the number of heat transfer sections is half the number of transition sections and contact sections, and wherein each heat transfer section transitions into two contact sections via two transition sections arranged at separate parts of the heat transfer section.

[0124] Embodiment 3. An electrically heatable metal foam component according to embodiment 1 or 2, wherein the length of the transition section is at least 0.3 times, in particular at least 0.5 times, the thickness of the metal foam material at a position of the heat transfer section adjacent to the transition section.

[0125] Embodiment 4. The electrically heatable metal foam component of Embodiment 2, wherein the length of the transition section is in the range of 1.0 to 5.0 times the thickness of the metal foam material of the heat transfer section at a location adjacent to the transition section.

[0126] Embodiment 5. The electrically heatable metal foam component according to at least one of the preceding embodiments, wherein more than one heat transfer section is electrically connected via a transition section and a contact section.

[0127] Embodiment 6. An electrically heatable metal foam component according to at least one of the preceding embodiments, wherein in the contact section, the cells of the metal foam material are compressed to such an extent that overlapping pillars that were arranged separately in space before compression are in direct contact with each other after compression; and / or wherein the metal foam material in the contact section is compressed so that its thickness is reduced by at least 60%, in particular at least 70%, at least 75%, at least 85% relative to the thickness of the uncompressed metal foam material.

[0128] Embodiment 7. An electrically heatable metal foam component according to at least one of the preceding embodiments, wherein the thickness of the metal foam material in the heat transfer section is in the range of 1.0 to 100 mm, in particular 1.5 to 75 mm, in particular 1.5 to 50 mm.

[0129] Embodiment 8. According to the electrically heatable metal foam component described in at least one of the preceding embodiments, the porosity of the metal foam material in the heat transfer section is preferably greater than or equal to 70%, particularly preferably greater than or equal to 80%, and very particularly preferably greater than or equal to 85%, and most preferably it can be 95% or greater.

[0130] Embodiment 9. The electrically heatable metal foam component according to at least one of the preceding embodiments, wherein the metal foam material at least in the heat transfer section has open pores.

[0131] Embodiment 10. An electrically heatable metal foam component according to at least one of the preceding embodiments, wherein the metal foam material at least in the heat transfer section has pores with a diameter of 10 μm to 10,000 μm, preferably 50 μm to 3000 μm, and particularly preferably 100 μm to 1500 μm.

[0132] Embodiment 11. The electrically heatable metal foam component according to at least one of the preceding embodiments, wherein the metal foam material has a tubular shape at least in the heat transfer section thereof.

[0133] Embodiment 12. The electrically heatable metal foam component according to at least one of Embodiments 1 to 10, wherein the metal foam material has a spiral shape at least in its heat transfer section, wherein insulating material is preferably arranged between adjacent strips of the spiral shape.

[0134] Embodiment 13. The electrically heatable metal foam component according to Embodiment 12, wherein the electrically heatable metal foam component comprises at least one, in particular at least two, heat transfer sections having a spiral shape.

[0135] Embodiment 14. The electrically heatable metal foam component according to embodiment 13, wherein at least two heat transfer sections having a helical shape are parallel to each other at least in one section thereof, so that at least a double helix of the metal foam material is formed.

[0136] Embodiment 15. The electrically heatable metal foam component of Embodiment 12 or 14, wherein an insulating material is arranged between the strips of the helical metal foam material or between adjacent strips of the helical metal foam material of at least a double helix.

[0137] Embodiment 16. An electrically heatable metal foam component according to embodiment 14 or 15, wherein in at least two heat transfer sections having a spiral shape, the two spiral sections are essentially wound around the same axis, one of the heat transfer sections has a smaller radius and is positioned in the cavity of the heat transfer section having a larger radius.

[0138] Embodiment 17. The electrically heatable metal foam component according to any one of Embodiments 14 to 16, wherein each of the at least two heat transfer sections having a spiral shape is electrically connected to each other via a contact section provided at each of the spiral heat transfer sections.

[0139] Embodiment 18. The electrically heatable metal foam component according to any one of Embodiments 1 to 10, wherein the electrically heatable metal foam component comprises at least one, in particular at least two, heat transfer sections having a plate shape.

[0140] Embodiment 19. The electrically heatable metal foam component according to Embodiment 19, wherein at least two heat transfer sections having a plate shape are arranged with a gap therebetween.

[0141] Embodiment 20. The electrically heatable metal foam component according to at least one of the preceding embodiments, wherein more than one heat transfer section is connected to one another such that they form a parallel circuit. [>>10xD]

[0142] Embodiment 21. The electrically heatable metal foam component according to at least one of embodiments 1 to 19, wherein more than one heat transfer section is connected to one another such that they form a series circuit. [5x D]

[0143] Embodiment 22. The electrically heatable metal foam component of at least one of the preceding embodiments, wherein the metal foam component further comprises electrically isolated portions between segments of the heat transfer section of the metal foam material.

[0144] Embodiment 23. The electrically heatable metal foam component of Embodiment 22, wherein the electrically isolated portion defines an electrical path through the metal foam material.

[0145] Embodiment 24. The electrically heatable metal foam component of at least one of the preceding embodiments, wherein the metal foam element comprises one or more fluid-impermeable portions.

[0146] Embodiment 25. The electrically heatable metal foam component of at least one of the preceding embodiments, wherein the electrically isolating portion is fluid impermeable.

[0147] Embodiment 26. The electrically heatable metal foam component of at least one of the preceding embodiments, wherein the electrically heatable metal foam component further comprises a conductive strip connected to the contact section.

[0148] Embodiment 27. The electrically heatable metal foam component of at least one of the preceding embodiments, wherein catalyst particles are disposed within the open pores of the metal foam.

[0149] Embodiment 28. An electrically heatable metal foam component according to at least one of the preceding embodiments, wherein the metal foam material comprises at least one catalytically active material, in particular a catalytically active material for converting gaseous and / or liquid reactants.

[0150] Embodiment 29. The electrically heatable metal foam component according to at least one of the preceding embodiments, wherein the catalytically active material is deposited on the metal foam material in the form of catalytic particles.

[0151] Embodiment 30. The electrically heatable metal foam component of at least one of the preceding embodiments, wherein the metal foam material is the catalytically active material.

[0152] Embodiment 31. An electrically heatable metal foam component according to at least one of the preceding embodiments, wherein the metal foam material comprises at least one of the elements Ni, Fe, Cr, Al, Nb, Ta, Ti, Mo, Co, B, Zr, Mn, Si, La, W, Cu, Ag, Au, Pd, Pt, Zn, Sn, Bi, Ce and / or Mg, preferably comprises at least one of the elements Ni, Fe, Cr and / or Al, and particularly preferably comprises at least one of the elements Ni and / or Al.

[0153] Embodiment 32. An electrically heatable metal foam component according to at least one of the preceding embodiments, wherein the metal foam material is a nickel-iron-chromium-aluminum (NiFeCrAl) alloy or a nickel-chromium-aluminum (NiCrAl) alloy.

[0154] Embodiment 33. A reactor device having a defined flow path for a fluid, the flow path being defined by a wall of the reactor device, wherein the flow path directs at least one fluid through the reactor device, and wherein an electrically heatable metal foam component according to at least one of the preceding embodiments is disposed within the flow path.

[0155] Embodiment 34. A reactor apparatus according to Embodiment 33, wherein within the flow path, the electrically heatable metal foam component has a downstream end and an upstream end, wherein the flow path from the upstream end to the downstream end of the electrically heatable metal foam component passes through the metal foam material.

[0156] Embodiment 35. A reactor device according to embodiment 33 or 34, wherein the metal foam component is designed and arranged so that the at least one fluid passes from the radial outside of the metal foam material to the radial inside of the metal foam material, or wherein the metal foam component is designed and arranged so that the at least one fluid passes from the radial inside of the metal foam material to the radial outside of the metal foam material.

[0157] Embodiment 36. A reactor device according to at least one of Embodiments 33 to 35, wherein the wall of the reactor device defines a tubular flow path, and in the electrically heatable metal foam component, the metal foam material has a tubular shape at least in its heat transfer section, which is arranged substantially concentrically with the tubular flow path defined by the reactor wall.

[0158] Embodiment 37. A reactor device according to at least one of Embodiments 33 to 35, wherein the wall of the reactor device defines a tubular flow path, and in the electrically heatable metal foam component, the metal foam material has a spiral shape at least in its heat transfer section, which is arranged substantially concentrically with the tubular flow path defined by the reactor wall.

[0159] Embodiment 38. A reactor device according to at least one of Embodiments 33 to 35, wherein the electrically heatable metal foam component includes at least one heat transfer section having a plate shape, wherein the at least one plate-shaped heat transfer section is arranged to be substantially parallel to the flow direction of the flow path.

[0160] Embodiment 39. The reactor device according to at least one of Embodiments 33 to 38, wherein the electrically heatable metal foam component has a length in the range of 1.0 mm to 500 mm, preferably 10 mm to 400 mm, more preferably 20 mm to 300 mm, when designed so that the fluid flows through or along the metal foam in the axial direction of the reactor device, or

[0161] Wherein, when designed so that the fluid flows through or along the metal foam in the radial direction of the reactor device, the length of the electrically heatable metal foam component is in the range of 5.0 mm to 5000 mm, more preferably in the range of 30 mm to 2000 mm, and even more preferably in the range of 50 mm to 1000 mm.

[0162] Embodiment 40. The reactor device of at least one of Embodiments 33 to 39, wherein in the reactor device, the metal foam is electrically connected to at least two electrodes such that the metal foam can be resistively heated when an electric current is conducted through the metal foam.

[0163] Embodiment 41. The reactor apparatus according to at least one of Embodiments 33 to 39, wherein an induction heater is included in the reactor apparatus for inductively heating the metal foam.

[0164] Embodiment 42. The reactor device according to at least one of Embodiments 33 to 39, wherein the reactor device further comprises an electromagnetic wave generator for dielectric heating of the metal foam.

[0165] Embodiment 43. A reactor apparatus according to Embodiment 42, wherein the electromagnetic waves are microwaves.

[0166] Embodiment 44. The reactor apparatus according to at least one of Embodiments 33 to 43, wherein the reactor apparatus is designed for continuous flow of at least one fluid.

[0167] Embodiment 45. The reactor device according to at least one of Embodiments 33 to 44, wherein the metal foam is contained within a reaction chamber of the reactor device.

[0168] Embodiment 46. The reactor device according to at least one of Embodiments 33 to 44, wherein the metal foam is arranged upstream of the reaction chamber of the reactor device.

[0169] Embodiment 47. The reactor arrangement according to at least one of Embodiments 33 to 46, wherein a catalyst is further arranged downstream of the metal foam.

[0170] Embodiment 48. The reactor assembly according to at least one of Embodiments 33 to 47, wherein the reactor assembly is used for treating exhaust gases from internal combustion engines, or for treating exhaust gases from industrial processes, or for supplying heat to industrial processes.

[0171] Embodiment 49. A method for treating a fluid, wherein the fluid flows through a reactor apparatus according to any one of Embodiments 33 to 48.

[0172] Embodiment 50. The method of Embodiment 49, wherein the gas is exhaust gas emitted by an internal combustion engine or by an industrial process.

[0173] Embodiment 51. A method according to embodiment 50, wherein the internal combustion engine is an engine of an automobile, in particular an engine of a hybrid automobile.

[0174] Embodiment 52. A method according to embodiment 51, wherein the fluid comprises steam and methane, in particular wherein the method is a steam methane reforming method.

[0175] Reference numerals

[0176] 10Electrically heatable metal foam parts

[0177] 12 Metal foam material

[0178] 14 contact section

[0179] 16 heat transfer sections

[0180] 18 transition sections

[0181] 19 radial inner section

[0182] 20 longitudinal end

[0183] 22 spiral incisions

[0184] 24 Reactor wall

[0185] 26 spiral strips

[0186] 26' first helical strip

[0187] 26" second spiral strip

[0188] 28 Fluid-impermeable sections

[0189] 30 frames

[0190] lLongitudinal axis.

Claims

1. An electrically heatable metal foam component (10), comprising a metal foam material (12), wherein the metal foam material has: at least one contact section (14) for making electrical contact with the metal foam material (12); at least one transition section (18); and at least one heat transfer section (16), wherein the transition section (18) is arranged between the contact section (14) and the heat transfer section (16), wherein in the contact section (14), the metal foam material (12) has a higher density, in particular is compressed, than in the heat transfer section (16), and wherein in the transition section (18), the degree of densification changes from the degree of densification in the contact section (14) to the metal foam material in the heat transfer section (16).

2. The electrically heatable metal foam component (10) according to claim 1, wherein in the transition section (18) of the metal foam (12), struts of the metal foam are unbroken; and / or The length of the transition section (18) is at least 0.3 times the thickness of the metal foam material (12) at a position of the heat transfer section (16) adjacent to the transition section (18).

3. The electrically heatable metal foam component (10) according to claim 1 or 2, More than one heat transfer section (16) is electrically connected via a transition section (18) and a contact section (14).

4. Electrically heatable metal foam component (10) according to at least one of the preceding claims, wherein in the contact section (14), the cells of the metal foam material (12) are compressed to such an extent that the overlapping columns are in direct contact with each other after compression; and / or The metal foam material (12) in the contact section (14) is compressed so that the thickness of the metal foam material is reduced by at least 60%, in particular at least 70%, at least 75%, at least 85% relative to the thickness of the uncompressed metal foam material (12).

5. Electrically heatable metal foam component (10) according to at least one of the preceding claims, The thickness of the metal foam material (12) in the heat transfer section (16) is in the range of 1.0 to 100 mm, in particular 1.5 to 75 mm, in particular 1.5 to 50 mm.

6. Electrically heatable metal foam component (10) according to at least one of the preceding claims, The porosity of the metal foam material (12) in the heat transfer section (16) is greater than or equal to 70%, particularly preferably greater than or equal to 80%, and very particularly preferably greater than or equal to 85%, and most preferably it can be 95% or more.

7. Electrically heatable metal foam component (10) according to at least one of the preceding claims, The metal foam material (12) at least in the heat transfer section (16) has pores with a diameter of 10 μm to 10,000 μm, preferably 50 μm to 5000 μm, particularly preferably 300 μm to 3000 μm, most preferably 1500 μm to 3000 μm.

8. Electrically heatable metal foam component (10) according to at least one of the preceding claims, More than one heat transfer section (16) is connected to one another such that they form a parallel circuit.

9. Electrically heatable metal foam component (10) according to at least one of claims 1 to 7, Therein, more than one heat transfer section (16) is connected to one another such that they form a series circuit.

10. Electrically heatable metal foam component (10) according to at least one of the preceding claims, The metal foam component further includes electrically isolating portions, such as interstitial gaps or insulating material, between segments of the heat transfer section (16) of the metal foam material (12).

11. Electrically heatable metal foam component (10) according to at least one of the preceding claims, The catalyst particles are arranged in the open pores of the metal foam material (12).

12. Electrically heatable metal foam component (10) according to at least one of the preceding claims, The metal foam material (12) is a catalytically active material.

13. Electrically heatable metal foam component (10) according to at least one of the preceding claims, The metal foam material (12) comprises at least one of the elements Ni, Fe, Cr, Al, Nb, Ta, Ti, Mo, Co, B, Zr, Mn, Si, La, W, Cu, Ag, Au, Pd, Pt, Zn, Sn, Bi, Ce, Mg, Ru, Rh, Ir and / or Os, preferably comprises at least one of the elements Ni, Fe, Cr and / or Al, and particularly preferably comprises at least one of the elements Ni and / or Al.

14. A reactor device having a defined flow path for a fluid, said flow path being bounded by walls of said reactor device, wherein the flow path directs at least one fluid through the reactor device, and Therein, an electrically heatable metal foam component (10) according to at least one of the preceding claims is arranged in the flow path.

15. The reactor device according to claim 14, The reactor device is used for treating exhaust gas from an industrial process, or for providing heat for an industrial process, or for treating exhaust gas from an internal combustion engine.

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