Segmented holding device for bulk material bodies

Abstract

NOT VISIBLE DUE TO STATUS OF PATENT

Description

[0001] SEGMENTED HOLDING DEVICE FOR BULK MATERIAL BODIES

[0002] The present invention relates to a holding device for bulk material bodies, which is particularly suitable for use in ammonia oxidation reactors, as well as to a reactor comprising such a holding device. The invention also relates to a process for the catalytic oxidation of ammonia.

[0003] Ammonia oxidation reactors are used in the synthesis of nitric acid according to the Ostwald process, in which ammonia (NH3) and oxygen (O2) are catalytically converted to nitrogen monoxide (NO) and water (H2O). The product gas stream is then fed into water, where the conversion to nitric acid takes place. Ammonia combustion is carried out at high temperatures (usually 800–950 °C) over catalysts made of platinum and / or platinum alloys. These are usually installed in the form of knitted or woven meshes in several layers within the reactor cross-section. Nitrogen (N2) and nitrous oxide (N2O) are produced as byproducts of ammonia combustion. Unlike NO and NO2, N2O does not undergo any further reactions and is released into the atmosphere after completing all process steps.To reduce the emission of environmentally harmful N2O, such reactors often contain additional catalytically active components that decompose the nitrous oxide downstream of the actual catalytic zone, in the direction of fresh gas flow. Typically, corresponding secondary catalysts are used as bulk material, provided in basket-like devices. Such catalyst baskets usually comprise a gas-permeable base plate onto which the bulk material is layered. The bulk material can exhibit catalytic activity; however, there are also applications in which the bulk material exhibits at least some catalytic activity and serves, for example, to support the catalyst mesh.

[0004] The movements and vibrations during operation can cause the bulk material to be compressed and / or compacted. This reduces the height of the bulk material. Particularly if the bulk material is intended to support the catalyst meshes above it, such compression can lead to cracks in the meshes.

[0005] Due to the high temperatures at which the ammonia oxidation reactor operates, the catalyst basket expands during operation, which can lead to uneven expansion of the gas-permeable base plate compared to the side walls of the basket. This differential expansion can, on the one hand, lead to a gap forming between the walls and the base plate through which the bulk material can fall. Another problem resulting from the thermal expansion differences between the gas-permeable base plate and the side walls is the formation of troughs or waves in the bulk material.

[0006] Both phenomena impair the bulk material structure, which can lead to a loss of combustion efficiency and gas slippage. To stabilize the bulk material, DE 102011112782 A1, for example, proposes installing a mesh-like device on the base plate to seal the gap between the base plate and the walls caused by thermal expansion. WO 2023232853 A1 proposes a catalyst basket consisting of interconnected modules arranged side by side and all of the same height to improve the bulk material structure under cyclic thermal loading. However, constructing catalyst baskets from a large number of modules is complex and inflexible.

[0007] Due to changing requirements regarding the catalytic activity of the bulk material, it is also desirable for the bulk material to be designed flexibly and variable. For example, it may be necessary to provide different bulk materials in different segments of the catalyst basket, which in turn must be kept separate and stabilized from each other. For example, it may be necessary to fill only a portion of the volume with N2O reduction catalysts and fill the remaining volume with catalytically inactive packing. Segmentation of materials with different levels of activity may also be necessary. Such segmentation can be particularly advantageous if it can be carried out simultaneously at different levels relative to the gas flow direction.In addition, it is desirable to be able to design such segments in a variable and flexible manner in order to meet changing requirements for different production campaigns.

[0008] The problems identified in the prior art are at least partially solved by a holding device for bulk material bodies, comprising an outer wall, a gas-permeable base plate, at least one rigid separating element, and at least one flexible and gas-permeable support element. The outer wall defines a volume that is closed off in one direction by the gas-permeable base plate, and the rigid separating element divides this volume into at least two main segments. The rigid separating element and the flexible and gas-permeable support element are arranged such that at least one of the main segments formed by the rigid separating element is divided into at least two subsegments.

[0009] The holding device according to the invention enables a stable yet variable design of the bed. Surprisingly, it has been shown that the volume of the catalyst basket can be divided particularly advantageously into several segments by combining rigid separating elements and flexible support elements. This reduces movement of the bulk material, while the flexible support elements enable further segmentation of the basket volume. In particular, the design according to the invention allows segments to be formed one behind the other or next to one another relative to the flow direction. Different bulk material bodies can be introduced into the holding device in two or more layers, for example in the form of packing elements for homogenizing the gas volume flow, such as uncoated Raschig rings, and / or in the form of bulk material bodies with a catalyst function, in particular for N2O reduction.

[0010] The present invention relates to a holding device for bulk material bodies, comprising an outer wall and a gas-permeable base plate. The outer wall defines a volume, which in turn is closed off in one direction by the gas-permeable base plate. In other words, the outer wall encloses a volume with a first and an opposite second opening, wherein the second opening is defined by the gas-permeable base plate.

[0011] The outer wall is arranged at the edge of the base plate so that it completely encloses the edge of the base plate. The space thus created is particularly suitable for accommodating bulk materials. Such holding devices can be used, for example, as catalyst baskets in flow reactors; in these cases, they are arranged in the reactor interior so that the process gases flow through them. The holding device is positioned so that the process gas flows in the flow direction first through the first opening of the holding device (opposite the gas-permeable base plate), passes through the device, and exits the holding device through the second opening in the outer wall or through the gas-permeable base plate. In other words, the flow direction is understood to be the direction along the shortest distance between the first opening and the gas-permeable base plate.Whenever reference is made to the flow direction in this application, this definition should always be used as a basis.

[0012] The diameter of the holding device can be constant across its height, but it can also increase or decrease. Height refers to the extension of the holding device parallel to the flow direction. The height of the holding device is typically in the range of 100 to 1000 mm. The holding device can have a diameter in the range of 800 to 6000 mm.

[0013] The gas-permeable base plate can be, for example, a perforated plate, a sieve, in particular a slotted sieve, a net, or a grate, for example a honeycomb grate. The gas-permeable base plate can be manufactured in one piece, or it can also be formed from multiple components. The gas-permeable openings in the base plate are typically smaller than the average size of the bulk material bodies that are arranged directly on it in the bed. The gas-permeable base plate can be flat, or it can have a U- or V-shaped cross-section. The shape of the gas-permeable base plate is not further limited and usually depends on the shape of the reactor in which it is used. For example, it can be round, oval, rectangular, square, hexagonal, or octagonal. The gas-permeable base plate is preferably round or substantially round.The shape of the gas-permeable base plate essentially determines the cross-sectional shape of the holding device parallel to the base plate.

[0014] The outer wall can, but does not have to, consist of several individual parts. The at least one outer wall can, for example, be an annular sheet metal element, which can be made in one piece or from multiple components. The outer wall is usually straight; in other words, it is practically not curved in the direction of flow. The outer wall can be arranged perpendicular to the base plate or at an angle to the vertical of the base plate; accordingly, the retaining device can have a cylindrical, trough-shaped, or conical shape.

[0015] The shape of the cross section of the holding device parallel to the flow direction is not further restricted; for example, the holding device can have a round, oval, rectangular, square, hexagonal or octagonal cross section along the flow direction; preferably, the holding device has a round or substantially round cross section.

[0016] The outer wall and the gas-permeable base plate can be connected to each other, but preferably they do not have a mechanical and / or positive connection in order to compensate for different thermal expansions during reactor operation. The holding device can have a circumferential gap between the outer wall and the gas-permeable base plate. In further configurations, the outer wall can have an internal support device, for example in the form of an at least partially circumferential support ring, on which the gas-permeable base plate can be arranged in a floating manner.

[0017] Suitable materials for the base plate and outer wall must withstand the conditions in the reactor during the process and are known to those skilled in the art. For example, nickel-chromium alloys (NiCr alloys) such as InconelßOO, iron-chromium-aluminum alloys (FeCrAl alloys) such as Megapyr or Kanthai, or heat-resistant stainless steels can be used, with NiCr alloys having proven particularly suitable. The gas-permeable base plate can be made of the same material as the outer wall, but different materials can also be used.

[0018] The holding device has at least one rigid separating element. The rigid separating element is characterized in particular by the fact that its shape changes little or not at all when the holding device is filled with bulk material, thus showing little or no flexibility under mechanical stress. The rigid separating element is arranged within the volume of the holding device; in other words, it is located above the gas-permeable base plate and within the outer wall.

[0019] The rigid separating element divides the volume enclosed by the outer wall into at least two main segments. A segment is understood to be a volume region within the holding device that is delimited in at least two directions by at least one element of the holding device, i.e. the at least one separating element, the outer wall, the gas-permeable base plate and / or the at least one support element. The segments are each completely separated from one another. The segments can be open in one direction, i.e. not delimited by one of the elements of the holding device. The rigid separating element is arranged such that gas can flow through the main segments within the volume. In other words, the rigid separating element does not close off the volume, in particular it does not make it gas-tight.

[0020] The rigid separating element can be made of, for example, a NiCr alloy such as Inconelß00, a FeCrAl alloy such as Megapyr or Kanthai, or a heat-resistant stainless steel. Sheets made of a NiCr alloy, especially Inconel600, have proven particularly advantageous.

[0021] The rigid separating element can, for example, be an annular sheet, which can be in one piece or consist of several components.

[0022] Preferably, the rigid separating element is aligned parallel to the flow direction; in particular, the rigid separating element is arranged such that gas flow through the holding device is impeded as little as possible. In particular, the rigid separating element can be aligned perpendicular to the gas-permeable base plate. The holding device can have more than one rigid separating element. Advantageously, the rigid separating element or the plurality of rigid separating elements are arranged around the central axis of the holding device. Such an arrangement allows, in particular, the formation of at least two concentric main segments.

[0023] The separating device(s) may have devices that can serve to stabilize the alignment of the separating device(s) on the gas-permeable base plate. Such stabilizing holding devices can be provided, for example, in the form of flat metal sheets. Such metal sheets can be attached perpendicular to the vertical extent of the separating device to an edge of the separating device, in particular parallel to the gas-permeable base plate; likewise, such metal sheets can be arranged perpendicular to the gas-permeable base plate and parallel to the flow direction. The stabilizing holding device(s) can be gas-permeable, i.e., have gas-permeable openings, but they can also be gas-impermeable.

[0024] The holding device also has at least one flexible and gas-permeable support element. The flexibility of the support element is characterized in particular by its elastic behavior under thermal load cycles and the influence of the bulk material. The gas permeability of the support element results from existing openings in its surface area.

[0025] The extensibility of the flexible and gas-permeable support element under mechanical and / or thermal stress is advantageously at least 0.05%, preferably at least 0.5%, in the surface direction. The extensibility in the surface direction should not exceed 10%, preferably 5%. Extensibility within this range ensures that the support element can adapt to thermal expansion without being damaged and without allowing bulk particles to pass through the gas-permeable openings.

[0026] The flexible and gas-permeable support element can be, for example, woven, warp-knitted, or knitted fabric, for example in the form of a net. Such sheet-like knit fabrics are particularly suitable as support elements because they are flexible and stretchable in at least one direction of their extension. They are typically made from wire or wires of the corresponding material. The flexible and gas-permeable support element can, for example, be a net made of a NiCr alloy such as Inconel 600, a FeCrAl alloy such as Megapyr or Kanthai, or a heat-resistant stainless steel. Support nets made of FeCrAl alloys, especially Megapyr or Kanthai, have proven particularly advantageous.

[0027] The flexible and gas-permeable support element preferably comprises at least one wire, which has, for example, a diameter of 0.01 to 3 mm, preferably 0.1 to 2 mm. The mesh size of the support element is not further limited; it can, for example, be in the range of 0.01 to 10 cm, in particular in the range of 0.05 to 1 cm. The openings of the gas-permeable support element are preferably smaller than those of the gas-permeable base plate; in particular, the openings have a smaller mesh size.

[0028] The at least one rigid separating element and the at least one flexible and gas-permeable support element are arranged such that at least one of the main segments formed by the rigid separating element is divided into at least two subsegments. The flexible and gas-permeable support element thus extends through at least one main segment. In other words, the volume delimited by the outer wall is divided into at least three segments. Such an arrangement allows a modular design of the volume of the holding device, which in turn enables the segmentation of the bulk material. Such bulk material segmentation makes it possible to optimize and coordinate both the gas flow across the reactor cross-section and the catalytic activity in the flow direction, i.e., perpendicular to the reactor cross-section.

[0029] The shape of the segments is not further limited; they can, for example, have a round, oval, rectangular, square, hexagonal, octagonal or ring-shaped cross-section and be cylindrical, hollow-cylindrical or cuboid-shaped

[0030] The at least one rigid separating element and the at least one flexible and gas-permeable supporting element can also be arranged so that more than three segments are formed.

[0031] Advantageously, the at least two sub-segments formed by the flexible and gas-permeable support element are arranged one behind the other in the flow direction. In particular, it has proven advantageous if at least two of the at least three segments have different heights; particularly preferably, the two segments with different heights are arranged one behind the other in the flow direction.

[0032] The flexible and gas-permeable support element can completely or partially span the cross-section of the holding device, advantageously it is arranged so that it spans the entire cross-section of the holding device

[0033] The flexible and gas-permeable support element is preferably arranged at least partially U-shaped in cross-section within the volume of the holding device, in particular within one of the main segments formed by the rigid separating device. The gas-permeable support element can also be arranged in a wave-like cross-section within the volume of the holding device, in particular, it can be arranged in a wave-like manner around and above the rigid separating element.

[0034] The flexible and gas-permeable support element is advantageously arranged such that its surface area is located at least partially in the central volume region of the holding device. The support element is preferably arranged at least partially parallel to the gas-permeable base plate. In such a configuration, the central volume region of the holding device, in other words, a central main segment, is advantageously divided into two subsegments. The subsegments can have the same or different heights in the flow direction, and they can also have the same or different volumes.

[0035] Preferably, the flexible and gas-permeable support element is arranged floatingly on and / or around the rigid separating element. In particular, the flexible and gas-permeable support element and the rigid separating element are not permanently connected to one another. A floating installation of the separating element and support element enables a holding device that stabilizes the contained bulk material even under high thermal loads and whose supporting effect is not impaired by thermal loads. It can also be particularly advantageous if neither the flexible and gas-permeable support element nor the rigid separating element are permanently connected to the outer wall. A permanent connection is understood here to mean a permanent and rigid fixation, for example by welding or soldering, i.e. a positive mechanical connection. Loose fixation should nevertheless explicitly be possible, for example by placing it on a suitable anchor device.Such anchoring devices can, for example, be provided in the gas-permeable base plate and can be designed in the shape of a hook or pin.

[0036] The holding device can also have more than one flexible and gas-permeable support element. A combination of several such support elements allows for an even more variable design of the internal volume of the holding device. The multiple support elements can have the same shape and / or the same size and / or the same material, or different shapes and / or sizes and / or materials. In preferred embodiments, the holding device can, for example, have an annular net arranged such that the opening is located centrally in the volume of the holding device, and another round net arranged floating on this opening.

[0037] The holding device is designed to hold bulk solids. Bulk solids are defined as shaped bodies made of temperature-resistant materials, which can be in the form of fillers without catalytic activity or equipped with a catalytically active material. The bulk solids can be in the form of spheres, granules, pellets, hollow cylinders, multi-hole cylinders, rings, tablets, cylinders, cubes, spoked wheels, trilobes, or quadrulobes, for example. Such bulk solids can be shaped using extrusion, granulation, or compression molding. The size or equivalent diameter of the bulk solids is selected so that the bed has a suitable packing density, the lowest possible pressure loss, and, optionally, a suitable catalytic activity.The diameters or sizes of such bulk material bodies can, for example, be in the range from 0.5 to 100 mm, preferably in the range from 1 to 50 mm, in particular in the range from 2 to 25 mm.

[0038] Suitable materials for bulk solids are known to those skilled in the art; particularly suitable materials include ceramic materials, metal oxides such as aluminum oxides or cerium oxides, metals, as well as zeolites or mixtures of the aforementioned materials. Materials for packing elements without catalytic activity include aluminum oxides. For catalytically active bulk solids, also called shaped catalyst elements, the material selection depends on the intended catalytic function; moreover, the material of the bulk solid itself may already be catalytically active. Bulk solids can also be formed from a shaped element without catalytic activity but equipped with a catalytically active component. The catalytically active component can be homogeneously distributed in the shaped element matrix or present as a catalytically active coating.Examples of catalytically active components include precious metal components, especially components of the platinum group metals, iron components, and / or transition metal components, especially cobalt components. A catalytically active component is understood to mean any compound or form of the corresponding metal, for example, the metallic form and / or the oxidic form.

[0039] Processes for producing catalytically active components and / or coatings are known to those skilled in the art. The application of catalytically active components can be achieved, for example, by dipping, pouring, pumping, or suctioning a coating suspension containing a catalytically active component or a corresponding precursor compound into the molded body. A drying step can then follow. Such processes are commonly referred to as washcoat processes. Alternatively or additionally, impregnation processes, precipitation, chemical vapor deposition (CVD), or spraying processes can also be used.

[0040] The holding device according to the invention is particularly suitable for simultaneously providing different types of bulk material bodies, for example, bulk material bodies of different sizes and / or different materials. In particular, the combination of catalytically inactive packing bodies with shaped catalyst bodies in different segments of the holding device is preferred.

[0041] The holding device can comprise additional components. For example, another gas-permeable device, such as a fabric or mesh, can be placed or attached directly to the gas-permeable base plate for further sealing. Such an additional gas-permeable device does not divide the volume into additional segments. Particularly for configurations that have a gap between the gas-permeable base plate and the outer wall, such an additional holding device can be arranged to further seal the gap.

[0042] The present invention also relates to a reactor equipped with a holding device according to the invention. The reactor is preferably a flow reactor, in particular an ammonia oxidation reactor.

[0043] In addition to the holding device, the reactor comprises other components, typically at least one reactor vessel in which the holding device is arranged. The arrangement can be such that the fluid flows through the holding device axially or radially.

[0044] For example, the reactor has anchoring devices by means of which the holding device can be attached to the reactor. Anchoring can be achieved by suspending the holding device from a corresponding fixture or, for example, by attaching the holding device to the reactor via a flange connection. Alternatively, the holding device can also be welded into the reactor.

[0045] In the reactor, the holding device is filled with bulk material bodies, which, as described above, can be packings without catalytic activity and / or shaped catalyst bodies. The bulk material bodies can have the same or different shapes and sizes; typically, at least the bulk material bodies in two of the at least three segments of the holding device differ from one another. For suitable bulk material bodies, reference is made to the statements made with regard to the holding device according to the invention, which also apply to the reactor according to the invention. Particularly advantageously, the holding device contains a catalyst bed that has catalytic activity with respect to N2O decomposition; in other words, the holding device advantageously contains at least partially a secondary catalyst bed.

[0046] Advantageously, the reactor comprises at least one further catalytic device, for example in the form of one or more catalyst gauzes, in particular in the form of catalyst gauzes made of a platinum alloy. Such catalytic devices are typically arranged upstream of the holding device according to the invention and are also referred to as primary catalysts.

[0047] In particular, the reactor may comprise a catalyst system as a further catalytic device. A catalyst system is understood herein to be an ensemble of meshes comprising at least one catalyst mesh. In other words, a catalyst system comprises a stack of meshes, of which at least one mesh has catalytic activity, in particular a noble metal mesh. A catalyst system may also comprise one or more meshes without a catalytic function, for example, catchment meshes, which serve to recover noble metal evaporating during operation, or support meshes, which serve to stabilize the catalyst system and typically do not contain any noble metal.

[0048] A precious metal mesh is a mesh that contains at least one precious metal wire. A precious metal wire is understood to be a wire that consists of at least one precious metal or that contains a significant proportion (> 50 wt.%) of precious metal. In the context of the present invention, precious metals is understood to be a metal selected from the group consisting of platinum group metals, gold and silver. Platinum group metals are the metals of the so-called platinum group, i.e. platinum (Pt), palladium (Pd), iridium (Ir), rhodium (Rh), osmium (Os) and ruthenium (Ru). The precious metal wire is preferably made of platinum, a platinum alloy, palladium or a palladium alloy. A platinum alloy contains more than 50 wt.% platinum, and other alloy components include, in particular, palladium, rhodium and ruthenium. A palladium alloy contains more than 50 wt.-% palladium, other alloy components include platinum, rhodium, ruthenium, nickel, tungsten and gold.

[0049] Suitable non-precious metal meshes include meshes made of heat-resistant steel, typically a FeCrAl alloy such as Megapyr or Kanthai, stainless steel, or heat-resistant alloys such as NiCr alloys. Support meshes made of Megapyr or Kanthai have proven particularly advantageous.

[0050] Depending on the reactor type, additional components may be present, for example, devices for absorbing the resulting products. In ammonia oxidation reactors, such devices are provided in the form of absorption towers. In such configurations, the holding device is advantageously arranged between the catalyst meshes and the absorption tower to provide the secondary catalyst zone.

[0051] The invention also relates to a process for the catalytic oxidation of ammonia, in which a process gas stream containing at least nitrous oxide (N2O) is passed through a holding device according to the invention. A process gas is understood to be a gas mixture produced by the catalytic conversion of a fresh gas containing ammonia.

[0052] Such a process, for example, initially comprises the conversion of an ammonia-containing fresh gas over a primary catalyst, typically in a temperature range of 800 to 900 °C. The primary catalyst can, for example, be a catalyst system described herein, which comprises at least one precious metal mesh. The resulting process gas comprises, in addition to the main products, nitrous oxide as a by-product. The process then comprises the conversion of this process gas in a holding device according to the invention, which expediently contains at least one bulk material body with catalytic activity for N2O decomposition. For this purpose, the process gas is passed in the direction of flow through the holding device containing the shaped catalyst bodies. For suitable bulk materials, reference is made to the statements made with regard to the holding device according to the invention, which also apply to the process according to the invention.

[0053] The invention is explained below with reference to illustrations and exemplary embodiments. Identical reference numerals designate identical parts in different embodiments; they are not explicitly mentioned for every embodiment. The illustrations are neither to scale nor do they correctly reflect the actual size ratios. Figure 1A shows a schematic of a vertically positioned flow reactor (1) for the heterogeneous catalytic combustion of ammonia. The catalyst system (2) forms the actual reaction zone of the flow reactor (1). The catalyst system (2) shown comprises several nets (4, 5) arranged one behind the other in the flow direction (3) of the fresh gas. The catalyst system (2) comprises a catalyst net group (4) and a noble metal-free support net (5) arranged underneath. A holding device for bulk material bodies (6) is arranged below the catalyst net group in the flow direction.

[0054] The fresh gas, for example, is an ammonia-air mixture that is heated to a preheating temperature and introduced into the reactor (1) from above under increased pressure. Upon entering the catalyst system (2), the gas mixture is ignited, followed by an exothermic combustion reaction. The following main reaction takes place:

[0055] 4 NH3 + 5 O2 -> 4 NO + 6 H2O

[0056] In this process, ammonia (NH3) is converted into nitrogen monoxide (NO) and water (H2O). The resulting nitrogen monoxide (NO) reacts with excess oxygen in the outflowing reaction gas mixture (symbolized by the directional arrow 7 indicating the flow direction of the outflow) to form nitrogen dioxide (NO2). The process gas is then passed through the holding device (6), which contains a catalyst component suitable for nitrous oxide decomposition. The resulting reaction gas mixture (symbolized by the directional arrow 8 indicating the flow direction) is finally converted with water in a downstream absorption system (not shown) to form nitric acid (HNO3).

[0057] Figure 1 B shows a cross-section of the flow reactor (1) along plane I parallel to the gas-permeable base plate. Plane I is located above the gas-permeable base plate (20) of the holding device (6), which is why it is not visible in Fig. 1 B. The shaped catalyst bodies and the bulk materials with which the holding device is filled during operation are also not shown for clarity. The holding device (6) has a round cross-section and is mounted within the reactor wall. The outer wall (21) of the holding device (6) encloses a volume that is divided into two main segments (HS1, HS2) by the separating device (22). Within the second segment HS2, a mesh (23) is arranged as a support device for shaped catalyst bodies (plane I runs through the mesh plane). This divides the segment HS2 into two sub-segments, which are located above and below the mesh (23) in the flow direction.

[0058] Figure 2 shows schematic cross-sectional views of various embodiments of holding devices according to the invention. Typically, the outer wall (21) is an annular sheet and the base plate (20) is a grid, each made of Inconel 600. The separating element (22) is preferably also an annular sheet made of Inconel 600. A net made of Kanthai is preferably used as a further support element (23). In all embodiments, the net (23) can simply be laid on top, but it can also be advantageous for it to be at least partially loosely attached to the base plate (20) and / or the outer wall (21). All of the features described can also be combined with one another as desired.

[0059] Fig. 2 A corresponds to the holding device (6) from Fig. 1. The plane I and the flow direction (3) are shown again. The separating element (22) is arranged within the outer wall (21) and divides the volume enclosed by the outer wall (21) into two segments. The separating element (22) is placed on the grid-shaped base (20). A net (23) is arranged above the separating element (22) in such a way that the central segment is in turn divided into two sub-segments (US1 and US2). The net (23) is arranged in a U-shape in the central segment and rests loosely on the separating element (22). The outer segment (HS1) is designed as a hollow cylinder and encloses the two cylindrical sub-segments (US1, US2) arranged one behind the other in the direction of flow.

[0060] In the embodiment shown in Fig. 2 B, the net (23) spans the entire cross-section of the holding device. In the outer area, or in the area of ​​the outer segment (HS1), the net rests on the base plate (20)—it is positioned such that the outer segment HS1 is not further subdivided.

[0061] In the embodiment shown in Fig. 2 C, the net (23) also spans the entire cross-section of the holding device and is arranged in a wave-like pattern. In the middle segment (HS2), it rests on the base plate (20) and surrounds this segment in a U-shaped cross-section. The outer segment is divided into two segments (US1 and US2) by the net. In the embodiment shown in Fig. 2 D, the net (23) divides both main segments formed by the separating device (22); the holding device (6) accordingly comprises a total of four segments (LIS1-4).

[0062] The embodiment according to Fig. 2 E comprises a net (23) resting on the separating element (22) with a centrally located opening (24). A further net (25) is arranged floating on this opening, spanning the opening (24). This modular arrangement of nets further improves the stability of the net structure against thermal load cycles. The separating element also comprises a support device (26), which further increases the stability of the separating device. This support device is, for example, a circumferential ring welded to the separating device.

[0063] A further embodiment having three segments is shown in Fig. 2 F. A net (23) rests on the separating element (22) and is arranged such that an opening (24) is present in the central main segment, which opening is spanned by a floating net (25), thereby forming two sub-segments (US1, US2). In addition, a further net (27) is placed along the outer wall (21). The two nets (23) and (27) span the entire height of the holding device (6) and are arranged such that they form an opening (28) above the base plate (2) in the region of the outer main segment (HS1). A further annular net (29) is arranged on this opening (28) to close the opening and seal off the volume of the holding device in the direction of the base plate (2).

Claims

CLAIMS 1. Holding device for bulk material bodies, comprising an outer wall which delimits a volume, a gas-permeable base plate which closes off the volume delimited by the outer wall in one direction, at least one rigid separating element which Volume into at least two main segments and at least one flexible and gas-permeable support element, wherein the rigid separating element and the flexible and gas-permeable support element are arranged such that at least one of the main segments formed by the rigid separating element is divided into at least two sub-segments.

2. Holding device according to claim 1, wherein the at least two sub-segments formed by the flexible gas-permeable material are arranged one behind the other in the flow direction.

3. Holding device according to claim 1 or 2, wherein at least two of the at least three segments have different heights.

4. Holding device according to claim 3, wherein the two segments with different heights are arranged one behind the other in the flow direction.

5. Holding device according to one of the preceding claims, wherein the rigid separating element is aligned parallel to a flow direction.

6. Holding device according to one of the preceding claims, wherein the flexible and gas-permeable support element spans the entire cross-section of the holding device.

7. Holding device according to one of the preceding claims, wherein the flexible and gas-permeable support element is arranged in a cross-section at least partially U-shaped within the volume of the holding device.

8. Holding device according to one of the preceding claims, wherein the flexible and gas-permeable support element is arranged floatingly on and / or around the rigid separating element.

9. Holding device according to one of the preceding claims, wherein the flexible and gas-permeable support element is woven, warp-knitted or knitted fabric.

10. Holding device according to one of the preceding claims, wherein the outer wall and the gas-permeable base plate have no mechanical and / or positive connection.

11. Holding device according to one of the preceding claims, wherein the holding device has more than one flexible and gas-permeable support element.

12. Holding device according to one of the preceding claims, wherein the diameter of the holding device is constant over its height.

13. Reactor comprising a holding device according to one of claims 1 to 12.

14. A process for the catalytic oxidation of ammonia, in which a process gas stream containing at least N2O is passed through a holding device according to one of claims 1 to 12.