Reactor for carrying out a chemical reaction

Abstract

The invention relates to a reactor for carrying out a chemical reaction in a process fluid using an M-phase alternating current in order to heat the process fluid. The reactor comprises a reactor wall; at least one group of M reaction tubes, each of which has an electrically heatable heating section that extends between a first and a second removal region for a respective heating length, each said heating section having a respective feed region in a region which extends over 20% to 80% of the heating length of said heating section; electrically conductive feed elements, wherein each group M is paired with the feed elements connected to the feed regions of the group, and different phases of the alternating current can be fed to different feed elements paired with a group; electrically conductive first and second removal elements, each group being paired with M first and M second removal elements connected to the first or second removal regions of the group; and at least one first and at least one second star bridge, wherein each group is paired with a first and a second star bridge, wherein for each group, the first removal elements paired with the group are connected to the first star bridge paired with the group; and the second removal elements paired with the group are connected to the second star bridge paired with the group. Figure 1

Description

[0001] Description

[0002] Reactor for carrying out a chemical reaction

[0003] The invention relates to a reactor for carrying out a chemical reaction in a process fluid using multiphase alternating current to heat the process fluid.

[0004] State of the art

[0005] A number of processes in the chemical industry utilize reactors in which one or more reactants are passed through heated reaction tubes and converted there, either catalytically or non-catalytically. The heating serves primarily to overcome the activation energy required for the chemical reaction to proceed. The reaction can be endothermic overall or, once the activation energy has been overcome, exothermic. The present invention particularly relates to strongly endothermic reactions.

[0006] Examples of such processes include steam cracking, various reforming processes, in particular steam reforming, dry reforming (carbon dioxide reforming), mixed reforming processes, alkane dehydrogenation processes, and the like. In steam cracking, the reaction tubes are guided through the reactor in the form of coils, which have at least one return bend in the reactor. In contrast, steam reforming typically uses tubes that run through the reactor without a return bend.

[0007] The invention is suitable for all such processes and reaction tube configurations. For purely illustrative purposes, reference is made to the articles "Ethylene," "Gas Production," and "Propene" in Ullmann's Encyclopedia of Industrial Chemistry, for example, the publications of April 15, 2009, DOI: 10.1002 / 14356007.a10_045.pub2, of December 15, 2006, DOI: 10.1002 / 14356007.a12_169.pub2, and of June 15, 2000, DOI: 10.1002 / 14356007.a22_211. The reaction tubes of such reactors are conventionally heated using burners. The reaction tubes are guided through a combustion chamber in which the burners are also located.

[0008] Currently, there is increasing demand for syngas and hydrogen produced with no or reduced local carbon dioxide emissions. However, this demand cannot be met by processes that use fired reactors due to the combustion of fossil fuels. Other processes are ruled out, for example, due to high costs. The same applies to the production of olefins and / or other hydrocarbons through steam cracking or the dehydrogenation of alkanes. In such cases, too, there is a desire for processes that, at least locally, emit lower amounts of carbon dioxide.

[0009] WO 2015 / 197181 A1 discloses a reactor in which a fluid flowing through a pipeline is heated, wherein the electrically conductive pipeline is connected to several phases of an alternating current source so that a star point connection is formed and heat is generated according to the electrical resistance of the pipeline.

[0010] The design limits the heated pipe length and thus the ohmic resistance. This results in a power supply with high current and low voltage to deliver the required heating power to the pipe, necessitating complex high-current feeds in terms of both mechanical and material properties.

[0011] Disclosure of the invention

[0012] This problem is solved by a reactor for carrying out a chemical reaction having the features of the independent claim.

[0013] The invention utilizes the measure of connecting each reaction tube to only one phase and establishing phase balance across multiple reaction tubes. The length heated per phase, and thus the resistance, in a reaction tube is thus increased compared to an arrangement in which a reaction tube is connected to multiple phases. This allows for a higher power input at a constant current (since P = RI 2 , where P: power, R: resistance, I: current), which can be achieved by increasing the voltage. Since each reaction tube only receives one power supply via a respective feed element, the number of technically complex high-current feeds and the resulting power losses can be reduced.

[0014] The reactor for carrying out a chemical reaction in a process fluid using multiphase alternating current to heat the process fluid, wherein the alternating current has a number M of phases, where M is an integer greater than one, comprises a reactor vessel formed by a thermally insulating reactor wall and at least one group with a plurality of reaction tubes, each group comprising M reaction tubes, each of the reaction tubes having an electrically heatable heating section extending with a respective heating length between a first and a second take-off region of the respective reaction tube, wherein the heating sections are arranged within the reactor vessel for at least 95% of their heating length and each have a feed region in a region extending from 20% to 80% of their heating length. The percentages in the statement "20% to 80%" refer to the position within the heating length, i.e.0% indicates the position of the first (or second) consumption area, 50% the center of the heating section and 100% the position of the second (or first) consumption area (i.e. no proportion is meant).

[0015] At the feed-in areas, which are connected to the power supply via the feed-in elements, a phase of the alternating current is fed into the heating sections, i.e., an alternating voltage corresponding to the respective phase is applied. At the take-off areas, which are connected to the star bridges via the take-off elements, the respective phase of the alternating current is taken from the heating sections, or removed. The star bridges balance the different phases of the alternating current.

[0016] The fact that the reaction tubes are electrically heatable or have an electrically heatable heating section means that the material used for the reaction tubes, and in particular the heating sections, is a material with electrical conductivity suitable for electrical heating. Examples include heat-resistant steel alloys, particularly heat-resistant chromium-nickel steel alloys. Such steel alloys can also be used for the power connections (through which the electrical currents are conducted into the reactor vessel), i.e., the feed elements and the take-off elements. For example, materials with the standard designations GX40CrNiSi25-20, GX40NiCrSiNb35- 25, GX45NiCrSiNbTi35-25, GX35CrNiSiNb24-24, GX45NiCrSi35-25, GX43NiCrWSi35- 25-4, GX10NiCrNb32-20, GX50CrNiSi30-30, G-NiCr28W, G-NiCrCoW, GX45NiCrSiNb45-35, GX13NiCrNb45-35, GX13NiCrNb37-25, or GX55NiCrWZr33- 30-04 according to DIN EN 10027, Part 1, "Materials", can be used.

[0017] The reactor wall encloses an area surrounded in all spatial directions by at least one reactor wall. Generally, the reactor wall is formed by several individual walls joined together to enclose an area; it could therefore also be referred to as a group of reactor walls, although the term "reactor wall" is used for simplification. The enclosed area, and thus also the reactor wall, can have any volumetric shape, but preferably that of a quadrangular prism. The reactor wall can have sealed structural elements (such as feedthroughs or viewing windows), but also permanently open and / or closable openings as connections to other system components, preferably for conditioning the atmosphere within the reactor wall, e.g., inlet nozzles for inert gas or outlet openings to a chimney tract.

[0018] The reactor vessel (which can also be referred to as the reactor box) is formed by the reactor wall, i.e., the reactor wall represents the wall(s) of the reactor vessel. Accordingly, the term "reactor wall" here is not to be understood in the sense of a tank for the process fluid. The area enclosed by the reactor wall is the interior of the reactor vessel. For the sake of simplicity, the area inside the reactor vessel (i.e., inside the reactor vessel) will also be referred to as "inside the reactor wall" in the following description. The term "inside the reactor wall" therefore means within the area enclosed by the reactor wall. Likewise, the area outside the reactor vessel is also referred to as "outside the reactor wall." The reactor wall reduces thermal losses and protects the area surrounding the reactor vessel or reactor from heat.Accordingly, the heating length should be located substantially within the region enclosed by the reactor wall, i.e., inside the reactor vessel, according to the invention at least for 95%, preferably at least for 98%, more preferably 100% (i.e., heating sections entirely within the region enclosed by the reactor wall). This arrangement is preferably symmetrical, i.e., if present (heating sections not 100% within the region enclosed by the reactor wall), those sections of the heating sections that lie outside the reactor vessel are arranged symmetrically with respect to the heating length. In particular, the removal regions can be located outside the reactor wall.

[0019] The feed region is preferably arranged in a region of the heating sections that extends from 30% to 70% of their heating length, more preferably in a region of the heating sections that extends from 40% to 60% of their heating length, and most preferably in a region of the heating sections that extends from 45% to 55% of their heating length. This corresponds to a symmetrical distribution of the flows from the feed regions to the first and second consumption regions.

[0020] The reactor further comprises electrically conductive feed elements, with each group being assigned M feed elements which are electrically conductively connected to the feed regions of the group, with different phases of the alternating current being fed or being able to be fed into different feed elements assigned to a group. The feed elements extend through the reactor wall and essentially represent current leads or current connections. The reactor also comprises electrically conductive first and second take-off elements, with each group being assigned M first take-off elements and M second take-off elements which are electrically conductively connected to the first take-off regions or second take-off regions of the group. The take-off elements serve to discharge the electrical currents supplied via the feed elements and the feed regions. The feed elements serve as high-current leads.The electrically conductive connection between the feed elements and the feed areas or between the take-off elements and the take-off areas can be made by means of a positive connection or a force-locking connection (e.g. sleeves) or a material connection (e.g. a welded connection), whereby combinations are conceivable.

[0021] The reactor further comprises at least one electrically conductive first star bridge and at least one electrically conductive second star bridge, each group being assigned to a first and a second star bridge. For each group, the first pickup elements assigned to the group are electrically connected to the first star bridge to which the group is assigned, and the second pickup elements assigned to the group are electrically connected to the second star bridge to which the group is assigned. Potential equalization between the phases is established via the star bridges.

[0022] Preferably, the at least one first and at least one second star bridge are arranged outside the reactor vessel. An advantage of arranging the star bridges outside the reactor vessel (i.e., outside the reactor wall) is that a material with lower heat resistance can be used there than would be necessary for an arrangement inside the reactor vessel. Thus, a material with high electrical conductivity, e.g., copper, can be selected.

[0023] Accordingly, between different phases, i.e. between different reaction tubes, the electrical resistance across the star bridge is significantly lower than the electrical resistance across the connection formed by fluid supply pipes and fluid supply header pipes, or fluid discharge pipes and fluid discharge header pipes connected to the reaction tubes. Fluid supply pipes here refer to pipes through which the process fluid is supplied to the respective reaction tube; correspondingly, fluid discharge pipes refer to pipes through which the process fluid is discharged from the respective reaction tube. Fluid supply header pipes are pipes connected to multiple supply pipes in order to distribute the process fluid coming from other parts of the plant among the multiple reaction tubes. Fluid discharge header pipes are pipes connected to multiple discharge pipes in order to collect the fluid coming from multiple reaction tubes after the chemical reaction for further distribution to other parts of the plant.The fluid supply tubes, together with the fluid supply manifolds, are referred to as the fluid supply tube assembly or supply header; the fluid discharge tubes, together with the fluid discharge manifolds, are referred to as the fluid discharge tube assembly or discharge header. The fluid supply tube assembly and the fluid discharge tube assembly form an electrical connection between the reaction tubes, parallel to the first and second star bridges, respectively.

[0024] Preferably, the electrical resistance between two reaction tubes in a group via the first and / or second star bridge is a maximum of 50%, more preferably a maximum of 25%, most preferably a maximum of 10%, of the electrical resistance via the fluid supply tube arrangement and / or fluid discharge tube arrangement that is parallel to it in terms of circuitry.

[0025] This is particularly advantageous because potential equalization is then essentially achieved via the star bridges, so that the occurrence of potential differences between the fluid supply pipe arrangement and the fluid discharge pipe arrangement, which could lead to electrical currents via the plant components outside the reactor, is reduced.

[0026] Preferably, the first and second removal regions are arranged within the reactor vessel, with the first and second removal elements having an elongated shape and extending through the reactor wall; more preferably, the heating sections are arranged entirely within the reactor vessel. Thermal losses can thus be reduced.

[0027] Preferably, if several groups are assigned to one of the at least one first star bridge, these several groups are assigned to the same second star bridge.

[0028] Furthermore, for a group of the at least one group, the first and second star bridges to which this group is assigned are preferably electrically connected to one another by means of a bridge connection. Possible potential differences between the star bridges can thus be compensated for. This arrangement can exist for different groups if the at least one group comprises several groups. Preferably, the reactor comprises one or more alternating current sources, each alternating current source providing alternating current with M phases on M phase lines; each group is assigned to one of the one or more alternating current sources; for each group, the feed elements assigned to the group are connected to the phase lines of the alternating current source to which the group is assigned.

[0029] Preferably, at least one star point is formed in at least one of the one or more AC power sources, wherein, for a group of the at least one group, the first and / or second star bridge to which the group is assigned is connected via one or more neutral conductors to the star point of the AC power source to which the group is assigned. This allows for certain variations in the current intensity between the phases.

[0030] Preferably, one of the one or more AC sources is assigned a plurality of groups, wherein these plurality of groups are assigned to the same first star bridge and the same second star bridge.

[0031] Preferably, each of the heating tube sections comprises several straight tube sections connected to one another by one or more return bends, with the number of tube sections more preferably being even. Thus, tube coils are formed, enabling a compact reactor design.

[0032] Preferably, the feed areas are located at one of the reversing bends. Since the reversing bends are located outside, close to the reactor wall, the high-current feeds formed by the feed elements can be kept relatively short.

[0033] Preferably, the removal elements are connected to electrically insulated holding devices for connection to a support structure, wherein the holding devices are connected to the respective removal element in an electrically insulated manner and / or are themselves electrically insulating. In particular, if the removal elements extend through the reactor wall, they can also assume a supporting function. The support structure is, for example, part of the production plant in which the reactor is installed.

[0034] Furthermore, at least one support device is preferably provided for each reaction tube for connection to the support structure, which is connected to the reaction tube, wherein the at least one support device is connected to the reaction tube in an electrically insulated manner and / or is itself designed to be electrically insulating, and more preferably is located in one of the return bends.

[0035] Preferably, all penetrations through the reactor wall for discharge elements, as well as for fluid discharge pipes and fluid supply pipes, are designed to be gas-tight using suitable devices, such as a sealing bellows. Such a gas-sealing device is electrically insulating, so that no electrical contact occurs between the component being passed through and the reactor wall. Such a device can also be provided for the power feed (i.e., for the feed elements), particularly when only slight thermal compensation movements occur, for example, with the power feed arranged at the top as shown in Figure 2.

[0036] A phase shift between any two different phases of the alternating current is preferably expressed as 2TT-k / M, where k is an integer in the range from 1 to M-1. With a symmetrical load, the phases at the star point or in the star bridges cancel each other out.

[0037] The chemical reaction can be a chemical reaction that takes place at least partially at a temperature in the range from 200°C to 1700°C, in particular from 300°C to 1400°C or from 400°C to 1100°C. The chemical reaction is preferably a chemical reaction that takes place at least partially at a temperature of at least 500°C, more preferably of at least 700°C, in particular at least partially in a temperature range from 500°C or 700°C to 1100°C. The electrical voltages / currents provided are accordingly suitable for providing corresponding heating outputs. Likewise, the reactor and the power source are designed to carry out chemical reactions at these temperatures and provide corresponding heating outputs.Preferably, the chemical reaction is one of the following: steam cracking, steam reforming, dry reforming (dry reforming, carbon dioxide reforming), propane dehydrogenation, or generally reactions with hydrocarbons which are carried out at least partially at more than SOOC.

[0038] The present invention will initially be described below with reference to reaction tubes and reactors used for steam cracking or steam reforming. However, the invention can also be used in other reactor types. In general, as mentioned, the reactor proposed according to the invention can be used to carry out all endothermic chemical reactions.

[0039] The invention is further explained below with reference to the accompanying figures, which illustrate embodiments of the present invention.

[0040] Short description of the characters

[0041] Figure 1 shows a perspective view of a reactor connected to an alternating current source according to a preferred embodiment of the invention;

[0042] Figure 2 shows a front view of a reactor according to another preferred embodiment of the invention; and

[0043] Figure 3 shows a front view of a reactor according to another preferred embodiment of the invention.

[0044] Detailed character description

[0045] In the figures, structurally or functionally corresponding elements are illustrated with identical or similar reference symbols and are not explained repeatedly for the sake of clarity.

[0046] Figure 1 shows a (largely) perspective view of a reactor 2 connected to an alternating current source 10 according to a preferred embodiment of the invention. The reactor 2 has a thermally insulating reactor wall 4, the contour of which is indicated in the figure as a dash-dot line, and a plurality of reaction tubes 6u, 6v, 6w through which the process fluid to be heated, in which the chemical reaction is to take place, flows. A reactor vessel is formed by the reactor wall as explained above. The reaction tubes form a group. The number of reaction tubes (in the group) corresponds to the number of phases of the alternating current source; here, for example, 3 phases, although another number greater than or equal to 2 is also possible. In general, several groups of reaction tubes can be provided, with the number of reaction tubes in each group corresponding to the number of phases.In this general case, one or more alternating current sources may be provided, wherein the phase terminals of an alternating current source may also be connected to the reaction tubes in different groups, ie it is possible for one alternating current source to supply one or more groups of reaction tubes with alternating current, these one or more groups being associated with the alternating current source that supplies them with alternating current.

[0047] Each of the reaction tubes 6u, 6v, 6w has a heating section 20 extending between a first discharge region 22 and a second discharge region 23. For the sake of clarity of the figure, the reference numerals here and below are representative of only one of several similar elements. The length of the reaction tube between the first and second discharge regions 22, 23, i.e., the heating section 20, is referred to as the heating length. This length extends over several turns of the coil formed by each of the reaction tubes. The heating section 20 of each reactor tube is arranged within the reactor wall 4.

[0048] More generally, the take-off areas 22, 23 can, unlike in Figure 1, also be located outside the reactor wall, in this case, which is illustrated in Figure 2, the heating sections extend through the reactor wall (whereby the section of the heating sections located outside the reactor wall should be as small as possible in order to avoid thermal losses), whereby the heating sections should be located within the reactor wall for at least 95% of their heating length.

[0049] The reactor wall 4 forms a substantially closed casing (with the exception of passages used for the supply and removal of process gas, the input and output of electricity, and the like) for the region of the reactor 2 through which the heating sections, in which the process fluid is to be heated, run, at least for the most part. The process fluid is supplied and removed by means of fluid supply pipes 26 and fluid removal pipes 27 connected to the reaction tubes, which are each connected to fluid supply manifold pipes 28 and 29, respectively.

[0050] Fluid discharge manifolds 29 are connected, through which the process fluid is conducted from other parts of the production plant to the reactor and, after the chemical reaction, is discharged from the reactor to these parts of the production plant. The fluid supply pipes 26, together with the fluid supply manifold pipes 28, form so-called supply headers (fluid supply arrangements); the fluid discharge pipes 27, together with the fluid discharge manifold pipes 29, form so-called discharge headers (fluid discharge arrangements).

[0051] Approximately in the middle, more generally between 20% and 80%, of the heating length between the first and second consumption areas 22, 23, each reaction tube 6u, 6v, 6w or its respective heating section 20 has a feed area 24. Each of the feed areas 24 is electrically connected to an electrically conductive feed element 32, which in turn is electrically connected to a phase or a phase line U, V, W of the alternating current source 10. The feed elements 32, which represent power connections, extend through the reactor wall 4 and have, for example, an elongated shape, one end of which is connected to the respective feed area 24 and the other end of which is connected to one of the phase lines U, V, W. The feed elements connected to feed areas of a group are assigned to the respective group.

[0052] The alternating current source 10 preferably provides multi-phase, here three-phase, alternating current with a predetermined alternating voltage. More generally, a different number M of phases is also conceivable. The phase shifts between the phases are preferably selected such that the voltages or currents cancel each other out at a star point, i.e., the phase shift between any two phases can be expressed in radians as 2irk / M, or in degrees as 360°-k / M, where k is an integer in the range from 1 to M-1. For three phases, this is 2TT / 3 or 4TT / 3, corresponding to 120° or 240°, respectively. The phase difference between two consecutive phases is then obtained with k=1, i.e., as 2n / M. The alternating current source 10 can be designed as an alternating current transformer, in particular as a high-current transformer. The primary side, i.e., the alternating current supply to the alternating current source 10, e.g.from a public supply network or a generator is shown here only in the form of hatched boxes, which symbolize primary-side transformer coils 12. Primary-side power supply lines are not shown in the figure. A primary-side alternating voltage can typically be several hundred to several thousand volts, e.g. 400 V, 690 V or 1.2 kV. Between the primary side of the power source 10 and any public supply network or a generator, at least one further transformer (not shown) may be interposed (possibly at least one regulating transformer which makes it possible to control the secondary-side alternating voltage or to set it within a certain voltage range) in order to obtain a suitable input voltage for the high-current transformer.Instead of or in addition to this intermediate at least one transformer, the input voltage can also be adjusted using one or more thyristor power controllers.

[0053] On the secondary side, phase lines or phase connections U, V, W are provided, to which the phases of the alternating current are provided. The phase lines U, V, W are supplied with electrical energy via secondary transformer coils, which are not shown in detail (it is merely shown that the phase lines run through the primary transformer coils 12 to indicate that they interact electromagnetically with each other). The secondary alternating voltage can expediently be in the range up to 300 V, approximately less than 150 V or less than 100 V, and even less than or equal to 50 V is possible. The secondary side is galvanically isolated from the primary side.

[0054] In the alternating current source 10, the phase lines U, V, W are connected to one another to form a star point 14 of the alternating current source 10. Grounding of this star point 14 is preferably omitted. The star point 14 is optionally connected to a neutral conductor N. The first tapping areas 22 are electrically conductively connected to electrically conductive first tapping elements 34, which in turn are electrically conductively connected to one another by an electrically conductive first star bridge 36. The second tapping areas 23 are electrically conductively connected to electrically conductive second tapping elements 35, which in turn are electrically conductively connected to one another by an electrically conductive second star bridge 37. The tapping elements that are connected to tapping areas of a group are assigned to the respective group.

[0055] Preferably, the first and second removal elements 34, 35 extend through the reactor wall 4, with the first and second star bridges 36, 37 more preferably (as shown in Figure 1) being located outside the reactor wall. If the removal regions are located outside the reactor wall, the removal elements do not extend through the reactor wall.

[0056] Furthermore, holding devices 40 are preferably provided, which are connected to the removal elements 34, 35 in an electrically insulated manner and / or are themselves electrically insulating. The removal elements can then have an elongated shape, with one removal end of the removal elements being connected to a removal region and an opposite holding end being connected to a holding device. The holding devices 40 are designed such that they can be connected to a support structure (not shown) of the production plant in which the reactor is installed. They therefore serve, in particular, to hold or support the reactor tubes (and elements connected to them).Additionally or alternatively, support means (not shown) connected to the heating sections 20 may be provided, which are connected to the heating sections 20 in an electrically insulated manner and / or are themselves electrically insulating and which extend through the reactor wall to be connected to the support structure so that the reactor tubes are held by means of the support means.

[0057] The alternating current is therefore fed or introduced into the heating sections 20 via the feed-in areas 24 and taken away or derived from these via the take-off areas 22, 23. Starting from the feed-in area 24 of a heating section 20, the electrical current flows, depending on the respective electrical resistances, on the one hand to the first take-off area 22 and on the other hand to the second take-off area 23. Since the various reaction tubes 6u, 6v, 6w are fed with different phases U, V, W of the alternating current, a corresponding phase shift between the phases ideally (i.e. with symmetrical loading) leads to potential equalization in the two star bridges 36, 37. In circuit terms, the star bridges form consumer-side star points.

[0058] Optionally, a neutral conductor N or several neutral conductors are provided, via which the star bridges 36, 37 are electrically connected to the alternating current source 10.

[0059] Preferably, at least one electrically conductive bridge connection 38 is further provided, which is electrically conductively connected to both the first star bridge 36 and the second star bridge 37.

[0060] The reaction tubes 6u, 6v, 6w shown in Figure 1, or their heating sections 20, are designed as tube coils, i.e., they comprise straight tube sections 42 that are connected to one another via lower return bends 44 and upper return bends 45. In the embodiment shown, the feed regions 24 are each provided at a lower return bend. The first and second take-off regions 22, 23 are arranged here, for example, at the upper ends of tube sections 42 in bend regions in which the corresponding tube sections 42 transition into the fluid supply tubes 22 and fluid discharge pipes 23, respectively. However, it is equally possible to provide the take-off regions and the feed regions in other regions of the tube coil.

[0061] In the example shown, the length of the sections between the feed-in area 24 and the first and second offtake areas 22, 23 each comprises three straight pipe sections and is thus significantly longer than in a pipeline (as in the prior art) connected to three phases, more precisely to one phase at each lower reversing bend, and in which the straight pipe sections are electrically connected to one another at their opposite ends. This means that the length of a reaction tube connected to a phase is approximately three times as long and has a correspondingly higher resistance. At a constant current, a correspondingly higher heating output is thus provided per phase and reaction tube, and in particular, fewer high-current feeds are necessary. The terms "top" / "bottom" refer only to the orientation in the figure and serve to distinguish the corresponding reversing bends. The actual orientation (i.e.The arrangement (relative to the Earth's gravitational field) of the pipe coils can also be different, e.g. the pipe coils could be lying down (pipe sections run horizontally) or the arrangement could be upside down compared to the one shown (take-off elements, star bridges and supply / discharge headers at the bottom;.

[0062] Feed elements above).

[0063] In Figure 1, each of the reactor tubes 6u, 6v, 6w or each heating section 20 has, for example, 6 straight pipe sections 42, i.e., it is divided into 3 U-shaped sections that are connected to one another via the upper return bends 45. A different number is also possible here, e.g., 2 straight pipe sections (1 U-shaped section), 4 straight pipe sections (2 U-shaped sections, see Figure 2), 8 straight pipe sections (2 U-shaped sections), etc. In principle, an odd number of straight pipe sections is also possible, see Figure 3.

[0064] In Figure 1, in each heating section 20, the feed area 24 is located exactly in the middle of the heating length between the first consumption area 22 and the second consumption area 23. Here, too, deviations are possible, ie the length (first heating length) of the heating section (first heating section) between the first consumption area 22 and the feed area 24 can be different from the length (second heating length) of the heating section (second heating section) between the feed area 24 and the second consumption area 23. The electrical current is then divided according to the electrical resistances of these two sections (first / second heating section), so that different heating outputs can be achieved in both sections.

[0065] Figure 1 shows only one group with several (exemplarily three) reaction tubes. In general, a reactor can comprise several such groups, wherein one or more alternating current sources can be provided, each of which provides alternating current for one or more groups, i.e. one or more groups are assigned to the same alternating current source. Likewise, several first star bridges and several second star bridges can be provided, wherein a single first / second star bridge can be connected to take-off elements assigned to different groups, i.e. these different groups are assigned to the same first / second star bridge, wherein groups assigned to the same first star bridge are preferably also assigned to the same second star bridge.Preferably, if several groups are assigned to the same AC power source, these several groups should also be assigned to the same first star bridge and the same second star bridge.

[0066] Figure 2 shows a front view of a reactor 52 according to a further preferred embodiment of the invention. This figure, like Figure 3, serves to illustrate different designs of reaction tubes or tube coils and corresponding connection options for the power supply, and therefore only one of the reaction tubes and the connections thereto is shown. The other reaction tubes (corresponding to the number of phases of the alternating current source), which are essentially arranged at a distance (parallel displacement) from the reaction tube shown perpendicular to the plane of the drawing, are designed similarly to that shown, with the difference that their feed areas are connected to different phases. Details or properties of the elements will not be repeated below unless they differ from those in Figure 1; the explanations in connection with the description of Figure 1 apply here.

[0067] The reactor 52 again has a reactor wall 54 and reaction tubes (arranged in a direction perpendicular to the plane of the drawing), with only one reaction tube 56u being visible in the front view. Each of the reaction tubes 56u has a heating section 20 with a heating length that extends between a respective first take-off region 22, which is connected to a first take-off element 34, and a respective second take-off region 23, which is connected to a second take-off element 35. The first take-off elements 34 are connected by a first star bridge 36, which extends perpendicular to the plane of the drawing; the second take-off elements 35 are connected by a second star bridge 37, which also extends perpendicular to the plane of the drawing.

[0068] Each reaction tube 56u or heating section consists of straight tube sections 42 connected by lower return bends 44 and an upper return bend 45 to form a coil consisting of 4 straight tube sections (2 U-shaped sections); similar arrangements are also possible with a different number of tube sections, e.g., 8 or 12 straight tube sections (4 or 6 U-shaped sections), etc.

[0069] In contrast to Figure 1, the feed area 24 is not located in a lower reversing bend here, but in the upper reversing bend 45; thus again in the middle of the heating section. This means that the consumption areas 22, 23 and the feed areas 24 are located on the same side (top) of the reactor. The feed area 24 of the reactor tube 56u visible here is connected to a phase line U of an alternating current source (not shown in detail). Accordingly, the feed areas of the other, not visible reactor tubes are connected to other phase lines of the alternating current source. Potential equalization of the various phases is again achieved via the star bridges 36, 37, so that the star bridges again form consumer-side star points in terms of circuitry.

[0070] Regardless of the shape of the pipe coils, in the embodiment of Figure 2 the first and second removal areas 22, 23 are located outside the reactor wall 54. Of course, a design as in Figure 1 is also possible, in which the removal areas are located within the reactor wall.

[0071] An electrically conductive bridge connection, which is electrically connected to both the first star bridge 36 and the second star bridge 37, and / or one or more neutral conductors connecting the star bridges to the neutral point of the AC power source, may also be provided. Holding devices 40 and / or support devices may also be provided. These elements are largely not shown in Figure 2.

[0072] Figure 3 shows a front view of a reactor 62 according to a further preferred embodiment of the invention. This figure, like Figure 2, serves to illustrate different designs of reaction tubes or tube coils and corresponding connection options for the power supply, and therefore only one of the reaction tubes and the connections thereto is shown. The other reaction tubes (corresponding to the number of phases of the alternating current source), which are essentially arranged at a distance (parallel displacement) from the reaction tube shown perpendicular to the plane of the drawing, are designed similarly to that shown, with the difference that their feed areas are connected to different phases. Details or properties of the elements will not be repeated below unless they differ from those in Figure 1; the explanations in connection with the description of Figure 1 apply here.

[0073] The reactor 62 again has a reactor wall 64 and reaction tubes (arranged in a direction perpendicular to the plane of the drawing), with only one reaction tube 66u being visible in the front view. Each of the reaction tubes 66u has a heating section 20 with a heating length that extends between a respective first take-off region 22, which is connected to a first take-off element 34, and a respective second take-off region 23, which is connected to a second take-off element 35. The first take-off elements 34 are connected by a first star bridge 36, which extends perpendicular to the plane of the drawing; the second take-off elements 35 are connected by a second star bridge 37, which also extends perpendicular to the plane of the drawing.

[0074] Each reaction tube 56u or each heating section consists of straight pipe sections 42, which are connected to one another by lower return bends 44 and upper return bends 45 to form a pipe coil. In contrast to the previous embodiments, an odd number of straight pipe sections 42 is provided (here, for example, 5, although another odd number is also conceivable). This results, on the one hand, in the first removal regions 22 (and correspondingly the first removal elements 34) being arranged at the top, while the second removal regions 23 (and correspondingly the second removal elements 35) are arranged at the bottom. See the above explanations of the terms "bottom" / "top".

[0075] On the other hand, this also means that the feed region 23, which is again arranged in a reversing bend (exemplarily in an upper reversing bend 45, although an arrangement in a lower reversing bend 44 is also possible), is not located in the middle of the heating section 20, i.e. not at 50% of the heating length. Rather, the length of the section between the feed region 23 and the first consumption region 22 is somewhat shorter than the length of the section between the feed region 23 and the second consumption region 24. In principle, it would also be possible (in all embodiments) to arrange the feed region in a straight pipe section; however, the arrangement in a reversing bend is preferred, since this generally results in the length, and thus the resistance, of the feed elements, which have to conduct electrical currents with high current intensity (e.g. several kA), which leads to a correspondingly high power loss, being kept relatively small.

[0076] The removal areas of the embodiment of Figure 3 are located within the reactor wall 54, so that the removal elements extend through the reactor wall, although it is also clearly conceivable that the removal areas are arranged outside the reactor wall.

[0077] One or more neutral conductors connecting the star bridges to the star point of the AC power source may also be provided (not shown in Figure 3). Holding devices 40 and / or support devices (not shown) may also be provided.

Claims

Claims: Reactor (2; 52; 62) for carrying out a chemical reaction in a process fluid using multiphase alternating current for heating the process fluid, wherein the alternating current has a number M of phases, where M is an integer greater than one, comprising a reactor vessel formed by a thermally insulating reactor wall (4; 54; 64); at least one group with several reaction tubes (6u, 6v, 6w; 56; 66), wherein each group comprises M reaction tubes, wherein each of the reaction tubes has an electrically heated heating section (20) extending with a respective heating length between a first and a second discharge region (22, 23) of the respective reaction tube, wherein the heating sections are arranged within the reactor vessel for at least 95% of their heating length and each has a feed-in region (24) in a region extending from 20% to 80% of their heating length;electrically conductive feed-in elements (32), wherein each group is assigned M feed-in elements which are electrically conductively connected to the feed-in areas of the group, wherein different phases of the alternating current are fed or can be fed into different feed-in elements assigned to a group; electrically conductive first and second pickup elements (34, 35), wherein each group is assigned M first pickup elements and M second pickup elements which are electrically conductively connected to the first pickup areas and second pickup areas of the group, respectively;at least one electrically conductive first star bridge (36) and at least one electrically conductive second star bridge (37), wherein each group is assigned to a first and a second star bridge, wherein for each group the first pickup elements assigned to the group are electrically connected to the first star bridge to which the group is assigned, and the second pickup elements assigned to the group are electrically connected to the second star bridge to which the group is assigned. Reactor according to claim 1, wherein the at least one first and the at least one second star bridge (36, 37) are arranged outside the reactor vessel. Reactor according to claim 2, wherein the first and second intake sections (22, 23) are arranged within the reactor vessel, and wherein the first and second intake elements (34, 35) have an elongated shape and extend through the reactor wall; wherein preferably the heating sections (20) are arranged completely within the reactor vessel. Reactor according to any one of the preceding claims, wherein, if several groups are assigned to one of the at least one first star bridge, these several groups are assigned to the same second star bridge. Reactor according to any one of the preceding claims, wherein, for one group of the at least one group, the first and the second star bridge (36, 37) to which this group is assigned are electrically connected to each other by means of a bridge connection (38).A reactor according to any one of the preceding claims, comprising one or more alternating current sources (10), wherein each alternating current source provides alternating current with M phases at M phase lines (U, V, W); wherein each group is assigned to one or more alternating current sources; wherein, for each group, the feed-in elements assigned to the group are connected to the phase lines of the alternating current source to which the group is assigned. A reactor according to claim 6, wherein at least one neutral point (14) is formed in at least one of the one or more alternating current sources, wherein, for a group of the at least one group, the first and / or the second neutral bridge to which the group is assigned is connected via one or more neutral conductors (N) to the neutral point of the alternating current source to which the group is assigned.Reactor according to one of claims 6 or 7, wherein one or more alternating current sources are assigned several groups, wherein these several groups are assigned to the same first star bridge and the same second star bridge.

9. Reactor according to one of the preceding claims, wherein each of the heating sections has several straight pipe sections (42) connected to each other by one or more reversing bends (44, 45); wherein preferably the number of pipe sections is even.

10. Reactor according to claim 9, wherein the feed-in areas (22, 23) are each located on one of the reversing loops (44).

11. Reactor according to one of the preceding claims, wherein the take-off elements (34, 35) are connected to electrically insulated holding devices (40) for connection to a support structure, wherein the holding devices are connected to the respective take-off element in an electrically insulated manner and / or are themselves electrically insulating.

12. Reactor according to one of the preceding claims, wherein at least one support device for connection with the support structure is provided for each reaction tube, which is connected to the reaction tube, wherein the at least one support device is connected to the reaction tube in an electrically insulated manner and / or is itself electrically insulated and, if dependent on claim 9, is preferably located in one of the reversing loops.

13. Reactor according to one of the preceding claims, wherein a phase shift between any two different phases of the alternating current, expressed as radians, is 2TT-k / M, where k is an integer in the range from 1 to M-1.

14. Reactor according to one of the preceding claims, wherein the chemical reaction is a chemical reaction which takes place at least partially at a temperature of at least 500 °C; wherein the chemical reaction is preferably one of the following reactions: steam cracking, steam reforming, dry reforming, propane dehydrogenation, a reaction with hydrocarbons which is carried out at least partially at more than 500 °C.