Reactors for carrying out chemical reactions

Abstract

The present invention relates to a reactor for carrying out chemical reactions in a process fluid using an M-phase alternating current for heating the process fluid, the reactor comprising a reactor wall, at least one group having M reaction tubes, each reaction tube having an electrically heatable heating section extending a respective heating length between first and second removal sections, each heating section having a respective feed area in an area extending over 20% to 80% of the heating length of the heating section, conductive feed elements, each group M associated with a feed element conductively connected to the feed area of ​​the group, such that different phases of the alternating current can be supplied to different feed elements associated with the group, and conductive first and second removal elements, each group M associated with a feed element conductively connected to the feed area of ​​the group, such that different phases of the alternating current can be supplied to different feed elements associated with the group, each group is combined with M first removal elements and M second removal elements conductively connected to the first removal region or the second removal region of the group; and at least one conductive first star bridge and at least one conductive second star bridge, each group being combined with a first and a second star bridge, and for each group, the first removal element associated with the group is connected to the first star bridge associated with the group, and the second removal element associated with the group is connected to the second star bridge associated with the group.

Description

[Technical Field]

[0001] The present invention relates to a reactor for carrying out chemical reactions in a process fluid using multiphase alternating current to heat the process fluid. [Background technology]

[0002] Reactors are used in chemical industry processes. In a reactor, one or more reactants are introduced through heated reaction tubes, where they are converted, either catalytically or non-catalytically. Heating is applied specifically to satisfy the activation energy requirements for the chemical reaction to occur. The reaction may proceed endothermically throughout or endothermically after the activation energy requirement is satisfied. The present invention is particularly concerned with strongly endothermic reactions.

[0003] Examples of such processes include steam cracking and various reforming processes, in particular steam reforming, dry reforming (carbon dioxide reforming), mixed reforming processes, and alkane dehydrogenation processes. In the case of steam cracking, the reaction tubes are guided through the reactor in the form of a tube coil. This tube coil has at least one U-bend within the reactor. On the other hand, tubes that generally extend through the reactor without a U-bend are used for steam reforming.

[0004] The present invention is suitable for all such treatments and embodiments of the reactor tube. Reference is made, by way of example only, to the chapters "Ethylene", "Gas Production", and "Propene" in Ullmann's Encyclopedia of Industrial Chemistry, such as the articles DOI: 10.1002 / 14356007.a10_045.pub2 published April 15, 2009, DOI: 10.1002 / 14356007.a12_169.pub2 published December 15, 2006, DOI: 10.1002 / 14356007.a22_211 published June 15, 2000.

[0005] The reaction tubes of the reactor in question are conventionally heated using burners, which are guided through a combustion chamber in which the burners are also located. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2015 / 197181 Summary of the Invention [Problem to be solved by the invention]

[0007] Currently, there is a growing demand for synthesis gas and hydrogen produced with no or reduced local carbon dioxide emissions. However, processes using combustion reactors generally cannot meet this demand because they involve the combustion of fossil fuels. Other processes are rejected, for example, due to high costs. This is also the case when steam cracking or alkane dehydrogenation produces olefins and / or other hydrocarbons. In such cases, there is a need for processes that at least have a reduced on-site carbon dioxide footprint.

[0008] Patent Document 1 discloses a reactor in which a fluid flowing through a pipeline is heated, where the conductive pipeline is connected to multiple phases of an AC power source to form a star point circuit, and heat is generated in response to the electrical resistance of the pipeline.

[0009] In terms of design, the length of the heated tube is limited, and therefore the ohmic resistance is also limited. As a result, only a power supply with high current intensity and low voltage can deliver the necessary heating power to the pipeline. This necessitates a high-current supply that is complex in terms of structure and materials. [Means for solving the problem]

[0010] This object is achieved by a reactor for carrying out chemical reactions having the features of the independent claims.

[0011] The present invention utilizes a means of achieving phase balance through multiple reactor tubes, with each reactor tube connected to only one phase. This allows the heating length, or resistance, of each phase in the reactor tube to exceed the configuration in which the reactor tubes are connected to multiple phases. This allows for a larger power input at constant current intensity than can be achieved by increasing the voltage (P=RI, where P is power, R is resistance, and i is current intensity). 2 Since there is only one current supply for each reactor tube via each power supply element, the number of technically complex high-current supplies and the power losses that occur within them can be reduced.

[0012] A method for carrying out a chemical reaction in a process fluid using a multiphase alternating current to heat the process fluid, the alternating current having M phases, where M is an integer greater than or equal to 2, includes a reactor vessel formed with an adiabatic reactor wall, and at least one group having a plurality of reaction tubes, each group including M reaction tubes, each reaction tube having an electrically heatable heating section extending a respective heating length between a first and a second removal section of each reaction tube, the heating section being disposed within the reactor vessel over at least 95% of the respective heating length, and each group having a feed section in a region extending from 20% to 80% of the heating length of the heating section. In this specification, the percentage "20% to 80%" refers to a position within the heating length. Specifically, 0% refers to the position of the first (or second) removal section, 50% refers to the midpoint of the heating section, and 100% refers to the second (or first) removal section (i.e., not a percentage).

[0013] In the supply area, connected to the power supply via a feed element, one phase of the AC current is provided or fed to the heating element, i.e., a corresponding AC voltage is applied to each phase. In the removal area, connected to a star bridge via a removal element, each phase of the AC current is removed or discharged from the heating element. The star bridge is used to balance the different phases of the AC current.

[0014] The fact that the reactor tube is electrically heatable or has an electrically heatable heating section means that the material used for the reactor tube, in particular the heating section, is a material with a suitable electrical conductivity for electrical heating. Examples include heat-resistant steel alloys, in particular heat-resistant chromium-nickel steel alloys. Such steel alloys can also be used for the power connections (through which the current flows into the reactor vessel), i.e., the power supply elements and removal elements. For example, the materials 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, which are standards described in DIN EN 10027 Part 1 "Materials," may be used.

[0015] The reactor wall encloses an area surrounded in all spatial directions by at least one reactor wall. Generally, the reactor wall is formed by a number of individual walls joined together to enclose the area. Therefore, it can also be referred to as a reactor wall group, but for simplicity's sake, the term "reactor wall" is used. The enclosed area, and therefore the reactor wall, can have any volumetric shape, but is preferably rectangular prism-shaped. The reactor wall can have sealing structural elements (such as feedthroughs or sight glasses), but can also have permanently open and / or closable openings for connection to other parts of the plant. This is preferably for adjusting the atmosphere within the reactor wall, for example, an inlet nozzle for inert gas or an outlet opening to a chimney.

[0016] The reactor wall forms the reactor vessel (which may also be referred to as a reactor box). That is, the reactor wall constitutes one or more walls of the reactor vessel. Therefore, the term "reactor wall" should not be understood to mean a tank for process fluids. The area enclosed by the reactor wall is the interior of the reactor vessel. In the following description, the area within the reactor vessel (i.e., the interior of the reactor vessel) will also be referred to as "inside the reactor wall" for simplicity. Therefore, the expression "inside the reactor wall" means within the area enclosed by the reactor wall. Similarly, the area outside the reactor vessel will also be referred to as "outside the reactor wall."

[0017] The reactor wall reduces heat loss and protects the reactor vessel or the surroundings of the reactor from heat. Therefore, according to the present invention, the heating length should be substantially contained within the area surrounded by the reactor wall, i.e., the reactor vessel, by at least 95%, preferably at least 98%, and more preferably 100% (i.e., the heating section is completely contained within the reactor wall). This configuration is preferably symmetrical. That is, if there are portions of the heating section outside the reactor vessel (i.e., not 100% of the heating section is within the area surrounded by the reactor wall), they are arranged symmetrically with respect to the heating length. Specifically, the removal area may be outside the reactor wall.

[0018] In either case, the supply region is preferably located in a region extending from 30% to 70% of the heating length of the heating section, more preferably from 40% to 60% of the heating length of the heating section, and most preferably from 45% to 55% of the heating length of the heating section, which corresponds to a symmetrical division of the current from the supply region to the first and second removal regions.

[0019] The reactor further comprises conductive feed elements, each group associated with M feed elements conductively connected to the feed area of ​​that group, and different phases of AC current are supplied or can be supplied to the different feed elements associated with the group. The feed elements extend through the reactor wall and essentially form a power supply or power connection. The reactor further comprises conductive first and second removal elements, each group associated with M first removal elements and M second removal elements conductively connected to the first or second removal area of ​​that group. The removal elements dissipate the current supplied through the feed elements and the feed area. The feed elements provide a high current supply.

[0020] The conductive connection between the feed element and the feed region, or between the removal element and the removal region, can be achieved by a form-fit connection, a pressure-fit connection (e.g., a sleeve), or an integral connection (e.g., a weld), and combinations thereof are also contemplated.

[0021] The reactor further comprises at least one electrically conductive first star bridge and at least one electrically conductive second star bridge, wherein each group is associated with a first and a second star bridge, and for each group, the first removal element associated with that group is conductively connected to the first star bridge associated with that group and the second removal element associated with that group is conductively connected to the second star bridge associated with that group. Potential balance between the phases is achieved via the star bridges.

[0022] Preferably, the at least one first star bridge and the at least one second star bridge are located outside the reactor vessel. One advantage of locating the star bridges outside the reactor vessel (i.e., outside the reactor wall) is that it allows the use of materials with lower thermal resistance than would be required for placement inside the reactor vessel. Therefore, a highly conductive material such as copper can be selected.

[0023] Therefore, the electrical resistance across the star bridge between phases, i.e., between different reactor tubes, is significantly smaller than the electrical resistance across the connections formed by the fluid supply tubes and fluid supply manifolds connected to the reactor tubes, or the fluid discharge tubes and fluid discharge manifolds connected to the reactor tubes. The fluid supply tubes refer to the tubes through which process fluids flow and are supplied to each reactor tube. In contrast, the fluid discharge tubes refer to the tubes through which process fluids flow and are discharged from each reactor tube. The fluid supply manifold is a tube connected to multiple supply tubes for distributing process fluids from other parts of the factory to multiple reactor tubes. The fluid discharge manifold is a tube connected to multiple discharge tubes for collecting the fluids from the multiple reactor tubes after the chemical reaction and sending them to other parts of the factory. The fluid supply tubes, together with the fluid supply manifold, are referred to as a fluid supply tube assembly or supply header. The fluid discharge tubes, together with the fluid discharge manifold, are referred to as a fluid discharge tube assembly or discharge header. The fluid supply tube assembly and the fluid discharge tube assembly form electrical connections between the reactor tubes, parallel to the first and second star bridges, respectively.

[0024] Preferably, the electrical resistance between two reactor tubes in a group across the first and / or second star bridge is at most 50%, more preferably at most 25%, and most preferably at most 10% of the electrical resistance in parallel with respect to the circuit across the fluid supply tube assembly and / or the fluid discharge tube assembly.

[0025] This is advantageous in this case, in particular because potential balance is achieved via the star bridge to reduce the occurrence of potential differences between the fluid supply tube assembly and the fluid discharge tube assembly, which could lead to current flow through other parts of the factory outside the reactor.

[0026] Preferably, the first and second bridge removal zones are disposed within the reactor vessel, the first and second bridge removal elements have an elongated shape and extend through the reactor wall, and more preferably, the heating element is disposed entirely within the reactor vessel, thereby reducing heat loss.

[0027] Preferably, when multiple groups are associated with one of the at least one first star bridge, the multiple groups are associated with the same second star bridge.

[0028] Furthermore, for one of the at least one group, the first and second star bridges associated with that group are conductively connected to each other by a bridge connection, thereby balancing potential differences that may occur between the star bridges. When the at least one group includes multiple groups, this configuration may be used for multiple groups.

[0029] Preferably, the reactor comprises one or more AC sources each providing M phases of AC on M phase lines, each group being associated with one of the one or more AC sources, and for each group, the feed element associated with that group being connected to the phase line of the AC source with which that group is associated.

[0030] Preferably, at least one star point is formed in at least one of the one or more AC sources, and for one of the at least one group, the first star bridge and / or the second star bridge associated with that group are connected to the star point of the AC source associated with that group via one or more neutral conductors, thereby allowing for some current intensity difference between the phases.

[0031] Preferably, one of the one or more alternating current sources is combined into multiple groups, and these multiple groups are combined with the same first star bridge and the same second star bridge.

[0032] Preferably, each heating tube section comprises a plurality of straight tube sections interconnected by one or more U-bends, and more preferably an even number of tube sections, thereby forming a tube coil that allows for a compact reactor design.

[0033] The feed regions are each preferably located in one of the U-bends. Because the U-bends are located outside and close to the reactor wall, the high current feed formed by the feed elements can be kept relatively short.

[0034] Preferably, the removal elements are connected to an electrically insulating holding device for connection to a support structure, which is electrically insulatingly connected to each removal element and / or is itself electrically insulating. In particular, if the removal elements extend through the reactor wall, they may also perform a support function. The support structure is, for example, the site where the reactor is installed in a production plant.

[0035] Furthermore, preferably, for each reaction tube at least one support device for connection to a support structure is provided, which support device is connected to the reaction tube, further preferably the at least one support device is connected to the reaction tube in an electrically insulating manner and / or is itself electrically insulating and is arranged within one of the U-bends.

[0036] Preferably, all feedthroughs through the reactor wall for the removal elements and the fluid discharge and supply tubes are gas-tight by suitable devices, such as sealing bellows. The devices for gas-tightness are designed to be electrically insulating, i.e., there are no electrical contacts between the reactor wall and the elements being fed in. In particular, if only small thermal equilibrium movements occur, for example, if the current supply is located above as shown in FIG. 2, the devices can also be provided for implementing the power supply (i.e., for the power supply elements).

[0037] The phase shift between two different phases of an AC current, expressed in radians, is 2πk / M, where k is an integer in the range 1 to M-1 in all cases. Thus, for symmetrical loads, the phases cancel at the star point or star bridge.

[0038] The chemical reaction may be a chemical reaction that at least partially proceeds at a temperature in the range of 200°C to 1700°C, in particular 300°C to 1400°C or 400°C to 1100°C. The chemical reaction is preferably a chemical reaction that partially occurs at least at 500°C, more preferably at least 700°C, in particular a chemical reaction that at least partially occurs within a temperature range of 500°C or 700°C to 1100°C. The voltage / current provided is therefore suitable for providing an appropriate heating power. Similarly, the reactor and the power supply are configured to carry out the chemical reaction at these temperatures and provide the corresponding heating power. Preferably, the chemical reaction is at least one of steam cracking, steam reforming, dry reforming (carbon dioxide reforming), propane dehydrogenation, and generally hydrocarbon-based reactions, which are at least partially carried out above 500°C.

[0039] The present invention will be described below primarily with respect to reactor tubes and reactors used for steam cracking or steam reforming. However, the present invention can also be used with other types of reactors. In general, as mentioned above, the proposed reactor can be used to carry out any endothermic chemical reaction.

[0040] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, which show embodiments of the invention. [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 1 is a perspective view of a reactor connected to an alternating current source according to a preferred embodiment of the present invention. [Figure 2] FIG. 2 is a front view of a reactor according to a further preferred embodiment of the present invention. [Figure 3] FIG. 3 is a front view of a reactor according to a further preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0042] In the drawings, elements that structurally or functionally correspond to one another are designated by the same or similar reference signs and will not be described repeatedly for the sake of clarity.

[0043] FIG. 1 shows a (roughly) perspective view of a reactor 2 connected to an alternating current source 10 according to a preferred embodiment of the present invention. The reactor 2 has an adiabatic reactor wall 4, the outline of which is shown in dashed lines in the figure, and a number of reactor tubes 6u, 6v, 6w through which a process fluid flows to be heated and in which a chemical reaction takes place. The reactor wall forms the reactor vessel as described above. The reactor tubes are arranged in groups. The number of reactor tubes (in a group) corresponds to the number of phases. Here, for example, three phases, but other numbers greater than one are also possible. In general, several groups of reactor tubes can be provided. The number of reactor tubes in each group corresponds to the number of phases. In this general case, one or more alternating current sources can be provided, the phase terminals of which can be connected to different groups of reactor tubes. That is, an alternating current source can supply alternating current to one or more groups of reactor tubes, and these groups or groups are associated with an alternating current source that supplies alternating current to them.

[0044] Each of the reactor tubes 6u, 6v, 6w has a heating section 20 extending between a first removal zone 22 and a second removal zone 23. For clarity of the drawings, reference numerals are used only here and hereafter to denote one of several similar elements. The length of the reactor tube, i.e., the heating section 20, between the first and second removal zones 22, 23 is referred to as the heating length, which here extends over several turns of the tube coil formed by each reactor tube. The heating section 20 of each reactor tube is disposed within the reactor wall 4.

[0045] More generally, unlike Figure 1, removal zones 22, 23 can also be located outside the reactor wall. In this case, shown in Figure 2, the heating section extends through the reactor wall (the portion of the heating section located outside the reactor wall should be minimized to avoid heat loss). The heating section should be located within the reactor wall for at least 95% of its heating length.

[0046] The reactor wall 4 forms a substantially closed enclosure (except for feedthroughs for supplying or discharging process gases, supplying or removing electrical current, etc.) for at least a large part of the area of ​​the reactor 2 through which the heating section extends, where the process fluids are heated. The supply and removal of the process fluids are carried out by fluid supply tubes 26 and fluid discharge tubes 27, which are connected to the reactor tubes and are respectively connected to a fluid supply manifold 28 and a fluid discharge manifold 29. Through the manifolds, the process fluids are introduced into the reactor from one of the other parts of the production plant and, after the chemical reaction, are discharged from the reactor again to that part of the production plant. The fluid supply tubes 26, together with the fluid supply manifold 28, form a so-called supply header (fluid supply assembly). The fluid discharge tubes 27, together with the fluid discharge manifold 29, form a so-called discharge header (fluid discharge assembly).

[0047] Approximately midway along the heating length between the first and second removal zones 22, 23, more typically between 20% and 80% thereof, each reactor tube 6u, 6v, 6w or each heating section 20 has a supply zone 24. Each supply zone 24 is conductively connected to a conductive feed element 32, which is conductively connected to a phase or phase wire U, V, W of the alternating current source 10. The feed elements 32, which represent so-called current terminals, extend through the reactor wall 4 and have, for example, an elongated shape, one end of which is connected to the respective supply zone 24 and the other end of which is connected to one of the phase wires U, V, W. The feed elements connected to groups of supply zones are associated with each set.

[0048] The AC current source 10 preferably provides a multiphase AC current, here a three-phase AC current, via an AC voltage. More generally, a different number M of phases is also conceivable. The phase shift between the phases is preferably selected so that the voltages or currents cancel each other at the star point. That is, the phase shift between any two phases can be expressed in radians as 2πk / M or in degrees as 360°k / M, where k is an integer ranging from 1 to M−1. Thus, for three phases, the phase difference is 2π / 3 or 4π / 3, corresponding to 120° or 240°. In this case, the phase difference between two consecutive phases is determined with k=1, i.e., 2π / M.

[0049] The AC current source 10 may be designed as an AC transformer, in particular a high-current transformer. Here, the primary side, i.e., the AC current supply to the power source 10 from the public grid or a power plant, is simply illustrated by a shaded box indicating the primary transformer coil 12. The primary power supply line is not shown. The primary AC voltage may typically be several hundred to several thousand volts, for example, 400 V, 690 V, or 1.2 kV. Between the primary side of the power source 10 and possibly the public grid or a power plant, a further transformer (which may be at least one regulating transformer, not shown, that controls and regulates the secondary AC voltage within a predetermined voltage range) may be interposed. This allows a suitable input voltage for the high-current transformer. Additionally or instead of this at least one interposed transformer, the input voltage may be set by one or more thyristor-based power supply controllers.

[0050] The secondary side is provided with phase wires or phase terminals U, V, W, through which the phases of the AC current are provided. The phase wires U, V, W are supplied with electrical energy via secondary transformer coils, not shown in detail (only the phase wires are shown extending through the primary transformer coil 12, thereby indicating their electromagnetic interaction). The secondary AC voltage is conveniently in the range up to 300 V, but could be, for example, 150 V or less, or 100 V or even 50 V or less. The secondary side is electrically isolated from the primary side.

[0051] The phase wires U, V, W are interconnected at the AC current source 10. This forms a star point 14 of the AC current source 10. Preferably, the grounding of this star point 14 is omitted. The star point 14 is optionally connected to the neutral wire N.

[0052] The first removal regions 22 are conductively connected to first conductive removal elements 34 that are conductively interconnected by a first conductive star bridge 36. The second removal regions 23 are conductively connected to second conductive removal elements 35 that are conductively interconnected via a second conductive star bridge 37. The removal elements connected to groups of removal regions are combined into respective groups.

[0053] Preferably, the first and second bridge removal elements 34, 35 extend through the reactor wall 4, and more preferably, the first and second star bridges 36, 37 are located outside the reactor wall (as shown in FIG. 1). If the removal regions are outside the reactor wall, the removal elements do not extend through the reactor wall.

[0054] Furthermore, preferably, holding devices 40 are provided, connected to the removal elements 34, 35, and are electrically insulating and / or are themselves electrically insulating. In this case, the removal elements may have an elongated shape, with their removal ends connected to the removal zone and their opposite holding ends connected to the holding devices. The holding devices 40 are configured to be connectable to a support structure (not shown) of the production plant in which the reactor is installed. Thus, they hold or support, in particular, the reactor tubes (and the elements connected thereto). Additionally or alternatively, support devices (not shown) connected to the heating unit 20 may be provided. These support devices are electrically insulating and / or are themselves electrically insulating and extend through the reactor wall so as to be connected to the support structure. The reactor tubes are thereby held by the support devices.

[0055] Thus, AC current is supplied or introduced into the heating section 20 via the supply region 24 and removed from the heating section 20 via the removal regions 22, 23. From the supply region 24 of the heating section 20, the current flows first to the first removal region 22 and then to the second removal region 23 according to their respective electrical resistances. Since different reactor tubes 6u, 6v, 6w are supplied with different phases U, V, W of AC current, if there is a corresponding phase shift between the phases, potential balance is ideally achieved in the two star bridges 36, 37 (i.e., due to symmetrical loads). In terms of circuitry, the star bridges form consumer star points.

[0056] Optionally, one or more neutral wires N or N are provided, via which the star bridges 36, 37 are conductively connected to the AC current source 10.

[0057] Preferably, at least one conductive bridge connection 38 is also provided, conductively connected to both the first star bridge 36 and the second star bridge 37 .

[0058] The reactor tubes 6u, 6v, 6w or their heating sections 20 shown in FIG. 1 are designed as tube coils, i.e., they comprise straight tube sections 42 interconnected via lower U-bends 44 and upper U-bends 45. In the illustrated embodiment, the feed zones 24 are provided in the lower U-bends, respectively. The first and second bridge removal zones 22, 23 are exemplarily arranged here at the upper ends of the tube sections 42, in the elbow regions, where the corresponding tube sections 42 overlap into the fluid supply tube 22 and the fluid discharge tube 23, respectively. However, it is also possible to provide the removal zones and the feed zones in separate regions of the tube coil.

[0059] In the illustrated example, the length of the section between the supply zone 24 and the first or second removal zone 22, 23 contains three straight tube sections in each case. This is therefore significantly longer than in the case of a pipeline connected to three phases (as in the prior art), more precisely to one phase at each lower U-bend, with straight tube sections electrically connected at their opposite ends. In particular, the length of the reactor tubes connected to one phase is tripled, with a corresponding increase in resistance. Therefore, under constant current intensity, the heating power generated for each phase and reactor tube is correspondingly higher, and in particular the number of high-power supplies required is reduced.

[0060] The designations "top" / "bottom" refer only to the orientation in the diagram, i.e., to distinguish between corresponding U-bends. The actual orientation of the tube coils (i.e., relative to the Earth's magnetic field) may also vary. For example, the tube coils may be laid out (tube sections running horizontally) or may be inverted from the illustrated configuration (with removal elements, star bridges, and supply / discharge headers at the bottom and feed elements at the top).

[0061] In FIG. 1, each of the reactor tubes 6u, 6v, and 6w, or each of the heating sections 20, exemplarily has six straight tube sections 42. That is, a configuration in which the tubes are divided into three U-shaped sections connected via an upper U-shaped bend 45 is conceivable. However, this number may vary. For example, two straight tube sections (one U-shaped section), four straight tube sections (two U-shaped sections, see FIG. 2), or eight straight tube sections (two U-shaped sections) are also possible. In principle, an odd number of straight tube sections is also possible. See FIG. 3.

[0062] 1, in each heating section 20, the supply region 24 is located exactly at the midpoint of the heating length between the first removal region 22 and the second removal region 23. Here too, variations are possible, i.e., the length (first heating length) of the heating section (first heating section) between the first removal region 22 and the supply region 24 can be different from the length (second heating length) of the heating section (second heating section) between the supply region 24 and the second removal region 23. In this case, the current is divided according to the electrical resistance of these two sections (first / second heating section), and therefore different heating powers can be achieved in the two sections.

[0063] FIG. 1 shows only one group having multiple (e.g., three) reaction tubes. Typically, a reactor may include multiple such groups, and one or more AC sources may be provided, each providing AC to one or more groups. That is, one or more groups are associated with the same AC source. Multiple first star bridges and multiple second star bridges may also be provided. Here, a single first / second star bridge may be connected to removal elements associated with different groups. That is, different groups are associated with the same first / second star bridge. It is also preferred that groups associated with the same first star bridge are also associated with the same second star bridge. Preferably, when multiple groups are associated with the same AC source, these multiple groups should also be associated with the same first star bridge and the same second star bridge.

[0064] FIG. 2 shows a front view of a reactor 52 according to a further preferred embodiment of the present invention. This figure, like FIG. 3, illustrates different designs of the reactor tubes or tube coils and the corresponding options for connections for the power supply. Therefore, only one reactor tube and its connections are shown. The other reactor tubes (corresponding to the number of phases of the AC power source) are essentially designed similarly to the illustrated reactor tube, except that they are arranged at a distance (parallel to each other) from the illustrated reactor tube, perpendicular to the plane of the drawing, and their supply areas are connected to different phases. Details or characteristics of the elements, unless they differ from those in FIG. 1, will not be repeated below; therefore, the description of the connections shown in FIG. 1 also applies here.

[0065] Again, reactor 52 has reactor wall 54 and reaction tubes (oriented perpendicular to the plane of the drawing). Only one reaction tube 56u is shown in front view as a representative example. Each reaction tube 56u has a heating section 20 with a heating length extending between a respective first removal zone 22 connected to a first removal element 34 and a respective second removal zone 23 connected to a second removal element 35. The first removal elements 34 are connected by first star bridges 36 extending perpendicular to the plane of the drawing. The second removal elements 35 are connected by second star bridges 37 also extending perpendicular to the plane of the drawing.

[0066] Each reactor tube 56u or heating section is comprised of straight tube sections 42 interconnected by a lower U-bend 44 and an upper U-bend 45 to form a tube coil of four straight tube sections (two U-sections). Similar configurations are possible with different numbers of tube sections, e.g., eight or twelve straight tube sections (four or six U-sections).

[0067] In contrast to FIG. 1, the supply area 24 is now not located in the lower U-bend, but in the upper U-bend 45, i.e., again at the midpoint of the heating section. The removal areas 22, 23 and the supply area 24 are therefore located on the same side (above) of the reactor. The supply area 24 of the reactor tube 56u shown here is connected to phase line U of an alternating current source (not shown in more detail). The supply areas of the other reactor tubes not shown are therefore connected to another phase line of the alternating current source. Here too, a potential balance of different phases is carried out across the star bridges 36, 37. Thus, again in terms of the circuit, the star bridges are consumer star points.

[0068] In the embodiment of Figure 2, regardless of the shape of the tubing coil, the first and second bridge removal regions 22, 23 are located outside the reactor wall 54. Of course, configurations such as Figure 1 are also possible, in which the removal regions are located within the reactor wall.

[0069] Again, conductive bridge connections may be provided that are conductively connected to both the first star bridge 36 and the second star bridge 37, and / or one or more neutral conductors that connect the star bridges to the star points of the AC current source. Similarly, holding devices 40 and / or carrier devices may be provided. These elements are generally not shown in Figure 2.

[0070] FIG. 3 shows a front view of a reactor 62 according to a further preferred embodiment of the present invention. This figure, like FIG. 2, illustrates different designs of the reactor tubes or tube coils and the corresponding options for connections for the power supply. Therefore, only one reactor tube and its connections are shown. The other reactor tubes (corresponding to the number of phases of the AC power source) are essentially designed similarly to the illustrated reactor tube, except that they are arranged at a distance (parallel to each other) from the illustrated reactor tube, perpendicular to the plane of the drawing, and their supply areas are connected to different phases. Details or characteristics of the elements, unless they differ from those in FIG. 1, will not be repeated below; therefore, the description of the connections shown in FIG. 1 also applies here.

[0071] Again, the reactor 62 has a reactor wall 64 and reaction tubes (oriented perpendicular to the plane of the drawing). Only one reaction tube 66u is shown in front view as a representative example. Each reaction tube 66u has a heating section 20 with a heating length extending between a respective first removal zone 22 connected to a first removal element 34 and a respective second removal zone 23 connected to a second removal element 35. The first removal elements 34 are connected by first star bridges 36 extending perpendicular to the plane of the drawing. The second removal elements 35 are connected by second star bridges 37 also extending perpendicular to the plane of the drawing.

[0072] Each reaction tube 56u or each heating section is composed of straight tube sections 42 interconnected by a lower U-bend 44 and an upper U-bend 45, forming a tube coil consisting of four straight tube sections (two U-sections). Unlike the above-mentioned embodiment, an odd number of straight tube sections 42 are provided (e.g., five here, but other odd numbers are also conceivable). This means that, on the one hand, the first removal zone 22 (and therefore the first removal element 34) is arranged at the top, and, on the other hand, the second removal zone 23 (and therefore the second removal element 35) is arranged at the bottom. Regarding the terms "bottom" / "top", please refer to the explanation above.

[0073] This also means that the supply area 23, which is again arranged in a U-bend (exemplary in the upper U-bend 45, but also in the lower U-bend 44), is not arranged at the midpoint of the heating section 20, i.e., at 50% of the heating length. Rather, the length of the section between the supply area 23 and the first removal area 22 is somewhat shorter than the length of the section between the supply area 23 and the second removal area 24. In principle (in all embodiments), it is also possible to arrange the supply area in a straight tube section. However, a U-bend is preferred, since this means that the length of the power supply element, which needs to conduct current at high current intensities (for example, several kA), i.e., its resistance, can generally be kept relatively small, resulting in correspondingly high power losses.

[0074] The removal region in the embodiment of Figure 3 is located within the reactor wall 54, such that the removal element extends through the reactor wall, although it is clear that embodiments in which the removal region is located outside the reactor wall are also contemplated.

[0075] Again, one or more neutral conductors may be provided (not shown in FIG. 3) connecting the star bridge to the star point of the AC current source. Similarly, a holding device 40 and / or a carrying device (not shown) may be provided.

Claims

1. A reactor (2; 52; 62) for carrying out a chemical reaction in a process fluid using a polyphase alternating current for heating the process fluid, said polyphase alternating current having M phases, M being an integer greater than or equal to 2, a reactor vessel formed by a thermally insulating reactor wall (4; 54; 64); at least one group having a plurality of reaction tubes (6u, 6v, 6w; 56; 66), each group including M reaction tubes, each reaction tube having an electrically heatable heating section (20) extending over a respective heating length between a first and a second removal section (22, 23) of each reaction tube, said heating section being disposed within the reactor vessel over at least 95% of each heating length, each group having a feed section (24) extending over 20% to 80% of the heating length of said heating section; conductive feed elements (32), each group M being associated with a feed element conductively connected to the feed area of ​​that group, different phases of the polyphase AC current being fed or can be fed to different feed elements associated with the group; conductive first and second removal elements (34, 35), each group being associated with M conductive first removal elements and M conductive second removal elements conductively connected to the first or second removal regions of that group; a reactor comprising at least one conductive first star bridge (36) and at least one conductive second star bridge (37), each group being associated with a conductive first and a conductive second star bridge, and for each group, the conductive first removal element associated with that group being conductively connected to the conductive first star bridge associated with that group, and the conductive second removal element associated with that group being conductively connected to the conductive second star bridge associated with that group.

2. 2. The reactor of claim 1, wherein the at least one electrically conductive first star bridge and the at least one electrically conductive second star bridge (36, 37) are located outside the reactor vessel.

3. 3. The reactor of claim 2, wherein the first and second removal regions (22, 23) are disposed within the reactor vessel, the conductive first and conductive second removal elements (34, 35) have an elongated shape and extend through the reactor wall, and the heating section (20) is disposed entirely within the reactor vessel.

4. 4. The reactor of claim 1, wherein when multiple groups are associated with one of the at least one electrically conductive first star bridge, the multiple groups are associated with the same electrically conductive second star bridge.

5. 5. The reactor of claim 1, wherein for one of the at least one groups, the electrically conductive first and second star bridges (36, 37) associated with that group are electrically conductively connected to each other by a bridge connection (38).

6. 6. The reactor according to claim 1, comprising one or more alternating current sources (10) each providing an alternating current of M phases on M phase lines (U, V, W), each group being associated with one or more of the alternating current sources, and for each group, the feeding element associated with that group being connected to the phase line of the alternating current source with which that group is associated.

7. 7. The reactor of claim 6, wherein at least one star point (14) is formed in at least one of the one or more alternating current sources, and for one of the at least one group, the first conductive star bridge and / or the second conductive star bridge with which the group is associated is connected to the star point of the alternating current source with which the group is associated via one or more neutral conductors (N).

8. 8. The reactor of claim 6 or 7, wherein one of the one or more alternating current sources is combined into multiple groups, and these multiple groups are combined with the same electrically conductive first star bridge and the same electrically conductive second star bridge.

9. 9. The reactor of any one of claims 1 to 8, wherein each of the heating sections comprises a plurality of straight tube sections (42) interconnected by one or more U-bends (44, 45).

10. 10. The reactor of claim 9, wherein each of the feed zones (22, 23) is located in one of the U-bends (44).

11. 11. A reactor according to any one of claims 1 to 10, wherein the conductive removal elements (34, 35) are connected to an electrically insulating holding device (40) for connection to a support structure, the holding device being electrically insulatingly connected to each of the conductive removal elements and / or being itself electrically insulating.

12. 12. The reactor according to claim 1, wherein for each reactor tube at least one support device for connection to the support structure is provided, which support device is connected to the reactor tube, and wherein the at least one support device is connected to the reactor tube in an electrically insulating manner and / or is itself electrically insulating.

13. 13. The reactor of any one of claims 1 to 12, wherein the phase shift between two different phases of the polyphase alternating current, expressed in radians, is 2πk / M, where k is an integer in the range of 1 to M-1 in each case.

14. 14. The reactor of any one of claims 1 to 13, wherein the chemical reaction occurs at least partially at a temperature of at least 500°C, the chemical reaction being selected from the group of steam cracking, steam reforming, dry reforming, propane dehydrogenation, and hydrocarbon-based reactions carried out at least partially at temperatures above 500°C.

Images