Apparatus and method for controllably conducting chemical reactions

Abstract

Provided is a method for controllably conducting a chemical reaction in a reactor having several reaction tubes, the reaction tubes having several electrically heatable tube sections, wherein an electrical connection is provided which is connected to at least one of the tube sections in a current input region, wherein at least one connection element is provided in a current output region and one connection element is connected to each of the tube sections, wherein the chemical reaction is one of the following reactions: steam cracking, steam reforming, dry reforming, dehydrogenation of propane, a reaction with a hydrocarbon, which is at least partially conducted above 500°C. The method comprises: guiding a process fluid through one or more reaction tubes; providing several variable voltages at several electrical connections, wherein several voltages are provided as phases of a multiphase alternating voltage, such that at least one connection element forms a star point; setting one or more voltages; detecting one or more measured values corresponding to one or more measured variables; changing the set several voltages such that the detected measured values correspond to predetermined values or predetermined value ranges of the measured variables. Furthermore, a device is provided, comprising a reactor, one or more measuring devices and a control device, wherein the control device is configured to carry out the method.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for adjustingly carrying out a chemical reaction in a reactor having at least one heatable reaction tube. Background Technology

[0002] Reactors are used in a range of processes in the chemical industry, in which one or more reactants are guided through heated reaction tubes and undergo catalytic or non-catalytic conversion there. Heating is particularly used to overcome the activation energy required for the chemical reaction to occur. The reaction can proceed generally endothermally or exothermally after the activation energy has been overcome. This invention relates particularly to strongly endothermic reactions.

[0003] Examples of these processes are steam cracking, various reforming processes—particularly steam reforming, dry reforming (carbon dioxide reforming), mixed reforming processes, and processes for alkane dehydrogenation. In steam cracking, the reaction tubes are guided through the reactor in the form of a coil with at least one U-bend, while in steam reforming, tubes that typically extend through the reactor without a U-bend are used.

[0004] This invention is applicable to all such processes and embodiments of reaction tubes. For illustrative purposes only, refer to the articles “Ethylene,” “Gas Production,” and “Propenes” in Ullmann’s Encyclopedia of Industrial Chemistry—for example, the publication of April 15, 2009, DOI: 10.1002 / 14356007.a10_045.pub2; the publication of December 15, 2006, DOI: 10.1002 / 14356007.a12_169.pub2; and the publication of June 15, 2000, DOI: 10.1002 / 14356007.a22_211.

[0005] Traditionally, the reaction tubes of the corresponding reactor are heated using a burner. The reaction tubes are guided through the combustion chamber of the burner, which is also arranged there.

[0006] However, as described, for example, in DE 10 2015 004 121 A1 (and similarly, EP 3 075 704 A1), the demand for syngas and hydrogen produced with little or no local CO2 emissions is currently increasing. However, processes using combustion reactors cannot meet this demand due to the combustion of fossil fuel carriers, as is typically the case. Other processes are rejected, for example, due to their high cost. The same applies to the production of olefins and / or other hydrocarbons via steam cracking or alkane dehydrogenation. In these cases, there is also an expectation for processes with at least minimal on-site CO2 emissions.

[0007] Against this background, the cited DE 10 2015 004 121 A1 proposes, in addition to combustion, an electrically heated reactor for steam reforming. Here, one or more voltage sources are used, providing three-phase AC voltage across three external conductors. Each external conductor is connected to a reaction tube. A star connection is formed, wherein the star point is achieved by a collector, with lines opening into the collector and the reaction tube electrically connected to the collector. In this way, the collector ideally remains without potential. The collector is arranged below and outside the combustion chamber relative to the vertical, and preferably extends laterally to the reactor tube or along the horizontal direction. WO 2015 / 197181 A1 also discloses a reactor in which the reaction tube is arranged in a star connection. WO 2020 / 035575 A1 relates to an apparatus for electrically heating a fluid by at least one direct current. DE 10 2011 077 970 A1 relates to a device with a conductive heating element arranged in a treatment chamber for the temperature treatment of corrosive gases.

[0008] During the operation of such reactors with electrically heated reaction tubes, changes in the electrical properties (resistance) of the reaction tubes may occur, and changes in the amount and / or composition of the reaction products can be expected. The aim is therefore to adapt the reactor's operating conditions, or the reaction parameters of the chemical reaction carried out therein, to these changes during operation. Furthermore, there is also the aim to adapt the electrical operating conditions to these changes—especially when using multiphase alternating voltage on an external conductor. Summary of the Invention

[0009] This objective is achieved by the method and apparatus for adjustingly carrying out chemical reactions according to embodiments of this application.

[0010] The chemical reaction takes place in several reaction tubes through which the process fluid (i.e., a fluid carrying reactants (typically a gas or gas mixture)) is passed. Sections of the reaction tubes are electrically heated, wherein the sections are connected via electrical connectors to one or more controllable power or voltage sources, where current or voltage is provided for electric heating. The voltage provided is a phase of a multiphase alternating voltage. According to the invention, the voltage applied to the electrical connectors can be changed—especially individually. On the one hand, changing the electrical properties makes it possible to maintain a constant heating power at the tube section. Changes in electrical properties may arise, for example, due to inductive effects caused by the electromagnetic field of the current-conducting components, variable temperatures within the reactor, a coke layer formed during operation, variable heat demands as a result of altered endothermic / exothermic reactions, or manufacturing tolerances or material variations. On the other hand, the heating power can be varied in a calibrated manner to enable adaptation of the composition of the reaction products, which is particularly dependent on the process temperature. Furthermore, the heating power can also be varied selectively to adjust the composition of the reaction products, which depends on the process temperature. In addition, the heating electricity can be varied in a targeted manner to allow for the adjustment of the amount of reaction products under controlled composition.

[0011] The chemical reaction is one of the following: steam cracking, steam reforming, dry reforming (carbon dioxide reforming), propane dehydrogenation, or generally a reaction with hydrocarbons—which is carried out at least partially above 500°C. More generally, the chemical reaction can be a reaction carried out at least partially in the temperature range of 200°C to 1700°C (and especially 300°C to 1400°C or 400°C to 1100°C). The chemical reaction is preferably carried out at least partially at a temperature of at least 500°C, more preferably at least 700°C, and especially at least partially in the temperature range of 500°C or 700°C to 1100°C. The provided voltage / current is accordingly adapted to provide the corresponding heating power. The reactor and power source are also configured to carry out the chemical reaction at these temperatures and provide the corresponding heating power.

[0012] More specifically, the reactor is provided with a plurality of reaction tubes having several electrically heated tube sections, wherein a plurality of electrical connectors are provided, each connected to at least one of the tube sections in a current input region, wherein at least one connecting element is provided in a current output region, and each of the tube sections is connected to a connecting element. Specifically, the method according to the invention for adjustingably carrying out a chemical reaction in a reactor includes: guiding process fluid through a plurality of reaction tubes; providing a plurality of variable voltages at a plurality of electrical connectors, wherein the voltages are provided as phases of a multiphase alternating voltage such that at least one connecting element forms a star point (connecting element star point); setting a plurality of voltages; detecting one or more measured variables; and changing the set plurality of voltages such that the measured value of the detected measured variable corresponds to a predetermined value or a predetermined range of values ​​of the measured variable.

[0013] In this case, the provided voltages are within one or more predetermined voltage ranges, which correspond to the heating power supplied to the electrically heated pipe section and enable the chemical reaction in the pipe section (i.e., heat the latter to a suitable temperature).

[0014] The measuring equipment and its arrangement for detecting these measured variables are described in conjunction with embodiments of the apparatus according to the invention. Changes or control of the voltage at the power connection occur based on the measured values ​​of the measured variables detected by the measuring equipment. This change occurs in such a way that the measured value corresponds to a specified value or range of values ​​of the measured variable. The term "corresponds" is here to be understood as the measured value being equal to or as close as possible to the specified value or within the specified range of values. Specifically, a control loop is thus implemented, wherein the voltage can be considered as the manipulated variable, and the measured variable can be considered as the control variable.

[0015] A voltage or corresponding current is provided as an alternating voltage or current. Current input occurs in the form of a multiphase alternating current entering a directly heated reaction tube or its tube section via M individually connected phases assigned to power connectors (each power connector is thus connected to one of the phases). The current-conducting reaction tube or tube section connected to the M phases via power connectors is advantageously also (in the current output region) conductively connected at the star point by connecting elements. The number of phases M is particularly 3, corresponding to the number of phases in a conventional three-phase alternating current source or three-phase alternating current power grid. However, in principle, the invention is not limited to using three phases, but can also use different (especially larger) numbers of phases (e.g., 2, 4, 5, 6, 7, or 8 phases). The phase offset is particularly 360° / M (i.e., 120° in the case of three-phase alternating current). The advantage of multiphase alternating current is that when the load is substantially symmetrical, the currents of each phase in the star point cancel each other out, so that no or only a small amount of electrical return current to the voltage or power source occurs. Therefore, a voltage is provided as a phase of the multiphase alternating voltage. The power source for this purpose is preferably a multiphase alternating current source.

[0016] Preferably, the measured variables include one or more of at least one temperature, at least one current intensity, and / or at least one material composition. Therefore, the control of the chemical reaction can occur based on at least one process temperature, at least one heating power (which depends on the current intensity), or at least one composition of the reaction products or original reactants (i.e., the material composition of the process fluid at the pipe inlet or outlet). Corresponding desired values / ranges can thus be achieved.

[0017] Several voltages can be changed in the same way, that is, they change together rather than independently of each other. Preferably, the several voltages change independently of each other, that is, each of the voltages can be set independently of the other voltages.

[0018] Preferably, one or more measurement variables include one or both of the following: the tube outlet temperature of the process fluid measured at the tube outlets of several reaction tubes, and / or the material composition of the process fluid measured at the tube outlets of several reaction tubes. More preferably, several voltages are varied such that the measured tube outlet temperature and / or the measured material composition are equal to or as close as possible to a predetermined tube outlet temperature and / or a predetermined material composition, or are within a predetermined range. The composition of the reaction products depends in particular on the process temperature used to carry out the chemical reaction (its tube outlet temperature is a measure), and can therefore be directly affected by said process temperature in terms of control techniques. By changing the voltage and thus the heating power, a specific desired composition of the reaction products can thus be achieved. If several reaction tubes are present, the measurement variables may accordingly include several tube outlet temperatures and / or several material compositions at the tube outlets. It is also possible, additionally or alternatively, to use corresponding temperatures or material compositions measured at one or more tube inlets as measurement variables; that is, the measurement variables may include one or more tube inlet temperatures and / or one or more tube inlet material compositions. In addition, the corresponding temperature measured at one or more intermediate locations on one or more reaction tubes may be used as a measurement variable, either additionally or alternatively. That is, the measurement variable may include the temperature at one or more intermediate locations on one or more reaction tubes.

[0019] Preferably, one or more measuring variables include one or both of the following: the temperatures of two or more pipe sections measured at each electrical connector, or the current intensities of two or more electrical connectors measured at each electrical connector. More preferably, several voltages at each electrical connector are controlled such that the measured pipe section temperature corresponds to a predetermined pipe section temperature, and / or the power output calculated from the current intensity at the pipe sections connected to each electrical connector corresponds to a predetermined power output. This makes it possible to supply heating power of different intensities to pipe sections connected to different electrical connectors, so that different temperatures can be set, especially at these different pipe sections. Here, the increased return current can occur via the neutral conductor.

[0020] If different sections of a single reaction tube (coil) are connected to different electrical connectors, a desired heating power profile or temperature profile along the reaction tube can be generated. Preferably, the method therefore includes setting different voltages at different sections of the reaction tube connected to the respective electrical connectors to supply different heating powers to these sections.

[0021] Preferably, one or more measurement variables include one or both of the following: The neutral conductor current intensity is measured at the neutral conductor, or the current intensity of two or more electrical connections is measured at each electrical connection. More preferably, the voltage is changed to minimize the neutral conductor current intensity, and / or to minimize the sum of the electrical connection current intensities calculated considering relative phase. In other words, the neutral conductor current intensity or the sum of the electrical connection current intensities should correspond as close as possible to a current intensity value of zero. This second possibility is particularly advantageous when no neutral conductor is provided. Clearly, such a voltage change can occur only within a specific voltage range corresponding to the heating power suitable or necessary for the chemical reaction (the voltage is therefore not set to zero). This can be at least partially compensated by this embodiment if an asymmetrical load occurs through the electrically heated pipe section (e.g., when the various pipe sections have various resistances).

[0022] An apparatus according to the invention for adjustably carrying out a chemical reaction in a process fluid comprises: a reactor having a plurality of reaction tubes, each reaction tube having a plurality of electrically heated tube sections, wherein a plurality of electrical connectors are provided, each connected to at least one of the tube sections in a current input region, wherein at least one connecting element is provided in a current output region, and each of the tube sections is connected to a connecting element such that at least one connecting element forms a star point (connecting element star point); at least one controllable power source (AC current source) configured to provide a plurality of variable voltages at the plurality of electrical connectors, wherein the power source provides a plurality of voltages as phases of a multiphase AC voltage; one or more measuring devices configured to detect one or more measured variables; and a control device connected to at least one power source and one or more measuring devices for communication, and configured to control at least one power source according to one or more measured variables. Here, tube sections connected to each phase of the same power source should be connected to the same connecting element. The change in voltage can (here, and also in the methods described above) consist of: a change in the magnitude of the voltage itself (e.g., through a variable transformer) and / or a change in the magnitude (especially the root mean square) of the voltage, which is averaged over time, for example through phase angle control or wave packet control (especially full wave control).

[0023] The control device is configured to perform one of the methods described above or further described. Specifically, the chemical reaction is one of the following: steam cracking, steam reforming, dry reforming, propane dehydrogenation, or reaction with hydrocarbons, which is carried out at least in part at temperatures above 500°C (i.e., the reactor is configured to carry out one of these chemical reactions).

[0024] Preferably, the one or more measuring devices include one or more of the following: one or more temperature sensors, which are more preferably configured to measure the temperature of at least one pipe section and / or the temperature of the process fluid at at least one pipe inlet and / or at least one pipe outlet and / or at least one pipe section; one or more current sensors, which are more preferably configured to measure the current intensity at at least one power connector and / or neutral conductor (which connects the connecting element to the power source at a star point); or one or more composition sensors, which are more preferably configured to measure the composition of the process fluid at at least one pipe inlet and / or at least one pipe outlet.

[0025] Voltages can be varied together in the same manner (i.e., power sources are configured accordingly), wherein at least one power source preferably includes a power controller, and in particular a thyristor power controller, by which the voltage can be changed. Alternatively, and more preferably, voltages can be changed independently of each other, wherein at least one power source preferably includes a variable transformer for each voltage, by which the voltage can be changed independently of each other. Furthermore, alternatively, or in addition to the power controller and / or variable transformer, power electronic components that achieve the same function (e.g., so-called flexible alternating current transmission systems (FACTS)) can also be provided.

[0026] The one or more measuring devices preferably include one or both of the following: one or more temperature sensors arranged at the outlets of the plurality of reaction tubes to measure one or more temperatures (outlet temperatures) of the process fluid; or one or more composition sensors arranged at the outlets of the plurality of reaction tubes to measure one or more compositional components of the process fluid. Alternatively or additionally, one or more temperature sensors and / or one or more composition sensors may also be arranged at the inlets of the plurality of reaction tubes to measure the inlet temperature or inlet composition.

[0027] Preferably, one or more measuring devices include one or both of the following: two or more pipe section temperature sensors arranged at the pipe sections connected to the respective electrical connectors; or two or more electrical connector current sensors arranged at the respective electrical connectors. These measuring devices can, in particular, measure the pipe section temperature and / or the electrical connector current intensity that can be used in the method according to the invention as described above. The control device is accordingly configured to regulate the temperature of the pipe sections and / or the heating power supplied to the pipe sections. If at least one power source can provide voltage independently of each other at the respective electrical connectors, the temperatures of the different pipe sections or the heating power supplied to them can be regulated independently of each other; that is, they can be set to different values / ranges.

[0028] Preferably, at least one power source is configured to provide voltage independently of each other, and one or more measuring devices include one or both of the following: a neutral conductor current sensor arranged on the neutral conductor connected to the connecting element; or a plurality of power connector current sensors arranged at each power connector. These sensors, in particular, can measure the neutral conductor current intensity and / or the power connector current intensity. More preferably (as already mentioned in conjunction with the method), the control device is configured to control at least one power source such that a voltage is provided at the power connector that minimizes the sum of the neutral conductor current intensity and / or the power connector current intensity, taking into account phase calculations. In principle, this establishes equipotential between elements connected by the neutral conductor (i.e., between the connecting element and the at least one power source). Specifically, this may also pose a risk of outward current flowing into the production system equipped with the device according to the invention and electrically connected via the reaction tube at the tube inlet and outlet, causing electrical interference or associated risks.

[0029] Within the scope of this application, the terms “connection”, “connector”, etc., shall be understood in the sense of a conductive connection, unless otherwise stated.

[0030] In addition to the electric heating of the tube section according to the invention, the method or apparatus can also provide non-electric heating of the reaction tube—for example, by fossil fuels. However, according to the invention, the progress of the chemical reaction is regulated by controlling the voltage applied to the electrical connector.

[0031] The invention is first described 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. Generally, as mentioned, the reactor proposed according to the invention can be used for all endothermic chemical reactions.

[0032] The invention will now be explained in more detail with reference to the accompanying drawings, which illustrate embodiments of the invention. Attached Figure Description

[0033] Figure 1 An apparatus according to a preferred embodiment of the present invention is shown; Figure 2 An apparatus according to another preferred embodiment of the present invention is shown; Figure 3 This illustrates a power source that can be used in the apparatus according to a preferred embodiment of the invention; Figure 4 This illustrates another power source that can be used in the apparatus according to a preferred embodiment of the invention; and Figure 5 A flowchart illustrating an embodiment of the method according to the present invention is shown. Detailed Implementation

[0034] In the accompanying drawings, elements that correspond to each other structurally or functionally are indicated by the same or similar reference numerals, and for clarity, they are not repeatedly explained. If the components of the apparatus are explained below, the corresponding explanation also relates to the method performed therewith in each case, and vice versa. The description in the drawings repeatedly refers to alternating current heating.

[0035] Figure 1 An apparatus for carrying out a chemical reaction is schematically shown according to an embodiment of the present invention.

[0036] The apparatus includes a reactor, indicated herein by 100, configured to carry out a chemical reaction. For this purpose, it particularly has a reaction tube 20 extending from an inlet 22 to an outlet 23 through an insulated reactor vessel 10, wherein several tube sections 24 (referred to herein only as 24 in both instances) extend in each case between a current input region 11 and a current output region 12 within the reactor vessel 10. The tube sections 24 form segments of the reaction tube 20, fluidly connected to each other in the current input region 11 and the current output region 12 respectively via bends in the reaction tube—more precisely, a first U-bend 26 in the current input region 11 and a second U-bend 27 in the current output region 12—to form a coil through which process fluid can be guided from the inlet 22 to the outlet 23. Here, the reaction tube 20 is exemplarily secured to a support structure (not shown in more detail) with a suitable suspension component 13, wherein retaining structures for different designs of the reaction tube are also conceivable in principle. It should be understood that, here and below, several reaction tubes may be provided in each case.

[0037] The materials used for the reaction tubes are materials with electrical conductivity suitable for the electric heating of the reaction tubes, such as heat-resistant steel alloys, and especially heat-resistant chromium-nickel steel alloys. These steel alloys can also be used for electrical connectors (through which current is conducted to the reactor vessel) and connecting elements (which are at least partially arranged in the reactor vessel). For example, materials with standard names according to DIN EN 10027, Part 1, “Materials” can be used: 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.

[0038] For the electric heating of pipe section 24 in power input area 11, pipe section 24 is electrically connected or capable of being electrically connected to the phase connectors U, V, W of a multiphase power source 50 (i.e., an alternating current source) in each case (hereinafter, one power source is explained, but several power sources may also be provided; the power source should therefore be understood in the sense of at least one power source, wherein the statement applies to all power sources). Switches and other specific connector types are not shown. Pipe section 24 is connected to power connectors 40 in power input area 11, wherein each of the power connectors 40 is respectively assigned one or more pipe sections (in Figure 1 (Two of them), and the corresponding power connectors are connected to the pipe section.

[0039] Power source 50 is controllable and configured to provide a variable voltage at power connector 40. For this purpose, phase connectors U, V, and W of power source 50 are connected to power connector 40. According to... Figure 1 In this embodiment, the electrical connector 40 is connected to the first U-bend 26, which in turn is connected to the conduit section 24, since the U-bend and the conduit section form part of the reaction tube. In this embodiment, the electrical connection between the electrical connector and the conduit section is thus indirectly created via the U-bend. However, at a deviation from this, a direct connection between the electrical connector and the conduit section is also possible; see, for example, [reference needed]. Figure 2 Examples are shown in the text.

[0040] In the embodiment of the invention shown here, the tube segments 24 are electrically connected to each other in the power output region 12 via connecting elements 42, which are connected to one or more reaction tubes 20 and arranged within the reactor vessel 10. A neutral conductor 44 and / or ground 46 may also be connected thereto. The neutral conductor 44 is connected to a corresponding connector of the power source 50—for example, to a star point of the power source. The current fed into the tube segments 24 in the current input region 11 is again delivered from the tube segments 24 in the current output region 12. In terms of the circuit, the connecting elements 42 form a star point, wherein, under conditions where the voltage source 50 provides a suitable power supply with a phase-shifted current (e.g., in the form of so-called alternating current) and the tube segments 24 provide a symmetrical load, the current or voltage cancels each other out, such that in this case no current flows via the neutral conductor 44 to the power source and / or ground 46.

[0041] Furthermore, a control device 60 is provided, which is connected to the power source 50 for communication, for example via a control line 52 (though any wired or wireless connection may be provided), and is configured to control the power source 50, particularly the voltage applied by the power source 50 to the power connector 40. For this purpose, the control device 60 is configured to perform the method according to the invention. The control device 60 (or the method implemented by the control device) performs this control based on measured variables detected by one or more measuring devices.

[0042] Specifically, temperature sensors, material composition sensors, and current sensors can be used as measuring devices. Figure 1 The figure illustrates, by way of example, several such measuring devices that can be used. The measuring devices are connected to the control unit 60 via wired or wireless connections for communication or data transmission, so that the measured variables detected by the measuring devices can be sent to the control unit. For clarity, these connections are not shown in the figure. It should also be noted that not all of the shown measuring devices are required, and different or additional measuring devices not shown may also be provided. The measuring devices provided and potentially used depend on which measured variables the control unit requires to perform the method.

[0043] Figure 1 The following measuring devices are shown: a temperature sensor 62 located at pipe outlet 23, which measures the temperature of the process fluid at the pipe outlet; a composition sensor 64 located at pipe outlet 23, which measures the composition of the process fluid at the pipe outlet or the proportion of a specific substance in the process fluid; a temperature sensor 63 (only one with a reference mark) arranged on pipe section 24 to measure the temperature of the corresponding pipe section; a current sensor 66 located on neutral conductor 44 to measure the current intensity of the current flowing in the neutral conductor (i.e., the current between connection element 42 and power source 50); and a current sensor 67 located at the power connector to measure the current flowing through the power connector.

[0044] Additionally or alternatively, the following measuring devices (not shown) may also be provided, such as: a temperature sensor at the pipe inlet 22 that measures the temperature of the process fluid at the pipe inlet; a composition sensor at the pipe inlet 22 that measures the composition of the process fluid at the pipe inlet or the proportion of a specific substance in the process fluid; and temperature sensors located on portions of the reaction tube 20 between pipe sections 24, for example, at the first or second U-bends 26, 27, to measure the reaction tube temperature between pipe sections.

[0045] Figure 2An alternative embodiment of the apparatus according to the invention is shown. In this embodiment, the reactor 200 has a plurality of reaction tubes 20a, 20b, 20c, each having electrically heated tube sections 24a, 24b, 24c. The reaction tubes extend through the insulated reactor vessel 10 and each has tube inlets 22a, 22b, 22c and tube outlets 23a, 23b, 23c for the process fluid to be treated. For further configurations, in conjunction with... Figure 1 The description provided again applies to the applicable scope; specifically, the reaction tube also extends through the insulated reactor vessel 10, wherein the tube section is located within the reactor vessel.

[0046] Pipe sections 24a, 24b, and 24c are connected to power connectors 40 in the current input region 11, for example, via sleeves 41. Power connectors 40 are connected to a power source 50, which is controllable and configured to provide a variable voltage at power connectors 40.

[0047] Furthermore, pipe sections 24a, 24b, and 24c are electrically connected to connecting element 42 in the current output region 12, such that the pipe sections are electrically connected to each other there. Connecting element 42 may also be connected to ground 46 and / or neutral conductor 44, wherein neutral conductor 42 is connected to a corresponding connector of power source 50.

[0048] Similarly, a control device 60 is provided, which is connected to the power source 50 via a wired or wireless means (e.g., via control line 52) for communication, so that the control device 60 can control the power source 50. Measurement variables detected by measuring devices—especially temperature sensors, material composition sensors, and current sensors—are also used for control.

[0049] By way of examples Figure 2 Several measuring devices are also shown, which can be used to detect the corresponding measured variables. The measuring devices are connected to the control unit 60 via wired or wireless connections for communication or data transmission, so that the measured variables detected by the measuring devices can be sent to the control unit. For clarity, these connections are not shown in the figures. It should also be noted that not all of the shown measuring devices are required, and additional measuring devices not shown may also be provided. The measuring devices provided and potentially used depend on which measured variables are required for the control unit to perform the method.

[0050] Figure 2The following measuring devices are shown: temperature sensors 62a, 62b, 62b located at pipe outlets 23a, 23b, 23c, which measure the temperature of the process fluid at the pipe outlets; composition sensors 64a, 64b, 64c located at pipe outlets 23a, 23b, 23c, which measure the composition of the process fluid at the pipe outlets or the proportion of a specific substance in the process fluid; temperature sensors 63a, 63b, 63c arranged on pipe sections 24a, 24b, 24c to measure the temperature of the corresponding pipe section; a current sensor 66 on the neutral conductor 44 for measuring the current intensity of the current flowing in the neutral conductor (i.e., the current between the connecting element 42 and the power source 50); and a current sensor 67 located at the power connector 40 for measuring the current flowing through the power connector.

[0051] Additionally or alternatively, the following measuring devices (not shown) may also be provided, such as: temperature sensors at pipe inlets 22a, 22b, 22c that measure the temperature of the process fluid at the pipe inlets; and composition sensors at pipe inlets 22a, 22b, 22c that measure the composition of the process fluid at the pipe inlets or the proportion of a specific substance in the process fluid.

[0052] Figure 1 and Figure 2 Specific embodiments of the apparatus according to the invention are shown, wherein, in particular, specific embodiments of the reaction tube and its connection to a power source are shown respectively. However, it should be emphasized that, within the scope of the claims (in the apparatus and method claims), other embodiments of the reaction tube and its electrical connection to one or more power sources are possible. Specifically, the reactor may comprise several coils (similar to...) Figure 1 ), where the latter are arranged, for example, in a stack-like manner, parallel to each other and at a certain distance from each other (from Figure 1 (Starting perpendicular to the drawing plane).

[0053] The group of coils (in the stack) can be further subdivided into subgroups, each assigned to a power source. It is possible for a subgroup to contain only one coil or for a single subgroup to contain all coils. Connectors are then assigned to each subgroup, with the coil section of the subgroup's coil connected to one of the connectors assigned to that subgroup. Each subgroup can also be assigned to a power source, with the phase of that power source connected to the connector assigned to that subgroup. For each subgroup, a connecting element is also provided to connect the coil section of that subgroup; it is also possible to provide one connecting element for each individual coil.

[0054] Similarly, a one-to-one relationship can exist between the connector and the coil (especially in the case of a U-shaped coil), meaning that all sections of the coil are connected to the same connector. Since each connector is connected to a different phase or voltage, the number of coils corresponds to the number of voltages or multiples thereof. One or more connecting elements then connect sections of various coils.

[0055] Figure 3 This illustrates a possible embodiment of a controllable power source 300 using a thyristor power controller for power control. The controllable power source has connectors on the input side for connection to a power source (e.g., a power network), wherein input terminals 302u, 302v, and 302w are provided for each phase (here, e.g., three) of an AC voltage source. A relatively high voltage is applied to the input—typically several hundred to several thousand volts (e.g., 400V, 690V, or 1.2kV). On the output side, the power source has output terminals 304U, 304V, and 304W, which are connected to the power connectors of an adjustable reactor (e.g., ...). Figure 1 or Figure 2 The power connector 40 of one of the reactors shown is connected. Additionally, a connector 304N for the neutral conductor is provided on the output side.

[0056] The power source 300 has power controllers 306u, 306v, and 306w—here, thyristor power controllers—by virtue of which the voltage applied to the input terminals can be interrupted or transmitted via lines 310u, 310v, and 310w to the high-current transformer 308. The multiphase high-current transformer 308—here, for example, in a delta / star configuration, where the connector 304N for the neutral conductor is connected to the star point—transforms the relatively high voltage applied between the input terminals into a lower voltage that simultaneously has a higher current intensity suitable for feeding into the tube section. The output voltage is preferably in the range of less than 300V, more preferably less than or equal to 150V, even more preferably less than or equal to 100V, and most preferably less than or equal to 50V.

[0057] By correspondingly controlling the power controllers 306u, 306v, and 306w—that is, by alternately interrupting and transmitting the voltage applied to the input of the high-current transformer (using thyristors)—the power delivered to the output side can be controlled. For this purpose, pulse width modulation (PWM) can be used during excitation. Preferably, the power controllers transmit only the full wave of the AC voltage applied to the input side, i.e., providing so-called pulse group operation or full-wave pulses, where a completely sinusoidal wave is switched through. This is used to reduce harmonic and correlation filter overhead to maintain voltage quality on the power supply network.

[0058] The control device 60 applies a control signal to the control line (not shown) based on an externally specified voltage requirement, thereby energizing the power controller.

[0059] Figure 4 Another possible embodiment of a controllable power source 400 is shown, employing a variable transformer for power control and allowing independent changes in the voltage at the output terminals. The controllable power source 400 has a connector on the input side for connection to a power source (e.g., a power supply network), wherein input terminals 402u, 402v, and 402w are provided for each phase (here, e.g., three) of an AC voltage source. Accordingly, a relatively high voltage is applied to the input terminals—typically several hundred to several thousand volts (e.g., 400V, 690V, or 1.2kV). On the output side, the power source has output terminals 404U, 404V, and 404W, which are connected to the power connector of an adjustable reactor (e.g., ...). Figure 1 or Figure 2 The power connector 40 of one of the reactors shown is connected. Additionally, a connector 404N for the neutral conductor is provided on the output side.

[0060] The power source 400 includes variable transformers 406u, 406v, and 406w, i.e., transformers whose output voltage is controllable or even fully controllable (i.e., from 0-100%) within a specific region. The output voltage of the variable transformers (which is relatively high in the case of requested heating power) is transformed into a lower voltage or a current with a higher current intensity by single-phase high-current transformers 408u, 408v, and 408w (which are connected to the variable transformer via lines 410u, 410v, and 410w), and supplied at the output terminals 404U, 404V, and 404W by the high-current transformers. The output voltage is preferably in the range of less than 300V, more preferably less than or equal to 150V, even more preferably less than or equal to 100V, and most preferably less than or equal to 50V. A connector 404N for the neutral conductor is connected here to a corresponding connector on each of the high-current transformers.

[0061] Here, for each of the output terminals 404U, 404V, and 404W, the output power can be controlled independently of the other output power because the associated variable transformers 406u, 406v, and 406w are energized accordingly, i.e., because the output voltage at the corresponding variable transformer is set accordingly. Control signals based on externally specified voltage requirements are also applied to the control line via the control device 60, energizing the power controller via the control line (not shown).

[0062] In addition to the independent controllability of each individual voltage, using a power source with a variable transformer offers further advantages. First, low-frequency voltage oscillations, which may occur due to the on / off process in embodiments with a power controller, can be avoided, in addition to harmonics. These low-frequency oscillations are disadvantageous because they may fall within the resonant frequency range of the reaction tubes to which electromagnetic forces are applied. Furthermore, when a suitable variable transformer is used, the voltage can be controlled from 0-100%, which is useful, for example, during reactor start-up / shutdown or during load changes; the on-current can also be limited as a result.

[0063] Figure 5 This indicates the basic sequence of the method according to the invention, wherein, preferably, is used, for example, in... Figure 1 or Figure 2 The apparatus according to the invention described herein includes a control device configured to perform a method. During the method, a process fluid or a plurality of process flows to be heated is guided through one or more reaction tubes of a reactor (step 502).

[0064] In step 504, voltage or current is first supplied to the power connection of the reactor. This is accomplished by a controllable power source. In step 506, the voltage is set to a specific value, for example, by a control device connected to and controlling the power source.

[0065] In step 508, one or more measured values ​​are detected, that is, the measured values ​​(e.g., temperature value, current intensity value) of the measured variable (e.g., temperature, current intensity value) are detected. The measured value is therefore the value of the measured variable at the corresponding measurement time point. For this purpose, as described above ( Figure 1 , Figure 2 ), and provide measuring equipment.

[0066] In step 510, the detected measurement value is compared with the specified value or target value of the corresponding measurement variable. It is determined whether the detected measurement value corresponds to a predetermined value of the measurement variable. Here, "corresponds" should be understood in a general sense, that is, the detected measurement value is equal to or as close as possible to the predetermined value, or is also within a specific range around the predetermined value.

[0067] If the detected measurement value corresponds to a predetermined value of the measured variable, the measured variable is measured again, i.e., the measurement value is detected again; the method then returns to step 508 (arrow 512). The voltage remains unchanged. On the other hand, if the detected measurement value does not correspond to a predetermined value of the measured variable, the voltage is reset, i.e., the method returns to step 506 (arrow 514). The voltage in each associated pipe section and the resulting heating power are thus changed so that the value of the measured variable changes and subsequently corresponds to a predetermined value of the measured variable, either later or after several setting steps. For this purpose, for example, a corresponding control algorithm is provided in the control device.

Claims

1. A method for adjustably carrying out a chemical reaction in a process fluid in a reactor having a plurality of reaction tubes (20, 20a, 20b, 20c), said reaction tubes (20, 20a, 20b, 20c) having several electrically heated tube sections (24, 24a, 24b, 24c), wherein, A plurality of electrical connectors (40) are provided, each of which is connected in a current input region (11) to at least one of the pipe sections. At least one connecting element (42) is provided in a current output region (12), and each of the pipe sections is electrically connected to a connecting element. The current input region (11) is arranged within the reactor vessel, and / or the current output region (12) is arranged within the reactor vessel. The chemical reaction is one of the following: steam cracking, steam reforming, dry reforming, propane dehydrogenation, or reaction with hydrocarbons. The chemical reaction is carried out at least partially above 500°C, including: (502) The process fluid is guided through the plurality of reaction tubes; A plurality of variable voltages are provided (504) at the plurality of electrical connectors, wherein the plurality of voltages are provided as phases of a multiphase AC voltage such that the at least one connecting element (42) forms a star point; Set the several voltages described in (506); The detection (508) corresponds to one or more measured values ​​of one or more measurement variables; The voltage settings are changed so that the detected measured value corresponds to a predetermined value or a predetermined range of values ​​for the measured variable. The measured variables include: - At least one temperature and / or material composition; and - At least one current intensity.

2. The method as described in claim 1, wherein, The voltages are changed in the same way.

3. The method as described in claim 1, wherein, The voltages change independently of each other.

4. The method according to any one of claims 1 to 3, wherein, The one or more measurement variables include one or both of the following: - The tube outlet temperature of the process fluid, measured at the tube outlet of the plurality of reaction tubes, and - The material composition of the process fluid as determined at the outlet of the plurality of reaction tubes; The voltages are changed in such a way that the measured tube outlet temperature and / or the measured material composition are equal to or as close as possible to the predetermined tube outlet temperature and / or the predetermined material composition.

5. The method according to any one of claims 1-3, wherein, The one or more measurement variables include one or both of the following: - Temperatures of two or more pipe sections measured at the points connected to the various electrical connections. - The current intensity of two or more electrical connections measured at each electrical connection; The voltages at each of the electrical connectors are controlled such that the measured pipe section temperature corresponds to a predetermined pipe section temperature, and / or the power output calculated from the current intensity at the pipe section connected to each of the electrical connectors corresponds to a predetermined power output.

6. The method according to any one of claims 1-3, wherein, The one or more measurement variables include one or both of the following: - The intensity of the neutral conductor current measured on the neutral conductor. - The current intensity of two or more electrical connections measured at each electrical connection.

7. The method according to claim 6, wherein, The voltages are changed in such a way that the neutral conductor current intensity is minimized, and / or the sum of the current intensities of the electrical connectors calculated taking into account relative phase is minimized.

8. An apparatus for adjustable chemical reaction in a process fluid, comprising: A reactor (100, 200) having a plurality of reaction tubes (20, 20a, 20b, 20c) having a plurality of electrically heated tube sections (24, 24a, 24b, 24c) having a plurality of power connectors (40) having a plurality of power connectors (40) having at least one of the tube sections in a current input region (11) having at least one connecting element (42) in a current output region (12) and each of the tube sections being connected to a connecting element such that the at least one connecting element (42) forms a star point; Its features are, A controllable power source (50) is configured to provide a plurality of variable voltages at the plurality of power connectors, wherein the power source provides the plurality of voltages as phases of a multiphase AC voltage; One or more measuring devices (62, 62a, 62b, 62c, 63, 63a, 63b, 63c, 64, 64a, 64b, 64c, 66, 67, 67a, 67b, 67C) are configured to detect one or more measurement variables, wherein the one or more measuring devices include one or more temperature sensors and / or material composition sensors and one or more current sensors; A control device (60) is connected to the power source and the one or more measuring devices for communication and is configured to control the power source according to the one or more measured variables; The measured variables include: - At least one temperature and / or material composition; and - At least one current intensity, The control device is configured to perform the method as described in any one of claims 1 to 7; and The reactor includes a reactor container (10); wherein the current input region (11) is arranged inside the reactor container, and / or the current output region (12) is arranged inside the reactor container.

9. The apparatus of claim 8, wherein, The power source (50) is configured to change the plurality of voltages together in the same manner, wherein the power source includes a thyristor power controller, by which the voltages can be changed.

10. The apparatus of claim 8, wherein, The power source (50) is configured to change the plurality of voltages independently of each other, wherein the power source for each voltage includes a variable transformer (406u, 406v, 406w) or a power electronic component that performs the function of a variable transformer.

11. The apparatus according to any one of claims 8 to 10, wherein, The one or more measuring devices include one or both of the following: - At least one temperature sensor (62, 62a, 62b, 62c) is arranged at the outlet (23, 23a, 23b, 23c) of the plurality of reaction tubes to measure the temperature of the process fluid. - At least one material composition sensor (64, 64a, 64b, 64c) is arranged at the outlet of the plurality of reaction tubes to measure the material composition of the process fluid.

12. The apparatus according to any one of claims 8 to 10, wherein, The one or more measuring devices include one or both of the following: - Two or more pipe section temperature sensors (63, 63a, 63b, 63c) are arranged on the pipe sections connected to the various electrical connectors. - Two or more electrical connector current sensors (67, 67a, 67b, 67c) are arranged at various electrical connectors.

13. The apparatus according to any one of claims 8 to 10, wherein, The reactor includes a plurality of electrical connections, and wherein the one or more measuring devices include one or both of the following: - A neutral conductor current sensor (66) is arranged on a neutral conductor (44) connected to the connecting element. - Several power connector current sensors (67, 67a, 67b, 67c) are arranged at each power connector.

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