Plasma Reactor

Abstract

A plasma reactor for decomposing hydrocarbon fluids capable of continuous operation for extended periods of time is described. The plasma reactor comprises a reactor chamber and a plasma torch, the plasma torch being attached to a reactor chamber wall, extending into the reactor chamber, and having a free end. The plasma torch comprises an inner tubular electrode and an outer tubular electrode at least partially surrounding the inner tubular electrode. A feed lance for distributing the hydrocarbon fluid is disposed within the inner tubular electrode and is displaceable relative to the tubular electrodes. The plasma reactor further comprises a plasma gas outlet for distributing a plasma gas, disposed between the inner and outer tubular electrodes, and an oxidizing fluid outlet for distributing an oxidizing fluid. The oxidizing fluid preferably comprises CO2 or HO, and the oxidizing fluid outlet is disposed within the inner tubular electrode.

Description

[Technical Field]

[0001] The present invention relates to a plasma reactor and a method for operating a plasma reactor. [Background technology]

[0002] Conventional technology Prior art plasma reactors for decomposing hydrocarbon fluids are known, and these plasma reactors comprise a reactor chamber and a plasma torch projecting into the reactor chamber and capable of generating high temperatures of over 1000° C. The hydrocarbon fluid is introduced into the plasma reactor and decomposed at high temperatures into an aerosol of carbon and hydrogen, i.e., H2 / C aerosol.

[0003] For example, International Publication WO 93 / 12634 describes such a plasma reactor, which includes a reactor chamber and a plasma torch attached to the reactor chamber wall, protruding into the reactor chamber, and having a free end. The plasma torch comprises an inner tubular electrode, an outer tubular electrode, and a feed lance for delivering a hydrocarbon fluid, the feed lance being disposed within the inner tubular electrode. In such known plasma reactors, carbon deposits can grow at the hydrocarbon fluid inlet (fouling) and clog the inlet. This can damage the electrode and cause process malfunctions. Therefore, various attempts have been made to prevent carbon deposits. Nevertheless, carbon deposits cannot be avoided, and only relatively short operating times for the plasma reactor can be achieved. Another problem is that the liquid-cooled feed lance is prone to electrical leakage, which can lead to damage to the electrode and the reactor. Summary of the Invention

[0004] Summary of the Invention The object of the present invention is to overcome the above-mentioned drawbacks, and in particular to provide a plasma reactor that can be operated continuously for a long period of time. This object is achieved by the plasma reactor according to claim 1 and the method for operating the plasma reactor according to claim 8.

[0005] The above and other problems are solved by a plasma reactor for decomposing hydrocarbon fluids, comprising a reactor chamber and a plasma torch, the plasma torch being attached to a reactor chamber wall, protruding into the reactor chamber, and having a free end. The plasma torch comprises an inner tubular electrode and an outer tubular electrode at least partially surrounding the inner tubular electrode. A feed lance for distributing the hydrocarbon fluid is disposed within the inner tubular electrode and is displaceable relative to the tubular electrodes by a sliding mechanism during operation of the plasma reactor. The sliding mechanism is thus configured to axially move the feed lance during operation when plasma is generated within the plasma reactor. The plasma reactor further comprises a plasma gas outlet for distributing a plasma gas, the plasma gas outlet being disposed between the inner and outer tubular electrodes. The plasma reactor further comprises an oxidizing fluid outlet for distributing an oxidizing fluid, the oxidizing fluid preferably comprising CO2 or HO, the oxidizing fluid outlet being disposed within the inner tubular electrode. The hydrocarbon fluid is preferably a gas and has a composition of CnHm, where n and m are integers, n≧1 and m≧2. A plasma gas source is connected to the plasma gas outlet, an oxidizing fluid source is connected to the oxidizing fluid outlet, and a hydrocarbon fluid source is connected to the feed lance. In this configuration, the distributed hydrocarbon fluid flows along the inner tubular electrode to the free end of the plasma torch, where plasma is generated during operation. In the absence of oxygen, the hydrocarbon fluid decomposes into a mixture of H2 and C particles (also known as H2 / C aerosol). Some of the C particles may form carbon deposits on the electrode. Meanwhile, graphite or carbon electrodes may erode or wear during operation under the influence of the plasma or arc between the electrodes.

[0006] On the other hand, by moving the feed lance relative to the tubular electrodes, it is possible to protect the electrodes by depositing carbon at different locations on the electrodes, and controlling the flow of hydrocarbon fluid through the feed lance can enhance carbon deposition.

[0007] On the other hand, if the electrode or feed lance has excessive carbon deposits, the carbon deposits can be reduced by controlling the location of the oxidizing fluid outlet and the flow of oxidizing fluid so that the oxidizing fluid reduces or consumes the carbon deposits, thereby keeping the feed channel of the feed lance open to the hydrocarbon fluid.

[0008] Third, the feed lance can be moved to a cooling zone, i.e., away from the plasma zone at the free end of the electrode, for example, at the start or end of a run, or when the electrode becomes shorter due to wear, and the worn electrode can then be restored to its original full length, extending the run time.

[0009] The inner and outer tubular electrodes each have a hollow interior space and preferably have a circular cross section. However, the electrodes may have any other cross-sectional shape. When the inner electrode is positioned within the interior space of the outer electrode, a gap through which plasma gas can pass is formed between the inner and outer electrodes. The electrodes are made of an electrically conductive, heat-resistant material that can withstand the temperatures in the plasma arc environment during operation. Examples of heat-resistant materials for the electrodes include metals, electrically conductive ceramic materials, carbon, graphite, etc., and these materials may be fiber-reinforced.

[0010] In a first embodiment of the plasma reactor, the oxidizing fluid outlet is part of the feed lance. For example, the feed lance is provided with a first outlet for the oxidizing fluid and a second outlet for the hydrocarbon fluid. In another embodiment of the plasma reactor, the oxidizing fluid outlet is formed by an annular space between the inner tubular electrode and the feed lance, and the oxidizing fluid is flowed between the inner surface of the inner electrode and the outer periphery of the feed lance. The distribution of the oxidizing fluid can be switched between two cases: depositing carbon on the electrode or reducing carbon deposits. That is, the oxidizing fluid supply source can be connected to the first oxidizing fluid outlet or to the annular space between the inner tubular electrode and the feed lance. In either case, the oxidizing fluid is distributed inside the inner tubular electrode, achieving the desired effects described above, i.e., selective electrode carbon deposition and carbon deposit reduction.

[0011] When the oxidizing fluid outlet is part of the supply lance, the plasma torch preferably comprises, inter alia, a supply lance formed by an inner tube and an outer tube at least partially surrounding the inner tube. In this case, the oxidizing fluid outlet is formed by the inner tube or by the space between the inner and outer tubes. When the oxidizing fluid outlet is formed by the inner tube, the oxidizing fluid does not directly contact the inner electrode. Advantageously, the inner and outer tubes of the supply lance are movable relative to each other in their longitudinal direction, allowing the tube openings to be positioned at different positions relative to the electrode and the free end of the plasma torch. This allows for better control of the location of carbon accumulation and decomposition. Again, the sliding mechanism is configured to axially move the inner and outer tubes of the supply lance during operation while plasma is being generated in the plasma reactor.

[0012] If the inner electrode is made of carbon or graphite, the oxidizing fluid may affect the inner electrode. In this case, it is advantageous if the oxidizing fluid outlet is part of the feed lance and is formed by the inner tube of the feed lance, and the outlet for distributing the hydrocarbon fluid is formed by the space between the inner and outer tubes. The hydrocarbon fluid is thus interposed like a protective curtain between the electrode and the oxidizing fluid distributed from the center.

[0013] In any of the above embodiments, a thermal insulating layer may optionally be placed on the outside of the feed lance or inside the inner electrode to protect these components from the heat of the plasma or from the heat from the inner electrode during operation.

[0014] In all of the above embodiments, the supply lance is optionally connected to the inner electrode by at least one conductive element, and the supply lance and the inner electrode have the same potential. This avoids or at least reduces the probability of electrical flashover from the electrode to the supply lance. Alternatively or additionally, the inner electrode or the supply lance may be provided with an insulating layer, which has both electrical and thermal insulating properties.

[0015] Advantageously, the feed lance is provided with structure for swirling the injected hydrocarbon fluid. Alternatively or additionally, the oxidizing fluid outlet is provided with structure for causing swirling of the oxidizing fluid, in particular CO and / or H O.

[0016] Preferably, the plasma reactor further includes an annular magnet arranged outside the reactor wall at the level of the free end of the electrode. The magnet can generate a Lorentz force to move the electric arc at the electrode and turbulent material flow in the reactor chamber. To enhance this favorable technical effect, a portion of the reactor wall close to the magnet is preferably made of an austenitic metal, in particular an austenitic steel, stainless steel, or a metal mixture containing an austenitic component. In an embodiment in which the inner electrode has a positive potential and the outer electrode has a negative potential, and the free ends of the electrodes are located at the upper end of the annular magnet, another technical advantage is obtained, since the operation of the arc is more stabilized. However, in a similar embodiment in which the free ends of the electrodes are located at the lower end of the annular magnet, the inner electrode has a negative potential, and the outer electrode has a positive potential, the operation of the arc can also be stabilized in a similar manner.

[0017] In an advantageous embodiment, the reactor chamber has an outlet opposite the plasma torch, and the heat exchanger is disposed directly at the outlet of the reactor chamber. Preferably, the outlet of the reactor chamber merges directly into the inlet of the heat exchanger. When the plasma reactor is configured to produce a synthesis gas stream comprising CO and H2, the heat exchanger is preferably configured to cool the synthesis gas stream from 800-1000°C, particularly 1400-1200°C, to a temperature range of 200-400°C. This serves as a quench, achieving synthesis gas immobilization and preventing reverse reactions. Optionally, the heat exchanger is designed to cool the synthesis gas stream within 1-3 seconds, particularly within 2 seconds.

[0018] The above objects and other problems are solved by a method of operating a plasma reactor according to any of the above-described embodiments, the method comprising the steps of: The mass flow rate of the oxidizing or hydrocarbon fluid is measured prior to distribution into the inner tubular electrode. The distribution of oxidizing fluid from the oxidizing fluid outlet is controlled based on the change in mass flow rate. During operation, carbon may deposit inside the inner electrode or at the outlet of the feed lance. At a constant feed pressure, the mass flow rate of the oxidizing or hydrocarbon fluid may vary depending on the amount of deposited carbon. A decrease in mass flow rate is associated with the accumulation of carbon deposits, as the carbon deposits reduce the cross-sectional flow area within the inner tubular electrode.

[0019] Similarly, the buildup of carbon deposits may change the inlet pressure of the oxidizing or hydrocarbon fluid while leaving the mass flow rate unchanged. Thus, to achieve a similar effect, the method may include the following steps: The pressure or pressure history of the oxidizing or hydrocarbon fluid is measured prior to dispensing into the inner tubular electrode. The pressure change controls the distribution of the oxidizing fluid from the oxidizing fluid outlet. or The mass flow rate or mass flow rate history of the oxidizing or hydrocarbon fluid is measured prior to distribution into the inner tubular electrode. The distribution of the oxidizing fluid from the oxidizing fluid outlet is controlled based on the variation in mass flow rate.

[0020] In this method, the distribution of oxidizing fluid is appropriately controlled based on changes in mass flow rate or pressure during distribution. That is, when carbon deposits are high, more oxidizing fluid is distributed, and when carbon deposits are low, less oxidizing fluid or no oxidizing fluid is distributed. The oxidizing fluid decomposes the carbon deposits. Therefore, by implementing this method, the above-mentioned desirable effects can be achieved. Furthermore, when very high temperatures, radiation, or other extreme conditions exist within the reactor chamber during operation, measuring the mass flow rate can provide feedback regarding the condition of the electrodes, oxidizing fluid outlet, and feed lance, as well as the buildup and deterioration of carbon deposits, which has not been possible until now.

[0021] In a first embodiment of the method, the oxidizing fluid is supplied through outlets in the supply lance, for example, a first outlet for the oxidizing fluid and a second outlet for the hydrocarbon fluid. In a second embodiment of the method, the oxidizing fluid is distributed through the annular space between the inner tubular electrode and the supply lance, with the oxidizing fluid passing between the inner surface of the inner electrode and the outer periphery of the supply lance. In a third embodiment of the method, the hydrocarbon fluid and the oxidizing fluid are distributed through a single or common tube of the supply lance either (a) alternately in time (first the hydrocarbon fluid, then the oxidizing fluid through the same tube, or vice versa), or (b) mixed together. In either case, the oxidizing fluid can remove carbon deposits, thereby keeping the supply channel for the hydrocarbon fluid open.

[0022] Additionally, the method may include variably mixing the hydrocarbon fluid, CO2, and / or HO based on a measured amount of wear of the at least one tubular electrode. Additionally, the hydrocarbon fluid, CO2, and / or HO may be variably mixed based on a measured amount of solids (i.e., solid carbon deposits) deposits on the at least one tubular electrode. For example, the amount of wear or solids deposits may be measured optically, such as by a laser, a camera, or other known optical methods.

[0023] Preferably, the feed lance is displaced axially relative to the inner tubular electrode based on changes in feed mass flow rate or pressure. Similarly, the oxidizing fluid outlet can be shifted axially relative to the inner tubular electrode.

[0024] In one embodiment, distributing the oxidizing fluid is performed through an outlet that is part of a feed lance, the feed lance comprising an inner tube and an outer tube at least partially surrounding the inner tube. In this case, a first aspect of the method provides for passing the oxidizing fluid through the inner tube and the hydrocarbon fluid through the space between the inner and outer tubes. In this way, the oxidizing fluid keeps the inner tube clean and the hydrocarbon fluid passes close to the inner electrode. In a second aspect of the method, this feed lance embodiment provides for passing the oxidizing fluid through the space between the inner and outer tubes. In this way, the oxidizing fluid passes close to the inner electrode, allowing for rapid reduction of carbon deposits on the electrode.

[0025] In any of the above method embodiments, a cooling gas having a lower temperature than the inner tubular electrode may be introduced through the feed lance when no hydrocarbon fluid is being introduced. For example, the cooling gas may have a temperature less than 700°C, preferably less than 550°C, due to the higher temperature of the inner tubular electrode. The cooling gas replaces the cooling effect of the hydrocarbon fluid and prevents cracking or other damage to the electrode and feed lance due to temperature changes.

[0026] Furthermore, in all embodiments of the above method, the pressure in the reactor chamber can be adjusted to a range of 10 to 30 bar. Similarly, in all embodiments of the above method, the temperature at the inlet of the heat exchanger can be adjusted to 1100 to 1300°C, preferably 1200°C. These measures improve the productivity of the plasma reactor. [Brief explanation of the drawings]

[0027] The invention, as well as its details and advantages, will now be explained with reference to preferred examples of embodiments shown in the drawings. [Figure 1] FIG. 1 shows a plasma reactor for decomposing hydrocarbon fluids. [Figure 2] FIG. 2 is an enlarged detail A of the plasma torch of FIG. [Figure 3]FIG. 3 is an enlarged detail A of the plasma torch of FIG. 1 during operation. [Figure 4] FIG. 4 is a diagram of the divided electrodes of the plasma torch of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0028] As used herein, terms such as up, down, right, left, and similar terms refer to the orientation or configuration shown in the figures and are used solely to describe the embodiments. These terms may indicate preferred orientations, but should not be construed in a limiting sense. Notably, the plasma reactor shown in FIG. 1 may be installed in different orientations, e.g., tilted or horizontal. Furthermore, terms such as "substantially," "nearly," and "about" mean that a deviation of ±10%, preferably ±5%, from the indicated value is acceptable. The term "hydrocarbon fluid" as used herein refers to a fluid (gas, aerosol, or liquid) containing hydrocarbons, such as natural gas, methane, liquefied petroleum gas, biogas, or a hydrocarbon-atomized liquid, or a mixture thereof.

[0029] The plasma reactor 1 according to the present disclosure comprises a reactor chamber 2 surrounded by a reactor wall 3, which comprises a lower portion 3a and a cover 3b. The reactor chamber 2 may be divided at different locations than those shown in FIG. 1 . The reactor chamber 2 is substantially cylindrical and has a central axis 4. A plasma torch 7 is attached to the reactor wall 3 (here attached to the cover 3b) and comprises an elongated electrode (shown in more detail in FIGS. 2 and 3 ). The plasma torch 7 is attached to the reactor wall 3 by an electrode holder or plasma torch holder (not shown). In the example of FIG. 1 , the cover 3b serves as the electrode holder, but an additional electrode holder may also be provided on the cover 3b. The plasma torch 7 comprises a base 9 attached to the reactor wall 3 (cover 3b or electrode holder). At its opposite end, i.e., the end opposite the base 9, the plasma torch 7 comprises a torch portion 11 at the free end 12 of the electrode, which protrudes into the reactor chamber 2. A plasma 13 is formed between and outside the electrodes by the plasma gas and the electric arc. An annular magnet 14 is positioned outside the reactor wall 3 at the level of the free ends 12 of the electrodes and influences the electric arc through magnetic force. The magnet 14 can cause the arc to move at the electrodes and the material in the reactor chamber 2 to rotate through the Lorentz force. To enhance this favorable effect, part of the reactor wall 2 may be made of an austenitic metal, particularly austenitic steel, stainless steel, or a metal mixture containing austenitic components. In a first further refinement, the free ends of the electrodes are located at the upper end of the annular magnet, with the inner electrode at a positive potential and the outer electrode at a negative potential. In a second further refinement, the free ends of the electrodes are located at the lower end of the annular magnet, with the inner electrode at a negative potential and the outer electrode at a positive potential. This combination of electrode potentials and magnet positions combines the force fields of the magnet and the arc, making arc operation more stable.

[0030] The plasma reactor 1 is provided with an outlet 15 at the other end of the reactor chamber 2, opposite the plasma torch 7, through which materials resulting from the decomposition of the injected hydrocarbon fluid can escape. The outlet 15 is positioned in the flow direction at the opposite end of the reactor chamber 2 and may be larger or smaller than shown. However, for ease of distinction, the outlet 15 is shown in FIG. 1 as being smaller than the reactor chamber. Optionally, a secondary outlet 16 may be provided at the lower end of the reactor chamber 2. A heat exchanger 17 is positioned directly at the outlet 15 of the reactor chamber 2. Preferably, the outlet 15 leads directly to the inlet of the heat exchanger 17. Since the plasma reactor 1 is configured to produce a synthesis gas stream comprising carbon monoxide (CO) and hydrogen (H), the heat exchanger 17 is designed to cool the synthesis gas stream from 800 to 1000°C, particularly from 1400 to 1200°C, so that the synthesis gas at the outlet of the heat exchanger 17 has a temperature in the range of 200 to 400°C. This configuration acts as a quench (stages and steps for cooling) to immobilize the syngas and prevent back reactions. For example, heat exchanger 17 is a tubular heat exchanger with multiple interconnected stages. Here, heat exchanger 17 is designed to cool the syngas stream within 1 to 3 seconds, preferably within 2 seconds.

[0031] The reactor chamber 2 may have an expanding flow cross-section that increases between the upper end (cover 3b) and the outlet 15 (measured perpendicular to the longitudinal extent of the second reactor chamber). Advantageously, the reactor chamber 2 does not include a substantial reduction in flow cross-section between the upper end and the outlet 15. In particular, the reactor chamber 2 may expand conically to provide a continuous and uniform increase in flow cross-sectional area. However, it is also possible to provide a stepwise increase, for example, to provide several different conical expansions. However, such an expanding flow cross-sectional area may remain the same in width relative to its length by a small amount (less than 10%).

[0032] FIG. 2 shows an enlarged detail A of the torch portion 11 at the free end of the plasma torch 7. The plasma torch 7 comprises an inner tubular electrode 18 and an outer tubular electrode 20 (see FIG. 3) surrounding the inner tubular electrode 18. Each of the electrodes 18 and 20 has a hollow interior and, in the illustrated example, a circular cross section. When the inner electrode 18 is disposed in the interior space of the outer electrode 20, a gap 24 (see FIG. 3) is formed between the electrodes 18 and 20. That is, the electrodes 18 and 20 are arranged so as to fit together in a cylindrical shape. The electrodes 18 and 20 are made of an electrically conductive, heat-resistant material (metal, electrically conductive ceramic material, carbon, or graphite) that can withstand the temperature of the plasma arc during operation. In the following description, the electrodes 18 and 20 are assumed to be made of carbon or graphite.

[0033] The gap 24 between the inner tubular electrode 18 and the outer tubular electrode 20 is connected to a plasma gas source (not shown), thus forming a plasma gas outlet for distributing the plasma gas into the reactor chamber 2. A number of valves are disposed between the plasma gas source and the gap 24, and the distribution of the plasma gas can be controlled via the valves.

[0034] The plasma torch 7 further includes a feed lance 22 for distributing the hydrocarbon fluid into the reactor chamber 2. The feed lance 22 is disposed inside the inner tubular electrode 18, i.e., in its hollow interior space 19, and is displaceable relative to the tubular electrodes. Optionally, an electrically and thermally insulating layer (not shown) may be disposed on the outside of the feed lance 22 or inside the inner electrode. The feed lance 22 may include a structure such as a guide vane or an inclined nozzle for swirling the introduced hydrocarbon fluid. Alternatively, a guide structure with a similar effect may be provided at the oxidizing fluid outlet to cause swirling of the oxidizing fluid, particularly carbon dioxide (CO2) and / or water (HO). The feed lance 22 is connected to a hydrocarbon fluid source (not shown).

[0035] The plasma torch 7 also has an oxidizing fluid outlet for dispensing an oxidizing fluid. The oxidizing fluid outlet is located within the inner tubular electrode and is connected to a source of oxidizing fluid. The oxidizing fluid is suitable for oxidizing carbon and preferably comprises carbon dioxide (CO2) or water (HO).

[0036] In a first embodiment of the plasma torch 7, the oxidizing fluid outlet is formed by the annular gap 23 between the inner tubular electrode 18 and the feed lance 22, where the oxidizing fluid is simply directed between the inside of the inner electrode and the outer periphery of the feed lance. This embodiment has the advantage of being able to quickly dissolve (i.e., oxidize) any carbon that has accumulated on the inner surface of the inner electrode 18. Preferably, however, the annular gap 23 is connected to a plasma gas source that does not oxidize or otherwise degrade the inner surface of the inner electrode 18.

[0037] 2 and 3, the oxidizing fluid outlet is part of a feed lance 22 having a first outlet 25 for the oxidizing fluid and a second outlet 26 for the hydrocarbon fluid. The feed lance 22 is formed, inter alia, by an inner tube 28 having an interior space 29 and an outer tube 30 surrounding the inner tube 28. An intermediate space 31 is therefore formed between the inner tube 28 and the outer tube 30. In this second embodiment of the plasma torch 7 as well, several operating modes (A), (B), (C) are provided, which may be applied sequentially in time.

[0038] First operating mode (A) 2 and 3, the oxidizing fluid passes through the interior space 29 of the inner tube 28, which forms the outlet for the oxidizing fluid. The hydrocarbon fluid passes through the intermediate space 31 between the inner tube 28 and the outer tube 30, which forms the outlet for the hydrocarbon fluid. In operation, the hydrocarbon fluid flows between the inner electrode 18 and the centrally distributed oxidizing fluid, preventing the oxidizing fluid from coming into direct contact with the inner electrode 18. When operating with carbon or graphite electrodes, this operating mode (A) has the advantage that the oxidizing fluid is less likely to deteriorate the inner electrode 18.

[0039] Second operating mode (B) In the configuration shown in Figures 2 and 3, the hydrocarbon fluid passes through the interior space 29 of the inner tube 28, which forms the hydrocarbon fluid outlet 26. The oxidizing fluid passes through the intermediate space 31 between the inner tube 28 and the outer tube 30, which forms the oxidizing fluid outlet. During operation, the oxidizing fluid flows between the inner electrode 18 and the centrally distributed hydrocarbon fluid, preventing the hydrocarbon fluid from directly contacting the inner electrode 18. This operating mode (B) has the effect of quickly dissolving (i.e., oxidizing) carbon deposited on the inner electrode 18. Compared to operating mode (A), this mode also has the effect of making it more difficult for carbon particles from the H2 / C aerosol to deposit on the inner electrode 18.

[0040] The feed lance 22 is displaceable relative to the tubular electrodes 18, 20 in the direction of the central axis 4. In particular, the feed lance 22 is displaceable relative to the inner electrode 18. Furthermore, the inner tube 28 and the outer tube 30 of the feed lance 22 may be displaceable relative to each other. For example, the inner tube 28 in FIG. 3 protrudes from the outer tube 30, while the ends of the tubes 28 and 30 in FIG. 2 are at the same level. This can affect the temperature ranges and flow characteristics when the hydrocarbon fluid and the oxidizing fluid are introduced.

[0041] Third operating mode (C) The hydrocarbon fluid and oxidizing fluid are distributed through a single or common tube of the feed lance, not shown, either (a) alternately with a time stagger (first the hydrocarbon fluid, then the oxidizing fluid, or vice versa, through the same tube), or (b) mixed together.

[0042] Optionally, at least one of the tubular electrodes 18, 20 comprises tubular segments 34 separated along the longitudinal axis of the electrode 18, 20. The tubular segments 34 are shell-shaped and together form the electrode 18, 20. Cutting the cylindrical tubular electrode 18, 20 twice along its longitudinal axis creates two shell-shaped tubular segments 34, each extending 180° and separated by two longitudinal slots. In FIG. 4 , the cylindrical tubular electrode 18, 20 is shown cut three times along its longitudinal axis (see longitudinal slots 35), resulting in three shell-shaped tubular segments 34, each extending 120°, that, when assembled, form the tubular electrode 18 or 20. The shell-shaped tubular segments 34 fit tightly together, and the longitudinal slots 35 are very small, ensuring little or no leakage of gas (i.e., plasma gas) between the tubular segments 34. For example, the shell-shaped tubular segments 34 may abut one another smoothly, may be configured with a convex and concave interface, or may be configured with a labyrinth seal.

[0043] Alternatively, at least one of the tubular electrodes 18, 20 comprises annular tubular sections (not shown) arranged in a row. The annular tubular sections can be interconnected, for example, by gluing, threading, or plugging. When three annular tubular sections are arranged in a row, the entire tubular electrode is formed by first, second, and third annular tubular sections that are threaded or plugged together. In this case, the first tubular section is located at the free end 12 of the plasma torch 7, the second tubular section is located in the middle, and the third tubular section is located at the distal end of the plasma torch 7, which is attached to the reactor chamber 2 (e.g., the cover 3b or the electrode holder).

[0044] The shell-shaped tube segment 34 or annular tubing helps compensate for differences in thermal expansion. The addition of the annular tubing allows the electrode length to be maintained within a certain range as the electrodes 18, 20 wear in the arc region. Furthermore, portions of the electrodes 18, 20 can be replaced, which is useful for electrodes made of carbon or graphite. The shell-shaped tube segment 34 or annular tubing can be secured by a mounting element, such as a pin (particularly a carbon or graphite pin).

[0045] In operation, the above-described plasma reactor 1 generally operates according to the following method for cracking hydrocarbon fluids.

[0046] The plasma gas is distributed between the inner tubular electrode 18 and the outer tubular electrode 20, and a portion of the plasma gas is excited by the arc between the electrodes to form the plasma 13. The plasma 13 is formed around the torch section 11. After passing through the arc, the plasma gas has an average temperature of over 2500°C, but can reach localized temperatures as high as 4900°C. Particularly if carbon or graphite electrodes are used in the plasma torch 7, as envisioned herein, portions of the electrodes 18, 20 may be eroded by the high temperature of the arc and electrical sparks.

[0047] A hydrocarbon fluid (preferably natural gas or methane) is distributed within the inner tubular electrode 18. At high temperatures within the reactor chamber 2, in the absence of oxygen, the hydrocarbon fluid is decomposed into hydrogen (H gas) and carbon (C particles). The carbon and hydrogen escape from the interior space 19 of the inner electrode 18 as H / C aerosol and travel in the direction of the central axis 4 to the outlet 15. A portion of the H / C aerosol can be removed via an additional outlet 16.

[0048] Some of the generated carbon may deposit on surrounding components, forming solid carbon deposits. In particular, the inner space 19 of the inner electrode 18 and the feed channel of the feed lance 22 may accumulate excessive carbon deposits and become completely clogged. This changes the operating characteristics. As the carbon deposits grow, the remaining flow cross-sectional area of ​​the inner space 19 of the inner electrode 18 and the feed channel of the feed lance 22 (i.e., the inner space 29 and the intermediate space 31) decreases. This results in a throttled flow of oxidizing fluid and / or hydrocarbon fluid, reducing the mass flow rate. A significant decrease in mass flow rate is an indication of severe carbon deposition. Little change in mass flow rate indicates no or only slight carbon deposition.

[0049] To maintain a constant mass flow rate, the supply pressure of the oxidizing fluid and / or hydrocarbon fluid may be increased initially to keep the mass flow rate the same.

[0050] If an increase in feed pressure is undesirable or insufficient to offset the throttling effect, an oxidizing fluid (CO₂ or HO) is distributed into the inner tubular electrode 18. Alternatively, or additionally, the feed lance may be displaced axially relative to the inner tubular electrode in response to changes in mass flow rate. The oxidizing fluid may oxidize carbon at the high operating temperatures within the reactor chamber 2 to form carbon monoxide (C + CO₂ - > ; CO) or synthesis gas (C + HO - > ; CO + H₂). Additionally, the feed lance is cooled by the hydrocarbon fluid and the oxidizing fluid.

[0051] In Figures 2 and 3, the feed lance comprises an inner pipe 18 and an outer pipe 20, allowing for the operating modes (A), (B) and (C) described above. Operation Mode (A) The oxidizing fluid passes through the inner space 29 of the inner pipe 28 , and the hydrocarbon fluid passes through the intermediate space 31 between the inner pipe 28 and the outer pipe 30 . Operation Mode (B): The hydrocarbon fluid passes through the inner space 29 of the inner pipe 28 , and the oxidizing fluid passes through the intermediate space 31 between the inner pipe 28 and the outer pipe 30 . Mode of Operation (C) Although not shown in the diagram, the hydrocarbon fluid and the oxidizing fluid are fed through a single or common tube of the feed lance either (a) alternately in time (first the hydrocarbon fluid, then the oxidizing fluid through the same tube, or vice versa), or (b) mixed together, so that the tube orifice can be moved to a position to remove or add carbon deposits.

[0052] The oxidizing fluid distribution process (ie, control of mass flow rate and supply pressure) is controlled according to the operating conditions of the plasma reactor 1 . -If severe carbon deposits are present, more oxidizing fluid will be dispensed. - When there is little or no carbon buildup, little or no oxidizing fluid is dispensed. Therefore, the oxidizing fluid does not need to be dispensed continuously, but can be dispensed intermittently. - If significant corrosion of the graphite or carbon electrode is observed, carbon deposits on the electrode may be desirable, and in this case too, little or no oxidizing fluid is discharged. Furthermore, in this situation, the first operating mode (A) is advantageous, since the hydrocarbon fluid passes through the intermediate space 31 between the inner tube 28 and the outer tube 30, i.e., in the vicinity of the inner electrode 18. If a significant mass flow reduction is detected at one of the outlets 25 or 26 of the supply lance 22, the oxidizing fluid may be specially distributed through the affected outlet 25 or 26.

[0053] Additionally, the variable mixing of hydrocarbon fluid, CO, and / or HO may be based on measured wear of at least one of the tubular electrodes or based on a measured amount of solids (e.g., solid carbon deposits) accumulated on one of the tubular electrodes. For example, the amount of wear or solid deposits can be measured optically, e.g., using a laser, camera, or other known optical method.

[0054] In all embodiments of the above-described method, plasma gas may be discharged through the annular gap 23 between the inner tubular electrode 18 and the feed lance 22 to blow the C particles away from the inner electrode 18 .

[0055] In all embodiments of the above-described method, a cooling gas having a lower temperature than the inner electrode 18 may be supplied through the supply lance 22 when no hydrocarbon fluid is being dispensed. Additionally, in all embodiments of the above-described method, the supply lance may be moved axially relative to the inner tubular electrode. In either case, the supply lance 22 is protected from thermal damage when the cooling effect of the hydrocarbon fluid is lost. The introduction of cooling gas may be beneficial during start-up and shutdown of operations.

[0056] Furthermore, the flow characteristics and turbulence of the fluid delivered through the delivery lance 22 are affected by the combined adjustment of (i) the axial position of the delivery lance 22, (ii) the amount or pressure of the fluid delivered, and (iii) the amount or pressure of the plasma gas delivered through the annular gap 23.

[0057] In all embodiments, any suitable gas or gas mixture can be selected as the plasma gas, either supplied externally to the plasma reactor or generated in the plasma reactor 1. By way of example, inert gases such as argon or nitrogen are suitable as plasma gases, while H2, CO or synthesis gas are also suitable gases, since these gases are produced anyway when hydrocarbons are cracked.

[0058] In all embodiments, the plasma reactor 1 may have additional inlets (not shown) for CO or HO in the direction of the central axis 4 between the plasma torch 7 and the outlet 15, i.e., in the direction of the flow of the H / C aerosol. These additional inlets for CO or HO are located at a sufficient distance along the central axis 4 from the plasma torch 7, where a temperature exceeding 1200°C is maintained, so that preferably more than 90% of the supplied hydrocarbon fluid is decomposed into H / C aerosol. In this case, the amount of CO or HO supplied to the reactor chamber 2 through the additional inlets for CO or HO is preferably greater than the amount of oxidizing fluid supplied through the supply lance 22. However, in a simple embodiment, it is also possible to supply the entire amount of oxidizing fluid (CO and / or HO) required for the process in the plasma reactor 1 through the supply lance 22.

[0059] Furthermore, in all embodiments of the above-described method, the pressure in the reactor chamber can be adjusted to a range of 10 to 30 bar. Similarly, in all embodiments of the above-described method, the temperature at the inlet of the heat exchanger can be adjusted to a range of 1100 to 1300°C, preferably 1200°C.

[0060] The concepts described herein are described in the context of a plasma reactor for cracking hydrocarbon fluids, but are also applicable to other plasma reactors and plasma torches that are affected by deposits on the electrodes or outlet.

[0061] Although the present invention has been described with reference to preferred embodiments, individual features of the described embodiments can be freely combined and used or substituted as long as they are compatible with each other. Likewise, individual features of the described embodiments can be omitted unless absolutely necessary. It should be understood that many variations and embodiments are possible and obvious to those skilled in the art within the scope of the claims.

Claims

1. A plasma reactor (1) for decomposing hydrocarbon fluids, comprising: a reactor chamber (2), and a plasma torch (7) attached to a wall of the reactor chamber (2), protruding into the reactor chamber (2), and having a free end (12), the plasma torch (7) comprising an inner tubular electrode (18) and an outer tubular electrode (20) at least partially surrounding the inner tubular electrode (18); a feed lance (22) for distributing the hydrocarbon fluid, the feed lance (22) being disposed inside the inner tubular electrode (18) and movable relative to the tubular electrodes (18, 20) by a slide mechanism; a plasma gas outlet for supplying plasma gas between the inner tubular electrode (18) and the outer tubular electrode (20); an oxidizing fluid outlet for dispensing the oxidizing fluid; The oxidizing fluid is preferably CO ２ or H ２ O, The plasma reactor (1), wherein the oxidizing fluid outlet is disposed within the inner tubular electrode (18).

2. 2. The plasma reactor (1) of claim 1, wherein the oxidizing fluid outlet is part of the supply lance (22) or is formed by a gap (23) between the inner tubular electrode (18) and the supply lance (22).

3. The feed lance (22) or oxidizing fluid outlet is provided with the distributed hydrocarbon fluid, CO ２ , and / or H ２ 3. The plasma reactor (1) of claim 2, further comprising a structure shaped to generate a turbulent flow of O.

4. the supply lance comprises an inner pipe and an outer pipe at least partially surrounding the inner pipe; 4. The plasma reactor (1) according to any one of claims 1 to 3, wherein the oxidizing fluid outlet is formed either by the inner pipe or by the space between the inner pipe and the outer pipe of the supply lance.

5. the feed lance is connected to the inner electrode by at least one conductive element; or 5. The plasma reactor (1) according to any one of claims 1 to 4, wherein the inner electrode or the supply lance is provided with an insulating layer, which has electrical and thermal insulating properties.

6. the plasma reactor comprises an annular magnet (14) arranged outside the reactor wall (3, 3a, 3b) at the level of the free ends (12) of the electrodes (18, 20), 6. The plasma reactor (1) according to any one of the preceding claims, wherein the part of the reactor wall close to the magnet is preferably made of austenitic steel, stainless steel or a metal mixture containing an austenitic component.

7. The reactor chamber (2) comprises an outlet (15) opposite the plasma torch (7), 7. The plasma reactor (1) according to any one of the preceding claims, wherein a heat exchanger (17) is arranged directly at the outlet (15) of the reactor chamber (2).

8. The plasma reactor (1) is a gas that contains CO and H ２ and configured to produce a synthesis gas stream comprising: the heat exchanger (17) is configured to cool the synthesis gas stream by 800-1000°C; The plasma reactor (1) according to claim 7, wherein the heat exchanger (17) is preferably configured to cool the synthesis gas stream within 1 to 3 seconds, particularly preferably within 2 seconds.

9. A method for operating a plasma reactor (1) according to any one of claims 1 to 8, comprising the steps of: measuring the mass flow rate of the oxidizing fluid or the hydrocarbon fluid prior to distribution into the inner tubular electrode (18); controlling the distribution of the oxidizing fluid from the oxidizing fluid outlet based on the change in mass flow rate; or or measuring the pressure of the oxidizing fluid or the hydrocarbon fluid prior to dispensing into the inner tubular electrode (18); and controlling the dispensing of the oxidizing fluid from the oxidizing fluid outlet based on the change in pressure.

10. Hydrocarbon fluid, CO ２ and / or H ２ variably mixing O; The hydrocarbon fluid, CO ２ and / or H ２ The variable mixture of O is based on wear of at least one of the tubular electrodes (18, 20), or The hydrocarbon fluid, CO ２ and / or H ２ 10. The method of claim 9, wherein the variable mixture of O is based on the amount of solids on at least one of the tubular electrodes (18, 20).

11. 11. The method of claim 9 or 10, wherein the supply lance (22) is displaced axially relative to the inner tubular electrode (18) based on the change in mass flow rate or pressure.

12. distributing the oxidizing fluid through an outlet that is part of the supply lance, the supply lance comprising an inner pipe and an outer pipe at least partially surrounding the inner pipe; the method providing the step of passing the oxidizing fluid through the inner pipe and passing the hydrocarbon fluid through a space between the inner pipe and the outer pipe; or 12. The method of any one of steps 9 to 11, wherein the method further comprises passing the oxidizing fluid through a space between an inner tube and an outer tube of the supply lance.

13. the step of distributing the oxidizing fluid is performed through an outlet in the supply lance comprising a first outlet for the oxidizing fluid and a second outlet for the hydrocarbon fluid; or the step of distributing the oxidizing fluid is performed through an annular space between the inner tubular electrode and the supply lance, with the oxidizing fluid passing between an inner surface of the inner electrode and an outer periphery of the supply lance; or 12. The method of any one of steps 9 to 11, wherein the hydrocarbon fluid and the oxidizing fluid are distributed through a single or common tube of the feed lance either (a) alternately in time through the same tube, or (b) mixed together.

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