Plasma Torch Assembly and Operation

Abstract

The plasma torch assembly includes a plurality of plasma torch apertures, each of which is adapted to receive a plasma torch. The plasma torch assembly also includes a working position for operation of the plasma torch, the working position being pressure sealed for high pressure operation of the plasma torch. The plasma torch assembly also includes means for moving each of the plasma torch apertures to the working position. In this manner, the plasma torch can be swapped in and out of the working position. A method of operating a plasma torch device including such a plasma torch assembly is also described.

Description

[Technical field]

[0001] The present invention relates to a plasma torch assembly and its operation, and in particular to a plasma torch assembly suitable for use in a reactor. [Background technology]

[0002] A plasma torch is a device that creates a plasma stream from a feed gas by the action of an electric arc between electrodes. Typically, this is a directed stream of plasma, and plasma torches are used for a variety of purposes, including cutting, welding, and gasifying waste materials.

[0003] One particular field of use for plasma torches, or plasma burners, is as a reactor for high temperature cracking. One process that uses such plasma burners is the Kvaerner process for cracking hydrocarbons to form carbon black and hydrogen. This is an endothermic reaction that occurs in the plasma burner at about 1600 degrees Celsius. The Kvaerner process reaction is:

number

[0004] Unlike most methods for forming hydrogen from hydrocarbons, carbon dioxide is not a by-product, so this may be a particularly clean way to form useful products from hydrocarbons such as methane, which are primarily treated as polluting waste gases. Although this is an attractive process for use in reactors, the high operating temperatures and pressures required, along with the limited life and maintenance needs of the plasma torches, make it difficult to operate plasma torch-based reactors without significant downtime. It would be desirable to address this issue in order to generate efficient reactor designs. Summary of the Invention

[0005] In a first aspect, the present invention provides a plasma torch assembly comprising a plurality of plasma torch apertures, each of the plasma torch apertures adapted to receive a plasma torch, a working position for operation of the plasma torch, the working position being pressure sealed for high pressure operation of the plasma torch, and a means for moving each of the plasma torch apertures to the working position.

[0006] In this manner, a plasma torch assembly can be provided that supports "hot swapping" between torches to minimize assembly downtime. If a torch needs to be taken out of service for maintenance or replacement, the plasma torch assembly can simply be reconditioned to move another torch, already prepared for operation, into the working position for use, e.g., by bringing it up to operating temperature.

[0007] In an embodiment, the plasma torch assembly may further include a feedthrough for providing input gas and electrical supplies to the plasma torch. The working position may then have a gas inlet connection and an electrical connection to the feedthrough. The gas inlet connection and the electrical connection to the feedthrough are pressure sealed since the plasma torch is configured to operate at high pressure.

[0008] Specific inputs and outlets may be provided to the feedthroughs for designated gases. These may be color coded or otherwise indicated graphically.

[0009] The plasma torch aperture may be disposed on the carousel, where the feedthrough may be provided on the longitudinal axis of the carousel. In a particular embodiment, there may be three plasma torch apertures disposed symmetrically about the longitudinal axis of the carousel.

[0010] The plasma torch assembly may further comprise means for locking the plasma torch aperture in the working position, which may also prevent effective operation of the plasma torch assembly without the plasma torch aperture in the working position.

[0011] In use, there may be multiple plasma torches, one positioned in each of the plasma torch apertures.

[0012] In a second aspect, there is provided a plasma torch reactor comprising the plasma torch assembly as set forth in the first aspect above, wherein the plasma torch assembly may be adapted such that after the plasma torch in the working position has been deactivated, the plasma torch is switchable to the working position for operation without substantial delay.

[0013] In a third aspect, a method of operating a plasma torch device is provided, the plasma torch device comprising a plasma torch assembly having a plurality of plasma torch apertures, each of the plasma torch apertures adapted to receive a plasma torch, one of the plasma torch apertures being in a working position for operation of the plasma torch, the working position being pressure sealed for high pressure operation of the plasma torch, a first plasma torch being disposed within the plasma torch aperture in the working position and a second plasma torch being disposed within another plasma torch aperture, the method including operating the first plasma torch, stopping operation of the first plasma torch, moving the plasma torch aperture in the plasma torch assembly such that the second plasma torch is in the working position, operating the second plasma torch, and cooling and removing the first plasma torch from the plasma torch device while the second plasma torch is operating.

[0014] This approach is particularly effective when the plasma torch device is installed in a plasma torch reactor, because the described hot swap process allows for effective continued use of the reactor even when the plasma torch needs to be replaced. This method may be used, for example, in a plasma torch reactor adapted to crack a hydrocarbon input gas into carbon and hydrogen.

[0015] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 shows a side view of a reactor according to an embodiment of the present invention. [Diagram 2] FIG. 1 shows a high level schematic diagram of the main functional elements of a reactor, according to an embodiment of the present invention. [Diagram 3] 1 shows a longitudinal cross-sectional view of a plasma torch from a reactor according to one embodiment of the present invention. [Figure 4] 4 shows a detail from the plasma torch of FIG. 3 showing additional elements of the anode and illustrating features that prevent carbon buildup. [Diagram 5] 4 shows the flow of reactive gases through the plasma torch of FIG. 3. [Figure 6A] 4 shows a side view and a cross-sectional view of a ring for a feed gas inlet for use in the plasma torch of FIG. 3. [Figure 6B] 4 shows a side view and a cross-sectional view of a ring for a feed gas inlet for use in the plasma torch of FIG. 3. [Figure 7] 1 illustrates a revolver system with a set of plasma torches and a feedstock system according to an embodiment of the present invention. [Figure 8] 8 illustrates a plasma torch in the process of removal from the revolver system of FIG. 7. [Figure 9A] 8 shows a gearing system for rotation of the revolver system of FIG. [Figure 9B]8 shows a gearing system for rotation of the revolver system of FIG. [Figure 10] 8 shows a feedstock system for use in the revolver of FIG. 7. [Figure 11] 1 illustrates an exemplary reaction process for a reactor system according to an embodiment of the present invention. [Figure 12] 12 illustrates a liquid metal pyrolysis reactor system powered by the plasma torch system of FIGS. 3-11 and including a housing for the plasma torch system. [Figure 13A] 13 illustrates a liquid metal circulation system of the reactor of FIG. 12 driven by a plasma torch. [Figure 13B] 13 illustrates a liquid metal circulation system of the reactor of FIG. 12 driven by a plasma torch. [Figure 14A] 13A and 13B provide different cross-sectional views of the liquid metal circulation system of FIG. [Figure 14B] 13A and 13B provide different cross-sectional views of the liquid metal circulation system of FIG. [Figure 15] 13 illustrates the liquid metal pyrolysis reactor of FIG. 12 in more detail. [Figure 16] 16 illustrates the feed system to the liquid metal pyrolysis reactor of FIG. 15 along with the carbon output. [Figure 17] 17 shows a feed system in the vortex chamber of the liquid metal pyrolysis reactor of FIG. 16. [Figure 18] 16 shows a vertical cross section through a portion of the liquid metal pyrolysis reactor of FIG. 15. [Figure 19] 1 shows a modified reaction flow for synthesis gas production. [Figure 20A] 2A-2C show different views of a second embodiment of a plasma torch for use in an embodiment of the present invention. [Figure 20B] 2A-2C show different views of a second embodiment of a plasma torch for use in an embodiment of the present invention. [Figure 21A] 11A-11C show different views of a third embodiment of a plasma torch for use in an embodiment of the present invention. [Figure 21B] 11A-11C show different views of a third embodiment of a plasma torch for use in an embodiment of the present invention. [Figure 22-1] FIG. 2 is a system diagram of a reactor system according to a further embodiment of the present invention. [Figure 22-2] FIG. 2 is a system diagram of a reactor system according to a further embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] General and specific embodiments of the invention are described below with reference to the drawings.

[0018] FIG. 1 provides a perspective view of a reactor according to an embodiment of the invention. The reactor 1 is formed as a pressure vessel 2 with an electrical input (not shown here, but FIG. 12 shows how this is integrated into the system) for powering the plasma torches, and a gas input 4 through which gaseous feedstock is introduced into the system. Each of these inputs is directed to a revolver assembly (not shown here, see FIGS. 7-9 and 12 for further details) that is adapted to fit into an assembly aperture 5, which houses a set of plasma torches and also provides gaseous feedstock to each plasma torch. The reactor shown here has multiple stages, with the plasma torches acting as the first reactor stage and the liquid metal reactor acting as a further reactor stage that consumes heat generated by the plasma torches. The reaction products include a heated gas, which in the main example considered below is hydrogen, and a heat exchanger uses the heated gas to bring the feedstock gas to the correct temperature for the reaction, effectively acting as a pre-reactor stage.

[0019] The reactor system is shown diagrammatically in FIG. 2. Gaseous input 11, e.g., a hydrocarbon such as methane, and additional hydrogen for cooling (although this may be recycled from the output products), are introduced to a plasma torch 12, which consumes the input feed gas providing a first set of output products such as carbon and hydrogen. These first output products pass as input 13 at high temperature to a liquid metal system 14, which then, in an embodiment, provides pyrolysis of further feed gas. Depending on the design, final output products 15, such as carbon, which may be extracted through the liquid metal or from the gaseous output, and hydrogen, which is output as a gas, are provided from the liquid metal reactor 14 after a separation process, and these final output products include the first output product from the plasma torch 12, and may be supplemented by further output products generated from pyrolysis in the liquid metal reactor 14. The pyrolysis reaction is endothermic, but there is enough heat present that the gaseous final output products are at a temperature significantly higher than desired for storage, so there is excess heat to be used. This heated gas output is then used by heat exchanger 16 to control the temperature of the feed gas for different stages of the reactor process. As noted further below, embodiments of the present invention may not require all of the features shown in the arrangement of Figure 2 to operate, and the arrangement of Figure 2 is a synergistic combination of a series of processes for particularly effective production of carbon and hydrogen from hydrocarbons such as methane. As noted further below, such processes may also be adapted to produce other output products, such as synthesis gas.

[0020] An embodiment of the plasma torch is shown in more detail in Figures 3-5. A longitudinal cross-section of the plasma torch 30 is provided in Figure 3. The plasma torch 30 is generally cylindrical and in the arrangement used in the embodiment of the invention it extends into a liquid metal circulation system 40 (discussed further below) where it injects directly into the liquid metal. The plasma torch has a central chamber 300 containing a cathode 31 and an anode 32. These can be any conductive material suitable for the conditions in the central chamber 300, carbon (graphite) can be used or any suitable metal or alloy, either homogeneous or with a suitable insert, for example copper with a hafnium insert is a possible option. Here, the cathode 31 is located towards the end of the plasma torch 30 away from the liquid metal reactor 39 and a ceramic cup-shaped end section 38 terminates the plasma torch. In alternative torch designs, the electrodes may be positioned in opposite directions, or an AC plasma torch may be used that only refers to the transmission of electrodes, rather than an anode and a cathode. The anode is generally cylindrical, but has a shaped inner surface 34 with a nozzle 35 and a diffusion section 36, which will be described in more detail below. A guard electrode 33 may be positioned between the cathode 31 and the anode 32, and again, those skilled in the art will appreciate that the electrode structure may be modified to achieve a desired electric field pattern within the plasma torch chamber, may include zero, one, or multiple intermediate electrodes, and multiple guard electrodes may be cascaded to help stabilize the spark for effective ignition or to prevent anode wear. A gas input 37 is provided to introduce gaseous feedstock into the reactor, and in the arrangement shown in FIG. 3, methane is introduced into the gas input 37 located at the guard electrode 33. As will be shown in more detail below, in different embodiments of the invention, different gas input locations are provided for different feedstock gases.While the following discussion is primarily directed to methane, it should be understood that other hydrocarbons may be used as well; for example, propane may be shipped in liquid form, but is readily vaporized due to reaction in the plasma torch reactor, and would therefore be another particularly suitable option for processing.

[0021] FIG. 4 illustrates one phenomenon in the use of the plasma torch 30 shown in FIG. 3 to decompose methane. In this reaction, methane decomposes into hydrogen gas and carbon at high temperatures through the action of the plasma torch spark, which may have a temperature of 6000 degrees Celsius, resulting in instantaneous decomposition. A practical problem is that this can result in carbon deposits 41 that clog the torch, which can significantly affect the efficiency of the process and result in significant downtime for maintenance. It would be desirable to prevent such carbon buildup and have both reaction products exit the plasma torch 30. One feature to achieve this is to protect the anode with a gas that inhibits buildup. This can be achieved by making the anode 32 porous, and the anode gas output 42 delivers gas (in this case hydrogen) through the anode to provide a protective curtain along the inside of the anode and inhibit carbon buildup. The gas is delivered at an angle to the anode so that it has a component of velocity towards the plasma torch output to achieve this protective curtain; alternatively, the component of velocity can be provided away from the plasma torch output, as this still provides a protective curtain to the electrode. In addition to providing a protective curtain, there can also be active erosion of the deposited carbon by hydrogen, which can react with the carbon in a reverse reaction back to methane, thus further eroding the deposited carbon. The hydrogen also serves to cool the anode, preventing it from being degraded. In addition to using a porous anode in this way, the cathode can also be made porous and cooled in a similar manner.

[0022] Further strategies are used to prevent carbon buildup: the anode shaping can also be arranged so that there are likely deposition points for carbon on the anode in the region of the spark gap with the operating torch, and the spark action can then further erode any carbon buildup.

[0023] Another feature that prevents carbon buildup is shown in FIG. 5, which illustrates the passage of gas through the plasma torch structure. Here, methane enters the plasma torch tangentially through the gas input 37 at the guard electrode, and this input methane moves towards the cathode following a generally spiral path. The gas input 37 here is provided through a ceramic ring 51, shown in more detail in FIGS. 6a and 6b. The ceramic ring 51 has galleries 52 for circulation of the input gas around the ring, allowing the input gas to pass through several channels 53 (four in the illustrated design) that deliver the input gas tangentially into the chamber, establishing both a spiral path for the output gas adjacent to the chamber wall, and also a vortex within the plasma torch chamber. This can be optimized taking into account the gas type, flow conditions, pressure, and temperature to achieve the desired flow pattern. The wall structure (particularly the wall roughness and geometry) encourages the outer spiral of gas to maintain its momentum and separate from the faster rotating inner spiral of gas, and the torch geometry forces the gas into an inner return spiral with a faster velocity and tighter inner circle. The gas adopts this tighter spiral as it travels between the cathode and the anode, and maintains it as it heats up, as it is broken down into carbon and hydrogen in the spark gap between the cathode and the anode. The formation of the plasma is rapid, typically taking less than a microsecond. Suitable tuning allows the gas to be tuned (by pressure, temperature, and density) to minimize the energy exchange between the spirals, similar to a tornado. This configuration already gives the output gas (in this case, hydrogen) a significant velocity towards the output of the plasma torch, preventing carbon condensation and deposition, as carbon forms in the center of the plasma torch chamber, not at the walls. Plasma contains energy-balanced ions and electrons in near thermal equilibrium, molecules are primarily broken down into atoms, and under the operating conditions of temperature and pressure in the plasma torch, the stable state of carbon exists as a gas, reducing the likelihood of carbon deposition. Plasma torch designs are generally arranged to promote reaction in the center of the chamber and suppress reaction at the walls, such that reaction products are preferentially driven from the plasma torch to the liquid metal reactor.The outer spiral cools and insulates the walls while preventing atomic carbon in the inner spiral from condensing on the walls. Hydrogen from the reaction passes through a nozzle 35, which creates an increase in velocity and a decrease in pressure according to the Venturi effect. The gas is then output from the plasma torch 30 at high temperature (and kinetic energy) through a diffuser 36, and the plasma exits the torch at supersonic speed. The cumulative effect of these features is that the carbon is generally carried into the plasma torch output without significant accumulation of deposits on the walls of the anode. The role of the diffuser 36 is to match the pressure of the output of the plasma torch with the next reactor stage, as described in more detail below. As mentioned herein, in the embodiments described in detail herein, the next reactor stage is a liquid metal reactor, and the liquid metal herein may also be used to directly interact with the torch, as discussed further below.

[0024] Alternative plasma torch designs for use in embodiments of the present invention are shown in Figures 20a and 20b (for a second torch embodiment) and Figures 21a and 21b (for a third torch embodiment). Figures 20a and 20b show a plasma torch in which the gas input line 200 is in line with the torch chamber, but the cathode 2031 and anode 2032 are separated by a spacer 201, where the cathode 2031 forms a cup end, with a smaller diameter passage area 202 formed through the anode that opens into a larger diameter passage area 203 for the plasma torch output. Figures 21a and 21b show an alternative embodiment with a swirl plate 2151 providing gas inflow into the chamber at a closed end adjacent to the tubular form of the cathode 2131 (here made of molybdenum). The anode 2132 is stepped as before, having a smaller diameter passage region 212 and a larger diameter passage region 213, but in this case these regions are shorter relative to the plasma chamber and the larger diameter passage region 213 terminates in a diffuser 214 of linearly increasing diameter.

[0025] This arrangement in the torch described above allows operation at high temperatures (above 6000 degrees Celsius at the reaction point) and high pressures in the torch, with a very high throughput of gaseous feedstock. With a power input of 200 kW to the plasma torch, an operating temperature in the torch chamber of 6000 degrees Celsius at the reaction point, and a pressure of 50 bar, approximately 72 kg / hour of methane can be processed using this design. The voltage across the electrodes is typically 150V to 600V, typically about 250V, and the operating current is 100A to 500A, typically about 200A. The feed gas can be preheated by using a heat exchanger, utilizing the heat released in the pyrolysis reaction (see further discussion below), while the hydrogen used to cool the anode is provided at a lower temperature.

[0026] High pressure operation of the plasma torch is common to the embodiments of the invention described herein, and the reaction system is typically contained within a pressure vessel, as shown in Figure 1. However, effective reactions can be achieved at a variety of pressure regimes, and the systems described herein are particularly suitable for operation at 50 barg (50 bars above atmospheric pressure), but are distinct from conventional approaches to the use of plasma torches in connection with pyrolysis by high pressure operation, in that use of the system at lower, but still high pressures (20 barg, 10 barg, or even 1 barg) allows for more efficient operation than temperatures operating at atmospheric pressure. As noted further below, operation at lower temperatures and with lower power torches is also possible (this is discussed further below with respect to Figure 22).

[0027] 7-10 illustrate a system for mounting a plasma torch and providing gaseous feedstock and power to the plasma torch in an embodiment of the invention.

[0028] One potential problem with this type of reactor design is that if the plasma torch needs to be maintained, the reactor can lose significant efficiency due to the long cycle times that require the plasma torch to be shut down. This is because the torch needs to be brought down to a much lower temperature and pressure for maintenance, and then brought back up to temperature and pressure to operate again. In an embodiment of the invention, the approach taken is to use multiple torches for each "torch position" in the reactor, one of the plasma torches is in the active position and ready to operate, and the other plasma torches are in other positions that can be removed or prepared for operation without affecting the actual operating torch. This approach can be effectively combined with an efficient system for providing power and gaseous feedstock to the plasma torches.

[0029] FIG. 7 shows one embodiment of this multiple torch approach, in which three torches 71, 72, 73 are mounted on a carousel or revolver 70. The revolver 70 can rotate about a longitudinal axis, but after rotation is locked in one of three positions in an active position or active bay where one of the three torches operates in the reactor. A feed-through system 74 is provided along the axis of the revolver 70, which is configured to provide gaseous feedstock and power to the plasma torch in the active position. The other two plasma torches are not in the active position, and they can be prepared for use or for extraction, for example, one of the two positions can be a "ready" position (or loading bay) where the torches reach operating temperature, and the other of the two positions can be a "cool-down" position (or cooling bay) where the previously active torches have cooled and are ready for removal for maintenance.

[0030] Figure 8 shows the plasma torch fitting into the torch positions in the revolver. The three torch positions are arranged symmetrically around the axis of the revolver, and the plasma torch slides in from the side away from the reactor until it is provided with a suitable pressure seal and locked into place so that pressure in the plasma torch chamber can be maintained as it is rotated into the active bay.

[0031] Figures 9A and 9B show a gear system 91 by which the bay of the revolver can be rotated between three available positions, although any suitable gear system can be used. A locking mechanism is provided so that the bay can only be locked in a specified position, and in the case of three bays this includes three possible locking positions. Figure 9B shows two ways in which this can be done. A pin 93 on the revolver cap can be used to penetrate the revolver core and lock the revolver in place. Alternatively, one of the gears, for example gear 92 of the stepper motor connection, can be locked in place with motor control (each of the gear shafts can be locked in this way if desired).

[0032] FIG. 10 illustrates a feedthrough system for use with the revolvers shown in FIGS. 7-9. A feedthrough system 74 is provided for each revolver to provide electrical and gaseous inputs to the torch in the active bay; inputs may also be provided to other bays (e.g., cooling gas to the cooling bay) if required, but generally the feedthrough system is configured to have inputs only to the active bay for use by the torch in the working position. In contrast to the torch, the feedthrough system employs a fixed configuration for the bays such that the correct inputs are provided to the active bay regardless of which torch is located in the active bay at any given time. Using this approach, specific input locations can be specified for specific input gases. In some cases this may be generally independent of the reaction in the plasma torch (e.g., cooler hydrogen may be input to cool the anode in several different reactions), but in other cases a specific gaseous input may be provided to enter the plasma torch at a specific location 75 for a specific reaction, and multiple gas inputs 37 (see FIG. 3) in the plasma torch may alternate between these supply outputs 75. The feed-through system can thus be coded (e.g., color coded) for a particular feed gas and a particular reaction. In FIG. 10, the gaseous inputs are shown, but the electrical connections are not. However, ceramic insulators 76 are shown separating the connections on the torch, particularly the electrical connections. With respect to the torch, this arrangement needs to be provided with an effective pressure seal to allow a pressure of 50 bar to be maintained within the plasma torch chamber during use. Although different approaches to the construction of a suitable feed system can be taken, the approach shown here uses a series of aligned disks, in this case metal disks 77 separated by ceramic insulating disks 78.

[0033] The feedstock system is described above with respect to only inputs, but may also be used for outputs. For example, if there is recycle (such as hydrogen that is produced as an output but is also used as a cooling gas), the recycle system may use both inputs and outputs through the feedstock system.

[0034] Note that different torches may in fact be used for different reactions, for example a torch may be designed with a feed input location optimized for methane and another torch may be designed with a different input location optimized for a different feed gas. These different input locations may be aligned with different locations on the feed system in such a way that only the correct input gas and torch combination may be used. It may also be possible to reconfigure the feed system so that the same feed gas can be fed to different locations for different torches (or different reactions), which may be accomplished by adding valves to the feed system with a set of valve positions preconfigured for a particular arrangement.

[0035] Before describing the other elements of the reactor, the overall reaction flow is described with reference to Figure 11. This reaction flow is specific to the cracking and pyrolysis of methane, but is used more generally herein to illustrate the different reaction processes that occur in different parts of the composite reactor. For example, other hydrocarbons, such as propane, can be used as feedstock hydrocarbons rather than methane in the plasma torch reactor as well as in the liquid metal reactor.

[0036] Two inputs to the system are shown: electricity 1101 and a hydrocarbon (in this case, methane) 1102. Two outputs are shown: hydrogen 1103 (although it should be noted that for other reactions, other output gases may be provided as well or instead, and that a portion of the hydrogen produced is recycled for use in the reaction process) and carbon black 1104.

[0037] Both inputs are provided to the plasma torch 1105, and in addition to power and the hydrocarbon feedstock, hydrogen is provided as an input. In the arrangement shown, a low temperature hydrogen input 1111 (here shown in the range of 200-400 degrees Celsius) is provided to the plasma torch 1105, for example, to cool the anode with the hot hydrocarbon 1112 (here shown at about 700 degrees Celsius) used as the reaction feedstock, and also to maintain the temperature and pressure of the reaction chamber and promote the flow of material through the plasma torch. As the plasma torch consumes electrical energy and produces a high temperature output, this is partially consumed by the pyrolysis reaction in the second reactor 1122, from which the heated output gas can be used in a heat exchanger 1121 to circulate the hydrocarbon feedstock, increasing the temperature from the low temperature hydrocarbon 1113 at about 200 degrees Celsius to the hot hydrocarbon 1112 at the plasma torch reaction temperature of about 700 degrees Celsius, the heat exchanger 1121 can also supply hydrogen at a cooler temperature to the plasma torch. This heat exchanger 1121 therefore effectively acts as the first reactor process, absorbing the heat of the finishing process and using it to bring the gases to the correct temperature required for the reaction stage.

[0038] The plasma torch 1105 itself acts as a second reactor 1122, providing hot hydrogen and (mainly) gasified carbon as output 1114. The plasma torch 1105 through its reaction products operates in the next reactor stage, which is the liquid metal pyrolysis reactor 1123. The plasma torch 1105 provides heat for this reaction, heating the metal (here lead) to reaction temperature and also provides rotation for the lead, allowing carbon to be extracted in the center of the reactor. Hotter hydrocarbons 1115 are provided from the heat exchanger 1121 as feedstock for the liquid metal pyrolysis reactor 1123. The hydrogen output 1116 provided at very high temperature (approximately 1200 degrees Celsius) from the exothermic reaction in the pyrolysis reactor is returned to the heat exchanger 1121 and partially recycled to the plasma torch 1105, while being provided mainly in the hydrogen gas output 1104 (at a lower temperature).

[0039] The liquid metal pyrolysis reactor is shown in more detail in Figures 12-18. Figure 12 illustrates the main elements of the reactor assembly. The torch attachment 121 is oriented in a liquid metal racetrack 122 that feeds into the main reactor volume 123. There is also a gas input 124 to the main reactor volume 123 that contains a vortex chamber 125. Liquid (molten) metal is delivered into the vortex chamber 125 to impart rotation to the liquid metal column, allowing the liquid metal to both initiate the pyrolysis reaction in the input gas and to act as a centrifuge and separate the reaction products towards the center of the rotating column. Carbon can then be extracted from the base of the reactor at the carbon output 126. Hydrogen rises from the liquid metal and is released from the top of the reactor through the hydrogen output 127. The reaction is carried out at high temperature and pressure (typically 800-1000 degrees Celsius and 50 bar).

[0040] This function may be usefully combined with that of a plasma torch even if the liquid metal system is not itself a reactor, in which case it acts only as a separator to separate the reaction products from the plasma torch powered by the energy of the plasma torch output. However, this leaves behind significant excess heat, and it has been found that making the liquid metal system itself a reactor used for the endothermic pyrolysis of further hydrocarbons leads to a particularly effective reactor system.

[0041] 13A and 13B show the plasma torch attachment and the liquid metal racetrack from different angles, and 14A and 14B show different cross-sectional views of these elements. As the liquid metal cools, it leaves the reaction chamber, the reaction products are separated, and then it passes through the liquid metal racetrack 122 through the elbow joint 128 towards the plasma torch attachment 121, where the plasma torch output is injected into the liquid metal. This heats the liquid metal to a temperature sufficient to initiate a pyrolysis reaction with hydrocarbons such as methane, and also carries the reaction products of the plasma torch reaction to the liquid metal reactor so that they can be collected from the system (methane passing from the plasma torch jet into the liquid metal can also be pyrolyzed at this point). The heated metal passes along the remainder of the liquid metal racetrack and enters the liquid metal reactor chamber from the bottom. The components of the racetrack structure must consequently withstand the high temperatures from the heated liquid metal, and they must also be adapted for expansion from the significant difference between the temperature during and outside the reaction process. The joint may be protected, for example, by the use of a molybdenum sleeve 141, as shown in FIG. 14B.

[0042] The plasma torch is designed to efficiently inject into the liquid metal racetrack 122, and in particular the plasma torch diffuser is designed to pressure match the outside of the torch. This has the advantage of supporting linear flow rather than turbulent flow within the liquid metal racetrack. The liquid metal may be made to swirl or swirl which acts to stabilize the plasma jet. The reaction products from the plasma torch, in the example shown, hydrogen and carbon, are carried into the liquid metal for subsequent separation in and output from the liquid metal reactor, as described below.

[0043] The liquid metal system can also serve to purge the output of the plasma torch reactor from impurities, for example, ethylene can be produced as a by-product, but then cracked again in the liquid metal system.

[0044] The liquid metal from the liquid metal system may have other functions. For example, the diffuser of the plasma torch may extend far enough into the liquid metal racetrack so that the liquid metal acts to clean the diffuser and prevent carbon buildup there; in embodiments, the diffuser section may be partially porous to support the flow of liquid metal. If desired, the liquid metal from the racetrack may even be driven to flood the plasma torch, rapidly quenching the reaction and stopping its operation. Thus, the liquid metal may be used to flood and thus clean the porous anode (and cathode, if used) structure.

[0045] This has implications for the operation of the system during shutdown and startup. When the plasma torch is stopped, some backfilling of the plasma torch structure from the liquid metal racetrack can be expected, and liquid metal may enter the torch chamber and solidify (depending on the metal choice) as the torch cools. If a porous electrode is used, the electrode, or at least the electrode closest to the torch aperture, may be flooded with liquid metal. This can be used beneficially for effective operation of the torch and to extend its working life. The electrode may be directly replenished with solidified metal, which may compensate for erosion during use. Restarting the plasma torch is usually accomplished using a high voltage pulse, which typically would have a significant aging effect on the electrode and torch structure in general. If liquid metal enters the torch chamber, especially if it forms a solid metal plug, the effect of starting the torch is significant softening. Such a solid metal plug typically forms the link between the electrodes of the plasma torch, and therefore the high voltage pulse typically results in a high current (perhaps 200A) passing through the plug, heating and melting it very quickly; the combination of plug melting and supply of feed gas to the torch results in rapid removal of the metal plug, while also providing a soft start to the plasma torch, reducing the aging effects of power cycling of the plasma torch; the result is a more effective autoignition process assisted by the liquid metal system. To make the release of the plug faster, this can be stimulated by injecting gas behind the plug, or by applying a vacuum in front of the plug to pressure it forward into the liquid metal system. Mechanical systems for engaging and ejecting the plug are also possible.

[0046] Lead, or mixtures containing lead, may be used as the liquid metal in the liquid metal system. Lead is a suitable choice because it is liquid at the reaction temperature without having a high vapor pressure and poses less toxicity problems than most other suitable metals. Gallium is also another possible choice, as is bismuth. One alloy used in an embodiment of the system is WR58, which contains bismuth and lead, available from William Rowland Ltd. The term "liquid metal" is used throughout this specification, but in embodiments, the circulating liquid does not have to be a metal itself, provided that it is liquid at the reactor temperature and supports the separation of the reaction products (supports further pyrolysis if acting as a reactor), but does not itself have further chemical reactions with the feed gas or pyrolysis reaction products. Some salts also have suitable properties. As mentioned above, if a cooling plug is used for the torch to self-ignite, the circulating liquid needs to become solid and somewhat conductive when the reactor gets cold.

[0047] As mentioned above, the liquid metal system is designed here to act not only as a separator but also as a reactor. Figure 15 provides a diagram of the vortex chamber 125 that forms the reaction chamber for the liquid metal pyrolysis reactor. The heated liquid metal is passed through this chamber from below together with the input gas, and the circulation in the vortex chamber 125 leads to a separation to the center of the circulating liquid metal column, with the reaction products separated by centrifugal action, carbon and hydrogen are first collected in a hat structure 151 at the top of the reactor. This can be used to collect clean hydrogen, which is the only gas at this point and can simply be released through a float valve. A liquid salt structure can be provided for the lead and carbon mixture to permeate in this structure, which separates the carbon from the lead, the process is completed by gravity, and the lighter carbon floats above both the heavier lead and the salt. This allows the carbon to be separated by dropping it through a chute in the central area of ​​the chamber. The base plate 152 below the vortex chamber 125 has through holes for gaseous input. The cooling metal exits through perforations in the side of the swirl chamber 125 and passes down through the base plate 152 where it circulates over the liquid metal racetracks shown in FIGS.

[0048] Further details of the vortex chamber 125 are shown in Figures 16-18.

[0049] Figure 16 shows the bottom of the liquid metal reactor vessel below the swirl chamber 125 where the reaction takes place. Hot metal heated from the plasma torch enters from below through metal inlet 161, along with reactant gases entering through gas inlet 162. Carbon is output through the bottom of the reactor at carbon output 163. Hydrogen is circulated down through the base plate 152 of the swirl chamber 125 for subsequent circulation and collection above the swirl chamber.

[0050] FIG. 17 shows the area above the base plate 152 of the vortex chamber 125. Liquid metal is input tangentially into the liquid metal column through elbow 171, which provides rotation to the liquid metal column so as to act as a centrifuge. Also shown in FIG. 17 is a permeate inlet 172 for further feed gas, in this case methane for pyrolysis. The permeate inlet 172 is now located just before the liquid metal from elbow 171, so that further feed gas permeates directly into the liquid metal stream for pyrolysis. This process can be further developed by using a suitable catalyst, for example nickel balls (not shown here) can be included in the vortex chamber 125, which extend the flow path of the injected methane and promote the reaction as well as clean the hydrogen of impurities. Nickel balls are an attractive option as they float on the lead (when used as the liquid metal) but sink in the salt, effectively trapping it in a separation layer. The connections through the base plate 152 are shown in more detail in the cross-sectional view of FIG. 18.

[0051] As described above, a heat exchanger system is provided that allows the heat generated in the reaction to be used to provide an input gas at the correct temperature for use in the reaction. The hydrogen output from the liquid metal reactor, which is at a high temperature (1200 degrees Celsius), is used to heat methane feedstock to feed both the plasma torch and the liquid metal pyrolysis reactor. A portion of this hydrogen output is cooled to a much lower temperature (e.g., 200-400 degrees Celsius) and used to cool the anode and cathode of the plasma torch, as described above.

[0052] Although the reactor embodiment described herein is adapted for the pyrolysis of methane, this reactor configuration can be used for several reactions. As mentioned in the discussion of the feedstock system, for example, various input gases can be used in different reactions, with selected gas input locations to achieve the correct circulation of gas throughout the plasma torch. Similarly, different inputs can be provided to the liquid metal reactor, rather than just methane, to achieve different reactions.

[0053] Although the reactor process described in the above examples is directed to the production of hydrogen and carbon from methane, the reactor structure used here can be adapted to other reaction processes. As shown in FIG. 19, after methane or another hydrocarbon is decomposed into hydrogen and carbon (191), either directly in a plasma torch or through subsequent pyrolysis in a liquid metal reactor, and separation (192) occurs in the liquid metal separator, synthesis gas (syngas or synthesis gas is a mixture of mainly hydrogen and carbon monoxide) can be produced (193) by adding carbon dioxide to the carbon stream as an additional input gas. Carbon dioxide is reduced by carbon to form carbon monoxide, which can be collected with hydrogen above the swirl chamber and extracted as synthesis gas. Using this approach, carbon monoxide is released outside the swirl chamber and permeates for collection at the top of the vessel. At that time there can be both hydrogen (from the hat above the swirl chamber) and syngas (from the top of the entire liquid metal reactor structure) outputs.

[0054] In the approach generally described above, heat from the plasma torch is used by an endothermic reaction, in the main example, methane pyrolysis, to establish an efficient hybrid reactor. While this is an effective use of the heat provided by the plasma torch, if there are alternative ways of using this heat, the liquid metal system need not be used as a reactor. In other embodiments, for example, the liquid metal system may be used essentially for separation of the hydrogen and carbon produced by the plasma torch reactor, in which case feeding of methane to the liquid metal system is not required.

[0055] While the majority of the heat from the plasma torch reactor is used by the endothermic methane pyrolysis reaction, a significant proportion of the heat is removed from the reactor with the hydrogen output provided at high temperatures (typically 1200 degrees Celsius). In the arrangement shown here, this is used to bring the feed gases, i.e. methane for the plasma torch and methane for the liquid metal reactor, up to reaction temperature in a conventional heat exchanger. As described above, a further output from the heat exchanger is preferably a low temperature hydrogen stream for electrode cooling. However, if there is an effective alternative use for this output heat, this heat exchanger need not be used and other approaches can be employed to bring the gas up to the appropriate reaction temperature, a hydrogen source at ambient temperature or another side reaction temperature can be used.

[0056] FIG. 22 is a system diagram of a reactor system according to a further embodiment of the invention. In this design, the operating temperature is lower, a liquid metal system transports the products from the torch for separation rather than providing an additional reactor stage, and no heat exchanger stage is used. This reactor system is designed for lower temperature operation (obviously the local temperature at the plasma spark would be significantly higher, but here for a typical temperature of 250° C. with a 200-300° C. operating range throughout the reactor), but also for high pressure operation (with a typical reactor pressure of 50 barg, and an operating range of 40-60 barg). In this arrangement, the hydrocarbon feed 2202, preferably methane, is provided at ambient temperature and is preheated to 80° C. before being provided to the plasma torch 2205. In this embodiment, a single plasma torch is used (there is no revolver). The system is designed for a throughput of 18 kg / hr, with the entire system operating around 50 barg. The plasma torch 2205 operates at 50 kW (maximum 800 VDC, 300 amps). The reaction products of hydrogen and carbon black are ejected into a liquid metal handling system (which may also be referred to as a quench reactor, which is equivalent to the "plasma reactor" in the arrangement of FIG. 11), in this case using WR58 alloy heated to at least 80° C., the liquid metal system 2214 being fed from a metal supply tank 2214a. The reaction products are extracted from the liquid metal handling system 2214 by an extraction system 2230, here comprising first and second cyclones 2231, 2232 and a pulse jet filter 2233 (with an alternative pulse jet filter that can be switched). Each of these systems deposits the carbon black as a solid while allowing the gas, which mainly contains hydrogen, to proceed to the next stage. In the arrangement shown, the first cyclone 2231 receives the flow from the reactor at 18 kg / hr, 48 barg and 200° C. A separator is required at this point as the solids deposited by the first cyclone 2231 are carbon black with some metal alloys.The second cyclone 2232 accepts an input at 17.66 kg / hr, 47 barg, and 190° C. and outputs gas at 4.96 kg / hr, 46 barg, and 185° C. while releasing more carbon black. This output is received by a pulse jet filter 2233 releasing more carbon black and outputs hydrogen gas which is cooled to ambient temperature in a cooler 2234. The carbon black is deposited in an intermediate bulk vessel 2235 and the arrangement shown optimizes deposition into the second and third bulk vessels such that most of the carbon black produced does not require separation from the liquid metal.

[0057] Further embodiments can be produced with higher operating temperatures up to the high temperature operation (which may be 1200° C.) of the arrangement of Figure 11. Such designs may use features of either or both of the arrangements of Figures 11 and 22 as appropriate, for example an intermediate design may have a heat exchanger similar to that shown in Figure 11 while using a separation arrangement of the type shown in Figure 22.

[0058] As one skilled in the art would understand, other embodiments of the plasma torch and reactor technologies and reaction processes described herein may be provided within the scope of the claims provided without being limited to specific features that are described in the embodiments but are not required by the claims.

Claims

1. 1. A plasma torch assembly comprising: a plurality of plasma torch apertures, each of the plasma torch apertures adapted to receive a plasma torch; a work position for operation of the plasma torch, the work position being pressure sealed for high pressure operation of the plasma torch; and means for moving each of said plasma torch apertures to said working position.

2. The plasma torch assembly of claim 1 further comprising a feedthrough for providing input gas and electrical supplies to the plasma torch.

3. The plasma torch assembly of claim 2 , wherein the work location has a gas inlet connection and an electrical connection to the feedthrough.

4. 3. The plasma torch assembly of claim 2, wherein specific inputs and outlets are provided at said feedthroughs for designated gases.

5. The plasma torch assembly of claim 1 , wherein the plasma torch aperture is disposed on a carousel.

6. A plasma torch assembly as described in claim 5, further comprising a feedthrough for providing input gas and electrical supply to the plasma torch, the feedthrough being provided on the longitudinal axis of the carousel.

7. 6. The plasma torch assembly of claim 5, wherein there are three plasma torch apertures symmetrically disposed about the longitudinal axis of the carousel.

8. The plasma torch assembly of claim 1 further comprising means for locking the plasma torch aperture in said working position.

9. 9. The plasma torch assembly of claim 8, wherein said means for locking a plasma torch aperture in said working position prevents operation of said plasma torch assembly without a plasma torch aperture in said working position.

10. The plasma torch assembly of claim 1 , further comprising a plurality of plasma torches, one disposed in each of the plasma torch apertures.

11. The plasma torch assembly of claim 1 , wherein the working location is pressure sealed for operation at 40 barg to 60 barg.

12. A plasma torch reactor comprising the plasma torch assembly according to any one of claims 1 to 11.

13. 13. The plasma torch reactor of claim 12, wherein the plasma torch assembly is adapted such that after the plasma torch in the working position is deactivated, the plasma torch can be switched to the working position for operation without substantial delay.

14. 1. A method of operating a plasma torch device, the plasma torch device comprising: a plasma torch assembly having a plurality of plasma torch apertures, each of the plasma torch apertures adapted to receive a plasma torch, one of the plasma torch apertures being in a working position for operation of the plasma torch, the working position being pressure sealed for high pressure operation, a first plasma torch being disposed within the plasma torch aperture at the working position and a second plasma torch being disposed within another plasma torch aperture, the method comprising: operating the first plasma torch; Stopping operation of the first plasma torch; moving the plasma torch aperture in the plasma torch assembly so that the second plasma torch is in the working position; operating the second plasma torch; and cooling and removing the first plasma torch from the plasma torch device while the second plasma torch is operating.

15. The method of claim 14 , wherein the plasma torch device is provided within a plasma torch reactor.

16. 16. The method of claim 15, wherein the plasma torch reactor is adapted to decompose a hydrocarbon input gas into carbon and hydrogen.

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