Plasma torch reactor and reaction method

Abstract

The chemical reactor comprises a plasma torch reactor and a liquid metal system. The plasma torch reactor receives at least one feed gas and provides a plasma torch output including reaction products. The liquid metal system receives the plasma torch output of the plasma torch reactor, separates the reaction products received from the plasma torch reactor, and provides them as output products to the chemical reactor. A method of cracking hydrocarbons provided as input to a chemical reactor comprising a plasma torch reactor and a liquid torch system is also described.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present disclosure relates specifically to the use of a plasma torch as a reactor for decomposing chemicals such as hydrocarbons. [Background technology]

[0002] A plasma torch is a device that generates 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:

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[0004] Unlike most methods for forming hydrogen from hydrocarbons, carbon dioxide is not a by-product, so this can be a particularly clean method for forming useful products from hydrocarbons such as methane, which are primarily treated as polluted waste gases. It would be desirable to be able to develop reactors and reaction processes that can be particularly effective in carrying out reaction processes such as the Kvaerner process through the use of plasma torches. Summary of the Invention

[0005] In a first aspect, the present invention provides a chemical reactor comprising: a plasma torch reactor adapted to receive at least one hydrocarbon feedstock gas and to provide a plasma torch output comprising hydrogen and carbon as reaction products from the plasma torch reactor; a non-reactive liquid system adapted to receive the plasma torch output of the plasma torch reactor, the non-reactive liquid system adapted to transfer reaction products away from the plasma torch reactor and to provide the reaction products as output products to the chemical reactor; and a pressure vessel containing the chemical reactor, the chemical reactor adapted for operation at substantially above ambient pressure.

[0006] Using this approach, plasma torches can be used very effectively as reactors for the cracking of hydrocarbons, with a non-reactive liquid system used to carry off (and in some embodiments, separate) the reaction products, which can work particularly well if one reaction product can be removed as a solid and another as a gas. Such chemical reactors can be adapted for operation above 10 barg, preferably above 30 barg, and in the embodiments described in detail herein, for operation in the range of 40 to 60 barg.

[0007] In an embodiment, the chemical reactor is adapted to be positioned so that the output of the plasma torch reactor imparts momentum to the liquid in the non-reactive liquid system. The non-reactive liquid system may also be adapted so that the output product is separated from the liquid metal by centrifugal action. In this way, the plasma jet generated as the plasma torch output has multiple purposes: it provides the reaction product and also provides energy (both heat and momentum) to drive the liquid system to act as a centrifuge. Using this approach, liquid salt may be used to remove the non-reactive liquid, such as the liquid metal, from the output product. The solid output product may then be extracted below the non-reactive liquid system by gravity.

[0008] In some embodiments, the liquid metal system is adapted for extraction of a gaseous output product from the top of the non-reactive liquid system. For example, a float valve is used for extraction of the gaseous output product. In other embodiments, one or more cyclones may be used for separation of a solid output product, such as carbon, from the gaseous output product. Because the solid output product may contain both carbon and non-reactive liquid in the first separation stage, further separation of the non-gaseous product may be required. In this arrangement, one or more cyclones may be placed in series with at least one pulse jet filter. In such cases, the solid output product may be deposited in one or more intermediate bulk vessels.

[0009] A further advantage of this approach is that the non-reactive liquid system can be adapted to convert contaminants from the plasma torch output. More generally, the non-reactive liquid system itself can be a liquid system reactor, and additional feed gas can be provided to the liquid system reactor. The plasma torch can then be adapted to heat the non-reactive liquid to a reaction temperature for the additional feed gas. The liquid system reactor can be adapted for endothermic reactions, thereby reducing the heat output of the chemical reactor from the heat output generated by the plasma torch reactor, and thereby providing a particularly effective way to use that heat.

[0010] The chemical reactor may also include a heat exchanger for using heat from the gaseous output product to raise the feed gas to the reaction temperature.

[0011] Such plasma torch reactors may be particularly adapted for the decomposition of methane, as this is a particularly desirable process; other hydrocarbons, such as propane, which are easily transportable and capable of efficient reaction, may also be used. When the non-reactive liquid system is itself a reactor, the additional feed gas supplied to the non-reactive liquid system may also contain hydrocarbons. Other reaction types are possible in non-reactive liquid systems to provide different outputs; for example, the additional feed gas may further contain carbon dioxide, which can react with carbon to form carbon monoxide, leading to the production of synthesis gas as an output product. The chemical reactor may be configured to provide both hydrogen and synthesis gas as separate gaseous output products.

[0012] The plasma torch may be adapted to be partially flooded with non-reactive fluid from the non-reactive fluid system when the plasma torch is shut down, which may benefit the torch by cleaning it, but may also have additional advantages for certain non-reactive fluid options. In embodiments, the non-reactive liquid may be a liquid at the operating temperature for the reactor and a solid at ambient temperature. The non-reactive liquid may be a metal, metal alloy, or salt. In particular, the non-reactive liquid may be a conductive metal or metal alloy (e.g., containing lead and / or bismuth).

[0013] In a second aspect, the present invention provides a method of cracking hydrocarbons in a reaction process comprising providing hydrocarbons as input to a chemical reactor comprising a plasma torch reactor and a non-reactive liquid system disposed within a pressure vessel, the reaction process operating at substantially above atmospheric pressure, the plasma torch reactor receiving the hydrocarbons as a feed gas and providing a plasma torch output comprising carbon and hydrogen as reaction products, the non-reactive liquid system receiving the plasma torch output of the plasma torch reactor and transferring the reaction products away from the plasma torch reactor to provide the reaction products as output products from the chemical reactor.

[0014] This approach is particularly effective for the clean and efficient production of hydrogen and carbon from hydrocarbons such as methane. The reaction process may operate above 10 barg, preferably above 30 barg, and more preferably for operation in the range of 40 to 60 barg.

[0015] The output of the plasma torch reactor is arranged to impart momentum to the non-reactive liquid of the non-reactive liquid system. Using this approach, the solid reaction products can be separated from the non-reactive liquid by centrifugal action.

[0016] The non-reactive liquid system may also convert contaminants received from the plasma torch reactor along with the reaction products. More generally, the non-reactive liquid system may be a liquid system reactor, and additional feed gas may be provided to the liquid system reactor. Using this approach, the plasma torch may heat the liquid to a reaction temperature for the additional feed gas. A very efficient approach is for the liquid system reactor to be adapted for endothermic reactions, which may then reduce the heat output of the chemical reactor from the heat output generated by the plasma torch reactor and provide a particularly effective way to use that heat output.

[0017] In an embodiment, a heat exchanger may be used to raise the feed gas to the reaction temperature using heat from the gaseous output product.

[0018] The method is particularly suitable for the cracking of methane, but may be advantageously used with other suitable hydrocarbons, such as propane.

[0019] If the non-reactive liquid system is itself a reactor, the additional feed gas may also include hydrocarbons. The additional feed gas may also include carbon dioxide for reaction with carbon to form carbon monoxide; if this is done, synthesis gas is provided as an output product.

[0020] In embodiments, the non-reactive liquid may be a metal, metal alloy, or salt. In particular, it may be a metal or metal alloy adapted to be liquid at the reaction temperature and solid at ambient temperature. With such an arrangement, the method may further include at least partially submerging the electrode of the plasma torch with the non-reactive liquid when the plasma torch is turned off to form a conductive plug. The method may then further include starting the plasma torch with the conductive plug disposed within the submerged electrode of the plasma torch and draining the material of the conductive plug into the non-reactive liquid system. [Brief explanation of the drawings]

[0021] Embodiments of the present invention will now be described, by way of example, with reference to the accompanying figures. [Figure 1] FIG. 1 shows a side view of a reactor according to an embodiment of the present invention. [Figure 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. [Figure 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. [Figure 5] The flow of reactive gases through the plasma torch of FIG. 3 is shown. [Figure 6A] 4A and 4B show side and cross-sectional views, respectively, of a ring for a feed gas inlet for use in the plasma torch of FIG. 3. [Figure 6B] 4A and 4B show side and cross-sectional views, respectively, 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 shows the 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. 7; [Figure 9B] 8 shows a gearing system for rotation of the revolver system of FIG. 7; [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 the liquid metal circulation system of the reactor of FIG. 12 driven by a plasma torch. [Figure 13B] 13 illustrates the 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. [Figure 14B] 13A and 13B provide different cross-sectional views of the liquid metal circulation system. [Figure 15] 13 illustrates in more detail the liquid metal pyrolysis reactor of FIG. 12. [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 the 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] 10A-10C show different views of a second embodiment of a plasma torch for use in embodiments of the present invention. [Figure 20B] 10A-10C show different views of a second embodiment of a plasma torch for use in embodiments of the present invention. [Figure 21A]10A-10C show different views of a third embodiment of a plasma torch for use in embodiments of the present invention. [Figure 21B] 10A-10C show different views of a third embodiment of a plasma torch for use in embodiments 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 INVENTION

[0022] General and specific embodiments of the present invention are described below with reference to the drawings.

[0023] FIG. 1 provides a perspective view of a reactor according to an embodiment of the present 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. These inputs each direct to a revolver assembly (not shown here; see FIGS. 7-9 and 12 for further details) 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 a 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 primary example discussed 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.

[0024] The reactor system is shown schematically in FIG. 2. Gaseous input 11, e.g., a hydrocarbon such as methane, and additional hydrogen for cooling (which may be recycled from the output products), are introduced into plasma torch 12, which consumes the input feed gas to provide a first set of output products, such as carbon and hydrogen. These first output products pass to liquid metal system 14 as input 13 at elevated temperature, which then, in embodiments, provides further pyrolysis of the 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 liquid metal reactor 14 after a separation process. These final output products include the first output product from plasma torch 12 and may be supplemented by additional output products generated from pyrolysis in liquid metal reactor 14. The pyrolysis reaction is endothermic, but there is enough heat present that the gaseous final output products are at temperatures 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.

[0025] An embodiment of the plasma torch is shown in more detail in Figures 3-5. A longitudinal cross-section of a plasma torch 30 is provided in Figure 3. The plasma torch 30 is generally cylindrical, and in the arrangement used in embodiments of the present 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 toward 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, meaning only that the electrodes are conductive rather than anode and 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 anode 32; again, those skilled in the art will understand that the electrode configuration may be modified to achieve a desired electric field pattern within the plasma torch chamber, may include zero, one, or more intermediate electrodes, and multiple guard electrodes may be cascaded to aid in spark stabilization for effective ignition or to prevent anode wear. A gas input 37 is provided for introducing gaseous feedstock into the reactor; in the arrangement shown in FIG. 3, methane is introduced into the gas input 37 located at the guard electrode 33. As will be described in more detail below, in different embodiments of the present invention, different gas input locations are provided for different feedstock gases.While the following discussion will be primarily directed to methane, it should be understood that other hydrocarbons may be used as well; for example, propane may be transported in liquid form but will readily vaporize due to reaction in the plasma torch reactor, making it another particularly suitable option for processing.

[0026] 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 can have a temperature of 6,000 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 impact the efficiency of the process and result in significant downtime for maintenance. It would be desirable to prevent such carbon buildup and ensure that 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 having the anode gas output 42 deliver gas (in this case, hydrogen) through the anode to provide a protective curtain along the inside of the anode and inhibit carbon buildup. To achieve this protective curtain, the gas is delivered at an angle relative to the anode so that it has a velocity component toward the plasma torch output; alternatively, the velocity component can be provided away from the plasma torch output, while still providing 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 deteriorating. In addition to using a porous anode in this way, the cathode can also be made porous and cooled in a similar manner.

[0027] 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; the spark action can then further erode any carbon buildup.

[0028] 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 gas input 37 at the guard electrode, and this input methane follows a generally spiral path toward the cathode. Gas input 37 here is provided through a ceramic ring 51, shown in more detail in FIGS. 6a and 6b. Ceramic ring 51 has galleries 52 for circulation of 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 the chamber wall and a vortex within the plasma torch chamber. This can be optimized, taking into account 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, while 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 anode and maintains it as it heats up because it is broken down into carbon and hydrogen in the spark gap between the cathode and anode. Plasma formation is rapid, typically taking less than one microsecond. Suitable tuning of the gas allows it to be tuned (by pressure, temperature, and density) to minimize energy exchange between the spirals, similar to a tornado. This configuration already imparts significant velocity to the output gas (in this case, hydrogen) toward the plasma torch output, preventing carbon condensation and deposition because carbon forms in the center of the plasma torch chamber rather than 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 a 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, so that reaction products are preferentially driven from the plasma torch to the liquid metal reactor.The outer spiral cools and insulates the walls, preventing atomic carbon in the inner spiral from condensing on the walls. Hydrogen from the reaction passes through nozzle 35, resulting in an increase in velocity and a drop in pressure due to the Venturi effect. The gas then exits the plasma torch 30 at high temperature (and kinetic energy) through diffuser 36, and the plasma exits the torch at supersonic speed. The cumulative effect of these features is to transport carbon into the plasma torch output without significant buildup of deposits on the anode walls. The role of diffuser 36 is to match the pressure of the plasma torch output with the next reactor stage, as described in more detail below. As noted 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.

[0029] 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 aligned 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 inlet into the chamber at a closed end adjacent the tubular cathode 2131 (here made of molybdenum). The anode 2132 is stepped as before, with 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.

[0030] This arrangement in the torch described above allows for operation at high temperatures (above 6000°C at the reaction point) and high pressures in the torch, with very high throughput of gaseous feedstock. With a 200 kW power input to the plasma torch and an operating temperature of 6000°C in the torch chamber at the reaction point and a pressure of 50 bar, approximately 72 kg / hr of methane can be processed using this design. The voltage across the electrodes is typically 150 V to 600 V, typically about 250 V, and the operating current is 100 A to 500 A, typically about 200 A. The feedstock gas can be preheated 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.

[0031] High-pressure operation of plasma torches is common to the embodiments of the invention described herein, with the reaction system typically contained within a pressure vessel, as shown in FIG. 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 distinguish from conventional approaches to the use of plasma torches in connection with pyrolysis by high-pressure operation; 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 FIG. 22).

[0032] 7-10 illustrate a system for mounting a plasma torch and providing gaseous feedstock and power to the plasma torch in accordance with an embodiment of the present invention.

[0033] 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 must be brought down to a much lower temperature and pressure for maintenance and then brought back up to temperature and pressure in order to operate again. In embodiments of the present invention, the approach taken is to use multiple torches for each "torch position" in the reactor, with one of the plasma torches in the active position and ready to operate, and other plasma torches 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.

[0034] 7 illustrates one embodiment of this multiple torch approach, in which three torches 71, 72, and 73 are mounted on a carousel or revolver 70. The revolver 70 can rotate about its longitudinal axis, but after rotation, one of the three torches is locked in one of three positions, in an active position or active bay, where it operates within the reactor. A feedthrough system 74 is provided along the axis of the revolver 70 and 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; they can be prepared for use or 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 torch has cooled and is ready for removal for maintenance.

[0035] Figure 8 shows the plasma torch fitting into the torch position on 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 an appropriate pressure seal to maintain pressure in the plasma torch chamber and locked into place as it is rotated into the active bay.

[0036] Figures 9A and 9B show a gear system 91 by which the revolver bay can be rotated between three available positions; any suitable gear system can be used. A locking mechanism is provided so that the bay can only be locked in a specified position; in the case of three bays, this includes three possible locking positions. Figure 9B shows two ways this can be done. A pin 93 on the revolver cap can be used to pierce 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).

[0037] FIG. 10 shows a feedthrough system for use with the revolvers shown in FIGS. 7-9. A feedthrough system 74 is provided for each revolver, providing electrical and gaseous inputs to the torch in the active bay; these inputs may also be provided to other bays (e.g., cooling gas to the cooling bay) if needed, 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 adopts a fixed configuration for the bay so 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 designated 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, specific gaseous inputs may be provided to enter the plasma torch at specific locations 75 for specific reactions, and the multiple gas inputs 37 (see FIG. 3) in the plasma torch may alternate with these feed outputs 75. The feed-through system may thus be coded (e.g., color-coded) for specific feedstock gases and specific reactions. 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. While different approaches to constructing a suitable feedstock system can be taken, the approach shown here uses a series of aligned disks; in this case, these are metal disks 77 separated by ceramic insulating disks 78.

[0038] Although the feedstock system is described above with reference to only inputs, it may also be used for outputs. For example, if there is recycle (e.g., as with hydrogen produced as an output but also used as a cooling gas), the recycle system may use both inputs and outputs through the feedstock system.

[0039] It should be noted here that different torches may in fact be used for different reactions; for example, a torch may be designed with a feedstock input location optimized for methane, and another torch may be designed with a different input location optimized for a different feedstock gas. These different input locations may be aligned with different locations on the feedstock system in such a way that only the correct input gas and torch combination can be used. Also, it may be possible to reconfigure the feedstock system so that the same feedstock gas can be supplied to different locations for different torches (or different reactions); this may be achieved by adding valves to the feedstock system with a set of valve positions preconfigured for a particular arrangement.

[0040] Before describing the other elements of the reactor, the overall reaction flow will be 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.

[0041] Two inputs to the system are shown: electricity 1101 and hydrocarbon (in this case, methane) 1102. Two outputs are shown: hydrogen 1103 (although it should be noted that other output gases or other reactions may be provided as well or instead, and that some of the hydrogen produced is recycled for use in the reaction process) and carbon black 1104.

[0042] Both inputs are provided to the plasma torch 1105; in addition to power and hydrocarbon feedstock, hydrogen is also provided as an input. In the arrangement shown, low-temperature hydrogen input 1111 (shown here in the 200-400°C range) is provided to the plasma torch 1105 to cool the anode, for example, with high-temperature hydrocarbon 1112 (shown here at approximately 700°C) used as the reaction feedstock, and to maintain the temperature and pressure of the reaction chamber and promote material flow through the plasma torch. As the plasma torch consumes electrical energy and produces a high-temperature output, this is partially consumed by a pyrolysis reaction in a second reactor 1122, from which the heated output gas can be used in a heat exchanger 1121 to circulate the hydrocarbon feedstock, raising the temperature from low-temperature hydrocarbon 1113 at approximately 200°C to high-temperature hydrocarbon 1112 at the plasma torch reaction temperature of approximately 700°C. 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.

[0043] The plasma torch 1105 itself acts as a second reactor 1122, providing hot hydrogen and (primarily) gasified carbon as output 1114. The plasma torch 1105, passing through its reaction products, operates in the next reactor stage, a 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 heat exchanger 1121 as feedstock for the liquid metal pyrolysis reactor 1123. The hydrogen output 1116, provided at very high temperatures (approximately 1200 degrees Celsius) from the exothermic reaction in the pyrolysis reactor, is returned to heat exchanger 1121 and partially recycled to the plasma torch 1105, while the hydrogen output 1116 (at a lower temperature) is primarily provided as hydrogen gas output 1104.

[0044] The liquid metal pyrolysis reactor is shown in more detail in Figures 12-18. Figure 12 illustrates the main elements of the reactor assembly. A torch mount 121 is oriented within a liquid metal racetrack 122 that feeds a main reactor volume 123. There is also a gas input 124 to the main reactor volume 123, which 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 within the input gas and act as a centrifuge, separating the reaction products toward the center of the rotating column. Carbon can then be extracted from the base of the reactor at carbon output 126. Hydrogen rises from the liquid metal and is released from the top of the reactor through hydrogen output 127. The reaction is carried out at high temperature and pressure (typically 800-1000 degrees Celsius and 50 bar).

[0045] This function can 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 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.

[0046] Figures 13A and 13B show the plasma torch mount and liquid metal racetrack from different angles, and Figures 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 toward the plasma torch mount 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, allowing them to 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. Components of the racetrack structure must be able to withstand the resulting high temperatures from the heated liquid metal, and they must also be adapted for expansion from the significant difference between temperatures during and outside the reaction process. The joint may be protected, for example, by the use of a molybdenum sleeve 141 as shown in Figure 14B.

[0047] 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 forced into a vortex or swirl, which acts to stabilize the plasma jet. 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.

[0048] 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.

[0049] The liquid metal from the liquid metal system can have other functions. For example, the diffuser of the plasma torch can 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 can be partially porous to support the flow of liquid metal. If desired, the liquid metal from the racetrack can even be driven to flood the plasma torch, rapidly quenching the reaction and stopping its operation. Thus, the liquid metal can be used to flood and thus clean the porous anode (and cathode, if used) structure.

[0050] This has implications for system operation during shutdown and startup. When the plasma torch is shut down, some backfilling of the plasma torch structure from the liquid metal racetrack can be expected; 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 beneficially used for effective operation of the torch and to extend its working life. The electrode can be directly replenished with solidified metal, which can compensate for erosion during use. Restarting a plasma torch is usually achieved using a high-voltage pulse, which typically has a significant aging effect on the electrode and torch structure as a whole. 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 200 A) passing through the plug, heating and melting it very quickly. The combination of plug melting and the supply of feed gas to the torch results in rapid removal of the metal plug while also providing a soft start for the plasma torch, reducing the aging effects of power cycling the plasma torch. The result is a more effective autoignition process assisted by the liquid metal system. To make plug release more rapid, this can be stimulated by injecting gas behind the plug or by applying a vacuum in front of the plug to force it forward into the liquid metal system. Mechanical systems for engaging and ejecting the plug are also possible.

[0051] Lead, or mixtures containing lead, can be used as the liquid metal in liquid metal systems. Lead is a suitable choice because it is liquid at reaction temperatures without a high vapor pressure and poses fewer toxicity issues than most other suitable metals. Gallium, as well as bismuth, is another possible choice. One alloy used in system embodiments is WR58, which contains bismuth and lead and is available from William Rowland Ltd. While the term "liquid metal" is used throughout this specification, in embodiments, the circulating liquid may not itself be a metal, provided that it is liquid at reactor temperatures and supports the separation of reaction products (supports further pyrolysis if acting as a reactor), but does not itself undergo further chemical reactions with the feed gas or pyrolysis reaction products. Many salts also have suitable properties. As mentioned above, if a cooling plug is used for torch autoignition, the circulating liquid must become solid and somewhat conductive when the reactor cools.

[0052] As mentioned above, the liquid metal system here is designed to function 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. Heated liquid metal is passed through this chamber from below along with the input gas. Circulation within the vortex chamber 125 leads to separation of the reaction products, along with the centrifugal separation, into the center of the circulating liquid metal column. Carbon and hydrogen are initially 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 through this structure. This separates the carbon from the lead, and the process is completed by gravity, with the lighter carbon floating above both the heavier lead and the salt. This allows the carbon to separate by dropping it down a chute in the central region of the chamber. The base plate 152 below the vortex chamber 125 has through-holes for gaseous input. The cooling metal exits through holes in the side of the swirl chamber 125 and passes down through the base plate 152 where it circulates on the liquid metal racetracks shown in FIGS.

[0053] Further details of the vortex chamber 125 are shown in Figures 16-18.

[0054] Figure 16 shows the lower part of the liquid metal reactor vessel below the swirl chamber 125 where the reaction occurs. Hot metal heated from the plasma torch enters from below through metal inlet 161, with reactant gas 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.

[0055] Figure 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, acting as a centrifuge. Also shown in Figure 17 is a permeate inlet 172 for additional feed gas, in this case methane for pyrolysis. The permeate inlet 172 is located just before the liquid metal entering from elbow 171, allowing the additional feed gas to permeate directly into the liquid metal stream for pyrolysis. This process can be further developed by using an appropriate catalyst; for example, nickel balls (not shown here) can be included in the vortex chamber 125 to extend the flow path of the injected methane, promoting the reaction and cleaning the impurity hydrogen. Nickel balls are an attractive option because they float on 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 Figure 18.

[0056] As described above, a heat exchanger system is provided that allows the heat generated in the reaction to be used to provide input gases at the correct temperature for use in the reaction. The hydrogen output from the liquid metal reactor, at a high temperature (1200°C), is used to heat methane feedstock for 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°C) and used to cool the anode and cathode of the plasma torch, as described above.

[0057] Although the reactor embodiment described herein is adapted for the pyrolysis of methane, this reactor configuration can be used for many 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 gases throughout the plasma torch. Similarly, different inputs can be provided to the liquid metal reactor, other than just methane, to achieve different reactions.

[0058] While 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 for other reaction processes. As shown in Figure 19, 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. After separation (192) occurs in the liquid metal separator, synthesis gas (syngas) (syngas or synthesis gas is a mixture of primarily hydrogen and carbon monoxide) can be produced by adding carbon dioxide (193) 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 vortex chamber and extracted as synthesis gas. Using this approach, carbon monoxide is released outside the vortex chamber and permeates for collection at the top of the vessel. At that time there can be an output of both hydrogen (from the hat above the swirl chamber) and syngas (from the top of the entire liquid metal reactor structure).

[0059] In the approach generally described above, heat from the plasma torch is used by an endothermic reaction, in the primary example, methane pyrolysis, to establish an efficient combined reactor. While this is an effective use of the heat provided by the plasma torch, if there are alternative ways to use this heat, a liquid metal system need not be used as a reactor. In other embodiments, for example, the liquid metal system may be used essentially for the separation of hydrogen and carbon produced by the plasma torch reactor, in which case a supply of methane to the liquid metal system is not required.

[0060] 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 hydrogen output provided at high temperatures (typically 1200°C). 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 temperatures in conventional heat exchangers. As described above, an additional 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 taken to raise the gases to the appropriate reaction temperature; a hydrogen source at ambient temperature or another side reaction temperature could be used.

[0061] 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 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 (here, for a normal temperature of 250°C with an operating range of 200-300°C throughout the reactor, although it is clear that local temperatures at the plasma spark will be significantly higher), but also for high pressure operation (with an operating range of 40-60 barg, with 50 barg as the normal reactor pressure). In this arrangement, the hydrocarbon feed 2202, preferably methane, is provided at ambient temperature and preheated to 80°C before being provided to the plasma torch 2205. In this embodiment, a single plasma torch is used (no revolver is present). The system is designed for a throughput of 18 kg / hr, with the entire system operating at around 50 barg. Plasma torch 2205 operates at 50 kW (maximum 800 VDC, 300 amps). The reaction products of hydrogen and carbon black are injected into a liquid metal handling system (sometimes called 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, liquid metal system 2214 supplied from metal supply tank 2214a. The reaction products are extracted from liquid metal handling system 2214 by extraction system 2230, here comprising first and second cyclones 2231, 2232 and 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 primarily 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. The solids deposited by the first cyclone 2231 are carbon black with some metal alloys, so a separator is needed at this point.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 pulse jet filter 2233 which releases more carbon black and outputs hydrogen gas which is cooled to ambient temperature in cooler 2234. The carbon black is deposited in intermediate bulk vessel 2235, the arrangement shown optimising deposition into the second and third bulk vessels so that the majority of the carbon black produced does not require separation from the liquid metal.

[0062] 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 Figure 11 and Figure 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.

[0063] As one skilled in the art will appreciate, other embodiments of the plasma torch and reactor technology and reaction processes described herein may be provided within the scope of the provided claims without being limited to specific features that are described in the embodiments but are not required by the claims.

Claims

1. 1. A chemical reactor comprising: a plasma torch reactor adapted to receive at least one hydrocarbon feed gas and provide a plasma torch output comprising hydrogen and carbon as reaction products from said plasma torch reactor; a non-reactive liquid system adapted to receive the plasma torch output of the plasma torch reactor, the non-reactive liquid system adapted to transfer the reaction products away from the plasma torch reactor and provide the reaction products as output products to the chemical reactor; a pressure vessel containing the chemical reactor, the chemical reactor being adapted for operation at substantially above ambient pressure.

2. 2. The chemical reactor of claim 1, wherein the chemical reactor is adapted for operation above 10 barg, preferably above 30 barg, more preferably for operation in the range of 40 to 60 barg.

3. 10. The chemical reactor of claim 1, wherein the chemical reactor is adapted such that the output of the plasma torch reactor is positioned to impart momentum to a non-reactive liquid in the non-reactive liquid system.

4. 4. The chemical reactor of claim 3, wherein the non-reactive liquid system is adapted such that output products are separated from the non-reactive liquid by centrifugation.

5. 5. The chemical reactor of claim 4 adapted for extraction of a solid output product from said non-reactive liquid system by gravity.

6. The chemical reactor of claim 1 , wherein the non-reactive liquid system is adapted to convert contaminants from the plasma torch output.

7. 10. The chemical reactor of claim 1, wherein the non-reactive liquid system is adapted for extraction of gaseous output products from an upper portion of the liquid metal system.

8. 8. The chemical reactor of claim 7, wherein a float valve is used for extraction of the gaseous output product.

9. 8. The chemical reactor of claim 7, wherein one or more cyclones are used for separation of solid output products from the gaseous output products.

10. 10. The chemical reactor of claim 9, wherein the one or more cyclones are disposed in series with at least one pulse jet filter.

11. 10. The chemical reactor of claim 9, wherein the solid output product is deposited in one or more intermediate bulk vessels.

12. 10. The chemical reactor of claim 1, wherein the non-reactive liquid system is a liquid system reactor and an additional feed gas is supplied to the liquid system reactor.

13. 13. The chemical reactor of claim 12, wherein the plasma torch is adapted to heat the non-reactive liquid metal to a reaction temperature for the additional feedstock gas.

14. 13. The chemical reactor of claim 12, wherein the liquid system reactor is adapted for endothermic reactions, thereby reducing the heat output of the chemical reactor from the heat output generated by the plasma torch reactor.

15. 10. The chemical reactor of claim 1 further comprising a heat exchanger for raising the feed gas to a reaction temperature using heat from the gaseous output product.

16. 10. The chemical reactor of claim 1, wherein the plasma torch reactor is adapted for the decomposition of methane.

17. The chemical reactor of claim 16, wherein the non-reactive liquid system is a liquid system reactor and an additional feedstock gas is supplied to the liquid system reactor, the additional feedstock gas also comprising a hydrocarbon.

18. 20. The chemical reactor of claim 17, wherein the additional feed gas further comprises carbon dioxide, the carbon dioxide being provided to react with carbon to form carbon monoxide, and a synthesis gas being provided as an output product.

19. 20. The chemical reactor of claim 18, wherein both hydrogen and syngas are provided as separate gaseous output products.

20. 10. The chemical reactor of claim 1, wherein the plasma torch is adapted to be partially flooded with the non-reactive liquid from the non-reactive liquid system when the plasma torch is shut off.

21. 10. The chemical reactor of claim 1, wherein the non-reactive liquid is a liquid at an operating temperature for the reactor and a solid at ambient temperature.

22. 10. The chemical reactor of claim 1, wherein the non-reactive liquid is a metal, a metal alloy, or a salt.

23. 23. The chemical reactor of claim 22, wherein the non-reactive liquid is a conductive metal or metal alloy.

24. 24. The chemical reactor of claim 23, wherein the non-reactive liquid comprises one or more of lead and bismuth.

25. 1. A method of cracking hydrocarbons in a reactive process, comprising providing hydrocarbons as an input to a chemical reactor comprising a plasma torch reactor and a non-reactive liquid system disposed within a pressure vessel, said reactive process operating at substantially above atmospheric pressure; the plasma torch reactor receives the hydrocarbon as a feed gas and provides a plasma torch output including carbon and hydrogen as reaction products; the non-reactive liquid system receives the plasma torch output of the plasma torch reactor; The method of claim 1, wherein the non-reactive liquid system receives the reaction products and transports the reaction products away from the plasma torch reactor to provide the reaction products as output products from the chemical reactor.

26. 26. The method of claim 25, wherein the reaction process operates above 10 barg, preferably above 30 barg, more preferably for operation in the range of 40 to 60 barg.

27. 26. The method of claim 25, wherein the output of the plasma torch reactor is positioned to impart momentum to the non-reactive liquid of the non-reactive liquid system.

28. 26. The method of claim 25, wherein the solid reaction products are separated from the liquid metal by centrifugation.

29. 26. The method of claim 25, wherein the non-reactive liquid system converts contaminants received from the plasma torch reactor along with the reaction products.

30. 26. The method of claim 25, further comprising a heat exchanger for raising the feed gas to the reaction temperature using heat from the gaseous output product.

31. 26. The method of claim 25, comprising the decomposition of methane.

32. 26. The method of claim 25, wherein the non-reactive liquid is a metal, a metal alloy or a salt.

33. 33. The method of claim 32, wherein the non-reactive liquid is a metal or metal alloy adapted to be liquid at reaction temperatures and solid at ambient temperatures.

34. 34. The method of claim 33, further comprising at least partially submerging an electrode of the plasma torch with the non-reactive liquid when the plasma torch is turned off to form a conductive plug.

35. 35. The method of claim 34, further comprising starting the plasma torch with the conductive plug disposed in the submerged electrode of the plasma torch and draining material of the conductive plug into the non-reactive liquid system.

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