Arc plasma reactor and metallurgical heat treatment method

Abstract

This invention provides an arc plasma reactor and a metallurgical heat treatment method, comprising: an anode crucible and a cathode; the anode crucible has a reaction chamber for containing materials, the reaction chamber having a bottom wall and side walls extending upward from the periphery of the bottom wall; the reaction chamber contracts inward in a horizontal direction to form a first reaction zone and a second reaction zone that are interconnected; the first reaction zone and the second reaction zone are arranged sequentially from top to bottom; the angle between the bottom wall and the side wall of the second reaction zone is an acute angle; the cathode is located above the anode crucible and is used to generate a plasma jet toward the reaction chamber. This invention has a simple structure and is easy to operate.

Description

Technical Field

[0001] This invention relates to the field of arc plasma metallurgy technology, and in particular to an arc plasma reactor and a metallurgical heat treatment method. Background Technology

[0002] Arc plasma, with its significant advantages of high temperature, high energy density, rapid heating rate, and controllable atmosphere, has been widely applied in fields such as metal oxide reduction, complex mineral activation, metallurgical slag resource utilization, high-temperature powder preparation, and vapor deposition / condensation material preparation. In arc plasma metallurgy or high-temperature material preparation, the arc core region can generate extremely high temperatures in a short time, causing rapid melting, reduction, evaporation, vaporization, or activation reactions of the reactants, generating products such as metal vapor, suboxide vapor, non-metal vapor, gaseous intermediates, or fine particle precursors. However, arc plasma heating exhibits significant local concentration; heat is mainly distributed in the arc column, arc root, and impact region. A large temperature gradient easily forms between the high-temperature zone at the crucible center and the crucible sidewalls, edges, and upper vapor space. Due to this uneven temperature distribution, products, after leaving the high-temperature arc core region, may prematurely condense, agglomerate, deposit, or fall back into the crucible material layer due to the rapid decrease in ambient temperature. This makes it difficult for the target product to be effectively captured by the subsequent collection system, thereby reducing product yield, powder collection efficiency, and process stability.

[0003] Taking arc plasma magnesium metallurgy as an example, magnesium-containing materials can rapidly generate magnesium vapor in the core region of the arc. However, after leaving the high-temperature core region, if the temperature of the crucible sidewall or upper gas phase space is insufficient, the magnesium vapor is prone to premature condensation and falls back into the material or slag, resulting in a decrease in the yield of metallic magnesium. Similarly, in the preparation of silicon micropowder, metal micropowder, or other high-temperature powder materials using arc plasma, if the gas phase products or high-temperature fine particles condense, agglomerate, or deposit prematurely in non-target locations inside the crucible, it will also lead to uncontrolled particle size distribution, reduced effective collection rate, and decreased product purity. Existing arc plasma reactors often fail to induce effective heat recirculation in the anode region by inducing high-temperature gas flow and molten pool flow after arc impact. The heat input from the arc is easily dissipated rapidly radially and axially, failing to effectively expand the stable high-temperature region and making it difficult to directionally guide the product escape direction. Therefore, this invention provides an arc plasma reactor and a metallurgical heat treatment method to solve the problems of large temperature gradients and low heat utilization rates in existing anode crucibles. Summary of the Invention

[0004] This invention provides an electric arc plasma reactor and a metallurgical heat treatment method, aiming to solve the technical problems of large temperature gradient and low heat utilization rate of existing anode crucibles.

[0005] To achieve the above objectives, the present invention provides an arc plasma reactor, comprising: an anode crucible and a cathode.

[0006] The anode crucible has a reaction chamber for containing materials, the reaction chamber having a bottom wall and side walls extending upward from the periphery of the bottom wall.

[0007] The reaction chamber contracts inward along the horizontal direction to form a first reaction zone and a second reaction zone that are interconnected.

[0008] The first reaction zone and the second reaction zone are arranged sequentially from top to bottom.

[0009] The angle between the bottom wall and the side wall of the second reaction zone is an acute angle.

[0010] The cathode is located above the anode crucible and is used to generate a plasma jet toward the reaction chamber.

[0011] According to an embodiment of this application, the ratio between the depth of the second reaction zone and the diameter of the bottom wall is 0.25 to 0.45.

[0012] The angle between the sidewall of the first reaction zone and the horizontal direction is 30~85°.

[0013] According to an embodiment of this application, the portion of the reaction chamber that contracts inward along the horizontal direction forms a connecting portion.

[0014] The connecting part connects the first reaction zone and the second reaction zone.

[0015] The ratio between the diameter of the connecting part and the diameter of the bottom wall is 0.35 to 0.75.

[0016] According to an embodiment of this application, the cathode includes a rod-shaped portion and a working end located at one end of the rod-shaped portion.

[0017] The ratio between the diameter of the rod-shaped portion and the diameter of the connecting portion is 0.15 to 0.65.

[0018] The working end faces the reaction chamber.

[0019] According to an embodiment of this application, at least the inner surface of the sidewall is provided with an insulating and high-temperature resistant coating.

[0020] The insulating high-temperature resistant coating covers at least the inner surface of the sidewall corresponding to the second reaction zone, but does not cover the anode arc-affected area on the bottom wall, so as to suppress the formation of bypass discharge or sidewall arc root between the cathode and the sidewall.

[0021] According to an embodiment of this application, the arc plasma reactor further includes a power supply assembly.

[0022] The cathode is electrically connected to the cathode output terminal of the power supply assembly.

[0023] The bottom wall of the anode crucible is electrically connected to the anode output terminal of the power supply assembly to form a transferred arc plasma between the cathode and the bottom wall.

[0024] According to an embodiment of this application, the arc plasma reactor is a transferred arc plasma reactor.

[0025] The cathode is a tungsten needle.

[0026] This invention provides a metallurgical heat treatment method using the aforementioned electric arc plasma reactor, comprising the following steps: S1: Provide the material to be processed and lay it at the bottom of the reaction chamber.

[0027] S2: Start the electric arc plasma reactor to generate a plasma jet that impacts and heats the material to be processed. After the reaction is completed, the product is obtained.

[0028] The operating current of the arc plasma reactor is 20A~200kA.

[0029] According to an embodiment of this application, the heating is performed under a protective atmosphere.

[0030] The reaction pressure is 1000~200000 Pa.

[0031] The reaction duration is ≤120 min.

[0032] The material to be processed includes at least one of metal oxides and silicon-containing raw materials.

[0033] According to embodiments of this application, the protective atmosphere includes an inert gas or a reducing gas.

[0034] The inert gas includes at least one of argon, nitrogen, helium, and neon.

[0035] The reducing gas includes at least one of hydrogen, methane, carbon monoxide, ethylene, and acetylene.

[0036] Compared with the prior art, the beneficial effects of the present invention are: The aforementioned arc plasma reactor and metallurgical heat treatment method significantly reduce the temperature gradient within the reaction chamber (especially the second reaction zone) by horizontally contracting the reaction chamber inward to form interconnected first and second reaction zones, and by creating an acute angle between the bottom wall and the sidewall of the second reaction zone. Specifically, horizontally contracting the reaction chamber induces a thermal reflux vortex in the second reaction zone under the action of the arc plasma, causing the heat input from the arc to reflux, remain, and redistribute within the second reaction zone, thereby increasing the average temperature and heat storage capacity of the second reaction zone. Furthermore, by defining an acute angle between the bottom wall and the sidewall of the second reaction zone, the coupling effect between the arc impact, molten pool flow, and thermal reflux vortex is enhanced, expanding the effective high-temperature zone and reducing the temperature gradient within the anode crucible. Moreover, the sidewall of the first reaction zone guides the vapor products generated after the material reaction to escape directionally towards the outside of the anode crucible or the condensation and collection area, reducing the loss of vapor due to condensation and falling back into the material zone after leaving the arc core area caused by a sudden temperature drop.

[0037] Moreover, the arc plasma reactor has a simple structure and is easy to operate, making it particularly suitable for arc plasma metallurgical heat treatment processes. Specifically, it improves the heating uniformity of magnesium-containing materials, reduces magnesium vapor loss, and increases the yield of metallic magnesium. Without shortening the safety electrode spacing, it enhances the controllability and effectiveness of plasma reactor heating, demonstrating significant industrial application value. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the structure of the electric arc plasma reactor in Embodiment 1 of the present invention; Figure 2 This is a simulation diagram of the heat storage reflux vortex formed in the reaction chamber of Embodiment 1 of the present invention, where heat accumulates. Figure 3 This is a heat flow simulation diagram of the reaction chamber in Comparative Example 1 of the present invention.

[0040] The attached figures are labeled as follows: 10, arc plasma reactor; 11, anode crucible; 12, cathode; 20, reaction chamber; 21, bottom wall; 22, side wall; 23, first reaction zone; 24, second reaction zone; 25, side wall of the second reaction zone; 26, side wall of the first reaction zone; 30, connecting part; 40, rod-shaped part; 41, working end.

[0041] The depth of the second reaction zone is H; the diameter of the connecting part is W1; the diameter of the rod-shaped part is D1; ​​the diameter of the bottom wall is D2; the angle between the bottom wall and the side wall of the second reaction zone is α; and the angle between the side wall of the first reaction zone and the horizontal direction is β.

[0042] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The technical solutions of the various embodiments of the present invention can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0045] To achieve the above objectives, the present invention provides an arc plasma reactor, comprising: an anode crucible and a cathode.

[0046] The anode crucible has a reaction chamber for containing materials, the reaction chamber having a bottom wall and side walls extending upward from the periphery of the bottom wall.

[0047] The reaction chamber contracts inward along the horizontal direction to form a first reaction zone and a second reaction zone that are interconnected.

[0048] The first reaction zone and the second reaction zone are arranged sequentially from top to bottom.

[0049] The angle between the bottom wall and the side wall of the second reaction zone is an acute angle.

[0050] The cathode is located above the anode crucible and is used to generate a plasma jet toward the reaction chamber.

[0051] In some embodiments, see Figure 1 The present invention provides an arc plasma reactor 10, comprising: an anode crucible 11 and a cathode 12.

[0052] The anode crucible 11 has a reaction chamber 20 for containing materials, the reaction chamber 20 having a bottom wall 21 and side walls 22 extending upward from the periphery of the bottom wall 21.

[0053] The reaction chamber 20 contracts inward in the horizontal direction to form a first reaction zone 23 and a second reaction zone 24 that are interconnected.

[0054] The first reaction zone 23 and the second reaction zone 24 are arranged sequentially from top to bottom.

[0055] The angle (α) between the bottom wall 21 and the side wall 25 of the second reaction zone is an acute angle.

[0056] The cathode 12 is located above the anode crucible 11 and is used to generate a plasma jet toward the reaction chamber 20.

[0057] In some embodiments, by providing a sidewall structure around the bottom wall, the high-temperature airflow that diffuses radially after impact is physically blocked, causing it to be deflected a second time and climb upward along the sidewall, thereby suppressing lateral stripping.

[0058] In some embodiments, the sidewall section of the second reaction zone is used to induce the formation of a thermal reflux region of the anode within the regenerative reaction chamber (i.e., the chamber in which the second reaction zone is located), thereby increasing the average temperature of the regenerative reaction chamber and reducing the probability of reaction product vapors condensing and falling back into the crucible.

[0059] In some embodiments, the sidewall section of the first reaction zone is used to guide the vapor of the reaction product from the heat storage reaction chamber through the connecting portion to the vapor guide chamber (i.e., the chamber where the first reaction zone is located).

[0060] The aforementioned arc plasma reactor and metallurgical heat treatment method significantly reduce the temperature gradient within the reaction chamber (especially the second reaction zone) by horizontally contracting the reaction chamber inward to form interconnected first and second reaction zones, and by creating an acute angle between the bottom wall and the sidewall of the second reaction zone. Specifically, horizontally contracting the reaction chamber induces a thermal reflux vortex in the second reaction zone under the action of the arc plasma, causing the heat input from the arc to reflux, remain, and redistribute within the second reaction zone, thereby increasing the average temperature and heat storage capacity of the second reaction zone. Furthermore, by defining an acute angle between the bottom wall and the sidewall of the second reaction zone, the coupling effect between the arc impact, molten pool flow, and thermal reflux vortex is enhanced, expanding the effective high-temperature zone and reducing the temperature gradient within the anode crucible. Moreover, the sidewall of the first reaction zone guides the vapor products generated after the material reaction to escape directionally towards the outside of the anode crucible or the condensation and collection area, reducing the loss of vapor due to condensation and falling back into the material zone after leaving the arc core area caused by a sudden temperature drop.

[0061] In some embodiments, the ratio (H / D2) between the depth (H) of the second reaction zone and the diameter (D2) of the bottom wall is 0.25 to 0.45.

[0062] In some embodiments, the angle (β) between the sidewall 26 of the first reaction zone and the horizontal direction is 30~85°.

[0063] In some embodiments, the angle between the sidewall of the first reaction zone and the horizontal direction is 30~75°.

[0064] In some embodiments, the angle between the sidewall of the first reaction zone and the horizontal direction is 60-85°.

[0065] In some embodiments, the angle between the sidewall of the first reaction zone and the horizontal direction is 65-75°.

[0066] In some embodiments, the portion of the reaction chamber 20 that contracts inward in the horizontal direction forms a connecting portion 30.

[0067] The connecting part 30 connects the first reaction zone 23 and the second reaction zone 24.

[0068] The ratio (W1 / D2) between the diameter (W1) of the connecting part and the diameter (D2) of the bottom wall is 0.35 to 0.75.

[0069] In some embodiments, the diameter of the connecting portion is smaller than the inner diameter of the bottom wall, so that the reaction chamber forms a heat storage reaction chamber (i.e., the second reaction zone) located below the connecting portion and a vapor guiding chamber (i.e., the first reaction zone) located above the connecting portion.

[0070] In some embodiments, the cathode 12 includes a rod-shaped portion 40 and a working end 41 located at one end of the rod-shaped portion.

[0071] The ratio (D1 / W1) between the diameter (D1) of the rod-shaped portion and the diameter (W1) of the connecting portion is 0.15 to 0.65.

[0072] The working end 41 faces the reaction chamber 20.

[0073] In some embodiments, the working end of the cathode (cathode electrode) extends into or is positioned toward the connection portion, enabling the formation of an electric arc plasma between the cathode and the anode crucible.

[0074] In some embodiments, by defining the angle between the bottom wall and the side wall of the second reaction zone as an acute angle, the ratio between the depth of the second reaction zone and the diameter of the bottom wall, the angle between the side wall of the first reaction zone and the horizontal direction, and the ratio between the diameter of the rod-shaped portion and the diameter of the connecting portion, a stable macroscopic reflux vortex can be formed inside the crucible, thereby confining the high-temperature plasma to circulate and convection above the material bed, improving the uniform temperature rise effect and heat utilization efficiency of the material bed.

[0075] In some embodiments, to achieve optimal performance, the ratios between the diameter of the rod-shaped portion and the diameter of the bottom wall, the angle between the bottom wall and the sidewall of the second reaction zone, and the ratio between the depth of the second reaction zone and the diameter of the bottom wall need to be set appropriately. If the ratio between the diameter of the rod-shaped portion and the diameter of the bottom wall is too small, the central impact is strong, but the entrainment of the entire reaction chamber is insufficient, easily leading to localized high temperatures only in the center, while the sidewall backflow is weak. If it is too large, the high-temperature airflow after impact is more likely to rebound directly along the axial direction, weakening the confinement effect of the radial backflow vortex. Similarly, if the angle between the bottom wall and the sidewall of the second reaction zone is too small, although the obstruction is enhanced, it easily leads to localized stagnation and heat accumulation dead zones at the bottom corner. If it is too large, the sidewall of the second reaction zone is too gentle, and the airflow easily escapes along the wall, with insignificant backflow. Furthermore, if the ratio between the depth of the second reaction zone and the diameter of the bottom wall is too small, the heat flow easily escapes laterally; if it is too large, a low-speed stagnation zone may appear at the bottom, resulting in a decrease in thermal circulation efficiency.

[0076] In some embodiments, the bottom wall is at least partially formed of conductive graphite material and electrically connected to the anode end of an external power source to serve as the anode arc-receiving region for the transferred arc plasma.

[0077] In some embodiments, at least the inner surface of the sidewall is provided with an insulating, high-temperature resistant coating.

[0078] The insulating high-temperature resistant coating covers at least the inner surface of the sidewall corresponding to the second reaction zone, but does not cover the anode arc-collecting area on the bottom wall. This suppresses the formation of bypass discharge or sidewall arc roots between the cathode and the sidewall, allowing the transferred arc plasma to preferentially establish itself between the cathode electrode and the bottom wall. It should be noted that bypass discharge refers to the phenomenon where the current does not close along a predetermined path between the cathode electrode and the bottom wall of the anode crucible (or the anode arc-collecting area on the bottom wall), but instead forms an additional discharge circuit through an unexpected conductive channel. Bypass discharge causes arc deflection, weakening the effective establishment of the transferred arc plasma in the bottom wall direction.

[0079] Sidewall arc roots refer to the phenomenon where the arc attachment point (i.e., the arc root) of the transferred arc plasma on the anode side does not stably form within the anode arc receiving area on the bottom wall of the crucible, but instead shifts and attaches to the sidewall of the crucible. The appearance of sidewall arc roots is usually caused by bypass discharge, which reduces plasma heating efficiency and easily causes local overheating or abnormal erosion of the sidewall.

[0080] The anode arc-bearing region refers to a localized conductive area on the bottom wall of the crucible, serving as the intended attachment site for the transferred arc plasma on the anode side. This region has an area smaller than the total area of ​​the crucible's bottom wall and does not cover the entire surface of the bottom wall.

[0081] In some embodiments, the insulating high-temperature resistant coating covers the inner wall of the first reaction zone and the inner wall of the second reaction zone, and the insulating high-temperature resistant coating avoids the anode arc-affected area on the bottom wall.

[0082] In some embodiments, the insulating high-temperature resistant coating includes at least one of an alumina coating, a zirconium oxide coating, a magnesium oxide coating, a boron nitride coating, a mullite coating, and a corundum coating.

[0083] In some embodiments, the insulating high-temperature resistant coating includes one of the following: alumina coating, zirconium oxide coating, magnesium oxide coating, boron nitride coating, mullite coating, and corundum coating.

[0084] In some embodiments, the thickness of the insulating high-temperature resistant coating is 0.1~5 mm.

[0085] In some embodiments, the arc plasma reactor further includes a power supply assembly.

[0086] The cathode is electrically connected to the cathode output terminal of the power supply assembly.

[0087] The bottom wall of the anode crucible is electrically connected to the anode output terminal of the power supply assembly to form a transferred arc plasma between the cathode and the bottom wall.

[0088] In some embodiments, the arc plasma reactor is a transferred arc plasma reactor.

[0089] The cathode is a tungsten needle.

[0090] Moreover, the arc plasma reactor has a simple structure and is easy to operate, making it particularly suitable for arc plasma metallurgical heat treatment processes. Specifically, it improves the heating uniformity of magnesium-containing materials, reduces magnesium vapor loss, and increases the yield of metallic magnesium. Without shortening the safety electrode spacing, it enhances the controllability and effectiveness of plasma reactor heating, demonstrating significant industrial application value.

[0091] This invention provides a metallurgical heat treatment method using the aforementioned electric arc plasma reactor, comprising the following steps: S1: Provide the material to be processed and lay it at the bottom of the reaction chamber.

[0092] S2: Start the electric arc plasma reactor to generate a plasma jet that impacts and heats the material to be processed. After the reaction is completed, the product is obtained.

[0093] The operating current of the arc plasma reactor is 20A~200kA.

[0094] In some embodiments, the operating current of the arc plasma reactor is 50A to 200A.

[0095] In some embodiments, the operating current of the arc plasma reactor is 150A~200A.

[0096] In some embodiments, the heating is performed under a protective atmosphere.

[0097] The reaction pressure is 1000~200000 Pa.

[0098] The reaction duration is ≤120 min.

[0099] The material to be processed includes at least one of metal oxides and silicon-containing raw materials.

[0100] The reaction pressure is 60,000~100,000 Pa.

[0101] The reaction lasts for 10 to 30 minutes.

[0102] In some embodiments, the material to be processed includes metal oxides or silicon-containing raw materials.

[0103] In some embodiments, the heating temperature is 2000~3000℃.

[0104] In some embodiments, the heating temperature is 2200~2800℃.

[0105] In some embodiments, the heating temperature is 2300~2600℃.

[0106] In some embodiments, the heating temperature is 2450~2550℃.

[0107] In some embodiments, the reaction duration is 15-25 minutes.

[0108] In some embodiments, the reaction duration is 15-20 minutes.

[0109] In some embodiments, the material to be processed includes metal oxides or silicon-containing raw materials.

[0110] In some embodiments, the material to be treated includes magnesium oxide and ferrosilicon, and is mixed in a ratio of (1.8~2.2):(1.1~1.5) of molar ratio of silicon in MgO to ferrosilicon, with MgO (wt%) = 52~53% and CaF2 (wt%) = 2.8~3.2%.

[0111] In some embodiments, the aforementioned transferred arc plasma reactor is used for argon arc plasma silicothermic reduction of magnesium. The materials to be processed are magnesium oxide and ferrosilicon. After the reduction reaction is completed, magnesium is obtained as the reduction product. It should be noted that the formula for calculating the yield of the magnesium product is: The yield of magnesium product (%) = the actual mass of magnesium product collected / the actual mass of magnesium product reduced × 100%.

[0112] In some embodiments, the protective atmosphere comprises an inert gas or a reducing gas.

[0113] The inert gas includes at least one of argon, nitrogen, helium, and neon.

[0114] The reducing gas includes at least one of hydrogen, methane, carbon monoxide, ethylene, and acetylene.

[0115] In some embodiments, the inert gas includes one of argon, nitrogen, helium, and neon.

[0116] In some embodiments, the reducing gas includes one of hydrogen, methane, carbon monoxide, ethylene, and acetylene.

[0117] In some embodiments, the protective atmosphere comprises an inert gas.

[0118] The inert gas includes argon.

[0119] In some embodiments, the argon flow rate is 15~25 L / min.

[0120] In some embodiments, the argon flow rate is 18~22 L / min.

[0121] To further illustrate the present invention, the following examples are provided: Example 1 An arc plasma reactor, see Figure 1Specifically, it is a transferred arc plasma reactor, comprising: an anode crucible, a cathode, and a power supply assembly. The cathode is a tungsten needle, electrically connected to the cathode output terminal of the power supply assembly. The bottom wall of the anode crucible is electrically connected to the anode output terminal of the power supply assembly to form a transferred arc plasma between the cathode and the bottom wall. At least the inner surface of the sidewall is provided with an insulating high-temperature resistant coating. The insulating high-temperature resistant coating at least covers the inner surface of the sidewall corresponding to the second reaction zone, but does not cover the anode arc-receiving area on the bottom wall, to suppress the formation of bypass discharge or sidewall arc roots between the cathode and the sidewall. The thickness of the insulating high-temperature resistant alumina coating is 1.5 mm to prevent bypass discharge.

[0122] The anode crucible has a reaction chamber for containing materials. The reaction chamber has a bottom wall and side walls extending upward from the periphery of the bottom wall. The reaction chamber narrows inward in the horizontal direction, forming a first reaction zone and a second reaction zone that are interconnected. The first and second reaction zones are arranged sequentially from top to bottom. The angle between the bottom wall and the side wall of the second reaction zone is an acute angle. The cathode is located above the anode crucible and is used to generate a plasma jet toward the reaction chamber. The ratio of the depth of the second reaction zone to the diameter of the bottom wall is 0.33. The angle between the side wall of the first reaction zone and the horizontal direction is 72°. The portion of the reaction chamber that narrows inward in the horizontal direction forms a connecting portion. The connecting portion connects the first and second reaction zones. The ratio of the diameter of the connecting portion to the diameter of the bottom wall is 0.55. The cathode has a rod-shaped portion and a working end located at one end of the rod-shaped portion. The ratio of the diameter of the rod-shaped portion to the diameter of the connecting portion is 0.25. The working end of the cathode faces the reaction chamber.

[0123] A metallurgical heat treatment method, employing the aforementioned transferred arc plasma reactor, performs argon arc plasma silicothermic reduction of magnesium, comprising the following steps: S1: Provide the material to be treated and lay it at the bottom of the reaction chamber; the material to be treated is magnesium oxide and ferrosilicon agent mixed in a ratio of 2:1.3 of silicon element in MgO and ferrosilicon, MgO (wt%)=52.8% and CaF2 (wt%)=3%.

[0124] S2: Start the transfer arc plasma reactor to generate a plasma jet to impact and heat the material to be processed. After the reaction is completed, the product is obtained. The working current of the transfer arc plasma reactor is 150A. Heating is carried out under argon (protective atmosphere). The reaction pressure is 100000Pa. The heating temperature is 2500℃. The reaction time is 20min.

[0125] Simulation results show that the effective high-temperature region above 1090℃ accounts for 100% of the second reaction zone. Product testing revealed a magnesium reduction rate of 93.25% and a magnesium yield of 95.38%. (See [link to relevant documentation]). Figure 2This indicates that the electric arc plasma reactor of Example 1 forms a heat storage zone in the second reaction zone. After the plasma jet impacts the bottom wall, a stable reflux vortex is formed inside the second reaction zone, which causes heat to circulate and accumulate above the material bed, making the temperature distribution on the surface and inside of the material to be treated more uniform and reaching above the magnesium boiling point. Magnesium vapor generation is stable, and the yield is improved.

[0126] Example 2 Compared to Example 1, the ratio between the depth of the second reaction zone and the diameter of the bottom wall was changed.

[0127] In Example 2, the ratio between the depth of the second reaction zone and the diameter of the bottom wall is 0.42, and the other steps are the same as in Example 1.

[0128] Simulation results show that the effective high-temperature region above 1090℃ still accounts for 100% of the second reaction zone, but argon gas stagnates at the bottom. After testing the product, the reduction rate of magnesium is 93.26% and the yield is 90.21%. This indicates that when using the arc plasma reactor of Example 2, the plasma jet impacts the bottom wall and forms a backflow vortex in the second reaction zone. However, the depth of the second reaction zone is too deep, which causes a local low-speed stagnation zone at the bottom, resulting in a certain degree of decrease in magnesium yield.

[0129] Example 3 Compared to Example 1, the ratio between the diameter of the connecting part and the diameter of the bottom wall was changed.

[0130] In Example 3, the ratio between the diameter of the connecting part and the diameter of the bottom wall is 0.40, and the other steps are the same as in Example 1.

[0131] Simulation results show that the effective high-temperature region above 1090℃ still accounts for 100% of the second reaction zone. The product was tested and found that the magnesium reduction rate was 93.13% and the yield was 88.78%. This indicates that when using the arc plasma reactor of Example 3, the plasma jet impacts the bottom wall and forms a backflow vortex in the second reaction zone. However, due to the narrow diameter of the connection, the gas phase escape resistance increases, resulting in a certain decrease in the magnesium yield.

[0132] Example 4 Compared to Example 1, the ratio between the diameter of the connecting part and the diameter of the bottom wall was changed.

[0133] In Example 4, the ratio between the diameter of the connecting part and the diameter of the bottom wall is 0.70, and the other steps are the same as in Example 1.

[0134] Simulation results show that the effective high-temperature region above 1090℃ accounts for 76.83% of the second reaction zone. The product was tested and found that the magnesium reduction rate was 88.48% and the yield was 79.25%. This indicates that in the arc plasma reactor of Example 4, the plasma jet impacts the bottom wall and forms a backflow vortex in the second reaction zone. However, the large diameter of the connection weakens the confinement and reversal effect of the high-temperature airflow, which reduces the heat circulation and accumulation capacity in the heat storage reaction chamber, thereby reducing the average temperature of the heat storage reaction chamber and weakening the heat utilization efficiency, resulting in a decrease in magnesium yield.

[0135] Example 5 Compared to Example 1, the ratio between the diameter of the rod-shaped portion of the cathode and the diameter of the connecting portion was changed.

[0136] In Example 5, the ratio between the diameter of the rod-shaped portion of the cathode and the diameter of the connecting portion is 0.45, and the other steps are the same as in Example 1.

[0137] Simulation results show that the effective high-temperature region above 1090℃ accounts for 100% of the second reaction zone. However, the electric arc fluctuates during the reaction, and the reaction stability decreases. The product was tested, and the magnesium reduction rate was 83.43% and the yield was 81.21%. This indicates that the electric arc plasma reactor of Example 5, due to the close proximity of the cathode and the sidewall, increases the possibility of arc instability, resulting in a certain decrease in both the magnesium reduction rate and the yield. Moreover, due to the increased diameter of the rod-shaped part of the cathode, the local high temperature intensifies, causing some raw material volatilization and reducing the purity of the product.

[0138] Example 6 An arc plasma reactor, specifically a transferred arc plasma reactor, comprises: an anode crucible, a cathode, and a power supply assembly. The cathode is a tungsten needle and is electrically connected to the cathode output terminal of the power supply assembly. The bottom wall of the anode crucible is electrically connected to the anode output terminal of the power supply assembly to form transferred arc plasma between the cathode and the bottom wall. At least the inner surface of the sidewall is provided with an insulating, high-temperature resistant coating. This insulating, high-temperature resistant coating at least covers the inner surface of the sidewall corresponding to the second reaction zone, but does not cover the anode arc-receiving area on the bottom wall, to suppress bypass discharge or sidewall arc root formation between the cathode and the sidewall. The insulating, high-temperature resistant alumina coating has a thickness of 1.5 mm to prevent bypass discharge.

[0139] The anode crucible has a reaction chamber for containing materials, the reaction chamber having a bottom wall and side walls extending upward from the periphery of the bottom wall; the reaction chamber narrows inward in the horizontal direction to form a first reaction zone and a second reaction zone that are interconnected; the first reaction zone and the second reaction zone are arranged sequentially from top to bottom; the angle between the bottom wall and the side wall of the second reaction zone is an acute angle; the cathode is located above the anode crucible and is used to generate a plasma jet toward the reaction chamber. The ratio of the depth of the second reaction zone to the diameter of the bottom wall is 0.33, the angle between the side wall of the first reaction zone and the horizontal direction is 72°, and the portion of the reaction chamber that narrows inward in the horizontal direction forms a connecting portion; the connecting portion connects the first reaction zone and the second reaction zone; the ratio of the diameter of the connecting portion to the diameter of the bottom wall is 0.55. The cathode has a rod-shaped portion and a working end located at one end of the rod-shaped portion; the ratio of the diameter of the rod-shaped portion to the diameter of the connecting portion is 0.25.

[0140] A metallurgical heat treatment method, employing the aforementioned transferred arc plasma reactor, uses argon arc plasma for industrial silicon evaporation and powder production. The steps are as follows: S1: Provide the material to be processed and lay it at the bottom of the reaction chamber; the material to be processed is 100g of industrial silicon.

[0141] S2: Start the transfer arc plasma reactor to generate a plasma jet to impact and heat the material to be processed. After the reaction is completed, the product is obtained. The working current of the transfer arc plasma reactor is 200A. Heating is carried out under argon (protective atmosphere) at a pressure of 60000Pa. The heating temperature is 2500℃. The reaction time is 20min.

[0142] The product was tested and the Si powder yield was 76.8%.

[0143] Comparative Example 1 Compared to Example 1, the structure of the anode crucible was changed.

[0144] In Comparative Example 1, the anode crucible has a standard flat-bottomed structure, and the reaction chamber of the anode crucible does not contract inward along the horizontal direction. The reaction chamber consists of a bottom wall and side walls. Other steps are the same as in Example 1, performing argon arc plasma silicothermic reduction of magnesium to obtain the product magnesium.

[0145] Simulation results show that the effective high-temperature region above 1090℃ accounts for 56.21% of the reaction zone in the anode crucible. Testing revealed a magnesium reduction rate of only 68.21%, a high content of unreacted MgO in the residue, and a magnesium yield of only 65.22%. (See [link to relevant documentation]). Figure 3Because the plasma heat flow in the flat-bottomed crucible spreads rapidly radially after impacting the bottom wall and rises vertically after impacting the side wall, it does not form a thermal backflow vortex in the anode reaction zone. At this time, the local temperature in the central area is high while the temperature of the surrounding material is insufficient, resulting in uneven heating of the material and thus a decrease in magnesium reduction rate and yield.

[0146] Comparative Example 2 Compared to Example 1, no insulating and high-temperature resistant coating was applied to the sidewalls of the anode crucible. Other steps were the same as in Example 1, involving argon arc plasma silicon thermal reduction of magnesium to obtain the product magnesium.

[0147] Tests showed that the magnesium reduction rate was 78.33% and the yield was 75.62%. During the reaction, the arc stability decreased and bypass discharge occurred frequently, which made the heating effect unstable and led to a decrease in the magnesium reduction rate and yield.

[0148] The aforementioned arc plasma reactor and metallurgical heat treatment method significantly reduce the temperature gradient within the reaction chamber (especially the second reaction zone) by horizontally contracting the reaction chamber inward to form interconnected first and second reaction zones, and by creating an acute angle between the bottom wall and the sidewall of the second reaction zone. Specifically, horizontally contracting the reaction chamber induces a thermal reflux vortex in the second reaction zone under the action of the arc plasma, causing the heat input from the arc to reflux, stagnate, and redistribute within the second reaction zone, thereby increasing the average temperature and heat storage capacity of the second reaction zone. Furthermore, by defining an acute angle between the bottom wall and the sidewall of the second reaction zone, the coupling effect between the arc impact, molten pool flow, and thermal reflux vortex is enhanced, expanding the effective high-temperature zone and reducing the temperature gradient within the anode crucible. Moreover, the sidewall of the first reaction zone guides the vapor products generated after the material reaction to escape directionally towards the outside of the anode crucible or the condensation and collection area, reducing the loss of vapor due to condensation and falling back into the material zone after leaving the arc core area caused by a sudden temperature drop.

[0149] Moreover, the arc plasma reactor has a simple structure and is easy to operate, making it particularly suitable for arc plasma metallurgical heat treatment processes. Specifically, it improves the heating uniformity of magnesium-containing materials, reduces magnesium vapor loss, and increases the yield of metallic magnesium. Without shortening the safety electrode spacing, it enhances the controllability and effectiveness of plasma reactor heating, demonstrating significant industrial application value.

[0150] In summary, the above-described technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An arc plasma reactor, characterized by, include: Anode crucible and cathode; The anode crucible has a reaction chamber for containing materials, the reaction chamber having a bottom wall and side walls extending upward from the periphery of the bottom wall; The reaction chambers contract inward in the horizontal direction to form a first reaction zone and a second reaction zone that are interconnected. The first reaction zone and the second reaction zone are arranged sequentially from top to bottom; The angle between the bottom wall and the side wall of the second reaction zone is an acute angle; The cathode is located above the anode crucible and is used to generate a plasma jet toward the reaction chamber; The ratio between the depth of the second reaction zone and the diameter of the bottom wall is 0.25 to 0.45; The angle between the sidewall of the first reaction zone and the horizontal direction is 30~85°; The part of the reaction chamber that contracts inward along the horizontal direction forms a connecting part; The connecting portion connects the first reaction zone and the second reaction zone; The ratio between the diameter of the connecting part and the diameter of the bottom wall is 0.35 to 0.75; The cathode includes a rod-shaped portion and a working end located at one end of the rod-shaped portion; The ratio between the diameter of the rod-shaped portion and the diameter of the connecting portion is 0.15 to 0.65; At least the inner surface of the sidewall corresponding to the second reaction zone is covered with an insulating high-temperature resistant coating, but the anode arc-affected area on the bottom wall is not covered.

2. The arc plasma reactor according to claim 1, characterized in that The working end faces the reaction chamber.

3. The arc plasma reactor of claim 1, wherein, The arc plasma reactor also includes a power supply assembly; The cathode is electrically connected to the cathode output terminal of the power supply assembly; The bottom wall of the anode crucible is electrically connected to the anode output terminal of the power supply assembly to form a transferred arc plasma between the cathode and the bottom wall.

4. The arc plasma reactor of claim 1, wherein, The electric arc plasma reactor is a transferred arc plasma reactor; The cathode is a tungsten needle.

5. A metallurgical heat treatment method, characterized by, The use of the arc plasma reactor according to any one of claims 1 to 4 includes the following steps: S1: Provide the material to be processed and lay it at the bottom of the reaction chamber; S2: Start the electric arc plasma reactor to generate a plasma jet that impacts and heats the material to be processed. After the reaction is completed, the product is obtained. The operating current of the arc plasma reactor is 20A~200kA.

6. The metallurgical heat treatment method according to claim 5, characterized in that, The heating is performed under a protective atmosphere; The reaction pressure is 1000~200000 Pa; The reaction duration is ≤120 min; The material to be processed includes at least one of metal oxides and silicon-containing raw materials.

7. The metallurgical heat treatment method according to claim 6, characterized in that, The protective atmosphere includes an inert gas or a reducing gas; The inert gas includes at least one of argon, nitrogen, helium, and neon; The reducing gas includes at least one of hydrogen, methane, carbon monoxide, ethylene, and acetylene.

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