Method for smelting magnesium metal through plasma electric arc furnace

Abstract

The invention provides a method for smelting magnesium metal through a plasma electric arc furnace. The method comprises the following steps: S1, adding magnesium-containing ore and a flux into a plasma electric arc furnace, melting under the action of plasma electric arc to form a high-magnesium slag molten pool, and discharging carbon dioxide flue gas; s2, a reducing agent is added into the high-magnesium slag molten pool for a reduction reaction, magnesium-poor slag is obtained, and magnesium steam is discharged; and S3, the magnesium steam is condensed and recycled, and liquid magnesium is obtained. The plasma electric arc furnace is adopted as a smelting place of magnesium metal, the high-temperature characteristic of the plasma electric arc is utilized, the temperature of the plasma electric arc furnace is up to 15000-30000 DEG C, magnesium-containing ore can be effectively melted, heat for molten pool reaction and heat balance is provided, meanwhile, the reduction operation difficulty is low, magnesium steam generated through reduction is recycled in a liquid state after being condensed, and the energy consumption is low. Semi-continuous production of magnesium can be achieved, and the operation rate and the direct recovery rate of magnesium metal are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium metal smelting, and in particular to a method for smelting magnesium metal in a plasma arc furnace. Background Art

[0002] Magnesium is one of the top ten nonferrous metals. Raw magnesium and magnesium alloys are widely used in transportation, electronic communications, medical treatment, aerospace, military and other fields. Currently, the main methods for magnesium smelting are electrolysis and thermal reduction. The electrolysis method includes processes such as the Dawu process (magnesium oxide chloride process), the carnallite process, the AMC process, and the Norsk process. It mainly dehydrates or melts a solution containing magnesium chloride from quartz, brine, or seawater to form a magnesium chloride melt, which is then electrolyzed. Electrolysis of magnesium smelting has the advantages of energy saving, good product uniformity, ease of large-scale industrial production, a continuous production process, and low production costs. However, the electrolysis method is also energy-intensive. The production process for preparing anhydrous magnesium chloride is difficult to control, the high-temperature dehydration of bischofite requires high energy consumption, the acidic atmosphere causes severe corrosion to equipment, and the production of difficult-to-treat wastewater, waste gas, and waste residue, causing serious environmental pollution.

[0003] Thermal reduction methods primarily include the Pidgeon process, the Balzano process, and the Magni process. The most widely used is the Pidgeon process, which involves using ferrosilicon to thermally reduce magnesium oxide (MgO) produced by calcining carbonate ore. The Pidgeon process boasts a short process flow, simple equipment, low plant investment, flexible production scale, and high purity of the finished magnesium. However, its main disadvantages include low thermal efficiency, a short reduction tank life, high reduction furnace costs, discontinuous production, poor working conditions, low automation, and high labor intensity.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The main purpose of the present invention is to provide a method to solve the problems of poor process control, high energy consumption, and serious environmental pollution caused by the production of wastewater, waste gas and waste residue in the electrolysis method in the existing magnesium smelting method; and the problems of low heat utilization rate, discontinuous production process and high labor intensity in the traditional thermal reduction method.

[0006] To achieve the above-mentioned object, according to one aspect of the present invention, a method for smelting metallic magnesium in a plasma arc furnace is provided, the method comprising: step S1, adding magnesium-containing ore and flux into a plasma arc furnace and melting them under the action of a plasma arc to form a high-magnesium slag molten pool, and discharging carbon dioxide flue gas; step S2, adding a reducing agent to the high-magnesium slag molten pool to carry out a reduction reaction to obtain magnesium-depleted slag, and discharging magnesium vapor; step S3, condensing and recovering the magnesium vapor to obtain liquid magnesium.

[0007] Furthermore, the plasma arc furnace includes a furnace body, the furnace body includes a furnace top, the furnace top is provided with a flue gas outlet, multiple plasma arc gun nozzles and multiple feeding ports, the flue gas outlet is arranged in the center of the furnace top, and the multiple plasma arc gun nozzles and multiple feeding ports are spaced apart on both sides of the flue gas outlet.

[0008] Furthermore, the furnace body also includes a furnace side wall, and a slag outlet and an air outlet are provided at the bottom of the furnace side wall, and the slag outlet is higher than the air outlet.

[0009] Furthermore, the outer side of the furnace body is provided with an insulation jacket, which is a molten steel jacket or a copper jacket, and the inner side of the furnace body is provided with a heat conducting layer, which is made of carbon bricks.

[0010] Furthermore, the mass ratio of flux to magnesium-containing ore is 0.1-0.2:1.

[0011] Furthermore, the magnesium-containing ore is dolomite and / or magnesite, and preferably the dolomite includes the following components by mass percentage: CaCO3: 35% to 55%, MgCO3: 45% to 65%; preferably, the mass content of MgCO3 in the magnesite is greater than 90%.

[0012] Furthermore, the particle size of the magnesium-containing ore is 50-200 mesh.

[0013] Furthermore, in terms of mass percentage, the flux includes Al2O3: 50-70%, Fe2O3: 10-20%, SiO2: 10-20%, TiO2: 5-10%, CaO: 1%-2%, and MgO: 1%-2%.

[0014] Furthermore, the particle size of the flux is 50-200 mesh.

[0015] Furthermore, the reducing agent is a siliceous reducing agent, and the mass content of silicon in the reducing agent is greater than 75%.

[0016] Furthermore, the reducing agent includes at least one of ferrosilicon and waste solar cells.

[0017] Furthermore, the particle size of the reducing agent is 100-300 meshes.

[0018] Furthermore, in step S1, the depth of the high-magnesium slag molten pool is 1 / 3-1 / 2 of the depth of the furnace body and hearth.

[0019] Furthermore, in step S2, the temperature of the reduction reaction is 1700-1800° C., and the vacuum degree of the reduction reaction is 25-135 kPa.

[0020] Furthermore, in step S2, the mass content of MgO in the magnesium-poor slag is 3%-5%.

[0021] Applying the technical solution of the present application, the method for smelting metallic magnesium using a plasma arc furnace provided in the present application adopts a plasma arc furnace as the smelting place for metallic magnesium, and utilizes the high temperature characteristics of the plasma arc, whose temperature is as high as 15,000-30,000°C, which can effectively melt magnesium-containing ore and provide heat for molten pool reaction and thermal balance. At the same time, its reduction operation is easy, and the magnesium vapor produced by the reduction is condensed and recovered in liquid form, which can realize semi-continuous production of magnesium and greatly improve the operating rate and direct recovery rate of metallic magnesium.

[0022] In addition, compared with the electrolytic process, the method for smelting metallic magnesium using a plasma arc furnace provided in this application has strong adaptability to raw materials, low energy consumption, and energy consumption reduced by 50%-70%; compared with the traditional thermal reduction process, the direct recovery rate of metallic magnesium is increased by 10%-20%, and energy consumption is reduced by 10%-20%. The single-series processing capacity can meet various scales such as 300 to 7,000 tons / year. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 shows a schematic cross-sectional view of a plasma arc furnace according to some embodiments of the present invention; and

[0025] Figure 2 A schematic cross-sectional view from another angle of a plasma arc furnace provided according to some embodiments of the present invention is shown.

[0026] The above drawings include the following reference numerals:

[0027] 100. Furnace body; 110. Furnace roof; 111. Flue gas outlet; 112. Plasma arc gun muzzle; 113. Feeding port; 120. Furnace sidewall; 121. Slag outlet; 122. Vent port; 130. Insulation jacket; 140. Heat-conducting layer; 150. Furnace bottom. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0029] As analyzed in the background of this application, existing magnesium smelting methods mainly include electrolysis and thermal reduction. The electrolysis method suffers from poor process control, high energy consumption, and the production of wastewater, waste gas, and waste residue, which causes serious environmental pollution. Traditional thermal reduction methods suffer from low thermal utilization, discontinuous production processes, and high labor intensity. To address these issues with existing magnesium smelting processes, this application provides a method for smelting metallic magnesium using a plasma arc furnace.

[0030] In a typical embodiment of the present application, the present application provides a method for smelting metallic magnesium in a plasma arc furnace, which includes the following steps: step S1, adding magnesium-containing ore and flux into a plasma arc furnace and melting them under the action of a plasma arc to form a high-magnesium slag pool, and discharging carbon dioxide flue gas; step S2, adding a reducing agent to the high-magnesium slag pool for a reduction reaction to obtain a magnesium-depleted slag, and discharging magnesium vapor; step S3, condensing and recovering the magnesium vapor to obtain liquid magnesium.

[0031] The method for smelting metallic magnesium using a plasma arc furnace provided in the present application adopts a plasma arc furnace as the smelting site for metallic magnesium, and utilizes the high temperature characteristics of the plasma arc, with a temperature of up to 15,000-30,000°C, which can effectively melt magnesium-containing ore and provide heat for molten pool reaction and thermal balance. At the same time, its reduction operation is easy, and the magnesium vapor produced by the reduction is condensed and recovered in liquid form, which can realize semi-continuous production of magnesium and greatly improve the operating rate and direct recovery rate of metallic magnesium.

[0032] In addition, compared with the electrolytic process, the method for smelting metallic magnesium using a plasma arc furnace provided in this application has strong adaptability to raw materials, low energy consumption, and energy consumption reduced by 50%-70%; compared with the traditional thermal reduction process, the direct recovery rate of metallic magnesium is increased by 10%-20%, and energy consumption is reduced by 10%-20%. The single-series processing capacity can meet various scales such as 300 to 7,000 tons / year.

[0033] In some embodiments of the present application, Figure 1 As shown, the plasma arc furnace includes a furnace body 100, and the furnace body 100 includes a furnace top 110. The furnace top 110 is provided with a flue gas outlet 111, multiple plasma arc gun nozzles 112 and multiple discharge ports 113, wherein the flue gas outlet 111 is arranged in the center of the furnace top 110, which can effectively reduce the expansion effect of the furnace body 100, and the multiple plasma arc gun nozzles 112 and the multiple discharge ports 113 are spaced apart on both sides of the flue gas outlet 111, which is beneficial to the uniform distribution of materials (containing magnesium ore and flux) in the furnace, and is also beneficial to the uniform distribution of reducing agents, which is beneficial to the continuity and stability of magnesium vapor production.

[0034] In some embodiments of the present application, Figure 1 As shown, the furnace body 100 further includes a furnace side wall 120 , and a slag outlet 121 and an air outlet 122 are provided at the bottom of the furnace side wall 120 , and the slag prevention outlet is higher than the air outlet 122 to facilitate continuous operation.

[0035] In some embodiments of the present application, the outer side of the furnace body 100 is provided with an insulation jacket 130 to help maintain a uniform temperature within the furnace body 100. The insulation jacket 130 is a steel jacket or a copper jacket, preferably a copper jacket. The inner side (furnace) of the furnace body 100 is provided with a heat-conducting layer 140. The heat-conducting layer 140 is constructed of carbon bricks to enhance the reducing atmosphere within the furnace body 100. Furthermore, the carbon bricks have strong thermal conductivity and can effectively maintain the temperature of the furnace wall.

[0036] In some embodiments of the present application, Figure 1 As shown, the plasma arc furnace adopts a flat furnace structure, which is conducive to reducing the height of the equipment, reducing the height difference of the equipment layout, and thus reducing the investment in plant construction.

[0037] In some embodiments of the present application, the furnace body 100 further includes a furnace bottom 150, which can be directly installed on the ground. A heat-conducting layer 140 is also provided on the inner side of the furnace bottom 150. This heat-conducting layer 140 is a carbon brick masonry layer. In some embodiments of the present application, each part of the furnace body 100 can adopt its own cooling method as needed, and a single elastic skeleton furnace is used to ensure a long furnace life.

[0038] In some embodiments of the present application, according to the process characteristics of magnesium vapor volatilization, a well-designed sealing structure of the furnace body 100 is required.

[0039] In some embodiments of the present application, in order to improve the melting efficiency of magnesium-containing ore, the mass ratio of solvent to magnesium-containing ore is preferably 0.1-0.2:1, such as 0.1:1, 0.12:1, 0.15:1, 0.16:1, 0.18:1, 0.2:1 or a range value consisting of any two values.

[0040] The magnesium-containing ore is commonly used in the art, preferably dolomite and / or magnesite. Specifically, the dolomite comprises the following components, by mass percentage: CaCO3: 35% to 55%, MgCO3: 45% to 65%. The main component of magnesite is MgCO3, and the mass content of MgCO3 is greater than 90%.

[0041] In order to further improve the melting efficiency and mixing uniformity of the magnesium-containing ore with the flux during the smelting process, the particle size of the magnesium-containing ore is preferably 50-200 mesh, such as 50 mesh, 80 mesh, 100 mesh, 120 mesh, 150 mesh, 180 mesh, 200 mesh or a range value consisting of any two values.

[0042] In order to further improve the melting efficiency of magnesium-containing ore, the flux preferably includes, by mass percentage, Al2O3: 50-70%, Fe2O3: 10-20%, SiO2: 10-20%, TiO2: 5-10%, CaO: 1%-2%, and MgO: 1%-2%. Specifically, in the flux, the mass content of Al2O3 is 50%, 55%, 60%, 65%, 70% or a range consisting of any two numerical values; the mass content of Fe2O3 is 10%, 12%, 15%, 18%, 20% or a range consisting of any two numerical values; the mass content of SiO2 is 10%, 12%, 15%, 18%, 20% or a range consisting of any two numerical values; the mass content of TiO2 is 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two numerical values; the mass content of CaO is 1%, 1.2%, 1.5%, 1.8%, 2% or a range consisting of any two numerical values; the mass content of MgO is 1%, 1.2%, 1.5%, 1.8%, 2% or a range consisting of any two numerical values.

[0043] In order to promote uniform mixing of the flux and the magnesium-containing ore, the particle size of the flux is preferably 50-200 mesh, such as 50 mesh, 80 mesh, 100 mesh, 120 mesh, 150 mesh, 180 mesh, 200 mesh or a range consisting of any two values.

[0044] In some embodiments, the reducing agent is a siliceous reducing agent, preferably a silicon reducing agent having a silicon mass content greater than 75%, including one or more silicon-containing substances such as ferrosilicon and waste solar panels.

[0045] In some embodiments, the particle size of the reducing agent is 100-300 mesh to facilitate better mixing with the magnesium-containing ore. Specifically, the particle size of the reducing agent is 100 mesh, 150 mesh, 200 mesh, 250 mesh, 300 mesh, or a range consisting of any two values.

[0046] In order to further improve the melting uniformity of the magnesium-containing material during the smelting process, so as to further improve the smelting efficiency and realize semi-continuous production, it is preferred to continuously add the magnesium-containing ore and flux so that the depth of the high-magnesium molten pool is 1 / 3-1 / 2 of the depth of the furnace chamber inside the furnace body 100, and then add the reducing agent to start smelting.

[0047] In order to further promote the reduction of magnesium in the magnesium-containing ore into magnesium vapor, it is preferred that in the above step S2, the temperature of the reduction reaction is 1700-1800°C, and the vacuum degree of the reduction reaction is 25-135 kPa.

[0048] Specifically, the temperature of the reduction reaction is 1700°C, 1720°C, 1750°C, 1780°C, 1800°C or a range consisting of any two values, and the vacuum degree of the reduction reaction is 25kPa, 50kPa, 75kPa, 100kPa, 120kPa, 135kPa or a range consisting of any two values.

[0049] In some embodiments, in step S2, the mass content of MgO in the magnesium-depleted slag is 3%-5%. After completing the first production cycle, a portion of the magnesium-depleted slag is retained in the furnace, and then flux and magnesium-containing ore are added to continue the second production cycle.

[0050] In some specific embodiments, a method for smelting magnesium metal in a plasma arc furnace comprises the following steps:

[0051] (1) adding flux and magnesium-containing ore into the plasma arc furnace from the feed port 113;

[0052] (2) The flux and magnesium-containing ore are melted at high temperature in the plasma arc to form a high-magnesium slag molten pool, while producing CO2 flue gas, which is discharged through the flue gas outlet 111;

[0053] (3) The plasma arc furnace is sealed and evacuated with a vacuum pump to maintain a vacuum degree of 25-135 kPa;

[0054] (4) Adding a reducing agent into the high-magnesium slag molten pool from the discharge port 113; under the action of the reducing agent, the high-magnesium slag is reduced, and the produced magnesium-poor slag is discharged from the slag discharge port 121, while the produced magnesium vapor is discharged through the flue gas outlet 111 and recovered by condensation to obtain liquid magnesium.

[0055] The beneficial effects of the present application will be further illustrated below with reference to examples and comparative examples.

[0056] Example 1

[0057] This embodiment provides a method for smelting magnesium metal in a plasma arc furnace. The method is carried out in a plasma arc furnace. Figure 1 and Figure 2 As shown, the plasma arc furnace includes a furnace body 100. The top of the furnace body 100 is provided with a flue gas outlet 111, multiple plasma arc gun nozzles 112, and multiple material discharge ports 113. The flue gas outlet 111 is located in the center of the furnace body 100, and the multiple plasma arc gun nozzles 112 and multiple material discharge ports 113 are spaced apart on either side of the flue gas outlet 111. A slag tapping port 121 and an air discharge port 122 are provided at the top of the furnace body 100, with the slag tapping port 121 being higher than the air discharge port 122. The outer surface of the furnace body 100 is covered with an insulation jacket 130, which is a copper water jacket. The interior of the furnace chamber of the furnace body 100 is built with a heat-conducting layer 140 made of carbon bricks.

[0058] The method comprises the following steps:

[0059] (1) adding a flux with a particle size of 100 mesh and dolomite with a particle size of 100 mesh into a plasma arc furnace from a feed port 113; wherein the flux comprises the following components by mass percentage: Al2O3: 68%, Fe2O3: 18%, SiO2: 15%, TiO2: 8%, CaO: 1%, MgO: 1%; and the mass ratio of the flux to the dolomite is 0.15:1;

[0060] (2) The flux and magnesium-containing ore are melted at high temperature in the plasma arc to form a high-magnesium slag molten pool. The depth of the high-magnesium slag molten pool is 1 / 3 of the furnace depth, and the molten pool temperature is 1600°C. At the same time, CO2 flue gas is produced and discharged through the flue gas outlet 111;

[0061] (3) The plasma arc furnace is sealed and evacuated with a vacuum pump to maintain a vacuum degree of 100 kPa;

[0062] (4) A closed spiral feeding device is used to add the reducing agent ferrosilicon powder (model FeSi75) into the high-magnesium slag molten pool from the discharge port 113; under the action of the reducing agent, the high-magnesium slag is reduced at a reduction temperature of 1750°C, and the produced magnesium-poor slag is discharged from the slag discharge port 121. At the same time, the produced magnesium vapor is discharged through the flue gas outlet 111 and condensed and recovered by a condensation system to obtain liquid magnesium.

[0063] Example 2

[0064] This embodiment provides a method for smelting metallic magnesium in a plasma arc furnace. The method is carried out in a plasma arc furnace, which is the same as the plasma arc furnace provided in the above embodiment 1.

[0065] The method comprises the following steps:

[0066] (1) adding a 100-mesh flux and 100-mesh dolomite (main components of dolomite: CaCO3: 39 wt%, MgCO3: 58 wt%) into a plasma arc furnace from a feed port 113; wherein the flux comprises the following components by mass percentage: Al2O3: 68%, Fe2O3: 18%, SiO2: 15%, TiO2: 8%, CaO: 1%, MgO: 1%; and the mass ratio of the solvent to the dolomite is 0.1:1;

[0067] (2) The flux and the magnesium-containing ore are melted at a high temperature in the plasma arc to form a high-magnesium slag molten pool. The depth of the high-magnesium slag molten pool is 1 / 2 of the depth of the furnace body 100, and the molten pool temperature is 1700°C. At the same time, CO2 flue gas is produced and discharged through the flue gas outlet 111;

[0068] (3) The plasma arc furnace is sealed and evacuated using a vacuum pump to maintain a vacuum degree of 135 kPa;

[0069] (4) A closed spiral feeding device is used to add the reducing agent ferrosilicon powder (model FeSi75) into the high-magnesium slag molten pool from the discharge port 113; under the action of the reducing agent, the high-magnesium slag is reduced at a reduction temperature of 1800°C, and the produced magnesium-poor slag is discharged from the slag discharge port 121. At the same time, the produced magnesium vapor is discharged through the flue gas outlet 111 and condensed and recovered by a condensation system to obtain liquid magnesium.

[0070] Example 3

[0071] The difference between this embodiment and embodiment 1 is that the mass ratio of flux to dolomite is 0.1:1.

[0072] Example 4

[0073] The difference between this embodiment and embodiment 1 is that the mass ratio of flux to dolomite is 0.05:1.

[0074] Example 5

[0075] The difference between this embodiment and embodiment 1 is that the mass ratio of flux to dolomite is 0.3:1.

[0076] Example 6

[0077] The difference between this embodiment and embodiment 1 is that in step (3) and step (4), the vacuum degree in the plasma arc furnace is adjusted to 25 kPa and the temperature is adjusted to 1700°C.

[0078] Example 7

[0079] The difference between this embodiment and embodiment 1 is that in step (3), the vacuum degree in the plasma arc furnace is adjusted to 20 kPa.

[0080] Example 8

[0081] The difference between this embodiment and embodiment 1 is that in step (3), the vacuum degree in the plasma arc furnace is adjusted to 150 kPa.

[0082] Example 9

[0083] The difference between this embodiment and embodiment 1 is that in step (4), the temperature in the plasma arc furnace is adjusted to 1600°C.

[0084] Example 10

[0085] The difference between this embodiment and embodiment 1 is that in step (4), the temperature in the plasma arc furnace is adjusted to 1900°C.

[0086] Example 11

[0087] The difference between this embodiment and embodiment 1 is that in step (1), magnesite with a particle size of 50 mesh (MgCO3 content>90wt%) is used to replace dolomite.

[0088] Example 12

[0089] The difference between this embodiment and embodiment 1 is that in step (1), magnesite with a particle size of 200 mesh (MgCO3 content>90wt%) is used to replace dolomite.

[0090] Comparative Example 1

[0091] This comparative example provides a method for smelting metallic magnesium, wherein dolomite (main components of dolomite: CaCO3: 39wt%, MgCO3: 58wt%) is calcined and chlorinated, and then the magnesium is smelted using an electrolytic process.

[0092] Comparative Example 2

[0093] This comparative example provides a method for smelting metallic magnesium, in which dolomite (main components of dolomite: CaCO3: 39wt%, MgCO3: 58wt%) is subjected to magnesium smelting using a traditional thermal reduction process - the Magni process.

[0094] Test example

[0095] The energy consumption required to produce one ton of magnesium by the magnesium smelting method in the above examples and comparative examples, the mass content of MgO in the magnesium-lean slag, and the direct recovery rate of Mg were tested, and the results are shown in Table 1 below.

[0096] The direct recovery rate of Mg is calculated as follows: direct recovery rate of Mg = [mass of liquid magnesium / (mass of dolomite × mass content of Mg in dolomite)] × 100%.

[0097] Table 1

[0098]

[0099]

[0100] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects: the method for smelting metallic magnesium in a plasma arc furnace provided in the present application adopts a plasma arc furnace as a smelting place for metallic magnesium, and utilizes the high temperature characteristics of the plasma arc. Its temperature is as high as 15,000-30,000°C, which can effectively melt magnesium-containing ore and provide heat for molten pool reaction and thermal balance. At the same time, its reduction operation is easy, and the magnesium vapor produced by the reduction is condensed and recovered in liquid form, which can realize semi-continuous production of magnesium and greatly improve the operating rate and direct recovery rate of metallic magnesium.

[0101] In addition, compared with the electrolytic process, the method for smelting metallic magnesium using a plasma arc furnace provided in this application has strong adaptability to raw materials, low energy consumption, and energy consumption reduced by 50%-70%; compared with the traditional thermal reduction process, the direct recovery rate of metallic magnesium is increased by 10%-20%, and energy consumption is reduced by 10%-20%. The single-series processing capacity can meet various scales such as 300 to 7,000 tons / year.

[0102] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for smelting magnesium metal in a plasma arc furnace, characterized in that: The method comprises: Step S1, adding magnesium-containing ore and flux into a plasma arc furnace and melting them under the action of a plasma arc to form a high-magnesium slag molten pool, and discharging carbon dioxide fume; Step S2, adding a reducing agent to the high-magnesium slag molten pool to perform a reduction reaction to obtain magnesium-poor slag, and discharging magnesium vapor; Step S3: condensing and recovering the magnesium vapor to obtain liquid magnesium.

2. The method for smelting magnesium metal in a plasma arc furnace according to claim 1, characterized in that: The plasma arc furnace comprises a furnace body (100), the furnace body (100) comprises a furnace top (110), the furnace top (110) is provided with a smoke outlet (111), a plurality of plasma arc gun nozzles (112) and a plurality of material discharge ports (113), the smoke outlet (111) is arranged at the center of the furnace top (110), and the plurality of plasma arc gun nozzles (112) and the plurality of material discharge ports (113) are arranged at intervals on both sides of the smoke outlet (111).

3. The method for smelting magnesium metal in a plasma arc furnace according to claim 1, characterized in that: The furnace body (100) further comprises a furnace side wall (120), and a slag tapping port (121) and an air outlet (122) are provided at the bottom of the furnace side wall (120), and the slag tapping port (121) is higher than the air outlet (122).

4. The method for smelting magnesium metal in a plasma arc furnace according to claim 1, characterized in that: The outer side of the furnace body (100) is provided with a heat-insulating jacket (130), which is a steel jacket or a copper jacket. The inner side of the furnace body (100) is provided with a heat-conducting layer (140), which is made of carbon bricks.

5. The method for smelting magnesium metal using a plasma arc furnace according to any one of claims 1 to 4, characterized in that: The mass ratio of the flux to the magnesium-containing ore is 0.1-0.2:1; And / or, the magnesium-containing ore is dolomite and / or magnesite, preferably the dolomite comprises the following components by mass percentage: CaCO3: 35% to 55%, MgCO3: 45% to 65%; preferably the mass content of MgCO3 in the magnesite is greater than 90%; And / or, the particle size of the magnesium-containing ore is 50-200 mesh.

6. The method for smelting magnesium metal in a plasma arc furnace according to any one of claims 1 to 4, characterized in that: According to mass percentage, the flux includes Al2O3: 50-70%, Fe2O3: 10-20%, SiO2: 10-20%, TiO2: 5-10%, CaO: 1%-2%, MgO: 1%-2%; And / or, the particle size of the flux is 50-200 mesh.

7. The method for smelting magnesium metal using a plasma arc furnace according to any one of claims 1 to 4, characterized in that: The reducing agent is a siliceous reducing agent, and the mass content of silicon in the reducing agent is greater than 75%; and / or, the reducing agent comprises at least one of ferrosilicon and waste solar panels; And / or, the particle size of the reducing agent is 100-300 mesh.

8. The method for smelting magnesium metal using a plasma arc furnace according to any one of claims 1 to 4, characterized in that: In the step S1, the depth of the high-magnesium slag molten pool is 1 / 3-1 / 2 of the depth of the furnace body (100).

9. The method for smelting magnesium metal using a plasma arc furnace according to any one of claims 1 to 4, characterized in that: In step S2, the temperature of the reduction reaction is 1700-1800° C., and the vacuum degree of the reduction reaction is 25-135 kPa.

10. The method for smelting magnesium metal using a plasma arc furnace according to any one of claims 1 to 4, characterized in that: In the step S2, the mass content of MgO in the magnesium-poor slag is 3%-5%.

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