System and method for preparing magnesium metal through vacuum carbon thermal reduction

Abstract

The invention belongs to the technical field of metallurgy, and particularly discloses a system and method for preparing magnesium metal through vacuum carbon thermal reduction.The system comprises a reactor cavity, a vacuumizing module and a temperature regulation and control module, a reaction area and a first condenser are arranged in the reactor cavity, and the reaction area is used for generating high-temperature mixed gas containing CO gas and magnesium steam; the first condenser is detachably mounted at the downstream of a high-temperature mixed gas containing CO gas and magnesium steam generated in the reaction zone, and the first condenser is used for generating solid magnesium containing solid carbon and solid magnesium oxide impurities; a high-temperature reaction melt is arranged in the reaction area and is used for receiving solid carbon and solid magnesium oxide from the first condenser; the vacuumizing module is used for vacuumizing the reactor cavity, and the temperature regulation and control module is used for detecting and controlling the temperature of each part in the reactor cavity. By adopting the technical scheme, the yield of metal magnesium is improved through the cavity structure of the reactor.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology and relates to a system and method for preparing metallic magnesium by vacuum carbothermal reduction. Background Technology

[0002] Magnesium and magnesium alloys are hailed as "green engineering materials of the 21st century" and "revolutionary medical metal materials." As the lightest structural metal in industrial applications, magnesium possesses advantages such as light weight, high specific strength, high specific stiffness, good biomechanical properties, and low corrosion rate. It is widely used in aerospace, military industry, nuclear energy industry, automotive industry, 3C industry, sacrificial anodes, and biomedicine. Currently, with rapid industrial development, global demand for magnesium is growing by 10% annually, indicating a promising future.

[0003] Currently, the main commercial methods for producing magnesium worldwide are electrolysis and the Pidgeon process. Electrolytic magnesium production involves two main steps: the production of magnesium chloride and the electrolytic production of magnesium. This method can be further divided into the anhydrous magnesium chloride electrolysis method using magnesite as raw material and the electrolysis method using seawater as raw material. While there are many electrolytic magnesium production processes, their basic principles are the same. However, current drawbacks of electrolytic magnesium production include: the difficulty in controlling the production process of anhydrous magnesium chloride; the need for high temperatures and acidic atmospheres for the dehydration of magnesium chloride, resulting in high energy consumption and severe equipment corrosion; and the pollution caused by wastewater, waste gas, and waste residue discharged during the electrolytic production process, leading to high treatment costs.

[0004] The Pidgeon process for magnesium smelting is a silicothermic reduction process for magnesium smelting developed by Canadian scientist Professor LMPidgeon in 1941. The principle of the Pidgeon process is as follows: calcined dolomite (CaO·MgO) and ferrosilicon (Si-Fe) containing 75% silicon are ground into fine powder in a certain proportion, pressed into pellets, and then placed in a vacuum reaction distillation tank made of heat-resistant alloy. The vacuum is evacuated to 1-13 Pa, and the pellets are heated to a high temperature of 1150-1200℃. The calcined dolomite (CaO·MgO) and ferrosilicon (Si-Fe) containing 75% silicon undergo a silicothermic reduction reaction as shown in reaction (1) to generate high-temperature magnesium vapor. The magnesium vapor undergoes a condensation reaction as shown in reaction (2) in the low-temperature condensation zone of the vacuum reaction distillation tank to crystallize into solid magnesium.

[0005] 2(CaO·MgO)(solid) + Si(solid) = 2CaO·SiO2(solid) + 2Mg(gas) (1)

[0006] Mg(gas) = ​​Mg(solid) (2)

[0007] The Pidgeon process for magnesium smelting has seen rapid development over the past 20 years due to its advantages, including quick plant construction, low investment, availability of multiple heat sources, and high product quality. However, its outdated production capacity, characterized by non-continuous production, high energy consumption, and the generation of solid waste and dust pollution, will gradually be phased out as domestic environmental regulations become increasingly stringent.

[0008] Vacuum carbothermal magnesium smelting process is considered a promising magnesium production process due to its advantages of low cost, low energy consumption, and low resource consumption. The principle of vacuum carbothermal magnesium smelting process is as follows: raw materials containing magnesium oxide and carbonaceous reducing agents are mixed in a certain proportion, pressed into pellets or not, and placed in the reactor cavity. The vacuum is evacuated to below 1000 Pa and heated to a high temperature of not less than 1200℃ under vacuum or inert gas atmosphere. The raw materials containing magnesium oxide and carbonaceous reducing agents undergo a carbothermal reduction reaction as shown in reaction formula (3) to generate high-temperature carbon monoxide gas and magnesium vapor. The magnesium vapor undergoes a condensation reaction as shown in reaction formula (2) in the low-temperature condensation zone of the vacuum reaction distillation tank to form solid crystalline magnesium.

[0009] C(solid / liquid) + MgO(solid / liquid) = CO(gas) + Mg(gas) (3)

[0010] Regarding the condensation reaction (2) of magnesium vapor, in such a case... Figure 7 In the three-phase equilibrium phase diagram of elemental magnesium shown, as long as the temperature of the high-temperature magnesium vapor is reduced to below 650℃ under a pressure below 333 Pa, the magnesium vapor can directly undergo a sublimation reaction to form solid magnesium. This cooling and sublimation of high-temperature magnesium vapor is easily achieved in engineering. However, despite decades of development and improvement, the vacuum carbothermal magnesium smelting process has not yet entered large-scale commercial production. This is mainly due to two unresolved technical problems in the vacuum carbothermal magnesium smelting process: firstly, the material reaction rate is too slow; and secondly, there are intractable reverse reactions, resulting in a very low yield of metallic magnesium.

[0011] The slow reaction rate of materials in the vacuum carbothermic magnesium smelting process is mainly due to the fact that conventional magnesium oxide-containing raw materials and carbonaceous reducing agents are solid within the reaction temperature range, resulting in a solid-solid reaction. To achieve a carbothermic reduction reaction between solid and solid reactants, the magnesium oxide-containing raw materials and carbonaceous reducing agents need to be ground, mixed, and pressurized into pellets, then placed at a high temperature of approximately 1200°C. This high pressure and high temperature approach brings magnesium oxide molecules and carbon atoms as close as possible, increasing their molecular kinetic energy to facilitate the chemical reaction between MgO and C. To accelerate the carbothermic reduction reaction rate, the industry has proposed modifying the solid-solid reaction into a solid-liquid or liquid-liquid reaction. This involves introducing a high-temperature molten mixture of magnesium oxide-containing and / or a high-temperature molten mixture of carbon-containing components to participate in the high-temperature carbothermic reduction reaction. Patent document CN102041398B proposes placing calcined magnesite and elemental carbon into a high-temperature molten CaO-MgO-Al2O3-SiO2 quaternary slag. The elemental carbon and MgO in the slag can undergo a rapid carbothermic reduction reaction, and the calcined magnesite is simultaneously added to the CaO-MgO-Al2O3-SiO2 quaternary slag. Patent documents CN103205583B, CN106011500A, and CN107541608A propose placing magnesium oxide-containing raw materials and carbonaceous reducing agents into a high-temperature molten metal M-carbon binary melt (M being one or more of iron, manganese, tin, and cerium). The magnesium oxide-containing raw materials and carbon in the binary melt can undergo a rapid carbothermic reduction reaction, and the carbonaceous reducing agent is simultaneously added to the metal M-carbon binary melt.

[0012] The reverse reaction of the vacuum carbothermal magnesium smelting process and the resulting low yield of metallic magnesium are the most difficult problems to overcome on its path to industrialization. The so-called reverse reaction of the vacuum carbothermal magnesium smelting process refers to the process in which, during the cooling and condensation of the high-temperature mixture of CO gas and magnesium vapor generated by the high-temperature carbothermal reduction reaction in the condensation zone, part of the magnesium vapor undergoes the reaction (2) as expected to generate solid magnesium, while the other part of the magnesium vapor inevitably reacts with CO gas (4) (i.e., the reverse reaction of reaction (3)) to generate solid carbon and solid magnesium oxide.

[0013] CO(gas) + Mg(gas) = ​​C(solid) + MgO(solid) (4)

[0014] On the one hand, from a thermodynamic point of view, reaction (3) occurs when the working temperature is higher than the critical reaction temperature of the carbothermic reduction reaction, and reaction (4) is the reverse reaction of reaction (3) when the working temperature is lower than the critical reaction temperature of the carbothermic reduction reaction. On the other hand, the common experimental conclusion of industry scholars is that high-temperature magnesium vapor and CO gas will not only react (4) during the cooling and condensation process, but also react (2). This is because the ratio of the number of magnesium vapor molecules to CO gas molecules in the high-temperature mixed gas generated by the carbothermic reduction reaction is 1:1. During the cooling and condensation process, some magnesium vapor molecules do not collide with CO gas molecules, or although they collide, they cannot cross the reaction barrier of reaction (4) because the temperature of magnesium vapor molecules or CO gas molecules is too low and their kinetic energy is too small. As a result, a considerable number of magnesium vapor molecules react (2) to generate solid magnesium, especially when high-temperature magnesium vapor and CO gas are rapidly cooled and condensed.

[0015] However, rapid cooling of high-temperature magnesium vapor and CO gas brings new problems: as mentioned in patent document CN115161478A, an Australian research team conducted supersonic condensation experiments using Laval nozzles and found that either the condensed magnesium powder easily clogged the nozzle, or the high-temperature and high-pressure process conditions without magnesium powder clogging the nozzle were too harsh and difficult to industrialize. The patent document also mentions that a team at the National Engineering Laboratory for Vacuum Metallurgy at Kunming University of Science and Technology discovered that due to the large distance between the reduction chamber and the condensation chamber and the excessively low condensation temperature, only powdered solid magnesium could be obtained, posing a risk of explosion during the process of opening the furnace to extract magnesium. In August 2022, the team at the National Engineering Laboratory for Vacuum Metallurgy of Kunming University of Science and Technology proposed an improved vacuum carbothermal magnesium smelting process in patent document CN115449648A. During the carbothermal reduction reaction under inert gas protection, high-temperature magnesium vapor and CO gas are guided into a multi-stage condensation zone within the condensation chamber. The temperature of the condensation chamber is controlled to maintain a temperature between 643K and 733K, achieving dynamic equilibrium in the condensation process of the gaseous products. Along the flow direction of the gaseous products, the temperature of each condensation zone within the condensation chamber gradually decreases. While this method of introducing inert protective gas and simultaneously implementing multi-stage condensation and cooling can reduce the probability of collisions between magnesium vapor molecules and CO gas molecules and decrease the extent of reaction (4), reaction (4) is still thermodynamically feasible and cannot guarantee the resolution of the reverse reaction and the resulting low yield of metallic magnesium. Summary of the Invention

[0016] The purpose of this invention is to provide a vacuum carbothermal reduction system and method for preparing metallic magnesium, thereby improving the yield of metallic magnesium.

[0017] To achieve the above objectives, the basic solution of the present invention is: a vacuum carbothermal reduction system for preparing metallic magnesium, comprising a reactor chamber, a vacuum module, and a temperature control module;

[0018] The top of the reactor chamber is equipped with a sealing cover and a gas outlet;

[0019] The reactor chamber is provided with a reaction zone and a first condenser in sequence. The reaction zone is used to heat the reactants located in the reaction zone and / or solid carbon and solid magnesium oxide from the first condenser to participate in the vacuum carbothermal reduction reaction to generate a high-temperature mixed gas containing CO gas and magnesium vapor.

[0020] The first condenser is detachably installed downstream of the high-temperature mixed gas containing CO gas and magnesium vapor generated in the reaction zone. The first condenser is used to receive the high-temperature mixed gas containing CO gas and magnesium vapor generated after the vacuum carbothermic reduction reaction in the reaction zone and cool it down to generate solid magnesium containing solid carbon and solid magnesium oxide impurities.

[0021] The reaction zone is equipped with a high-temperature reaction melt to receive solid carbon and solid magnesium oxide from the first condenser.

[0022] The vacuum module is connected to the gas outlet of the reactor cavity through a pipe and is used to evacuate the reactor cavity so that the reactor cavity has the reaction vacuum required for the vacuum carbothermal reduction reaction when the vacuum carbothermal reduction reaction is required to be carried out.

[0023] The temperature control module is located inside and / or around the reactor cavity and is used to detect and control the temperature at various points inside the reactor cavity.

[0024] The working principle and beneficial effects of this basic scheme are as follows: This technical scheme prepares a high-temperature mixed gas containing CO gas and magnesium vapor by vacuum carbothermal reduction in the reactor chamber of the vacuum carbothermal reduction magnesium production system. The high-temperature mixed gas is cooled and condensed, and the reverse reaction products of cooling and condensation, solid carbon and solid magnesium oxide, participate again in the vacuum carbothermal reduction to prepare a high-temperature mixed gas containing CO gas and magnesium vapor. This is expected to fundamentally solve the problem of low magnesium yield caused by the reverse reaction and improve the magnesium yield.

[0025] Furthermore, the first condenser includes a first cylindrical body, and there is a gap between the outer wall of the first cylindrical body and the inner wall of the reactor cavity.

[0026] The spacing between the outer wall of the first cylinder and the inner wall of the reactor cavity is appropriately set to ensure that the first cylinder can be easily removed and to ensure the heat dissipation effect from the first cylinder to the reactor cavity.

[0027] Furthermore, the reactor cavity also includes a second condenser for receiving magnesium vapor from the first condenser and cooling and condensing it, the second condenser being located on the side of the first condenser in the reactor cavity away from the reaction zone;

[0028] The second condenser includes a second cylinder, with a gap between the outer wall of the second cylinder and the inner wall of the reactor cavity. The second cylinder is provided with at least two second tops with several through holes, and the through holes of any two adjacent second tops are staggered to form a Z-shaped gas channel.

[0029] When the temperature in the first condenser is adjusted to above 650℃ and the temperature in the second condenser is adjusted to below 650℃, the solid magnesium in the first condenser will turn into magnesium vapor and enter the second condenser for cooling and condensation.

[0030] Furthermore, the temperature control module includes a temperature measuring unit, a heating unit, and a heat dissipation unit;

[0031] The temperature measurement unit includes multiple temperature sensors;

[0032] The heating unit includes one or more of the following: flame heating mechanism, resistance wire heating mechanism, and electromagnetic induction heating mechanism.

[0033] The heat dissipation unit includes one or more of the following: water cooling mechanism, air cooling mechanism, and liquid refrigerant heat dissipation mechanism.

[0034] Select appropriate devices and mechanisms as needed for ease of use.

[0035] Furthermore, it also includes a scraping mechanism disposed inside the first cylinder. The scraping mechanism includes a moving shaft and a scraping plate disposed on the moving shaft. The outer edge of the scraping plate is in contact with the inner wall of the first cylinder. The moving shaft drives the scraping plate to reciprocate along the axial direction of the first cylinder inside the first cylinder to scrape off the cooling reaction products adhering to the inner wall of the first cylinder.

[0036] Alternatively, the scraping mechanism includes a rotating shaft and a first spiral blade disposed on the rotating shaft. The outer edge of the first spiral blade is in contact with the inner wall of the first cylinder. The rotating shaft drives the first spiral blade to rotate around the axis of the first cylinder inside the first cylinder to scrape off the cooling reaction products adhering to the inner wall of the first cylinder.

[0037] The cooling reaction products on the inner wall of the first cylinder are scraped off using a scraping mechanism. The structure is simple and easy to use.

[0038] Furthermore, the vacuum carbothermic reduction system for preparing metallic magnesium also includes a loading and unloading mechanism disposed within the first cylinder. The loading and unloading mechanism includes a rotating shaft and a second helical blade disposed on the rotating shaft. The outer edge of the second helical blade is in contact with or spaced from the inner wall of the first cylinder. The second helical blade is located at one end of the first cylinder adjacent to the reaction zone.

[0039] When the rotating shaft does not drive the second spiral blade to rotate around the axis of the first cylinder inside the first cylinder, the reactant material can be placed on the second spiral blade. The reactant material is naturally stacked and there are gaps between the reactant materials.

[0040] When the first high-temperature mixed gas or the second high-temperature mixed gas containing CO gas and magnesium vapor generated in the reaction zone enters the first condenser, the first high-temperature mixed gas or the second high-temperature mixed gas cools down the surface of the reactant material on the second spiral blade and reacts to generate solid magnesium containing solid carbon and solid magnesium oxide impurities that adhere to the surface of the reactant material.

[0041] When the rotating shaft drives the second spiral blade to rotate around the axis of the first cylinder inside the first cylinder, the reaction material containing solid magnesium impurities, which is adhered to the surface of the second spiral blade, slides down and is fed into the high-temperature reaction melt in the reaction zone. The solid magnesium is heated and turns into magnesium vapor. The solid carbon, solid magnesium oxide and the reaction material participate in the vacuum carbothermal reduction reaction to generate a second high-temperature mixed gas containing CO gas and magnesium vapor.

[0042] The rotating shaft drives the second spiral blade to rotate, thereby allowing the material placed on the second spiral blade to be discharged, which is convenient for operation.

[0043] Furthermore, it also includes a slag pushing mechanism, which blows high-pressure inert gas into the high-temperature reaction melt in the reaction zone to push the useless slag material in the high-temperature reaction melt away from the high-temperature reaction melt.

[0044] Non-molten, useless slag material that does not participate in the vacuum carbothermal reaction is pushed away from the high-temperature reaction melt, so as to ensure that solid carbon and solid magnesium oxide from the first condenser can directly contact the high-temperature reaction melt and participate in the vacuum carbothermal reduction reaction.

[0045] This invention also provides a method for preparing metallic magnesium by vacuum carbothermal reduction, which is carried out in the reactor chamber of the vacuum carbothermal reduction method for preparing metallic magnesium described in this invention, and includes the following steps:

[0046] S1, the reactants in the reaction zone participate in the vacuum carbothermic reduction reaction to generate a first high-temperature mixed gas containing CO gas and magnesium vapor;

[0047] The temperature inside the first condenser is controlled to be below 650°C. The first high-temperature mixed gas enters the first condenser to cool down and react to generate solid magnesium containing solid carbon and solid magnesium oxide impurities.

[0048] S2, control the temperature in the first condenser to be below 650°C, and move the solid magnesium, solid carbon and solid magnesium oxide formed in the first condenser in step S1 to the high-temperature reaction melt in the reaction zone. The solid magnesium is heated to become magnesium vapor, and the solid carbon and solid magnesium oxide participate in the vacuum carbothermal reduction reaction. The magnesium vapor and the product of the vacuum carbothermal reduction reaction are mixed to form a second high-temperature mixed gas containing CO gas and magnesium vapor.

[0049] Alternatively, the temperature in the first condenser is controlled to be higher than 650°C and the temperature in the second condenser is lower than 650°C. The solid magnesium formed in the first condenser in step S1 is heated to become magnesium vapor and then enters the second condenser to cool and condense into solid magnesium. The temperature in the first condenser is controlled to be lower than 650°C. The solid carbon and solid magnesium oxide formed in the first condenser in step S1 are moved to the high-temperature reaction melt located in the reaction zone. The solid carbon and solid magnesium oxide participate in the vacuum carbothermal reduction reaction. The product of the vacuum carbothermal reduction reaction is a second high-temperature mixed gas containing CO gas and magnesium vapor.

[0050] S3, control the temperature inside the first condenser to be below 650°C, the second high-temperature mixed gas enters the first condenser, cools down and reacts to generate solid magnesium containing solid carbon and solid magnesium oxide impurities;

[0051] S4. If the solid magnesium obtained in step S3 reaches the expected magnesium metal yield, the operation is stopped; if the expected magnesium metal yield is not reached, steps S2 and S3 are repeated until the expected magnesium metal yield is reached.

[0052] This method for preparing metallic magnesium using vacuum carbothermal reduction ensures that the yield of metallic magnesium meets the standards and is easy to use.

[0053] Furthermore, the reactants in the reaction zone include carbon-containing materials and magnesium oxide-containing materials;

[0054] The carbon-containing materials include one or more of graphite, metallurgical coke, semi-coke, coal, charcoal, and activated carbon.

[0055] The magnesium oxide-containing materials include one or more of magnesium oxide, calcined magnesite, calcined dolomite, dehydrated serpentine, and dehydrated brucite.

[0056] The pretreatment method for the reactants in step S1 is as follows: the reactants are ground into powder separately, mixed in a molar ratio of elemental carbon to magnesium oxide (0.9-1.1):1, with or without the addition of iron-carbon alloy powder, and pressed into pellets with a diameter of 5 mm to 50 mm.

[0057] Setting the composition of the reactants facilitates subsequent use.

[0058] Furthermore, the high-temperature reaction melt includes one or two of the following: a carbon-containing molten alloy liquid with a temperature not lower than 1200°C and a multi-element slag containing magnesium oxide with a temperature not lower than 1200°C.

[0059] The reactants and / or solid carbon and solid magnesium oxide from the first condenser enter the high-temperature reaction melt to participate in the vacuum carbothermic reduction reaction to generate a high-temperature mixed gas containing CO gas and magnesium vapor.

[0060] The material composition of the high-temperature reaction melt facilitates the incorporation of corresponding solid carbon and solid magnesium oxide into it, making it a molten state. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the vacuum carbothermal reduction system 1000 for preparing metallic magnesium according to Embodiment 1 of the present invention;

[0062] Figure 2 This is a schematic diagram of the structure of the vacuum carbothermal reduction system 2000 for preparing metallic magnesium according to Embodiment 2 of the present invention;

[0063] Figure 3 This is a schematic diagram of the vacuum carbothermal reduction system 3000 for preparing metallic magnesium according to Embodiment 3 of the present invention;

[0064] Figure 4 This is a schematic flowchart of the method for preparing metallic magnesium by vacuum carbothermal reduction according to Embodiment 1 of the present invention;

[0065] Figure 5 This is a schematic flowchart of the method for preparing metallic magnesium by vacuum carbothermal reduction according to Embodiment 2 of the present invention;

[0066] Figure 6 This is a schematic flowchart of the method for preparing metallic magnesium by vacuum carbothermal reduction according to Embodiment 3 of the present invention;

[0067] Figure 7 This is the three-phase equilibrium phase diagram of elemental magnesium.

[0068] The reference numerals in the accompanying drawings include:

[0069] Reference numerals in Example 1: Vacuum carbothermic reduction system for preparing metallic magnesium 1000, reactor chamber 1100, tank 1110, sealing cover 1120, gas outlet 1130, reaction zone 1140, reactant pellets 1141, high-temperature reaction melt 1142, reaction vessel 1145, first cylinder 1151, first top 1152, moving shaft 1171, scraper 1172, first heat baffle 1181, second heat baffle 1182, gas inlet 1190, vacuum module 1200, heating unit 1320, heat dissipation unit 1330, gas flow direction Z1;

[0070] Reference numerals in Example 2: Vacuum carbothermic reduction system for preparing metallic magnesium 2000, reactor cavity 2100, tank 2110, sealing cover 2120, gas outlet 2130, reaction zone 2140, reactant pellets 2141, high-temperature reaction melt 2142, reaction vessel 2145, first cylinder 2151, second cylinder 2161, second top 2162, rotating shaft 2171, first spiral blade 2172, first heat baffle 2181, second heat baffle 2182, gas inlet 2190, vacuum module 2200, heating unit 2320, heat dissipation unit 2330, gas flow direction Z2;

[0071] Reference numerals in Example 3: Vacuum carbothermic reduction system for preparing metallic magnesium 3000, reactor cavity 3100, tank 3110, sealing cover 3120, gas outlet 3130, reaction zone 3140, high-temperature reaction melt 3142, reactant pellet two 3143, reactant pellet three 3144, reaction vessel 3145, first cylinder 3151, second cylinder 3161, second top 3162, rotating shaft 3171, first helical blade 3172, second helical blade 3181, gas inlet 3190, vacuum module 3200, heating unit 3320, heat dissipation unit 3330, gas flow direction Z3. Detailed Implementation

[0072] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0073] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0074] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0075] Example 1

[0076] This invention discloses a vacuum carbothermic reduction system 1000 for preparing metallic magnesium, such as... Figure 1 As shown, it includes a reactor chamber 1100, a vacuum module 1200 and a temperature control module. The main body of the reactor chamber 1100 is a tank 1110. The top of the reactor chamber 1100 is provided with a sealing cover 1120 and a gas outlet 1130. The gas outlet 1130 is located on the sealing cover 1120.

[0077] The reactor chamber 1100 is provided with a reaction zone 1140 and a first condenser in sequence. The reaction zone 1140 is used to heat the reactants located in the reaction zone 1140 and / or solid carbon and solid magnesium oxide from the first condenser to participate in the vacuum carbothermal reduction reaction to generate a high-temperature mixed gas containing CO gas and magnesium vapor.

[0078] The first condenser is detachably installed downstream of the high-temperature mixed gas containing CO gas and magnesium vapor generated in the reaction zone 1140. The first condenser receives the high-temperature mixed gas containing CO gas and magnesium vapor generated after the vacuum carbothermal reduction reaction in the reaction zone 1140, cools it, and reacts it to generate solid magnesium containing solid carbon and solid magnesium oxide impurities. Preferably, the first condenser includes a first cylinder 1151, with a gap between the outer wall of the first cylinder 1151 and the inner wall of the reactor cavity 1100. The first cylinder 1151 has two first tops 1152 with several through holes, and the through holes of the two first tops 1152 are staggered to form a Z-shaped gas channel. The heat dissipation path of the first condenser is: inside the first cylinder 1151, the wall of the first cylinder 1151, the tank 1110, and the heat dissipation unit 1330 outside the tank 1110, thus ensuring heat dissipation effect.

[0079] The reaction zone 1140 is located below the first cylinder 1151 of the first condenser. A reaction vessel 1145 (such as a reaction crucible) is provided within the reaction zone 1140. The reaction vessel 1145 is made of high-purity graphite or Al2O3-SiC-C series high-temperature resistant material. A high-temperature reaction melt 1142 is placed inside the reaction vessel 1145, which is used to receive solid carbon and solid magnesium oxide from the first cylinder 1151. A vacuum module 1200 is connected to the gas outlet 1130 of the reactor chamber 1100 via a pipe, and is used to evacuate the reactor chamber 1100 to ensure that the reactor chamber 1100 has the required reaction vacuum level for the vacuum carbothermal reduction reaction, and the gas pressure inside the reactor chamber 1100 does not exceed the critical reaction pressure for the vacuum carbothermal reduction reaction.

[0080] A temperature control module is located inside and / or around the reactor cavity 1100, used to detect and control the temperature at various points inside the reactor cavity 1100. Preferably, the temperature control module includes a temperature measuring unit, a heating unit 1320, and a heat dissipation unit 1330. The temperature measuring unit includes multiple temperature sensors. The heating unit 1320 includes one or more of a flame heating mechanism, a resistance wire heating mechanism, and an electromagnetic induction heating mechanism. The heat dissipation unit 1330 includes one or more of a water cooling mechanism, an air cooling mechanism, and a liquid refrigerant (such as water, liquid nitrogen, liquid ammonia, etc.) heat dissipation mechanism.

[0081] In a preferred embodiment of the present invention, the vacuum carbothermic reduction system 1000 for preparing metallic magnesium further includes a scraping mechanism disposed within a first cylinder 1151. The scraping mechanism includes a moving shaft 1171 and a plurality of scraper plates 1172 disposed on the moving shaft 1171. The outer edge of the scraper plates 1172 is in contact with the inner wall of the first cylinder 1151. The moving shaft 1171 drives the scraper plates 1172 to reciprocate within the first cylinder 1151 along the axial direction of the first cylinder 1151 to scrape off the condensed (cooling) reaction products adhering to the inner wall of the first cylinder 1151.

[0082] In a preferred embodiment of the present invention, a detachable heat baffle is provided between the reaction zone 1140 and the first cylinder 1151 to achieve temperature isolation between the relatively high-temperature reaction zone 1140 and the relatively low-temperature first condenser. The heat baffle includes a first heat baffle plate 1181 and a second heat baffle plate 1182, which are positioned along the heat radiation path from the reaction zone 1140 to the first condenser. In this embodiment, the first heat baffle plate 1181 and the second heat baffle plate 1182 are arranged parallel to each other vertically. Both the first heat baffle plate 1181 and the second heat baffle plate 1182 have several through holes for the high-temperature mixed gas and the cooling reaction products to pass through. The through holes on the first heat baffle plate 1181 and the through holes on the second heat baffle plate 1182 are staggered to reduce the unobstructed direct heat radiation from the reaction zone 1140 to the first condenser.

[0083] In a preferred embodiment of the present invention, the vacuum carbothermic reduction system for preparing metallic magnesium further includes a slag-pushing mechanism. This mechanism blows high-pressure inert gas into the high-temperature reaction melt 1142 within the reaction zone 1140, pushing away unwanted slag from the high-temperature reaction melt 1142. The slag-pushing mechanism includes a gas inlet 1190 located on the side of the reaction zone 1140, connected to an argon gas nozzle, which blows gas into the reaction zone 1140 to push the slag.

[0084] Non-molten, useless slag material that does not participate in the vacuum carbothermal reaction is pushed away from the high-temperature reaction melt 1142 inside or on the surface of the high-temperature reaction melt 1142, so as to ensure that solid carbon and solid magnesium oxide from the first condenser can directly contact the high-temperature reaction melt 1142 and participate in the vacuum carbothermal reduction reaction.

[0085] like Figure 4 As shown, the present invention also provides a method for preparing metallic magnesium by vacuum carbothermal reduction, which is carried out within the reactor chamber 1100 of the vacuum carbothermal reduction system 1000 of the present invention, and includes the following steps:

[0086] S1. Take pig iron blocks with fewer impurities such as silicon, sulfur, and phosphorus (mainly iron and carbon), and crush them into pig iron fragments with a diameter of less than 30mm for later use.

[0087] Graphite and high-purity magnesium oxide are ground into powder separately, and then mixed evenly according to the molar ratio of elemental carbon to magnesium oxide of 1:1. The mixture is then fed into a high-pressure roller briquetting machine to be pressed into several reaction material pellets 1141 with a diameter of 5mm to 50mm, and dried for later use.

[0088] The obtained pig iron fragments are placed into the reaction container 1145 of the reaction zone 1140, and the obtained reaction material pellets 1141 are placed on the pig iron fragments in the reaction container 1145.

[0089] The vacuum module 1200 is activated to evacuate the reactor chamber 1100. The output power of the vacuum module 1200 is controlled to ensure that the pressure inside the reactor chamber 1100 is below 333 Pa.

[0090] The temperature control module includes a temperature measuring unit, a heating unit 1320, and a heat dissipation unit 1330, which control the temperature inside the first condenser to 0℃~650℃ and maintain it continuously, and control the temperature inside the reaction vessel 1145 to rise to 1200℃~1700℃ and maintain it continuously.

[0091] The reactants in reaction zone 1140 participate in the vacuum carbothermic reduction reaction to generate a first high-temperature mixed gas containing CO gas and magnesium vapor. Specifically, the pig iron fragments in reaction vessel 1145 melt to form a high-temperature iron-carbon alloy melt (i.e., high-temperature reaction melt 1142). The magnesium oxide in the reactant pellets 1141 in reaction vessel 1145 reacts with the carbon in the iron-carbon alloy melt 1142 in a rapid carbothermic reduction reaction as shown in reaction formula (3) to generate a first high-temperature mixed gas containing CO gas and magnesium vapor. The carbon in the reactant pellets 1141 enters the iron-carbon alloy melt (i.e., high-temperature reaction melt 1142) to replenish the carbon consumed in the iron-carbon alloy melt (i.e., high-temperature reaction melt 1142) due to the carbothermic reduction reaction (3).

[0092] The first high-temperature mixed gas enters the first condenser for cooling and reaction to generate solid magnesium containing solid carbon and solid magnesium oxide impurities. Specifically, the first high-temperature mixed gas containing CO gas and magnesium vapor enters the first cylinder 1151 of the first condenser along the gas flow direction Z1, cools down, undergoes reactions (2) and (4), and forms solid magnesium containing solid carbon and solid magnesium oxide impurities. The solid carbon, solid magnesium oxide, and solid magnesium mainly condense and adhere to the inner wall of the first cylinder 1151 and are located below the scraper 1172. The remaining CO gas in the first high-temperature mixed gas that did not participate in reaction (4) is output through the gas outlet 1130 of the reactor cavity 1100.

[0093] S2, after all the reactant pellets 1141 in the reaction vessel 1145 have reacted, control the temperature in the first condenser to 0℃~650℃ and the temperature in the reaction vessel 1145 in the reaction zone 1140 to 1200℃~1700℃, and transfer the solid magnesium, solid carbon and solid magnesium oxide formed in the first condenser in step S1 to the high-temperature reaction melt 1142 located in the reaction zone 1140. The solid magnesium is heated to become magnesium vapor, and the solid carbon and solid magnesium oxide participate in the vacuum carbothermal reduction reaction. The magnesium vapor and the product of the vacuum carbothermal reduction reaction are mixed to form a second high-temperature mixed gas containing CO gas and magnesium vapor.

[0094] Specifically, once all the reactant pellets 1141 in the reaction vessel 1145 have participated in the vacuum carbothermal reduction reaction, and all the high-temperature mixed gas containing CO gas and magnesium vapor generated is cooled in the first condenser, the reaction forms solid magnesium containing solid carbon and solid magnesium oxide impurities that adhere to the inner wall of the first cylinder 1151. The moving shaft 1171 is driven to move downward, and the moving shaft 1171 drives the scraper 1172 to move downward relative to the first cylinder 1151. During this process, the solid carbon, solid magnesium oxide and solid magnesium on the inner wall of the first cylinder 1151 will be scraped off and pass through the first heat baffle 1181 and the second heat baffle 1182, and finally fall into the high-temperature iron-carbon alloy melt (i.e., the high-temperature reaction melt 1142).

[0095] Solid magnesium falling into the molten iron-carbon alloy (i.e., high-temperature reaction melt 1142) heats up and turns into magnesium vapor. Solid magnesium oxide falling into the molten iron-carbon alloy (i.e., high-temperature reaction melt 1142) undergoes a rapid carbothermic reduction reaction with carbon in the molten iron-carbon alloy (i.e., high-temperature reaction melt 1142), as shown in reaction formula (3). The magnesium vapor and the product of the vacuum carbothermic reduction reaction mix to form a second high-temperature mixed gas containing CO gas and magnesium vapor. Solid carbon falling into the molten iron-carbon alloy (i.e., high-temperature reaction melt 1142) enters the molten iron-carbon alloy (i.e., high-temperature reaction melt 1142) to replenish the carbon consumed in the molten iron-carbon alloy (i.e., high-temperature reaction melt 1142) due to the carbothermic reduction reaction (3).

[0096] S3, control the temperature of the first condenser to 0℃~650℃ and keep it warm. The second high-temperature mixed gas containing CO gas and magnesium vapor generated in step S2 enters the first condenser along the gas flow direction Z1, cools down, undergoes reaction (2) and reaction (4) and forms solid magnesium containing solid carbon and solid magnesium oxide impurities. The solid magnesium containing solid carbon and solid magnesium oxide impurities mainly condenses and adheres to the inner wall of the first cylinder 1151 and is located below the scraper 1172. The remaining CO gas in the second high-temperature mixed gas that did not participate in reaction (4) is output through the gas outlet 1130 of the reactor cavity 1100.

[0097] S4. If the solid magnesium obtained in step S3 reaches the expected magnesium metal yield (e.g., 80%), the operation is stopped, the vacuum carbothermal reduction magnesium production system 1000 is cooled down, the vacuum is broken, and the magnesium product is taken out; if the expected magnesium metal yield is not reached, steps S2 and S3 are repeated until the expected magnesium metal yield is reached.

[0098] Example 2

[0099] This invention discloses yet another vacuum carbothermic reduction system for preparing metallic magnesium, such as... Figure 2 As shown.

[0100] The vacuum carbothermal reduction system for preparing metallic magnesium 2000 has the following distinguishing features compared to the vacuum carbothermal reduction system for preparing metallic magnesium 1000:

[0101] (1) The first condenser of the vacuum carbothermal reduction preparation system 2000 for preparing metallic magnesium only includes a first cylinder 2151, but does not have a first top matching the first cylinder 2151.

[0102] (2) The vacuum carbothermic reduction system 2000 for preparing metallic magnesium also includes a second condenser for receiving magnesium vapor from the first condenser and cooling and condensing it. The second condenser is located on the side of the first condenser in the reactor cavity 2100 away from the reaction zone 2140. The second condenser includes a second cylinder 2161, with a gap between the outer wall of the second cylinder 2161 and the inner wall of the reactor cavity 2100. The second cylinder 2161 is provided with two second tops 2162 with several through holes. The through holes of the two second tops 2162 are staggered to form a Z-shaped gas channel. When the temperature in the first condenser is adjusted to above 650°C and the temperature in the second condenser is adjusted to below 650°C, the solid magnesium in the first condenser will turn into magnesium vapor and enter the second condenser for cooling and condensation. The heat dissipation path of the second condenser is: inside the second cylinder 2161, the wall of the second cylinder 2161, the tank 2110, and the heat dissipation unit 2330 outside the tank 2110, thus ensuring the heat dissipation effect.

[0103] (3) The vacuum carbothermal reduction system for preparing metallic magnesium 2000 also has a scraping mechanism set in the first cylinder 2151, but the scraping mechanism is not a structure in which a moving shaft drives multiple scraping plates, but a structure in which a rotating shaft 2171 drives the first spiral blade 2172: the outer edge of the first spiral blade 2172 is attached to the inner wall of the first cylinder 2151, and the rotating shaft 2171 drives the first spiral blade 2172 to rotate around the axis of the first cylinder 2151 in the first cylinder 2151 to scrape off the cooling reaction products adhering to the inner wall of the first cylinder 2151.

[0104] like Figure 5 As shown, the present invention also provides a method for preparing metallic magnesium by vacuum carbothermal reduction, which is carried out in the reactor cavity 2100 of the vacuum carbothermal reduction magnesium preparation system of the present invention, and includes the following steps:

[0105] S1. Take pig iron blocks with fewer impurities such as silicon, sulfur, and phosphorus (mainly iron and carbon), and crush them into pig iron fragments with a diameter of less than 30mm for later use.

[0106] Metallurgical coke and calcined magnesite are ground into powder separately, and then mixed evenly according to the molar ratio of elemental carbon to magnesium oxide of 1:1. The mixture is then fed into a high-pressure roller briquetting machine to be pressed into several reaction material pellets 2141 with a diameter of 5mm to 50mm, and dried for later use.

[0107] The obtained pig iron fragments are placed into the reaction container 2145 of the reaction zone 2140, and the obtained reaction material pellets 2141 are placed on the pig iron fragments in the reaction container 2145.

[0108] The vacuum module 2200 is activated to evacuate the reactor chamber 2100. The output power of the vacuum module 2200 is controlled to ensure that the pressure inside the reactor chamber 2100 is below 333 Pa.

[0109] The temperature control module includes a temperature measuring unit, a heating unit 2320, and a heat dissipation unit 2330, which control the temperature inside the first condenser to 0℃~650℃ and maintain it continuously, and control the temperature inside the reaction vessel 2145 to rise to 1200℃~1700℃ and maintain it continuously.

[0110] The reactants in reaction zone 2140 participate in the vacuum carbothermic reduction reaction to generate a first high-temperature mixed gas containing CO gas and magnesium vapor. Specifically, the pig iron fragments in reaction vessel 2145 melt to form a high-temperature iron-carbon alloy melt (i.e., high-temperature reaction melt 2142). The magnesium oxide in the reactant pellets 2141 in reaction vessel 2145 reacts with the carbon in the high-temperature reaction melt 2142 in a rapid carbothermic reduction reaction as shown in reaction formula (3) to generate a first high-temperature mixed gas containing CO gas and magnesium vapor. The carbon in the reactant pellets 2141 enters the iron-carbon alloy melt (i.e., high-temperature reaction melt 2142) to replenish the carbon consumed in the iron-carbon alloy melt (i.e., high-temperature reaction melt 2142) due to the carbothermic reduction reaction (3).

[0111] The first high-temperature mixed gas enters the first condenser for cooling and reaction to generate solid magnesium containing solid carbon and solid magnesium oxide impurities. Specifically, the first high-temperature mixed gas containing CO gas and magnesium vapor enters the first cylinder 2151 of the first condenser along the gas flow direction Z2, cools down, undergoes reactions (2) and (4), and forms solid magnesium containing solid carbon and solid magnesium oxide impurities. The solid carbon, solid magnesium oxide, and solid magnesium mainly condense and adhere to the inner wall of the first cylinder 2151 and are located below the first spiral blade 2172. The remaining CO gas in the first high-temperature mixed gas that did not participate in reaction (4) is output through the gas outlet 2130 of the reactor cavity 2100.

[0112] S2, after all the reactant pellets 2141 in the reaction vessel 2145 have reacted, control the temperature in the first condenser to 650℃~1200℃ and the temperature in the second condenser to 0℃~650℃. The solid magnesium adhering to the inner wall of the first cylinder 2151 in step S1 becomes magnesium vapor due to heating. The solid carbon and solid magnesium oxide adhering to the inner wall of the first cylinder 2151 will not undergo carbothermic reduction reaction because they have not reached the carbothermic reduction reaction temperature and are not in close contact. The magnesium vapor leaves the first condenser and enters the second condenser. The magnesium vapor cools down and condenses into solid magnesium in the second condenser. The solid magnesium mainly adheres to the inner wall of the second cylinder 2161.

[0113] The temperature in the first condenser is controlled to 0℃~650℃, the temperature in the second condenser is controlled to 0℃~650℃, and the temperature in the reaction vessel 2145 of the reaction zone 2140 is controlled to 1200℃~1700℃. The solid carbon and solid magnesium oxide formed in the first condenser in step S1 are moved to the high-temperature reaction melt 2142 located in the reaction zone 2140. The solid carbon and solid magnesium oxide participate in the vacuum carbothermal reduction reaction to generate a second high-temperature mixed gas containing CO gas and magnesium vapor.

[0114] Specifically, the rotating shaft 2171 is driven to rotate, and the rotating shaft 2171 drives the first spiral blade 2172 to rotate around the axis of the first cylinder 2151 inside the first cylinder 2151. During this process, the solid carbon and solid magnesium oxide on the inner wall of the first cylinder 2151 will be scraped off and pass through the first heat baffle 2181 and the second heat baffle 2182, and finally fall into the high-temperature reaction melt 2142.

[0115] Solid magnesium oxide falling into the high-temperature reaction melt 2142 undergoes a rapid carbothermic reduction reaction with carbon in the high-temperature reaction melt 2142, as shown in reaction formula (3), and generates a second high-temperature mixed gas containing CO gas and magnesium vapor. Solid carbon falling into the high-temperature reaction melt 2142 enters the high-temperature reaction melt 2142 and replenishes the carbon consumed in the high-temperature reaction melt 2142 due to the carbothermic reduction reaction (3).

[0116] S3, control the temperature of the first condenser to 0℃~650℃ and keep it warm. The second high-temperature mixed gas containing CO gas and magnesium vapor generated in step S2 enters the first condenser along the gas flow direction Z2, cools down, undergoes reaction (2) and reaction (4) and generates solid magnesium containing solid carbon and solid magnesium oxide impurities. The solid magnesium containing solid carbon and solid magnesium oxide impurities mainly condenses and adheres to the inner wall of the first cylinder 2151 and is located below the first spiral blade 2172. The remaining CO gas in the second high-temperature mixed gas that did not participate in reaction (4) is output through the gas outlet 2130 of the reactor cavity 2100.

[0117] S4. If the solid magnesium obtained in the second cylinder 2161 in step S2 and the solid magnesium obtained in the first cylinder 2151 in step S3 reach the expected magnesium metal yield (e.g., 80%), the operation is stopped, the vacuum carbothermal reduction magnesium metal preparation system 2000 is cooled, the vacuum is broken, and the magnesium product is taken out; if the expected magnesium metal yield is not reached, steps S2 and S3 are repeated until the expected magnesium metal yield is reached.

[0118] Example 3

[0119] This invention discloses yet another vacuum carbothermal reduction system 3000 for preparing metallic magnesium, such as... Figure 3 As shown.

[0120] The vacuum carbothermal reduction system for preparing metallic magnesium 3000 has the following distinguishing features compared to the vacuum carbothermal reduction system for preparing metallic magnesium 2000:

[0121] The vacuum carbothermal reduction system for preparing metallic magnesium 3000 also includes a loading and unloading mechanism disposed within a first cylinder 3151. The loading and unloading mechanism includes a rotating shaft 3171 and a second helical blade 3181 disposed on the rotating shaft 3171. The second helical blade 3181 has through holes spaced apart with a diameter smaller than that of the reactant pellets 3144 for the passage of high-temperature mixed gas. The outer edge of the second helical blade 3181 is attached to or spaced from the inner wall of the first cylinder. The second helical blade 3181 is located at one end of the first cylinder 3151 adjacent to the reaction zone.

[0122] When the rotating shaft 3171 does not drive the second spiral blade 3181 to rotate around the axis of the first cylinder 3151 inside the first cylinder 3151, the reactant pellets 3144 can be placed on the second spiral blade 3181. The reactant pellets 3144 are naturally stacked and there are gaps between the reactant pellets 3144.

[0123] When the rotating shaft 3171 drives the second spiral blade 3181 to rotate around the axis of the first cylinder 3151 inside the first cylinder 3151, the reactive material pellets 3144 on the second spiral blade 3181 slide down and are fed into the high-temperature reactive melt in the reaction zone.

[0124] In this embodiment, the loading and unloading mechanism also functions as a heat shield to achieve temperature isolation between the relatively high-temperature reaction zone 1140 and the relatively low-temperature first condenser.

[0125] like Figure 6 As shown, the present invention also provides a method for preparing metallic magnesium by vacuum carbothermal reduction, which is carried out within the reactor cavity 3100 of the vacuum carbothermal reduction magnesium preparation system described in the present invention, and includes the following steps:

[0126] S1. Prepare a quaternary mixture of CaO-MgO-Al2O3-SiO2 according to the molar ratio of CaO:MgO:Al2O3:SiO2 = 37%:18%:20%:25%, grind it into powder and set it aside.

[0127] Coal and calcined dolomite are ground into powder separately and mixed evenly according to a molar ratio of elemental carbon to magnesium oxide of 1:1. The mixture is then fed into a high-pressure roller briquetting machine to press into several reaction material pellets with a diameter of 5mm to 50mm. The reaction material pellets are divided into two batches, namely reaction material pellet two 3143 and reaction material pellet three 3144, and dried for later use.

[0128] The prepared CaO-MgO-Al2O3-SiO2 quaternary mixture is placed into the reaction vessel 3145 of the reaction zone 3140, and the obtained reaction material pellets 3143 are placed on the CaO-MgO-Al2O3-SiO2 quaternary mixture in the reaction vessel 3145.

[0129] The vacuum module 3200 is activated to evacuate the reactor chamber 3100. The output power of the vacuum module 3200 is controlled to ensure that the pressure inside the reactor chamber 3100 is below 333 Pa.

[0130] The temperature control module includes a temperature measuring unit, a heating unit 3320, and a heat dissipation unit 3330, which control the temperature inside the first condenser to 0℃~650℃ and maintain it continuously, and control the temperature inside the reaction vessel 3145 to rise to 1200℃~1700℃ and maintain it continuously.

[0131] The reactants in reaction zone 3140 participate in the vacuum carbothermic reduction reaction to generate a first high-temperature mixed gas containing CO gas and magnesium vapor. Specifically, the quaternary mixture of CaO-MgO-Al2O3-SiO2 in reaction vessel 3145 melts to form a high-temperature multi-element slag (i.e., high-temperature reaction melt 3142). The carbon in the reactant pellet 2 3143 in reaction vessel 3145 reacts with the magnesium oxide in the multi-element slag (i.e., high-temperature reaction melt 3142) in a rapid carbothermic reduction reaction as shown in reaction formula (3) to generate a first high-temperature mixed gas containing CO gas and magnesium vapor. The magnesium oxide in the reactant pellet 2 3143 enters the multi-element slag (i.e., high-temperature reaction melt 3142) to replenish the magnesium oxide consumed in the multi-element slag (i.e., high-temperature reaction melt 3142) due to the carbothermic reduction reaction (3).

[0132] The first high-temperature mixed gas enters the first condenser for cooling and reaction to generate solid magnesium containing solid carbon and solid magnesium oxide impurities. Specifically, the first high-temperature mixed gas containing CO gas and magnesium vapor enters the first cylinder 3151 of the first condenser along the gas flow direction Z3, cools down, undergoes reactions (2) and (4), and forms solid magnesium containing solid carbon and solid magnesium oxide impurities. The solid carbon, solid magnesium oxide, and solid magnesium mainly condense and adhere to the inner wall of the first cylinder 3151 and the reaction material pellets 3144 inside the first cylinder 3151, and are located below the first spiral blade 3172. The remaining CO gas in the first high-temperature mixed gas that did not participate in reaction (4) is output through the gas outlet 3130 of the reactor cavity 3100.

[0133] S2, after all the reactant pellets 3143 in the reaction vessel 3145 have reacted, control the temperature in the first condenser to 0℃~650℃ and the temperature in the reaction vessel 3145 in the reaction zone 3140 to 1200℃~1700℃, and move the solid magnesium, solid carbon and solid magnesium oxide formed in the first condenser in step S1 to the high-temperature multi-element molten slag (i.e. high-temperature reaction melt 3142) located in the reaction zone 3140. The solid magnesium is heated to become magnesium vapor, and the solid carbon and solid magnesium oxide participate in the vacuum carbothermal reduction reaction. The magnesium vapor and the products of the vacuum carbothermal reduction reaction are mixed to form a second high-temperature mixed gas containing CO gas and magnesium vapor.

[0134] Specifically, the rotating shaft 3171 is driven to rotate, and the rotating shaft 3171 drives the first helical blade 3172 and the second helical blade 3181 to rotate around the axis of the first cylinder 3151 inside the first cylinder 3151. During this process, the solid magnesium, solid carbon and solid magnesium oxide on the inner wall of the first cylinder 3151, as well as the reaction material pellets 3144 with solid magnesium, solid carbon and solid magnesium oxide adhering to the surface of the first cylinder 3151, will fall off and eventually fall into the high-temperature multi-element slag (i.e., high-temperature reaction melt 3142).

[0135] Carbon and magnesium oxide in the reactant pellet 3144 falling into the multi-component slag (i.e., high-temperature reaction melt 3142) participate in the vacuum carbothermic reduction reaction. Solid magnesium falling into the multi-component slag (i.e., high-temperature reaction melt 3142) is heated to become magnesium vapor. Carbon falling into the multi-component slag (i.e., high-temperature reaction melt 3142) and magnesium oxide in the multi-component slag (i.e., high-temperature reaction melt 3142) undergo a rapid vacuum carbothermic reduction reaction as shown in reaction formula (3). Magnesium oxide falling into the multi-component slag (i.e., high-temperature reaction melt 3142) enters the multi-component slag (i.e., high-temperature reaction melt 3142) to replenish the magnesium oxide consumed by the carbothermic reduction reaction (3) in the multi-component slag (i.e., high-temperature reaction melt 3142). The product of the vacuum carbothermic reduction reaction and the magnesium vapor are mixed to form a second high-temperature mixed gas containing CO gas and magnesium vapor.

[0136] S3, control the temperature of the first condenser to 0℃~650℃ and keep it warm. The second high-temperature mixed gas containing CO gas and magnesium vapor generated in step S2 enters the first condenser along the gas flow direction Z3, cools down, undergoes reaction (2) and reaction (4) and forms solid magnesium containing solid carbon and solid magnesium oxide impurities. The solid magnesium containing solid carbon and solid magnesium oxide impurities mainly condenses and adheres to the inner wall of the first cylinder 3151 and the reaction material pellets 3144 in the first cylinder 3151 and is located below the first spiral blade 3172. The remaining CO gas in the second high-temperature mixed gas that did not participate in reaction (4) is output through the gas outlet 3130 of the reactor cavity 3100.

[0137] S4. Repeat steps S2 and S3 until all the reactant pellets 3144 in the first cylinder 3151 enter the high-temperature multi-element slag (i.e., high-temperature reaction melt 3142) in the reaction vessel 3145 in the reaction zone 3140 and fully participate in the vacuum carbothermal reduction reaction. The solid magnesium containing solid carbon and solid magnesium oxide impurities generated by the cooling reaction in the first condenser mainly condenses and adheres to the inner wall of the first cylinder 3151.

[0138] S5, control the temperature in the first condenser to 0℃~650℃ and the temperature in the reaction vessel 3145 of the reaction zone 3140 to 1200℃~1700℃, and move the solid magnesium, solid carbon and solid magnesium oxide formed in the first cylinder 3151 in step S4 to the high-temperature multi-element molten slag (i.e. high-temperature reaction melt 3142) located in the reaction zone 3140. The solid magnesium is heated to become magnesium vapor, and the solid carbon and solid magnesium oxide participate in the vacuum carbothermal reduction reaction. The magnesium vapor and the product of the vacuum carbothermal reduction reaction are mixed to form a second high-temperature mixed gas containing CO gas and magnesium vapor.

[0139] Specifically, the rotating shaft 3171 is driven to rotate, and the rotating shaft 3171 drives the first helical blade 3172 and the second helical blade 3181 to rotate around the axis of the first cylinder 3151 inside the first cylinder 3151. During this process, solid magnesium, solid carbon and solid magnesium oxide on the inner wall of the first cylinder 3151 will be scraped off and eventually fall into the high-temperature multi-element slag (i.e., high-temperature reaction melt 3142).

[0140] Solid magnesium falling into the multi-element slag (i.e., high-temperature reaction melt 3142) is heated to become magnesium vapor. Carbon falling into the multi-element slag (i.e., high-temperature reaction melt 3142) undergoes a rapid carbothermic reduction reaction with magnesium oxide in the multi-element slag (i.e., high-temperature reaction melt 3142), as shown in reaction formula (3). Magnesium oxide falling into the multi-element slag (i.e., high-temperature reaction melt 3142) enters the multi-element slag (i.e., high-temperature reaction melt 3142) to replenish the magnesium oxide consumed by the carbothermic reduction reaction (3) in the multi-element slag (i.e., high-temperature reaction melt 3142). The product of the vacuum carbothermic reduction reaction and the magnesium vapor are mixed to form a second high-temperature mixed gas containing CO gas and magnesium vapor.

[0141] S6, control the temperature inside the first condenser to 0℃~650℃ and the temperature inside the reaction vessel 3145 to 1200℃~1700℃;

[0142] The second high-temperature mixed gas generated in step S5 enters the first condenser along the gas flow direction Z3, cools down, undergoes reaction (2) and reaction (4) and forms solid magnesium containing solid carbon and solid magnesium oxide impurities. The solid carbon, solid magnesium oxide and solid magnesium mainly condense and adhere to the inner wall of the first cylinder 3151 and are located below the first spiral blade 3172. The remaining CO gas in the high-temperature mixed gas that did not participate in the reaction is output through the gas outlet 3130 of the reactor cavity.

[0143] S7. After steps S5-S6, the amount of solid magnesium containing solid carbon and solid magnesium oxide impurities adhering to the inner wall of the first cylinder 3151 obtained in step S6 is greater than that obtained in step S4, thus increasing the magnesium metal yield. If the expected magnesium metal yield (e.g., 80%) has been reached at this point, the production process is stopped, the vacuum carbothermal reduction magnesium production system is cooled, the vacuum is broken, and the magnesium product is removed. If the expected magnesium metal yield has not yet been reached, steps S5-S6 are repeated until the expected magnesium metal yield is achieved.

[0144] S8, raise the temperature of the first condenser to 650℃~1200℃ and keep it at that temperature, and control the temperature of the second condenser to rise to 0℃~650℃ and keep it at that temperature.

[0145] At this point, the solid carbon and solid magnesium oxide adhering to the inner wall of the first cylinder 3151 will not undergo carbothermic reduction because they have not reached the carbothermic reduction reaction temperature and are not in close contact. However, the solid magnesium adhering to the inner wall of the first cylinder 3151 will turn into magnesium vapor due to heating. This magnesium vapor will leave the first condenser and enter the second condenser. The magnesium vapor entering the second condenser will condense into solid magnesium during the cooling process, and this solid magnesium will mainly adhere to the inner wall of the second cylinder 3161. The metallic magnesium obtained on the inner wall of the second cylinder 3161 has a higher purity.

[0146] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0147] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A vacuum carbothermic reduction system for preparing metallic magnesium, characterized in that, Includes reactor chamber, vacuum module, and temperature control module; The top of the reactor chamber is equipped with a sealing cover and a gas outlet; The reactor chamber is provided with a reaction zone and a first condenser in sequence. The reaction zone is used to heat the reactants located in the reaction zone and / or solid carbon and solid magnesium oxide from the first condenser to participate in the vacuum carbothermal reduction reaction to generate a high-temperature mixed gas containing CO gas and magnesium vapor. The first condenser is detachably installed downstream of the high-temperature mixed gas containing CO gas and magnesium vapor generated in the reaction zone. The first condenser is used to receive the high-temperature mixed gas containing CO gas and magnesium vapor generated after the vacuum carbothermic reduction reaction in the reaction zone and cool it down to generate solid magnesium containing solid carbon and solid magnesium oxide impurities. The reaction zone is equipped with a high-temperature reaction melt to receive solid carbon and solid magnesium oxide from the first condenser. The vacuum module is connected to the gas outlet of the reactor cavity through a pipe and is used to evacuate the reactor cavity so that the reactor cavity has the reaction vacuum required for the vacuum carbothermal reduction reaction when the vacuum carbothermal reduction reaction is required to be carried out. The temperature control module is located inside and / or around the reactor cavity and is used to detect and control the temperature at various points inside the reactor cavity.

2. The vacuum carbothermic reduction system for preparing metallic magnesium as described in claim 1, characterized in that, The first condenser includes a first cylinder, and there is a gap between the outer wall of the first cylinder and the inner wall of the reactor cavity.

3. The vacuum carbothermic reduction system for preparing metallic magnesium as described in claim 1, characterized in that, The reactor cavity also includes a second condenser for receiving magnesium vapor from the first condenser and cooling and condensing it. The second condenser is located on the side of the reactor cavity away from the reaction zone of the first condenser. The second condenser includes a second cylinder, with a gap between the outer wall of the second cylinder and the inner wall of the reactor cavity. The second cylinder is provided with at least two second tops with several through holes, and the through holes of any two adjacent second tops are staggered to form a Z-shaped gas channel.

4. The vacuum carbothermic reduction system for preparing metallic magnesium as described in claim 1, characterized in that, The temperature control module includes a temperature measuring unit, a heating unit, and a heat dissipation unit; The temperature measurement unit includes multiple temperature sensors; The heating unit includes one or more of the following: flame heating mechanism, resistance wire heating mechanism, and electromagnetic induction heating mechanism. The heat dissipation unit includes one or more of the following: water cooling mechanism, air cooling mechanism, and liquid refrigerant heat dissipation mechanism.

5. The vacuum carbothermic reduction system for preparing metallic magnesium as described in claim 2, characterized in that, It also includes a scraping mechanism disposed inside the first cylinder. The scraping mechanism includes a moving shaft and a scraping plate disposed on the moving shaft. The outer edge of the scraping plate is in contact with the inner wall of the first cylinder. The moving shaft drives the scraping plate to reciprocate along the axial direction of the first cylinder inside the first cylinder to scrape off the cooling reaction products adhering to the inner wall of the first cylinder. Alternatively, the scraping mechanism includes a rotating shaft and a first spiral blade disposed on the rotating shaft. The outer edge of the first spiral blade is in contact with the inner wall of the first cylinder. The rotating shaft drives the first spiral blade to rotate around the axis of the first cylinder inside the first cylinder to scrape off the cooling reaction products adhering to the inner wall of the first cylinder.

6. The vacuum carbothermic reduction system for preparing metallic magnesium as described in claim 2, characterized in that, It also includes a loading and unloading mechanism disposed in the first cylinder, the loading and unloading mechanism including a rotating shaft and a second helical blade disposed on the rotating shaft, the outer edge of the second helical blade being in contact with or having a gap between it and the inner wall of the first cylinder, and the second helical blade being located at one end of the first cylinder adjacent to the reaction zone; When the rotating shaft does not drive the second spiral blade to rotate around the axis of the first cylinder inside the first cylinder, the reactant material can be placed on the second spiral blade. The reactant material is naturally stacked and there are gaps between the reactant materials. When the first high-temperature mixed gas or the second high-temperature mixed gas containing CO gas and magnesium vapor generated in the reaction zone enters the first condenser, the first high-temperature mixed gas or the second high-temperature mixed gas cools down the surface of the reactant material on the second spiral blade and reacts to generate solid magnesium containing solid carbon and solid magnesium oxide impurities that adhere to the surface of the reactant material. When the rotating shaft drives the second spiral blade to rotate around the axis of the first cylinder inside the first cylinder, the reaction material containing solid magnesium impurities, which is adhered to the surface of the second spiral blade, slides down and is fed into the high-temperature reaction melt in the reaction zone. The solid magnesium is heated and turns into magnesium vapor. The solid carbon, solid magnesium oxide and the reaction material participate in the vacuum carbothermal reduction reaction to generate a second high-temperature mixed gas containing CO gas and magnesium vapor.

7. The vacuum carbothermic reduction system for preparing metallic magnesium as described in claim 1, characterized in that, It also includes a slag pushing mechanism, which blows high-pressure inert gas into the high-temperature reaction melt in the reaction zone to push the useless slag material in the high-temperature reaction melt away from the high-temperature reaction melt.

8. A method for preparing metallic magnesium by vacuum carbothermic reduction, characterized in that, The process is carried out within the reactor chamber of the vacuum carbothermic reduction system for preparing metallic magnesium as described in any one of claims 1-7, and includes the following steps: S1, the reactants in the reaction zone participate in the vacuum carbothermic reduction reaction to generate a first high-temperature mixed gas containing CO gas and magnesium vapor; The temperature inside the first condenser is controlled to be below 650°C. The first high-temperature mixed gas enters the first condenser to cool down and react to generate solid magnesium containing solid carbon and solid magnesium oxide impurities. S2, control the temperature in the first condenser to be below 650°C, and move the solid magnesium, solid carbon and solid magnesium oxide formed in the first condenser in step S1 to the high-temperature reaction melt in the reaction zone. The solid magnesium is heated to become magnesium vapor, and the solid carbon and solid magnesium oxide participate in the vacuum carbothermal reduction reaction. The magnesium vapor and the product of the vacuum carbothermal reduction reaction are mixed to form a second high-temperature mixed gas containing CO gas and magnesium vapor. Alternatively, the temperature in the first condenser is controlled to be higher than 650°C and the temperature in the second condenser is lower than 650°C. The solid magnesium formed in the first condenser in step S1 is heated to become magnesium vapor and then enters the second condenser to cool and condense into solid magnesium. The temperature in the first condenser is controlled to be lower than 650°C. The solid carbon and solid magnesium oxide formed in the first condenser in step S1 are moved to the high-temperature reaction melt located in the reaction zone. The solid carbon and solid magnesium oxide participate in the vacuum carbothermal reduction reaction. The product of the vacuum carbothermal reduction reaction is a second high-temperature mixed gas containing CO gas and magnesium vapor. S3, control the temperature inside the first condenser to be below 650°C, the second high-temperature mixed gas enters the first condenser, cools down and reacts to generate solid magnesium containing solid carbon and solid magnesium oxide impurities; S4. If the solid magnesium obtained in step S3 reaches the expected magnesium metal yield, the operation is stopped; if the expected magnesium metal yield is not reached, steps S2 and S3 are repeated until the expected magnesium metal yield is reached.

9. The method for preparing metallic magnesium by vacuum carbothermal reduction as described in claim 8, characterized in that, The reactants in the reaction zone include carbon-containing materials and magnesium oxide-containing materials; The carbon-containing materials include one or more of graphite, metallurgical coke, semi-coke, coal, charcoal, and activated carbon. The magnesium oxide-containing materials include one or more of magnesium oxide, calcined magnesite, calcined dolomite, dehydrated serpentine, and dehydrated brucite. The pretreatment method for the reactants in step S1 is as follows: the reactants are ground into powder separately, mixed in a molar ratio of elemental carbon to magnesium oxide (0.9-1.1):1, with or without the addition of iron-carbon alloy powder, and pressed into pellets with a diameter of 5 mm to 50 mm.

10. The method for preparing metallic magnesium by vacuum carbothermal reduction as described in claim 8, characterized in that, The high-temperature reactive melt includes one or two of the following: a carbon-containing molten alloy liquid with a temperature not lower than 1200°C and a multi-element slag containing magnesium oxide with a temperature not lower than 1200°C. The reactants and / or solid carbon and solid magnesium oxide from the first condenser enter the high-temperature reaction melt to participate in the vacuum carbothermic reduction reaction to generate a high-temperature mixed gas containing CO gas and magnesium vapor.

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