Magnesium metal and method for preparing magnesium metal by using suspended calcined dolomite

Abstract

The invention discloses magnesium metal and a method for preparing the magnesium metal by using suspended-state calcined dolomite, and the method comprises the following steps: firstly, carrying out suspended calcination treatment on the dolomite to obtain calcined dolomite; the content of magnesium oxide in the dolomite is greater than 19%; the temperature of the suspension calcination treatment is 900-1000 DEG C, and the time is 5-40 seconds; the water content of the calcined dolomite is controlled not to exceed 8%, and after the calcined dolomite is mixed with silicon iron and fluorite, the mixture is pressed into pellets; and the material balls are subjected to vacuum thermal reduction treatment, and metal magnesium is prepared. According to the method, the suspension calcination technology and silicothermic magnesium smelting are combined, the calcination time is remarkably shortened, energy consumption is reduced, the quality of calcined products is improved, the reduction rate in the magnesium smelting process reaches 90% or above, and the purity of metal magnesium reaches 99.95% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of metal magnesium smelting, and relates to metal magnesium and a method for preparing the metal magnesium by utilizing suspended calcined dolomite. Background Art

[0002] Silicon thermal magnesium refining is a smelting technology that uses a reducing agent containing silicon to reduce the magnesium element in magnesium-containing raw materials to elemental magnesium under high temperature, vacuum or normal pressure conditions. It is a type of thermal reduction magnesium refining. The main raw material of silicon thermal magnesium refining is calcium magnesium oxide (CaMgO2, or CaO·MgO), which is the product of calcining dolomite (the main component is calcium magnesium carbonate CaMg[CO3]2), which is often called calcined white in the industry. Usually, 75# ferrosilicon, whose main component is elemental silicon, is used as a reducing agent, and a small amount of fluorite, whose main component is calcium fluoride (CaF2), is used as a catalyst. Therefore, dolomite calcination, as the first step of silicon thermal magnesium refining, directly determines the subsequent yield and quality of raw magnesium. At present, the mainstream calcination method of dolomite for magnesium refining is rotary kiln calcination. In this process, the dolomite blocks are in a piled state. Due to problems such as poor air circulation, uneven temperature distribution, and too close contact between particles, the raw materials will be sintered, stick to the furnace, and insufficient calcination. Therefore, the raw and under-burned rate of dolomite exceeds 10%, resulting in low hydration activity of the calcined white product and large loss on ignition, resulting in low output rate of raw magnesium and poor purity of crude magnesium. At the same time, because the rotary kiln calcination rotation continuously throws off the dolomite blocks, blocks with high explosion resistance are required to ensure the uniformity and efficiency of the calcination process, avoid material pulverization and wall adhesion, and the broken materials or ores with low explosion resistance cannot be effectively utilized. Under the current situation of limited mining of high-quality dolomite mines, the size of the ore is often difficult to reach the ideal state. The suspension calcination technology can effectively utilize the small size or even powder, and at the same time make the material in a suspended state, avoiding long-term contact and friction with the equipment, which enables the use of more types of dolomite for production, alleviates the shortage of high-quality ore, and reduces the dependence and cost of raw material procurement. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a magnesium metal and a method for preparing the magnesium metal by calcining dolomite in a suspended state, thereby solving the technical problems in the prior art that the output rate of raw magnesium by silicon thermal method for smelting magnesium is low and the purity of the obtained crude magnesium is poor.

[0004] The present invention is achieved through the following technical solutions: A method for preparing metallic magnesium by using suspended calcined dolomite comprises the following steps: S1: performing suspension calcination treatment on dolomite to obtain calcined dolomite; the magnesium oxide content in the dolomite is greater than 19%; the temperature of the suspension calcination treatment is 900-1000°C, and the time is 5-40s; S2: controlling the moisture content of the calcined white to be no more than 8%, mixing it with ferrosilicon and fluorite, and pressing it into pellets; S3: performing vacuum thermal reduction treatment on the pellets to obtain metallic magnesium.

[0005] Preferably, the average particle size of the dolomite is less than 150 μm.

[0006] Preferably, the average particle size of the dolomite is 50 μm.

[0007] Preferably, the dolomite is ore tailings, crushed materials or dolomite with a hexagonal rhombus crystal structure.

[0008] Preferably, the mass ratio of the calcined silicon to ferrosilicon and fluorite is 100:(18-20):(1.6-3).

[0009] Preferably, during the pressing process into pellets, the pressure is not less than 8 MPa.

[0010] Preferably, during the vacuum thermal reduction treatment, the vacuum degree is 0~20Pa.

[0011] Preferably, during the vacuum thermal reduction treatment, the reduction temperature is 1200-1300° C. and the time is 2-3 hours.

[0012] Preferably, before the material balls are subjected to vacuum thermal reduction treatment, the material balls are dried at 500-600° C. for 2-3 hours.

[0013] A magnesium metal is prepared by the above method; the purity of the magnesium metal is greater than 99.95%.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention discloses a method for preparing metallic magnesium by calcining dolomite in a suspended state. The method selects dolomite with a magnesium oxide content greater than 19%, ensures that the effective magnesium content in the raw material is sufficiently high, and the dolomite with a high magnesium oxide content can provide more magnesium sources, thereby improving the yield and quality of the final product, and then controls the temperature of the suspended calcination treatment to be 900-1000°C and the time to be 5-40s. Compared with the traditional long-term calcination, this high-temperature short-time calcination method can significantly improve production efficiency and reduce energy consumption. At the same time, due to the short time, it can reduce impurities that may be generated during the calcination process, and maintain the product Purity, the calcined white obtained in this process has excellent hydration activity and low loss on ignition, among which the hydration activity is greater than 30% and the loss on ignition is less than 0.5%. Such product quality provides good conditions for the subsequent thermal reduction process; high hydration activity means that the calcined white is more likely to react with the reducing agent during the reduction process, thereby improving the reduction efficiency; and the low loss on ignition reduces the loss caused by the combustion of impurities, further ensuring the purity of the final product; this method further controls the water content of the calcined white to not exceed 8%, thereby improving the purity and yield of the product raw magnesium, and finally, through ball pressing and vacuum thermal reduction treatment, metallic magnesium is obtained. In summary, this method effectively achieves the high-purity and high-yield preparation of metallic magnesium through raw material selection, efficient suspension calcination, and strict control of product quality and moisture content.

[0015] Furthermore, the average particle size of the dolomite is less than 150 μm, which can make the dolomite present a better suspension state, effectively carry out the heat exchange and calcination process, and ensure the quality of the calcined dolomite.

[0016] Furthermore, the average particle size of the dolomite is 50 μm, which allows the dolomite to be quickly decomposed in the calcination system, thereby ensuring the quality of the calcined dolomite.

[0017] Furthermore, the dolomite is ore tailings, crushed materials or dolomite with a hexagonal rhombus crystal structure, which can make use of more types of dolomite for production, alleviate the problem of shortage of high-quality ore materials, and reduce the dependence on and cost of raw material procurement. In addition, the dolomite with a hexagonal rhombus crystal structure has poor anti-explosion performance and cannot be used in the traditional rotary kiln for magnesium refining, resulting in a waste of resources. The method adopts the suspension calcination technology to effectively realize the utilization of dolomite with poor anti-explosion performance and realize resource utilization.

[0018] Furthermore, the ratio of calcined silicon to ferrosilicon and fluorite is 100:(18-20):(1.6-3), which can ensure the reduction rate while controlling the cost.

[0019] Furthermore, during the pressing process of forming the pellets, the pressure is not less than 8 MPa, so that the strength of the pellets can be ensured while ensuring the escape channel of magnesium vapor.

[0020] Furthermore, during the vacuum thermal reduction treatment, the vacuum degree is 0~20Pa. Under high vacuum conditions, the oxygen partial pressure is very low, the collision probability between oxide molecules and oxygen molecules is greatly reduced, the stability of the oxide will be reduced, making the oxide molecules more likely to lose oxygen atoms, thereby reducing the activation energy of the reduction reaction. In addition, the vacuum environment not only reduces the stability of the oxide, but also increases the rate of the thermal reduction reaction. Under vacuum conditions, due to the absence of interference from gas molecules, collisions between metal oxide molecules are more frequent. Such frequent collisions promote effective contact and reaction between the reducing agent and the oxide, thereby increasing the reaction rate; at the same time, from a thermodynamic point of view, the vacuum condition reduces the pressure of the system, thereby changing the equilibrium condition of the reduction reaction. For reduction reactions with gas generation, the vacuum helps to lower the equilibrium temperature of the reduction reaction, which means that under vacuum conditions, the equilibrium state of the reduction reaction can be reached even at a lower temperature, thereby achieving effective reduction. Therefore, ensuring a low vacuum degree can allow the reduction reaction to occur at a lower reaction temperature, while increasing the yield of magnesium metal, improving product quality, and achieving efficient magnesium metal preparation at a lower temperature.

[0021] Furthermore, during the vacuum thermal reduction treatment, the reduction temperature is 1200-1300° C. and the time is 2-3 hours, which can allow the reduction reaction to proceed fully and ensure the reduction rate of metallic magnesium.

[0022] Furthermore, before the material balls are subjected to vacuum thermal reduction treatment, the material balls are dried at 500-600° C. for 2-3 hours, which can reduce problems such as ferrosilicon oxidation caused by water absorption of the raw materials and ensure the reduction rate and quality of the original magnesium. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 The figure is a schematic flow chart of the method for preparing metallic magnesium by calcining dolomite in a suspended state in the present invention; Figure 2 This is a photograph of crystalline magnesium prepared by suspension calcination in one embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0026] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0027] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0028] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0029] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0030] like Figure 1 As shown, the present invention provides a method for preparing metallic magnesium by using suspended calcined dolomite, comprising the following steps: S1: After screening dolomite, suspension calcination treatment is performed to obtain calcined dolomite; the magnesium oxide content in the dolomite is greater than 19%; the temperature of the suspension calcination treatment is 900-1000°C, and the time is 5-40s; Of course, screening treatment may not be performed before suspension calcination treatment. By controlling the air intake of the suspension calcination treatment, the material can be effectively suspended. Of course, it is further preferred that the average particle size of the dolomite is less than 150 μm through screening treatment, the particle size of the material is more uniform, and the effect of suspension calcination will be better. It is further preferred that the average particle size of the dolomite is 50 μm.

[0031] The dolomite is ore tailings, crushed materials or dolomite with a hexagonal rhombus crystal structure. The explosion-proof performance of dolomite with a hexagonal rhombus crystal structure is relatively poor. When calcined using rotary kiln technology, the quality requirements of the raw materials are relatively high, but the suspension calcination technology realizes the effective utilization of crushed materials, powders and even dolomite with relatively poor explosion-proof performance. Among them, ore tailings refer to the remaining parts after ore mining and preliminary processing, which are usually not directly used for the main product. These tailings are regarded as waste due to low grade, impurities or other reasons. Ore tailings usually contain low concentrations of useful components (such as magnesium oxide) and may contain high impurity content. In the process of preparing magnesium metal, ore tailings can be used as one of the raw materials, and magnesium oxide therein is extracted and converted into magnesium metal through suspended calcination, silicon thermal reduction and other steps; crushed materials refer to smaller particles or fragments produced due to various reasons (such as mechanical crushing, wear, impact, etc.) during ore mining, processing, transportation or storage. These crushed materials may come from the dolomite ore itself or may be by-products produced during the processing. The crushed material usually has irregular shapes and sizes, and may contain impurities to varying degrees. However, similar to ore tailings, the useful components in the crushed material (such as magnesium oxide) can still be extracted and utilized through appropriate processes. The crushed material can also be used as one of the raw materials for preparing magnesium metal. Through suspended calcination and silicon thermal reduction, the magnesium oxide in the crushed material can be converted into magnesium metal. Dolomite with poor explosion resistance refers to dolomite that is easily broken or explosively decomposed under external forces (such as mechanical shock, thermal stress, etc.). This dolomite may have low explosion resistance due to internal defects, unstable structure or uneven composition. In the process of preparing magnesium metal, dolomite with poor explosion resistance can also be used as one of the raw materials. Through suspended calcination and silicon thermal reduction, the magnesium oxide in it can be converted into magnesium metal.

[0032] S2: controlling the moisture content of the calcined white to be no more than 8%, mixing it with ferrosilicon and fluorite, and pressing it into pellets; The mass ratio of the calcined silicon to the ferrosilicon and the fluorite is 100:(18-20):(1.6-3). In addition, during the pressing process into pellets, the pressure is not less than 8 MPa.

[0033] In this step, controlling the water content of the calcined white to no more than 8% is the key to ensuring the smooth progress of the subsequent reduction process and the quality of the final product. The method for controlling the water content of the calcined white can be: Drying treatment: Add an appropriate amount of desiccant (such as anhydrous calcium chloride, silica gel, etc.) to the calcined white to remove moisture through physical adsorption. Use hot air drying, vacuum drying or microwave drying to dry the calcined white to remove excess moisture. These methods can be selected according to the characteristics of the calcined white and the production scale.

[0034] Storage condition control: Store calcined white in a dry, well-ventilated environment to avoid exposure to humid air. Control the temperature and humidity of the storage environment, such as using a dehumidifier or air conditioner to adjust the indoor humidity to ensure that calcined white does not absorb moisture from the air.

[0035] Sealed packaging: Sealed packaging is used to reduce the contact area and time between the calcined white and the air, thereby reducing the absorption of moisture. Use packaging materials such as moisture-proof bags or vacuum packaging bags to further reduce the impact of moisture.

[0036] Online monitoring and adjustment: During the production process, the moisture content of calcined white is monitored in real time through online moisture monitoring equipment. According to the monitoring results, the drying treatment or storage conditions are adjusted in time to ensure that the moisture content of calcined white is always kept below 8%.

[0037] Ferrosilicon and fluorite are important additives in the preparation of magnesium metal. Ferrosilicon acts as a reducing agent and undergoes a reduction reaction with magnesium oxide in calcined white to produce magnesium metal. The silicon content of ferrosilicon is usually required to be above 75% to ensure the smooth progress of the reduction reaction. Fluorite acts as a flux and catalyst, which can reduce the temperature of the reduction reaction, increase the reaction rate, and help separate and collect magnesium metal. The calcium fluoride (CaF2) content in fluorite should be above 94% to ensure its fluxing and catalytic effects. When mixing it with ferrosilicon and fluorite with calcined white, ensure that the components are evenly distributed to avoid local concentrations that are too high or too low.

[0038] Pressing into balls can improve the packing density and reaction efficiency of the raw materials. The regular shape of the balls is conducive to uniform distribution and heat transfer in the reduction furnace. The specific pressing method is to feed the evenly mixed raw materials into the ball press for pressing. The parameters of the ball press, such as pressure, rotation speed and mold size, should be adjusted according to the characteristics of the raw materials and production requirements. During the pressing process, it is necessary to ensure that the shape of the balls is regular, the size is uniform, and they have a certain strength and hardness to withstand the high temperature and vacuum conditions during the reduction process. The water content of the balls should be controlled within a certain range to avoid excessive water vapor generated during the reduction process to affect the reaction efficiency. In addition, the particle size distribution of the balls should be uniform to ensure uniform heating and reaction in the reduction furnace.

[0039] S3: Under a vacuum degree of 0-20 Pa, the material balls are subjected to vacuum thermal reduction treatment to obtain metallic magnesium, wherein during the vacuum thermal reduction treatment, the reduction temperature is 1200-1300° C. and the time is 2-3 hours.

[0040] In a preferred embodiment, before the ball is subjected to vacuum thermal reduction treatment, the ball is dried at 500-600° C. for 2-3 hours.

[0041] The material-to-magnesium ratio refers to the mass ratio of the amount of feed (i.e., the total mass of reducing agent, raw materials, etc.) to the crude magnesium output during the silicon thermal magnesium smelting process. The size of the material-to-magnesium ratio and the purity of the reduced magnesium metal are important parameters for measuring the reduction efficiency of magnesium in the reduction process. The purity of the magnesium metal obtained by this method is greater than 99.95%, and the material-to-magnesium ratio is 5.5~6.0, which shows that this method has significant advantages in the preparation of high-purity magnesium metal, and the raw material utilization rate is high, and the production cost is relatively low. These characteristics make this method have broad application prospects and important economic value in the field of magnesium metal preparation.

[0042] The invention discloses a magnesium metal and a method for preparing the magnesium metal by calcining dolomite in a suspended state. The method comprises the following steps: grinding dolomite to a suitable particle size and then calcining it in a suspended state to obtain calcined white powder with a hydration activity greater than 30%, mixing it with a reducing agent and fluorite powder, and then forming a ball under a certain pressure. After drying the ball material, the magnesium metal is reduced by vacuum reduction.

[0043] The method of the present invention combines the suspension calcination technology with the silicon thermal method for magnesium smelting. By utilizing the characteristics of the suspension calcination technology such as suspended reaction and high heat exchange efficiency, tailings, crushed materials, and dolomite with poor explosion resistance can be efficiently utilized. At the same time, the calcination time can be significantly shortened, energy consumption can be reduced, and the quality of the calcined products can be improved, providing stable and high-quality raw materials for the subsequent reduction and magnesium smelting process. It alleviates the current problems of scarcity and high cost of high-quality dolomite ore, and the unstable quality of calcined white that affects the reduction rate and the quality of original magnesium. The reduction rate of the method of the present invention can reach more than 90% in the magnesium smelting process, and the purity of metallic magnesium can reach more than 99.95%.

[0044] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0045] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0046] Example 1 Dolomite powder with an average particle size of 80 microns was suspended and calcined. The calcination temperature was set to 950°C and the calcination time was 10s. The moisture content was controlled at 5% after storage for 1 week. The ball was made and the pressure was set to 80MPa. After drying (600°C, 2h), a ball suitable for silicon thermal magnesium smelting industrial production was obtained. The obtained ball was reduced at 1200°C for 3h in an industrial reduction furnace to obtain reduced crude magnesium. The material-magnesium ratio can reach 6.24.

[0047] Example 2 Metal magnesium is prepared using dolomite with a magnesium oxide content of 19.2%. First, dolomite powder with an average particle size of 50 microns is screened and subjected to suspension calcination treatment, wherein the calcination temperature is 1050°C, the calcination time is 5s, and the hydration activity of the obtained calcined white is 32.47%. Then, the moisture content of the calcined white is controlled to 5%, and it is mixed with ferrosilicon and fluorite, pressed into material balls, dried, and vacuum reduced. During the vacuum reduction process, the vacuum degree is 1.5~9Pa, the temperature is 1300°C, and the time is 3h. The material-magnesium ratio of this process is 5.77, and the purity of the crystalline magnesium is 99.9566%. A photo of the metal magnesium obtained by this method can be seen in Figure 2 As can be seen from the figure, the crude magnesium has dense crystals, good metallic luster, and no oxide film on the surface. The purity of the metal magnesium prepared in this embodiment was tested by direct reading spectrometer method. The specific data is shown in Table 1. As can be seen from Table 1, the purity of the reduced crude magnesium can reach 99.9566%.

[0048] Table 1 Reduced magnesium purity data

[0049] Example 3 A method for preparing metallic magnesium by using suspended calcined dolomite comprises the following steps: S1: After screening the ore tailings, dolomite ore tailings with an average particle size of 100 μm are obtained, and then suspended calcination treatment is performed to obtain calcined white; the magnesium oxide content in the dolomite ore tailings is 20%; the temperature of the suspended calcination treatment is 900° C. and the time is 40 seconds; S2: controlling the moisture content of the calcined white to 7%, mixing it with ferrosilicon and fluorite, and pressing it into pellets; The mass ratio of the calcined silicon to the ferrosilicon and the fluorite is 100:18:1.6. In addition, during the pressing process of the pellets, the pressure is 10 MPa.

[0050] S3: drying the pellets at 500° C. for 3 h, and then performing vacuum thermal reduction treatment on the pellets at a vacuum degree of 10 Pa to obtain metallic magnesium, wherein the reduction temperature during the vacuum thermal reduction treatment is 1300° C. and the time is 2 h.

[0051] The material-magnesium ratio of the method of this embodiment is 5.65, and the purity of the obtained crude magnesium is 99.9570%.

[0052] Example 4 A method for preparing metallic magnesium by using suspended calcined dolomite comprises the following steps: S1: After screening the ore fragments, dolomite ore fragments with an average particle size of 50 μm are obtained, and then suspended calcination treatment is performed to obtain calcined white; the magnesium oxide content in the dolomite ore fragments is 22%; the temperature of the suspended calcination treatment is 1000° C. and the time is 5 seconds; S2: controlling the moisture content of the calcined white to 5%, mixing it with ferrosilicon and fluorite, and pressing it into balls; The mass ratio of the calcined silicon to the ferrosilicon and the fluorite is 100:20:3. In addition, during the pressing process of the pellets, the pressure is 15 MPa.

[0053] S3: drying the pellets at 600° C. for 2 h, and then performing vacuum thermal reduction treatment on the pellets at a vacuum degree of 20 Pa to obtain metallic magnesium, wherein the reduction temperature during the vacuum thermal reduction treatment is 1200° C. and the time is 3 h.

[0054] The material-magnesium ratio of the method of this embodiment is 5.99, and the purity of the obtained crude magnesium is 99.9557%.

[0055] Example 5 A method for preparing metallic magnesium by using suspended calcined dolomite comprises the following steps: S1: After screening dolomite, dolomite with an average particle size of 150 μm is obtained, and then suspended calcination is performed to obtain calcined white; the magnesium oxide content in the dolomite is 25%; the temperature of the suspended calcination treatment is 950° C. and the time is 20 seconds; S2: controlling the moisture content of the calcined white to 5%, mixing it with ferrosilicon and fluorite, and pressing it into balls; The mass ratio of the calcined silicon to the ferrosilicon and the fluorite is 100:19:2. In addition, during the pressing process of the pellets, the pressure is 15 MPa.

[0056] S3: drying the pellets at 550° C. for 2.5 h, and then performing vacuum thermal reduction treatment on the pellets at a vacuum degree of 10 Pa to obtain metallic magnesium, wherein the reduction temperature during the vacuum thermal reduction treatment is 1250° C. and the time is 2.5 h.

[0057] The material-magnesium ratio of the method of this embodiment is 5.89, and the purity of the obtained crude magnesium is 99.9557%.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing magnesium metal by calcining dolomite in a suspended state, characterized in that: The following steps are involved: S1: performing suspension calcination treatment on dolomite to obtain calcined dolomite; the magnesium oxide content in the dolomite is greater than 19%; the temperature of the suspension calcination treatment is 900-1000°C, and the time is 5-40s; S2: controlling the moisture content of the calcined white to be no more than 8%, mixing it with ferrosilicon and fluorite, and pressing it into pellets; S3: performing vacuum thermal reduction treatment on the pellets to obtain metallic magnesium.

2. The method for preparing metallic magnesium by calcining dolomite in a suspended state according to claim 1, characterized in that: The average particle size of the dolomite is less than 150 μm.

3. The method for preparing magnesium metal by calcining dolomite in a suspended state according to claim 1, characterized in that: The average particle size of the dolomite is 50 μm.

4. The method for preparing magnesium metal by calcining dolomite in a suspended state according to claim 1, characterized in that: The dolomite is ore tailings, crushed materials or dolomite with a hexagonal rhombus crystal structure.

5. The method for preparing metallic magnesium by calcining dolomite in a suspended state according to claim 1, characterized in that: The mass ratio of the calcined quartz to ferrosilicon and fluorite is 100:(18-20):(1.6-3).

6. The method for preparing metallic magnesium by calcining dolomite in a suspended state according to claim 1, characterized in that: During the pressing process into pellets, the pressure is not less than 8 MPa.

7. The method for preparing metallic magnesium by calcining dolomite in a suspended state according to claim 1, characterized in that: During the vacuum thermal reduction treatment, the vacuum degree is 0-20Pa.

8. The method for preparing metallic magnesium by calcining dolomite in a suspended state according to claim 1, characterized in that: During the vacuum thermal reduction treatment, the reduction temperature is 1200-1300° C. and the time is 2-3 hours.

9. The method for preparing metallic magnesium by calcining dolomite in a suspended state according to claim 1, characterized in that: Before the material balls are subjected to vacuum thermal reduction treatment, the material balls are dried at 500-600° C. for 2-3 hours.

10. A magnesium metal obtained by the method according to any one of claims 1 to 9; the purity of the magnesium metal is greater than 99.95%.

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