Method for increasing yield by adding magnesium oxide into calcined dolomite

Abstract

The invention discloses a method for increasing yield by adding magnesium oxide into calcined dolomite, which comprises the following steps: calcining dolomite to obtain calcined dolomite; adding exogenous magnesium oxide into the calcined dolomite according to the content of magnesium oxide in the dolomite to obtain optimized calcined dolomite; and the optimized calcined dolomite, silicon iron and fluorite are subjected to mixing, ball pressing and vacuum reduction, and the magnesium ingot is prepared. The technical problems that in the prior art, the magnesium content of dolomite is low, the quality is poor, the overall production cost is increased, the material-magnesium ratio is difficult to reduce, and silicon iron is wasted are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of magnesium smelting technology and relates to a method for increasing yield by adding magnesium oxide to calcined dolomite. Background Technology

[0002] In the silicothermic magnesium smelting industry, dolomite is an indispensable raw material, and its importance is self-evident. The silicothermic magnesium smelting process has specific and strict requirements for the quality of dolomite; high-quality dolomite must meet the key condition of a near 1:1 molar ratio of magnesium oxide to calcium oxide. However, the reality is far from optimistic. With the continuous mining of high-quality dolomite resources, its reserves are decreasing, and the quality of dolomite available on the market is gradually declining. Currently, most common dolomite on the market has a low magnesium oxide content, making it difficult to meet the high-quality standards required for silicothermic magnesium smelting.

[0003] While low-quality dolomite is relatively inexpensive, seemingly reducing raw material procurement costs, it brings numerous disadvantages to the entire production process. Due to the insufficient magnesium content in dolomite, it's difficult to effectively reduce the feed-to-magnesium ratio during subsequent reduction processes. The feed-to-magnesium ratio refers to the proportion of raw materials participating in the reaction to the magnesium produced; a higher ratio means more raw materials are needed to produce a certain amount of magnesium, undoubtedly increasing production costs. Furthermore, in the batching stage, the poor quality of dolomite necessitates adjustments to the batching ratio to ensure the reaction proceeds normally, leading to waste of auxiliary raw materials such as ferrosilicon. Ferrosilicon plays a crucial role in the silicothermic magnesium smelting process; its waste not only increases raw material costs but also affects the economics of magnesium smelting.

[0004] Faced with these problems caused by low-quality dolomite, how to improve the reaction efficiency of this type of ore without increasing the complexity of equipment and processes has become a pressing technical challenge for the current magnesium smelting industry using the silicothermic process. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for increasing yield by adding magnesium oxide to calcined dolomite, thereby solving the technical problems of low magnesium content and poor quality of dolomite, which leads to increased overall production costs, difficulty in reducing the magnesium-to-silicon ratio, and waste in the prior art.

[0006] This invention is achieved through the following technical solution: A method for increasing yield by adding magnesium oxide to calcined dolomite includes the following steps: S1: Calcining dolomite yields calcined white dolomite; based on the magnesium oxide content in the dolomite, exogenous magnesium oxide is added to the calcined white dolomite to obtain optimized calcined white dolomite. S2: The optimized calcined white metal is mixed with ferrosilicon and fluorite, granulated, and vacuum reduced to obtain magnesium ingots.

[0007] Preferably, in step S1, when calcining dolomite, if suspension calcination is used, the dolomite is crushed to a particle size of less than 150 μm, and then the crushed dolomite is calcined at 950~1200℃ for 5~10s to obtain the calcined dolomite.

[0008] Preferably, in step S1, when calcining dolomite, if a rotary kiln method is used, the dolomite is directly calcined at 900~1200℃ to obtain calcined dolomite.

[0009] Preferably, in step S2, the mass ratio of the optimized calcined white metal to ferrosilicon and fluorite is (80~100):(16~20):(1~3).

[0010] Preferably, in step S2, the particle size of the exogenous magnesium oxide is less than 150 μm, the particle size of the ferrosilicon is less than 150 μm, and the particle size of the fluorite is less than 150 μm.

[0011] Preferably, when magnesium is smelted using a suspension calcination method, the mixing time in step S2 is 10-30 minutes.

[0012] Preferably, when magnesium is smelted using a suspension calcination method, in step S2, if the total mass of the optimized calcined white metal, ferrosilicon, and fluorite is less than 500g, the mixing time is 10-15min; otherwise, the mixing time is 15-30min.

[0013] Preferably, in step S2, during the briquetting process, the mixed material is poured into a mold with a diameter of 30mm and pressed into shape under a pressure of 80~130Mpa for 10~40s.

[0014] Preferably, in step S2, the vacuum reduction process has a vacuum degree of 20 Pa, a reduction temperature of 1050~1350℃, and a reduction time of 2~4 h.

[0015] A magnesium ingot is obtained by the method described above.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for increasing yield by adding magnesium oxide to calcined dolomite. This method adds magnesium oxide powder to low-grade calcined dolomite, fully utilizing the previously low-value dolomite due to its poor quality, thus increasing its utilization value and reducing the overall cost of magnesium smelting. The method is simple to operate, requiring only the addition of magnesium oxide powder during the existing mixing process, without additional equipment investment or complex process modifications. This avoids the burden of additional equipment procurement and process adjustments for enterprises, indirectly reducing production costs. By precisely incorporating magnesium oxide powder (exogenous MgO), this method forms a "dual magnesium source synergistic system" with the endogenous MgO in the calcined dolomite, reducing the magnesium-to-silicon ratio from 6.2-7.0 in traditional processes to 5.5-5.8, effectively lowering the ratio. Without adding magnesium oxide powder, directly adding ferrosilicon and fluorite in proportion for reduction results in some ferrosilicon being wasted due to incomplete reaction. Adding magnesium oxide powder optimizes the reaction conditions, ensuring all ferrosilicon participates in the reaction, improving ferrosilicon utilization and avoiding resource waste. Ferrosilicon is the most expensive part of the entire smelting process, so reducing its waste will lower production costs.

[0017] Furthermore, in step S1, when calcining dolomite, if suspension calcination is used, the dolomite is crushed to a particle size of less than 150 μm, and then the crushed dolomite is calcined at 950~1200℃ for 5~10 seconds to obtain the calcined white dolomite. Crushing the dolomite to a particle size of <150 μm significantly increases the specific surface area, making the calcination reaction more complete. Combined with the high temperature of 950~1200℃, calcination can be completed in only 5~10 seconds, which is dozens of times more efficient than the traditional rotary kiln method (which takes several hours). Fine particles and short calcination time reduce the risk of over-burning or under-burning, ensuring uniform activity of the calcined white dolomite (MgO·CaO) and providing stable raw materials for subsequent reduction reactions.

[0018] Furthermore, in step S1, when calcining dolomite using a rotary kiln, the dolomite is directly calcined at 900~1200℃ to obtain calcined dolomite. Direct calcination eliminates the need for pre-crushing (compared to suspension calcination), adapting to dolomite raw materials of different particle sizes and reducing the requirements for raw material pretreatment. The rotary kiln is a mature industrial piece of equipment that can be used for magnesium smelting without additional modifications, making it suitable for technological upgrades in small and medium-sized enterprises.

[0019] Furthermore, in step S2, the optimized mass ratio of calcined white metal to ferrosilicon and fluorite is (80~100):(16~20):(1~3). This process precisely controls the molar ratio of reactants, reducing side reactions and ensuring more thorough magnesium reduction. Through the efficient utilization of the "dual magnesium source synergistic system" (internal + external MgO) and ferrosilicon, the magnesium-to-material ratio is reduced to 5.5~5.8, significantly lowering raw material consumption compared to the traditional process (6.2~7.0). Simultaneously, the fixed ratio reduces batch variations, ensuring magnesium ingot purity ≥99.95%.

[0020] Furthermore, in step S2, the particle size of the exogenous magnesium oxide is less than 150 μm, the particle size of the ferrosilicon is less than 150 μm, and the particle size of the fluorite is less than 150 μm. This size increases the contact area, accelerates the reduction reaction rate, and shortens the vacuum reduction time. In addition, fine particles reduce reaction dead zones, ensuring that ferrosilicon and fluorite fully participate in the reaction and avoiding waste. At the same time, uniform fine particles are beneficial to material densification, improve briquetting strength, and reduce pulverization during transportation and reduction.

[0021] Furthermore, when magnesium is smelted using the suspension calcination method, in step S2, the mixing time is 10-30 minutes. This mixing time ensures that the optimized calcined white metal, ferrosilicon, and fluorite are fully dispersed, avoiding local component deviations that could affect the reduction efficiency.

[0022] Furthermore, when magnesium is smelted using the suspension calcination method, in step S2, if the total mass of the optimized calcined white metal, ferrosilicon, and fluorite is less than 500g, the mixing time is 10-15min; otherwise, the mixing time is 15-30min. This process ensures stable mixing quality in large-scale production. At the same time, graded control reduces human error and improves process repeatability.

[0023] Furthermore, in step S2, during the pelletizing process, the mixed material is poured into a 30mm diameter mold and pressed into shape under a pressure of 80-130 MPa for 10-40 seconds. The 80-130 MPa pressure, combined with the 30mm mold, increases the pellet density and compressive strength, reducing pulverization within the reduction furnace. The 10-40 second pressing time balances production pace and pellet quality, preventing cracks caused by pressing too quickly or inefficient pressing due to pressing too slowly. This pressing process not only increases pellet density but also reduces gas permeation resistance, promoting the escape of magnesium vapor during vacuum reduction.

[0024] Furthermore, in step S2, during the vacuum reduction process, the vacuum degree is 20 Pa, the reduction temperature is 1050~1350℃, and the reduction time is 2~4 h. Here, the vacuum degree of 20 Pa effectively reduces the partial pressure of magnesium vapor and promotes the forward reaction; the temperature gradient of 1050~1350℃ covers the active range of ferrosilicon reduction, ensuring that MgO is fully decomposed. The reduction cycle of 2~4 h is shortened by more than 50% compared with the traditional process (6~8 hours), significantly improving the equipment utilization rate. At the same time, low-temperature reduction reduces energy consumption, and the vacuum environment avoids the generation of nitrogen oxides, which meets the requirements of low-carbon smelting. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A photograph of the magnesium ingot prepared in Example 1 of this invention; Figure 2 This is a photograph of the magnesium ingot obtained in Example 2 of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0028] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0029] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0030] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0031] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0032] This invention provides a method for improving yield by adding magnesium oxide to calcined dolomite. By adding magnesium oxide to the dolomite, the calcium-to-magnesium ratio in the raw material reaches 1:1, thereby significantly improving the calcination reaction rate. The specific steps are as follows: (1) Preparation of calcined white: calcined dolomite is used to obtain calcined white; Specifically: If calcined dolomite is prepared by suspension calcination, the dolomite is crushed to a particle size of less than 150μm using a crusher, and then the crushed dolomite is placed in a suspension calcination device and suspended calcined at 950~1200℃ for 5~10s to obtain calcined dolomite. If calcined dolomite is prepared by rotary kiln method, the blocky dolomite is directly calcined in rotary kiln at 900~1200℃ to obtain calcined dolomite; (2) Add exogenous magnesium oxide to the calcined white to obtain optimized calcined white, so that the molar ratio of magnesium oxide to calcium oxide in the optimized calcined white is 1:1; then, based on the mass of the optimized calcined white, add ferrosilicon and fluorite, mix evenly, and obtain mixed raw materials; The optimized mass ratio of calcined white metal to ferrosilicon and fluorite is (80~100):(16~20):(1~3).

[0033] The exogenous magnesium oxide has a particle size of less than 150 μm, the ferrosilicon has a particle size of less than 150 μm, and the fluorite has a particle size of less than 150 μm.

[0034] If the magnesium oxide content in a certain batch of dolomite is 17%, then after adding exogenous magnesium oxide, the molar ratio of magnesium oxide to calcium oxide in the optimized calcined dolomite is 1:1. Then, according to the weight of the optimized calcined dolomite, ferrosilicon and fluorite are added, so that the mass ratio of optimized calcined dolomite to ferrosilicon and fluorite in the mixed raw materials is 100:20:3.

[0035] If magnesium is smelted using a traditional rotary kiln, the second mass of magnesium oxide, ferrosilicon, fluorite, and calcined white metal are mixed and then poured into a ball mill for crushing and mixing to obtain a mixed raw material.

[0036] If a batch of dolomite contains 18.5% magnesium oxide, adding exogenous magnesium oxide will make the molar ratio of magnesium oxide to calcium oxide in the optimized calcined dolomite 1:1. Then, based on the weight of the optimized calcined dolomite, ferrosilicon and fluorite are added, so that the mass ratio of optimized calcined dolomite to ferrosilicon and fluorite in the mixed raw material is 82.4:16.2:1.2. The optimized calcined dolomite, ferrosilicon and fluorite are added to a ball mill for crushing and mixing to obtain the mixed raw material.

[0037] When using the suspension calcination method for magnesium smelting, the optimal mixing time for calcined white metal, ferrosilicon, and fluorite is 10-30 minutes, aiming for complete mixing without stratification or adhesion. More specifically, if the total mass of the raw materials is less than 500g, the mixing time is 10-15 minutes; if the total mass of the raw materials is greater than 500g, the mixing time is 15-30 minutes. Here, the total mass of the raw materials refers to the total mass of the optimized calcined white metal, ferrosilicon, and fluorite.

[0038] (3) Press the mixed raw materials into a ball; specifically, the mixed raw materials can be poured into a mold with a diameter of 30 mm and pressed for 10 to 40 seconds under a pressure of 80 to 130 MPa. During the pressing process, the prepared ball is required to break into at most three pieces when dropped from a height of 1 m.

[0039] (4) Vacuum reduction of the pellets to obtain magnesium ingots; Specifically: the material balls are placed into a vacuum reduction furnace, the vacuum pump is turned on, and the reduction program is started after the vacuum degree is reduced to below 20 Pa. Vacuum reduction is carried out at 1050~1350℃, preferably 1200~1300℃, to obtain magnesium ingots.

[0040] The method in this invention involves adding exogenous magnesium oxide to low-grade calcined dolomite to optimize the molar ratio of magnesium oxide to calcium oxide in the calcined dolomite to 1:1. For example, if the magnesium oxide content in the raw dolomite is 17%, an appropriate mass of magnesium oxide powder needs to be added after calculation to optimize the molar ratio of magnesium oxide to calcium oxide in the calcined dolomite to 1:1. Compared with the traditional method, this invention forms a "dual magnesium source synergistic system" by precisely incorporating magnesium oxide powder, i.e., exogenous MgO, with the endogenous MgO in the calcined dolomite. This reduces the magnesium ratio from 6.2~7.0 in the traditional process to 5.5~5.8, thereby improving the magnesium yield. The purity of the obtained magnesium ingot is ≥99.95%. Furthermore, this method is applicable to traditional rotary kiln calcination and suspension calcination, and has wide applicability.

[0041] This invention addresses a series of problems in the application of low-quality dolomite by introducing magnesium oxide powder into calcined dolomite, a method with numerous significant advantages. Firstly, from the perspective of increasing yield, regardless of the calcination method, adding an appropriate amount of magnesium oxide powder to low-grade block or powdered calcined dolomite in a certain proportion can effectively increase magnesium yield and reduce the magnesium-to-material ratio. This means that with the same raw material input, more magnesium product can be obtained, thereby improving production efficiency. Regarding resource utilization, if magnesium oxide powder is not added and ferrosilicon and fluorite are directly added in proportion for reduction, some ferrosilicon will be wasted due to incomplete reaction. Ferrosilicon is the most expensive component in the entire smelting process; its waste not only causes resource depletion but also increases production costs. Adding magnesium oxide powder improves the utilization rate of ferrosilicon, ensuring its complete participation in the reaction and avoiding resource waste. This method is simple to operate, requiring no additional equipment investment or complex process modifications; it can be completed simply by adding magnesium oxide powder to the existing mixing process, without imposing additional equipment procurement and process adjustment burdens on enterprises. Economic efficiency is also a prominent feature of this method. The method in this invention makes full use of inexpensive magnesium oxide raw materials, significantly improving the utilization value of low-quality dolomite. This allows dolomite, which was originally of low value due to its poor quality, to play a greater role, thereby reducing the overall cost of magnesium smelting. Furthermore, this method has the advantages of being environmentally friendly and sustainable. By optimizing the calcium-magnesium ratio, it reduces energy and raw material consumption during the reduction process, which is conducive to energy conservation and emission reduction, aligns with the current concept of green development, and is of great significance to the sustainable development of the magnesium smelting industry.

[0042] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0043] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0044] Example 1 Magnesium oxide powder (exogenous magnesium oxide) was added to low-grade calcined dolomite powder (magnesium oxide content 18.5%) obtained by suspension calcination to obtain optimized calcined dolomite. The molar ratio of magnesium oxide to calcium oxide in the optimized calcined dolomite was 1:1. Then, based on the mass of the optimized calcined dolomite, the mass ratio of the optimized calcined dolomite to ferrosilicon and fluorite was controlled at 82.4:16.2:1.2 for batching and mixing, with a mixing time of 15 min. After pressing, pellets were obtained and fed into a reactor for silicothermic reduction reaction at 1200℃ for 120 min to obtain magnesium ingots.

[0045] In this embodiment, the magnesium-to-material ratio is 5.5, and the purity of the magnesium ingots obtained in this embodiment meets the national standard 9995A.

[0046] Figure 1 The image shows a photograph of the magnesium ingot obtained in Example 1 of this invention. As can be seen from the image, high-quality magnesium ingots can be obtained through this method.

[0047] Comparative Example 1 The difference between this comparative example and Example 1 is that no exogenous magnesium oxide was added to the calcined white metal. Instead, magnesium ingots were obtained by directly mixing, pressing, and reducing ferrosilicon and fluorite.

[0048] In this comparative method, the magnesium-to-material ratio is 6.2.

[0049] Comparing Example 1 with Comparative Example 1, it is shown that after adding magnesium oxide, the magnesium-to-material ratio decreased from 6.2 to 5.5, increasing the yield. The final obtained metallic magnesium purity was over 99.95%, and the reaction efficiency was high, meeting the requirements of industrial production.

[0050] Example 2 Magnesium oxide powder (exogenous magnesium oxide) was added to low-grade calcined dolomite blocks (magnesium oxide content 17%) obtained by conventional rotary kiln calcination to obtain optimized calcined dolomite, with a molar ratio of magnesium oxide to calcium oxide of 1:1. Then, based on the quality of the optimized calcined dolomite, the mass ratio of optimized calcined dolomite to ferrosilicon and fluorite was controlled at 100:20:3 for batching. The batch was then poured into a ball mill for crushing and mixing for 30 minutes. After pressing, pellets were obtained and fed into a reactor for silicothermic reduction reaction at 1300℃ for 120 minutes.

[0051] In this embodiment, the magnesium-to-material ratio is 5.8, and the magnesium ingots obtained in this embodiment meet the national standard 9995A.

[0052] Figure 2 The image shows a photograph of the magnesium ingot obtained in Example 2 of this invention. As can be seen from the image, high-quality magnesium ingots can be obtained through this method.

[0053] Comparative Example 2 The difference between this comparative example and Example 2 is that magnesium oxide powder was not added to the calcined white metal. Instead, magnesium oxide was directly mixed with ferrosilicon and fluorite, granulated, and reduced to obtain magnesium ingots.

[0054] In this comparative example, the magnesium-to-material ratio is 6.5, and the purity of the magnesium ingots obtained in this comparative example meets the national standard 9995A.

[0055] Comparing Example 2 with Comparative Example 2, it is shown that after adding magnesium oxide, the magnesium-to-material ratio decreased from 6.5 to 5.8, increasing the yield. The final obtained metallic magnesium purity was over 99.95%, and the reaction efficiency was high, meeting the requirements of industrial production.

[0056] Example 3 Taking suspension calcination technology and low-grade dolomite (MgO=17%, CaO=30.5%) as an example, the technical solution of the present invention is described.

[0057] (1) Raw materials and preparation 1000g of powdered dolomite with 17% MgO and 30.5% CaO was selected. The molar amount of MgO was (1000g×17%) / 40g / mol=4.22mol, and the molar amount of CaO was (1000g×30.5%) / 56g / mol=5.44mol. Therefore, the molar amount of exogenous magnesium oxide to be added was 1.22mol, or 49.2g. The particle size of this exogenous magnesium oxide was ≤50μm, which is industrial grade.

[0058] (2) Preparation of calcined white Dolomite was crushed to a particle size of <150μm and fed into a suspension calcination device. It was calcined at 950℃ for 10s to obtain calcined dolomite (mass = 1000×(1-47.8%) = 522g, note: the total weight loss of dolomite during calcination is about 47.8%).

[0059] (3) Mixed raw materials 522g of calcined white metal was mixed with 49.2g of exogenous MgO to obtain 571g of optimized calcined white metal. 114.2g of ferrosilicon (particle size ≤100μm, 75SiFe) and 17.1g of fluorite (particle size ≤80μm) were added at a mass ratio of 100:20:3 (optimized calcined white metal: ferrosilicon: fluorite).

[0060] Mixing conditions: Total mass = 571 + 114.2 + 17.1 = 702.3g > 500g, mix for 30 minutes (planetary mixer, speed 200rpm), no stratification or sticking after mixing.

[0061] (4) Press molding The mixed raw materials are poured into a cylindrical mold with a diameter of 30 mm and pressed under a pressure of 80 MPa to obtain material balls (the mass of a single ball is approximately 50 g).

[0062] (5) Vacuum reduction The pellets are loaded into a vacuum reduction furnace, the vacuum pump is turned on to evacuate to 15 Pa (≤20 Pa), the temperature is raised to 1200℃, and reduction is carried out for 8 hours. After reduction, the condensed magnesium vapor is collected and cast into ingots.

[0063] In this embodiment, the magnesium-to-material ratio is 5.6, which is superior to traditional processes, resulting in a magnesium yield of approximately 92% and a magnesium ingot purity of 99.96%.

[0064] Example 4 Taking rotary kiln calcination of medium-grade dolomite (MgO=18.5%, CaO=28.5%) as an example.

[0065] (1) Raw materials and preparation 1000g of blocky dolomite with 18.5% MgO and 28.5% CaO was selected. The molar amount of MgO was (1000g×18.5%) / 40g / mol=4.63mol, and the molar amount of CaO was (1000g×28.5%) / 56g / mol=5.09mol. Therefore, the molar amount of exogenous magnesium oxide to be added was 0.46mol, or 18.4g. The particle size of this exogenous magnesium oxide was ≤50μm, which is industrial grade.

[0066] (2) Preparation of calcined white The blocky dolomite was directly fed into a rotary kiln and calcined at 900℃ for 2 hours (traditional rotary kiln process) to obtain calcined dolomite (mass = 522g).

[0067] (3) Mixed raw materials Calcined white (522g) was mixed with exogenous MgO (18.4g) to obtain 540.4g of optimized calcined white. 106g of ferrosilicon (75SiFe) and 7.87g of fluorite were added at a mass ratio of 82.4:16.2:1.2 (optimized calcined white: ferrosilicon: fluorite).

[0068] Mixing conditions: Add the three materials to a ball mill (20mm diameter steel balls, 40% filling rate), crush and mix for 25 minutes (300rpm), and the output particle size is ≤100μm.

[0069] (4) Press molding The mixed raw materials are poured into a cylindrical mold with a diameter of 30 mm and pressed under a pressure of 98 MPa to obtain material balls (the mass of a single ball is approximately 50 g).

[0070] (5) Vacuum reduction The pellets were loaded into the vacuum reduction furnace, the vacuum pump was turned on to evacuate to 10 Pa, the temperature was raised to 1300℃, and the reduction was carried out for 7 hours.

[0071] In this embodiment, the magnesium-to-material ratio is 5.7, which is better than the traditional process. The magnesium yield is about 91%, and the magnesium ingot purity is 99.95%.

[0072] Example 5 Taking suspension-calcined, medium-to-high grade dolomite (MgO=19%, CaO=29.3%) as an example (1) Raw materials and preparation 1000g of powdered dolomite with 19% MgO and 29.3% CaO was selected. The molar amount of MgO was (1000g×19%) / 40g / mol=4.75mol, and the molar amount of CaO was (1000g×29.3%) / 56g / mol=5.23mol. Therefore, the molar amount of exogenous magnesium oxide to be added was 0.48mol, or 19.2g. The particle size of this exogenous magnesium oxide was ≤50μm, which is industrial grade.

[0073] (2) Preparation of calcined white Dolomite was crushed to a particle size of <150μm and then suspended and calcined at 1200℃ for 5s (high temperature and short time calcination) to obtain 522g of calcined white stone.

[0074] (3) Mixed raw materials 522g of calcined white powder was mixed with 19.2g of exogenous MgO to obtain 541.2g of optimized calcined white powder. 108.2g of ferrosilicon and 12.0g of fluorite were added at a mass ratio of 90:18:2. Mixing conditions: Total mass 541.2g + 108.2g + 12.0g = 661.4g > 500g, mix for 20 minutes.

[0075] (4) Press molding The pressure is 130 MPa.

[0076] (5) Vacuum reduction The pellets were loaded into the vacuum reduction furnace, the vacuum pump was turned on to evacuate to 20 Pa, the temperature was raised to 1100℃, and the reduction was carried out for 10 hours.

[0077] In this embodiment, the magnesium-to-material ratio is 5.8, which is better than the traditional process. The magnesium yield is about 90%, and the magnesium ingot purity is 99.95%.

[0078] Example 6 Taking rotary kiln calcined, near-high-grade dolomite (MgO=20%, CaO=28.5%) as an example (1) Raw materials and preparation 1000 kg of blocky dolomite with a MgO content of 20% and a CaO content of 28.5% was selected. The molar amount of MgO was (1000 g × 20%) / 40 g / mol = 5 mol, and the molar amount of CaO was (1000 g × 28.5%) / 56 g / mol = 5.09 mol. Therefore, the molar amount of exogenous magnesium oxide to be added was 0.09 mol, or 3.6 g. The particle size of this exogenous magnesium oxide was ≤50 μm, which is industrial grade.

[0079] (2) Preparation of calcined white Calcination at 1200℃ in a rotary kiln for 1.5 hours yielded 522g of calcined white powder.

[0080] (3) Mixed raw materials Calcined white (522g) was mixed with exogenous MgO (3.6g) to obtain 525.6g of optimized calcined white. At a mass ratio of 82.4:16.2:1.2 (optimized calcined white: ferrosilicon: fluorite), 103g of ferrosilicon (75SiFe) and 7.65g of fluorite were added.

[0081] Mixing conditions: Add the three materials to a ball mill (20mm diameter steel balls, 40% filling rate), crush and mix for 25 minutes (300rpm), and the output particle size is ≤100μm.

[0082] (4) Press molding Same as Example 1.

[0083] (5) Vacuum reduction Drain to 18 Pa, heat to 1250℃ (preferred midpoint range), and reduce for 7.5 h.

[0084] In this embodiment, the material-to-magnesium ratio is 5.5, which is better than the traditional process. The magnesium yield is about 93%, and the magnesium ingot purity is 99.97%.

[0085] Example 7 Taking suspension-calcined, extremely low-grade dolomite (MgO=16%, CaO=31.5%) as an example (1) Raw materials and preparation 1000 kg of powdered dolomite with 16% MgO and 31.5% CaO was selected. The molar amount of MgO was (1000g × 16%) / 40g / mol = 4mol, and the molar amount of CaO was (1000g × 31.5%) / 56g / mol = 5.63mol. Therefore, the molar amount of exogenous magnesium oxide to be added was 1.63mol, or 65.2g. The particle size of this exogenous magnesium oxide was ≤50μm, which is industrial grade.

[0086] (2) Preparation of calcined white The particles were crushed to <150μm and then suspended and calcined at 1000℃ for 8s to obtain 522g of calcined white powder.

[0087] (3) Mixed raw materials 522g of calcined white metal was mixed with 65.2g of exogenous MgO to obtain 587.2g of optimized calcined white metal. 117.4g of ferrosilicon (particle size ≤100μm, 75SiFe) and 17.6g of fluorite (particle size ≤80μm) were added at a mass ratio of 100:20:3 (optimized calcined white metal: ferrosilicon: fluorite).

[0088] Mixing conditions: Total mass = 587.2 + 117.4 + 17.6 = 722.2g > 500g, mix for 30 minutes (planetary mixer, speed 200rpm), no stratification or sticking after mixing.

[0089] (4) Press molding Same as Example 1.

[0090] (5) Vacuum reduction Drain to 12 Pa, heat to 1350℃ (upper limit of range), and reduce for 6 hours (high temperature shortens the reduction time).

[0091] In this embodiment, the magnesium-to-material ratio is 5.7, which is better than the traditional process. The magnesium yield is about 91%, and the magnesium ingot purity is 99.96%.

[0092] Example 8 Taking rotary kiln calcination of conventional grade dolomite (MgO=17.5%, CaO=29.5%) as an example.

[0093] (1) Raw materials and preparation 1000g of blocky dolomite with MgO content of 17.5% and CaO content of 29.5% is selected. The molar amount of MgO is (1000g×17.5%) / 40g / mol=4.38mol and the molar amount of CaO is (1000g×28.5%) / 56g / mol=5.09mol. Therefore, the molar amount of exogenous magnesium oxide to be added is 0.71mol, or 28.4g.

[0094] (2) Preparation of calcined white Calcination at 1050℃ in a rotary kiln for 1.8 hours yielded 522 kg of calcined white powder.

[0095] (3) Mixed raw materials Calcined white (522g) was mixed with exogenous MgO (28.4g) to obtain 550.4g of optimized calcined white. 110.1g of ferrosilicon (75SiFe) and 14.5g of fluorite were added at a mass ratio of 95:19:2.5 (optimized calcined white: ferrosilicon: fluorite).

[0096] Mixing conditions: Total mass 675g > 500g, mix for 25 minutes.

[0097] (4) Press molding Strictly following the 30mm diameter mold and 98MPa pressure pressing method, the material ball breaks into two pieces when dropped from 1m.

[0098] (5) Vacuum reduction The pressure was reduced to 16 Pa, the temperature was raised to 1280℃, and the reduction was carried out for 7 hours.

[0099] In this embodiment, the magnesium-to-material ratio is 5.6, which is better than the traditional process. The magnesium yield is about 93%, and the magnesium ingot purity is 99.95%.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for increasing yield by adding magnesium oxide to calcined dolomite, characterized in that, Includes the following steps: S1: Calcining dolomite yields calcined white dolomite; based on the magnesium oxide content in the dolomite, exogenous magnesium oxide is added to the calcined white dolomite to obtain optimized calcined white dolomite. S2: The optimized calcined white metal is mixed with ferrosilicon and fluorite, granulated, and vacuum reduced to obtain magnesium ingots.

2. The method for increasing yield by adding magnesium oxide to calcined dolomite according to claim 1, characterized in that, In step S1, when calcining dolomite, if suspension calcination is used, the dolomite is crushed to a particle size of less than 150 μm, and then the crushed dolomite is calcined at 950~1200℃ for 5~10s to obtain the calcined dolomite.

3. The method for increasing yield by adding magnesium oxide to calcined dolomite according to claim 1, characterized in that, In step S1, when calcining dolomite, if the rotary kiln method is used, the dolomite is directly calcined at 900~1200℃ to obtain calcined dolomite.

4. The method for increasing yield by adding magnesium oxide to calcined dolomite according to claim 1, characterized in that, In step S2, the optimized mass ratio of calcined white metal to ferrosilicon and fluorite is (80~100):(16~20):(1~3).

5. The method for increasing yield by adding magnesium oxide to calcined dolomite according to claim 1, characterized in that, In step S2, the particle size of the exogenous magnesium oxide is less than 150 μm, the particle size of the ferrosilicon is less than 150 μm, and the particle size of the fluorite is less than 150 μm.

6. The method for increasing yield by adding magnesium oxide to calcined dolomite according to claim 1, characterized in that, When magnesium is smelted using the suspension calcination method, in step S2, the mixing time is 10~30 min.

7. The method for increasing yield by adding magnesium oxide to calcined dolomite according to claim 1, characterized in that, When magnesium is smelted using the suspension calcination method, in step S2, if the total mass of the optimized calcined white metal, ferrosilicon, and fluorite is less than 500g, the mixing time is 10-15min; otherwise, the mixing time is 15-30min.

8. The method for increasing yield by adding magnesium oxide to calcined dolomite according to claim 1, characterized in that, In step S2, during the briquetting process, the mixed material is poured into a mold with a diameter of 30mm and pressed into shape under a pressure of 80~130Mpa for 10~40s.

9. The method for increasing yield by adding magnesium oxide to calcined dolomite according to claim 1, characterized in that, In step S2, during the vacuum reduction process, the vacuum degree is 20 Pa, the reduction temperature is 1050~1350℃, and the reduction time is 2~4 h.

10. A magnesium ingot, characterized in that, It is prepared by the method described in any one of claims 1 to 9.

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