A method for producing magnesium and olivine by silicon-thermal reduction of magnesite resources

Abstract

A method for producing magnesium and forsythite by silicon-thermal method using magnesite resources belongs to the technical field of magnesium smelting. The method uses vacuum or relative vacuum technology, takes magnesite resources as raw materials, and uses ferrosilicon as a reducing agent. The method produces magnesium metal and separates the produced magnesium slag to obtain metal iron and high-quality magnesium-silicon forsythite, realizes high-value and full-quantitative utilization of the magnesium slag, and avoids large storage of the magnesium slag. Meanwhile, the method accurately judges the calcination endpoint based on online detection of CO2 concentration, realizes calcination-reduction integration, promotes the reaction of SiO2 and MgO in the magnesium slag to generate magnesium-silicon forsythite by adjusting the temperature and atmosphere, and can be directly used for refractory materials or building materials, thereby improving the resource utilization rate and greatly shortening the production cycle.

Description

Technical Field

[0001] This invention relates to the field of magnesium smelting technology, specifically to a method for producing olivine by using magnesite resources via a silicothermic process. Background Technology

[0002] Magnesium, hailed as a "green metal material of the 21st century," boasts significant applications and immense economic value in industries and fields such as automobiles, 3C electronics, aerospace, medical, steel, fuel cells, robotics, and the low-altitude economy, thanks to its lightweight, high strength, and 100% recyclability. China is a major magnesium resource country, possessing the world's largest reserves, and is also a major producer of primary magnesium due to its cost advantages.

[0003] Magnesium, as an important lightweight metal material, currently accounts for approximately 95% of my country's total primary magnesium production through the Pidgeon process. However, the traditional Pidgeon process requires high temperatures above 1200℃ and high vacuum (≤10Pa), resulting in enormous energy consumption and the release of large amounts of CO2 during calcination, leading to high carbon emissions. Existing processes primarily use dolomite as raw material, exhibiting poor adaptability to low-grade magnesite (MgCO3), and the utilization rate of the reducing agent ferrosilicon is insufficient, resulting in waste of iron resources. Furthermore, traditional reduction furnaces require periodic cooling and dismantling for magnesium extraction, making continuous operation impossible and resulting in low production efficiency. Although the process has been continuously improved to reduce energy consumption and pollution, it remains a high-pollution, high-energy-consumption, and intermittent metallurgical process. Therefore, it is essential to develop disruptive technologies to completely resolve the drawbacks of high energy consumption and large emissions in Pidgeon process magnesium smelting.

[0004] Forsterite refractories, due to their high melting point, low thermal conductivity and coefficient of linear expansion, as well as good chemical and high-temperature stability, are widely used in the preparation of biological scaffolds and metallurgical furnace linings. Solid-state reaction synthesis of forsterite, using magnesium oxide and quartz as raw materials, is currently the most commonly used method. However, this process requires holding at temperatures above 1300℃ for more than 10 hours, resulting in high energy consumption and low production efficiency. While existing advanced technologies, such as vapor deposition and sol-gel methods, can be used to prepare high-performance forsterite products, their high cost and complex processes prevent large-scale industrial application. Therefore, achieving low-cost co-production of forsterite would solve the production challenges of forsterite.

[0005] In recent years, relevant practitioners in my country have also conducted some research on magnesium smelting from magnesite. Patent CN118957304A discloses a magnesium smelting method of vacuum low-temperature composite reduction and reducing agent regeneration. This method uses an aluminum-silicon alloy as a reducing agent, which is uniformly mixed with magnesium oxide or calcined magnesite and placed in a high-temperature furnace for vacuum low-temperature composite reduction to obtain crude magnesium. The slag produced from magnesium smelting is mixed with a carbonaceous reducing agent and placed in a vacuum melting furnace for carbothermic reduction to prepare an aluminum-silicon alloy reducing agent, thereby regenerating the reducing agent and reducing production costs. Patent CN118147457A discloses a regenerative vertical tank reduction furnace for magnesium smelting and its process. The patent uses calcined dolomite or magnesite, ferrosilicon and fluorite as raw materials, which are pressed into pellets in a certain proportion and then loaded into the reduction tank through the upper flange. The reduction tank is equipped with a central plug and a heating element at the center. The magnesium vapor, the reduction product, enters the external crystallizer under the action of external vacuum. After the reaction is completed, the temperature control program of the reduction furnace is turned off, the crystallized magnesium is taken out and the tank is sealed. The heat exchange valve is opened to complete the preheating of the adjacent cold tank and the raw materials therein. The adjacent reduction tank continues to be heated and reduced, and the operation is repeated in a cycle.

[0006] In summary, existing technologies make it difficult to simultaneously produce high-quality magnesium silicate olivine from low-grade magnesite resources while smelting metallic magnesium. Summary of the Invention

[0007] The purpose of this invention is to smelt metallic magnesium from low-grade magnesite resources, providing a method for co-producing olivine from magnesite using a silicothermic process. This invention employs vacuum or near-vacuum technology, using magnesite as raw material and ferrosilicon as a reducing agent. While smelting metallic magnesium, the generated magnesite slag is separated to obtain metallic iron and high-quality magnesium olivine, achieving high-value and full-scale utilization of the magnesite slag and avoiding large-scale stockpiling.

[0008] The technical solution adopted by this invention to solve its technical problem is:

[0009] A method for producing olivine by smelting magnesium using magnesite resources via a silicothermic process includes the following steps:

[0010] Step 1. Using magnesia as raw material and ferrosilicon as reducing agent, crush and grind the magnesia and ferrosilicon separately;

[0011] Step 2. The ground magnesite resources are calcined in a closed reaction device to obtain solid products and CO2. The CO2 generated during the calcination process is captured in real time.

[0012] Step 3. The product of Step 2 is subjected to a reduction reaction under vacuum or relative vacuum conditions, using intermittent or continuous smelting to obtain magnesium vapor; excess magnesium oxide reacts with the silicon dioxide generated in the reduction reaction at high temperature to form magnesium silicate olivine.

[0013] Step 4. The magnesium vapor obtained from the reduction is condensed into liquid magnesium in the condenser along with argon gas;

[0014] Step 5. After the magnesium vapor is condensed, the separated argon gas is fed into the reduction furnace for recycling;

[0015] Step 6. Iron removal is performed on the ferrosilicon to obtain high-quality magnesium ferrosilicon.

[0016] In step 2, the calcination process is as follows: magnesite resources are calcined in a closed reaction device to generate calcined white metal and carbon dioxide, and the generated carbon dioxide is captured in real time; the calcined white metal is mixed with ferrosilicon, binder, and flux, and then pelletized to obtain pellets, which are the solid products; wherein, the proportions of magnesite resources, ferrosilicon, flux, and binder added by mass percentage are: magnesite resources 60wt.%~80wt.%, ferrosilicon 15wt.%~25wt.%, flux 0~10wt.%, and binder 0~5wt.%.

[0017] Alternatively, in step 2, the calcination process is as follows: Magnesia resources are mixed with ferrosilicon, binder, and flux, then pressed into pellets and calcined in a closed reaction apparatus to generate flue gas. The carbon dioxide concentration in the flue gas is monitored and captured in real time. Calcination is considered complete when the carbon dioxide concentration in the flue gas decreases to ≤1 vol%. The solid particles in the flue gas are a mixture of magnesium oxide and ferrosilicon, which is the solid product. The mass percentages of magnesia resources, ferrosilicon, flux, and binder are: magnesia resources 30 wt.%–50 wt.%, ferrosilicon 30 wt.%–40 wt.%, flux 0–20 wt.%, and binder 0–10 wt.%.

[0018] The closed reaction equipment is an externally heated closed rotary kiln or vertical kiln; it adopts negative pressure continuous calcination; CO2 is captured and purified, and 3.67 tons of high-purity CO2 are produced per ton of magnesium captured; the concentration of the high-purity CO2 is 99.9% to 100%.

[0019] In step 1, the content of calcium oxide, sodium oxide, and potassium oxide in the magnesite resource, by mass ratio, is: calcium oxide ≤ 5 wt.%, sodium oxide + potassium oxide ≤ 0.1 wt.%.

[0020] Magnesite resources are one or more of the following: magnesite ore, magnesite flotation concentrate, magnesium oxide obtained from light calcination of magnesite, brucite, and magnesium oxide obtained from light calcination of brucite.

[0021] Magnesite contains ≥90 wt.% magnesium carbonate.

[0022] The particle size of magnesite resources is ≤40mm, the particle size of ferrosilicon is ≤5mm, the particle size of flux is ≤74μm, and the particle size of binder is ≤74μm.

[0023] The pressure for pressing the pellets is 15MPa-200MPa, and they are pressed into magnesium-containing pellets with a pellet size of 20mm-50mm.

[0024] The flux is fluorite, and the binder is one or more of bentonite, water glass, and polyvinyl alcohol.

[0025] In step 3, the conditions for the reduction reaction of the solid product are as follows:

[0026] The reduction of magnesium-containing pellets was carried out in a vacuum magnesium smelting equipment at a temperature of 1250℃~1300℃, with a magnesium reduction rate of ≥85%.

[0027] Alternatively, the reduction of magnesium-containing pellets can be carried out in a relatively vacuum air-solid reaction packed bed at a reaction temperature of 1250℃~1600℃, with argon as the circulating gas in the relative vacuum, and the magnesium reduction rate ≥90%.

[0028] Alternatively, the reduction of magnesium-containing pellets can be carried out in a relative vacuum molten pool blowing reaction device at a reaction temperature of 1450℃~1700℃. The relative vacuum is achieved by using argon as the circulating gas, and the magnesium reduction rate is ≥90%.

[0029] In step 3, the chemical reaction that occurs is as follows:

[0030] 4MgO + Si = Mg (g) ↑+Mg2SiO4 (1)

[0031] When using magnesite as raw material, the material-to-magnesium ratio is 7:1. Magnesium slag contains olivine phase, as well as impurities such as silicon and calcium oxides and metallic iron. The discharged magnesium slag is melted or cooled in a reducing or neutral atmosphere and then magnetically separated to obtain metallic iron and tailings. The metallic iron recovery rate is ≥90%. After chemical purification of the tailings, high-quality magnesium silicate olivine products can be co-produced.

[0032] The high-quality magnesium silicate olivine is an olivine refractory material, and its components, by mass parts, include: MgO≥40wt.%, SiO2≤42wt.%, Fe2O3≤10wt.%, CaO≤2.0wt.%, Al2O3≤2.0wt.%, meeting the industry standard for sintered magnesium silicate olivine for refractory materials.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. This invention proposes a method for producing olivine by smelting magnesium using magnesite resources via a silicothermic process. Magnesite (MgCO3) or brucite is used to replace dolomite. Compared with dolomite, the magnesium ratio in the raw material is reduced by more than 30%. Production is achieved by combining the method with an externally heated reduction furnace.

[0035] 2. During the calcination process, the online detection of CO2 concentration at the top of the relative vacuum reduction furnace accurately determines the calcination endpoint, realizing integrated calcination-reduction, greatly shortening the production cycle, and reducing the direct energy consumption of calcination and reduction by more than 30%.

[0036] 3. During the reduction process, an inert gas circulation system is constructed to achieve efficient condensation of magnesium vapor and gas reuse, reducing operating costs. Furthermore, by controlling the temperature and atmosphere, the reaction between SiO2 and MgO in the magnesium slag is promoted to generate magnesium silicate olivine, which can be directly used in refractory materials or building materials, improving resource utilization.

[0037] 4. After cooling in a reducing atmosphere, the magnesium slag obtained from reduction is magnetically separated to recover metallic iron, resulting in high-quality magnesium silicate olivine products. This achieves high-value and slag-free utilization of magnesite resources, with a comprehensive utilization rate of 100% for magnesium slag. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] In the embodiments of the present invention, the magnesite resource is one or more of the following: magnesite ore, magnesite flotation concentrate, magnesium oxide obtained by light calcination of magnesite, brucite, and magnesium oxide obtained by light calcination of brucite.

[0040] The present invention will be further described below with reference to embodiments.

[0041] Example 1:

[0042] Using magnesite as raw material and ferrosilicon as a reducing agent, the magnesite and ferrosilicon are crushed and ground separately. The magnesite contains 5 wt.% calcium oxide, 0.1 wt.% sodium oxide and potassium oxide, and 90 wt.% magnesium carbonate.

[0043] The calcination of magnesite resources is carried out in an externally heated, closed rotary kiln using continuous negative pressure calcination. CO2 is directly captured during the calcination process and purified to a concentration of 100%, suitable for food-grade CO2. Each ton of magnesite produced yields 3.67 tons of high-purity CO2. A carbon dioxide concentration detector is installed at the top of the externally heated, closed rotary kiln to monitor the CO2 concentration in the flue gas in real time. Calcination is considered complete when the CO2 concentration drops to 1 vol%.

[0044] Calcined magnesite white powder is mixed with ferrosilicon, bentonite, and fluorite, and then briquetted. The particle size of the calcined magnesite white powder is ≤40mm, the ferrosilicon particle size is ≤5mm, the fluorite particle size is ≤74μm, and the bentonite particle size is ≤74μm. The addition ratio of calcined magnesite white powder, ferrosilicon, fluorite, and bentonite by mass percentage is: 60wt.% calcined magnesite white powder, 25wt.% ferrosilicon, 10wt.% fluorite, and 5wt.% bentonite. The briquetting pressure is 200MPa, and the mixture is pressed into magnesium-containing pellets with a pellet size of 20mm.

[0045] The pressed magnesium-containing pellets are added to existing vacuum magnesium smelting equipment and subjected to a reduction reaction under vacuum using a batch smelting method. The reduction reaction temperature is 1300℃, and the magnesium reduction rate is 86%.

[0046] The magnesium vapor obtained from the reduction is condensed into molten magnesium in the condenser along with argon gas. After the magnesium vapor is condensed, the separated argon gas is fed into the reduction furnace for recycling.

[0047] Magnesia smelting using magnesite as raw material, with a feed-to-magnesia ratio of 7:1, produces magnesia slag dominated by the olivine phase. The discharged magnesia slag is melted or cooled in a reducing or neutral atmosphere, followed by magnetic separation to separate metallic iron and magnesium silicate olivine products. The metallic iron recovery rate is 90%. After removing iron and other impurities from the magnesia slag, olivine refractory materials can be obtained. The magnesium silicate olivine product contains 40 wt.% MgO, 42 wt.% SiO2, 10 wt.% Fe2O3, 2.0 wt.% CaO, and 0.5 wt.% Al2O3, and can be used as a refractory material.

[0048] Example 2:

[0049] Using magnesite as raw material and ferrosilicon as a reducing agent, the magnesite and ferrosilicon are crushed and ground separately. The magnesite contains 2.5 wt.% calcium oxide, 0.01 wt.% sodium oxide and potassium oxide, and 98 wt.% magnesium carbonate.

[0050] The calcination of magnesite resources is carried out in an externally heated, closed rotary kiln using continuous negative pressure calcination. CO2 is directly captured during the calcination process and purified to a concentration of 100%, suitable for food-grade CO2. Each ton of magnesite yields 3.67 tons of high-purity CO2. A carbon dioxide concentration detector is installed at the top of the externally heated, closed rotary kiln to monitor the CO2 concentration in the flue gas in real time. Calcination is considered complete when the CO2 concentration drops to 0.2 vol%.

[0051] Calcined magnesite white powder is mixed with ferrosilicon, bentonite, and fluorite, and then briquetted. The particle size of the calcined magnesite white powder is ≤5mm, the ferrosilicon particle size is ≤3mm, the fluorite particle size is ≤74μm, and the bentonite particle size is ≤74μm. The addition ratio of calcined magnesite white powder, ferrosilicon, fluorite, and bentonite by mass percentage is: 80wt.% calcined magnesite white powder, 15wt.% ferrosilicon, 5wt.% fluorite, and 0wt.% bentonite. The briquetting pressure is 50MPa, and the mixture is pressed into magnesium-containing pellets with a pellet size of 50mm.

[0052] The pressed magnesium-containing pellets are added to existing vacuum magnesium smelting equipment and subjected to a reduction reaction under vacuum using a batch smelting method. The reduction reaction temperature is 1250℃, and the magnesium reduction rate is 87%.

[0053] The magnesium vapor obtained from the reduction is condensed into magnesium particles in the condenser along with argon gas. After the magnesium vapor is condensed, the separated argon gas is fed into the reduction furnace for recycling.

[0054] Magnesia smelting using magnesite as raw material, with a feed-to-magnesium ratio of 7:1, produces magnesia slag dominated by the olivine phase. The discharged magnesia slag is melted or cooled in a reducing or neutral atmosphere, followed by magnetic separation to separate metallic iron and magnesium silicate olivine products. The metallic iron recovery rate is 92%. After removing iron and other impurities from the magnesia slag, olivine refractory materials can be obtained. The magnesium silicate olivine product contains 45 wt.% MgO, 36 wt.% SiO2, 6 wt.% Fe2O3, 1.8 wt.% CaO, and 0.9 wt.% Al2O3, and can be used as a refractory material.

[0055] Example 3:

[0056] Using magnesite as raw material and ferrosilicon as a reducing agent, the magnesite and ferrosilicon are crushed and ground separately. The magnesite contains 3.5 wt.% calcium oxide, 0.03 wt.% sodium oxide and potassium oxide, and 92 wt.% magnesium carbonate.

[0057] The calcination of magnesite resources is carried out in an externally heated, closed rotary kiln using continuous negative pressure calcination. CO2 is directly captured during the calcination process and purified to a concentration of 100%, suitable for food-grade CO2. Each ton of magnesite produced yields 3.67 tons of high-purity CO2. A carbon dioxide concentration detector is installed at the top of the externally heated, closed rotary kiln to monitor the CO2 concentration in the flue gas in real time. Calcination is considered complete when the CO2 concentration drops to 0.6 vol%.

[0058] Calcined magnesite white powder is mixed with ferrosilicon, polyvinyl alcohol (PVA), and fluorite, and then briquetted. The particle size of the calcined magnesite white powder is ≤20mm, the ferrosilicon particle size is ≤4mm, the fluorite particle size is ≤74μm, and the PVA particle size is ≤74μm. The addition ratio of calcined magnesite white powder, ferrosilicon, fluorite, and PVA by mass percentage is: 70wt.% calcined magnesite white powder, 20wt.% ferrosilicon, 5wt.% fluorite, and 5wt.% PVA. The briquetting pressure is 80MPa, and the mixture is pressed into magnesium-containing pellets with a pellet size of 40mm.

[0059] The pressed magnesium pellets are fed into a relative vacuum reduction apparatus for a reduction reaction under relative vacuum. Continuous smelting is employed, with argon as the circulating gas for the relative vacuum. The magnesium pellets are pressed using a gas-solid reaction packed bed, the reduction reaction temperature is 1600℃, and the magnesium reduction rate is 95%.

[0060] The magnesium vapor obtained from the reduction is condensed into molten magnesium in the condenser along with argon gas. After the magnesium vapor is condensed, the separated argon gas is fed into the reduction furnace for recycling.

[0061] Magnesia smelting using magnesite as raw material, with a feed-to-magnesium ratio of 7:1, produces magnesia slag dominated by the olivine phase. The discharged magnesia slag is melted or cooled in a reducing or neutral atmosphere, followed by magnetic separation to separate metallic iron and magnesium silicate olivine products. The metallic iron recovery rate is 95%. After removing iron and other impurities from the magnesia slag, olivine refractory materials can be obtained. The magnesium silicate olivine product contains 43 wt.% MgO, 38 wt.% SiO2, 8 wt.% Fe2O3, 1.5 wt.% CaO, and 2.0 wt.% Al2O3, and can be used as a refractory material.

[0062] Example 4:

[0063] Using magnesite as raw material and ferrosilicon as a reducing agent, the magnesite and ferrosilicon are crushed and ground separately. The magnesite contains 0.5 wt.% calcium oxide, 0.08 wt.% sodium oxide and potassium oxide, and 94 wt.% magnesium carbonate.

[0064] The calcination of magnesite resources is carried out in an externally heated, closed vertical kiln using continuous negative pressure calcination. CO2 is directly captured during the calcination process and purified to a concentration of 100%, suitable for food-grade CO2. Each ton of magnesite produced yields 3.67 tons of high-purity CO2. A carbon dioxide concentration detector is installed at the top of the externally heated, closed vertical kiln to monitor the CO2 concentration in the flue gas in real time. Calcination is considered complete when the CO2 concentration drops to 0.4 vol%.

[0065] Calcined magnesite white powder is mixed with ferrosilicon, water glass, and fluorite, and then briquetted. The particle size of the calcined magnesite white powder is ≤15mm, the particle size of the ferrosilicon is ≤1mm, the particle size of the flux is ≤74μm, and the particle size of the water glass is ≤74μm. The addition ratio of calcined magnesite white powder, ferrosilicon, fluorite, and water glass by mass percentage is: 75wt.% magnesite white powder, 20wt.% ferrosilicon, 0wt.% fluorite, and 5wt.% water glass. The briquetting pressure is 150MPa, and the mixture is pressed into magnesium-containing pellets with a pellet size of 25mm.

[0066] The pressed magnesium pellets are added to a reduction apparatus under relative vacuum, where a reduction reaction is carried out using continuous smelting. Argon is used as the circulating gas for the relative vacuum. The magnesium pellets are pressed using a gas-solid reaction packed bed, the reduction reaction temperature is 1250℃, and the magnesium reduction rate is 90%.

[0067] The magnesium vapor obtained from the reduction is condensed into molten magnesium in the condenser along with argon gas. After the magnesium vapor is condensed, the separated argon gas is fed into the reduction furnace for recycling.

[0068] Magnesia smelting using magnesite as raw material, with a feed-to-magnesia ratio of 7:1, produces magnesia slag dominated by the olivine phase. The discharged magnesia slag is melted or cooled in a reducing or neutral atmosphere, followed by magnetic separation to separate metallic iron and magnesium silicate olivine products. The metallic iron recovery rate is 96%. After removing iron and other impurities from the magnesia slag, olivine refractory materials can be obtained. The magnesium silicate olivine product contains 42 wt.% MgO, 38 wt.% SiO2, 6 wt.% Fe2O3, 0.8 wt.% CaO, and 1.9 wt.% Al2O3, and can be used as a refractory material.

[0069] Example 5:

[0070] Using magnesite as raw material and ferrosilicon as a reducing agent, the magnesite and ferrosilicon are crushed and ground separately. The magnesite contains 4 wt.% calcium oxide, 0.06 wt.% sodium oxide and potassium oxide, and 93 wt.% magnesium carbonate.

[0071] The calcination of magnesite resources is carried out in an externally heated, closed vertical kiln using continuous negative pressure calcination. CO2 is directly captured during the calcination process and purified to a concentration of 100%, suitable for food-grade CO2. Each ton of magnesite produced yields 3.67 tons of high-purity CO2. A carbon dioxide concentration detector is installed at the top of the externally heated, closed vertical kiln to monitor the CO2 concentration in the flue gas in real time. Calcination is considered complete when the CO2 concentration drops to 0.8 vol%.

[0072] Calcined magnesite white powder is mixed with ferrosilicon, water glass, and fluorite, and then briquetted. The particle size of the calcined magnesite white powder is ≤30mm, the particle size of the ferrosilicon is ≤2mm, the particle size of the flux is ≤74μm, and the particle size of the water glass is ≤74μm. The addition ratio of calcined magnesite white powder, ferrosilicon, fluorite, and water glass by mass percentage is: 75wt.% calcined magnesite white powder, 18wt.% ferrosilicon, 5wt.% fluorite, and 2wt.% water glass. The briquetting pressure is 20MPa, and the mixture is pressed into magnesium-containing pellets with a pellet size of 30mm.

[0073] The pressed magnesium pellets are added to a reduction apparatus under relative vacuum, where a reduction reaction is carried out using continuous smelting. Argon is used as the circulating gas for the relative vacuum. The magnesium pellets are pressed using a jet-type molten pool reactor. The reduction reaction temperature is 1580℃, and the magnesium reduction rate is 95%.

[0074] The magnesium vapor obtained from the reduction is condensed into magnesium particles in the condenser along with argon gas. After the magnesium vapor is condensed, the separated argon gas is fed into the reduction furnace for recycling.

[0075] Magnesia smelting using magnesite as raw material, with a feed-to-magnesium ratio of 7:1, produces magnesia slag dominated by the olivine phase. The discharged magnesia slag is melted or cooled in a reducing or neutral atmosphere, followed by magnetic separation to separate metallic iron and magnesium silicate olivine products. The metallic iron recovery rate is 93%. After removing iron and other impurities from the magnesia slag, olivine refractory materials can be obtained. The magnesium silicate olivine product contains 46 wt.% MgO, 35 wt.% SiO2, 10 wt.% Fe2O3, 1.2 wt.% CaO, and 1.6 wt.% Al2O3, and can be used as a refractory material.

[0076] Example 6:

[0077] Using magnesite as raw material and ferrosilicon as a reducing agent, the magnesite and ferrosilicon are crushed and ground separately. The magnesite contains 1 wt.% calcium oxide, 0.05 wt.% sodium oxide and potassium oxide, and 95 wt.% magnesium carbonate.

[0078] The calcination of magnesite resources is carried out in an externally heated, closed vertical kiln using continuous negative pressure calcination. CO2 is directly captured during the calcination process and purified to a concentration of 100%, suitable for food-grade CO2. 3.67 tons of high-purity CO2 are produced per ton of magnesite. A carbon dioxide concentration detector is installed at the top of the externally heated, closed vertical kiln to monitor the CO2 concentration in the flue gas in real time. Calcination is considered complete when the CO2 concentration drops to 0.3 vol%.

[0079] Calcined magnesite white powder is mixed with ferrosilicon, polyvinyl alcohol, and fluorite, and then briquetted. The particle size of the calcined magnesite white powder is ≤10mm, the ferrosilicon particle size is ≤1.5mm, the fluorite particle size is ≤74μm, and the polyvinyl alcohol particle size is ≤74μm. The addition ratio of calcined magnesite white powder, ferrosilicon, fluorite, and polyvinyl alcohol by mass percentage is: 78wt.% magnesite white powder, 18wt.% ferrosilicon, 2wt.% fluorite, and 2wt.% polyvinyl alcohol. The briquetting pressure is 180MPa, and the mixture is pressed into magnesium-containing pellets with a pellet size of 20mm.

[0080] The pressed magnesium pellets are added to a reduction apparatus under relative vacuum, where a reduction reaction is carried out using continuous smelting. Argon is used as the circulating gas for the relative vacuum. The magnesium pellets are pressed using a jet-type molten pool reactor. The reduction reaction temperature is 1550℃, and the magnesium reduction rate is 93%.

[0081] The magnesium vapor obtained from the reduction is condensed into molten magnesium in the condenser along with argon gas. After the magnesium vapor is condensed, the separated argon gas is fed into the reduction furnace for recycling.

[0082] Magnesia smelting using magnesite as raw material, with a feed-to-magnesium ratio of 7:1, produces magnesia slag dominated by the olivine phase. The discharged magnesia slag is melted or cooled in a reducing or neutral atmosphere, followed by magnetic separation to separate metallic iron and magnesium silicate olivine products. The metallic iron recovery rate is 92%. After removing iron and other impurities from the magnesia slag, olivine refractory materials can be obtained. The magnesium silicate olivine product contains 44 wt.% MgO, 40 wt.% SiO2, 8 wt.% Fe2O3, 0.5 wt.% CaO, and 1.8 wt.% Al2O3, and can be used as a refractory material.

[0083] Example 7:

[0084] Using magnesite as raw material and ferrosilicon as a reducing agent, the magnesite and ferrosilicon are crushed and ground separately. The magnesite contains 1 wt.% calcium oxide, 0.05 wt.% sodium oxide and potassium oxide, and 95 wt.% magnesium carbonate.

[0085] The calcination of magnesite resources is carried out in an externally heated, closed vertical kiln using continuous negative pressure calcination. CO2 is directly captured during the calcination process and purified to a concentration of 100%, suitable for food-grade CO2. 3.67 tons of high-purity CO2 are produced per ton of magnesite. A carbon dioxide concentration detector is installed at the top of the externally heated, closed vertical kiln to monitor the CO2 concentration in the flue gas in real time. Calcination is considered complete when the CO2 concentration drops to 0.3 vol%.

[0086] Calcined magnesite white powder is mixed with ferrosilicon, polyvinyl alcohol, and fluorite, and then briquetted. The particle size of the calcined magnesite white powder is ≤10mm, the ferrosilicon particle size is ≤1.5mm, the fluorite particle size is ≤74μm, and the polyvinyl alcohol particle size is ≤74μm. The addition ratio of calcined magnesite white powder, ferrosilicon, fluorite, and polyvinyl alcohol by mass percentage is: 78wt.% calcined magnesite white powder, 18wt.% ferrosilicon, 2wt.% fluorite, and 2wt.% polyvinyl alcohol. The briquetting pressure is 15MPa, and the mixture is pressed into magnesium-containing pellets with a pellet size of 20mm.

[0087] The pressed magnesium pellets are added to a reduction apparatus under relative vacuum, where a reduction reaction is carried out using continuous smelting. Argon is used as the circulating gas for the relative vacuum. The magnesium pellets are pressed using a jet-type molten pool reactor. The reduction reaction temperature is 1450℃, and the magnesium reduction rate is 92%.

[0088] The magnesium vapor obtained from the reduction is condensed into molten magnesium in the condenser along with argon gas. After the magnesium vapor is condensed, the separated argon gas is fed into the reduction furnace for recycling.

[0089] Magnesia smelting using magnesite as raw material, with a feed-to-magnesium ratio of 7:1, produces magnesia slag dominated by the olivine phase. The discharged magnesia slag is melted or cooled in a reducing or neutral atmosphere, followed by magnetic separation to separate metallic iron and magnesium silicate olivine products. The metallic iron recovery rate is 92%. After removing iron and other impurities from the magnesia slag, olivine refractory materials can be obtained. The magnesium silicate olivine product contains 44 wt.% MgO, 40 wt.% SiO2, 8 wt.% Fe2O3, 0.5 wt.% CaO, and 1.8 wt.% Al2O3, and can be used as a refractory material.

Claims

1. A method for co-producing olivine from magnesium using a silicon thermal process based on magnesite resources, characterized in that, Includes the following steps: Step 1. Using magnesia as raw material and ferrosilicon as reducing agent, crush and grind the magnesia and ferrosilicon separately; Step 2. The ground magnesite resources are calcined in a closed reaction device to obtain solid products and CO2. The CO2 generated during the calcination process is captured in real time. Step 3. The product of Step 2 is subjected to a reduction reaction under relative vacuum conditions, using intermittent or continuous smelting to obtain magnesium vapor; excess magnesium oxide reacts with the silicon dioxide generated in the reduction reaction at high temperature to form magnesium silicate olivine. Step 4. The magnesium vapor obtained from the reduction is condensed into liquid magnesium in the condenser along with argon gas; Step 5. After the magnesium vapor is condensed, the separated argon gas is fed into the reduction furnace for recycling; Step 6. Iron removal is performed on the ferrosilicon to obtain high-quality magnesium ferrosilicon.

2. The method for co-producing olivine from magnesium using a silicon thermal process based on magnesite resources according to claim 1, characterized in that, In step 2, the calcination process is as follows: Magnesium ore is calcined in a closed reaction device to produce calcined white metal and carbon dioxide. The generated carbon dioxide is captured in real time. The calcined white metal is mixed with ferrosilicon, binder, and flux, and then pelletized to obtain pellets, which are the solid products. The proportions of magnesite resources, ferrosilicon, flux, and binder added by mass percentage are as follows: magnesite resources 60wt.%~80wt.%, ferrosilicon 15wt.%~25wt.%, flux 0~10wt.%, and binder 0~5wt.%.

3. The method for co-producing olivine from magnesium using a silicon thermal process based on magnesite resources according to claim 1, characterized in that, In step 2, the calcination process is as follows: the magnesia resource is mixed with ferrosilicon, binder and flux and then pressed into pellets. The pellets are then calcined in a closed reaction device to generate flue gas. The carbon dioxide concentration in the flue gas is monitored in real time and captured. When the carbon dioxide concentration in the flue gas decreases to ≤1 vol%, the calcination is considered complete. The solid particles in the flue gas are a mixture of magnesia and ferrosilicon, which is the solid product. The proportions of magnesite resources, ferrosilicon, flux, and binder added by mass percentage are as follows: magnesite resources 30wt.%~50wt.%, ferrosilicon 30wt.%~40wt.%, flux 0~20wt.%, and binder 0~10wt.%.

4. A method for co-producing olivine from magnesite using a silicothermic process according to claim 2 or 3, characterized in that, The closed reaction equipment is an externally heated closed rotary kiln or vertical kiln; it adopts negative pressure continuous calcination; After CO2 capture, it is purified, and 3.67 tons of high-purity CO2 are produced per ton of magnesium capture; the concentration of the high-purity CO2 is 99.9%~100%.

5. A method for co-producing olivine from magnesite using a silicothermic process according to claim 2 or 3, characterized in that, Magnesite resources are one or more types of magnesite ore and magnesite flotation concentrate; The flux is fluorite, and the binder is one or more of bentonite, water glass, and polyvinyl alcohol.

6. A method for co-producing olivine from magnesium using a silicon thermal process based on magnesite resources according to claim 5, characterized in that, The particle size of magnesite resources is ≤40mm, the particle size of ferrosilicon is ≤5mm, the particle size of flux is ≤74μm, and the particle size of binder is ≤74μm. The content of calcium oxide, sodium oxide, and potassium oxide in magnesite resources, by mass ratio, is as follows: calcium oxide ≤ 5 wt.%, sodium oxide + potassium oxide ≤ 0.1 wt.%; The magnesium carbonate content in the magnesite is ≥90 wt.%.

7. A method for co-producing olivine from magnesite using a silicothermic process according to claim 2 or 3, characterized in that, In step 1, the pressure of pressing the pellets is 15MPa-200MPa, and the pellets are pressed into magnesium-containing pellets with a size of 20mm-50mm.

8. A method for co-producing olivine from magnesite using a silicothermic process according to claim 2 or 3, characterized in that, In step 3, the conditions for the reduction reaction of the solid product are as follows: The reduction of magnesium-containing pellets was carried out in a relatively vacuum air-solid reaction packed bed at a reaction temperature of 1250℃~1600℃. Argon was used as the circulating gas in the relatively vacuum environment, and the magnesium reduction rate was ≥90%. Alternatively, the reduction of magnesium-containing pellets can be carried out in a relatively vacuum molten pool blowing reaction device at a reaction temperature of 1450℃~1700℃. The relatively vacuum is achieved by using argon as the circulating gas, and the magnesium reduction rate is ≥90%.

9. A method for co-producing olivine from magnesium using a silicon thermal process based on magnesite resources according to claim 5, characterized in that, When using magnesite as raw material, the material-to-magnesium ratio is 7:

1. The discharged magnesia slag is melted or cooled in a reducing or neutral atmosphere and then magnetically separated to obtain metallic iron and tailings. The metallic iron recovery rate is ≥90%. After chemical purification of the tailings, high-quality magnesium silicate olivine products are obtained.

10. A method for co-producing olivine from magnesite using a silicothermic process according to claim 2 or 3, characterized in that, The high-quality magnesium silicate olivine is an olivine refractory material, and its components, by mass parts, include: MgO≥40wt.%, SiO2≤42wt.%, Fe2O3≤10wt.%, CaO≤2.0wt.%, Al2O3≤2.0wt.%.