WO2024056107A1 - Green and environmentally friendly method for producing magnesium by means of aluminothermic reduction - Google Patents

Abstract

A method for producing magnesium by means of aluminothermic reduction, the method comprising the following steps: mixing, at a certain ratio until uniform, magnesium oxide and an aluminum powder that have particle sizes meeting standards; pressing same into clumps after uniform mixing, and adding same to a vacuum feeding device; heating same in a vacuum environment and maintaining the temperature, wherein the material clumps are heated in a high-temperature material pipe to undergo a reduction reaction so as to generate magnesium vapor and a solid reduction slag; and continuing heating same in the vacuum environment and maintaining the temperature, so as to make the solid reduction slag generate magnesia-alumina spinel. In the method for producing magnesium by means of aluminothermic reduction, heating processes at different temperatures are respectively carried out in the same reaction container at different time periods, and two products, i.e. high-purity crude magnesium and magnesia-alumina spinel, are respectively produced; and there is no need to use a reduction furnace composed of an induction furnace and a microwave heating furnace, the whole heating reaction process flow can be realized by using a microwave heating furnace alone, and therefore the process is more concise and optimized, operation is simpler, and the production procedure is more consistent.

Description

A green and environmentally friendly method for producing magnesium by thermite reduction Technical field

The invention belongs to the technical field of non-ferrous light metal metallurgy, and in particular relates to a green and environmentally friendly method for producing magnesium by thermite reduction.

Background technique

Magnesium is the third largest metal structural material after steel and aluminum, and it is also the lightest metal structural material used in engineering so far. Its atomic weight is 24.305, and its density is 1.74, which is only equivalent to 64% of aluminum, 25% of zinc, and 23% of steel. Therefore, magnesium and its alloys have low specific gravity, high specific strength, excellent electromagnetic shielding performance, and good shock absorption performance; they are resistant to alkali , kerosene, gasoline and mineral oil are stable; excellent forgeability and processing performance; the specific strength and specific stiffness of magnesium alloy are second only to titanium alloy and alloy structural steel, significantly better than aluminum alloy, and much higher than engineering plastics; impact resistance, The machinability and recyclability are better than aluminum alloys, so magnesium and its alloys are known as green engineering materials in the 21st century.

The smelting processes of magnesium mainly include electrolysis and thermal reduction. In the 20th century, 80% of the world's raw magnesium production was produced by electrolysis and 20% by thermal reduction. After the 1990s, the output of raw magnesium by thermal reduction method increased rapidly. In addition, the production cost of electrolysis method was high and the pollution was serious. Electrolysis methods at home and abroad were closed down one after another. At present, 85% of the world's raw magnesium is produced by thermal reduction.

The principle of electrolytic magnesium smelting is to electrolyze molten anhydrous magnesium chloride and decompose it into magnesium and chlorine gas. Its process includes two major processes: magnesium chloride production and electrolytic magnesium production. Representative processes include: the electrolysis method of producing anhydrous magnesium chloride using seawater as raw material; the electrolysis method of anhydrous magnesium chloride using magnesite as raw material. Characteristics of the electrolysis method: high process requirements, easy to achieve automation and large-scale production, but large investment, high production costs, serious pollution, and relatively poor product quality.

Thermal reduction methods are divided into silicon thermal reduction method, aluminothermic reduction method and carbothermal reduction method. Magnesium smelting by thermal reduction method started in 1913 and has a history of nearly a hundred years. The first reduction of magnesium oxide using silicon as a reducing agent was achieved in 1924 by Л.X. Anjiping and A.Ф. Arabeyshev. In 1932, Anjiping and Arabyshev succeeded in producing magnesium by reducing magnesium oxide using aluminum-silicon alloy as a reducing agent. In 1941, Professor L.M. Pidgeon of the University of Toronto in Canada established a pilot plant for magnesium smelting by reducing and calcining dolomite with ferrosilicon in Ottawa and achieved success. In 1942, the Canadian government established a silothermal magnesium smelting plant with an annual output of 5,000 tons of magnesium in the Halley Dolomite Mine. Since then, the Pidgeon process has become the second largest method for industrial magnesium refining.

The silicon thermal reduction method can be divided into four types according to the equipment used: Pidgeon Process, Balzano Process, Magnetherm Process and MTMP method.

The carbothermal reduction method uses magnesite or magnesium oxide as raw material and carbon as the reducing agent to produce magnesium metal. Experimental studies have found that the reaction speed is fast, the reduction cycle is reduced, the relative cost is low, and the degree of automation is high. However, the product separation is difficult and difficult to recover. The reaction product is magnesium powder, which has the risk of explosion; reversible reactions are prone to occur. At present, this process method has not been applied and developed in the market.

Thermite magnesium smelting is an emerging magnesium smelting technology. This method uses magnesite and dolomite as raw materials and metallic aluminum as the reducing agent to produce magnesium metal. Experimental studies have found that the reaction temperature of magnesium production decreases when aluminum is used as the reducing agent. , fast reaction speed, short reduction cycle, high purity of crude magnesium; reduction slag can be used, etc. Due to its high cost, this process method cannot be applied in the market at present.

The Pidgeon process is the main method for producing magnesium in my country. The main problems of magnesium smelting by the Pidgeon method are:

The comprehensive utilization rate of resources is low (a large amount of reduced slag and waste gas are discharged out of order), the degree of automation is low (manual loading and slag removal is required and continuous production is not possible), and the energy consumption is high (the heating method is external heating and there is a large amount of waste gas, Reduction slag is produced), and the operating environment is unfriendly (natural gas is used as the heating energy, a large amount of waste gas is discharged, a large amount of dust is generated during charging and slag discharging, and there is thermal radiation from the reduction furnace and slag during slag discharging).

Chinese invention patent CN201410345802.6 proposes a method for rapid and continuous magnesium refining. This process uses inert gas to protect the magnesium vapor generated by the reaction from being oxidized. Although the reduction reaction time is relatively reduced, the heating method still uses external heating. Moreover, the ignition loss in the raw materials is high, so a large amount of waste gas and waste residue will be produced after the reaction, resulting in a waste of resources and energy. The operating environment is unfriendly, the degree of automation is low, and the labor intensity is high.

Chinese patent CN201610498925.2 proposes a vacuum induction furnace magnesium making system and a magnesium making method. This method uses an induction furnace instead of a traditional reduction furnace and uses low-cost carbon as a reducing agent. The degree of automation is improved and labor intensity is reduced, but the reaction During the process, it is very difficult to suppress the reverse reaction. At the same time, this method produces a large amount of carbon monoxide and carbon dioxide gas, which is difficult to collect and separate. Moreover, the product after crystallization and condensation of this method is not solid block magnesium, but solid powder and granular form. , for which there is a pure risk of explosion in the collection.

Chinese invention patent CN00124698.4 proposes an internal thermal magnesium smelting production process and equipment. The heating method is external heating and ferrosilicon is used as the reducing agent. However, a large amount of waste gas and waste residue will be generated after the reaction, causing a loss of resources and energy. Wasteful, unfriendly operating environment, low degree of automation, and high labor intensity.

Chinese invention patent N200810232855 proposes a microwave heating Pidgeon process for magnesium smelting. Although the reduction furnace has changed the heating method and achieved environmentally friendly operation, high degree of automation, low labor intensity, and no waste gas, it still uses calcined white powder. As the raw material, ferrosilicon is the reducing agent and fluorite is the catalyst, so the material to magnesium ratio is as high as that of the Pidgeon process. Therefore, after the reaction, not only a large amount of reducing slag is produced and needs to be discharged, but the energy consumption is relatively high, and the resources are obtained. Good use.

Chinese invention patent CN200510047081.1 provides a method for smelting magnesium by aluminothermic reduction and calcined magnesite. The reduction tank is still used for heating. The raw materials are magnesite, dolomite, and aluminum. There is still a large amount of waste gas, waste residue, and energy. Low utilization.

Chinese invention patent CN110512094.B proposes a clean and continuous reduction process of magnesium. It uses an integrated reduction furnace combined with an induction furnace and a microwave oven. However, it is difficult for the induction furnace to uniformly heat solid material clumps, so this method is very difficult to reduce. The efficiency is affected, and the residue generated by the first reaction needs to be transferred before the second reaction can be carried out. The production process is incoherent. Due to the redundancy of equipment, the one-time investment is large and the process operation is relatively complex.

Contents of the invention

The invention provides a green and environmentally friendly aluminothermic magnesium reduction production method, aiming to achieve green, environmentally friendly, energy-saving and intelligent production of magnesium smelting and reduction. This process can achieve different temperatures in different time periods in the same reaction vessel. Heating and heat preservation produce two products, high-purity crude magnesium and magnesium-aluminum spinel respectively, thus solving the problem that combined equipment and complex processes should be used to produce magnesium and magnesia-aluminum spinel.

The invention is realized in this way. A green and environmentally friendly method for producing magnesium by thermite reduction method includes the following steps:

S1: Evenly mix magnesium oxide and aluminum powder with qualified particle size in proportion, mix and press into briquettes;

S2: Add the material clumps obtained in S1 into the vacuum feeding device;

S3: The vacuum feeding device puts the material briquettes into the high-temperature material tube of the microwave reduction furnace, and heats and maintains the temperature in a vacuum environment. The material briquettes are heated in the high-temperature material tube and undergo a reduction reaction, producing magnesium vapor, solid reduction slag, and magnesium vapor. After being passed into the condensation and crystallization device for condensation and crystallization, solid high-purity crude magnesium is obtained;

S4: Continue to heat up and maintain the temperature in a vacuum environment, the solid reduction slag further reacts in the high-temperature material tube, and the solid reduction slag generates magnesia-aluminum spinel;

S5: Cut the produced magnesia-aluminum spinel through a vacuum cutting device;

The above process is carried out under vacuum conditions.

Preferably, in the S1, the particle sizes of magnesium oxide and aluminum powder are both ≤100 mesh, the MgO content in magnesium oxide is ≥96%, and the Al content in aluminum powder is ≥99.9%.

Preferably, in the S1, the weight ratio of magnesium oxide to aluminum powder is 3.05~3.25:1.

Preferably, in S3, the vacuum degree is within 10 Pa, and the temperature is maintained after heating to a temperature of 900 to 1200°C. The heat preservation time is 20 to 70 minutes.

Preferably, in the S4, the vacuum degree is within 10pa, and the heating is continued until the temperature is 1200-1600°C and then kept warm, and the keeping time is 90-200 minutes.

beneficial effects

Compared with the existing technology, the beneficial effects of the present invention are: the green and environmentally friendly aluminothermic reduction magnesium production method of the present invention is mainly aimed at the Pidgeon process, which has a wide range of applications in domestic and foreign markets, and its production and labor environment It has poor quality, high labor intensity, high energy consumption, low degree of automation, high carbon dioxide emissions, and low comprehensive utilization rate of resources, but provides a green, energy-saving, and intelligent process for reducing magnesium;

This method uses microwave heating as the heating method instead of the natural gas combustion heating method, and there is no waste water discharge; magnesium oxide is used instead of calcined white, and aluminum is used instead of ferrosilicon as the reducing agent. Since the pressed material clumps have strong wave-absorbing ability, their High heating efficiency, fast heating speed, uniform heating and strong controllability;

This method performs reactions by heating at different temperatures twice in the same high-temperature material tube. In the first stage, the material mass is heated to undergo a reduction reaction to generate magnesium vapor and solid reduction slag. The magnesium vapor is condensed and crystallized to obtain solid high-purity crude magnesium. In the second stage, the solid reduction residue produced in the first stage is further heated at a higher temperature, and the second stage reaction generates magnesia-aluminum spinel. The two stages of reaction process do not interfere with each other, and there is no need to transport the residue of the first stage reaction. , two reactions can be completed in the high-temperature material tube, so that the reduced slag can be better utilized. There is no need to use a reduction furnace composed of an induction furnace and a microwave heating furnace. The entire heating reaction process can be realized by using a microwave heating furnace alone. The process It is more optimized, the operation is simpler, the production process is more coherent, the required production equipment is simpler, the investment cost is lower, there is no waste residue and waste gas emissions, which improves the comprehensive utilization of resources, the production process is green, environmentally friendly, energy-saving, and the operating environment is better.

Implementation

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

The present invention provides a technical solution: a green and environmentally friendly aluminothermic reduction magnesium production method, which includes the following steps:

S1: Evenly mix magnesium oxide and aluminum powder with qualified particle size in proportion, and press them into briquettes after mixing; the particle sizes of magnesium oxide and aluminum powder are both ≤100 mesh, the MgO content in magnesium oxide is ≥96%, and the Al content in aluminum powder ≥99.9%. The weight ratio of magnesium oxide to aluminum powder is 3.05~3.25:1.

S2: Add the material clumps obtained in S1 into the vacuum feeding device;

S3: The vacuum feeding device puts the material briquettes into the high-temperature material tube of the microwave reduction furnace, and heats and insulates them in a vacuum environment. The vacuum degree is within 10pa. It is heated to a temperature of 900~1200℃ and then insulated. The holding time is 20~ For 70 minutes, the material briquettes are heated in the high-temperature material tube to undergo a reduction reaction, producing magnesium vapor and solid reduction slag. The magnesium vapor is passed into the condensation and crystallization device to condense and crystallize to obtain solid high-purity crude magnesium; microwave heating has an effect on the material briquettes. The heating effect is internal heating.

S4: Continue to heat up and maintain the temperature in a vacuum environment. The vacuum degree is within 10pa. Continue heating to a temperature of 1200~1600℃ and then keep it warm. The holding time is 90~200 minutes. The solid reduction slag further reacts in the high-temperature material tube. The solid reduction slag Generate magnesia-aluminum spinel;

S5: Cut the produced magnesia-aluminum spinel through a vacuum cutting device.

The above process is carried out under vacuum conditions.

The entire heating process of the high-temperature material tube of the present invention is carried out under vacuum conditions. Due to the different ratios of raw materials, the quality of the crude magnesium product is less affected, but the quality of the magnesia-aluminum spinel product is greatly affected, and the solid reduction slag , due to the difference in heating temperature, it has a greater impact on the quality of magnesia-aluminum spinel products.

For the product crude magnesium, the temperature is controlled in the range of 900°C to 1180°C, and the reaction time is controlled in the range of 30 minutes to 70 minutes. Crystallized magnesium with a high purity of more than 99.90% magnesium, that is, crude magnesium, can be obtained.

The product magnesia-aluminum spinel, the temperature is controlled in the range of 1200℃ to 1600℃, and the reaction time is controlled in the range of 90 minutes to 200 minutes. A spinel product containing more than 90% of MgO.Al ₂ O ₃ can be obtained, that is, magnesia-aluminum. Spinel.

First, test the pressed material clumps for their wave absorption ability and heating rate in the microwave oven:

Put the pressed material clump into the crucible in the microwave oven, set the heating time to 60 minutes, check the temperature rise data every 15 minutes and record it in Table 1;

Time(Min)	15	30	45	60
Temperature (℃)	217.5	499.5	834	1131
Heating rate (℃/Min)	14.5	18.8	22.3	19.8
Wave absorption ability	powerful	powerful	Stronger	powerful

Table 1

From the heating rate in Table 1, it can be seen that the material briquettes used in this process have strong microwave absorption capabilities, thus verifying that microwave heating technology can be applied to material briquettes pressed with raw material magnesium oxide and reducing agent aluminum.

Test the impact of the heating reaction on the reduction rate of crude magnesium and the quality of magnesia-aluminum spinel under the same conditions of vacuum degree, heating temperature, and raw material purity, but with different heating times:

Add the pressed material clumps into the vacuum feeding device, add the material clumps into the high-temperature material tube of the microwave reduction furnace, close and seal all valves connected to the furnace body, start the vacuum system and start vacuuming. When the vacuum reaches When 10Pa, start the microwave power supply and control system and start heating. When the temperature rise reaches 1150℃, start keeping warm. The keeping time is set to 20, 30, 45, 60, and 70 minutes respectively. The vacuum degree is controlled within 10Pa. The reaction generates The magnesium vapor and solid reduction slag are produced, and the magnesium vapor enters the condensation and crystallization device and crystallizes into solid crude magnesium in the crystallizer. The microwave reduction furnace continues to heat the materials in the high-temperature material tube under vacuum conditions, and the solid reduction slag is heated in the microwave Further reaction occurs in the high-temperature material tube of the reduction furnace. When the temperature rise reaches 1450°C, heat preservation begins. The heat preservation times are controlled to 90, 120, 150, 180, and 200 minutes respectively. The vacuum is controlled within 10 Pa. After the reaction, the magnesium aluminum spindle is The stone is transported from the high-temperature material pipe to the vacuum discharge device, and then the product in the vacuum discharge device is discharged.

As the holding time is different, the reduction rate of crude magnesium and the quality of magnesia-aluminum spinel are shown in Table 2-1 and Table 2-2:

Vacuum Pa	10	10	10	10	10
MgO content% in magnesium oxide	96	96	96	96	96
Al content % in aluminum powder	99.9	99.9	99.9	99.9	99.9
Reduction temperature℃	1150	1150	1150	1150	1150
Restore holding time Min	20	30	45	60	70
Reduction rate of crude magnesium %	76.4	89.7	92.3	92.5	92.7

table 2-1

Under the above conditions of the same vacuum degree, reduction temperature, and raw materials, the reduction rate of crude magnesium gradually increases with the extension of the holding time. When the time exceeds 45 minutes, the reduction rate of crude magnesium is more affected as the time is extended. Small.

Vacuum Pa	10	10	10	10	10
MgO content% in magnesium oxide	96	96	96	96	96
Al content % in aluminum powder	99.9	99.9	99.9	99.9	99.9
Insulation temperature℃	1450	1450	1450	1450	1450
Keeping timeMin	90	120	150	180	200
Content % of MgO.Al2O3 in magnesia-aluminum spinel	81.6	88.7	92.2	94.7	95.1

Table 2-2

Under the above conditions of the same vacuum degree, holding temperature, and raw materials, the content of MgO.Al ₂ O ₃ in the magnesia-aluminum spinel gradually increases as the holding time increases. When the time exceeds 150 minutes, as the holding time increases, The extension has little effect on the content of MgO.Al ₂ O ₃ in magnesia-aluminum spinel.

Test the impact on the reduction rate of crude magnesium and the quality of magnesia-aluminum spinel when the heating reaction is carried out under the same conditions of vacuum degree, heating time, and raw material purity, but at different heating temperatures:

Add the pressed material clumps into the vacuum feeding buffer device, add the material clumps into the microwave reduction furnace, close all valves connected to the furnace body and seal them, start the vacuum system and start vacuuming, when the vacuum reaches 10Pa, Start the microwave power supply and control system and start heating. The temperatures are controlled at 900, 1000, 1100, 1150, and 1200°C for the reduction reaction. The holding time is controlled at 45 minutes. The vacuum degree is controlled within 10 Pa. The magnesium vapor generated by the reaction It enters the condensation and crystallization device and crystallizes into solid crude magnesium in the crystallizer; at the same time, the microwave reduction furnace continues to heat the materials in the high-temperature material tube, and the solid reduction slag further reacts in the high-temperature material tube of the microwave reduction furnace. When the temperature rise reaches a certain Start the insulation when the temperature reaches 1200, 1250, 1350, 1450, 1500℃ respectively. The insulation time is controlled to 150 minutes. The vacuum degree is controlled within 10Pa. After the reaction is completed, the magnesia-aluminum spinel is transported from the high-temperature material tube. into the vacuum unloading device, and then discharge the product in the vacuum unloading device.

Among them, with the difference of holding time, the reduction rate of crude magnesium and the quality of magnesia-aluminum spinel are shown in Table 3-1 and 3-2:

Vacuum Pa	10	10	10	10	10
MgO content% in magnesium oxide	96	96	96	96	96
Al content % in aluminum powder	99.9	99.9	99.9	99.9	99.9
Restore holding time Min	45	45	45	45	45
Reduction temperature℃	900	1000	1100	1150	1200
Reduction rate of crude magnesium %	53.1	78.3	85.7	92.4	92.6

Table 3-1

Under the above conditions of the same vacuum degree, holding time, and raw materials, as the reduction temperature increases, the reduction rate of crude magnesium gradually increases. When the reduction temperature exceeds 1150°C, as the reduction temperature increases, the reduction rate of crude magnesium will increase. The reduction rate has little impact.

Vacuum Pa	10	10	10	10	10
MgO content% in magnesium oxide	96	96	96	96	96
Al content % in aluminum powder	99.9	99.9	99.9	99.9	99.9
Keeping timeMin	150	150	150	150	150
Insulation temperature℃	1200	1250	1350	1450	1500
Content % of MgO.Al2O3 in magnesia-aluminum spinel	66.2	70.6	87.3	92.2	93.7

Table 3-2

Under the above conditions of the same vacuum degree, holding time, and raw materials, as the holding temperature rises, the content of MgO.Al ₂ O ₃ in the high magnesium aluminum spinel gradually increases. When the holding temperature exceeds 1450°C, as the temperature The increase has little effect on the content of MgO.Al ₂ O ₃ in magnesia-aluminum spinel.

Test the impact of the heating reaction on the reduction rate of crude magnesium and the quality of magnesia-aluminum spinel under the same conditions of vacuum degree, heating time and heating temperature, but the purity of the raw materials is different:

Add the pressed material clumps into the vacuum feeding device, add the material clumps into the high-temperature material tube of the microwave reduction furnace, close and seal all valves connected to the furnace body, start the vacuum system and start vacuuming. When the vacuum reaches When 10Pa, start the microwave power supply and control system and start heating and temperature rise. When the temperature rise reaches 1150°C, start holding. The holding time is controlled to 45 minutes. The holding temperature is controlled to 1150°C. The vacuum is controlled within 10Pa to carry out the reduction reaction. , where the MgO content % in the material briquette magnesium oxide and the Al content % in the corresponding aluminum powder are (90, 99) (92, 99.3) (94, 99.5) (96, 99.7) (98, 99.5) respectively. The reaction The generated magnesium vapor enters the condensation and crystallization device and crystallizes into solid crude magnesium in the crystallizer; at the same time, the microwave reduction furnace continues to heat the materials in the high-temperature material tube under vacuum conditions, and the solid reduction slag further reacts in the microwave high-temperature material tube. When the temperature rise reaches a certain temperature, heat preservation begins. The temperature is controlled at 1450°C, the vacuum is controlled within 10 Pa, and the heat preservation time is controlled at 150 minutes. After completion, the magnesia-aluminum spinel is transported from the high-temperature material tube to the vacuum unloading device. The product in the vacuum discharge device is then discharged.

Among them, with the difference of holding time, the reduction rate of crude magnesium and the quality of magnesia-aluminum spinel are shown in Table 4-1 and 4-2:

VacuumPa	10	10	10	10	10
Reduction temperature℃	1150	1150	1150	1150	1150
Restore holding time Min	45	45	45	45	45
MgO content% in magnesium oxide	90	92	94	96	98
Al content % in aluminum powder	99.0	99.3	99.5	99.7	99.95
Reduction rate of crude magnesium %	91.7	92.3	92.1	92.4	92.6

Table 4-1

Under the above conditions of the same vacuum degree, holding time and holding temperature, as the magnesium oxide and aluminum content in the raw material increases, the reduction rate will be less affected.

Vacuum Pa	10	10	10	10	10
Reaction temperature℃	1450	1450	1450	1450	1450
Keeping timeMin	150	150	150	150	150
MgO content% in magnesium oxide	90	92	94	96	98
Al content % in aluminum powder	99.0	99.3	99.5	99.7	99.95
Content % of MgO.Al2O3 in magnesia-aluminum spinel	85.8	88.7	89.6	92.4	96.3

Table 4-2

Under the above conditions of the same vacuum degree, holding time, and holding temperature, as the purity of the raw material increases, the content of MgO.Al ₂ O ₃ in the corresponding product magnesia-aluminum spinel gradually increases. When the holding temperature exceeds 1450°C, The increase in the content of MgO and Al in the corresponding raw materials corresponds to the gradual increase in the content of MgO.Al ₂ O ₃ in the magnesia-aluminum spinel and exceeds 90%. Therefore, in the raw materials, the MgO content in magnesium oxide should be ≥96%, and the Al content in aluminum powder should be ≥99.9%.

The above descriptions of the present invention are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection.

Claims (5)

1. A green and environmentally friendly method for producing magnesium by aluminothermic method, which is characterized in that it includes the following steps:

   S1: Evenly mix magnesium oxide and aluminum powder with qualified particle size in proportion, mix and press into briquettes;

   S2: Add the material clumps obtained in S1 into the vacuum feeding device;

   S3: The vacuum feeding device puts the material briquettes into the high-temperature material tube of the microwave reduction furnace, and heats and maintains the temperature in a vacuum environment. The material briquettes are heated in the high-temperature material tube and undergo a reduction reaction, producing magnesium vapor, solid reduction slag, and magnesium vapor. After being passed into the condensation and crystallization device for condensation and crystallization, solid high-purity crude magnesium is obtained;

   S4: Continue to heat up and maintain the temperature in a vacuum environment, the solid reduction slag further reacts in the high-temperature material tube, and the solid reduction slag generates magnesia-aluminum spinel;

   S5: Cut the produced magnesia-aluminum spinel through a vacuum cutting device;

   The above process is carried out under vacuum conditions.
2. A green and environmentally friendly thermite reduction magnesium production method as claimed in claim 1, characterized in that: in the S1, the particle sizes of magnesium oxide and aluminum powder are both ≤100 mesh, and the MgO content in the magnesium oxide is ≥96%. , Al content in aluminum powder is ≥99.9%.
3. A green and environmentally friendly aluminothermic reduction magnesium production method as claimed in claim 1, characterized in that: in the S1, the weight ratio of magnesium oxide to aluminum powder is 3.05~3.25:1.
4. A green and environmentally friendly aluminothermic reduction magnesium production method as claimed in claim 1, characterized in that: in the S3, the vacuum degree is within 10pa, and the heat preservation is performed after heating to a temperature of 900 to 1200°C for a heat preservation time 20 to 70 minutes.
5. A green and environmentally friendly aluminothermic reduction magnesium production method as claimed in claim 1, characterized in that: in said S4, the vacuum degree is within 10pa, and the heating is continued until the temperature is 1200-1600°C and then the heat preservation time is 90 to 200 minutes.