A production device and a production method of 4N-grade high-purity magnesium

Abstract

The application discloses a production device and method for producing 4N high-purity magnesium. The device takes a sponge titanium inverted U-shaped reduction distillation furnace as a main equipment body, and liquid magnesium heat preservation feeding ports and liquid level detection devices are additionally arranged on a hot end reactor; a collecting sleeve is additionally arranged in the cold end reactor. The production method takes liquid crude magnesium produced by an electrolysis method as raw material, adds the liquid magnesium into the hot end reactor, heats and distills under vacuum conditions to vaporize the magnesium, and the magnesium vapor migrates to the cold end reactor along the inverted U-shaped channel and is condensed and crystallized on the surface of the collecting sleeve to obtain 4N high-purity magnesium. The single feeding amount of the application can reach 2 tons, and the single furnace output is more than 4 times of that of a traditional equipment; a semi-continuous production mode is adopted, continuous feeding of the hot end and intermittent discharging of the cold end can be realized; the vacuum system, the heating system and the furnace body structure of the sponge titanium inverted U-shaped furnace are fully reused, special equipment does not need to be additionally arranged, the equipment investment cost is greatly reduced, the process flow is short, and the application is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal refining technology, specifically to a vacuum distillation production apparatus and method for high-purity magnesium, and more particularly to a production method for producing 4N grade high-purity magnesium using an existing sponge titanium inverted U-shaped reduction distillation furnace. Background Technology

[0002] High-purity magnesium typically refers to magnesium with a purity of ≥99.99% (4N grade or higher). It is a crucial raw material for preparing high-performance magnesium alloys, aerospace structural materials, electronic packaging materials, and special reducing agents. With the rapid development of the new energy, aerospace, and semiconductor industries, the market demand for high-purity magnesium continues to grow, while simultaneously placing higher demands on product purity and batch stability.

[0003] Currently, the industrial production of high-purity magnesium mainly adopts the vacuum distillation method. Taking advantage of the fact that the vapor pressure of magnesium is much higher than that of impurity elements such as iron, silicon, nickel, and copper, magnesium is vaporized by vacuum heating and collected in the condensation zone, thereby achieving the separation of impurities.

[0004] The existing high-purity magnesium production technology has the following main drawbacks:

[0005] 1. Low single-furnace capacity: Due to limitations in equipment structure and thermal uniformity, the single output of traditional high-purity magnesium distillation furnaces is generally below 500 kg. Large-scale production requires multiple machines to be connected in parallel, resulting in a large footprint and high maintenance costs.

[0006] 2. High equipment specialization: High-purity magnesium distillation requires specially designed and manufactured vacuum furnace equipment, which has high investment costs, long construction period, and high barriers to entry for enterprises to switch production or expand production.

[0007] 3. Poor production continuity: Most processes are intermittent, with feeding, distillation, discharging, and furnace cleaning carried out sequentially. This results in low equipment utilization and difficulty in improving production efficiency.

[0008] On the other hand, the sponge titanium industry widely uses inverted U-shaped reducing distillation furnaces for magnesian reduction to produce sponge titanium. These machines feature large-volume vacuum chambers, high-power heating systems, and high-vacuum units, with single furnace volumes reaching several cubic meters, designed to process tons of reaction materials. However, the sponge titanium market experiences cyclical fluctuations, and some companies face issues such as idle equipment or insufficient capacity utilization. How to revitalize existing equipment and expand product categories has become an urgent problem for the industry.

[0009] To date, there have been no reports of using sponge titanium inverted U-shaped furnaces to directly produce high-purity magnesium, achieving a single-furnace output of 2 tons and semi-continuous production. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of existing high-purity magnesium production technologies, such as low single-furnace capacity, high equipment investment, and low production efficiency. It provides a production apparatus and method for producing 4N grade high-purity magnesium using a sponge titanium inverted U-shaped furnace. This method directly utilizes an inverted U-shaped reduction distillation furnace used in sponge titanium production, eliminating the need for additional specialized equipment. It achieves a single-batch production of 2 tons of 4N high-purity magnesium and allows for semi-continuous operation, significantly improving production efficiency and reducing production costs.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A production apparatus for 4N grade high-purity magnesium uses an inverted U-shaped reducing distillation furnace, similar to that used in sponge titanium production, as the main body of the equipment. It includes a hot-end reactor, a cold-end reactor, and an inverted U-shaped steam channel connecting the two. A liquid magnesium heat-insulating feed inlet and a liquid level detection device are added to the hot-end reactor. A collection sleeve is added inside the cold-end reactor.

[0013] Preferably, the liquid level detection device is a radar liquid level gauge, which is connected to the central tube of the hot end reactor of the inverted U-shaped reduction distillation furnace via a flange.

[0014] Preferably, the collecting sleeve is made of low-carbon steel or stainless steel, and the surface roughness Ra of the sleeve is ≤6.3μm.

[0015] A method for producing 4N grade high-purity magnesium, using any of the aforementioned production apparatus, includes the following steps:

[0016] (1) Feeding: The liquid crude magnesium produced by electrolysis is injected into the hot end reactor, with a single feeding amount of 1.5 to 2.5 tons;

[0017] (2) Connect the cold end reactor and the hot end reactor of the reducing distillation furnace through an inverted U-shaped steam channel;

[0018] (3) Vacuum distillation: Start the vacuum unit to evacuate the reducing distillation furnace, control the absolute pressure in the reducing distillation furnace to 10-100 Pa, heat the hot end reactor to 650-800℃ and keep it at that temperature, so that the liquid magnesium vaporizes to form magnesium vapor.

[0019] (4) Condensation and collection: Magnesium vapor enters the cold end reactor through an inverted U-shaped steam channel and condenses and crystallizes on the inner wall of the collection sleeve at a temperature of 450-580℃ to obtain high-purity magnesium ingots;

[0020] (5) Semi-continuous operation: During the distillation process, liquid crude magnesium is added to the hot end reactor to maintain the stability of the hot end liquid level; after the high-purity magnesium on the cold end collection sleeve accumulates to the set amount, the vacuum is broken by cooling, the collection sleeve is removed and replaced with a new sleeve, and production is resumed.

[0021] Preferably, the absolute pressure inside the reducing distillation furnace in step (3) is controlled at 20-50 Pa; the vacuum distillation process is divided into a heating stage and a constant temperature distillation stage: the heating stage heats up to 650-800℃ at a rate of 50-100℃ / h; the constant temperature distillation stage is held for 12-24 hours.

[0022] Preferably, the purity of the liquid crude magnesium in step (1) is 99.5% to 99.8%, and the feeding temperature is 680 to 750°C.

[0023] Preferably, the hot end reactor is equipped with a liquid magnesium heat-insulating inlet and a liquid level detection device, and the liquid level in the hot end reactor is maintained at a position where the magnesium liquid occupies 60% to 80% of the effective volume of the hot end reactor; the condensation collection in step (4) adopts an intermittent discharge mode, the single collection amount of the sleeve is 1.8 to 2.2 tons, and the collection cycle is 18 to 30 hours.

[0024] Preferably, when replacing the collecting sleeve in step (4), the disassembly and assembly operations are carried out under an argon protective atmosphere, and the operation time is ≤2 hours.

[0025] Preferably, the obtained high-purity magnesium product has a purity ≥99.99% and impurity elements Fe≤10ppm, Si≤8ppm, Ni≤5ppm, and Cu≤5ppm.

[0026] Preferably, the process also includes step (6): after distillation for a period of time, the residual magnesium liquid enriched with impurities at the bottom of the hot end reactor is periodically discharged, with a discharge cycle of 5 to 8 collection sleeve cycles, and the residual magnesium liquid is returned to the electrolysis system or treated separately.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Significantly increased production capacity: Utilizing the large-volume cavity of the sponge titanium inverted U-shaped furnace, the output of high-purity magnesium in a single batch can reach 2 tons, which is 4 times that of the traditional 500kg-class high-purity magnesium distillation furnace, significantly improving the production capacity of a single furnace and reducing the number of equipment units and floor space.

[0029] 2. Equipment reuse and low investment: The existing sponge titanium inverted U-shaped reduction distillation furnace can be used directly, and its vacuum unit, heating system, furnace shell and control system can be reused. Only a few internal components such as the collection sleeve need to be added. There is no need to develop new equipment. The equipment modification cost is less than 20% of that of a dedicated high-purity magnesium furnace, which greatly reduces fixed asset investment and revitalizes idle capacity.

[0030] 3. Semi-continuous production with high efficiency: The semi-continuous mode of continuous feeding at the hot end and intermittent discharge at the cold end avoids the time loss caused by frequent temperature rises and falls and furnace start-ups and shutdowns in traditional intermittent processes. The effective operating rate of the equipment is increased by more than 30%, and the output per unit time is significantly increased.

[0031] 4. Stable and reliable product purity: Based on the principle of vacuum distillation, the separation is achieved by utilizing the difference in vapor pressure between magnesium and impurity elements. Combined with the gas-liquid separation effect of the inverted U-shaped channel, it can stably produce 4N grade (≥99.99%) high-purity magnesium. The contents of major impurities such as Fe, Si, Ni, and Cu are all controlled below 10ppm, which meets the requirements of high-end applications.

[0032] 5. Flexible process and strong adaptability: The same inverted U-shaped furnace can produce both sponge titanium and high-purity magnesium. Enterprises can flexibly adjust their product structure according to market conditions and enhance their ability to resist risks. Liquid magnesium comes directly from the electrolysis workshop, reducing the remelting process and lowering energy consumption and burn-off. Attached Figure Description

[0033] Figure 1 is a schematic diagram of the production device of the present invention. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1 As shown, the production apparatus of the present invention uses an inverted U-shaped reduction distillation furnace used in the production of sponge titanium as the main body of the equipment, including a hot-end reactor 1, a cold-end reactor 2, and an inverted U-shaped steam channel 3 connecting the two.

[0036] A liquid magnesium inlet 5 and a liquid level detection device 7 are added to the hot-end reactor 1; a collection sleeve 4 is added inside the cold-end reactor. In the figure, 8 is the residual magnesium liquid discharge port in the hot-end reactor, and 6 is the vacuum interface of the cold-end reactor. The liquid level detection device 7 is a radar liquid level gauge, connected to the central tube of the hot-end reactor of the inverted U-shaped reduction distillation furnace via a flange. A graphite gasket is also installed to ensure a tight seal.

[0037] Example 1

[0038] This embodiment utilizes an existing 12-ton sponge titanium inverted U-shaped reduction distillation furnace at a titanium plant to produce 4N grade high-purity magnesium. A stainless steel collecting sleeve is added to the cold-end reactor of the inverted U-shaped furnace. The sleeve has a diameter of 800mm, a height of 2500mm, a wall thickness of 10mm, and its inner wall is polished to Ra≤6.3μm. The hot-end reactor retains the original heating system and vacuum interface, and adds a liquid magnesium insulation inlet 5 and a liquid level detection device 7. The specific implementation steps are as follows:

[0039] (1) Feeding: Liquid crude magnesium produced in the electrolysis workshop, with a purity of 99.7% and a temperature of 700℃, is injected into the hot end reactor 1 through the liquid magnesium insulated feed port 5 connected to the insulated pipe. The initial feed amount is 2 tons, and the liquid level reaches 70% of the effective volume of the hot end reactor.

[0040] (2) Connect the cold end reactor 2 and the hot end reactor 1 of the reducing distillation furnace through an inverted U-shaped steam channel 3;

[0041] (3) Vacuum distillation: Start the Roots-slide valve vacuum unit and pump the furnace to an absolute pressure of 30 Pa; turn on the hot end heating device and heat up to 720°C at a rate of 80°C / h to enter the isothermal distillation stage. Maintain the hot end temperature at 720±10°C and the furnace pressure at 25~35 Pa. Liquid magnesium continues to vaporize, and magnesium vapor enters the cold end through the inverted U-shaped channel.

[0042] (4) Condensation and collection: The cold end temperature is controlled at 500-520℃, and magnesium vapor condenses and crystallizes on the surface of the collection sleeve.

[0043] (5) Semi-continuous operation: Four hours after distillation begins, the liquid magnesium feed valve is opened, and liquid magnesium is added to the hot end at a rate of approximately 100 kg / h. The feed rate is automatically adjusted by the liquid level sensor to maintain a stable liquid level at the hot end. After 24 hours of continuous distillation, approximately 2 tons of high-purity magnesium are deposited on the collection sleeve. Heating and feeding are stopped, the furnace body is cooled to below 300°C, high-purity argon is introduced to atmospheric pressure, the cold end cap is opened, the collection sleeve is lifted out, a new sleeve is replaced, and the vacuum is re-evacuated and heated to resume production. The sleeve replacement operation takes approximately 1.5 hours.

[0044] (6) After distillation for a period of time, the residual magnesium liquid enriched with impurities at the bottom of the hot end reactor is periodically discharged. Every 7 cylinder replacement cycles, about 200 kg of residual magnesium liquid is discharged from the bottom of the hot end reactor and returned to the electrolytic magnesium workshop for re-electrolysis.

[0045] The pure magnesium produced in this embodiment was tested: after demolding and surface cleaning, the high-purity magnesium ingots were sampled and tested. The magnesium purity was 99.992%, with Fe content of 8ppm, Si content of 6ppm, Ni content of 3ppm and Cu content of 2ppm, reaching the 4N grade high-purity magnesium standard.

[0046] Example 2

[0047] The operating parameters in this embodiment are basically the same as those in Embodiment 1, except that:

[0048] The hot-end distillation temperature was set at 680℃, the absolute pressure inside the furnace was controlled at 15Pa, and the constant-temperature distillation time was 28 hours. Approximately 1.95 tons of high-purity magnesium were collected from a single sleeve. The product purity was tested to be 99.994%, with Fe content of 7ppm, Si content of 5ppm, Ni content of 2ppm, and Cu content of 2ppm. The purity was slightly better than that of Example 1, but the production cycle was correspondingly longer.

[0049] Example 3

[0050] The operating parameters in this embodiment are basically the same as those in Embodiment 1, except that:

[0051] The initial feed rate is 1.6 tons, the hot end temperature is 760℃, the furnace pressure is 50Pa, the distillation cycle is 20 hours, and the output per sleeve is approximately 1.85 tons. The product purity is 99.991%, meeting the 4N grade requirements. The production pace is faster, making it suitable for high-output operation modes.

[0052] Comparative Example

[0053] A traditional vertical high-purity magnesium vacuum distillation furnace with an effective volume of 0.8 cubic meters is used. A single batch of 500 kg of crude magnesium is fed, the distillation temperature is 700℃, the vacuum degree is 30 Pa, and the distillation cycle is 18 hours, producing approximately 460 kg of high-purity magnesium with a purity of 99.99%. The average daily output of a single furnace is approximately 613 kg, which is only about 1 / 3 of the daily output of a single furnace of this invention, and it is a completely intermittent production process with low equipment utilization.

[0054] As can be seen from the above embodiments, the present invention utilizes a sponge titanium inverted U-shaped furnace to produce 4N grade high-purity magnesium, with a single furnace output of up to 2 tons and a product purity that is stable at over 99.99%. It can achieve semi-continuous production, with low equipment investment and high production efficiency, and has significant economic advantages and industrial application value.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A production apparatus for 4N grade high-purity magnesium, characterized in that, The equipment uses an inverted U-shaped reducing distillation furnace used in the production of sponge titanium as the main body, including a hot-end reactor, a cold-end reactor, and an inverted U-shaped steam channel connecting the two; a liquid magnesium heat-insulating feed inlet and a liquid level detection device are added to the hot-end reactor; and a collection sleeve is added inside the cold-end reactor.

2. The production apparatus according to claim 1, characterized in that: The liquid level detection device is a radar liquid level gauge, which is connected to the central tube of the hot end reactor of the inverted U-shaped reduction distillation furnace via a flange.

3. The production apparatus according to claim 1 or 2, characterized in that: The collecting sleeve is made of low-carbon steel or stainless steel, and the surface roughness Ra of the sleeve is ≤6.3μm.

4. A method for producing 4N grade high-purity magnesium, characterized in that, The production apparatus according to claim 1 or 2 includes the following steps: (1) Feeding: The liquid crude magnesium produced by electrolysis is injected into the hot end reactor, with a single feeding amount of 1.5 to 2.5 tons; (2) Connect the cold end reactor and the hot end reactor of the reducing distillation furnace through an inverted U-shaped steam channel; (3) Vacuum distillation: Start the vacuum unit to evacuate the reducing distillation furnace, control the absolute pressure in the reducing distillation furnace to 10-100 Pa, heat the hot end reactor to 650-800℃ and keep it at that temperature, so that the liquid magnesium vaporizes to form magnesium vapor. (4) Condensation and collection: Magnesium vapor enters the cold end reactor through an inverted U-shaped steam channel and condenses and crystallizes on the inner wall of the collection sleeve at a temperature of 450-580℃ to obtain high-purity magnesium ingots; (5) Semi-continuous operation: During the distillation process, liquid crude magnesium is added to the hot end reactor to maintain the stability of the hot end liquid level; after the high-purity magnesium on the cold end collection sleeve accumulates to the set amount, the vacuum is broken by cooling, the collection sleeve is removed and replaced with a new sleeve, and production is resumed.

5. The production method according to claim 4, characterized in that: The absolute pressure inside the reducing distillation furnace in step (3) is controlled at 20-50 Pa; the vacuum distillation process is divided into a heating stage and a constant temperature distillation stage: the heating stage heats up to 650-800℃ at a rate of 50-100℃ / h; the constant temperature distillation stage is held for 12-24 hours.

6. The production method according to claim 4 or 5, characterized in that: The purity of the liquid crude magnesium in step (1) is 99.5% to 99.8%, and the feeding temperature is 680 to 750℃.

7. The production method according to claim 4 or 5, characterized in that: The hot end reactor is equipped with a liquid magnesium heat-insulating feed inlet and a liquid level detection device. The liquid level in the hot end reactor is maintained at a position where the liquid magnesium occupies 60% to 80% of the effective volume of the hot end reactor. The condensation collection in step (4) adopts an intermittent discharge mode, with a single collection volume of 1.8 to 2.2 tons and a collection cycle of 18 to 30 hours.

8. The production method according to claim 7, characterized in that, When replacing the collection sleeve in step (4), the disassembly and assembly operations are carried out under an argon protective atmosphere, and the operation time is ≤2 hours.

9. The production method according to claim 4 or 5, characterized in that: The obtained high-purity magnesium product has a purity of ≥99.99% and impurity elements Fe≤10ppm, Si≤8ppm, Ni≤5ppm, and Cu≤5ppm.

10. The production method according to claim 4 or 5, characterized in that, The production method further includes step (6): after distillation for a period of time, the residual magnesium liquid enriched with impurities at the bottom of the hot end reactor is periodically discharged. The discharge cycle is 5 to 8 collection sleeve cycles. The residual magnesium liquid is returned to the electrolysis system or treated separately.

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