Metal impurity element separation device and method

Abstract

The invention belongs to the field of metal purification, and particularly relates to a metal impurity element separation device and method. The invention provides a magnesium-zinc separation method and device aiming at the problem that magnesium and zinc are difficult to separate in a traditional vacuum distillation technology. According to the magnesium-zinc separation method, a magnetic field is used for rapidly stirring a metal melt, and it is ensured that the flowing direction of the metal melt is parallel to a solid / liquid interface at the front edge of the solid / liquid interface. The stirring in the form can effectively reduce the thickness of a solute enrichment layer, increase the liquid phase diffusion coefficient and reduce the effective distribution coefficient. The device is composed of a crucible unit, a crystallizer unit, a magnet stirring unit, a vacuum unit and the like. The device utilizes the rotation of the magnet to promote the magnesium melt to flow, reduce the effective distribution coefficient and obtain the high-purity magnesium ingot. The device is simple in structure, convenient to operate and beneficial to application and popularization.

Description

Technical Field

[0001] The invention belongs to the field of metal purification, and in particular relates to a device and method for separating metal impurity elements. Background Art

[0002] Ultrapure magnesium is widely used in high-tech fields such as semiconductors, biomedicine, and new energy. In the semiconductor field, the purity of metallic magnesium is generally required to be higher than 99.9999% (calculating all metal impurity elements). High impurity content will seriously affect the performance of semiconductor devices. In the biomedical field, the purity of magnesium is required to be higher than 99.99%, and the higher the purity, the better. This is because a high content of impurity elements will seriously reduce the corrosion rate of magnesium alloys in the body, causing corrosion failure of magnesium alloy devices. For example: The Chinese patent (CN102802689B) points out that pure magnesium with a purity of 99.95%, 99.98%, 99.998%, and 99.999% has a corrosion rate of 50 mg / cm 2 / day, 2 mg / cm 2 / day, 0.01 mg / cm 2 / day, 0.008 mg / cm 2 / day. At present, the main method for preparing high-purity magnesium with a purity higher than 99.99% is vacuum distillation. The vacuum distillation method can remove almost all metallic impurity elements in magnesium to extremely low contents, but it is difficult to remove the impurity element zinc by this method. This is because the saturated vapor pressures of magnesium and zinc are close, and the separation coefficient of zinc in magnesium is close to 1. The zinc content of the original magnesium ingots currently sold on the market is generally 20~80ppm. If the impurity zinc cannot be effectively removed, it is difficult to use the original magnesium ingots to prepare high-purity magnesium with a purity higher than 99.999%. In order to effectively separate the impurity element zinc from magnesium, researchers have tried different methods. For example: US Patent (US005582630A) points out that by precisely controlling the condensation temperature in different intervals of vacuum distillation, effective separation of magnesium and zinc can be achieved, but the yield of high-purity magnesium is low. The Chinese patent (CN 116855749 A) ​​designs a device that separates magnesium and zinc by controlling temperature and pressure to obtain 99.99% pure magnesium. At present, the method of removing impurity element zinc is still based on vacuum distillation technology, but vacuum distillation technology has problems such as poor separation of magnesium and zinc and low yield. Multiple vacuum distillations are required to reduce the zinc content to below 1ppm. Therefore, how to effectively remove zinc impurity elements with a separation coefficient close to 1 is a key issue in the preparation of high-purity magnesium. Summary of the invention

[0003] In order to solve the above-mentioned technical problems, this application provides the following technical solutions: The purpose of the present invention is to solve the problem that magnesium and zinc are difficult to separate, and to provide a method and device for separating magnesium and zinc. In order to reflect the general situation, the letters A and B are used to represent the metal impurity element and the metal to be purified, respectively, wherein the separation coefficient of the metal impurity element A and the metal B is close to 1, and the distribution coefficient of the metal impurity element A in the metal B is less than 1.

[0004] The basic idea of ​​the present invention is to utilize the difference in solubility of the metal impurity element A in the solid / liquid phase of the metal B. Since the equilibrium distribution coefficient of the metal impurity element A in the metal B is ( k 0) is less than 1. During the solidification process of metal B, the metal impurity element A is concentrated in the liquid phase, the content of the metal impurity element A in the solid phase is reduced, and the purity of metal B is improved. In the actual solidification process, due to the deviation from equilibrium solidification, the effective distribution coefficient ( k e ) Characterizes the redistribution process of solutes during solidification. Effective distribution coefficient k e It can be expressed as follows: ;

[0005] In the above formula, V is the solidification rate, d is the thickness of the solute-enriched layer at the front of the solid / liquid interface, and D is the diffusion coefficient of metal A in liquid metal B.

[0006] Based on the above formula, the effective distribution coefficient can be reduced by reducing the solidification rate V, reducing the solute enrichment layer thickness d and increasing the liquid phase diffusion coefficient D. k e From the perspective of actual production, reducing the solidification rate is not conducive to improving the purification efficiency. Therefore, reducing the thickness of the solute enrichment layer and increasing the liquid phase diffusion coefficient D are effective means to enhance the separation degree of metal impurity elements A and metal B during the solidification process.

[0007] The present invention provides a metal impurity element separation device to solve the problem that the prior art is difficult to separate metals, comprising: A crucible unit, comprising a crucible and a heating furnace; the crucible contains a metal B melt, and the metal B melt contains a metal impurity element A; the separation coefficient of the metal impurity element A and the metal B is close to 1, and the distribution coefficient of A in B is less than 1; A crystallizer unit, which is located at the bottom of the crucible unit, comprises an inner sleeve, a water-cooled copper sleeve, a dummy rod, a seeding ingot and a high-purity metal ingot; the inner sleeve is installed inside the water-cooled copper sleeve, the seeding ingot is fixed on the dummy rod, the seeding ingot moves up and down along the inner sleeve with the dummy rod, and a slightly convex solid / liquid interface is formed between the high-purity metal ingot and the metal B melt; A magnetic stirring unit, comprising a magnet mounted on a rotating shaft, wherein the electromagnetic force generated by the rotation of the magnet drives the metal B melt to flow in a direction parallel to the solid / liquid interface; The vacuum unit comprises a cavity, wherein the cavity is provided with an air inlet, and the crucible unit, the crystallizer unit and the magnetic stirring unit are all arranged in the vacuum cavity.

[0008] Preferably, the heating furnace is heated by resistance heating or induction coil heating.

[0009] Preferably, the material of the crucible is selected from high-purity graphite or high-purity aluminum titanate.

[0010] Preferably, the metal A is zinc, and the metal B is magnesium.

[0011] Furthermore, the metal B melt is formed by melting high-purity crystals or metal B ingots containing 1-1000 ppm of impurity element A.

[0012] Preferably, the inner sleeve is made of high-purity graphite.

[0013] Preferably, the magnetic stirring unit is arranged at the bottom or both sides of the crucible unit.

[0014] Preferably, the magnet is a water-cooled permanent magnet or an electromagnet.

[0015] Preferably, the magnet is a circular magnet.

[0016] Preferably, the seeding ingot is a high-purity metal B ingot with a purity of not less than 99.99%.

[0017] Preferably, the cavity is a water-cooled stainless steel cavity.

[0018] Preferably, the vacuum unit further comprises a high-purity gas cylinder, a pressure gauge and a vacuum pump, the high-purity gas cylinder is connected to the cavity via an air inlet, and the vacuum pump is connected to the cavity via a bellows.

[0019] The present invention also provides a method for separating metal impurity elements, which uses the above-mentioned metal impurity element separation device for separation, comprising the following steps: S1: adding metal B containing metal impurity element A as a raw material into a crucible, and heating the crucible under a protective atmosphere to form a melt of metal B containing metal A; S2: introducing cooling water into the water-cooled copper sleeve for water-cooling circulation, and rotating the magnet to make the metal B melt containing metal A flow in a clockwise or counterclockwise direction in a direction parallel to the solid / liquid interface; S3: Pull the ingot rod downward in the vertical direction to drive the seeding ingot and the high-purity metal ingot to move downward. Under the cooling of the water-cooled copper sleeve, the solid / liquid interface between the high-purity metal ingot and the melt is made to be a flat interface, and slightly higher than the bottom surface of the crucible. During the pulling process, the metal impurity element A is continuously enriched at the front of the solid / liquid interface and is carried away by the flowing metal B melt, and is evenly mixed with the metal B melt in the crucible under the stirring action of the magnet; S4: Take out the high-purity metal ingot, determine the cutting position according to the purity requirement, cut off the part with high metal A content on the top of the high-purity metal ingot, and obtain a high-purity metal ingot with low metal impurity element A content.

[0020] The metal impurity element separation method is to use a magnetic field to quickly stir the metal B melt, and the flow direction of the metal B melt at the front of the solid / liquid interface is parallel to the solid / liquid interface. This form of flow can quickly take away the solute in the solute-enriched layer and mix it evenly with the melt in other areas, effectively reducing the thickness of the solute-enriched layer. The flowing metal melt increases the liquid phase diffusion coefficient. Under the combined effect of these two effects, the effective distribution coefficient is reduced, which is conducive to the segregation of the impurity element A to the liquid phase, thereby reducing the content of the metal impurity element A in the solid phase B and improving the purity of the solid phase B.

[0021] The technical solution of the present invention has the following advantages over the prior art: (1) The present invention utilizes the rotation of magnets to promote the melt flow of metal B parallel to the solid / liquid interface, reduce the thickness of the solute enrichment layer at the front of the solid / liquid interface, increase the liquid phase diffusion coefficient, reduce the effective distribution coefficient, and enrich the metal impurity element A in the liquid phase to obtain a high-purity metal ingot. This solves the problem of difficulty in separating metal B and metal impurity element A by vacuum distillation; (2) The present invention has a simple structure, is easy to operate, and is easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 2 is a schematic diagram of the structure of the device of the present invention.

[0023] Figure 2 2 is another structural schematic diagram of the relative positions of the magnet and the crucible of the device of the present invention.

[0024] Explanation of the accompanying drawings: 11-crucible, 12-crucible cover, 13-heating furnace, 21-magnesium melt, 22-solid / liquid interface, 23-high-purity magnesium ingot, 24-seedling ingot, 25-seedling rod, 31-inner sleeve, 32-water-cooled copper sleeve, 33-water inlet, 34-water outlet, 41-magnet, 42-rotating shaft, 51-stainless steel cavity, 52-pressure gauge, 53-high-purity gas cylinder, 54-vacuum pump, 55-first vacuum valve, 56-second vacuum valve. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Example 1

[0026] The metal impurity element separation device is mainly composed of a crucible unit, a crystallizer unit, a magnet stirring unit and a vacuum unit.

[0027] The crucible unit is composed of a crucible 11 , a crucible cover 12 and a heating furnace 13 . The crucible 11 is covered with the crucible cover 12 , and the heating furnace 13 is placed outside the crucible 11 .

[0028] The crystallizer unit is composed of an inner sleeve 31, a water-cooled copper sleeve 32, a water inlet 33 and a water outlet 34. The inner sleeve 31 is installed inside the water-cooled copper sleeve 32, and the water inlet 33 and the water outlet 34 are installed outside the water-cooled copper sleeve 32. The inner sleeve 31 and the water-cooled copper sleeve 32 are installed at the lower part of the crucible 11.

[0029] The magnetic stirring unit is composed of a magnet 41 and a rotating shaft 42. The magnet 41 is mounted on the rotating shaft 42, and the magnet 41 is mounted at a certain distance from the bottom of the crucible 11.

[0030] The vacuum unit is composed of a stainless steel cavity 51, a pressure gauge 52, a high-purity gas cylinder 53, a vacuum pump 54, a first vacuum valve 55, and a second vacuum valve 56. The pressure gauge 52 is connected to the stainless steel cavity 51, the high-purity gas cylinder 53 is connected to the stainless steel cavity 51, the second vacuum valve 56 is installed on the gas pipe between the high-purity gas cylinder 53 and the stainless steel cavity 51, the vacuum pump 54 is connected to the stainless steel cavity 51, and the first vacuum valve 55 is installed on the bellows between the vacuum pump 54 and the stainless steel cavity 51. In addition, the magnesium melt 21 is inside the crucible 11, the seeding ingot 24 is installed on the seeding rod 25, and the high-purity magnesium ingot 23 grows above the seeding ingot 24, and a solid / liquid interface 22 is formed between the high-purity magnesium ingot 23 and the magnesium melt 21. Example 2

[0031] The device is the same as the metal impurity element separation device of Example 1, except that the magnets 41 are installed on both sides of the crucible 11 . Example 3

[0032] A distilled magnesium product containing 30 ppm zinc was used as the raw material. Figure 1The seeding ingot 24 is mounted on the seeding rod 25, and the seeding rod 25 is raised until the upper surface of the seeding ingot 24 is flush with the bottom surface of the crucible 11. The raw material is placed in the crucible 11, and the stainless steel cavity 51 is evacuated to 10 by the vacuum pump 54. -4 Pa, close the first vacuum valve 55. Open the vacuum valve 56, pass the high-purity argon gas in the high-purity gas cylinder 53 into the stainless steel cavity 51 until the pressure in the stainless steel cavity is 1.1atm, and close the second vacuum valve 56. Pass cooling water into the water-cooled copper sleeve 32 through the water inlet pipe 33 and the water outlet pipe 34. Turn on the heating furnace 13 to heat the crucible 11 to 700°C, keep it warm for 40 minutes, completely melt the raw materials, and obtain the magnesium melt 21. Turn on the magnet stirring system, and the magnet speed is 600 rpm. The magnesium melt flows counterclockwise, and the flow direction of the metal melt at the front of the solid / liquid interface is parallel to the solid / liquid interface. The zinc solute enriched at the front of the interface is taken away by the magnesium melt, the thickness of the solute enrichment layer is reduced, and the liquid phase diffusion coefficient is increased. Turn on the pulling system, and pull the ingot rod downward at a rate of 3 mm / min until the pulling is completed. Turn off the pulling system and stop the magnet stirring. After the heating furnace is cooled to room temperature, the stainless steel cavity furnace door is opened, the high-purity magnesium ingot 23 is taken out, and the upper end is cut off at the position where the zinc content is 10 ppm, and the lower end is a high-purity magnesium ingot with an average zinc content of less than 10 ppm. Example 4

[0033] High-purity magnesium ingots containing 80ppm zinc are used as raw materials. Figure 2 The seeding ingot 24 is mounted on the seeding rod 25, and the seeding rod 25 is raised until the upper surface of the seeding ingot 24 is flush with the bottom surface of the crucible 11. The raw material is placed in the crucible 11, and the stainless steel cavity 51 is evacuated to 10 by the vacuum pump 54. -4Pa, close the first vacuum valve 55. Open the vacuum valve 56, pass the high-purity argon gas in the high-purity gas cylinder 53 into the stainless steel cavity 51 until the pressure in the stainless steel cavity is 1.1atm, and close the second vacuum valve 56. Pass cooling water into the water-cooled copper sleeve 32 through the water inlet pipe 33 and the water outlet pipe 34. Turn on the heating furnace 13 to heat the crucible 11 to 750°C, keep warm for 30 minutes, completely melt the raw materials, and obtain the magnesium melt 21. Turn on the magnet stirring system, and the magnet speed is 800 rpm. The magnesium melt flows clockwise, and the flow direction of the metal melt at the front of the solid / liquid interface is parallel to the solid / liquid interface. The zinc solute enriched at the front of the interface is taken away by the magnesium melt, the thickness of the solute enrichment layer is reduced, and the liquid phase diffusion coefficient is increased. Turn on the pulling system, and pull the ingot rod downward at a rate of 2mm / min until the pulling is completed. Close the pulling system and stop the magnet stirring. After the heating furnace is cooled to room temperature, the stainless steel cavity furnace door is opened, the high-purity magnesium ingot 23 is taken out, and the upper end is cut off at the position where the zinc content is 10 ppm, and the lower end is a high-purity magnesium ingot with an average zinc content of less than 10 ppm.

[0034] Effect evaluation

[0035] The present invention utilizes a magnetic field to rapidly stir the molten metal, and the flow direction of the molten metal at the front of the solid / liquid interface is parallel to the solid / liquid interface. This form of flow energy can quickly carry away the solute in the solute-enriched layer and mix it evenly with the melt in other areas, effectively reducing the thickness of the solute-enriched layer. The flowing molten metal increases the liquid phase diffusion coefficient. Under the combined action of these two effects, the effective distribution coefficient is reduced, which is conducive to the segregation of the impurity element zinc to the liquid phase, thereby reducing the content of zinc impurity elements in the solid phase magnesium and improving the purity of the solid phase magnesium. The problem of difficulty in separating magnesium and zinc during vacuum distillation purification of magnesium is solved. The present invention has a simple structure, is easy to operate, and is easy to apply and promote.

[0036] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A metal impurity element separation device, characterized in that: include, A crucible unit, comprising a crucible and a heating furnace; the crucible contains a metal B melt, and the metal B melt contains a metal impurity element A; the separation coefficient of the metal impurity element A and the metal B is close to 1, and the distribution coefficient of A in B is less than 1; A crystallizer unit, which is located at the bottom of the crucible unit, comprises an inner sleeve, a water-cooled copper sleeve, a dummy rod, a seeding ingot and a high-purity metal ingot; the inner sleeve is installed inside the water-cooled copper sleeve, the seeding ingot is fixed on the top of the dummy rod, the seeding ingot moves up and down along the inner sleeve with the dummy rod, and a slightly convex solid / liquid interface is formed between the high-purity metal ingot and the metal B melt; A magnetic stirring unit, comprising a magnet mounted on a rotating shaft, wherein the electromagnetic force generated by the rotation of the magnet drives the metal B melt to flow in a direction parallel to the solid / liquid interface; The vacuum unit comprises a cavity, wherein the cavity is provided with an air inlet, and the crucible unit, the crystallizer unit and the magnetic stirring unit are all arranged in the vacuum cavity.

2. The metal impurity element separation device according to claim 1, characterized in that: The heating furnace is heated by resistance heating or induction coil heating.

3. The metal impurity element separation device according to claim 1, characterized in that: The material of the crucible is selected from high-purity graphite or high-purity aluminum titanate, and the material of the inner sleeve is high-purity graphite.

4. The metal impurity element separation device according to claim 1, characterized in that: The metal A is selected from zinc, and the metal B is selected from magnesium.

5. The metal impurity element separation device according to claim 1, characterized in that: The magnetic stirring unit is arranged at the bottom or both sides of the crucible unit.

6. The metal impurity element separation device according to claim 1, characterized in that: The vacuum unit also includes a high-purity gas cylinder, a pressure gauge and a vacuum pump. The high-purity gas cylinder is connected to the cavity through an air inlet, and the vacuum pump is connected to the cavity through a bellows.

7. A method for separating metal impurity elements, characterized in that: The separation is performed using the metal impurity element separation device according to any one of claims 1 to 6, comprising the following steps: S1: adding metal B containing metallic impurity element A as a raw material into a crucible, and heating the crucible under a protective atmosphere to form a melt of metal B containing metallic impurity element A; S2: Cooling water is introduced into the water-cooled copper sleeve for water-cooling circulation, and the solid / liquid interface is kept flat and slightly higher than the bottom surface of the crucible. At the same time, the magnet is rotated to make the metal B melt containing the metal impurity element A flow in a direction parallel to the solid / liquid interface; S3: pulling the dummy rod in the vertical direction to drive the seeding ingot and the high-purity metal ingot to move downward until they are completely solidified to obtain a high-purity metal ingot; S4: Take out the high-purity metal ingot, determine the cutting position according to the purity requirement, cut off the part with high metal A content on the top of the high-purity metal ingot, and obtain a high-purity metal ingot with low metal A content.

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