A preparation method of high-purity magnesium sulfate

Abstract

The present invention discloses a method for preparing high-purity magnesium sulfate, which relates to the technical field related to the preparation of magnesium sulfate. By using a circulating grinding reactor, the ore powder is repeatedly ground during the leaching process. The acid leaching process is beneficial to the grinding of the ore powder, and at the same time, the grinding also improves the utilization rate of the ore and the reaction rate. The two promote each other. In addition, a large amount of time is saved and the process time is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field related to the preparation of magnesium sulfate, and specifically to a method for preparing high-purity magnesium sulfate. Background Art

[0002] The method for preparing high-purity magnesium sulfate mentioned in the background art is that currently, high-purity magnesium sulfate widely used in high-end electronic component materials and picture tube production is mainly prepared by dissolving concentrated sulfuric acid in water, then mixing it with magnesium-containing ore, and then purifying it. However, the magnesium sulfate prepared by this method has a low purity and a high impurity content.

[0003] In addition, during the traditional production of magnesium sulfate, in order to pursue a higher utilization rate, the ore usually needs to be finely ground to improve the leaching rate. However, the grinding time is long, which will lengthen the entire production process and increase the production cost. At the same time, sulfuric acid in the traditional method is difficult to be reused and has a high loss. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing high-purity magnesium sulfate to solve the problems in the above background that the traditional method has a long production process, sulfuric acid is difficult to be reused, and the loss is high.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A method for preparing high-purity magnesium sulfate, comprising the following steps:

[0006] S1. Ore pretreatment: First, perform magnetic separation on the forsterite ore to remove the iron components therein, then wash it with water to remove the surface impurities, and then dry the washed forsterite at 90 °C for 1.5 hours to obtain pretreated forsterite, and then crush the pretreated forsterite;

[0007] S2. Leaching: Add the pretreated forsterite powder and sulfuric acid with a concentration of 15 mol / L into a circulating grinding reaction kettle, and at the same time use the reaction kettle for water bath heating, react at a constant temperature of 180 °C for 3 h, and then filter the slurry;

[0008] S3. Primary crystallization: Transfer the above filtered liquid to a crystallization reaction kettle for primary crystallization. During primary crystallization, add magnesium sulfate heptahydrate as a crystal seed for crystallization, and then perform solid-liquid separation through vacuum filtration to obtain crude magnesium sulfate crystals. The filtrate after filtration is returned to S2 for use as acid liquid;

[0009] S4. Neutralization and hydrolysis: First, add the crude magnesium sulfate crystals into a neutralization reaction kettle, inject deionized water to dissolve them, heat them in a water bath at a constant temperature of 60 °C to obtain a crude magnesium sulfate solution, then continuously stir, and at the same time continuously add magnesium oxide to adjust the pH value of the solution;

[0010] S5. Secondary crystallization: Add the purified magnesium sulfate solution obtained from neutralization and hydrolysis into an evaporation crystallization reactor, and perform crystallization by means of vacuum isothermal evaporation. After crystallization is completed, vacuum filter the slurry to achieve solid-liquid separation and obtain a high-purity magnesium sulfate solution;

[0011] S6. Drying: Put the obtained high-purity magnesium sulfate solution into a drying oven for drying. The drying temperature is controlled at 80 °C and the drying time is 1.5 h;

[0012] The circulating grinding reactor used in the leaching step includes a reaction tank. A water bath heating tank is arranged outside the reaction tank. A circulating inner pipe is arranged inside the reaction tank. A central drive shaft penetrates through the circulating inner pipe. A drive motor is fixedly connected to the upper end of the central drive shaft. An upper opening is formed at the upper end of the circulating inner pipe. A funnel is welded around the upper opening. A first filter slot is formed at the lower end of the circulating inner pipe. A first filter screen is arranged in the first filter slot. An outer circulation coil is arranged outside the circulating inner pipe. An inner circulation coil is arranged at the upper end of the central drive shaft. The central drive shaft and the circulating inner pipe are connected by gear transmission;

[0013] An elevating grinding barrel is arranged at the lower end of the circulating inner pipe. Second filter slots are formed around the elevating grinding barrel. A second filter screen is arranged in the second filter slots. A feeding and discharging pipe is rotatably connected to the lower end of the circulating inner pipe. A slag discharge port is formed on one side of the lower end of the feeding and discharging pipe, and a liquid inlet is formed on the other side. The filtrate obtained after filtration in the primary crystallization is injected back into the reaction tank through the liquid inlet to wash the filter residue filtered in S2.

[0014] Further, a central gear is fixedly connected to the upper end of the central drive shaft. A tooth ring is fixedly connected to the inner side of the upper end of the circulating inner pipe. The central gear and the tooth ring are connected by transmission gears.

[0015] Further, ceramic grinding balls are accommodated in the elevating grinding barrel. A stirring rod is welded to the lower end of the central drive shaft.

[0016] Further, a positioning disk is fixedly connected to the lower end of the central drive shaft. The positioning disk is located below the elevating grinding barrel. A slag falling hole is formed below the elevating grinding barrel. The positioning disk blocks the lower part of the slag falling hole.

[0017] Further, a lifting rod is fixedly connected to the lower part of the elevating grinding barrel. The lifting rod penetrates through the feeding and discharging pipe. A lifting disk is fixedly connected to the lower end of the lifting rod. An electromagnetic telescopic rod is arranged between the lifting disk and the feeding and discharging pipe.

[0018] Further, when performing ore pretreatment in S2, the crushing particle size of the forsterite powder reaches 200 mesh sieve, and the obtained forsterite powder particle size is less than 75 μm. The mesh number of the first filter screen is 400 mesh, and the mesh number of the second filter screen is 800 mesh.

[0019] Further, when adding forsterite powder in S2, it is added into the funnel, and the solid-liquid ratio of the forsterite powder to sulfuric acid is 1:20.

[0020] Further, in S3, the initial crystallization temperature for the primary crystallization is 90 °C, the final crystallization temperature is 25 °C, and the crystallization time is 10 h.

[0021] Further, when performing neutralization hydrolysis in S4, magnesium oxide is gradually added, and the final pH is controlled at 6.

[0022] Further, when performing secondary crystallization in S5, the crystallization temperature is controlled at 110 °C.

[0023] Further, in S3, the initial crystallization temperature for the primary crystallization is 90 °C, the final crystallization temperature is 25 °C, and the crystallization time is 10 h.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] A method for preparing high-purity magnesium sulfate proposed by the present invention, by using a circulating grinding reaction kettle, repeatedly grinding the ore powder during the leaching process. The acid leaching process is beneficial to the grinding of the ore powder, and at the same time, the grinding also improves the utilization rate and reaction rate of the ore. The two promote each other. In addition, a large amount of time is saved, and the process time is shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a method for preparing high-purity magnesium sulfate of the present invention;

[0027] Figure 2 It is a schematic diagram of the structure of the circulating grinding reaction kettle of the present invention;

[0028] Figure 3 It is a schematic cross-sectional view of the circulating grinding reaction kettle of the present invention;

[0029] Figure 4 It is a schematic cross-sectional view of the lifting grinding barrel of the present invention;

[0030] Figure 5 It is a schematic diagram of the structure of the lifting grinding barrel of the present invention;

[0031] Figure 6 It is a schematic diagram of the gear structure of the present invention.

[0032] Reference numerals in the figure: 1, reaction tank; 2, water bath heating tank; 3, inner circulation pipe; 301, upper opening; 302, funnel; 303, first filter tank; 304, first filter screen; 305, outer circulation coil; 4, central drive shaft; 401, inner circulation coil; 402, stirring rod; 5, drive motor; 6, lifting and grinding barrel; 601, second filter tank; 602, second filter screen; 603, slag dropping hole; 604, lifting rod; 605, lifting plate; 606, electromagnetic telescopic rod; 7, positioning plate; 8, feeding and discharging pipe; 801, slag outlet; 802, liquid inlet; 9, central gear; 10, toothed ring; 11, transmission gear. Specific implementation mode

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] As Figure 1 shown, a method for preparing high-purity magnesium sulfate includes the following steps:

[0035] I. Ore pretreatment: First, the forsterite ore is subjected to magnetic separation to remove the iron components therein, and then washed with water to remove the surface impurities. Then, the washed forsterite is dried at 90 °C for 1.5 hours to obtain pretreated forsterite. Then, the pretreated forsterite is crushed to a particle size of 200 mesh sieve to obtain forsterite powder with a particle size less than 75 μm, which is convenient for subsequent separation and treatment.

[0036] II. Leaching: The pretreated forsterite powder and sulfuric acid with a concentration of 15 mol / L are added to a circulating grinding reaction kettle, and the solid-liquid ratio of the forsterite powder to sulfuric acid is 1:20. At the same time, the reaction kettle is used for water bath heating, and the reaction is carried out at a constant temperature of 180 °C for 3 h, and then the slurry is filtered.

[0037] III. Primary crystallization: The above-filtered liquid is transferred to a crystallization reaction kettle for primary crystallization, and magnesium sulfate heptahydrate is added as a seed crystal during primary crystallization.

[0038] Since the crystal structure of magnesium sulfate heptahydrate is a compound composed of sulfate ions, magnesium ions, and seven water molecules, in the crystal, magnesium ions form stable coordination bonds with sulfate ions and water molecules. This structure enables magnesium sulfate heptahydrate to effectively serve as a seed crystal during the crystallization process, helping to form uniform and complete magnesium sulfate crystals. When magnesium sulfate heptahydrate is heated, it gradually loses its crystallization water and turns into anhydrous magnesium sulfate. This process involves a complex thermal dehydration mechanism, where the bonding ability of each water molecule is different, resulting in different forms of dehydration curves at different temperatures. This thermal dehydration characteristic allows magnesium sulfate heptahydrate to effectively control the growth and morphology of crystals during the crystallization process, thereby improving the purity and quality of the final product.

[0039] The initial crystallization temperature for the first crystallization is 90 °C, and the final crystallization temperature is 25 °C. A PID controller is used to adjust according to the difference between the actual temperature and the set temperature, thereby precisely controlling the temperature during the crystallization process. The temperature of the crystallization reactor is controlled by adjusting the heating and cooling temperature control system to ensure the stability and accuracy of the temperature.

[0040] After 10 hours of crystallization, solid-liquid separation is carried out by vacuum filtration to obtain crude magnesium sulfate crystals.

[0041] IV. Neutralization and hydrolysis: Hydrolysis precipitation, as a purification method, converts soluble metals into relatively insoluble precipitates by adding precipitating agents. Usually, neutralizing agents are used to adjust the pH value of the solution to reduce the solubility of metal ions. Common alkaline neutralizing agents include CaO, MgO, caustic alkali, or mixtures of these alkaline compounds, etc. To avoid introducing new ions, here we use MgO as the neutralizing agent.

[0042] First, add the crude magnesium sulfate crystals into the neutralization reactor and inject deionized water for dissolution. Heat it in a constant temperature water bath at 60 °C to obtain a crude magnesium sulfate solution. Then, continuously stir while continuously adding magnesium oxide to adjust the pH value of the solution, thereby removing impurities such as iron, aluminum, and chromium in the crude magnesium sulfate crystals.

[0043] Since neutralization and hydrolysis at high pH will cause a large amount of Mg to be lost due to adsorption or hydrolysis in the precipitate, while neutralization and hydrolysis at low pH will result in a relatively high concentration of residual impurities in the solution, thus affecting the purity of the final product. Therefore, it is crucial to carry out neutralization and hydrolysis at an appropriate pH. Through experiments, we found that when the pH value reaches 6, the removal efficiency of most impurities is relatively high. The removal rate of Fe in the solution reaches 99.98%, the removal rate of Al reaches 99.95%, and the removal rate of Cr reaches 99.81%. However, when the pH exceeds 6, Fe and Cr will remain stable and no longer increase, but the loss rate of Mg will gradually increase, and at the same time, the removal rate of Al will instead decrease, which will cause the loss of Mg and the increase of Al impurities. Therefore, the final pH should be controlled around 6.

[0044] After the pH value of the solution is adjusted, vacuum filtration is carried out on the solution to achieve solid-liquid separation, and a relatively pure magnesium sulfate solution is obtained.

[0045] V. Secondary crystallization: Add the purified magnesium sulfate solution obtained by neutralization hydrolysis to an evaporation crystallization reactor, and carry out crystallization by means of vacuum isothermal evaporation.

[0046] The crystallization process is divided into two stages: nucleation and crystal growth. The driving force for both stages is the supersaturation of the solution, which is related to temperature, pressure, and solvent type. When the temperature is between 0-75 °C, the solubility of magnesium sulfate in water increases with the increase of temperature. When the temperature is between 75-100 °C, the solubility decreases with the increase of temperature, showing the characteristic of inverse solubility. The saturated solubility curve of a substance is fixed, while the position of the supersaturation curve is not fixed. By different crystallization methods, solutions with different degrees of saturation can be obtained. As the solvent continues to evaporate, the solution generates supersaturation and is in an unstable state, and the solute gradually precipitates from the solution.

[0047] It is known from experiments that when the crystallization temperature is between 30-70 °C, the main phase of the final product is MgSO 4 ·6H 2 O. When the crystallization temperature is 80 °C, the final product is mainly composed of MgSO4·6H2O and a small amount of MgSO 4 ·5H 2 O. When the temperature is above 100 °C, hydrated magnesium sulfate begins to be dehydrated by heat to form MgSO 4 , but when the temperature reaches above 1100 °C, MgSO 4 begins to decompose into SO 3 gas and MgO solid. Therefore, the temperature of secondary crystallization should be controlled at about 110 °C.

[0048] After crystallization is completed, vacuum filtration is carried out on the slurry to achieve solid-liquid separation, and a high-purity magnesium sulfate solution is obtained.

[0049] Drying: Put the obtained high-purity magnesium sulfate solution into a drying oven for drying. The drying temperature is controlled at 80 °C, and the drying time is 1.5 h.

[0050] The key factors affecting the leaching rate of MG include the particle fineness of ore powder and sulfuric acid and the uniformity of distribution of ore powder in sulfuric acid. The particle fineness of ore is related to the grinding time during ore pretreatment. Therefore, appropriately extending the grinding time can greatly improve the leaching rate of MG. However, extending the grinding time means extending the production process, which will undoubtedly increase the production cost. Therefore, we use a new type of circulating grinding reactor to leach forsterite powder. The circulating grinding reactor can make sulfuric acid circulate and continuously grind forsterite powder at the same time, so that grinding and acid leaching overlap in time, which not only enhances the grinding effect but also saves grinding time.

[0051] like Figure 2 - Figure 6 As shown, the circulating grinding reactor includes a reaction tank 1, a water bath heating tank 2 is arranged outside the reaction tank 1, a circulating inner tube 3 is arranged inside the reaction tank 1, a central driving shaft 4 runs through the circulating inner tube 3, and a driving motor 5 is fixedly connected to the upper end of the central driving shaft 4.

[0052] An upper opening 301 is provided at the upper end of the circulating inner tube 3, and a funnel 302 is welded around the upper opening 301. A first filter tank 30303 is provided at the lower end of the circulating inner tube 3, and a first filter screen 304 is arranged in the first filter tank 30303. An outer circulating coil 305 is arranged on the outer side of the circulating inner tube 3, and an inner circulating coil 401 is arranged on the upper end of the central driving shaft 4. A central gear 9 is fixedly connected to the upper end of the central driving shaft 4, and a gear ring 10 is fixedly connected to the inner side of the upper end of the circulating inner tube 3. The central gear 9 and the gear ring 10 are connected through a transmission gear 11. In this way, when the driving motor 5 drives the central driving shaft 4 to rotate, the inner circulation coil 401 will also rotate, thereby pushing the acid liquid inside the inner circulation tube 3 downward, and then allowing the acid liquid to enter the reaction tank 1 through the first filter tank 303, and then the central driving shaft 4 drives the inner circulation tube 3 to rotate in the opposite direction through the gear, and then the outer circulation coil 305 pushes the acid liquid upward, so that the acid liquid will cover the funnel 302 upward and enter the inner circulation tube 3 through the upper opening 301, forming a complete acid liquid flow cycle, instead of stirring, so that the acid liquid and the ore powder are fully in contact.

[0053] A lifting and grinding barrel 6 is arranged at the lower end of the circulating inner pipe 3. Second filter grooves 601 are formed around the lifting and grinding barrel 6, and second filter meshes 602 are arranged in the second filter grooves 601. Ceramic grinding balls are accommodated in the lifting and grinding barrel 6. A stirring rod 402 is welded to the lower end of the central drive shaft 4. Thus, when the inner circulation coil 401 pushes the acid solution inside the circulating inner pipe 3 downward, the acid solution will overflow into the reaction tank 1 through the first filter mesh 304. However, the mesh number of the first filter mesh 304 is 400 meshes. Therefore, the ore powder that has passed through a 200-mesh sieve during pretreatment will be blocked by the first filter mesh 304 and thus accumulate in the lifting and grinding barrel 6. At the same time, the central drive shaft 4 will also drive the stirring rod 402 to rotate, driving the ceramic grinding balls to collide and grind with each other, further finely grinding the ore powder. The finely ground ore powder can be fully mixed and reacted with the acid solution through the first filter mesh 304.

[0054] A positioning disk 7 is fixedly connected to the lower end of the central drive shaft 4. The positioning disk 7 is located below the lifting and grinding barrel 6. A slag falling hole 603 is formed below the lifting and grinding barrel 6. The positioning disk 7 blocks the lower part of the slag falling hole 603. The lower end of the circulating inner pipe 3 is rotatably connected to a feeding and discharging pipe 8. A lifting rod 604 is fixedly connected to the lower part of the lifting and grinding barrel 6. The lifting rod 604 penetrates through the feeding and discharging pipe 8, and a lifting disk 605 is fixedly connected to the lower end of the lifting rod 604. An electromagnetic telescopic rod 606 is arranged between the lifting disk 605 and the feeding and discharging pipe 8. A slag outlet 801 is formed on one side of the lower end of the feeding and discharging pipe 8, and a liquid inlet 802 is formed on the other side. Thus, when the leaching is completed, the electromagnetic telescopic rod 606 can be started to raise the lifting disk 605, thereby driving the lifting and grinding barrel 6 to rise through the lifting rod 604, so that the second filter groove 601 on the lifting and grinding barrel 6 coincides with the first filter groove 30303 on the circulating inner pipe 3. Thus, the acid solution can sequentially pass through the second filter mesh 602 and the first filter mesh 304. The mesh number of the second filter mesh 602 is 800 meshes, which will block the ground ore powder. While the lifting and grinding barrel 6 is rising, the lifting and grinding barrel 6 will also be separated from the positioning disk 7. Thus, the slag falling hole 603 below the lifting and grinding barrel 6 is opened. In this way, the slag blocked by the second filter mesh 602 can fall into the feeding and discharging pipe 8 through the slag falling hole 603. The leaching solution filtered by the second filter mesh 602 and the first filter mesh 304 can be collected for primary crystallization. The remaining acid solution after primary crystallization can be poured into the reaction tank 1 again through the liquid inlet 802. The poured acid solution can also wash the slag in the feeding and discharging pipe 8 to ensure that Mg in the slag is fully leached.

[0055] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0056] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-purity magnesium sulfate, characterized in that: The following steps are involved: S1. Ore pretreatment: First, the forsterite ore was magnetically separated to remove the iron component, and then washed with water to remove surface impurities, and then the washed forsterite was dried at 90 ° C for 1.5 hours to obtain pretreated forsterite, and then the pretreated forsterite was crushed; S2. Leaching: The pretreated forsterite powder and 15 mol / L sulfuric acid were added to a circulating grinding reactor, the solid-liquid ratio of the forsterite powder to the sulfuric acid was 1:20, and the reactor was heated in a water bath at 180 ° C for 3 h, and then the slurry was filtered; S3. Primary crystallization: The filtered liquid was transferred to a crystallization reactor for primary crystallization, magnesium sulfate heptahydrate was added as a seed crystal for crystallization, and then solid-liquid separation was performed by vacuum filtration to obtain crude magnesium sulfate crystals, and the filtrate after filtration was returned to S2 for use as an acid solution; S4. Neutralization and hydrolysis: First, crude magnesium sulfate crystals are added to a neutralization reactor, and deionized water is injected to dissolve, and heated in a water bath at a constant temperature of 60°C to obtain a crude magnesium sulfate solution, which is then continuously stirred while continuously adding magnesium oxide to adjust the pH value of the solution; S5. Secondary crystallization: The purified magnesium sulfate solution obtained by neutralization and hydrolysis was added to an evaporation crystallization reactor, and crystallization was performed by vacuum evaporation at a constant temperature. After the crystallization was completed, the slurry was vacuum filtered to achieve solid-liquid separation to obtain a high-purity magnesium sulfate solution; S6. Drying: The obtained high-purity magnesium sulfate solution is placed in a drying oven for drying. The drying temperature is controlled at 80° C. and the drying time is 1.5 h.

2. A method for preparing high-purity magnesium sulfate according to claim 1, characterized in that: The circulating grinding reactor used in the leaching step comprises a reaction tank (1), a water bath heating tank (2) is arranged outside the reaction tank (1), a circulating inner tube (3) is arranged inside the reaction tank (1), a central driving shaft (4) passes through the circulating inner tube (3), a driving motor (5) is fixedly connected to the upper end of the central driving shaft (4), an upper opening (301) is provided at the upper end of the circulating inner tube (3), a funnel (302) is welded around the upper opening (301), a first filtering tank (303) is provided at the lower end of the circulating inner tube (3), a first filtering screen (304) is arranged in the first filtering tank (303), an external circulating coil (305) is arranged outside the circulating inner tube (3), and the central driving shaft (4) is fixedly connected to the upper end of the central driving shaft (4). An inner circulation coil (401) is arranged at the upper end of the central driving shaft (4), and the central driving shaft (4) is connected to the inner circulation tube (3) via a gear transmission. A lifting grinding barrel (6) is arranged at the lower end of the inner circulation tube (3), and a second filter tank (601) is arranged around the lifting grinding barrel (6). A second filter screen (602) is arranged in the second filter tank (601). The lower end of the inner circulation tube (3) is rotatably connected to an inlet and outlet pipe (8), and a slag outlet (801) is arranged on one side of the lower end of the inlet and outlet pipe (8), and a liquid inlet (802) is arranged on the other side. The filtrate obtained by filtering after the primary crystallization is injected back into the reaction tank (1) through the liquid inlet (802) to wash the filtered residue in S2.

3. A method for preparing high-purity magnesium sulfate according to claim 2, characterized in that: The upper end of the central drive shaft (4) is fixedly connected to a central gear (9), the inner side of the upper end of the circulating inner tube (3) is fixedly connected to a gear ring (10), and the central gear (9) and the gear ring (10) are connected in transmission via a transmission gear (11).

4. A method for preparing high-purity magnesium sulfate according to claim 2, characterized in that: Ceramic grinding balls are contained in the lifting grinding barrel (6), and a stirring rod (402) is welded to the lower end of the central driving shaft (4).

5. A method for preparing high-purity magnesium sulfate according to claim 2, characterized in that: A positioning plate (7) is fixedly connected to the lower end of the central driving shaft (4), and the positioning plate (7) is located below the lifting grinding barrel (6). A slag drop hole (603) is provided below the lifting grinding barrel (6), and the positioning plate (7) is blocked below the slag drop hole (603).

6. A method for preparing high-purity magnesium sulfate according to claim 2, characterized in that: A lifting rod (604) is fixedly connected below the lifting grinding barrel (6), the lifting rod (604) passes through the inlet and outlet pipes (8), and a lifting plate (605) is fixedly connected to the lower end of the lifting rod (604), and an electromagnetic telescopic rod (606) is provided between the lifting plate (605) and the inlet and outlet pipes (8).

7. A method for preparing high-purity magnesium sulfate according to claim 2, characterized in that: When the ore is pretreated in S2, the crushing particle size of the forsterite powder reaches a 200-mesh sieve, and the particle size of the obtained forsterite powder is less than 75 μm. The mesh number of the first filter screen (304) is 400 mesh, and the mesh number of the second filter screen (602) is 800 mesh.

8. A method for preparing high-purity magnesium sulfate according to claim 1, characterized in that: In S3, the initial crystallization temperature of the first crystallization is 90° C., the final crystallization temperature is 25° C., and the crystallization time is 10 h.

9. The method for preparing high-purity magnesium sulfate according to claim 1, wherein: During the neutralization and hydrolysis in S4, magnesium oxide is gradually added to control the final pH at 6.

10. The method for preparing high-purity magnesium sulfate according to claim 1, characterized in that: When the secondary crystallization is performed in S5, the crystallization temperature is controlled at 110°C.

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