A method for preparing low-zinc crude magnesium by silicon thermal reduction

Abstract

The present invention relates to the technical field of primary magnesium smelting, and particularly to a method for preparing low-zinc crude magnesium by silicon thermal reduction. The method proposed by the present invention utilizes the characteristic that there is a large temperature difference between the impurity zinc vapor and magnesium vapor generated in the silicon thermal reduction method for magnesium smelting, so that the impurity zinc is preferentially generated and escapes first, and then is separated from magnesium. Specifically, it includes the following steps: in the reduction stage of the silicon thermal reduction method for magnesium smelting, the raw materials for silicon thermal reduction of magnesium are first heated to a first temperature range, that is, the temperature range in which zinc vapor is generated but magnesium vapor is not generated, and vacuum heat preservation is carried out on it. After the impurity zinc is preferentially generated and escapes, it is then heated to a second temperature range to generate magnesium vapor, and then low-zinc magnesium is obtained by condensation. In the silicon thermal reduction crude magnesium prepared based on the method provided by the present invention, the content reduction of impurity zinc can reach 65.2%. This method alleviates the long-standing problem of difficult separation of magnesium and zinc from the source of silicon thermal reduction method for magnesium smelting.

Description

Technical Field

[0001] The present invention belongs to the technical field of primary magnesium smelting and relates to a method for preparing low-zinc crude magnesium by silicon thermal reduction. Background Art

[0002] Magnesium is an important strategic metal in the country. Due to its excellent properties such as light weight, high specific strength, and good biocompatibility, it shows important application value and broad application prospects in the fields of aerospace, 3C products, biomedical materials, etc. In recent years, with the rapid development of the fields of aerospace, electronic information, and semiconductors, in order to improve the performance and stability of downstream magnesium-based materials, the requirements for the purity of raw materials have been continuously increasing, and the importance of magnesium purification has become increasingly prominent. However, research shows that it is difficult to separate the impurity zinc from magnesium by existing magnesium purification methods, which not only becomes a key factor restricting the upward grading of magnesium ingots, affecting the economic benefits of enterprises, but also becomes a bottleneck problem in the preparation of ultra-high purity magnesium.

[0003] Currently, the main purification methods for metallic magnesium are flux refining method and vacuum distillation method. Among them, the flux refining method removes most of the oxides in the magnesium melt by adding a refining agent. However, except for potassium and sodium, other metal impurities generally do not react with the refining agent, so it is difficult to reduce the zinc content of impurities. The vacuum distillation method utilizes the difference in the saturated vapor pressures of magnesium and impurities to separate the impurities from the main metal during the evaporation and condensation processes (US5582630A, US20030145684A1, US20210102271A1). However, since the saturated vapor pressure of zinc is close to and slightly greater than that of magnesium, during the conventional distillation process, zinc is extremely likely to volatilize into the magnesium vapor. Although some research has controlled a lower temperature at the distillation end based on the difference in the evaporation temperatures of magnesium and zinc to make zinc evaporate preferentially in large quantities, the evaporation efficiency at low temperatures is low. If a higher vacuum degree is used to improve the efficiency, it will pose a vacuum degree requirement as high as 10 - 4 Pa for the vacuum equipment (CN102766769B). There is also some research attempting to control from the condensation end, by controlling the temperature of the condensation zone and setting up multi-stage condensation trays to separate magnesium and zinc. However, usually only 1 - 2 trays can truly meet the requirements, and the yield of low-zinc high-purity magnesium is low and the cost is high (CN116377250A). Therefore, there is an urgent need to find an effective, simple and low-cost method for preparing low-zinc magnesium. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a method for preparing low-zinc crude magnesium by silicon thermal reduction, thereby solving the technical problem that in the existing magnesium purification technology, the impurity zinc cannot be separated from magnesium by a simple and effective method.

[0005] The present invention is realized through the following technical solutions:

[0006] A method for preparing low-zinc crude magnesium by silicon thermal reduction. Under the condition that the vacuum degree is less than 20 Pa, the magnesium smelting raw materials are subjected to zinc removal treatment in a controlled first temperature range to generate and escape zinc vapor; then the system temperature is raised to a second temperature range for silicon thermal reduction to generate magnesium vapor, and the low-zinc magnesium is obtained by condensation.

[0007] Preferably, the forms of zinc existing in the raw materials for magnesium smelting by the silicon thermal method are zinc oxide and elemental zinc.

[0008] Preferably, the first temperature range is 550-950 °C.

[0009] Preferably, the heat preservation time in the first temperature range is 2-5 h.

[0010] Preferably, the second temperature range is 1050-1300 °C.

[0011] Preferably, the preparation process is carried out in one set of equipment or in two sets of equipment.

[0012] Preferably, when preparing in one set of equipment, the equipment includes a vapor generation section, a first condensation zone and a second condensation zone; during preparation, the vacuum degree of the equipment is controlled below 20 Pa, the magnesium smelting raw materials are placed in the vapor generation section, the temperature of the vapor generation section is controlled in the first temperature range to condense and collect the generated zinc vapor in the first condensation zone, and then the temperature of the vapor generation section is controlled in the second temperature range to condense and collect the generated magnesium vapor in the second condensation zone.

[0013] Preferably, the first condensation zone and the second condensation zone are located on the same side or both sides of the vapor generation section.

[0014] Preferably, when preparing in two sets of equipment, both sets of equipment include an evaporation section and a condensation section; during preparation, the vacuum degree of the equipment is controlled below 20 Pa, and the temperature of the evaporation section of one set of equipment is controlled in the first temperature range to achieve zinc evaporation, and vacuum heat preservation is carried out to collect zinc vapor in the condensation section of the equipment; then the zinc-removed raw materials are put into another set of equipment, the temperature of the evaporation section of the other set of equipment is controlled in the second temperature range to generate magnesium vapor, and vacuum heat preservation is carried out to collect magnesium vapor in the condensation section of the equipment.

[0015] A kind of low-zinc crude magnesium is obtained by the above method.

[0016] At present, the preparation of high-purity magnesium mainly includes the following processes: ① preparing crude magnesium by silicon thermal reduction; ② removing most of the oxides in the crude magnesium by flux refining method to purify it into commercial primary magnesium; ③ using the primary magnesium as raw material to prepare high-purity magnesium by vacuum distillation method. However, due to the zinc saturated vapor pressure being close to and slightly greater than that of magnesium, it is difficult to separate the impurity zinc from magnesium by conventional vacuum distillation method, and the yield is low and the cost is high. To solve the above problems, in the present invention, the content of impurity zinc is reduced in the part of preparing crude magnesium by silicon thermal method, which is the pre-stage of vacuum distillation.

[0017] The silicon thermal method is the main method for preparing primary magnesium at present, and its reduction link is one of the key steps for preparing high-quality primary magnesium. In this link, the raw materials for magnesium production by silicon thermal method are placed in a reduction tank and directly heated to 1050-1300°C under the condition that the vacuum degree is less than 20 Pa, and a silicon thermal reduction reaction occurs to generate magnesium and various impurity vapors, which flow to the crystallizer under the drive of pressure difference and are condensed into crude magnesium. In the above process, due to the different reaction participation and physical properties such as saturated vapor pressure of magnesium and impurity zinc, there is a difference between the generation and condensation temperatures of magnesium and zinc vapors, and this difference can be used to find a method for separating magnesium and zinc. Specifically, in the reduction link of magnesium production by silicon thermal method, taking advantage of the large temperature difference between the generation of impurity zinc vapor and magnesium vapor, the raw materials for magnesium production by silicon thermal method are first heated to the temperature range where zinc vapor is generated but magnesium vapor is not generated, and vacuum insulation is carried out to make the impurity zinc escape preferentially, and then the temperature is raised to the temperature where magnesium vapor is generated, and the low-zinc magnesium is condensed and collected.

[0018] That is, the present invention provides a method for preparing low-zinc crude magnesium by silicon thermal reduction. Under the condition of controlling the system vacuum degree not greater than 20 Pa, the first temperature range is controlled to be 550-950°C to carry out zinc removal treatment on the raw materials for magnesium production for 2-5 h, so that zinc vapor is generated and escapes; the system temperature is raised to the second temperature range of 1050-1300°C for silicon thermal reduction to generate magnesium vapor, and the magnesium vapor is condensed and collected to obtain the low-zinc crude magnesium.

[0019] Among them, the temperature of the first temperature range is preferably 950°C, and the treatment time is preferably 2-3 h.

[0020] In the present invention, the raw materials for producing magnesium by the silicothermic process are briquettes, which are prepared through processes such as crushing, fine grinding, mixing, and briquetting of the products after calcining dolomite, ferrosilicon, and fluorite. After statistics, the briquettes generally contain 33.57 wt.% MgO, 47.20 wt.% CaO, 0.5548 wt.% SiO2, 0.2236 wt.% Al2O3, 0.3906 wt.% Fe2O3, 0.0570 wt.% MnO, 0.0013 wt.% ZnO, 0.0005 wt.% PbO, 12.9231 wt.% Si, 3.5856 wt.% Fe, 0.2952 wt.% Al, 0.0004 wt.% Zn, 0.0144 wt.% Mn, and 1.1279 wt.% CaF2.

[0021] Taking the above raw material components as input parameters, the present invention conducts thermodynamic calculations on the generation behaviors of magnesium and impurity zinc during the silicothermic reduction reaction. Considering the factors of vapor generation and gas expansion caused by temperature rise during the reaction, resulting in an increase in internal pressure, the pressure range for calculation is selected as 100 - 300 Pa, which is the pressure after vapor generation in the system. The calculation results show that the starting generation temperature of impurity zinc vapor is approximately 500 - 550 °C thermodynamically, while the starting generation temperature of magnesium vapor is approximately 950 - 1050 °C thermodynamically, with a difference of nearly 450 °C. In addition, the present invention calculates the evaporation temperatures of magnesium and zinc during vacuum distillation. The results show that within the same pressure range, the generation temperatures of magnesium and zinc vapors differ by only 100 °C thermodynamically. Compared with the relatively small difference in the generation temperatures of magnesium and zinc vapors in the vacuum distillation method, the relatively large difference in the generation temperatures of magnesium and zinc vapors in the reduction stage of the silicothermic process for producing magnesium provides a suitable separation window. Therefore, the present invention proposes to utilize the characteristic of the large difference in the generation temperatures of magnesium and zinc vapors in the silicothermic process for producing magnesium, select a temperature range of 550 - 950 °C, keep the raw materials under vacuum insulation, allow the impurity zinc vapor to escape preferentially, and then raise the temperature to the generation temperature of magnesium vapor, and condense to obtain low-zinc magnesium, thereby achieving effective separation of magnesium and zinc.

[0022] In the reduction stage of the silicothermic process for producing magnesium in the present invention, by utilizing the characteristic of the large difference in the generation temperatures of impurity zinc vapor and magnesium vapor, two temperature ranges are controlled to achieve the sequential escape of zinc vapor and magnesium vapor respectively. First, heat the raw materials for the silicothermic process for producing magnesium to the first temperature range, that is, the temperature range where zinc vapor is generated but magnesium vapor is not generated, keep it under vacuum insulation, allow the impurity zinc to escape preferentially, and then raise the temperature to the second temperature range to generate magnesium vapor, and then condense to obtain low-zinc magnesium.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] 1. The present invention utilizes the large difference in the temperature of impurity zinc vapor and magnesium vapor in silicon thermal magnesium smelting, and vacuum-insulates the raw materials for silicon thermal magnesium smelting in the temperature range where impurity zinc vapor is generated but magnesium vapor is not generated, so that impurity zinc vapor escapes from the raw materials first. The method proposed by the present invention has a significant zinc removal effect, avoiding the high content of impurity zinc from becoming a limiting factor for the upward rating of magnesium ingots, and is also expected to lay a raw material foundation for the preparation of ultra-high purity magnesium.

[0025] 2. The method proposed in the present invention can not only reduce the content of impurity zinc, but also has a certain removal effect on the moisture in the raw materials and impurities with a lower generation temperature than zinc, such as potassium, sodium and lead, and can further reduce the impurities in metallic magnesium.

[0026] 3. The method proposed in the present invention can effectively remove zinc without introducing any new impurities, thereby ensuring the purity and stability of the system.

[0027] Furthermore, the first temperature range is 550-950° C., which can effectively allow zinc vapor to escape.

[0028] Furthermore, the vacuum insulation time in the first temperature range is 2 to 5 hours, which can allow the zinc vapor to fully escape.

[0029] Furthermore, the second temperature range, i.e., the temperature range of the silicon thermal reduction reaction of the magnesium raw material in the silicon thermal process is 1050-1300° C., which can effectively generate magnesium vapor. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 This is a thermodynamically calculated diagram of the generation process of impurity zinc vapor and magnesium vapor in silicon thermal method of magnesium smelting as the temperature changes.

[0032] Figure 2 This is a comparison chart of the impurity zinc content in the crystalline magnesium obtained before and after zinc removal from the raw material for magnesium smelting by the silicon thermal method in Comparative Example 1 and Example 1 of the present invention. DETAILED DESCRIPTION

[0033] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art with respect to the present invention. In case of conflict, the definition in this specification shall prevail.

[0034] The theories or mechanisms described and disclosed in the present invention, whether right or wrong, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0035] In the present invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges shall be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0036] In the present invention, unless otherwise specified, the terms "comprising", "including", "containing", "having", or similar expressions cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0037] In the present invention, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as within the scope described in this specification.

[0038] The present invention discloses a method for preparing low-zinc crude magnesium by silicon thermal reduction. Under the condition that the vacuum degree is less than 20 Pa, the magnesium smelting raw materials are subjected to zinc removal treatment by controlling the first temperature range to generate and escape zinc vapor; the system temperature is raised to the second temperature range for silicon thermal reduction to generate magnesium vapor, and the low-zinc magnesium is obtained by condensation. In the present invention, the forms of zinc in the magnesium smelting raw materials by the silicon thermal method are zinc oxide and elemental zinc. Among them, in the specific operation process, the first temperature range is 550-950 °C, and the heat preservation time in the first temperature range is 2-5 h to fully realize the generation and escape of impurity zinc vapor, and the second temperature range is 1050-1300 °C to effectively realize the generation of magnesium vapor.

[0039] Meanwhile, for the separation of magnesium vapor and zinc vapor in the present invention, impurities zinc can be separated from magnesium in different devices. First, the raw materials for producing magnesium by the silicothermic process are vacuum-insulated in a heating device, and then the raw materials are placed in another heating device with segmented temperature control for silicothermic reduction. This method can directly achieve the effective separation of impurity zinc and magnesium. To simplify the operation process, another optional method is to separate impurity zinc from magnesium in the same heating device with segmented temperature control. By setting a temperature control program, it is divided into a vapor generation section and a condensation section. The raw materials are placed in the vapor generation section and vacuum-insulated within the temperature range where zinc vapor is generated but magnesium vapor is not. After zinc vapor is fully generated and deposited in the condensation section, the temperature is raised to the temperature at which magnesium vapor is generated, and crystalline magnesium is obtained by condensation. A small amount of zinc-rich part is removed to obtain low-zinc magnesium. To further optimize the separation effect, an impurity zinc condensation area and a low-zinc magnesium condensation area can be respectively set in the condensation section. The two condensation areas can be on the same side of the vapor generation section or on both sides of the vapor generation section, and zinc is separated by the method of two-way condensation. In addition, during the stage of generating zinc vapor, the temperature of the condensation end can be raised to allow zinc vapor to escape fully, and then it is cooled, and the temperature of the raw materials is raised to the temperature at which magnesium vapor is generated to obtain low-zinc magnesium.

[0040] In addition, based on the idea of the present invention, in the present invention, the temperature and time of heat preservation can be directly controlled to increase the time interval between the generation and condensation of impurity zinc vapor and magnesium vapor to achieve their separation. At the same time, when it is inconvenient to control the temperature, the separation of the two can be achieved by controlling the pressure in the system to increase the temperature at which magnesium vapor is generated, so that at the conventional temperature of the silicothermic reduction reaction, magnesium vapor is not generated or is generated in a small amount, but zinc vapor is fully and preferentially generated and escapes.

[0041] The following further elaborates the present invention with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0042] Conventional instrument equipment in the art is used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0043] Example 1

[0044] (1) Weigh about 240 g of the raw materials for producing magnesium by the silicothermic process, put them into a closed container, and evacuate to below 20 Pa. Heat through a heating device to a temperature range where impurity zinc vapor is generated but magnesium vapor is not, and keep it under vacuum insulation to let the impurity zinc vapor escape.

[0045] (2) Load the raw materials for producing magnesium by the silicothermic process after zinc removal treatment into a three-stage temperature-controlled heating device, and evacuate to below 20 Pa. Heat the raw materials for producing magnesium by the silicothermic process to 1250 - 1300 °C to carry out the silicothermic reduction reaction and obtain low-zinc magnesium.

[0046] Taking the statistically analyzed composition of the raw materials for producing magnesium by the silicothermic process as input parameters, the generation processes of magnesium and impurity zinc during the silicothermic reduction reaction with temperature change are obtained through thermodynamic calculations. From Figure 1 It can be seen that during the process of producing magnesium by the silicothermic process, the generation temperature of impurity zinc vapor is 500 - 550 °C, and the generation temperature of magnesium vapor is about 950 - 1000 °C. It can be known that carrying out vacuum insulation in this temperature range can make the impurity zinc vapor preferentially escape from the raw materials. Then heating to the magnesium vapor generation temperature can obtain low-zinc magnesium.

[0047] In this embodiment, the zinc removal temperature of the raw materials is 950 °C, and the insulation time is 5 hours.

[0048] According to the above method, after the raw materials after zinc removal treatment are subjected to silicothermic reduction, 41.1 g of low-zinc magnesium is obtained.

[0049] Analyzing the content of each element in pure magnesium, the magnesium purity in the low-zinc magnesium prepared in this embodiment reaches 99.991%, the impurity zinc content is 8 ppm, and the content results of impurity elements are shown in Table 1.

[0050] Table 1

[0051]

[0052] Example 2

[0053] Different from Example 1, in this embodiment, the zinc removal temperature of the raw materials for producing magnesium by the silicothermic process is set to 900 °C.

[0054] After the raw materials after zinc removal treatment are subjected to silicothermic reduction, 41.1 g of low-zinc magnesium is obtained.

[0055] Analyzing the content of each element in pure magnesium, the magnesium purity in the low-zinc magnesium prepared in this embodiment reaches 99.987%, the impurity zinc content is 19 ppm, and the content results of the remaining impurity elements are shown in Table 2.

[0056] Table 2

[0057]

[0058] Example 3

[0059] Different from Example 1, in this example, the zinc removal holding time of the raw materials for magnesium smelting by the silicothermic process is set to 2 hours.

[0060] After the raw materials are subjected to zinc removal treatment and then silicothermically reduced, 40.8 g of low-zinc magnesium is obtained.

[0061] Analyzing the content of each element in the analytical pure magnesium, the magnesium purity in the low-zinc magnesium prepared in this example reaches 99.990%, the impurity zinc content is 8 ppm, and the content results of the remaining impurity elements are shown in Table 3.

[0062] Table 3

[0063]

[0064]

[0065] Example 4

[0066] Different from Example 1, in this example, the impurity zinc is separated from magnesium in the same segmented temperature-controlled heating device.

[0067] The segmented temperature-controlled heating device is divided into a steam generation section and a low-zinc magnesium collection section, and the raw materials are placed in the steam generation section. When holding at a temperature range where zinc vapor is generated but magnesium vapor is not generated, the low-zinc magnesium collection section is heated, so that the zinc vapor fully escapes to the non-collection low-temperature area, and then the low-zinc magnesium collection section is cooled, and the steam generation section is heated to the magnesium vapor generation temperature to obtain low-zinc magnesium.

[0068] Example 5

[0069] Different from Example 1, in this example, the impurity zinc is separated from magnesium in the same segmented temperature-controlled heating device.

[0070] The segmented temperature-controlled heating device is divided into a steam generation section and a condensation section, and the raw materials are placed in the steam generation section. Condensation sections are arranged on both the upper and lower sides of the steam generation section, with one side being the impurity zinc condensation area and the other side being the low-zinc magnesium collection area. When holding at a temperature range where zinc vapor is generated but magnesium vapor is not generated, the impurity zinc condensation area is set to a low temperature, and vacuum is pumped from this direction to condense the zinc vapor in the impurity zinc condensation area. After the zinc vapor is fully condensed, the low-zinc magnesium collection area is set to a low-temperature area, and vacuum is pumped from this direction to obtain low-zinc magnesium, that is, zinc is separated from magnesium by the method of two-way condensation.

[0071] Example 6

[0072] Different from Example 1, in this example, the impurity zinc is separated from magnesium in the same segmented temperature-controlled heating device.

[0073] The segmented temperature-controlled heating device is divided into a steam generation section and a condensation section, and the raw material is placed in the steam generation section. An impurity zinc condensation area and a low zinc-magnesium condensation area are respectively arranged in the condensation section, and the two condensation areas are on the same side of the steam generation section. When the temperature is raised to the temperature range where zinc vapor is generated but magnesium vapor is not generated and kept warm, the zinc vapor is condensed in the impurity zinc condensation area after being generated, and when the temperature is raised to the temperature where magnesium vapor is generated, low zinc-magnesium is collected in the low zinc-magnesium condensation area.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that when the temperature is lower than the temperature at which impurity zinc vapor is generated, the magnesium production raw materials by the silicothermic process are kept under vacuum at a temperature of 200 °C for 2 hours.

[0076] After the magnesium production raw materials by the silicothermic process are subjected to silicothermic reduction, 42.3 g of crystalline magnesium is obtained.

[0077] Analyzing the contents of various elements in the pure magnesium, the magnesium purity in the crystalline magnesium prepared in this example reaches 99.981%, the impurity zinc content is 20 ppm, and the content results of the remaining impurity elements are shown in Table 4.

[0078] Table 4

[0079]

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that when the temperature is lower than the temperature at which impurity zinc vapor is generated, the magnesium production raw materials by the silicothermic process are kept under vacuum at a temperature of 500 °C for 5 hours.

[0082] After the magnesium production raw materials by the silicothermic process are subjected to silicothermic reduction, 42.7 g of crystalline magnesium is obtained.

[0083] Analyzing the contents of various elements in the pure magnesium, the magnesium purity in the crystalline magnesium prepared in this example is 99.983%, the impurity zinc content is 23 ppm, and the content results of the remaining impurity elements are shown in Table 5.

[0084] Table 5

[0085]

[0086] After remelting the crystalline magnesium in Example 1 and the crystalline magnesium in Comparative Example 1 and performing a purity test, the impurity zinc content can be obtained, as Figure 2 shown. After vacuum insulation at a temperature lower than the temperature at which impurity zinc vapor is generated, the impurity zinc content in the crystalline magnesium is 23 ppm. After vacuum insulation in the temperature range where impurity zinc vapor is generated but magnesium vapor is not generated, the impurity zinc in the crystalline magnesium is reduced to 8 ppm, and the reduction rate is 65.2%. Therefore, the zinc removal method provided by the present invention can effectively separate impurity zinc from magnesium.

[0087] By comparing the contents of impurity sodium and lead in Comparative Example 1 and Comparative Example 1, it can be found that the contents of both have decreased. It can be seen that the present method can not only effectively separate impurity zinc and magnesium, but also has a certain removal effect on moisture in the raw material and impurities such as potassium, sodium, and lead whose production temperature is lower than that of zinc.

[0088] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing low-zinc crude magnesium by silicon thermal reduction, characterized in that, Under the condition that the vacuum degree is less than 20 Pa, control the first temperature range to carry out zinc removal treatment on the magnesium smelting raw materials, so that zinc vapor is generated and escapes; raise the system temperature to the second temperature range for silicothermic reduction to generate magnesium vapor, and condense to obtain the low-zinc crude magnesium; The first temperature range is 550 - 950 °C; The second temperature range is 1050 - 1300 °C; The preparation process is carried out in one set of equipment or two sets of equipment; When prepared in one set of equipment, the equipment includes a vapor generation section, a first condensation zone, and a second condensation zone; during preparation, control the equipment vacuum degree to be below 20 Pa, place the magnesium smelting raw materials in the vapor generation section, control the temperature of the vapor generation section to be in the first temperature range, so that the generated zinc vapor is condensed and collected in the first condensation zone, and then control the temperature of the vapor generation section to be in the second temperature range, so that the generated magnesium vapor is condensed and collected in the second condensation zone; When prepared in two sets of equipment, both sets of equipment include an evaporation section and a condensation section; during preparation, control the equipment vacuum degree to be below 20 Pa, and control the temperature of the evaporation section of one set of equipment to be in the first temperature range to realize the generation of zinc vapor, keep it under vacuum, and realize the collection of zinc vapor in the condensation section of the equipment; then put the zinc-removed raw materials into another set of equipment, control the temperature of the evaporation section of the other set of equipment to be in the second temperature range to realize the generation of magnesium vapor, keep it under vacuum, and realize the collection of magnesium vapor in the condensation section of the equipment.

2. The method for preparing low-zinc crude magnesium by silicon thermal reduction according to claim 1, characterized in that, The forms of zinc existing in the magnesium smelting raw materials by the silicothermic method are zinc oxide and elemental zinc.

3. A method for preparing low-zinc crude magnesium by silicon thermal reduction according to claim 1, characterized in that, The heat preservation time in the first temperature range is 2 - 5 h.

4. A method for preparing low-zinc crude magnesium by silicon thermal reduction according to claim 1, characterized in that, The first condensation zone and the second condensation zone are located on the same side or both sides of the vapor generation section.

5. A low-zinc crude magnesium, characterized in that, Obtained by the method according to any one of claims 1 - 4.

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