Method for removing iron-rich impurities in magnesium based on titanium mesh and silicon particle composite filtration

Abstract

The invention relates to the technical field of magnesium metal purification, in particular to a method for removing iron-rich impurities in magnesium based on titanium mesh and silicon particle composite filtration, which comprises the following steps: S1, cleaning and drying a graphite piece; s2, assembling the dried graphite piece, the raw material coarse magnesium, the titanium mesh and the pure silicon particles to form an assembly, and putting the assembly into a furnace body; s3, the industrial electrolytic crude magnesium is heated under the vacuum condition; and S4, after heating is stopped, the furnace is cooled to the room temperature, and the product crystal magnesium is obtained. According to the method, high-temperature vacuum sublimation is conducted on industrial electrolytic coarse magnesium under vacuum, iron atoms and iron-rich particles in magnesium steam are adsorbed and intercepted by adding a titanium mesh and silicon particle composite filter material, efficient removal of impurity iron is achieved, meanwhile, the titanium mesh and the silicon particles are high in melting point and resistant to high temperature and cannot react with the magnesium steam, and new impurities cannot be brought to a system.

Description

Technical Field

[0001] This invention relates to the field of magnesium purification technology, specifically a method for removing iron-rich impurities from magnesium based on composite filtration of titanium mesh and silicon particles. Background Technology

[0002] Magnesium and magnesium alloys possess advantages such as lightweight, high specific strength, high damping, and good biocompatibility, making them promising candidates for applications in aerospace, transportation, electronics, and biomedicine. However, the excellent properties of magnesium are highly susceptible to the influence of trace impurities. Iron at the ppm level (parts per million) significantly degrades the corrosion resistance of magnesium and magnesium alloys, hindering their large-scale application in lightweighting. This is particularly true for primary magnesium produced by electrolysis (electrolytic magnesium). During the electrolytic magnesium smelting process, brine dehydration occurs under an HCl atmosphere, and partial dissolution in the brine storage tanks and pipelines may allow iron impurities to enter the MgCl2, resulting in generally high iron content (approximately 200–500 ppm) in electrolytic magnesium. Therefore, research on advanced iron removal processes for magnesium raw materials with such high iron impurities (such as electrolytic magnesium) is crucial.

[0003] Currently, the main method for removing iron impurities from magnesium is deep refining with additives combined with static sedimentation. Additives such as sponge titanium and zirconium tetrachloride are added to the magnesium melt to react with Fe, forming insoluble intermetallic compounds (such as Fe₂Ti and FeZr₃). After static sedimentation, these compounds separate from the magnesium melt. However, the iron content in magnesium refined by this method is usually still above 20 ppm, failing to meet the 99.99% (4N) high-purity magnesium standard. Furthermore, excessive use of additives may introduce secondary pollution. Vacuum distillation, based on the difference in saturated vapor pressure between the main metal and impurity elements, achieves impurity separation during evaporation and condensation. To suppress impurity co-volatilization, traditional vacuum distillation typically controls the evaporation temperature at 650-700℃, close to the magnesium melting point. At this temperature, the magnesium evaporation rate is slow, resulting in low production efficiency. In addition, in order to improve separation efficiency, traditional vacuum distillation equipment is often equipped with multi-stage trays, which are complex in structure. The trays in the high-temperature zone are rich in impurities such as iron and silicon, while the trays in the low-temperature zone are rich in impurities such as zinc and potassium. Usually, only the middle 1 to 2 trays can yield high-purity magnesium, resulting in a generally low yield of high-purity magnesium.

[0004] In addition, there are existing technologies that use elemental silicon filter materials for gas-phase magnesium purification (such as CN110835694B), but these methods focus on using the solid solution effect of silicon with impurities such as Mn, Al, and Ca to achieve removal, and have not been designed and verified for the specific removal of high iron content impurities in magnesium.

[0005] In summary, existing methods struggle to balance deep iron removal, production efficiency, and yield. Therefore, there is an urgent need for a novel magnesium purification method that can efficiently and deeply remove iron impurities from magnesium while simultaneously achieving high production efficiency, high yield, and simplified equipment. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides a method for removing iron-rich impurities from magnesium using a composite filtration system based on titanium mesh and silicon particles.

[0007] This invention is achieved through the following technical solution: A method for removing iron-rich impurities from magnesium using a composite filtration system based on titanium mesh and silicon particles includes: S1, Clean and dry the graphite parts assembly; S2, assemble the dried graphite components, raw magnesium, titanium mesh and pure silicon particles to form an assembly and place it into the furnace body; the assembly includes a sublimation zone, a filtration zone and a crystallization zone in sequence along the magnesium vapor flow direction; the sublimation zone is provided with a graphite blind plate for supporting the raw magnesium; the filtration zone is provided with a titanium mesh and pure silicon particles stacked on the titanium mesh; and a single-hole graphite plate for condensing magnesium vapor is provided below the crystallization zone. S3, the assembly is heated under vacuum conditions so that the sublimation zone, filtration zone and crystallization zone reach and maintain the set temperature, so that the raw material crude magnesium is sublimated and the magnesium vapor is condensed and crystallized in the condensation zone after removing iron impurities in the filtration zone. S4. After heating is stopped, the furnace is cooled to room temperature to obtain the product crystalline magnesium.

[0008] Preferably, the method employs a tubular heating furnace, and the graphite component assembly is disposed within the tubular heating furnace. The graphite component assembly includes a first graphite component a1, a second graphite component a2, a graphite blind plate b1, a third graphite component a3, a fourth graphite component a4, a graphite ring b2, a fifth graphite component a5, a sixth graphite component a6, a seventh graphite component a7, an eighth graphite component a8, a first single-hole graphite plate, a ninth graphite component a9, a second single-hole graphite plate, and a tenth graphite component a10, arranged sequentially and detachably connected.

[0009] Preferably, in S1, drying includes external drying and internal drying. During external drying, the temperature is 200℃ and the time is 2h. During internal drying, the graphite parts a1, a2, a1, a3, a4, a2, a6, a7, a8, a1, a9, a2, a10, a1, a10, and a10 are assembled and placed in the furnace. The vacuum degree is below 10Pa. The temperature is first raised to 500℃ at 10℃ / min and held for 30min, then raised to 800℃ at 10℃ / min and held for 3h. After the holding period, the temperature is lowered to 500℃ at 10℃ / min and then naturally cooled.

[0010] Preferably, the raw material crude magnesium is industrial electrolytic magnesium ingot.

[0011] Preferably, in S2, the size of the crude magnesium raw material is smaller than the inner diameter of any graphite part in the graphite part assembly, but larger than the aperture of the first single-hole graphite plate.

[0012] Preferably, in S2, before assembly, the titanium mesh and pure silicon particles are acid-washed and dried; during drying, the temperature is 200℃ and the time is 2h.

[0013] Preferably, the pore size of the titanium mesh is 75~100μm.

[0014] Preferably, the diameter of the silicon particles is 10-15 mm and the stacking height is 30-50 mm.

[0015] Preferably, in S3, the vacuum degree is less than 10 Pa. During heating, the temperature of the sublimation zone is 800~900℃, the temperature of the filtration zone is 700~750℃, and the temperature of the condensation zone is 550~600℃. The heating process is as follows: each temperature zone is first heated to 500℃ and held for 30 min, then heated to the required temperature of each temperature zone and held for 3 h. After the holding period, the temperature is lowered to 500℃ and then naturally cooled to room temperature. The heating rate and cooling rate are both 10℃ / min.

[0016] The method for removing iron-rich impurities from magnesium using a composite filtration system based on titanium mesh and silicon particles results in crystalline magnesium with iron impurity content reduced to 4 ppm, aluminum impurity content reduced to 2 ppm, manganese impurity content below 1 ppm, silicon impurity content below 20 ppm, nickel impurity content below 1 ppm, and zinc impurity content below 1 ppm.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for removing iron-rich impurities from magnesium using a composite filter of titanium mesh and silicon particles. The method involves high-temperature vacuum sublimation of industrial electrolytic crude magnesium under vacuum conditions. By adding a composite filter material of titanium mesh and silicon particles, impurity atoms and particles in magnesium vapor are adsorbed and intercepted, providing an efficient and effective method for removing iron impurities from electrolytic magnesium. This is because the iron impurities in the electrolytic magnesium purification system of this invention exist in the form of solid-solid atoms, elemental substances, and compound particles. The composite filter structure of titanium mesh and silicon particles can chemically adsorb gaseous iron atoms and physically intercept solid iron-rich particles, achieving deep and efficient removal of iron impurities. Furthermore, the high melting point and high temperature resistance of titanium mesh and silicon particles prevent them from reacting with magnesium vapor and introducing new impurities into the system.

[0018] Traditional vacuum distillation methods, to avoid the co-evaporation of impurities, are mostly carried out at low temperatures of 650-700℃, resulting in slow magnesium evaporation rates and low efficiency. This invention, through thermodynamic calculations and experimental verification, significantly increases the sublimation zone temperature to 800-900℃. According to the Clausius-Clapeyron equation, the saturated vapor pressure of magnesium increases exponentially with increasing temperature. Within this temperature range, the evaporation rate can be increased by more than an order of magnitude compared to traditional methods, greatly improving production efficiency. Most importantly, this invention, at high evaporation rates, achieves deeper removal of iron impurities through the synergistic impurity removal effect of the titanium mesh and silicon particle composite filter material.

[0019] This method simplifies the purification process. In this invention, major impurities such as iron are efficiently intercepted and enriched in the filtration zone, eliminating the need for complex multi-stage tray structures. The simplified device structure allows for direct condensation of purified magnesium vapor into high-purity magnesium in the crystallization zone, resulting in a significantly higher product yield than traditional multi-stage distillation processes. The method provided by this invention can reduce the iron content in industrial electrolytic crude magnesium to 4 ppm, an effect difficult to achieve with single filter media or traditional methods. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure and graphite component arrangement of a tubular heating furnace; Figure 2 It includes a thermal diagram of the formation energy of intermetallic compounds between different filter materials and industrial electrolytic magnesium components, and a schematic diagram of the market prices of different filter materials. Figure 3 The image shows the morphology of the high-purity magnesium obtained in Example 1. Figure 4 This is a schematic diagram showing the content of deposited substances in the gas phase in the presence of titanium mesh and silicon particle filter media. Figure 5 This is a schematic diagram showing the changes in iron content in magnesium before and after purification in Comparative Examples 1, 2, and 1 of the present invention. Figure 6 This is a schematic diagram showing the macroscopic morphological changes of the titanium mesh and silicon particle filter media before and after use in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the titanium mesh under a scanning electron microscope (SEM) and the EDS results before the experiment. Figure 8 This is a schematic diagram of the scanning electron microscope (SEM) and EDS results of the titanium mesh after the experiment; Figure 9 This is a schematic diagram of the scanning electron microscope (SEM) and EDS results of the silicon particles before the experiment; Figure 10 This is a schematic diagram of the silicon particles after the experiment using a scanning electron microscope (SEM) and the EDS results. Detailed Implementation The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0021] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0022] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0023] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0024] This invention discloses a method for removing iron-rich impurities from magnesium based on a composite filtration of titanium mesh and silicon particles. The method employs a tubular heating furnace, in which a graphite component assembly is disposed. The graphite component assembly includes a first graphite component a1, a second graphite component a2, a graphite blind plate b1, a third graphite component a3, a fourth graphite component a4, a graphite ring b2, a fifth graphite component a5, a sixth graphite component a6, a seventh graphite component a7, an eighth graphite component a8, a first single-hole graphite plate, a ninth graphite component a9, a second single-hole graphite plate, and a tenth graphite component a10, arranged sequentially and detachably connected.

[0025] The internal cavity of the furnace is arranged in sequence as a sublimation zone, a filtration zone, and a crystallization zone. A graphite blind plate is set in the sublimation zone, and raw material crude magnesium is placed on the graphite blind plate. A graphite ring is set at the boundary between the sublimation zone and the filtration zone. The filtration zone is equipped with a filter assembly, which includes a titanium mesh and pure silicon particles stacked on the titanium mesh. The titanium mesh is fixed by the graphite ring. A single-hole graphite plate is set below the crystallization zone.

[0026] In this assembly, all graphite parts have a diameter of 4mm. Parts a1 to a7 are 200mm high, part a8 is 100mm high, and parts a9 to a10 are 50mm high. A graphite blind plate b1 is placed between the second graphite part a2 and the third graphite part a3. The raw material is placed in the third graphite part a3. Parts a3 to a4 are in the sublimation zone. A graphite ring b2 is used to fix a filter screen with a pore size of 75 to 100μm. Pure silicon particles with a diameter of 10 to 15mm are stacked on the titanium mesh with a stacking height of 30 to 50mm. Parts a5 to a6 form the filtration zone. The first single-hole graphite plate b3 is used as a magnesium vapor condensation base. The second single-hole graphite plate b4 is used to capture residual magnesium vapor. Parts a8 to a9 form the condensation zone. The graphite parts are connected in sequence by threads.

[0027] Using industrial electrolytic magnesium ingots as raw material for crude magnesium, the specific operating methods include: S1, Clean and dry the graphite components; wherein, drying includes external drying and internal drying. During external drying, the temperature is 200℃ and the time is 2h. During internal drying, the graphite components are assembled in the following order: first graphite component a1, second graphite component a2, graphite blind plate b1, third graphite component a3, fourth graphite component a4, graphite ring b2, fifth graphite component a5, sixth graphite component a6, seventh graphite component a7, eighth graphite component a8, first single-hole graphite plate, ninth graphite component a9, second single-hole graphite plate and tenth graphite component a10 and placed in the furnace. The vacuum degree is below 10Pa. First, the temperature is raised to 500℃ at 10℃ / min and held for 30min. Then, the temperature is raised to 800℃ at 10℃ / min and held for 3h. After the holding period, the temperature is lowered to 500℃ at 10℃ / min and then allowed to cool naturally.

[0028] S2, assemble the dried graphite components, industrial electrolytic magnesium ingots, titanium mesh and pure silicon particles into an assembly, and place the assembly into the furnace body; The assembly is a tubular structure comprising a sublimation zone, a filtration zone, and a crystallization zone. The sublimation zone is equipped with a graphite blind plate to support the industrial electrolytic magnesium ingot. The filtration zone is equipped with a titanium mesh and pure silicon particles deposited on the titanium mesh, which is fixed by a graphite ring. A single-hole graphite plate is located below the crystallization zone to condense magnesium vapor. The assembly sequence is as follows: first graphite component a1, second graphite component a2, graphite blind plate b1, industrial electrolytic magnesium ingot, third graphite component a3, fourth graphite component a4, titanium mesh, graphite ring b2, pure silicon particles, fifth graphite component a5, sixth graphite component a6, seventh graphite component a7, eighth graphite component a8, first single-hole graphite plate, ninth graphite component a9, second single-hole graphite plate, and tenth graphite component a10.

[0029] Among them, the size of the industrial electrolytic magnesium ingot is smaller than the inner diameter of the graphite part, but larger than the aperture of the single-hole graphite plate.

[0030] Before assembly, the titanium mesh and pure silicon particles are acid-washed and dried; during drying, the temperature is 200℃ and the time is 2 hours.

[0031] S3. The assembly is heated under a vacuum condition below 10 Pa to bring the sublimation zone, filtration zone, and crystallization zone to and maintain their set temperatures. This causes the industrial electrolytic crude magnesium to sublimate, and the magnesium vapor, after passing through the filtration zone to remove iron impurities, condenses and crystallizes in the condensation zone. Specifically, during heating, the temperature of the sublimation zone is 800~900℃, the temperature of the filtration zone is 700~750℃, and the temperature of the condensation zone is 550~600℃. The heating process is as follows: each temperature zone is first raised to 500℃ and held for 30 minutes, then raised to the required temperature of each zone and held for 3 hours. After the holding period, the temperature is lowered to 500℃ and then allowed to cool naturally. The heating and cooling rates are both 10℃ / min.

[0032] S4. After heating is stopped, the furnace is cooled to room temperature to obtain the product crystalline magnesium.

[0033] The present invention also discloses a crystalline magnesium obtained by the method described above for removing iron-rich impurities from magnesium using a composite filtration method based on titanium mesh and silicon particles.

[0034] This invention discloses a method for removing iron-rich impurities from magnesium using a composite filter of titanium mesh and silicon particles. Based on a vacuum sublimation process, the method involves using a composite filter material of titanium mesh and silicon particles to purify iron-containing impurities from magnesium vapor. The raw material, crude magnesium, is heated, during which metallic magnesium and some impurities co-vaporize. The magnesium vapor passes through the composite filter material of titanium mesh and silicon particles, where the iron-containing impurities are adsorbed and intercepted. After the magnesium vapor is condensed and crystallized on a graphite plate at the condenser end, low-iron, high-purity magnesium is obtained.

[0035] The vacuum tube furnace contains a sublimation zone, a filtration zone, and a crystallization zone. Magnesium vapor moves through these zones sequentially under vacuum. The sublimation zone is filled with crude magnesium and heated to 800-900°C. Electrolytic magnesium vaporizes at this high temperature, producing magnesium vapor, which carries iron-rich inclusions, including iron atoms, elemental iron, and iron compounds, into the gas phase. The filtration zone contains a titanium mesh with silicon particles deposited on it. The filtration zone temperature is 700-750°C. Magnesium vapor from the sublimation zone moves towards the filtration zone under vacuum. The magnesium vapor does not react with the filter media, but the iron atoms and iron-rich particles carried by the vapor react chemically with the filter media or are physically intercepted and deposited, thus removing iron impurities from the magnesium vapor. The purified magnesium vapor then sublimates and crystallizes in the crystallization zone at 550-600°C, yielding high-purity magnesium.

[0036] The composite filter structure composed of titanium mesh and silicon particles was chosen to achieve efficient removal of iron impurities from electrolytic magnesium because the filter material for electrolytic magnesium needs to meet the following requirements: First, the melting point of the filter material must be significantly higher than the process temperature (≥1073 K) to ensure that it does not melt or sublimate at high temperatures; second, the filter material needs to not react with magnesium vapor to avoid introducing new impurities; third, the filter material needs to have a high chemical affinity for iron impurities to form stable compounds for deep adsorption; fourth, the material should be widely available, reasonably priced, and suitable for industrial applications. Based on the above principles, a systematic evaluation of various candidate materials (Si, Mn, Ti, Cr, Cu, Zr, W, Co, Sc, etc.) was conducted. Figure 2 As shown, thermodynamic calculations indicate that Ti and Si have low formation energies with Fe, suggesting that they are prone to combining with impurities. Meanwhile, the melting points of Ti and Si are both higher than the process temperature, and they do not react with magnesium. Considering both performance and cost, titanium and silicon exhibit the best overall advantages, so Ti and Si were selected as filter materials.

[0037] The present invention also discloses a method for removing iron-rich impurities from magnesium by composite filtration based on titanium mesh and silicon particles, which reduces the iron impurity content in crystalline magnesium to 4 ppm, the aluminum impurity content to 2 ppm, the manganese impurity content to less than 1 ppm, the silicon impurity content to less than 20 ppm, the nickel impurity content to less than 1 ppm, and the zinc impurity content to less than 1 ppm.

[0038] Example 1 The raw material used is primary magnesium ingots produced by Qinghai Salt Lake Magnesium Industry Co., Ltd. using the electrolytic method (with a high iron impurity content; specific composition is shown in Table 1). The specific steps are as follows: Table 1 Chemical composition of industrial electrolytic crude magnesium ingots

[0039] Magnesium ingots are placed into a vacuum tube furnace, which is heated by silicon carbide rods. The furnace allows for independent temperature control in six zones, and a temperature field from high to low can be created within the tube by setting temperature parameters. The furnace tube is 1800 mm long and made of corundum, with a high-purity graphite inner cavity nested within. The tubes are connected by graphite tube threads, and both ends of the furnace are sealed with stainless steel flanges. The furnace can be switched between horizontal and vertical orientations via an electric push rod. The electric furnace is equipped with a rotary vane vacuum pump to evacuate the tube furnace, ensuring a system vacuum level of less than 10 Pa. A water chiller connected to the upper and lower flanges is used for circulating cooling of the tube furnace, preventing overheating.

[0040] S1, clean the graphite parts and dry them in an oven at 200℃ for 2 hours; according to... Figure 1Assemble the graphite components by connecting them sequentially with threads; place the assembled graphite assembly into a tubular furnace and seal it with a flange; evacuate to negative pressure and bake at high temperature for 3 hours at 800℃, then remove it after cooling.

[0041] S2, Before the experiment, the magnesium ingot was cut into magnesium blocks of approximately 2×4×5 cm. The total mass of the raw pure magnesium casting rod was found to be 103g. According to... Figure 1 The graphite components are arranged as follows: a graphite blind plate b1 is placed between the second graphite component a2 and the third graphite component a3, and the raw material is placed in the third graphite component a3. A graphite ring b2 is placed between the fourth graphite component a4 and the fifth graphite component a5, and the titanium mesh is fixed by the graphite ring b2. Silicon particles are deposited on the titanium mesh. A first single-hole graphite plate b3 is placed between the eighth graphite component a8 and the ninth graphite component a9 as a magnesium vapor condensation base. A second single-hole graphite plate b4 is placed between the ninth graphite component a9 and the tenth graphite component a10 to capture residual magnesium vapor. Then the graphite components are connected in sequence by threads to form an assembly.

[0042] S3. Place the assembly inside the tubular furnace and seal it with a flange. Turn on the water chiller and vacuum pump, and evacuate the furnace until the vacuum level is below 10 Pa. Turn on the temperature controller of the tubular furnace and set the temperature control program. Set the temperature of the sublimation zone (raw material placement temperature zones 1-2) to 800℃, so that the electrolytic magnesium is vaporized at high temperature to generate magnesium vapor; set the temperature of the filtration zone (filter material placement temperature zones 3-5) to 700℃, and place titanium mesh and silicon particle filter material in the filtration zone; set the temperature of the crystallization zone (temperature zone 6) to 600℃, and the purified magnesium vapor condenses and crystallizes on the crystallization plate. First, raise the temperature to 500℃ and hold for 30 minutes, then raise it to the set temperature of each temperature zone and hold for 3 hours, and then lower it to 500℃ and allow it to cool naturally. The heating and cooling rates are both 10℃ / min.

[0043] S4. After the tubular furnace is cooled to room temperature, the flange is opened, the crystalline magnesium collected from the condensation end is removed, weighed, and 98.2g of high-purity crystalline magnesium is obtained.

[0044] Figure 3 The crystalline magnesium obtained in Experimental Example 1 has the specific composition shown in Table 2, in which the iron impurity content is 4 ppm, which meets the national standard GB / T 3499-2023 Mg9999.

[0045] Table 2 Chemical composition of crystalline magnesium in Example 1

[0046] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that in step 2, only a titanium mesh is placed in the temperature transition zone.

[0047] In Comparative Example 1, following the method of Example 1, the total mass of the raw material pure magnesium casting rod was weighed to be 101.2 g. The magnesium in the crystallizer was collected and weighed, and the mass of the obtained high-purity crystalline magnesium was 99.9 g. Its specific composition is shown in Table 3. Table 3 Chemical composition of crystalline magnesium in Comparative Example 1

[0048] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that, in step 2, filter material was not placed in the temperature transition zone.

[0049] In Comparative Example 2, following the method of Example 1, the total mass of the raw material pure magnesium casting rod was weighed to be 112.4 g. The magnesium in the crystallizer was collected and weighed, and the mass of the obtained crystalline magnesium was 106.2 g. Its specific composition is shown in Table 4. Table 4 Chemical composition of crystalline magnesium in Comparative Example 2

[0050] The purity of the crystalline magnesium samples obtained in Example 1, Comparative Example 1, and Comparative Example 2 was tested after remelting, and the results are as follows: Figure 4 As shown, from Figure 4 It is known that the iron content in the raw magnesium is 258 ppm. Without the addition of titanium mesh and silicon particle filter media for purification, the iron content of impurities in the crystalline magnesium sample is 76 ppm. After filtration through titanium mesh alone, the iron content is further reduced to 28 ppm, but it still does not meet the national standard for 4N Mg (Fe < 20 ppm). After adding titanium mesh and silicon particle filter media, the iron content of impurities in the crystalline magnesium is 4 ppm, which meets the national standard for 4N Mg. In Comparative Example 1, only titanium mesh filtration was used. Although the titanium mesh can intercept some iron-rich particles, its pore size still allows some micron-sized iron-rich particles to pass through and enter the condensation end. Therefore, relying solely on titanium mesh has limited effect on removing iron impurities (including gaseous atoms and solid particles) from magnesium vapor. The iron content in Experimental Example 1 is much lower than that in the Comparative Example, indicating that the composite filtration of titanium mesh and silicon particles can effectively remove iron impurities entrained in magnesium vapor generated during vacuum sublimation of electrolytic magnesium. Other impurities in the raw magnesium have also been reduced: aluminum impurity content has decreased to 2 ppm, manganese impurity content to less than 1 ppm, silicon impurity content to less than 20 ppm, nickel impurity content to less than 1 ppm, and zinc impurity content to less than 1 ppm.

[0051] Example 1 selected titanium mesh and silicon particles as filter media, and calculated the reactivity of titanium mesh and silicon particles with iron, such as... Figure 5As shown, within the filtration zone, both titanium mesh and silicon particle filter media exhibit a strong chemical affinity for gaseous iron atoms. The equilibrium solid solubility of iron in magnesium is known to be approximately 10 ppm. Assuming that all of this dissolved iron enters the gas phase during sublimation, thermodynamic calculations indicate that in the presence of titanium or silicon, gaseous iron atoms can react with them to form stable compounds (such as FeTi and FeSi2), thereby reducing the iron content in the gas phase to a negligible level. Simultaneously, titanium and silicon do not react with magnesium vapor under the process conditions and do not introduce secondary pollution, thus demonstrating good selectivity.

[0052] Macroscopic morphology observation, scanning electron microscopy (SEM) observation, and energy-dispersive X-ray spectroscopy (EDS) analysis were performed on the titanium mesh and silicon particle filter media before and after filtration in Example 1. The results are as follows: Figures 6-10 As shown.

[0053] Figure 6 As can be seen, the surface color of the titanium mesh and silicon particle filter media changed after use, and obvious impurities were deposited, indicating that during the purification process, the titanium mesh and silicon particle filter media deposited and intercepted some impurities in the magnesium vapor. The titanium mesh and silicon particles can provide condensation and reaction sites for gaseous iron atoms. At the same time, the pores of the titanium mesh can initially intercept flocculent and large-sized inclusions, while the three-dimensional stacked structure of the silicon particles provides larger collision and deposition sites for particle inclusions, further enhancing the physical interception effect on particle inclusions.

[0054] Figures 7-8 As can be seen, the titanium mesh intercepted inclusions after use. Under high magnification, granular inclusions were found on the surface of the titanium mesh. Before use, the titanium mesh contained titanium and carbon elements, while after use, impurity elements such as Fe, Al, and Si were detected on its surface. This indicates that the titanium mesh effectively intercepted iron-rich particle inclusions and other impurity phases during the filtration process.

[0055] Figures 9-10 As can be seen, the surface of the silicon particles loses its luster after use, and a layer of deposit, appearing grayish-brown, is present. Before use, the silicon particles contained silicon, carbon, and oxygen; after use, the surface of the silicon particles showed deposited iron-rich particle inclusions. This indicates that the titanium mesh and silicon particle filter material synergistically remove iron impurities through two mechanisms: first, physically intercepting solid iron-rich particles entrained in magnesium vapor; and second, through surface chemical adsorption and reaction with iron atoms to generate stable compounds, achieving deep removal of gaseous iron atoms, thereby effectively removing iron impurities from magnesium vapor.

[0056] In summary, this invention provides a method for removing iron-rich impurities from magnesium based on a composite filter of titanium mesh and silicon particles. By improving efficiency through high-temperature sublimation and synergistic iron removal by the composite filter material of titanium mesh and silicon particles, it successfully solves the industry problem of balancing deep iron removal and production efficiency in electrolytic magnesium. Furthermore, this method is simple, has a high yield, is suitable for large-scale production, and has significant industrial application value.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for removing iron-rich impurities from magnesium using a composite filtration system based on titanium mesh and silicon particles, characterized in that, include: S1, Clean and dry the graphite parts assembly; S2, the dried graphite components, raw magnesium, titanium mesh, and pure silicon particles are assembled into an assembly, and the assembly is placed into the furnace body; the assembly is a tubular structure that sequentially includes a sublimation zone, a filtration zone, and a crystallization zone, wherein the sublimation zone is provided with a graphite blind plate for supporting the raw magnesium; the filtration zone is provided with a titanium mesh and pure silicon particles stacked on the titanium mesh, and the titanium mesh is fixed by a graphite ring; a single-hole graphite plate is provided below the crystallization zone for condensing magnesium vapor; S3, the assembly in the furnace is heated under vacuum conditions so that the sublimation zone, filtration zone and crystallization zone reach and maintain the set temperature respectively, so that the raw material crude magnesium is sublimated and the magnesium vapor is condensed and crystallized in the condensation zone after the iron impurities are removed by the filtration zone. S4. After heating is stopped, the furnace is cooled to room temperature to obtain the product crystalline magnesium.

2. The method for removing iron-rich impurities from magnesium based on composite filtration of titanium mesh and silicon particles according to claim 1, characterized in that, The method employs a tubular heating furnace, in which a graphite component assembly is disposed. The graphite component assembly includes a first graphite component a1, a second graphite component a2, a graphite blind plate b1, a third graphite component a3, a fourth graphite component a4, a graphite ring b2, a fifth graphite component a5, a sixth graphite component a6, a seventh graphite component a7, an eighth graphite component a8, a first single-hole graphite plate, a ninth graphite component a9, a second single-hole graphite plate, and a tenth graphite component a10, arranged sequentially and detachably connected.

3. The method for removing iron-rich impurities from magnesium based on composite filtration of titanium mesh and silicon particles according to claim 2, characterized in that, In S1, drying includes external drying and internal drying. During external drying, the temperature is 200℃ and the time is 2h. During internal drying, the graphite parts a1, a2, b1, a3, a4, b2, a5, a6, a7, a8, a1, a9, a2, and a10 are assembled and placed in the furnace. The vacuum degree is below 10Pa. The temperature is first raised to 500℃ at 10℃ / min and held for 30min. Then, the temperature is raised to 800℃ at 10℃ / min and held for 3h. After the holding period, the temperature is lowered to 500℃ at 10℃ / min and then naturally cooled.

4. The method for removing iron-rich impurities from magnesium based on composite filtration of titanium mesh and silicon particles according to claim 2, characterized in that, The raw material, crude magnesium, is industrial electrolytic magnesium ingot.

5. The method for removing iron-rich impurities from magnesium based on composite filtration of titanium mesh and silicon particles according to claim 2, characterized in that, In S2, the size of the raw material crude magnesium is smaller than the inner diameter of any graphite part in the graphite part assembly, but larger than the aperture of the first single-hole graphite plate.

6. The method for removing iron-rich impurities from magnesium based on composite filtration of titanium mesh and silicon particles according to claim 2, characterized in that, In S2, before assembly, the titanium mesh and pure silicon particles are acid-washed and dried; during drying, the temperature is 200℃ and the time is 2h.

7. The method for removing iron-rich impurities from magnesium based on composite filtration of titanium mesh and silicon particles according to claim 2, characterized in that, The pore size of the titanium mesh is 75~100μm.

8. The method for removing iron-rich impurities from magnesium based on composite filtration of titanium mesh and silicon particles according to claim 2, characterized in that, The diameter of the silicon particles is 10~15mm, and the stacking height is 30~50mm.

9. The method for removing iron-rich impurities from magnesium based on composite filtration of titanium mesh and silicon particles according to claim 2, characterized in that, In S3, the vacuum degree is less than 10 Pa. During heating, the temperature of the sublimation zone is 800~900℃, the temperature of the filtration zone is 700~750℃, and the temperature of the condensation zone is 550~600℃. The heating process is as follows: each temperature zone is first heated to 500℃ and held for 30 min, then heated to the required temperature of each temperature zone and held for 3 h. After the holding period, the temperature is lowered to 500℃ and then naturally cooled to room temperature. The heating rate and cooling rate are both 10℃ / min.

10. A crystalline magnesium obtained by the method for removing iron-rich impurities from magnesium using a composite filtration method based on titanium mesh and silicon particles as described in claim 9, characterized in that, The iron impurity content in the crystalline magnesium decreased to 4 ppm, the aluminum impurity content decreased to 2 ppm, the manganese impurity content was less than 1 ppm, the silicon impurity content was less than 20 ppm, the nickel impurity content was less than 1 ppm, and the zinc impurity content was less than 1 ppm.

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