CN116103515A - CaO filter material-based low-cost and high-efficiency aluminum removal method for smelting magnesium by silicothermic process - Google Patents

CaO filter material-based low-cost and high-efficiency aluminum removal method for smelting magnesium by silicothermic process Download PDF

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CN116103515A
CN116103515A CN202310084209.XA CN202310084209A CN116103515A CN 116103515 A CN116103515 A CN 116103515A CN 202310084209 A CN202310084209 A CN 202310084209A CN 116103515 A CN116103515 A CN 116103515A
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cao
magnesium
aluminum
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单智伟
郑芮
杨博
杨唯一
王鹏飞
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Xian Jiaotong University
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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Abstract

The invention relates to the technical field of original magnesium smelting, in particular to a low-cost and high-efficiency aluminum removal method for silicon smelting magnesium based on CaO filter materials. The aluminum removal method is to use CaO filter materials for purifying and removing aluminum-containing impurities in magnesium vapor, and comprises the following steps: heating raw materials for smelting magnesium by a silicothermic process, reacting to generate magnesium vapor, removing aluminum-containing impurities from the magnesium vapor through the CaO filter material, and condensing and crystallizing to obtain low-aluminum high-purity magnesium. The filter material and the method provided by the invention have low cost, can be directly grafted with the existing main production method of metal magnesium by a silicothermic method, can greatly reduce the impurity aluminum content in crude magnesium by adopting the CaO filter material, can reach 90 percent in the reduction ratio, have low preparation cost, and can be widely applied to magnesium vapor purification of silicothermic magnesium to remove aluminum-containing impurities.

Description

CaO filter material-based low-cost and high-efficiency aluminum removal method for smelting magnesium by silicothermic process
Technical Field
The invention relates to the technical field of original magnesium smelting, in particular to a low-cost and high-efficiency aluminum removal method for silicon smelting magnesium based on CaO filter materials.
Background
The metal magnesium has good biocompatibility due to the characteristics of high specific strength, strong reducibility and the like, and has good application prospect in the fields of light weight of rail transit, strategic metal reducing agents, degradable implant materials and the like. However, if the upstream metal magnesium has high impurity content and large fluctuation, the performance of the downstream magnesium-based material is often remarkably deteriorated, so that the application of the upstream metal magnesium is far from expectations. Taking impurity aluminum as an example, in the application aspect of the degradable implant material, aluminum has neurotoxicity and can cause Alzheimer disease; in the aspect of serving as a reducing agent for preparing the electronic grade high-purity titanium, aluminum impurities in the high-purity titanium sponge are mainly transmitted to magnesium metal, and are difficult to remove in the subsequent process.
At present, the main production mode of commercial metal raw magnesium is a silicothermic reduction method, which mainly refers to calcining dolomite (CaO, mgO), ferrosilicon (Si (Fe)), fluorite (CaF) 2 ) The mixed materials react to generate magnesium vapor under the vacuum condition of about 1200 ℃ and about 20Pa, and then the magnesium vapor is condensed to form crystalline magnesium. However, the raw magnesium produced by this method suffers from high impurity aluminum content and large fluctuation.
Early scholars have proposed high impurity aluminum content, large fluctuation and fluorite (CaF) 2 ) Regarding the formation of Al F, and gives a measure of "raw metal magnesium having an ultra-low aluminum impurity content can be produced by reducing or even discarding fluorite powder". Although effective, fluorite is a catalyst commonly used in the silicothermic smelting of magnesium, which can significantly improve the reaction efficiency and yield per unit production cycle, and the method of raw material control is not easy to operate. In addition, there is a vapor deposition method (CN 110724825B, CN110835694B, CN 110835695B) of purifying magnesium by using a filter material to assist in removing impurities, but the filter material is generally metal or semi-metal, which has high cost in mass production and application, and mainly removes aluminum impurities in the form of simple substance, while aluminum impurities exist in other forms in the silicothermic process.
In view of this, there is a need to find a simple, efficient way to remove aluminum without affecting yield at low cost.
Disclosure of Invention
In order to achieve the purpose, the invention provides a low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on CaO filter materials. The aluminum removal method can be directly connected with a silicon-heat magnesium smelting production process, and magnesium vapor generated by silicon heat reduction is filtered through a CaO filter material or a filter structure containing a CaO coating, and aluminum-containing impurities in the magnesium vapor are purified and removed.
The invention aims to provide a low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on CaO filter materials.
According to the purpose of the invention, the low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process is to use CaO filter materials for purifying and removing aluminum-containing impurities in magnesium vapor, and comprises the following steps of: heating raw materials for smelting magnesium by a silicothermic process, reacting to generate magnesium vapor, removing aluminum-containing impurities from the magnesium vapor through the CaO filter material, and condensing and crystallizing to obtain high-purity magnesium.
In the invention, the raw materials for silicon and heat smelting magnesium are pellets, which contain 28.53wt.% MgO, 40.12wt.% CaO and 0.62wt.% SiO 2 A l of 0.16wt.% 2 O 3 0.28wt.% Fe 2 O 3 0.05wt.% MnO, 0.0005wt.% PbO, 0.001wt.% ZnO, 21.94% Si, 6.14wt.% Fe, 0.51wt.% A l, 0.276wt.% Ca, 0.023wt.% Mn, 0.0006wt.% Zn, 0.0009wt.% Pb, 0.005wt.% P, 1.32wt.% CaF 2 0.014wt.% CaCO 3 . As is evident from thermodynamic calculations of the pellets of the above components, the main products of the gas phase at 1250℃are Mg, si O, ca, al F (aluminum monofluoride, CAS No. 13595-82-9), caF when the hydrothermal reduction reaction occurs 2 Mn, si, fe, etc.; and the gas phase substance is expected to form stable compounds or simple substances, such as Ca-Si-O, ca-A l-Si-O, ca-A l-F-O, fe, mn and the like, in the gradual cooling and condensing process.
As for aluminum-containing impurities, the existence form of the main aluminum-containing impurities in high-temperature magnesium vapor generated by the reduction of magnesium by a silicothermic method is Al F (g), and therefore, the Ca-A l-F-O high-aluminum sediment phase can be obtained by adopting Ca-O-containing substances to induce Al F codeposition, and Al F (g) in the magnesium vapor is removed. The invention selects CaO as the filter material, calculates the reactivity between CaO and A.sub.l.F (g),it can be seen that CaO and A.sub.l.F (g) are both significantly reduced in the range 1250-1050℃and the reduction is greatest at 1050 ℃; the invention also calculates the condition of CaO after adding the entire system of silicon-heat magnesium-smelting and impurity-magnesium-containing steam, and can be seen that CaO obviously consumes A/F (g) in the gas phase and forms a substance Ca 12 A l 14 F 2 O 32 . Although a large amount of Ca vapor is generated in the system by using the CaO filter material, the Ca vapor can be deposited and removed in the subsequent vapor continuous cooling process, can be removed in a large amount in the refining link of the magnesium smelting by the silicothermic process, and can not bring impurity influence to the crystalline magnesium system.
The CaO filter material-based low-cost and high-efficiency aluminum removal method for magnesium smelting by a silicothermic process is preferable, and the aluminum-containing impurity is A l F.
According to the low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on the CaO filter materials, preferably, the working temperature of the CaO filter materials is 600-1250 ℃; further preferably, the operating temperature of the CaO filter is 1050 to 1250 ℃.
In the low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on the CaO filter material, preferably, the heating temperature of the raw material for smelting magnesium by the silicothermic process is controlled to be 1250-1300 ℃.
In the low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on the CaO filter material, preferably, the CaO filter material adopts CaO raw materials to be naturally filled or compacted on the movement path of the magnesium vapor, and the CaO raw materials are any one of blocks, balls, powder and flakes; when the CaO raw material is in a block shape, the diameter is 8-20 mm; when the CaO raw material is spherical, the diameter is 0.3-8 mm; when the CaO raw material is in powder form, the grain diameter is 1-300 mu m; when the CaO raw material is in a sheet shape, the thickness is 0.1-5 mm.
In the low-cost and high-efficiency aluminum removal method for silicothermic magnesium smelting based on the CaO filter, preferably, the CaO filter is a carrier containing CaO, and the carrier is arranged on the movement path of the magnesium vapor.
The low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on the CaO filter material is characterized in that the CaO filter material is coated or immersed on a carrier, and comprises the following steps:
the saidThe carrier being immersed in Ca (OH) 2 In suspension, so that the carrier is coated or impregnated with Ca (OH) 2 A coating;
coating the inside with Ca (OH) 2 Is taken out, dried and thermally decomposed to obtain the product.
The CaO filter material-based low-cost and high-efficiency aluminum removal method for magnesium smelting by a silicothermic process is preferable, wherein the drying temperature is 190-1200 ℃, and the drying time is 0.5-2 h.
The Ca (OH) is preferable in the low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on CaO filter materials 2 The mass percentage of the suspension is 1-50 wt%.
Since the reaction of CaO solid and A l F (g) is gas-solid reaction, the larger the specific surface area of CaO solid is, the larger the contact surface of CaO solid and A l F (g) is, the larger the reaction degree is, and the higher the utilization rate of CaO is; in order to increase the specific surface area of CaO and improve the utilization rate of CaO, a CaO coating can be coated on the filtering mechanism, and the purpose is to arrange the CaO filter material on the path of magnesium vapor, thereby purifying and removing aluminum-containing impurities in the magnesium vapor.
In the present invention, ca (OH) 2 The suspension can be prepared by dissolving CaO and water, or Ca (OH) with the mass percentage of 1-50 wt.% obtained by other modes 2 And (3) suspending liquid.
The beneficial effects of the invention are as follows:
1. the impurity aluminum in the silicon-thermal magnesium smelting system mainly exists in the forms of A l and A l F (aluminum monofluoride) gas, and the CaO filter material can remove A l and A l F gas in a targeted manner and form high-aluminum Ca 12 Al 14 F 2 O 32 The sediment has obvious aluminum removal effect; meanwhile, the action temperature of the CaO filter material is obviously higher than the deposition temperature of magnesium vapor, so that the deposition of magnesium vapor can not be caused when the CaO filter material is used for fully capturing impurity aluminum, and the deposition distance of aluminum and magnesium can be obviously pulled apart to separate the aluminum and the magnesium; the CaO filter material does not react with magnesium vapor, and the purification efficiency is good;
2. the CaO filter material can also play roles in providing impurity condensation heterogeneity nuclear sites, physically intercepting dust particles and the like on the basis of high-efficiency aluminum removal, and can further reduce impurities in magnesium vapor;
3. the CaO filter material is a mineral filter material and is a main component in the raw materials for smelting magnesium by a silicothermic process, and is rich and easy to obtain and low in cost;
4. the invention utilizes Ca (OH) 2 The method for preparing the CaO coating by soaking the filtering structure in the suspension and carrying out reheat decomposition can further increase the specific surface area of CaO serving as a filtering material and improve the utilization rate of the CaO, thereby saving the CaO consumption and further reducing the cost.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of thermodynamic calculation reaction conditions of the Al F and excessive CaO filter materials in magnesium vapor at different temperatures;
FIG. 2 is a diagram showing the change of the composition of the thermodynamically calculated gas phase and condensed matter before and after CaO filter materials are added into the gas phase system for silicon heat smelting magnesium of the present invention;
FIG. 3 is a graph showing the change of magnesium purity before and after CaO filter addition in comparative example 1 and example 1 of the present invention;
FIG. 4 is a schematic diagram showing macroscopic morphology change of CaO filter materials before and after use in example 1 of the present invention;
FIG. 5 is a schematic view of a Scanning Electron Microscope (SEM) before and after the CaO filter of example 1
FIG. 6 is a graph showing the energy spectrum dispersion X-ray spectrum (EDS) before and after the CaO filter is used in example 1 of the present invention;
FIG. 7 is a schematic view of X-ray diffraction (XRD) of CaO filter in example 1 of the invention, before and after use.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, based on the examples herein, which are within the scope of the invention as defined by the claims, will be within the scope of the invention as defined by the claims.
Examples
Based on the attached figures 1-7, the embodiment provides a low-cost and high-efficiency aluminum removal method for silicothermic magnesium smelting based on CaO filter materials, which is based on the silicothermic magnesium smelting process, and uses the CaO filter materials for purifying and removing aluminum-containing impurities in magnesium vapor, and comprises the following steps: heating raw materials for smelting magnesium by a silicothermic process, reacting to generate magnesium vapor, removing aluminum-containing impurities from the magnesium vapor through the CaO filter material, and condensing and crystallizing to obtain low-aluminum high-purity magnesium.
In this embodiment, the silicothermic magnesium production process comprises the following steps: placing the raw materials for smelting magnesium by a silicothermic process into a closed container, and vacuumizing the closed container to ensure that the vacuum degree of the closed container is 10Pa; heating the closed container to remove aluminum-containing impurities from magnesium vapor through CaO filter materials arranged in the closed container, and crystallizing to obtain low-aluminum high-purity magnesium.
In the embodiment, a reaction zone, a temperature transition zone and a crystallization zone are sequentially arranged in a closed container in the silicon thermal magnesium smelting process, the reaction zone, the temperature transition zone and the crystallization zone form a channel for magnesium vapor to move, and the movement path of the magnesium vapor under the vacuum effect is sequentially the reaction zone, the temperature transition zone and the crystallization zone;
wherein, the reaction zone is used for filling raw materials for smelting magnesium by a silicon thermal method, and the raw materials for smelting magnesium by the silicon thermal method filled in the reaction zone are heated, so that magnesium vapor is generated by the reaction of the raw materials at 1250-1300 ℃, and the magnesium vapor contains aluminum impurities, and the main existence form of the aluminum element is A l F;
the CaO filter material is arranged in the temperature transition zone, magnesium vapor generated by the reaction in the reaction zone moves to the temperature transition zone under the vacuum effect, and the magnesium vapor contacts with the CaO filter material, so that aluminum element impurities in the magnesium vapor are removed, and the purified magnesium vapor is purified;
and arranging a crystallizer in the crystallization zone, and sublimating and crystallizing the purified magnesium vapor in the crystallization zone to obtain high-purity magnesium solid.
In the embodiment, the temperature of the magnesium smelting process by a silicon thermal method is controlled to be 200-1300 ℃, and the three sections corresponding to the reaction zone, the temperature transition zone and the crystallization zone are respectively controlled;
the first section is heated corresponding to the reaction zone, and the temperature of the first section is controlled to be 1250-1300 ℃; because the raw materials in the reaction zone absorb heat during reaction, the temperature control in the first section is mainly heat increment, namely, heat energy is provided for the reaction zone, so that the raw materials react at 1250-1300 ℃ to generate magnesium vapor;
the second section heats the temperature transition zone, and the temperature of the second section is controlled to be 600-1250 ℃; the temperature control of the second section is mainly heat increment and heat dissipation in cooperation, and because the initial temperature of magnesium vapor generated by the reaction is higher than 600-1250 ℃, the magnesium vapor needs to be properly cooled in a temperature transition zone, and the temperature of the magnesium vapor is adjusted to the working temperature of the CaO filter material for purification; however, when the temperature of the magnesium vapor in the temperature transition zone is too high in heat dissipation, so that the temperature of the magnesium vapor is too low, the risk of crystallization of the magnesium vapor in the temperature transition zone exists, and the temperature transition zone needs to be heated at the moment; the purpose of the method is to adjust the temperature of a temperature transition zone, especially adjust the CaO filter in the temperature transition zone in the optimal working temperature, and purify and remove aluminum element impurities in magnesium vapor to obtain purified magnesium vapor.
The third section is used for controlling the temperature of the crystallization area, and the temperature of the third section is controlled to be 200-600 ℃; the temperature control of the third section is mainly heat dissipation, and a heat exchanger is arranged in the crystallization area, so that heat dissipation of magnesium vapor can be promoted, and the magnesium vapor is sublimated and crystallized into solid; for heat dissipation in cooperation with purified magnesium vapor, the heat exchanger can be a water-cooled heat exchanger; in order to allow the magnesium vapour to sublimate and crystallize from the reaction zone through the temperature transition zone and in the crystallization zone, an alternative is to connect a vacuum to the side of the crystallization zone remote from the temperature transition zone.
In some examples, the aluminum-containing impurity is ai; in the purification and removal of magnesium vapor, the CaO filter material not only can remove A l element, but also can remove the A/F formed by A l element and F element, so that A l element and F element in magnesium products are synchronously reduced.
In some examples, the CaO filter material has a working temperature of 600-1250 ℃ for removing aluminum-containing impurities; in order to ensure that the CaO filter is at an optimal working temperature, an alternative way is to arrange the CaO filter in the temperature transition zone to purify and remove aluminum-containing impurities in the magnesium vapor.
In some examples, the CaO filter material has a working temperature of 1050-1250 ℃ for removing aluminum-containing impurities; in order to ensure that the CaO filter is purified at the optimum operating temperature, it is an option to place the CaO filter in a region of 1050-1250℃in the temperature transition zone, depending on the temperature distribution region in the temperature transition zone.
In some examples, the temperature of the heating is controlled to 1250-1300 ℃; an alternative way is to heat the reaction zone so that the temperature of the reaction zone is controlled to 1250-1300 ℃ and magnesium vapor with corresponding temperature is generated, and the magnesium vapor is properly and reasonably cooled, so that the temperature transition zone can meet the requirements of the working temperature for removing aluminum-containing impurities and the working temperature for crystallizing in the crystallization zone, and the temperature transition zone and the crystallization zone are not required to be heated and heated.
In some examples, the above CaO filter material is disposed on a movement path of magnesium vapor by natural filling or compaction using a CaO raw material, where the CaO raw material is any one of a block, a sphere, a powder, and a sheet; in an alternative mode, the closed container is horizontally placed, and a reaction zone, a temperature transition zone and a crystallization zone are sequentially arranged in the closed container in the horizontal direction, and CaO filter materials are filled in the temperature transition zone, so that the dead weight effect of the CaO filter materials and the movement path of magnesium vapor form a shearing effect, and the CaO filter materials are fully contacted with the magnesium vapor to purify and remove aluminum-containing impurities; in another alternative, the CaO feedstock is placed in the temperature transition zone of the closed vessel in a tangible structure by compacting it into a solid but microporous cylindrical shape, a hollow toroidal cylindrical shape, a hollow and porous toroidal cylindrical shape, a hollow square cylindrical shape, a hollow and porous square cylindrical shape, a hollow round cake shape, a hollow and porous round cake shape, a hollow square cake shape, a hollow and porous square cake shape, or other tangible structure, and stacked in the temperature transition zone.
In some examples, when the CaO feedstock is in the form of blocks, the diameter is 8 to 20mm.
In some examples, the diameter is 0.3 to 8mm when the CaO feedstock is spherical.
In some examples, when the CaO feedstock is in powder form, the particle size is 1 to 300 μm.
In some examples, when the CaO feedstock is in the form of a sheet, the thickness is between 0.1 and 5mm.
In some examples, the CaO filter is a CaO carrier including CaO, the CaO carrier being disposed on a movement path of the magnesium vapor; in order to facilitate the temperature of the temperature control zone or remove other impurities in magnesium vapor, a filter screen and other structures with special functions can be arranged in the temperature transition zone, and the structures with special functions can be used as a carrier of CaO; one way is to fill CaO feedstock into the passages of the carrier that allow magnesium vapor to pass through to contact the magnesium vapor to remove aluminum-containing impurities; another way is to coat or impregnate the surface of the carrier with CaO component, so that the CaO coating layer is formed on the surface of the carrier and used as a filter material for removing aluminum-containing impurities.
In some examples, the CaO carrier is formed by coating or impregnating CaO on a carrier, and the step of coating or impregnating CaO on the carrier includes:
immersing the support in Ca (OH) 2 In suspension to coat or impregnate the carrier with Ca (OH) 2 A coating;
coating the inside with Ca (OH) 2 And (3) taking out the carrier, drying and thermally decomposing to obtain the carrier coated or immersed with CaO.
In some examples, the above-described drying temperature is 190-1200 ℃ and the drying time is 0.5-2 hours.
In some examples, the drying is not limited to drying in an oven, but may be performed in other environments satisfying a temperature of 190-1200deg.C, such as a temperature transition region operating at a drying temperature range, where Ca (OH) may be applied 2 Is placed in a temperature transition zone, and according to the requirements of the production process of magnesium smelting by a silicothermic process, the temperature of the temperature transition zone is 600-1250 ℃, so that Ca (OH) can be added 2 Drying and decomposing to obtain CaO; the carrier carrying CaO can be reserved in the temperature transition zone, and after the raw materials for smelting magnesium by a silicothermic process are filled, the silicothermic process can be continued to smelt magnesium, and aluminum-containing impurities in magnesium vapor can be removed based on CaO purification.
In some examples, the Ca (OH) described above 2 The mass percentage of the suspension is 1-50 wt%.
In some examples, the Ca (OH) described above 2 The suspension is prepared by mixing CaO and water.
In some examples, caO may also be formed on the support from CaCO 3 、Ca(HCO 3 ) 2 The precursor is decomposed and formed, and the precursor can be formed by reacting other raw materials.
In some examples, the above-mentioned compacting body or carrier is not limited to CaO material alone, and CaO may be blended with other filter materials that are beneficial to purifying magnesium vapor, for example, pure iron filter materials disclosed in CN201911178561.X, simple substance silicon filter materials disclosed in CN201911178325.8, nickel-based filter materials disclosed in CN201911178562.4, etc., where the dosage ratio is naturally adjusted according to adaptability to the impurity removal effect of magnesium vapor.
To illustrate the effect of CaO filter in removing aluminum-containing impurities from magnesium vapor generated by silicothermic magnesium production, the following experimental examples, comparative examples and experimental examples are provided:
experimental example 1
(1) Weighing 300g of raw materials for smelting magnesium by a silicothermic process, and placing the raw materials in a reaction zone of a sealed container; vacuumizing the inside of the closed container, wherein the vacuum degree is 10Pa;
(2) Heating a reaction zone of the container to enable the conventional ball to generate silicon thermal reduction reaction to generate magnesium vapor, purifying the magnesium vapor through CaO filter materials, and then condensing and crystallizing to obtain high-purity magnesium; the heating is carried out in three sections, wherein the first section heats the reaction zone of the closed container, and the temperature is 1250 ℃; the second section heats the temperature transition zone of the closed container, caO filter materials are arranged in the temperature transition zone, and the working temperature of the second section is 800-1250 ℃; the third section is to the crystallization area of the closed container, a crystallizer for collecting the desublimated crystal magnesium is arranged in the crystallization area, and the working temperature of the third section is 600 ℃.
The raw materials for smelting magnesium by silicothermic reduction are pellets, which contain 28.53wt.% MgO, 40.12wt.% CaO and 0.62wt.% SiO 2 A l of 0.16wt.% 2 O 3 0.28wt.% Fe 2 O 3 0.05wt.% MnO, 0.0005wt.% PbO, 0.001wt.% ZnO, 21.94% Si, 6.14wt.% Fe, 0.51wt.% A l, 0.276wt.% Ca, 0.023wt.% Mn, 0.0006wt.% Zn, 0.0009wt.% Pb, 0.005wt.% P, 1.32wt.% CaF 2 0.014wt.% CaCO 3 . As is evident from thermodynamic calculations on conventional pellets of the above components, the main products of the gas phase at 1250℃are Mg, siO, ca, al F (aluminum monofluoride, CAS No. 13595-82-9), caF when the hydrothermal reduction reaction occurs 2 Mn, si, fe, etc.; and the gas phase substance is expected to form stable compounds or simple substances, such as Ca-Si-O, ca-A l-Si-O, ca-A l-F-O, fe, mn and the like, in the gradual cooling and condensing process. For impurity aluminum, the initial presence of impurity aluminum in the impurity magnesium-containing vapor at high temperature is A l (g) and A.sub.l.F (g), while the high aluminum deposit phase is Ca-A l-F-O, it is seen that co-deposition of Ca and O containing species is required to deposit more A l (g) and A.sub.l.F (g).
In the present invention, caO was selected as a filter medium, and the reactivity between CaO and Al F (g) was calculated as shown in FIG. 1.
From FIG. 1, it can be seen that CaO(s), A l (g) and A.sub.l.F (g) are significantly reduced in the range of 1250-1050℃and the reduction is greatest at 1050 ℃.
The present invention also calculates the CaO after adding the entire system of the silicon-heat refined magnesium containing miscellaneous magnesium vapor, as shown in FIG. 2.
From FIG. 2, it can be seen that CaO consumes significantly A l (g) and A.sub.l.F (g) in the gas phase and forms Ca 12 Al 14 F 2 O 32 The material. Although the CaO filter generates a large amount of Ca vapor in the system, the Ca vapor can be deposited and removed in the process of continuously cooling the subsequent vapor and can also be deposited in siliconIs largely removed in the refining step of magnesium smelting by a thermal method, and does not bring impurity influence to a crystalline magnesium system.
In step (2) of this example, the CaO filter was in the form of a block having a diameter of 10mm, and the CaO filter was filled in the filter unit.
In step (2) of this embodiment, the CaO filter material has an operating temperature in the temperature transition zone of 1185-1228 ℃.
After 120mi of silicon thermal reduction reaction according to the above method, crystalline magnesium in the crystallizer was collected and weighed to obtain 43.7g of pure magnesium from which aluminum was removed.
The content of each element in the pure magnesium was analyzed, and the purity of magnesium in the low-aluminum high-purity magnesium prepared in this example was 99.986%, and the content of impurity elements was as shown in table 1.
TABLE 1
Figure BDA0004068464030000111
Experimental example 2
This embodiment differs from embodiment 1 in that:
in this example, the CaO filter is placed in the temperature transition zone, and the operating temperature of the CaO filter is 1050-1139 ℃.
After 120mi of silicon thermal reduction reaction, crystalline magnesium in the crystallizer was collected and weighed to obtain 43.4g of pure magnesium with aluminum removed.
The content of each element in the pure magnesium was analyzed, and the purity of magnesium in the low-aluminum high-purity magnesium prepared in this example was 99.988%, and the content of impurity elements was as shown in table 2.
TABLE 2
Figure BDA0004068464030000121
Experimental example 3
This embodiment differs from embodiment 1 in that:
in this example, caO filter was used in the form of a block having a diameter of 20mm.
After 120mi of silicon thermal reduction reaction, crystalline magnesium in the crystallizer was collected and weighed to obtain 42.6g of pure magnesium with aluminum removed.
The content of each element in the pure magnesium was analyzed, and the purity of magnesium in the low-aluminum high-purity magnesium prepared in this example was 99.986%, and the content of impurity elements was as shown in table 3.
TABLE 3 Table 3
Figure BDA0004068464030000122
Experimental example 4
This embodiment differs from embodiment 1 in that:
in the embodiment, the CaO filter material is hollow and has a porous cake shape, the outer diameter of the CaO filter material is 45mm, the thickness of the CaO filter material is 5mm, a central hole is arranged at the center of the porous wafer, and the aperture of the CaO filter material is 25mm; 10 round holes are arranged on the filtering structure around the circumference of the central hole, and the aperture of the round holes is 6mm.
Experimental example 5
This embodiment differs from embodiment 1 in that:
in this embodiment, a carrier containing CaO is disposed in the temperature transition zone, the carrier is a filter, and the preparation of coating the surface with CaO includes the following steps:
preparing Ca (OH) with the mass percentage of 1-50 wt% 2 The suspension was placed on Ca (OH) with the filter 2 In suspension, ca (OH) is caused to 2 The suspension submerges the filter and Ca (OH) is coated on the surface of the filter 2 ；
Coating the surface with Ca (OH) 2 The filter is taken out and is arranged at the tank opening of a reduction tank of a silicon thermal reduction magnesium smelting system, the filter is heated by depending on the naturally formed temperature gradient of the reduction tank, and the temperature of the filter is controlled to be 800-1250 ℃ so as to lead Ca (OH) 2 And (3) generating CaO through a dehydration reaction, and obtaining the filter with the CaO coating on the surface.
Comparative example
This comparative example is different from example 1 in that in step (2), no CaO filter material was provided in the temperature transition section.
This comparative example was conducted in the same manner as in example 1, and magnesium in the mold was collected and weighed to obtain crystalline magnesium having a mass of 43.2g.
Test examples
The crystalline magnesium samples obtained in example 1 and comparative example 1 were subjected to purity test after remelting, as shown in fig. 3;
as can be seen from FIG. 3, when the CaO filter was not added, the impurity aluminum content in the crystalline magnesium sample was 109.5ppm, whereas when the CaO filter was added, the impurity aluminum content in the crystalline magnesium was 6.3ppm, and the aluminum content in Experimental example 1 was far lower than that in the comparative example, and it can be seen that the use of the CaO filter can effectively purify and remove Al and Al F in magnesium vapor generated by the hot refining of magnesium from silicon.
Macroscopic morphology observation, scanning Electron Microscope (SEM) observation, energy dispersive X-ray spectroscopy (EDS) analysis, and X-ray diffraction (XRD) phase analysis were performed on CaO filter materials before and after filtration in experimental example 1, and the results are shown in fig. 4 to 7.
As can be seen from fig. 4, the external dimensions of the CaO filter were changed before and after the CaO filter was used, indicating that no loss pollution to the magnesium vapor system was present during the use; obvious attachments are arranged on the surface of the used CaO filter material, and the color changes, which indicates that the CaO filter material deposits and blocks impurities in magnesium vapor.
As can be seen in FIG. 5, the CaO filter is loose and porous before use, and the particle units have a size of about 1-2um; and after the CaO filter material is used, the pores of the CaO filter material are obviously closed, and the size of the particle units is increased to more than 20 mu m.
As can be seen from fig. 6, the CaO filter after use has F and Al as elements that are significantly increased compared to the CaO filter before use, indicating that the CaO filter can not only purify Al (g) in magnesium vapor but also trap Al F.
In FIG. 7, it is seen that the CaO filter material before use contains only one of CaO, but the CaO filter material after use contains Ca in addition to CaO 12 Al 14 F 2 O 32 The material shows that the CaO filter mainly collects aluminum-containing impurities in magnesium vapor generated by silicothermic smelting of magnesium in the form of adsorption filtration and generated compounds, and can remove Al F in particular.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims (10)

1. The low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on CaO filter materials is characterized in that the CaO filter materials are used for purifying and removing aluminum-containing impurities in magnesium vapor, and the method comprises the following steps: heating the raw materials for smelting magnesium by a silicothermic process, reacting to generate magnesium vapor, removing aluminum-containing impurities from the magnesium vapor through the CaO filter material, and condensing and crystallizing to obtain the low-aluminum high-purity magnesium.
2. The low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on CaO filter materials according to claim 1, wherein the aluminum-containing impurity is AlF.
3. The low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on CaO filter materials according to claim 1, wherein the working temperature of the CaO filter materials for removing aluminum-containing impurities is 600-1250 ℃.
4. The method for removing aluminum from CaO filter based on low-cost and high-efficiency magnesium smelting by a silicothermic process, which is characterized in that the working temperature of removing aluminum-containing impurities of the CaO filter is 1050-1250 ℃.
5. The low-cost and high-efficiency aluminum removal method for silicothermic magnesium production based on CaO filter materials according to any one of claims 1 to 4, wherein the heating temperature of the silicothermic magnesium production raw material is controlled to be 1250-1300 ℃.
6. The low-cost and high-efficiency aluminum removal method for silicothermic magnesium smelting based on CaO filter materials according to any one of claims 1 to 4, wherein the CaO filter materials are arranged on the movement path of magnesium vapor by natural filling or compaction by CaO raw materials, and the CaO raw materials are any one of blocks, spheres, powder and flakes; when the CaO raw material is in a block shape, the diameter is 8-20 mm; when the CaO raw material is spherical, the diameter is 0.3-8 mm; when the CaO raw material is in powder form, the grain diameter is 1-300 mu m; when the CaO raw material is in a sheet shape, the thickness is 0.1-5 mm.
7. The low-cost and high-efficiency aluminum removal method for silicothermic magnesium production based on CaO filter according to any one of claims 1 to 4, wherein the CaO filter is a carrier containing CaO, and the carrier is arranged on the movement path of the magnesium vapor.
8. The low-cost and high-efficiency aluminum removal method for silicothermic magnesium production based on CaO filter materials according to claim 7, wherein the CaO filter materials are coated or immersed with CaO on a carrier, and the method comprises the following steps:
immersing the carrier in Ca (OH) 2 In suspension, so that the carrier is coated or impregnated with Ca (OH) 2 A coating;
coating the inside with Ca (OH) 2 Is taken out, dried and thermally decomposed to obtain the product.
9. The low-cost and high-efficiency aluminum removal method for smelting magnesium by a silicothermic process based on CaO filter materials according to claim 8, wherein the drying temperature is 190-1200 ℃ and the drying time is 0.5-2 h.
10. The low-cost and high-efficiency aluminum removal method for producing magnesium by silicothermic process based on CaO filter according to claim 8, wherein said Ca (OH) is characterized by 2 The mass percentage of the suspension is 1-50 wt%.
CN202310084209.XA 2023-02-08 2023-02-08 CaO filter material-based low-cost and high-efficiency aluminum removal method for smelting magnesium by silicothermic process Pending CN116103515A (en)

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