Preparation method and application of high-purity light magnesium oxide for silicon steel grade and new energy automobile by using magnesite tailings
Patent Information
- Application Number
- CN202611002504.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-07
- Publication Date
- 2026-09-11
AI Technical Summary
（1）原料多采用菱镁矿精矿，极少以菱镁矿尾矿为原料实现规模化高值化利用，尾矿资源化技术路线缺失；
本发明以菱镁矿尾矿为原料，通过焙烧活化、铵盐-柠檬酸耦合浸出、多级精准除杂、均相沉淀、超临界CO2干燥及低温轻烧一体化绿色工艺，成功制备出硅钢级、新能源车用高纯轻质氧化镁：
Abstract
Description
Technical Field
[0001] This invention belongs to the fields of mineral processing, industrial solid waste resource utilization, and high-purity inorganic functional material preparation technology. Specifically, it relates to a method for preparing silicon steel grade and high-purity lightweight magnesium oxide for new energy vehicles using magnesite tailings, and its preparation and application. Background Technology
[0002] Magnesite is a superior magnesium resource in my country. During the beneficiation process, a large amount of tailings are generated. The MgO content in the tailings can usually reach 35% to 40%. Long-term stockpiling not only occupies land resources, but also easily causes magnesium ion loss and dust pollution, resulting in significant resource waste and environmental risks.
[0003] Existing technologies for magnesium oxide preparation face the following bottlenecks: (1) Most of the raw materials used are magnesite concentrate, and very few magnesite tailings are used as raw materials to achieve large-scale high-value utilization. There is a lack of tailings resource utilization technology. (2) Conventional acid leaching and ammonium salt single-component leaching have poor selectivity, and impurities such as boron, iron, calcium, and sodium are difficult to remove to the ppm level, which cannot meet the high purity requirements of silicon steel grade and new energy grade. (3) Traditional oven drying + high-temperature calcination process easily leads to particle sintering and agglomeration, resulting in a small specific surface area of the product (30~80m²). 2 High bulk density (0.6~1.0 g / cm³) 3 ), low activity level, unable to adapt to high-end functional scenarios; (4) The process has a large consumption of acid and alkali, a low mother liquor recovery rate (<30%), and a large wastewater discharge, which is prone to secondary pollution and does not meet the requirements of green manufacturing. (5) It is difficult to achieve the synergistic goals of high purity, light weight, high activity, low cost and green development at the same time, and there is a lack of complete sets of technologies that can be adapted to both high-end scenarios of silicon steel and new energy. Summary of the Invention
[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing silicon steel grade and high-purity lightweight magnesium oxide for new energy vehicles using magnesite tailings, and its applications, achieving the following core objectives: (1) Using magnesite tailings as raw material, realize the high-value-added resource utilization of low-grade magnesium resources and turn waste into treasure; (2) Deeply remove harmful impurities such as boron, iron, calcium, and sodium to meet silicon steel grade and new energy grade standards; (3) Preparation of magnesium oxide with high specific surface area, light weight, and high activity; (4) It achieves efficient recycling of leaching agent, and the process is green, low-carbon, and free of secondary pollution, making it industrially practical.
[0005] The technical solution adopted by this invention to solve its technical problem is as follows: A silicon steel grade and a high-purity lightweight magnesium oxide for new energy vehicles, meeting the following conditions: MgO purity: ≥99.5wt%; B2O3: ≤20ppm; Fe2O3: ≤50ppm; CaO: ≤100ppm; Na2O: ≤50ppm; Specific surface area: ≥150m² 2 / g; Bulk density: 0.2~0.4 g / cm³ 3 ; Particle size D50: 1~5μm.
[0006] Crystal form and surface characteristics: The product as a whole has an amorphous structure with trace amounts of weakly crystalline flaky porous aggregates. The grains are small, the crystallinity is low, and the degree of lattice distortion is high. The microstructure presents a loose honeycomb porous morphology. This microstructure is formed by supercritical CO2 low-pressure drying to suppress capillary shrinkage, combined with medium-low temperature light calcination. It does not belong to the dense and complete crystalline structure of conventional calcined magnesium oxide and is a unique characteristic structure of this process. The products are divided into two categories: ① High-purity lightweight magnesium oxide for silicon steel: It is prepared by completing only the following preparation steps (1) to (6) in sequence, without the need for hydrophobic modification process; ② Magnesium oxide for new energy vehicle batteries: It is prepared by completing the preparation steps (1) to (7) in sequence, and is additionally treated with silane coupling agent dry hydrophobic modification. After modification, hydrophobic organic functional groups are introduced on the surface of the product, the hydrophobic contact angle is ≥110°, and it is resistant to organic electrolyte wetting and corrosion.
[0007] A method for preparing silicon steel grade and high-purity lightweight magnesium oxide for new energy vehicles includes the following steps: (1) Tailings pretreatment and roasting activation Magnesite tailings are crushed and ground to ≤200 mesh, then roasted and activated at 400~550℃ for 1~2 h to decompose magnesium carbonate and activate the crystal lattice, thereby enhancing magnesium leaching activity. (2) Coupled selective leaching A composite leaching system of ammonium chloride and citric acid was used, with a molar ratio of 3-5:1, a solid-liquid ratio of 1:4-1:8, a temperature of 80-105℃, and a leaching time of 1-3 hours. Magnesium was selectively dissolved, while impurities such as silicon and aluminum remained in the slag phase and were separated. The magnesium leaching rate was ≥95%. (3) Three-stage deep impurity removal Iron removal by hydrogen peroxide oxidation (pH 4.0~5.0) → specific boron removal by N-methylglucosamine resin → sodium decalcification via nanofiltration membrane with a molecular weight cutoff of 150~300 Da, ensuring impurities meet standards; based on the volume of leachate to be treated, the chelating resin loading amount is 50~120 g / L leachate, controlling the leachate flow space velocity through the resin column to 1~3 BV / h, with a boron removal rate ≥98%; iron removal by oxidation uses 25%~30% hydrogen peroxide as the oxidant, with the hydrogen peroxide addition amount being 1.2~2.0 times the amount of iron element oxidized in the leachate; the system pH is adjusted to 4.0~5.0 to allow Fe... 3+ Complete precipitation separation with iron removal rate ≥99%; nanofiltration membrane with molecular weight cutoff of 150~300Da, achieving deep removal of calcium, sodium and potassium ions; (4) Homogeneous precipitation Using urea as a precipitant, homogeneous precipitation was carried out to prepare a basic magnesium carbonate precursor with uniform particle size and low agglomeration. (5) Supercritical drying The precursor is dried using supercritical CO2 at a pressure of 7.4–12.0 MPa and a temperature of 31–50°C. The CO2 fluid continuously circulates and washes the inside of the drying vessel to avoid pore collapse and hard agglomeration caused by capillary tension during the drying process, thus preserving the loose, porous, and lightweight structure of the precursor. (6) Low-temperature light calcination activation The dried precursor was lightly calcined at 550~700℃ for 1~3 h to decompose and obtain high-purity light magnesium oxide. (7) Airflow classification and modification The product can be air-graded and can be dry-modified by using silane coupling agents at 110~130℃. After modification, the product has a hydrophobic contact angle ≥110°, making it suitable for new energy batteries, electrolytes, and separator applications. (8) Mother liquor and leachate circulation Ammonium salts and citric acid are recovered from the leaching mother liquor and membrane separation concentrate and returned to the leaching process for recycling, with a recovery rate of ≥95% and near-zero waste discharge.
[0008] Compared with the prior art, the beneficial effects of the present invention include: This invention uses magnesite tailings as raw material and employs an integrated green process involving roasting activation, ammonium salt-citric acid coupled leaching, multi-stage precise impurity removal, homogeneous precipitation, supercritical CO2 drying, and low-temperature light calcination to successfully produce silicon steel grade, high-purity lightweight magnesium oxide suitable for new energy vehicles. 1. High-value utilization of solid waste yields significant resource benefits. Using inexpensive magnesite tailings as raw material to replace high-quality magnesite concentrate reduces raw material costs by more than 40%, alleviating the pressure of high-quality magnesite resource shortage.
[0009] 2. Deep impurity removal, industry-leading purity. Through a three-stage precision impurity removal system consisting of iron removal by oxidation, boron removal by chelating resin, and deep decalcification and sodium removal by nanofiltration membrane, harmful impurities such as boron, iron, calcium, and sodium can be reduced to the ppm level. The product's MgO purity is ≥99.5 wt%, and key impurity indicators fully meet the stringent standards for silicon steel grade and new energy battery materials, solving the industry pain points of insufficient purity and difficulty in controlling impurities in traditional processes.
[0010] 3. Lightweight and highly active, suitable for high-end functional scenarios. Supercritical drying + low-temperature calcination process, product specific surface area ≥150 m² 2 / g, with a bulk density of only 0.2~0.4 g / cm³. 3 With uniform particle size, good dispersibility, and high reactivity, it possesses advantages of being lightweight, porous, and highly active that traditional calcined magnesium oxide cannot match, making it a perfect match for high-end applications such as silicon steel insulating coatings, power batteries, and solid electrolytes.
[0011] 4. Green and circular processes, meeting requirements. The leaching agent recovery rate is ≥95%, wastewater discharge is near zero, there is no secondary pollution, the process flow is short, energy consumption is low, and it has clean production attributes.
[0012] 5. High-end application scenarios and outstanding market value. The product can improve battery cycle life by more than 15%, can be mass-produced, and has great promotional value. Detailed Implementation
[0013] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0014] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0015] This embodiment provides a system apparatus for preparing the high-purity light magnesium oxide of this application, which includes the following steps in sequence: (1) Tailings crushing and grinding equipment; (2) Calcination and activation furnace; (3) Selective leaching reactor; (4) Solid-liquid separation device; (5) Oxidation and iron removal reaction vessel; (6) Boron-specific chelating resin boron removal column; (7) Nanofiltration / electrodialysis membrane separation device; (8) Homogeneous precipitation reactor; (9) Supercritical CO2 drying device; (10) Low-temperature light-fired furnace; (11) Integrated airflow staged modification machine; (12) Finished goods warehouse.
[0016] Magnesite tailings are fed sequentially into a tailings crushing and grinding unit for pulverization and refinement. The powder is then conveyed to a roasting and activation furnace for lattice activation. The activated ore is fed into a selective leaching reactor for coupled leaching. The leaching mixture is sent to a solid-liquid separation unit for filtration, and the solid waste is separated and transported off-site. The magnesium-containing filtrate flows sequentially through an oxidation iron removal reactor, a boron-specific chelating resin boron removal column, and a nanofiltration / electrodialysis membrane separation unit to complete three-stage impurity removal. The purified high-purity magnesium solution is sent to a homogeneous precipitation reactor to prepare a precursor suspension. The suspension is filtered to collect the solid precursor, which is then sent to a supercritical CO2 drying unit for drying. The dried powder is then sent to a low-temperature light calcination furnace for calcination. The calcined product is sent to an integrated airflow classification and modification machine for classification and processing. Silicon steel grade materials are directly sent to the finished product warehouse after classification. Battery-specific materials are classified and hydrophobically modified before entering the finished product warehouse. All leaching waste and membrane concentrate are uniformly recycled, purified, and returned to the leaching reactor for reuse.
[0017] This implementation method uses the following raw materials: typical components of magnesite tailings. Component content MgO 38.2wt% SiO2 26.5wt% CaO 1.8wt% Fe2O3 0.9wt% B 96ppm Loss on ignition 12.3 wt% Example 1: High-purity lightweight magnesium oxide of silicon steel grade (1) The tailings are fed into the crushing and grinding unit 1 and crushed and ground until all of them pass through a 200-mesh sieve; the powder is continuously conveyed to the roasting and activation furnace 2 and roasted at a constant temperature of 500℃ for 1.5 hours to complete the activation. (2) Activated mineral powder is put into selective leaching reactor 3, and a mixed leaching solution with a molar ratio of ammonium chloride to citric acid of 4:1 is prepared. The solid-liquid ratio is 1:6, and the temperature is raised to 95°C and leaching is carried out by stirring for 2 hours. (3) The leaching mixture is pumped into the solid-liquid separation device 4 for pressure filtration and separation. The waste residue is discharged and the magnesium filtrate is transferred to the oxidation reaction tank 21. Hydrogen peroxide with a mass fraction of 27.5% is added through the dosing device 22. The amount of hydrogen peroxide is 1.5 times the theoretical amount of iron element oxidation in the solution. The pH of the system is controlled to be stable at 4.5 by relying on the pH online monitoring 23. The oxidation precipitation and iron removal are completed by thorough stirring. (4) After iron removal, the filtrate is sent to the boron removal resin column 24 via the circulation pump 27. The resin loading is 80 g / L of filtrate, and the liquid hourly space velocity is 2 BV / h to complete selective boron removal. The boron-removed filtrate enters the nanofiltration membrane module 26 for cross-flow filtration to remove calcium and sodium impurities. The purified magnesium solution is collected in the clear liquid tank 28. (5) The purified magnesium solution was transported to the homogeneous precipitation reactor 8, urea was added to carry out the homogeneous precipitation reaction, and the basic magnesium carbonate precursor was collected by filtration after the reaction was completed. (6) The precursor is fed into the supercritical drying vessel 31 via the feeding device 36, and the pressurization system 33 adjusts the pressure inside the vessel to 8.5 MPa and the temperature to 40°C to complete the supercritical CO2 circulating drying. (7) The dried powder is conveyed to the light calcination furnace 34 in a closed manner, and the temperature control system 35 is set to 620℃ for constant light calcination for 2 hours. After calcination, the powder is sent to the airflow classification and modification integrated machine 11 for classification and screening. No hydrophobic modification is performed. Finally, it is sent to the finished product warehouse 12 to obtain silicon steel grade high-purity light magnesium oxide.
[0018] Product testing results Project Indicators MgO purity 99.62wt% B2O3 16ppm Fe2O3 38ppm CaO 76ppm Na2O 29ppm Specific surface area 186m² 2 / g Bulk density 0.27 g / cm³ 3 D50 2.1μm Conclusion: It fully meets the national standard for silicon steel grade magnesium oxide and the internal control standard for new energy materials.
[0019] Example 2: High-purity lightweight magnesium oxide specifically for lithium batteries in new energy vehicles The entire process flow and parameters of the initial crushing and grinding, calcination and activation, coupled leaching, three-stage impurity removal, homogeneous precipitation, supercritical drying, and low-temperature light calcination are consistent with those of Example 1. The calcined magnesium oxide powder is transported to the air classifier and modifier integrated machine 11, where particle size classification is first completed, and then a silane coupling agent is added. Dry hydrophobic modification is carried out at 120°C in a closed system. After the modification is completed and the powder is naturally cooled, it is discharged into the finished product silo 12 in a closed system to obtain high-purity magnesium oxide for batteries.
[0020] Product testing and application results: hydrophobic contact angle 116°; used in lithium battery separator coating testing, it reduces battery self-discharge rate at high temperature storage by 22% and increases cycle life by 16%.
[0021] Example 3: High-purity lightweight magnesium oxide of silicon steel grade (lower parameter range) Tailings were crushed and ground to 200 mesh, and activated in a roasting and activation furnace at 430℃ for 2 hours. In the leaching vessel, the ammonium chloride:citric acid molar ratio was 3:1, the solid-liquid ratio was 1:4, the leaching temperature was 82℃, and the leaching was maintained at this temperature for 3 hours. Iron removal was achieved using 25% hydrogen peroxide, with an addition amount 1.2 times the theoretical oxidation value of iron, and the system pH was controlled at 4.1. Boron removal resin was loaded at a concentration of 55 g / L of filtrate, with a liquid hourly space velocity (LISH) of 3 BV / h. Urea was homogeneously precipitated after nanofiltration membrane purification. Supercritical drying was performed at a pressure of 7.6 MPa and a temperature of 32℃. The calcined material was then calcined at a constant temperature of 560℃ for 3 hours in a light-calcining furnace. After classification, silicon steel grade finished products were directly obtained.
[0022] Test results: Project Indicators MgO purity 99.53% B2O3 18ppm Fe2O3 42ppm CaO 91ppm Na2O 41ppm Specific surface area 157m² 2 / g Bulk density 0.35 g / cm³ 3 D50 3.7μm It meets the requirements for silicon steel usage.
[0023] Example 4: High-purity magnesium oxide for new energy batteries (higher parameter range) Tailings were crushed and ground to 200 mesh and activated in a roasting furnace at 540℃ for 1 hour; leaching was performed with an ammonium chloride:citric acid molar ratio of 5:1, a solid-liquid ratio of 1:8, a leaching temperature of 103℃, and a leaching time of 1.2 hours; iron removal was achieved using 30% hydrogen peroxide, with an addition amount 1.9 times the theoretical value for iron, and the pH was controlled at 4.9; chelating resin was loaded with 110 g / L filtrate at a space velocity of 1 BV / h; after membrane separation to remove impurities, a precursor was prepared by precipitation; supercritical drying was performed at a pressure of 11 MPa and a temperature of 48℃; calcination was carried out in a light-burning furnace at 680℃ for 1.5 hours; subsequent dry hydrophobic modification with silane was performed at 130℃.
[0024] Detection application results: Project Indicators MgO purity 99.65% B2O3 14ppm Fe2O3 33ppm CaO 69ppm Na2O 26ppm Specific surface area 192m² 2 / g Bulk density 0.23 g / cm³ 3 Hydrophobic contact angle of 121°; 17% improvement in cycle life for lithium battery applications.
[0025] Comparative Example 1: Traditional process for preparing magnesium oxide for silicon steel by leaching of magnesite concentrate with a single ammonium salt High-grade magnesite concentrate was selected as the raw material, and tailings were not used; conventional roasting and activation were carried out at 500℃; only ammonium chloride aqueous solution was used for leaching, without citric acid coordination and selective leaching; the leaching solution was simply oxidized with hydrogen peroxide to remove iron, without boron-specific chelating resin or nanofiltration membrane for deep decalcification and sodium removal; the precipitated product was dried in an electric heating oven at normal pressure with hot air; the dried powder was calcined at 860℃ to prepare magnesium oxide, without supercritical drying or low-temperature gradient calcination process; no surface modification treatment was carried out throughout the process.
[0026] Finished product inspection: Project Indicators MgO purity 98.2% B2O3 145ppm Fe2O3 92ppm CaO 235ppm Na2O 138ppm Specific surface area 64m² 2 / g Bulk density 0.78 g / cm³ 3 The boron and calcium impurities are seriously excessive, making it unsuitable for use in high-end oriented silicon steel insulation coatings; the leaching agent recycling rate is only 26%, resulting in a large amount of waste liquid generated.
[0027] Comparative Example 2: Conventional process for preparing lightweight magnesium oxide for batteries from commercial magnesium carbonate feedstock The raw material is purchased industrial magnesium carbonate powder, and the solid waste of magnesite tailings is not utilized. The precursor is prepared by conventional hydrothermal precipitation and dried in an oven with hot air. It is calcined at a conventional constant temperature of 750℃. The subsequent simple surface modification is carried out by wet spraying. The process includes a non-coupled selective leaching system, a three-stage precision impurity removal system, and a supercritical drying process.
[0028] Applications in finished product testing: Project Indicators MgO purity 99.1% B2O3 78ppm Fe2O3 65ppm CaO 156ppm Specific surface area 93m² 2 / g Bulk density 0.59 g / cm³ 3 Hydrophobic contact angle of 92°; used in lithium battery separator coating, high-temperature self-discharge rate only decreases by 9%, and battery cycle life is improved by less than 8%; raw material cost is high, and it cannot dispose of tailings solid waste.
[0029] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A high-purity, lightweight magnesium oxide for silicon steel and new energy vehicles prepared using magnesite tailings, characterized in that: MgO purity ≥ 99.5 wt%, B2O3 ≤ 20 ppm, Fe2O3 ≤ 50 ppm, CaO ≤ 100 ppm, Na2O ≤ 50 ppm; specific surface area ≥ 150 m² 2 / g, bulk density 0.2~0.4g / cm³ 3 The particle size D50 is 1~5μm; it has an amorphous or weakly crystalline structure, and when used in the battery field, the surface hydrophobic contact angle is ≥110°.
2. A method for preparing the high-purity light magnesium oxide of claim 1, characterized in that, Includes the following steps: (1) The magnesite tailings are crushed and ground to ≤200 mesh, and then roasted and activated at 400~550℃ for 1~2 h; (2) An ammonium chloride + citric acid coupled leaching system was adopted, with a solid-liquid ratio of 1:4 to 1:8, and leaching was carried out at 80 to 105°C for 1 to 3 hours. The magnesium-containing leachate was obtained by solid-liquid separation, and the magnesium leaching rate was ≥95%. (3) Multi-stage deep impurity removal of leachate: iron removal by oxidation, boron removal by chelating resin, and calcium and sodium removal by nanofiltration membrane separation; (4) Add urea as a precipitant to carry out homogeneous precipitation and obtain basic magnesium carbonate precursor; (5) The precursor is dried by supercritical CO2 at a pressure of 7.4~12.0MPa and a temperature of 31~50℃ to maintain the porous structure of the precursor; (6) The dried precursor was activated by low-temperature calcination at 550~700℃ for 1~3 h to obtain high-purity light magnesium oxide.
3. The method according to claim 2, characterized in that, In step (2), the molar ratio of ammonium chloride to citric acid is 3~5:
1. Citric acid acts as a complexing agent to enhance the selective leaching of magnesium and inhibit the dissolution of silicon and aluminum impurities.
4. The method according to claim 2, characterized in that, In step (3), the chelating resin is an N-methylglucosamine type boron-specific chelating resin; based on the volume of the leachate to be treated, the amount of chelating resin used is 50-120 g / L leachate, the space velocity of the leachate flowing through the resin column is controlled at 1-3 BV / h, and the boron removal rate is ≥98%.
5. The method according to claim 2, characterized in that, In step (3), oxidative iron removal uses 25%–30% hydrogen peroxide as the oxidant, and the amount of hydrogen peroxide added is 1.2–2.0 times the amount of iron element oxidized in the leachate; the pH of the system is adjusted to 4.0–5.0 to allow Fe to be removed. 3+ Complete precipitation separation with an iron removal rate of ≥99%; the nanofiltration membrane has a molecular weight cutoff of 150~300 Da, achieving deep removal of calcium, sodium, and potassium ions.
6. The method according to claim 2, characterized in that, The leachate mother liquor is evaporated and concentrated to recover ammonium salt and citric acid, which are then returned to step (2) for recycling. The recovery rate is ≥95%, achieving near-zero waste discharge.
7. The method according to claim 2, characterized in that, It also includes step (7): using a silane coupling agent to perform dry hydrophobic modification of magnesium oxide at a modification temperature of 110~130℃, and the hydrophobic contact angle of the modified product is ≥110°.
8. The application of the high-purity light magnesium oxide according to claim 1, characterized in that, It is used as a release agent and film-forming agent for the high-temperature annealing insulating coating of grain-oriented silicon steel.
9. The application of the high-purity light magnesium oxide according to claim 1, characterized in that, Used as an additive for lithium battery electrolytes in new energy vehicles, as a separator coating, a modifier for solid electrolyte matrix or magnesium-based anode materials.
10. The application of the high-purity light magnesium oxide according to claim 9, characterized in that, The high-purity, lightweight magnesium oxide improves the cycle life of lithium batteries by more than 15% and reduces the self-discharge rate at high-temperature storage by ≥20%.