Method for preparing high-activity magnesium oxide micro-powder by using low-grade magnesite
Patent Information
- Application Number
- CN202611162551.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-03
- Publication Date
- 2026-10-09
AI Technical Summary
[0004]然而，在沉淀环节，普遍采用氨水等外加碱液直接滴加的方式，滴加过程中，碱液滴入处会瞬间产生极高的局部过饱和度，导致爆发性成核，使得晶核的形成与生长极不均匀，获得的氢氧化镁前驱体粒子粒径分布宽、无序团聚严重、形貌难以控制
本发明方法通过引入微波辅助均相沉淀技术，以尿素作为潜伏型沉淀剂，替代了传统的外加氨水滴加方式，在微波场的整体均匀加热下，尿素于整个溶液体系内匀速水解，缓慢、均一地释放出和
，彻底消除了局部过饱和现象，实现了纳米晶核的同步爆发与均匀生长。
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Figure CN122877776A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of magnesium oxide micron powder preparation technology, and in particular to a method for preparing highly active magnesium oxide micron powder using low-grade magnesite. Background Technology
[0002] High-activity magnesium oxide micropowder (typically referring to magnesium oxide with a specific surface area greater than 100 m² / g and a citric acid activity value less than 30 seconds) plays an irreplaceable role in high-end adsorbent materials, antibacterial agents, catalyst carriers, rubber reinforcing agents, and fine ceramics due to its high specific surface area, abundant surface alkaline sites, and excellent reactivity. my country has abundant magnesite reserves, but high-quality resources are increasingly depleted, with large quantities of low-grade magnesite (…) Content 60%~85%) due to the presence of high content of associated substances , , Impurities such as these make it difficult to obtain high-purity, high-activity magnesium oxide products through simple mechanical crushing or direct calcination.
[0003] Chemical purification and reconstruction are the mainstream approaches to achieving high-value utilization of low-grade magnesite. Among them, the ammonium salt recycling method has attracted much attention due to its ability to achieve closed-loop recycling of additives and high product purity. Its typical process flow is as follows: low-grade magnesite is lightly calcined and activated, then leached with ammonium chloride solution to obtain crude magnesium chloride solution. After purification and impurity removal, alkaline precipitants such as ammonia are added to the refined magnesium chloride solution to obtain magnesium hydroxide precursor. This precursor is then washed, dried, and calcined to obtain magnesium oxide product.
[0004] However, in the precipitation stage, the common method is to directly add external alkaline solutions such as ammonia. During the addition process, extremely high local supersaturation is instantly generated at the point where the alkaline solution is introduced, leading to explosive nucleation. This results in highly uneven formation and growth of crystal nuclei, and the obtained magnesium hydroxide precursor particles have a wide particle size distribution, severe disordered agglomeration, and difficult morphology control. Even with low-temperature processes, it is difficult to obtain magnesium oxide with ultra-high specific surface area and activity from such coarse and hard agglomerated precursors during subsequent calcination. The specific surface area of the product is usually limited to 100~200 m / g, and the citric acid activity value can generally only reach about 30 seconds, which limits its extension to higher value-added applications. Furthermore, the direct ammonia precipitation method requires precise control of the dropping rate and system pH, has a narrow operating window, is greatly affected by human factors, has poor batch stability, and requires a complex ammonia absorption and recovery system, making the process cumbersome. Summary of the Invention
[0005] This invention provides a method for preparing highly active magnesium oxide micro powder using low-grade magnesite. By utilizing low-grade magnesite, the morphology, size, and structure of the precursor can be precisely controlled, thereby stably preparing magnesium oxide micro powder with higher specific surface area and better activity.
[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a method for preparing highly active magnesium oxide micro powder using low-grade magnesite, comprising: S1, low-grade magnesite is crushed and ground to obtain fine mineral powder, and then lightly calcined at 750~900℃ for 1~2 hours to obtain lightly calcined magnesium oxide powder; S2, lightly calcined magnesium oxide powder is mixed with ammonium chloride solution and stirred and leached at 80~95℃ for 1.5~2.5 hours. After solid-liquid separation, crude magnesium chloride solution is obtained. S3, the crude magnesium chloride solution is purified to remove impurities, and a high-purity magnesium chloride solution is obtained; S4, prepare a high-purity magnesium chloride solution with a concentration of 1.0~1.5 mol / L. The solution was prepared by adding urea and a structure-directing agent, and then mixing thoroughly to obtain the reaction solution. S5. The reaction solution is placed in a microwave field and heated to 90~100℃, and the reaction is kept at this temperature for 30~90 minutes to gradually hydrolyze urea into basic magnesium carbonate precursor slurry. S6, the basic magnesium carbonate precursor slurry is subjected to solid-liquid separation, washing and drying to obtain basic magnesium carbonate precursor powder. S7. The precursor powder is calcined at 500~550℃ for 1.5~2.5 hours, cooled, and then depolymerized and classified to obtain highly active magnesium oxide micro powder.
[0007] The beneficial effects of the technical solution provided by this invention include at least the following: The method of this invention introduces microwave-assisted homogeneous precipitation technology, using urea as a latent precipitant to replace the traditional method of adding ammonia dropwise. Under the uniform heating of the entire microwave field, urea hydrolyzes at a constant rate throughout the solution system, slowly and uniformly releasing urea. and This completely eliminates the phenomenon of local oversaturation and achieves synchronous explosion and uniform growth of nanocrystal nuclei.
[0008] The method of this invention can directly use low-grade magnesite as raw material, and through selective leaching of ammonium salts and a matching deep purification process, it can effectively remove impurities such as silicon, iron, aluminum, and calcium to obtain a high-purity magnesium chloride solution, ensuring the high purity of the final product. Attached Figure Description
[0009] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0010] Figure 1 This is a flowchart of a method for preparing highly active magnesium oxide micro powder using low-grade magnesite, provided in an embodiment of the present invention. Detailed Implementation
[0011] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
[0012] Please refer to Figure 1 This is a flowchart of a method for preparing highly active magnesium oxide micro powder using low-grade magnesite, provided in an embodiment of the present invention.
[0013] First Embodiment A method for preparing highly active magnesium oxide micro powder using low-grade magnesite includes the following steps: S1: Low-grade magnesite is coarsely crushed by a jaw crusher and finely ground by a ball mill to obtain fine ore powder with a 92% pass rate through a 200-mesh sieve; the fine ore powder is fed into a rotary kiln and lightly calcined at 850℃ for 1.5 hours, and after cooling, active lightly calcined magnesia powder is obtained.
[0014] S2: Prepare a 22wt% ammonium chloride solution (partially from the circulating mother liquor and supplemented with fresh ammonium chloride). Add lightly calcined magnesium oxide powder to the ammonium chloride solution at a liquid-to-solid ratio of 5:1 (mL / g). In a reactor equipped with a stirrer and a reflux condenser, heat to 90°C and stir for 2 hours to leach. The ammonia gas released from the reaction is absorbed by condensation to prepare 10% ammonia water for later use. The leachate is filtered while hot through a plate and frame filter press to obtain a crude magnesium chloride solution. The filter cake is washed with water and used as a building material raw material.
[0015] S3: Heat the crude magnesium chloride solution to 65°C, slowly add 1.2 times the theoretical amount of 30% hydrogen peroxide, and stir for 30 minutes to oxidize. Then, while stirring, slowly add the 10% ammonia water recovered in step S2, adjust the pH of the solution to 5.8, heat to 85°C and stir for 30 minutes to allow iron and aluminum to form hydroxide colloids. Next, add 10% excess ammonium oxalate according to the stoichiometric ratio of calcium content, and continue stirring for 40 minutes. Send the slurry into a precision microfiltration machine to obtain a clear and transparent high-purity magnesium chloride solution, and test its... , The content of all samples was less than 10 mg / L.
[0016] S4: Detection of high-purity magnesium chloride solution The concentration is 1.25 mol / L. Urea is added to it, so that the urea reacts with... The molar ratio of the two components was 3:1, and the mixture was stirred to dissolve. Then, polyvinylpyrrolidone (PVP-K30) was added to make its concentration in the solution 1.0 g / L. The mixture was stirred at room temperature for 20 minutes to obtain a clear reaction solution.
[0017] S5: Send the reaction solution into the atmospheric pressure microwave reactor (loading coefficient 65%), turn on the stirring (150 rpm) and reflux condenser; set the microwave power to 600 W, quickly heat to 95℃ (about 8 minutes), and then react at a constant temperature of 95℃ for 60 minutes; the slurry gradually turns into a milky white thick state, stop the microwave, and let it cool naturally to 45℃.
[0018] S6: Separate the slurry into solid and liquid components using a centrifuge and collect the mother liquor. Wash the filter cake three times with 70℃ hot pure water, each time with a liquid-to-solid ratio of 8:1, until the washing liquid is used... No test results The washed filter cake was mixed with water to form a slurry with a solid content of 20%, and then spray-dried at an inlet air temperature of 200℃ and an outlet air temperature of 85℃ to obtain a fluffy white basic magnesium carbonate precursor powder. SEM showed that the powder was a flower-shaped microsphere with a diameter of about 2m and a thickness of about 15 nm assembled from nanosheets.
[0019] S7: The precursor powder is placed in a box-type resistance furnace and heated to 520°C at 3°C / min under air atmosphere, held for 2 hours, and then cooled naturally; the calcined product is deagglomerated by an air jet mill and turbine-classified to obtain magnesium oxide micro powder with a D50 of 3.2m.
[0020] Second Embodiment The difference between this embodiment and the first embodiment is as follows: In step S4, sodium citrate is used as the structure-directing agent at a concentration of 1.2 g / L; in step S5, the microwave constant temperature reaction temperature is 98°C and the reaction time is 50 minutes; in step S6, the calcination temperature is 500°C and the holding time is 2.5 hours. The remaining steps and conditions are the same.
[0021] Third Embodiment In this embodiment, step S2 uses an ammonium chloride solution with a concentration of 25 wt% and a liquid-to-solid ratio of 4:1; step S4 uses urea and... The molar ratio is 2.8:1, with no additional structure-directing agent added (concentration 0); step S5 uses a microwave power of 800 W. The rest is the same as in the first embodiment. Fourth embodiment Based on the first embodiment, the mother liquor obtained from solid-liquid separation in step S6 (mainly containing ammonium chloride, unreacted urea, etc.) is collected, concentrated by vacuum evaporation to an ammonium chloride concentration of about 23 wt%, and after determining the urea content, an appropriate amount of fresh urea and ammonium chloride is added and returned to step S2 as a leaching agent for the next batch of leaching. The ammonia gas that escaped in step S5 is absorbed and used for pH adjustment in step S3.
[0022] Furthermore, it should be noted that the present invention can be provided as a method, apparatus, or computer program product. Therefore, embodiments of the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, embodiments of the present invention can take the form of a computer program product implemented on one or more computer-usable storage media containing computer-usable program code.
[0023] The embodiments of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, terminal devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.
[0024] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing terminal equipment to cause a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.
[0025] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, including a defined element by a statement does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.
[0026] Finally, it should be noted that the above description represents a preferred embodiment of the present invention. It should be pointed out that although preferred embodiments have been described, those skilled in the art, once they understand the basic inventive concept of the present invention, can make various improvements and modifications without departing from the principles described herein. These improvements and modifications should also be considered within the scope of protection of the present invention. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention.
Claims
1. A method for preparing highly active magnesium oxide micro powder using low-grade magnesite, characterized in that, include: S1, low-grade magnesite is crushed and ground to obtain fine mineral powder, and then lightly calcined at 750~900℃ for 1~2 hours to obtain lightly calcined magnesium oxide powder; S2, lightly calcined magnesium oxide powder is mixed with ammonium chloride solution and stirred and leached at 80~95℃ for 1.5~2.5 hours. After solid-liquid separation, crude magnesium chloride solution is obtained. S3, the crude magnesium chloride solution is purified to remove impurities, and a high-purity magnesium chloride solution is obtained; S4, prepare a high-purity magnesium chloride solution with a concentration of 1.0~1.5 mol / L. The solution was prepared by adding urea and a structure-directing agent, and then mixing thoroughly to obtain the reaction solution. S5. The reaction solution is placed in a microwave field and heated to 90~100℃, and the reaction is kept at this temperature for 30~90 minutes to gradually hydrolyze urea into basic magnesium carbonate precursor slurry. S6, the basic magnesium carbonate precursor slurry is subjected to solid-liquid separation, washing and drying to obtain basic magnesium carbonate precursor powder. S7. The precursor powder is calcined at 500~550℃ for 1.5~2.5 hours, cooled, and then depolymerized and classified to obtain highly active magnesium oxide micro powder.
2. The method for preparing highly active magnesium oxide micro powder using low-grade magnesite as described in claim 1, characterized in that, S1 involves crushing and grinding low-grade magnesite to obtain fine ore powder, which is then lightly calcined at 750-900℃ for 1-2 hours to obtain lightly calcined magnesia powder. The fine mineral powder needs to be sieved through a 200-mesh screen, and the overall pass rate of the fine mineral powder must be 90%.
3. The method for preparing highly active magnesium oxide micro powder using low-grade magnesite as described in claim 1, characterized in that, In step S2, lightly calcined magnesium oxide powder is mixed with ammonium chloride solution and stirred and leached at 80-95°C for 1.5-2.5 hours. After solid-liquid separation, a crude magnesium chloride solution is obtained, wherein: The concentration of the ammonium chloride solution needs to be maintained at 20-25 wt%. The ratio of the lightly calcined magnesium oxide powder to the ammonium chloride solution is 4:1 to 6:
1.
4. The method for preparing highly active magnesium oxide micro powder using low-grade magnesite as described in claim 1, characterized in that, S3 purifies and removes impurities from the crude magnesium chloride solution to obtain a high-purity magnesium chloride solution, wherein: S301, an oxidizing agent is added to a crude magnesium chloride solution to make the solution... Oxidized to ; S302, then a precipitant is added under vigorous stirring to adjust the pH of the solution to 5.5~6.0, so that the metal impurities in the solution form hydroxide precipitates; S303, with the addition of soluble sulfates or oxalates, makes... Precipitation occurs; S304 uses precision filtration equipment to precisely filter the slurry to obtain a high-purity magnesium chloride solution.
5. The method for preparing highly active magnesium oxide micro powder using low-grade magnesite as described in claim 4, characterized in that, in: The oxidant is hydrogen peroxide with a concentration of 30%; The precipitant is ammonia water recovered during the leaching of crude magnesium chloride solution, with a concentration of 8-12%.
6. The method for preparing highly active magnesium oxide micro powder using low-grade magnesite as described in claim 1, characterized in that, S4 involves preparing a high-purity magnesium chloride solution with a concentration of 1.0~1.5 mol / L. The solution was mixed with urea and a structure-directing agent to obtain a reaction solution, wherein: The urea and The molar ratio is 2.5:1 to 3.5:1; The structure-directing agent is either polyvinylpyrrolidone or sodium citrate, and the target concentration of both in the final reaction solution is 0.5~1.5 g / L.
7. The method for preparing highly active magnesium oxide micro powder using low-grade magnesite as described in claim 1, characterized in that, In step S5, the reaction solution is heated to 90-100°C in a microwave field and kept at this temperature for 30-90 minutes, causing urea to gradually hydrolyze and generate a basic magnesium carbonate precursor slurry, wherein: The microwave heating power is 400~800 W, the heating rate is controlled at 10~15℃ / min, and the reaction is continuously stirred and reflux condenser is configured to recover the escaped ammonia gas.
8. The method for preparing highly active magnesium oxide micro powder using low-grade magnesite as described in claim 1, characterized in that, S6 involves solid-liquid separation, washing, and drying of the basic magnesium carbonate precursor slurry to obtain basic magnesium carbonate precursor powder, wherein: The drying process employs spray drying, with an inlet air temperature of 180~220℃ and an outlet air temperature of 80~90℃.
9. The method for preparing highly active magnesium oxide micro powder using low-grade magnesite as described in claim 1, characterized in that, In step S7, the precursor powder is calcined at 500-550℃ for 1.5-2.5 hours, cooled, and then depolymerized and classified to obtain highly active magnesium oxide micro powder, wherein: The calcination process is carried out in an air atmosphere, with a heating rate of 2~5℃ / min and a calcination temperature of 500~550℃; the resulting highly active magnesium oxide micro powder has a specific surface area of 200~300 m / g and a citric acid activity value of less than 10 seconds.
10. The method for preparing highly active magnesium oxide micro powder using low-grade magnesite as described in claim 1, characterized in that, The low-grade magnesite The content needs to be maintained between 60% and 85%.