A method for preparing periclase-forsterite gradient composite hollow spheres

Abstract

The present invention relates to a preparation method of a periclase-forsterite gradient composite hollow sphere, and belongs to the field of alkaline thermal insulation refractory materials. The preparation method comprises the following steps: according to the ratio of 75-95wt% of magnesium-rich silicate minerals, 1-10wt% of light-burned magnesia, and 1-15wt% of natural quartz by mass percentage, grinding into a fine powder, adding a binder of 4-6wt% of the sum of the above raw material percentages, and granulating; then, using the spherical particles obtained by granulation in step 1 as cores, 10-30wt% of light-burned magnesia is wrapped to obtain an internal SiO2-rich heterogeneous spherical particle blank; finally, the coated spherical particles are subjected to high temperature firing, and gradient composite hollow spheres are obtained after cooling. The present invention adopts a wrapping composite-in-situ diffusion reaction pore-forming process, and regulates the diffusion reaction path by the composition of the heterogeneous sphere, thereby forming an in-situ hollow structure. The outer shell of the hollow sphere is mainly composed of periclase phase, and the forsterite phase gradually increases from the surface of the spherical shell to the inside, forming a spherical shell structure with a gradient distribution of periclase-forsterite phase.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory materials, and particularly relates to a method for preparing periclase-forsterite gradient composite hollow spheres. Background Art

[0002] Alkaline refractory materials refer to refractory materials with MgO as the main chemical composition. They have excellent high-temperature performance and resistance to alkaline slag and are widely used in high-temperature industrial fields such as the steel industry, cement industry, and non-ferrous metal smelting. However, there are few insulation products suitable for alkaline refractory furnace linings, which leads to high thermal conductivity and serious heat loss in related high-temperature facilities. CN106946558A discloses a forsterite-periclite-spinel composite lightweight refractory material and a preparation method thereof. The method uses magnesium oxide as the main raw material and introduces inorganic pore-increasing agents such as glass beads, fly ash, and perlite to prepare a high-strength and low-conductivity alkaline lightweight refractory material. However, the pore-increasing agent contains a large amount of low-melting substances, which is not conducive to the high-temperature performance of the material. Publication number CN112573935A discloses a method for preparing forsterite-magnesium-aluminum spinel insulating refractory materials. The forsterite-magnesium-aluminum spinel insulating refractory materials are prepared by a two-step calcination process. This method uses high-temperature decomposition of magnesium carbonate raw materials to form pores, which not only increases CO2 emissions, but also the resulting forsterite and magnesium-aluminum spinel composite phase causes its corrosion resistance to be worse than that of periclase.

[0003] Hollow sphere refractory materials have the advantages of high strength and good corrosion resistance. They can effectively reduce the average thermal conductivity of refractory components, thereby improving the thermal insulation and heat insulation effect of high-temperature facilities. At present, the template method and the electric melting spray method are the main methods for preparing ceramic hollow spheres. CN116120044A provides a method for preparing energy-saving and wear-resistant zirconium corundum composite hollow sphere casting materials. The method uses polyethylene balls as templates for granulation. The process involves slurry filtration and ball molding. The process is complex and time-consuming. Chen Zhening (Chen Zhening, et al. Preparation, structure and properties of lightweight spinel hollow sphere ceramics [J], Journal of Materials Science and Engineering, 2022, 40(03): 412~417+422.) prepared magnesium aluminum spinel hollow sphere ceramics using the electric melting spray process. The hollow spheres obtained by this method have high strength and high operating temperature. However, the electric melting method requires high energy consumption and is not easy to prepare gradient composite hollow spheres. Therefore, it is necessary to develop an efficient preparation process for alkaline refractory hollow balls. While ensuring the performance of alkaline refractory materials, the pore structure should be introduced to reduce the heat conduction of high-temperature facilities, which will have a positive role in reducing carbon emissions from high-temperature industries. Summary of the Invention

[0004] The present invention addresses the shortcomings of the prior art by providing a method for preparing periclase-forsterite gradient composite hollow spheres. This method addresses the shortcomings of the prior art by providing a method for preparing periclase-forsterite gradient composite hollow spheres. The method utilizes the physical properties of periclase and forsterite to develop gradient composite hollow spheres with high strength, low thermal conductivity, and excellent corrosion resistance, taking into account the fact that periclase has the best corrosion resistance among alkaline refractory materials, while forsterite has the lowest thermal conductivity (1 / 4 to 1 / 3 of periclase). Furthermore, the two phases exhibit excellent compatibility.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing periclase-forsterite gradient composite hollow spheres comprises the following steps:

[0007] Step 1: Grind 75-95 wt% of magnesium-rich silicate mineral, 1-10 wt% of light-burned magnesia, and 1-15 wt% of natural quartz into a 500-mesh fine powder, and add 4-6 wt% of a binder based on the sum of the above raw materials and mix them;

[0008] Step 2: granulating the mixed raw materials in a disc granulator, and sieving to obtain spherical particles with a particle size of 0.2-0.4 mm;

[0009] Step 3: Using the above-mentioned spherical particles as cores, the granulator is rotated to wrap 10-30 wt% of light-burned magnesia based on the spherical particles to obtain a non-homogeneous spherical particle body rich in SiO2.

[0010] Step 4: fully drying the obtained spherical particle green body, sintering it at high temperature in a high-temperature furnace according to a heating system, and obtaining the periclase-forsterite gradient composite hollow sphere after cooling in the furnace.

[0011] Furthermore, the magnesium-rich silicate mineral in step 1 is talc, and the SiO2 content of the raw material after ignition is 50-55wt%, and the MgO content is 40-45wt%.

[0012] Furthermore, in step 1, the MgO content of the light-burned magnesia is ≥95.0wt%, and the SiO2 content of the natural quartz is ≥99.5wt%.

[0013] Furthermore, the binder in step 1 is yellow dextrin.

[0014] Furthermore, the mixing condition in step 1 is spraying a binder to assist granulation at a rotation speed of 20-80 r / min.

[0015] Furthermore, in step 4, the high temperature firing is carried out according to the diffusion reaction characteristics of the raw materials. That is, the temperature is increased from 1400-1450° C. to 1600-1650° C. for 1 hour and then calcined for 2 hours to obtain spherical particles with a hollow structure.

[0016] Furthermore, the outer shell of the hollow sphere obtained by the preparation method is mainly composed of a periclase phase (accounting for about 50-90%), and has a gradient composite structure in which the forsterite phase gradually increases from the surface of the sphere shell to the inside.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention uses abundant magnesium-rich silicate minerals as the primary raw material and employs a composite coating-in-situ diffusion reaction pore-forming process to produce hollow spheres suitable for use in alkaline refractory materials. This method boasts high pore-forming efficiency and is pollution-free during production.

[0019] 2. The present invention generates a low thermal conductivity forsterite phase in situ on the inner side of the spherical shell through the diffusion reaction of magnesium-rich silicate. The outer layer of the spherical shell is a periclase phase with excellent corrosion resistance. It can give full play to the advantages of the gradient composite of alkaline high-temperature phases, while ensuring the performance of the alkaline refractory components, and effectively reduce the heat loss of high-temperature facilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The microstructure and Mg and Si element distribution diagram of the cross section of the periclase-forsterite gradient composite hollow sphere prepared in Example 1 of the present invention;

[0021] Figure 2 This is a morphology diagram of the cross section of the periclase-forsterite gradient composite hollow sphere prepared in Example 1 of the present invention after solidification. DETAILED DESCRIPTION

[0022] The technical solutions and effects of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto. Example 1

[0023] This embodiment provides a method for preparing periclase-forsterite gradient composite hollow spheres, comprising the following steps:

[0024] First, 90 wt% of talc, 6 wt% of natural quartz, and 4 wt% of light-burned magnesia are ground into a 500-mesh fine powder, and 6 wt% of yellow dextrin binder, which is the sum of the above raw materials, is added and mixed;

[0025] Secondly, the mixed raw materials are granulated in a disc granulator and sieved to obtain spherical particles with a particle size of 0.2~0.4mm;

[0026] Then, the spherical particles are used as cores and coated with 30 wt% light-burned magnesia based on the spherical particles under the rotation of a granulator to obtain a non-homogeneous spherical particle body with rich SiO2 inside;

[0027] Finally, the obtained spherical particle body is fully dried, kept at 1400℃ for 1 hour, then heated to 1650℃ and kept at this temperature for 1 hour in a high temperature furnace for calcination, and then cooled in the furnace to obtain the periclase-forsterite gradient composite hollow sphere. Its microstructure and Mg and Si element distribution are shown in the figure. Figure 1 As shown, the morphology after curing is as follows Figure 2 As shown, the median particle size is 1.25 mm, the average shell thickness is 0.33 mm, and it is added to light-burned magnesia at a mass fraction of 30% and pressed into a cylindrical sample. The average strength of the test is 10.9 MPa. Example 2

[0028] This embodiment provides a method for preparing periclase-forsterite gradient composite hollow spheres, comprising the following steps:

[0029] First, 85wt% of talc, 5wt% of natural quartz, and 10wt% of light-burned magnesia are ground into a 500-mesh fine powder, and 5wt% of yellow dextrin binder, which is the sum of the above raw materials, is added and mixed;

[0030] Secondly, the mixed raw materials are granulated in a disc granulator and sieved to obtain spherical particles with a particle size of 0.2~0.4mm;

[0031] Then, the spherical particles are used as cores and coated with 20 wt% light-burned magnesia based on the spherical particles under the rotation of a granulator to obtain a non-homogeneous spherical particle body with rich SiO2 inside;

[0032] Finally, the resulting spherical particle body was thoroughly dried and calcined in a high-temperature furnace at 1450°C for 1 hour, then raised to 1650°C for 2 hours. After cooling in the furnace, the periclase-forsterite gradient composite hollow spheres were obtained. These hollow spheres were added to light-burned magnesia at a mass fraction of 30% and pressed into cylindrical specimens, demonstrating an average strength of 11.2 MPa. Example 3

[0033] This embodiment provides a method for preparing periclase-forsterite gradient composite hollow spheres, comprising the following steps:

[0034] First, 78wt% of talc, 10wt% of light-burned magnesia, and 12wt% of natural quartz were ground into 500-mesh fine powder, and 6wt% of yellow dextrin binder, which was the sum of the above raw materials, was added and mixed;

[0035] Secondly, the mixed raw materials are granulated in a disc granulator and sieved to obtain spherical particles with a particle size of 0.2~0.4mm;

[0036] Then, the spherical particles are used as cores and coated with 15 wt% light-burned magnesia based on the spherical particles under the rotation of a granulator to obtain a non-homogeneous spherical particle body with rich SiO2 inside;

[0037] Finally, the resulting spherical particle body was thoroughly dried and calcined in a high-temperature furnace at 1400°C for 1 hour, then raised to 1650°C for 2 hours. After cooling in the furnace, the periclase-forsterite gradient composite hollow spheres were obtained. These hollow spheres were added to light-burned magnesia at a mass fraction of 30% and pressed into cylindrical specimens, demonstrating an average strength of 25.5 MPa.

[0038] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing periclase-forsterite gradient composite hollow spheres, characterized in that: The preparation method comprises the following steps: Step 1: Grind 75-95 wt% of magnesium-rich silicate mineral, 1-10 wt% of light-burned magnesia, and 1-15 wt% of natural quartz into a 500-mesh fine powder, and add 4-6 wt% of a binder based on the sum of the above raw materials and mix them; Step 2: granulating the mixed raw materials in a disc granulator, and sieving to obtain spherical particles with a particle size of 0.2-0.4 mm; Step 3, using the above-mentioned spherical particles as cores, wrapping 10-30wt% of light-burned magnesia based on the spherical particles under the rotation of a granulator to obtain a non-homogeneous spherical particle body rich in SiO2; Step 4: fully drying the obtained spherical particle green body, sintering it at high temperature in a high-temperature furnace according to a heating system, and obtaining the periclase-forsterite gradient composite hollow sphere after cooling in the furnace.

2. The method for preparing periclase-forsterite gradient composite hollow spheres according to claim 1, wherein In step 1, the magnesium-rich silicate mineral is talc, and the raw material has a SiO2 content of 50-55wt% and a MgO content of 40-45wt% after burning.

3. The method for preparing periclase-forsterite gradient composite hollow spheres according to claim 1, wherein In the step 1, the MgO content of the light-burned magnesia is ≥95.0wt%, and the SiO2 content of the natural quartz is ≥99.5wt%.

4. The method for preparing periclase-forsterite gradient composite hollow spheres according to claim 1, wherein The binder in step 1 is yellow dextrin.

5. The method for preparing periclase-forsterite gradient composite hollow spheres according to claim 1, wherein The mixing condition in step 1 is to spray a binder to assist granulation at a rotation speed of 20-80 r / min.

6. The method for preparing periclase-forsterite gradient composite hollow spheres according to claim 1, wherein: In the step 4, the high temperature firing is carried out according to the diffusion reaction characteristics of the raw materials. The temperature is raised from 1400-1450° C. for 1 hour to 1600-1650° C. for 2 hours to obtain spherical particles with a hollow structure.

7. The method for preparing periclase-forsterite gradient composite hollow spheres according to claim 1, wherein: The outer shell of the hollow sphere obtained by the preparation method is mainly composed of a periclase phase, and has a gradient composite structure in which the forsterite phase gradually increases from the surface of the sphere shell to the inside.

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