Magnesium-manganese-aluminum composite spinel brick and preparation method thereof

Abstract

The invention belongs to the technical field of refractory materials, and particularly relates to a magnesium-manganese-aluminum composite spinel brick and a preparation method thereof. The preparation method comprises the following steps: by taking 4-ethoxy-3-methylphenylboronic acid as a modifier, introducing boric acid ester groups on the surfaces of phenolic resin hollow microspheres to prepare boric acid ester modified phenolic resin hollow microspheres; the preparation method comprises the following steps: modifying alkaline silica sol by using epoxy organic silicon resin, introducing an organic polymer to the particle surface of the alkaline silica sol to prepare modified silica sol, and mixing the modified silica sol with sodium hexametaphosphate to prepare the composite binder. According to the invention, high-purity magnesia, fused magnesia, fused hercynite, alpha-Al2O3 micro powder, manganese dioxide powder, metal manganese powder, a composite binder and boric acid ester modified phenolic resin hollow microspheres are compounded; the prepared magnesium-manganese-aluminum composite spinel brick has excellent mechanical properties, high temperature resistance, corrosion resistance and kiln coating hanging performance while keeping low heat conductivity.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory materials, and in particular relates to a magnesium-manganese-aluminum composite spinel brick and a preparation method thereof. Background Art

[0002] The idea of ​​using a new dry-process rotary kiln to treat domestic waste is to simultaneously treat, utilize, and avoid secondary pollution of urban domestic waste. Its use is called the application of secondary raw fuel in the cement industry. Using a new dry-process cement rotary kiln to treat domestic waste must ensure the production of cement products, no pollution to cement products, no damage to the environment, and has very high requirements for lining bricks. Harmful elements such as Cl, Na, and S contained in domestic waste will form strong acids and alkalis during the firing process, affecting the life of lining bricks. Considering seasonal changes, garbage classification and treatment, and coordinated disposal of different wastes, etc., higher requirements are put forward for cement rotary kiln lining bricks and the entire use conditions. After the development of magnesia-aluminum-manganese spinel bricks has achieved certain results, along with the sharp increase in domestic domestic waste, cement rotary kilns have increasingly dominated the treatment of domestic waste. How to develop a product that can not only have the performance of chrome-free bricks on the basis of chrome-free, but also resist the erosion of fly ash and strong acids and alkalis has always been the research direction. In the process of preparing magnesium aluminum manganese spinel bricks, high-purity sintered magnesia, a small amount of manganese compounds and other additives are used as the main raw materials, and sintered at medium and high temperatures. The product has low porosity, high density, excellent performance at room temperature, good thermal shock stability, kiln skin performance, wear resistance, and chemical corrosion resistance. It has obvious advantages and is suitable for the coordinated treatment of domestic waste.

[0003] The patent with application number CN201210437246.6 provides a magnesia carbon brick with added manganese dioxide, including the following raw materials: fused magnesia sand, flaky graphite powder, metal aluminum powder, silicon powder, manganese dioxide fine powder, and phenolic resin. The invention adds manganese dioxide, and the metal aluminum powder of the magnesia carbon brick is directly converted into alumina during use, and then becomes manganese aluminum spinel with a melting point of up to 1850°C, which not only inhibits the formation of easily hydrated products aluminum carbide and aluminum nitride, but also significantly improves the hydration resistance of the magnesia carbon brick. The formation of manganese aluminum spinel is accompanied by volume expansion, which also improves the density of the magnesia carbon brick structure, so that the magnesia carbon brick has greater high-temperature strength, and at the same time blocks the channel for gas entry, so that the magnesia carbon brick has better antioxidant properties. In addition, the high melting point of manganese aluminum spinel also ensures the slag resistance of the magnesia carbon brick; however, the magnesia carbon brick provided by the invention has a low apparent porosity and a high thermal conductivity. When used in the calcining zone and transition zone of a cement kiln, it will cause a high cylinder temperature, resulting in Safety hazards; The patent with application number CN202110991680.8 provides a microporous magnesia-iron-aluminum spinel brick for the firing zone of a cement rotary kiln, including the following raw materials: microporous high-purity magnesia sand, fused magnesia sand, fused ferroaluminum spinel, polylight balls, silica sol and industrial manganese powder. The invention has good refractory properties, high high-temperature strength, good thermal stability, resistance to various corrosions, small heavy-burned fiber changes, and low thermal conductivity by adding polylight balls into the mixer. After use, the thermal conductivity of the magnesia-iron-aluminum spinel brick is greatly reduced. By adding microporous high-purity magnesia sand and fused magnesia sand to the mixer, the thermal conductivity of the product is further reduced, thereby reducing the temperature of the cement kiln cylinder, reducing the heat dissipation of the cement rotary kiln, reducing energy consumption, and at the same time reducing carbon dioxide emissions, reducing air pollution, and solving the problems of high thermal conductivity and large coal consumption. However, the strength of the magnesia-iron-aluminum spinel brick provided by the invention needs to be further improved, and it is difficult to meet the diversified market needs. Summary of the invention

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a magnesium-manganese-aluminum composite spinel brick and a preparation method thereof. The magnesium-manganese-aluminum composite spinel brick has the characteristics of high strength, low thermal conductivity, high temperature resistance, corrosion resistance, etc., and can meet diversified market demands.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0006] A magnesium-manganese-aluminum composite spinel brick comprises the following raw materials in parts by weight: 20-30 parts of high-purity magnesia sand with a particle size of 3-5mm, 10-15 parts of high-purity magnesia sand with a particle size of 1-3mm, 10-15 parts of high-purity magnesia sand with a particle size of 0-1mm, 1-4 parts of fused iron-aluminum spinel with a particle size of 1-3mm, 3-6 parts of fused iron-aluminum spinel with a particle size of 0-1mm, 20-40 parts of fused magnesia sand, 2-4 parts of α-Al2O3 micropowder, 0.6-1.0 parts of manganese dioxide powder, 0.4-0.8 parts of metallic manganese powder, 2-4 parts of composite binder, and 5-7 parts of borate-modified phenolic resin hollow microspheres; the composite binder is prepared by mixing modified silica sol and sodium hexametaphosphate, and the mass ratio of the modified silica sol to the sodium hexametaphosphate is 25-35:1;

[0007] The preparation method of the modified silica sol is:

[0008] The silicone resin is dissolved in toluene to obtain a mixed solution. Under stirring conditions, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and salicylic acid are mixed evenly, and the temperature is raised to 80-100°C. The mixed solution is added dropwise, and the addition is completed within 30-50 minutes. The reaction is carried out for 3-5 hours. Bisphenol A is then added, and the reaction is continued for 1-3 hours. Toluene is evaporated to obtain an epoxy silicone resin. Under stirring conditions, the alkaline silica sol is heated to 70-80°C, the epoxy silicone resin is added, the reaction is carried out for 3-6 hours, and the modified silica sol is obtained.

[0009] Phenolic resin hollow microspheres are a new chemical material with a special hollow structure, wherein the core is hollow and the outer layer is phenolic resin. The material has the characteristics of low density, low thermal conductivity, excellent thermal stability, low thermal conductivity and low heat conduction coefficient, and can absorb electromagnetic waves. The material is often used as a filler for composite materials, and the mechanical and thermal properties of the composite materials are improved while reducing the quality of the products. The material can be used as an additive for lightweight adhesives in building materials and chemical industry, and the hollow microspheres of phenolic resin can also be coated on the surface of the material as an ablation layer after being bonded with resin to protect the internal structure of the material. In order to further expand its scope of application, the present invention utilizes 4-ethoxy-3-methylphenylboronic acid to modify the hollow microspheres of phenolic resin, introduces borate groups on the surface of the hollow microspheres of phenolic resin, improves the bonding property of the hollow microspheres, and the boron atoms in the borate groups can also form boron-containing ceramic structures during the sintering process, which significantly improves the high temperature resistance and corrosion resistance of the material. Inorganic binders have the advantages of high and low temperature resistance, low cost, not easy to age, simple structure and high adhesion. These characteristics make inorganic binders perform well in a variety of application scenarios, especially in environments that need to withstand extreme temperature changes. As a binder for refractory materials, alkaline silica sol can absorb a large amount of water molecules and other substances due to its high adsorption and surface activity. At the same time, it also has high chemical stability and heat resistance, and can exist stably under high temperature conditions. When alkaline silica sol comes into contact with other materials, the active groups in the silica sol will be adsorbed on the surface of the material to form a layer of silica sol film, and form a "suction cup"-like force, which makes the materials adsorb to each other and show excellent adhesion. However, conventional alkaline silica sols have poor stability and low surface functionalization, and cannot meet the special requirements of certain industries. The present invention first uses silicone resin and epoxy silane to prepare epoxy silicone resin, and then uses epoxy silicone resin to modify the surface of alkaline silica sol to obtain modified silica sol, which improves the stability and adhesion of alkaline silica sol, and also improves the compatibility of modified silica sol with borate-modified phenolic resin hollow microspheres. The present invention significantly improves its stability and gel concentration by introducing organic polymers on the surface of alkaline silica sol, so that it shows new application potential.

[0010] Furthermore, the mass ratio of the silicone resin, 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane, salicylic acid, and bisphenol A is 5:8-12:0.3-0.5:0.4-0.6, the amount of silicone resin added to toluene is 0.25-0.55 g / mL, the mass ratio of the alkaline silica sol to the epoxy silicone resin is 20:0.5-1.5, the colloidal particle size of the alkaline silica sol is 15-25 nm, the SiO2 content is 20-30%, and the pH is 9-11.

[0011] Furthermore, the preparation method of the borate-modified phenolic resin hollow microspheres is as follows: dispersing the phenolic resin hollow microspheres in xylene, heating to 55-75° C., adding 4-ethoxy-3-methylphenylboronic acid, stirring and reacting for 3.5-4.5 hours, cooling to room temperature, separating the solid from the liquid, washing and drying the solid, and obtaining the borate-modified phenolic resin hollow microspheres.

[0012] Furthermore, the mass ratio of the phenolic resin hollow microspheres to 4-ethoxy-3-methylphenylboronic acid is 10:2.5-4.5, and the mass volume ratio of the phenolic resin hollow microspheres to xylene is 0.5-1.5 mg / mL.

[0013] The present invention also provides a method for preparing a magnesium-manganese-aluminum composite spinel brick, comprising the following steps:

[0014] Add high-purity magnesia with a particle size of 3-5mm, high-purity magnesia with a particle size of 1-3mm, and fused iron-aluminum spinel with a particle size of 1-3mm into a mixer, premix for 2-4 minutes, add a composite binder, mix for 5-10 minutes, and then add high-purity magnesia with a particle size of 0-1mm, fused iron-aluminum spinel with a particle size of 0-1mm, fused magnesia, α-Al2O3 powder, manganese dioxide powder, metallic manganese powder, borate modified phenolic resin hollow microspheres, continue to mix for 15-25 minutes, and after pressing and molding by a press, first dry at 100-150°C for 24-72 hours, then sinter at 1450-1550°C for 5-8 hours, and naturally cool to room temperature to obtain magnesium-manganese-aluminum composite spinel bricks.

[0015] The present invention has the following beneficial effects:

[0016] The present invention uses 4-ethoxy-3-methylphenylboronic acid as a modifier, introduces borate groups on the surface of the hollow microspheres of phenolic resin through the dehydration condensation reaction of boron hydroxyl groups and phenolic hydroxyl groups in the hollow microsphere structure of phenolic resin, improves the adhesion of the hollow microspheres, and the boron atoms in the borate groups can also form boron-containing ceramic structures during the sintering process, which are attached to the magnesium-manganese-aluminum spinel material, not only providing additional heat insulation functions, but also protecting the material from erosion and damage by the external environment, thereby significantly improving the high temperature resistance and corrosion resistance of the material. During the sintering process, the borate-modified hollow microspheres of phenolic resin can form circular micropores in the internal structure of the magnesium-manganese-aluminum composite spinel brick, increase the gas-solid interface in the brick structure, increase the phonon scattering of solid-phase heat conduction, thereby effectively reducing the thermal conductivity of the brick, and the circular micropores can also provide stress buffering for the magnesium-manganese-aluminum composite spinel brick in the process of rapid cooling and rapid heating, thereby improving its thermal shock resistance. In addition, during the sintering process, the carbon in the phenolic resin hollow microspheres can be modified by borate to create a reducing atmosphere, which can avoid Fe 2+ Oxidized to Fe 3+This results in a larger volume effect in the magnesium-manganese-aluminum composite spinel brick during firing or use, thereby ensuring the stability of the product.

[0017] The present invention utilizes organosilicon resin and epoxysilane to prepare epoxy organosilicon resin, and then introduces organic polymer on the surface of alkaline silica sol particles through ring-opening addition reaction of epoxy organosilicon resin and alkaline silica sol, thereby improving the stability and adhesion of modified silica sol, and improving the compatibility of modified silica sol and hollow microspheres of borate-modified phenolic resin. By compounding modified silica sol, sodium hexametaphosphate, and hollow microspheres of borate-modified phenolic resin, the bonding force of the composite binder is significantly enhanced, and the connection strength between the raw material components before sintering is effectively improved, thereby increasing the density of the product after sintering. The silicon dioxide structure in the modified silica sol can also sinter with the aluminum oxide in the raw material to form a mullite structure, further improving the thermal stability of the material.

[0018] The present invention combines high-purity magnesia and fused magnesia as raw materials, and compound fused ferroaluminum spinel. After high-temperature heat treatment, the Fe in the fused ferroaluminum spinel is 2+ and Mg in periclase 2+ The annular cracks formed by the ion exchange reaction have a good promoting effect on the flexibility of the magnesium-manganese-aluminum spinel composite material. 2+ Diffusion into magnesia sand improves the kiln skin performance of the sample, and the dense reaction zone formed by the reaction between fused iron-aluminum spinel and magnesia sand, the volume expansion during the reaction process blocks the pores, improves the density of the reaction sintering zone, and effectively inhibits the secondary penetration of cement clinker. The reaction sintering zone of a certain thickness can also improve the bonding strength between the raw material components, and at the same time improve the anti-stripping property of the composite material under high temperature thermal shock, thereby improving the mechanical strength and thermal shock resistance of magnesium-manganese-aluminum composite spinel bricks. By compounding α-Al2O3 micropowder, sintering can be promoted, and iron ions and aluminum ions can form in-situ spinel and continuous or semi-continuous solid solutions with magnesium oxide, which can significantly improve the high-temperature performance of the material. By compounding manganese dioxide powder and metallic manganese powder, manganese ions can replace part of magnesium ions in the periclase crystal structure during sintering to form a stable structure, thereby ensuring the sintering stability and solid solubility of the product, as well as the volume stability and good kiln skin performance of the product.

[0019] The preparation process provided by the present invention ensures the bonding strength between the raw material components, improves the purity and stability of the material through the sintering process, and ensures the consistency and reliability of the material. The magnesium-manganese-aluminum composite spinel brick provided by the present invention has excellent mechanical properties, high temperature resistance, corrosion resistance and kiln skin performance while maintaining low thermal conductivity. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] High-purity magnesia, particle size is 5-3mm, 3-1mm, 0-1mm, its chemical composition (w) mainly includes: MgO 95.44%, CaO1.50%, SiO2 1.56%, Fe2O3 0.93%, Al2O3 0.31%, volume density is 3.27g / cm 3 ; Fused iron-aluminum spinel, particle size 3-1mm, 0-1mm, its chemical composition (w) mainly includes: Al2O3 50.59%, Fe2O3 44.91%, SiO21.22%, MgO 0.96%, CaO 0.38%, volume density 4.24g / cm 3 , fused magnesia, particle size ≤ 0.074mm, its chemical composition (w) mainly includes: MgO 98.12%, CaO 0.9%, SiO2 0.32%, Fe2O3 0.41%, Al2O3 0.05%, volume density 3.44g / cm 3 ; α-Al2O3 powder, particle size is 500 mesh, its chemical composition (w) mainly includes: A12O3>99.3%, SiO2≤0.10%, Fe2O3≤0.04%, Na2O≤0.5%; manganese dioxide powder, effective content 70-75%, particle size is 325 mesh; metal manganese powder, particle size is 500 mesh, manganese content ≥99%; silicone resin, brand Dow Corning, model Z-6018, purchased from Guangzhou Huitu New Materials Co., Ltd.; phenolic resin hollow microspheres, item number FR-F-007-1, average particle size 40-70μm, purchased from Henan Fanrui Composite Materials Research Institute Co., Ltd. The raw materials used in the following examples are all common commercial products.

[0022] Example 1

[0023] A magnesium-manganese-aluminum composite spinel brick comprises the following raw materials in parts by weight: 25 parts of high-purity magnesia sand with a particle size of 3-5mm, 12 parts of high-purity magnesia sand with a particle size of 1-3mm, 12 parts of high-purity magnesia sand with a particle size of 0-1mm, 3 parts of fused iron-aluminum spinel with a particle size of 1-3mm, 4 parts of fused iron-aluminum spinel with a particle size of 0-1mm, 30 parts of fused magnesia sand, 3 parts of α-Al2O3 micropowder, 0.8 parts of manganese dioxide powder, 0.6 parts of metallic manganese powder, 3 parts of composite binder, and 6 parts of borate-modified phenolic resin hollow microspheres; the composite binder is prepared by mixing modified silica sol and sodium hexametaphosphate, and the mass ratio of the modified silica sol to the sodium hexametaphosphate is 30:1;

[0024] The preparation method of the modified silica sol is as follows: dissolving an organic silicone resin in toluene to obtain a mixed solution, mixing 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and salicylic acid evenly under stirring at 180 rpm, heating to 90°C, adding the mixed solution dropwise, and completing the addition within 40 minutes, reacting for 4 hours, then adding bisphenol A, and continuing the reaction for 2 hours. After the reaction is completed, heating to 118-120°C, distilling off toluene, and obtaining an epoxy organic silicone resin; heating the alkaline silica sol under stirring at 180 rpm, and heating the alkaline silica sol to 90°C. The mixture was heated to 75°C, epoxy silicone resin was added, the reaction was continued for 5 hours, and the mixture was cooled to room temperature to obtain a modified silica sol; wherein the mass ratio of silicone resin, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, salicylic acid, and bisphenol A was 5:10:0.4:0.5, the amount of silicone resin added to toluene was 0.45 g / mL, the mass ratio of alkaline silica sol to epoxy silicone resin was 20:1, the colloidal particle size of the alkaline silica sol was 15-25 nm, the SiO2 content was 25%, and the pH was 9-11;

[0025] The preparation method of borate-modified phenolic resin hollow microspheres is as follows: disperse the phenolic resin hollow microspheres in xylene, heat to 65°C, add 4-ethoxy-3-methylphenylboronic acid, react for 4 hours under stirring at 160rpm, cool to room temperature, separate the solid and the liquid, take the solid, wash it three times with acetone, and vacuum dry it at 80°C for 12 hours to obtain borate-modified phenolic resin hollow microspheres; wherein the mass ratio of the phenolic resin hollow microspheres to 4-ethoxy-3-methylphenylboronic acid is 10:3.5, and the mass volume ratio of the phenolic resin hollow microspheres to xylene is 1 mg / mL.

[0026] A method for preparing a magnesium-manganese-aluminum composite spinel brick comprises the following steps:

[0027] Add high-purity magnesia with a particle size of 3-5mm, high-purity magnesia with a particle size of 1-3mm, and fused iron-aluminum spinel with a particle size of 1-3mm into a mixer, premix for 3 minutes, then add a composite binder, mix for 8 minutes, and then add high-purity magnesia with a particle size of 0-1mm, fused iron-aluminum spinel with a particle size of 0-1mm, fused magnesia, α-Al2O3 micropowder, manganese dioxide powder, metallic manganese powder, and borate-modified phenolic resin hollow microspheres, continue mixing for 20 minutes, press and form on a 1000-ton press, first dry at 130°C for 48 hours, then sinter at 1500°C for 6 hours, and naturally cool to room temperature to obtain magnesium-manganese-aluminum composite spinel bricks; the pressing and forming operation can be carried out using conventional techniques in the field.

[0028] Example 2

[0029] A magnesium-manganese-aluminum composite spinel brick comprises the following raw materials in parts by weight: 20 parts of high-purity magnesia sand with a particle size of 3-5mm, 15 parts of high-purity magnesia sand with a particle size of 1-3mm, 15 parts of high-purity magnesia sand with a particle size of 0-1mm, 1 part of fused iron-aluminum spinel with a particle size of 1-3mm, 6 parts of fused iron-aluminum spinel with a particle size of 0-1mm, 20 parts of fused magnesia sand, 4 parts of α-Al2O3 micropowder, 1 part of manganese dioxide powder, 0.4 parts of metallic manganese powder, 4 parts of composite binder, and 5 parts of borate-modified phenolic resin hollow microspheres; the composite binder is prepared by mixing modified silica sol and sodium hexametaphosphate, and the mass ratio of the modified silica sol to the sodium hexametaphosphate is 25:1;

[0030] The preparation method of the modified silica sol is as follows: dissolving an organic silicone resin in toluene to obtain a mixed solution, mixing 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and salicylic acid evenly under stirring at 180 rpm, heating to 90°C, adding the mixed solution dropwise, and completing the addition within 40 minutes, reacting for 4 hours, then adding bisphenol A, and continuing the reaction for 2 hours. After the reaction is completed, heating to 118-120°C, distilling off toluene, and obtaining an epoxy organic silicone resin; heating the alkaline silica sol under stirring at 180 rpm, to 75° C., adding epoxy silicone resin, reacting for 5 hours, and cooling to room temperature to obtain modified silica sol; wherein the mass ratio of silicone resin, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, salicylic acid, and bisphenol A is 5:12:0.5:0.6, the amount of silicone resin added to toluene is 0.45 g / mL, the mass ratio of alkaline silica sol to epoxy silicone resin is 20:0.5, the colloidal particle size of alkaline silica sol is 15-25 nm, the SiO2 content is 25%, and the pH is 9-11;

[0031] The preparation method of borate-modified phenolic resin hollow microspheres is as follows: disperse the phenolic resin hollow microspheres in xylene, heat to 55°C, add 4-ethoxy-3-methylphenylboronic acid, react for 4.5 hours under stirring conditions of 160rpm, cool to room temperature, separate the solid and the liquid, take the solid, wash it three times with acetone, and vacuum dry it at 80°C for 12 hours to obtain borate-modified phenolic resin hollow microspheres; wherein the mass ratio of the phenolic resin hollow microspheres to 4-ethoxy-3-methylphenylboronic acid is 10:4.5, and the mass volume ratio of the phenolic resin hollow microspheres to xylene is 1 mg / mL.

[0032] A method for preparing a magnesium-manganese-aluminum composite spinel brick is prepared according to the method described in Example 1, except that after being pressed and formed, it is first dried at 150° C. for 24 hours and then sintered at 1450° C. for 8 hours.

[0033] Example 3

[0034] A magnesium-manganese-aluminum composite spinel brick comprises the following raw materials in parts by weight: 30 parts of high-purity magnesia sand with a particle size of 3-5 mm, 10 parts of high-purity magnesia sand with a particle size of 1-3 mm, 10 parts of high-purity magnesia sand with a particle size of 0-1 mm, 4 parts of fused iron-aluminum spinel with a particle size of 1-3 mm, 3 parts of fused iron-aluminum spinel with a particle size of 0-1 mm, 40 parts of fused magnesia sand, 2 parts of α-Al2O3 micropowder, 0.6 parts of manganese dioxide powder, 0.8 parts of metallic manganese powder, 2 parts of composite binder, and 7 parts of borate-modified phenolic resin hollow microspheres; the composite binder is prepared by mixing modified silica sol and sodium hexametaphosphate, and the mass ratio of the modified silica sol to the sodium hexametaphosphate is 35:1;

[0035] The preparation method of the modified silica sol is as follows: dissolving an organic silicone resin in toluene to obtain a mixed solution, mixing 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and salicylic acid evenly under stirring at 180 rpm, heating to 90°C, adding the mixed solution dropwise, and completing the addition within 40 minutes, reacting for 4 hours, then adding bisphenol A, and continuing the reaction for 2 hours. After the reaction is completed, heating to 118-120°C, distilling off toluene, and obtaining an epoxy organic silicone resin; heating the alkaline silica sol under stirring at 180 rpm, and heating the alkaline silica sol to 90°C. The mixture was heated to 75°C, epoxy silicone resin was added, the reaction was continued for 5 hours, and the mixture was cooled to room temperature to obtain a modified silica sol; wherein the mass ratio of silicone resin, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, salicylic acid, and bisphenol A was 5:8:0.3:0.4, the amount of silicone resin added to toluene was 0.45 g / mL, the mass ratio of alkaline silica sol to epoxy silicone resin was 20:1.5, the colloidal particle size of the alkaline silica sol was 15-25 nm, the SiO2 content was 25%, and the pH was 9-11;

[0036] The preparation method of borate-modified phenolic resin hollow microspheres is as follows: disperse the phenolic resin hollow microspheres in xylene, heat to 75°C, add 4-ethoxy-3-methylphenylboronic acid, react for 3.5 hours under stirring conditions of 160rpm, cool to room temperature, separate the solid and the liquid, take the solid, wash it three times with acetone, and vacuum dry it at 80°C for 12 hours to obtain borate-modified phenolic resin hollow microspheres; wherein the mass ratio of the phenolic resin hollow microspheres to 4-ethoxy-3-methylphenylboronic acid is 10:2.5, and the mass volume ratio of the phenolic resin hollow microspheres to xylene is 1 mg / mL.

[0037] A method for preparing a magnesium-manganese-aluminum composite spinel brick is prepared according to the method described in Example 1, except that after being pressed and formed, it is first dried at 100° C. for 72 hours and then sintered at 1550° C. for 5 hours.

[0038] Comparative Example 1

[0039] A magnesium-manganese-aluminum composite spinel brick, the raw material composition of which is according to the method described in Example 1, except that the modified silica sol is replaced by alkaline silica sol.

[0040] A method for preparing a magnesium-manganese-aluminum composite spinel brick is prepared according to the method described in Example 1.

[0041] Comparative Example 2

[0042] A magnesium-manganese-aluminum composite spinel brick, whose raw material composition is according to the method described in Example 1, except that the borate-modified phenolic resin hollow microspheres are replaced by phenolic resin hollow microspheres.

[0043] A method for preparing a magnesium-manganese-aluminum composite spinel brick is prepared according to the method described in Example 1.

[0044] Comparative Example 3

[0045] A magnesium-manganese-aluminum composite spinel brick, whose raw material composition is according to the method described in Example 1, except that the modified silica sol is replaced by alkaline silica sol, and the borate-modified phenolic resin hollow microspheres are replaced by phenolic resin hollow microspheres.

[0046] A method for preparing a magnesium-manganese-aluminum composite spinel brick is prepared according to the method described in Example 1.

[0047] The magnesium-manganese-aluminum composite spinel bricks prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to relevant performance tests. The room temperature compressive strength test was carried out in accordance with GB / T 5072-2023 "Test method for room temperature compressive strength of refractory materials"; the high temperature flexural strength test was carried out in accordance with GB / T 3002-2004 "Test Method for High-Temperature Flexural Strength of Refractory Materials"; For thermal shock resistance test, the sample was dried at 120°C to constant weight, transferred to a drying oven at 250-300°C and kept for 2h, then kept at 1100°C for 30min, the sample was taken out and blown with cold air for 5min, and the above hot and cold alternating test was repeated 5 times. The thermal shock resistance was expressed by the retention rate of the sample's room-temperature compressive strength, and the calculation formula was: Room-temperature compressive strength retention rate (%) = room-temperature compressive strength of the sample after thermal shock / room-temperature compressive strength of the sample before thermal shock × 100%; The apparent porosity and bulk density tests were carried out in accordance with GB / T2997-2000 "Test Method for Bulk Density, Apparent Porosity and True Porosity of Dense Shaped Refractory Products"; The thermal conductivity test was carried out in accordance with GB / T The load softening temperature test was carried out in accordance with GB / T 5989-2008 "Test method for softening temperature under load of refractory materials - differential heating method"; the corrosion resistance test was carried out in accordance with GB / T 14983-2008 "Test method for alkali resistance of refractory materials"; the kiln lining performance test was carried out in accordance with JC / T 2463-2018 "Static test method for kiln lining of refractory materials for cement kiln", and the bonding strength was used to indicate the quality of the refractory kiln lining performance; the above tests were repeated three times and the average value was taken. The test results are shown in Table 1. As can be seen from Table 1, compared with Comparative Examples 1-3, the magnesium-manganese-aluminum composite spinel bricks prepared in Examples 1-3 maintain a relatively suitable apparent porosity, bulk density and low thermal conductivity, and also have relatively excellent room temperature compressive strength, high temperature flexural strength, thermal shock resistance, load softening temperature, corrosion resistance and bonding strength. As can be seen from the data in the table, the alkaline silica sol and the phenolic resin hollow microspheres are modified respectively, and the modified silica sol, borate-modified phenolic resin hollow microspheres and other raw material components work synergistically, and the prepared magnesium-manganese-aluminum composite spinel bricks have excellent mechanical properties, high temperature resistance, corrosion resistance and kiln skin performance while maintaining low thermal conductivity.

[0048] Table 1 Test results of relevant properties of magnesium-manganese-aluminum composite spinel bricks

[0049] Test items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Normal temperature compressive strength / MPa 94 97 92 77 75 68 High temperature flexural strength / MPa 12.7 13.5 12.4 10.3 10.8 9.4 Room temperature compressive strength retention rate / % 89.2 90.1 89.3 82.0 83.2 76.8 Apparent porosity / % 20 19 22 24 23 26 <![CDATA[Bulk density (g / cm 3 )]]> 2.72 2.81 2.64 2.53 2.58 2.46 Thermal conductivity (W / (m·K)) 1.92 2.03 1.85 1.80 1.72 1.60 Softening temperature / ℃ 1805 1814 1797 1752 1730 1694 Corrosion resistance / % 3.2 3.5 3.6 4.0 4.2 4.5 Bond strength / MPa 22.6 21.8 21.4 17.9 18.3 16.4

[0050] Although the embodiments of the present application 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 the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A magnesium-manganese-aluminum composite spinel brick, characterized in that: The invention comprises the following raw materials in parts by weight: 20-30 parts of high-purity magnesia with a particle size of 3-5mm, 10-15 parts of high-purity magnesia with a particle size of 1-3mm, 10-15 parts of high-purity magnesia with a particle size of 0-1mm, 1-4 parts of fused iron-aluminum spinel with a particle size of 1-3mm, 3-6 parts of fused iron-aluminum spinel with a particle size of 0-1mm, 20-40 parts of fused magnesia, 2-4 parts of α-Al2O3 micropowder, 0.6-1.0 parts of manganese dioxide powder, 0.4-0.8 parts of metallic manganese powder, 2-4 parts of composite binder, and 5-7 parts of borate-modified phenolic resin hollow microspheres; the composite binder is prepared by mixing modified silica sol and sodium hexametaphosphate, and the mass ratio of the modified silica sol to the sodium hexametaphosphate is 25-35:1; The preparation method of the modified silica sol is: The silicone resin is dissolved in toluene to obtain a mixed solution. Under stirring conditions, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and salicylic acid are mixed evenly, and the temperature is raised to 80-100°C. The mixed solution is added dropwise, and the addition is completed within 30-50 minutes. The reaction is carried out for 3-5 hours. Bisphenol A is then added, and the reaction is continued for 1-3 hours. Toluene is evaporated to obtain an epoxy silicone resin. Under stirring conditions, the alkaline silica sol is heated to 70-80°C, the epoxy silicone resin is added, the reaction is carried out for 3-6 hours, and the modified silica sol is obtained.

2. The magnesium-manganese-aluminum composite spinel brick according to claim 1, characterized in that: The mass ratio of the silicone resin, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, salicylic acid and bisphenol A is 5:8-12:0.3-0.5:0.4-0.

6.

3. The magnesium-manganese-aluminum composite spinel brick according to claim 1, characterized in that: The amount of the organic silicon resin added to the toluene is 0.25-0.55 g / mL.

4. The magnesium-manganese-aluminum composite spinel brick according to claim 1, characterized in that: The mass ratio of the alkaline silica sol to the epoxy silicone resin is 20:0.5-1.

5.

5. The magnesium-manganese-aluminum composite spinel brick according to claim 1, characterized in that: The alkaline silica sol colloidal particle size is 15-25nm, the SiO2 content is 20-30%, and the pH is 9-11.

6. The magnesium-manganese-aluminum composite spinel brick according to claim 1, characterized in that: The preparation method of the borate-modified phenolic resin hollow microspheres is as follows: dispersing the phenolic resin hollow microspheres in xylene, heating to 55-75° C., adding 4-ethoxy-3-methylphenylboronic acid, stirring and reacting for 3.5-4.5 hours, cooling to room temperature, separating the solid from the liquid, washing and drying the solid, and obtaining the borate-modified phenolic resin hollow microspheres.

7. The magnesium-manganese-aluminum composite spinel brick according to claim 6, characterized in that: The mass ratio of the phenolic resin hollow microspheres to 4-ethoxy-3-methylphenylboronic acid is 10:2.5-4.

5.

8. The magnesium-manganese-aluminum composite spinel brick according to claim 6, characterized in that: The mass volume ratio of the phenolic resin hollow microspheres to xylene is 0.5-1.5 mg / mL.

9. The method for preparing the magnesium-manganese-aluminum composite spinel brick according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: adding high-purity magnesia with a particle size of 3-5 mm, high-purity magnesia with a particle size of 1-3 mm, and fused iron-aluminum spinel with a particle size of 1-3 mm into a mixer, premixing for 2-4 minutes, adding a composite binder, mixing for 5-10 minutes, and then adding high-purity magnesia with a particle size of 0-1 mm, fused iron-aluminum spinel with a particle size of 0-1 mm, fused magnesia, α-Al2O3 micropowder, manganese dioxide powder, metal manganese powder, and borate-modified phenolic resin hollow microspheres, continuing to mix for 15-25 minutes, pressing and molding with a press, drying at 100-150° C. for 24-72 hours, sintering at 1450-1550° C. for 5-8 hours, and naturally cooling to room temperature to obtain a magnesium-manganese-aluminum composite spinel brick.