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

Abstract

The application belongs to the technical field of refractory materials, and particularly relates to a magnesium-manganese-aluminum composite spinel brick and a preparation method thereof. 4-ethoxy-3-methylphenylboronic acid is used as a modifier to introduce borate ester groups on the surface of phenolic resin hollow microspheres to prepare borate ester modified phenolic resin hollow microspheres; epoxy organosilicon resin is used to modify alkaline silica sol to introduce organic polymers on the surface of particles to prepare modified silica sol, and the modified silica sol is mixed with sodium hexametaphosphate to prepare a composite binder. High-purity magnesia, fused magnesia, fused iron-aluminum spinel, alpha-Al2O3 micro powder, manganese dioxide powder, metal manganese powder, the composite binder and the borate ester modified phenolic resin hollow microspheres are compounded to prepare the magnesium-manganese-aluminum composite spinel brick, which has excellent mechanical properties, high-temperature resistance, corrosion resistance and kiln skin hanging performance while maintaining low thermal conductivity.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a magnesium-manganese-alumina composite spinel brick and its preparation method. Background Technology

[0002] The approach to municipal solid waste (MSW) treatment using a novel dry-process rotary kiln is a method that simultaneously processes, utilizes, and avoids secondary pollution. This method is referred to as the application of secondary raw materials in the cement industry. Using a novel dry-process rotary kiln for MSW treatment must ensure that cement production is pollution-free, environmentally friendly, and places high demands on the lining bricks. Harmful elements such as Cl, Na, and S in MSW can form strong acids and alkalis during firing, affecting the lifespan of the lining bricks. Considering seasonal variations, waste sorting, and the co-processing of different wastes, higher requirements are placed on the cement rotary kiln lining bricks and the overall operating conditions. Following the achievements in magnesium-aluminum-manganese spinel bricks, and with the rapid increase in domestic MSW, cement rotary kilns are increasingly playing a dominant role in MSW treatment. Developing bricks that possess the performance of chromium-free bricks while resisting fly ash and strong acid / alkali corrosion has been a long-standing research direction. In the preparation of magnesium-aluminum-manganese spinel bricks, high-purity sintered magnesia and a small amount of manganese compounds are used as the main raw materials, combined with medium-to-high temperature firing. The product has low porosity, high density, excellent room temperature performance, good thermal shock stability, kiln lining resistance, wear resistance, and chemical erosion resistance, with obvious advantages, making it suitable for co-processing municipal solid waste.

[0003] Patent application CN201210437246.6 discloses a magnesia-carbon brick with added manganese dioxide, comprising the following raw materials: fused magnesia, flake graphite powder, metallic aluminum powder, silicon powder, fine manganese dioxide powder, and phenolic resin. This invention, by adding manganese dioxide, allows the metallic aluminum powder in the magnesia-carbon brick to directly transform into alumina during use, and then into manganese aluminum spinel with a melting point as high as 1850℃. This not only inhibits the formation of easily hydrated products such as aluminum carbide and aluminum nitride, significantly improving the hydration resistance of the magnesia-carbon brick, but also, due to the volume expansion accompanying the formation of manganese aluminum spinel, increases the density of the magnesia-carbon brick structure, giving it high high-temperature strength. Simultaneously, it blocks the gas entry channels, resulting in good oxidation resistance. Furthermore, the high melting point of manganese aluminum spinel ensures the slag resistance of the magnesia-carbon brick. However, the magnesia-carbon brick provided by this invention has a low apparent porosity and a high thermal conductivity. When used in the calcination zone or transition zone of a cement kiln, it can lead to a high cylinder temperature, causing… Safety Hazards: Patent application number CN202110991680.8 provides a microporous magnesium-iron-aluminum spinel brick for use in the firing zone of a cement rotary kiln, comprising the following raw materials: microporous high-purity magnesia, fused magnesia, fused iron-aluminum spinel, polyhydroxyl powder, silica sol, and industrial manganese powder. This invention, by adding polyhydroxyl powder to the mixing mill, exhibits good refractory properties, high high-temperature strength, good thermal stability, resistance to various corrosions, minimal reheat fiber change, and low thermal conductivity. After use, it significantly reduces the thermal conductivity of the magnesium-iron-aluminum spinel brick. By adding microporous high-purity magnesia and fused magnesia to the mixing mill, the thermal conductivity of the product is further reduced, thereby lowering the temperature of the cement kiln shell, reducing heat dissipation from the cement rotary kiln, reducing energy consumption, and simultaneously reducing carbon dioxide emissions and air pollution. This solves the problem of high thermal conductivity and large coal consumption. However, the strength of the magnesium-iron-aluminum spinel brick provided by this invention still needs further improvement and is difficult to meet the diversified market demands. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a magnesium-manganese-aluminum composite spinel brick and its preparation method. This magnesium-manganese-aluminum composite spinel brick has the characteristics of high strength, low thermal conductivity, high temperature resistance, and corrosion resistance, and can meet diverse market demands.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

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

[0007] The modified silica sol is prepared by:

[0008] Organosilicon resin was dissolved in toluene to obtain a mixture. Under stirring, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane was mixed evenly with salicylic acid and heated to 80-100℃. The mixture was added dropwise over 30-50 minutes. The reaction was allowed to proceed for 3-5 hours. Bisphenol A was then added, and the reaction continued for 1-3 hours. Toluene was removed by evaporation to obtain epoxy-based organosilicon resin. Under stirring, alkaline silica sol was heated to 70-80℃, and epoxy-based organosilicon resin was added. The reaction was allowed to proceed for 3-6 hours. The mixture was then cooled to room temperature to obtain modified silica sol.

[0009] Phenolic resin hollow microspheres are a novel chemical material with a hollow core and an outer layer of phenolic resin, possessing a unique hollow structure. They exhibit characteristics such as low density, low thermal conductivity, excellent thermal stability, low thermal conductivity and thermal conductivity coefficient, and the ability to absorb electromagnetic waves. They are commonly used as fillers in composite materials, reducing product weight while improving the mechanical and thermal properties of the composite material. They can be used as additives in lightweight adhesives in building materials and chemical industries, or as ablative layers on material surfaces after being bonded with resin to protect the internal structure of the material. To further expand their application range, this invention modifies phenolic resin hollow microspheres using 4-ethoxy-3-methylphenylboronic acid, introducing borate ester groups onto the surface of the hollow microspheres. This improves the adhesion of the hollow microspheres, and the boron atoms in the borate ester groups form a boron-containing ceramic structure during sintering, significantly improving the material's high-temperature resistance and corrosion resistance. Inorganic binders possess advantages such as high and low temperature resistance, low cost, resistance to aging, simple structure, and high adhesion. These characteristics make them excellent in various applications, especially in environments requiring extreme temperature variations. Alkaline silica sol, as a binder for refractory materials, exhibits high adsorption and surface activity, enabling it to adsorb large amounts of water molecules and other substances. It also possesses high chemical stability and heat resistance, allowing it to remain stable at high temperatures. When alkaline silica sol comes into contact with other materials, the active groups in the silica sol adsorb onto the material surface, forming a silica sol film. This film creates a "suction cup"-like force, causing the materials to adhere together and exhibiting excellent adhesion. However, conventional alkaline silica sols suffer from poor stability and low surface functionalization, failing to meet the specific requirements of certain industries. This invention first prepares an epoxy-based silicone resin using organosilicon resin and epoxy silane, then uses this epoxy-based silicone resin to surface-modify the alkaline silica sol, resulting in a modified silica sol. This modified silica sol improves both its stability and adhesion, while also enhancing its compatibility with borate-modified phenolic resin hollow microspheres. By introducing organic polymers onto the surface of the alkaline silica sol, this invention significantly improves its stability and gel concentration, revealing new application potential.

[0010] Furthermore, the mass ratio of the organosilicon resin, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, salicylic acid, and bisphenol A is 5:8-12:0.3-0.5:0.4-0.6, the amount of organosilicon resin added to the toluene is 0.25-0.55 g / mL, the mass ratio of the alkaline silica sol to the epoxy organosilicon resin is 20:0.5-1.5, the 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 ester modified phenolic resin hollow microspheres is as follows: phenolic resin hollow microspheres are dispersed in xylene, heated to 55-75℃, 4-ethoxy-3-methylphenylboronic acid is added, the mixture is stirred for 3.5-4.5 h, cooled to room temperature, the solid and liquid are separated, the solid is washed and dried to obtain borate ester 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-to-volume ratio of the phenolic resin hollow microspheres to xylene is 0.5-1.5 mg / mL.

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

[0014] 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 are added to a mixer and premixed for 2-4 minutes. Then, a composite binder is added and the mixture is mixed for 5-10 minutes. Next, 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 micro powder, manganese dioxide powder, metallic manganese powder, and borate ester modified phenolic resin hollow microspheres are added and the mixture is mixed for another 15-25 minutes. After being pressed into shape, the mixture is first dried at 100-150℃ for 24-72 hours, then sintered at 1450-1550℃ for 5-8 hours and naturally cooled to room temperature to obtain magnesia-manganese-aluminum composite spinel bricks.

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

[0016] This invention uses 4-ethoxy-3-methylphenylboronic acid as a modifier. Through the dehydration condensation reaction of boron hydroxyl groups with the phenolic hydroxyl groups in the hollow phenolic resin microsphere structure, borate ester groups are introduced onto the surface of the hollow phenolic resin microspheres, improving the adhesion of the hollow microspheres. Furthermore, the boron atoms in the borate ester groups form a boron-containing ceramic structure during sintering, adhering to the magnesium-manganese-aluminum spinel material. This not only provides additional thermal insulation but also protects the material from external environmental erosion and damage, thus significantly improving the material's high-temperature resistance and corrosion resistance. During sintering, the borate-modified phenolic resin hollow microspheres form circular micropores within the internal structure of the magnesium-manganese-aluminum composite spinel brick, increasing the gas-solid interface in the brick structure and amplifying phonon scattering during solid-phase thermal conductivity, thereby effectively reducing the brick's thermal conductivity. The circular micropores also provide stress buffering within the magnesium-manganese-aluminum composite spinel brick during rapid heating and cooling, enhancing its thermal shock resistance. Furthermore, during the sintering process, a reducing atmosphere can be created by modifying the carbon in the phenolic resin hollow microspheres with borate esters, which can prevent Fe from being deposited. 2+ Oxidized to Fe 3+This results in a significant volume effect in magnesium-manganese-aluminum composite spinel bricks during firing or use, thereby ensuring product stability.

[0017] This invention utilizes organosilicon resin and epoxy silane to prepare an epoxy-based organosilicon resin. Then, through a ring-opening addition reaction between the epoxy-based organosilicon resin and alkaline silica sol, an organic polymer is introduced onto the surface of the alkaline silica sol particles, improving the stability and adhesion of the modified silica sol and enhancing the compatibility between the modified silica sol and borate-modified phenolic resin hollow microspheres. By using modified silica sol, sodium hexametaphosphate, and borate-modified phenolic resin hollow microspheres in combination, the adhesive force of the composite binder is significantly enhanced, effectively improving the connection strength between the raw material components before sintering, thereby increasing the density of the sintered product. The silica structure in the modified silica sol can also sinter with the alumina in the raw materials to form a mullite structure, further improving the thermal stability of the material.

[0018] This invention combines high-purity magnesia and fused magnesia as raw materials, and blends them with fused iron-aluminum spinel. After high-temperature heat treatment, the Fe in the fused iron-aluminum spinel is reduced. 2+ Mg in periclase 2+ The annular cracks formed by the ion exchange reaction have a good promoting effect on the flexibility of magnesium manganese aluminum spinel composites. Meanwhile, Fe... 2+ The diffusion of magnesia into the magnesia improves the kiln lining performance of the sample. Furthermore, the dense reaction zone formed by the reaction between fused iron-aluminum spinel and magnesia, with its volume expansion during the reaction blocking pores, increases the density of the reaction sintering zone, effectively inhibiting secondary penetration of cement clinker. A reaction sintering zone of a certain thickness also improves the bonding strength between the raw material components and enhances the composite material's resistance to spalling under high-temperature thermal shock, thereby improving the mechanical strength and thermal shock resistance of the magnesia-manganese-aluminum composite spinel brick. The addition of α-Al₂O₃ micropowder promotes sintering, and iron and aluminum ions can form in-situ spinel and continuous or semi-continuous solid solutions with magnesia, significantly improving the material's high-temperature performance. The addition of manganese dioxide powder and metallic manganese powder allows manganese ions to replace some magnesium ions in the periclase crystal structure during sintering, forming a stable structure. This ensures both the sintering stability and solid solution of the product, as well as its volume stability and good kiln lining performance.

[0019] The preparation process provided by this invention ensures the bonding strength between the raw material components. Through the sintering process, the purity and stability of the material are improved, ensuring the consistency and reliability of the material. The magnesium-manganese-alumina composite spinel brick provided by this invention maintains low thermal conductivity while also possessing excellent mechanical properties, high-temperature resistance, corrosion resistance, and kiln lining adhesion. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] High-purity magnesia, with particle sizes of 5-3mm, 3-1mm, and 0-1mm, has a chemical composition (w) mainly including: MgO 95.44%, CaO 1.50%, SiO2 1.56%, Fe2O3 0.93%, Al2O3 0.31%, and a bulk density of 3.27 g / cm³. 3 Fused iron-aluminum spinel, with grain sizes of 3-1 mm and 0-1 mm, has the following main chemical composition (w): Al₂O₃ 50.59%, Fe₂O₃ 44.91%, SiO₂ 1.22%, MgO 0.96%, CaO 0.38%, and a bulk density of 4.24 g / cm³. 3 Fused magnesia, with a particle size ≤0.074mm, has the following main chemical composition (w): MgO 98.12%, CaO 0.9%, SiO2 0.32%, Fe2O3 0.41%, Al2O3 0.05%, and a bulk density of 3.44g / cm³. 3 The following materials were used: α-Al₂O₃ micro powder with a particle size of 500 mesh, whose main chemical composition (w) included: Al₂O₃ > 99.3%, SiO₂ ≤ 0.10%, Fe₂O₃ ≤ 0.04%, Na₂O ≤ 0.5%; manganese dioxide powder with an effective content of 70-75% and a particle size of 325 mesh; metallic manganese powder with a particle size of 500 mesh and a manganese content ≥ 99%; silicone resin, brand Dow Corning, model Z-6018, purchased from Guangzhou Huitu New Materials Co., Ltd.; and phenolic resin hollow microspheres, item number FR-F-007-1, with an average particle size of 40-70 μm, purchased from Henan Fanrui Composite Materials Research Institute Co., Ltd. All raw materials used in the following examples were commercially available 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 with a particle size of 3-5 mm, 12 parts of high-purity magnesia with a particle size of 1-3 mm, 12 parts of high-purity magnesia with a particle size of 0-1 mm, 3 parts of fused iron-aluminum spinel with a particle size of 1-3 mm, 4 parts of fused iron-aluminum spinel with a particle size of 0-1 mm, 30 parts of fused magnesia, 3 parts of α-Al₂O₃ micro powder, 0.8 parts of manganese dioxide powder, 0.6 parts of metallic manganese powder, 3 parts of composite binder, and 6 parts of borate ester modified phenolic resin hollow microspheres; wherein the composite binder is prepared by mixing modified silica sol and sodium hexametaphosphate, and the mass ratio of modified silica sol to sodium hexametaphosphate is 30:1;

[0024] The modified silica sol is prepared as follows: Organosilicon resin is dissolved in toluene to obtain a mixture. Under stirring at 180 rpm, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and salicylic acid are mixed evenly and heated to 90°C. The mixture is then added dropwise over 40 minutes. The reaction is allowed to proceed for 4 hours, followed by the addition of bisphenol A and a further 2 hours. After the reaction is complete, the temperature is raised to 118-120°C to remove toluene, yielding an epoxy-based organosilicon resin. Under stirring at 180 rpm, alkaline silica sol is then heated... The mixture was heated to 75℃, and epoxy-based organosilicon resin was added. The reaction was carried out for 5 hours and then cooled to room temperature to obtain modified silica sol. The mass ratio of organosilicon resin, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, salicylic acid, and bisphenol A was 5:10:0.4:0.5. The amount of organosilicon resin added to toluene was 0.45 g / mL. The mass ratio of alkaline silica sol to epoxy-based organosilicon resin was 20:1. The colloidal particle size of alkaline silica sol was 15-25 nm, the SiO2 content was 25%, and the pH was 9-11.

[0025] The preparation method of boronic acid ester modified phenolic resin hollow microspheres is as follows: phenolic resin hollow microspheres are dispersed in xylene, heated to 65℃, and 4-ethoxy-3-methylphenylboronic acid is added. The mixture is reacted for 4 hours under stirring at 160 rpm, cooled to room temperature, and the solid and liquid are separated. The solid is washed three times with acetone and dried under vacuum at 80℃ for 12 hours to obtain boronic acid ester modified phenolic resin hollow microspheres. The mass ratio of phenolic resin hollow microspheres to 4-ethoxy-3-methylphenylboronic acid is 10:3.5, and the mass-to-volume ratio of phenolic resin hollow microspheres to xylene is 1 mg / mL.

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

[0027] 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 are added to a mixer and premixed for 3 minutes. Then, a composite binder is added and the mixture is mixed for 8 minutes. Next, 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 micro powder, manganese dioxide powder, metallic manganese powder, and borate ester modified phenolic resin hollow microspheres are added and the mixture is mixed for another 20 minutes. After pressing and molding on a 1000-ton press, the brick is first dried at 130℃ for 48 hours, then sintered at 1500℃ for 6 hours, and then naturally cooled to room temperature to obtain the magnesium-manganese-aluminum composite spinel brick. The pressing and molding operation can be carried out using conventional techniques in this 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 with a particle size of 3-5 mm, 15 parts of high-purity magnesia with a particle size of 1-3 mm, 15 parts of high-purity magnesia with a particle size of 0-1 mm, 1 part of fused iron-aluminum spinel with a particle size of 1-3 mm, 6 parts of fused iron-aluminum spinel with a particle size of 0-1 mm, 20 parts of fused magnesia, 4 parts of α-Al₂O₃ micro powder, 1 part of manganese dioxide powder, 0.4 parts of metallic manganese powder, 4 parts of composite binder, and 5 parts of borate ester modified phenolic resin hollow microspheres; wherein the composite binder is prepared by mixing modified silica sol and sodium hexametaphosphate, and the mass ratio of modified silica sol to sodium hexametaphosphate is 25:1;

[0030] The modified silica sol is prepared as follows: Organosilicon resin is dissolved in toluene to obtain a mixture. Under stirring at 180 rpm, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and salicylic acid are mixed evenly and heated to 90°C. The mixture is then added dropwise over 40 minutes. The reaction is allowed to proceed for 4 hours, followed by the addition of bisphenol A and a further 2 hours of reaction. After the reaction is complete, the temperature is raised to 118-120°C to remove toluene, yielding an epoxy-based organosilicon resin. The alkaline silica sol is then heated under stirring at 180 rpm. At 75℃, epoxy-based organosilicon resin was added, and the reaction was carried out for 5 hours. After cooling to room temperature, modified silica sol was obtained. The mass ratio of organosilicon resin, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, salicylic acid, and bisphenol A was 5:12:0.5:0.6. The amount of organosilicon resin added to toluene was 0.45 g / mL. The mass ratio of alkaline silica sol to epoxy-based organosilicon resin was 20:0.5. The colloidal particle size of alkaline silica sol was 15-25 nm, the SiO2 content was 25%, and the pH was 9-11.

[0031] The preparation method of borate-modified phenolic resin hollow microspheres is as follows: phenolic resin hollow microspheres are dispersed in xylene, heated to 55℃, and 4-ethoxy-3-methylphenylboronic acid is added. The mixture is reacted at 160 rpm for 4.5 h, cooled to room temperature, and the solid and liquid are separated. The solid is washed three times with acetone and dried under vacuum at 80℃ for 12 h to obtain borate-modified phenolic resin hollow microspheres. The mass ratio of phenolic resin hollow microspheres to 4-ethoxy-3-methylphenylboronic acid is 10:4.5, and the mass-to-volume ratio of 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 molded, 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 with a particle size of 3-5 mm, 10 parts of high-purity magnesia with a particle size of 1-3 mm, 10 parts of high-purity magnesia 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, 2 parts of α-Al₂O₃ micro powder, 0.6 parts of manganese dioxide powder, 0.8 parts of metallic manganese powder, 2 parts of composite binder, and 7 parts of borate ester modified phenolic resin hollow microspheres; wherein the composite binder is prepared by mixing modified silica sol and sodium hexametaphosphate, and the mass ratio of modified silica sol to sodium hexametaphosphate is 35:1;

[0035] The modified silica sol is prepared as follows: Organosilicon resin is dissolved in toluene to obtain a mixture. Under stirring at 180 rpm, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane and salicylic acid are mixed evenly and heated to 90°C. The mixture is then added dropwise over 40 minutes. The reaction is allowed to proceed for 4 hours, followed by the addition of bisphenol A and a further 2 hours. After the reaction is complete, the temperature is raised to 118-120°C to remove toluene, yielding an epoxy-based organosilicon resin. Under stirring at 180 rpm, alkaline silica sol is then heated... The mixture was heated to 75℃, and epoxy-based organosilicon resin was added. The reaction was carried out for 5 hours and then cooled to room temperature to obtain modified silica sol. The mass ratio of organosilicon resin, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, salicylic acid, and bisphenol A was 5:8:0.3:0.4. The amount of organosilicon resin added to toluene was 0.45 g / mL. The mass ratio of alkaline silica sol to epoxy-based organosilicon resin was 20:1.5. The colloidal particle size of 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: phenolic resin hollow microspheres are dispersed in xylene, heated to 75℃, and 4-ethoxy-3-methylphenylboronic acid is added. The mixture is reacted for 3.5 h under stirring at 160 rpm, cooled to room temperature, and the solid and liquid are separated. The solid is washed three times with acetone and dried under vacuum at 80℃ for 12 h to obtain borate-modified phenolic resin hollow microspheres. The mass ratio of phenolic resin hollow microspheres to 4-ethoxy-3-methylphenylboronic acid is 10:2.5, and the mass-to-volume ratio of 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 molded, 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 the same as described in Example 1, except that the modified silica sol is replaced with 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, the raw material composition of which is the same as described in Example 1, except that the borate ester modified phenolic resin hollow microspheres are replaced with 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, the raw material composition of which is the same as described in Example 1, except that: the modified silica sol is replaced with alkaline silica sol, and the borate ester modified phenolic resin hollow microspheres are replaced with 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-alumina 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 conducted according to GB / T 5072-2023 "Test Method for Room Temperature Compressive Strength of Refractory Materials"; the high temperature flexural strength test was conducted according to GB / T The test shall be conducted in accordance with GB / T 2002-2004 "Test Method for High Temperature Flexural Strength of Refractory Materials"; the thermal shock resistance test shall be conducted by drying the sample to constant weight at 120℃, then transferring it to a drying oven at 250-300℃ for 2 hours, then holding it at 1100℃ for 30 minutes, removing the sample, and blowing it with cold air for 5 minutes. This alternating hot and cold test shall be repeated 5 times. The thermal shock resistance is expressed by the retention rate of the sample's room temperature compressive strength, calculated as follows: 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 shall be conducted in accordance with GB / T 2997-2000 "Test Method for Bulk Density, Apparent Porosity and True Porosity of Dense Shaped Refractory Products"; the thermal conductivity test shall be conducted in accordance with GB / T The tests were conducted according to GB / T 5989-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Heat Flow Meter Method"; the softening temperature test was conducted according to GB / T 14983-2008 "Test Method for Softening Temperature of Refractory Materials under Load - Differential Heating Method"; the corrosion resistance test was conducted according to GB / T 14983-2008 "Test Method for Alkali Resistance of Refractory Materials"; the kiln lining performance test was conducted according to JC / T 2463-2018 "Static Test Method for Kiln Lining Performance of Refractory Materials for Cement Kilns", with the bonding strength indicating the quality of the refractory kiln lining performance; all tests were repeated three times and the average value was taken. The test results are shown in Table 1. As shown in Table 1, compared with Comparative Examples 1-3, the magnesium-manganese-alumina composite spinel bricks prepared in Examples 1-3 maintained suitable apparent porosity, bulk density, and low thermal conductivity, while also possessing superior room-temperature compressive strength, high-temperature flexural strength, thermal shock resistance, load softening temperature, corrosion resistance, and bonding strength. The data in the table also show that by modifying alkaline silica sol and phenolic resin hollow microspheres, the modified silica sol, borate-modified phenolic resin hollow microspheres, and other raw material components worked synergistically to prepare magnesium-manganese-alumina composite spinel bricks that, while maintaining low thermal conductivity, also possess excellent mechanical properties, high-temperature resistance, corrosion resistance, and kiln lining adhesion.

[0048] Table 1. Test results of relevant performance of magnesium-manganese-alumina composite spinel bricks

[0049] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 room temperature pressure resistance / 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[Volume 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 embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A magnesium-manganese-alumina composite spinel brick, characterized in that, The raw materials include the following parts by weight: 20-30 parts of high-purity magnesia with a particle size of 3-5 mm, 10-15 parts of high-purity magnesia with a particle size of 1-3 mm, 10-15 parts of high-purity magnesia with a particle size of 0-1 mm, 1-4 parts of fused iron-aluminum spinel with a particle size of 1-3 mm, 3-6 parts of fused iron-aluminum spinel with a particle size of 0-1 mm, 20-40 parts of fused magnesia, 2-4 parts of α-Al₂O₃ micro powder, 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 ester modified phenolic resin hollow microspheres; wherein the composite binder is prepared by mixing modified silica sol and sodium hexametaphosphate, and the mass ratio of modified silica sol to sodium hexametaphosphate is 25-35:1; The modified silica sol is prepared by: Organosilicon resin was dissolved in toluene to obtain a mixture. Under stirring, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane was mixed evenly with salicylic acid and heated to 80-100℃. The mixture was added dropwise over 30-50 minutes. The reaction was allowed to proceed for 3-5 hours. Bisphenol A was then added, and the reaction continued for 1-3 hours. Toluene was removed by evaporation to obtain epoxy-based organosilicon resin. Under stirring, alkaline silica sol was heated to 70-80℃, and epoxy-based organosilicon resin was added. The reaction was allowed to proceed for 3-6 hours. The mixture was then cooled to room temperature to obtain modified silica sol.

2. The magnesium-manganese-alumina composite spinel brick according to claim 1, characterized in that, The mass ratio of the organosilicon 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 organosilicon resin added to the toluene is 0.25-0.55 g / mL.

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

5.

5. The magnesium-manganese-alumina composite spinel brick according to claim 1, characterized in that, The alkaline silica sol has a particle size of 15-25 nm, a SiO2 content of 20-30%, and a pH of 9-11.

6. The magnesium-manganese-alumina composite spinel brick according to claim 1, characterized in that, The method for preparing the borate ester modified phenolic resin hollow microspheres is as follows: phenolic resin hollow microspheres are dispersed in xylene, heated to 55-75℃, 4-ethoxy-3-methylphenylboronic acid is added, the mixture is stirred for 3.5-4.5 hours, cooled to room temperature, the solid and liquid are separated, the solid is washed and dried to obtain borate ester modified phenolic resin hollow microspheres.

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

9. The method for preparing magnesium-manganese-aluminum composite spinel bricks according to any one of claims 1-8, characterized in that, The process includes the following steps: adding 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 and premixing for 2-4 minutes; then adding a composite binder and mixing for 5-10 minutes; then adding 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 micro powder, manganese dioxide powder, metallic manganese powder, and borate ester modified phenolic resin hollow microspheres and continuing to mix for 15-25 minutes; after pressing and molding, drying at 100-150℃ for 24-72 hours, sintering at 1450-1550℃ for 5-8 hours, and naturally cooling to room temperature to obtain magnesia-manganese-aluminum composite spinel bricks.