High-strength heat-insulating castable for hydrogen metallurgy as well as preparation method and application of high-strength heat-insulating castable

Abstract

The invention belongs to the technical field of refractory materials for hydrogen metallurgy, and discloses a high-strength heat-insulating castable for hydrogen metallurgy as well as a preparation method and application of the high-strength heat-insulating castable. The invention discloses a high-strength heat-insulating castable which comprises the following raw materials in percentage by mass: 15-25% of modified aluminum oxide hollow spheres with the particle size of 5-3mm, 7-13% of modified aluminum oxide hollow spheres with the particle size of 3-2mm, 2-4% of modified aluminum oxide hollow spheres with the particle size of 2-1mm, 7-11% of modified perlite with the particle size of 3-0.074 mm, 18-28% of quartz powder, 4-6% of silicon dioxide powder, 25-35% of pure calcium aluminate cement and 0.5-2% of yttrium oxide powder. A water reducing agent accounting for 0.05-0.15% of the total mass of the raw materials, a pore forming agent accounting for 0.03-0.07% of the total mass of the raw materials and water accounting for 17-21% of the total mass of the raw materials are added. The castable disclosed by the invention has the comprehensive properties of high strength, low heat conductivity, high volume stability and excellent H2 / CO erosion resistance, and meets the comprehensive harsh requirements of hydrogen metallurgy application scenarios.

Description

Technical Field

[0001] This invention belongs to the technical field of refractory materials for hydrogen metallurgy, specifically relating to a high-strength heat-insulating castable for hydrogen metallurgy, its preparation method, and its application. Background Technology

[0002] Among numerous low-carbon and green metallurgical approaches, hydrogen metallurgy is considered the most effective and mature way to reduce carbon emissions in the steel industry. Hydrogen metallurgy processes are characterized by high chemical reactivity and complex furnace atmospheres (containing H2, H2O, CO, CH4, etc.). Traditional refractory materials are prone to hydrogen erosion, structural deterioration, and performance degradation in a hydrogen environment, leading to production fluctuations and shortened service life. To date, hydrogen metallurgical refractory materials still face many pressing technical challenges in practical applications. (1) Hydrogen molecules are small in size and have extremely strong permeability, which leads to the destruction of the "skeleton" in the material structure, forming pores and cracks, significantly reducing the strength and density of the material; (2) In the hydrogen metallurgy process, H2, as a reducing agent, is oxidized to H2O, which leads to the partial pressure of water vapor in the furnace being much higher than that of the traditional process, which will generate huge stress inside the refractory material, causing the lining to crack, pulverize, and eventually collapse; (3) Hydrogen molecules have a higher velocity than oxygen, which leads to an increase in their thermal conductivity, which places higher demands on the thermal insulation performance of the heat-insulating refractory material; (4) Hydrogen metallurgy process (especially intermittent hydrogen production based on renewable energy) may cause frequent start-up and shutdown of the reactor or temperature fluctuations. In addition, the injection of cold hydrogen may also cause local thermal shock. Under rapid cooling and heating, the refractory material will crack due to uneven thermal expansion and contraction. If the thermal shock stability of the refractory material is not good, the cracks will rapidly expand and connect, eventually leading to the peeling off of the lining. Therefore, refractory materials have become a key factor that severely limits the service life of vertical shaft furnaces, and research and development of refractory materials for their operating conditions are very necessary. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a high-strength heat-insulating castable for hydrogen metallurgy, its preparation method and application. The castable has comprehensive properties such as high strength, low thermal conductivity, high volume stability and excellent resistance to H2 / CO erosion, which meets the comprehensive and demanding requirements of hydrogen metallurgy application scenarios.

[0004] To solve the technical problem proposed in this invention, this invention provides a high-strength heat-insulating castable for hydrogen metallurgy, comprising the following raw materials in the following mass percentages: 15-25% modified alumina hollow spheres with a particle size of 5-3 mm, 7-13% modified alumina hollow spheres with a particle size of 3-2 mm, 2-4% modified alumina hollow spheres with a particle size of 2-1 mm, 7-11% modified perlite with a particle size of 3-0.074 mm, 18-28% quartz powder, 4-6% silica powder, 25-35% pure calcium aluminate cement, and 0.5-2% yttrium oxide powder, plus 0.05-0.15% water-reducing agent, 0.03-0.07% pore-forming agent, and 17-21% water by mass of the above raw materials.

[0005] In the above scheme, the modified alumina hollow spheres and modified perlite are obtained by impregnating alumina hollow spheres and perlite with zirconium aluminum composite sol and then drying them.

[0006] Furthermore, the mass ratio of zirconium oxide to aluminum oxide in the zirconium-aluminum composite sol is 1:(2~3.2), and the pH is 3~4.

[0007] Furthermore, the impregnation is vacuum impregnation, with a vacuum degree of -0.085 to -0.095 MPa.

[0008] Furthermore, the impregnation is a three-stage gradient impregnation: the first stage uses a zirconium-aluminum composite sol with a solid content of 8-13%, impregnates for 10-20 minutes, and then dries at 78-85℃ for 3-4 hours; the second stage uses a zirconium-aluminum composite sol with a solid content of 18-23%, impregnates for 20-30 minutes, and then dries at 95-105℃ for 3-5 hours; the third stage uses a zirconium-aluminum composite sol with a solid content of 30-40%, impregnates for 30-60 minutes, and then dries at 115-125℃ for 3-6 hours.

[0009] Furthermore, the hollow alumina spheres are formed by melting alumina raw materials and then blowing them using high-pressure gas.

[0010] Furthermore, the pressure of the high-pressure gas is 0.6~0.8MPa, and the flow rate is 10~30 m³ / s. 3 / h.

[0011] Furthermore, the hollow alumina spheres have an Al₂O₃ content of 99.1~99.5 wt%, a SiO₂ content of 0.15~0.28 wt%, an Fe₂O₃ content ≤0.03 wt%, a Na₂O content ≤0.17 wt%, a K₂O content ≤0.02 wt%, and a bulk density of 0.5~1.2 g / cm³. 3 .

[0012] Furthermore, the bulk density of hollow alumina spheres with a particle size of 5-3 mm is 0.52-0.68 g / cm³. 3The bulk density of hollow alumina spheres with a particle size of 3-2 mm is 0.65-0.78 g / cm³. 3 The bulk density of hollow alumina spheres with a particle size of 2-1 mm is 0.79-0.95 g / cm³. 3 .

[0013] In the above scheme, the modified perlite has an Al2O3 content of 10.1~13.5wt%, a SiO2 content of 64.2~75.8wt%, an Fe2O3 content ≤0.73wt%, a K2O+Na2O ≤0.9wt%, and a bulk density of 0.08~0.15g / cm³. 3 .

[0014] In the above scheme, the quartz powder has a SiO2 content of 98.9~99.5wt%, an Fe2O3 content of ≤0.12wt%, a K2O+Na2O content of ≤0.2wt%, and a particle size of ≤0.074mm.

[0015] In the above scheme, the silica powder has an Al2O3 content of 0.21~0.28wt%, a SiO2 content of 94.2~95.6wt%, an Fe2O3 content of ≤0.13wt%, a K2O+Na2O content of ≤0.2wt%, and a particle size of 0.3~5μm.

[0016] In the above scheme, the pure calcium aluminate cement is CA70 cement, with an Al2O3 content of 68.54~70.22wt%, a CaO content of 29.2~30.3wt%, an Fe2O3 content of ≤0.43wt%, a K2O+Na2O content of ≤0.2wt%, and a S content of ≤0.08wt%.

[0017] In the above scheme, the Y2O3 content of the yttrium oxide powder is 99.92~99.96wt%, the Fe2O3 content is ≤0.001wt%, the K2O+Na2O is ≤0.003wt%, and the particle size is ≤0.044mm.

[0018] In the above scheme, the water-reducing agent is composed of polycarboxylate-based water-reducing agent, sodium hexametaphosphate, and naphthalene-based water-reducing agent.

[0019] Furthermore, the mass ratio of the polycarboxylate superplasticizer, sodium hexametaphosphate, and naphthalene superplasticizer is (1.5~2):1:(0.5~0.8).

[0020] Furthermore, the polycarboxylate superplasticizer is FS20, and the naphthalene superplasticizer is FDN.

[0021] In the above scheme, the pore-forming agent is prepared by mixing sodium dodecylbenzenesulfonate, cellulose ether, polyethylene glycol and glycol ether and then reacting them under temperature and pressure.

[0022] Further, the mass ratio of sodium dodecylbenzenesulfonate, cellulose ether, polyethylene glycol and glycol ether is (10~12):1:(0.8~1.1):(5~7).

[0023] Furthermore, the reaction temperature of the heating and pressurizing reaction is 35~50℃, the reaction pressure is 0.5~0.7MPa, and the reaction time is 24~36h.

[0024] Furthermore, the cellulose ether is one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methyl cellulose.

[0025] Furthermore, the molecular weight of the polyethylene glycol is 5800~6200.

[0026] Furthermore, the glycol ether is one of propylene glycol methyl ether and tripropylene glycol methyl ether.

[0027] In the above scheme, the high-strength heat-insulating castable for hydrogen metallurgy has an Al2O3 content ≥ 50%, an Fe2O3 content ≤ 0.4%, a K2O + Na2O ≤ 0.3%, and a bulk density of ≤ 1.25 g / cm³ at 110℃ for 24h. 3 The bulk density at 1000℃ for 3 hours is ≤1.15 g / cm³. 3 The compressive strength at 110℃ for 24 hours is ≥10MPa, the compressive strength at 1000℃ for 3 hours is ≥7MPa, the linear change rate after burning at 1000℃ for 3 hours is -0.3% to +0.3%, the thermal conductivity at a hot surface temperature of 300℃ is ≤0.355 W / (m·K), the thermal conductivity at a hot surface temperature of 600℃ is ≤0.405 W / (m·K), the thermal conductivity at a hot surface temperature of 900℃ is ≤0.485 W / (m·K), and the percentage of damage index after corrosion in a H2-CO mixed gas at 1000℃ for 144 hours is ≤6%.

[0028] The present invention also provides a method for preparing a high-strength heat-insulating castable for hydrogen metallurgy, comprising the following steps: mixing modified alumina hollow spheres of various particle sizes, modified perlite, quartz powder, silica powder, pure calcium aluminate cement and yttrium oxide powder, adding a water-reducing agent and a pore-forming agent and mixing, and finally adding water and mixing to obtain a high-strength heat-insulating castable.

[0029] In the above scheme, the stirring rate is controlled at 12~15 r / min. If the stirring speed is too slow, the activation energy is insufficient, and the powder is prone to agglomeration; if the stirring speed is too fast, it will damage the structure of the lightweight aggregate.

[0030] This invention also provides an application of a high-strength heat-insulating castable for hydrogen metallurgy, which can be used as the inner lining of hydrogen metallurgical pipelines. The application method is as follows: the high-strength heat-insulating castable is poured into a mold and vibrated to compact it. After curing, the mold is removed, and the material is baked and then heated to the working temperature for service.

[0031] In the above scheme, the maintenance conditions are natural maintenance, and the maintenance time is 24~48 hours.

[0032] In the above scheme, the baking is a three-stage baking: the first stage baking temperature is 110~130℃, and the holding time is 72~96h; the second stage baking temperature is 340~360℃, and the holding time is 36~48h; the third stage baking temperature is 590~620℃, and the holding time is 24~36h.

[0033] Furthermore, the heating rate of the first stage of baking is 2~3℃ / min, the heating rate of the second stage of baking is 3~4℃ / min, and the heating rate of the third stage of baking is 4~5℃ / min.

[0034] The technical concept of this invention is as follows: This invention designs a novel castable for hydrogen metallurgy, cleverly balancing high strength, excellent thermal insulation, resistance to H2 / CO erosion, and good volume stability—properties that are often mutually restrictive in traditional materials. The aggregate system of this castable uses lightweight, high-strength hollow alumina spheres modified with zirconium-aluminum composite sol and perlite to jointly construct a low thermal conductivity, high-strength skeleton structure, synergistically achieving low density, high strength, and excellent thermal insulation. Pure calcium aluminate cement is used as the main binder, giving the material high strength at room temperature. Micron-sized silica powder is added, utilizing its ball-bead effect to improve the fluidity of the castable; cement and silica powder together optimize the slurry structure and workability. Quartz powder is introduced, utilizing its micro-expansion caused by sintering and crystal transformation in the 600-1000℃ range to compensate for high-temperature shrinkage, optimizing the strength and linear shrinkage rate at medium and high temperatures. Quartz powder and the aggregate system form a stable bond at high temperatures, regulating volume change. By controlling the Fe2O3 content and alkali metal content of the material, the ability to resist H2 / CO reduction erosion is significantly improved. Specifically: 1) Optimized aggregate system, balancing lightweight, thermal insulation, and high strength: Alumina hollow spheres modified with zirconium-aluminum composite sol are used as the main aggregate, supplemented with perlite modified with zirconium-aluminum composite sol. Alumina hollow spheres possess high melting point, high strength, and low thermal conductivity, forming a high-strength thermal insulation framework as the main aggregate. After modification with zirconium-aluminum composite sol, the sol penetrates to the contact points of the spheres. After drying and sintering, a high-strength ZrO2-Al2O3 composite ceramic "glue" is formed, transforming loose "point contact" into strong "surface connection" or even "volume connection." This significantly improves the material's compressive and flexural strength, and substantially enhances its fracture toughness and thermal shock resistance. Perlite modified with zirconium-aluminum composite sol further increases its closed-cell rate, enhancing thermal insulation and reducing gas permeability. The zirconium-aluminum composite sol coating layer improves its high-temperature stability and corrosion resistance. The modification employs a three-stage gradient impregnation process, which significantly improves the impregnation depth and filling rate compared to single impregnation. By achieving close packing through multi-level particle gradation, it maintains high compressive strength at a low bulk density.

[0035] 2) High-proportion pure calcium aluminate cement bonding system, breaking through the strength bottleneck of traditional lightweight materials: Increasing the content of pure calcium aluminate cement to 25-35% significantly increases the amount of hydration products, giving the castable excellent strength at room temperature and medium temperature. However, excessively high proportions of pure aluminate cement will significantly reduce strength at medium and high temperatures (900-1000℃) because the hydration products undergo phase transformation and structural reorganization at high temperatures, leading to a loss of bonding strength. By adding silica micro-powder to react with Al2O3 in the cement to generate mullite; at the same time, the high-temperature crystal phase transformation of quartz powder can act as a sintering agent, generating a liquid phase or promoting solid-phase diffusion at medium and high temperatures, which can significantly reduce the sintering temperature and accelerate densification, ultimately achieving the goal of improving the strength at medium and high temperatures; in addition, the introduction of yttrium oxide significantly promotes the diffusion and migration of alumina grain boundaries, promoting sintering densification, thereby enhancing the high-temperature strength of high-proportion pure calcium aluminate cement and overcoming the bottleneck of low strength in traditional lightweight materials.

[0036] 3) Matrix System Design for Controlled Volume Stability: By optimizing the particle size distribution of the material and introducing a medium-to-high temperature stable phase, and based on the principle of close packing and the micro-expansion compensation of quartz powder at 600~1000℃, precise volume control of the castable at high temperatures is achieved. Specifically, by using lightweight aggregates with multi-level particle size distribution and ultrafine powders, the system achieves the most compact packing state, thereby reducing the shrinkage tendency during sintering. Simultaneously, the introduction of quartz powder into the matrix allows for micro-expansion during crystal phase transformation at medium and high temperatures, effectively offsetting the inherent shrinkage of the material at high temperatures through its moderate volume expansion. These synergistic effects ensure that the linear shrinkage rate of the castable after heat treatment at 1000℃ for 3 hours is stably controlled within the range of -0.3% to +0.3%, exhibiting significantly better volume stability than traditional materials. This not only effectively maintains the long-term fit between the castable and the pipe structure but also fundamentally solves the problems of cracking and spalling caused by thermal expansion and contraction.

[0037] 4) Raw material control to enhance resistance to reducing atmosphere: By controlling the raw materials, the overall Fe2O3 content of the final material is ≤0.4%, and K2O+Na2O is ≤0.3%, which reduces the content of variable valence oxides and avoids structural damage caused by reduction in H2 / CO atmosphere from the root. In CO or CH4 atmospheres, alkali metals are extremely strong catalysts for carbon deposition. Even in hydrogen metallurgical environments, CO remains, and carbon deposition within the pores of the castable generates significant internal stress, leading to material pulverization, cracking, and spalling. K2O and Na2O themselves have very low melting points; they react with the main components of the castable (such as Al2O3 and SiO2) to form minerals such as potassium nepheline (K2O•Al2O3•2SiO2) and leucite (K2O•Al2O3•4SiO2). These minerals have large volume expansion and low melting points, severely eroding the structural strength and thermal shock resistance of the castable. Simultaneously, the volume expansion accompanying the K2O and Na2O phase transformation leads to internal stress, triggering cracking and structural spalling. Therefore, high K2O and Na2O content exacerbates the penetration and corrosion of H2 and CO media into the material, which is the reason for the control measures in this invention. Furthermore, the use of high-purity aggregates and a binding system endows the castable with excellent erosion resistance and high-temperature volume stability.

[0038] 5) Admixtures: A composite water-reducing agent is used to achieve ultimate optimization of the rheological properties of the castable under extremely low water content (17-21%). This not only ensures workability but also forms a dense green body structure within the matrix, laying a solid foundation for high strength. A pore-forming agent constructs a uniform, closed, micron-level hierarchical pore structure in situ within the dense matrix. This carefully designed microstructure maximizes heat conduction resistance, achieving excellent thermal insulation performance, while avoiding the weakening effect of disordered large pores on material strength. The synergistic effect of the composite water-reducing agent and the pore-forming agent achieves a unity of "skeletal densification" and "pore functionalization," increasing material strength by 30-50%.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes lightweight, high-strength hollow alumina spheres modified with zirconium-aluminum composite sol and perlite to form a lightweight, high-strength, heat-insulating aggregate. It innovatively employs a high proportion of pure calcium aluminate cement as a binder, synergistically combining silica powder, quartz powder, and yttrium oxide powder. This significantly improves the castable's room-temperature bonding strength and medium-to-high-temperature ceramic bonding strength, successfully solving the core problem of insufficient strength in lightweight materials. Simultaneously, the quartz powder forms a stable bond with the aggregate system at high temperatures, regulating volume changes and enhancing volume stability. Ultimately, excellent strength is achieved at a relatively low bulk density. Furthermore, the thermal conductivity is controlled at a low level across different temperature ranges, and it exhibits excellent resistance to H2 / CO erosion, demonstrating balanced and superior comprehensive performance. Detailed Implementation

[0040] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0041] The raw materials used in the following examples have the following properties: quartz powder has a SiO2 content of 98.9~99.5wt%, Fe2O3 content ≤0.12wt%, K2O+Na2O ≤0.1wt%, and particle size ≤0.074mm; silica powder has an Al2O3 content of 0.21~0.28wt%, SiO2 content of 94.2~95.6wt%, Fe2O3 content ≤0.13wt%, K2O+Na2O ≤0.15wt%, and particle size of 0.3~5μm. The pure calcium aluminate cement is CA70 cement, with an Al2O3 content of 68.54~70.22wt%, a CaO content of 29.2~30.3wt%, an Fe2O3 content ≤0.43wt%, a K2O+Na2O ≤0.2wt%, and a S content ≤0.08wt%. The yttrium oxide powder has a Y2O3 content of 99.92~99.96wt%, an Fe2O3 content ≤0.001wt%, a K2O+Na2O ≤0.003wt%, and a particle size ≤0.044mm.

[0042] Example 1 A high-strength heat-insulating castable for hydrogen metallurgical pipelines. This invention comprises the following raw materials in weight percentages: 18% modified alumina hollow spheres with a particle size of 5-3 mm, 13% modified alumina hollow spheres with a particle size of 3-2 mm, 3% modified alumina hollow spheres with a particle size of 2-1 mm, 10% modified perlite with a particle size of 3-0.074 mm, 24% quartz powder, 5% silica powder, 26% pure calcium aluminate cement, and 1% yttrium oxide powder, plus 0.12% water-reducing agent, 0.04% pore-forming agent, and 18% water by weight of the total raw materials.

[0043] In this embodiment, the hollow alumina spheres used are produced by melting alumina raw materials and then using a pressure of 0.7 MPa and a flow rate of 25 m³ / h. 3 The alumina hollow spheres are produced by blowing high-pressure gas at a pressure of / h. After cooling, they are sieved and sorted. The Al2O3 content of the alumina hollow spheres is 99.1~99.5wt%, SiO2 content is 0.15~0.28wt%, Fe2O3 content is ≤0.03wt%, Na2O content is ≤0.17wt%, and K2O content is ≤0.02wt%. The bulk density of the alumina hollow spheres with a particle size of 5~3mm is 0.52~0.68g / cm³. 3 The bulk density of hollow alumina spheres with a particle size of 3-2 mm is 0.65-0.78 g / cm³. 3The bulk density of hollow alumina spheres with a particle size of 2-1 mm is 0.79-0.95 g / cm³. 3 Modified alumina hollow spheres and modified perlite are prepared by combining alumina hollow spheres and perlite.

[0044] The modified alumina hollow spheres and modified perlite were prepared by a three-stage vacuum impregnation modification using a zirconium-aluminum composite sol: the first stage used a zirconium-aluminum composite sol with a solid content of 10%, impregnated for 12 min, and then dried at 80℃ for 3 h; the second stage used a zirconium-aluminum composite sol with a solid content of 20%, impregnated for 25 min, and then dried at 100℃ for 4 h; the third stage used a zirconium-aluminum composite sol with a solid content of 35%, impregnated for 45 min, and then dried at 120℃ for 5 h. The mass ratio of zirconium oxide to alumina in the zirconium-aluminum composite sol used was 1:2.2, and the pH was 3.9.

[0045] The obtained modified perlite had an Al2O3 content of 10.1–13.5 wt%, a SiO2 content of 64.2–75.8 wt%, an Fe2O3 content ≤0.73 wt%, a K2O+Na2O content ≤0.9 wt%, and a bulk density of 0.08–0.15 g / cm³. 3 .

[0046] In this embodiment, the water-reducing agent is a mixture of polycarboxylate-based water-reducing agent FS20, sodium hexametaphosphate, and naphthalene-based water-reducing agent FDN in a mass ratio of 1.8:1:0.6.

[0047] In this embodiment, the pore-forming agent was prepared by mixing sodium dodecylbenzenesulfonate, hydroxypropyl methylcellulose, polyethylene glycol (molecular weight 5900) and propylene glycol methyl ether in a mass ratio of 12:1:1:6 and reacting the mixture at 40°C and 0.55 MPa for 30 h.

[0048] Example 2 A high-strength heat-insulating castable for hydrogen metallurgical pipelines. This invention comprises the following raw materials in weight percentages: 20% modified alumina hollow spheres with a particle size of 5-3 mm, 10% modified alumina hollow spheres with a particle size of 3-2 mm, 2.5% modified alumina hollow spheres with a particle size of 2-1 mm, 9.5% modified perlite with a particle size of 3-0.074 mm, 23% quartz powder, 4% silica powder, 30.2% pure calcium aluminate cement, and 0.8% yttrium oxide powder, plus 0.15% water-reducing agent, 0.05% pore-forming agent, and 17.5% water by weight of the total raw materials.

[0049] In this embodiment, the hollow alumina spheres used are produced by melting alumina raw materials and then using a pressure of 0.75 MPa and a flow rate of 28 m³ / s. 3The alumina hollow spheres are produced by blowing high-pressure gas at a pressure of / h. After cooling, they are sieved and sorted. The Al2O3 content of the alumina hollow spheres is 99.1~99.5wt%, SiO2 content is 0.15~0.28wt%, Fe2O3 content is ≤0.03wt%, Na2O content is ≤0.17wt%, and K2O content is ≤0.02wt%. The bulk density of the alumina hollow spheres with a particle size of 5~3mm is 0.52~0.68g / cm³. 3 The bulk density of hollow alumina spheres with a particle size of 3-2 mm is 0.65-0.78 g / cm³. 3 The bulk density of hollow alumina spheres with a particle size of 2-1 mm is 0.79-0.95 g / cm³. 3 Alumina hollow spheres and perlite are used to make modified alumina hollow spheres and modified perlite.

[0050] The modified alumina hollow spheres and modified perlite were prepared by a three-stage vacuum impregnation modification using a zirconium-aluminum composite sol: the first stage used a zirconium-aluminum composite sol with a solid content of 11%, impregnated for 14 min, and then dried at 80℃ for 3 h; the second stage used a zirconium-aluminum composite sol with a solid content of 20%, impregnated for 25 min, and then dried at 100℃ for 5 h; the third stage used a zirconium-aluminum composite sol with a solid content of 33%, impregnated for 48 min, and then dried at 120℃ for 4 h. The mass ratio of zirconium oxide to alumina in the zirconium-aluminum composite sol used was 1:2.6, and the pH was 3.6.

[0051] The obtained modified perlite had an Al2O3 content of 10.1–13.5 wt%, a SiO2 content of 64.2–75.8 wt%, an Fe2O3 content ≤0.73 wt%, a K2O+Na2O content ≤0.9 wt%, and a bulk density of 0.08–0.15 g / cm³. 3 .

[0052] In this embodiment, the water-reducing agent is composed of polycarboxylate-based water-reducing agent FS20, sodium hexametaphosphate, and naphthalene-based water-reducing agent FDN mixed in a mass ratio of 1.7:1:0.7. In this embodiment, the pore-forming agent was prepared by mixing sodium dodecylbenzenesulfonate, hydroxymethyl methyl cellulose, polyethylene glycol (molecular weight 6000) and propylene glycol methyl ether in a mass ratio of 11:1:0.9:6.5 and reacting the mixture at 40°C and 0.6 MPa for 28 h.

[0053] Example 3 A high-strength heat-insulating castable for hydrogen metallurgical pipelines. This invention comprises the following raw materials in weight percentages: 23% modified alumina hollow spheres with a particle size of 5-3 mm, 8% modified alumina hollow spheres with a particle size of 3-2 mm, 4% modified alumina hollow spheres with a particle size of 2-1 mm, 8.5% modified perlite with a particle size of 3-0.074 mm, 22.5% quartz powder, 5% silica powder, 28.1% pure calcium aluminate cement, and 0.9% yttrium oxide powder, plus 0.15% water-reducing agent, 0.05% pore-forming agent, and 17.8% water by weight of the total raw materials.

[0054] In this embodiment, the hollow alumina spheres used are produced by melting alumina raw materials and then using a pressure of 0.75 MPa and a flow rate of 30 m³ / h. 3 The alumina hollow spheres are produced by blowing high-pressure gas at a pressure of / h. After cooling, they are sieved and sorted. The Al2O3 content of the alumina hollow spheres is 99.1~99.5wt%, SiO2 content is 0.15~0.28wt%, Fe2O3 content is ≤0.03wt%, Na2O content is ≤0.17wt%, and K2O content is ≤0.02wt%. The bulk density of the alumina hollow spheres with a particle size of 5~3mm is 0.52~0.68g / cm³. 3 The bulk density of hollow alumina spheres with a particle size of 3-2 mm is 0.65-0.78 g / cm³. 3 The bulk density of hollow alumina spheres with a particle size of 2-1 mm is 0.79-0.95 g / cm³. 3 Alumina hollow spheres and perlite are used to make modified alumina hollow spheres and modified perlite.

[0055] The preparation method of modified alumina hollow spheres and modified perlite is as follows: Alumina hollow spheres and perlite are modified by three-stage vacuum impregnation using a zirconium-aluminum composite sol: The first stage uses a zirconium-aluminum composite sol with a solid content of 12%, impregnating for 15 min and then drying at 80℃ for 3 h; the second stage uses a zirconium-aluminum composite sol with a solid content of 21%, impregnating for 23 min and then drying at 100℃ for 4 h; the resulting modified perlite has an Al2O3 content of 10.1~13.5 wt%, a SiO2 content of 64.2~75.8 wt%, an Fe2O3 content ≤0.73 wt%, a K2O+Na2O ≤0.9 wt%, and a bulk density of 0.08~0.15 g / cm³. 3 The zirconium-aluminum composite sol used had a zirconium oxide to aluminum oxide mass ratio of 1:3 and a pH of 3.2.

[0056] In this embodiment, the water-reducing agent is a mixture of polycarboxylate-based water-reducing agent FS20, sodium hexametaphosphate, and naphthalene-based water-reducing agent FDN in a mass ratio of 1.7:1:0.8.

[0057] In this embodiment, the pore-forming agent was prepared by mixing sodium dodecylbenzenesulfonate, hydroxypropyl methylcellulose, polyethylene glycol (molecular weight 6100) and propylene glycol methyl ether in a mass ratio of 11:1:1:6.8 and reacting the mixture at 40°C and 0.65 MPa for 26 h.

[0058] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the alumina hollow spheres and perlite are not modified.

[0059] Comparative Example 2 The only difference between Comparative Example 2 and Example 2 is that the zirconium-aluminum composite sol is replaced with silica sol.

[0060] Comparative Example 3 The only difference between Comparative Example 3 and Example 3 is that the Fe2O3, K2O and Na2O content of the raw materials are not controlled, and the Fe2O3 content of the prepared casting material is 1.52% and the K2O+Na2O content is 2.83%.

[0061] The performance of the castables in each embodiment and comparative example was tested, and the test results are shown in the table below.

[0062] Table 1 Performance test results of the examples

[0063] Table 2 Comparative Performance Test Results

[0064] The above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A high-strength heat-insulating castable for hydrogen metallurgy, characterized in that, The raw materials include the following by weight percentages: 15-25% modified alumina hollow spheres with a particle size of 5-3 mm, 7-13% modified alumina hollow spheres with a particle size of 3-2 mm, 2-4% modified alumina hollow spheres with a particle size of 2-1 mm, 7-11% modified perlite with a particle size of 3-0.074 mm, 18-28% quartz powder, 4-6% silica powder, 25-35% pure calcium aluminate cement, and 0.5-2% yttrium oxide powder, plus 0.05-0.15% water-reducing agent, 0.03-0.07% pore-forming agent, and 17-21% water by weight of the total mass of the above raw materials; the modified alumina hollow spheres and modified perlite are obtained by impregnating the alumina hollow spheres and perlite with zirconium aluminum composite sol and then drying them.

2. The high-strength heat-insulating castable for hydrogen metallurgy according to claim 1, characterized in that, The impregnation is vacuum impregnation with a vacuum degree of -0.085 to -0.095 MPa; the impregnation is a three-stage gradient impregnation: the first stage uses a zirconium-aluminum composite sol with a solid content of 8-13%, impregnates for 10-20 minutes, and then dries at 78-85℃ for 3-4 hours; the second stage uses a zirconium-aluminum composite sol with a solid content of 18-23%, impregnates for 20-30 minutes, and then dries at 95-105℃ for 3-5 hours; the third stage uses a zirconium-aluminum composite sol with a solid content of 30-40%, impregnates for 30-60 minutes, and then dries at 115-125℃ for 3-6 hours.

3. The high-strength heat-insulating castable for hydrogen metallurgy according to claim 1, characterized in that, The hollow alumina spheres are formed by melting alumina raw materials and then blowing them with high-pressure gas; the pressure of the high-pressure gas is 0.6~0.8MPa, and the flow rate is 10~30 m³ / s. 3 / h; the hollow alumina spheres have an Al2O3 content of 99.1~99.5wt%, a SiO2 content of 0.15~0.28wt%, a Fe2O3 content ≤0.03wt%, a Na2O content ≤0.17wt%, a K2O content ≤0.02wt%, and a bulk density of 0.5~1.2g / cm³. 3 ; The zirconium-aluminum composite sol has a zirconium oxide to aluminum oxide mass ratio of 1:(2~3.2) and a pH of 3~4.

4. The high-strength heat-insulating castable for hydrogen metallurgy according to claim 1, characterized in that, The modified perlite has an Al2O3 content of 10.1–13.5 wt%, a SiO2 content of 64.2–75.8 wt%, an Fe2O3 content ≤0.73 wt%, a K2O+Na2O content ≤0.9 wt%, and a bulk density of 0.08–0.15 g / cm³. 3 The water-reducing agent is composed of polycarboxylate-based water-reducing agent, sodium hexametaphosphate, and naphthalene-based water-reducing agent; the pore-forming agent is prepared by mixing sodium dodecylbenzenesulfonate, cellulose ether, polyethylene glycol, and glycol ether and then reacting them under temperature and pressure.

5. The high-strength heat-insulating castable for hydrogen metallurgy according to claim 5, characterized in that, The mass ratio of the polycarboxylate superplasticizer, sodium hexametaphosphate, and naphthalene superplasticizer is (1.5~2):1:(0.5~0.8); the mass ratio of sodium dodecylbenzenesulfonate, cellulose ether, polyethylene glycol, and glycol ether is (10~12):1:(0.8~1.1):(5~7); the reaction temperature of the heating and pressurizing reaction is 35~50℃, the reaction pressure is 0.5~0.7MPa, and the reaction time is 24~36h.

6. The high-strength heat-insulating castable for hydrogen metallurgy according to claim 1, characterized in that, The quartz powder has a SiO2 content of 98.9~99.5wt%, an Fe2O3 content of ≤0.12wt%, a K2O+Na2O content of ≤0.2wt%, and a particle size of ≤0.074mm; the silica powder has an Al2O3 content of 0.21~0.28wt%, a SiO2 content of 94.2~95.6wt%, an Fe2O3 content of ≤0.13wt%, a K2O+Na2O content of ≤0.2wt%, and a particle size of 0.3~5μm.

7. The high-strength heat-insulating castable for hydrogen metallurgy according to claim 1, characterized in that, The pure calcium aluminate cement is CA70 cement, with an Al2O3 content of 68.54~70.22wt%, a CaO content of 29.2~30.3wt%, an Fe2O3 content ≤0.43wt%, a K2O+Na2O ≤0.2wt%, and a S content ≤0.08wt%; the yttrium oxide powder has a Y2O3 content of 99.92~99.96wt%, an Fe2O3 content ≤0.001wt%, a K2O+Na2O ≤0.003wt%, and a particle size ≤0.044mm.

8. The high-strength heat-insulating castable for hydrogen metallurgy according to claim 1, characterized in that, The high-strength heat-insulating castable for hydrogen metallurgy has an Al2O3 content ≥50%, an Fe2O3 content ≤0.4%, a K2O+Na2O content ≤0.3%, and a bulk density of ≤1.25 g / cm³ at 110℃ for 24 hours. 3 The bulk density at 1000℃ for 3 hours is ≤1.15 g / cm³. 3 The compressive strength at 110℃ for 24 hours is ≥10MPa, the compressive strength at 1000℃ for 3 hours is ≥7MPa, the linear change rate after burning at 1000℃ for 3 hours is -0.3% to +0.3%, the thermal conductivity at hot surface temperature is ≤0.355 W / (m·K) at 300℃, ≤0.405 W / (m·K) at 600℃, and ≤0.485 W / (m·K) at 900℃.

9. A method for preparing a high-strength heat-insulating castable for hydrogen metallurgy as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Modified alumina hollow spheres of various particle sizes, modified perlite, quartz powder, silica powder, pure calcium aluminate cement, and yttrium oxide powder are mixed together, then water-reducing agent and pore-forming agent are added and mixed, and finally water is added and mixed to obtain high-strength thermal insulation castable.

10. A method for applying a high-strength heat-insulating castable for hydrogen metallurgy as described in any one of claims 1 to 8, characterized in that, Includes the following steps: High-strength heat-insulating castable is poured into the mold and vibrated to compact it. After curing, the mold is removed, and the material is baked and then heated to the working temperature for service. The baking process consists of three stages: the first stage baking temperature is 110~130℃, and the holding time is 72~96h; the second stage baking temperature is 340~360℃, and the holding time is 36~48h; the third stage baking temperature is 590~620℃, and the holding time is 24~36h.

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