Corundum silicon carbide mullite castable for zinc oxide refining rotary kiln

Abstract

The corundum-silicon carbide-mullite castable is prepared from sintered mullite particles, silicon carbide fine powder, activated aluminum oxide micro powder, silicon dioxide micro powder, composite rare earth oxide fine powder, aluminum titanate fine powder, a binding agent, a water reducing agent, explosion-proof fibers and porous composite corundum-silicon carbide particles. The porous composite corundum-silicon carbide particles are formed by sintering fused corundum particles and nano silicon carbide powder through in-situ reaction, micron-sized pore channels which are communicated with one another are formed in the porous composite corundum-silicon carbide particles, and the surfaces of the particles are coated with a compact mullite-corundum complex phase layer, so that thermal stress can be effectively buffered, and permeation of zinc and alkali vapor can be blocked; the low thermal expansion characteristic of aluminum titanate and the grain boundary purification effect of rare earth oxide are matched, thermal shock resistance and erosion resistance are synergistically improved, and excellent thermal shock resistance, chemical erosion resistance, high strength and wear resistance are shown under the harsh working condition of the zinc oxide rotary kiln.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of corundum silicon carbide mullite castable, in particular to a corundum silicon carbide mullite castable for zinc oxide extraction rotary kiln. BACKGROUND

[0002] The zinc oxide rotary kiln is a key equipment for recovering zinc oxide from zinc-containing slag in pyrometallurgical smelting. The inner lining refractory material is directly exposed to a strong corrosive atmosphere of high temperature, alkali metal vapor, zinc vapor and sulfur dioxide, and at the same time, it bears the thermal stress caused by the rolling impact of the material and the severe temperature fluctuation. In order to ensure the stable operation of the rotary kiln, the inner lining material needs to have high refractoriness, excellent thermal shock resistance, excellent wear resistance and strong chemical corrosion resistance. The corundum-silicon carbide-mullite castable is a high-performance amorphous refractory material developed to adapt to such harsh conditions.

[0003] At present, the inner lining of the zinc oxide rotary kiln has been widely used with magnesia-alumina-chrome bricks. The material resists chemical corrosion to some extent by relying on the chromium oxide component, but it has high apparent porosity, low room temperature strength, poor wear resistance, and high thermal expansion coefficient, which leads to insufficient thermal shock resistance, and is easy to cause structural spalling due to the penetration of gas phase corrosion medium along the brick joints and the action of thermal stress. In addition, the magnesia-alumina-chrome brick may produce carcinogenic hexavalent chromium compounds in production and use, which poses a threat to the environment and health. Although the subsequent development of aluminum-chromium-zirconium-silicon composite bricks attempts to improve the performance, they still have environmental risks due to the use of chromium-containing raw materials, and their dense structure does not significantly improve the thermal shock resistance, and the overall penetration resistance is still limited.

[0004] The core problem that the existing technology cannot solve is that, on the one hand, the dense refractory bricks or castables with high thermal conductivity will cause serious heat loss on the surface of the kiln body, increase the cost of energy consumption, and the material lacks effective microporous structure to buffer thermal stress, so the improvement of thermal shock resistance is limited. On the other hand, gas phase corrosion media such as zinc and alkali vapor can easily penetrate through the open pores of the material or weakly combined particles, causing the formation of internal metamorphic layers, and the volume expansion during the secondary mullitization process, if not effectively controlled, will exacerbate the generation of microcracks in the matrix, thereby significantly reducing the corrosion resistance and overall service life of the material. SUMMARY

[0005] The existing problems in the prior art are that the existing corundum silicon carbide mullite castable has insufficient thermal shock resistance to cope with severe temperature fluctuations and limited resistance to zinc and alkali vapor penetration and corrosion under the harsh conditions of the zinc oxide rotary kiln, which restricts its service life and energy efficiency. In view of the above technical problems, the present application provides a corundum silicon carbide mullite castable for zinc oxide extraction rotary kiln.

[0006] The technical scheme of the present application is: a corundum silicon carbide mullite castable for zinc oxide extraction rotary kiln, which is composed of the following components in percentage by mass: 15-25% of sintered mullite particles, 8-15% of silicon carbide fine powder, 5-10% of active alumina powder, 3-8% of silica powder, 1-4% of composite rare earth oxide fine powder, 1-3% of aluminum titanate fine powder, 2-5% of binder, 0.05-0.15% of water reducing agent, 0.01-0.1% of anti-explosion fiber, and the balance of porous composite corundum-silicon carbide particles; wherein the porous composite corundum-silicon carbide particles are formed by in-situ reaction sintering of fused corundum particles and nano silicon carbide powder, have micron-level interconnected pores inside, and the outer surface of the porous composite corundum-silicon carbide particles is a dense multi-phase layer composed of mullite and corundum crystals; the apparent porosity of the porous composite corundum-silicon carbide particles is 15-25%, and the average pore size is 5-15 microns.

[0007] Description: By in-situ reaction sintering of fused corundum particles and nano silicon carbide powder in an inert atmosphere, micron-level interconnected pores are formed inside the aggregate to effectively buffer thermal stress, and a dense mullite-corundum multi-phase layer is generated on the surface, which acts as a strong barrier to significantly block the penetration of corrosive media such as zinc and alkali vapor. Aluminum titanate can further compensate and inhibit internal stress of the material when the temperature changes dramatically due to its unique thermal expansion anisotropy and low thermal expansion coefficient; and the specific proportion of composite rare earth oxide fine powder can purify the grain boundary and promote sintering densification at high temperature through the active element effect, and react with the matrix components to generate high-temperature stable phases, both of which synergistically strengthen the binding network of the matrix at the micro level, thereby improving the thermal shock resistance, high-temperature strength and corrosion resistance. In addition, the scheme uses a composite binding system of pure calcium aluminate cement and silica sol, which takes into account good construction performance at room temperature and the advantage of avoiding the introduction of too much low-melting substance at high temperature, ensuring the stability of the material's performance within the entire temperature range.

[0008] Further, the Al2O3 content of the sintered mullite particles is 72-75wt%, and the particle size distribution is: 40-50% of particles with a particle size of 3-5mm, 30-40% of particles with a particle size of 1-3mm, and the balance of particles with a particle size of less than 1mm.

[0009] Description: Increasing the Al2O3 content of the sintered mullite particles to 72-99.9wt% significantly improves the refractoriness and high-temperature volume stability of the material. The optimized particle size distribution achieves the closest packing, not only improving the density and strength of the castable, reducing the amount of water used for construction, but also optimizing the stress distribution between the internal particles through the synergistic effect of different particle sizes, thereby enhancing the thermal shock resistance and corrosion resistance of the material.

[0010] Further, the SiC content of the silicon carbide fine powder is 97-99.4wt%, and the particle size is 1-45μm.

[0011] Description: The high-purity and fine-grained silicon carbide fine powder can uniformly fill the gaps between the aggregates. High-purity SiC has excellent oxidation resistance and thermal conductivity at high temperatures, which can effectively strengthen the matrix and improve the overall wear resistance and thermal shock stability of the material. Its reducing property helps to inhibit the action of some oxidative corrosion media.

[0012] Further, the composite rare earth oxide fine powder is a mixture of yttrium oxide and cerium oxide with a mass ratio of 1-3:1, and the particle size is 1-10μm.

[0013] Description: The use of a specific mass ratio of yttrium oxide and cerium oxide composite rare earth oxide fine powder takes advantage of the active element effect of rare earth elements. They can preferentially distribute in the grain boundaries, purify the grain boundary impurities, promote sintering densification, and react with the matrix components to form high-temperature stable phases, thereby significantly improving the high-temperature mechanical properties and corrosion resistance of the material.

[0014] Further, the Al2TiO5 content of the aluminum titanate fine powder is 95-99.9wt%, and the particle size is 1-30μm.

[0015] Description: The introduction of high-purity, fine-grained aluminum titanate fine powder takes advantage of the unique low thermal expansion coefficient and anisotropic thermal expansion behavior of aluminum titanate, which can effectively compensate and inhibit the internal stress generated by the material when the temperature fluctuates sharply, thereby further enhancing the thermal shock resistance of the castable in cooperation with the porous aggregate.

[0016] Further, the binder is a composite system of pure calcium aluminate cement and silica sol, wherein the pure calcium aluminate cement accounts for 60-80% of the total mass of the binder, and the balance is silica sol.

[0017] Description: The use of a composite binder system of pure calcium aluminate cement and silica sol combines the advantages of both. Pure calcium aluminate cement provides sufficient hardening strength at room temperature to ensure demolding and initial strength; silica sol forms a high-temperature resistant silicate network to provide stronger binding force at medium and high temperatures, avoiding the introduction of too many low-melting-point phases by traditional binders, which affects the high-temperature performance, and ensuring the smooth transition of the material's strength throughout the temperature range.

[0018] A preparation method of a corundum silicon carbide mullite castable for a zinc oxide refining rotary kiln, comprising the following steps: S1, preparing porous composite corundum-silicon carbide particles: Take 70-85wt% of the electrically fused corundum particles and the balance of the nano silicon carbide powder as raw materials, then add 1-3% of the total mass of the polyvinyl alcohol solution as a temporary binder, mix uniformly, and then press into shape, sinter at 1650-1800℃ for 2-4 hours in an inert atmosphere, and then break and sieve after slow cooling in the furnace to obtain porous composite corundum-silicon carbide particles with a particle size of 1-5mm; the particle size of the electrically fused corundum particles is 3-5mm, and the particle size of the nano silicon carbide powder is 1-100nm; S2, raw material premixing: According to the proportion, the sintered mullite particles, silicon carbide powder, active alumina powder, silica powder, composite rare earth oxide powder and aluminum titanate powder are placed in a mixer and dry mixed for 10-20 minutes to obtain a uniform matrix premix powder; S3, stirring and mixing: The porous composite corundum-silicon carbide particles prepared in step S1 are added to the matrix premix powder of step S2, and stirred at low speed for 5-10 minutes to mix them preliminarily, then the binder and water reducing agent are added according to the proportion to obtain dry materials, then 5-8% of water based on the total mass of the dry materials is added, and stirred at high speed for 10-15 minutes until the material is in a uniform plastic state, finally the explosion-proof fiber is added and stirred at low speed for 3-5 minutes to disperse uniformly, to obtain a casting slurry; S4, casting and curing: The casting slurry obtained in step S3 is poured into a kiln lining mold with pre-installed anchoring parts, and vibrated on a vibration table to compact it, then the surface is smoothed and cured at a temperature of 15-25℃ and a humidity of 90-97% for 24-48 hours, and then the lining body is obtained after demolding; S5, drying and heat treatment: The lining body of step S4 is slowly heated to 110-120℃ at a heating rate of 15-25℃ / hour, and then kept at this temperature for 12-24 hours to completely remove free water; then sintered at 1350-1450℃ under a reducing atmosphere at a rate of 30-50℃ / hour for 3-5 hours, and then cooled in the furnace to obtain the finished product of the castable.

[0019] Description: Porous composite corundum-silicon carbide particles are prepared, at high temperature, aluminum ions and silicon ions will diffuse and react, forming a mullite phase on the surface of the particles, and part of the alumina will remain in the corundum phase, thus forming a mullite-corundum composite phase layer. In addition, above 1650℃, the nucleation and growth of mullite occurs at the interface of Al2O3 and SiO2, and the growth rate is determined by Al 3+ and Si 4+The diffusion control through the mullite lattice also helps to form a dense complex phase layer on the particle surface. The dry mixing of the matrix powder in step S2 helps to ensure the uniform dispersion of various fine powders and additives, laying the foundation for the subsequent formation of a homogeneous and high-performance matrix structure, avoiding local composition deviation leading to performance weaknesses. The specific high and low speed stirring speed and feeding sequence in step S3 aims to ensure uniform mixing of porous aggregates and matrix while avoiding excessive shear force that damages the special porous structure of the aggregate or leads to uneven distribution of the explosion-proof fiber, thereby obtaining a well-worked and structurally complete castable slurry. The curing in a high temperature and humidity environment for 24-48 hours in step S4 is beneficial to the full hydration of the binder, enabling the lining to obtain sufficient demolding strength and initial strength to prevent cracking. The drying stage in step S5 ensures slow water discharge to prevent cracking caused by steam pressure. Subsequent sintering in a reducing atmosphere at 1350-1450°C can effectively protect the silicon carbide component from excessive oxidation and promote the formation of more stable phases in the matrix, ultimately enabling the material to obtain excellent sintering strength and high temperature performance.

[0020] Further, the inert atmosphere in S1 is an argon atmosphere, and its flow rate is controlled at 5-10 L / min; the reducing atmosphere in S5 is a mixed gas of nitrogen and hydrogen with a volume ratio of 8-9:1.

[0021] Description: In step S1, argon with precise flow control is used as the inert protective atmosphere, and its core role is to provide an absolutely oxygen-free environment for the in-situ synthesis of porous composite corundum-silicon carbide particles. This can effectively prevent the oxidation of nano-silicon carbide powder during high-temperature sintering at 1650-1800°C, ensuring that it can undergo the pre-designed and sufficient in-situ reaction with fused corundum, thereby forming a uniform and interconnected micron-scale pore structure inside the particles. At the same time, stable argon flow ensures the uniformity of the furnace atmosphere and temperature field, promoting the uniform formation of a dense mullite-corundum complex phase layer on the particle surface, which is the structural basis for achieving excellent thermal shock resistance and erosion resistance of the aggregate; nitrogen as the main gas provides a stable environment, while the introduction of a suitable amount of hydrogen (10%) can maintain a low oxygen partial pressure in the furnace, and its key role is to prevent the silicon carbide component in the castable from being excessively oxidized, thereby preserving its high-temperature strength and thermal conductivity. This weak reducing atmosphere also promotes the sintering densification of the matrix components, facilitating the formation of high-performance phases while avoiding the generation of harmful low-valence oxides, ultimately significantly improving the high-temperature volume stability and erosion resistance of the castable.

[0022] Further, the high-speed stirring speed in S3 is 200-300 rpm, and the low-speed stirring speed is 80-120 rpm.

[0023] Note: High-speed stirring ensures that the porous composite aggregate, various fine powders, binders and water can be quickly and uniformly mixed, so that the slurry reaches the required plastic state. Subsequent switching to low-speed stirring when adding the easily damaged components such as explosion-proof fibers can effectively avoid the destruction of the length distribution of the explosion-proof fibers and the damage to the precise pore structure of the porous composite corundum-silicon carbide particles prepared in advance, thereby ensuring the excellent workability of the castable slurry and the overall homogeneity of the formed lining.

[0024] The beneficial effects of the present application are: The present application significantly improves the comprehensive performance of the material in high-temperature and corrosive environments through unique component design and structural innovation. The micron-scale interconnected pores inside the porous composite corundum-silicon carbide particles can effectively buffer the thermal stress caused by rapid temperature fluctuations, thereby significantly enhancing the thermal shock resistance of the castable and preventing cracking and spalling. At the same time, the dense mullite-corundum composite layer on the surface of the particles cooperates with the silicon carbide powder, active alumina powder and silica powder in the matrix to form an excellent erosion-resistant barrier, effectively resisting chemical corrosion and penetration of zinc vapor, alkali metal vapor and sulfur-containing atmospheres. In addition, the sintered mullite particles in the formula contribute to good high-temperature volume stability and thermal shock resistance, the introduction of composite rare earth oxide powder and aluminum titanate powder further optimizes the high-temperature mechanical properties and thermal shock resistance of the material, and the composite binding system of pure calcium aluminate cement and silica sol ensures good workability and high-temperature strength. The synergistic effect of multiple components enables the castable to have excellent thermal shock resistance, outstanding chemical corrosion resistance, high refractoriness and good wear resistance under the harsh working conditions of the zinc oxide rotary kiln, significantly extending the service life of the kiln lining. DETAILED DESCRIPTION

[0025] To further illustrate the methods adopted by the present application and the effects achieved, the technical solutions of the present application will be described clearly and completely in conjunction with experiments.

[0026] Example 1: A corundum silicon carbide mullite castable for zinc oxide smelting rotary kiln, which is composed of the following components in mass percentage: 20% of sintered mullite particles, 11% of silicon carbide fine powder, 8% of active alumina micro powder, 5% of silica micro powder, 3% of composite rare earth oxide fine powder, 2% of aluminum titanate fine powder, 3.5% of binder, 0.1% of water reducing agent, 0.05% of anti-explosion fiber, and the balance of porous composite corundum-silicon carbide particles; wherein the porous composite corundum-silicon carbide particles are formed by in-situ reaction sintering of fused corundum particles and nano silicon carbide powder, have micron-level interconnected pores in the interior, and a dense mullite-corundum composite layer is coated on the surface of the particles; the apparent porosity of the porous composite corundum-silicon carbide particles is 21%, and the average pore size is 10 μm; the Al2O3 content of the sintered mullite particles is 73 wt%, and the particle size distribution is that the particles with a particle size of 4-4.5 mm account for 45%, the particles with a particle size of 1.5-2.5 mm account for 35%, and the balance is particles with a particle size less than 1 mm; the SiC content of the silicon carbide fine powder is 98 wt%, and the particle size is 25-35 μm; the composite rare earth oxide fine powder is a mixture of yttrium oxide and cerium oxide with a mass ratio of 2:1, and the particle size is 5-7 μm; the Al2TiO5 content of the aluminum titanate fine powder is 97 wt%, and the particle size is 15-25 μm; the binder is a composite system of pure calcium aluminate cement and silica sol, wherein the pure calcium aluminate cement accounts for 70% of the total mass of the binder, and the balance is silica sol.

[0027] Example 2: The preparation method of the corundum silicon carbide mullite castable for zinc oxide smelting rotary kiln of Example 1, which comprises the following steps: S1, preparing porous composite corundum-silicon carbide particles: Take 78 wt% of fused corundum particles and the balance of nano silicon carbide powder as raw materials, add 2% of polyvinyl alcohol solution as a temporary binder based on the total mass of the raw materials, uniformly mix, and then press into shape, sinter at 1700°C for 3 hours under an inert atmosphere, break and sieve after furnace cooling, and obtain porous composite corundum-silicon carbide particles with a particle size of 3-4 mm; the fused corundum particles have a particle size of 4-4.5 mm, and the nano silicon carbide powder has a particle size of 50-70 nm; the inert atmosphere is an argon atmosphere, and the flow rate is controlled at 9 L / min; S2, raw material premixing: Mix the sintered mullite particles, silicon carbide fine powder, active alumina micro powder, silica micro powder, composite rare earth oxide fine powder, and aluminum titanate fine powder in a mixer for 15 minutes to obtain a uniform base premix powder; S3, stirring and mixing: The porous composite corundum-silicon carbide particles prepared in step S1 are added into the matrix premixed powder described in step S2, and stirred at low speed for 7 minutes to preliminarily mix, then the binder and water reducing agent are added according to the proportion to obtain dry materials, then 6.5% of water based on the total mass of the dry materials is added, and stirred at high speed for 12.5 minutes until the materials present a uniform plastic state, finally the anti-explosion fiber is added, and stirred at low speed for 4 minutes to uniformly disperse, to obtain the castable slurry; the rotating speed of high speed stirring is 250 rpm, and the rotating speed of low speed stirring is 100 rpm. S4, casting and curing: The castable slurry obtained in step S3 is poured into a kiln lining mold with preset anchor, and vibrated to compact on a vibration table, and after the surface is smoothed, the lining body is obtained by curing for 36 hours under the condition that the temperature is 20℃ and the humidity is 95%, and then demolding; S5, drying and heat treatment: The lining body described in step S4 is slowly heated to 115℃ at a heating rate of 20℃ / hour, and kept for 18 hours; then sintered by heating to 1400℃ at a rate of 40℃ / hour under a reducing atmosphere, and kept for 4 hours, and the castable product is obtained after furnace cooling; the reducing atmosphere is composed of a mixed gas of nitrogen and hydrogen with a volume ratio of 8.5:1.

[0028] Example 3: This example is basically the same as example 1, except that it is composed of the following components with mass percentage: 15% of sintered mullite particles, 8% of silicon carbide fine powder, 5% of active alumina micro powder, 3% of silica micro powder, 1% of composite rare earth oxide fine powder, 1% of aluminum titanate fine powder, 2% of binder, 0.05% of water reducing agent, 0.01% of anti-explosion fiber, and the balance of porous composite corundum-silicon carbide particles; wherein the porous composite corundum-silicon carbide particles are formed by in-situ reaction sintering of fused corundum particles and nano silicon carbide powder, and have micron-level interconnected pores in the interior, and a dense mullite-corundum composite layer on the surface of the particles; the apparent porosity of the porous composite corundum-silicon carbide particles is 15%, and the average pore size is 5μm.

[0029] Example 4: This example is basically the same as Example 1, except that it is composed of the following mass percentages of components: 25% sintered mullite particles, 15% silicon carbide fine powder, 10% active alumina micro powder, 8% silica micro powder, 4% composite rare earth oxide fine powder, 3% aluminum titanate fine powder, 5% binder, 0.15% water reducing agent, 0.1% anti-explosion fiber, and the balance of porous composite corundum-silicon carbide particles; wherein the porous composite corundum-silicon carbide particles are formed by in-situ reaction sintering of fused corundum particles and nano silicon carbide powder, have micron-scale interconnected pores in the interior, and have a dense mullite-corundum composite layer on the surface of the particles; the apparent porosity of the porous composite corundum-silicon carbide particles is 25%, and the average pore size is 15 μm.

[0030] Example 5: This example is basically the same as Example 1, except that the Al2O3 content of the sintered mullite particles is 72 wt%, and the particle size distribution is as follows: 40% of the particles have a particle size of 3-4 mm, 30% of the particles have a particle size of 1-2 mm, and the balance of the particles have a particle size of less than 1 mm.

[0031] Example 6: This example is basically the same as Example 1, except that the Al2O3 content of the sintered mullite particles is 75 wt%, and the particle size distribution is as follows: 50% of the particles have a particle size of 4-5 mm, 40% of the particles have a particle size of 2-3 mm, and the balance of the particles have a particle size of less than 1 mm.

[0032] Example 7: This example is basically the same as Example 1, except that the SiC content of the silicon carbide fine powder is 97 wt%, and the particle size is 1-15 μm; the composite rare earth oxide fine powder is a mixture of yttrium oxide and cerium oxide in a mass ratio of 1:1, and the particle size is 1-5 μm; the Al2TiO5 content of the aluminum titanate fine powder is 95 wt%, and the particle size is 1-15 μm; and the binder is a composite system of pure calcium aluminate cement and silica sol, wherein the pure calcium aluminate cement accounts for 60% of the total mass of the binder, and the balance is silica sol.

[0033] Example 8: This example is basically the same as Example 1, except that the SiC content of the silicon carbide fine powder is 99.4 wt%, and the particle size is 35-45 μm; the composite rare earth oxide fine powder is a mixture of yttrium oxide and cerium oxide in a mass ratio of 3:1, and the particle size is 8-10 μm; the Al2TiO5 content of the aluminum titanate fine powder is 99.9 wt%, and the particle size is 25-30 μm; and the binder is a composite system of pure calcium aluminate cement and silica sol, wherein the pure calcium aluminate cement accounts for 80% of the total mass of the binder, and the balance is silica sol.

[0034] Example 9: The raw material components of this example are basically the same as those of Example 1, and the preparation method of the castable product is basically the same as that of Example 2, except that the preparation method of the castable product comprises the following steps: S1, preparing porous composite corundum-silicon carbide particles: Take 70wt% of fused corundum particles and the balance of nano-silicon carbide powder as raw materials, and add 1% of polyvinyl alcohol solution based on the total mass of the raw materials as a temporary binder, mix uniformly, and then press into shape, sinter at 1650°C for 2 hours under an inert atmosphere, break and sieve after slow cooling in the furnace, to obtain porous composite corundum-silicon carbide particles with a particle size of 1-2mm; the fused corundum particles have a particle size of 3-4mm, and the nano-silicon carbide powder has a particle size of 1-30nm; the apparent porosity of the porous composite corundum-silicon carbide particles is 15%, and the average pore size is 5μm; S2, raw material premixing: Mix the sintered mullite particles, silicon carbide powder, active alumina powder, silica powder, composite rare earth oxide powder, and aluminum titanate powder in a mixer for 10 minutes to obtain a uniform matrix premix powder; S3, stirring and mixing: Add the porous composite corundum-silicon carbide particles prepared in step S1 to the matrix premix powder of step S2, stir at low speed for 5 minutes to mix them initially, then add the binder and water reducing agent according to the proportion to obtain dry materials, and then add water accounting for 5% of the total mass of the dry materials, stir at high speed for 10 minutes until the materials are in a uniform plastic state, finally add the explosion-proof fiber and stir at low speed for 3 minutes to disperse uniformly, to obtain a castable slurry; S4, casting and curing: Pour the castable slurry obtained in step S3 into a kiln lining mold with pre-installed anchoring elements, and vibrate on a vibration table to compact, then smooth the surface and place it under the conditions of a temperature of 15°C and a humidity of 90% for 24 hours of curing, then demold to obtain a lining body; S5, drying and heat treatment: Slowly heat the lining body to 110°C at a heating rate of 15°C / hour and maintain for 12 hours, then heat to 1350°C at a rate of 30°C / hour under a reducing atmosphere, and sinter for 3 hours, then cool in the furnace to obtain the castable product.

[0035] Example 10: The raw material components of this example are basically the same as those of Example 1, and the preparation method of the castable product is basically the same as that of Example 2, except that the preparation method of the castable product comprises the following steps: S1, preparing porous composite corundum-silicon carbide particles: Take 85wt% of the electrically fused corundum particles and the balance of the nano silicon carbide powder as raw materials, then add 3% of the total mass of the raw materials polyvinyl alcohol solution as a temporary binder, mix uniformly, then press into shape, sinter at 1800℃ for 4 hours in an inert atmosphere, slowly heat to 120℃ at a rate of 25℃ / hour and keep for 24 hours, then sinter at 1450℃ for 5 hours in a reducing atmosphere at a rate of 50℃ / hour, cool in the furnace, then break up and sieve to obtain porous composite corundum-silicon carbide particles with a particle size of 4-5mm; the electrically fused corundum particles have a particle size of 4-5mm, the nano silicon carbide powder has a particle size of 90-100nm, and the porous composite corundum-silicon carbide particles have an apparent porosity of 25% and an average pore size of 15μm; S2, raw material premixing: Mix the sintered mullite particles, silicon carbide powder, active alumina powder, silica powder, composite rare earth oxide powder, and aluminum titanate powder in a mixer for 20 minutes to obtain a uniform base premix powder; S3, stirring and mixing: Add the porous composite corundum-silicon carbide particles prepared in step S1 to the base premix powder of step S2, stir at low speed for 10 minutes to mix them initially, then add the binder and water reducing agent according to the ratio to obtain dry materials, then add 8% of the total mass of the dry materials, and stir at high speed for 15 minutes until the materials are in a uniform plastic state, finally add the explosion-proof fiber and stir at low speed for 5 minutes to disperse them uniformly to obtain a castable slurry; S4, casting and curing: Pour the castable slurry obtained in step S3 into a kiln lining mold with pre-installed anchoring elements, compact it on a vibration table, smooth the surface, and then place it in a temperature of 25℃ and humidity of 97% for 48 hours of curing, then demold to obtain a lining body; S5, drying and heat treatment: Slowly heat the lining body to 120℃ at a rate of 25℃ / hour and keep for 24 hours, then sinter at 1450℃ for 5 hours in a reducing atmosphere at a rate of 50℃ / hour, cool in the furnace, and obtain the castable product.

[0036] Example 11: The raw material components of this example are basically the same as those of Example 1, and the preparation method of the castable product is basically the same as that of Example 2, except that the inert atmosphere in S1 is an argon atmosphere with a flow rate of 5 L / min, and the reducing atmosphere in S5 is a mixed gas of nitrogen and hydrogen with a volume ratio of 8:1.

[0037] Example 12: The raw material components of this example are basically the same as those of Example 1, and the preparation method of the castable product is basically the same as that of Example 2, except that the inert atmosphere in S1 is an argon atmosphere, and the flow rate is controlled at 10 L / min; the reducing atmosphere in S5 is a mixed gas of nitrogen and hydrogen in a volume ratio of 9:1.

[0038] Example 13: The raw material components of this example are basically the same as those of Example 1, and the preparation method of the castable product is basically the same as that of Example 2, except that the high-speed stirring speed in S3 is 200 rpm, and the low-speed stirring speed is 80 rpm.

[0039] Example 14: The raw material components of this example are basically the same as those of Example 1, and the preparation method of the castable product is basically the same as that of Example 2, except that the high-speed stirring speed in S3 is 300 rpm, and the low-speed stirring speed is 120 rpm.

[0040] Comparative Example 1: This comparative example is basically the same as Example 1, except that the porous corundum-silicon carbide composite particles are not used, but equal mass of ordinary fused corundum particles with an apparent porosity of 4% and an average pore size of 0-1 μm are used as aggregates. The proportions of the remaining components and the preparation process are consistent with Example 1.

[0041] Comparative Example 2: This comparative example is basically the same as Example 1, except that the composite rare earth oxide fine powder is not added, and an equal amount of active alumina powder is used instead. The proportions of the remaining components and the preparation process are consistent with Example 1.

[0042] Comparative Example 3: This comparative example is basically the same as Example 1, except that the heat treatment atmosphere in step S5 is changed to static air instead of reducing nitrogen-hydrogen mixed gas, and the remaining preparation process parameters are exactly the same as those of Example 1.

[0043] In order to explore the properties of the corundum-silicon carbide-mullite castable of the above examples and comparative examples, the main materials were determined according to the experimental formula, and the samples were tested. The bulk density and apparent porosity were determined according to GB / T 2997-2015 "Test Methods for Bulk Density, Apparent Porosity and True Porosity of Dense Shaped Refractory Products" using the Archimedes principle, i.e. after drying, the sample was saturated by immersion, and the mass was calculated. The cold modulus of rupture was determined by three-point bending test according to GB / T 3001-2017 "Test Method for Cold Modulus of Rupture of Refractory Materials". The thermal shock resistance was tested according to GB / T 30873-2014 "Test Method for Thermal Shock Stability of Refractory Materials", and the strength retention rate was calculated after simulating high temperature rapid cooling cycles. The corrosion resistance was tested according to the equivalent method of ASTM C863 standard, and the strength loss was evaluated after holding in high temperature corrosion medium. As shown in Table 1. The specific exploration is as follows: Table 1 Performance test table of corundum silicon carbide mullite castable sample of examples 2-14, control examples 1-3

[0044] 1. Explore the influence of porous composite corundum-silicon carbide aggregate on the performance of castables: As shown in Table 1, compare Example 2, Example 9, Example 10 and Control Example 1. Example 9 has the best thermal shock resistance of 89.8% due to its high porosity aggregate design, but the relative weak corrosion resistance is 80.6%. Example 2 performs balanced as a benchmark, with thermal shock resistance and corrosion resistance of 84.9% and 88.2% respectively. Example 10 achieves the optimal corrosion resistance of 95.4% through high-end aggregate parameters, but the thermal shock resistance is slightly lower at 81.2%. Control Example 1 uses dense aggregate, with a sharp deterioration in thermal shock resistance to 52.1% and a corrosion resistance of only 75.2%, confirming that the porous structure is the key to buffering thermal stress.

[0045] 2. Explore the influence of raw material component-related parameters on the performance of castables: As shown in Table 1, compare Example 2, Example 7, Example 8 and Control Example 2. Example 8 has the highest corrosion resistance of 93.9% due to the use of high-purity composite rare earth oxides and aluminum titanate, and excellent strength. Example 7 has a comprehensive performance decline due to the lower purity of the additive, with a corrosion resistance of 84.2%. Example 2 maintains a stable level with a corrosion resistance of 88.2%. Control Example 2 completely lacks rare earth oxides, with a sharp drop in corrosion resistance to 68.1% and the lowest strength, indicating that functional additives are indispensable for matrix strengthening and corrosion resistance.

[0046] By comparing Example 3 and Example 4, the trade-off relationship between component ratio and performance can be clearly seen. Example 3 has a lower component content, a higher apparent porosity, excellent thermal shock resistance, but relatively lower corrosion resistance and weaker strength at room temperature. This shows that low component ratio is beneficial to forming a more open porous structure, improving the thermal stress buffering capacity, but at the cost of density and chemical corrosion resistance. Conversely, Example 4 has a higher component ratio, the lowest apparent porosity, the highest corrosion resistance, and significantly improved strength, but slightly lower thermal shock resistance. This trade-off shows that a high proportion of components can enhance density and corrosion resistance through more compact packing and abundant matrix phase enhancement, but slightly sacrifices the thermal shock buffering effect of porosity.

[0047] Examples 5 and 6 demonstrate the optimization of microstructure by adjusting the Al203 content and grading of mullite particles. Example 5 has lower Al203 content and finer grading, which results in slightly lower bulk density and strength than Example 6. More importantly, Example 6 has better erosion resistance than Example 5, because higher Al content and optimized grading promote more uniform particle packing and reduce the penetration path of erosion media. Meanwhile, both of them have high thermal shock resistance, which indicates that moderately increasing the Al content and coarse particle ratio of mullite particles can enhance the matrix continuity and balance the strength and thermal stability.

[0048] 3. Effect of heat treatment atmosphere on the properties of castables: As shown in Table 1, Example 2, Example 11, Example 12 and Comparative Example 3 are compared. Example 12 has the best performance with 90.9% erosion resistance under optimized reducing atmosphere. Example 11 has 89.6% erosion resistance, which is the second. Example 2 has 88.2% erosion resistance under standard reducing atmosphere, which has moderate performance. Comparative Example 3 is treated in air atmosphere, which dramatically reduces the erosion resistance to 55.1% and significantly decreases the thermal shock resistance, which proves that reducing atmosphere is crucial to protect the silicon carbide component and maintain the structural integrity.

[0049] 4. Effect of mixing process parameters on the properties of castables: As shown in Table 1, Example 2, Example 13 and Example 14 are compared. Example 14 has the best uniformity by high-speed mixing, which slightly increases the flexural strength to 15.0 MPa and the erosion resistance to 90.1%. Example 13 has 14.1 MPa flexural strength and 87.1% erosion resistance by low-speed mixing, which has slightly lower performance. Example 2 has 14.2 MPa flexural strength and 88.2% erosion resistance as the benchmark, which indicates that optimized mixing can indirectly improve the durability by improving the uniformity of the microstructure, and the influence is less than the component design.

Claims

1. A corundum silicon carbide mullite castable for zinc oxide refining rotary kiln, characterized by, Consist of the following quality percentage of components: 15-25% sintered mullite particles, 8-15% silicon carbide fine powder, 5-10% active alumina powder, 3-8% silica powder, 1-4% composite rare earth oxide powder, 1-3% aluminum titanate powder, 2-5% binder, 0.05-0.15% water reducing agent, 0.01-0.1% explosion-proof fiber and the balance of porous composite corundum-silicon carbide particles.

2. A corundum silicon carbide mullite castable for zinc oxide smelting rotary kiln according to claim 1, characterized in that, The Al2O3 content of the sintered mullite particles is 72-75wt%, and the particle size distribution is: the particles with a particle size of 3-5mm account for 40-50%, the particles with a particle size of 1-3mm account for 30-40%, and the balance is particles with a particle size of less than 1mm.

3. A corundum silicon carbide mullite castable for zinc oxide smelting rotary kiln according to claim 1, characterized in that, The SiC content of the silicon carbide fine powder is 97-99.4wt%, and the particle size is 1-45μm.

4. A corundum silicon carbide mullite castable for zinc oxide smelting rotary kiln according to claim 1, characterized in that, The composite rare earth oxide powder is a mixture of yttrium oxide and cerium oxide with a mass ratio of 1-3:1, and the particle size is 1-10μm.

5. A corundum silicon carbide mullite castable for zinc oxide smelting rotary kiln according to claim 1, characterized in that, The Al2TiO5 content of the aluminum titanate powder is 95-99.9wt%, and the particle size is 1-30μm.

6. A corundum silicon carbide mullite castable for zinc oxide smelting rotary kiln according to claim 1, characterized in that, The binder is a composite system of pure calcium aluminate cement and silica sol, wherein the pure calcium aluminate cement accounts for 60-80% of the total mass of the binder, and the balance is silica sol.

7. A method for preparing a corundum-silicon carbide-mullite castable for zinc oxide extraction rotary kilns according to any one of claims 1-6, characterized in that, Comprise the following steps: S1, preparation of porous composite corundum-silicon carbide particles: Take 70-85wt% of fused corundum particles and the balance of nano silicon carbide powder as raw materials, and add 1-3% of polyvinyl alcohol solution as a temporary binder based on the total mass of the raw materials, mix uniformly, and then press into shape, sinter at 1650-1800℃ for 2-4 hours under inert atmosphere, cool in the furnace, break and sieve to obtain porous composite corundum-silicon carbide particles with a particle size of 1-5mm; the fused corundum particles have a particle size of 3-5mm, and the nano silicon carbide powder has a particle size of 1-100nm; S2, raw material premixing: Mix the sintered mullite particles, silicon carbide fine powder, active alumina powder, silica powder, composite rare earth oxide powder and aluminum titanate powder in a mixer for 10-20 minutes to obtain a uniform base premix powder; S3, stirring and mixing: Add the porous composite corundum-silicon carbide particles prepared in step S1 to the base premix powder of step S2, stir at low speed for 5-10 minutes to mix them initially, then add the binder and water reducing agent according to the proportion to obtain dry materials, add 5-8% of water based on the total mass of the dry materials, and stir at high speed for 10-15 minutes until the materials are in a uniform plastic state, finally add the explosion-proof fiber and stir at low speed for 3-5 minutes to disperse uniformly, to obtain a casting slurry; S4, casting and curing: Pour the casting slurry obtained in step S3 into a kiln lining mold with pre-installed anchoring elements, compact it on a vibration table, smooth the surface, and then place it under the conditions of a temperature of 15-25℃ and a humidity of 90-97% for 24-48 hours of static curing, then demold to obtain a lining body; S5, drying and heat treatment: Slowly heat the lining body in step S4 to 110-120℃ at a temperature increasing rate of 15-25℃ / h, and keep the temperature for 12-24 h; then sinter under a reducing atmosphere at a rate of 30-50℃ / h to 1350-1450℃, keep the temperature for 3-5 h, and then cool down in the furnace to obtain the castable product.

8. A method for the preparation of corundum-silicon carbide-mullite castable for zinc oxide extraction rotary kiln according to claim 7, characterized in that, The inert atmosphere in S1 is argon atmosphere, and the flow rate is controlled at 5-10 L / min; the reducing atmosphere in S5 is a mixed gas of nitrogen and hydrogen with a volume ratio of 8-9:

1.

9. A method of producing corundum-silicon carbide-mullite castable for zinc oxide refining rotary kiln according to claim 7, characterized in that, The rotating speed of high-speed stirring in S3 is 200-300 rpm, and the rotating speed of low-speed stirring is 80-120 rpm.

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