High-strength nanometer polycrystal gunning material for non-ferrous smelting furnace and preparation method thereof

Abstract

This invention belongs to the field of refractory materials technology, and relates to a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces and its preparation method. The high-strength nano-polycrystalline spraying material comprises the following raw materials in parts by weight: 30-45 parts high-purity fused magnesia, 15-20 parts fused magnesia-chromium sand, 5-7 parts fused chromium corundum, 10-20 parts polycrystalline nano-magnesium oxide, 3-5 parts CA-80 type calcium aluminate cement, 3-5 parts silica sol, 8-15 parts chromium oxide micropowder, and 2-3 parts sodium carboxymethyl cellulose. After spraying onto copper smelting anode furnaces (Kaldor furnaces), the corrosion resistance, thermal shock stability, and service life are improved.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces and its preparation method. The spraying material is particularly effective against easily corroded areas such as the molten pool, furnace door, and furnace opening of crude copper refining furnaces, such as anode furnaces (Kaldor furnaces). Background Technology

[0002] In the field of non-ferrous metal smelting (such as the Kaldor furnace for anode furnaces used in crude copper refining), magnesia-chrome bricks, as the main furnace lining material, have long been used as the refractory lining material for core parts of furnaces such as the molten pool, furnace door, and furnace mouth due to their excellent high-temperature resistance (able to withstand the high temperature of copper liquid at 1100-1350℃) and resistance to copper slag erosion. Their performance directly determines the operational stability and production continuity of the smelting furnace, and they are the core basic components that ensure the efficient advancement of the crude copper refining process. However, during long-term service, magnesia-chrome bricks must withstand the combined effects of multiple harsh working conditions. On the one hand, the high-speed scouring of molten copper at 1100-1350℃ will continuously wear down the surface of the bricks. Components such as iron oxide and silicon dioxide in the slag will also react chemically with the magnesia-chrome bricks to form low-melting-point phases, leading to chemical corrosion of the bricks. On the other hand, the sudden temperature changes caused by the start-up and shutdown of the smelting furnace and copper tapping operations, with temperature differences reaching hundreds of degrees Celsius, can easily generate thermal stress inside the bricks, causing damage such as spalling, cracking, and erosion pits. At the same time, the expansion of molten copper after it penetrates into the pores of the bricks will further exacerbate structural damage. To prevent further damage from causing safety accidents such as kiln leakage and structural failure, the damaged parts need to be repaired in a timely manner. However, such repair work often requires the furnace to be shut down – that is, the current refining process is interrupted, and the furnace temperature is allowed to drop from 1100-1350℃ to a safe operating temperature below 300℃. This process takes 8-16 hours before workers can enter the furnace or carry out repairs using specialized equipment. After the repairs are completed, the temperature needs to be raised back to the required production temperature, which takes another 12-24 hours. The whole process is time-consuming and cannot be carried out simultaneously with production.

[0003] Frequent repairs and shutdowns caused by damage to magnesia-chrome bricks have become a key bottleneck restricting the efficiency of non-ferrous metal smelting, with negative impacts permeating the entire production process: crude copper production per unit time can decrease by 15%-25%, severely reducing production efficiency; during shutdowns, the direct cost of a single repair is generally between 80,000 and 200,000 yuan, significantly increasing production costs; more importantly, frequent hot and cold cycles accelerate the aging of magnesia-chrome bricks and the metal shell of the smelting furnace, shortening the service life of magnesia-chrome bricks from the designed 3-4 months to 2-3 months, advancing the overall maintenance cycle of the furnace, and increasing equipment replacement costs by an average of 25%-40% annually; after each shutdown... Reheating requires a large amount of fuel, with the energy consumption of a single heating cycle equivalent to 2-4 days of normal production. The extra energy consumed annually due to furnace shutdowns for heating accounts for 10%-18% of the company's total energy consumption, exacerbating energy waste and environmental pressure. Frequent furnace shutdowns and heating cycles can lead to instability in the temperature and flow fields inside the smelting furnace. For example, in the process of refining crude copper, furnace temperature fluctuations can cause uneven copper liquid composition and incomplete removal of impurities, ultimately resulting in fluctuations in the grade of anode copper, with purity dropping from 99.5% to below 99.2%. This increases the difficulty and cost of subsequent electrolytic refining processes, significantly reduces the product's market competitiveness, and affects the stability of product quality.

[0004] Spraying, as a common repair method, is widely used for the maintenance of furnace linings in steel ladles, electric furnaces, and converters, achieving good results. In recent years, spraying has also begun to be used in copper smelting and non-ferrous smelting as a way to improve furnace linings. For example, Chinese patent CN101113101A, magnesia-based spraying material for copper smelting, uses magnesia-chrome sand, sintered magnesia, and forsterite as raw materials, and has achieved good results in reverberatory furnaces; however, its use in anode furnaces and Kaldor furnaces is rarely reported. The reasons for this are as follows: Traditional spraying materials have the following technical defects: their apparent porosity is ≥18%, resulting in low density. Molten copper and slag can easily penetrate into the lining through these pores, leading to insufficient corrosion resistance and peeling of the sprayed layer from the substrate. Their service life is typically only 3-5 days. Traditional spraying materials use micron-level fine powder as an additive, which has insufficient activity and cannot effectively refine the grains. This results in uneven thermal expansion coefficients and poor thermal shock stability, making them prone to cracking after 5-8 cycles of 1100℃-room temperature thermal shock. Furthermore, traditional spraying materials lack efficient sintering aids, resulting in slow sintering speeds. Under anode furnace conditions, it takes 8-12 hours to complete sintering and densification, during which time they are easily eroded by the initial high-temperature slag, leading to low repair efficiency.

[0005] Therefore, developing a high-strength spraying material with good corrosion resistance, thermal shock stability, good sintering speed, and long service life to significantly improve the service life of magnesia-chrome brick furnace linings, reduce repair frequency, and achieve hot repair has become an important issue that urgently needs to be addressed in the field of non-ferrous metal smelting, and is also the purpose of this invention. Summary of the Invention

[0006] This invention provides a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces and its preparation method, overcoming the defects of existing spraying materials for copper smelting anode furnaces (Kaldor furnaces) such as poor erosion resistance, insufficient thermal shock stability, and slow sintering.

[0007] A high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces comprises the following raw materials in parts by weight: 30-45 parts high-purity fused magnesia, 15-20 parts fused magnesia-chromium sand, 5-7 parts fused chromium corundum, 10-20 parts polycrystalline nano-magnesia, 3-5 parts CA-80 type calcium aluminate cement, 3-5 parts silica sol, 8-15 parts chromium oxide micro powder, and 2-3 parts sodium carboxymethyl cellulose.

[0008] Furthermore, high-purity fused magnesia has the following main components: MgO ≥ 97%, CaO ≤ 1.0%, SiO2 ≤ 0.8%, Fe2O3 ≤ 0.5%, and loss on ignition ≤ 0.5%; with a particle size of 3-5 mm.

[0009] Furthermore, fused magnesium chromium sand has the following main components: MgO ≥ 65%, Cr2O3 20%-25%, Al2O3 ≤ 3%, Fe2O3 ≤ 2%; particle size 0-3mm.

[0010] Furthermore, the main components of fused chromium corundum are: Cr2O3≥25%, Al2O3≥70%, SiO2≤1.0%, Fe2O3≤0.5%, TiO2≤0.3%, and particle size≤0.074mm.

[0011] Furthermore, the main indicators of polycrystalline nano magnesium oxide are: particle size 10-50nm, specific surface area 80-120m² / g, purity ≥99.5%, impurities Fe2O3≤0.05%, CaO≤0.1%, SiO2≤0.1%, and grain size ≤30nm and grain boundary content 15%-20% in the crystal structure.

[0012] Furthermore, CA-80 type calcium aluminate cement has the following main components: Al2O3 ≥ 80%, CaO ≤ 18%, SiO2 ≤ 0.5%, Fe2O3 ≤ 0.5%, initial setting time ≥ 45 min, final setting time ≤ 120 min; particle size 0.045 mm.

[0013] Furthermore, the silica sol has the following characteristics: main components: SiO2: 25%-30%, Na2O: ≤0.3%, pH value: 8-10, particle size: 10-20nm, density: 1.15-1.20g / cm³. 3 .

[0014] Furthermore, the chromium oxide micro powder has the following main components: Cr2O3 ≥ 98%, Fe2O3 ≤ 0.3%, SiO2 ≤ 0.5%, CaO ≤ 0.2%, and particle size ≤ 0.045 mm.

[0015] Furthermore, sodium carboxymethyl cellulose has the following properties: purity ≥ 99%, viscosity 500-800 mPa·s (2% aqueous solution, 25℃), and moisture content ≤ 10%.

[0016] A method for preparing a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces includes the following steps:

[0017] Step 1: First, put polycrystalline nano magnesium oxide, chromium oxide micro powder, fused chromium corundum, and CA-80 calcium aluminate cement into a double spiral V-shaped mixer and premix for 10-15 minutes to ensure uniform mixing and no obvious agglomeration, thus obtaining a premixed material.

[0018] Step 2: Use a sand mixer to mix the materials. The order of adding materials is as follows: First, add granular materials: high-purity fused magnesia sand 3-5mm and fused magnesia-chromium sand 0-3mm, mix and stir for 5-10 minutes, then add premixed materials and stir for 10-15 minutes; the total mixing time is 15-25 minutes to ensure that the raw materials are mixed evenly and obtain a mixture.

[0019] Step 3: Preparation of spraying slurry: Add silica sol, clean water and sodium carboxymethyl cellulose to the mixture from step 3, stir for 10-15 minutes, control the slurry moisture content to 18%-22% and the viscosity at 25℃ to 500-800 mPa·s, to obtain a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces.

[0020] Nanocrystalline magnesium oxide is a novel high-performance fine inorganic material. It is typically prepared from magnesium chloride, urea, alkyl magnesium chloride, etc., using methods such as chemical precipitation and hydrothermal methods to produce nanoscale magnesium hydroxide powder, which is then calcined at high temperatures. It consists of numerous nanoscale grains connected by grain boundaries, exhibiting characteristics such as small particle size and large specific surface area. It has wide applications in various fields including ceramic materials, catalysts, and electrical insulation materials. Nanometer: a unit of measurement; 1 nanometer = 10⁻⁶ nanometers. -9Nanoscale magnesium oxide, with particle or grain sizes ranging from 1 to 100 nanometers (approximately several to tens of times the diameter of a single atom), possesses properties not found in ordinary magnesium oxide due to its small size, such as high specific surface area and strong adsorption. Polycrystalline: refers to the crystal structure of the material; polycrystalline magnesium oxide is composed of numerous tiny, randomly oriented crystals (called "grains") connected by grain boundaries. The core benefits of polycrystalline nanoscale magnesium oxide in magnesium-chromium materials include enhanced high-temperature stability: it has good compatibility with the main components of magnesium-chromium materials (magnesium oxide and chromium oxide), can fill micro-gaps within the material, improve structural density at high temperatures, and reduce slag erosion. Suppressing chromium volatilization: At high temperatures, magnesium-chromium materials easily generate toxic hexavalent chromium oxides. Nanoscale magnesium oxide can stabilize the valence state of chromium through lattice doping, reducing the volatilization of hexavalent chromium and improving safety in use. Enhanced Corrosion Resistance: The copper molten metal and slag in the anode furnace are highly corrosive. The high purity and high melting point of polycrystalline nano-magnesium oxide enhance the resistance of the sprayed material to copper molten metal and slag, effectively preventing their penetration and corrosion, and extending the service life of the sprayed layer. Optimized Sintering Performance: Polycrystalline nano-magnesium oxide can act as a sintering aid, lowering the sintering temperature of the sprayed material, promoting rapid sintering and densification at lower temperatures, reducing porosity and defects, and improving the density and strength of the sprayed layer. Improved Thermal Shock Resistance: Its nano-sized particles refine the grain structure of the sprayed material, reducing internal stress caused by uneven thermal expansion, making the sprayed layer less prone to cracking and peeling during sudden temperature changes, thus improving thermal shock resistance. Enhanced Adsorption Performance: The surface of polycrystalline nano-magnesium oxide has oxygen and magnesium defects, exhibiting strong chemical adsorption capabilities. It can adsorb harmful gases and impurities in the furnace, purifying the furnace atmosphere and improving the smelting effect of the anode furnace.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0022] 1. High-purity polycrystalline nano-magnesium oxide is selected: This polycrystalline nano-magnesium oxide is prepared by a modified precipitation method. The purity of the polycrystalline nano-magnesium oxide is ≥99.5%, the impurity content is ≤0.25%, and it is free of agglomeration and has high purity. 2. Precise control of raw material composition: High-purity fused magnesia, fused magnesia-chromium sand, and composite binders are used, and the content of key components (such as the upper limit of Fe2O3 and Al2O3 content) is strictly controlled to avoid the negative impact of impurities on the performance of the spraying material. 3. Synergistic effect of anti-erosion components: Chromium corundum (Cr2O3≥25%, Al2O3≥70%) is added, which works synergistically with magnesia-chromium sand and chromium oxide micro powder to ensure that the sprayed layer contains Cr2O3≥10% and Al2O3≥6%, blocking slag penetration. 4. Nano-reinforcement and densification: Polycrystalline nano-magnesium oxide (particle size 10-50nm) is selected to promote low-temperature sintering of the sprayed layer, improve the bulk density (≥2.45g / cm³) and thermal shock stability, and solve the problem of rapid local erosion.

[0023] 2. Significantly improved corrosion resistance: Polycrystalline nano-magnesium oxide promotes densification of the spraying material (apparent porosity ≤12%), and magnesium chromium spinel is evenly distributed, reducing the corrosion rate of copper slag to ≤0.12mm / h, which is more than 50% lower than that of traditional spraying materials (0.25-0.3mm / h).

[0024] 3. Significantly improved thermal shock stability: Polycrystalline magnesium oxide refines the grain size of the spraying material to 20-50μm during use, increases the number of grain boundaries, and at the same time, corundum and magnesium oxide form a spinel thermally stable phase, enabling the spraying material to undergo more than 15 thermal shock cycles from 1100℃ to room temperature (compared to only 5-8 cycles for traditional spraying materials), without cracks or peeling.

[0025] 4. Faster sintering speed: The low-temperature sintering activity is improved, and densification can be completed in 4-6 hours after spraying (traditional spraying materials require 8-12 hours), shortening the downtime for anode furnace repair.

[0026] 5. Extended service life: According to actual use by a certain company, the lining in the furnace mouth area can be used for 10-15 days after each spraying (50mm spraying thickness, while traditional spraying materials can only be used for 3-5 days), increasing the service life of the furnace by about 30-45 heats (about 3 heats per day), increasing output by 4500-6750 tons. The furnace mouth cover can be used for 20 days, greatly improving the service life of the furnace mouth (from 4 months to 7 months), reducing the cost of refractory materials for the maintenance of residual anodes in the anode furnace by 480,000 yuan / year, while strengthening the furnace mouth of the anode furnace, improving the safe operation of the kiln, and increasing the amount of cold copper that can be processed in the anode furnace. Detailed Implementation

[0027] To facilitate understanding of the present invention, the technical solution of the present invention will be fully described below in conjunction with specific embodiments. However, the embodiments described below are only some embodiments of the present invention, not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] A high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces comprises the following raw materials in parts by weight: 30-45 parts high-purity fused magnesia, 15-20 parts fused magnesia-chromium sand, 5-7 parts fused chromium corundum, 10-20 parts polycrystalline nano-magnesia, 3-5 parts CA-80 type calcium aluminate cement, 3-5 parts silica sol, 8-15 parts chromium oxide micro powder, and 2-3 parts sodium carboxymethyl cellulose.

[0029] Furthermore, high-purity fused magnesia has the following main components: MgO ≥ 97%, CaO ≤ 1.0%, SiO2 ≤ 0.8%, Fe2O3 ≤ 0.5%, and loss on ignition ≤ 0.5%; particle size 3-5mm; high purity reduces the impact of impurities on resistance to erosion.

[0030] Furthermore, fused magnesium chromium sand has the following main components: MgO ≥ 65%, Cr2O3 20%-25%, Al2O3 ≤ 3%, Fe2O3 ≤ 2%; particle size 0-3mm; Cr2O3 is introduced to react with MgO to form magnesium chromium spinel MgCr2O4, which enhances the resistance to copper liquid penetration.

[0031] Furthermore, fused chromium corundum has the following main components: Cr2O3 ≥ 25%, Al2O3 ≥ 70%, SiO2 ≤ 1.0%, Fe2O3 ≤ 0.5%, TiO2 ≤ 0.3%, and particle size ≤ 0.074 mm. It utilizes the synergistic effect of the high refractoriness of high Al2O3 and the slag resistance of Cr2O3 to block the chemical dissolution of slag and melt penetration, while resisting the structural loosening caused by the furnace atmosphere.

[0032] Furthermore, the main indicators of polycrystalline nano magnesium oxide are: particle size 10-50nm, specific surface area 80-120m² / g, purity ≥99.5%, impurities Fe2O3≤0.05%, CaO≤0.1%, SiO2≤0.1%, and grain size ≤30nm and grain boundary content 15%-20% in the crystal structure.

[0033] Furthermore, CA-80 type calcium aluminate cement has the following main components: Al2O3 ≥ 80%, CaO ≤ 18%, SiO2 ≤ 0.5%, Fe2O3 ≤ 0.5%, initial setting time ≥ 45 min, final setting time ≤ 120 min; particle size 0.045 mm (excessive CaO can easily generate low-melting-point calcium magnesium olivine).

[0034] Furthermore, the silica sol has the following main components: SiO2: 25%-30%, Na2O: ≤0.3%, pH value 8-10, particle size 10-20nm, density 1.15-1.20g / cm³ (excessive Na2O will reduce corrosion resistance); at high temperatures, it transforms into amorphous SiO2, which reacts with MgO to form forsterite (Mg2SiO4), enhancing the high-temperature bonding strength.

[0035] Furthermore, the chromium oxide micro powder has the following main components: Cr2O3 ≥ 98%, Fe2O3 ≤ 0.3%, SiO2 ≤ 0.5%, CaO ≤ 0.2%, and particle size ≤ 0.045 mm (to ensure uniform dispersion); the addition of Cr2O3 promotes the uniform formation of magnesium chromium spinel and avoids local component segregation.

[0036] Furthermore, sodium carboxymethyl cellulose has the following properties: purity ≥ 99%, viscosity 500-800 mPa·s (2% aqueous solution, 25℃), and moisture content ≤ 10%; it improves slurry flowability and prevents nozzle clogging during spraying.

[0037] A method for preparing a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces includes the following steps:

[0038] Step 1: First, put polycrystalline nano magnesium oxide, chromium oxide micro powder, fused chromium corundum, and CA-80 calcium aluminate cement into a double spiral V-shaped mixer and premix for 10-15 minutes to ensure uniform mixing and no obvious agglomeration, thus obtaining a premixed material.

[0039] Step 2: Use a sand mixer to mix the materials. The order of adding materials is as follows: First, add granular materials: high-purity fused magnesia sand 3-5mm and fused magnesia-chromium sand 0-3mm, mix and stir for 5-10 minutes, then add premixed materials and stir for 10-15 minutes; the total mixing time is 15-25 minutes to ensure that the raw materials are mixed evenly and obtain a mixture.

[0040] Step 3: Preparation of spraying slurry: Add silica sol, clean water and sodium carboxymethyl cellulose to the mixture from step 3, stir for 10-15 minutes, control the slurry moisture content to 18%-22% and the viscosity at 25℃ to 500-800 mPa·s, to obtain a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces.

[0041] The spraying material is used for the lining repair of non-ferrous metal smelting furnaces such as anode furnaces (Kaldor furnaces). It is suitable for easily corroded parts such as molten pools, furnace doors, and furnace openings. After spraying, the sprayed layer meets the comprehensive product indicators after firing at 1500℃: MgO≥60%, Cr2O3≥10%, Al2O3≥6%, bulk density≥2.45g / cm³, and adhesion rate≥95%. It is suitable for furnace temperatures ranging from 1100-1350℃ and can withstand long-term corrosion from molten copper (Cu≥98%, Fe≤1.5%, S≤0.05%) and slag (FeO+SiO2≤35%, CaO≤10%, Al2O3≤5%). It solves the problem of rapid corrosion caused by chemical dissolution, melt penetration, and loose structure due to atmosphere in magnesia-chrome bricks.

[0042] Example 1.

[0043] 44 parts of high-purity fused magnesia (3-5mm, MgO 97.5%), 20 parts of fused magnesia-chromium sand (0-3mm, Cr2O3 22%), 7 parts of fused chromium corundum (0.074mm, Cr2O3 28%, Al2O3 71%), 10 parts of polycrystalline nano-magnesium oxide (10-50nm), 4 parts of CA-80 type calcium aluminate cement (0.045mm), 3 parts of silica sol, 10 parts of chromium oxide micro powder (0.045mm), and 2 parts of sodium carboxymethyl cellulose.

[0044] A method for preparing a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces includes the following steps:

[0045] Step 1: First, put polycrystalline nano magnesium oxide, chromium oxide micro powder, fused chromium corundum, and CA-80 calcium aluminate cement into a double spiral V-shaped mixer and premix for 10 minutes to ensure uniform mixing and no obvious agglomeration, thus obtaining a premixed material.

[0046] Step 2: Use a sand mixer to mix the materials. The order of adding materials is as follows: first add granular materials: high-purity fused magnesia sand 3-5mm, fused magnesia chrome sand 0-3mm, mix for 7 minutes, then add premixed materials and stir for 10 minutes; the total mixing time is 17 minutes, so that the raw materials are mixed evenly to obtain a mixture.

[0047] Step 3: Preparation of spraying slurry: Add silica sol, clean water, and sodium carboxymethyl cellulose to the mixture from Step 3. The amount of clean water is 24% of the total solid mass. Stir for 10 minutes and control the slurry moisture content to 18% and the viscosity at 25℃ to 500 mPa·s to obtain a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces.

[0048] Spraying application: Use a wet spraying machine with a spraying pressure of 0.6-0.8MPa (too low a pressure will result in insufficient spraying, while too high a pressure will result in excessive rebound). Spray the areas to be repaired on the anode furnace and Kaldor furnace, and allow them to cure naturally for 2-4 hours to ensure that the binder is fully hydrated before putting them into use.

[0049] Performance test results: After firing at 1500℃: MgO 67.2%, Cr2O3 15.3%, Al2O3 8.1%, bulk density 2.51g / cm³, adhesion rate 97%; room temperature compressive strength 35MPa, after firing at 1500℃ 45MPa, erosion resistance rate 0.10mm / h, no cracks after 18 thermal shocks, furnace mouth lining service life 10 days, furnace mouth cover service life 20 days.

[0050] Example 2.

[0051] 43 parts of high-purity fused magnesia (3-5mm, MgO 97.2%), 17 parts of fused magnesia-chromium sand (0-3mm, Cr2O3 24%), 5 parts of fused chromium corundum (0.074mm, Cr2O3 25%, Al2O3 73%), 15 parts of polycrystalline nano-magnesium oxide (10-50nm), 5 parts of CA-80 type calcium aluminate cement (0.045mm), 4 parts of silica sol, 8 parts of chromium oxide micro powder (0.045mm), and 3 parts of sodium carboxymethyl cellulose.

[0052] A method for preparing a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces includes the following steps:

[0053] Step 1: First, put polycrystalline nano magnesium oxide, chromium oxide micro powder, fused chromium corundum, and CA-80 calcium aluminate cement into a double spiral V-shaped mixer and premix for 12 minutes to ensure uniform mixing and no obvious agglomeration, thus obtaining a premixed material.

[0054] Step 2: Use a sand mixer to mix the materials. The order of adding materials is as follows: first add granular materials: high-purity fused magnesia sand 3-5mm, fused magnesia chrome sand 0-3mm, mix and stir for 8 minutes, then add premixed materials and stir for 10 minutes; the total mixing time is 18 minutes, so that the raw materials are mixed evenly to obtain a mixture.

[0055] Step 3: Preparation of spraying slurry: Add silica sol, clean water, and sodium carboxymethyl cellulose to the mixture from Step 3. The amount of clean water is 26% of the total solid mass. Stir for 10 minutes, control the slurry moisture content to 20%, and the viscosity at 25℃ to 700 Pa·s to obtain a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces.

[0056] Spraying application: Use a wet spraying machine with a spraying pressure of 0.6-0.8MPa (too low a pressure will result in insufficient spraying, while too high a pressure will result in excessive rebound). Spray the areas to be repaired on the anode furnace and Kaldor furnace, and allow them to cure naturally for 2-4 hours to ensure that the binder is fully hydrated before putting them into use.

[0057] Performance test results: After firing at 1500℃: MgO 70.1%, Cr2O3 13.4%, Al2O3 7.1%, bulk density 2.48g / cm³, adhesion rate 96%; room temperature compressive strength 42MPa, after firing at 1500℃ 55MPa, erosion resistance rate 0.12mm / h, no cracks after 16 thermal shocks, furnace mouth lining service life 12 days, furnace mouth cover service life 21 days.

[0058] Example 3.

[0059] 30 parts of high-purity fused magnesia (3-5mm, MgO 97.8%), 18 parts of fused magnesia-chromium sand (0-3mm, Cr2O3 20%), 7 parts of fused chromium corundum (0.045mm, Cr2O3 30%, Al2O3 70%), 20 parts of polycrystalline nano-magnesium oxide (10-50nm), 3 parts of CA-80 type calcium aluminate cement, 5 parts of silica sol, 15 parts of chromium oxide micro powder (0.045mm), and 2 parts of sodium carboxymethyl cellulose.

[0060] A method for preparing a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces includes the following steps:

[0061] Step 1: First, put polycrystalline nano magnesium oxide, chromium oxide micro powder, fused chromium corundum, and CA-80 calcium aluminate cement into a double spiral V-shaped mixer and premix for 15 minutes to ensure uniform mixing and no obvious agglomeration, thus obtaining a premixed material.

[0062] Step 2: Use a sand mixer to mix the materials. The order of adding materials is as follows: first add granular materials: high-purity fused magnesia sand 3-5mm, fused magnesia-chromium sand 0-3mm, mix and stir for 10 minutes, then add premixed materials and stir for 10 minutes; the total mixing time is 20 minutes to ensure that the raw materials are mixed evenly and obtain a mixture.

[0063] Step 3: Preparation of spraying slurry: Add silica sol, clean water, and sodium carboxymethyl cellulose to the mixture from Step 3. The amount of clean water is 22% of the total solid mass. Stir for 10 minutes and control the slurry moisture content to 22% and the viscosity at 25℃ to 800 mPa·s to obtain a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces.

[0064] Spraying application: Use a wet spraying machine with a spraying pressure of 0.6-0.8MPa (too low a pressure will result in insufficient spraying, while too high a pressure will result in excessive rebound). Spray the areas to be repaired on the anode furnace and Kaldor furnace, and allow them to cure naturally for 2-4 hours to ensure that the binder is fully hydrated before putting them into use.

[0065] Performance test results: After firing at 1500℃: MgO 62.3%, Cr2O3 20.7%, Al2O3 7.3%, bulk density 2.53g / cm³, adhesion rate 98%; room temperature compressive strength 52MPa, after firing at 1500℃ 70MPa, erosion resistance rate 0.09mm / h, no cracks after 20 thermal shocks, furnace mouth lining service life 15 days, furnace mouth cover service life 23 days.

[0066] Comparative Example 1.

[0067] The mixture consisted of 63 parts high-purity fused magnesia (0-5mm, MgO 97%), 20 parts fused magnesia-chromium sand (0.074mm, Cr2O3 20%), 5 parts lightly calcined magnesia powder (MgO 90%, 320 mesh), 6 parts CA-80 type calcium aluminate cement (0.045mm), 2 parts silica sol, 3 parts chromium oxide micro powder (0.045mm), and 1 part sodium carboxymethyl cellulose; the added water was ordinary tap water (pH 6.8), used at 20% of the total solid mass. The spraying material was prepared using traditional methods and sprayed onto the areas to be repaired in the anode furnace and Kaldor furnace.

[0068] Performance test results: After firing at 1500℃: MgO 79.6%, Cr2O 37.5%, Al2O 35.7%, bulk density 2.28g / cm³, adhesion rate 89%; room temperature compressive strength 25MPa, erosion resistance rate 0.28mm / h, cracks formed after 7 thermal shocks, furnace mouth lining service life 5 days, furnace mouth cover service life 10 days.

[0069] As can be seen from the comparison, the spraying material of the present invention, by introducing polycrystalline nano-magnesium oxide, achieves a significant improvement in comprehensive properties such as compressive strength, erosion resistance, thermal shock stability, density, and sinterability, and its service life far exceeds that of traditional spraying materials. This creates favorable conditions for improving production efficiency and reducing smelting costs in non-ferrous smelting furnaces such as anode furnaces.

[0070] The scope of protection for this invention relates to the application of functional polycrystalline nano-magnesium oxide materials (which may be polycrystalline nano-magnesium oxide synthesized by different methods), and the manufacturing process of high-strength polycrystalline nano-spraying materials. The variation in the amount of polycrystalline nano-magnesium oxide added is merely a simple operation by a technician and is essentially still a selection and application of the protected functional material; therefore, it remains within the scope of protection of this patent.

Claims

1. A high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces, characterized in that, The raw materials include the following parts by weight: 30-45 parts high-purity fused magnesia, 15-20 parts fused magnesia-chromium sand, 5-7 parts fused chromium corundum, 10-20 parts polycrystalline nano magnesium oxide, 3-5 parts CA-80 type calcium aluminate cement, 3-5 parts silica sol, 8-15 parts chromium oxide micro powder, and 2-3 parts sodium carboxymethyl cellulose.

2. The high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces according to claim 1, characterized in that, The high-purity fused magnesia has the following main components: MgO ≥ 97%, CaO ≤ 1.0%, SiO2 ≤ 0.8%, Fe2O3 ≤ 0.5%, and loss on ignition ≤ 0.5%; with a particle size of 3-5 mm.

3. The high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces according to claim 1, characterized in that, The fused magnesium chromium sand has the following main components: MgO≥65%, Cr2O320%-25%, Al2O3≤3%, Fe2O3≤2%; and a particle size of 0-3mm.

4. The high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces according to claim 1, characterized in that, The fused chromium corundum has the following main components: Cr2O3 ≥ 25%, Al2O3 ≥ 70%, SiO2 ≤ 1.0%, Fe2O3 ≤ 0.5%, TiO2 ≤ 0.3%, and particle size ≤ 0.074 mm.

5. The high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces according to claim 1, characterized in that, The polycrystalline nano-magnesium oxide has the following main indicators: particle size 10-50nm, specific surface area 80-120m² / g, purity ≥99.5%, impurities Fe2O3≤0.05%, CaO≤0.1%, SiO2≤0.1%, and grain size ≤30nm with a grain boundary content of 15%-20%.

6. The high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces according to claim 1, characterized in that, The CA-80 type calcium aluminate cement has the following main components: Al2O3 ≥ 80%, CaO ≤ 18%, SiO2 ≤ 0.5%, Fe2O3 ≤ 0.5%, initial setting time ≥ 45 min, final setting time ≤ 120 min, and particle size 0.045 mm.

7. The high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces according to claim 1, characterized in that, The chromium oxide micro powder has the following main components: Cr2O3 ≥ 98%, Fe2O3 ≤ 0.3%, SiO2 ≤ 0.5%, CaO ≤ 0.2%, and particle size ≤ 0.045 mm.

8. A method for preparing a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces, characterized in that, Includes the following steps: Step 1: First, premix polycrystalline nano magnesium oxide, chromium oxide micro powder, fused chromium corundum, and CA-80 calcium aluminate cement to obtain a premixed material; Step 2: Use a sand mixer to mix the materials. The order of adding materials is as follows: first add granular materials: high-purity fused magnesia and fused magnesia-chromium sand, mix and stir, then add premixed materials and stir to obtain a mixture. Step 3: Preparation of spraying slurry: Add silica sol, clean water and sodium carboxymethyl cellulose to the mixture from step 3, mix and stir, control the moisture content and viscosity of the slurry, and obtain a high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces.

9. The method for preparing high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces according to claim 8, characterized in that, The mixing time in step 1 or step 3 is 10-15 minutes.

10. The method for preparing high-strength nano-polycrystalline spraying material for non-ferrous metal smelting furnaces according to claim 8, characterized in that, In step 3, the slurry has a moisture content of 18%-22% and a viscosity of 500-800 mPa·s at 25℃.