Method for producing high impermeability phosphate bonded silicon carbide refractory bricks

Abstract

The present application relates to the technical field of refractory materials, in particular to a preparation method of high anti-permeability phosphate bonded silicon carbide refractory brick. The raw materials of the preparation method include high bauxite clinker, silicon carbide aggregate, zirconia micropowder, graphene, aluminum dihydrogen phosphate solution, magnesium-aluminum complex powder, clay and silicon dioxide micropowder. The preparation steps are as follows: after the silicon carbide aggregate is dried after removing iron by hydrochloric acid, the aggregate is co-milled with the pre-dried high bauxite clinker, zirconia micropowder and graphene to obtain powder A; after the aggregate is wet-milled with part of the aluminum dihydrogen phosphate solution and water, powder A, clay and silicon dioxide micropowder are added for further mixing and milling, and the remaining aluminum dihydrogen phosphate and magnesium-aluminum complex are added to obtain plastic mud; the mud is formed by high-pressure molding, dried in two stages, and fired at gradient temperature in a weak reducing atmosphere. The method significantly improves the anti-permeability of the refractory brick, and realizes the microporization of the pores of the refractory brick and the high anti-permeability effect through the synergistic effect of composite bonding phase, gradient firing and physical barrier.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, and in particular to a method for preparing highly impermeable phosphate-bonded silicon carbide refractory bricks. Background Technology

[0002] In the fields of high-temperature metallurgy, chemical engineering, and energy conversion, refractory bricks, as the core lining material for smelting vessels, reaction towers, and transmission channels, directly determine the service life of equipment and production safety due to their ability to resist the permeation of liquid metals, molten slag, and high-temperature gaseous media. However, under the current technological system, the impermeability of refractory bricks still has significant shortcomings, making it difficult to meet the industrial demands of multi-media, high-temperature, and long-cycle processes. Specific problems manifest in the following scenarios:

[0003] In the aluminum electrolysis industry, the lining of the aluminum melting furnace needs to be in constant contact with liquid aluminum at temperatures above 1200°C. Traditional aluminum-resistant refractory bricks (such as CN115594491A) use magnesium-aluminum complex binders and boron nitride to improve impermeability, reducing the penetration depth of molten aluminum to 0-1mm. However, their requirements for raw material purity (Al2O3 ≥ 99%) and a 24-hour low-temperature treatment process increase production costs by 40%. Furthermore, they are only optimized for a single medium like molten aluminum and are insufficient to cope with the combined erosion from slag or corrosive gases.

[0004] Iron and steel metallurgy: Equipment such as blast furnaces and ladles need to withstand the scouring of molten iron at temperatures above 1400℃ and the erosion of slag. Ordinary phosphate-bonded high-alumina bricks (such as CN101544504A) have unoptimized anti-permeability structures, resulting in an apparent porosity generally >18%. Oxides such as FeO and MnO in the molten iron can easily penetrate into the brick body through interconnected pores, reacting with Al2O3 to form low-melting-point phases. This leads to an erosion rate of up to 5mm / year at the slag line, shortening the average service life of the equipment by 40% compared to the design.

[0005] Chemical and Calcination Equipment: In chemical reactors, coal gasification furnaces, and cement rotary kilns, refractory bricks need to resist the combined erosion of molten slag, alkali metals, and high-temperature gases. Although graphene-containing corrosion-resistant bricks improve slag resistance through a corundum-zirconia system, the interfacial bonding between silicon carbide aggregate and graphene is weak, and at high temperatures, the difference in thermal expansion coefficients (SiC: 4.5 × 10⁻⁶) leads to corrosion problems. -6 / ℃; Graphene: -3.0×10 -6 / ℃) is prone to micro-cracks, and corrosive gases can seep in through the cracks, causing the internal structure to pulverize. Traditional fire channel wall bricks are not designed with anti-seepage structures, and molten materials seep into the brick joints, causing the fire channel wall to deform.

[0006] The above problems can be summarized into three major technical contradictions: First, the single anti-permeability method, which only targets the aluminum liquid and is difficult to deal with the multi-media composite erosion of aluminum liquid, slag and gas; Second, the interface mismatch of functional materials, such as the difference in thermal expansion coefficients between graphene and silicon carbide leading to the formation of microcracks, sacrificing anti-permeability in exchange for other properties; Third, the conflict between process and cost, such as the fact that although low temperature treatment reduces energy consumption, the requirement for raw material purity leads to high costs, which limits large-scale application.

[0007] As metallurgical processes become more high-temperature and large-scale, developing a new type of refractory brick technology that combines multi-media impermeability has become a key bottleneck in the green transformation of high-temperature industries. Summary of the Invention

[0008] Based on the problems existing in the above-mentioned background technology, the present invention proposes a method for preparing highly impermeable phosphate-bonded silicon carbide refractory bricks, the steps of which are as follows.

[0009] Step 1: By weight, the following raw materials are included: 50-65 parts high-alumina bauxite clinker, 15-25 parts silicon carbide aggregate, 5-10 parts zirconium oxide micro powder, 2-5 parts graphene, 4-8 parts aluminum dihydrogen phosphate solution, 1-3 parts magnesium aluminum complex powder, 5-8 parts clay and 3-6 parts silica micro powder.

[0010] Step 2: Soak silicon carbide aggregate in 10% hydrochloric acid for 2 hours to dissolve metallic iron impurities, wash with water until neutral, and dry at 110°C for 4 hours to eliminate the risk of hydrolysis; dry high-alumina bauxite clinker, zirconium oxide micro powder and graphene at 110°C for 4 hours respectively, and then put them into a ball mill for dry mixing for 30 minutes to obtain co-milled powder A.

[0011] Step 3: Pour the silicon carbide aggregate soaked and de-ironized in Step 2 into a mixing mill, add 70% of the total amount of aluminum dihydrogen phosphate solution and deionized water and wet-mill for 15 minutes, then add co-milling powder A, clay and silica powder, and continue mixing for 10 minutes; finally, add the remaining 30% aluminum dihydrogen phosphate solution and magnesium aluminum complex powder and mix to obtain mud.

[0012] Step 4: Press the mud obtained in Step 3 into brick blanks in a press, and dry the brick blanks in sections;

[0013] Step 5: Firing refractory bricks under a weak reducing atmosphere according to the following procedure: in the first stage, the temperature is increased to 600℃ at 3℃ / min and held for 4 hours; in the second stage, the temperature is increased to 1200-1250℃ at 2℃ / min and held for 5 hours; in the third stage, the brick blanks are naturally cooled to room temperature.

[0014] Preferably, in step 1, the high-alumina bauxite clinker contains ≥85% Al2O3 and ≤1.2% Fe2O3 by mass; the silicon carbide aggregate contains ≥98% SiC by mass; the zirconia micropowder contains ≥95% ZrO2 by mass; the graphene sheet diameter is 1–5 μm; and the density of the aluminum dihydrogen phosphate solution is 1.46–1.48 g / cm³. 3 The MgO / Al2O3 molar ratio in the magnesium-aluminum complex powder is 1:2, and the SiO2 mass percentage in the silica micro powder is ≥97%.

[0015] Preferably, the zirconium oxide micro powder d 50 =1~3μm, the particle size of the clay is ≤0.088mm, and the silica micro powder is d 90 <3μm.

[0016] Preferably, in step 2, the moisture content of the co-milled powder A is <0.5% to prevent the subsequent binder from failing and to avoid the formation of pores due to residual moisture during subsequent mixing.

[0017] Preferably, in step 3, the water-to-material ratio of the deionized water to the silicon carbide aggregate is 0.05:1, and the plasticity index of the clay is 18-22.

[0018] Preferably, in step 4, the clay is molded under a pressure of 120 MPa and held under pressure for 60 seconds.

[0019] Preferably, in step 4, the segmented drying of the shaped brick blank is carried out according to the following steps: in the first stage, the brick blank is dried at a temperature of 50°C for 24 hours; in the second stage, the temperature is increased to 110°C at a rate of 2°C / min and then kept at that temperature for 12 hours to completely remove the bound water and make the moisture content <1%, thereby avoiding drying cracks and providing a uniform moisture distribution for subsequent firing.

[0020] Preferably, in step 5, the weak reducing atmosphere is CO, and the CO concentration is 2% to 4% to suppress silicon carbide oxidation.

[0021] Compared with existing technologies, this invention achieves a breakthrough improvement in the impermeability of refractory bricks through the synergistic effect of raw material optimization, binder innovation, and process innovation, while reducing production costs. Specifically, this is reflected in the following aspects:

[0022] 1) High-purity silicon carbide (SiC≥98%) is used to form a physical barrier substrate by utilizing the high thermal stability of silicon carbide. The substrate is filled with micropores at high temperature. The two work together to build a double barrier, which can significantly reduce the combined erosion rate of aluminum liquid, slag and corrosive gases, and significantly extend the service life of equipment.

[0023] 2) A composite bonding system of aluminum dihydrogen phosphate-magnesium aluminum complex was developed, which achieves rapid molding through low-temperature curing and generates a stable phosphotungsten-type AlPO4 phase during high-temperature firing, balancing energy saving in low-temperature processing with structural strength in high-temperature conditions. Compared with traditional barium sulfate binders, the decomposition temperature of the bonding phase in this invention is increased by 200℃, ensuring stable impermeability under high-temperature conditions.

[0024] 3) Under a weak reducing atmosphere, a segmented process combining 600℃ pretreatment and 1200-1250℃ firing ensures uniform grain growth and the formation of the densest packing. Testing revealed that the product's apparent porosity was reduced to below 12%, pore size decreased to submicron levels, and penetration depth was significantly improved.

[0025] This invention achieves a 15% reduction in production costs while improving impermeability by over 30%, through systematic optimization of materials, processes, and structures. It is suitable for high-temperature impermeability requirements in various scenarios such as aluminum electrolysis cells and blast furnaces, providing key technical support for extending the lifespan and saving energy in high-temperature industrial equipment. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] The preparation method of high-permeability phosphate-bonded silicon carbide refractory bricks includes the following steps.

[0029] Step 1: By weight, the following raw materials are included: 57 parts high-alumina bauxite clinker, 20 parts silicon carbide aggregate, 6 parts zirconia micro powder, 3 parts graphene, 5 parts aluminum dihydrogen phosphate solution, 1 part magnesium aluminum complex powder, 5 parts clay and 3 parts silica micro powder.

[0030] Step 2: Soak silicon carbide aggregate in 10% hydrochloric acid for 2 hours to remove iron, wash with water until neutral, and dry at 110℃ for 4 hours; dry high-alumina bauxite clinker, zirconia micro powder and graphene at 110℃ for 4 hours respectively, and then put them into a ball mill for dry mixing for 30 minutes to obtain co-milled powder A.

[0031] Step 3: Pour the silicon carbide aggregate soaked and de-ironized in Step 2 into a mixing mill, add 70% of the total amount of aluminum dihydrogen phosphate solution and deionized water (the water-to-silicon carbide aggregate water ratio is 0.05:1), and wet-mill for 15 minutes. Then add co-milling powder A, clay, and silica powder, and continue mixing for 10 minutes. Finally, add the remaining 30% aluminum dihydrogen phosphate solution and magnesium-aluminum complex powder, and mix to obtain mud with a plasticity index of 20.

[0032] Step 4: Press the mud obtained in Step 3 into a mold at a pressure of 120MPa in a press and hold the pressure for 60s to form a brick blank; dry the formed brick blank in sections according to the following steps: the first stage is to dry at a temperature of 50℃ for 24 hours, and the second stage is to heat up to 110℃ at a rate of 2℃ / min and then hold the temperature for 12 hours.

[0033] Step 5: Under a weakly reducing CO atmosphere with a CO concentration of 2%, fire the refractory bricks according to the following procedure: in the first stage, heat the bricks at 3℃ / min to 600℃ and hold for 4 hours; in the second stage, heat the bricks at 2℃ / min to 1200-1250℃ and hold for 5 hours; in the third stage, allow the brick blanks to cool naturally to room temperature.

[0034] Example 2

[0035] The preparation method of high-permeability phosphate-bonded silicon carbide refractory bricks includes the following steps.

[0036] Step 1: By weight, the following raw materials are included: 50 parts high-alumina bauxite clinker, 15 parts silicon carbide aggregate, 9 parts zirconia micro powder, 5 parts graphene, 7 parts aluminum dihydrogen phosphate solution, 2 parts magnesium aluminum complex powder, 6 parts clay and 6 parts silica micro powder.

[0037] Step 2: Soak silicon carbide aggregate in 10% hydrochloric acid for 2 hours to remove iron, wash with water until neutral, and dry at 110℃ for 4 hours; dry high-alumina bauxite clinker, zirconia micro powder and graphene at 110℃ for 4 hours respectively, and then put them into a ball mill for dry mixing for 30 minutes to obtain co-milled powder A.

[0038] Step 3: Pour the silicon carbide aggregate soaked and de-ironized in Step 2 into a mixing mill, add 70% of the total amount of aluminum dihydrogen phosphate solution and deionized water (the water-to-silicon carbide aggregate water ratio is 0.05:1), and wet-mill for 15 minutes. Then add co-milling powder A, clay, and silica powder, and continue mixing for 10 minutes. Finally, add the remaining 30% aluminum dihydrogen phosphate solution and magnesium-aluminum complex powder, and mix to obtain mud with a plasticity index of 18.

[0039] Step 4: Press the mud obtained in Step 3 into a mold at a pressure of 120MPa in a press and hold the pressure for 60s to form a brick blank; dry the formed brick blank in sections according to the following steps: the first stage is to dry at a temperature of 50℃ for 24 hours, and the second stage is to heat up to 110℃ at a rate of 2℃ / min and then hold the temperature for 12 hours.

[0040] Step 5: Under a weakly reducing CO atmosphere with a CO concentration of 3%, fire the refractory bricks according to the following procedure: in the first stage, heat the bricks at 3℃ / min to 600℃ and hold for 4 hours; in the second stage, heat the bricks at 2℃ / min to 1200-1250℃ and hold for 5 hours; in the third stage, allow the brick blanks to cool naturally to room temperature.

[0041] Example 3

[0042] The preparation method of high-permeability phosphate-bonded silicon carbide refractory bricks includes the following steps.

[0043] Step 1: By weight, the following raw materials are included: 65 parts high-alumina bauxite clinker, 15 parts silicon carbide aggregate, 5 parts zirconium oxide micro powder, 2 parts graphene, 4 parts aluminum dihydrogen phosphate solution, 1 part magnesium aluminum complex powder, 5 parts clay and 3 parts silica micro powder.

[0044] Step 2: Soak silicon carbide aggregate in 10% hydrochloric acid for 2 hours to remove iron, wash with water until neutral, and dry at 110℃ for 4 hours; dry high-alumina bauxite clinker, zirconia micro powder and graphene at 110℃ for 4 hours respectively, and then put them into a ball mill for dry mixing for 30 minutes to obtain co-milled powder A.

[0045] Step 3: Pour the silicon carbide aggregate soaked and de-ironized in Step 2 into a mixing mill, add 70% of the total amount of aluminum dihydrogen phosphate solution and deionized water (the water-to-silicon carbide aggregate ratio is 0.05:1), and wet-mill for 15 minutes. Then add co-milling powder A, clay, and silica powder, and continue mixing for 10 minutes. Finally, add the remaining 30% aluminum dihydrogen phosphate solution and magnesium-aluminum complex powder, and mix to obtain mud with a plasticity index of 22.

[0046] Step 4: Press the mud obtained in Step 3 into a mold at a pressure of 120MPa in a press and hold the pressure for 60s to form a brick blank; dry the formed brick blank in sections according to the following steps: the first stage is to dry at a temperature of 50℃ for 24 hours, and the second stage is to heat up to 110℃ at a rate of 2℃ / min and then hold the temperature for 12 hours.

[0047] Step 5: Under a weakly reducing CO atmosphere with a CO concentration of 4%, fire the refractory bricks according to the following procedure: in the first stage, heat the bricks at 3℃ / min to 600℃ and hold for 4 hours; in the second stage, heat the bricks at 2℃ / min to 1200-1250℃ and hold for 5 hours; in the third stage, allow the brick blanks to cool naturally to room temperature.

[0048] Example 4

[0049] The preparation method of high-permeability phosphate-bonded silicon carbide refractory bricks includes the following steps.

[0050] Step 1: By weight, the following raw materials are included: 50 parts high-alumina bauxite clinker, 25 parts silicon carbide aggregate, 5 parts zirconia micro powder, 2 parts graphene, 5 parts aluminum dihydrogen phosphate solution, 3 parts magnesium aluminum complex powder, 7 parts clay and 3 parts silica micro powder.

[0051] Step 2: Soak silicon carbide aggregate in 10% hydrochloric acid for 2 hours to remove iron, wash with water until neutral, and dry at 110℃ for 4 hours; dry high-alumina bauxite clinker, zirconia micro powder and graphene at 110℃ for 4 hours respectively, and then put them into a ball mill for dry mixing for 30 minutes to obtain co-milled powder A.

[0052] Step 3: Pour the silicon carbide aggregate soaked and de-ironized in Step 2 into a mixing mill, add 70% of the total amount of aluminum dihydrogen phosphate solution and deionized water (the water-to-silicon carbide aggregate ratio is 0.05:1), and wet-mill for 15 minutes. Then add co-milling powder A, clay, and silica powder, and continue mixing for 10 minutes. Finally, add the remaining 30% aluminum dihydrogen phosphate solution and magnesium-aluminum complex powder, and mix to obtain mud with a plasticity index of 19.

[0053] Step 4: Press the mud obtained in Step 3 into a mold at a pressure of 120MPa in a press and hold the pressure for 60s to form a brick blank; dry the formed brick blank in sections according to the following steps: the first stage is to dry at a temperature of 50℃ for 24 hours, and the second stage is to heat up to 110℃ at a rate of 2℃ / min and then hold the temperature for 12 hours.

[0054] Step 5: Under a weakly reducing CO atmosphere with a CO concentration of 3%, fire the refractory bricks according to the following procedure: in the first stage, heat the bricks at 3℃ / min to 600℃ and hold for 4 hours; in the second stage, heat the bricks at 2℃ / min to 1200-1250℃ and hold for 5 hours; in the third stage, allow the brick blanks to cool naturally to room temperature.

[0055] Example 5

[0056] The preparation method of high-permeability phosphate-bonded silicon carbide refractory bricks includes the following steps.

[0057] Step 1: By weight, the following raw materials are included: 51 parts high-alumina bauxite clinker, 15 parts silicon carbide aggregate, 6 parts zirconium oxide micro powder, 5 parts graphene, 8 parts aluminum dihydrogen phosphate solution, 3 parts magnesium aluminum complex powder, 8 parts clay and 4 parts silica micro powder.

[0058] Step 2: Soak silicon carbide aggregate in 10% hydrochloric acid for 2 hours to remove iron, wash with water until neutral, and dry at 110℃ for 4 hours; dry high-alumina bauxite clinker, zirconia micro powder and graphene at 110℃ for 4 hours respectively, and then put them into a ball mill for dry mixing for 30 minutes to obtain co-milled powder A.

[0059] Step 3: Pour the silicon carbide aggregate soaked and de-ironized in Step 2 into a mixing mill, add 70% of the total amount of aluminum dihydrogen phosphate solution and deionized water (the water-to-silicon carbide aggregate water ratio is 0.05:1), and wet-mill for 15 minutes. Then add co-milling powder A, clay, and silica powder, and continue mixing for 10 minutes. Finally, add the remaining 30% aluminum dihydrogen phosphate solution and magnesium-aluminum complex powder, and mix to obtain mud with a plasticity index of 20.

[0060] Step 4: Press the mud obtained in Step 3 into a mold at a pressure of 120MPa in a press and hold the pressure for 60s to form a brick blank; dry the formed brick blank in sections according to the following steps: the first stage is to dry at a temperature of 50℃ for 24 hours, and the second stage is to heat up to 110℃ at a rate of 2℃ / min and then hold the temperature for 12 hours.

[0061] Step 5: Under a weakly reducing CO atmosphere with a CO concentration of 2%, fire the refractory bricks according to the following procedure: in the first stage, heat the bricks at 3℃ / min to 600℃ and hold for 4 hours; in the second stage, heat the bricks at 2℃ / min to 1200-1250℃ and hold for 5 hours; in the third stage, allow the brick blanks to cool naturally to room temperature.

[0062] Example 6

[0063] The preparation method of high-permeability phosphate-bonded silicon carbide refractory bricks includes the following steps.

[0064] Step 1: By weight, the following raw materials are included: 55 parts high-alumina bauxite clinker, 20 parts silicon carbide aggregate, 10 parts zirconia micro powder, 2 parts graphene, 4 parts aluminum dihydrogen phosphate solution, 1 part magnesium aluminum complex powder, 5 parts clay and 3 parts silica micro powder.

[0065] Step 2: Soak silicon carbide aggregate in 10% hydrochloric acid for 2 hours to remove iron, wash with water until neutral, and dry at 110℃ for 4 hours; dry high-alumina bauxite clinker, zirconia micro powder and graphene at 110℃ for 4 hours respectively, and then put them into a ball mill for dry mixing for 30 minutes to obtain co-milled powder A.

[0066] Step 3: Pour the silicon carbide aggregate soaked and de-ironized in Step 2 into a mixing mill, add 70% of the total amount of aluminum dihydrogen phosphate solution and deionized water (the water-to-silicon carbide aggregate ratio is 0.05:1), and wet-mill for 15 minutes. Then add co-milling powder A, clay, and silica powder, and continue mixing for 10 minutes. Finally, add the remaining 30% aluminum dihydrogen phosphate solution and magnesium-aluminum complex powder, and mix to obtain mud with a plasticity index of 21.

[0067] Step 4: Press the mud obtained in Step 3 into a mold at a pressure of 120MPa in a press and hold the pressure for 60s to form a brick blank; dry the formed brick blank in sections according to the following steps: the first stage is to dry at a temperature of 50℃ for 24 hours, and the second stage is to heat up to 110℃ at a rate of 2℃ / min and then hold the temperature for 12 hours.

[0068] Step 5: Under a weakly reducing CO atmosphere with a CO concentration of 3%, fire the refractory bricks according to the following procedure: in the first stage, heat the bricks at 3℃ / min to 600℃ and hold for 4 hours; in the second stage, heat the bricks at 2℃ / min to 1200-1250℃ and hold for 5 hours; in the third stage, allow the brick blanks to cool naturally to room temperature.

[0069] Example 7

[0070] The preparation method of high-permeability phosphate-bonded silicon carbide refractory bricks includes the following steps.

[0071] Step 1: By weight, the following raw materials are included: 60 parts high-alumina bauxite clinker, 16 parts silicon carbide aggregate, 7 parts zirconium oxide micro powder, 2 parts graphene, 4 parts aluminum dihydrogen phosphate solution, 1 part magnesium aluminum complex powder, 5 parts clay and 5 parts silica micro powder.

[0072] Step 2: Soak silicon carbide aggregate in 10% hydrochloric acid for 2 hours to remove iron, wash with water until neutral, and dry at 110℃ for 4 hours; dry high-alumina bauxite clinker, zirconia micro powder and graphene at 110℃ for 4 hours respectively, and then put them into a ball mill for dry mixing for 30 minutes to obtain co-milled powder A.

[0073] Step 3: Pour the silicon carbide aggregate soaked and de-ironized in Step 2 into a mixing mill, add 70% of the total amount of aluminum dihydrogen phosphate solution and deionized water (the water-to-silicon carbide aggregate water ratio is 0.05:1), and wet-mill for 15 minutes. Then add co-milling powder A, clay, and silica powder, and continue mixing for 10 minutes. Finally, add the remaining 30% aluminum dihydrogen phosphate solution and magnesium-aluminum complex powder, and mix to obtain mud with a plasticity index of 20.

[0074] Step 4: Press the mud obtained in Step 3 into a mold at a pressure of 120MPa in a press and hold the pressure for 60s to form a brick blank; dry the formed brick blank in sections according to the following steps: the first stage is to dry at a temperature of 50℃ for 24 hours, and the second stage is to heat up to 110℃ at a rate of 2℃ / min and then hold the temperature for 12 hours.

[0075] Step 5: Under a weakly reducing CO atmosphere with a CO concentration of 2%, fire the refractory bricks according to the following procedure: in the first stage, heat the bricks at 3℃ / min to 600℃ and hold for 4 hours; in the second stage, heat the bricks at 2℃ / min to 1200-1250℃ and hold for 5 hours; in the third stage, allow the brick blanks to cool naturally to room temperature.

[0076] Example 8

[0077] The preparation method of high-permeability phosphate-bonded silicon carbide refractory bricks includes the following steps.

[0078] Step 1: By weight, the following raw materials are included: 53 parts high-alumina bauxite clinker, 18 parts silicon carbide aggregate, 7 parts zirconium oxide micro powder, 3 parts graphene, 5 parts aluminum dihydrogen phosphate solution, 2 parts magnesium aluminum complex powder, 6 parts clay and 6 parts silica micro powder.

[0079] Step 2: Soak silicon carbide aggregate in 10% hydrochloric acid for 2 hours to remove iron, wash with water until neutral, and dry at 110℃ for 4 hours; dry high-alumina bauxite clinker, zirconia micro powder and graphene at 110℃ for 4 hours respectively, and then put them into a ball mill for dry mixing for 30 minutes to obtain co-milled powder A.

[0080] Step 3: Pour the silicon carbide aggregate soaked and de-ironized in Step 2 into a mixing mill, add 70% of the total amount of aluminum dihydrogen phosphate solution and deionized water (the water-to-silicon carbide aggregate water ratio is 0.05:1), and wet-mill for 15 minutes. Then add co-milling powder A, clay, and silica powder, and continue mixing for 10 minutes. Finally, add the remaining 30% aluminum dihydrogen phosphate solution and magnesium-aluminum complex powder, and mix to obtain mud with a plasticity index of 20.

[0081] Step 4: Press the mud obtained in Step 3 into a mold at a pressure of 120MPa in a press and hold the pressure for 60s to form a brick blank; dry the formed brick blank in sections according to the following steps: the first stage is to dry at a temperature of 50℃ for 24 hours, and the second stage is to heat up to 110℃ at a rate of 2℃ / min and then hold the temperature for 12 hours.

[0082] Step 5: Under a weakly reducing CO atmosphere with a CO concentration of 4%, fire the refractory bricks according to the following procedure: in the first stage, heat the bricks at 3℃ / min to 600℃ and hold for 4 hours; in the second stage, heat the bricks at 2℃ / min to 1200-1250℃ and hold for 5 hours; in the third stage, allow the brick blanks to cool naturally to room temperature.

[0083] Examples 1-8 above were tested for their resistance to aluminum melt penetration according to industry standard YB / T 4577-2016. The test results are shown in the table below:

[0084]

[0085] As can be seen from the table, the preparation method of this invention takes low-cost high-alumina bauxite clinker (Al2O3≥85%) as the core, and achieves microstructural densification and blockage of permeation channels through graphene-modified bonding phase and gradient sintering process. The aluminum dihydrogen phosphate-magnesium aluminum complex composite system significantly enhances the matrix bonding strength at high temperature. The surface of silicon carbide aggregate is acid-washed to remove iron, and the surface is toughened by zirconia micro powder and a physical barrier layer is constructed to achieve excellent triple barrier properties of aluminum liquid / slag / corrosive gas. This provides key technical support for the longevity and cost reduction of high-temperature equipment such as aluminum electrolytic cells and blast furnaces.

[0086] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a high impermeability phosphate bonded silicon carbide refractory brick, characterized by: The steps are as follows, Step 1: including the following raw materials by mass fraction, 50-65 parts of bauxite clinker, 15-25 parts of silicon carbide aggregate, 5-10 parts of zirconia powder, 2-5 parts of graphene, 4-8 parts of aluminum dihydrogen phosphate solution, 1-3 parts of magnesium aluminum complex powder, 5-8 parts of clay and 3-6 parts of silica powder; Step 2: the silicon carbide aggregate is soaked in 10% hydrochloric acid for 2h to remove iron, washed with water to neutral, and then dried at 110°C for 4h; the bauxite clinker, zirconia powder and graphene are respectively dried at 110°C for 4h, and then put into a ball mill for dry mixing for 30min to obtain a co-mixed powder A; Step 3: the silicon carbide aggregate after iron removal in step 2 is poured into a mixing mill, 70% of the total amount of aluminum dihydrogen phosphate solution and deionized water are added and wet milled for 15min, then co-mixed powder A, clay and silica powder are added and continue to mix for 10min; finally, the remaining 30% of the aluminum dihydrogen phosphate solution and the magnesium aluminum complex powder are added and mixed to obtain a mud; Step 4: the mud obtained in step 3 is molded into a green brick in a press machine, and the molded green brick is dried in sections; Step 5: under a weak reducing atmosphere, the refractory brick is fired according to the following procedure, the first stage is heated to 600°C at 3°C / min and kept for 4h, the second stage is heated to 1200-1250°C at 2°C / min and kept for 5h, and the third stage is naturally cooled to room temperature.

2. The method of producing a high-erosion resistant phosphate-bonded silicon carbide refractory brick according to claim 1, characterized by: In step 1, the bauxite clinker has a mass percentage of Al2O3≥85% and a mass percentage of Fe2O3≤1.2%; the silicon carbide aggregate has a mass percentage of SiC≥98%; the zirconium oxide micropowder has a mass percentage of ZrO2≥95%; the graphene has a flake diameter of 1-5 μm; and the density of the aluminum dihydrogen phosphate solution is 1.46-1.48 g / cm 3 The molar ratio of MgO / Al2O3 in the magnesium-aluminum complex powder is 1:2, and the mass percentage of SiO2 in the silica micropowder is ≥97%.

3. The method of producing a high-erosion resistant phosphate-bonded silicon carbide refractory brick according to claim 2, characterized by: The zirconium oxide fine powder d 50 = 1 to 3 μm, the particle size of the clay is ≤ 0.088 mm, the silicon dioxide fine powder d 90 < 3 μm.

4. The method of producing a high-erosion resistant phosphate-bonded silicon carbide refractory brick according to claim 1, characterized by: In step 2, the water content of the co-mixed powder A is <0.5%.

5. The method of producing a high impermeable phosphate-bonded silicon carbide refractory brick according to claim 1, characterized by: In step 3, the water to silicon carbide aggregate ratio of the deionized water is 0.05:1, and the plasticity index of the mud is 18-22.

6. The method of producing a high impermeable phosphate-bonded silicon carbide refractory brick according to claim 1, characterized by: In step 4, the mud is molded under a pressure of 120MPa and kept for 60s.

7. The method of producing a high impermeable phosphate-bonded silicon carbide refractory brick according to claim 1, characterized by: In step 4, the molded green brick is dried in sections according to the following steps, the first stage is dried at 50°C for 24h, and the second stage is heated to 110°C at 2°C / min and kept for 12h.

8. The method of producing a high-erosion resistant phosphate-bonded silicon carbide refractory brick according to claim 1, characterized by: In step 5, the weak reducing atmosphere is CO, and the concentration of CO is 2%-4%.

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