Special-shaped anti-seepage heat-insulating refractory brick applied to aluminum electrolysis cell and its laying mortar

Abstract

This invention discloses a shaped, seepage-proof, and heat-insulating refractory brick and its masonry mortar for use in aluminum electrolysis cells. Traditional refractory bricks suffer from problems such as large joint gaps, difficult positioning, and poor sealing. The refractory brick of this invention features mortise and tenon structures on its four sides for splicing. The raw material composition and weight percentages are as follows: bauxite clinker (below 2mm): 12%–20%; soft kaolin powder (180–220 mesh): 45%–55%; quartz sand (below 1mm): 25%–32%; polylactic acid mullite powder (180–220 mesh): 2%–4%; dolomite powder (180–220 mesh): 2%–4%. The brick body of this invention uses a semi-circular mortise and tenon structure, matching the mortar to the brick material, ensuring precise positioning during construction, transforming straight joints into curved gaps, significantly extending the penetration path, and substantially improving heat insulation and seepage prevention performance. It can effectively block the penetration of cryolite, sodium vapor, and molten aluminum.

Description

Technical Field

[0001] This invention relates to the field of refractory materials for aluminum electrolytic cells, specifically to a special-shaped anti-seepage and heat-insulating refractory brick used in aluminum electrolytic cells, and a special masonry mortar adapted to the special-shaped brick, belonging to the field of preparation and application technology of refractory materials for non-ferrous metal smelting. Background Technology

[0002] Aluminum electrolytic cells are core equipment in the aluminum smelting industry. Their lining structures are subjected to harsh conditions such as high temperatures, erosion by cryolite molten salt, and penetration by sodium vapor and molten aluminum over long periods. The seepage prevention and heat insulation performance of the lining, as well as the quality of its construction, directly determine the service life and operating costs of the electrolytic cell. The sides, cathode perimeter, bottom, and corners of the aluminum electrolytic cell are weak points in terms of seepage prevention and heat insulation. Traditional straight refractory bricks cannot meet the construction requirements of this structure, resulting in problems such as large splicing gaps, difficulty in positioning, and poor sealing.

[0003] The existing anti-seepage refractory bricks used in aluminum electrolysis cells are mostly conventional straight brick structures with simple external dimensions, and generally suffer from the following technical defects: First, the bricks are spliced ​​using planar butt joints, resulting in straight mortar joints and short penetration paths. Cryolite molten salt and sodium vapor can easily penetrate through the brick joints, leading to poor anti-seepage effects. Second, the raw material formula of the refractory bricks is singular, making it difficult to simultaneously achieve high strength, anti-seepage, and thermal insulation performance. Most bricks have high porosity and high thermal conductivity, which cannot effectively block molten salt erosion and result in poor thermal insulation, leading to increased energy consumption in the electrolysis cell. Third, the matching masonry mortar has a large difference in material from the brick body, and the coefficients of thermal expansion are mismatched. At high temperatures, the brick joints are prone to cracking and falling off, and the mortar joints lose their sealing properties. In addition, ordinary mortar has low high-temperature bonding strength and high shrinkage rate, making it impossible to form a continuous and homogeneous anti-seepage masonry. Fourth, the construction of dry anti-seepage materials suffers from problems such as uneven on-site mixing, large performance fluctuations, high apparent porosity, and poor anti-seepage effects, making it difficult to meet the requirements of efficient and long-term operation of aluminum electrolysis cells.

[0004] Furthermore, existing masonry mortars generally suffer from poor workability, susceptibility to water seepage and mortar sagging, and difficulty in achieving adequate mortar joint fullness, making them unsuitable for use in high-temperature seepage prevention and insulation areas of aluminum electrolytic cells. In summary, existing refractory materials and masonry techniques for seepage prevention in aluminum electrolytic cells cannot simultaneously address the synergistic issues of masonry compatibility, seepage prevention and insulation, high-temperature stability, and ease of construction. This results in a short overall lifespan for the electrolytic cell lining, frequent maintenance, and hinders the efficient and low-cost development of the aluminum smelting industry. Summary of the Invention

[0005] This invention aims to solve technical problems such as poor compatibility of refractory brick masonry in aluminum electrolytic cells, easy leakage at brick joints, difficulty in achieving both seepage prevention and heat insulation of refractory bricks, insufficient high-temperature performance of masonry mortar, and short overall lifespan of the lining. It provides a special-shaped seepage-proof and heat-insulating refractory brick and its masonry mortar that have good masonry compatibility, low porosity, impermeability, erosion resistance, high temperature resistance, and overall seepage prevention for use in aluminum electrolytic cells.

[0006] To achieve the above objectives, the present invention employs the following technical means: a special-shaped seepage-proof and heat-insulating refractory brick for use in aluminum electrolysis cells, wherein the raw material composition and weight percentage are as follows: bauxite clinker (below 2mm): 12%–20%; soft kaolin powder (180–220 mesh): 45%–55%; quartz sand (below 1mm): 25%–32%; polylight mullite powder (180–220 mesh): 2%–4%; dolomite powder (180–220 mesh): 2%–4%.

[0007] Preferably, the raw material composition and weight percentage of the special-shaped seepage-proof and heat-insulating refractory bricks used in aluminum electrolysis cells are as follows: bauxite clinker (below 2mm): 15%–18%; soft kaolin powder (180–220 mesh): 48%–52%; quartz sand (0.1–1mm): 28%–30%; polylight mullite powder (180–220 mesh): 2%–3%; dolomite powder (180–220 mesh): 3%–4%.

[0008] The performance indicators of the raw materials are as follows: bauxite clinker: SiO2≥50%, Al2O3≤40%, Fe2O3≤1.0%, refractoriness≥1750℃, bulk density≥2.50g / cm³; soft kaolin: SiO2≥50%, Al2O3≤30%; quartz sand: SiO2≥92%; polylactic acid mullite: Al2O3≥40%; dolomite powder: CaO≥40%.

[0009] Due to the optimization of the raw material formula, bauxite clinker is selected to improve the refractoriness of the product; soft kaolin powder is selected to reduce the apparent porosity of the product and improve its plasticity and binding properties; quartz sand is selected to improve the seepage prevention effect of the product; polylight mullite powder is selected to further reduce the thermal insulation coefficient of the product; and dolomite powder is selected to increase the CaO and MgO content of the product, so that the four oxides in the product are combined together and act as a binder. Therefore, the interaction of the selected raw materials maximizes the satisfaction of the product's design requirements. The physicochemical properties of the irregular seepage-proof and heat-insulating refractory bricks prepared with the weight percentage and raw material indicators mentioned above are: SiO2 content ≥69%, Al2O3 content ≤20%, MgO content 1%-2%, CaO content 1%-2%, and bulk density: 2.05 g / cm³. 3The compressive strength at room temperature is 30 MPa, the refractoriness is 1550℃, the apparent porosity is 20%, the thermal conductivity is 0.37 W / m:K at 400℃ and 0.52 W / m:K at 800℃, the thermal expansion coefficient of shaped bricks is 1000℃, and the coefficient of thermal expansion using the top rod method is 0.52%. All of the above physical and chemical properties fully exceed the design requirements.

[0010] Furthermore, the irregularly shaped seepage-proof and heat-insulating refractory brick used in aluminum electrolysis cells includes a brick body 1. The four sides of the brick body 1 are respectively provided with opposing mortise and tenon structures for splicing. The mortise and tenon structure includes a tenon 2 provided in the middle of one side of the brick body along the length direction and extending through its entire length, and a mortise 2-1 provided on the opposite side that matches the shape of the tenon 2; and a flange 3 provided in the middle of one side of the brick body along the width direction and extending through its entire width, and a groove 3-1 provided on the opposite side that matches the flange 3.

[0011] Preferably, the cross-sections of the tenon 2 and the flange 3 are semi-circular or trapezoidal.

[0012] A method for preparing irregularly shaped, seepage-proof, heat-insulating refractory bricks for use in aluminum electrolysis cells includes the following steps: A. Raw material pretreatment: Select hard bauxite raw material blocks with a block size ≥40mm, calcine them in a vertical kiln at 1300℃ to produce bauxite clinker, and crush them to less than 2mm; grind soft kaolin, polylight mullite and dolomite to 180-220 mesh respectively, crush quartz sand to less than 1mm, and screen them for later use.

[0013] B. Mixing: Weigh each raw material according to the proportion, put them into a mixer and mix for 10-15 minutes until uniform.

[0014] C. High-pressure molding: Using friction presses, hydraulic presses and other exhaust processes, the mixed materials are pressed into irregularly shaped brick blanks with mortise and tenon structures.

[0015] D. Drying: The brick blanks are dried in stages at 80-160℃.

[0016] E. Firing: The dried brick blanks are kept in a tunnel kiln at the highest temperature of 1280-1330℃ for 2-3 hours, and then gradually cooled and fired.

[0017] The present invention also provides a mortar for laying the above-mentioned irregularly shaped, seepage-proof, heat-insulating refractory bricks, which is composed of dry-based raw materials and additives. The dry-based raw materials are composed of the following components and weight parts: 35-45 parts of clay clinker powder; 25-35 parts of fine quartz powder; and 25-35 parts of soft refractory clay.

[0018] The added components and their weight percentages are as follows: 4–6 parts adhesive; 0.15–0.25 parts carboxymethyl cellulose; 0.1–0.2 parts sodium tripolyphosphate; and 18–22 parts purified tap water. The adhesive is one of the following: a 45%–50% aluminum dihydrogen phosphate solution, silica sol, or water glass.

[0019] Furthermore, the dry base raw material components and their weight parts are as follows: 40 parts of clay clinker powder, 30 parts of quartz fine powder, 30 parts of soft refractory clay, 5 parts of aluminum dihydrogen phosphate solution, 0.2 parts of carboxymethyl cellulose, 0.2 parts of sodium tripolyphosphate, and 20 parts of clean tap water.

[0020] The performance indicators of the masonry mortar raw materials are as follows: clay clinker powder is 325 mesh, Al2O3 ≥ 35%, refractoriness ≥ 1650℃; quartz fine powder particle size ≤ 0.074mm, and soft refractory clay plasticity index ≥ 15.

[0021] The preparation process includes the following steps: dry base raw materials are put into a forced mixer and dry-mixed for 3-5 minutes, carboxymethyl cellulose is added and stirred for 2 minutes, aluminum dihydrogen phosphate solution is added and stirred for 2 minutes, tap water is added in batches and stirred for 3-5 minutes, the mixture is allowed to stand for 10 minutes and then stirred again for 1 minute to obtain a paste-like slurry.

[0022] Masonry requirements: mortar joint thickness 1–2 mm, mortar joint fullness ≥95%.

[0023] The principle of synergistic effect between brick and mortar: The main components of the masonry mortar are highly consistent with the matrix of the irregularly shaped waterproof and heat-insulating refractory bricks, with similar coefficients of thermal expansion, sintering behavior, and chemical reactivity. Under high-temperature conditions, the mortar and the brick surface undergo synchronous solid-phase reaction, forming a dense structure similar to the brick body in the brick joint area, eliminating weak points at the interface; at the same time, the tenon and mortise structure extends the penetration path and blocks convection, making the masonry form a continuous, homogeneous, and integral waterproof and heat-insulating system.

[0024] Beneficial effects 1. The present invention applies to the irregular seepage-proof and heat-insulating refractory bricks used in aluminum electrolysis cells. Through the innovation of brick structure, the brick adopts a semi-circular or trapezoidal tenon and mortise structure, which allows for precise positioning during construction. It transforms straight seams into curved gaps, significantly extending the penetration path and greatly improving the heat insulation and seepage prevention performance. It can effectively block the penetration of cryolite, sodium vapor, and aluminum liquid.

[0025] 2. By rationally proportioning multiple components, refining the pore size, reducing the apparent porosity, and improving the interparticle bonding force, the brick body simultaneously possesses comprehensive properties such as high strength, low porosity, impermeability, erosion resistance, high temperature resistance, and thermal insulation.

[0026] 3. The mortar and brick materials are well-matched, preventing cracking and peeling at high temperatures. It has good workability, high mortar joint fullness, low raw material cost, and simple process, making it suitable for batch construction on site.

[0027] 4. The bricks and mortar form an integral seepage-proof and heat-insulating lining, replacing dry seepage-proof materials. The construction quality is stable, the cycle is short, the service life of the lining is extended by 3-5 years, and the operation and maintenance costs of the electrolytic cell are reduced. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the three-dimensional structure of the irregularly shaped anti-seepage and heat-insulating refractory bricks used in aluminum electrolysis cells according to the present invention.

[0029] Figure 2 This is a three-dimensional structural diagram of the multiple bricks assembled in this invention.

[0030] Figure 3 This is a three-dimensional structural diagram of the multi-brick corner splicing state of the present invention.

[0031] In the diagram: brick 1, tenon 2, mortise 2-1, flange 3, groove 3-1. Detailed Implementation

[0032] The present invention will be further described below with reference to embodiments.

[0033] A special-shaped, seepage-proof, heat-insulating, and refractory brick for use in aluminum electrolysis cells includes a brick body 1. The four sides of the brick body 1 are respectively provided with opposing mortise and tenon structures for splicing. Splicing is achieved through the interlocking of these mortise and tenon structures. Each mortise and tenon structure includes a tenon 2 extending along the entire length of one side of the brick body, located in the middle; and a mortise 2-1 matching the shape of the tenon 2 on the opposite side. Furthermore, a flange 3 extending along the width of one side of the brick body, located in the middle; and a groove 3-1 matching the flange 3 on the opposite side. The cross-sections of the tenon 2 and the flange 3 are semi-circular or trapezoidal.

[0034] The raw material composition and weight percentage of the special-shaped waterproof and heat-insulating refractory brick are shown in Table 1 below:

[0035] The performance indicators of the raw materials are as follows: bauxite clinker: SiO2≥50%, Al2O3≤40%, Fe2O3≤1.0%, refractoriness≥1750℃, bulk density≥2.50g / cm³; soft kaolin: SiO2≥50%, Al2O3≤30%; quartz sand: SiO2≥92%; polylactic acid mullite: Al2O3≥40%; dolomite powder: CaO≥40%.

[0036] A method for preparing irregularly shaped, seepage-proof, heat-insulating refractory bricks for use in aluminum electrolysis cells includes the following steps: A. Raw material pretreatment: Select hard bauxite raw material blocks with a block size ≥40mm, calcine them in a vertical kiln at 1300℃ to produce bauxite clinker, and crush them to less than 2mm; grind soft kaolin, polylight mullite and dolomite to 180-220 mesh respectively, crush quartz sand to less than 1mm, and screen them for later use.

[0037] B. Mixing: Weigh each raw material according to the proportion, put them into a mixer and mix for 10-15 minutes until uniform.

[0038] C. High-pressure molding: Using friction presses, hydraulic presses and other exhaust processes, the mixed materials are pressed into irregularly shaped brick blanks with mortise and tenon structures.

[0039] D. Drying: The brick blanks are dried in stages at 80-160℃.

[0040] E. Firing: The dried brick blanks are kept in a tunnel kiln at the highest temperature of 1280-1330℃ for 2-3 hours, and then gradually cooled and fired.

[0041] The geometric dimensions of the bricks produced are: length 200–400mm, width 100–250mm, and thickness 50–150mm, which can be adapted to the masonry needs of different parts of the aluminum electrolysis cell, improving the fit and masonry efficiency.

[0042] The chemical composition (percentage) of the bricks is shown in Table 2:

[0043] The performance tests and results of the bricks are shown in Table 3:

[0044] As shown in Table 3, the seepage-proof and heat-insulating refractory brick prepared by this invention is significantly superior to traditional formulas in key physical properties such as bulk density, compressive strength, and thermal conductivity. In particular, the depth of penetration by cryolite corrosion is greatly reduced (≤2.0 mm), indicating that its seepage-proof ability is greatly improved.

[0045] The vertical and horizontal mortar joints at the joints of adjacent bricks 1 are filled with masonry mortar, which is composed of dry base materials and additives. The raw material components are listed in Table 4 by weight percentage.

[0046] The performance indicators of the raw materials are as follows: clay clinker powder is 325 mesh, Al2O3 ≥ 35%, refractoriness ≥ 1650℃; quartz fine powder particle size ≤ 0.074mm, and soft refractory clay plasticity index ≥ 15.

[0047] The process for preparing masonry slurry includes the following steps: dry base raw materials are put into a forced mixer and mixed for 3-5 minutes, carboxymethyl cellulose is added and mixed for 2 minutes, aluminum dihydrogen phosphate solution is added and mixed for 2 minutes, tap water is added in batches and mixed for 3-5 minutes, the mixture is left to stand for 10 minutes and then stirred again for 1 minute to obtain a paste-like slurry.

[0048] The flexural bond strength of the above-mentioned slurry after drying at 110℃ for 24 hours is ≥0.6MPa; the flexural bond strength after firing at 1100℃ for 3 hours is ≥2.5MPa; and the linear shrinkage rate of the slurry after firing at 1100℃ is ≤±0.6%. Overall impermeability of masonry (simulated masonry construction: mortar joint thickness 1–2 mm, mortar joint fullness ≥95%): Test Method: The irregularly shaped impermeable and heat-insulating refractory bricks from Examples 1-4 were used to construct test samples using masonry mortar. The samples were then air-dried at room temperature for 24 hours to achieve surface drying and shaping. A low-temperature drying process with a gradient temperature increase followed: 60℃ for 2 hours → 100℃ for 3 hours → 150℃ for 4 hours → 180℃ for 4 hours. Only after complete dehydration could the samples be used for long-term operation under high-temperature conditions of 1000–1300℃. After static crucible erosion in cryolite melt at 950℃ for 48 hours, the samples were cut perpendicular to the brick joints, and the maximum penetration depth, area, and refractoriness were measured. The results are shown in Table 5.

[0049] The embodiment of the "seepage-proof and heat-insulating brick + masonry mortar" masonry has a uniform penetration depth, with a maximum of ≤2.0mm. No additional penetration channels were observed at the brick joints, and the fire resistance was significantly improved.

Claims

1. A shaped, seepage-proof, heat-insulating refractory brick for use in aluminum electrolysis cells, characterized in that, The raw material composition and weight percentage are as follows: bauxite clinker (below 2mm): 12%–20%; soft kaolin powder (180–220 mesh): 45%–55%; quartz sand (below 1mm): 25%–32%; polylight mullite powder (180–220 mesh): 2%–4%; dolomite powder (180–220 mesh): 2%–4%.

2. The irregularly shaped, seepage-proof, heat-insulating, and refractory brick for use in aluminum electrolysis cells according to claim 1, characterized in that, The raw material composition and weight percentage are as follows: bauxite clinker (below 2mm): 15%–18%; soft kaolin powder (180–220 mesh): 48%–52%; quartz sand (below 1mm): 28%–30%; polylight mullite powder (180–220 mesh): 2%–3%; dolomite powder (180–220 mesh): 3%–4%.

3. A shaped, seepage-proof, heat-insulating, and refractory brick for use in aluminum electrolysis cells according to claim 1 or 2, characterized in that, The performance indicators of the raw materials are as follows: bauxite clinker: SiO2≥50%, Al2O3≤40%, Fe2O3≤1.0%, refractoriness≥1750℃, bulk density≥2.50g / cm³; soft kaolin: SiO2≥50%, Al2O3≤30%; quartz sand: SiO2≥92%; polylactic acid mullite: Al2O3≥40%; dolomite powder: CaO≥40%.

4. A shaped, seepage-proof, heat-insulating, and refractory brick for use in aluminum electrolysis cells according to claim 3, comprising a brick body (1), characterized in that, The brick body (1) has four sides respectively provided with opposite mortise and tenon structures for splicing. The mortise and tenon structure includes a tenon (2) that extends along the length direction and penetrates the entire length of one side of the brick body, and a mortise (2-1) that matches the shape of the tenon (2) on the opposite side; and a flange (3) that extends along the width direction and penetrates the entire width of one side of the brick body, and a groove (3-1) that matches the flange (3) on the opposite side.

5. The irregularly shaped, seepage-proof, heat-insulating, and refractory brick for use in aluminum electrolysis cells according to claim 4, characterized in that, The cross-sections of the tenon (2) and flange (3) are semi-circular or trapezoidal.

6. A method for preparing irregularly shaped, seepage-proof, heat-insulating refractory bricks for use in aluminum electrolysis cells, characterized in that, Includes the following steps: A. Raw material pretreatment: Select hard bauxite raw material blocks with a block size ≥40mm, calcine them in a vertical kiln at 1300℃ to produce bauxite clinker, and crush them to less than 2mm; grind soft kaolin, polylight mullite and dolomite to 180-220 mesh respectively, crush quartz sand to less than 1mm, and screen them for later use. B. Mixing: Weigh each raw material according to the proportion, put them into a mixer and mix for 10-15 minutes until uniform; C. High-pressure molding: Using friction press, hydraulic press and other exhaust processes, the mixed materials are pressed into irregular brick blanks with mortise and tenon structure; D. Drying: The brick blanks are dried in stages at 80-160℃. E. Firing: The dried brick blanks are kept in a tunnel kiln at a maximum temperature of 1280-1330℃ for 2-3 hours, and then gradually cooled and fired.

7. A mortar for laying the above-mentioned irregularly shaped, seepage-proof, heat-insulating, and refractory bricks, characterized in that, It is composed of dry base raw materials and added components. The dry base raw material components and their weight parts are: 35-45 parts of clay clinker powder; 25-35 parts of fine quartz powder; and 25-35 parts of soft refractory clay. The added components and their weight percentages are as follows: 4–6 parts adhesive, 0.15–0.25 parts carboxymethyl cellulose, 0.1–0.2 parts sodium tripolyphosphate, and 18–22 parts clean tap water.

8. The masonry mortar according to claim 7, characterized in that, The dry base raw material components and their weight proportions are as follows: 40 parts clay clinker powder, 30 parts quartz fine powder, 30 parts soft refractory clay, 5 parts aluminum dihydrogen phosphate solution, 0.2 parts carboxymethyl cellulose, 0.2 parts sodium tripolyphosphate, and 20 parts clean tap water; the binder in the added components is one of aluminum dihydrogen phosphate solution with a concentration of 45%–50%, silica sol, or water glass.

9. The masonry mortar according to claim 7 or 8, characterized in that, The raw material performance indicators are as follows: clay clinker powder is 325 mesh, Al2O3 ≥ 35%, refractoriness ≥ 1650℃; quartz fine powder particle size ≤ 0.074mm, soft refractory clay plasticity index ≥ 15; the preparation process includes the following steps: Add the dry base raw materials into a forced mixer and dry mix for 3–5 minutes. Add carboxymethyl cellulose and continue mixing for 2 minutes. Then add aluminum dihydrogen phosphate solution and mix for 2 minutes. Add tap water in batches and mix for 3–5 minutes. Let the mixture stand for 10 minutes and then stir again for 1 minute to obtain a paste-like slurry.

10. An aluminum electrolytic cell, characterized in that, The vertical and horizontal mortar joints at the joints of the irregularly shaped, seepage-proof, heat-insulating, and refractory bricks of the aluminum electrolytic cell as described in any one of claims 1-6, arranged in a staggered manner, are filled with the masonry mortar as described in any one of claims 7-9.

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