A high-strength alkali-resistant lightweight refractory castable and preparation method thereof

Abstract

The invention discloses a high-strength alkali-resistant lightweight refractory castable, comprising raw materials, wherein the raw materials include the following mass fractions of aggregate and matrix material, wherein the aggregate includes 55-75 parts of lightweight mullite refractory particles, and the matrix material includes 12-18 parts of refractory clay fine powder, 3-6 parts of barium carbonate fine powder, 3-6 parts of zircon fine powder, 4-8 parts of magnesium aluminum hydrotalcite fine powder, 2-4 parts of silica sol and 4-10 parts of pure calcium aluminate cement. The high-strength alkali-resistant lightweight refractory castable prepared by the invention has the characteristics of high strength, good volume stability and strong resistance to alkaline medium erosion.

Description

Technical Field

[0001] The invention relates to the field of castables, and in particular to a high-strength alkali-resistant lightweight refractory castable and a preparation method thereof. Background Art

[0002] Alkali-resistant castables are widely used in alkali-corroded industrial kilns in the steel, nonferrous metal, glass, machinery, petrochemical and other industries. Existing alkali-resistant castables usually contain a high content of silica. On the one hand, the alkali-resistant principle is to use silica to react with alkali metal oxides at high temperature to form a high-viscosity liquid phase, forming a glaze protective layer to prevent the penetration and erosion of alkali metal melts. On the other hand, alkali-resistant castables usually use pure calcium aluminate cement as a binder. The destruction of the cement glue structure under medium temperature conditions causes a significant decrease in strength. In order to improve its medium temperature strength, silicon micropowder is usually introduced. Therefore, the silica content in existing alkali-resistant castables is usually as high as 40% or more. However, too high a silica content is not good for the high-temperature performance of the material, and it is easy to cause excessive shrinkage of the material during firing, resulting in an increased scrap rate. For example, the patented technology "An alkali-resistant castable based on waste building ceramics and its preparation method" (CN 104804827 A) uses waste building ceramics, waste silicon carbide boron plates, alumina powder, silica fume, and aluminate cement as the main raw materials to prepare an alkali-resistant castable based on waste building ceramics. However, its silica content is high and the maximum use temperature is low. The patented technology "A lightweight refractory alkali-resistant castable formula" (CN 101973770 A) uses waste pottery, lightweight materials, silicon micropowder, and aluminate cement as the main raw materials to prepare a lightweight refractory alkali-resistant castable. However, its silica content is as high as more than 50%, the high temperature performance is poor, and the use temperature is low. The patented technology "A low-aluminum, low-thermal-conductivity, alkali-resistant castable" (CN 106830958 B) uses pyroxene, plate-shaped corundum powder, alumina powder, composite alkali-resistant powder, silica powder, microporous mullite, magnesium-aluminum spinel, perovskite, solid pore-forming agent, and pure calcium aluminate cement as main raw materials. The obtained low-aluminum, low-thermal-conductivity, alkali-resistant castable has a lower aluminum content and thus a lower thermal conductivity, but it also has the defects of high silica content and low operating temperature. Summary of the invention

[0003] The purpose of the present invention is to provide a high-strength alkali-resistant lightweight refractory castable.

[0004] The invention also provides a method for preparing a high-strength alkali-resistant lightweight refractory castable.

[0005] The innovation of the present invention is that the high-strength alkali-resistant lightweight refractory castable prepared by the present invention has the characteristics of high strength, good volume stability and strong resistance to erosion by alkaline media.

[0006] To achieve the above-mentioned purpose of the invention, the technical solution of the present invention is: a high-strength alkali-resistant lightweight refractory castable, comprising raw materials, wherein the raw materials include the following weight parts of aggregate and matrix material, the aggregate includes 55-75 parts of lightweight mullite refractory particles, and the matrix material includes 12-18 parts of refractory clay fine powder, 3-6 parts of barium carbonate fine powder, 3-6 parts of zircon fine powder, 4-8 parts of magnesium aluminum hydrotalcite fine powder, 2-4 parts of silica sol and 4-10 parts of pure calcium aluminate cement.

[0007] Furthermore, the Al2O3 content in the lightweight mullite refractory particles is 70-80wt%; and the particle size of the lightweight mullite refractory particles is 0.088-8mm.

[0008] Furthermore, the Al2O3 content of the refractory clay fine powder is 30-45wt%; and the particle size of the refractory clay fine powder is ≤0.088mm.

[0009] Furthermore, the particle size of the barium carbonate fine powder is ≤45 μm.

[0010] Furthermore, the ZrO2 content in the zircon fine powder is ≥63wt%; and the particle size of the zircon fine powder is ≤74μm.

[0011] Furthermore, the molar ratio of MgO to Al2O3 in the magnesium-aluminum hydrotalcite fine powder is 1.5-2.5; and the particle size of the magnesium-aluminum hydrotalcite fine powder is ≤45 μm.

[0012] Furthermore, the SiO2 content of the silica sol is 25-35wt%; the pH value of the silica sol is 9-11.

[0013] Furthermore, the Al2O3 content of the pure calcium aluminate cement is 70-80wt%, and the CaO content is 20-30wt%; the particle size of the pure calcium aluminate cement is ≤0.088mm.

[0014] A preparation method of a high-strength alkali-resistant lightweight refractory castable comprises the following steps: taking materials according to a formula, first mixing a matrix material, then adding the mixed matrix material into the aggregate and mixing evenly; then adding 3 to 10 parts by weight of water, stirring evenly, vibrating to form, and curing at room temperature for 12 to 24 hours; and finally keeping warm at 110 to 200°C for 12 to 36 hours to obtain a finished product.

[0015] The beneficial effects of the present invention are:

[0016] 1. The silica sol and magnesium aluminum hydrotalcite fine powder introduced into the matrix material of the present invention can react in situ to form a MgO-SiO2-Al2O3 binding system, which can not only accelerate the hydration and hardening of pure calcium aluminate cement; but also, under medium temperature conditions, it can also play the role of an auxiliary binder to improve the medium temperature strength of the castable.

[0017] 2. The barium carbonate fine powder introduced in the present invention can be decomposed into highly active barium oxide during the service life of the material, and together with pure calcium aluminate cement, it can form a bonding network, which can not only improve the bonding strength, but also reduce the probability of cracking of the cementitious structure of cement hydration products under medium temperature conditions, thereby improving the strength of the castable.

[0018] 3. During the service process of the castable, a part of the magnesium-aluminum hydrotalcite fine powder introduced in the present invention can form magnesium-aluminum spinel with fine grain size in situ, and a part forms a liquid phase containing MgO with other components in the matrix. Magnesium-aluminum spinel itself has good alkali resistance. At the same time, the magnesium-aluminum spinel crystal phase can also play a role of supporting the skeleton in the matrix, improving the strength and high-temperature volume stability of the castable. In addition, in conventional alkali-resistant castables, the mullite phase is easily decomposed under the erosion of alkaline substances such as K2O and Na2O, resulting in structural collapse. The MgO-containing liquid phase formed by the magnesium-aluminum hydrotalcite fine powder in the matrix can promote the formation, precipitation and development of mullite grains in the matrix, which not only inhibits the decomposition of mullite, but also increases the content of mullite phase in the castable, thereby increasing the strength, high-temperature volume stability and alkali resistance of the castable.

[0019] 4. The zircon fine powder introduced in the present invention can improve the viscosity of the liquid phase in the material without affecting the high-temperature performance of the castable; at the same time, the barium carbonate fine powder introduced in the present invention can form celsium feldspar in the matrix during service, and it also has good resistance to alkali and sulfate corrosion, further improving the alkali resistance of the castable.

[0020] 5. In the present invention, due to the effects of zircon fine powder, magnesium aluminum hydrotalcite fine powder and barium carbonate fine powder, the prepared castable has a higher solid phase content and a lower glass phase content. At the same time, the in-situ reaction to generate spinel, calcium aluminate, mullite, celsium feldspar, etc. is accompanied by volume expansion. Therefore, its volume shrinkage during the firing process and service process is relatively small, and the volume stability is excellent.

[0021] 6. The high-strength alkali-resistant lightweight refractory castable prepared by the present invention has been tested: the cold flexural strength at 110°C is 5~8MPa; the cold flexural strength after firing at 1100°C×3h is 7~9MPa; the linear change rate after firing at 1100°C×3h is -0.3%~-0.2%; the operating temperature exceeds 1300°C; the mass change rate after static crucible method alkali resistance test is less than 0.3%. Implementation

[0022] The technical solutions in the embodiments of the present invention will be described clearly and completely below.

[0023] The described embodiments are only some embodiments of the present invention, rather than all embodiments.

[0024] Embodiment 1: A high-strength alkali-resistant lightweight refractory castable, comprising raw materials, the raw materials comprising the following weight parts of aggregate and matrix material, the aggregate comprising 55 parts of lightweight mullite refractory particles, the matrix material comprising 12 parts of refractory clay fine powder, 3 parts of barium carbonate fine powder, 3 parts of zircon fine powder, 4 parts of magnesium aluminum hydrotalcite fine powder, 2 parts of silica sol and 4 parts of pure calcium aluminate cement; the Al2O3 content in the lightweight mullite refractory particles is 70wt%; the particle size of the lightweight mullite refractory particles is 0.088~8mm; the Al2O3 content of the refractory clay fine powder is 30wt% %; the particle size of refractory clay fine powder is ≤0.088mm; the particle size of barium carbonate fine powder is ≤45μm; the ZrO2 content in zircon fine powder is 63wt%; the particle size of zircon fine powder is ≤74μm; the molar ratio of MgO to Al2O3 in magnesium-aluminum hydrotalcite fine powder is 1.5; the particle size of magnesium-aluminum hydrotalcite fine powder is ≤45μm; the SiO2 content of silica sol is 25wt%; the pH value of silica sol is 9; the Al2O3 content of pure calcium aluminate cement is 70wt%, and the CaO content is 30wt%; the particle size of pure calcium aluminate cement is ≤0.088mm.

[0025] Embodiment 2: A high-strength alkali-resistant lightweight refractory castable, comprising raw materials, the raw materials comprising the following weight parts of aggregate and matrix material, the aggregate comprising 65 parts of lightweight mullite refractory particles, the matrix material comprising 15 parts of refractory clay fine powder, 5 parts of barium carbonate fine powder, 5 parts of zircon fine powder, 6 parts of magnesium aluminum hydrotalcite fine powder, 3 parts of silica sol and 7 parts of pure calcium aluminate cement; the Al2O3 content in the lightweight mullite refractory particles is 75wt%; the particle size of the lightweight mullite refractory particles is 0.088~8mm; the Al2O3 content of the refractory clay fine powder is 37wt% %; the particle size of refractory clay fine powder is ≤0.088mm; the particle size of barium carbonate fine powder is ≤45μm; the ZrO2 content in zircon fine powder is 65wt%; the particle size of zircon fine powder is ≤74μm; the molar ratio of MgO to Al2O3 in magnesium-aluminum hydrotalcite fine powder is 2; the particle size of magnesium-aluminum hydrotalcite fine powder is ≤45μm; the SiO2 content of silica sol is 30wt%; the pH value of silica sol is 10; the Al2O3 content of pure calcium aluminate cement is 75wt%, and the CaO content is 25wt%; the particle size of pure calcium aluminate cement is ≤0.088mm.

[0026] Embodiment 3: A high-strength alkali-resistant lightweight refractory castable, comprising raw materials, the raw materials comprising the following weight parts of aggregate and matrix material, the aggregate comprising 75 parts of lightweight mullite refractory particles, the matrix material comprising 18 parts of refractory clay fine powder, 6 parts of barium carbonate fine powder, 6 parts of zircon fine powder, 8 parts of magnesium aluminum hydrotalcite fine powder, 4 parts of silica sol and 10 parts of pure calcium aluminate cement; the Al2O3 content in the lightweight mullite refractory particles is 80wt%; the particle size of the lightweight mullite refractory particles is 0.088~8mm; the Al2O3 content of the refractory clay fine powder is 45wt% %; the particle size of refractory clay fine powder is ≤0.088mm; the particle size of barium carbonate fine powder is ≤45μm; the ZrO2 content in zircon fine powder is ≥63wt%; the particle size of zircon fine powder is ≤74μm; the molar ratio of MgO to Al2O3 in magnesium-aluminum hydrotalcite fine powder is 2.5; the particle size of magnesium-aluminum hydrotalcite fine powder is ≤45μm; the SiO2 content of silica sol is 35wt%; the pH value of silica sol is 11; the Al2O3 content of pure calcium aluminate cement is 80wt%, and the CaO content is 20wt%; the particle size of pure calcium aluminate cement is ≤0.088mm.

[0027] Example 4: A method for preparing a high-strength, alkali-resistant, lightweight refractory castable, comprising the following steps: taking materials according to the formula of Example 1, first mixing the matrix material, then adding the mixed matrix material to the aggregate and mixing evenly; then adding 3 parts by mass of water, stirring evenly, vibrating to form, and curing at room temperature for 12 hours; finally, keeping warm at 110°C for 12 hours to obtain a finished product.

[0028] The high-strength alkali-resistant lightweight refractory castable prepared in this embodiment has been tested: the cold flexural strength at 110°C is 5MPa; the cold flexural strength after firing at 1100°C×3h is 8MPa; the linear change rate after firing at 1100°C×3h is -0.28%; the operating temperature exceeds 1300°C; the mass change rate after the static crucible method alkali resistance test is less than 0.3%.

[0029] Example 5: A method for preparing a high-strength, alkali-resistant, lightweight refractory castable, comprising the following steps: taking materials according to the formula of Example 2, first mixing the matrix material, then adding the mixed matrix material to the aggregate and mixing evenly; then adding 7 parts by mass of water, stirring evenly, vibrating to form, and curing at room temperature for 18 hours; finally, keeping warm at 150°C for 24 hours to obtain a finished product.

[0030] The high-strength alkali-resistant lightweight refractory castable prepared in this embodiment has been tested: the cold flexural strength at 110°C is 6 MPa; the cold flexural strength after firing at 1100°C×3h is 7 MPa; the linear change rate after firing at 1100°C×3h is -0.26%; the operating temperature exceeds 1300°C; the mass change rate after the static crucible method alkali resistance test is less than 0.3%.

[0031] Example 6: A method for preparing a high-strength, alkali-resistant, lightweight refractory castable, comprising the following steps: taking materials according to the formula of Example 3, first mixing the matrix material, then adding the mixed matrix material to the aggregate and mixing evenly; then adding 10 parts by mass of water, stirring evenly, vibrating to form, and curing at room temperature for 24 hours; finally, keeping warm at 200°C for 36 hours to obtain a finished product.

[0032] The high-strength alkali-resistant lightweight refractory castable prepared in this embodiment has been tested: the cold flexural strength at 110°C is 8 MPa; the cold flexural strength after firing at 1100°C×3h is 8 MPa; the linear change rate after firing at 1100°C×3h is -0.25%; the operating temperature exceeds 1300°C; the mass change rate after the static crucible method alkali resistance test is less than 0.3%.

[0033] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

Claims

1. A high-strength alkali-resistant lightweight refractory castable, comprising raw materials, characterized in that: The raw materials include the following parts by mass of aggregate and matrix material. The aggregate includes 55 - 75 parts of lightweight mullite refractory particles, and the matrix material includes 12 - 18 parts of refractory clay fine powder, 3 - 6 parts of barium carbonate fine powder, 3 - 6 parts of zircon fine powder, 4 - 8 parts of magnesium aluminum hydrotalcite fine powder, 2 - 4 parts of silica sol, and 4 - 10 parts of calcium aluminate cement.

2. The high-strength alkali-resistant lightweight refractory castable according to claim 1, characterized in that: The Al₂O₃ content in the lightweight mullite refractory particles is 70 - 80 wt%; the particle size of the lightweight mullite refractory particles is 0.088 - 8 mm.

3. The high-strength alkali-resistant lightweight refractory castable according to claim 1, characterized in that: The Al₂O₃ content in the refractory clay fine powder is 30 - 45 wt%; the particle size of the refractory clay fine powder is ≤ 0.088 mm.

4. The high-strength alkali-resistant lightweight refractory castable according to claim 1, characterized in that: The particle size of the barium carbonate fine powder is ≤ 45 μm.

5. The high-strength alkali-resistant lightweight refractory castable according to claim 1, characterized in that: The ZrO₂ content in the zircon fine powder is ≥ 63 wt%; the particle size of the zircon fine powder is ≤ 74 μm.

6. The high-strength alkali-resistant lightweight refractory castable according to claim 1, characterized in that: The molar ratio of MgO to Al₂O₃ in the magnesium aluminum hydrotalcite fine powder is 1.5 - 2.5; the particle size of the magnesium aluminum hydrotalcite fine powder is ≤ 45 μm.

7. The high-strength alkali-resistant lightweight refractory castable according to claim 1, characterized in that: The SiO₂ content in the silica sol is 25 - 35 wt%; the pH value of the silica sol is 9 - 11.

8. The high-strength alkali-resistant lightweight refractory castable according to claim 1, characterized in that: The Al₂O₃ content in the calcium aluminate cement is 70 - 80 wt%, and the CaO content is 20 - 30 wt%; the particle size of the calcium aluminate cement is ≤ 0.088 mm.

9. A method for preparing the high-strength alkali-resistant lightweight refractory castable according to any one of claims 1 to 8, characterized in that: It includes the following steps: Take materials according to the formula, first mix the matrix material evenly, then add the evenly mixed matrix material into the aggregate and mix evenly; then add 3 - 10 parts by mass of water, stir evenly, vibrate and form, cure at room temperature for 12 - 24 hours; finally, keep warm at 110 - 200 °C for 12 - 36 hours to obtain the finished product.