Spinel lightweight castable and preparation process thereof

Abstract

The spinel light-weight castable is prepared by the following steps: intensively and uniformly mixing 40-80 parts by weight of light-weight aggregate, 3-10 parts by weight of activated alumina powder, 2-8 parts by weight of light-burned magnesia powder, 10-20 parts by weight of ceramic fibers and 2-8 parts by weight of magnesium aluminate spinel hollow spheres, adding 5-10 parts by weight of a composite binder, 0.5-1 part by weight of a hardening agent and 5-8 parts by weight of water, uniformly stirring again, and carrying out casting molding to obtain the spinel light-weight castable. And curing at room temperature for 24-48 hours, demolding and baking to obtain the lightweight castable which has the advantages of good anti-stripping performance, burst resistance, low heat conductivity coefficient and high strength and can serve at 1350-1600 DEG C.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory materials and relates to a spinel lightweight castable and a preparation process thereof. Background Art

[0002] Magnesium-aluminum spinel exhibits excellent high temperature resistance, spalling resistance, erosion resistance, wear resistance, and thermal shock resistance in alkaline atmosphere or alkaline working environment. It is used in steel smelting, cement kilns, lime kilns and other fields. The demand for energy saving in high-temperature industries is particularly urgent. However, the current spinel lightweight castable public technologies CN200610125542.7, CN201811068700.9, and CN202210586408.6 all use calcium aluminate cement as a binder, which makes the performance of magnesium-aluminum spinel lightweight castables worse at high temperatures above 1350°C, causing structural spalling and collapse, limiting its high-temperature use; CN201010595986.3 uses a cement-free bonding method, but it relies too much on the addition of SiO 2 The raw materials increase the content of high-temperature silicate liquid phase, which also makes it unable to serve in high-temperature environment. How to make magnesium-aluminum spinel lightweight bricks have high strength at low, medium and high temperatures is an urgent problem to be solved. The medium-temperature strength cannot rely on the addition of SiO 2 The amount of solution is to add more SiO 2 It can lower the reaction temperature and promote sintering to obtain higher medium-temperature strength, but it will inevitably lead to a decrease in high-temperature performance.

[0003] In order to solve the above technical problems, the present invention adds a very small amount of SiO 2 In order to reduce the sintering temperature and obtain good medium-temperature strength, the high-temperature performance of the castable is not damaged. At the same time, the air permeability of the fiber-built skeleton is used to obtain anti-stripping and anti-burst functions, and the fiber reinforcement makes the lightweight castable stable in strength over the entire temperature range. A composite binder is used to replace the calcium silicate or calcium aluminate cement used as a binder in traditional lightweight thermal insulation castables to improve the high temperature resistance and corrosion resistance of the lightweight thermal insulation castable, so that the lightweight castable of the present invention can be used for a long time at a high temperature of >1350°C, and the maximum service temperature can reach 1600°C. Summary of the invention

[0004] The spinel lightweight castable of the present invention has the following raw material proportions by weight:

[0005] (1) Lightweight aggregate, 40-80 parts;

[0006] (2) 3 to 10 parts of activated alumina powder;

[0007] (3) Lightly burned magnesia powder, 2 to 8 parts;

[0008] (4) Ceramic fiber, 10-20 parts;

[0009] (5) 2 to 8 parts of magnesium aluminate spinel hollow spheres;

[0010] (6) composite binder, 5 to 10 parts;

[0011] (7) Hardener, 0.5-1 part;

[0012] (8) Water, 5 to 8 parts.

[0013] The lightweight aggregate is spinel lightweight aggregate, porous spinel ceramic or a mixture of the two.

[0014] The lightweight aggregate comprises three particle sizes of 0.2-1 mm, 1-3 mm, and 3-5 mm, and the three particle sizes are mixed in a ratio of 1:1-3:2-5.

[0015] The particle size of the activated alumina powder is 0.074-0.147 mm.

[0016] The particle size of the light-burned magnesia powder is 0.074-0.147 mm.

[0017] The ceramic fiber is spinel ceramic fiber, alumina ceramic fiber or a mixture of the two, and has a length of 0.1 to 20 cm.

[0018] The diameter of the magnesium aluminum spinel hollow sphere is 0.40-1.2 μm.

[0019] The composite binder is a mixture of water-based organic silicon resin and complex aluminum-magnesium sol, and the ingredients of the composite binder meet the requirements of MgO:Al 2 O 3 :SiO 2 The molar ratio is 4:5:2.

[0020] The hardener is polyamide.

[0021] The preparation method of the castable is as follows: lightweight aggregate, activated alumina powder, light-burned magnesia powder, ceramic fiber, and magnesia-alumina spinel hollow balls are vigorously mixed evenly, a composite binder, a hardener and water are added, the mixture is stirred evenly again, and cast into shape.

[0022] The curing and baking method of the castable is as follows: after curing at room temperature for 24 to 48 hours, the castable is demoulded, baked at 110 to 200° C. for 24 to 48 hours, and then heated to the service temperature at a heating rate of ≤20° C. / h to obtain a lightweight thermal insulation castable with good anti-stripping performance, anti-cracking, low thermal conductivity and high strength at a service temperature of 1350 to 1600° C.

[0023] The composite binder used in the present invention is a mixture of water-based silicone resin and complex aluminum-magnesium sol. The water-based silicone resin can act as a water reducer at room temperature. At the same time, it reacts with a hardener to solidify and shape, and is bonded with the complex magnesium-aluminum sol after hydration. After drying, an interlaced structure is formed and embedded between the particles and the fine powder, thereby improving the bonding strength of the lightweight castable blank. At high temperatures, the silicone resin covering the surface of spinel and alumina is eventually converted into active amorphous silica, which undergoes a solid solution reaction with the active alumina to promote sintering, reduce the sintering temperature, and improve the medium-temperature strength of the castable.

[0024] At the same time, the alumina and magnesium oxide produced by the high-temperature decomposition of the complex magnesium-aluminum sol have high reaction activity, and react with the active alumina and light-burned magnesia in the raw materials to generate magnesium-aluminum spinel in situ to promote sintering and improve the high-temperature strength of the castable. Through multiple coupling reactions at low, medium and high temperatures, the strength of the spinel lightweight castable is less sensitive to temperature, and the strength remains relatively stable at room, medium and high temperatures, and the flexural strength in the full temperature range exceeds 3.5MPa.

[0025] The beneficial effects of the present invention are as follows:

[0026] (1) The castable has high strength, with a room temperature compressive strength of ≥18MPa, and a flexural strength of ≥3.5MPa in the full temperature range of 110℃×24h, 900℃×24h, 1350℃×24h, and 1600℃×24h, which meets the service requirements of a single-layer lining material to bear its own weight and resist the scouring and friction of hot air flow.

[0027] (2) The thermal conductivity of the castable is low. At 1100°C, the thermal conductivity is ≤0.2W·m -1 ·K -1 , at 1400℃, thermal conductivity ≤0.25W·m -1 ·K -1 , thermal insulation effect is good.

[0028] (3) The castable has good high-temperature volume stability. After heat treatment at 1350℃×3h, 1450℃×3h, and 1600℃×3h, the linear change rate is ≤±0.3%.

[0029] (4) The production cost of the castable is low. Compared with the double-layer design of a heavy working layer and a light insulation layer, the weight of the single-layer lining castable of the present invention is reduced by more than 60%, the lining is thinned by more than 50%, the amount of materials used is reduced, and the cost is reduced. DETAILED DESCRIPTION

[0030] Example 1

[0031] The spinel lightweight castable of the present invention has the following raw material proportions by weight:

[0032] (1) lightweight aggregate, 80 parts;

[0033] (2) 3 parts of activated alumina powder;

[0034] (3) Lightly burned magnesia powder, 2 parts;

[0035] (4) Ceramic fiber, 10 parts;

[0036] (5) 2 parts of magnesium aluminum spinel hollow spheres;

[0037] (6) composite binder, 5 parts;

[0038] (7) Hardener, 0.5 part;

[0039] (8) Water, 5 parts.

[0040] Furthermore, the lightweight aggregate is one of spinel lightweight aggregate and porous spinel ceramic or a mixture of the two; the lightweight aggregate comprises three particle sizes of 0.2-1 mm, 1-3 mm and 3-5 mm, and the three particle sizes are proportioned in a ratio of 1:1:2; the particle size of the activated alumina powder is 0.074-0.147 mm; the particle size of the light-burned magnesia powder is 0.074-0.147 mm; the ceramic fiber is spinel ceramic fiber, and its length is 0.1-20 cm; the diameter of the magnesium aluminum spinel hollow sphere is 0.40-1.2 μm; the composite binder is a mixture of water-based silicone resin and complex aluminum magnesium sol powder, and the ingredients of the composite binder meet the requirements of MgO:Al 2 O 3 :SiO 2 The molar ratio is 4:5:2; the hardener is polyamide.

[0041] Preparation method: After vigorously mixing lightweight aggregate, activated alumina powder, light-burned magnesia powder, ceramic fiber, and magnesia-alumina spinel hollow balls, add composite binder, hardener and water, stir evenly again, and cast into shape.

[0042] Curing and baking: demould after curing at room temperature for 24 hours, bake at 200℃ for 24 hours, and then heat to the service temperature at a heating rate of ≤20℃ / h.

[0043] The room temperature compressive strength of Example 1 is relatively high, reaching 20MPa; its flexural strength is stable in the whole temperature range, all exceeding 3.5MPa, the flexural strength is 4.0MPa at 110℃×24h, the flexural strength is 3.8MPa at 900℃×24h, the flexural strength is 4.0MPa at 1350℃×24h, and the flexural strength is ≥3.7MPa at 1600℃×24h; its thermal conductivity is also low, with good thermal insulation effect, the thermal conductivity is 0.19W·m at 1100℃ -1 ·K -1, the thermal conductivity is 0.25 W·m -1 ·K -1 ; its re-firing phase change rate is very low, and it has good high-temperature volume stability. After heat treatment at 1350°C for 3 hours, the linear change rate is -0.15%, after heat treatment at 1450°C for 3 hours, the linear change rate is -0.17%, and after heat treatment at 1600°C for 3 hours, the linear change rate is -0.19%, which can meet the service environment at 1600°C.

[0044] Example 2

[0045] A spinel lightweight castable of the present invention, by weight, the raw material ratio is as follows:

[0046] (1) Lightweight aggregate, 40 parts;

[0047] (2) Activated alumina powder, 10 parts;

[0048] (3) Light-burned magnesite powder, 8 parts;

[0049] (4) Ceramic fiber, 20 parts;

[0050] (5) Magnesium aluminate spinel hollow spheres, 8 parts;

[0051] (6) Composite binder, 10 parts;

[0052] (7) Hardening agent, 1 part;

[0053] (8) Water, 8 parts.

[0054] Furthermore, the lightweight aggregate is one or a mixture of two of spinel lightweight aggregate and porous spinel ceramics; the lightweight aggregate includes three particle sizes of 0.2 - 1 mm, 1 - 3 mm, and 3 - 5 mm, and the three particle sizes are proportioned according to a ratio of 1:3:5; the particle size of the activated alumina powder is 0.074 - 0.147 mm; the particle size of the light-burned magnesite powder is 0.074 - 0.147 mm; the ceramic fiber is alumina ceramic fiber, and its length is 0.1 - 20 cm; the diameter of the magnesium aluminate spinel hollow spheres is 0.40 - 1.2 μm; the composite binder is a mixture of water-based silicone resin and complex aluminum-magnesium sol powder, and the composite binder formulation satisfies the molar ratio of MgO:Al 2 O 3 : SiO 2 is 4:5:2; the hardening agent is polyamide.

[0055] Preparation method: After strongly mixing the lightweight aggregate, activated alumina powder, light-burned magnesite powder, ceramic fiber, and magnesium aluminate spinel hollow spheres evenly, add the composite binder, hardening agent, and water, stir evenly again, and cast into shape.

[0056] Curing and baking: After curing at room temperature for 48 hours, demould, then bake at 160℃ for 48 hours, and then heat to the service temperature at a heating rate of ≤20℃ / h.

[0057] The room temperature compressive strength of Example 2 is relatively high, reaching 18MPa; its flexural strength is stable in the whole temperature range, all exceeding 3.5MPa, the flexural strength is 3.6MPa at 110℃×24h, the flexural strength is 3.5MPa at 900℃×24h, the flexural strength is 3.8MPa at 1350℃×24h, and the flexural strength is ≥3.5MPa at 1600℃×24h; its thermal conductivity is also low, with good thermal insulation effect, the thermal conductivity is 0.18W·m at 1100℃ -1 ·K -1 , thermal conductivity 0.23W·m at 1400℃ -1 ·K -1 Its re-burning phase change rate is very low, and its high-temperature volume stability is good. The linear change rate after heat treatment at 1350℃×3h is -0.17%, after heat treatment at 1450℃×3h is -0.20%, and after heat treatment at 1600℃×3h is -0.25%, which can meet the service environment of 1600℃.

[0058] Example 3

[0059] The spinel lightweight castable of the present invention has the following raw material proportions by weight:

[0060] (1) Lightweight aggregate, 60 parts;

[0061] (2) 8 parts of activated alumina powder;

[0062] (3) lightly burned magnesia powder, 6 parts;

[0063] (4) ceramic fiber, 15 parts;

[0064] (5) 4 parts of magnesium aluminum spinel hollow spheres;

[0065] (6) composite binder, 8 parts;

[0066] (7) hardener, 0.8 part;

[0067] (8) Water, 6 parts.

[0068] Furthermore, the lightweight aggregate is one of spinel lightweight aggregate and porous spinel ceramic or a mixture of the two; the lightweight aggregate comprises three particle sizes of 0.2-1 mm, 1-3 mm and 3-5 mm, and the three particle sizes are proportioned in a ratio of 1:2:4; the particle size of the activated alumina powder is 0.074 mm-0.147 mm; the particle size of the light-burned magnesia powder is 0.074 mm-0.147 mm; the ceramic fiber is a mixture of spinel ceramic fiber and alumina ceramic fiber of equal mass, and its length is 0.1-20 cm; the diameter of the magnesium aluminum spinel hollow sphere is 0.40-1.2 μm; the composite binder is a mixture of water-based silicone resin and complex aluminum magnesium sol powder, and the ingredients of the composite binder meet the requirements of MgO:Al 2 O 3 :SiO 2 The molar ratio is 4:5:2; the hardener is polyamide.

[0069] Preparation method: After vigorously mixing lightweight aggregate, activated alumina powder, light-burned magnesia powder, ceramic fiber, and magnesia-alumina spinel hollow balls, add composite binder, hardener and water, stir evenly again, and cast into shape.

[0070] Curing and baking: After curing at room temperature for 48 hours, demould, then bake at 200℃ for 24 hours, and then heat to the service temperature at a heating rate of ≤20℃ / h.

[0071] The room temperature compressive strength of Example 3 is relatively high, reaching 19MPa; its flexural strength is stable in the whole temperature range, all exceeding 3.5MPa, the flexural strength is 3.7MPa at 110℃×24h, the flexural strength is 3.6MPa at 900℃×24h, the flexural strength is 3.9MPa at 1350℃×24h, and the flexural strength is ≥3.6MPa at 1600℃×24h; its thermal conductivity is also low, with good thermal insulation effect, the thermal conductivity is 0.19W·m at 1100℃ -1 ·K -1 , thermal conductivity 0.24W·m at 1400℃ -1 ·K -1 Its re-burning phase change rate is very low, and its high-temperature volume stability is good. The linear change rate after heat treatment at 1350℃×3h is -0.16%, after heat treatment at 1450℃×3h is -0.18%, and after heat treatment at 1600℃×3h is -0.24%, which can meet the service environment of 1600℃.

[0072] Comparative Example 1

[0073] A spinel lightweight castable, comprising MgO:Al in the composite binder described in Example 1 2 O 3 :SiO 2The molar ratio of is adjusted to 2:2:5, the other components and processes remain unchanged, and the preparation method and curing method are the same as those in Example 1. Compared with Example 1, Comparative Example 1 relies on a higher sintering temperature to obtain better strength and denser sintering.

[0074] Comparative Example 2

[0075] A spinel lightweight castable, the composite binder and hardener in Example 1 are replaced with calcium aluminate cement as a binder, the other components remain unchanged, the addition amount of calcium aluminate cement is 5.5 parts by weight, and the preparation method and curing method are the same as those in Example 1. The properties of the prepared castable are shown in Table 1. At 1300°C, obvious linear shrinkage begins to occur, the shrinkage rate becomes significantly larger, and structural collapse occurs at 1600°C, and the performance is lost. It can be seen that the use of calcium aluminate cement as a binder cannot meet the high temperature resistance performance.

[0076] Comparative Example 3

[0077] A spinel lightweight castable, the composite binder and hardener in Example 1 are replaced by complex aluminum-magnesium sol, the other components remain unchanged, the addition amount of complex aluminum-magnesium sol is 5.5 parts by weight, and the preparation method and curing method are the same as those in Example 1. The properties of the prepared castable are shown in Table 1, and it can be seen that under the medium temperature condition of 900°C, the flexural strength decreases significantly, and the flexural strength begins to rise in the high temperature range from 1350°C to 1600°C, but there is still a large gap compared with Example 1. The reduction in flexural strength under such medium temperature conditions may have an adverse effect on the structural stability of the castable. Therefore, the use of complex aluminum-magnesium sol alone as a binder has the problem of low medium temperature strength, and at the same time, it also causes the problem of requiring a higher sintering temperature.

[0078] Table 1 Comparison of castable properties prepared in Examples and Comparative Examples

[0079]

[0080]

Claims

1. A spinel lightweight castable, the raw material ratio is as follows by weight: (1) Lightweight aggregate, 40-80 parts; (2) 3 to 10 parts of activated alumina powder; (3) Lightly burned magnesia powder, 2 to 8 parts; (4) Ceramic fiber, 10-20 parts; (5) 2 to 8 parts of magnesium aluminate spinel hollow spheres; (6) composite binder, 5 to 10 parts; (7) Hardener, 0.5-1 part; (8) Water, 5 to 8 parts.

2. The casting material according to claim 1, characterized in that: The lightweight aggregate is spinel lightweight aggregate, porous spinel ceramic or a mixture of the two. The lightweight aggregate contains powders with three particle sizes of 0.2-1mm, 1-3mm and 3-5mm, and the three particle size powders are mixed in a ratio of 1:1-3:2-5.

3. The casting material according to claim 1, characterized in that: The particle size of the activated alumina powder is 0.074-0.147 mm.

4. The casting material according to claim 1, characterized in that: The particle size of the light-burned magnesia powder is 0.074-0.147 mm.

5. The casting material according to claim 1, characterized in that: The ceramic fiber is spinel ceramic fiber, alumina ceramic fiber or a mixture of the two, and has a length of 0.1 to 20 cm.

6. The casting material according to claim 1, characterized in that: The diameter of the magnesium aluminum spinel hollow sphere is 0.40-1.2 μm.

7. The casting material according to claim 1, characterized in that: The composite binder is a mixture of water-based organic silicon resin and complex aluminum-magnesium sol, and the ingredients of the composite binder satisfy the molar ratio of MgO:Al2O3:SiO2 of 4:5:

2.

8. The casting material according to claim 1, characterized in that: The hardener is polyamide.

9. The method for preparing a casting material according to any one of claims 1 to 8, characterized in that: After vigorously mixing lightweight aggregate, activated alumina powder, light-burned magnesia powder, ceramic fiber, and magnesia-alumina spinel hollow balls, add composite binder, hardener and water, stir evenly again, and pour into shape.

10. The method for curing and baking a castable according to any one of claims 1 to 9, characterized in that: After curing at room temperature for 24 to 48 hours, demoulding is carried out, and after baking at 110 to 200°C for 24 to 48 hours, the temperature is increased to the service temperature at a heating rate of ≤20°C / h to obtain the casting material.

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