A semi-lightweight alumina-based mullite homogenized castable and a preparation method thereof

Abstract

The application discloses a semi-lightweight bauxite-based mullite homogeneous material castable and a preparation method thereof. The castable is composed of raw materials, including a closed-pore bauxite-based mullite material, a bauxite-based mullite homogeneous material, 200-mesh 80 bauxite clinker, 92 silica fume, coke bauxite powder, active alumina powder and pure calcium aluminate cement, and at least one of the following is additionally added: an anti-explosion fiber, sodium tripolyphosphate and sodium hexametaphosphate. The various raw materials and additives are uniformly premixed, stirred with water, and then cast, demolded, maintained, dried and fired. After cooling to room temperature, the finished semi-lightweight bauxite-based mullite homogeneous material castable is obtained. Compared with traditional castables, the product can reduce the bulk density of the castable and the load of high-temperature equipment, and has obvious heat insulation effect and can reduce energy consumption.

Description

I. TECHNICAL FIELD

[0001] The present application relates to a semi-lightweight refractory material, in particular to a semi-lightweight alumina-based mullite homogeneous castable and a preparation method thereof. II. BACKGROUND

[0002] The global green and low-carbon development trend has become a trend. For high-temperature industries, energy saving and consumption reduction will be one of the effective ways to achieve this goal. The traditional lightweight refractory material has poor use effect due to its large and many through pores and low strength, while the lightweight alumina-based mullite homogeneous material not only can improve the utilization rate and added value of low-grade bauxite ore or tailings, but also can prepare high-strength and low-conductivity refractory raw materials with stable performance, uniform composition and structure by designing lightweight and porous medium mullite homogeneous aggregate, which can replace traditional high-alumina clinker and be applied in shaped and unshaped refractory materials, so as to effectively achieve the purpose of energy saving and consumption reduction.

[0003] At present, the heat insulation layer of high-temperature kiln equipment is mostly lightweight refractory material, and the working lining is mostly heavy refractory material, which has poor integrity, especially the combined part of the composite layer, which is prone to cracking. Research has shown that the closer to the working environment, the more significant the heat preservation and insulation effect. However, due to the influence of the strength of the traditional lightweight heat-insulating refractory material, it cannot be used for working lining, and the heavy refractory material has high thermal conductivity and poor heat insulation effect. Therefore, a refractory material with simple construction, good integrity and heat insulation, and meeting the working condition requirements of working lining is urgently needed, so the semi-lightweight alumina-based mullite homogeneous castable is developed. III. SUMMARY

[0004] The technical problem to be solved by the present application is that according to the development status and existing problems of the refractory material for high-temperature kiln, the present application provides a semi-lightweight alumina-based mullite homogeneous castable and a preparation method thereof. The refractory castable prepared by the technical scheme of the present application can not only be used in the heat insulation layer, but also be directly used in the working lining, and is suitable for the positions of the three times air pipe, kiln head cover and grate cooler of the cement rotary kiln, and the positions of the ladle cover and tundish permanent lining in the metallurgical industry.

[0005] In order to solve the above problems, the technical scheme adopted by the present application is:

[0006] The application provides a semi-lightweight bauxite-based mullite homogeneous material castable, which is composed of 8-18% of 5-8mm closed bauxite-based mullite material, 6-12% of 3-5mm closed bauxite-based mullite material, 11-15% of 1-3mm closed bauxite-based mullite material, 16-19% of 0-1mm closed bauxite-based mullite material, 0-7% of 5-8mm bauxite-based mullite homogeneous material, 0-6% of 3-5mm bauxite-based mullite homogeneous material, 0-4% of 1-3mm bauxite-based mullite homogeneous material, 0-6% of 0-1mm bauxite-based mullite homogeneous material, 9% of 200-mesh 80 bauxite clinker, 5% of 92 silica flour, 10% of coke bauxite powder, 5% of active alumina powder and 7% of pure calcium aluminate cement, and an additive accounting for 0.1-0.3% of the total mass of the raw materials.

[0007] According to the semi-lightweight bauxite-based mullite homogeneous material castable, the closed bauxite-based mullite material has a volume density of 2.35±0.5g / cm 3 , a water absorption of 7.0±1.0%, an apparent porosity of 16.5±1.0%, a true density of 3.1±0.5g / cm 3 , and an average pore size of ≤100μm.

[0008] According to the semi-lightweight bauxite-based mullite homogeneous material castable, the closed bauxite-based mullite material has an Al2O3 mass percentage of ≥60%, an Fe2O3 mass percentage of ≤2.5%, and a mullite phase content of ≥90%.

[0009] According to the semi-lightweight bauxite-based mullite homogeneous material castable, the bauxite-based mullite homogeneous material has an Al2O3 mass percentage of ≥60%, an Fe2O3 mass percentage of ≤2.5%, a volume density of ≥2.67g / cm 3 , and a water absorption of ≤2.5%.

[0010] According to the semi-lightweight bauxite-based mullite homogeneous material castable, the 80 bauxite clinker has an Al2O3 mass percentage of ≥80%, an Fe2O3 mass percentage of ≤2.5%, a loss on ignition of ≤0.2%, and a 200-mesh screening rate of ≥90%; the 92 silica flour has an SiO2 mass percentage of ≥92%, an Fe2O3 mass percentage of ≤2.0%, and a loss on ignition of ≤3.0%; the coke bauxite powder has an Al2O3 mass percentage of 45%≤45%≤50%, an Fe2O3 mass percentage of ≤3.0%, and a 325-mesh screening rate of ≥90%; the active alumina powder has an Al2O3 mass percentage of ≥99% and a D50 of ≤3μm; and the pure calcium aluminate cement has an Al2O3 mass percentage of 50%≤50%≤60% and a 325-mesh screening rate of ≥80%.

[0011] According to the semi-lightweight alumina-based mullite homogeneous material castable described above, the additive agent is at least one of anti-explosion fiber, sodium tripolyphosphate and sodium hexametaphosphate.

[0012] In addition, a preparation method of the semi-lightweight alumina-based mullite homogeneous material castable is provided, and the preparation method comprises the following steps:

[0013] a. Various raw materials and additive agents are weighed according to the proportioning ratio of the castable described above;

[0014] b. The weighed various raw materials and additive agents are premixed, and a mixture is obtained after uniform mixing;

[0015] c. Water accounting for 7-9% of the total weight of the raw materials is added to the obtained mixture for mixing and stirring until uniform;

[0016] d. The mixture uniformly stirred with water is cast in a mold, and after hardening and demolding, the product is naturally cured for 24 hours;

[0017] e. The product after natural curing is dried in an oven at 110°C for 24 hours;

[0018] f. The product obtained after drying is fired, and after cooling to room temperature, the semi-lightweight alumina-based mullite homogeneous material castable is obtained.

[0019] According to the preparation method of the semi-lightweight alumina-based mullite homogeneous material castable described above, the firing temperature in step f is 1100°C or 1300°C, and the holding time is 3 hours.

[0020] The closed-pore alumina-based mullite material used in the technical solution of the present application is prepared according to the method disclosed in CN 201610839110.6 (CN 106431434 B).

[0021] The alkali resistance crucible of the product obtained after drying is detected according to the method 2 molten alkali crucible method in GB / T 14983-2008.

[0022] In the technical solution of the present application, after the product is fired and cooled to room temperature, the finished product is detected for bending and compressive strength, and the thermal conductivity index is measured when heated to 850°C.

[0023] The positive beneficial effects of the present application are:

[0024] 1. The refractory castable prepared by the technical scheme of the present application can not only be used in the heat insulation layer, but also can be directly used for the working lining, and is suitable for the positions of the three-time air pipe, the kiln head cover and the grate cooler of the cement rotary kiln, and the positions of the ladle cover, the tundish permanent lining and the like in the metallurgical industry. Compared with the traditional castable, the semi-lightweight castable prepared by the present application is optimized from using the traditional high alumina bauxite clinker to using the closed pore bauxite-based mullite material, on the one hand, the bulk density of the castable is reduced, and the load of the high-temperature equipment in the building material industry and the metallurgical industry can be reduced by at least 7%, on the other hand, the heat preservation and heat insulation effect is obvious, and the present application has been applied to the metallurgical industry, the building material industry, the hazardous waste industry and the like, and the temperature of the outer shell of the high-temperature equipment is reduced by at least 30 DEG C, so that the energy consumption and the carbon emission are reduced, and the high-temperature industry is helped to save energy and reduce emission.

[0025] 2. The refractory castable prepared by the technical scheme of the present application is simple to construct, and can replace the working lining and the heat insulation lining of the high-temperature kiln and furnace, and has good overall stability, and the cracking and delamination phenomenon in the traditional composite layer construction mode is avoided.

[0026] 3. In the technical scheme of the present application, the main material is the bauxite-based homogeneous material, the main crystal phase of the aggregate is mullite phase, the content of the mullite phase is greater than 90%, the high-temperature thermal strength is high, the chemical composition and the phase structure are uniform, the quality fluctuation is small, the performance is stable, and the service life is long, and the service cycle of the high-temperature equipment can be prolonged.

[0027] 4. The present application and the traditional scheme taking high alumina clinker as the main aggregate are compared in terms of alkali resistance, and the experimental results show that the closed pore bauxite-based mullite material used in the present application has higher content of silicon oxide than the high alumina clinker, and the high-temperature liquid phase generated at high temperature can block the pores of the sample and prevent the penetration of the alkaline oxide. Therefore, the semi-lightweight castable prepared by the technical scheme of the present application has obvious advantages in alkali resistance. Four, brief description of the drawings:

[0028] Figure 1 It is the appearance comparison diagram of the alkali resistance crucible of the high alumina clinker castable and the semi-lightweight bauxite-based mullite castable prepared by the embodiment 1 of the present application.

[0029] Figure 2 It is the section comparison diagram of the alkali resistance crucible of the high alumina clinker castable and the semi-lightweight bauxite-based mullite castable prepared by the embodiment 1 of the present application.

[0030] In the figure, the A sample is the traditional castable scheme crucible taking high alumina bauxite clinker as the main aggregate, and the B sample is the semi-lightweight castable crucible of the present application taking the closed pore bauxite-based mullite material as the main aggregate. Five, specific implementation mode:

[0031] The present application is further described below in combination with the embodiments, but does not limit the scope of the technical scheme protected by the present application.

[0032] The bulk density of the closed pore bauxite-based mullite material used in the following examples is 2.35±0.5 g / cm 3 , the water absorption is 7.0±1.0%, the apparent porosity is 16.5±1.0%, the true density is 3.1±0.5 g / cm 3 , and the average pore size is ≤100 μm; the closed pore bauxite-based mullite material has an Al2O3 mass percentage ≥60%, a Fe2O3 mass percentage ≤2.5%, and a mullite phase content ≥90%. The bauxite-based mullite homogenized material has an Al2O3 mass percentage ≥60%, a Fe2O3 mass percentage ≤2.5%, a bulk density ≥2.67 g / cm 3 , and a water absorption ≤2.5%. The 80 bauxite clinker has an Al2O3 mass percentage ≥80%, a Fe2O3 mass percentage ≤2.5%, a loss on ignition ≤0.2%, and a 200 mesh sieve passing rate ≥90%; the 92 silica ash has an SiO2 mass percentage ≥92%, a Fe2O3 mass percentage ≤2.0%, and a loss on ignition ≤3.0%; the calcined bauxite powder has an Al2O3 mass percentage 45%≤Al2O3 mass percentage ≤50%, a Fe2O3 mass percentage ≤3.0%, and a 325 mesh sieve passing rate ≥90%; the active alumina micropowder has an Al2O3 mass percentage ≥99%, and a D50 ≤3 μm; and the pure calcium aluminate cement has an Al2O3 mass percentage 50%≤Al2O3 mass percentage ≤60%, and a 325 mesh sieve passing rate ≥80%.

[0033] Example 1:

[0034] The semi-lightweight bauxite-based mullite homogenized material castable according to the present application has a raw material composition consisting of, in mass percentage, 18% of the closed pore bauxite-based mullite material of 5-8 mm, 12% of the closed pore bauxite-based mullite material of 3-5 mm, 15% of the closed pore bauxite-based mullite material of 1-3 mm, 19% of the closed pore bauxite-based mullite material of 0-1 mm, 9% of the 80 bauxite clinker of 200 mesh, 5% of the 92 silica ash, 10% of the calcined bauxite powder, 5% of the active alumina micropowder, and 7% of the pure calcium aluminate cement, and additionally, 0.2% of the additive (consisting of 0.1% of sodium tripolyphosphate and 0.1% of sodium hexametaphosphate) based on the total mass of the various raw materials.

[0035] Example 2:

[0036] The semi-lightweight bauxite-based mullite homogeneous material castable according to the present application is prepared by using the following raw materials in percentage by mass: 8% of 5-8mm closed bauxite-based mullite material, 6% of 3-5mm closed bauxite-based mullite material, 11% of 1-3mm closed bauxite-based mullite material, 16% of 0-1mm closed bauxite-based mullite material, 7% of 5-8mm bauxite-based mullite homogeneous material, 6% of 3-5mm bauxite-based mullite homogeneous material, 4% of 1-3mm bauxite-based mullite homogeneous material, 6% of 0-1mm bauxite-based mullite homogeneous material, 9% of 200-mesh 80 bauxite clinker, 5% of 92 silica flour, 10% of coke bauxite powder, 5% of active alumina powder, and 7% of pure calcium aluminate cement, and 0.1% of the admixture (sodium tripolyphosphate) accounting for the total mass of the raw materials.

[0037] Example 3:

[0038] The semi-lightweight bauxite-based mullite homogeneous material castable according to the present application is prepared by using the following raw materials in percentage by mass: 8% of 5-8mm closed bauxite-based mullite material, 6% of 3-5mm closed bauxite-based mullite material, 11% of 1-3mm closed bauxite-based mullite material, 16% of 0-1mm closed bauxite-based mullite material, 7% of 5-8mm bauxite-based mullite homogeneous material, 6% of 3-5mm bauxite-based mullite homogeneous material, 4% of 1-3mm bauxite-based mullite homogeneous material, 6% of 0-1mm bauxite-based mullite homogeneous material, 9% of 200-mesh 80 bauxite clinker, 5% of 92 silica flour, 10% of coke bauxite powder, 5% of active alumina powder, and 7% of pure calcium aluminate cement, and 0.1% of the admixture (sodium tripolyphosphate) accounting for the total mass of the raw materials.

[0039] The preparation method of the semi-lightweight bauxite-based mullite homogeneous material castable according to the present application is as follows:

[0040] a. The raw materials and the admixture are weighed according to the proportioning ratio of the castable according to any one of Examples 1-3;

[0041] b. The weighed raw materials and the admixture are premixed to obtain a mixture;

[0042] c. The obtained mixture is mixed and stirred with 8% of water accounting for the total weight of the raw materials;

[0043] d. The mixture stirred with water is cast in a mold, and after hardening and demolding, it is naturally cured for 24h;

[0044] e. The product after natural curing is dried in an oven at 110℃ for 24h;

[0045] f、dry the product obtained after, the firing temperature is 1100 DEG C, the holding time is 3h, after firing, cooling to room temperature, get product semi-lightweight alumina-based mullite homogeneous material castable.

[0046] In the technical scheme of the present application, the product is cooled to room temperature after firing, and the bending and compressive strength of the finished product is detected, and the thermal conductivity index is measured when heated to 850 DEG C. The relevant performance detection data of the semi-lightweight alumina-based mullite homogeneous material castable prepared by examples 1-3 of the present application are shown in tables 1-3.

[0047] Table 1 related performance detection data of the castable prepared by example 1 of the present application

[0048]

[0049] Table 2 related performance detection data of the castable prepared by example 2 of the present application

[0050]

[0051] Table 3 related performance detection data of the castable prepared by example 3 of the present application

[0052]

[0053] As can be seen from tables 1-3, with the increase of the amount of closed pore alumina-based mullite material, the volume density and thermal conductivity of the castable sample after different temperature treatment are significantly reduced, the physical strength is equivalent, and the alkali resistance of the castable prepared by example 1 is compared with the traditional castable scheme using high alumina bauxite clinker as the main aggregate. Figure 1 and Figure 2 As can be seen from the appearance and cross-sectional view of the alkali-resistant crucible, the sample A in the figure is the traditional castable scheme using high alumina bauxite clinker as the main aggregate, and the sample B in the figure is the semi-lightweight castable crucible using closed pore alumina-based mullite material as the main aggregate. As can be seen from the comparison, the castable prepared by the present application has first-class alkali resistance, and the crucible does not appear alkali cracking, and the penetration area of alkaline oxides is small, while the traditional castable scheme crucible has serious alkali cracking, and the penetration area of alkaline oxides is large. Therefore, the semi-lightweight castable of the present application has excellent alkali resistance.

[0054] At present, the semi-lightweight castable prepared by the present application has been used in the field of domestic cement rotary kiln head cover, and after use, the shell temperature is reduced by about 30 DEG C, and it can still operate normally after more than one and a half years, and the heat preservation and insulation effect is remarkable.

Claims

1. A semi-lightweight bauxite-based mullite homogenized castable, characterized by: The castable is composed of 8-18% of 5-8mm closed pore bauxite-based mullite material, 6-12% of 3-5mm closed pore bauxite-based mullite material, 11-15% of 1-3mm closed pore bauxite-based mullite material, 16-19% of 0-1mm closed pore bauxite-based mullite material, 0-7% of 5-8mm bauxite-based mullite homogenate, 0-6% of 3-5mm bauxite-based mullite homogenate, 0-4% of 1-3mm bauxite-based mullite homogenate, 0-6% of 0-1mm bauxite-based mullite homogenate, 9% of 200 mesh 80 bauxite clinker, 5% of 92 silica flour, 10% of coke bauxite powder, 5% of active alumina powder and 7% of pure calcium aluminate cement, and 0.1-0.3% of an additive is additionally added to the total mass of the raw materials; The bulk density of the closed-pore bauxite-based mullite material is 2.35±0.5 g / cm 3 , the water absorption is 7.0±1.0%, the apparent porosity is 16.5±1.0%, the true density is 3.1±0.5 g / cm 3 , and the average pore size of the pores is ≤100 μm; The Al2O3 content of the closed pore bauxite-based mullite material is ≥60%, the Fe2O3 content is ≤2.5%, and the mullite phase content is ≥90%; The additive is at least one of explosion-proof fiber, sodium tripolyphosphate and sodium hexametaphosphate.

2. The semi-lightweight alumina-based mullite homogenized castable according to claim 1, characterized by: The alumina-based mullite homogeneous material has a mass percentage of Al2O3 of ≥60%, a mass percentage of Fe2O3 of ≤2.5%, a volume density of ≥2.67 g / cm 3 , and a water absorption of ≤2.5%.

3. The semi-lightweight alumina-based mullite homogenized castable according to claim 1, characterized by: The Al2O3 content of the 80 bauxite clinker is ≥80%, the Fe2O3 content is ≤2.5%, the loss on ignition is ≤0.2%, and the 200 mesh screening rate is ≥90%; the SiO2 content of the 92 silica flour is ≥92%, the Fe2O3 content is ≤2.0%, and the loss on ignition is ≤3.0%; the Al2O3 content of the coke bauxite powder is 45%-50%, the Fe2O3 content is ≤3.0%, and the 325 mesh screening rate is ≥90%; the Al2O3 content of the active alumina powder is ≥99%, and the D50 is ≤3μm; and the Al2O3 content of the pure calcium aluminate cement is 50%-60%, and the 325 mesh screening rate is ≥80%.

4. A process for the preparation of semi-lightweight bauxite based mullite homogenized castable characterized by, The preparation method comprises the following steps: a. weighing the raw materials and the additive according to the proportion of the castable of claim 1; b. pre-mixing the weighed raw materials and the additive to obtain a mixture; c. adding 7-9% of water to the mixture and mixing and stirring until uniform; d. casting the mixture in a mold, hardening and demolding, and then naturally curing for 24h; e. drying the product after natural curing in an oven at 110℃ for 24h; f. firing the dried product, cooling to room temperature, and obtaining the product, i.e. semi-lightweight bauxite-based mullite homogenate castable.

5. The process for the preparation of semi-lightweight alumina-based mullite homogenized castable according to claim 4, characterized in that: In step f, the firing temperature is 1100℃ or 1300℃, and the holding time is 3h.

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