Method for preparing alumina carbon refractory material

Abstract

The invention discloses a method for preparing an alumina carbon refractory material, and belongs to the field of refractory materials. The preparation method comprises the following steps: 1) mixing Asphcarb asphalt powder and alumina aggregate to obtain mixed powder; (2) mixing the mixed powder, a composite antioxidant and aluminum oxide fine powder, performing extrusion forming, putting a green body into a tablet press, and performing forming under the pressure of 150MPa to obtain a green body; and 3) carrying out microwave heat treatment on the green body to prepare the alumina carbon refractory material. The method is characterized in that Asphcarb asphalt powder in a microwave electromagnetic field is used for absorbing electromagnetic waves so as to perform carbonization and temperature rise, so that the material is integrally heated until asphalt is uniformly distributed in the refractory material to realize bonding between particles and a matrix, and the mechanical property of the refractory material can be effectively promoted and improved; meanwhile, the carbon content is increased, the heat conductivity of the material is remarkably improved, and the thermal shock resistance of the material is improved.

Description

Technical Field

[0001] The invention belongs to the field of refractory materials, and in particular relates to a method for preparing an alumina carbon refractory material. Background Art

[0002] Refractory materials are an important industrial basic material, and are widely used as various high-temperature resistant materials in all industries involving high temperatures, such as metallurgy, glass, cement, petrochemicals, energy and environmental protection. In recent years, the rapid development of industry, especially the development of new high-temperature technologies and new steel smelting technologies, has put forward more stringent requirements for refractory materials. Studies have shown that with the decrease of carbon content (from ~20wt% to ~5wt%), the apparent porosity of aluminum-carbon refractory materials decreases, the bulk density increases, and the flexural strength at room temperature and high temperature is improved. The change in slag erosion resistance is not obvious, but the thermal shock resistance decreases significantly, which promotes the development of refractory materials towards high technology, high performance and even high precision. The high-temperature performance, high-temperature mechanical properties, thermal shock resistance and erosion resistance of materials are improved and optimized through the design of carbon content of materials.

[0003] Microwaves are a type of high-frequency electromagnetic waves that are widely used in industrial and household fields. Microwave sintering is a sintering process in which the microwave electromagnetic field interacts with the material, causing the surface and interior of the sintered material to heat up evenly and quickly at the same time, while other parts (such as the kiln wall) are hardly heated. Microwaves have a unique property, namely, they can penetrate various gases, which makes microwave heating synthesis reactions under atmosphere protection extremely easy. Microwaves can reduce the activation energy required for the reaction. By controlling the sintering temperature, microwave sintering can successfully achieve low-temperature sintering of refractory materials. Microwave sintering can quickly complete the sintering process at a lower temperature (usually lower than the temperature required by traditional methods), usually within a few minutes to a few hours, while traditional sintering methods often take hours or even days. Microwave sintering consumes less energy and is more efficient than traditional sintering methods, which can save energy and shorten production cycles.

[0004] Asphcarb as a petrochemical by-product has the problems of low utilization value and difficult treatment. How to effectively utilize it and enhance its added value has become an urgent problem to be solved.

[0005] At present, the preparation method of refractory materials mainly relies on high-temperature sintering, which has a long high-temperature cycle, low efficiency, high energy consumption, and is prone to produce toxic substances that pollute the environment. Therefore, it is also necessary to explore new sintering methods. Summary of the invention

[0006] The purpose of the present invention is to provide a microwave sintering method for alumina carbon refractory materials, which can achieve uniform mixing and rapid sintering of refractory materials under atmospheric pressure conditions, with a fast heating rate and a short sintering time, thereby solving the problems of uneven mixing of traditional refractory materials, inability to evenly disperse asphalt into the refractory materials, and large energy consumption and long sintering cycle when most refractory materials are fired in high-temperature furnaces, thereby solving the main problems of high consumption and low output in the refractory materials industry from the root.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a microwave sintering method for an alumina carbon refractory material, comprising the following steps: 1) Mixing Asphcarb asphalt powder and alumina aggregate to obtain mixed powder; 2) Mix the mixed powder, composite antioxidant and alumina fine powder and extrude them, then put the green body into a tablet press to obtain a green body. 3) The green body is subjected to microwave heating to prepare an alumina carbon refractory material.

[0008] Preferably, the alumina powder, Asphcarb asphalt powder, metal Al powder and Mg-A1 alloy powder are all micron-sized; Preferably, in step 2), the composite antioxidant is a composite of metal Al powder and Mg-A1 alloy in a mass ratio of 1:1, and the added amount is 0-50% of the total mass of the components.

[0009] Preferably, the extrusion molding pressure in step 2) is 150 MPa, and the holding time is 1 to 3 minutes; Preferably, the frequency of the microwave heating is 918 MHz, and the output power is 25 KW.

[0010] Preferably, the microwave heating conditions in step 3) are: when the temperature is less than or equal to 500°C, the power is increased by 5KW every 5-10 minutes; when the temperature is greater than 600°C, the heating rate is adjusted to reduce the temperature to about 500°C, and this is repeated for 1-2 hours.

[0011] Preferably, the green body is placed in a heat-retaining structure for microwave heating.

[0012] Preferably, after the green body is placed in the heat preservation device, the green body is covered with calcined alumina powder, and the alumina powder is covered with graphite.

[0013] Preferably, the thermal insulation structure is composed of a multi-layer structure, which comprises, from the inside to the outside, an alumina hollow ball layer, a quartz thermal insulation layer, an alumina fiber cotton layer, a mullite sheet layer and an alumina sagger layer.

[0014] Compared with the prior art, the present invention has the following beneficial effects: During microwave sintering of alumina carbon refractory materials, as the temperature rises, the Asphcarb pitch powder in the refractory green body absorbs microwaves and gradually carbonizes and decomposes into colloids, asphaltene and various gases, which evenly penetrate into every corner of the refractory materials. During the decomposition of the Asphcarb pitch powder, gas is discharged at the same time, pushing and promoting the remaining colloids and asphaltene to be distributed in the refractory materials. The adhesion and connection between the particles and the matrix in the refractory materials are achieved; in addition, during the microwave sintering process, the increase in the carbon content in the Asphcarb pitch powder significantly improves the thermal conductivity and oxidation resistance of the material, and improves the thermal shock resistance of the material.

[0015] High-energy electromagnetic waves can significantly accelerate the decomposition of Asphcarb asphalt powder in refractory materials. The CH 4 , CO 2 , CO, H 2 O, aldehydes, etc. will promote the uniform distribution of Asphcarb pitch powder. At the same time, by ensuring that the material is heated quickly and evenly as a whole, we can effectively avoid the energy problem caused by high-temperature heating loss in the ordinary sintering process, and thus prevent the problem of low energy utilization. Microwave sintering focuses more on heating Asphcarb pitch powder to sinter and prepare refractory materials, and emphasizes the importance of uniform distribution of asphalt to avoid potential uneven heating problems. As the sintering temperature increases, the gas generated continues to increase, and the decomposition rate of Asphcarb pitch powder continues to increase. The decomposition rate of Asphcarb pitch powder obtained at 500-600℃ is the largest, which is most suitable for preparing refractory materials. Conventional pressureless sintering is difficult to achieve refractory sintering at this temperature, and the heating rate of conventional pressureless sintering is slower than that of microwave sintering and the energy consumption rate is high. This shows that microwave sintering can not only achieve low-temperature sintering of refractory materials, but also quickly sinter refractory materials. In the case of high carbon content, the thermal shock resistance of alumina carbon is significantly improved. By controlling the decomposition temperature of the Asphcarb pitch powder in the furnace, the thermal shock resistance of the alumina carbon refractory material after sintering can be effectively regulated, so that the Asphcarb pitch powder can be fully decomposed.

[0016] During microwave sintering, particles inside the material can be heated more evenly, resulting in a more uniform grain distribution and a denser structure, avoiding the temperature gradient that usually exists in the heating of the material inside during traditional sintering, thereby avoiding local over- or under-burning. The repeated temperature control process of microwave sintering can promote or inhibit the formation of a part of the phase, making the phase composition of the final product completely different from that of traditional sintering. Microwave sintering can achieve lower porosity because its rapid heating helps reduce gas release and pore formation, thereby improving the density of the material. Traditional methods will produce more pores and structural defects. Because the materials formed by microwave sintering have a more uniform structure and lower porosity, they usually have superior mechanical properties, such as compressive strength and thermal shock resistance.

[0017] Compared with the existing preparation process of alumina carbon refractory materials, the present invention effectively improves the added value of Asphcarb asphalt powder by combining the use of Asphcarb asphalt powder and microwave sintering technology. At the same time, compared with the existing technology, the present invention can significantly reduce processing costs and improve production efficiency, and its microstructure and phase composition are also different from traditional sintering methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the XRD pattern of the asphalt sintered sample; Figure 2 This is the XRD pattern of the sintered sample in Example 1. DETAILED DESCRIPTION

[0019] The present invention provides a microwave sintering method for an alumina carbon refractory material, comprising the following steps: 1) Mix Asphcarb asphalt powder and alumina aggregate in a mass ratio of 1:1 to obtain a mixed powder; 2) The mixed powder is mixed with the composite antioxidant and / or alumina fine powder and then extruded, and then the green body is placed in a tablet press and molded at a pressure of 150 MPa to obtain a green body. 3) The green body is subjected to microwave heating to prepare an alumina carbon refractory material.

[0020] In the present invention, the alumina powder, Asphcarb pitch powder, metal Al powder and Mg-A1 alloy powder are all micron-sized; the mass ratio of alumina powder, Asphcarb pitch powder, metal Al powder and Mg-A1 alloy powder is 4:2:2.

[0021] In the present invention, the composite antioxidant in step 2) is a composite of metal Al powder and Mg-A1 alloy in a mass ratio of 2:2, and the added amount is 0-25% of the mass of the mixed powder, more preferably 10-22%, and more preferably 15-20%.

[0022] In the present invention, the extrusion molding pressure in step 2) is 150 MPa and the holding time is 1 to 3 minutes.

[0023] In the present invention, the frequency of the microwave heating is 918 MHz, and the output power is 25 KW.

[0024] In the present invention, the conditions for microwave heating in step 3) are: When the temperature is less than or equal to 500°C, the power is increased by 5KW every 5-10 minutes; when the temperature is greater than 600°C, the heating rate is adjusted to reduce the temperature to about 500°C, and this is repeated for 1-2 hours. When the temperature is greater than 500°C, the heating rate is adjusted to 10-20°C / min, the temperature is increased to 550-600°C, and the temperature is kept for 60-120 minutes. More preferably, it is 550-590°C.

[0025] In the present invention, the green body is placed in a heat preservation structure and placed together with the heat preservation structure in a microwave resonant cavity for microwave heating. The microwave source is turned on, the input power is intermittently adjusted from low to high, and the reflected power is recorded. The temperature change is recorded above 400°C.

[0026] In the present invention, the heat-insulating structure is composed of multiple layers and is made into a microwave sintering device.

[0027] In the present invention, the microwave resonant cavity can adopt a conventional structure, and the distribution of the position of the magnetron can ensure that the microwave field intensity in the resonant cavity is uniform; an exhaust device and a probe hole for inserting a far-infrared radiation thermometer are provided on the top of the cavity; an infrared thermometer monitors the sample temperature in the resonant cavity in real time, and the measured temperature range is 400-600°C.

[0028] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention. Example 1

[0029] 1) Mix 20 g of alumina aggregate and 20 g of Asphcarb asphalt powder to obtain a mixed powder; 2) Weigh 20g of metal A1 powder and Mg-A1 alloy powder in a mortar, mix 20g of alumina fine powder with the above powder and composite antioxidant, stir evenly, pour into a mold for extrusion molding, the pressing pressure is 70MPa, and the holding time is 2min; 3) Using an isostatic press to press the preformed green body to obtain a disc-shaped green body, the pressing pressure is 150 MPa, and the pressure is maintained for 120 seconds; 4) Place the green body in an insulation structure consisting of a multilayer structure of alumina hollow ball layer, quartz insulation layer, alumina fiber cotton layer, mullite sheet layer and alumina sagger layer from inside to outside, and place it together with the insulation structure in a microwave resonant cavity, turn on the microwave source, and adjust the input power intermittently from low to high, and increase the input power evenly every 10 minutes below 500°C; after the measured temperature is displayed at 500°C, increase the input power according to the heating rate, and maintain the heating rate at 10~20°C / min. When the temperature rises to 550°C, keep the temperature within the range of 550-600°C, and keep it warm for 30 minutes. During the sintering process, record the reflected power and temperature changes, and turn off the microwave source. Example 2

[0030] The microwave heating method for in-situ formation of magnesia-alumina spinel in alumina-carbon refractory material in this embodiment comprises the following steps: 1) 20g of alumina aggregate, 20g of Asphcarb asphalt powder, 20g of metal A1 powder, Mg-A1 alloy powder and composite antioxidant are mixed and stirred uniformly to obtain a mixed powder; 2) After the above powders are stirred evenly, they are poured into a mold for extrusion molding at a pressing pressure of 70 MPa and a holding time of 2 min; 3) Using an isostatic press to press the preformed green body to obtain a disc-shaped green body, the pressing pressure is 150 MPa, and the pressure is maintained for 120 seconds; 4) Place the green body in an insulation structure consisting of a multilayer structure of alumina hollow ball layer, quartz insulation layer, alumina fiber cotton layer, mullite sheet layer and alumina sagger layer from inside to outside, and place it together with the insulation structure in a microwave resonant cavity, turn on the microwave source, and adjust the input power intermittently from low to high, and increase the input power evenly every 10 minutes below 500°C; after the measured temperature is displayed at 500°C, increase the input power according to the heating rate, and maintain the heating rate at 10~20°C / min. When the temperature rises to between 500°C and 600°C, keep it warm for 30 minutes. During the sintering process, record the reflected power and temperature changes, and turn off the microwave source. Example 3

[0031] 1) Mix 15 g of alumina powder and 15 g of Asphcarb asphalt powder to obtain a mixed powder; 2) Weigh 15g of the mixed powder in a mortar, stir 15g of the mixed powder with alumina fine powder, pour it into a mold for extrusion molding, the pressing pressure is 50MPa, and the holding time is 1min; 3) Using an isostatic press to press the preformed green body to obtain a disc-shaped green body, the pressing pressure is 150 MPa, and the pressure is maintained for 90 seconds; 4) Place the green body in an insulation structure consisting of a multilayer structure of alumina hollow ball layer, quartz insulation layer, alumina fiber cotton layer, mullite sheet layer and alumina sagger layer from the inside to the outside, and place it together with the insulation structure in a microwave resonant cavity, turn on the microwave source, and adjust the input power intermittently from low to high. Increase the input power evenly every 5 minutes below 500°C. After the measured temperature is displayed at 500°C, increase the input power according to the heating rate to maintain the heating rate at 10~20°C / min. When the temperature rises to between 500°C and 600°C, keep it warm for 90 minutes. Record the reflected power and temperature changes during the sintering process, and turn off the microwave source. Example 4

[0032] 1) Mix 15 g of alumina powder and 15 g of Asphcarb asphalt powder to obtain a mixed powder; 2) Weigh 20g of the mixed powder in a mortar, mix 20g of alumina fine powder with the above powder, stir evenly, pour into a mold and extrude into shape, the pressing pressure is 80MPa, and the holding time is 3min; 3) Using an isostatic press to press the preformed green body to obtain a disc-shaped green body, the pressing pressure is 300 MPa, and the pressure is maintained for 60 seconds; 4) Place the green body in an insulation structure consisting of a multilayer structure consisting of alumina hollow ball layer, quartz insulation layer, alumina fiber cotton layer, mullite sheet layer and alumina sagger layer from inside to outside, and place it together with the insulation structure in a microwave resonant cavity, turn on the microwave source, and adjust the input power intermittently from low to high. Increase the input power evenly every 5 minutes below 500°C. After the measured temperature is displayed at 500°C, increase the input power according to the heating rate. Keep the heating rate at 10~20°C / min, then increase the input power. When the temperature rises to between 500°C and 600°C, keep it warm for 120 min. Record the reflected power and temperature changes during sintering. Turn off the microwave source.

[0033] Comparative Example 1 Alumina carbon bricks fired at 500℃-600℃ for 12 hours using a tunnel kiln.

[0034] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Flexural performance (Mpa) 10.33 9.67 8.625 7.82 6.86 <![CDATA[Density (kg / m 3 )]]> 2.545 2.515 2.465 2.433 2.58 Apparent porosity (%) 15.86 17.785 18.455 19.32 23.435 Compressive strength (Mpa) 58 55 50 43 30 Table 1 Alumina Carbon Brick Performance Comparison It can be seen from Table 1 that the product of Example 1 has the best comprehensive performance. At the same time, compared with the prior art comparative example 1, the various performances of Examples 1-4 are better than those of Comparative Example 1, especially in terms of apparent porosity. In the technical solution of the present invention, the Asphcarb asphalt powder is heated by microwaves to enable the brick body to obtain a lower apparent porosity. On the other hand, since Examples 1-4 use microwave heating, the overall heating time is greatly shortened compared with traditional tunnel kiln firing, so the processing cost and processing time are also greatly reduced compared with Comparative Example 1.

[0035] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an alumina carbon refractory material, characterized in that: The following steps are involved: 1) Mix Asphcarb asphalt powder and alumina aggregate in a mass ratio of 1:1 to obtain a mixed powder; 2) Mixing the mixed powder with the composite antioxidant and / or alumina fine powder and then extruding the mixture, and then placing the green body into a tablet press to form a green body. 3) The green body is subjected to microwave heating to prepare an alumina carbon refractory material.

2. The method for preparing an alumina carbon refractory material according to claim 1, characterized in that: Step 2) The composite antioxidant is a composite of metal A1 powder and Mg-A1 alloy in a mass ratio of 1:1, and the added amount is 0-50% of the total mass of the components.

3. The method for preparing an alumina carbon refractory material according to claim 1, characterized in that: The aluminum oxide, Asphcarb asphalt powder and composite antioxidant are all micron-sized.

4. The method for preparing an alumina carbon refractory material according to claim 1, characterized in that: Step 2) The extrusion molding pressure is 150 MPa, and the holding time is 1-3 min.

5. The method for preparing an alumina carbon refractory material according to claim 1, characterized in that: The amount of the alumina fine powder added is 0-50% of the total mass of the component.

6. The method for preparing an alumina carbon refractory material according to claim 1, characterized in that: The microwave heating conditions described in step 3) are: frequency 918 MHz, output power 25 KW, when the temperature is less than or equal to 500 ° C, the power is increased by 5 KW every 5-10 minutes; when the temperature is greater than 600 ° C, the heating rate is adjusted to reduce the temperature to 500 ° C, and this is repeated for 1-2 hours.

7. The method for preparing an alumina carbon refractory material according to claim 1, characterized in that: In step 3), the green body is placed in a heat-insulating structure for microwave heating.

8. The method for preparing an alumina carbon refractory material according to claim 7, characterized in that: The heat-insulating structure is composed of a multi-layer structure.

9. The method for preparing alumina carbon refractory material according to claim 7-8, characterized in that: After the green body is placed in the heat preservation device, the green body is covered with calcined alumina powder, and the alumina powder is covered with graphite.

10. The method for preparing an alumina carbon refractory material according to claim 7, characterized in that: The multilayer structure comprises, from the inside to the outside, an alumina hollow ball layer, a quartz heat-insulating layer, an alumina fiber cotton layer, a mullite sheet layer and an alumina sagger layer.

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