Method for preparing refractory brick by using carbon-carbon composite material quitting service in photovoltaic thermal field

Abstract

The invention discloses a method for preparing refractory bricks from carbon fibers recovered from a carbon-carbon composite material quitting service in a photovoltaic thermal field, and relates to the technical field of refractory materials. According to the method, carbon fibers in the carbon-carbon composite material of the photovoltaic thermal field are subjected to cleaning, drying, length control and other treatments, and then refractory raw materials such as kaolin, magnesium oxide and aluminum oxide and binding agents and additives such as phenolic resin are prepared according to a specific proportion. Then, dry-mixing the powder and the carbon fibers, wet-mixing the granules and the binding agent by a horizontal mixer, and finally mixing by a double-shaft paddle mixer to ensure that the materials are uniform; afterwards, a brick press and a steel mold are used for compression molding, drying is conducted through a drying kiln, firing is conducted through an electric furnace, precise temperature and time control is conducted in all stages, and finally polishing finishing and quality detection are conducted. The prepared refractory brick is excellent in performance, has good high temperature resistance, erosion resistance and thermal shock resistance, opens up a new way for reutilization of photovoltaic thermal field wastes, and has remarkable economic and environmental benefits.

Description

Technical Field

[0001] The present application relates to the technical field of refractory materials, and in particular to a method for preparing refractory bricks using a carbon-carbon composite material that uses photovoltaic thermal field exit service. Background Art

[0002] With the rapid development of the photovoltaic industry, carbon-carbon composite materials in photovoltaic thermal fields have been withdrawn from service in large numbers after a certain period of service. If these waste carbon-carbon composite materials are discarded directly, they will not only occupy a large amount of land resources, but also cause potential pollution to the environment due to the non-degradable components such as carbon fibers contained in them. At the same time, as a key material for kiln linings in high-temperature industrial fields such as steel, ceramics, and glass manufacturing, the market demand for refractory bricks continues to rise, and the performance requirements are becoming more and more stringent. The raw materials for the preparation of traditional refractory bricks are facing the dilemma of resource shortages and rising costs. In this context, how to realize the resource utilization of photovoltaic thermal field waste and improve the performance of refractory bricks has become a problem to be solved.

[0003] Therefore, developing a method for preparing refractory bricks by effectively utilizing carbon fibers recycled from carbon-carbon composite materials that have been retired from photovoltaic thermal fields is of great significance for improving resource utilization and reducing production costs. Summary of the invention

[0004] In response to the above technical problems, the present application solves the problem of preparing refractory bricks with excellent performance by recycling and pretreating carbon fibers in carbon-carbon composite materials, mixing them with refractory raw materials, and undergoing processes such as molding, drying, and firing.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted in this application is: a method for preparing refractory bricks using carbon-carbon composite materials that have been withdrawn from photovoltaic thermal fields, comprising the following steps:

[0006] Step 1: Prepare raw materials: Prepare raw materials, carbon fiber, refractory raw materials, binders and additives.

[0007] Step 2: first dry-mix the refractory raw materials and carbon fibers, then wet-mix the binder and the granular materials, and finally final-mix the dry-mixed and wet-mixed materials together.

[0008] Step 3: Use a brick press and steel mold to press the bricks.

[0009] Step 4: Drying using a drying kiln or drying room.

[0010] Step 5: Use high temperature equipment such as electric furnaces and gas furnaces for firing.

[0011] Step 6: Use grinders, grinding wheels and other tools to grind and trim the refractory bricks.

[0012] Preferably, the carbon fibers in step 1 are derived from carbon-carbon composite materials that have been removed from photovoltaic thermal field service and are pre-treated by washing and drying.

[0013] Preferably, the amount of carbon fiber added in step 1 is between 0.2% and 10% of the total amount of the refractory raw material.

[0014] Preferably, the refractory raw materials in step 1 include kaolin, silica, alumina, etc., and the particle size of the powder material is not greater than 0.2 mm, and the particle size of the granular material is 0.3-5 mm.

[0015] Preferably, in step 2, the dry mixing time is 10-30 minutes, the wet mixing time is 10-30 minutes, and the final mixing time is 20-30 minutes.

[0016] Preferably, in step three, the pressing pressure is 50-300 MPa, and the holding time is 5-15 seconds.

[0017] Preferably, in step 4, the drying temperature is 120-180° C. and the drying time is 20-40 hours.

[0018] Preferably, in step five, the mixture is first fired at room temperature for 2-5 hours, then fired at high temperature for 30-35 hours, and finally slowly cooled to room temperature.

[0019] Compared with the prior art, the technical solution provided by this application has the following beneficial effects:

[0020] 1. The present invention innovatively recycles and reuses the carbon fibers in the carbon-carbon composite materials that have been retired from photovoltaic thermal fields, turning waste into treasure, effectively reducing the pollution of waste to the environment, reducing dependence on traditional refractory raw materials, alleviating resource pressure, and conforming to the current environmental protection concept of sustainable development.

[0021] 2. The present invention reasonably mixes refractory raw materials such as kaolin, magnesium oxide, and aluminum oxide, and sinters them in a high-temperature electric furnace through a strict heating and insulation procedure, so that the refractory bricks can be stably used in a high-temperature environment and meet the needs of high-temperature industries such as steel smelting.

[0022] 3. The silicon carbide component of the present invention forms antioxidant whiskers at high temperatures, and the alkaline anti-corrosion environment provided by raw materials such as magnesium oxide can effectively resist the corrosion of slag, melt, etc. on refractory bricks, extend the service life of the kiln lining, and reduce industrial production costs.

[0023] 4. The carbon fiber of the present invention is evenly distributed inside the brick body. With its excellent toughness, it can buffer thermal stress under frequent temperature changes, prevent cracking and peeling of refractory bricks, and ensure continuous and stable operation of the kiln.

[0024] 5. The present invention ensures that each refractory brick has uniform and consistent physical and chemical properties, from the precise screening of raw materials in the preparation stage, the multi-step fine operation of mixing ingredients, to the strict process parameter control of each link of molding, drying and firing, to the post-processing grinding and finishing and comprehensive quality inspection, providing reliable guarantee for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the process flow chart of this application; DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0028] Disassemble and collect carbon fibers from carbon-carbon composite materials that have been retired from photovoltaic thermal fields. These carbon fibers may have impurities such as silicides and carbides, as well as pollutants such as dust, attached to their surfaces during the service of photovoltaic thermal fields, and need to be cleaned. Use a suitable chemical cleaning agent, such as a weak alkaline solution, to soak the carbon fibers under mild stirring conditions for 30-60 minutes, then rinse with clean water until neutral, and then place in a drying oven and dry at 80-120°C for 2-4 hours to remove surface moisture.

[0029] According to the performance requirements of specific refractory bricks, the length of carbon fiber is precisely controlled between 3-50mm by cutting equipment. For example, for refractory bricks that require higher toughness, a fiber length of 10-30mm is preferred. The amount of carbon fiber added is determined according to the final use and performance requirements of the refractory bricks, generally between 0.2%-10% of the total amount of refractory raw materials. If refractory bricks are prepared for high temperature and frequent thermal shock environments, the preferred amount of carbon fiber added is 2%-5%.

[0030] When selecting refractory raw materials, kaolin, silica, alumina, etc. can be selected. The particle size of the powder material is not more than 0.2mm, preferably not more than 0.12mm; the particle size of the granular material is 0.3-5mm, preferably 1-1.2mm. The proportion is based on the specific formula requirements, with magnesium oxide and / or aluminum oxide accounting for 70%-90%, silicon carbide accounting for 1%-4%, graphite accounting for 0.5%-10%, and aluminum accounting for 0.3%-1%.

[0031] Binders include phenolic resin, asphalt, etc., and additives include plasticizers, water reducers, etc. When phenolic resin is used as the binder, it needs to be formulated according to its viscosity and curing characteristics. For different seasons or ambient temperatures, solvents can be added to dilute it appropriately to ensure its fluidity. The amount added is generally between 1% and 8% of the total amount of refractory raw materials. In terms of additives, plasticizers are added in appropriate amounts according to the plasticity of the raw materials. If the mixed material is found to be too dry and difficult to shape, plasticizers can be added at a ratio of 0.1% to 0.5% to improve the processing performance of the material. Water reducers are used to reduce water consumption to avoid drying and cracking of bricks due to excessive moisture. The general addition amount is 0.2% to 0.8%.

[0032] When mixing the raw materials, the refractory raw materials and the carbon fibers are first dry-mixed, and then the binder and the granular materials are wet-mixed, and finally the dry-mixed and wet-mixed materials are finally mixed together.

[0033] Dry mixing is to mix the powder material and refractory fiber without adding liquid. The powder material and refractory fiber are initially evenly dispersed, so that they can contact and combine more fully when mixed with other materials later, laying the foundation for the stability of the final refractory brick performance. In this application, kaolin, silica, alumina and other powder materials are evenly distributed with carbon fiber to avoid the situation where there are too many or too few carbon fibers in some parts.

[0034] During the specific operation, a high-efficiency mixer is used, such as a horizontal mixer, a twin-shaft paddle mixer, etc., and the mixing time is generally 10-30 minutes.

[0035] Wet mixing is to mix the granules and the binder. Through the action of the binder, the granules can be better bonded together to form a material with a certain viscosity and plasticity for subsequent molding operations. In this application, binders such as phenolic resin and asphalt can effectively combine granules with a particle size of 0.3-5 mm and give the material a certain shape retention ability.

[0036] During the specific operation, a high-efficiency mixer is also used, and the mixing time is usually 10-30 minutes.

[0037] Final mixing is to mix the materials obtained by dry mixing and wet mixing again. It ensures that the various components in the mixture are highly evenly dispersed, eliminates possible agglomeration or local component segregation, and makes the performance of the refractory bricks more uniform and stable. In this application, although the materials after dry mixing and wet mixing have achieved a certain degree of uniformity, the two materials need to be further mixed to ensure the quality of the final product.

[0038] During the specific operation, a mixer is used to mix for 20-30 minutes to ensure that the various ingredients are evenly distributed.

[0039] Use a brick press and a steel mold to press the brick blank. Fill the final mixed material evenly into the steel mold and use a brick press to press and form it. The molding pressure is precisely controlled between 50-300MPa according to the specific formula and the size of the brick blank. For example, for refractory bricks with higher density requirements, the molding pressure is close to 300MPa. The holding time is generally 5-15 seconds. During the holding process, the pressure sensor is used to monitor the pressure change in real time to ensure that the pressure is stable to ensure the density of the brick blank. After molding, the brick blank is removed from the mold through the demoulding device, and the brick blank is immediately trimmed to remove defects such as burrs and burrs to make the brick blank have a regular appearance.

[0040] Use a drying kiln or drying room for drying operations, and set up an air curtain at the entrance of the drying kiln to prevent cold air from entering the kiln directly. Depending on the size and moisture content of the bricks, the drying temperature is generally between 120-180°C, and the drying time is generally between 20-40 hours. Install temperature and humidity sensors at different locations in the drying kiln to monitor temperature and humidity changes in real time. Control the drying temperature and humidity to avoid cracking or deformation of the bricks.

[0041] When firing, use an electric furnace as the firing equipment. Before use, check the heating elements and insulation materials of the electric furnace to ensure the normal operation of the equipment. Place the dried bricks neatly in the furnace of the electric furnace and set the heating program. Heat up from room temperature to 150-185℃ at a rate of ≤20℃ / min. This stage is mainly to remove the residual moisture and a small amount of volatiles in the bricks. During the heating process, use a gas analyzer to monitor the changes in the gas composition in the furnace to ensure that the volatiles are discharged smoothly. After reaching the set temperature, keep warm for 2-5 hours to make the internal structure of the bricks initially stable.

[0042] Then the temperature is raised to 1550-1700℃ at a rate of ≤80℃ / min. During this rapid heating process, the shrinkage of the bricks is closely monitored and the size changes of the bricks are monitored by laser displacement sensors. If abnormal shrinkage is found, the heating rate is adjusted in time. After reaching the high temperature range, the temperature is kept between 1550-1700℃ for 30-35 hours. This is the key firing stage, which allows the raw materials to fully react, form a stable ceramic phase and crystal structure, and improve the performance of refractory bricks.

[0043] After firing, slowly cool down to room temperature in the furnace at a speed of ≤350℃ / min, using a combination of air cooling and natural cooling of the furnace body. In the early stage of cooling, appropriately increase the air cooling intensity, and gradually reduce the air cooling as the temperature drops. Use the temperature controller to accurately adjust the cooling speed to avoid cracks in the bricks due to too fast cooling, and ensure the quality of the refractory bricks.

[0044] After being made, the surface of the refractory brick is polished with a grinder. According to the purpose and precision requirements of the brick, the appropriate grinding wheel size is selected. For example, for refractory bricks with high surface flatness requirements, 80-120 mesh grinding wheels are selected. During the grinding process, the feed speed of the grinder is controlled at 5-10mm / min to ensure a smooth surface and remove defects such as surface crusts and bulges generated during the firing process. At the same time, the edge of the brick is trimmed with a grinding wheel to make it sharp and accurate in size.

[0045] It is also necessary to align the quality inspection. First, the appearance quality inspection is carried out. The surface flatness, color uniformity, and dimensional deviation of the refractory bricks are checked by combining visual and measuring tools. The surface flatness error is controlled within ±0.5mm, and the dimensional deviation meets the corresponding national standards. Then the physical performance test is carried out. The compressive strength of the refractory bricks is measured using a universal material testing machine, and the compressive strength is required to be no less than the design standard value; the thermal expansion coefficient is measured by a thermal expansion meter to determine its dimensional stability at high temperatures; the thermal conductivity is measured using a thermal conductivity meter to ensure that the use requirements are met. Only refractory bricks that meet various test indicators can enter the market.

[0046] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing refractory bricks using carbon-carbon composite materials that have been withdrawn from photovoltaic thermal fields, characterized in that The following steps are involved: Step 1: Prepare raw materials: Prepare raw materials, carbon fiber, refractory raw materials, binders and additives; Step 2: first dry-mix the refractory raw material and the carbon fiber, then wet-mix the binder and the granular material, and finally final-mix the dry-mixed and wet-mixed materials together; Step 3: Use a brick press and steel mold to press the brick embryo; Step 4: Drying in a drying kiln or drying room; Step 5: Use high temperature equipment such as electric furnace and gas furnace for firing; Step 6: Use grinders, grinding wheels and other tools to grind and trim the refractory bricks.

2. The method for preparing refractory bricks using carbon-carbon composite materials that have been withdrawn from photovoltaic thermal fields according to claim 1, characterized in that: The carbon fibers in step 1 are derived from carbon-carbon composite materials that have been removed from photovoltaic thermal field services and are pre-treated by washing and drying.

3. The method for preparing refractory bricks using carbon-carbon composite materials that have been withdrawn from photovoltaic thermal fields according to claim 1, characterized in that: In the step 1, the amount of carbon fiber added is between 0.2% and 10% of the total amount of the refractory raw material.

4. The method for preparing refractory bricks using carbon-carbon composite materials that have been decommissioned from a photovoltaic thermal field according to claim 1, characterized in that: In the step 1, the refractory raw materials include kaolin, silica, alumina, etc., and the particle size of the powder material is not greater than 0.2 mm, and the particle size of the granular material is 0.3-5 mm.

5. The method for preparing refractory bricks using carbon-carbon composite materials that have been withdrawn from photovoltaic thermal field service according to claim 1, characterized in that: In the step 2, the dry mixing time is 10-30 minutes, the wet mixing time is 10-30 minutes, and the final mixing time is 20-30 minutes.

6. The method for preparing refractory bricks using carbon-carbon composite materials that have been decommissioned from a photovoltaic thermal field according to claim 1, characterized in that: In the step 3, the pressing pressure is 50-300 MPa, and the holding time is 5-15 seconds.

7. The method for preparing refractory bricks using carbon-carbon composite materials that have been decommissioned from a photovoltaic thermal field according to claim 1, characterized in that: In the step 4, the drying temperature is 120-180° C. and the drying time is 20-40 hours.

8. The method for preparing refractory bricks using carbon-carbon composite materials that have been decommissioned from a photovoltaic thermal field according to claim 1, characterized in that: In the step 5, the mixture is first fired at room temperature for 2-5 hours, then fired at high temperature for 30-35 hours, and finally slowly cooled to room temperature.

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