A method for producing silicon carbide from silicon carbide smelting dross

Abstract

The application provides a method for preparing silicon carbide by smelting silicon carbide scraps, which comprises the following steps of: configuring reaction materials; loading the furnace; sending power for smelting; discharging the furnace and the like, wherein the loading method of the furnace is as follows: in the silicon carbide smelting furnace, the furnace load is divided into new materials, silicon carbide scraps and heat preservation materials; the heat preservation materials are distributed around the furnace, and are respectively 1m-1.4m away from the bottom of the smelting furnace and the wall of the smelting furnace; the silicon carbide scraps are arranged below the furnace body and in the region 1m-2m higher than the heat preservation materials at the bottom of the furnace and 1m-2m away from the top of the furnace core; and the rest of the furnace body is distributed with the new materials. Through the distribution process design of the silicon carbide scraps, the silicon carbide scraps are reused for smelting, and the effect of resource utilization of waste is achieved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide preparation technology, and is a silicon carbide smelting method, particularly a method for preparing silicon carbide using silicon carbide smelting waste. Background Technology

[0002] Silicon carbide waste is a mixture of low-melting-point impurities and substances such as silicon carbide, calcium oxide, and graphite discharged from the high-temperature reaction zone in the middle of the furnace during the silicon carbide smelting process.

[0003] The difference between waste material and insulation material is that waste material is formed in the area between the reaction zone and the insulation material zone of the silicon carbide smelting furnace. Waste material contains more impurities and has a more complex composition.

[0004] During the smelting process, due to the high temperature and pressure in the reaction zone of the furnace, impurities in the reactants, especially metallic impurities, vaporize and are emitted towards the periphery of the furnace core under high temperature and pressure. When the impurity gas is about to reach the insulation material area, the temperature drops, causing impurities to accumulate in the transition zone between the reactants and insulation material. This area of ​​reactants is called waste material. During the silicon carbide smelting process, the impurities discharged during the slag removal process are basically accumulated in the waste material, resulting in a high impurity content in the waste material. The silicon carbide reactants in the waste material area are not fully reacted, leading to an unstable silicon carbide ratio, making it impossible to recover and use as reactants for silicon carbide smelting. On the other hand, since the silicon carbide smelting furnace is built of refractory bricks, fragments of refractory bricks fall into the waste material, and since the furnace walls are made of steel, rust from the furnace walls also falls into the waste material. In addition, when silicon carbide is tapped from the furnace, the graphite in the furnace inevitably contaminates the waste material and silicon carbide, making the waste material unusable and unable to be returned to the furnace for further smelting.

[0005] In addition, carbon and silicon-based materials are calcined at high temperatures in a smelting furnace. The temperature in the area where the waste material is located is relatively lower than that in the furnace core, but it is still in a high-temperature environment. After the carbonaceous raw materials in this area are calcined at high temperatures, they become carbon materials, which causes the carbonaceous raw materials to become conductive. This causes changes in the structure, physical properties, and chemical properties of the waste material and silicon carbide.

[0006] The aforementioned reasons result in a complex composition of impurities in the waste material, making it highly conductive. If used as insulation material, it could potentially burn out the furnace walls during the smelting process. This portion of the waste material cannot be directly used as reactant; if it is directly recycled back into the furnace, it will cause flame propagation. Therefore, the conventional method for disposing of silicon carbide reaction waste material is to pile it up in a waste warehouse, which not only occupies space but also wastes resources.

[0007] Therefore, it is necessary to develop a method for smelting silicon carbide using waste materials. Summary of the Invention

[0008] To address the problem of unusable waste materials and resulting resource waste, this application proposes a method for preparing silicon carbide from silicon carbide smelting waste materials. Through material proportioning, waste material charging distribution, and power supply process design, this application achieves the recycling of waste materials for silicon carbide smelting, realizing the resource utilization of waste. This application is specifically implemented through the following technical solution.

[0009] A method for preparing silicon carbide using silicon carbide smelting waste includes: preparing reactants, charging a furnace, smelting by electric current, and unloading from the furnace; wherein, the charging step specifically includes: in the silicon carbide smelting furnace, the furnace charge is divided into: virgin material, waste material, insulating material, and core material; the insulating material is distributed around the perimeter of the silicon carbide smelting furnace, with a thickness of 1m to 1.4m at the bottom and sides, and a thickness of 0.4m to 0.6m at the top; the waste material is distributed in the area below the core material in the smelting furnace, 1m to 2m above the upper edge of the insulating material at the bottom, and in the area 1m to 2m above the core material in the smelting furnace; the core material is distributed in the axial center of the smelting furnace, and the remaining areas in the smelting furnace are distributed with virgin material.

[0010] In this application, waste material is added to the furnace charge as reactant. However, this waste material contains metallic impurities and conductive carbon. If the waste material is arranged arbitrarily, it may be too close to the furnace wall. The conductive components in the waste material can cause the furnace wall to become conductive and burn out. If the waste material is too close to the furnace core, the conductive components in the waste material may also cause sparking. Because silicon carbide smelting furnaces have a narrow horizontal distance and a high vertical height, the waste material is only suitable for arrangement in the vertical direction to avoid sparking due to the waste material being too close to the furnace core, and also to avoid the furnace wall being too close, which could lead to the furnace wall burning out.

[0011] Compared to the conventional silicon carbide smelting furnace process, the further improvement of this application lies in the reaction preparation step:

[0012] New material preparation: Mix carbonaceous raw materials and silicon raw materials, add water and stir until the carbonaceous raw materials and silicon raw materials are evenly mixed, and the carbon-silicon ratio is 0.67-0.72:1;

[0013] Waste material preparation: Screen waste materials smaller than 50mm, test the waste material composition, and supplement carbonaceous raw materials and / or silicon raw materials according to the waste material composition. Add the supplemented raw materials and waste materials to water and mix them evenly so that the carbon-silicon ratio in the waste material is 0.67 to 0.72:1.

[0014] Because the composition of the waste material generated in each batch and from each region is not consistent, the composition of the waste material must be tested before it is used to smelt silicon carbide. Based on the test results, a certain amount of carbonaceous or silicon-based raw materials are added to the waste material. Since the impurities in the waste material are mainly metallic, the slag discharged during the smelting process is contained within the slag blocks. After the metallic gaseous impurities liquefy, they adhere to the reactants, resulting in larger waste material blocks containing more impurities. Therefore, when recovering waste material, all blocks larger than 50mm must be screened out.

[0015] Compared with the ordinary silicon carbide smelting furnace process, the further improvement of this application is that the power supply smelting step is as follows: after the furnace loading step is completed, the smelting is carried out for 12 days. During the power supply process, the furnace start-up power is 62% of the rated power. After one day of start-up, the power supply power reaches 80% of the rated power. After stable operation for 11 days, the power supply is stopped and the furnace is allowed to cool naturally.

[0016] Since the waste material is mainly unreacted silicon carbide, running at full load will result in energy waste. After one day of furnace startup, the power supply can reach 80% of the rated power to raise the furnace charge temperature to 2700℃~3000℃. At this temperature, all metal impurities will vaporize. Under high temperature and pressure, the vaporized impurities diffuse outward from the furnace core.

[0017] In this invention, the silicon content of the siliceous raw material is ≥98%; the fixed carbon content of the carbonaceous raw material is >83%, the ash content is 2% to 7%, and the volatile matter is 7% to 9.5%.

[0018] The composition of the waste material is 29%–30% Si and 20%–21% C.

[0019] The siliceous raw material is quartz sand, and the carbonaceous raw material is one or more of anthracite and Taixi coal.

[0020] The key technical effects of this application are:

[0021] 1. In order to solve the problem of unusable waste materials and resource waste caused by existing waste materials, this application proposes a method for preparing silicon carbide from waste materials in silicon carbide smelting. This application realizes the recycling of waste materials for silicon carbide smelting through material proportioning and waste material charging distribution, and achieves the effect of resource utilization of waste.

[0022] 2. This application, through the distribution setting of the furnace charge, arranges the waste material as reactant in the lower and upper parts of the furnace core, avoiding the phenomenon of furnace charge scorching due to the waste material being too close to the furnace core, and also avoiding the phenomenon of furnace wall being burned due to the furnace charge being too close to the furnace wall, thus realizing the safe and reasonable utilization of waste material as reactant.

[0023] 3. Since the composition of the waste material produced in each batch and in each region is not consistent, the composition of the waste material must be tested before using the waste material to smelt silicon carbide. Based on the test results, a certain amount of carbonaceous or siliconaceous raw materials should be added to the waste material to ensure that the carbon-silicon ratio in the waste material is 0.67 to 0.72:1, which meets the material balance ratio for silicon carbide smelting. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the furnace charge distribution in the preparation method of this application;

[0025] Figure 2 This is a schematic diagram of the furnace charge distribution in the preparation method of Comparative Example 7;

[0026] In the diagram: 1. Furnace wall; 2. Insulating material; 3. Furnace core material; 4. New material; 5. Waste material. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] A method for preparing silicon carbide from silicon carbide smelting waste includes:

[0029] Preparation of reactants: For virgin material preparation: Mix carbonaceous and silicon raw materials and add water while stirring until uniformly mixed. The carbon-to-silicon ratio should be 0.67–0.72:1. In the virgin material, the mass ratio of fixed carbon to silicon in the carbonaceous and silicon raw materials is called the carbon-to-silicon ratio. For waste material preparation: Screen waste materials smaller than 50 mm, inspect their composition, and supplement with carbonaceous and / or silicon raw materials according to their composition. Add the supplemented raw materials and waste materials to water and mix evenly until the carbon-to-silicon ratio in the waste material is 0.67–0.72:1. The carbon-to-silicon ratio in the waste material represents the mass ratio of carbon to silicon components. The silicon content of the silicon raw material is ≥98%. The fixed carbon content of the carbonaceous raw material is >83%, ash content is 2%–7%, and volatile matter is 7%–9.5%. The composition of the waste material is Si 29%–30%, C 20%–21%.

[0030] In the following specific embodiments, the furnace is loaded, as follows: Figure 1The silicon carbide smelting furnace has a cross-sectional dimension of 6m wide and 8m high. The furnace charge is divided into: new material 4, spent material 5, insulating material 2, and core material 3. The insulating material 2 is distributed around the furnace wall 1, with a thickness of 1m to 1.4m at the bottom and sides, and 0.4m to 0.6m at the top. The spent material is distributed in the area below the core material, 1m to 2m above the upper edge of the insulating material at the bottom, and in the area 1m to 2m above the core material. The core material is distributed axially in the center of the furnace, with a cross-sectional dimension of 0.32m × 0.32m. The remaining areas of the furnace are filled with new material.

[0031] After the furnace loading process is completed, the furnace is powered on for 12 days. During the power supply, the furnace start-up power is 62% of the rated power. One day after the furnace is started, the power supply reaches 80% of the rated power. After 11 days of stable operation, the power supply is stopped and the furnace is allowed to cool naturally.

[0032] Because silicon carbide smelting furnaces are large, the carbon-silicon ratio in each zone cannot be guaranteed to be constant during each charging and smelting process. Therefore, in actual charging, the carbon-silicon ratio inside the silicon carbide smelting furnace ranges from 0.67 to 0.72:1.

[0033] The present invention will be illustrated below through specific embodiments.

[0034] Example 1

[0035] Preparation of reactants:

[0036] New material preparation: Mix anthracite and quartz sand and add water to stir, so that the carbonaceous and siliceous raw materials are evenly mixed, and the carbon-silicon ratio is 0.67-0.72:1;

[0037] Waste material preparation: Screen waste materials with a particle size of less than 50 mm, and check the waste material composition to be Si 29%~30%, C 20%~21%, and the carbon-silicon ratio of the waste material composition to meet 0.67~0.72:1;

[0038] Furnace charging: In silicon carbide smelting furnaces, the furnace charge is divided into: new charge, waste charge, insulation charge, and furnace core charge;

[0039] The insulation material is distributed around the inside of the silicon carbide smelting furnace, with a thickness of 1m at the bottom and sides and a thickness of 0.4m at the top.

[0040] The waste material is distributed in two areas: one in the area below the furnace core material and 1.3m to 1.7m above the upper edge of the furnace bottom insulation material, and the other in the area 1.3m to 1.7m above the furnace core material.

[0041] The furnace core material is distributed axially at the center of the smelting furnace.

[0042] The remaining areas within the smelting furnace are filled with new materials.

[0043] Powered smelting: After the furnace loading process is completed, the furnace is powered on for 12 days. During the power supply process, the furnace start-up power is 25,000 kW. One day after the furnace is started, the power supply power reaches 32,000 kW. After running stably for 11 days, the power supply is stopped and the furnace is allowed to cool naturally.

[0044] Remove from the oven: After natural cooling, remove from the oven.

[0045] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0046] Example 2

[0047] The only difference between Example 2 and Example 1 is the change in the distribution of the furnace charge during the charging process. Specifically:

[0048] Furnace charging: In a silicon carbide smelting furnace, the furnace charge is divided into: virgin charge, spent charge, insulating charge, and core charge. The insulating charge is distributed around the perimeter of the silicon carbide smelting furnace, with a thickness of 1m at the bottom and sides, and 0.5m at the top. The spent charge is distributed in the area below the core charge and 1-2m above the upper edge of the insulating charge at the bottom of the furnace, and also in the area 1-2m above the core charge. The core charge is distributed along the axial center of the furnace, while the remaining areas are filled with virgin charge.

[0049] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0050] Example 3

[0051] The only difference between Example 3 and Examples 1-2 is the change in the distribution of the furnace charge during the charging process. Specifically:

[0052] Furnace charging: In a silicon carbide smelting furnace, the furnace charge is divided into: virgin charge, spent charge, insulating charge, and core charge. The insulating charge is distributed around the perimeter of the silicon carbide smelting furnace, with a thickness of 1.4m at the bottom and sides, and 0.5m at the top. The spent charge is distributed in the area below the core charge, 1-1.5m above the upper edge of the insulating charge at the bottom, and in the area 1.3-1.7m above the core charge. The core charge is distributed along the axial center of the furnace, while the remaining areas are filled with virgin charge.

[0053] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0054] Example 4

[0055] The only difference between Example 4 and Examples 1-3 is the change in the distribution of the furnace charge during the charging process. Specifically:

[0056] Furnace charging: In a silicon carbide smelting furnace, the furnace charge is divided into: new material, waste material, insulating material, and core material. The insulating material is distributed around the perimeter of the silicon carbide smelting furnace, with a thickness of 1m at the bottom and sides and 0.5m at the top. The waste material is distributed in the area below the core material in the smelting furnace, 1.5-2m above the upper edge of the bottom insulating material, and in the area 1.5-2m above the core material in the smelting furnace. The core material is distributed in the axial center of the smelting furnace, and the new material is distributed in the remaining areas of the smelting furnace.

[0057] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0058] Comparative Example 1

[0059] The difference between this comparative example and Example 1 is that the carbon-to-silicon ratio in the prepared reactants is 0.61–0.67:1. All other aspects are the same as in Example 1.

[0060] Preparation of reactants:

[0061] Waste material preparation: Screen waste materials with a particle size of less than 50 mm, and check the waste material composition to find that Si is 29.5% to 30.5%, C is 18.5% to 19.5%, and the carbon-silicon ratio of the waste material composition is 0.61 to 0.67:1.

[0062] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 1 is that the carbon-to-silicon ratio in the reactant is 0.72–0.75:1. All other aspects are the same as in Example 1.

[0065] Preparation of reactants:

[0066] Waste material preparation: Screen waste materials with a particle size of less than 50 mm, and check the waste material composition to find that Si is 28% to 29%, C is 21% to 22%, and the carbon-silicon ratio of the waste material composition is 0.72 to 0.78:1.

[0067] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0068] Comparative Example 3

[0069] The only difference between Comparative Example 3 and Example 1 is the distribution of the furnace charge, specifically:

[0070] Furnace charging: In silicon carbide smelting furnaces, the furnace charge is divided into: new charge, waste charge, insulation charge, and furnace core charge;

[0071] The insulating material is distributed around the silicon carbide smelting furnace, with a thickness of 1m at the bottom and sides and 0.4m at the top. The waste material is distributed in the area below the furnace core material and above the upper edge of the furnace bottom insulating material, and in the area 2m to 2.5m above the furnace core material. The furnace core material is distributed in the axial center of the smelting furnace, and the remaining areas of the smelting furnace are distributed with new material.

[0072] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0073] Comparative Example 4

[0074] The only difference between Comparative Example 4 and Example 1 is the distribution of the furnace charge, specifically:

[0075] Furnace charging: In a silicon carbide smelting furnace, the furnace charge is divided into: new material, waste material, insulating material, and core material. The insulating material is distributed around the perimeter of the silicon carbide smelting furnace, with a thickness of 1m at the bottom and sides and 0.4m at the top. The waste material is distributed in the area below the core material in the smelting furnace, 1.3m to 1.7m above the upper edge of the bottom insulating material, and in the area 0.5m to 1.0m above the core material in the smelting furnace. The core material is distributed in the axial center of the smelting furnace, and the remaining areas of the smelting furnace are distributed with new material.

[0076] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0077] Comparative Example 5

[0078] The only difference between Comparative Example 5 and Example 1 is the distribution of the furnace charge, specifically:

[0079] Furnace charging: In a silicon carbide smelting furnace, the furnace charge is divided into: new material, waste material, insulating material, and core material. The insulating material is distributed around the perimeter of the silicon carbide smelting furnace, with a thickness of 1m at the bottom and sides and 0.4m at the top. The waste material is distributed in the area below the core material in the smelting furnace, 2m to 2.5m above the upper edge of the bottom insulating material, and in the area 1.3m to 1.7m above the core material in the smelting furnace. The core material is distributed in the axial center of the smelting furnace, and the remaining areas of the smelting furnace are filled with new material.

[0080] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0081] Comparative Example 6

[0082] The only difference between Comparative Example 6 and Example 1 is the distribution of the furnace charge, specifically:

[0083] Furnace charging: In a silicon carbide smelting furnace, the furnace charge is divided into: new material, waste material, insulating material, and core material. The insulating material is distributed around the perimeter of the silicon carbide smelting furnace, with a thickness of 1m at the bottom and sides and 0.4m at the top. The waste material is distributed in the area below the core material in the smelting furnace, 0.5m to 1m above the upper edge of the bottom insulating material, and in the area 1.3m to 1.7m above the core material in the smelting furnace. The core material is distributed in the axial center of the smelting furnace, and the remaining areas of the smelting furnace are filled with new material.

[0084] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0085] Comparative Example 7

[0086] The only difference between Comparative Example 7 and Example 1 is the distribution of the furnace charge. Figure 2 Specifically:

[0087] Furnace charging: In a silicon carbide smelting furnace, the furnace charge is divided into: new charge, waste charge, insulation charge, and core charge. The insulation charge is distributed around the perimeter of the silicon carbide smelting furnace, with a thickness of 1m at the bottom and sides and 0.4m at the top. The waste charge is distributed in the following areas: below the core charge, 1.3m to 1.7m above the upper edge of the bottom insulation charge; 1.3m to 1.7m above the core charge; and 0.8m to 1.3m from the sidewall insulation charge on both sides of the core charge. The core charge is distributed in the axial center of the furnace, and the remaining areas of the furnace are filled with new charge.

[0088] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0089] Comparative Example 8

[0090] The only difference between Comparative Example 8 and Example 1 is the change in the power-smelting process, specifically:

[0091] Powered smelting: After the furnace loading process is completed, the furnace is powered on for 12 days. During the power supply process, the furnace start-up power is 25,000 kW. One day after the furnace is started, the power supply power reaches 28,000 kW. After running stably for 11 days, the power supply is stopped and the furnace is allowed to cool naturally.

[0092] Remove from the oven: After natural cooling, remove from the oven.

[0093] After the furnace is removed from the oven, the products are graded and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0094] Comparative Example 9

[0095] The only difference between Comparative Example 9 and Example 1 is the change in the power-smelting process, specifically:

[0096] Powered smelting: After the furnace loading process is completed, the furnace is powered on for 12 days. During the power supply process, the furnace start-up power is 25,000 kW. One day after the furnace is started, the power supply power reaches 40,000 kW. After running stably for 11 days, the power supply is stopped and the furnace is allowed to cool naturally.

[0097] After the furnace is removed from the oven, the products are graded, and the condition of the furnace core, furnace walls, etc. are checked. See Table 1 for details.

[0098] Table 1. Product grade distribution and smelting furnace conditions obtained from each embodiment.

[0099]

[0100] As can be seen from the above embodiments 1 to 4, this application utilizes waste material to smelt silicon carbide. Through material proportioning and waste material charging distribution, the waste material is recycled for silicon carbide smelting, achieving the effect of waste resource utilization. Furthermore, no furnace wall burning or furnace sparking occurs during the smelting process.

[0101] As can be seen from Example 1 and Comparative Examples 1 to 2 above, only when the silicon carbide ratio in the waste material is between 0.67 and 0.72:1 can the unreacted materials in the waste material be guaranteed to react fully, resulting in a higher first-grade product yield.

[0102] As can be seen from the above Examples 1-4 and Comparative Examples 3-8, abnormal furnace conditions will not occur only in the area below the furnace core material in the silicon carbide smelting furnace, which is 1-2m above the upper edge of the furnace bottom insulation material, and in the area distributed in the smelting furnace 1-2m above the furnace core material, when there is a lack of material.

[0103] In Comparative Example 3, the waste material located above the furnace core was too close to the furnace top, causing the furnace top insulation material and the furnace top to be scorched.

[0104] In Comparative Example 4, the waste material located above the furnace core was too close to the furnace core, causing sparking inside the furnace, which resulted in a serious decline in the quality of silicon carbide products in and around that area.

[0105] In Comparative Example 5, the waste material located below the furnace core was too close to the furnace core, causing sparking inside the furnace, which resulted in a serious decline in the quality of silicon carbide products in and around that area.

[0106] In Comparative Example 6, the furnace charge located below the furnace was too close to the furnace bottom, causing the furnace bottom to be scorched.

[0107] Compared to Example 1, in Comparative Example 7, waste material was placed on both sides of the furnace core as reactant. This caused not only the furnace charge on both sides of the furnace core to experience sparking, but also the furnace wall to be scorched. The reason for the furnace wall scorching and furnace sparking was that the furnace wall was close to the furnace core, which resulted in the waste material being close to both the furnace core and the furnace wall, causing the furnace charge to spark and the furnace wall to be scorched.

[0108] Through Examples 1 and Comparative Examples 9-10, it was found that Example 1 used lower power and consumed less energy compared to normal smelting of fresh furnace charge. Unlike conventional silicon carbide smelting processes that use only quartz sand and anthracite as raw materials, Example 1 fully utilized waste material as reactant in the furnace. Since the main components of waste material are incompletely reacted quartz sand and anthracite, as well as some impurities, Example 1, even with reduced power, did not affect the silicon carbide smelting process compared to using only quartz sand and anthracite as raw materials. Comparative Example 9, with its reduced smelting power, resulted in incomplete reaction of the material, leading to a low first-grade product yield. Comparative Example 10 used normal smelting power, but the difference in first-grade product yield between Example 1 and Example 1 was minimal. Therefore, from an energy-saving perspective, the power-supply smelting process of Example 1 is preferred.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing silicon carbide by smelting silicon carbide waste material, comprising: configuring a reaction material, charging a furnace, electrically smelting, and discharging the furnace; characterized in that the charging step specifically comprises: in a silicon carbide smelting furnace, the charging furnace material is divided into: new material, waste material, heat preservation material, and core material; the heat preservation material is distributed around the inside of the silicon carbide smelting furnace, with a thickness of 1m-1.4m at the bottom and sides, and a thickness of 0.4-0.6m at the top; the waste material is distributed in an area 1m-2m above the heat preservation material at the bottom of the smelting furnace, and an area 1m-2m above the core material in the smelting furnace; the core material is distributed axially in the center of the smelting furnace, the remaining area in the smelting furnace is distributed as new material.

2. The method of claim 1, wherein the method is characterized by: the reaction material step specifically comprises: new material configuration: mix carbonaceous raw material and siliceous raw material and add water to stir, so that the carbon and silicon in the new material are uniformly mixed, with a carbon-silicon ratio of 0.67-0.72:1; waste material configuration: screen waste material below 50mm, test the composition of the waste material, and supplement the configuration of carbonaceous raw material and / or siliceous raw material according to the composition of the waste material, and mix the supplemented raw material and waste material with water to make the carbon-silicon ratio in the waste material 0.67-0.72:

1.

3. The method of preparing silicon carbide from silicon carbide smelter scraps according to claim 1, wherein the electric smelting step specifically comprises, after the charging step is completed, electrically smelting for 12 days, during which the starting power is 62% of the rated power, the power reaches 80% of the rated power after one day of starting, and then runs smoothly for 11 days before stopping the power supply and naturally cooling.

4. The method of preparing silicon carbide from silicon carbide smelting scraps according to claim 1 or 2, wherein: the siliceous raw material has a silicon content of ≥98%; the carbonaceous raw material has a fixed carbon content of >83%, an ash content of 2%-7%, and a volatile content of 7%-9.5%.

5. The method of preparing silicon carbide from silicon carbide smelting scraps according to claim 1 or 2, wherein: the composition of the waste material is Si: 29%-30%, C: 20%-21%.

6. The method of claim 4 wherein the silicon carbide is produced from the silicon carbide smelter scrap. the siliceous raw material is quartz sand, and the carbonaceous raw material is one or more of anthracite and Taixi coal.

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