Waste material recovery process based on silicon carbide composite material production

Abstract

The invention relates to the technical field of silicon carbide composite material production, in particular to a waste material recovery process based on silicon carbide composite material production. At present, a waste material recovery process for silicon carbide composite material production has the problems of low purity, low separation rate and low recovery rate. The problem is solved by a method for obtaining silicon carbide by finely grinding and crushing the waste material, dipping, stirring and dispersing, and carrying out flotation separation. In the recovery process, the particle size of crushed waste material fragments is 0.12-2.48 microns, and the accumulated content of silicon carbide in the fragments reaches 99.50%; when the content of silicon carbide in a floating material after flotation treatment is 99.30% and the content of superfine silicon powder in a sinking material is 95.90%, the separation effect is optimal, and the purity of silicon carbide is 92.59%; the process technology complexity is low; the recovery concentration of the leaching acid liquor after the waste materials are treated is 99.80%; the recovery rate of the silicon carbide after burning and carbon removal is 99.50%, and the purity is 99.99%.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide composite material production, and specifically to a waste material recycling process based on the production of silicon carbide composite materials. Background Art

[0002] Currently, industrial silicon carbide is produced using raw materials such as pure silica sand and fine carbon like petroleum coke within the electric furnace temperature range of 2200 - 2480°C. Silicon carbide, with its excellent properties including wide bandgap, low density, low thermal expansion, excellent thermal shock / oxidation / chemical resistance, high hardness, and high thermal conductivity, is widely used in abrasive tools, ceramics, insulation materials, metallurgical applications, refractory materials, and wear-resistant materials. Silicon carbide composites have developed rapidly in the past few decades, and polymer impregnation and pyrolysis (PIP) for preparing complex large-sized components is one of the main technical routes for preparing silicon carbide composites. During the production process of silicon carbide composites, on the one hand, production waste materials are generated, and on the other hand, silicon carbide raw materials need to be mined from nature, causing damage to the environment. Therefore, the recycling of waste materials from silicon carbide composite production has become a very important process for resource utilization. The waste materials mainly include silicon carbide and silicon powder. Therefore, the waste material recycling process for silicon carbide composite production needs to recycle ultra-fine silicon powder and silicon carbide.

[0003] Patent CN110775979B discloses a method for recovering high-purity silicon and silicon carbide from crystal silicon cutting waste. The silicon cutting waste is mixed with an organic solution, stirred, filtered, washed with water, and then dried. The dried silicon cutting waste is placed in an atmosphere furnace for high-temperature treatment, cooled to room temperature, and then the silicon cutting waste is mixed with an acid solution, washed with water, filtered, and dried. The dried silicon cutting waste is placed in a flotation cell, a flotation solution is added, the pH is adjusted, and the flotation machine is started for flotation. After the flotation is completed, the floating material and the sinking material are respectively filtered, washed with water, and dried. The process is simple and easy to implement, environmentally friendly and economical. The present invention simplifies the recycling process of crystal silicon and silicon carbide and reduces the amount of industrial solid waste. However, this method causes solution leakage during the production process and has safety hazards such as high temperature, high pressure, and dust, which not only reduces the recovery rate but also pollutes the environment.

[0004] Patent CN108441640B discloses a method of acid dissolving waste diamond abrasives to remove other metals soluble in acid, filtering to recover diamond, tungsten carbide particles and other substances insoluble in acid (such as silicon dioxide, silicon carbide, etc.); subjecting the mixture of diamond, tungsten carbide particles and substances insoluble in acid obtained after acid washing and filtering to alkali treatment, washing and filtering at high temperature to recover the filter residue as diamond micropowder, adjusting the pH value of the filtrate with acid solution to precipitate silicic acid, continuing to adjust the pH value with acid solution to precipitate tungstic acid, drying the tungstic acid, and preparing ultrafine tungsten metal powder by a reduction process. The invention has low cost, relatively less pollution, and remarkable economic and environmental benefits; this method is not suitable for large-scale production, is difficult to mass produce or automate, is prone to secondary mixing during the treatment process, and has poor separation effect.

[0005] Patent CN212348905U discloses a waste material recovery device based on the production of silicon carbide composite materials, which relates to the technical field of silicon carbide composite material production. The waste material recovery device for the production of silicon carbide composite materials includes a mixing cylinder, a waste material feeding mechanism, a dispersion medium tank, a primary separation mechanism and a secondary separation mechanism. The waste material feeding mechanism and the dispersion medium tank are respectively arranged at both ends of the top of the mixing cylinder, a stirring mechanism is arranged inside the mixing cylinder, and the secondary separation mechanism is arranged directly below the mixing cylinder. By setting a lifting baffle, a moving U-shaped plate, an upper liquid outlet pipe, a middle liquid outlet pipe and a lower liquid outlet pipe, the liquid in the internal separation tank is divided into upper, middle and lower parts by upper and lower partition plates after separation, so that the accuracy of the material during suction separation is better, avoiding secondary mixing of the material. By setting the primary separation mechanism and the secondary separation mechanism, the two-stage separation can greatly improve the separation effect, and ultrasonic and microwave technologies are adopted to further improve the separation efficiency and effect; this recovery device has good separation effect and is suitable for large-scale or industrial production of a full-automatic production line; however, the fineness of the crushed particles of the waste material in this structure is insufficient, resulting in a low recovery rate of the waste material.

[0006] Patent CN113999972B discloses a production process for the resource utilization of waste metal composite materials, which relates to the technical field of metal composite materials. The process realizes the resource utilization of waste metal composite materials through a metal separation system, an extraction ion exchange and back-extraction system, electrodialysis, ultrasonic and copper carbonate crystallization technologies to obtain copper crystals, fine metal powders, zinc salts and copper carbonate crystallization products. The production process is carried out on a full-automatic production line in a closed environment, and all the generated waste gases and waste liquids are treated by corresponding environmental protection equipment and then recycled for reuse, achieving zero emissions and not causing any environmental pollution. The solid waste mainly comes from the waste filter cartridges generated during the filtration process. There are no safety hazards such as high temperature, high pressure and dust during the production process, and the separation effect and recovery effect are good; however, this method has a relatively cumbersome process, involves multiple technologies, and the recovery rate of the final recovered materials is not high, and it is not simple and easy to operate.

[0007] Patent CN114850183B discloses a waste material recovery process based on silicon carbide composite materials, which specifically includes the following steps: Step 1, pour the materials into a crushing mechanism for multiple crushing; Step 2, discharge the crushed materials into a dispersion tank for dispersion; Step 3, after the dispersed materials are layered, extract them layer by layer to the next process for subsequent processing; The present invention relates to the technical field of silicon carbide. This waste material recovery process based on silicon carbide composite materials, by setting a multi-layer separation structure inside the dispersion tank, does not affect the up and down circulation inside the dispersion tank when the inner elliptical tube is erected, and can separate its inner cavity when laid flat, so that the layered extraction device can achieve layered extraction of solutions in different layers of the dispersion tank. The separation structure can also isolate the liquid flow between the upper and lower layers, completely avoiding secondary mixing. At the same time, the internal layered structure can maximize the sealing effect, and the solution is not easy to leak. This method crushes the materials sufficiently and has a high recovery rate; Although the process method in this patent can separate in a short time, it still cannot achieve complete recovery, has a low recovery purity, and has a relatively high cost in terms of the recovery material device. At present, the waste material recovery process based on silicon carbide composite materials has problems of low purity, low separation and recovery rates.

[0008] Therefore, a waste material recovery process based on silicon carbide composite materials is proposed. Summary of the Invention

[0009] The purpose of the present invention is to provide a waste material recovery process based on silicon carbide composite materials. By gradually and finely grinding and crushing the waste materials produced from silicon carbide composite materials, washing and drying with water, impregnating and stirring and dispersing with leaching acid solution at a solid-liquid ratio of 1:20, filtering the acid-treated waste materials, removing the leaching acid solution, purifying the removed leaching acid solution and reusing it, then washing and drying the filtered acid-treated waste materials, adding water and flotation reagents to obtain a flotation solution, separating the floating materials floating on the upper layer from the sinking materials precipitating on the lower layer after flotation, filtering, washing and drying, and finally obtaining silicon carbide solids of the floating materials and ultrafine silicon powder of the sinking materials; Among them, the particle size of the crushed waste material fragments is 0.12 - 2.48 μm, and the silicon carbide content in the accumulated crushed waste material fragments reaches 99.50%; When the silicon carbide content of the floating materials on the upper layer after flotation treatment is 99.30% and the ultrafine silicon powder content of the sinking materials on the lower layer is 95.90%, the separation effect is the best, and the purity of silicon carbide is 92.59%; The waste material recovery process technology based on silicon carbide composite materials has low complexity; The recovery concentration of the leaching acid solution after treating the waste materials is 99.80%; The recovery rate of silicon carbide after carbon removal by burning is 99.50%, and the purity is 99.99%.

[0010] To achieve the above purpose, the present invention provides the following technical solutions:

[0011] A waste material recycling process based on the production of silicon carbide composites. The preparation method of the waste material includes the following steps:

[0012] S1 Refine and grind the waste material produced from silicon carbide composites to obtain crushed waste material fragments;

[0013] S2 Burn off carbon from the crushed waste material fragments. Load the waste material fragments with a quartz boat, place them in a tube furnace for heating, take them out after cooling, and obtain crushed carbon-removed waste material fragments; wash with water 2-3 times and dry to obtain dry crushed carbon-removed waste material fragments;

[0014] S3 Prepare leaching acid solution. Add the dry crushed carbon-removed waste material fragments to the leaching acid solution for dispersion; impregnate the dry crushed carbon-removed waste material fragments with the leaching acid solution at a solid-liquid ratio of 1:20. After impregnation, stirring and dispersion, obtain waste material treated with acid solution. Filter the waste material treated with acid solution to remove the leaching acid solution; the removed leaching acid solution is purified and reused. The filtered carbon-removed waste material treated with acid solution is washed with water and dried to obtain dry carbon-removed waste material treated with acid solution;

[0015] S4 Add water and flotation reagents to the dry carbon-removed waste material treated with acid solution to obtain a flotation solution; adjust the flotation solution with a pH regulator, stir evenly until the pH value is 1-12. After the flotation starts and ends, separate the floating material floating on the upper layer from the sinking material precipitating on the lower layer to obtain separated carbon-removed waste material;

[0016] S5 Filter, wash with water and dry the floating material and the sinking material of the separated carbon-removed waste material respectively to obtain silicon carbide of the upper floating material and ultrafine silicon powder of the lower sinking material.

[0017] Preferably, the grinding is carried out using a silicon carbide ingot as the grinding ball.

[0018] Preferably, the particle size of the crushed waste material fragments is 0.12 - 2.48 μm.

[0019] Preferably, the leaching acid solution is selected from one or more of hydrochloric acid solution, nitric acid solution and hydrofluoric acid solution.

[0020] The preparation method of the leaching acid solution:

[0021] Prepare hydrofluoric acid solutions with mass percentages of 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5% at a solid-liquid ratio of 1:20 for the dry crushed waste material fragments, and add 1.0% hydrochloric acid solution or 2.0% nitric acid solution respectively before this process.

[0022] Preferably, the impregnation time is 0.5 - 2 h.

[0023] Preferably, the impregnation stirring speed is 100 - 500 r / min.

[0024] Preferably, the flotation reagent is one or more of polyetheramine, ethylene diamine oxalate, polyoxyethylene ether, dodecylamine, octadecylamine.

[0025] Preparation method of flotation solution:

[0026] Add 1500 μL of flotation reagent with a concentration of 0.1 mol / L and dilute it with water to 1500 mL to obtain the flotation solution.

[0027] Preferably, the pH regulator is divided into an acidic regulator and a basic regulator according to acidity and alkalinity. The acidic regulator is hydrochloric acid, and the basic regulator is ammonia water.

[0028] Preferably, the purification process method of the removed leaching acid solution is a process method of converting hydrofluoric acid in the removed leaching acid solution into fluorosilicic acid by using a hydrofluoric acid capturer, converting fluorosilicic acid into fluorosilicate, removing silicon by adding alkali to form silicon dioxide and fluoride salt, and then regenerating hydrofluoric acid from the fluoride salt; the specific process method is as follows:

[0029] Add an excessive amount of hydrofluoric acid capturer to the removed leaching acid solution, then heat and distill under reduced pressure in stages, add alkali to remove silicon, and filter out silicon dioxide; after filtering out the silicon dioxide, further concentrate and crystallize, reduce the filtered silicon dioxide with reducing carbon to silicon, and reuse it for the excessive hydrofluoric acid capturer again. After crystallization, filter out the fluoride salt and then heat and dehydrate for recovery; add sulfuric acid and heat to 200 - 300 °C, and the generated hydrogen fluoride gas is liquefied by ice water and can be reused for the hydrofluoric acid solution in the waste material recovery process for the production of silicon carbide composites.

[0030] A waste material recovery process based on the production of silicon carbide composites, the waste material includes the ultrafine silicon powder and the silicon carbide; the waste material is recovered by the recovery process described in any one of the above; during the recovery process, the particle size of the crushed waste material fragments is 0.12 - 2.48 μm, and the silicon carbide content in the accumulated crushed waste material fragments reaches 99.50%; when the silicon carbide content in the upper floating material after flotation treatment is 99.30% and the ultrafine silicon powder content in the lower sinking material is 95.90%, the purity of silicon carbide is 92.59%; the waste material recovery process for the production of silicon carbide composites has low technical complexity; the recovery concentration of the leaching acid solution after treating the waste material is 99.80%; the recovery rate of silicon carbide after burning to remove carbon is 99.50%, and the purity is 99.99%.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. The waste material recovery process for the production of silicon carbide composites in the present invention is carried out by dissolving the waste material with leaching acid solution. The leaching acid solution that has treated the waste material is purified by a process method in which a hydrofluoric acid capturer is used to convert the hydrofluoric acid in the removed leaching acid solution into fluorosilicic acid, the fluorosilicic acid is converted into fluorosilicate, alkali is added to remove silicon, and its fluoride salt is regenerated into hydrofluoric acid. The leaching acid solution used in the recovery process achieves zero discharge; the recovery concentration of the removed leaching acid solution collected during the purification process reaches 99.80%; the concentration of the recovered acid solution is relatively high, the solution does not leak, the substances in the waste material do not flow away, and the recovery rate of silicon carbide also increases; during the recovery process, the leakage and mixing accumulation of the acid solution are avoided, so there are no safety hazards such as high temperature, high pressure, and dust.

[0033] 2. In the flotation method used in the waste material recovery process of the present invention, 1500 μL of a flotation reagent with a concentration of 0.1 mol / L and water are added to the waste material to prepare a flotation solution. The waste material slurry is layered by mixing with the flotation solution, separating silicon carbide and silicon; this method avoids secondary mixing during recovery, and the separation effect is also the best; after flotation treatment, the silicon carbide content in the upper floating material is 99.30%, and the ultrafine silicon powder content in the lower sinking material is 95.90%.

[0034] 3. The waste material recovery process in the present invention uses silicon carbide ingots as grinding balls for fine grinding and pulverization. The characteristics of this material as a grinding ball are that its high hardness, chemical stability, and toughness enable it to be used for free grinding, and it is the material with the highest hardness, so it is often used for difficult-to-grind materials. In the present invention, the main substance recovered is silicon carbide, and using silicon carbide ingots as grinding balls does not introduce impurities. Moreover, this method fully pulverizes the waste material particles and has a high recovery rate; by measuring the particle size distribution of the pulverized waste material fragments, the particle size of the pulverized waste material fragments is 0.12 - 2.48 μm, and the silicon carbide content in the cumulative waste material fragments reaches 99.50%, which is convenient for more sufficient subsequent recovery and collection and has a higher purity.

[0035] 4. The waste material recovery process used in the present invention uses relatively few technologies. The recovery of waste material is achieved through the process technology of leaching acid solution impregnation to remove trace elements. It is simple and easy to operate, with low technical complexity and a high recovery rate of silicon carbide; the leaching acid solution uses the 3.0 mass percentage% hydrofluoric acid solution, the impregnation time is 1 h, and when the impregnation dispersion stirring speed is 300 r / min, when the leaching acid solution treats the waste material, the leaching acid solution reacts fully with the waste material, and the impregnation effect is the best. The silicon carbide content in the leaching acid solution after treating the waste material is 12.50%, and the silicon carbide recovery rate is 87.50%.

[0036] 5. The waste material recovery process in the present invention uses the process technology of grinding and pulverizing - burning and decarbonizing - leaching with acid solution to remove trace elements - flotation separation, which improves the recovery rate and purity under the condition of the lowest process cost. The recovery rate of silicon carbide is 99.50%, and the purity is 99.99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 FIG. is a process flow chart of a waste material recovery process based on the production of silicon carbide composites;

[0038] Figure 2 FIG. shows the silicon carbide content in the leaching acid solution of different acid types and concentrations and the leaching acid solution after treating the waste material;

[0039] Figure 3 FIG. shows the leaching acid solution of different acid types and concentrations and the recovery rate of silicon carbide;

[0040] Figure 4 FIG. shows the silicon carbide content in the leaching acid solution after treating the waste material with different impregnation times;

[0041] Figure 5 FIG. shows different impregnation times and the recovery rate of silicon carbide. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] Please refer to Figures 1 to 5 , the present invention provides a waste material recovery process based on the production of silicon carbide composites, and the technical solution is as follows:

[0044] Example 1

[0045] S1 Wash the waste material with water 2 - 3 times, filter to obtain the waste material solid, collect and reserve the solid substance, and dry it to obtain the dried waste material solid;

[0046] S2 Prepare the leaching acid solution, the leaching acid solution is a 1.0 mass percentage% hydrofluoric acid solution, add the dried waste material to the leaching acid solution for dispersion, impregnate the dried waste material and the leaching acid solution at a solid - liquid ratio of 1:20 for 0.5 h to obtain the waste material treated with the acid solution;

[0047] S3 Separate the waste material treated with the acid solution, the separation medium is water, and obtain the waste material after layering;

[0048] The separated waste materials after step S4 are filtered for the upper and lower layers respectively. The solid particles in the upper layer are silicon carbide, and the solid particles in the lower layer are ultrafine silicon powder.

[0049] The solid particles in the upper and lower layers in step S5 are washed with water, and the leaching acid solution is removed by centrifugation.

[0050] The solid particles in the upper and lower layers after removing the leaching acid solution are washed 3 times with deionized water, and then dehydrated and dried to obtain silicon powder and silicon carbide solid.

[0051] Example 2 - 18

[0052] Refer to the components and concentrations of the leaching acid solution in Example 1, and the differences are shown in Table 1.

[0053] Table 1 Components and Concentrations of the Leaching Acid Solution

[0054]

[0055]

[0056] Content and Recovery Rate of Silicon Carbide in Example 19

[0057] Figure 2 and Figure 3 are respectively the content and recovery rate of silicon carbide in the leaching acid solution of different acid types and concentrations before and after treating the waste materials. When treated with single hydrofluoric acid or the mixed acid of "hydrofluoric acid and 2.0 mass percentage % nitric acid", compared with the mixed acid of "hydrofluoric acid and 1.0 mass percentage % hydrochloric acid", the content of silicon carbide is lower, and the recovery rate of silicon carbide is relatively lower; as the mass fraction of hydrofluoric acid increases, when treated with the mixed acid of "hydrofluoric acid and 2.0 mass percentage % nitric acid", the content and recovery rate of silicon carbide basically remain unchanged, indicating that the mixed acid of "hydrofluoric acid and 2.0 mass percentage % nitric acid" has no modification effect on the waste materials; when treated with 3.0 mass percentage % single hydrofluoric acid and the mixed acid of "hydrofluoric acid and 1.0 mass percentage % hydrochloric acid", the content of silicon carbide gradually decreases, while the recovery rate of silicon carbide gradually increases; indicating that both of them have modification effects on the waste materials; from Figure 2 、 Figure 3 and the analysis data results in Table 1, it can be seen that when treated with 3.0 mass percentage % hydrofluoric acid in Example 5, the content of silicon carbide in the leaching acid solution after treating the waste materials is the lowest, which is 30%, and the recovery rate of silicon carbide is the highest, which is 70%.

[0058] Example 20

[0059] S1 Wash the waste materials with water 2 - 3 times, filter to obtain the waste material solid, collect and reserve the solid substance, and dry to obtain the dried waste material solid.

[0060] S2 Configure the leaching acid solution, the leaching acid solution is a 3.0 mass percentage% hydrofluoric acid solution, add the dried waste material to the leaching acid solution for dispersion, impregnate the dried waste material and the leaching acid solution at a solid-liquid ratio of 1:20 for 1 h to obtain the waste material treated with the acid solution;

[0061] S3 Separate the waste material treated with the acid solution, the separation medium is water, to obtain the layered waste material;

[0062] S4 Filter the upper and lower layers of the layered waste material separately. The upper-layer solid particles are silicon carbide, and the lower-layer solid particles are ultrafine silicon powder;

[0063] S5 Wash the upper and lower layer solid particles with water and centrifugally remove the leaching acid solution;

[0064] S6 Wash the upper and lower layer solid particles after removing the leaching acid solution 3 times with deionized water, and then dehydrate and dry to obtain silicon powder and silicon carbide solid.

[0065] Examples 21-22

[0066] Refer to the impregnation time of Example 20, the difference is that the impregnation time of Example 21 is 1.5 h, and the impregnation time of Example 22 is 2 h.

[0067] Effect of impregnation time of leaching acid solution on enrichment effect of silicon carbide in Example 23

[0068] From Figure 4 and Figure 5 it is found that with the increase of the impregnation time of the leaching acid solution, after 1.5 h, the content and recovery rate change not significantly. This may be because the reaction is relatively rapid in the initial stage. When the impregnation time is 1 h in Example 20, the reaction is basically complete, and the content of silicon carbide in the leaching acid solution after treating the waste material is the lowest, the content is 25.00%, the impregnation effect is the best, and the recovery rate is 75.00%.

[0069] Example 24

[0070] S1 Wash the waste material with water 2-3 times, filter to obtain the waste material solid, collect and reserve the solid substance, and dry to obtain the dried waste material solid;

[0071] S2 Configure the leaching acid solution, the leaching acid solution is a 3.0 mass percentage% hydrofluoric acid solution, add the dried waste material to the leaching acid solution for dispersion, impregnate the dried waste material and the leaching acid solution at a solid-liquid ratio of 1:20, stir and disperse the mixed solution, the stirring speed is 100 r / min, and the impregnation time is 1 h to obtain the waste material treated with the acid solution;

[0072] S3 Separate the waste material treated with the acid solution, the separation medium is water, to obtain the layered waste material;

[0073] For the waste materials after layering described in S4, the upper and lower layers are filtered separately. The solid particles in the upper layer are silicon carbide, and the solid particles in the lower layer are ultrafine silicon powder.

[0074] For the solid particles in the upper and lower layers described in S5, they are washed with water and the leaching acid solution is removed by centrifugation.

[0075] For the solid particles in the upper and lower layers after removing the leaching acid solution in S6, they are washed 3 times with deionized water, then dehydrated and dried to obtain silicon powder and silicon carbide solid.

[0076] Examples 25 - 28

[0077] Referring to the steps of Example 24, the differences are listed in Table 2.

[0078] Effect of different stirring speeds on the enrichment effect of silicon carbide during the dispersion process in Example 29

[0079] According to the method of Example 19, the silicon carbide content and the recovery rate of recovered silicon carbide in the acid solution after treating the waste materials are analyzed, and the results are shown in Table 2.

[0080] Table 2 Stirring speeds, silicon carbide content in the acid solution after treating the waste materials, and silicon carbide recovery rates in Examples 20, 24 - 28

[0081] Stirring speed / r / min Silicon carbide content / % Silicon carbide recovery rate / % Example 20 / 27.50 72.50 Example 24 100 17.60 82.40 Example 25 200 16.40 83.60 Example 26 300 12.50 87.50 Example 27 400 16.30 83.70 Example 28 500 17.20 82.80

[0082] It is found from Table 2 that in Example 26, the stirring speed is 300 r / min, the silicon carbide content in the leaching acid solution after treating the waste materials is the lowest, which is 12.50%, the impregnation effect is the best, and the silicon carbide recovery rate is 87.50%.

[0083] Examples 30 - 32

[0084] Referring to the steps of Example 26, the difference is that the step S2 in Examples 5, 20, and 26 is changed as follows:

[0085] Prepare the leaching acid solution, and add the crushed dry carbon - removed waste material fragments to the leaching acid solution for dispersion; the crushed dry carbon - removed waste material fragments and the leaching acid solution are impregnated at a solid - liquid ratio of 1:20, the mixed solution is stirred and dispersed, the stirring speed is 100 r / min, the impregnation time is 1 h to obtain the waste material treated with the acid solution, filter the waste material treated with the acid solution to remove the leaching acid solution; the removed leaching acid solution is purified and reused, the filtered carbon - removed waste material treated with the acid is obtained, then washed with water and dried to obtain the dry carbon - removed waste material treated with the acid.

[0086] The purification process method of the leaching acid solution removed is to add an excessive amount of hydrofluoric acid capturer (the excessive hydrofluoric acid capturer is silicon) to the removed leaching acid solution, then perform fractional heating and vacuum distillation, add alkali to remove silicon, and filter out silicon dioxide; after filtering out the silicon dioxide, further concentrate and crystallize, the filtered silicon dioxide is reduced with reducing carbon to become silicon, and is reused as an excessive hydrofluoric acid capturer, after crystallization, filter out fluorinated salts, and then heat and dehydrate for recovery; add sulfuric acid and heat to 200-300 °C, and the generated hydrogen fluoride gas is liquefied by ice water, and can be reused in the hydrogen fluoride solution of the waste material recovery process for the production of silicon carbide composites.

[0087] Concentration of the recovered acid in Example 33

[0088] Weigh 3 mL of waste acid from the waste acid recovered in Examples 30-32 and place it in a 250 mL conical flask, add 15 mL of distilled water, mix evenly and weigh with a balance, then add 2-3 drops of bromocresol green indicator, and perform standard titration with sodium hydroxide solution until the solution changes from yellow to blue.

[0089] Calculation method of total acidity:

[0090] a% = (CV ÷ m) × 0.03646 × 100

[0091] In the formula, C - molar mass of the standard solution of sodium hydroxide solution

[0092] V - volume of the sodium hydroxide standard solution

[0093] m - mass of 3 mL of waste

[0094] 0.03646 - mass of hydrogen chloride in grams equivalent to 1 mL of sodium hydroxide standard solution

[0095] The results are shown in Table 3.

[0096] Table 3 Types, concentrations, impregnation times, stirring speeds of the leaching acid solutions in Examples 30-32 and the concentration of the recovered acid

[0097]

[0098] From the above results, it is obtained that the leaching acid solution is 3.0 mass percentage % hydrofluoric acid, and by using the method of Example 32, the concentration of the recovered hydrofluoric acid waste acid solution reaches 99.80%.

[0099] Example 34

[0100] S1 Add the waste material produced in the production of silicon carbide composites to the grown silicon carbide ingot as a grinding ball for fine grinding and crushing to obtain crushed waste material fragments;

[0101] S2 Wash the crushed waste fragments with water 2 - 3 times, filter and dry to obtain crushed and dried waste fragments;

[0102] S2 Prepare leaching acid solution, add the crushed and dried waste fragments into the leaching acid solution for dispersion; impregnate the crushed and dried waste fragments and the leaching acid solution at a solid - liquid ratio of 1:20, stir and disperse the mixture, with a stirring speed of 100 r / min and an impregnation time of 1 h to obtain waste fragments treated with acid solution. Filter the waste fragments treated with acid solution to remove the leaching acid solution; the removed leaching acid solution is purified and reused. The filtered waste fragments treated with acid are washed with water and dried to obtain dry waste fragments treated with acid;

[0103] S3 Separate the dry waste fragments treated with acid, with the separation medium being water, to obtain the waste after stratification;

[0104] S4 Filter the upper and lower layers of the waste after stratification respectively. The upper - layer solid particles are silicon carbide solids, and the lower - layer solid particles are ultrafine silicon powder;

[0105] S5 Wash the upper and lower - layer solid particles with water and centrifugally remove the leaching acid solution;

[0106] S6 Wash the upper and lower - layer solid particles after removing the leaching acid solution 3 times with deionized water, then dehydrate and dry to obtain silicon powder and silicon carbide solids.

[0107] Particle size distribution of the crushed waste fragments in Example 35

[0108] Measure and compare the particle size distributions of the crushed waste fragments in Examples 32 and 34 using a Zeta PALS light - scattering particle size distribution analyzer. The results are shown in Table 4.

[0109] Table 4 Particle size distributions of the crushed waste fragments in Examples 32 and 34

[0110]

[0111] In the range of 0.12 - 9.34 μm, it is mainly silicon, fine-grained silicon carbide, and metal impurities, etc. While in the range of 9.34 - 32.41 μm, it is mainly larger-grained silicon carbide; as can be seen from Table 4, the particle size of the waste fragments after crushing in Example 32 without refinement and grinding is 3.12 - 17.01 μm, and the silicon carbide content in the cumulative waste fragments reaches 81.92%. In Example 34 where a grown silicon carbide ingot is added as a grinding ball for refined grinding and crushing, the particle size of the waste fragments after crushing is 0.12 - 2.48 μm, and the silicon carbide content in the cumulative waste fragments after crushing reaches 99.50%; thus, it can be known that adding a grown silicon carbide ingot as a grinding ball for refined grinding and crushing enables the waste particles to be fully refined and crushed, facilitating subsequent recycling and collection.

[0112] Example 36

[0113] S1 Add the waste materials produced from the silicon carbide composite material and use the grown silicon carbide ingot as a grinding ball for refined grinding and crushing to obtain crushed waste fragments.

[0114] S2 Wash the crushed waste fragments with water 2 - 3 times, filter and dry them to obtain crushed and dried waste fragments.

[0115] S2 Prepare the leaching acid solution, add the crushed and dried waste fragments to the leaching acid solution for dispersion; impregnate the crushed and dried waste fragments and the leaching acid solution at a solid-liquid ratio of 1:20, stir and disperse the mixed solution, with a stirring speed of 100 r / min and an impregnation time of 1 h to obtain waste fragments treated with the acid solution. Filter the waste fragments treated with the acid solution to remove the leaching acid solution; the removed leaching acid solution is purified and reused. The filtered waste fragments treated with the acid solution are washed with water and dried to obtain dry waste fragments treated with the acid solution.

[0116] S4 Add 1500 μL of polyetheramine with a concentration of 0.1 mol / L to the dry waste fragments treated with the acid solution, and dilute it with water to 1500 mL to obtain a flotation solution; adjust the flotation solution with hydrochloric acid, stir evenly, separate the floating materials floating on the upper layer and the sinking materials precipitating on the lower layer after the start and end of flotation to obtain separated waste fragments.

[0117] S5 Filter, wash with water and dry the floating materials and sinking materials of the separated waste fragments respectively to obtain silicon carbide solids of the floating materials and ultrafine silicon powder of the sinking materials.

[0118] Example 37

[0119] Refer to the steps of Example 36, with the differences shown in Table 5.

[0120] Table 5 Flotation reagent types and pH regulators for Examples 37 - 45

[0121]

[0122] Example 46 Phase composition and content of the upper and lower layer solids after flotation treatment

[0123] In Examples 36 - 45, the waste powder modified with an acidic solution as a surfactant was subjected to flotation treatment. The floating material was silicon carbide solid, and the sinking material was ultrafine silicon powder. According to the literature ("Research on the Recycling Technology of Silicon Chips in Wire Sawing Slurry for Solar Cell Wafers", "Materials Review", Huang Meiling et al., 2010 - 05 - 25), the K - value method and the full - spectrum fitting quantitative method of D8 - Focus in XRD quantitative analysis were used, combined with experimental calibration and correction; the actual content = 0.63×analysis result of the K - value method = 0.97×analysis result of the full - spectrum fitting quantitative method. The results are shown in Table 6.

[0124] Table 6 Content of silicon carbide solid in the upper floating material and ultrafine silicon powder in the lower sinking material of Examples 36 - 45

[0125] Upper layer silicon carbide solid content / % Lower layer ultrafine silicon powder content / % Example 34 75.60 72.70 Example 36 98.90 96.70 Example 37 96.40 97.50 Example 38 95.60 96.40 Example 39 98.20 96.90 Example 40 89，50 92.40 Example 41 99.30 95.90 Example 42 94.70 93.40 Example 43 95.80 96.70 Example 44 92.30 93.40 Example 45 90.40 91.20

[0126] In Example 41, polyetheramine was added as a flotation reagent and hydrochloric acid was used as a pH regulator. From the data in Table 6, it can be seen that in Examples 34, 36 - 45, for Example 41, the content of silicon carbide solid in the upper floating material is 99.30%, and the silicon content in the lower sinking material is 95.90%. The phase composition content of the upper and lower layer solids is the best, and the separation effect is the best.

[0127] Example 48

[0128] For the floating material solid recovered by the waste material recovery process based on silicon carbide composite materials, in addition to silicon carbide, there may also be free carbon. Referring to the steps of Example 41, the difference lies in step S2:

[0129] The crushed waste material fragments are calcined to remove carbon. The waste material fragments are taken with a quartz boat, placed in a tube furnace for heating, taken out after cooling, and the crushed carbon - removed waste material fragments are obtained; they are washed with water 2 - 3 times and dried to obtain the dry crushed carbon - removed waste material fragments.

[0130] Example 49 Analysis of silicon carbide purity

[0131] Samples of 0.0500 g were respectively weighed from the recovered silicon carbide in Examples 26, 32, 34, 41, and 47, placed in a high - temperature muffle furnace for burning, and then the carbon content in the silicon carbide was measured by the infrared absorption method, so as to calculate the purity of the silicon carbide. The calculation results are shown in Table 7.

[0132] Table 7 Recovery rate and purity of the floating material silicon carbide recovered in Examples 26, 32, 34, 41, and 47

[0133] Recovery rate of silicon carbide / % Purity of silicon carbide / % Example 26 87.50 62.74 Example 32 92.24 75.87 Example 34 94.82 84.21 Example 41 97.84 92.59 Example 47 99.50 99.99

[0134] As can be seen from Table 7, the best silicon carbide recovery effect and the highest purity are achieved in Example 47, with a recovery rate of 99.50% and a purity of 99.99%.

[0135] In summary, the waste material recovery process for silicon carbide composite materials of the present invention gradually and finely grinds and crushes the waste materials produced from silicon carbide composite materials, washes and dries them, impregnates, stirs and disperses them. The leaching acid solution removed is purified and reused. Then, the acid-treated waste materials after filtration are washed and dried, water and flotation reagents are added to obtain a flotation solution. After flotation, the floating materials floating on the upper layer are separated from the sinking materials precipitating on the lower layer. Finally, silicon carbide solids of the floating materials and ultrafine silicon powder of the sinking materials are obtained. During the recovery process, the particle size of the crushed waste material fragments is 0.12 - 2.48 μm, and the silicon carbide content in the cumulative fragments reaches 99.50%. After flotation treatment, the silicon carbide content of the floating materials on the upper layer is 99.30%, and the ultrafine silicon powder content of the sinking materials on the lower layer is 95.90%. The separation effect is the best, and the purity of silicon carbide is 92.59%. The complexity of the process technology is low. The recovery concentration of the leaching acid solution after treating the waste materials is 99.80%, the recovery rate of silicon carbide after burning to remove carbon is 99.50%, and the purity is 99.99%. Under the condition of low cost, the problems of low purity, low separation and low recovery rate existing in the waste material recovery process for silicon carbide composite materials are solved.

[0136] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A waste material recycling process based on the production of silicon carbide composites, characterized in that: The preparation method of the waste material includes the following steps: S1 Refine and grind the waste material produced from the silicon carbide composite material to obtain crushed waste material fragments; S2 Burn off carbon from the crushed waste material fragments. Load the waste material fragments with a quartz boat, place them in a tube furnace for heating, take them out after cooling, and obtain crushed carbon-removed waste material fragments; wash them with water 2-3 times and dry them to obtain crushed dry carbon-removed waste material fragments; S3 Prepare a leaching acid solution. Add the crushed dry carbon-removed waste material fragments to the leaching acid solution for dispersion; impregnate the crushed dry carbon-removed waste material fragments and the leaching acid solution at a solid-liquid ratio of 1:

20. After impregnation, stirring and dispersion, obtain waste material treated with acid solution. Filter the waste material treated with acid solution to remove the leaching acid solution; the removed leaching acid solution is purified and reused. The filtered carbon-removed waste material treated with acid solution is washed with water and dried to obtain dry carbon-removed waste material treated with acid solution; S4 Add water and a flotation reagent to the dry carbon-removed waste material treated with acid solution to obtain a flotation solution; adjust the flotation solution with a pH regulator, stir evenly until the pH value is 1-12, and separate the floating material floating on the upper layer from the sinking material precipitating on the lower layer after the flotation is completed to obtain separated carbon-removed waste material; S5 Filter, wash with water and dry the floating material and the sinking material of the separated carbon-removed waste material respectively to obtain silicon carbide of the upper floating material and ultrafine silicon powder of the lower sinking material.

2. The waste material recycling process based on silicon carbide composite material production according to claim 1, characterized in that: The grinding and crushing is carried out using a silicon carbide ingot as a grinding ball.

3. The waste recycling process based on silicon carbide composite material production according to claim 1 is characterized in that: The particle size of the crushed waste material fragments is 0.12-2.48 μm.

4. A waste material recycling process based on the production of silicon carbide composite materials according to claim 1, characterized in that: For the leaching acid solution, one or more of hydrochloric acid solution, nitric acid solution and hydrofluoric acid solution are selected.

5. A waste material recycling process based on the production of silicon carbide composite materials according to claim 1, characterized in that: The impregnation time is 0.5-2 h.

6. The waste material recycling process based on silicon carbide composite material production according to claim 1 is characterized in that: The impregnation stirring speed is 100-500 r / min.

7. A waste material recycling process based on the production of silicon carbide composites according to claim 1, characterized in that: The flotation reagent is one or more of polyetheramine, ethylene diamine oxalate, polyoxyethylene ether, dodecylamine, octadecylamine.

8. A waste material recycling process based on the production of silicon carbide composites according to claim 1, characterized in that: The pH regulator is divided into an acidic regulator and a basic regulator according to the acidity. The acidic regulator is hydrochloric acid and the basic regulator is ammonia water.

9. A waste material recycling process based on the production of silicon carbide composite materials according to claim 1, characterized in that: The purification process method of the removed leaching acid solution is a process method of using a hydrofluoric acid capturer to convert hydrofluoric acid in the removed leaching acid solution into fluorosilicic acid, converting fluorosilicic acid into fluorosilicate, adding alkali to remove silicon to form silicon dioxide and fluorinated salt, and regenerating hydrofluoric acid from the fluorinated salt.

10. A waste material recycling process based on the production of silicon carbide composite materials according to claim 1, characterized in that: The waste materials include the ultrafine silicon powder and the silicon carbide; the waste materials are obtained by recycling through the recycling process described in any one of claims 1-9; during the recycling process, the particle size of the crushed waste material fragments is 0.12-2.48 μm, and the silicon carbide content in the cumulative crushed waste material fragments reaches 99.50%; when the silicon carbide content in the upper floating material after flotation treatment is 99.30% and the ultrafine silicon powder content in the lower sinking material is 95.90%, the purity of silicon carbide is 92.59%; the recycling process technology of the waste materials produced by the silicon carbide composite material is of low complexity; the recovery concentration of the leaching acid solution after treating the waste materials is 99.80%; the recovery rate of silicon carbide after carbon removal by burning is 99.50%, and the purity is 99.99%.

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