Method for preparing silicon carbide by adding biomass ash to reinforce waste graphite and silicon waste

Abstract

The present application relates to a kind of biomass ash addition reinforced waste graphite and silicon waste material preparation silicon carbide method, belong to secondary resource utilization technical field.It includes: (1) pretreatment: drying, calcining remaining ash to biomass, waste graphite is broken, screened with silicon waste material;(2) biomass ash and waste graphite, silicon waste material are ground and mixed uniformly according to certain proportion and loaded into high-purity graphite crucible;(3) the mixture is placed in muffle furnace, vacuum, let the mixture react at high temperature, during the reaction process, the component in biomass ash plays the role of reinforcement, promotes waste graphite and silicon waste material to produce silicon carbide;(4) after reaction, when product cools to room temperature, obtain high-purity silicon carbide product.The present application makes full use of waste graphite, silicon waste material and biomass ash and other wastes, not only realizes the recycling of resources, reduces production cost, also reduces the influence of waste on environment;The method is simple and easy to operate, suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing silicon carbide from waste graphite and silicon waste materials by adding biomass ash, and belongs to the technical field of secondary resource utilization. BACKGROUND

[0002] With the rapid development of science and technology, graphite and silicon are widely used in many fields such as electronics, semiconductors, new energy and the like. However, a large amount of waste graphite and silicon waste materials are generated in the production and use process. The accumulation of these waste materials not only occupies a large amount of land resources, but also may cause pollution to soil, water and air, bringing great pressure to the environment. At the same time, as important resources, the reserves of graphite and silicon are not inexhaustible, and the effective utilization of waste resources has become an inevitable requirement for sustainable development.

[0003] Silicon carbide is an important material with excellent performance. It has high hardness, high melting point, high thermal conductivity, high chemical stability and the like, and is widely used in abrasive tools, refractory materials, semiconductor devices, high-temperature structural materials and the like. With the development of various industries, the demand for silicon carbide continues to grow. The traditional production method of silicon carbide often relies on high-purity carbon source and silicon source, which has high cost and large energy consumption.

[0004] Using waste graphite and silicon waste materials as main raw materials, and adding biomass ash to prepare high-quality silicon carbide, not only provides a new way for the reuse of waste resources, but also reduces the production cost of silicon carbide and improves the resource utilization efficiency, which has important practical significance and broad application prospect.

[0005] At present, the related patents for preparing silicon carbide from waste graphite and silicon waste materials are: a high-quality silicon carbide prepared from diamond wire cutting waste (CN107651690A); a high-quality silicon carbide prepared from crystal silicon cutting waste (CN107651691A). The above patents all prepare high-quality silicon carbide from cutting waste. The existing technology does not involve the preparation of silicon carbide from biomass and waste graphite.

[0006] In the patent 2024111964714, an attempt is made to use biomass in combination with alkali metal carbonate or hydroxide to prepare high-purity silicon. In the later research and exploration, a technology for preparing high-purity silicon carbide is formed, and the present application is obtained. SUMMARY

[0007] The present application is proposed in view of the fact that the existing technology does not have any record of using biomass ash to strengthen silicon waste and waste graphite to prepare high-quality silicon carbide. The present application solves the problem of environmental pollution caused by silicon waste and waste graphite, avoids resource waste, and utilizes the strengthening effect of biomass such as coffee shell to turn waste into treasure, bringing great economic benefits.

[0008] The application discloses a method for preparing silicon carbide by adding biomass ash to reinforce waste graphite and silicon waste materials, and specific steps are as follows.

[0009] (1) The silicon waste material and the waste graphite are respectively crushed, ground and screened to obtain powders, and the silicon waste material powder and the waste graphite powder are obtained, and the particle size distribution of the obtained powders is 50-150 μm.

[0010] (2) The selected biomass is dried and crushed to obtain a biomass powder.

[0011] (3) The biomass powder is loaded into a corundum crucible, and is calcined and heat preserved under an oxygen-containing atmosphere; after the heat preservation is completed, the temperature is lowered to obtain biomass ash.

[0012] (4) The biomass ash, the silicon waste material powder and the waste graphite powder are ground and uniformly mixed according to a certain proportion to obtain a mixture, the mixture is loaded into a high-purity graphite crucible and is placed in a muffle furnace, vacuum is drawn, and a temperature rising program is set to make the mixture react at high temperature; the mixture is composed of A and the biomass ash, wherein A is composed of the silicon waste material powder and the waste graphite powder according to a mass ratio of 65-70:30-35; the content of the biomass ash in the mixture is 1-10%; and the vacuum calcination temperature is 1410-1700 DEG C.

[0013] (5) After the reaction is completed, the product is cooled to room temperature to obtain a high-purity silicon carbide product.

[0014] In the method for preparing silicon carbide by adding biomass ash to reinforce waste graphite and silicon waste materials, the silicon waste material and the waste graphite are screened to realize the particle size distribution of 50-150 μm in step (1).

[0015] In the method for preparing silicon carbide by adding biomass ash to reinforce waste graphite and silicon waste materials, the biomass is selected from at least one of coffee shell, tobacco straw, cotton straw, rice straw, wheat straw, corn straw and soybean straw, preferably at least one of coffee shell, rice hull and rice straw, and more preferably coffee shell and tobacco straw.

[0016] In the method for preparing silicon carbide by adding biomass ash to reinforce waste graphite and silicon waste materials, the calcination temperature is 600-1000 DEG C, and the heat preservation time is 60-180 min in step (3). The heat preservation time is controlled to be 60-180 min in the application, so that the biomass is completely calcined and only the ash is left. If the heat preservation time is too short, the biomass carbon cannot be completely burned, and other problems occur. In the actual production process, the temperature rising rate can be controlled to be 5-15 DEG C / min, for example, 10 DEG C / min or 12 DEG C / min.

[0017] The biomass ash is added to strengthen the abandoned graphite and the silicon waste material to prepare the silicon carbide in the method, and in step (4), the silicon waste material content in the mixture A is 65-70 wt.%, the abandoned graphite content is 30-35 wt.%, and in the mixture, the biomass ash content is 1-10 wt.%, preferably 1-2.5%, and more preferably 1-2%.

[0018] The biomass ash is added to strengthen the abandoned graphite and the silicon waste material to prepare the silicon carbide in the method, and in step (4), the vacuum degree of vacuum roasting is 10 -3 -50 Pa, the vacuum roasting temperature is 1410-1700 DEG C, and the holding time is 60-240 min. In the actual production process, the heating rate can be controlled at 5-20 DEG C / min, such as 10 DEG C / min, 12 DEG C / min, 15 DEG C / min, etc.

[0019] As preferred, after the tobacco straw is roasted in an air atmosphere, the biomass ash content in the mixture is 1-1.1%.

[0020] The biomass ash is added to strengthen the abandoned graphite and the silicon waste material to prepare the silicon carbide in the method, and in step (5), the purity of the obtained silicon carbide is greater than or equal to 95.3%. After optimization, the purity of the silicon carbide is greater than 98%.

[0021] At present, the carbon thermal reduction is a promising method due to its economy, high efficiency and large-scale preparation. In the carbon thermal reduction process, the raw materials (carbon source and silicon source) have important influence on the formation of SiC. At present, petroleum coke (or coal coke) is mainly used as the raw material to produce SiC in the industry. The abandoned graphite is used to replace the graphite as the carbon source for preparing SiC, and the micro-silicon powder waste material generated in the industrial production is used to replace the silicon source, so that the cost of preparing SiC can be reduced. In addition, some alkali metals such as K and Na elements in the biomass ash can delay the graphitization of the carbon source and promote the generation of SiC.

[0022] The present application has the following beneficial effects:

[0023] The preparation of silicon carbide from abandoned graphite and silicon waste material by using biomass ash has the following beneficial effects:

[0024] 1. The abandoned graphite and the silicon waste material are reused, which avoids the waste of these resources and reduces the dependence on primary resources. The present application conforms to the concept of circular economy, is helpful to realize the sustainable utilization of resources, and reduces the pressure on the environment.

[0025] 2. The biomass ash is originally a waste, and the resource utilization of the biomass ash is realized by using it to prepare silicon carbide. The quality of the silicon carbide is improved by adding the biomass ash to strengthen and / or catalyze the reaction process. Compared with the traditional preparation method, the use of abandoned graphite and silicon waste material can reduce the raw material cost.

[0026] 3. Reduce the pollution of waste graphite and silicon waste and biomass ash to the environment, reduce the pressure of waste disposal; It is possible to have lower energy consumption and less greenhouse gas emission during preparation, and it is more environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM image of silicon carbide product in Example 1.

[0028] Figure 2 SEM image of silicon carbide product in Comparative Example 1. DETAILED DESCRIPTION

[0029] The application will be further described in conjunction with the specific embodiments, but the scope of protection of the application is not limited to the content described.

[0030] The mass percentage of Si in the silicon waste powder used in the examples and comparative examples of the application is 75-88%;

[0031] The mass percentage of C in the waste graphite powder used in the examples and comparative examples of the application is 70-85%. In the examples and comparative examples of the application, most of the impurities will float to form slag during smelting; therefore, during laboratory operation, after cooling, the upper layer of impurities (the upper layer is in the direction of the opening of the crucible) can be directly cut off or polished off, so as to obtain a silicon carbide product with high purity. In industrial applications, the slag can be removed by skimming.

[0032] Example 1:

[0033] A method for preparing silicon carbide by adding and strengthening waste graphite and silicon waste with biomass ash, the specific steps are as follows:

[0034] (1) The silicon waste and waste graphite are respectively crushed, ground and sieved to obtain silicon waste powder and waste graphite powder, the particle size of the silicon waste powder is 75 μm, and the particle size of the waste graphite powder is 75 μm;

[0035] (2) The tobacco straw is treated to remove the untreated tobacco leaves, and then dried and crushed to obtain tobacco straw powder;

[0036] (3) The tobacco straw powder is loaded into a corundum crucible, and placed in a muffle furnace, and heated to 600℃ at a heating rate of 10℃ / min, and kept at 600℃ for 120min in air, and then cooled in the furnace to obtain tobacco straw ash;

[0037] (4) 1 wt.% tobacco stalk ash, 99 wt.% A were mixed uniformly and loaded into a high-purity graphite crucible, which was placed in a muffle furnace, vacuumized to 10 Pa, and heated to 1500°C at 10°C / min, and vacuum baked for 120 min; the A was composed of 70 wt.% silicon waste powder and 30 wt.% waste graphite powder;

[0038] (5) After the end of the heat preservation, the product was cooled to room temperature, and the upper surface impurities were removed to obtain a high-purity silicon carbide product.

[0039] The purity of the silicon carbide obtained in this example was 98.91%.

[0040] Example 1-1

[0041] The other conditions were consistent with those of Example 1, except that equal amounts of coffee shell powder were used to replace the tobacco stalk powder.

[0042] The purity of the silicon carbide obtained in this example was 98.31%.

[0043] Example 1-2

[0044] The other conditions were consistent with those of Example 1, except that equal amounts of rice husk powder were used to replace the tobacco stalk powder; the purity of the silicon carbide obtained in this example was 95.47%.

[0045] Example 1-3

[0046] The other conditions were consistent with those of Example 1, except that equal amounts of cotton stalk powder were used to replace the tobacco stalk powder.

[0047] The purity of the silicon carbide obtained in this example was 96.40%.

[0048] Example 1-4

[0049] The other conditions were consistent with those of Example 1, except that equal amounts of rice stalk powder were used to replace the tobacco stalk powder.

[0050] The purity of the silicon carbide obtained in this example was 96.77%.

[0051] Example 1-5

[0052] The other conditions were consistent with those of Example 1, except that equal amounts of wheat stalk powder were used to replace the tobacco stalk powder.

[0053] The purity of the silicon carbide obtained in this example was 97.83%.

[0054] Example 1-6

[0055] Other conditions are consistent with example 1, except that the same mass of corn stalk powder is used to replace tobacco stalk powder;

[0056] The purity of silicon carbide obtained in this example is 95.14%.

[0057] Examples 1-7

[0058] Other conditions are consistent with example 1, except that the same mass of corn stalk powder is used to replace tobacco stalk powder;

[0059] The purity of silicon carbide obtained in this example is 97.33%.

[0060] Example 2:

[0061] A method for preparing silicon carbide by adding biomass ash to strengthen waste graphite and silicon waste, the specific steps are as follows:

[0062] (1) The silicon waste and waste graphite are crushed, ground and sieved to obtain silicon waste powder and waste graphite powder, the particle size of the silicon waste powder is 50 μm, and the particle size of the waste graphite powder is 50 μm;

[0063] (2) The coffee shell is dried and crushed to obtain coffee shell powder;

[0064] (3) The coffee shell powder is loaded into a corundum crucible and placed in a muffle furnace, and the temperature is raised to 700℃ at a rate of 10℃ / min, and the temperature is kept for 120min in air, and the coffee shell ash is obtained after cooling in the furnace after the end of the heat preservation;

[0065] (4) 2wt.% coffee shell ash and 98wt% A are mixed uniformly and loaded into a high-purity graphite crucible, and placed in a muffle furnace, and vacuumized to a vacuum degree of 10 -3 Pa in the furnace, and vacuumized to a vacuum degree of 10

[0066] (5) After the end of the heat preservation, the product is cooled to room temperature, and the upper surface impurities are removed to obtain high-purity silicon carbide product.

[0067] The purity of silicon carbide obtained in this example is 98.1%.

[0068] Example 3

[0069] A method for preparing silicon carbide by adding biomass ash to strengthen waste graphite and silicon waste, the specific steps are as follows:

[0070] (1) crushing, grinding and sieving the silicon waste and the waste graphite to obtain silicon waste powder and waste graphite powder, the particle size of the silicon waste powder being 100 μm and the particle size of the waste graphite powder being 100 μm;

[0071] (2) drying and crushing the rice husk to obtain rice husk powder;

[0072] (3) loading the rice husk powder into a corundum crucible and placing it in a muffle furnace, and heating it to 800 ℃ at a heating rate of 10 ℃ / min, and keeping it at 800 ℃ for 90 min under air, and then cooling it to room temperature to obtain rice husk ash;

[0073] (4) taking 3 wt.% of the rice husk ash and 97 wt.% of A, mixing them uniformly, loading them into a high-purity graphite crucible, placing the crucible in a muffle furnace, and vacuumizing the furnace to a vacuum degree of 20 Pa, and then heating it to 1550 ℃ at a heating rate of 10 ℃ / min, and keeping it at 1550 ℃ for 150 min; the A is composed of 68 wt.% of silicon waste powder and 32 wt.% of waste graphite powder;

[0074] (5) after the keeping, cooling the product to room temperature, and removing the upper surface impurities to obtain a high-purity silicon carbide product.

[0075] The silicon carbide obtained in this example has a purity of 96.37%.

[0076] Example 4

[0077] A method for preparing silicon carbide by adding biomass ash to reinforce waste graphite and silicon waste, and the specific steps are as follows:

[0078] (1) crushing, grinding and sieving the silicon waste and the waste graphite to obtain silicon waste powder and waste graphite powder, the particle size of the silicon waste powder being 125 μm and the particle size of the waste graphite powder being 125 μm;

[0079] (2) drying and crushing the cotton straw to obtain cotton straw powder;

[0080] (3) loading the cotton straw powder into a corundum crucible, placing it in a muffle furnace, and heating it to 900 ℃ at a heating rate of 10 ℃ / min, and keeping it at 900 ℃ for 120 min under air, and then cooling it to room temperature to obtain cotton straw ash;

[0081] (4) taking 4 wt.% of the cotton straw ash and 96 wt.% of A, mixing them uniformly, loading them into a high-purity graphite crucible, placing the crucible in a muffle furnace, and vacuumizing the furnace to a vacuum degree of 10 Pa, and then heating it to 1600 ℃ at a heating rate of 10 ℃ / min, and keeping it at 1600 ℃ for 180 min; the A is composed of 67 wt.% of silicon waste powder and 33 wt.% of waste graphite powder, -3

[0082] ​(5) After the end of the heat preservation, the product is cooled to room temperature to obtain a high-purity silicon carbide product.

[0083] The purity of the silicon carbide obtained in this example is 96.95%.

[0084] Example 5

[0085] A method for preparing silicon carbide by adding biomass ash to reinforce waste graphite and silicon waste, the specific steps are as follows:

[0086] (1) The silicon waste and waste graphite are crushed, ground and sieved to obtain silicon waste powder and waste graphite powder, the particle size of the silicon waste powder is 150 μm, and the particle size of the waste graphite powder is 150 μm;

[0087] (2) The corn straw is dried and crushed to obtain corn straw powder;

[0088] (3) The corn straw powder is loaded into a corundum crucible and placed in a muffle furnace, and heated to 1000℃ at a heating rate of 10℃ / min, and heat preserved for 60min under air condition, and then cooled in the furnace to obtain coffee shell ash;

[0089] (4) 4wt.% coffee shell ash and 96wt% A are uniformly mixed and loaded into a high-purity graphite crucible, and placed in a muffle furnace, and vacuumized to a vacuum degree of 50Pa in the furnace, and heated to 1500℃ at a heating rate of 10℃ / min for vacuum roasting for 240min; the A is composed of 66wt.% silicon waste powder and 34wt.% waste graphite powder;

[0090] (5) After the end of the heat preservation, the product is cooled to room temperature to obtain a high-purity silicon carbide product.

[0091] The purity of the silicon carbide obtained in this example is 97.59%.

[0092] Comparative Example 1

[0093] A method for preparing silicon carbide by adding biomass ash to reinforce waste graphite and silicon waste, the specific steps are as follows:

[0094] (1) The silicon waste and waste graphite are crushed, ground and sieved to obtain silicon waste powder and waste graphite powder, the particle size of the silicon waste powder is 75 μm, and the particle size of the waste graphite powder is 75 μm;

[0095] (2) 70wt.% silicon waste powder and 30wt.% waste graphite powder are uniformly mixed and loaded into a high-purity graphite crucible, and placed in a muffle furnace, and vacuumized to a vacuum degree of 10Pa in the furnace, and heated to 1500℃ at a heating rate of 10℃ / min for vacuum roasting for 120min;

[0096] (3) After the end of the heat preservation, the product is cooled to room temperature to obtain a high-purity silicon carbide product.

[0097] The purity of the silicon carbide obtained in the present comparative example is 93.78%, and there is obvious Si impurity in the product.

[0098] Comparative Example 2

[0099] A method for preparing silicon carbide by adding biomass ash to reinforce waste graphite and silicon waste, the specific steps are as follows:

[0100] (1) The silicon waste and waste graphite are crushed, ground and sieved to obtain silicon waste powder and waste graphite powder, the particle size of the silicon waste powder is 50 μm, and the particle size of the waste graphite powder is 50 μm;

[0101] (2) 69wt.% of the silicon waste powder and 31wt.% of the waste graphite powder are mixed uniformly and loaded into a high-purity graphite crucible, which is placed in a muffle furnace, and vacuumized to a vacuum degree of 10 Pa in the furnace, and then heated to 1450℃ at a rate of 10℃ / min, and vacuumized for 180 min; -3

[0102] (3) After the end of the heat preservation, the product is cooled to room temperature to obtain a high-purity silicon carbide product.

[0103] The purity of the silicon carbide obtained in the present comparative example is 91.84%.

[0104] Comparative Example 3

[0105] A method for preparing silicon carbide by adding biomass ash to reinforce waste graphite and silicon waste, the specific steps are as follows:

[0106] (1) The silicon waste and waste graphite are crushed, ground and sieved to obtain silicon waste powder and waste graphite powder, the particle size of the silicon waste powder is 100 μm, and the particle size of the waste graphite powder is 100 μm;

[0107] (2) 67wt.% of the silicon waste powder and 33wt.% of the waste graphite powder are mixed uniformly and loaded into a high-purity graphite crucible, which is placed in a muffle furnace, and vacuumized to a vacuum degree of 20 Pa in the furnace, and then heated to 1550℃ at a rate of 10℃ / min, and vacuumized for 150 min;

[0108] (3) After the end of the heat preservation, the product is cooled to room temperature to obtain a high-purity silicon carbide product.

[0109] The purity of the silicon carbide obtained in the present comparative example is 89.27%.

[0110] ​The specific embodiments of the present application are described above in detail, but the present application is not limited to the above-described embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application.

Claims

1. A method for preparing silicon carbide from waste graphite and silicon waste material with biomass ash addition reinforcement, characterized by, The method comprises the following steps: (1) crushing, grinding and screening the silicon waste and the waste graphite respectively to obtain silicon waste powder and waste graphite powder, wherein the particle size of the obtained powder is distributed in the range of 50-150 μm; (2) drying and crushing the selected biomass to obtain biomass powder; (3) loading the biomass powder into a corundum crucible, roasting and heat preserving the biomass powder in an oxygen-containing atmosphere, and cooling the biomass powder after the heat preserving to obtain biomass ash; (4) grinding and uniformly mixing the biomass ash with the silicon waste powder and the waste graphite powder according to a certain proportion to obtain a mixture, loading the mixture into a high-purity graphite crucible, and placing the mixture in a muffle furnace to allow the mixture to react at high temperature under vacuum; the mixture is composed of A and the biomass ash, wherein A is composed of the silicon waste powder and the waste graphite powder according to a mass ratio of 65-70:30-35; the content of the biomass ash in the mixture is 1-10%; and the vacuum roasting temperature is 1410-1700 ℃; (5) after the reaction is completed, cooling the product to room temperature to obtain a high-purity silicon carbide product.

2. A method of preparing silicon carbide from waste graphite and silicon waste material, enhanced by the addition of biomass ash according to claim 1, characterized by: The biomass in step (2) is at least one selected from coffee shells, tobacco stalks, cotton stalks, rice stalks, wheat stalks, corn stalks, soybean stalks and rice husks.

3. A method of preparing silicon carbide from waste graphite and silicon waste material, enhanced by the addition of biomass ash, according to claim 2, characterized by: The biomass in step (2) is at least one selected from coffee shells, rice husks, rice stalks and tobacco stalks.

4. A method of preparing silicon carbide from waste graphite and silicon waste material, enhanced by the addition of biomass ash, according to claim 1, characterized by: In step (3), the roasting temperature is 600-1000 ℃, and the heat preserving time is 60-180 min.

5. A method of preparing silicon carbide from waste graphite and silicon waste material, enhanced by the addition of biomass ash, according to claim 1, characterized by: In step (4), the content of the silicon waste in the mixture A is 65-70 wt.%, the content of the waste graphite in the mixture A is 30-35 wt.%, and the content of the biomass ash in the mixture is 1-2.5%.

6. A method of preparing silicon carbide from waste graphite and silicon waste material, enhanced by the addition of biomass ash, according to claim 5, characterized by: The tobacco stalks are roasted in an air atmosphere, and the content of the biomass ash in the mixture is 1-1.1%.

7. A method of preparing silicon carbide from waste graphite and silicon waste material fortified with biomass ash according to claim 1, characterized by: In step (4), the vacuum degree of vacuum baking is 10 -3 50 Pa, and the holding time is 60 to 240 min.

8. A method of preparing silicon carbide from waste graphite and silicon waste material fortified with biomass ash according to claim 1, characterized by: The purity of the silicon carbide obtained in step (5) is greater than 98%.

9. A method of preparing silicon carbide from waste graphite and silicon waste material fortified with biomass ash according to claim 1, characterized by: The purity of the silicon carbide obtained in step (5) is greater than 98%.

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