CN114180541A - Method for recovering and purifying waste silicon nitride - Google Patents
Method for recovering and purifying waste silicon nitride Download PDFInfo
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- CN114180541A CN114180541A CN202111610803.5A CN202111610803A CN114180541A CN 114180541 A CN114180541 A CN 114180541A CN 202111610803 A CN202111610803 A CN 202111610803A CN 114180541 A CN114180541 A CN 114180541A
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- silicon nitride
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/068—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with silicon
- C01B21/0687—After-treatment, e.g. grinding, purification
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/068—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with silicon
- C01B21/0682—Preparation by direct nitridation of silicon
Abstract
The invention discloses a method for recovering and purifying waste silicon nitride, and the obtained high-purity silicon nitride can be used for quartz crucible coatings, refractory materials and the like. The specific content of the invention is as follows: the silicon nitride coating on the inner surface of the waste quartz crucible is used as a silicon nitride raw material and contains a small amount of silicon dioxide, simple substance silicon, trace metal and other impurities; after ball milling and crushing of the silicon nitride raw material, metal impurities are removed by adopting high-gradient magnetic separation, silicon dioxide is removed by reverse flotation, and high-temperature simple substance silicon nitride is converted into silicon nitride to obtain high-purity silicon nitride. The method realizes high-purity recycling of the silicon nitride coating on the inner surface of the waste quartz crucible, saves resources and solves the problem of pollution of solid wastes.
Description
Technical Field
The invention relates to deep processing, deep utilization and resource utilization of industrial solid emissions, in particular to a method for recycling silicon nitride on the inner surface of a waste quartz crucible.
Background
The polycrystalline silicon ingot is cast in a quartz crucible, and a high-purity silicon nitride coating needs to be coated on the inner surface of the quartz crucible in the production process, and the silicon nitride coating can play a role of a release agent, so that the polycrystalline silicon ingot can be conveniently released from the quartz crucible. After the polycrystalline silicon ingot is demolded, the quartz crucible with the inner surface coated with silicon nitride is treated as waste. Because high-purity silicon nitride is expensive, the silicon nitride on the inner surface of the quartz crucible is directly discarded as waste, which not only increases the cost and wastes resources, but also causes the pollution of solid waste. Therefore, the method has important significance for recycling the silicon nitride coating on the inner surface of the quartz crucible, purifying and preparing high-purity silicon nitride and recycling.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for recovering and purifying waste silicon nitride, so as to realize the recovery and utilization of the silicon nitride.
In order to achieve the purpose, the specific technical scheme of the invention is as follows:
a method for recovering and purifying waste silicon nitride takes a silicon nitride coating on the surface of a waste quartz crucible as a silicon nitride raw material, wherein the silicon nitride coating contains a small amount of silicon dioxide, simple substance silicon, trace metal and other impurities, and the specific recovery and purification operation steps are as follows: the silicon nitride raw material is subjected to ball milling, screening, high-gradient magnetic separation, reverse flotation, cleaning, drying, high-temperature nitridation, cooling and classification to obtain the high-purity silicon nitride.
A method for recovering and purifying waste silicon nitride, wherein: and (3) grinding and grading the silicon nitride on the surface of the waste quartz crucible by ball milling and screening, and selecting a silicon nitride raw material with the granularity of less than or equal to 45 um.
A method for recovering and purifying waste silicon nitride, wherein: magnetic separation, adopting high gradient magnetic separation to remove trace metal impurities of the silicon nitride raw material.
A method for recovering and purifying waste silicon nitride, wherein: and (3) reverse flotation, namely, adopting a flotation reagent taking an amine collecting agent and modified starch as a regulator to perform reverse flotation removal on a small amount of silicon dioxide in the silicon nitride raw material.
A method for recovering and purifying waste silicon nitride, wherein: high-temperature nitridation, namely performing high-temperature nitridation treatment on a small amount of simple substance silicon in the silicon nitride raw material by adopting a direct nitridation method in high-purity nitrogen at 1250-.
In the invention, caking exists between the silicon nitride coating on the inner surface of the quartz crucible and silicon dioxide, simple substance silicon and metal or between the silicon nitride coating and the silicon dioxide, the simple substance silicon and the metal, so that ball milling and crushing are needed to separate silicon nitride from impurities; and simultaneously screening, and selecting silicon nitride with proper granularity (less than or equal to 45 um) as a recovered and purified silicon nitride raw material.
In the invention, silicon dioxide and simple substance silicon are main impurities in the silicon nitride raw material, and common hydrofluoric acid or alkaline aqueous solution is not adopted to carry out chemical reaction with the silicon dioxide to remove the silicon dioxide and the simple substance silicon
In the invention, a reverse flotation technology is selected, and a flotation reagent consisting of an amine collecting agent and modified starch as a regulator is used for removing a small amount of silicon dioxide by reverse flotation, so that the aim of purifying silicon nitride is fulfilled, acid and alkali pollution is avoided, and the danger of acid and alkali operation is also avoided.
In the invention, the silicon nitride after reverse flotation and pure water cleaning is fully dried by adopting a vacuum drying method, and preparation is made for high-temperature nitridation.
In the invention, a high-temperature nitridation method is adopted to treat simple substance silicon: in high purity N2The treatment time is 0.5-2 h at 1250-. Meanwhile, the reverse flotation reagent is decomposed and volatilized at high temperature, no residue is generated, and high-purity silicon nitride is not polluted.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The present invention is described in further detail below with reference to examples.
Example 1:
(1) ball milling and crushing: carrying out ball milling crushing on the silicon nitride raw material collected from the surface of the waste quartz crucible, and screening to obtain the silicon nitride raw material with the particle size of less than or equal to 45 um;
(2) high gradient magnetic separation: carrying out high-gradient magnetic separation on the silicon nitride raw material obtained in the step (1) to remove metal impurities;
(3) reverse flotation: the silicon nitride powder treated in the step (2) is subjected to reverse flotation by a flotation reagent which is composed of dodecylamine as a collecting agent and modified starch as a regulator,
(4) cleaning and drying: cleaning silicon nitride powder obtained by reverse flotation in the step (3) by using pure water and ultrasonic waves, and drying the silicon nitride powder in vacuum at the vacuum degree of less than or equal to 0.08MPa and the drying temperature of 200 ℃;
(5) high-temperature nitriding: putting the silicon nitride powder obtained in the step (4) into high-purity N2Nitriding at 1300 ℃ for 1 h in the atmosphere to obtain silicon nitride;
(6) cooling and grading: and (5) cooling and grading the silicon nitride powder obtained in the step (5) to obtain the high-purity silicon nitride powder.
Example 2:
(1) ball milling and crushing: carrying out ball milling crushing on the silicon nitride raw material collected from the surface of the waste quartz crucible, and screening to obtain the silicon nitride raw material with the particle size of less than or equal to 45 um;
(2) high gradient magnetic separation: carrying out high-gradient magnetic separation on the silicon nitride raw material obtained in the step (1) to remove metal impurities;
(3) reverse flotation: carrying out reverse flotation on the silicon nitride powder treated in the step (2) by using a flotation reagent consisting of lauramide as a collecting agent and modified starch as a regulator;
(4) cleaning and drying: cleaning silicon nitride powder obtained by reverse flotation in the step (3) by using pure water and ultrasonic waves, and drying the silicon nitride powder in vacuum at the vacuum degree of less than or equal to 0.08MPa and the drying temperature of 220 ℃;
(5) high-temperature nitriding: putting the silicon nitride powder obtained in the step (4) into high-purity N2Nitriding at 1280 ℃ for 1.5 h in the atmosphere to obtain silicon nitride;
(6) cooling and grading: and (5) cooling and grading the silicon nitride powder obtained in the step (5) to obtain the high-purity silicon nitride powder.
Claims (5)
1. The method for recovering and purifying the waste silicon nitride is characterized in that a silicon nitride raw material is purified by three methods of high-gradient magnetic separation, reverse flotation and high-temperature nitridation to obtain high-purity silicon nitride.
2. The method for recycling and purifying the waste silicon nitride as claimed in claim 1, wherein the method comprises the following steps:
(1) ball milling and crushing: carrying out ball milling and crushing on the silicon nitride raw material collected from the inner surface of the waste quartz crucible, and screening to obtain the silicon nitride raw material with a proper particle size;
(2) high gradient magnetic separation: carrying out high-gradient magnetic separation on the silicon nitride raw material obtained in the step (1);
(3) reverse flotation: performing reverse flotation on the silicon nitride powder treated in the step (2);
(4) cleaning and drying: ultrasonically cleaning the silicon nitride powder obtained by the step (3) by using pure water, and drying;
(5) high-temperature nitriding: performing high-temperature nitridation treatment on the silicon nitride powder obtained in the step (4);
(6) cooling and grading: and (5) cooling and grading the silicon nitride obtained in the step (5) to obtain high-purity silicon nitride powder.
3. The method for recycling and purifying waste silicon nitride as claimed in claim 2, wherein the particle size of the silicon nitride raw material obtained in step (1) is less than or equal to 45 um.
4. The method as claimed in claim 2, wherein the step (4) is vacuum drying, the vacuum degree is less than or equal to 0.08MPa, and the drying temperature is 200-240 ℃.
5. The method as claimed in claim 2, wherein the step (5) is a high temperature nitridation process at 1250-1350 ℃ for 0.5-2 h.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202111610803.5A CN114180541A (en) | 2021-12-27 | 2021-12-27 | Method for recovering and purifying waste silicon nitride |
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| CN202111610803.5A CN114180541A (en) | 2021-12-27 | 2021-12-27 | Method for recovering and purifying waste silicon nitride |
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| CN114180541A true CN114180541A (en) | 2022-03-15 |
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| CN202111610803.5A Pending CN114180541A (en) | 2021-12-27 | 2021-12-27 | Method for recovering and purifying waste silicon nitride |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116495709A (en) * | 2023-05-08 | 2023-07-28 | 衡阳凯新特种材料科技有限公司 | Method for recycling silicon nitride powder |
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2021
- 2021-12-27 CN CN202111610803.5A patent/CN114180541A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116495709A (en) * | 2023-05-08 | 2023-07-28 | 衡阳凯新特种材料科技有限公司 | Method for recycling silicon nitride powder |
| CN116495709B (en) * | 2023-05-08 | 2024-02-09 | 衡阳凯新特种材料科技有限公司 | Method for recycling silicon nitride powder |
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