Method for removing impurity barium in crystallization layer of waste quartz crucible, method for preparing high-purity quartz sand and high-purity quartz sand

Abstract

The present disclosure relates to a method for removing impurity barium in a crystallization layer of a waste quartz crucible, a method for preparing high-purity quartz sand, and high-purity quartz sand, the method for removing impurity barium comprising the following steps: S1: separating the crystallization layer of the waste quartz crucible from the body of the waste quartz crucible to obtain a separated crystallization layer; S2: subjecting the separated crystallization layer to acid corrosion to obtain a corroded crystallization layer; the acid used in the acid corrosion is one of hydrochloric acid, sulfuric acid or hydrofluoric acid. The present disclosure can fully remove the impurity barium element in the crystallization layer of the waste quartz crucible by separating the crystallization layer on the surface of the waste quartz crucible from the body of the quartz crucible and then subjecting the crystallization layer to acid corrosion purification treatment.

Description

Technical Field

[0001] This disclosure relates to the field of quartz crucible recycling and purification technology, specifically to a method for removing barium impurities from the crystallization layer of waste quartz crucibles, a method for preparing high-purity quartz sand, and high-purity quartz sand. Background Technology

[0002] In the single-crystal pulling process, there are generally two methods to quickly form a uniform crystallized shell (cristobalite) on the inner surface of the quartz crucible. One method involves spraying a coating onto the inner surface of the quartz crucible during manufacturing. High-purity barium hydroxide solution is typically used, with high-purity carbon dioxide as the carrier gas. The crucible is then dried and packaged. During the spraying process, a chemical reaction occurs, generating barium carbonate on the surface of the quartz crucible. In the melting stage (under high temperature), the barium carbonate decomposes to form barium oxide. Since quartz glass crystallization is a nucleation process that spreads from impurities or imperfect surfaces, barium oxide reacts with silicon dioxide to form barium silicate. Therefore, barium ultimately exists on the surface of the quartz crucible in the form of barium silicate. Secondly, barium carbonate powder is added directly to the silicon material during crystal pulling. At high temperature, barium carbonate decomposes to generate barium oxide, which is dispersed in the molten silicon. As the silicon liquid flows, the barium oxide either becomes free or diffuses to the surface of the quartz crucible. When it comes into contact with the surface of the quartz crucible, it will react on the inner surface of the crucible to generate barium silicate.

[0003] Therefore, regardless of the process used during crystal pulling, the crystallized layer inside the waste crucible will always contain barium impurities. When recycling and reusing waste quartz crucibles, the presence of barium impurities can easily cause crystallization in the product, and the content of barium impurities is usually between 10 and 100 ppm. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method for removing barium impurities from the crystallization layer of a waste quartz crucible, a method for preparing high-purity quartz sand, and high-purity quartz sand. This removal method can effectively remove barium impurities from the crystallization layer.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a method for removing barium impurities from the crystallization layer of a waste quartz crucible, the method comprising the following steps:

[0006] S1: Separate the crystallized layer of the waste quartz crucible from the waste quartz crucible body to obtain the separated crystallized layer;

[0007] S2: The separated crystallized layer is acid-etched to obtain the etched crystallized layer;

[0008] The acid used in the acid corrosion is one of hydrochloric acid, sulfuric acid, or hydrofluoric acid.

[0009] Optionally, the acid corrosion reaction temperature is 25℃~80℃, preferably 50℃~80℃; the reaction time is 10min~60min, preferably 25min~40min.

[0010] Optionally, the acid used for acid etching is hydrochloric acid, and the mass percentage concentration of the hydrochloric acid is 5% to 38%; preferably 25% to 38%; the mass ratio of the hydrochloric acid to the crystallized layer is (1 to 3):1, preferably (1 to 2):1; and the barium content in the separated crystallized layer is below 60 ppm.

[0011] Optionally, the barium content in the separated crystallized layer is 20 ppm or more, and the weight ratio of hydrochloric acid to the separated crystallized layer is (1.5-2):1; or,

[0012] The barium content in the separated crystallized layer is 10-20 ppm, and the weight ratio of hydrochloric acid to the separated crystallized layer is (1-1.5):1; or,

[0013] The barium content in the separated crystallized layer is 0-10 ppm, and the weight ratio of hydrochloric acid to the separated crystallized layer is (1-1.2):1.

[0014] Optionally, the crystallization rate of the crystallization layer is above 99%, and the particle size of the crystallization layer is 5-15 mm.

[0015] Optionally, the separation includes subjecting the waste quartz crucible to at least one thermal shock treatment to obtain the thermally shock treated waste quartz crucible body and the crystallized layer;

[0016] The thermal shock treatment includes heating the waste quartz crucible to a first temperature and then cooling it to a second temperature; the first temperature is 150-1100℃, preferably 500-1000℃; the second temperature is below 50℃; and the average cooling rate is above 100℃ / min, preferably above 200℃ / min.

[0017] Optionally, the heating includes heating to a first temperature at a heating rate of 5–30°C / min; the heating time is 3–10 min; and the number of thermal shock treatments is 1–4 times; preferably, the heating rate is 10–30°C / min, and the number of thermal shock treatments is 2–4 times.

[0018] Optionally, the cooling time is 1 to 5 minutes, preferably less than 3 minutes; the cooling method is any one of air cooling, wind cooling, oil cooling, water cooling and coolant cooling.

[0019] Optionally, the method further includes coarsely crushing and cleaning the waste quartz crucible before thermal shock treatment;

[0020] The coarse crushing includes crushing the waste quartz crucible into blocks to obtain blocky waste quartz crucibles; the particle size of the blocky waste quartz crucibles is 30-150mm; the coarse crushing includes manual crushing and / or mechanical crushing;

[0021] The cleaning process includes washing the blocky waste quartz crucible with water.

[0022] Optionally, the method further includes vibrating and sieving the product of the thermal shock treatment, wherein the material over the sieve is the waste quartz crucible body and the material under the sieve is the crystallized layer.

[0023] Optionally, the aperture of the vibrating screen is 75% to 85% of the particle size of the blocky waste quartz crucible; preferably, it is 80% of the particle size of the blocky waste quartz crucible.

[0024] The second aspect of this disclosure provides a method for preparing high-purity quartz sand using a waste quartz crucible, comprising the following steps:

[0025] S1: The method provided in the first aspect of this disclosure is used to remove barium impurities from the crystallized layer of the waste quartz crucible to obtain the etched crystallized layer.

[0026] S2: The etched crystallized layer is washed with water and finely ground to obtain a finely ground crystallized layer; the finely ground crystallized layer is subjected to color sorting, magnetic separation, mixed acid washing and calcination to obtain high-purity quartz sand.

[0027] The third aspect of this disclosure provides a high-purity quartz sand, wherein the high-purity quartz sand is obtained by washing, fine grinding, color sorting, magnetic separation, mixed acid washing and calcination of the crystallization layer of waste quartz crucible; the barium content of the high-purity quartz sand is less than 1.5 ppm, and / or the yield is more than 95%.

[0028] Through the above technical solution, this disclosure can completely remove the barium impurity in the crystallization layer of the waste quartz crucible by separating the crystallization layer on the surface of the waste quartz crucible from the quartz crucible body and then subjecting the crystallization layer to acid etching purification treatment.

[0029] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0030] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0031] In this disclosure, the waste quartz crucible is mainly divided into the waste quartz crucible body and the crystallization layer. The waste quartz crucible body refers to the middle layer of the waste quartz crucible and is in an amorphous state. The crystallization layer refers to the inner and outer layers of the waste quartz crucible and is in a crystalline state.

[0032] The first aspect of this disclosure provides a method for removing barium impurities from the crystallization layer of a waste quartz crucible, comprising the following steps:

[0033] S1: Separate the crystallized layer of the waste quartz crucible from the waste quartz crucible body to obtain the separated crystallized layer;

[0034] S2: The separated crystallized layer is acid-etched to obtain the etched crystallized layer;

[0035] The acid used in the acid corrosion is one of hydrochloric acid, sulfuric acid, or hydrofluoric acid.

[0036] The removal method disclosed herein can effectively remove barium impurities from the crystallization layer of waste quartz crucibles.

[0037] According to one embodiment of this disclosure, the acid used for acid etching is hydrochloric acid, and the mass percentage concentration of the hydrochloric acid is 5% to 38%, preferably 25% to 38%; the weight ratio of the hydrochloric acid to the crystallized layer is (1 to 3):1, preferably (1 to 2):1. The acid solution used in this disclosure needs to be able to remove barium silicate from the crystallized layer and remove the generated impurities. The inventors have found that using hydrochloric acid can better recover the crystallized layer and remove the barium impurity. By further controlling the mass percentage concentration of the hydrochloric acid and the weight ratio of the hydrochloric acid to the crystallized layer, the crystallized layer can be in full contact with the acid, increasing the reaction area, thereby effectively removing the barium element from the crystallized layer and reducing the barium content to below 1.5 ppm.

[0038] According to this disclosure, the barium content in the separated crystallized layer is less than 60 ppm.

[0039] In a further embodiment, the barium content in the separated crystallized layer is above 20 ppm, and the weight ratio of hydrochloric acid to the separated crystallized layer is (1.5-2):1. The above embodiment, by controlling the weight of hydrochloric acid used for acid corrosion based on the barium content in the separated crystallized layer, can further improve the removal rate of barium impurities, reducing the barium content to below 1.5 ppm, while avoiding resource waste in actual production.

[0040] In one embodiment, the barium content in the separated crystallized layer is 10-20 ppm, and the weight ratio of hydrochloric acid to the separated crystallized layer is (1-1.5):1. By controlling the weight of hydrochloric acid used for acid etching according to the barium content in the separated crystallized layer, the removal rate of barium impurities can be further improved, reducing the barium content to below 1.5 ppm, while avoiding resource waste in actual production.

[0041] In one embodiment, the barium content in the separated crystallized layer is 0-10 ppm, and the weight ratio of hydrochloric acid to the separated crystallized layer is (1-1.2):1. By controlling the weight of hydrochloric acid used for acid etching according to the barium content in the separated crystallized layer, the removal rate of barium impurities can be further improved, reducing the barium content to below 1.5 ppm, while avoiding resource waste in actual production.

[0042] According to one embodiment of this disclosure, the reaction temperature of the acid corrosion is 25℃~80℃, preferably 50℃~80℃; the reaction time is 10min~60min, preferably 25min~40min. In the above preferred embodiment, it is beneficial to increase the reaction rate of the acid corrosion, allowing the barium in the crystallized layer to react fully with the acid, effectively removing the impurity barium element, and reducing the barium content to below 1.5ppm.

[0043] According to this disclosure, the crystallization rate of the crystallized layer is above 99%; the particle size of the crystallized layer is 5-15 mm; the main reaction between the acid solution and the crystallized layer is: BaSiO3 + 2HCl = H2SiO3 + BaCl2. The inventors have found that the particle size of the crystallized layer is closely related to the removal of Ba; a suitable particle size of the crystallized layer is conducive to the full reaction between the acid solution and Ba, further improving the removal rate of Ba; at the same time, it avoids the H2SiO3 sol generated by the reaction adhering to the surface of fine particles and preventing the corrosion reaction from proceeding, which is conducive to the smooth progress of the reaction.

[0044] According to another embodiment of this disclosure, the separation includes subjecting the waste quartz crucible to at least one thermal shock treatment to obtain a thermally shock treated waste quartz crucible body and a crystallized layer; the thermal shock treatment includes heating the waste quartz crucible to a first temperature and then cooling it to a second temperature; the first temperature is 150–1100°C, preferably 500–1000°C; the second temperature is below 50°C; and the average cooling rate is 100°C / min or higher, preferably 200°C / min or higher. The above embodiment facilitates the separation of the waste quartz crucible body from the crystallized layer, achieving a crystallization layer peeling ratio of over 90%, and fully recovering the crystallized layer.

[0045] In another specific embodiment, the heating includes heating to a first temperature at a heating rate of 5–30°C / min; the heating time is 3–10 min; the number of thermal shock treatments is 1–4; preferably, the heating rate is 10–30°C / min, and the number of thermal shock treatments is 2–3; the cooling time is 1–5 min, preferably less than 3 min; the cooling method can be any one of air cooling, wind cooling, oil cooling, water cooling, and coolant cooling. The wind cooling can be ordinary wind cooling or high-speed wind cooling. The above embodiments are beneficial for separating the waste quartz crucible body from the crystallized layer, fully recovering the crystallized layer, and the stripping ratio of the crystallized layer can reach more than 90%.

[0046] Waste quartz crucibles mainly consist of two crystalline layers (inner and outer) and the crucible body. During the pulling of single-crystal silicon, the furnace temperature exceeds 1400℃. At high temperatures (above 1200℃), crystalline β-cristobalite crystals begin to precipitate from the quartz glass. When the crucible cools (200℃~300℃), the β-cristobalite rapidly transforms into α-cristobalite, accompanied by a volume change of approximately 2.8%. Therefore, the crystalline layer of the waste quartz crucible is primarily α-cristobalite. The volume effect caused by the phase transition leads to localized stress and cracks within the crystalline layer. Numerous cracks also appear between the crystalline layer and the quartz glass of the crucible body, loosening the connection between them. Furthermore, there is a difference in the coefficient of thermal expansion between the α-cristobalite precipitated after crucible cooling and the quartz glass; the coefficient of thermal expansion of α-cristobalite is significantly greater than that of quartz glass.

[0047] This method utilizes the volume change from β-cristobalite to α-cristobalite and the difference in thermal expansion coefficients between α-cristobalite crystals and quartz glass to subject waste quartz crucibles to thermal shock treatment. By heating the waste quartz crucible to a specific temperature and then rapidly cooling it, significant thermal stress and volume change are generated on the surface of the crystalline layer, causing cracks and fragmentation, thus allowing the crystalline layer to peel off from the quartz body. During the thermal shock treatment, when the cooled crystalline layer (α-cristobalite) is reheated, the temperature rises to a certain level, and the α-cristobalite reverts to β-cristobalite, accompanied by a 2.8% volume change. If the temperature is further increased, melting may occur; therefore, the temperature range must be controlled. The inventors discovered that when the heating temperature is controlled between 150 and 1100°C and the cooling temperature is controlled below 50°C, α-cristobalite will not revert to β-cristobalite. In cristobalite, due to the difference in thermal expansion coefficients between the precipitated α-cristobalite crystals and quartz glass, the volume effect caused by the phase transition generates localized stress and cracks within the crystalline layer of the quartz material, leading to rapid peeling of the crystalline layer (α-cristobalite). Furthermore, by controlling the heating rate between 5 and 30 °C / min, the difference between the α-cristobalite crystals and quartz glass changes rapidly, causing a surge in stress and cracks, thus enabling even better peeling of the crystalline layer. The peeling ratio of the crystalline layer can reach over 70%, achieving complete separation of the waste quartz crucible body from the crystalline layers inside and outside the crucible.

[0048] Furthermore, the number of thermal shocks can effectively improve the degree of peeling of the crystallized layer from the quartz body; an appropriate number of thermal shocks is beneficial to the detachment of the quartz crucible body. When the number of thermal shocks is set to 2 to 4 times, the peeling ratio can be effectively improved, while preventing the quartz crucible body from falling into the crystallized layer; the control of heating temperature, heating rate and average cooling rate further increases the difference in thermal expansion coefficient between the crystallized layer and the quartz crucible body, further effectively separating the crystallized layer from the waste quartz crucible body, so that the peeling ratio of the crystallized layer can reach more than 90%.

[0049] In another embodiment, the method further includes coarse crushing and cleaning of the waste quartz crucible before thermal shock treatment; the coarse crushing includes breaking the waste quartz crucible into blocks to obtain blocky waste quartz crucibles; the particle size of the blocky waste quartz crucibles is 30-150 mm; the coarse crushing includes manual crushing and / or mechanical crushing; the cleaning includes washing the blocky waste quartz crucibles with water, which can be done using ultrasonic cleaning to remove dust and other stains from the surface of the waste quartz crucibles. The above-mentioned preferred particle size of the blocky waste quartz crucibles is beneficial to the subsequent thermal shock and vibratory screening treatment, and can better separate the crystallized layer from the waste quartz crucible body, with a crystallization layer peeling ratio of over 90%.

[0050] According to another embodiment of this disclosure, the method further includes vibrating and screening the waste quartz crucible body and the crystallized layer after thermal shock treatment, wherein the material over the screen is the waste quartz crucible body and the material under the screen is the crystallized layer; the aperture of the vibrating screen is 75% to 85% of the particle size of the blocky waste quartz crucible, preferably 80% of the particle size of the blocky waste quartz crucible. The above-mentioned preferred aperture ensures that all the stripped crystallized layer falls under the screen, and the material over the screen is all quartz glass body.

[0051] The second aspect of this disclosure provides a method for preparing high-purity quartz sand using a waste quartz crucible, comprising the following steps:

[0052] S1: The method provided in the first aspect of this disclosure is used to remove barium impurities from the crystallized layer of the waste quartz crucible to obtain the etched crystallized layer.

[0053] S2: The etched crystallized layer is washed with water and finely ground to obtain a finely ground crystallized layer; the finely ground crystallized layer is then subjected to color sorting, magnetic separation, mixed acid washing and calcination to obtain high-purity quartz sand.

[0054] According to one embodiment of this disclosure, the etched crystallized layer is washed with water until neutral, dried, and then finely ground to the required particle size, for example, 70–350 μm. The finely ground crystallized layer is then subjected to sieving, color sorting, magnetic separation, mixed acid washing, and calcination to obtain high-purity quartz sand. Those skilled in the art will know that calcination removes volatile substances, moisture, and other impurities from the quartz sand; magnetic separation is performed to remove magnetic impurities and waste materials, such as iron and nickel; and mixed acid washing removes soluble impurity ions, such as Al. 3+ or Ca 2+ Ions; colored impurities and substances other than pure white in the crystallized layer are removed by color sorting to obtain qualified high-purity quartz sand. The processing conditions and operation methods of color sorting, magnetic separation, mixed acid washing and calcination can be conventional technical means in this field, and this disclosure does not impose any special limitations.

[0055] The third aspect of this disclosure provides a high-purity quartz sand, which is obtained by washing, fine grinding, color sorting, magnetic separation, mixed acid washing and calcination of the crystallization layer of waste quartz crucible; the barium content of the high-purity quartz sand is less than 1.5 ppm, and / or the yield is more than 95%.

[0056] The high-purity quartz sand prepared according to the method of this disclosure uses waste quartz crucibles as raw materials, which is inexpensive and has a barium content of less than 1.5 ppm. This allows it to be effectively used in the preparation of various quartz products, such as in the preparation of quartz crucibles for Czochralski-grown monocrystalline silicon for solar energy.

[0057] The high-purity quartz sand prepared according to the method of this disclosure can be obtained, for example, from the crystallized layer of a waste quartz crucible through water washing, fine grinding, color sorting, magnetic separation, mixed acid washing, and calcination. The crystallized layer of the waste quartz crucible can be separated from the waste quartz crucible and obtained through an acid etching reaction. The yield after the acid etching reaction is above 95%, and the yield is calculated as (mass of the crystallized layer after acid etching / mass of the crystallized layer before acid etching) × 100%. This method is low in cost and can be effectively applied to large-scale production.

[0058] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0059] In the embodiments described below, the inductively coupled plasma atomic emission spectrometer used for testing is a Varian 700-OES instrument.

[0060] Unless otherwise specified, all chemical reagents used in this disclosure are commercially available products.

[0061] Example 1

[0062] S1: The waste quartz crucible is coarsely crushed into blocky waste quartz crucibles with a particle size of 40mm. The surface of the blocky waste quartz crucibles is washed with water to remove dust and other stains. After cleaning, it is subjected to thermal shock treatment 3 times. The high-temperature furnace is heated to 900℃ at 25℃ / min and heated for 5min. Then, the blocky waste quartz crucibles are immediately cooled by water for 2min. After thermal shock, the blocky waste quartz crucibles are screened by vibration with a sieve aperture of 32mm. The material on the sieve is the waste quartz crucible body, and the material under the sieve is the crystallized layer. The crystallized layer after separation of the waste quartz crucibles is obtained. The particle size of the separated crystallized layer is 5-15mm, and the peeling ratio of the crystallized layer is 99.5%. The barium content in the crystallized layer before corrosion is detected.

[0063] S2: The separated crystallized layer was immersed in a 36% hydrochloric acid solution, with a weight ratio of hydrochloric acid solution to crystallized layer of 1.5:1. The reaction temperature was 50℃ and the reaction time was 30 min, resulting in the etched crystallized layer. The barium content after etching is shown in Table 1.

[0064] Examples 2-10

[0065] Similar to Example 1, Examples 2 to 10 were set up according to Table 1, and the barium content in the crystalline layer after corrosion was detected. The test results are shown in Table 1.

[0066] Example 11

[0067] The method was the same as in Example 1, except that sulfuric acid was used and the mass percentage concentration of the sulfuric acid was 98%. The barium content in the crystalline layer after corrosion was detected, and the test results are shown in Table 1.

[0068] Example 12

[0069] The procedure was the same as in Example 1, except that the thermal shock treatment was performed three times. The high-temperature furnace was heated to 550°C at a rate of 15°C / min, heated for 5 minutes, and cooled for 2 minutes. The peeling ratio of the crystallized layer was 93%. The barium content in the crystallized layer after corrosion was detected, and the test results are shown in Table 1.

[0070] Example 13

[0071] The method is the same as in Example 1, except that the first heating temperature is 550°C, the heating rate is 5°C / min, the number of thermal shock treatments is 2, the average cooling rate is 275°C / min, the peeling ratio of the crystallized layer is 78%, and the barium content in the crystallized layer after corrosion is detected. The test results are shown in Table 1.

[0072] Example 14

[0073] The method is the same as in Example 1, except that the first heating temperature is 200°C, the heating rate is 25°C / min, the number of thermal shock treatments is 3, the average cooling rate is 100°C / min, the peeling ratio of the crystallized layer is 84%, and the barium content in the crystallized layer after corrosion is detected. The test results are shown in Table 1.

[0074] Example 15

[0075] The method was the same as in Example 1, except that the average cooling rate was 25°C / min, the peeling ratio of the crystallized layer was 84%, and the barium content in the crystallized layer after corrosion was detected. The test results are shown in Table 1.

[0076] Example 16

[0077] The method was the same as in Example 1, except that the first heating temperature was 80°C, the average cooling rate was 40°C / min, the peeling ratio of the crystallized layer was 0, and the barium content in the crystallized layer after corrosion was detected. The test results are shown in Table 1.

[0078] Example 17

[0079] The method was the same as in Example 1, except that the acid used was hydrofluoric acid with a mass percentage concentration of 20%. The barium content in the crystalline layer after corrosion was detected, and the test results are shown in Table 1.

[0080] Table 1

[0081]

[0082]

[0083] Test Example 1

[0084] The barium content was determined according to JY / T0567-2020 "General Rules for Inductively Coupled Plasma Atomic Emission Spectrometry". The test results are shown in Table 1.

[0085] As shown in Table 1, the method provided in this disclosure can effectively remove barium impurities from the crystallized layer of waste quartz crucibles. A comparison of Example 6 and Example 1 shows that, within the preferred weight ratio range of hydrochloric acid to the crystallized layer in this disclosure, barium impurities in the crystallized layer of waste quartz crucibles can be removed more effectively, with the barium content in the crystallized layer after acid etching being below 1.5 ppm. A comparison of Example 7 and Example 1 shows that, at the preferred reaction temperature for acid etching in this disclosure, barium impurities in the crystallized layer of waste quartz crucibles can be removed more effectively, with the barium content in the crystallized layer after acid etching being below 1.5 ppm. A comparison of Example 8 and Example 1 shows that, at the preferred reaction time in this disclosure, barium impurities in the crystallized layer of waste quartz crucibles can be removed more effectively, with the barium content in the crystallized layer after acid etching being below 1.5 ppm. Furthermore, a comparison of Example 4 and Example 2 shows that, within the preferred hydrochloric acid concentration range in this disclosure, barium impurities in the crystallized layer of waste quartz crucibles can be removed more effectively. A comparison of Examples 1 and 11 shows that the hydrochloric acid preferred in this disclosure can better remove barium impurities and facilitates the recovery of the crystallized layer. A comparison of Examples 9 and 10 with Example 1 shows that the particle size range of the crystallized layer in this disclosure is beneficial for more thorough removal of barium impurities from the crystallized layer of the waste quartz crucible, and the barium content in the crystallized layer after acid etching is below 1.5 ppm. A comparison of Examples 12 to 16 with Example 1 shows that by controlling the heating temperature and average cooling rate of the thermal shock treatment of the waste quartz crucible, the waste quartz crucible body can be separated from the crystallized layer. Furthermore, under the preferred thermal shock treatment range of 2-3 times, a heating temperature of 500-1000°C, a heating rate of 10-30°C / min, and an average cooling rate of 200°C / min or higher, the separation effect between the waste quartz crucible body and the internal and external crystallized layers is better, with a separation ratio of over 90%, achieving complete separation. By comparing Example 17 with Example 1, it can be seen that the hydrochloric acid preferred in this disclosure can better remove barium impurities, and after the acid corrosion reaction, the yield of the crystallized layer after the acid corrosion reaction is higher.

[0086] The etched crystallized layers obtained in Examples 1 to 17 above are washed with water and finely ground to obtain finely ground crystallized layers. The finely ground crystallized layers are then subjected to color sorting, magnetic separation, mixed acid washing, and calcination to obtain high-purity quartz sand with a purity of over 99.99%. The high-purity quartz sand obtained in this disclosure can be applied to the photovoltaic industry.

[0087] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0088] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0089] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for removing barium impurities from the crystallization layer of a waste quartz crucible, characterized in that, Includes the following steps: S1: Separate the crystallized layer of the waste quartz crucible from the waste quartz crucible body to obtain the separated crystallized layer; the waste quartz crucible is a used waste quartz crucible obtained through a single crystal pulling process; the crystallized layer contains barium silicate; S2: The separated crystallized layer is acid-etched to obtain the etched crystallized layer; The barium content in the separated crystallized layer is below 60 ppm; The acid used in the acid corrosion is hydrochloric acid or sulfuric acid; When the acid used for acid etching is hydrochloric acid, the mass percentage concentration of the hydrochloric acid is 5%~38%; the weight ratio of the hydrochloric acid to the separated crystallized layer is (1~3):1; When the acid used for acid etching is sulfuric acid, the mass percentage concentration of the sulfuric acid is 98%; the weight ratio of the sulfuric acid to the separated crystallized layer is 1.5:

1.

2. The removal method according to claim 1, wherein, The acid corrosion reaction temperature is 25℃~80℃; the reaction time is 10min~60min.

3. The removal method according to claim 2, wherein, The reaction temperature for acid corrosion is 50℃~80℃.

4. The removal method according to claim 2, wherein, The reaction time is 25 min to 40 min.

5. The removal method according to claim 1, wherein, The hydrochloric acid has a mass percentage concentration of 25% to 38%.

6. The removal method according to claim 1, wherein, The weight ratio of the hydrochloric acid to the separated crystallized layer is (1~2):

1.

7. The removal method according to claim 1, wherein, The barium content in the separated crystallized layer is above 20 ppm, and the weight ratio of hydrochloric acid to the separated crystallized layer is (1.5~2):1; or, The barium content in the separated crystallized layer is 10-20 ppm, and the weight ratio of hydrochloric acid to the separated crystallized layer is (1-1.5):1; or, The barium content in the separated crystallized layer is 0~10ppm, and the weight ratio of hydrochloric acid to the separated crystallized layer is (1~1.2):

1.

8. The removal method according to claim 1, wherein, The crystallization rate of the crystallization layer is above 99%, and the particle size of the crystallization layer is 5~15mm.

9. The removal method according to claim 1, wherein, The separation includes subjecting the waste quartz crucible to at least one thermal shock treatment to obtain the waste quartz crucible body and the crystallized layer after thermal shock treatment; The thermal shock treatment includes heating the waste quartz crucible to a first temperature and then cooling it to a second temperature; the first temperature is 150~1100℃; the second temperature is below 50℃; and the average cooling rate is above 100℃ / min.

10. The removal method according to claim 9, wherein, The first temperature is 500~1000℃.

11. The removal method according to claim 9, wherein, The average cooling rate is above 200℃ / min.

12. The removal method according to claim 9, wherein, The heating includes heating to a first temperature at a heating rate of 5~30℃ / min; the heating time is 3~10min; and the thermal shock treatment is performed 1~4 times.

13. The removal method according to claim 12, wherein, The heating rate is 10~30℃ / min.

14. The removal method according to claim 12, wherein, The thermal shock treatment is performed 2 to 4 times.

15. The removal method according to claim 9, wherein, The cooling time is 1 to 5 minutes, and the cooling method is any one of air cooling, wind cooling, oil cooling, water cooling, and coolant cooling.

16. The removal method according to claim 15, wherein, The cooling time is less than 3 minutes.

17. The removal method according to claim 9, wherein, The method also includes coarsely crushing and cleaning the waste quartz crucible before thermal shock treatment; The coarse crushing includes crushing the waste quartz crucible into blocks to obtain blocky waste quartz crucibles; the particle size of the blocky waste quartz crucibles is 30~150mm; the coarse crushing includes manual crushing and / or mechanical crushing; The cleaning process includes washing the blocky waste quartz crucible with water.

18. The removal method according to claim 17, wherein, The method further includes vibrating and screening the waste quartz crucible body and the crystallized layer after thermal shock treatment, with the waste quartz crucible body being the material that passes through the screen and the crystallized layer being the material that passes through the screen.

19. The removal method according to claim 18, wherein, The mesh size of the vibrating screen is 75% to 85% of the particle size of the blocky waste quartz crucible.

20. The removal method according to claim 19, wherein, 80% of the particle size of blocky waste quartz crucibles.

21. A method for preparing high-purity quartz sand using a waste quartz crucible, wherein, Includes the following steps: S1: Remove the barium impurity in the crystallized layer of the waste quartz crucible by the removal method described in any one of claims 1 to 20 to obtain the etched crystallized layer; S2: The etched crystallized layer is washed with water and finely ground to obtain a finely ground crystallized layer; the finely ground crystallized layer is subjected to color sorting, magnetic separation, mixed acid washing and calcination to obtain high-purity quartz sand.

22. A high-purity quartz sand, wherein, The high-purity quartz sand is obtained by washing, fine grinding, color sorting, magnetic separation, mixed acid washing and calcination of the crystallization layer of waste quartz crucible; the barium content of the high-purity quartz sand is less than 1.5 ppm and / or the yield is more than 95%; the method for removing barium impurities in the crystallization layer of the waste quartz crucible is the removal method described in any one of claims 1 to 20.

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