Method for preparing high-purity quartz sand using waste quartz crucible, high-temperature furnace, method for preparing high-purity quartz sand, and high-purity quartz sand

Abstract

The present disclosure relates to a method for preparing high-purity quartz sand from waste quartz crucibles, a high-temperature furnace, a method for preparing high-purity quartz sand, and high-purity quartz sand. The method comprises: pretreating waste quartz crucibles to obtain pretreated quartz sand; contacting the pretreated quartz sand with a chlorinating gas in a high-temperature furnace to perform chlorination treatment, thereby obtaining chlorination-treated quartz sand; performing first heating treatment on the chlorination-treated quartz sand in the high-temperature furnace under an inert treatment atmosphere, and controlling the pressure in the high-temperature furnace to be a first furnace pressure; subsequently performing second heating treatment, and controlling the pressure in the high-temperature furnace to be a second furnace pressure, thereby obtaining dehydroxylated and debubbled quartz sand; the first heating is performed at a temperature of 700-1200°C and a pressure of 0.01-1 KPa; the second heating is performed at a temperature of 800-1300°C, and the vacuum degree of the second furnace pressure is 10-80 KPa. The method of the present disclosure can simultaneously solve the problems of high impurity content, high hydroxyl content, and many bubbles in waste crucibles.

Description

Technical Field

[0001] This disclosure relates to the field of recycling and purifying quartz crucibles, specifically to a method for preparing high-purity quartz sand using waste quartz crucibles, a high-temperature furnace, a method for preparing high-purity quartz sand, and high-purity quartz sand. Background Technology

[0002] In the Czochralski (CZ) single-crystal silicon growth process, quartz crucibles are required. As disposable products, quartz crucibles are consumed in large quantities. After use, they typically require additional costs for disposal, further increasing production costs. Currently, the main raw material used in domestic quartz crucible production is high-purity quartz sand. With industry development and resource depletion, the cost of quartz sand is rising, further increasing production costs.

[0003] Therefore, recycling waste quartz crucibles, especially preparing them into high-purity quartz sand, is of great strategic importance. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method for preparing high-purity quartz sand using waste quartz crucibles, a high-temperature furnace, and the method and high-purity quartz sand itself. This method can simultaneously solve the three major problems faced when recycling waste quartz crucibles: high impurity content, high hydroxyl content, and severe bubble growth. The high-purity quartz sand prepared by this method has an impurity content that meets the requirements for high-purity quartz sand used in the photovoltaic industry. After being melted into a quartz crucible, the hydroxyl content is below 50 ppm, and the product has no bubble growth problem.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a method for preparing high-purity quartz sand using a waste quartz crucible, the method comprising the following steps:

[0006] Waste quartz crucibles are pretreated to obtain pretreated quartz sand;

[0007] The pretreated quartz sand is brought into contact with chlorine gas in a high-temperature furnace to undergo chlorination treatment, thereby obtaining chlorinated quartz sand.

[0008] Under an inert atmosphere, the chlorinated quartz sand is subjected to a first heating treatment in the high-temperature furnace, and the pressure inside the high-temperature furnace is controlled at the first furnace pressure; then a second heating treatment is performed, and the pressure inside the high-temperature furnace is controlled at the second furnace pressure, to obtain quartz sand after dehydroxylation and deaeration treatment.

[0009] The temperature of the first heating is 700–1200℃, and the pressure inside the first furnace is 0.01–1 kPa; the temperature of the second heating is 800–1300℃, and the vacuum degree of the pressure inside the second furnace is 10–80 kPa.

[0010] Optionally, the method further includes: performing a first purification treatment on the high-temperature furnace before the chlorination treatment; the first purification treatment includes purifying the high-temperature furnace by introducing the inert treatment atmosphere; the conditions of the first purification treatment include: a temperature of 150-250°C and a time of 5-10 min.

[0011] Optionally, the chlorine gas is chlorine and / or hydrogen chloride, preferably chlorine; the chlorination treatment conditions include: a temperature of 500–1000°C and a time of 30–120 min.

[0012] Optionally, the chlorination treatment includes a second purification of the interior of the high-temperature furnace;

[0013] The second purification process includes introducing an inert atmosphere into the high-temperature furnace for a second purification; the second purification time is 2 to 8 minutes.

[0014] Optionally, the temperature of the first heat treatment is 850–1050°C, the pressure inside the first furnace is 0.01–0.08 kPa, and the time is 30–180 min; and / or,

[0015] The temperature of the second heating treatment is 900–1100℃, the vacuum degree of the second furnace pressure is 20–70 kPa, and the time is 30–120 min.

[0016] Optionally, the pretreatment includes one or more of coarse crushing, ultrasonication, fine grinding, color sorting, magnetic separation, and acid washing;

[0017] The pretreated quartz sand has a particle size of 70–350 μm, and the proportion of quartz sand with a particle size between 70 and 350 μm is more than 90%, with a total metal impurity content of 30–50 ppm.

[0018] The second aspect of this disclosure provides a high-temperature furnace for use in the method described in the first aspect of this disclosure, the high-temperature furnace comprising a chlorine gas inlet, an inert gas inlet, a chlorine gas outlet, an inert gas outlet, a vacuum valve, a feeding furnace door, and a discharging furnace door;

[0019] The furnace chamber of the high-temperature furnace is made of quartz glass. Optionally, the furnace chamber of the high-temperature furnace is formed as a horizontal quartz glass cylinder, which can rotate around an axis.

[0020] The third aspect of this disclosure provides a method for preparing high-purity quartz sand using the high-temperature furnace described in the second aspect of this disclosure, comprising the following steps:

[0021] The pretreated quartz sand is loaded into a high-temperature furnace. The chlorine gas inlet, chlorine gas outlet and vacuum valve are closed. An inert treatment atmosphere is introduced from the inert treatment gas inlet to perform the first purification of the furnace.

[0022] After the first purification is completed, close the inert gas inlet, inert gas outlet and vacuum valve, and introduce chlorination atmosphere through the chlorination gas inlet for chlorination treatment;

[0023] After chlorination is completed, the chlorine gas inlet, chlorine gas outlet and vacuum valve are closed, and an inert treatment atmosphere is introduced from the inert treatment gas inlet to perform a second purification of the furnace.

[0024] After the second purification is completed, the chlorine gas inlet, chlorine gas outlet, inert gas outlet and vacuum valve are closed, and the chlorinated quartz sand is subjected to the first heating treatment in an inert atmosphere.

[0025] After the first heat treatment is completed, close the chlorine gas inlet, chlorine gas outlet, inert gas inlet, and inert gas outlet, open the vacuum valve, and proceed with the second heat treatment.

[0026] Optionally, during the chlorination treatment, the first heating treatment, and the second heating treatment steps, the horizontal quartz glass cylinder is continuously rotated around an axis.

[0027] The fourth aspect of this disclosure provides a high-purity quartz sand, which is obtained by coarse crushing, ultrasonication, fine grinding, color sorting, magnetic separation, acid washing and chlorination of waste quartz crucible; the total amount of metallic impurity elements in the high-purity quartz sand is less than 20 ppm.

[0028] Optionally, the high-purity quartz sand further includes dehydroxylation and degassing treatment after the chlorination treatment; the high-purity quartz sand, after being melted into a crucible, has a hydroxyl content of less than 50 ppm and / or a bubble content of less than 0.01%.

[0029] Through the above technical solution, this disclosure further reduces the metal impurity content in waste quartz crucibles by controlling the process conditions of chlorination, dehydroxylation, and degassing in a high-temperature furnace. It also solves the problems of high hydroxyl content and numerous bubbles encountered when recycling waste quartz crucibles. The chlorination, dehydroxylation, and degassing steps are completed in the same equipment, reducing production costs and improving enterprise economic efficiency. This disclosure produces high-purity quartz sand that meets the requirements of the photovoltaic industry using waste quartz crucibles. The total amount of metal impurities in this high-purity quartz sand is below 20 ppm, the hydroxyl content is below 50 ppm, and the product has no bubble growth problem.

[0030] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0032] Figure 1 This is a schematic diagram of the high-temperature furnace apparatus in Example 1.

[0033] Explanation of reference numerals in the attached figures

[0034] 1: Inert gas inlet; 2: Chlorine gas inlet; 3: Vacuum valve; 4: Quartz glass tube; 5: Chlorine gas outlet; 6: Inert gas outlet; 7: Discharge furnace door; 8: Feed furnace door; 9: High-temperature furnace Detailed Implementation

[0035] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0036] Waste quartz crucibles contain a large number of impurities, hydroxyl groups, and air bubbles, all of which will affect the quality of subsequent quartz sand.

[0037] In existing technologies, high-temperature chlorination is generally used to remove alkali metals and alkaline earth metals from quartz sand; dehydroxylation is used to reduce the hydroxyl content in recycled sand and increase the high-temperature viscosity of the molten product; however, this method is only applied to the production of quartz products or quartz sand, and is rarely mentioned in the recycling of waste crucibles; and the removal of bubbles in the bubble layer of waste quartz crucibles has not been mentioned.

[0038] The first aspect of this disclosure provides a method for preparing high-purity quartz sand using a waste quartz crucible, the method comprising the following steps:

[0039] Waste quartz crucibles are pretreated to obtain pretreated quartz sand;

[0040] The pretreated quartz sand is brought into contact with chlorine gas in a high-temperature furnace to undergo chlorination treatment, thereby obtaining chlorinated quartz sand.

[0041] Under an inert atmosphere, the chlorinated quartz sand is subjected to a first heating treatment in a high-temperature furnace, and the pressure inside the high-temperature furnace is controlled at the first furnace pressure; then a second heating treatment is performed, and the pressure inside the high-temperature furnace is controlled at the second furnace pressure, to obtain quartz sand after dehydroxylation and deaeration treatment.

[0042] The temperature of the first heating is 700–1200℃, and the pressure inside the first furnace is 0.01–1 kPa; the temperature of the second heating is 800–1300℃, and the vacuum degree of the pressure inside the second furnace is 10–80 kPa.

[0043] The method disclosed herein can simultaneously solve the problems of high impurity content, high hydroxyl content, and numerous bubbles encountered when recycling waste quartz crucibles. It can prepare high-purity quartz sand that meets the requirements of the photovoltaic industry using waste quartz crucibles. The total amount of metallic impurity elements in the high-purity quartz sand is below 20 ppm, and the hydroxyl content after melting into a crucible is below 50 ppm, with no bubble growth problem.

[0044] According to this disclosure, the inert treatment atmosphere can be one of nitrogen, helium or argon.

[0045] According to one embodiment of this disclosure, after the pretreatment, the high-temperature furnace undergoes equipment leak testing. In one specific embodiment, equipment leak testing includes sealing the high-temperature furnace, evacuating the furnace to a maximum vacuum, and checking the sealing effect. The above embodiments ensure the safe use of the equipment.

[0046] According to one embodiment of this disclosure, a first purification treatment is performed on the high-temperature furnace before the chlorination treatment. In a further embodiment, the first purification treatment includes introducing an inert atmosphere into the high-temperature furnace for purification. The conditions for the first purification treatment include: a temperature of 150–250°C, preferably 180–220°C, and a time of 5–10 minutes, preferably 6–9 minutes. The above embodiments are beneficial for removing water vapor and air from the furnace, ensuring safety during subsequent chlorination treatment.

[0047] According to one embodiment of this disclosure, the chlorination treatment includes introducing chlorine gas into the high-temperature furnace for chlorination. In a further embodiment, the purity of the chlorine gas is 99.9% or higher, preferably 99.99% or higher; the chlorine gas is chlorine and / or hydrogen chloride, preferably chlorine; the conditions for the chlorination treatment include: a temperature of 500–1000°C, preferably 600–900°C; and a time of 30–120 min, preferably 60–120 min. The above embodiments facilitate the formation of gaseous chlorides from metallic impurities in the quartz sand lattice, further removing the content of metallic impurities, such as iron, aluminum, titanium, alkali metals, and alkaline earth metals. In one embodiment, the gas discharged from the chlorination treatment is neutralized, for example, using sodium hydroxide or potassium hydroxide. The neutralization method can be a conventional technique in the art and is not specifically limited herein.

[0048] According to one embodiment of this disclosure, the chlorination treatment is followed by a second purification of the furnace interior of the high-temperature furnace; in a further embodiment, the second purification includes introducing an inert treatment atmosphere into the high-temperature furnace for a second purification; the second purification time can be 2-8 minutes, preferably 3-7 minutes. The above embodiments are beneficial for removing chlorine gas that was not discharged during the chlorination treatment and for preventing chlorine gas from corroding the high-temperature furnace.

[0049] According to one embodiment of this disclosure, chlorinated quartz sand is subjected to a first heat treatment under an inert atmosphere. The conditions for the first heat treatment include: a temperature of 700–1200°C, preferably 850–1050°C; a furnace pressure of 0.01–1 kPa, preferably 0.01–0.08 kPa; and a time of 30–180 min, preferably 35–120 min. In a further embodiment, after the first heat treatment is completed, the inert atmosphere is stopped from being introduced into the furnace, and the pressure inside the high-temperature furnace is controlled to a second furnace pressure. The vacuum degree of the second furnace pressure is 10–80 kPa, preferably 20–70 kPa, and the temperature is 800–1300°C, preferably 900–1100°C. The second heat treatment is performed under these conditions, and the time is 30–120 min, preferably 35–100 min. The above-described implementation method facilitates the gradual reduction of hydroxyl content in quartz sand through diffusion. Simultaneously, the high-temperature negative pressure conditions within the high-temperature furnace allow the gas in the bubble layer of the waste quartz crucible to diffuse to the outside of the quartz sand particles, reducing bubble pressure and enabling rapid bubble growth and rupture for release. This not only reduces the hydroxyl content in the quartz sand but also achieves the purpose of bubble removal.

[0050] According to this disclosure, the pretreatment includes one or more of coarse crushing, ultrasonication, fine grinding, color sorting, magnetic separation, and acid washing. Those skilled in the art will know that magnetic separation is used to remove magnetic impurities and waste materials, such as iron and nickel; acid washing removes soluble impurity ions, such as Al. 3+ and Ca 2+ Ions, etc.; color sorting removes colored impurities and substances other than pure white. The processing conditions and operating methods of coarse crushing, ultrasonication, fine grinding, color sorting, magnetic separation and acid washing can be conventional technical means in this field, and this disclosure does not impose any special limitations.

[0051] According to one embodiment of this disclosure, the pretreated quartz sand has a particle size of 70–350 μm, preferably 100–300 μm; the proportion of quartz sand with a particle size between 70 and 350 μm is more than 90%; and the total content of metallic impurities is 30–50 ppm, preferably 30–45 ppm. The above embodiment is beneficial for obtaining qualified high-purity quartz sand and for reducing the generation of bubbles during the melting of high-purity quartz sand.

[0052] The second aspect of this disclosure provides a high-temperature furnace for use in the method described in the first aspect of this disclosure. The high-temperature furnace includes a chlorine gas inlet, an inert gas inlet, a chlorine gas outlet, an inert gas outlet, a vacuum valve, a feed furnace door, and a discharge furnace door.

[0053] According to this disclosure, the furnace chamber of the high-temperature furnace is made of quartz glass. In one embodiment, the furnace chamber is formed as a horizontal quartz glass cylinder, which is rotatable around an axis. In another embodiment, the vacuum valve is connected to a vacuum pump. These embodiments facilitate uniform heating of the quartz sand during chlorination, the first heating treatment, and the second heating treatment, thereby facilitating the removal of hydroxyl groups and air bubbles from the quartz sand.

[0054] The third aspect of this disclosure provides a method for preparing high-purity quartz sand using the high-temperature furnace described in the second aspect of this disclosure. The pretreated quartz sand is loaded into the high-temperature furnace, the chlorine gas inlet, chlorine gas outlet and vacuum valve are closed, and an inert treatment atmosphere is introduced from the inert treatment gas inlet to perform a first purification inside the furnace.

[0055] After the first purification is completed, close the inert gas inlet, inert gas outlet and vacuum valve, and introduce chlorination atmosphere through the chlorination gas inlet for chlorination treatment;

[0056] After chlorination is completed, the chlorine gas inlet, chlorine gas outlet and vacuum valve are closed, and an inert treatment atmosphere is introduced from the inert treatment gas inlet to perform a second purification of the furnace.

[0057] After the second purification is completed, the chlorine gas inlet, chlorine gas outlet, inert gas outlet and vacuum valve are closed, and the chlorinated quartz sand is subjected to the first heating treatment in an inert atmosphere.

[0058] After the first heat treatment is completed, close the chlorine gas inlet, chlorine gas outlet, inert gas inlet, and inert gas outlet, open the vacuum valve, and proceed with the second heat treatment.

[0059] In a further embodiment, during the chlorination treatment, the first heating treatment, and the second heating treatment steps, the horizontal quartz glass cylinder is continuously rotated around an axis.

[0060] The above-described embodiments ensure uniform heating of the quartz sand during chlorination, the first heating treatment, and the second heating treatment, resulting in better removal of hydroxyl groups and reducing the content of air bubbles. This facilitates chlorination, dehydroxylation, and degassing within the same equipment, while simultaneously addressing the issues of high hydroxyl and air bubble content in the quartz sand. Furthermore, the gas from the inert treatment atmosphere outlet can be recycled, reducing production costs and improving the economic benefits for enterprises. The method disclosed herein can be applied to the recycling and treatment of quartz products in other industries.

[0061] The fourth aspect of this disclosure provides a high-purity quartz sand, which is obtained by coarse crushing, ultrasonication, fine grinding, color sorting, magnetic separation, acid washing and chlorination treatment using waste quartz crucibles; the high-purity quartz sand can meet the requirements for impurity elements in GB / T 32649-2016 "High-purity quartz sand for photovoltaic use", and the total amount of metallic impurity elements is below 20 ppm.

[0062] In a further embodiment, the high-purity quartz sand further includes dehydroxylation and degassing treatment after the chlorination treatment; the hydroxyl content of the high-purity quartz sand after being melted into a crucible is below 50 ppm, and / or the bubble density is below 0.01%. The high-purity quartz sand can be used in the photovoltaic industry.

[0063] According to one embodiment of this disclosure, the method further includes washing and drying the quartz sand after dehydroxylation and deaeration treatment to obtain high-purity quartz sand. The washing and drying processes are conventional techniques in the art and will not be described in detail here. For example, deionized water can be used to wash the quartz sand after dehydroxylation and deaeration treatment.

[0064] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0065] Unless otherwise specified, all chemical reagents used in this disclosure are commercially available products.

[0066] The elemental impurity content was tested on a Varian 700-OES inductively coupled plasma atomic emission spectrometer.

[0067] The hydroxyl content was tested using a Nicolet 6700 Fourier transform infrared spectrometer manufactured by Thermo Fisher Scientific in the United States.

[0068] Example 1

[0069] Adopting such Figure 1 The equipment shown processes silica sand:

[0070] (1) The waste quartz crucible was subjected to coarse crushing, ultrasonication, fine grinding, color sorting, magnetic separation and acid washing pretreatment. The pretreated quartz sand had a particle size of 70-350μm accounting for 92% and a total metal impurity content of 50ppm.

[0071] (2) Load the pretreated quartz sand into the high-temperature furnace, close the feed furnace door (8) and the discharge furnace door (7), seal the feed furnace door (8) and the discharge furnace door (7), evacuate the high-temperature furnace to the ultimate vacuum, check the sealing effect inside the furnace, and perform equipment leak detection.

[0072] (3) After the leak detection is completed, close the chlorine gas inlet (2), chlorine gas outlet (5) and vacuum valve (3), and introduce nitrogen gas from the inert gas inlet (1) to perform the first purification in the furnace. The temperature of the first purification is 200℃ and the time is 8 minutes. Water vapor and furnace gas are discharged from the inert atmosphere outlet.

[0073] (4) After the first purification is completed, close the inert gas inlet (1), the inert gas outlet (6) and the vacuum valve (3), and introduce chlorine gas through the chlorine gas inlet (2) for chlorination treatment. The exhaust gas is discharged from the chlorine gas outlet (5). The chlorination treatment temperature is 900℃, the heating time is 60min, and the purity of the chlorine gas used is 99.99%.

[0074] (5) After the chlorination treatment is completed, close the chlorination gas inlet (2), chlorination gas outlet (5) and vacuum valve (3), and introduce nitrogen gas from the inert gas inlet (1) to perform a second purification in the furnace; the purification time is 6 minutes.

[0075] (6) After the second purification is completed, close the chlorine gas inlet (2), chlorine gas outlet (5), inert gas outlet (6) and vacuum valve (3), and introduce nitrogen into the furnace for the first heating treatment. The temperature of the first heating treatment is 800℃, the pressure is 0.05KPa, and the time is 50min. After the first heating treatment is completed, close the chlorine gas inlet (2), chlorine gas outlet (5), inert gas inlet (6) and inert gas outlet (6), stop the gas supply to the furnace, open the vacuum valve (3), and control the vacuum degree in the furnace to 40KPa, the temperature to 900℃, and the heating time to 60min to complete the second heating treatment.

[0076] (7) The quartz sand after dehydroxylation and deaeration treatment is washed and dried.

[0077] Example 2

[0078] The method in this embodiment is the same as in embodiment 1, except that the chlorination treatment is carried out at a temperature of 900°C for 120 minutes.

[0079] Example 3

[0080] The method in this embodiment is the same as in embodiment 1, except that the temperature of the first heating treatment is 1000℃, the pressure is 0.05KPa, and the time is 90min; the temperature of the second heating treatment is 1050℃, the time is 60min, and the vacuum degree is 60KPa.

[0081] Example 4

[0082] The method in this embodiment is the same as in embodiment 1, except that the first heating treatment and the second heating treatment are not performed in this embodiment.

[0083] Comparative Example 1

[0084] The method of this comparative example is the same as that of Example 1, except that this comparative example does not perform chlorination treatment, first heating treatment and second heating treatment.

[0085] Comparative Example 2

[0086] Use natural quartz sand.

[0087] Test Example 1

[0088] The impurity element content of the quartz sand obtained in Examples 1-4 and Comparative Example 1 was detected, and the test results are shown in Table 1.

[0089] Table 1

[0090]

[0091] According to the data in Table 1, the method of this disclosure, after chlorination treatment of waste quartz crucibles, can achieve a purity that meets the requirements for impurity elements in GB / T 32649-2016 "High-purity Quartz Sand for Photovoltaics". A comparison between Comparative Example 1 and Example 1 shows that the high-purity quartz sand after chlorination treatment has calcium, sodium, and titanium content that meets the requirements of GB / T 32649-2016, and the total amount of metallic impurities is below 20 ppm, also meeting the requirements of GB / T 32649-2016. A comparison between Example 2 and Example 1 shows that within the preferred chlorination treatment time range of this disclosure, the chlorination impurity removal effect is better.

[0092] Test Example 2

[0093] Quartz sand from Examples 1-4 and Comparative Examples 1-2 was melted into quartz crucibles using the same melting process. The hydroxyl content and bubble content in the quartz crucibles were measured. The hydroxyl content was measured by cutting the transparent layer of the quartz crucible into thin slices of a certain thickness and detecting the hydroxyl content using a Fourier transform infrared spectrometer. The bubble content was measured using an optical microscope to detect the bubble content on the inner surface of the quartz crucible; bubble density = bubble area / microscope field of view area. Specific results are shown in Table 2.

[0094] Table 2

[0095] hydroxyl content in crucible / ppm bubble density / % Example 1 43 0.0078 Example 2 44 0.0071 Example 3 30 0.0064 Example 4 116 0.0235 Comparative Example 1 120 0.0267 Comparative Example 2 46 0.0066

[0096] According to the data in Table 2, the high-purity quartz sand prepared by the method of this disclosure has reduced hydroxyl content and bubble density after being remelted into a quartz crucible. A comparison of Examples 1-3 and Example 4 shows that the high-purity quartz sand of this disclosure, after dehydroxylation and degassing treatment, has a hydroxyl content of less than 50 ppm and a bubble density of less than 0.01%, which can reach the level of the crucible made of natural quartz sand in Comparative Example 2. Comparative Example 1, which does not use the chlorination treatment, first heating treatment and second heating treatment of this disclosure, has a high hydroxyl content and a high bubble content, and its quality is far lower than that of the crucible made of natural quartz sand.

[0097] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. 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.

[0098] 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.

[0099] 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 producing high purity quartz sand from spent quartz crucibles, characterized by, The method comprises the following steps: The waste quartz crucible is pretreated to obtain pretreated quartz sand; the waste quartz crucible contains impurities, hydroxyl groups and bubbles; The pretreated quartz sand is contacted with chlorination gas in a high-temperature furnace to perform chlorination treatment, and chlorination-treated quartz sand is obtained; The chlorination-treated quartz sand is subjected to first heating treatment in the high-temperature furnace under an inert treatment atmosphere, and the pressure in the high-temperature furnace is controlled to be a first furnace pressure; then, the quartz sand is subjected to second heating treatment, and the pressure in the high-temperature furnace is controlled to be a second furnace pressure, to obtain hydroxyl group-removed and bubble-removed quartz sand; The temperature of the first heating is 700-1200℃, and the first furnace pressure is 0.01-1KPa; the temperature of the second heating is 800-1300℃, and the vacuum degree of the second furnace pressure is 10-80KPa.

2. The method of claim 1, wherein, The method further comprises: before the chlorination treatment, performing first purification treatment in the high-temperature furnace; The first purification treatment comprises purifying the high-temperature furnace by introducing the inert treatment atmosphere into the high-temperature furnace; and the conditions of the first purification treatment comprise: a temperature of 150-250℃ and a time of 5-10min.

3. The method of claim 1, wherein, The chlorination gas is chlorine and / or hydrogen chloride; and the conditions of the chlorination treatment comprise: a temperature of 500-1000℃ and a time of 30-120min.

4. The method of claim 1, wherein, The chlorination gas is chlorine.

5. The method of claim 1, wherein, After the chlorination treatment, second purification is performed in the high-temperature furnace; The second purification comprises purifying the high-temperature furnace by introducing the inert treatment atmosphere into the high-temperature furnace; and the second purification time is 2-8min.

6. The method of claim 1, wherein, The temperature of the first heating treatment is 850-1050℃, the first furnace pressure is 0.01-0.08KPa, and the time is 30-180min; and / or, the temperature of the second heating treatment is 900-1100℃, the vacuum degree of the second furnace pressure is 20-70KPa, and the time is 30-120min.

7. The method of claim 1, wherein, The pretreatment comprises one or more of rough breaking, ultrasonic treatment, fine grinding, color selection, magnetic separation and acid pickling; The particle size of the pretreated quartz sand is 70-350μm, the proportion of the particle size of the quartz sand in the range of 70-350μm is more than 90%, and the total content of metal impurities is 30-50ppm.

8. A high purity quartz sand, characterized by, The waste quartz crucible is subjected to rough breaking, ultrasonic treatment, fine grinding, color selection, magnetic separation, acid pickling and chlorination treatment; the waste quartz crucible contains impurities, hydroxyl groups and bubbles; the chlorination treatment comprises: The acid-pickled quartz sand is contacted with chlorination gas in a high-temperature furnace to perform chlorination treatment, and chlorination-treated quartz sand is obtained; After the chlorination treatment, hydroxyl group removal and bubble removal treatment are performed: The chlorination-treated quartz sand is subjected to first heating treatment in the high-temperature furnace under an inert treatment atmosphere, and the pressure in the high-temperature furnace is controlled to be a first furnace pressure; then, the quartz sand is subjected to second heating treatment, and the pressure in the high-temperature furnace is controlled to be a second furnace pressure, to obtain hydroxyl group-removed and bubble-removed quartz sand; The first heating temperature is 700-1200 DEG C, and the first furnace pressure is 0.01-1 KPa; the second heating temperature is 800-1300 DEG C, and the second furnace pressure is 10-80 KPa; After the high-purity quartz sand is melted into a crucible, the hydroxyl content is less than 50 ppm, and the bubble density is less than 0.01%; The total amount of metal impurity elements in the high-purity quartz sand is less than 20 ppm.

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