Method for preparing 5N grade quartz sand for quartz crucible by high-temperature oscillating chloridizing roasting

Abstract

The application provides a method for preparing 5N-grade quartz sand for quartz crucible by high-temperature oscillation chlorination roasting, which comprises the following steps: firstly, first roasting treatment is performed on the quartz sand in a first temperature range, so that alpha-quartz of the quartz sand is fully converted into beta-quartz; secondly, second roasting treatment is performed on the quartz sand in a second temperature range under a negative pressure system, so that beta-quartz is fully converted into alpha-quartz; thirdly, the above steps are repeated multiple times, so that lattice impurities in the quartz sand crystal are fully enriched on the surface of the quartz sand; fourthly, the quartz sand is subjected to hot-pressing leaching treatment, and a hot-pressing leaching product is obtained; and finally, the hot-pressing leaching product is washed to neutral, filtered and dried, and 5N-grade ultra-pure quartz sand for quartz crucible is obtained; the preparation method has good purification effect and remarkable economic benefits, and is suitable for popularization and use in industry.

Description

Technical Field

[0001] This invention relates to the field of high-purity quartz purification and detection, and in particular to a method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting. Background Technology

[0002] Quartz (SiO2) is an important non-metallic mineral material. Ordinary quartz sand is commonly used in ceramics, glass, and glass products. Ultrapure quartz sand (SiO2 content ≥ 99.999%), due to its excellent thermal, optical, and electrical properties, is widely used in strategic emerging industries such as semiconductors, fiber optic communications, aerospace, military, and electronics. With the rapid development of the semiconductor and photovoltaic industries, ultrapure quartz materials are becoming increasingly important. Ultrapure quartz sand requires a high SiO2 content, while impurity elements (such as Fe, Al, K, Na, Li, and Ca) also need to be reduced to very low levels. Currently, domestically produced quartz sand has a high impurity content and many inclusions, resulting in quartz crucibles that are often opaque or contain bubbles, which greatly limits the sustainable development of the semiconductor and photovoltaic industries.

[0003] Natural quartz resources generally contain impurities such as associated minerals, gas-liquid-solid inclusions, lattice substitutions, and interstitial metal elements. In particular, lattice impurity elements are difficult to separate effectively using conventional beneficiation methods, which is a major technical challenge in the field of high-purity quartz sand.

[0004] Therefore, there is an urgent need for a method to prepare 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting in order to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting, which can solve the technical problem of difficulty in removing lattice impurities in vein quartz.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting, comprising the following steps:

[0007] S10, the quartz sand is subjected to the first calcination treatment within the first temperature range, so that the α-quartz of the quartz sand is fully transformed into β-quartz.

[0008] S20, under negative pressure system and in the second temperature range, quartz sand is subjected to a second calcination treatment to fully transform β-quartz into α-quartz;

[0009] S30, repeat steps S10 and S20 multiple times to allow lattice impurities inside the quartz sand crystals to be fully enriched on the surface of the quartz sand.

[0010] S40 is used to perform hot-press leaching treatment on quartz sand to obtain hot-press leaching products;

[0011] S50, the hot-pressed leaching product is washed until neutral, filtered and dried to obtain 5N grade ultrapure quartz sand for quartz crucibles.

[0012] Preferably, in step S10, the first temperature range is 673–873°C.

[0013] Preferably, in step S10, the gas atmosphere for the first calcination treatment is a mixture of Cl2, HCl and N2; wherein the gas ratio of Cl2, HCl and N2 is 1:3:4, and the gas flow rate of the mixture is 600-800 mL / min.

[0014] Preferably, in step S10, the quartz sand is subjected to a first roasting treatment using a tubular roasting furnace, and the holding time for the first roasting treatment is 1 to 3 hours.

[0015] Preferably, in step S10, the rear end of the tubular roasting furnace is connected to a tail gas treatment device, which includes a saturated NaOH solution.

[0016] Preferably, in step S20, the pressure range of the negative pressure system is 0.04 to 0.06 MPa.

[0017] Preferably, in step S20, the second temperature range is 373–473°C, and the holding time for the second calcination treatment is 1–3 hours.

[0018] Preferably, in step S30, by repeating steps S10 and S20 three to six times, the lattice impurities inside the quartz sand crystals are fully enriched on the surface of the quartz sand.

[0019] Preferably, in step S40, a high-pressure reactor is used for hot-press leaching treatment, the leaching temperature of the hot-press leaching treatment is 120-140°C, and the leaching time of the hot-press leaching treatment is 5-10 hours.

[0020] Preferably, in step S40, the liquid-to-solid ratio of the quartz sand to the leachate in the hot-pressed leaching product is 0.5–1.5 mL·g. -1 The leachate is composed of HCl:HF:NH4Cl = (3-5 mol·L⁻¹) -1 ):(1~2mol·L -1 :(2~4mol·L -1 A mixed solution of ).

[0021] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention provides a method for preparing 5N grade quartz sand for quartz crucibles using high-temperature oscillating chlorination roasting, comprising the following steps: First, the quartz sand undergoes a first roasting treatment within a first temperature range to fully transform α-quartz into β-quartz; second, the quartz sand undergoes a second roasting treatment under a negative pressure system and within a second temperature range to fully transform β-quartz into α-quartz; third, the above steps are repeated multiple times to fully enrich the lattice impurities inside the quartz sand crystals onto the surface of the quartz sand; finally, the quartz sand... Hot-press leaching is performed to obtain a hot-press leaching product. Finally, the hot-press leaching product is washed until neutral, filtered, and dried to obtain 5N grade ultrapure quartz sand for quartz crucibles. This invention first subjectes the quartz sand to multiple oscillating calcination treatments, causing repeated crystal transformations (interconversion between α-quartz and β-quartz), thereby fully enriching the lattice impurities of the quartz sand to the surface. Then, hot-press leaching is used to dissolve the surface layer to efficiently remove lattice impurities, ultimately obtaining 5N grade ultrapure quartz sand for quartz crucibles. This method has good purification effect, significant economic benefits, and is suitable for industrial application. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting according to an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting, so as to meet the demand of the semiconductor and photovoltaic industries for ultrapure quartz sand.

[0025] Please see Figure 1 , Figure 1 This is a schematic flowchart of a method for preparing 5N grade quartz sand for quartz crucibles using high-temperature oscillating chlorination roasting, as provided in an embodiment of the present invention. The preparation method includes the following steps:

[0026] S10 involves the first calcination treatment of quartz sand within the first temperature range, which allows the α-quartz in the quartz sand to fully transform into β-quartz.

[0027] Specifically, S10 also includes:

[0028] First, a tubular calcining furnace is used to calcine quartz sand (vein quartz, also known as low-temperature quartz, with a crystal type of α-quartz) at a first temperature range of 673 to 873°C for 1 to 3 hours, so that the crystal type of quartz sand is fully transformed from α-quartz to β-quartz. During this process, the lattice volume increases and lattice impurities inside the quartz are enriched on the quartz surface.

[0029] Secondly, a mixture of chlorine, hydrogen chloride, and nitrogen is continuously introduced into the tubular roasting furnace. The gas ratio is Cl2:HCl:N2 = 1:3:4, and the gas flow rate is 600-800 ml / min. Specifically, Cl2 and HCl, through high-temperature chlorination roasting, cause some lattice impurities of the quartz sand to be vaporized and discharged in the form of chlorides, while N2 is further carried out of the tubular roasting furnace by the chlorinated metal impurity ions after the aforementioned chlorine treatment for complete removal. Compared with traditional chlorination roasting, this method reduces the amount of chlorine used and can also act as a carrier to further remove impurity elements.

[0030] Meanwhile, a saturated NaOH solution is installed at the rear end of the tubular roasting furnace to recover the exhaust gas after the reaction, thus avoiding environmental pollution and safety hazards caused by the leakage of mixed gas.

[0031] S20, under negative pressure and within the second temperature range, performs a second calcination treatment on quartz sand to fully transform β-quartz into α-quartz.

[0032] Specifically, S20 also includes:

[0033] First, the pressure inside the tubular calcining furnace is adjusted to a negative pressure state (at this time, the mixed gas in step S10 is extracted), and the system pressure is controlled at 0.04 to 0.06 MPa. At the same time, the quartz sand (vein quartz) is calcined at a second temperature range of 373 to 473°C for 1 to 3 hours, so that the crystal type of the quartz sand is fully transformed from β-quartz to smaller α-quartz. Impurities in the crystal lattice can further migrate to the quartz surface, and the negative pressure state can further remove impurities on the surface of the quartz sand that have not been carried away by the chlorination gas.

[0034] S30 involves repeatedly performing steps S10 and S20 to ensure that lattice impurities inside the quartz sand crystals are fully enriched on the surface of the quartz sand.

[0035] Specifically, S30 also includes:

[0036] First, repeat steps S10 and S20 three to six times to fully transform the crystal type of quartz sand from α-quartz to β-quartz and then back to α-quartz. During the process of increasing and decreasing the lattice volume, lattice impurities are fully enriched from the bulk phase to the surface of the quartz sand.

[0037] After the oscillating roasting is completed, the roasted quartz sand is immediately poured into ultrapure water for water quenching. Then, it is washed with ultrapure water, filtered, and dried to obtain the oscillating roasted quartz sand. Since the oscillating roasting is a high-temperature operation, the cooling is completed by water quenching. At the same time, the drastic temperature change causes cracks to form on the particle surface to remove impurities.

[0038] S40 is used to perform hot-press leaching treatment on quartz sand to obtain hot-press leaching products.

[0039] Specifically, S40 also includes:

[0040] The quartz sand after oscillation and calcination was placed in a high-pressure reactor, and the liquid-solid ratio of the quartz sand to the leachate was controlled at 0.5–1.5 mL·g. -1 ;

[0041] The leachate was composed of HCl:HF:NH4Cl = (3–5 mol·L⁻¹) -1 ):(1~2mol·L -1 :(2~4mol·L -1 A mixed solution of ) is subjected to hot-press leaching to fully remove lattice impurities enriched on the surface of the quartz sand to obtain the hot-press leaching product; specifically, the leaching temperature is 120-140℃ and the leaching time is 5-10h.

[0042] S50, the hot-pressed leaching product is washed until neutral, filtered and dried to obtain 5N grade ultrapure quartz sand for quartz crucibles.

[0043] Specifically, the S50 also includes:

[0044] After hot-press leaching is completed, the hot-pressed leached quartz sand is washed with ultrapure water until neutral, filtered and dried to obtain 5N grade ultrapure quartz sand for quartz crucibles.

[0045] The following detailed embodiments illustrate the implementation of the above-described method for preparing 5N grade quartz sand for quartz crucibles using high-temperature oscillating chlorination roasting. Quartz is selected as the preferred mineral in all the following embodiments. In other embodiments, the preferred method can be applied to other types of minerals, which is not limited here.

[0046] Example 1:

[0047] In this embodiment, vein quartz with a SiO2 content of 99.99% is used as the object, and the above-mentioned method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting is applied. The specific steps are as follows:

[0048] Step one involves calcining quartz sand in a tubular furnace at a high temperature of 770℃ for 3 hours, allowing α-quartz to fully transform into β-quartz. During this process, the lattice volume increases, and lattice impurities inside the quartz accumulate on the quartz surface. Simultaneously, a mixed gas of Cl2, HCl, and N2 is continuously introduced into the system at a ratio of Cl2:HCl:N2 = 1:3:4 and a flow rate of 600 mL / min. Cl2 and HCl, through high-temperature chlorination calcination, allow some lattice impurities to vaporize and be discharged as chlorides. N2 is further carried out of the tubular furnace by the chloride metal impurity ions treated by the Cl2 and HCl gases, thereby reducing impurity ions in the quartz sand. Compared with traditional chlorination calcination, this method reduces chlorine consumption and acts as a carrier to further remove impurity elements. Furthermore, a saturated NaOH solution is installed at the rear end to recover the tail gas, preventing the leakage of Cl2 and HCl from the mixed gas and avoiding environmental pollution and safety hazards.

[0049] Step 2: Adjust the calcination system to negative pressure, control the system pressure to 0.06 MPa, control the low-temperature vacuum calcination conditions, maintain the temperature at 380℃, and hold for 3 hours to transform β-quartz into smaller α-quartz. Impurities in the lattice can further migrate to the quartz surface, and the vacuum system can further and fully remove impurities on the quartz surface that have not been carried away by chlorination gas.

[0050] Step 3: Repeat steps 1 and 2 three times each to fully transform α-quartz into β-quartz and then back into α-quartz. During the process of increasing and decreasing the lattice volume, lattice impurities are fully enriched from the bulk phase to the surface of the quartz sand. After the oscillating calcination is completed, the calcined quartz sand is immediately poured into ultrapure water for water quenching, then washed with ultrapure water, filtered, and dried to obtain the oscillating calcined quartz sand.

[0051] Step four: Place the quartz sand after oscillation and calcination into a high-pressure reactor, controlling the liquid-to-solid ratio of quartz sand to leachate to be 0.5 mL·g. -1 The leachate has the following composition: HCl:HF:NH4Cl = 3 mol·L⁻¹ -1 1 mol·L -1 4 mol·L -1 The mixed solution was subjected to hot-press leaching to fully remove lattice impurities enriched on the surface of the quartz sand. The leaching temperature was 120°C and the leaching time was 8 hours.

[0052] Step 5: After hot-press leaching is completed, the hot-pressed leached quartz sand is washed with ultrapure water until neutral, filtered and dried to obtain ultrapure quartz sand.

[0053] The ultrapure quartz sand prepared in Example 1 has a SiO2 content of 99.999%, which meets the standard of 5N grade ultrapure quartz sand. The content of each impurity element is shown in Table 1.

[0054] Example 2:

[0055] In this Example 2, vein quartz with a SiO2 content of 99.99% is used as the object. The method for preparing 5N grade quartz sand for quartz crucibles by high-temperature chlorination and oscillation calcination described above is applied. The specific steps are as follows:

[0056] Step 1: Quartz sand is roasted in a tubular roasting furnace under high temperature conditions, with the temperature controlled at 870℃ and the holding time at 3 hours, so that α-quartz is fully converted into β-quartz. At the same time, a mixed gas of chlorine, hydrogen chloride, and nitrogen is continuously introduced into the system. The gas ratio is Cl2:HCl:N2 = 1:3:4, and the gas flow rate is 800 mL / min. Saturated NaOH solution is set at the rear end to recover the tail gas after the reaction, so as to avoid environmental pollution and safety hazards caused by leakage of mixed gas.

[0057] Step 2: Adjust the calcination system to negative pressure, control the system pressure to 0.04 MPa, control the low-temperature vacuum calcination conditions, maintain the temperature at 470℃, and hold for 2 hours to transform β-quartz into smaller α-quartz. Impurities in the lattice can further migrate to the quartz surface, and the vacuum system can further and fully remove impurities from the quartz surface that have not been carried away by chlorine gas.

[0058] Step 3: Repeat steps 1 and 2 five times each to fully convert α-quartz into β-quartz and then back into α-quartz. After the oscillating roasting is completed, immediately pour the roasted quartz sand into ultrapure water for water quenching, then wash with ultrapure water, filter, and dry to obtain the oscillating roasted quartz sand.

[0059] Step four: Place the quartz sand after oscillation and calcination into a high-pressure reactor, controlling the liquid-to-solid ratio of quartz sand to leachate to be 1.0 mL·g. -1 The leachate is HCl:HF:NH4Cl = (4 mol·L⁻¹) -1 ):(1.5mol·L -1 ):(3mol·L -1 A mixed solution of ) was subjected to hot-press leaching to fully remove lattice impurities enriched on the surface of the quartz sand. The leaching temperature was 130℃ and the leaching time was 6h.

[0060] Step 5: After hot-press leaching is completed, the hot-pressed leached quartz sand is washed with ultrapure water until neutral, filtered and dried to obtain ultrapure quartz sand.

[0061] The SiO2 content in the ultrapure quartz sand prepared in Example 2 is 99.9991%, which meets the standard of 5N grade ultrapure quartz sand. The content of each impurity element is shown in Table 1.

[0062] Example 3:

[0063] In Example 3, vein quartz with a SiO2 content of 99.99% was used as the subject. The method for preparing 5N grade quartz sand for quartz crucibles by high-temperature chlorination and oscillating calcination described above was applied. The specific steps are as follows:

[0064] Step 1: Quartz sand is roasted in a tubular roasting furnace under high temperature conditions, with the temperature controlled at 670℃ and the holding time at 2 hours, so that α-quartz is fully converted into β-quartz. At the same time, a mixed gas of chlorine, hydrogen chloride, and nitrogen is continuously introduced into the system. The gas ratio is Cl2:HCl:N2 = 1:3:4, and the gas flow rate is 800 mL / min. Saturated NaOH solution is set at the rear end to recover the tail gas after the reaction, so as to avoid environmental pollution and safety hazards caused by leakage of mixed gas.

[0065] Step 2: Adjust the calcination system to negative pressure, control the system pressure to 0.04 MPa, control the low-temperature vacuum calcination conditions, maintain the temperature at 470℃, and hold for 2 hours to transform β-quartz into smaller α-quartz. Impurities in the lattice can further migrate to the quartz surface, and the vacuum system can further and fully remove impurities from the quartz surface that have not been carried away by chlorine gas.

[0066] Step 3: Repeat steps 1 and 2 six times each to fully convert α-quartz into β-quartz and then back into α-quartz. After the oscillating calcination is completed, immediately pour the calcined quartz sand into ultrapure water for water quenching, then wash with ultrapure water, filter, and dry to obtain the oscillating calcined quartz sand.

[0067] Step four: Place the quartz sand after vibration and calcination into a high-pressure reactor, controlling the liquid-to-solid ratio of quartz sand to leachate to be 1.5 mL·g. -1 The leachate is HCl:HF:NH4Cl = (5 mol·L⁻¹) -1 ):(2mol·L -1 :(4mol·L -1 A mixed solution of ) was subjected to hot-press leaching to fully remove lattice impurities enriched on the surface of the quartz sand. The leaching temperature was 140℃ and the leaching time was 8h.

[0068] Step 5: After hot-press leaching is completed, the hot-pressed leached quartz sand is washed with ultrapure water until neutral, filtered and dried to obtain ultrapure quartz sand.

[0069] The SiO2 content in the ultrapure quartz sand prepared in Example 3 is 99.9992%, which meets the standard of 5N grade ultrapure quartz sand. The content of each impurity element is shown in Table 1.

[0070] Comparative Example 1:

[0071] In Comparative Example 1, vein quartz with a SiO2 content of 99.99% was used as the subject. The method for preparing 5N grade quartz sand for quartz crucibles using the above-mentioned high-temperature chlorination and oscillating calcination was applied. The specific steps are as follows:

[0072] Step 1: Quartz sand is roasted in a tubular roasting furnace under high temperature conditions, with the temperature controlled at 870℃ and the holding time at 2 hours, so that α-quartz is fully converted into β-quartz. At the same time, a mixture of chlorine, hydrogen chloride, and nitrogen is continuously introduced into the system. The gas ratio is Cl2:HCl:N2 = 1:1:1, and the gas flow rate is 700 mL / min. Saturated NaOH solution is set at the rear end to recover the tail gas after the reaction, so as to avoid environmental pollution and safety hazards caused by leakage of mixed gas.

[0073] Step 2: After chlorination roasting, the roasted quartz sand is immediately poured into ultrapure water for water quenching. Then, it is washed with ultrapure water, filtered, and dried to obtain the roasted and water-quenched quartz sand.

[0074] Step 3: Place the calcined and water-quenched quartz sand into a high-pressure reactor, controlling the liquid-to-solid ratio of quartz sand to leachate to be 0.5 mL·g. -1 The leachate is HCl:HF:NH4Cl = (3 mol·L⁻¹) -1 ):(1mol·L -1 :(4mol·L -1 A mixed solution of ) was subjected to hot-press leaching to fully remove lattice impurities enriched on the surface of the quartz sand. The leaching temperature was 120℃ and the leaching time was 10h.

[0075] Step four: After hot-press leaching is completed, the hot-pressed leached quartz sand is washed with ultrapure water until neutral, filtered and dried to obtain ultrapure quartz sand.

[0076] The SiO2 content in the ultrapure quartz sand prepared in Example 3 was 99.998%, which did not meet the standard of 5N grade ultrapure quartz sand. The content of each impurity element is shown in Table 1.

[0077] Specifically, the SiO2 content and the content of each impurity in the ultrapure quartz sand prepared in Examples 1-3 and Comparative Example 1 were detected by inductively coupled plasma mass spectrometry (ICP-MS), as shown in Table 1:

[0078] impurity elements Example 1 Example 2 Example 3 Comparative Example 1 Al 6.63 5.87 5.37 8.74 B 0.00 0.00 0.00 0.00 Fe 0.19 0.16 0.11 0.56 K 0.10 0.08 0.03 0.55 Na 0.05 0.02 0.01 0.94 Li 0.09 0.07 0.01 0.31 Ca 0.53 0.37 0.14 1.28 Mg 0.00 0.00 0.00 0.76 Ti 1.59 1.42 1.36 2.71 Mn 0.05 0.04 0.02 0.09 Cu 0.17 0.14 0.08 0.35 Ni 0.09 0.04 0.02 0.14 Cr 0.00 0.00 0.00 0.01 Total content 9.49 8.21 7.15 16.44 <![CDATA[SiO2 content (%)]]> 99.999 99.9991 99.9992 99.998

[0079] Table 1. Impurity element content (μg / g) in quartz sand products of various examples and comparative examples.

[0080] The comparison shows that the SiO2 content in the ultrapure quartz sand prepared in Examples 1 to 3 is greater than or equal to 99.999%, meeting the standard of 5N grade ultrapure quartz sand. However, the SiO2 content in the ultrapure quartz sand prepared in Comparative Example 1 is 99.998%, which does not meet the standard of 5N grade ultrapure quartz sand. The above results indicate that the method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting provided by the present invention can effectively improve the SiO2 content in ultrapure quartz sand through oscillating roasting.

[0081] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0082] 1. This invention provides a method for preparing 5N-grade quartz sand for quartz crucibles using high-temperature oscillating chlorination roasting. This method allows lattice impurities in quartz to fully accumulate on the surface, and then the surface is dissolved by leaching to efficiently remove these impurities. During the temperature oscillating roasting process, quartz undergoes a phase transformation. When the temperature is above 573°C, α-quartz transforms into β-quartz; when the temperature is below 573°C, β-quartz transforms back into α-quartz. During the phase transformation, the lattice impurities inside the quartz increase in volume due to the twisting of the silicon-oxygen tetrahedra, causing the impurities to accumulate on the quartz surface. Temperature oscillating roasting further increases the number of phase transformations, allowing the lattice impurities to fully migrate and accumulate on the quartz surface. The surface-accumulated impurities are then dissolved by leaching, resulting in 5N-grade ultrapure quartz sand for quartz crucibles.

[0083] 2. The present invention provides a method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting. Using vein quartz as raw material, ultrapure quartz sand with SiO2 content ≥99.999% is prepared, which can meet the demand of the semiconductor and photovoltaic industries for ultrapure quartz sand. This method has high purification efficiency for lattice impurities and significant economic benefits, and is suitable for industrial application.

[0084] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not exhaustive, please refer to the descriptions in other embodiments. The above embodiments only illustrate the implementation of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting, characterized in that, Includes the following steps: S10, a tubular roasting furnace is used to perform a first roasting treatment on the quartz sand within a first temperature range and hold it at that temperature for 1 to 3 hours, so that the α-quartz of the quartz sand can be fully transformed into β-quartz; the first temperature range is 673 to 873°C, and the gas atmosphere of the first roasting treatment is a mixed gas composed of Cl2, HCl and N2, with a gas ratio of Cl2, HCl and N2 of 1:3:

4. S20, the quartz sand is subjected to a second calcination treatment under a negative pressure system and within the second temperature range and kept at the temperature for 1 to 3 hours to allow the β-quartz to fully transform into the α-quartz; the second temperature range is 373 to 473°C. S30, repeat steps S10 and S20 multiple times to allow lattice impurities inside the quartz sand crystal to be fully enriched on the surface of the quartz sand. S40, the quartz sand is subjected to hot-press leaching treatment to obtain hot-press leaching product; S50, the hot-pressed leaching product is washed until neutral, filtered and dried to obtain 5N grade ultrapure quartz sand for quartz crucibles.

2. The method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting according to claim 1, characterized in that, In step S10, the gas flow rate of the mixed gas is 600~800 mL / min.

3. The method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting according to claim 1, characterized in that, In step S10, the rear end of the tubular roasting furnace is connected to a tail gas treatment device, which includes a saturated NaOH solution.

4. The method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting according to claim 1, characterized in that, In step S20, the pressure range of the negative pressure system is 0.04~0.06MPa.

5. The method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting according to claim 1, characterized in that, In step S30, by repeating steps S10 and S20 three to six times, lattice impurities inside the quartz sand crystals are fully enriched on the surface of the quartz sand.

6. The method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting according to claim 1, characterized in that, In step S40, the hot-press leaching treatment is carried out in a high-pressure reactor. The leaching temperature of the hot-press leaching treatment is 120~140℃, and the leaching time of the hot-press leaching treatment is 5~10h.

7. The method for preparing 5N grade quartz sand for quartz crucibles by high-temperature oscillating chlorination roasting according to claim 6, characterized in that, In step S40, the liquid-to-solid ratio of the quartz sand to the leachate in the hot-pressed leaching product is 0.5~1.5 mL·g. -1 The leachate is HCl:HF:NH4Cl = (3~5 mol·L⁻¹) -1 ):(1~2mol·L -1 :(2~4mol·L -1 A mixed solution of ).

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