Deep removal method for lattice impurities and inclusions in high-purity quartz sand

Abstract

The invention particularly discloses a deep removal method for lattice impurities and inclusion in high-purity quartz sand. The method comprises the steps of calcination water quenching, ultrasonic acidification, first-stage roasting, second-stage roasting, secondary water quenching, hot-pressing acid leaching and cleaning and drying. According to the method, through calcination water quenching, ultrasonic acidification, two-stage roasting, secondary water quenching and hot-pressing acid leaching, lattice impurities and tiny inclusion bodies in the high-purity quartz sand can be deeply removed, the purity of the purified quartz sand reaches 4N8 and even 5N grade or above, and then the technical problems existing in the prior art are solved.

Description

Technical Field

[0001] The present application belongs to the technical field of deep purification processing of quartz sand, and in particular relates to a method for deep removal of lattice impurities and inclusions in high-purity quartz sand. Background Art

[0002] With the rapid development of the semiconductor, optical fiber, and photovoltaic industries, demand for ultrapure quartz sand of grades 4N8 and above, even 5N, has surged. The presence of metallic impurities such as Fe, Al, Ti, K, Na, and Li in quartz sand severely limits the high-temperature resistance, mechanical strength, conductivity, and service life of quartz products. However, traditional acid leaching and flotation processes are ineffective in removing lattice impurities. Furthermore, micron-sized gas-liquid inclusions are difficult to break during conventional roasting due to insufficient thermal expansion. Lattice impurities in quartz sand are primarily categorized as lattice substitution impurities and charge compensation impurities. Lattice substitution impurities refer to the isomorphic substitution of Si4+ atoms by trivalent Al3+, Fe3+, and tetravalent Ti4+ atoms, forming new tetrahedra. Charge compensation impurities, on the other hand, arise from the substitution of trivalent impurity metal atoms for Si4+, causing charge non-conservation within the crystal structure. Consequently, monovalent metal ions such as Li+, Na+, and K+ fill the tetrahedra as charge-compensating atoms to achieve charge balance. Inclusions in quartz sand are mainly divided into fluid inclusions and mineral inclusions. Among them, fluid inclusions can be further divided into gas phase, liquid phase and gas-liquid two-phase. Water is a common fluid, and alkali metal (Li+, Na+, K+) and alkaline earth metal (Ca2+Mg2+) ions in quartz are also present in large quantities in fluid inclusions; as for mineral inclusions, minerals associated with quartz such as common feldspar, mica, etc. may appear as mineral inclusions in quartz. Among them, some larger inclusions can be removed by calcination and water quenching, etc., but small inclusions of several microns or even submicron level are difficult to remove.

[0003] Patent publication number CN119240714A discloses a method for calcining and water quenching to purify quartz sand. This method improves the removal efficiency of gas-liquid inclusions by combining high-temperature calcination with water quenching. However, there are still some shortcomings. The calcination temperature needs to reach 1200-1300℃. At high temperatures, quartz easily melts to form a solid solution, which hinders the diffusion of impurities. Water quenching requires 0-70℃ pure water, which has high requirements for water quality and cooling system. Moreover, this method mainly targets the rupture of gas-liquid inclusions, but has no effect on Al2O3 in the lattice. 3 +、Fe 3+ The removal effect of isomorphous impurities is limited.

[0004] Patent publication number CN118666282A discloses a method for the simultaneous deep removal of lattice impurities and inclusions from high-purity quartz sand. This method proposes a method for purifying high-purity quartz sand by combining electric heating and microwave heating. However, it still has the following technical limitations: The combined heating method consumes a lot of energy. Although it can activate impurities in a targeted manner, the microwave equipment requires additional energy input, and the electric heating must maintain a high temperature of 1200–1300°C, resulting in significantly higher overall energy consumption than traditional single heating processes. Furthermore, gaseous chlorinating agents (such as Cl2 and HCl) are prone to leakage at high temperatures, and no tail gas purification measures are specified, potentially resulting in residual Cl2 or HCl acid mist pollution.

[0005] Patent publication number CN118908228A discloses a multi-field coupling assisted high-purity quartz sand impurity removal method. This method uses the combined action of temperature field (calcination) + ultrasonic field + infrared light field + laser field to cause thermal expansion and microcracks in the gas-liquid inclusions inside the quartz sand. Combined with the thermal stress generated by cold quenching (rapid cooling), the probability of inclusion rupture is greatly increased. The laser field acts precisely on the impurity-rich area to destroy the Al 3+ 、Fe 3+ The combination of lattice impurities and Si-O bonds exposes them to the surface, and then the ultrasonic field is combined with the cavitation effect to enhance the cleaning efficiency of acid leaching or alkaline washing to improve the dissolution efficiency of impurities. However, the synergistic effect of multiple physical fields such as ultrasonic field and laser field requires precise control of parameters, and the actual production stability is poor, and the high valence elements (such as Ti) are not specifically solved. 4+ 、B 3+ ) lattice impurity removal problem, Al 3+ 、Ti 4+ Isomorphic impurities still rely on traditional chlorination roasting process. Microwave assistance can only improve the migration efficiency of surface impurities, but it is difficult to remove Al in deep lattice. 3+ 、Ti 4+ In view of this, it is extremely urgent to study a method for deep removal of lattice impurities and inclusions in high-purity quartz sand. Summary of the Invention

[0006] This application is made in view of the above technical problems and aims to provide a method for deep removal of lattice impurities and inclusions in high-purity quartz sand that can effectively remove lattice impurities.

[0007] To solve the above technical problems, the present application provides a method for deep removal of lattice impurities and inclusions in high-purity quartz sand, the method comprising:

[0008] Calcination and water quenching: 4N grade quartz sand is fed into a first preset temperature for calcination and then immediately poured into cold water for water quenching, wherein the first preset temperature is 900-1000°C;

[0009] Ultrasonic acidification: acidifying the water-quenched quartz sand with the first mixed acid under the assistance of ultrasound, and then washing it to a neutral temperature and drying it after the acidification is completed;

[0010] Calcination: Add ammonium chloride and aluminum chloride to the dried quartz sand, mix well, and calcine under an inert atmosphere, wherein the mass of ammonium chloride and aluminum chloride is 1-5% of the mass of the dried quartz sand. The specific calcination steps are:

[0011] In the first stage, the temperature is raised to 400-600℃ at a heating rate of 1-3℃ / min and kept at this temperature for 0.5-1.5h.

[0012] The second stage is calcination, with a heating rate of 4-6℃ / min, heating to 800-1000℃ and keeping warm for 1-3h;

[0013] Secondary water quenching: immediately pour the quartz sand after the second stage of roasting into cold water for secondary water quenching;

[0014] Hot-press acid leaching, filtering the quartz sand after the second water quenching, then pouring the filtered quartz sand into a reaction vessel and adding the second mixed acid, and then placing it in a drying container for reaction, wherein the reaction temperature is 100-120 ° C, and the reaction time is 4-8 hours;

[0015] Clean and dry the dried quartz sand until it is neutral and dry it.

[0016] In some embodiments, during the calcination and water quenching process, 4N grade quartz sand is placed in a rotary tube furnace at a first preset temperature and calcined for 20-40 minutes.

[0017] In some embodiments, during the ultrasonic acidification process, the ultrasonic temperature is 50-80° C., and the ultrasonic time is 0.5-1.5 h.

[0018] In some embodiments, the first mixed acid is hydrochloric acid, hydrofluoric acid, and oxalic acid in a volume ratio of 2:2:1.

[0019] In some embodiments, the second mixed acid is hydrochloric acid, nitric acid, and hydrofluoric acid in a volume ratio of 3:1:1.

[0020] In some embodiments, a two-stage alkali liquid absorption tower is used to capture the tail gas after the second stage roasting.

[0021] In some embodiments, during the cleaning and drying process, the drying temperature is 100-120°C.

[0022] Compared with the prior art, the present application provides a method for deep removal of lattice impurities and inclusions in high-purity quartz sand. First, large fluid inclusions in the quartz sand are removed by calcination and water quenching, and cracks are generated. Based on ultrasonic acidification, on the one hand, impurities on the surface of the quartz sand can be removed, and on the other hand, ultrasonic treatment can further generate new fine cracks, which is conducive to the first mixed acid entering the interior of the quartz sand to selectively corrode tiny mineral inclusions of aluminosilicates, thereby increasing the contact opportunity between the first mixed acid and the tiny fluid inclusions. During the first stage of roasting, ammonium chloride decomposes into ammonia and hydrogen chloride gas. The released hydrogen chloride can remove sodium ions and potassium ions in the lattice gaps of the quartz sand, and at the same time accumulates in the closed micro-regions of the lattice to form local high pressure, further enhancing the mechanical stripping effect on the lattice defects. During the second stage of roasting, a solid-solid reaction occurs at high temperature, and aluminum chloride directly reacts with the aluminosilicates in the quartz sand lattice to generate SiCl4, AlOCl, and Al2O3, while causing gas phase infiltration, and part of AlCl3 decomposes into Cl - The vapor penetrates into the lattice defects, combines with Al3+ to generate AlCl3 gas, and then chlorinates and volatilizes with K+ and Na+ plasma. The Al in AlCl3 3+ It can also react with impurity ions in the lattice (such as Fe 3+ 、Ti 4+ ) are replaced by NH4Cl, generating volatile chlorides (FeCl3, TiCl4), which escape at high temperatures. Furthermore, the residual HCl in NH4Cl further activates the surface of the quartz sand, synergistically enhancing the chlorination efficiency of metal impurities with AlCl3. Secondary water quenching can further rupture tiny fluid inclusions in the quartz sand. Hot-pressing acid leaching can deeply remove residual metal impurities. Therefore, the method for deeply removing lattice impurities and inclusions in high-purity quartz sand provided in this application can deeply remove lattice impurities and inclusions in high-purity quartz sand, allowing the purified quartz sand to reach a purity of 4N8 or even 5N or above. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a process flow chart of the method for deep removal of lattice impurities and inclusions in high-purity quartz sand in this application. DETAILED DESCRIPTION

[0025] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] refer to Figure 1 As shown, the embodiment of the present application provides a method for deep removal of lattice impurities and inclusions in high-purity quartz sand, the method comprising:

[0027] Calcination and water quenching: 4N grade quartz sand is calcined at a first preset temperature of 900-1000°C and immediately poured into cold water for water quenching. Specifically, the 4N grade high-purity quartz sand is first calcined in a rotary tube furnace at the first preset temperature for 20-40 minutes. The calcined high-purity quartz sand is then immediately poured into cold water for water quenching. This process utilizes temperature differences to induce different stresses inside and outside the high-purity quartz sand, thereby removing larger fluid inclusions from the sand. The cracks created during this process also increase the area exposed to impurities within the sand during subsequent acid leaching.

[0028] Ultrasonic acidification: The water-quenched quartz sand is acidified with a first mixed acid under ultrasound assistance, and after the acidification is completed, it is cleaned to a neutral temperature and dried. The ultrasonic temperature is 50-80°C, the ultrasonic time is 0.5-1.5 hours, and the first mixed acid refers to hydrochloric acid, hydrofluoric acid and oxalic acid in a volume ratio of 2:2:1. During this process, the first mixed acid can remove impurities on the surface of the high-purity quartz sand, and ultrasound can further produce new fine cracks in the quartz sand. The fine cracks are conducive to the hydrofluoric acid in the first mixed acid entering the interior of the quartz sand to selectively corrode tiny mineral inclusions of aluminum silicates, while also increasing the contact area between the first mixed acid liquid and the tiny fluid inclusions.

[0029] Calcination: Add ammonium chloride and aluminum chloride to the dried quartz sand, mix well, and calcine under an inert atmosphere, wherein the mass of ammonium chloride and aluminum chloride is 1-5% of the mass of the dried quartz sand. The specific calcination steps are:

[0030] In the first stage, the temperature is raised to 400-600℃ at a heating rate of 1-3℃ / min and kept at this temperature for 0.5-1.5h.

[0031] The second stage is calcination, with a heating rate of 4-6℃ / min, heating to 800-1000℃ and keeping warm for 1-3h;

[0032] Specifically, the first stage of calcination is dominated by NH4Cl, which decomposes into NH3 and HCl gases. The released HCl gas can first remove impurities such as Na+ and K+ in the lattice gap, creating a cleaner reaction environment for the subsequent AlCl3 treatment of aluminosilicate impurities. At the same time, the decomposed gas accumulates in confined micro-regions (such as quartz grain boundaries), forming local high pressure, enhancing the mechanical stripping effect on the quartz sand lattice defects, promoting pore expansion, and providing more paths for AlCl3 penetration.

[0033] The second stage of calcination is dominated by AlCl3. The temperature of the second stage is relatively high. Solid-solid reaction can occur at high temperature. AlCl3 directly reacts with the aluminosilicate (Al-O-Si structure) in the quartz lattice, destroying the bond to generate SiCl4, AlOCl, and Al2O3. At the same time, it can also cause gas phase penetration, and part of AlCl3 decomposes into Cl - The vapor penetrates into the lattice defects (vacancies, dislocations), combines with Al3+ to generate AlCl3 gas, and then chlorinates and volatilizes with K+ and Na+ plasma. The Al in AlCl3 3+ It can also react with impurity ions in the lattice (such as Fe 3+ 、Ti 4+ ) are replaced to generate volatile chlorides (FeCl3, TiCl4), which escape at high temperatures; in addition, the residual HCl in NH4Cl further activates the quartz surface and synergizes with AlCl3 to enhance the chlorination efficiency of metal impurities.

[0034] It should be noted that during the roasting process, an inert gas (such as nitrogen, helium or argon) needs to be introduced for protection to prevent oxidation of metal chlorides; in order to avoid environmental pollution, a two-stage alkali liquid absorption tower is used to capture the tail gas after the second stage of roasting.

[0035] Secondary water quenching: the quartz sand after the second stage of roasting is immediately poured into cold water for secondary water quenching; the secondary water quenching can further break the tiny fluid inclusions in the quartz sand.

[0036] Hot-press acid leaching: the quartz sand after secondary water quenching is filtered, then poured into a reaction vessel and a second mixed acid is added, and then placed in a drying vessel for reaction, wherein the reaction temperature is 100-120°C and the reaction time is 4-8 hours. In this process, the second mixed acid refers to hydrochloric acid, nitric acid and hydrofluoric acid in a volume ratio of 3:1:1, and the reaction vessel refers to a reactor. By subjecting the filtered high-purity quartz sand to high-temperature acidification, the residual metal impurities in the quartz sand can be further removed.

[0037] Cleaning and drying: cleaning the dried quartz sand to neutrality and drying it, wherein the drying temperature is 100-120°C.

[0038] In the above embodiment, calcination and water quenching, ultrasonic acidification, two-stage roasting, secondary water quenching and hot-pressing acid leaching can deeply remove lattice impurities and microinclusions in high-purity quartz sand, and make the purity of the purified quartz sand reach 4N8 or even 5N level or above. Compared with directly introducing Cl2 and HCl, using NH4Cl and AlCl3 as solid additives is safer, less expensive, and requires less addition, and is suitable for industrial applications.

[0039] In the above embodiment, the volume ratio of hydrochloric acid, hydrofluoric acid and oxalic acid in the first mixed acid can be any numerical ratio within (2±0.5):(2±0.5):1. For example, the volume ratio of hydrochloric acid, hydrofluoric acid and oxalic acid in the first mixed acid can be (2:2:1), (1.5:2:1), (1.5:1.5:1), (2:1.5:1), (2.5:2:1), (2.5:2.5:1), (2:2.5:1), (2.3:2.3:1), etc.

[0040] In the above embodiment, during the calcination and water quenching process, the first preset temperature can be any value between 900-1000°C. For example, the first preset temperature can be 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, etc.; the calcination time of the pegmatite at the first preset temperature can be any value between 20-40min. For example, the calcination time can be 20min, 22min, 24min, 26min, 28min, 30min, 32min, 34min, 36min, 38min, 40min, etc.

[0041] In the above embodiment, during the ultrasonic acidification process, the ultrasonic temperature can be any value within 50-80°C, and for example, it can be 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, etc.; the ultrasonic time can be any value within 0.5-1.5h, and for example, it can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, etc.

[0042] In the above embodiment, during the roasting process, the mass of ammonium chloride and aluminum chloride is any value within 1-5% of the mass of the dried quartz sand. For example, the mass of ammonium chloride and aluminum chloride is 1%, 2%, 3%, 4%, 5%, etc. of the mass of the dried quartz sand.

[0043] In the above embodiment, during the first stage of roasting, the heating rate can be any value within 1-3°C / min, and for example, it can be 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, etc.; the temperature of the first stage roasting can be any value within 400-600°C, and for example, it can be 400°C, 450°C, 500°C, 550°C, 600°C, etc., and the first stage roasting holding time can be any value within 0.5-1.5h, and for example, it can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, etc.

[0044] In the above embodiment, during the second stage roasting process, the heating rate can be any value within 4-6°C / min, and for example, it can be 4°C / min, 4.5°C / min, 5°C / min, 5.5°C / min, 6°C / min, etc.; the temperature of the first stage roasting can be any value within 800-1000°C, and for example, it can be 800°C, 850°C, 900°C, 950°C, 1000°C, etc., and the second stage roasting holding time can be any value within 1-3h, and for example, it can be 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, 3h, etc.

[0045] In the above embodiment, during the hot pressing acid leaching process, the reaction temperature of the quartz sand and the second mixed acid can be any value within 100-120°C, and for example, it can be 100°C, 105°C, 110°C, 115°C, 120°C, etc.; the reaction time can be any value within 4-8h, and for example, it can be 4h, 4.2h, 4.4h, 4.6h, 4.8h, 5h, 5.2h, 5.4h, 5.6h, 5.8h, 6h, 6.2h, 6.4h, 6.6h, 6.8h, 7h, 7.2h, 7.4h, 7.6h, h, 7.8h, 8h, etc.; the volume ratio of hydrochloric acid, nitric acid and hydrofluoric acid in the second mixed acid can be any numerical ratio within (3±1):(1±0.5):1. For example, the volume ratio of hydrochloric acid, nitric acid and hydrofluoric acid in the second mixed acid can be (4:1.5:1), (4:1.2:1), (4:1:1), (3.5:1.5:1), (3.5:1:1), (3.5:0.5:1), (3:1.5:1), (3:1.2:1), (3:1:1), (3:0.5:1), (3:0.8:1), etc.

[0046] The following examples further describe the present disclosure. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all reagents and starting materials used in the examples are commercially available or synthesized according to conventional methods, and all instruments and equipment used in the examples are commercially available.

[0047] Example 1

[0048] 1) Take 1±0.2 kg of high-purity quartz sand and calcine it in a rotary tube furnace at 900°C for 40 minutes. Then immediately pour the calcined quartz sand into cold water for quenching.

[0049] 2) Ultrasonic acidification, ultrasonic temperature 50°C, ultrasonic time 1.5h;

[0050] 3) calcining, adding ammonium chloride and aluminum chloride, the mass of ammonium chloride and aluminum chloride is 1% of the mass of quartz sand, wherein:

[0051] In the first stage, the temperature was raised to 400°C at a heating rate of 1°C / min and kept at this temperature for 1.5h in a nitrogen atmosphere.

[0052] The second stage of calcination was carried out at a heating rate of 5°C / min to 900°C and kept at this temperature for 1h in a nitrogen atmosphere.

[0053] 4) Secondary water quenching;

[0054] 5) Hot-press acid leaching: the reaction temperature of quartz sand and the second mixed acid is 100°C and the reaction time is 8 hours;

[0055] 6) Wash and dry to obtain the finished product.

[0056] Example 2

[0057] 1) Take 1±0.2 kg of high-purity quartz sand and calcine it in a rotary tube furnace at 950°C for 30 minutes. Then immediately pour the calcined quartz sand into cold water for quenching.

[0058] 2) Ultrasonic acidification, ultrasonic temperature 65°C, ultrasonic time 1 h;

[0059] 3) calcining, adding ammonium chloride and aluminum chloride, the mass of ammonium chloride and aluminum chloride is 3% of the mass of quartz sand, wherein:

[0060] In the first stage, the temperature was raised to 500°C at a heating rate of 2°C / min and kept at this temperature for 1 h in a nitrogen atmosphere.

[0061] The second stage of calcination was carried out at a heating rate of 6°C / min to 1000°C and kept at this temperature for 2h in a nitrogen atmosphere;

[0062] 4) Secondary water quenching;

[0063] 5) Hot-press acid leaching: the reaction temperature of quartz sand and the second mixed acid is 110°C and the reaction time is 6 hours;

[0064] 6) Wash and dry to obtain the finished product.

[0065] Example 3

[0066] 1) Take 1±0.2 kg of high-purity quartz sand and calcine it in a rotary tube furnace at a temperature of 1000°C for 20 minutes. Then immediately pour the calcined quartz sand into cold water for quenching.

[0067] 2) Ultrasonic acidification, ultrasonic temperature 80°C, ultrasonic time 0.5h;

[0068] 3) roasting, adding ammonium chloride and aluminum chloride, the mass of ammonium chloride and aluminum chloride is 5% of the mass of quartz sand, wherein:

[0069] In the first stage, the temperature was raised to 600°C at a heating rate of 3°C / min and kept at this temperature for 0.5h in a nitrogen atmosphere.

[0070] The second stage of calcination was carried out at a heating rate of 4°C / min to 800°C and kept at this temperature for 3 h in a nitrogen atmosphere.

[0071] 4) Secondary water quenching;

[0072] 5) Hot-press acid leaching: the reaction temperature of quartz sand and the second mixed acid is 120°C and the reaction time is 4 hours;

[0073] 6) Wash and dry to obtain the finished product.

[0074] Comparative Example 1

[0075] Same as Example 1, except that there is no secondary water quenching step.

[0076] Comparative Example 2

[0077] Same as Example 2, except that no aluminum chloride is added during the calcination process.

[0078] Comparative Example 3

[0079] The same as Example 3, but different from Example 3 is that the roasting process is carried out in an air atmosphere.

[0080] Comparative Example 4

[0081] The same as Comparative Example 2, except that ammonium chloride is not added during the roasting process.

[0082] Comparative Example 5

[0083] The same as Comparative Example 1, except that there is no hot pressing acid leaching step.

[0084] Comparative Example 6

[0085] Same as Comparative Example 3, except that there is no ultrasonic acidification step.

[0086] The finished products obtained in Examples 1-3 and Comparative Examples 1-6 were subjected to content analysis. The analysis results are shown in Table 1. In Table 1, the numerical value of SiO2 represents the percentage content of SiO2 in the obtained finished products, and the unit of other impurity contents is ppm.

[0087] Table 1: Content analysis results of finished products obtained from Examples 1-3 and Comparative Examples 1-6

[0088] <![CDATA[SiO2]]> Zn P Ni Fe B Mn Cr Mg Cu Ti Ca A1 Na Li K Total impurities Example 1 99.9985 0.01 0.12 0.01 0.18 0.05 0.02 0.01 0.03 0.01 1.36 0.83 11.31 0.67 0.11 0.22 14.94 Example 2 99.9985 0.02 0.06 0.01 0.13 0.05 0.01 0.03 0.05 0.01 1.35 0.77 11.27 0.59 0.16 0.18 14.69 Example 3 99.9986 0.02 0.08 0.02 0.15 0.03 0.01 0.02 0.04 0.02 1.31 0.61 10.59 0.74 0.19 0.14 13.97 Comparative Example 1 99.9977 0.03 0.18 0.03 0.78 0.15 0.02 0.04 0.26 0.03 1.35 1.38 14.66 1.86 1.34 1.03 23.14 Comparative Example 2 99.9968 0.03 0.46 0.01 1.67 0.36 0.23 0.07 0.09 0.05 1.58 1.46 18.58 2.84 1.76 2.56 31.75 Comparative Example 3 99.9967 0.03 0.35 0.01 1.79 0.28 0.51 0.05 0.22 0.02 1.81 2.02 20.34 2.56 0.58 2.04 32.61 Comparative Example 4 99.9961 0.13 0.65 0.01 1.88 0.32 0.56 0.06 0.06 0.04 2.39 1.56 22.35 3.24 2.34 3.03 38.62 Comparative Example 5 99.9972 0.03 0.27 0.01 1.33 0.19 0.15 0.01 0.45 0.03 1.42 1.89 16.56 2.25 1.38 1.59 27.56 Comparative Example 6 99.9959 0.23 0.45 0.11 2.04 0.45 0.45 0.12 0.33 0.12 2.65 2.23 23.04 3.56 2.11 2.78 40.67

[0089] As can be seen from Table 1, the SiO2 (%) content in Examples 1-3 is all above 99.9985%, while the SiO2 (%) content in Comparative Examples 1-5 is all below 99.998%. In particular, Comparative Example 1 does not have a water quenching step after calcination, resulting in the inability of the tiny fluid inclusions in the sand to completely burst, affecting the subsequent acidification and impurity removal. Comparative Example 5 is based on Comparative Example 1 but without the final hot pressing and acid leaching step, which can neither remove the impurities in the tiny inclusions nor deeply remove the impurities remaining during the calcination process, and the total impurities are further increased. Comparative Example 2 does not use AlCl3, resulting in a lack of chlorine penetration in the second stage of calcination, making it difficult to deeply remove lattice impurities. Comparative Example 4 does not use NH4Cl on the basis of Comparative Example 2, and cannot pre-activate the lattice impurities or increase the pore size channels of the quartz sand, which is not conducive to the subsequent deep lattice impurity removal by AlCl3. Comparative Example 3 does not have N2 protection during the calcination process, and the presence of oxygen easily penetrates Fe 2+ 、Mn 2+ 、Ti 3+ Oxidized to a high valence state (Fe 3+ 、Mn 4+ 、Ti 4+ ), which will inhibit the formation of chlorides. Na+, K+, Ca2+, Mg2+, etc. are also easy to form oxides with oxygen, which reduces the reaction activity with the chlorinating agent, resulting in an increase in their residual amount. When there is no N2 protection, the Al-O bond is more stable at high temperature, and oxygen easily inhibits the formation of AlCl3, resulting in an increase in the residual Al amount. Comparative Example 6 lacks the ultrasonic acidification step. Since the sand surface is not effectively cleaned, some NH4Cl will be consumed later to remove surface impurities. In addition, due to the lack of acid solution, the interior of the quartz is not effectively removed, which increases the difficulty of deep impurity removal during subsequent roasting.

[0090] In summary, the method for deep removal of lattice impurities and inclusions in high-purity quartz sand provided in this application can produce 4N8 grade high-purity quartz sand, and the inclusion content in the prepared high-purity quartz sand is also relatively low, meeting the quality requirements of high-purity quartz sand for photovoltaic use.

[0091] The above is a detailed introduction to the method for deep removal of lattice impurities and inclusions in high-purity quartz sand provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the core idea of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for deep removal of lattice impurities and inclusions in high-purity quartz sand, characterized in that: The method comprises: Calcination and water quenching: 4N grade quartz sand is fed into a first preset temperature for calcination and then immediately poured into cold water for water quenching, wherein the first preset temperature is 900-1000°C; Ultrasonic acidification: acidifying the water-quenched quartz sand with the first mixed acid under the assistance of ultrasound, and then washing it to a neutral temperature and drying it after the acidification is completed; Calcination: Add ammonium chloride and aluminum chloride to the dried quartz sand, mix well, and calcine under an inert atmosphere, wherein the mass of ammonium chloride and aluminum chloride is 1-5% of the mass of the dried quartz sand. The specific calcination steps are: In the first stage, the temperature is raised to 400-600℃ at a heating rate of 1-3℃ / min and kept at this temperature for 0.5-1.5h. The second stage is calcination, with a heating rate of 4-6℃ / min, heating to 800-1000℃ and keeping warm for 1-3h; Secondary water quenching: immediately pour the quartz sand after the second stage of roasting into cold water for secondary water quenching; Hot-press acid leaching, filtering the quartz sand after the second water quenching, then pouring the filtered quartz sand into a reaction vessel and adding the second mixed acid, and then placing it in a drying container for reaction, wherein the reaction temperature is 100-120 ° C, and the reaction time is 4-8 hours; Clean and dry the dried quartz sand until it is neutral and dry it.

2. The method for deep removal of lattice impurities and inclusions in high-purity quartz sand according to claim 1, wherein: During the calcination and water quenching process, 4N grade quartz sand is placed in a rotary tube furnace at a first preset temperature and calcined for 20-40 minutes.

3. The method for deep removal of lattice impurities and inclusions in high-purity quartz sand according to claim 1, wherein: During the ultrasonic acidification process, the ultrasonic temperature is 50-80° C., and the ultrasonic time is 0.5-1.5 h.

4. The method for deep removal of lattice impurities and inclusions in high-purity quartz sand according to claim 3, wherein: The first mixed acid refers to hydrochloric acid, hydrofluoric acid and oxalic acid in a ratio of (2±0.5):(2±0.5):

1.

5. The method for deep removal of lattice impurities and inclusions in high-purity quartz sand according to claim 1, wherein: The second mixed acid refers to hydrochloric acid, nitric acid and hydrofluoric acid in a volume ratio of (3±1):(1±0.5):

1.

6. The method for deep removal of lattice impurities and inclusions in high-purity quartz sand according to claim 1, wherein: A two-stage alkali liquid absorption tower is used to capture the tail gas after the second stage of roasting.

7. The method for deep removal of lattice impurities and inclusions in high-purity quartz sand according to claim 1, wherein: During the cleaning and drying process, the drying temperature is 100-120°C.

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