Quartz deep purification method based on enhanced chloridizing roasting

Abstract

The invention discloses a quartz deep purification method based on enhanced chloridizing roasting, and relates to the technical field of mineral processing and non-metallic material purification. According to the technical scheme, the method comprises the following steps: taking a pretreated quartz sand raw material, adding the pretreated quartz sand raw material into a composite solution of a solid-phase chlorinating agent and a fluxing agent, and performing infiltration, low-temperature evaporative crystallization and high-temperature drying treatment to obtain a core-shell coated product; placing the core-shell coated product in a tubular roasting furnace, synchronously introducing nitrogen into the roasting furnace, and performing high-temperature roasting to obtain quartz roasted sand; the method comprises the following steps: heating, stirring and leaching quartz calcine by using a mixed acid solution, washing a heating, stirring and leaching product to be neutral, and carrying out suction filtration and drying to obtain the high-quality quartz sand. According to the method, the chlorination contact interface and the reaction uniformity can be enhanced, the roasting temperature is reduced, the method has remarkable advantages in the aspects of purification efficiency, economy and environmental protection, and a reliable technical path is provided for green and efficient purification of high-quality quartz sand.

Description

A method for deep purification of quartz based on enhanced chlorination roasting Technical Field

[0001] This invention relates to the field of mineral processing and non-metallic material purification technology, specifically to a method for deep purification of quartz based on enhanced chlorination roasting. Background Technology

[0002] High-purity quartz (SiO2 content ≥ 99.99 wt%) is a core basic material for high-tech industries such as integrated circuits, optical fiber communication, photovoltaic energy, and precision optics. It possesses excellent physicochemical properties, including high temperature resistance, corrosion resistance, low thermal expansion, and high light transmittance. Its demand is rapidly increasing with the rapid development of emerging industries such as artificial intelligence, big data, and autonomous driving. However, the high impurity content in natural quartz ore cannot directly meet the raw material properties required by these emerging industries. Therefore, processing natural quartz ore into high-purity quartz products through a series of deep physicochemical purification processes to increase strategic resource reserves has become a research hotspot and key breakthrough direction for the silicon-related industries.

[0003] Quartz ore is widely found in igneous, sedimentary, metamorphic, and hydrothermal veins. Its impurities are complex in composition and structure, and can be classified into three main categories based on their occurrence: independent gangue minerals, fluid inclusions, and lattice impurities. Independent gangue minerals (including feldspar, mica, pyrite, calcite, etc.) are typically attached to the surface of the host quartz mineral or embedded in the gaps between the host mineral grains. These minerals exhibit good liberation, and conventional physical beneficiation processes such as gravity separation, magnetic separation, and flotation can effectively remove these impurities, achieving preliminary purification of the quartz ore. Inclusions are impurity components retained within the host mineral crystals due to interfacial interactions during quartz crystal growth and mineralization. Based on their location within the quartz grains, they can be divided into externally fractured inclusions and internally intact inclusions. Impurities in fractured inclusions are exposed and can be dissolved through mixed acid leaching, while intact inclusions cannot be separated from the host quartz crystal because they cannot come into contact with the acid solution. Lattice impurities refer to atomic impurity elements (Fe, Al, Ti, etc.) that substitute for Si in silicon-oxygen tetrahedra in an isomorphic manner. 4+ Upon entering the interior of the quartz lattice, alkali metal ions (Li) correct the charge imbalance caused by lattice replacement. + Na + K + These impurities (such as silicon-oxygen tetrahedra) fill the tetrahedral channels, thus providing charge compensation. These lattice impurities are tightly bound by the silicon-oxygen tetrahedral structure, and their solid solution properties make them difficult to remove deeply using conventional physical beneficiation and chemical acid leaching processes.

[0004] High-temperature chlorination roasting, as one of the core technologies for deep purification of quartz sandstone, removes lattice impurities and interstitial atomic impurities from quartz ore. It is combined with conventional physical beneficiation and chemical acid leaching processes to form a multi-stage deep purification process. Impurities such as alkali metals, alkaline earth metals, and residual inclusions on the surface of quartz particles undergo selective reactions with chlorinating agents (HCl, Cl2, NaCl, CaCl2, etc.) at high temperatures (around 1000℃) to generate low-boiling-point gaseous metal chlorides. These impurities are then separated from the solid-phase quartz sandstone through gas-phase migration, achieving deep purification. Chlorination roasting can be divided into gas-phase chlorination and solid-phase chlorination based on the contact state between the chlorinating agent and the material. Gas-phase chlorination roasting, due to the advantages of high activity, good fluidity, strong diffusivity, and high mass transfer efficiency of chlorinating agents (HCl, Cl2), can precisely control the sufficient contact with fine quartz particles, making it the mainstream process for purifying and preparing high-purity quartz (such as 4N8, i.e., 99.998%). However, gaseous chlorinating agents are highly corrosive gases, requiring extremely strict reaction environments and posing a significant risk of environmental pollution. Furthermore, they have high effective calcination temperatures (1000~1200℃) and high operating costs, and currently only Unimin in the United States has achieved industrial application.

[0005] Solid-phase chlorination involves uniformly mixing a chlorinating agent (NaCl, CaCl2, etc.) with quartz particles, with direct contact at the reaction interface. High-temperature roasting is then performed in an oxygen-deficient or weakly oxidizing atmosphere. Impurities are converted into volatile metal chlorides, which escape through the gas phase and are separated. After roasting, the solid-phase quartz sand needs to be acid-washed or water-quenched to remove residual chlorides or reaction products. Compared to gas-phase chlorination, solid-phase chlorination offers advantages such as simpler equipment, higher safety, lower cost, and better reaction uniformity. The use of solid chlorinating agents to replace gaseous chlorinating agents is currently receiving increasing attention. The current mainstream solid-phase chlorination roasting process involves layering the chlorinating agent with fine quartz particles, followed by mechanical stirring or grinding to homogenize the material. However, this method suffers from drawbacks due to differences in density, particle size, and particle shape between the quartz raw material and the chlorinating agent. Furthermore, simple mechanical mixing cannot break up particle agglomerates, severely affecting the uniformity of the mixture. Inhomogeneous mixtures directly affect the efficiency of the chlorination roasting reaction, hindering the effective roasting temperature. In some areas, the impurity removal rate fails to meet expectations, restricting the consistency and stability of the high-purity quartz sand quality. To compensate for the effects of uneven mixing, it is often necessary to increase the amount of chlorinating agent. However, chlorination roasting has strict limits on the amount of chlorinating agent. Excessive addition of chlorinating agent will not only increase the cost of raw materials, but also cause new pollution to the product.

[0006] In summary, the core contradiction in current quartz sand chlorination roasting technology lies in the conflict between demanding impurity removal effects and high purification costs, as well as stringent environmental requirements. Existing gas-phase and solid-phase chlorination methods struggle to balance economic efficiency and environmental friendliness. Therefore, developing a novel, highly efficient, energy-saving, safe, and environmentally friendly deep purification technology for quartz is of great significance for improving the purity and stability of quartz sand products, promoting industrial upgrading, and facilitating large-scale industrial applications. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing solid-phase chlorination roasting processes, such as uneven material mixing and contact, excessively high roasting temperatures, and poor product quality consistency. This invention proposes a deep purification method for quartz based on enhanced chlorination roasting. This method specifically enhances the chlorination contact interface and reaction uniformity, reduces the effective roasting temperature, and has advantages such as simple process flow, good economy, and green safety. The technical solution of this invention: A deep purification method for quartz based on enhanced chlorination roasting. According to an embodiment of the present invention, the method includes the following steps: S1: Pretreated quartz sand raw material is added to a composite solution of chlorinating agent and flux for wetting, low-temperature evaporation crystallization, and high-temperature drying to obtain a core-shell coated product; S2: The core-shell coated product is placed in a tubular roasting furnace, nitrogen is simultaneously introduced into the furnace, and high-temperature roasting is performed to obtain quartz roasted sand; S3: The quartz roasted sand is subjected to heating and stirring leaching treatment with a mixed acid solution, and the heated and stirred leaching product is washed until neutral, filtered, and dried to obtain high-quality quartz sand; wherein, steps S1 and S2 together constitute an enhanced chlorination roasting process, through solution wetting, the chlorinating agent / flux is uniformly coated on the surface of mineral particles in microcrystalline form, achieving close contact at the molecular microscale and increasing the reaction interface, accelerating chloride ion diffusion, and improving the chlorination reaction rate. In some embodiments, the quartz sand raw material in step S1 is natural quartz ore, including one or more of quartz sandstone, powdered quartz, and quartzite. In some embodiments, the pretreatment process includes crushing and grading, grinding and sample preparation, gravity separation, magnetic separation, flotation, and chemical acid leaching. In some embodiments, the SiO2 content in the pretreated quartz sand raw material is ≥99.5 wt%, and the particle size is 120~200 mesh. In some embodiments, the impregnation in step S1 is carried out under mechanical stirring conditions, with a stirring intensity of 1000~2500 rpm, and the liquid-solid ratio of the composite solution to the quartz sand raw material is 2:1~5:1 ml / g, for example, 3:1 ml / g, 4:1 ml / g, etc.; the evaporation and crystallization temperature is 40~70℃, for example, 50℃, 60℃, etc., and the time is 12~24h, for example, 14h, 16h, 18h, 20h, etc.; the drying temperature is 90~105℃, and the time is 4~8h. In some embodiments, the solid-phase chlorinating agent includes one or more of sodium chloride, calcium chloride, and potassium chloride, and is used in an amount of 1-5% of the mass of the quartz sand raw material, such as 2%, 3%, 4%, etc. The inventors have discovered that by adding an appropriate amount of flux in the quartz solid-phase chlorination roasting process, the defects in the quartz crystal can be increased and the lattice interface activated, thereby reducing the roasting temperature and improving the chlorination roasting impurity removal efficiency, especially improving the removal rate of difficult-to-remove impurities such as Al / Fe. In some embodiments, the flux includes one or more of sodium carbonate, ammonium chloride, sodium fluoride, and calcium fluoride, and is used in an amount of 0.5-3% of the mass of the quartz sand raw material, such as 1%, 1.5%, 2%, 2.5%, etc.In some embodiments, the furnace tubes of the tubular roasting furnace in step S2 are made of high-purity quartz; the nitrogen flow rate is 400~800 ml / min, for example 500 ml / min, 600 ml / min, 700 ml / min, etc., and is used as a protective / purging gas during the mixed chlorination roasting; the target temperature for the high-temperature roasting is 850~1200℃, for example 900℃, 950℃, 1000℃, 1150℃, etc. In some embodiments, the heating rate of the high-temperature roasting is 5~8℃, the holding time after reaching the target temperature is 2~4 hours, the cooling rate is 8~10℃ until room temperature, and nitrogen protection is maintained throughout the process. In some embodiments, the mixed acid solution in step S3 is a mixed solution of hydrochloric acid and sulfuric acid, wherein the concentration of hydrochloric acid is 2~5 mol / L, for example 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, etc., and the concentration of sulfuric acid is 1~3 mol / L, for example 1.5 mol / L, 2 mol / L, 2.5 mol / L, etc.; the liquid-solid ratio of the heating and stirring leaching is 20:1~50:1 ml / g, for example 25 ml / g, 30 ml / g, 40 ml / g, etc., the stirring intensity is 800~1500 rpm, the heating temperature is 70~90℃, and the time is 4~6 h.

[0008] In some embodiments, the high-quality quartz sand contains ≥99.95 wt% SiO2, and can be widely used in the outer / middle layer of photovoltaic crucibles, mid-to-high-end quartz tubes and rods, electric light sources, and some electronic auxiliary materials. Compared with the prior art, the beneficial effects of the present invention include: 1. The solid-phase chlorination roasting method provided by the present invention completely avoids the use of corrosive gaseous chlorinating agents such as HCl and Cl2, significantly reducing production safety risks and environmental pollution risks. At the same time, it can also alleviate the corrosion of furnace linings and pipelines by high-temperature chlorine-containing atmospheres, extend equipment life, reduce maintenance costs, and meet the requirements of green chemical industry. 2. By impregnating and crystallizing the quartz sand raw material with the chlorinating agent solution to form a core-shell coating structure, the chlorinating agent is uniformly wrapped on the surface of mineral particles in the form of microcrystals, achieving close contact at the microscopic molecular level, increasing the chlorination contact reaction interface, shortening the mass transfer distance during the roasting reaction, accelerating chloride ion diffusion, and improving the chlorination roasting rate. This avoids the uneven mixing caused by differences in particle size and density during traditional grinding and mixing, which limits the reaction interface and leads to local over-chlorination or incomplete reaction. Furthermore, the solid-phase chlorination coating method allows for precise control of the chlorinating agent dosage, reducing high energy consumption, equipment corrosion, and subsequent waste gas treatment burden caused by excessive use. 3. Using a solid-phase chlorinating agent combined with a flux for enhanced chlorination roasting of quartz ore raw materials can lower the quartz phase transition temperature, increase lattice defects, thereby lowering the effective chlorination roasting temperature, improving material flowability, and enhancing the impurity removal efficiency of chlorination roasting. 4. The quartz deep purification method provided by this invention can increase the purity of quartzite ore from 99.5 wt% to over 99.95 wt%, obtaining high-quality quartz sand that meets the raw material quality requirements for photovoltaic crucible outer / middle layers, mid-to-high-end quartz tubes and rods, electric light sources, and some electronic auxiliary materials. In summary, this invention has significant advantages over traditional gas-phase chlorination roasting and single-solid-phase chlorination roasting in terms of economy, environmental protection, and impurity removal efficiency, and is of great significance for promoting the high-purity quartz deep purification industry and facilitating large-scale industrial applications. Attached Figure Description

[0009] Figure 1 is a process flow diagram of the enhanced chlorination roasting deep purification of quartz according to the present invention. Figure 2 is an optical micrograph of the high-quality quartz sand obtained by purification in all embodiments and comparative examples of the present invention. Figure 3 is a SEM image of the high-quality quartz sand obtained by purification in all embodiments and comparative examples of the present invention. Detailed Implementation

[0010] The present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way. Unless otherwise specified, the materials used in the following embodiments and comparative examples are all commercially available products that can be directly purchased in the art or prepared according to conventional methods in the art. Unless otherwise specified, the mixing or reaction temperature is room temperature. The present invention addresses the existing problems by providing a method for deep purification of quartz based on enhanced chlorination roasting. Figure 1 is a process flow diagram of the enhanced chlorination roasting deep purification of quartz according to the present invention. Example 1 (1) Pretreated quartz sandstone was selected as the quartz sand raw material, with a SiO2 content ≥99.85 wt% and a particle size of 120~160 mesh. Weigh 10g of quartz sand raw material and transfer it to 20ml of composite solution (NaCl+NH4Cl) for mechanical stirring and impregnation. The amount of NaCl is 1% of the mass of quartz sand raw material, the amount of NH4Cl is 0.5% of the mass of quartz sand raw material, the solvent is deionized water, and the stirring intensity is 1500rpm. Place the impregnated material in a blower drying oven for low-temperature evaporation and crystallization. The temperature is set at 50℃ and the time is 16h until the material is a dry, loose white-grayish-white mixture. After the low-temperature evaporation and crystallization is completed, adjust the temperature of the blower drying oven to 105℃ for high-temperature drying treatment. The drying time is 8h to remove the physically adsorbed moisture on the surface of the material and obtain the core-shell coated product. (2) Spread the core-shell coated product evenly in a quartz boat dish and transfer it to the middle part of the tubular roasting furnace. Connect the nitrogen gas path system and set the nitrogen gas flow rate to 500ml / min. Before formal heating, pre-purge the furnace with nitrogen gas for 10min for cleaning. Then, the high-temperature roasting operation of the tubular roasting furnace was started. The target temperature of the high-temperature roasting was set to 950℃, the roasting heating rate was 5℃, the holding time after reaching the target temperature was 2h, the cooling rate was 10℃ until room temperature, and the nitrogen gas flow rate was maintained constant throughout the process. The roasting tail gas was fed into two alkaline bottles (one 20% NaOH + the second 10% NaOH) for treatment. The roasted solid product is quartz roasted sand. (3) The quartz roasted sand was added to a hydrothermal reactor containing a mixed acid solution for heating, stirring and leaching treatment. The mixed acid solution was a mixed solution of hydrochloric acid and sulfuric acid, with a concentration of 3mol / L for hydrochloric acid and 2mol / L for sulfuric acid. The volume of the mixed acid solution used was 400ml (liquid-solid ratio 40:1ml / g), the stirring intensity was 1200rpm, the heating temperature was 80℃, and the time was 4h. After the heating, stirring and leaching was completed, the heated and stirred leaching product was washed with deionized water until neutral, filtered, and dried to obtain high-quality quartz sand. The contents of impurity elements such as Fe, Al, Mg, Ca, Na, Li, K, and Ti in high-quality quartz sand products were analyzed by ICP-MS testing, and the SiO2 content was calculated using the difference method, as shown in Table 1.Example 2 (1) Pretreated powdered quartz was selected as the raw material for quartz sand, with a SiO2 content ≥ 99.70 wt% and a particle size of 180~200 mesh. 10g of quartz sand raw material was weighed and transferred to 40ml of composite solution (NaCl+NaF) for mechanical stirring and impregnation. The amount of NaCl was 2% of the mass of the quartz sand raw material, the amount of NaF was 2% of the mass of the quartz sand raw material, the solvent was deionized water, and the stirring intensity was 1500rpm. The impregnated material was placed in a forced-air drying oven for low-temperature evaporation and crystallization. The temperature was set at 70℃ and the time was 18h until the material was a dry, loose white-grayish-white mixture. After the low-temperature evaporation and crystallization was completed, the temperature of the forced-air drying oven was adjusted to 105℃ for high-temperature drying treatment. The drying time was 8h to remove the physically adsorbed moisture on the surface of the material and obtain the core-shell coated product. (2) Spread the core-shell coated product evenly in a quartz boat dish, transfer it to the middle part of the tubular roasting furnace, connect the nitrogen gas path system, set the nitrogen flow rate to 500 ml / min, and pre-purge the furnace with nitrogen for 10 min before formal heating. Then start the high-temperature roasting operation of the tubular roasting furnace, set the target temperature of high-temperature roasting to 900℃, the roasting heating rate to 5℃, the holding time after reaching the target temperature to 2 h, and the cooling rate to 10℃ until room temperature. Maintain a constant nitrogen flow rate throughout the process. The roasting tail gas is treated by passing it through two alkaline solution bottles (one stage 20% NaOH + the second stage 10% NaOH). The roasted solid product is quartz roasted sand. (3) The quartz calcined sand was added to a hydrothermal reactor containing a mixed acid solution for heating and stirring leaching. The mixed acid solution was a mixture of hydrochloric acid and sulfuric acid, with a concentration of 3 mol / L for hydrochloric acid and 2 mol / L for sulfuric acid. The volume of the mixed acid solution was 400 ml (liquid-solid ratio 40:1 ml / g), the stirring intensity was 1200 rpm, the heating temperature was 80℃, and the time was 4 h. After the heating and stirring leaching was completed, the leaching product was washed with deionized water until neutral, filtered, and dried to obtain high-quality quartz sand. The content of impurity elements such as Fe, Al, Mg, Ca, Na, Li, K, and Ti in the high-quality quartz sand product was analyzed by ICP-MS, and the SiO2 content was calculated by the difference method, as shown in Table 1. Example 3 (1) Pretreated quartzite was selected as the raw material for quartz sand, with a SiO2 content ≥99.55 wt% and a particle size of 120~150 mesh.Weigh 10g of quartz sand raw material and transfer it to 30ml of composite solution (KCl+Na2CO3) for mechanical stirring and impregnation. The amount of KCl is 4% of the mass of quartz sand raw material, the amount of Na2CO3 is 5% of the mass of quartz sand raw material, the solvent is deionized water, and the stirring intensity is 2000rpm. Place the impregnated material in a blower drying oven for low-temperature evaporation and crystallization. The temperature is set at 65℃ and the time is 24h until the material is a dry, loose white-grayish-white mixture. After the low-temperature evaporation and crystallization is completed, adjust the temperature of the blower drying oven to 100℃ for high-temperature drying treatment. The drying time is 6h to remove the physically adsorbed moisture on the surface of the material and obtain the core-shell coated product. (2) Spread the core-shell coated product evenly in a quartz boat dish and transfer it to the middle part of the tubular roasting furnace. Connect the nitrogen gas path system and set the nitrogen gas flow rate to 600ml / min. Before formal heating, pre-purge nitrogen gas for 8min to clean the furnace. Then, the high-temperature roasting operation of the tubular roasting furnace was started. The target temperature of the high-temperature roasting was set to 1000℃, the roasting heating rate was 5℃, the holding time after reaching the target temperature was 2h, and the cooling rate was 10℃ until room temperature. The nitrogen gas flow rate was maintained throughout the process. The roasting tail gas was fed into two alkaline bottles (one 20% NaOH + the second 10% NaOH) for treatment. The roasted solid product was quartz roasted sand. (3) The quartz roasted sand was added to a hydrothermal reactor containing a mixed acid solution for heating, stirring and leaching treatment. The mixed acid solution was a mixture of hydrochloric acid and sulfuric acid, with a concentration of 4.5mol / L for hydrochloric acid and 3mol / L for sulfuric acid. The volume of the mixed acid solution used was 500ml (liquid-solid ratio 50:1ml / g), the stirring intensity was 1500rpm, the heating temperature was 90℃, and the time was 6h. After the heating, stirring and leaching was completed, the heated and stirred leaching product was washed with deionized water until neutral, filtered, and dried to obtain high-quality quartz sand. The contents of impurity elements such as Fe, Al, Mg, Ca, Na, Li, K, and Ti in the high-quality quartz sand product were analyzed by ICP-MS, and the SiO2 content was calculated using the difference method, as shown in Table 1. Comparative Example 1 differs from Example 1 in that the composite solution used in step (1) is only NaCl solution, without the addition of flux; the target temperature for high-temperature calcination in step (2) is 1100℃; other aspects are the same as in Example 1.

[0011] Compared with Example 1, Comparative Example 2 differs in that step (1) involves weighing quartz sand raw material, NaCl, and NH4Cl at masses of 10g, 0.1g, and 0.05g respectively, pouring them into a mixer, and mixing the materials for 10 minutes to obtain a uniform mixture; then, the mixture is evenly spread in a quartz boat and subjected to high-temperature calcination in step (2); the rest is the same as in Example 1.

[0012] Compared with Example 1, Comparative Example 3 differs in that only 10g of quartz sand raw material is weighed in step (1); in step (2), a nitrogen / hydrogen chloride mixed gas circuit system is connected, the mixed gas flow rate is set to 500ml / min (where the HCl concentration is 5%), nitrogen is only introduced for 10min to clean the furnace before formal heating, the target temperature for high-temperature roasting is set to 1200℃, and after the target temperature is maintained, the HCl gas circuit is first closed, and the nitrogen flow rate is maintained constant throughout the process; the rest is the same as in Example 1.

[0013] Table 1. SiO2 content and impurity element content of each example and comparative product.

[0014] As shown in Table 1, the SiO2 content in the high-quality quartz sand obtained in Examples 1-3 of this invention is above 99.95%. The effective roasting temperature of Example 1 is lower than that of Comparative Example 1, indicating that under similar purification conditions, adding flux in the chlorination roasting process can reduce the effective roasting temperature. This is because the flux can increase the quartz lattice defects and improve the material flowability. The high-quality quartz sand of Example 1 has higher purity than that of Comparative Example 2. The Na ion concentration in Comparative Example 2 is about 9 times higher than that of Example 1. This is because the solid-phase chlorinating agent and the quartz sand raw material are not mixed evenly, resulting in local over-chlorination. Comparative Example 3 has the highest effective roasting temperature among all examples and comparative examples. This is because gas-phase chlorination needs to overcome the high chemical stability of SiO2 and enhance the energy of gas-phase reactants to break the Si-O bonds. Figure 2 shows the optical micrographs of the high-quality quartz sand obtained from each example and comparative example. As can be seen from Figure 2, the rock samples corresponding to each example and comparative example are almost entirely composed of quartz particles, with an extremely uniform and clean structure. The impurity mineral content is extremely low and they are distributed in an isolated state. Comparative Examples 1 and 3 show uneven fan-shaped or banded variations in brightness within the particles, which is due to the excessively high calcination temperature altering the stress distribution within the crystals or causing lattice distortion. Figure 3 shows the SEM images of the high-quality quartz sand obtained from the purification of each example and comparative example. As shown in Figure 3, the particle surface of Example 1 is smooth and intact, exhibiting a typical conchoidal fracture. The particles are mainly in surface contact and concave-convex contact, with tight bonding, indicating that they have undergone strong compaction and pressure solution processes. The quartz particles of Examples 2 and 3 have submicron to nano-sized fine mineral particles attached to their surface, which, according to preliminary energy dispersive spectroscopy, may be aluminosilicates. This impurity is the direct cause of the high aluminum content. Due to the high calcination temperature, Comparative Examples 1 and 3 show smooth vitrified regions and the disappearance of the original particle morphology.

[0015] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications may still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions may be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for deep purification of quartz based on enhanced chlorination roasting, characterized in that, The method includes the following steps: S1: Take the pretreated quartz sand raw material and add it to a composite solution of solid chlorinating agent and flux for wetting, low-temperature evaporation crystallization and high-temperature drying to obtain a core-shell coated product; S2: The core-shell coated product is placed in a tubular roasting furnace, and nitrogen is simultaneously introduced into the furnace for high-temperature roasting to obtain quartz roasted sand; S3: The quartz roasted sand is subjected to heating and stirring leaching treatment with a mixed acid solution. The heated and stirred leaching product is washed until neutral, filtered, and dried to obtain high-quality quartz sand.

2. The method for deep purification of quartz based on enhanced chlorination roasting according to claim 1, characterized in that, The quartz sand raw material mentioned in step S1 is natural quartz ore, including one or more of quartz sandstone, powdered quartz, and quartzite; and / or, the pretreatment process includes crushing and grading, grinding and sample preparation, gravity separation, magnetic separation, flotation, and chemical acid leaching; and / or, the SiO2 content in the pretreated quartz sand raw material is ≥99.5wt%, and the particle size is 120~200 mesh.

3. The method for deep purification of quartz based on enhanced chlorination roasting according to claim 1, characterized in that, The impregnation in step S1 is carried out under mechanical stirring conditions, with a stirring intensity of 1000~2500 rpm, and the liquid-solid ratio of the composite solution to the quartz sand raw material is 2:1~5:1 ml / g; the evaporation crystallization temperature is 40~70℃, and the time is 12~24h; the drying temperature is 90~105℃, and the time is 4~8h; and / or, the solid phase chlorinating agent includes one or more of sodium chloride, calcium chloride, and potassium chloride, and the amount used is 1~5% of the mass of the quartz sand raw material; and / or, the fluxing agent includes one or more of sodium carbonate, ammonium chloride, sodium fluoride, and calcium fluoride, and the amount used is 0.5~3% of the mass of the quartz sand raw material.

4. The method for deep purification of quartz based on enhanced chlorination roasting according to claim 1, characterized in that, The tube material of the tubular roasting furnace in step S2 is high-purity quartz; the nitrogen flow rate is 400~800 ml / min, which is used as a protective / purging gas during the chlorination roasting of the mixed materials; the target temperature of the high-temperature roasting is 850~1200℃; and / or, the heating rate of the high-temperature roasting is 5~8℃, the holding time after reaching the target temperature is 2~4h, the cooling rate is 8~10℃ until room temperature, and nitrogen protection is provided throughout the process.

5. The method for deep purification of quartz based on enhanced chlorination roasting according to claim 1, characterized in that, The mixed acid solution mentioned in step S3 is a mixed solution of hydrochloric acid and sulfuric acid, wherein the concentration of hydrochloric acid is 2~5 mol / L and the concentration of sulfuric acid is 1~3 mol / L; the liquid-solid ratio of the heating and stirring leaching is 20:1~50:1 ml / g, the stirring intensity is 800~1500 rpm, the heating temperature is 70~90℃, and the time is 4~6 h.

6. The method for deep purification of quartz based on enhanced chlorination roasting according to claim 1, characterized in that, The high-quality quartz sand contains ≥99.95wt% SiO2.

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