Method for morphology and particle size control of high-purity quartz sand

Abstract

The present application relates to a morphology and particle size control method of high-purity quartz sand, and belongs to the technical field of high-purity quartz sand. The control method adopts hydrochloric acid compounded with citric acid chelating agent and is assisted with ultrasonic stirring leaching to deeply remove metal impurities in internal fissures and inclusions of quartz tailings powder; all processes adopt non-metal processing equipment such as quartz disc mill to completely eliminate secondary metal pollution introduced by steel crushing and grinding equipment; then, through segmented sintering pretreatment in a protective atmosphere, coarse and fine two-stage quartz disc mill grading grinding is matched to realize synchronous control of product particle size accurate screening and particle shaping, so that the particles tend to be near equiaxed morphology; the prepared high-purity quartz sand has a total metal impurity content of less than or equal to 15 ppm, a yield of greater than or equal to 85%, and a needle flake particle ratio of less than or equal to 5%; and the finished product has high tap density and excellent powder fluidity, and the stacking performance is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of high-purity quartz sand technology, and particularly relates to a method for controlling the morphology and particle size of high-purity quartz sand. Background Technology

[0002] High-purity silica sand is a core material for strategic emerging industries such as photovoltaics, semiconductors, and high-end optical glass. Its purity, particle size uniformity, and particle morphology directly determine the quality stability and service life of downstream devices. In the photovoltaic field, high-purity, high-bulk-density silica sand can effectively improve the thermal shock resistance and high-temperature structural integrity of quartz crucibles, reduce defects such as crystallization and bubbles, and extend the service life of crucibles. In the semiconductor and high-end optics fields, silica sand with stable impurity content and uniform particle morphology is a key prerequisite for ensuring the consistency of thermal and optical performance of quartz devices. Therefore, low-cost, large-scale preparation of high-performance, high-purity silica sand with controllable morphology and uniform particle size has become a core technological need that urgently needs to be addressed in this field.

[0003] The production process of high-end vein quartz ore into photovoltaic and electronic-grade quartz sand generates a large amount of fine-grained tailings. This tailings is mainly composed of crystalline silicon dioxide, with particle sizes ranging from 1μm to 50μm, and a primary SiO2 purity of 99.8% to 99.95%, providing a good raw material foundation for the production of medium- to high-end quartz sand. However, due to its small particle size and complex impurity distribution, coupled with secondary pollution introduced by friction and wear of steel equipment during the beneficiation and crushing process, the total metal impurity content of the tailings fluctuates between 50ppm and 200ppm. Currently, most of this tailings are sold at low prices as low-end industrial filler or directly stockpiled as solid waste, and the potential value of high-quality quartz resources has not been fully explored and efficiently utilized.

[0004] Currently, the mainstream processes for the resource utilization of quartz tailings and the preparation of high-purity quartz sand are unable to meet the high-value conversion requirements of fine-grained tailings powder, exhibiting significant technological shortcomings. Conventional quartz tailings resource utilization processes primarily involve granulation and classification of tailings powder using steel equipment, coupled with simple acid washing to remove surface impurities. This only removes free metal impurities from the surface of the particles, failing to remove deep-seated impurities such as those filling particle cracks and weak inclusions. The finished product typically has a SiO2 purity below 99.9% and a total metal impurity content exceeding 100 ppm, failing to meet the 99.998% purity requirement for high-end, high-purity quartz sand. Furthermore, the steel processing equipment continuously introduces secondary metal contamination, and impact crushing easily generates a large number of needle-like, flaky, and angular irregular particles. The yield of 60-250 mesh target particle size finished products is only around 50%, resulting in low bulk density and poor flowability, making it difficult to apply to the mid-to-high-end quartz product field. The process for preparing high-purity quartz sand from natural lump ore involves multiple purification steps, including gravity separation, flotation, multi-stage strong acid leaching, and high-temperature calcination. While it can mass-produce 99.998% high-purity quartz sand, the overall process is cumbersome, consumes a large amount of reagents, and incurs high equipment investment costs, resulting in persistently high production costs. Furthermore, the process system is designed specifically for large lump ore and is not adapted to the material characteristics of fine-grained tailings powder, making it unsuitable for direct application in the purification and processing of tailings powder. Additionally, natural lump ore, after mechanical crushing, often exhibits an irregular angular structure, making it difficult to produce high-density, equiaxed, high-purity quartz sand even after subsequent shaping, thus hindering precise control over particle size and morphology.

[0005] Therefore, there is an urgent need to develop a method for integrated control of the morphology and particle size of high-purity quartz sand adapted to quartz tailings powder raw materials. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problems of insufficient removal of deep impurities, easy introduction of secondary metal pollution during processing, difficulty in coordinating and accurately controlling particle size and particle morphology, and complex process flow and high production cost in the existing high-value utilization process of quartz tailings.

[0007] To address the aforementioned technical problems, this invention provides a method for controlling the morphology and particle size of high-purity quartz sand. This method employs a hydrochloric acid compounded with citric acid chelating agent, supplemented by ultrasonic stirring leaching, which can deeply remove metallic impurities contained in internal cracks and inclusions of quartz tailings powder. The entire process utilizes non-metallic processing equipment such as quartz disc mills, completely eliminating secondary metal contamination introduced by steel crushing and grinding equipment. Furthermore, through protective atmosphere segmented sintering pretreatment combined with coarse and fine two-stage quartz disc milling for graded grinding, precise particle size screening and particle shaping are simultaneously achieved, resulting in particles approaching a near-equiaxed morphology. The high-purity quartz sand prepared using this method has a total metal impurity content ≤15ppm, a yield ≥85%, and a needle-like / flaky particle ratio ≤5%. The finished product possesses high tap density and excellent powder flowability, with significantly improved packing performance. This provides a high-performance, industrially feasible technical path for the low-cost, large-scale, high-value production of high-end, high-purity quartz sand suitable for the photovoltaic and semiconductor fields using quartz beneficiation tailings solid waste.

[0008] The purpose of this invention is to provide a method for controlling the morphology and particle size of high-purity quartz sand, comprising the following steps: S1. Quartz tailings powder, hydrochloric acid and chelating agent are dispersed in water and leached using ultrasonic-assisted stirring. Then, the mixture is washed and subjected to high-gradient iron removal to obtain a mixed slurry. S2. The mixed slurry described in S1 is filtered and dried to obtain a mixed powder. S3. The mixed powder described in S2 is sintered to obtain a sintered blank. S4. The sintered billet described in S3 is subjected to coarse grinding and then screened to obtain coarsely ground quartz sand. S5. The coarsely ground quartz sand described in S4 is subjected to fine grinding and then screened to obtain the high-purity quartz sand.

[0009] In one embodiment of the present invention, in S1, the quartz tailings powder has a primary silica purity of 99.8%-99.95%, a total metal impurity content of 50ppm-200ppm, and a particle size of 1μm-50μm.

[0010] In one embodiment of the present invention, in S1, the chelating agent is citric acid.

[0011] In one embodiment of the present invention, in S1, the concentration of quartz tailings powder in the mixed slurry is 35wt%-45wt%, the concentration of hydrochloric acid is 1.0wt%-2.3wt%, and the concentration of chelating agent is 0.1wt%-0.3wt%.

[0012] In one embodiment of the present invention, in S1, the leaching treatment is performed at a temperature of 70°C-90°C for a time of 90 min-150 min.

[0013] In one embodiment of the present invention, in S2, the drying is performed at 180°C-230°C until the moisture content of the material is ≤0.08%.

[0014] In one embodiment of the present invention, in S3, the sintering is carried out under a protective atmosphere by first heating the powder to 530°C-640°C at a rate of 5°C / min-7°C / min and holding it for 2.5h-4h to remove hydroxyl groups and trace organic matter adhering to the powder surface; then heating the powder to 1080°C-1200°C at a rate of 3°C / min-5°C / min and holding it for 3h-5h to cause the powder particle interface to melt and form a slight adhesion between the particles at the neck.

[0015] In one embodiment of the present invention, in S4, the coarse grinding process adopts a quartz disc mill with a disc gap of 0.5mm-1.2mm, a relative speed difference of 22r / min-28r / min, and a single batch coarse grinding process duration of 20min-32min.

[0016] In one embodiment of the present invention, in S5, the fine grinding process uses a quartz disc mill with a disc gap of 0.18mm-0.32mm, a relative speed difference of 15r / min-21r / min, and a single batch fine grinding process duration of 15min-25min.

[0017] In one embodiment of the present invention, in S4 and S5, the screening after coarse grinding and fine grinding is performed using a 60-mesh and a 250-mesh double-layer vibrating screen.

[0018] The technical solution of the present invention has the following advantages compared with the prior art: (1) The method described in this invention is based on the impurity occurrence characteristics and particle properties of quartz tailings powder to build an integrated preparation system of "deep impurity removal - metal-free processing - graded morphology and particle size control", which has multiple synergistic technical advantages: On the one hand, it constructs a composite impurity removal system of ultrasonic acid leaching chelation synergistic high gradient iron removal, which can simultaneously treat four types of impurities: free impurities on the surface of raw materials, impurities filling particle cracks, weak inclusion impurities, and ferromagnetic secondary pollution caused by wear of steel equipment. By using ultrasonic cavitation, it enhances the penetration ability of low concentration hydrochloric acid into the internal cracks of particles, fully dissolves deep metal impurities, and combines citric acid chelating agent with dissolved metal ions to form stable complexes, avoiding the re-adsorption of impurities on the particle surface during water washing. Then, the ferromagnetic debris in the slurry is removed by high gradient iron removal. The multi-process synergistic purification can significantly reduce the total metal impurity content of the raw materials; On the other hand, it constructs a full quartz metal-free processing system. All material contact parts in the coarse grinding, fine grinding and screening process are made of high-purity quartz disc mills, and the entire process is steel-free. The components come into contact with the materials, eliminating the secondary introduction of metal impurities such as iron, chromium, and nickel from the source. This stabilizes the low impurity level after deep impurity removal at the front end, eliminating the need for secondary purification at the back end, simplifying the overall process and reducing equipment and reagent costs. Simultaneously, a two-stage quartz disc mill differentiated and synergistic control mechanism is established. The coarse grinding process uses a larger disc gap and a higher relative rotational speed difference to rapidly crush the loose sintered billet obtained from segmented sintering, quickly cutting into the target particle size range and completing preliminary shaping, reducing over-grinding. The fine grinding process reduces the disc gap and lowers the rotational speed difference to flexibly shape the coarse grinding product, only grinding the sharp edges of the particles without causing deep crushing. Combined with a double-layer vibrating screen, a closed-loop recycling system for coarse and fine materials is achieved, effectively improving the yield of target particle size products. The resulting product has a low proportion of needle-like and flaky particles, and the near-equiaxed particle structure reduces powder porosity, improves tap density and powder flowability, and its performance is suitable for mid-to-high-end applications such as photovoltaic quartz crucible outer layer sand and high-end electronic optical fillers.

[0019] (2) The method described in this invention uses quartz tailings powder, a by-product of mineral processing, as the main raw material. The raw material cost is significantly lower than that of natural vein quartz lumps. The process eliminates high-energy-consuming and high-cost processes such as flotation, hydrofluoric acid strong corrosion leaching, and high-temperature purification and calcination. In addition, the closed-loop recycling of materials throughout the process reduces raw material loss. The overall production cost is significantly lower than that of the process of preparing high-purity quartz sand of the same purity from natural lumps. The entire impurity removal system only uses low-concentration hydrochloric acid compounded with citric acid and does not use highly toxic and corrosive agents such as hydrofluoric acid. The waste liquid does not contain fluoride ions, reducing the pressure of waste treatment and environmental protection investment. The comprehensive utilization rate of tailings in the whole process is high, taking into account both solid waste reduction and green and clean production. It can produce high-end high-purity quartz sand with precise controllable morphology and particle size at low cost and on a large scale. The industrialization and promotion value is outstanding. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0021] In this invention, unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] In this invention, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] In this invention, unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods, and the materials and reagents used are commercially available unless otherwise specified. Example 1

[0024] The method for controlling the morphology and particle size of high-purity quartz sand in this embodiment specifically includes the following steps: S1. Weigh 4 kg of high-purity vein quartz beneficiation by-product tailings powder (primary silica purity is 99.85%, total metal impurity content is 120 ppm, and particle size range is concentrated between 2 μm and 40 μm), and use deionized water to prepare a slurry with a solid content of 40 wt%. Add 1.5 wt% hydrochloric acid and 0.2 wt% citric acid to the slurry in sequence. Under ultrasonic assistance, heat to 80℃ and stir for 120 min. After leaching, use a four-stage countercurrent rinsing process to wash until the system is neutral. Then, use a high gradient electromagnetic iron remover to remove ferromagnetic debris from the slurry to obtain a mixed slurry. S2. The mixed slurry is subjected to plate and frame filter press filtration. The resulting filter cake is sent to a closed drying device lined with high-purity quartz and dried at 200°C until the material moisture content is 0.06%, thus obtaining mixed powder. S3. The mixed powder is fed into a sintering furnace lined with high-purity quartz. Under a nitrogen atmosphere, the temperature is first raised to 600℃ at a rate of 6℃ / min and held for 3 hours for low-temperature devolatilization treatment. Then, the temperature is raised to 1150℃ at a rate of 4℃ / min and held for 4 hours for sintering treatment to obtain sintered billet. S4. The sintered billet is fed into a quartz disc mill for coarse grinding. The gap between the grinding discs is adjusted to 0.8 mm and the relative speed difference between the grinding discs is 25 r / min. The coarse grinding time for a single batch is 25 min. After coarse grinding, a double-layer vibrating screen of 60 mesh and 250 mesh is used for screening. The material on the 60 mesh screen is returned to the quartz disc mill for re-grinding, and the material under the 250 mesh screen is sent to the front-end tailings powder slurry preparation process for reuse. The material retained by the double-layer vibrating screen is the coarsely ground quartz sand. S5. The coarsely ground quartz sand is fed into a quartz disc mill for fine grinding. The gap between the grinding discs is adjusted to 0.25 mm and the relative speed difference between the grinding discs is 18 r / min. The fine grinding time for a single batch is 20 min. After fine grinding, a double-layer vibrating screen of 60 mesh and 250 mesh is used for screening. The 60 mesh material is returned to the quartz disc mill for re-grinding, and the material under the 250 mesh screen is sent to the front-end tailings powder slurry process for reuse. The material retained by the double-layer vibrating screen is high-purity quartz sand. Example 2

[0025] The method for controlling the morphology and particle size of high-purity quartz sand in this embodiment specifically includes the following steps: S1. Weigh 4 kg of high-purity vein quartz beneficiation by-product tailings powder (primary silica purity is 99.92%, total metal impurity content is 80 ppm, and particle size range is concentrated between 1 μm and 35 μm), and use deionized water to prepare a slurry with a solid content of 38 wt%. Add 1.2 wt% hydrochloric acid and 0.15 wt% citric acid to the slurry in sequence. Under ultrasonic assistance, heat to 75℃ and stir for 100 min. After leaching, use a four-stage countercurrent rinsing process to wash until the system is neutral. Then, use a high gradient electromagnetic separator to remove ferromagnetic debris from the slurry to obtain a mixed slurry. S2. The mixed slurry is subjected to plate and frame filter press filtration. The resulting filter cake is sent to a closed drying device lined with high-purity quartz and dried at 220°C until the material moisture content is 0.05% to obtain mixed powder. S3. The mixed powder is fed into a sintering furnace lined with high-purity quartz. Under a nitrogen atmosphere, the temperature is first raised to 550°C at a rate of 5°C / min and held for 2.5 hours for low-temperature devolatilization treatment. Then, the temperature is raised to 1100°C at a rate of 3°C / min and held for 3.5 hours for sintering treatment to obtain sintered billets. S4. The sintered billet is fed into a quartz disc mill for coarse grinding. The gap between the grinding discs is adjusted to 0.7 mm and the relative speed difference between the grinding discs is 23 r / min. The coarse grinding time for a single batch is 30 min. After coarse grinding, a double-layer vibrating screen of 60 mesh and 250 mesh is used for screening. The material on the 60 mesh screen is returned to the quartz disc mill for re-grinding, and the material under the 250 mesh screen is sent to the front-end tailings powder slurry preparation process for reuse. The material retained by the double-layer vibrating screen is coarsely ground quartz sand. S5. The coarsely ground quartz sand is fed into a quartz disc mill for fine grinding. The disc gap is adjusted to 0.2 mm and the relative speed difference between the discs is 16 r / min. The fine grinding time for a single batch is 22 min. After fine grinding, a double-layer vibrating screen of 60 mesh and 250 mesh is used for screening. The 60 mesh material is returned to the quartz disc mill for re-grinding, and the material under the 250 mesh screen is sent to the front-end tailings powder slurry process for reuse. The material retained by the double-layer vibrating screen is high-purity quartz sand. Example 3

[0026] The method for controlling the morphology and particle size of high-purity quartz sand in this embodiment specifically includes the following steps: S1. Weigh 4 kg of high-purity vein quartz beneficiation by-product tailings powder (primary silica purity is 99.9%, total metal impurity content is 180 ppm, and particle size range is concentrated between 5 μm and 50 μm). Prepare a slurry with a solid content of 42 wt% using deionized water. Add 2.0 wt% hydrochloric acid and 0.25 wt% citric acid to the slurry in sequence. Heat to 85℃ under ultrasonic assistance and stir for 140 min. After leaching, wash the system with a four-stage countercurrent rinsing process until the system is neutral. Then remove ferromagnetic debris from the slurry using a high gradient electromagnetic iron remover to obtain a mixed slurry. S2. The mixed slurry is subjected to plate and frame filter press filtration. The resulting filter cake is sent to a closed drying device lined with high-purity quartz and dried at 190°C until the material moisture content is 0.07%, thus obtaining mixed powder. S3. The mixed powder is fed into a sintering furnace lined with high-purity quartz. Under a nitrogen atmosphere, the temperature is first raised to 620°C at a rate of 7°C / min and held for 3.5 hours for low-temperature devolatilization treatment. Then, the temperature is raised to 1180°C at a rate of 5°C / min and held for 4.5 hours for sintering treatment to obtain sintered billets. S4. The sintered billet is fed into a quartz disc mill for coarse grinding. The gap between the grinding discs is adjusted to 1.0 mm and the relative speed difference between the grinding discs is 27 r / min. The coarse grinding time for a single batch is 22 min. After coarse grinding, a double-layer vibrating screen of 60 mesh and 250 mesh is used for screening. The material on the 60 mesh screen is returned to the quartz disc mill for re-grinding, and the material under the 250 mesh screen is sent to the front-end tailings powder slurry preparation process for reuse. The material retained by the double-layer vibrating screen is the coarsely ground quartz sand. S5. The coarsely ground quartz sand is fed into a quartz disc mill for fine grinding. The disc gap is adjusted to 0.3 mm and the relative speed difference between the discs is 20 r / min. The fine grinding time for a single batch is 18 min. After fine grinding, a double-layer vibrating screen of 60 mesh and 250 mesh is used for screening. The 60 mesh material is returned to the quartz disc mill for re-grinding, and the material under the 250 mesh screen is sent to the front-end tailings powder slurry process for reuse. The material retained by the double-layer vibrating screen is high-purity quartz sand. Comparative Example 1

[0027] Take the same high-purity vein quartz beneficiation tailings powder as in Example 1, prepare a mixed acid solution containing 6.5 wt% hydrochloric acid and 1.5 wt% citric acid, and pickle it at room temperature for 45 minutes with stirring at a solid-liquid ratio of 1:1.8. After pickling, wash it with a four-stage countercurrent rinsing process until the system is neutral, and then dry it at 115°C until the material moisture content is 0.06%. The dried material is fed into a double-roll crusher with high manganese steel rollers for crushing, and the roller gap is controlled at 0.3 mm and the roller linear speed is 4 m / s to obtain quartz sand. Comparative Example 2

[0028] It is basically the same as Example 1, except that the S3 operation is not performed. Comparative Example 3

[0029] It is basically the same as Example 1, except that the operation of S5 is not performed. Comparative Example 4

[0030] The process is basically the same as in Example 1, except that citric acid was not introduced during the preparation of the mixed slurry. Test Example 1

[0031] The high-purity quartz sand prepared in the examples and comparative examples was tested: (1) Total metal impurity content: The total metal impurity content was determined by inductively coupled plasma mass spectrometry (ICP-MS). After the sample was digested and brought to a constant volume, the content of various metal elements was determined by the instrument and the total metal impurity content was obtained by summing them up. (2) Particle size yield: Weigh the mass of material in the 60-250 mesh range and divide it by the total mass of the sample to calculate the target particle size yield; (3) Proportion of needle-like and flaky particles: The proportion of needle-like and flaky particles was determined by using an optical microscope combined with image analysis. After the slide was prepared, the aspect ratio of the particles was statistically analyzed by collecting images of the field of view. Particles with a major axis / minor axis ≥ 3 were identified as needle-like and flaky particles. The proportion of needle-like and flaky particles was calculated by dividing the total mass of the sample. (4) Tapped density: The tapped density is determined by a tapped density meter. The dry quartz sand is loaded into a standard graduated cylinder and tapped until the volume is stable. The tapped density is obtained by dividing the mass of the powder by the volume after tapping. (5) Angle of repose: The angle of repose is measured by using a dedicated angle of repose measuring instrument with the injection method. After the powder falls freely and accumulates to form a stable cone, the angle between the inclined planes is measured from multiple angles, and the average value is taken as the angle of repose. Table 1 shows the final measured results: Table 1

[0032] As can be seen from Table 1, the overall performance of the high-purity quartz sand prepared in the examples is significantly better than that of the four comparative sample groups, showing comprehensive advantages in terms of metal impurity control, target particle size output, particle morphology regularity, powder packing and flow properties.

[0033] Comparing Example 1 and Comparative Example 1, it can be seen that Comparative Example 1 has a significantly higher content of metal impurities, a lower target particle size output, a significantly increased proportion of needle-like and flaky irregular particles, a lower powder compaction density, and a larger angle of repose. This is because Comparative Example 1 uses simple acid washing at room temperature to remove surface impurities, lacking a supporting system of ultrasonic chelation for deep impurity removal and high gradient iron removal. At the same time, the crushing equipment is made of steel, continuously introducing secondary metal contamination throughout the processing. Furthermore, the single impact crushing method lacks segmented sintering pretreatment and two-stage flexible shaping and grinding, making it easy for the material to be over-crushed and produce a large number of angular and flaky particles, resulting in poor powder accumulation and flowability.

[0034] Comparing Example 1 and Comparative Example 2, it can be seen that the target particle size yield of Comparative Example 2 decreased significantly, the proportion of irregularly shaped particles increased significantly, the tap density decreased, and the powder flowability deteriorated. This is because after Comparative Example 2 omitted the segmented sintering process, the fine tailings powder was in a loose micro powder state, which was very easy to over-crush during the grinding process. A large amount of material fell into the fine screen and formed waste. The loose green body formed by the slight bonding between particles was lacking. Controllable crushing could not be achieved during grinding, and it was difficult to complete the preliminary shaping. The final product had a wide particle size distribution and poor particle morphology.

[0035] Comparing Example 1 and Comparative Example 3, it can be seen that the target particle size yield of Comparative Example 3 decreased, the proportion of needle-shaped and flaky particles increased significantly, and the bulk density and flowability deteriorated. This is because Comparative Example 3, which only uses a single-stage quartz disc mill, cannot achieve the differentiated division of labor of "coarse crushing + fine shaping". The single grinding parameter has to crush the material and grind the edges, which can easily lead to two extreme situations: insufficient crushing or excessive grinding. It is difficult to simultaneously take into account particle size control and particle edge trimming, and it is impossible to obtain quartz sand particles with a near-equiaxed morphology.

[0036] Comparing Example 1 and Comparative Example 4, it can be seen that the total metal impurity content of Comparative Example 4 is significantly increased, while the particle size, morphology and powder properties are not significantly changed. This is because the system of Comparative Example 4 lacks citric acid chelating agent, so the metal ions dissolved by acid washing cannot form stable complexes. During the water washing stage, the metal ions will be re-adsorbed on the cracks and surface of the quartz particles, which greatly weakens the deep impurity removal effect. The chelating agent only acts on the impurity removal stage and will not affect the material grinding, particle shaping and particle size distribution.

[0037] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for controlling the morphology and particle size of high-purity quartz sand, characterized in that, Includes the following steps: S1. Quartz tailings powder, hydrochloric acid and chelating agent are dispersed in water and leached using ultrasonic-assisted stirring. Then, the mixture is washed and subjected to high-gradient iron removal to obtain a mixed slurry. S2. The mixed slurry described in S1 is filtered and dried to obtain a mixed powder. S3. The mixed powder described in S2 is sintered to obtain a sintered blank. S4. The sintered billet described in S3 is subjected to coarse grinding and then screened to obtain coarsely ground quartz sand. S5. The coarsely ground quartz sand described in S4 is subjected to fine grinding and then screened to obtain the high-purity quartz sand.

2. The method for controlling the morphology and particle size of high-purity quartz sand according to claim 1, characterized in that, In S1, the quartz tailings powder has a primary silica purity of 99.8%-99.95%, a total metal impurity content of 50ppm-200ppm, and a particle size of 1μm-50μm.

3. The method for controlling the morphology and particle size of high-purity quartz sand according to claim 1, characterized in that, In S1, the chelating agent is citric acid.

4. The method for controlling the morphology and particle size of high-purity quartz sand according to claim 1, characterized in that, In S1, the concentration of quartz tailings powder in the mixed slurry is 35wt%-45wt%, the concentration of hydrochloric acid is 1.0wt%-2.3wt%, and the concentration of chelating agent is 0.1wt%-0.3wt%.

5. The method for controlling the morphology and particle size of high-purity quartz sand according to claim 1, characterized in that, In S1, the leaching treatment is carried out at a temperature of 70°C-90°C for a time of 90 min-150 min.

6. The method for controlling the morphology and particle size of high-purity quartz sand according to claim 1, characterized in that, In S2, the drying process involves drying the material at 180℃-230℃ until the moisture content is ≤0.08%.

7. The method for controlling the morphology and particle size of high-purity quartz sand according to claim 1, characterized in that, In S3, the sintering is carried out under a protective atmosphere by first heating to 530℃-640℃ at a rate of 5℃ / min-7℃ / min and holding for 2.5h-4h, and then heating to 1080℃-1200℃ at a rate of 3℃ / min-5℃ / min and holding for 3h-5h.

8. The method for controlling the morphology and particle size of high-purity quartz sand according to claim 1, characterized in that, In S4, the coarse grinding process uses a quartz disc mill with a disc gap of 0.5mm-1.2mm, a relative speed difference of 22r / min-28r / min, and a single batch coarse grinding process duration of 20min-32min.

9. The method for controlling the morphology and particle size of high-purity quartz sand according to claim 1, characterized in that, In S5, the fine grinding process uses a quartz disc mill with a disc gap of 0.18mm-0.32mm, a relative speed difference of 15r / min-21r / min, and a single batch fine grinding process duration of 15min-25min.

10. The method for controlling the morphology and particle size of high-purity quartz sand according to claim 1, characterized in that, In S4 and S5, 60-mesh and 250-mesh double-layer vibrating screens are used for screening after coarse grinding and fine grinding, respectively.

Images