Method for synthesizing high-purity quartz sand from common quartz sand
Through chemical precipitation method and multi-stage filtration separation process, the problem of difficulty in preparing high-purity quartz sand is solved, and the preparation of quartz sand with high purity and low impurity content is achieved, which is suitable for high-end optical and semiconductor fields.
Patent Information
- Application Number
- CN202510578092.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-28
- Publication Date
- 2025-07-11
AI Technical Summary
It is difficult to effectively use ordinary quartz sand to prepare high-purity quartz sand in the prior art, especially in the fields of semiconductors, quartz crucibles and fiber optic communications for high purity and low impurity content.
Chemical precipitation method is adopted, including synthesis of water glass, hydrolysis, drying and melting, breaking and screening, magnetic separation, chlorination and roasting, and electric field removal and other process steps, and high-purity quartz sand is prepared through multi-stage filtration and high-voltage electric field separation.
The preparation of high-purity quartz sand has been achieved, with a purity of 99.9999%, and an impurity content of less than 9ppm. It is suitable for high-end optical and semiconductor fields, and meets the requirements of high purity, pollution-free and high temperature resistance.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of fine chemical synthesis, and specifically relates to a method for synthesizing high-purity synthetic quartz sand from ordinary quartz sand. Background Art
[0002] Quartz sand is a hard, wear-resistant, and chemically stable silicate mineral. Due to its unique physical and chemical properties, it is widely used not only in traditional industries such as casting, metallurgy, rubber, abrasives, ceramics, and construction, but also plays an irreplaceable role in high-tech fields such as aerospace, IT, communication, and solar cells. In China, the preparation of high-purity quartz sand mostly uses high-quality raw materials such as crystal and vein quartz ore. However, with the gradual depletion of high-quality mineral resources, the cost of high-purity quartz sand is extremely high. At the same time, China has rich ordinary quartz sand mineral resources. Therefore, exploring a method for refining high-purity quartz sand from ordinary quartz sand has great practical significance.
[0003] The production of synthetic quartz sand does not depend on the purity requirements of natural quartz minerals and can be prepared through chemical processes. Also, due to its higher purity and better optical properties, etc., in addition to being widely used in the high-end optical field, it also meets the requirements of semiconductor processes for high-purity, pollution-free, and high-temperature-resistant quartz products. Especially as the line width of semiconductor chips becomes narrower and narrower, ordinary natural quartz materials can no longer meet the requirements of high-end production processes, and synthetic quartz has become an important component in the etching process of semiconductor chips below the 10nm process.
[0004] High-purity quartz sand usually refers to quartz powder with a silicon dioxide content higher than 4N - 8N, which is the main raw material for quartz glass, quartz crucibles, optical communication, quartz tubes, quartz rods, and semiconductor chips, etc. For special material application fields such as quartz crucibles, high-purity quartz sand with a purity of usually more than 99.99%, an impurity content below 22ppm, and a single alkali metal (potassium, sodium, lithium) content less than 1ppm is required. In the prior art, high-purity quartz sand is mainly obtained by purifying natural ores. Due to the complex composition of the ores, it is very difficult to purify it to 99.99% or even higher. Moreover, the requirements for purity in semiconductor, quartz crucible, and optical fiber communication quartz sand are getting higher and higher, and it is very difficult to improve the natural purification method any further. Especially most ores often contain elements such as structural aluminum, lithium, boron, iron, and titanium, resulting in the finished products not meeting the requirements. Summary of the Invention
[0005] The purpose of the present invention is to solve the deficiencies of the prior art and provide a method for synthesizing high-purity quartz sand from ordinary quartz sand by using the chemical precipitation method.
[0006] The present invention is achieved through the following technical solutions:
[0007] A method for synthesizing high-purity quartz sand from ordinary quartz sand, and the technological process consists of six steps:
[0008] Step 1: Sodium silicate synthesis process Set the modulus of sodium silicate, meter and add ordinary quartz sand and lye into a drum-type rotary reactor in proportion, introduce high-pressure steam into the reactor for heating and pressurization, control the pressure at 0.8 - 1.2 MPa, the reaction temperature at 150 - 250 °C, keep the reactor jacket heated by steam for insulation, end the reaction after 6 - 15 hours, cool down to 30 - 50 °C, relieve the pressure through the pressure relief valve of the reactor, filter the reaction product through a three-stage pressure filtration device, and pump the product after impurity removal into a multi-effect evaporation concentrator, and concentrate it under vacuum to the required concentration.
[0009] Step 2: Hydrolysis process Batchwise and alternately pump the sodium silicate solution synthesized in Step 1 and the prepared dilute acid solution into the reactor in proportion, heat up the interlayer by steam, stir rapidly, and assist with ultrasonic waves. Through online pH value detection, alternately add the sodium silicate solution and the dilute acid solution. Flocculent precipitation will be generated during the reaction. After the addition of the sodium silicate solution is completed and the pH is adjusted and controlled with the acid solution, turn off the ultrasonic system, keep stirring for aging at a constant temperature for 30 - 120 minutes and then stop. Filter the mixed solution through a pressure filtration device, wash the precipitate with deionized water 1 - 4 times, and centrifuge to remove excess water to obtain a filter cake product.
[0010] Step 3: Drying and melting process Place the filter cake product from Step (2) in a dryer and dry it at 150 - 300 °C for 1 - 5 hours until the moisture content ≤ 0.5%. Then place it in a melting furnace, melt it at a temperature of 1500 - 2000 °C and a pressure of 0.01 - 0.08 Mpa for 0.5 - 5 hours, and blow and cool it with an inert gas to obtain a transparent quartz mass.
[0011] Step 4: Crushing, screening and magnetic separation process Coarsely crush the quartz mass obtained in Step 3 with a box-type crusher, finely grind it with an autogenous mill, then screen out products with corresponding particle sizes through a screening machine, re-send the unqualified particle sizes to the autogenous mill for fine grinding, and send the qualified materials to a high-gradient vertical ring magnetic separator for magnetic separation.
[0012] Step 5: Chlorination roasting process Send the product from Step 4 to the quartz tube of a chlorination roasting furnace through a conveyor belt and a distributor, add a chlorinating agent, heat it to 800 - 1000 °C for chlorination reaction for 10 - 60 minutes, and cool and discharge through a cooling device.
[0013] Step 6: Electric field impurity removal process Feed the product of Step 5 into the high-voltage electric field impurity removal device through a distributor, control the voltage of the high-voltage electric field to be 5 - 30 KV, and further separate and purify according to the difference in the charges carried by the product impurities; after impurity removal, the product is sent to a dust-free workshop for vacuum packaging.
[0014] Step 1: Process for synthesizing sodium silicate: The modulus is controlled between 1.0 and 2.5. This modulus has good water solubility, low viscosity, does not require adding a filter aid, and is easy to filter and remove impurities.
[0015] The process for synthesizing sodium silicate; the content of ordinary quartz sand is between 90% and 99%, and Fe2O3 is between 0.06% and 0.02%.
[0016] Step 1: Process for synthesizing sodium silicate: The alkali is one or a mixture of sodium hydroxide and potassium hydroxide in any proportion, and the concentration of the alkali solution is between 10% and 60%.
[0017] Step 1: Process for synthesizing sodium silicate: The reaction pressure is controlled at 0.7 - 1.5 MPa, the temperature is 120 - 190 °C; the reaction time is 5 - 20 hours.
[0018] Step 1: Process for synthesizing sodium silicate: Filtration and concentration: Some impurities and unreacted substances will be generated in the synthesized sodium silicate solution, which need to be removed by filtration. The filtration in the present invention is a multi-stage filtration method, and usually a pressure filter or a vacuum filter is used to ensure the purity and quality of the product; the synthesized sodium silicate solution has a high water content, and the water needs to be evaporated through a vacuum concentration operation; a multi-effect evaporative concentrator is used for concentration, and vacuum is pumped to improve the concentration efficiency.
[0019] Step 1: Process for synthesizing sodium silicate: Multi-stage pressure filtration system. The present invention uses a three-stage filtration system of primary filtration, fine filtration, and ultra-fine filtration to remove impurities. The first-stage filtration is primary filtration, mainly removing unreacted quartz sand particles, and the aperture of the filter screen is 100 - 250 meshes; the second-stage filtration is fine filtration, with a mesh aperture of 250 - 500 meshes, mainly removing impurities attached to quartz sand, reaction precipitates, and lattice impurities; the third-stage filtration is ultra-fine filtration, with a filter screen aperture of 500 - 1000 meshes, mainly removing mud-like and colloidal precipitates generated by the reaction.
[0020] Step 1: Process for synthesizing sodium silicate: Concentration. The synthesized sodium silicate solution has a high water content, and the water needs to be evaporated through a concentration operation. A multi-effect evaporation concentrator is used, and it is concentrated to a sodium silicate solution with a solid content of 10 - 50%.
[0021] Step 2: Hydrolysis process: Add sodium silicate and dilute acid solution alternately, mainly to prevent the self-polymerization of silicic acid in the acidic solution. Since the self-polymerized monosilicic acid gradually polymerizes into polysilicic acid, forming a network gel structure, it is not conducive to dehydration, drying, and washing with deionized water to remove impurities.
[0022] Step 2: Hydrolysis process: The dilute acid solution is one or a mixture of any proportions of sulfuric acid, hydrochloric acid, phosphoric acid, sulfonic acid, and nitric acid, preferably one of sulfuric acid, sulfonic acid, and hydrochloric acid; the acid concentration is controlled at 5-25%.
[0023] Step 2: Hydrolysis process: The hydrolysis stirring speed is controlled at 200-600 rpm, and ultrasonic waves are supplemented by an ultrasonic system with an ultrasonic frequency of 25-100 kHz. The pH value of the solution is controlled online at 6-9.5, the reaction temperature is 35-85 °C, and the reaction time is 2-6 hours.
[0024] Step 2: Hydrolysis process: The mixed solution is filtered through a pressure filtration system. The pore size of the filter cloth is 0.5-1 micron, the filtration pressure is 0.2-0.8 MPa, and the centrifugal drying rate is 2000-3500 r / min; the deionized water used is ultrapure water with a resistivity ≥ 18.2 MΩ·cm (25 °C).
[0025] Step 3: Drying and melting process: The drying temperature is 150-300 °C, and the moisture content of drying is ≤ 0.5%; the melting temperature is 1800-2000 °C, the pressure is 0.01-0.08 MPa, melting is carried out for 0.5-5 hours, and the product is cooled to room temperature by passing low-temperature nitrogen or argon.
[0026] Step 4: Crushing, screening, and magnetic separation process: The product of step 3 is first crushed by a box crusher, then finely ground by an autogenous mill, and the discharged material is screened by a screening machine. The particle size is controlled at 70-200 mesh, and the powder is magnetically separated by a high-gradient vertical ring magnetic separator with a magnetic field strength of 12000-18000 GS.
[0027] Step 5: Chlorination roasting process: The chlorinating agent is a solid chlorinating agent such as sodium hydrogen fluoride, sodium bisulfite, sodium bisulfate, sodium chloride; ammonium chloride, and the gaseous chlorinating agent is chlorine and hydrogen chloride gas. One or a mixture of any proportions of them is selected.
[0028] Preferably, the present invention selects a gaseous chlorinating agent. Specifically, a mixture of hydrogen chloride and chlorine in a volume ratio of 1:1-1:10 is selected, the intake air volume is 2-50 ml / min, the chlorination temperature is 600-1200 °C, and the chlorination time is 5-60 min.
[0029] Step 6: Electric field impurity removal process: The electric field impurity removal process is a method of separating and purifying substances using a high-voltage electric field. Utilizing the conductivity difference between quartz and impurities, charged particles are moved in the electric field to achieve separation; the electric field voltage is controlled at 5-30 KV, the feed particle size is 0.08-0.45 mm, and the material impurity removal temperature is 30-60 °C.
[0030] Beneficial effects
[0031] The present invention synthesizes high-purity quartz sand using ordinary quartz sand as the raw material. The raw material source is wide and abundant, overcoming the bottleneck limitation that the existing purification technology severely depends on the high-quality requirements of natural quartz ore.
[0032] The present invention uses the chemical precipitation method to synthesize high-purity quartz sand from ordinary quartz sand, which has higher purity and better optical properties. It is especially suitable for use in the production of photovoltaic materials, quartz crucibles, and fiber optic cables, and also meets the requirements of semiconductor processes for high-purity, pollution-free, and high-temperature-resistant quartz products.
[0033] The present invention is convenient for operation and control, has low energy consumption of products, less environmental pollution, high synthesis efficiency, and high product purity, and is suitable for continuous large-scale production. Specific embodiments
[0034] Example 1
[0035] A method for synthesizing high-purity quartz sand from ordinary quartz sand, the process of which consists of six steps:
[0036] Step 1: Process for synthesizing water glass
[0037] Equipment and raw material ratio: One 8m 3 stainless steel 316 high-pressure reactor; the product modulus is 1.5; 2.1 tons of ordinary quartz sand (SiO2 content 98%, Fe2O3 content 0.06%), and 6.1 tons of 30% caustic soda solution; Measure 6.1 tons of 30% alkali solution and add it to the drum-type rotary reactor. Start stirring, add 2.1 tons of ordinary quartz sand, directly introduce high-pressure steam into the reactor, control the pressure at 0.9 - 1.2 MPa, and the temperature at 180 - 190 °C; the jacket of the reactor is passed with steam for heat preservation, stop the reaction after 10 hours, cool down to 30 - 50 °C, relieve the pressure with the pressure relief valve, send the material in the reaction tank to the buffer tank for preliminary precipitation for about 2 hours, and pump the supernatant of the buffer tank to the three-stage pressure filtration device for pressure filtration. The first-stage filtration filter screen is 200 meshes; the second-stage filter screen density is 500 meshes; the third-stage filter screen pore diameter is 850 meshes; the product after impurity removal is sent to the multi-effect evaporation concentrator, and vacuum concentrated to a 40% concentration product.
[0038] Step 2: Hydrolysis process In a 10-cubic-meter hydrolysis tank, 8.75 tons of a 40% solution of the sodium silicate solution synthesized in Step 1 and 10.9 tons of a 15% dilute hydrochloric acid solution prepared are used. For the first time, 1 / 6 of the total amount of the sodium silicate solution is added to the reaction kettle, and the temperature is raised to 60 °C. Then, 1 / 6 of the total amount of the dilute hydrochloric acid is added dropwise, and the stirring speed is controlled at 500 rpm / min. At the same time, ultrasonic waves are supplemented, and the ultrasonic waves are controlled at 60 KHz. By online controlling the pH value at 6 - 8, and then the remaining sodium silicate solution and dilute acid solution are added alternately in 5 times, each time with 1 / 6 of the total amount. After the last batch of sodium silicate is added dropwise and the pH is adjusted to 6 - 8 with dilute hydrochloric acid, the ultrasonic system is turned off. After stirring at a constant temperature for 30 - 120 minutes, it is stopped. The mixed solution is filtered through a pressure filtration system, and the pore size of the filter cloth is 0.5 - 1 micron. The precipitate is washed 1 - 4 times with deionized water, and the excess water is centrifugally dried at a rate of 2500 r / min to obtain a filter cake product.
[0039] Step 3: Drying and melting process Place the filter cake product from Step 2 in a dryer and bake at 200 °C for 3 hours until the moisture content ≤ 0.5%. Then place it in a melting furnace and melt at a temperature of 1900 °C and a pressure of 0.01 - 0.08 Mpa for 3 hours. The product is cooled to ≤ 60 °C by purging with room-temperature nitrogen to obtain a transparent quartz mass.
[0040] Step 4: Crushing, screening and magnetic separation process The quartz mass from Step 3 is roughly crushed by a box-type crusher, sent to an autogenous mill for fine grinding, screened by a 100-mesh sieve, and the material enters a high-gradient vertical ring magnetic separator. The product is obtained by magnetic separation with a magnetic field intensity of 18000 GS.
[0041] Step 5: Chlorination roasting process The product from Step 4 is sent through a conveyor belt and a hopper to the quartz tube of a chlorination roasting furnace. Heat it to 1000 °C, and introduce a mixed gas of chlorine and hydrogen chloride from the discharge end. The volume ratio of the mixed gas is 1:1, and the intake volume is 10 ml / min. React for 30 minutes. The discharge product is cooled by water spraying on the quartz tube and discharged after cooling to ≤ 60 °C.
[0042] Step 6: Electric field impurity removal process The product from Step 5 is sent into an electric field impurity remover through a hopper. Control the voltage of the electric field at 20 KV. After the material is purified by the electric field, it is sent to a dust-free workshop and vacuum-packed into products.
[0043] This invention is detected by an ICP-OMS plasma spectrometer and the hydrofluoric acid volatilization method, reaching ultra-pure quartz sand (6N) with a SiO2 content of 99.9999%. The total impurity content of the obtained high-purity quartz sand is < 9 ppm, and the hydroxyl content is < 60 ppm. The technical indicators can meet the needs of high-end quartz application fields, as shown in Table 1.
[0044] Table 1
[0045] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It is not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A method for synthesizing high-purity quartz sand from ordinary quartz sand, characterized in that: This process consists of six steps: Step 1: Sodium silicate synthesis process: Set the modulus of sodium silicate. Meter ordinary quartz sand and lye in proportion and add them to a drum-type rotary reactor. Introduce high-pressure steam into the reactor to heat and pressurize. Control the pressure at 0.8 - 1.2 MPa and the reaction temperature at 150 - 250 °C. Keep the reactor jacket with steam for heat preservation. After 6 - 15 hours of reaction, cool down to 30 - 50 °C. Release the pressure through the pressure relief valve of the reactor. The reaction product is filtered through a three-stage pressure filtration device. After removing impurities, the product is pumped into a multi-effect evaporation concentrator and vacuum concentrated to the required concentration. Step 2: Hydrolysis process: Intermittently add the sodium silicate solution synthesized in Step 1 and the prepared dilute acid solution in proportion into the reactor in batches. Heat up the interlayer with steam, stir rapidly, and assist with ultrasonic waves. Intermittently add the sodium silicate solution and the dilute acid solution through on-line pH detection. Flocculent precipitates are generated during the reaction. After the addition of sodium silicate is completed and the pH is adjusted by the acid solution, turn off the ultrasonic system. Keep stirring at a constant temperature for 30 - 120 minutes and then stop. The mixed solution is filtered through a pressure filtration device. Wash the precipitate with deionized water 1 - 4 times. Centrifuge to remove excess water to obtain a filter cake product. Step 3: Drying and melting process: Place the filter cake product from Step (2) in a dryer and dry at 150 - 300 °C for 1 - 5 hours until the moisture content ≤ 0.5%. Then place it in a melting furnace and melt at a temperature of 1500 - 2000 °C and a pressure of 0.01 - 0.08 Mpa for 0.5 - 5 hours. Purge and cool down with inert gas to obtain a transparent quartz mass. Step 4: Crushing, screening, and magnetic separation process: Coarsely crush the quartz mass obtained in Step 3 with a box-type crusher, finely grind it with an autogenous mill, and then screen out products with corresponding particle sizes through a screening machine. The unqualified particle sizes are sent back to the autogenous mill for fine grinding. The qualified materials are sent to a high-gradient vertical ring magnetic separator for magnetic separation. Step 5: Chlorination roasting process: Send the product from Step 4 through a conveyor belt and a distributor into the quartz tube of a chlorination roasting furnace, add a chlorinating agent, heat to 800 - 1000 °C for chlorination reaction for 10 - 60 minutes, and cool and discharge through a cooling device. Step 6: Electric field impurity removal process: Send the product from Step 5 through a distributor into a high-voltage electric field impurity removal device, control the voltage of the high-voltage electric field at 5 - 30 KV, and further separate and purify according to the difference in the charges carried by the impurities in the product. The product after impurity removal is sent to a dust-free workshop for vacuum packaging.
2. The process according to claim 1, characterized in that: In the sodium silicate synthesis process of Step 1, the modulus is controlled at 1.0 - 2.5, the content of the ordinary quartz sand is between 90 - 99%, and Fe2O3 is between 0.06 - 0.02%.
3. The process according to claim 1, characterized in that: In the sodium silicate synthesis process of Step 1, a multi-stage pressure filtration system is used. A three-stage filtration system of primary filtration, fine filtration, and ultra-fine filtration is used to remove impurities. The first-stage filtration is primary filtration, and the filter screen aperture is 100 - 250 mesh; the second-stage filtration is fine filtration, and the mesh aperture is 250 - 500 mesh; the third-stage filtration is ultra-fine filtration, and the filter screen aperture is 500 - 1000 mesh.
4. The process according to claim 1, characterized in that: The hydrolysis process in Step 2: The stirring speed is controlled at 200 - 600 rpm, the ultrasonic frequency is 25 - 100 kHz, the pH value of the solution is controlled online at 6 - 9.5, the reaction temperature is 35 - 85 °C, and the reaction time is 2 - 6 hours.
5. The process according to claim 1, characterized in that: The hydrolysis process in Step 2: The mixed solution is filtered through a pressure filtration system. The pore size of the filter cloth is 0.5 - 1 micron, the filtration pressure is 0.2 - 0.8 MPa, and the centrifugal drying rate is 2000 - 3500 r / min; The deionized water used is ultrapure water with a resistivity ≥ 18.2 MΩ·cm (25 °C).
6. The process according to claim 1, characterized in that: The drying and melting process in Step 3: The drying temperature is 150 - 300 °C, and the moisture content after drying is ≤ 0.5%; The melting temperature is 1800 - 2000 °C, the pressure is 0.01 - 0.08 MPa, the melting time is 0.5 - 5 hours, and the product is cooled to room temperature by passing low-temperature nitrogen or argon gas.
7. The process according to claim 1, characterized in that: The chlorination roasting process in Step 5: The chlorinating agent is a gaseous chlorinating agent, a mixture of hydrogen chloride and chlorine with a volume ratio of 1:1 - 1:10, the inlet gas volume is 2 - 50 ml / min, the chlorination temperature is 600 - 1200 °C, and the chlorination time is 5 - 60 min.
8. The process according to claim 1, characterized in that: The electric field impurity removal process in Step 6: The electric field voltage is controlled at 5 - 30 KV, the feed particle size is 0.08 - 0.45 mm, and the material temperature is 30 - 60 °C.