A method for producing high purity silicon dioxide

Abstract

The application discloses a method for preparing high-purity silicon dioxide, which comprises the following steps: step 1) raw material pretreatment: dust collected in a single crystal silicon pulling tail gas treatment and argon recovery process is preliminarily treated; step 2) controllable combustion oxidation treatment: the pretreated dust is subjected to low-oxygen-concentration combustion oxidation in a closed rotary kiln; step 3) ammonia water-oxalic acid complexation washing: the dust after the oxidation treatment is subjected to ammonia water-oxalic acid complexation washing; step 4) vacuum thermal desorption treatment: the dust after the washing is subjected to vacuum thermal desorption treatment; and step 5) product purification: the dust after the desorption is subjected to purification treatment, so as to obtain a high-purity silicon dioxide product. The application is simple in operation, easy in process parameter control, suitable for industrialized production, and does not need to use organic solvents, so that environmental pollution caused by a traditional liquid phase method is avoided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-purity silicon dioxide preparation and relates to a method for preparing high-purity silicon dioxide. BACKGROUND

[0002] High-purity silicon dioxide is an indispensable key basic material in high-tech industries such as semiconductors, optical fiber communication, aerospace, and national defense and military fields, and its purity requirement is extremely high, usually reaching more than 99.99%, and in some high-end application scenarios, the purity is required to reach more than 99.9999%. High-purity quartz sand is an important raw material for preparing high-purity silicon dioxide, and its quality has a great influence on the quality of silicon single crystals. At present, the production of high-purity silicon dioxide worldwide mainly relies on natural quartz ore, and a series of physical purification processes such as mechanical crushing, acid leaching, flotation, and magnetic separation are used to obtain it. However, the shortage of high-purity quartz ore is becoming increasingly prominent.

[0003] In order to cope with the shortage and quality problems of natural quartz ore, some artificial synthesis methods have also been tried in the industry, such as chemical synthesis methods, including gas phase method and liquid phase method. However, these methods have obvious drawbacks. The gas phase method uses SiCl4 as raw material to synthesize by high-temperature hydrolysis, which requires high equipment and the byproduct HCl is highly corrosive; the liquid phase method can accurately control the particle size, but has problems such as high raw material cost and environmental hazards of organic solvents, and these methods all rely on high-purity silicon sources, and have not fundamentally solved the problem of raw material dependence.

[0004] In the process of single crystal silicon pulling, a large amount of silicon dioxide dust is brought out in the process of tail gas treatment and argon recovery. Analysis shows that this dust has low impurity content, high purity, and good particle characteristics, and is very suitable as a raw material for preparing high-purity silicon dioxide. Unfortunately, most of these dusts are currently treated as industrial waste, without effective resource utilization, not only causing great waste of resources, but also possibly causing environmental problems and safety hazards such as dust pollution.

[0005] The prior art document CN114853025A discloses a method for preparing high-purity silicon dioxide from silica ash. In this method, silica ash is used as raw material, and after removing impurities by acid cooking, the silica ash is reacted with caustic soda to generate liquid sodium silicate. 8-hydroxyquinoline is added to the liquid sodium silicate to complex and precipitate the metal impurities in the sodium silicate. After filtration, high-purity sodium silicate is obtained. The high-purity sodium silicate is salted out with acid, and the precipitate silica is calcined to obtain high-purity silicon dioxide. However, the reaction temperature, reaction time, and solid-liquid ratio of the method for purifying high-purity sodium silicate still need to be further optimized to obtain high-purity silicon dioxide with higher purity.

[0006] The prior art document CN118047383A discloses a synthesis method of high-purity quartz, which uses high-purity silicon single element and ultra-pure water as reactants, and an alkali substance as a catalyst to prepare high-purity silicon sol. The solid-liquid separation is performed by any one of direct drying, freeze-drying, gel freeze-drying, and spray drying. Finally, densification is performed. However, in the preparation step of the high-purity silicon sol, the type and amount of the catalyst, and the PH value of the reaction system still need to be further optimized to improve the purity and yield of the product.

[0007] Therefore, a method for preparing high-purity silicon dioxide is designed to overcome the above problems. SUMMARY

[0008] The present application aims to overcome the shortcomings of the prior art and provide a method for preparing high-purity silicon dioxide, which is simple to operate, easy to control process parameters, suitable for industrial production, and does not require the use of organic solvents, thereby avoiding environmental pollution caused by traditional liquid-phase methods.

[0009] The present application is achieved by the following technical solution: a method for preparing high-purity silicon dioxide, comprising the following steps:

[0010] Step 1) Raw material pretreatment: collecting and preliminarily treating the dust generated in the single crystal silicon pulling tail gas treatment and argon recovery process;

[0011] Step 2) Controllable combustion oxidation treatment: performing low-oxygen-concentration combustion oxidation of the pretreated dust in a closed rotary kiln;

[0012] Step 3) Ammonia-oxalic acid complexation washing: washing the oxidized dust with ammonia-oxalic acid complexation;

[0013] Step 4) Vacuum thermal desorption treatment: performing vacuum thermal desorption treatment on the washed dust;

[0014] Step 5) Product purification: purifying the desorbed dust to obtain high-purity silicon dioxide products.

[0015] As a preferred embodiment, the step 1) is specifically as follows:

[0016] 1) Collect and sieve the dust generated in the single crystal silicon pulling tail gas treatment and argon recovery process, and remove agglomerated particles and impurities;

[0017] 2) Dry the sieved dust under inert gas protection to remove moisture;

[0018] 3) Perform particle size analysis and classification on the dried dust, and select particles with a particle size of 0.5-5 μm.

[0019] As a preferred embodiment, the step 2) is specifically as follows:

[0020] 1) Place the sorted dust in a sealed rotary kiln, introduce argon and nitrogen, and adjust the oxygen concentration to control it at 3-5%;

[0021] 2) Heat to 300-400℃ and maintain for 30 minutes to convert SiO into SiO2, with a conversion rate of over 99%;

[0022] 3) Allow it to cool naturally to room temperature to obtain the oxidized dust.

[0023] Preferably, step 3) specifically includes:

[0024] 1) Prepare an ammonia-oxalic acid complex washing solution by mixing 5% NH4OH, 3% oxalic acid and 0.5% EDTA-2Na in a mass ratio of 5:3:0.5;

[0025] 2) Add the oxidized dust to the washing liquid and stir at 80°C for 2 hours to remove impurities such as fluorine, chlorine, calcium and potassium;

[0026] 3) Collect the precipitate by filtration, and wash it with deionized water and ethanol 3-5 times in sequence to remove residual impurities.

[0027] Preferably, step 4) specifically includes:

[0028] 1) Place the washed dust in a horizontal vacuum furnace and evacuate to 10°C. -3 Pa;

[0029] 2) Heat to 300℃ at a heating rate of 2-5℃ / min and hold for 1 hour;

[0030] 3) Continue heating to 600℃ and hold for 2 hours to break molecular bonds under high temperature and vacuum conditions, thereby removing the bound fluorine.

[0031] 4) Allow it to cool naturally to room temperature to obtain the desorbed dust.

[0032] Preferably, step 5) specifically includes:

[0033] 1) Heating the dust to 800-1000℃ at a heating rate of 2-3℃ / min under inert gas protection;

[0034] 2) Keep warm for 2-3 hours to remove organic impurities;

[0035] 3) Allow it to cool naturally to room temperature to obtain a high-purity silica product.

[0036] The beneficial effects of this invention are as follows:

[0037] 1. The method for preparing high-purity silica designed in this invention, by using a controllable combustion oxidation treatment device to carry out low-oxygen concentration combustion oxidation in a closed rotary kiln, effectively solves the shortage and quality problems of natural quartz ore, overcomes the influence of fluid inclusions and mineral inclusions in traditional purification processes, and realizes the preparation of high-purity silica;

[0038] 2. This invention utilizes the dust generated during the treatment of tail gas from monocrystalline silicon crystal pulling and argon recovery as raw material. Through a multi-step processing technology, it achieves effective resource utilization of dust, avoids resource waste caused by industrial waste treatment, and reduces environmental problems and safety hazards such as dust pollution.

[0039] 3. This invention employs an ammonia-oxalic acid complexation washing method for the deep removal of fluorine, chlorine, calcium, and potassium. Through a synergistic complexation system, it achieves efficient removal of various impurities and effectively improves the purity of the product.

[0040] 4. This invention employs a vacuum thermal desorption method to remove bound fluorine. By breaking molecular bonds under high temperature and vacuum conditions, efficient removal of fluorine is achieved, ensuring the purity of the final product.

[0041] 5. The preparation method of the present invention is simple to operate, the process parameters are easy to control, it is suitable for industrial production, and it does not require the use of organic solvents, thus avoiding the environmental pollution caused by traditional liquid phase methods. Attached Figure Description

[0042] Figure 1 This is the overall flowchart of the present invention. Detailed Implementation

[0043] To enable those skilled in the art to more clearly understand the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0044] In the description of this invention, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", "lateral", and "vertical" is based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of describing this invention, and is not intended to indicate or imply that the device or component referred to must have a specific orientation, and therefore should not be construed as a limitation of this invention.

[0045] The invention will now be described in detail with reference to the accompanying drawings: Figure 1 As shown, a method for preparing high-purity silica includes the following steps:

[0046] Step 1) Raw material pretreatment: The dust collected during the treatment of tail gas from monocrystalline silicon crystal pulling and argon recovery is preliminarily treated;

[0047] Step 2) Controlled combustion oxidation treatment: The pretreated dust is subjected to low-oxygen concentration combustion oxidation in a closed rotary kiln;

[0048] Step 3) Ammonia-oxalic acid complexation washing: The dust after oxidation treatment is washed with ammonia-oxalic acid complexation.

[0049] Step 4) Vacuum thermal desorption treatment: The washed dust is subjected to vacuum thermal desorption treatment;

[0050] Step 5) Product purification: The desorbed dust is purified to obtain high-purity silica product.

[0051] Specifically, step 1) is as follows:

[0052] 1) Collect and sieve the dust generated during the treatment of tail gas from monocrystalline silicon crystal pulling and the argon recovery process to remove agglomerated particles and impurities;

[0053] 2) The sieved dust is dried under inert gas protection to remove moisture;

[0054] 3) Perform particle size analysis and classification on the dried dust, and select particles with a particle size of 0.5-5μm.

[0055] Step 2) specifically refers to:

[0056] 1) Place the sorted dust in a sealed rotary kiln, introduce argon and nitrogen, and adjust the oxygen concentration to control it at 3-5%;

[0057] 2) Heat to 300-400℃ and maintain for 30 minutes to convert SiO into SiO2, with a conversion rate of over 99%;

[0058] 3) Allow it to cool naturally to room temperature to obtain the oxidized dust.

[0059] Step 3) specifically refers to:

[0060] 1) Prepare an ammonia-oxalic acid complex washing solution by mixing 5% NH4OH, 3% oxalic acid and 0.5% EDTA-2Na in a mass ratio of 5:3:0.5;

[0061] 2) Add the oxidized dust to the washing liquid and stir at 80°C for 2 hours to remove impurities such as fluorine, chlorine, calcium and potassium;

[0062] 3) Collect the precipitate by filtration, and wash it with deionized water and ethanol 3-5 times in sequence to remove residual impurities.

[0063] Step 4) specifically involves:

[0064] 1) Place the washed dust in a horizontal vacuum furnace and evacuate to 10°C.-3 Pa;

[0065] 2) Heat to 300℃ at a heating rate of 2-5℃ / min and hold for 1 hour;

[0066] 3) Continue heating to 600℃ and hold for 2 hours to break molecular bonds under high temperature and vacuum conditions, thereby removing the bound fluorine.

[0067] 4) Allow it to cool naturally to room temperature to obtain the desorbed dust.

[0068] Step 5) specifically involves:

[0069] 1) Heating the dust to 800-1000℃ at a heating rate of 2-3℃ / min under inert gas protection;

[0070] 2) Keep warm for 2-3 hours to remove organic impurities;

[0071] 3) Allow it to cool naturally to room temperature to obtain a high-purity silica product.

[0072] The core features of this invention are as follows:

[0073] Low oxygen concentration (3-5%) rotary kilns suppress violent heat release during combustion and prevent dust splashing;

[0074] Combustion volatilization (approximately 30%) → ammoniation conversion (60%) → vacuum bond breaking (10%);

[0075] The EDTA-oxalic acid complexation system targets and removes K / Ca.

[0076] Example 1: A method for preparing high-purity silica, comprising the following steps:

[0077] Step 1) Raw material pretreatment: The dust collected during the treatment of tail gas from monocrystalline silicon crystal pulling and argon recovery is preliminarily treated;

[0078] 1) Collect the dust generated during the treatment of tail gas from monocrystalline silicon crystal pulling and argon recovery process and sieve it using a 200-mesh standard sieve to remove agglomerated particles and impurities;

[0079] 2) The sieved dust was dried at 120°C for 4 hours under inert gas protection to remove moisture;

[0080] 3) The dried dust was analyzed using a laser particle size analyzer, and particles with a size of 0.5-5μm were selected.

[0081] Step 2) Controlled combustion oxidation treatment: The pretreated dust is subjected to low-oxygen concentration combustion oxidation in a closed rotary kiln;

[0082] 1) Place the sorted dust in a closed rotary kiln, introduce argon and nitrogen, and adjust the oxygen concentration to 3-5%, with the argon flow rate at 2L / min and the nitrogen flow rate at 8L / min;

[0083] 2) Heat to 300℃ and maintain for 30 minutes to convert SiO into SiO2, achieving a conversion rate of 99.5%;

[0084] 3) Allow it to cool naturally to room temperature to obtain the oxidized dust.

[0085] Step 3) Ammonia-oxalic acid complexation washing: The dust after oxidation treatment is washed with ammonia-oxalic acid complexation.

[0086] 1) Weigh 5% NH4OH, 3% oxalic acid and 0.5% EDTA-2Na in a mass ratio of 5:3:0.5, add deionized water and stir evenly to prepare ammonia-oxalic acid complex washing solution.

[0087] 2) Add the oxidized dust to the washing liquid and stir at 80℃ for 2 hours at a stirring speed of 200 rpm to remove impurities such as fluorine, chlorine, calcium and potassium;

[0088] 3) The precipitate was collected by vacuum filtration and washed three times with deionized water and anhydrous ethanol, each time for 5 minutes, to remove residual impurities.

[0089] Step 4) Vacuum thermal desorption treatment: The washed dust is subjected to vacuum thermal desorption treatment;

[0090] 1) Place the washed dust in a horizontal vacuum furnace, pump air for 2 minutes, then turn off the vacuum pump and allow it to naturally reach a vacuum level of 10. -3 Pa;

[0091] 2) Heat to 300℃ at a heating rate of 2℃ / min and hold for 1 hour;

[0092] 3) Continue heating to 600℃ and hold for 2 hours to break molecular bonds under high temperature and vacuum conditions, thereby removing the bound fluorine.

[0093] 4) Allow it to cool naturally to room temperature to obtain the desorbed dust.

[0094] Step 5) Product purification: The desorbed dust is purified to obtain high-purity silica product.

[0095] 1) The dust was heated to 800℃ at a heating rate of 2℃ / min under inert gas protection;

[0096] 2) Keep warm for 2 hours to remove organic impurities;

[0097] 3) Allow it to cool naturally to room temperature to obtain a high-purity silica product.

[0098] Example 2: A method for preparing high-purity silica, comprising the following steps:

[0099] Step 1) Raw material pretreatment: The dust collected during the treatment of tail gas from monocrystalline silicon crystal pulling and argon recovery is preliminarily treated;

[0100] 1) Collect the dust generated during the treatment of tail gas from monocrystalline silicon crystal pulling and the argon recovery process, and sieve it using a 180-mesh standard sieve to remove agglomerated particles and impurities;

[0101] 2) The sieved dust is dried at 150℃ for 5 hours under inert gas protection to remove moisture;

[0102] 3) The dried dust was analyzed using a laser particle size analyzer, and particles with a size of 0.5-5μm were selected.

[0103] Step 2) Controlled combustion oxidation treatment: The pretreated dust is subjected to low-oxygen concentration combustion oxidation in a closed rotary kiln;

[0104] 1) Place the sorted dust in a closed rotary kiln, introduce argon and nitrogen, and adjust the oxygen concentration to 3-5%, with the argon flow rate at 1.5L / min and the nitrogen flow rate at 9L / min;

[0105] 2) Heat to 400℃ and maintain for 30 minutes to convert SiO into SiO2, achieving a conversion rate of 99.8%;

[0106] 3) Allow it to cool naturally to room temperature to obtain the oxidized dust.

[0107] Step 3) Ammonia-oxalic acid complexation washing: The dust after oxidation treatment is washed with ammonia-oxalic acid complexation.

[0108] 1) Weigh 5% NH4OH, 3% oxalic acid and 0.5% EDTA-2Na in a mass ratio of 5:3:0.5, add deionized water and stir evenly to prepare ammonia-oxalic acid complex washing solution.

[0109] 2) Add the oxidized dust to the washing liquid and stir at 80℃ for 2 hours at a stirring speed of 250 rpm to remove impurities such as fluorine, chlorine, calcium and potassium;

[0110] 3) The precipitate was collected by vacuum filtration and washed five times with deionized water and anhydrous ethanol, each time for 6 minutes, to remove residual impurities.

[0111] Step 4) Vacuum thermal desorption treatment: The washed dust is subjected to vacuum thermal desorption treatment;

[0112] 1) Place the washed dust in a horizontal vacuum furnace, pump air for 3 minutes, then turn off the vacuum pump and allow it to naturally reach a vacuum level of 10. -3 Pa;

[0113] 2) Heat to 300℃ at a heating rate of 5℃ / min and hold for 1 hour;

[0114] 3) Continue heating to 600℃ and hold for 2 hours to break molecular bonds under high temperature and vacuum conditions, thereby removing the bound fluorine.

[0115] 4) Allow it to cool naturally to room temperature to obtain the desorbed dust.

[0116] Step 5) Product purification: The desorbed dust is purified to obtain high-purity silica product.

[0117] 1) The dust was heated to 1000℃ at a heating rate of 3℃ / min under inert gas protection;

[0118] 2) Keep warm for 3 hours to remove organic impurities;

[0119] 3) Allow it to cool naturally to room temperature to obtain a high-purity silica product.

[0120] The specific embodiments described herein are merely illustrative of the principles and effects of the invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this invention.

Claims

1. A method for preparing high-purity silica, characterized in that, The method includes the following steps: Step 1) Raw material pretreatment: The dust collected during the treatment of tail gas from monocrystalline silicon crystal pulling and argon recovery is preliminarily treated; Step 2) Controlled combustion oxidation treatment: The pretreated dust is subjected to low-oxygen concentration combustion oxidation in a closed rotary kiln; Step 3) Ammonia-oxalic acid complexation washing: The dust after oxidation treatment is washed with ammonia-oxalic acid complexation. Step 4) Vacuum thermal desorption treatment: The washed dust is subjected to vacuum thermal desorption treatment; Step 5) Product purification: The desorbed dust is purified to obtain high-purity silica product.

2. The method for preparing high-purity silicon dioxide according to claim 1, characterized in that, Step 1) specifically refers to: 1) Collect and screen the dust generated during the exhaust gas treatment and argon recovery process to remove agglomerated particles and impurities; 2) The sieved dust is dried under inert gas protection to remove moisture; 3) Perform particle size analysis and classification on the dried dust, and select particles with a particle size of 0.5-5μm.

3. The method for preparing high-purity silicon dioxide according to claim 1, characterized in that, Step 2) specifically refers to: 1) Place the sorted dust in a sealed rotary kiln, introduce argon and nitrogen, and adjust the oxygen concentration to control it at 3-5%; 2) Heat to 300-400℃ and maintain for 30 minutes to convert SiO into SiO2, with a conversion rate of over 99%; 3) Allow it to cool naturally to room temperature to obtain the oxidized dust.

4. The method for preparing high-purity silicon dioxide according to claim 1, characterized in that, Step 3) specifically refers to: 1) Prepare an ammonia-oxalic acid complex washing solution by mixing 5% NH4OH, 3% oxalic acid and 0.5% EDTA-2Na in a mass ratio of 5:3:0.5; 2) Add the oxidized dust to the washing liquid and stir at 80°C for 2 hours to remove fluorine, chlorine, calcium and potassium; 3) Collect the precipitate by filtration, and wash it with deionized water and ethanol 3-5 times in sequence to remove residual impurities.

5. The method for preparing high-purity silicon dioxide according to claim 1, characterized in that, Step 4) specifically refers to: 1) Place the washed dust in a horizontal vacuum furnace and evacuate to 10°C. -3 Pa; 2) Heat to 300℃ at a heating rate of 2-5℃ / min and hold for 1 hour; 3) Continue heating to 600℃ and hold for 2 hours to break molecular bonds under high temperature and vacuum conditions, thereby removing the bound fluorine. 4) Allow it to cool naturally to room temperature to obtain the desorbed dust.

6. The method for preparing high-purity silicon dioxide according to claim 1, characterized in that, Step 5) specifically involves: 1) Heating the dust to 800-1000℃ at a heating rate of 2-3℃ / min under inert gas protection; 2) Keep warm for 2-3 hours to remove organic impurities; 3) Allow it to cool naturally to room temperature to obtain a high-purity silica product.

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