Method for preparing high-purity silicon dioxide

Abstract

The invention relates to a method for preparing high-purity silicon dioxide. The method comprises the following steps: 1) raw material pretreatment: carrying out primary treatment on dust collected in monocrystalline silicon crystal pulling tail gas treatment and argon recovery processes; (2) controllable combustion oxidation treatment: carrying out low-oxygen-concentration combustion oxidation on the pretreated dust in a closed rotary kiln; (3) ammonia water-oxalic acid complexing washing: carrying out ammonia water-oxalic acid complexing washing on the oxidized dust; according to the method, operation is easy, technological parameters are easy to control, the method is suitable for industrial production, no organic solvent is needed, and 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 has strong corrosive property; 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 source and do not fundamentally solve 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, which is very suitable for use 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, the type and amount of the catalyst, and the PH value of the reaction system in the preparation step of the high-purity silicon sol 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: Step 1) Raw material pretreatment: collecting and preliminarily treating the dust collected in the single crystal silicon pulling tail gas treatment and argon recovery process; Step 2) Controllable combustion oxidation treatment: performing low-oxygen-concentration combustion oxidation of the pretreated dust in a closed rotary kiln; Step 3) Ammonia-oxalic acid complexation washing: washing the dust after oxidation treatment with ammonia-oxalic acid complexation; Step 4) Vacuum thermal desorption treatment: performing vacuum thermal desorption treatment on the washed dust; Step 5) Product purification: purifying the desorbed dust to obtain high-purity silicon dioxide product.

[0010] As a preferred embodiment, the step 1) is specifically: 1) Collecting and sieving the dust generated in the single crystal silicon pulling tail gas treatment and argon recovery process, and removing agglomerated particles and impurities; 2) Drying the sieved dust under inert gas protection to remove moisture; 3) Performing particle size analysis and classification on the dried dust, and selecting particles with a particle size of 0.5-5 μm.

[0011] As a preferred embodiment, the step 2) is specifically: 1) Placing the classified dust in a closed rotary kiln, introducing argon and nitrogen, and adjusting the oxygen concentration to 3-5%; 2) heating to 300-400℃, maintaining for 30 min, converting SiO into SiO2, conversion rate reaching more than 99%; 3) naturally cooling to room temperature to obtain the dust after oxidation treatment.

[0012] As preferred, the step 3) is specifically: 1) preparing an ammonia water-oxalic acid complex washing solution, preparing a mixed solution of 5% NH4OH, 3% oxalic acid and 0.5% EDTA-2Na at a mass ratio of 5:3:0.5; 2) adding the dust after oxidation treatment into the washing solution, stirring at 80℃ for 2h to remove impurities such as fluorine, chlorine, calcium and potassium; 3) collecting the precipitate by suction filtration, and washing with deionized water and ethanol for 3-5 times in sequence to remove residual impurities.

[0013] As preferred, the step 4) is specifically: 1) placing the dust after washing into a horizontal vacuum furnace, vacuumizing to 10 -3 Pa; 2) heating to 300℃ at a heating rate of 2-5℃ / min, maintaining for 1h; 3) continuously heating to 600℃, maintaining for 2h, removing combined fluorine by molecular bond energy breaking in a high-temperature vacuum environment; 4) naturally cooling to room temperature to obtain the dust after desorption.

[0014] As preferred, the step 5) is specifically: 1) heating the dust to 800-1000℃ at a heating rate of 2-3℃ / min under inert gas protection; 2) maintaining for 2-3h to remove organic impurities; 3) naturally cooling to room temperature to obtain the high-purity silicon dioxide product.

[0015] The beneficial effects of the present application are as follows: 1. The method for preparing high-purity silicon dioxide designed in the present application effectively solves the problems of shortage and quality of natural quartz mine by using a controllable combustion oxidation treatment device to perform low-oxygen concentration combustion oxidation in a closed rotary kiln, and overcomes the influence of fluid inclusions and mineral inclusions in the traditional purification process, realizing the preparation of high-purity silicon dioxide; 2. The present application uses the dust generated in the single crystal silicon pulling tail gas treatment and argon recovery process as raw material, realizes the effective resource utilization of the dust through a multi-step treatment process, avoids the resource waste caused by industrial waste treatment, and reduces environmental problems and safety hazards such as dust pollution; 3. The present invention uses an ammonia-oxalic acid complex washing method to deeply remove fluorine, chlorine, calcium, and potassium. Through the synergistic complex system, it achieves efficient removal of multiple impurities and effectively improves the purity of the product; 4. This invention uses vacuum thermal desorption to remove bound fluorine. By breaking molecular bonds in a high-temperature vacuum environment, it achieves efficient fluorine removal and ensures the purity of the final product. 5. The preparation method of the present invention is simple to operate, the process parameters are easy to control, and it is suitable for industrial production. It does not require the use of organic solvents, thus avoiding the environmental pollution caused by traditional liquid phase methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the overall flow chart of the present invention. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to more clearly understand the objectives, technical solutions and advantages of the present invention, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0018] In the description of the present invention, it should be understood that the orientations or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “inside”, “outside”, “horizontal” and “vertical” are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or component referred to must have a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0019] The present invention will be described in detail below with reference to the accompanying drawings: Figure 1 As shown, a method for preparing high-purity silicon dioxide comprises the following steps: Step 1) Raw material pretreatment: preliminary treatment of dust collected during the single crystal silicon pulling tail gas treatment and argon recovery process; Step 2) Controlled combustion and oxidation treatment: The pretreated dust is subjected to low-oxygen concentration combustion and oxidation in a closed rotary kiln; Step 3) Ammonia-oxalic acid complex washing: The dust after oxidation treatment is subjected to ammonia-oxalic acid complex washing; Step 4) Vacuum thermal desorption treatment: vacuum thermal desorption treatment is performed on the washed dust; Step 5) Product purification: The desorbed dust is purified to obtain a high-purity silica product.

[0020] Wherein, the step 1) is specifically as follows: 1) Collect and screen the dust generated during the single crystal silicon pulling tail gas treatment and argon recovery process to remove agglomerated particles and impurities; 2) Dry the screened dust under inert gas protection to remove moisture; 3) The dried dust is subjected to particle size analysis and classification, and particles with a particle size of 0.5-5 μm are selected.

[0021] The step 2) is specifically as follows: 1) The classified dust is placed in a closed rotary kiln, argon and nitrogen are introduced, and the oxygen concentration is adjusted to 3-5%; 2) The temperature is raised to 300-400℃ and maintained for 30 min, so that SiO is converted into SiO2, and the conversion rate is more than 99%; 3) After natural cooling to room temperature, the dust after oxidation treatment is obtained.

[0022] The step 3) is specifically as follows: 1) An ammonia water-oxalic acid complex washing solution is prepared, and a mixed solution of 5% NH4OH, 3% oxalic acid and 0.5% EDTA-2Na is prepared according to a mass ratio of 5:3:0.5; 2) The dust after oxidation treatment is added to the washing solution, stirred at 80℃ for 2 h, and impurities such as fluorine, chlorine, calcium and potassium are removed; 3) The precipitate is collected by suction filtration, and then washed with deionized water and ethanol for 3-5 times in sequence to remove residual impurities.

[0023] The step 4) is specifically as follows: 1) The dust after washing is placed in a horizontal vacuum furnace, and vacuum is extracted to 10 -3 Pa; 2) The temperature is raised to 300℃ at a temperature raising rate of 2-5℃ / min, and the temperature is maintained for 1 h; 3) The temperature is continuously raised to 600℃, and the temperature is maintained for 2 h, so that the combined state fluorine is removed by molecular bond energy breaking in a high-temperature vacuum environment; 4) After natural cooling to room temperature, the dust after desorption is obtained.

[0024] The step 5) is specifically as follows: 1) The dust is heated to 800-1000℃ at a temperature raising rate of 2-3℃ / min under the protection of inert gas; 2) The temperature is maintained for 2-3 h to remove organic impurities; 3) After natural cooling to room temperature, the high-purity silicon dioxide product is obtained.

[0025] The core features of the application are as follows: The low oxygen concentration (3-5%) rotary kiln inhibits the intense heat release of combustion, and prevents dust splashing; Combustion volatilization (about 30%) → ammoniation conversion (60%) → vacuum bond breaking (10%); The EDTA-oxalic acid complex system targets the removal of K / Ca.

[0026] Example 1: A method for preparing high-purity silicon dioxide, comprising the following steps: Step 1) Raw material pretreatment: preliminary treatment of dust collected during the single crystal silicon pulling tail gas treatment and argon recovery process; 1) Collect the dust generated during the single crystal silicon pulling tail gas treatment and argon recovery process and sieve it with a 200-mesh standard sieve to remove agglomerated particles and impurities; 2) Dry the sieved dust at 120°C for 4 hours under inert gas protection to remove moisture; 3) The dried dust is analyzed by a laser particle size analyzer, and particles with a size of 0.5-5 μm are selected.

[0027] Step 2) Controlled combustion and oxidation treatment: The pretreated dust is subjected to low-oxygen concentration combustion and oxidation in a closed rotary kiln; 1) Place the classified dust in a closed rotary kiln, introduce argon and nitrogen, and adjust the oxygen concentration to 3-5%, with the argon flow rate of 2L / min and the nitrogen flow rate of 8L / min; 2) Raise the temperature to 300°C and maintain for 30 minutes to convert SiO into SiO2 with a conversion rate of 99.5%; 3) Cool naturally to room temperature to obtain oxidized dust.

[0028] Step 3) Ammonia-oxalic acid complex washing: The dust after oxidation treatment is subjected to ammonia-oxalic acid complex washing; 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 an ammonia-oxalic acid complex detergent; 2) Add the oxidized dust to the scrubbing liquid and stir at 80°C for 2 hours at a stirring speed of 200 rpm to remove impurities such as fluorine, chlorine, calcium and potassium; 3) Use a vacuum filtration device to collect the precipitate, and wash it with deionized water and anhydrous ethanol three times, each washing time for 5 minutes, to remove residual impurities.

[0029] Step 4) Vacuum thermal desorption treatment: vacuum thermal desorption treatment is performed on the washed dust; 1) Place the washed dust in a horizontal vacuum furnace, pump the vacuum pump for 2 minutes, then turn off the vacuum pump and naturally evacuate to 10 -3 Pa; 2) Heating to 300°C at a rate of 2°C / min and holding for 1 hour; 3) Continue to heat up to 600℃ and keep it for 2 hours to break the molecular bonds under high temperature and vacuum environment to remove the bound fluorine; 4) Naturally cool to room temperature to obtain the desorbed dust.

[0030] Step 5) Product purification: purify the desorbed dust to obtain high-purity silicon dioxide product.

[0031] 1) Heat the dust to 800℃ at a heating rate of 2℃ / min under inert gas protection; 2) Keep warm for 2h to remove organic impurities; 3) Naturally cool to room temperature to obtain high-purity silicon dioxide product.

[0032] Example Two: A method for preparing high-purity silicon dioxide, comprising the following steps: Step 1) Raw material pretreatment: preliminarily treat the dust collected in the single crystal silicon pulling tail gas treatment and argon recovery process; 1) Collect the dust generated in the single crystal silicon pulling tail gas treatment and argon recovery process and sieve it using a 180-mesh standard sieve to remove agglomerated particles and impurities; 2) Dry the sieved dust at a temperature of 150℃ for 5h under inert gas protection to remove moisture; 3) Perform particle size analysis on the dried dust using a laser particle size analyzer and select particles with a particle size of 0.5-5μm.

[0033] Step 2) Controllable combustion oxidation treatment: perform low-oxygen-concentration combustion oxidation on the pretreated dust in a closed rotary kiln; 1) Place the classified dust in a closed rotary kiln, introduce argon and nitrogen, and adjust the oxygen concentration to 3-5%, wherein the argon flow rate is 1.5L / min and the nitrogen flow rate is 9L / min; 2) Heat to 400℃ and maintain for 30min to convert SiO into SiO2, with a conversion rate of 99.8%; 3) Naturally cool to room temperature to obtain the oxidized dust.

[0034] Step 3) Ammonia-oxalic acid complex washing: perform ammonia-oxalic acid complex washing on the oxidized dust; 1) Weigh 5% NH4OH, 3% oxalic acid and 0.5% EDTA-2Na according to the mass ratio of 5:3:0.5, add deionized water, and stir uniformly to prepare an ammonia-oxalic acid complex washing solution; 2) Add the oxidized dust to the washing solution, stir at 80℃ for 2h at a stirring speed of 250rpm to remove impurities such as fluorine, chlorine, calcium and potassium; 3) Use a vacuum filtration device to collect the precipitate and wash it with deionized water and anhydrous ethanol for 5 times in sequence, with each washing time being 6min to remove residual impurities.

[0035] Step 4) Vacuum thermal desorption treatment: the washed dust is subjected to vacuum thermal desorption treatment; 1) The washed dust is placed in a horizontal vacuum furnace, and after 3 minutes of pumping by a vacuum pump, the vacuum pump is closed and naturally vacuumed to 10 -3 Pa; 2) The temperature is raised to 300℃ at a rate of 5℃ / min, and the temperature is kept for 1h; 3) The temperature is continuously raised to 600℃, and the temperature is kept for 2h, and the combined state fluorine is removed by breaking the molecular bond energy in the high-temperature vacuum environment; 4) The temperature is naturally cooled to room temperature, and the desorbed dust is obtained.

[0036] Step 5) Product purification: the desorbed dust is subjected to purification treatment, and high-purity silicon dioxide product is obtained.

[0037] 1) The dust is heated to 1000℃ at a rate of 3℃ / min under the protection of inert gas; 2) The temperature is kept for 3h, and the organic impurities are removed; 3) The temperature is naturally cooled to room temperature, and high-purity silicon dioxide product is obtained.

[0038] The specific embodiments described herein are merely illustrative of the principles of the present application and its efficacy, and are not intended to limit the present application. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

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

2. The method for preparing high-purity silicon dioxide according to claim 1, wherein The step 1) is specifically as follows: 1) Collect and screen the dust generated during tail gas treatment and argon recovery to remove agglomerated particles and impurities; 2) Dry the screened dust under inert gas protection to remove moisture; 3) Analyze and classify the dried dust to select particles with a size of 0.5-5μm.

3. The method for preparing high-purity silicon dioxide according to claim 1, wherein The step 2) is specifically as follows: 1) Place the classified dust in a closed rotary kiln, introduce argon and nitrogen, and adjust the oxygen concentration to 3-5%; 2) Raise the temperature to 300-400℃ and maintain for 30 minutes to convert SiO into SiO2 with a conversion rate of over 99%; 3) Allow to cool naturally to room temperature to obtain oxidized dust.

4. The method for preparing high-purity silicon dioxide according to claim 1, wherein The step 3) is specifically as follows: 1) Prepare ammonia-oxalic acid complex cleaning solution by preparing a mixed solution of 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 scrubbing 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, wherein The step 4) is specifically as follows: 1) Place the washed dust in a horizontal vacuum furnace and evacuate to 10 -3 Pa; 2) Heat to 300°C at a rate of 2-5°C / min and keep warm for 1 hour; 3) Continue to heat up to 600℃ and keep it for 2 hours to break the molecular bonds under high temperature and vacuum environment to remove the bound fluorine; 4) Allow to cool naturally to room temperature to obtain the desorbed dust.

6. The method for preparing high-purity silicon dioxide according to claim 1, wherein The step 5) is specifically as follows: 1) Heat 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 to cool naturally to room temperature to obtain high-purity silica product.

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