CN108793176B - Method for preparing ultrapure quartz sand by taking silicon tetrafluoride as raw material - Google Patents
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- CN108793176B CN108793176B CN201810819016.3A CN201810819016A CN108793176B CN 108793176 B CN108793176 B CN 108793176B CN 201810819016 A CN201810819016 A CN 201810819016A CN 108793176 B CN108793176 B CN 108793176B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
- C01B33/181—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process
- C01B33/183—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process by oxidation or hydrolysis in the vapour phase of silicon compounds such as halides, trichlorosilane, monosilane
- C01B33/184—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by a dry process by oxidation or hydrolysis in the vapour phase of silicon compounds such as halides, trichlorosilane, monosilane by hydrolysis of tetrafluoride
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
The invention provides a method for preparing ultrapure quartz sand by taking silicon tetrafluoride as a raw material, which comprises the following steps: adding mineralizer and ultrapure water into a reaction kettle, introducing silicon tetrafluoride gas, and heating for reaction; adding quartz crystal nucleus into the reaction kettle, and then gradually reducing the temperature and pressure in the reaction kettle, wherein the quartz crystal nucleus grows into quartz crystal; when the granularity of the quartz crystal is more than 48 mu m, the pressure and the temperature of the reaction kettle are reduced, and the materials are discharged; solid-liquid separating the material; and drying the solid, namely the ultra-pure quartz sand. The product prepared by the method has high quality, and the high-purity quartz sand can reach 6N level.
Description
Technical Field
The invention relates to the field of preparation of ultrapure quartz sand, in particular to a method for preparing ultrapure quartz sand by taking silicon tetrafluoride as a raw material.
Background
Quartz sand is one of the most common and widely used nonmetallic mineral raw materials in nature. The quartz products are widely applied to the high and new technical fields of electronic industry, semiconductors, solar energy, laser, aerospace and the like by unique high temperature thermal stability (such as direct water cooling at 1200 ℃, quartz glass not bursting), excellent optical performance and super strong mechanical and chemical properties. Along with the increasing application of high-quality quartz in the high-tech field, the demand for high-purity quartz sand is increased, and the quality requirement for quartz sand products is increased; a remarkable characteristic of the high-purity quartz sand product is that SiO2 in the product is more than or equal to 99.99% -99.9999%, and the content of iron and aluminum is limited in a very low range. Quartz sand for quartz crucible for single crystal silicon rod pulling requires even less than 6ppm of all impurities. The quartz sand cannot be produced in China, and is imported from abroad, and the price per ton is as high as 8 ten thousand yuan per RMB.
The production technology and equipment of the high-purity quartz sand are constantly researched and developed all over the world so as to meet the requirements of the development of the high-purity quartz sand in the high-tech field of the country. There are also many scientific research institutions and manufacturing companies in China for developing high-purity quartz sand products, and some patent publications are disclosed.
The patent CN 103101919A discloses a method for preparing ultrafine crystalline silica by utilizing quartz tailings, wherein the ultrafine crystalline silica is obtained by wet grinding and acid washing of the quartz tailings; after complex process operation, obtaining silica with an average particle size of 200+ -30 nm; but the silica content of the final product can only be increased by an order of magnitude compared to the starting material (e.g. from SiO 2. Gtoreq.99% to SiO 2. Gtoreq.99.9%).
According to the method for preparing high-purity quartz sand by using the patent CN 101948235A, through the working procedures of manually sorting, roughing, calcining, water quenching, crushing, carefully selecting and pickling, separating, drying, magnetic separation, screening and the like, impurities in quartz ore are removed, so that the SiO2 of part of the product is more than or equal to 99.99%, the SiO2 of part of the product is more than or equal to 99.95%, and the SiO2 of the other part of the product is more than or equal to 99.90%. The method has complex process and difficult waste acid treatment, and the silicon dioxide content in the product still cannot meet the quality requirement of the monocrystalline silicon crucible.
The patent CN1225513C adopts the method for preparing the superfine high-purity quartz material by adopting the vein quartz, adopts domestic high-quality vein quartz (SiO 2 is more than or equal to 99 percent) as a raw material, and ensures that the SiO2 content reaches 99.99 to 99.999 percent and the impurity content is less than 100ppm through the procedures of coarse crushing, impurity removal by an electrostatic separation method, superfine crushing, impurity removal by a high-gradient magnetic separation method, microwave treatment, impurity removal by a complexation method, post treatment and the like. The patent has complex process and high manufacturing cost, the impurity content in the product can only reach less than 100ppm, and compared with the quartz sand for the polysilicon crucible, which requires the impurity content to be less than 6ppm, the patent has larger gap.
The method for preparing spherical nano single crystal quartz particles by using patent CN 102618926B adopts nano silicon dioxide colloid as a raw material, and comprises the steps of hydrothermal reaction, centrifugal sedimentation, water washing, drying and the like under the conditions of mixing and stirring to obtain monodisperse spherical nano single crystal quartz particles; the spherical nano quartz particles can be used for surface polishing treatment of ultra-large scale integrated circuit packaging materials, semiconductor industry, precise valves, hard magnetic disks and magnetic heads. Because the silica colloid is amorphous silica, the amorphous silica is used for preparing spherical nano monocrystalline quartz particles under the process conditions of reaction temperature of 150-230 ℃ and pressure of 5-20 atm, so that the amorphous silica is used for surface polishing treatment of ultra-large scale integrated circuit packaging materials and semiconductor industry, precise valves, hard magnetic discs, magnetic heads and the like. The key point of the technology is that the prepared quartz is in nano scale, and not quartz sand.
The patent CN100335683C hydrothermal method for producing large-size artificial optical quartz crystal adopts hydrothermal temperature difference method to grow crystal in high pressure kettle. The patent has high operating pressure (the pressure P=145-150 MPa), strict temperature difference control (the temperature difference delta T=30-50 ℃), and direct influence on crystal quality by seed crystal orientation (the seed crystal orientation is that a Y axis is taken as a length direction, an X axis is taken as a width direction, and a Z axis is taken as a length direction); the growth rate is slow, but large-size quartz crystals (size z=240-250 mm, x=140-150 mm, y=290 mm, weight=20-25 Kg) can be grown. The crystal is colorless and transparent, and has no cracks, bubbles, bicrystals and smooth growth hillocks; the product percent of pass is high, so that the production cost is high, and the application range of the product is 'large-size optical retarder and other optical crystal fields requiring large size'; the technical key point is to prepare large-size crystal. Obviously, such quartz crystals cannot be used for manufacturing high purity quartz crucibles.
The mineral separation, purification and deep processing development of the quartz sand in China are relatively late, and the domestic high-quality quartz sand resources are relatively less, so that the prior art cannot produce a high-purity quartz sand product with the impurity content of less than 6ppm. How to develop a technology for producing high-purity quartz sand products with low cost, which meets the requirements of high-technical fields in China on the high-purity quartz sand, and has important significance for promoting the economic development of Chinese people.
Disclosure of Invention
The invention provides a method for preparing ultrapure quartz sand by taking silicon tetrafluoride as a raw material, which solves the problem of high impurity content of the quartz sand prepared in the prior art.
The technical scheme of the invention is realized as follows:
a method for preparing ultrapure quartz sand by taking silicon tetrafluoride as a raw material comprises the following steps:
adding mineralizer and ultrapure water into a reaction kettle, introducing the silicon tetrafluoride gas, and heating for reaction;
adding quartz crystal nucleus into the reaction kettle, and then gradually reducing the temperature and pressure in the reaction kettle, wherein the quartz crystal nucleus grows into quartz crystal; when the granularity of the quartz crystal is more than 48 mu m, the pressure and the temperature of the reaction kettle are reduced, and the materials are discharged;
solid-liquid separating the material; and drying the solid, namely the ultra-pure quartz sand.
As a preferable technical scheme, the process conditions of the heating step are as follows: the temperature is 250-330 ℃ and the pressure is 25-90MPa.
As the preferable technical proposal, the pressure of the reaction kettle is set to be normal pressure to 20MPa and the temperature to be normal temperature to 200 ℃ before the materials are discharged.
As a preferable technical scheme, when the granularity of the quartz crystal is more than 48 mu m or/and less than 500 mu m, the pressure and the temperature of the reaction kettle are reduced, and materials are discharged.
As a preferable technical scheme, the mineralizer is one of fluosilicic acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid. More preferably, the mineralizer is a mixture of several of fluosilicic acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, and the like.
As a preferred embodiment, the quartz crystal nucleus is SiO 2 More than or equal to 99.99 percent and the granularity is less than 25 mu m. The quartz crystal nucleus is obtained by directly crushing high-purity quartz sand.
As a preferred technical scheme, the quartz crystal nucleus is mixed with ultrapure water to form a suspension state, and the suspension state is pressed into the reaction kettle by pressure.
As a preferable technical scheme, the material after the solid-liquid separation is washed by ultra-pure dilute hydrochloric acid or/and ultra-pure water.
As a preferable technical scheme, the reaction kettle consists of 2-6 reactors in series connection: the 1 st reaction kettle is used as a silicon dioxide dissolution kettle; the plurality of reaction kettles at the back are used as quartz crystallization kettles, and the temperature and pressure level differences are formed among the quartz crystallization kettles in sequence; the material flows from the first autoclave to the subsequent autoclaves in sequence.
As a preferable technical scheme, the content of the ultrapure quartz sand is SiO 2 More than or equal to 99.999 percent; even the content of the ultra-pure quartz sand is SiO 2 ≥99.9999％。
As a preferable technical scheme, the silicon tetrafluoride gas is prepared by the following method: the common quartz sand reacts with hydrofluoric acid, and fluosilicic acid solution is purified after the reaction is completed; and mixing the fluosilicic acid solution with concentrated sulfuric acid to generate silicon tetrafluoride gas and hydrogen fluoride gas, and condensing and separating to obtain the silicon tetrafluoride gas and hydrogen fluoride liquid.
As a preferable technical scheme, the concentrated sulfuric acid is sulfuric acid with mass fraction more than 75%.
The pressure in the reaction kettle is generated by heating water, mineralizer or high-pressure gas connected with the reaction kettle.
Advantageous effects
1. The product quality is high; the high-purity quartz sand can reach 6N grade.
2. The investment is saved, the process is simple, and the production cost is low.
3. Develop a new market application for amorphous silicon dioxide.
4. Provides technical support for manufacturing the ultra-pure quartz sand in large scale and low cost.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
A method for preparing ultrapure quartz sand by taking silicon tetrafluoride as a raw material comprises the following steps:
step S1: preparation of silicon tetrafluoride gas
Adding 600kg of 50% hydrofluoric acid and 155kg of common quartz sand into a fluosilicic acid reaction kettle, and purifying fluosilicic acid after the reaction is completed; the reaction process is normal pressure, and the reaction temperature is kept to be not more than 50 ℃. Introducing pure fluosilicic acid into a silicon tetrafluoride reaction kettle, and adding 170kg of 98% concentrated sulfuric acid under the stirring condition; the reaction process is also normal pressure to 0.4MPa, and the reaction temperature is kept at not more than 190 ℃. The generated silicon tetrafluoride gas and hydrogen fluoride gas are separated by a condenser to obtain silicon tetrafluoride gas and hydrogen fluoride liquid. The hydrofluoric acid with 55% mixed with water is reused for reaction with common quartz sand.
Step S2: adding mineralizer and 2500kg of ultrapure water into the first autoclave, heating to ensure that the temperature in the first autoclave is 250 ℃, keeping the pressure in the autoclave at 30MPa, and introducing the silicon tetrafluoride gas obtained in the step S1; in this example, 110kg of 98% sulfuric acid and 90kg of 35% fluosilicic acid were used as the mineralizer.
Step S3: the materials in the step S2 are introduced into a second autoclave, and SiO is added at the same time 2 Quartz crystal nucleus with granularity less than 25 microns and greater than or equal to 99.99%, and the quartz crystal nucleus is fully mixed with ultrapure water before being added into the reaction kettle to form suspension state and pressed into the reaction kettle by pressure. Then slowly reducing the temperature and pressure in the kettle, keeping the temperature at 220 ℃ and the pressure at 25MPa. The quartz crystal nucleus grows up gradually into quartz sand.
Step S4: after 4 hours, sampling and detecting that the granularity of quartz crystals in the second autoclave is larger than 48 mu m; the temperature in the second autoclave was gradually lowered to 200℃and the pressure was reduced to 20MPa. Discharging the material in the second autoclave. Maintaining the temperature and pressure in the second autoclave at appropriate values can save energy and time for re-feeding.
Step S4: after solid-liquid separation, the solid was washed with a high-purity hydrochloric acid diluted solution (10% content) and washed with pure water 3 times. And drying the solid, namely the ultra-pure quartz sand.
Example 2
A method for preparing ultrapure quartz sand by taking silicon tetrafluoride as a raw material comprises the following steps:
step S1: preparation of silicon tetrafluoride gas
Adding 1200kg of 50% hydrofluoric acid and 310kg of common quartz sand into a fluosilicic acid reaction kettle, and purifying fluosilicic acid after the reaction is completed; the reaction process is normal pressure, and the reaction temperature is kept to be not more than 50 ℃. Introducing pure fluosilicic acid into a silicon tetrafluoride reaction kettle, and adding 340kg of 98% concentrated sulfuric acid under the stirring condition; the reaction process is also normal pressure to 0.4MPa, and the reaction temperature is kept at not more than 190 ℃. The generated silicon tetrafluoride gas and hydrogen fluoride gas are separated by a condenser to obtain silicon tetrafluoride gas and hydrogen fluoride liquid. The hydrofluoric acid with 55% mixed with water is reused for reaction with common quartz sand.
Step S2: adding mineralizer and 3000kg of ultrapure water into the first autoclave, heating to ensure that the temperature in the first autoclave is 330 ℃, keeping the pressure in the autoclave at 35MPa, and introducing the silicon tetrafluoride gas obtained in the step S1; the mineralizer in the embodiment adopts 200kg of sulfuric acid with the mass fraction of 98%.
Step S3: and (2) feeding the materials in the step (S2) into a second autoclave, and simultaneously adding a suspension of quartz crystal nuclei, wherein the temperature of the second autoclave is kept at 315 ℃ and the pressure is kept at 33MPa. The material was left for 40 minutes.
Step S4: and (3) feeding the materials in the step (S3) into a third high-pressure resistant autoclave, wherein the temperature of the third high-pressure resistant autoclave is kept at 280 ℃ and the pressure is kept at 31MPa. The material was left for 40 minutes.
Step S5: and (3) feeding the materials in the step (S4) into a fourth autoclave, and keeping the temperature of the fourth autoclave at 250 ℃ and the pressure at 29MPa. The material was left for 40 minutes.
Step S6: and (5) feeding the materials in the step (S5) into a fifth autoclave, and keeping the temperature of the fifth autoclave at 250 ℃ and the pressure at 25MPa.
Step S7: and sampling and analyzing the granularity of quartz crystals from the fifth high-pressure resistant autoclave, and gradually reducing the temperature in the fifth high-pressure resistant autoclave to 200 ℃ and the pressure to 20MPa when the granularity of quartz crystals is more than 48 mu m. Discharging the materials in the fifth autoclave.
Step S8: after solid-liquid separation, cleaning the solid with pure water; and drying the solid, namely the ultra-pure quartz sand.
Example 3
A method for preparing ultrapure quartz sand by taking silicon tetrafluoride as a raw material comprises the following steps:
step S1: preparation of silicon tetrafluoride gas
Adding 960kg of 50% hydrofluoric acid and 248kg of common quartz sand into a fluosilicic acid reaction kettle, and purifying fluosilicic acid after the reaction is completed; the reaction process is normal pressure, and the reaction temperature is kept to be not more than 50 ℃. Introducing pure fluosilicic acid into a silicon tetrafluoride reaction kettle, and adding 272kg of concentrated sulfuric acid with the mass fraction of 98% under the stirring condition; the reaction process is also normal pressure to 0.4MPa, and the reaction temperature is kept at not more than 190 ℃. The generated silicon tetrafluoride gas and hydrogen fluoride gas are separated by a condenser to obtain silicon tetrafluoride gas and hydrogen fluoride liquid. The hydrofluoric acid with 55% mixed with water is reused for reaction with common quartz sand.
Step S2: adding mineralizer and 2500kg of ultrapure water into the autoclave, heating to ensure that the temperature in the first autoclave is 280 ℃, keeping the pressure in the autoclave to be 90MPa, and introducing the silicon tetrafluoride gas obtained in the step S1; the mineralizer in this example was selected from the group consisting of 110kg of 32% hydrochloric acid and 90kg of 50% phosphoric acid.
Step S3: adding quartz crystal nucleus which is SiO into the autoclave 2 Crystal material with granularity smaller than 25 μm and not less than 99.99%, which is obtained by directly crushing high-purity quartz sand; fully mixing with ultrapure water before adding into the reaction kettle to form a suspension state, and pressing into the reaction kettle by pressure. Then slowly reducing the temperature and pressure in the kettle, and gradually growing quartz crystal nucleus into quartz sand.
Step S4: and when the granularity of the quartz sand is larger than 200 mu m through sampling analysis, gradually reducing the pressure in the autoclave to normal pressure, reducing the temperature to room temperature, and discharging the material in the second autoclave.
Step S5: after solid-liquid separation, cleaning the solid with pure water; and drying the solid, namely the ultra-pure quartz sand.
Example product detection index values are shown in table 1.
As can be seen from Table 1, the purity of the high purity silica sand reached 99.9999% (grade 6N).
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (6)
1. The method for preparing the ultrapure quartz sand by taking silicon tetrafluoride as a raw material is characterized by comprising the following steps of:
adding mineralizer and ultrapure water into a reaction kettle, introducing silicon tetrafluoride gas, and heating for reaction; the mineralizer is one or a mixture of a plurality of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acetic acid; the heating process conditions are as follows: the temperature is 250-330 ℃ and the pressure is 25-90MPa;
mixing quartz crystal nucleus with ultrapure water to form a suspension state, pressing the suspension state into the reaction kettle through pressure, and then gradually reducing the temperature and the pressure in the reaction kettle, wherein the quartz crystal nucleus grows into quartz crystals; when the granularity of the quartz crystal is more than 48 mu m, the pressure and the temperature of the reaction kettle are reduced, and the materials are discharged; the quartz crystal nucleus is SiO 2 Crystal material with granularity less than 25 μm and more than or equal to 99.99%; the reaction kettle consists of 2-6 reactors in series: the 1 st reaction kettle is used as a silicon dioxide dissolution kettle; the plurality of reaction kettles at the back are used as quartz crystallization kettles, and the temperature and pressure level differences are formed among the quartz crystallization kettles in sequence; the materials flow from the first autoclave to the latter autoclaves in sequence;
solid-liquid separating the material; drying the solid, namely the ultra-pure quartz sand; the content of the ultrapure quartz sand is SiO 2 ≥99.999%。
2. The method for preparing ultrapure quartz sand by using silicon tetrafluoride as a raw material according to claim 1, wherein the pressure of the reaction kettle is set to be normal pressure to 20MPa and the temperature is set to be normal temperature to 200 ℃ before the material is discharged.
3. The method for preparing ultrapure quartz sand by using silicon tetrafluoride as a raw material according to claim 1, wherein the quartz crystal nucleus is obtained by directly crushing high-purity quartz sand.
4. The method for preparing ultrapure quartz sand by using silicon tetrafluoride as a raw material according to claim 1, wherein the material after solid-liquid separation is washed with ultrapure dilute hydrochloric acid or/and ultrapure water.
5. The method for preparing ultrapure quartz sand by using silicon tetrafluoride as a raw material according to claim 1, wherein the content of the ultrapure quartz sand is SiO 2 ≥99.9999%。
6. The method for preparing ultrapure quartz sand by using silicon tetrafluoride as a raw material according to claim 1, wherein the silicon tetrafluoride gas is prepared by the following method: the common quartz sand reacts with hydrofluoric acid, and fluosilicic acid solution is purified after the reaction is completed; and mixing the fluosilicic acid solution with concentrated sulfuric acid to generate silicon tetrafluoride gas and hydrogen fluoride gas, and condensing and separating to obtain the silicon tetrafluoride gas and hydrogen fluoride liquid.
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