Low-hydroxyl low-inclusion quartz sand and method for producing the same

Abstract

The application provides a low-hydroxyl low-inclusion quartz sand and a preparation method thereof. The preparation method comprises the following steps: 1) mixing silicate, deionized water and alcohol, and performing hydrolysis treatment to obtain a hydrolysis product; 2) adjusting the pH of the hydrolysis product to be greater than 7 to obtain a gel; and 3) heating the gel to a molten state and performing bubbling treatment using an inert gas to obtain the low-hydroxyl low-inclusion quartz sand. The preparation method provided by the application can obtain a quartz sand product with low hydroxyl content and low inclusion quantity, and has the characteristics of relatively simple synthesis process and low energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to a low-hydroxyl and low-inclusion quartz sand, in particular to a low-hydroxyl and low-inclusion quartz sand and a preparation method thereof, and belongs to the field of photovoltaics. BACKGROUND

[0002] The quartz sand is used for making quartz crucibles in the field of photovoltaics. The high hydroxyl content of the quartz sand can cause the crucible to soften and deform easily, and the high inclusion content of the quartz sand can cause the quality of the crystal to decrease. Therefore, the quartz crucible is made of low-hydroxyl and low-inclusion quartz sand.

[0003] At present, the methods for preparing low-hydroxyl and low-inclusion quartz sand are generally electric melting, gas refining, gas deposition and PCVD plasma gas deposition. Although the hydroxyl and inclusion contents of the quartz sand prepared by the above methods are low, the above methods have defects of complex synthesis process and high energy consumption.

[0004] Therefore, it has become the current research direction to develop a preparation method of low-hydroxyl and low-inclusion quartz sand with a relatively simple synthesis process and low energy consumption. SUMMARY

[0005] The present application provides a preparation method of low-hydroxyl and low-inclusion quartz sand, which has the characteristics of low hydroxyl and inclusion contents, a relatively simple synthesis process and low energy consumption.

[0006] The present application also provides a low-hydroxyl and low-inclusion quartz sand, which has the characteristics of low hydroxyl content and inclusion number.

[0007] The present application provides a preparation method of low-hydroxyl and low-inclusion quartz sand, which comprises the following steps:

[0008] 1) mixing silicate, deionized water and alcohol, and performing hydrolysis treatment to obtain a hydrolysis product;

[0009] 2) adjusting the pH of the hydrolysis product to be greater than 7 to obtain a gel;

[0010] 3) heating the gel to a molten state and performing bubble treatment using an inert gas to obtain low-hydroxyl and low-inclusion quartz sand.

[0011] The preparation method as described above, wherein in the bubble treatment, the bubble gas pressure P and the standard gas pressure P g meet 0.8P g ≤P≤1.2P g .

[0012] The standard gas pressure P gThe depth h0 of the molten glass body, the depth d0 of the air duct inserted into the glass body, and the distance L between the two air ducts satisfy the following relationship:

[0013] P g = 2.5 * d0 + 50 / R max ;

[0014] R max = max [0.5 * (h0 - d0), 0.5L];

[0015] Wherein:

[0016] P g : standard atmospheric pressure, kPa;

[0017] h0: depth of the molten gel, mm;

[0018] d0: depth of the air duct inserted into the molten gel, mm;

[0019] L: distance between the two air ducts, mm.

[0020] The preparation method as described above, wherein the bubble gas pressure P is equal to the standard atmospheric pressure P g .

[0021] The preparation method as described above, wherein in step 2), after adjusting the pH of the hydrolysis product to be greater than 7, the hydrolysis product is further subjected to an aging treatment.

[0022] The preparation method as described above, wherein in step 3), before heating the gel to a molten state, the gel is further subjected to a drying treatment.

[0023] The preparation method as described above, wherein in step 3), before heating the gel to a molten state, the gel is further subjected to a first calcination treatment.

[0024] The preparation method as described above, wherein the first calcination treatment comprises calcining in an oxygen-containing environment for 6-24h at a calcination temperature of 450-600℃.

[0025] The preparation method as described above, wherein in step 3), before heating the gel to a molten state, the gel is further subjected to a second calcination treatment.

[0026] The preparation method as described above, wherein the second calcination treatment comprises calcining in a vacuum for 6-24h at a calcination temperature of 900-1400℃

[0027] The present application also provides a low-hydroxyl and low-inclusion quartz sand prepared by any of the above methods, wherein the hydroxyl content of the low-hydroxyl and low-inclusion quartz sand is less than 15ppm, and the inclusion content is less than 10 per square centimeter.

[0028] The application provides a preparation method of low-hydroxyl and low-inclusion quartz sand. The inert gas is used for bubble treatment, so that the quartz sand with low hydroxyl and low inclusion can be prepared. Meanwhile, the method has the advantages of simple preparation process and low energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A schematic diagram of a bubble treatment device is shown in the figure;

[0030] Figures 2 to 5 A schematic diagram of a bubble elimination process in the bubble treatment is shown in the figure.

[0031] BRIEF DESCRIPTION OF DRAWINGS

[0032] 1-air bubble; 2-microbubble; 3-air guide pipe; 4-fused gel. DETAILED DESCRIPTION

[0033] In order for those skilled in the art to better understand the scheme of the application, the application is further described in detail below. The following specific embodiments are only used to describe the principles and characteristics of the application, and the examples are only used to explain the application, and do not limit the scope of the application. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0034] The application provides a preparation method of low-hydroxyl and low-inclusion quartz sand, which comprises the following steps:

[0035] 1) mixing silicate, deionized water and alcohol, and performing hydrolysis treatment to obtain a hydrolysis product;

[0036] 2) adjusting the pH of the hydrolysis product to be greater than 7 to obtain a gel;

[0037] 3) heating the gel to a fused state and performing bubble treatment using inert gas to obtain low-hydroxyl and low-inclusion quartz sand.

[0038] The preparation method provided by the application does not limit the selection of silicate. For example, the silicate can be at least one selected from the group consisting of ethyl silicate, propyl silicate, butyl silicate, amyl silicate, isopropyl silicate, isobutyl silicate, isoamyl silicate, dimethyl silicate, diethyl silicate and diisopropyl silicate. In an embodiment, the silicate is at least one selected from the group consisting of ethyl silicate, propyl silicate and butyl silicate.

[0039] In step 1), the hydrolysis treatment refers to the reaction of the silicate with deionized water to form hydrolysis products composed of silicic acid and alcohol. Since the silicate is insoluble in water, alcohol is added to increase the solubility of the silicate in water, thereby increasing the hydrolysis rate of the silicate. The preparation method provided by the present application does not limit the selection of alcohol, for example, the alcohol can be selected from at least one of methanol, ethanol, n-propanol, n-butanol, n-pentanol, isopropyl alcohol, isobutyl alcohol, isoamyl alcohol, and isopropyl alcohol. In an embodiment, the silicate is selected from at least one of methanol, ethanol, and n-propanol.

[0040] In step 2), when the pH of the hydrolysis product is adjusted to be greater than 7, a gel can be obtained, and the main component of the gel is a loose body of silica formed by dehydration condensation of silicic acid. The loose body of silica is a kind of silica species with a loose three-dimensional network structure formed by interconnected silicon-oxygen tetrahedron (SiO4) structures. The preparation method provided by the present application does not limit the selection of the basic substance used to adjust the pH of the hydrolysis product to pH>7, as long as it can achieve the effect of making the pH of the hydrolysis product pH>7. In an embodiment, the basic substance is selected from at least one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium carbonate aqueous solution, potassium carbonate aqueous solution, sodium bicarbonate aqueous solution, and barium hydroxide aqueous solution. In an embodiment, the basic substance is selected from at least one of ammonia, sodium carbonate aqueous solution, and sodium hydroxide aqueous solution.

[0041] The preparation method provided by the present application does not specifically limit the pH of the hydrolysis product, as long as it satisfies pH>7. In an embodiment, the pH of the hydrolysis product is 8-12, and preferably, the pH is 8.5-10.5.

[0042] In step 3), the present application does not specifically limit the heating temperature for heating the gel to a molten state, as long as the temperature can melt the gel into a molten state and is not higher than the melting point of the heating-easy and gas-conducting tube material. In a specific embodiment, the heating temperature is 1800°C.

[0043] When the gel is heated to a molten state, the loose body of silica is completely dehydrated to obtain a molten silica. Subsequently, the molten silica is subjected to bubbling treatment with an inert gas, that is, the inert gas is introduced into the molten silica to obtain a quartz sand product with low hydroxyl content and number of inclusions. The present application does not limit the specific device for performing the bubbling treatment, for example, the device shown in FIG. 1 can be used. Figure 1 Figure 1 In the device shown in FIG. 2, at least two gas-conducting tubes are inserted into the gel heated to a molten state to a certain depth, and the inert gas is introduced into the molten gel through the gas-conducting tubes. In the bubbling treatment, the depth of the molten gel is denoted as h0, the depth of the insertion of the gas-conducting tube into the molten gel is denoted as d0, and the distance between the two gas-conducting tube openings is denoted as L.

[0044] ​The inventors observed that during the heating and melting process, the hydroxyl groups and other impurities in the gel generate gas upon heating, producing microbubbles in the molten gel. These bubbles can only be eliminated from the molten gel by diffusing them to the liquid surface. However, since the rising speed of bubbles is directly proportional to the square of the bubble radius and inversely proportional to the liquid viscosity, and given the small radius of microbubbles and the high viscosity of the molten gel, the diffusion rate of these microbubbles to the liquid surface is very slow. Bubbles that fail to diffuse to the surface in time remain in the quartz sand product as inclusions.

[0045] When molten gel is bubbled using an inert gas, the resulting quartz sand product exhibits lower hydroxyl content and fewer inclusions. The inventors speculate that this may be due to factors such as... Figure 2 As shown, the air duct ( Figure 2 (Not shown in the image) Introducing air bubbles into the molten gel; these air bubbles are much larger than the microbubbles in the molten gel. As the bubbling process continues, inert gas is continuously introduced, such as... Figure 3 As shown, the bubble size gradually increases and detaches from the gas delivery tube (not shown in the figure), moving towards the liquid surface of the molten gel; when the boundary of the bubble comes into contact with the boundary of the microbubble, as... Figure 4 As shown, the superfilled air bubble and the microbubble merge, the gas in the microbubble enters the superfilled air bubble, the microbubble disappears, and thus the microbubble that was in contact with the superfilled air bubble is eliminated.

[0046] Because the air bubbles are relatively large, they rise quickly, and this rising speed gradually increases as they merge with the microbubbles during the ascent. Figure 5 As shown, when the air bubble rises to the surface of the molten gel, it bursts, releasing the internal gas to the outside of the molten gel. Similarly, through a period of bubbling treatment, the number of microbubbles within the molten gel can be significantly reduced, thus producing quartz sand products with lower inclusion content.

[0047] Meanwhile, because the hydroxyl groups in the molten gel are continuously converted into microbubbles during the heating process, the quartz sand product obtained by bubbling the molten gel with inert gas has a lower hydroxyl content in addition to a lower inclusion content.

[0048] The preparation method provided by this invention does not impose any restrictions on the selection of the inert gas, as long as it does not undergo a redox reaction with the impurities contained in the quartz sand. For example, the inert gas can be selected from at least one of argon, helium, neon, and nitrogen.

[0049] The preparation method provided by the present application does not limit the bubble gas pressure used in the bubble treatment, and can meet the requirements of forming aerated bubbles in the molten gel and breaking the aerated bubbles after floating to the liquid surface.

[0050] In an embodiment, the bubble treatment of the molten gel using inert gas is carried out in a vacuum environment. The bubble treatment in a vacuum can accelerate the breaking of the aerated bubbles and timely extract the gas released by the breaking of the aerated bubbles, so that the hydroxyl content and the number of inclusions of the quartz sand product are lower.

[0051] It can be understood that, in order to make the hydrolysis rate of silicate faster and thus make the preparation method provided by the present application have higher production efficiency, in an embodiment, after the silicate, deionized water and alcohol are mixed, an acidic catalyst is further added to the mixture, and heating and stirring are further carried out. The present application does not limit the type of acidic catalyst, the heating temperature and the stirring time, and can only meet the technical effect of accelerating the hydrolysis rate of silicate. In a specific embodiment, the acidic catalyst can be selected from at least one or a combination of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, citric acid, phosphoric acid, formic acid, hydrofluoric acid, etc., the heating temperature is 60-90℃, and the stirring time is 0.5-3h.

[0052] Further, in order to obtain a quartz sand product that is more convenient to use, in an embodiment, after the bubble treatment, the obtained low-hydroxyl and low-inclusion quartz sand is further cooled and crushed.

[0053] The preparation method of the low-hydroxyl and low-inclusion quartz sand provided by the present application uses silicate as a raw material, and carries out bubble treatment on the gel obtained by hydrolysis of the silicate after burning and melting, which effectively reduces the hydroxyl content and the number of inclusions in the finished quartz sand. Therefore, the quartz sand prepared by using the preparation method has the characteristics of low hydroxyl content and low inclusion number. At the same time, the preparation method uses bubble treatment to reduce the hydroxyl content and the number of inclusions in the quartz sand product, so the preparation method also has the characteristics of relatively simple synthesis process and low energy consumption compared with the prior art.

[0054] In a specific embodiment, the inventors found that when the bubble gas pressure P and the standard atmospheric pressure P g meet 0.8P g ≤P≤1.2P g , the quartz sand product with lower hydroxyl content and lower inclusion number can be obtained.

[0055] wherein the standard atmospheric pressure P g is calculated by using the following method:

[0056] 1) P g =2.5*d0+50 / R max ;

[0057] 2)R max = max [0.5*(h0-d0), 0.5L];

[0058] The meaning of R in formula 2) is that the larger value between 0.5*(h0-d0) and 0.5L is taken as R max .

[0059] The inventors speculate that the reason for this phenomenon is that, when the depth of the molten gel, the depth of the insertion of the air duct into the molten gel, and the distance between the two air ducts are constant, a proper bubbling gas pressure can generate gas-filled bubbles of a proper size in the molten gel. The gas-filled bubbles of this size not only float to the surface of the molten gel in a shorter time, but also absorb more micro-bubbles during the floating process. Therefore, when the bubbling gas pressure P is equal to the standard atmospheric pressure P g , the obtained quartz sand product has a lower content of hydroxyl groups and a lower number of inclusions. g When the bubbling gas pressure P satisfies 0.8P g ≤ P ≤ 1.2P , the obtained quartz sand product has a lower content of hydroxyl groups and a lower number of inclusions.

[0060] Further, when the bubbling gas pressure P is equal to the standard atmospheric pressure P g , the obtained quartz sand product has a lower content of hydroxyl groups and a lower number of inclusions.

[0061] In one embodiment, after adjusting the pH of the hydrolysis product to be greater than 7, the hydrolysis product is further subjected to an aging treatment. The aging treatment refers to keeping the hydrolysis product at a certain temperature for a period of time to obtain a gel. The inventors have found that the quartz sand product prepared from the gel obtained through the aging treatment has a lower content of hydroxyl groups and a lower number of inclusions, as well as a higher density. The inventors speculate that the reason for this is that the aging treatment not only promotes the removal of impurities such as hydroxyl groups from the hydrolysis product, but also makes the SiO2 loose bodies in the gel obtained through the aging treatment form a more compact structure, thereby making the quartz sand product have the above-mentioned characteristics.

[0062] The present application does not limit the treatment time of the aging treatment, but a too long treatment time will not only increase the manufacturing cost, but also reduce the production efficiency. Therefore, the relationship between the treatment time and the manufacturing cost needs to be balanced to determine the most appropriate treatment time. In one embodiment, the treatment time is 0.5-12h.

[0063] The present application also does not limit the treatment temperature of the aging treatment, and in one embodiment, the treatment temperature is 80℃.

[0064] Further, before heating the gel to a molten state, the gel is further subjected to a drying treatment. The drying treatment can remove water and organic matter and other impurities from the gel, so that there are fewer hydroxyl groups and other impurities generated due to the decomposition of water and organic matter in the subsequent heating and melting process, thereby obtaining quartz sand with a lower content of hydroxyl groups and a lower number of inclusions.

[0065] It can be understood that, in order to remove the impurities in the gel to the maximum extent, in an embodiment, the gel is washed with deionized water before the drying treatment.

[0066] The present application does not limit the treatment environment, treatment temperature and treatment time of the drying treatment, as long as the water and organic matter in the gel can be removed. In an embodiment, the gel is dried in air at a temperature of 100-180°C for not less than 6 hours. The drying treatment in air can oxidize the organic matter in the gel with oxygen in the air, so that a quartz sand product with lower hydroxyl content and inclusion number is obtained.

[0067] In an embodiment, before the gel is heated to a molten state, the gel is subjected to a first calcination treatment. The first calcination treatment can remove the residual organic matter and water in the gel, and also promote the lattice rearrangement of the quartz crystal, so that the original oxygen defects in the quartz crystal are moved, eliminated or combined, thereby preparing a quartz sand product with a more stable structure.

[0068] The present application does not limit the treatment environment, treatment temperature and treatment time of the first calcination treatment, as long as the water and organic matter in the gel can be removed. In an embodiment, the gel is calcined in air at a temperature of 240-800°C for not less than 6 hours. The drying treatment in air can oxidize the organic matter in the gel with oxygen in the air, so that a quartz sand product with lower hydroxyl content and inclusion number is obtained.

[0069] Further, when the first calcination treatment includes calcination in an oxygen-containing environment for 6-24h at a temperature of 450-600°C, the suitable calcination temperature and time can more completely remove the water and organic matter in the gel, so that the prepared quartz sand product has lower hydroxyl content and inclusion number.

[0070] When the preparation method includes both the drying treatment and the first calcination treatment, the present application does not limit the execution order of the two treatments. In an embodiment, the gel can be subjected to the drying treatment first, the product obtained by the drying treatment is subjected to the first calcination treatment, and then the product obtained by the first calcination treatment is heated to a molten state and subjected to the bubbling treatment, so that a quartz sand with low hydroxyl and low inclusion is finally obtained.

[0071] In another embodiment, before the gel is heated to a molten state, the gel is subjected to a second calcination treatment. The second calcination treatment can accelerate the volatilization and decomposition of the water and organic matter in the gel, and further improve the purity of the quartz sand product.

[0072] The present application does not limit the processing environment, processing temperature and processing time of the second calcination process, and can achieve the effect of removing water and organic matter in the gel. In one embodiment, the gel can be subjected to the second calcination process in a vacuum, the processing temperature is 800-1600°C, and the processing time is not less than 6 hours. Performing the second calcination process in a vacuum can accelerate the discharge of gaseous decomposition products from the gel, thereby obtaining a quartz sand product with lower hydroxyl content and inclusion number.

[0073] Further, when the second calcination process includes calcination in a vacuum for 6-24h at a calcination temperature of 900-1400°C, the prepared quartz sand product has a lower hydroxyl content and inclusion number.

[0074] When the preparation method simultaneously includes the drying process and the second calcination process, the present application does not limit the execution order of the two processes. In one embodiment, the gel is first subjected to the drying process, the product obtained by the drying process is subjected to the second calcination process, and then the product obtained by the second calcination process is heated to a molten state and subjected to the bubbling process, thereby obtaining a low-hydroxyl and low-inclusion quartz sand.

[0075] When the preparation method simultaneously includes the first calcination process and the second calcination process, the present application does not limit the execution order of the two processes. In one embodiment, the gel is first subjected to the first calcination process, the product obtained by the first calcination process is subjected to the second calcination process, and then the product obtained by the second calcination process is heated to a molten state and subjected to the bubbling process, thereby obtaining a low-hydroxyl and low-inclusion quartz sand.

[0076] When the preparation method simultaneously includes the drying process, the first calcination process and the second calcination process, the present application does not limit the execution order of the three processes. In one embodiment, the gel is first subjected to the drying process, the product obtained by the drying process is subjected to the first calcination process, the product obtained by the first calcination process is subjected to the second calcination process, and then the product obtained by the second calcination process is heated to a molten state and subjected to the bubbling process, thereby obtaining a low-hydroxyl and low-inclusion quartz sand.

[0077] The second aspect of the present application protects a low-hydroxyl and low-inclusion quartz sand obtained by any one of the above preparation methods. The low-hydroxyl and low-inclusion quartz sand has a hydroxyl content of less than 15ppm and an inclusion content of less than 10 per square centimeter.

[0078] The preparation method of the low-hydroxyl and low-inclusion quartz sand provided by the present application will be described in detail below in conjunction with specific embodiments.

[0079] Example 1

[0080] The present application provides a low-inclusion quartz sand preparation method, which includes the following steps:

[0081] 1) Mix 30 kg of tetraethyl orthosilicate, 60 kg of deionized water, and 30 kg of ethanol, add 5 kg of 1 mol / L hydrochloric acid as an acidic catalyst, heat to 60°C and stir for 1.5 hours to completely hydrolyze the tetraethyl orthosilicate to obtain a hydrolysis product.

[0082] 2) Add ammonia water to the hydrolysis product at a rate of 150 g / min until the pH is 9.5, and place it in a constant temperature environment at 80°C for 4 hours to obtain a gel.

[0083] 3) Wash the gel with deionized water, separate and dry treat at a temperature of 120°C for 8 hours to obtain a dry product.

[0084] 4) Perform a first calcination treatment on the dry product in air at a temperature of 550°C for 8 hours to obtain a first calcination product.

[0085] 5) Perform a second calcination treatment on the first calcination product in a vacuum at a temperature of 1300°C for 10 hours to obtain a second calcination product.

[0086] 6) Heat the second calcination product to 1800°C to melt it, pour it into a heated molybdenum container, insert a gas guide tube and introduce argon gas for bubbling treatment. The liquid surface depth is h0=110 mm, the gas guide tube insertion depth is d0=60 mm, the two adjacent gas guide tube axes converge at L=70 mm, and the bubbling pressure is P=151.4 kPa. After 1 hour of treatment, the gas guide tube is removed and the molten material is cooled. In this example, P g =151.4 kPa, P=P g .

[0087] 7) Take out the cooled material, crush it with a hammer and separate the quartz sand with a particle size of 100-200 mesh through a screening device.

[0088] Quartz sand sample A1 is prepared.

[0089] Example 2

[0090] This example is basically the same as Example 1, except that methyl orthosilicate is used instead of tetraethyl orthosilicate, and methanol is used instead of ethanol. Quartz sand sample A2 is prepared.

[0091] Example 3

[0092] This example is basically the same as Example 1, except that in step 2), the pH is adjusted to 10.5. Quartz sand sample A3 is prepared.

[0093] Example 4

[0094] This example is basically the same as Example 1, except that in step 4), the first roasting treatment temperature is 600°C. Quartz sand sample A4 is produced.

[0095] Example 5

[0096] This example is basically the same as Example 1, except that in step 5), the second roasting treatment temperature is 1400°C. Quartz sand sample A5 is produced.

[0097] Example 6

[0098] This example is basically the same as Example 1, except that in step 6), the heating temperature is 2000°C, and after melting, the molten material is poured into a molybdenum container heated and kept warm. Quartz sand sample A6 is produced.

[0099] Example 7

[0100] This example is basically the same as Example 1, except that in step 1), hydrochloric acid is not added. Quartz sand sample A7 is produced.

[0101] Example 8

[0102] This example is basically the same as Example 1, except that in step 4), the first roasting treatment is performed in a nitrogen atmosphere. Quartz sand sample A8 is produced.

[0103] Example 9

[0104] This example is basically the same as Example 1, except that in step 5), the second roasting treatment is performed in a nitrogen atmosphere. Quartz sand sample A9 is produced.

[0105] Example 10

[0106] This example is basically the same as Example 1, except that the gas guide tube insertion depth is d0=80mm, the two adjacent gas guide tube axes converge at L=60mm, and the bubbling pressure is P=201.7kPa. In this example, P g =201.7kPa, P=P g . Quartz sand sample A10 is produced.

[0107] Example 11

[0108] This example is basically the same as Example 1, except that the gas guide tube insertion depth is d0=40mm, the two adjacent gas guide tube axes converge at L=80mm, and the bubbling pressure is P=101.3kPa. In this example, P g =101.3kPa, P=P g . Quartz sand sample A11 is produced.

[0109] Example 12

[0110] This example is basically identical with Example 1, except that the liquid surface depth is h0= 150 mm, the gas duct insertion depth is d0= 90 mm, the two adjacent gas duct axes converge at L = 50 mm, and the bubbling pressure is P = 226.7 kPa. In this example, P g = 226.7 kPa, P = P g . Quartz sand sample A12 was produced.

[0111] Example 13

[0112] This example is basically identical with Example 1, except that the liquid surface depth is h0= 80 mm, the gas duct insertion depth is d0= 50 mm, the two adjacent gas duct axes converge at L = 80 mm, and the bubbling pressure is P = 126.3 kPa. In this example, P g = 126.3 kPa, P = P g . Quartz sand sample A13 was produced.

[0113] Example 14

[0114] This example is basically identical with Example 10, except that the bubbling pressure is P = 400 kPa. In this example, P g = 201.7 kPa, P does not satisfy the relationship 0.8P g ≤ P ≤ 1.2P g . Quartz sand sample A14 was produced.

[0115] Example 15

[0116] This example is basically identical with Example 11, except that the bubbling pressure is P = 200 kPa. In this example, P g = 101.3 kPa, P does not satisfy the relationship 0.8P g ≤ P ≤ 1.2P g . Quartz sand sample A15 was produced.

[0117] Example 16

[0118] This example is basically identical with Example 12, except that the bubbling pressure is P = 100 kPa. In this example, P g = 226.7 kPa, P does not satisfy the relationship 0.8P g ≤ P ≤ 1.2P g . Quartz sand sample A16 was produced.

[0119] Example 17

[0120] This example is basically identical with Example 13, except that the bubbling pressure is P = 300 kPa. In this example, P g= 126.3 kPa, P does not satisfy 0.8P g ≤ P ≤ 1.2P g Relationship. Quartz sand sample A17 was prepared.

[0121] Example 18

[0122] The present application provides a method for preparing low-inclusion quartz sand, comprising the following steps:

[0123] 1) Mix 30 kg of tetraethyl orthosilicate, 60 kg of deionized water, and 30 kg of ethanol, add 5 kg of 1 mol / L hydrochloric acid as an acidic catalyst, heat to 60°C and stir for 1.5 hours to completely hydrolyze the tetraethyl orthosilicate, and obtain a hydrolysis product.

[0124] 2) Add ammonia water to the hydrolysis product at a rate of 150 g / min until the pH value is 9.5 to obtain a gel.

[0125] 3) Heat the gel to 1800°C to melt it, pour it into a heated and insulated molybdenum container, insert a gas guide tube and introduce argon gas for bubbling treatment. The liquid level depth is h0=110 mm, the gas guide tube insertion depth is d0=60 mm, the two adjacent gas guide tube axes converge at L=70 mm, and the bubbling pressure is P=300 kPa. After 1 hour of treatment, the gas guide tube is removed and the molten material is cooled. In this example, P g = 151.4 kPa, P does not satisfy 0.8P g ≤ P ≤ 1.2P g Relationship.

[0126] 4) Take out the cooled material, crush it with a hammer, and separate the quartz sand with a particle size of 100-200 mesh through a screening device.

[0127] Quartz sand sample A18 was prepared.

[0128] Example 19

[0129] This example is basically the same as Example 18, except that the bubbling pressure is P=180 kPa. In this example, P g = 151.4 kPa, P satisfies 0.8P g ≤ P ≤ 1.2P g Relationship. Quartz sand sample A19 was prepared.

[0130] Example 20

[0131] This example is basically the same as Example 19, except that the bubbling pressure is P=151.4 kPa. In this example, P g = 151.4 kPa, P=P g . Quartz sand sample A20 was prepared.

[0132] Example 21

[0133] The present application provides a method for preparing low-inclusion quartz sand, comprising the following steps:

[0134] 1) Mix 30 kg of tetraethyl orthosilicate, 60 kg of deionized water and 30 kg of ethanol, add 5 kg of 1 mol / L hydrochloric acid as an acidic catalyst, heat to 60°C and stir for 1.5 hours to completely hydrolyze the tetraethyl orthosilicate, and obtain a hydrolysis product.

[0135] 2) Add ammonia water to the hydrolysis product at a rate of 150 g / min until the pH value is 9.5, and place it in a constant temperature environment at 80°C for 4 hours to obtain a gel.

[0136] 3) Heat the gel to 1800°C to melt it, pour it into a heated molybdenum container, insert a gas guide pipe and introduce argon gas for bubbling treatment. The liquid surface depth is h0=110 mm, the gas guide pipe insertion depth is d0=60 mm, the two adjacent gas guide pipe axes converge at L=70 mm, and the bubbling pressure is P=151.4 kPa. After 1 hour of treatment, the gas guide pipe is removed, and the molten material is cooled. In this example, P g =151.4 kPa, P=P g .

[0137] 4) Take out the cooled material, crush it with a hammer and separate the quartz sand with a particle size of 100-200 mesh through a screening device.

[0138] Quartz sand sample A21 is prepared.

[0139] Example 22

[0140] The present application provides a method for preparing low-inclusion quartz sand, comprising the following steps:

[0141] 1) Mix 30 kg of tetraethyl orthosilicate, 60 kg of deionized water and 30 kg of ethanol, add 5 kg of 1 mol / L hydrochloric acid as an acidic catalyst, heat to 60°C and stir for 1.5 hours to completely hydrolyze the tetraethyl orthosilicate, and obtain a hydrolysis product.

[0142] 2) Add ammonia water to the hydrolysis product at a rate of 150 g / min until the pH value is 9.5, and place it in a constant temperature environment at 80°C for 4 hours to obtain a gel.

[0143] 3) Wash the gel with deionized water, dry the separated product at a temperature of 120°C for 8 hours to obtain a dry product.

[0144] 4) The dry product is heated to 1800℃ to melt it, poured into a molybdenum container heated and maintained at temperature, the gas sparge pipes are inserted and argon is introduced to perform the sparging process. The liquid level depth is h0=110mm, the sparge pipe insertion depth is d0=60mm, the two adjacent sparge pipe axes converge at L=70mm, and the sparging pressure is P=151.4kPa. In this example, P g =151.4kPa, P=P g . After 1 hour of treatment, the sparge pipes are removed and the molten material is cooled.

[0145] 5) The cooled material is removed, broken with a hammer and separated by sieving equipment to isolate the quartz sand having a particle size between 100-200 mesh.

[0146] The quartz sand sample A22 is obtained.

[0147] Example 23

[0148] The present application provides a method for preparing low-inclusion quartz sand, comprising the following steps:

[0149] 1) 30kg of tetraethyl orthosilicate, 60kg of deionized water and 30kg of ethanol are mixed, 5kg of 1mol / L hydrochloric acid is added as an acidic catalyst, heated to 60℃ and stirred for 1.5 hours to completely hydrolyze the tetraethyl orthosilicate, and a hydrolysis product is obtained.

[0150] 2) Ammonia is added to the hydrolysis product at a rate of 150g / min until the pH value is 9.5, and the gel is placed in a constant temperature environment at 80℃ for 4 hours to obtain a gel.

[0151] 3) The gel is washed with deionized water, separated and dried to obtain a dry product.

[0152] 4) The dry product is subjected to a first calcination treatment in air at a temperature of 800℃ for 8 hours to obtain a first calcination product.

[0153] 5) The first calcination product is heated to 1800℃ to melt it, poured into a molybdenum container heated and maintained at temperature, the gas sparge pipes are inserted and argon is introduced to perform the sparging process. The liquid level depth is h0=110mm, the sparge pipe insertion depth is d0=60mm, the two adjacent sparge pipe axes converge at L=70mm, and the sparging pressure is P=151.4kPa. In this example, P g =151.4kPa, P=P g . After 1 hour of treatment, the sparge pipes are removed and the molten material is cooled.

[0154] 6) The cooled material is removed, broken with a hammer and separated by sieving equipment to isolate the quartz sand having a particle size between 100-200 mesh.

[0155] A quartz sand sample A23 was prepared.

[0156] Example 24

[0157] This example is basically the same as Example 23, except that in step 4), the treatment temperature of the first calcination treatment is 550°C.

[0158] A quartz sand sample A24 was prepared.

[0159] Example 25

[0160] This example is basically the same as Example 1, except that in step 5), the treatment temperature of the second calcination treatment is 700°C.

[0161] A quartz sand sample A25 was prepared.

[0162] Comparative Example 1

[0163] This comparative example is basically the same as Example 1, except that in step 2), no ammonia water is added. A quartz sand product B1 was prepared.

[0164] Comparative Example 2

[0165] This comparative example is basically the same as Example 1, except that in step 2), the pH value is 7. A quartz sand product B2 was prepared.

[0166] Comparative Example 3

[0167] This comparative example is basically the same as Example 1, except that step 6) is not performed. A quartz sand product B3 was obtained.

[0168] Comparative Example 4

[0169] This comparative example is basically the same as Example 1, except that in step 6), air is used for the bubbling treatment. A quartz sand product B4 was obtained.

[0170] Test Example

[0171] 1. The hydroxyl content of the sample was measured using the following method:

[0172] 1) Accurately weigh 0.02 g of the sample and 0.8 g of KBr, and grind in a marquis mortar for at least 5 min, with no obvious grain feeling after grinding;

[0173] 2) Accurately weigh 0.2 g from the ground and diluted sample, and as evenly as possible, spread on a tablet press mold, with a pressure of 3.0 MPa, wait for 60 seconds after reaching 3.0 MPa, and then release the pressure;

[0174] 3) First, the background value of the instrument is obtained by analyzing the empty sample, then the sample is put into the infrared spectrometer for testing, repeated three times, and the average value of the two parallel results is selected and recorded in Table 1.

[0175] 2) The number of inclusions in the sample is measured using the following method:

[0176] 1) Take 10g of prepared quartz sand powder, put it into a straight barrel molybdenum crucible, compact it, and then put it into a vacuum graphite furnace, and treat it at 1850℃ for 2h under vacuum environment;

[0177] 2) Take out the melted quartz sheet, go through slicing-coarse grinding-fine grinding-polishing-epoxy, grind the other side of the sheet after epoxy according to the above grinding and polishing process, polish it to a thickness of 0.3mm-0.5mm, place the prepared sheet under a microscope at a magnification of 400-500, and observe it. The area in the field of view can be determined by the scale sample, and the number of inclusions per square centimeter is calculated and recorded in Table 1.

[0178] Table 1. Sample inclusion number and hydroxyl content record table

[0179]

[0180]

[0181] From Table 1, we can see that:

[0182] 1) Compared with quartz sand samples B1 and B2 obtained by not adjusting the pH value of the hydrolysis product to be greater than 7 during preparation, the hydroxyl content and inclusion number of quartz sand samples A1-A25 obtained by adjusting the pH value of the hydrolysis product to be greater than 7 during preparation are significantly reduced.

[0183] 2) Compared with quartz sand sample B3 obtained by not using inert gas for bubbling treatment during preparation, and quartz sand sample B4 obtained by using air for bubbling treatment, the hydroxyl content and inclusion number of quartz sand samples A1-A25 obtained by using inert gas for bubbling treatment during preparation are lower.

[0184] 3) Compared with quartz sand sample A8 obtained by first roasting in nitrogen, and quartz sand sample A9 obtained by second roasting in nitrogen, the hydroxyl content and inclusion number of quartz sand samples A1-A7, A10-A13 obtained by first roasting in air and second roasting in vacuum environment are lower.

[0185] 4) The hydroxyl content and inclusion number of quartz sand samples A1-A7, A10-A13, which are obtained by performing the first roasting treatment in air and the second roasting treatment in a vacuum environment at 900-1400℃, are lower than those of quartz sand sample A8, which is obtained by performing the first roasting treatment in nitrogen, quartz sand sample A9, which is obtained by performing the second roasting treatment in nitrogen, and quartz sand sample A25, which is obtained by performing the second roasting treatment at 700℃.

[0186] 5) The hydroxyl content and inclusion number of quartz sand samples A14-A17, which are obtained by performing the preparation process in which the bubbling gas pressure P satisfies the relationship 0.8P g g ≤P≤1.2P g , are lower than those of quartz sand samples A1-A7, A10-A13, which are obtained by performing the preparation process in which the bubbling gas pressure P satisfies the relationship 0.8P g g ≤P≤1.2P g .

[0187] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein; and such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.​​

Claims

1. A method for producing low-hydroxy, low-inclusion quartz sand, characterized by, The method comprises the following steps: 1) mixing silicate, deionized water and alcohol, and performing hydrolysis treatment to obtain a hydrolysis product; 2) adjusting the pH of the hydrolysis product to be greater than 7 to obtain a gel; 3) heating the gel to a molten state and performing bubbling treatment using inert gas to obtain low-hydroxyl and low-inclusion quartz sand; The bubbling treatment using inert gas comprises introducing gas bubbles into the molten gel using a gas guide tube, and the size of the gas bubbles is greater than that of the micro-bubbles in the molten gel; In the bubbling process, the bubbling pressure P is different from the standard pressure P. g Satisfying 0.8P g ≤P≤1.2P g ; The standard atmospheric pressure P g The depth h0 of the molten gel, the depth d0 of the insertion of the air duct into the molten gel, and the distance L between the two air duct openings satisfy the following relationship: P g = 2.5 * d0 + 50 / R max ; R max =max[0.5*(h0-d0),0.5L] wherein: P g : Standard atmospheric pressure, kPa; h0: the depth of the molten gel, mm; d0: the depth of the gas guide tube inserted into the molten gel, mm; L: the distance between the two gas guide tube openings, mm.

2. The production method according to claim 1, characterized by, The bubble gas pressure P is equal to the standard pressure P g .

3. The preparation method according to claim 1, characterized in that, In step 2), after adjusting the pH of the hydrolysis product to be greater than 7, the method further comprises aging treatment of the hydrolysis product.

4. The production method according to any one of claims 1 to 3, characterized by, In step 3), before heating the gel to a molten state, the method further comprises drying treatment of the gel.

5. The production method according to any one of claims 1 to 3, characterized by, In step 3), before heating the gel to a molten state, the method further comprises first calcination treatment of the gel to obtain a first calcination product.

6. The production method according to claim 5, wherein The first calcination treatment comprises calcining in an oxygen-containing environment for 6-24 h, and the calcination temperature is 450-600℃.

7. The preparation method according to claim 5, characterized in that, The method further comprises second calcination treatment of the gel to obtain a second calcination product.

8. The preparation method according to claim 7, characterized in that, The second calcination treatment comprises calcining in a vacuum for 6-24 h, and the calcination temperature is 900-1400℃.

9. A low-hydroxy, low-inclusion quartz sand, characterized in that, The low-hydroxyl and low-inclusion quartz sand prepared by the method of any one of claims 1-8 has a hydroxyl content of less than 15 ppm and an inclusion content of less than 10 per square centimeter.

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