System and method for preparing quartz sand

Abstract

A method for preparing silica sand includes the following steps: reacting a silicon tetrahalide with an alcohol reagent to generate a first reaction mixture; separating the first reaction mixture to obtain a haloalkoxysilane, a first recovered alcohol, and a first hydrogen halide; adding the haloalkoxysilane to an aqueous solution containing a hydrogen halide reagent to generate a second reaction mixture; separating the second reaction mixture to obtain a silica sol, a second recovered alcohol, and a second hydrogen halide; washing and drying the silica sol to obtain a silica sand precursor; and subjecting the silica sand precursor to sintering decarburization and dehydroxylation treatment to obtain the silica sand; wherein the method further includes a recovery step: combining the first recovered alcohol and the second recovered alcohol to obtain the alcohol reagent, and combining the first hydrogen halide and the second hydrogen halide to obtain the hydrogen halide reagent. Additionally, this application also provides a system for preparing silica sand.

Description

Technical Field

[0001] This application relates to the field of inorganic non-metallic material preparation technology, specifically to a system and method for preparing quartz sand. Background Technology

[0002] Quartz materials are widely used in integrated circuits, semiconductors, aerospace, lasers and other fields due to their advantages such as spectral characteristics, high temperature resistance, chemical stability and electrical insulation. As an important raw material for quartz materials, the purity requirements of quartz sand are constantly increasing with the development of fine manufacturing.

[0003] Existing quartz sand is mostly purified from natural quartz minerals through multiple processes such as rough selection, crushing, sintering, pulverizing, impurity removal, and flotation. The process is complex and causes heavy environmental pollution. Moreover, it is difficult to meet the demand for higher purity due to the limitations of ore quality and process.

[0004] Regarding synthetic routes, existing technologies are usually based on raw materials such as silicon halides or organosilanes: direct hydrolysis of silicon halides is a violent reaction and byproducts inhibit particle growth, which can easily lead to small particles; organosilane routes are mild but slow and often require cosolvents / catalysts, making the process cumbersome. Summary of the Invention

[0005] In view of this, this application provides a system and method for preparing quartz sand to reduce pollution and improve preparation efficiency, while taking into account both reaction rate and process controllability.

[0006] In a first aspect, this application provides a method for preparing quartz sand, comprising the following steps: reacting a silicon tetrahalide with an alcohol reagent to generate a first reaction mixture; separating the first reaction mixture to obtain a haloalkoxysilane, a first recovered alcohol, and a first hydrogen halide; adding the haloalkoxysilane to an aqueous solution containing a hydrogen halide reagent to generate a second reaction mixture; separating the second reaction mixture to obtain a silica sol, a second recovered alcohol, and a second hydrogen halide; washing and drying the silica sol to obtain a quartz sand precursor; subjecting the quartz sand precursor to sintering decarburization and dehydroxylation treatment to obtain the quartz sand; wherein the method further comprises a recovery step: merging the first recovered alcohol and the second recovered alcohol to obtain the alcohol reagent, and merging the first hydrogen halide and the second hydrogen halide to obtain the hydrogen halide reagent.

[0007] Based on the first aspect, in some possible implementations, the alcohol reagent includes at least one of methanol, ethanol, propanol, and butanol, the silicon tetrahalide includes at least one of silicon tetrachloride, silicon tetrabromide, and silicon tetraiodide, and the purity of the silicon tetrahalide is not less than 99.9999%.

[0008] Based on the first aspect, in some possible implementations, in the step of generating the first reaction mixture, the reaction temperature is 0 to 50°C, and the molar ratio of the tetrahalide to the alcohol reagent is 1:(0.5 to 10).

[0009] Based on the first aspect, some possible implementations also include the step of: adjusting the molar ratio of the tetrahalide to the alcohol reagent so that the number of halogen substitutions in the haloalkoxysilane is 0 to 3.

[0010] Based on the first aspect, in some possible implementations, the step of separating the first reaction mixture includes distillation separation, wherein the distillation conditions are: the first hydrogen halide separation temperature is 5-35°C, the first recovered alcohol separation temperature is 60-100°C, and the haloalkoxysilane separation temperature is 105-170°C.

[0011] Based on the first aspect, in some possible implementations, the aqueous solution of the hydrogen halide reagent has a pH of 0 to 4, and the aqueous solution is prepared using water with a resistivity ≥18.2 MΩ·cm.

[0012] Based on the first aspect, in some possible implementations, in the step of generating the second reaction mixture, the reaction temperature is 20–100°C, and the molar ratio of water to haloalkoxysilane in the aqueous solution is 1:(4–50).

[0013] Based on the first aspect, in some possible implementations, the separation step of the second reaction mixture includes heating and evaporation, wherein the heating and evaporation conditions are: heating temperature of 50 to 100°C, pH rising to 3 to 7 during the separation process, and gelation occurring to obtain a silica sol in the form of silica gel.

[0014] Based on the first aspect, in some possible implementations, the silica sol is cleaned until the conductivity is ≤1μS / cm.

[0015] Based on the first aspect, in some possible implementations, the temperature for drying the silica sol is 80–300°C, and the drying time is 15–20 h.

[0016] Based on the first aspect, in some possible implementations, the particle size distribution of the quartz sand precursor is 500 nm to 5 mm, obtained by crushing and sieving.

[0017] Based on the first aspect, in some possible implementations, the sintering decarburization treatment is carried out in an oxygen-containing environment at a temperature of 400–600°C, with an oxygen content of 5%–100% and a treatment time of 10–80 h; the dehydroxylation treatment is carried out in an air, vacuum, or other gas environment at a temperature of 900–1300°C and a treatment time of 20–100 h.

[0018] Secondly, this application provides a system for preparing quartz sand, comprising a first reaction unit, a first separation unit, a second reaction unit, a second separation unit, a sand making unit, an alcohol circulation loop, and a hydrogen halide circulation loop. The first reaction unit includes a first reactor, which has a tetrahalide inlet, an alcohol inlet, and a first outlet. The first separation unit includes a first distillation column, whose first inlet is connected to the first outlet of the first reactor, and which has a haloalkoxysilane outlet, a first recovered alcohol outlet, and a first hydrogen halide outlet. The second reaction unit includes a second reactor, which has a haloalkoxysilane inlet, a hydrogen halide aqueous solution inlet, and a second outlet, wherein the haloalkoxysilane inlet is connected to the haloalkoxysilane outlet of the first distillation column.

[0019] The second separation unit includes an evaporator separator and a second distillation column. The evaporator separator has a feed inlet, a silica sol outlet, and a steam outlet. The second feed inlet of the evaporator separator is connected to the second outlet of the second reactor. The steam outlet of the evaporator separator is connected to the third feed inlet of the second distillation column. The second distillation column has a second recovered alcohol outlet and a second hydrogen halide outlet. The sand making unit includes a washing device, a drying device, a crushing and screening device, a medium-temperature sintering furnace, and a high-temperature sintering furnace. The feed end of the washing device is connected to the silica sol outlet of the evaporator separator, and the washing device, drying device, crushing and screening device, medium-temperature sintering furnace, and high-temperature sintering furnace are sequentially connected along the material flow direction. The alcohol circulation loop includes a recovered alcohol collection pipe, an alcohol recovery tank, and an alcohol circulation pipeline. The recovered alcohol collection pipe is connected to the first recovered alcohol outlet of the first distillation column and the second recovered alcohol outlet of the second distillation column, respectively. The recovered alcohol collection pipe is connected to the alcohol recovery tank, and the alcohol recovery tank is connected to the alcohol inlet of the first reactor via the alcohol circulation pipeline. The hydrogen halide circulation loop includes a hydrogen halide collection pipe, a hydrogen halide absorption device, and an acid delivery pipeline. The hydrogen halide collection pipe is connected to the first hydrogen halide outlet of the first distillation column and the second hydrogen halide outlet of the second distillation column, respectively. The hydrogen halide collection pipe is connected to the hydrogen halide gas inlet of the hydrogen halide absorption device. The hydrogen halide absorption device has a water inlet and a hydrogen halide aqueous solution outlet. The hydrogen halide aqueous solution outlet is connected to the hydrogen halide aqueous solution inlet of the second reactor via the acid delivery pipeline.

[0020] Based on the second aspect, in some possible implementations, the first reactor is a closed reactor, equipped with a stirring assembly and a cooling jacket, the cooling jacket being connected to a temperature control device, and the tetrahalide inlet and alcohol inlet of the first reactor being connected to a metering pump and / or a mass flow controller, respectively.

[0021] Based on the second aspect, in some possible implementations, the first distillation column and / or the second distillation column both include a column body, a reboiler, a top condenser, and a reflux line, and the first hydrogen halide outlet of the first distillation column is located at the top gas phase outlet, the first recovered alcohol outlet is located at the top condensate outlet and / or the side stream distillate outlet, and the haloalkoxysilane outlet is located at the bottom outlet.

[0022] Based on the second aspect, in some possible implementations, the hydrogen halide absorption device includes an absorption tower and an acid storage tank. The absorption tower is provided with a packing section and a demisting section, and the outlet of the hydrogen halide aqueous solution is connected to the acid storage tank. The acid storage tank is connected to the second inlet of the second reactor via an acid delivery pipeline.

[0023] Based on the second aspect, in some possible implementations, the evaporator includes a heating assembly, a gas-liquid separation chamber, and an exhaust pipe, the exhaust pipe being connected to the feed inlet of the second distillation column, and the evaporator is further provided with a vacuum interface and connected to a vacuum unit.

[0024] Based on the second aspect, in some possible implementations, the cleaning device includes a cleaning tank, an ultrapure water supply pipeline, and a conductivity detector, wherein the conductivity detector is disposed on the liquid outlet pipeline of the cleaning tank; the drying device is a drying furnace; and the crushing and screening device includes a crusher and a non-metallic vibrating screen, wherein the screen material of the non-metallic vibrating screen is nylon.

[0025] Based on the second aspect, in some possible implementations, the medium-temperature sintering furnace is equipped with an oxygen supply interface, a tail gas emission port and an atmosphere control component, the high-temperature sintering furnace is equipped with a vacuum interface and connected to a vacuum unit, and both the medium-temperature sintering furnace and the high-temperature sintering furnace are equipped with a temperature control device and a furnace temperature detection component.

[0026] In this application, silicon tetrahalide is first reacted with an alcohol reagent to generate a first reaction mixture, which is then separated to obtain a haloalkoxysilane. This transforms the silicon source from silicon tetrahalide into an intermediate more suitable for subsequent reactions in an aqueous system, thereby improving the problem of process control difficulties caused by the direct entry of silicon tetrahalide into the aqueous phase. Subsequently, the haloalkoxysilane is added to an aqueous solution containing a hydrogen halide reagent to form a second reaction mixture, which is then separated to obtain a silica sol. This allows the silicon source to form a sol morphology under aqueous conditions, providing a uniform precursor system for subsequent sand formation. Furthermore, by washing and drying the silica sol, a quartz sand precursor is obtained, which removes residual components that can be carried out with the washing process from the sol system and forms a solid precursor suitable for sintering. The quartz sand precursor is then subjected to sintering decarburization and dehydroxylation treatment, which effectively reduces the carbon-related and hydroxyl-related components in the final quartz sand, thereby improving the quality stability and application adaptability of the quartz sand product.

[0027] Furthermore, this application obtains a first recovered alcohol, a second recovered alcohol, a first hydrogen halide, and a second hydrogen halide in two separate separation processes. Through a recycling step, the recovered alcohols are combined as alcohol reagents, and the recovered hydrogen halides are combined as hydrogen halide reagents, achieving the recycling of both alcohol and hydrogen halide reagents. Therefore, this method, while producing quartz sand, reduces the repeated consumption of external reagents, decreases the amount of separation byproducts flowing into the discharge system, thereby reducing overall resource consumption and environmental burden, and improving the continuous operation capability and economic efficiency of the process. Attached Figure Description

[0028] Figure 1 A flowchart illustrating a method for preparing quartz sand according to an embodiment of this application.

[0029] Figure 2 This is a schematic diagram of a system for preparing quartz sand according to an embodiment of this application.

[0030] Explanation of main component symbols

[0031] 10: First reaction unit; 11: First reactor; 111: Silicon tetrahalide inlet; 112: Alcohol inlet; 113: First outlet;

[0032] 20: First separation unit; 21: First distillation column; 211: First feed inlet; 212: Halogenated alkoxysilane outlet; 213: First recovered alcohol outlet; 214: First hydrogen halide outlet;

[0033] 30: Second reaction unit; 31: Second reactor; 311: Haloalkoxysilane inlet; 312: Hydrogen halide aqueous solution inlet; 313: Second discharge port;

[0034] 40: Second separation unit; 41: Evaporator separator; 411: Second feed inlet; 412: Silica sol outlet; 413: Steam outlet; 42: Second distillation column; 421: Third feed inlet; 422: Second recovered alcohol outlet; 423: Second hydrogen halide outlet;

[0035] 50: Sand making unit; 51: Washing device; 52: Drying device; 53: Crushing and screening device; 54: Medium-temperature sintering furnace; 55: High-temperature sintering furnace;

[0036] 60: Alcohol circulation loop; 61: Alcohol recovery collection pipe; 62: Alcohol recovery tank; 63: Alcohol circulation pipeline;

[0037] 70: Hydrogen halide circulation loop; 71: Hydrogen halide collecting pipe; 72: Hydrogen halide absorption device; 73: Acid delivery pipeline;

[0038] 100: A system for preparing quartz sand. Detailed Implementation

[0039] The embodiments of this application are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application; it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; where there is no conflict, the implementation methods and features of the implementation methods of this application can be combined with each other; many specific details are set forth in the following description to provide a full understanding of this application, and the described implementation methods are only a part of the implementation methods of this application, and not all of the implementation methods.

[0040] In related technologies, existing synthesis methods for improving the purity of quartz sand typically involve direct hydrolysis of silicon halides. However, the reaction is vigorous, and byproducts such as hydrogen halides inhibit particle growth, resulting in small and unevenly pure quartz sand particles. Furthermore, while existing purification methods such as acid washing and flotation can obtain high-purity quartz sand from natural ores, these processes are complex, polluting, and the purity is difficult to achieve above 99.9999%. Therefore, this application improves the quartz sand preparation process by introducing the recycling of alcohol and hydrogen halide reagents in addition to alcoholysis and hydrolysis, and optimizing the parameters of each step to improve the purity, particle uniformity, and yield of quartz sand, while simultaneously achieving environmentally friendly production.

[0041] Please see Figure 1 Based on this, one embodiment of this application provides a method for preparing quartz sand, the method comprising:

[0042] Step 1 (S1): Reaction of tetrasilane with an alcohol reagent produces the first reaction mixture. This step generates a haloalkoxysilane intermediate via alcoholysis, avoiding the violent reaction of direct hydrolysis and improving process controllability.

[0043] In this embodiment, the silicon tetrahalide can be at least one of silicon tetrachloride, silicon tetrabromide, or silicon tetraiodide, and its purity is not less than 99.9999%. The alcohol reagent can be at least one of methanol, ethanol, propanol, or butanol. The molar ratio of silicon tetrahalide to alcohol reagent is 1:(0.5-10), for example, it can be 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:6, 1:8, 1:10, or any value within the range of any two of the above values; by adjusting the molar ratio, the degree of substitution in the alcoholysis reaction can be controlled, thereby controlling the number of halogen substitutions in the obtained haloalkoxysilane to be 0-3 (e.g., 0, 1, 2, or 3).

[0044] Taking the reaction of silicon tetrahalide with ethanol as an example, when the molar ratio of silicon tetrahalide to ethanol is 1:4, all four halogen atoms are replaced by ethoxy groups in ethanol, yielding unreacted tetraethoxysilanes; when the molar ratio is 1:3, three halogen atoms are replaced by ethoxy groups, yielding monohalotriethoxysilanes; when the molar ratio is 1:2, two halogen atoms are replaced by ethoxy groups, yielding dihalodiethoxysilanes; and when the molar ratio is 1:1, one halogen atom is replaced by an ethoxy group, yielding trihalomonoethoxysilanes. When the molar ratio is between these typical ratios, the resulting product is usually a mixture of compounds with adjacent degrees of substitution. When the ethanol ratio is greater than 1:4, the main product is still tetraethoxysilane, with some unreacted ethanol present; when the ethanol ratio is less than 1:1, the main product is still trihalomonoethoxysilane, with some unreacted silicon tetrahalide present. The hydrogen halide generated during the reaction has poor solubility in ethanol and ethoxysilane, and can enter the distillation column through the gas phase pipeline; the liquid phase after the reaction is completed is usually a mixture of haloethoxysilane, hydrogen halide and a small amount of residual ethanol, and is fed into the distillation unit of step two for subsequent separation through pipeline.

[0045] In this embodiment, the alcoholysis reaction occurs at a temperature of 0–50°C, for example, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, or any value within the range of any two of the above values, preferably 5–15°C. Specifically, the reaction is carried out in a reactor equipped with a cooling jacket or heat exchanger to maintain a stable temperature, which is beneficial for controlling the reaction rate and preventing side reactions.

[0046] Step 2 (S2): Separate the first reaction mixture to obtain a haloalkoxysilane, a first recovered alcohol, and a first hydrogen halide.

[0047] In this embodiment, the separation is achieved using a distillation method. Specifically, by utilizing the differences in volatility (boiling point) of the components in the first reaction mixture, multiple partial vaporization and condensation processes enrich the lighter components (low-boiling-point substances) in the gas phase and the heavier components (high-boiling-point substances) in the liquid phase, thereby achieving the separation and purification of each component. These distillation conditions ensure efficient separation and recovery of byproducts.

[0048] Specifically, the first hydrogen halide separation temperature is 5 to 35°C, for example, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, or any value within the range of any two of the above values.

[0049] The first recovery alcohol separation temperature is 60–100°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C, or any value within the range of any two of the above values.

[0050] The separation temperature of haloalkoxysilanes is 105–170°C, for example, 105°C, 120°C, 140°C, 150°C, 160°C, 170°C, or any value within the range of any two of the above values.

[0051] Step 3 (S3): The haloalkoxysilane is added to an aqueous solution containing a hydrogen halide reagent to generate a second reaction mixture. This step involves a hydrolysis reaction to generate a silica sol.

[0052] In this embodiment, the aqueous solution of the hydrogen halide reagent has a pH of 0–4, for example, 0, 1, 2, 3, 4, or any value within the range of any two of the above values. This aqueous solution is prepared with water having a resistivity ≥18.2 MΩ·cm to minimize the introduction of impurities. Furthermore, an aqueous solution with a pH of 1–2 is beneficial for controlling the hydrolysis rate and reducing particle unevenness caused by rapid gelation.

[0053] In this embodiment, the hydrolysis reaction temperature is 20–100°C, for example, 20°C, 40°C, 50°C, 60°C, 80°C, 100°C, or any value within the range of any two of the above values. The molar ratio of water to haloalkoxysilane is 1:(4–50), for example, 1:4, 1:10, 1:20, 1:30, 1:40, 1:50, or any value within the range of any two of the above values.

[0054] Step 4 (S4): Separate the second reaction mixture to obtain silica sol, second recovered alcohol and second hydrogen halide.

[0055] In this embodiment, the separation includes heating and evaporation at a temperature of 50–100°C, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, or any combination of two of the above values; during the process, the pH rises to 3–7, for example, 3, 4, 5, 6, 7, or any combination of two of the above values, and gelation occurs to obtain a silica sol in the form of a silica gel. These conditions promote the volatilization and recovery of alcohols and hydrogen halides.

[0056] Step 5 (S5): Clean and dry the silica sol to obtain the quartz sand precursor.

[0057] In this embodiment, the material is cleaned until the conductivity is ≤1 μS / cm, for example ≤1, ≤0.5, ≤0.1 μS / cm or lower, and the cleaning assembly equipped with a conductivity detector is used for real-time monitoring. The drying temperature is 80–300℃, for example 80℃, 100℃, 150℃, 200℃, 250℃, 300℃ or any combination of two of the above values, for 15–20 hours, for example 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours or any combination of two of the above values. The resulting precursor particle size distribution is 500nm–5mm, for example 500nm, 1μm, 10μm, 100μm, 1mm, 5mm or any combination of two of the above values, obtained through crushing and sieving. The sieving is performed using a vibrating screen made of non-metallic material such as nylon to avoid contamination by metallic impurities.

[0058] Step 6 (S6): The quartz sand precursor is subjected to sintering decarburization and dehydroxylation treatment to obtain the quartz sand.

[0059] In this embodiment, sintering decarburization is carried out in an oxygen-containing environment at a temperature of 400–600°C, such as 400°C, 450°C, 500°C, 550°C, 600°C, or any value within the range of any two of the above values; an oxygen content of 5%–100%, such as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or any value within the range of any two of the above values, preferably 20%–40%; and a time of 10–80 hours, such as 10 hours, 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, or any value within the range of any two of the above values.

[0060] Dehydroxylation is carried out in air, vacuum, or other gaseous environments at temperatures ranging from 900 to 1300°C, such as 900°C, 1000°C, 1100°C, 1200°C, 1300°C, or any combination of two of these values; for times ranging from 20 to 100 hours, such as 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, 100 hours, or any combination of two of these values. These treatments ensure the removal of carbon and hydroxyl impurities, improving purity.

[0061] Step 7: The recovery step includes merging the first and second recovered alcohols to obtain an alcohol reagent (S71), and merging the first and second hydrogen halides to obtain a hydrogen halide reagent (S72). A portion of the hydrogen halide reagent can proceed to step 3 (S3), while another portion can be absorbed by water to obtain a saturated acid as a byproduct. All the alcohol reagent proceeds to step 1 (S1), achieving zero net consumption of the alcohol reagent. The initial feed consists of an alcohol reagent, silicon tetrahalide, and water; the final products are quartz sand and saturated hydrogen chloride acid as a byproduct.

[0062] The method of this application reduces pollution and improves efficiency through recycling, and can obtain quartz sand with a purity of ≥99.9999%, uniform particles, and low impurity content.

[0063] An embodiment of this application also provides a quartz sand, which is obtained by the above preparation method, has a purity of ≥99.9999%, uniform particles, and low impurity content.

[0064] Please see Figure 2 One embodiment of this application also provides a system 100 for preparing quartz sand, including a first reaction unit 10, a first separation unit 20, a second reaction unit 30, a second separation unit 40, a sand making unit 50, an alcohol circulation loop 60, and a hydrogen halide circulation loop 70.

[0065] The first reaction unit 10 includes a first reactor 11, which is provided with a silicon tetrahalide inlet 111, an alcohol inlet 112 and a first outlet 113.

[0066] The first separation unit 20 includes a first distillation column 21. The first feed inlet 211 of the first distillation column 21 is connected to the first discharge outlet 113 of the first reactor 11. The first distillation column 21 is provided with a haloalkoxysilane outlet 212, a first recovered alcohol outlet 213 and a first hydrogen halide outlet 214.

[0067] The second reaction unit 30 includes a second reactor 31, which is provided with a haloalkoxysilane inlet 311, a hydrogen halide aqueous solution inlet 312, and a second outlet 313. The haloalkoxysilane inlet 311 is connected to the haloalkoxysilane outlet 212 of the first distillation column 21.

[0068] The second separation unit 40 includes an evaporator 41 and a second distillation column 42. The evaporator 41 is provided with a second feed inlet 411, a silica sol outlet 412, and a steam outlet 413. The second feed inlet 411 of the evaporator 41 is connected to the second outlet 313 of the second reactor 31, and the steam outlet 413 of the evaporator 41 is connected to the third feed inlet 421 of the second distillation column 42. The second distillation column 42 is provided with a second recovered alcohol outlet 422 and a second hydrogen halide outlet 423.

[0069] The sand making unit 50 includes a washing device 51, a drying device 52, a crushing and screening device 53, a medium-temperature sintering furnace 54, and a high-temperature sintering furnace 55. The feed end of the washing device 51 is connected to the silica sol outlet 412 of the evaporator separator 41, and the washing device 51, the drying device 52, the crushing and screening device 53, the medium-temperature sintering furnace 54, and the high-temperature sintering furnace 55 are connected sequentially along the material flow direction.

[0070] The alcohol circulation loop 60 includes a recovery alcohol collection pipe 61, an alcohol recovery tank 62, and an alcohol circulation pipeline 63. The recovery alcohol collection pipe 61 is connected to the first recovery alcohol outlet 213 of the first distillation column 21 and the second recovery alcohol outlet 422 of the second distillation column 42. The recovery alcohol collection pipe 61 is connected to the alcohol recovery tank 62, and the alcohol recovery tank 62 is connected to the alcohol inlet 112 of the first reactor 11 via the alcohol circulation pipeline 63.

[0071] The hydrogen halide circulation loop 70 includes a hydrogen halide collecting pipe 71, a hydrogen halide absorption device 72, and an acid delivery pipe 73. The hydrogen halide collecting pipe 71 is connected to the first hydrogen halide outlet 214 of the first distillation column 21 and the second hydrogen halide outlet 423 of the second distillation column 42. The hydrogen halide collecting pipe 71 is connected to the hydrogen halide gas inlet of the hydrogen halide absorption device 72. The hydrogen halide absorption device 72 has a water inlet, a hydrogen halide aqueous solution outlet, and a by-product outlet. The hydrogen halide aqueous solution outlet is connected to the hydrogen halide aqueous solution inlet 312 of the second reactor 31 via the acid delivery pipe 73. The by-product outlet is used to discharge excess hydrogen halide aqueous solution.

[0072] In this embodiment, the first reactor 11 is a closed reactor, equipped with a stirring assembly and a cooling jacket. The cooling jacket is connected to a temperature control device, and the tetrahalide inlet 111 and the alcohol inlet 112 of the first reactor 11 are respectively connected to a metering pump and / or a mass flow controller.

[0073] In this embodiment, the first distillation column 21 and / or the second distillation column 42 both include a column body, a reboiler, a top condenser, and a reflux pipeline. The first hydrogen halide outlet 214 of the first distillation column 21 is located at the top gas phase outlet, the first recovered alcohol outlet 213 is located at the top condensate outlet and / or the side stream distillate outlet, and the haloalkoxysilane outlet 212 is located at the bottom outlet.

[0074] In this embodiment, the hydrogen halide absorption device 72 includes an absorption tower and an acid storage tank. The absorption tower is equipped with a packing section and a demisting section, and the outlet of the hydrogen halide aqueous solution is connected to the acid storage tank. The acid storage tank is connected to the inlet 312 of the hydrogen halide aqueous solution of the second reactor 31 via an acid delivery pipeline 73. The acid storage tank is also equipped with a by-product outlet to discharge excess hydrogen halide aqueous solution.

[0075] In this embodiment, the evaporator 41 includes a heating component, a gas-liquid separation chamber, and an exhaust pipe. The exhaust pipe is connected to the feed inlet of the second distillation column 42, and the evaporator 41 is further provided with a vacuum interface and connected to a vacuum unit.

[0076] In this embodiment, the cleaning device 51 includes a cleaning tank, an ultrapure water supply pipeline, and a conductivity detector, with the conductivity detector installed on the outlet pipeline of the cleaning tank; the drying device 52 is a drying furnace; and the crushing and screening device 53 includes a crusher and a non-metallic vibrating screen, with the screen material of the non-metallic vibrating screen being nylon.

[0077] In this embodiment, the medium-temperature sintering furnace 54 is equipped with an oxygen supply interface, a tail gas discharge port and an atmosphere control component, the high-temperature sintering furnace 55 is equipped with a vacuum interface and connected to a vacuum unit, and both the medium-temperature sintering furnace 54 and the high-temperature sintering furnace 55 are equipped with a temperature control device and a furnace temperature detection component.

[0078] The present application's solution will be explained below with reference to embodiments. Those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the present application. Unless otherwise stated, reagents, software, and instruments involved in the following embodiments that are not specifically mentioned are all conventional commercially available products or open-source materials.

[0079] Example 1:

[0080] 6N silicon tetrachloride (purity 99.9999%) and 6N ethanol were mixed in a 1:3 molar ratio in an alcoholysis system and reacted at 20°C for 8 hours. Distillation yielded high-purity hydrogen chloride, high-purity ethanol, and high-purity monochlorotriethoxysilane. The ethanol was returned to the alcoholysis system for further reaction. The high-purity monochlorotriethoxysilane was reacted with a hydrochloric acid solution (pH=1) prepared with high-purity hydrogen chloride at a 1:30 molar ratio at 40°C for 6 hours to obtain a silica sol. Heating to pH=5 at 70°C yielded a silica gel. The distilled ethanol and hydrochloric acid were separated by distillation and fed into the alcoholysis system and the high-purity hydrogen chloride pipeline, respectively. Excess high-purity hydrogen chloride was absorbed using ultrapure water for the production of high-purity saturated hydrochloric acid.

[0081] The prepared silica gel was mechanically stirred and washed with ultrapure water until its conductivity was 0.8 μS / cm. After drying at 100℃ for 20 h, quartz sand was obtained. Quartz sand with a particle size of 100 μm-500 μm was obtained by crushing and sieving with rollers. After sintering at 400℃ for 10 h in a pure oxygen environment and vacuum sintering at 1200℃ for 40 h, high-purity synthetic quartz sand was obtained with a purity of 99.99995%, hydroxyl content <1 ppm, and carbon content 3 ppm.

[0082] Example 2:

[0083] 6N silicon tetrachloride and 6N ethanol were mixed in a 1:4 molar ratio in an alcoholysis system and reacted at 10°C for 10 h. Distillation yielded high-purity hydrogen chloride, high-purity ethanol, and high-purity tetraethoxysilane. The ethanol was returned to the alcoholysis system for further reaction. The high-purity tetraethoxysilane was reacted with a hydrochloric acid solution (pH=1) prepared with high-purity hydrogen chloride at a 1:20 molar ratio at 50°C for 8 h to obtain a silica sol. Heating to pH=4 at 80°C yielded a silica gel. The distilled ethanol and hydrochloric acid were separated by distillation and fed into the alcoholysis system and the high-purity hydrogen chloride pipeline, respectively. Excess high-purity hydrogen chloride was absorbed using ultrapure water for the production of high-purity saturated hydrochloric acid.

[0084] The prepared silica gel was mechanically stirred and washed with ultrapure water until its conductivity was 0.3 μS / cm. After drying at 130℃ for 16 h, quartz sand was obtained. Quartz sand with a particle size of 50 μm-400 μm was obtained by crushing and sieving with rollers. After sintering at 600℃ for 40 h in a pure oxygen environment and vacuum sintering at 1150℃ for 60 h, high-purity synthetic quartz sand was obtained with a purity of 99.99998%, hydroxyl content <1 ppm, and carbon content <1 ppm.

[0085] Example 3:

[0086] 6N silicon tetrachloride and 6N methanol were mixed in an alcoholysis system at a molar ratio of 1:2 and reacted at 5°C for 10 hours. Distillation yielded high-purity hydrogen chloride, high-purity methanol, and high-purity tetramethoxysilane. The methanol was returned to the alcoholysis system for further reaction. The high-purity tetramethoxysilane was reacted with a hydrochloric acid solution (pH=2) prepared with high-purity hydrogen chloride at a molar ratio of 1:30 at 40°C for 6 hours to obtain a silica sol. Heating to pH=5 at 60°C yielded a silica gel. The distilled methanol and hydrochloric acid were separated by distillation and fed into the alcoholysis system and the high-purity hydrogen chloride pipeline, respectively. Excess high-purity hydrogen chloride was absorbed using ultrapure water for the production of high-purity saturated hydrochloric acid.

[0087] The prepared silica gel was mechanically stirred and washed with ultrapure water until its conductivity was 0.1 μS / cm. After drying at 180℃ for 12 h, quartz sand was obtained. Quartz sand with a particle size of 100 μm-400 μm was obtained by jaw crushing and sieving. After sintering at 450℃ for 80 h in a 50% oxygen environment and vacuum sintering at 1000℃ for 100 h, high-purity synthetic quartz sand was obtained with a purity of 99.999990%, hydroxyl content <1 ppm, and carbon content <1 ppm.

[0088] Example 4:

[0089] 6N silicon tetrachloride and 6N propanol were mixed in an alcoholysis system at a molar ratio of 1:3 and reacted at 40°C for 10 hours. Distillation yielded high-purity hydrogen chloride, high-purity propanol, and high-purity tetrapropoxysilane. The propanol was returned to the alcoholysis system for further reaction. The high-purity tetrapropoxysilane was reacted with a hydrochloric acid solution (pH=1) prepared with high-purity hydrogen chloride at a molar ratio of 1:10 at 80°C for 12 hours to obtain a silica sol. Heating to pH=7 at 90°C yielded a silica gel. The distilled propanol and hydrochloric acid were separated by distillation and fed into the alcoholysis system and the high-purity hydrogen chloride pipeline, respectively. Excess high-purity hydrogen chloride was absorbed using ultrapure water for the production of high-purity saturated hydrochloric acid.

[0090] The prepared silica gel was mechanically stirred and washed with ultrapure water until its conductivity was 0.1 μS / cm. After drying at 300℃ for 8 h, quartz sand was obtained. Quartz sand with a particle size of 500 nm-500 μm was obtained by ball milling and sieving. After sintering at 500℃ for 20 h in a 20% oxygen environment and vacuum sintering at 1200℃ for 80 h, high-purity synthetic quartz sand was obtained with a purity of 99.999991%, hydroxyl content <1 ppm, and carbon content <1 ppm.

[0091] Example 5:

[0092] 6N silicon tetrachloride and 6N methanol were mixed in a 1:1 molar ratio in an alcoholysis system and reacted at 5°C for 10 hours. Distillation yielded high-purity hydrogen chloride, high-purity methanol, and high-purity tetramethoxysilane. The methanol was returned to the alcoholysis system for further reaction. The high-purity tetramethoxysilane was reacted with a pH=2 hydrochloric acid solution prepared using high-purity hydrogen chloride at a molar ratio of 1:10 at 50°C for 4 hours to obtain a silica sol. Heating to pH=4 at 80°C yielded a silica gel. The distilled methanol and hydrochloric acid were separated by distillation and fed into the alcoholysis system and the high-purity hydrogen chloride pipeline, respectively. Excess high-purity hydrogen chloride was absorbed using ultrapure water for the production of high-purity saturated hydrochloric acid.

[0093] The prepared silica gel was mechanically stirred and washed with ultrapure water until its conductivity was 0.3 μS / cm. After drying at 250℃ for 10 h, quartz sand was obtained. Quartz sand with a particle size of 200 μm-5 mm was obtained by hammer crushing and sieving. After sintering at 600℃ for 40 h in an 80% oxygen environment and vacuum sintering at 900℃ for 100 h, high-purity synthetic quartz sand was obtained with a purity of 99.99998%, hydroxyl content <1 ppm, and carbon content <1 ppm.

[0094] Example 6

[0095] 6N silicon tetraiodide and 6N methanol were mixed in an alcoholysis system at a molar ratio of 1:3 and reacted at 25°C for 10 hours. Distillation yielded high-purity hydrogen iodide, high-purity methanol, and high-purity tetramethoxysilane. The methanol was returned to the alcoholysis system for further reaction. The high-purity tetramethoxysilane was reacted with a hydroiodic acid solution (pH=1) prepared with high-purity hydrogen iodide at a molar ratio of 1:15 at 80°C for 10 hours to obtain a silica sol. Heating to pH=4 at 80°C yielded a silica gel. The distilled methanol and hydrogen iodide were separated by distillation and fed into the alcoholysis system and the high-purity hydrogen iodide pipeline, respectively. Excess high-purity hydrogen iodide was absorbed using ultrapure water for the production of high-purity saturated hydroiodic acid.

[0096] The prepared silica gel was mechanically stirred and washed with ultrapure water until its conductivity was 0.1 μS / cm. After drying at 200℃ for 15 h, quartz sand was obtained. Quartz sand with a particle size of 40 μm-500 μm was obtained by jaw crushing and sieving. After sintering at 500℃ for 50 h in a 60% oxygen environment and vacuum sintering at 1050℃ for 70 h, high-purity synthetic quartz sand was obtained with a purity of 99.999991%, hydroxyl content <1 ppm, and carbon content <1 ppm.

[0097] This application tested the purity, hydroxyl content, and carbon content of the quartz sand prepared in Examples 1-6. Specifically, inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the content of trace impurity elements in the quartz sand samples, and the purity of the quartz sand was calculated accordingly; spectrophotometry and / or thermogravimetric analysis (TGA) were used to determine the hydroxyl content of the quartz sand; and infrared spectroscopy was used to determine the carbon content of the quartz sand. The test results are shown in Table 1.

[0098] Table 1. Performance test results of quartz sand in Examples 1-6 of this application.

[0099]

[0100] It can be observed that, based on the results in Table 1, consistent conclusions and patterns can be drawn from the following multiple dimensions:

[0101] (1) Analysis from the perspective of the feeding system (silicon source and alcohol type / ratio): Examples 1-5 used silicon tetrachloride as the silicon source, and Example 6 used silicon tetraiodide as the silicon source. The alcohol reagents covered ethanol, methanol, and propanol, and the molar ratio of silicon tetrahalide / alcohol covered 1:1 to 1:4. Despite the differences in the feeding system, the purity of the quartz sand obtained in Examples 1-6 all reached 99.99995% or higher, with Examples 3, 4, and 6 reaching or exceeding 99.99999%. This indicates that the method of this application has good adaptability to different silicon tetrahalide / alcohol combinations and can stably obtain high-purity quartz sand within a wide feeding window.

[0102] (2) Analysis from the perspective of cleaning process conditions (cleaning endpoint conductivity): In Table 1, the cleaning endpoint conductivity of Example 1 is 0.8 μS / cm, and its purity is 99.99995%. When the cleaning endpoint conductivity is reduced to 0.3 μS / cm (Examples 2 and 5) or further reduced to 0.1 μS / cm (Examples 3, 4, and 6), the corresponding purity increases to 99.99998% or higher, and can reach 99.99999% or higher. It can be seen that the cleaning endpoint conductivity, as a characterization index of soluble ion residue, is significantly correlated with the final purity, indicating that reducing ion residue through thorough cleaning is beneficial to further improving the purity and batch stability of quartz sand.

[0103] (3) Analysis from the perspective of decarbonization process conditions (temperature / oxygen environment / time combination): Example 1 used a medium-temperature decarbonization condition of 400℃, pure oxygen, and 10h, with a final carbon content of 3 ppm. However, Examples 2-6, after decarbonization treatment under higher temperatures and / or longer durations, combined with different oxygen contents (20%-100% oxygen environment), all achieved carbon contents of <1 ppm. This comparison shows that decarbonization treatment has a significant effect on carbon residue control, and its effect is closely related to the combination of temperature, oxygen environment, and treatment time. Within the process window given in this application, increasing the decarbonization intensity (e.g., increasing temperature, extending time, or optimizing the oxygen environment) can effectively reduce carbon content.

[0104] (4) Analysis from the perspective of dehydroxylation process conditions (temperature / atmosphere / time combination): The hydroxyl content of Examples 1 to 6 is all <1 ppm, and the dehydroxylation conditions cover multiple combinations of 900-1200℃ and 40-100h (all in vacuum environment). For example, Example 1 can achieve <1 ppm under the conditions of 1200℃ and 40h, while Example 5 can also achieve <1 ppm under the conditions of 900℃ and 100h. It can be seen that the dehydroxylation treatment has a wide adjustable process window and can stably achieve the target of low hydroxyl content under different temperature-time combinations.

[0105] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A system for producing quartz sand, characterized by, It includes a first reaction unit, a first separation unit, a second reaction unit, a second separation unit, a sand making unit, an alcohol circulation loop, and a hydrogen halide circulation loop; The first reaction unit includes a first reactor, which is provided with a silicon tetrahalide inlet, an alcohol inlet, and a first outlet. The first separation unit includes a first distillation column, the first feed inlet of the first distillation column is connected to the first discharge outlet of the first reactor, and the first distillation column is provided with a haloalkoxysilane outlet, a first recovered alcohol outlet and a first hydrogen halide outlet; The second reaction unit includes a second reactor, which is provided with a haloalkoxysilane inlet, a hydrogen halide aqueous solution inlet, and a second outlet. The haloalkoxysilane inlet is connected to the haloalkoxysilane outlet of the first distillation column. The second separation unit includes an evaporator and a second distillation column. The evaporator is provided with a second feed inlet, a silica sol outlet and a steam outlet. The second feed inlet of the evaporator is connected to the second discharge outlet of the second reactor. The steam outlet of the evaporator is connected to the third feed inlet of the second distillation column. The second distillation column is provided with a second recovered alcohol outlet and a second hydrogen halide outlet. The sand making unit includes a washing device, a drying device, a crushing and screening device, a medium-temperature sintering furnace, and a high-temperature sintering furnace. The feed end of the washing device is connected to the silica sol outlet of the evaporator separator, and the washing device, drying device, crushing and screening device, medium-temperature sintering furnace, and high-temperature sintering furnace are connected sequentially along the material flow direction. The alcohol circulation loop includes a recovered alcohol collection pipe, an alcohol recovery tank, and an alcohol circulation pipeline. The recovered alcohol collection pipe is connected to the first recovered alcohol outlet of the first distillation column and the second recovered alcohol outlet of the second distillation column, respectively. The recovered alcohol collection pipe is connected to the alcohol recovery tank, and the alcohol recovery tank is connected to the alcohol inlet of the first reactor via the alcohol circulation pipeline. The hydrogen halide circulation loop includes a hydrogen halide collecting pipe, a hydrogen halide absorption device, and an acid delivery pipeline. The hydrogen halide collecting pipe is connected to the first hydrogen halide outlet of the first distillation column and the second hydrogen halide outlet of the second distillation column. The hydrogen halide collecting pipe is also connected to the hydrogen halide gas inlet of the hydrogen halide absorption device. The hydrogen halide absorption device has a water inlet and a hydrogen halide aqueous solution outlet. The hydrogen halide aqueous solution outlet is connected to the hydrogen halide aqueous solution inlet of the second reactor via the acid delivery pipeline.

2. The system of claim 1, wherein, The first reactor is a closed reactor, equipped with a stirring assembly and a cooling jacket. The cooling jacket is connected to a temperature control device, and the tetrahalide inlet and alcohol inlet of the first reactor are respectively connected to a metering pump and / or a mass flow controller.

3. The system according to claim 2, characterized in that, The first distillation column and / or the second distillation column each include a column body, a reboiler, a condenser at the top of the column, and a reflux pipeline. The first hydrogen halide outlet of the first distillation column is located at the top gas phase outlet, the first recovered alcohol outlet is located at the top condensate outlet and / or the side stream distillate outlet, and the haloalkoxysilane outlet is located at the bottom outlet.

4. The system of claim 3, wherein, The hydrogen halide absorption device includes an absorption tower and an acid storage tank. The absorption tower is equipped with a packing section and a demisting section, and the outlet of the hydrogen halide aqueous solution is connected to the acid storage tank. The acid storage tank is connected to the inlet of the hydrogen halide aqueous solution of the second reactor via an acid delivery pipeline.

5. The system of claim 3, wherein, The evaporator separator includes a heating assembly, a gas-liquid separation chamber, and an exhaust pipe. The exhaust pipe is connected to the feed inlet of the second distillation column, and the evaporator separator is further provided with a vacuum interface and connected to a vacuum unit.

6. The system of claim 3, wherein, The cleaning device includes a cleaning tank, an ultrapure water supply pipeline, and a conductivity detector. The conductivity detector is installed on the liquid outlet pipeline of the cleaning tank. The drying device is a drying furnace. The crushing and screening device includes a crusher and a non-metallic vibrating screen. The screen material of the non-metallic vibrating screen is nylon.

7. The system of claim 3, wherein, The medium-temperature sintering furnace is equipped with an oxygen supply interface, a tail gas emission port and an atmosphere control component. The high-temperature sintering furnace is equipped with a vacuum interface and connected to a vacuum unit. Both the medium-temperature sintering furnace and the high-temperature sintering furnace are equipped with temperature control devices and furnace temperature detection components.

8. A method for producing quartz sand using the system for producing quartz sand according to any one of claims 1 to 7, characterized by, Includes the following steps: Silicon tetrahalide is reacted with an alcohol reagent to generate the first reaction mixture; The first reaction mixture was separated to obtain a haloalkoxysilane, a first recovered alcohol, and a first hydrogen halide; The haloalkoxysilane is added to an aqueous solution containing a hydrogen halide reagent to generate a second reaction mixture; The second reaction mixture was separated to obtain silica sol, a second recovered alcohol, and a second hydrogen halide; The silica sol was cleaned and dried to obtain a silica sand precursor. The quartz sand precursor is subjected to sintering decarburization and dehydroxylation treatment to obtain the quartz sand. The method further includes a recycling step: The first recovered alcohol and the second recovered alcohol are combined to obtain the alcohol reagent, and The first hydrogen halide and the second hydrogen halide are combined to obtain the hydrogen halide reagent.

9. The method of claim 8, wherein, The alcohol reagent includes at least one of methanol, ethanol, propanol, and butanol, and the silicon tetrahalide includes at least one of silicon tetrachloride, silicon tetrabromide, and silicon tetraiodide, and the purity of the silicon tetrahalide is not less than 99.9999%.

10. The method of claim 8, wherein, In the step of generating the first reaction mixture, the reaction temperature is 0–50°C, and the molar ratio of the silicon tetrahalide to the alcohol reagent is 1:(0.5–10).

11. The method of claim 8, wherein, It also includes the step of adjusting the molar ratio of the tetrahalide to the alcohol reagent so that the number of halogen substitutions in the haloalkoxysilane is 0 to 3.

12. The method of claim 8, wherein, The step of separating the first reaction mixture includes distillation separation, wherein the distillation conditions are: the first hydrogen halide separation temperature is 5-35°C, the first recovered alcohol separation temperature is 60-100°C, and the haloalkoxysilane separation temperature is 105-170°C.

13. The method of claim 8, wherein, The aqueous solution of the hydrogen halide reagent has a pH of 0 to 4, and the aqueous solution is prepared using water with a resistivity ≥ 18.2 MΩ·cm.

14. The method of claim 8, wherein, In the step of generating the second reaction mixture, the reaction temperature is 20–100°C, and the molar ratio of water to haloalkoxysilane in the aqueous solution is 1:(4–50).

15. The method of claim 8, wherein, The separation step of the second reaction mixture includes heating and evaporation, wherein the heating and evaporation conditions are: heating temperature of 50-100°C, pH rising to 3-7 during the separation process, and gelation occurring to obtain silica sol in the form of silica gel.

16. The method of claim 8, wherein, Clean the silica sol until the conductivity is ≤1μS / cm.

17. The method of claim 8, wherein, The temperature for drying the silica sol is 80–300°C, and the drying time is 15–20 h.

18. The method of claim 8, wherein, The quartz sand precursor has a particle size distribution of 500 nm to 5 mm and is obtained by crushing and sieving.

19. The method according to claim 8, characterized in that, The sintering decarburization treatment is carried out in an oxygen-containing environment at a temperature of 400–600°C and an oxygen content of 5%–100% for a treatment time of 10–80 h. The dehydroxylation treatment is carried out in an air, vacuum, or other gas environment at a temperature of 900–1300°C for a treatment time of 20–100 h.

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