Plasma method preparation process of high-purity quartz sand

Abstract

The invention relates to the technical field of quartz sand preparation, and particularly discloses a plasma method preparation process of high-purity quartz sand, which comprises the following steps: 1, pretreating raw materials, crushing common quartz sand until the particle size is 50-200mu m, washing with water to remove silt, and drying until the water content is less than or equal to 0.5%; the vertical gas-solid fluidized bed reactor is adopted, the plasma exposure path of quartz sand particles is prolonged through a spiral flow channel reaction cavity of the vertical gas-solid fluidized bed reactor, argon plasma can make full contact with the surfaces of the particles within the suspension heating treatment time of 0.1-10 s, metal impurities on the surfaces are effectively removed, multiple stages of plasma nozzles are arranged in a layered mode in the axial direction of a spiral flow channel, and therefore the effect of improving the stability of the gas-solid fluidized bed reactor is achieved. And in cooperation with a segmented temperature control mode, the first temperature zone removes organic matter and volatile metal impurities adsorbed on the surface, and the second temperature zone pushes gasification of metal oxides through thermodynamic equilibrium, so that deep impurities are further removed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of quartz sand preparation, and particularly relates to a plasma method for preparing high-purity quartz sand. BACKGROUND

[0002] Traditional thermal purification methods such as high-temperature chlorination involve passing chlorine gas or other gases into the quartz sand at high temperatures to react with impurities in the quartz sand, generating volatile chlorides to achieve the purpose of purification. However, this method also has some problems. High-temperature chlorination needs to be carried out in a high-temperature environment, which has high energy consumption and increases production costs. At the same time, the quartz sand may undergo crystal transformation and structural changes under high-temperature conditions, affecting its physical and chemical properties. In addition, the chlorides generated during the chlorination process are corrosive, which has high requirements for equipment materials, and the tail gas treatment is difficult, which is easy to cause secondary pollution.

[0003] Plasma is a macroscopically electrically neutral gas-like substance composed of a large number of charged particles (including electrons, ions) and neutral particles, and is called the fourth state of matter. Plasma has the characteristics of high temperature, high energy density, and high activity, and can generate high-temperature heat sources, high-energy particle beams, and active free radicals, providing a unique physical and chemical environment for material purification.

[0004] In recent years, plasma technology has been widely concerned and applied in the field of material purification. In the aspect of metal material purification, plasma smelting technology can effectively remove gas impurities and non-metallic inclusions in metals, improving the purity and performance of metals. For example, in the preparation of high-end metal materials such as titanium alloys and high-temperature alloys, plasma smelting technology plays an important role; in the aspect of semiconductor material purification, plasma chemical vapor deposition (PCVD) and plasma immersion ion implantation (PIII) technologies can achieve precise modification and impurity removal on the surface of semiconductor materials, improving the performance and reliability of semiconductor devices.

[0005] Although plasma technology has many advantages in the preparation of high-purity quartz sand, the existing plasma preparation technology for high-purity quartz sand still has some deficiencies. The existing vertical gas-solid fluidized bed reactor has certain limitations in the plasma exposure path of quartz sand particles and temperature gradient control. For example, the design of the spiral flow channel reaction cavity may not ensure the uniform distribution and sufficient contact of quartz sand particles with plasma in the reactor, leading to incomplete purification of some particles and affecting the overall purity and quality stability of the product. Therefore, a plasma method for preparing high-purity quartz sand is proposed. SUMMARY

[0006] The purpose of the present application is to provide a plasma method for preparing high-purity quartz sand to solve the problems raised in the background art.

[0007] To achieve the above object, the application provides the following technical scheme.

[0008] A plasma method for preparing high-purity quartz sand, comprising:

[0009] Step one: pretreat the raw material, crush the ordinary quartz sand to a particle size of 50-200 μm, dry it to a water content of ≤0.5% after removing the silt by washing with water;

[0010] Step two: carry out rough purification of the quartz sand after washing with water by plasma, inject the pretreated quartz sand into a vertical gas-solid fluidized bed reactor, and carry out suspension heating treatment by passing in argon plasma, the time of the suspension heating treatment being 0.1-10 s, to remove the surface metal impurities;

[0011] Step three: carry out deep purification of the quartz sand raw material by hydrogen-oxygen mixed gas plasma for secondary treatment, the treatment time being 0.5-5 s;

[0012] Step four: cool and screen the quartz sand, quickly cool the quartz sand after the reaction to room temperature, and screen the high-purity quartz sand product with a particle size of 100-150 μm;

[0013] Step five: carry out closed-loop treatment of the tail gas, collect the metal oxide impurities in the reaction tail gas, separate the metal elements by an electric field, and recycle the remaining gas after deoxidation and drying to the plasma generator.

[0014] Preferably, the vertical gas-solid fluidized bed reactor comprises a spiral flow channel reaction cavity, a multi-stage plasma nozzle and a rapid cooling sleeve, the spiral flow channel reaction cavity is used to prolong the plasma exposure path of the quartz sand particles; the multi-stage plasma nozzle is used to be arranged axially in layers along the reaction cavity of the spiral flow channel, to realize temperature gradient control; and the rapid cooling sleeve uses liquid nitrogen or circulating cooling water to rapidly cool the quartz sand at the outlet, to prevent secondary adsorption of impurities.

[0015] Preferably, the treatment parameters of the hydrogen-oxygen mixed gas plasma treatment stage are that the plasma torch working frequency is 10-50 kHz, the voltage is 5-20 kV; the pressure in the reaction cavity is 0.1-1 MPa, and the oxygen partial pressure in the reaction cavity is ≤0.3 MPa, to inhibit the oxidation phenomenon.

[0016] Preferably, in the step five, the tail gas closed-loop treatment step further comprises:

[0017] Step one: collect the gasified metal oxide by a condenser, the condensing temperature of the condenser being -50-50 ℃;

[0018] Step two: the electric field separator adopts a direct current high voltage electric field, the voltage of the high voltage electric field is 5-50kV, and the high voltage electric field is graded and recycled according to the difference of ionization energy of metal elements;

[0019] Step three: the deoxidizing tower is filled with a palladium-based catalyst, and after residual oxygen and hydrogen are reacted to generate water, the water is removed.

[0020] Preferably, the purity index of the high-purity quartz sand product is: the content of silicon dioxide is greater than or equal to 99.998%; the total metal impurity content is less than or equal to 10ppm; the hydroxyl content is less than or equal to 3ppm; and the particle size distribution D50 is 120±10um.

[0021] Preferably, in the step two, the plasma rough purification stage adopts a segmented temperature control mode, the segmented temperature control mode includes a first temperature zone, a second temperature zone and a third temperature zone, the first temperature zone is an inlet section, the second temperature zone is a core section, and the third temperature zone is an outlet section.

[0022] Preferably, the temperature of the first temperature zone is 3000-5000℃, so as to remove surface adsorbed organic matter and volatile metal impurities; the temperature of the second temperature zone is 8000-12000℃, so as to promote the gasification of metal oxides through thermodynamic equilibrium; and the temperature of the third temperature zone is 2000-3000℃, so as to inhibit the sintering of quartz sand particles, and at the same time make the gasified metal impurities completely condense in the tail gas system.

[0023] Preferably, the pitch of the spiral flow channel of the spiral flow channel reaction cavity is 0.5-2 times the diameter of the reaction cavity, so as to ensure that the particle residence time distribution index (PDI) of the quartz sand particles is less than or equal to 0.3; and the surface of the spiral flow channel is coated with boron nitride.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The present application crushes ordinary quartz sand to a particle size of 50-200um, increases the particle surface area, makes the subsequent treatment easier to perform, removes mud and other surface easily detached impurities by water washing, and dries to a water content of less than or equal to 0.5%, so as to avoid the influence of water on the subsequent plasma treatment effect, and lay a foundation for deep purification.

[0026] The vertical gas-solid fluidized bed reactor, the spiral flow channel reaction cavity of which prolongs the plasma exposure path of the quartz sand particles, enables the argon plasma to fully contact the particle surface within a suspension heating treatment time of 0.1-10s, effectively removes the surface metal impurities, and the multi-stage plasma nozzle is arranged in layers along the axial direction of the spiral flow channel, realizes temperature gradient control, cooperates with the segmented temperature control mode, removes the surface adsorbed organic matter and volatile metal impurities in the first temperature zone, promotes the gasification of metal oxides in the second temperature zone through thermodynamic equilibrium, and further removes the deep impurities. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A step flow chart of the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0029] As shown in the figure, a plasma method for preparing high-purity quartz sand comprises the following steps: Figure 1

[0030] Step one: pretreat the raw material, crush the ordinary quartz sand to a particle size of 50-200 μm, dry it to a water content of ≤0.5% after removing the silt by washing with water;

[0031] Step two: carry out plasma rough purification on the quartz sand after washing with water, inject the pretreated quartz sand into a vertical gas-solid fluidized bed reactor, and carry out suspension heating treatment by inputting argon plasma, the suspension heating treatment time is 0.1-10 s, and the surface metal impurities are removed;

[0032] The present application is further specifically described as follows: in step two, the plasma rough purification stage adopts a segmented temperature control mode, the segmented temperature control mode comprises a first temperature zone, a second temperature zone and a third temperature zone, the first temperature zone is an inlet section, the second temperature zone is a core section, and the third temperature zone is an outlet section, the temperature of the first temperature zone is 3000-5000 ℃, so as to remove the surface adsorbed organic matter and volatile metal impurities; the temperature of the second temperature zone is 8000-12000 ℃, so as to promote the gasification of metal oxides by thermodynamic equilibrium; and the temperature of the third temperature zone is 2000-3000 ℃, the third temperature zone is used for inhibiting the sintering of quartz sand particles, and at the same time, the gasified metal impurities are completely condensed in the tail gas system;

[0033] The present application is further specifically described as follows: the vertical gas-solid fluidized bed reactor comprises a spiral flow channel reaction cavity, a multi-stage plasma nozzle and a rapid cooling sleeve, the spiral flow channel reaction cavity is used for prolonging the plasma exposure path of the quartz sand particles; the multi-stage plasma nozzle is used for being arranged in an axial layered manner along the reaction cavity of the spiral flow channel, so as to realize temperature gradient control; the rapid cooling sleeve is used for rapidly cooling the outlet quartz sand by using liquid nitrogen or circulating cooling water, so as to prevent secondary adsorption of impurities; the pitch of the spiral flow channel of the spiral flow channel reaction cavity is 0.5-2 times the diameter of the reaction cavity, so as to ensure that the particle residence time distribution coefficient (PDI) of the quartz sand particles is ≤0.3; and the spiral flow channel surface is coated with boron nitride;

[0034] ​The treatment parameters of the hydrogen-oxygen mixed gas plasma treatment stage are that the plasma torch working frequency is 10-50 kHz, the voltage is 5-20 kV, the pressure in the reaction cavity is 0.1-1 MPa, and the oxygen partial pressure in the reaction cavity is ≤0.3 MPa, so as to inhibit the oxidation phenomenon.

[0035] Step three: the quartz sand raw material is subjected to plasma deep purification, and is subjected to secondary treatment through hydrogen-oxygen mixed gas plasma, and the treatment time is 0.5-5 s;

[0036] The purity index of the high-purity quartz sand product is that the silicon dioxide content is ≥99.998%, the total metal impurity content is ≤10 ppm, the hydroxyl content is ≤3 ppm, and the particle size distribution D50 is 120±10 μm.

[0037] Step four: the quartz sand is cooled and screened, the quartz sand after reaction is rapidly cooled to room temperature, and the high-purity quartz sand product with a particle size of 100-150 μm is selected through screening;

[0038] Step five: the tail gas is subjected to closed loop treatment, the metal oxide impurities in the reaction tail gas are collected, the metal elements are recovered through electric field separation, and the remaining gas is deoxidized and dried and then recycled to the plasma generator;

[0039] The closed loop treatment step of the tail gas in step five further comprises:

[0040] Step one: the gasified metal oxide is collected through a condenser, and the condensation temperature of the condenser is-50℃ to 50℃;

[0041] Step two: the electric field separator adopts a direct current high voltage electric field, the voltage of the high voltage electric field is 5-50 kV, and the metal elements are recovered in stages according to the ionization energy difference;

[0042] Step three: the palladium-based catalyst is filled in the deoxidation tower, and the residual oxygen and hydrogen are reacted to generate water and then removed;

[0043] As known from the above, the plasma method preparation process of the high-purity quartz sand aims to remove various impurities in ordinary quartz sand through a series of fine steps, utilize the high energy characteristics of plasma, and finally obtain a high-purity quartz sand product with high purity, specific particle size distribution and excellent performance, and the whole process covers key links such as raw material pretreatment, plasma rough purification, plasma deep purification, cooling and screening, and tail gas closed loop treatment, and each link closely cooperates to realize efficient preparation of high-purity quartz sand;

[0044] Crushing common quartz sand to a particle size of 50-200 μm, the purpose of crushing is to increase the surface area of quartz sand particles, making it easier to remove impurities in the subsequent treatment process, smaller particle size can provide more reaction contact points, improve the purification efficiency;

[0045] Removing the dirt and other impurities on the surface of the quartz sand by water washing, the dirt and other impurities on the surface of the quartz sand are usually relatively weak, and under the scouring action of the water flow, these impurities can be effectively separated, thereby preliminarily purifying the surface of the quartz sand;

[0046] Drying the quartz sand after water washing to a water content of ≤0.5%, the water content may affect the stability of the plasma and the treatment effect in the subsequent plasma treatment process, drying treatment can ensure that the quartz sand enters the plasma treatment link in a dry state, ensuring the smooth progress of the process;

[0047] The vertical gas-solid fluidized bed reactor structure, the spiral flow channel reaction cavity: its unique spiral flow channel design prolongs the plasma exposure path of the quartz sand particles, the quartz sand particles move with the gas flow in the spiral flow channel, which can more fully contact with the plasma, so that the plasma can comprehensively and deeply treat the impurities on the surface of the particles, improving the uniformity and thoroughness of impurity removal. At the same time, the surface of the spiral flow channel is coated with boron nitride, which has good high-temperature resistance and corrosion resistance, can protect the reaction cavity from being eroded by plasma and high temperature, and prolong the service life of the reactor. The pitch of the spiral flow channel is designed to be 0.5-2 times the diameter of the reaction cavity, which can ensure that the particle residence time distribution index (PDI) is ≤0.3, so that the residence time of the particles in the reaction cavity is relatively uniform, further improving the consistency of the purification effect;

[0048] Axially layered arrangement along the reaction cavity of the spiral flow channel to realize temperature gradient control, different temperature zones of the plasma nozzles can produce plasma of different temperatures to meet the needs of the segmented temperature control mode. In the plasma rough purification stage, the segmented temperature control mode is adopted, including the first temperature zone (the inlet section), the second temperature zone (the core section) and the third temperature zone (the outlet section);

[0049] First temperature zone: temperature is 3000-5000 ℃, this temperature zone is mainly used for removing organic matter and volatile metal impurities adsorbed on the surface of the quartz sand. Organic matter will decompose at high temperature to generate small molecule gas and volatilize; volatile metal impurities will also gasify in this temperature range, thereby separating from the surface of the quartz sand;

[0050] Second temperature zone: temperature is 8000-12000 ℃, the gasification of metal oxides is driven by thermodynamic equilibrium. In this high-temperature environment, the metal oxides on the surface of the quartz sand reach the gasification point and are converted into gaseous form, further separating from the quartz sand;

[0051] The third temperature zone has a temperature of 2000-3000°C, which is used to inhibit sintering of the quartz sand particles, prevent the quartz sand from melting and sticking at high temperature, maintain the independence of the particles and good particle size distribution, and make the gasified metal impurities completely condense in the tail gas system, facilitating subsequent tail gas treatment and metal impurity recovery;

[0052] The outlet quartz sand is rapidly cooled by liquid nitrogen or circulating cooling water. When the quartz sand particles come out of the high-temperature reaction cavity, rapid cooling can prevent the impurities from being adsorbed onto the surface of the quartz sand particles again during the cooling process, thereby ensuring the purification effect;

[0053] The argon plasma is introduced for suspension heating treatment, and the suspension heating treatment time is 0.1-10s. The argon plasma has the characteristics of high temperature and high energy density, and can instantaneously heat the quartz sand particles. The surface metal impurities undergo physical and chemical changes, such as gasification and decomposition, at high temperature, thereby realizing the removal of the surface metal impurities;

[0054] The hydrogen-oxygen mixed gas plasma is used for secondary treatment, and the treatment time is 0.5-5s. The hydrogen-oxygen mixed gas plasma has stronger oxidizing property and activity, and can further remove the residual impurities in the quartz sand, especially those deep-level impurities that are not completely removed in the rough purification stage. The plasma torch has a working frequency of 10-50kHz and a voltage of 5-20kV. By adjusting these parameters, the energy and activity of the plasma can be controlled, so that the plasma can more effectively react with the impurities in the quartz sand. The pressure in the reaction cavity is 0.1-1MPa, and the oxygen partial pressure in the reaction cavity is ≤0.3MPa, so as to inhibit the oxidation. The appropriate pressure condition can ensure the stability of the plasma and the smooth progress of the reaction, and the control of the oxygen partial pressure can prevent the quartz sand (mainly composed of silicon dioxide) from being excessively oxidized during the treatment process, thereby affecting the quality and performance of the product;

[0055] The quartz sand after the reaction is rapidly cooled to room temperature. Rapid cooling can not only prevent secondary adsorption of impurities, but also quickly fix the physical state of the quartz sand particles, thereby maintaining the performance after purification;

[0056] The high-purity quartz sand product with a particle size of 100-150μm is selected by screening. The screening can remove particles with a particle size that does not meet the requirements, thereby ensuring that the product has a uniform particle size distribution and meets the index requirement of a particle size distribution D50=120±10μm of the high-purity quartz sand product;

[0057] The condenser has a condensing temperature of -50°C to 50°C. Within this temperature range, the gasified metal oxides are condensed into solid or liquid forms, thereby being collected and achieving the preliminary separation of the metal oxides from the gas;

[0058] The direct current high voltage electric field has a voltage of 5-50 kV, and different metal elements are recovered by grading according to the ionization energy difference; different metal elements have different ionization energies, and under the action of the high voltage electric field, the charged metal ions are deflected to different degrees according to their charge amount and mass, so that the different metal elements are recovered by grading, and the recovery and utilization rate of metal resources is improved;

[0059] The deoxidation tower is filled with a palladium-based catalyst, and the residual oxygen and hydrogen are reacted to generate water, which is removed. The palladium-based catalyst can catalyze the reaction of hydrogen and oxygen to generate water vapor, which is then discharged by a suitable method, thereby removing the residual oxygen in the tail gas, so that the remaining gas can be recycled to the plasma generator after being deoxidized and dried, realizing the recycling of resources and the environmental protection of the process.

[0060] The purity index of the high-purity quartz sand product is: the content of silicon dioxide is ≥99.998%; the total metal impurity content is ≤10 ppm; and the hydroxyl content is ≤3 ppm. Through the above series of plasma preparation processes, including raw material pretreatment to remove surface easily removable impurities, plasma rough purification and deep purification to remove surface and internal impurities, tail gas closed loop treatment to prevent secondary pollution of impurities, etc., the content of metal impurities, hydroxyl and other impurities in the quartz sand can be effectively reduced, the purity of silicon dioxide is improved, thereby meeting the high-purity index requirements of the high-purity quartz sand product, and it can be widely used in high-end fields such as semiconductors, photovoltaics, optical fibers, etc.

[0061] Through the above technical scheme, the ordinary quartz sand is crushed to a particle size of 50-200 μm, the particle surface area is increased, the subsequent treatment is easier to perform, the mud and other surface easily removable impurities are removed by water washing, and the water content is ≤0.5% after drying, so as to avoid the influence of water on the subsequent plasma treatment effect and lay a foundation for deep purification.

[0062] The vertical gas-solid fluidized bed reactor is adopted, the spiral flow channel reaction cavity prolongs the plasma exposure path of the quartz sand particles, so that the argon plasma can fully contact the particle surface within the suspension heating treatment time of 0.1-10 s, and the surface metal impurities are effectively removed. The multi-stage plasma nozzle is arranged in layers along the axial direction of the spiral flow channel, temperature gradient control is realized, and the first temperature zone (3000-5000 ℃) removes the surface adsorbed organic matter and volatile metal impurities, and the second temperature zone (8000-12000 ℃) further removes the deep impurities by thermodynamic equilibrium driving metal oxides to gasify.

[0063] The hydrogen-oxygen mixed gas plasma secondary treatment is 0.5-5s, and the strong oxidation and activity thereof are used to remove the impurities remaining after the rough purification, the plasma torch working frequency is 10-50kHz, the voltage is 5-20kV, the pressure in the reaction cavity is 0.1-1MPa, and the oxygen partial pressure is ≤0.3MPa, which can ensure effective removal of impurities and inhibit excessive oxidation to ensure product purity; the conditions are accurately controlled in the whole process, which effectively reduces the introduction and residual of hydroxyl, so that the hydroxyl content of the product is ≤3ppm, meeting the demand of high-end field for low-hydroxyl-content quartz sand;

[0064] After cooling, the product with a particle size of 100-150μm is selected by screening, so that the particle size distribution D50 is 120±10μm, which ensures the uniformity of the particle size of the product and improves the quality and consistency of the product, meeting the strict requirements of different application scenarios for the particle size of quartz sand;

[0065] The spiral flow channel reaction cavity: the unique spiral flow channel design with a pitch of 0.5-2 times the diameter of the reaction cavity ensures that the particle residence time distribution index (PDI) is ≤0.3, so that the particles stay in the reaction cavity for an even time, improving the reaction efficiency of the plasma and the particles and shortening the treatment time; liquid nitrogen or circulating cooling water is used for quenching the outlet quartz sand, preventing secondary adsorption of impurities, quickly fixing the physical state of the quartz sand, reducing the cooling time, and improving the overall process efficiency;

[0066] In the hydrogen-oxygen mixed gas plasma treatment stage, by accurately controlling the plasma torch working frequency, voltage, pressure in the reaction cavity and oxygen partial pressure and other parameters, the reaction conditions are optimized under the premise of ensuring the purification effect, the treatment speed is improved, and high-efficiency purification is realized;

[0067] The gaseous metal oxide is collected by the condenser at a temperature of-50℃ to 50℃, realizing the preliminary separation of the metal oxide and the gas, and providing convenience for subsequent metal recovery; the electric field separator uses a direct-current high-voltage electric field with a voltage of 5-50kV, and the metal elements are graded and recovered according to the difference in ionization energy, improving the recovery rate of metal resources, reducing the production cost, and reducing the pollution of metal impurities to the environment; the remaining gas is catalyzed by a palladium-based catalyst in a deoxidizing tower to remove the residual oxygen and hydrogen after reacting to form water, realizing the recycling of the deoxidized and dried gas to the plasma generator, saving gas resources and reducing process operation cost;

[0068] The boron nitride has good high-temperature resistance and corrosion resistance, and coating on the surface of the spiral flow channel can protect the reaction cavity from being eroded by plasma and high temperature, prolong the service life of the reactor, and ensure long-term stable operation of the process; the multi-stage plasma nozzle is arranged in layers along the axial direction of the spiral flow channel, temperature gradient control is realized, the temperature distribution in the reaction cavity is uniform, local overheating or overcooling phenomenon is avoided, and the stability and controllability of the process are improved.

[0069] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, the scope of the present application being defined by the appended claims and their equivalents.

Claims

1. A plasma preparation process for high-purity quartz sand, characterized in that: include: Step 1: Pre-treat the raw materials, crush the ordinary quartz sand to a particle size of 50-200μm, wash it with water to remove the sediment, and then dry it to a moisture content of ≤0.5%; Step 2: Plasma-purify the washed quartz sand. The pretreated quartz sand is injected into a vertical gas-solid fluidized bed reactor and subjected to suspension heating treatment by introducing argon plasma. The suspension heating treatment lasts for 0.1 to 10 seconds to remove surface metal impurities. Step 3: Plasma deep purification of the quartz sand raw material, and secondary treatment with hydrogen and oxygen mixed gas plasma, the treatment time is 0.5 to 5 seconds; Step 4: Cooling and screening the quartz sand, quickly cooling the reacted quartz sand to room temperature, and screening to select high-purity quartz sand products with a particle size of 100-150 μm; Step 5: Close the loop of the tail gas to collect the metal oxide impurities in the reaction tail gas, separate and recover the metal elements through the electric field, and then deoxidize and dry the remaining gas and recycle it back to the plasma generator.

2. The plasma preparation process for high-purity quartz sand according to claim 1, characterized in that: The vertical gas-solid fluidized bed reactor includes a spiral flow channel reaction chamber, a multi-stage plasma nozzle and a rapid cooling sleeve. The spiral flow channel reaction chamber is used to extend the plasma exposure path of quartz sand particles; the multi-stage plasma nozzle is used to be arranged in axial layers along the spiral flow channel reaction chamber; the rapid cooling sleeve uses liquid nitrogen or circulating cooling water to rapidly cool the outlet quartz sand.

3. The plasma preparation process for high-purity quartz sand according to claim 1, characterized in that: The processing parameters of the hydrogen-oxygen mixed gas plasma treatment stage are as follows: the plasma torch operating frequency is 10-50 kHz, the voltage is 5-20 kV; the pressure in the reaction chamber is 0.1-1 MPa, and the oxygen partial pressure in the reaction chamber is ≤0.3 MPa.

4. The plasma preparation process for high-purity quartz sand according to claim 1, characterized in that: In step five, the exhaust gas closed-loop treatment step further includes: Step 1: collecting the vaporized metal oxides through a condenser, wherein the condensation temperature of the condenser is -50°C to 50°C; Step 2: The electric field separator uses a DC high voltage electric field with a voltage of 5-50kV, and performs graded recovery according to the difference in ionization energy of the metal elements; Step 3: The deoxidation tower is filled with a palladium-based catalyst to react the residual oxygen with hydrogen to generate water and then remove it.

5. The plasma preparation process for high-purity quartz sand according to claim 1, characterized in that: The purity indicators of the high-purity quartz sand product are: silicon dioxide content ≥99.998%; total metal impurity content ≤10ppm; hydroxyl content ≤3ppm; particle size distribution D50 =120±10μm.

6. The plasma preparation process for high-purity quartz sand according to claim 1, characterized in that: In step 2, the plasma rough purification stage adopts a segmented temperature control mode, which includes a first temperature zone, a second temperature zone and a third temperature zone. The first temperature zone is the inlet section, the second temperature zone is the core section, and the third temperature zone is the outlet section.

7. The plasma preparation process for high-purity quartz sand according to claim 6, characterized in that: The temperature of the first temperature zone is 3000-5000°C to remove organic matter and volatile metal impurities adsorbed on the surface; the temperature of the second temperature zone is 8000-12000°C to promote the gasification of metal oxides through thermodynamic equilibrium; the temperature of the third temperature zone is 2000-3000°C, and the third temperature zone is used to inhibit the sintering of quartz sand particles and completely condense the vaporized metal impurities in the exhaust system.

8. The plasma preparation process for high-purity quartz sand according to claim 2, characterized in that: The pitch of the spiral flow channel of the spiral flow channel reaction chamber is 0.5-2 times the diameter of the reaction chamber; the surface of the spiral flow channel is coated with boron nitride.

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