High-purity quartz sand purification method based on microwave synergistic gradient high-voltage electric field

Abstract

The invention discloses a high-purity quartz sand purification method based on a microwave synergistic gradient high-voltage electric field, raw ore is pretreated and purified to obtain a semi-finished product of the high-purity quartz sand, and the obtained semi-finished product of the high-purity quartz sand is treated by the following steps: S1, microwave activation; the semi-finished product of the high-purity quartz sand is subjected to two-stage microwave activation through a microwave rotary furnace, so that micron / nano-scale impurity particles in the semi-finished product of the high-purity quartz sand are subjected to pre-electrification and magnetization treatment; and S2, gradient high-voltage electric field impurity removal: constructing a multi-stage gradient high-voltage electric field, introducing the quartz sand treated in the step S1 into the multi-stage gradient high-voltage electric field, and directionally removing micron / nano-scale impurity particles attached to the surface of the quartz sand through the electric field intensity of each stage of gradient high-voltage electric field and the transportation direction of the quartz sand in the gradient high-voltage electric field to obtain a high-purity quartz sand finished product. And micron / nano-scale impurity particles generated in the purification process are subjected to targeted impurity removal.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-purity quartz sand preparation, and particularly relates to a high-purity quartz sand purification method based on microwave cooperation with a gradient high-voltage electric field, and specifically relates to a purification method for removing micron / nanometer level impurity particles on the surface of quartz sand through microwave activation pretreatment and synergistic effect of a multi-stage gradient high-voltage electric field. BACKGROUND

[0002] High-purity quartz sand is a core basic material in high-tech fields such as photovoltaics, semiconductors, and optical fiber communication, and the purity thereof directly determines the performance and reliability of terminal products. Photovoltaic-grade high-purity quartz sand requires SiO2 content ≥ 99.998%, and Fe ≤ 0.5 ppm; semiconductor-grade high-purity quartz sand requires SiO2 ≥ 99.998%, and is more stringent for single impurity elements other than Al, such as Fe < 0.1 ppm, and the impurity element content of high-purity quartz directly determines the quality of large-size semiconductor-grade crucibles for wafer production. At present, China basically relies on imports from the United States for semiconductor-grade high-purity quartz sand, and mainly relies on imports from Japan for semiconductor-grade synthetic quartz sand, and the realization of the domestic substitution of semiconductor-grade high-purity quartz sand is an important task for solving the national strategic demand.

[0003] There are generally various impurities in natural quartz ore, mainly including three types of recognized impurity forms, namely lattice impurities (Al, Fe, Ti, etc.), inclusion impurities (fluid inclusions and mineral inclusions), and associated mineral impurities (rutile, feldspar, mica, etc.). Existing purification technologies mainly use process combinations such as sorting, crushing, sand making, magnetic separation, flotation, acid leaching, gravity separation, and high-temperature chlorination to purify these three types of impurity minerals, and obtain photovoltaic-grade (4N8-grade) high-purity quartz sand; however, various impurities caused by the production process are also included in the industrialization, such as a large number of micron / nanometer level Fe-containing impurity particles that are tightly attached to the surface of high-purity quartz sand after the friction between the magnetic disk of a magnetic separator and quartz sand, and after the reaction of crusher debris with acid; such impurities exist in all domestic and foreign semiconductor-grade and photovoltaic-grade high-purity quartz sand products, and are the main form of Fe impurity elements in high-end high-purity quartz sand; the difference between domestic and foreign technical capabilities lies in the fact that imported semiconductor-grade high-purity quartz sand can better remove such micron / nanometer level impurity particles, and achieve an Fe < 0.1 ppm index, In the prior art, CN115321544A discloses an ultrasonic vibration-electrosorption cleaning method for high-purity quartz sand, which uses ultrasonic vibration to assist in separating metal ions and charged particles on the surface of quartz sand, and simultaneously uses an electric adsorption technology to adsorb metal ions, charged particles, and the like in the solution to the electrodes on both sides, and the method mainly removes the metal ions and charged ions adsorbed on the surface of high-purity quartz sand, and it is difficult to act on micron / nanometer level impurity particles that have not been activated, and therefore can only achieve an Fe > 0.2 ppm.

[0004] As CN120205338A discloses a microwave-conductivity assisted flotation method, by the way of conductivity assisted flotation, the alkali metal impurities inside the quartz sand after pre-treatment such as roasting are transferred along the micro-cracks or quartz surface under the influence of the external current / electric field, and the reagent molecules are adsorbed on the new charge area of the quartz surface by electrostatic action under the assistance of microwaves, and then deep purification is achieved, but deep flotation can only target mineral impurity particles, and it is difficult to remove micron / nano-level impurity particles.

[0005] As CN119076205A discloses a microwave magnetization roasting-gradient magnetic separation iron removal method and purification process for quartz ore, the Fe gas-liquid inclusions inside the quartz sand are evaporated and converted into magnetic substances at a specific temperature by microwave heating, and part of the gas-liquid inclusions are broken under internal pressure; then gradient magnetic separation is performed to remove various magnetic impurity minerals and micro-fine magnetic inclusions inside the quartz sand, but it mainly targets the gas-liquid inclusions inside the quartz sand and the associated minerals outside, and has no targeted impurity removal effect on micron / nano-level impurity particles.

[0006] The above existing technical solutions have no targeted impurity removal effect on micron / nano-level impurity particles generated in the purification process, and cannot well achieve deep impurity removal of micron / nano-level impurity particles attached to the surface of high-purity quartz sand. SUMMARY

[0007] Therefore, the present application provides a high-purity quartz sand purification method based on microwave cooperation with gradient high-voltage electric field, which can achieve deep impurity removal of micron / nano-level impurity particles attached to the surface of high-purity quartz sand, and can obtain ultra-high-purity quartz sand with SiO2 content ≥ 99.998% and Fe < 0.1 ppm by cooperating with other purification procedures.

[0008] The technical solution adopted by the present application to solve the above technical problems is: a high-purity quartz sand purification method based on microwave cooperation with gradient high-voltage electric field, the raw ore is pretreated and purified to obtain a semi-finished product of high-purity quartz sand, and the obtained semi-finished product of high-purity quartz sand is processed as follows: S1, microwave activation, the semi-finished product of high-purity quartz sand is subjected to two-stage microwave activation by a microwave rotary furnace to pre-charge and magnetize the micron / nano-level impurity particles in the semi-finished product of high-purity quartz sand, wherein the first-stage microwave activation process utilizes the selective heating characteristics of microwaves to form a local high-temperature area on the surface of the quartz sand, causing the micron / nano-level impurity particles to undergo lattice distortion or surface desorption, and the second-stage microwave activation process drives the micron / nano-level impurity particles to undergo oxidation-reduction reaction through thermodynamics, Inert protective gas is introduced during the microwave activation and cooling stages, and ultrasonic vibration is performed during the cooling stage; S2, gradient high-voltage electric field impurity removal, a multi-stage gradient high-voltage electric field is constructed, and the quartz sand treated by S1 is passed into the multi-stage gradient high-voltage electric field, the micron / nanometer level impurity particles attached to the surface of the quartz sand are removed through the electric field strength of each stage of the gradient high-voltage electric field and the transport direction of the quartz sand in the gradient high-voltage electric field, and a high-purity quartz sand product is obtained.

[0009] Preferably, the pretreatment includes cleaning, secondary crushing, calcining, water quenching, and sand making of the raw ore to obtain the quartz raw sand, wherein the cleaning is high-pressure water gun washing of the raw ore to remove the attached clay minerals, and the purification treatment includes magnetic separation, acid leaching, flotation, drying, high-temperature chlorination, Magnetic separation, the quartz raw sand obtained after the pretreatment is put into a magnetic separator for gradient magnetic separation, Acid leaching, the quartz sand treated by the magnetic separation is put into an acid leaching reactor to remove mineral impurities through reaction with mixed acid, Flotation, the quartz sand treated by the acid leaching is put into a flotation machine, a flotation reagent is added for flotation, and the quartz sand is rinsed after the flotation to remove residual reagents, Drying, the quartz sand treated by the flotation is preliminarily dewatered by a centrifugal machine, and then is deeply dried by a high-temperature rotary furnace, High-temperature chlorination, the quartz sand treated by the drying is put into a high-temperature chlorination reactor to react with hydrogen chloride gas at high temperature to obtain a semi-finished product of high-purity quartz sand.

[0010] Preferably, the particle size of the quartz sand obtained after the secondary crushing of the raw ore is ≤5 cm, the quartz sand after the crushing is calcined at 700-1100℃ for 5-30 min, is then put into a water tank for water quenching, and is dried after the water quenching to make sand, and the particle size of the quartz sand after the drying to make sand is in the range of 50-230 mesh.

[0011] Preferably, the gradient magnetic separation is divided into permanent magnet and electromagnetic, wherein the magnetic field strength of the permanent magnet is 0.5-1.5T, and the magnetic field strength of the electromagnetic is 2.0-3.0T.

[0012] Preferably, the acid used in the acid leaching is one or a combination of oxalic acid, hydrochloric acid, hydrofluoric acid, nitric acid, and sulfuric acid, and deionized water is added, the acid leaching temperature is 70℃-130℃, the sand / liquid ratio is 1:0.5-1:1.5, and the acid leaching time is 4h-24h.

[0013] Preferably, the flotation reagents used in the flotation operation include one or more of pH regulators, collectors, and frothers; the pH regulator is one or a mixture of several of citric acid, sulfuric acid, hydrochloric acid, and hydrofluoric acid; the collector is one or a mixture of several of sodium dodecylhydroxylamine, butyl ammonium black medicine, salicylhydroxamic acid, and methyl isobutyl carbinol; the frother is pine oil or MIBC (methyl isobutyl ketone); and the pulp concentration in the flotation is controlled to be 25-50%.

[0014] Preferably, the centrifugal dewatering speed of the centrifuge in the drying treatment is 1000-3500 r / min, the moisture content of the feed is 15-30%, and the dewatering time is 3-8 min; the temperature of the high-temperature rotary furnace in the drying treatment is 600-1000℃, and the drying time is 10-40 min.

[0015] Preferably, the temperature of the high-temperature chlorination is 1000-1300℃, the high-temperature chlorination time is 2-7h, and the flow rate of the hydrogen chloride gas introduced into the high-temperature chlorination reaction furnace is 0.2-2L / min.

[0016] Preferably, the microwave activation in step S1 is divided into two stages, the first-stage microwave activation has a power density of 500-1500 W / kg and a temperature of 350-650℃, and lasts for 10-30 minutes; the second-stage microwave activation has a power density of 1500-2500 W / kg and a temperature of 900-1100℃, and lasts for 10-30 minutes; the inert protective gas in step S1 is one or a combination of argon and nitrogen; the ultrasonic vibration frequency in step S1 is 50kHz–120kHz, and the vibration time is 1-20min.

[0017] Preferably, the multi-stage gradient high-voltage electric field constructed in step S2 is a two-stage gradient high-voltage electric field, the first-stage gradient high-voltage electric field has a strength of 20-50 kV / m, the quartz sand transportation direction is vertical rapid falling body, and is suitable for micrometer / nanometer impurity particles with high magnetic response; the second-stage gradient high-voltage electric field has a strength of 40-80 kV / m, the quartz sand transportation direction is horizontal, and is suitable for micrometer / nanometer impurity particles with low magnetic response; and the gas medium used in the gradient high-voltage electric field impurity removal is one or a combination of several of dry air, nitrogen, and argon.

[0018] Compared with the prior art, the gain effect of the application is that the application adopts two-stage microwave activation process to realize directional regulation of micron / nano-level impurity particles on the surface of quartz sand, wherein the first-stage microwave activation process utilizes the selective heating characteristics of microwaves to form a local high-temperature area on the surface of quartz sand, so that the micron / nano-level impurity particles are subjected to lattice distortion or surface desorption, so as to enhance the surface charge density and electrostatic response ability thereof, thereby providing a basis for subsequent electrostatic separation, and the second-stage microwave activation process is aimed at the most common micron / nano-level impurity particles containing Fe (main components are Fe, Mn, Cr, etc.) on the surface of quartz sand particles, and generates magnetic phases such as Fe3O4 or FeO with magnetism through thermodynamic driving of oxidation-reduction reaction of the impurity particles, so as to improve the magnetic response characteristics of nano-level Fe impurities, and enable the impurities to be separated efficiently through the magneto-electric synergistic effect in a subsequent high-voltage electric field.

[0019] During the microwave activation and cooling process, high-purity inert protective gas (such as argon or nitrogen) is introduced into the system to maintain a closed atmosphere environment, so as to effectively inhibit the charge relaxation and secondary oxidation reaction of the micron / nano-level impurity particles due to the change of oxygen partial pressure in the cooling process, and ensure that the stability and charge characteristics of the magnetic conversion product are not destroyed; the quartz sand and the impurities attached to the surface are physically separated by using ultrasonic vibration in the cooling stage, so as to make good pretreatment for subsequent high-point electric field directional impurity removal.

[0020] In the multi-stage gradient high-voltage electric field process, the micron / nano-level impurity particles are removed by stages through the differentiation of electric field intensity and direction, which are aimed at the high-magnetic-response Fe3O4 or FeO type magnetic micron / nano-level impurity particles and the low-magnetic-response or non-magnetic micron / nano-level impurity particles, respectively, inert gas is continuously introduced during the high-voltage electric field action process to prevent the decrease of electrostatic adsorption force caused by water vapor adsorption, and ensure the stability of the separation process.

[0021] Through the combination of the above microwave activation treatment and the multi-stage gradient high-voltage electric field impurity removal process, the removal efficiency of micron / nano-level impurity particles is significantly improved, and the residual amount of Fe element after treatment can be as low as 0.01 ppm. BRIEF DESCRIPTION OF DRAWINGS

[0022] The application will be described in further detail below with reference to the drawings and preferred embodiments, but those skilled in the art will appreciate that the drawings are only drawn for the purpose of explaining the preferred embodiments and therefore should not be regarded as limiting the scope of the application. In addition, unless specifically indicated, the drawings only schematically represent the composition or structure of the described objects and can include exaggerated displays, and the drawings are not necessarily drawn to scale.

[0023] Figure 1 For Example 1 - quartz sand surface after high-temperature chlorination; Figure 2Example 1 - Quartz sand after purification by microwave activation in combination with a gradient high-voltage electric field; Figure 3 Example 2 - Quartz sand surface after high-temperature chlorination; Figure 4 Example 2 - Quartz sand after purification by microwave activation in combination with a gradient high-voltage electric field; Figure 5 Flow chart of the purification method. DETAILED DESCRIPTION

[0024] Preferred embodiments of the present application will be described in detail below with reference to the attached drawings. Those skilled in the art will appreciate that the description is merely descriptive, exemplary and should not be interpreted as limiting the scope of protection of the present application.

[0025] It should be noted that similar reference numerals refer to similar items in the following drawings, and therefore, once an item is defined in one drawing, it can no longer be defined and explained in subsequent drawings.

[0026] Example 1 :

[0027] Figure 5 As shown, a high-purity quartz sand purification method based on microwave in combination with a gradient high-voltage electric field, the raw ore is pretreated and purified to obtain high-purity quartz sand semi-finished product, the obtained high-purity quartz sand semi-finished product is processed as follows: S1, microwave activation, the high-purity quartz sand semi-finished product is subjected to two-stage microwave activation in a microwave rotary furnace to pre-charge and magnetize the micron / nanometer level impurity particles in the high-purity quartz sand semi-finished product, wherein the first-stage microwave activation process utilizes the selective heating characteristics of microwaves to form a local high-temperature area on the surface of the quartz sand, causing the micron / nanometer level impurity particles to undergo lattice distortion or surface desorption, and the second-stage microwave activation process drives the micron / nanometer level impurity particles to undergo oxidation-reduction reaction through thermodynamics; inert protective gas is introduced during the microwave activation and the cooling stage after activation, and ultrasonic vibration is performed during the cooling stage.

[0028] S2, gradient high-voltage electric field impurity removal: a multi-stage gradient high-voltage electric field is constructed, the quartz sand after S1 processing is introduced into the multi-stage gradient high-voltage electric field, the micron / nanometer level impurity particles attached to the surface of the quartz sand are removed through the electric field strength of each stage of the gradient high-voltage electric field and the transport direction of the quartz sand in the gradient high-voltage electric field, and a high-purity quartz sand product is obtained.

[0029] The application adopts two-stage microwave activation process to realize directional regulation of micron / nano-level impurity particles on the surface of quartz sand. In the first stage of microwave activation process, the selective heating characteristics of microwave are used to form a local high temperature area on the surface of quartz sand, so that the micron / nano-level impurity particles are subjected to lattice distortion or surface desorption, so as to enhance the surface charge density and electrostatic response ability, and provide a basis for subsequent electrostatic separation. In the second stage of microwave activation process, the most common Fe-containing micron / nano-level impurity particles (main components are Fe, Mn, Cr, etc.) on the surface of quartz sand particles are subjected to oxidation-reduction reaction driven by thermodynamics to generate magnetic phases such as Fe3O4 or FeO with magnetism, so as to improve the magnetic response characteristics of nano-level Fe impurities, and enable them to be separated efficiently through magneto-electric synergistic effect in the subsequent high-voltage electric field.

[0030] During the microwave activation and cooling process, high-purity inert protective gas (such as argon or nitrogen) is introduced into the system to maintain a closed atmosphere environment, effectively inhibit the charge relaxation and secondary oxidation reaction of micron / nano-level impurity particles caused by the change of oxygen partial pressure during the cooling process, and ensure the stability and charge characteristics of the magnetic conversion product are not damaged; ultrasonic vibration is used in the cooling stage to physically separate the quartz sand and the impurities attached to the surface, and to make good pretreatment for the subsequent high-point electric field directional impurity removal.

[0031] In the multi-stage gradient high-voltage electric field process, the differences in electric field strength of each stage of gradient high-voltage electric field and the transportation direction of quartz sand in the gradient high-voltage electric field are used to respectively target Fe3O4 or FeO-containing magnetic micron / nano-level impurity particles with high magnetic response and micron / nano-level impurity particles with low magnetic response or non-magnetic, so as to realize the graded removal of micron / nano-level impurity particles. Inert gas is continuously introduced during the action of high-voltage electric field to prevent the decrease of electrostatic adsorption force caused by water vapor adsorption, and to ensure the stability of the separation process.

[0032] Through the combination of the above microwave activation treatment and multi-stage gradient high-voltage electric field impurity removal process, the removal efficiency of micron / nano-level impurity particles is significantly improved, and the residual amount of Fe element after treatment can be as low as 0.01 ppm.

[0033] The microwave activation in step S1 is divided into two stages. The first stage microwave activation has a power density of 500-1500 W / kg and a temperature of 350-650°C, and the duration is 10-30 minutes. The microwave selective heating characteristics are used to form a local high temperature area on the surface of the quartz sand, so that the micron / nano-sized impurity particles are subjected to lattice distortion or surface desorption. The second stage microwave activation has a power density of 1500-2500 W / kg and a temperature of 900-1100°C, and the duration is 10-30 minutes. The microwave activation is aimed at the most common Fe-containing micron / nano-sized impurities (mainly composed of Fe, Mn, Cr, etc.) on the surface of the quartz sand particles. Through thermodynamic driving, the oxidation-reduction reaction is generated to generate magnetic phases such as Fe3O4 or FeO, thereby improving the magnetic response characteristics of the nano-sized Fe impurities. The inert protective gas in step S1 is one of argon, nitrogen, or a combination of the two. The frequency of the ultrasonic vibration in step S1 is 50 kHz-120 kHz, and the vibration time is 1-20 min.

[0034] The multi-stage gradient high-voltage electric field constructed in step S2 is a two-stage gradient high-voltage electric field. The first stage gradient high-voltage electric field has a strength of 20-50 kV / m, and the quartz sand transportation direction is vertical rapid falling body, which is suitable for micron / nano-sized impurity particles with high magnetic response. The second stage gradient high-voltage electric field has a strength of 40-80 kV / m, and the quartz sand transportation direction is horizontal, which is suitable for micron / nano-sized impurity particles with low magnetic response. The gas medium used in the gradient high-voltage electric field impurity removal is one or a combination of several of dry air, nitrogen, and argon.

[0035] The pretreatment includes cleaning, two-stage crushing, calcination, water quenching, and sand making of the raw ore to obtain quartz raw sand. The cleaning is high-pressure water gun washing of the raw ore to remove attached clay minerals. The purification treatment includes magnetic separation, acid leaching, flotation, drying, and high-temperature chlorination.

[0036] Magnetic separation: The quartz raw sand obtained after pretreatment is put into a magnetic separator for gradient magnetic separation.

[0037] Acid leaching: The quartz sand after magnetic separation is put into an acid leaching reactor to remove mineral impurities through reaction with mixed acid.

[0038] Flotation: The quartz sand after acid leaching is put into a flotation machine, flotation reagents are added for flotation, and the quartz sand is rinsed after flotation to remove residual reagents.

[0039] Drying: The quartz sand after flotation is preliminarily dewatered by a centrifugal machine, and then deeply dried by a high-temperature rotary furnace.

[0040] High temperature chlorination, the quartz sand after drying treatment is put into high temperature chlorination reaction furnace, and reacts with hydrogen chloride gas at high temperature to obtain high purity quartz sand semi-finished product.

[0041] The quartz sand obtained after the primary ore is crushed by the secondary crusher has a particle size of ≤5 cm. The quartz sand after crushing is calcined at 700-1100℃ for 5-30 min, then is put into a water tank for water quenching, and is dried to obtain sand. The particle size of the quartz sand after drying is in the range of 50-230 mesh.

[0042] The gradient magnetic separation includes permanent magnet and electromagnetic. The magnetic field strength of the first stage permanent magnet is 0.5-1.5T, and the magnetic field strength of the second stage electromagnetic is 2.0-3.0T.

[0043] The acid used in the acid leaching treatment is one or a combination of oxalic acid, hydrochloric acid, hydrofluoric acid, nitric acid, and sulfuric acid, and deionized water is added. The acid leaching temperature is 70℃~130℃, the sand / liquid ratio is 1:0.5~1:1.5, and the acid leaching time is 4h~24h.

[0044] The flotation reagents used in the flotation operation include one or more of pH adjusters, collectors, and frothers. The pH adjuster is one or a mixture of citric acid, sulfuric acid, hydrochloric acid, and hydrofluoric acid. The collector is one or a mixture of sodium dodecylhydroxylamine, butyl ammonium black medicine, salicylhydroxamic acid, and methyl isobutyl carbinol. The frother is pine oil or MIBC (methyl isobutyl ketone). The pulp concentration in the flotation is controlled to be 25-50%.

[0045] In the drying treatment, the centrifuge has a centrifugal dewatering speed of 1000~3500 r / min, the feed moisture content is 15~30%, and the dewatering time is 3~8 min. In the drying treatment, the high temperature rotary furnace has a temperature of 600~1000℃, and the drying time is 10~40min.

[0046] In the high temperature chlorination, the temperature is 1000-1300℃, the high temperature chlorination time is 2-7h, and the flow rate of the hydrogen chloride gas introduced into the high temperature chlorination reaction furnace is 0.2-2L / min.

[0047] In this embodiment, the granite pegmatite in Andhra Pradesh, India is used as the experimental raw material, the primary ore has been sorted, and the quartz content is about 70%. The specific steps of the purification treatment experiment are as follows: Step one, the primary ore is pretreated to obtain quartz raw sand with a particle size of 50-160 mesh.

[0048] Step two, magnetic separation, the quartz raw sand is put into a magnetic separator for gradient magnetic separation. The magnetic field strength of the first stage permanent magnet is 1.5T, and the magnetic field strength of the second stage electromagnetic is 2.5T.

[0049] Step three, acid leaching, after the magnetic separation of quartz sand, into the acid leaching reactor, by the reaction with the mixed acid solution to remove mineral impurities; acid leaching of the acid used is concentrated hydrofluoric acid: concentrated sulfuric acid: deionized water = 3:1 mixed acid, acid leaching temperature is 100℃, sand / liquid ratio is 1:0.5, acid leaching time is 20h.

[0050] Step four, flotation, after the acid leaching of quartz sand, into the flotation machine for flotation, slurry concentration is 30%, pH regulator is a mixture of citric acid and hydrochloric acid, collector is sodium dodecyl hydroxamic acid, butyl ammonium black drug, foaming agent is pine oil, after 3 times of flotation, rinse 5 times.

[0051] Step five, drying, after the flotation of quartz sand, through the centrifuge for preliminary dehydration, centrifugal dehydration speed is 1500 r / min, the moisture content of the feed is about 16~18%, dehydration time is 5 min; then through the high temperature rotary furnace at 800℃ for deep drying, drying time is 30 min.

[0052] Step six, high temperature chlorination, after the drying of high purity quartz sand, high temperature chlorination, temperature is 1000℃, chlorination holding time is 2h, the flow rate of introduced hydrogen chloride gas is 0.5 L / min.

[0053] Step seven, microwave activation, after the high temperature chlorination of quartz sand, through the microwave rotary furnace for two stage microwave activation, pre-charging and magnetizing treatment of micron / nanometer level impurity particles, the first stage microwave activation power density is 1200 W / kg, temperature is 550℃, duration 10 min; the second stage microwave activation power density is 1800 W / kg, temperature is 950℃, duration 10 min. In the process of microwave activation and cooling, argon gas is introduced as a protective gas; in the cooling stage, the use of ultrasonic vibration for the pretreatment of physical separation of high purity quartz sand and surface attached impurities, ultrasonic frequency is 50 kHz, vibration time is 10 min.

[0054] Step eight, gradient high voltage electric field impurity removal, after the microwave activation of quartz sand, into the transmission channel with high voltage electric field, the first stage gradient high voltage electric field strength is 20 kV / m, the quartz sand transport direction is vertical falling body, the second stage gradient high voltage electric field strength is 40 kV / m, the quartz sand transport direction is horizontal, the gas medium is dry air.

[0055] The above experiment after purification treatment, the surface of the obtained high purity quartz sand nano particles are observed and compared (SEM-EDS, scanning electron microscope-X ray energy spectrometer), the results are shown in Figure 1 , Figure 2 : there are a large number of micron / nanometer level impurity particles on the surface of the quartz sand after high temperature chlorinationFigure 1 ), while the quartz sand purified by microwave activation combined with gradient high-voltage electric field (GHEF) (GHEF-2) Figure 2 ) has almost no micron / nanometer level impurity particles on the surface; the impurity element content in the high-purity quartz sand is analyzed by ICP-OES (inductively coupled plasma spectrometry), and the comparison results are shown in Table 1; after the microwave activation combined with gradient high-voltage electric field purification, the total amount of impurity elements decreases by 1.08 ppm, and the Fe element decreases from 0.30 ppm to 0.03 ppm, reaching the impurity index of semiconductor-grade quartz sand.

[0056] Table 1 ICP detection results of high-purity quartz sand in Example 1 (unit: ppm) Al B Ba Ca Cr Cu Fe Ge K Li Mg Mn Na Ni P Ti Zr Sum After high temperature chlorination of Example 1 11.83 0.11 0.05 1.02 0.01 0.00 0.30 1.02 0.19 0.44 0.00 0.01 0.09 0.00 0.90 1.45 0.30 17.72 Final product sand of Example 1 11.56 0.07 0.04 0.85 0.00 0.00 0.03 1.00 0.04 0.44 0.00 0.00 0.08 0.00 0.80 1.44 0.29 16.64 Example 2:

[0057] Compared with the purification experiment of Example 1, the purification experiment of this example 2 only adjusts the intensity of the gradient high-voltage electric field, the intensity of the first gradient high-voltage electric field is 30 kV / m, and the intensity of the second gradient high-voltage electric field is 50 kV / m, and the other steps and methods remain the same as those of Example 1, the same batch of test raw materials is used, and the same method is used for characterization. The results show that, Figure 3 show that the micron / nanometer level impurity particles on the surface of the quartz sand are more common with Fe impurities, Figure 4 show that almost no impurities are found on the surface of the quartz sand purified by microwave activation combined with gradient high-voltage electric field; the comparison results of the impurity content of the quartz sand are shown in Table 2; after the microwave activation combined with gradient high-voltage electric field purification, the total amount of impurity elements decreases by 1.38 ppm, and the Fe element decreases from 0.34 ppm to 0.02 ppm, reaching the impurity index of semiconductor-grade quartz sand.

[0058] Table 2 ICP detection results of high-purity quartz sand in Example 2 (unit: ppm) Al B Ba Ca Cr Cu Fe Ge K Li Mg Mn Na Ni P Ti Zr Sum After high temperature chlorination of Example 2 11.29 0.12 0.06 1.15 0.01 0.00 0.34 1.15 0.21 0.46 0.00 0.01 0.10 0.00 1.01 1.63 0.34 17.88 Final product sand of Example 2 11.01 0.08 0.04 0.88 0.00 0.00 0.02 1.12 0.05 0.45 0.00 0.00 0.09 0.00 0.85 1.60 0.31 16.50 Example 3:

[0059] The test raw material is vein quartz from Altai region in Xinjiang, and the raw ore has been separated, with a quartz content of about 95%; compared with the purification experiment of Example 1, the purification experiment of this example 3 only changes the type of quartz raw ore as raw material, and the other steps and methods remain the same as those of Example 1, and the same method is used for characterization.

[0060] The comparison results of the impurity content of the quartz sand are shown in Table 3; after the microwave activation combined with gradient high-voltage electric field purification, the total amount of impurity elements decreases by 1.41 ppm, and the Fe element decreases from 0.32 ppm to 0.02 ppm, reaching the impurity index of semiconductor-grade quartz sand.

[0061] Table 3 ICP detection results of high-purity quartz sand in Example 3 (unit: ppm) Al B Ba Ca Cr Cu Fe Ge K Li Mg Mn Na Ni P Ti Zr Sum After high temperature chlorination of Example 3 9.65 0.11 0.05 0.73 0.00 0.00 0.32 0.78 0.21 0.49 0.00 0.00 0.10 0.00 0.90 1.38 0.47 15.19 Final product sand of Example 3 9.42 0.08 0.02 0.65 0.00 0.00 0.02 0.74 0.05 0.48 0.00 0.00 0.05 0.00 0.81 1.05 0.41 13.78 Example 4:

[0062] The test raw material is vein quartz in Altai region of Xinjiang, and the raw ore has been separated, with a quartz content of about 95%; compared with the purification experiment of Example 3, the purification experiment of this Example 4 only adjusts the microwave activation parameters: the power density of the first stage microwave activation is 1500 W / kg, the temperature is 650℃, and the duration is 15 min; the power density of the second stage microwave activation is 2200 W / kg, the temperature is 1050℃, and the duration is 15 min. The other steps are consistent with the experimental steps and methods of Example 3, and the same method is used for characterization.

[0063] The impurity content results of the comparative quartz sand are shown in Table 4, and after the purification by microwave activation and gradient high-voltage electric field, the total amount of impurity elements decreases by 1.80 ppm, among which the Fe element decreases from 0.34 ppm to 0.02 ppm, reaching the impurity index of semiconductor-grade quartz sand.

[0064] Table 4 ICP detection results of high-purity quartz sand in Example 4 (unit: ppm) Al B Ba Ca Cr Cu Fe Ge K Li Mg Mn Na Ni P Ti Zr Sum After high temperature chlorination of Example 4 11.29 0.12 0.06 1.15 0.01 0.00 0.34 1.15 0.21 0.46 0.00 0.01 0.10 0.00 1.01 1.63 0.34 17.88 Final product sand of Example 4 10.85 0.08 0.04 0.78 0.00 0.00 0.02 1.12 0.05 0.45 0.00 0.00 0.09 0.00 0.85 1.50 0.25 16.08 Example 5:

[0065] The test raw material is vein quartz in Altai region of Xinjiang, and the raw ore has been separated, with a quartz content of about 95%; compared with the purification experiment of Example 3, the purification experiment of this Example 5 adjusts the microwave activation parameters: the power density of the first stage microwave activation is 1500 W / kg, the temperature is 650℃, and the duration is 15 min; the power density of the second stage microwave activation is 2200 W / kg, the temperature is 1050℃, and the duration is 15 min; this Example 5 also adjusts the intensity of the gradient high-voltage electric field, with the intensity of the first stage gradient high-voltage electric field being 30 kV / m, and the intensity of the second stage gradient high-voltage electric field being 50 kV / m; the other steps of this Example 5 are consistent with the experimental steps and methods of Example 3, and the same method is used for characterization.

[0066] The impurity content results of the comparative quartz sand are shown in Table 5, and after the purification by microwave activation and gradient high-voltage electric field, the total amount of impurity elements decreases by 2.09 ppm, among which the Fe element decreases from 0.28 ppm to 0.01 ppm, reaching the impurity index of semiconductor-grade quartz sand.

[0067] Table 5 ICP detection results of high-purity quartz sand in Example 5 (unit: ppm) Al B Ba Ca Cr Cu Fe Ge K Li Mg Mn Na Ni P Ti Zr Sum After high temperature chlorination of Example 5 9.85 0.13 0.06 0.91 0.01 0.00 0.28 1.21 0.21 0.45 0.00 0.01 0.12 0.00 1.00 1.70 0.34 16.28 Final product sand of Example 5 Ba Ca Cu Fe Ge Li Mg Mn Na Ni Ti Sum After high temperature chlorination of Example 5 Final product sand of Example 5 9.09 0.08 0.02 0.62 0.00 0.00 0.01 1.18 0.05 0.45 0.00 0.00 0.05 0.00 0.85 1.54 0.25 14.19 The above describes the method for purifying high-purity quartz sand based on microwave and gradient high-voltage electric field. The principle and implementation of the present application are described by using specific examples. The above examples are only used to help understand the present application and core ideas. It should be pointed out that those skilled in the art can make some improvements and modifications to the present application without departing from the principle of the present application, and these improvements and modifications also fall within the protection scope of the present application.

Claims

1. A method for purifying high-purity quartz sand based on microwave cooperation with gradient high-voltage electric field, wherein the raw ore is pretreated and purified to obtain a semi-finished product of high-purity quartz sand, characterized in that, The obtained high-purity quartz sand semi-finished product is processed by the following steps: S1, microwave activation, the high-purity quartz sand semi-finished product is subjected to two-stage microwave activation by a microwave rotary furnace to pre-charge and magnetize the micron / nanometer level impurity particles in the high-purity quartz sand semi-finished product, wherein the first-stage microwave activation process utilizes the selective heating characteristics of microwaves to form a local high-temperature area on the surface of the quartz sand, causing the micron / nanometer level impurity particles to undergo lattice distortion or surface desorption, and the second-stage microwave activation process drives the micron / nanometer level impurity particles to undergo oxidation-reduction reaction through thermodynamics, Inert protective gas is introduced during the microwave activation and cooling stages, and ultrasonic vibration is performed during the cooling stage; S2, gradient high-voltage electric field impurity removal, a multi-stage gradient high-voltage electric field is constructed, and the quartz sand after S1 processing is introduced into the multi-stage gradient high-voltage electric field, the micron / nanometer level impurity particles attached to the surface of the quartz sand are removed through the electric field strength of each stage of the gradient high-voltage electric field and the transport direction of the quartz sand in the gradient high-voltage electric field, and a high-purity quartz sand finished product is obtained.

2. The method according to claim 1, wherein the method is characterized by, The pretreatment includes cleaning, two-stage crushing, calcination, water quenching, and sand making of the raw ore, wherein the cleaning is high-pressure water gun washing of the raw ore to remove attached clay minerals, and the purification treatment includes magnetic separation, acid leaching, flotation, drying, high-temperature chlorination, Magnetic separation, the quartz raw sand obtained after the pretreatment is put into a magnetic separator for gradient magnetic separation, Acid leaching, the quartz sand after the magnetic separation treatment is put into an acid leaching reaction kettle to remove mineral impurities through reaction with mixed acid, Flotation, the quartz sand after the acid leaching treatment is put into a flotation machine, flotation reagents are added for flotation, and the quartz sand is rinsed after flotation to remove residual reagents, Drying, the quartz sand after the flotation treatment is subjected to preliminary dewatering by a centrifugal machine and then deep drying by a high-temperature rotary furnace, High-temperature chlorination, the quartz sand after the drying treatment is put into a high-temperature chlorination reaction furnace to react with hydrogen chloride gas at high temperature to obtain a high-purity quartz sand semi-finished product.

3. The method according to claim 2, wherein the method is characterized by, The particle size of the quartz sand obtained after two-stage crushing of the raw ore is ≤5 cm, the quartz sand after crushing is calcined at 700-1100℃ for 5-30 min, then put into a water tank for water quenching, and then dried to make sand, and the particle size of the quartz sand after drying and sand making is in the range of 50-230 mesh.

4. The method according to claim 2, wherein the method is characterized by, The gradient magnetic separation is divided into permanent magnet and electromagnetic, wherein the magnetic field strength of the permanent magnet is 0.5-1.5T, and the magnetic field strength of the electromagnetic is 2.0-3.0T.

5. The method according to claim 2, wherein the method is characterized by, The acid used for acid leaching is one or a combination of several of oxalic acid, hydrochloric acid, hydrofluoric acid, nitric acid, and sulfuric acid, and deionized water is added, the acid leaching temperature is 70℃~130℃, the sand / liquid ratio is 1:0.5~1:1.5, and the acid leaching time is 4h~24h.

6. The method according to claim 2, wherein the method is characterized by, The flotation reagent used in the flotation operation includes one or more of pH adjuster, collector and frother; the pH adjuster is one or a mixture of several of citric acid, sulfuric acid, hydrochloric acid and hydrofluoric acid; the collector is one or a mixture of several of sodium dodecylhydroxylamine, butyl ammonium black drug, salicylhydroxamic acid and methyl isobutyl carbinol; the frother is pine oil or MIBC (methyl isobutyl ketone); the pulp concentration in the flotation is controlled to be 25-50%.

7. The method according to claim 2, wherein the method is characterized by, The centrifugal dewatering speed of the centrifuge in the drying treatment is 1000-3500 r / min, the moisture content of the feed is 15-30%, and the dewatering time is 3-8 min; the temperature of the high-temperature rotary furnace in the drying treatment is 600-1000 DEG C, and the drying time is 10-40 min.

8. The method according to claim 2, wherein the method is characterized by, The temperature of the high-temperature chlorination is 1000-1300 DEG C, the high-temperature chlorination time is 2-7 h, and the flow rate of the hydrogen chloride gas introduced into the high-temperature chlorination reaction furnace is 0.2-2 L / min.

9. The method according to claim 1, wherein the method is characterized by, The microwave activation in step S1 is divided into two stages, the first stage microwave activation has a power density of 500-1500 W / kg, a temperature of 350-650 DEG C, and a duration of 10-30 min; the second stage microwave activation has a power density of 1500-2500 W / kg, a temperature of 900-1100 DEG C, and a duration of 10-30 min; the inert protective gas in step S1 is one or a combination of argon and nitrogen; the ultrasonic vibration frequency in step S1 is 50 kHz-120 kHz, and the vibration time is 1-20 min.

10. The method according to claim 1, wherein the method is characterized by, The multi-stage gradient high-voltage electric field constructed in step S2 is a two-stage gradient high-voltage electric field, the first-stage gradient high-voltage electric field has a strength of 20-50 kV / m, the quartz sand transportation direction is vertical rapid falling body, and is suitable for micrometer / nanometer impurity particles with high magnetic response; the second-stage gradient high-voltage electric field has a strength of 40-80 kV / m, the quartz sand transportation direction is horizontal, and is suitable for micrometer / nanometer impurity particles with low magnetic response; the gas medium used in the gradient high-voltage electric field impurity removal is one or a combination of several of dry air, nitrogen and argon.

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