Method for preparing high-purity quartz sand from white marble

Abstract

The application provides a method for preparing high-purity quartz sand from white granite, and belongs to the technical field of high-purity quartz sand preparation. The application comprises raw material selection, crushing and screening, sand preparation and grading, scrubbing and desliming, magnetic separation and gravity separation, flotation operation, one-time acid washing and drying, calcination and water quenching, two-time acid washing and drying, high-temperature chlorination, three-time acid washing and sand baking. The application discloses, for the first time, preparation of high-purity quartz sand from white granite, and through the above process, high-purity quartz sand with stable product quality and high purity can be obtained.

Description

Technical Field

[0001] This invention relates to the field of high-purity quartz sand preparation technology, and in particular to a method for preparing high-purity quartz sand using leucogranite. Background Technology

[0002] High-purity quartz is a strategic non-metallic mineral resource, mainly used in the semiconductor industry, quartz glass, photovoltaics, electric light sources, aerospace and other fields. In the semiconductor field, the key container for pulling polycrystalline silicon into monocrystalline silicon is the quartz crucible, and the quartz crucible must use high-purity quartz sand of grade 4N8 or higher as raw material.

[0003] High-purity quartz from leucogranite is characterized by its large scale, high quality, and stable properties. The Spruce Pine pegmatite deposit in North Carolina, USA, is a typical representative of high-purity quartz from leucogranite pegmatite globally. Siliconware Precision Industries (SPIC) in the United States uses Spruce Pine pegmatite (leucogranite) to produce its IOTA series of high-purity quartz sand products, which almost monopolize the high-end quartz sand market internationally. Currently, there are no reports on the preparation of high-purity quartz sand from leucogranite.

[0004] The invention patent with publication number CN 115709999A discloses a method for extracting high-purity quartz sand from granite pegmatite. The method includes the following steps: (1) calcination and water quenching; (2) crushing and screening; (3) flotation; and (4) acid washing. Using this method, high-purity quartz sand with a purity of 3N6 or higher can be obtained by flotation of granite pegmatite ore from different regions. This method involves directly calcining and water quenching the granite pegmatite raw material. Since the quartz content in the granite pegmatite raw material is relatively low, whole-material calcination is not conducive to energy saving, and the calcination process can easily lead to impurities entering the quartz particles.

[0005] The invention patent with publication number CN 115870088A discloses a method for preparing 4N5 grade high-purity quartz from pegmatite, including the following steps: pegmatite is crushed, ground, classified, and subjected to gravity separation to obtain heavy minerals, medium minerals, and light minerals. The light minerals are mica powder. The medium minerals are subjected to magnetic separation to obtain magnetic and non-magnetic minerals. The magnetic minerals and heavy minerals are tailings. Large pieces of mica (+2mm) are collected during the crushing process as large mica concentrate. The non-magnetic minerals are subjected to flotation to obtain mica powder, feldspar powder, and quartz rough concentrate. The quartz rough concentrate is subjected to calcination, water quenching, ultrasonic acid leaching, and thermal leaching to obtain 4N5 grade high-purity quartz. This method uses all-particle-size materials entering the beneficiation system without pre-classification, which increases the difficulty of separation to a certain extent and is not conducive to the removal of impurities and the stability of product quality.

[0006] Currently, there are no reports on the preparation of high-purity quartz sand from leucogranite. Therefore, in order to solve the current technical problems, accelerate the industrialization of high-purity quartz sand preparation from leucogranite, and achieve controllable and readily available high-purity quartz resources, it is urgent to provide a simple method for preparing high-purity quartz sand from leucogranite that produces stable product quality, high purity, and low production cost. Summary of the Invention

[0007] In view of this, in order to solve the problem that there is no existing technology for preparing high-purity quartz sand using leucogranite, the present invention provides a method for preparing high-purity quartz sand using leucogranite. The method involves raw material selection, crushing and screening, sand making and grading, scrubbing and desliming, magnetic separation and gravity separation, flotation, multiple acid washing, high-temperature chlorination and sand baking processes to obtain high-purity quartz sand with stable product quality and high purity.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for preparing high-purity quartz sand from bleached granite includes the following steps:

[0010] Step S1: Raw material selection, selecting white granite ore samples with purification potential;

[0011] Step S2: Crushing and screening. The white granite ore sample selected in step S1 is crushed and screened to obtain crushed product one.

[0012] Step S3: Sand making and grading. The crushed product is made into sand and graded to obtain coarse-grained product and fine-grained product. The coarse-grained product is returned, and the fine-grained product is the raw sand.

[0013] Step S4: Scrubbing and desliming: Wash the raw sand to remove the ore mud and clean the surface of the ore particles.

[0014] Step S5: Magnetic separation and gravity separation. The raw sand after scrubbing and desliming in step S4 is subjected to magnetic separation to obtain magnetic products and non-magnetic products. The non-magnetic products are then subjected to gravity separation to obtain gravity-separated light mineral products, gravity-separated heavy mineral products, and gravity-separated intermediate products.

[0015] Step S6: Flotation operation, the intermediate product of gravity separation is slurry prepared, and inhibitors, modifiers, activators and collectors are added in sequence for flotation to float out impurity minerals and obtain flotation concentrate;

[0016] Step S7: First acid washing and drying. The flotation concentrate is acid washed, followed by multi-stage washing and drying to obtain first acid washed sand, which is then screened to obtain -0.1mm particle size product and 0.1-0.18mm particle size product.

[0017] Step S8: Calcination and water quenching. The 0.1-0.18mm particle size product is calcined, then quickly removed and poured into cold water for water quenching to obtain clinker.

[0018] Step S9: Secondary pickling and drying. The clinker is subjected to secondary pickling to remove impurities. After pickling, it is subjected to multi-stage cleaning and drying to obtain secondary pickled sand.

[0019] Step S10: High-temperature chlorination, the secondary pickled sand is subjected to a chlorination reaction to obtain chlorinated sand;

[0020] Step S11: Three-stage acid washing. Chlorinated sand is acid washed three times to remove impurities. After acid washing, it is cleaned in multiple stages and dried to obtain three-stage acid-washed sand.

[0021] Step S12: Sand baking. The sand that has been acid-washed three times is first dehydrated and then baked at high temperature to obtain high-purity quartz sand.

[0022] Preferably, in step S1, the purification potential of quartz in white granite is determined by microscopic identification. The conditions for having purification potential are: -0.10mm quartz particles ≤5%, biotite content ≤3%, potassium feldspar content ≤5%, quartz content ≥20%, and quartz particles with gas-liquid inclusions distributed in a planar manner ≤5.

[0023] Preferably, the magnetic field strength of the magnetic separation operation in step S5 is 1.6-1.8T.

[0024] Preferably, the process flow used in the flotation operation in step S6 is a process flow in which mica and feldspar are floated preferentially in sequence.

[0025] Preferably, in step S6, the inhibitor is one or more of sodium hexametaphosphate and sodium silicate, the modifier is sulfuric acid, the activator is one or more of hydrofluoric acid, sodium fluoride, and ammonium fluoride, and the collector is a combination of anionic and cationic collectors.

[0026] Preferably, the dosage of the inhibitor is 200-500 g / t, the pH value is adjusted to 1.9-3.1 by the adjuster, the dosage of the activator is 500-1000 g / t, and the dosage of the collector is 100-200 g / t.

[0027] The dosage of the inhibitor, activator, and collector is based on the original granite ore sample.

[0028] Preferably, the acid used in the pickling operation in steps S7, S9 and S11 is one or more of hydrofluoric acid, phosphoric acid, nitric acid, sulfuric acid and hydrochloric acid. Preferably, hydrochloric acid, hydrofluoric acid and sulfuric acid are used in a mass ratio of 3:1:1, and the mass concentration of the mixed acid composed of hydrochloric acid, hydrofluoric acid and sulfuric acid is 10-20%.

[0029] Preferably, the calcination temperature in step S8 is 800-1000 degrees Celsius, and the calcination time is 30-150 minutes.

[0030] Preferably, in step S10, the high-temperature chlorination temperature is 1000-1200 degrees Celsius.

[0031] Preferably, in step S12, the sand baking temperature is 700-1100 degrees Celsius, and the sand baking time is 5-15 minutes.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) This invention is the first to use leucogranite as a raw material for preparing high-purity quartz sand. Since leucogranite mainly exists in the form of rock masses, has large reserves, stable ore properties, and is easy to mine, the use of leucogranite to prepare high-purity quartz sand has the characteristics of stable product properties and is conducive to industrialization.

[0034] (2) The sand-making product is sorted and acid-washed in full size, and then the acid-washed sand is graded, realizing the step-by-step utilization of quartz resources.

[0035] Using a rod mill, the grinding media of the rod mill are mainly in line contact, which can help reduce the over-grinding of quartz and improve the sand production rate.

[0036] The combined magnetic and gravity separation process can separate a large number of magnetic minerals, flaky mica, heavy minerals, etc., reducing the content of impurity minerals in the selection and helping with subsequent purification.

[0037] (3) The calcination and water quenching process mainly utilizes the difference in the expansion coefficients of gangue minerals and quartz to further improve the selective dissociation between the two through the calcination and water quenching process, which is conducive to improving product purity and stabilizing product quality.

[0038] (4) The flotation adopts a priority flotation process, which can achieve the comprehensive recovery of feldspar and mica while preparing high-purity quartz sand. Feldspar can be used as ceramic raw material and mica can be used as insulating material, which has the characteristics of advanced production process. At the same time, the flotation is carried out by combining anion and cation collectors, which can achieve the synergistic effect of anion and cation collectors. This not only enhances the collecting ability of the collector, but also increases the selectivity of the collector, which is conducive to stabilizing product indicators and reducing the loss of quartz sand.

[0039] (5) High-temperature chlorination can target the removal of impurities such as alkali metals, alkaline earth metals, residual inclusions, and lattice impurities on the surface of high-purity quartz particles, thereby achieving further purification and stabilizing product indicators.

[0040] In summary, the method for preparing high-purity quartz sand from white granite provided by this invention can obtain high-purity quartz sand with stable product quality and high purity. Attached Figure Description

[0041] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0042] A method for preparing high-purity quartz sand from bleached granite includes the following steps:

[0043] Step S1: Raw material selection. Select white granite ore samples with purification potential. Preferably, microscopic identification is used to determine the purification potential of quartz in white granite. Preferably, representative white granite blocks are taken, light sections are prepared, and identification is performed under a polarizing microscope to determine the purification potential of quartz in white granite.

[0044] The conditions for having purification potential are: -0.10mm quartz particles ≤5%, biotite content ≤3%, potassium feldspar content ≤5%, quartz content ≥20%, and quartz particles with gas-liquid inclusions distributed in a planar manner ≤5.

[0045] Step S2: Crushing and screening. The white granite ore sample selected in step S1 is crushed and screened to obtain crushed product one. Preferably, the coarse crushing, medium crushing, fine crushing and screening operations are combined into a three-stage closed-circuit process to crush and screen the white granite ore sample. The particle size of crushed product one is preferably 0-10mm.

[0046] Step S3: Sand making and grading. The crushed product is subjected to sand making and grading. The sand making and grading system forms a closed loop to obtain coarse-grained products and fine-grained products. The coarse-grained product is returned, and the fine-grained product is the raw sand. Preferably, sand making equipment is used for sand making and grading. The sand making equipment is preferably one of a sand making machine, ball mill, or rod mill, and more preferably a rod mill. The particle size of the fine-grained product is preferably -0.45mm, and more preferably -0.18mm with a content ≥95%.

[0047] Step S4: Scrubbing and desliming: Wash the raw sand to remove the ore mud and clean the surface of the ore particles.

[0048] Step S5: Magnetic and gravity separation. The raw sand after scrubbing and desliming in step S4 is subjected to magnetic separation to obtain magnetic and non-magnetic products. The non-magnetic products are then subjected to gravity separation to obtain gravity-separated light mineral products, gravity-separated heavy mineral products, and gravity-separated intermediate products. Among them, minerals with a lower specific gravity, such as mica and fine mud, can be identified as gravity-separated light mineral products, while minerals with a higher specific gravity, such as rutile, garnet, magnetite, and tourmaline, can be identified as gravity-separated heavy mineral products. Feldspar and quartz can be identified as gravity-separated intermediate products.

[0049] In step S5, the magnetic separation operation preferably uses one or more of a high-gradient magnetic separator and an electromagnetic slurry machine, and the magnetic field strength is preferably 1.6-1.8T; the equipment used for gravity separation is preferably a shaking table.

[0050] Step S6: Flotation operation, the intermediate product of gravity separation is slurry adjusted, and inhibitor, modifier, activator and collector are added in sequence for flotation to float out impurity minerals and obtain flotation concentrate. The preferred number of flotation operations for mica is 1-3 times, and the preferred number of flotation operations for feldspar is 2-4 times.

[0051] In step S6, the preferred process flow for the flotation operation is a process flow in which mica and feldspar are floated in sequence.

[0052] The inhibitor is preferably one or more of sodium hexametaphosphate and sodium silicate, with a preferred dosage of 200-500 g / t. The modifier is preferably sulfuric acid. The activator is preferably one or more of hydrofluoric acid, sodium fluoride, and ammonium fluoride, with a preferred dosage of 500-1000 g / t. The collector is preferably a combination of anion and cation collector, with a preferred dosage of 100-200 g / t. The dosage of the inhibitor, activator, and collector is based on the white granite ore sample. For example, 200-500 g of inhibitor, 500-1000 g of activator, and 100-200 g of collector are added per ton (t) of white granite ore sample.

[0053] It should be noted that, for mica flotation, the collector is preferably dodecylamine, and for feldspar flotation, the collector is preferably a combination of anion and cation collectors, more preferably one of oleic acid + dodecylamine, sodium petroleum sulfonate + dodecylamine, sodium oleate + dodecylamine, oxidized paraffin soap + dodecylamine, oleic acid + octadecylamine, sodium petroleum sulfonate + octadecylamine, sodium oleate + octadecylamine, or oxidized paraffin soap + octadecylamine.

[0054] Step S7: First acid washing and drying. The flotation concentrate is acid washed, followed by multi-stage cleaning and drying to obtain first acid washed sand. The sand is then screened to obtain -0.1mm and 0.1-0.18mm particle size products. The -0.1mm particle size can be used to process high-purity silica powder, and the 0.1-0.18mm particle size product is used to prepare high-purity quartz sand for crucibles, thus realizing the tiered utilization of quartz resources.

[0055] In step S7, the acid used in the pickling operation is one or more of hydrofluoric acid, phosphoric acid, nitric acid, sulfuric acid, and hydrochloric acid. It is preferred to use hydrochloric acid, hydrofluoric acid, and sulfuric acid in a mass ratio of 3:1:1. The mass concentration of the mixed acid composed of hydrochloric acid, hydrofluoric acid, and sulfuric acid is preferably 10-20%.

[0056] Step S8: Calcination and water quenching. The 0.1-0.18mm particle size product is calcined (preferably placed in a calcination furnace), then quickly removed and poured into cold water for water quenching to obtain clinker. The preferred calcination temperature is 800-1000 degrees Celsius, and the preferred calcination time is 30-150 minutes.

[0057] Step S9: Secondary pickling and drying. The clinker is subjected to secondary pickling to remove impurities. After pickling, it is subjected to multi-stage cleaning and drying to obtain secondary pickled sand.

[0058] In step S9, the acid used in the pickling operation is one or more of hydrofluoric acid, phosphoric acid, nitric acid, sulfuric acid, and hydrochloric acid. It is preferred to use hydrochloric acid, hydrofluoric acid, and sulfuric acid in a mass ratio of 3:1:1. The mass concentration of the mixed acid composed of hydrochloric acid, hydrofluoric acid, and sulfuric acid is preferably 10-20%.

[0059] Step S10: High-temperature chlorination (preferably carried out in a high-temperature chlorination furnace), the secondary pickled sand is subjected to a chlorination reaction to obtain chlorinated sand. The high-temperature chlorination temperature is preferably 1000-1200 degrees Celsius. The chlorinating agent is preferably one or more of NaCl, KCl, CaCl, NH4Cl, HCl, and Cl2. The chlorination pipe used is a synthetic high-purity quartz pipe with a SiO2 purity of not less than 99.999%.

[0060] Step S11: Three-stage acid washing. Chlorinated sand is acid washed three times to remove impurities. After acid washing, it is cleaned in multiple stages and dried to obtain three-stage acid-washed sand.

[0061] In step S11, the acid used in the pickling operation is one or more of hydrofluoric acid, phosphoric acid, nitric acid, sulfuric acid, and hydrochloric acid. It is preferred to use hydrochloric acid, hydrofluoric acid, and sulfuric acid in a mass ratio of 3:1:1. The mass concentration of the mixed acid composed of hydrochloric acid, hydrofluoric acid, and sulfuric acid is preferably 10-20%.

[0062] Step S12: Sand baking. The sand that has been acid-washed three times is first dehydrated and then baked at high temperature to obtain high-purity quartz sand. The baking temperature is 700-1100 degrees Celsius and the baking time is 5-15 minutes. The instrument used for baking is a high-purity quartz tube with SiO2 purity of not less than 99.999%.

[0063] The technical solution of the present invention will be clearly and thoroughly described below with reference to the accompanying drawings and specific embodiments.

[0064] Microscopic analysis of a granite from Henan province revealed that the main minerals were plagioclase (61%), quartz (25%), muscovite (8%), potassium feldspar (3%), biotite (2%), and epidote (1%). The quartz was found to be subhedral to anhedral granular, with a long axis ranging from 0.2 to 2.0 mm in diameter, and oriented. Fluid inclusions were small, mostly linear, with two planar inclusions, and grain sizes ranging from 1 to 3 μm. The quartz grains in this ore exhibited good crystal form and were relatively pure under microscopic examination, demonstrating potential for the preparation of high-purity quartz. The multi-element analysis results of the raw ore are shown in Table 1.

[0065] Table 1. Results of multi-element analysis of raw ore

[0066]

[0067] Example 1

[0068] Step S1: Raw material selection, selecting a white granite from Henan Province with the above-mentioned purification potential;

[0069] Step S2: Crushing and screening. The coarse crushing, medium crushing, fine crushing and screening operations are combined into a three-stage closed-circuit process to crush and screen the raw granite ore sample to obtain crushed product one with a particle size of 0-10mm.

[0070] Step S3: Sand making and classification. The crushed product is processed by rod milling and classified. The sand making and classification system is a closed loop. The coarse particles are returned, and the fine particles are the raw sand. The fine particles have a particle size of -0.18mm and a content of 96.54%.

[0071] Step S4: Scrubbing and desliming: Wash the raw sand to remove the ore mud and clean the surface of the ore particles.

[0072] Step S5: Magnetic separation and gravity separation. The raw quartz sand is subjected to magnetic separation with a magnetic field strength of 1.6T to obtain magnetic and non-magnetic products. The non-magnetic products are then subjected to gravity separation to obtain gravity-separated light mineral products, gravity-separated heavy mineral products, and gravity-separated intermediate products.

[0073] Step S6: Flotation operation. The intermediate product from gravity separation is prepared by adding depressant, modifier, activator, and collector in sequence for flotation. For mica flotation, sulfuric acid is used as the modifier to adjust the pH to 3.5, sodium hexametaphosphate is used as the depressant at a dosage of 200 g / t, and dodecylamine is used as the collector at a dosage of 100 g / t. The number of flotation operations is 1 roughing operation. For feldspar flotation, sulfuric acid is used as the modifier to adjust the pH to 2.5, sodium fluoride is used as the activator, and the roughing dosage is 500 g / t. The collector is oleic acid + dodecylamine, and the roughing dosage is 100 g / t. The number of scavenging operations is 1, and the dosage of scavenging reagents is halved compared to roughing.

[0074] Step S7: First acid washing and drying. The flotation concentrate is acid washed with hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and a mixed acid mass concentration of 10%. After acid washing, it is washed in multiple stages and dried to obtain first acid washed sand, which is then screened to obtain a -0.1mm particle size product and a 0.1-0.18mm particle size product.

[0075] Step S8: Calcination and water quenching. Place the 0.1-0.18mm particle size product in a calcination furnace for calcination at 800 degrees Celsius for 30 minutes. Then quickly remove it and pour it into cold water for water quenching to obtain clinker.

[0076] Step S9: Secondary pickling and drying. The clinker is subjected to secondary pickling using hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and a mixed acid mass concentration of 10%. This removes impurities from the surface and cracks of the quartz sand. After pickling, the sand undergoes multi-stage cleaning and drying to obtain secondary pickled sand.

[0077] Step S10: High-temperature chlorination. The secondary pickled sand is placed in a high-temperature chlorination furnace for chlorination reaction. The high-temperature chlorination temperature is 1000 degrees Celsius, the chlorinating agent is Cl2, and the chlorination pipe used is a synthetic high-purity quartz pipe with SiO2 purity not less than 99.999% to obtain chlorinated sand.

[0078] Step S11: Three-stage acid washing. The chlorinated sand is acid washed three times with hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and a mixed acid mass concentration of 10%. This removes impurities from the surface of the quartz sand. After acid washing, the sand is cleaned in multiple stages and dried to obtain three-stage acid-washed sand.

[0079] Step S12: Sand baking. The sand that has been acid-washed three times is dehydrated and then baked at a high temperature of 700 degrees Celsius for 15 minutes. The instrument used for baking is a high-purity quartz tube with a SiO2 purity of not less than 99.999%, thus obtaining high-purity quartz sand.

[0080] Table 2 Chemical analysis results of the high-purity quartz sand sample from Example 1

[0081]

[0082]

[0083] Example 2

[0084] Step S1: Raw material selection, selecting a white granite from Henan Province with the above-mentioned purification potential;

[0085] Step S2: Crushing and screening. The coarse crushing, medium crushing, fine crushing and screening operations are combined into a three-stage closed-circuit process to crush and screen the raw granite ore sample to obtain crushed product one with a particle size of 0-10mm.

[0086] Step S3: Sand making and grading. The crushed product is processed by rod milling and grading. The sand making and grading system is a closed loop. The coarse particles are returned, and the fine particles are the raw sand. The quartz raw sand has a particle size of -0.18mm and a content of 98.32%.

[0087] Step S4: Scrubbing and desliming: Wash the raw sand to remove the ore mud and clean the surface of the ore particles.

[0088] Step S5: Magnetic separation and gravity separation. The raw quartz sand is subjected to magnetic separation with a magnetic field strength of 1.8T to obtain magnetic and non-magnetic products. The non-magnetic products are then subjected to gravity separation to obtain gravity-separated light mineral products, gravity-separated heavy mineral products, and gravity-separated intermediate products.

[0089] Step S6: Flotation operation. The intermediate product from gravity separation is prepared by adding depressant, modifier, activator, and collector in sequence for flotation. For mica flotation, sulfuric acid is used as the modifier to adjust the pH to 4. Sodium hexametaphosphate is used as the depressant at a dosage of 300 g / t. Dodecylamine is used as the collector at a dosage of 150 g / t. The number of flotation operations is 2 roughing operations. For feldspar flotation, sulfuric acid is used as the modifier to adjust the pH to 2.0. Sodium fluoride is used as the activator. The roughing dosage is 1000 g / t. Sodium oleate + dodecylamine is used as the collector. The roughing dosage is 150 g / t. The number of scavenging operations is 3. The dosage of scavenging reagents is halved compared to roughing.

[0090] Step S7: First acid washing and drying. The flotation concentrate is acid washed with hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and a mixed acid mass concentration of 20%. After acid washing, it is washed in multiple stages and dried to obtain first acid washed sand, which is then screened to obtain a -0.1mm particle size product and a 0.1-0.18mm particle size product.

[0091] Step S8: Calcination and water quenching. Place the 0.1-0.18mm particle size product in a calcination furnace for calcination at a temperature of 1000 degrees Celsius for 150 minutes. Then quickly remove it and pour it into cold water for water quenching to obtain clinker.

[0092] Step S9: Secondary pickling and drying. The clinker is subjected to secondary pickling using hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and a mixed acid mass concentration of 20%. This removes impurities from the surface and cracks of the quartz sand. After pickling, the sand undergoes multi-stage cleaning and drying to obtain secondary pickled sand.

[0093] Step S10: High-temperature chlorination. The secondary pickled sand is placed in a high-temperature chlorination furnace for chlorination reaction. The high-temperature chlorination temperature is 1200 degrees Celsius, the chlorinating agent is Cl2, and the chlorination pipe used is a synthetic high-purity quartz pipe with SiO2 purity not less than 99.999% to obtain chlorinated sand.

[0094] Step S11: Three-stage acid washing. The chlorinated sand is acid washed three times with hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and a mixed acid mass concentration of 20%. This removes impurities from the surface of the quartz sand. After acid washing, the sand is cleaned in multiple stages and dried to obtain three-stage acid-washed sand.

[0095] Step S12: Sand baking. The sand that has been acid-washed three times is dehydrated and then baked at a high temperature of 1100 degrees Celsius for 5 minutes. The instrument used for baking is a high-purity quartz tube with a SiO2 purity of not less than 99.999%, thus obtaining high-purity quartz sand.

[0096] Table 3 Chemical analysis results of the high-purity quartz sand sample from Example 2

[0097]

[0098] Example 3

[0099] Step S1: Microscopic identification. Take a representative piece of white granite, prepare a slide, and identify it under a polarizing microscope to determine the purification potential of quartz in the white granite.

[0100] Step S2: Crushing and screening. The coarse crushing, medium crushing, fine crushing and screening operations are combined into a three-stage closed-circuit process to crush and screen the raw granite ore sample to obtain crushed product one with a particle size of 0-10mm.

[0101] Step S3: Sand making and grading. The crushed product is processed by rod milling and grading. The sand making and grading system is a closed loop. The coarse particles are returned, and the fine particles are the raw sand. The quartz raw sand has a particle size of -0.18mm and a content of 100.00%.

[0102] Step S4: Scrubbing and desliming: Wash the raw sand to remove the ore mud and clean the surface of the ore particles.

[0103] Step S5: Magnetic separation and gravity separation. The raw quartz sand is subjected to magnetic separation with a magnetic field strength of 1.7T to obtain magnetic and non-magnetic products. The non-magnetic products are then subjected to gravity separation to obtain gravity-separated light mineral products, gravity-separated heavy mineral products, and gravity-separated intermediate products.

[0104] Step S6: Flotation operation. The intermediate product from gravity separation is prepared by adding depressant, modifier, activator, and collector in sequence for flotation. For mica flotation, sulfuric acid is used as the modifier to adjust the pH to 3.2, sodium hexametaphosphate is used as the depressant at a dosage of 500 g / t, and dodecylamine is used as the collector at a dosage of 200 g / t. The number of flotation operations is 1 roughing operation. For feldspar flotation, sulfuric acid is used as the modifier to adjust the pH to 2.8, sodium fluoride is used as the activator, and the roughing dosage is 800 g / t. The collector is sodium petroleum sulfonate + octadecylamine, and the roughing dosage is 200 g / t. The number of scavenging operations is 2, and the dosage of scavenging reagents is halved compared to the roughing dosage.

[0105] Step S7: First acid washing and drying. The flotation concentrate is acid washed with hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and a mixed acid mass concentration of 15%. After acid washing, it is washed in multiple stages and dried to obtain first acid washed sand, which is then screened to obtain a -0.1mm particle size product and a 0.1-0.18mm particle size product.

[0106] Step S8: Calcination and water quenching. Place the 0.1-0.18mm particle size product in a calcination furnace for calcination at 900 degrees Celsius for 90 minutes. Then quickly remove it and pour it into cold water for water quenching to obtain clinker.

[0107] Step S9: Secondary pickling and drying. The clinker is subjected to secondary pickling using hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and a mixed acid mass concentration of 15%. This removes impurities from the surface and cracks of the quartz sand. After pickling, the sand undergoes multi-stage cleaning and drying to obtain secondary pickled sand.

[0108] Step S10: High-temperature chlorination. The secondary pickled sand is placed in a high-temperature chlorination furnace for chlorination reaction. The high-temperature chlorination temperature is 1100 degrees Celsius, the chlorinating agent is Cl2, and the chlorination pipe used is a synthetic high-purity quartz pipe with SiO2 purity not less than 99.999% to obtain chlorinated sand.

[0109] Step S11: Three-stage acid washing. The chlorinated sand is acid washed three times with hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and a mixed acid mass concentration of 15%. This removes impurities from the surface of the quartz sand. After acid washing, the sand is cleaned in multiple stages and dried to obtain three-stage acid-washed sand.

[0110] Step S12: Sand baking. The sand that has been acid-washed three times is dehydrated and then baked at a high temperature of 1000 degrees Celsius for 10 minutes. The instrument used for baking is a high-purity quartz tube with a SiO2 purity of not less than 99.999%, thus obtaining high-purity quartz sand.

[0111] Table 4 Chemical analysis results of the high-purity quartz sand sample from Example 3

[0112]

[0113] As can be seen from Tables 1-4, by using the preparation method of the present invention, high-purity quartz sand was prepared from leucogranite, and the purity was increased from 73.91% to over 99.99%.

[0114] The main mechanism of this invention is as follows:

[0115] (1) Since the main minerals in white granite are feldspar, quartz, mica, etc., the product after sand making is sorted by full particle size and acid washed, and then the acid washed sand is graded, realizing the step utilization of quartz resources. At the same time, this process only calcines and quenches the qualified particle size flotation concentrate (quartz sand). The flotation concentrate has a fine and uniform particle size, which can shorten the calcination time and greatly reduce the amount of ore entering the calcination operation. Compared with the whole material entering the calcination operation, the production cost is greatly reduced.

[0116] (2) Due to the difference in the expansion coefficient between different minerals, the degree of expansion after heating is different. After rapid water quenching and cooling, micro-cracks are formed between different minerals, which facilitates the selective dissociation and crushing of quartz particles, which is beneficial to improving the sand production rate of the product and reducing the content of impurities in the product.

[0117] (3) Since the main minerals in granite pegmatite are feldspar, quartz and mica, mica is in sheet form and has a certain toughness. The rod mill can effectively protect the sheet structure of mica. Feldspar has reduced strength after calcination and water quenching. After grinding, it is easy to muddy. Quartz has a large hardness and is not easy to be over-crushed during the grinding process, which can effectively protect the yield of the target particle size quartz.

[0118] (4) The flotation adopts a priority flotation process, which can achieve the comprehensive recovery of feldspar and mica while preparing high-purity quartz sand. Feldspar can be used as ceramic raw material and mica can be used as insulating material, which has the characteristics of advanced production process. At the same time, the flotation is carried out by combining anion and cation collectors, which can achieve the synergistic effect of anion and cation collectors. This not only enhances the collecting ability of the collector, but also increases the selectivity of the collector, which is conducive to stabilizing product indicators and reducing the loss of quartz sand.

[0119] (5) High-temperature chlorination is mainly used to remove alkali metals, alkaline earth metals, residual inclusions, and lattice impurities from the surface of high-purity quartz particles. For lattice impurities, a trivalent metal is typically paired with a monovalent metal to replace tetravalent silicon, such as Al. 3+ and Na + Replacement of Si 4+ Impurities react with chlorinating agents at high temperatures to form chlorides, such as AlCl3, NaCl, and KCl. The chlorides then vaporize at high temperatures and are carried away by the gas flow, achieving further purification.

[0120] The above are merely preferred embodiments of the present invention; however, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity quartz sand from bleached granite, characterized in that, Includes the following steps: Step S1: Raw material selection. Select white granite ore samples with purification potential. In step S1, the purification potential of quartz in white granite is determined by microscopic identification. The conditions for having purification potential are: -0.10mm quartz particles ≤5%, biotite content ≤3%, potassium feldspar content ≤5%, quartz content ≥20%, and quartz particles with gas-liquid inclusions distributed in a planar manner ≤5. Step S2: Crushing and screening. The white granite ore sample selected in step S1 is crushed and screened to obtain crushed product one. Step S3: Sand making and grading. The crushed product is made into sand and graded to obtain coarse-grained product and fine-grained product. The coarse-grained product is returned, and the fine-grained product is the raw sand. Step S4: Scrubbing and desliming: Wash the raw sand to remove the ore mud and clean the surface of the ore particles. Step S5: Magnetic and gravity separation. The raw sand after scrubbing and desliming in step S4 is subjected to magnetic separation to obtain magnetic and non-magnetic products. The non-magnetic products are then subjected to gravity separation to obtain gravity-separated light mineral products, gravity-separated heavy mineral products, and gravity-separated intermediate products. Based on the specific gravity of the ore, mica and fine mud are identified as gravity-separated light mineral products, rutile, garnet, magnetite, and tourmaline are identified as gravity-separated heavy mineral products, and feldspar and quartz are identified as gravity-separated intermediate products. Step S6: Flotation operation, the intermediate product of gravity separation is slurry prepared, and inhibitors, modifiers, activators and collectors are added in sequence for flotation to float out impurity minerals and obtain flotation concentrate; Step S7: First acid washing and drying. The flotation concentrate is acid washed, followed by multi-stage washing and drying to obtain first acid washed sand, which is then screened to obtain -0.1mm particle size product and 0.1-0.18mm particle size product. Step S8: Calcination and water quenching. The 0.1-0.18mm particle size product is calcined, then quickly removed and poured into cold water for water quenching to obtain clinker. Step S9: Secondary pickling and drying. The clinker is subjected to secondary pickling to remove impurities. After pickling, it is subjected to multi-stage cleaning and drying to obtain secondary pickled sand. Step S10: High-temperature chlorination, the secondary pickled sand is subjected to a chlorination reaction to obtain chlorinated sand; Step S11: Three-stage acid washing. Chlorinated sand is acid washed three times to remove impurities. After acid washing, it is cleaned in multiple stages and dried to obtain three-stage acid-washed sand. Step S12: Sand baking. The sand that has been acid-washed three times is first dehydrated and then baked at high temperature to obtain high-purity quartz sand.

2. The method for preparing high-purity quartz sand from bleached granite according to claim 1, characterized in that: The magnetic field strength for the magnetic separation operation in step S5 is 1.6-1.8T.

3. The method for preparing high-purity quartz sand from bleached granite according to claim 1, characterized in that: The process flow used in the flotation operation in step S6 is a process flow in which mica and feldspar are floated preferentially in sequence.

4. The method for preparing high-purity quartz sand from bleached granite according to claim 1, characterized in that: In step S6, the inhibitor is one or more of sodium hexametaphosphate and sodium silicate, the modifier is sulfuric acid, the activator is one or more of hydrofluoric acid, sodium fluoride, and ammonium fluoride, and the collector is a combination of anion and cation collector.

5. The method for preparing high-purity quartz sand from bleached granite according to claim 4, characterized in that: The inhibitor is used at a dosage of 200-500 g / t, the pH is adjusted to 1.9-3.1 by the adjuster, the activator is used at a dosage of 500-1000 g / t, and the collector is used at a dosage of 100-200 g / t. The dosage of the inhibitor, activator, and collector is based on the original granite ore sample.

6. The method for preparing high-purity quartz sand from bleached granite according to claim 1, characterized in that: The acid used in the pickling operations in steps S7, S9 and S11 is one or more of hydrofluoric acid, phosphoric acid, nitric acid, sulfuric acid and hydrochloric acid.

7. The method for preparing high-purity quartz sand from bleached granite according to claim 1, characterized in that: The calcination temperature in step S8 is 800~1000 degrees Celsius, and the calcination time is 30~150 minutes.

8. The method for preparing high-purity quartz sand from bleached granite according to claim 1, characterized in that: In step S10, the high-temperature chlorination temperature is 1000~1200 degrees Celsius.

9. A method for preparing high-purity quartz sand from bleached granite according to any one of claims 1-8, characterized in that: In step S12, the sand baking temperature is 700-1100 degrees Celsius, and the sand baking time is 5-15 minutes.

Images