Method for preparing high-purity quartz sand from granite pegmatite and high-purity quartz sand

Abstract

This invention provides a method for preparing high-purity quartz sand from granite pegmatite, belonging to the field of high-purity quartz sand processing technology. The invention includes the following steps: crushing and screening, washing and color sorting, primary calcination and water quenching, sand making and grading, magnetic and gravity separation, flotation, secondary calcination and water quenching, primary acid washing and drying, high-temperature chlorination, secondary acid washing, and sand baking. The method for preparing high-purity quartz sand from granite pegmatite provided by this invention is simple, has low production costs, and can obtain high-purity quartz sand with stable product quality and high purity.

Description

Technical Field

[0001] This invention relates to the field of high-purity quartz sand processing technology, and in particular to a method for preparing high-purity quartz sand from granite pegmatite and the high-purity quartz sand prepared by the method. Background Technology

[0002] High-purity silica sand 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 silica sand of grade 4N8 or higher as raw material.

[0003] Granite pegmatite-type high-purity quartz is characterized by its large scale and high quality. Many experts and scholars have begun to study the key technologies and methods for preparing high-purity quartz sand from granite pegmatites. Among them, the Henan Provincial Institute of Geology and related research teams found granite pegmatites in the eastern Qinling Mountains with rock, mineral, and geochemical characteristics very similar to those of the Spruce Pine region in the United States. They systematically studied its geological background, tectonic conditions, distribution patterns, identification markers, and evaluation standards. Furthermore, based on the mineralogical characteristics of the ore, they innovatively developed a complete set of technologies, including rapid identification technology, manual sorting technology, fine separation and purification technology, new flotation reagent technology, deep impurity removal technology, directional impurity removal technology, process intensification technology, and key equipment technology. They have also successfully prepared high-purity quartz sand of different grades in the laboratory.

[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 from 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 granite pegmatite raw material is relatively low, whole-material calcination is not energy-efficient, and the calcination process easily leads to impurities entering the quartz particles. The invention patent with publication number CN 115870088 A 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.

[0005] Therefore, in order to solve the current technical problems, accelerate the industrialization of high-purity quartz sand preparation from granite pegmatite, 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 granite pegmatite that produces stable, high-purity, and low-cost products. Summary of the Invention

[0006] In view of this, in order to solve the technical problem of low purity of high-purity quartz sand in the existing technology, on the one hand, the present invention provides a method for preparing high-purity quartz sand from granite pegmatite, which adopts the following process steps in sequence: crushing and screening, washing and color sorting, primary calcination and water quenching, sand making and grading, magnetic separation and gravity separation, flotation, secondary calcination and water quenching, primary acid washing and drying, high-temperature chlorination, secondary acid washing and sand baking, which can obtain high-purity quartz sand with stable product quality and high purity.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing high-purity quartz sand from granite pegmatite includes the following steps:

[0009] Step S1: Crushing and screening. The granite pegmatite raw ore sample is crushed and screened to obtain intermediate particle size product and fine particle product 1. The coarse particle product is directly returned to the closed loop for recycling crushing and screening.

[0010] Step S2: Washing and color sorting. The intermediate particle size product obtained in step S1 is washed to remove the ore slime, and then color sorted using a color sorter to obtain quartz raw material and waste.

[0011] Step S3: Calcination and water quenching. The quartz raw material obtained in step S2 is placed in a calcining furnace for calcination, and then quickly taken out and poured into cold water for water quenching to obtain quartz clinker.

[0012] Step S4: Sand making and grading. The quartz clinker obtained in step S3 is subjected to sand making and grading to obtain intermediate-sized quartz raw sand and fine-grained product II.

[0013] Step S5: Magnetic separation and gravity separation. The quartz raw sand obtained in step S4 is subjected to magnetic separation to obtain magnetic products and non-magnetic products. The non-magnetic products are subjected to gravity separation to obtain gravity-separated light mineral products, gravity-separated heavy mineral products and gravity-separated intermediate products.

[0014] Step S6: Flotation operation. The intermediate product obtained in step S5 is slurry-adjusted, and inhibitors, modifiers, activators and collectors are added in sequence for flotation to obtain flotation concentrate.

[0015] Step S7: Secondary calcination and water quenching. The flotation concentrate obtained in step S6 is placed in a calcining furnace for calcination, and then quickly taken out and poured into cold water for water quenching to obtain flotation concentrate clinker.

[0016] Step S8: First acid washing and drying. The flotation concentrate clinker obtained in step S7 is acid washed, then cleaned and dried to obtain first acid washed sand.

[0017] Step S9: High-temperature chlorination. The primary pickled sand obtained in step S8 is placed in a high-temperature chlorination furnace for chlorination reaction to obtain chlorinated sand.

[0018] Step S10: Secondary acid washing. The chlorinated sand obtained in step S9 is subjected to secondary acid washing to remove impurities from the surface of the quartz sand, resulting in secondary acid-washed sand.

[0019] Step S11: Sand baking. The secondary acid-washed sand obtained in step S10 is dehydrated and then baked at high temperature to obtain high-purity quartz sand. Before packaging, a dry magnetic check is performed as needed.

[0020] Preferably, in step S1, the particle size range of the intermediate particle size product is 3 to 50 mm.

[0021] Preferably, in step S4, the particle size of the raw quartz sand is 0.074-0.45 mm.

[0022] Preferably, in step S5, the equipment used for magnetic separation is one or more of a high-gradient magnetic separator and an electromagnetic slurry machine, with a magnetic field strength of 1.6-1.8T.

[0023] Preferably, in step S6, the collector is a combination of anionic and cationic collectors, and the dosage is 100-200 g / t.

[0024] Preferably, in step S9, the high-temperature chlorination temperature is 1000–1200 degrees Celsius.

[0025] Preferably, in step S11, the baking temperature is 700-1100 degrees Celsius, and the baking time is 5-15 minutes.

[0026] Preferably, the calcination temperature in steps S3 and S7 is 800–1000 degrees Celsius, and the calcination time is 30–150 min.

[0027] Preferably, the acid used in the pickling operation in steps S8 and S10 is one or more of hydrofluoric acid, phosphoric acid, nitric acid, sulfuric acid, and hydrochloric acid.

[0028] The present invention also provides a high-purity quartz sand, which is prepared by the above-mentioned method for preparing high-purity quartz sand from granite pegmatite, wherein the purity of the high-purity quartz sand is greater than 99.99%.

[0029] The method for preparing high-purity quartz sand from granite pegmatite provided by this invention comprises the following steps: crushing and screening, washing and color sorting, primary calcination and water quenching, sand making and grading, magnetic and gravity separation, flotation, secondary calcination and water quenching, primary acid washing and drying, high-temperature chlorination, secondary acid washing, and sand baking. Compared with the prior art, this method has the following advantages:

[0030] The present invention provides a method for preparing high-purity quartz sand from granite pegmatite. The method is simple, has low production cost, and can obtain high-purity quartz sand with stable product quality and high purity. The specific details are as follows:

[0031] (1) Since the main minerals in granite pegmatite are feldspar, quartz, mica, etc., the quartz content is generally 20-40%, and the quartz crystals are relatively large. According to the individual liberation, the ore is crushed into intermediate particle size products of 3-50mm. Then, the intermediate particle size products are washed to clean the surface of the minerals, which is conducive to the identification of quartz by color sorting. Then, through the color sorter pre-sorting, a large amount of feldspar and mica can be thrown out. The quartz mineral content can be enriched from 20-40% to more than 90%, which not only reduces the gangue minerals entering the subsequent process, but also greatly reduces the amount of ore entering the calcination operation. Compared with the whole material entering the calcination operation, the production cost is greatly reduced.

[0032] (2) 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.

[0033] (3) Narrow-grained quartz sand is used for sorting. This can screen out flaky mica in advance, reduce the amount of large and fine mica entering the subsequent process, and avoid the inclusion caused by uneven particle size. In addition, narrow-grained sand can reduce the amount of material entering the sorting process, resulting in lower production costs.

[0034] (4) The flotation adopts a priority flotation process, which can achieve comprehensive recovery of feldspar and mica while preparing high-purity quartz sand, and has the characteristics of advanced production process. At the same time, the flotation is carried out by a combination of anion and cation collectors, which can achieve the synergistic effect of anion and cation collectors. This not only enhances the collecting ability of the collectors, but also increases the selectivity of the collectors, which is conducive to stabilizing product indicators and reducing the loss of quartz sand.

[0035] (5) Mixed acid operation can deeply remove impurity elements such as aluminum, calcium, potassium, and sodium, and dry magnetic inspection can further remove magnetic minerals brought in by the equipment or not completely removed, further stabilizing product purity and quality. Attached Figure Description

[0036] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0037] like Figure 1 As shown, this invention provides a method for preparing high-purity quartz sand from granite pegmatite, comprising the following steps:

[0038] Step S1: Crushing and screening. The granite pegmatite ore sample is crushed and screened to obtain intermediate particle size product and fine particle product. The coarse crushing, medium crushing and screening operations are combined into a two-stage closed-circuit process to crush and screen the granite pegmatite ore sample.

[0039] Step S2: Washing and color sorting. The intermediate particle size product obtained in step S1 is washed to remove the ore mud and clean the surface of the ore particles. Then, a color sorter is used to perform color sorting to obtain quartz raw material and waste.

[0040] Step S3: First calcination and water quenching. The quartz raw material obtained in step S2 is placed in a calcining furnace for calcination, and then quickly taken out and poured into cold water for water quenching to obtain quartz clinker. The calcination temperature is 800-1000 degrees Celsius and the calcination time is 30-150 minutes. Generally speaking, in order to make the heat treatment reaction of the ore complete, the larger the feed particle size, the longer the calcination time.

[0041] Step S4: Sand making and grading. The quartz clinker obtained in step S3 is subjected to sand making and grading to obtain intermediate-sized quartz raw sand and fine-grained product II. The sand making and grading is carried out by sand making. The sand making equipment is preferably one of sand making machine, ball mill, and rod mill, more preferably rod mill. The particle size of intermediate-sized quartz raw sand is preferably 0.074-0.45mm, more preferably 0.11-0.18mm.

[0042] Step S5: Magnetic and gravity separation. The quartz sand obtained 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. The equipment used for magnetic separation is preferably 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.

[0043] Step S6: Flotation operation. The intermediate product obtained in step S5 is slurry-adjusted, and inhibitors, modifiers, activators, and collectors are added sequentially for flotation to remove impurity minerals such as mica and feldspar, resulting in a flotation concentrate. The preferred process flow for the flotation operation is a process flow of sequential preferential flotation of mica and feldspar. 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. The inhibitor is preferably one or more of sodium hexametaphosphate and sodium silicate, with a preferred dosage of 200-500 g / t. The preferred modifier is sulfuric acid, which is used to adjust the pH value to 1.9-3.1. The preferred activator is one or more of hydrofluoric acid, sodium fluoride, and ammonium fluoride, with a preferred dosage of 500-1000 g / t. The preferred collector is a combination of anionic and cationic collectors, with a preferred dosage of 100-200 g / t.

[0044] Step S7: Secondary calcination and water quenching. The flotation concentrate obtained in step S6 is placed in a calcining furnace for calcination, and then quickly taken out and poured into cold water for water quenching to obtain flotation concentrate clinker. The calcination temperature is 800-1000 degrees Celsius and the calcination time is 30-150 minutes. Generally speaking, in order to make the heat treatment reaction of the ore complete, the larger the feed particle size, the longer the calcination time.

[0045] Step S8: First-time acid washing and drying. The flotation concentrate clinker obtained in step S7 is acid washed, then cleaned, dried, and subjected to dry magnetic inspection to obtain first-time acid-washed sand. The acid used in the acid washing operation is preferably one or more of hydrofluoric acid, phosphoric acid, nitric acid, sulfuric acid, and hydrochloric acid, more preferably hydrochloric acid, hydrofluoric acid, and sulfuric acid, with a preferred mass ratio of 3:1:1 and a preferred mixed acid mass concentration of 10-20%. The magnetic field strength for dry magnetic inspection is preferably 1.6-2.0T.

[0046] Step S9: High-temperature chlorination. The primary pickled sand obtained in step S8 is placed in a high-temperature chlorination furnace for chlorination reaction to obtain chlorinated sand. The preferred high-temperature chlorination temperature is 1000-1200 degrees Celsius. The preferred chlorinating agent is one or more of NaCl, KCl, CaCl, NH4Cl, HCl, and Cl2. The preferred chlorination pipe used for high-temperature chlorination is a synthetic high-purity quartz tube with a SiO2 purity of not less than 99.999%.

[0047] Step S10: Secondary acid washing. The chlorinated sand obtained in step S9 is subjected to secondary acid washing to remove impurities from the surface of the quartz sand, resulting in secondary acid-washed sand. The type of acid used in the acid washing operation is preferably one or more of hydrofluoric acid, phosphoric acid, nitric acid, sulfuric acid, and hydrochloric acid. More preferably, hydrochloric acid, hydrofluoric acid, and sulfuric acid are used. The mass ratio is preferably 3:1:1, and the mass concentration of the mixed acid is preferably 10-20%.

[0048] Step S11: Sand baking. The secondary acid-washed sand obtained in step S10 is 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 preferred instrument for baking is a high-purity quartz tube.

[0049] The technical solution of the present invention will be clearly and thoroughly described below with reference to specific embodiments.

[0050] The main minerals in this granite pegmatite are plagioclase, quartz, potassium feldspar, and mica, with contents of 45%, 37%, 8%, and 8%, respectively, and small amounts of magnetite, chlorite, and calcite. The quartz grains in this ore have good crystal form and are relatively pure under microscopic examination, indicating potential for preparing high-purity quartz. The multi-element analysis results of the raw ore are shown in Table 1.

[0051] Table 1. Results of multi-element analysis of raw ore

[0052]

[0053] Example 1

[0054] S1) Crushing and screening: The granite pegmatite sample is subjected to two-stage closed-circuit crushing and screening to obtain intermediate particle size products of 3-30mm.

[0055] S2) Washing and color sorting: Wash the intermediate particle size product obtained in step S1 to remove the ore mud and clean the surface of the ore particles. Then, use a color sorter to perform color sorting to obtain quartz raw material and waste.

[0056] S3) One-time calcination and water quenching: The quartz raw material is placed in a calcination furnace for calcination at a temperature of 800 degrees Celsius for 30 minutes. Then it is quickly taken out and poured into cold water for water quenching to obtain quartz clinker.

[0057] S4) Sand making and grading: The quartz clinker is made into sand and graded. The sand making and grading system is a closed loop. The coarse particles are returned. The sand making equipment is a rod mill to obtain intermediate-sized raw quartz sand with a particle size of 0.11-0.18mm.

[0058] S5) Magnetic separation and gravity separation: The raw quartz sand is subjected to magnetic separation. The equipment used for magnetic separation is one or more of a high gradient magnetic separator and an electromagnetic slurry machine. The magnetic field strength is 1.6T. Magnetic products and non-magnetic products are obtained. The non-magnetic products are subjected to gravity separation. The equipment used for gravity separation is a shaking table. Gravity separation light mineral products, gravity separation heavy mineral products and gravity separation intermediate products are obtained.

[0059] S6) Flotation operation: The intermediate product from gravity separation is slurry-adjusted and flotation is carried out using a process flow of priority flotation of mica and feldspar. Sodium hexametaphosphate 200g / t, sulfuric acid to adjust the pH value to 1.9, hydrofluoric acid 500g / t (added after the mica flotation operation), and dodecylamine + oleic acid (3:1) 100g / t are added in sequence. The mica flotation operation is carried out in 1 flotation operation to float out mica, and the feldspar flotation operation is carried out in 2 flotation operations to float out feldspar, to obtain flotation concentrate;

[0060] S7) Secondary calcination and water quenching: The flotation concentrate is placed in a calcination furnace for calcination at a temperature of 800 degrees Celsius for 30 minutes. Then, it is quickly taken out and poured into cold water for water quenching to obtain flotation concentrate clinker.

[0061] S8) First pickling and drying: The flotation concentrate clinker is pickled 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 pickling, it is washed in multiple stages, dried and checked with a dry magnetic field strength of 1.6T to obtain first pickled sand.

[0062] S9) High-temperature chlorination: The primary 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.

[0063] S10) Secondary acid washing: Chlorinated sand is subjected to secondary acid washing. The acid washing formula is hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and the mass concentration of the mixed acid is 10%. Impurities on the surface of the quartz sand are removed. After acid washing, multi-stage cleaning is performed to obtain secondary acid-washed sand.

[0064] S11) Sand roasting: The secondary acid-washed sand is dehydrated and then roasted at a high temperature of 700 degrees Celsius for 15 minutes. The instrument used for sand roasting is a high-purity quartz tube, thus obtaining high-purity quartz sand.

[0065] Table 2 Chemical analysis results of the high-purity quartz sand sample from Example 1

[0066]

[0067] Example 2

[0068] S1) Crushing and screening: The granite pegmatite sample is crushed and screened in two stages in a closed circuit to obtain intermediate particle size products of 10-50mm.

[0069] S2) Washing and color sorting: Wash the intermediate particle size product obtained in step S1 to remove the ore mud and clean the surface of the ore particles. Then, use a color sorter to perform color sorting to obtain quartz raw material and waste.

[0070] S3) One-time calcination and water quenching: The quartz raw material is placed in a calcination furnace for calcination at a temperature of 1000 degrees Celsius for 150 minutes. Then it is quickly taken out and poured into cold water for water quenching to obtain quartz clinker.

[0071] S4) Sand making and grading: The quartz clinker is made into sand and graded. The sand making and grading system is a closed loop. The coarse particles are returned. The sand making equipment is a rod mill to obtain intermediate-sized raw quartz sand with a particle size of 0.11-0.18mm.

[0072] S5) Magnetic separation and gravity separation: The raw quartz sand is subjected to magnetic separation. The equipment used for magnetic separation is one or more of a high gradient magnetic separator and an electromagnetic slurry machine. The magnetic field strength is 1.8T. Magnetic products and non-magnetic products are obtained. The non-magnetic products are subjected to gravity separation. The equipment used for gravity separation is a shaking table. Gravity separation light mineral products, gravity separation heavy mineral products and gravity separation intermediate products are obtained.

[0073] S6) Flotation operation: The intermediate product from gravity separation is slurry-adjusted and flotation is carried out using a process flow of mica and feldspar priority flotation. Sodium hexametaphosphate 500g / t, sulfuric acid to adjust the pH value to 3.1, hydrofluoric acid 1000g / t (added after the mica flotation operation), and dodecylamine + oleic acid (3:1) 200g / t are added in sequence. The mica flotation operation is carried out 3 times to float out mica, and the feldspar flotation operation is carried out 4 times to float out feldspar, to obtain flotation concentrate;

[0074] S7) Secondary calcination and water quenching: The flotation concentrate is placed in a calcination furnace for calcination at a temperature of 1000 degrees Celsius for 150 minutes. Then, it is quickly taken out and poured into cold water for water quenching to obtain flotation concentrate clinker.

[0075] S8) First pickling and drying: The flotation concentrate clinker is pickled 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 pickling, it is washed in multiple stages, dried and checked with a dry magnetic field strength of 2.0T to obtain first pickled sand.

[0076] S9) High-temperature chlorination: The primary 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.

[0077] S10) Secondary acid washing: Chlorinated sand is subjected to secondary acid washing. The acid washing formula is hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and the mass concentration of the mixed acid is 20%. Impurities on the surface of the quartz sand are removed. After acid washing, multi-stage cleaning is performed to obtain secondary acid-washed sand.

[0078] S11) Sand roasting: The secondary acid-washed sand is dehydrated and then roasted at a high temperature of 1100 degrees Celsius for 5 minutes. The instrument used for sand roasting is a high-purity quartz tube, thus obtaining high-purity quartz sand.

[0079] Table 3 Chemical analysis results of the high-purity quartz sand sample from Example 2

[0080]

[0081] Example 3

[0082] S1) Crushing and screening: The granite pegmatite sample is subjected to two-stage closed-circuit crushing and screening to obtain intermediate particle size products of 5-20mm.

[0083] S2) Washing and color sorting: Wash the intermediate particle size product obtained in step S1 to remove the ore mud and clean the surface of the ore particles. Then, use a color sorter to perform color sorting to obtain quartz raw material and waste.

[0084] S3) One-time calcination and water quenching: The quartz raw material is placed in a calcination furnace for calcination at a temperature of 900 degrees Celsius for 120 minutes. Then it is quickly taken out and poured into cold water for water quenching to obtain quartz clinker.

[0085] S4) Sand making and grading: The quartz clinker is made into sand and graded. The sand making and grading system is a closed loop. The coarse particles are returned. The sand making equipment is a rod mill to obtain intermediate-sized raw quartz sand with a particle size of 0.11-0.18mm.

[0086] S5) Magnetic separation and gravity separation: The raw quartz sand is subjected to magnetic separation. The equipment used for magnetic separation is one or more of a high gradient magnetic separator and an electromagnetic slurry machine. The magnetic field strength is 1.7T. Magnetic products and non-magnetic products are obtained. The non-magnetic products are subjected to gravity separation. The equipment used for gravity separation is a shaking table. Gravity separation light mineral products, gravity separation heavy mineral products and gravity separation intermediate products are obtained.

[0087] S6) Flotation operation: The intermediate product from gravity separation is slurry-adjusted and flotation is carried out using a process flow of prioritizing mica and feldspar flotation. Sodium hexametaphosphate 300g / t, sulfuric acid to adjust the pH value to 2.5, hydrofluoric acid 800g / t (added after the mica flotation operation), and dodecylamine + oleic acid (3:1) 150g / t are added in sequence. The mica flotation operation is carried out 2 times to float out mica, and the feldspar flotation operation is carried out 3 times to float out feldspar, to obtain flotation concentrate;

[0088] S7) Secondary calcination and water quenching: The flotation concentrate is placed in a calcination furnace for calcination at a temperature of 900 degrees Celsius for 120 minutes. Then, it is quickly taken out and poured into cold water for water quenching to obtain flotation concentrate clinker.

[0089] S8) First pickling and drying: The flotation concentrate clinker is pickled 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 pickling, it is washed in multiple stages, dried and checked with a dry magnetic field strength of 1.7T to obtain first pickled sand.

[0090] S9) High-temperature chlorination: The primary 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.

[0091] S10) Secondary acid washing: Chlorinated sand is subjected to secondary acid washing. The acid washing formula is hydrochloric acid, hydrofluoric acid and sulfuric acid in a mass ratio of 3:1:1 and the mass concentration of the mixed acid is 15%. Impurities on the surface of the quartz sand are removed. After acid washing, multi-stage cleaning is performed to obtain secondary acid-washed sand.

[0092] S11) Sand roasting: The secondary acid-washed sand is dehydrated and then roasted at a high temperature of 1000 degrees Celsius for 10 minutes. The instrument used for sand roasting is a high-purity quartz tube, thus obtaining high-purity quartz sand.

[0093] Table 4 Chemical analysis results of the high-purity quartz sand sample from Example 3

[0094]

[0095] The inventive principle of this invention is as follows:

[0096] (1) Since the main minerals in granite pegmatite are feldspar, quartz, mica, etc., the quartz content is generally 20-40%, and the quartz crystals are relatively large. According to the liberation of the individual particles, the ore is crushed to intermediate particle size products of 3-50mm. If the quartz crystals are relatively large, the intermediate particle size products can be controlled to be coarser, which can ensure the effect of liberation and enrichment, reduce the powdering rate, and improve the product recovery rate. If the quartz crystals are relatively small, the crushing particle size needs to be reduced. Then, the intermediate particle size products are washed to clean the surface of the minerals, which is conducive to the identification of quartz by color sorting. Then, through the color sorter pre-sorting, a large amount of feldspar and mica can be thrown out, and the quartz mineral content can be enriched from 20-40% to more than 90%. This not only reduces the gangue minerals entering the subsequent process, but also greatly reduces the amount of ore entering the calcination operation. Compared with the whole material entering the calcination operation, the production cost is greatly reduced.

[0097] (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.

[0098] (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.

[0099] (4) Narrow-grained quartz sand is used for sorting. This can screen out flaky mica in advance, reduce the amount of large and fine mica entering the subsequent process, and avoid the inclusion caused by uneven particle size. In addition, narrow-grained sand can reduce the amount of material entering the sorting process, resulting in lower production costs.

[0100] (5) 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.

[0101] (6) Mixed acid operation can deeply remove impurity elements such as aluminum, calcium, potassium, and sodium, and dry magnetic inspection can further remove magnetic minerals brought in by the equipment or not completely removed, further stabilizing product purity and quality.

[0102] (7) 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.

[0103] 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 granite pegmatite, characterized in that: Includes the following steps: Step S1: Crushing and screening. The granite pegmatite raw ore sample is crushed and screened to obtain intermediate particle size product and fine particle product. Step S2: Washing and color sorting. The intermediate particle size product obtained in step S1 is washed to remove the ore slime, and then color sorted using a color sorter to obtain quartz raw material and waste. Step S3: Calcination and water quenching. The quartz raw material obtained in step S2 is placed in a calcining furnace for calcination, and then quickly taken out and poured into cold water for water quenching to obtain quartz clinker. Step S4: Sand making and grading. The quartz clinker obtained in step S3 is subjected to sand making and grading to obtain intermediate-sized quartz raw sand and fine-grained product II. Step S5: Magnetic separation and gravity separation. The quartz raw sand obtained in step S4 is subjected to magnetic separation to obtain magnetic products and non-magnetic products. The non-magnetic products are subjected to gravity separation to obtain gravity-separated light mineral products, gravity-separated heavy mineral products and gravity-separated intermediate products. Step S6: Flotation operation. The intermediate product obtained in step S5 is slurry-adjusted, and inhibitors, modifiers, activators and collectors are added in sequence for flotation to obtain flotation concentrate. The collector is a combination of anion and cation collector, and the dosage is 100-200g / t. Step S7: Secondary calcination and water quenching. The flotation concentrate obtained in step S6 is placed in a calcining furnace for calcination, and then quickly taken out and poured into cold water for water quenching to obtain flotation concentrate clinker. Step S8: First acid washing and drying. The flotation concentrate clinker obtained in step S7 is acid washed, then cleaned and dried to obtain first acid washed sand. Step S9: High-temperature chlorination. The primary pickled sand obtained in step S8 is placed in a high-temperature chlorination furnace for chlorination reaction to obtain chlorinated sand; wherein, the high-temperature chlorination temperature is 1000~1200 degrees Celsius. Step S10: Secondary acid washing. The chlorinated sand obtained in step S9 is subjected to secondary acid washing to remove impurities from the surface of the quartz sand, resulting in secondary acid-washed sand. Step S11: Sand baking. The secondary acid-washed sand obtained in step S10 is 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.

2. The method for preparing high-purity quartz sand from granite pegmatite according to claim 1, characterized in that: In step S1, the particle size range of the intermediate particle size product is 3~50mm.

3. The method for preparing high-purity quartz sand from granite pegmatite according to claim 1, characterized in that: In step S4, the particle size of the raw quartz sand is 0.074-0.45 mm.

4. The method for preparing high-purity quartz sand from granite pegmatite according to claim 1, characterized in that: In step S5, the equipment used for magnetic separation is one or more of a high-gradient magnetic separator and an electromagnetic slurry machine, with a magnetic field strength of 1.6-1.8T.

5. The method for preparing high-purity quartz sand from granite pegmatite according to claim 1, characterized in that: The calcination temperature in steps S3 and S7 is 800~1000 degrees Celsius, and the calcination time is 30~150 min.

6. The method for preparing high-purity quartz sand from granite pegmatite according to claim 1, characterized in that: The acid used in the pickling operations in steps S8 and S10 is one or more of hydrofluoric acid, phosphoric acid, nitric acid, sulfuric acid, and hydrochloric acid.

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