A full-process acid-free semiconductor-grade quartz sand purification process

Abstract

The invention discloses a full-process acid-free semiconductor-grade quartz sand purification process, comprising: coarse crushing of raw ore to obtain coarse crushed ore with an average particle size of 1-3 cm; color sorting of the coarse crushed ore to select coarse crushed ore with a mica and / or feldspar content exceeding the detection limit, and washing and drying the remaining coarse crushed ore; roasting and water quenching the dried coarse crushed ore, and fine crushing and sand making to obtain quartz sand particles with a mesh size of 60-160; magnetic separation of the quartz sand particles to obtain magnetic mineral impurities; soaking the magnetically separated quartz sand in a scrubbing agent for 1-2 hours, and then scrubbing it under microwave assistance for 3-4 hours; performing reverse flotation on the scrubbed quartz sand and drying it; magnetic separation of the obtained quartz sand to obtain magnetic mineral impurities again; repeating the soaking, scrubbing, reverse flotation and drying operations on the obtained quartz sand; and chlorinating and purifying the obtained quartz sand with ammonium chloride solid at 1100-1200° C. to obtain semiconductor-grade quartz sand.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor-grade quartz sand preparation, and in particular to a full-process acid-free semiconductor-grade quartz sand purification process. Background Art

[0002] High-purity quartz sand refers to quartz with SiO2 purity ≥99.99%. Due to its excellent chemical stability, high temperature resistance, low thermal expansion coefficient and high light transmittance, it plays an irreplaceable role in many high-tech industries.

[0003] In the semiconductor field, quartz crucibles used in the manufacture of single crystal silicon, as well as key components in semiconductor processing, such as quartz boats, quartz tubes, and diffusion furnaces, are all made from ultra-high-purity quartz sand (SiO2 purity ≥ 99.9992%). Because the presence of metallic impurities in quartz sand can significantly affect the resulting high-precision quartz products, the semiconductor industry places extremely high demands on the purity of quartz sand. In particular, the impurity content of Ca, Fe, and alkali metals (such as Na, K, and Li) must be controlled within 2 ppm.

[0004] The purification process for high-purity quartz sand involves a series of steps, including ore crushing, high-temperature calcination, water quenching, sand making and screening, flotation, acid washing, and high-temperature chlorination. Flotation, as the most crucial step in the purification process, effectively removes the vast majority of mineral and metallic impurities. Flotation is a mineral processing method that utilizes differences in the physical and chemical properties of mineral surfaces (such as chemical adsorption, physical adsorption, and hydrophilicity and hydrophobicity) to separate quartz from impurities. Its core mechanism involves manipulating the mineral surface properties through reagents, allowing bubbles to selectively carry hydrophobic minerals for separation. Its high efficiency and flexibility make it an indispensable technology in modern mineral processing. However, current flotation efficiency in high-purity quartz purification is often low, failing to effectively remove mineral impurities adhering to the quartz surface. Therefore, a more efficient flotation process is needed.

[0005] In addition to flotation, pickling is also a key improvement step in the purification of high-purity quartz sand. Currently, pickling often requires volatile acids (such as hydrochloric acid and hydrofluoric acid), and the large-scale nature of industrial production creates a high demand for acid. This, in turn, places additional pressure on the purification process, including acid transportation and storage, equipment corrosion, and worker health hazards. Furthermore, the post-processing of waste acid must comply with environmental requirements, which also places certain pressures on production costs.

[0006] After searching, the following prior art is available:

[0007] Patent specification with publication number CN1562743A discloses a method for producing ultrapure quartz sand, which comprises preparing coarse silica sand by crushing and screening; removing surface impurities by hot acid leaching; removing bubbles and cracks inside the sand grains by cold explosion; and better removing foreign matter inside the mineral particles by ultrasonic vibration pickling.

[0008] Patent specification with publication number CN116143133A discloses a method for preparing high-purity quartz sand, which includes multiple steps such as flotation and pickling. The pickling mainly uses sulfuric acid, hydrochloric acid, nitric acid or hydrofluoric acid with an acid concentration of 5% to 20%. The acid is stirred at a constant temperature of 30 to 100°C for 2 to 24 hours.

[0009] Patent specification with publication number CN102120583A discloses a method for purifying high-purity quartz sand for crucibles and lining materials used in the electronics industry. The purification method includes multiple steps such as flotation and pickling. The pickling requires a ratio of 30% hydrochloric acid to 35% hydrofluoric acid (150 kg of hydrochloric acid and 40 kg of hydrofluoric acid per ton of quartz sand).

[0010] Patent specification with publication number CN110127708A discloses a method for purifying high-purity quartz sand with SiO2 purity ≥99.99%. The method includes multiple steps such as flotation and pickling. Flotation requires the use of hydrofluoric acid and NaOH / KOH as pH regulators, dodecylamine as a capture agent, and No. 2 oil as a foaming agent to float out feldspar mineral impurities under pH conditions of 2.0~3.0.

[0011] Patent specification with publication number CN119158691A discloses a method for preparing high-purity quartz sand, which includes using hydrochloric acid as a pickling agent and using hydrogen chloride as a calcining agent.

[0012] Patent specification with publication number CN119080008A discloses a process for preparing and processing high-purity quartz sand from quartz ore with high iron and aluminum content, including pickling the quartz sand with mixed acid and maintaining the temperature at 80-90°C; the subsequent process requires chlorination and purification of the quartz sand under hydrogen chloride gas and 1100-1200°C.

[0013] The above patented technologies all have the following problems:

[0014] 1) The purification process of high-purity quartz sand inevitably uses volatile acids, including hydrochloric acid and even hydrofluoric acid. Considering the large-scale use in industrial production, in the long term, it not only has a strong corrosive effect on equipment, but also poses a certain degree of harm to the health of workers. In particular, there are strict requirements for the storage and transportation of acids.

[0015] 2) The removal effect of metal impurities is limited. The cumulative content of Ca, Fe and alkali metals (Na, K, Li, etc.) often exceeds 10 ppm, which cannot meet the needs of the semiconductor field. Summary of the Invention

[0016] In response to the above-mentioned technical problems and the shortcomings in the field, the present invention provides a full-process acid-free semiconductor-grade quartz sand purification process. On the one hand, by optimizing the process (replacing the traditional pickling process with a microwave scrubbing process and selecting a suitable scrubbing agent), the use of volatile acids such as hydrochloric acid and hydrofluoric acid is avoided. On the other hand, by using a more selective flotation agent, the flotation efficiency is improved, and impurities on the quartz surface, especially metal impurities, are efficiently removed.

[0017] A full-process acid-free semiconductor-grade quartz sand purification process comprises the following steps:

[0018] S01: The raw ore is coarsely crushed to obtain coarse ore with an average particle size of 1-3 cm;

[0019] S02: Color sorting the coarse ores, picking out the coarse ores with mica and / or feldspar content exceeding the detection limit, and washing and drying the remaining coarse ores;

[0020] S03: roasting and water-quenching the coarse ore after drying in step S02, and finely crushing and sand-making to obtain quartz sand particles of 60-160 mesh;

[0021] S04: Magnetic separation of quartz sand particles to separate magnetic mineral impurities;

[0022] S05: Soaking the magnetically separated quartz sand in a scrubbing agent for 1-2 hours, and then scrubbing it under microwave assistance for 3-4 hours; the solvent of the scrubbing agent is water, and the scrubbing agent contains 5wt%-10wt% of sodium oxalate, 5wt%-10wt% of sodium citrate, and 5wt%-10wt% of disodium ethylenediaminetetraacetic acid;

[0023] S06: Perform reverse flotation on the quartz sand scrubbed in step S05 and dry it; the impurity mineral flotation agent used in the reverse flotation operation has the following structure: , where n is 7-11;

[0024] S07: The quartz sand obtained in step S06 is subjected to magnetic separation again to separate magnetic mineral impurities;

[0025] S08: Repeat the operations of step S05 and step S06 once on the quartz sand obtained in step S07;

[0026] S09: using ammonium chloride solid to chlorinate and purify the quartz sand obtained in step S08 at 1100-1200° C. to obtain semiconductor-grade quartz sand.

[0027] In step S01, the raw ore may include granite pegmatite ore, etc.

[0028] Preferably, in step S01, the ore with a particle size greater than 3 cm after coarse crushing is recovered and further coarse crushed.

[0029] Preferably, in step S02, the color sorting uses a laser light source.

[0030] Preferably, in step S04 and step S07, an electromagnetic separator is used for magnetic separation. Further preferably, the background magnetic field strength of the electromagnetic separator is 5000-6000 GS.

[0031] Preferably, in step S04 and step S07, the magnetic separation time is 2-4 hours.

[0032] Preferably, in step S05, the usage ratio of the quartz sand and the scrubbing agent is 1-1.5 kg / L.

[0033] Preferably, in step S05, the soaking temperature is 50-60°C.

[0034] Preferably, in step S05, the microwave is in pulse mode.

[0035] Preferably, in step S05, the frequency of the microwave is 2-2.45 GHz.

[0036] Preferably, in step S06, the reverse flotation operation specifically includes:

[0037] Transfer the quartz sand scrubbed in step S05 to a flotation machine and add water to prepare a quartz sand slurry;

[0038] Sodium citrate is added to the quartz sand slurry and stirred, followed by adding a quartz inhibitor and stirring, followed by adding the impurity mineral flotation agent and stirring, and then adding a frother and aerating to perform quartz reverse flotation. During the process, the quartz is stirred and the foam is scraped off, and the impurities float out with the foam to wash the quartz sand remaining in the flotation machine.

[0039] Preferably, in step S06, the temperature of the water used to prepare the quartz sand slurry is 50-60°C.

[0040] Preferably, in step S06, the mass concentration of quartz sand in the quartz sand slurry is 45% to 55%, for example, 50%.

[0041] Preferably, in step S06, based on the solid mass in the quartz sand slurry, the amount of sodium citrate added is 20-25 g / 500 kg.

[0042] Preferably, in step S06, the stirring time after adding the sodium citrate is 20-30 minutes.

[0043] Preferably, in step S06, the quartz inhibitor includes sodium fluorosilicate.

[0044] Preferably, in step S06, based on the solid mass in the quartz sand slurry, the amount of the quartz inhibitor added is 20-25 g / 500 kg.

[0045] Preferably, in step S06, the stirring time after adding the quartz inhibitor is 20-30 minutes.

[0046] Preferably, in step S06, based on the solid mass in the quartz sand slurry, the added amount of the impurity mineral flotation agent is 60-70 g / 500 kg.

[0047] Preferably, in step S06, the stirring time after adding the impurity mineral flotation agent is 20-30 minutes.

[0048] Preferably, in step S06, the foaming agent includes pine oil.

[0049] Preferably, in step S06, based on the solid mass in the quartz sand slurry, the amount of the foaming agent added is 10-15 g / 500 kg.

[0050] Preferably, in step S06, the time for performing quartz reverse flotation by aeration is 20-30 minutes.

[0051] Preferably, in step S09, based on the mass of the quartz sand obtained in step S08, the amount of solid ammonium chloride used is 100-120 g / 500 kg.

[0052] Preferably, in step S09, the holding time at 1100-1200° C. is 5-6 h.

[0053] Preferably, in step S09, the quartz sand after chlorination purification is quenched with water and dried to obtain semiconductor-grade quartz sand.

[0054] Compared with the quartz content in the raw ore, the recovery rate of semiconductor-grade quartz sand obtained by the full-process acid-free semiconductor-grade quartz sand purification process of the present invention is greater than 73%.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. The purification process of the present invention does not use hazardous chemicals such as acids (including acid liquids, acid gases, etc.), especially avoids the use of volatile acids and chlorine, which greatly reduces the production costs of enterprises and potential safety hazards.

[0057] 2. The addition of the microwave scrubbing process and the improvement of the flotation process in the present invention can effectively reduce the impurity content in the final finished sand, especially the content of Fe, Ca and alkali metal (Na, K, Li, etc.) impurities to less than 2 ppm, meeting the use requirements of semiconductor-grade high-purity quartz sand. DETAILED DESCRIPTION

[0058] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention and are not intended to limit the scope of the invention. The operating methods in the following examples where no specific conditions are specified are generally performed under conventional conditions or as recommended by the manufacturer.

[0059] Example 1:

[0060] Mineral raw materials:

[0061] Taking a batch of granite pegmatite ore from a certain region of India as an example, a material analysis was conducted. The mass content of quartz in the ore was 44.23%, the mass content of feldspar was 26.40%, the mass content of mica was 16.78%, the mass content of hematite / magnetite was 6.32%, the mass content of kyanite was 5.29%, and the mass content of other impurity minerals such as rutile and ilmenite was less than 1%.

[0062] Specific operation process of purification process:

[0063] (1) Preprocessing process:

[0064] The raw ore is coarsely crushed using a crusher to obtain coarse ore with an average particle size of 1-3 cm. Ore with a particle size greater than 3 cm after coarse crushing is returned to the crusher for further crushing. The coarse ore with an average particle size of 1-3 cm is color-sorted using a laser light source to remove coarse ore with high impurities such as mica and feldspar. The screened coarse ore is then washed and dried. The dried coarse ore is roasted and water-quenched, and finely crushed to obtain quartz sand particles with a mesh size of 60-160. The obtained quartz sand particles are magnetically separated using an electromagnetic separator with a background magnetic field strength of 6000 GS and a separation time of 2 hours to separate magnetic mineral impurities.

[0065] (2) Microwave-assisted scrubbing process:

[0066] 500 kg of magnetically separated quartz sand was placed in a scrubbing agent in a scrubbing machine. The scrubbing agent was 500 L of a water mixture with a mass fraction of 5% sodium oxalate, 5% sodium citrate, and 5% disodium ethylenediaminetetraacetic acid. The temperature was controlled at 50°C and soaked for 1 hour. Then, the sand was scrubbed for 3 hours under microwave assistance. The microwave was in pulse mode and the microwave frequency was 2.45 GHz. After scrubbing, the quartz sand was rinsed with clean water to clean it.

[0067] (3) Flotation process:

[0068] The scrubbed quartz sand is poured into a flotation machine. The preliminarily purified raw sand is stirred and rinsed once with 50°C warm water to prepare a quartz sand slurry with a mass concentration of 50%. Sodium citrate is added to the quartz sand slurry in the flotation machine at a rate of 20g / 500kg (500kg is based on the solid mass of the quartz sand slurry, the same below) and stirred for 20 minutes. A quartz inhibitor, sodium fluorosilicate, is then added to the slurry at a rate of 20g / 500kg and stirred for 20 minutes. An impurity mineral flotation agent, ODA, is then added at a rate of 60g / 500kg and stirred for 20 minutes. Pine oil, 10g / 500kg, is then added as a frother and quartz reverse flotation is performed with aeration for 30 minutes. During this period, the quartz is stirred and scraped to remove impurities with the foam. After flotation, the resulting quartz sand is rinsed two to three times with deionized water to remove any residual agent on the mineral surface, thereby obtaining fine quartz sand. The dried quartz sand is subjected to the aforementioned magnetic separation, scrubbing and flotation again.

[0069] The impurity mineral flotation agent ODA has the following structure: , where n=7.

[0070] (4) Chlorination roasting process:

[0071] The quartz sand dried after flotation is sent to a roasting furnace, and ammonium chloride solid is added. The amount of ammonium chloride solid is 100g / 500kg quartz sand. The temperature is controlled at 1100℃ for roasting for 5 hours. The roasted quartz sand is then placed in water for quenching, rapidly cooled with cooling water, and then dried to obtain the final semiconductor-grade high-purity quartz sand.

[0072] The test results show that semiconductor-grade quartz sand can be obtained according to the above process parameters and conditions, with a recovery rate of 73.25% (compared with the quartz content in the original ore), and the obtained product quartz sand has a grade (purity) of 99.9992%. Its main metal content indicators are shown in Table 1 below (unit: ppm, by mass).

[0073] Table 1

[0074]

[0075] Example 2:

[0076] Mineral raw materials:

[0077] Taking a batch of granite pegmatite ore from a certain region in India as an example, a material analysis was conducted. The mass content of quartz in the ore was 54.81%, the mass content of feldspar was 18.94%, the mass content of mica was 10.22%, the mass content of hematite / magnetite / ilmenite was 11.96%, the mass content of kyanite was 3.08%, and the mass content of other impurity minerals such as rutile and apatite was less than 1%.

[0078] The specific operation process of the purification process is the same as that of Example 1.

[0079] The test results show that semiconductor-grade quartz sand can be obtained according to the above process parameters and conditions, with a recovery rate of 79.86% (compared with the quartz content in the original ore), and the obtained product quartz sand has a grade (purity) of 99.9993%. Its main metal content indicators are shown in Table 2 below (unit: ppm, by mass).

[0080] Table 2

[0081]

[0082] Example 3:

[0083] Mineral raw materials:

[0084] Taking a batch of granite pegmatite ore from a certain region in India as an example, a material analysis was conducted. The mass content of quartz in the ore was 50.12%, the mass content of feldspar was 23.91%, the mass content of mica was 12.21%, the mass content of kyanite was 5.72%, the mass content of hematite / magnetite / ilmenite was 5.11%, and the mass content of other impurity minerals such as rutile and apatite was less than 3%.

[0085] The specific operation process of the purification process is the same as that of Example 1.

[0086] The test results show that semiconductor-grade quartz sand can be obtained according to the above process parameters and conditions, with a recovery rate of 76.96% (compared with the quartz content in the original ore), and the obtained product quartz sand has a grade (purity) of 99.9992%. Its main metal content indicators are shown in Table 3 below (unit: ppm, by mass).

[0087] Table 3

[0088]

[0089] Comparative Example 1:

[0090] The mineral raw materials are the same as those in Example 1.

[0091] The specific operation process of the purification process differs from that of Example 1 in that the microwave-assisted scrubbing process is replaced by an acid wash process. The acid wash process is as follows: 500 kg of quartz sand after magnetic separation and screening is added to a reactor. 300 L of mixed acid is prepared by mixing 38% hydrochloric acid and 49% hydrofluoric acid in a volume ratio of 2:1 for acid washing. The reactor temperature is maintained at 80-90°C for 8 hours. After the acid wash, the residue on the surface of the quartz sand is rinsed with clean water, and the next step of flotation is carried out. Furthermore, the quartz sand dried after the first flotation is subjected to the aforementioned magnetic separation, acid wash, and flotation again. The remaining operation process is the same as in Example 1.

[0092] The test results show that high-purity quartz sand can be obtained according to the above process parameters and conditions, with a recovery rate of 88.72% (compared with the quartz content in the original ore), and the obtained grade (purity) of the obtained quartz sand is 99.991%. According to various indicators, the quartz sand product of this comparative ratio cannot meet the demand for semiconductor-grade quartz sand. Its main metal content indicators are shown in Table 4 below (unit is ppm, by mass).

[0093] Table 4

[0094]

[0095] Comparative Example 2:

[0096] The mineral raw materials are the same as those in Example 1.

[0097] The specific operation of the purification process differs from that of Example 1 in that the flotation process is as follows: quartz sand is floated using sulfuric acid as a modifier at a pH of 2-4, and a combination of 600g / 500kg of dodecylamine, sodium dodecylsulfonate, and sodium oleate (mass ratio 3:2:1) as a capture agent. The capture agent is added in stages, with the initial addition controlled at 60% of the total amount during flotation, followed by gradual additions of 20% and 20% of the remaining capture agent. This ensures a more uniform and stable flotation process, prevents excessive initial capture agent consumption, and ensures that the capture agent concentration remains at an optimal level throughout the flotation process. Immediately after flotation, multiple water washes are performed using deionized water to thoroughly remove any residual capture agent. The dried quartz sand is then subjected to the aforementioned magnetic separation, scrubbing, and flotation procedures. The remaining operations are identical to those of Example 1.

[0098] The test results show that high-purity quartz sand can be obtained according to the above process parameters and conditions, with a recovery rate of 80.13% (compared with the quartz content in the original ore), and the obtained grade (purity) of the obtained quartz sand is 99.97%. According to various indicators, the quartz sand product of this comparative ratio cannot meet the demand for semiconductor-grade quartz sand. Its main metal content indicators are shown in Table 5 below (unit is ppm, by mass).

[0099] Table 5

[0100]

[0101] In summary, the present invention's full-process acid-free semiconductor-grade quartz sand purification process has the following characteristics:

[0102] First, color sorting is introduced during the pretreatment of quartz sand, and mica and feldspar are effectively removed from the coarse sand through a laser light source;

[0103] The second is to introduce a microwave-assisted scrubbing process to replace the traditional pickling process. Through the microwave treatment of a specific frequency and a specific scrubbing agent, the scrubbing agent can penetrate into the sand particles, achieving a better pickling effect.

[0104] The third is to optimize the flotation process and improve the flotation effect by using more efficient flotation agents.

[0105] Fourth, the entire process is safe and environmentally friendly, and no volatile acids such as hydrochloric acid, hydrofluoric acid, or highly dangerous acidic gases such as hydrogen chloride and chlorine are used.

[0106] Fifth, the purification process has obvious impurity removal effect. The cumulative content of key metal elements Fe, Ca, Ti and alkali metals (Na, K, Li, etc.) is less than 2 ppm, which meets the semiconductor industry's demand for quartz sand.

[0107] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A full-process acid-free semiconductor-grade quartz sand purification process, characterized in that: Including steps: S01: The raw ore is coarsely crushed to obtain coarse ore with an average particle size of 1-3 cm; S02: Color sorting the coarse ores, picking out the coarse ores with mica and / or feldspar content exceeding the detection limit, and washing and drying the remaining coarse ores; S03: roasting and water-quenching the coarse ore after drying in step S02, and finely crushing and sand-making to obtain quartz sand particles of 60-160 mesh; S04: Magnetic separation of quartz sand particles to separate magnetic mineral impurities; S05: Soaking the magnetically separated quartz sand in a scrubbing agent for 1-2 hours, and then scrubbing it under microwave assistance for 3-4 hours; the solvent of the scrubbing agent is water, and the scrubbing agent contains 5wt%-10wt% of sodium oxalate, 5wt%-10wt% of sodium citrate, and 5wt%-10wt% of disodium ethylenediaminetetraacetic acid; S06: Perform reverse flotation on the quartz sand scrubbed in step S05 and dry it; the impurity mineral flotation agent used in the reverse flotation operation has the following structure: , where n is 7-11; S07: The quartz sand obtained in step S06 is subjected to magnetic separation again to separate magnetic mineral impurities; S08: Repeat the operations of step S05 and step S06 once on the quartz sand obtained in step S07; S09: using ammonium chloride solid to chlorinate and purify the quartz sand obtained in step S08 at 1100-1200° C. to obtain semiconductor-grade quartz sand.

2. The full-process acid-free semiconductor-grade quartz sand purification process according to claim 1, characterized in that: In step S01, the ore with a particle size greater than 3 cm after coarse crushing is recovered and further coarse crushed.

3. The full-process acid-free semiconductor-grade quartz sand purification process according to claim 1, characterized in that: In step S02, the color sorting is performed using a laser light source.

4. The full-process acid-free semiconductor-grade quartz sand purification process according to claim 1, characterized in that: In step S04 and step S07, an electromagnetic separator is used for magnetic separation, the background magnetic field strength of the electromagnetic separator is 5000-6000 GS, and the magnetic separation time is 2-4 hours.

5. The full-process acid-free semiconductor-grade quartz sand purification process according to claim 1, characterized in that: In step S05: The usage ratio of the quartz sand and the scrubbing agent is 1-1.5 kg / L; The soaking temperature is 50-60°C; The microwave is in pulse mode, and the frequency of the microwave is 2-2.45 GHz.

6. The full-process acid-free semiconductor-grade quartz sand purification process according to claim 1, characterized in that: In step S06, the reverse flotation operation specifically includes: Transfer the quartz sand scrubbed in step S05 to a flotation machine and add water to prepare a quartz sand slurry; Sodium citrate is added to the quartz sand slurry and stirred, followed by adding a quartz inhibitor and stirring, followed by adding the impurity mineral flotation agent and stirring, and then adding a frother and aerating to perform quartz reverse flotation. During the process, the quartz is stirred and the foam is scraped off, and the impurities float out with the foam to wash the quartz sand remaining in the flotation machine.

7. The full-process acid-free semiconductor-grade quartz sand purification process according to claim 6, characterized in that: In step S06: The temperature of the water used to prepare the quartz sand slurry is 50-60°C; The mass concentration of quartz sand in the quartz sand slurry is 45% to 55%; Based on the solid mass in the quartz sand slurry, the amount of sodium citrate added is 20-25 g / 500 kg; The stirring time after adding the sodium citrate is 20-30 minutes; The quartz inhibitor includes sodium fluorosilicate; Based on the solid mass in the quartz sand slurry, the amount of the quartz inhibitor added is 20-25 g / 500 kg; The stirring time after adding the quartz inhibitor is 20-30 minutes; Based on the solid mass in the quartz sand slurry, the added amount of the impurity mineral flotation agent is 60-70 g / 500 kg; The stirring time after adding the impurity mineral flotation agent is 20-30 minutes; The foaming agent includes pine oil; Based on the solid mass in the quartz sand slurry, the amount of the foaming agent added is 10-15 g / 500 kg; The time for the aeration to carry out quartz reverse flotation is 20-30 minutes.

8. The full-process acid-free semiconductor-grade quartz sand purification process according to claim 1, characterized in that: In step S09, based on the mass of the quartz sand obtained in step S08, the amount of ammonium chloride solid used is 100-120 g / 500 kg.

9. The full-process acid-free semiconductor-grade quartz sand purification process according to claim 1, characterized in that: In step S09, the holding time at 1100-1200° C. is 5-6 h.

10. The full-process acid-free semiconductor-grade quartz sand purification process according to claim 1, characterized in that: In step S09, the quartz sand purified by chlorination is quenched with water and dried to obtain semiconductor-grade quartz sand.

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