High-purity quartz sand generally refers to quartz fine powder with SiO2 content higher than 99.9%. It is mainly used in IC integrated circuits and quartz glass industries. Its high-grade products are widely used in large-scale and ultra-large scale integrated circuits, optical fibers, lasers, In space and military. High-purity quartz sand is a neutral inorganic filler, does not contain crystal water, does not participate in the chemical reaction of the filler. It is a very stable mineral filler widely used in plastics, rubber, ceramics and coatings, which can increase the product. A variety of new features can also save a lot of raw materials.

Quartz sand purification

Quartz sand purification is a difficult separation technique to remove small or trace impurities in quartz sand to obtain refined quartz sand or high-purity quartz sand (such as electronic grade products). In recent years, the main process of domestic production and production of high-purity quartz sand is as follows: the ore-bearing silica is washed and washed by the washing machine. After the crusher is coarsely broken, the qualified quartz material is put into the baking furnace and fired at a temperature of 850 ° C to 980 ° C. After 6 hours, after roasting, the quartz material is dragged into clear water for water quenching, and then manually sorted to remove impurities, sent to the crusher for crushing and sieving, and then the quartz sand passing through the screen is sent to the magnetic separator, magnetic After the selection, the quartz sand is put into an acid cylinder equipped with HCl and HF mixed acid for one week, and then subjected to flotation, dehydration, baking, cooling and packaging to obtain high-purity quartz sand.

The main process and technical requirements for quartz sand purification:

1. Rough selection: remove obvious impurities and foreign matter from various quartz ore;

2, crushing: using a professional crusher to crush the quartz ore to particles with a particle size of 1~20mm;

3. Water quenching: The quartz particles after being burned are rapidly cooled in cold water to achieve the purpose of removing bubbles, water marks and some encapsulated impurities inside the mineral, so that the minerals are cracked. Quartz calcination water quenching treatment is also called thermal crushing, which means that quartz crystal transformation occurs when calcined at high temperature (α quartz→β quartz→β-scale quartz), which increases the volume and the degree of defects in the crystal becomes more serious. When the volume of the crystal suddenly becomes small when water quenching, the internal stress at the crystal defect rapidly increases to cause the crystal to break at the defect. The crystal breaks at the defect, exposing the inclusions in the original quartz and the impurities in the crack to the surface of the particle, which can be easily removed by acid treatment.

4. Crushing: The raw material is made into ultra-fine quartz sand with a particle size of 5~50μm by wet or dry grinding;

5. High-latitude magnetic magnetic separation: high-strength magnetic separation beneficiation equipment with magnetic field strength of 50~15000 Gauss is selected, and the raw materials themselves and the iron and other simple substances introduced during the operation and the compounds with weak magnetic properties are taken out;

6. Grading: The grading equipment is used to divide the raw materials into products of various particle size ranges according to the standard. In the subsequent processing, the raw materials are separately processed according to the particle size range;

7. Calcination: using a professional roasting furnace, the quartz ore particles are calcined at 300 ° C ~ 1500 ° C for 2 to 5 hours;

8. Water crushing: The burned quartz particles are quickly placed in room temperature hot water to be cooled, and the easily soluble substances formed by calcination are dissolved, and the solubility of the soluble substances in the water is increased by heating the water for 0.5 to 2 hours. .

9. Flotation: adding flotation agent to the quartz sand fine powder after water pulverization, and removing impurities having a specific gravity of less than 1;

10. Deionized water washing: Washing off residual flotation agent and impurities on the surface of quartz sand with deionized water;

11. Drying: first remove the large amount of water by air drying (drying) after deionized water washing, and then drying in special drying equipment and heating to 100 ° C ~ 200 ° C;

12. Acid leaching: adding the dried quartz sand to the dipping tank, and rapidly adding the acid (sulfuric acid, hydrochloric acid, nitric acid or hydrofluoric acid) used for acid leaching under the condition of dry high temperature, the acid concentration is 5% to 20%. constant stirring at 30 ℃ ~ 100 ℃ 2 to 24 hours to remove fines quartz sand of trace metals and non-metallic impurities; acid leaching is an important step in the purification process of high purity quartz sand, either prepared Quartz glass for electric light sources is also a process that must be used to prepare quartz materials for photovoltaics and semiconductor devices. Acid leaching is mainly for the removal of acid-soluble metal oxides and partial silicate minerals. After undergoing roasting water quenching, sorting, and strong magnetic separation, most oxides and impurity minerals have been removed, but some oxides and impurity minerals are present in grain boundaries, micro-cracks and crystals, which is somewhat difficult to remove. Long-term acid leaching to remove such impurities.

13. Deionized water washing: the acid leached material is washed with deionized water to remove the acid solution contained in the raw material until neutral;

14. Drying and packaging: The raw materials are dried by special drying equipment, and vacuum-packed in the purification workshop to obtain the products. Source: Mineral Network

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