High purity quartz sand generally refers to quartz powder with SiO2 content above 99.9%. It is mainly used in IC integrated circuit and quartz glass industry. Its high grade products are widely used in large-scale and ultra large scale integrated circuit, optical fiber, laser, space and military. High purity quartz sand is a neutral inorganic filler. It does not contain crystalline water and does not participate in the chemical reaction of the filled material. It is a very stable mineral filler. It is widely used in plastics, rubber, ceramics and coatings. It can not only increase the new functions of the products, but also save a lot of raw materials.
Purification of quartz sand
Quartz sand purification is a highly difficult separation technology to remove trace or trace impurities from quartz sand and obtain refined quartz sand or high purity quartz sand, such as electronic grade products. In recent years, the main technological process of producing high purity quartz sand in domestic production is as follows: after washing the silt by the washing machine of the raw mineral, the qualified quartz material is put into the roaster and roasted for 6 hours at the temperature of 850 C ~980 C after the crushing machine is broken. After roasting, the quartz material is dragged into water for water quenching and the impurities are removed by artificial selection. It is sent into the crusher for crushing and sieving, and then sent into the magnetic separator through the quartz sand of the sieve. After magnetic separation, the quartz sand is soaked in the acid cylinder with HCl and HF mixed acid for a week, and then the high purity quartz sand is made by flotation, dehydration, baking, cooling and packing.
The main process and technical requirements for the purification of quartz sand
1. Rough selection: remove the obvious impurities and foreign matters in various quartz raw ores;
2. Crushing: crushing the quartz ore to a particle size of 1~20mm by using a professional crusher;
3. Water quenching: the burnt quartz particles are cooled quickly in cold water to remove the bubbles, water lines and some inclusions in the minerals, so that the minerals are cracked. Quartz calcining water quenching is also called thermal crushing, which refers to the crystalline transformation of quartz during high temperature calcination (alpha quartz, beta quartz, beta scale quartz), which makes the volume increase, the original defect degree in the crystal becomes more serious. When the water quenched, the volume of the crystal suddenly becomes smaller and the internal stress at the crystal defect increases rapidly to promote the crystal. A method of breaking up at a defect. The crystal is broken at the defect, exposing impurities in the inclusions and cracks in the original quartz to the surface of the particles, which can be easily removed when the acid is treated;
4. Crushing: using wet or dry grinding to make raw materials with a particle size of 5 ~ 50 μm ultra-fine quartz sand;
5. High-ladder magnetic magnetic selection: Select high-ladder magnetic magnetic separation equipment with a magnetic field strength of 50 to 15,000 Gaussian, remove the raw material itself and the iron and other elemental elements introduced during the operation, and these elemental compounds with weak magnetism;
6. Grading: Using grading equipment to divide raw materials into a variety of granularity products according to standards, in the subsequent treatment, according to the granularity range are treated separately;
7. Roasting: Using a professional roasting furnace, quartz ore particles are roasting for 2 to 5 hours under conditions of 300 °C ~ 1500 °C;
8. Water fragmentation: The burned quartz particles are quickly cooled in hot water at room temperature, dissolved in the soluble material produced by roasting, and heated to water for 0.5 to 2 hours to increase the solubility of this part of the soluble material in water;
9. Flotation: After breaking the water, the quartz sand fine powder is added to the flotation agent to remove impurities with a specific gravity of less than 1;
10. Deionized water washing: Deionized water washing to remove residual flotation agents and quartz sand surface impurities;
11. Drying: The deionized quartz sand is first dried(dried) and other large quantities of water are removed, and then dried in special drying equipment and heated to 100 °C ~ 200 °C;
12. Acid immersion: Add dried quartz sand to the dip tank and quickly add acid(sulfuric acid, hydrochloric acid, nitric acid or hydrofluoric acid) used for acid immersion under dry and high temperature conditions. The concentration of acid is 5 % to 20 %. Stir at a constant temperature of 2 to 24 hours at 30 °C ~ 100 °C to remove trace metals and non-metallic impurities in quartz fine powder; Acid leaching is one of the important processes in the purification process of Gaochun quartz sand. Whether it is the preparation of quartz glass for electric light sources or the preparation of quartz raw materials for photovoltaic and semiconductor devices, it must be used. Acid immersion is mainly to remove acid soluble metal oxides and some silicate minerals. After undergoing baking, quenching, picking, and strong magnetic separation, most oxide and impurity minerals have been removed, but some oxides and impurity minerals are still in the grain boundary, micro-fissure, and crystal bodies, removing some difficulties, so use For a long time of acid leaching, To remove such impurities.
13. Deionized water washing: The raw material after acid immersion is washed with deionized water to remove the acid contained in the raw material until it is neutral;
14. Drying and packaging: drying the raw materials with special drying equipment and vacuum packing in the purification workshop to get the products.