How to produce high purity quartz sand for crucible?

This paper introduces in detail the preparation of quartz sand for quartz crucible.

Crucible is mainly used in smelting industry. Its raw materials are metal and non-metal. It is the consumption equipment of smelting industry. Today's top product of crucible is semiconductor grade high-purity quartz glass crucible. Quartz glass crucible is a key necessity in the production of monocrystalline silicon. There is no other material to replace it. It is a consumable vessel for drawing large-diameter monocrystalline silicon. One crucible is used for each furnace of monocrystalline silicon production.

As monocrystalline silicon is the raw material for large-scale integrated circuit production, it has very strict requirements for crucible, so it also puts forward higher requirements for the raw materials for crucible manufacturing. Therefore, it is of great practical significance to develop a manufacturing method of quartz sand for quartz crucible with low impurity content.



Sinonine provides a processing method of quartz sand for quartz crucible, which can produce qualified high-purity quartz sand for crucible. The production method has strong operability and good quality.

The specific steps of high purity sand processing are as follows:
 
1.Select quartz stone with aluminum content no more than 11ppm, iron, calcium, magnesium, titanium, nickel, manganese, copper, lithium, sodium potassium, cobalt and boron content no more than 40 ppm, and silicon dioxide content more than 99.95% as raw material, clean and remove impurities from the raw material, and then primary crushing it to a diameter of 4-5 cm to obtain a first grade quartz material;

2.The first class quartz material is then selected and graded for further impurity removal, and then the sorted selected quartz material is put into the electric furnace, heated to 950 ℃ to 970 ℃ for 3 to 5 hours, and cooled to obtain the second grade quartz material;

3.The second class quartz material is sorted and cleaned again, and then it is crushed to a diameter of no more than 2cm. The roller crusher and vibrating screen are used to carry out three-stage grinding and cyclone classification screening, and the quartz sand with a diameter of 425 μ m to 88 μ m is screened out. Then the high-intensity magnetic separator is used to carry out magnetic separation treatment on the quartz sand to obtain the third class quartz material;

4.Add hydrochloric acid of 28-32% and hydrofluoric acid of 33-36% to the third grade quartz material, add hydrochloric acid of 145-155kg and hydrofluoric acid of 45-55kg to each ton of third grade quartz material, and then add pure water to immerse the third grade quartz material, pickling at 10 ℃ - 37 ℃ for 24-72h; then filter out the acid washing solution, wash with water until the acid washing solution is completely removed to obtain the fourth grade quartz material;

5.Add 1-1.5% sodium carbonate solution to the fourth grade quartz material, the weight ratio of the sodium carbonate solution to the fourth grade quartz material is 33-36:1000, then add pure water to immerse the fourth grade quartz material, and wash it for 50-70 minutes at 42 ℃-46 ℃; then filter out the alkali washing solution, wash it with water until the alkali washing solution is completely removed to obtain the fifth grade quartz material;

6.Use the ultrasonic equipment to carry out the ultrasonic vibration treatment on the fifth grade quartz material; then add the hydrochloric acid solution with the concentration of 28-32% to the grade-5 quartz material, add 80-120kg hydrochloric acid to each ton of fifth grade quartz material, then add pure water to immerse the fifth grade quartz material, pickling at 45 ℃-55 ℃ for 60-100min, then filter out the acid washing solution, wash with water until the acid washing solution is completely removed to obtain the sixth grade quartz material;

7.Put the sixth grade quartz into the flotation machine, immerse the sixth grade quartz with pure water at 40 ℃- 60 ℃, and then add the flotation agent to it for flotation. The flotation agent is a mixture of ammonia, oleic acid, palmitic acid, kerosene, ammonia fluoride and isooctanol. Add 0.1-0.2kg ammonia water, 0.4-0.6kg oleic acid, 0.1-0.3kg palmitic acid, 0.3-0.4kg kerosene, 0.1-0.2kg ammonia fluoride Kg, 0.7-0.8kg of isooctanol, after flotation, the flotation solution is filtered, washed with pure water at 50 ℃-60 ℃ until the flotation solution is completely removed, and seventh grade  quartz material is obtained;

8. Immerse the seven grade quartz material in pure water of 50 ℃-60 ℃, and then put chlorine into it for chlorination treatment. After chlorination treatment, filter the solution to obtain quartz sand; then immerse the quartz sand in 75% - 95% alcohol, wash it with alcohol for 60-80 minutes, filter the alcohol solution, and wash it with pure water until the alcohol solution is completely removed. Put the quartz sand into the sand roaster for 780 ℃-810 ℃ baking. After baking, use the magnetic separator for the first time After the second magnetic separation, the final quartz sand is obtained by 425 μ m electric sieve.



According to the genesis mechanism of mineral impurity, fluid impurity and non element impurity in quartz raw materials, the production process of quartz sand with scientific process, strong operability and suitable for industrial production is designed. The content of impurities in quartz sand for quartz crucible made by this method is low, including aluminum Al <5.5pm, iron Fe< 0.15ppm, titanium Ti<3.1ppm, calcium Ca<0.45pm: magnesium Mg<0.02ppm; Na<0.85ppm; K <0.25ppm; Li<0.10pm; SiO2>99.99%, total content of impurities<12.37ppm. The quartz sand produced by this method can be completely applied to the raw materials of high-purity and low aluminum quartz crucible for quartz crucible in semiconductor electronic industry, which is of great significance to the development of semiconductor electronic industry.