May. 06, 2024
Minerals & Metallurgy
Silica sand is a versatile material with a wide range of applications due to its unique properties, including high purity, hardness, and resistance to chemical and physical weathering. Some of the primary uses of silica sand include:
However, natural silica contains many impurities, and silica sand needs to be purified to meet the requirements of various industrial uses. How is silica sand processed?
Procedures for crude quartz stone need to go through for high purity silica sand processing plant | quartz sand processing plant | frac sand processing plant
MINGYUAN Heavy Industrial Equipment can provide solutions and equipment for silica processing plants. The production process of silica sand includes 4 stages of crushing, grinding, purifying, and drying.
1. Silica crushing process
Primary crushing
Silica raw ore is hard and needs to be crushed by a jaw crusher to reduce its size. The crushed product is sent to the circular vibrating screen for screening. The qualified silica is sent to the next stage.
Secondary crushing
After the screening, the unqualified silica stone is sent to the hydraulic cone crusher by the belt conveyor for secondary crushing and screening.
2. Silica scrubbing process
Scrubbing is to remove the iron thin film and muddy impurities on the silica surface through mechanical force and friction between mineral particles. Silica rock is often scrubbed with a rod abrasive.
The crushed silica is sent to the powder silo for storage and sent to the rod mill by the ore feeder for grinding. This process can enhance the scrubbing effect and separate the silica from impurities as much as possible to achieve optional particle size.
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Washing silica sand
The ground silica sand is sent to the spiral classifier for classification, and at the same time, the silica sand can be washed to remove impurities and dust on the surface.
3. Silica sand purifying process
Magnetic separation of silica sand
Silica sand usually contains some iron impurity minerals, such as hematite, limonite, ilmenite, pyrrhotite, tourmaline, hornblende, and so on. These iron-containing impurities may be embedded in the particles and adhere to the surface of the silica sand.
Features of silica sand magnetic separator:
Flotation of silica sand
It is difficult to separate minerals such as mica and feldspar from silica sand, and the common method is to use cationic collectors. Sulfuric acid or hydrochloric acid is commonly used to lower the pH and activate the mica and feldspar surfaces.
A cationic collector is added to the silica sand slurry, making mica and feldspar minerals hydrophobic and forming a froth layer. The froth layer is skimmed off the surface of the flotation cell. The remaining particles are mainly silicon dioxide.
Features of silica sand flotation machine:
4. Silica sand drying process
Dry the purified silica sand to reduce its water content to a certain level. Pack the selected silica sand for easy storage and transportation.
Features of silica sand dryer:
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Quoting from this paper: Haus R., Prinz S., Priess C. (2012) Assessment of High Purity Quartz Resources. In: Götze J., Möckel R. (eds) Quartz: Deposits, Mineralogy and Analytics. Springer Geology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-22161-3_2
What purity level is required in naturally occurring silica in order to be used for manufacturing semiconductors?
As high as possible.
...high purity quartz with total impurity levels less than 20 ppm...
20 ppm means that the silica has to be 99.998% pure. It is extremely hard to find silica that pure in nature.
More specifically:
Specific requirements as to tolerable limiting values differ from industry to industry. In the lamp tubing and optics industries aluminium content in the refined quartz concentrate should not exceed 20 ppm, other metals should be less than 1 ppm, and total impurities less than 30 ppm. For semiconductor base materials and crucibles aluminium content should be even lower, specified to less than 10 ppm, other metals less than 0.1 ppm, and total impurities not to exceed 15 ppm.
Feedstock for solar silicon used in the photovoltaic industry should generally have boron and phosphorus contents in the sub-ppm range since these elements are most difficult to remove and negatively affect the performance of the solar cells (Geerligs et al. 2002).
For microelectronics applications, e.g. in epoxy moulding compounds, uranium and thorium, both responsible for soft errors by alpha radiation, should be less than 2 ppb, and in low alpha applications, even less than 0.5 ppb.
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