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The quartzite is first sent to the jaw crusher for coarse crushing, and then sent to the cone crusher for medium and fine crushing after reasonable screening by the circular vibrating screen. The unqualified materials are returned to the cone crusher for re-crushing after the same screening. The quartzite that meets the sand making requirements is driven by the conveyor into the sand making machine for sand making and shaping to obtain 0-5mm silica sand.
The quartzite material contains a large amount of clay minerals, so the silica sand needs to be cleaned and desludged.
[Scope of application of washing]: It is suitable for minerals that can be simply washed to remove clay. The general silica sand particle size is 0.075-1.0mm, while the clay mineral particle size is <50μm, generally less than 20μm.
[Washing]: Different sand washing equipment can be used for cleaning, such as washing tank, hydrocyclone, upflow hydraulic classifier, etc. At present, the upward hydraulic classifier is mostly used. Fine-grained minerals are discharged as slurry in the form of top overflow, while coarse and heavy particles are discharged from the bottom.
[Screening]: Coarse sand can be removed by a 0.5-1.0mm wet screen to separate silica sand and clay minerals from each other in the water medium.
Scrubbing refers to the use of mechanical force and friction between sand particles to remove film iron, binding and mud impurity minerals on the surface of silica sand, and further grind unaggregated mineral aggregates. After the classification operation, the silica sand will be further purified.
Currently, there are mainly mechanical scrubbing, rod scrubbing, high-efficiency and strong drug scrubbing and ultrasonic scrubbing. The mechanical floor washing equipment is a rotary floor washing machine with a strong floor washing capacity of 200-250T/H.
Magnetic separation is mainly used to remove magnetic minerals in silica sand. For example, weakly magnetic minerals such as hematite, limonite, and biotite can be removed by a strong magnetic separator, while strongly magnetic minerals such as magnetite, titanomagnetite, and pyrrhotite can be removed by a weak magnetic separator.
Silica sand has a complex composition. In addition to iron-containing minerals, it often contains mica, feldspar and clay minerals. Some impurities in silica sand, such as feldspar and mica, cannot be removed by magnetic separation, but can be separated by different collectors. Generally, the purity of silica sand can be increased to 99% after washing, desliming, magnetic separation and flotation.
The acid leaching method is used to remove iron from silica sand. It is based on the fact that silica sand is insoluble in acid (except hydrofluoric acid), while impurity minerals containing Fe can be dissolved by acid solution, so iron minerals in silica sand can be removed. .
The purity of silica sand after flotation can reach 99.5-99.9%. If silica sand is further purified, impurities in the form of spots and inclusions on the surface of silica particles must be treated by acid leaching. According to the requirements of different impurity minerals (Fe, Al, Ti, Cr) in silica sand for different industrial uses, mixed acid leaching treatment with different concentrations and ratios is carried out.
In addition, acid leaching time, mineral particle size and slurry agitation will affect the removal efficiency. Therefore, various factors must be reasonably controlled to reduce the cost of silica sand washing plant.
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