Classification of silica
Silica, also known as quartz stone and quartz sand, accounts for about 26% of the weight of the earth's crust, ranking second only to ore-rich feldspar. Its texture is hard, often in the form of crystal or granular, massive aggregates and the appearance of silica is milky white, grayish white, faint yellow, etc., with a distinct luster. Quartz is by far the most common form while tridymite, cristobalite and hydrous silica mineral opals are not common, and only a few areas with vitreous silica, coesite and quartz have been reported coupled with several other forms produced in the laboratory but have not been found in nature.
Silica can be divided into crystalline silica (recrystallized quartzite) and cemented silica (cemented quartzite). In the sand making process, in light of different silica structures, suitable equipment should be selected to ensure the granularity, structure and purity of the finished product.
Crystalline silica
The crystalline silica generally showing appearances like a milky white, off-white, canary yellow, and reddish brown, has a bright luster, smooth and continuous section, sharp edges and corners with great hardness and strength. The vein quartz with a shell-like cross section appearances dense block, pure white, translucent and oily luster, in addition, its crystal particles are visually discernible which more than 2 mm.
Crystalline silica belongs to metamorphic rock formed by the recrystallization of siliceous sandstone (quartz sandstone). The siliceous cement in the siliceous sandstone recrystallizes on the surface of the original quartz particles under geological conditions then becomes an enlarged part of the quartz particles. Therefore, structural features shows that crystalline silica are composed of crystalline quartz particles between which there is no cement or very little (3% to 8%). Owing to recrystallization during the metamorphism, the quartz particles are closely connected to constitute a variety of crystallized structures like sawtooth, granite and mosaic which are not found in the original siliceous sandstone thus the complicated structure requires 69 -type jaw crusher with high crushing efficiency.
Vein quartz which also belongs to crystalline silica, is igneous rock characterized by large quartz particles (>2 mm), high purity (SiO2>99%), showing low conversion during calcination, large expansion, difficulty to be used in brick making.
cemented silica
The appearance of cemented silica is white, grayish white, yellowish gray, black, red, etc. And the section is dense and shell-shaped without obvious granular structure, the sharp edges and luster.
Quartz particles are sedimentary rock formed by the combination of silica cements whose structure is mainly composed of cryptocrystalline secondary quartz, and the content of cement is usually about 30% to 75%. The quartz particles crystallization in the cemented are small with a large amounts of impurities thus being easy to change upon heating. So when it comes to improve broken materials quality, 69-mode jaw crusher with stable performance is the best choice.
With its own rich chemical elements, Silica is widely used after processing, creating high value and broad market, in addition, Market demand for large crushing process contributes to a high production of silica hence 69-type jaw reducers come into being.
What is the use of processed silica? Global demand for industrial silica sands is expected to grow 5.6% per year, reaching 305 million metric tons until 2019. China is still the biggest consumer of quartz sand, being expected to keep its leading position with one-third of global demand by 2019. China, also the largest country with a huge glass industry in the world, will continue to enhance the industrial sand consumption for doors and windows, electronic displays, photovoltaic panels and other flat glass products and the rise of China's glass bottle industry (especially liquor beverage bottles) will further promote the sales of silica sand.
In India, casting activities will move forward at a healthy pace, stimulating the demand for quartz sand molds for cars, machine tools, wind turbines, and other metal castings. Due to the rapid increase in the production of glass products, metal casting and hydraulic fracturing activities, Indonesia's quartz sand industry sales are expected to grow strongly in 2019.
The special properties of commercial silica, such as chemistry, purity, particle size, color, inertness, hardness and high temperature resistance, make it the key to all walks of life and an economically irreplaceable one widely used in the industrial sector to provide raw materials for the downstream market with high added value.
Silica Sands Application Fields:
Glass: The main raw materials of flat glass, float glass, glass products, optical glass, glass fiber, glass equipment, conductive glass, glass cloth and anti-radiation special glass.
Ceramics and refractory materials: Raw glazes and porcelain blanks, high silica bricks for kiln, ordinary silica bricks and silicon carbide.
Metallurgy: raw materials, additives and flux of silicon metal, ferrosilicon alloy and silicon aluminum alloy, which proves that silica sand plays a key role in the production of ferrous and non-ferrous metals, acting as a cosolvent to decrease the melting point and viscosity.
Construction: used for concrete, cementitious materials, road construction materials, artificial marble, cement physical property testing materials (ie. cement standard sand).
Chemicals: Silica sand is used in various chemical fields such as soaps, dyes, detergents and paints.
Machinery: The main raw material of foundry sand, abrasive materials (blasting, hard grinding paper, sandpaper, abrasive cloth, etc.).
Aerospace: its intrinsic molecular chain structure, crystal shape and lattice change rules make it high-temperature resistance, small thermal expansion coefficient, high insulation, corrosion resistance, piezoelectric effect, resonance coupled with unique optical properties.
After processing, being used in many industries, finished silica sand and silicon powder enjoy high price and broad market where silica sand is usually used in construction, ceramics and metallurgy while silicon powder is used in glass, chemical, machinery and aerospace. Processing silica through silica sand and silica fume production lines is particularly important, which makes the jaw crusher being a primary crushing plant an essential part.
At present, jaw crusher usually is the first step of a silicon ore processing and PE-600 x 900 is the most popular one maned for its feed port size of 600×900 mm which can be widely used in the processing of 50-160 tons of materials. Its maximum feed size is 500 mm, and the discharge port adjustment range is 65-160 mm, which can handle large-tonnage silica materials to meet the production needs of high-volume silica.
How does it handle silicon? The silicon raw material is firstly sent by a vibrating feeder from the top feed port to the crushing chamber with the molars. Movable jaw teeth push the material onto the wall with great force and then press the material into smaller stones. The movement of the molars is supported by an eccentric shaft throughout the entire frame. When the rising angle between the movable jaw and the movable jaw toggle plate becomes large, thus promoting the movable jaw plate close to the fixed jaw, while the material is squeezed, rubbed, smashed in multiple breaking. When the moving jaw goes down, the angle between the movable jaw and the toggle plate is smaller, and the moving jaw plate leaves the fixed plate under the action of the tie rod and the spring at the same time crushed silica discharged from the crushing chamber mouth to achieve mass production as crushing motor being periodically crushed with the continuous rotation of the motor.
Obviously jaw crusher is the first step of sand production line in which the larger silica raw material is first uniformly sent to the jaw crusher by a vibrating feeder, then the crushed material is sent to a cone crusher or an impact crusher for the next reducing. The reduced material is sieved into two sizes hence material that meets the feed particle size can be directly sent to the sand maker for producing silica sand which should be washed into the final pure silica sand at last. While larger material which does not meet the size needs to be returned to the crusher until it is suitable for the sand maker and finally, the end sand needs to be dried with an industrial dryer or drying natural dynamics. Therefore, this entire production line is simple, less equipment and cost savings to customers thus the final pure silica sand can be sold to the downstream market at a higher price.
In the silicon powder production line, the jaw crusher also plays a key role. The original size of silica raw material is crushed into a jaw crusher through a vibrating screen, and after being crushed to meet the feed particle size requirements of the Raymond mill, the wollastonite particles are sent to the storage bin by the bucket elevator, then The material is evenly and continuously sent to the main machine grinding chamber for grinding by the electromagnetic vibrating feeder. The ground silica powder is sent to the classifier for classification under the driving of the fan airflow to make silica powder conformed to the fineness requirement to separated into the large cyclone collector and then discharged in the powder discharge tube, then the silica powder is finished.
Why PE-600×900 jaw crusher can crush silicon? PE series crusher is widely used in soft and hard ore crushing as well as mining and construction. Adopting advanced intelligent technology and touch screen operation mode, it displays production status in real time and can start with a single button. And the material used to cast the entire machine is of consistent quality and makes the machine work smoothly with fewer failures. Special structure makes silica gel easily crushed and the output exceeds customer expectations, in addition, the final product is uniform, pure in quality, free of dust and impurities, which can create higher economic benefits for customers. During the process of silica processing, a small amount of dust and wear debris are inevitably generated, which hinders the smooth running of the machine and causes wear of the parts while the final quality requirements for silica sand and silica fume are very strict thus the fewer impurities, the higher the purity of silica sand and silica powder, the higher the value it produces. That’s why the user should pay attention to the wear of the machine and the corrosion of water vapor.
Moreover, the feed port size of PE-600×900 jaw crusher is 600 mm×900 mm, and the maximum feed size is 500 mm which can fully satisfy the silica inlet because the common silica raw material size is 200-400 mm. Owing to the large market demands of silica, silica sand and silicon powder, the production line requirements are relatively large which cause a small jaw crusher not to meet the feed size and output requirements. However, the large jaw crusher, such as PE-1200×1500, has a feed port size of 1200×1500 mm with a maximum feed force of 1020 mm that is not suitable for processing silica raw materials and if you choose large equipment, you need to invest more money without high-performance cost ratio because the medium-sized jaw crusher can fully meet the silica production requirements.
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