Metallic silicon, also known as industrial silicon or crystalline silicon, usually in the furnace by the carbon reduction of silicon dioxide and obtained. Its main purpose is as a non-ferrous alloy additives and the production of semiconductor silicon, silicone raw materials.
In China, metal silicon is usually classified according to the content of the three main impurities, iron, aluminum and calcium. According to the metal silicon in the iron, aluminum, calcium percentage content, metal silicon can be divided into 553,441,411,421,3303,3305,2202,2502,1501,1101 and other different grades. (For metal silicon numbers: first and second codes are the percentages of iron and aluminum, and the third and fourth positions represent the calcium content. For example, 553 represents the iron and aluminum content of 5%, 5% , 3%; 3303 represents the iron and aluminum calcium content of 3%, 3%, 0.3%)
Metallic silicon production using carbon thermal method, that is, with silica, carbon reductant in the mine furnace smelting method. The silicon thus obtained has a purity of from 97% to 98%, and such silicon can generally be used for metallurgical purposes. If you want to get a higher grade of silicon, you need to be refined to remove impurities, get the purity of 99.7% to 99.8% of the metal silicon.
To quartz sand as raw material smelting of metal silicon, including quartz sand block, preparation of charge and mineral furnace smelting a few steps.
In general, high-quality quartz sand will be used directly for the production of high-grade quartz glass products, and even processed into gem-level, such as crystal, tourmaline and other products. The level is slightly worse but the reserves are larger, mining conditions slightly better, the surrounding electricity is cheaper to produce metal silicon.
At present, China's production of silicon metal carbon thermal process of production process: commonly used is the silica as raw material, petroleum coke, charcoal, wood chips, low ash coal as a reducing agent, in the mine heating furnace high temperature smelting, from silica To restore the metal silicon, which is no slag submerged arc high temperature smelting process.
Therefore, although the silicon metal is extracted from the silicon, but not all of the silica are suitable for the production of silicon metal. The ordinary sand we have seen in everyday practice is not the real raw material of silicon metal, but the quartz sand used in the above-mentioned industrial production, and undergoes a multi-step reaction to complete the transformation from sand to metal silicon.