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Silicon metal, also known as industrial silicon or crystalline silicon, is usually made by reducing silicon dioxide from carbon in an electric furnace. Silicon metal is a product smelted from quartz and coke in an electric furnace, with the content of the main component silicon element at about 98% (in recent years, 99.99% Si content is also included in silicon metal), and the remaining impurities are iron, aluminum, calcium, etc. Its main use is as an additive for non-iron-based alloys and as a starting material for the production of semiconductor silicon and organic silicon.

In China, silicon metal is usually classified according to the content of its three main impurities: iron, aluminum, and calcium. According to the percentage content of iron, aluminum and calcium in silicon metal, silicon metal can be divided into different grades such as 553, 441, 411, 421, 3303, 3305, 2202, 2502, 1501 and 1101. (Regarding the source of silicon metal numbering: the codes 1 and 2 are for the percentage content of iron and aluminum, and the third and fourth two represent the content of calcium. For example, 553 represents that the content of calcium iron and aluminum in it is 5%, 5%, 3%; 3303 represents that the content of calcium iron and aluminum in it is 3%, 3%, 0.3%)

Silicon metal is produced by the carbothermal method, which is a method of smelting with silica and a carbonaceous reducing agent in a mineral-heating furnace. The purity of the silicon thus produced is 97% to 98%, and such silicon can generally be used for metallurgical purposes. To obtain a higher grade of silicon, it is necessary to refine it again to remove impurities and obtain silicon metal with a purity of 99.7% to 99.8%.

The smelting of silicon metal from quartz sand consists of several steps, including quartz sand lumping, preparation of furnace charge and smelting in a mineral-heating furnace.

Generally speaking, the best quartz sand is directly used to produce high-grade quartz glass products, and even processed into gemstone grade products such as crystal and tourmaline. The lesser grade, but with larger reserves, better mining conditions and cheaper electricity around, is suitable for the production of silicon metal.

At present, the production process route of carbon thermal method for the production of silicon metal in China: the commonly used is to take silica as raw material, petroleum coke, charcoal, wood chips, low ash coal, etc. as reducing agent, high-temperature melting in the mineral-heated electric furnace to reduce silicon metal from silica, which is a slagless submerged arc high-temperature melting process.

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