Silicon metal, also known as industrial silicon or crystalline silicon, is usually produced by reducing silicon dioxide with carbon in an electric furnace. Its main uses are as additives for non-iron-based alloys and starting materials 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. (About the source of metal silicon numbers: the first and second codes represent the percentage content of iron and aluminum, and the third and fourth digits represent the calcium content. For example, 553 represents the iron, aluminum, and calcium content of 5% and 5%. , 3%; 3303 represents that the content of iron, aluminum, and calcium is 3%, 3%, 0.3%)
The Production Process of Silicon Metal
Metal silicon is produced using the carbothermal method, which is a method of smelting silica and carbonaceous reducing agents in a submerged arc furnace. The purity of the silicon produced in this way is 97% to 98%, and such silicon can generally be used for metallurgical purposes. If you want to obtain higher-grade silicon, you need to refine it to remove impurities to obtain silicon metal with a purity of 99.7% to 99.8%.
Smelting silicon metal using quartz sand as raw material includes quartz sand block making, charge preparation, and submerged arc furnace smelting.
Generally speaking, high-quality quartz sand will be directly used to produce high-end quartz glass products, and even processed into gem-level products such as crystal, tourmaline, and other products. Those with slightly lower grades but larger reserves, slightly better mining conditions, and cheaper surrounding electricity are suitable for the production of silicon metal.
At present, the production process route of the carbothermal method for producing metal silicon in China is: silica is commonly used as raw material, petroleum coke, charcoal, wood chips, low-ash coal, etc. are used as reducing agents, and it is smelted at high temperature in a submersible electric furnace to obtain silica from silica. Metal silicon is restored, which is a slag-free submerged arc high-temperature smelting process.
Application Fields of Silicon Metal
The downstream applications of silicon metal are mainly organic silicon, polysilicon, and aluminum alloys.
Organic silicon has the highest requirements for silicon metal, which requires chemical grade, and the corresponding model is 421#, followed by polysilicon, with commonly used models 553# and 441#, and aluminum alloy has the lowest requirements. However, in recent years, the demand for organic silicon and polysilicon has increased, and its proportion has increased. Large, aluminum alloy demand not only did not increase but also decreased. This is also a major factor that leads to the seemingly high silicon metal production capacity, but the low operating rate, and the serious shortage of high-grade metal silicon in the market.
The Future Trend of Silicon Metal
In the next 5 to 10 years, the market demand for silicon metal will continue to increase steadily. As cars become more popular in more and more places, the amount of silicon metal used in the aluminum alloy industry will continue to increase. In addition, the chemical industry will also become the main driving force for the increase in demand for silicon metal.
Judging from the current development trend of the industrial chain, the following new changes may occur in the industrial silicon market in the next few years, which will affect the development of the entire industry: First, the dividends of power reform and the uncertainty of self-supplied power grids; second, the market Demand may experience low or zero growth; finally, new technologies, production, and sales models impact the entire market.
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