Industrial silicon smelting requires strict control over the raw materials used. Silica and carbonaceous reducing agents are the two primary materials utilized in this process. The requisite specifications for the raw materials are stringent due to the strict requirements on the content of aluminum, calcium, and iron in the resulting industrial silicon. The silica used must have a SiO2 content greater than 99.0%, with Al2O3 less than 0.3%, Fe2O3 less than 0.15%, CaO less than 0.2%, and MgO less than 0.15%. In addition, the particle size should fall within the range of 15-80mm.
The carbonaceous reducing agent used should also meet certain criteria. It should have a high fixed carbon content, low ash content, and good chemical activity. Typically, low ash petroleum coke or pitch coke is used as the reducing agent. However, these materials have low resistivity and poor reaction abilities, necessitating the addition of charcoal or wood blocks that have low ash content, high resistivity, and strong reaction abilities. A small quantity of low-ash bituminous coal is also added to sinter the charge.
While the addition of charcoal or wood blocks is beneficial, using too much of these materials will increase the cost of the product and make furnace conditions disorderly. This can result in difficulties in tapping and other issues. Therefore, it is crucial to use the appropriate quantities of each material to ensure efficient, cost-effective industrial silicon smelting.
