Due to different uses, industrial silicon is categorised into different specifications. According to the content of iron, aluminium and calcium in metalloid silicon, metalloid silicon can be divided into different grades, such as 553, 441, 3303, 2202,1101 and so on. Additional products of non-metallic silicon are micro silica powder, edge silicon, black silicon, metallic silicon slag and so on. Among them, micro silica powder, also called micro silica fume, is widely used in refractory and concrete industries.
The raw materials for smelting industrial silica are mainly silicon dioxide and carbonaceous reducing agents. Since the aluminium, calcium and iron content of industrial silicon is strictly limited, the raw material requirements are also particularly stringent. In silica, SiO2>99.0%, Al2O3<0.3%, Fe2O3<0.15%, CaO<0.2%, MgO<0.15%; the particle size is 15-80mm.
The principles of selecting carbon-containing reducing agents are: high fixed carbon, low ash content and good chemical activity. Low ash petroleum coke or pitch coke is usually used as the reducing agent. However, due to the low resistivity and weak reactivity of these two types of coke, some petroleum coke should be replaced by charcoal (or wood chips) with low ash content, high resistivity and strong reactivity. Some low ash bituminous coal should also be added to sinter the charge. It should be noted that the excessive or complete use of charcoal will not only increase the cost of production, but also lead to the disturbance of furnace conditions, such as burning and destruction due to poor sintering of the material surface, making it difficult to form a blast furnace. In the high-temperature reaction zone, a SiC layer is easily formed on the furnace floor, making it difficult to drain the steel.