Production process of silicon calcium alloy
It is generally believed that the chemical reaction expression of smelting si ca alloy is
CaO + SiO2 + 3 c - CaSi + 3 co write
But at high temperature, lime and silica first form calcium silicate slag with low melting point, which makes the carbon reduction reaction difficult to proceed. Calcium has a low boiling point and is volatile to produce calcium vapor. Moreover, SiO2 is reduced to SiO(gas), so the gases discharged from the furnace are CO, Ca(gas) and SiO(gas). The loss of calcium and silicon in furnace gas is about 10% each. When SiO(gas) and Ca(gas) pass through the material layer, they react with carbon, and most of them are converted into CaC2 and SiC. Therefore, the reactivity of carbonaceous reducing agent is very important for smelting silicon calcium alloy. CaC2 and SiC are produced at high temperature by the same carbon of calcium oxide and silica, which are intermediate products in the production of silica-calcium alloy. A portion is eventually left in the slag, so the production of silicon calcium alloy is smelted by slag. Virtually all industrial production methods of silicon and calcium alloys are based on CaC2 as the transition product. The density of silicon calcium alloy is slightly lower than that of slag, and the si-Ca alloy is basically concentrated in the upper part of molten pool during smelting process, which is the characteristic of smelting silicon calcium alloy. Special measures must be taken to separate it from the slag when it is removed from the furnace. According to the above analysis, there are three processes for smelting silicon calcium alloy by electrocarburization (reduction), namely, mixed feeding method, layered feeding method and calcium carbide method. Electrosilicon thermal (reduction) method is also one of the methods to produce silicon calcium alloy.
