The Process Of Smelting Metallic Silicon With Silicon Oxide Minerals Is A Slag Free Process

Chemical silicon smelting requires strict selection of silica, which not only requires low impurity content, but also requires high mechanical strength, sufficient thermal stability, and appropriate particle size composition. It is best to use silica for chemical silicon smelting. Natural forms of silica exist either as independent quartz minerals, or as rocks almost entirely composed of silica - silica, or as sandstone in the form of silica. The impurities and adhesives in silicon oxide minerals used in the production of chemical silicon are completely reduced, partially reduced, and some enter the product silicon in the form of compounds or generate slag during the smelting process. This not only increases energy consumption, reduces product quality, but also creates difficulties in the smelting process. Therefore, strict requirements are placed on the chemical composition of silica containing minerals used in chemical silicon smelting. SiO2 should be greater than 99%, Fe2O3 should be less than 0.15%, Al2O3 should not be greater than 0.2%, CaO should not be greater than 0.1%, and the total amount of impurities should not exceed 0.6%. The silica used must be washed with water and the surface cleaned before melting.
The silica entering the furnace requires a certain particle size. The particle size of silica is an important process factor in smelting. The suitable particle size of silica is influenced by various factors such as the type of silica, electric furnace, capacity, operating conditions, and the type and particle size of reducing agents, and should be determined based on specific smelting conditions. In general, 6300KVA three-phase electric furnace (completed in Dawu Silicon Plant in 1983) requires silica particle size of 8-100mm, 3200KVA three-phase electric furnace requires silica particle size of 8-80mm, and the proportion of intermediate particle size composition is larger. When the particle size is too large, it is easy to cause unreacted silica to enter the liquid silicon due to the inability to adapt to the sticking material and reaction speed of the ramming furnace, resulting in an increase in slag volume, difficulty in furnace discharge, reduced silicon recovery rate, increased energy consumption, and even an increase in furnace bottom, affecting normal production. If the particle size is too small, although it can increase the contact surface of the reducing agent and facilitate the reduction reaction, the gas produced during the reaction process cannot be smoothly discharged, which will slow down the reaction speed. Grains pass through hours. The impurities brought in will increase again, affecting product quality. Silica generally smaller than 5mm should not be used in production.