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The process of smelting metal silicon from silicon oxide minerals is a slag-free process. The selection of silica in chemical silicon smelting is relatively strict, not only with less impurity content, but also high mechanical strength, sufficient thermal stability, and suitable particle size composition. 

It is best to use silica for chemical silicon smelting. In its natural form, silica occurs either as an isolated quartz mineral, or as silica, a rock formed almost entirely of silica, or as sandstone in the form of silica. During the smelting process, some of the impurities and adherents contained in silicon oxide minerals for the production of chemical silicon are completely reduced, some are partially reduced, and some enter the product silicon in the form of compounds or generate slag. This not only increases energy consumption, reduces product quality, but also causes difficulties in the smelting process. Therefore, there are strict requirements on the chemical composition of silicon oxide-containing minerals used in chemical silicon smelting. It is required that SiO2 is greater than 99%, Fe2O3 is less than 0.15%, Al2O3 is not greater than 0.2%, CaO is not greater than 0.1%, and the sum of impurities is not greater than 0.6%. 

The silica used must be washed with water before smelting to keep the surface clean. The silica into the furnace is required to have a certain particle size. The particle size of silica is an important process factor in smelting. The suitable particle size of silica is affected by various factors such as the type of silica, electric furnace, capacity, operating conditions, and the type and particle size of the reducing agent, and should be determined according to specific smelting conditions. In general, the 6300KVA three-phase electric furnace requires a silica particle size of 8-100mm, and the 3200KVA three-phase electric furnace requires a silica particle size of 8-80mm, and the proportion of the intermediate particle size is larger. When the particle size is too large, unreacted silica will easily enter the liquid silicon because it cannot be adapted to the furnace binder and reaction speed, resulting in an increase in the amount of slag, difficulty in getting out of the furnace, a decrease in the recovery rate of silicon, and an increase in energy consumption, which may even result in furnace failure. bottom rise, affecting normal production. If the particle size is too small, although the contact surface of the reducing agent can be increased, which is beneficial to the reduction reaction, the gas produced during the reaction cannot be discharged smoothly, and the reaction speed will be slowed down. Granularity too small. The impurities brought in will increase again, affecting product quality. Silica less than 5mm generally should not be used in production.