Algerian Silica Behavior Study at High Temperature for Carbothermic Process

Silica is used as raw material for metallurgical grade silicon production intended for photovoltaic field. Our work consists to study the silica behavior (sandstones, quartz) from two Algerian deposits tested at high temperature in a muffle furnace. These tests show the capacity of the silica to produce very fine particles, which have an adverse effect during carbothermic process. The quartz veins from Tirek deposit (Hoggar region) and sandstone from El-Taref deposit were used as raw material (97-98% SiO2). Optical microscopy shows the presence of deformations and recrystallizations in quartz. These defects directly influence the behavior of the silica at high-temperature. The qualitative characterization at high temperature (brust tests) allows us to determine the silica thermal and mechanical properties. Based on these tests, we deduce the friability index (FI), strength thermal index (STI) and the heat index (HI) of every type of examined silica. The quartz sample from Tirek deposit presents the most required values, which are respectively HI = 52-56%, FI = 8.75-11.25%, TSI = 23.31-23.93. The obtained results show us the feasibility of using this silica in the submerged arc furnace, to obtain metallurgical grade silicon.