Abstract:Due to the high density of bismuth element, it is easy to precipitate in the process of carbothermic reduction smelting of industrial silicon, resulting in uneven distribution of impurities in the industrial silicon obtained from smelting, so it is of great significance to study the kinetic behavior of bismuth in the carbothermic reduction reaction and provide theoretical guidance for the control of bismuth in industrial silicon smelting. The effects of different carbon reducing agents on the carbon thermal reduction of bismuth trioxide were studied by thermogravimetric analysis. The results show that petroleum coke as reducing agent has better reducing properties duo to its higher activity than graphite. The phase transition sequence of the reduction products of bismuth trioxide at different temperatures is Bi2O3→intermediate oxide Bi2O2.5→Bi. The kinetics of bismuth trioxide carbothermic reduction reaction at different heating rates was studied by thermogravimetric analysis. The average apparent activation energy of bismuth trioxide carbothermic reduction reaction is 142.41 kJ/mol and the pre-exponential factor is 2.96×109 s-1 by iso-conversion method, Kissinger method and ?atava-?esták method. The reaction mechanism belongs to the phase boundary reaction, and the differential form of the corresponding kinetic equation is 3(1—α)2/3.