Thermal Decomposition Kinetics of Dolomite in Pre-prepared Pellets for Magnesium Production

A novel silicothermic process was put forward in order to some the problems in Pidgeon process, including a loss of 5% fine powder produced during the calcination of dolomite and the easy deliquescence for calcined dolomite. For this method, pre-prepared pellets, which consist of dolomite, ferrosilicon, fluorite, and binder are prefabricated before calcination, and then the calcined pellets are used directly for magnesium production. The difference of decomposition behavior and thermal decomposition kinetics between pre-prepared pellets and pure dolomite were studied by thermogravimetry (TG) and differential thermal analysis (DTA) under non-isothermal conditions at different heating rates (4, 8, 16, and 30 K/min). The thermal decomposition data were analyzed using non-isothermal models and some isoconversional methods. The decomposition temperature of dolomite in pre-prepared pellets was lower than that in pure dolomite due to the higher thermal conductivity of ferrosilicon. The values of the activity energy for the two stages decomposition of dolomite are 270 and 280 kJ mol⁻¹ respectively in pre-prepared pellets, which were lower than pure dolomite.