Kinetics of oxychlorination of chromite: Part I. Effect of temperature

Nonisothermal thermogravimetric (TG) analysis was used to evaluate the reactivity of a chromite mineral [(Fe2+, Mg)(Cr, Al, Fe3+)2O4] towards Cl2+CO, Cl2+N2 and Cl2+O2 gaseous mixtures up to 1000°C. Full chlorination and volatilization of reaction products were achieved at about 975°C using Cl2+CO, while only about 40% of the sample have reacted at 1000°C using Cl2+N2 and Cl2+O2. The effect of the temperature on the oxychlorination with Cl2+O2 of the chromite mineral was studied between 600 and 1050°C using isothermal TG measurements. The results show that the oxychlorination of chromite occurs in two stages. The initial stage of the oxychlorination was characterized by average values of apparent activation energy of about 151 and 57 kJ/mol for the temperatures lower and higher than 825°C, respectively. While a value of about 262 kJ/mol was found for the second stage of the oxychlorination process between 925 and 1050°C. The effects of temperature on the oxychlorination of the simple chromite constituents (Cr2O3, Fe2O3 and MgO) were also studied.