Kinetics of oxychlorination of chromite Part I. Effect of temperature

Nonisothermal thermogravimetric (TG) analysis was used to evaluate the reac tivity of a chromite mineral [(Fe2+, Mg)(Cr, Al, Fe3+)(2)O-4] towards Cl-2 + CO, Cl-2 + N-2 and Cl-2 + O-2 gaseous mixtures up to 1000 degreesC. Full chlorination and volatilization of reaction products were achieved at about 975 degreesC using Cl-2 + CO, while only about 40% of the sample have reac ted at 1000 degreesC using Cl-2 + N-2 and Cl-2 + O-2. The effect of the temperature on the oxychlorination with Cl-2 + O-2 Of the chromite mineral was studied between 600 and 1050 degreesC using isotherma l TG measurements. The results show that the oxychlorination of chromite oc curs in two stages. The initial stage of the oxychlorination was characteri zed by average values of apparent activation energy of about 151 and 57 kJ/ mol for the temperatures lower and higher than 825 degreesC, respectively. While a value of about 262 kJ/mol was found for the second stage of the oxy chlorination process between 925 and 1050 degreesC. The effects of temperat ure on the oxychlorination of the simple chromite constituents (Cr2O3, Fe2O 3 and MgO) were also studied. (C) 2001 Elsevier Science B.V. All rights res erved.