Processing of magnesium bearing materials by dry chlorination - An overview of kinetic aspects
Résumé
This paper is focused on the reactivity of Cl 2 towards MgO in presence of a reducing (CO) and oxidizing (O 2) agent at temperatures up to 1025 °C. Kinetics parameters are determined by thermogravimetry under isothermal conditions. The overviewed results showed that the carbochlorination (Cl 2 +CO) occurred at temperatures lower than oxychlorination (Cl 2 +O 2). The reaction of MgO with Cl 2 +CO from 425 °C to 600 °C proceeds with an activation energy (E a) of about 49 kJ/mol, while the reaction rate does not longer depend on the temperature between 600 and 675 °C. The reaction of MgO with Cl 2 +O 2 at 850-1025 °C was characterized by a value of E a of 214 kJ/mol indicating that the overall rate of the process is controlled by the rate of chemical reaction. Oxychlorination can also be used for removing the impurities contained in the industrial magnesium raw materials. Further, the behavior of the MgO in chlorine atmosphere leads to give an insight about the reaction mechanisms useful for the selective chlorination of complex ores and concentrates containing magnesium oxide.
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