KINETIC ANALYSIS OF ISOTHERMAL DECOMPOSITION PROCESS OF ZINC LEACH RESIDUE IN AN INERT ATMOSPHERE. THE ESTIMATION OF THE APPARENT ACTIVATION ENERGY DISTRIBUTION

Thermal decomposition of zinc leach residue has been studied in a tubular furnace under a constant nitrogen gas flowing, at four different operating temperatures (600 degrees C, 750 degrees C, 950 degrees C, and 1150 degrees C). Using a detailed kinetic analysis, it was shown that the investigated process can be described by a two-parameter autocatalytic Sestak-Berggren reaction model. It was noted that the apparent activation energy values E-a increase progressively with a degree of conversion, accompanied by the appearance of a convex Arrhenius dependence. This behavior is a characteristic of a system of parallel competing reactions. It was concluded that the investigated isothermal decomposition process is characterized by unusually very low preexponential factor and low values of the apparent activation energy. Based on the derived density distribution function of E-a values, it was concluded that the isothermal decomposition process probably occurs through four reaction steps, where each step is characterized by one parallel reaction.