Non-isothermal thermoanalytical studies on the salt roasting of chalcopyrite using KCl

In an earlier study [1], the isothermal kinetics of salt roasting of chalco pyrite under an oxidizing atmosphere using KCl was studied in the temperatu re range 523-773 K. The salt roasting reaction was found to be chemically c ontrolled at temperatures below 600 K both under static air and oxygen atmo sphere. At higher temperatures, the process was not thermally activated bec ause of a change in the chemistry of the process. In the present study, the salt roasting of chalcopyrite using KCl under oxygen and static air atmosp here was studied by non-isothermal thermoanalytical studies up to 723 K. Th e effect of salt content, heating rate and particle size on the salt roasti ng behavior was studied using TG/DTA techniques at a programmed linear heat ing rate. The TG and DTA studies reveal two distinct chemical processes, on e operative up to 620 K and the other from 620 to 723 K. The integral metho d of Coats and Redfern was used for the treatment of non-isothermal kinetic data. The non-isothermal analysis confirmed the chemical control mechanism at temperatures below 620 K. However, the activation energy for the proces s derived from non-isothermal thermogravimetric analysis is almost twice as that deduced from isothermal measurements. In the temperature range 620-72 3 K, the kinetic data still obeys the interfacial reaction control model al though the activation energy in this temperature range is very low. (C) 200 1 Elsevier Science B.V. All rights reserved.