Determination of kinetic aspects from the non-isothermal chlorination of tungsten minerals

The main kinetic aspects of the chlorination of tungsten minerals with chlorine and sulphur dioxide were analyzed from data obtained under non-isothermal conditions. The tungsten minerals studied were wolframite, scheelite and a scheelite-wolframite concentrate. The collected minerals were milled and then concentrated by means of gravity separation. Chlorinations were made in a vertical reactor with a static bed and upward flow of reactive gases using an empirical methodology that was established taking into account the most important physicochemical features of the system. The rate equation and the apparent activation energy for each tungsten mineral were determined by the integration method using a characteristic temperature to evaluate the temperature integral. An easy applicable criterion was used to determine the corresponding values of the characteristic temperature. Results obtained allowed to establish that the movement of an interface controls the wolframite chlorination and that the presence of non-volatile reaction products affects the chlorination of scheelite and of the scheelite-wolframite concentrate. An operative sequence was proposed to determine the temperature range (initial and final) in which the respective rate equation selected from nonisothermal data maintained its validity. Finally, the characteristic temperature was calculated by a frequently used route and results obtained were compared in each case.