SOUZA, S. E.; SOUZA, Severino Emenegildo de.
Abstract:
In the present work, the influence of temperature, particle diameter and acid concentration on the conversion of scheelite as a function of time was studied. in the reaction: CaWO s + 2HCl, v H WO, s + CaCl 2.
4 (a) 2M (s) 2 (aq). Scheelite conversion was followed by determining the concentration of Ca + 2 ions as a function of time. A laboratory scale equipment was designed and assembled; in order to enable kinetic measurements reaction under isothermal and total mixing conditions. Different kinetic models for the reaction were tested; It was concluded that the classical kinetic model: r - kCnA is not representative of the reaction for the whole range of conversions.
The nucleation model was tested: In = ktm • ('"Xs) and the constants m and k were calculated by linear regression using a computer. This model agrees with experimental data across the conversion range. For concentrates with an average particle diameter equal to 68u (-200 / 25Oles) 100% of scheelite concentrate was converted into tungstic acid within four and a half hours of reaction with 6 Molar hydrochloric acid and temperature 80 ° C. For diameters greater than 68u, there was a reduction in the rate of reaction. The acid concentration variable exerts less influence on the reaction rate: compared with the particle diameter and temperature variables.
