Kinetics and Mechanism of Wolframite Concentrate Interaction with Potassium Carbonate during Sintering

The kinetics and mechanism of interaction of wolframite concentrate with potassium carbonate during sintering in the temperature range of 25–1000 °C were studied. The sequence of phase transformations in an oxidizing atmosphere of air was established using thermal, X-ray spectral and X-ray phase analyses, as well as gas mass spectrometry. It was shown that in the temperature range of 520–820 °C, water-soluble potassium tungstate, its eutectic mixture with the initial reagent, and ferrite phases, iron and manganese oxides with a variable oxidation state are formed. A change in the wolframite composition during sintering was revealed, accompanied by a decrease in the proportion of iron, which is confirmed by an increase in the unit cell parameters of the FeMnWO phase. The kinetics of the process is described by a single-stage model with a dominant effect of autocatalytic nucleation, the activation energy is 56.6–56.9 kJ/mol. The obtained results are important for the development of technologies for processing wolframite concentrates to obtain soluble compounds.