Oxidation Kinetics of Vanadium Slag Roasting in the Presence of Calcium Oxide

The isothermal and non-isothermal oxidation kinetics of a converter vanadium slag in the presence of calcium oxide was studied using thermal analysis. The isothermal experimental data for the whole oxidation process are described in terms of the equation [1-(1-alpha)(2/3)] = kt with E-a = 20.42 kJ mol(-1) at lower temperatures of 400-500 degrees C, and described by [(1-alpha)(-1/3) - 1](2) = kt with E-a = 227.66 kJ mol(-1) at temperature higher than 500 degrees C. In the nonisothermal oxidation study, heating rate greatly affects the oxidation process. Using a heating rate of 3 degrees C min(-1) results in overlapping oxidations of vanadium spinel and augite over temperature range of 608-959 degrees C, which is described by the 3/2 order reaction. Increasing the heating rate to 5 degrees C min(-1) or 10 degrees C min-1, only oxidation of vanadium spinel takes place in temperature range of 657-914 degrees C and 691-954 degrees C respectively, both described by the third order chemical reaction. As the slag particle decreases from 250 mu m to 48 mu m, the kinetic equation for describing the overlapping oxidation process changes from the Anti-Zhuravlev equation with internal diffusion controlling to reaction limiting equations.