Intrinsic Kinetics of Chlorination of WO^sub 3^ Particles With Cl^sub 2^ Gas Between 973 K and 1223 K (700 °C and 950 °C)

Chlorination is one of the methods applied in extractive metallurgy for the treatment of minerals to obtain valuable metals, such as titanium and zirconium. The possibility of applying chlorination metallurgy to other metals such as tungsten was the major aim of this study. The kinetics of the chlorination of tungsten oxide (WO^sub 3^) particles has been investigated by thermogravimetry between 973 K and 1223 K (700 °C and 950 °C) and for partial pressures of chlorine ranging from 15 to 70 kPa. The starting temperature for the reaction of WO^sub 3^ with chlorine is determined to be about 920 K (647 °C). The influence of chlorine diffusion through the bulk gas phase and through the particle interstices in the overall rate was analyzed. In the absence of these two mass-transfer steps, a reaction order of 0.5 with respect to chlorine partial pressure, and an activation energy of 183 kJ/mol were determined. For tungsten oxide particles of less than 50-µm size, a complete rate expression has been obtained. [PUBLICATION ABSTRACT]