The process of tungsten recovery by means of autoclaving and solvent extraction with tricaprylamine (Alamine 336) has been studied and the settling in combined mixer-settlers characterized.
The batch autoclaving tests evaluated the effects of operating variables such as reaction temperature, $Na_2CO_3/WO_3$ ratio, sodium carbonate concentration, reaction time and particle size.
For the solvent extraction process, the effects of operating variables such as the concentration of sulfuric acid, temperature, mixing time, pH and Alamine 336 concentration in solvent were studied by batch experiments. This was followed by modelling of the solvent regeneration and the extraction processes. From these models, the equilibrium constants were estimated, the equilibrium isotherm obtained and compared with experimental results. A two stage countercurrent system was operated continuously, the yield of tungsten in this unit being higher than 99.9%.
The combined mixer-settlers were used for continuous solvent extraction process. The empirical formula for the transient behavior of the emulsion band of thickness H in time t were obtained as
dH/dt = (Q/A) - UØ
where Q is the feed rate of emulsion, A the settler area and UØ the rate of coalescence. And a scale-up considerations were given for the continuous settler and its application to the combined mixer-settlers.
Finally, the economy of the solvent extraction process were considered with the combined mixer-settler plants compared against conventional plants.
