Fundamental studies for high temperature processing of tungsten leaching residues for alloy formation

The first step in the production of tungsten is to enrich tungsten from two minerals wolframite((Fe,Mn)WO_(4))and scheelite(CaWO_(4))through the leaching process.The leaching residue usually contains a certain amount(2-5 wt%)of WO_(3) which is higher than that in the tungsten ore(generally less than 1 wt%).In addition,the leaching residue may also consist of other valuable elements such as Cu,Ta,Nb,Sn,Sc,Mn and Fe.Understanding the phases and their compositions present in the residue is one of the key steps for the efficient utilization.The typical residue sample is carefully analysed by electron probe X-ray microanalysis and X-ray fluorescence.A high-temperature process,which includes pre-reduction at 1000-1100℃and smelting reduction at 1450-1500℃,is proposed to efficiently recover the valuable elements.Experimental work and thermo-dynamic calculations confirmed that most of the valuable elements can be economically recovered with optimum conditions.