High Temperature Processing of Tungsten Slag

Abstract

Tungsten is extraordinarily important for a broad range of industrial processes. It has the highest melting point of all metals (3410 °C) and a high density of 19.3 g/cm3. Tungsten carbide is known as one of the hardest materials. Tungsten is economically extractable from the two minerals wolframite ((Fe,Mn)WO4) and scheelite (CaWO4) through the intermediate ammonium paratungstate (APT). Tungsten concentrates are usually digested either by concentrated NaOH solution or by soda to form sodium tungstate solution which is further converted to APT. The leaching residue (tungsten slag) separated from the sodium tungstate solution consists of significant valuable metals such as W, Mo, Cu, Sn, Mn and Fe. These metals can be efficiently recovered by high temperature process with optimum conditions. Experimental work and thermodynamic calculations confirmed that most of the valuable metals can be concentrated to a low-melting point alloy and the clean slag can be used for cement additives.