Reduction of ammonium paratungstate generated during hydrometallurgical processing of tungsten-copper borings

Abstract

Tungsten-copper (W-Cu) alloy is employed for manufacturing heavy duty contactors, relays, switches etc. During production of such components, W-Cu turnings/borings are generated. At CSIR-NML, a process for recovering tungsten and copper from tungsten-copper borings containing 46.01% W, 53.78% Cu, 0.13% Fe and other minor metals as high purity tungsten powder and copper powder has been developed. In the present work, a detailed investigation on reduction of ammonium paratungstate (APT) having purity 99.95% by hydrogen gas to produce high purity tungsten powder is presented. The various process parameters such as temperature, time and flow rate of hydrogen gas have been optimized. At the temperature of 800 degrees C and 0.1 lpm flow rate a reduction of 77.78% was observed up to 2h time. At 900 degrees C, with increase in flow rate from 0.1 lpm to 0.3 lpm the increase in reduction was found to be from 63.88% to 99.99% at 1h time. At still high temperature of 1000 degrees C, almost complete reduction was obtained at 0.1 lpm flow rate in 1h time. The effect of bed-depth was also carried out. At all temperatures chemical reaction was the rate determining step