Critical Review of Chemical Metallurgy of Tungsten

Abstract

Tungsten is one of the most important refractory metals as it is used in the production of numerous end use items such as tungsten and tungsten carbide parts. Tungsten is also used in the manufacturing of steels, super alloys, and catalysts. Other applications of tungsten are in the manufacturing of tungsten-copper and tungsten-silver composites. Tungsten from its concentrates and secondary sources is processed as high-purity ammonium para tungstate (APT). Currently, there are two main APT production processes: one uses solid ion exchange and the other uses liquid ion exchange. Both processes use multiple process steps and generate large amount of process wastewater. Other serious problem of APT production is the difficulty in the availability of tungsten sources especially to the plants outside China. The ore concentrates available to some tungsten processors in the market may be low grade ores and/or the high grade ores containing large amount of critical impurities such as Mo and/or radioactive elements. This paper will discuss some of these issues and also some process-related issues such as equipment scaling, loss of LIX solvents, tungsten losses in the overall process, and large volume of process waste water, especially in the solid ion exchange method. Due to the proprietary nature of the work, literature from only presentations and publications will be presented. This paper will also discuss the recent literature, related to new conceptual APT process which could lead to increased efficiency, energy reduction, and waste minimization.