Revisiting the Kellogg diagrams: roaster diagrams and their usefulness in pyrometallurgy

ABSTRACT

While predominance area diagrams (PADs) are useful for the determination of the stable phases in the metal–sulfur–oxygen system, they are constructed at constant temperature. Varying the temperature results in shifting of the equilibrium lines and the stability areas thereof. Since the available tools in hands of an extractive metallurgist are temperature and oxygen potential, a more useful diagram would be one that shows the stability areas of different phases as a function of temperature and percent of oxygen in the roast gas. Such diagrams, called ‘roaster’ diagrams, derive directly from PADs. Although such diagrams are used by extractive practitioners, this type of diagram is unavailable in the open literature. In this paper, the relationship between the PADs and roaster diagrams is discussed and PADs and roaster diagrams for the Zn–S–O and Pb–S–O ternary systems are constructed. This information will serve as the foundation for more complex four-component systems to follow in subsequent publications.

KEYWORDS:

• Predominance area diagrams
• pyrometallurgy
• roaster diagrams
• sulfide roasting

Acknowledgements

Dr. Andrew Larson, former Professor of Metallurgical Engineering, Colorado School of Mines is the originator of roaster diagrams so far as the authors are able to trace the subject origins. The content provided in this paper is part of MET 321 course material (High Temperature Extraction, Concentration, and Recycling) taught by the authors at the South Dakota School of Mines and Technology.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.