Hot stage processing of metallurgical slags

Slags are an indispensable tool for the pyrometallurgical industry to extract and purify metals at competitive prices. Large volumes are produced annually, leading to important economical and ecological issues regarding their afterlife. To maximise the recycling potential, slag processing has become an integral part of the valorisation chain. However, processing is often directed solely towards the cooled slag. In this article, the authors present an overview of the scientific studies dedicated to the hot stage of slag processing, i.e. from the moment of slag/metal separation to complete cooling at the slag yard. Using in-depth case studies on C2S driven slag disintegration and chromium leaching, it is shown that the functional properties of the cooled slag can be significantly enhanced by small or large scale additions to the high temperature slag and/or variations in the cooling path, even without interfering with the metallurgical process. The technology to implement such hot stage processing steps in an industrial environment is currently available. No innovative technological solutions are required. Rather, advances in hot stage slag processing seem to rely primarily on further unravelling the relationships between process, structure and properties. This knowledge is required to identify the critical process parameters for quality control. Moreover, it could even allow to consciously alter slag compositions and cooling paths to tailor the slag to a certain application.