Value Recovery from Metallurgical Slags

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The metals extraction and recycling industries generate vast amounts of “slag”, a molten solution consisting of mostly oxides such as lime, silica and alumina. Traditionally, the material was regarded as a waste, and stored in piles or pits close to the smelting facilities. However, driven by the more stringent environmental regulations, need for resources, and economic factors, the recycling of slag has gained considerable attention and is partially practiced. The industry is however far from realizing all the value of metallurgical slags: minerals exceeding 600 million tonnes and thermal energy equivalent to 34 million tonnes of coal, each year. The present study aims at understanding and addressing some of the most critical challenges from fundamental perspective that would allow recovery of both the thermal and material values of slags by converting them to suitable materials for high value products. The research program explores the structural changes in the slags when they are cooled under various conditions, to allow their conversion to products such as cement feedstock and glass ceramics, and at the same time, transfer their thermal energy to another media. Additionally, the modification of slag by specific cooling conditions, addition of other materials, or oxidation/reduction will be investigated, aiming to recover of valuable elements from slag. Metallurgical slags have a very wide range of chemical composition. It is therefore the primary objective of this research program to understand the crystallization behavior of slag, as well as the speciation of different elements in slag in a very fundamental level. Such investigation is expected to establish correlations that would allow prediction of important parameters such as extent and rate of crystallization and mineral constituents of final slag from the initial composition and processing conditions (e.g. cooling rate, gas atmosphere, etc). The outcomes will be exceptionally significant for both creating a scientific knowledge base, as well as advancing industry's ability to realize all the value of slag and move towards more sustainable practices. The long term benefits are a cleaner metal extraction and recycling industry, reduced pressure on the earth resources, and training several graduate and undergraduate students with expertise in the fields of materials processing, waste treatment, and materials characterization.