Materials recovery from residues of integrated steel making process: experimental investigation on briquettes production

The recovery of residues from the integrated steel making process and their subsequent re-use inside the production cycle itself represent an exciting challenge, which can have strong economic and environmental implications. The aim of this study was to verify the feasibility of recovering and reusing residues from the steel production process of the ILVA steelworks. In detail, the residues of the steel process were tested in order to produce briquettes to be re-introduced as a ferrous source in the converters during the transformation process of hot metal into steel. For the scope, experimentations were carried out on a pilot briquetting plant; several mixtures, with contents varying between 70 and 80% slag and between 10 and 30% stock-house dust and sludge from steel shop n.2 were tested. As binders, hydrated lime and beet molasses were added in varying amounts. Results showed how each mixture was able to make briquettes of good consistency and integrity. However, the “mixture 2b”, consisted of a molasses and hydrated lime content of 8% and 2.7%, respectively, was found to be optimal in terms of crush resistance (CS = 75.33 daN/ briquette) and iron content (29%). The large-scale mass balance of the entire steelworks has made it possible to estimate the potential annual production volume of briquettes as well as the amount of iron to be recovered.