Residues of industrial HT processes: composition and challenges

Michele Dondi (CNR-ISTEC Faenza)

High-throughput manufacturing of inorganic products makes often use of high temperature processes, particularly to transform minerals into metals, ceramics, glasses, cements, and various chemicals. These production processes can generate different kinds and amounts of residues at every stage. In addition, products at the end of their life usually turn into residues as well. The aim of this work is to overview the chemical and mineralogical composition of inorganic wastes stemming from the HT industrial processing. Residues are distinguished in relation to their origin (intentional, unintentional, physiological) and physical status (ash, slag, sludge, dust, wastewaters). They are classified (waste, by-product, "non-waste"; hazardous, non-hazardous) and the main technological issues for recycling risen. Case studies of waste generation are discussed to outline processes and materials composition: inorganic chemical processes (alumina, titania, phosphorus oxide); energy production (coal and biomass thermal power plants); metallurgical processes (ferrous and non-ferrous); glasses, ceramics and refractories (container glass, ceramic tiles); cementitious materials (cement and lime). The characteristics of industrial wastes from HT processes constitute the main technological challenge to be overcome in the transition towards a Circular Economy by scaling up a successful waste recycling.