Application of quenching to polycrystalline metallurgical slags to reduce comminution energy and increase mineral liberation

Metallurgical slags could potentially mineralize a large portion of the CO2 resulting from metals production. However, to efficiently mineralize CO2 the reactive minerals must be liberated from unreactive species. The inherent inefficiencies in mechanical grinding methods requires large energy expenditure, diminishing the net CO2 mineralization. As metallurgical slags are produced at high temperatures, quenching has the potential to induce micro-fractures throughout the slag due to thermal stresses. Calculation of mineralogically-dependent fracture stresses, geometric considerations, and material-dependent thermal properties were used to determine the ability of quenching to liberate minerals from heterogeneous slag. Feedbacks of diffusion and fracturing were evaluated for a range of compositions representative of metallurgical slags. The results indicate that grain size distribution and the convection coefficient are the primary determinants of the efficacy of quenching-based fracturing and liberation. Single-stage quenching of 1300 K slag in 300 K water was found, on average, to reduce the grinding energy for mineral liberation of slowly solidified slag by 27.1% - 40.4%, pit-solidified slag by 0.0% - 16.7%, and rapidly-solidified slag by 0.0% - 28.6%. Variations in fracture extent within slag of a single grain size distribution were due in order of decreasing importance to: the convection coefficient, the degree of feedback from fracturing on heat transfer, the mineralogy, and the porosity. Such secondary effects were found to be suppressed as grain size distribution increased.