Slags containing critical minerals concentrated in artificial phases, so-called engineered artificial minerals (EnAMs), are a novel source of critical raw materials. To liberate the EnAMs, the slags need to be comminuted, reducing the size of the particles. This work investigated the dependence of the breakage behavior on particle size and mineral structure during the comminution of an EnAM-containing slag. Piston-die experiments were performed for particles in the 3 mm to 5 mm size range. Nanoindentation and two-roller breakage tester experiments were performed for those in the 50 µm to 200 µm size range. The investigations were accompanied by X-ray computed tomography (XCT) and scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDX) measurements as well as a micro X-ray fluorescence analysis to examine the mineral microstructure. It was found that the commonly assumed exponential connection between particle size and strength differed in the two size ranges. This behavior can be linked to different grain and cluster sizes, which were found in the investigation of the mineral microstructure. In addition to particle size, it was found that mineral structure plays an important role when characterizing the breakage behavior.

A previously developed texture inheritance model is used to investigate the interactions be-tween particle microstructure and breakage behavior in discrete element method (DEM) sim-ulations of high pressure grinding rolls (HPGR). The texture inheritance model uses spherical particles to reduce computation cost, allowing simulations of large-scale processes while pre-serving particle microstructure during breakage events. To validate the setup, a benchmark is performed using a simpler reference case without breakage.By implementing and varying a composition dependent peak-force breakage criterion, the influence of particle composition on comminution and liberation behavior are investigated. Evaluations are based on material throughput, breakage rate, degree of liberation and particle size distributions.Initially, the volumetric fraction of each phase is used to weight the breakage strength of the respective phase. Subsequently, the breakage strength of one phase is systematically varied to assess the influence of strength differences between material phases on breakage behav-ior in the HPGR process.The results for discharge speed, flow rate, and normalized stress distributions in the bench-mark show good agreement with reference data. The analysis of the influence of microstruc-ture on breakage behavior indicates that weaker grains lead to a higher proportion of fines and correspondingly higher degrees of liberation.In cases attempting to isolate the influence of the composition dependent breakage criterion, only marginal effects were observed. The absence of stronger effects is likely due to insuffi-cient liberation in the process and model limitations. Potential improvements include increas-ing grain size in the microstructure or reducing the gap size in the HPGR process.