High Pressure Grinding Rollers (HPGR) mills are widely used in the cement and mineral processing industries due to their significant advantages in improving crushing efficiency and reducing energy consumption. Despite these benefits, the HPGR mill often encounters uneven grinding along the roll width, a phenomenon known as the edge effect, which severely affects the productivity and efficiency of the grinding process. Although numerous studies have explored and analysed the edge effect in HPGR mills, the generating causes and quantitative analysis of its impacts are still insufficiently understood.
This study conducted a DEM study to analyse the edge effect of HPGR mills under different operation conditions, with particular focus on the effects roll thickness, roll diameter and grinding pressure. The model was calibrated and validated by a lab-scale HPGR. By examining throughput, particle-wall interaction force and product size along the roll width, significant variations between the edges and the centre were observed. The simulation results indicated that roll thickness significantly influences edge effects: thinner rolls provide a more uniform distribution of throughput whereas thicker rolls concentrate throughput at the centre, exacerbating the edge effects. Additionally, increasing roll thickness leads to uneven compression of particles, resulting in coarser particles at the edges. Increasing grinding pressure slightly increases edge effects but has a minimal impact on overall throughput. Although higher grinding pressures produce smaller particle sizes, the overall distribution of particle sizes is not significantly affected by the edge effect. Variations in roll diameter showed that larger roll diameters mitigates the edge effect, thereby increasing throughput and improving the uniformity of product size. Finally, a power-law equation was proposed to characterise the variations and the power index was linked to the degree of edge effects.
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