The HPGR is capable of handling particle sizes up to approximately 50mm. The essence of the process is to avoid single particle crushing and to aim for a compressive grinding of the material in the particle bed Single particle crushing would increase the wear of the roll surface through high point-loads and shear, and would cause damage to the autogenous wear surface. For ideal inter-particle compression, grinding the feed particle sizes should be smaller than the operating gap between the rolls. In actual applications, the top size of a feed distribution can contain particles of up to about 70% greater than the operating gap.
A High Pressure Grinding Roll produces a particle size distribution (PSD) that is wider, with more fines, than a tertiary crusher (e.g. cone crusher) would produce. There is that the compressive force not only acts on the coarse end of the PSD, but through out the particle bed on both coarse and fine particles, including the fine particles derived from the initially coarser fractions
