Por: Dr. Francisco J. Sotillo, PerUsa EnviroMet, Inc. AbstractThe understanding of the comminution mechanism in a bed of particles is of utmost importance for taking advantage of this technology. Comminution in a bed of particles is the only mechanism that allows selective comminution. Consequently, the bed of particles principles by which a high-pressure grinding rolls (HPGR) or high-pressure roll mill (HPRM) works are discussed to show the potential benefits of this mechanism. Depending on the liberation size of the impurities, the HPGR allows to selective grind those impurities with respect to the phosphate minerals.HPGR reduces the energy consumption for up to 50% and increases the grinding efficiency with respect to those parameters for rod mill grinding, and improve attrition scrubbing and flotation feed preparation of the material in downstream operations. If further grinding of the material is required for complete liberation of the ore, it will require significant less energy and will maintain the phosphate minerals at a coarser size fraction improving their recovery.Thus, the use of laboratory HPGR has been investigated to improve the separation efficiency of High-Dolomite, and Ultra-High-Clay and High-Clay minerals (kaolinite) from apatite in downstream operations on the beneficiation of different phosphate ores of sedimentary origin. Consequently, this paper includes characterization studies on dolomite phosphate ores, data of the applied PerUsa EnviroMet, Inc. physical model of the HPGR to develop preliminary comminution data; and laboratory HPGR evaluations to determine crushing parameters, such as feed rates, rolls speed and gap, and applied torque, pressure and energy.Complementary work on lab rod mill grinding, and flotation studies were conducted to assess dolomite/francolite separation efficiency. The HPGR tests show that commercial products for all mines can be obtained. Recoveries of 74% to 82% of P2O5 and rejections of 46% - 83% of MgO were reported with specific energy consumption of 20% to 50% of that of a laboratory rod mill. In the case of kaolinite/apatite separation, Ultra-High-Clay Phosphate ore prepared at minus 9-mm nominal size fraction for was submitted to HPGR tests resulting in 42.45% P2O5 recovery and 80.81% Al2O3 rejection with specific energy consumption of 1.34 KWh/t.The results for HPGR of 2x0.02-mm particle size for High-Clay Phosphate ore was modeled according to the Ultra-High-Clay results using PerUsa EnviroMet Inc. Model, the results showed an increase in both the recovery from 63.4% to 73.2% of P2O5 and rejection from 70% to 84% of Al2O3, with specific energy consumption of 3.88 KWh/t.