In most mineral processing industries, hydrocyclone separators are operated at high feed solids content in the comminution circuits. Computational fluid dynamic (CFD) models developed so far are unable to predict the accurate classification behavior at high feed solid loadings. The dense slurry CFD model adopts algebraic slip mixture (ASM) model corrected with shear lift and hindered settling velocity-based drag forces to account for fluid-particle interactions and granular flow options for particle-particle interactions. The slurry rheology is modeled with a fine fraction-corrected Newtonian viscosity model. This model is utilized for running the multiphase simulations in five hydrocyclones (75-381 mm) at different design and operating conditions for the feed solids content varying between 0 and 65% by weight. Turbulence is modeled using the large Eddy simulation (LES) model. The results are analyzed in terms of air core diameter, water split, solid split, cut size, and sharpness of separation. In 75 and 250 mm hydrocyclones, the modified ASM model can predict accurate performance characteristics, including fine and coarse particle misplacement up to 30 wt % feed solids. Slight deviations are observed in the fine fraction recovery for the 50 wt % and higher feed solids content. Further, the same model is tested to predict the roping phenomena in a 381 mm hydrocyclone. © 2021 American Chemical Society.