| At PCS Phosphate's Aurora, North Carolina mining operation, seashell concentration as high as 50 wt.% contaminates the 40 mm. x 1.70 mm size fraction of coarse phosphate pebble. Similarities in surface chemistry between seashell and francolite pebble result in an economically unacceptable CaO to P 2O5 ratio in concentrate produced by conventional fatty acid froth flotation. This study focuses on beneficiation of the coarse phosphate pebble size fraction by exploiting differences in breakage characteristics between seashell and francolite. Investigations involving vertical shaft impact crushers, fluidized bed calcination and conventional grinding circuits were conducted. The multiphase preferential comminution phenomenon was successfully modeled and simulated by MODSIM(TM). A process is proposed that recovers 70% of the P2O5 in the coarse phosphate pebble size fraction while lowering the CaO to P2O5 ratio from 2.50 to 1.72. |
