Oil shale beneficiation by froth flotation

It was found that froth flotation is capable of upgrading oil shale to improve the oil yield in the Fischer assay from 0.117 to 0.175 1/kg at 75% organic recovery in 50% of the rock. Feed particle size affected the float yield and grade and thus the separation efficiency. For economic reasons, grinding to very small particle sizes was avoided. With moderate grinding, particles < 75 μm required less frother and collector to float than particles ⪢ 150 μm and the selectivity was lower for < 75 μm particles. The best separation efficiency was achieved at a feed particle size of 500-150 μm. As the quantities of frother and collector increased, both the float yield and the percentage organic recovery increased, but the percentage mineral rejection decreased. As a result, the separation efficiency reached a maximum at float yields of 40–50%. The types of frother and collector affected the float yield. However, they had no significant effect on the grade of float if the amounts of frother and collector were controlled to achieve the same float yields.