Impact of the grinding method on oil shale flotation

Abstract

Oil shale’s natural floatability depends on its organic content which is negatively affected by the presence of inorganic impurities. Thus, the feed preparation, particularly in the crushing and grinding processes, affects the liberation of organic components as well as their surface properties. In this article, attrition scrubbing and ball milling, as different feed preparation techniques, were used to study their effects on oil shale flotation. The ground products using either technique were floated, using either pine oil or sodium oleate. The flotation results indicated that the organic recovery was improved using both reagents with higher improvement in the case of pine oil. Starting from 10% organics in the feed, the floated organics, at pH 3 using 0.4 kg/t pine oil and particle size of −0.1 + 0.045 mm, are improved to 23.5% and 17.8% using ball mill and attrition products, respectively. Interestingly, at a higher pine oil dosage, floated attrition products result in a higher grade and recovery than the ball mill products. The shearing mechanism in attrition is found to be more suitable for liberating organics in oil shale whereas maximum organic content and recovery of 25.7% and 91.4%, respectively were achieved using 7.5 kg/t pine oil.