The Effect of Oil Types and Additives on the Separation by Flotation of Unconverted Coal and Mineral Matter from Liquefaction Products

Abstract

The flotation behavior of various solids (H-coal vacuum bottoms, SRC solids, and pure clays) of different sizes dispersed in light cycle oil (LCO) or H-coal or clarified solvent refined coal oil (SRC) is studied with CO₂ bubbles under semi-batch operation after precooking (at 100°–120°) the solids in oils for 30 minutes. In all cases maximum flotation efficiency is achieved with a bulk liquid temperature of 110°, and a 30 to 40° temperature gradient between the liquid and the upper foam layer. The flotation of particles is best with LCO containing 6% cresol as additive. The separation is negligible with SRC oil because of high viscosity. With H-coal solids dispersed in LCO (+ 6% cresol) the separation is 85% with 100 μm particles and only 10% with 10 - 15 μm particles. By the addition of an agglomerating solvent (5% to 10% decane) the separation of 10 μm particles is increased to 45%. With respect to the separation of pure clays and minerals (dispersed in LCO) the separation of wollastonite (70% with 100 μm particles) is better than that of illite (35% with 100 μm particles). The flotation of kaolinite is always found to be insignificant.