Development of a gas-promoted oil agglomeration process: Air-promoted oil agglomeration of moderately hydrophobic coals. 2: Effect of air dosage in a model mixing system

In a selective oil agglomeration process for cleaning coal, fine-size particles are suspended in water and treated with a water-immiscible hydrocarbon which can range from pentane to heavy fuel oil. Vigorous agitation is applied to disperse the oil and to produce frequent contacts between oil-coated particles. In Part 1 of this series of papers, it was shown that a definite amount of air had to be present in a laboratory mixing unit which produced a moderate shear rate in order to form compact, spherical agglomerates in an aqueous suspension of moderately hydrophobic coal using heptane or hexadecane as an agglomerate. In this paper, the effects of different amounts of air including dissolved air are discussed. The results indicate that a small amount of air will trigger the process of agglomeration, and even the air dissolved in water under equilibrium conditions at room temperature and pressure is sufficient to promote agglomeration provided it is released from solution