Preparation of coal agglomerates using a water-in-oil emulsion

The conventional oil agglomeration process utilises an immiscible organic liquid, such as diesel, to agglomerate coal in an aqueous suspension of coal and mineral particles. With the application of agitation, the organic liquid selectively wets the surface of the coal and subsequently binds the coal particles together to form agglomerates. During this process, the mineral matter remains finely dispersed and hence the coal agglomerates can be retrieved by passing the material over a screen. This process achieves high quality beneficiation of the fine coal, and very effective dewatering of the product. While this is a remarkably effective process the technology has not been adopted because of the very poor economics, due to the high cost of the oil. In this work an alternative immiscible binding agent consisting of a high internal phase (HIP) water-in-oil emulsion was used. This binding agent provides the interfacial functionality of the oil, with the space filling functionality provided by the stabilised water drops of the emulsion. Thus far, the HIP emulsion has successfully agglomerated fine coal in an aqueous suspension and, in addition, has done so at a lower oil requirement than when pure diesel oil was used. A two-to-three fold reduction in organic liquid consumption was achieved when the HIP emulsion was used in the place of pure diesel oil. Further reductions in the organic liquid consumption are anticipated in the future if improved methods of preparing the emulsion are realised.