97/02537 Recovery of fine coal from coal preparation plants and tailings ponds by selective oil agglomeration

Abstract

Environmental pressures are mounting over the practice of washery rejects disposal in tailings ponds and it is also recognized that reject fines are a valuable source of coal. Oil agglomeration has always been a potential candidate for fine coal recovery, but it has failed to see widespread use in the past, due mainly to the high cost of the oil. A hitherto unutilized source of low cost rejects oil was used successfully as an agglomerating agent in laboratory studies and favorable economics have been demonstrated. High yields of reduced ash coal have been obtained, with low oil to coal loadings. The oil is abundant, low in sulfur, ash and heavy metals, and has a low toxicity. Effective utilization of the oil required the development of a suitable emulsion chemistry, capable of handling the changing properties of the various feeds (thickener feed, thickener underflow and tailings pond). With successful development of the process in the laboratory, a PDU scale up followed, incorporating a number of novel ideas. Inclusion of an aeration technique enhanced flotation, allowed higher coal yields and facilitated the removal of water and mineral matter from the coal agglomerates. A pilot plant of two tonnes per hour is beingmore » installed in a coal washery located in Nth Western NSW, based upon the laboratory and PDU studies. There are two coal sources, one an underground coal seam and the other an open cut. Reject fines from both these sources will undergo processing in the agglomeration plant, as well as material from a large tailings pond. The laboratory studies, PDU studies and pilot plant will be discussed and an economic assessment of the PDU presented.« less