Dense-medium beneficiation of fine (minus 0.5 mm) coal is not a new concept and has been used in South Africa previously. The dense-medium fine coal plant operated for almost 18 years and, despite proving a difficult plant to operate, did succeed in producing a fine coal product with a low ash content of 7%. No other beneficiation process available could achieve this.
Dense-medium beneficiation of fine coal was also used inother countries, of which the plants at Homer City in the USA and Curragh in Australia were the best known. The first application of dense-medium cleaning of fine coal was.
however, at the Tertre plant in Belgium1. This plant was built in 1957. About nine years later, a second fine coal densemedium plant was built at the Winterslag Mine, also in Belgium. According to reports, this plant operated satisfactorily for a period of some 17 years.
Today, not one of these dense-medium plants remains operational.Spirals were introduced into the South African coal industry in the early 1980s and soon became accepted as the fine coal beneficiation process of choice. Currently, almost every coal processing plant in South Africa employs spirals to beneficiate fine coal.
Although spirals are normally capable of yielding products of acceptable quality, there are some instances,especially in the case of the No. 4 Seam coal, where spiralscannot produce the required product quality. It then becomes more economical to discard the raw fine coal than to process it with spirals. Obviously, this practice does not make the best use of the available coal reserves.
There is a definite need to produce fine coal at a higher product quality than that which is possible with spirals. For this reason, dense-medium beneficiation of fine coal was reconsidered.