Cleaning of Coals in a Stripa Heavy Medium Separator: Effect of Particle Size

The Stripa is an autogeneous heavy medium separator originally developed in Sweden for the processing of iron ores. The major difference between a Stripa and a conventional heavy medium separator is that a Stripa employs heavy medium or the ore itself. Although the Stripa has been used for concentrating ores such as iron and chromite, it has not been applied in coal preparation. In this study, a pilot scale Stripa with a capacity of 2.5 t/h is tested on -50+10 mm bituminous, subbituminous and lignitic coals. The effects of medium density and buoyancy force as a function of panicle size have been investigated. The performance of the Stripa was evaluated for each size using the parameters, the probable error of separation (Ep) and the degree of washability (N). Under the optimum conditions, both parameters indicate that the Stripa performs better with increasing particle size, the optimum being -50+19 mm. The comparison of the performance of the Stripa with that of the Baum jig indicates that Stripa can be used in coal preparation circuits as an alternative to jigs in the size range of -100+10 mm. Simplicity, low initial investment, and low operating and maintenance costs make the Stripa a plausible candidate for coarse coal cleaning.