Medium Quality and DMC Performance – Composition of Plant Mediums

Abstract

Detailed audits on the dense medium cyclone (DMC) circuits were conducted in an Australian Coal Association Research Project (ACARP) at a number of coal preparation plants in the NSW and Queensland coalfields of Australia. It was found that there were significant differences in the size distributions and the composition of the mediums between these plants. The amount of nonmagnetics in the medium was not constant, and this could have implications on the performance of the DMC circuit. At two of the plants involved, there were both primary and secondary DMC circuits. The results from these plants provide clear evidence that mediums are much more stable at higher densities due to the much higher volume fraction of particles in the medium leading to greater hindering of particle settling. It was found that a good quantitative description of the size distribution of the medium could be obtained by assuming that it had four constituents, clay with a mean nominal size of about 0.010 mm, magnetite with a mean nominal size of 0.040 mm, fine coal with a mean nominal size of 0.080 mm, and small coal with a mean nominal size of 0.450 mm.