Medium Quality and DMC Performance: Influence of Small Coal

Abstract

The issue of what is the size at which the particles in the Dense Medium Cyclone (DMC) separation system cease to be part of the medium and act as individual particles was considered. Previous work had assumed that the fine (less than about 0.150 mm) coal was part of the medium, but that the small (about 0.4 mm) coal particles in the medium behaved as individual entities. This hypothesis suggested that three effects should be observable from analysis of the data: 1. A significant reduction in the effective volume fraction of particles present in the medium; 2. The experimentally measured values of RD50 should be described by the effective volume fraction of magnetite and clay using Equation 4 after discounting the volume fraction of the small coal; 3. The increase in the RD50 values for systems with clay and fine coal are clearly related to their actual volume fractions. Obviously, these are also associated with Equation 4. Also, all three have been shown to be present. It can be concluded that even while the small coal is in the medium and would add to the apparent density of the medium, it does not contribute to the effective medium.