Effect of Medium Composition on Dense Medium Cyclone Operation

The importance of the amount of nonmagnetic material present in a medium to the stability of the medium and the subsequent density of separation has been the focus by the authors on a number of recent ACARP projects. A method for quantifying the composition of a medium in terms of magnetite, clay, fine coal, and small coal was demonstrated and, using a series of pilot-scale experiments, the effect that each of these components have on the DMC operation was investigated. This has been extended by developing a more complete understanding of the roles of the clay and fine coal and that of the small coal. This article discusses some of the results of this work and the effect that the changing medium composition has on the efficiency of the DMC. A case study and plant data showing the medium composition from plant startup are also included in the discussion. Research has shown that magnetite by itself at feed medium densities below 1.4 is less stable then a mixture containing magnetite clay and or fine coal (nonmagnetic>20% w/w) and that the density of the underflow is the most affected stream. The research also shows that the small coal (above 0.2mm) does not play a role in stabilizing the medium. Understanding these dynamic relationships is important in understanding the actual density of separation that a DMC is operating and the stability of this operation. This relationship is also important when conducting plant audits of the DMC circuit particularly in regards to circuit stabilization times.