Coal Preparation

The Affect of Dynamic Changes in Medium Quality in Coal Processing

Coal Preparation » Gravity Separation

Published: February 13Project Number: C20051

Get ReportAuthor: Michael O’Brien, Bruce Firth, Clint McNally and Andrew Taylor | CSIRO

Research has shown that the amount of non‐magnetic material in the correct medium solids will have an effect on the operation of a dense medium cyclone (DMC) particularly when operating at correct medium densities less than a relative density (RD) of 1.4. ACARP projects C15053 and C18040 have indicated that a concentration of approximately 20% by weight in the medium solids is required at these lower densities to achieve a stable medium and to keep the density differential (difference between the DMC underflow medium density and the overflow medium density) below 0.4. These projects also concluded that particles greater than about 200 microns were not part of the medium and did not affect the properties of the medium. It is also recognised that it takes time to reach a point where the non magnetic material is stable and that a loss of feed may result in a reduction of the non magnetic material in the medium.

This project looked at the time taken for the non magnetic material in the correct medium to stabilise from plant start up and investigated the consequences of reducing the feed mass rate, loss of feed and changes in density and feed type.

Four main audits were carried out where the correct medium was sampled regularly from the time the plant started processing feed. In addition samples of the correct medium were taken after the correct medium density was changed, feed rate varied. These samples were analysed for the amount of non magnetic present in the solids, the non‐magnetic and magnetic material sized using a laser sizer and the densities of the components determined using a helium pycnometer. From these samples a peak deconvolution technique was performed to determine the amounts of the different non magnetic types present in the correct medium solids. Data from previous ACARP projects where the correct medium samples had been taken and analysed were also included in the analysis.


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