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MEI Online: Gravity Concentration: Latest News: December 23rd 2003

:: Mineral Density Separator Predicts Plant Performance  

MINTEK has developed and tested a prototype mineral density separator (MDS) that can be used to characterise ores into different density classes, evaluate and predict dense-media and jigging plant efficiencies, as well as to design and optimise processing plants.

The MDS is capable of fractionating an ore sample into different density fractions at densities exceeding 4.0 - this being the highest limit of heavy-liquid separation where a mixture of tetrabromo-ethane and milled ferrosilicon is used. The unit can treat material that falls within the size range 2 mm to 30 mm, with a step-up ratio of <4:1. However, a 2 mm x 0.5 mm sample has also been successfully tested.

The MDS is a PLC-controlled, pneumatic unit with a cylindrical chamber consisting of a number of rings clamped together and connected to a water/air chamber or hutch. The pulsations are provided by pneumatic valves, with the PLC controlling the frequency and the upstroke, holding and release times. After each run, the contents of the chamber are removed in separate layers and sampled for density determination and chemical analysis.

The MDS uses a release analysis92 approach to separate the sample into closely spaced density fractions, provided a narrow feed size range is used. Alternatively, the test will determine the potential separation at a given feed size distribution, residence time and operating conditions.

The testwork yields information on the relationships between:

  • recovery and grade or recovery and density at different residence times
  • grade versus density at equilibrium (washability), and
  • recovery versus residence time at the required grade.

Mintek has conducted a large number of tests on various materials, including iron and manganese ores, chromite, coal, diamondiferous gravels, and tantalite. The results have shown that increased residence times result in improved separation at the finer sizes and at lower densities. Processing narrower size ranges will increase separation efficiency. The information from fractionation can be used to design and optimise processing plant performance by direct measurement of the effects of variables such as residence time and particle size distribution. The results can also be used to predict mineral separation in a plant, evaluate plant efficiencies, and to develop accurate scale-up models from a comparison of batch and plant operations.

The MDS also lessens reliance on organic heavy liquids for developing washability data, thereby reducing safety, health and environmental concerns.



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