Coal Preparation » Gravity Separation
This investigation was carried out under an ACARP grant with additional support provided through BHP's sponsorship of AMIRA Coal Preparation project 239A. This allowed JKMRC to provide technical advice and assistance throughout the trial.
The comparison was conducted between normal and long bodied cyclones with similar pressure-throughout characteristics.
Substantial effort and expense went into establishing, in an industrial environment, a test facility which provided the ability to accurately measure flow rates for overflow and underflow from both cyclones. These are critical parameters for partitioning calculations.
Unfortunately, the trial failed to realise the project objective of determining whether a long bodied cyclone could achieve greater yield, at the same product ash, than a normal cyclone in a situation where high near gravity separation was attempted. The main reasons for this were an inability to maintain stable operations on both cyclones under normal operating conditions and feed rates. Feed rate, medium density and inlet pressure variability contributed to this situation, although much of the problem stemmed from the heavy loading to which the plant was subjected. These matters could be adequately addressed due to time constraints and production pressures.
The test program was therefore curtailed, but it was clearly shown that under the conditions established, both cyclones could effect a reasonably efficient separation. Some of the test philosophy will be carried into the ACIRL pilot scale project on long bodied cyclones. It is still considered that industrial scale trials, under more appropriate plant conditions, would answer many of the outstanding questions.