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Bypass Control |
 Preparation Plant Bypass Control This technique is designed to:
- Maximise the amount of saleable coal from each tonne mined
- Reduce total washery costs by reducing washery throughput
- Optimise washery operations, by allowing it to operate at constant settings
- Permit an increase in total saleable coal, without expanding the washery
- Adjust the product quality by automatically varying the proportion of raw coal in the product.
- Provide real time data on the final product available for delivery.
Meeting customer specifications often requires washing coal. Washing
adds to the cost of production, adds moisture (thus reducing energy
content), and reduces yield. Washery operators may be adjusting cut
points continuously, trying to maximise recoveries whilst trying to
stay within customer specifications.
The solution is to "set and forget" the washery - allow it to operate at a
constant cutpoint which produces coal within the specification. Then try and
minimise the amount of coal presented to the washery, by routing a proportion
of raw coal around the process (and obtain a 100% yield on this portion). The
proportion bypassing the washery will depend on the quality of the washery
product, and how well it meets specification. The more coal bypassed, the less
load on the washery.
The COALSCAN on-line analyser continuously monitors the combined washed
and bypassed blended coal, calculating how much raw coal can be
included with the washed product, without exceeding the specification.
The COALSCAN then automatically controls a bypass flop gate between the
ROM stockpiles and the washery, and reviews the result, keeping track
in real time of the resulting coal quality. |
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Rather than having to rely on laboratory results, (only available hours or days after the sampled coal has passed though the plant) these online analysers have helped improve quality control in coal preparation plants.
David Hornsby and Tony Partridge,
Australian Coal Review
April 1998
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Coal
