Improving the separation efficiency of the knelson concentrator using air injection

Recent test data have shown that the Knelson concentrator can provide a more efficient separation than froth flotation when cleaning coal in the 150 × 25 μm particle size range. To further improve the performance of this enhanced gravity separator, air bubbles were injected into the feed stream in an attempt to decrease the apparent density of the coal particles due to the formation of bubble-coal particle agglomerates. The test data showed that air injection had a significant impact on operating characteristics and separation performance. Coal recovery was increased by 10 to 20 absolute percentage points, while a 2 percentage point drop in the minimum product ash content was also achieved.