The objective of this study was to evaluate various multi-stage circuit arrangements that may be used to improve the column flotation of micronized coal. Laboratory flotation tests were performed with two different samples of Pittsburgh No. 8 seam coal. The first coal, Coal A, was ground to two different particle sizes and subjected to both column and conventional flotation. These tests were performed to obtain an initial understanding of the operational behavior of the column process and to compare the results with those of conventional flotation. The second coal, Coal B, was used in the actual testing of three different column circuit arrangements. The experimental test results were compared to simulated results obtained using a rate-based flotation model constructed in the present work. Several hypothetical flotation circuits were also examined using the simulation model and experimental flotation rate data.

The circuit test results showed that each of the different circuit configurations possessed specific advantages in terms of throughput capacity, combustible recovery, ash rejection and sulfur rejection. However, the overall performance curves for each circuit were all found to fall on or just below the maximum separation curve predicted using the release analysis technique. Also, the simulated results in almost all cases predicted better results than what was actually obtained. This discrepancy was attributed to the inability of the rate-based model to adequately describe restrictions associated with the carrying capacity of the column froth.