Coal maceral separation using column flotation

Recent studies have found that coal macerals have properties which may allow their use as high-valued products. A conceptual approach for the production of individual maceral concentrates utilizing column flotation is presented in this publication. Before maceral separation,the coal was ground to the particle size corresponding to near complete liberation of the macerals, which was approximately 4 gmm for an Illinois No. 6 seam coal. The production of maceral concentrates using flotation was based on the differences in the flotation rates among the various macerals, which was manipulated by adjustment of the medium pH. An increase in pH from 8 to 11 resulted in an order of magnitude reduction in the flotation rate of the vptinite maceral group while the corresponding reduction for the inertinite group was about 50% . On the other hand, the kinetic rate for the vitrinite group remained unchanged. By using pH control and column flotation, the inertinite content was increased from 7.5 % to 50% . Although the upgrading of the other two maceral groups was not as significant, it was evident that the success of the maceral enrichment for a given coal is dependent on the maceral liberation characteristics and the magnitude of the flotation kinetic rate differences among the macerals.