The 'Grab and Run' revisited - improving selectivity between organic and inorganic components in conventional coal froth flotation

Conventional coal froth flotation has been used for decades to upgrade the finest fraction of coal (0.60 mm X 0 or 0.147 mm X 0) in commercial coal cleaning plants. While this fraction amounts to a modest 5-10% of the plant feed in typical U.S. coal cleaning plants, it can amount to over half of the feed to pond fine recovery circuits. Proper operation of the froth flotation circuit becomes critical, especially for these pond fine circuits. Much has been made of column flotation cell performance. However, the high capital cost, the requirement for large amounts of compressed air for some cell designs, and the often higher reagent cost, cannot often be justified in the overall economics of a typical coal cleaning plant and, especially, for pond fine recovery. By selecting operating conditions that improve the selectivity between the organic and inorganic fractions of the coal, conventional coal flotation cell performance can approach the performance of column flotation cells. Operators can successfully accomplish this by selecting circuitry like the 'Grab and Run' circuit, with operating conditions that allow for the increased drainage of ash-forming and sulfur-bearing minerals from the froth. This paper provides a review of data regarding flotation circuitry that gives coal flotation operators guidance in selecting the best operating conditions for conventional coal froth flotation cells. (C) 2000 Elsevier Science B.V. All rights reserved.