FUEL PROCESSING TECHNOLOGY, vol.90, no.10, pp.1300-1304, 2009 (SCI-Expanded)
It is well known that higher rank coals are inherently hydrophobic whereas lower rank coals are more hydrophilic. Because of the hydrophilic character of low-rank coals, they are difficult to float even at high dosages of oily collectors. In the present study, the floatability behavior of a hydrophilic lignitic coal was investigated with and without low-temperature heat treatment using a column flotation and a Denver notation cell. The floatability and hydrophobicity of the coal were investigated upon heating the coal at 105 degrees C. After heating it was found that the floatability, hydrophobicity, and separation efficiency of lignite increased dramatically. A change in the hydrophobicity of lignite before and after the low-temperature heating was determined by FTIR spectroscopy. On the other hand, reverse flotation experiments applied in natural, alkaline, and acidic conditions yielded rather good results. A concentrate assaying 1.52% total sulfur was obtained at natural pH from a feed of 2.50% sulfur. (C) 2009 Elsevier B.V. All rights reserved.