BENEFICIATION OF COAL FROM IMPOUNDED COAL WASTE

The potential for recovery and purification of fine coal particles fro m the impounded waste of a coal cleaning plant using a two-stage, two- solvent system was investigated. The two-solvent system consisted of a first-stage fluid (a mixture of n-dodecane and 2-propanol) used to se parate fine coal particles from ash-forming impurities, and a second-s tage fluid, the U.S. Environmental Protection Agency (EPA) toxicity ch aracteristic leaching procedure (TCLP) solvents, used to remove sulfur and mineral impurities from the recovered coal. The degree of separat ion of organic matter from inorganic impurities was examined as a func tion of the fraction of n-dodecane in the first-stage fluid, and settl ing time. The results show a general trend of increasing organic matte r recovery with increasing fraction of n-dodecane. The most ash remova l was obtained with a fuse-stage fluid of 4% n-dodecane and 96% 2-prop anol by volume. Mineral and sulfur removal from the recovered coal was negligible. Further treatment with TCLP solvents in the second stage showed significant removal from the recovered coal (over 70%) of iron, manganese, and sodium. Sulfur and calcium removal was poor (less than 50%); it is likely that these are bound in the organic matrix. The en ergy content ol the final recovered coal produce was 34.9 MJ/kg, an in crease of 22.2% over the 28.59 MJ/kg of the impounded waste.