Method for Extracting Coal from a Coal Refuse Pile.
Chem Abstr 112:162 082M 1991 Jul; :
The method comprises soaking the coal refuse pile with an aqueous alkali solution and distributing an oxygen-containing gas throughout the coal refuse pile for a time period sufficient to effect oxidation of the coal. The method further comprises leaching the coal refuse pile with an aqueous alkali solution to solubilize and extract the oxidized coal as alkali salts of humic acids and collecting the resulting solution. Ca(oh)2 may be added to the solution of alkali salts of humic acids to form precipitated humates useful as low-ash, low-sulfur solid fuels.
Chem. Abstr. 112:162,082M, July 30, 1991 U.S. Pat. 5,035,722