No abstract

Samples of 100-mesh Upper Freeport, Pittsburgh No. 8, and Illinois No. 6 seam coals from the Argonne Premium Coal Sample Program were analyzed by scanning electron microscopy based automated image analysis (SEM-AIA) for mineral composition, particle size, and association of the minerals with the organic matrix. The association results were used to predict cleanability, i.e., anticipated coal recovery versus mineral rejection, for density-and surface-based cleaning processes.Distributions showing the association of each mineral with coal indicate preferential liberation for calcite in all three coals and for some of the pyrite in Illinois and Pittsburgh coals. Generally, the Pittsburgh coal appeared to be the most easily cleaned, based on association considerations only. The predicted cleanabilities of the Upper Freeport and Illinois coals were similar for density-based processes, and the Upper Freeport coal appeared to be slightly more cleanable than the Illinois coal for surface-based processes.

A set of 34 as-shipped coal samples from operating Illinois mines is available for this study to determine the forms of chlorine and sulfur and leachability of chlorine during wet grinding and froth flotation. The forms of chlorine may be inorganic, ionic, and organic. The forms of organic sulfur will include organic sulfide and thiophenic sulfur. Chlorine can be leached from coal during wet grinding. The potential for removal of chlorine from the samples during fine (-200 mesh) and ultrafine (-400 mesh) wet-grinding and during froth flotation designed primarily for removal of pyrite and ash will be determined. In addition, the organic/inorganic affinities of trace elements in as-shipped Illinois coals will be assessed so that the current physical coal cleaning results may be better interpreted.