Excerpt from Sulfur Reduction of Illinois Coals: Washability Studies; Part 2

Part 1 of this study indicated that the washability characteristics of Illinois coals crushed to a maximum size of 1 inches usually did not vary significantly from the washability characteristics of the same coals when crushed to a maximum size of inch. Because the results with the two size ranges were similar and since the -inch maximum size would allow the use of a smaller quantity of coal for the washability tests, a -inch maximum size was used for all tests described in this report. The minimum size of 28 mesh (tyler screen series) was selected because (1) it was considered the finest size of Illinois coal that could be readily separated by gravity methods, and (2) only a small proportion of the coal would be finer than 28 mesh after crushing and screening in stages to the maximum size of inch.

During Part 1 of the investigation, a l-ton sample of raw coal, which generally was sampled in 20 to 30 increments through most of one shift of Oper ation, was obtained from the tipple; a few samples were obtained from the pit. None of the samples was considered representative of a mine's output. A differ ent method of sampling was used for the study described in this report. Instead of obtaining a l-ton sample, an approximately 80-pound sample, which will be referred to subsequently as a column sample, was cut from each of three freshly exposed coal faces at separate working areas of a mine. This procedure pro Vided a total sample of about 240 pounds per mine. Although these samples may not be representative of the output of the mine either, they are considered to be superior to those obtained by the tipple or pit-sampling procedure used in Part 1 of this study. Pace - channel samples, from which mineral bands of more than inch in thickness were excluded in accordance with U. S. Bureau of Mines procedures (holmes, also were cut from the same general locations.

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