Abstract
Factors affecting on grindability of coal are as follows, 1) coal rank, 2) inorganic constituents, 3) micro-crackin coal, 4) coal petrographic constitution, etc.of these factors, it is discussed here how petrographic constitution affects on the grindability about seven Hokkaido coals.
Each coal sieved into 16×30 U. S. mesh was separated by float and sink method and each fraction was appropriated to proximate analysis, petrographic analysis and measurement of Hardgrove grindability index (H. I.).
From these experimental results it was observed that the statistical linear relation ships existed between H. I. and the volume of vitrite or vitrite+clarite. In case of low ash coal H. I. seems to be influenced by petrographic constitution, but scarcely influenced by ash content. Calculating H. I. of each microlithotype from correlation equations H. I.of vitrite is nearly equal to, or slightly greater than that of clarite, and H. I. of durite (durite I+durite II=exinite durite) is lower than that of vitrite and clarite.
In case of standardization of the Hardgrove method for Japanese coal, the coal showing narrow variation of petrographic constitution should be selected as the standard coal.
