Grindability of Coal
Effect of Crystalline Mineral Matter in coal on the Grindability
1966 Volume 45 Issue 12 Pages 843-850
Details
1966 Volume 45 Issue 12 Pages 843-850
The grindability of high ash coal seems to be influenced by the mineral matter in coal as well as coal petrographic constitution etc. It is discussed in this paper on the gridability of the high ash coals, especially how crystalline minerals in coal have influence on the grindability. Each coal after sieving into 16×30 U. S. mesh was ground by the Hard grove mill so that more than 70% of original weight would pass through a 200 U. S. mesh sieve, removing the fines which was passed through a 200 mesh sieve at each 60 revolutions. The fines and the residue were appropriated to quantitative estimation of crystalline minerals by means of X-ray analysis and measurement of ash content. Petrographic analysis and microscopic observation were done for the original coals and their residual ones.
From these experimental results the influence of each mineral on the grindability is summarized as follows:
Quartz: The influence of quartz on the grindability varies with the mode of occurence in coal. In the case of the sample in which quartz occurs as fine grains (less than about 50 microns across), the grindability seems to be unaffected directly by quartz, while it occurs as comparative coarse grains (more than 100 microns across), the grindability seems to be subject to a bad influence.
Carbonates: Calcite, aragonite and dolomite appears to have similar influence on the grindability. In the case that the thin films composed of very fine crystals of carbonates occur reticulately in coal, their existence seems to have a favorable effect on the grinda bility, however the grindability seems to be rather subject to a bad effect in the case that carbonate menerals occur as comparative coarse grains.
Feldspars: Plagioclase was only found as feldspar mineral in a few coals. The influence of plagioclase on the grindability appears to be similar to the case of quartz.
Clay minerals: Kaolin minerals, illite and montmorillonite were detected mainly within coaly shale and shale. However the effect of these minerals on the grindability is not distinct.
