The effect of rank and particle size on the plastic behaviour of coal

Abstract

When a particle of coal is compressed, failure will occur either by degradation or by plastic deformation depending on the experimental conditions. An analysis of the compression of a cube of coal between platens suggests that the type of failure is dependent on the cube size and on several physical properties of the coal that are rank dependent. The analysis also shows that there is a critical particle size, above which failure cannot occur by plastic deformation, which is rank dependent. The critical size is found to be smaller if the particle is irregular in shape, and it is dependent on the compressive strength of the particle which is known to vary with the method of compression. Evidence in support of the analysis is provided from experiments on the extent of aggregation (which is linked with plastic deformation) of a number of coals ground in a laboratory roll crusher. The results suggest that the extent of aggregation is dependent on the critical particle size and on the grindability of the coal.