Physical abrasion index

In addition to its chanical properties, the efficient use of a coal also requires a knowledge of its physical properties, such as its density (which is dependent on a combination of rank and mineral matter content), hardness, and grindability (both related to coal composition and rank). Other properties include its abrasion index (derived mainly from coarse-grained quartz) and the particle size distribution. Float-sink testing may also be included with the analysis process. This involves separating the (crushed) coal into different density fractions as a basis for assessing its response to coal preparation processes. Float-sink techniques may also be used to provide a coal sample that represents the expected end product of a preparation plant, in order to assess the quality of the coal that will actually be sold or used rather than the in situ or ROM material represented by an untreated (raw) coal sample. 

Chemical composition, particle morphology, particle size and particle size distribution, brightness, refractive index, specific surface, particle charge and abrasiveness are commonly used to characterize papermaking fillers. Table 2.5 summarizes some chemical and physical data of fillers and fibers. More detailed information is given in the following paragraphs. 

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