An approach toward a combined scheme for the petrographic classification of fly ash: Revision and clarification

Hower and Mastalerz's classification scheme for fly ash is modified to make more widely acceptable. First, proper consideration is given to the potential role of anthracite in the development of isotropic and anisotropic chars. Second, the role of low-reflectance inertinite in producing vesicular chars is noted. It is shown that noncoal chars in the fuel can potentially produce chars that have the potential to stretch the limits of the classification. With care, it is possible to classify certain biomass chars as being distinct from coal-derived chars.