PYRITE AND ILLITE ASSOCIATIONS IN 2 EASTERN US BITUMINOUS COALS

The ash transformation and deposition behavior of pyrite and illite, w hich are commonly identified with slagging, are influenced by the mann er in which the minerals occur in the fuel. An enhanced computer contr olled scanning electron microscopy technique was used to analyze the m ineral content of individual coal particles in samples of two pulveriz ed fuels. The particle-by-particle analysis determined whether individ ual mineral grains were included or excluded. It also provided informa tion on which mineral species were likely to be found in the same coal particle with pyrite or illite. Illite typically appeared as included particles and was associated with a variety of other silicate species . In contrast, pyrite tended not to associate with other minerals and showed a significantly higher fraction of excluded particles. Such det ailed observations of coal mineral distributions and associations prov ide additional insight into the mechanisms which govern fly ash format ion.