Petrographic analysis can give useful information about the combustion
of pulverized coal. However, the relations between maceral types and
reactivity are not simple; for example, not all inertinites are inert,
and not all vitrinites are reactive. This is a consequence of the for
mal definition of macerals and the variations between coals from diffe
rent parts of the world. The reflectance values of the maceral groups
and the associations of the different macerals, determined as microlit
hotypes, also need to be taken into account. Mineral matter also has a
n effect on the type of char formed, and the situation is further comp
licated by the different char characterization schemes in the literatu
re. The main conclusion from this review is that any predictive system
needs to take all these factors into account, especially reflectance.