Which means that the terms corresponding to ash hopper and bottom ash can be neglected when compared to the fly ash one.
The terms ð100 2 AiÞ in Eqs. (4) and (15) are, by definition, the unburned fuel (carbon) for the refuse collected in the different locations. Having in mind that q4 is expressed as an unburned loss, it is convenient at this moment to introduce the relation Cuf ¼ 100 2 Afa as the unburned carbon in the fly ash. For this reason, Eq. (4) can be rewritten as