stoichiometric oxygen is 100%. A heat exchange tube is used to
control the bed temperature. As seen in the figure, RDF combustion
shows different characteristics from that of sawdust combustion.
Due to its small particle sizes and light weight, sawdust combusts
primarily in the splashing zone. It is difficult to increase the bed
temperature over 750 C. This results in the peak temperatures in
the splashing zone increasing from 830 to 925 C when the bed
temperature increases from 650 to 750 C. However, RDF combusts
primarily in the bed zone due to its density. The peak temperatures
appear at the level a little higher than the feeding inlet, and it increases
from 729 to 815 C when the bed temperature increases
from 700 to 800 C.
RDF combustion has lower temperature levels compared with
sawdust. The RDF temperature distribution is nearly uniform with
no sharp changes at each cross-section except at the elevation of
z ¼ 1.05 m, and it is not affected by the excess oxygen ratio. The bed
zone combustion fraction of RDF is much higher than that of
sawdust and the heat removed from the bed zone of RDF combustion
by heat exchange tube is also higher than that of sawdust
combustion. Therefore, the freeboard temperature of RDF is lower
than that of sawdust combustion at the same bed temperatures.