Page 70 - Wastewater Solids Incineration Systems

Combustion Theory 39

3.0 EFFECTS OF OPERATING PARAMETERS

Using heat and material balances to examine the effects of the various parameters is
useful. In Figure 4.1, the TTPC or furnace exhaust temperature has been varied for a
constant feed cake input at three different air preheat temperatures. The concept of
availability is again used and represents the y axis. Gross heat input includes not only
the heat of combustion contributed by the volatile solids but also the sensible heat in
the preheated combustion air. The TTPC is plotted along the x axis. The intersection
of each curve with the zero availability line represents the temperature that the par-
ticular example feed cake would reach if burned in a furnace with zero heat loss
under the conditions listed. As temperatures fall below that point, availability is pos-
itive and heat would have to be removed. At temperatures greater than that point,

Sludge Analysis M.A.F.
Carbon 56.12%
Hydrogen 8.12%
Oxygen 26.22%
Nitrogen 6.94%
Sulfur 2.60%
HHV, Btu/Lbm M.A.F. 11,952
Percent Ash, Dry Basis 45.00%

FIGURE 4.1 Available heat versus exhaust temperature (XS excess; M.A.F. moisture ash-free;
Btu/lb 2.326 kJ/kg; 0.555 6[°F] °C).