Page 66 - Wastewater Solids Incineration Systems

Combustion Theory 35

TABLE 4.1 Typical proximate analysis of digested biosolids.

Parameter As received Dry basis
Moisture (%) 70.00 0.00
Ash (%) 14.16 47.19
Volatiles (%) 14.98 49.94
Fixed carbon (%) 0.86 2.87
HHV
kJ/kg 3936 13 120
Btu/lb 1692 5 640
HHV (moisture, ash-free basis):
kJ/kg 24 840
Btu/lb 10 680

Incineration systems may process raw sludge or digested biosolids, or both.
Some modern merchant facilities receive a wide variety of feed types. An example
of fuel analyses of digested biosolids is shown in Tables 4.1 through 4.3. These
data are representative of the information that should be received from a well-
qualified laboratory with broad experience in analyzing biomass, municipal solid
waste, and WWTP residuals.
Laboratory analysis should always be reviewed to make sure that it is thermody-
namically reasonable. The importance of this step cannot be overstressed. The stan-
dard ASTM procedures were developed for coal, and occasionally there are chemi-
cals or compounds present that can skew results. Another important fact to bear in

TABLE 4.2 Typical ultimate analysis of digested biosolids.
Parameter Dry basis (%) Moisture, ash-free (%)
Carbon 29.64 56.12
Hydrogen 4.29 8.12
Oxygen 13.85 26.22
Nitrogen 3.66 6.94
Sulfur 1.37 2.60
Ash 47.19 0.00