Page 67 - Wastewater Solids Incineration Systems

36 Wastewater Solids Incineration Systems

TABLE 4.3 Typical elemental analysis of ash
in digested biosolids.
Parameter Dry basis (%)
SiO 44.94
2
Al O 14.30
2 3
TiO 0.80
2
Fe O 14.69
2 3
CaO 11.63
MgO 2.63
Na O 1.21
2
K O 0.54
2
P O 5.94
2 5
Cl 0.06
SO 1.96
3
CO 1.30
2

mind when reviewing these analyses is that the term “volatiles” in proximate
analyses has a different meaning than “volatile solids” testing common in municipal
WWTP applications. The volatiles in proximate analysis do not include fixed carbon;
volatile solids in WWTP residuals analysis do include the fixed carbon.
There are several ways to check for thermodynamic validity. The best way is to
take the weight fraction values of C, H, O, N, and S and insert them to one of several
equations that are commonly used to calculate higher heating value (HHV) from an
ultimate analysis. One of the most frequently used is the DuLong equation:

kJ/kg 337 C 1419 (H O/8) 143.2 S
Btu/lb 144.95 C 610 (H O/8) 57.70 S

The DuLong equation was originally derived for high rank coals, however, and
may give high results when used for determining the HHV of WWTP residuals.
Another option is to use the Mott-Spooner equation:

kJ/kg 336.1 C 1419.3 H 94.2 S 153.3 O 0.72 O
2
Btu/lb 144.5 C 610.2 H 40.5 S 65.9 O 0.310 O
2