Page 263 - Biofuels Refining and Performance

242 Chapter Eight

R′ O C CH 2 CH 2 (CH ) R
2 n
Radical splitting O

)
2 n
•CH 2 CH 2 (CH 2 n R + R′ O C• R′ O C CH • + •CH 2 (CH ) R
2
Chain O O
Chain
composition n+1
decomposition n-1
R' O C CH 2 CH CH (CH 2 n R R′ O C CH (CH ) 2 n R
)
2 2 2
O O
Disproportionation
2•CH 2 CH 2 (CH ) R CH 2 CH (CH 2 n R + CH 3 CH 2 (CH ) 2 n R
)
2 n
Figure 8.18 Mechanistic aspects of the formation of hydrocarbons by cracking of lipids [58].
It is worth mentioning that the ash content (Table 8.9) includes nat-
ural catalysts (e.g., alumina and silicates) that substantially influence
the yield and composition of LTC products. Table 8.9 shows results of
the conversion of these organic residues. Yields of oil, solid product,
Cl, NaHCO ), and noncondensable gases
water, volatile salts (NH 4 3
(NCG: CO , H , C-1–C-4 alkanes and different alkenes) are given in Fig
2
2
8-19. Digested sludge produces less oil than aerobically stabilized
sludge. This correlates with the carbon content in Table 8.9. The food
chain of anaerobic bacteria efficiently removes organic carbons as biogas
(CH /CO 2 ). Thus it is no longer available for the production of oil in sub-
4
sequent LTC. AM shows higher yields of oil due to its higher content
of fat and proteins (Table 8.9). The viscosities of untreated oils at 40 C
2
2
2
are as follows: DS, 14 mm /s; AS, 35 mm /s; AM, 27 mm /s; and MBM,
2
21 mm /s. In comparison, diesel from a filling station has a viscosity of
TABLE 8.9 Chemical and Physical Characteristic Substrates for LTC
Parameter AS DS AM MBM
Dry solids, % 95.0 79.6 94.3 95.0
Ash content, % 35.1 40.7 23.2 38.2
Protein, % 32.9 26.6 52.3 49.6
Fat, % — — 14.4 8.9
Calcium as Ca, % — 9.6 9.7 20.1
Phosphorus as P 2 O 5 , % — 6.3 8.7 16.0
NCV, MJ/kg 14.2 9.9 18.8 15.4
C, % 31.6 23.0 42.5 30.5
H, % 4.4 5.0 6.6 4.8
N, % 5.0 3.3 8.3 7.6
S, % 0.6 1.0 0.5 0.3
AS: aerobically stabilized sewage sludge; DS: digested sewage sludge;
AM: animal meal; MBM: meat and bone meal.