Environmental Engineering Reference
In-Depth Information
C
a
H
b
O
c
S
d
N
e
+ rH
2
O
Î
mCH
4
+ sCO
2
+ dH
2
S + eNH3
(1)
in order to evaluate the amount of the reaction products which build up the biogas and, hence,
the biogas production.
Table 12 summarises the calculation procedure steps and table 13 reports the calculation
results.
Table 12. Summary of calculation procedure for biogas production estimation.
Humid fraction
TS
Inert
VS
BC
RE
VS
REMOVED
Brutal
chemical
formula
Wet %
[kg/h]
%
[kg/h]
% TS
% TS
[kg/h]
% VS
%
[kg/h]
Paper and cardboard
2,57
120
75,00
90
9,90
99,90
81
50,00
60,00
24
CHO
Organic fraction
54,85
2550
35,00
893
5,00
99,95
848
82,00
60,00
417
C
18
H
28
O
10
Pruning scrap
13,02
605
55,00
333
23,70
99,76
254
60,00
60,00
91
C
5
H
10
O
2
Plastics
1,43
66
95,00
63
4,90
99,95
60
-
60,00
-
-
Metals
7,01
326
88,00
287
94,50
99,06
16
-
60,00
-
-
Wood
2,95
137
80,00
110
1,50
99,99
108
72,00
60,00
47
C
2
H
3
O
Glass
15,36
714
98,00
700
98,90
99,01
8
-
60,00
-
-
Textiles
2,81
131
90,00
118
22,30
99,78
91
54,00
60,00
30
CH
2
O
Table 13. Results of the biogas production modelling.
CH
4
CO
2
2
S
NH
3
Produced [kg/h]
210,82
438,34
5,05
7,24
Produced [kmol/h]
13,14
9,96
0,15
0,43
Produced [Nm
3
/h]
294,34
223,11
3,36
9,63
Volume composition [%]
55,49
42,06
0,63
1,82
The overall biogas production resulted to be about 530 Nm
3
/h, which correspond to about
0,11 Nm
3
of biogas per kg of humid fraction or 0,36 Nm
3
per kg of VS, which resulted
coherent with literature data (Mata-Alvarez , 2002). Being the biogas LHV of about 19.420
kJ/Nm
3
(on the basis of the CH
4
volumetric fraction) and assuming an electric conversion
efficiency of 0,35 for the reciprocating engine, the power output was calculated and reported
in table 14, with the overall efficiency of the process (the ratio between the net power output
and the entering power with the humid fraction).
Table 14. Anaerobic digestion with energy recovery cycle synthetic results
Humid fraction
Waste mass flow rate [kg/h]
4.650
Waste LHV [kJ/kg]
3.647
Entering thermal power [kW]
4.711
Net Power output [kW]
1.002
Net efficiency [%]
21,27
CO
2
mass flow rate output [kg/h]
438
