10.1.2 Fixed dome plants
Design calculation
Sizing factors
Daily substrate input, Sd
Retention time,RT
Daily gas production, G
Storage capacity, Cs
Digester volume, Vd
Gasholder volume, Vg=G•Cs
Vd : Vg
Example
= 115 l/d
= 70 days
= 2.5 m³/d
= 60%
= 8 m³
= 1.5 m³
= 5.3 : 1
Sample calculation
R = (0.76 • 8)1/3= 1.85 m
r = 0.52 R= 0.96 m
h = 0.40 R= 0.72 m
p = 0.62 R= 1.14 m
Tab. 10.1: Calculating parameters for fixed-dome biogas plant (Source: Sasse
1984.OEKOTOP)
Vg : Vd
R
r
h
p
1:5
(0.76 • Vd)1/3
0.52 R
0.40 R
0.62 R
1:6
(0.74 • Vd)1/3
0.49 R
0.37 R
0.59 R
1:8
(0.72 • Vd)1/3
0.45 R
0.32 R
0.50 R
Fig. 10.5: Conceptual drawing of
fixed-dome biogas plant. Vg
gasholder volume, Vd digester
volume. (Source: OEKOTOP,
Sasse)
Fig. 10.6: Constructional drawing of
a fixed-dome plant. Vd = 8 m³, V =
1.5 m³. Material requirements:
Excavation 25 m³, Foundation 2.2
m³, Masonry 2.0 m³, Rendered area
22.0 m², Sealed area 7.0 m².
(Source: OEKOTOP, Sasse, BEP
Tanzania)
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