3. The drum level indicates of gas volume. So the volume of stored gas is easily
visualized.
4. No gas leakage.
5. The well-maintained metal gas holder has a lifespan of 3–12 years depending on
the humidity.
Disadvantages of Floating Drum Digester
1. Highly expensive.
2. Heat loss through metal gasholder.
3. Regular painting of gasholder.
4. UV rays can damage the main gas pipe, so regular maintenance is important.
5. Sometimes the steel drum can get stuck (Sasse 1988; Kossmann et al. 1999).
3.7.1.4 Fixed-Dome Digesters
The archetype of fixed-dome digester was first experimented in China. The plant
contained a closed-dome shape digester with a fixed fermentation chamber and
gasholder, a feedstock inlet, and a compensation tank. To reduce the cost of plant
construction, researchers have developed a fixed-dome digester (Fig. 3.10). Instead
of high-value drum, the dome acts as a gasholder. So the fixed-dome digesters are
otherwise called as drum less digesters. Generally, the complete plant is constructed
beneath the ground to maintain the absolute environment for anaerobic fermentation
Fig. 3.9 Schematics and work flow of a floating drum type digester (or Gobar gas plant). (Modified
from Florentino 2003; Samer 2012; Sasse 1988; Vögeli et al. 2014)
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