77
depending on the amount of slurry accumulated in the displacement tank (or compensation / hydraulic chamber). The pressure is at its highest when the gasholder is
full of gas when an equivalent volume of slurry is push upward into the displacement tank; and the pressure is 0 when all gas is used. Gas pressure typically varies
between 2 and 15 kPa (Gunnerson et al. 1986).
5.2.1.1.2 Indian Digesters
The Deenbandhu digester is the archetype of all fixed-dome digesters with a manhole at the outlet tank. The digester can resist higher structural forces compared to
the Chinese digester types as the dome is a closed structure. Another advantage is
that the gasholder is closed that reduces the risk of leaks compared to a Chinese
digester, which has a manhole at the top of the gasholder (Balasubramaniyam
et al. 2008).
5.2.1.1.3 Floating Drum Digesters
The floating drum digester was introduced by the Khadi and Village Industry
Commission and was later branded as the KVIC digester (Singh and Sooch 2004).
The floating drum digester is fed semicontinuously and has a relatively high depthto- width ratio. A barrier is placed in the middle of the digester to promote mixing
and prevent short-circuiting (direct substrate flow from the entrance to the exit)
(Gunnerson et al. 1986). Biogas accumulates at the headspace of a movable inverted
steel drum that serves as the upper part of the digester.
5.2.1.2 Prefabricated On-Site Biogas Plants
5.2.1.2.1 Fiber-Reinforced Plastic (FRP) Digesters
The technical designs of fixed-dome FRP biodigesters can be classified in different
ways according to the major features of the digester, such as the full FRP digester
and the partial FRP digester (usually upper-dome part only) based on the integrity
of FRP structural materials; top-mounted hydraulic chamber and lateral-placed
hydraulic chamber based on the placement of hydraulic (displacement) chamber;
spherical, ellipsoidal, and cylindrical based on the shape of digester body; modular
type and integral type based on assembly work; and differences in digester volume.
Sizes of these plants are typically in the range of 4–9 m
3
.
5 Anaerobic Digestion of Rice Straw for Biogas Production
depending on the amount of slurry accumulated in the displacement tank (or compensation / hydraulic chamber). The pressure is at its highest when the gasholder is
full of gas when an equivalent volume of slurry is push upward into the displacement tank; and the pressure is 0 when all gas is used. Gas pressure typically varies
between 2 and 15 kPa (Gunnerson et al. 1986).
5.2.1.1.2 Indian Digesters
The Deenbandhu digester is the archetype of all fixed-dome digesters with a manhole at the outlet tank. The digester can resist higher structural forces compared to
the Chinese digester types as the dome is a closed structure. Another advantage is
that the gasholder is closed that reduces the risk of leaks compared to a Chinese
digester, which has a manhole at the top of the gasholder (Balasubramaniyam
et al. 2008).
5.2.1.1.3 Floating Drum Digesters
The floating drum digester was introduced by the Khadi and Village Industry
Commission and was later branded as the KVIC digester (Singh and Sooch 2004).
The floating drum digester is fed semicontinuously and has a relatively high depthto- width ratio. A barrier is placed in the middle of the digester to promote mixing
and prevent short-circuiting (direct substrate flow from the entrance to the exit)
(Gunnerson et al. 1986). Biogas accumulates at the headspace of a movable inverted
steel drum that serves as the upper part of the digester.
5.2.1.2 Prefabricated On-Site Biogas Plants
5.2.1.2.1 Fiber-Reinforced Plastic (FRP) Digesters
The technical designs of fixed-dome FRP biodigesters can be classified in different
ways according to the major features of the digester, such as the full FRP digester
and the partial FRP digester (usually upper-dome part only) based on the integrity
of FRP structural materials; top-mounted hydraulic chamber and lateral-placed
hydraulic chamber based on the placement of hydraulic (displacement) chamber;
spherical, ellipsoidal, and cylindrical based on the shape of digester body; modular
type and integral type based on assembly work; and differences in digester volume.
Sizes of these plants are typically in the range of 4–9 m
3
.
5 Anaerobic Digestion of Rice Straw for Biogas Production