This lecture discusses the evolution of various biogas plant models

1. Biogas plant types –
engineering design of
biogas plants
Lecture 15
By
Dr.S. PUGALENDHI, Er. T. AYISHA NAZIBA, , Dept. of REE, AEC & RI, TNAU, Coimbatore-03

2. Biogas system
Wet
Substrates moved around as liquid
slurries
TS = 3-15%
RT = 20-40 days.
Dry
Substrates in a stackable form - pile -
structure and porosity -warmed.
Warm water is sprayed, collected and
recycled.
The percolate is biologically active -
methanization

5. Biogas plants
Industrial
Batch
Continuous
Semi-batch
Dry fermentation
Small scale
Fixed dome
Floating drum
Balloon
Low-Cost Polyethylene
Tube Digester
Horizontal
Earth pits
Ferro-cement Plants

6. Industrial

7. Fixed dome
• Digester with a fixed, non-movable gas holder, which sits on top of the digester.
• When gas production starts, the slurry is displaced into the compensation tank.
• Technical suitability (stability, gas- and liquid tightness);
• cost-effectiveness;
• availability in the region and transport costs;
• availability of local skills for working with the particular building material.

8. CAMARTEC MODEL
JANATA MODEL DEENABANDHU MODEL
AKUT
AKUT Maendaleo
CHINESE MODEL

9. Factors Fixed dome Floating drum Tubular design Plastic containers
Gas storage
Internal Gas storage up
to 20 m³ (large)
Internal Gas storage
drum size (small)
Internal eventually
external plastic bags
Internal Gas storage
drum sizes (small)
Gas pressure
Between 60 and 120
mbar
Upto 20 mbar Low, around 2 mbar Low around 2mbar
Skills of contractor
High; masonry,
plumbing
High; masonry,
plumbing, welding
Medium; plumbing Low; plumbing
Availability of Material yes yes yes yes
Durability Very high >20 years High; drum is weakness
Medium; Depending on
chosen liner
Medium
Agitation
Self agitated by Biogas
pressure
Manual steering
Not possible; plug flow
type
Evtl Manual steering
Sizing 6 to 124 m³ digester vol Up to 20 m³ Combination possible
Up to 6 m³ digester vol
Methane emission High Medium Low Medium

10. Floating drum
• 1956, Jashu Bhai J Patel from India designed - popularly called Gobar
gas plant.
• It consist of an underground digester (cylindrical or dome-shaped) and
a moving gas-holder.
KVIC Pragati model Ganesh model
BORDA model

11. Low-Cost Polyethylene Tube Digester
• Applied in Bolivia (Peru, Ecuador, Colombia, Centro America and Mexico)
• The 2 coats of 300 micron tubular polyethylene film is bended around a 6
inch PVC drainpipe - wound with rubber strap of recycled tire-tubes.
• With this system a hermetic isolated tank is obtained
Because the tubular polyethylene is flexible, it is necessary to construct a
"cradle" which will accommodate the reaction tank, so that a trench is
excavated.

12. Balloon
• Heat-sealed plastic or rubber bag (balloon)- combining digester and gas-
holder.
• The gas is stored in the upper part of the balloon.
• The inlet and outlet are attached directly to the skin of the balloon.
• Materials - weather- and UV resistant - stabilized, reinforced plastic or
synthetic caoutchouc.
• Other materials - RMP (red mud plastic), Trevira and butyl.
• Useful life-span = 2-5 years.
• Standardized prefabrication at low cost,
• low construction sophistication,
• ease of transportation,
• shallow installation suitable for use in areas with a high groundwater table;
• high temperature digesters in warm climates;
• uncomplicated cleaning,
• emptying and maintenance;
• difficult substrates like water hyacinths can be used