Design two (2) equal volume pancake type anaerobic digestion system. Design parameters are: Design example) • Amount of

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Design two (2) equal volume pancake type anaerobic digestion
system. Design parameters are:
Design example) • Amount of sludge: 24,000 GPD • % solids: 3.5%
(80% primary and 20% WAS) • 68% VS/TS • Design digestion
temperature: 55°C or 131°F (Thermophilic digestion temperature) •
Feed sludge temperature: 70°F (Southern region) • 18 day SRT •
Completely mixed pancake type tank, Flat bottom • 45% VSR assumed
due to higher digestion temperature • Biogas volume: 12 ft3 /lb VSR
• Biogas heat value: 600 btu/ft3 • Boiler efficiency: 80% • Tank
heat loss = 1 btu/hr/1000ft3
(a) Dimension of the tank (Diameter and tank height in ft.)
Assume SF = 1.1
(b) Daily biogas volume generation (ft3 /day)?
(c) Total heat requirement for the digester. Please include heat
for sludge and tank loss. Assume that raw sludge temperature is
70°F. Use safety factor, 1.35.
(d) Design total heat generation in a dual fuel boiler in
btu/hr. Use boiler efficiency, 80%. (e) Heat generated from biogas
is enough to cover total heat requirement for thermophilic
digestion? If not, how much (in ft3 ) natural gas is required
daily? Use 1,000 btu/ft3of natural gas and boiler efficiency of
80%