FLOW CHART
The two commonly used types
of bio-gas plants are:
a) Floating drum type, and
b) Fixed dome type.
The commonly used model of bio-gas plants are:
a) Floating drum design:
i) KVIC model,
ii) Pre-fabricated ferro-cement digester model, and
iii) Pragati model.
b) Fixed dome type:
i) Janta model, and
ii) Deenbandhu model.
Design Parameters taken for Bio Methanation
·
Feed
Substrate Total Solid Concentration(TSC):
8-9 % (For Cow dung)
·
Ratio
of Dung to Water: 1:1
·
Bio
Gas produced : 0.06 cu mtr / kg dung (Summer 47 degree)
·
0.03
cu mtr / kg dung (winter 8 degree)
·
Temperature
: 35 degree centigrade
·
PH
– 7-8
·
Retention
Time : 30 days (For temp 25-35 Degree Cent)
·
Depth
of the plant is between 4 to 6 m according to the size
·
Depth
to diameter ratio between 1.0 to 1.3
·
When
the digester diameter exceeds 1.6 m, a partition wall is provided in the
digester
·
Average
gas production from dung may be taken as 40 lit/kg. of fresh dung
·
One
Cu. m gas is equivalent to 1000 litres
http://archive.unu.edu/unupress/unupbooks/80362e/80362E0j.htm
FIG. 3. Chinese Biogas Plant Design
The digester is of standard KIVC design, consisting of a cylindrical underground chamber using 23-cm (9 in.) brick walls and a concrete floor. It has two standard 10-cm (4 in.) cement household pipes for the inlet and outlet. A feed trough, slurry pit, and soaking pit for the digested slurry are provided. Figure 1 shows the details. The only departure from the standard design is provision of a water trough to hold the gas holder (as explained below).
The gas holder consists of a geodesic dome made of wood, to which a vinyl balloon is secured. The balloon is made of heat-sealed vinyl fabric available on the market. The whole assembly sits inside a water trough that serves two purposes: it prevents gas leakage through the water seal if filled with 20 to 30 cm of water, and it helps to anchor the balloon. Hooks around the gas dome also help to secure the structure so that it does not blow off under pressure. The dome struts and hubs were made as shown in figure 2A and B.
| Design of Biogas Plant | |
| Number of cows | 4 |
| Assuming 1 cow produces | 10 kg of dung/day |
| Amount of dung produced by 4 cows | 40 kg |
| Amount of gas produced by 1 kg of dung | 0.05 m� |
| Amount of gas produced by 40 kg of dung | 2 m� |
| Daily requirement of gas for cooking and lighting | |
| for 1 person | 0.5 to 0.6 m� |
| 2 m� of gas per day will provide cooking and lighting for | 2/ 0.6 to 2/0.5= 3 or 4 persons |
| Using a 1:1 ratio of cow dung and water: | |
| Daily input of cow dung | 40 kg |
| Daily input of water | 40 kg |
| Total input | 80 kg |
| Volume of the well required | |
| (45 times the daily input) | 80 x 45 = 3,600 kg |
| 100 kg of dung and water occupy | 1 m� |
| 3,600 kg of dung and water occupy | 3.6 m� |
| Digester tank capacity required | 3.6 m� |
| 70 % of 2 m� gas | [70 x 2] /100 = 1.4 m� |
| Digester tank capacity | 3.6 m� |
| Gas holder capacity required | 1.4 m� |
Assume 1.75 m as the internal diameter of the digestion tank.
| The depth required will be | 1.5 m |
| Using a 20 cm thick wall, the external diameter will be | 1.75+0.2+0.2m = 2.15 m |
A hemispherical PVC balloon is used as the gas collecter.
| Assuming diameter of the dome to be | 1.9 m |
| Volume of the dome (half sphere) | 1.795 m� |
| Design of Dome to Support the Gas Holder | |
| Type | 2 frequency dome,Class I, |
| Method I | |
| Diameter of dome | 1.95 m |
| Radius of dome | 0.975 m = 38.38 in. |
| Length of struts (including hubs) | |
| Long struts | radius of dome x 0.618= 23.75 in. |
| Short struts | radius of dome x 0.5465= 21 in. |
| Distance from centre of hub to centre of hole at end of strut | 2.75 in. |
| Length from centres of holes at each end of strut to ends of strut | 1.5 in. |
| Actual length of long struts | 23.75 in. - (2 x 2.75 in.) |
| + (2 x 1.5 in.) = 21.25 in. | |
| Hole-to-hole distance | 18.25 in. |
| Actual length of short struts | 21 in. - (2 x 2.75 in.)+ (2 x 1.5 in.) = 18.5 in. |
| Hole-to-hole distance | 15.5 in. |
| Number of long struts required | 35 |
| Number of short struts required | 30 |
| Number of five-element hubs required | 6 |
| Number of six-element hubs required | 20 |
How much Biogas can I produce?
The following is a calculator for estimating the amount of biogas your operation can produce. The calculator is a guideline only and should not be used for design purposes.
Choose the biogas production number that applies to your operation...
Example: 600 sow farrow to finish operation, choose Farrow to Finish
The following is a calculator for estimating the amount of biogas your operation can produce. The calculator is a guideline only and should not be used for design purposes.
Choose the biogas production number that applies to your operation...
Example: 600 sow farrow to finish operation, choose Farrow to Finish
Hogs |
Cubic metres biogas per hog per year
Farrow to Finish
720
Farrow to Wean
222
Farrowing
174
Weaner
24
Feeder
78
Dairy
Cubic metres biogas per cow per year
Freestall
860
Multiply the number of animals by biogas production number...
Example: 600 hogs x 720 m3 biogas / hog / yr = 432000 m3 biogas / year
Multiply the result by the numbers below for cogeneration of electricity and heat...
____________ x 1.7 kWh/ m3 biogas = _________ kWh of electricity per year
____________ x 7.7 MJ/ m3 biogas = _________ MJ of heat per year
Multiply the result by the numbers below for heat production using boiler....
____________ x 15 MJ/ m3 biogas = _________ MJ of heat per year
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