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Biogas Plant Lay-out of Pipeline

Biogas Plant Lay-out of Pipeline

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The gas pipe conveying the gas from the plant to point of user is vulnerable to damages by people, domestic animals and rodents.  Therefore, only light quality galvanized iron pipe should be used which must be, where possible, buried 30 cm (1 foot) below ground level.  Fittings in the pipeline must be sealed with zinc putty, Teflon tape or jute and paint.  Any other sealing agent, like grease, paint only, soap etc. must not be used.  The use of fittings, especially unions, should be kept to a minimum to reduce the risk of leakage.  No fittings should be placed between the main gas valve and the dome gas pipe.  The pipe size, inside diameter should be between .6 and 1 Cm.  Pipe size is determined by the size of the digester, (amount of gas produced) and amount of gas required in the house. (Are the stove, heater lights going to be used simultaneously?)

Figure 11.1: Schematic for Condensate Drain Valve in Gas Line.

Construction of Gas Line Condensate Drain Valve Box.

The biogas generated from the digester is saturated with water vapor.  This water vapor will condense on the walls of the pipeline.  If the condensate is not removed regularly, it will ultimately clog the pipeline.  For this reason, a water drain or trap is installed in the pipeline.  The position of the water drain should be vertically below the lowest point of the pipeline so water will flow by gravity to the trap.  Water is removed by opening the drain.  As this has to be done periodically, the drain must be easily accessible and protected in a well-maintained drain pit.  To connect burners to gas pipelines use of transparent polyethylene hose must be avoided.  Only the best quality neoprene, rubber hose should be used.  Other biogas appliances should be mounted and connected to the galvanized iron pipe.  As soon as there is gas production, all joints and taps must be inspected for leakage by applying a thick soap solution and observing for foam movement.     Page 19 of 24 12.  Compost Pits Compost pits are an integral part of the biogas plant; no plant is complete without them.

A minimum of two compost pits must be dug near to the Outlet Chamber overflow in such a way that the slurry can run freely into the pits.  Enough earth body must remain however, at least 1 meter, between the pits and the outlet chamber to avoid cracking of the chamber walls.  The total volume of the compost pits must be at least equal to the plant volume.  The earth excavated from the compost pits is used for backfilling of the inlet and outlet chamber and for top filling on the dome.

Compost pits

Photo 12.1: Compost Pits with Brick Walls for Stability

The compost pits can also be filled with agricultural residues and the slurry from the plant for a nitrogen and nutrient rich fertilizer.  Compost Pits are utilized by alternating discharge flow allowing the full pit to evaporate and leach into the soil while the other is being filled.  Once the pit material desiccates to the consistency of humus, the material could be removed for
agricultural application as fertilizer.





Biogas Appliances

The biogas fuel is used for cooking, heating and lighting.  Propane and biogas appliances areppropriate for use with biogas.

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