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After reading this article you will learn about the design of bio-gas plant with diagram.
The bio-gas plant has been diagrammatically represented in the Fig. 11.1. The size varies with amount of cow dung available. If 50kgs of dung is available from three animals, the bio-gas plant consists of a masonry fermentation tank or a digester, 3.6 metres deep and with an internal diameter of 1.5 metres in its lower two third portion.
A steel drum of diameter 1.5 metres which acts as the gas holder is inverted over the fermentation tank, it is held by three iron chains that pass over three pulleys which have been fitted a i the top of three iron posts (Only two have been shown in Fig. 11.1).
A small masonry tank has been built by the side of the fermentation tank. A pipe joins the bottom of the small tank with the bottom of the digester or the fermentation tank.
A small outlet has been provided at one side of the fermentation tank for overflow of the digested cattle dung. Similarly, an outlet is also present for the gas, provided with a stop cock or a regulator. To begin the operation of the bio-gas plant, 50kgs of dung are mixed with 50 litres of water. Then this slurry and 50kgs of slurry from another bio-gas plant is poured in the small tank.
This 50kgs slurry from another gas plant serves as the inoculum to start the fermentation process in the fermentation tank or digester. These materials go down into the fermentation tank and begin to decompose within about ten days, when another mixture of about 250kgs of cattle dung and about 250 litres of water are added to the inlet tank.
As more gas is evolved, further quantities of the mixture of cattle dung and water is added to the inlet tank every alternate day, until the fermentation tank or digester is filled up.
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The gas is collected in the collecting drum which slowly rises. This gas collecting drum is suitably counter-posed with weights to facilitate the collection of gas. When the gas collecting drum is completely filled, it rises to its maximum. The gas may be used for cooking, by opening the gas stop cock. Gas production is maximum in the summer. The optimum temperature for maximum gas production is 30°C to 35°C.
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