Question

Compare the relative performances of a floating drum and fixed dome type biogas plants

Answer 1

A fixed-dome plant comprises of a closed, dome-shaped digester with an immovable, rigid gas-holder and a displacement pit, also named 'compensation tank'. The gas is stored in the upper part of the digester. When gas production commences, the slurry is displaced into the compensating tank. Gas pressure increases with the volume of gas stored, i.e. with the height difference between the two slurry levels. If there is little gas in the gas-holder, the gas pressure is low.

Floating-drum plants consist of an underground digester and a moving gas-holder. The gas-holder floats either directly on the fermentation slurry or in a water jacket of its own. The gas is collected in the gas drum, which rises or moves down, according to the amount of gas stored.

Answer 2

The idea of biogas as a diesel fuel substitute is a very old concept and is a very attractive option.

It has a bright prospect in a country rich in agricultural products and poor in petrol resources.

A study on this aspect was and the report  concluded that while running a diesel engine in dual fuel mode i-e on a combination of diesel and biogas about  62% to 64% of diesel fuel is saved as well as  an annual saving is obtained at  Rs. 3486/m3 and 3379/m3 capacity when running on dual fuel mode also, with respect to gas produced from fixed dome and floating drum biogas digesters respectively.

The less saving in floating type design is due to gas losses from the plant as compared to fixed dome biogas digester where a system is sufficiently leakproof preventing gas leakage.

Therefore airtight.

Fixed dome biogas digester save the money and also environment-friendly.

Running engine by using floating type biogas digester consumed 6.35% more diesel than fixed dome design.