Environmental Engineering Reference
In-Depth Information
8.9
Gate valve.
8.10
Butterfly valve.
Gate valves function by lifting and shutting a gate to let pass or suspend
the flow (Fig. 8.9). They close tightly, but lifting and shutting of the gate
using a hand wheel is rather slow. In case of fibrous substrates, the gate must
be equipped with a cutter to prevent leakage. Butterfly valves are also used
to block the flow in a pipe (Fig. 8.10). The closing disc, fixed to a rod, is
connected to an actuator on the outside of the valve, which allows the valve
to be positioned parallel (valve open) or perpendicular (valve closed) to the
flow. This valve type can be closed and opened quickly, but it does not close
completely tight. Check valves allow material flow in only one direction.
They are used when backflow must be prevented. As impurities can cause
leakages, a gate valve must be installed in addition to a check valve.
8.5
Site characteristics and plant layout
The layout of a biogas plant can take various forms. It must be elaborated
specifically for each project, depending on site characteristics such as size,
form and existing infrastructure. Some basic rules concerning the require-
ments of a plant site and the integration of a biogas project in a given
framework are as follows.
.
A site with sufficient space is compulsory, including storage areas, zones
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