Civil Engineering Reference
In-Depth Information
Fig. 6.3
Watertube boiler
basic circuit
6.5.1 Steam Watertube Boilers
In watertube boilers water circulates inside the tubes and flue gas outside. The basic
principle is shown in the circuit diagram in Fig.
6.3
. Water circulation is generally
caused by the density difference between the mixture of hot water and steam
formed in the heated side of the circuit, generally called a riser, and the cooler
water in the unheated side. Inside the drum, placed in the upper part of the circuit,
steam is released. In normal operating conditions, water flows continuously from
the drum through the cooler water downcomer and up the riser to the drum where
steam is released. Industrial boilers have many parallel riser circuits carrying the
steam and water mixture and few larger downcomers forming a loop.
Watertubes, like other industrial boilers, can be classified by tube shape and
arrangement (horizontal, inclined, etc.), by the number of drums, capacity, or
pressure.
Watertube units typically have capacities between 5 t of steam per hour
and a hundred or more and they are able to produce high-pressure
steam.
The basic and auxiliary elements of a watertube boiler are shown in Fig.
6.4
. The
following points can be emphasized:
