With the spray attemperation or desuperheater method, fine jets of water on steam condensate is sprayed through nozzles into the steam in its passage between the first and second stages of superheaters.
In order to achieve this, the temperature of steam is measured and any variation from a desired value is detected by a controller. The latter then sends out a signal to the regulating valve in the injection line.
The system as shown in Fig.5 is suitable for sugar plant boilers where the mass of the superheater and hence, thermal inertia time is small. This greatly minimises the time lag in the heat transfer.
Source: Avant-Garde