High pressure steam frequently passes through pressure reducing stations resulting in superheated steam at the point of use. Steam may also be superheated before reticulation.
Desuperheaters are used to reduce the temperature of the steam close to saturation, this requires a temperature feedback loop which controls the spray based on the desired steam outlet temperature (desuperheated temp.)
Applied Vacuum design and manufacture 2 types of Desuperheater.
Desuperheaters are used to reduce the temperature of the steam close to saturation, this requires a temperature feedback loop which controls the spray based on the desired steam outlet temperature (desuperheated temp.)
Applied Vacuum design and manufacture 2 types of Desuperheater.
Spray Type Desuperheater
These desuperheaters spray a direct spray of cooling water into the superheated steam line, the fine spray is evaporated into the superheated steam resulting in a reduced temperature. This require cooling water usually 1500kPa above the steam pressure. Spray type desuperheaters are limited within the range of steam flows and temperature they can handle as the maximum turndown is 4:1. Atomising desuperheaters are used for higher turndowns where there is a range of steam flows and varying temperature. |
Steam Atomising Type Desuperheater
These units utilise high pressure steam to atomise the cooling water. This action also allows a very large turndown ratio of up to 40:1 – especially with recycling of excess spray water. The high turndown ratio allows for the desuperheater to operate over a varying steam flow and temperature which is common within plant operation. The atomising steam pressure must be approximately twice that of main stream pressure. Below is a typical control flow diagram of an atomising type desuperheater. |