Power

Desuperheaters for power generation

Desuperheaters are typically used to reduce and condition the temperature of superheated steam in power plants, which is often used as an energy source for mechanical power generation in steam turbines. In plants that generate steam for both power generation, and process applications, the generated steam has to be diverted directly to the process side, for instance when the power demand drops or in case of an emergency. This could mean that because of low turbine loads either turbine exhaust steam will be too hot, or in case of emergency that the turbine bypass steam has a far too high temperature for the downstream process conditions.

Turbine bypass desuperheating

When a Desuperheater is deployed to reduce the pressure of superheated steam that is supplied around a turbine or another power engine, this usually called ‘turbine bypass desuperheating’. The letdown (=reduced) steam is still strongly superheated, and although it could have reached the required pressure level at the outlet of the steam-reducing valve, it is usually still unsuitable for use owing to its temperature.
In the steam turbine back pressure system to which the steam is fed, the basic requirement is to maintain the pressure and the temperature of this back pressure steam at a constant level, undependable of the load of the steam turbine.

Desuperheating of turbine exhaust steam

Desuperheaters are also used to control the temperature of turbine exhaust steam. In a backpressure turbine the downstream steam temperature is a function of steam load to the turbine. Usually at low turbine loads the steam temperature gets too high and desuperheating will be required to assure proper operation of the downstream installed process equipment. Frequently this downstream equipment consists of heat exchangers that are preferably fed with steam at a temperature as close as possible to the saturation temperature.