thermal de-aeratorsReading time:
Steam stripping is often used to remove oxygen and dissolved carbon dioxide present in a steam generator’s feed water.
This process is implemented in thermal de-aerators where conditions in the saturating steam’s pressure and temperature are maintained so that the dissolved gases pass into the steam phase and are continually removed, with a portion of this to the outside.
Thermal degassing is carried out according to the laws described below :
Henry’s Law : The level of concentration of a gas dissolved in a liquid is proportional to its partial atmospheric pressure above the liquid; i.e. deoxygenation is made easier if the atmosphere above the liquid is low in oxygen.
Winkler’s Law :The solubility of gas is inversely proportional to temperature.Below is a graph showing oxygen content in natural water, according to water temperature, for an atmosphere of 1,000mb.
Depending upon their design, degremont® thermal de-aerators can be grouped into :
- Integrated storage thermal de-aerators: degassing tank;
- Separated storage thermal de-aerators: degassing unit with packing.
These units must be equipped with safety devices :
- An air inlet valve, designed to avoid the creation of a vacuum following sudden condensation of steam;
- Protective measures against excessive pressure: hydraulic siphon or valve(s), according to the degassing pressure;
- Protective measure against obstruction: siphon or overflow.