thermal de-aerators

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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.

Oxygen content natural waterSecured image
Figure 5. Oxygen content in natural water, according to water temperature, for an atmosphere of 1000mb.

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.
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