Gestra’s feedwater tank and deaerating dome solutions effectively remove dissolved gases such as oxygen, carbon dioxide, and other non-condensable which have a negative effect.  The design meets essential thermodynamic requirements to achieve optimal performance and improve cost efficiency.

The feedwater deaerating system for boiler feedwater consists of the SW feedwater tank and the NDR deaerator dome. This system removes dissolved gases like oxygen, carbon dioxide and other gaseous substances from the condensate and softened water. We tailor the size and thermodynamic characteristics of our feedwater deaerating system to customer specifications.

The make-up water and return condensate enter the NDR deaerator dome, which is fitted with a series of welded tray compartments for maximum trickling. Heating steam is fed from below into the NDR deaerator dome, which is mounted on top of the SW feedwater tank. The deaerated make-up water and return condensate flow directly from the deaerated dome into the feedwater tank. A steam injector installed in the lower part of the feedwater tank is used to heat up the feedwater to approx. 107 °C.

Oxygen and carbon dioxide are dissolved in water according to Dalton’s law of absorption, which states that gas solubility in a solution decreases together with the gas partial pressure above the station. The gas solubility in water therefore decreases as the water temperature rises. The make-up water and return condensate are distributed over the series of trays, coming into direct contact with the heating steam. This counterflow process reduces the solubility of oxygen and carbon dioxide, thus removing these gases. The released gases, known as flash steam, work their way to the top of the vessel, where they are vented from the deaerator done via the vent line.

We recommend a temperature-controlled heating system for warming up a cold feedwater tank. From a feedwater temperature of 70 °C, a pressure-controlled heating steam supply must be used during commissioning. Due to the fact that the feedwater temperature is above 100 °C, a minimum inlet height to the boiler feed pump is required to prevent the formation of steam bubbles in the pump housing.

With the GESTRA feedwater deaerating system, the oxygen content can be reduced down to 0.02 mg/l.