Deaeration tower

Deaeration towers are mechanical devices that mostly utilize the principle of lower gas solubility in water at lower pressure to remove dissolved acid gases and/or oxygen from produced waters or seawater prior to their reuse or disposal. Removal of hydrogen sulfide and carbon dioxide can be accomplished via gas stripping, but oxygen removal is the most common application as oxygen greatly enhances the corrosiveness of water, particularly in the presence of H2S or CO2.

Gas or vacuum stripping is influenced by the temperature of the water, the amount of oxygen in the water, and the partial pressure exerted by the gas mixture. Gas stripping uses a stream of natural or other inert gas to dilute the vapor phase and shift the equilibrium of the dissolved gases. This reduces the partial pressure of the oxygen in the gas mixture and causes the oxygen to come out of the water. This is accomplished by the contact of the water with the inert gas. Water enters the tower at the top and falls to the bottom cascading over trays in the process tower. The inert gas enters the tower at the bottom and exits at the top, making intimate contact with the water along the way. The oxygen content can be reduced to approximately 0.5 ppm using this process, but the actual quantity is dependent upon the quality of the gas used for stripping.

Vacuum stripping utilizes the principle of reduction of partial pressure to effect the removal of oxygen from produced waters. The pressure in the tower is reduced to the point that the water boils (water will boil at 60 °F at a pressure of 0.25 psia). The process is similar to gas stripping except a vacuum pump is used to reduce the pressure in the tower. In essence, vacuum stripping is away to achieve low temperature boiling. The tower is packed to achieve a high surface area for the relief and removal of dissolved oxygen to less than 0.5 ppm in most applications.