South-Tek Systems’ Nitrogen Gas Generators provide a reliable, on-demand supply of nitrogen as the sweep gas for water degasification. They are cost-effective, safe, and convenient, offering a relatively quick return on investment.
How are Nitrogen Generators Used for Sweep Gas?
Contactors, or membrane contactors, are devices that enable direct contact between a gaseous phase and a liquid phase for mass transfer, without dispersing one phase into the other. A common application for these devices is the removal of oxygen from water. For this purpose, membrane contactors function with liquid water on one side of the hydrophobic membrane, while a nitrogen sweep gas and vacuum are applied to the other side. Since the membrane is hydrophobic, it prevents liquid water from passing through its pores into the gas side.
By adjusting the nitrogen partial pressure, oxygen can be removed from the water side of the contactor. This process is governed by the Young-Laplace equation, also known as the breakthrough pressure equation. The design of the membrane contactor permits a breakthrough pressure exceeding 150 pounds per square inch.
With nitrogen as the sweep gas and a lower pressure in a vacuum, oxygen from the water stream migrates through the hollow fibers because it is attracted to the lower-pressure side of the contactor. Additionally, the quality of the sweep gas, along with the breakthrough pressure, is also crucial to the process.
Purity Levels: Depending on the final process for which the regasified water is used, different levels of nitrogen purity are acceptable as the sweep gas. For most nitrogen applications involving sweep gas, purity levels exceeding 99.99% are required. This allows the sweep gas to accommodate larger ratios of oxygen during degasification.
The water is introduced into the contactor on the outside (shell-side), while the vacuum or sweep gas flows through the inside of the contactor’s hollow fiber (lumen-side). This process occurs with the water and vacuum or sweep gas flowing in opposite directions within the contactors. The nitrogen sweep pulls the oxygen away from the water, venting it outside the process. The end result is water that is now free of free-flowing oxygen molecules and can be used in various applications, from corrosion protection to food and beverage processes.
A PSA nitrogen gas generator from South-Tek Systems efficiently produces the N2 needed on-site through a simple and safe mechanical air separation process. For more information regarding membrane contactors, visit Liqui-Cel at www.liquicel.com.