Articles
RSSMembrane Contactors: An Introduction To The Technology
January 8, 2003
By Fred Wiesler
Membrana-Charlotte
Over the last 3 years, the designs of microporous membrane contactors for gas-transfer applications have rapidly developed. These newly designed contactors have moved the technology from small laboratory-scale devices, limited to 5 to 10 gallons per minute (gpm) capacity, to large-scale industrial devices designed for water treatment systems operating at 1,000 to more than 2,000 gpm. Since these devices are relatively new, the technology is often misunderstood. This article discusses the theory and principals of operation of membrane contactors in an effort to give users a better understanding of the technology.
Background
Membrane contactors are devices that allow a gaseous phase and a liquid phase to come into direct contact with each other, for the purpose of mass transfer between the phases, without dispersing one phase into the other. A typical use for these devices is the removal or dissolution of gases in water.
The concept of using membranes to bring two phases into contact with one another is not new. However, recent developments in the design of the contactors have greatly increased their efficiency and capacity. These developments have brought membrane contactors out of the laboratory and made them economical for medium- and large-scale industrial uses.
For removal of dissolved gasses from an aqueous stream, membrane contactors are operated with the aqueous fluid flow on one side of a hydrophobic membrane and a sweep gas and/or a vacuum applied to the other side of the membrane. Since the microporous membrane is hydrophobic, the membrane will not allow liquid water to pass through the pore into the gas side of the membrane. The membrane essentially acts as a support between the gas and liquid phases that allows them to interface at the pore. By adjusting the partial pressure of the gas in contact with the water, gases can be selectively removed or dissolved into water.
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