Vacuum swing adsorption
Vacuum swing adsorption (VSA) is a non-cryogenic gas separation technology.
Using special solids, or adsorbents, VSA segregates certain gases from a gaseous mixture under minimal pressure according to the species' molecular characteristics and affinity for the adsorbents. These adsorbents (e.g., zeolites) form a molecular sieve and preferentially adsorb the target gas species at near ambient pressure. The process then swings to a vacuum to regenerate the adsorbent material.
VSA differs from cryogenic distillation techniques of gas separation as well as pressure swing adsorption (PSA) techniques because it operates at near-ambient temperatures and pressures. VSA may actually be best described as a subset of the larger category of PSA. It differs primarily from PSA in that PSA typically vents to atmospheric pressures, and uses a pressurized gas feed into the separation process. VSA typically draws the gas through the separation process with a vacuum. For oxygen and nitrogen VSA systems, the vacuum is typically generated by a blower. Hybrid VPSA systems also exist. VPSA systems apply pressurized gas to the separation process and also apply a vacuum to the purge gas. VPSA systems, like one of the portable oxygen concentrators, are among the most efficient systems, measured on customary industry indices, such as recovery (product gas out/product gas in), productivity (product gas out/mass of sieve material). Generally, higher recovery leads to a smaller compressor, blower, or other compressed gas or vacuum source and lower power consumption. Higher productivity leads to smaller sieve beds. The consumer will most likely consider indices which have a more directly measurable difference in the overall system, like the amount of product gas divided by the system weight and size, the system initial and maintenance costs, the system power consumption or other operational costs, and reliability.
See also
References
- Hutson, Nick D.; Rege, Salil U.; and Yang, Ralph T., “Air Separation by Pressure Swing Absorption Using Superior Absorbent,” National Energy Technology Laboratory, Department of Energy, March 2001
- Adsorption Research, Inc., “Absorption is the Solid Solution,”
- Ruthven, Douglas M., Principles of Absorption and Absorption Process, Wiley-InterScience, Hoboken, NJ, 2004, p. 1
- Yang, Ralph T., “Gas Separation by Absorption Processes,”Series on Chemical Engineering, Vol. I, World Scientific Publishing Co., Singapore, 1997
- Ruthven, Douglas M.; Shamsuzzman Farooq, Kent S. Knaebel (1993). Pressure Swing Adsorption. Wiley-VCH. ISBN 9780471188186.
- Santos, João C.; Magalhães, Fernão D.; and Mendes, Adélio, “Pressure Swing Absorption and Zeolites for Oxygen Production,”in Processos de Separação, Universidado do Porto, Porto, Portugal