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[[Image:Air_Stripper_for_Wikipedia.png|thumb|right|250px|Figure 1. An air stripper]] | |||
'''Air stripping''' is the transferring of [[Volatility (chemistry)|volatile]] components of a liquid into an air stream. It is a [[chemical engineering]] technology used for the purification of groundwaters and wastewaters containing volatile compounds. | |||
Volatile compounds have relatively high [[vapor pressure]] and low aqueous solubility characterized by the compound’s dimensionless [[Henry's law]] coefficient, which is the ratio of the concentration in air that is in equilibrium with its concentration in water. Pollutants with relatively high Henry’s Law coefficients can be economically stripped from water. These include [[BTEX]] compounds ([[benzene]], [[toluene]], [[ethylbenzene]], and [[xylene]] found in gasoline, and solvents including [[trichloroethylene]] and [[tetrachloroethylene]]. [[Ammonia]] can also be stripped from wastewaters. Since Henry’s law coefficient increases with temperature, stripping is easier at warmer temperatures. | |||
==Air strippers== | |||
Although any device that promotes contact between air and water strips some volatile compounds, air strippers are usually packed towers or [[Theoretical tray|tray]] towers operated with countercurrent flow of water and air. Packed towers, such as shown in Figure 1, usually use engineered or random plastic packings. Design criteria for packed towers include surface area provided by the packing, column height and diameter, and air to water flow rates. | |||
Since many of the compounds stripped are [[National Emissions Standards for Hazardous Air Pollutants|hazardous air pollutants]], the air exiting a stripper may require emissions control. [[Activated carbon #Applications|Carbon adsorption]] is often used and [[catalytic oxidation]] is another option. | |||
==References== | |||
* {{cite book|author=Henry Z. Kister|title=[[Distillation Design]]|edition=1st Edition|publisher=McGraw-Hill|year=1992|id=ISBN 0-07-034909-6}} | |||
* {{cite book|author=Perry, R.H. and Green, D.W. (Editors)|title=[[Perry's Chemical Engineers' Handbook]]|edition=7th Edition|publisher=McGraw-Hill|year=1997|id=ISBN 0-07-049841-5}} | |||
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External links: | |||
* [http://www.frtr.gov/matrix2/section4/4_50.html Air Stripping] from a website page of the Federal Remediation Technologies Roundtable | |||
* [http://www.jaeger.com/Brochure/airstripping.pdf Air Stripping of VOCs from Water] | |||
* [http://www.usace.army.mil/publications/design-guides/dg1110-1-3/entire.pdf Air Stripping, Design Guide 1110-1-3] from website page of the [[U.S. Army Corps of Engineers]] | |||
Revision as of 22:03, 11 September 2010
Air stripping is the transferring of volatile components of a liquid into an air stream. It is a chemical engineering technology used for the purification of groundwaters and wastewaters containing volatile compounds.
Volatile compounds have relatively high vapor pressure and low aqueous solubility characterized by the compound’s dimensionless Henry's law coefficient, which is the ratio of the concentration in air that is in equilibrium with its concentration in water. Pollutants with relatively high Henry’s Law coefficients can be economically stripped from water. These include BTEX compounds (benzene, toluene, ethylbenzene, and xylene found in gasoline, and solvents including trichloroethylene and tetrachloroethylene. Ammonia can also be stripped from wastewaters. Since Henry’s law coefficient increases with temperature, stripping is easier at warmer temperatures.
Air strippers
Although any device that promotes contact between air and water strips some volatile compounds, air strippers are usually packed towers or tray towers operated with countercurrent flow of water and air. Packed towers, such as shown in Figure 1, usually use engineered or random plastic packings. Design criteria for packed towers include surface area provided by the packing, column height and diameter, and air to water flow rates.
Since many of the compounds stripped are hazardous air pollutants, the air exiting a stripper may require emissions control. Carbon adsorption is often used and catalytic oxidation is another option.
References
- Henry Z. Kister (1992). Distillation Design, 1st Edition. McGraw-Hill. ISBN 0-07-034909-6.
- Perry, R.H. and Green, D.W. (Editors) (1997). Perry's Chemical Engineers' Handbook, 7th Edition. McGraw-Hill. ISBN 0-07-049841-5.
External links:
- Air Stripping from a website page of the Federal Remediation Technologies Roundtable
- Air Stripping of VOCs from Water
- Air Stripping, Design Guide 1110-1-3 from website page of the U.S. Army Corps of Engineers