EDC Ozone Systems of Irving, Texas, uses Pressure Swing Adsorption (PSA) Oxygen Generators to increase oxygen concentration in feed gas for its ozone generators, which has helped improve effectiveness while minimizing undesirable introduction of nitrogen into the water being treated.
The PSA oxygen generators are manufactured by AirSep Corporation of Buffalo, NY, and offer an alternative to conventional air dryers for all ozone applications.
The PSA process uses a synthetic zeolite molecular sieve to adsorb nitrogen from air at high pressure and release it at low pressure, greatly increasing the concentration of oxygen in the exit gas.
The generators provide a continuous, on-site supply of oxygen-enriched air with a -100 degrees F (-73 degrees C) dew point at purities ranging from 70 to 95 percent. Units are available in standard or custom designs, with outputs ranging from 12 to 70,000 scf/hr, to provide feed gas for ozone generators ranging in output from grams per hour to tons per day, as well as for a wide variety of other commercial and industrial applications.
Quality Considerations
David Capehart, EDC Ozone Systems applications specialist, said the primary reason for the companys selection of oxygen generators over conventional air dryers was manufacturing quality.
Quality Considerations
"We think of our ozone generators as manufacturing facilities for ozone," he said. "In any manufacturing process, raw material quality and quantity is critical to the quality and quantity of the final product. Our final product is ozone, which is made from oxygen. But the ambient air we breathe is comprised of only about 21 percent oxygen, with the rest 78 percent nitrogen and 1 percent assorted other gases."
Quality Considerations
The use of even the highest quality dried air, but still containing nitrogen, would be considered contamination in many water treatment applications, Capehart said. "Some waters are poised on the brink of exceeding allowable nitrite/nitrate levels. These waters might not be considered as candidates for ozone treatment if the only feed gas available to us was dried ambient air still burdened with nitrogen."
Maximizing Efficiency
Capehart said his company had found that mass transfer of ozone into the water being treated is much more efficient when using a smaller gas stream with a higher concentration of ozone.
Maximizing Efficiency
"Driving a gas into a liquid is a challenge, no matter how small the volume of gas," he said. "It is much more efficient to mix a pound of ozone into a body of water if the ozone is contained in a gas stream that is not burdened with a large quantity of useless baggage such as nitrogen." The resultant higher concentration of ozone provides advantages that are especially significant in wastewater applications, Capehart said .
Maximizing Efficiency
"Its like having three times as many soldiers available at a critical point in a battle," he said. "The high concentration ozone can set off chain reactions that might not be initiated when dried ambient air is used for feed gas."
Price Considerations
Capehart said that price, while not the primary reason for selecting AirSep PSA oxygen generation technology, was nevertheless a favorable aspect.
Price Considerations
"For example," he said, "two of their smaller units are equivalent in price to a desiccant dryer and associated air compressor, receiver tank, auto condensate purge, etc. that would be required to feed a typical application for us. But the dollars-per-gram-per-hour of ozone generation is less than one-half as much with oxygen as the feed gas. Furthermore, electrical consumption is also more affordable when using oxygen in the same scenario. Oxygen feed electrical consumption is 72 percent of the desiccant feed electrical consumption, based on kw hours used per pound per day of ozone produced."
Price Considerations
EDC Ozone Systems offers units ranging in ozone output from 28 gram/hr to 2700 grams per hour, with larger units designed to be serviceable while on-line if necessary, and all units featuring state-of-the-art control options.
Price Considerations
Applications include disinfection; taste and odor control; color removal; oxidation; VOC reduction; iron and manganese removal; and scale/deposit control.
