subject: Vacuum Swing Adsorption - Slitting Machine Manufacturer - Cut To Length Line Manufacturer [print this page] Comparison of VSA to PSA Comparison of VSA to PSA
The simplicity of the VSA process may allow for greater efficiency and cost savings, and less maintenance vis--vis PSA systems. The VSA process operates on the steepest part of the isotherm curves and thus has the potential to extract maximum sieve and power efficiencies. The integrated rotary lobe blower, which also serves as a vacuum regenerator, results in low feed pressure. The dramatically lower pressure swings in the VSA system eliminate the need for a feed air compressor, which translates into lower power consumption for VSA systems. As a result, power savings of as much as 50% can be achieved, when compared to the most simple PSA systems. However, VPSA systems typically have comparable or better power efficiencies.
The low pressure air input into the absorber vessel in combination with the high efficiency of the vacuum applied during the desorption stage means that a single absorption vessel may be used. In contrast to traditional PSA systems, which require feed air compressors as well as process valves and associated dryers and feed air filtering systems, this single-vessel VSA system eliminates many of the design problems associated with two-bed PSA.
Maintenance issues typically associated with two-bed PSA systems are greatly reduced with VSA technology. VSA systems are less susceptible to sieve dusting because the pressure swings are of a lower order of magnitude. These lower operating pressures also eliminate any water condensate. Overall, VSAs are not as susceptible to humid environments as PSA systems, while PSA feed compressors require water removal hardware, and oil-removal hardware if an oil-lubricated compressor is utilized. Oil-less compressors are available, but are typically higher priced than oil-lubricated compressors. The above-mentioned rotary lobe blower is a rotary device that does not require the high level of routine maintenance typical of air compression systems. The use of a vacuum step provides a superior regeneration of the molecular sieve, thus extending sieve life. Overall, the VSA absorber vessel has much longer service life than two-bed PSA vessels, which commonly need re-packing of sieve material every 35 years.
Commercial uses
The design simplicity and efficiency that VSA technology offers has generated products that are more energy- and cost-efficient than traditional gas separation units. VSA processes are used at refineries, chemical and petrochemical plants, water treatment facilities, and landfills. VSA technology is used to purify air, soil, water, and hydrogen, and to manufacture oxygen, nitrogen, and hydrogen.
VSA technology plays an increasingly important role in the commercial production of oxygen. Oxygen concentrators that use VSA processes are a more lucrative and reliable option than oxygen cylinders for many industries. Its mobility and constant supply of oxygen makes it a perfect choice for governments and aid organizations in their emergency medicine and disaster relief operations, as well as for district hospitals in developing nations. Other commercial applications of oxygen concentrators include the fields of aquaculture and high-altitude work environments, including in the mining industry or the Goldmud-Lhasa railroad in Tibet. VPSA technology has allowed the development of a portable oxygen concentrator weighing less than 15 pounds (7kg), but with continuous flows of oxygen up to 3 LPM and pulse flows up to an equivalent of 7.2 LPM.
For the oil and gas industry, the production of liquid nitrogen via PSA technology is key in cases where a high nitrogen flow rate and/or high discharge pressure is required. As an inert gas, nitrogen is preferred over air for cleaning out newly drilled wells as well as maintaining old wells. In addition, nitrogen is used for fracturing, pipeline purging and drying, cementing, and pressure maintenance.
See also
Oxygen concentrator
References
Hutson, Nick D.; Rege, Salil U.; and Yang, Ralph T., ir Separation by Pressure Swing Absorption Using Superior Absorbent, National Energy Technology Laboratory, Department of Energy, March 2001
Adsorption Research, Inc., bsorption is the Solid Solution,1]
Ruthven, Douglas M., Principles of Absorption and Absorption Process, Wiley-InterScience, Hoboken, NJ, 2004, p.1
Yang, Ralph T., as Separation by Absorption Processes,eries on Chemical Engineering, Vol. I, World Scientific Publishing Co., Singapore, 1997
Ruthven, Douglas M.; Farooq, Shamsuzzaman; and Knaebel, Kent S., Pressure Swing Absorption, Wiley-VCH, Weinheim, Germany, 2001
Santos, Joo C.; Magalhes, Ferno D.; and Mendes, Adlio, ressure Swing Absorption and Zeolites for Oxygen Production,n Processos de Separao, Universidado do Porto, Porto, Portugal
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