Published on : 05 August 20194 min reading time
An oxygen generator is a device that generates oxygen from a specific source (usually ambient air) by providing a mixture of oxygen-enriched gases. Visit www.novairindustries.com/ and learn further more information about oxygen generators. Generally, an oxygen generator uses the technology known as “pressure swing adsorption”, a physical process for the separation of gas mixtures by pressure adsorption. This type of medical device is widely used for the supply of oxygen in sanitary applications, particularly when liquid or pressurized oxygen is too dangerous or impractical, as for example in private homes or in other contexts.
Operating an oxygen generator
Oxygen generators operate on the principle of the rapid adsorption of the atmospheric pressure swing (PSA) of nitrogen onto a zeolite molecular sieve. The nitrogen is then removed. This type of adsorption system is therefore substantially a “filter” for nitrogen that allows other atmospheric gases to safely pass the zeolite sieve. At the end of this process, high concentration oxygen remains as the main residual gas.
PSA technology is a reliable, fast, convenient and cost-effective technique for small- and medium-quantity oxygen generation, while cryogenic separation is more suitable for producing higher volumes. The porous zeolite at high pressures adsorbs large amounts of nitrogen, because of its large contact area. In a second step, after the separation of oxygen and other gases that are not adsorbed, through another passage, the nitrogen is de-adsorbed molecular sieve.
An oxygen generator is simply an air compressor, two full cylinders of zeolite pellets, a pressure equalization tank, and a few valves and tubes. In the first half of the cycle, a first cylinder receives air from the compressor for about 3 seconds. Meanwhile, the pressure in the first cylinder increases from atmospheric pressure to a pressure of about twice normal atmospheric pressure (typically 20 psi / 138 kPa, or 2.36 absolute atmospheric pressure) and the zeolite saturates with nitrogen.
Once in the first cylinder, at the end of the first half of the cycle, a concentration close to that of pure oxygen is reached (small amounts of argon, CO2, water vapor, radon and other minor atmospheric components remain unscreened by the zeolite), a valve opens and the oxygen enriched gas flows to the pressure equalization tank, which is connected to the oxygen tube for the patient. At the end of the first half of the cycle, another change of position of the valve occurs, so that the air of the compressor is directed towards the second cylinder. As the enriched oxygen moves to the reservoir, the pressure in the first cylinder decreases, allowing the nitrogen to be de-adsorbed and to begin to dilute again in the gas.
During the second half of the cycle, the position of the valve also changes, which allows the gas in the first cylinder to be purged with ambient air. At the same time, the oxygen generation in the equalization pressure tank is maintained and does not fall below about 90%. The pressure in the tube that carries oxygen from the compensation tank to the patient remains constant due to the presence of a pressure reducer.
The old generator units were characterized by a cycle of about 20 seconds and were able to emit up to 5 liters per minute of an oxygen-containing mixture in a percentage greater than 90%. Starting in 1999, units capable of delivering up to 10 liters per minute, with the same concentration, were placed on the market.
Oxygen generators, through the PSA system, are an economically convenient source of oxygen. They are safer, less expensive, and tendentially more practical than cryogenic oxygen tanks or conventional liquid oxygen cylinders. They find application in different fields and industries besides the medical industry, for example in the pharmaceutical field, water treatment and in the production of glass.