Oxygen and PSA
Adsorber column (sieve bed)
Adsorber columns, which WHO’s Foundations of medical oxygen systems (2023) calls sieve beds, are the chambers of a PSA oxygen plant that hold a zeolite molecular sieve retaining almost all the nitrogen in the compressed air while the oxygen passes through; AIGA 113/20 describes the typical oxygen 93 generator as composed of two such vessels.
In WHO’s Foundations of medical oxygen systems (17 February 2023), the oxygen passes through the molecular sieve along with a few other elements. AIGA 113/20 (EIGA Doc 195) describes the two vessels of the typical oxygen 93 generator as containing the molecular sieves, with a system that controls the opening and closing of the inlet and vent valves. It asks for a filtration system downstream of the adsorber vessels to prevent any release of molecular sieve dust, with the pressure differential across it monitored to check that the adsorbers are not deteriorated. In its background to Ph. Eur. 3098, EDQM notes that gas quality is controlled by the plant design and the specification of the materials in the adsorption columns.
In the ULTRACON concentrator used in ULTRAOX plants, the PSA unit contains two columns: in the high pressure step the adsorbent retains the contaminants in the compressed air and oxygen is obtained, and in the low pressure step the retained contaminants are released and the adsorbent is regenerated. The ULTRAOX 2022 datasheet says the zeolite can last up to 10 years or more without replacement in good conditions.
Sources
- WHO, Foundations of medical oxygen systems (17 February 2023), section 2.1
- AIGA 113/20 (EIGA Doc 195), Safe design and operation of on site generation of oxygen 93% for medicinal use, sections 4.3.1 and 6.10
- EDQM, Ph. Eur. monograph 3098 Oxygen (98 per cent): history
- ULTRACON datasheet, p. 2
- ULTRAOX Technical Data Sheet 2022, p. 4 and p. 14
Ultra Controlo figures come from its technical datasheets. Third-party facts were read at the source on the date shown.