BCAS 2018

www.bcas.org.uk 39 Technology Guide Nitrogen on-site production Nitrogen has widespread applications in various manufacturing sectors due its inert nature compared to normal air. It is used in food and drink manufacture (modified atmosphere packaging), pharmaceutical manufacturing, for purging equipment, tanks, and pipelines of flammable vapours and gases. It provides an inert atmosphere for laser cutting, soldering and heat treatment. BCAS reports. A n alternative to traditionally sourcing nitrogen in bottles or liquid, delivered to site, is to produce nitrogen on site from a compressed air system. Nitrogen forms approximately 78% of the earth’s atmosphere, and therefore it is the main constituent of the air drawn into a typical compressor intake. Standard factory type oil-injected screw or rotary vane compressors are suitable sources of the required compressed air input. Two main technologies are used to separate the nitrogen gas from ambient air; Pressure Swing Adsorption (PSA) and membrane technology. The PSA method uses a carbon molecular sieve (CMS) to remove oxygen. The membrane technology works on the principle that the relative speed of gases, their molecular size and ability to pass through a semi permeable cellular structure; preferentially separates the faster gases such as oxygen, carbon dioxide and water vapour from the slower nitrogen gas. Nitrogen safety Nitrogen should be considered in exactly the same manner as compressed air with regards to pressure systems legislation, equipment, and compressed gas safety. Compressed nitrogen represents the added hazard in that the oxygen has been removed and it cannot support life. All equipment, pipework, vessels, processes and machines should be clearly labelled to warn that they contain nitrogen and that it is a potential asphyxiant. Nitrogen has no properties to warn people of its presence, thus it can act as an asphyxiant by displacing the oxygen in air to levels below those needed for the brain to remain active. Inhalation of excessive amounts of nitrogen can cause dizziness, vomiting, loss of consciousness, and death. Advantages of on-site nitrogen generation ● The unit gas cost to produce nitrogen is typically up to 90% less than traditional supplies. ● No large stored volumes of potentially asphyxiant gas. ● Ambient temperature gas removes the risk of cold burns associated with liquid nitrogen. ● Low pressure gas @ 5-10 barg. Far fewer safety issues than with 300 barg high pressure cylinders and associated manual handling of heavy cylinders. For further help and information please contact the BCAS Technical Office Nitrogen production