Safety and Sustainability
January 1, 2009
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Cryogenic liquids are produced in bulk quantities in
large plants called air separating units (ASUs). After the air has been
liquefied in the ASU process, the components of air ― nitrogen, oxygen, argon and
xenon (optional) ― are separated by conventional distillation, albeit at
extremely low temperatures (-325°F [-198°C]). LIN is most commonly manufactured
offsite, transported in tank trailers to the user’s site, and stored in an
insulated storage vessel. The LIN inventory can be managed remotely with
automatic replenishment from the vendor. For large users, an ASU can be
co-located at the use point.
LIN can produce severe tissue burns, so cryogenic systems must be insulated properly. When heated, LIN will expand to more than 600 times its original volume. Piping delivery systems therefore should be validated by a cryogenic specialist prior to design and commissioning.
Nitrogen gas is a simple asphyxiant, and adequate ventilation must be provided to prevent the ambient oxygen concentration from reaching dangerously low levels. However, unlike many other refrigerant chemicals, nitrogen is nontoxic and is not a greenhouse gas and therefore can be vented into the atmosphere with no negative consequences. This capability makes post-process handling relatively straightforward since no provisions for recovery of the nitrogen are required. The gas simply can be vented to a safe location.
LIN can produce severe tissue burns, so cryogenic systems must be insulated properly. When heated, LIN will expand to more than 600 times its original volume. Piping delivery systems therefore should be validated by a cryogenic specialist prior to design and commissioning.
Nitrogen gas is a simple asphyxiant, and adequate ventilation must be provided to prevent the ambient oxygen concentration from reaching dangerously low levels. However, unlike many other refrigerant chemicals, nitrogen is nontoxic and is not a greenhouse gas and therefore can be vented into the atmosphere with no negative consequences. This capability makes post-process handling relatively straightforward since no provisions for recovery of the nitrogen are required. The gas simply can be vented to a safe location.
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