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Safety and Sustainability
by Dr. Charlie Samer and Dr. Brian Roy, Air Products
January 1, 2009
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.
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Dr. Charlie Samer and Dr. Brian Roy, Air Products
Charlie Samer, Ph.D., is a senior research engineer at Air Products,
Allentown, Pa., a supplier of atmospheric, process and specialty gases. Brian
Roy, Ph.D., is the marketing manager for the industrial cryogenics segment at
Air Products. For more information, call (800) 654-4567 (code 672), e-mail
gigmrktg@airproducts.com or visit www.airproducts.com/food.
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