Transcript Inert Gas Purification Systems

Inert Gas Purification
Systems
Why do we need them???
• Many of the materials used in research and
development today are extremely air
sensitive, and can be dangerous in the
presence of air.
• Purifiers are designed to remove oxygen,
moisture and nitrogen/hydrogen from an
inert gas to one part per million.
• Safety is also a critical issue in experiments
and research today.
Purifier Components
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Circulation blower
Copper catalyst
Molecular Sieve
Vacuum pump
Solenoid Assembly
Pressure control
Regeneration control
Manual footswitch
• Isolation valves
(automatic or manual)
• Solvent removal
systems
• Titanium reactor (in
the case of N2/H2
removal)
• Exhaust traps
Purifier theory
The purpose of a purifier is to remove
oxygen and water from an inert gas
flowing through a controlled
atmosphere system such as a glovebox.
The typical purifier contains two
purification agents. One agent is a
molecular sieve that removes water
by the process of molecular
adsorption.The other agent is called
Q5 and is an oxygen reactant
material.
Oxygen removal
• Oxygen removal from argon, helium, or
nitrogen is accomplished with a
reactant/catalyst known as Q5, a material
consisting of finely divided copper on an
alumina matrix. The copper reacts with
oxygen to form copper (II) oxide.
Moisture removal
• Moisture is removed by a molecular sieve
enclosed in the same container as the
oxygen reactant. Also removed by the
molecular sieve at ambient temperatures are
carbon dioxide, nitrogen dioxide, hydrogen
sulfide, carbon monoxide and many organic
compounds including: Alcohols, aromatics,
amines, halogenated compounds,
oxygenated compounds, hydrocarbons and
organic acids.
Regeneration Theory
• To restore the purification capability of the
material two reactions must take place.
• The H2O trapped by the sieve must be
removed completely.
• The O2 must be removed from the Q5
reactant by reduction using hydrogen and
heat.
Regeneration theory (cont.)
• The restoration of the sieve is accomplished
by heating the material to vaporize the
water. A dry gas is passed over the sieve
that carries the water vapor out of the
column.
• Restoration of the the Q5 is accomplished
by passing a H2 rich gas through the hot
reactant. The H2 reacts with the saturated
reactant to form metallic Cu and H20. The
water is then pumped out.
Materials that can damage the
purifier
• In general, any chemical that reacts with copper to
form a more stable compound than copper (II)
oxide will damage the oxygen reactant.
• Volatile compounds containing sulfur or halogens
are the most common of this type.
• Also, alcohols, phosphenes, arsines, arsinate, and
mercury vapor may also damage the oxygen
reactant. If any of these materials are to be used in
large quantities, a suitable trap should be installed.
• Organic solvents will also damage the
molecular sieve with long term exposure.
Selecting a purifier
• Consider !
• The size of the Glove-box
• Determine the leak rates if applicable
• Calculate the frequency of ante chamber
operation
• Determine the desired purity level
Circulating Vs Purging
• When purging a glove-box the atmosphere
in the box can only achieve an O2 and H2O
level that is present in the source gas.
• Purging a box can be very expensive
depending on the gas and the volume of the
box to be purged.
• When using a closed loop circulation
purifier the supply gas does not need be
pure. It is the job of the purifier to remove
H2O and O2 in the gas to the <1ppm level.
• The system only uses gas when transferring
in and out of the box.
Purifier options
• Purifiers can be configured with dual
columns for continuous operation.
• They can be configured for different flow
rates.
• In addition to standard configurations
custom solvent traps can be supplied for
removal of harmful materials that can
damage catalyst.
• Nitrogen/hydrogen removal systems are
also available.
Utilities required
• Two separate gases are required for standard
purifiers.
• Inert gas: Argon, Nitrogen or Helium with a
delivery pressure of approx. 35psi
• Regeneration gas: Your choice of a 4-5% mixture
of H2 in argon or nitrogen. Helium is not
recommended due to low molecular weight.
• Electrical service: (varies depending on
configuration) typically 115 VAC/20 A.
• Venting: application specific
Instrumentation
• In order to determine the conditions of the
atmosphere in the glove-box the following
analyzers are available.
• Moisture
• Oxygen
• Nitrogen
• Other custom systems are available, i.e.
GC/MS