Gas Purification Technologies - Impurity Removal Efficiencies

Diffusion process characterizes the volume capacity. The volume capacity refers to the total volume of impurities that the getter can hold before it must be replaced. Volume capacity determines the getter lifetime.
Different impurities have different volume capacities, i.e. getter is more efficient at removing some impurities than others
Total amount of impurities that the getter material can hold is a function of the:

inlet gas quality
average flow

Capacity (equilibrium)

   Often measured in Volume Impurity/Volume Bed
   Unique for each impurity in each material, often dependent on "media" operating conditions
   (Pressure, temperature, impurity balance)
Efficiency (kinetics)

   Space Velocity/aspect ratio-key elements in design
   Purification "curve" is unique for each impurity at a given operating condition
   1 ppb performance common

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