PEAK
Scientific Instruments Ltd
ZA300 Zero Air Gas Generator
Instructions for use Manual
30
th
March 2005
ZA300 issue 3
10
Moisture / Removal: -
The first process utilizes a 'Pressure Swing Adsorption' (PSA) method to further treat the air. This is
where moisture can be selectively adsorbed from compressed air into a porous crystalline sieve material.
The adsorption process is aided by the electrostatic interaction between the adsorbent sieve material and
the gaseous adsorbate. The Peak Scientific Instruments Ltd. PSA dryer system utilizes the 'Skarstrom'
process where there are two columns of adsorbent used alternatively and described as follows: -
The un-treated air is passed via a '5 port-2 position' (5/2) pneumatic control valve into one of the sieve
columns where moisture is removed. Some of the dried gas is back-purged down the other column to
atmosphere which creates a regeneration effect. A simple cam timer eventually causes the 5/2 valve to
change columns and the other regenerated sieve column now generates the dried gas. Again some dried
gas is back purged down the other column to atmosphere to cause a regeneration effect. This process
repeats itself approximately every 2 minutes indefinitely.
Zero Air
Generation
The second process utilizes a 'Zero Air' catalytic combustion chamber. This works on the principle of
catalytic oxidation where hydrocarbons from the incoming compressed air supply are
cracked
to carbon
dioxide and water. The hydrocarbon level in the form of methane is reduced to <0.1ppm, for this process
to work the catalyst requires to be heated to approximately 400 degrees Celsius. Any CO present in the
air supply is also converted to CO
2
.
After the catalytic chamber the air passes through a simple cooling coil to a filter which removes bulk
moisture and any further particulate down to a level of 5 micron. The filter incorporates an auto-drain
mechanism which will release any accumulated water from the filter bowl when the level is sufficiently
high. The water passes out through a drain bulkhead at the bottom of the side of the cabinet.
Because water and also carbon dioxide are created in the Catalytic Process there is a necessity to
effectively remove them both.
