4A Molecular sieve is an alkali alumino-silicate. It is the
sodium form of the Type A crystal structure and has an effective
pore opening of 4 angstroms. It is used to dehydrate air and gases
in regenerative compressed air dryers and static drying. Molecular
sieves are regenerated by heating and purging. Regeneration
temperatures must be 400° to 600° F but are not to exceed 1000° F.
The degree of regeneration depends on the temperature reached in
purge. Molecular sieves are often used as a polishing layer for
dewpoints to 120° F.
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- Dewpoints Down to 100° F. and Lower: molecular
sieves are often used as a polishing layer in dryers to achieve
dewpoints down to 120°F. This product is the most effective
desiccant for low inlet, relative humidities, generally below
- Uniform Size = Low Pressure Drop in a packed bed,
molecular sieve provides a low pressure drop which minimizes
channeling and maximizes utilization of the whole drying capacity
of the compressed air dryer tower.
- Round Smooth Beads/Low Abrasion: This feature of
molecular sieves also contributes greatly to lower pressure drop.
Importantly, it means far less dusting, migrativion / attrition and
longer life by not allowing clogging of desiccant pores.
||4 x 8
||2.5 - 4.5
||45 lbs./ ft3
|Equilibrium water capacity
|Heat of adsorption
||1800 BTU/ lb Water
|Moisture retention @ relative humidity @
|@ 90% RH
|@ 60% RH
|@ 10% RH