Commercial sorbents possess large surface areas (from 200 to 1000 sq. meters per gram).

Silica Gel

Sieves

Alumina

ADSORBENTS/DESICCANTS

The best desiccants are solid materials which combine very large surface areas with strong surface forces.  The most common materials that possess this combination are silica gels, activated alumina, activated charcoal, and molecular sieves.  In the case of the alumina or charcoal, the term "activated" refers to some treatment which increases the surface area, or accessibility, to the surface.

Adsorbents come in many shapes, such as round balls, pellets (extrusions) and irregular granules, which are used for dynamic systems.  Sizes will vary from less than 1/16" to 1/2".  Preferred Physical Characteristics are

· Chemically Inert
· Physically Durable
· Easily Regenerated
· Thermally Stable
· Larger Surface Area for Adsorption

Silica Gel
Silica gel is slightly acidic in nature and is resistant to all organic acids, except HF, and is attacked by alkaline materials.  It, therefore, cannot be used in a basic environment.  Checking the pH of the condensate prior to the bed may be used to determine if alkaline attack is a possibility.

Molecular Sieves
Molecular sieves are alkaline in nature and are attacked by mineral acids in contrast to silica gel.  However, strong basic environments can attack the binder materials and eventually weaken them physically.

Activated Alumina
Activated alumina is alkaline in nature and subject to attack by mineral acids, as are the molecular sieves.  Operation in an acidic environment will lead to formation of extremely fine dust due to the attack of the binder that holds the desiccant together.

Process Systems, LLC can provide a full range of desiccants for any application. 


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