Desiccant Solutions are able, to Advise, Source & Supply most desiccants which are commercially used throughout industry:
Molecular Sieves
Molecular Sieves are a type of synthetic “zeolite”, (from the Greek “Boiling Stone”). They consist of an alkaline metal form (Potassium, Sodium or Calcium) bound together by a clay binder. Internally, the structure is a mass of uniform sized, interlinked cavities. This structure allows for a massive surface area relative to its mass. The cavities will typically range from between 3-10 Angstroms in size. Below is the typical designation used throughout industry:
3A will adsorb molecules of 3 angstroms or smaller (Potassium type).
4A will adsorb molecules of 4 angstroms or smaller (Sodium type).
5A will adsorb molecules of 5 angstroms or smaller (Calcium type).
13X will adsorb molecules of 10 angstroms or smaller (Sodium type).
1 Angstrom = 0.1 nanometre
Orange to Green(OTG) Silica gel
Orange to green desiccant is one of the 3 main types of indicating silica gel used throughout industry. The base material is the same, the difference lies in the active colour change ingredients. The material may be seen in the following states (approximate guide only):
Orange – 3-12% saturation
Orange/Green – 10-20% saturation
Green – 20% + saturation
The above guide will also be dependent upon the temperature of the desiccant at the time of inspecting.
Beaded Orange to green desiccant is commonly found in both beaded & granular formats. The beaded product is far less friable & therefore will produce less dust when compared to the granular. Another consideration when choosing between the two types is the gas flow characteristics. Beaded material will offer a more uniform flow through the bed when compared to granular.
Activated Clay (BC) (Bentonite)
Bentonite clay which is a natural product which is mined as opposed to being manufactured. It is then dried (fired) to produce an adsorbent material for use in desiccation applications. The clay has a good adsorption capacity very similar to that of silica gel.
Activated Alumina(AA)
Activated alumina desiccant is an aluminium oxide material, which has many properties and is used extensively throughout industry for many different applications. We are primarily focused on the moisture retention characteristics for removal of moisture vapour from air & gas streams.
Activated Alumina is used in the majority of adsorption compressed air drying systems. For the following reasons:
Low energy to reactivate on desorption cycle.
Uniform bead size (3-6mm typical).
Resilient to both thermal and pressure shock.
Low dusting.
Low pressure drop characteristics.
Relative low cost.
< -40°C DP (125ppmV) dewpoint achieve.
Activated Carbon(AC)
Activated carbon is a form of carbon which undergoes different processes to create a highly porous structure which can be tailored for specific applications.
The starting point is usually a coal or similar high carbon content product which is treated chemically or by steam, to create the activated product. Once activated the carbon, has the ability to adsorb a wide range of different contaminants.
Activated carbon is extensively in Air separation / treatment to remove oil vapour, hydrocarbon vapours & odours.
Available in both granular and pellet format.
Silica Gel(SG)
Silica gel is one of the most used desiccant products for general ambient moisture removal. It is basically a refined form of silcon dioxide, the silica gel is produced by the combination of sulphuric acid & sodium silicate. This produces a highly porous structure very, random in nature when compared to other desiccants discussed.
For desiccation purposes the silica gel has the capacity of adsorbing up 25% (@ 25oC) of its own weight of water from the surrounding atmosphere. It will go on to achieve higher adsorption rates, but these cease to be classified as desiccated environments.
Silica gel is produced in granular & beaded forms.
Additional Desiccant Products
Orange to Clear (OTC) indicating silica gel, can be used in applications which require a lower level of humidity to be maintained before changing. Typical change level 6-8% loading by weight. Orange to clear silica gel is available in both beaded & granular form.
Blue to Pink (BTP) indicating silica gel is still used throughout the world, although not so much through Europe, primarily owing to legislative reasons. Blue to Pink indicating silica gel has very similar characteristics to the Orange to Green material. Therefore, it is a direct like for like replacement in terms of operating performance.
Carbon Molecular Sieves (CMS) is extensively used in PSA nitrogen generators for local production of high purity nitrogen for such applications as laser cutting. On-site generation means the operator can have 24/7 availability of nitrogen, rather than relying on stocks of bottled gas.
Calcium Chloride (CC) is commonly used in the production of shipping container desiccant solutions. Often binding agents will be added to reduce the deliquescing of corrosive fluids. The main advantage Calcium Chloride has over non-deliquescing products is its massive adsorption capacity.
Hopcalite (H) is a catalyst that is often used in conjunction with conventional desiccants. One of the main uses of Hopcalite is in breathing air systems. It has the ability to convert carbon monoxide into carbon dioxide which is much easier to remove / separate.