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Desiccant removal and installation

A&B Group removes desiccants (molecular sieve & activated alumina) by use of our vacuum trucks. A confined space entry is required by qualified entrants. This must be overseen by a competent trained rescue team. All confined spaces are considered non life sustaining until proven otherwise.
The material is vacuumed into our trucks and then transported to an approved landfill for disposal. Normally a screen is installed between the different types of material. Once the top layer is removed the screen is rolled up and removed from the vessel. The remainder of the material is then vacuumed from the vessel. Special care must be given on installation. The bottom layer of material must be gently installed into the vessel and leveled before the screen can be installed. Top layer can then be installed and leveled in the same manner.
Molecular sieve is a material containing tiny pores of a precise and uniform size that is used as an adsorbent for gases and liquids.
Molecules small enough to pass through the pores are adsorbed while larger molecules are not. It is different from a common filter in that it operates on a molecular level and traps the adsorbed substance. For instance, a water molecule may be small enough to pass through the pores while larger molecules are not, so water is forced into the pores which act as a trap for the penetrating water molecules, which are retained within the pores. Because of this, they often function as a desiccant.
A molecular sieve can absorb water up to 22% of its own weight. The principle of adsorption to molecular sieve particles is somewhat similar to that of size exclusion chromatography, except that without a changing solution composition, the adsorbed product remains trapped because in the absence of other molecules able to penetrate the pore and fill the space, a vacuum would be created by desorption.
Activated Alumina is used as a desiccant by a process called adsorption. The water in the air actually sticks to the alumina itself in between the tiny passages, as the air passes through them. The water molecules become trapped so that the air is dried out as it passes through the filter. This process is reversible, and if the alumina desiccant is heated to about 200C it will release all of the water stored in it. This process is called regenerating the desiccant. Air always has some water in it; one way to measure the amount of water in the air is the air's dew point.

Typical Elemental Analysis

















Oxygen (by difference)


Net Total


Bound Water




* All analyses are shown in elemental form even though the actual forms present are mixed glassy silicates. Free silica may be present in small amounts, characteristic of the particular ore body. More specific information may be obtained from the ore supplier involved.

Typical Physical Properties
Refractive Index
Free Moisture, Maximum
pH (of water slurry)
6.5 - 8.0
Specific Gravity
2.2 - 2.4
Bulk Density (loose weight)
As desired but usually in the 2-25 lb/ft3 range (32-400 kg/m3)
Mesh Size Available
As desired, 4-8 mesh and finer
Softening Point
1600-2000F (871-1093C)
Fusion Point
2300-2450F (1260-1343C)
Specific Heat
0.2 Btu/lbF (387 J/kgK)
Thermal Conductivity at 75F (24C)
.27-.41 Btuin/hft2F(.04-.06 W/mK)
Solubility .......Soluble in hot concentrated alkali and HF Moderately soluble (<10%) in 1N NaOH
Slightly soluble (<3%) in mineral acids (1N)
Very slightly soluble (<1%) in water or weak acids


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