What is a Desiccant?
A desiccant material naturally attracts moisture from both gases and liquids. This moisture is adsorbed or retained within the desiccant and can be released again when heated. There are various types of desiccant materials, but Aggreko's dehumidifiers use what is known as 'Silica Gel' as the desiccant within the drying wheels.
Silica gel is a porous granular form of silica which is made from Sodium Silicate. The internal structure of each silica granule is made up of a network of interconnecting microscopic pores, which by a process called 'physical adsorption' or 'capillary condensation', attract and hold moisture within each granule. This trapped moisture can then, with the addition of heat, be released from the desiccant. This desiccant can then be used again and again.
As low ambient temperatures do not restrict the material, silica gel ensures desiccant dryers can be used all year round.
The Drying Process
- The desiccant wheel rotates slowly.
- As air is drawn through the wheel, the water molecules are removed and retained by the silica gel that is impregnated within the wheel itself.
- The air is now dry and is blown into the room or building.
- This dry air encourages evaporation to take place and therefore buildings, etc become dry.
- The water, now trapped in the wheel, is removed by heating the wheel and the vaporised water is blown outside.