Why PURCHASING MOLECULAR SIEVES

Molecular sieves are used commercially to purify gas streams and as desiccants to remove water or reduce humidity. This article focuses chiefly on what you need to know when buying a desiccant dryer, although the basic principles may apply to other applications as well.

How a Molecular Sieve 5A Works

The material used in an industrial molecular sieve has small uniform pores. When other substances come in contact with the molecular sieve, the molecules that are the right size to fit in the pores will be adsorbed. The molecules that are too large to fit will not. Molecular sieves function at the microscopic level, therefore their sizes are measured in angstroms. Pore sizes 3? and 4? will adsorb water while larges sizes remove larger hydrocarbons.

Regeneration and Reuse of Molecular Sieve For Hydrogen Purification

While some Zeolite 5A molecular sieves that remove alcohols and aromatic hydrocarbons use pressure to regenerate the sieve, the molecular sieves that are used for water-adsorption are usually regenerated by heating. For most industrial purposes, these temperatures range from about 250° to 450°F, similar to baking temperature settings for a standard kitchen oven.

Although Prices are higher than other forms of desiccant dehumidification, molecular sieves are also more efficient. The actual costs per unit and final value will depend upon other factors such as the volume to be dehumidified and level of dryness needed. 

Molecular sieves have excellent capacity for and rates of adsorption, even at elevated temperatures. They are the only desiccant that is selective for molecular size.