DEC IMPIANTI - molecular sieves
Heart of our dehydration systems, molsieves are adsorbents made up of aluminosilicate crystalline polymers (zeolite), composed of a three-dimensional network of channels (pores). For a given zeolite formulation and structure, the pores have the unique characteristic of being all the same size, giving a particularly developed adsorption properties, which means they are capable of separating or removing one substance from another, on a molecular scale. Molecular sieves differ from other adsorbents such as silica gel or activated alumina which show very wide pore distributions; molecular sieves pores are usually available with selectable size of 3÷10 Å, while those of a typical silica gel average about 50 Å, and activated carbon averages 10÷500 Å.
Synthetic zeolites can be tailored to meet industrial specifications: molecular sieves remove selectively polar components such as water (but also methanol, CO2 & H2S), showing an extremely high adsorption capacity, even at very low concentrations. They come in many forms, including beads & pellets. The molecular sieve, type, size and shape selection is determined by the requested operation.
While the structure of zeolite molecular sieves is very hard to damage, unless facing hydrothermal damaging, the binder could be chemically attacked or weakened (due to presence of acids), leading to dust formation or formation of agglomerates (chunks): the result is loss of access to adsorptive surface, and in the case of chunk formation, the channeling of flow (adsorption and regeneration), with drastic performance downgrade.
Proper selection of zeolite and binder will reduce the chances of degradation, increasing the life of the adsorbent.
The rate of aging, and the time for replacement, are highly individual characteristics of the type of service, the particular system, design, and feed characteristics. We, at DEC LAB, will be glad to make specific suggestions about testing any system, and will evaluate samples of the molecular sieves if they can be obtained from the unit. A combination of test data from the operating plant, and adsorbent analysis, over several periods, should provide a very complete profile on the aging curve.