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Introduction
: Molecular Sieves are Crystalline Metal Allumino Silicate
with a three dimensional interconnecting network structure
of silica and alumina tetrahedra. The widely used Zeolite
A is represented by the formula Na12[(AlO2)12(SiO2)12]xH2O.
This Molecular Sieve offers maximum degree of selectivity
because of its crystalline structure and uniform defined
pore diameter.
Regeneration
of Molecular Sieve : The original adsorption capacity
of a Molecular Sieve is recovered by regeneration. In
order to maintain continuos operation, the adsorption
continues in a second bed during the regeneration of
the saturated bed,. There are different methods of regeneration
based on the similar principle. The conditions in the
adsorber are modified in such a way that they correspond
to a very low loading on the adsorbent.
Thermal
regeneration : This involves heating to a temperature
at which the adsorption capacity is reduced to a low
level so that the adsorbate leaves molecular sieve,
This method is commonly used. Heating of the adsorber
bed is best carried out indirectly with a steam of hot
gas. This serves as a purge medium to remove the desorbed
molecules from the bed. In practice the regeneration
is carried out at temperature between 180’C. to
300’C.
Regeneration
by pressure swing : In this method, the pressure
on the adsorber is released so that partial pressure
on the impurities lowers remarkably.
Regeneration
by Purging : In this method adsorbent is regenerated
by Purging by pure medium e.g. liquid or gas without
impurities.
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