Understanding Activated Alumina Adsorbent
One of the most commonly used adsorbents,
Activated Alumina is known for its numerous pores and large surface area. Both
these features help the adsorbent take in more moisture molecules over a larger
area. Another highlight of Activated Alumina as a desiccant is that it can take
in all the liquids and gases without undergoing any kind of physical as well as
chemical transformation. Activated Alumina functions by the means of a process
known as adsorption. This desiccant is mainly used for drying air. The presence
of humidity molecules in the air can prove to be quite harmful as it can lead
to problems like ice formation, corrosion in the machines. Thus, it becomes highly
important to remove moisture molecules from air for the smooth functioning of
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The functioning of the Activated Alumina
adsorbent is very simple. The air, which is meant to be dehumidified, is passed
through the Activated Alumina. As it passes through all the moisture present in
the air will stick to the Alumina and only the dried air will pass forward. The
vapor molecules in the air are trapped in the Activated Alumina desiccant.
Thus, with the help of the alumina adsorbent, the air is completely dried.
Activated Alumina in Air drying
Sometimes it becomes important that all the
moisture present is removed from the air being circulated. If compressed air
having a pressure dew point of around -40 °C / -40 F or lesser is what is
needed, then one should opt for a heat less adsorption dryer, which is both
energy as well as cost effective. These heats less adsorption dryers carry out
their work with the help of desiccant material like Activated Alumina or
Molecular Sieve. These two desiccants are best suited to remove all traces of
moisture from the compressed air.
The functioning of the heat less adsorption
dryer is explained as follows:- The dryer consists of two identical adsorption
towers filled with equal amounts of either Activated Alumina or Molecular
Sieve. There is no hard-and-fast rule that only one type of desiccant can be
used. Either of the two can be used as both are equally effective.
As the drying process begins, the
compressed air moves from the bottom to the top of the tower and as it passes
through the Activated Alumina desiccant, all the moisture present is readily
absorbed. As the moisture intake takes place, the desiccant bed will start to
get heavy and eventually become saturated. When the desiccant in the first
tower is completely saturated, it automatically shuts down.
The next step is to remove the saturated
desiccant from the first tower. The desiccant is purged by passing dry
compressed air from the top of the tower to the bottom and for it to come in
contact with the ejected moisture molecules.
So while all this is happening in the first
tower, what is going on in the second tower, you may ask? During the time
period when the desiccant in the first tower is being regenerated, the second
tower is functioning as normal. This is in order to ensure that there is a
continuous flow of dried air in the system.
While the desiccant bed of one tower will
be regenerated, the other tower will be in production in order to guarantee a
continuous flow of dried air. The ever flowing stream of dried compressed air
is an indication that both the towers filled with Activated Alumina desiccant
are functioning smoothly.
There are many factors influencing how the
adsorption dryers perform. These include the temperature of the dryers, their
operating pressure as well as flow. If the operating temperatures are raised
beyond a certain point, it will drastically affect the production process.
