In a Nutshell:
As important size reduction is, another unit operation that works oppositely with
size reduction is also equally as important. The concept of enlarging the size of the
particle is as vital as reducing its particle size in the chemical engineering field. The unit
operation that works according to this concept is called the size enlargement operation.
This mechanical unit operation involves the use of mechanical forces such as pressure,
gravitational and centrifugal forces to reduce the size of particulate solids. Also,
temperature can also cause size enlargement of particles.
Any industry, or any field that would require a certain size for ease in handling
and product specifications would most probably have used a size reduction equipment.
This is because there are at least two basic reasons why size enlargement is utilized in
particle technology: better flowability and ease in handling. The industries that heavily
utilize this operation are the food, agriculture, pharmaceutical, and construction industry.
In particle size enlargement operation, there are at least three general methods
that are incorporated: agitation, pressure compaction and elevated temperatures.
Firstly, agitation is the method that is used by granulators that agglomerate particles by
agitating them.
Image 1. A schematic of an agitation size enlargement operation
Examples of equipment that utilize the concept of agitation to enlarge particle
size are the following: drum granulators, disc granulators, mixer granulators, spray
dryers and prilling. On one hand, the first three granulators use mechanical means such
as introducing centrifugal and gravitational forces to allow particles to stick to each other
with the aid of a binding agent. On the other hand, spray dryers and prilling use air
instead of mechanical means to give particles a way to agglomerate and stick to each
other also with the aid of a binding agent.
