Chemical Engineering September 2023 - 22

Cover Story
Part 1
Optimizing FluidizedBed
Drying Processes
Modern control technologies and industrial automation strategies can help processors use
fluidized-bed dryers to drive competitiveness and profitability
Alan Messenger
Optimal Industrial
Automation
T
IN BRIEF
WHY FLUIDIZED-BED
DRYING?
A CLOSER LOOK AT
FLUIDIZED-BED DRYING
ENHANCING DRYER
CAPABILITIES
UPGRADING CONTROL
SYSTEMS
SKILLED AUTOMATION
SPECIALISTS
CASE STUDY EXAMPLES
CONCLUDING REMARKS
he ability of fluidized-bed dryers to
achieve exceptional performance
and deliver high-quality results in
the controlled, gentle and homogeneous
drying of wet solids is unparalleled.
This is why these units have long been integral
to operations in the pharmaceutical,
chemical and food-and-beverage industries.
To benefit from optimal fluidized-bed
drying operations, companies need to keep
up with the evolution of control technologies
and industrial automation. In so doing,
companies can stay ahead of the game,
delivering high-quality products with short
lead times and costs.
Why fluidized-bed drying?
Among the most common equipment
classes in a variety of manufacturing industries,
dryers are fundamental in the processing
of goods. Reducing the water content
of a bulk solid material slows the growth of
microorganisms and insects, suppresses
undesirable reactions that can deteriorate
the material, and also decreases its weight.
Drying therefore improves the shelf life, storability
and transportability of products.
A variety of drying methods are available
to support highly diverse processes and
needs. One such method is fluidized-bed
drying, which relies on feedstock fluidization,
whereby a high-pressure, hot air stream
passes vertically through a perforated plate
into the bed of solid particles in the feedstock
bed. As the hot air passes through the
container, granules are suspended in the
rising air and begin to dry. The solid bed is
therefore converted into a boiling liquid, and
said to reach a fluidized state. The continuously
moving mass of particles, in constant
contact with the gas stream, which takes
away the moisture as vaporized liquid, results
in highly efficient drying. The gas, as
well as any solvent from the feedstock,
passes through a filtered outlet and can then
be recycled for reuse.
22
Given the nature of this process, fluidized-bed
drying is extremely common when
handling powders or granules in chemical,
agrochemical, ceramic and pharmaceutical
manufacturing as well as food-and-beverage
processing. In practice, this hot-air-driven solution
is a mainstay in granulation operations
for oral solid dosage (OSD) pharmaceutical
production, as it offers a highly effective framework
to form strong bonds for the agglomeration
of powder formulations. As a result,
it is possible to obtain perfectly compressed
products, such as tablets and caplets.
A closer look at fluidized-bed drying
Methods that use hot air in this fashion are extremely
valuable because high-quality setups
offer high drying rates, contributing to optimal
throughput, short cycle times, thermodynamic
efficiency and uniform moisture reduction
while minimizing the potential for mechanical
damage to the products. Moreover,
these units typically feature a long service life,
due to the absence of any moving parts. This
requires limited investment for maintenance
and repairs and minimal downtime (Figure 1).
While fluidized-bed dryer hardware can run
for many years - many units installed over
35 years ago are still operating - the control
system that regulates the process should be
updated regularly. Regular updates can help
manufacturers improve the time-, cost- and
Shutterstock
FIGURE 1. Fluidized-bed dryer hardware, like the equipment
shown here, can run for many years, but plants should consider
updating the control system regularly
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
SEPTEMBER 2023
http://WWW.CHEMENGONLINE.COM
Chemical Engineering September 2023

Table of Contents for the Digital Edition of Chemical Engineering September 2023
