Chemical Engineering July 2017 - 9

Electrostatic spray drying protects heat-sensitive products
A
spray-drying technology
that
applies
an electrical
charge to feedstock as it
exits the atomizing nozzle
allows significant reductions in processing
temperature and can eliminate
downstream processing steps.
The charge application can improve
control over particle morphology,
lengthen shelflife of products and
lower energy consumption.
Fluid Air, a division of Spraying
Systems Co. (Aurora, Ill.; www.
fluidairinc.com),
launched a new
technology, known as PolarDry, in
late 2016 after five years of internal
development. The company is
now testing PolarDry with products
of potential users. These include
heat-sensitive or easily oxidized
compounds, such as proteins, active
pharmaceutical ingredients,
nutraceuticals, vitamins, antibiotics
and chemicals.
As feedstock slurry and atomizing
gas pass through PolarDry's
CMS-5741-Powerof7-Idea-CE_FINAL.pdf 1 6/1/17 4:20 PM
nozzle, a charge is applied, so that
each product-containing droplet
has an electrical charge. Within
the charged droplets, the molecules
of high-polarity solvent (usually
water) pick up a higher proportion
of electrons and achieve
a higher charge density, while the
less polar product molecules pick
up fewer electrons.
The repulsive forces of like
charges drive the solvent to the surface
of the droplet, while the spraydrying
product tends to remain in
the center, explains Joseph Szczap,
director of operations at Fluid Air.
" This creates an ideal situation for
drying, and the solvent will evaporate
efficiently at much lower temperatures
- 80°C or even ambient
temperatures - compared to traditional
spray-drying processes, " he
says, which typically use temperatures
of 200-250°C.
Fluid Air has also developed a
method for applying the charge in
a pulsed manner, so that a mixture
of fast-drying (charge on) and
slow-drying
particles
(charge
off)
is formed. " When the wet and dry
particles collide, they form agglomerates, "
Szczap says, so users can
spray-dry and agglomerate in the
same vessel.
" Electrostatic spray drying technology
will open up processing of a
whole new branch of active ingredients
that previously could not be
produced in powder form due to
the high temperatures of traditional
spray drying, " Szczap remarks, and
may offer an economical alternative
to freeze-drying that will dramatically
cut processing time.
Also,
PolarDry's
conditions
are
well suited for microencapsulation
applications. With lower temperatures,
the encapsulated products retain
higher levels of active ingredient.
Requiring less raw materials results
in considerable cost savings, says
the company.
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Chemical Engineering July 2017

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