Chemical Engineering June 2016 - 22

the Process Technology Division of
Alfa Laval (Richmond, va.; www.
alfalaval.us). " However, because we
are able to employ technologies that
allow these models to withstand increased
pressure and temperature
requirements, they are finding use
in process applications that benefit
from the lighter weight and smaller
footprint they provide. "
for example, Alfa Laval's newest
introduction, the DuroShell, is a
specially engineered plate-and-shell
heat exchanger that is suitable for
demanding duty in high-pressure,
high-temperature and corrosive applications.
Designed for use up to
100 bars and at temperatures up
to 842°f, the unit provides excellent
thermal performance that results in
maximum heat recovery using minimal
heating or cooling media, which
cuts fuel consumption, energy costs
and the environmental impact. The
small footprint and light weight also
minimize installation, operating and
maintenance costs and the gasketfree
construction provides security
against leakage, while the fully
welded design allows for the high
operating pressures and optimizes
resistance fatigue.
Spiral heat exchangers are also
employing advancements. The availability
of materials in continuous-coil
form, coupled with improvements in
the design and fabrication machinery
that allow the use of heavier plate
thicknesses, have enabled manufacturers
to push the boundaries of
operation for today's spiral heat exchangers
to pressures as high as 650
psi (45 barg), says Gooch's Shamsi.
A spiral heat exchanger offers
processors certain operational advantages
due to its inherent circular
design, curved, single-flow channels,
rectangular flow cross-section,
large surface area-to-volume ratio
and compact geometry. In liquidto-liquid
services, the continuously
curving, single-flow passages induce
high-shear rates that tend to
scrub away deposits as they form,
which reduces fouling and makes
spiral heat exchangers suitable for
handling tough fluids, such as process
slurries, sludge and media with
suspended solids or fibers, whether
on one side or on both sides, all of
22
Watlow
Figure 3. Optimax's EFD technology provides
advanced flow without compromising the integrity
of the fluid, heating elements or vessel
which are difficult for traditional multichannel
heat exchangers. In vaporto-liquid
duties, a large flow crosssection
perpendicular to vapor flow,
a short condensing zone, and often
column-mounted execution, ensure
extremely low pressure drops, making
spiral heat exchangers suitable
for condensing of overhead vapors
from distillation columns operating
under deep vacuum.
Designs for special applications
In pharmaceutical applications,
users demand exchangers that
eliminate any possibility of cross
contamination, which requires either
gasket-free construction or intermediate
chambers that collect potential
leaks, says edgar Steffin, head of
marketing for the Qvf product line
with DeDietrich Process Systems
GmbH (mainz, Germany; www.qvf.
com). Avoiding contamination of the
pharmaceutical product also requires
the use of materials approved by the
U.S. food and Drug Admin. (fDA;
Silver Spring, md.; www.fda.gov) for
contact with the product, as well.
fine-chemicals applications also
require more low-temperature process
steps, notes Steffin. " for batch
processes, this means huge temperature
ranges during a process cycle.
Increased usage of closed cooling
circuits, which operate at pressures
up to 6 bars (gage) are common, as
well, " he says. " Both these factors
are difficult on materials of construction
and applied sealing technology. "
As an answer, his company offers
Qvf heat exchangers (figure 1),
which are made of inert materials with
proven sealing systems or seal-free
solutions. " Our Qvf coil-type heat
exchangers are made of borosilicate
glass 3.3 and are single-piece units
where the tube coil is fused to the
shell, so that no seals are required,
which eliminates the risk of crosscontamination
between the service
medium and the product. They offer
heat-exchange surface areas up
to 15 m2. for higher heat-transfer
rates, we offer Qvf shell-and-tube
heat exchangers made with highly
corrosion-resistant SiC or borosilicate
glass 3.3 up to 27 m2. These
are designed for the condensation
and tempering of highly corrosive
products up to 6 barg. "
Some applications, such as those
that involve fluids that are highly viscous
and difficult to process (as in
the the polymer, plastic and food
industries), require a different heat
exchanger technology altogether,
says Steve Willis, sales manager
for the chemical market, with National
Oilwell varco (NOv; Houston;
www.nov.com/mixing). " enhanced
surface heat-exchanger technology
was often the traditional method for
heat transfer in these difficult applications,
but we determined that by
adding mixing to the problem, you
can increase heat transfer and eliminate
burning, scorching and uneven
heat history in delicate applications
like tempering chocolate, extrusion
cooling of foam and cooling of adhesives
for pelletizing, " he says.
So, NOv offers Kenics heat exchangers
(figure 2), which are
equipped with streamlined Kenics
static mixer elements to offer uniChemiCal
engineering www.Chemengonline.Com june 2016
http://www.alfalaval.us http://www.qvf http://www.fda.gov http://www.nov.com/mixing http://www.Chemengonline.Com
Chemical Engineering June 2016

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