Chemical Engineering November 2013 - 20

Alfa Laval
Newsfront
The New
Face oF heaT
exchaNgers
Evolving heat-exchanger technology
allows different types and designs
to find use in the CPI
W
hen it comes to heat exchangers,
chemical processors
have a lot to consider.
The most common concerns
include fouling, heat-transfer efficiency,
and the ability of the equipment
to handle the high temperatures, high
pressures and corrosive materials associated
with the manufacturing of
chemicals. And heat-exchanger manufacturers
are continuously tweaking
existing technologies to better suit the
unique needs of the users in the chemical
process industries (CPI).
Many processes in the CPI require
heating or cooling, or both at certain
points, which can consume a lot of
energy. Heat exchangers play an important
role in maximizing the use of
energy in many of these heating and
cooling applications by transferring
heat efficiently and recovering heat for
reduced energy use and environmental
impact. Heat exchangers are used
for heating, cooling, condensing and
evaporation duties in many processes.
" The challenge, " says Carl T. Kozacki,
APV industrial sales director
with SPX Flow Technology (Charlotte,
N.C.; www.spx.com), " is to find
the best heat transfer technology for
the specific application. This will depend
upon process parameters, such
as operating temperatures and pressures,
cleanliness of the fluids being
handled, and concerns over fouling, to
name a few. The right balance needs
to be found to cover process performance,
thermal efficiency, accessibilFigure
1. A compact and self-cleaning design make
Alfa Laval's spiral heat exchanger a good choice for
the CPI, as these exchangers can handle everything
from dirty fluids to high-vacuum condensation
ity, cleanability and productivity, all
while keeping lifecycle costs and initial
capital investment low. "
Read on to learn about how the
technology is evolving to include new
twists on existing designs that make
the latest generation of heat exchangers
suitable for the toughest applications
the CPI can dish out.
Fighting fouling
" Fouling is by far the toughest problem
for any heat exchanger, but it is
especially so in the high-temperature,
corrosive environment associated
with the chemical processing industry, "
says Klas Abrahamsson, regional
product manager with Alfa Laval
(Richmond, Va.; www.alfalaval.com).
" The nature of any heat exchanger
is that there will be fouling, so the
question becomes, What type of heat
exchanger and what design can withstand
high temperatures and pressures
and retain energy efficiency
even when fouled? "
Abrahamsson says that although
they have been around for many
years, spiral heat exchangers were
not considered for use in chemical
processing applications until recently.
A spiral heat exchanger is a circular
heat exchanger with two concentric
spiral channels, one for each fluid.
The curved channels provide optimum
heat transfer and flow conditions for
a wide variety of fluids, while keeping
the overall size of the unit to a minimum
(Figure 1).
20 ChemiCal engineering www.Che.Com november 2013
" Spiral heat exchangers were introduced
decades ago for use in the pulpand-paper
industry, which couldn't use
shell-and-tube exchangers because
they became fouled too easily and
often. While they are finding more use
in chemical processing and petroleum
refining, there are still many process
engineers that haven't come across or
considered using them, " Abrahamsson
continues.
" They are not low cost, but we consider
them problem solvers in these
heavy-duty applications because they
solve the fouling problem, which prevents
downtime, saves money and easily
provides a return on investment.
Spiral heat exchangers are easy to
maintain and are workhorses. "
Abrahamsson says spiral heat exchangers
are versatile and can handle
everything from dirty fluids to highvacuum
condensation. A self-cleaning
design reduces operating and maintenance
costs. The design offers high
heat-transfer efficiency and the ability
to handle two highly fouling fluids.
Modern
plate-heat-exchanger
designs, including gasketed, semiwelded
pairs, and fully welded units,
provide yet another solution to conquering
fouling on the heat-transfer
surface and provide end users with a
variety of options to better meet applications
requirements, according to
APV's Kozacki.
For example, Kozacki explains, an
all-welded hybrid unit is a cross between
shell-and-tube and plate tech
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Chemical Engineering November 2013

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