LCI Corporation
Contact: Lynda Smith
4433 Chesapeake Drive
Charlotte, NC 28216
U.S.
Phone: 704 394 8341
Fax: 704 392 8507
Our extruders are mainly used for powder extrusion not in the plastic industry.
An LCI thin film evaporator (TFE) or wiped film evaporator (WFE) provides short residence time and open, low pressure drop configuration, allowing continuous, reliable processing of many heat sensitive or viscous materials without product degradation.
Simply stated, LCI thin-film separation technology quickly separates volatile from less volatile components using indirect heat transfer and mechanical agitation of a flowing product film under controlled conditions.
However, technology is but one part of the picture. Between idea and operation, a sophisticated mix of services is strategically arrayed to bring about the desired economic and environmental result. LCI (formerly Luwa Corporation) is uniquely equipped to turn your toughest separation problems into professionally executed, commercially reliable solutions.
by William B. Glover, P.E., Engineering Manager
William L. Hyde, Business Manager
LCI Corporation, Charlotte, North Carolina
Reprinted from the February 1997 edition of
Evaporation of
Difficult Products
T H E M A G A Z I N E O F T H E C H E M I C A L I N D U S T RY PrCohceemssiicnagl
he key to efficient, economical concentration,
distillation or devolatilization
of a product is selecting the
technique best suited to the process.
Tubular evaporators of batch or continuous
types, such as forced circulation,
rising Þlm and falling Þlm, have been
widely used successfully with a variety of
materials. However, they have been less
successful with heat-sensitive, viscous,
fouling or high-boiling liquids.
Degradation due to long residence time,
fouling of the heat transfer surface,
plugging of tubes, and low heat transfer
coefficients and high pressure drops due
to high viscosities are common operating
problems.
horizontal, and can have cylindrical or
tapered thermal bodies and rotors.
The agitated thin-Þlm or "wiped-Þlm"
evaporator consists of two major
assemblies: a heated body and a rotor. The
rotor may be one of several zero-clearance
designs (wiping), a rigid Þxed-clearance
type or, in the case of a tapered rotor, an
adjustable-clearance construction may be
used. The majority of thin-Þlm evaporators
in operation today is the vertical design
with a cylindrical Þxed-clearance rotor.
Within the vertical design evaporator,
the product enters the unit tangentially
above the heated zone and is distributed
evenly over the inner circumference of the
body wall by tne rotor (Fig. 2). Product
spirals down the wall
while bow waves
developed by the
rotor blades generate
highly turbulent flow
and optimum heat
flux (Fig. 1). Volatile
components evaporate
rapidly. Vapors
can flow either cocurrently
or, more
commonly, countercurrently,
and are
ready for condensing
or subsequent
processing as they
leave the unit.
Non-volatile
components are
discharged at the
bottom outlet.
Continuous washing
by the bow waves
minimizes fouling of
the thermal wall
where the product or
T
Evaporation of difficult products
Heated Wall
Bow Wave
Turbulent
Liquid Film
Rotor
Blade
How agitated thin-film
technology works
Agitated thin-Þlm evaporation has been
very successful with difficult-to-handle
products. Simply stated, the method quickly
separates the volatile from the less volatile
components using indirect heat transfer
and mechanical agitation of the flowing
product Þlm under controlled conditions.
The separation is normally made under
vacuum conditions to maximize DT while
maintaining the most favorable product
temperature, and to maximize volatile
stripping and recovery.
A variety of thin-Þlm evaporator designs
is commercially available today. Thin-Þlm
evaporators can be either vertical or
Fig. 1. Operating mechanisms of agitated thin-film evaporation.
Agitated thin-film evaporation overcomes common problems
William L. Hyde, Business Manager
William B. Glover, P.E., Engineering Manager
LCI Corp., Charlotte, NC
EVAPORATION/DISTILLATION/CRYSTALLIZATION
February 1997 CHEMICAL PROCESSING
Concentrate
Vapor
(co-current)
Vapor
(counter-
current)
Feed
Heating
Jacket
Product
Flow
Rotor
residue is most concentrated.
The combination of short residence
time, narrow residence time distribution,
high turbulence and rapid surface renewal
permits the agitated thin-Þlm evaporator
to successfully handle heat-sensitive, viscous
and fouling streams. Low product inventory
and operation at near-equilibrium conacids;
n PuriÞcation of isocyanates;
n PuriÞimprovements of essential oils;
n Improved shelf life and reactivity for
herbicides, insecticides and fungicides.
Concentrating foods, pharmaceuticals
Temperature-sensitive food and pharmaceutical
products with the highest
quality standards can be successfully
concentrated by thin-Þlm processors.
Diluted feedstocks can be concentrated
to Þnal speciÞcation in seconds without
recirculation, thereby preserving quality
and yield.
As the solids content of the stream
increases, temperature sensitivity and
viscosity generally increase, creating the
need for short residence time. Agitated
thin-Þlm technology fulÞlls these needs
while inducing high heat transfer.
Typical applications are:
n ÒDryingÓ of lecithin to 99.5%;
n Concentration of sugar solutions to
99.9%;
n Concentration of enzymes, vitamins
and proteins;
n Concentration of fruit and vegetable
purees;
n Concentration of cheesebase;
n Concentration of biological solutions;
n Stripping of solvents from vegetable
and plant extracts;
n Removal of water and solvents from
fermentation broths (e.g., antibiotics).
Resource recovery
Agitated thin-Þlm evaporation systems
are used extensively in the puriÞcation
and recovery of resources such as solvents
and oils. The ability of agitated thin-Þlm
evaporation systems to handle difficult
streams and their ßexibility make them
well-suited to this application.
Typical applications for puriÞcation
and recovery include:
n Recycling solvents from paints,
greases, oils and resins;
n Recovery of organic products from
tars and residues;
n Recovery of acetic acid from waste
residue streams;
n Vacuum distillation and puriÞcation
of used motor oils;
n Distillation and recovery of pure
glycerine from crude streams;
n Volume reduction of inorganic salt
ditions in the process
zone are important for
highly reactive products.
Agitated thin-Þlm evaporators
have a wide
processing ßexibility,
and a single system can
often be designed to
process different
products under varied
operating conditions.
Agitated thin-Þlm
technology is a good
choice for processes or
products containing
vaporizable or partly
vaporizable components
that must be removed
to improve quality,
yield/recovery, operating
economy or environmental
containment.
Sensitive organic
chemicals
Agitated thin-Þlm
evaporation systems are
widely used in the
distillation of highboiling
and temperaturesensitive
organics. The
short residence time and
the ability to operate at
low internal pressure
and without static head
(reducing boiling points)
results in products of
Fig. 2. Vertical agitated thin-film evaporation.
excellent quality and high yields.
When stripping an organic volatile from
a fluid, a bottoms with minimum volatile
content can be obtained. This is accomplished
by a high mass transfer rate in the
diffusion of volatiles from the thin agitated
Þlm. Many such organic materials are hard
to handle because of their high boiling
points, high melting points, tendency to
foul heat transfer surfaces and the potential
for degradation when exposed to heat.
Typical applications for this process
include:
n PuriÞcation of chlorinated hydrocarbons,
monomers and other chemical intermediates;
n Purification and separation of
components in petrochemicals and in
natural oils;
n Purification and separation of fatty
Agitated thin-Þlm evaporation
systems are widely
used in the distillation of
high-boiling and temperature-
sensitive organics.
EVAPORATION/DISTILLATION/CRYSTALLIZATION
February 1997 CHEMICAL PROCESSING
streams in the nuclear industry;
n Recovery of polymer in plastic-coated
paper recycling.
Devolatilization of viscous products
For many products, viscosity increases
rapidly as concentration rises or polymerization
reactions near completion. This
is an area where mechanically agitated,
transported thin-Þlm processors provide
a signiÞcant advantage.
Specially designed rotors make it possible
to transport materials with viscosities of
up to 15 million cp through the evaporator.
Agitated thin-Þlm evaporators also provide
higher heat and mass transfer efÞciencies
for viscous ßuids than are possible with
other equipment, such as flash pots and
vented extruders.
Typical applications for devolatilization
are:
n Removal of reactants, solvents and
monomers to ppm levels from engineering
and other thermoplastics;
n Removal of monomers and volatile
solvents from acrylic resins;
n Removal of free phenol and water
from phenolic resins;
n Reaction and removal of caprolactam
from Nylon 6;
n Removal of monomers from silicone
polymers;
n Reaction and removal of condensates
from polyesters.
The mechanical and process technologies
for mechanically agitated thin-Þlm
evaporation systems are proven and reliable
and should be considered whenever an
application proves difficult for conventional
tubular evaporators. Frequently a tubular
and agitated thin-film evaporation
combination is the optimum solution.
n To receive more information on agitated
thin-film evaporationÑLCI Corporation,
Charlotte, NC.
LCI Corporation
PO Box 16348
Charlotte NC 28297-8804
Phone 704-394-8341
Fax 704-392-8507
Email info@lcicorp.com
www.lcicorp.com
