United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-84-033 May 1984
Project Summary
Hydrocarbon Solvent Recovery
in the Presence of Resin
Contaminants
Jim L Turpin
A system was developed to recover
acetone from an air stream in which
there were suspended epoxy resin
particles. This recovery problem is
encountered in the manufacture of fiber
glass reinforced plastic pipe. It is repre-
sentative of many other industrial situa-
tions that require the recovery of hydro-
carbon solvents from a gaseous stream
containing resin particles in order to
eliminate atmospheric pollution.
The system developed was' a three-
state low temperature condensation
process preceded by a cascade
impactor. A scale model of the system
was designed and constructed. It was
tested in the laboratory and on a split
stream of an actual plant process.
Roughly 95 percent of the resin
particles were removed in the impactor.
The first stage condenser operated at
42°F and removed the residual resin
particles and roughly 80 percent of the
water brought in with the ambient air.
The second stage operated at -31 °F and
achieved residual water removal.
Acetone of 99 percent purity was
recovered in the third stage operating at
-85°F.
A full-scale system was designed to
process 3800 cfm of air containing
0.92 (vol) percent acetone and 1.25 x
105 Ib/ft3 of resin particles. The fixed
capital investment for this system was
estimated to be $758,000.
The developed impactor-condenser
system is a technically feasible process.
It may be considered as a possible
alternative in any solvent recovery
application. An economic evaluation
will be required for each potential
application, with the final decision to
utilize the process being based on the
economics of the specific recovery
problem.
The full report was submitted by the
University of Arkansas to fulfill Grant
No. CR807577-01-0 under the joint
sponsorship of the U.S. Environmental
Protection Agency and A. O. Smith-
Inland. Inc. It covers the period August
15, 1980 to September 15,1982, and
work was completed September 15,
1982.
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory. Cincinnati, OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Hydrocarbon solvents are utilized in
many industrial processing schemes
which require recovery of these solvents
from a gaseous stream in order to elimi-
nate atmospheric pollution. Much is
known about solvent recovery, and it is
practiced widely in the chemical indus-
tries. However, recovery solutions are
complicated in instances where certain
contaminants are present in the
discharge stream.
One process for manufacturing rein-
forced plastic pipe utilizes acetone as a
solvent for the resin. The gaseous
discharge from the process is an acetone-
contaminated air stream, which also
contains resin particles and certain other
chemical decomposition products. These
resin particles plug conventional
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recovery equipment such as adsorption
beds and filters. Other examples of this
type of recovery problem are found in the
plastics industry, especially in the
production and utilization of epoxy resins.
It is concluded from available produc-
tion figures that the problem of
hydrocarbon recovery in the presence of
resin contaminants is potentially very
large. Extensive consultation with
leading manufacturers of recovery and
cleanup equipment reveals that
commercially available off-the-shelf
systems are not satisfactory. Thus, the
objectives of this research project were:
(1) to develop a system which will
economically recover a solvent
from a gaseous stream containing
suspended contaminants such
resins,
(2) to construct and test a scale model
of the recovery system, and
(3) to design, specify equipment, and
estimate installed costs for a full-
scale recovery system.
The A. O. Smith-Inland (AOS-I) Inc.
manufactures fiber glass reinforced
plastic pipe at their Little Rock, Arkansas,
plant. In the AOS-I process, glass fibers
are pulled through a vat of epoxy resin
and acetone solvent where they are
impregnated with the resin. The resin-
coated fibers travel from the vat over hot
drums.
A continuous strip of fiber glass rein-
forced plastic (which is later processed
into plastic pipe) is formed on the drums.
The solvent, acetone, is vaporized from
the hot drums, picked up by a blower-
induced air stream passing up over the
drums, moved into the hood covering the
tape machine, and exhausted from the
process. The violent vaporization of the
acetone on the hot drum surface erupts
resin particles into the air stream, where
they are captured and ultimately
transported into the exhaust ductwork.
Ambient water vapor enters with the air
stream.
AOS-I had previously installed an
acetone recovery system which included
a water scrubber, parallel carbon
adsorption beds, and a distillation
column. This unit became permanently
inoperative after only a very short time.
Due to the low efficiency of the water
scrubber, resin carry-over plugged the
adsorption beds and corroded the
distillation unit. Scrubber screens and
spray nozzles, were also plugged with
epoxy.
Because this acetone-resin system is
representative and because difficulty was
encountered in dealing with it, the
system was studied in this project. The
acetone concentration in the air stream is
well below the lower explosive limit, and
it is expected that other such processes
exhibit air stream concentrations com-
parable to these. It is likely that these air
streams are discharged directly to the
atmosphere by most, if not all, of the
industry.
Methodology for Acetone
Recovery
Several alternatives were considered,
including incineration, water spray
scrubbers, bag and panel filters, and
molecular sieves. It was concluded that
the optimum methodology for acetone
recovery would involve the use of a
cascade impactor to remove the bulk of
the resin particle contaminants, followed
by a staged condenser system to recover
high purity acetone.
A system using three condenser
stages was conceived. The first stage
would operate with a water pool of 42-
50°F to remove roughly 80 percent of the
water plus the residual resin particles
escaping the impactor. The second stage
would operate with a glycol-water
mixture at -31 °F to remove essentially all
of the remaining water. The third stage
would operate with a liquid acetone pool
at -85°F to remove up to 90 percent of the
acetone at greater than 98 percent purity.
A scale model impactor and condenser
system was designed and constructed.
The design basis for the model was 90
cfm air flow. The impactor was a flat-
plate, cascade type, with provision for
variation of the number of plates, the
spacing between plates, the plate-to-
bottom clearance, and the slot dimen-
sions of the plate.
A55-gailonbarrelwitha removable top
was used for each of the three stages. The
process air stream from the impactor was
sparged into the bottom of stage one and
then passed overhead and sparged into
the bottom of stages two and three in
order.
The model was tested utilizing a
simulated process stream. This was
followed by extensive experimental test-
ing on a split-stream of the main process
stream at the Little Rock, Arkansas, plant
of A. O. Smith-Inland.
Results
For the impactor, resin removal effi-
ciencies of close to 95 percent were
common. Impactor pressure drops were m
approximately three inches of water. ^
Drainage of the resin from the impactor
was good, and extended periods of
operation could be achieved without
plugging.
A linear velocity of 2000 ft/min in the
baffle slots appeared to be a feasible
compromise value as the design basis for
. the full-scale impactor. Lower velocities
reduce the collection efficiency, whereas
pressure drop increases as the velocity
increases.
For the model condenser system,
stable operation with pool temperature
near the desired values was achieved.
The experimental program demonstrated
that low temperature condensation is a
technically viable process for recovery of
acetone. The required heat transfer,
mass transfer, and component separa-
tion can be achieved in three stages.
Several different types of equipment
can be used to achieve the three-stage
recovery. The required heat and mass
transfer can occur in liquid baths of the
sort that were utilized in this experiment-
al program, in counter-current flow
packed beds, or in finned-tube heat
exchangers. Calculations were made for
each in order to compare the three -
processes. U
The conclusions drawn from 1hese ^
preliminary calculations are that either
packed columns or finned exchangers
would be satisfactory for stages two and
three, with the decision to be based on
the economics of the two systems. Stage
one would require a packed bed with a
few inches of liquid pool in the bottom for
removal of the residual resin particles. A
finned exchanger would not be
acceptable for stage one because of its
susceptibility to plugging by the resin.
Several changes were evaluated in the
processing sequence in order to get
better heat integration. The finalized
process flow sheet, including a material
and energy balance summary, is included
in Figure 1.
The process flow sheet and process
description were submitted to several
companies for a price quotation on the
equipment, From these quotes, it was
estimated that the total installed cost of
the project would be $758,000.
Conclusions
The three-stage low temperature con-
densation process may be considered as
a possible alternative in any solvent
recovery application. Stage temperatures ^
and other operating parameters are fixed ^1
by the particular system involved, by the
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QT-I = -678000 Btu/hr QC.2A = -285330 Btu/hr Qc-2B = -139560 Btu/hr
, = -311280 Btu/hr
QHX-I = 285330 Btu/hr
Cascade
Refrigeration
Unit
ToAtm
Dia. Conduit
Qconduit = -91500 Btu/hr
v
Resin Waste
Basis: 3810 CMF Air Flow at 128°F Ambient - 100°F, 85°F D.P.
To Acetone
Storage
Stream
8
M N
Air, Ib/hr
Acetone, Ib/hr
Water, Ib/hr
Restn. Ib/hr
Temperature, °F
15400
310
404
2 SB
128
154OO
310
404
0 15
128
270
15400
310
404
105
3760
1 19448
43
3760
119130
43
10
318
0 15
43
3750
119130
38
15400
300
86
42
154OO
290
12
0
10
74
0
15400
281
3
-25
9
9
-25
15400
21
Trace
-85
260
3
-85
15400
21
Trace
-16
Figure 1. Process flow sheet for Acetone Recovery Project.
specifications on the final effluent, and by
the specifications on the recovered
component. The process would be
adapted to meet these specifications and
the technical feasibility affirmed.
Technical feasibility can probably be
attained for most recovery problems by
proper selection of operating parameters.
Material and energy balances would
then be completed, equipment selected
and sized, and the economics
determined. The final decision for any
potential application would be made at
that point.
Jim L Turpin is with the University of Arkansas, Fayetteville, AR 72701.
Mark J. Stutsmart is the EPA Project Officer (see below).
The complete report, entitled "Hydrocarbon Solvent Recovery in the Presence of
Resin Contaminants." (Order No. PB 84-148 170; Cost: $8.50, subject to
change) will be available only from:
National Technical Information Service
528S Port Royal Road
Springfield, v'A 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
U S. GOVERNMENT PRINTING OFFICE, 1984 — 759-015/7698
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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