United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-96/109
October 1996
&EPA Project Summary
Assessment of Styrene Emission
Controls for FRP/C and Boat
Building Industries
Emery J. Kong, Mark A. Bahner, and Sonji L. Turner
This study evaluated several con-
ventional and novel emission control
technologies that have been used or
could be used to treat styrene emis-
sions from open molding processes in
fiberglass-reinforced plastics/compos-
ites (FRP/C) and fiberglass boat build-
ing facilities. Control costs for these
conventional and novel technologies
were developed and compared for
three hypothetical plant sizes. The re-
sults of this cost analysis indicate that
(1) preconcentration by adsorption fol-
lowed by desorption for recovery or
oxidation appears to reduce the over-
all cost of styrene control, particularly
at the lower styrene concentrations
(less than 100 ppm) typically found at
these facilities, and (2) increasing the
styrene concentration (i.e., lowering
flow rate) of the exhaust streams can
significantly reduce cost per ton of
styrene removed for all technologies
examined, because capital and operat-
ing costs decrease with decreasing ex-
haust flow rate. Therefore, a company
should evaluate methods to increase
concentrations (i.e., reduce flow rates)
of the exhaust stream before consid-
ering any add-on control devices. This
report also presents air flow manage-
ment practices and enclosure concepts
that could be used to create a concen-
trated exhaust stream while maintain-
ing a safe working environment.
This Project Summary was developed
by EPA's National Risk Management
Research Laboratory's Air Pollution
Prevention and Control Division, Re-
search Triangle Park, NC, 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
The fiberglass-reinforced plastics/com-
posites (FRP/C) and fiberglass boat build-
ing industries have many alternatives for
reducing styrene emissions. Styrene emis-
sions can be reduced by (1) using resin
materials and application equipment that
generate lower styrene emissions, (2) im-
proving operator techniques to reduce
overspray, (3) changing from open- to
closed-molding processes, and (4) using
add-on emission control devices. The
amount of reduction achieved by these
alternatives, taken separately or in vari-
ous combinations, can vary widely.
Lacking the regulatory mandates, add-
on pollution control systems are not often
used to reduce styrene emissions in the
FRP/C and boat building industries. Low
concentrations and high airflow rates also
have made conventional emission con-
trols very expensive and, in some cases,
less efficient in destroying the emissions.
The FRP/C and boat building industries
need information on the applicabilities and
costs of conventional and emerging add-
on pollution control technologies so they
can make informed decisions about the
use of controls to reduce their emissions.
To meet this need, the cost and perfor-
mance of several conventional and emerg-
ing add-on pollution control technologies
and air flow management practices poten-
tially applicable to these industries were
evaluated.
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This report summarizes the results of
literature reviews and control cost analy-
ses. The report includes background in-
formation about the industries and the
characteristics of their emissions, assess-
ment of various pollution control technolo-
gies, analyses of control costs, and an
evaluation of air flow management prac-
tices that may reduce worker exposure
and control costs. The appendixes include
costing procedures for various pollution
control technologies and a spreadsheet
cost model for these control technologies.
This report provides preliminary techni-
cal and cost information to FRP/C and
boat building companies for their use in
selecting add-on pollution control technolo-
gies. Companies should identify those
technologies that fit their production pro-
cesses and contact the vendors of those
technologies for more accurate informa-
tion on equipment costs.
Styrene Emission Control
Technologies
This report presents a technical evalua-
tion of conventional, novel, and emerging
add-on pollution control technologies that
have been used or could be used to re-
duce styrene emissions from FRP/C and
boat building facilities.
Conventional Technologies
Conventional technologies include com-
bustion (i.e., thermal and catalytic oxida-
tion), adsorption, and condensation, which
have traditionally been used to treat vola-
tile organic compound (VOC) emissions.
The effectiveness and the advantages/dis-
advantages of their application are pre-
sented for each conventional technology.
Novel Technologies
Novel technologies are those that have
been applied in the last decade to treat
low-concentration emissions. These tech-
nologies have been installed in European
and Japanese FRP/C or boat building fa-
cilities to treat styrene emissions or in the
U.S. to treat paint booth emissions or or-
ganic vapors from soil remediation. These
novel technologies include (1) hybrid sys-
tems that preconcentrate VOCs by ad-
sorption, then desorb VOCs for recovery
by condensation or for destruction by ther-
mal/catalytic oxidation; (2) a biofiltration
process that utilizes biodegradation to re-
move VOC emissions; and (3) a process
that applies ultraviolet (UV) light and ozone
in a wet system to disintegrate VOCs into
carbon dioxide and water, and removes
smaller organics in the exhaust gas by
adsorption.
Five preconcentration/recovery/oxidation
hybrid systems are evaluated: (1) MIAB
system, (2) Thermatrix PADRE system,
(3) Polyad system, (4) rotary concentrator
system by Durr Industries, and (5) fluid-
ized-bed preconcentration system by
REECO/Environmental C&C.
Emerging Technologies
Emerging technologies are those that
are just beginning to be explored via field
applications and pilot testing after under-
going several years of laboratory evalua-
tions. Two emerging technologies are
evaluated: a membrane vapor recovery
technology and a photocatalytic oxidation
process that treat VOCs in the air at am-
bient temperatures in the presence of UV
light and a catalyst.
Control Cost Analyses
Total annualized costs for all control
technologies were calculated using the
general procedures outlined in the EPA
Office of Air Quality Planning and Stan-
dards (OAQPS) Control Cost Manual and
cost data collected from equipment ven-
dors and other sources. A computer
spreadsheet model was developed to per-
form cost calculations. Based on the quan-
tity of styrene emitted and the control effi-
ciencies of these technologies, the costs
per ton of styrene removed were calcu-
lated from annualized costs. Control costs
for all control technologies were analyzed
for three hypothetical plants, treating 20,
100, and 400 tons* per year of styrene
emissions.
The cost analyses show that (1) cost-
per-ton of styrene removed decreases as
the inlet concentration increases (i.e., ex-
haust flow rate decreases), and (2)
preconcentration technologies appear to
reduce the cost of styrene control, par-
ticularly at lower styrene inlet concentra-
tions. The results of the cost analyses
suggest that reducing the inlet flow rates
to control devices is a good approach to
making any control technology more eco-
nomically feasible.
Air Flow Management Practices
Current ventilation systems in FRP/C
and boat building facilities are primarily
designed to provide an environment that
is safe for workers and produces good
product quality. General ventilation, also
called dilution ventilation, supplies an
ample amount of makeup air to dilute the
(*) For readers more familiar with metric units, 1 ton =
0.907 tonne.
contaminants to an acceptable air quality
level in the workplace. This common prac-
tice produces high-volume, low-concen-
tration exhaust streams. The cost analy-
sis indicates that these high-volume, low-
concentration exhaust streams make emis-
sion control systems more expensive. It is
also more expensive to heat or cool large
volumes of makeup air.
Proper air flow management would cap-
ture emissions at the point of generation
and prevent mixing contaminated air with
clean air. Thus, proper air flow manage-
ment can maintain a safe environment for
operators, while significantly decreasing
exhaust flow rates. These reduced ex-
haust flow rates (increased concentrations)
can reduce control costs.
This report presents several air flow
management practices and concepts that
could be applied to minimize air flow vol-
umes at FRP/C and boat building facili-
ties. These practices and concepts include:
local air flow management, spray booth
modifications, and enclosures.
Local Air Flow Management
Local air flow management involves cap-
turing air pollutants directly at the emis-
sion source; therefore, the amount of air
to be ventilated is minimized. In an open
space, this can be done by blowing
makeup air toward the emission source
and capturing the emission with an ex-
haust hood at the other end (a push/pull
ventilation system). Capture efficiency is
generally better for a push/pull system
than for an exhaust hood alone.
Spray Booth Modifications
Spray booths are commonly used in the
FRP/C and boat building industries, espe-
cially for gel coat and resin sprayup op-
erations, and for parts (i.e., items being
manufactured) that can fit into a spray
booth. Using a spray booth can prevent
cross-contamination created by general
ventilation, because styrene emissions are
captured and exhausted directly.
In a typical spray booth, a mold is
placed in the center of the booth. Air is
drawn into the front opening of the booth,
travels past the mold, and exits through a
filter bank at the rear of the booth. Dry
filter media are used to capture overspray,
and the media are replaced frequently to
protect the duct work and exhaust sys-
tem. The captured emissions are vented
to the atmosphere or to an emission con-
trol device. Several modifications to spray
booth design could increase pollutant con-
centration and decrease exhaust flow, thus
making downstream emission controls
more cost-effective.
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Recirculation
The concept of recirculation had its ori-
gin in the spray painting industry, as a
means of lowering exhaust flow rates (and
therefore treatment costs) in paint spray
booths. Recirculation involves redirecting
a portion of the spray booth exhaust
stream back into the spray booth. The
recirculation stream may be reintroduced
at any location in the spray booth (e.g.,
near the inlet face, or at the center of the
booth). For a spray booth with recircula-
tion alone, the increase in inlet concen-
tration to a control device is directly re-
lated to the amount of recirculation. The
disadvantage of recirculation is the po-
tential for increased worker exposure, un-
less fresh makeup air is provided to the
operator through a duct, or the operator
wears a respirator.
Split-Flow Design
In a typical (horizontal-flow) spray booth,
the part being sprayed does not extend to
the full height of the spray booth. There-
fore, most of the spraying and post-spray-
ing emissions occur near the bottom of
the booth. A split-flow painting spray booth
design takes advantage of this fact. In this
design, higher-concentration exhaust air
from the bottom of the booth is directed to
an emission control device, while
lower-concentration air from the top of the
booth is recirculated. The main advantage
of a split-flow design is that it produces an
increase in VOC concentrations going to
a control device; however, the area to be
split must be specific to each spray booth,
based on the actual spraying pattern and
concentrations at various locations.
Other Design Modifications
In a typical spray booth in an FRP/C
facility, a mold is placed in the center of
the booth. The arrangement of the mold
within the booth is such that higher con-
centrations are drawn through the center
of the filter bank, rather than through the
top or sides of the filter bank. A spray
booth can be modified to take advantage
of this spatial difference in concentrations.
Modification would involve constructing a
smaller, centrally located exhaust device.
The higher-concentration exhaust collected
by this device would be directed to an
emission control device. The lower-con-
centration exhaust could be vented to at-
mosphere or recirculated in the spray
booth.
In addition to spatial differences in emis-
sions within spray booths, temporal (time-
related) variations in emissions can be
used to increase concentrations to the
emission control device. The centrally lo-
cated exhaust device could be activated
to capture high-concentration exhaust dur-
ing the spraying period. The main exhaust
of the spray booth would be operating
continuously during the nonspraying or
low-concentration period. Periods of high
emissions could be determined by con-
centration measurements, or high emis-
sions could be assumed to occur during
any period of spraying (i.e., the small ex-
haust unit is activated by the spray-gun
trigger). Fresh makeup air can be sup-
plied to areas occupied by the operator.
Enclosures
Enclosures provide a physical barrier
between the emissions and the surround-
ing environment, and they can reduce or
eliminate the dispersion of styrene vapors
from a production process. However, the
styrene concentration within the enclosure
must be kept below 2,500 ppm (25% of
the lower explosive limit) by ventilation. If
an enclosure is ventilated, the exhaust
concentration is inversely related to the
exhaust flow rate. Therefore, an enclo-
sure can be used to confine emissions or
to create a low-flow-rate, high-concentra-
tion exhaust stream for destruction.
Conclusions and
Recommendations
Exhaust streams from open molding pro-
cesses in the FRP/C and boat building
facilities are generally at low styrene con-
centrations and high air flow rates. Gen-
eral (dilution) ventilation is usually used to
ensure that worker exposure is less than
that allowed by Occupational Safety and
Health Administration (OSHA) standards.
Treating this low-concentration, high-air-
flow stream is more expensive than treat-
ing a low flow rate at higher concentra-
tion. Due to the general practice of dilu-
tion ventilation and the current lack of
specific regulations that require add-on
emission controls, these control devices
are not commonly used in the FRP/C and
boat building industries.
Of the limited number of add-on control
devices used in the FRP/C facilities in the
U.S., thermal and catalytic oxidation are
the most common. Costs of alternative
technologies have been compared, includ-
ing biofiltration and preconcentration fol-
lowed by recovery or oxidation, with
straight thermal and catalytic oxidation.
Preconcentration technologies followed by
recovery or oxidation appear to reduce
the cost of styrene control, particularly at
the lower styrene concentrations (less than
100 ppm) typically found at FRP/C and
boat building facilities. However, this ap-
parent reduction in cost is significantly af-
fected by the equipment cost assump-
tions used in this cost analysis. Therefore,
FRP/C companies should compare the
costs of competing technologies on a case-
by-case basis.
The capital and operating costs of all
emission control devices are strongly re-
lated to the flow rate of the incoming
stream. Cost analyses indicate that, for all
control devices examined, cost per ton of
styrene removed decreases as styrene
inlet concentration increases (i.e., as the
air flow rate decreases). Therefore, it is
probably economical to concentrate the
exhaust air stream, using proper air flow
management practices or enclosures, be-
fore application of add-on emission con-
trol devices.
Proper air flow management techniques,
which capture emissions at the source, or
enclosures, which prevent plant air from
diluting styrene emissions, can reduce the
exhaust flow rate and increase styrene
concentration in the exhaust streams from
FRP/C and boat building facilities. These
approaches can maintain a safe working
environment and produce a high-concen-
tration exhaust stream that makes add-on
emission control devices less expensive.
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Emery J. Kong, Mark A. Bahner, and Sonji L Turner are with Research Triangle Institute,
Research Triangle Park, NC 27709.
Norman Kaplan is the Project Officer (see below)
The complete report, entitled "Assessment ofStyrene Emission Controls for FRP/C and
Boat Building Industries,"(Order No. PB97-104640; Cost: $31.00, subjecttochange)will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
National Risk Management Research Laboratory
Air Pollution Prevention and Control Division
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-96/109
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