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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