United States
               Environmental Protection
               Agency	
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
               Research and Development
EPA/600/SR-92/058   May 1992
EPA       Project  Summary
                Controlling Odorous
                Emissions from  Iron
                Foundries

                Gerhard Gschwandtner and Susan Fairchild
                 The main process sources of odors
               in an iron foundry are  (1) mold and
               core making, (2) casting, and (3) sand
               shakeout. The odors are usually caused
               by chemicals, which may be presenlt
               as binders and other additives to thei
               molding sand, or as breakdown prod-
               ucts when these chemicals are  sub-
               jected to molten  iron  as it is poured
               into molds. There are many binder for-
               mulations;  typical formulations arei
               based on using some form of an oil,,
               urethane, formaldehyde, phenol, or fu
               ran.  Common additives include coal;)
               cereals and starches, clays, and refrac-
               tory  minerals such as silica.  A great
               many possible compounds  can bei
               formed when these chemicals are ex-
               posed to molten iron. Common  parr
               ticulate removal technologies may alsoj
               reduce odors, although the odors are>
               probably caused by vapor-phase com-
               pounds that are not well controlled by
               cyclones and bag filters.  Carbon ad-
               sorption may be effective but might
               also be very expensive. Wet scrubbers
               with special additives in the water may
               be more effective but have drawbacks!
               such as generating a waste water treat-
               ment requirement and the potential for
               corrosion. Another technology report-
               edly used in Europe is biofiltration.
                 This Project Summary was developed
               by EPA's Air and Energy Engineering
               Research Laboratory,  Research Tri-
               angle Park, NC, to announce key  find-
               ings 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 control of industrial odor can be
difficult. The choice of a control method
depends on many technical and economic
considerations. The chemical characteris-
tics of the odorous pollutant, the volume
of emissions to be treated, and the manu-
facturing process are only a few consider-
ations. There are many types of odor con-
trol, including masking, various removal
techniques,  and process modifications.
This report describes several removal tech-
niques including wet chemical scrubbing,
biofiltration, adsorption,  and  new emerg-
ing  techniques.  The adaptation of these
controls to a particular process can be
complicated and requires careful planning.
  Many pollutants have low odor thresh-
olds and require the removal of extremely
small concentrations from large volumes
of air. This is technically difficult and may
require huge amounts of energy, capital
investment, and large control devices de-
pending on the options selected. Further-
more, odor may not be completely con-
trolled, arid some level of odor may per-
sist despite the addition of controls.
  Once the  decision is made to  control
odor, the course of action may be deter-
mined by the availability of water, energy,
and waste water treatment facilities. Most
control  methods employ  water sprays,
tanks,-and mists  to trap water-soluble
chemicals and particulate. In the absence
of sufficient quantities of water, it may be
necessary to consider using other meth-
ods such  as  carbon adsorption or
biofiltration.
                                                                  Printed on Recycled Paper

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Discussion

Sources of Odorous Emissions
in Iron Foundries
   In an earlier report, the U.S. EPA iden-
tified major sources of air toxic pollutant
emissions in iron foundries. Of these pol-
lutants, organic compounds are the most
odorous, although  metals  and dust may
also be sources of odor. The main sources
of organic emissions in iron foundries are
mold and core making operations, casting
operations, and sand shakeout.
  Mold  and core making may be  subdi-
vided according to  resin sand operations,
commonly  referred to as  shell molding,
green sand operations,  and stack  mold-
ing. In general, these processes have the
greatest potential to release odors because
of the relatively high concentrations of or-
ganics in the uncontrolled emissions.
  Most  organic emissions originate from
the casting process when molten metal is
poured into a mold. During this process,
chemical reactions involving various  binder
ingredients are driven by the intense heat
of the molten metal. The resulting gas-
eous  emissions may be the products of
numerous  reactions of  the initial binder
ingredients, the  products  of decomposi-
tion, and the reactions among the prod-
ucts of  decomposition.  In  addition, fine
particulate  matter is released during cast-
ing.  PMt?  emission factors range from
2,500 to 4.2 x 10* mg/Mg of metal poured.
Foundry dust typically contains inorganic
emissions such as nickel, lead, boron, and
chromium,  depending on the composition
of the poured metal and its impurities.
  The uncontrolled removal of castings
from sand molds during the sand shakeout
process releases moisture, dust, resin and
binder fumes, and products of thermal de-
composition. Information on volatile organic
compound  (VOC) emission factors is rare,
but some information is available for par-
ticulate, matter that suggests a wide  range
of PM)0 emissions from 85 x 103 to 9 x 106
mg/Mg of iron castings.
  Most odorous emissions originate from
mold and core making operations and from
casting  operations. These emissions re-
sult from the use of chemical binders and
resin and sand additives.

Odor Thresholds
  The threshold concentration for odor de-
tection and recognition varies from person
to person  and  from compound to com-
pound. Many articles  have been written
on odor evaluations and threshold values.
Odor  detection varies depending on  the
compound  being evaluated  and on  the
presence of other  compounds that may
mask or enhance the odor. Some com-
pounds may be offensive even in low con-
centrations, especially certain sulfur com-
pounds, while others, such as certain es-
ters, may be less objectionable.

Determining Acceptable Levels
of Odors
  Due to the subjective nature of odors, it
is difficult to establish an acceptable level
of exposure, especially when many com-
pounds and emission sources are involved.
Ideally, the concentration of an odorous
compound should be below  the odor
threshold. While emission  controls  help
reduce the odor, some pollutants such as
thiols (mercaptans) require virtual elimina-
tion before they are undetectable.
  Objective evaluation of an odor should
be the first step in controlling it. ft is im-
portant to know which compound or com-
binations  of compounds  is  causing  the
odor. Usually, an independent, third-party
assessment of unwanted odor is  neces-
sary to form an objective conclusion. Both
on-s'rte and community surveys can pro-
vide important information for identifying
sources of the  odor,  establishing condi-
tions that elicit complaints in the affected
community, and confirming odor levels pre-
dicted by source sampling,  analysis, and
atmospheric dispersion estimation tech-
niques.

Selecting a Control Efficiency
  Not all odorous compounds may  be suf-
ficiently controlled with the  same  control
device. For example,  one compound may
require only 99%  control  efficiency while
another may require 99.999% control effi-
ciency to reduce the  concentration below
its odor threshold value. In this case, two
different control devices may be  needed
to solve the odor problem.
  Rather  than attempting to reduce  all
odorous emissions simultaneously, reason-
able available  control technology  should
be applied first to  reduce total emissions,
including particulate  matter  and  organic
compounds. In addition, the dispersion and
dilution of the emissions should be  en-
hanced to the  maximum extent possible.
A comprehensive  approach to controlling
foundry emissions  is  better than control-
ling each odorous pollutant individually.

Selecting the Best Control
Option
  Several methods are available for con-
trolling odor from  iron foundries. Aside
from reducing overall  emissions and good
operating practices, emission control tech-
nologies that are applicable to iron foundry
processes include:
  • Fabric filtration
  • Adsorption (activated charcoal)
  • Wet scrubbers with chemical additives
  • Biofiltration
  • Photocatalytics and oxidization
  There are several basic considerations
when selecting one of these control tech-
niques for an iron foundry. The ideal tech-
nology would be one that does not require
water, energy, or maintenance, costs little,
effectively removes many  different odor-
ous compounds,  and produces no solid or
hazardous  waste.  The ideal technology
would also not interfere with existing pro-
cess operations and conditions.
  Fabric filtration is essential to remove
sand and other fine particulate matter and
should be used first before controlling or-
ganic compounds  by  other means. The
control efficiency of various types of wet
scrubbers can be enhanced by using vari-
ous chemical additives. The ideal additive
is one that creates harmless waste in small
quantities, does not affect process equip-
ment, and does not require special treat-
ment, conditioning, or monitoring.
  Selection of a chemical additive requires
judgment and knowledge about the chemi-
cal reactions with the targeted pollutants.
Many companies can recommend and sup-
ply chemical additives usually in conjunc-
tion with a particular type of scrubber. The
particular  requirements should  be care-
fully analyzed beforehand, and all aspects
of the wet scrubber (including waste dis-
posal,  supply requirements, and system
operation and maintenance requirements)
should be considered.
  Incineration, thermal oxidation, and cata-
lytic oxidation are generally not suitable to
iron foundries because of the  large air
flow rates. Odor masking, a technique
where a stronger pleasant odor  is added
to the exhaust stream, generally has  not
provided consistent and  satisfactory  re-
sults.

Deciding What Is Feasible and
Reasonable
  Many environmental regulations use the
words  "feasible" and "reasonable"  when
describing  control  requirements.  In the
case of odor control, specific requirements
are often unclear and left to interpretation.
Since the ideal  control technology does
not exist,  iron foundry operators wishing
to control odorous emissions must accept
some level of inconvenience or expense.
This report provides basic information that
can be used in comparing and selecting a
control technology.
  Whether a technology is feasible or rea-
sonable depends on the circumstances of
the foundry. For example, shortage of wa-

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ter would eliminate many of the traditional    elude the use  of certain  chemical adcli-    advantages over older, traditional systems
wet  scrubbers  described in  this report.    tives in wet scrubbers.                     and should be considered.  These  new
The  need to reduce maintenance costs,      As technology  changes,  better and    methods have been tried and  proven at
for example, might preclude the use  of    proven systems may become available.    many different industries here and abroad
carbon adsorption, while the lack of on-    Currently,  atomized mist  scrubbers,    and can be adapted to the major sources
site  waste disposal  facilities  might pre-    biofiltration, and photocatalytics offer many    of odor at iron foundries.
                                                                          •&V.S. .GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40253

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   Gerhard Gschwandtner and Susan Fairchild are with E. H. Pechan and Associates,
     Durham, NC 27707.
   Robert a McCrlllls is the EPA Project Officer (see below).
   The complete report, entitled "Controlling Odorous Emissions from Iron Foundries,"
     (OrderNo. PB92-166 925/AS; Cost: $17.00, subject to change) 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:
          Air and Energy Engineering Research Laboratory
          U.S. Environmental Protection Agency
     	Research Triangle Park, NC 27711
 United States
 Environmental Protection
 Agency
Center for Environmental
Research Information
Cincinnati, OH 45268
      BULK RATE
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   PERMIT No. G-35
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Penalty for Private Use $300
EPA/600/SR-92/058

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