United States
Environmental Protection
Agency
Industrial Environmental Research -^
Laboratory x W s
Research Triangle Park NC 27711 '/?i*
Research and Development
EPA-600/S2-83-044 Aug. 1983
&EPA Project Summary
Demonstration of the Use of
Charged Fog in Controlling
Fugitive Dust from Large-Scale
Industrial Sources
Edward T. Brookman and Kevin J. Kelley
Although charged fogging has been
widely applied to industrial sources of
fugitive dust little data are available
regarding fogger control effectiveness
on particulate matter. To obtain such
data, a full-scale demonstration of a
charged fogger was conducted on
several industrial fugitive emission
sources. The sources tested included a
primary rock crushing operation, a
secondary rock crushing operation, a
molten iron spout hole at a blast furnace
cast house, and a coke screening opera-
tion. The fogger evaluated was the
"Fogger IV" manufactured by the Ritten
Corporation. The report presents and
discusses the results of these four
source tests.
The report also presents and dis-
cusses the results of three other source
tests. The same charged foggers were
used, along with a charged fogger de-
veloped by AeroVironment Inc., Pasa-
dena, CA. The sources for field testing
the two foggers were a stainless steel
slab torch cutting operation, a conveyor
transfer operation at a recycle (sinter)
plant and a limestone crusher/con-
veyor operation.
In general, the tests showed that (1)
the control of emissions by the two
foggers are generally comparable, (2)
fogger efficiency depends on the posi-
tions of the foggers in relation to the
source, and (3) charging a water spray
appears to increase its effectiveness in
controlling particulate matter emis-
sions by up to 40 percent
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory, Research 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
A spray of fine water droplets is a well
known means of airborne dust removal.
Various types of scrubbers rely on water
droplets to remove entrained particles
from streams, and direct water sprays are
often used in mining and material handling
for dust suppressioa Unfortunately, water
sprays are not very effective in removing
dust from ambient air.
One way to improve the effectiveness of
water sprays is to apply an electrical charge
to the spray that is opposite in polarity to
the charge on the dust to be suppressed
Most industrial pollutants and naturally
occurring fugitive dusts acquire an electro-
static charge as they are dispersed into the
air. Exposing this charged airborne ma-
terial to an oppositely charged water spray
enhances contact between the particulate
matter and the water droplets. After
contact is made, the wetted particulate
matter agglomerates rapidly and falls out
of the atmosphere.
The effectiveness of these charged sprays
can be improved by atomizing the water
droplets, producing a fog. The fineness of
the fog droplets enhances the charge-
carrying capability of the spray. Previous
work has shown greatest effectiveness
when water droplet size is similar to that of
the dust particles to be controlled. There is
also the benefit of reduced operating costs
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since less water is required when fog is
used.
A device that produces such a fine spray
and applies an electrostatic charge to it is
known as a charged fogger. The charged
fogger is intended primarily for fugitive
dust sources that cannot reasonably be
controlled conventionally, such as by hood-
ing. Such sources include material-handl-
ing (transfer points and conveyors), truck
and railroad car loading and unloading,
front-end loaders, ship loading, grain silos,
and mining.
Although charged fog has been widely
applied to industrial sources of fugitive
dust, little quantitative data are available
on fogger control effectiveness on particu-
late matter. To obtain such data, a full-
scale demonstration of a charged fogger
was conducted on several appropriate
industrial fugitive emission sources. Par-
ticular interest was in testing the largest
fogger, designated "Fogger IV," manu-
factured by the Ritten Corporation of Ard-
more, PA, on several sources in the iron
and steel industry and the sand and gravel
industry.
After many visits to iron and steel plants
and sand and gravel companies, several
sources were selected for Phase I field-
testing the charged fogger:
• Sand and gravel company: primary
rock crushing.
• Sand and gravel company: secondary
rock crushing.
• Iron and steel plant: molten iron
spout hole at a cast house.
• Iron and steel plant: coke screening.
Comcidentally with the EPA fogger test
program, Armco, Inc., agreed with EPA
Region 5 to set aside funds to demonstrate
the use of electrostatically charged fog on
several fugitive dust sources at Armco's
plants.
To provide Armco with state-of-the-art
information on charged fog technology,
two types of charged foggers were to be
field tested under Armco's agreement: the
Ritten Corporation's Fogger IV, and a fog-
ger developed by AeroVironment, Inc. (AV)
of Pasadena, CA. Compared with the Ritten
fogger, the AV fogger uses a different
method of charging the fog and a different
method of fog dispersal. Testing both
foggers side- by-side would give a basis for
comparison for future decisions to select a
charged fogger.
The sources selected for Phase-11 field-
testing the two foggers were at Armco
plants and included:
• A stainless steel slab torch cutting
operation.
• A conveyor transfer operation at a
recycle plant.
• A limestone crusher/conveyor trans-
fer operation.
The report gives results of both Phase I
and 11 charged fogger tests.
Summary and Conclusions
Results of the seven field tests led to
several conclusions regarding the perform-
ance, operation, and field installation of
the foggers tested.
Performance
• Charging a water spray appears to
increase its effectiveness in controll-
ing particulate matter emissions by
up to 40 percent
• The two Ritten foggers, operating at
a combined water flow rate of approx-
imately 160 l/hr, were capable of
60 percent effectiveness in controlling
particulate matter emissions. For
control efficiencies greater than 90
percent, water flow rates of 300 -
400 l/hr would most likely be re-
quired for the sources tested.
• The Ritten and AeroVironment charg-
ed foggers were essentially compar-
able in terms of baseline emissions
reduction and increase in effectiveness
due to charging.
• The foggers tested did not visually
improve plume opacity because
• • The fog itself has an opacity
associated with it
• • The fogger water flow rates
were insufficient to completely
control the quantity of emissions
generated.
• • Several of the sources were
hot causing the fog to turn to
steam and thus add to the visible
plume.
Operation
• Both foggers are extremely difficult
to operate in subfreezing ambient
temperatures. This problem might
be alleviated either by adding glycerin
to the water or using steam instead
of water. Both solutions have been
successfully demonstrated in the
laboratory.
• Both foggers, as designed, are not
rugged enough to withstand the
harsh environments often asso-
ciated with industrial dust sources
(e.g., molten metal, heavy dust
plumes, caustic materials).
• The nose cone and control panel of
the Ritten fogger should be rede-
signed to allow for easier access to
the inner workings. As designed,
Fogger IV is extremely difficult to
work on in the field.
Field Installation
• The foggers should be run with as
low a fan speed as possible to avoid
dust reentrainment The fan speed
should be no greater than that neces-
sary to carry the fog to the source.
• Foggers should be placed above a
dust source and aimed down upon it
This should help to isolate the ag-
glomerated particles at the source.
In general, both foggers, as designed,
show promise, but have design and opera-
tional problems. The problems include
dust reentrainment from the fan-forced air
used to carry the fog to the source, freeze-
ups in cold weather, frequent shorting of
electronics, lack of mobility, and water
flow limitations. Both foggers were proto-
types, and the tests focused primarily on
evaluating the two different concepts.
However, neither fogger is ready for use in
industry and neither performed much bet-
ter than the other.
Future development of the Ritten foggers
is no longer with the Ritten Corporation,
which terminated their business after the
study began. Ritten foggers are now being
manufactured and sold by the Sonic De-
velopment Corporation. Sonic is incorpo-
rating their sonic dry-fog nozzles into the
Ritten induction ring foggers. To date.
Sonic is developing a prototype Fogger I
(the original, small Ritten fogger) using a
1 5 l/hr (4 gph) water flow nozzle that
produces droplets in the 1 - 40 jum range.
They are also planning a Fogger IV with a
Sonic nozzle. Some of the inherent prob-
lems of the Ritten foggers have been
addressed by Sonic personnel. They have
eliminated waterlines to the gauges and
heat-traced those leading to the nozzles,
which should eliminate freeze-ups. They
are also using a nozzle that produces finer
droplets which should increase the charge/
droplet ratio and thus capture efficiency.
Sonic has also put the controls in a separate
industrial-strength box to reduce mainte-
nance. The product line offered should be
a significant improvement over the proto-
types tested during the study.
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Edward T. Brookman and Kevin J. Kelley are with TRC Environmental Consultants,
Inc.. East Hartford, CT06108.
Robert C. McCrillis is the EPA Project Officer (see below).
The complete report, entitled "Demonstration of the Use of Charged Fog in
Controlling Fugitive Dust from Large-Scale Industrial Sources," (Order No. PB
83-2 J 7 828; Cost: $14.50, 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:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
ft US GOVERNMENT PRINTING OFFICE 1983-659-017/7149
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