CD A U.S. Environmental Protection Agency Industrial Environmental Research EPA-600/7-77-1 31
Ci /\ Office of Research and Development Laboratory «/*^-»%
Research Triangle Park, North Carolina 27711 November 1977
USE OF ELECTROSTATICALLY
CHARGED FOG FOR CONTROL OF
FUGITIVE DUST EMISSIONS
Interagency
Energy-Environment
Research and Development
Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield. Virginia 22161.
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EPA-600/7-77-131
November 1977
USE OF ELECTROSTATICALLY
CHARGED FOG FOR CONTROL OF
FUGITIVE DUST EMISSIONS
by
Stuart A. Hoenig
University of Arizona
Department of Electrical Engineering
Tucson, Arizona 85721
Grant No. R805228
Program Element No. EHE623
EPA Project Officer: Dennis C. Drehmel
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, N.C. 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, D.C. 20460
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THE USE OF ELECTROSTATICALLY CHARGED FOG FOR CONTROL
OF DUST FROM OPEN SOURCES
First Quarterly Report
For the Period
1 June 1977 - 31 August 1977
For
ENVIRONMENTAL PROTECTION AGENCY
Research Triangle Park
North Carolina 27711
Grant No. R805228010
Stuart A. Hoenig
Principal Investigator
University of Arizona
Tucson, Arizona
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UNIVERSITY OF ARIZONA EXPERIENCE IN THE CONTROL OF DUST,
FUME AND SMOKE BY MEANS OF ELECTROSTATICALLY
CHARGED WATER FOG
by
Stuart A. Hoenig, Professor
Department of Electrical Engineering
The University of Arizona
Tucson, Arizona 85721
Acknowledgements:
Many organizations and individuals contributed to this work;
University of Arizona laboratory personnel included Mr. Werner V.
Alchenberger, Mr. Joseph B. Bidwell, Mr. and Mrs. Douglas K. Darlington,
Dr. Charles F. Russ, Mr. Christian W. Savitz, Mr. Steven W. Schroder and
Mr. Carl R. Tornquist. Federal agencies, corporations and industrial
organizations included the American Foundrymen's Society, the Ransburg
Corporation, the ARO Corporation, the National Aeronautics and Space
Administration, the Environmental Protection Agency, and the National
Institute of Occupational Safety and Health.
Notice: Much of the data given in this paper was reported at
the 1976-1977 meetings of the American Industrial Hygiene Association.
More recent results have been added as the data became available.
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Disclaimer Statement
This report has been reviewed by Dr. Stuart A. Hoenig, and the
Environmental Protection Agency (EPA), and has been approved for publica-
tion. Approval does not signify the views and policies of the Environ-
mental Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
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TABLE OF CONTENTS
Page
LIST OF ILLUSTRATIONS v
SUMMARY viii
CONCLUSIONS ix
RECOMMENDATIONS . x
I. INTRODUCTION 1
II. EXPERIMENTAL STUDIES 2
A. Generation of Charged Fog 4
B. Dust Tunnel Studies 6
C. Effects of Reduced Water Flow and Chemical Additives ... 9
D. Studies of Coal Particulates and Coal Tar Volatiles .... 11
E. Control of Dust From Hand Grinders/ Chippers and Sanders . 15
III. INDUSTRIAL TESTING 16
A. Cement Plant "A" 17
B. Copper Company "A" 17
C. Steel Casting Company "A" 18
D. Steel Company "B" 19
IV. HUMIDITY INCREASE DUE TO FOGGING 19
REFERENCES 22
iv
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List of 11 lustrations
1. Dust Generator and Impaction Sampler
2. Dust Tunnel System
3. Modified Impaction Sampler
4. Charge versus Particle Size (slate)
5. Charge versus Particle Size (granite)
6. Charge versus Particle Size (clay)
7. Charge versus Particle Size (trap rock)
8. Charge versus Particle Size (magnetite)
9. Charge versus Particle Size (foundry dust)
10. Charge versus Particle Size (shale)
11. Charge versus Particle Size (fly ash)
12. Charge versus Particle Size (copper concentrate)
13. Charge versus Particle Size (cement quarry material)
14. Charge versus Particle Size (cement clinker)
15. Charge versus Particle Size (silica sand)
16. Charge Decay versus Time and Particle Size (silica sand)
17. Dust Density versus Size, with and without Fogging (foundry dust)
18. Dust Density versus Size, with and without Fogging (foundry dust)
19. Dust Density versus size, with and without Fogging (foundry dust)
20. Dust Density versus Size, with and without Fogging (silica sand)
21. Dust Density versus Size, with and without Fogging (silica flour)
22. Dust Density with and without Fogging (magnesium oxide)
23. Dust Density versus Size, with and without Fogging (silicon carbide)
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VI
24. Dust Density versus Size, with and without Fogging (nickel mine
precipitator dust)
25. Dust Density with and without Fogging (bauxite ore)
26. Dust Density with and without Fogging (iron oxide, dolomite,
cement clinker and calcium oxide)
27. Dust Density with and without Fogging (sulfur)
28. Dust Density with and without Fogging (Pb 0 )
29. Dust Density with and without Fogging (rock salt)
30. Dust Density with and without Fogging (burning Carbamite)
31. Dust Density versus Size, with and without Fogging (silicate copper
ore)
32. Dust Density versus Size, with and without Fogging (grey lead/red
lead mixture)
33. Dust Density versus Size, with and without Fogging ttrona orel
34. Dust Reduction with Various Water Flow Rates (foundry dust)
.35. Dust Density versus Size, with and without Fogging (iron ore
crusher dust)
36. Dust Density with and without Fogging (coking coal)
37. Coal Tar Volatile Particulate Density versus Size with and without
Fogging (coking coal)
38. Effect of Charged Fog on Coke Oven Vapors
39. Sulfur Dioxide Level with and without Charged Fog
40. Experimental Apparatus for High Temperature S0_/Fly Ash Studies
41. Sulfur Dioxide Level with and without Charged Fog (381 C)
42. Dust Density versus Size, with and without Fogging (power plant
fly ash)
43. Dust Density versus Size, with and without Fogging (power plant
fly ash at 200 C)
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vii
44. Dust and SO Density versus Size, with and without Fogging (power
plant fly ash)
45. Dust and SO? Density versus Size, with and without Fogging (power
plant fly ash)
46. Dust Density and SO Level with and without Fogging (340 C)
47. Fly Ash, SO_ Agglomerates with and without Charged Fog
48. Dust Control on a Hand Grinder
49. Dust Control on a Hand Held Chipper
50. Test Set-up Cement Plant "A"
51. Test Set-up Cement Plant "A"
52. Dust Density versus Particle Size, with and without Fogging
(Cement Plant "A")
53. Dust Density versus Particle Size, with and without Fogging
(Cement Plant "A")
54. Test Set-up at Copper Company "A"
55. Dust Density with and without Charged Fog (Copper Company "A")
56. Test Set-up and Results (drop box, Copper Company "A")
57. Test Set-up Steel Casting Company "A"
58. Effect of Charged Fog on Total Respirable Dust and Free Silica
59. Dust Density with and without Charged Fog (Cream-Tex)
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Summary
We have demonstrated that most industrial pollutants acquire an
electrostatic charge as they are dispersed into the air. If this charged,
airborne material, is exposed to an oppositely charged water fog there is
enhanced contact between the particulates and the fog droplets. After
contact is made the wetted particulates agglomerate rapidly and fall out
of the atmosphere.
This technique has been tested on a wide variety of industrial
pollutants ranging from silica flour to sulfur dioxide and fly ash. In
general, there has been significant suppression with a minimum of water
fog. The system is therefore suited to control of moving or fugitive
dust sources where the usual duct and baghouse systems are too costly or
ineffective.
Vlll
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Conclusions
We suggest that charged fog has a significant potential for
suppression of dust from open sources. This technique would be most
suitable for control of fugitive dust that cannot be easily contained
or captured by hoods.
The data further suggests that charged fog might be used ahead
of an electrostatic precipitator, scrubber or bag filter to agglomerate
fine particles and increase the efficiency of the dust control system.
Other studies have indicated that charged fog can be used to
suppress fumes, i.e., SO by inducing them to absorb on ambient dust
particles. If this can be further substantiated it may proved an
important weapon in the battle to clean up the environment.
IX
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Recommenda t i ons
We suggest that the present research program on the use of
charged fog to suppress respirable dust be continued and expanded to a
wider range of applications. Topics of particular interest might
include:
1. Development of dust control systems for moving sources, i.e.,
lift trucks and in-plant vehicles;
2. Control systems for open field stackers which are impossible
to hood and result in significant dust fallout;
3. Coke oven facilities that are significant polluters and very
difficult to control by conventional means;
4. Smelters and power plants which produce both dust and SCL.
Here we would expect to induce the SO to absorb on the dust
before agglomeration occurs. Subsequent dust fallout or
collection would remove both pollutants.
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I. Introduction
Beginning in 1973 a number of studies were done at the University
of Arizona to determine if electrostatic charging was a factor in the
levitation of dust on Mars. No Mars dust samples were available and
tests were run on a variety of industrial, and naturally occurring,
particulate materials. The results indicated that in the great major-
ity of cases the respirable materials (below eight micrometers in dia-
meter) were charged and that the finer (one micrometer) particles were
almost always charged negatively.
These results suggested that it might be possible to suppress
industrial pollutants by exposing them to an oppositely charged water
fog. The electrostatic effect would encourage fog-dust contact and
the wetted particulates would be expected to agglomerate and fall out.
There were several potential advantages to a system of this type.
1. The quantity of water involved would be very low thereby
conserving water resources in the arid southwest. Limited
water use would permit the application of fog on water
sensitive materials, i.e., flour, cement, etc.
2. A system of this type would be suitable for control of
moving dust sources, i.e., trucks, sweepers, front loaders,
where conventional methods could not possibly be used.
3. Water fog agglomeration might be used to enhance the opera-
tion of electrostatic precipitators which are known to have
reduced efficiency for fine (one micrometer) particulates.
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If the particulates could be agglomerated ahead of the pre-
cipitator the system effectiveness would be greatly increased.
4. Many aerosols, i.e., SO,, NO , NH are water soluble and
fc X j
would be expected to interact with charged water fog. The
droplets might absorb on ambient dust particles (that are in
the process of agglomerating) thereby removing both the dust
and the aerosol at the same time. Another mechanism might
involve direct fog induced agglomeration of the smoke or
aerosol. Once again the large drops would be expected to fall
out quite rapidly.
11. Experimental Studies
The first investigation was aimed at a determination of the
charge vs. size spectrum for typical industrial dusts, after grinding
and dispersion into the air. The test materials, obtained from a
variety of sources, were ground and dispersed by means of the arrastra
mill shown in Figure 1. The powdered material was blown into a small
dust tunnel, sampled and analyzed by a modified Anderson-2000 Company
Impaction Sampler* (shown in Figure 3). Typical results in terms of
charge** vs. particle size are shown in Figures 4 through 15; i.e.,
*The sampler flow rate was 28.2 1/min., a sample run required some
nine minutes.
**we recognised that it would be advantageous to have the charge data
in "absolute rather than relative units. However, a study of the litera-
ture, i.e., Loeb Ref 2ab and some laboratory tests indicated that the
process would be difficult, time consuming and subject to severe error.
In any case the important fact was that the dust was charged and that the
respiratory material was predominately negative in sign. Constraints of
time and funding precluded any further effort to measure absolute charge
for the industrial materials of interest.
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3
4 slate, 5 granite, 6 clay, 7 trap rock, 8 magnetite, 9 foundry dust,
10 shale, 11 fly ash, 12 copper concentrate, 13 cement quarry material,
14 cement clinker, and 15 silica sand. In view of the toxicity of
silica dust, it was of interest to observe the decay of the silica
charge as a function of time and particle size. The data is shown in
Figure 16. It is apparent that the smallest respiratory material is
most highly charged and decays quite slowly. This may be connected
with the pathogenic effect of silica. Experimental studies of this
question were reported in Reference 1.
The data of Figures 4 through 15 indicates that the respira-
tory-size material was always charged and that generally the charge
was negative in sign. There have been a number of studies on the
question of how and why dust charging occurs, i.e., Loeb (2a,b),
Harper (3), Gallo and Lama (4). There is no general agreement but we
prefer the theory of Gallo and Lama that predicts a negative charge
on the smaller dust particles. In this connection it is important to
note the effect of impurities as discussed by Loeb. His book indicates
that when pure quartz is ground there are as many positive as negative
particles, at every size level. When the quartz was contaminated with
a metal (platinum) a predominance of negative charge was observed (2a,
b). In this connection it is important to note that small dust particles
are frequently contaminated with absorbed metals from vapors generated
during combustion or melting (5). An effect of this type may be re-
sponsible for the results of Figures 4 through 15.
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In any case, the above data suggests that under normal con-
ditions respiratory dust will not agglomerate and fall out, because
the uniformity of charge will reduce the number of particle collisions.
Since most particles are negative and the earth's surface normally
carries a negative charge (6), it appears that electrostatic levitation
would further reduce the rate at which such particles fall out of the
atmosphere.
Many attempts have been made to encourage dust agglomeration
by wetting down the dust; however, the difficulties of generating a
micron sized fog and inducing the fog to make contact with the dust
particles has almost precluded the use of fogging to control open air
dust problems. (Some closed dust control systems use electrostatic
techniques to charge the dust. The charged particles are then sprayed
with oppositely charged water which is effective in making contact with
the dust. This method requires a closed vessel and the dust must be
properly charged by induction or ion diffusion. The resultant system
is complex and only suited for dust that has been captured by hoods
and collectors (7)).
A. Generation of Charged Fog
We have made use of a modified commercial* electrostatic paint
spray gun plus a University of Arizona designed apparatus** for genera-
tion of highly dispersed, micron sized, fog that carries a positive or
*Provided by the Ransburg Corporation of Indianapolis, Indiana.
**A commercial version of this system is marketed by the Ransburg
Corporation.
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negative charge, as desired. No clogging or deposits have been observed
after many hours of operation, with ion treated tap water.
Information on the droplet spectrum, generated by the fogging
system, was not available from the manufacturer of the spray nozzles.*
An evaluation of the droplet spectrum was done by collecting the drops
on a microscope slide coated with MgO and measuring the spot diameters
with a reticule in the microscope (8). There was a significant decrease
in drop size with the charging voltage "on". We suggest this was due
to electrostatically induced fracture of water droplets (9). The micro-
scope data indicated that more than seventy five per cent of droplets
were less than fifty micrometers in diameter.
Another experiment, designed to measure the electrostatic charge
per droplet, made use of a fog gun and an electrically isolated metal
dewar cooled by a mixture of dry ice and acetone. The fog condensed on
the walls of the dewar and the resultant electrical current was measured
by a picoammeter driving a chart recorder. Integration of the current
versus time yielded the total charge delivered to the dewar. The dewar
was weighed at the beginning and end of the experiment to determine the
total quantity of fog condensed. Assuming that the average droplet size
was some twenty five microns, the average number of elementary charges
per droplet was found to be 8«10 . This may be compared with the cal-
culated data of reference 10 which indicates a maximum charge of some
6.5-10^ eiementary charges for this size droplet.
*Spraying Systems Company, Wheaton, Illinois
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We might note here that droplet charging was by induction and
as the density of the spray cone increases there is a tendency for
charging to be limited to the outside of the cone. Direct contact
charging is more efficient but may lead to problems of electrical leak-
age back through the water line to the tank. This leakage may be limit-
ed by using long plastic tubes, of small diameter, to provide a high
resistance path. We have found it more effective to deliver a mixture
of air and water rather than a solid column of water to the nozzle.
The air bubbles effectively block the electrical leakage (as long as
plastic tubing is used) and we have found it possible to isolate volt-
ages up to 20 kV by this technique.
B. Dust Tunnel Studies
The interaction between industrial dusts and charged fog was
investigated in the dust tunnel shown in Figure 2. The charged fog
and the dust were blown in at one end of the tunnel, and an industrial
vacuum cleaner was used to extract the remaining dust at the other end.
The Anderson Sampler was connected some two feet from the downstream
end of the tunnel. Several attempts were made to measure the airflow
in the tunnel so that sampling could be done isokinetically. Unfor-
tunately the flow velocity in the tunnel varied from day to day as the
vacuum cleaner bag loaded up so it was not practical to choose a fixed
velocity for isokinetic sampling. The variations during a given run
were not large enough to affect the data and the primary interest was
in comparing the dust density with and without charged fog.
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Typical results with this system, using foundry dust, are
shown in Figure 17; without the fog, the dust level was quite high.
There was some decrease in the dust level with uncharged fog, but
with positively charged fog the decrease was dramatic. (The choice
of positively charged fog was made on the basis of Figure 9 that in-
dicated the respirable material was (-) in sign.)
Other data of this type, on foundry dust, is shown in Figures
17, 18 and 19. In Figures 17 and 18, the water flow to the gun was
held constant, but the time of grinding was varied in order to change
the dust particle spectrum.
In Figure 18, the emphasis was on the 0.5 to 4 micron respira-
tory range, while in Figure 19 the dust was ground still further to
build up the one micron fraction. In both cases, the charged fog was
very effective in controlling the dust. This is especially evident in
Figure 19 at the one micron level. These results might have been an-
ticipated from Figure 9 where it was shown that the one micron sized
foundry dust had a negative charge. We would expect this dust to inter-
act quite strongly with oppositely charged fog. Figures 17, 18 and 19
indicate that this interaction did, in fact, occur.
Other studies of this type were done with silica sand and silica
flour to determine if similar results could be obtained. The data is
shown in Figures 20 and 21. It seems quite clear that the charged fog
system is effective in reducing these particulates.
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8
Further data on magnesium oxide dust is shown in Figure 22*.
Here the interest was in the rate of reduction of dust density after
fogging began and for this reason data was taken as a function of time.
It is apparent that there was a substantial reduction after 0.5 minutes,
when charged fog was used. In contrast, we note that the effect of un-
charged fog was only really apparent after some two minutes. This dif-
ference is a measure of the effect of charging as a mechanism for im-
proving the contact between dust and water fog.
Other data showing the effect of charged fog on silicon carbide
dust and nickel mine precipitator dust are shown in Figures 23 and 24.
Data on bauxite ore, calcium oxide, dolomite, cement clinker, iron oxide,
sulfur and Pb 0 are shown in Figures 25, 26, 27 and 28. Here again
3 4
charged fog was effective in suppressing all of these dusts, provided
that the proper polarity was used. Similar results were obtained with
rock salt, the fumes from burning Carbamite (an ammonium nitrate com-
pound used for underground blasting), a silicate ore sample provided
by a local mine, and a mixture of lead oxides from a battery production
facility, Figures 29, 30, 31 and 32.
*Some of this data was obtained with a GCA Corporation RD-101 Dust
Monitor. This unit makes use of a beta ray absorption system and in
some cases, where there was significant absorption of fog by the dust,
it appeared that the dust plus uncharged fog density was higher than
the initial dust density itself. The data was corrected for this water
absorption, as shown in the figures, by subtracting a percentage from
each vertical bar. This value was obtained by taking the difference
between the no-fog and the uncharged fog data, dividing by the height
of the uncharged fog bar and multiplying the other data bars by this
value.
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9
In all of the above cases there was a significant difference
between the effects of positive versus negatively charged water fog.
This would be expected from the earlier discussion of dust charging.
However, we have noted some cases in which the charge of the fog does
not have a significant effect on the suppression of respirable dust.
Typical examples are shown in Figures 32 and 33 for an industrial red
lead and trona dust Na.CO_•NaHCO.•2H.O from a commercial mine. We sus-
pect that these samples contain materials that charge both positively
and negatively (a mixture of red lead and sulfur would display this
characteristic). Little coagulation occurs when the materials are
very dry, if charged fog is used one of the components is wetted and
agglomeration of both species occurs. This is speculation at present
and the phenomena will be the subject of further investigation.
C. Effects of Reduced Water Flow and Chemical Additives
Another aspect of the study was aimed at evaluating the effects
of reduced water flow on dust control. Typical results are shown in
Figure 32, where we have plotted the percent reduction of respirable
foundry dust with uncharged (30 ml/min) and with charged water at flow
rates of 30, 16 and 3.2 ml per minute. The largest reduction was ob-
served with charged fog at 30 ml/min, but the significant reduction
was observed even at 3.2 ml/min. This suggests that only a limited
amount of fog will be required for effective dust control. A calcu-
lation of the effect of these fog levels on the humidity, in a typical
foundry, is given at the end of the paper.
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10
There have been suggestions that various dust control chemicals,
detergents, etc., be added to the water in order to improve the dust
control system or make the agglomerates more stable. We have resisted
this idea on the basis that no dust control chemicals have FDA approval
for human exposure. Anyone working in the area where the charged fog
was used could certainly be exposed to the vapors and the effects of
dust control chemicals have simply not been evaluated in this mode. We
have done studies with various mixtures of glycerine (glycerol) and
water in cases where the fogging technique might be used at low tempera-
tures. (Subfreezing temperatures are frequently encountered in the
iron mines of Minnesota and Ontario.) Glycerine has FDA- approval for
oral, dermal and rectal application and a 50/50 mixture with water has
a freezing point of -23 C.
Typical glycerine/water data with iron mine crusher dust is
shown in Figure 35. Here the dust was run first with (+) and (-)
charged water and then the experiment was repeated with a 50/50 glycer-
ine water mixture. In both cases the (+) charged fog was most effective
with a slight bias in favor of the pure water rather than the water
glycerine mixture though the difference was not very significant.
We suggest that mixtures of glycerine and water can be used for
dust suppression and may be especially valuable under freezing conditions
or when there is a tendency for the dust to redisperse. In the case of
certain lead dusts, the glycerine seems to hold the agglomerate together
even in weak 10/90 glycerine/water solutions.
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D. Studies of Coal Particulates and Coal Tar Volatiles
The increased burning of coal raises the hazard of greater
public exposure to fly ash, coal particulates and the volatiles gener-
ated when coal is heated. An investigation of the effect of charged
fog on these pollutants involved first the grinding of coal*, in a
nitrogen atmosphere to preclude explosions, to obtain a fine powder.
This powder was blown into the dust tunnel with nitrogen (in place
of air) and fogged. Typical results are shown in Figure 36. As usual
the respirable material was found to be negative and was effectively
suppressed by positively charged fog.
To investigate coal tar volatiles, a metal pipe some 100 mm in
diameter was cut off and sealed with screw caps to form a closed tube
some 300 mm long. The tube was filled with coarsely ground coal*, pro-
vided with a 10 mm tube to permit vapors to escape and heated to 700 C
in a small oven. The vapors were blown into an outside dust tunnel and
exposed to charged fog. Two experiments were done. One was to observe
volatile particulates that were usually collected on filters. The other
experiment was aimed at observing benzene solubles. The data on volatile
particulates is shown in Figure 37. The (+) charged fog was most effective
in reducing this pollutant.
Measurement of these benzene soluble vapors involved drawing
the fumes through a bubbler containing a benzene solution for absorption;
the benzene was then analysed by a gas chromatograph (GC). A typical
*Pittsburg Seam #8 Coking Coal (Ohio)
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12
test involved first making a GC run with benzene alone, then a run was
made with benzene after absorption of coal tar volatiles, and a last
run was made with benzene and coal tar volatiles where the volatiles
were fogged, with (+) fog, before reaching the benzene absorbent.
Typical results are shown in Figure 38. In the presence of
charged fog there was a marked reduction in pickup of benzene solubles
by the bubbler suggesting that this material had been induced to ag-
glomerate and fallout in the tunnel before reaching the collecting device.
We suggest that there may well be applications for charged fog in the
control of coal dust and coal tar volatiles.
Experiments with SO and Fly Ash Plus SO . Sulfur dioxide is
2 2
found as a purely gaseous pollutant in certain copper smelting operations
but in most cases is associated with substantial quantities of dust or
particulate matter. This is especially the case in coal fired power
plants where control of fine (one micrometer) fly ash and S0_ is dif-
ficult with conventional precipitators, wet scrubbers and bag houses.
Our first studies, of S0_ alone, were designed to observe the
interaction, if any, between charged fog and S0_. There had been some
indication that SO- aerosols were negatively charged and to investigate
this, S0_ was provided from burning sulfur or commercial tank, and ex-
posed to charged water fog. Typical results, at room temperature, are
shown in Figure 39. Experimental data obtained in the heated test rig
of Figure 40 produced the data shown in Figure 41. There seems to be
no question that (+) charged fog is effective in reducing the level of
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13
SO even at 381 C. We suggest that the fog combines with the SO to
form large drops of H SQ. whose vapor pressure is low enough to preclude
evaporation even at the test temperatures.
The experiments with fly ash began with "pure" fly ash (without
added SO ). Typical results are shown in Figure 42. The (-) charged fog
seemed to be most effective in this case, but this result may be limited
to the particular fly ash involved or to the fact that the test was run
at ambient temperature. After consultation with the power company
involved, the study was repeated with the fly ash at 200 C. Once again
charged fog was effective in suppressing the dust (typical results are
shown in Figure 43), but several experiments indicated that now the (+)
charged fog was most effective. We have no explanation for this at the
moment. The question of charging as a function of external parameters,
i.e., heating, is under investigation at the moment.
At this point, we began experiments with mixtures of SO and
fly ash. There have been many reports (Reference 11, pages 105-189)
of improvements in collection and adhension characteristics of fly ash
in the presence of SO. or NH . In fact, most commercial fly ash addi-
tives contain one or both of these chemicals. It is worth noting that
the exact mode in which these chemicals serve to improve collection is
by no means clear and one objective of our experiment was to clarify the
SO fly ash interaction.
The first studies involved grinding the fly ash in the arrastra
mill and blowing, it into the dust tunnel while at the same time adding
a measured flow of SO . The sulfur dioxide studies were hampered by a
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14
a lack of detection apparatus but the experiment served to define
possible applications of the charged fog technique. Typical results
at ambient temperature are shown in Figure 44. The addition of SO
raised the measured dust level appreciably. We associate this with
absorption of SO onto the dust thereby raising the weight of the
particles. With (+) charged fog there was a significant reduction in
the dust level. If SO. was not present the dust reduction was even
greater suggesting that in the presence of SO. some of the injected fog
is taken up by the gas and therefore unavailable to the dust. In an
industrial situation this could be remedied by simply increasing the
quantity of charged fog.
For the next experiment we were able to make some numerical
determinations of SO level, by a wet chemical technique, and typical
results for dust and SO are shown in Figure 45. Here the initial
dust density is shown with an added SO. content equivalent to 13.2 mg/m .
After fogging the dust level fell to the lower curve and the S0_ level
fell below the sensitivity of our instrument 0.26 mg/nr.
The next set of studies made use of the experimental system
shown in Figure 40. Here the interest was to determine the effects,
if any, of the high temperature on the reaction. Typical results are
shown in Figure 46. There was a significant reduction in dust density
and a moderate reduction in the SO level. The limited effect of the
fog on the SO_ may be due to the use of a different and much more acid
fly ash, from a local mine. This ash may have captured a majority of
the fog so rapidly that little was left to absorb SO . These effects
will be investigated in more detail as the program developes.
-------
15
These SO /fly ash investigations are obviously in the very
beginning stages, equipment is still being ordered and set up. Never-
theless, there is every indication that when a mixture of SO and fly
ash is exposed to charged fog the fog divides between the SO and the
fly ash. Fog absorbed by the fly ash is tightly held and induces dust
agglomeration; the fog that interacts with the SO forms dilute sulfuric
acid that is absorbed by the dust particles to produce a highly adhesive
agglomerate. Two photographs are shown in Figure 47; the upper shows the
agglomerate formed with SO plus fly ash, the lower shows the effect of
adding charged fog. Not only are the agglomerates somewhat larger but
there are whiskers which we suspect are sulfur since they could not be
imaged in the scanning electron microscope.
These absorption and agglomeration effects suggest that it
might be possible to remove both pollutants (SO and fly ash) at the
same time by spraying with charged fog. The resultant agglomerates are
large (typically thirty micromenters) and ideally suited to collection
by precipitators or wet scrubbers. This combination of effects could
significantly improve the control systems installed on a wide variety
of power plants and smelters.
E. Control of Dust From Hand Grinders, Chippers and Sanders
These tools are a source of dust and since they are often used
in confined areas, where hoods would interfere with the work, they are
a potential factor in workman injury. Some companies have marketed
collectors and vacuum manifolds to go on the grinder but in general
-------
16
these units have not been popular because they change the balance of
the tool and interfere with the workman's view.
We have developed* a system for adding small quantities of
water fog to the contact area between the tool and the work. This
effectively reduces the respirable dust level while at the same time
acting as a cooling agent. Typical results with a grinder and chipper
are shown in Figures 48 and 49. In each case there was a significant
reduction in dust level and operator comments indicated that grinding
seemed more efficient. The water dispensing and controlling system
did not interfere with the operation of the tool.
Arrangements are being made with a manufacturer of hand tools
to bring this device into the commercial market. Further development
of systems to reduce dust during wire brushing, swing grinding and
electric arc washing are under way.
III. Industrial Testing
The laboratory work, while encouraging, was not a guarantee
that the system would operate in the more rigorous environment of the
industrial plant. For this reason, a test program was organized at
several locations in southern Arizona and at a number of other industries
in various parts of the United States and Canada. For some tests the
University participated directly in the setup and operation of the exper-
iment. In other cases the fog guns were simply loaned or rented to the
*This device is the subject of a patent disclosure to the
Ransburg Corporation of Indianapolis, Indiana.
-------
17
organization for try out. This proved to be a problem in some situations
where corporate personnel were not familiar with dust sampling procedures
or how to set up for a test of this kind. As a result there were some
inconclusive tests and in a few cases negative results were obtained.
This problem is being slowly solved as test equipment is refined and
more time is available for assisting the corporation during the test.
Some of the results obtained by the author, or by industrial
personnel, under controlled conditions, are discussed below. At the
present time tests are under way at some fifty industrial locations.
A. Cement Plant "A"
A sample was taken from the belt conveyor in the quarry surge
building. The dust was tested in the system, shown in Figure 2 and
the results are shown in Figure 13. It is clear that this dust was
primarily negative in sign, and positively charged fog should be used.
The in-plant fog tests made use of two modified Ransburg REA guns,
mounted as shown in Figures 50 and 51. The curtains shown in Figure 51
were used to prevent dust from blowing in or out of the test area. In
the case of Figure 50, we were interested in the dust suppression right
at the hoppers. In Figure 51, the reduction in dust in the working area
was of importance. The results are shown in Figures 52 and 53. In both
cases, there was significant reduction in the dust level.
B. Copper Company "A"
Dust samples were taken from a concentrate conveyor in the
smelter and tested in the dust tunnel of Figure 2. The charge vs. size
-------
18
data was shown in Figure 12. It is clear that the smaller respirable
material is positive in sign, indicating that negatively charged fog
should be used.
The experimental set up for this test made use of one Ransburg
REA gun, as shown in Figure 54. There was some difficulty with high
ambient winds blowing the dust and fog about, but it was possible to take
data by sampling with a GCA RD-101 beta ray adsorption system. The
results are shown in Figure 55.
In another test, at the same company, the fog gun was set up at a
conveyor drop box as shown in Figure 56. Some eleven samples were taken
without fog and seven samples with (+) charged fog. The average reduction
in dust level was some 65.4%. This was felt to be satisfactory in view
of the many other dust sources in the area and the high winds that happened
to be blowing that day.
C. Steel Casting Company "A"
The test area for this study was a standard railroad boxcar used
for shipping silica sand. Under normal conditions, the dust level during
unloading was quite high. The control system involved four RAnsburg REA
guns fastened to the inside roof of the boxcar as shown in Figure 57.
The dust levels during unloading were monitored by MSA Gravimetric Dust
Samplers for a two hour working period. The total dust level and the
fraction of free silica were measured with and without charged fog. The
results are shown in Figure 58. It is apparent that both the total dust
concentration and the respirable silica level were significantly reduced.
-------
19
It is interesting to note that the free silica was reduced by a factor of
1. 09
Q* , g = 57.4, suggesting that the positively charged fog was most effec-
tive on the negatively charged (Figure 15) silica dust. This very signi-
ficant effect is a measure of the effectiveness of the charged fog tech-
nique. Further experiments in this facility are planned.
D. Steel Company "B"
One of the more troublesome operations in this facility was the
bag splitting room where operators were exposed to high levels of respi-
rable dust. This area was set up with two fog guns blowing into the
splitting hood. Samples were taken at two fixed points in the hood area
and a third sampler was attached to the workman and operated by a battery
driven pump.
Typical results are shown in Figure 59. There was a significant
dust reduction at the fixed locations but the greatest improvement was
measured by the sampler on the workman. This was most encouraging and
further studies in this faciltiy are under way.
IV. Humidity Increase Due to Fogging
This is of some importance in areas where the addition of water
vapor might damage delicate equipment or interfere with industrial
operations. To evaluate this effect, we consider a fog gun air flow of
some 100 SCFH (2.8m /Hr) and a water flow of some A ml/min or 2.21 •
10~3 A Ib/min (1.003 .
-------
20
This air flow will mix with ambient air after it leaves the gun.
In an open-shop situation, where the supply of ambient air is essentially
unlimited, the mixture ratio will be about 100 giving an effective air
4 3
flow of some 10 SCFH 283 m /Hr ^toward-the target. If this "factory air"
is 80°F (26.7.C) at; 50%" RH,' its^-initial moisture content- will be 0.011 lb-
H o per Ib air (0.011 g H 0/g air).
The density of air at the above conditions is some 0.079 Ib/SCF
(0.00128 g/m ). This flow represents some 13.2 Ib/min (6000 g/min) of
air with an initial water vapor content of 0.145 Ib HO (65.83 g HO).
fL £t
In the flow of water to the fog gun is some 30 ml/min (a rather
large value), the total water added per minute will be some 0.064 Ib HO
(29.1 g HO).' If we add this to the initial water vapor level of 0.145
Ib (65.83 g HO) the total is 0.209 Ib HO (94.9 g HO) or 0.0159 Ib
H 0/lb air (0.0159 g H 0/g air). The new RH (assuming constant tempera-
ture conditions) is some 70%, insufficient to damage industrial appartus.
If the water flow is reduced to some 5 ml/min (0.011 Ib/min), the
fogging technique is still quite effective (Figure 34). Under these
conditions, the RH rises from an initial 50% RH to some 67% RH (assuming
constant temperature).
This calculation has been done for open shop conditions. In
ducts or tunnels where the flow of ambient air is limited, higher relative
humidity values will be generated. If this is a problem, it should be
possible to further reduce the water flow, provided that better atomization
of the water can be achieved. The number of drops obtained from a given
4 3
volume of water varies as the third power of the radius, i.e., V = — TTR .
-------
21
The limiting charge per drop varies as the square of the radius NE ~ AR
(where A is a constant). Reducing R by a factor of 10 increases the
number of drops by a factor of 1000. The allowable charge per drop de-
creases by a factor 100, permitting an approximate gain in effectiveness
of a factor of 10. Conversely, the quantity of water might be reduced by
a factor of 10 without loss of efficiency.
In the case cited above reduction of water flow from 5 ml to 0.5 ml
per minute reduces the rise in relative humidity from some 17% RH to less
than 1% RH.
-------
22
References
1. Summerton, J. E., et al., "Silicosis: 1. The Mechanism of Homolysis
by Silica," Journal of Molecular Pathology, 26, 113-28, (1977).
2.a Kunkel, W. B., "The Static Electrification of Dust Particles on
Dispersion into a Cloud," Journal Appl. Phys., 21, pg. 820, 1950.
b Loeb, L. B., Static Electrification, Springer, Berlin, 1958.
3. Harper, W. R., Contact and Frictional Electrification, Oxford Univ.
Press, New York, 1967.
4. Gallo, C. F., W. L. Lama, "Classical Electrostatic Description of
the Work Function and lonization Energy of Insulators," IEEE
Transactions on Industry Applications, Vol. 1A-1'2, No. 1, pg. 7,
(1976).
5. Natusch, D.F.S., et al., "Toxic Trace Elements: Preferential
Concentration in Respirable Particles," Science, 183, No. 4121,
pg. 183, 1974.
6. Israel, H., Atmospheric Electricity, Vol. !_, 11, U. S. (Department
of Commerce NTIS, Springfield, Virginia, 1973.
7. "Particle Charging Aids—Wet Scrubbers Sub-Efficiency," Chemical
Engineering, pg. 74, July 21, 1975.
8. May, K. R., "The Measurement of Airborne Droplets by the Magnesium
Oxide Method," J. Sci. Instr., 27, pg. 128 (1950)
9. Doyle, A., et al, "Behavior of Evaporating Electrically Charged
Droplets," Jnl. Coll. Sci., 19_, 136, (1964)
10. Davies, C. N., Aerosol Science, pg. 63, Academic Press, New York,
1966.
11. Blake, D. E., PB 260-499, Symposium on Particulate Control in Energy
Processes, Sept. 1976, available from National Technical Information
Service, Springfield, Va. 22161.
-------
COMPRESSED
AIR
FLOWMETER
DRIVE MOTOR
A
m/i/mm/,
ARRASTRA
MILL
I
IMPACTION
DUST SAMPLER
DUST GENERATOR AND SAMPLING SYSTEM
-------
ANDERSON
IMPACTION
SAMPLER
JO VACUUM CLEANER
AND OUTSIDE EXHAUST
BLANK -OFF
PLATE
EXPERIMENTAL '1 PUST TUNNEL
-------
AIR AND
DUST INTAKE
TYPICAL
STAGES
3 OF 6
TREK VOLT
METER
ANDERSON - 2000
IMPACTION SAMPLER
SEQUENTIAL
SWITCHING
SYSTEM
VACUUM
PUMP
PERFORATED PLATE
\
/
SILVER
PAINT
\
PLEXIGLAS 2.5mm *
SPRING
PLATE J ______
-------
II
PARTICLE SIZE
MICROMETERS
3 RUNS
(SLATE)
W////////////////////////7/M//.
I 1
INDICATES SPREAD
OF THE DATA
6 5
H
3 21 01
Q^ (ARBITRARY UNITS)
-------
II
0
PARTICLE SIZE
MIC ROMETE RS
3 RUNS
( GRANITE )
INDICATES SPREAD
OF THE DATA
3 2 I
CHARGE (ARBITRARY UNITS)
-------
II
PARTICLE SjZE
MICROMETERS
3 RUNS
( CLAY)
INDICATES SPREAD
OF THE DATA
w/m///////,
5 4 32 10
CHARGE (ARBITRARY UNITS)
-------
- PARTICLE SIZE
MICROMETERS
3 RUNS
(TRAP ROCK)
INDICATES SPREAD
OF THE DATA
i 1
7//M//MM////I
i
3 2 I
CHARGE (ARBITRARY UNITS)
-------
II
PARTICLE SIZE
MICROMETERS
3 RUNS
(MAGNETITE ORE)
i 1
INDICATES SPREAD
OF THE DATA
I 2. 3
CHARGE (ARBITRARY UNITS)
-------
II
PARTICLE SIZE
MICROMETERS
5 RUNS
( FOUNDRY DUST )
l ,
INDICATES SPREAD
OF THE DATA
W//////////////////////////////M
-i
o
5432 10
CHARGE (ARBITRARY UNITS)
I 2 3
-------
II
PARTICLE SIZE
MICROMETERS
3 RUNS
(SHA LE )
INDICATES SPREAD
OF THE DATA
54
CHARGE
3 a I 0
( ARBITRARY UNITS )
-------
PARTICLE SIZE
MICROMETERS
II
10
8
BAR SHOWS SPREAD
OF THE DATA
( 3 RUNS )
ELY ASH 5BOM POWER PLANT "A1
[11
<-)
'ARBITRARY UNITS)
-------
Y//////////////////7///A
7
PARTICLE SIZE
M I C R 0 f ,1 E T E R S
6
-5
- 4
-2
- I
(-) CHARGE
10
B_
i 1
INDICATES SPREAD OF DATA
DUST FROM CONCENTRATE CONVEYOR
COPPER;COMPANY "A"
(-H CHARGE ARBITRARY UNITS
2
_t_
4
-------
-8
-7
-6
5
PARTICLE SIZE
MICROMETERS
-4
3
K/////////////////////I
___ , j
E
//
71
i —
71
2
-I
(-) CHARGE
5 43
CEMENT COMPANY "A"
DUST FROM QUARRY SURGE
STORAGE -CONVEYOR
INDICATES SPREAD OF DATA
(+) CHARGE
345
-------
6
-7
PARTICLE SIZE
MICROMETERS
6
- 5
4
3
2
- I
(-) CHARGE
543
'///A
CEMENT COMPANY "A"
CLINKER DUST FROM BELT TO
STORAGE AREA
H INDICATES SPREAD OF DATA
(+) CHARGE
i 1
5
i
-------
W////////////A
PARTICLE SIZE
MICROMETERS
5 RUNS
( SILICA SAND)
INDICATES SPREAD
OF THE DATA
W////M////////////////////.
i i I
ABOVE II
12
10 8 G 4 20
CHARGE (ARBITRARY UNITS)
246
-------
8i
6
4
2
8
CHARGE UNITS
( ARBITR ARY )
PHARYNX
SECONDARY
BRONCHI
AVERAGE OF 3 TESTS
RESPIRATORY PENETRATION
SILICA DUST
4.7 - 7.0 u
0.65-1.1 u
& 6 t
X ( M I N U T E S )
10
II
-------
10
8
DUST DENSITY
INITIAL DUST
DUST LEVEL
(NO FOG )
UNCHARGED
FOG
^CHARGED
FOG
DIAMETER IN MICRONS
8
MATERIAL (FOUNDRY DUST) CONTINUOUS OPERATION
DUST AIR FLOW 50SCFH
FOG WATER FLOW 30ml/min ( 0.475 gal/hr )
17
-------
DUST DENSITY mt* /
0
MATERIAL, FOUNDRY DUST
CONTINUOUS OPERATION
FOG WATER FLOW 30 ml/mfn
FOG GUN AIR FLOW 100 SCFH
DATA CORRECTED FOR WATER
PICK-UP ON COLLECTION PLATES
INITIAL DUST '
LEVEL (NO FOG)
UNCHARGED
FOG
(-HCHARGED
FOG
PARTICLE
DIAMETER
( MICRONS)
Q
-------
12 -
8 -
DUST DENSITY ™Q/m3
MATERIAL FOUNDRY DUST
CONTINUOUS OPERATION
FOG WATER FLOW 30ml/m|n
FOG GUN AIR% FLOW 100 SCFH
DATA CORRECTED FOR WATER
PICK-UP ON COLLECTION PLATES
CHARGED FOG
INITIAL DUST LEVEL (NO FOG)
UNCHARGED FOG
PARTICLE
DIAMETER
{ MICRONS )
-------
7
DUST DENSITY
D mg/ M3
INITIAL DUST
DENSITY (TOTAL)
'20.3 mg / M3
DENSITY AFTER FOGGING
WITH UNCHARGED FOG ( TOTAL)
10.1 mg / M3
DENSITY AFTER FOGGING WITH (+) CHARGED
FOG ( TOTAL) 1.5 mg / M3
2.0
DIAMETER
3.0
4.0
( MICRONS )
DUST DENSITY VS SIZE BEFORE AND AFJER FOGGING
FOG DENSITY 2.4 ml / M3 ( SILICA SAND )
-------
DUST DENSITY
mg /
30
20
MATERIAL - SILICA FLOUR
DUST TUNNEL DATA
3 RUNS
WATER FLOW 30 ml/ min
AIR FLOW 100 SCFH
INITIAL DUST
LEVEL
10
WITH ( + ) FOG
PARTICLE SIZE ( MICRONS )
0
6
8
-------
30 r
Mg 0 DUST
RESPIRATORY
FRACTION ONLY
mg/
AIR FLOW 100 SCFH
WATER FLOW 30 ml / min
25
20
UNCHARGED
FOG
INITIAL DUST
LEVEL
10
GCA
BETA
RD-IOI
DUST MONITOR
+ CHARGED
FOG
START OF RUN
TIME (MIN)
-------
20
18
16
14
12
10
8
DUST DENSITY
mg /
0
SILICON CARBIDE FURNACE DUST
30 % SIC
50 % Si 02
20 % IRON OXIDES
TEMPERATURE 23° C (AMBIENT)
INITIAL DUST LEVEL
AFTER SPRAYING WITH UNCHARGED FOG
EFFECT OF ( + ) CHARGED FOG
0.0
2.0
3.0 4.0 5.0 6.0 7.0 8.0
PARTICLE SIZE ( MICRONS)
9.0 10.0
-------
DUST DENSITY
mg /
INITIAL DUST
LEVEL
MIXED
( NiO
FROM
PRECIPITATOR DUST
NIS , Ni3 S4 )
FACILITY
/1EN£JO
SUDBURY , CANADA
WATER FLOW 30 ml / MIN.
EFFECT OF ( +)
CHARGED FOG
PARTICLE DIAMETER MICROMETERS
I g | | |
I 23 4 5
8
10
-------
BAUXITE ORE FROM DUVAL CORP.
20 \-
15 k
10 \-
DUST DENSITY
mg/m3 WATER FLOW 30 ml/min
AIR FLOW 100 SCFH
-
•
-
•
•^M
VERTICAL BARS SHOW
DATA SPREAD
1 ' ' .
DATA TAKEN WITH GCA CORP.
RDM -101 BETA RAY DUST MONITOR
RESPIRABLE DUST ONLY
nl
NO FOG
(-) FOG
(+) FOG
-------
MODEL
i M IN t m
RDM-tOI
wn « fcUA CORPORATION
BETA RAY DUST MONITOR
MATERIALS PROVIDED BY KAISER STEEL CO.
FONTANA CALIFORNIA
42
38
34
30
26
22
18
14
10 •
6 •
2
1 ) INITIAL
DUST LEVE
2). DUST PLUS UNCHARG
«••
L
E
3) DUST PLUS 30ml/mi]n
4) DUST PLUS 20ml/mjn
5 ) DUST PLUS 30 ml
6 ) DUST PLUS 20 ml
DATA BARS ARE '
DUST DENSITY
mg / m3
CORRECTION FOR
k
•
•
•
—
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I
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\
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mmmm
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NEGATIVE FC
;
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V
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/
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/
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\
/
/
/
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/
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y
/
\
/
\
/
6 123 5 1235 X~N 1 2 3
DOLOMITE CEMENT &*) FeO
CLINKER
-------
2.0
DUST DENSITY
mg / m3
SULFUR SUPPLIED BY
DUVAL SULFUR COMPANY
1.5
1.0
.5
.0
BARS SHOW SCATTER
OVER 3 RUNS
LABORATORY TEST DATA
FOG WATER FLOW 30ml/min
AIR FLOW 100 SCFH
6CA CORP. RDM-101
BETA RAY DUST MONITOR
RESPIRABLE FRACTION ONLY
I
NO FOG
(-) FOG
(+) FOG
-------
DUST DENSITY
mg /
8
BARS SHOW SCATTER
OVER 3 RUNS
MATERIAL RED LEAD
Pb304
LABORATORY TEST DATA
FOG WATER FLOW 30 ml'/ min
AIR FLOW 100 SCFH
GCA CORP. RDM 101
BETA RAY DUST MONITOR
RESPIRABLE FRACTION ONLY
NO FOG
(-) FOG
(+) FOG
-------
20
DUST DENSITY
mg / m^
ROCK SALT FROM AVERY ISLAND, LA.
DATA LIMITED TO RESPIRABLE DUST
15
10 -
5 -
WM
-
^•M
1
BARS SHOW SCATTER
OVER 3 RUNS
FOG WATER FLOW 30ml/ min
AIR FLOW 100 SCFH
DATA TAKEN WITH GCA CORP.
RDM -101 BETA RAY
DUST MONITOR
NO FOG
(-) FOG
(+) FOG
(21
-------
DUST
DENSITY
mg / m^
FOG -
DUST
GCA UNIT
20
15
10
BURNING
CARBAMITE
D X 10' PIPE
VERTICAL BARS SHOW
SCATTER OVER 3 RUNS
LABORATORY TEST RESULTS
WITH MINE DUST
FUMES FROM BURNING
CARBAMITE AND FOG
RESPIRABLE DUST LEVELS
ONLY DATA TAKEN WITH
GCA CORP. RDM-101
BETA RAY DUST MONITOR
FOG WATER FLOW 30 ml / min
AIR FLOW 100 SCFH
NO FOG
(-) FOG
(+)FOG
-------
30
26
22
18
14
10
mg /
DUST DENSITY
LABORATORY TEST RESULTS
CONTROL OF DUST WITH CHARGED FOO
AIR FLOW 150 SCFH
FOG WATER FLOW 10 ml / min
SILICATE ORE SAMPLE
FROM KCC—RMD
FINE ORE TUNNEL
INITIAL
DUST LEVEL
PARTICLE DIAMETER ( MICROMETERS )
8
10
-------
7 h
6
5
1.0
7
6
5
O.I
mg/
MG
DUST
DENSITY
LABORATORY TEST OF CHARGED FOG FOG FOR
DUST CONTROL
GREY LEAD OXIDE / RED LEAD MIXTURE
SPONTANEOUS CHARGE (-)
FOG GUN AIR FLOW 150 SCFH
FOG GUN WATER FLOW 35ml/min
DUST LEVEL NO FOG
DUST
VACUUM
CLEANE.R
61
DUST LEVEL (4-) FOG
ANDERSON 2000
SAMPLER FOG GUN
PARTICLE DIAMETER (MICROMETERS)
8
-------
45
39
33
27
21
15
0
DUST DENSITY
LABORATORY TESTS OF DUST CONTROL
WITH CHARGED FOG , TRONA DUST FROM
SAMPLE 2
AIR FLOW 150 SCFH
WATER FLOW 15 ml / min
INITIAL DUST LEVEL
UNCHARGED FOG
PARTICLE DIAMETER (MICROMETERS)
0
8
10
-------
% REDUCTION IN OUST LEVEL AT
too
90
a/s
BU
\j\j
70
60
50
40
30
20
10
_ VARIOUS WATttt t-LUW KATt.5,
FOUNDRY DUST CONTINUOUS OPERATIC
•
M
m
•
.
»•
lm
mm
mm
mm
I
(J
|
/
X
X
X
^
V
^
A
1
/
^-^
^^>^..^ INITIAL RESPIRATORY DUST
LEVEL ( BELOV/
6p) 26.7 m9/r.i
AFTER FOGGING WITH UN-
|
/
|
•y
^
^
/ y
^
' -ft^. • ^CHARGED FOG
1 ( 21.4 m?/M^ )
30 m/M N
3.2 ml/MIN CHARGED FOG
/^ { 9.14 m9/M3 )
/
16.5 mI/MIN CH
f( 8.38 mVM3 )
\ \ 30 mI/MIN
\ y \ ( 5.22 mV
\ \v y
1 \H
11
7 7
7 7
7 7
7 7
7 7
7 7
7 /
7 7
7 7
7 7
V 7
i i
ARGED FOG
CHARGE'D FOG
M3 ^ *x.
\
1 1
-------
DENSITY
II
6 -
CRUSHER DUST
STEEP ROCK IRON MINE
ATIKOKAN , ONTARIO CANADA
AIRFLOW 100 SCFH
FOG WATER FLOW 30 ml / min
DUST WITH UNCHARGED FOG
INITIAL DUST LEVEL
DUST WITH (-) CHARGED FOG
AND GLYCERINE 50 % v/v
DUST WITH (-) CHARGED FOG
DUST WITH (4-) CHARGED FOG
AND GLYCERINE 50 % v/v
DUST WITH (4-) CHARGED FOG
12345678
PARTICLE DIAMETER ( MICROMETERS )
-------
DUST
DENSITY 1
5.9
BARS SHOW SCATTER
OVER 3 RUNS
PITTSBURGH SEAM 8
COKING COAL (OHIO)
LABORATORY TEST DATA
FOG WATER FLOW 30ml/min
AIR FLOW 100 SCFH
GCA CORP.
BETA RAY
RESPIRABLE
RDM - 101
DUST MONITOR
FRACTION ONLY
n
I
NO FOG
(-) FOG
(+) FOG
-------
3.0
2.0
1.0
0.0
0
COAL TAR VOLATILES
FOG WATER FLOW 30 ml / min
15'
INITIAL LEVEL
COKE OVEN
FUME
(-) CHARGED FOG
10" DIA.
PVC PIPE
SAMPLER
AFTER FOGGING WITH UNCHARGED FOG
) CHARGED FOG
(371
2.0 3.0
PARTICLE
4.0 5.0 6.0 7.0 8.0
DIAMETER ( MICROMETERS)
90
-------
8
PEAK HEIGHT
" ARBITRARY UNITS
EFFECT OF CHARGED FOG ON COKE
OVEN VAPORS
POWDERED COAL COKED AT 700 C.
FOG WATER FLOW 30 ml / min
HEWLETT PACKARD MODEL 700
GAS CHROMATOGRAPH
SILICON GUM RUBBER COLUMN SE-
BENZENE ONLY
COAL TAR VOLATILES
'lN BENZENE
COAL TAR VOLATILES
/AND (+) FOG
-------
8
mg
NO FOG
(-) CHARGED FOG
BARS SHOW SCATTER
FOR 3 RUNS
(+) CHARGED FOG
S02 LEVEL WITH AND WITHOUT CHARGED FOG ,
FOG WATER FLOW 30'ml/min.
-------
,0V EN
THERMO-
COUPLE
S02 AND DUST
FOG
INJECTOR
S02 / DUST
ABSORPTION
SYSTEM
0.028 M3
TEST CHAMBER
PADDLE STIRRER
AIR
DUST
SO,
SULFUR DIOXIDE / DUST EXPERIMENTAL SYSTEM
-------
20
18
16
14
12
10
8
S02 CONCENTRATION
PPM X I02
[-5.3 g /m3
LABORATORY TESTS OF S02 CONTROL BY
MEANS OF CHARGED FOG 0.028 m3 TEST
CHAMBER AT 700 F°, 381 C°
LIQUID INJECTION 3 ml AT 6 KV
VERTICAL BARS
SHOW THE SCATTER
OVER FOUR RUNS
INITIAL S02
LEVEL
(+) FOG
(-) FOG
/:
NO
CHARGE
-------
26
24
22
20
18
16
14
12
10
8
'DUST
LEVEL
POWER PLANT FLY ASH FROM
4 CORNERS , NEW MEXICO
WATER FLOW
SOm'/min
AIR FLOW
100 SCFH
MEAN OF 3 RUNS
DUST LEVEL
FOG
CHARGED FOG
» CHARGED FOG
I 2 3
PARTICLE
4 5
DIAMETER
6 7
( MICRONS )
-------
34
mg
/m3
30
26
22
DUST
DENSITY
18
14
10
INITIAL DUST DENSITY
POWER PLANT FLY ASH
FLY ASH INJECTED INTO DUST
TUNNEL AT 200 °C ( 392 °F)
WATER FLOW 30ml / MIN.
AFTER SPRAYING WITH
(4-J CHARGED FOG
[4-3,
1.0 2.0 3.0
PARTICLE
4.0 5.0 6.0 7.0 8.0
DIAMETER { MICROMETERS )
9.0
-------
8.0
DUST
DENSITY
7.0 -
6.0 -
5.0 -
4.0 -
DUST - MIDWEST FLY ASH
AIR FLOW 200 SC F H
FOG WATER FLOW 30ml / min
INITIAL DUST LEVEL WITH
S02 AT 13.1 mg / m3
DUST LEVEL
DUST,
-AND
CHARG
0.0
2.0 3.0 4.0 5.0
PARTICLE SIZE
6.0 7.0 8.0
Ml CROMETERS
-------
ao
7.0
6.0
5.0
4.0
3.0
2.0
1.0
INITIAL FLY ASH LEVEL
S02 LEVEL 13.2 mg / m^
MID - WEST FLY ASH
AIR FLOW 100 SCFH
WATER FLOW 30 ml / mln
DUST TUNNEL STUDY
WITH (+) CHARGED
FOG, S02 LEVEL
BELOW 0.26mg/m3
PARTICLE SIZE
MICROMETERS
i t | | a i
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
-------
OF CHARGED FOG ON S02 AND
EFFECT
COPPER COMPANY FLY ASH , OPERATING TEMPERATURF
340 -C. 645 F , LABORATORY TESTS IN 1 FT.3
DUST CHAMBER
210
S02 CONCENTRATION
PPM
180
150
120
90
60
30
140
BARS SHOW THE
SCATTER OVER 120
TWO RUNS
100
I
NO
FOG
(40,
FOG
80
60
40
20
DUST DENSITY
mg /
I
I
NO
FOG
(40
FOG
-------
,' -- cv
:.A:-« ^:' i
FLY ASH / SO
AGGLOMERATE
r .= >.'
k ^^?>i-13%-^M--Tj;;.p:
FLY ASH / S 0^ / CHARGED FOG AGGLOMERATE
—*| - [<— 30 y m (47"
-------
DUST DENSITY
mg /m3
LABORATORY TEST RESULTS , USE OF WATER
FOG TO CONTROL DUST FROM AN AIR
DRIVEN GRINDER
ARO CORP. MODEL 7025 KH5C AT 5000 RPM
GRINDING CAST IRON
FOG WATER FLOW
50 ml / min
TO SAMPLER
-I
80 mm
PARTICLE DIAMETER (MICROMETERS)
(48
0
8
-------
1
8
PARTICLE
mg
0
DENSITY
LABORATORY TESTS OF DUST CONTROL BY MEANS OF WATER FOG
ARO CORP. MODEL 85OOLOO CHIPPING HAMMER
WATER FLOW 50 ml / m3
CHIPPER IMPACT AREA
6"D. ROCK CORE \
( GREY GRANITE )
WITH WATER
FLOW
CHIPPING DRY
TO ANDERSON
SAMPLER
PARTICLE DIAMETER ( MICROMETERS )
8
-------
STATION "A"
•STATION "B"
o
FOG GUNS
r?
«*G
TO SAMPLER
£^
rvi
BELT
51
•/I • ' / 1 ' ' / / / ' ' i ' / / 1 / // / / ' / / / / / ' ' / / / 1 ' / ' '
/ ' /
TEST SST UP CEMENT PLANT "A"
BO]
-------
WALL
FOG GUNS
BELT
•EDGE OF BELT PLATFORM
i
SAMPLING
STATION
5' ( 152cm )
ABOVE FLOOR
2' ( 50.7cm)
FLOOR TO
CEILING
CURTAIN
I
j 5' (152 cm)
8' (244cm )
PLAN VIEW OF SURGE BUILDING
CEMENT PLANT "£»
-------
4.0
ARIZONA
Rl LLITO
PORTLAND CEMENT
PLANT FEB. 26, 1976
CO.
3.0
2.0
1.0
INITIAL DUST LEVEL
STATIONS "A" AND "B"
WATER FLOW RATE "1
94.6 ml / min
AIR FLOW RATE
200 S C F H
DUST
DENSITY
DATA POINT
UNCERTAIN
> 2 GUNS
STATION "A"
STATION "B"
+ CHARGED FOG
PARTICLE SIZE ( MICROMETERS )
8
10
II
-------
DUST DENSITY
EXPERIMENTAL RESULTS
'SURGE BIULDING
CEMENT PLANT "A"
WATER FLOW RATE
60 ml / min
AIR FLOW RATE
200 S C F H
INITIAL DUST LEVEL
DUST LEVEL AFTER 30
MINUTES OF POSITIVE FOG
DATA
UNCERTA IN
DUST LEVEL AFTER 5 MINUTES
OF POSITIVE FOG
23456 78
PARTICLE SIZE (MICROMETERS) (53;
-------
W/KfrySK ^'
SAMPLING STATION
BELT
EXPERIMENTAL SET-UP CONCENTRATE CONVEYOR COPPER COMPANY "A"
154)
-------
10.6
DUST DENSITY
mg / m3
RESPIRABLE
FRACTION
ONLY
NO FOG
TOTAL DUST
DENSITY
WATER FLOW
60 m I / mi n
CHARGED FOG
WATER FLOW
30 ml / mi n
CHARGED FOG
COPPER C 0. "A "
DATA FROM CONCENTRATE CONVEYER
-------
EXPERIMENTAL STUDY COPPER COMPANY A CONCENTRATE
PLANT DROP BOX
RESPIRABLE DUST ONLY
INITIAL DUST LEVEL AVERAGE OF II RUNS 6.95 mg/m3
DUST LEVEL WITH (+) FOG AVERAGE OF 7 RUNS 2.45 mg/m:
NET REDUCTION —65.4%
6'91~45 100 = 65.4 %
b.
•«•*-£.
0
o
Q
»
TOP VIEW
BELT
FLOW
\DRIVE
ROLLER
FOG GUN-
GCA UNIT
•DROP BOX
5'
FRONT VIEW
BTG
-------
•RANSBURG REA
TYP — 4 PLACE S
GUN
WORK
ARE A
DOORWAY
RAI LROAD
BOX CAR
SAND
TEST SET-UP AT
CASTING CO. A
(57,
-------
TOTAL RESP1RABLE DUST
FREE SILICA ONLY
LEVELS OF RESPIRABLE DUSV
15
10
1.5
INITIAL ( TOTAL )
DUST LEVEL
mg
/ m3
1.0
h 0.5
CASTING CO. 'V
INITIAL FREE
SILICA LEVEL
EFFECT OF
(4-) CHARGED
FOG I20ml/min
EFFECT OF
(-I-) CHARGED
FOG 120 ml / min
-------
160
140
120
100
80
60
40
20
NO FOG
DUST DENSITY
ARBITRARY UNITS
SAMPLE TAKEN ON
WORKMAN IN THE ENCLOSURE
EFFECT OF (+) CHARGED FOG ON DUST
LEVELS IN FOUNDRY BAG SPLITTING ROOM
MATERIAL CREAM-TEX
32% ALUMINA
52% SILICON DIOXIDE
STEEL COMPANY B
DATA TAKEN WITH MSA PERSONNEL
SAMPLERS
FOG WATER FLOW 45 ml / min
FOG GUN AIR FLOW 150 SCFH
AREA SAMPLES IN .ENCLOSURE
5* WIDE , 31 HIGH , 2 '/fc' DEEP
TWO LOCATIONS (A,B)
A
NO FOG
B
NO FOG
(+) FOG
(+) FOG
(+)FOG
-------
TECHNICAL REPORT DATA
(Please read Imtructiom on rtie reverie before completing)
1. REPORT NO.
EPA-600/7-77-131
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Use of Electrostatically Charged Fog for Control of
Fugitive Dust Emissions
5. REPORT DATE
November 1977
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Stuart A. Hoenig
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
University of Arizona
Department of Electrical Engineering
Tucson, Arizona 85721
10. PROGRAM ELEMENT NO.
EHE623
11. CONTRACT/GRANT NO.
Grant R805228
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OP REPORT AND PERIOD COVERED
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OP REPORT AND Pt
Final; 12/76-10/77
14. SPONSORING AGENCY CODE
EPA/600/13
is. SUPPLEMENTARY NOTES
Mail Drop 61, 919/541-2925.
prOject officer for this report is Dennis C. Drehmel,
ABSTRACT
report gives results of tests of the use of electrostatically charged fog
to control a wide variety of industrial pollutants , ranging from silica flour to SO2 and
fly ash. It has been demonstrated that most industrial pollutants acquire an electro-
static charge as they are dispersed into the air. If this charged airborne material is
exposed to an oppositely charged water fog there is enhanced contact between the
particulates and the fog droplets. After contact is made, the wetted particulates
agglomerate rapidly and fall out of the atmosphere. The tests showed that, in general,
there has been significant suppression with a minimum of water fog. The technique is
therefore well suited to control of moving or fugitive dust sources where the usual
hooding and control systems cannot be applied.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lOENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Dust
Emission
Electrostatics
Fog
Air Pollution Control
Stationary Sources
Particulate
Fugitive Emissions
13B
11G
20C
14B
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report/
Unclassified
21. NO. OF PAGES
92
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
------- |