EPA-600/2-76-100
April 1976
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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 five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has -been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
demonstrate instrumentation, equipment and methodology to repair or prevent
environmental 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
EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental
Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the
views and policy of the Agency, nor does mention of trade
names or commercial products constitute endorsement or
recommendation for use.
This document is available to the public through the National Technical informa-
tion Service, Springfield. Virginia 22161
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EPA-600/2-76-100
April 1976
UNIVERSITY OF WASHINGTON
ELECTROSTATIC SPRAY SCRUBBER
EVALUATION
by
MichaelJ. Pilat and Daniel F. Meyer
University of Washington
Department of Civil Engineering
Seattle, Washington 98195
Grant No. R-803278
ROAPNo. 21ADL-048
Program Element No. 1AB012
EPA Project Officer: Dale L. Harmon
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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CONTENTS
CONTENTS iii
LIST OF FIGURES v
LIST OF TABLES vii
ACKNOWLEDGEMENTS viii
I SUMMARY AND CONCLUSIONS 1
II RECOMMENDATIONS 3
III RESEARCH OBJECTIVES 4
IV EXPERIMENTAL EQUIPMENT AND PROCEDURES 5
A. Electrostatic Scrubber Apparatus 5
1. Description of Overall System 5
2. Cooling Tower 5
3. Particle Charging Corona Sections 8
4. Water Spray Towers 10
5. Demister Section 14
6. Test Ducts 14
7. Fan 15
8. High Voltage Power Supplies 15
9. Water Supply System 16
10. Water Drain System 17
B. Description of Source Test Equipment 17
1. General 17
2. UW Mark III Cascade Impactor 17
3. Water Charge to Mass Ratio 20
4. Aerosol Charge to Mass Ratio 20
C. Description of Sources 20
iii
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Contents (concluded)
1. Dioctyl Phthalate (OOP) 20
2. Pulverized Coal Fired Boiler 22
V RESULTS 23
A. Test Conditions 23
1. Dioctyl Phthalate 23
2. Coal Fired Boiler 23
B. Particle Collection Efficiency 25
1. Dioctyl Phthalate 25
2. Coal Fired Boiler 25
VI DISCUSSION RESULTS 38
A. Dioctyl Phthalate 38
1. Influence of Gas Residence Time 38
2. Influence of Water to Gas Ratio and Applied
Nozzle Voltage 38
3. Influence of Aerosol and Droplet Charging 41
B. Pulverized Coal Fired Boiler 41
1. Influence of Applied Nozzle Voltage 41
2. Influence of Water to Gas Ratio 41
C. Error Analysis 45
VII REFERENCES 47
Appendix A - OOP Test Conditions 48
Appendix B - Pulverized Coal Fired Boiler Test Conditions 57
Appendix C - Error Analysis of Size Dependent Particle
Collection Efficiency 61
IV
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LIST OF FIGURES
1. General Layout of Electrostatic Scrubber Pilot Plant 6
2. Cooling Tower 7
3. Particle Charging Corona Section 9
4. Collection Plate Flushing System 11
5. Spray Tower #1 Nozzle Configuration 12
6. Spray Tower #2 Nozzle Configuration 13
7. UW Cascade Impactor Sampling Train 19
8. Sampling Train for Aerosol Charge to Mass 21
9. Collection Efficiency vs. Particle Size for OOP Test No. 1 26
10. Collection* Efficiency vs. Particle Size for OOP Test No. 2 27
11. Collection Efficiency vs. Particle Size for OOP Test No. 3 28
12. Collection Efficiency vs. Particle Size for OOP Test No. 4 29
13. Collection Efficiency vs. Particle Size for OOP Test No. 5 30
14. Collection Efficiency vs. Particle Size for OOP Test No. 6 31
15. Collection Efficiency vs. Particle Size for OOP Test No. 7 32
16. Collection Efficiency vs. Particle Size for OOP Test No. 8 33
17. Collection Efficiency vs. Particle Size for Coal Fired
Boiler Test No. 1 34
18. Collection Efficiency vs. Particle Size for Coal Fired
Boiler Test No. 2 35
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LIST OF FIGURES (continued)
19. Collection Efficiency vs. Particle Size for Coal Fired
Boiler Test No. 3 36
20. Influence of Gas Residence Time on Particle Collection
Efficiency 39
21. Influence of Water to Gas Ratio and Water Droplet
Charging Voltage on Particle Collection Efficiency 40
22. Influence of Aerosol and Droplet Charging on Particle
Collection Efficiency 42
23. Influence of Water Droplet Charging Voltage on Particle
Collection Efficiency 43
24. Influence of Water to Gas Ratio on Particle Collection
Efficiency 44
25. Error Bands in the Size Dependent Particle Collection
Efficiency Curves 46
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LIST OF TABLES
1. High Voltage Power Supply Units 15
2. Source Test Parameters and Measurement Techniques 18
3. Coal Analysis-As Received Basis 22
4. Summary of OOP Test Conditions 24
5. Summary of Coal Fired Boiler Test Conditions 25
6. OOP Test No. 1 Parameters - Appendix A 49
7. OOP Test No. 2 Parameters - Appendix A 50
8. OOP Test No. 3 Parameters - Appendix A 51
9. OOP Test No. 4 Parameters - Appendix A 52
10. OOP Test No. 5 Parameters - Appendix A 53
11. OOP Test No. 6 Parameters - Appendix A 54
12. OOP Test No. 7 Parameters - Appendix A 55
13. OOP Test No. 8 Parameters - Appendix A 56
14. Coal Fired Boiler Test No. 1 Parameters - Appendix B 58
15. Coal Fired Boiler Test No. 2 Parameters - Appendix B 59
16. Coal Fired Boiler Test No. 3 Parameters - Appendix B 60
17. Error Analysis for OOP Test No. 6 - Appendix C 64
18. Error Analysis for OOP Test No. 7 - Appendix C 65
19. Error Analysis for OOP Test No. 8 - Appendix C 66
vii
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ACKNOWLEDGEMENTS
The authors wish to express their appreciation for the assistance
and cooperation of the Project Officer, Mr. Dale Harmon, Chemical
Engineer in the Particle Technology Branch of the Environmental Protec-
tion Agency.
Vlll
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SECTION I
SUMMARY AND CONCLUSIONS
A 1,700 m /hr (1,000 acfm) University of Washington Electrostatic
Spray Scrubber pilot plant was designed and constructed inside a 12.2
meter (40 foot long) trailer for use in evaluating the collection effi-
ciency of particulate emissions at field locations. The pilot plant
consists of a cooling tower, two corona sections which charge the parti-
cles to a negative polarity, two spray towers into which positively
charged water droplets are sprayed and an electrostatic mist collector.
The pilot plant was tested on both a dioctyl phthalate (OOP) aerosol
and emissions from a pulverized coal fired boiler. The OOP tests showed:
a) 99.8% collection efficiency for a 0.5 micron diameter particle
when operating at a gas flow of 569 m^/hr (335 acfm), particle
and droplet charging voltages of -70 kV and +25 kV, respectively
and a water to gas ratio of 13.43 gal/1,000 acf.
b) 90% collection efficiency for a 0.5 micron diameter particle
when operating at a gas flow of about 1,700 m^/hr (1,000 acfm),
particle and droplet charging voltages of -70 kV and +25 kV,
respectively and a water to gas ratio of about 6 gal/1,000 acf.
c) 23.5% collection efficiency for a 0.5 micron diameter particle
when operating at a gas flow of 1,648 m3/hr (970 acfm), particle
and droplet charging voltages of 0 and +15 kV, respectively
(i.e., uncharged particles and charged droplets) and a water to
gas ratio of 6.18 gal/1,000 acf.
d) 10.0% collection efficiency for a 0.5 micron diameter particle
when operating at a gas flow of 1,645 m^/hr (968 acfm), no par-
ticle and droplet charging (i.e., operating as a conventional
spray tower) and a water to gas ratio of 6.20 gal/1,000 acf.
The tests on the emissions from the coal fired boiler showed:
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a) 99.1% collection efficiency for a 0.5 micron diameter particle
when operating at a gas flow of 1,694 nr/hr (997 acfm), parti-
cle and droplet charging voltages of -65 kV and +20 kV, respec-
tively and a water to gas ratio of 5.82 gal/1,000 acf. The out-
let concentration of the aerosol during this test was 0.002 gr/
sdcf.
b) 76.0% collection efficiency for a 0.6 micron diameter particle
when operating at a gas flow of 1,801 m3/hr (1,060 acfm), parti-
cle and droplet charging voltages of -60 kV and +20 kV, respec-
tively and a water to gas ratio of 2.36 gal/1,000 acf. The out-
let concentration of the aerosol during this test was 0.013 gr/
sdcf.
The OOP and coal fired boiler tests showed that the particle collec-
tion efficiency increased as:
a) The aerosol and/or droplet changed from an uncharged to a
charged state.
b) The gas residence time in the pilot plant increased.
c) The voltage applied on the water droplet spray nozzles increased.
d) The water to gas ratio (i.e., gal/1,000 acf) increased.
In conclusion, it appears that the University of Washington Electro-
static Spray Scrubber has the capability of effectively collecting fine
particles in the 0.3 to 1.0 micron diameter size range when operated
with water usage rates in the 3-6 gal/I,000 acf range. Further, the
system has a significantly higher particle collection efficiency than a
conventional water spray tower operating with no electrostatic charging.
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SECTION II
RECOMMENDATIONS
After this first year's research project on the U.W. Electrostatic
Scrubber which consisted mainly of the design and construction of the
portable pilot plant facility, extensive testing at field sites is need-
ed in order to correlate the particle collection efficiency as a function
of particle size to the design and operating parameters of this pilot
plant.
We also recommend that the results from the extensive field testing
program be used in comparison with theoretically predicted particle col-
lection efficiency as a function of size.
Finally, we recommend that the pilot plant be used to demonstrate
its effectiveness for simultaneous control of particulate and S02 emis-
sions from coal fired boilers.
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SECTION III
RESEARCH OBJECTIVES
The objectives of the research performed under the auspices of
Environmental Protection Agency Grant Number R803278-01-0 were to:
1. Demonstrate the effectiveness of the University of Washington
electrostatic wet scrubber for controlling the emissions of fine parti-
cles from coal-fired plants.
2. With a portable 1,700 m3/hr (1,000 cfm) pilot plant of the
University of Washington electrostatic wet scrubber, obtain the data
needed to design a larger electrostatic scrubber system.
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SECTION IV
EXPERIMENTAL EQUIPMENT AND PROCEDURES
A. ELECTROSTATIC SCRUBBER APPARATUS
1. Description of Overall System
The major components of the pilot plant include a gas cooling tower,
an inlet and outlet test duct, two particle charging corona sections, two
charged water droplet spray towers and a demister. Auxiliary equipment
includes transitional ductwork between major components and a fan. The
pilot plant is housed in a 12.2 meter (40 foot) long trailer and can be
easily transported to different emission sources.
The general layout of the pilot plant is shown in Figure 1. Incom-
ing gases enter the top of the trailer to be treated in the vertical gas
cooling tower and then turn vertically upward to enter the inlet test
duct. After moving down through the inlet test duct, the gases enter the
first of three horizontal passes.
The first pass contains both particle charging corona sections and
the first of two water spray towers. The two coronas are at either end
of this pass and are separated by spray tower #1. Spray tower #2 com-
prises the entire second horizontal pass and the last (third) pass con-
tains the demister.
At the outlet of the third horizontal pass, the gases enter the top
of the outlet test duct and are then directed to the fan before being ex-
hausted through the trailer roof.
2. Cooling Tower
The cooling tower is designed to lower the gas temperature to below
121°C (250°F) in order to maintain structural integrity of the system
which is constructed of steel and fiberglass reinforced plastic. The
cooling tower, as shown in Figure 2, is 0.36 meters (14 inches) in dia-
meter x 2.98 meters (9 feet - 8 inches) in height and is constructed of
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COOLING TOWER SCHEMATIC
7
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12 gage T. 304 stainless steel. Cooling water is introduced through four
ports spaced at 0.61 meter (2 feet) intervals on one side of the tower
and is sprayed vertically upward from the tower's center!ine. Four Bete
Model W 10080 F full cone stainless steel nozzles used for spraying are
capable of delivering up to 11.35 liters/min (3.0 gpm) at 50 psig. A
funnel built into the bottom of the spray tower extends through the
trailer floor for cooling water removal.
3. Particle Charging Corona Sections
Particle charging corona sections are located at either end of the
first horizontal gas passage. The corona shells are constructed from
4.76 mm (3/16 inches) wall thickness fiberglass reinforced plastic (FRP)
with interior dimensions of 0.61 meters (24 inches) wide x 1.07 meters
(42 inches) high x 1.52 meters (60 inches) long in the direction of gas
flow. Access to a corona interior is through removable 4.76 mm (3/16
inches) FRP end plates which are normally bolted to 5.08 cm (2 inches)
full perimeter face flanges on either end of a corona.
The coronas are designed to operate in either a single or double
lane gas passage mode. Switching from one to another requires rearrange-
ment of the adjustable collection plates and discharge frame(s). The
width of individual gas lane(s) for either mode is maintained at 0.30
meters (12 inches) and the discharge frame to collection plate spacing is
therefore 0.15 meters (6 inches). Figure 3 shows a cutaway schematic of
a corona set up for single lane operation.
The overall dimensions of the discharge frame shown in Figure 3 are
0.70 meters (27-1/2 inches) high x 1.14 meters (45 inches) long. The
frame is constructed from 6.35 mm x 19.05 mm (1/4 inch x 3/4 inch) T. 304
stainless steel rectangular bar stock members. Eight members each 0.69
meters (27 inches) high are spaced vertically and perpendicularly to gas
flow and form a grid type pattern.
The collection plates shown in Figure 3 are 1.05 meters (41-1/4
inches) high x 1.50 meters (59 inches) long and are constructed from 11
gage T. 316 stainless steel. The plates serve as full chamber baffles to
keep the gases within the confines of the single lane passage.
A negative corona is used to charge the particles negatively. This
is accomplished by maintaining the discharge frame(s) at a high negative
potential and the collection plates at a neutral or ground potential.
The discharge frame is electrically isolated from all other components
inside the corona. This isolation is provided by suspending the frame
on two 2.54 cm (1 inch) diameter T. 303 stainless steel rods which are
connected to porcelain insulators. The Ceramaseal Model 902B1353-6 in-
sulators are housed in 0.30 meter (12 inches) diameter x 0.61 meter (24
inches) long x 6.35 mm (1/4 inch) wall thickness plexiglass tubes which
are centered 1.07 meters (42 inches) apart and are located on top of the
corona shells. Two 0.30 meter (12 inches) to 0.36 meter (14 inches) x
7.62 cm (3 inches) FRP reducting flanges are used to join the plexiglass
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tubes to the corona top.
The insulators are continually flushed with a supply of heated purge
air. The temperature of the purge air is maintained at about 49°C
(120°F) and an even flow across a plexiglass tube section is obtained by
introducing the purge air through a distribution plate having approxi-
mately 10% hole area. The flushing face velocity of the purge air is
set at about 0.18 meters per second (0.6 feet per second). This same
purge air distribution flange also serves as a support flange in that an
insulator, and hence the discharge frame(s), is bolted directly to it.
The high voltage lead-in to the discharge frame is through one of the two
feed-through type insulators.
A water flushing system designed to clean the collection plates is
utilized in both coronas and is shown schematically in Figure 4. Two
water spray headers are situated inside the top of each corona shell.
Water is sprayed through Bete Model 45080 80° stainless steel fan nozzles
and covers the entire active portion of the collection plates.
At the nominal gas flow rate of 1,700 m^/hr (1,000 cfm), the gas
velocity in the corona is 1.45 meters per second (4.76 feet per second)
for single lane operation and 0.72 meters per second (2.38 feet per sec-
ond) for double lane operation. The corresponding gas residence times
are 1.05 and 2.10 seconds. By varying the volume of air flow through the
system, however, the gas residence time can range from 0.70 seconds
(single lane operation at 2.548 nr/hr (1,500 cfm)) to 4.20 seconds (dou-
ble lane operation at 850 nH/hr (500 cfm)).
4. Water Spray Tower
The first of two spray towers used in the pilot plant is situated
in the middle of the first horizontal gas passage (between the two
coronas) while the second spray tower comprises the entire second hori-
zontal gas passage. Both spray tower are 0.91 meters (3 feet) diameter
x 4.76 mm (3/16 inch) wall thickness and are constructed from FRP. The
length of the two spray towers is 3.05 meters (10 feet) and 7.36 meters
(24 feet) for tower #1 and #2 respectively.
A total of 27 Bete Model L-40 stainless steel full cone nozzles are
used to produce water droplets in the two towers. All nozzles spray in
the direction of gas flow (cocurrently). The first spray tower contains
nine nozzles arranged on three spray headers (three nozzles per header).
The nozzles on each header are arranged on a 0.46 meter (18 inches) dia-
meter equally spaced (120° apart) circular pattern. The arrangement of
the spraying pattern in tower #1 is shown schematically in Figure 5.
Nine headers with a total of 18 spray nozzles (two nozzles per head-
er) are employed in spray tower #2. The nozzles in this tower are
arranged in an alternately spaced vertical and horizontal pattern as
shown in Figure 6.
A positive charge is imparted to the water droplets by maintaining
the nozzles at a positive potential (direct charging). The nozzles are
electrically isolated from the spray tower walls by introducing heated
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purge air through 7.62 cm (3 inches) diameter x 10.16 cm (4 inches) long
polyvinyl chloride (PVC) entry caps which are situated on top of the two
spray towers (see Figure 5 and 6). Both the water and the high voltage
lead-in cable enter through a 6.35 mm (1/4 inch) diameter street tee fit-
ting connected to the middle of each entry cap. Individual spray nozzle
headers are also attached to the entry caps. .,
At the nominal air flow volume of 1,700 m /hr (1,000 cfm), the gas
velocity inside the spray towers is 0.72 meters per second (2.35 feet per
second). This corresponds to a gas residence time of 4.21 and 10.21 sec-
onds in spray towers #1 and #2 respectively or a total gas residence time
of 14.46 seconds. However, by varying the total air volume flow in the
pilot plant, the total gas residence time in the spray towers can be
maintained at any point between 7.23 and 21.69 seconds.
The water flow rate through all 27 spray nozzles is 28.76 liters per
minute (7.6 gpm) at 40 psig. The system can be operated with as little
as 8.33 liters per minute (2.2 gpm), however, by decreasing the pressure
to 20 psig and by shutting off the water supply to 16 (independently con-
trolled) of the 27 nozzles.
Thus, by adjusting both the air and water flow volumes, the water to
gas ratio can be maintained at any point between 1.5 and 15.2 gal/1000 acf.
5. Demister Section
The demister is situated in the middle of the third and last hori-
zontal pass and is used to remove entrained water droplets from the air
stream. The demister is identical to the coronas with the following
three exceptions:
(a) The discharge frame is maintained at a positive potential.
(b) The demister is not equipped with a collection plate flushing
system.
(c) The demister is 5.08 cm (2 inches) shorter in height.
The last point noted above necessitates an equivalent shortening of the
discharge frame and collection plates.
6. Test Ducts
The inlet and outlet test ducts are located immediately before the
first corona and immediately after the demister respectively (see Figure
1). Both test ducts are constructed from 4.76 mm (3/16 inch) wall thick-
ness FRP and are 0.30 meter (12 inches) diameter x 1.22 meters (4 feet)
long. Vertical gas flow in a downward direction is employed because it
14
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allows the most convenient positioning of the particle sizing source test
equipment used and described in Section IV-B, Description of Source Test
Equipment. The particle sizing source test equipment also dictated the
size of the test ports which are 7.62 cm (3 inches) wide x 15.24 cm (6
inches) high. The test ports are located three duct diameters downstream
and one duct diameter upstream from flow disturbances.
7. Fan
The fan used to induce the air flow (i.e., clean side) through the
pilot plant is a New York Blower Model RFE-12. The straight bladed fan
wheel and housing are constructed from FRP. The fan is driven through a
split pulley belt drive by a Westinghouse 5 HP, 208 volt, 3 phase motor
turning at 1,800 rpm and is capable of delivering up to 2,548 m3/hr
(1,500 cfm) at 20.32 cm (8 inches) water column (WC) static pressure.
The fan has a horizontal inlet and a vertical outlet. A 4.76 mm (3/16
inch) FRP wall thickness x 0.30 meter (12 inches) diameter exhaust duct
containing an adjustable damper extends up through the trailer roof.
8. High Voltage Power Supplies
Three high voltage power supply units used in the pilot plant serve
the coronas, demister and water droplet charging. All three units oper-
ate off a 110 V, 60 Hz, 1 0 supply and are equipped with multirange vol-
tage and current meters on the high voltage output side. The units are
also equipped with overvoltage and overcurrent surge protection. The
three power supplies are described in the following table.
Table 1. HIGH VOLTAGE POWER SUPPLY UNITS
Source
Coronas
Demister
Droplet
Charging
Model
Universal Voltronics
BAG - 70 - 25
Hipotronics
#860-16
Hipotronics
#825-40
-
Polarity
Negative
Positive
Positive
Rated Output
kV
70
60
25
mA
25
16
40
A Model P-30 spark rate controller manufactured by L. L. Little,
15
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Inc. is capable of maintaining the spark rate in the coronas at any pre-
set level up to 500 sparks per minute.
9. Water Supply System
All water usage and monitoring is controlled from a single control
board situated on an interior trailer side wall proximate to the inlet
test duct. Before reaching the control board, however, incoming water
passes through a filter and a Watts Model U-5 pressure reducing valve
with a controllable outlet set point between 25-75 psig. Water then
passes through a main flow meter (7.6 - 75.6 liters per minute (2-30 gpm)
Fisher-Porter Model 2235597 Ratosight rotometer) and a 2.54 cm (1 inch)
true union PVC ball valve which acts as a main shut off valve. From the
main shut off valve, the water enters a 2.54 cm (1 inch) diameter PVC
pipe which serves as a supply manifold for seven water applications in
the trailer. The seven take-offs from the supply manifold are through
1.27 cm (1/2 inch) diameter PVC pipes and all seven are equipped with
true union PVC ball valves and 0-60 psig pressure gages. The seven water
users are described below:
(a) Test duct cleaning system
One Bete Model W10080 F full cone stainless steel spray nozzle
is positioned at the top of both the inlet and outlet test ducts.
Since only infrequent cleaning is required at these two locations,
water flow rate is not monitored.
(b) Corona collection plate flushing system
The details of these two users have been specified in Section
IV.A.3. - Particle Charging Corona Sections. Again, flow is not
monitored due to infrequent use.
(c) Cooling tower spray system
This user, described in Section IV.A.2. - Cooling Tower, is
equipped with a Fisher-Porter Model 2235621 3.8 - 41.6 liters per
minute (1-11 gpm) Ratosight rotometer.
(d) Water spray towers
Water usage in each of the two water spray towers is controlled
from two supply lines. This is accomplished by splitting the flow
above the flow meter which is positioned on the 1.27 cm (1/2 inch)
diameter PVC pipe take-off from the main supply manifold. Thus, the
two lines which take-off from the supply manifold are split into
four individually controllable lines which then lead to the spray
16
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nozzle headers.
The rotometers for these two sources are Fisher-Porter Models
2235573 0.7 - 3.6 liters per minute (.2-2 gpm) and 2235621 3.8 -
41.6 liters per minute (1-11 gpm) Ratosights for spray towers #1 and
#2 respectively.
The main water control board is also equipped with necessary fit-
tings and valves to accommodate reuse of the drain water from spray tower
#2 into spray tower #1. This recycle system has not yet been put into
service, however.
10. Water Drain System
Water is currently used on a once through basis in the pilot plant
although a partial recycle system will be employed in future studies.
Individual drains leading through the trailer floor serve the cooling
tower, both corona collection plate flushing systems, both water spray
towers and the outlet test duct cleaning system. Water used to clean the
inlet test duct runs into the drain serving corona #1 and water collected
in the demister exits through the #1 spray tower drain. All drains are
equipped with water legs (locks) to insure that no air leakage into the
system occurs.
B. DESCRIPTION OF SOURCE TEST EQUIPMENT
1. General
The following table indicates the source test equipment used to
measure various parameters. Further information concerning charge to
mass measurements and the UW Cascade Impactor is given below.
2. UW Mark III Cascade Impactor
A UW Mark III Cascade Impactor was used to measure both particle
size distribution and mass concentration at both the inlet and outlet
test ducts. The impactor provides this information by segregating the
aerosol sample into eight discrete size intervals (seven collection
plates plus one final filter). The aerosol weight on each state provides
size distribution information and the total weight is used to determine
the mass concentration. The basic components of a sampling train utiliz-
ing a UW Mark III Cascade Impactor are shown schematically in Figure 7.
The impingers are used to collect water vapor in the sample air stream
and provide a basis for calculating the moisture content of the gas
17
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Table 2. SOURCE TEST PARAMETERS AND MEASUREMENT TECHNIQUES
Parameter
Equipment
Air
a. velocity and volume
b. temperature
c. moisture
d. atmospheric pressure
e. static pressure
Water Spray Towers
a. water flow
b. water charge to mass
Aerosol
a. mass concentration
b. size distribution
c. aerosol charge to mass
S-type pilot tube with
draft gage
thermometer
wet and dry bulb thermometer
and checked by volume of
condensate
barometer
Magnehelic gage
rotometers
digital multimeter
UW Mark III Cascade Impactor
UW Mark III Cascade Impactor
digital multimeter
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stream which may be checked against the wet bulb - dry bulb determina-
tion. The dry gas meter is used to determine isokinetic sampling condi-
tions as well as the total sample volume.
By conducting simultaneous particle size distribution tests at both
the inlet and outlet test ducts, the size dependent collection efficiency
curve of the pilot plant may be measured.
3. Hater Charge to Mass
The metal water traps (legs) on the drains serving both #1 and #2
spray towers are connected to ground through a digital multimeter capable
of reading milliamps. Shielded cable is used to eliminate stray current.
The current measured by the multimeter together with the water flow rate
through the spray nozzles permit determination of the water charge to
mass ratio. Proper measurement techniques require that the particle
charging corona sections be inactive to avoid measuring the influence of
the negative charges carried by the particles and that all spray nozzles
be electrically isolated from the spray tower walls.
4. Aerosol Charge to Mass Ratio
Aerosol charge to mass ratios are determined by withdrawing an aero-
sol sample between corona #1 and spray tower #1. The basic components of
this sampling train are shown schematically in Figure 8. The impinger is
used to remove any entrained water droplets and the aerosol is collected
on a 47 mm glass fiber filter. The metal filter holder is housed in a
grounded metal box and shielded cable is used to eliminate interference
from external electric fields which can cause high background current
readings. The cable is connected to ground through a multimeter capable
of measuring nanoamps. The current and the aerosol accumulation rate
(weight per time) are used to calculate the charge to mass ratio. The
dry gas meter is required to determine isokinetic sample conditions.
C. DESCRIPTION OF SOURCES
1. Dioctyl Phthalate (POP)
A OOP test aerosol was generated by an air aspiration technique de-
scribed by Parrish and Schneider (1968). The aerosol was introduced
directly into the top of the cooling tower and had an initial mass mean
diameter between 1-2 microns with a geometric standard deviation of about
2.75. The OOP aerosol at the cooling tower outlet had a mass concentra-
tion in the .008 to .14 grains/acf range.
20
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21
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2. Pulverized Coal Fired Boiler
A Riley Stoker Corporation pulverized coal fired boiler operating on
the University of Washington campus was used for a test source for the
pilot plant. The boiler is rated at 120,000 Ibs steam per hour with out-
let steam conditions of 343°C (650°F) and 400 psig. The boiler burns a
low sulfur Western United States (Utah) coal with a typical analysis as
given in Table 3.
The air stream sample taken from the boiler was obtained through a
0.15 meter (6 inches) diameter port at right angles (non-isokinetic) to
the main gas stream flow. The port is located in the boiler breeching
behind an air preheater and ahead of a conventional electrostatic pre-
cipitator.
Table 3. COAL ANALYSIS-AS RECEIVED BASIS
Item
Moisture
Ash
Volatile
Fixed Carbon
Sulfur
H.H.V.
Units
%
%
%
%
%
Btu/lb
Amount
6.66
5.12
45.73
42.49
0.65
12,819
22
-------
SECTION V
RESULTS
A. TEST CONDITIONS
1. Dioctyle Phthalate (POP)
Eight simultaneous inlet and outlet tests were conducted using the
OOP aerosol. A detailed itemization of the test conditions is presented
in Tables 6 through 13 which are located in Appendix A. The items speci-
fied in these tables include the air flow volume and temperature at the
outlet test duct, the volume of water sprayed into towers #1 and #2, the
conditions of the three power supplies (kV and mA), the inlet and outlet
test duct aerosol characteristics (mass mean diameter, standard geometric
deviation and concentration) and the collection efficiency figured on a
mass basis. As an aid to discussing the OOP test results, however, Table
4 summarizes the conditions of the eight tests.
Tests number 1 through 6 were all conducted with the aerosol and
water droplets charged to opposite polarity. The air flow through the
pilot plant, which is inversely related to the gas residence time, varied
from a low of 569 nrVhr (335 acfm) in test number 3 to a high of about
1,700 nr/hr (1,000 acfm) in test number 6. The water to gas ratio (gal/
1,000 acf) ranged from a low of 6.36 in test number 6 to a high of 13.43
in test number 3. Particle charging voltage in the corona sections was
maintained at 70 kV in all of the first six tests while the voltage main-
tained on the spray tower nozzles was either 15 or 25 kV.
Test number 7 employed uncharged aerosol and droplets while test 8
employed uncharged aerosol and charged droplets. Test number 7 corres-
ponds to operating the pilot plant as a conventional spray tower.
2. Coal Fired Boiler
Three simultaneous tests were conducted on emissions from the Uni-
versity of Washington pulverized coal fired boiler. The conditions
during the test are presented in Tables 16, 17 and 18 located in Appendix
23
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B while a summary of the test conditions is presented in the following
table.
Table 5. SUMMARY OF COAL FIRED BOILER TEST CONDITIONS
Test
No.
1
2
3
Gas Flow at Outlet
Test Duct (acfm)
997
974
1,060
Water to Gas Ratio
(gal/1,000 acf)
5.82
5.72
2.36
Voltages (kV)
Coronas
65
65
65
Spray
20
15
20
The boiler was baseloaded at about 67% of rated capacity during the
three tests and sootblowing was encountered during the second test.
B. PARTICLE COLLECTION EFFICIENCY
1. Dioctyl Phthalate
Figures 9 through 16 show the collection efficiency of the pilot
plant as a function of particle size. Included in these figures are some
of the operating condition parameters which are present in Table 4 plus
the overall particle collection calculated on a mass basis.
The collection efficiency for a 0.5 micron diameter particle ranged
from a high of 99.8% in test number 3 to a low of 10.0% in test number 8.
These same two tests had an overall mass basis collection efficiency of
99.68% and 24.98% respectively.
When operating the pilot plant at the nominal air flow of about
1,700 m3/hr (1,000 cfm) with both aerosol and water droplets charged and
with a water to gas ratio of about 6 gal/1,000 acf, the collection effi-
ciency of a 0.5 micron diameter particle was about 90% while the overall
mass basis collection efficiency was 89.00% (see Figure 14, test number
6).
2. Coal Fired Boiler
Figure 17, 18 and 19 present the particle collection efficiency of
25
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the pilot plant as a function of particle size. The overall mass basis
particle collection efficiency plus some pilot plant operating conditions
are also noted on these three figures.
The collection efficiency of a 0.5 micron diameter particle ranged
from a high of 98.0% in test number 1 to a low of 47.0% in test number 3.
These same two tests had overall mass basis particle collection effi-
ciencies of 99.48% and 96.09% for tests 1 and 3, respectively.
37
-------
SECTION VI
DISCUSSION OF RESULTS
A. DIOCTYL PHTHALATE (OOP)
1. Influences of Gas Residence Time
The particle collection efficiency is directly related to the gas
residence time such that an increase in gas residence time provides an
increase in particle collection efficiency at any given particle size.
For example, test 4 used both spray towers and had a 37% longer gas re-
sidence time than test 2 which used only one spray tower. Accordingly,
test 4 had a collection efficiency for a 0.5 micron diameter particle
of 98.5% compared to 91.5% for test 2. The corresponding overall mass
basis collection efficiency increased from 94.68% to 98.14%.
The size dependent collection efficiency curves for these two tests
have been plotted on one graph and are presented in Figure 20. This
figure shows that the particle collection efficiency becomes independent
(i.e., is unchanged) of gas residence time for particle diameters greater
than about 4-6 microns.
2. Influence of Water to Gas Ratio and Applied Nozzle Voltage
Particle collection efficiency increases with both increasing water
to gas ratios and increasing voltage applied on the water spray nozzles.
Thus, the size dependent particle collection efficiency curve can be
maintained by an increase in the water droplet charging voltage and a
decrease in the water to gas ratio. This may be seen in a comparison of
test 4 (8.90 gal/1,000 acf and 25 kV droplet charging voltage) and test
5 (12.71 gal/1,000 acf and 15 kV droplet charging voltage). The particle
collection efficiency curves for these two tests are presented in Figure
21 which shows that the difference in particle collection efficiency is
only 1.6/o at 0.5 micron diameter, 0.2% at 0.75 microns diameter and 0.1%
at 1.0 and 2.0 micron diameters.
38
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3. Influence of Aerosol and Droplet Charging
Particle collection efficiency at any given size increases when
either the particles or water droplets change from an uncharged to a
charged condition. For example, test 7 utilized uncharged particles with
uncharged droplets (conventional spray tower), test 8 utilized uncharged
particles with charged droplets, and test 6 utilized charged particles
with charged droplets. The size dependent particle collection efficiency
curves for these three tests have been combined in Figure 22 which shows
that the collection efficiency for a 0.5 micron diameter particle in-
creases from 10.0% in test 7 (both uncharged) to 23.5% in test 8 (parti-
cles uncharged and droplets charged) to 91.5% in test 6 (both charged).
The corresponding overall mass basis particle collection efficiencies in-
creased from 24.98% to 49.75% to 89.00%.
B. COAL FIRED BOILER
1. Influence of Applied Nozzle Voltage
Particle collection efficiency at any given particle size increases
as the water droplet charging voltage is increased. For example, test 2
(15 kV droplet charging voltage) had a 96.5% collection efficiency for a
0.5 micron diameter particle while test 1 (20 kV droplet charging vol-
tage) had a corresponding 99.1% collection efficiency. Collection effi-
ciency at other particle sizes may be seen in Figure 23 which presents
the efficiency curves for these two tests. The overall mass basis col-
lection efficiency was 98.07% and 99.48% for tests 2 and 1, respectively.
2. Influence of Water to Gas Ratio
Particle collection efficiency is directly related to the water to
gas ratio (gal/1,000 acf) such that an increase in water to gas ratio
provides an increase in the particle collection efficiency at any given
particle size. For example, test 3 (2.36 gal/1,000 acf) and a 76.0% col-
lection efficiency at 0.6 micron diameter while the corresponding effi-
ciency for test 1 (5.82 gal/1,000 acf) was 97.8%. The particle size
dependent collection efficiency curves for these two tests are presented
in Figure 24. The overall mass basis particle collection efficiency in-
creased from 96.09% to 99.48% for test 3 and 1, respectively. This re-
latively small increase in overall efficiency is due to the fact that the
mass mean diameter of the coal fired boiler particles at the inlet test
duct is quite large (averages about 7.25 microns).
41
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C. ERROR ANALYSIS
The development of an expression for the maximum error in the size
dependent collection efficiency curve is presented in Appendix C. This
expression was used to calculate the error bands for OOP test 7 (parti-
cles and droplets uncharged), 8 (particles uncharged and droplets
charged) and 6 (particles and droplets charged). A summary of the cal-
culations are also presented in Appendix C (Tables 17-19).
Figure 25 shows the size dependent particle collection efficiency
curves from these three tests together with their respective error bands.
All three tests had a maximum error due to weighing uncertainties of
about ±4% for particle sizes less than about 2 microns diameter. The
uncertainty increased at larger particle sizes due to the fact that size
distribution of the test sample was relatively small (average mass mean
diameter - 1.32 microns).
Figure 25 also shows that the error bands do not overlap for parti-
cle diameters less than 4.5 microns and, thus, the differences in the
efficiency curves result from differences in the pilot plant operating
conditions (e.g., particle and droplet charging) and not from uncertain-
ties introduced by weighing errors.
45
-------
c
O)
c
o
o
0>
o
u
o
o.
c
0)
•o
c
«
a.
0)
•o
O)
N
O)
JC
•o
o
o
h.
k.
LLl
to
c o
o c
^1 01
O "o
CL U
4-
-------
1.
2.
3.
Bevington, P. R..
McGraw-Hill, New
SECTION VII
REFERENCES
Data Reduction and
York, (1969).
Error for the Physical Sciences,
Oglesby, S., Jr., A Manual of Electrostatic Precipitation Technology,
Report Number APTD-0610, Prepared for The National Air Pollution
Control Administration (1970).
Parrish, E. C
of Installed
sented at
and Schneider, R. W., Review of Inspection and Jesting
Particulate Air Filters at ORNL, Pre-
Experience in
by the Inter-
High-Efficiency
Symposium On Ot
the Symposium On Operating and Developmental
the Treatment of Airborne Radioactive Wastes, Sponsored
national Atomic Energy Agency, (1968).
47
-------
APPENDIX A
48
-------
Table 6. OOP TEST NO. 1 PARAMETERS
Item
A.
B.
C.
D.
E.
Gas at Outlet Test Duct
1 . temperature
2. volume
Water
1 . water to gas ratio
2. charge per mass
High Voltage Power Supplies
1. particle charging corona sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
Aerosol
1 . inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
Collection Efficiency
1 . mass basis
2. size dependent
Units
3 °C (°F)
m /hr (acfm)
gal/1,000 acf
10"6coul/gm
kV
mA
kV
mA
kV
mA
microns
gr/sdcf
microns
gr/sdcf
°i
/£>
Amount
18.0 (64.4)
455 (774)
5.81
n.a.
70
0.8
25
2.0
50
0.2
1.53
2.95
0.0084
0.64
3.83
0.0007
92.14
See Figure 9
Note: 1) Corona #1 and spray tower #1 inactive.
49
-------
Table 7. OOP TEST NO. 2 PARAMETERS
Item
A. Gas at Outlet Test Duct
1 . temperature
2. volume
B. Water
1 . water to gas ratio
2. charge per mass
C. High Voltage Power Supplies
1. particle charging corona sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
D. Aerosol
1 . inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
E. Collection Efficiency
1 . mass basis
2. size dependent
Units
3 °C (°F)
m /hr (acfm)
gal/1,000 acf
10"6coul/gm
kV
mA
kV
mA
kV
mA
microns
gr/sdcf
microns
gr/sdcf
%
Amount
21.0 (69.8)
906 (533)
8.44
n.a.
70
0.6
25
1.7
50
0.1
1.39
2.75
0.0327
0.50
2.96
0.0019
94.68
See Figure 10
Note: 1) Corona #1 and spray tower #1 inactive.
50
-------
Table 8. OOP TEST NO. 3 PARAMETERS
Item
A. Gas at Outlet Test Duct
1 . temperature
2. volume
B. Water
1 . water to gas ratio
2. charge per mass
C. High Voltage Power Supplies
1. particle charging corona sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
D. Aerosol
1 . inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
E. Collection Efficiency
1 . mass basis
2. size dependent
Units
3 °C (°F)
m /hr (acfm)
gal/1,000 acf
10-6cou1/gm
kV
mA
kV
mA
kV
mA
microns
gr/sdcf
microns
gr/sdcf
°i
lo
Amount
18.0 (64.4)
569 (335)
13.43
n.a.
70
0.5
25
2.7
51
0.1
1.51
2.74
0.0155
2.14
1.97
0.0001
99.68
See Figure 11
Note: 1) Corona #1 and spray tower #1 inactive.
51
-------
Table 9. OOP TEST NO. 4 PARAMETERS
Item
A. Gas at Outlet Test Duct
1 . temperature
2. volume
B. Water
1 . water to gas ratio
2. charge per mass
C. High Voltage Power Supplies
1. particle charging corona sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
D. Aerosol
1 . inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
E. Collection Efficiency
1. mass basis
2. size dependent
Units
3 °C (°F)
m /hr (acfm)
gal /I, 000 acf
10~6 coul/gm
kV
mA
kV
mA
kV
mA
microns
gr/sdcf
microns
gr/sdcf
01
la
See Fie
Amount
15.0 (59.0)
875 (515)
8.90
91.6
70
1.5
25
3.8
55
0.1
1.18
2.73
0.1297
0.55
5.60
0.0024
98.14
ure 12
52
-------
Table 10. OOP TEST NO. 5 PARAMETERS
Item
A. Gas at Outlet Test Duct
1 . temperature
2. volume
B. Water
1 . water to gas ratio
2. charge per mass
C. High Voltage Power Supplies
1. particle charging corona sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
D. Aerosol
1 . inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
E. Collection Efficiency
1 . mass basis
2. size dependent
Units
3 °C (°F)
m /hr (acfm)
gal/1,000 acf
10"6 coul/gm
kV
mA
kV
mA
kV
mA
microns
gr/sdcf
microns
gr/sdcf
%
Amount
9.0 (48.2)
815 (480)
12.71
24.5
70
1.6
15
3.6
58
0.2
2.07
2.38
0.0976
0.68
5.96
0.0044
95.45
See Figure 13
53
-------
Table 11. OOP TEST NO. 6 PARAMETERS
Item
A. Gas at Outlet Test Duct
1 . temperature
2. volume
B. Water
1 . water to gas ratio
2. charge per mass
C. High Voltage Power Supplies
1. particle charging corona sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
D. Aerosol
1 . inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
E. Collection Efficiency
1 . mass basi s
2. size dependent
Units
3 °C (°F)
m /hr (acfm)
gal /I, 000 acf
10~6 coul/gm
kV
mA
kV
mA
kV
mA
microns
-
gr/sdcf
microns
-
gr/sdcf
%
Amount
14.0 (57.2)
1,629 (959)
6.36
96.2
70
1.5
25
4.3
55
0.1
1.17
2.83
0.0362
0.40
5.45
0. 0040
89.00
See Figure 14
54
-------
Table 12. OOP TEST NO. 7 PARAMETERS
Item
A. Gas at Outlet Test Duct
1 . temperature
2. volume
B. Water
1 . water to gas ratio
2. charge per mass
C. High Voltage Power Supplies
1. particle charging corona sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
D. Aerosol
1 . inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
E. Collection Efficiency
1 . mass basis
2. size dependent
Units
o °C (°F)
nr/hr (acfm)
gal/1,000 acf
10~6 coul/gm
kV
mA
kV
mA
kV
mA
microns
gr/sdcf
microns
gr/sdcf
°i
la
Amount
13.0 (55.4)
1,645 (968)
6.20
0
0
0
0
0
0
0
1.31
2.95
0.0302
0.99
3.03
0.0227
24.98
See Figure 15
55
-------
Table 13. OOP TEST NO. 8 PARAMETERS
Item
A. Gas at Outlet Test Duct
1. temperature
2. volume
B. Water
1 . water to gas ratio
2. charge per mass
C. High Voltage Power Supplies
1. particle charging corona sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
D. Aerosol
1 . inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
E. Collection Efficiency
1 . mass basis
2. size dependent
Units
3 °C (°F)
m /hr (acfm)
gal/1,000 acf
10~6 coul/gm
kV
mA
kV
mA
kV
mA
microns
gr/sdcf
microns
gr/sdcf
of
la
See Fi<
Amount
13.0 (55.4)
1,648 (970)
6.18
23.5
0
0
15
5.4
0
0
1.49
3.04
0.0400
0.69
3.15
0.0201
49.75
fure 16
56
-------
APPENDIX B
COAL FIRED BOILER TEST CONDITIONS
57
-------
Table 14. COAL FIRED BOILER TEST NO. 1 PARAMETERS
Item
A. Boiler Steam Rate
B. Gas at Outlet Test Duct
1 . temperature
2. volume
C. Water
1 . water to gas ratio
2. charge per mass
D. High Voltage Power Supplies
1. particle charging corona
sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
E. Aerosol
1 . inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
F. Collection Efficiency
1 . mass basis
2. size dependent
Units
103kg/hr(103lb/hr)
3°C (°F)
m /hr (acfm)
gal /I, 000 acf
10~6 coul/gm
kV
mA
kV
mA
kV
mA
microns
-
gr/sdcf
microns
-
gr/sdcf
01
10
Amount
176 (80)
24.5 (76.1)
1,694 (997)
5.82
40.9
65
1.2
20
11.0
55
0.3
9.04
3.34
0.402
2.30
2.13
0.002
99.48
See Figure 17
58
-------
Table 15. COAL FIRED BOILER TEST NO. 2 PARAMETERS
Item
A. Boiler Steam Rate
B. Gas at Outlet Test Duct
1 . temperature
2 . vo 1 ume
C. Water
1 . water to gas ratio
2. charge per mass
D. High Voltage Power Supplies
1. particle charging corona
sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
E. Aerosol
1. inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
F. Collection Efficiency
1. mass basis
2. size dependent
Units
103kg/hr(103lb/hr)
3°C (°F)
m/hr (acfm)
gal/1,000 acf
10~6 coul/gm
kV
mA
kV
mA
kV
mA
microns
gr/sdcf
microns
gr/sdcf
V
h
Amount
181 (82)
27.0 (80.6)
1,723 (1,014)
5.72
20.4
60
1.0
15
2.2
55
0.2
6.69
3.98
0.347
2.04
2.13
0.007
98.07
See Figure 18
59
-------
Table 16. COAL FIRED BOILER TEST NO. 3 PARAMETERS
Item
A. Boiler Steam Rate
B. Gas at Outlet Test Duct
1 . temperature
2. volume
C. Water
1 . water to gas ratio
2. charge per mass
D. High Voltage Power Supplies
1. particle charging corona
sections
a. voltage
b. current
2. water spray tower sections
a. voltage
b. current
3. demister
a. voltage
b. current
E. Aerosol
1 . inlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
2. outlet test duct
a. mass mean diameter
b. geometric standard deviation
c. concentration
F. Collection Efficiency
1 . mass basis
2. size dependent
Units
03kg/hr(103lb/hr)
3°C (°F)
m /hr (acfm)
gal/1,000 acf
10"6 coul/gm
kV
mA
kV
mA
kV
mA
microns
-
gr/sdcf
microns
-
gr/sdcf
%
Amount
176 (80)
35.0 (95.0)
1,801 (1,060)
2.36
14.1
60
1.5
20
2.7
55
0.4
5.54
2.14
0.338
2.38
2.04
0.013
96.09
See Figure 19
60
-------
APPENDIX C
ERROR ANALYSIS OF SIZE DEPENDENT COLLECTION EFFICIENCY
61
-------
1 . General
Bevington (1969) reports that the fractional error (e) of the pro-
duct of two variables is simply the sum of fractional errors of the two
variables.
For, X = YZ
Simarly, for an expression of the sum of two variables, the actual
(6) errors are additive.
For, X = Y + Z
6X = <$Y + 6Z
The fractional (e) and actual (6) errors of a variable (X) are re-
lated by:
ex = 6x/x
2. Particle Collection Efficiency
The particle collection efficiency for a control device (n) is re-
lated to the inlet and outlet concentrations (C^ and C ) by:
Thus, the fractional error in this collection efficiency (e ) is
given by: n
en = % - CQ)
or
en = 6(C. - C0)/(C. - CQ) + 6Ci/Ci (1)
Assuming that the only errors introduced in the concentrations terms
(C-j and C0) result from weighing uncertainties, the actual error in the
concentration is related to two times the weighing error (We) because the
concentration term is calculated from the difference in the final and
tare weights (Wf and W^) of the collected sample.
62
-------
C a Wf - Wt
or
6C a <5Wf + 6Wt
a 2 We
Equation (1) may be rewritten:
en a 4V(Ci - Co} + 2We/Ci (2)
Equation (2) can be used to calculate the fractional error in par-
ticle collection efficiency by introducing a conversion factor to change
C-j and C0 to weight terms. It should also be noted that equation (2) is
valid for either the overall collection efficiency or the efficiency cal-
culated at any given particle size.
3. Application
Equation (2) has been used to calculate the fractional and actual
errors in the particle collection efficiency for OOP tests 6, 7 and 8.
The following three tables (17, 18 and 19) show the particle size, inlet
and outlet particle concentrations, collection efficiency and fractional
and actual errors in the collection efficiency.
63
-------
Table 17. ERROR ANALYSIS FOR OOP TEST 6.
Particle
Size
(microns)
0.33
0.38
0.44
0.52
0.60
0.70
0.82
0.96
1.11
1.51
2.06
2.80
3.80
5.17
7.02
Concentrations
(gr/sdcf)
Inlet
0.00101
.00119
.00137
.00156
.00173
.00189
.00201
.00210
.00211
.00207
.00184
.00149
.00112
.00077
. 00048
Outlet
0.00014
.00014
.00014
.00014
.00014
.00014
.00013
.00013
.00012
.00011
.00009
.00008
.00006
.00005
.00003
Collection
Efficiency
(«)
85.8
88.0
89.6
90.8
91.9
92.7
93.4
94.0
94.3
94.9
95.1
95.0
94.6
94.0
92.8
Fractional
Error
±0.074
± .063
± .053
± .047
± .042
± .038
± .035
± .034
± .034
± .035
± .038
± .047
± .064
± .094
± .150
Actual
Error
(%)
± 6.3
± 5.5
± 4.7
± 4.3
± 3.8
± 3.5
± 3.3
± 3.2
± 3.2
± 3.3
± 3.6
± 4.5
± 6.0
± 8.8
±13.9
64
-------
Table 18. ERROR ANALYSIS FOR OOP TEST 7.
Particle
Size
(microns)
0.34
0.46
0.53
0.62
0.72
0.84
0.98
1.14
1.56
2.11
2.87
3.90
4.56
5.31
6.19
7.21
Concentrations
(gr/sdcf )
Inlet
0.00091
.00105
.00120
.00133
.00146
.00157
.00165
.00170
.00169
.00155
.00131
. 001 03
.00089
.00075
.00062
.00050
Outlet
0.00088
. 00097
.00107
.00114
.00121
.00124
.00124
.00124
.00115
.00099
.00079
.00059
. 00049
.00045
.00032
.00025
Collection
Efficiency
(%)
3.9
7.6
11.0
14.2
17.5
21.1
24.9
26.8
31.7
36.5
39.9
43.2
44.8
46.4
48.0
49.5
Fractional
Error
±1.595
± .616
± .388
± .272
± .211
± .168
± .135
± .112
± .106
± .105
± .116
± .139
± .156
± .234
± .212
± .256
Actual
Error
(%)
± 6.2
± 4.7
± 4.2
± 3.7
± 3.7
± 3.5
± 3.4
± 3.0
± 3.4
± 3.8
± 4.6
± 6.0
± 7.0
±10.8
±10.2
±12.7
65
-------
Table 19. ERROR ANALYSIS FOR OOP TEST 8.
Particle
Size
(microns)
0.34
0.40
0.47
0.54
0.63
0.74
0.86
1.00
1.59
2.18
2.94
4.00
5.44
7.40
8.62
Concentrations
(gr/sdcf)
Inlet
0.00093
.00110
.00128
.00146
.00163
.00180
.00195
.00208
.00219
.00209
.00182
.00148
.00112
.00078
.00064
Outlet
0.00089
.00096
.00101
.00105
.00106
.00106
.00106
.00102
.00082
.00065
.00049
.00034
.00021
.00013
.00009
Collection
Efficiency
(%)
4.6
13.1
20.7
27.8
34.8
40.9
45.9
50.8
62.5
68.7
73.2
77.3
80.9
83.9
85.2
Fractional
Error
±1.572
± .480
± .264
± .182
± .137
± .100
± .093
± .080
± .066
± .065
± .073
± .086
± .105
± .156
± .187
Actual
Error
tt)
± 7.2
± 6.3
± 5.5
± 5.0
± 4.8
± 4.1
± 4.2
± 4.1
± 4.1
± 4.5
± 5.3
± 6.6
± 8.5
±13.1
±15.9
66
-------
TECHNICAL REPORT DATA
(Please read instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-7 6-100
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
University of Washington Electrostatic Spray
Scrubber Evaluation
5. REPORT DATE
April 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Michael J. Pilat and Daniel F. Meyer
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
University of Washington
Department of Civil Engineering
Seattle, Washington 98195
10. PROGRAM ELEMENT NO.
1AB012; ROAP 21ADL-048
11. CONTRACT/GRANT NO.
Grant R-803278
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 12/74-12/75
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES project officer for this report is D.L. Harmon, Mail Drop 61,
Ext 2925.
IB. ABSTRACT
repOr(. gjves results of an evaluation of the effectiveness of a 1700
cu m/hr (1000 cfm) portable electrostatic spray scrubber in controlling fine particle
emissions. The multiple-pass scrubber, designed, constructed, and tested by the
University of Washington, combines oppositely charged aerosol particles and water
droplets in two water spray towers. Negatively energized aerosol charging sections
(coronas) precede each spray tower. The pilot plant was tested on artificially gene-
rated dioctyl phthalate (DOP) aerosol and on emissions from a pulverized coal-fired
boiler. Collection of a 0. 5 micron diameter DOP particle ranged from 10. 0 to 99. 8%.
The 10% test was conducted with all high voltage sources inactive. The overall mass
collection efficiency for the two DOP tests was 24. 98% and 99. 6%, respectively. The
boiler emission tests showed a collection efficiency for a 0. 5 micron diameter par-
ticle ranging from 47. 0% to 98. 0%. Conditions during the 47. 0% test included a low
water spray rate. Because of the relatively large inlet size distribution, the overall
mass collection efficiency decreased only from 99. 58% to 96. 09% for the two boiler
emission tests.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Air Pollution
Scrubbers
Electrostatics
Dust Control
Aerosols
Coal
Combustion
Air Pollution Control
Stationary Sources
Fine Particles
Collection Efficiency
Dioctyl Phthalate Aero-
sol
13B
07A
20C
07D
2 ID
21B
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
75
2O. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
67
------- |