Environmental
Sndysiirial
laboratory
Wowsmber 1979
TD
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Selected Experiments,
1978
Interagency
Energy/Environment
R&D 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 INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of ttie transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Mention of trade names or commercial products does not con-
stitute 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-600/7-79-238
November 1979
EPA/IERL-RTP Pilot Electrostatic
Precipitator - Selected Experiments, 1978
by
D.W. VanOsdell (RTI), LE. Sparks, G.H. Ramsey,
and B.E. Daniel
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Program Element No. EHE624A
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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ABSTRACT
This report deals with experiments run on a pilot-scale electrostatic
precipitator located at IERL-RTP. The precipitator is a dedicated
experimental tool which is operated for experiments originated and
designed both in-house and by EPA contractors.
Five distinct test series conducted between March and October 1978
are described in this report. The areas of study were precharger
operation, precipitator operating characteristics, reentrainment,
parameter variation with position within precipitator, and effects of
humidity.
The results of the precharger test series were inconclusive; removal
efficiency was 10 to 20 percent better with the precharger for most size
ranges, but its operation was erratic in this preliminary test. The
reentrainment test demonstrated that sparking produced more and larger
particulate than other reentrainment mechanisms. No pattern of size
distribution change was established.
The study of flow, mass, and particle size as a function of sample
probe position showed that parameter variations do exist. The data
collected was not sufficient to fully establish the differences.
The study of the effects of humidity on collection efficiency
demonstrated that increased moisture had a strong impact on improved
performance. The moisture lowers the particulate resistivity, allowing
increased electrical fields. Efficiency correlated well with voltage in
the form:
P = 6.59xl08V"5-46
where P = penetration, %
V = voltage, kV.
2
The correlation coefficient, r , was 0.97.
-------
TABLE OF CONTENTS
Abstract ii
List of Figures iv
List of Tables v
Acknowledgment vi
1.0 Summary 1
2.0 IERL-RTP Pilot-Scale ESP 3
2.1 Introduction 3
2.2 Design Features 3
2.3 Particulate Measurements 12
3.0 Preliminary Precharger Experiments, March 1978 15
3.1 Introduction 15
3.2 Design of Experiment 16
3.3 Results 18
4.0 ESP Efficiency Runs 23
4.1 Introduction 23
4.2 Results 23
5.0 Reentrainment Studies 28
5.1 Introduction 28
5.2 Results 28
6.0 Parameter Variation with Position in ESP 36
6.1 Introduction 36
6.2 Design of Experiment 36
6.3 Results 36
7.0 Humidification Runs 47
7.1 Introduction 47
7.2 Experimental Design 47
7.3 Results 47
7.4 Conclusions 52
References 54
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LIST OF FIGURES
No. Page
2.1 Diagram of pilot-scale ESP 4
2.2 Clean-plate VI curve for pilot-scale ESP 11
3.1 Schematic drawing of EPA/SoRI precharger, March 1978 17
3.2 Inlet and outlet size distributions, precharger runs 19
3.3 Penetrations for precharger runs 20
3.4 Precharger operating parameters, March 16, 1978 21
3.5 Precharger operating parameters, March 21, 1978 22
4.1 Effect of inlet particle size on efficiency 25
4.2 Particle penetrations; efficiency runs 3/28/78 to
3/30/78 and 5/8/78 to 5/11/78 26
4.3 Particle penetrations, efficiency runs, 5/12/78 to 5/17/78. .27
5.1 Reentrainment study, April 8, 1978 30
5.2 Reentrainment study, April 7, 1978 31
5.3 Size distributions for April 8, 1978, reentrainment study . .32
5.4 Size distributions for April 7, 1978, reentrainment study . .33
5.5 Size distributions for April 7, 1978 34
6.1 Velocity distribution in ESP, May 30, 1978 37
6.2 Velocity distribution in ESP, May 31, 1978 38
6.3 Mass loading variation in ESP 39
6.4 Variation of size distribution within ESP 40
6.5 Particle size distributions at different sampling
locations, May 31, 1978 41
6.6 Particle distributions at different sampling
points, June 1, 1978 42
6.7 Particle size distributions at different sampling
positions, June 5, 1978 43
6.8 Effect of particle generation equipment
temperature on size distribution, June 6, 1978 45
6.9 Effect of particle generation equipment
temperature on size distribution, June 7, 1978 4°
7.1 Correlation of voltage and penetration, exponential fit . . .49
7.2 Correlation of voltage and penetration, power law fit . . . .50
7.3 Penetrations for humidification runs 51
7.4 VI curves for ESP Section 1 53
IV
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LIST OF TABLES
No. Page
2.1 Flow Distributions at Different Plate Spacings 6
3.1 Precharger Runs, March 1978 18
4.1 ESP Conditions During Efficiency Runs 24
5.1 Summary of the Operating Conditions and the
Number of Distributions (April 7 and 8, 1978) 29
7.1 Summary of Humidification Runs 48
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ACKNOWLEDGEMENT
The assistance of coauthor VanOsdell is acknowledged. His contri-
bution was funded under U.S. Environmental Protection Agency Grant No.
R805897 with Research Triangle Institute.
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1.0 SUMMARY
This report deals with experiments run on a pilot-scale electrostatic
precipitator (ESP) located at IERL-RTP. The ESP is a dedicated experimental
tool which is operated for experiments originated and designed both in-
house and by EPA contractors. Experiments designed by contractors are
generally reported separately; work which originated in-house and was
completed between March and October 1978 is included in this report.
This experimental work falls into five categories, each described
in a separate section of the report. The first group of runs were the
preliminary precharger experiments, March 1978. An experimental pre-
charger test section designed by Southern Research Institute was installed
in the ESP and operated for 3 days. The test was designed more as a
trial run for the precharger concept than as a complete experimental
investigation. The results were inconclusive, although the precharger
appeared to improve collection. A second-generation precharger has
since been installed permanently on the ESP.
The second data set was concerned with general characterization of
ESP operation, with particular attention to ESP efficiency. The data
indicate that the ESP electrical conditions control efficiency and that
back-corona and sparking control electrical conditions.
A series of runs were made in April 1978 to study reentrainment
effects. Only 2 days were devoted to the study, and scatter makes the
data difficult to interpret. Rapping appears to generate a larger
particle size distribution than that which is generated by simple viscous
reentrainment.
The effect of sample location within the ESP on the values of some
experimental variables was investigated with several runs in May and
June 1978. The velocity profile across the ESP is relatively flat
except within 2 cm or so of the walls. Mass loading increases slightly
toward the wall, and there is an increase in the mean diameter as the
probe is moved closer to the wall.
-------
The last series of runs included in this report is a 10 run set
concluded in October 1978. The humidity of the carrier gas was changed
by steam injection, and its effect on ESP operation studied. The data
indicate that the increased humidity improves performance and that the
improved performance is due to improved electrical characteristics (re-
duced resistivity) of the dust. The overall penetration correlated very
well with ESP voltage. The best fit was obtained with a power function:
penetration was inversely proportional to voltage to the 5.45 power.
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2.0 IERL-RTP PILOT-SCALE ESP
2.1 INTRODUCTION
The IERL-RTP pilot-scale ESP was constructed as a dedicated experi-
mental tool for the investigation of factors which influence ESP operation.
The performance of an ESP can be described in terms of inputs (dust, gas
rate and conditions, electrical parameters, etc) and its functional
characteristics (number of sections, flow channels, plate areas, baffling,
etc.). The complexity of the total ESP system, the cost of experimenta-
tion, and the difficulty of controlling variables preclude careful
single-variable study in an industrial ESP. The pilot-scale ESP was
built to overcome these difficulties. The pilot unit has the flexibility
to allow the study of the effects of individual functional groups on ESP
performance. To achieve this flexibility, the pilot-scale ESP features:
1. readily adjustable plate spacing,
2. readily adjustable wire number, spacing, and type,
3. temperature control from ambient to 350°C,
4. gas velocities from 0.3 to 6.0 m/sec,
5. sampling ports between each pair of sections, and
6. extensive electrical monitoring equipment.
2.2 DESIGN FEATURES
Physical Characteristics
The pilot-scale ESP consists of an inlet section, transition/test
section, and four dust collection sections followed by ducting which
leads to an exhaust blower and stack. In cross section the ESP is
roughly 2 m high by 1 m wide overall, and the overall length is about 15
m. The ESP was designed and installed by Denver Research Institute* and
was fabricated by Stainless Equipment Company**. Figure 2.1 is an
elevation of the ESP, roughly to scale.
The inlet section of the ESP is about 4 m long, with the same cross
section as the remainder of the unit. Ambient air is drawn directly
into the ESP through a coarse screen. The burners used for temperature
control and the aerosol and steam injection ports are located in this
section.
Denver Research Institute, University of Denver, Denver, Colorado 80210.
**
Stainless Equipment Company, 2829 S. Santa Fe Drive, Englewood, Colorado 80110.
3
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- STEAM INJECTION
•AEROSOL INJECTION
TO ORIFICE
PLATE AND
BLOWER
SAMPLING
PORTS
A B
SAMPLING
PORTS
C
SAMPLING
PORTS
D
SAMPLING
PORTS
E
SAMPLING
PORTS
F
BURNERS I 1
i i n
o
o
o
11
0
o
«:
o
0
0
(E)
^•^
®
0
^•^
(D
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RAPPER
BOX
SECTION
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SECTION
2
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SECTION
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'
SECTION
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HOPPER
INLET TRANSITION/TEST
SECTION SECTION
Figure 2.1 Diagram of pilot-scale ESP.
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The transition/test section normally serves only to allow flow
development as the gas nears the sampling ports. This section can be
removed to allow insertion of test modules of various types.
There are four identical dust collection sections in the direction
of flow. There is only one lane for gas flow; the collection plates are
1.22 m square and parallel. Plate-to-plate spacing can be readily
varied from 12.7 to 38 cm. The specific collector area (SCA) of the ESP
2 3
is 28 m /m /sec at a plate spacing of 23 cm and a gas velocity of 1.5
m/sec. The discharge electrodes are wires hung from an overhead support;
they can easily be moved to change the number of wires, wire-to-wire
spacing, and wire type. Access to the wires is through the hinged side
of the pilot unit.
Gas Flow and Conditioning
The carrier gas in the ESP is ambient air; the air can be condi-
tioned by heating, steam injection, gas injection, and aerosol injection.
Flow distribution has been measured within the ESP and is relatively
uniform. Although plate spacing is variable in the dust collection
sections, the inlet and outlet duct sizes are fixed. Transition plates
before the first section and after the last reduce the abruptness of the
change in cross section. These plates do not ensure a totally uniform
flow field, particularly at the inlet of the first dust collection
section at narrow plate spacing. As might be expected, the flow rate is
highest toward the center of the flow lane (Table 2.1), with a slight
drop at the vertical centerline, probably due to the wires. The coefficient
of variation (CV) of the flow rate is used as a measure of smoothness of
flow. The narrowest plate spacing has the highest variation for two
reasons: the transition is sharpest, and the velocity traverse includes
more points close to the wall because the traverse point spacing is
reduced at close plate spacings.
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Table 2.1. Flow Distributions at Different Plate Spacings
Plate Spacings
Volumetric
Flow Rate
Low
Medium
High
Range of CV in
Each Section
38 cm
Avg. Velocity, CV,
m/sec %
38.4 46
100.7 45
188.0 49
15-25%
25 cm
Avg. Velocity,
m/sec
65.6
98.5
182.0
0.10-0.20
10-20%
13 cm
CV, Avg. Velocity, CV,
% m/sec %
37 31 .4 56
43 78.4 66
58 138.0 58
0.05-0.38
5-38%
Baffling is used extensively throughout the ESP to reduce the
extent of sneakage. Sneakage is estimated based on flow measurements
made in the hoppers, between sections, and through the top of the ESP.
It is estimated that sneakage through the top of the impactor sections
amounts to 7 to 9 percent of the gas flow and that sneakage through the
hoppers amounts to about 3 percent of the gas.
Temperature of the ESP is controlled by two heating systems. The
primary system consists of three 125,000 kcal/hr LPG burners. The
temperature of the ESP can be controlled to between ambient and 350°C.
The second heating system consists of electric strip heaters in the dust
collection sections which are designed to make up heat losses down the
length of the ESP.
The'gas burners are controlled by a thermocouple in the inlet
section. This control thermocouple maintains the temperature within
±5°C of the setpoint. There are temperature gradients both vertically
-------
within each section and down the length of the ESP (in spite of the
supplementary heaters). At various burner rates and with different
burners, the vertical temperature gradient is 30 to 45°C in the inlet
section. Vertical gradients have not been determined in the dust
collection sections. Temperature drop down the length of the ESP
amounts to about 10°C per section even with the supplementary heaters.
The ESP can be heated to its maximum operating temperature in about
an hour with the three main burners on full. After attaining the operating
range, the temperature can be maintained with only one burner.
Humidity Control
Humidity is controlled (above ambient water loadings) by steam
injection. An LPG-fired boiler generates the steam, which is injected
under pressure. The most commonly used pressure has been 378 kPa
absolute. Steam flow rate is not monitored.
Aerosol Generation/Dispersion
Aerosol can be injected into the ESP at five ports just upstream of
the temperature controlling thermocouple. The dust used to date has
been flyash from Illinois coal burned at a Detroit Edison Co. power
plant. The flyash to be reentrained is delivered to a hopper by an
adjustable screw feeder. Low-cost, commercial sandblast guns draw on
the hopper and inject the flyash into the ESP. A cyclone is installed
in the line between the feeder hopper and the sandblast guns to remove
the largest particles and reduce particle fallout in the inlet region of
the ESP. Air pressures of 2 to 8 MPa (10 to 60 psig) have been used to
drive the aerosol injection; at 3 MPa (15 psig), an air flow of about
15.5 a/sec (10 scfm) is required. The dust from the sandblast guns is
directed into the air flow in the ESP to maximize its dispersal.
Operation has been studied with two and three sandblast guns. Two-
gun operation gives satisfactory results; the vertical mass distribution
at section A was determined to have a coefficient of variation of 0.14.
Measurements of the horizontal distribution at the middle port of section
A had a coefficient of variation of 0.12 for a 25-cm plate spacing and
0.04 for a 38-cm plate spacing, indicating that the dust is well distributed
across the duct.
7
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Electrical System
The four dust collection sections are identical: the description
of one will suffice for all. For safety reasons, numerous electrical
and mechanical interlocks remove all voltages from the ESP sections when
the integrity of the machine is breached. These interlocks are not
included in the description below.
Transformer/Rectifier Sets--Each power supply is a Hipotronics*
T8100-10, capable of delivering 0-100 kV dc at 10 mA. Rectification is
by solid-state diodes in either half- or full-wave bridge configurations.
The output of the power supply can be filtered with a 0.01 yF capacitor,
or the capacitor can be disconnected. The power supply contains an
internal voltage divider resistor for measuring output voltage; the
return connection of the power supply is used for measuring direct
current.
The primary voltage is changed from zero to 208 V ac by a variable
transformer. Current limiting devices between the transformer output
and power supply input protect the power supply during sparkover. These
devices comprise a high inductance choke in series with high wattage
resistors which are switchable in values of zero, 5, 10, and 20 ohms.
When measuring high operating voltages and currents, the series resistance
must be lowered.
Corona Frame and Collecting Plates—High voltage is supplied to the
corona wires through the corona frame, which is a 5-cm diameter pipe 1.25
m long, with closed, rounded ends. It is suspended at each end from rods
which pass up into the rapper box. These support rods are enclosed in
cylindrical metal tunnels and terminate at the top in large corona balls
(about 20 cm in diameter). The balls rest on insulating plates across
the top of each tunnel, which serve as both electrical insulators and
seals to prevent infiltration.
The corona frame can support weighted wires in a variety of configura-
tions. Over the 1.3-m length of the high-voltage frame, 48 wire receptacles
are spaced 2.5 cm apart, allowing from 2 to 10 or 12 wires per section
to be set up quickly and easily. The receptacles are cone-shaped depressions
which match cones swaged to the upper ends of the corona wires; the wire
*
Hipotronics, Inc., Drawer A, Brewster, New York 10590.
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cones hang in the receptacles and support the weight of the wire. For
the work included in this report, the wires were a standard 0.32 cm (0.125
inch) in diameter.
2
Each collecting plate has an effective area of 1.5 m , and each is
hung from a support that travels on a rotating threaded rod. When the
rod is turned, using an external crank, the supports travel toward or
away from one another to vary the plate spacing. The motion is symmet-
rical with respect to the corona wires.
An air-operated rapper above each plate moves with it. The air
lines, flexible enough to accommodate the plate motion, also electrically
isolate the rapper from the system ground. Rapper operation is now auto-
matic, controlled by a card-programmable timer. For much of the work
reported here, operation was manual.
The collector plate is electrically isolated from its support frame
by strips of a mica-based material. The entire plate area opposite the
corona wires is electrically connected, separate from the frame and
baffles at the sides and bottom of the frame. A lead from the collector
plate in each electrical section returns to the power supply ground
through a sensing resistor, permitting direct measurement of plate
current from both collectors in each section. Separate leads from each
plate are connected externally for this measurement; however, the current
to each plate can be measured using each lead individually.
Measurement System—The measurement system of the pilot-scale ESP
consists of transducers, signal conditioning preamplifiers, digitizing
and display circuits, and a hard-copy printer. Outputs from the voltage
transducers range from zero to 1 V full-scale; from the current transducers,
from zero to 5.0 V full-scale; from the temperature tranducers, zero to
100 mV full-scale; and from the pressure transducer for the flow measure-
ment, zero to 10 V full-scale.
Voltage and current signals can be viewed directly on a dual-
channel oscilloscope, one section at a time, selected by switches. For
measurement, all signals are filtered and amplified or attenuated between
zero and 100 mV by a separate preamplifier for each signal channel. The
filtering removes noise pulses and power-line-induced pickup from the
conditioned signals and helps protect the preamplifier inputs from
surges during sparking.
9
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Preamplifier outputs are sampled in succession at the rate of about
twice a second by a multiplexer. The multiplexer output is fed to an
analog-to-digital converter (ADC). The ADC produces a three-digit
representation of the signal presented to it by the multiplexer and puts
that representation on a data bus. The data on the bus is put into the
proper display unit by an unlatching pulse fed to that unit. The unlatching
pulses are directed by a digital multiplexer that operates in the same
sequence as the signal multiplexer.
In normal operation, each display is updated approximately twice a
second. The multiplexer can be locked onto any channel for more rapid
updating.
The same data bus feeds a parallel-to-serial converter whose output
goes to a standard 80-character thermal line printer. The data are
punctuated and formatted by characters stored in a read-only memory
(ROM). A heading that can be printed manually is also stored in the
ROM. Data printing can be initiated manually at any time or can be
performed automatically at 1- or 10-minute intervals, controlled by a
digital clock. The clock operates continuously from the power line,
providing initiation pulses and time of data collection for each line on
the printer. A manual keyboard on the printer can be used to enter
information about the data being printed.
Voltage/Current Characteristics—The variation of corona current
(I) with applied voltage (V) has been measured for the pilot-scale ESP
under various conditions. As a base case, the VI curve for the ESP with
clean plates and wires and with careful alignment of all components is
presented in Figure 2.2. The VI curves for sections 1, 2, and 3 are all
essentially coincident with each other and with theoretical predictions.
The section 4 curve was different because of the different plate-to-
plate spacing, but it too is consistent with theoretical predictions. Dirty
plate VI curves tend to show measurable current before theory would
predict corona.
10
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3.0
m
O
2.0
1.0
CONDITIONS
Wires: 0.32 cm (0.125 in.) diameter
Wire-to-wire spacing: 22.8 cm (9 in.)
Plate-to-plate spacing: 25.4 cm (10 in.)
Ambient temperature: 26° C (78° F)
LEGEND
O SECTION 1
O SECTION 2
• SECTION 3
D SECTION 4
(fit
40
45
50
Voltage, kV
55
60
Figure 2.2 Clean-plate VI curve for pilot-scale ESP.
11
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2.3 PARTICULATE MEASUREMENTS
Particulate Mass Concentrations
The participate mass concentration in the pilot ESP is determined
by collecting the participate from a measured gas volume on a tared
filter and determining the collected mass gravimetrically. The sample
is collected isokinetically using a sharp-edged nozzle of 1.27-cm diameter
stainless steel tubing. The sample is normally collected over 15
o
minutes, for a sample volume of 85-142 a (3-5 ft ). The sample is
collected on a 49-mm glass fiber filter. The filter is placed in a
labeled, disposable aluminum pan; filter and pan are weighed; the filter
is inserted into the filter holder; and the sample probe assembled. The
probe is then inserted in the duct, the sampling pump is started, and
the flow rate is adjusted to give isokinetic sampling conditions. The
sample is taken from the duct centerline.
After the sample has been collected, the filter is removed, placed
in the same aluminum sample pan, and reweighed. Dust which collected in
the filter holder is brushed into the pan. The nozzle and probe assembly
are washed with acetone; the rinsings are collected in a second tared
pan. The probe wash solvent is evaporated and the participate mass
remaining in the pan determined.
The total sampled mass is the sum of the filter and probe catches.
The gas volume is measured with a dry gas meter. Approximate temp-
erature corrections are made in the gas volume.
Particulate Size Distributions - Impactors
The primary particle sizing instrument used on the pilot ESP is the
MRI* cascade impactor. The procedures used are generally those suggested
by the manufacturer. The MRI impactor uses lightweight, removable collec-
tion substrates. For use on the pilot ESP, the substrates are coated
(fD
with grease (Apiezon^L or H dissolved in toluene, the toluene then
baked out).
*
Meteorology Research, Inc., Box 637, Altadena, California 91001.
12
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The impactor sample train consists of the sample nozzle, the
impactor, temperature and pressure measurements after the impactor, an
orifice for flow measurement, a dry gas meter, and the sample pump.
The orifice is used to set the sample flow rate, but gas meter
readings are used for final data reduction. The measured gas rate
through the impactor is corrected from meter temperature to stack
temperature. The impactor substrates (in aluminum sample pans) are
tared on a balance to a precision of 0.1 mg. Stage weights are deter-
mined after the sample run on the same balance.
Impactor data reduction requires that stage cut diameters (d^n's)
be determined for each stage from flow conditions and impactor parameters.
The pilot ESP data are reduced using software developed for the TI-59
programmable calculator . The data reduction utilizes the conventional
impactor equation cast in the form:
dA50i
. l
1
QxlO"8
where: y = viscosity of gas, poise
D,= diameter of holes on ith stage, cm
N-= number of holes on ith stage
Q = gas rate, x,/min
KrQ.:= impaction parameter for 50% collection efficiency on ic stage
dA50i= aeroc|ynam1'c diameter at 50% collection efficiency on i stage.
The aerodynamic diameter (dA50i) defined by this equation is that of
Mercer and Stafford and does not require calculation of the Cunningham
slip correction factor.
For use, Equation 1 is rewritten in the form:
where: Ci = stage constant for the ith stage, C. = 0.135 ir D.3N-K5Q..
The constant C.. has been determined empirically for each stage of
the MRI impactor.
13
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The program receives as input the temperature, pressure, flow rate,
and stage weights for the run. The output is in the form of stage
dA(-oi's and the cumulative mass fraction of particulate smaller than the
indicated d.™. •
Particle penetrations as a function of size are also calculated
using TI-59 software. The derivative of the function describing the
cumulative undersize fraction (with respect to particle size) must be
known for both inlet and outlet in order to calculate the penetration.
A mathematical spline fit is used to achieve a smooth curve through the
data generated in the impactor data reduction. The spline fit program
fits the data, calculates derivatives at the desired particle diameters,
and then calculates particle penetrations at those diameters.
Optical Particle Sizing
A Climer^Model 208 Particle Analyzer is used for optical particle
sizing. The gas stream must be diluted to allow use of the Climet on
the ESP inlet. The Climet provides directly the cumulative number of
particles of sizes greater than 0.3 urn, 0.5 um, 1.0 urn, 3 urn, 5 ym, and
10 um diameters (as calibrated with polystyrene latex spheres). Data is
reduced to particles of a given size by assigning the incremental number
of particles between two diameters to the geometric mean of the two
diameters. For example, if 1.3x10 particles are counted as greater
than 0.3 pm in size, and 0.7x10 particles counted as greater than 0.5
urn, the difference, 600,000, is the number of particles between 0.3 and
0.5 \>m. If it is necessary to assign a size to this data to plot a
distribution, the geometric mean of the sizes is used.
Velocity Measurements
Gas velocities in the ESP are calculated from the orifice plate
measurements made at the flow controller.
Light Absorption Measurements
The MRI Plant Process Visometer (PPV) is used to measure light
absorption within the ESP. The PPV indicates real time trends in the
particle concentrations.
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3.0 PRELIMINARY PRECHARGER EXPERIMENTS, MARCH 1978
3.1 INTRODUCTION
The presence of high resistivity dust (>5xlO n«cm) reduces the
efficiency of an ESP. This is thought to be due to a reduction in
particle charging effectiveness. The high resistivity dust experiences
high internal electric fields and subsequent electrical breakdown and
back-corona. The back-corona produces a bipolar ion field; competing
effects of the negative and positive ions result in reduced net charging
efficiency.
In research sponsored by EPA, Southern Research Institute has
devised and investigated the performance of a three-electrode system for
controlling the effects of back-corona. The device, a particle precharger,
includes both of the usual electrodes, the discharge "wire" and the
passive "plates." In addition, it includes a screen electrode, biased
to a high negative voltage relative to the plate, but lower than the
wire voltage. The screen is placed close to the plate («2 cm). Negative
ions generated close to the wire and the particles to which they attach
are able to proceed from wire to plate without much interference from
the screen (the negative screen bias repels the negative ions). The
particles are collected on the plate as desired. However, the positive
ions generated by the onset of back-corona are attracted to the screen
and captured, improving the net charging effect.
Following the precharger in an operating ESP is a collector section
(for this experiment the remainder of the pilot-scale ESP served as the
collector). If the precharger works well, the particle leaving the
precharger is adequately charged; corona in the collector section is
then unnecessary. For maximum efficiency the collector section should
be operated with a minimum of current and high electric fields. Thus
collector design should be somewhat different from normal ESP design,
attempting to minimize corona while maintaining the electric field.
15
-------
Laboratory tests were encouraging and, in an effort to prove out
the concept on a larger scale, a precharger was designed and built for
use on the IERL-RTP pilot ESP.
The precharger replaced the transition section of the ESP for
testing. Figure 3.1 shows the approximate dimensions and configuration
of the pilot precharger.
3.2 DESIGN OF EXPERIMENT
Operation of the pilot precharger was tested at the IERL-RTP ESP on
March 15, 16, and 21, 1978, in three runs. Operating conditions for the
ESP are:
Gas Flow:
Temperature:
Plate Spacing:
Wi res:
Dust :
Rapping:
Electrical:
22.7 m /min (800 cfm) on March 15 and 16, 1978
28.3 tn3/min (1000 cfm) on March 21, 1978
149°C (300°F)
25.4 cm (10 in.)
11 wires per section, 10.2 cm (4 in.)
flyash injected by sandblast guns
manual; frequency not recorded
attempted to maintain 0.1 to 0.2 mA current in
each section at a voltage just below the spark
1evel.
March 15, 1978:
March 16, 1978:
March 21, 1978:
0.1 to 0.2 mA current at
41 to 48 kV at start, 36-42 kV at end
0.1 to 0.2 mA current, voltage not
recorded
current erratic, 0.64 to 1.47 mA
at start, 1.1 to 3.07 mA at end.
The testing included total particulate mass sampling at inlet and
outlet, impactor particle size determinations at inlet and outlet, and
monitoring of precharger operation.
The precharger was off during the March 15 run, and on during the
March 16 and March 21 runs. When in operation, the discharge wire
current and the screen voltages were both kept constant; corona wire
voltage was nearly constant throughout the tests. An abbreviated data
sheet for the runs is presented in Table 3.1.
16
-------
fO
Figure 3.1 Schematic drawing of EPA/SoRI precharger, March 1978.
-------
Table 3.1. Precharger Runs, March 1978
Date (1978)
3/15 3/16 3/21
3
Dust Loading, g/m
Inlet
Outlet
0.405
0.164
0.422
0.058
0.307
0.078
ESP Efficiency, % 59.6 86.2 74.4
MMD, ym
Inlet
Outlet
Precharger
o
Flow, m /min
Temp., °C
6.97
4.58
Off
22.6
149
7.28
3.72
On
22.6
149
6.04
4.99
On
28.3
149
3.3 RESULTS
Inlet and outlet size distributions for the three runs are presented
in Figure 3.2. Penetrations as a function of particle size are presented
in Figure 3.3. Precharger operating parameters throughout the March 16
and 21 runs are presented graphically in Figures 3.4 and 3.5, respec-
tively.
ESP efficiency was somewhat higher during the precharger operation,
although this was not an exhaustive test. Problems with the ESP current
during the March 21 run make that data difficult to evaluate. The tests
served bes-t to prove out several features of precharger operation and
allow better design of a second generation unit which has since been
installed at the IERL-RTP pilot ESP. Collector design to prevent problems
such as the instability which occurred on March 21 has been one of the
major points investigated.
18
-------
98
95
90
80
o>
•3 70
"8
1 eo
50
I 40
o
'•&
£ 30
£
I 20
10
1
3
3
u
0.5
0.2
0.1
I I I
LEGEND
O March 15, 1978
D March 16, 1978
A March 21, 1978
Inlet Sample
Outlet Sample
0.5 0.8 1
2 3456 8 10
Particle size, jum
20
Figure 3.2 Inlet and outlet size distributions, precharger runs.
19
-------
I
I
£
80
60
40
20
10
8
O 3-15-78 PRECHARGER OFF
A 3-16-78 PRECHARGER ON
D 3-21-78 PRECHARGER ON
0.8 1 2 4 6 8 10
Particle Size, M">
Figure 3.3 Penetrations for precharger runs.
20
-------
I
a
a
30
20
10
Corona Wire Voltage
r~ •
i
i
i
i
Screen '
Current / *
i ,A / '
/: /\
n ' \ i
", / \ ;
•* Screen (Guard) Voltage j / \ ,'
11 \ '
1 ' \ M>
1 ! » '
1 ' \ '
• . \ '
i' \ >
n \ '
n \ i
'i i, \ '
'i i1 \ i
! \ i
/ i
r^/ \*~*
1 \
^ i i. Corona
^. ,'_» * Wire Current "
/ i ' i
/ \ i '
/ \ i
/ LJ
-'" i v -^' i i i
6
5
4
to
1
3 1
0
2
1
20
40
60
80
100
Elapsed time, min
Figure 3.4 Precharger operating parameters, March 16,1978.
21
-------
20
Corona Wire Voltage
o
i
Q.
Q.
10
Screen Voltage
CO
U
Screen
Current
Corona
Wire Current
.-. T~
I
I
20
40 60
Elapsed time, min
80
Figure 3.5 Precharger operating parameters, March 21,1978.
22
-------
4.0 ESP EFFICIENCY RUNS
4.1 INTRODUCTION
The general operating characteristics of the pilot ESP, with parti-
cular attention to efficiency, were investigated with two sets of runs:
one set of three runs was initiated in late March 1978; the other
comprised 9 days of operation in mid-May 1978. The run conditions for
these 12 runs are summarized in Table 4.1, along with particulate mass
loadings, mean diameters, and overall efficiency values.
4.2 RESULTS
Figure 4.1 is a presentation of overall efficiency as a function of
inlet mass median diameter (MMD). The runs made in March differ notice-
ably from those runs made in May. The obvious differences are in gas
rate (higher in May) and temperature (lower in May). For the March
runs, inlet MMD made little difference with respect to efficiency; back-
corona problems required that the voltage be reduced from the March 28
run to the March 29 run, then even further to the March 30 run. The
reduction in field strength dominates, leading to reduced efficiency.
For the May runs, inlet MMD was a stronger variable. We must assume that
these runs were fairly constant electrically, although the electrical
data were not recorded.
Particle penetration as a function of size is presented in Figures
4.2 and 4.3 for the March and May runs.
23
-------
Table 4.1. ESP Conditions During Efficiency Runs
Date MMO, \*m Mass Loading, mq/m-
(1978) Inlet Outlet Inlet Outlet
3/28 10.2
3/30
10.0
5.64
3/29 9.62 6.79
7.3
0.453 0.0230
0.416 0.0624
0.391 0.0984
Efficiency,
93.8
85.0
Temperature, Gas Rate,
C m-/niin
5/8
5/10
5/11
5/12
5/15
5/16
5/17
5/18
5/20
8.51
9.33
10.1
13.8
9.09
9.56
6.10
14.3
9.46
3.57
3.15
2.45
2.1
2.43
3.18
l.i/
1.73
3.67
0.132
0.327
0.459
1.820
0.148
0.810
0.797
1.014
1.18
0.0126
0.0203
0.0053
0.0074
0.0153
0.0227
0.0152
0.0035
0.0359
90.5
93.8
98.8
99.6
89.7
97.6
98.1
99.65
96.77
Comments
149 22.6 Voltage 38 to 42 kV at
start; 25 to 35 kV at end
Current 0.45 to 1.1 mft at
start; 1.5 to 3.4 mA at end
149 22.6 Voltage 28 to 35 kV at
start; 24 to 32 kV at end
Current 1.1 to 1.8 mA at
start; 1.6 to 5.6 niA at end
149 22.6 Voltage 28 to 31 kV at start;
24 to 27 kV at end
Had problems with back-corona.
16
19
17
17
13
16
17
19
20
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
NOTES: Plate spacing: 25.4 cm. Wires: 7 wires/section at 17.8 cm spacing. Electrical:
without causing sparking. Rapping: manual.
Maximum voltage
-------
100 -
o
o
o o
90
.22
'«
HI
80
LEGEND
A Data taken 3/28/78 to 3/30/78
T = 149° C; Flow of 22.6 m3/min
O Data taken 5/8/78 to 5/20/78
T = 13-20° C; Flow of 34 m3/min
70
8
10 11 12 13 14
Inlet mass median diameter,
Figure 4.1 Effect of inlet particle size on efficiency.
25
-------
100
80
60
40
20
10
8
O
V
O_
1
0.8
0.6
0.4
0.2
0.1
LEGEND
O 3-28-78
A 3-29-78
D 3-30-78
• S-&78
A 5-10-78
• 5-11-78
0.1 0.2 0.4 0.6 0.8 1
2 4 6 8 10 20 40 60
Particle Size, Mm
Figure 4.2 Particle penetrations; efficiency runs 3/28/78 to 3/30/78 and
5/8/78 to 5/11/78.
26
-------
100
80
60
40
20
10
8
6
0*
C 4
.2
+•»
2
1
1
0.8
0.6
0.4
0.2
0.1
T I
LEGEND
V 5-1278
O 5-15-78
A 5-16-78
D 5-17-78
0 5-18-78
0.1
0.2 0.4 0.6 0.8 1
20
40
2 4 6 B 10
Particle Size, JLCITI
Figure 4.3 Particle penetrations, efficiency runs, 5/12/78 to 5/17/78.
27
-------
5.0 REENTRAINMENT STUDIES
5.1 INTRODUCTION
An investigation of ESP reentrainment was initiated in early April
1978. The test work was designed to look primarily at the effects of
sparking within the ESP. The ESP was loaded with dust by operating with
both flyash injection and ESP on. The flyash feed was stopped once the
ESP was loaded, and particle distributions at the outlet were monitored
using the Cl imet particle counter. Various sections of the ESP were
turned on and off, and sections were made to spark with the downstream
sections on and off. Table 5.1 summarizes the operating conditions for
both test days and presents the particle number distributions.
5.2 RESULTS
Total particle counts for the two days of operation are presented
in Figures 5.1 and 5.2. Looking first at the April 8 data, Figure 5.1,
it can be seen that the effects of sparking are noticeable in the parti-
cle counts. Sparking in sections 1,3, and 4 produced higher particle
counts than were present without sparking, even though downstream preci-
pitator sections were on. Sparking in section 2 did not produce high
counts. The April 7 data (Figure 5.2) are not completely consistent
with those taken April 8. Sparking produced high particle counts only
when sections 1 and 3 were sparked. For sections 1 and 2, data were
collected under sparking conditions with the downstream sections on and
off. In both cases, having the collector sections on reduced the
particle count.
The "outlet, power on" versus the "outlet, power off" data collected
April 7 indicates that particles reentrained by viscous forces could be
significant; the April 8 data contradicts this position, indicating that
sparking is the major contributor to reentrainment.
Figures 5.3, 5.4, and 5.5 present the particulate distributions for
the reentrainment study. The distributions are cumulative number percent
with size greater than indicated. As represented, larger distributions
are above and to the left of the smaller distributions. The size distribution
28
-------
Table 5.1. Sumary of the Operating Conditions and the Number
Distributions (April 7 and 8, 1978)
Run Description
4/7/78
Inlet
Outlet
Outlet
Spark 1
Spark 1
Spark 2
Spark 2
Spark 3
Spark 4
478778"
Inlet -
Outlet
Outlet
Outlet
Outlet
Outlet
Outlet
Outlet
(Power on, 0.2 mA)
(Power off)
; Power on 2,3, & 4
, Power off
, Power off 3 & 4
, Power on 1 ,3 & 4
, Power on 1 ,2 & 4
, Power on 1 ,2 & 4
Dust feed off
- Dust feed on, 0.20 mA
power on
- Feed off, power on
- Spark 1; 2,3, & 4 on
- Spark 2; 1 ,3, & 4 on
- Spark 3; 1,2, & 4 on
- Spark 4; 1,2, & 3 on
- Power off
Power on Sec. 1; 2,3, & 4 off
Number of Percent with Size >
0.3 um 0.5 um 1.0 um 3.0 um
100.
100.
100.
100.
100.
100.
100.
100.
100.
100.
100.
100.
100.
100.
100.
100.
100.
0
0
0
0
0
0
0
0
0
0
00
00
00
.00
.00
.00
.00
100.00
6.24
4.
6,
29
25
15
19
40
25
6
66
12
37
21
40
52
10
8
.39
.45
.15
.01
.04
.83
.99
.10
.78
.98
.65
.74
0.
0.
0.
5.
6.
2.
3
12
5
0
20
1
14
32
21
44
,67
,30
.98
.48
.18
.28
.66
.97
.66
.18
.88 5.03
.91
.04
.70
.53
14
21
1
1
.10
.68
.66
.04
0.01
0.00
0.02
0.04
0.17
0.03
0.03
0.36
0.04
0.03
0.28
0.06
1.03
0.28
1.23
2.02
0.10
0.03
Indicated Size
5.0 um 10.0 um
0.00
0.00
0.00
0.01
0.06
0.01
0.01
0.10
0.01
0.01
0.08
0.01
0.29
0.10
0.37
0.07
0.03
0.02
0.
0.
0.
0.
0.
0.
0.
0.
0.
0
0
0
00
00
00
00
01
00
.00
,QZ
,00
.00
.01
.00
0.04
0
0
0
0
0
.01
.06
.10
.00
.00
29
-------
150
X
Crt
0)
•S TOO
8
(0
Q.
50
<"oB
'=
O
P
1^
-------
150
u>
£
O
r
&
§
t
CD
Q.
100
50
01
_i
z
°0
a.
IT u.
-------
10
5
4
3
1.0
0.7
0.5
0.4
0.3
LEGEND
O Outlet; power on
• Outlet; power off
A Outlet; spark 1; 2, 3, & 4 on
V Outlet; spark 1; 2, 3, & 4 off
A Outlet; spark 2; 1, 3, & 4 off
V Outlet; spark 2; 1, 3, & 4 on
® Outlet; spark 3; 1, 2,
E Outlet; spark 4; 1, 2,
&4
&
60 50 40 30 20 10 5 21 0.5 0.2 0.1 0.05 0.01
Cumulative number percent greater than
Figure 5.3 Size distributions for April 8, 1978, reentrainment study.
32
-------
LEGEND
A Inlet; feed off. power on
O Outlet; feed on, power on
O Outlet; feed off, power on
• Outlet; feed off, power off
V Outlet; section 1 on; 2,3, & 4 off
70 60 SO 40 30 20 10 5 21 0.5 0.2 0.1 0.05 0.01
Cumulative number percent greater than
Figure 5.4 Size distributions for April 7, 1978, reentrainment study.
33
-------
10
£
a.
1 ,
.2
1.0
0.7
0.5
0.4
0.3
LEGEND
O Outlet, feed off, power on
0 Outlet, feed off, power off
^ Spark 1; 2, 3, & 4 on
@ Spark 2; 1, 3, & 4 on
© Spark 3; 1, 2, & 4 on
© Spark 4; 1, 2, & 3 on
70 60 50 40 30 20 10 5 21 0.5 0.2 0.1 0.05 0.01
Cumulative number percent greater than
Figure 5.5 Size distributions for April 7, 1978.
34
-------
data indicate that sparking produces larger participate than that produced
by other reentrainment mechanisms. This was true for both days' runs.
No pattern of size distribution change was established with regard to
the section sparked.
35
-------
6.0 PARAMETER VARIATION WITH POSITION IN ESP
6.1 INTRODUCTION
A series of experimental runs was made in May and June 1978 to
investigate the consistency of particle parameters within the ESP. The
tests consisted of impactor and velocity traverses at the ESP inlet
(with the ESP power off) as well as some data at other sample ports.
The vertical particle size distribution was not examined in this series
of runs.
6.2 DESIGN OF EXPERIMENT
The ESP was operated at 25.4 cm plate spacing throughout the parti-
cle size distribution runs (5-31-78 to 6-5-78). The temperature was
ambient except for the June 7 run, when it was raised to about 80°C.
Flyash injection was by sandblast gun. The flow rate was kept constant
at about 107 m/min during the test.
6.3 RESULTS
Figure 6.1 presents the velocity distribution both horizontally and
vertically at the inlet. Considerable variation between sampling ports
is evident; across the duct the velocity profile appears relatively flat
to within 2 cm or so of the ESP sidewall. The velocity distribution is
less uniform at the bottom sample port, probably due to the baffles.
These velocity distribution data are fairly consistant with those obtained
previously, although the variation at the bottom of the duct is larger
than expected. Figure 6.2 is another velocity distribution measured the
following day. Figure 6.3 is a presentation of mass loading as a function
of probe position. The loadings close to the wall are about 20 percent
above the average for each day. The mass mean diameter data presented
in Figure 6.4 show a general trend for an increase in particle size as
the probe nears the wall. The incomplete data from June 6 contradict
this trend near the center of the ESP.
The complete particle distributions for the runs presented in Figure
6.4 are presented in Figures 6.5, 6.6, and 6.7 (for May 31, June 1, and
June 5, respectively). The complete distributions for May 31 and June 1
36
-------
120
100 -
Plate spacing: 25.4 cm
Wire spacing: 17.8cm
20
505
Distance from centerline, cm
10
15
Figure 6.1 Velocity distribution in ESP, May 30, 1978.
-------
120
ESP
Centerline
100
c
I
E
|
>
60
40
468
Distance from wall, cm
10
12
Figure 6.2 Velocity distribution in ESP, May 31, 1978,
38
-------
ESP
C enter! ine
1.20
1.0
CO
en
I 0.8
•o
CO
0.6
O May 31, 1978
A June 1,1978
468
Distance from wall, cm
10
12
Figure 6.3 Mass loading variation in ESP.
39
-------
I
.2
I
re
a
10
9
8
7
6
5
4
LEGEND
O May 31. 1978
A June 1,1978
° June 5, 1978
ESP
Center line
4 6 8 10
Distance from wall, cm
12
Figure 6.4 Variation of size distribution within ESP.
-------
10
7
5
E
a.
I
« 1.0
t
! 0.7
0.5
0.3
0.2
0.1
LEGEND
O Duct midpoint
A 6.35 cm from wall
V 2.54 cm from wall
D 1.27 cm from wall
0.1 0.2 0.5 1.0 2.0
5 10 20 30 40 50 60 70 80
Cumulative percent of mass less thin 059
90 95
Figure 6.5. Particle size distributions at different sampling locations. May 31, 1978.
-------
10
I 2
•5
c
1.0
0.7
0.5
0.4
0.3
0.2
0.1
LEGEND
O Duct midpoint
A 6.35 cm from wall
V 2.54 cm from wall
D 1.27 cm from wall
0.1 0.2 0.5 1 2 5 10 20 30 40 50 60 70 80 90
Cumulative percent of mass less than Djg
Figure 6.6 Particle distributions at different sampling points, June 1, 1978.
42
-------
10
E
a
•>"
,H
1 i-n
"«
'x
£ 0.7
0.5
0.4
0.3
0.2
0.1
LEGEND
O Duct midpoint
A 1.27 cm from wall
0..1 0.2 0.5 1.0 2
5 10 20 30 40 50 60 70 80 90
Cumulative percent of mass less than
Figure 6.7 Particle size distributions at different sampling positions, June 5, 1978.
43
-------
show a general particle size increase closer to the precipitator wall;
the June 5 data, at two locations only, increase in size toward the
duct center.
Figures 6.8 and 6.9 present data from five essentially replicate
runs made over 2 days. Two of the runs, 6-6-1 and 6-7-1, involved
operation of the dust feed equipment without auxiliary heat; the other
three runs included some form of heat, as indicated. The trend is for
larger particle size distributions with the heated dust injection
equipment, although it is not a strong trend.
-------
E
a.
O Sandblast equip, not heated
A Sandblast equip, heated (75° C)
Sample port A-2, June 6,1978
0.1
0.1 0.2 0.5 1
2 5 10 20 30 40 50 60 70 80
Cumulative percent of mass less than Dgg
Figure 6.8 Effect of particle generation equipment temperature on
size distribution, June 6, 1978.
45
-------
10
E
3.
1.0
0.7
0.5
0.4
0.3
0.2
LEGEND
O Sandblast equip, not heated
A Sandblast equip, heated (80° C)
n ESP burners on, inlet at 90° C
Sample port A-2, June 7,1978
0.1
0.1 0.2 0.5 1.0 2 5 10 20 30 40 50 60 70 80
Cumulative percent of mass less than 050
Figure 6.9 Effect of particle generation equipment temperature on
size distribution, June 7, 1978.
46
-------
7.0 HUMIDIFICATION RUNS
7.1 INTRODUCTION
A series of tests were run in September and October 1978 to investi-
gate the effects of increased relative humidity on ESP performance. The
humidity was controlled by steam injection as described below. The test
series included 10 runs.
7.2 EXPERIMENTAL DESIGN
The operating parameters for the ESP during these tests are outlined
below. Electrically, the ESP was operated at a voltage just below
sparking, and the electrical data were recorded.
Gas Flow : 28 m3/min (1000 cfm)
Temperature : 135 °C (275 °F)
Dust Injection : Flyash; by sandblast guns
Rapping : Section 1 rapped every 4.5 tnin
Section 2 rapped every 10 min
Sections 3 and 4 rapped once per 99 min program
Plate Spacing : 23 cm (9 in.) all sections
Wires : 23 cm (9 in.) spacing all sections, all tests
except wire spacing of 7.6 cm (3 in.) in
sections 3 and 4 from 8/30/78 to 9/18/78
Steam : 378 kPa absolute when on
Humidity : Ambient («2%) when steam off; 6-8% with steam on,
7.3 RESULTS
A summary of the data collected during the humidification runs is
presented in Table 7.1. The collection efficiency of the ESP was definitely
enhanced by the increased humidity of the carrier gas. The scatter in
the data at low humidity led to a search for a stronger correlation.
Figures 7.1 and 7.2 show that the average section 1 voltage during a
run was a satisfactory independent variable. The correlation is very
good for both exponential and power function fits, with the power function
? 2
correlation being slightly better (r of 0.974 to an r of 0.971 for the
exponential).
Particulate size distributions were determined by impactor for the
inlet and outlet of the ESP, and the penetrations were calculated when
possible, as presented in Figure 7.3.
47
-------
Table 7.1. Summary of Humidification Runs
Date Inlet Dust Loading, ESP
(1978) q/m3 Efficiency, % Penetration, %
8/30
9/11
9/12
9/13
9/14
9/18
£ 9/29
10/3
10/4
10/5
1.01
1.12
1.05
1.08
0.92
0.80
1.21
1.14
1.14
0.98
93.1
83.8
85.6
95.1
95.9
97.2
77.4
80.2
97.9
98.2
6.9
16.2
14.4
4.9
4.1
2.8
22.6
19.8
2.1
1.8
Mass Median
,, . „ ! Diameter, ym
Water Volume
% Inlet Outlet
2.3
2.3
2.3
7.2
7.4
6.3
1.8
1.8
7.4
7.6
10.7
11.3
10.1
10.0
8.1
7.2
12.0
10.2
10.1
12.1
6.0
6.0
6.1
6.4
3.5
3.8
8.2
7.0
3.6
3.6
Section 1
Average Voltage
Not available
25.4
25.9
30.3
30.5
35.0
22.4
24.8
36.5
36.6
Plate and Wire Spacings: plate-to-plate--22.9 cm (9 in.); wire-to-wire all sections--22.9 cm (9 in.) for
9/29/78 to 10/5/78; sections 1 and 2—22.9 cm (9 in.), sections 3 and 4--7.6 cm
(3 in.) 8/30/78 to 9/18/78
Temperature: 135°C (275°F)
Rapping Program: Section 1 every 4.5 min; section 2 every 10 min; sections 3 and 4 once per 100 min.
-------
30 U
20
10
I
20
P = penetration, %
V = Voltage, kV
30
Average voltage, ESP section 1, kV
40
Figure 7.1 Correlation of voltage and penetration, exponential fit.
49
-------
20
10
I" 7
§ c
B 5
3.
S 5
o
1
10
P = 6.59X108V5-46
P = Penetration. %
V = Voltage, kV
50
20 30 40
Average voltage, ESP section 1, kV
Figure 7.2 Correlation of voltage and penetration, power law fit.
60
50
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70
60
40
20
•S 10
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Along with the normal automatic record of electrical data, VI
curves for each section were obtained before and after the runs. A
summary of these data is presented in Figure 7.4 for ESP section 1.
These data were recorded directly from the ESP data bus on an X-Y
recorder. The voltage was advanced manually. The detail presented in
this plot is not available from an incremental VI plot. In every case,
low humidity runs did not reach the voltage possible under high humidity
conditions at equivalent current settings. The VI characteristics
following a run were always less desirable than at the beginning of a
run. The high humidity air was sufficient to improve the VI characteris-
tics even before any dust had been collected.
7.4 CONCLUSIONS
The effect of the high humidity was apparently to improve the
electrical characteristics of the dust, thereby allowing more intensive
collection fields and higher efficiencies. The improvement in collec-
tion is a very strong function of voltage, showing that modest improve-
ments in field strength can have a significant effect on efficiency.
52
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AMBIENT HUMIDITY RUNS HIGH HUMIDITY (6-8%) RUNS
VI curve before VI curve VI curve
VI curve after after before
CD
*--
£
3.0 '
2.0
1.0
20 30
Voltage, kV
Figure 7.4 VI curves for ESP Section 1.
40
53
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REFERENCES
1. Sparks, L.E., Cascade Impactor Data Reduction with SR-52 and TI-59
Programmable Calculators, EPA-600/7-78-226 (NTIS PB 290 710),
November 1978.
2. Mercer, T.T. and R.G. Stafford, "Impaction from Round Sets,"
Ann. Occupational Hygiene. Vol 12, pp. 41-48, 1969.
3. Pontius, D.H., P.V. Bush, and I.E. Sparks, "A New Precharger for
Two-stage Electrostatic Precipitation of High Resistivity Dust,"
Published in Symposium on the Transfer and Utilization of Particulate
Control Technology: Volume I. Electrostatic Precipitators, EPA-
600/7-79-044a (NTIS PB 295 226), pp. 285, February 1979.
54
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/7-79-238
2.
3. RECIPIENT'S ACCESSION-NO.
TITLE AND SUBTITLE
EPA/IERL-RTP Pilot Electrostatic Precipitator—Selected
Experiments, 1978
5. REPORT DATE
November 1979
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
D.W. VanOsdell (RTI), L.E. Sparks, G.H. Ramsey, and
B.E. Daniel
8. PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME AND ADDRESS
See block 12.
10. PROGRAM ELEMENT NO.
EHE624A
11. CONTRACT/GRANT NO.
NA (Inhouse)
2. 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: 6/78 - 6/79 .
14. SPONSORING AGENCY CODE
EPA/600/13
5. SUPPLEMENTARY NOTES IERL-RTP project officer is Leslie E. Sparks, Mail Drop 61, 919/
541-2925.
6. ABSTRACT The report describes experiments with a pilot-scale electrostatic precipita-
tor (ESP) at EPA/IERL-RTP. The ESP is a dedicated experimental tool, operated for
experiments originated and designed both in-house and by EPA contractors. Five
distinct test series, between March and October 1978, are described: precharger opera-
tion, ESP operating characteristics, reentrainment, parameter variation with position
within ESP, and effects of humidity. The precharger test results were inconclusive;
removal efficiency was 10-20% better with the precharger for most size ranges, but
its operation was erratic. In the reentrainment test, sparking produced more and
larger particulate than other reentrainment mechanisms. No size distribution change
pattern was established. The study of flow, mass, and particle size as a function of
sample probe position showed that parameter variations do exist; however, insufficient
data was collected to fully establish the differences. In the study of the effects of
lumidity on collection efficiency, increased moisture had a strong impact on improved
performance. Moisture lowered the particulate resistivity, allowing increased elec-
trical fields. Efficiency correlated well with voltage in the form: P=6.59 x 10 to
the 8th power x V to the -5.46 power where P=penetration, %, and V"voltage, kV. The
correlation coefficient, r2, was 0.97.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COS AT I Field/Group
Pollution
Electrostatic Precipitators
Tests
Humidity
Pollution Control
Stationary Sources
Precharging
Reentrainment
Sparking
13B
13H
14B
13. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
61
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
55
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