x>EPA
         United States
         Environmental Protection
         Agency
          Industrial Environmental Research
          Laboratory
          Research Triangle Park NC 27711
EPA-600/7-79-052
February 1979
Characterization of the
EPA/IERL-RTP
Pilot-Scale Precipitator

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 m 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 the 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. Approval does not signify that the contents  necessarily reflect
the  views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.

This document is available to the public through t.rie National Technical Informa-
tion Service, Springfield, Virginia 22161.

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                                EPA-600/7-79-052

                                     February 1979
   Characterization of the
EPA/IERl-RTP  Pilot-Scale
            Precipitator
                     by

         P.A. Lawless (RTI), B.E. Daniel, and G.H. Ramsey

             Environmental Protection Agency
            Office of Research and Development
          Industrial Environmental Research Laboratory
          Research Triangle Park, North Carolina 27711
              Program Element No. EHE624A
              EPA Project Officer: L.E. Sparks
                  Prepared for

          U.S. ENVIRONMENTAL PROTECTION AGENCY
            Office of Research and Development
               Washington, DC 20460

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                                ABSTRACT
     The EPA/IERL-RTP pilot-scale electrostatic precipitator is a research
device used for testing and verifying new precipitator concepts and models
of precipitator operation.  This report describes the basic capabilities of
the precipitator, and contains measurements of precipitator operating
characteristics which were obtained in the first months of investigation.
                                    ii

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                               TABLE  OF  CONTENTS
                                                                      Page
ABSTRACT                                                               :L
FIGURES                                                                V
TABLES                                                                  V
ACKNOWLEDGMENT                                                         vi
Section
  1.0  INTRODUCTION                                                     1
       1.1  Design Features                                             1
       1.2  Credits                                                     4
  2.0  OPERATION OF THE ESP ELECTRICAL SYSTEM                           4
       2.1  Transformer-Rectifier Sets                                  4
       2.2  Corona Frame and Collecting Plates                          4
       2.3  Measurement System                                          5
       2.4  Voltage-Current Characteristics                             6
  3.0  TEMPERATURE CONTROL AND MEASUREMENT                             13
       3.1  Control and Measurement Thermocouple Placement             13
       3.2  Temperature Profile                                        15
       3.3  Time to Equilibrate                                        15
       3.4  Uneven Temperature Distribution                            19
  4.0  GAS FLOW DISTRIBUTION                                           19
       4.1  Measurement Techniques                                     20
       4.2  Flow Velocity Results                                      20
       4.3  Sneakage Measurements                                      22
       4.4  Variation of Velocity Through the ESP                      23
  5.0  AEROSOL GENERATION AND DISPERSION                               27
       5.1  Aerosol Generator                                          27
       5.2  Fly Ash Size Distribution                                  28
       5.3  Iron Oxide Size Distribution                               30
  6.0  PLANNED FUTURE EXPERIMENTS                                      30
       6.1  ESP/Scrubber Combinations                                  34
       6.2  Comparison of Eastern and Western Fly Ash                  34
       6.3  Variations of Wire and Plate Geometry                      35
       6.4  Residence Time Experiments                                 35
  7.0  SUMMARY AND CONCLUSIONS                                         36
  8.0  REFERENCES                                                      36
       APPENDIX A.  ESP FLOW CONTOUR PLOTS                             37
                                     iii

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                                 FIGURES
No.
1.1   Diagram of pilot-scale ESP
2.1   Sample of the printer output
2.2   Theoretical V-I curve and experimental data points at 20C
2.3   Theoretical V-I curve and experimental data points at 118C
2.A   Theoretical V-I curve and experimental data points at 216C
2.5   Theoretical V-I curve and experimental data points at 350C
2.6   Dirty plate data
3.1   Location of thermocouples on the ESP
3.2   Temperature profile along the ESP
3.3   Approach of ESP to operating temperature
4.1   A typical velocity contour plot
4.2   Variation of flow velocity with location.  Plate spacing
      12.7 cm
4.3   Variation of flow velocity with location.  Plate spacing
      25.4 cm
4.4   Variation of flow velocity with location.  Plate spacing
      38 cm
                                                                    Page
      Inlet and outlet size distributions
      Inlet size distribution with cyclone
      Inlet size distribution for iron oxide dust
5.1
5.2
5.3
Al.A-E   Flow distribution in nominal 5-in. channel.
         flow of 42 m3/min.
         Flow distribution in nominal 5-in. channel.
         flow of 23.5 m3/min.
         Flow distribution in nominal 5-in. channel.
         flow of 7.0 m3/min.
         Flow distribution in nominal 10-in. channel.
         flow of 77 m3/min.
         Flow distribution in nominal 10-in. channel.
         flow of 42.5
A2.A

A3.A

A4.A

A5;A

A6.A

A7.A

A8.A
    -E
    -E
    -E
    -E
    -E
    -D
    -E
         Flow distribution in nominal 10-in. channel.
         flow of 28 m /min.
         Flow distribution in nominal 15-in. channel.
         flow of 89 m3/min.
         Flow distribution in nominal 15-in. channel.
         flow of 49 m^/min.


ts at 20C
ts at 118C
its at 216C
its at 350C





: spacing
: spacing
; spacing



Volume
Volume
Volume
Volume
Volume
Volume
Volume
Volume
3
7
9
10
11
12
14
16
17
18
21
24
25
26
31
32
33
38-42
43-47
48-52
53-57
58-62
63-67
68-71
72-76
                                   IV

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                                 TABLES
No.                                                                 Page
4.1   Normalized Standard Deviation                                  27
5.1   Particulate Distribution                                       29

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                            ACKNOWLEDGMENT
     The contributions of P. A. Lawless of the Research Triangle Institute
were funded by EPA under contract 68-02-2612, Task 36.
                                     vi

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1.0  INTRODUCTION
     The performance of an electrostatic precipitator (ESP) can be described
in terms of the ESP's inputs (dust characteristics, gas flow and temperature,
electrical operating points) and functional units (number of sections, plate
areas, baffling, etc.).  However, the complexity of the total ESP system,
the cost of conducting experiments, and the difficulty of controlling
variables in industrial operations preclude evaluating the effectiveness of
each variable in full-scale  ESP's operating on industrial processes.   Thus,
it was desirable to construct a dedicated pilot-scale ESP with enough flexi-
bility for an experimental investigation of the effects of individual
functional units on overall performance.
     In addition to allowing direct experiments on its operation, the pilot-
scale ESP is a valuable verification tool for evaluating a computer analysis
model describing ESP behavior.   A preliminary computer model of an ESP
                                                                   123
system has been developed and modified under EPA/IERL-RTP contracts '  ' .
The purpose of the modification was to upgrade the model to more closely
predict the behavior of real ESP systems.  The pilot-scale ESP is an easily
controlled experimental unit providing data for evaluating the computer
model under ideal and non-ideal conditions.
1.1  Design Features
     To make the pilot-scale ESP as flexible as possible, its design incor-
porated the following features:
          1.  The ESP can be operated over a temperature range
              of ambient to 350C, at gas velocities from 0.3
              to 6 m/sec (1 to 20 fps).
          2.  Gas velocity distribution through the ESP is
              uniform:  normalized standard deviation is less
              than 0.25.
          3.  Sampling ports at the inlet and outlet and between
              electrical sections permit measuring gas velocity
              distribution, mass loading, temperature distribution,
              particulate resistivity, and gas composition.
          4.  Total gas volume flow is measured at the ESP outlet.

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          5.   Extensive baffling maintains sneakage through the
              ESP as low as practical.
          6.   Gases can be injected upstream of the precipitator.
          7.   The collection plates are 1.2 m high and plate-to-
              plate spacing can be varied from 12.7 to 38 cm (5
              to 15 in.); wire-duct geometry is used.
          8.   The specific collector area (SCA) of the ESP is
              28 m2/m3/sec (140 ft2/1000 acfm) at a plate
              spacing of 23 cm and a gas velocity of 1.5 m/sec.
          9.   There are four electrical sections in the
              direction of flow, and there is only one lane
              for gas flow.
         10.   The collector electrodes  are isolated from
              ground so that the current to them can be
            .  measured directly.
         11.   The number of corona wires, wire-to-wire spacing,
              and type of wire electrode used can be changed
              easily.
         12.   The power supplies can operate to 100 kV with
              current up to 10 mA, half- or full-wave
              rectified, filtered or unfiltered.
         13.   Current and voltage waveforms can be displayed
              on an oscilloscope for monitoring.
         14.   Currents and voltages for all sections,  the
              temperatures of the inlet and outlet of each
              section, and the pressure drop across the flow
              measuring orifice are measured, displayed
              digitally, and can be recorded on a line printer.
     Figure 1.1 is a schematic view of  the precipitator showing the relative
location of major parts.  It is approximately to scale.  Detailed discussions
of ESP major subsystems follow.

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              Sampling
               Ports
                 A
        Sampling
         Ports
           B
Sampling
 Ports
   C
Sampling
 Ports
   D
                                                                                             Sampling
                                                                                               Port
                                                                                                F
Sampling
 Ports
    E
Gas
irners Injection
Ports f |
O

/ \
1 t
\ /
^ _ X

o
 0 
0
o  0
O
o
o  0












Rapper
Box
Section 1





r~i






O

O


O







Section 2





n






0

o


o







Section 3





n






O

O


O







Section 4





r~i






\
0

o


o
                                                                         o
 Aerosol
Injection
  Ports
Hopper
                                Figure 1.1.   Diagram of pilot-scale  ESP.

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1.2  Credits
     The pilot-scale ESP was designed and installed by Denver Research
Institute.*  The Institute also constructed and calibrated the measurement
system.  The ESP was fabricated by Stainless Equipment Company.**
2.0  OPERATION OF THE ESP ELECTRICAL SYSTEM
     Since lERL-RTP's ESP consists of four identical sections, a description
of one section will suffice for understanding the operation of the unit.
For safety reasons, numerous interlocks, both electrical and mechanical,
remove all voltages from the ESP sections when the integrity of the machine
is breached; for instance, for sampling between sections.   Description of the
electrical system will not include these interlocks.
2.1  Transformer-Rectifier Sets
     Each power supply is a Hipotronics*** T8100-10, capable of delivering
0-100 kV dc at 10 mA.  Rectification is accomplished 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 left disconnected.  The power supply contains an internal voltage
divider resistor for measuring the output voltage; the return connection
of the power supply is available for measuring dc.
     The primary voltage is changed from zero to 208 Vac 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
high operating voltages and currents are to be measured, the series resist-
ance must be lowered.
2.2  Corona Frame and Collecting Plates
     High voltage is supplied to the corona wires through the corona frame,
a 5-cm diameter pipe, 1.25 m long, with closed rounded ends.  It is suspended
  *Denver Research Institute, University of Denver, Denver, CO 80210.
 **Stainless Equipment Co., 2829 S. Santa Fe Drive, Englewood, CO 80110.
***Hipotronics, Inc., Drawer A, Brewster, NY 10509.

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from above at each end by rods which pass up into the rapper box.   The
support rods hang in cylindrical metal tunnels, spaced well away from the
rods, 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.
     The corona frame is shaped to support weighted wires in a variety of
configurations.  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 ends of the corona wires; the
wire cones hang in the receptacles and support the weight of the wire.  In
the early stages of using the ESP, the wires have been a standard 0.32 cm
(1/8 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 symmetrical 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.
     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.
2.3  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.  The outputs from the voltage transducers range from zero

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to 1 V full-scale; from the current transducers, from zero to 0.5 V full-
scale; from the temperature transducers, zero to 100 mV full-scale; and from
the pressure transducer for the flow measurement, 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.
     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 the unit in question.  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 up-
dating, if necessary.
     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 contin-
uously 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.
     Figure 2.1 is a sample of the digital output.
2.4  Voltage-Current Characteristics
     The variation of corona current (I) with applied voltage (V) was
measured with clean collection plates and wires at four temperatures covering
the operating range of the ESP.  As the operating temperature rises, the ESP

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10-24-77
                              THIS  IS  fl  SflMPLE OF THE
                              PRINTER  OUTPUT flT RMBIENT
                                    CONDITIONS

 UKU IlMfl  U2KU  I2MFI  U3KU  ISMfl   U4KU  I4Mfl T1F T2F T3F T4F T5F TPF  DP    TIME
-59.9s0.40 -58.3s0.33 -60.7:0.39 -61.0:0.33 060 060 061  057 063 057 0.16 02s58
-59.7s0.39 -58.2:0.33 -60.7:0.39 -61.0:0.38 060 060 061  057 063 057 0.17 02:59
-59.8:0.39 -53,2:0.32 -60.7:0.38 -60.9:0.38 061 061 06P  058 063 058 0.17 03:00
-59.7:0.40 -58.2:0.32 -60.-7s0.38 -61.0:0.38 061 061 062  058 064 058 0.16 03:01
-59.7:0.40-58.2:0.32 -60.7:0.38 -61.9:0.38 061 061 062  058 863 058 0.15 03:02
-60.0:0.40 -58.3:0.33 -69.8:0.39 -6!.1:0.38 060 060 062  057 062 057 0017 03:P3
-59.9:0.40 -58.3s9.32 -60.8:0.38 -61.0:0.38 061 061 063  058 664 058 0.14 03:04
-59.9:0.40 -58.3s0.32 -60.8:0.38 -61.1:0.33 061 .061 063  058 064 058 0.13 03:05
-59.880.40 -58.380.32 -60.7:0.38 -61.180.38 061 061 063  058 064 058 0.14 03805


-59.4:0.40-58.480.32 -60.9:0.38 -61.2:0.38 061 061 063  059 064 059 0.17 03:10
-59.9s0.40 -58.4:0.32 -60.8:0.38 -61.2s0.38 061 061 063  059 064 059 0.15 03:20
-59.8:0.40-58.3:0.32 -60.8:0.38 -61.1:0.37 062 062 063  059 064 058 0.16 03s30
-feO.0s0.40 -58.580.32 -61.0s0.39 -61.3s0.38 061 062 063  059 064 059 0.16 03840
-59.9:0.40 -58.480.31 -60.9:0.37 -61.280.37 063 062 064  060 065 059 0.17 03s50
 Figure 2.1.   Sample of printer output showing manual information entry, stored heading, and
            automatic data collection features.

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starting voltage decreases and the slope of the curve becomes steeper.  The
clean-plate V-I curves are compared with a theoretical curve predicted by a
computer model similar to that in Reference 4.  Figures 2.2 through 2.5
compare the results of the measurements and model predictions.  The input
parameters for the model are the same as the physical dimensions of the
electrical section:  wire diameter is 0.3175 cm; wire-to-plate spacing is
0.127 m; wire-to-wire spacing is 0.305 m, giving four wires per section;
                          2
single-plate area is 1.5 m ; and the roughness factor is 1.0.
     The temperatures used in the model were typical of those measured
between the sections.  The ion mobility used obeyed the power-law relation:

              y(T) = 1.684 x 10~4 (-r^r) 1<63 m2/V-sec        (2-1)
where T is the absolute temperature in kelvins.  This temperature dependence
is considerably stronger than expected (where the exponent is equal to 1.0),
but was experimentally derived from mobility measurements on laboratory air
using a Beta/VII Plasma Chromatograph.*  The value of mobility at any tem-
perature affects primarily the slope of the V-I curve.  Predicted and
measured slopes are in good agreement.
     The disagreement between theory and experiment,  in terms of starting
voltage and low current characteristics, is not explained simply.  Part can
be attributed to localized corona emitted from a small area; i.e., the
Trichel pulses.  A surface irregularity may allow the corona to be initiated
at that point at a voltage much lower than the model predicts.  For higher
voltages, the glow discharge envelops the whole corona wire, as the model
assumes.  The small slope of the V-I curve, in the low current portion of
the experimental data, is probably due in part to the waveform of the
applied voltage.  Full-wave-rectified unfiltered dc voltage has a peak value
considerably higher than its average value.  Thus for a part of the cycle,
corona initiation can occur, even though the average voltage is less than
the corona start voltage.  This effect was not suspected when the V-I curves
*An ion-mobility spectrometer manufactured by the Franklin GNO Corp.,
 P.O. Box 3206, West Plam Beach, FL 33402.

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Z.bG
2*00
1 .75
\ .50
0.751-
   0 '	B-
                                                             X  0
                                                           X
                      X,T,
    30
40
        50

WIRE VOLT AGE,; kV
60
   Figure 2.2.  Theoretical V-I curve and experimental data points at
                20C (68F)..  o - Section 2; x - Section 4;Q -  calculated
                starting voltage.
                                     9

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  2.50
  2.00-
  1 .75
  1 ,50-
H 1 .2b
  0.75
  0<50
        -a-
                    x
                    m
                                                                    X
                  30
        40



WIRE VOLTAGE, kV
45
  Figure 2.3.  Theoretical V-I curve and experimental data points at 118C (245F)

              o - Section 2; .x - Section 3; D- calculated starting voltage.
                                     10

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  2.50
                                                                    O

                                                                   o
                                                                O
   1 .75
   1 .50
H  1.25
3.
   0.75h
   0.50
      20
           -B-
                    X
30          35
    WIRE VOLTAGE,  kV
40
45  '
50
    Figure 2.4.  Theoretical V-I curve and experimental  data  points  at  216C
                 (421F).  o - Section 2;  x - Section 3; Q-  calculated
                 starting voltage.
                                    11

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2.50r
                                                                  O
  .75f
1 -5Cf
0.75(
             -B-
                                          O
    15
 25            30
WIRE VOLTAGE, kV ;
35
 Figure 2.5.   Theoretical V-I curve and experimental data points at 350C
              (,662F).   o - Section 2; D - calculated starting voltage.

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were measured, and so cannot be quantitatively tested.   In the future, V-I
curves should be measured with filtered dc.
     The model under-predicts the starting voltage as the temperature rises;
this is apparent as a voltage offset between the theory and experimental
points, and is a deficiency in the model that bears further investigation.
     Some V-I curves were also measured after the precipitator had been in
operation with fly ash for an extended period.  The collection plates were
thoroughly rapped before the measurement.  The theoretical model cannot yet
account for the effects of dust on the plates and corona wires, so the
experimental data are shown, in Figure 2.6, along with the predicted theo-
retical curve for clean-plate conditions.  The experimental points exhibit
both an offset to lower voltages, which can be explained as an increased
roughness of the wires, and a hysteresis between increasing voltages and
decreasing voltages.  This hysteresis is associated with the presence of
dust, and is probably an indication of back-corona.  The arrow in Figure 2.6
indicates a point of sharply increasing current, characteristic of the onset
of back-corona.  Back-corona was expected with the current density and ash
resistivity used for this test.  Laboratory measurements indicate that the
resistivity of the dust at the experimental conditions of gas moisture
                                    12
content and temperature was about 10   ohm-cm.
3.0  TEMPERATURE CONTROL AND MEASUREMENT
     The pilot-scale ESP has two separate  temperature measuring systems.
The first is in the control module, near the ESP inlet.  The second is the
operating measurement system which gives the temperature of the gas stream
at numerous points along the length of the ESP.  Both systems use thermo-
couple transducers to measure temperature.  Figure 3.1 shows the locations
of the thermocouples on the ESP.
3.1  Control and Measurement Thermocouple Placement
     The two control thermocouples (1 and 2) are symmetrically above and
below the midline of the precipitator.  Thermocouple 1 is an over-temperature
cutoff sensor which shuts down the burners at a predetermined temperature.
Thermocouple 2 is the controller which is servoed to the burners.  Th& con-
troller has both proportional and rate-proportional action, and the
                                    13

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  2,50
                                 -X-
  2..
  2<00-
  1 .75-
  1 .50
gl.25
  1 .00
  0,75
  0.50
                    X
                                         X
                                                o
                                              o
               X
         -e-
     25
30
35             40
WIRE VOLTAGE, kV
45
50
 Figure 2.6.  Dirty plate data.  The curve is the clean plate theoretical
              characteristic,  o - data points for increasing current;
              x - data points for decreasing current; D - calculated
              starting voltage.  Arrow indicates change of slope.

                                       14

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temperature at equilibrium, as measured by the controller, is stable
within  5C.
     The measuring thermocouples for the ESP electrical sections are between
sections of the ESP inlet and outlet.  Thus, the average temperature of any
section can be computed, as well as the temperature gradient along the
length of the ESP.  Thermocouple F (in Figure 3.1), at the flow measuring
orifice, determines gas temperature, a factor in measuring gas flow.
3.2  Temperature Profile
     With the burners at the inlet end, there is a thermal gradient along
the length of the ESP, due to heat losses through the ESP walls.  Electric
heater strips, inside the ESP walls, correct for these losses.  Each electri-
cal section has separate heaters in the upper and lower halves of the walls,
with power controls for each group in each section.  These heaters have
almost no measurable effect at 350C, the maximum operating temperature.  At
much lower temperatures, the measured temperature can be raised by 5 to 10C.
(Note that measurements have not yet been made near the bottom of each
section.  Note also that the heaters can be expected to have more effect
there.)
     Figure 3.2 shows a plot of the temperature profile along the ESP at a
nominal operating temperature of 350C.  The temperature drop is 43C along
the ESP length, or about 10C per section.  The total change, about 7 per-
cent in absolute temperature, is rather small.  The point at location F
indicates that the temperature continues to drop in the outlet pipe, but is
not related to the gradient through the precipitator proper.
3.3  Time to Equilibrate
     Figure 3.3 shows the ESP approaching normal operating conditions.  It
is a plot of temperatures measured from a cold start to a nominal 350C
operating temperature.  The burner control was advanced in stages to avoid
excessive temperature overshoot in the first hour, which is reflected in
some of the surges measured by thermocouple A.  The temperatures are near
equilibrium after the first hour, and change only a few percent after that.
Thermocouple A shows the greatest variation since it is the most responsive
to changes in burner output.  For operation at lower temperatures, the
                                    15

-------
r ; i
r-i 1 .. - 1 n 1
i
W o Ql

v /
 _ X

o
o
o ^
o
o
O A.
0 Q2
f
r

.,






o






0


O

B





n 1 In

I 1







o


0






o


o





	  1
L
1 N
o.






o


o
A
Figure 3.1.  Location of ^thermocouples  on  the  ESP.

-------
      400
      300
CJ

o
w
&
p
200
w
w
H
      100
                             LOCATION, Thermocouple
           Figure 3.2.   Temperature profile along the ESP.
                                   17

-------
     400
u
o
W

BJ


H
     300 -
 200 -
     100 -
       0
                                                       160
                            80          120



                             TIME, roiru



Figure 3.3.  Approach of ESP to operating temperature.
200

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approach to equilibrium can be accelerated by judicious allowance of tem-
perature overshoot at the inlet.
     In achieving the operating temperature, using all three burners (rated
at 0.5 x 10  Btu/hr each) gives the most rapid rate of rise.  Once the steady
state condition is obtained, a single burner has sufficient operating margin
to maintain the equilibrium temperature, at least for moderate airflow rates.
3.4  Uneven Temperature Distribution
     In addition to the temperature gradient along the length of the ESP,
there is also a vertical gradient at any point within the ESP.  This has not
been carefully measured over the length of the ESP, but the following obser-
vations have been made:
          1.  The controlling thermocouple (No. 2) is 0.3 m below
              the over-temperature thermocouple (No. 1).
          2.  During high burner output, thermocouple 1 indicates
              temperatures as much as 80C higher than thermocouple 2.
          3.  When equilibrium is approached, the difference de-
              creases to about 45C.
          4.  Measurement thermocouple A also reads a higher tem-
              perature than thermocouple 1 under these conditions.
     Operating the ESP with only the lowest burner can reduce the difference
between thermocouples 1 and 2 to about 30C.  This also slightly reduces the
gradient along the length of the ESP:  thermocouples A and B read somewhat
lower than with all burners on, and thermocouples C and D read slightly
higher.
     The magnitude of the vertical temperature gradient in each section
remains to be measured, and compensated for by the use of the heaters within
the walls.
4.0  GAS FLOW DISTRIBUTION
     The gas flow distribution for an ESP includes both the variation of gas
velocity across the ESP channel and sneakage, the percentage of flow that
bypasses the active collection area.  The gas velocity variation can be
described in terms of linear flow velocity; however, sneakage is more
properly described as more-difficult-to-measure volume flow.

                                    19

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4.1  Measurement Techniques
     Gas velocity distribution was measured, for set flow rates and plate
spacings, by traversing the channel from wall to wall at each sampling port,
using a hot-wire anemometer.  For wide plate spacings,  traverse points were
2.54 cm apart; for the narrowest plate spacing, the traverse points were
1.27 cm apart.
     Three sampling ports are between each pair of sections and at the inlet
and outlet.  They are spaced 0.305 m apart in line, and the center port is
at the midline of the ESP.  The wall separation at the position of the inlet
ports is 33 cm.  A movable set of plates provides a transition to the first
section's collector plates.  Similarly, at the outlet,  a second set of
transition plates connects the outlet collector plates to the exhaust duct.
In this case, the sampling ports penetrate the transition plates, so that
the actual spacing depends on the setting of the adjacent collector plates.
     Although sneakage is a volume flow concept, the measurement of sneakage
was performed with linear velocities.  The hot-wire anemometer was inserted
in sampling ports on top of the ESP, between each pair of sections and at
the inlet and outlet, and also through the hopper drain at the bottom of
each section.  These measurements were taken near baffles in both the upper
and lower parts of the ESP; the baffles would be expected to have considerable
influence on the velocities obtained.
4.2  Flow Velocity Results
     Flow velocity distribution is presented in two ways:  as a contour plot
of flow velocity throughout the volume of the channel;  and as a plot of mean
velocity as a function of location along the ESP.  Figure 4.1 is a typical
contour plot'; although the velocities are in metric units, the traverse
locations are in English units for convenience.
     The contours correspond to mean velocity and to mean velocity i no,
where a is the standard deviation of the velocities measured.  The flow is
reasonably uniform over the major cross section of the ESP.  A depression of  .
gas velocity near the ESP center line corresponds to the position of the
corona wires.  Appendix A shows contour plots for various spacings and flow
velocities.
                                    20

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w
H
w
g
o
pel




to
M
Q
         en'    r~?
                                                    O
                     4 . b       3-0       1.1        G        -I.E.

                                       DISTANCE FROM CENTER, in.
-6.
-1 ,
Figure 4.1.  A typical  velocity contour plot.  Numbers in the plotting.area  are measured
             velocities in  meters/min.   The mean velocity is 38.4 meters/min (126 ft/min).

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4.3  Sneakage Measurements
     Since.only a linear flow velocity was measured at the top and bottom
of the ESP to characterize sneakage, it must be related to a volume flow
rate by multiplying by an appropriate cross-sectional area, and presented
as a percentage of the total volume flow.
     At the top of the ESP, where the corona frame is suspended, no corona
is generated, and so no particle charging occurs.   However, there is a
substantial electric field, and charged particles  entering that region will
be collected.  The cross-sectional area of the top of the precipitator
changes with plate spacing and is approximately 9  percent of the total
cross section for flow at all spacings.
     A single baffle extends across the flow channel between electrical
sections, from the roof of the precipitator to just below the corona frame.
Velocity measurements indicate that this single baffle is remarkably
ineffective.  Flow velocities, measured from within 2.5 cm of the roof to
well below the baffle, ranged from 80 to 100 percent of> the average flow
velocity in the duct; however, the component of the flow in a vertical
plane was not measured.  This held true for all plate spacings used.  On a
volume flow basis then, sneakage through the top section amounts to 7-9 per-
cent, at least for uncharged particles.  For charged particles, since some
collection is possible, sneakage would be less.
     At the bottom of the precipitator, 15 cm deep vertical baffle plates
form the floor of the flow channel.  The movable plates can be removed
easily to change the configuration.  For these measurements, there were 17
baffles per section, spaced 7.5 cm apart, with spacing determined primarily
by wire configuration.  A second baffle below the  movable baffles minimizes
the flow of gas in the lowest parts of the hopper.  The hoppers are inverted
pyramids with cross-sectional areas independent of the collector plate
separation.  However, the area of the baffles exposed to the gas flow is
directly dependent on collector plate spacing.  The effective cross-sectional
area is therefore difficult to calculate; however, its upper bound would be
about 20 percent of the duct area.  Measured gas velocities within the
hopper, averaged over a vertical traverse, ranged  from about 10 percent of
                                    22

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the mean gas flow velocity (at the widest plate spacing) to about 15 percent
(at the closest plate spacing).   This places an upper bound on sneakage
through the hoppers at 3 percent, for both charged and uncharged particles.
4.4  Variation of Velocity Through the ESP
     Although plate spacing is variable, the inlet and outlet duct sizes are
fixed.  Transition plates reduce the abruptness of the change in cross
section.  Figures 4.2 through 4.4 illustrate the effects of the change in
size from inlet to outlet.  Because the port locations shown do not strictly
correspond to physical separations, the curves indicate trends rather than
actual variation with distance.   The axis is offset to indicate this.  There
is no plate spacing which minimizes the disturbance produced by both inlet
and outlet simultaneously.  Either the outlet produces a disturbance that
extends upstream for wide plate spacings and high flows, or the inlet dis-
turbance propagates downstream for narrow plate spacings at all flows.
     A measure of the smoothness of flow throughout the ESP is the standard
deviation of velocities about the mean value.  A convenient number to use is
the normalized standard deviation, equal to the standard deviation divided
by the mean.
     Within any single section,  the normalized standard deviation is a
measure of the uniformity of velocity across the duct flow area, and indicates
how uniformly dust is carried through the ESP.  Over the entire ESP, the
normalized standard deviation measures, in addition to the cross-sectional
variations, the longitudinal variation of velocity.  In general, the smaller
the normalized standard deviation, the better, because the collection of
particles is not linear in transport velocity, but rather in residence time.
Therefore,' variations in velocity about a mean value do not average out in
the collection of dust, and the overall efficiency with a varying velocity
is lower than for the case when all the particles are transported at the
mean velocity.
     Table 4.1 gives examples of the normalized standard deviation for dif-
ferent plate spacings and flow rates for the entire ESP, and ranges for
sectional normalized standard deviations.  The narrowest plate spacing has
the highest deviations for two reasons:  the variation in velocity from
                                    23

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    240_
    200
c
rl
O

3
w



g
w
a
    160
120
 80
     40
                               B           C




                               LOCATION,  Port
   Figure 4.2.   Variation of flow velocity with location.


                spacing is 12.7 cm with three flow rates.
                                                       Plate
                                  24

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    240
    200
     160
o
.o
w

g
120
      80
      40
       01-
                                B           C


                                LOCATION,  Port
                                                   D
 Figure 4.3.   Variation of flow velocity with location.

               is  25.4 cm with three flow rates.
                                                     Plate spacing
                                 25

-------
    200
    160
c
H
o
I-J
w
    120
      80
     40
                                                        D
                               LOCATION,  Port
      Figure  4.4.   Variation of flow velocity with location.

                   with three flow rates.
Plate spacing 38 cm
                                             26

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inlet to outlet is the greatest for this case; and, because sectional veloc-
ity traverses were taken with half the step size used on the spacings, the
measurements include more of the low-velocity boundary layer points near
each wall.  The latter effect lowers the mean value in each section and
increases the normalized standard deviation of each section, except for the
inlet section.
                TABLE 4.1.  NORMALIZED STANDARD DEVIATION

Plate Spacing
Volume
Flow Rate
Low
Medium
High
Range of NSD
in each section
38 cm
Velocity,
m/sec
38.4
100.7
188.0

NSD
0.46
0.45
0.49
0.15-0.25
25 cm
Velocity,
m/sec
65.6
98.5
182.0

NSD
0.37
0.43
0.58
0.10-0.20
13 cm
Velocity,
m/sec
31.4
78.4
138.0

NSD
0.56
0.66
0.58
0.05-0.38

     The overall standard deviation is needed when the ESP is to be
described in terms of a single mean gas velocity.  If more detailed calcula-
tions allow for sectional values of gas velocity, then sectional values for
the normalized standard deviation are appropriate.
5.0  AEROSOL GENERATION AND DISPERSION
5.1  Aerosol Generator
     Aerosol can be injected into the ESP at five ports, in a vertical line
upstream of the controlling thermocouples.  Aerosol is injected at these
ports using low-cost, commercial, pneumatic sandblast guns, operating at an
air pressure of 2 x 10  to 8 x 10  Pa  (10 to 60 psig).  At 3 x 10  Pa
(15 psig), a volume flow of about 15.5 /s  (10 scfm)  is required.
     Dust is delivered by an Acrison* screw-feeder to a single sandblast
hopper.  The flow of air through each gun creates a reduced pressure which
*Acrison,  Inc., 20-T Empire Boulevard, Moonachie, NJ 07074.
                                    27

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draws the dust from the hopper and injects it into the ESP.  Tubes in the
ESP direct the dust from each gun into the face of the air flow to maximize
its dispersal.  If the supply air is kept dry, the guns should not clog.
     Several gun configurations were tried, trying for the most uniform
distribution of dust at the ESP inlet.  Extensive measurements were made for
two configurations:  one with three guns and one with two guns.  Uniformity
of distribution was determined by sampling with an MRI* impactor downstream
of the injection site.  Table 5.1 shows the total mass of particles collected
for each configuration.
     The two-gun operation was deemed satisfactory for use with the ESP and
had the advantage of requiring less supply air.  The maldistribution of
particulate using three guns was traced to a combination of effects:  dif-
ficulty in dividing the dust from the screw-feeder equally between the guns
and partial blockage of the guns due to moisture in the supply air, a
condition aggravated by the extra air required by the third gun.
     Additional refinements of the two-gun technique involved individual
pressure regulators and a dust-feed divider to give more even distribution
of dust to the two guns.  Under these conditions, the vertical normalized
standard deviation was reduced to 0.14 at Section A.   Measurements of the
horizontal distribution, at the middle port of Section A, produced normalized
standard deviations of 0.12 for a 25-cm plate spacing and 0.04 for a 38-cm
plate spacing, indicating that the dust is well dispersed across the duct
area.
     Additional experiments showed considerable particle fallout in the inlet
region of the ESP.  To correct this problem, which made frequent cleaning
necessary, a small cyclone was inserted in the line between the feeder and
the sandblast guns.  This cyclone effectively removed all particles larger
than 10 ym (aerodynamic diameter).  There is little fallout in the ESP when
the cyclone is used.
5.2  Fly Ash Size Distribution
     The utility fly ash used in the particulate distribution runs was.also
used in tests of the operating ESP.  The inlet and outlet size distributions
*Meteorology Research, Inc., Box 637, Altadena, CA 91001.

                                    28

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                 TABLE  5.1.  PARTICULATE DISTRIBUTION
Gun
Arrangement *
9
0
9
0



0

0
0
0








Sampling Port
Upper

Middle

Lower


Upper

Middle

Lower


Upper

Middle
Lower


Port Location
Section B,
after first
electrical
section



Section A,
before first
electrical
section



Section B
(traverse
sampling)



Amount Collected
mg
68.6

130.3

26.9
mean = 75.3
NSD =0.69
73.9

58.1

89.5
mean = 73.8
NSD =0.21
67.1

95.7
146.0
mean = 102.9
NSD = 0.39
*The gun locations are blackened.
                                    29

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were measured with an MRI impactor.  Figure 5.1 shows the results of a
series of runs at 120C operating temperature.  Each curve is the average
of six individual runs at the same temperature and flow rate.  Log-normal
curve fits to this averaged inlet data give a mass median diameter (MMD)
of 22 urn with a geometric standard deviation of 3.3 for each.  At a temper-
ature of 350C, the inlet MMD was 24 vim with the same standard deviation.
The difference in MMDs is not significant.
     The ESP was operated with three electrical sections energized:  a
power supply problem in the fourth section resulted in the outlet distribu-
tions shown in Figure 5.1.  The MMD has been decreased to about 7 ym and the
geometric standard deviation reduced slightly to about 3.  Mass samples
taken at the inlet and outlet indicated a collection efficiency of 98-99
percent under these conditions.
     Figure 5.2 shows the fly ash size distribution with the cyclone.  It is
approximately log-normal with an MMD of 7 urn and a geometric standard devia-
tion of 2.4.
     Impactor data taken on the inlet size distribution over a long period
of time indicate that the aerosol generator is very stable, both during a
particular day's work and in day-to-day operation.  Light absorption meas-
urements made with an MRI Plant Process Visimeter also indicate stability.
5.3  Iron Oxide Size Distribution
     A short series of experiments was conducted to determine the ability
of the aerosol generator to feed iron oxide dust.  Figure 5.3 shows the iron
oxide particle size distributions.
     The iron oxide tended to plug the sandblast guns, probably due to
moisture in the air lines or in the dust itself.  If the hoppers and feed
lines could be heated to minimize the moisture problem, the aerosol gener-
ator probably would be able to operate successfully for long periods.
6.0  PLANNED FUTURE EXPERIMENTS
     With the pilot-scale ESP in operation, attention has been given to
the course of experiments planned for early investigation.  These include
experiments aimed at resolving current problems encountered in operating
ESPs and at understanding the processes involved in precipitation.
                                    30

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    100
     30
   10.0
0
3.
W
N
M
CO

w
    3.0
     1.0
     0.3
     0.1
                                     '        III
               0.1
   10       30    50    70       90


CUMULATIVE PERCENT
99
            Figure 5.1.   Inlet  and  outlet size distributions.


                                      31

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     100 r-
      30
     10
e
3.
L>g   f. _

M   3.0
w


w

o
    1.0
    0.3
    0.1
                                               I      1      I
               0.1
                Figure 5.2.
       10       30    50    70



          CUMULATIVE PERCENT



Inlet size distribution with cyclone.





          32
90
99

-------
  100
    30
    10
6
3.
w
M
t/3


w
   3.0
   1.0
   0.3
   0.1
                                     I
          I
I
               0.1
10       30    50


CUMULATIVE  PERCENT
    70
90
99
            Figure 5.3.  Inlet size distribution  for  iron oxide dust.
                                       33

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6.1  ESP/Scrubber Combinations
     Venturi scrubbers are effective particulate control devices for moderate
to large particles, but their effectiveness decreases rapidly for fine par-
ticles.  Their actual effectiveness depends on the pressure drop across the
venturi, with more fine particles collected at higher pressure drops.  The
energy expended in collection increases proportionately with pressure drop.
     It has been claimed that, if the particulate entering the scrubber is
electrically charged, the collection efficiency for fine particles can be
enhanced without requiring a high venturi pressure drop.  A moderately
efficient ESP could thus be teamed with a low pressure drop scrubber to
obtain the collection efficiency of a high pressure drop scrubber, but at a
lower operating cost.  Some commercial control devices have been designed
using this concept.
     The pilot-scale ESP will be used to test this collection scheme.  ESP
operating conditions can be varied to approximate a moderately efficient ESP
to feed the scrubber, and it can also be turned off.  The ESP's aerosol
injection system will provide the proper loading for the scrubber as the
ESP/scrubber combination.  Particle penetration (as a function of size) and
collection efficiencies of the two configurations will be compared to deter-
mine the merits of the combination.
6.2  Comparison of Eastern and Western Fly Ash
     Some western high altitude ESPs fail to operate at the efficiencies
for which they were designed, and compare unfavorably with similar eastern
ESPs.  The operating characteristics of the western units suggest that they
are in a back-corona regime, even though coal resistivity is in the range
where back-corona is not normally encountered.
     Back-corona may be due to some as yet unexplained location-related
phenomenon, such as an altitude effect, or it may be related to a property
of the fly ash other than its resistivity.  The first cause must be inves-
tigated in the field, but the second can be investigated in the pilot-scale
ESP.
     Eastern and western fly ashes of comparable resistivity will be tested
in the ESP, with particular care given to the measurement of V-I curves to
                                    34

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detect back-corona.  The collection efficiency of each type will also be
measured.  The overall objective of the experiments will be to determine if
western fly ash characteristics degrade ESP performance significantly more
than those of eastern fly ash.
6.3  Variations of Wire and Plate Geometry
     Considerations of particle charging in an ESP show that the particles
acquire most, if not all, of their charge in the first few feet (or even
inches) of the ESP.  Thereafter, only the precipitation operation occurs.
Precipitation is a function of electric field only, and the objective of
maximizing electric field can be met by raising the operating voltage of
the later sections.  Back-corona and sparking can occur, however, if the
current in the section increases as the voltage increases.
     It is possible to change the V-I characteristics of a given electrical
section by varying wire-to-plate spacing, wire-to-wire spacing, and wire
diameter.  The precise effects of these variations are described in
Reference 1.  The goal of experiments on the pilot-scale ESP will be to
determine the effectiveness of raising the operating voltage at a given
current by varying the geometry of the wires and plates, both with regard to
collection efficiency and control of back-corona and sparking.
6.4  Residence Time Experiments
     Models of the precipitation process show a non-linear dependence of the
collection efficiency of particles on the length of time spent in the ESP.
The dependence is such that an ensemble of particles moving with instanta-
neous velocities widely distributed around a mean value is collected less
efficiently than another ensemble of particles all moving at the same mean
velocity.
     Approximations of this behaviour have been made in the models, but the
empirical evidence to test the models on this point is lacking.  The pilot-
scale ESP will be used to investigate experimentally the effects of residence
time on ESP efficiency.  Tracer studies and careful measurements of flow rate
and direction will be made to determine the actual departures from ideal
conditions and the effects of those conditions on collection efficiency.
Methods of modelling this behaviour will be investigated in order to improve
upon the approximations currently used.

                                    35

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7.0  SUMMARY AND CONCLUSIONS
     The initial measurements and tests of the pilot-scale ESP indicate that
it performs to or exceeds its specifications.  The aerosol generator, though
quite simple, performs well and is stable.  Temperature control is good,
although some work needs to be .done to measure and, if need be, to correct
the vertical temperature gradient.  Electrical and temperature readouts are
convenient and provide a quick permanent record of experimental conditions.
The variable plate spacing and the easy access of the ESP allow rapid
modification of the wire-duct geometry, which is a valuable experiment
feature.
     Some observations were made during the first few months of operation
of other features of the pilot-scale ESP.  The first is that automatic
power supplies, which control operating voltage by detecting current or
spark rate changes, are not needed for the ESP.  (Manual supplies control
current level adequately, and sparking is avoided in normal operation.)
A second is that an automatic program to control the plate rappers would be
desirable.  (In several-hour test runs, the plates should be rapped on a
regular schedule to realistically reflect the amount of dust reentrained
during rapping.)  A third is that some type of corona wire and corona frame
rapping should be included, because significant amounts of dust accumulate
on the wires and frame.
     Future measurements will doubtless improve understanding of the capa-
bilities and limitations of the pilot-scale ESP, but even now it is clear
that it is a versatile research tool.
8.0  REFERENCES
1.  Nichols, G. B. and J. P. Gooch.  "An Electrostatic Precipitator Perform-
    ance Model," EPA-650/2-74-132 (NTIS PB 238923), July 1972.
2.  Gooch, J.  P., J. McDonald, and S. Oglesby, Jr.  "A Mathematical Model
    of Electrostatic Precipitation," EPA-650/2-75-037 (NTIS PB 246188),
    April 1975.
3.  Work performed under EPA Contracts 68-01-4141 and 68-02-2612.
4.  McDonald,  J. R., W. B.  Smith, H. W. Spencer, III, and L. E. Sparks.
    "Mathematical Model for Calculating Electrical Conditions in Wire-Duct
    Electrostatic Precipitation Devices," Journal of Applied Physics, 48,
    2231, 1977.

                                    36

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                                APPENDIX A
                          ESP FLOW CONTOUR PLOTS

     This Appendix contains flow contour plots for the ESP for three nominal
channel widths and a number of flow conditions.   Numbers in the plotting
area are the measured values of flow velocity in meters per minute.   For
convenience, traverse point locations are in inches and the distance from
the centerline in feet.*  The unlabelled contour lines have the values of
the mean of the measured velocities and the mean  integer multiples of the
standard deviation.   All measurements were at ambient temperature.   Locations
of the sections referred to in this Appendix are in Figure 1.1.  The fact
that the width of Section A is fixed and that the width of Section E depends
only slightly on plate spacing should be kept in mind.
*Readers more familiar with the metric system should convert these units to
 that system:  in. x 2.5 = cm; and ft x 0.3 = m.
                                    37

-------
00
     w
     H
     En
     w
     CJ
     H
     CO
        '8-0
          2.1
  1.2       0    "   - \ . 2

DISTANCE FROM CENTER, in.
-2.4
-3.S
-4.S
-G..O
            Figure Al.A.
Flow distribution in nominal  5  in.  channel.   Velocities in m/min for a volume

flow of 42 nr/min.  Section A.

-------
                                             -1.0
-1 .5
-2.0
-2-5
              DISTANCE FROM CENTER, in.
Figure Al.B.  Same conditions as  Figure  Al.A.   Section B.

-------
14-1
W
H
3
W
 '
W
U
M
Q
   '3.0
1.2       ,6        G        - . 6

       DISTANCE FROM CENTER, n
-1 .,
-1.3
-2.4
-3.0
                     Figure Al.C.   Same conditions as Figure  AJ..A.. , Section C.

-------
 1 .
1.0        -^        0       -.S
      DISTANCE FROM CENTER, in.
                                              -1 .0
-1 .5
-2.0
Figure Al.D.  Same conditions as Figure  Al.A.   Section D.

-------
CJ 	
 '3.5
2.8
M       1.4        -7        0       -.7

               DISTANCE  FROM CENTER,  in.
-2.1
-2.3
-3.!
                    Figure  Al.E.   Same conditions as Figure Al.A.   Section E.

-------
U)
w
H
53
w
CJ

1
       w
       CJ
       H
       CO
       M
       Q
                                                         0        -1 .2      -2

                                             DISTANCE FROM CENTER,  in.
-3.C
                                                                                               -B.G
              Figure A2.A.  Flow distribution in nominal 5-in.  channel.  Velocities in m/min  for a volume

                            flow <-i 23-.5 m3/min.   Section A.

-------
                  -5        G        --C      -1



                DISTANCE FROM  CENTER,  in.
-i .8
-2 ,.
-3 .0
Figure A2.B.  Same  conditions as Figure A2.A.  Section  B.

-------
-p-
Ol
                            \ -3
1.2        .. C        0        - . C

       DISTANCE FROM CENTER, in.
-2
-3 .0
                           Figure A2.C.  Same conditions  as  Figure A2.A.  Section C.

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 2.5
1.5      t  0       ,5        0        - . b      -1.0      -1.5

                DISTANCE FROM  CENTER,  in.
                                                                   -2.0
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Figure A2.D.  Same conditions  as  Figure A2.A.  Settiqn D.

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2 .!
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       DISTANCE  FROM CENTER,  in.
                                                       -2,
-2 .3
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 Figure  A2.E.   Same conditions as Figure A2.A.   Section  E.

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                            3 
2-6
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DISTANCE FROM CENTER, in.
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           Figure A3.A.  Flow distribution in nominal 5-in. channel.   Velocities  in m/min for a voln
                         flow of 7.0 m^/min.  Section A.

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                                            DISTANCE FROM CENTER,  In.
                            Figure A3.B.  Same  conditions as Figure A3 .A".  Section B.

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                DISTANCE FROM CENTER,  in.
Figure A3.C.  Same conditions as Figure A3.A.  Section  C.

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                             Figure A3.D.   Same conditions as Figure  A3.A.   Section D.

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                                            DISTANCE FROM CENTER, in.
-2.8     -3.5
                            Figure A3.E.  Same conditions  as  Figure  A3.A.   Section E.

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    Figure A4.A.  Flow  distribution in  nominal 10-in. channel.

                  flow  of 77 m-Vmin.  Section A.
                                             Velocities in m/min for a volume

-------
CM 	
 '5-0
4.0      3.0       2.0       1.0       0       -1 .0
                      DISTANCE FROM CENTER,  in.
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                Figure A4.B.  Same conditions  as Figure A4.A.  Section.  B.

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                  4.0
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     DISTANCE FROM CENTER, in.
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                         Figure A4.C.   Same  conditions as Figure A4.A.  Section C.

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2-2      1.1        0       -1 .1
     DISTANCE  FROM CENTER,  in. '
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                 DISTANCE FROM CENTER, in.
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                                 DISTANCE FROM CENTER, .in.
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                                                                                                        -6.5
           Figure  A5.A.   Flow distribution in nominal 10-in. channel.  Velocities  in m/min for a. volume

                          flow of 42.5 m^./min.  Section A.

-------
Ul
          '5.0
4.0      3.0
2.0      1.0       0       -1.0
   DISTANCE FROM CENTER, in.
-2.0     -3.0     -4.0
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  o

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 4-1
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                   Figure A5.E.   Same  conditions as Figure A5.A.  Section  E.

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         4.8
   3.6
2.4
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-2.4
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                                DISTANCE  FROM CENTER,  in.
Figure A6.A.
Flow distribution in nominal  10-in.  channel.
flow of 28 m-Vmin.  Section A.
                                  Velocities in m/min for a volume

-------
'5.0
4.0
3.0
2.0      1.0       0       -1.0
      DISTANCE FROM CENTER, in.
-2.0     -3.0
-4.0
-5.0
                 Figure  A6.B.   Same  conditions as Figure A6.A.  Section B.

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w
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         -2.0     -3.0      -4.0      -5.0
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                 5-2
3.9
2.6      1.3       0       -1.3      -2.6

       DISTANCE FROM CENTER, in.
-3.9
       Figure A7.A.   Flow distribution in nominal 15-in. channel.   Velocities in.m/min for a volume
                     flow of 89 m^/min.  Section A.

-------
ON
VO
        '7.0
                           4 .
2.8      1 .-i       0        -1.4

     DISTANCE FROM CENTER,  in.
-2.3
-4 .2
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-------
     A .5
3.0      \ .5       G       -1,5



  DISTANCE'FROM CENTER,  In.
-3.0
-4
-6.0
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Figure A7.C.  Same conditions as  Figure  A7.A.   Section C.

-------
6-0
4.E
3.0
 l.S        0        -I.E.      -3.0
-DISTANCE FROM CENTER, in.
-4.S
-6-0
-7.5
            Figure A7.D.   Same conditions as Figure  A7.A.   Section D.

-------
ro
                 5.2
3.3      2.6
  1.3       0       -1.3
DISTANCE FROM CENTER, in.
-2.6      -3.9      -S.i
-6.E
         Figure A8.A.  Flow distribution in nominal 15-in. channel.  Velocities in m/min for a volume
                       flow of  49 m^/min.   Section A.  .   '"....

-------
-J
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                 6.0
4 .
3.0      1.5       0       -l.S      -3.0

       DISTANCE FROM CENTER, in.
                                                       -4.b
-6.0
-7.5
                          Figure A8.B.  Same conditions  as  Figure A8.A.   Section B.

-------
'7.0
5.G
4 .
2.8      1.4       0       -1 .
     DISTANCE FROM  CENTER,  in.
                                             -2.8
-4 .i
-5.6
                                                                                  -7.0
                 Figure A8.C.   Same conditions as Figure A8.A.  Section C.

-------
01
                  5.6
4 .2
2.8      1.4       o       -1.
     DISTANCE  FROM CENTER,  in.
-2.8     -4.2
-5.6
-7.0
                         Figure A8.D.   Same conditions as Figure A8.A.  Section D.

-------
                   1.2   .    0       -1.2     -2.4
                DISTANCE FROM CENTER,  in.
-3.G     -4.8
-6,3
Figure A8.E.  Same conditions as Figure  A8.A.   Section E.

-------
                                TECHNICAL REPORT DATA
                          (Please read Instructions on the reverse before completing)
1. REPORT NO.
 EPA-600/7-79-052
                           2.
                                                       3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
 Characterization of the EPA/EERL-RTP Pilot-Scale
 Precipitator
                                5. REPORT DATE
                                 February 1979
                                6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
 P.A.Lawless (RTI),  B.E.Daniel,  and G.H.Ramsey
                                                       8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
                                                       10. PROGRAM ELEMENT NO.
                                                       EHE624A
 See Block 12.
                                11. CONTRACT/GRANT NO.
                                                       N.A.
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
                                Inhouse; 9/77 - 5/78
                                14. SPONSORING AGENCY CODE
                                  EPA/600/13
is. SUPPLEMENTARY NOTES jERL-RTP project officer is L.E. Sparks, MD-61, 919/541-2925.
16. ABSTRACT
          The report describes the EPA/TERL-RTP pilot scale electrostatic precip-
 itator, a research device used for testing and verifying new precipitator concepts
 and models of precipitator operation.  It describes the basic capabilities of the
 precipitator, and contains measurements of precipitator operating characteristics
 which were obtained in the first months of investigation. The precipitator  performed
 to its design specifications in  initial tests,  and its utility as a research tool was
 quickly established.  Several proposed experiments which will be performed on the
 precipitator are described.
17.
                             KEY WORDS AND DOCUMENT ANALYSIS
                 DESCRIPTORS
                                           b.IDENTIFIERS/OPEN ENDED TERMS
                                             c. COSATI Field/Group
 Pollution
 Research
 Dust
 Aerosols
 Electrostatic Precipitators
 Coronas
Fly Ash
Measurement
Pollution Control
Stationary Sources
Particulate
Back Corona
13B
14B
11G
07D
131
20C
21B
18. DISTRIBUTION STATEMENT
 Unlimited
                                           19. SECURITY CLASS (This Report)
                                           Unclassified
                                                                    21. NO. OF PAGES
                                                  83
                    20. SECURITY CLASS (Thispage)
                    Unclassified
                                             22. PRICE
EPA Form 2220-1 (9-73)
                  77

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