&EPA
         United States
         Environmental Protection
         Agency
          Industrial Environmental Research
          Laboratory
          Research Triangle Park NC 27711
EPA-600/7-79-245
November 1979
University of Washington
Electrostatic Scrubber
Tests: Combined
Particulate and S02
Control

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-
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    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
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essary environmental data and control technology. Investigations include analy-
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                                       EPA-600/7-79-245

                                          November 1979
         University of Washington
      Electrostatic Scrubber Tests:
Combined  Paniculate and 862 Control
                          by

                     Michael J. Pilat

                    University of Washington
                  Department of Civil Engineering
                   Seattle, Washington 98195
                     Grant No. R806035
                  Program Element No. EHE624A
                EPA Project Officer: Dale L. Harmon

              Industrial Environmental Research Laboratory
            Office of Environmental Engineering and Technology
                 Research Triangle Park, NC 27711
                       Prepared for

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

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                              Abstract

         o
A 1700 am /hr (lOOOacfm) University of Washington Electrostatic Spray
Scrubber pilot plant was tested on the coal-fired boiler unit no.  2 at
Centralia Power Plant to demonstrate its effectiveness for controlling
fine particle and sulfur dioxide emissions.   The multiple pass, portable
pilot plant operates by combining oppositely charged aerosol  particles
and water droplets in two spray towers.   Aerosol  charging sections at
a negative polarity precede each spray tower.   The pilot plant was
operated utilizing only one corona section and one spray tower.  A liquor .
recycle system was constructed, giving the pilot plant the capability
to operate in an open-loop or closed-loop mode.  All sulfur dioxide
tests were run in an open-loop operating mode using either water or
NapCO- solution as a scrubbing liquor.

Simultaneous inlet and outlet source tests using the UW mark 10 and
Mark 20 Cascade Impactors provided size dependent and overall  mass basis
particle collection efficiency data.  Measured overall particle collection
efficiencies ranged from 98.99% to 99.80% depending upon scrubbing
operating conditions.  Particle mass concentrations measured  at the scrubber
outlet ranged from 0.0074 gm/sdm  (0.00324 gr/sdcf) to 0.0015 gm/sdm
(0.00065 gr/sdcf).

Sulfur dioxide concentrations at the inlet and outlet of the pilot plant
were .measured with a Thermo Electron Model 40 Sulfur Dioxide Analyzer.
Sulfur dioxide collection efficiencies ranged from 8.02% to 97.41%
depending on the scrubber operating conditions, inlet sulfur dioxide
concentration and the type of scrubbing liquor used.

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                              TABLE OF CONTENTS

                                                                       Page

   I.   SUMMARY AND CONCLUSIONS                                           1

  II.   RECOMMENDATIONS                                                   2

 III.   RESEARCH OBJECTIVES                                               3

  IV.   DESCRIPTION OF SOURCE                                             4

   V.   DESCRIPTION OF UW ELECTROSTATIC SCRUBBER APPARATUS                8

       A.   Review of Previous Work                                       8
       B.   Description of Overall  System                                 8
       C.   Cooling Tower                                                10
       D.   Particle Charging Corona Section                             10
       E.   Water Spray Towers                      •                     12
       F.   Mist Eliminator                                              15
       G.   Test Ducts                                                   15
       H.   Fans                                                         15
       I.   High Voltage Power Supplies                                  17
       J.   Liquor Control Panel  in the Scrubber Trailer                 17
       K.   Purge Air Heating System                                     18

  VI.   DESCRIPTION OF THE LIQUOR RECYCLE SYSTEM                         20

       A.   Description of Overall  System                                20
       B.   Liquor Tanks                                                 20

 VII.   EXPERIMENTAL PROCEDURES AND TEST EQUIPMENT                       23

       A.   UW Mark 10-20 Cascade Impactor Trains                        23
       B.   TECO Model 40 S02 Analyzer                                   23

VIII.   PARTICULATE COLLECTION EFFICIENCY RESULTS                        26

       A.   General Test Description                                     26
       B.   Particulate Collection Efficiency                            26

  IX.   SULFUR DIOXIDE COLLECTION EFFICIENCY RESULTS                     39

       A.   General Test Descriptions                                    39
       B.   S02 Collection Efficiency                                    39

           1.  Results Using Water as a Scrubbing Liquor                39
           2.  Results Using Na^CO., Solution as a Scrubbing Liquor      44

   X.   REFERENCES                                                       50
                                      IV

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                               LIST OF FIGURES
                                                                          Page
IV-1      Photograph of UW Electrostatic Spray Scrubber Located at          5
          Boiler  Unit ND. 2, Centralia Power Plant
IV-2      Photograph of Liquor Recycle Trailer Location at Centralia        6
          Power Plant
IV-3      Schematic of Ducting Arrangement to UW Electrostatic Spray        7
          Scrubber Pilot Plant at Centralia Power Station
V-l       General  Layout of Electrostatic Scrubber Pilot Plant              9
V-2       Cooling Tower Schematic                                          11
V-3       Particle Charging Corona Section                                 13
V-4       Collection Plate Flushing System                                 14
V-5       Spray Header and Nozzle Arrangement Typical to Spray Towers      16
          #1 and #2
V-6       Heated Purge Air System                                          19
VI-1      General  Layout of the Liquor Recycle System                      21
VII-1     UW Mark 10-20 Cascade Impactor Sampling System Schematic         25
VIII-1    Particle Collection Efficiency and Penetration vs. Particle      28
          Size for Impactor Tests 1-4 and 7-8 (Log-Normal Approximation)
VIII-2    Particle Collection Efficiency and Penetration vs. Particle      29
          Size for Impactor Tests 2 and 3 (Log-Normal Approximation)
VIII-3    Particle Collection Efficiency and Penetration vs. Particle      30
          Size for Impactor Tests 2 and 3 (Parabolic curve fit)
VIII-4    Particle Mass Distribution vs. Particle Size for Impactor        32
          Test 2
VIII-5    Particle Mass Distribution vs. Particle Size for Impactor        33
          Test 3
VIII-6    Inlet and Outlet Particle Size Distributions for Impactor        34
          Tests 1-4 (Log-Normal Approximation)
VIII-7    Inlet and Outlet Particle Size Distributions for Impactor        35
          Tests 7-8 (Log-Normal Approximation)

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List of Figures (Con't.)

                                                                          Page

VIII-8    Inlet and Outlet Particle Size Distributions for Impactor        36
          Test 3 (Log-Normal Approximation and Actual Data)

VIII-9    Particle Mass Concentration for Particles Less Than Stated       37
          Diameter for,Impactor Tests 1-4

VIII-10   Particle Mass Concentration for Particles Less Than Stated       38
          Diameter for Impactor Tests 7-8

IX-1      Liquor-to-Gas Ratio vs. SCL Collection Efficiency for Tests      41
          Using Water as a Scrubbing Liquor

IX-2      Inlet SCL Concentration vs. SCL Collection Efficiency for        42
          Tests Using Water as a Scrubbing Liquor

IX-3      Change in SCL Collection Efficiency vs. Spray Voltage for        43
          Tests Using water as a Scrubbing Liquor

IX-4      Liquor-to-Gas Ratio vs. SCL Collection Efficiency for Tests      47
          Using NapCCL Solution as a Scrubbing Liquor

IX-5      Inlet S02 Concentration vs. SCL Collection Efficiency at         48
          Constant Stoichiometric Ratios

IX-6      Stoichiometric Ratio vs. SCL Collection Efficiency at            49
          varying L/G and Spray Voltage

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Table V-l
Table VII-1
Table VIII-1

Table IX-1

Table IX-2
                LIST OF TABLES

High Voltage Power Supply Units
Source Test Parameters and Measurement Techniques
Results of Cascade Impactor Tests 1-4 and 7-8 at
Centralia Power Plant
Results of S02 Tests at Centralia Power Plant Using
Water as a Scrubbing Liquor
Results of S(L Tests at Centralia Power Plant Using
Na2C03 Solution as a Scrubbing Liquor
Page
 17
 24
 27

 40

 45
                                     vii

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                   ABBREVIATIONS AND SYMBOLS USED

acfm          Actual cubic feet per minute
akm           Actual 1,000 cubic meters
C             Cunningham slip correction factor
dj-Q           Particle aerodynamic cut diameter of cascade impactor  jet stage
D.            Diameter of jet in cascade impactor stage
 \J
fps           Feet per second
gm/sdm        Grams per standard dry cubic meter
gpm           Gallons per minute
KV            Kilovolts
i             Liters
L/G           Liquid to gas flow rate ratio
MPa           Pressure 1,000,000 pascals
psig          Pounds per square inch
SCA           Specific collection plate area
sm            Standard cubic meter
SR            Stoichiometric ratio (moles of sodium carbonate per mole of inlet
              sulfur dioxide)
V,            Gas velocity in jet
 J
W             Watts

                                GREEK SYMBOLS
y             Gas viscosity
y             Micron
TCQ           Inertial impaction parameter at 50% collection  efficiency  for
              particles of aerodynamic diameter dr«
                                   vm

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                          ACKNOWLEDGEMENTS
The assistance, cooperation, and advice of our Project Officer, Dale L.
Harmon, Chemical Engineer, Particle Technology Branch, Industrial
Environmental Research Laboratory at the Environmental Protection  Agency
is greatly appreciated.  The cooperation of Ted Phillips,  Tom White,
Pete Steinbrenner, and Bob Werner of the Pacific Power & Light Company
was very helpful.  The assistance of University of Washington staff and
students including  Terrell Gault, Gary Raemhild, Tracey Steig, Phil
Ayers, Steve Plotkin, Eric Piehl, and Jim Wilder is acknowledged.
Terrell Gault wrote his MSE thesis on sulfur dioxide collection with
the UW Electrostatic Scrubber.   After receiving his MSE degree, Terrell
served as Project Engineer doing much of the combined sulfur dioxide
and particulate collection study at the Centralia Power Plant.
                                   ix

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                                Section I

                         SUMMARY AND CONCLUSIONS
The University of Washington Electrostatic Spray Scrubber portable pilot
plant was tested at the Pacific Power and Light Steam Generating Plant
in Centralia, Washington on coal fired boiler no. 2 to demonstrate its
effectiveness in simultaneous control of particulate and sulfur dioxide
emissions.  The pilot plant consists of a cooling tower, two corona sections
which charge the particles to a negative polarity, two spray towers into
which positively charged water droplets are sprayed and an electrostatic
mist eliminator.  A liquor recycle system, that gives the capability of
open-loop or closed-loop modes has four tanks and two pumps.

The unit was operated using only one corona section and one spray tower
and the liquor system in an open loop mode.  Overall particle collection
efficiencies ranged from 98.99% to 99.80% depending upon the scrubber
operating conditions.  Using UW Mark 10 and Mark 20 Cascade Impactors,
particle size distributions from O.OSy to 30. y aerodynamic diameter were
measured at the inlet and outlet of the electrostatic scrubber.

Inlet and outlet sulfur dioxide concentrations were measured with a Thermo
Electron Model 40 S02 Analyzer.  SO^ collection efficiencies ranged from
8.0% to 97.4% for various operating conditions.  The efficiency was seen
to increase with an increase in spray voltage, liquor-to-gas ratio,
stoichiometric ratio, and inlet SOp concentration.

In conclusion it appears that the UW Electrostatic Spray Scrubber can
effectively collect particulate emissions from a coal fired boiler with
relatively low water usage and low corona section plate area.  Further,
enhanced SO, collection efficiencies with electrostatic charging of the
scrubbing liquor implies that less alkaline material would be needed
with a charged scrubbing system for the same S02 collection efficiency.

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                               Section II

                             RECOMMENDATIONS
To better evaluate the effectiveness of the UW Electrostatic Scrubber for
control of participate and S02 emissions, it is recommended that additional
testing should be done with tne closed loop liquor recycle system using
lime scrubbing liquor.  Extended field tests of 24 hours or more are
recommended to test the chemical and flow characteristics of the effluent
sludge, to check the capability of the pilot plant to electrostatically
charge liquor droplets that contain a high level  of solids, and to optimize
operating conditions for minimum scaling.

After this year's testing of the scrubber at a coal-fired boiler, additional
testing at field sites is recommended to optimize the design and operating
parameters of the pilot plant for simultaneous control  of particulate and
SOp emissions.  A field source with a continuous  high level of sulfur dioxide
would result in greater gas concentrations at the scrubber outlet.  A higher
S02 concentration would allow a broader range of  scrubber operating conditions
to be tested and increase the statistical reliability of the data.

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                               Section III

                           RESEARCH OBJECTIVES
The objectives of the research performed under the auspices of Environ-
mental Protection Agency Research Grant Number R803278-01  were to:

     1.  Demonstrate the effectiveness of the University of Washington
         Electrostatic Scrubber for simultaneously controlling the
         emissions of sulfur oxide and particulates emitted from coal-
         fired power plants.

     2.  Determine the effect of electrostatic charging of the scrubbing
         liquor on the sulfur oxide absorption rate and collection
         efficiency.

     3.  Use the 1,700 m3/hr (1000 acfm) portable pilot plant of the UW
         Electrostatic Scrubber to obtain the data needed to design
         larger control systems.

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                               Section IV

                        DESCRIPTION OF THE SOURCE
The Centralia Steam-Electric Project located near Centralia,  Washington
is a coal-fired electric power generating station owned by eight Northwest
utilities and operated by Pacific Power and Light Company  personnel.   The
plant contains two units which have a combined generating  capacity of
1,330,000 kilowatts of electricity (665,000 kilowatts per  unit).  The two
boilers, manufactured by Combustion Engineering, are pulverized coal  fired
type, each with a designed steam rate of 2,400,000 kilograms  (5,200,000
pounds) per hour at 16.6 MPa (2400 psig) at the turbine inlet.   The two
turbine generators were manufactured by Westinghouse Electric Corporation,
each with a guaranteed rating of 664,898 kilowatts.   The primary fuel is
sub-bituminous C coal which comes from a strip mine adjacent  to the plant.
The coal has a design heating value of 18,100 joules/gm.(8100 BTU's per
pound).  Fly ash particulate emission is controlled by two electrostatic
precipitators.

In October   1977, the U of W Electrostatic Spray Scrubber was  transported
to the Centralia Power Plant.  The sample gas stream (approximately 1500
acfm) was tapped from the outlet of boiler unit number 2.   A  .3m (12 inch)
sampling scoop was installed (facing upstream) at the center  point of the
transition duct between the air preheater and the precipitator.  .25m (10
inch) diameter aluminum ducting connects the sampling scoop to  the scrubber,
which is located approximately 18 m (60 feet) below on the ground level.
Due to the high negative static pressure in the main duct, a  Dayton centri-
fugal blower was installed at the scrubber inlet to boost  the air flow
capabilities.     Fig.IV-1 shows the location of the scrubber trailer (on
the right) and the laboratory trailer (on the left).  The  liquor recycle
trailer is located at the back end of the scrubber trailer as shown in
Fig.  IV-2.  A schematic of the ducting arrangement showing the  lengths of
duct from the sampling scoop to the inlet of the pilot plant  is shown in
Fig.  IV-3.

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                                                  •
Fig. IV-1.  Photograph of UW Electrostatic  Spray Scrubber Located
            at Boiler Unit No.  2,  Centralia Power  Plant

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Fig. IV-2.   Photograph of Liquor  Recycle Trailer at Centralia
            Power Plant

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       ftlR.
                              m
          18.0m
MATERIAL:

 10" £>//}.
DUCT/^a
                        TOLERANCE:

                           .X ±
                           .XX ±
                                             GAS  FL0W
             .XXX
                                                 UNIVERSITY OF WASHINGTON
                                                   DEPARTMENT OF CIVIL ENGINEERING
                                                DRAWING NO.
                        DRAWING BY:
                        APPROVED BY:
                                          SCALE:
                                         DATE:
                                         DATE:
Fig. IV-3.  Schematic of Ducting Arrangement to UW  Electrostatic Spray
            Scrubber Pilot Plant at Centralia  Power Station

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                                Section V

           DESCRIPTION OF UW ELECTROSTATIC SCRUBBER APPARATUS
A.  Review of Previous Work

    Penney (1944) patented an electrified liquid spray test precipitator
    involving particle charging by corona discharge and droplet charging
    by either ion impaction or induction.  Penney's system consisted of
    a spray scrubber with electrostatically charged water droplets col-
    lecting aerosol  particles charged to the opposite polarity.  Kraemer
    and Johnstone (1955) reported theoretically calculated single droplet
    (50 micron diameter droplet charged negatively to 5,000 volts) col-
    lection efficiencies of 332,000% for 0.05 micron diameter particles
    (4 electron unit positive charges per particle).  Pilat, Jaasund, and
    Sparks (1974) reported on theoretical calculation results and labora-
    tory tests with an electrostatic spray scrubber apparatus.  Pilat
    (1975) reported on field testing during 1973-74 with a 1,700 am3/hr
    (1000 acfm) UW Electrostatic Scrubber (Mark IP model) funded by the
    Northwest Pulp and Paper Association.  Pilat and Meyer (1976) reported
    on the design and testing of a newer 1700 am3/hr (1000 acfm) UW Elec-
    trostatic Scrubber (Mark 2P model) portable pilot plant.  Pilat,
    Raemhild, and Prem (1978) reported on tests of the UW Electrostatic
    Scrubber at a steel plant.  Pilat and Raemhild (1978) reported on
    tests of the UW Electrostatic Scrubber at a coal-fired plant.  The
    UW Electrostatic Scrubber (patent pending) has been licensed to the
    Pollution Control Systems Corporation (of Renton and Seattle, Washington)
    for production and sales.

B.  Description and Overall System

    The major components of the pilot plant include a gas cooling tower,
    an inlet and outlet test duct, two particle charging corona sections,
    two charged water droplet spray towers, and a mist eliminator.  Auxil-
    iary equipment includes transition ductwork between major components
    and a fan.  The pilot plant is housed in a 12.2 m (40 feet) long
    trailer and can be transported easily to different emission sources.

    The general layout of the pilot plant is shown in Fig. V-l.  Incoming
    gases enter the top of the trailer to be treated in the. vertical gas
    cooling tower and then turn vertically upward to enter the inlet test
    duct.  After moving down through the inlet test duct, the gases enter
    the first of three horizontal passes.

    The first pass contains both particle charging corona sections and the
    first of two water spray towers.  The two coronas are at either end of
    this pass and are separated by spray tower #1.  Spray tower #2 comprises
    the entire second horizontal pass and the last (third) pass contains
    the mist eliminator.  Due to the extremely high collection efficiencies
    when both coronas and towers were used, during this testing only corona
    #2 and spray tower #2 were used.

                                    8

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INCOMING
 GASES
          COOLING
          TOWER
                     INLET TEST DUCT
                         SPRAY TOWER  NO. 2
                              CORONA NO I
                                                         EXHAUST
                                                          GASES
                                                               SECTION  A-A

                                                         CROSS SECTIONAL VIEW OF
                                                      THREE PASS HORIZONTAL SECTION
                                       OUTLET  TEST DUCT.
                                                             Mist
                                                          Eliminator
                            SPRAY TOWER NO. 2
SPRAY  TOWER NO. I
CORONA NO. 2
                                                         ELEVATION VIEW
                     Fig. V-l.  General  Layout of Electrostatic Scrubber Pilot Plant

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    At the outlet of the third horizontal  pass,  the gases enter the top of
    the outlet test duct and are then directed to the fan before being
    exhausted through the trailer roof.

C.  Cooling Tower

    The cooling tower is designed to lower the gas temperature to below
    1210C (250°F) in order to maintain structural integrity of the system,
    which is constructed of steel and fiberglass reinforced plastic. The
    cooling tower, as shown in Fig. V-2, is .36 m (1 ft.  2 in.) in diameter
    x 2.98 m (9 ft. 8 in.) in height and is constructed of 21  gage T. 304
    stainless steel.  Cooling water is introduced through four ports spaced
    at .61 m (2 ft.) intervals on one side of the tower and is sprayed
    vertically upward from the tower's center!ine.  Four Bete  Model W 10080 F
    full cone stainless steel nozzles used for spraying are capable of
    delivering up to 11.4 im (3.0 gpm) at .45 mPa (50 psig).  A funnel  built
    into the bottom of the spray tower extends throught the trailer floor for
    cooling water removal.

D.  Particle Charging Corona Section

    Only the corona section at the. downstream end of the first horizontal
    gas passage (corona #2) was used.  The corona shell is constructed  from
    4.8 mm (3/16 in.) wall thickness fiberglass reinforced plastic (FRP)
    with interior dimensions of  .61 m wide x 1.07 m high x 1.52 m long
    (2 ft. x 3 ft. 6 in. x 5 ft.) in the direction of gas flow.  Access
    to a corona interior is through removable FRP end plates
    which are normally bolted to 5.1 cm (2 in.) full perimeter 3.2 mm
    (1/8 in.) thick face glanges on either end of a corona.

    The corona is designed to operate in either a single or double lane1
    gas passage mode.  Switching from one to another requires  rearrangement
    of the adjustable collection plates and discharge frame(s).  The width
    of individual gas lane(s) for either mode is maintained at .3 m (1  ft.)
    and the discharge frame to collection plate spacing is therefore .15m
    (6 in.).  Fig. V-3 shows a cutaway schematic of a corona set up for
    single lane operation.  The  testing at Centralia Power Plant was
    performed with a single lane corona section.

    The overall dimensions of the discharge frame shown in Fig. V-3 are  .70 m
    high x 1.14 m long (27^ in.  x 3 ft. 9 in.).  The frame is  constructed
    of 6.4 mm x 1.91 cm  (% in. x 3/4  in.) T. 304 stainless steel rectangular
    bar stock members.   Prior to the Centralia test program these frames were
    modified  by welding 3.2 mm  (1/8  in.) diameter stainless steel rods  in
    4.45 cm (1-3/4  in.)  lengths  perpendicular to the vertical'  members of
    each discharge frame.  The spikes have sharp points on both ends and
    are welded at 5.0 cm (2 in.) intervals.  This modification has decreased
    the plate to frame spacing by 6.4 mm (1/4  in.).

    The collection  plates shown  in Fig. V-3 are 1.05 m high x  1.5 m long    .,
    (41-1/4 in x 59 in.), giving each plate a cross sectional  area of 1.58 m ,
    which  is used in the calculations for SCA.  They are constructed from 11
    gage T. 316 stainless steel.  The plates  serve as full chamber baffles
    to keep the gases within the confines of  the single lane passages.

                                      10

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E
to
E
5
E
in

evi
                            •3
                                o
                                UJ
                             V
                                          .36m 0-12 go.
                                          T.  304  S.S.
                                          SPRAY NOZZLE
                                          ( I OF 4 SHOWN)
                                5.1 cm 0 x 5.1  cm
                                CLOSE NIPPLE
                                (4 LOCATIONS)
                                          .30m 0
                                          T.  304
                                        - 12 go.
                                       S.S.
  Fig. V-2. Cooling Tower Schematic
                     11

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   A negative corona  is used to charge the particles negatively.  This is
   accomplished by maintaining the discharge frame(s) at a high negative
   potential and  the  collection plates at a neutral or ground potential.
   Field  strengths generated in corona #2 is 6.15 KV/cm (15.61 KV/in.)
   Corona power supplies are discussed in all other components inside the
   corona.   This  isolation  is provided by suspending the frame on two
    2.5 cm (1 in.) diameter  T. 303 stainless steel rods which are connected
   to  porcelain insulators.  The Ceramaseal Model 902B1353-6 insulators are
   housed in .3m diameter  x .61 m long x 6.4 mm wall thickness (1 ft. x
   2 ft.  x 1/4 in.) plexiglass tubes which are centered 1.07 m (3 ft. 6 in.)
   apart  and are  located on top of the corona shells.  Two .30 m to  .36 m x
   7.6 cm (1 ft.  to 1  ft. 2 in. x 3 in.) FRP reducing flanges are used to
   join the plexiglass tubes to the corona top.

   The insultators are continually flushed with a supply of heated purge
   air.   The temperature of the purge air is maintained at about 49°C
    (120°F)  and an even flow across a plexiglass tube section is obtained by
    introducing the purge air through a distribution plate having approxi-
   mately 10% hole area.  The flushing face velocity of the purge air is
    set at about  .18 m/sec.  (0.6 fps).  This same purge air distribution flange
   also serves as a support flange in that an insulator is bolted directly to
    it.  The high  voltage lead-in to the discharge frame is through a feed-
   through type insulator.

    The collection plate and discharge frame flush system is shown schema-
    tically in Fig. V-4.  A  continuous wall wash is supplied to the collection
    plates through 2.5 cm (1 in.)  FRP square tube which had 3.2 mm (1/8 in.)
    diameter holes drilled diagonally into the corner adjacent to the collection
    plate. .The discharge frame  flush is an intermittent spray supplied by two
    Bete 80° fan  nozzles.  The corona section and the mist eliminator are
    equipped with  this flushing  system.

    At  the nominal gas flow  rate of  1,700 am3/hr. (1000 acfm) the gas velo-
    city in the corona is 1.45 m/sec  (4.76 fps)  for single lane operation
    and .72 m/sec. (2.36 fps) for  double lane operation.  The corresponding
    gas residence  times are  1.05 and  2.10 seconds.  By varying the volume
    of  air flow through the  system,  however, the gas  residence time can
    range  from 0.70  seconds  (single  lane operation at 2550 am /hr. (1,500
    acfm)) to 4.20 seconds  (double lane operation at  850 anr/hr.  (500 acfm)).

E.   Water  Spray Towers

    The only spray tower  used  in  the pilot  plant during  these  tests comprises
    the entire  second  horizontal  gas  passage.  The  spray  tower  is  .91 m
    in  diameter  x 4.8  mm wall  thickness  (3  ft. x 3/16 in.) and  is constructed
    from FRP.  The length  of the spray  tower  is  7.32  m  [24 ft.).  Gas velocity
    in  the spray  tower at  a  nominal  gas  flow of  1700  arrH/hr.  (1000 acfm  )  is
    0.72 m/sec.  (2.36  fps).   The corresponding gas  residence  time  is  10.17
    seconds.

    Utilizing a  single spray header in  the  tower, a maximum of 12  nozzles  can
    be used in  the tower.   The  total  number of nozzles  used can  vary  depending
    on the type of nozzle,  the  total  water  flow  rate  and  the  pressure head

                                    12

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                    REMOVABLE GROUND PLATE (&S.)
                      FOR  ONE  LANE OPERATION
                HIGH VOLTAGE
                FEEDER CABLE
              HIGH
        VOLTAGE  INSULATOR
          DISCHARGE  FRAME
           SUSPENSION ROD
     HIGH VOLTAGE
    DISCHARGE FRAME
  GAS  INLET
AND  OUTLET OPENING
PURGE AIR DUCT
   FRP WALLS
   S.S. GROUND PLATE (OUTER)
   FOR TWO LANE OPERATION
                                                       Stainless Stee-1- Discharge Spikes
                          GROUND  PLATE ALIGNMENT
                            AND SUPPORT BARS
                        F1g. V-3.  Particle Charging Corona Section

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Collection Plate Flush
                              COLLECTION PLATES
                              (SINGLE LANE OPERATION)
                                                                   PURGE AIR AND HIGH
                                                                   VOLTAGE  ENTRY(PURGE
                                                                   AIR DUCTS, INSULATORS,
                                                                   SUSPENSION RODS AND
                                                                   DISCHARGE FRAME) OMITTED
                                                                   FOR  CLARITY
                                                                   Discharge Frame Sprays
S
CORONA SHELL
                     Fig. Y-4.  Collection Plate Flushing System

-------
    desired.  All nozzles spray in the direction of gas flow (co-currently).
    A total of 5 to 7 nozzles were used in the Centralia tests,  depending
    on the desired flow rate.  Bete TF6FCN full  cone fog nozzle/header
    arrangement typical for the spray tower is shown schematically in
    Fig. V-5.

    A positive charge is imparted to the water droplets by maintaining the
    nozzles at a positive potential (direct charging).   The nozzles are
    electrically isolated from the spray tower walls by introducing heated
    purge air through 7.6 cm diameter x 10.2 cm long (3 in. x 4  in.)
    polyvinyl chloride (PVC) entry caps which are situated on top of the
    two spray towers (see Fig. V-5).  Both the water and the high voltage
    lead-in cable enter through a 6.4 mm (1/4 in.) diameter street tee
    fitting connected to the middle of each entry cap.

F.  Mist Eliminator

    The mist eliminator is situated in the middle of the third and last
    horizontal pass and is used to remove entrained water droplets from the
    airstream.  The mist eliminator is identical to the corona sections,
    with the exception of the discharge frame being maintained at a posi-
    tive potential and the total height being 5.1 cm (2 in.) shorter
    (necessitating an equivalent shortening of the discharge frame and
    collection plates).

G.  Test Ducts

    The inlet and outlet test ducts are located immediately before the
    first corona and immediately after the mist eliminator, respectively
    (see Fig. V-l).  Both test ducts are constructed from 4.8 mm wall
    thickness (3/16 in.) FRP and are .30 m in diameter  x 1.22 m  long
    (1 ft. x 4 ft.).  Vertical gas flow in a downward direction  is employed
    because it allows the most convenient positioning of the particle sizing
    source test equipment used and described in Section VI, "Particulate
    Sampling Apparatus."  The particle sizing source test equipment also
    dictated the size of the test ports which are .15 m wide x .46 m high
    (6 in. x 1 ft. 6 in.).  The test ports are located  three duct diameters
    downstream and one duct diameter upstream from flow disturbances.

H.  Fan

    The fan used to induce the air flow (i.e., clean side) through the
    pilot plant is a New York Blower Model RFE-12.  The straight-bladed
    fanwheel and housing are constructed from FRP.  The fan is driven
    through a split pulley belt drive by a Westinghouse 3.7 kW (5 hp), 208 volt,
    3-phase motor turning at 1,800 rpm and is capable of delivering up to
    2550 am3/hr. (1500 acfm) at 20.3 cm (8 in.) water colume (WC) static
    pressure.  The fan has a horizontal inlet and vertical outlet.  A
    4.8 mm (3/16 in.) FRP wall thickness x .30 m (1 ft.) diameter exhaust
    duct containing an adjustable damper extends up through the  trailer
    roof.

                                    15

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CT1
                                                 WATER HIGH
                                                 VOLTAGE
                                                    NOZZLE
                        Fig. V-5.  Spray Header and Nozzle Arrangement Typical
                                to Spray Towers «1 and »2.

-------
    As previously mentioned,  a  Dayton  centrifugal blower was  installed at
    the scrubber inlet to increase the air  flow capabilities  at the
    Centralia Power Plant.

I.   High Voltage Power Supplies

    Three high voltage power supply units used in the pilot plant  serve  the
    corona,  mist eliminator,  and water droplet charging.   All  three  units
    operate off a 110 volt, 50  Hz, 1  0 supply and are equipped with  multi-
    range voltage and current meters on the high voltage output side.  The
    units are also equipped with overvoltage and overcurrent  surge protection.
    The power supplies used for the corona section
    are equipped with spark rate controllers.   The
    which energizes the mist eliminator has a  L.L.
    voltage control and the NWL. unit for corona #2
    rate controller.  The three power supplies are
    table.
and the mist eliminator
Universal Voltronics'unit
Little P-30 automatic
has an integrated NWL spark
described in the following
              Table V-l.   High Voltage Power Supply Units
Source
Corona #2
Mist Eliminator
Droplet Charging
Model
NWL
Universal Voltronics
Hipotronics #825-40
Polarity
Negative
Negative
Positive
Rated Peak
Output
KV
90
70
25
mA
30
25
40
J.  Liquor Control Panel in the Scrubber Trailer

    The water supply system for the cooling tower, spray tower and corona
    flushing system is controlled at a single control panel situated near
    the inlet sampling port.  Two different sources supply water to the
    control panel:  charged water (either recycled or fresh) and uncharged
    fresh water.

    The charged  liquor is  used in the spray tower.  It is pumped from a
    sump tank in the liquor recycle trailer by a Gould centrifugal pump
    model 3196ST.  This  pump  provides the necessary liquor flow requirements
    of .79 MPa (100 psig)  and a maximum of 45.4 fc/min. (12 gpm) to the
    spray tower.  Since  the spray charging is achieved by applying from 0
    to 30 KV at  the throat of each nozzle, the pump will also be at an
    elevated potential.   It is therefore electrically  isolated on a micarda
    base with a  FRP cover.
                                     17

-------
    The uncharged fresh water is used in the gas cooling tower (approxi-
    mately 11.4 £/min.  (3 gpm) and the corona section flushing system (the
    flow rate is unmonitored).
                       '.
K. •  Purge Air Heating System

    The purge air heating system is schematically illustrated in Fig.  V-6.
    The system consists of both commercially available and custom built
    components.  The fan is a Barry Blower model BUF-90 Junior Fan em-
    ploying a 248.3W (1/3 hp) motor with a maximum capacity of 850 cubic
    meter per hour (500 acfm).  The discharge air then passes through a
    custom design Nelco Duct Heater.  It is a 9 Kw heating unit with 4
    stages to regulate the degree of heating required.  The duct heater
    operated on 208V, 30 power with a 110V control source which is external
    of the heater.  A custom designed distribution plenum follows the
    heater and provides an adjustable purge air supply to the high voltage
    access points on the corona section, the mist eliminator section and the
    spray header in the tower.
                                    18

-------
FRESH WATER
MAKE-UP
SPRAY —
    RECYCLE SUMP
CORONA NO. I
                                                            MIST
                                                          ELIMINATOR
                                 DISTRIBUTION  PLENUMAr
                     DUCT
                    HEATER
i
                                                                   FILTER
                                                                             CORONA N02
•AfJ<>PURGE AIR
—J   INLET
                                                        ELEVATION VIEW
                                                       MIST ELIMINATOR
                                                        "PLAN VIEW"
                                    F1g. V-6.  Heated Purge Air System

-------
                              Section VI

               DESCRIPTION OF THE LIQUOR RECYCLE SYSTEM


A.  Description of Overall System

    In order to use the Electrostatic Scrubber Pilot Plant to obtain data
    needed to design larger control systems, the design of the liquor recycle
    system was to enable the scrubber to operate in a "closed loop" mode.
    The design was to be flexible so different scrubbing liquors could be used
    with minimum modification to the system.  The system has been built in a
    moving van trailer so it is portable.  The design also makes the recycle
    system integrable with the present systemi i.e., the same electrical
    isolation system is used.

    The major components of the recycle system include a mix tank, two
    alkaline slurry mixing tanks, two clarifying tanks, a sump tank and two
    pumps.  All plumbing  between the equipment is done with PVC Schedule
    80 pipe.  The system is housed in a 12.2 m (40 ft.) long trailer and can
    be easily transported to different emissions sources with the other parts
    of the UW Electrostatic Scrubber Pilot Plant.

    Fig. VI-1 shows the layout of the liquor recycle system.  The effluent
    of the scrubber goes first into a mix tank which is outside the back door
    of the trailer.  Alkaline slurry such as lime or Na2C03 is mixed in the
    208 liter (55 gal.) drums above the mix tank and then added as a liquid
    solution to this tank.  From the mix tank the liquid passes a flow control
    panel where it is divided into two streams.

    One stream is directly recycled into the sump tank, and the other is
    bled into the clarifying tanks.  The latter stream then joins the
    recycling stream before being pumped into the sump tank.  From this tank
    the liquor is pumped into the scrubber.

    When operating in an "open-loop" liquor recycle mode the 7.6 cm (3 in.)
    drain to the mix tank was disconnected and ducted to the power plant water
    treatment system.  Fresh water was then supplied to the mix tank at the
    same consumption rate as supplied to the spray tower.
    Water and Na?CO^ solution were the scrubbing liquors for open-loop
    testing.       J


B.  Liquor Tanks

    The mix tank is a 510 liter (135 gal.), .91 m (3 ft.) diameter, 1.22 m
    (4 ft.) high tank that was purchased on a previous EPA grant.  The alkaline
    slurry mixing tanks are two teflon line 208. liter (55 gal.) drums.  Flow
    out of these tanks can be measured by sight glasses on the side of each tank.
    From the mix tank the liquor is pumped through a Gould Model 3196 ST pump
    to the flow control .panel.

                                    20

-------
             Alkaline Slurry Tanks
                    *
                                                     Control Rox
                                                         4
ro
                           Fig.  VI-1.  General Layout  of the Liquor Recycle System

-------
The first clarifying tank is 2.13 m (7 ft.) high and 1.52 m (5 ft.) wide.
The liquor from the control box splits into two streams before entering the
tank.  This helps minimize the disturbance of the settling material by the
incoming stream.  A baffle plate is also suspended near these outlets for
the solids in the stream to impinge against.  The diameter of the tank was
experimentally determined by the settling character!'sites of sludge composed
of flyash, lime and calcium carbonate.  Knowing the solids flux as a function
of suspended solids concentration and assuming a maximum 38 liter influent
flowrate of 5% slurry into the tank, the tank must be at least 1.4 m (4.6 ft.)
in diameter.  Its circular design is to prevent scale formation that could   ;
happen in the corners of square tanks.  The bottom of the tank has a 60
angle so the settled sludge can flow to the bottom drain without mechanical
assistance.

The second clarifying tank is 1.19 m (4 ft.) high and 1.19 m wide.  The feed
from the first to the second settling tank is by gravity.  Makeup water lost
by sludge removal from the first tank as well as Mq  if additional alkalinity
is needed in the lime/limestone system.  A 2.2 kW (3 hp), 3600 rpm, 110 v,
10 Deming centrifugal pump transfers the liquor from the second clarifying
tank to a point where it mixes with the liquor recycle stream and goes into
the sump tank.  The sump tank is a .91 m (3 ft.) diameter 1.52 m (5 ft.)
high tank also purchased on a previous grant.  As discussed in Section V-J
(page 17) the Gould Model 3196 St pump, housed in the main pilot plant trailer
sprays the liquor into the spray tower from this tank.
                                 22

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                            Section VII

             EXPERIMENTAL PROCEDURES AND TEST EQUIPMENT


The field test measurements for the UW Electrostatic  Scrubber  are  listed  in
Table VII-I.

A.  UW Mark 10-20 Cascade Impactors

    The Mark 10 and Mark 20 Cascade Impactors were used  to measure both particle
    size distribution and masis concentration at both  the inlet and outlet test
    ducts, respectively.  The impactors provide this  information by segregating
    the aerosol sample into discrete size intervals.   The weight on each  plate
    provides size distribution information and the total  weight is used to
    determine the mass concentration.  The Mark 10 has been  designed for  high
    particle concentrations characteristic of the scrubber's inlet and uses  27
    stages plus one final filter to reduce overloading.   The Mark  20 is designed
    for low particle concentrations as exist at the outlet of  the  scrubber and
    has 14 stages plus one final filter.  Both impactors utilize reduced
    absolute pressure in the last impactor stages to  size particles as small as
    .OByin diameter (aerodynamic).

    The basic components of a sampling train utilizing a UW  Cascade Impactor
    as shown schematically in Fig.  VII-1.  The impingers in  the condenser unit
    are used to collect water vapor in the sample air stream and provide  a basis
    for calculating the moisture content of the gas stream which may be checked
    against the wet and dry bulb determination.  The  dry gas meter is used to
    determine the total sample volume.  The absolute  pressure  gauge measures
    the pressure on the last stage  of the impactor.

    By conducting simultaneous particles size distribution tests at both  the
    inlet and outlet test ducts, the size-dependent collection efficiency curve
    of the pilot plant may be measured.

B.  TECO Model 40 S02 Analyzer

    A Thermo Electron Model 40 Fluorescent S02 Analyzer  was  used to measure
    SOo levels in the gas stream at the inlet and outlet of  the pilot plant.  The
    principle of operation of  this monitor is based  upon; the measurement of
    the fluorescence of S02 produced by its absorption of ultraviolet radiation.

    A sample gas conditioning unit  was designed and fabricated at  UW.  The
    unit samples the gases from the inlet or outlet ducts, passes  the gases
    through heated Teflon tubing, through a heated 19 x  90 mm  glass fiber
    thimble filter, through a Greenburg-Smith impinger containing  sulfuric
    acid (for removing excess water vapor), and then  through heated Teflon
    tubing into the TECO instrument.

    A strip chart recorder was attached to the S02 analyzer.   This allowed for
    continuous monitoring of the S02 concentration being  measured.   Each  data
 .  point in this report represents a 5 minute average as recorded on the strip
    chart.  By knowing the inlet and outlet S02 concentrations and gas flow  .
    rates, the S02 collection efficiency of the scrubber pilot plant could be
    calculated.

                                     23

-------
    Table VII-1.   Field Test Parameters  and Measurement Methods
              Parameter
     Measurement Methods
1.   Gas properties
      - Sulfur dioxide concentration

      - Velocity
      - Volumetric flow rate
      - Temperature
      - Moisture
Continuous instrumentation,
batch source tests
Pi tot tube
Orifice flow meter
Thermometer, thermocouples
Wet-dry bulb, continuous
instrument
2.   Particle properties
      - Size distribution
      - Mass concentration
UW Mark 10-20 Cascade Impactor
UW Mark 10-20 Cascade Impactor
3.  Liquor properties
      - PH
      - Sulfite concentration
      - Sulfate concentration
      - Suspended solids
      - Flow rate
      - Pressure
pH meter
Titration with KI-KIO.
Gravemetric
Filtration
Rotameters
Pressure gauge
4.  Scrubber conditions
      - Particle charging voltage
      - Particle charging current
      - Liquor charging voltage
      - Liquor charging current
      - Mist eliminator voltage
      - Mist eliminator current
      - Gas pressure drop
Voltmeter on power supply
Ammeter on power supply
Voltmeter on power supply
Ammeter on power supply
Voltmeter on power supply
Ammeter on power supply
Static pressure taps
                                  24

-------
MARK 10 OR MARK 20
 CASCADE IMPACTOR
                                     STACK WALL
                                          SYSTEM 10/20 PORT
                                         MOUNTING PLATE
                                               SYSTEM 10/20
                                                SAMPLE PROBE
 ISOKINETIC
  NOZZLE
ro
tn
    GAS
    FLOW
                                                                                   FLOW CONTROL VALVE
                                       SYSTEM 10/20
                                     INSTRUMENT BOX
                                                               SAMPLE LINE
                                                              CONDENSER UNIT     VACUUM PUMP
                                                               CONNECTING CORD
                                                                                          DRY
                                                                                          GAS
                                                                                         METER
                              Fig. VII-1.  UW Mark 10-20 Cascade Impactor Sampling System Schematic

-------
                             Section VIII

               PARTICIPATE COLLECTION EFFICIENCY RESULTS
A.  General Test Description

    The first series of participate collection efficiency measurements  on
    the UW Electrostatic Spray Scrubber were performed with the unit in
    the open-loop mode.  The scrubbing liquor for these tests was water.

B.  Particulate Collection Efficiency Measurements

    Results of inlet-outlet impactor tests 1-4 and 7-8 are shown in Table
    VIII-1.  Scrubber operating parameters (corona voltage, mist eliminator
    voltage and liquor flow rate) were held constant for tests 1-4 and  7-8
    with a variation in spray voltage from 0 to 10 KV,  A significant
    variation in the inlet gas flowrate from 31.2 sdm /min.  (1101  sdcfm
    (1449 acfm)) to 36.2 sdm .min. (1281 sdcfm (1637 acfm)) was  noted.
    This variation was unavoidable.  With both the scrubber I.D. fan and
    booster fan operating at full capacity, a variation in the negative
    static at the outlet of the air preheater (due to varying boiler
    conditions) resulted in subsequent variations in inlet gas flow. This
    created changes in the parameters L/G, SCA, and gas residence time.

    The overall particle collection efficiency for tests 1-4 and 7-8
    ranged from 98.99% to 99.80% (0.20% to 1.01% penetration).  The
    particle collection efficiency and penetration as a function of
    particle size (aerodynamic cut diameter of cascade impactor stages,
    d50) for these tests are shown in Fig. VIII-1.  The symbols on the
    carves of Figure VIII-1 are computer calculated collection efficiency
    points and are on the graph only to identify the curves.  The
    aerodynamic cut diameter of the impactor stages is defined as the
    diameter of the particle of unit density collection with 50% efficiency
    and is calculated by:


                                  18.
                                          '
                            50 "    CVj

    where  y is the gas viscosity, Dj the jet diameter, ₯,.« the inertial
    impaction parameter at 50% collection efficiency, for particles of
    diameter d™, C the Cunningham correction factor, and Vj the gas velocity
    in the jet aiameter.  The collection efficiency particles greater than
    .3 microns diameter was above 90% for each of these tests.
                                 •

    Figures VIII-2 and VIII-3 are the lognormal approximation and the
    parabolic fit curve of the actual collection efficiency for test 2 and 3.
    Test 2 was run with electrostatically charged liquor and test 3 was not.
    Both tests had approximately the same overall collection efficiency
    (99.55% for test 2 vs. 99.58% for test 3), and this is reflected by
    the lognormal approximation.  The actual  collection efficiency curves
    show the increase in collection of particles below .5 v diamaeter.
                                  26

-------
Test
No.
1
2
3
4
7
8
Date
3/01/79
3/02/79
3/02/79
3/14/79
5/02/79
5/02/79
Inlet
Gas Flow
sdm /min
(sdcfm)
34.6
(1223)
34.5
(1219)
36.2
(1281)
36.0
(1270)
33.1
(1168)
31.2
(1101)
Outlet
Gas Flow
sdm3/min
(sdcfm)
51.7
(1825)
50.1
(1769)
50.7
(1791)
48.8
(1724)
44.0
(1553)
46.2
(1631)
Particle Mass Cone.
gm/sdm3
(grains/sdcf )
Inlet
1.0973
(0.47952)
0.9185
(0.40142)
1.0913
(0.47690)
1.2688
(0.55448)
1.0198
(0.44566)
1.1011
(0.48117)
Outlet
0.0074
(0.00324)
0.0029
(0.00126)
0.0033
(0.00146)
0.0049
(0.00214)
0.0016
(0.00069)
0.0015
(0.00065)
Overal 1
Coll. Eff.
(*)
98.99
99.55
99.58
99.48
99.79
99.80
Penetration
<*)
1.01
0.45
0.42
0.52
0.21
0.20
Total Liquor
Flow Rate
l/min. (gpm)
60.6 (16)
60.6 (16)
60.6 (16)
60.6 (16)
60.6 (16)
60.6 (16)
Corona
Voltage
(kV)
(-)90
90
90
90
90
90
Spray
Voltage
(kV)
0
(+)10
0
10
10
0
Demister
Vol tage
(kV)
(*)60
60
60
60
60
60
SCA
mZ/sm3/m1n
(ftZ/scfm)
0.091
: (0.028)
0.091
(0.028)
0.087
(0.026)
0.087
(0.027)
0.095
(0.029)
0.101
(0.031)
L/G
1/aKm3
(gal/1000 acf)
1.14 (10.6)
1.12 (10.4)
1.05 (9.8)
1.02 (9.5)
1.13 (10.5)
1.18 (11.0) '
Gas Residence Time (sec.)
Corona
Section
0.86
0.86
0.82
0.83
0.90
0.95
Spray
Tower •
8.32
8.35
7.95
8.01
8.71
9.25
Mist
Eliminate*
0.82
0.82
0.78
0.79
0.86
0.91
ro
               Table VIII-1.   Results of Cascade  Impactor Tests 1-4 and 7-8 at Centralia Power Plant.

-------
    99.99
    99.9
 UJ
 (_>
 OH
 LU
 Q_
 O

 UJ
 i—i
 (J
 U_
 UJ
 O
 UJ
 O
 O

 LU
 *-l
 CJ
    99.0
    90.0
    0.0
                                                        T—no-2
UW Electrostatic  Scrubber
  Central!a  Power Plant
     March-May  1979

          Units

  Overall Efficiency (%)

  Overall Penetration (%)

  SCA (m2/.(sm3/niin))
  L/G (£/akm3)
Test
No.
1
2
3
4
7
8
Symbol
o
©
A
+
X
X
Overal 1
Eff.
98.99
99.55
99.58
99.48
99.79
99.80
Pen.
1.01
0.45
0.42
0.52
0.21
0.20
SCA
.091
.091
.087
.095
.095
.101
L/G
1.14
1.12
1.05
1.02
1.13
1.18
      6-00   10"1      2         5      10°     2         5      101
               PflRPICLE RERODYNflMIC DIRMETER. DSO(MICRONS)
Fig. VIII-1.
   Particle Collection Efficiency and Penetration vs. Particle
   Size for Impactor Tests 1-4 and 7-8(Log-Normal Approximation)
                                      28

-------
 ).99
99.9
UJ

<£
UJ
Q.
u_
UJ
 _
UJ


O
O

UJ

d
a:
a:
a.
   99.0
90.0
    0.0
        UW Electrostatic Scrubber
          Central ia Power Plant
             March-May 1979


        Test  Eff.   ,   SCA
         No.   (%):Cm2/(sm:Vmin))
                                      L/G
            2
            3
            99.55
            99.58
0.091
0.087
1.12

1,05
  Voltage(kV)
Corona  Spray

C-)90   C+110
   90       0
  6.00
                   2        5     10°     2        5      101

              PHRTICLE flERODYNRMIC DIflMETER. D50(MICRONS)
                                                                     10-z
                                                                        O
                                                                        I—I
                                                                        t—
                                                                        cc
                                                                        a:
                                                                     UJ
                                                                     o_
Fig.  VIII-2.
           Particle- Collection Efficiency and Penetration vs. Particle
           Size for Impactor Tests 2 and 3 (Log-Normal Approximation)
                                      29

-------
   99.9
CJ
a:
UJ
a.
UJ
u_
w 99.0
o
UJ
o
0

UJ
g 90.0
o.
    o.o
                                                                  1-110-2
           UW Electrostatic Scrubber

             Central!a Power Plant

                March-May 1979
                                        L/G

                                     U/akm3)
                                     Voltage(kV)
                                   Corona  Spray
2   9.9.55

3   99.58
0.091

0.091
                                                                        u

                                                                     6  UJ
                                                                        Q_
                                                                     8  —
                                                           CC

                                                         2  £
     6.00   10-*      2        5     10°     2         5      101

              PRRTICLE flERODYNHMIC DIflMETER. D50(MICRONS)
Fig. VIII-3.
  Particle  Collection Efficiency and Penetration vs.  Particle
  Size  for  Impactor Tests  2 and 3 (Parabolic Curve Fit)
                                      30

-------
Particle mass distributions for tests 2 and 3 are shown in Figures VIII-4
and VIII-5. Oh these graphs the particle collection efficiency is the area
between the scrubber inlet and outlet mass distribution lines.  As with
the actual efficiency curve, the maximum removal is measured above 10 y
diameter particles and the minimum with the dcn equal  to approximately
.5 y.                                        bu

The cumulative size distribution for tests 1-4 and 7-8 measured at the
inlet and outlet of the scrubber are shown in Figures  VIII-6 and VIII-7.
The particle mass mean diameter (particle diameter at  which 50% of the
particle mass is greater than this diameter and 50% less) was in the
22.2 to 65.6 micron diameter range at the scrubber inlet and in the
0.74 to 5.91 micron diameter range at the scrubber outlet.  There is a
good correlation between the actual particle size distribution as measured
with the cascade impactors and the straight line (log-normal) approximation
as seen with test 3 in Fig. VIII-8, so this report uses the log normal
size distribution.

The particle mass concentrations (grains/sdcf) less than the stated particle
aerodynamic diameter, d5Q (microns) for these tests are shown in Fig. VIII-9
and VIII-10.  The curves in these graphs illustrate the reduction in particle
size range at the inlet and outlet of the scrubber.

Particle mass concentrations measured at the scrubber  outlet for tests 1-4
and 7-8 ranged from 0.0015 gn/sdm3 (.00065 grains/sdcf) to 0.0074 gm/sdm3
(.00324 grains/sdcf).  The difference between the particulate grain'loading
at the scrubber inlet and outlet prevented simultaneous sampling.  Despite
sampling times at the outlet as high as 1 hour, low weights on the impactor
substrates were experienced.
                                 31

-------
            UW Electrostatic  Scrubber
              Centralia  Power Plant
                 March 2,  1979
            Eff.  Pen.      9 SCA,        l/G,   Voltage(kV)
            (%)   (%)     (nf/(snr/min))f£/akm3)  Corona  Spray
           99.55 0.45
10
                      2         5     10°
                      DIHMETER.  MICRONS

VIII-4.  Particle Mass Distribution vs.  Particle Size for Impactor
         Test 2
                                       32

-------
              UW  Electrostatic  Scrubber
               Centralia  Power Plant
                   March 2,  1979
              Eff.   Pen.     .  SCA,          L/G,    Voltage(kV)
              (%)    (%)    (mz/(sm3/Piin))(l/akm3)  Corona  Spra^
10-4

  10
,-2
2
10
2         5     10°
OIRMETER.  MICRONS
       Fig.  VIII-5.  Particle Mass Distribution vs. Particle Size for Impactor
                     Test 3
                                         33

-------
100.0

 80.0

 60.0

 50.0
 40.0

 30.0


 20.0
 10.0

  8.0

1 6.0
es.o

1 4.0

£ 3.0
ui

§2.0
o

< 1.0
a.
   .8
   .6
   .5

   .4

   .3


   .2
  0.1
UW Electrostatic  Scrubber
  Centralia Power Plant
     March-May 1979
      Inlet Size
     Distribution
                             /'    /   /  Outlet Size
                             /    /   /   Distribution


                          '    '   '
J	I__J	I
                     i i   /  i  i   i  i   i	i
      001
      Fig.
 01  0.2 Q5 I   2    5   10   20 30 4O  50 60 70 BO  90  95


            % of MASS  LESS  THAN STATED  DIAMETER
                                                        99   998 99.9  99.99
 VIII-6.  Inlet  and  Outlet Particle Size Distributions  for Impactor
         Tests  1-4  (Log-Normal  Approximation)

                               34

-------
100.0

 80.0

 60.0

 50.0

 40.0

 30.0


 20.0
 10.0

  8.0

le.o
|5.0

14.0

?(3.0
bl


52.0
kl

O

&
   .8

   .6

   .5
   .4

   .3


   .2
 0.1
     UW Electrostatic  Scrubber
       Centralia Power Plant
          March-May  1979
             Inlet Size
            Distribution
                                                 Outlet Size
                                                Distribution
0.01   0.1  0.2 Q5 I  2   5   10   20  30  4O  50 60 70 80  90  95


                 % Of  MASS  LESS  THAN STATED  DIAMETER
                                                                    99   99S 99.9  99.99
      Fig.  VIII-7.  Inlet and Outlet Particle Size Distributions for Impactor
                   Tests 7-8 (Log-Normal  Approximation)
                                     35

-------
CO

D
o:
LJ
UJ

UJ

CE
i—i
a
OH
OC
O.
D
4
2
ioi
8
6
4
2
10°
8
6
4
2
10-1
8
6
4
2
• n-7



-









/
/
'
/
j
/
















est 3








X
/-"/
/
»




















nlet







/
"7












^
*~


/
/






/
s
J
/
/
^












^X" X
x^' y

/
/
/







/
















/
A












/
/
^














y
/
/
^
X

























/
/
/

/
y























/
X
f

/
/
f
























/
7
/
j
s






—


















/
/
//
/










^
— L(












/
//
/
/ X
1 /
' '



































Test 3 Outlet










ctual
g Horma



















kppn



















ximati



















)n









                       10       20304050607080      90

                                   PERCENTflGE SMflLLER  (BY WEIGHT)
                                                    95
        Fig. VIII-8.
Inlet and Outlet  Particle Size Distributions for Impactor
Test 3 (Log-Normal Approximation and Actual Data)

                       36

-------
a
CO
t—»
cr
s
  UJ
  GC
  •—t
  O
  UJ
  u
  s
  I
  CO
  CO
  to
10"
 8
 6
 4
  UJ
  o
  CO
  o
             I I I T I I
           UW Electrostatic Scrubber
             Centralia Power Plant
                March-May 1979
                      Inlet Size
                    Distribution
                                                Outlet Size
                                               Distribution
                                            Test 1  •
                                                 2  »
                                                 3  *
                                                 4  •*-
     3.00  5     10~*     2        5     10°     2       5     10*
             PflRTICLE flERODYNRMIC DIRMETER. D50IMICRONS)
                                                                 2  3.00
Fig.  VIII-9. Particle Mass Concentration for Particle Less Than Stated
             Diameter for Impactor Tests 1-4.
                                      37

-------
   ;3.00
UJ

CJ
t—•
I—
o:
cc
Q_
    8

    6
O
CO

CO
 a:
 UJ

 UJ

 cc
 i— •
 O
 a:
 cc
 a.

 a
 UJ

 cc

 CO
CO
CO    .,
UJ  10-3

-1  8
z
O  6
UJ
CJ

o
CJ

CO
CO

£  8
     ur«-
     6
   3.00
          UW  Electrostatic Scrubber
            Centralia Power Plant
                March-May 1979
                          Inlet Size
                         Distribution
          8
                                                          -«—B—t
              7
              or'
                         .J*~'
                                                Outlet  Size
                                               Distribution
              8
3.00   5     MT1    2       5     10°     2        S    101

         PflRTICLE  flERODYNflMIC DlflMETER. D50(MICRONS)
                                                                 2  3.00
Fig.  VIII-10. Particle Mass Concentration for  Particles  Less  Than  Stated
              Diameter for Impactor Tests 7-8.
                                       38

-------
                              Section IX

                  SULFUR DIOXIDE COLLECTION EFFICIENCY


A.  General Test Description

    S02 collection efficiency measurements on the UW Electrostatic Spray
    Scrubber were performed with the unit in an open-loop operating mode.
    In the open loop mode fresh water was added to the mix tank at the same
    consumption rate as supplied to the tower, and the scrubber effluent
    sent to the power plant water treatment system.   Tests were run with fresh
    water and with Na2C03 solution.  Concentrated Na2CO,  liquor was added to
    the mix tank at a fixed rate during the .latter tests.  S02 collection
    efficiency measurements, described in Section VII, were performed on the
    scrubber in both operating modes.


B.  S02 Collection Efficiency

    1.  Results Using Water as a Scrubbing Liquor

        initial SO, collection efficiency tests were performed with water
        on March 16th.  Also at the beginning of each test day with open-
        loop system, several tests were run using water as a scrubbing liquor
        The results of inlet/outlet S02 measurements are  shown in Table IX-1
        As with the particulate tests a significant variation in the inlet
        gas flow rate from 32.9 sdm /min.  (1163 sdcfm) to 41.5 sdm /min.
        (1465 sdcfm).  This created changes in gas residence time and L/G..
        Inlet S02 concentrations varied from 270 ppm to 1300 ppm.  Using
        water as a scrubbing liquor, the overall S09 collection efficiency
        ranged from 16.21% to 50.82%.              *

        Test series 2 demonstrated the effect of the corona charge and spray
        voltage charge.  With particle charging corona section off the
        SO, removal increased from 17.56% to 20.09% by increasing the spray
        voftage from 0 to 7.5 KV.  With the corona on the collection efficiency
        was increased to 25.48%.  At this condition as with test series 1,
        the spray voltage did not have a significant effect on the S02
        collection efficiency.

        Test Series 3 demonstrated the  effect of L/G on  S02 removal.  With
        the sprays off, S02 collection was 8.02% due to SO, absorption by-the
        wet wall corona sections.  As the L/G was increasea to 1.10 £/akm
        (10.3 gal/1000 acf), the collection efficiency increased to 23.46%.
        These results are illustrated in Fig. IX-1.

        A comparison of test series 1, 4, 5 and 7 shows the effect of inlet
        S0? concentration on S02 collection efficiency.  This comparison is
        plotted on Fig. IX-2.  S02 removal ranged from 16.21% at 270 ppm
        inlet SO, to 50.82% at 1300 ppm.  The reason for  this increased
                                      39

-------
Table IX-1.     Results of S02 Tests  at  Centralia  Power  Plant  Using Water as  a  Scrubbing
               Liquor.
Test Series
No. & Date
1
3-16-79
2
3-16-79


3
3-16-79

4
3-30-79
5
4-18-79
6
4-18-79
7
5-03-79
Inlet
Gas Flow
sdm /mln
(sdcfm)
37.2
(1314)
37.2
(1314)


37.2
(1314)

36.9
(1302)
41.5 .
(1465)
38.4
(1356)
32.9
(1163)
Outlet
Gas Flow
sdm /mi n
(sdcfm)
48.9
(1728)
48.9
(1728)


48.9
(1728)

46.2
(1632)
50.3
(1777)
49.8
(1757)
43.8
(1547)
S02
Concentration
(ppm)
Inlet
430
430
430
415
415
415
415
490
490
490
490
1300
615
615
500
500
270
270
Outlet
258
249
252
260
252
235
235
342.5
315
302.5
286
510
375
365
310'
290
170
160
Overal 1
Collection
Efficiency
(%)
21.05
23.80
22.88
17.56
20.09
25.48
25.48
8.02
15.41
18.76
23.46
50.82
26.04
28.01
19.67
24.85
16.21
21.14
Stoichiometric
Ratio
/ moles alkali «
\nole inlet S02'
0
0





0






L/G
fc/akm3
(gal/lOOOacf )
'1.10
(10.3)
1.10
(10.3)

0
0.53 (5.0)
0.80 (7.5)
1.10(10.3)
1.06
(9.9)
0.93
(8.6)
0.80
(7.5)
0.94
(8.8)
Corona
Charge
(kV)
(-)70
70
70
0
0
90
90
90
90
90
90
90
90
90
90
90
90
90
Spray
Vol tage
(kV)
0
( + )5
10
0
7.5
0
7.5
0
0
0
0
0
0
7.5
0
15
0
10
Demister
Vol tage
(kV)
(+)60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60

-------
                              L/G  (gal/1000 acf)
                             5.
           10.
   25
           UW Electrostatic Scrubber
             Centralia Power Plant
                March-May 1979
   20
o

-------
   60
              I         I         I
           UW Electrostatic Scrubber
             Centralia Power Plant
                March-May 1979
   50
   40
01
•r-
O
c
o
(J
O>
 e\j
o
1/5
   30
   20
   10
                                I
Test  Series #1,4,5,  and  7

Mater Liquor

{=• = 0.93-1.10 -e/akm3
b
Spray Voltage = 0 kV

TF6FCN Fog Nozzle
Spray Pressure = .79 MPa

      I        I
             200     400       600      800     1000

                              In  (ppm average)
                     1200
1400
         Fig.  IX-2. S02 Collection Efficiency vs.  Inlet  SOo  Concentration
                    for Tests Using Water  as a  Scrubbing Liquor
                                   42

-------
0)
•r-
O
CU

§  3
o

IO
.c
O
                       I
          UW Electrostatic Scrubber
            Centralia Power Plant
              March-May 1979
 Test Series #1,5,6, & 7

 Water Liquor

 {jr =  0.74-1.10 £/akm3 _

 TF6FCN Fog  Nozzle

 Pressure  =  .79 MPA


I     	I
                                         10

                             Spray Voltage (kV)
                 15
        fig.  IX-3.  Change in SO, Collection Efficiency vs. Spray
                   Voltage for Tests Using Water as a Scrubbing
                   Liquor
                                  43

-------
    removal is that a higher inlet S02 concentration raises the rate
    of mass transfer at the gas-liquia interface.

    The greatest effect of spray voltage upon S0«  collection was seen
    in test series 6.  By increasing the spray voltage from  0  to
    15KV,the efficiency was raised from 19.67% to  24.85%.   Fig. IX-3
    illustrates the change in S0? collection efficiency vs.  the spray
    voltage change in test series 1, 5, 6, and 7.

2.  Tests Using Na2C03 Solution as a Scrubbing Liquor
    S02 collection efficiency tests were run with Na?C(L liquor in March
    through May 1979.  For these tests, concentrated^Na«C03 solution
    (10% by weight) was metered into the mix tank at a rate designed to
    give a desired stoichiometric ratio.  The pilot plant was run for
    one half hour prior to each reading to allow the sodium carbonate
    concentration to equilibrate throughout the entire liquor system.

    As shown in Table IX-2 five sets of tests were conducted.  The over-
    all results of these tests showed the effect of spray voltage,
    stoichiometric ratio (SR), liquor-to-gas ratio (L/G), and inlet S(L
    efficiency varied from 38.38% to 97.41% using Na2C03 scrubbing liqoor.

    During test series 1-N the inlet S0? concentration was 1200 ppm,
    the highest encountered during these tests.  Even with the low
    stoichiometric ratio of .36, a collection efficiency of greater than
    71% was realized.  By increasing the spray voltage from 0   to 10 KV,
    the SO,, efficiency was increased by 2.1% when the SR = .29, "and by
    1.5% at SR = .36.

    Test series 2-N and 3-N demonstrate the effect of L/G upon S02
    collection efficiency as shown in Fig. IX-4.  With inlet S02 Concen-
    trations approximately the same, raising the L/G from 0.87 to
    0.96 Vaknr increased the S02 removal from 8% to 16%.  An increase
    in collection efficiency was also seen with the application of
    charge to the sprays, this difference being greater at lower stoich-
    iometric ratios.

    Inlet S02 concentrations of Runs 4 and 5 were only 265 ppm and 350 ppm,
    respectively, which resulted in corresponding low S0? collection
    efficiencies.  Fig. IX-5 illustrates the effect of inlet S02 concen-
    tration upon S0? efficiency with SR constant.  Despite low Tnlet S02
    levels test 5-N does show an increase in S0? removal from 45% to
    78% by increasing the SR from 0.33 to 1.75.  Collection efficiency
    at all stoichiometric ratios was increased by application of a 10 KV
    spray voltage as seen in Fig. IX-6.
                                   44

-------
              Table IX-2.
suits of SO, Tests at Centralia Power Plant Using Na2CO, Solution as
Scrubbing Liquor.                                      J
Test Series
No. & Date
1-N
3-30-79


2-N
4-18-79


3-N
4-19-79



4-N
5-3-79














Inlet
Gas Flow
sdm /mln
(sdcfm)
36.9(1302)
36.9 1302)
36.9(1302)
36.9(1302)
41.5(1465)
41.5
38.4
38.4
1465
1356)
1356)
35.9(1268)
35.9(1268)
35.9(1268)
35.9(1268)
35.9(1268)
32.7
32.7
32.7
32.7
1156)
1156)
1156)
1156)
32.7(1156)
32.7
32.7
32.7
1156)
1156)
1156)
33.8(1192)
33.8(1192)
33.8(1192)
33.8(1192)
33.8(1192)
33.8(1192)
33.8(1192)
33.8(1192)
Outlet
Gas flow
sdirr /mln
(sdcfm)
46.2(1632)
46.2(1632)
46.2(1632)
46.2(1632)
50.3(1777
50.3(1777
49.8(1757
49.8(1757
48.0
48.0
48.0
48.0
1695
1695
1695
1695








48.0(1695)
43.8(1547)
43.8(1547)
43.8(1547)
43.8(1547)
43.8(1547)
43.8(1547)
43.8(1547)
43.8(1547)
46.4(1637)
46.
46.
46.
46.
46.
46.
46.
1637
1637
1637
1637
1637
1637






1637)
S02
Concentration
(ppm)
Inlet
1200
1200
1200
1200
590
590
500
500
600
600
540
540
480
255
255
255
255
255
265
265
265
265
265
265
265
265
265
275
275
Outlet
350
330
275
260
85
80
14
10
230
215
112
108
52
70
66
66
62
60
52
55
58
66
63
98
95
115
111
115
118
Overall
Collection
Efficiency
(%)
63.44
65.53
71.27
72.84
81.95
83.01
96.37
97.41
48.76
52.10
72.27
73.26
85.52
63.26
65.36
65.36
67.46
68.51
73.74
72.23
70.71
65.80
67.35
49.21
50.77
40.40
42.48
42.57
41.07
Stoichiometric
Ratio
moles Na0CO,
/ l .t \
lmole inlet S02'
.29
.29
.36
.36
.66
.66
1.55
1.55
.37
.37
.82
.82
1.90
1.07
.07
.07
.07
' .07
.21
.21
.21
.82
.82
.60
.60
.45
.45
.45
.45
L/G
fc/akm3
(gal/lOOOacf)
1.06
1.06
1.06
1.06
9.9)
9.9
9.9)
9.9)
0.93 (8.6)
0.93
0.98
8.6)
9.2)
0.98 (9.2)
0.87 (8.1)
0.87 (8.1)
0.87 (8.1)
0.87 (8.1)
0.87 (8.1)
0.94 (8.8)
0.94
0.94
0.94
0.94
0.94
0.94
0.94
8.8)
8.8
8.8)
8.8
8.8)
8.8)
8.8)
0.91 (8.5)
0.91 (8.5)
0.91 (8.5)
0.91
0.91
0.91
0.91
0.91
8.5)
8.5)
8.5)
8.5)
8.5)
Corona
Charge
(kV)
(-)90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
Spray
Voltage
(kV)
0
(+)io
0
10
0
7.5
0
7.5
0
7.5
0
7.5
0
0
7.5
10
0
7.5
0
7.5
0
0
7.5
0
10
0
7.5
15
0
Demister
Voltage
(kV)
(+)60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
60
01

-------
             Table IX-2 (cont.)
Results of SO,, Tests at Centralia Power Plant Using
as a Scrubbing Liquor.
Solution
Test Series
No. & Date
5-N
5-17-79









Inlet
Gas Flow
sdm /min
(sdcfm)
32.3(1142)
32.3(1142)
32.3(1142)
32.3(1142)
32.3(1142)
36.8(1300)
36.8(1300)
36.8(1300)
36:8(1300)
36.8(1300)
36.8(1300)
Outlet
Gas Flow
sdm /min
(scdfm)
45.2(1595)
45.2(1595)
45.2(1595)
45.2(1595)
45.2(1595)
47.1(1662)
47.1(1662)
47.1(1662)
47.1(1662)
47.1(1662)
47.1(1662)
S02
Concentration
(pptn)
Inlet
340
340
355
355
355
338
338
330
330
360
360
Outlet
140
142.5
130
122
120
no
105
97
103
63
61
Overall
Collection
Efficiency
(V
42.49
41.46
48.85
52.00
52.79
58.39
60.28
62.42
60.10
77.63
78.34
Stoichiometric
Ratio
moles Na.CO.
/ £• J \
W>le inlet S02'
.33
.33
.42
.42
.42
.53
.53
.68
.68
1.25
1.25
L/G
a/a km3
(gal/lOOOacf)
0.88 (8.2)
0.88 (8.2)
0.88 (8.2)
0.88 (8.2)
0.88 (8.2)
0.77 (7.2)
0.77
0.77
0.77
7.2)
7.2)
7.2)
0.77 (7.2)
0.77 (7.2)
Corona
Charge
(kV)
90
90
90
90
90
90
90
90
90
90
90
Spray
Voltage
(kV)
10
0
0
10
14.5
0
10
10
0
0
10
Demister
Voltage
(kV)
60
60
60
60 .
60
60
60
60
60
60
60
en

-------
       UW Electrostatic Scrubber
         Centralia Power Plant
            March-May 1979
                  Test Series  #2-N

                  Na2C03 Liquor

                  r = 0.96
                           545 ppm (average)
                  TF6FCN Fog Nozzle
                  Pressure = .79 MPa
20
                     .5                 1.0

                       Stoichiometric Ratio
1.5
      Fig-  IX-4.   Effect of L/G on S02  Collection  Efficiency  For
                  Tests Using  Na2C03  Solution  as a Scrubbing  Liquor
                              47

-------
IQCf
   90
   80
   70
u
c
a;
•i—
U
   60 —
   5C
U
QJ
O
(_>

evj
   30
 20
10
    300
                     I               I
          UW Electrostatic Scrubber
            Central!a Power Plant
               March-May 1979
                             0.33
                                     Na2C03 Liquor

                                     | = 0.77 - 0.93 £/akm3

                                     Spray Voltage = 0 kV

                                     TF6FCN Fog Nozzle

                                     Spray Pressure = .79 MPa

                                    I	I
                400              500             600

                        S02  In  (ppm average)
700
            Fig. IX-5. S02 Collection Efficiency vs. Inlet SOo
                       Concentration at Varying Stoichiometric Ratios
                                  48

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    80
                   I             I     :
           UW Electrostatic  Scrubber
             Centralia  Power Plant
                March-May  1979
     70
o;
«    60
o
•^
•(->
o
o
o-
 C\I
o
to
     50
                                   Na2C03  Liquor

                                   {jr =  .82 £/akm3

                                   S02  In  = 345 ppm (average)
                                   TF6FCN  Fog Nozzle

                                   Pressure = .79  MPa
    40
      .25
              1
I
1
,50           .75         1.00

          Stoichiometric Ratio
          1.25
             1.50
               Fig.  IX-6.  Effect of Stoichiometric Ratio and Spray
                          Voltage on S02 Collection Efficiency
                                     49

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                               Section X

                              REFERENCES
1.  Kraemer, H. F. and H. F. Johnstone (1955) "Collection of aerosol
         particles in the presence of electric field," Ind. Engr.
         Chem. 47 2426.

2.  Penney, G. W. (1944) "Electrified liquid spray dust precipitator,"
         U.S. Patent No. 2,357,354.

3.  Pilat, M. J., S. A. Jaasund, and L. E. Sparks (1974) "Collection
         of aerosol particles by electrostatic droplet spray scrubbers."
         Envir. Sci. & Tech. £ 340-348.

4.  Pilat, M. J. (1975) "Collection of aerosol particles by electro-
         static droplet spray scrubber," APCA Journal 25_ 176-178.

5.  Pilat, M. J. and D. F. Meyer (1976) "University of Washington
         Electrostatic Spray Scrubber evaluation"  Final Report on
         Grant No. R-803278, EPA Report No. EPA-600/2-76-100 (NTIS
         No. PB 2526537AS).

6.  Pilat, M. J., G. A. Raemhild, and A. Prem (1978) "University of
         Washington Electrostatic Scrubber tests at a steel plant,"
         EPA Report No. EPA-600/7-78-177a.

7.  Pilat, M. J. and G. A. Raemhild (1978) "University of Washington
         Electrostatic Scrubber tests at a coal-fired power plant,"
         EPA Report No. EPA-600/7-78-177b.
                                  50

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                                TECHNICAL REPORT DATA
                         (Please read Inunctions on the reverse before completing)
1. REPORT NO.
 EPA-600/7-79-245
                           2.
                                                      3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
University of Washington Electrostatic Scrubber
 Tests: Combined Particulate and SO2 Control
                                 5. REPORT DATE
                                  November  1979
                                 6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)

M.J.Pilat
                                 8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
University of Washington
Department of Civil Engineering
Seattle, Washington  98195
                                 10. PROGRAM ELEMENT NO.
                                 EHE624A
                                 11. CONTRACT/GRANT NO.

                                 Grant No. R806035
12. SPONSORING AGENCY NAME AND ADDRESS
 EPA, Office of Research and Development
 Industrial Environmental Research Laboratory
 Research Triangle Park, NC 27711
                                 13. TYPE OF REPORT AND PERIOD COVERED
                                 Final: 6/78 - 8/79	
                                 14. SPONSORING AGENCY CODE
                                   EPA/600/13
15. SUPPLEMENTARY NOTES IERL-RTP project officer is Dale L. Harmon, Mail Drop 61, 919/
541-2925.  EPA-600/7-78-177a and -177b are earlier related reports.
16. ABSTRACT
         The report gives results of tests of a 1700 a cu m/hr University of Wash-
 ington electrostatic spray scrubber pilot plant on a coal-fired boiler to demonstrate
 its effectiveness for controlling fine particle and SO2 emissions. The multiple-pass
 portable pilot plant operates by combining oppositely charged aerosol particles and
 water droplets in two spray towers. Aerosol charging sections at a negative polarity
 precede each spray tower. For these tests, the pilot plant used only one charging
 section and one spray tower. A liquor recycle system was constructed, permitting
 the pilot plant to operate in an  open- or  closed-loop mode. All SO2 tests were run
 in an open-loop mode using either water or Na2CO3 solution as the scrubbing liquor.
 Simultaneous inlet and outlet source tests  using cascade impactors provided size-
 dependent and overall mass basis particle collection efficiency data. Measured over-
 all particle collection efficiencies were  98.99%-99. 80%, depending on scrubbing
 operating  conditions. SO2 collection efficiencies were 8.02%-97.41%, depending on
 the scrubber operating conditions, inlet SO2 concentration,  and the type of scrubbing
 liquor used.
17.
                             KEY WORDS AND DOCUMENT ANALYSIS
                DESCRIPTORS
                                          b.lDENTIFIERS/OPEN ENDED TERMS
                                              c. COSATI Field/Group
 Pollution
 Flue Gases
 Scrubbers
 Electrostatics
 Desulfurization
 Dust
 Aerosols	
Sodium Carbonates
Pollution Control
Stationary Sources
Particulate
13B
2 IB
07A,13I
20C
07D
11G
07B
18. DISTRIBUTION STATEMENT
 Release to Public
                                          19. SECURITY CLASS (This Report)
                                          Unclassified
                                              21. NO. OF PAGES
                                                  60
                     20. SECURITY CLASS (This page)
                      Unclassified
                                              22. PRICE
EPA Form 2220-1 (9-73)
                                         51

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