Environmental Protection Technology Series
                                   CONTROL  OF
RECLAMATION (SINTER] PLANT  EMISSIONS
    USING ELECTROSTATIC  PRECIPITATORS
                         Industrial Environmental Researun Laooratory
                              Office of Research and Development
                             U.S. Environmental Protection Agency
                        Research Triangle Park, North Carolina  27711

-------
                  RESEARCH  REPORTING SERIES
Research reports o.f the  Office  of Research-and Development,
U.S. Environmental Protection "Agency,  have been grouped into
five series.  These five broad  categories were established to
facilitate further development  and application of environmental
technology.  Elimination of  traditional  grouping was consciously
planned to foster technology transfer  and a maximum interface in
related fields.  The  five  series  are:

          1.  Environmental  Health Effects Research
          2.  Environmental  Protection Technology
          3.  Ecological Research
          4.  Environmental  Monitoring
          5.  Socioeconomic  Environmental Studies

This report has been  assigned to  the ENVIRONMENTAL PROTECTION
TECHNOLOGY series.  This series describes research performed
to develop and demonstrate instrumentation,  equipment and
methodology to repair or prevent  environmental degradation from
point and non-point sources  of  pollution.   This work provides the
new or improved technology required for  the control and treatment
of pollution sources  to  meet environmental quality standards.

                      EPA REVIEW NOTICE

This report has been reviewed by the U. S. Environmental Protection
Agency, and approved for publication.  Approval does not signify that
the contents necessarily  reflect the views and policies of the Agency, nor
does mention of trade names or commercial products constitute endorse-
ment or recommendation for use.
This document is available  to  the  public  through the National
Technical Information Service,  Springfield,  Virginia  22161.

-------
                  CONTROL OF

RECLAMATION  (SINTER) PLANT EMISSIONS

  USING  ELECTROSTATIC  PRE CIPITATORS
                         by

                   John Varga, Jr.

            Battelle-Columbus Laboratories
                   505 King Avenue
                Columbua, Ohio 43201


           Contract No. 68-02-1323, Task 32
                ROAPNo. 21AQR-042
             Program Element No. 1AB015


         EPA Task Officer:  Robert C. McCrillis

      Industrial Environmental Research Laboratory
        Office of Energy, Minerals, and Industry
          Research Triangle Park, NC  27711


                    Prepared for

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

                    January 1976

-------
                            SUMMARY
The general aspects concerning the production of sinter in the inte-
grated iron and steel industry are discussed as an introduction to the
discussion on the control of emissions from sinter-plant windboxes.
Some technical design information is presented, as are data pertain-
ing to the characteristics of emissions.  A limited amount of informa-
tion is provided concerning the procedures used to develop the  required
design criteria for the construction of electrostatic precipitators.

        "This report was  prepared in response to Item AM-1-3
        of the Protocol of the First Working Meeting of the
        USA/USSR Task Force on Abatement of Air Pollution
        from  the Iron and Steel Industry. "
                            PEOEPAT

PaccMaxpHBaioTCfl npotfjieMH  otfmero xapaKTepa,
npw  npoHsBOBCTBe arnoMepaxa B MeTajuiyprMqecKoK
           3ia  patfoTa HBJineTCH BBe^enMeM B paccMorpeHHe
          KOHTpojiH BHCJpocos M3 BosflyxoflysoK  arjiOMepauH-
OHHHX $a(5pMK.  HaH MaTepHan TeXHHqeCKO-KOHCTpyKTHBHOrO
xapaKTepa, a Tarae aanHbie oTHocnmHecH K xapaKtepwcTHKaM
Bbi(5pocoB. HpeflCTaBjieHbi  HeKOTopue  aaHHue o MeTOflHKe  pas-
pafiOTKH KOHCTpyKTHBHMX  KpMTepH6B,  H6O(5xOflMMblX
HHH  3JieKTpO$MJIbTpOB.
        OTOT flOKjiaa noflroTOBJien B  cornaciiw  c nyHKTOM
        AM-I-3  npoTOKOJia  FlepBoro Pa6ouero CoBemaHHH Pa
        6otieii Tpynnu CU1A/CCCP no Bopb(5e c
        BoaflyuiHoro BaccewHa MeTajuiyprwuecKOM
        HOCTbK).

-------
                       TABLE OF CONTENTS

                                                                Page
I.  INTRODUCTION	     1

II.  TRENDS OF SINTER USE IN THE U.S. INTEGRATED
 IRON AND STEEL INDUSTRY	     3

III.  AIR POLLUTION CONTROL  FOR RECLAMATION
 (SINTER) PLANTS	     5

IV.  CHARACTERIZATION OF EMISSIONS	    11

V.  RECLAMATION (SINTER) PLANT ELECTROSTATIC
 PRECIPITATOR DESIGN CHARACTERISTICS	    21

      Basic Electrostatic Precipitator Parts	    21
           Dry-Dust-Collection Fundamentals ......    23
           Factors Affecting Dry Electrostatic
             Precipitator Operation	    28
           Dry Electrostatic Precipitator Design Methods .   .    40
      Wet Electrostatic Precipitator	       50
           Wet-Dust-Collection Fundamentals ......    50
      Horizontal-Flow Wet Electrostatic Precipitator   ...    58
      Range of Applications	    60
           Reclamation (Sinter) Plant Design Specifications   .    61
           Reclamation (Sinter) Plant Electrostatic
             Precipitator Design  Data	    61

VI.  REFERENCES  .   .   .	    71
                         LIST OF FIGURES
Figure 1.  Trend in the use of sinter in the metallic
           burden of U. S. blast furnaces	     4

Figure 2.  Trend in the use of limestone in blast furnace
           sinter as shown by the use of limestone in
           the sinter mix  .      	     4

-------
                          LIST  OF FIGURES
                              (Continued)

                                                                  Page
Figure 3.   Effect of temperature and sinter basicity on
            resistivity of sinter-plant particulate	      8

Figure 4.   Effect of sinter basicity on the collection
            efficiency of an electrostatic precipitator ....      9

Figure 5.   Flow diagram of a typical reclamation
            (sinter) plant  	     12

Figure 6.   Size distribution of particulates entering
            dust collecting systems	     14

Figure 7.   Size distribution of sinter plant particulates
            collected by  different types of dust collecting
            equipment	     14

Figure 8.   Size distribution of particulates released to the
            atmosphere after passing through sinter plant
            cleaning systems	     16

Figure 9.   Particle-size distribution of  sinter machine dust  .     17

Figure 10.  Two possible rectifier circuits for an
            electrostatic precipitator	     22

Figure 11.  Typical duct  electrostatic precipitator   ....     23

Figure 12.  Voltage waveform for unfiltered half-wave
            and full-wave rectification	     29

Figure 13.  Waveform in electrostatic precipitator
            after  discharge	     30

Figure 14.  Dust-collection efficiency as  related to peak
            voltage for a typical  electrostatic precipitator  .   .     33

Figure 15.  Electrostatic precipitator efficiency
            as affected by gas flow	     34
                                   iv

-------
                          LIST OF FIGURES
                             (Continued)

                                                                 Page

Figure  16.  A typical relationship between dust resistivity
            and temperature, for a gas improperly conditioned
            for the 93 to 204 C (200 to 400 F) range   ....    39

Figure  17.  Relationship between precipitation-rate
            parameter w  and resistivity of fly ash	    42

Figure  18.  Relationship between the  sulfur content in
            electric utility plant fuel  and the precipitation-
            rate parameter to at 149 C (300 F)  ......    44

Figure  19.  Collection efficiency  as affected by power rate
            per unit gas flow	    45

Figure  20.  Relationship between collection efficiency and
            seetionalization (number  of bus sections per
            unit gas flow)  for utility fly-ash precipitators  .   .    45

Figure  21.  Relationship between precipitation-rate
            parameter w and power density for fly
            ash precipitators	    48

Figure  22.  Electrical resistivity of reclamation (sinter)
            plant dust as  affected by gas temperature and
            sinter mixture	    67

Figure  23.  Relationship between the  sulfur content in
            electric-utility-plant fuel and the precipitation
            rate parameter	    67

Figure  24.  Collection efficiency  as affected by the ratio
            of collection area to gas velocity	    69

                          LIST OF TABLES

Table 1.   Reclamation (Sinter) Plants in the U. S,
           Integrated Iron and Steel Industry	     6

Table 2.   Sinter-Mix Composition	    13

-------
                           LIST OF TABLES
                             (Continued)

                                                                Page

Table 3.   Composition of Particulate Emissions	    15

Table 4.   Gaseous Emissions From Reclamation
           (Sinter) Plants	    16

Table 5.   Size Distribution of Particulates  Entering
           the Atmosphere From an Electrostatic-
           Precipitator-Controlled Sinter Plant	    18

Table 6.   (Plant D) Gaseous Emissions Entering the
           Atmosphere From an Electrostatic Precipitator
           Controlled Sinter  Plant	    19

Table 7.   Representative  Precipitation Rates, co,
           for Various Applications	    42

Table 8.   Number  of Rappers in Electrostatic
           Precipitators for  Various Applications	    46

Table 9,   Nomenclature for Wet-Dust-Collection
           Fundamentals	    53

Table 10.  Equipment Specifications	    62

Table 11.  Reclamation (Sinter) Plant Data for  Figure 22   ..    68

Table 12.  Reclamation (Sinter) Plant Electrostatic-
           Precipitator Characteristics	    70
                                   VI

-------
                         I.  INTRODUCTION
The use of sintering processes to improve the characteristics of
blast-furnace burden materials has long been an accepted practice
in the integrated iron and steel industry.  In recent years,  as the
need increased for recovering the metallic values from the dusts
and scrap generated by the various  iron and steelmaking  processes,
the plants have become known as reclamation plants, rather than as
sinter plants.

A major problem in the control of emissions from a reclamation
plant  is the minimizing of emissions from the windbox  of the  sinter-
ing machines.  The integrated iron  and steel industry in the United
States has  used  many types of control equipment in attempts to con-
trol emissions from sinter machines,  with electrostatic precipitators,
cyclones,  and scrubbers being used on 93 percent of the sinter
machines.

This Protocol Report discusses the application of electrostatic pre-
cipitators for the control of sintering-machine  windbox emissions,
and is based on  available published  information and additional
information supplied by iron and steel  companies.

-------
             II.  TRENDS OF SINTER USE IN THE U.S.
             INTEGRATED IRON AND STEEL INDUSTRY
The integrated iron and steel industry of the United States operates
45 reclamation plants having a total of 72 sintering strands.  The
reclamation plants consist of 2,9 single-strand plants, 10 double-
strand plants, 3 plants having 3  strands, 2 plants with 4 strands,
and  1 plant  with 6 strands.  During 1974,  the integrated iron and
steel industry produced 36, 985>, 182 metric tons (40, 769, 185 net tons)
of blast furnace sinter. (1)  The greatest tonnage of sinter was pro-
duced in 1964 and amounted  to 49, 518, 907 metric tons (54, 585, 251
net tons).  The trend in the percentage of sinter used in the metallic
burden (iron ore + pellets +  sinter) of blast furnaces  is shown in
Figure 1.  The year 1961  was the year of greatest percentage use  of
sinter, 44 percent of the blast-furnace metallic burden.  The de-
crease in use of sinter has beein caused by the increase in production
and use of pellets in the U. S. integrated iron and steel industry.

Although there has been a decline in the use  of sinter in blast furnaces,
the sinter that is being made iti more  and more  of the self-fluxing
variety (high basicity).  The trend in  increased  basicity is illustrated
by the increased use of limestone in the sinter mix as shown in Figure
2.  Integrated iron and steel plants that are heavily committed to the
use of self-fluxing sinter are using limestone in amounts even
greater than the average illustrated in Figure 2.

-------
            50
Q
CC
m
o
_i
_i
<
UJ
5
u.
O
I-
LU
         1-
         o
            40
            30
            20

             1960
                1965
                            1970
                                      1974
                              YEAR
Figure 1.   Trend in the use of sinter in the metallic
            burden of U. S.  blast furnaces
     20

  X
  I „
  CC £
  UJ U
  g I
  w £
  - I 10

  §1
                           I  '  '  '  '  I  '  '  '
               1960
                          1965         1970      1974
                              YEAR
  Figure 2.  Trend in the use of limestone in blast
              furnace  sinter as  shown by the use of
              limestone in the sinter mix
                           4

-------
                III.  AIR POLLUTION CONTROL FOR
                 RECLAMATION (SINTER) PLANTS
The emissions associated with reclamation-plant operation are pri-
marily particulates  that become entrained in the combustion air as
it is drawn through the sinter mix into the windbox. However,  sulfur
dioxide,  carbon monoxide,  and hydrocarbons may also occur in the
emissions, depending on the operating practice  of(a particular rec-
lamation plant.  Sulfur dioxide may originate from sulfur contained
in the ore and the coke that are used as part of the sinter mix and
in the fuel used to ignite the mixture, and it may also originate from
the sulfur contained in machining oils that adhere  to steel turnings,
which are recycled to a reclamation plant to recover the metallic
values.   Machining oils are  also the principal source of hydrocarbons
in reclamation-plant windbox emissions.

Electrostatic precipitators,  scrubbers, and cyclones are the princi-
pal means for controlling emissions from the windboxes of sinter
machines, while baghouses are the preferred method for control  at
other reclamation-plant locations,  such as  sinter  discharge,  crush-
ing,  screening, and material-transfer points.  The reclamation
plants in the U. S.  integrated iron and steel industry are listed in
Table 1.  The distribution of air pollution control  equipment used on
the windbox of sinter machines is as follows:
                	Type of Control	   Number

                Electrostatic Precipitator       22
                Cyclones                        11
                Scrubbers                        9
                Baghouse                        1
                Steam Ejector                    1
                Mechanical                       1
                   Total                        "45

-------
TABLE 1.  RECLAMATION (SINTER) PLANTS IN THE U. S. INTEGRATED IRON AND STEEL INDUSTRY
Company
Alan Wood Steel Co.
Bethlehem Steel'Corp.

) It I Steel Corp.
U. S. Steel Corp.






W-P Steel Corp.
Bethlehem Steel Corp.
J & I Steel Corp.
Bethlehem Steel Corp.

National Steel Corp.
W-P Steel Corp.
Armco Steel Corp.
J & L Steel Corp.
Republic Steel Corp.


U. S. Steel Corp.

Youngstown S & T Co.
Armco Steel Corp.
National Steel Corp.
Inland Steel Co.
U. S, Steel Corp.

Youngstown S & T Co.
Bethlehem Steel Corp.
Interlake Steel Corp.
National Steel Corp.
Republic Steel Corp.
U. S. Steel Corp.
I-H, Wisconsin Steel
Republic Steel Corp.
U. S. Steel Corp.
Lone Star Steel Co.
Armco Steel Corp.
CF 4 I Corp.
U. S. Sreel Corp.
Kaiser Steel Corp.
Location
Swedeland, Pa.
Bethlehem, Pa.
Johnstown, Pa
Aliquippa, Pa.
Braddock, Pa.
McKeesport. Pa.
Rankln, Pa.
Saxonburg, Pa.


Falrless Hills, Pa.
Monessen, Pa.
Lackawanna. N. Y.
Star Lake, N. Y.
Sparrows Point, Md.

Welrton, W. Va.
E. Steubenvtlle. W. Va.
Mlddletown, Ohio
Cleveland, Ohio
Cleveland, Ohio
Youngstown, Ohio
Warren, Ohio
Lorain, Ohio
Youngstown, Ohio
Campbell, Ohio
Ashland, Ky.
Ecourse, Michigan
East Chicago, Ind.
Gary, Ind.

Indiana Harbor, Ind.
Burns Harbor, Ind.
South Chicago, 111.
Granite City, 111.
South Chicago, 111.
South Chicago, 111.
South Chicago. 111.
Gadsden, Ala,
Falrfield, Ala.
Lone Star. Texas
Houston, Texas
Pueblo. Colorado
Geneva, Utah
Fontana, Cal.
No. of
Strands
3
4
2
1
1
1
1
1
1
1
2
1
2
2
6
1
2
1
1
1
1
1
1
1
1
2
1
1
1
2
3
1
1
1
1
1
3
1
1
4
1
1
2
2
2
Estimated
Annual
Capacity,
net tons
475,000
2,400,000
1, 100, 000
2,700,000
600,000
325,000
600,000
1,500,000
1, 500, 000
1.500.000
3, 000, 000
500, 000
1, 100, 000
1,400,000
3, 600. 000
4,250,000
2, 800, 000
550, 000
900, 000
900; 000
400.000
500, 000
400, 000
500,000
1. 500, 000
800,000
800, 000
2,000,000
1.200,000
1.500.000
5,200,000
1.200,000
2.000.000
750,000
1,000,000
400,000
2.200.000
500. 000
500, 000
2, 500, 000
300.000
500. 000
900.000
900. 000
1,300,000
Alt Pollution Control
Ignition
Fuel
Coke -oven gas
Natural gas
Natural gas
Coke-oven gas
Mixed gas
Natural gas
Natural gas
Natural gas
Natural gas
Natural gas
Mixed gas
Coke-oven gas
Coke -oven gas
Fuel oil
Coke -oven gas

Coke-oven gas
Coke -oven gas

Natural gas
Coke-oven gas
Coke-oven gas
Coke -oven gas
Natural gas
Natural gas
Natutal gas
Natural gas
Coke-oven gas
Coke -oven gas
Mixed gas
Natural gas
Natural gas

Coke-oven gas
Coke-oven gas
Coke-oven gas
Natural gas
Coke -oven gas
Coke -oven gas
Natural gas
Natural gas
Coke-oven gas
Coke-oven gas
Mixed gas
Coke -oven gas
Machine
Wind box
Scrubber
ESP
ESP
Cyclones
ESP
Scrubber
ESP
ESP
ESP
ESP
ESP
ESP
ESP
Cyclones
ESP
Scrubber
Cyclones
Scrubber
Scrubber
ESP
Cyclones
Cyclones
Cyclones
Cyclones
ESP
Cyclones
Mechanical
Scrubber
ESP
ESP
ESP
ESP
Scrubber
ESP
Scrubber
Cyclones
ESP
Scrubber
Cyclones
ESP
Scrubber
Steam Ejector
ESP
ESP
Baghouse
Machine
Discharge
Baghouse
Baghouse
Scrubber












Baghouse
Wet separators

Recycle
Multlcyclones









Baghouse
Baghouse

Baghouse

Cyclones




Baghouse


Baghouse
Scrubber

Crushing &
Screening

Baghouse
Scrubber





Baghouse



Scrubber

Scrubber
Baghouse
Wet separators

Baghouse
Multlcyclones










Baghouse

Baghouse
Baghouse
Baghouse

Baghouse








References
(2.3)
(4,5,6,7)
(8.9)
(10,11,12)
(13)
(14)
(15)

(16,17)

(13)
(18)
(19)
(13.20)
(13,21)
(13,22)
(13.23)
(24)
(25)
(13,26)
(13.27,28)
(13,28)
(13,28)
(13,29)
(30)
(13.31)
(32)
(33)
(34.35)
(13)
(36)
(13)
(37)
(38,39)
(40.41,42)
(13)
(43,44)
(45)
(13)
(13)
(15)
(15)
(13,46,47)
(13,15)
(48,49)

-------
Most sintering operations that use electrostatic precipitators  as
control equipment for windbox omissions also use cyclones, or
mechanical collectors, between the windbox and the fan.  In the pre-
ceding tabulation, 10 sinter machines are listed as having cyclones
for the  control of windbox emissions.  The  cyclones are the only air
pollution control devices on these  10 machines.

With respect to the control of emissions, developments in blast-
furnace technology have created problems for the reclamation-plant
operator.  The  increased use of high-basicity sinter introduces
higher limestone additions  to the sinter mixture.  The relationship
between temperature and resistivity for six different sinter-plant
dusts is shown in Figure 3.' "'  The effect  of sinter basicity on the
efficiency of an electrostatic precipitator is shown in Figure 4.'-^'
The variations in resistivity and the effects of basicity are the rea-
sons that the control of sinter plant emissions  is difficult.  The
problem of different  resistivities may result in the installation of
additional electrostatic-precipitator chambers, with one group de-
signed to collect the  iron oxide particulates and another group to
collect  the limestone particulates.  In some instances, electrostatic
precipitators  were replaced by scrubbers to overcome the problem
of different properties of the two types  of emissions.

Integrated  iron  and steel plants that have facilities for making
finished steel products, such as threaded pipe,  generate oily ma-
chine turnings which are sent to the reclamation plant for recovery
of the metallic values.  The oil on the turnings  creates problems in
electrostatic precipitators,  and in some cases hydrocarbons will
pass through a scrubber  system.  Electrostatic-precipitator col-
lector plates become coated with films  of oil, which makes removal
of the dusts difficult  and  in some cases impossible.  If a steel plant
is committed  to the recovery of oily turnings in its reclamation plant,
the trend is to use high-energy wet scrubbers for air pollution
control, rather than  electrostatic precipitators.  The three  newest
reclamation plants under construction or recently placed into opera-
tion in the  United States (those located at Bethlehem Steel Corpora-
tion's Sparrows Point and Burns Harbor plants, and the Armco Steel
Corporation's plant at Middletown, Ohio) all have high-energy
scrubbers  as  the primary air pollution control equipment on the
sinter-plant windbox. (*•*, 22, 25, 37)

-------
      100
V

o


>

£
C/}
LU
OC
   10
     12
   10
     ,11
   10
     10
    109
                       TEMPERATURE, F
                      200              300
                                            400
        i  i  i i I i i  i T  | i ri ii IT i i I i i  i i I i i  n
                                        PLANT A
                                      BASICITY 4.0
                                                CaCO, -
                        PLANT A
                      BASICITY 4.0
                       PLANT B
                     BASICITY 1.0
                     PLANT C
                    BASICITY 4.0
                     PLANT D
                   BASICITY 4.0
  PLANT E
BASICITY 1.0

i   .   .
                                             ,  .  .   I
          50
                        100            150
                       TEMPERATURE, C
                                          200
Figure 3.   Effect of temperature and sinter basicity on
            resistivity of sinter-plant particulate
                             8

-------
  100
   90
~  85
£
0  80
o
UL
ul  75



   70
   65
    0.5     0.7
0.9      1.1      1.3
  SINTER BASICITY
1.5     1.7
Figure 4.  Effect of sinter basicity on the collection
            efficiency of an electrostatic precipitator

-------
              IV.  CHARACTERIZATION OF EMISSIONS
Emissions from reclamation plants usually consist of the following:
(1) minor amounts of dust generated in the handling and grinding of raw
materials, (2) particulates that are drawn down through the grate bars
of the sintering machine, (3) combustion gases from ignition and firing
of the sinter mix, and (4) dust generated during the cooling,  crushing
and screening operations. Points of emission are indicated in the flow
sheet in Figure 5 for a typical reclamation plant.  Circled numbers on
the flow sheet are indexes to the circled numbers in the following dis-
cussion on the characterization of emissions.

  (T)  Iron Ore Dust.  Particles are rounded to elongated in shape and
can have a size as small as 2 microns.  Larger particles are opaque,
and red-orange when viewed under top light.  Individual small grains
are transparent and blood-red. (51)  The particulates consist mostly of
Fe2O3 or Fe3O4,  some  silica,  and  limestone, with a Mohs hardness of
5 and a specific gravity  of 5.2.

  (2)  Limestone Dust.  Primarily the mineral calcite.  It is  colorless,
with light-transmitting characteristics varying from transparent to
translucent.  Because of their good cleavage,  particles generally occur
as rhombohedra.  Fragments may also  occur as prisms. (->!)  The Mohs
hardness is 3 and the specific  gravity 2. 7.

  (3)  Coke Dust.  Particles are opaque, irregularly shaped,  quite
porous, and rough with some  straight, sharp edges.  They are gray to
black in reflected light and are cibout 90 percent carbon. (^1)

  (4)  Combustion Products.  Gases leaving the sintering strand are
the result of the combustion of coke or coal in the sinter mix and of the
fuels used to ignite the sinter mixture.  Fuel for ignition is primarily
coke-oven gas or natural gas,  with some  use of mixed gas or fuel oil.
Hydrogen sulfide in  the coke-oven gas and sulfur in the coke  or coal in
                                 11

-------
COARSE ORE

LIMESTONE COKE

i

                                            DUST]  [COLLECTED DUST
                                          ATMOSPHERE
Figure 5.   Flow diagram of a typical reclamation (sinter) plant.
                                12

-------
the sinter mix can lead to sijlfur dioxide emissions in the off-gas.
Even though an excess of air is drawn through the sinter mix to assure
oxidizing conditions, in most caises it is insufficient to burn the hydro-
carbons  completely  in the sinter mix (hydrocarbons originating from
oily turnings and volatiles in coal and coke); thus unburned hydro-
carbons  may be present in the sinter-plant off-gas.  Incomplete com-
bustion also produces carbon monoxide in the off-gas.

  (D   ©    (Z)  Sinter Dust.  Dust may contain particles of iron
oxides, calcite, iron-calcium silicates, and quartz.  Iron oxide can be
opaque,  black, rounded particles of magnetite (Fe^Q^) with angular
faces and/or dense, rounded,  elongated, and nearly spherical agglomer-
ates of hematite (Fe2O3).  Calciite occurs as  smooth, rounded parti-
cles, and quartz as  a transparent, rounded particle. The iron-calcium
silicates are transparent, vitreous,  colorless to yellow to  green, and
irregularly rounded with smooth surfaces. l-*l)

  Qj)  Atmospheric Emissions.  Characterization of emissions to the
atmosphere are discussed below, on the basis of work reported by
plants in the U.S. integrated iron and steel industry.

Data pertaining to the sinter-mis composition from three sinter plants,
the chemical compositions of particulate emissions, and the composi-
tions of gaseous emissions are given in Tables 2, 3, and 4,
respectively. (52, 53)

                TABLE 2.  SINTER-MIX COMPOSITION

                            weight percent
 Sinter-Mix Components         Plant F       Plant G         Plant H
Iron ore
Dry blast-furnace dust
Blast-furnace filter cake
Melt-shop slag
Rolling-mill scale
Basic -oxygen-furnace dust
Miscellaneous dust
Limestone or dolomite
Coke
29.1
1.3
15.8
6.5
11.5
3.5
0.0
28.2
4. 1

82. 0


0.0
0.0
0.0
15.0
3.0
49.5
5.6
4.9
0.0
7.6
0.0
6.7
20.8
4.9
                                 13

-------
      o
      111
      z
      ui
      DC
      LU
      O
      OC
      UI
      a.
      a
      LU
100
 90
 80
 70
 60
 50
 40
 30
 20
 10
  0
   1
                       i 11ui
11 nl    i  i i  i11nl
                                                              i   i  i i i in
                           10            100            1000
                                 PARTICLE SIZE, microns
                               10000
Figure  6.   Size  distribution of particulates entering dust collecting
             systems
                      100
                       90
                       80
                       70
                       60
                       50
                       40
                       30
                       20
         PLANT F
       MULTICYCLONES-
                        10
                                   100
                                              1000
                                                        10000
                                  PARTICLE SIZE, microns
                             'Policeman is an enlarged section of the duct
                              containing baffles and a right-angle bend.
  Figure  7.   Size distribution of sinter plant particulates collected
               by different types  of dust collecting equipment
                                      14

-------
     TABLE 3.  COMPOSITION OF PARTICULATE EMISSIONS

                           weight percent
Particulate Component
Fe2O3
CaO
MgO
K20
Si02
A1203
Na20
ZnO
MnO
Chlorides
Sulfates
Hydrocarbons
Other
Loss on Ignition
Total
Plant F
33.9
7. 1
5.3
5.2
4.8
2.6
1.6
0.4
0.2
8.5
7.5
7. 4
1.6
13.9
100.0
Plant G
11.7
10.9
0.4
0.6
2.4
4.3
0.8
0. 1
0. 1
3.0
16.5
36.9
0.0
12.3
100.0
Plant H
28.0
15.0
2.0
8. 1
4.6
2.5
0.0
0.0
0.0
8.8
2. 1
0.0
0. 0
28.9
100.0
The  size distributions of participates entering the dust-collecting sys-
tems in Plants F and G are shown in Figure 6. (52)  The size distribu-
tions of particulates collected by different dust-collection equipment in
Plants F and G are shown in Figure 7(52)^ an(j the size distribution of
particulates released to the atmosphere from Plants F, G,  H and I
are shown in Figure 8. (52> 53> 54)

Particle-size distributions of particulates entering a mechanical col-
lector vary over a considerable range, as shown in Figure 9. ^  '  The
size range of the particulates lesaving the mechanical collector and
entering the electrostatic precipitator is of a smaller magnitude than
that  of particulates entering the mechanical collector.
                                  15

-------
       TABLE 4.  GASEOUS EMISSIONS FROM RECLAMATION
                  (SINTER) PLANTS


Gaseous Component
Sulfur dioxide
Chlorides
Fluorides
Ammonia

Milligrams per Cubic Meter
Plant F Plant G Plant H
78.0 65.0 36-65
80.0 32.0 5-44
8.0 0.5 0.00
0.0 2.6 0.00
Volume
Percent
Plant H




Carbon dioxide
Carbon monoxide or
  illuminants
Oxygen
               4o
 3.4- 5.0

 0.4- 0.9
16.5-18.1
               100

               90

               80

               70

               60

               50

               40

               30

               20

               10

                0
 PLANT G\  \

X \\
                 1
          5    10         50   100

             PARTICLE SIZE, microns
                                                          500
        Figure 8.   Size distribution of particulates released to the
                   atmosphere after passing through sinter plant
                   cleaning systems
                                   16

-------
 LU
 N
 CO
 UJ
 o
 <
 LU
 OC
 o
 LJL
 Q
 01
 z
 <
 LU
 OC
 LU
 O
 CC
 LU
 O.
 I-

 C3
 LU
 §
 O
99.9
99.8
99.5
99.0
98.0
95.0

90.0

80.0
70.0
60.0
50.0
40.0
30.0
20.0

10.0
 5.0
 2.0
 1.0
 0.5
 0.2
 0.1
,   SIZE RANGE OF DUST FROM MECHANICAL
COLLECTOR TO ELECTROSTATIC PRECIPITATOR
                            SIZE RANGE OF DUST FROM SINTER
                          MACHINE TO MECHANICAL COLLECTOR
                                           I
                                             i i
                                        J_
                                                                  i i  i
        1
              345     10    20  30   50    100
                          PARTICLE SIZE, microns
                                              200 300   500   1000
      Figure 9.   Particle-size distribution of sinter machine dust

During 1975, emission tests were made on a sinter plant having elec-
trostatic precipitators as the wlndbox air pollution control system.
The sinter machine has four strands with an estimated production
capacity of about 227 metric tons (250 net tons) per hour.   The  sinter
mix composition was as follows:
             Sinter-Mix Components
     Iron ore

     Reclaimed oily mill scale and flue dust

     Reclaimed basic oxygen furnace slag

     Limestone and dolomite

     Coal

                           Total
                                              Weight Percent

                                                     52

                                                      8

                                                     17

                                                     16

                                                      7

                                                    100
                                   17

-------
The sinter produced has a basicity varying between 1. 0 and 1. 5,  which
is in the range of self-fluxing and superfluxing sinter,  for the particular
plant operation.  Windbox exhausts are controlled by multiclones, fol-
lowed by electrostatic precipitators.  One electrostatic precipitator is
used to control emissions from two sinter strands,  and each is de-
signed to operate at a gas flow rate of 10, 903 m^/min  (385, 000 acfm)
at 118 C (245  F).  The size distributions of particulates collected dur-
ing two tests are given in Table 5. (54)  xhe variation in the size distri-
butions is not explained in the test report.  However, this may have
been caused by the  day-to-day variations in the fineness of the mate-
rials charged to the sinter mix.

  TABLE 5.   SIZE  DISTRIBUTION OF PARTICULATES ENTERING
              THE ATMOSPHERE FROM AN ELECTROSTATIC-
              PRECIPITATOR-CONTROLLED SINTER PLANT

                             (Plant I)
       Particulate Size,     Cumulative Weight Percent Retained
           microns            Test No.  1         Test No. 2
>12.00
7.50
5. 10
3.50
2.20
1. 10
0.68
0.46
<0.46
54.36
62.56
65.05
66.62
69.22
70.49
72.50
73.56
100.00
10.43
21. 50
30.97
40.20
47.89
58.65
66.99
76.48
100.00
        Note: Particle size determinations were made with an
              Andersen Cascade Impactor.
Gaseous emissions obtained from the same tests are given in
Table 6. (54)
                                  18

-------
    TABLE 6.  (PLANT I) GASEOUS EMISSIONS ENTERING THE
               ATMOSPHERE FROM AN ELECTROSTATIC
               PRECIPITATOR CONTROLLED SINTER PLANT
Gaseous Component
Condensable hydrocarbons
Noncondensable hydrocarbonsi
Fluoride
Carbon monoxide
Sulfur dioxide
Sulfur trioxide
Nitrogen oxides
Milligrams
Nm3
1.036
812. 11
3.21
'— •
—
—
—
Grains
SCFD*
0. 000453
0.3539
0.00140
-
—
—
—
ppm
-
230
-
8000
900
11.5
71.4
'Standard cubic foot (dry).
For Plant I,  particulate contents at the electrostatic precipitators were
as follows:
    Average ESP inlet
    Average ESP outlet
mg/m3 (dry)

    595

     69
grains/ft3 (dry)

      0.26

      0. 0.3
This corresponds to a collection efficiency of 88. 4 percent.  Total emis
sions to the atmosphere amounted to 23. 4 kg per hour (51.6 pounds per
hour). This was equivalent to 0. 214 kg per tonne (0.428 pound per net
ton) of sinter.
                                  19

-------
       V.  RECLAMATION (SINTER) PLANT ELECTROSTATIC
             PRECIPITATOR DESIGN CHARACTERISTICS
 This section of the report concerns design fundamentals for duct-type
 (i.e., those that use plates for collection),  wet and dry electrostatic
 precipitators.  Electrostatic precipitators using tubular or pipe
 collectors are not considered.
 BASIC ELECTROSTATIC PRECIPITATOR PARTS*

 The three basic parts of any precipitator installation are:

       (1)  Power supply
       (2)  Collection area       i
       (3)  Dust-removal area.

. The power supply generally consists of a single-phase, hjLgh-voltage
 transformer,  appropriate control equipment, and a bridge rectifier
 circuit.  The  rectifier circuit can be either  a full-wave or double
 half-wave circuit,  as  shown in Figure 10.

 Rectifier design has progressed from the mechanical rectifier to the
 high-voltage Kenotron vacuum tube, selenium,  or  silicon rectifiers.
 Normal transformer ratings are  between 15 and 25-kva, 440-volt
 primary and 50 to 75-kv secondary.  In order to limit short-circuit
 current surges, the transformer primary circuit usually contains a
 ballast resistance or a reactor.  Manual  or  automatic control is used
 to regulate electrical  conditions in the precipitator dust-collection
 area.

 The collection area consists of duct collection electrodes with high-
 voltage discharge electrodes uniformly spaced and of uniform length,
 "Reprinted from Iron and Steel Engineer. Electrostatic Precipitator Primer.  J. Katz, by permission
 of the Association of Iron and Steel Engineers;  pp. 21-40, May 1964.
                                  Zl

-------
                        HIGH VOLT.
                        TRANS.
            BRIDGE
            RECTIFIER
PRECIPITATOR
(-) PROPER
               LOW VOLTAGE
               INPUT
FULL-WAVE CIRCUIT SCHEMATIC

TlGtiU
TRANS.
                                   BRIDGE     PRECIPITATOR
                                   RECTIFIER   (-) PROPER
               LOW VOLTAGE
               INPUT
                                                 -Hck
                                         GRD.
                                         RETURN^
                    DOUBLE HALF-WAVE CIRCUIT SCHEMATIC

           Figure 10.  Two possible rectifier circuits for an
                       electrostatic precipitator

as illustrated in Figure 11.   Collecting electrodes (the metal  surfaces
that collect the  particles) are at ground potential and are connected
directly to the frame of the precipitator.  The collecting-surface
design varies with the manufacturing company and process.  The duct
collecting surface may consist of perforated or solid metal plates up
to 6. 1 x 1.4 meters (20 x 4-1/2 feet).  Normally a precipitator has
three to four duct sections in series.  The duct width may be  200 mm
(8 inches) although 250-mm  (10-inch) ducts are sometimes employed
in cleaning gases that contain large quantities of dust.  There can be
five or  six discharge electrodes equally spaced in each 1.4-meter
(4. 5-foot) duct section.   These discharge electrodes receive the high-
voltage  rectifier output and are suspended in parallel from a frame-
work that is insulated from ground by ceramic insulators.
                                 22

-------
   THE MAIN DISCHARGE
   ELECTRODE FRAME IS
   SUSPENDED BY POST
   INSULATORS FROM THE
   PRECIPITATOR ROOF.
   THUS MAINTAINING
   ELECTRICAL CLEARANCE
   FROM GROUNDED
   COLLECTING PLATES.
   USUALLY STIFFENER —
   BAFFLES ARE PRESENT
   ON ENDS TO HELP
   MINIMIZE DUST
   EROSION.
 DIRTY GAS FLOW
                                                       •CLEAN GAS FLOW
COLLECTING PLATES ARE
TIED INTO THE TOP SHELL
OF THE PRECIPITATOR.
SPACER PLATES AT THE
BOTTOM KEEP PLATES
PROPERLY ALIGNED.
PLATES CAN BE RAPPED
SEPARATELY OR IN
SECTIONS BY A BAR
CONNECTING THE ENDS
OR BOTTOMS.
          Figure 11.   Typical duct electrostatic precipitator


Dust removal is accomplished either mechanically or hydraulically,
depending on the physical state of the process.  Most applications
involve a dry process; the collected dust is removed by rapping or
vibrating the plates.   The method used to remove material from the
collecting surfaces is most important to minimize particulate reen-
trainment and electrical disturbances.  Material vibrated from the
collecting plates falls into hoppers  for  subsequent removal.

Dry-Dust-Collection Fundamentals

Before discussing each of the major factors affecting the collection
of particulates with electrostatic precipitators,  it would be  well to
understand the process fundamentals.  Simply stated, the process
consists of charging dust particles  with a corona discharge  and then
passing them through an electric field where  they are attracted to
the collecting surfaces.
                                   23

-------
There are five basic kinds of electrical discharge through a gas
spacing between a high voltage circuit:

      (1)   The dark discharge is not visible although chemical
           action occurs.  The current increases nearly
           linearly with voltage.

      (2)   The glow or corona is the most frequent initial
           discharge and is accompanied by a hissing  noise.
           Current increases  much faster than voltage.
      (3)   The brush discharge usually falls midway between
           corona and a spark.  It consists of a number of
           small sparks ending in space and originates in
           surface irregularities or abnormalities in the
           conductors.  Current increases  with possibly a
           slight drop in voltage.

      (4)   The spark is a common discharge that is unstable
           in that the increased current lowers  the voltage
           appreciably.   It is  the sudden rush of electric
           current through the gas,  and is limited only by
           the circuit power supply.  The spark is the most
           complete form of gas "breakdown".
      (5)   The arc  is not ionization by collison  as are the
          preceding four categories but arises from other
          discharges.  Current density is very high,  while
          the voltage decreases to a low value.   This dis-
          charge is particularly unstable unless  the current
          is limited by an external  electrical circuit
           resistance.

In order for a current to flow across a gas space, ionization must
be started and sustained by electron acceleration and collision with
gas molecules causing a cumulative effect.

For the case of a negative wire in a cylinder,  the following explana-
tion describes the corona current ionization principle:  Electrons
are released from  the wire surface by a positive-ion impact or photo-
electric emission.   These accelerating electrons in short movements
near the wire surface generate new electrons and positive  ions by
molecular impact.   The electrons quickly move away from the wire
and attach to gas molecules to form negative ions or produce  new
                                24

-------
collisions.  Once the corona glow begins,  ultraviolet radiation may
produce  additional photoelectrons at the wire surface.  As this
electron collision continues,  the negative ions build  a dense cloud
throughout the space between the active region near  the wire and the
passive anode.  The effect of this ion space charge is to help limit
the ionizing field near the discharge wire and also to stabilize the
corona discharge.

This ion movement has two main charging effects on dust particles
in the precipitator region between the electrodes.

      (1)  Suspended dust particles are bombarded toward the
          anode under the force of a strong electric  field.
      (2)  Ion diffusion causes the negative ions to attach
          themselves to  dust piarticles  less than 0.2 micron
          in size and,  by this method,  transport these
          smaller particles to the collecting plate.

The following expresses  the principles  of the electron precipitator
in theory.

Migration velocity or precipitation rate of particles:

                                a EQ Ep
                           «*   2?re                           (1)

where
       a = particle radius, microns
      Ep = strength of field in which particles are  charged,
           statvolts/cm
      EQ = strength of field in which particles are  collected,
           statvolts/cm (normally the field close to  the
           collecting plates)
       9 = viscosity or frictional resistance coefficient of
           the gas, poises
       TT= 3.1416.
Collection efficiency of precipitator:

                                   •M
                          T] = 1. - e  V    '                      (2)

                                 25

-------
where

      A  = effective collecting electrode area of the precipitator,
           sq m (sq ft)
       V = gas flow rate through the precipitator, cu m per sec
           (cu ft per sec)
       e = base of natural logarithms = 2. 718
       c*> = migration velocity, m per sec (ft per sec).

The equation for efficiency is known as  the Deutsch-Anderson
equation.

Equation (1) shows that an increase in both particle  size and electric
fields, EQ and E_, will increase precipitator performance,  while
increased gas viscosity will adversely affect performance.  A study
of Equation (2) shows that the precipitator efficiency increases with
increasing values of the exponent - A w/V.  Therefore, as  the pre-
cipitator electrode area becomes greater and the migration velocity
increases, precipitator performance improves.  At the same time,
if the gas flow rate increases, the precipitator performance
decreases.

To  illustrate the velocity with which a single dust particle moves to
the collecting surface under the influence of an electric force, the
following example is given for a typical steel-mill gas:
       a = 1 micron particle = 10"'  cm
      EQ = 4. 8 kv/cm = 16 statvolts/cm
      Ep = 6. 0 kv/cm = 20 statvolts/cm
       9 = 2. 7 x 10~4 gas viscosity  at 260 C (500 F),  poises.

From Equation (1),  the migration velocity is:
                     -     IP"4 x 16 x 20
                   " ~ 2 x 3. 14 x 2.7 x 10-4


                   = 18.9 cm/sec = 0.62 ft/sec.


                                26

-------
If the discharging wire is 100 mm (4 inches) from the collecting plate
and the gas flow through the duct is  1. 22 m/sec (4 ft/sec), the dust
particle would reach the collecting surface in approximately 0. 6 meter
(2  feet) of duct length.

Under similar dust and precipitator conditions  but with the gas cooled
to  150 C (300 F), the gas viscosity decreases to 2.3 x 10   poises:


                    -     10"4 x 16 x 20
                   " ~  2x3. 14 x 2.3 x  10-4

                   co =  22. 2 cm/sec = 0. 73 ft/sec.

To determine the effect on  conditions in the first example by increas-
ing the average arid peak precipitator voltages  by 20 percent:


                         10-4 x 19.2 x 24
                   co =
                      2x3. 14 x 2.7 x 10-4

                   w = 27. 2 cm/sec = 0. 9 ft/sec.

The dust particle drift velocity to the collecting plate increased 50 per-
cent when the precipitator voltages increased 20 percent.

Consider the first example except that the average dust particle size
is now 5 microns:

                        5 x 10'4 x 16 x 20
                   OJ =
                      2x3. 14 x 2.7 x 10-4

                   co = 95 cm/siec =3.1 ft/sec.
                                27

-------
 Thus, a 5-micron particle should reach the collecting plate in about
 0.43 feet of duct length with the 4-fps gas flow.   When this is com-
 pared with the migration velocity of a 1-micron dust particle,  it
 points up the need for an accurate dust-radius measurement to
 obtain the correct migration velocity for any gas.

 To calculate a precipitator collection efficiency using an average
 dust particle size  of 1-micron radius,  substitute the original example
 migration velocity in Equation (2):

                                 0. 189 Ac

                      Tl-l-e  r~~T~~.

 A typical precipitator duct might have the following physical
 parameters:

      Collecting surface A
         = 6. 2 m high x 3. 6 m long x 2 sides = 44. 6  sq m
         = (20 ft high x  12 ft  long x 2  sides = 480 sq ft).

      Dust gas flow rate V at duct conditions
         = 6. 2 m high x 0. 2 m wide x 1. 22 m/sec =  1. 51 cu m/sec
         = (20 ft high x  0. 667 ft [ 8-inch spacing] x 4 ft/sec =
            53.4 cu ft/sec).

Substituting for A and V in Equation 2:

                       0. 189 x 45. 1   /        0.62 x 480 \
            ~   i            -            i          53-4    I
            7) =  1 - e                = \ 1 - e              /
            T) =  1 - 0. 0037

            7) =  0. 996 or  99. 6 percent.

These equations help to explain precipitator performance scientifically.
However, other factors result in discrepancies.

Factors Affecting Dry Electrostatic
Precipitator Operation

The difficulties  of dust adhering to the collecting plates, poor gas
distribution and spark-over conditions are three factors that reduce
the theoretical migration velocity.  Each precipitator application will
determine the deviation of the u> factor from field data.   This provides
a base for future installation calculations as well as a means for

                                 28

-------
comparing precipitators in the same application.  The succeeding
paragraphs will discuss the major factors that affect precipitation.

The  migration velocity, w, is quite sensitive to the voltage since the
electric fields appear as a product in Equation 1.   Therefore,  the
object is to obtain maximum voltage with proper corona current
flow for maximum collection efficiency.   The major factors that
determine this condition are:

      (1) Applied voltage frequency and waveform

      (2) Spark-over characteristics

      (3) Electrode characteristics

      (4) Gas flow rate

      (5) Gas flow distribution

      (6) Dust concentration

      (7) Dust composition, including particle  size and
          resistivity

      (8) Gas temperature,  pressure and humidity.

Applied Voltage,  Frequency and Waveform — The rectifier input is
conventional 60-hertz power.  Therefore, half-wave and full-wave
energization contains 60 and 120 pulses/sec, respectively,  as shown
in Figure 12.

                  k1 CYCLE = 1/60 SEC ~j
                                         EACH SECTION
                                         OBTAINS ONE
                                         PULSE PER CYCLE
                   UNFILTERED HALF-WAVE ENERGIATION AT
                          POINT A - FIGURE 10
                 0|
                   UNFILTERED FULL-WAVE ENERGIZATION AT
                          POINT B - FIGURE 10

      Figure 12.  Voltage waveform for unfiltered half-wave and
                   full-wave  rectification
                                  29

-------
Negative polarity is used.  The negative wave is impressed on the
discharge  electrode while the grounded collecting electrode serves
as the positive terminal.  Negative polarity on the electron-emitting
discharge  wire has proved superior in that it allows a higher spark-
over potential to be reached in the precipitator before a voltage
breakdown occurs between the two electrodes.

Consider the precipitator proper as a number of parallel capacitors
in which the high-voltage discharge  electrode  and the collecting
electrode form the plates of the capacitor while the gas serves as
the capacitor  dielectric.  Therefore,  every voltage pulse tends to
charge this precipitator capacitance,  which provides a natural
voltage filter  as  this capacitance discharges through the gas resis-
tance, changing the actual precipitator voltage waveform to that  of
Figure 13.  The  maximum and minimum voltages are  now simply
Ep and Em.
                    CYCLED 1/60SEC*|
                                         VOLTAGE DECAY
                                         BETWEEN PULSES
                    PRECIPITATOR HALF-WAVE VOLTAGE
                    MEASURED AT POINT C - FIGURE 10
                    PRECIPITATOR FULL-WAVE VOLTAGE
                     MEASURED AT POINT D - FIGURE 10
  Figure 13.  Waveform in electrostatic precipitator after discharge


The current output with half-wave energization is one-half that of
full-wave energization.  Also,  the voltages E_ and Em of the full-
wave  waveform are closer (i.e., the full-wave Ep is  slightly less
than the  half-wave E ),  while the full-wave Em is greater than the
half-wave Em.  Half-wave energization has several advantages  over
full-wave in most installations.
                                 30

-------
Two of the major advantages are:

      (1)  The  same rectifier output can be distributed to
          smaller precipitator areas,  as shown in Figure 10.
          This construction necessitates additional switching
          and bus connections.  However, the continuity of
          operation and collection efficiency will usually
          benefit from this construction since localized
          trouble in one section will not affect the  electrical
          characteristics  in other sections.

      (2)  The  half-wave,  because of the time lag between
          voltage pulses,  is less likely to sustain a voltage
          breakdown between electrodes.

If,  in Equation 1, EQ is the average field voltage, then EQ = 1/2
(E  + Em).  These measurements can  be obtained by oscilloscope
readings across appropriate voltage dividers.  Typical field voltages
in duct precipitators  are:

      E  = 3.X9 to 5. 9 kv/cm (10 to 15 kv/in.)

      Em = °- 3 to 0.  5 kv/cm (7 to 12 kv/in.).

Total corona current comprises a gas  ionic current and a dust cur-
rent in which electrons attach themselves to  a dust particle. The
ionic current is approximately 95 percent of this total current.
Oscilloscope readings of current waveforms  show that conductivity
of an electron tube rectifier is  in the range of 60 to 80 percent of
each half cycle.  The ratio of peak current to average current should
be 4. 0 to 5. 0 for efficiency.  The current will vary from 10 to 30
ma/100 sq m (1000 sq ft) of collecting  area.

Alteration of the waveform by a, pulse method of energization has
definite potential advantages,  but this technique has never been used
commercially.  Certainly,  the adjustment of voltage,  frequency,  and
waveform to fit individual  precipitators could benefit efficiency,
especially for high-sparking conditions between discharge wire and
collection plate.

Spark-Over Characteristics - The voltage breakdown between elec-
trodes for a given precipitator depends on many complex variables
                                 31

-------
and is the point of maximum power input.  Field measurements have
shown that under normal conditions,  50 to 100 voltage breakdowns
(spark-overs) per minute are tolerable.  On the basis of half-wave
energization with a possible 3600 pulses per minute,  additional power
input can be obtained with  100 sparks per minute  since the voltage
collapse during the spark-over is more than offset by the higher
input during the nonsparking cycle.   One must differentiate between
spark-over and a power arc in that a spark-over  is 1/2-cycle dura-
tion  or less while  a power arc may last several cycles and is quite
detrimental to  precipitator performance.  Some precipitator applica-
tions will not spark within power-supply input limitations because of
dust and gas conditioning.   In most cases, the quantity of water
carried by the  gases  and the gas temperature play an important part
in this phenomenon.

Electrode Characteristics  - Electrode configuration determines
voltage and current  characteristics.  Diameter and shape of the
discharge electrode  determines the  initial voltage required to start
a corona discharge.   For most practical gas applications, this
voltage varies  from  16 to 26 kv.  In addition to material strength,
two important factors that affect the  operation of  the discharge elec-
trode are the wire diameter and  curvature of the  corona-emitting
surface. The smaller the  wire diameter,  the  greater is the corona
current for any given voltage.  The  spacing between the discharge
wire and collecting surface determines the required voltage.  If the
discharge wire is  not centered perfectly within the collecting area,
the spark-over voltage is reduced.  Higher stress concentration
exists in the reduced clearance between the wire  and  collecting elec-
trode.  This phenomenon of concentration points becomes very
important with some  types of collecting surfaces.  Surface imperfec-
tions and slight differences in collection-plate construction can reduce
spark-over voltage.   Figure 14 shows the  relationship between field
voltage and collection efficiency  and  illustrates the importance of
providing maximum  field voltage. Imperfections  or stress concen-
trations in electrode  design should be minimized, especially with
dusts resistive to  current.  The  solid collecting plate is a recent
design that minimizes spark-over between electrodes.  Dust buildup
on the discharge electrode, by producing a change in  electrode con-
figuration,  can cause stress concentrations at the bottom and the top
of the dust deposit.  Dust buildup on  the discharge wire tends to re-
duce corona current.  The close  spacing between discharge wires
can also result in  current reduction.
                                32

-------
                100
                 95
               +•*
               c
               8
               8. 90

               o
               5 85
               o
                 80
                 75
                 70
                              NOTE EFFECT OF
                              SMALL INCREASE IN
                              VOLTAGE ON EFFICIENCY
                      	>• INCREASES IN 2-KV STEPS
                            TYPICAL RANGE IS 32 TO 60 KV
                     PRECIPITATOR PEAK VOLTAGE, kilovolts
       Figure 14.  Dust-collection efficiency as related to peak
                   voltage for a typical electrostatic
                   precipitator


Changing the wire-to-wire spacing alters current-voltage relation-
ships. When the discharge wires  are relatively far apart, the
current per unit length of wire tends to remain  constant.  As the
wires are spaced closer  and closer, the starting voltage increases,
which tends to lower the  current.  Therefore, there is an optimum
wire-to-wire spacing for which the total current is a maximum, and
practice  indicates that  this spacing should be 150 percent of wire-to-
plate spacing.  An interesting aspect of wire-to-wire  spacing is that
the field strength near  the plate is less midway between wires than
it is directly opposite the wires.   Therefore, the closer the discharge
wires are to each other,  the higher the average field strength until
the current is suppressed.

The corona current  also  depends  on the wire-to-plate spacing and
changes  inversely as the  square: of the ratio between two different
spacings.  If the wire-to-plate sipacings were reduced from 100 to
75 mm (4 to 3 inches),  the corona current would practically double.
                                 33

-------
However, if the wire spacing were increased from  100 to 125 mm
(4 to 5 inches),  the corona current would decrease about one third.

Gas Flow Rate — Collection efficiency of the precipitator  is designed
on a gas-volume basis.   However,  the effect of gas flow on perfor-
mance is sensitive to several factors:

      (1)  In a high-sparking unit where power input must be
          less than required to reach the designed collection
          efficiency, improved collection can be obtained
          at 70  to 80 percent of precipitator gas-volume
          rating. Actually, a distinct difference in perfor-
          mance will be  noted under  these conditions,  as
          illustrated in Figure 15.
               100
  95
+-•

I 90
a
>•"
^ 85
—
o
u- 80
ui
z
O 75
             o
             ui
             8
                70
                                     CURVE A
                                  GOOD CONDITION
                                         CURVE B
                                           POOR
                                         DISTRIBUTION
          CURVE C
       HEAVY SPARKING
                       I
              I
I
I
I
                 80   90  100  110  120  130   140
                         GAS FLOW, percent of rating
                                     150
         Figure  15.  Electrostatic precipitator efficiency as
                     affected by gas  flow
                                 34

-------
      (2)  With maximum voltage fields and power input,  gas
          volume overloads of 10 to 25 percent have little
          effect on collection efficiency.  In fact, the dust
          size determines just how much excess volume  is
          possible,  since  reentrainment in the gas is greater
          with large-dust-particle collection and is minimized
          with fume and wet collection.  Migration drift
          velocity is greatest with maximum voltage which
          can overcome gas flows of even 4.6 m/sec  (15 ft/
          sec) through collecting areas of some cleaning
          applications.

Gas Flow Distribution - Precipitator performance may deviate from
design calculations because of poor gas distribution through the pre-
cipitator inlet.  Consider an installation designed for 95 percent
collection efficiency where one-half the precipitator is treating
75 percent of the gas volume.  Depending on the  dust, a 5 to 20 per-
cent decrease in collection efficiency may result.  This condition
is the same as overloading the one half of the precipitator with
150 percent of rated gas volume.

In an inlet cross section composed of 20 to 30 equal areas,  the designer
should assure that no single area deviates more  than 10 to 15 percent
from the average  cross-sectional flow.  It is important that minimum
gas turbulence coincide with the optimum gas pattern.  Minimum gas
turbulence is a direct function of inlet flue design and gas flow direct-
ing vanes and baffles if used.  Usually the gas  flow from a particular
process travels at high velocities (from 9. 1  to 18. 3 m/sec (30 to 60
ft/sec) and must be  reduced to 1. 5 to 3. 0 m/sec (5 to 10 ft/sec) at
the precipitator inlet.  Careful study at this  stage of the design can
often insure  a highly efficient unit.   If the  size of the installation or
critical nature of the process warrants the additional cost, gas-flow
pattern can be investigated in scaled-down glass models of the pro-
posed structures.  However,  duplicating actual gas-flow conditions
in glass-model studies presents many problems.

To help reduce gas turbulence and poor distribution, low-pressure-
drop plates across the  precipitator inlet are normally employed.
However, a low-pressure  drop across these plates may not^ drastically
alter existing conditions.  After the  unit goes into operation,  it is
wise to measure the distribution pattern across the  inlet with a pitot
tube or other suitable means.  Field alterations can be made  on the
basis of actual measured results.

                                  35

-------
The kind of dust collected by the precipitator influences the effect of
gas distribution on precipitator efficiency.  In most cases, fumes or
fine dust have less effect than gases containing larger dust particles.
In the last analysis, poor gas distribution reduces collection efficiency
appreciably since it adversely affects the electrical characteristics.
The power input of a precipitator section is limited by the lowest
spark-over point of that section.
Dust Concentration — An interesting facet of electrostatic precipitation
is the effect that the quantity of dust has on the cleaning process.  The
dust concentration does not basically influence the precipitator's size
for any given efficiency.  The following facts should be considered
when dust concentrations are heavy.  First,  the quantity of dust alters
voltage-current characteristics:  more  dust  increases  voltage and
reduces current.  Second, frequent dust removal  from the collecting
electrode should minimize dust reentrainment in the gas stream.
Third,  if the dust quantity is great enough,  the first section may re-
quire 254-mm-wide (10-inch-wide) ducts to eliminate a possible spark-
over caused by excessive voltage buildup.

If the dust is discharged to the atmosphere,  the dust quantity must
meet minimum stack discharge specified by community air-pollution
ordinances.  Considering two different gas concentrations of 2. 3 and
34 grams/cu m  (1. 0 and 15 grains/std cu ft) flowing through a 95 per-
cent efficient precipitator,  comparative  outlet dust discharges would
be as follows:
           (2. 3 grams/cu m) x (1. 0-0. 95) = 0. 12 gram/cu m
          (34. 0 grams/cu m) x (1. 0-0. 95) = 1. 70 grams/cu m

       (1. 0 grains/std  cu ft) x (1. 0-0. 95) = 0. 05 grain/std cu ft
      (15. 0 grains/std  cu ft) x (1. 0-0. 95) = 0. 75 grain/std cu ft.
In order to obtain an outlet discharge of 0. 12 gram/cu m (0. 5 grain/
std cu ft) with an inlet concentration of 34 grams/cu m (15 grains/std
cu ft) the following precipitator efficiency is required:

            /      0. 12 gram/cu m \ . „      , _
            (1.0-      *	-.	 1 100 = 99. 67 percent
            \       34. 0 grams/cu m /

          f, ^    0. 05 grain/std cu ft \ . nn   nn , _
           1.0-      s .	/—:	   100 = 99. 67 percent  .
          \      15. 0 grains/std cu ft /

This efficiency can be obtained with the electrostatic precipitator but
the process should warrant the additional cost of carefully optimizing
the design.
Typical dust concentrations  in iron and  steel industry waste gases are:
                                  36

-------
      Open-hearth furnace -  0. 12 to 3. 43 grams/cu m (0. 05 to
       1. 5 grains/std cu ft)

      Basic blast  furnace after usual primary dust collection -
       9 to 11 grams/cu m (4. 0 to 5. 0 grains/std cu ft)

      Oxygen steelmaking furnace -  9  to 21 grams/cu m (4. 0 to
       9. 0 grains/std cu ft) average

      Ferromanganese blast furnace after primary dust collec-
       tion - 23 to 34 grams/cu m (10. 0 to 15. 0 grains/std cu ft).

Particle Size and  Resistivity  - The migration velocity is directly
affected  by dust-particle size as noted  in the basic formula. Small
particles are more difficult to precipitate out of the gas stream than
large particles, and require higher power and voltage to remove.
Although the coarser particle is more  easily collected,  it may also
be more easily lost to the gas stream through reentrainment resulting
from vibration of  the collection plate or erosion caused by gas eddy
currents.   .    .

This lack of dust adhesion is  a major  factor in reducing the actual
precipitator efficiency below  a value predicated by the calculated mi-
gration velocity.  For example,  although the large particle does reach
the collecting plate in a shorter time,  reentrainment in the gas stream
can take place throughout the length of the precipitator until,  finally,
the particle is lost to the atmosphere.   The coarse or large particle
is important in some applications in that it may keep the submicron
dust from impacting on  the collecting plate.

Particle size in waste gases from open-hearth processes  will  generally
vary from <0. 5  to 5 microns,  and from 15 to 25 microns and larger
from sintering-plant operations.  The  smaller particles of ferrous
oxide come from open-hearth, electric-furnace,  and oxygen-vessel
fumes.   Submicron particles  are difficult to precipitate  and have a
tendency to suppress corona current if numerous enough.   This charac-
teristic is similar to the space charge around a discharge electrode.
Voltage-current relationship  is marked by high precipitator voltage
and practically nil corona current.  Although high-voltage fields are
desirable, the electrostatic collecting  process still requires sufficient
corona current to sustain ionic movement to the collecting plates.

Another  interesting effect of dust-particle size is the  influence on
visual stack discharge.  The  finer particles cause the stack discharge

                                  37

-------
to appear quite dense, while the actual weight of dust in a given
volume of gas could fall well within air-pollution ordinance require-
ments.  This phenomenon,  caused by the greater surface area of
submicron particles per unit weight,  is significant not only from a
community goodwill standpoint,  but more importantly because of the
fact that the emissions are respirable particles.

In previous paragraphs, maximum power input and high-voltage fields
were prerequisites for efficient performance.  Although the several
factors discussed earlier will  tend to lower spark-over voltages,
the optimum electrical characteristics depend primarily on the resis-
tivity of the particular dust. In other words, will the dust resist or
will it react favorably to the corona current flow?

High-resistivity dust causes severe sparking between electrodes so
the power input must be reduced to reach the desirable spark-over
rate of 50 to 100  sparks per minute.  Under these conditions,  precipi-
tator performance sometimes  runs 5  to 20 percent below design values.
The chemical composition of the dust particle directly affects its
electrical characteristics.  However, proper gas  temperature and
humidity can alter the dust-resistivity range to  obtain good results.
In some cases, additional  water, steam, or a special conditioning
gas can be injected into the gas stream  to realize  optimum electrical
results.

With the wet process of removing deposits from collecting surfaces,
excessive spark-over because  of dust resistivity is insignificant.
Where a highly resistive dust is deposited on dry collecting surfaces,
a voltage gradient across the dust  layer can be high enough to emit
its own corona discharge.   This situation can disturb electrical condi-
tions,  with excessive sparking at lowered voltages or with excessive
current at greatly lowered voltages without sparking.  This second
condition can produce enough positive ions to counteract the negative
space charge and  significantly reduce the migration rate.  The term
back-discharge or back-corona commonly describes  this  situation.
Low gas moisture content  with the absence of certain chemical impuri-
ties in the temperature range 116 to 232 C (240  to 450 F)  is likely to
cause a highly  resistive dust condition.

Temperature,  Pressure, and Humidity  - In any particular  precipitator
installation,  varying temperature,  pressure, or humidity will cause
some change in electrical  characteristics.  Since higher gas
                                  38

-------
temperature will decrease  gas density, lower precipitator voltages
and higher currents are usually  obtained.  Higher gas pressure will
have an opposite effect by increasing the voltage and decreasing the
corona current.  This phenomenon parallels the effect that increased
dust concentration has on corona power.  In addition, if a highly
resistive dust is1 encountered, the resistivity can.be varied by either
increasing or decreasing gas temperature from a maximum resistivity
operating range.  This maximum resistivity will vary with the kind of
dust, but the band  width will normally encompass 50 to 80 C (90 to
150 F) as illustrated in Figure  16.
               E
               V
               CO
               o
     Figure 16.
                  10
                   13:
                             DUST TEMPERATURE, F
                         100   200    300   400    500
                                    600
                   ^12
                   •>11
               E2  10
               cc
                   ,10
                  109
                  10*
                          T
              T
I
                       EACH KIND OF
                       DUST WILL SHOW
                       VARYING CURVES
                       DUE TO MOISTURE
                       AND PRESSURE
                           50   100   150  200  250
                             DUST TEMPERATURE, C
                                   300
A typical relationship between dust resistivity and
temperature for a gas improperly conditioned for
the 93 to 204 C (200 to 400 F) range
Moisture affects the electrical conditions indirectly and directly.
Moisture indirectly decreases dust resistivity, while it directly in-
creases the spark-over voltage appreciably.  In the gas-temperature
range below 260 C (500 F),  the indirect and direct effects from the
addition of moisture are equally beneficial.  Over 260 C (500 F),  the
direct effect of raising the spark-over voltage predominates.
                                   39

-------
Increasing the moisture content usually produces a rise in precipitator
voltage and a drop in current.

Dust Removal From Collection Plates - One factor not included in the
fundamental precipitation formula but of major practical concern is the
vibration or rapping method employed to remove dust buildup from
electrode surfaces.  Various equipment and methods are available but
all should

      (1) Minimize irregular dust buildup on electrode  surfaces
          to reduce spark-over possibilities

      (2) Offer rapping cycles of short enough duration to
          eliminate dust puffs through the stack

      (3) Determine the type of rapping system, whether
          vibrating or  single blow, that provides optimum dust
          removal with special dust composition, temperature,
          and humidity conditions
      (4) Design the collecting area controlled by each plate
          rapping system as small as economically possible

      (5) Provide  for varying the rapping magnitude between
          inlet and outlet precipitator sections

      (6) Above all, the pattern of any rapping system should
          be determined from internal inspection if poor pre-
          cipitator performance is attributed to inefficient
          rapping.

Dry Electrostatic  Precipitator
Design Methods

The two  methods used in the design of all electrostatic precipitators
both rely on empirical  relationships developed by equipment manufac-
turers over their years of construction experience.   The first method
is based on the conventional Deutsch-Anders on efficiency equation
and the second method  approaches the design from the standpoint of
the electrical requirements.  These methods must obviously give
compatible results.  They differ mainly in the fundamental way in
which design is approached.
                                  40

-------
Dry Electrostatic Precipitator Design Method I - A common approach
to the selection of the area of collecting plate required is to utilize
the Deutsch-Anderson equation
                     1  '    7) = 1 - e

where

       T) = efficiency
      AC = effective electrode collecting area, sq cm (sq ft)
       V = gas flow rate through the precipitator, cu cm/sec (cu ft/sec)
       w = migration velocity,  cm/sec (ft/sec) (precipitation-rate'
           parameter)
       e = base of natural logarithms  = 2. 718.

The critical parameter in this equation is the precipitation rate w.
This parameter varies with each installation,  depending upon resis-
tivity arid particle  size of the dust,  quality of gas flow,  reentrainment
losses, and sectionalization, among other factors.   The values  of
u) are selected by the equipment manufacturers on the basis of past
experience with a particular dust, or from the composition of the dust
that can be related to past experience.  Each precipitator manufacturer
therefore has a file of experience from whi.ch a precipitation rate
parameter can be selected,  and this file of information is kept as
proprietary data.

The values of the precipitation-rate parameter oo vary with the applica-
tion as a result of variations in dust properties.  Variations also occur
within each application area.  Table 7 lists the average values of
precipitation-rate parameter for various applications, and the range
of values that might be expected within each application.  From this
table,  it is apparent that the spread in the values of  the precipitation-
rate parameter is large in  some instances,  such as  in fly-ash precipi-
tator s, and within a reasonably narrow range in others.

The major problem in the design of precipitators based on this
approach is the selection of the  precipitation-rate parameter for the
specific application.   Several techniques  can be used to narrow  the
uncertainty of the value of to to be used.   If the in situ resistivity of
dust is known, the precipitation-rate parameter can  be  determined
for some applications. Figure 17 shows  the variation in co with
                                   41

-------
TABLE 7.  REPRESENTATIVE PRECIPITATION RATES, w, FOR
           VARIOUS APPLICATIONS

Application
Utility fly ash
Pulp and paper
Sulfur ic acid
Cement (wet)
Smelter
Open hearth
Cupola
Blast furnace
Sinter plant
n.a. - data not available.
3 20 ill
cc
LU
1-
LU -•— .
1 16'-
cc
0.
LU g
< i 10 -
CC o
1
g
< 5 -
o
LU
? n iti
109
Average
cm/sec ft/sec
13.1 0.43
7.6 0.25
6.3 0.24
10.7 9.35
1.8 0.06
4.9 0.16
3.1 0.10
10.9 0.36
n. a. n. a.

i i i i ij i i i i i



^

^x.
^v
>S
^






, .,..1 , . . ,,
1010
Range
cm/sec ft/sec
4.0-28.4 0.13-0.67
6.4- 9.5 0.21-0.31
6.1- 8.6 0.20-0.28
0.3-12.4 0.30-0.40
n. a. n. a.
n. a. n. a.
n. a. n. a.
6.1-14.0 0.20-0.46
2.3-11.5 0.07-0.38

. . ,j 	 -OO"




- 0.492


|
\ - 0.328 -'
\ 4
\
\
X. - 0.164
*»*^.-i

i 1 1 1 i i i i i i i i n nnn
1011 1012
                         RESISTIVITY, ohm-cm

  Figure 17. Relationship between precipitation-rate parameter
             w and resistivity of fly ash
                               42

-------
resistivity for fly-ash precipitators.  If the precipitator being designed
is a replacement for, or an addition to  an existing unit, resistivity can
be measured, and the uncertainty in the value of w can be  reduced.
Alternatively,  if a  similar installation is available, measurements of
resistivity can be made and the value of to selected with some confidence.

The data from Figure 17 apply only to fly ash or to a dust with similar
properties.  If the  particle size differs  significantly,  the absolute
values of to will change, although the general character of the curves
would be similar.

In situ resistivity data have not been determined to the  same degree in
applications  other than in fly ash precipitators, so that statistically
reliable  data relating to and resistivity are not generally available.

If it is impractical to select to on the basis of resistivity,  other factors
can often be  used.  In fly-ash precipitators, resistivity is  influenced
by the sulfur content of the fuel,  and relationships have been developed
between  precipitation-rate parameter to and percentage of sulfur con-
tent.  Figure 18 shows a curve developed for a  group of fly-ash precipi-
tators burning coals  with varying sulfur contents.  On a statistical
basis, the precipitation rate can  be predicted within reasonable accur-
acy.  However, on an individual installation,  the variations are too
great to  predict to with acceptable precision on the basis of sulfur
content alone.  In many instances, the only information available  is
the sulfur content of  the coal, and designs are sometimes based solely
upon this parameter.

Particle size of the dust is a very important consideration in deter-
mining the value of to for design purposes.  Referring to Table  5,  the
variations in to between the various application areas are due largely
to particle-size variations.  In cement  kilns, the alkali content of
the raw material alters the size distribution of the dust.  Metallurgi-
cal operations characteristically produce smaller size dusts from
high-temperature melting operations.   Size of dusts  from recovery
boilers in pulp and paper mills can change with temperature.  These
factors result in variations in precipitation-rate parameters between
the various applications, and within the  same application area.

When the selection of precipitation-rate parameter has  been made,
the area of collecting surface required  to achieve a given  efficiency
when handling a given gas volume can be determined.
                                  43

-------
                 20
                                      0.656
              o
              cc
              LU
              LU
              5
                 15
                                      0.492
Ill
DC
 i
g
s
                 10
                                      0.328
                                                    0.164
             O
             ui
             cc
             a.
                            1         2        3
                     SULFUR CONTENT OF COAL, percent
                                                   0.000
     Figure  18.  Relationship between the sulfur content in electric
                 utility plant fuel and the precipitation-rate
                 parameter u> at 149 C (300 F)

The power required for a particular application is determined on an
empirical basis. ' The power requirements for a given application are
related to the efficiency and the gas volume handled.  Figure  19  is
a curve showing the power requirements  per unit of gas volume for
two applications:  fly-ash precipitation and pulp- and paper-mill
recovery boiler precipitation.  Similar curves can be developed  for
other applications.  The  second step in design,  therefore,  is to deter-
mine the total power requirements  based on efficiency and gas flow.
Note that the recovery-boiler  precipitators require greater power
per unit of gas flow to achieve the same efficiency as that of a fly-ash
precipitator.  This is primarily due to differences in particle size of
the dust and  is related to the precipitation-rate parameter.

Figure 20 shows the variation in collection efficiency with the number
of independently powered bus sections.  The number of sections
required to reach a given efficiency can be determined from curves
                                  44

-------
                              POWER RATE, watts/1000 cu ft/min
                                 200       300      400      500
                               600
                            FLY ASH
                          PRECIPITATOR
                                          RECOVERY BOILER
                                            PRECIPITATOR
                           500         1000         1500
                            POWER RATE, watts/100 cu m/min
                               2000
      Figure 19.  Collection efficiency as affected by power rate per
                   unit gas flow
                         NUMBER OF BUS SECTIONS PER 100,000 cu FT/MIN
                           0123456
                        99.9
                     §
                     2L
                        99.0
                        90.0
                     O  80.0
                     UJ
                     _i
                        70.0
                     8
                        60.0
                        50,r
                               T
T
I
                                                  I
                           0      0.5       1.0      1.5      2.0
                           NUMBER OF BUS SECTIONS PER 1000 CU M/MIN
Figure 20.  Relationship between collection efficiency and sectionalization
             (number  of bus sections per  unit gas flow) for utility fly-ash
             precipitators
                                       45

-------
for the  specific application.  The relationship shown in Figure 21 is
for fly-ash precipitators and was developed from empirical relation-
ships from a large number of tests.

The above procedure will provide a rational basis for arriving at plate
area, total power, and degree of sectionalization required.  It should
be recognized that the selection of the value of w and the curves relat-
ing power and sectionalization requirements are all interrelated.
If inadequate sectionalization is used, a lower value  of u> would result,
the precipitator could not be operated at the required power level,
and the  efficiency would be reduced.  Consequently,  curves relating
the design parameter should be internally consistent.

The type and number of rappers for the collecting and discharge
electrodes depend upon the properties of the dust,  gas properties,
current densities, and the configuration of the electrodes and  elec-
trode support structures.  High-resistivity dust is usually harder to
remove because of the increased force holding it to the  plate.   L/ow-
temperature operation also tends to give a moist dust that is more
difficult to remove.   Table 8 shows the number of rappers per unit
are of collecting electrode  and the number per unit length of dis-
charge wire for a group of installations.

           TABLE 8.  NUMBER OF RAPPERS IN ELECTROSTATIC PRECIPITATORS
                   FOR VARIOUS APPLICATIONS
Application
Utilities
Pulp and paper
Metals
Cement
Collection
Number Rappers
100 Square Meters
0.27-0.97
0.27-1.07
0.12-0.88
0.35-0.56
Electrode
Number Rappers
1000 Square Feet
0.25-0.90
0.25-0.99
0.11-0.82
0.33-0.52
Corona
Number Rappers
100 Meters
0.03-0.22
0.07-0.10
0.09-0.16
0.06-0.11
Electrode
Number Rappers
1000 Feet
0.09-0.66
0.21-0.32
0.28-0.50
0.19-0.33
The following example will serve to illustrate this design approach.
Design an electrostatic precipitator for a pulverized fuel boiler with
the following given conditions :
                                  46

-------
      (1)  Dust resistivity,  7 x 1010 ohm-cm

    •  (2)  Ga's temperature,  .149  C.(30.0 F)  .
      (3)  Gas volume,. 21, 240 actual cu m/min (750, 000 actual.
          cu ft/min)                .     . .       .

      (4)'  Sulfur content, 1. 8 percent
      '. , r            '    '               *            ''      '     '
      (5)  Efficiency, 99 percent.                    .

Example:

      (a)  Select a precipitation-rate parameter.
          From Figure 17 the precipitation-rate parameter corres-
          ponding to a dust resistivity of 7 x 10*0 ohm-cm is about
      .    10.7 cm/sec or  6. 4 m/min (0.35 ft/sec or  21. 0 ft/min)

   . .  (b)  From the Deutsch-Anders on equation

                                   /AC"\

                          r)=l-e  '  V'
or rearranging
                          .    V      100
                          A,= — In
         _ 21,240      100            _ 750,000    	1
      Ac ~  A A   in  inn _ QQ      Ac ~    ?!    in inn
                         w     100 - r)

                                               00
      6.4      100 - 99        c     21      100 - 99
   = 3319 In  100                = 35,700 In 100
   = 15, 285 sq m               = 164, 000 ft2.

(c)  Compute total power requirements.
    From Figure  19, power required for 99 percent efficiency
    is 495 watts/100 cu m/min (140 watts/1000 cu ft/min).
    For 21, 240 cu m/min  (750, 000 cu ft/min),  total power =
    212.4 x 495 = 105,000 watts (750 x 140 = 105,000 watts).
(d)  Determine number of bus sections.
    From Figure 20, number of bus  sections required is 1. 22/
    1000 cu m/min (3. 5/100, 000 cu ft/min).
    21. 24 cu m/min x 1. 22 = 26 bus  sections (7. 5 cu ft/min x
    3. 5 = 26  bus  sections).
(e)  Determine the number of rappers required  on the basis of
    past experience  (see Table 8).

                            47

-------
Dry Electrostatic Precipitator Design Method II - A second approach
to the  sizing of precipitators is to determine the electrical charac-
teristics first and then develop relationships that relate efficiency
and power requirements to the required collection-surface area.  The
concept of the electrical approach is based on the theoretical factors
that influence the precipitation-rate parameter, that is, the current
required to charge the particles and provide the space charge field,
and the voltage required to establish the electrostatic collection field.

In this design method, the curves relating efficiency and corona power
density are developed on an empirical basis.  The curves are the same
as that for Design Method I,  and are given for fly ash and recovery
boiler  precipitators in Figure  19.  Figure 21 is an empirically devel-
oped curve  showing relationship between precipitation-rate parameter
  20
-? 18
I
3 '6
tr
£ 14
LU
1 12
cc
£ 10
i s

I 6
!r 4
                            POWER DENSITY, watts/sq ft
                    0  0.1 0.2  0.3 0.4  0.5 0.6 0.7  0.8 0.9  1.0 1.1 1.2
                      I
I
I  I   I  I
                                         T  I
                      I  I  I   I  I  I  I   I  I  I  I   I
0.660

0.595

0.530

0.465

0.400 0

0.335 £
   3
0.270

0.205

0.140

0.075

0.000
                            4  567 8  9  10 11 12  13
                             POWER DENSITY, watts/sq m
    Figure 21.   Relationship between precipitation-rate parameter
                 w and power density for fly ash precipitators

w and corona power density.  Since the  total power has been determined
previously,  the collecting surface area can be computed from the data
read from Figure 21.  The number of independent bus sections can be
determined in the same manner as in Method I.  The following example
will serve to illustrate the design procedure based on this method.

Example:
      (a)  Select a precipitation-rate parameter.
           From experience with this coal,  the precipitation rate
           parameter is selected to be 10. 7 cm/sec (0. 35 ft/sec).
                                   48

-------
      (b)  Compute corona power.
          From Figure  19, power per unit volume corresponding
          to a collection efficiency of 99 percent is 495 watts/100 cu
          m/min (140 watts/1000 cu ft/min).

          The total power is then computed:

                   4Q(i watts
             p _   y3 watts—x 21,240 cu m/min =105,000 watts.
                 100 cu m/min
             p = i/n        •  x 750,000 cu ft/min = 105, 000 . watts J
                 1000 cu ft/mm      '

      (c)  Determine collection electrode area.
          From Figure 21, for w =  10. 7 cm/sec (0. 35 ft/sec), power
          density = ,6. 89  watts/sq m (0. 64 watts/sq ft).

          Collection electrode area = 105, 000 watts x -. — •— f - -—
                                         '           6. 89 watts
                                   =  15,240 sq m

          Collection electrode area = 105, 000 watts x '     * -
                                                       .
                                     , /  ™~    ,     - 64 watts
                                   = 164, 000 sq ft

      (d)  Number of electrical sections.                         •
          From Figure 20, the number of sections per 1000 cu m/
          min at 99 percent efficiency = 1. 22 (sections per 100, 000
          cu ft/min = 3.5).                                       ,

          Number of sections  =  . -.--. — '• - ; — — x 21, 240 cu m/min
                                1000 cu m/min
                              =  26.

          Number of sections  =  . . . nnn' - 7-7 — — x 750, 000 cu ft/min
                                100, 000 cu ft/mm      '
                              = 26.

It should be noted that the curves relating the various factors in
Method II must also be mutually compatible.  The major difference
between these two design methods is that the empirical data are used
to arrive at the collecting-surface area as opposed to the use of the
Deutsch-Anderson equation. In the examples shown, the precipitation-
rate parameter to was used in both instances.  However, it is possible
to develop other relationships  that would eliminate the necessity for
arriving at a value  of co altogether.  Such relationships would be
empirical and would be subject to the  same degree of uncertainty as
the  selection of the precipitation- rate  parameter.

                                  49

-------
A more fundamental approach to precipitator design would be that
based upon theoretical factors such as particle size,  gas composition,
dust resistivity,  precipitator dimensions, and other input conditions.
This method is discussed in the following section.  However, at this
time, techniques for design based only on theoretical relationships have
not been developed to  the extent that they can be used on a commercial
basis.

WET ELECTROSTATIC PRECIPITATOR

The use of wet electrostatic precipitators for control of emissions from
industrial sources was generally  restricted to rather specialized appli-
cations such as on acid mist, coke-oven off-gas, blast furnaces, and
detarring applications.  The method of cleaning was in most cases
intermittent  and of the wetted-wall type.
As a result of much more stringent local, state, and federal emission
regulations,  condensable materials were added to the total particulate
loading.  The removal of organic  condensables, which are very difficult
to wet and which form small droplets in the 0. 1 to 2-micron range, re-
quires scrubber pressure drops in the range from 100 to 150 cm (40 to
60 inches)  of water gage.  Since the wet electrostatic precipitator is
always operated at saturation temperature (100 percent relative humid-
ity), it will remove  organic materials with a condensation temperature
higher than or equal to the  gas saturation temperature.  It will also re-
move solid dust particles in the submicron range and gaseous contami-
nants soluble in the  spraying liquor.  The removal of emissions is done
with very low energy consumption and a pressure drop usually less than
12. 7 mm (0.  5 inch)  of water gage.  The electric power input through
the high-voltage power supplies is quite low, from 1. 8 to 2. 8 kw per
100 actual  cu m/min (0. 5 to 0. 8 kw per 1000 actual cu ft/min).
      The recent development of a continuously sprayed,  parallel plate,
frame electrode and horizontal flow design has provided industry with a
realistic alternative to high-energy scrubbers.  The theory of operation,
description of the design, range of applications,  limitations of the
method for performance prediction,  and the energy consumption are
discussed in  the following sections.

Wet-Dust-Collection Fundamentals(55)

The corona generation and  the charging and discharging processes in
the wet electrostatic precipitator  are,  in general terms,  similar to what
takes place in a conventional dry  electrostatic precipitator except for
some important differences.
                                  50

-------
Since the gas in the wet precipitator is always saturated with water
vapor, there the current and voltage relationship is somewhat different
from that in the dry precipitator.  With increasing amounts of water
vapor, the spark-over voltage increases  (i.e., the voltage at which the
field breaks down), but the corona current at a given voltage is  lower.
When solid particles and droplets enter the electrostatic field, they will
cause a local distortion of the electrostatic field between the electrode
and the collecting plate.  Some of the electric Afield lines intersect the
particles, and ions generated.by the corona discharge will tend  to travel
along lines of maximum voltage gradient  or along the field lines; there-
fore, some of the ions will collide with the particles and the charge
gradually builds up on the particles.

This process continues until the charge on the particles  is so high that
it diverts the electric-field  lines away from the charged particles, pre-
venting new ions from colliding with the dust particle.   When this state
has been reached,  the particles are said  to be saturated with charge.
Theory shows that the saturation charge value and charging time are
dependent upon electric-field strength, size  of the particle, the dielec-
tric  constant of the particle, and the relative position of the particle in
the field.  This charging process is said  to be field dependent and is the
dominant process down to a particle size  of  0. 2 |Um. For smaller
particles,  the  so-called diffusion charging process is the dominant
mechanism; this is governed by the random thermal motion of the ions
and is not limited to a saturation charge.

As soon as the charging process of the particle starts,  the resulting
electrostatic force will pull the particle towards the collecting plate.
This force, together with the gravitational and the drag forces,  and the
gas flow distribution in the field determine the particle  trajectory and
its point of collection.

In a dry electrostatic  precipitator,  the dust buildup on the collecting
plate limits the maximum voltage at which the precipitator can operate.
For dust layers with high resistivity (greater than 2 x ICr^ ohm-cm)
the voltage drop can be from 10 to 20 kv.  This condition lowers the field
strength in the space between the electrode and the dust deposit surface,
and results in a lower saturation charge,  which again gives a lower
electrostatic force.  If, on the other hand, the resistivity of the dust
layer is lower than 10' ohm-cm, the electrostatic force holding the dust
particle on the plates  is low, and reentrainment can become a serious
problem during the electrode and plate cleaning (rapping) cycle  and also
during the steady operation,  having the overall effect of lowering the
precipitator collection efficiency.
                                  51

-------
For a continuously sprayed wet electrostatic precipitator,  the pre-
viously discussed problems are nonexistent.  The spray liquid drops
form a film on the collecting plates which continuously washes off the
dust that is being collected; the resistivity of the liquid  film is the
governing factor in the dust-discharging process and not the resistivity
of the dust layer itself.  Reentrainment problems are also nonexistent,
since the collected particles are instantaneously and continuously re-
moved from the point of collection and are washed down as a light
slurry.  The exit loading is,  therefore, much more stable and does  not
have the characteristic sharp increase that the dry electrostatic pre-
cipitator has during the collection plate and electrode rapping cycles.

Therefore,  for a wet electrostatic precipitator, the operation is not
influenced by the resistivity of the dust layer.  The  major parameters
that must be considered are the particles' dielectric constant and size.

In order to better understand the  effect of low dielectric constants on
horizontal migration distance  of the particle,  a mathematical model of
the particle collection mechanism was developed.  The  analysis was
based upon a field charging process and a particle or droplet which had
to traverse the whole net field spacing (one half of the plate-to-plate
spacing).  Particles of different sizes with dielectric constants of 2,
10, and 78 were investigated.

The unit consisted of parallel  collecting plates with  a separation of 2r.
The velocity profile between the plates was  assumed to  be flat (plug  flow)
and turbulent drag forces were neglected. Centered between two plates
was an electrode frame, with  electrode spacing assumed sufficiently
close to provide an approximately uniform electrostatic field near the
plate  surface.  The field strength was approximately 70 percent of the
field that was to be produced by a solid discharge plate  electrode, or

                           E = -0. 70  dv/dr.                         (3)

The nomenclature for the equations is given in Table 9.

The current density under no-load condition will  be

                               J = i/Ac.                             (4)

The ionic space charge can be determined from the  current density —
electric field equation:

         J = N0epiE  (E  = mean electrostatic field strength).         (5)
                                   52

-------
TABLE 9. NOMENCLATURE FOR WET-DUST-COLLECTION
           FUNDAMENTALS
       A         =      67Taf)/m = constant
       Ac        =      Collection area
       aj        =      Particle diameter
        d.
       B         =      qsE/m = constant
       ci        =      Particle inlet loading
       c0        =      Particle outlet loading
       E         =      Electrostatic field strength
       e         =      Electric charge
       F         =      Force
       g         =      Gravitational constant
       i         =      Current
       J         =      Current density
       In        =      Natural logarithm
       m        =      Particle mass
       N0        =      Number density of free ions
       V         =      Gas flow rate
       q         =      Charge
       qs        =      Saturation charge
       r         =      Net field spacing
       sx        =      Transverse distance
       sz        =      Horizontal distance
       T         =      Migration time for collection
       t         =      Time
       v         =      Voltage
       w         =      Velocity
       wgas      =      Gas average velocity
       wx        =      Transverse particle velocity
       wz        =      Horizontal particle velocity
       x         =      Transverse horizontal distance
       y         =      Vertical distance
       z         =      Horizontal axial distance
       £         =      Dielectric  constant
       eo        =      Permittivity of free space
       9         =      Viscosity of gas
       T]         -      Collection  efficiency
       |Uj_        =      Carrier mobility of the gas
       71         -      3.1416
       T         =      Charging time constant
       w         =      Migration velocity parameter
                              53

-------
The saturation charge for a nonconductive particle is

                                 £       2
                         qs =  ^^z^o^-                        <6>

The relative dielectric constant,  e, for a conducting particle approaches
infinity and is equal to one for a perfect insulator.

The expression for the charge as a function of time is

                                                                   (7)
where r is a charging time constant or

                             r =. 4e0/N0.e/i                         (8)

The particle-size range examined is larger than 0.2 /um, so the diffu-
sion charge can be omitted.

If we  start with a particle entering the field halfway between two plates
and without any charge, the force balance is divided into three different
components:

      x - axis, the direction of the electrostatic field
               (transverse to gas flow)
      y - axis, the direction of the gravitation force
               (vertically down)

      z - axis, the direction of the gas flow
               (horizontal and axial).

The force balance is then as follows:

                      2FX =  Fqe - Fx - Fix = 0                    (9)

                      2Fy =  Fg  - Frjy - Fiy = 0                   (10)

                      2FZ =  F^ - Fiz  = 0 .                      (11)

The electrostatic force can be expressed as

                              Fqe - qE .                          (12)


                                   54

-------
Substituting Equations (3),  (6), and (7) in Equation (12) gives
                                    ...
                                    N0eju

which shows the influence of the dielectric constant, the particle size,
and the field strength on the electrostatic force.

The gravitational force  is

                              Fg = mg .                            (14)

The viscous force, assuming Stoke 's Law applies (laminar flow), is

                              F^ = 67rad0w                          (15)

and the inertia force can be expressed as

                            FL = m dw/dt .                         (16)

If we  assume that a spherical  particle with a radius a is moving in this
field, it will be charged to carry an  amount  of g (coul) charges,  and the
force balance in the transverse direction, after substituting Equations
(12),  (15), and (16) in Equation (9), becomes:

                   qE = 67Tad7}wx - m dwx/dt = 0 .                  (17)

Substituting Equation  (7) into Equation (17) gives
                         t
                     qs     E "67Tad0Wx= m~dT;
let

                     A =67rade/mand B = qsE/m .                   (19)

Substituting this in Equation (18) and integrating gives
r>           /t
  -
                                     -At
                                J
                                o
                                   55

-------
          r e-At
The term \  — - — dt cannot be integrated but can be approximated using
          %J  t"r i
a series solution:
                                        oo
            Je~adx          u T           V          n
            -g^- dx = e-*db [In (b+x) +  )  [ad(b+x)J  /n-n i
                                       n=l

Then,  by using this expression in Equation (20) and integrating it once
more with the  following initial conditions

                t = 0, wx = wxo = 0 and sx = sxo = 0 ,

the travel distance sx becomes
       sx =  \  wxdt = f- (t - ^-(1 - e ~Ati + re
                     A \    A
                      oo
                      F i
          .  ("in —+  )  [(A  (t+T)]n -  (AT)n)/n-n.'~| -Tin—.      (21)
            L.   T    l_j                          J        T
                     n=l

The migration distance is from 0 to 15 centimeters (0 to 6 inches), and
the migration time, T, needed for the  particle to be collected can then
be found for sx =  15 centimeters (6 inches) by a trial-and-error solu-
tion of Equation (21).

In order to  obtain the horizontal distance needed for the particles to be
collected, the force balance in the z direction must be  considered,  i. e. ,
Equation (10).  This expression becomes

                   67Ta(j0 (wgas  - wz)  = m dwz/dt ,                 (22)

where (wgas - wz) is the  relative velocity between the particle and the
gas.   Integrating Equation (22), using  the constants given by Equa-
tion (\9) gives
tion (19) gives
                             i     -Af \        -Af
                             I 1     .** l> I i        •** l»
                 wz = wgas  (l  - e    ) +wzoe
                                   56

-------
where wzo is the initial particle velocity along the z-axis.  The hori-
zontal travel distance becomes, then,
         T                             '             .           .
= Jwzdt = wgas  [t + j   e-At-l]  -iwzo   e-At-l  .   (24)
    sz
Then,  by using the travel time calculated from Equation (19),  the hori-
zontal traveling distance can be  calculated as a  function of particle
(droplet) size and dielectric constant.  With two-5 /Jm particles  or con-
densed droplets, one with a dielectric constant of 2  (e. g., a. condensed
hydrocarbon droplet) and one with a dielectric constant of 78 (e. g. ,
pure water droplet),  migration of these two particles across a field
spacing of 15 centimeters  (6 inches) with an applied voltage  of 50 kv
and a gas velocity of 0. 9 m/sec  (3 ft/sec) will take a horizontal  dis-
tance of  2. 2  m (7. 2 ft) and 1.2m (3. 9 ft), respectively.  There-
fore,  the low dielectric  particle takes almost twice  the horizontal
distance before being collected;  this analysis  points to the fact that
condensable  hydrocarbons (tars) and other materials with a  low
dielectric constant will be much more difficult to collect than con-
ductive particles, and this has been confirmed by measurements.

When considering the removal of condensable hydrocarbons  (tar mist),
it should be remembered that the dielectric constants for petroleum
distillates are quite low'-(i.e., around 2).  For example,  hexane (C^H^)
has a dielectric constant of  2 and a boiling point of 69 C (156 F), toluene
(CyHg) has a dielectric constant of 2. 15 and a boiling point of 110 C
(230 F),  and naphthalene (CjQHg) has a dielectric constant of 2. 54 and
a boiling point of 218 C (424 F).   Other organic  liquids lik-e phenol form-
aldehyde resin have a dielectric constant of 6. 6.  Pure water  has a
dielectric constant of 78.

The removal efficiency of  the wet electrostatic precipitator  on a:given
gas and dust stream  is a function of six basic parameters:

                       Collection Area
                       Operating Voltage
                       Discharge Current
                       Liquid-to-Gas  Ratio
                       Treatment Time
                       Local Average Velocity.
                                   57

-------
The performance is often stated by the so-called migration velocity.
The higher the migration velocity is, the better the particulate removal
efficiency or the smaller the wet electrostatic precipitator in terms of
collection area needed to treat the gas flow.  The relationship between
migration velocity and wet electrostatic precipitator performance is
given below.

                      u = -V/A 0. 508 In (c0/Ci) ,                    (25)

similar to the migration Equation (1).

The efficiency of the unit is given by

                          T)= (l-c0/Ci) 100 ,                        (26)

and when substituting Equation (25),

                       7)= (l-e(-Aw/0.508Q), 100                   (27)

which is another expression for the  Duets ch-Anders on Equation (2).

The migration velocity w is a performance parameter that does not in
reality relate directly to the  speed at which the particles  migrate to the
collecting plates.  It is a "catch-all" which also includes  all  operating
parameters not included in Equation (25).


HORIZONTAL-FLOW WET ELECTROSTATIC
PRECIPITATOR

One of the wet electrostatic precipitators can be characterized as a con-
tinuously sprayed, horizontal-flow,  parallel-plate,  and solid-discharge
electrode type.  In terms of gaseous absorption, it  can be characterized
as a combination cocurrent and a cross-flow scrubber.

In the application of a wet electrostatic precipitator, it is very important
that the gas to be treated is saturated with water vapor to prevent the
water inside the wet electrostatic precipitator from evaporating, which
causes loss of washing water and dry zones on the internal members.
The saturation of the gas can be done in a spray tower or scrubber up-
stream of the wet electrostatic precipitator, or it can be  done in the
inlet section of the wet electrostatic precipitator, or both.
                                   58

-------
In addition, it is also necessary to obtain a uniform velocity profile
across the wet electrostatic precipitator, and the diffusion of the flow
from the inlet duct velocity down to the wet electrostatic precipitator
face velocity has to be  performed in the inlet section.  Furthermore,
by spraying cocurrent into the inlet section, some of the coarser parti-
cles will be removed and the gas-absorption process will be started.
To accomplish this, sections of baffles and sprays are located in the
inlet cone of the wet electrostatic precipitator.

After passing through the  sections of transverse baffles, the dirty gas
stream then enters into the first electrostatic field.  Water sprays
located above the electrostatic-field sections introduce the proper
amount of water droplets to the gas stream for washing of internal sur-
faces. The particulates and the water droplets in the electrostatic field
pick up a charge and migrate to the collecting plates.   The collected
water droplets form a continuous downward-flowing film over all the
collecting plates and keep them clean.  The water film and the collected
particulates flow down  the collecting plates into the troughs below,
which are sloped to a drain.

The  transverse-baffle gas-distribution system combined with the ex-
tended electrode, located upstream and downstream of each field,  insures
complete gas-flow uniformity from passage to  passage, and collects
particulates and droplets by impingement, and by electrostatic forces.
Also, the extended discharge electrode system improves the  collection
efficiency by increasing effective collection area.  At the entry of a
field, particles not captured by the transverse baffles are given an
advance  charge by the forward extended electrode before they come into
proximity of the collecting plates.  Thus charged, the particles  start
immediately to migrate toward the leading edge of the plates.  It has
been found that the downstream side of the baffles at the exit of a field
collects a considerable amount of material.  The very small charged
particles escaping the parallel-plate field are pulled into the wake of the
baffles by the slight vacuum resulting from the turbulent dissipation of
energy.  Since the particles have an electrostatic charge, some of them
will  be collected on the back side of the baffles.

All baffles systems are arranged so that a walkway runs across the front
and the back of each of the electrostatic fields.   The discharge  electrode
frames are mounted on collar-type,  high-voltage support insulators.
Insulator compartments are heated and pressurized to prevent moisture
and particulate leakage into  the insulator compartment.
                                   59

-------
In any particulate and/or gaseous removal process where a liquid is
used,  it is important to remove the carryover liquid drops and mists
before reaching the outlet of the equipment.  It has been found that doing
this electrostatically is highly efficient.  Hence, the last section is
operated dry, thereby establishing an electrostatic barrier that the
liquid  droplets cannot penetrate.  The mist collects on the front side of
the baffles, and the downstream side is dry.  However, some small
dust particles can penetrate and these will collect on the  downstream
baffles.  Therefore, this surface is  washed intermittently to  prevent
buildup of particulates.

RANGE OF APPLICATIONS

During the past 2 years, many new applications have been piloted and
units have  been sold and installed following successful  pilot-plant work.
The wet electrostatic precipitator can be used for applications on gas
streams containing  relatively light dust loading of submicron particles
and/or condensed organic materials  forming a submicron fume.
Ordinarily these applications would require very-high-pressure-drop
scrubbers.  The energy consumption and operating costs are less than
what would be needed to operate scrubbers.  The water-treatment
requirements for the wet electrostatic precipitator would be the same as
those for scrubbers.

In some  applications,  where the dust resistivity is either very high or
very low, the wet electrostatic  precipitator can also be applied success-
fully in competition with dry electrostatic precipitators.

Wet electrostatic precipitators  have  been installed for  the following
applications:

      (1)  On Soderberg aluminum reduction cells (pot  lines),
          both of the vertical and horizontal stud type, for
          simultaneous  removal of aluminum oxides,  solid and
          gaseous fluorides, tar mist (condensable hydrocar-
          bons), and SO2

      (2)  On carbon-anode baking furnaces for removal of car-
          bon particles,  tar mists, and SO2

      (3)  On fiber-glass resin  application section and  forming
          lines for  removal of short broken glass fibers,
          phenolic resins,  and  tars

                                  60

-------
      (4)  In molybdenum sulfate roasting,  downstream of a
          scrubber for removing ammonium sulfite - sulfate
          aerosols  which form in the ammonia scrubbing
          process and SC>2.

Wet electrostatic precipitators are now being manufactured and installed

      (1)  For upgrading of low-pressure-drop scrubbers  on
          phosphate rock driers for removal of the submicron
          particles and SO2

      (2)  On coke-oven batteries when connected to a continuous
          shed or hood along the push side of the battery where
          the coke is pushed into the railroad car.   Here the  wet
          electrostatic precipitator will remove the fine carbon
          particles and the condensable hydrocarbons during  the
          push cycle.  In addition, the wet electrostatic precipi-
          tator will collect any emissions caused by door  leakage
          on the push side.

A wet electrostatic precipitator has been designed to meet the require-
ments for controlling reclamation (sinter) plant emissions.


Reclamation (Sinter) Plant Design Specifications

Table 10 provides information concerning a wet electrostatic  precipitator
for controlling emissions from a sinter plant producing about 2, 300, 000
metric tons (2, 530, 000 net tons) of high-basicity sinter annually. *

Reclamation (Sinter) Plant
Electrostatic  Precipitator Design Data

There is very little specific design information available in the published
literature relating to the design of reclamation (sinter) plant electro-
static precipitators.  Information presented in this section is indicative
of the data that have been published.

Particulate Characteristics-The electrical  resistivity of the particulates
is an important design factor, and an example of the variations in elec-
trical resistivity  as affected by the temperature of the gas and the sinter
mixture is shown in Figure 22. (55)

"Used with the permission of MikroPul Corporation, November 27, 1974.
                                   61

-------
                           TABLE 10.  EQUIPMENT SPECIFICATIONS
                            Gas Conditioner (Absorber) Specifications
Operating Data

  Inlet Volume
  Inlet Temperature
  Inlet Moisture Content:
   Percent Volume
   Humidity

  Inlet Gas Density
  Outlet Volume (Saturated)
  Outlet Temperature
  Outlet Humidity

  Outlet Gas Density
  Inlet Paniculate Loading
  Inlet Condensable Loading
  Total Inlet Loading
  Expected Outlet Paniculate Loading
  Expected Outlet Condensable
   Loading
  Total Expected Outlet Loading
  Pressure Drop Across Absorber
  Gas Velocity
  Treatment Time
  Number of Absorbers
Operating and Performance Data
 Volume at saturated conditions
 Temperature at saturated conditions
 Inlet Loading
   Paniculate
   Condensable
   Total

 Guaranteed Overall (Absorber
   and Precipitator) Efficiency,
   percent
 Guaranteed Total Outlet Loading
 Pressure Drop Across Precipitator
   Including Gas Distribution
   Devices,  but excluding losses
   across dampers
 Gas Velocity
 Treatment Time
8,496 actual cu m/min
202-204 C

12   /
0. 3^9 kg water vapor/kg
  dry gas
0. 7106 kg/cu m
6, 519 actual cu m/min
      kg water vapor/kg dry
  gas
0.9817 kg/cu m
0. 1961 gram/cu m
0. 2591 gram/dry cu m
0.4552 gram/dry cu m
0. 0785 gram/dry cu m
0. 1943 gram/dry cu m

0. 2728 gram/dry cu m
2. 54 cm water gage
2. 92 m/sec
+1. 88 sec
Two (2)
     I Precipitator
3,260 cu m/min
60 C

0.0785 gram/dry cu m
0.1943 gram/dry cu m
0. 2728 gram/dry cu m

92.45


0. 034 gram/dry cu m
127 -mm  water gage
0. 832 m/sec
8.79 sec
300, 000 actual cu ft/min
395-400 F

12
0.8464 Ib water vapor/lb dry
  gas
0. 04436 Ib/cu ft
230,000 actual cu ft/min
140 F
0.153 Ib water vapor/lb dry
  gas
0. 06128 Ib/cu ft
0. 0857 grain/dry  std cu ft
0.1132 grain/dry  std cu ft
0.1989 grain/dry  std cu ft
0. 0343 grain/dry  std cu ft
0. 0849 grain/dry  std cu ft

0.1192 grain/dry  std cu ft
1.0-inch water gage
9. 59 ft/sec
+1. 88 sec
Two (2)
115,100 cu ft/min
140 F

0. 0343 grain/dry std cu ft
0.0849 grain/dry std cu ft
0.1192 grain/dry std cu ft

92.45


0. 015 grain/dry std cu ft
0. 5-inch water gage
2. 73 ft/sec
8. 79 sec
                                              62

-------
                                      TABLE 10.  (Continued)
Arrangement
  Number of Precipitators
  Chambers (Number)/Precipitator
  Fields (Number and Length)/
   Precipitator
  Casing Material and Thickness
  Casing Design Pressure - Positive
  Number of Hoppers per Precipitator
  Hopper Material and Thickness
  Type of Hopper
  Insulator Compartment Materials
   and Thickness
  Number of Insulator Compartments
   per Precipitator
  Precipitator Internal Gas
   Distribution Devices
    (a) Types
    (b) Quantity and Location per
        Precipitator
    (c) Material and Thickness
  Number, Type,  and Size of
   Access Doors per Precipitator
    (a) Roof
    (b) Shell
    (c) Insulator Compartments
    (d) Inlet
    (e) Outlet
  Access Walkways Internal
                                           Precipitator
4
1
3, 183 m

6.35 mm
254-mm water gage
3
6.35 mm
Sloping
2.72 mm
Transverse baffles
Two sets - inlet nozzle
One set - inlet 1st field
Two sets - between stages
One set - mist eliminator
1.56 mm, X18H11M
5, 0. 61 m x 1.37 m
2, 0.61 m x 1.37 m
6, 0.61 m x 1.37 m
1, 0.61 m x 1.37 m
1, 0. 61 m x 1.37 m
4
1
3, 6ft

1/4-inch mild steel
10-inch water gage
3
1/4-inch mild steel
Sloping
12-gage mild steel
16-gage, Type 316
2 ft x 4. 5 ft
2 ft x 4. 5 ft
2 ft x4. 5 ft
2 ft x 4. 5 ft
2 ft x 4. 5 ft
Mild steel expanded metal grating between fields
                              Collecting System - per Precipitator
 Number of Gas Passages
 Spacing of Gas Passages
 Collecting Plate Material and
   Thickness
 Collecting Plate Effective Length
 Collecting Plate Effective Height
 Active Collecting Surface Area
   Plate Area
   Transverse Baffle Section Area
   Total
28
30.5 cm
1.95 mm, X18H11M

5. 5 m
7.6 m
2, 341 sq m

  390 sq m
2,731 sq m
12 inches
14-gage, Type 316

18 feet
25 feet
25, 200 sq ft

 4,200 sqft
29,400 sqft
                                               63

-------
                                   TABLE 10.  (Continued)
Discharge Electrode - Type,
  Material and Thickness
Type Transformer Rectifier
Number of Transformer Rectifiers
  (a)  Voltage Rating,  kv (dc) avg.
  (b)  Current Rating,  ma (dc) avg.
      (for pure resistive loads)
Number of Transformer Rectifier
  Control Cabinets
Construction of Transformer
  Rectifier Control Cabinets
Transformer Rectifier  Insulation
  Fluid
Wave Form of High Voltage
Number and Type of High Voltage
  Switches
Key Interlocks
  Control Cabinets
  Transformer Rectifiers
  Access Doors
Type of Transformer Rectifier
  Controls
Maximum Ambient  Temperature
  for Transformer Rectifier, C
Connected Load kva/Precipitator
  Transformer-Rectifier
  Insulator Heater and  Blower
Total Connected Load KVA/
  Precipitator
Power Distribution
  Individual Breakers Each Control
   Cabinet
  Central Distribution  Panel
   High Voltage System
  3.11mm, 1X16M13ME


High Voltage Electrical Set

  Silicon
  3/unit
  55
  1,000

  3/unit

  NEMA. 12

  Pyranol

  Full Wave
  3/Grounded
  Yes
  Yes
  Yes
  Thyristor

  40
  235
  28
  263
  Yes

  No
11-gage,  Type 316L
                Operating Liquid Characteristics for Precipitator and Absorber
                                          Absorber Feed
Liquor Rate
Liquor Pressure at Nozzles

Liquor Source
Evaporation Rate
  5678 1/min     1500 gal/min
  293 kg/sq m    60 Ib/sq in.
                   gage
           pH-Controlled Recycled Treated Liquor
  378 1/min      100 gal/min
      Precipitator Feed
2839 1/min      750 gal/min
293 kg/sq m     60  Ib/sq in.
                 gage
                                              64

-------
                                   TABLE 10.  (Continued)
                  Operating Liquid Characteristics for Precipitator and Absorber

                                      Absorber Feed                 Precipitator Feed
Liquor Quality:
  The following typical liquor quality
  observed during the pilot-plant study
  is required for efficient absorber and
  precipitator operation.

pH                                        9.6                              9.2

                                          mg/1                           mg/1
     i
Phenophthalein Alkalinity as CaCOg        1,450                           1,390
Methyl Orange Alkalinity as CaCOg        3,800                           3,410
Chloride as Cl                             240                             194
Sulfate as SO4                           3,750                           3,650
Hardness as CaCOg                          24                               25
Calcium as CaCOg                           8                               8
Magnesium as CaCOg                       16                               17
Silica as SiO2                              10. 5                             10.1
Total Solids                            10,652                          10, 224
Dissolved Solids                         10,488                          10,090
Suspended Solids                           164                             134
Total Iron as Fe                              7.9                             6.4
Aluminum as Al                             1.8                             1.6
Zinc as  Zn                                  0.4                             0.3
Lead as  Pb                                   6.5                             3.9
Cadmium as Cd                              0.18                            0.10
Molybdenum as Mo                          1    .                           1
Fluoride as F                               42                               40
Oil and  Grease                              79                             108
Total Carbon                              570                             300
Total Inorganic Carbon                     420                             200
Total Organic Carbon                      150                             100
                                             65

-------
                          GAS TEMPERATURE, F
                  100  150   200   250   300   350  400
ICAL RESISTIVITY, ohm-cm
ELECTR
1 x 10'°
1 x 1014
1 x 1013
•<
1 x 109
1 x 108
I I I I I
PLANT 1
^^"V^, 0.6% MOISTURE
PLANT J
6% MOISTURE -— ^>--^.
> <
PLANT K
6% MOISTURE — ~~^^V.
i 1 i i . . 1 i i I i 1 . i i i 1
                     50        100       150        200
                            GAS TEMPERATURE, C


Figure  22.  Electrical resistivity of reclamation (sinter) plant dust
            as affected by gas temperature and sinter mixture
             0.656
          o
          I
          25  °-492
          UJ
             0.328
          <  0.164
          o
          HI
          or
          O.
                                   TEMP - 149 C
                                         (300 F)
                                    I
I
      20
      15
      10
                 0123
                  SULFUR CONTENT OF THE COAL, percent
 Figure 23.  Relationship between the sulfur content in electric-
             utility-plant coal and the precipitation-rate parameter
                                  66

-------
Sinter mix composition,  particulate size,  and gas data are listed in
Table  ll.(56)

         TABLE  11.  RECLAMATION  (SINTER) PLANT DATA
                      FOR FIGURE 22
          Parameter
Plant J
Plant K
Sinter Mixture
Iron ore and metallics, percent
Limestone or dolomite, percent
Coke, percent
Particle Size, percent -10 microns
Gas Analysis
Sulfur oxides, ppm
Moisture content, percent
Temperature

90
9
1
60

300
15
121 C (250 F)

64
35
1
45

30
10
93 C (200 F)
It is known that the sulfur content of reclamation-plant off-gas affects
the collection of emissions.  While such data are not available for
reclamation-plant off-gas, Figure 23 shows the relationship between the
sulfur content in fuel and the precipitation-rate parameter to for  electric-
utility electrostatic precipitators. (55)

The effect of various reclamation (sinter)-plant electrostatic-
precipitator variables on collection efficiency is shown in Figure 24.(^ '>

The limited amount of information available on reclamation (sinter)-
plant electrostatic precipitators is given  in Table 12. (34, 54, 55, 58, 59)

Reclamation (sinter) plant electrostatic precipitators are typically
single-stage,  horizontal-flow units.   The chambers  and hoppers are
usually fabricated of'plain-carbon steel, and may or  may not be thermally
insulated. (55)  Plain-carbon steels have, not performed as well as  desired
because of the corrosive conditions that can be generated by the  reaction
of sulfur oxides with moisture to fprm acids.  This acid corrosion
necessitates the replacement of electrodes,  collector plates, and internal
supporting members,  causing excessive maintenance costs and short
service  life, as compared with other equipment used in an iron and steel
plant.
                                  67

-------
     0.0
    99
    98
    97
•*-•
c
Q)
B   96
 .   95
o   94
2   '
LU
g   92
t   90
O
o
o
o
   80
   70
   60
   50
   40
   20
                       Ac (COLLECTION AREA), sq ft
                       wgas 
-------
TABLE 1Z.  RECLAMATION (SINTER)  PLANT ELECTROSTATIC-PRECIPITATOR CHARACTERISTICS
Plant Location
Annual Production
metric tona
net tons
Strands, number
Air Volume
cu m/sec
cu ft/min
Air Temperature
C
F
Pressure Differential
kg/sq m
inches of water
Gas Velocity
cm/sec
ft/ sec
Treatment Time, seconds
Charge Section
Number of Ducts
Width
centimeters
inches
Height
meters
feet
Length
meters
feet
Number of Electrodes
Size
mm
in.2
Type of Suspension
Power
Collection Section
Number of Plates
Height
meters
feet
Length
meters
feet
Number of Electrodes
Bethlehem Steel Corp. ,
Johnstown,
Pennsylvania

998,000
1, 100,000
2

100
213,000

115
240

762
30





37

23
9

7.3
24

2.7
9
436

6
0. 0093
Plumb Bob


76






872
Inland Steel Co. ,
East Chicago,
Indiana

1,089.000
1,200,000
1

215
457,000

191
375

889
35

195
6.4
2.3


















136

2.3
7. 5

7. 3
24. 0

Plant L, Plant I
Eastern Reference
Pennsylvania (54)

454,000 2,177,000
500,000 2,400,000
1 4 (2 per ESP)

80 180
170,000 385,000

149 118
300 245

660 1070
26 42

174
5. 7
4.2


















70

1.8
6.0

7.3
24.0
1600
                                            69

-------
                         VI.  REFERENCES
 (1) Annual Statistical Report,  American  Iron and Steel Institute,
    1974_,  pp. 65, 72.

 (2) Ess,  T. J. ,  Alan Wood Steel Company, Iron and Steel Engineer,
    39: AW4-AW22, March 1962.

 (3) Annual Report,  Alan Wood Steel Company, ^972.

 (4) Fosdick,  A.  H.  , Operating Features and Practices  at the
    Bethlehem Sintering Plant.  AIME Blast Furnace, Coke Oven,
    and Raw Materials Proceedings.  7:106-118, 1948.

 (5) Gas Cleaning System for Bethlehem's Sintering Plant.  Blast
    Furnace and Steel Plant. 59:60,  January  1971.

 (6) The Bethlehem  Plant's New $2. 4-Million Stack Gas  Cleaning
    System.  American Metal Market, p.  6,  December 9,  1970.

 (7) Sinter Line Baghouse Collector Still Going Strong.   Iron and Steel
    Engineer. 45:124,  February 1968.

 (8) Ess,  T. J. Bethlehem's Johnstown Plant. . . A Century of Pio-
    neering.  Iron and  Steel Engineer.  30:J2-J20, April 1953.

 (9) Air Pollution Control System Installed at Bethelehem's Johnstown
    Plant.  Blast Furnace and Steel Plant.  56:917,  October 1963.

(10) Lassen, E. ,  Jones and Laughlin Steel Corporation's Aliquippa
    Works.  Blast Furnace and  Steel Plant. 54:957-958, October 1966.
                                                                 ^.u.i.ii-i .1 —

(11) J & L  Operating Largest Single Strand Iron Ore  Sintering Line.
    Industrial Heating. 28:1682-1690, September J96J..

                                  70

-------
(12) Air Pollution Control Continues at JfyL Aliquippa Works.   In-
    dustrial Heating. 31:486,500, March 1964^

(13) Communication from R.  C.  McCrillis,  Environmental Protection
    Agency. April  25, 1975..

(14) Harris, E.  R. , and Beiser, F. R. Cleaning Sinter  Plant Gas With
    a Venturi Scrubber.  Journal of the Air Pollution Control Associa-
    tion.  15:46-49,  February 1965.

(15) Communication from B. Steiner,  April 9, 1975.

(16) Air Emission Control Facility at United States  Steel Corp. "s
    Saxonburg,  Pa. , Sintering Plant.   Iron and  Steel Engineer.
    46:45,  April 1969.

(17) Faigen, M.  R. , Kyler, E.  B. ,  and Plummer,  W. S.  Recent
    Improvements  at United States Steel —Saxonburg Sinter Plant.
    AIME Ironmaking Proceedings.   29:310-318,  1970.

(18) To Add Sinter Plant at Monessen Works. Iron and Steel Engineer.
    41: 50,  April 1964.

(19) Edwards. L. H. Equipment and Operational Changes Made to Up-
    grade an Old Sinter  Plant.  AIME Ironmaking Proceedings.  29:328-
    333,  1970.

(20) Two J&L, Sintering Machines Served  by Vertical Shaft Sinter
    Cooler. Industrial Heating.  28:514-516,  March 1961.

(21) Kraner, H.  M. , and Hauser, R.  E.   New Sintering Plant Facilities
    at Sparrows Point.  Blast Furnace and Steel Plant.  44:757-759,
    July 1956.

(22) Largest in Western  Hemisphere.  Journal of Metals.  24:8, June
    1972.

(23) Watson, G.  W.  Weirton No. 2 Sinter Plant.  Iron and Steel
    Engineer. 36:105-108, June 1959.

(24) Cleaning System Turnkey Contract.  American Metal Market.
    p. 14, September 3, 1971.
                                  71

-------
(25) Communication from B. Steiner.  June 25,  19.75.,  ,

(26) Loofboro, K. A. J&L's Cleveland Works Sinter Plant.  Iron and
     Steel Engineer. 36:101-104, June

(27) Ess,  T.  J.  Republic Builds for D.P.C.  Iron and Steel Engineer.
     21:R18-R38, October 1944.               .

(28) Republic  Steel Plants and Facilities. Republic Steel Corporation.
     28 p. February 1967.

(29) Austermiller, E. O. , and Cureton, W. A. Design and Operation
     of National Tube's Sintering Plant.  Iron and Steel Engineer.-
     28:111-117,  October 1951.    . .      .

(30) Slater, R. A. Construction and Design Involved in a New Sintering
     Plant.-  Iron  and Steel Engineer.  37:114-117, December 1960.

(31) Cromwell, D.  P.  Operations and Practice,  Campbell Sintering
     Plant.  AIME  Blast Furnace, Coke Oven, and Raw Materials
     Proceedings. 7:86-89,  1948. _.  .                     .

(32) Armco Completes Sintering Unit at Ashland Plant.  Iron and Steel
     Engineer., 35:146-152,  October 1958..

(33) Baranyi,  J.  F.  Results of Design Changes in Sinter  Plants.  Iron
     and Steel  Engineer. 42:85-90, December 1965.

(34) Frame, C. P., and Els on, R. J.  The Effects of Mechanical. Equip-
     ment on Controlling Air Pollution at No. 3 Sintering Plant, Indiana
     Harbor Works,  Inland Steel Company.  Journal of the Air Pollu-
     tion  Control Association.  13:600-603,  December 1963.

(35) Inland Steel Shuts  Down Two Sintering  Lines at Indiana Harbor
     Works. Blast Furnace and Steel Plant.  55:660, July 1967.

(36) Young,  T. A. , Jr. Gary Steel Works Experience With Dust
     Control at Number 3 Sinter Plant.  Blast Furnace and Steel Plant.
     56:1057-1063,  December  1968.           •    .

(37) Bethlehem Tells Details of Proposed Sintering Plant.  American
    Metal Market,  p.  4, November 2  1972.
                                  72

-------
(38) Bayr, R.  B. , and Wachowiak,  R. J.  Elimination of Hydrocarbon
    Emissions From the Sinter Plant.  AIME Ironmaking Proceedings.
    31:55-58, 1972.

(39) A New $700, 000 Baghouse.  Skillings Mining Review.  64(18):28,
    May 3,  1975.

(40) Corzilius, W. R.  Sintering Plant Expands  Blast Furnace and Open
    Hearth Capacity.  Blast Furnace and Steel Plant.  47:44-50,
    January 1959.

(41) Sinter Plant Baghouse Cleaner for Granite City Steel.  Blast
    Furnace and  Steel Plant.  59:241, April 1971.

(42) Scrubber  System For Granite City.  American Metal Market.
    p. 6, December 4, 1973.

(43) Pollution  Control Project.  American Metal Market, p. 4,
    September 4,  1970.

(44) A New Baghouse  Type Dust Collecting System.  American Metal
    Market,  p. 3, December 28, 1970.

(45) Menke,  G. V.  Sintering Plant Emission Control Wisconsin
    SteelWorks.  Preprint AIME Ironmaking Conference.  10 p.  1972.

(46) CF&I Steel Installing Electrical Precipiators To  Control Iron Ore
    Dust At Its Pueblo Plant.  Blast Furnace and Steel Plant. 57:82,
    January 1969.

(47) Egley, B. D.  Selection of Gas Cleaning Equipment For an Ore
    Preparation Plant.  Iron and Steel Engineer. 47:111-115, November
    1970.

(48) Kaiser Steel  Starts Operation of New Pollution Control Unit.
    American Metal Market,  p. 18,  August 9, 1971.

(49) Nowak,  T. T. Sinter Plant  Baghouse.  AIME Ironmaking Proceed-
    ings.  31:75-84,  1972.

(50) Communication From R.  L. Bump,  Research-Cottrell, Inc.,  to
    J. Varga, Jr.  July 31,  1975.
                                 73

-------
(51.) McCrone, W. C. ,  et. al.  The Particle Atlas.  Ann Arbor . Science
   ' Publishers,  Inc. Ann Arbor, Michigan. 153-236,  (1967).

(52) Manning, G. E. , and Rower, F.  E.  A Characterization of Air
    Pollutants From Sintering Plant Induced Draft Stacks.  AIME
    Ironmaking Proceedings.  30:452-460   (1971).

(53) Suitlas,  J. R.  Emission Characteristics  and Pilot Plant Studies
    on a Sintering Plant Windb.ox Discharge.  AIME Ironmaking
    Proceedings, 30:461-470  (1971).

(54) Communication from  R. C. McCrillis  to  J.  Varga, Jr.

(55) Oglesby, S. , Jr.,  and Nichols,  G.  B.   A  Manual of Electrostatic
    Precipitator Technology, Part II — Application Areas..  The
    National Air Pollution Control Administration,  Division of Process
    Control Engineering.  PB 196381. 487-502  (August 25, 1970).

(56) Bakke, E. ,  The Application of Wet Electrostatic Precipitators for
    Control of Fine Particulate Matter, Paper presented at the
    Symposium on Control of Fine Particulate Emissions From Indus-
    trial Sources for the Joint U. S. -U. S. S.R. Working Group, Sta-
    tionary Source Air Pollution Control Technology.  San  Francisco,
    California.  27 pp.  (January 15-18, 1974).

(57) Oglesby,  S. , Jr.,  and Nichols,  G. B.   A  Manual of Electrostatic
    Precipitator Technology, Part I - Fundamentals.   The National
    Air Pollution Control Administration, Division of Process Control
    Engineering.  PB 196380.  203-217 (August 25,  1970).

(58) Communication from R. C. McCrillis to J. Varga,  Jr. April 25,
    1975.

(59) Communication from W.  McShane to J.  Varga, Jr.  July 11,  1975.
                                 74

-------
                                  TECHNICAL REPORT
                           (Please read Instructions on the reverse
                              DATA
                              before completing)
 1. REPORT NO.
  EPA-600/2-76-002
                             2.
                                     3. RECIPIENT'S ACCESSION-NO.
 4. TITLJE AND SUBTITLE
 Control of Reclamation (Sinter) Plant Emissions
    Using Electrostatic Precipitators
                                     5. REPORT DATE
                                     January 1976
                                     6. PERFORMING ORGANIZATION CODE
 7. AUTHOR(S)
 John Varga, Jr.
                                                         8. PERFORMING ORGANIZATION REPORT NO
 9. PERFORMING ORdANIZATION NAME AND ADDRESS
 Battelle-Columbus Laboratories
 505 King Avenue
 Columbus, Ohio  43201
                                     10. PROGRAM ELEMENT NO.
                                     1AB015; ROAP 21AQR-042
                                     11. CONTRACT/GRANT NO.

                                     68-02-1323, Task 32
 12. SPONSORING AGENCV 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; 3/15-8/15/75	
                                     14. SPONSORING AGENCY CODE
 15. SUPPLEMENTARY NOTES
 IB. ABSTRACT Tne repOrt briefly reviews the sintering process as it applies to the U.S.
 integrated iron and steel industry.  The review includes data on characteristics of
 the emissions, and a list of all the iron and steel reclamation (sinter) plants  in the
 U.S., their annual capacity, and the types of emission control equipment used.  The
 report contains a detailed discussion of the theoretical and practical aspects  of
 designing both wet and dry electrostatic precipitators (ESPs) to control the sinter
 machine windbox emissions.  It gives design specifications for a proposed wet ESP
 installation on a large modern sinter plant.
 7.
                              KEY WORDS AND DOCUMENT ANALYSIS
                 DESCRIPTORS
                                            b.lDENTIFIERS/OPEN ENDED TERMS
                                                 c. COSATl Field/Group
 Air Pollution
 Iron and Steel
    Industry
 Electrostatic
    Precipitators
 Reclamation
Sintering
Sintering Furnaces
Design
Specifications
Air Pollution Control
Stationary Sources
Sinter Plants
Sinter Machine Windbox
13B
11F
13H
13A
 8. DISTRIBUTION STATEMENT
                                            19. SECURITY CLASS (ThisReport)
                                            Unclassified
 Unlimited
                                                 21. NO. OF PAGES
                                                      81
                        20. SECURITY CLASS (This page)
                        Unclassified
                                                 22. PRICE
EPA Form 2220-1 (9-73)
                                            75

-------