-------
0

H


m
m


I
n



!
         5
         •a. 16, ooo J
         § 12,000 -


         «*

         55


         B  8, 000 -
Sf
"o
o>
         
-------
                  -713-
                Table 19.13

      Precipitator Gas Velocity (Design)
Phosphoric Acid Mist Precipitator 1927-1969

Velocity
Interval
fps
2-3
3-4
4-5
5-6
6-7
7-8
Totals
No. of
Install.
1
4
1
4
0
2
12
No. of
Pptrs.
1
5
1
5
0
6
18
Pptr. Capacity
Thousand acfm
in Interval
1.6
22.3
3.0
48.8
0
62.0
137.7
% of Installations
in Velocity
Interval
8.3
33.3
8.3
33.3
-
16.7
100
-------
                    -714-
                 Table 19.14

   Precipitator Inlet Temperature.(Design)
Phosphoric Acid Mist Precipitator 1927-1969

Pptr.
Inlet
Temp.
°F
100-150
150-200
200-250
250-300
Totals


No. of
Install.
-
6
1
4
11


No. of
Pptrs.
-
13
2
5
20

Pptr. Capacity
Thousand acfm
in Interval
-
58.8
26
46.9
131.7
•;
% of Installations
in
Interval
-
54.5
9.1
36.3
100
                                     SOUTHERN RESEARCH INSTITUTE
-------
                                 -715-
number of installations, precipitators, and gas volumes are also shown.

      Table 19.15 is a  summary of several inlet loadings.

      Bar graphs of the data showing input parameters are shown in
Figures 19.27  to 19.29.

      Table 19.16 presents a summary of the range of actual performance
data--gas velocity,  inlet gas temperature, and loading—with the mean
value of each parameter.   Values of field strength and input power are
not available.

   Economics--phosphoric acid mist precipitator costs. Cost data for
several precipitators have been reported in Table  19.17 for 10 to 12 year
periods.  Both FOB and installed costs are included when available.  The
limited data preclude graphical presentation.  No maintenance or operat-
ing costs  are available from this source.

   General observations and discussion of trends - phosphoric acid mist
precipitator.  The data presented indicate that the use of electrostatic pre-
cipitators for  phosphoric  acid mist control applications has declined in
recent years.   Since the demand for high purity phosphoric acid from the
combustion process has not declined,  it is evident that other factors are
responsible.

      It is believed that the following are among the more important of
these factors:

      Many of the precipitators were installed with mechan-
      ical rectifiers, and maintenance problems were appre-
      ciable.  Further, while stainless steels are  relatively
      resistant to phosphoric acid, maintenance problems
      associated with sparking and resulting corrosion have
      been troublesome.  Lead, while resistant, lacks the
      useful temperature  range necessary for this  applica-
      tion in which  temperature upsets are not infrequent.

      The trend now appears to be toward high energy variable orifice
scrubbers for this application.
-------
                    -716-
                  Table 19.15

Precipitator Inlet Loading (gr/scf) (Performance)
  Phosphoric Acid Mist Precipitator 1927-1969

Inlet
Loading
£r/scfd
4-10
10-16
16-22
22-28
28-34
Totals

No. of
Install.
1
1
1
0
A
5

No. of
Pptrs.
2
2
2
-
3
9

Pptr. Capacity
Thousand acfm
26.0
35.8
1.6
-
13.2
76.6
% of Installations
in
Interval
20
20
20
-
40
100
                                      SOUTHERN RESEARCH INSTITUTE
-------
                                -717-
5

4
CQ
§
•fH
rt
t— 1
•3
** 3
(0 «'
c
"o
0)
1 2
2
1














Note: Numbers above bars
are total acfm in thou-
o« q R1 sands.
•y 01-° Numbers in paren-
(6)












(6)












thesis are number
of precipitators.








62.0


(6)

                    3456
                      Precipitator Design Velocity,  fps
8
Figure 19.27.  Distribution of Phosphoric Acid Mist Precipitator Design
               Velocity, 1927-1969.
-------
                           -718-
   6-
    5-
09
to

•M.
o

0)
   4_
    2-
                    58.8
                   (13)
Note:  (a) Numbers above bars
          are total acfm in
          thousands.

       (b) Numbers in paren-
          thesis are number of
          precipitators
                                         46.9
                               26
                               (2)
                                          (4)
    100        150        200        250        300        350
             Precipitator Design Inlet Temperature,  °F

  Figure 19. 28.  Distribution of Phosphoric Acid Mist Precipitator
                 Design Temperature, 1927-1969.
                                            SOUTHERN RESEARCH INSTITUTE
-------
                                    -719-
  2  -
3
i— *
rt
*>
in
d
1—4
"8
6
Hi
           r
10        15         20         25         30
       Prectpltator Actual Load, gr/scfd
                                                                        35
     Figure 19. 29.  Distribution of Phosphoric Acid Mist Precipitator Actual
                    Inlet Loading, 1927-1969.
-------
                               -720-
                            Table 19.16

                     Range of Performance Data
                 JPhqsphoric Acid Mist Precipitator

Parameter
Parameter
Range
No. of
Install.
Mean Value
of Parameter
Gas
Velocity, fps          2.1 to 7.2         4               5.1

Inlet
Temperature, °F      140 to 285         5            203

Inlet Loading,
gr/scfd                 4 to 33          5             20.3
-------
                               -721-
                             Table 19.17

               Phosphoric Acid Mist Precipitator Cost

                             $/acfm
Design
Efficiency
Range
Gas Volume Range - Thousands acfm
0-9.9
FOB Installed
10-19.9
FOB Installed
20-40
FOB Installed
                             (a) 1927-1939
Less than 95      -

95-98.9           -    12.4(1)

More than 99 +
4.90(2)
                             (b) 1940-1950
Less than 94.9    -

95-99             -    12.2 (1)

More than 99      - '   19.4 (2)
         8(1)
Note: Numbers in parentheses are number of installations in which
      costs were averaged.
-------
                                  -722-
19.7  PRECIPITATORS FOR THE CARBON BLACK INDUSTRY

      Carbon black is the ultra-fine carbonaceous product of the incomplete
combustion of hydrocarbon oils and gases.  The bulk of the product is used
for reinforcement of rubber; speciality grades are produced for ink and
paint applications.

      Three major processes have been used for the production of carbon
black:  the furnace process,  the channel process, and the thermal process.
The greatest percentage is made by the furnace process,  which is illustrated
in Figure 19.30. Incomplete combustion is effected in a refractory lined
furnace.  A variety  of oil and gas furnace designs is available.   The particle
size produced in the furnace process (0. 02 - 0. 2ju) is intermediate between
that of the channel and the thermal process.

      The channel process uses an array of small natural  gas flames oper-
ated with insufficient air.  The black formed is deposited by impingement
on the underside of moving steel channels, and is subsequently removed
by stationary scraper blades.

      In the thermal process, natural gas is pyrolyzed into hydrogen and
carbon over heated checkerwork.   The process is cyclic,  with alternate
heating and cracking operations.  Initially,  the combustion of natural gaa
or other fuels with air heats the furnace to about 3000°F.  Following the
heating cycle, natural gas alone is fed to the hot furnace where it is decom-
posed,  producing carbon black.  This process produces a rather large
particle size product.

      Most of the following discussion is limited to recovery from the fur-
nace process.

      The gas from the furnace (2200-2600° F) is cooled by radiation ftnd
water sprays to 450-500°F, after which fine carbon  black particles ai*f»
agglomerated in an electrostatic precipitator.  The  agglomerated pat*
tides,  0.4 to lOju in size, are then collected in a mechanical cyclone*
The product is then pelletized and packaged. About 18% of the black m&y
be collected in the precipitator and 72% more in the cyclones.   Bag filters
are sometimes used following the cyclones, achieving over 99%  recovery.
                                                 SOUTHERN RESEARCH INSTITUTE
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                     Secondary
                     Cyclones
                                                                                              to
                                                                                              CO
                                                                                      Storage
                                                                                       Bin
                            Pelletizer
Elevator
Figure 19.30.  Flow Diagram of Oil Furnace Process for Carbon Black Showing Precipitator
               Use.
-------
                                  -724-
      Particulate loading varies with the process and fuel.  Values are
between 10 to 50 gr/scf;  lower values occur with natural gas feed, higher
with oil cracking processes.  Average particle size in the precipitator
inlet gas ranges from 0. 02 to 0. 4|u.

   Gas  composition.   Typical composition of the precipitator inlet gas is
as follows:

                                      Volume % (Wet Basis)

            Carbon Dioxide                      3. 0
            Oxygen                              0.3
            Carbon Monoxide                    6. 0
            Hydrogen                           8.0
            Acetylene                           0. 5
            Methane,  Ethane,  etc.               0.2
            Nitrogen                           41
            Water                              40

   Description of electrostatic precipitator and subsystem.  The precipi-
tator most commonly used in the  dry carbon black process is a single-
stage horizontal flow duct type precipitator.  The shell is heat-insulated
and provided with a preheat system,  purge vents, and explosion hatches.
Both inlet and outlet flues are provided with isolation dampers so that
the precipitator-cyclone system can be completely  shut off from the rest
of the plant during heatup  and purging.

   Electrode system.  In general, the high voltage  discharge electrode
and support systems used are those described in ChapterlQ  Part I.
Because of the relatively high corrosion  rate, a form of rod curtain
collecting electrode may be used.

      Collected carbon black sticks to both the discharge as well as the
collecting electrodes very tenaciously, thus requiring strong cleaning
methods.  Both discharge electrodes and collecting electrodes are usu-
ally cleaned by the use of  air vibrators.

      As the precipitator is used  chiefly  as a particle agglomerator
the major fraction of the collection subsequently effected in a cyclone,
or baghouse, no specially designed gas flow control devices  are used.
                                                  SOUTHERN RESEARCH INSTITUTE
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                                  -725-
   Precipitate removal systems.  Precipitate removal from the bottom of
a carbon black collector is by either a combination scraper-screw conveyor
from a flat bottom pan, or by a screw conveyor in a trough-type hopper.
In both cases, the black is conveyed directly to a pelletizer.

   Carbon black precipitatorapplications.  Very little information is avail-
able on carbon black precipitators.  It is estimated that nearly one hundred
sets of combined precipitator-cyclone units have been built since 1926.
Some limited and incomplete data for the period 1942 to 1956 are presented
in Table 19.18.  No domestic carbon black installations have been noted
since 1958.  It should be noted that design efficiency values are based on
overall precipitator-cyclone performance.  No breakdown of individual
performance value is available for the precipitator or cyclone.

      Design efficiency values were not reported for all installations.   More-
over, in some cases, more than one efficiency value is specified; this refers
to the performance for different grades of black which were  Collected in the
same installation.
                                 Table 19. 18

               Carbon Black Precipitator Installations 1942-1956
Year
1942
1943
1944
1945
1947
1948
1952
1956
No. of
Install.
2
5
1
1
1
1
2
1
No. of
Pptrs.
6
1.0
1
4
1
1
4
1
Capacity acfm
240,000
123,950
40, 000
80, 000
40, 000
75,000
120, 000
40, 000
Design Efficiency %
90
-92
90
90
96
96
93/97
90
-------
                                    -726-
      Cost Figures are quite limited and pertain to the period 1942-1952.
Values reported are shown in Table 19. 19.
                              Table 19.19

                       Carbon Black Precipitator
                         Cost Data (1942-1952)
Year
1942-1945
1952
Installation
Capacity
80,000-160,000
80, 000
Design
Efficiency
90
93/97
Cost $ acfm
FOB Install.
--- 1.50
3.7 4.45
No. of Cases
(2)
(1)
Differences in cost result from difference in design efficiency as  well, a®
auxiliaries included in some jobs.

      The range of statistics reported is summarized in Table 19.20.
-------
                                   -727-
                                Table 19.20

                     Range of Performance Statistics
                  Carbon Black Precipitators (1942-1956)

     Parameter   	Range  	Mean Value   No.  of Data
Actual Gas Velocity
Inlet Gas Temperature
Inlet Particulate Load
Field Strength
Input Power
3.2
410
6 -


- 8.0FPS
- 500° F
50 gr/scf


5.6
459
22.3
NO DATA
NO DATA ,
6
8
9


   General observations, design methodology, and discussion of trends.
The precipitator has served for years as a means of agglomerating carbon
black particles, some as small as 0. 02|u.  The high conductivity of the
black particles prevents good collection.  Cyclones follow and remove the
bulk of the black,  although additional control devices are now being required
for air pollution control. Considering the limited hopper catch which can
be directly attributed to the precipitator, other agglomerating techniques
appear to be gaining favor.  In general,  a variety of collection control de-
vices is being used in series.  Baghouses play an important role in many
current collection schemes.
-------
                                  -728-
                              CHAPTER 19
                             BIBLIOGRAPHY
1.     "Production of Elemental Phosphorus by the Electric Furnace
      Method, " TVA Chemical Engineering Report No. 3 (1952).

2-     Private communication from TVA.

3.     Heinrlchj R. F. and Anderson J. R., " Electro-Prec ipitators ift
      the Chem. Industry —Their Applications, Cost,  and Operation, "
      Brit. Chem.  Eng. 2  p 75 (Feb.  1957).

4.     Shreve,  R. N.,  Chemical Process Industries.  3rd Ed., McGraw-Hill,
      New York (1&67).
                                               SOUTHERN RESEARCH IN
-------
                                   -729-
                               CHAPTER 20
        THE APPLICATION OF ELECTROSTATIC PRECIPITATORS
             IN CLEANING MUNICIPAL INCINERATOR DUSTS
      While a great many small and intermediate scale incinerators have
 been designed and utilized for combustion applications such as household
 trash and industrial waste products, the major application for electrostatic
 precipitators is on large municipal incinerators.

      These incinerators,  which are most often centrally located in an
 urban area, have become an increasingly important means of reducing
 combustible refuse  to an inert residue.  Due primarily to widely varying
 waste composition and burning characteristics, these large incinerators
 are a potential source of particulate emissions.

      In Europe, electrostatic precipitation is widely utilized for particu-
 late control on municipal incinerators, and a few installations  are being
 built in the United States.

      Because of the limited number of installations,  statistical, data for
 this application are  sparse; however,  the more significant factors  and
 trends in the use of precipitators for this service are being discussed
 in this report.
20.1  TYPES OF INCINERATORS

      While some municipal incinerators in the United States are designed
to utilize the heat generated for such purposes as space boating,  water
heating,  preheating combustion air, or providing steam for plant equip-
ment,  most are designed solely to reduce refuse to an inert residue.  In
Europe,  heat utilization from incineration is practiced extensively for
electric  power generation and steam heating.

      There are two principal furnace designs in general use for munici-
pal incinerators--batch and continuous feed.  A  1966 survey of U. S. in-
cinerators shows that batch feed furnaces are generally limited to a max-
imum capacity of about 250 tons per day.  Larger furnaces are the con-
tinuous feed type,  and the trend in recent years has been to this type.
                                                  SOUTHERN RESEARCH INSTITUTE
-------
                                   -730-
Incinerator furnace walls may be either water cooled or refractory lined.
Water- cooled walls achieve longer furnace life,  and are capable of with-
standing higher temperatures.

      Many municipalities operate their incinerators only five days a week
or on the days of refuse collection.  This presents loading,  startup,  and
shutdown problems.  Where the heat content of the refuse is low, or where
the moisture content  is high,  incinerators may require an auxiliary fuel.
In some cases,  auxiliary fuel is  used only on startup.
20. 2  INCINERATOR CAPACITIES

      Refuse incinerators are made in a wide variety of sizes to service
apartment buildings,  office buildings, and commercial establishments,
however, the principal use of electrostatic precipitators has been on large
municipal incinerators.   The following discussion will  be limited to these
applications.

      A  comprehehsive survey made in the United States in 1966 shows  a
trend tow;ard increasing.furnace and plant capacities.  These data are
shown in Table 20.1.   The largest  multifurnace plants reported, in this
survey process 1200 tons of refuse  per 24-hour day, and the largest
European plant reported a total capacity of 2400 tons of refuse per day.
                                Table 20.1

      Range of Plant and Furnace Capacities for Municipal Incinerators
           Installed and,;Rebuilt from 1945-1965 - U. S. and Canada

                Reported No.     Plant Capacity    Furnace Capacity
     Interval      in Interval        tons/day            tons/day	
                                  Low   High       Low       High

     1945-49        16            50      BOO        50         175
     1950-54        44            80     1000        50         250
     1955-59        52            50     1200        5.0         300
     1960-65        60           100     1200        50         350
lRefer to the bibliography for this chapter.
-------
                                  -731-
20.3  REFUSE PROPERTIES

      Refuse consumed in municipal incinerators includes varying amounts
of rubbish,  trash, garbage,  and other wastes.  The composition varies,
depending upon the season,  weather,  location, standard of living, etc.
Furnace ash can make up more than 60% by weight of refuse in winter
where coal  is the predominant residential fuel.  In the United Kingdom,
Belgium, and Czechoslovakia, ash forms a large percentage of refuse,
comprising 30-65% of the total.  Paper constitutes a large portion of the
refuse in the United States, Canada,  and the Scandinavian countries,  rang-
ing from around 40 to 70% of the total, but is as low as 3% in Poland. The
metal and plastic content of refuse is greater in the United States than else-
where.   High moisture  content garbage forms a greater percentage of
Japanese refuse than it does in North America or Europe. '3

      Bulky refuse is composed of such  things as logs,  tree stumps,
truck tires, furniture,  and mattresses.   This type refuse is  usually
collected separately and burned in special incinerators   Certain indus-
trial wastes such as oil sludges,  tars, polymers,  and rubber chunks
are sometimes given special treatment.4

      The composition of the refuse from a group of selected  countries
is given in Table 20. 2.   These countries were selected because most
published literature on  incinerators concerns these countries.2.3
                                Table 20. 2

       Refuse Composition of Selected Countries (weight percentage)

                                  Organic
                  Ash    Paper   Matter    Metals    Glass   Misc.

Canada               5       70      10       5        5       5
France             24       30      24       4        4      14
Japan (Tokyo)       19       25      41       3        3       9
Sweden               0       55      12       6       15      12
United Kingdom  30-40    25-30   10-15      5-8      5-8    5-10
United States        10       42      23       8        6      11
West Germany      30       19      21       5       10      15
                                                SOUTHERN RESEARCH INSTITUTE
-------
                                   -732-
      Refuse composition affects incineration and air pollution control in
several ways.  Residential furnace ash has little,  if any,  heating value.
Therefore, where ash content is high, the heating  content of the refuse is
low.  Likewise, where refuse contains a large percentage of paper,  the
heating value is high.  In some  situations where the heating value is low,
supplemental fuel,  such as natural gas,  oil,  or coke, is used  in incinerators.
Generally, the heating value of  refuse is higher  in the United States than in
Europe and Japan as shown in Table 20. 3.

      The moisture content of refuse varies widely,  with the main varia-
ble being the garbage content.  Moisture in the refuse reduces the flame
temperature, which decreases the burning rate,  and in  some cases the
refuse must be dried before  entering the combustion chamber  of the in-
cinerator.

      Refuse in the United States contains more metals  and plastic than
that of Europe  or Japan.  Low melting point metals can  cause  trouble
by welding to,  and interfering with,  the  operation of moving parts of in-
cinerator grates.  When chloride-containing plastics are incinerated,
corrosive hydrogen chloride fumes are formed,  and incinerator com-
ponents must be made to contend with this corrosion problem. ' 5

      The density of refuse,  which varies with its  composition and
moisture content,  is estimated  to be from 300 to 400 Ib  per cubic yard
in the United States.1
20.4  EMISSION PROPERTIES

      The amount and particle size range of particulate emissions leav-
ing an incinerator combustion chamber vary in different situations.
Such factors as refuse composition, method of feeding,  completeness
of combustion, and operating procedures are responsible for these var-
iations. 6

      The combustion of paper illustrates the effect of composition on
partieulate matter properties.  Paper ash is generally of a relatively
large size,  has a low specific gravity,  and has low electrical resistivity.
These properties must be considered when selecting air pollution con-
trol equipment where the paper content of the refuse is high5.
-------
                                  -733-



                               Table 20.3

                        Incinerator Heating Value


                                   Maximum     Minimum      Median

United States (41 plants reporting   8000 Btu/lb   3375 Btu/lb    5043 Btu/lb
     from 1950 to 1966)


Paris                             4500 Btu/lb   1600 Btu/lb

Tokyo                             2345 Btu/lb    902 Btu/lb
                                                 SOUTHERN RESEARCH INSTITUTE
-------
                                   -734-
      Reciprocating grate and rotary kiln type incinerators have a larger
amount of particulate matter at the furnace exit than the other common
types of plants.

      The rate of furnace emission has been found to vary from 10 to 60
Ib of dust per ton of refuse burned. Modern incinerators operate with an
emission rate of about 35 Ib per ton of refuse.  Based  on using 50% excess
air for combustion,  the 35 Ib per ton can be expressed as 1. 58 grains per
cubic foot.

      The particle size range of the particulate matter also varies con-
siderably.   Usually, the same factors which decrease  the amount of par*
ticulates will decrease the size of the individual particles.  Figure 20.1
gives particle size distribution of fly ash measured at  the point where it
leaves the  combustion chamber of an incinerator.7

      The density of the dust which leaves the incinerator combustion
chamber varies from about 125 Ib per cubic foot to about 187 Ib per
cubic foot.7

      The electrical resistivity of the particulate matter at the outlet of
the combustion chamber varies with temperature and particle size dis-
tribution in addition to refuse composition, completeness of combustion,
and moisture content.  Figure 20.2 shows the resistivities of various
samples taken from municipal incinerators in the United States and
Great  Britain.

      Resistivity characteristics for the U. S. Samples are for the lefcfi
than 74-micron diameter size fraction taken from the  combustion cham-
ber.  Resistivity values for the total sample were not  obtained due to the
high conductivity and carbon content of the coarser particles, according
to the authors.8

      Resistivities for the samples from Great Britain are shown for
moisture conditions corresponding to the outlet of an incinerator (45*G
water dew point),  and after evaporative spray cooling  (75°C water dew
point).

      The temperature of the exhaust gases from incinerator combustion
chambers is dependent upon several variables.   These include type of
-------
w
o

H


m
o
-I



n
     (U
     -M
     V

     s
     ClI

     s
M

0)

-3


t
100
too
RO

60

dn
itU
20
10



fi




1

00
• O
Oc

OA
• t
On
•*
0 1




:





















































































































































































<4
A/
A X
y























A
r
























/
/\
\
/























/
^
\
/




















•»•
/
/>
r
y
\.
/





















•«
/


^
>























X
y
\ V
V/r
X






















y
X
y























/
/\
^
N^
^





















A
^ *
\
, \
r\/
/
-Ba









L













\ /
x
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tige o






















/




f Valu



























es






















































































































































































































                                                                                                                    CO

                                                                                                                    en
                                                                                                                     i
      .01 .05 .1 .2  0.5  1   2     5    10    20  30  40  50 60  70   80    90   95    98 99 99.599.899.9  99.99



                                    Percent by Weight less than Particle Size Indicated



         Figure 20..1.  Particle Size  Distribution of Incinerator Emissions Prior to Conditioning.
-------
                                    -736-
                     10"
                    6
                    u
                    I
                    s
                    •gio10

                    I?
                    :H
                    •*j
                    to
                    •sic)9
                    u
                    K
                              Tl    I
i    i     r
                          0   100  200 300  400  500 600 700


                                Temperature, °F

1-2-3:  Resistivity of the less than 14^. fraction from three installations (Ref. 8).


    A:  Water dewpoint 45° indirect heat extraction (Ref. 9).
    B:  Water dewpoint 75°C  evaporative spray cooling (Ref.  9).
    Figure 20. 2,  Electrical Resistivity of Municipal Incinerator Dust.
-------
                                   -737-
furnace construction,  heating value and moisture content of the refuse,
completeness of combustion,  amount of excess air,  use of auxiliary
fuel,  and ambient temperature.  Temperatures of at least 1500°F are
required for the burnout of smoke and the oxidation of mos' odorous
compounds.  Exhaust  gas temperatures as high as 2500°F are  reported
for furnaces with  water-cooled walls, but they must be held at lower
levels for refractory furnaces.

      Composition of the gases from incinerators varies according to
the products being burned.  Average and maximum values for various
gases from a number  of incinerators in the United States8 and the United
Kingdom9 are listed in Tables  20.4 and  20. 5,  respectively.
 20. 5 INCINERATOR EMISSION CONTROL

      One of the earliest used, and least efficient methods of dust emis-
 sion control on  municipal incinerators is the dry settling chamber.  Com-
 bustion gases enter the chamber where the velocity is greatly reduced.
 This allows combustion of some  of the suspended particles to be com-
 pleted,  and some of the larger particles are deposited.  Up to 20% of the
 ash dust can be  removed this way.7

      In some installations,  a water  spray is used in combination with a
 settling chamber.   This combination can remove up  to 30% of the fly ash.
 The water spray is useful in reducing the temperature of the gases for
 downstream equipment such as emission control equipment or induced
 draft blowers.7

      Mechanical collectors in which centrifugal force separates dust
 from the gas are frequently utilized.   Collection efficiency depends on
 particle size, and ranges from 75  to 80% for particles larger than 20
 microns.  Efficiencies drop off rapidly for particles less than about 10
 microns in size.

     Wet scrubbers which  remove dust particles by impaction on
water drops can be effective in ash removal from incinerator gases.
 The efficiency of these scrubbers is  dependent upon the relative velo-
city and drop size of the water.   Scrubbers are highly efficient in par-
ticulate removal.  The resultant  humidity of the stack gas is high, so
                                                  SOUTHERN RESEARCH INSTITUTE
-------
                                                       Table 20.4
                                Incinerator Emission Properties—-United States
                                                 Installation No. 1
Installation No. 2
Installation No. 3
  Temperature, °F

  Water Vapor, % by vol

  COa,  % by vol

  Oa, % by vol

  Volume (thous), acfm**

  Volume (thous), sdcfm*

  Refuse Charged, tons/hour

  Underfire Air, scfm/sq ft of grate

  Participate Emission,  gr/sdcf*

  Particulate Emission,  Ib/hour

  Particulate Emission,  Ib/ton refuse charged
Maximum
1673
24. 2
7.3
15.5
170.0
45.2
15.8
68.7
0.745
231
18.9
Average
1469
7.8
6.0
13.7
143.0
33.8
12.9
41.8
0.553
156
12.4
Maximum
1360
4.9
6.7
14 9
158
45.2
11.0
130
0.820
308
36.6
Average
1211
4.4
5.0
13.8
142
40
9.8
105
0.694
241
25.1
Maximum
1714
18.7
7.8
14.8
72.0
14.7
5.3
21.9
0. 540
56.3
11.0
Average
1593
8.7
7.0
13.3
64.9 J,
CO
14.1 «?
5.1
17.5
0.380
46.1
9.1
  * Standard dry gas at 29.92 in. Hg and 32°F
* * cfm at actual conditions of temperature and humidity.
-------
                             -739-
                        Table 20. 5
         Analysis of Gases from Incinerator Grates
Oxides of nitrogen
Hydrogen sulfide
Carbon dioxide
Carbon monoxide
Oxygen
Hydrogen
Methane
Sulfur dioxide
Chlorine
Hydrocyanic acid
Alcohol vapors
Phosgene
A r sine
Mercury
Ammonia
NO &NOa
H,S
CO,
CO
o,
H,
CH4
SO,
Clt
HCN
CHgOH, C,HBOH
COC1,
AsH,
Hg
NH.
Average
Heading
100 ppm
Nil
6.0-7.0%
Trace
15%
Nil
Nil
80/90 ppm
Trace
Trace
Nil
Nil
Nil
Nil
Nil
Maximum
Beading
200 ppm
Nil
11.5%
0.9%
18%
Nil
Nil
192 ppm
2. 5 ppm
3 . 0 ppm
Nil
Nil
Nil
Nil
Nil
                                             SOUTHERN RESEARCH INSTITUTE
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                                   -740-
                                                                  7
there Is almost always a visible vapor plume at the top of the stack.   High
energy requirements and corrosion are problems associated with wet  scrub-
bers in this application.
20.6  USE OF ELECTROSTATIC PRECIPITATORS ON MUNICIPAL
      INCINERATORS

      Electrostatic precipitators are used extensively throughout Europe for
control of emissions from municipal incinerators.  Several installations
have been made in the United States and Canada within recent years,  as shown
in Table 26/6.

      Because  of the high temperature of the gases from the incinerator fur-
nace,  some means of gas cooling is required.  In some  installations waste
heat boilers are incorporated either as an integral part  of the furnace or as
a separate unit.  Where heat recovery equipment is not  used, cooling towers
equipped with water sprays are utilized for control of the inlet gas tempera-
ture.

      The design of the spray cooling towers Is critical  to the successful
performance of the precipitators.   The primary requirements are that there
be complete evaporation of the water in the chamber with no moisture carry-
over to the precipitator.  Otherwise, the dust will tend to cake  or form a
slurry, which will give rise to buildup within the cooling tower  and also pre-
sent dust removal problems.

      There are a number of alternative designs for  cooling towers used
by various manufacturers.   The principal variations are the location of the
gas inlet,  location of the water  sprays, pressure of the  water to the  sprays,
and the method of controlling the quantity of water to the cooling tower.

      Factors influencing the evaporation of water in the tower are the
temperature of the inlet gas, size of the water droplets,  and the time of
contact of the water with the gases.  Temperature of the gas from an in-
cinerator furnace varies with the type and quantity of refuse being burned.
Since the  heat transfer rate is directly proportional to gas  temperature,
it follows that lower gas temperatures require longer contact times  or
greater surface area for complete  evaporation.

      The heat transfer rate is  also related to the total  surface area
exposed to the gas.  Thus,  the smaller the droplet size,  the greater the
-------
                                     -741-
                                  Table 20. 6

Electrostatic Precipitators Installed on Municipal Incinerators in North America
                Location

                Refractory Units:

                   City of Stamford,  Conn.
                   NYC South Shore
                   Brooklyn

                   NYC Southwest
                   Brooklyn

                   Dade County,
                   Florida
   Collector
 Manufacturer
Univ. Oil. Prod.
(Air Correction Div.)

Research-
Cottrell

Wheelabrator/
Lurgi

Wheelabrator/
Lurgi
                Water Wall:

                   City of Montreal,
                   Quebec  (Von Roll)

                   City of Braintree,
                   Mass.  (Detroit Stoker)

                   City of Hamilton,
                   Ontario (C &E Boiler)

                   City of Chicago,
                   Illinois

                   Eastman Kodak
                   Rochester, N.  Y.
                   (suspension burning)
Research-
Cottrell

Wheelabrator/
Lurgi

Wheelabrator/
Lurgi

Wade/
Rothemuhle

Wheelabrator/
Lurgi
                                                    SOUTHERN RESEARCH INSTITUTE
-------
                                   -742-
 surface area for a given water volume.  Water sprays used in cooling
 towers are of the hydraulic atomization type,  since gas velocities in the
 chambers are low.  In general,  the size of the water droplet from a hy-
 draulic atomizer is inversely related to  the hydraulic pressure.  How-
'ever,  the size reduction decreases rapidly after  a given pressure is
 reached.  Water pressures vary with each manufacturer and range from
 30 to 600 psi.

       The time that the water droplet is  in contact with the gas stream is
 related to the size of the cooling tower and the volume of gas handled.
 Whitehead and Darby9 made a study of the flow patterns in cooling towers
 and point out that velocity gradients within the cooling towers can reduce
 the effective contact time.   Consequently, gas flow characteristics within
 the tower must be taken into consideration in  cooling tower design.

       Control of water to the cooling tower can be achieved by grouping
 sprays in banks under  thermostatic control to bring in the number of
 sprays required to maintain the gas temperature in the desired range.
 This type of step control is used on many types of cooling towers.

       An alternative system is the use of the "spill back" principal,  in
 which water is supplied to  the spray nozzles through  concentric pipes.
 The nozzles are of the type to provide adequate atomization while varying
 the throughput, thus giving a continuously variable temperature control.
 Continuous flow through the water supply system also provides for cool-
 ing of the piping.

       The interior of the spray cooling chamber is equipped with refrac-
 tory lining,  as is the ductwork leading from the incinerator furnace. The
 linings can be made of refractory brick or of  a gunned refractory mix.

       Since  the precipitator and fan can be damaged by exposure to the
 temperature of the exit furnace gases, provision should be made to  by-
 pass the gases around  the precipitator in case of failure of the water
 supply or other components of the system.

       Figure 20. 3 is a schematic diagram of a complete system  showing
 the cooling tower,  precipitator, and emergency gas bypass system.
-------
                                 -743-
Spray Ring Mains

      Tower Inlet
                                 ...Emergency Valve

                                   Emergency Stack
           Precipitator Gas
           Distribution System
                                         Rapping and High
                                            Tension Room
                                                    High
                                                  Tension
                                                 Rectifier
                              Stack

                            ^-Sampling
                              Holes for Gas
                              Cleanliness
                              Test
Discharge
Electrodes
Collecting
Electrodes
    Figure 20.3  General Layout of Electrostatic Gas Cleaning Plants for
                 Municipal Incinerators (Reference 9)
                                                   SOUTHERN RESEARCH INSTITUTE
-------
                                   -744-
      Electrostatic precipitators used in the collection of fly ash from
waste incinerators are generally of the single-stage, duct type with hori-
zontal gas flow.  Insulation is generally required on the shell to minimize
corrosion due to condensation of the incinerator gases.  The dust removal
systems are from pyramidal or flat  draft type hoppers.  Discharge elec-
trodes are of the weighted wire types in the case of the American precipi-
tators or the supported frame electrodes in the case of the  European de-
signs.  Collection electrodes and electrification equipment  can be of sev-
eral types, depending upon the manufacturer.  These are described in
Chapter 10, Part I.   Rappers  can be of the impact type,  either electro-
magnetic, mechanical, or pneumatic.  In addition to conventional rappers,
water sprays are sometimes installed under the precipitator roof to wash
down the electrodes.

      Size and power requirements for precipitators utilized in collection
of dust from municipal incinerators  are determined from past experience
on similar service.   The collection surface area requirements are related
to the efficiency, gas volume, and precipitation rate parameter by the
Deutsch-Anderson equation.  Plots of the specific collection area and
power rate as a function of collection efficiency for a few installations are
shown in Figures 20. 4 and 20. 5.  A  range for the precipitation rate param-
eter and power density is shown in Figure 20. 6.

      Tiie value of precipitation rate parameter varies  according to the
size distribution of the particles being collected, the resistivity of the col-
lected dust, the density of the individual particles,  and the  particle com-
position.   These in turn depend on the nature of the refuse being burned.
Carbon, resulting from the combustion of paper, is particularly difficult
to precipitate since  it has low electrical resistivity and can lose its charge
on contact with the collection electrode and  be reentrained.  This factor,
coupled with variations in dust particle size and gas composition, results
in values of precipitation rate parameter over a reasonably wide range.

      Values of precipitation rate parameter for municipal  incinerator
precipitators in European installations vary from around 4-10 cm/sec.
Data on U. S. installations  are insufficient to present statistically mean-
ingful values of w.

      Table 20.7 below is a summary of available data on a single precipi-
tator installation on a municipal incinerator showing some important param-
eters.
-------
 g
w

§
#
o


I
U
       69.9
      90
                                       -745-
                                   w * 10 cm/seo^

                                                 -*r
                                                             -Q__l.
                                                                      4 cm/sec
                                                            A Design



                                                            O Test
                      0.1
0.2
0.3
0.4
0.5
0.6
                                                           A   ft*
                          Specific Collection Surface Area, —
           Figure 20.4. Relationship Between Collection Efficiency and Specific

                        Collection Area for Municipal Incinerators.
                                                       SOUTHERN RESEARCH INSTITUTE
-------
                                    -746-
 a.
 0)
•1-4
 O
Si
tM

«
 d
 o
•43
 y
 v
d
 o
U
    99 9
-------
                                -747-
S

§
K


§
    18.3
15.25
      o
      4>

12.2 £

      S
      u



 9.15
      6.10



      3.05 .
                     0.1        0.2         0.3



                        Power Density, watts/ft2
                                                   0.4
     Figure 20.6.  Relationship Between the Power Density and Precipitation

                   Rate Parameter for Electrostatic Precipitators Operating

                   on Effluents from Municipal Incinerators.
                                                SOUTHERN RESEARCH INSTITUTE
-------
                                   -748-
                                 Table 20. 7

                     Municipal Incinerator Installation

      Conditioning Tower
      Water circulation rate
      Water evaporation loss
      Water pressure
      Tower dimensions

      Precipitator

      Gas volume
      Collecting electrode area
      Gas velocity
      Cross-sectional area
      No. gas passages
      No. fields
      Length of field
      No. of plate rappers
      No. of discharge electrode
          rappers
      Power supply
      Efficiency
      Gas temperature
135 gpm
 90 gpm
6001b/in.2
 16 ft, 9 in.
dia x 42 ft, 12 in.  high
135, 000 acfm
 19. 500 ft2
      4.6 ft/sec
    486 ft"
     27
      1
     14 ft
     28

     27
1-700 mA - 1-500 mA,  45 kV
     95%
550 - 600° F
      The ranges of erected costs for 93-95% collection efficiency units,  with
capacities of 64, 000-569, 000 acfm, were 0. 44  to 0. 66 $/acfm (1968).

      No data are available for United States installations.  Table 20.8 is a
summary of performance data obtained on German incinerator installations
operating on  refuse,  refuse and coal,  or refuse and oil.

      Figure 20. 7 indicates precipitation rate parameters as a function of
gas temperature.  The variation in precipitation is probably due to the change
in resistivity of the dust more than any other single factor.  The spread in
the data can be due to the variation in resistivity due  to dust and gas compo-
sition as well as gas  velocity variations and variations  in precipitator design
and condition of repair.
-------
                                                                                                Table  20.8
                                                                             Summary  of Performance   Data
X
m
n
 Plant/Unit

 Test Number

 Firing Mode

 Rated Gas Volume, ft'/sec
   Gas Temp'F

 Actual Gas Volume, 1000 x stfm
   Gas Temp ' F

 Percent of Rating, %

 Anticipated Pptr. Inlet Dust Cone., gr/scf

 Actual (Test) Pptr. Inlet Dust Cone..  gr/scf

 Actual (Test) Pptr. Outlet Dust Cone., gr/scf

Guaranteed Collection Efficiency (Corrected
   for Actual Test Conditions per Manufacturer's
   Correction Factors), %

 Actual (Test Collection Efficiency), %

 Pptr. Design Gas Velocity at Rated Volume (v),
   fi/sec

 Pptr. Actual (Test) Gas Velocity (v).  ft/sec
 Relative pptr. Size. Design      A_
   Based on rated flow, sec/ft   V

 Relative pptr. Size, Actual      _A_
   Based on actual flow, sec/ft   V

 Design pptr.  Performance w (w design),  ft/sec

 Actual pptr. Performance w (w  actual), ft/sec

 Pptr. Electrical Energization Data
   Ai Secondary Kilovolts Inlet (kV) (Inlet/Outlet)
   B) Secondary Milliamps (mA)     (Inlet/Outlet)
   Cl Input Power (AxB) (Kilowatts) (Inlet/Outlet)
   D) Power Density-Watts per 1000 acfm  (Inlet/Outlet)
   El Power Densny-Watts per ft1   (Inlet/Outlet)
   F) Field StrengtlcKtlpvolts per inch (Znlet/Outlet)
   G) Sparking Intensity/Frequency
Plant 1
1
2
Coal Only
163.5 163.5
284- 284*
104
247-
112
1.97
2.39
0.0105
97.94
99.56
2.48
2.77
29.80
26.68
0.130
0.203
41 2/44.4
260/308
10.7/13.7
103/126
.220/.281
0.87/0.94
108
257-
115
1.97
2.44
0.0325
97.49
98.67
2.48
2.86
29 80
25.88
0.124
0.167
40 8/43 7
240/381
9 79; 16 6
90 6'1M
201 342
0.86/0 92
1
Plant 2
2
Coal and Refuae
2200 2200
320* 320*
140
310'
111
1 97/8.95
S 12
0. 0128
99.25
99 75
3 35
3 714
22 07
19 91
0.222
0 301
30/34
600/560
18 0/19.0
128.6/136
370/ 391
63/0 72
140
310'
111
1.97/6.95
8.64
0.0178

99 79
3.35
3.714
22.07
19.1
-
0 323
31/34
640/650
19.8/22 1
141 7/157 9
407 ...454
0.65/0.72

3
Refuse Only
103
315-
-
6.95
6.76
0.00774

99.89
2.73
-
27.10
-
0.251
32/33
640/650
20 5/21.4
198.8/206
421/440
0 68/0.70

1
Coal
5720
302-
345
308'
101
2 19-8.75
1 16
0.0089
97.97
99.24
3.15
3.19
25.41
25.22
.153
.193
38.2/37.2
850/940
26.5/34.9
76.9/101
183; . 241
0.80/0 77

2
Coal
5720
302*
348
313'
101
2.19-8.75
1.51
0.0166
98.00
98.90
3. IS
3.21
25.41
25.05
.154
.180
37 2/37 8
585/775
21.8/29 3
62. 5/84. 2
.ISO/. 202
0.77/0.80

3
Coal
(Low Load)
5720
302
244
284-
71.3
2.19-8.75
9 51
0.0060
99.55
99.37
3.15
2.26
25.41
35.64
213
142
.
Plant 3
4
Coal-40 TPH
Refuse
7200
338-
418
324*
96.8
2.19-8.75
3.06
0.0108
•9.55
9*.6S
3.98
3.86
20.18
20.83
268
271
32.2/32.6
750/720
24.2/23.5
57 8/56.2
167/162
0.68/0.69

5
Coal-40 TPH
Refuse
7200
338-
432
336*
100
2.19-8.7S
3.06
0.00503
99.50
99.84
3.98
3.99
20.18
20 16
.163
.319
30.5/32.2
735/870
22 4/28.0
51.9/64.8
155/.193
0.65/0.68

6
Coal-40 TPH
Refuse
7200
338-
3(4
326'
88 7
2 19-8.75
3 24
0.00896
99 72
99.72
3.98
3. S3
20.18
22.74
.291
258
32.2/32.2
600/660
19.3/21.3
50.3/55.3
133/147
0.68/0.68

7
Coal-40 TPH
Refuse
7200
338-
403
328"
93. S
2. 19-8 75
1.66
0.0133
99.54
99.20 1
3.98 CD
1
3 72
20.18
20.58
.267
235
32.2/32.8
620/684
20.0/22.4
49.S/SS.7
. 138/.155
0.68/0.69
PI
 Notes-  1) All tests, unless noted, performed at lull boiler steaming load.

        2)  Ali efficiency data calculated on oasis of dust loadings at (0* C - 760 n-m Bgi

        3)  Precjpitator sizing calculated from original metric units .
           recalculations in English units will compound rounding-off
           errors from unit-conversions.
-H

n
-------
                         Table  20. 8  (Continued)  - Summary of Performance  Data
 Plant/Unit

 Test Number

 Firing Mode

 Rated Gas Volume, fl^/sec
   Gas Temp ° ?

 Actual Gas Volume, 1000 x acfm
   Gas Temp °F

 Percent  of Rating,  %

 Anticipated Pptr. Inlet Dust Cone., gr/scf

 Actual (Test) Pptr. Inlet Dust Cone.,  gr/scf

 Actual (Test) Pptr. Outlet Dust Cone., gr/scf

Guaranteed Collection Efficiency (Corrected
   for Actual Test Conditions per Manufacturer's
   Correction Factors),  %

 Actual (Test Collection Efficiency), %

 Pptr. Design Gas Velocity at Rated Volume  (v),
   ft/sec

 Pptr. Actual (Test) Gas Velocity (v),  ft/sec

 Relative pptr. Size, Design      A_
   Based on rated flow, sec/ ft   V

 Relative pptr. Size, Actual      A.
   Based on actual flow, sec/ft   V

 Design pptr. Performance w  (w design), ft/sec

 Actual pptr. Performance w  (w actual), ft/sec

 Pptr. Electrical Energization Data
   A) Secondary Kilovolts Inlet (kV) (Inlet/Outlet)
   B) Secondary Milliatnps (mA)    (Inlet/Outlet)
   C) Input Power (AxB) (Kilowatts)  (Inlet/Outlet)
   D) Power Density-Watts per 1000 acfm (Inlet/Outlet)
   E) Power Density-Watts per ft2 (Inlet/Outlet)
   F) Field Strength-Kilovolts per inch (Inlet/Outlet)
   G) Sparking Intensity/Frequency
Plant 4
                                     Plant 5
1
Refuse
1550
500°
91
455°
a7.7
3.94
4.81
0.0158
98.85
99.67
3.82
3.74
14.00
14.32
.408
.399
31.5/29
265/267
8.3/7.7
91.7/85
.401/.372
0.74/0.68
2
Refuse
1550
500"
92
468°
98.9
3.94
5.69
0,0184
98.95
99.68
3.82
3.77
14.00
14.16
.319
.406
31/29
313/310
9.7/9.0
105/97.7
. 466/.4S2
0.73/0.68

Refuse and
Oil
2870
410°
156
375°
95.2
1.81
1.67
0. 0169
98.5
98.22
3.68
3.51
12.17
12.79
328
.315
-

Refuse and
Oil
2870
410°
127
375°
77.4
1.81
1.83
0.0207
99.5
98.87
3.68
2.85
12.17
15.73
.435
.285
-

Refuse and
Oil
2870
410"
161
362°
98
1.81
1.47
0. 0210
97.9
98.57
3.68
3.61
12.17
12. 42
.317
.342
26.5/21.8
484/588
12.8/12.8
79.7/79.6
.S66/.366
0.61/0.50

Refuse and
Oil
2870
410°
111
360°
67.6
1.81
1.10
0.00283
99.5
99.74
3.68
2.49
12.17
18.02
.435
.330
26.8/22.4
503/575
13.5/12.9
121/116
.385/.S68
0.61/0.51









,
-a
tn
O
i





Notes:  1) All tests, unless noted, performed at full boiler steaming load.

        2) All efficiency data calculated on basis of dust loadings a' (0°C - 760 mm Hg)

        3)  Precipitator sizing calculated from original metric units .  . .
           recalculations in English units will compound rounding-off
          errors from unit- conversions.
-------
                             -751-
 o
 V
 CO


"a
 u
   14
   12
 , 10
§   8

&
(X

oj   A
ai   O

K


8
                                         O European


                                         O U. S.
                200
                           300
400
500
600
                    Gas Temperature, °F



    Figure 20. 7.  Variation in Precipitation Rate Parameter With Gas

                 Temperature for Municipal Incinerator Precipitators.
                                             SOUTHERN RESEARCH INSTITUTE
-------
                                   -752-
20.7  ECONOMICS

         Cost data on U. S. installations are limited because of the limited
number of installations.  The two installations for which costs are available
range from  $1.68/acfm to $2.90/acfm.  These are "turnkey11 costs (1968)
for 95% efficiency.  Costs include pilings, foundations,  supports,  flues,
heat insulation,  piping, and wiring as well as the precipitator and power
supply.  The costs do not include buildings.

         Operating cost data for the two installations are not available since
they have not been in operation for sufficient time to accumulate  data.  How-
ever, operating costs can be estimated based on power requirements and
capital costs assuming maintenance costs consistent with other precipitator
applications.  Table 20.9 shows estimated operating costs for two  size pre-
cipitators.  For this estimate, capital charges are based on 12^%  of the
installed costs.   Maintenance costs  are computed  on the basis of 1% of the
installed costs per year.
                                Table 20. 9

       Estimated Operating Costs for Electrostatic Precipitators for
                 	Municipal Incinerator Dust Collection	•
         Gas Flow (acfm)                    250, 000    130, 000
         Installed Cost ($ 1968)              420, 000    390, 000
         Capital Charges (12.5%)              52, 500     48,800
         Maintenance Costs (1% of cap)         4, 200      3, 900
         Precipitator Energy1 Costs              605        336
         Fan Energy Costs2                    1,760        923
            Total Yearly Operating Costs
            1 shift (2000 hr) basis            59,105     53,959

Computed on basis of precipitator input power (see Figure 20. 5) 2000 hrs
 opr/year (1 shift) and 1. 5 cents/kwh energy costs and 60% power supply
 efficiency.

2Computed on basis of 1" water pressure drop,  50% efficiency for the fan
 and motor combination.
              v x p x 74R   -irt-s
              6356        X 10
-------
                                    - 761 -
      In the temperature ranges in which catalyst dust precipitators operate,
the electrical resistivity can be relatively high.  White1 reports that the
resistivity of a typical aluminum silicate catalyst dust is around 5 x 10U
ohm-cm with no conditioning.   The addition of about 20 ppm of ammonia
to the gas stream reduces the  resistivity to about 1010 ohm-cm.  In the
example reported by White,  the precipitator efficiency increased from
about 99% without conditioning to 99.8% with conditioning.

      The precipitator for the  collection of catalyst in the petroleum
cracking  process  is generally  a single-stage, horizontal-flow, duct type.
An earlier vertical-flow design has been largely superceded by the present
horizontal-flow type.  The shell is constructed of steel,  which is sometimes
insulated  on the inside with gunite or with mineral wool  insulation  on the
outside.  The fines collected are of little value and are normally discarded.
21.3  DETARRING

      This discussion of detarring of gases from the petroleum industry
encompasses the related areas of gasification of solid fuels as well as
petroleum,  since the same type of electrostatic precipitator is common
to all of these operations.   Minor modifications such as those found in
precipitators for acetylene production are  covered within the appropriate
section.

      The electrostatic precipitator  most commonly utilized for detarring
and cleaning of gaseous products is a single-stage vertical wire and pipe
unit, as illustrated in Figure 21.4.

      The shell is typically cylindrical,  with the electrodes suspended from
a top header. The high voltage support insulators for the header are  mounted
in external turrets which are heated to prevent moisture condensation.  In
some instances, these compartments are kept under continuous inert  gas
purge.
1 Refer to the bibliography for this chapter.
                                                   SOUTHERN RESEARCH INSTITUTE
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                           -762-
                            High Voltage
                            .Insulator
                                           Compartment
       Support
       Insulator
   Steam Coil

 High Tension   jf  \
 Support Frame"
Collecting
Electrode Pipes

      Shell
 High Tension
   Electrode

   Electrode
    Weight —•
Gas Deflector
 Cone
                               Collected

                               Out
 Figure 21.4.  A Single-Stage Vertical Wire and Pipe Unit.
-------
                                    -763
      In most cases the collected oils and tars are free flowing, and no
 mechanical .rapping devices are required to remove the material from
 the collecting electrode pipes.  Removal of the accumulated drainage
 from a collection sump is accomplished through a liquid trap.

      In some instances,  the  cleaning of acetylene for example, water
 flushing accomplishes the removal of the adherent material.   This proce-
 dure is described in the section on acetylene production.

   Shale oil.  The process for separating oil from shale is shown  in the
 typical flow diagram, Figure 21. 5.  The shale to be processed is fed into
 a retort where heat is applied to drive off the gas, oil,  and carbonaceous
 residue.  From the retort, the gas is passed through indirect water coolers
 to reduce the temperature.  Most of  the condensable material condenses
 as a  submicron  size mist in the  cooler.  The mist-laden gas is then passed
 through the precipitator,  where the condensed oil and carbonaceous  residue
 are separated, to the next stage  for further processing.  The oil and car-
 bonaceous material collected in the precipitator sump are  removed by a
 pump which transfers it to various locations for further separation and
 processing.

   Acetylene.  Natural gas is used as the primary raw material in the pro-
 duction of acetylene.  The gas is burned in an oxygen-limited atmosphere
 under controlled temperature and pressure.  The gaseous  products consist
 of from 50 to 55% hydrogen, from 30 to 35% carbon monoxide,  and from 7
 to 9% acetylene.   Because of  the explosion  hazards involved,  the oxygen
 content is rigidly controlled to a fraction of 1%.  In addition to the gases,
 submicron size particulate carbon is also produced and carried along by
 the gas as a smoke.  Prior to entering the  precipitator,  the gas is passed
 through a direct-contact water cooler where the temperature is reduced to
 about 100°F.  Some carbon is removed in the cooler.  The gas then enters
 a series of electrostatic precipitators where practically all of the remain-
 ing carbon is removed from the gas.  The precipitator is operated at a
 normal positive pressure  of from 1 to 2 Ib  per square inch to prevent air
 in-leakage.   The high voltage insulator compartments  are kept under con-
 tinuous purge with inert nitrogen gas.  After leaving the precipitator,  the
 cleaned gas is further processed to separate the various products. A sim-
 ple process flow  diagram  of acetylene manufacture is shown in Figure 21.6.

      Since the carbonaceous  material collected is not free flowing,  the
inside surface of the collecting pipes is continuously flushed by a film of
                                                   SOUTHERN RESEARCH INSTITUTE
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     Oil Shale
 Fuel Air
Flue Gas
              Recuperative
              Stoves
N Retort
                                                 Electrostatic
                                                 Precipitator
                                                                Gas Blower
                                                                                               01
                                                                   Shale Oil
                                                                   Product Gas
                    Figure 21. 5.  Oil Shale Retorting Process.
-------
                                                              Solvent
                Fuel
   Hydrocarbon

        Feed
                 Steam
c

X
m
31
m
99
O




3
V



Fuel
j "




r
Ci



•
\
;



t—


—
t




^
•••••

-
_
T
MBM«

—
— i

                  Aromatics


                  To Stack
                            T
                                     c. w.
                          TvX/
  Wulff Furnace

(Cracking Stroke)
                 T
                 Quench
                 Tower
     Y
                                                       Off-Gas
                                                                                     Ethylene

                                                                                     Product
                 Acetylene Product
                                   Recycle to    I

                                       ornpres-
     e cycle

      JConTp
                                                                 sors

                                                                Solvent,*
                                                                        y
Stabilizer    Acetylene

             Stripper
   Figure 21.6.  Acetylene (Wulff Process).
O5
CJ1
I
m
-------
                                  -766-
water from overflow weirs attached to the top of the pipe.  A pond water
supply system  is provided as an integral part of the top support header.
The precipitator is further provided with sprays located under the roof
for additional pond and pipe cleaning.  The bottom of the shell is designed
as a sump to collect the  water/carbon mix.  Following removal, the mix-
ture is pumped to a treatment plant where the water is separated,  and the
carbon pelletized.

   Manufactured fuel gas. In the process  for manufacturing carburetted
water or producer gas, the  initial gas known as "blue  gas" is made by pass-
ing steam through a bed  of incandescent carbon in the form of coke or
anthracite coal.  There are two cycles,  designated in  plant parlance as
"make" and "blow. "  By means of automated regulating equipment,  super-
vised by the gas maker and  his assistant,  the coal or coke is fed to the
gas generator and air is admitted under the bed during the "blow" cycle.
The air is then shut off and  steam is admitted for the "make" cycle.  The
residue ash is then withdrawn.  Carburetted blue  gas is a mixture of blue
gas (or water gas as it is often termed—made as above) and oil gas  formed
by the cracking of oil in  a chamber through which the blue gas passes.

      The carburetting process enriches the blue  gas to as much as 700 Btu
per cubic foot of gas,  depending on the amount of oil used.  With the pre-
sent day use of natural gas,  it is customary practice to mix natural gas with
the above gases, the mixture being automatically controlled by means  of
calorimetric equipment.  Prior to entering the precipitator, the gas is passed
through a direct-contact water cooler where the temperature is reduced to
around 100°F and saturated  with water vapor.  In the cooler,  some  of the
tars and oils contained in the gas are removed by the water sprays, and
sulfur compounds and other gaseous material are removed from the system
in purifiers located after the electrostatic precipitator. A process flow
diagram of production of carburetted water gas is shown in Figure 21. 7-

      Inasmuch as the tars and oils collected in the precipitator are free
flowing,  no devices are required to aid in  removing the collected material
from the collecting pipes.  The free flowing material drains from the col-
lecting electrode into a sump below and to an external tar pot through a
liquid trap. From the tar pot, the liquid is pumped to its final point of
reuse or disposal.
-------
                                  -753-
where
      v = gas volume acfm,
      p = pressure in. water,
      eff * fan and motor efficiency, and
      fan energy = kW.
                                                   SOUTHERN RESEARCH INSTITUTE
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                                 -754-
                            CHAPTER 20
                           BIBLIOGRAPHY
1.  Stephenson, J.  W. and Cafiero, A.  S., "Municipal Incinerator Design
    Practices and Trends," Proceedings of 1966 National Incinerator
    Conference, p 1 (May 1966).                     ~

2.  Matsumoto, K. , Asukota, R. and Kawashima, T., "The Practice of
    Refuse Incineration in Japan Burning of Refuse with High Moisture
    Content and Low Calorific Value," Proceedings of 1968 National
    Incinerator Conference, p 180 (May 1968).                    ~~

3.  Bump, R. L.,  "The Use of Electrostatic Precipitators on Municipal
    Incinerators,"  JAPCA, p 803 (Dec. 1968).

4.  Kaiser, E. R. , "The Incineration of Bulky Refuse II,"  Proceedings
    of 1968 National Incinerator Conference,  p  129 (May 1968).

5.  Feldman,  M. M. ,  "Particulate Emission Control for Municipal
    Incinerators,"  New Developments in Air Pollution Control, Metropolitan
    Engineers Council on Air Resources, p 70 (Oct.  1967).

6.  Bump, R. L. , "European Installations, "  New Developments in Air
    Pollution Control,  Metropolitan Engineers Council on Air Resources,
    n 85 (OctT 1967).

7.  Fernandes, J. H. , "incinerator Air Pollution Control," Proceedings
    of 1968 National Incinerator Conference,  p  101 (May
8.  Walker, A. B. and Schmitz, F. W. , "Characteristics of Furnace
    Emissions from Large,  Mechanically Stoked Municipal Incinerators,"
    Proceedings of 1966 National Incinerator Conference, p 64 (May 1966).

9.  Whitehead,  C. and Darby, K. , "Cleaning of Gases from the Incineration
    of Waste Materials,"  Paper No. 6, The Institute of Fuel Conference on
    the Incineration of Municipal and Industrial Waste, Brighton, England
    (Nov.  1969).
-------
                                   -755-
                              CHAPTER 21
                ELECTROSTATIC PRECIPITATORS IN THE
               	PETROLEUM INDUSTRY	

21.1  INTRODUCTION

      The principal uses of electrostatic precipitators in the petroleum
industry are for the collection of particulate emission from fluidized bed
catalytic  cracking units and  removal of tar from various gas streams, such
as fuel gases,  acetylene, and shale oil distillation gases.

      The first of these areas,  recovery of catalyst dust,  originated with
the production of high octane gasoline  in fluid catalytic cracking units
during World War II.  In order to economically operate these units,
electrostatic precipitators were used to recover catalyst from the discharge
stream of the catalyst regenerators.   While improvement of mechanical
collectors inside the regenerators has eliminated the process requirement
for electrostatic precipitators, precipitators  are presently used as control
devices for the recovery of catalyst fines produced by attrition of the
catalyst.

      The second major application of electrostatic precipitation is
encountered in the detarring of gases produced in a variety of processes.
The gasification of organic material for the production of these gases results
in the formation of small amounts of tars and oils which must be removed
prior to further use.  Similar applications exist for the related area of solid
fuel gasification.

      The precipitation of tars from fuel gases is technically straightforward
inasmuch as the precipitated tars are  free flowing, and steady operating con-
ditions can be maintained without the rapping  and reentrainment problems
associated with dry precipitators. Since the sparking inherent in precipi-
tator operation would ignite  the gas,  the gas-oxygen ratio must be main-
tained  outside combustion limits to eliminate  the fire or explosion hazard.
Fuel-air ratio sensors operate automatic control equipment to provide this
safeguard.  Precipitators for detarring applications are reasonably trouble
free,  except for occasional corrosion  problems.  Installation costs and
operating efficiencies are so favorable for this application  that other tech-
niques for detarring are not generally considered.

     A relatively new application of electrostatic precipitators is in the
removal of tar, fine carbon, and oil mist from the acetylene gas manufac-
tured from naptha or crude oil.
                                                     SOUTHERN RESEARCH INSTITUTE
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                                  -756-


      Another relatively new application in the petrochemical field is the
utilization of precipitators for the removal of tars from oil shale distil-
lation gases.  Electrostatic  precipitators have been successfully employed
in this application for cleaning the gases which are subsequently condensed
arid treated to produce petrochemical products.

      Each of these application areas will be discussed in more detail in
subsequent sections.
21. 2  CATALYTIC CRACKING

      In the fluidized bed catalytic cracking process,  the precipitator is
employed as a secondary collection system for mechanical collectors
located in the top of the fluid catalyst regenerator.  A typical flow diagram
of a fluid cracking unit is shown in Figure 21. 1.  In the production of high
octane gasoline,  oil and powdered catalyst are mixed in a reactor where
the oil is vpporized,  and the cracking reaction occurs.  Spent catalyst,
containing residual carbon  (or coke) from the catalytic cracking process
taking place in a reactor,  is mixed with combustion air and fed to the
regenerator to reactivate the catalyst.  Reactivation consists of burning off
the coke or residual  carbon formed on the catalyst during the cracking
process.  After regeneration,  the hot incinerated catalyst  is mixed with
crude oil and recycled to the reactor.

      The gaseous products of combustion are exhausted from the top of the
regenerator through  a series of mechanical collectors.  These mechanical
collectors remove all but a very small percentage of fine  catalyst and
return it directly to the process.  The catalyst escaping with the discharge
gas may be collected in an  electrostatic precipitator in order to comply
with air pollution regulations.   Gases leaving the regenerator may be
cooled with steam or water sprays to protect down-stream equipment.

      The regenerator may be followed by waste heat steam  boilers that
recover some of the  energy and further reduce the gas temperature prior
to entering the final catalyst-removal precipitator.   The following param-
eters are typical of the process:
-------
                                  -757-
                    Mechanical
                    Collector
                  Regenerator
Flue Gas
Waste Heat Boiler
         Fractionator
                        Regenerator
                        Standpipe —
          1
                          Reactor
        Feed
  Preheater
Oil __
Feed'
                     -•-Waste
                       Heat Boiler
        Figure 21.1.  Flow Diagram of Fluid Cracking Unit.
                                                   SOUTHERN RESEARCH INSTITUTE
-------
                                   -758-


             Regenerator bed temperature - 1250°F

             Regenerator outlet temperature - 1100 to 1250°F

             Regenerator gas pressure - 5 to 40 pslg

             Precipitator inlet temperature - 400° to 800°F

             Dry flue gas analysis (% by volume)

             N2 = 87% - 81%

             CO2 = 6% - 9%

             CO = 6% - 7%

             Oa- 1% - 3%

             SO2 = trace

             Hydrocarbons = trace

             Moisture content = 10% to 30% by volume

      The dust concentration entering the precipitator depends on the type
catalyst, the particular process, and the type of mechanical collectors used.
The normal dust concentration following the mechanical collector varies
between 0. 02 and 1 gram per std cu ft.

      The particle size is 90 - 99% less than 44|i in diameter.  Figure 21. 2
shows a typical particle size distribution in the precipitator inlet gas in a
catalytic cracking regeneration system.  The bulk density of the dust is on
the order of 5 to 20 pounds per cubic foot.  Oxides of alumina are the base
material in most catalysts.   The surface of the catalyst may be coated with
other material in order to obtain maximum catalyst activity.

      The typical electrical resistivity  of catalyst dust measured in the  lab-
oratory for a gas temperature range of 300° to 600°F containing about 25%
water vapor is shown in Figure 21.3.
-------
   99.9

   99.8


   99.5


   99
 §98
r-l
 o
   90
 g 80
   70


   60
M
ra
-1  40
3

8  30
h

&
m  20
I10
J3
U
    2.0  -
    1.0
                            -759-
        0. 6 0-8 1     2      4   6  8  10    20    40

                  Particle Diameter  (in microns)
60  80 100
Figure 21. 2.  An Analysis of Particle Size Distribution in a Gas

              Stream to Electrostatic Precipitator for One Type

              of Catalyst
                                             SOUTHERN RESEARCH INSTITUTE
-------
                          -760-
  IxlO1
  1x10
a
o
I

a

•g


l£
a


•5
CO
•r-l
0)


K

•*->
0)


Q
  1x10
      10
  1x10
  1x10
  1x10
        100
                   200       300        400

                          Gas Temperature,
500
600
Figure 21.3.  Electrical Resistivity of One Particular Type

              Precipitator Inlet Catalyst Dust (23% Moisture

              Content by Volume) - Measured in Laboratory.
-------
                   Hydrocarbon

                       Feed
                           To Waste Heat Boiler
         Air
         Steam
                    Generator
          Consumer
c

X
PI
X
                                                                                   Scrubber
                                                                                                    OJ
                                                                                                    -a
                         Gas

                        Holder
                           Purifier
Electrostatic

Precipitator
                                                              Tar

                                                              Sump
m

71
n
X

z


H


m
Figure 21. 7. A Process Flow Diagram of Production of Carburetted Water Gas.
-------
                                  -768-
   Solid fuel carbonization.  The carbonization processes,  in general,  con-
sist of the heating of solid fuel materials,  such as coals, lignite,  and peat,
to temperatures between 1020° and 1560°F in the  absence of air.   The fuel
is subsequently decomposed into semi-coke, tar, and gas.

      In addition to the coke and gas, substantial yields of liquid by-products
are produced, which  may be further processed to  gasoline, diesel  oil, fuel
oil and  waxes.

      A typical process for carbonization is illustrated in Figure  21.8.  The
electrostatic precipitator is utilized for the removal of tar  from the circula-
tion and carbonizer  gases leaving the carbonizing chamber.
21. 4  DEVELOPMENT OF ELECTROSTATIC PRECIPITATOR IN THE
      PETROCHEMICAL INDUSTRY2

      One of the earliest Cottrell electrical precipitators installed was for
the cleaning of illuminating gas.  It consisted of an experimental single pipe
unit operated by Professor J. Davidson of the University of British Columbia
in 1914 on coal and carburetted water gas at the Vancouver Gas Company.
About the same time,  similar experiments were carried out on producer gas
at the Minnesota Steel Company at  Duluth, Minnesota and at the Ann Arbor
Gas Company.

      In these first applications,  gas was usually treated following the wash
boxes or scrubbers at low temperature,  so that the tar was collected  in the
presence of water. Shortly thereafter, in 1916, a similar precipitator was
operated on carburetted water gas  at about 500°F at the Tacoma Gas Company.
These early experimental and semi-commercial operations soon led to regu-
lar commercial installations.  In 1924, there were 5 such installations in the
United States cleaning about 70 million cu ft/day, and only 8 years later there
were over 75 installations handling about !•£ billion cu ft/day.  These were
largely used on carburetted water gas and coke oven gas.  Virtually all of
the precipitators operated at temperatures from 75° to 125°F at atmospheric
pressures.  Typical collection efficiencies ranged from 95 to 99%.  By
January 1949, there were about 275 installations which included a total of
393 precipitators.
-------
                                 -709-
Coke •*-
Coal Feed Wash Oil
1 I
Car
boni

Pre-
coole
•
izer 	 " 	 " 	
\
^ FSp 	 ,_ Afte
•r Cool
Waahor
Separator


\ I
r ^ Final
i* T* ^^oolcr*
Liquor C
1 1
Tar Tar
    Figure 21.8.  Flow Diagram for Typical Coal Carbonization Process.
                                                    SOUTHERN RESEARCH INSTITUTE
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                                  -770-
      By 1962, there were about 600 tar precipitators treating 5 million cfm
of fuel gas.  Since 1952,  there have been fewer than 25 additional tar preci-
pitators installed;  some  of these were replacements for the older  units.
  ?
      Although the average number of yearly installations  has been declining,
there is always the possibility of applications to entirely new fields,  such as
shale oil gas, acetylene,, etc.   With the advent of World War II, catalytic
cracking processes for production of such war materials as aviation gaso-
line,  butylenes, toluene, etc.  became  important.  As a result,  many cata-
lytic cracking plants were quickly designed and constructed throughout the
United States, and many  electrical precipitators were installed in these cata-
lytic cracking plants for  recovering fine catalyst from catalyst regenerators.
After World War II, the demands  of these stragetic materials decreased con-
siderably and the  number of yearly installations of precipitators in the area
of catalytic cracking has been declining.

      Table 21.1 is a summary of the electrostatic precipitator installations
for catalyst recovery in fluid catalytic cracking for the period  1940-1962.
The number of installations, the total gas volume processed, the efficiency
(averaged  on a weighted volume basis), and the average precipitator size in
terms of gas volume handled are also shown in the table.   Figure 21. 9 shows
the trend  in the 5-year average installed precipitator capacity  in fluid cata-
lytic cracking operations.

      Tcble 21.2 is a summary of the application of electrostatic precipita-
tors for tar and oil mist  removal in the manufacture of carburetted water
gas, oil gas,  reformed gas, shale and oil gas, and acetylene.  The range
of collection efficiencies  for each application, the inlet gas temperature,
and the total gas volume are also given in the table.

      Figure 21.10 shows the  installed electrostatic precipitator capacity
for tar and oil mist removal in carburetted water  gas for 5-year intervals
between 1940-1960.

   Economics.  Precipitator cost data for both catalytic cracking application
and fuel gas application are summarized in Tables 21.3, 21.4,  and 21.5.
Figure 21. 11  indicates the FOB and erected costs for detarrlng precipitators.
These costs are for a 95% efficient  precipitator and are average costs over
the period  1959-1969. The costs  are  flange to flange and  do not include
ductwork.
-------
                                  -771-
                               Table 21.1

A Summary of Application Data on Electrostatic Precipitator Installations
                 in Catalytic Cracking Units 1940-1967

Yearly
Interval
1940-1944
1945-1949
1950-1954
1955-1962
1966-1967
* Estimated
No. of
Install.
24
13
3
2
3

Total acfm
Gas Volume
in 1000's
2,099
802
472
488
300*

Average Yearly Pptr.
Volume over the
Period in 1000's
420
160.4
94.4
61
100*

Weighted Eff.
on acfm Basis
%
99.5
99.3
96
97.2
-

                                                 SOUTHERN RESEARCH INSTITUTE
-------
   5.0
 I 4.0
 o
 cti

"b
 S 3.0
 3
 to
 rt
 O

 h
 O
 +J
 cd
 PL,
2.0
    1.0
       1930     1935
                     1940
             to
              I
                                                             1960
                                                                   1965
1970
1975
      Figure 21.9.  Installed Precipitator Gas Volume Trend in Catalytic Cracking Units Over 1940-

                    1962 (Based on Yearly Average acfm per Five Years) and 1966-1967 (Estimated).
-------
                             -773-
                         Table 21.2

A Summary of Application Data on Electrostatic Precipitator on
 Various Applications for Removing Tar and Oil Mist 1940-1963

Type of No. of
Applications Install.
Carburetted
Water Gas 55
Oil Gas 3
Reformed Gas 3
Shale Oil Gas 2
Acetylene 1
Suspended Total Gas Temperature Collecting Eff.
Matters Vol. acfm °F %
Tar and 315,800 70-110 95
Oil Mist
Tar and 18,200 80-100 95-98
Oil Mist
tar and 3,200 80-100 95-98.5
Oil Mist
Tar and 20,900 100-200 95-97.5
Oil Mist
Tar and 42,100 100 99-92
Oil Mist

                                           SOUTHERN RESEARCH INSTITUTE
-------
 o
 03
in
 O
 CO
 a
 O
 •.-I
 o
 0)
    2,5 .
    2.0
 
-------
                              -775-
                          Table 21.3




FOB Cost of Precipitators for Catalytic Cracking Units 1951-1962

Avg. Gas Volume
Year 1000' s acftn * Avg. Design Efficiency
1951
1953
1954
1958
1962
* Numbers
235 (1)
175 (2)
6(1)
149.2 (2)
254 (1)
in parenthesis
80
92
95
97.5
96.5
are number of installations
Avg. FOB Cost
% $/acfm
0.426
0.78
3.78
1.168
0.48
used in determining cosl
                                               SOUTHERN RESEARCH INSTITUTE
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                                 -776-









                            Table 21.4



     Cost * of Detarring Precipitator in Fuel Gas Area 1945-1956

Year
1945
1946
1947
1948
1949
1950
1954
1956
Gas Volume in
lOOO's acfm
34. 22
63.6
104.8
40.75
3.2
9.5
6.6
7.2
Design Efficiency
%
95
95
95
95
95
95
95
95
Average FOB Cost
$/acfm
1.72
1.94
1.98
2.18
2.25
2.3
2.3
2.3
* Based on the cost of precipitator installation in carburetted water gas.
-------
                                -777-
                             Table 21. 5



        Cost*  of De tar ring Precipitators in Fuel Gas 1959-1969
Year
1959
1960
1962
1966
1967
1968
1969
Gas Volume in
1000' s acfm
11.64
11
23
11.4
30
55.6
83
Design Efficiency
%
95
95
95
95
95
95
95
Cost in {
Erected
-
4.46
2.63
-
-
-
1.43
|> /acfm
FOB
2.44
-
-
2.69
2.45
1.1
-
* Based on the cost of precipitater installation in coke oven gas.
                                                 SOUTHERN RESEARCH INSTITUTE
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                                     -778-
   10.00
CO

j!   i.oH
o
Q
CO
o
U

i-,
o
+->
ed
«   o.io-4
£
                    Erected Cost
                           L+
                                              Indicates Data Spread
      0.01
                             0.10
1.00
10.00
                      Gas Volume through Precipitator, 10 acfm
       Figure 21.11.  Cost of Detarring Precipitators with 95% Collecting
                     Efficiency (1959-1969).
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                                    -779-
   Performance statistics.  The important operating parameters  in each of
the major areas, catalyst recovery and oil mist and tar removal, are sum-
marized in Tables 21. 6 and 21. 7.  The data given in the tables show the
maximum, minimum, and average  values of gas volume,  gas temperature,
inlet loading, and collection efficiency.

   Design considerations* Selection of the size and power requirements for
a particular  design specification follows the general methodology  outlined  in
Chapter 9, Part I.  The proposed manufacturer selects a precipitation rate
parameter for the stated  operating conditions.  The selection is made from
company proprietary data. The  required  collection electrode area is com-
puted from the Deutsch-Anderson equation.  The  power supply and section-
alization requirements are established from the proprietary empirical data
bank.

      Table 21. 8 is a summary of design and field test data on two precipi-
tators installed on fluid catalytic cracking units as  reported by the American
Petroleum Institute.3 Table 21. 9 shows design and performance data on two
precipitators collecting powdered catalyst with ammonia injections.

   General observations and discussion of trends.  The main application of
electrostatic precipitation in the petroleum industry has been its use in the
collection of catalyst fines from  catalytic  cracking  operations used in the
production of high octane gasoline.  The surge  in use was during World War
II when most of the installations  were made.  With  the advent of the jet air-
craft in recent years, the demand for high octane aviation gasoline has been
replaced by demands for  lower octane  jet fuel which does not have the same
production requirements.  Hence, the  number of  new catalytic cracking units,
and the number of electrostatic precipitators for  this service has  declined
as illustrated in Figure 21.3.  Electrostatic precipitators as particulate
emission control devices  are still being utilized on catalytic cracking units,
however, and at least 3 units were sold for this designated purpose during
the 1966-67 period.4

      The detarring of fuel gases, although strictly not a part of the petro-
leum  industry, has been included due to close process relationship, and
similar precipitator design factors.  Again, this  application appears to be
declining, with uses primarily dictated by a local supply and demand situa-
tion, since the use of pipeline natural gas  has replaced manufactured gases
as the major gaseous fuel source in the United  States.
                                                   SOUTHERN RESEARCH INSTITUTE
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                                 -780-
                            Table 21.6
         A Summary of Application Data*  for Precipitators in
            Fluid Catalytic Cracking Application 1951-1962
Parameter
Gas Volume, 1000's acfm/pptr.
Gas Temperature, °F
Inlet Loading, # /hr
Collecting Efficiency, %
Precipitation Rate,* * w ft/ sec
Maximum
254
850
2800
99.7
0.39
Minimum
6
450
77
80
0.1
Average
152.6
610
1444
95
0.26
* These data based on 7 installations.
** Average of 3 test and 2 design w's.
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                                -781-
                             Table 21.7

               A Summary of Performance Data* in Fuel Gas
                        Application 1940-1956
Parameter
Gas Volume, IGOO's acfm/pptr.
Gas Temperature, *F
Inlet Loading, gr/scf**
Collecting Efficiency,
Design Precipitation Rate, w ft/sec
Maximum
16.72
120
-
95
0.55
Minimum
3.5
70
-
95
0.32
Average
5.75
90
0.8-2.5
95
0.45
* These data based on 55 installations.

**A tar camera had been applied for efficiency test of detarring precipitators.
   Testing by this means consists essentially of comparing color densities for
   filter papers after exposure to the inlet and outlet gas.  The average inlet
   loading in this application is about 0.8-2. 5 gr/scf.
                                                  SOUTHERN RESEARCH INSTITUTE
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                                         -782-
                                     Table 21.8
                    Field Tests on Fluid Catalytic Cracking Units *
Collecting electrode area, sq ft
Rated gas-handling capacity,  acfm
Test gas-handling capacity, acfm
Specified inlet catalyst concentration, gr/scf
Test inlet catalyst concentration, gr/scf
Guaranteed collection efficiency, %
Test collection efficiency, %
Test inlet catalyst loading, tons per day
Catalyst
Gas composition, dry basis, mole %:
      CO2
      02
      CO
      N2
Moisture,  mole %
Ammonia addition rate, Ib per hr
Stack catalyst concentration,  gr/scf
Stack catalyst loss,  tons per day
Precipitator operating pressure, psig
Rapping cycles:
      Discharge electrodes

      Collecting electrodes

Computed particle drift velo.city, fps
                                                   No.  1
 73,800 at 515°F
120,000 at 515°F
      5 to 25
     25.7
     99.6
     99.77
  1,085
   Synthetic

      7.2
      5.1
      3.2
     84.5
     34.5
     15
      0.531
      2.4
      0

     No data

     No data
   No. 2

137,760
 99,900 at 600°F
138,000 at 470°F
      4.4  to 22
     24.4
     99.6
     99.77
    132    .
  Sylthetic *

      9.1
      3.0
      6.3
     81.6
     31.4
      9.4
      0.0538
      0.3
      3.0

2-hr cycle, 6-sec
    duration
30-min cycle,  10-
  sec duration
      ,0.10
Note: Iruel concentration probably is ahead of mechanical collectors.
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                                  -783-
                               Table 21. 9

   Design and Performance Data for Two Powdered Catalyst Precipitators
Rated Gas Volume acfm              100, 000

Gas Temperature                    400°F

Collection Surface Area              34,400

Design Efficiency                    99. 6%

Test Efficiency                      99. 7%

Test Gas Velocity

Design Precipitation Rate,  ft/sec     0.27

Test Precipitation Rate,  ft/sec	0. 361
40, 000

400°F

16,300

99. 5%

99. 8%

62, 000 at 350°P

0.22

0.392
il-2 cfm of NH3 conditioning
zl cfm of NH3 conditioning
                                                  SOUTHERN RESEARCH INSTITUTE
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                                   -784-
      The major potential use of precipitators in the petroleum industry
appears to lie in new applications,  two of which are shale oil processing
and acetylene manufacturing* However, the total market appears to be
small compared to potential applications in other  major industries.  It
should be noted that the use of precipitators for these detarring type appli-
cations is not one  where air pollution is involved, but instead, one of pro-
cess and/or product improvement and control.
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                                  -785-
                              CHAPTER 21
                            BIBLIOGRAPHY
1.  White, H. J., Industrial Electrostatic Precipitation,  Addison-
    Wesley (1963).

2.  Cole, W. H.,  "Electrical Precipitation - Tar, " unpublished
    Research-Cottrell, Inc.  report (May 1950).

3.  "Removal of Particulate Matter from Gaseous Wastes," report
    prepared by the Chemical Engineering Department of the University
    of Cincinnati for the American Petroleum Institute (1958).

4.  Manufacturer's Report of Air Pollution Control Equipment Sales
    (1966-1967).  IGCI report, Contract CPA 22-69-5.
                                                  SOUTHERN RESEARCH INSTITUTE
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                                  -786-
                               CHAPTER22
         THE APPLICATION OF ELECTROSTATIC PRECIPITATORS
                 IN THE NONFERROUS METALS INDUSTRY
      Applications of electrostatic precipitators in the nonferrous metals
industry have been in the removal of participates for the purpose of air
pollution control, cleaning of gas for process purposes, and for recovery
of metallic ore-containing dusts  for further processing.

      The primary nonferrous metals of interest are copper, lead, zinc,
and aluminum.  The main processes in the extraction of these metals from
their ores are:  (1) dressing, (2) roasting,  (3) sintering, (4) smelting and
refining, and (5) electrolytic reduction.  These functions are carried  out
in a number  of different types of equipment, depending upon the nature of
the ore and the particular plant design.

      The commercial use of electrostatic precipitators has been standard
practice by copper,  lead, and zinc smelters in cleaning the off-gases from
the extraction process.  Precipitators are also used in the electrolytic
reduction of  bauxite to produce aluminum.

22. 1  HISTORICAL DEVELOPMENT

      Although precipitator applications in the smelter field were made
initially to abate the smoke nuisance,  an even greater usefulness was found
in recovering the valuable copper, lead, and zinc oxides and other com-
pounds  carried out of the stacks  in the form of dust and fume from the
furnace operations.  Most of the  western smelters designed and built their
own precipitators under patent license agreements.  As a result, strik-
ing differences developed in their precipitation practice.  Experimental
work on the electrostatic treatment of copper converter furnace gases
was started as early as  1911.  A year later the work was extended to a
full-scale unit of 50, 000 cfm capacity.  As a result of successful experi-
ence on converter gases, experimental work was extended to the treat-
ment of gases from lead blast furnaces, roasters, and reverberatory
furnaces.

      Development of electrostatic precipitators for large smelters was in
the direction of large pipes,  12 to 36 inches in diameter and 20 feet long,
                                                  SOUTHERN RESEARCH INSTITUTE
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                                   -787-
to handle the large volume gas flows.  These large diameter electrodes
required rectifier sets to operate at very high voltage to generate the
corona and maintain the electric field.  Experimental units of up to 48
inches in diameter with rectifiers operating at voltages  up to 200 kV were
tried on an experimental scale.  However,  difficulties in handling the high
voltage led to the use of plate-type electrodes in a vertical-flow precipita-
tor for this type service.

      During the early work on converter gases, it was  found that even
practically complete removal of the lead fume and clarification of the gas
at a temperature of 600-700°F still resulted in a cloudy  discharge from
the stack.  To obtain complete clearance of the stack it  was  necessary to
cool the gases to about 200°F.  The explanation lay in the presence of
arsenic trioxide and sulfur trioxide in the gas (which were both in the vapor
phase at 600-700°F but condensed to fine fumes at 200°F). This suggested
the possibility of effecting fractional condensation and separation of the
fumes and vapors  present by cooling the gases in several steps and using
precipitation at  each step to collect the component condensed at that
temperature.  The process was demonstrated by the  separation of refined,
snow-white arsenic trioxide fume from the  furnace gases.

      Over the years precipitator applications in smelters have continued
to increase.   They are used extensively on  copper, lead, and zinc reduc-
tions; copper roasters, converters, and reverberatory  furnaces; sintering
machines, blastfurnaces, and reverberatory furnaces in lead recovery
operations;  and roasting of ore concentrates  in zinc processing.

      The largest  smelter precipitator in this country is a central gas-
treating installation which was built and placed in operation in 1919.  Gas
flows of over  two million cfm are handled in the precipitator.  This pre-
cipitator,  in addition to the gas volume handled,  is notable for the size
and capacity of its rectifier equipment which comprises  12 full-wave
mechanical rectifiers, each powered by a 100 kV, 75 kVA high-voltage
transformer.

      In the aluminum industry, the application of electrostatic precipi-
tators was studied as early as  1918 on exhaust gas from baking ovens pro-
cessing electrodes used in the  Hall electrothermic cell for the extraction
of aluminum from bauxite.  An experimental unit for cleaning ventilating
gases from alumina reduction cells was successfully operated in 1951
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                                 -788-
and resulted in the full-scale installation of precipitators (dry type) to treat
over a million cfm of gas.

      Subsequently, electrostatic precipitators have been applied to carbon
plants,  bauxite dryers, alumina calciners,  remelt furnaces,  etc.

      Other miscellaneous applications in the metallurgical field are cad-
mium recovery from zinc sinter machines,  lead blast furnaces,  tin smelt-
ing, and nickel smelting.

      Another application which developed in the early 1920"s was the recov-
ery of gold from furnace and chemical operations at the United States Assay
Office in New York City.  This installation treated 70, 000 cfm of gas at an
efficiency of over 95 percent.  The gold recovered in fume deposits from the
precipitator amounted to  about $ 11, 000 per annum.  Subsequently,  similar
installations were made at several United States mints.  Another application
of some importance is  the treatment of fumes from furnace operations for
the production of metallic silver in connection with the electrolytic refining
of copper.

      The production statistics in the United States of the four most impor-
tant nonferrous  metals for the period 1935 through 1967 are shown in
Figure  22. 1.

22. 2  NONFERROUS METAL PROCESSING

      The process  of extracting nonferrous  metals from their ores is carried
out in a variety  of processing equipment.  The particular steps in the re-
duction process and the type of processing equipment vary with the type of
ore.  The furnaces for roasting, smelting and refining of lead, copper, and
zinc are described in the  following sections.

   Sintering process.  A  sintering machine  is used to convert metallic ores,
fines, and plant process dust into larger pieces which can be handled more
readily during further plant processing.  The sinter machine itself is similar
to that used in ferrous metal processing;  see Figure 22. 2.
                                                   SOUTHERN RESEARCH INSTITUTE
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                                -789-
    5000
  1
  t; 2000
 *
 w
 § 1000

 e
 i  800
 e
 .3
 •w
 8

 1 500
 0,

 •a
 1
 »4
S
I800
  100
     1935   1940
                                                    1965     1970
           22. lt  Non(errous
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                            -790-
      < h ETii J Rr^a F-"JTia EiT'iJ, fc.-,,-.aiJ 13
           LJ—I—LJ
                                   f
G3
Figure 22.2.  Use of an Electrostatic Precipitator on Ore Sintering
            Machine Exhaust Gas.
                                           SOUTHERN RESEARCH INSTITUTE
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                                  -791-
      In preparing the material for sintering, the ore is mixed with coke
and additives, when required.  A further preparation,  in some cases, con-
sists of dampening the mix so it packs better.  The mix is then uniformly
spread across the moving grates of the sinter machine and ignited by gas-
fired burners.  Air is induced through the bed in order to support burning
as the grate moves toward the discharge end.  At the tail end, the sinter
is dropped off the grate,  spray-cooled and then transported to the point of
further processing.

      The combustion air induced down through the bed is collected in a
multiplicity of wind boxes located below the traveling grates.  From the
wind boxes, the gas is transported to the cleaning  equipment which usually
includes a primary mechanical collector preceding the precipitator.  The
main fan is located between the precipitator and  the stack.

      The precipitator usually used in conjunction  with the newer zinc sin-
tering machines is a single stage,  horizontal flow, plate type.  The shell is
constructed of steel and insulated by internal guniting if corrosive conditions
exist.  The hoppers are either trough type, with a screw conveyor along
the bottom, or a flat pan type basin with a drag scraper.  The discharge
electrode system can be of the wire type or any of several discharge  elec-
trode configurations described in Chapter 10, Part I. The collecting
electrode system is a shielded flat plate type.  Discharge electrodes  are
often cleaned  by means of magnetic vibrators,  and air vibrators are used
on the collecting plates.  Gas and/or particulate conditioning, if required
to lower particulate resistivity, is by water spray or steam carefully con-
trolled so that the resulting moisture/temperature conditions do not create
a corrosive atmosphere.

   Ore roasting.  Raw ore can be either roasted to completion or partially
roasted in preparation for further processing.  Prior to roasting, the ore
is crushed and screened to control the particle size.  Depending on the  kind
of ore, the type roaster and/or end products, the size can vary from walnut-
sized chunks to  a fine powder.  The nature of the ore to be treated, the
kind of roast required, the tonnage of ore to be handled, and the cost of
installation and  operation, have resulted in a great diversity of forms in
the apparatus  for roasting ores.  The following are the most common types
of ore roasters:
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                                   -792-
    Multiple hearth furnace

      The multiple hearth furnace is probably the most popular type of ore
roaster furnace in use today.   It consists of a vertical cylinder of steel plate
lined with refractory brick and divided in hearths of arch construction.  There
can be as few as four hearths or as many as 16 or more depending on the
application.  The  hearth floor and walls, and the roof of the furnace are
lined with brick to protect metal parts, as well as to conserve heat. There
is a central shaft  to which are attached the rabble arms, two for each hearth.
This central shaft also contains the pipes which conduct the cooling air or
water to the arms.  To each arm is fixed seven to nine rakes or rabbles.
The rotation of this  shaft, which is driven by a motor and train of gears
beneath the furnace, is of the order of a revolution in one-half to two minutes.
Ore is fed upon the upper hearth, which, being warmed by the heat generated
in the roasting operation, serves to dry the crude ore.  The rabbles are so
adjusted that the ore is gradually moved from the outer edge of the upper
hearth toward the  center and falls through a drop  hole onto Hearth No.  1.
The ore then moves across this hearth to a slot near the outer edge, through
which it drops onto Hearth No. 2, and thus in zig-zag fashion the ore pro-
gresses through the furnace until it finally drops into a car or conveyor
beneath the lowest hearth.  All furnaces have doors on each hearth for
visual observation,  repairs,  and admission of air.  Once the ore is ignited,
the reaction itself furnishes enough heat to make the process a self-sus-
taining one for the most rough roasting. However, some ores are so diffi-
r-Mlt to roast or so low in sulfur that additional heat must be applied.

    Flash roaster

      The primary use of flash roasters is in removing sulfur from zinc ore.
The sulfur and zinc bearing ore is blown into a combustion chamber along
with preheated air.  The combustion chamber is usually preheated by gas  or
oil until the temperature is around 1600 to 1700°F.  Ore and heated air are
introduced in the combustion chamber and the flash combustion of sulfur
occurs.  With proper conditions of draft,  and with the proper ore composition,
the burning becomes self-supporting and the gas jets may be turned off.
Under some conditions, such as very high moisture content in the ore, it
may become necessary to add auxiliary fuel such  as powdered coal  or to keep
the gas jets on;  however, this  is unusual and undesirable.
                                                 SOUTHERN RESEARCH INSTITUTE
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                                  -793-
      The sinter from the flash chamber drops to the roaster hearths where
it is rabbled and further combustion occurs,  so that the final sinter usually
has less than 1% sulfur as compared to about 30% in the original ore.

     Fluid-Bed roaster

      A more recent type  of roaster is the fluid-bed reactor.  Either dry
or slurry feeding can be used.  Low pressure air is introduced into a wind-
box  and passes up through an air distribution plate near the bottom of the
reactor.  Operation of this system is continuous.  As feed enters the bed,
it is fluidized and immediately brought to roasting temperature.  The
roasted material overflows into  a pipe placed at "surface level11 and passes
out of the reactor through a cooler.

      When a precipitator is used for air pollution control, a flue is con-
nected to the top of the roaster.  Prior to entering the precipitator, the gas
is tempered in either a dry bottom cooling tower or by mixing with colder
atmospheric air. Normally, the type precipitator used to clean the gases
coming from roasters is  a single-stage,horizontal-flow, plate-type unit.  The
shell is constructed of steel and the dust hoppers are of pyramidal  design.
Where condensation may  occur,  the precipitator is insulated on  the outside.
   Smelting and  refining.  Smelting and refining operations are for the pur-
pose of removing unwanted impurity elements and adding alloying materials
to produce     desired metal composition.  The smelting and refining opera-
tions are again carried out in a variety of types of furnaces depending on the
type of material  being processed.  The most common types of furnaces are
described as follows.

     Reverberatory furnace

      By definition,  a reverberatory furnace is one in which the materials
being processed  are in direct contact with an incandescent flame.  Heating
is by direct radiation from the flame, walls and ceiling of the furnace.
The  furnace is fired by either gas or oil.  The primary use of this  furnace
is for melting solids for the purpose of refining or alloying metals  to a
specific mixture  of materials or assay.  This is accomplished by regulating
the feed by the additions of chemicals,  called "fluxing", or in some cases
by the control of  temperature as in "sweatbug".  The unwanted materials
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                                  -794-


come off as a dross or boil out as gases,  such as fluorine,  chlorine,  etc.,
which are carried away with the off-gases.

      The design of a furnace varies widely,  depending on its particular
use.  Furnace sizes also vary widely from about 500 Ib  per heat to 50 tons
per heat.   The smaller units normally have cylindrical shells, and are of
the tilting type.  The larger furnaces are  fixed, having tap-holes for metal
pouring.  The dross is usually skimmed off.   Many large furnaces have
double hearths operating at different temperatures for better  control.  A
popular type furnace is one provided with  a charging well located adjacent
to the furnace but having a common bath.  Other furnaces have charging
doors at the sides.

      Basically,  the gas control problem associated with reverberatory
type furnaces is one of ventilation.  This is because in most cases some
form of hooding is involved.  The smaller fixed units generally utilize
canopy hooding.  The tilting types use either adjustable type  hoods or plenum
hoods.  The smallest units often use movable flexible flues.  The large
fixed units exhaust directly from the furnace with canopy hoods over charg-
ing wells and doors. In addition to venting the furnace proper, various
operating locations  include tap holes, metal runways, holding pots,  and
pouring areas which are also vented.

      The problem of cleaning the  gases coming from a reverberatory
furnace installation  falls  into two broad categories.  The first is where
only particulate is to be removed from the gas.  The second is where  cer-
tain objectional gases,  such as  produced by the fluxing operation, must be
removed in addition to the particulate matter.

     A single-stage, vertical-flov^ pipe-type  precipitator is customarily
used if only particulate is to be removed.   The shell is constructed of mild
steel and is normally uninsulated.   The hopper is usually pyramidal in design.

     Where gaseous contaminants must be removed in addition to particu-
lates, the precipitator is preceded by a wash tower or scrubber.  The con-
taminant gases are removed by scrubbing with water or a neutralizing
solution.  The scrubber is usually an integral part of the precipitator. The
precipitator proper  is usually a single-stage,  vertical-flow  unit of the wet
type, which eliminates  the  carryover water  spray along with the particulates.
Because of the corrosive nature of the wet precipitate,  the  shell  is constructed
of either steel with a corrosion-proof lining,  concrete or wood.
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                                  -795-


      The precipitator in the dry system can utilize weighted wire discharge
electrodes or other types as described in Chapter 10, Part I.

      Exposed steel pipes are usually used as collecting electrodes in cases
where very hot gases are treated by a precipitator.   The pipes are left unin-
sulated,  causing gas and dust cooling by radiation.  The pipes are between
eight inches and twelve inches in diameter,  and are arranged vertically
between  a top and  bottom plenum header.  Pipe banks are generally arranged
for two pass operation.  The gas enters the top header section of the first
bank,  flows downward,  reverses and flows upward through the second bank,
exiting through the top header.

      The cleaning of the exposed pipe collecting electrodes  requires vigor-
ous action because of the tacky nature of the dust collected on the cool sur-
face.  Usually a form of the swing-hammer pipe rapper is used.   The mech-
anism consists of a motor-driven oscillating shaft running horizontally
across the precipitator between rows of collecting pipes. Hammer heads
are connected to the shaft by spring leaf arms and strike against anvils
attached to the collecting pipes near the bottom.  The rapping blow can be
varied by adjusting the arc  length of the hammer swing and/or controlling
the operating time.  Vertically operated air vibrators, located on the roof,
are employed for discharge electrode cleaning.

      The precipitate removal systems used to transport the hopper catch
for small and large installations are, respectively,  container removal
and screw conveyor.

      For wet precipitators, discharge electrodes are usually square wires
using support insulators with orifices for suspension.  In this design, the
high voltage insulators are  located  in compartments on the roof.   A bus
beam is  mounted on the top  of the insulators.  The discharge electrode as-
sembly is supported from the bus beam by hanger rods which pass through
open metal sleeves fastened to the underside of the roof.  The sleeves, or
orifices, are continuously purged with a  small amount of air in order to
keep the  dirty gas from reaching the insulators  in the compartment.  Purg-
ing is either by inleakage when the  system is under vacuum, or through the
use of a pressure blower when the system is pressurized.

      Since  the system is wet and subject to extreme corrosion,  a different
type of collecting electrode  is required.   Transite plates are usually used
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                                 -796-
in such wet and low temperature corrosive environments.  The plates are
constructed from one inch thick transite board, supported at the  ends,  and
spaced on about ten inch centers.  A number of standard size sheets, usually
eight feet by four feet,  are combined to make up the desired  size collecting
electrode.   The plates  depend on the wetted surface for electric current con-
duction and metallic bars placed along the edges of the plates form a ground-
ing network.  The precipitator is arranged for vertical gas flow.   The tran-
site plates are kept washed by carry-over water entering the precipitator
from the preceding scrubber.  In addition,  sprays are provided under the
roof for periodic spraying.

      In the wet system, a slanted  hopper bottom is generally used,  with col-
lected material removal by a slurry hopper system.

     Blast furnace

      The use of blast furnaces for large nonferrous smelting operations has
been largely replaced in recent years by other means. However,  of those
still in operation,  electrostatic precipitators are used more  often with the
larger blast furnaces,  which  are nearly all in the copper and lead smelting
process.  Many metals such as cobalt, nickel, tin and silver are by-products
of the reduction operation  of copper and/or lead  smelting.

      In the copper smelting process, the blast furnace is a shaft furnace.
The charge consists of ore, fuel, and flux.   The hot gas from the combus-
U ••! of the fuel rises up through the furnace countercurrent to the descending
charge.  As reduction in slagging proceeds, the  matte and slag formed de-
scend to the crucible.   Smelting in a blast furnace may be performed by the
reducing,  pyritic,  or semi-pyritic process.

      In the reducing process, the  oxide or rough-roasted ore is  mixed with
flux and only enough carbonaceous  fuel to furnish the necessary heat to carry
out the reduction of the oxide.  The blast of air should oxidize only  the car-
bon, and none of the sulfur.

      In pyritic smelting,  an  attempt is made to save coke by using  the heat
of the oxidization of sulfur to promote the reactions of matting and slagging.
Although theoretically there may be sufficient heat generated in the  furnace
for this purpose, it is usually necessary to use 1-3% of coke.
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                                  -797-
      The most common type of smelting today is the semi-pyritic process,
because it is carried out with ores which do not contain enough sulfides for
pyritic smelting and yet may not require roasting.  The amount of coke used
varies from 3-16% of the weight of the charge.

      A blast furnace used to smelt lead ores is slightly different from that
used for copper reduction.   The difference is in the construction of the cru-
cible.   In the lead blast furnace the crucible is deep and the lead, as it is
reduced in the furnace  and collects in the crucible,  is removed from beneath
the slag and matte by means of a lead well  or a syphon pump.

      A nonferrous blast furnace is connected to the inlet of an electrostatic
precipitator through a duct system.  As a temperature control measure, pro-
visions are made  either to dilute the flue gas with ambient air, or to cool it
with a dry bottom water spray gas cooler.

      The type of  precipitator used in connection with  a nonferrous blast
furnace is a single-stage, two-pass,  vertical-flow pipe unit similar to that
used on reverberatory  furnace gas.  The shell  and  pyramidal hoppers are
fabricated of mild steel and  are usually left uninsulated.

   Converters.  In the  nonferrous metallurgical industry, a converter is
used to convert matte (a mixture of iron and copper sulfide) to metallic cop-
per.  In addition to the  base metal produced in  the converter, some precious
metals such as gold and silver are recovered.  Most  of the impurities such
as arsenic,  antimony,  lead,  and zinc are volatilized as oxides and are car-
ried out of the  converter with the  sulfur dioxide exhaust gas.

      During the conversion process, air in small bubbles is  forced through
the molten matte contained in the  converter.  When the blast of air from the
tuyere mouth enters the molten matte, the  sulfides  are oxidized.  The sul-
fur dioxide formed escapes through the converter mouth while the ferrous
oxide unites with the silica of the  flux to form a slag.  The heat of forma-
tion of this slag, together with that produced in the  oxidation of the sulfur
and iron, is sufficient to keep the bath molten.

      There are several kinds of converters in general use.   The two most
popular are the "Bessemer Converter" and the "Tilting Horizontal Converter."
The gas discharge  ports of the converter are coupled to a flue system which
transports the gas  to an electrostatic precipitator,  where the condensed
-------
                                    -798-
metallic fumes are removed.  The gas is cleaned preparatory to process-
ing in the acid plant.

      The precipitator employed for the removal of metallic fume from the
gas emitted by a nonferrous metal converter is of the single stage type.   The
gas flows horizontally through ducts formed by the collecting electrodes.   The
dust hoppers are of the pyramidal type.  The shell and hoppers are connected
to their respective flue systems by nozzle type transitions.  The discharge
electrodes are weighted twisted squares suspended from support insulators
with bushings.  The collecting electrode plates are made of standard cor-
rugated steel  sheets.  The dust precipitated in the troughs is shielded from
the main gas stream, thus minimizing reentrainment.  The plates are ten to
twenty feet in height and from three to six feet in the direction of gas flow.

   Cupola furnace. A cupola in the nonferrous industry is used as a furnace
to melt and reduce copper,  brasses, bronzes, and lead.  It is essentially an
ooen top refractory lined cylinder,  equipped with a charging door about one-
half of the way up,  and air ports (known as tuyeres) at the bottom.  Air is
supplied from a forced-draft blower.  Alternate charges of metal, coke and
limestone and/or flux are placed on top of the burning coke bed to fill the
cupola.  The heat generated melts  the metal, which is drawn off through a
cap hoi: .

      When a  precipitator is used for  air pollution control,  a flue is con-
nected to the top of the  cupola.  A by-pass hood or damper is installed as
part of the flue connection.   Prior  to entering the precipitator, the gas is
cooled in either a dry bottom spray cooling tower or by mixing with cooler
atmospheric air.

      The typical precipitator used  to clean the gas  coming from a cupola is
a single stage, horizontal flow, plate  type unit.  The shell is constructed of
steel and is operated without thermal  insulation.
22.3  ELECTROLYTIC REDUCTION OF ALUMINUM

      Metallic aluminum is produced by electrolytic reduction of alumina
(A12O3) dissolved in a molten bath or cryolite (A1F3 • 2NaF).  The electrodes
used are either prebaked carbon or a continuous anode type.  Both electrodes
                                                    SOUTHERN RESEARCH INSTITUTE
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                                  -799-
are composed of petroleum coke with pitch as a binder.  In the prebaked
operation the anodes are prefabricated and baked prior to use.  In the
Soderberg cells, a paste mixture of coke and tar is added to a compartment
over the cell and baked by the heat into a solid anode as it descends.  Elec-
trolytic, thermal,  and chemical action in the cell evolves carbon and alumina
dust,  and both participates and  gaseous fluorides.   Present practice is to
incorporate an effective hood over  and/or around each "pot" through which
sufficient ventilating air is drawn to contain the emitted fume, ore and car-
bon dust as well as the  pitch in  the case of Soderberg  electrodes.  The gas
from a number  of pots is collected in a common flue system and then passed
from a mechanical collector which removes about 50% of the solids.  The
collector,  usually  a mechanical type,  discharges the gas into  the precipitator
where most of the  remaining fluorine particulate is removed.  Before the gas
is discharged to the atmosphere, it is passed through a scrubbing tower to
remove the residual gaseous fluorine.  Figure 22.3 is a schematic  of an
emission control system installed for cleaning Soderberg cell  gases at an
aluminum  plant in  Germany.

     The gas volume handled is  about 1500 to 2000 acfm per pot.  The
temperature is  about 200° F, while the moisture content is low,  usually less
than 2. 5%  by volume.  The moisture is mostly atmospheric moisture carried
in ventilating air and can be as  low as 1%.  See Figure 22. 4.

    The precipitators used in connection with the electrolytic  reduction of
alumina are single-stage,  horizontal-flow duct units.   The hoppers are of a
pyramidal design.  Because of the  relatively low temperature  and humidity,
no heat insulation is used.

    Table 22.1  shows design and performance data for two precipitators
installed on aluminum reduction furnaces.

22.4  PRODUCTION OF PRIMARY COPPER

    Production  processes.  Primary copper is  produced by smelting or
leaching methods,  usually followed by electrolytic refining.  In general,
sulfide  ores are treated by smelting, and oxide  ores are treated by
leaching.

    In the  smelting process there are usually five steps.  These are:

    (1) concentration by selective  flotation,

    (2) roasting,   •
-------
           Main
           Duct
Burner
       \
                              -800-
                     Electrostatic Dust
                       Precipitator
                                           Wet
                                           Scrubbers
                                                   Stack
                                                         Spray
                                                         Separator
   Soderberg Aluminum
    Reduction Cell
Figure 22.3.  Purification System for Soderberg Cell Gases.
                                                 SOUTHERN RESEARCH INSTITUTE
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                              -801-
   Bauxite
           Screen JJ
        Clay and  *
       Impurities
          Fuel

Drying     JWate£^c==, I
Kiln       \          JLJLI

III
                                                        Lime  Soda
                                                              Ash
    Pig
 Aluminum
                                    Steam
                                 Mech
                                  Rectifiers
                             L~ Red
                     Air     W Mud
                           Thickener
                             t
\
   Casting
                        Electrolytic
                          Reduction
                            Pot
                  Kiln
             Alumina
       ,e*tt,'
       $tf& Cryolite
       Figure 22.4.  Flow Diagram for Aluminum Production.
-------
                                 -802-
                               Table 22.1
                       Design Performance Data for
                Aluminum Reduction Furnace Precipitators
                                       No. 1               No. 2
Rated gas flow, acfm                   57,500              115,000
Gas temperature, °F                      212                  212
Collecting surface area,  sq ft            8, 820               17, 700
Gas velocity, ft/sec                         3.93                 3.9
Design efficiency,  %                        90                   90
Design precipitation rate, ft/sec              0. 25                 0. 25
Test gas volume, acfm                  55, 000              115, 000
Test efficiency,  %                          98                   91.5
Test precipitation rate,  ft/sec                0.41                 0.27
Corona power, w/1000 cfm                 180
1Moisture content lower than precipitator No. 1
 (0. 9 as compared with 2. 4)
                                                 SOUTHERN RESEARCH INSTITUTE
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                                    -803-
      (3)  smelting,

      (4)  converting,

      (5)  fire, or electrolytic refining.

All of these steps,  with the exception of electrolytic refining, may result in
the generation of particulate matter.

      Selective flotation is almost exclusively used in beneficiation of sulfide
ores.  In flotation processes, the finely ground ore is mixed with water and
selected chemical reagents and agitated with air to produce a heavy froth.
The reagents are selected such that the mineral particles are carried to the
surface in the froth while gangue particles remain in suspension and are
pumped to a settling lake.   The resulting concentrate contains copper sul-
fides as well as some sulfides of other metals. After drying, this concen-
trate is ready to be roasted, or in some cases, sent directly to the smelter.

      The objectives of roasting are:  (1) to  eliminate some of the sulfur from
the concentrate by  changing the sulfides into gaseous oxides and (2) to vola-
tize zinc,  arsenic, and antimony present as impurities.

      Roasting is conducted in multiple  hearth furnaces or in fluid bed
roasters as described previously.  After removing some of the sulfur as
SO2, the roasted material  is known as calcine and is ready for smelting.

      The  exit gas temperature during roasting is about 1200°F,  and gas
volumes range from 5, 000 to 1, 500, 000 cu ft, depending on size of the  roasters,
with an SO2 concentration of 5-14%.  The SO2 may be recovered and used
to produce sulfuric acid.   The dust in the stack gases ranges from 3 to 6%
of the roaster feed  and produces a dust concentration of 6-10 grains per
std cu ft.   The dust is primarily composed of sulfide concentrate feed
materials.  Gas cleaning may be accomplished by wet scrubbing, bag
houses, or electrostatic precipitators. ' Some operating statistics of
multiple hearth roasters are given in Table  22. 2.1>2

      Stack gas volumes from fluid bed roasters average from 6, 000 to
10,000 scfm,  with SO2  concentrations of 8-14%.   Dust recovery is affected
by cyclones and electrostatic precipitators.   Table 22.3 presents some
operating characteristics of fluid bed roasters.
*Refer to the bibliography for this chapter.
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                               -804-






                              Table 22.2



           Operating Data of Multiple Hearth Roasting Furnaces
 Furnace




^Utilization




Capacity




Charge




Moisture Content






 Waste Gas Factors




Off Gas Volume




SOa - Content






Dust




Content in Raw Gas




Chemical Composition






Dust Removal




Type of Separator




Efficiency Rate
 roasting of mixed copper concentrate



 140 ton/day




 mixed copper concentrates and flux
4500-5000 scfm




5-14%-vol
6-10 grains/scf



   Cu, 10% S, 26%
ESP and scrub




95-99%
                                                SOUTHERN RESEARCH INSTITUTE
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                               -805-
                              Table 22.3
                          Fluid Bed Roasters
Furnace

Utilization

Capacity

Charge


Waste Gas Factors

Off Gas Volume

SOa - Content


Dust

Dust Removal
 Types of Separator

Efficiency
Roasting of mixed cu concentrates

140-250 tons /day

Mixed copper concentrates
6.000-10,000 scfm

8-14%-vol
Cyclone in series, ESP

95-99%
-------
                                     -806-
      After roasting, the first step in smelting is to produce a molten sul-
fide of iron and copper.  This is generally accomplished in reverberatory
furnaces ranging from  22-38 ft in width and 96-125 ft in length.  The fur-
nace is fired by burners located at one end and the charge is fed in along
the furnace walls.  The slag formed during melting is lighter than the  matte
and easily separates from it.  When needed, the  molten matte is drawn
from  the furnace through a tap hole near the bottom of the furnace.

      Stack gas volumes from matte furnaces average 45, 000 to 65, 000 scfm
with SO2 concentrations of 0. 5 to 3. 5%.   The dust load averages 2  to 5 gr/scf,
with the dust being composed primarily of copper,  zinc, silica, and sul-
fur.1' 2 The dust is usually greater than 5u  in diameter, with only limited
amounts of smaller particulate,  and collection equipment usually  consists
of electrostatic precipitators or baghouses.  Some operating data on cop-
per reverberatory furnaces are given in Table 22.4.

    Matte converting

      Copper has  a lower affinity for oxygen than iron has for sulfur.   This,
coupled with the fact that oxidation of iron and sulfur liberates large amounts
of heat, makes it  possible to blow  copper matte with air to oxidize any iron
sulfide present and form SOg and iron oxide.  If any copper is oxidized, it
immediately reacts with iron sulfide to produce iron oxide.  Since iron oxide
forms an  easily fusible slag with silica, it is necessary to add sufficient
silica to the molten mass to form the desired slag, and all the iron can be
removed as liquid iron silicate.

      These reactions are usually  carried out in a copper  converter consist-
ing of a refractory-lined horizontal drum about 13 ft in diameter and approxi-
mately 30 ft long.  This drum is fitted with  an opening at the top through
which the furnace is charged and through which gases escape when the fur-
nace is in operation.  Along one side of the  furnace is a large pipe which
delivers air to the furnace through a series of small pipes called  tuyeres
that enter the furnace through the side.

      Matte is charged into the converter directly from the smelting rever-
beratory furnace and the blow begins immediately.  Silica is added as  a
flux as the temperature of the bath rises and slag is removed and ultimately
the furnace is nearly full of molten copper sulfide. At this point slagging
is complete and the final blow begins.  Oxidation continues until all the
                                                    SOUTHERN RESEARCH INSTITUTE
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                                 -807-
                               Table 22.4

                 Operating Data for Reverberatory Furnaces
Furnace

Utilization

Capacity

Waste-Heat Steam Production

Charge



Waste Gas Factors

Off Gas Volume

    -Con tent


Dust

Content in Raw Gas

Chemical Composition


Dust Removal

Type of Separator

Efficiency
Melting of copper concentrates

500 ton/day

300 ton/day

Hot roasted material (500° C), quartz
and limestone,  molten copper slag
45,000-65,000 scfm

13%-vol
2-5 grains/scf

6. 2% Cu,  13.0% Zn,  13. 07o S
Wet scrubbers and electrostatic precipitator

95-99%
-------
                                 -807-
                               Table 22.4

                 Operating Data for Reverberatory Furnaces
Furnace

Utilization

Capacity

Waste-Heat Steam Production

Charge



Waste Gas Factors

Off Gas Volume

    -Con tent


Dust

Content in Raw Gas

Chemical Composition


Dust Removal

Type of Separator

Efficiency
Melting of copper concentrates

500 ton/day

300 ton/day

Hot roasted material (500° C), quartz
and limestone,  molten copper slag
45,000-65,000 scfm

13%-vol
2-5 grains/scf

6. 2% Cu,  13.0% Zn,  13. 07o S
Wet scrubbers and electrostatic precipitator

95-99%
-------
                                    -808-
sulfur has been removed and molten copper remains.  If the metal is cast
and solidified at this time,  the product is known as blister copper because
of gases liberated during solidification which produce blisters on the sur-
face of the cast metal.

      The chemical reactions occurring in  the converter are as follows:

                     FeS. + | O2  =  FeO  +  SO2 (gas)

                     FeO + SiO2 -*  FeO  •  SiO2  (slag)

                     Cu2S + O2 = 2Cu + SO2  (gas)

      These reactions are exothermic and continue as long as there is sul-
fur in the metal and as  long as oxygen is supplied.  The operating tempera-
ture is usually about 2250° F. Off-gas volumes of 12, 000-15, 000 cfm are
common and higher flow rates of over 30, 000 scfm have been reported.  The
SO2 content of the off-gas usually averages  about  3. 5 to 7. 0%.  The dust level
in the off-gas runs from 5 to 6 grains  per std cu ft and consists of copper,
zinc,  silica, sulfur,  and iron.  Dust removal from the effluent stream is
usually accomplished by means  of electrostatic precipitators or baghouses.3
Soine operating data are presented in  Table 22. 5.

   Itefining of blister copper.  Blister copper  is purified either by fire or
elec Lrolytic methods.   The furnaces used for fire refining are small rever-
beratory type furnaces  or  a revolving furnace  similar to the copper conver-
ter.   There are a group of fuel burners  to melt the  charge or maintain it in
the molten condition throughout  the  refining operation.   Air is forced through
the molten material to  secure complete  oxidation of all  impurities and then
the oxides are allowed  to rise to the surface of the quiet pool, from which
they are skimmed and then returned to the  converter.  The  oxidizing treat-
ment  is followed by a reducing treatment known as poling.   This is done by
forcing the ends of green logs into the pool  of molten metal.  The highly
reducing gases resulting from the destructive  distillation of the green logs
reduce most of the copper oxide present in  the  metal.  The  resulting product
is called tough-pitch copper and is a useable product in this form.  It will,
however,  contain any gold or silver which may have been present in the
copper.  No information is available on  emissions produced during poling
of the copper.
                                                     SOUTHERN RESEARCH INSTITUTE
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                                -809-
                               Table 22. 5
               Operating Data for a Copper-Matte Converter
Furnace
 Utilization




 Capacity (copper)




 Specific Furnace Load




 Heat  Consumption




 Charge



 Moisture Content






 Waste Gas Factors




 Off-Gas Volume




    -Content






 Dust




 Content in Raw Gas



 Chemical Composition






 Dust Removal




 Type of Separator




Efficiency
Converting of copper matte



35 ton/ charge



2 charge/day



Exothermic process



Molten copper,  matte and solid quartz



None
12,000-13,000scfm




4%-vol
5-6 grains/ft



1.2% Cu, 18.0% Zn,  10% S
Electrostatic and cloth




95-99%
-------
                                   -810-
      A second method of purifying copper is electrolytic refining.  When
an impure copper anode and a cathode are immersed in a solution of cop-
per sulfate and an electric current is imposed across the cell,  copper from
the anode will enter the solution,  and copper ions in the solution will mi-
grate to the cathode and be deposited as metallic copper.  Impurities from
the anode are liberated and settle to the bottom of the cell as a slime.   Pure
copper is precipitated on the cathode.  No particulate emissions are evolved
in this process.

      Figure 22. 5 is a flow diagram showing the steps  in the copper extraction
and refining process.

22. 5  PRODUCTION OF PRIMARY LEAD

      Oxide and sulfide types of lead ore are the only ones that occur in suf-
ficient quantities to be commercially important.  Oxide ores can be directly
reduced in a lead blast furnace charged with ore,  coke and a flux.   Sulfide
ores must first be converted to oxides.  This is accomplished by roasting or
sintering in an oxidizing atmosphere on a traveling bed sinter machine to com-
bust the sulfur and produce a sintered product. After sintering, the material
is charged into a lead blast furnace for reduction to lead bullion.
                         .' v
   Emissions from sinter beds.  Sinter beds used in sintering of lead  sulfide
ores range in size from 3. 5 ft wide and 22 ft long to 10 ft wide and about  120
ft long.  The sinter bed travels in a continuous loop and capacities range  from
about 1. 5 to 2. 75 tons of charged  material per square ft of bed per day.

      The predominate chemical reaction  occurring in the sinter bed is the
oxidation of lead and other metal sulfides present.  In order to achieve good
combustion efficiencies, the sulfide ores are first finely ground and pellet-
ized with coke breeze.  The green pellets  are placed on the sinter bed, ig-
nited,  and combustion is sustained by forced air flow through the bed.   Stack
gas volumes  range from 100 to 220 scfm/sq ft of bed and may contain  up to
about 8% SO2.  Gases also contain small amounts of water vapor,  carbon
dioxide, hydrogen fluoride and silicon tetrafluoride as  atmospheric con-
taminants.

      The dust carried by the gases from the sinter bed may amount to as
much as 5-20% of the feed to the sinter machine.  The dust  usually contains
40-65% lead, 10-20% zinc,  and 8-12% sulfur with traces of other elements
                                                    SOUTHERN RESEARCH INSTITUTE
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                                     -811-
 Combined
    Feed
 Nat.Gas Fue
    Air
            Matte
       Steam
                                    Recycled
                              Silica
          Converter Slag
                                                                      Stack
                                                   Flues
Figure 22. 5.
Flow Diagram Showing Steps  in the Copper Extraction and
Refining Process.
-------
                                  -812-


including selenium, arsenic, cadmium, and tellurium.  The amount of each
will generally correspond to the composition of the sinter bed material.  '
Table 22. 6 presents some general operating data on sintering installations.1>4

      Because  of the high metal content of the particulate of the off-gases,
it is economically justifiable to collect them.  Baghouses and electrostatic
precipitators with operating efficiencies of 95-99% are commonly used.   The
particulate matter in the  gas stream is generally greater than 5^ in size,
although there  may be some fine metallic  fumes. . After collection, the par-
ticulate matter is recirculated  into the sinter bed with new feed ore.

   Lead  blast furnace operation.  After conversion of the sulfides on the sin-
ter machine, the material is charged into a blast furnace along with coke and
limestone.  In  the blast furnace, the following reactions occur:

                    C + O2   -   CO2

                    CO2 +  C  + heat  -  2 CO-

                    PbO + CO +  heat   -   Pb +  CO2

The molten lead collects in the furnace  hearth along with the iron-lime-
silicate slag.  Because of the marked difference in density between the
lead bullion and the slag, separation is  easily effected.

      Some general operating data for blast furnaces are presented in
Table 22. 7.  Blast furnace capacity ranges from 60 to 500 tons per day
throughout.  From 8 to 13% of the charge  will be coke and from 240-800 scf
of flue gases are produced per Ib of coke burned.  The dust content of the
raw stack gases ranges from 2 to 6. 5 grains per scf.  Primary cleaning of
the  raw gas may be done by centrifugal  separators,  but high cleaning
efficiency usually requires the use of baghouses or electrostatic precipi-
tators.4

   Refining of lead.  The end product of the lead blast furnace is an impure
lead which may contain copper, nickel,  arsenic,  silver, gold,  tin, antimony,
and other minor constituents.  In order to purify the  lead and remove the
other elements, further refining is  necessary.

      In  electrolytic refining, the lead bullion is cast into anode plates and
placed in electrolysis tanks.  In this operation,  electric current causes the
                                                  SOUTHERN RESEARCH INSTITUTE
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                                 -813-
                                Table 22. 6
                 Operating Data for Sintering Installations
 Sinter Machine

 Utilization

 Capacity

 Feed

 Moisture content of charge

 Ignited by
Roasting and sintering of galena

50-250 tons/day galena

Concentrate, pre-roasted ore,  flux

6-10%

Gas, oil,  coal,dust
 Waste-Gas Factors

 Volume

 Sulphur dioxide content

 Temperature prior to dust
      removal
48-56 ft /lb sinter

1. 5-8% by volume
300° C
Dust

Dust content of raw gas

Chemical composition
0.9-6.5 grains/scf

40-65% lead
10-20% zinc
 8-12% sulphur and traces of elements
       corresponding to composition of
       mixture
Dust Precipitation

Equipment
Primary:

centrifugal
separators
Secondary:

electrostatic precipi-
tator,  bag filters
Efficiency
80-90%
95-99%
-------
                                    -814-
                                  Table 22. 7
                       Operating Data for Blast Furnaces
Reducing Furnaces

Utilization

Capacity

Fuel Consumption
Reduction-smelting of sinter, ore, lead
scrap and slag with coke and flux
60-500 ton/day  throughput

8-13% coke
Waste-Gas Factors
Volume
    - Content
240-800 scf/lb coke

Less than 16% volume
Dust
Dust Content of Raw Gas
Chemical Composition
2-6. 5 grains/scf

Greatly varying shares of sulphates,
oxides, lead sulfide and coke dust
Dust Precipitation

Equipment
Efficiency
Primary:

Centrifugal
Separators

80-90%
Secondary:

Electrostatic precipi-
tators,  bag filters

95-99%
                                                     SOUTHERN RESEARCH INSTITUTE
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                                   -815-
lead to dissolve in a complex water solution at the anode, and at the same
time lead already dissolved is plated out on the cathode in pure form.   The
impurities are left behind at the anode or remain in solution and must be
reclaimed in subsequent operations.  No particulate emissions are expected
during purification of lead by electrolysis.4

      In kettle or reverberatory furnace refining of lead bullion, the treat-
ment is more complex, but the recovery of the by-products is simpler and
faster.  There are several such refining processes or modifications,  but
basically they have the following steps:

      (1)  Softening,  where oxygen is employed to produce a liquid slag
containing the more  readily oxidizable elements, including antimony,
arsenic,  tin,  and zinc.

      (2)  Noble element removal,  where zinc is added to produce a dross
containing the silver,  gold, copper, and nickel,4 and

      (3)  De-bismuthing,  where magnesium or clacium is added to form a
dross which can  be skimmed  off.

Each of these dross  materials must be further treated to  obtain separation
of the desired elements.  The remaining lead usually has a purity of 99. 999%.

      Very little information  exists on atmospheric emissions produced
during lead refinement.  Undoubtedly,  the reverberatory  stack gases con-
tain small amounts of lead and zinc, but quantitative estimates are not
available.

      A final method of purifying lead is the Imperial process,  which is
basically a tower distillation  method.   In this process, lead bullion from
a blast furnace is heated  in a vacuum  chamber to evaporate lead, zinc, and
other volatile metals.   These elements may then be separated in the vapor
phase by controlling the temperature along the length of the condensation
column.   No particulate emissions are produced in this process.  Figure
22. 6 is a schematic  diagram  of the process showing the location of electro-
static precipitators for lead blast furnace cleaning.  Figure 22.7 shows a
rotary furnace rather  than a blast furnace.
-------
                                -816-
                              Wire and Tube Precipitator
Crude Gas from_
the Furnaces
  Cooling Medium——4~fjfc-
       Evaporating
           Cooler
                      Dust
         ID-Fan-*-\

Dust  Dust
 Figure 22. 6.  Schematic Diagram  Showing Electrostatic Precipitators
               Used for Blast Furnace Gas.
                                                    SOUTHERN RESEARCH INSTITUTE
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                                     -817-
Galena
Concentrate
   Soda Ash
     Coal
                         -
                  Sintering
                  Machine
To Siflfuric Ac^d Plant or Chimney
                                         Electro*
                                        Precipitatoi
               Electro-
               Precipitator
                                   Bullion II •+-
                              I
                           Bullion
    Slag
1 U '
try Furnace II
1
|P Slag
_- 1
T Short Eotary Furnace
Bullion I
o^ag
— -
1^
1
,
» «


                   Zinc-Bearing
                    Fuel Dust
Figure 22. 7.  Electrostatic Precipitator Operating on a Rotary Furnace.
-------
                                  -818-
22. 6  ZINC REDUCTION

      Most zinc produced in the United States is extracted from ores con-
taining both zinc and lead sulfides,  although some zinc and copper-zinc ores
are processed.   The ores are concentrated,  usually by flotation, prior to
the extraction process.

      The concentrated ore is dried and processed in a roaster to convert
the zinc  sulfides into a dense oxide. The sulfur dioxide off-gases are often
used to produce sulfuric acid by the contact process, which is  described
in the  chapter on chemical industry applications.
i              !
      Metallic zinc is produced from the roasted ore by retorting,  electroly-
sis, or fractional distillation.

      Roasting of zinc ores takes  place in one of several types of furnaces.
In this country, there are 12 plants reportedly roasting zinc  ores  using fluid
bed, flash, multiple hearth, and Ropp roasters.  The Ropp roaster is the
oldest type furnace in use.   It is a type of reverberatory furnace which has
largely been replaced by more modern roasters.  Table 22.8 lists the  opera-
ting temperature, capacity,  dust  emission, and percentage of SO2 in the
off gas.

      Figure 22. 8 is a flow diagram for a zinc plant utilizing a retort
process  for zinc reduction.  In this process the roasted ore  is mixed with
coal and briquetted prior to  charging into the retort.  As  indicated in the
flow chart, the roaster calcine is sintered to agglomerate it  prior to sub-
sequent processing.  Table 22.9 shows the capacity, dust, and SO2 con-
centration in the off gas for  typical zinc sintering  operations.

      In  the retort process,  the charge,  consisting of roasted ore and coke,
is charged  into the retort and  heated to a temperature where the zinc oxide
reacts with the carbon to produce zinc metal and CO2.  At these tempera-
tures,  the zinc comes off as vapor and is led to a  condenser, where conden-
sation to molten  zinc occurs.  The molten zinc from the condenser is tapped
at intervals and cast into billets.

      In  the electrolytic process,  sulfuric acid is  used to dissolve the zinc
ore to form the electrolyte for the electro-deposition process.  Zinc is
plated  out on aluminum electrodes,  which are then stripped for recovery of
the zinc.
                                                   SOUTHERN RESEARCH INSTITUTE
-------
                                    -819-


                                  Table 22.8

                       Typical Zinc Roasting Operations1


Type of Roaster
Multihearth
Multihearth2
Ropp8
Fluid Bed4
(Dorr -Oliver)
Fluid Bed8
(Dorr-Oliver)
Fluid Bed
(Lurgi)
Suspension
Fluid Column

Operating
Temp, °F
1200-1350
1600-1650
1200

1640

1650

1700
1800
1900
Feed
Capacity
ton/ day
50-120
250
40-50

140-225

240-350

240
120-350
225
Dust in
Off Gas
% of feed
5-15
5-15
5

70-80

75-85

50
50
17-18

Off Gas
SO,
4.5-6.5
4. 5-6. 5
0.7-1.0

7-8

10-12

9-10
8-12
11-12

Volume
scfm
5,000-6,000
5, 000-6, 000
20,000-35,000

6,000-10,000

6,000-10,000

6,000-10,000
10,000-15,000
N. A.
 Dead roast except where noted otherwise.

8First stage is a partial roast in multihearth, second state is a dry-feed
 dead roast in Dorr-Oliver fluid bed.

 Partial roast.

4Slurry feed.
-------
                                   -820-
                         Feed
                   Zinc and Lead Ore
           Shaft
           Furnac
       Slag

        Lead
        and Precious Metals
        Copper Matte
                    Exit Gas to Gas
                    Washing System

                  Cooling Launder

                    Lead Recirculated
                    to Condenser
                      Zinc
           Separation
Hot Blast
Figure 22. 8.   Flow Diagram for a Zinc Plant Utilizing a Retort Process
               for Zinc Reduction.
                                                   SOUTHERN RESEARCH INSTITUTE
-------
                                  -821-


                                Table 22.9

                     Typical Zinc Sintering Operations
Case;                                 1             2

Total Charge Capacity,
 tons per day                     240-300        400-450       550-600

Machine Size, ft                   3.5 x 45       6 x 97         12 x 168

Dust in Off Gas, % of feed              5            5-7            5-10

Off Gas SQj Content, %             1. 5-2. 0         0.1          1. 7-2.4
-------
                                  -822-
      Residues from the zinc processes often contain lead, gold, and silver,
which can be economically recovered by subsequent processing.

      Dust collection equipment in the production of zinc is usually required
on the effluents from dryers, roasters, and sinter machines.  The dry pro-
cesses of dust removal are bag filters  and electrostatic precipitators.  Wet
processes consist of scrubbers.   The choice of the type of dust collection
equipment depends upon the  individual situation and each application has to
be decided on its own merit.

22. 7  SUMMARY OF PRECIPITATOR OPERATION CONDITIONS
 6
      As  indicated previously, design of precipitators for the nonferrous
metals industry is largely handled by the smelters on a do-it-yourself basis.
Table 22.10 lists the basic design data for 3 converter gas precipitators, ,3
copper roaster reverberatory furnaces, 1 sinter machine, and  1 acid mist
precipitator.  Figure 22. 9 shows  the variation in efficiency with _ ratio for

the 3 converter gas,  2 roaster gas, and 1 sinter machine gas precipitator
for which data are available.

22. 8  PRECIPITATOR INSTALLATIONS AND ECONOMICS

      A summary of available statistics on precipitator performance in
nonferrous metallurgical industries is  shown in Table 22. 11.  Statistics
on roasters, sinter  machines, miscellaneous nonferrous, and the alumi-
num industry applications are contained in Tables 22. 12 through 22. 15,
respectively.

      Available records  on these applications are limited, and  therefore
estimates on total precipitator use would be highly speculative.  In general,
the aluminum  industry offers the most promise for possible increased use
of electrostatic precipitators.

   Economics.  Precipitator cost data for roasters,  sinter machines, and
the various aluminum applications are presented  in Tables 22.16 through 22.18,
respectively.   Due to the limited amount of data,  no attempt  has been made
to adjust the costs to a common base.

   Performance statistics.   Due to the limited amount of performance data
available  and the fact that most of them are old and  do not reflect present
day state-of-the-art performance, no statistical analysis has been attempted.
                                                SOUTHERN RESEARCH INSTITUTE
-------
                                        Table 22.10

                            Summary of Electrostatic Precipitators*
                               in Western Smelters Prior to 1920
Precipitator
Application
Converter Gas
Roasters and
Reverberatory
Furnaces
Sintering
Machine
Acid Mist (using
No. of
Install.
3
3
1
1
Volume of
Gas Treated
(lO'acfm)
519
2,475
172
27
Precipitator
Gas Velocity
(fos)
1.3-5.6
2.6-15
8
6.5
Efficiency
Range
(%)
90-99.6
75-85
94.5
_—
Comments
Due t- type -precipitator
Pipe and ductprecipitators
Pipe precipitator
Pipe precipitator
                                                                                                        I
                                                                                                        00
roaster gases)
Total
8
3,193
*Most of these precipitators were built by the smelter owners themselves under
 patent licensing agreements
-------
                                       -824-
   99.9
 >; 99
 c

 d>
• rH

 U
w

fl
o
•r-l
•«-»
U
U
   90











Sinter Macl:
n




A
.< /
/
/
/
/
/
/












line ^
/
/
/
/
o
Vplant I
/Plant 1
Plant 2














>
/
/
/, ,,

/
/
/
/
/ OP1
y
^

w = 0. 065 :


replant 2 (converter;





I (converter












)
QSint€




ant 1 (conve


?t/see (2. 05













rter)



cm/sec)








jr Machine
OConverter Gas Precipitator
^Copper Roasters














                    0.4        0.8          1.2         1.6        2.0


                         Specific Collection Electrode Area,  ft2/cfm



       Figure 22.9.  Collection Efficiency as a Function of Specific Collection

                     Electrode Area (ft2/cfm) for Nonferrous Installations.
                                                       SOUTHERN RESEARCH INSTITUTE
-------
                           Table 22.11




Precipitator Performance in the Nonferrous Metallurgical Industries
Preclpttator Application
1. Converter Gas



2.

3.
4.
Plant 1
Plant 2
Plants
1
i
TM»e _
Duct
Duct
Duct
Copper Roasters and
Reverberator? Furnaces
Plant 1 Pipe
Plant 2 Duct
Plants
Sintering
Plant 1
Acid Mist
Plant 1
Duct
(Vertical Flow)
Pipe
Pipe
to. of
Units Collection Test Gas Test Treatment
or Area Vol Vol Time
Pipes sq ft 1000 eta ft/sec sec

20 43.200 28.9 1.3 22
30 95.0(0 119.0 4.4 12
72 201.960 379 9.6 8
1512
12"xl2' 57.000 350 4.9 2.4
27 110.880 629 11-19 2.2
20 403.200 1900 2.6 8
1800
6"xl2' 33.930 171.8 8.1 1.5
294
10" x 12' 7.980 27 6.5 3.7
Sqrt Dust
per mA Collection Performance
Collection Area Electrical per per day w
sqft/ 1000 cftn Set 1000 »q ft tons Efficiency ft/sec

1900 4320 7-12 99.0-90.6 0.05-0.06
836 4790 96 0.069
539 4200 11.8 29 90 0.07
163 6333 75 0.14
177 4100 24-94 90-100
269 79kVAsets 9-6 89 0.12
40320
197 ISkVAseta 47 $ 94.5 0.24
3393
295 3990




CO
CO
en
i



-------
                          Table 22. 12


Electrostatic Precipitator on Roasters* Period 1923 through 1969
Precipitator
Contract
Year
1923-1929
1930-1939
1940-1949
1950-1959
0
-1
z
m
X
•a
Z
m
a
o
X
v>
H
c
H
m

1960-1969




Totals


*This includes

No. of
Install
10
15
6
4

7




42


hearth.

Number of
Precipitators
12
19
9
6

12




58


Total Gas Accumulated Weighted Design
Volume Gas Volume Efficiency on
(10s acfm) (103 acfm) acfm Basis (%)
260. 7 260. 7 94. 9
405.2 665.9 95.0
197. 4 863. 3 96. 8
200. 6 1063. 9 96. 5

379.4 1443.3 98.0




1,443.3


flash, and fluid roasters for zinc, zinc-lead,
molybdenum sulfide and pyrites.








                                                                                            I
                                                                                           00
                                                                                           CO
                                                                                           Oi
                                                                                            I
-------
                                    Table 22. 13

                  Summary of Electrostatic Precipitators for Cadmium
                   Recovery Zinc Sinter Machines (1935 through 1955)
Precipitator
  Contract
    Year
                         Total Gas
No. of     Number of     Vplume
Install.    Precipitators  (10 acfna)
                         Accumulated
                         Gas Volume
                          (10s acfro)
                           Design Efficiency
                             Prorated on
                           acfm Basis
1935-1944
1945-1955
 8
19
 420. 5
                           594. 5
520.5
                          1015.0
95.0
                                95.0
                                                                                                    00
Totals
15
26
1015.0
Note: No record of any new installations since 1955.
-------
                                        -828-
                                      Table 22.14

                Summary of Electrostatic Precipitators for Miscellaneous
                               Nonferrous Applications (*)
                	1924 through 1968	
                                                                      Design
Precipitator    Number of       Number of       Total Gas        Efficiency Range
Application     Installations    Precipitators   Volume (10  cfm)          (%)	
1.  Tin
    Smelting

2.  Copper
    Smelting

3.  Lead
    Blast
    Furnace

4.  Precious
    Metals
                 6
                25


              1478


                47



               208
                      98.0


                      95.0


                   90.0-95.0



                      90.0
   Totals
12
21
1758
* Does not include aluminum industry applications.
                                                       SOUTHERN RESEARCH INSTITUTE
-------
                                        •829-
                                     Table 22. 15

             Summary of Design and Application Parameters on Electrostatic
                        Precipitators for the Aluminum Industry
            	(1940 through 1967)	
Precipitator
Application
                  DESIGN
Temperature
     of  -
             RANGE

Gas Volume
    Per                   Dust
Precipitator   Efficiency  Loading
 (l(f acfm)	(%)      (gr/acfm)
Comments
1.  Carbon Plants   50-175
   (Carbon & Coke
      Dust)
2. Alumina
   Calcine rs
   350-600
3. Aluminum      200-225
   Pot Line
4. Remelt
   Furnace
   200-600
5. Soderberg      150-200
     Gases
                15-200     ;  98.0-99.0   10-40
 60-200       95.0-99.0    5-10
               100-125       90.0-95.0    0.1
  10-25            95.0
                  50              90.0    0.1
                                      App r ox im ately
                                      10 installations
Approximately
10 installations

Approximately
15 precipitators
                                      Approximately
                                      30 precipitators
-------
                   -830-






                Table 22. 16




Cost Data for Electrostatic Precipitators for

Precipitator
Contract
Year
1946
1951
1953
1954
1966


1967

1969
UNIT COST $ /acfm
FOB Erected Total Gas
Volume
(103 acfm)
1. 97 42. 0
2.17 41.0
3.40 , 37.5
6.75 12.0
1.90 26.2
6. 00 20. 0
4. 25 47. 0
0.90 81.5
4.60 33.0
1.75 79.2

Design
Efficiency
(%)
98
98
96
95
99
98
97
95
99
99
                                 SOUTHERN, RESEARCH INSTITUYE
-------
                 -831-
               Table 22.17

Economics on Electrostatic Precipitators for
  Cadmium Recovery Zinc Sinter Machines
UNIT COST $ /acfm
Precipitator FOB Erected
Contract
Year
1945 0. 98
1946 1. 20
1947 1. 18
1951 0.90
1953 3. 00
1955 2. 00
Total
Gas Volume
(103 acfm)
150
100
50
150
12.5
32.0
Design
Efficiency
(%)
95
95
95
95
95
95
-------
                             -832-






                           Table 22.18



Economics on Electrostatic Precipitators in the Aluminum Industry
Precipitator
Contract
Year
1956


1962
1965
1967
1951
1953
1951
1952
(a) CALCINERS
UNIT COST $ /acfm
FOB Erected Total
Gas Volume
(103 acfm)
0. 75 126
0. 68 90
0. 46 400
1.10 50
0.66 60
0.72 70
(b) POTLINE AND SODERBERG GASES
0.70 1,380
1.00 1,320
(c) CARBON PLANT
1.90 70
2. 00 10
Design
Efficiency
(%)
98
95
98.9
93
78
95
90
90
98
95
                                          SOUTHERN RESEARCH INSTITUTE
-------
                                 -833-
Instead,  individual measurements for a number of installations in the roaster
and sinter machine applications are presented to indicate the process param-
eters such as gas volume, gas temperature, dust loading, etc. These data
are presented in Tables 22.19 and 22.20.

   Design methodology.  The procedures used in the selection of types of pre-
cipitators for dust control in the noferrrous metals industry are discussed in
the sections describing the particular process equipment.

      The methodology for determining the collecting plate area is similar
to that used in sizing precipitators for other application areas, in that the
basic Deutsch-Anderson equation is used.  This equation, which relates
efficiency to collection plate area,  gas volume, and precipitation rate
parameter is

                       N = 1 - exp (— w)

      As in the other application areas,  the critical parameter in deter-
mining the collecting plate area is the value of the parameter w, which
depends  upon the resistivity and particle size of the dust, quality of gas
flow, reentrainment of the dust, and the particulars of the precipitator
design.

      As indicated previously, design of precipitators for the nonferrous
metals industry is largely handled by the smelters.
-------
                -834-
             Table 22.19

Performance Statistics on Roaster Gas
      Electrostatic Precipitators
             (1933-1953)

Installation
Number
1
2
3
4
5
6
7
8
9
10

Gas Volume
(103 acfrn)
15.5
6.25
15.8
13.1
20.0
18.5
17.7
13.3
18.5
50.4
•
Efficiency
(%)
97.4
97.8
96.5
95.0
95.1
98.8
98. 0
96.0
94.9
86.8

Gas Velocity
(ft /sec)
2.3
1.2
1.5
1.4
4.8
2.0
2.9
1.5
2.0
2.8
Dust
Loading
(gr/scfd)
40.0
5.1
8.6
6.2
1.9
15.0
1.1.7
9.5
7-1
9.3
Gas
Temp
CF).
1100
450
450
540
900
500
900
900
500
500
                                 SOUTHERN RESEARCH INSTITUTE
-------
                     -835-
                  Table 22. 20

  Performance Statistics on Cadmium Recovery
Zinc Sinter Machine Gas Precipitators (1935-1955)

Installation
Number
1
2
3
4
5
6

Gas Volume
(10? acfm)
35
35.4
54.3
35.4
26.1
11.0

Efficiency
(%)
97.0
95.8
94.1
97.4
91.7
96.5

Dust Load
(gr/scfd)
1.59
3.96
1.24
4.99
1.17.
0.38
Gas
Temp
(oF)
220
205
200
192
250
213
-------
                                 -836-
                              CHAPTER 22
                            BIBLIOGRAPHY
1.  "System Study for Control of Emissions Primary Non-Ferrous Smelting
   Industry, "  Arthur G.  McKee and Co. (June 1969).

2.  "Restricting Dust Emissions from Copper-Ore Smelter, "  VDI-2101,
   Kommission Reinhaltung der Luft (January 1960).   '

3.  "Restricting Emissions of Dust from Copper Scrap Smelters, " VDI-2101.
   Kommission Reinhaltung der Luft (January 1960).

4.  "Restricting Dust and Sulphur Dioxide Emissions from Lead Smelter, "
   VDI-2285.  Kommission Reinhaltung der Luft (Sept. 1961).
                                                  SOUTHERN RESEARCH INSTITUTE
-------
                                 -837-
                               CHAPTER 23
        THE APPLICATION OF ELECTROSTATIC PRECIPITATORS
   TO THE CLEANING OF HIGH PRESSURE. HIGH TEMPERATURE GASES
      The cleaning of gases at high temperature and pressure is a unique
application for electrostatic precipitators.  Above about 600°F, fabric fil-
tration is not suitable because of limitations on the fabric material. Aqueous
scrubbers are also not suitable at temperatures much above the boiling point
of water.  Some consideration has been given to the use of inorganic liquid
scrubbers at elevated temperatures; however,  costs are generally high so
that at the present time there is no commercial use of high temperature
inorganic liquid scrubbers.

23. 1  HIGH PRESSURE, HIGH TEMPERATURE PROCESSES

      There are several processes which require either high pressure or
high temperature gas cleaning or a combination.of the two.  These processes
are discussed as special applications in which there may be potential for
expanded  uses of electrostatic precipitators.

   High temperature coal gasification.  One of the earliest uses of electro-
static precipitators in high temperature gas cleaning was in the removal of
solids from gases produced in the high temperature gasification of coal.
Early work in this  area was in connection with the development of coal-fired,
gas turbine locomotives.   The U.  S.  Bureau of Mines has conducted research
and pilot-scale developmental studies of coal gasification over a period of
many years.

      In the process of gasification, finely divided coal is burned in a fluidized
bed chamber that is maintained at high pressure and temperature, typically
1500°F and 600 psi. The gases produced in the process are used to drive gas
turbines for electric power generation.

      Fly ash generated in the gasification process must be  removed before
the gas can be used in gas turbines, since the dust would erode the turbine
blades.

      Pilot-plant gasification systems have been operated by the U. S. Bureau
of Mines and gas cleaning by electrostatic precipitators has been demonstra-
ted on these pilot-scale plants.  However,  at the present time,  economic
factors do not favor the gasification process, and no full-scale  plants  have
been built.
                                                   SOUTHERN RESEARCH INSTITUTE
-------
                                -838-
   Waste incineration with gas turbines.  A second type of gas cleaning
application involving  high pressure and temperature is in the cleaning of
gas from incinerators in which the gas is to be used to power gas turbines
for electric power generation.  In many types of incinerators, the disposal
of waste material is an exothermic process, and recovery of heat from the
effluent gases is  economically important.  Most heat recovery systems
involve the production of steam in waste heat boilers located at the exit of
the incinerators.  Recent studies indicate that a more economical method
of heat recovery may result from the use of effluent gases to drive a gas
turbine which, in turn,powers an electric power generator.  This system
requires that the particulate be removed from the gases to prevent erosion
of the blades of the gas turbine.

      Current studies of the technique of direct turbine drive from incin-
erator gases are being conducted under contract with the Bureau of Solid
Wastes.

      The pilot plant  system being investigated is shown schematically in
Figure 23. 1.  The refuse is sorted, shredded,  and dried in a rotary drier;
It is then transported to a pressurized fluid-bed combustion chamber.  Com-
bustion air is  supplied under pressure from a blower coupled to the turbine
shaft.  The gas flows upwardly through a combustion zone and then out of the
chamber through primary cyclonic type collectors.  The fly ash collected
in the cyclone is  blown out of the reactor and combined with the bottom ash
from the fluid-bed chamber.

      After leaving the  reactor, the gas, underpressure, is passed through
an electrostatic precipitator for a final cleaning prior to being delivered to
the turbine.   Additional heat can be recovered by a waste heat boiler located
in the exit gas stream from the turbine.

23. 2  INFLUENCE OF TEMPERATURE AND PRESSURE
      ON PRECIPITATOR PERFORMANCE

      Temperature and pressure of the gas  have several important effects
on precipitator performance.  First, gas viscosity increases with tempera-
ture.  For example,  the viscosity of air at 200°F is about 0. 02 centipoise
and increase to about 0. 04 at temperatures around  1200°F.  From the
equation defining migration velocity, a twofold increase in gas viscosity
reduces the migration velocity proportionately.  Consequently, one would
anticipate reduced performance due to the increase in gas viscosity.
*Refer to the bibliography for this chapter.
-------
                                                                         740* F ».   360° F
c

X
m

z
PI

9)
O
X

z ',


H
C

m
                                                 TURBO-ELECTRIC
                                                    i SUBSYSTEM
                                              AIR INT
                                                              U
 740° F
                                                          MECHANICAL
                                                          COLLECTOR
                                                                                            EXHAUST
                                   SEPARATOR _—,
                                                                      ELECTRICAL
                                                                      COLLECTOR
                                  PRESSURIZED

                                     FEEDER
                                                                                                        oo
                                                                                                        CO
                                                                                                        CO
U
Figure 23.1.  Schematic Diagram of Pilot Plant for Incinerator Gas Turbine System
              Utilizing Electrostatic Precipitator for Fine Cleaning of Turbine Gas.
-------
                                -840-
      A second influence of temperature and pressure on performance is
the gas volume.  Gas volume is directly proportional to the absolute gas
temperature and  inversely proportional to pressure.  These effects tend
to offset each  other when high pressure and temperature are both involved,
so that gas density is not much affected.

      Finally, gas temperature and pressure influence the volt age-cur rent
relationships by altering the corona starting voltage and sparking conditions.
Increasing temperature tends to lower the corona starting voltage and reduce
the voltage at  which sparking occurs.  Increasing pressure, on the other
hand, tends to increase the corona starting potential and the voltage at which
the sparking begins.

      With negative corona, limitations on current and voltage occur at
relatively low temperatures at atmospheric pressure.  However, at high
pressures,  adequate voltage can be maintained to give good precipitation.
On the other hand, positive corona generation is not affected to as great
an extent and experience indicates that positive corona precipitators may
be superior to negative corona at temperatures higher than about 1500°F.

      A discussion of the voltage-current characteristics and the influence
of temperature and pressure is given in detail in Chapter 1, Part I.

23. 3  PRECIPITATORS FOR HIGH TEMPERATURE,
      HIGH PRESSURE OPERATION

 '     Precipitators for high temperature,   high pressure service can be of
several types, providing allowance is made for thermal expansion,  and for
accommodating the high pressures.  The latter complicates the problem of
dust removal and of providing electrical power to the precipitator.

      A pilot unit for  high temperature, high pressure dust collection that
has been operated in limited tests consists of an 8-inch diameter pipe, 15
feet long with  three 0.109 in. diameter wires twisted together as the discharge
electrode.   The collecting  surface area Is 31.4 ft2 with a cross-sectional
area of 0. 35 ft2.

      Migration velocities  of about 0. 23 to 0. 26 were obtained when precipi-
tating a simulated dust (alumina)  with a mass median diameter of about
2.75M with field strengths  (voltage/electrode spacing) of 10-11 kV/in.
-------
                                -841-


     Projections to full size units would  indicate the following:


                                Table 23. 1

               Projections from Pilot Precipitator Tests for
              	Cleaning of Turbine Gas
          Gas flow (mass)                       210 Ib/sec
          Temperature                          1650° - 1700°F
          Pressure                             100 psig
          Gas velocity                          8.25 ft/sec
          Gas volume                           43, 500 acfm
          No. of 8 in. precipitator tubes         250
          Collecting area                        8400 ft2
          Tube  Length                          16 ft
          Length of discharge wire               4000 ft
          Voltage                               50 kV,  avg.
          Current                              2680 mA
          Precipitation rate parameter (w)       0.26 ft/sec

      These values are preliminary, based on extrapolation of the pilot-
scale unit; however, they indicate the range of values that might be
expected.

23. 4  CLEANING OF NATURAL GAS IN PIPELINES

      An application of precipitators to the cleaning of high pressure gas at
low temperatures is in the removal  of submicron oil fume from natural,gas.
In the transmission of natural gas in pipelines,  compressors release small
amounts of lubricating oil which accumulate  in the pipeline and cause
loss in transmission efficiency.  Manual cleaning of the pipeline is accom-
plished  by passing a plug (called a pig) through the pipeline to remove the
oil deposits.  The process of pigging is expensive and economics would
seem to favor the reduction of the frequency of pigging by removal of the
oil mist.  In the past,  filters, scrubbers,  and cyclones have been used in
this application. However, high pressure electrostatic precipitation has
been used in this application, with apparent satisfaction.
                                                   SOUTHERN RESEARCH INSTITUTE
-------
                                 -842-
      Table 23. 2 shows the precipitator design and operating conditions for
gas pipeline cleaning.

                                Table 23.2

                         Gas Pipeline Precipitator
                         Design and Operating Data
      Gas composition
      Gas temperature
      Gas pressure
      Gas viscosity
      Gas density ratio (basis 60°F, 15 psi)
      Gas density (specific gravity = 0.6
                  relative to air)
      Gas flow rate, millions of scf per day
      Gas flow rate at standard conditions
      Gas flow rate at conditions
      Collection efficiency
      Oil mist collected
      Particle size
      Installation
      Pressure vessels

      Particle concentration

      Precipitator voltage
      Precipitator current
      Corona power
      Duct Reynolds No.
      Pressure drop
      Power input
94% methane
90° - 130°P
830 - 860 psi
1.2 x 10"4 poise
51.5 av,

2. 36 Ib/cu ft
300 - 400
208, 000 - 278, 000 scfm
4,000- 5,400 cfm
99% by weight
9-10 gal/d max
0.1 - 1 micron
2 parallel pptrs  on 26" pipeline
ASME code, 900 psi;
hydraulic test,  1800 psi
7 x 10~5 to 2.4 x 10"4gr
scf (0. 0034 - 0. 012 gr acf)
55 - 58 kV av.
80 - 90 mA DC
1 watt/cfm
1.4 x 106
0.1 psi
12 kVA
-------
                                   -843-
      One installation of a precipitator for natural gas pipeline was made in
1967.  It is a horizontal-flow, duct-type consisting of two parallel units,  each
unit consisting of two 5-foot sections 2 feet high, with 3-inch duct spacing.
Each precipitator unit is contained in a 36-in. diameter pressure vessel
shell designed for 900 psi at  140°F.  Conical inlet and outlet transition
sections approximately  6 ft long connect to the 18-in. diameter pipe.

      The precipitator is equipped with a wash-in-place system  composed of
a pipe manifold and spray nozzles above the plates.  The spray system capa-
city is 48 gal/min at 10 psi.  Kerosene-type  hydrocarbon fluid is used for
washing.

      The discharge electrode system  consists of wires, 10 mils in diameter,
strung under tension between a top and bottom support frame.  The wires are
centered between adjacent collecting plates.   The high voltage discharge
frame is supported  by insulators located in and fastened to  the sides of the
precipitator.

      The collecting electrodes are flat metallic  sheets carried  by top and
bottom spacer bars.  Openings are provided  in the plates to accept the
passage  of the high  voltage support members.  The downstream end of
each plate is equipped with a  shield in order  to eliminate any reentrain-
ment of  oil from the end of the plate.

   Energization system  for pipeline precipitator.  The  high voltage ener-
gization  system consists of a dry-type,  encapsulated, high-voltage,  step-up
transformer, coupled with a full-wave,  solid-state rectifier,  and is provided
with a fully automatic control system.   The power pack is contained in a
compartment appended to the precipitator and is  exposed to full  gas  line
pressure. The low voltage line  controls are  located externally to the
pipe lines.

      Since the precipitate is free flowing,  removal consists of draining
the precipitator pan to an appended pressurized sump from  where the oil
is periodically blown out by pipeline pressure.

   Economics.  The FOB cost of pipeline precipitators  to handle 2 x 109 scf
per day of natural gas at 800  psia at  98. 5% collection efficiency  is reported
to be on  the order of $10/acfm.
                                                 SOUTHERN RESEARCH INSTITUTE
-------
                                 -844-


                            CHAPTER 23
                          BIBLIOGRAPHY
1. Brown, R. F., "An Experimental High Temperature-High Pressure
   Precipitator Module Design and Evaluation," Final Report on
   Contract P. H. 198.3, Research-Cottrell, Inc., Bound Brook,
   New Jersey (Sept. 26,  1969).

2. Shale, C. C., et al.,  "Characteristics of Positive Corona for* Electrical
   Precipitation at High Temperatures and Pressures,"  Bureau of Mines
   Report of Investigations No.  6397, No. 3  (1964).

3. Hall, H. J.,  Brown, R. F., Eaton, J. B. and Brown, C.  A.,  "Removal
   of Lube Fume Raises  Line Efficiency," Oil and Gas Journal (September
   9, 1968).
-------
                                   -845-
                               CHAPTER 24
                   NEW PRECIPITATOR APPLICATIONS
      The choice of the type of dust control equipment for any gas
cleaning application depends upon economic and process factors.  In
many instances,  a particular type of dust control equipment may
historically have been utilized for certain types of service, and trends
are often followed when control equipment is selected for an application
in which there has been a history of successful performance in similar
service.  In a number of application areas, a variety of types of dust
control equipment has been used  successfully, and the choice in such
cases is dependent upon local factors or often upon personal preferences.

      The major types of equipment for control of industrial dust
emissions are mechanical collectors,  fabric filters,  electrostatic pre-
cipitators,  and wet scrubbers. Mechanical or inertial collectors can
be of the low-loss type such as cinder traps,  which are  used to prevent
fallout of large particles in the vicinity of the plant, or of the high-
draft-loss type for higher collection efficiency.

      Mechanical cyclone collectors are of the high-draft-loss type and
are used on particles in the 10-200|i range.  The efficiency of cyclone
collectors varies with the size of the  dust, and decreases rapidly for
particles under IQju diameter.  Figure 24.1 shows the collection effi-
ciency of a mechanical cyclone collector as a function of particle  size
and pressure dropf  Mechanical collectors are often  used in combination
with electrostatic precipitators for control of fly ash from power  plant
boilers.

     Wet scrubbers remove particulate from a gas stream by
impinging the gas against water fog or a wetted surface.  The simplest
type of scrubber involves a water spray to provide small diameter liquid
particles which contact the dust-laden gas.  On contact,  the dust
particles are transferred from the gas stream to the scrubbing liquid
and are removed from the gas along with the liquid under the influence
of centrifugal or gravitational forces.  Simple spray  chamber or packed
tower scrubbers are inefficient for removal of small size dust.

     For small particles, high energy wet scrubbers are used to achieve
high collection efficiencies. The collection efficiency for a given size is
iRefer to the bibliography for this chapter.
                                                     SOUTHERN RESEARCH INSTITUTE
-------
                                -846-
100
                                                       10% less than 10
                                                       20%
 40
                   1.0              2.0
                      Pressure Drop, in. of water
3.0
4.0
  Figure 24.1.  Performance of Typical Mechanical Cyclone Dust
                Collector (Reference 1).
-------
                                   -847-

directly related to the gas pressure drop across the scrubber,  and for
high collection efficiencies of small particles, pressure drops  of
3-100 in.  water are used.  An added advantage of the wet scrubber is
that gas absorption can also occur during the process of particulate
removal.   Major difficulties involved in wet scrubbing lie in high
operating costs if large gas volumes are to be handled, disposal of the
scrubbing liquid or sludge, and loss of plume buoyancy.  Steam plumes
formed from scrubbing hot gases are a further disadvantage of wet
scrubbers,  and if steam plume suppression is required, costs  are often
high.

      The power required to move gas against a given pressure drop is
given by


      P -  v x p x 746
            6356 XT]

where
      v =  gas volume handled, cfm,
      p =  pressure drop, in.  water,
      P =  input power, kW, and
      7j =  combined fan and motor efficiency.
      For a gas volume of 1x10  cfm and a 10 in. pressure drop, the
power required for a 50% efficient fan and motor combination would be

      _.    1x106 x 10 x 746  _  OOAA,,W
      P  =    6356 x 0. 50    '  2360kW'

      Fabric filters are intrinsically high efficiency collection  devices,
and are particularly suited to controlling dusts where low gas volumes
are handled.  Fabric filters are limited to temperatures less than about
600°F,  to effluents that do not chemically attack the fabric,  and to  dusts
that do not clog or foul the collectors.

      Economic considerations in the  selection of dust control equipment
include capital investment,  operating  costs, and maintenance costs of
the dust control facility.

      The installed or capital cost comparisons for a particulate control
system must be carefully made for the specific application.   They include
                                                     SOUTHERN RESEARCH INSTITUTE
-------
                                   -848-
the cost for the control device itself, installation costs, and cost of
                                                         -      2  '
any auxiliary equipment that may be required.  Edmisten,  et al.,
presents typical capital  cost data for low, medium, and high collection
efficiencies of dry centrifugal collectors,  wet collectors,  electrostatic
precipitators,  and fabric filters.  These are given in Figures 24. 2
through 24. 5.  Figure 24.6 shows installed cost of electrostatic preci-
pitators as a function of gas volume handled.

      Installation, operating,  and maintenance costs for the various
types of collectors are summarized in Table 24.1.

      Figure 24. 7 is a comparison of the total accumulated costs  of an
electrostatic precipitator, fabric filter, and wet scrubber, for collection
of a particular fine dust. The procedure used in. calculating the costs
is as follows:

  Total Accumulated Cost = FOB Cost + Installation Cost -f (Annual

        Operating  Cost + Annual Maintenance Cost)  (t Years)

      Cost (Electrostatic Precipitation)  = $136, 000 + $  5, 500 t

      Cost (Fabric Filter)              = $ 110, 500 + $ 24, 500 t

      Cost (Wet Scrubber)              = $  37, 500 + $51,500 t
Data used in the calculations are those of Walker3 and are shown in a
comparative breakdown in Table 24. 1.  The total costs are for a small
(100, 000 cfm) installation.

      The economic considerations in the selection of dust control
equipment should be resolved for a particular application based on
analyses which indicate the long-term costs of comparative dust control
equipment.  The cost analyses should be carefully studied to insure that
they are made on a comparable basis.  Generalized cost data,  even within
a given application area,  can be in error by a considerable margin if dust
and gas properties vary,  as they often do.   Consequently,  the  cost analyses
-------
                                -849-
                                                i	r	p.  -T--
                                                           103 acfm
                                            Cost of indicated efficiency may
                                            vary * 20% of reported figure.
                         50        100

                      Gas Volume Through Collector, 10s acfm
L	I	L_JL_L_
  500      1000
Figure 24. 2.  Purchase Cost of Dry Centrifugal Collectors (Reference 2).
                                                  SOUTHERN RESEARCH INSTITUTE
-------
                                        -850-
1000
 500
 100


3

|


£lO
i  I I  I
                        i
                                                   III!
             J	1—i   I  i  i
           TT
                                                                               i~r i
                      5      10                50      100

                           Gas Volume Through Collector,  101 acftn
J	1	1	l_JL_l_Ll_
                                                500     1000
           Figure 24. 3.  Purchase Cost of Wet Collectors  (Reference 2).
-------
                                     -851-
1000
                                                       Cost of indicated efficiency
                                                       may vary — 20% of reported
                                                       figure.
                                                                     500
1000
                         Gas Volume Through Collector,  10s acfm
   Figure 24. 4.   Purchase Cost of High-Voltage Electrostatic Precipitators
                   (Reference 2).
                                                         SOUTHERN RESEARCH INSTITUTE
-------
                                          -852-
100
 50

 .10
-------
                                     -853-
1000 r-
                                                            300     500
                                                            Gas Volume, 10s acfm
                               50         100

                            Gas Volume Through Collector,  10  acfm
500
    Figure 24.6.  Installed Cost of High-Voltage Electrostatic Precipitators
                   (Reference 2).
                                                       SOUTHERN RESEARCH INSTITUTE
-------
                                   -854-
                               Table 24.1

               Comparison between Particulate Control Costs
               	  for a 100. OOP cfm Unit  (Ref. 3)
                         Electrostatic
                          Precipitator     Fabric Filter     Wet Scrubber*
FOB Cost
$80, 000
$85, 000
*Does not include clarifiers and liquid treatment systems.
 $30, 000
(Mild Steel)
Installation
Operating Per Year
Maintenance Per Year
56, 000
3,000
2, 500
25, 500
7, 000
17, 500
7,500
50, 000
1,500
-------
              500. 000h
c

X
l"l
71
z
5
m
z

-4

5



m
            2300,000
            09
            O

            O
                                                                  Electrostatic Precipitator
                                                           i
                                                           oo
                                                           en
                                                           en
                                                           i
3         4

  Time,  years
               Figure 24. 7.  Comparative Costs for Participate Control for 100, 000 cfm Installation
-------
                                   -856-
should be based on specific data for a given plant as opposed to a
generalized analyses.  For example, the initial cost of an electrostatic
precipitator is directly related to the collection surface area required.
This surface area requirement is,  in turn,  a function of the precipitation
rate parameter,  which can vary by factors of 2 or more depending on
dust resistivity and particle size.  Hence, the  initial cost of an electro-
static precipitator can be in error by a like amount.

      As another example, the energy requirement to achieve a given
efficiency in a wet scrubber is dependent on particle size.  Thus, rather
severe  changes in operating costs could result from an error in particle
size assumptions.  As a  generality, the accuracy of a particular cost
estimate is directly related to the time,  effort, and ability put into its
preparation.

      Factors  other than cost also influence the selection of the type of
dust control equipment.   An electrostatic precipitator normally operates
in a sparking condition,  so that combustible materials are not generally
candidates for control by precipitators.  Applications of this type include
feed or flour mill effluents and coal grinding dusts.  However, precipita-
tors are used in collection of tar and other materials where air can be
excluded to prevent the buildup of a combustible mixture.

      Fabric filters are normally limited to applications with gas
temperatures less than about 600°F due to heat damage to the types of
fabrics available.  Some  types of dust  are also difficult to collect with
fabric filters because of  their tendency to clog the fabric and increase
the pressure drop excessively.

      Wet scrubber applications are limited to those in which disposal of
the slurries can be achieved without creating a serious pollution problem.

24.1  APPLICATION OF  ELECTROSTATIC PRECIPITATORS

      The use of electrostatic precipitators is  generally best suited to
those areas in which large gas volumes are to  be handled, and where high
efficiency collection of relatively small particles is desired.  The use of
electrostatic precipitators for participate emission  control has steadily
increased since it was first introduced for industrial dust control.
Figure  24.8 shows the total shipments of various types of particulate
control devices for 1963  and 1967.  As can be seen,  the 1967 shipments
of electrostatic precipitators were  about 2. 6 times those of 1963, indica-
ting a substantial growth  pattern.
-------
                                 -857-
 Electrostatic
     Precipitators
Fabric Filters
Mechanical
     Collectors
Participate
     Scrubbers
                               Total Shipments $ x 103
1963
           1967
                         1963
                               1967
1963
                                  1967
                        1963
           1967
Figure 24. 8.  Total Shipments of Various Types of Particulate
              Control Devices for 1963 and 1967.
                                                SOUTHERN RESEARCH INSTITUTE
-------
                                   -858-
      This growth, however,  is due principally to the large usage in coal-
fired electric power generating plants.  The rapid expansion of the power
generating capacity in this country has been accompanied by corresponding
increases in precipitator sales to that industry since precipitators,  either
separately or in combination with mechanical collectors,  are the only type
of dust control equipment used to any significant degree.

      Table 24. 2 is a compilation of the number of electrostatic precipi-
tators installed in all of the applications  in which they are used in this
country.  This table indicates several trends in the application of electro-
static precipitators in which changes  in the process  itself or the intro-
duction of new control systems have altered the use of electrostatic precipi-
tators to a substantial degree.

      The use of electrostatic precipitators to control emissions in the
major application areas is discussed  in the chapters covering those
applications.  Trends in the type of dust  control equipment used, and
general trends in the growth of the industry = are also included as they
affect the future use of electrostatic precipitators.

      In terms of new uses for electrostatic precipitators, possibilities
exist for the application of precipitators  where other control techniques are
used  and in areas where no dust control  is currently practiced.

      Table 24. 3 shows a breakdown of sales of dust control equipment
used  in various processes during the period 1966-1967.4  The processes
are identified by SIC categories.  The figure clearly shows  the major
areas in which the  various types of dust control equipment are used  and
the relative use of  each type of control equipment in each process.
Opportunities for the use of electrostatic precipitators in areas where
other types of dust control equipment predominates depend   primarily
upon  economic factors.  There are,  however,  as discussed previously,
other considerations on which choice  is made.

      One of the major  limitations of electrostatic precipitators is the
difficulty in handling high resistivity dusts.  If the dust resistivity is
higher than about 5 x 1010 ohm-cm,  a condition of reverse ionization or
back  corona occurs which seriously impairs the collection efficiency.
To minimize the effect,  the collecting plate area must be substantially
increased to reduce the current density, or other corrective measures
must be taken which can result in high costs and make electrostatic
precipitators less competitive in certain  applications.
-------
                      -859-
                     Table 24. 2
A Summary of Electrostatic Precipitator Application
1920-
Application Area 1924
Fly Ash 1
Metallurgical
Ore roasters, zinc or lead zinc
Ore roasters, molybdenum sulfide
Ore roasters, pyrites
Aluminum (carbon plant)
Soderberg pots
Aluminum remelt furnaces
Aluminum prebake potllne
Cryolite recovery
Cadmium recovery zinc sinter mach
Copper
Lead blaat furnace
Gold and silver
Tin smelting
Scarfing machine
Sintering machine
Blast furnace
BOF
Open hearth
Sinter machine gas
Chemical
Sulfuric acid
Acid mist
Phosphorus electric furnace
Phosphate
Phosphoric acid mist
Dl sodium metaphosphate
Rock Products
Alumina calciner
Cement kiln (wet)
Cement kiln (dry)
Cement plant dryers and mills
Gypsum
Petroleum
Catalytic crackers
Pulp and Paper
Pulp mill
Paper mill
Tar Recovery
1 Prior to 1930
"1960-1969
'1930-1939
1925- 1930- 1935-
1929 1934 1939
11 12 56

91 2 8
V 1 1
2 1 3





5
1
31 3
1 2
1


4 17








2 1



73
14»
*
1*
4



63* 20 33


1940-
1944
74

8
1
1
2
2



5

1

2


29






2

3


3


3

24
12
62


1945- 1950-
1949 1954
90 63

2 2

1
3

3
3
1
4 4


1


1
24 26

2
2

15
3
2 2
2
1 2
1

3
1 7
3
3 18

13 3
28 20
2 2
82 35


1955-
1959
90

1



1
2
2






4
7
21

9
2

10
12
1

1



24
17
2
19

2
37
11
14


1960-
1964
87














3
7*
6
2
a


1
5
2





17
6
3
10


2
25
6


1965-
1969
171

1








1

2

1


5
4
3

4
8
1




1
17
3
1


15
31



Total
655

33
5
8
5
3
5
5
1
18
2
7
6
3
8
15
127
7
23
7

30
28
10
2
10
1


73
43
58
A9
+e
114
71
282


-------
                             -860-
SALES OK DUST CONTROL EQUIPMENT USED IN VAH1OU3 PROCESSES DUHING THE PERIOD 1M6-IM7
                                                                            LEGEND:
                                                                              ELECTROSTATIC.
                                                                              MECHANICAL
INDUSTRIAL CLASSIFICATION


All EqufcHMiu, N.E.C.



CMUlrad

Oil Or«4

Induilrlil hMUn pilot*
Ciil


Oil

W«ud «wl bark




Mlnli*



Iru.


Copper


l.r.J

Zinc

S.I.C. NO.


0000



0000010

OOIOOIO

OQK)
TSoooto




•0400M




1000



'•"


IOM


10)0

to«o

no*








MHMHHHMMBMMMSIilSi


























LOGARITHMIC SCALE
HO*



































»!<""



mnMintmiMii laimiiiiMiMiiiiiMiiMWiii































• WET SCRUBBER MMMUd
y»

1

MM



































































-------
   -861-
IA HI.h 24. S (CONTINUFD)
I.KUKNU:
  EI.RCTKOSTATIC.
  MECHANICAL

  FABRIC FILTER
INDUSTRIAL CLASSIFICATION
Aluminum



mineral*, except fu*t*





M«ui product!
Mum •Uuflhtcrlnfl plant*


Mv*l proecflBlng ytlKittt

<'annt.'(l SUVA pre*«rved fruit*.






Hour Mnd other griin mill product*





SM|fUJ-


C«nc Nuiitti1. «MM*»iit ralliitng only

Cun« augar r«Htilii|

Itt-ei *ug«»-

S.I.C. NO
1050


:






9010
3011


U13

2030












2050


2091

200t

lots

S10*










	


















	
"saesiMMissMlffl







S104






































$10* 1






































10*






































                                SOUTHERN RESEARCH  INSTITUTE
-------
                                                                                     -862-
 INDUSTRIAL CLASSIFICATION    S.I.C. NO.  $10*
Confectionery and rtteted products
Ctmdy and other confecUon«ry
product*
Chocolate and cocoa product!
MiHcetlanooutt food preparation*
and kindred product*
Animal and mnrinfl fata and oil*
 OuttVe routing
ShurU'iiitig and cooking oil*
      e mill product*
       i and related producta
l.tinitK-i- mid wood product*,
vxcrpt furnllura
l-'uriilttire wid fixturea
                                   2070
                                   20BO
                                   2200
                                   2400
                                    0001400
      TABLE 94.3 (CONTINUED)


ito4                           sio*
                                                                                                                                              ELECTSOSTATIC
                                                                                                                                              MECHANICAL
                                                                                                                                              FABRIC FILTER
                                                                                                                                              WET SCRUBBER
-------
                                                                                    -863-
                                                                              TABLE 24 9  (CONTINUED)
 INDUSTRIAL CLASSIFICATION	S.I.C. NO. »10*
Paper and Killed product*
                                                                         MO-
t.KGKNJ*
  KI.ECTROSTAW
  MECHANICAL

  FABRIC KILTED
  WET SCRUBBER
                                                                                                                                    $10-
Pulp mill*
                                     •omit
  Diguater
                                     eosaen
  Hvcovery lumace
 I'itper ntilla.  except building
 pu|ier mill*
 Bulldini paper and bulldln(
 board tnllla
 Printing and Dubllihing
 C'liuinlcal and allied product*
 ImluatHal Inorganic and
 urgunlc cliemlcala
                                                                                                                SOUTHERN RESEARCH  INSTITUTE
-------
    -864-
M BLK 14 a (CON TmUKU)
I.KtiKMU:
  ELECTROSTATIC
  MECHANICAL
  FABRIC FILTER
  WET SCRUBBER
INDUSTRIAL CLASSIFICATION





Induatrial gases

Intermediate coal tar products


liiorgetilc pigmanls



Organic chemicals







Suirurlc acid


Plastic materiel* and synthetic rssins
aynthetlc rubber, synthetic and other
man-made fiber*, except glsss

Plastic materials and resins



Synthetic rubber

Soap, detergents, and cleaning
preparations; perfumes, cosmetics.


Soap and other detergent*


Polish and sanitation goods

S.I.C. HO.





1819

IBIS






S»>»







•011819




1810

mi



Mil

W0

2841



8841

tiff







— —











XKHH iKOXimwmxssmK.
Kxm&SKatia






************







—







$10*



















amftemmummft























MO*











































1 Uf

' '









































-------
    -865-
TABLE 24.3 (CONTINUED)
LEGEND:
  ELECTROSTATIC I
  MECHANICAL

  FABRIC FILTER
  WET SCRUBBER
INDUSTRIAL CLASSIFICATION
Surface Kttv* agenti

Toilet preparation*


viiamftla. and allied produeta


Gum and wood chemicals


i-xi-ept activated


Agricultural cjiemlcale


rVrtilltera




pnoephalee


KrrtllUera, mixing only

Agricultural chemical!, N.E.C.

MlecellMMOiia chemical producta



Ulue and gelatin


r:«|>loalvee

S.I.C. NO.
IM3

M44


»iO


8»«9


MWMei


»76


2171




IOOW7I


*7J

Ml*

MM



*M1


MM

UOf















WKtfl(KKH«ie^WK«aW.M











	 ^ 	


ffllltttKMMlBaMn
"



(K»S.iiiSi»»W««»«S»««»SaSiS«»l



tin1


































HMI



IMJ


































•



tuC





































	
                         SOUTHERN  RESEARCH  INSTITUTE
-------
-866-
TABLE 24.3 (CONTINUED)
INDUSTRIAL CLASSIFICATION S.I.C. NO. $ 10? 1 10* $10*
Printing Ink
Carbon black
Furnace black
Chemical preparations
I'i irolrum refining and
rt-laU-d Industrie*
Petroleum refining
t'btalytic cracking
I'uving and roofing material*
Having mixture* and block*
,.„,.,. -,,„.
MldcelluieoUB producu of
petroleum and coal
l.ubricHting oils wid gr«ftB«ft
iviruluum and coal producu
MM
IMS
800JW5
J8»»
1«00
«,
9002911
2950
m
9002OT1
2910
29B2

»99



























ami«*si^i»ssM»^a»s(^«t8««



























































LKGEND:
ELECTROSTATIC I 	 iii.iiiii.iiin
WET SCRUBBER






'•












-------
    -867-
TAm.K»4 3 (CONTINUKD)
I.KCFNU:
  ELECTROSTATIC c
  MKCHAN1CAL
  FABRIC FILTER
  WET 9CRUBBEH
INDUSTRIAL CLASSIFICATION

plaatlc product*


Tirea and Inner tubta

Rubber footwear

fabricated rubber prodneta, N.E.C

MiBcellaneoiia plutic product*




leather tanning and fintahinf
Stone, clay, glaaai and
concrete producta


Klat flaw

Ulaait and glaeaware, preaaed
itr blown

ulaaa cotitalnera












S.I. C. NO.

9000


JOIO

3010

30>0

9070




1110

3200


9110

3120

3211

92M







(003241


HO"


wmmmmmsmtiimimiiiiitm


mmmmmimmmimmmm
mm#mms»*«Mft!&tmi" *™^&«a«w&aiTi«^^?













tio'





1
f






























*
-------
                                                                                      -868-
                                                                                TABS,E 14.3 (CONTINUE!!)
I.KGKNO.
   EI.ECTHO6TATIC I
   MECHANICAL
   FABRIC FILTER
   WET SCRUBBER
 INDUSTRIAL CLASSIFICATION      S.l.C. NO.  * 10*
                                                                            MO1
                                                                                                                                          *10"
  Cooling
  Grinding
  Silu
          day product*
 Hricfc ami structural tile
(. r.i y refractories
Structural clay products, N. E. C.
Concrete, gypsum, and plaster
["om.r
-------
-869-
TAM1.K 24 3 (rONTINUFU)
INDUSTRIAL CLASSIFICATION s.l.C NO $10* nn« * „»
	 	 	 • 	 — .— 	 _ 	 , 	 . 	 »*U $10
Gypaum product*
Cut aion* and alone product*
AiTMlw. aabeatoa, and mtacellaneoua
nunmrtalhc mineral product*
Altraalve product*
Mtitcrala. (round or treated
Noiirlay refractorla*
Primary metal Indvatrlea
IKn»t fui-nace*. ateel vorkv, and
rullliifl and finlahlnf mill*
HliiMt rurnacc*
opvu hearth
HHMK uxyutn furnace
••vinlvrmg
c.,_
Or, ,.„„,...
JJti
MIO
1MO
„,,
""
9MT
UOR
9910
«0099I2
touiia
•019312





D0499I1
•053912



mmmmmmmimmmm





^^^^m^^mmm,
_















\



















«-«. <«««- 	 **~ ^^^^— «™»
'
^A^:^KW::-^%-:';^;.W^^.::-ic^&^^y&»:

•smtHf"t*lfSilf^ m s i*.iJ»MSiS(«»4«

•t~^^-^m^'ms''>ifmmsiiw--it



K ^^M^^^m^m^mm^











MMSII>MII!mMI&aM«MMMMMM

















!r™r3r~-* " .-..«-, .-,-.•>.,»-,





_


'







I.I-:I;KNM-.
WETSCRUBBEN «®«»S8«Safi».i**;
tin*






- 	 ~ ~ 	 " ~ ~ " 	 ~
s-»:'«,s«»;;:js












i
             SOUTHERN RESEARCH INSTITUTE
-------
                                                                                      -870-
                                                                                TARLK 24 3 (CONTINUED)
                                                                                                                                                KLEC'THI KTATIC
                                                                                                                                                MKCIIANK'AL
                                                                                                                                                FABRIC KILTER
                                                                                                                                                WET SCRUBBER
 INDUSTRIAL CLASSIFICATION      B.l.C. NO.  >10*
»10*
                                                                                                         910'
 Pyrite routers
 Klrdric furnac
K UM-U otm-lallurgical products
Stcei wir« drawing
( nld finishing of steel shapes
It nit utid steal foundries
 Grinding
  ">lu>t blasting
  SjinJ handling
                                     90633)2
                                                                                  ®8$$mmmmmmmmm *
-------
                                                                            871
                                                                     TABLE 24 3  (CUNTINUKU)
                                                                                                                         I.KfiKNII:
                                                                                                                            ELECTHflSTATIC
                                                                                                                            MKCIIANICAl.
                                                                                                                            FABRIC KILTER
                                                                                                                            WET SCRUBBER
INDUSTHIA1 CLASSIFICATION     S.I.C. NO. itfl"
                                                                                          *to'
Electric induction furnace
Electric arc furnace
Primary ameltlng and refining
of nonferroua nwtata
Primary amelUng and refining
Cuppet rrverbet atory furnace
Copper converter
Primary ameltlng and refining of lead
primary amelting and refining of cine
Zinc roaster
titulary production of aluminum
I'l . Mtry aim/iling and refining of
r.u.»irrrou» nu-lala. N E.C
tlfinenlal phoa.
Mulylideiiuin
s. . ufldnry anielttng antl refining of
80USJO
•063320
3330
9991
•011911
•029991
9931
3333
•003333
3334
!33»
•003339
•03133«
3340



mmmm^v^mmmmm




1



	
^^^mxmmm^mzm^
MM
* '?. ;^:; Ktff '-?f -.v\:K 'v^S-i- ;-,*; > "'• - 'J:-^ ;\~~-: '<%?~¥^\



m^.^^^^^mmmm




..

	 •.••-.K,.-..-is«.t,««
-™
rTyffWT-r .f^f,^ff^iKr^afmmaatasssXS^
f±:rrr ::f!r±!!!:l



tsxiii^smsiMsimKfisimi









-S5s»« 	 * 	 *•-» 	 as*:!s;««ss;«is
'OiSftsWSsW



^i«!i«S.;:;«SSi««!™:^



^«»w«a«»««W!««»g





^^Z!^II^^


i

















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                                                                                                 SOUTHERN  RESEARCH  INSTITUTE
-------
-872-
TABI.K 24 3 (CON TWUEUI
INDUSTRIAL cukssincAtioN s. i.e. NO. $10* *io* »io*
Aluminum castings
HruM, bronze, copper castings
N.'i|frrri»us routing*. N.E.C.
MtMvi'llaneuwM primary
ItlfUl priMjtiCtS
'•i unary meul Induatrlft*. N E.C.
Kubricated m«la! products
Mscheitery, except electrical
1 h-ttrltul machinery
I'i amtporjallun <*tiul)Jii«fnl
MutcvUaiifuuH muiufacturfng
lOdurill-ieB
Klurlric, gas. and sanitary services
Met trie cumpanlea and syttlems
( u»l
33<1
3912
M6S
3590
3389
3400
3900
3600
3700
31100
3900
4(00
4910

•00491 1





... . . . . ,














mmm^m^m^itmvmm


••-•^'V!i!...Wa!,vX|.!t'*",!!-V :•* " •:• . -S* !* tV!:":W



1 T













;S:;iS%:":':v~x:^;::^W:^.y.K?v?-





»««*:««.:** -,-•«*,; 
-------
                                                                                      -873-
                                                                               TABU: 2« 3  (CONTINUE)
I.KlIKNIk
  KI.KCTHOSTATIO
  MKCNANICAI.
  FABRIC PII.TKH
  WKT SCRUBBER
  INDUSTRIAL CLASSIFICATION      S.I.C. NO.  UP*
Siuiilary vei-vlcca
 (•uinimrrcU! and tndufltrUl
  Munlclp«l
  Aulo body and scrap wire
        Hludge (invl
  WIIMU- liquid (inrinvralora)
I'AHTK'ULATIE C<1NTHHI. 1OTAI--

         Fl.r'CTHOSTATIC     *67.«»5,5Z1


         MKCIIANK-AI.         M.OM.UI


         KAIIKIC KII.TEH       >'. '•». ••'

         WKTSCBIIBUEH       33.ia.ttl
                                     9014(53
                                                                                                       «ia*
                                                                                                              SOUTHERN RESEARCH  INSTITUTE
-------
                                    -874-


      One serious drawback in the use of precipitators for some dust
collection problems has been an inability to obtain data on which to base
a size determination if changes in the process or fuel  are made.  In
some instances,  precipitators designed to operate at efficiencies of
90% have resulted in efficiencies of 60-70%  in practice.  These instances
occur with sufficient frequency that adverse attitudes toward precipitators
are often developed.

      The future application of electrostatic precipitators would appear
to be  along the lines  of existing installations, probably enhanced by the
necessity for high temperature gas cleaning.  However,  increased
activity in air pollution control should extend electrostatic precipitator
usage  into areas of municipal incinerators,  foundry  cupolas, and  perhaps
other processes.  Advances in precipitator technology, which would
reduce precipitator  size requirements,  would further  enhance  the existing
economic advantage associated with low power requirements for electro-
static precipitators.
-------
                                  -875-
                             CHAPTER 24
                            BIBLIOGRAPHY
    ~uel Engineering Data.  Section F-2, National Coal Association,
    Washington, D.  C.  (September 1961).

2.  Edmisten,  N.  G., and Banyard, F. C.,  "A Systematic Procedure
    for Determining the Cost of Controlling Participate Emissions
    from Industrial  Sources, " National Air Pollution Control Association
    Meeting (June 1969).

3.  Walker, A. B., and Frisch, N. W., "Scrubbing Air, " Sci and  Tech,
    p. 18 (Nov-Dec  1969).

4-  Manufacturer's  Report  of Air Pollution Control Equipment Sales,
    1966 and 1967.  IGCI Report on Contract CPA 22-69-5.
                                                  SOUTHERN RESEARCH INSTITUTE
-------