v>EPA
              United States
              Environmental Protection
              Agency
             Industrial Environmental Research
             Laboratory
             Research Triangle Park NC 27711
EPA-600/8-78-005a
June 1978
              Research and Development

Participate  Control
Highlights:
Fine Particle
Scrubber Research

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                 RESEARCH REPORTING SERIES


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

     1.  Environmental Health Effects Research

     2.  Environmental Protection Technology

     3.  Ecological Research

     4.  Environmental Monitoring

     5.  Socioeconomic Environmental Studies

     6.  Scientific and Technical Assessment Reports (STAR)

     7.  Interagency Energy-Environment Research and Development

     8.  "Special" Reports

     9.  Miscellaneous Reports

This report has been assigned to the SPECIAL REPORTS series. This series is
reserved for reports which are intended to meet the technical information needs
of specifically targeted user groups. Reports in this series include Problem Orient-
ed Reports, Research Application Reports, and Executive Summary Documents.
Typical of these reports include state-of-the-art analyses,  technology assess-
ments, reports on  the results of major research and development efforts, design
manuals, and user manuals.
                        EPA REVIEW NOTICE

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

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                                   EPA-600/8-78-005a
                                             June 1978
 Participate  Control Highlights:
Fine Particle Scrubber Research
                         by

                   S. Calvert and R. Parker

                       A.P.T., Inc.
                4901 Morena Boulevard, Suite 402
                  San Diego, California 92117
                   Contract No. 68-02-2190
                 Program Element No. EHE624
               EPA Project Officer: Dennis C. Drehmel

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

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

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                           ABSTRACT

     Since 1970, the U.S. EPA has been actively involved in re-
search and development work in the field of fine particle scrub-
bing.  The overall objective has been to develop and demonstrate
low pressure drop scrubbing systems capable of controlling fine
particle emissions.  Major accomplishments of the EPA scrubber
program have included:  publication of the Scrubber Handbook;
development and demonstration of flux force/condensation scrub-
bing; generation of extensive scrubber performance data; develop
ment of design methods and criteria for entrainment separation;
development and evaluation of novel devices for fine particle
control; and presentation of two technical symposia on fine par-
ticle scrubbing.
                                11

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                            CONTENTS

Introduction	1
Wet Scrubber Systems Study	2
Flux Force/Condensation Scrubbing 	 3
Performance Data	3
Liquid Entrainment	6
Novel Devices	9
EPA Program Goals 	 9
Bibliography	1
                            FIGURES
Figure 1.  Generalized F/C scrubber system	4
Figure 2.  Particle size distribution before and after
           condensation	5
Figure 3.  Entrainment separator performance cut diameters.  .7
Figure 4.  Throughput of horizontal and inclined baffle
           units, as restricted by reentrainment	8
Figure 5.  A.P.T. cut/power plot	11
                             TABLES
Table 1.  List of projects related to scrubber research
          and development sponsored by Industrial Environ-
          mental Research Laboratory - Research Triangle
          Park (IERL-RTP) 	
10
                               111

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                 FINE PARTICLE SCRUBBER RESEARCH

INTRODUCTION
Fine Particles
     In recent years fine particles have come to be recognized
as a significant type of air pollutant.  Fine particles may be
defined as solid or liquid aerosol particles smaller than three
microns (<3 ym) in diameter.  These particles present the major
health hazard because they are not filtered out by the human
upper respiratory tract.  They deposit deep within the lungs
where they can cause significant respiratory damage.  Fine par-
ticles also contribute to haze and smog formation.  Unfortunately,
fine particle emissions are very difficult to control.
Wet Scrubbers
     Wet scrubbers are one of the major types of air pollution
control equipment which have the capability of controlling fine
particle emissions.  A wet scrubber is any device which uses a
liquid in the separation of particulate or gaseous pollutants
from a gas stream.  This broad definition includes a wide variety
of scrubber designs.
     There are many reasons why scrubbers are prominent in the
field of fine particle control.  They are ideally suited for
situations where both particulate and gaseous pollutants must
be controlled.  They can be used to control explosive gases and
dust without fire hazard.  They can handle very hot gases, re-
ducing the gas temperature by evaporation.  Also scrubbers are
generally more compact than their principal competitors: baghouses
and electrostatic precipitators.
     Of course there are also problems associated with the use
of wet scrubbers.   They often have a relatively large power re-
quirement in order to obtain sufficient collection efficiency for

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fine particles.  Liquid drops can be entrained in the gas flow
leaving the scrubber, thus lowering the overall collection effi-
ciency.  Particles smaller than about one-half micron are extreme-
ly difficult to collect with conventional scrubbers.  The availa-
bility of a water supply may be a problem in some areas.  Scrubbers
may be subject to severe corrosion problems, and also, scrubbers
can present liquid waste disposal problems.
     Therefore, there has been a need for further development and
demonstration of lower pressure drop scrubbers capable of con-
trolling fine particle emissions.  The EPA has taken a leading
role in this area.

WET SCRUBBER SYSTEMS STUDY
     When EPA initiated the Wet Scrubber Systems Study in 1970
the state-of-the-art was largely empirical.   Each application
was considered to be a special case which could only be dealt
with on the basis of long and specific experience.   Engineering
design was based on a primitive, cut-and-try approach and often
resulted in an expensive overdesign to cover the wide range of
uncertainty. There was also very little scrubber performance
information available.
     In the Wet Scrubber Systems Study all available information
concerning wet scrubber theory and practice  was reviewed and
evaluated.  The best available engineering design methods were
evaluated and where necessary new or revised methods were developed
to provide as sound a basis as possible for  predicting performance.
The result of this study was the publication in 1972 of the "Scrub-
ber Handbook," which was widely recognized as the most extensive
and authoritative engineering text on the subject.
     Several paths which might lead to improved scrubber tech-
nology were pointed out in the Wet Scrubber  Systems Study recom-
mendations.  Among those were the following  topics:
     1. To study phenomena which can exert forces other than in-
ertial forces on particles and, where warranted to develop equip-
ment to use these forces for particle collection.

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     2.  To  compare  the  new  and  generally  untested  design methods
with reliable scrubber performance data.
     3.  To  study  entrainment  separators  (or  "mist  eliminators")
and develop improved design methods and equipment.

FLUX FORCE/CONDENSATION SCRUBBING
     In  line with the first topic, a major thrust was aimed at
developing and demonstrating Flux Force/Condensation (F/C)
scrubbers.  In an F/C scrubber water vapor is condensed from the
gas.  A  representative F/C scrubbing system is illustrated in
Figure 1.  Some of  the water condenses on the particles  causing
their mass to increase and thereby making them easier to collect.
The rest of the water vapor sweeps particles with it as it moves
toward the cold surface and condenses.
     A series of F/C scrubbing studies progressing from theory
through  experiment  and into industrial demonstration have pro-
duced a  useful body of engineering knowledge.  It is now possible
to make  reliable process designs and cost estimates for F/C
scrubbing from the  starting point of small scale sampling studies
of the emission under consideration.  Depending on the specific
set of circumstances, F/C scrubbing can be economically superior
to conventional scrubbing and in some cases may be technically
feasible where conventional scrubbing is not.  Figure 2 shows
the effect of condensation on particle size distribution for a
realistic set of conditions based on field measurements. If a
venturi  scrubber were used to obtain 85% collection efficiency
on the initial particle size distribution, a pressure drop of
190 cm W.C. would be required.  Were condensation and particle
growth to occur, only 75 cm W.C. pressure drop would be required
for 85%  efficiency.

PERFORMANCE DATA
     Fine particle  scrubber performance data for a number of
industrial sources have been measured under several EPA contract
programs.  These have yielded the most detailed and precise body

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               CLEAN GAS
            55C
   WATER O
     IMPACTOR
              SAT.  A  GAS
            55C   **
            0.12g/g
   WATER >
    CONDENSER
              SAT.  A,  GAS
           74C
           0.36g/g
   WATER
        -o
    SATURATOR
    HOT A  GAS
1,000C
O.Olg/g
                   A  G
Figure 1.   Generalized F/C scrubber system,

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    3.0,
    1.0
H

PJ
o
u
    0. 5
    0.1
              GROWN
                                INITIAL
   I
J	I
I
I
                                               PS
                                               n
                                                p

                                               q'  =

                                               f  =
                         0.75


                         109/DNcm3



                         0.3


                         0.25
I
I
                   10
  30     50     70



DRY MASS \ UNDERSIZE
90  95
       Figure  2.   Particle  size distribution before and after

                  condensation.

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of information available on the measurement of collection effi-
ciency as a function of particle size in industrial systems.
Many improvements of testing instruments and methodology have been
made as the result of this work.
     All of the scrubber performance studies include a comparison
of the measured efficiency with that predicted by means of the
available mathematical models.   In cases where there was dis-
agreement the model was re-examined and sometimes revised.  One
very useful and practical engineering design tool which was
developed through the EPA program is the particle cut diameter
versus scrubber power relationship created by A.P.T.  This "cut/
power" relationship in conjunction with a general design pro-
cedure which originated in the  Wet Scrubber System Study enables
one to make a rapid and usefully accurate estimate of the power
required to achieve a given efficiency for a specific particle
size distribution.

LIQUID ENTRAINMENT
     Entrainment from scrubbers has proven to be the potential
cause of very serious reduction in performance and even opera-
bility.  Power plant scrubbers  which utilize concentrated sus-
pensions or solutions have been especially susceptible to en-
trainment problems.  EPA contract and in-house efforts have been
aimed at this problem for several years.
     The results have been new  knowledge of the efficiency, capa-
city, and pressure drop of entrainment separators, and of the
size distribution of the entrained mist.  Figure 3 is a cut/power
plot which illustrates the efficiency characteristics of several
types of entrainment separator.  The effect of separating element
orientation on capacity limitations is shown in Figure 4.  Here
again, the EPA program has expanded the rational basis for the
engineering design of better, more reliable, more economical
equipment.

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w
H
W
Q
E-
U
  100
   50
10
                    I
                      I
                                      T
                                    A,B = BAFFLES, 6 ROWS (30, 45)
                                    C,D = TUBE BANK, 6 ROWS (1 cm, 0.3 cnj
                                    E = PACKING (2.5 cm DIA.)
                                    F = MESH (0.029 cm DIA.)
      0.01
               0.05  0.1
10
                            0.51            5
                      PRESSURE DROP, cm W.C.
Figure 3.  Entrainment separator performance cut diameters.
50

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   10
LO


c
E-i

O
ii

o-
   10
     _ 5

                           BAFFLE  INCLINATION
                              TO HORIZONTAL
   10
              SUPERFICIAL GAS VELOCITY,  m/s

 Figure  4.   Throughput of horizontal and inclined
            baffle  units, as restricted  by reentrainment

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NOVEL DEVICES
     Other EPA contract programs have been directed toward the
exploration, development and demonstration of unusual or new
technology for fine particle collection.  These include electro-
statically augmented scrubbers, foam scrubbers, and other novel
scrubbing devices.  Mobile bed scrubbers, whose performance in
practical installations has covered a puzzling range of effi
ciencies, have been studied in detail with regard to particle
collection and entrainment.

EPA PROGRAM GOALS
     Table 1 lists the major fine particle scrubber research
and development projects sponsored by the IERL-RTP.  The broad
objective of this program is to develop and demonstrate low
pressure drop (30-50 cm water) scrubber systems capable of
collecting at least 90% by mass of particles smaller than three
microns in diameter.  This objective is illustrated in Figure 5,
which shows the performance of conventional scrubbers in terms of
a cut/power plot.  For situations where free steam is available,
F/C scrubbing approaches this objective.
     To resolve some of the problems associated with scrubbers,
the EPA has sponsored studies in the areas of entrainment
separation, liquid utilization, energy consumption, and particle
wettability.  The EPA also owns a truck-mounted mobile scrubber
unit for testing the suitability of venturi and sieve plate
scrubbers on different industrial sources.
     EPA has sponsored two symposia dealing with fine particle
scrubbing.  The first symposium was in May, 1974 in San Diego.
The second was in May, 1977 in New Orleans.  These symposia
stimulated and generated new ideas for fine particulate control
by bringing  together experts in the development and use of wet
scrubbers.
     They also provided means for the transfer of technology
between researchers and users of wet scrubber technology.

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    TABLE 1.  LIST OF PROJECTS RELATED TO SCRUBBER RESEARCH AND DEVELOPMENT
              SPONSORED BY INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
              RESEARCH TRIANGLE PARK (IERL-RTP)
   Starting Date
                  Title
                                              Contractor
       1970


       1971

 September 1972
 December 1972

   June 1973
 September 1973

  October 1973

 December 1973

   June 1974

      1974


   June 1974

   July 1974

   July 1974

  August 1974
 September 1974

  January 1975
  February 1975

   April 1975
   June 1975
  August 1975

November 1975

September 1976
September 1976
Wet Scrubber Systems Study
Flux Force/Condensation Scrubber Feasibility
Fine Particle Scrubber Performance Tests
Systems of Charged Droplets and Electric
Fields for Removal of Submicron Particulates
Wet Scrubber Entrianment Separation
Pilot Scale Demonstration of Charged Drop-
let Scrubbing
Wet Scrubber Development II (F/C Scrubbers)
Wet Scrubber Liquid Utilization

Foam Scrubbing for Fine Particle Control

Growth of Fine Particles by Condensation

Fine Particle Collection with University
of Washington Electrostatic Scrubber
Evaluation of Novel Control Devices
F/C Scrubber Demonstration Plant on
Secondary Metal Recovery Furnace
Evaluation of Wet Scrubbers for Control of
Particulate Emissions from Utility Boilers
Operation of EPA-Owned Mobile Units,  Aero-
dynamic Test Chamber, and Pilot Scrubbers
Rocket Motor Emissions Control
Entrainment Characteristics of Mobile Bed
Scrubbers
Evaluation of Horizontal Scrubber
Evaluation of Systems for Control of
Rocket Motor Test Pad Emissions
Evaluation of Electrostatic Scrubber
Wet Scrubber Energy Utilization
Effects of Interfacial Properties on
Fine Particle Scrubbing
Mobile Bed F/C Scrubbers for Collection
of Fine Particles
Superior Entrainment Separator
F/C Scrubber Demonstration Plant on a
Foundry Cupola
A.P.T., Inc.
A.P.T., Inc.
A.P.T., Inc.
  M.I.T.

A.P.T., Inc.
TRW Corporation

A.P.T., Inc.
Stanford Research
    Institute
Monsanto Research
    Corporation
Stanford Research
    Institute
University of
   Washington
A.P.T., Inc.
Southern Research Inst.
GCA, Meterology
Research Inc.
A.P.T., Inc.

Meterology Research Inc.
A.P.T., Inc.
Monsanto Research Corp.

A.P.T., Inc.
A.P.T., Inc.

A.P.T., Inc.
A.P.T., Inc.

TRW Corporation
Stanford Research Inst.
Meterology Research Inc.

A.P.T., Inc.

A.P.T., Inc.
A.P.T., Inc.
                                        10

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<
OS
tu
E-
c
H;
CJ
   1.0
         20
      30
40 5
                              SCRUBBER POWER, W/m3/min
                                     100         200
                                                     500
     2  -
   O.S
   0.4
   0.3  _
   0.2
                  10
                   20     30   40  50         100
               GAS PHASE PRESSURE DROP, cm W.C.
               Figure 5.  A.P.T. cut/power plot.
                                                                     200
       la.

       Ib.
        2.

       3a.

       3b.
       3c.
        4.
Sieve-plate column with foam density of 0.4 g/cm3 and 0.5cm
hole diameter.  The number of plates does not affect the
relationship much (experimental data and mathematical model).
Same as la except 3.2 mm hole diameter.
Packed column with 2.5  cm rings or saddles. Packing depth does
not affect the relationship much (experimental data and
mathematical model).
Fibrous packed bed with 0.3 mm dia. fiber, any depth (experi
mental data and mathematical model).
Same as 3a except 0.1 mm dia. fibers.
Same as 3a except 0.05 mm dia. fibers.
Gas atomized spray (experimental data from large Venturis,
orifices, and rod type units, plus mathematical model).
Mobile bed with 1 to 3 stages of fluidized hollow plastic
spheres (experimental data from pilot plant and large-scale
power plant scrubbers).
                                   11

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                        BIBLIOGRAPHY


     Much of the work cited has been reported in the following
references.


Scrubber Handbook (Volume 1), Final Report and Bibliography
     (Volume II) by Seymour Calvert, Jhuda Goldshmid, David
     Leith and Dilip Mehta.  EPA #CPA 70-95, NTIS #PB 213-016,
     published August, July 1972 respectively.

Feasibility of Flux Force/Condensation Scrubbing for Fine Particle
     Collection, Seymour Calvert, Jhuda Goldshmid,  David Leith
     and Nikhil Jahvari. EPA 650/2-73-036, NTIS #PB 227-307,
     October 1973.

Fine Particle Scrubber Performance Tests, Seymour Calvert,
     Nikhil Jhaveri, and Shui-Chow Yung.   EPA 650/74-093,
     NTIS #PB 240-325, October 1974.

Entrainment Separators for Scrubbers-Initial Report, Seymour
     Calvert, Shui-Chow Yung and James Leung.  EPA 650/2-74-119a,
     NTIS #PB 241 189, October 1974.

Entrainment Separators for Scrubbers-Final Report,  Seymour Calvert,
     Shui-Chow Yung and James Leung.  EPA 650/2-74-119b,  NTIS
     #PB 248-050,  August 1975.

Study of Flux Force/Condensation Scrubbing of Fine Particles,
     Seymour Calvert,  Nikhil Jhaveri and Timothy Huisking.
     EPA 600/2-75-018, NTIS #PB 249-297,  August 1975.

Venturi Scrubber Performance Model, Shui-Chow Yung, Seymour
     Calvert and Harry F. Barbarika. EPA 650/2-75-021b, NTIS
     #PB 271-515, August 1977.

Second EPA Fine Particle Scrubber Symposium, Richard Parker
     and Seymour Calvert, EPA 600/2-77-193, NTIS #PB 273-828,
     September 1977.

Proceedings of E.P.A.-A.P.T. Fine Particle Scrubber Symposium,
     Seymour Calvert (editor). EPA 650/2-74-112, NTIS #PB 239-335,
     May, 1974.

Fine Particle Collection by a Flux Force/Condensation Scrubber:
     Pilot Demonstration, Seymour Calvert and Shamim Gandhi,
     EPA 600/2-77-238, PB 277-075, December 1977.

                               12

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                                TECHNICAL REPORT DATA
                          (Please read Instructions on the reverse before completing)
 1. REPORT NO.
 EPA-600/8-78-005a
                           2.
                                                      3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
 Particulate Control Highlights: Fine Particle
   Scrubber Research
                                                      5. REPORT DATE
                                                       June 1978
                                                      6. PERFORMING ORGANIZATION CODE
 7. AUTHOR(S)

 S. Calvert and R. Parker
                                                      8. PERFORMING ORGANIZATION REPORT NO.
 9. PERFORMING ORGANIZATION NAME AND ADDRESS
 A.P.T. , Inc.
 4901 Morena Boulevard, Suite 402
 San Diego, California 92117
                                                      10. PROGRAM ELEMENT NO.

                                                      EHE624
                                                      11. CONTRACT/GRANT NO.
                                                      68-02-2190
 12. SPONSORING AGENCY NAME AND ADDRESS
 EPA, Office of Research and Development
 Industrial Environmental Research Laboratory
 Research Triangle Park, NC 27711
                                                      13. TYPE OF REPORT AND PERJOD COVERED
                                                      Task Final; 5/77-3/78	
                                                      14. SPONSORING AGENCY CODE
                                                       EPA/600/13
 15. SUPPLEMENTARY NOTES IERL-RTP project officer is Dennis C. Drehmel, Mail Drop 61,
 919/541-2925. EPA-600/8-77-020a, -020b, and -020c are earlier reports in this
 series.
 16. ABSTRACTThe report gives highlights of fine particle scrubber research performed
 by, or under the direction of,  EPA's Industrial Environmental Research Laboratory
 (IERL-RTP) at Research Triangle Park, North Carolina. The U.S.  EPA has been
 actively involved in research and development in the field of fine particle scrubbing
 since 1970.  Its overall objective has been to develop and demonstrate low pressure
 drop scrubbing systems capable of controlling fine  particle emissions. Major
 accomplishments of EPA's scrubber program have included: publication of the
 Scrubber Handbook; development and demonstration of flux force/condensation
 scrubbing; generation of extensive scrubber performance data; development of
 design methods  and criteria for entrainment separation; development and evaluation
 of novel devices for fine particle control; and presentation of two technical symposia
 on fine particle  scrubbing (in 1975 and 1977).
 7.
                             KEY WORDS AND DOCUMENT ANALYSIS
                 DESCRIPTORS
                                          b.lDENTIFIERS/OPEN ENDED TERMS
                                                                  c. COSATI Field/Group
 Pollution
 Dust
 Scrubbers
 Gas Scrubbing
 Entrainment
 Separators
                                          Polluation Control
                                          Stationary Sources
                                          Particulate
                                          Flux Force/Condensa-
                                           tion
                                          Entrainment Separation
13B
11G
07A
13H
07D
 3. DISTRIBUTION STATEMENT
 Unlimited
                                          19. SECURITY CLASS (This Report)
                                          Unclassified
                                                                  21. NO. OF PAGES
                                                                      17
                                          20. SECURITY CLASS (Thispage)
                                          Unclassified
                                                                  22. PRICE
EPA Form 2220-1 (9-73)
                                        13

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