EPA-650/2-75-024-a
MARCH 1975
Environmental  Protection  Technology  Series
                                                        $!$$$$i£$&:

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                         EPA-650/2-75-024-0
         PENTAPURE
IMPINGER  EVALUATION
                by

          Douglas W. Cooper

           GCA Corporation
           Burlington Road
      Bedford, Massachusetts 01730
        Contract No. 68-02-1487
          ROAP No. 21ADL-004
       Program Element No. 1AB012
    EPA Project Officer: Dale L. Harmon

       Control Systems Laboratory
   National Environmental Research Center
    Research Triangle Park, N. C. 27711
            Prepared for

 U.S. ENVIRONMENTAL PROTECTION AGENCY
  OFFICE OF RESEARCH AND DEVELOPMENT
       WASHINGTON, D. C. 20460

             March 1975

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                         EPA REVIEW NOTICE

This report has been reviewed by the IMalionul Envi romnenlal Research
Center - Research Triangle Park, Office of Research and Development ,
EPA, and approved for publication.  Approval does not signify thai I he-
contents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
                    RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S.  Environ
mental Protection Agency, have been grouped into series.  These broad
categories were established to facilitate further development and applica-
tion of environmental technology.  Elimination of traditional grouping was
consciously planned to foster technology transfer and maximum interface
in related fields.  These 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
          9. MISCELLANEOUS

This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series.  This series describes  research performed to
develop and demonstrate instrumentation, equipment and methodology
to repair or prevent  environmental degradation from point and non-
point sources of pollution.  This work provides the new or improved
technology required for the control and treatment of pollution sources
to meet environmental quality standards.
This document is available to the public for sale through the National
Technical Information Service,  Springfield,  Virginia 22161.
                                   11

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                                ABSTRACT

A novel spray scrubber, the Pentapure (Purity Corporation, Elk Grove
Village, Illinois) was tested as part of a program to identify novel
high efficiency fine particle control devices.  The tests were made
using the emissions from a gray iron foundry after they had exited from
a spray cooling chamber.  Their mass median aerodynamic diameter was
0.5 pm, as determined with cascade impactor samples.  Inlet and out-
let samples were taken with cascade impactors and with total mass
measuring sampling trains.  Total mass efficiency was found to be 10.0
±2.5 percent on this fine dust.  The particle aerodynamic diameter for
which the efficiency would be 50 percent was estimated to be between 2
and 4 pm, determined from cascade impactor analysis and from theoretical
predictions of the performance.  The pressure drop across the Pentapure
scrubber was 1.5 x 10^ N/m2 (6" H20) and the measured efficiencies cor-
responded to those expected from venturi scrubbers having somewhat less
pressure drop.  The Pentapure is not an efficient fine particle collector.
                                iii

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                               CONTENTS




                                                                     Page




Abstract                                                             ill




List of Figures                                                      v




List of Tables                                                       vi




Sections




I      Conclusions                                                   1




II     Recommendations                                               2




III    Introduction                                                  3




IV     Collection Efficiency Tests                                   5




V      Power Consumption and Costs                                   38




VI     Appendices                                                    42




VII    References                                                    57
                                 iv

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                                FIGURES

No.                                                                  Page
1      Schematic Diagram of Purity Corp. Impingement Scrubber,
       the Pentapure Scrubber                                        4

2      Schematic of Sampling Positions                               6

3      RAG Train Schematic for EPA - Method 5 Sampling               10

4      Andersen In-Stack Impactor Sampling Train Schematic           16

5      Pre-Impactor for Sampling in a Spray                          18

6      Heater/Drier for Sampling in a Spray                          19

7      Inlet Particle Size Distribution                              21

8      Outlet Particle Size Distribution                             22

9      Collection Efficiency Versus Aerodynamic Diameter, Data
       Means for Pentapure Scrubber                                  25

10     Venturi Pressure Drop and Efficiency for Different f
       Factors and Particle Diameters (Corrected Version of
       Scrubber Handbook Figure)                                     33

11     Corrected Venturi Performance Curves With Pentapure
       Scrubber Data Added                                           34

12     Data and Approximate Theory Predictions (see Table 12)
       (f = 0.25,  0.50; QL/Qg  = 0.57 x 10~3)  for Pentapure
       Scrubber                                                      37

13     Interval Adjustment Diagram                                   56
                                 v

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                               •  TABLES

No.

1       Stack  and  Sample Moisture Contents                             9

2       RAG Filter Weighings and  Reweighings                           11

3       Comparison of Inlet and Outlet Flows  (Dry, STP)                11

4       Results for Total Mass  Emissions Sampling, Inlet to
        Purity Scrubber                                                12

5       Results for Total Mass  Emissions Sampling, Purity
        Scrubber,  Outlet Concentrations, Mass Efficiencies             13

6       Mean Masses (Six Tests) Captured by Filters, Probes,
        Cyclones for Inlet and  Outlet Total Mass Samples               15

7       Impingement Scrubber Particle Collection Efficiencies
        From Impactor Data, Tests 6 and 7                              23

8       Impingement Scrubber Particle Collection Efficiencies
        From Impactor Data, Tests 8A and 8B                            23

9       Impingement Scrubber Particle Collection Efficiencies
        From Impactor Data, Tests 9A and 9B                            24

10     Mean Collection Efficiency, Impactor Data                      24

11     Data From Two Andersen Mark III Cascade Impactors
        Sampling Same Iron Oxide Aerosol (Mapico Black) at
        470 cm3/s                                                     28

12     Approximate Theoretical Efficiencies for Purity Corp.
        Impingement Scrubber                                          31

13     Theoretical Pressure Drop Needed for 50 Percent
       Collection Efficiency at the Listed Particle Sizes
       for a Venturi Scrubber                                        36

14     Average Pressure Drops Across Purity Scrubber                 39

15     Impactor Data,  Run 6,  Inlet                                   43

16     Impactor Data,  Run 7,  Inlet                                   44

17     Impactor Data,  Run 8A,  Inlet                                  45

18     Impactor Data,  Run 8B,  Inlet                                  46
                                 vi

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                                TABLES




N^L                                                                  Page




19     Impactor Data, Run 9A, Inlet                                  47




20     Impactor Data, Run 9B, Inlet                                  48




21     Impactor Data, Run 6, Outlet                                  49




22     Impactor Data, Run 7, Outlet                                  50




23     Impactor Data, Run 8A, Outlet                                 51




24     Impactor Data, Run 8B, Outlet                                 52




25     Impactor Data, Run 9A, Outlet                                 53




26     Impactor Data, Run 9B, Outlet                                 54
                               vii

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                                SECTION I
                               CONCLUSIONS

This evaluation was one of a series of such evaluations being conducted
by the Environmental Protection Agency to identify novel devices which
are capable of highly efficient collection of fine particulates.  The
Pentapure scrubber, made by Purity Corporation (Elk Grove Village, Il-
linois), had substantially less than 50 percent collection efficiency on
fine particulates, those smaller than about 3 urn diameter, and thus did
not satisfy this objective.

On a foundry dust having a mass median aerodynamic diameter of 0.5 ym
after it exited a spray cooling system, the Pentapure scrubber gave
10.0 ±2.5 percent overall mass efficiency.  The aerodynamic diameter
for which particle size the device would be 50 percent efficient was
estimated to be between 2 and 4 ym from measurements with cascade im-
pactors at the scrubber inlet and outlet; this confirmed mathematical
estimates of the collection efficiency.  The pressure drop across the
Pentapure scrubber was 1.5 x 103 N/m2 (611 1^0) and the efficiencies
achieved were equivalent to those for venturi scrubbers using pressures
from 3.3  x 102 N/m2  to  1.25  x  103  N/m2 (1.3"  H20  to  5"  H20).

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                               SECTION II
                             RECOMMENDATIONS

The Pentapure scrubber does not give high efficiency for collecting fine
particles and should not be investigated further for that purpose.

In those situations in which a low-energy venturi scrubber would be
suitable, the use of the Pentapure scrubber might be considered as  well.

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                               SECTION  III
                               INTRODUCTION

This work was done  to evaluate the Purity Corporation  impingement
scrubber, the "Pentapure" scrubber, with respect to its collection
efficiency  for fine particles  (diameters smaller than  about 3ym) and
its power consumption and associated costs.

A diagram of the scrubber is shown in  Figure  1.  Dust laden air
mixes with water spray.  The mixture accelerates in the converging sec-
tion, causing particle-droplet collisions and perhaps  particle-particle
collisions as well.  The mixture is directed in a jet  at the impinge-
ment surface and undergoes rapid deceleration, causing more collisions
and causing the droplets, along with particles they have caught, to
strike the surface, from which they run off and form a slurry.  The air
exhaust contains any uncaptured particulate material and droplets.

The tests were conducted at a  gray iron foundry, with  the collection
efficiency determined by measuring the particle mass concentrations at
the scrubber inlet  and outlet.  These emissions were generally in the
fine particle range, the larger particles having been removed by cool-
ing sprays and a separation chamber.  Power consumption was determined
from measurements of both the pressure drop across the scrubber and
the volume air flow through the scrubber.  Cost estimates are given
which allow cost comparisons with other forms of particulate control
equipment.

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            WATER
            SPRAY
 AIR
INLET
                                       IMPINGEMENT
                                         SURFACE
   AIR
EXHAUST
                             CONVERGING
                               SECTION
                                                                WATER
                                                                SLURRY
                                                                EXIT
Figure 1.  Schematic diagram of Purity Corp. impingement scrubber,  the Pentapure scrubber

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                              SECTION  IV
                     COLLECTION EFFICIENCY TESTS

 EQUIPMENT, PROCEDURE, AND RESULTS

 Total Mass Efficiency

 The  tests were designed  to  give the  fine particulate  (< 3 ^m diameter)
 collection efficiency of the scrubber  section of the Purity Corp. instal-
 lation, which will be referred to here as the scrubber.  Figure  2 shows
 schematically the installation at the  foundry and the location of the
 sampling equipment.  Two kinds of efficiency determinations were made:
 total mass efficiency on the aerosol which entered the scrubber, and mass
 efficiency as a function of particle aerodynamic diameter on the same
 aerosols, using Andersen in-stack impactors.
The methods published in the Federal Register (December 23, 1971) were used
as guidelines for the total mass efficiency determinations where feasible.
If this were a test of conformance to "Standards of Performance for New
Stationary Sources," there would be a legal requirement to adhere strictly
to the test methods indicated in the Federal Register, but such is not the
case.  (Method 1, for example, says that "this method is not intended to
apply to gas streams other than those emitted directly to the atmosphere
without further processing."  One is without a mandated test procedure in
such cases and must proceed as good engineering judgment dictates.)  What
is required is a scientifically sound measurement of the inlet and outlet

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               SAMPLING
               POSITIONS
          SEPARATION
          CHAMBER
PENTAPURE
SCRUBBER
                                        TM
Figure 2.  Schematic of sampling positions

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mass  throughputs,  or,  equivalently,  inlet  and  outlet dry  gas  concentra-
tions  at  standard  conditions,  as done here.

The positions  of the sampling  points on  the  traverse were as  follows:  At
the inlet to the irapinger  scrubber,  the  samples were taken  3-1/2 diameters
downstream from the separation chamber and about  1-1/2 diameters upstream
from  the  converging section of the scrubber  impinger.  The  duct diameter
was 1.12  m (44 inches).  We designed the tests for a forty-point traverse,
twenty each on diameters vertical and horizontal  in the horizontal ducting.
Early  tests indicated  the  presence of water  for the first 10  cm or so at
the bottom of  the  horizontal duct, so one  of the  tests (run 6) had 15 of
20 vertical traverse points; for the other two tests reported, the diam-
eter was  recalculated  as 1.02  m (40  inches) and twenty-point  traverses
designed  on the basis  of this  new diameter,  19 of 20 of these being taken
in run 9  and 20 of 20  taken in run 10.   As will be seen,  the aerosol which
reached the impinger scrubber  after  the  separation chamber  was one of fine
particulates,  precisely those  for which  spatial inhotnogeneity is least.
At the outlet, the ports were  in a 0.92  m diameter (36 inches) stack,
6 diameters downstream from a  flow obstruction and 2 diameters upstream
from the  outlet.   Two  perpendicular traverses of  12 points  each were made
here through ports labeled east and north.  In both cases the points were
chosen appropriate for equal-area sampling, following the guidelines in
the Federal Register.

Determination  of the stack gas velocity  and flow rate followed Method 2
in the Federal Register cited  above.  The pitot tube was  connected to the
sampling  probe.  The gas velocity was calculated using Equation (2-2) of
Method 2  and the dry gas volumetric flow rate calculated  using Equation
(2-3), based upon  our  measurements of water vapor and gas velocity.

Water  vapor concentrations were obtained in two ways, following Method 4.
The first was  a determination  of the amount of water caught by impingers
and the second by  assuming saturation at the stack temperature and

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obtaining saturation water vapor  concentrations  from psychometric  charts
(Jorgenson,  1970).  Both determinations are  given  in Table  1.  To  cal-
culate the amount of dry gas  sampled,  the  %  1^0  obtained  from  the  impinger
samples was  used.

The determination of the particulate emissions concentrations  was  done
following, in general, Method 5 of the Federal Register cited.  Figure 3
shows a schematic diagram of  the  Research  Appliance Co. (RAC)  sampling
train used to do the sampling.  Filters were pre-dried at least 24 hours
with Drierite dessicant at about  70°F.  After the  tests,  they  were dried
similarly.   Table 2 gives the filter number, the initial weight, the
weights after one day and after three  days and the difference  in the
final weights of 13 filters, reweighed by  a  different operator.  This
tested for lack of adequate drying and for differences between operators.
The mean weight change was 0.0024 g between  weighings, which is to be
compared with net loadings which averaged  ~1 g, an insignificant  weighing
error of a few tenths of a percent of  the net weights used to  determine
concentrations.

As a check on the flow determination, one can compare the inlet and outlet
volume flow  rates, dry air at STP.  If there are no leaks in the control
systems, these should be identical and their difference would  be an esti-
mate of flow determination error.  Table 3 gives the inlet and outlet
flows as measured for the runs indicated and gives the ratio of the two
flows.   The average absolute difference between  these ratios and 1.00 is
+0.041.  The mean is 1.024.  If there are no leaks, the flow determina-
tion error would be about 4 percent.  The average absolute difference
between the readings and the mean is 0.034,.

Results for the determinations of mass concentrations and total mass ef-
ficiencies are summarized in Tables 4 and 5.  Each diameter traverse
is listed as a run.   The inlet and the outlet each were traversed  simul-
taneously.   The process ran daily for about  two hours.   To achieve the

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           Table 1.   STACK AND SAMPLE MOISTURE CONTENTS
Run
5

6

7

8
1
9

10

rt
Location
I
0
I
0
I
0
I
0
I
0
I
0
Stack
temperature
oF
135
79
123
66
144
81
120
104
126
80
137
85
°C
57
26
51
19
62
27
49
40
52
27
58
29
Stack
saturation
% H20
17.3
3.3
12.5
2.2
21.8
3.6
11.5
7.3
13.6
3.4
18.2
4.1
Sample
% H20
by impingers
12.8
10.5
7.8
7.7
11.9
11.1
13.1
9.4
11.1
9.2
13.8
10.7
I = inlet,  0 = outlet.

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              STACK WALL
 HEATED PROBE,
 PITOT TUBE
             PITOT
             MANOMETER
HEATED FILTER
HOLDER AND
CYCLONE'
IMPINGER
TRAIN,  4  IM-
PING ERS IN
1CF. BATH
                                                                THERMOMETER
                                                                AND CHECK
                                                                VALVE
                                   VACl'OI MNE
• OUTLET





ORIFICE





MANOMETER



DRY GAS
1NLKT AND
OUTLET
THERMO-
METERS


1
I
BY -PASS
VALVE

AIR-TIGHT
PIJMP
MAIN
i

- VALVE

                                                                          VACUUM GAGE
Figure 3.  RAC train  schematic for EPA - method 5 sampling

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      Table 2.  RAG FILTER WEIGHINGS AND REWEIGHTNGS
Filter
no.
277
278
279
280
251
252
276
271
238
253
202
204
205
Run
1
1
2
2
3
3
4
4
5
4
5
6
6
Initial weights
(g)
0.6580
0.6938
0.6809
0.6592
0.6589
0.6693
0.6541
0.6814
0.6982
0.7047
0.7001
0.6827
0. 7029
Final weights (g)
1-day
drying
1.3016
1.8896
1.1395
1.6974
1.1140
2.0582
1.0000
1.8426
2.2653
1.2722
2.1610
2.2436
2.0283
3 -day
drying
1.3008
1.8975
1.1415
1.6976
1. 1200
2.0644
0.9980
1.8411
2.2657
1.2585
2.1685
2.2530
2.0376
Final weight
change
(g)
-0.0008
+0.0079
+0.0020
40.0002
+0.0060
+0.0062
-0.0020
-0.0015
+0.0004
-0.0137
+0.0075
+0.0094
+0.0093
Table 3.  COMPARISON OF INLET AND OUTLET FLOWS (DRY, STP)



Run
5 + 6
7 + 9
10 + 1
^ ^
Flow (10J ft°/min)

Inlet
r 19.38
18.64
18.99
Outlet
18.87
19.92
19.55


Outlet/inlet
flow ratio
0.973
1.069
1.029
                         11

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            Table 4.  RESULTS FOR TOTAL MASS EMISSIONS  SAMPLING,  INLET  TO PURITY SCRUBBER
Run
5
6
7
8
9
10
5 + 6
7 + 9
8 + 10
Sample
net
weight
(mg)
1661.3
1679.4
1505.5
1265.9
1348.0
1285.0
3340.7
2853.5
2550.9
Stack
concentrations
(g/m3)
0.871
0.990
0.903
0.793
0.740
0.824
0.902
0.818
0.808
(gr/ft3)
0.3804
0.4325
0.3942
0.3461
0.3232
0.3600
0.3938
0.3571
0.3530
Dry STP
stack flow
(m3/s)
8.79
9.43
8.47
9.12
9.13
8.81
9.15
8.80
8.96
K £t3^
\ min/
18.63
19.98
17.95
19.33
19.35
18.66
19.38
18.64
18.99
Percentage
water
content
12.84
7.75
11.92
13.09
11.09
13.82
10.43
11.49
13.45
Isokinetic
percentage
107.2
104.4
108.0
108.2
103.8
109.0
105.8
105.9
108.7
Samp le
duration
(min)
100.0
90.0
90.0
80.0
95.0
80.0
190.0
185.0
160.0
Traverse
(horizontal/
vertical)
H
V
H
H
V
V
H-V
H-V
H-V
Comments
  1.  Probe not exactly 90° to duct during vertical runs,

               5 min. per pt., 20 pts.
               6 min. per pt., top 15 pts.
               5 min. per pt., first 18 pts,
               4 min. per pt., 20 pts.
               5 min. per pt., 19 pts.
               4 min. per pt., 20 pts.
1.
2.
Probe i
RUN 5
RUN 6
RUN 7
RUN 8
RUN 9
RUN 10

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   Table  5.  RESULTS FOR TOTAL  MASS EMISSIONS  SAMPLING, PURITY SCRUBBER, OUTLET  CONCENTRATIONS,
              MASS EFFICIENCIES
Run
5
6
7
1
9
10
5+6
7 + 9
10+1
Sample
net weight
("8)
1723.8
1774.3
1810.0
1220.3
1546.8
1745.0
3498.1
3356.8
2965.3
Stack
(g/n>3)
0.850
0.810
0.777
0.652
0.704
0.745
0.830
0.742
0.705
Concentration
fer/ft3)
0.3711
0.3539
0.3395
0.2849
0.3076
0.3252
0.3624
0.3239
0.3080
Dry, STP
(n>3/5)
8.48
9.35
9.19
8.84
9.63
9.63
8.9i
9.40
9.23
Stack flow
(103 ft3/ir.in)
17.97
19.80
19.47
18.72
20.40
20.41
18.87
19.92
19.55
Water
content
10.50
7.71
11.13
9.44
9.17
10.74
9.07
10.19
10.19
Isokinetlc
percentage
85.4
83.6
90.4
90.7
94.1
90.0
84.5
92.3
90.4
Traverse
duration
(min.)
96.0
96.0
96.0
80.0
83.0
93.0
192.0
179.0
173.0
Traverse
perpendicular
L - parallel
L
P
L
P
P
L
L-P
L-P
L-P
Efficiency
(taass I)
2.44
18.17
13.88
17.68
5.03
9.67
7.97
9.30
12.75
Comments
  1.  RUNS 5,  6, 7 - 8 min per pt., 12 ptfi.
     RUN 1-8 min per pt., 9 & 11 skipped.
     RUN 9-8 min per pt., 10-1/2 pts.
     RUN 10-7 nin per pt. for 10 pts.
     Keep: 12th Pt. saopled 8 min.

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Method 5 minimum of 5 min per traverse point for the 40-point two-diameter
traverse on the inlet required 200 min, so one diameter was done one day
at the same time one diameter was being done at the outlet.  The next day,
the other pair of diameters were traversed.  A complete cross-section is
the sum of the two one-diameter traverses.   Although there is a belief on
the part of some that the Method 5 directions preclude taking the traverses
on different days, this is not to be found in the specifications for
Method 5.   Normal operating procedure is to take one inlet-outlet pair of
traverses followed by another pair of inlet-outlet traverses on the per-
pendicular diameters and to combine them, 90 that the only difference would
be the degree to which day-to-day variations exceed hour-to-hour variations
on processes which run for several hours.  A measure of the variability is
the standard deviation, and the  inlet concentrations (Table 4) had a
                 •j                                      q
mean  of 0.854 g/nr and a standard deviation of 0.088 g/m  , which means
about a 10 percent standard deviation due to differences between traverse
positions and days.  This indicates that neither the day-to-day variations
nor the differences between sampling the inlet horizontally or vertically
produced major variation in the  data.  Because the size distribution was
primarily submicron, one would not expect major variations due to con-
centration gradients.  Because the processes are very similar from day to
day,  one would not expect major  variations in the mean concentrations.
The data confirm these expectations  (10 percent deviation  in concentration),

The mean mass percentage efficiency was (7.97 + 9.30+ 12.75)/3 = 10.01
percent.  The standard deviation of this number is  [((10.01 - 7.97)2 +
(10.01 - 9.30)2 + (10.01 - 12.75)2)  /(3 - 1)1 1/2 or 2.47 percent.  Thus,
the efficiency of the scrubber on the rather fine aerosol which reached it
after traversing the sprays and  the separation chamber was:

                         E^ - (10.01 + 2.47) 7.
                                   14

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 As will be shown, the particles were primarily submicron, on a mass
 basis,  with a mass median aerodynamic diameter at the inlet of about
 0.5 \im.  Such fine particles are relatively easy to sample, but they
 are difficult for conventional scrubbers to collect.
     fineness of the aerosol was reflected in the relatively small
 amounts  which deposited in the  probe and cyclone portions of the total
 mass sampling train.   Table 6 gives the average mass collected  in
 these portions of the  sampling  train for six tests  each at inlet and
 outlet of the scrubber.
           Table 6.  MEAN MASSES (SIX TESTS) CAPTURED BY
                     FILTERS, PROBES, CYCLONES FOR INLET
                     AND OUTLET TOTAL MASS SAMPLES


Probe
Cyclone
Filter
Inlet
mass (mg)
50.4
48.8
1358.3
mass %
3.46
3.35
93.19
Outlet
mass (mg)
93.5
53.4
1489.8
mass %
5.70
3.26
91.02
Collection Efficiency Versus Aerodynamic Diameter

To measure the collection efficiency as a function of aerodynamic
diameter, impactors  (Andersen In-Stack Impactors) were used simultan-
eously upstream and downstream from the scrubber, as has been done
elsewhere (for example by Horvath and Rossano, 1970, and Cooper and
Anderson, 1974).  Figure  4  gives a schematic of  the sampling  flow
train used.  An impactor was used to remove spray droplets larger
than 15 urn aerodynamic diameter and heating tapes were used to dry
those remaining.  The impactors were operated at c.14 liter per min,
         i   M
2.4 x 10~  m /s (0.5 cfm).  Dry air flow was measured with an orifice
meter and the amount of moisture collected in the condenser noted.
                                  15

-------

PRE IMPACTOR,
HEATED AND
INSULATED
N
0
Z
z
L
E
1-

STACK
WALL

HEATED AND
INSULATED
PROBE
1



ANDERSEN IM-
PACTOR, FILTER
HEATED AND
INSULATED
vArniiM

PIPE v
ELBOW
' ^
T.TNK
                                                                             THERMOMETER
      I
INLET
OUTLET
PUMP

















MAIN
VALVE
1
DILUTION
VALVE




AMBIENT


|
1
TWO

MANOMETERS ,
ONE STATIC
ONE DYNAMIC

g 	 rONPFNSKR

i
1
THERMOMETER





            Figure  4.   Andersen in-stack irapactor sampling train schematic

-------
    pre-impactor for removing spray droplets Is shown in Figure 5.
         O
At 240 cm /s it has a calculated 50-percent efficiency for particles
having an aerodynamic diameter of 15 (im, and about 10 percent at 10
lim, based upon equations for circular impactors having the same jet-
to-wall and jet diameter dimensions (Fuchs, 1964).

The heater section is shown in Figure 6.  At the  240 cm /s flow rate,
particle losses due to gravity settling will be less than 5 percent for
particles with aerodynamic diameters less than 10 (am, by calculation
                                                                 2
for turbulent flow (Fuchs, 1964).  Using a heating tape of 3 x 10  W
to wrap this heater and heat it, we measured an increase in gas tem-
perature from ambient which corresponded to 1.8 w heat transfer.  Ini-
tial use of this system for the scrubber evaluation revealed that this
was not enough heat to evaporate all the droplets, so the heating cap-
ability was augmented by adding downstream from this heater 76 cm
(30 in.) of 1.27 cm i.d. (1/2 in.) metal tubing wrapped with heating
tape, which experiments indicated would add 1.2 w more heating power.
Ihis was sufficient heating; no longer were the symptoms of inadequate
heating observed:  excessively rapid increase in pressure drop across
impactor filter, deterioration of the impactor collection substrates,
presence of particles on the largest size classification stages.

Size Distributions and Collection Efficiencies

Hie impactor samples were taken approximately isokinetically.  The
problems with trying to take isokinetic samples is that there is a
flow velocity profile, and one does not want to change the impactor
flow to match the velocity because the flow rate  determines the particle
size classification intervals, which should not be changed during a run.
Changing nozzle diameters at each sampling point  is  impractical.  The
samples were taken for 5 minutes or so, moved from one to another of
about five traverse positions on each traverse diameter during  the
sampling.  The more detailed data presentations are  contained in Appen-
dix A .  The size classification intervals were calculated from

                                   17

-------
                  1"
1" I.D.
                       —|  1/2"
              SCREW CAP
    1"
 1/2"  I.D.
 1-1/2"
                T
             1/2"

i;
\
i
j"
f) ii
\
                                1/2"
                                I.D.
Figure 5.  Pre-impactor for sampling in a spray
                       18

-------
                                                           12
vo
               TO CONNECT TO
               PRE-IMPACTOR
                3/8'
£ —



* IN
i




i




1/2" I.D. OUT *
1/2" I.D.

L 	
\- 6"
r *


                                                                                                          TO CONNECT
                                                                                                          TO IN-STACK
                                                                                               2" I.D.
                                    Figure 6.  Heater/drier for  sampling  in a spray

-------
 formulas supplied by the manufacturer.  The method for reducing the
 data from somewhat different flow rates to identical sizing intervals
 is given in Appendix B  .

 Figures 7 and 8 show the particle size distribution for the inlet
 and outlet aerosols as  the cumulative mass percentage having aerody-
 namic diameters as large as or larger than the values on the abscissa.
 The mass median diameters were 0.5 um at the inlet and 0.4 ^m at the
 outlet, definitely a submicronic aerosol.   The fineness of the aerosol
 made it difficult to evaluate collection efficiencies outside the fine
 particle range (0 to 3 ^m) because the collection stages in the finest
 sizing intervals would approach the maximum recommended loadings (20
 mg) before  much material accumulated in the larger sizing intervals.
 As was done before (Cooper and  Anderson, 1974),  weight  changes of 0.3
 mg or less  were treated  as the  inequality <0.3 mg in  calculating effi-
 ciencies.   Two traverses of mutually perpendicular diameters were  com-
 bined to form one concentration value for  each  sizing interval by  taking
 the total mass deposited and dividing by the  total volume sampled.  The
 numerical results of  this analysis  are presented in Tables  7 through  10.
 Graphically these results are depicted in Figure 9.   The  device  was not
 an efficient  collector of fine  particulates, which is not an unexpected
 result  considering the low pressure  drop across  the scrubbing  section,
 an average  of  6.06 in. H20 «  1.51 x  103 N/m2.

 Possible explanations of the  negative  efficiencies (greater concentra-
 tion  of mass at  the outlet  in a  size  interval than at the inlet) in-
 clude:  agglomeration, deagglomeration, or other  change in particle
 size distribution without  increase or  decrease in total mass; produc-
 tion of particles, such  as  by spray  introduced between inlet and out-
 let; random data errors  in  the vicinity of zero efficiency; undetected
 systematic error.  Particle production and random errors are discussed
next.
                                  20

-------




*
0.
Q
2
H
at
w
0
w
RCENTAC
w
P-I
CO
1




TEST NO.
99
98
95
90
80

70
60
50
40
30
20
10
5

2
1
O 6 INLET, HORIZONTAL TRAVERSE, 21 NOV. '74
^ 7 INLET, VERTICAL TRAVERSE, 22 NOV-. '74
+ 8A INLET, VERTICAL TRAVERSE, 25 NOV. '74
X 8B INLET, HORIZONTAL TRAVERSE, 25 NOV. '74
D 9A INLET, HORIZONTAL TRAVERSE, 26 NOV. '74
*• 9B INLET, .VERTICAL TRAVERSE, 26 NOV. '74
1 1 1 1 1 1 1 1 1 III 1 1 1 1 I T
— _
— —
~ —
_
O
- 0 -
y
+ ^J
A
D t*
x A
— i _
+ A A
D ^ P
X t) A
D -P
^ f
Q x _
x ~
i i i i i i i i | ill I i i i i i
.3 .4 .5 .6 .7 .8 .9 U> 20 3X) 40 5.0 1Q
         AERODYNAMIC DIAMETER,  D
Figure 7.  Inlet particle size distribution
                     21

-------
TEST NO.










-X
Q.
Q
1
H
0!
w
0
PC
3
w
u

-------
Table 7.  IMPINGEMENT SCRUBBER PARTICLE COLLECTION EFFICIENCIES
          FROM IMPACTOR DATA, TESTS 6 AND 7
Inlet
Stage
1
2
3
4
5
6
7
8
Fines
Concentration
(8/m3)
0.012
0.013
0.014
0.010
0.016
0.090
0.078
0.082
0.149
Outlet
Stags
1
2
3
4
5
6
7
8
Fines
Concentrat ion
(g/n>3)
(<) 0.004
(<) 0.004
0.008
0.009
0.009
0.016
0.055
0.172
0.252
Aerodynamic
diameter
(urn)
12.8
8.0
5.4
3.7
2.3
1.21
0.74
0.50
<0,50
Collection
efficiency
(%)
>58.3
>69.2
42,9
10.0
43.8
82.2
29.5
-109.8
- 69.1
Table 8.  IMPINGEMENT SCRUBBER PARTICLE COLLECTION EFFICIENCIES
          FROM IMPACTOR DATA, TESTS 8A AND 8B
Inlet
Stage
1
2
3
4
5
6
7
8
Fines
Concentration
(g/m3)
< 0.004
<0 . 004
<0.004
0.009
0.007
0.016
0.050
0.107
0.265
Outlet
Stage
1
2
3
4
5
6
7
8
Fines
C one e nt r a t i on
(g/m3)
<0.004
1.0.004
1.0.004
<0.004
<0.004
0.008
0.029
0.107
0.267
Aerodynamic
diameter
(ym)
12.8
8.0
5.4
3.7
2.3
1.21
0.74
0.50
<0.50
Collection
efficiency
ry\
{/o)
—
—
—
>55,6
>42.9
50.0
42.0
0.0
- 0.7
                             23

-------
Table 9.  IMPINGEMENT SCRUBBER PARTICLE COLLECTION EFFICIENCIES
          FROM IMPACTOR DATA, TESTS 9A AND 9B
Inlet
Stage
1
2
3
4
5
6
7
8
Ftnes
Concentration
(g/m3)
1.0.004
£0.004
£0.004
< 0.004
< 0.004
0.014
0.033
0.085
0.203
Outlet
Stage
1
2
3
4
5
6
7
8
Fines
Concentration
(g/m3)
< 0.004
<0.004
< 0.004
.10.004
^0.004
0.014
0.041
0.081
0.244
Aerodynamic
diameter
(fim)
12.8
8.0
5.4
3.7
2.3
1.21
0.74
0.50
<0.50
Collection
efficiency
(%)





0.0
-24.2
4.7
-20.2
                   Table 10.
MEAN COLLECTION
EFFICIENCY,
IMPACTOR DATA
Mean
aerodynamic
diameter
(fim)
3.0
1.75
0.98
0.62
0.25

Mean
efficiency
(%)
43.8
44.1
15.8
-38.5
-30.0
                              24

-------
     98
  O
  z
  UJ

  - 95
UJ



O
jll 90


UJ
O
O


UJ
CD
     80
h-
z
UJ
O
o:
UJ  50
Q.
      0


    -40




   -100
                  2345678

                   AERODYNAMIC  DIAMETER,
                                                           1.0
                                                         2.0
                                                        5-°  §
                                                           10
                                                        20
UJ
z
UJ
a.

UJ
o
                                                               UJ
                                                               O
                                                               a:
                                                               UJ
                                                               a.
                                                          50
                                                        100


                                                        140
                                                         200
                                                       10
Figure  9.  Collection efficiency versus aerodynamic  diameter, data
          means for Pentapure  scrubber
                               25

-------
 Particle Generation by Scrubber

 Hard  water may contain as much as 30 gr/gallon = 510 g/m  of dissolved
 calcium and magnesium salts (Rose,  1966),  soft water has < 5 gr/gallon
         3                              3                 ~
 = 86  g/m .   At ~ 10 gr/gallon = 171 g/m ,  the total spray of 85 gallon/
                -3  3
 min = 0.46 x 10   ra /s would  produce a  grain loading for this air  flow
               3            3
 of 0.044 gr/ft  = 0.101 g/m .   Whatever fraction of the spray was  in-
 troduced between scrubber inlet and outlet sampling positions would
 tend  to lessen measured efficiency  to the  degree that the solids formed
 from  the spray and not captured outweighed the solids caught by spray
 and scrubber.   Negative efficiencies would occur if the spray intro-
 duced more solids than it captured  for  any size interval measured  with
 the Andersen impactor.   Ihe negative efficiencies  for the finest aero-
 sol fraction (< 0.50 |_im)  in impactor tests 6,  J ,  and 8A, B and 9A, B
                                                2
 came  from outlet concentrations being < 0.1 g/m  greater than the
 inlet concentrations,  which might be explained by  this  mechanism.
 Sensitivity  to Measurement Error

 The  efficiency E  is defined as  the

                            E = 1 - m_/m
where m9  is  the appropriate outlet concentration and m.. is the corres-
ponding inlet concentration.  The change in the efficiency measurement,
dE, with  respect  to changes dm. and dtru in the measured concentrations
is given  by

                  dE =  (dE/onO dm][

which can be shown to be

                  dE •  (ti^/n^)  (dm1/m]L)
                                 26

-------
which has an absolute magnitude
                                  dm.     dmn

As the efficiency tends to zero, the fractional errors are magnified
as this equation indicates.  If the concentrations have a 5-percent
relative error (dm./m , dm./nu = 0.05), the error in the efficiency
determination would be dE < + 10 percent at E = 0.0 percent,
                          f\f *—
dE < + 5 percent at E = 50 percent and dE < + 1 percent at E = 90
   m ~                                    nt ~~
percent.

In our laboratory tests using these two impactors to sample simultan-
eously an iron oxide aerosol, we found a correlation coefficient
averaging better than 0.998.  One of these two tests is shown in
Table 11.  From the data from sizing intervals having 0.3 mg or
greater, the average absolute percentage difference between the two
impactor concentration determinations was 13 percent, which means the
individual errors dnu/m  and dm /m  were about one-half this; at zero
efficiency, the average absolute difference from zero of the measure-
ments would be about 13 percent, as many negative as positive.  This
would also partially explain some negative efficiency values.

In another set of tests, these made with the Andersen In-Stack Impac-
tors side-by-side at the outlet of a power plant baghouse (Nucla,
Colorado), the total mass concentrations determined by the two impac-
tors were compared for 22 separate runs.  The average absolute dif-
ference between the impactors was 74 percent of the geometric mean con-
centration and the average difference was 15 percent, indicating that
most of the error was random rather than a consistent bias.  These
differences were substantially higher than those noted in the labora-
tory tests, one reason for which may be the unusually low concentra-
tion (0.0034 gr/scf = 0.0078 g/ra ) and long sampling time (6 hr).   A
more important reason was the difference in the size distributions,

                                27

-------
           Table 11.  DATA FROM TWO ANDERSEN MARK III CASCADE IMP ACTORS SAMPLING SAME IRON OXIDE AEROSOL
                      (MAPICO BLACK) AT 470 cm3/s

Impactor
Stage

1
2
3
4
5
6
7
8
Filter
Total
Mass
Mass collected
Impactor
#4601

0.4
0.3
0.6
0.8
2.0
9.6
3.3
0.1
0.6

17.7
Impactor
#4602

0.2
0.2
0.4
0.7
1.9
9.7
3.8
0.2
0.5

17.6
Percentage of
total mass
Impactor
#4601

2
2
3
5
11
1 54
19
1
3

100
Impactor
#4602

1
1
2
4
11
55
22
1
3

100
Cumulative mass
percentage
Impactor
#4601

2
4
7
12
23
77
96
97
100


Impactor
#4602

1
2
4
8
19
74
96
97
100


Effective
Diameter
(|im)
Dc«
50
9.6
6.0
4.0
2.75
1.75
0.9
0.54
0.36



00
                       Correlation  coefficient:
0.998

-------
 the power plant aerosols having a mass median  diameter  of  8.7  ;tm,
 about  four  times  larger  than  the  laboratory  aerosols  and  ten times
 larger  than the foundry  aerosol;  the  larger  aerosols  are more  prone
 to unrepresentative  sampling  and  to losses.  The  differences between
 impactors are believed to have been nearer those  experienced in  the
 laboratory  tests  than those experienced with the  baghouse  effluent
 tests.

 THEORETICAL EFFICIENCY COMPARED WITH  EXPERIMENTAL

 The Scrubber Handbook gives the following formula for the  penetration
 of a venturi scrubber:

          Pn = exp (2 Q_ u  pT D. F(K , f)/55  Q   u )
                       L  g   L  d     p         g   g
                                                3
where   Q   = volume  flow of scrubbing liquid,  cm  /s
         J_r
        u   = gas velocity at  scrubber throat,  cm/s
                                           3
        P   = scrubbing liquid density, g/cm
        D,  = scrubbing droplet mean diameter,  cm
  F(K  , f)  = inertial collision function
     P                          3
        Q   = gas volume flow, cm /s
         o
        (j.   = gas viscosity, poise
         o

 The function F(K  , f) depends upon a Stokes parameter, K , given by

                    K  = u  d  2/9 a  D.  ,
                     p    g  pa    Kg  d
where d   is the particle aerodynamic diameter (V g/cm /cm), and F
       pa
depends upon the parameter f, which is determined empirically and in-
cludes effects of mean gas droplet relative velocity and droplet-
particle wetting.  In the range where collection is appreciable
(K  > 1) , an approximate form given in the Scrubber Handbojok for F is

                   F(K , f) - - 0.156 K  f2  .

                                29

-------
The  resulting  expression  for  the penetration becomes:
              (-  (6.:
Pn = exp ( - (6.3 x 10"4) f2 QL ug2
 The  factor  f is usually between 0.25 and 0.5.  Here Q_/Q  was <
                3            -3                      L  g     ~
 85 gal/20,000  ft  - 0.57 x  10  .  Ihe gas flow at the throat was
         3
 20,000  ft /min through a 2-foot diameter opening or 6,366 ft/min,
                  2
 which is 32.4  x 10  cm/s =  u .  The scrubbing liquid density was
    /  3                     8         -4
 1 g/cm  and the air viscosity 2.1 x 10   poise.  For f = 0.5 and
d   = 1 x 10   cm J g/cm
 pa
       -4     /  ,  3
             V 8/c
         (•
     Pn = exp  -  (6'3 * 10"4)(0.5)2C0.57 x 10"3)(10.5 x 1Q6)(1 x

                                     (4.41 x 10"8)
     Pn = 0.808.



Table 12 gives the calculated pentrations using this formula for

both f = 0.25 and f = 0.50.  These calculations are approximate,

partly because the scrubber geometry is somewhat different from that

of the usual venturi , though not so different that their major collec-

tion mechanism differs:  the impaction of particulate material on

droplets, followed by the capture of the droplets.



In the Scrubber Handbook, the following equation is derived to corre-

late fractional penetration, Pn, of particles having given aerodynamic

diameter, d  , with pressure drop,  AP:
           pa
            Pn = exp
               /   6.1 x
               (


               V
                              10"9 (d  )2 AP f2 p.
                               30

-------
Table 12.  APPROXIMATE THEORETICAL EFFICIENCIES FOR PURITY CORP.
           IMPINGEMENT SCRUBBER
Particle
aerodynamic
diameter
(nm)
0.5
1.0
2.0
3.0
4.0
6.0
8.0
10.0
Assuming f = 0.25
Fractional
penetration
(Pn)
0.987
0.948
0.808
0.618
0.425
0.146
0.0327
0.0048
Percentage
efficiency
(%)
1.3
5.2
19.2
38.2
57.5
85.4
96.7
99.52
Assuming f - 0.50
Fractional
penetration
(Pn)
0.948
0.808
0.425
0.146
0.0327
0.00046
1 x 10-6
mm mm
Percentage
efficiency
<%)
5.2
19.2
57.5
85.4
96.7
99.95
100
100
                               31

-------
where   u   - gas viscosity, poise
         o
       d    = particle aerodynamic diameter, L
        pa                                 2
        p   = scrubbing  liquid density, g/cm
AP
             pressure drop across scrubber, cm H?0  (980 dynes/cm  ,
             98 N/m2)
          f = empirical constant, related to relative gas/liquid
             velocity and coverage
Figure 10 is a corrected version of one from the Scrubber Handbook.
the aerodynamic diameters indicated for f = 0.25, which that reference
indicated was best, and for f = 0.5, which Calvert (1974) indicated
was the best fit for coal-fired power plant emissions (fly ash).  The
dependence on f is striking, being just as strong as the dependence
upon particle size; doubling f halves the particle size caught with a
given efficiency at a given pressure drop.  For the same particle
size, the factor of 2 in the different f values corresponds to a fac-
tor of 4 in the pressure drop required to achieve a particular pene-
tration.

The scrubber is not identical to a venturi scrubber,  but basically
both types use the acceleration and deceleration of the air to pro-
duce relative velocity gradients between the airborne particulates
and the collecting droplets.  The Purity scrubber collection effi-
ciency is expected to be related to the pressure drop across the
scrubbing section in much the same way the venturi scrubber effi-
ciency is.  Figure 10 has the penetration versus pressure drop
curves for typical venturi scrubber performance (from Scrubber Hand-
book,  by  Calvert, et al., 1972).   The open circles and triangles
on the figure are the measured efficiencies for the Purity scrubber
at the aerodynamic diameters indicated.
                               32

-------
                          INCHES  H2O
                        40  JO   60   70
                                 "1	
90
    100
         no
             120
                                      i     i    I    l\	I
 130
—I—
                                                     VENTURI
                                                     PENETRATION.
                                                     PRESSURE DROP
               5*10^     10x10*     I5«IO*     20»IOJ    25*10*     N/mz
                              PRESSURE  DROP
Figure  10.   Venturi  pressure  drop and efficiency for  different  f
             factors  and particle diameters  (corrected version of
             Scrubber Handbook figure )
                                   33

-------
         5 10 15 20
                           INCHES  H2O
                             50   60    70
   0-OQIl  ill.!   U	1
    60   90   100   UO  120   130	UO
                                                         1	I—


                                                       VENTURI
                                                       PENETRATION,
                                                       PRESSURE DROP
                                                      O DATA,f=0.25
                                                      A DATA, f =0.50
I     I    I     l\   I     I	I
              5*IOS     10*10*    ISMO3     20-10*     25«I05     N/m2

                               PRESSURE  DROP
Figure 11.,  Corrected venturi performance  curves with Pentapure
              scrubber data  added
                                    34

-------
Depending upon which f factor value is more appropriate for this situa-
                                                                         3
tion (0.25 or 0.5), the device was equivalent to a venturi with 0.75 x 10
           32                                                    i
to 1.8 x 10  N/m  (3 to 7 in. H,0) pressure drop or 0.19 to 0.45 x 10J
   2
N/m  (0.75 to 1.8 in. H-0).  From the Scrubber Handbook equation 5.3.6-12,
                                                                   2
the following equation can be derived to give the pressure, Ap (N/m ),
required for a venturi scrubber to have 50 percent efficiency and particle
aerodynamic diameter d  :
     *                pa
                                     oo       22
                     Ap = 1.114 x KT p  /p  d    f
                                        g   L  r

Values derived from this equation are given in Table 13 and Figure 12.
Figure 12 is based upon the next to last table, Table 12, and has the
non-negative impactor data points for the scrubber superimposed on a
graph of the percentage efficiency versus particle aerodynamic diameter
with two different f values, showing a 50 percent efficiency somewhere
around 2 ym to 4 ym aerodynamic diameter.

The final result of a theoretical analysis performed on this type of
scrubber by Midwest Research Institute was that the particle size for
                                                                •5
which the efficiency would be 50 percent was 3 urn for a 2.8 g/cm  density
particle, which corresponds to a 5 vm aerodynamic diameter (K.P. Ananth,
MRI, personal communication, December 1974).

In summary, the theoretical analysis and the experimental results indicate
that the collection efficiency reaches 50 percent between 2 and 4 um
aerodynamic diameter and increases for the larger particle sizes, but
decreases for the smaller sizes, at least down to a few tenths microns.
                                 35

-------
Table 13.  THEORETICAL PRESSURE DROP NEEDED FOR 50 PERCENT
           COLLECTION EFFICIENCY AT THE LISTED PARTICLE
           SIZES FOR A VENTURI SCRUBBER

Particle
aeroydnamic
( P m)
1
2
3
4
5
Pressure drop

f • 0.25
N/m2
5.8 x 103
1.44 x 103
0.64 x 104
0.36 x 103
0.23 x 103
"H20
24
6.0
2,6
1.5
0.93
f - 0.50
N/m2
1.44 x 103
0.36 x 103
0.16 x 103
90
57
"H20
5.8
1.5
0.64
0.36
0.23
                          36

-------
                                        NON-NEGATIVE
                                        IMPACTOR DATA
                    23456789
                     AERODYNAMIC  DIAMETER,|xm
Figure  12.  Data and approximate theory predictions  (see Table 12)
           (f = 0.25, 0.50;  QL/QB - 0-57 x 10~3)  for Pentapure
           scrubber

-------
                                SECTION V
                       POWER CONSUMPTION AND  COSTS

 The  power  used  by  the  scrubber  is  predominantly  the  pressure drop  of
 the  air  going through  the  scrubber (Ap)  times  the  flow  rate of  the
 air  (Q ) in actual volume  terms.
      O

 The  pressure drop  across the  scrubber  was determined by making  static
 pressure measurements  at the  scrubber  inlet  (where the  samples  were
 obtained) and the  scrubber outlet  (just before the fan).  The inlet
 readings were made for each  total  mass sampling  point on the traverse,
 by using the static reading of  the pitot-static  tube.   The outlet
 readings were made every five minutes  during the first  half hour the total
 mass samples were  taken, by using  an upright unit  density  oil manometer.

 The  average values for the measurements for  the  pressure drops  are
 given in Table  14.

 Flow and pressure  drop were:
            Q   -  25.0  x  103  ft3/min  =11.8 m3/s
             O
          Ap  =  6.06" HO =     1.51 x 103 N/m
Thus, the air power consumption in watts was an average 17.8 kw.  A
standard estimate of the electrical power necessary to achieve this
air flow power is to assume combined efficiency for pumps and fans
                               38

-------
of 0.6, which would make the electrical power consumption for this
operation 29.7 kw.  The fan and motor combination at the site was
rated at 75 hp. = 5.6 x 104 w. = 56 kw.
       Table  14.   AVERAGE  PRESSURE  DROPS  ACROSS  PURITY SCRUBBER
Run #
5
6
8
9
Inlet
static
pressure
("H20)
1.89
1.88
1.86
1.94
No. of
readings
20
15
20
19
Outlet
static
pressure
("H20)
7.76
7.79
8.17
7.83
No. of
readings
7
7
6
6
Net pressure
drop
Ap, (" H20)
5.87
5.91
6.31
5.89
det
pressure
drop
(N/mz)
1.46 x 103
1.47 x 103
1.57 x 103
1.47 x 103
WATER CONSUMPTION
The operators of the installation reported that the spray flow was 85
                       -3  3
gallons/min. = 5.4 x 10   m /s.  The water flow to air flow ratio was
thus about 4.4 gal/1000 s.c.f.m. or 0.46 x 10
                                             -3
Manufacturer's
literature puts the water used for the cleaning spray at about 0.7 x
  -433                 3
10   m /m  (0.5 gal/1000 ft ) volume of water to volume of air ratio.
                                                                  3   ?
Most of the spray was used to cool the gas, approximately  3 x  10~ mj/s
               3
(50 gal/1000 ft ) if all the cooling were done by evaporation.   There
exists some discrepancy between the reported water flow, the calculated
cooling water usage, and the manufacturer's literature, but the start-
ing temperature used for the gas  (1400°F = 760°F) is only a typical
value from the literature,  and the water flow was not actually
measured for the spray nozzles.  For the comparison, we have accepted
the manufacturer's value and have accepted his contention that only
about 1/3 of this cannot be reused; thus, the water consumption has
been placed at 0.17 gal/1000 ft3 or 0.023 x 10~3 m /m3.
                               39

-------
 COSTS
 The  costs  of  the scrubber are discussed briefly next,  with comparison
 made in  terms of a  venturi scrubber,  which also collects  particles
 through  spray scrubbing.

 Fixed Costs

 The  manufacturers have  informed  us  that the equipment  and installa-
 tion costs of the Pentapure scrubber  are not substantially different
 from those for a venturi  scrubber.  If  this were roughly  $100,000 for
 a  19 nr/s  (40,000 c.f.m.)  installation  (see Scrubber Handbook  for
 cost data and ranges),  then the  amortization over 20 years would give
 $5,000 per year  cost, the  interest  on the  loan  (8 percent of capital
 investment) would be about  $400  yearly,  and the insurance about $1,000
 per  year.  These would  be as  nearly the same for the two  types of
 scrubber as their capital  investments are  (purchase price plus
 installation  costs).

 Variable Costs

 Labor and maintenance are estimated as  one  percent of  the capital
 investment per year, thus about  $1,000  per  year  for both :types of
 scrubber.  The cost of  electric  power (at $0.025  per kw.-hr.) for
 19 m3/s (40,000  c.f.m.) would be:

     Pentapure power cost =  60 kw. x 8000 (hr./yr.) x ($0.025/kw.-hr.)
                          -   $12,000  per year.

The mid-range values of the pressure drop for a venturi scrubber
                                                    2     2
having a similar collection efficiency were  3.1 x 10  N/m   (1.25"
                  3     2
HO)  and 1.24 x  10  N/m  (5" HO),  depending upon  the  conditions which
                               40

-------
affect the f factor discussed above.  This means a power consumption
of between about 12 kw. and 50 kw. so that

   Venturi power cost = (12 to 50 kw.)  (8000 hr./yr.)  ($0.025/kw.-hr.)
                      = $2,400 to $10,000 per year.

The manufacturer reports the cleaning spray (as opposed to the cool-
                            -433                           3
ing spray) is about 0.7 x 10   m  per m  of air ( 0.5  gal./lOOO ft. ).
Cost estimates in the Scrubber Handbook used 1.1 x 10   m3/m3 (8.4
             3
gal./lOOO ft. ) for a venturi scrubber.   In both units, much of the
water would be reused.  If none of the water for the Pentapure
scrubber were reused, the cost for a 19 m /s (40,000 c.f.m.) unit would
                                                             3
be about $6,400 per year,  using a water cost of $0.50/100 ft. .
Scrubbers are generally designed so as to reuse the water.  If the
lower water spray concentration means lower water consumption (that
fraction not reused), then the Pentapure might provide a cost savings
with respect to water consumption in comparison with the venturi
scrubber.  Both require some handling of the liquid wastes, the cost
of which we do not estimate here.
                              41

-------
                               SECTION VI
                               APPENDICES

APPENDIX A, IMPACTOR DATA

In Tables VI.1 to VI.12 are the data obtained by the cascade impactor
sampling of the Purity Corp. Pentapure Scrubber at the foundry operation
on which it was tested.   Tests tables give the run number, the data,
the location, the impactor flow rate (at impactor conditions) in c.f.m.
     3
and m /s, the sampling time duration, the total volume samples in that
time, the temperature immediately downstream from the impactor, and the
concentration as mass per volume dry standard air.  Appendix B indicates
how these data were handled to make the particle sizing intervals coincide.
                                42

-------
               Table 15.  IMPACTOR DATA, RUN 6, INLET
Run # 6
Date  11/21/74
Location  Inlet
                                 -4  3
Impactor Flow 0.53  CFM, 2.5 x 10   m Is
Time 11 min = 660 s.
Sample Volume 5.95 ft3, 1.69 x 10"  m
Impactor Temperature 12  C
Concentration 0.170  gr/ft3, 0.387 g/m3
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
(jim)
13.0
8.1
5.5
3.8
2.4
1.23
0.75
0.51


Net weight
(g)
0.0015
0.0009
0.0015
0.0011
0.0020
0.0182
0.0135
0.0104
0.0163
0.0654
% on stage
2.3
1.4
2.3
1.7
3.1
27.8
20.6
15.9
24.9

Concentration
(g/m3)
0.009
0.005
0.009
0.007
0.012
0.108
0.080
0.062
0.096
0.387
% > stated
size
2.3
3.7
6.0
7.7
10.8
38.6
59.2
75.1


                                 43

-------
                Table 16.  IMPACTOR DATA, RUN 7, INLET
/
Run # 7
Date  11/22/74
Location  inlet
Impactor Flow 0.50  CFM, 2.4 x 10   m /s
Time  4 min =* 240 s.
Sample Volume 2.05 ft  , 5.81 x 10"2 m3
Impactor Temperature 12  C
Concentration  0.298 gr/ft3, 0.680 g/m3
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
(nm)
13.4
8.4
5.6
3.9
2.4
1.27
0.77
0.53


i
Net weight
(g)
0.0010
0.0020
0.0018
0.0011
0.0009
0.0021
0.0039
0.0077
0.0190
0.0395
% on stage
2.5
5.1
4.6
2.8
2.3
5.3
9.9
19.5
48.0

Concent rat ion
(g/m3)
0.017
0.034
0.031
0.019
0.015
0.036
0.067
0.133
0.327
0.680
% > stated
size
2.5
7.6
12.2
15.0
17.3
22.6
32.5
52.0



-------
                Table 17.   IMPACTOR DATA, RUN 8A, INLET
Run # 8A
Date  11/25/74
Location  Inlet
                                   i  f\
Impactor Flow 0.72  CFM, 3.4 x 10   m /s
Time  5 min = 300 s.
                      3           -23
Sample Volume 2.64  ft , 7.48 x 10   m
Impactor Temperature  132 c
Concentration 0.203   gr/ft3, 0.464 g/m3
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
(fim)
12.7
8.0
5.3
3.7
2.3
1.20
0.73
0.49


Net weight
<8>
0.0004
0.0008
0.0006
0.0009
0.0006
0.0013
0.0023
0.0057
0.0221
0.0347
7, on stage
1.1
2.4
1.7
2.6
1.7
3.7
6.7
16.4
63.7

Concentration
(g/m3)
0.005
0.011
0.008
0.012
0.008
0.017
0.031
0.076
0.295
0.464
% > stated
size
1.1
3.5
5.2
7.8
9.5
13.2
19.9
36.3



-------
              Table  18.  IMPACTOR, DATA, RUN 8B, INLET
Run # 8B
Date  11/25/74
Location  Inlet
                                 -4  3
Impactor Flow 0.77  CFM, 3.6 x 10   m /s
Time  5 min =300 s.
Sample Volume 2.78 ft3, 7.87 x 10"2 m3
Impactor Temperature 139 c
                          3           3
Concentration 0.205  gr/ft , 0.470 g/m
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
Om)
12.4
7.7
5.2
3.6
2.25
1.16
0.70
0.47


Net weight
(8)
0.0000
0.0003
-0.0002
0.0005
0.0005
0.0015
0.0063
0.0110
0.0169
0.0370
7, on stage
< 0.9
< 0.9
< 0.9
1.3
1.3
4.0
17.0
29.8
45.7

Concentration
(g/m3)
<0.004
<0.004
<0.004
0.006
0.006
0.019
0.080
0.140
0.215
0.470
% > stated
size


0.9
2.2
3.5
7.5
24.5
54.3


                                 46

-------
              Table 19.  IMPACTOR DATA, RUN 9A, INLET
Run #  9A
Date   11/26/74
Location  inlet
                                 4  3
Impactor Flow 0.73  CFM, 3.4 x 10  m /s
Time  5 min = 300 s.
                     3           23
Sample Volume 2.66  ft , 7.53 x 10  m
Impactor Temperature 123 C
Concentration 0.170  gr/ft3, 0.388 g/m3
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
Qim)
12.6
7.8
5.2
3.6
2.3
1.18
0.71
0.48


Net weight
(g)
0.0000
0.0001
0.0000
0.0003
0.0002
0.0010
0.0013
0.0056
0.0207
0.0292
7. on stage
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
3.4
4.4
19.1
70.9

Concentration
(g/m3)
<0.004
<0.004
<0.004
<0 . 004
<0.004
0.013
0.017
0.074
0.275
0.388
7. > stated
size




2.2
5.6
10.0
29.1


                                 47

-------
               Table 20.   IMPACTOR DATA,  RUN 9B,  INLET
Run #  9B


Date   11/26/74


Location  Inlet

                                 -4  3
Impactor Flow 0.69  CFM, 3.3 x 10   m /s


Time  5 min = 300 s.

                     3           -23
Sample Volume 2.74 ft  , 7.76 x 10   m


Impactor Temperature  88 C

                          3           3
Concentration 0.131  gr/ft , 0.300 g/m
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
(jim)
12.5
7.8
5.2
3.6
2.3
1.17
0.71
0.48


Net weight
(g)
0 . 0000
0.0002
0.0001
0.0001
0.0003
0.0015
0.0045
0.0075
0.0091
0.0233
7. on stage
< 1.3
< I-3
< 1.3
< 1.3
< 1.3
6.3
19.3
32.3
39.0

Concentration
(g/m3)
<0.004
<0.004
<0.004
<0.004
<0.004
0.019
0.058
0.097
0.117
0.300
% > stated
size




3.1
9.4
28.7
61.0


                                48

-------
             Table 21.  IMPACTOR DATA, RUN 6, OUTLET
Run # 6
Date  11/21/74
Location  Outlet
                                  /   1
Itnpactor Flow 0.58  CFM, 2.7 x 10~  in /s
Time  6 min = 360 s.
Sample Volume  3.17ft  , 8.98 x 10   m
Impactor Temperature 49  C
Concentration  0.213 gr/ft3, 0.487 g/m3
Stage
1
2
3
A
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
Qim)
13.0
8.2
5.5
3.8
2.4
1.23
0.75
0.51


Net weight
(8)
-0.0012
0.0003
0.0010
0.0010
0.0005
0.0020
0.0063
0.0113
0.0213
0.0437
7. on stage
< 0.6
< 0.6
2.3
2.3
1.2
4.5
14.4
25.9
48.7

•
Concentration
(g/m3)
<0.003
<0.003
0.011
0.011
0.006
0.022
0.070
0.126
0.237
0.487
% > stated
size

0.7
3.0
5.3
6.5
11.0
25.4
51.3


                               49

-------
               Table 22.  IMPACTOR DATA, RUN 7, OUTLET
Run # 7
Date  11/22/74
Location  Outlet
                                  /  Q
Impactor Flow 0.88  CFM, 4.2 x 10   m /s
Time  6 min = 360 s.
                     3           -23
Sample Volume  3.08ft  , 8.72 x 10   tn
Impactor Temperature 233 C
                          3           3
Concentration 0.249  gr/ft , 0.571 g/tn
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
(Mm)
12.5
7.8
5.2
3.6
2.3
1.17
0.70
0.47



Net weight
(g)
0.0006
0 . 0004
0.0004
0.0006
0.0010
0.0010
0.0049
0.0190

0.0219
0.0498
7. on stage
1.2
0.8
0.8
1.2
2.0
2.0
9.8
38.2

44.0

Concentration
(g/m3)
0.007
0.005
0.005
0.007
0.011
0.011
0.056
0.218

0.251
0.571
% > stated
size
1.2
2.0
2.8
4.0
6.0
8.0
17.8
56.0



                                 50

-------
             Table 23.  IMPACTOR DATA,  RUN 8A,  OUTLET


Run # 8A

Date  11/25/74

Location  Outlet
                                  /  ^
Impactor Flow 0.70  CFM, 3.3 x 10   m /s

Time  5 min = 300 s.
                      3           -23
Sample Volume 2.71 ft , 7.67 x 10   m

Impactor Temperature  58  C
                          3           3
Concentration 0.172   gr/ft , 0.392 g/m
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
(Hm)
12.0
7.5
5.0
3.5
2.2
1.13
0.68
0.46



Net weight
(g)
0.0000
0.0000
0.0000
0.0001
0.0001
0.0006
0.0018
0.0070

0.0205
0.0301
7. on stage
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
2.0
5.9
23.2

68.1

Concentration
(g/m3)
<0.004
<0.004
<0.004
<0.004
<0.004
0.008
0.023
0.091

0.267
0.392
% > stated
size




0.8
2.8
8.7
31.9



                                 51

-------
              Table  24.  IMPACTOR DATA, RUN 8B, OUTLET
Run # 8B
Date  11/25/74
Location  Outlet
Impactor Flow 0.66  CFM, 3.1 x 10"  m /s
Time  5 min = 300 s.
Sample Volume 2.79 ft ,  7.90 x 10"2 m3
Impactor Temperature  76 C
                          3           3
Concentration 0.191  gr/ft ,  0.437 g/m
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
tym)
12.6
7.9
5.3
3.7
2.3
1.19
0.72
0.49


Net weight
(g)
-0.0001
0.0000
0.0000
-0.0001
0.0003
0.0009
0.0041
0.0100
0.0192
0.0345
% on stage
< 0.9
< 0.9
< 0.9
< 0.9
< 0.9
2.5
11.9
29.1
55.6

Concent rat ion
(g/m3)
<0.004
<0.004
<0.004
<0.004
<0.004
0.011
0.052
0.127
0.243
0.437
7. > stated
size



-
0.9
3.4
15.3
44.4


                                52

-------
             Table 25.  IMPACTOR DATA, RUN 9A, OUTLET



Run #  9A


Date  11/26/74


Location  Outlet
                                  /  *i

Impactor Flow 0.59  CFM, 2.8 x 10   m /s


Time  5 min = 300 s.
                      3           -23
Sample Volume 2.70 ft , 7.65 x 10   m

                        o    '
Impactor Temperature  44  C

                          3           3
Concentration  O.lrj3  gr/ft , 0.349 g/m
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
(jim)
12.9
8.0
5.4
3.7
2.3
1.21
0.74
0.50


Net weight
(g)
-0.0003
-0.0001
0.0000
-0.0002
0.0000
0.0005
0.0015
0.0042
0.0205
0.0267
7, on stage
< 1.1
< 1.1
< l-1
< 1.1
< 1-1
2.0
5.7
15.8
76.8

Concentration
(g/m3)
<0.004
<0.004
<0.004
<0.004
<0.004
0.007
0.020
0.055
0.268
0.349
% > stated
size





1.7
7.4
23.2


                               53

-------
             Table  26.  IMPACTOR DATA, RUN 9B, OUTLET

Run #  9B
Date   11/26/74
Location   Outlet
                                  /   1
Impactor Flow  0.46 CFM, 2.2 x 10~  m /s
Time   5min = 300 s.
Sample Volume  2.20ft3, 6.23 x 10"2  m3
Impactor Temperature  29 C
                          3           3
Concentration  0.185 gr/ft , 0.424 g/m
Stage
1
2
3
4
5
6
7
8
Back up
filter
Total
Aerodynamic
diameter
fyim)
14.3
8.9
6.0
4.2
2.6
1.35
0.83
0.57


Net weight
(g)
0.0000
0.0000
-0.0002
-0.0008
0.0002
0.0010
0.0036.
0.0064
0.0152
0.0264
7. on stage
< 1.2
< I-2
< I-2
< I-2
< 1.2
3.8
13.7
24.3
57.6

Concentration
(g/m3)
<0.005
<.0.005
£0.005
£0.005
<0.005
0.016
0.058
0.103
0.244
0.424
% > stated
size




0.6
4.4
18.1
42.4


                               54

-------
APPENDIX B, COMPARING SIZE DISTRIBUTION DATA HAVING DIFFERENT SIZING
INTERVALS
For a variety of reasons,  particle  size distribution data may have been
obtained by multi-stage or multi-channel instruments with different size
intervals.  To change concentration reading M., obtained for particles
between a  -  and a ,  into  concentration readings M * over the interval
 *       *
a. 1 to a  one estimates the  concentration in the portion of the interval
which is different by using the  average concentration per unit particle
size obtained from the intervals adjacent to the portion in question.
This is shown in Figure VI-1,  and the equations are given for making
this transformation.   This is, essentially, a linear interpolation.

To apportion the material  M.  collected between a. - and a  to standard
             *     *       1                    i-1      I
intervals a  - to a :

Ml = Ml + \ (al  " al) [V(al ~ aO)  + M2/(a2  "  al

M* = M2 + i (a* - a2)  [M2/(a2 - aj + M3/(a3 - a^ J


        -\ (ai- ai>  [V(ai -V + V(a2 -
          1 , *     s  r   ,,
          2 U3 - a3)  |_V(a4  - a3> + M3/(a3 ' V

          2 (a2 ' a2}  [M2/(a2 " ai} + M3/(a3 " a2]
By induction,
    M. =M+AM.  -AM.
                  [V(a± - ai-
  A MQ - 0.
                                 55

-------
                      M
o
Ui
> — *
1
M,
1
1
r1 AM,
r
r
I I i
1 1 1
I i I
1 1 1
1 1 1
I 1 l
HI ' i
•00001 i M
VOOJ .. 1 r~lvl4
S\W M3 V/////A \ '
^SS^ Y/////A \ 1 1
                                      a.
                                                 '2          U3
                                                       *
                                     Figure 13.  Interval adjustment diagram

-------
                               SECTION VII

                               REFERENCES
 1.  Ananth, K. P.  Evaluation of  the Pentapure Scrubber.   Final Report  on
    Contract 68-02-1324, Task Order No. 8, Prepared  for Control Systems
    Laboratory, Office of Research and Development,  Environmental Pro-
    tection Agency, Research Triangle Park, North Carolina 27711, 1974.

 2.  Calvert, S.  Engineering Design of Wet Scrubbers.  J.  Air Pollution
    Control Association, 24:929,  1974.

 3.  Calvert, S., J. Goldschmid, D. Leith, and D. Mehta.  Scrubber Handbook.
    Control Systems Division, Office of Air Programs, Environmental Pro-
    tection Agency, Research Triangle Park, North Carolina 27711, 1972.

4.  Cooper, D. W. and D. P. Anderson.  Dynactor Scrubber Evaluation.  Final
    Report on Contract 68-02-1316, Task Order No. 6, Prepared for Office
    of Research and Development, Environmental Protection  Agency, Washing-
    ton, D. C., July 1974.

5.  Fuchs, N.  A.  Mechanics of Aerosols.  Pergamon, New York, New York
    (1964).

6.  Horvath, H. and A. T. Rossano.  Technique for Measuring Dust Collector
    Efficiency as a Function of Particle Size.  J. Air Pollution Control
    Association, 20:244-246, 1970.

7.  Jorgensen, R. (ed.).  Fan Engineering.  7th Edition, Buffalo Forge  Co.,
    Buffalo, New York (1970),

8.  Rose, A. and E. R. Rose.  The Condensed Chemical Dictionary.  Reinhold
    Publ., New York (1966).
                                   57

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                                TECHNICAL REPORT DATA
                          (Please read Iiiunictions on the reverse before completing)
                           2.
 1. ML Dt)H T NO.
  E PA - 6 50/2 - 7 5-02 4 - a
 4. TIT L.I AN 13 SUU TITLE

 Pentapure Impinger Evaluation
 7. AUTHOH(S)
 Douglas W. Cooper
9. PERFORMING ORG "VNIZATION NAME AND ADDRESS

 GCA Corporation
 Burlington Road
 Bedford, Massachusetts 01730
12. SPONSORING AGENCY NAME AND ADDRESS
 EPA, Office of Research and Development
 NERC-RTP, Control Systems Laboratory
 Research Triangle Park, NC 27711
                                                      3. RECIPIENT'S ACCESSION NO.
             5. REPORT DATE
             March 1975
                                                      6. PERFORMING ORGANIZATION CODE
                                                      8. PERFORMING ORGANIZATION REPORT NO.
             GCA-TR-75-5-G(l)
             10. PROGRAM ELEMENT NO.
             1AB012; ROAP 2LADL-004
             11. CONTRACT/GRANT NO.
             68-02-1487
             13. TYPE OF REPORT AND PERIOD COVERED
             Test No.  1: 10-11/74	
             4. SPONSORING AGENCY CODE
 5. SUPPLEMENTARY NOTES
  ABSTHACTThe reporf gives results of testing a novel spray scrubber, the Pentapure
 (Purity Corporation, Elk Grove Village, Illinois), as part of a program to identify
 novel, high efficiency, fine particle control devices.  Emissions from a gray iron
 foundry were tested after they had exited from  a spray cooling chamber.  Their mass
 median aerodynamic diameter was 0. 5 micrometers, as determined with cascade
 impactor samples. Inlet and outlet samples were taken with cascade impactors and
 with total mass measuring sampling trains. T9tal mass efficiency was found to be
 10. 0 + or - 2. 5% on this fine dust. The particle aerodynamic  diameter for which the
 efficiency would be 50% was estimated to be between 2 and 4 micrometers,
 determined from cascade impactor analysis and from theoretical performance
 predictions. The pressure drop across the Pentapure scrubber was 1500 N/sq m
 (6 in. H2O) and the measured efficiencies corresponded to those expected from
 venturi scrubbers having somewhat less pressure drop.  The Pentapure scrubber
 is not an efficient fine particle collector.
                             KEY WORDS AND DOCUMENT ANALYSIS
                DESCRIPTORS
Air Pollution
Scrubbers
Evaluation
Dust
Dust Collectors
                                          b.lDENTIFIERS/OPEN ENDED TERMS
Air Pollution Control
Stationary Sources
Pentapure Impinger
Spray Scrubbers
Fine Particulate
                         c. COSATI Field/Gioup
13B
07A

11G
13A
  DISTRIBUTION STATEMENT
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
66
 Unlimited
20. SECURITY CLASS (Thispage)
Unclassified
                                                                   22. PRICE
EPA Toil* JJ20-1 (i-73)
                                       59

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