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
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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
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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
-------
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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