PROTOTYPE CONSTRUCTION AND
FIELD DEMONSTRATION
OF THE
PARALLEL CYCLONE SAMPLING TRAIN
FINAL REPORT Contract 68-02-0258
waiter c. me crone associates, inc.
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Report to
Environmental Protection Agency
Durham Contract Operations
Research Triangle Park
North Carolina 27711
PROTOTYPE CONSTRUCTION AND
FIELD DEMONSTRATION
OF THE
PARALLEL CYCLONE SAMPLING TRAIN
FINAL REPORT Contract 68-02-0258
Date: 15 December 1972
MA Number: 2425
Copy of
waiter c. me crone associates, inc.
2820 SOUTH MICHIGAN AVENUE CHICAGO, ILLINOIS 60616
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FINAL REPORT FOR CONTRACT 68-02-0258 (MA 2425)
INTRODUCTION
This final report is submitted in fulfillment of our contrac-
tual agreement under contract 68-02-0258, and summarizes the detailed infor-
mation included in our four monthly status reports submitted throughout the
contract period. The purpose of the contract was to construct and test a pro-
totype parallel-cyclone particle sampler which we had designed under contract
EHSD-71-25.
PROTOTYPE CONSTRUCTION
During the first two months of the contract the design of the
parallel cyclone sampling train was reviewed, the necessary components to be
purchased were ordered and the construction of the cyclones and by-pass filter
was completed. Layout and assembly of the final prototype system was some-
what modified from the initial designs; assembly was initiated in June and com-
pleted in September. Although the design details of the unit have been detailed
i
in our monthly reports, some of the important features are summarized here.
The parallel multicyclone sampling train consists of five
main units: the sampling box, two heat exchangers and two air flow control
boxes. Figure 1 shows how the cyclones and by-pass filter are combined with
the gas pumping and control systems. The system components are all con-
structed from corrosion-resistant materials. For example, the cyclones and
by-pass filter are nickel-plated brass, the condenser-evaporater-chiller sec-
tions of the heat exchangers are type 304 stainless steel, the gas pumps are
Teflon coated; sour gas meters are used in place of regular gas meters, and
stainless steel and Teflon tubing are used in the gas control systems.
The physical appearance of the sampler is illustrated in
Figures 2, 3, 4 and 5. Figure 2 shows the relative size and shape of the by-
pass filter holder and the three types of cyclones. Figures 3 and 4 show the.
assembled sampler unit and Figure 5 shows the assembled sampling train as
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set up for laboratory testing.
Our initial design for the system included the construction of
a 6-cfm gas pumping and metering system to be utilized in conjunction with the
parallel cyclone samplers. It was originally thought that the pump, gas meter
and the other associated accessories (i. e., pyrometer, manometer, orifice
meter etc.) could be housed in the same container. However, the control box
was estimated to weigh over 90 pounds, too heavy for field use. The initial con-
figuration was somewhat modified and the final configuration is shown in Figures
1 and 5. The 6-cfm pump and gas meter were housed in the cyclone air-flow
control box and the other accessories were housed in the filter air-flow control
box.
PROTOTYPE TESTING
Prototype testing was actually divided into five separate tasks.
First, the theoretical and experimental operational characteristics of the three
cyclone types (T-1B, T-2A and T-3B) were compared. Second, the manifold
functioning was experimentally verified. Third, so that any necessary design
modifications could easily be made before final assembly, operational tests were
made on the individual cyclones prior to assembly into the sampling train.
Fourth, the assembled sampling train was tested using the wind tunnel under
simulated wet scrubber conditions. And fifth, the sampling train was field
tested at the TVA Wet Limestone Scrubbing Facility, Paducah, Kentucky.
Operational Characteristics Comparison
The variations of pressure drop (AP) and particle cut-off
size were first calculated for different flow rates and then the cyclones were
tested to determine the actual values under operation. The pressure drop across
each cyclone was measured with a manometer and the instantaneous flow rates
were measured with a calibrated orifice meter at various flow rates (Q) ranging
from 0.2 to 4.5 cfm under room conditions of 72 °F and a relative humidity of 60%.
In order to compare the actual pressure drops with the
theoretically predicted values for the cyclones, the Q vs. AP curves for each
have been plotted on Figures 6, 7 and 8. Figures 6 and 7 show that the actual
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pressure drops across the T-1B and T-2A cyclones agree very well with the pre-
dicted values. In fact, the best fit curve of experimental data for T-1B very
nearly coincides with the predicted curve. The actual pressure drop curve for
T-2A parallels the theoretical one and differs by about 35% for flow rates rang-
ing from 0.4 to 1.0 cfm. Although the actual pressure drops across the T-1B
and T-2A agree with the predicted values, the actual and theoretical pressure
drops across T-3B do not agree well; the actual pressure drops are about 15
times greater than the predicted values (Figure 8). The differences are attri-
buted to the pressure drop across the manifold atop the T-3B cyclone, since this
pressure drop was not considered during the calculations.
Manifold Testing
The manifold was designed to split the intake air into four
controlled volumes; one into each of the three cyclones and one into the by-pass
filter (see Figure 3). It must split the gas stream into four volumes in propor-
tion to the required quantit3' of air flow for each cyclone. By varying the filter
flow, isokinetic sampling can be achieved. The manifold was designed so that
the particle loading and size distribution would be unchanged in each of the four
gas streams. Two experiments were performed to test this requirement.
The tests were made at room conditions with various flow
rates: one test with equal air flow through each of the four units (three T-1B and
one T-2A cyclone) and another test with different flow rates. For equal rates,
a flow of 0.75 cfm was chosen; and for the second set of conditions, the flow rates
were set at 0.3, 0.6, 0.9 and 1.2 cfm so that the proportion of air volume was 1,
2, 3 and 4, respectively. Air flows through the four units were properly ad-
justed prior to the tests by using manometers and the actual pressure drop curves
presented in Figures 6 and 7. Since only three manometers were available, the
flow rates through only two units and the total flow rate through the whole system
were continuously monitored.
In these tests, the flyash and limestone mixture of particles
was generated by an acoustic dust feeder and then passed through the precollec-
tor, the manifold, the cyclones, and the by-pass filter. At the end of each test,
the weight of particles collected by the precollector, the cyclones and by-pass
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filter were weighed and their size distributions were measured. Although the
experimental data did not agree perfectly with the theoretical requirement, the
manifold worked reasonably well. The deviation of experimental and theoretical
results was believed due to the slight variation of flow rates during the test.
The flow rates through two of the units might have been slightly reduced during
the test due to the pressure drop developed by the increasing dust loading of the
filters.
The manifold functioning was also evaluated from the unifor-
mity of particle size distribution passing through the four manifold outlets. The
actual size distributions at the four manifold outlets agree very well under both
sets of flow rates. Slight variations in the size distributions are believed due to
errors in particle sizing and flow control variations.
In short, the results obtained from the manifold tests indicate
that the manifold is capable of splitting dust-laden air into the four outlets with-
out changing the size distribution and mass loading of particles significantly.
The manifold was therefore considered well designed and no modifications were
necessary.
Component Testing
In order to simulate stack conditions with a wind tunnel and
to measure particle size distribution with a Climet particle counter, it was im-
portant to obtain information on the function of these two pieces of equipment
under such conditions.
The tests indicated that the Climet and wind tunnel func-
tioned properly. However, when we attempted to simulate the stack conditions
at the inlet and outlet of the wet scrubber with the wind tunnel and obtain a cali-
bration curve for each cyclone, the attempt was unsuccessful due to the follow-
ing difficulties:
1) In simulating the outlet stack condition of 90.5% relative
humidity, the probe was plugged with condensate and the
optical sensing chamber in the Climet particle counter was
flooded with water when the wind tunnel air was driven
through the system. This caused the particle counter to
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fail.
2) In simulating the inlet condition, 1.7% relative humidity,
in which flyash and limestone particles were added to the
wind tunnel, the sensing chamber of the Climet particle
counter was overloaded with particles, and hence the
counter also failed.
Due to these difficulties, particle size distribution measure-
ment was shifted from the Climet particle counter to the Millipore TrMC particle
counter.
Wind tunnel conditions during component testing closely si-
mulated the inlet condition of a wet scrubber: 300 °F and 112 °F of dry and wet
temperatures, with 147 grams of particles added to the wind tunnel and circu-
lating at 3000 fpm. The dust-laden air of the wind tunnel was drawn through the
probe, passed through the cyclone and filter and then measured with an orifice
meter. A i/8-in. probe was used for the T-1B and T-2A cyclones, whereas
a 3/8-in. probe was used for the T-3B cyclone. Various flow rates ranging
from 0.3 to 3 cfm were used for the three cyclone models. Only one test was
made under each condition with a sampling time of 30 minutes in each case. In
order to compensate for the loss due to particle decay in the wind tunnel, about
3 grams of particles (flyash and limestone mixture) were added to the wind
tunnel prior to each test. At the end of each test, the particles collected by the
cyclone and the absolute filter were respectively weighed and their size distri-
butions determined with the TT MC counter.
Knowing the quantity and size distribution of those particles
collected and of those that passed through the cyclone, the collection efficiency
of each cyclone was determined. These results are plotted in Figures9, 10 and
11.
The cut-off size of each cyclone the particle size with 50%
collection efficiency was then easily obtained from these collection efficiency
curves. The cut-off sizes for each of the cyclones at various sampling flow
rates are presented in Table land are plotted in Figures 12, 13 and 14. In
order to compare the experimental and theoretical cut-off sizes of each cyclone,
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the AP vs. X curves in figures 6, 7 and 8 were transformed into Q vs. X
J" 50
curves and superimposed on Figures 12, 13 and 14. The theoretical cut-off
sizes of these cyclones corresponding to the flow rates used in the tests are
also presented in Table 1.
Since Die 50% efficiency sizes (d ) obtained from laboratory
oU
tests do not agree well with the design values, we were somewhat disappointed
with the results obtained in this preliminary calibration test. Theoretically
the d should decrease progressively as flow rate increases, as shown by the
solid curves on these figures. However, this was not consistently observed in
our tests. Also, the cross-overs of collection efficiency curves for a given
cyclone under various test flow rates as appeared on Figures, 10 and 11 were
not expected.
The differences between the theoretical and experimental
d,_0 value obtained are believed attributable to the following factors:
1) Cyclone construction: Cyclone dimensions calculated
by optimization procedures in cyclone design do not
always give round numbers for machining. Therefore
slight modifications were made during machining, par-
ticularly for the cyclone inlet and outlet dimensions.
Since the inlet and outlet dimensions affect the collec-
tion efficiency of a cyclone, these design modification
variances would cause the collection efficiency to vary
somewhat.
2) Variation in particle density used in the cyclone design
and experiment: A density of 2.4 gm/cc for the glass
beads was assumed in the cyclone design, whereas the
density of the flyash and limestone particles used in the
experiments ranged from 1 gm/cc to over 6 gm/cc.
Since d is a function of particle density, particle den-
ou
sity variations would effect the resultant d . value.
50
3) Variation in particle concentration and size distribution
in the wind tunnel: Testing of the wind tunnel has shown
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that the particle concentration and size distribution vary
from time to time during experiments. Therefore, since
the collection efficiency of a cyclone is related to mass
loading and particle size, variations in particle concentra-
tion and size distribution in the wind tunnel would also vary
the collection efficiencies.
4) Particle sizing and counting: Since the ^MC particle counter
is accurate only for particles greater than 1 /im in size,
particles smaller than 1 jLtm were manually counted by com-
paring their images with images of larger known particles.
Therefore, an error could have possibly been introduced
during particle counting and sizing.
5) Random error in experiment: Since only one test run was
performed under each experimental condition and since a
number of variables are involved in the determination of
cyclone collection efficiency, the results obtained from each
single test would not likely represent the true value. Addi-
tional testing would be required to obtain a statistically
meaningful result.
Although the preliminary cyclone calibration data do not agree
well with the theoretical predictions, the cyclones were capable of separating
particles below 10 ^m. We fell that whether the experimental data agree with the
theoretical prediction is immaterial as long as the actual cyclone cut-off sizes
are known. The data obtained in this preliminary calibration served as a guide
in determining the approximate flow rates for the desired cut-offs in our labo-
ratory prototype test.
Assembled Prototype Testing
The main purpose of the assembled sampling train laboratory
test was to establish the actual cut-off values for the three cyclones at flow rates:
1.2 cfm for cyclone No. 1 T-1B; 0.5 cfm for No. 2 T-1B; 0.5 cfm for T-2A;
2.7 cfm for cyclone T-3B; and 0.5 cfm for the by-pass filter. The approximate
size cut-off for each cyclone corresponding to these flow rates is 0.5, 1.4 and
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6 p.m, respectively. In addition, the laboratory prototype test was also intended
to test the mechanical performance of the sampling train components: gas flow
control and metering system, heating controls, temperature monitoring system
etc.
The prototype tests were performed using the wind tunnel at
the same conditions as in the individual component tests. The wind tunnel at-
mosphere closely simulated the inlet condition of a wet scrubber: 300 °F and
112°F of dry and wet temperatures with 147 grams of flyash and limestone par-
ticles added to the wind tunnel and circulating at about 3000 fpm. A 1/2-in.
heated probe with a 1/2-in. button hook sampling nozzle was used in the test.
The operation procedure for the sampling train is briefly described as follows:
1. Weigh four 47 mm filters with a microbalance;
2. Mount the filters on the by-pass filter holder and the filter
holders attached to each cyclone;
3. Assemble the sampling cyclones in the sampling box and
connect the gas transport system;
4. Heat the sampling probe and sampling box to 250 °F;
5. Adjust the flow rate through each sampling cyclone by
referring to the pressure vs. flow rate curve for each
cyclone as presented in Figures 6-8. To obtain 1.2 and
0.5 cfm air flow through cyclone T-1B and 0.5 through
cyclone T-2A, a corresponding pressure drop of 26,
4.5 and 0.13 inches of water is required. Since the
three cyclones draw air from the same inlet, flow rate
adjustment in one cyclone would slightly vary the flow
rate of others. Careful re-adjustment of the three flow
rates through the three cyclones is therefore required.
This can be achieved by nearly simultaneously adjusting
the three flow control valves located on the top of the
sampling box;
6. Record the initial readings of the two gas meters and then
start the two pumps simultaneously;
7. Adjust the by-pass filter air flow to obtain isokinetic sam-
pling conditions. This can be achieved by adjusting the
pressure drop across the orifice meter to the correspond-
ing pitometer reading.
8. Record temperature readings on the two gas meters;
9. Maintain a constant flow rate through each cyclone during
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the sampling period;
10. At the end of each sampling period, reweigh all filters and
all samples collected by each cyclone.
Particle size distributions of the cyclone and filter samples
were determined by optical microscopy. The collection efficiency of each cyclone
at the test flow rate was established based on the quantity and size distribution
of particles collected by each cyclone and filter. Results of the collection effi-
ciency calculations are plotted in Figures 15, 16, 17 and 18.
It is seen from these figures that the particle collection effi-
ciency data obtained from the three runs for a given cyclone at a given flow rate
fall short of a smooth curve, especially those for cyclones T-2A and T-3B. It
is, in fact, difficult to fit a curve to the experimental data for these two cyclones.
Despite these scattered experimental data, these figures indicate that the cut-
off sizes of cyclones T-1B and T-2A are very close to the expected values. How-
ever, the cut-off size of cyclone T-3B, about 3.5 Mm, was considerably smaller
than the expected value of 6 jum. This is probably due to the fact that more air
flow than the preset flow of 2.7 cfm was drawn through cyclone T-3B during the
test. The observed actual flow rate through this cyclone was 2.93 cfm.
In summary, the results of the laboratory prototype tests
show that the parallel multicyclone particle sampler is capable of separating par-
ticles in the desired size ranges provided the flow rate through each cyclone is
well controlled.
Field Demonstration of the Parallel Multicyclone Particle Sampler
The field demonstration of the parallel multicyclone particle
sampler was performed on October 16 and 17 at the TVA power station in Paducah,
Kentucky. The sampling procedures in the field test were essentially identical
to the laboratory prototype test. Three samples were taken, both from the inlet
and outlet of the wet scrubber.
Knowing the weight of the particles collected by each cyclone
and filter, the cumulative particle size distribution (by mass) of the aerosol
drawn through the probe was calculated.
The results of the sampling train field test were very satis-
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factory. According to the design criteria of the wet scrubber, 50 cumulative
weight percent of the particles at the scrubber inlet should be smaller than 11 pun
and all particles in the outlet should be less than 5 ^m. This means that at the
flow rate set in the field test a substantial fraction of particles would be collected
by the precollector at the inlet. It also implies that practically no particles would
be collected by the precollector and only a very small fraction of particles would
be collected by cyclone T-2A at the outlet. These were verified by the field test
data.
The anticipated performance of the parallel multicyclone par-
ticle sampler was also indicated by the distinct color of the particles collected by
cyclone T-1B and its back-up filter. While the particles collected by the cyclone
appeared gray, those collected by the back-up filter were black, indicating flyash
and a fine oil mist, respectively.
Determination of particle size distribution by use of this
sampler was also found to be very promising. The data indicate that the parallel
multicyclone particle sampler is capable of providing sufficient data for the es-
tablishment of cumulative mass curves. The outlet size data obtained in Paducah
fits very well to a straight line when plotted on arithmetic probability paper.
This indicates the particle mass size distribution is "normal". Since a straight
line can be both fairly well fitted to the inlet data plotted on an arithmetic proba-
bility and a log probability paper, the actual pattern of particle size distribution
at the inlet was inconclusive.
SUMMARY
Although the parallel multicyclone particle sampler was found
capable of providing sufficient data to establish particle size distribution of an
aerosol, the application of the sampler was limited by sampling time. We found
in the laboratory prototype tests and the field demonstration that the pressure
drop across the back-up and by-pass filters developed quickly and a constant flow
rate through each cyclone was maintained only in the first few minutes. This
means that, if gravimetric analyses are desired, extended sampling times might
be necessary and the sampler would therefore lose its accuracy in such instances.
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To help correct this dcficiencj', modification of the sampling
train is recommended. Although a pump of larger capacity would extend the sam-
pling time, the increased volume and weight make this modification undesirable.
The best way to extend the sampling time is to enlarge the filter holders from the
present 47 mm to 3 inches.
Another important consideration in the performance of this
sampler is an accurately known cut-off size for each cyclone at operational flow
rates. In the laboratory prototype test, reproducibility of cyclone collection effi-
ciency data was not very good due to the limitation of three test runs. Since the
establishment of particle size distribution by the use of this equipment depends
very much on the actual cut-off size of each cyclone, we recommend a more com-
plete set of calibration experiments to measure the collection efficiency of each
cyclone.
We acknowledge that the successful development of the pro-
totype parallel multicyclone sampling train was through the direct efforts of
Drs. Walter C. McCrone and Hsing C. Chang.
Respectfully submitted,
Donald A. Brooks
Executive Vice President
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TABLE 1
Type of
Cyclone
T-1B
T-2A
T-3B
Comparison of experimental cut-off
theoretical cut-off sizes of cyclones
sampling flow rates.
Flow Rate
(cfm)
0.3
0.5
0.8
1.0
0.4
0.6
0.8
1.0
2.0
2.5
3.0
sizes with
at various
Cut-off size (^m)
Experimental
2.1
1.3
1.8
1.0
6.5
2.6
2.3
2.6
8.5
4.7
5
Theoretical
1.7
1.05
0.65
0.51
6.0
3.6
2.7
2.2
9
7.5
6.4
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Sampling box
3re-collector
and
manifold
Heat
exchanger
Heat
exchanger
Cyclone air
flow control
box
Filter air
flow control
box
FIGURE 1. Block diagram of the McCrone parallel multicyclone sampling train.
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^^^^ ^Br
FIGURE 2 Shape and relative size of by-pass filter
holder and sampling cyclones
FIGURE 3 Assembly of sampling cyclones
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FIGURE 4 Assembled sampling box
FIGURE 5 Complete train of parallel multicyclone
participate sampler
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-p-;-:
te
:::::.-._.vi':i:: Best fil curve of .--_!..:".:.": :
;...:. frrzr:";:~~:i~ experimental data;.-";-.
" i i :
' -' : ' - i' " ;
Theoretical precHction
0.1
8 10 12 """ 14 1G 18
Pressure Drop (in. of water)
FIGURE 6 Comparison o! actual pi'cssure drop with
theoretical pressure drop across cyclone
T-1B
24 2G
- 1G
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3 .... n
J'cst lit curvd of -
i mental data .
0.1
Pressure Drop (in. of water)
FIGUUK 7 Comparison of actual pressure drop with
theoretical pressure drop across cyclone
T-2A
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3
rt
Theoretical prediction
0.01 0.02 0.04 O.OG 0.080.1
0.2
0.-
Pressure Drop (in. of water)
FIGt'RE 8
Comparison of actual pressure drop with theoretical
pressure drop across cyclone T-3B and manifold
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FIGURE 9 Particle collection efficiency of cyclone T-1B
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FIGURE 10
Particle collection efficiency of Cyclone T-2A
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. . . . . .
,
Particle Size; I (inri)'. \
FIGURE 11 Particle collection efficiency of cyclone T-3B
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0.2
FIGURE 12
0.4
O.G
Flow Kate, (efm)
Comparison of oqioinmonta] cut-off si/-e \vith tlieorotic
cut-off size of cyclone T-1B.
il
- 22
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9
8_
7~
6_.
5_.
4
O
O
o
N
^H
w
0)
I(
!
rt ,
ft 1-
0 2
FIGURE 13
D7G 0.8
Flow Rale, (cfm)
1.0
Comparison of experimental cut-off size with theoretical
cut-off size of cyclone T-2A.
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FIGURE 14 Comparison of experimental cut-off size with theoretical
cut-off size of cyclone T-3B.
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lOOi
80-
iJV-l-
: 1.:: :
o
o
_0
*
o
o
CO-
40
-?-
tSe
!,: :
donc
20-
j-'
I-: !::
o-w
6 8
Particle Size
10
12
14
16
tc
in
FIGURE 15 Particle collection efficiency of cyclone T-1B
operated at a flow rate of 1. 2 cfm
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100
w
CH
O
i . ;..::.:: !..::
J, [:.!':.. I- :::!:::!::::;:::
Particle Size
i
to
FIGURE 16 Particle collection efficiency of cyclone T-1B
operated at a flow rate of 0.5 cfm
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100
o
U
80 i
. ' 1 . t 1 - . I - i . . - .:...-(
to
-o
468
Particle Size (Mm)
FIGURE 17 Particle collection efficiency of cyclone T-2A
operated at a flow rate of 0.5 cfm
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100
80
o
c
o
'o
o
o
I*
II
o
u
Particle Size
t-o
cc
FIGURE 18 Particle collector efficiency of cyclone T-3B
operated at a flow rate of 2.7 cfm
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