United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-88/055 Aug. 1989
&EPA Project Summary
PM10 Source Measurement
Methodology: Field Studies
William E. Farthing, Randal S. Martin, Sherry S. Dawes, and Ashley D.
Williamson
' i \
Two candidate measurement
methods, Constant Sampling Rate
(CSR) and Exhaust Gas Recycle
(EGR), have been developed to
measure emissions of in-stack PM10>
particulate matter with aerodynamic
diameter less than 10 urn. Two field
tests were performed at the clinker
cooler exhaust of a Portland cement
plant to quantify precision and
comparability of these techniques. In
addition, accuracy was determined
for total particulate measurement by
comparison to Method 17. In the first
test, two EGR trains were operated
parallel to two Method 17 trains. In
the second test, two CSR trains and
one EGR train were operated parallel
to two Method 17 trains. Although
small, an observed difference be-
tween the techniques, combined with
the results of laboratory studies
reported elsewhere, led to an
increase in the length of sampling
nozzles. This modification improved
the particle sizing device perform-
ance and is incorporated into the
nozzle geometries described in the
application guides for CSR and EGR.
This Project Summary was devel-
oped by EPA's Atmospheric Research
and Exposure Assessment Laboratory,
Research Triangle Park, NC, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Methods are needed for measurement
of PM10 emissions from stationary
sources to support the ambient PM10
standard for suspended particulate
matter. The Quality Assurance Division of
the Atmospheric Research and Exposure
Assessment Laboratory at Research
Triangle Park, NC, (AREAL/RTP) has
directed development and testing of two
promising techniques for source in-stack
PM10 measurements. The full report
summarizes test procedures and pre-
sents results of two field tests at a
Portland cement plant.
To measure PM10 emissions, aerosol
particles with aerodynamic size less than
10 nm must be distinguished from larger
particles. Both PM10 techniques under
study use an inertia! size separation
device such as a cyclone or a cascade
impactor to aerodynamically classify
aerosol particles in situ. The higher
inertia relative to aerodynamic drag of
particles larger than 10 \im causes them
to be collected in the size separator,
whereas smaller particles pass through
the device with the sampled gas and are
collected on a filter. The particle size cut
of such a device is a unique function of
the flow rate and gas conditions, density,
and viscosity. Thus, to maintain a fixed
size cut at 10 urn, the flow rate cannot be
varied as in EPA Methods 5 or 17 to
maintain isokinetic sampling. One of the
PM10 techniques, the Constant Sampling
Rate (CSR) approach, uses standard
sampling hardware with an altered
traversing protocol to restrict anisokinetic
sampling bias to defined, acceptable
limits. The other technique uses a new
sampling train concept which incor-
porates Exhaust Gas Recycle (EGR) to
adjust the sampling rate independently
while maintaining the required flow rate
through the size separator. The EGR
technique is designed to be comparable
to Methods 5 or 17 for measuring total
particulate emissions as well as deter-
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mining PM10. In general, the CSR tech-
nique is intended for PM10 measure-
ments only, although it is appropriate in
many circumstances for measurement of
total particulate emissions.
Results of four previous field evalua-
tions indicated good agreement between
EGR and CSR for PM10 and between
EGR and Method 17 for total particulate
mass. However, a difference of 10% was
indicated between EGR and Method 17
by one test using simultaneous runs with
collocated trains. Differences of about
10% between PM10 measurements by
EGR and CSR were suggested by the
results at two sites, but the sign of the
differences was not consistent from site
to site. Previous tests did not measure
precision directly. As variations between
the techniques are much smaller than
source variations, simultaneous measure-
ments by collocated trains are needed to
determine either precision or accuracy.
Procedures
The two field tests were conducted at
the outlet of a gravel bed filter system
that was used to control the emissions
from the clinker coolers of two 500-t/day
Portland cement kilns. Fans blow ambient
air through the cooler bed. The bulk of
this air is passed to the kilns while the
remaining portion is drawn off through the
gravel bed filter by an ID fan. The
exhaust stack is circular with three 6-in.
ports located around the stack at 90°
increments.
Cleaning of the gravel bed filter is a
cyclic process which produces brief
variations in particulate concentration,
gas velocity, and temperature. At any
given time during these tests, seven of
eight modules of the gravel bed filter
were on-line while one was being cleaned
by back-flushing with heated ambient
aair. When the back-flush air changed
from one module to another, every 4.7
min, an exhaust puff 1/2 min in duration
was usually visible. The temperature
dropped 5 to 10% (in °C) within seconds
requiring about 1 min to recover in an
exponential fashion. Pitot readings also
had a spike lasting 5 to 10 seconds. No
attempt was made to alter operation of
the sampling trains during these excur-
sions. Care was taken to avoid initiating
or ending sampling runs near these varia-
tions.
The precision of the EGR technique
and accuracy for total particulate matter
were evaluated in the first test (CP4).
Four collocated sampling trains were
operated simultaneously. The spacing
between sampling nozzles was about 4
in. Two of these were EGR trains with a
commercial version of Cyclone I of the
SRI/EPA five-stage series cyclones used
as the PM10 size separator. The other
two trains were Method 17 trains. Seven
replicate sets of sampling runs were
performed over a four-day period with
each set lasting two hours.
In the second test (CP5), the precision
of the CSR technique, the comparability
of CSR and EGR, and the accuracy of
both techniques for total particulate
matter were evaluated. Five collocated
sampling trains were operated simultan-
eously. One of the EGR trains and both
of the Method 17 trains of test CP4 were
combined with two CSR trains, each
equipped with a commercial version of
Cyclone 1, for test CP5. The spacing be-
tween the five sampling nozzles was
about 5 in. Nine replicate sets of
sampling runs were performed over a
five-day period with each set lasting two
hours.
Results and Discussion
During test CP4 the stack gas velocity
and temperature averaged 12 m/s (40
ft/s) and 131°C (267'F). During test CP5
these averaged 10 m/s (34 ft/s) and 93 °C
(200° F). Significant variation in both
velocity and temperature occurred during
the runs. Velocity varied by as much as
-23 to +16% from the mean, and
temperature varied as much as -67 tc
+ 55°C. These ranges of variation do noi
include the brief variations encounterec
when the cleaning cycle changec
modules.
Because the CSR maintains the
sample flow rate required for a 10-iim
size cut, the percent isokinetic is
important. The average percent isokinetic
for these runs ranged from 81 to 125%
The range permitted by this protocol foi
these sampling conditions was 67 tc
150%. The average percent isokinetic foi
the EGR and Method 17 was well withir
the required 100 ± 10%.
The total particulate mass collected by
the trains ranged from 400 to 500 mg
with the Method 17 trains, 200 to 500 mg
with the CSR trains, and 100 to 300 me
with the EGR trains. The concentrations
of particulate matter >10 iim and <1C
iim averaged 94 and 93 mg/dscrr
respectively, with standard deviations o;
24 and 21%. The PM10 fraction averagec
near 50% with a standard deviation o1
5%. This feature was helpful ir
distinguishing differences between trains
because much of the particulate mass
was near the nominal size cut of the
cyclones.
Observed biases between trains ir
paired runs of the same technique were
found to be small. Table 1 gives values ol
precision observed in these tests where
precision is defined as standard deviatior
from the mean combining within anc
between train variation for a technique
Accuracy is also given in Table 1 for tola
mass as the average deviation frorr
Method 17 results in paired runs. Values
in parentheses give 95% confidence
intervals. Comparisons of EGR and CSF
results for PM10 indicated a difference o
16.2 ± 6.7%.
In principle, the differences observec
between the EGR and Method 17 result:
and between the EGR and CSR results
could be due to differences in the degree
of isokinetic sampling. Correlatior
Table 1.
Precision and Accuracy (Percent) Measured in Tests CP4 and CP5
EGR
SIMS
Metf?od 17
PMW
3.7
(2.1^9.5)
4.3
(2.1-+8.6)
Total mass
3.0
(i.a-+a.o)
5.5
(3.S-+12.3)
4.7
(3.5-»7.7)
PM10 fraction
1.5
(0.9-+4. 1)
3.6
(1.8-+7.1)
Total mass
-9.2 ±3.6
-1.8 ±4.4
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^analysis was performed to determine how
iuch of the differences could be
"attributed to anisokinetic sampling. It was
found that some of the variation in
differences between the EGR and
Method 17 results was correlated to the
percent isokinetic, as indicated by a
correlation coefficient of 0.83. However,
this analysis still indicated a net dif-
ference of -10%. The differences
between EGR and GSR for PM10 were
found to show no correlation with percent
isokinetic.
Conclusions and
Recommendations
Precision was good for all of the
techniques and parameters studied in
these tests. At a stable source, variations
between runs with different trains using
the same technique can be expected to
have a standard deviation from the mean
of 5% or less. The precision of Method
17 was found to be at this same level for
this source.
The accuracy of the EGR and CSR
techniques for total particulate concen-
tration was found to be -10 and -2%
respectively. The cause of the small but
apparent bias of the EGR trains is not
known but may relate to the geometry of
the sampling nozzles1 and perturbation of
gas flow at the nozzle inlet introduced by
the cyclone body. The EGR nozzles
protruded 2.8 cm (1.1 in.) in front of the
cyclone with a 30° outside taper. The
CSR nozzles protruded 3.3 cm (1.3 in.) in
front of the cyclone with a 20° outside
taper.
The observed difference between the
CSR and EGR trains for PM10 concen-
tration averaged 16 ± 6.7%. The prob-
able cause of this difference was
revealed in laboratory measurements
subsequent to this field test.1 The collec-
ion efficiency of Cyclone I was found to
increase (smaller size cut) as the nozzle
1 Williamson, Ashley D., William E Farthing.
Thomas E Ward, and M Rodney Midgett, 1987
"Effects of Sampling Nozzles on the Particle
Collection Characteristics of Inertial Sizing
Devices". Paper 87-70 5, 80th Annual Meeting,
Air Pollution Control Association, New York, NY.
inlet diameter and length decreased.
Nonrecycle nozzles with geometry and
inlet diameters near those used in this
test had a small effect upon cyclone
performance, reducing the size cut by
less than 0.5 urn. The EGR nozzle and
recycle rates used in this test caused a
decrease of 2 to 3 nm in the size cut.
Thus, it appears that the cyclone used
with the EGR nozzle collected particles
with sizes below 10 u.m more efficiently
than did the CSR cyclone, passing less
particulate matter on to the filter to be
classified as PM10.
It is recommended that nozzles be
extended in length to eliminate possible
sampling bias. It is also recommended
that nozzles used with other size sepa-
ration devices, such as cascade
impactors, be similarly improved and/or
tested.
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William E. Farthing, Randal S. Martin, Sherry S. Dawes, and Ashley D. Williamson
are with Southern Research Institute, Birmingham, AL 35255.
Thomas £ Ward is the EPA Project Officer (see below).
The complete report, entitled "PM10 Source Measurement Methodology: Field
Studies," (Order No. PB 89-194 2781 AS; Cost: $21.95, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-88/055
AGEHCY
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