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United States
Environmental Protection
Agency
Environmental Monitoring Systems
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S4-85/037 June 1985
Project Summary
Develop, Evaluate and Validate
Continuous Emission
Monitors for Designated
Hazardous Pollutants
George W. Scheil
The objectives of this project were:
(1) to assess the state of the art of
commercially-available continuous emis-
sion monitors of vinyl chloride monomer
(VCM) and {2} to conduct actual exper-
iments to evaluate two monitors in the
laboratory and in a (six month) field
testing program.
A single process GC modified for
dual-channel operation, with both a
flame ionization detector and a photo-
ionization detector, were used during
this study to represent the two moni-
toring systems. Three one-week EPA
Method 106 tests were conducted
during the six-month field testing pro-
gram to measure the relative accuracies
of the monitors at a VCM plant.
The precision of both types of detec-
tors was in the 1 % range when evaluated
in the laboratory.
The relative accuracies for both types
of detectors were <10% for VCM con-
centration between 2 to 10 ppm.
This Project Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory. Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering Infor-
mation at back}.
Introduction
This project concerned itself with: (1)
commercially-available continuous emis-
sion monitors (CEM) for vinyl chloride
monomer (VCM); (2) their reliability in
long-term field operation; and (3) the
relative accuracies of the CEMs compared
to the EPA reference method.
The project focused on the six-month
field testing program and the use of EPA
reference Method 106 to measure the
relative accuracies of the CEMs during
the field test. Because of the very low
concentration of VCM in the stack emis-
sions, the sampling line was connected to
a process line, and nitrogen was used to
dilute the VCM concentration to the 1-10
ppm, which was the CEM measurement
range.
Two types of signals, digital and analog,
were collected and sent by telephone line
to the data processor. The maintenance
trips for changing compressed gases on
the gas chromatographs were made every
other week. Additional trips were made
as needed, whenever there were process
upsets and GC shut-downs.
Three one-week. Method 106 Tedlar
bag samp!e/GC-FID analyses were con-
ducted with the sampling line tie-ins to
the CEMs, to measure the relative accu-
racies of the FID and PID.
Apparatus and Procedure
A process GC manufactured by Applied
Automation (Model 102) was used for
this work. A Hnu System, inc.. Model
PI 52 photoionization detector (PID) with
a 10.2 ev lamp and a BC-2 instrument
control computer (Action Instruments)
were selected and installed up-stream in
series to the FID detector on the Applied
Automation process GC.
The laboratory experiments were de-
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signed to evaluate the separation of the
vinyl chloride from the possible inter-
ferent species present in the process gas
stream. A process gas stream sample
was collected and analyzed. Significant
concentrations of ethylene, ethylene di-
chonde, and small amounts of light
chlorinated hydrocarbons and hydrogen
chloride were found present in the gas
stream. Analytical windows for the detec-
tors were set, back flush time was
determined, and non-stainless steel parts
on the instrument were replaced due to
the corrosive nature of the hydrogen
chloride present in the stream. After all
the parameters were optimized, a one-
month reliability test wes conducted in
the laboratory.
The instrument was installed at a VCM
plant, was connected to a reactor off-gas
stream, which was diluted with nitrogen
to bring the vtnyi chloride concentration
down to the 1 to 10 ppm range.
The process GC measyred the VCM
concentration every two minutes, and
two readings were recorded from each
detector (FID and PID) as analog and
digital readings. The field record was
transmitted by modem approximately
once each day, which included the 51
hours of data immediately preceding the
phone call An inspection trip was made
to the field site every other week to check
the instrument, change gases, and verify
the transmitted data. Calibration was
conducted by remote control over the
telephone line once a day.
Three one-week EPA reference Method
106 tests were conducted during the six-
month field test program; during the first
week following the installation, the thir-
teenth week, and the last week of the field
program. Each test consisted of taking
twelve one-hour integrated bag samples,
and the VCM measurements were made
immediately at the completion of each
sample collection on a separate gas
chromatograph.
Results and Discussion
The selection of the Applied Automation
Model 102 process GC was primarily due
to limitation of funds and the ready-
availability of the GC in this laboratory.
The selection of the PID with a digital
integrator to be installed in series with
the FID on the process GC was partially
due to funds limitation and partially
because the separation of the vinyl chlo-
ride from other interferences was the
same for FID or PID, and a second set of
column and oven ware not necessary.
Because remote-linkage of the data
systems was necessary, the compatibil-
ities and the electron noise insulation
were very important in the selection of
the digital integrator and the data system.
An Epson HX-20 briefcase computer and
a Wirteck MCS analog interface were
chosen and connected to the 8C-2 digital
integrator system to eliminate the noise
problems.
A month-long laboratory test resulted
in a net of 97% of usable data recovery.
less than 3% span drift (with 10 ppm
VCM), and the precisions of the four
method combinations were all within 1%.
The field testing program started during
November 1983 Overall data recovery
efficiency was approximately 80%. Severe
weather conditions during January and
February of 1984 caused significant
problems in the continuing operation of
the field monitors becayse the monitors
were installed outdoors in a trailer,
without heating dyring the winter. (The
test site was in the state of Louisiana, and
the severe winter conditions were un-
ysual and. therefore, not expected.)
The relative accuracy measurements
by use of the Method 106 for three one-
week bag samples gave a bias within 8%
by average. In general, when the concen-
tration level dropped to below 1 ppm i
the sampling line, the relative accuracies
become far worse (approximately 30%).
This was due to the calibration problems
of the monitor in this low concentration
range. While the VCM concentrations
stayed in the 2 to 10 ppm range, the
relative accuracies stayed within 2 to 3%.
Conclusions and
Recommendations
Both detectors (FID and P10) success-
fully completed 6 months of operation
under the field conditions. Because of its
better sensitivity, and the fact that only
one compressed gas {carrier gas) is
needed for its operation, the PID is a
better choice than the FID for long-term
remote field operation.
During the field evaluation program,
non-linearity of the monitor calibration
was developed. This may be caused by
the increasing contamination of the
column by the heavier fraction in the
sample gas or by the degradation of the
colyrnn packing material. Additional
studies should be directed toward under-
standing this problem.
George W. Scheil is with Midwest Research Institute, Kansas City. MO 64110.
Jimmy C. Pau is the EPA Project Officer fsee below).
The complete report entitled "Develop, Evaluate and Validate Continuous
Emission Monitors for Designated Hazardous Pollutants." (Order No, PB 85-
20? 176/AS; Cost: $10,00. 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:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
u s. GOVEBMMerr PRINTING OFFICE: IMS-SSMK/ZTOM
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