United States
Environmental Protection
Agency
Atmospheric Sciences ^
Research Laboratory *• ,
Research Triangle Park NC 27711 Vf,
Research and Development
EPA/600/S3-87/035 Feb. 1988
&ERA Project Summary
Evaluation of a Method Using an
FID for Methanol Measurement in
Auto Exhaust
Peter A. Gabele, William D. Ray, John Duncan, and Charles Burton
This report evaluates a simplified
technique for estimating methanol
emission rates in auto exhaust. The
technique, referred to as the FID
Bubbled Method or FBM, is based in
principle on the notion that while hydro-
carbons are not readily absorbed in
water, methanol is. Hence, by using a
Flame lonization Detector to measure
the organic mass in samples before and
after bubbling them in water, the
quantity of methanol originally present
can be estimated by taking the differ-
ence between the measurements.
Evaluation of the method was done by
comparing methanol measurements
using the FBM with measurements
made using an established reference
method. Results showed poor to fair
agreement between the two method*.
The FID Bubbled Method appeared
better at estimating methanol emission
rates from evaporative tests than ex-
haust tests and also exhibited better
accuracy for sample containing higher
levels of methanol. When test data
obtained with the FBM are used to
calculate total organic mass emission
rates, the results are within 3 percent
of results obtained using the relatively
complex method in the proposed stan-
dard for methanol cars.
This Project Summary was developed
by EPA's Atmospheric Sciences Re-
search 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 In-
formation at back).
Introduction
In August 1986, the EPA published a
notice of proposed rulemaking for stan-
dards for emissions from methanol-fueled
motor vehicle engines. Since that time,
comments regarding the proposed stan-
dard have been solicitated from a number
of automobile manufacturers. Of the
comments received, many have addressed
the "overly complex" instrumentation
requirement set forth in the standard for
measurement of organic compounds. In
accordance with the proposed standard,
gas and liquid chromatographs (GCs and
LCs) would be required for methanol and
formaldehyde analyses in addition to the
flame ionization detectors (FIDs) required
for regulated hydrocarbon analyses.
The consensus of recommendations
received from commentators proposes
that the separate measurements of
methanol and formaldehyde not be re-
quired, thus eliminating the need for GC
and LC analyses. Manufacturers contend
that reasonably accurate measurement
of total organics can be had through the
sole application of an FID, in one form or
another. Some further suggest or recom-
mend the use of correction factors to
account for differences in FID response
and photochemical reactivity between the
organic components.
With regard to these comments, the
concerns of instrument complexity are
valid and sole use of the FID to measure
total organics would greatly simplify the
procedure. The use of a correction factor
to compensate for the FIDs low response
to methanol would be appropriate if the
fraction of methanol to total organic
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emissions remained constant, however,
the fraction varies significantly with fuel
and vehicle. Correction factors appropriate
to a given situation might be estimated
based on experience or perhaps through
use of simplified approximation methods.
One simplified method, referred to here
as the FID Bubbled Method (FBM), mea-
sures total organics with an FID, bubbles
the sample through water to remove the
methanol fraction, then remeasures the
remaining hydrocarbon (HC) fraction. The
difference between the total organics and
the remaining HC fraction represents an
estimate of the methanol fraction.
The principal objective of this study
was to evaluate methanol measurements
made using the FBM on emissions for a
methanol-fueled automobile. Basically it
consisted of comparing methanol mea-
surement made using a technique known
as the FID Bubbled Method or FBM with
measurements made using an established
reference method. The reference method
utilized a gas chromatograph to analyze
methanol which had been trapped in a
water solution.
The test vehicle, a 1983 Methanol
Escort, was driven through a series of
FTP driving cycles on a chassis dynamo-
meter. For each test run, three sets of
data were obtained corresponding to the
cold transient (CT), hot stabilized (HS),
and warm transient (WT) test phases of
the FTP. Two fuels were used during the
study: M-85 fuel (a blend containing 85
percent methanol/15 percent unleaded
wintergrade gasoline) and M-100 fuel
(pure methanol). Use of both fuels enabled
evaluation of the FBM over a wider range
of possible methanol emission rates.
Conclusions and
Recommendations
The following conclusions have been
made based on the experimental study
carried out using both the FBM and GC
method (reference method) for measuring
methanol levels in auto exhaust:
1. Comparison between the FBM and GC
method for methanol measurement are
fair to poor with differences between
methods ranging from 11 to 112 percent.
2. Comparison between the methods is
better with methanol evaporative emis-
sions than with methanol exhaust emis-
sions. Comparison is worst for emissions
from the Hot Stabilized Test Phases where
methanol concentrations are the lowest
(<4ppm).
3. Absorbtion of some non-methanol
organics (<10 percent) in the bubbled
water solution contributes to method
error. However, the main source of
method error is probably associated with
the hot FID's response sensitivity to water
vapor in the bubbled sample.
When data obtained from the FBM are
used to calculate the total organic ex-
haust emissions (OMHCE) from the Escort,
the results are close to those calculated
using data obtained from separate FID,
GC (methanol), and LC (formaldehyde)
analyses. With the Methanol Escort
operating on M-85 fuel, the FBM produces
a result for total organic matter emissions
about 2.6 percent lower than the refer-
ence method. With the M-100 fuel, the
difference between methods is less than
1 percent.
Based on the results obtained in this
study, the main source of error with the
FBM is likely associated with the response
sensitivity of the detector to high water
vapor concentrations in the bubbled
sample. Further studies should be under-
taken to better understand this phe-
nomena and its effect on analyzer
accuracy. Use of sample dryers before
analysis should also be investigated as a
means of removing water vapor from
samples which have been bubbled in
water.
The EPA authors Peter A. Gabele and William D. Ray are with the Atmospheric
Sciences Research Laboratory. Research Triangle Park, NC 27711; John
Duncan and Charles Burton are with Northrop Services, Inc., Research
Triangle Park. NC 27709.
Peter A. Gabele is the EPA Project Officer (see below).
The complete report, entitled "Preliminary Evaluation of a Method Using an
FID for Measurement of Methanol in Auto Emissions," (Order No. PB 88-
104 344/AS; Cost: $9.95. 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 Officer can be contacted at:
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711 <•
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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