PB 205 893
MEASUREMENT OF NON-METHANE HYDROCARBONS
Oscar Saenz-, Jr.', et al
Southwest Research Institute
Houston, Texas
June 1971
NATIONAL TECHNICAL INFORMATION SERVICE
Distributed ... 'to foster, serve
and promote the nation's
economic development
and technological
advancement.'
U.S. DEPARTMENT OF COMMERCE
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MEASUREMENT OF NON-METHANE HYDROCARBONS
Contract CPA 70-40
SwRI Project 21-2811
Prepared for:
Office of Measurement Standardization
Division of Chemistry and Physics
Air Pollution Control Office
Environmental Protection Agency
June, 1971
SOUTHWEST RESEARCH INSTITUTE
SAN ANTONIO HOUSTON
-------
BIBLIOGRAPHIC DATA 11. Report No.
SH.I!ET APTD-0905
.1. J Jtl~ and Sub~1tle , i. , .
I 7" :
: l:;~.ur~:"t Of" NO~-~t~ari~,.H:~~~ca~bT~ " , ' '" " . ,," ,
7. Aucbor(s)
Oscar Saenz, Jr., Clarence A. Boldt, Jr., David S'. Tarazi
9. Performing Organization Name and Address
f"
3. Recipient's Accession No.
.;
, \ i
S. Report Date
'June 1971
6.
"
''<
7
8. Performing Organization Rept.
No.
10. Project/Task/Work Unit No.
SwRI Pro1ect 21-2811
11. . Conuacth6alx No.
" .
,
r ,.
Southwest Research Institute
3600 Yoakum
Houston, Texas
'\
. f1 "'"1 \:J' '..-
\, . , .::' "';J
(.t . ~ ~
"
'.
1,
CP A 70-40
u ,
77006
,,, ~
12. Sponsoring Organization Name and Address
Office of Measurement Standardization
Division of Chemistry and Physics
Air Pollution Control Office
Environmental Protection Agency ."
15. Supplementaty Notes DISCLAIMER: This r~port was furnished to the Environmental Protection
Agency, Air Pollution Control-Otfice, in fulfillment of Contract No. CPA 70-40.
: \.fe:~~~cit~nt of so-called ''non-methane hydrocarbons,r' ~~)t~e-n carried out in a mobile lab
oratory using a flame ionization detector. Total hydrocarbons ~,'\measured by running
air directly through the detector. Methane was measured by running air through a methane
saturated carbon column which retained all organic contaminants other than methane. The
, . '.fference was then the "rion-methane hydrocarbons. '~'Two methods of measurement were used
(1) The air stream was diverted alternately through\the detector or through the carbon
column and then the detector; the total hYdrOCarbo~n measurement for several consecutive
cycles was averaged, and the methane measurement fo comparable cycles was averaged; the
difference was then the measure of non-methane hy ocarbons for ~he entire period. (2)
Air was admitted to a plastic bag over a period Qf time, after which the total hydrocar-
bon and methane content of the collected sample ,was determined; again, the difference
was the non-methane hydrocarbon value for the ,i'amp1ing period. Temtserature control of
the carbon adsorbent is important and may be,'critica1. Temperature variations during
sampling affect the methane capacity of the/carbon, causing errors in measurement. Ser-'
vi,.ce, ,li fe of the carbon is .sltor.t_,fOI--B.__,COij;t1n\1OUs....JnQni..t..Q.ring__int;!..tI.Ym~t.. J:rt~:re.a6_ing th.e.
amount of carbon increases service life ,,'but also increases time lag and decreases re-
sponse time of the instrument. Also, increasing the amount of carbon increases the possi
b1e error due to temperature variations--'.,',Bag sampling may be. superior to continuous
monitoring, depending on circumstances ""One instr1;JD1ent can analyze samples collected at--
a number of monitoring stations. Carefu1pu~ging of plastic bags is required to avoid
errors due to desorption of organic constituents of the p1as't1c~'Sensitivity appears to
be marginal in view of the federal standards. The method is subject to error due to .
difficulties in calibration, temperature control, and other variab1es.O'-'Iherefore, good
results can be obtained only by well trained and experienceq. personnel. I
17. Key Words and Document Analysis. 178. Descriptors ",
Air pollution Atmospheric composition Continuoussamp1irtg ,
Hydrocarbons Gas sampling' Monitors
Gas an~lvsi~ Temperature Calibrating
171t. IdencilT4!'rs/Opeo-Ended Terms'
--,
13. Type of R~port & Period I
Coveted '
,
/'
"
14.
- .
" I
I
i
17e. COSATI Field/Group
18. AvaHability,Statement
13B, 14/02
I
,.
.
Unlimited
19.. Security Class (This
. Re~~)T .
120. Secunty Class (This
Pag~-
. UNCLAS~IFIED
21. No. of Pages
32
22. Price
KMiI NTI...110070)
USCOMM.OC 4032g.P7 1 (!)
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~ ~TITLE: Measurement of non-methane hydrocarbons I i
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MEASUREMENT OF NON-METHANE HYDROCARBONS
Contract CPA 70-40
SwRI Project 21-2811
Prepared for:
Office of Measurement Standardization
Division of Chemistry and Physics.
Air Pollution Control Office.
Environmental Protection Agency
by
Oscar Saenz, J r.
Clarence A. Boldt, Jr.
David S. Tarazi
June, 1971
APPROVED BY:
?MreJ- c. ~
Herbert C. McKee
Assistant Director
Department of Chemi.stry
and Chemical Engineering
SOUTHWEST
RES EAR C H
INSTITU.TE
3600 YOAKUM
HOUSTON. TEXAS 77006
,
-------
f-- - ----
'~". '.
, '.
"'A
Measurement of so-called "non-methane hydrocarbons" has been
carried out in a mobile laboratory us ing a flame ionization detector.
Total hydrocarbons were measured by running air directly through the
detector. Methane was measured by running air through a methane-
saturated carbon column which retained all organic contaminants other
than methane. The difference was then the :lnon-methane hydrocarbons. II
"',
. .
SUMMAR Y AND CONCLUSIONS
.,
,~ Two methods. of measurement were used: '--'" .
, .'" "" .. " ,'. "-"" ......-~,....._...~.,..,~--~ M'~_.-'--'- .-..,_..~...---
/\
,,1.
(2.~
The air stream was diverted alternately through the d~tector
or through the carbon column and then the detector; The
total hydrocarbon measurement for several consec"'utive
cycles was averaged, and the methane measurement for
comparable cycles was averaged; the difference was then
the measure of non-methane hydrocarbons for the entire
period .-~, .
. -. .,.-J'
Air was admitted to a plastic bag over a period of time,
after which the total hydrocarbon and m~.thane content of
the col~ected sample was determined) Again, the difference
was the non-methane hydrocarbon value for the sampling
period. -....\
" The following conclusions resulted from this work:
'''"'-:--...,
. Temperature control of the carbon adsorbent is important
and may be critical. Temperature variations during sam-
pling affect the methane capacity of the carbon, causing
er ro rs_~~. ~~~~..~-~~.~~~~-~--~
2. .... Service life of the carbon is short for a continuous moni-
toring instrument. Increas ing the amount of carbon
increases service life, but also increases time lag and
decrease~ response ti~e of the instrument. Also,
increasing the amount of carbon increases the possible
error due to temperature variations. ----.
1.
'" """".." ""~- _. ,.,..~_. ,............... --.,' .-
".
,
3.
'Bag sampling may be superior to continuous monitoring,
depending on circumstances. One instrument can analyze
samples collected at a number of monitoring statio,ns.
Careful purging of plastic bags is required to avoid errors
due to desorption of organlc constituents of the plastic ""'-"-..
'I
'.
""\
I -~
it
-------
1.-"'-
\
4.'AsensitivitY appears to be marginal in view of th.e..proposed
(and recently revised and adoptedrfederal standards. -',
..', .'~, . A' .. ',8" ~
5.
- -
The method is subject to error due to difficulties in calibra-
tion, temperature control, and other variables. Therefore,
good results can be obtained only by well trained and
experienced personnel.
~-~-:..-:--'--..........-......... "-..". ", "'. ,.
"..
iii
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TABLE OF CONTENTS
Page
1. INTRODUCTION 1
II. DESCRIPTION OF SYSTEM 2
III. COLUMN 5
IV. ADSORBENT EV ALUA TION 6
V. OPERATION OF THE ANALYZER 13
VI. CALIBRA TION PROCEDURE 14
VII. AMBIENT SAMPLING 16
VIII. CALCULATIONS 18
IX. RESULTS OF AMBIENT SAMPLING 19
X. ADDITIONAL SAMPLING RESULTS 22
XI. BIBLIOGRAPHY 23
APPENDIX
Total Hydrocarbon and Methane Analyzer
Operating Conditions A-I
List. of Suppliers A-2
iv
-------
i Figure
1
2
3
4
5
6
7
8
Table
I
ILLUSTRA TIONS
Flow System for Total Hydrocarbon and Methane
Atialyzer Using Beckman Model l09-A Ahalyzer
Typical Strip Chart Recordings of Total Hydro- /.
carbons and Methane on Ambient Samples Taken /:.
Near Industrial Site . /
Evaluation of Activated Charcoal by Gas Chromato-
graphy (Separation Made on Silica Gel Column)
Evaluation of Activated Charcoal by Gas Chromato-
graphy (Separation Made in Porapak Q Column)
Adsorption of Methane and Ethane by Activated
o
Charcoal at 25 C (Charcoal not Preheated)
Adsorption of Methane and Ethane by Activated
o
Charcoal at 25 C (Charcoal Preheated)
Adsorption of Methane and Ethane by Activated
o
Charcoal at 0 C
Adsorption of Ethane by Burrell High Activity
Charcoal at Various Temperatures'
TABLES
Comparison of Data for Total Hydrocarbons,
Methane, and Non-Methane Hydrocarbons
v
Page
3
4
7
8
9
10
11
12
Page
20-21
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I. INTRODUCTION
The method in use at Southwest Research Institute to measure
non-methane hydrocarbons is a combination of two methods entitled
"Continuous Analysis of Methane" and "Tentative Method for the Con-
tinuous Measurement of Total Hydrocarbons in the Atmosphere"
(Flame lonization Method). These methods were obtained from
EPA-APCO for evaluation.
The analysis of methane is carried out by passing the ambient
sample continuously through an activated charcoal sorption tube which
adsorbs all organic contaminants except methane. The methane is
then analyzed by a flame ionization instrument. The column is no
longer usable when heavier organic compounds begin to elute. For
this reason, a close check has to be performed on the scrubber column
periodically.
The total hydrocarbons, on the other hand, are analyzed with
a flame ionization instrument without the charcoal column. The dif-
ference between the measured total hydrocarbons and methane repre-
sents the non-methane hydrocarbons.
-------
2
II.
DESCRIPTION OF SYSTEM
A Beckman ;Model I09-A Total Hydrocarbon Analyzer was
modified in order to make it capable of analyzing both parameters
consecutively and automatically. The flow system of the instrument
is shown in Figure 1. A programmer has been installed that allows
the instrument to sample automatically in the following time sequence:
Step 1
2
3
4
- zero
- total hydrocarbons
- zero
- methane
1 minute
5 minutes
1 minute
5 minutes
This sequence can run repetitively as long as desired. At the
end of the sampling period, the recorder (strip chart) data for the total
hydrocarbons and the methane as shown in Figure 2 are read and
averaged. The difference of thes e averages represents the average
non-methane hydrocarbons over a unit period of time.
. .
-------
ambient sample
\
4 - po rt
manLlal
selector
valves
cut-off,
soleno id
valve for
instrument
inlet
bag sample inlet
I
methane
, standard
inlet
c ut-'
off
valve
pressure
regulator
0-20 psig
"
methane ethane
standard inlet
CD
pump
swi tch
Figure 1.
~ 22 .~~ /min
~ 50 cc/min
= primary bypass
- rotamete r
= 0-10 ..i /min
secondary bypass rotameter
0-84 cc/min
switching
solenoid:,ll .
valve
sa~le
capfllary
L-_~-
activated
charcoal
column
50-70 cc/min
0° C
burner
6'
- --,
I
I
I
I
----1
fuel
25#
air
25#
Flow System for Total Hydrocarbon and Methane Analyzer
Using Beckman Model 109-A Analyzer
UJ
-------
4
non-
HC
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Figure 2. Typical Strip Chart Recordings of Total Hydrocarbons
and Methane on Ambient Samples Taken Near Industrial Site
-------
5
III.
COLUMN
The carbon sorption column used in the instrument cons ists of
a 10" long x 1/2" ID glass U tube packed with 5-10 grams of Burrell's
high activity chromatographic grade charcoal. This charcoal was
purchaseJ from Curtin Scientific Company. As shown in Figu~e 1,
the column is attached in parallel to a bypass column through a solenoid
valve. This solenoid valve, which serves as a switching device, is
connected to the programmer. The adsorbent may be preheated 6-12
hours at 1200 C prior to use. It is not necessary to condition it with
methane prior to its use as will be explained later. The flow of
ambient air through the column is maintained at a rate of 50-60 cc/min.
-------
IV. ADSORBENT EVALUATION
Before selecting the charcoal presently used in the system,
various brands and types of charcoal were investigated. The evalua-
tion was performed in the laboratory with the aid of a Per kin-Elmer
Model 900 gas chromatograph equipped with a flame ionization detector.
Five and ten grams of each brand of charcoal were packed into glass
U tubes, as previously described, and evaluated one at a time. A pre-
pared gas mixture, containing 5 ppm methane and 2 ppm ethane, was
passed continuously through the column and through a gas sampling
valve in the gas chromatograph at a flow rate of 50-60 cc/min. The
columns were evaluated at 0° C and 25° C for adsorption efficiencies.
Eluent samples were introduced into the gas chromatograph at "0" time
and time intervals thereafter through the gas sampling valve. The
gaseous mixture was analyzed by making a separation of the methane
and ethane components in the normal gas chromatographic technique
by using a 5" x 1/4" OD silica gel column or a 5" x 1/8" Porapak Q
column as shown in Figures 3 and 4, respectively. By employing this
technique, data were obtained showing the exact time methane and ethane
"broke through" the charcoal columns. The time at which ethane "broke
through" represents the life duration of the column under the conditions
investigated.
After it was determined that Burrell's high activity charcoal
was more efficient than the other charcoals under the conditions investi-
gated, various experiments were performed. These experiments were
run for the purpose of determining the adsorption capacity of the activated
charcoal for ethane at 0° C and 25° C. As expected, the results showed
a higher adsorption efficiency at the lower temperature. This is illus-
trated in Figures 5 through 7 and summarized in Figure 8, which is a
plot of data showing the loading characteristics of the Burrell high activity
charcoal for 2 ppm ethane at 0° C and 25° C. This figure clearly illus-
trates that when the adsorption temperature is kept at 0° C, the charcoal
which has not been preheated adsorbs almost four times as much ethane
as compared to the amount adsorbed at a temperature of 25 C. Based
on these findings, the column on the instrument used at SwRI is always
maintained at 0° C by placing the column in an ice bath.
-------
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Evaluation of Activated Charcoal by Gas Chromatography
(Separation Made on Silica Gel Column) .
Ar.a 5 mJn
-------
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Figure 4.
Evaluation of Activated Charcoal by Gas Chromatography
(Separation Made in Porapak Q Column)
-------
rT""j~.V~". ^L^-r,^,
Figure 5. Adsorption of Methane and Ethane by Activated Charcoal at 25 C
(Charcoal not Preheated)
-I
-jS^hane-^t-uilBltrpfcolumn "
eirSrt outlet of column- - -.-
r i - i < - . i - . i -
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charcoal-ipa-cked-in pqlyethylene-tube
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120 . iso io
Tme in Min.utes;
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ane -a
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iorbetit -' 10 gra.m|s Burjrell high ;
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'ethyl en e -tube : i i 1 i j
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; 2 pipm. ethane in nitrogen [
.1 ; Flow rate of gas mixjture through ;
; " ' / * /' ' '
^column -! 61 cc/min continuous
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-------
Figure 7. Adsorption of Methane and Ethane by Activated Charcoal at 0 C
-------
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- '::.-~ _..._--....._~-_.
--- ,.. -- - --- - ---." -~ - . - --
"-------
. --~-- ~~-- --
! i
i_.~.'~~-_.-_._- _.
-------
13
V. OPERATION OF THE ANALYZER
The "start-up" procedure for the Beckman Model 109-A Total
Hydrocarbon Analyzer will not be discussed since this information can
be obtained from the manufacturer's handbook. The following discus-
sion on the calibration and sampling techniques of the modified
instrument whose flow schematic is shown in Figure 1 assumes that the
instrument has been started and ample warm-up time has been allotted.
-------
VI.
CALIBRATION PROCEDURE
Prior to ambient sampling, the analyzer is calibrated by con-
tinuously flowing a methane standard (1-10 ppm Cl14 in air) into the
instrument. It is necessary to determine the t.p (flow) across the
instrument sample capillary in order to obtain a recorder response
which can be related to the concentration of methane in the calibration
gas.
The procedure for calibrating the analyzer is as follows:
(Refer to Figure 1.)
Turn off the samp1e~ump @ and shut off needle valve
on primary bypass
-------
15
6.
Continue adjusting pressure regulator G) slowly until
a stable and desired response is observed on the instru-
ment recorder. Once the desired response is achieved,
record the 6p observed on the sample pressure gage @ ,
which indicates the flow across the sample capillary.
The value obtained represents the calibration point
which will be used when performing the ambient sampling.
7.
Turn off cutoff valve 0 ' and return selector valves CD
and @ to ambient sampling mode. The instrument is
now ready for ambient sampling. .
-------
1.
2.
3.
4.
5.
6.
7.
16
Vil. AMBIENT SAMPLING
After the selector valves have been placed in the ambient mode
position and the programmer placed in the zero (manual) position,
turn on 'the sample pump @. Readjust the zero on the instrument
meter and recorder.
Slightly op~n the primary bypass valve @. This valve is used
as a primary sample splitter. Its purpose is to bypass the
majority o'f th~ total flRw delivered by the samp~e pump @ .
This extremely large flow, about 5-8 -'/min, is unqesirable
since it will rapidly load the charcoal colu.m:n and thus decrease
its life duration. As mentioned previously, only a flow not to
exceed 70 cc/min can be tolerated through the CQlum~.
Turn programmer to CH4, manual mode. This allows, the
ambient sample to flow through the charcoal column ~ which
has been imniersed in an ice bath and maintained at 0, C.
The prima~y bypass valve @ which controls the flow through
the system 1S. then adjusted to obtain a reading on the sample
pressure gag~ @ which is identical to the calibratio~ value
~~. .
After Step, 4 has been accomplished, the programmer is then
manually moved to the THC mode, which allows t~e sample
to flow through the bypass column (j) and into the, detector. .
The flow. is ag~in adjusted as was, done in Step 4 tp obtain the
calibration v~lue on the sample pressure gage @ . However,
this flow is adjusted this time with a needle valve. found on
the bypass (j). This valve simulates a pres,s,ure; drop across
the bypass equa,l to the b,p across the charcoal column.
The instrument is now ready to perform ambient sampling.
The sampling, sequence is then started by placil1g the pro~
. . ,
grammer i~ the zero mode position. This position activates
, . ,
the cutoff sole~oid which in turn cuts off the sample flow,
thus allowing the zeroing of the instrument electronically.
Turn the progr,ammer switch to the automatic position, and
the following ~equence of events, which was discussed pre-
viously, takes place: .
, '
"
o<~
-------
17
Step 1 - zero 1 minute
2 - total hydrocarbon analysis 5 minutes
3 - zero 1 minute
4 - methane analysis 5 minutes
This sequence is allowed to run as long as desired.
-------
ViII.
CALCULA TIONS
At the end of the sampling period, the strip chart recording
which contains data for both total hydrocarbons and methane is read
by determining peak heights for each determination. The values of
each THC determination and methane determination are averaged
separately and conipared to the calibration data. The difference
between the two averages represents the non-methane hydrocarbons
expressed in parts per million for that sampling period.
18
-------
19
IX.
RESULTS OF AMBIENT SAMPLING
The system shown in Figure 1 and already described has been
in use in SwRl's mobile laboratory for about six months. Data were
obtained near various industrial plants and in downtown Houston,
usually close to point sources. Some of these data are shown in
Table I. The sampling was done on a 4-6 hour sampling day, at which
time methane was analyzed 50 percent of the time. The column was
changed prior to each sampling day to insure reliability and confidence
in the analys is. Occas ional checks were made on the columns at the
end of each sampling day with the aid of the prepared gas mixture and
a gas chromatograph. To date, the columns have performed very
satisfactorily.
-------
20
Table I
COMPARISON OF DATA FOR TOTAL HYDROCARBONS.
METHANE. AND NON-METHANE HYDROCARBONS,
Continuo~s Sampling V s. Composite Sampling
Using Tedlar Sampling Bags
Total HC Methane, Non-Methane HC
u.pW ind ppm ppm ppm
or ,Avrg. Bag Avrg. Bag Avrg. Bag
Date Location Down Cont. Samp. CC!:n..,~:, Samp. Cont. SamE'
Nov. 25. 1970 Plant A DW 4.0 4.0 3.3 3.7 0.7 0.3
DW' 3.7 4.2 3.1 3~3 0.6 0.9
UW 2.1 2.3 2.3 2.4 0.0 0.0
UW 2.4 2.6 2.5 2.6 0.0 0.0
Jec. 9 Plant A. DW 3.3 4.0 1.4 1.7 1.9 2. 3
UW 1.3 1.7 1.2 1.2 O. 1 0.5
UW 1.8 2.2 1.6 1.5 0.2 0.7
Dec. 17 Plant A DW 6.5 6.3 4.0 3.9 2.5 2.4
DW 4.9 4.6 4.2 3.4 0.7 1.2
UW 4. 1 4.5 4.3 4.5 0.0 0.0
Feb. 9. 1971 Plant A DW 6.4 6.2 5.9 5.8 0.5 0.4
;DW 5.3 5.4 5.5 5.3 0.0 O. 1
UW 5.0 5.0 5.1 5.0 0.0 0.0
DW 5.3 5.4 5.3 "5.2 0.0 0.2
Dec. 1. 1970 Plant B DW 9.3 9.3 5.7 5.7 3.6 3.6
DW 12.6 12.6 4.8 5.7 7.8 6.9
UW 2.7 3.0 3.0 2.7 0.0 0.3
DW 2.7 3.0 2. 1 2.1 0.6 0.9
Jan. 7. 1971 Plant B, DW i 4.8 4.8 3.4 3.4 1.4 1.4
,
DW 10.9 11. 9 3.4' _,3.6 7.5 8.3
DW 3.1 3.4 2.8 ;2.6 0.3 0.8
UW 2.3 2.4 2.2 2.2 0.1 0.2
Mar. 4 Plant B DW 6.3 5.6 5. 1 j, 1.2 1.6
4.0
DW 3.7 3.8 3.8 3.8 0.0 0.0
DW 6.6 6.0 5. 1 5.5 0.5 0.5
UW 3.5 3.3 4.0 3.6 0.5 0.7
1,1
, "
-
"
-------
21
Table I (Continued)
Total HC Methane Non- Methane HC
Upwind ppm ppm ppm
or Avrg. Bag Avrg. Bag Avrg. Bag
Date Location Down Cont. Samp. Cont. Samp. Cont. Samp.
Dec.20,1970 Plant C UW 5.6 5.2 5.6 5.2 0.0 0.0
DW 6.9 6.4 5.4 5.4 1.5 1.0
Jan. 27, 1971 . plant C DW 6.6 6.6 5.7 6.0 0.9 0.6
DW 6.8 6.6 6.1 6.3 0.7 0.3
DW 8.7 7.8 7.7 7.5 1.0 0.3
UW 5. 1 5.2 4.8 4.4 0.3 0.8
Feb. 10 Plant C DW 2.8 3.0 2.1 2.2 0.7 0.8
DW 2.7 2.6 2.7 2.6 0.0 0.0
UW 6.0 6.4 6.5 6.4 0.0 0.0
DW 8.6 8.4 7.7 7.8 0.9 0.6
Mar. 3 Plant C DW 3.4 3.4 3.0 3.0 0.4 0.4
DW 3.5 3.6 3.3 3.4 0.2 0.2
UW 3.3 3.Z 3.4 3.6 0.0 0.0
DW 4.9 4.9 4.6 4.4 0.3 0.5
Mar.10 Plant C DW 4. 1 4. 1 3.9 3.9 0.2 0.5
DW 3.7 4.0 3.7 4.0 0.0 0.0
DW 4.9 4.3 4.5 4.4 0.4 0.0
Mar. 16 Houston DW 6.3 6.5 6.0 6.0 0.3 0.5
(downtown DW 7.3 8.5 7.6 8.7 0.0 0.0
area) DW 7.7 8.4 8.4 9.0 0.0 0.0
UW 7.8 7.8 8.2 8. 1 0.0 0.0
-------
22
x.
ADDITIONAL SAMPLING RESULTS
In addition to obtaining continuous analytical data on methane
and total hydrocarbons, simultaneous time-integrated samples were
obtained also in Tedlar bags. The primary problem encountered in
bag sampling was the tendency of plastic bags to desorb organic con-
stituents that contaminated the sample. Tedlar was selected because
this contamination was less with Tedlar than with other plastic materials,
and even here exhaustive heating and purging was necessary prior to
using a bag for this purpose. Frequent checks of background contami-
nation with purified air were necessary to insure. freedom from error
due to this cause. .
These bag 'samples were analyzed at the end of the sampling
period, and the results compared with the average.s.of the continuous
samples. The results of the THC and CHi in the sampling bags have
generally compared very favorably with the averages of the continuous
samples for each particular period of sampling as shown in Table I.
Since the proposed federal standard requires the non-methane average
for a period of thr'ee hours, the use of the sampling"bag may be more
practical. In this" technique, it is unnecessary to change the charcoal
scrubber column often, since the frequency of its usage is decreased
tremendously.
'/
-------
23
XI.
BIB LIOGRAPHY
A1tshuller, A. P., Ortman, G. C., Saltzman. B. E., and Neligan,
R. E., "Continuous Monitoring of Methane and Other Hydrocarbons
in Urban Atmospheres," Journal of Air Pollution Control As sociation.
16:87-9: (1966).
Ortman, Gordon C., "Monitoring Methane in the Atmosphere With a
Flame Ionization Detector." Analytical Chemistry, 38:644-646 (1966).
"Continuous Analysis of Methane. II APCO. received bySwRI July. 1970.
for evaluation (unpublished).
"Tentative Method for Continuous Measurement of Total Hydrocarbons
in the Atmosphere" (Flame Ionization Method). SAC. received by SwRI
February. 1971. for evaluation (unpublished).
-------
APPENDIX
\~,
-------
A-I
TOTAL HYDROCARBON AND METHANE ANALYZER
Operating Conditions
1.
Flow through carbon column
~ 50-60 cc/min
2. Flow through sample capillary ~ 3 cc/min
3. Flow through primary bypass ~ 2..t/min
4. Flow through secondary bypass ~ 50 cc/min
5.
Temperature
00 C
-------
'TOTAL HYDROCARBON AND METHANE ANALYZER
List of Suppliers
1.
Four-port Manual Selector Valves
Circle Seal Model P4-4l8
Distributor: Womack Machine Supply Company
4006 Dennis - P. O. Box 8807Z
Houston, Texas 77004
Z.
Solenoid ,Valves - Three- port
Asco "Red Hat"
Cat. No. 83Z043
Distributor:
not available
3.
Flowmeters
Predictability: O-lO.1./min
0-84 cc/min
Cat. No. 36-541-Zl
Cat. No. 36-541-03
Distributor:
Greiner Scientific Corporation
ZZ North More Street
New York, New York 1001.3
4.
p:ressur,e Regulator
Fisher'Model 1- 088
O-ZO psig
Distributor:
Fisher Scientific Company
P. O. Box 1307 .
Houston, Texas. 77001
A-2
------- |