( 9 ) \Vanp, C. C., Davis. L. I., -Jr., LVu, C. H.. dapar, S.. Niki. H.. \Veinstock, H., S'cic>ric,c, 189, 797 (19751. ( 10) LVu. C. H.. LVang, C. C.. .Japar, S. M., Davis, I,. I.. -Jr., Hanahusa. hl.. Killinger. D.. Niki, H., \Veinstock. €3., I n t . J . Chc>ni.Kinet., 8 , 765 (1976). (11) Akimoto. H.. Sakamaki. F.. Hoshino. M., Inoue. G.. Okuda, M., Enriron. Sci. Techno/., 13, 53 (1979). (12) Akimoto, H., Hoshino. M., Inoue. G., Sakamaki, F., Washida, N.. Okuda, M.,Enriron. S e i . Techno[., 13, 471 (1979). (13) Akimoto. H.. Inoue. G.. Sakamaki, F., Hoshino, M., Okuda, M.,
J . J p n . Soc. Air Poilut., 13, 266 11978). (14) Research Report from the National Institute for Environmental Studies, Tsukuba, Ibaraki, ,Japan, R-4-78, Aug 1978, pp 67-93, (161 .Japar. S.hl., \Vu. ('. H.. Niki, H., J . P h p ('hcrn., 78, 2;118 (19741. ( 1 6 ) Atkinson, I?.. Pitts. .J. h'.,.Jr.. ,/. ('hcn7. f ) / i > s . ,63, :3591 ( l 9 7 5 ) , ( 1 7) (;laSSlJn. LV. A,, Tuesday, [:, s., J . ,Air P(Ji/l!t.( ' ( J r l t / ' l J / A.S.\rJ('..20, 239 (1970). Hecpiced f o r r e t ~ i e uA p r i i 6 , 1979. Accepted October L'I, 1979
Analysis of Stack Gases Using a Portable Gas Chromatographic Sampling and Analyzing System Donald L. Miller", John S. Woods, Kenneth W. Grubaugh, and Linda M. Jordon Michigan Division Analytical Laboratories, Dow Chemical U.S.A., Midland, Mich. 48640
w EPA method No. 5 for the determination of particulate emission requires the dry molecular weight of the gas. A gas chromatographic (GC) technique has been developed as a substitute for the chemical ORSAT technique. T h e GC technique has several advantages: one, the stack gas can be analyzed rapidly for Cog, 0 2 , CO, and Ng directly; two, the sample for the GC analysis is obtained via an on-stream sampling system, thus reducing potential contamination as opposed t o the necessary "grab" samples and containers for the ORSAT analyzer; three, the analog signal from the GC is interfaced simultaneously to a recorder and integrator, thus giving a graphical and digital readout. T h e GC sampling and analysis system is described, and a procedure for preparing gas mixtures is presented. Data showing the correlation among t h e theoretical composition, GC analysis, and ORSAT analyses of gas mixtures and stack gases are presented. T h e majority of the commonly used sampling procedures
(EPA,ASME, and ASTM) for determining particulate matter in incinerator stack gas also requires the determination of its gaseous components, namely Cog, 0 2 , CO, and nitrogen by difference ( I , 2). T h e sampling procedures also state that the gaseous components be determined by the ORSAT analyzer ( 3 )or comparable apparatus. it'e have developed an on-stream gas chromatographic (GC) gas sampling and analyzing system that we think is not only comparable but better than the ORSAT analyzer for the following reasons: First, the stack gas can be analyzed much faster than by the ORSAT analyzer. During the 15 to 20 min it takes to collect samples and determine C O Y ,0 2 , and CO by t h e ORSAT analyzer, five samples can be analyzed for t h e above components and nitrogen by the on-stream GC system. Second, the GC analysis is much more representative of the actual gas composition than is the ORSAT analysis. T h e gas composition can change drastically during the 15 min required for ORSAT analysis on grab samples. Third, since there are no hottles of absorbing solutions in the GC system, there will be no breakage of bottles or mixture or contamination of solutions. This GC system is portable. All of t h e components are mounted on a 2 ft X 3 ft laboratory cart, and the entire assembly can he taken to the gas source for rapid, repetitive analysis. There are several portable gas chromatographs t h a t are commercially available, including the portable GC manufactured hy the Carle Co., the portable gas chromatograph made by Analytical Instrument Development Inc., and the 0013-936X/80/0914-97$01 .OO/O
@ 1980 American Chemical Society
Model T C D 1010 produced by Baseline Industries. Also, other gas chromatographic techniques have been used to determine the above components in gas streams. Beke ( 4 ) separated N2, O., and CO from mixtures containing Con, NO?, and SF,; using a series-parallel combination of Porapak-Q a t 25 "C and molecular sieve 5A a t 82 "C. Swan (S)determined HZ, o:?, NZ, and CO in CO2 by passing the mixture through a precolunin of porous polymer material, which absorbed the COP preferentially. T h e other components passed through and were separated on a molecular sieve column and detected by a helium ionization detector. Golden and Yeung ( 6 )determined trace amounts of O:j, N.0, COZ, CHJ. H2O. and CO in gases using long-path absorption infrared techniques. However, our system is not only a gas chromatograph hut a gas chromatograph sampling and analyzing system with several advantageous features which are as follows: (1)I t contains an Alltech concentric column, which allows the gas mixture to be analyzed for COZ, 0 2 , N., and CO a t ambient temperature in less than 3 min without temperature programming, valve switching, or column back flushing. (2) T h e GC detector is connected to an integrator that measures and prints out the peak areas instantaneously, and the actual percentages of the components can be calculated immediately on the site. (3) A stainless steel or quartz glass probe can he placed in the incinerator hot zone and the gas can be either pumped through a valving system and sample loop into the chromatograph or it can bypass it. (4) The valves can he switched and a standard gas mixture passed into the GC allowing for instant calibration. In the following section of the paper the system will be described in detail, and accurate methods for making u p standard mixtures will be presented along with the analysis of the mixture by both GC and ORSAT. Also, the analysis of the stack gas from a waste incinerat,or will he discussed.
Experimental Description of the Apparatus. A diagram of the assembled apparatus is shown in Figure 1. T h e chromatograph is a Gow Mac dual column unit equipped with a concentric column and a thermal conductivity detector. Helium is the carrier gas. T h e detector is wired in parallel to both a recorder and integrator (Hewlett Packard Model 3370A). The data are presented simultaneously as a chromatogram and a digital printout of the peak areas. T h e GC column is a stainless steel concentric column with the following dimensions: inner column, '/x in.; outer column, '/A in.; column length, 6 f t . T h e inner column is packed with Volume 14, Number 1, January 1980
97
-
7
A . lh“ ss Needle Valve B.C ,D.G % “ ss Ball Valves E - Gas Sampling Valve F - Gauge, 0 3 0 ‘ Hg Vacuum
y
l
h
f
, Stainless Steel or Vicor Probe
Figure 1. Assembled GC sampling and analyzing system
Table 1. ORSAT Analysis of Matheson Standard Gas Mixture VOI
%
cop
VOI
% 02
voi % CO
vol % N2 (by difference)
9.0 9.0 9.4 9.4 9.4 9.4 9.6 9.6 9.6 9.6 av 9.4
5.8 6.1 5.6 5.6 5.4 5.4 5.6 5.6 5.6 5.6 5.6
4.2 3.9 4.0 4.0 4.0 4.0 3.8 3.8 3.8 3.9
81.0 81.0 81.0 81.0 81.2 81.2 81.0 81.0 81.0 81.0 81.0
RSDa 4.9
7.1
6.8
0.2
3.8
Composite CO, 0,. N, On Inner Porap CO, On Inner
6 Ft Concentric Column Outer Column 114” Molecular Sieve
F
Inner Column 1/8“ Porapak
Flow R a t e - 50 rnlimin T e m p . Room Temp
0, O n Outer Molecular Sieve
N, On Outer Molecular Sieve
Analysis of Matheson Co.
a
co2
02
co
9.92%
5.89%
4.18%
N p (by
difference)
80.0 1yo
RSD = relative standard deviation at 9 5 % confidence level.
Porapak, and the outer column is packed with Molecular Sieve ;iA. The unit is manufactured by Alltech Associates, Inc., 202 Campus Drive, Arlington Heights, Ill. T h e sampling system consists of the following components: a six-port GC gas sampling valve, manufactured by the Carle Co. (E in Figure 1);four ljJ-in. stainless steel ball valves (B, C, D, and G); a %-in. stainless steel needle valve (A); l/,-HP “Gast” rotary pump; a 2 in. x 10 in. glass drying tube filled with 8 mesh indicating desiccant; a 0 to 30 in. Hg vacuum gauge (F); and a ‘lis in. X 24 in. stainless steel or quartz glass probe. T h e lines in the sampling system are %-in. stainless steel. T h e line from C and G to the pump is “B-in. o.d. rubber vacuum tubing. Valve G is used as a bypass. T h e standard gas mixture consists of carbon dioxide, oxygen, carbon monoxide, 98
Environmental Science & Technology
CO On Outer Molecular Sieve
0
1
2
3
Retention Time (Minutes)
Figure 2.
Chromatogram of standard gas mixture
6rnm Vacuum Stopcock
20mm
I
OD
Heavy Wall Rubber Vacuum
and the remainder nitrogen. I t was purchased from the Matheson Co., 932 Paterson Plank Rd., East Rutherford, N.J. O'iO'iX (Analysis is shown in Table I.) Operation of the Apparatus. With t h e above sampling system either a standard mixture or a gas sample can be analyzed using the following GC conditions: helium flow rate, 50 mL/min; oven temperature, ambient temperature; injection port temperature, ambient temperature; detector temperature, 100 "C.When a standard mixture is analyzed, valves A and 1) are opened and B and C are closed. E is turned so t h a t the standard purges the sampling loop. Pressure from the gas cylinder (-2 to 5 psig) pushes the mixture through the system. IVhen all of the air in the lines has been replaced by t h e standard mixture (-30 s), valve A is closed. Valve D is closed and valve E is turned, diverting the measured volume of gas in the sample loop into the chromatograph a t atmospheric pressure. T h e integrator is activated. From the resulting chromatogram (see Figure 2) and integrator printout, factors are calculated (percentage component in mixture/peak area of component) that are used to calculate the respective component concentrations in unkpown mixtures. When stack gas is to be analyzed, the probe is placed in t h e stack. Valve G is opened. T h e p u m p is turned on and a d justed t o pull approximately 300 mL/min through the system. After I! min of line flushing, valve G is closed, valves A and D are closed. and valves B and C are opened. After 1 min. valves R and C are closed. Valve D is opened momentarily to adjust the pressure in the line to atmospheric and then closed. Valve E is turned to d'ivert the stack gas sample into t h e chromatograph. Component concentrations are calculated by multiplying the component chromatographic peak area by its response factor.
ORSAT GC Validation. A known mixture of carbon dioxide, carbon monoxide, and oxygen (balance is nitrogen) was purchased from t h e Matheson c'o. This mixture was analyzed ten times using the ORSAT analyzer by two different operators. Results are shown in Table I along with the analysis of the Matheson Co. T h e ORSAT method is a technique for measuring the components in a gas mixture volumetrically. The gas is successively passed through carbon dioxide, oxygen, and carbon monoxide absorbing solutions. and the resulting volume decreases are measured. Known dilutions of this standard mixture were made with prepurified nitrogen. These dilutions were made hy partial pressure adjustments using a vacuum manifold, as shown in Figure 3. T h e system was evacuated to less than I m m of mercury using the vacuum pump. T h e system was isolated from the pump by closing stopcock A. T h e desired partial pressures of the standard mixture and nitrogen (contained in ;-IA hags made of Saran film) were measured into the system through stopcocks B and C. T h e diluted mixture was pumped into a third bag using the rotary pump after opening stopcock D. T h e theoretical compositions of the diluted mixtures were calculated as follows: 70
pressure of standard x r~ (201in standard co, = partial total pressure
"
=
%CO =
partial pressure of standard x r'c total pressure
0 2
in standard
partial pressure of standard x "; CO in standard total pressure
Volume 14, Number 1, January 1980
99
Table II. Theoretical Composition, ORSAT, and Gas Chromatographic Analysis lheor
% ORSAT
GC
0.8 1.2 0.3 97.7 1.6 1.6 0.6 96.2 2.3 1.9 0.9 94.9 4.7 3.2 1.9 90.4 6.4 4.0 2.7 86.9 8.0 4.9 3.3 83.8
0.6 0.9 0.5 98.0 1.4 1.4 0.6 96.6 2.4 1 .o 1.0 95.6 4.7 2.6 2.0 90.7 6.0 3.0 2.8 88.2 8.3 3.9 3.7 84.1
0.9 1.5 0.4 97.2 1.2 1.8 0.8 96.2 2.5 2.1 0.9 94.5 4.6 3.2 1.8 90.4 7.2 3.7 3.0 86.1 7.9 5.0 3.2 83.9
VOI
mixture A (60mmHg Matheson Std., 600 mmHg N) mixture B (107mmHg Matheson Std., 458 mmHg N2) mixture C ( 1 25 mmHg Matheson Std., 458 mmHg N2) mixture D
(355mmHg Matheson Std., 355 mmHg N2) mixture E (450 mmHg Matheson Std., 210 mmHg N2) mixture F (600mmHg Matheson Std., 100 mmHg N2) a
Nitrogen is calculated by difference
These diluted mixtures were then analyzed by both the gas chromatographic and ORSAT methods. The results are shown in Table 11. Precision and Detection Limits. T h e relative standard deviations (RSD)for the ORSAT analysis a t t h e 95% confidence level are shown in Table I. T h e relative standard deviations for the analysis of t h e gas standard mixtures by gas chromatography for COY,0 2 , CO, and N2 are 2.9,4.3,6.0, and 4.2, respectively. These values refer to several compilations of data of the GC method in which the averages are shown in Table I1 for the comparisons. T h e sensitivity was defined as the ratio of the signal to the noise; this ratio was set equal to three. T h e detection limit of these four components on this equipment is approximately 0.1% by volume.
Table 111. Refuse Incinerator Stack Gas Analysis time (p.m.)
12:55
l:oo 1:lO 1:15 1:20 1:25 1:30 1:35 1:40 1:45 1 :50
COP
15.4 12.6 13.5 16.8 15.2 10.8 9.5 8.0 6.8 5.8 8.1
02
4.3 3.1 2.6 3.0 4.8 7.5 9.9 11.9 12.8 11.5 11.9
co 0.1 0.2 0.1
N2
80.5 83.9 82.3 80.5 77.2 80.8 79.3 79.7 79.8 81.6 80.1
refuse incinerator. T h e sampling probe was placed after the secondary combustion chamber and just before the primary spray quench chamber. T h e probe was connected by copper tubing to the analyzer, which was positioned about 30 ft away in the control room. An analysis of stack gas was carried out every 5 or 10 min. The results are shown in Table 111. The COZ analysis varied from 12.6 to 16.8‘%in the 15-min interval from 1:00 to 1:15 p.m. Also in the 15-min interval from 1:30 to 1345 p.m., the CO? changed from 9.5 to 5.8%.As shown in the results during 15 min, the gas composition can change considerably. With one “on-line” sampler and ORSAT analyzer and single operator, only one sample can be taken and analyzed in approximately 15 min. T h e “on-line” sampler and gas chromatographic system and single operator can take and analyze more samples in a comparable time period. This rapid on-stream analysis gives incinerator operators almost immediate knowledge of the incinerator efficiency and allows them to quickly make the necessary adjustments.
Acknowledgment LVe wish to thank Mrs. Esther Harsh for the final proofreading and typing of this paper.
Literature Cited
Results a n d Diqcussion
( 1 ) F r d . Regist., 39 (No. 1161, 20793, Method 5 (,June 14, 1974). 12) F e d . Regist., 36 (No. 247), 24886, Method 3 (Dec 23, 1971). ( 3 ) bloody, A. H., Stevens, G. E., Chemist-Anal>si,17, 15 (1928). ( 4 ) Heke, R., Ingenieiirs, 1 I , 41-4 (1970). (5) Swan, K., IValker, J . A,, I:.K. A t . Energy A u t h . Rerzct. Group, TRG Rep., No. 1867 (1969). (6)Golden, B. 31..Yeung, E. S., Anal. Chem., 37, 21:32 (1975).
The above gas chromatographic sampling system was used to analyze the stack gases during a burning operation a t a
Kcceii~ed /or recieii. 1Voc.ember 6 , 1978. Acceptcd Soi,embpr 9, 1979.
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Environmental Science & Technology
