Environmental Monitoring Series
STANDARDIZATION OF METHOD 11 AT A
PETROLEUM REFINERY: Volume I
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved methods
and instrumentation for the identification and quantification of environmental
pollutants at the lowest conceivably significant concentrations. It also includes
studies to determine the ambient concentrations of pollutants in the environment
and/or the variance of pollutants as a function of time or meteorological factors.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
STANDARDIZATION OF METHOD 11
AT A PETROLEUM REFINERY
VOLUME I
by
George W. Scheil
Michael C» Sharp
Midwest Research Institute
Kansas City, Missouri 64110
EPA Contract No. 68-02-1098, Task 6
EPA Project Officer
M. Rodney Midgett
Quality Assurance Branch
Environmental Monitoring and Support Laboratory
Research Triangle Park
North Carolina 27711
Environmental Monitoring and Support Laboratory
Office of Research and Development
U«S» Environmental Protection Agency
Research Triangle Park
North Carolina 27711
-------
DISCLAIMER
This report has been reviewed by the Environmental Monitoring and
Support Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement of
recommendation for use.
-------
FOREWORD
Midwest Research Institute (MRI), under Task 6 of EPA Contract No.
68-02-1908, conducted in-house work toward the standardization of Method
11 (Federal Register. Vol. 39, March 8, 1974, pp. 9321^9323) as applied
to the analysis of t^S in petroleum refinery fuel gases.
The results of this in-house work are given in this report. Further
work on the method was done under Task 8 of EPA Contract No. 6802-1908.
This continuation of efforts was a collaborative test to evaluate the ac-
curacy and precision of the modified Method 11. The results of the work
done under Task 8 are given in Volumes II and III.
Approved for:
MIDWEST RESEARCH INSTITUTE
\
Larry Sfliahnon, Director
Environmental and Materials
Sciences Division
April 4, 1977
iii
-------
ABSTRACT
Method 11 (Federal Register. 3£, pp. 9321-9323, March 8, 1974), "De-
termination of Hydrogen Sulfide Missions from Stationary Sources," is sub-
ject to serious mercaptan interferences. Mercaptans are also efficiently
collected by the alkaline cadmium impinger solution used and the resulting
mercaptides react with the iodine titrant to give high results. Several al-
ternate absorbing reagents were evaluated for minimum interferences. The pH
of each of several cadmium and zinc salt solutions was adjusted to obtain a
high collection efficiency for I^S with minimum mercaptan collection. The
most selective absorbing solution was 0.16 M cadmium sulfate at a pH of 3.0.
The H2S collection efficiency for three midget impingers containing this so-
lution was 96%, and a mercaptan concentration equal to the H2S present gave
results about 5% high.
A ruggedness test was then used to evaluate the effect of 14 variables
on the analysis. The results of the test indicated that the most important
variables were cadmium concentration, pH, and the spacing between the im-
pinger tip and the bottom of the impinger. The optimized procedure was then
field tested at three refineries on a variety of process streams. No serious
problems with the procedure were found. The laboratory and field tests were
then used to write a final version of the procedure in preparation for a
collaborative test of the method (the collaborative test is covered in Vol-
ume II of this report).
This report was submitted in fulfillment of Task 6 of Contract No. 68-
02-1098 by Midwest Research Institute under the sponsorship of the U.S.
Environmental Protection Agency. This report covers a period from August 1,
1974 to November 1, 1975, and work was completed as of December 31, 1976.
iv
-------
CONTENTS
Foreword •• ill
Abstract iv
Figures vi
Tables . . . vii
Acknowledgment* • viii
!• Introduction. 1
2. Laboratory Test Facility 3
3. Evaluation of Alternative Analysis Procedures 7
4. Tests for Ruggedness and Collection Efficiency. ..... 12
5. Field Testing 16
Appendices
A. Method 11 - Determination of Hydrogen Sulfide Emissions
From Stationary Sources. 21
B. Tentative Method for the Determination of Hydrogen Sulfide
Emissions From Stationary Sources 31
C« Ruggedness Test Data 41
D. Tentative Method for the Determination of Hydrogen Sulfide
Emissions From Stationary Sources. ..... 45
E. Tentative Method for the Determination of Hydrogen Sulfide
Emissions From Stationary Sources. ........... 57
-------
FIGURES
Number Page
1 H2S Sampling Manifold 4
2 Schematic Drawing and Photographs of the Diffuser 6
3 Sample Conditioning System for Field Tests . 18
A-l H2S Sampling Train 26
B-l H2S Sampling Train 36
D-l H2S Sampling Train 51
E-l H2S Sampling Train 63
vi
-------
TABLES
Number Pa%e
1 Cadmium Acetate Absorbent Results 9
2 Test Results of CdSO^, Cd Formate, and Zn Acetate Absorbing
Reagent Systems. ..... .... 11
3 Procedure Variables and Results of Ruggedness Test 14
4 Measurement of Methyl and Ethyl Mercaptan Interferences. ... 15
5 Field Test Results - West Texas Feedstock 16
6 Field Test Results - Western Alberta Feedstock 19
7 Field Test Results - Middle East Sour Feedstock 20
A-l Field Data 27
B-l Field Data 36
C-l Test Design Matrix 43
C-2 Results of Ruggedness Test - Blanks and H2S Measured 44
vii
-------
ACKNOWLEDGEMENTS
Task 6 was conducted under the technical management of Mr. Paul C.
Constant, Jr., Head, Environmental Measurements Section of MRI's Environ-
mental and Materials Sciences Division, who is the program manager.
Dr. George Scheil was task leader. He was assisted by Messrs. John LaShelle,
Bruce DaRos, Thomas Merrifield, and Michael Sharp of MRI. Dr. Joseph Knoll,
Quality Assurance Branch, U.S. Environmental Protection Agency (EPA), con-
ducted laboratory tests of the various methods in cooperation with MRI»
The assistance of Mr. T. M. Nairn, Jr., of the Cosden Oil and Chemical
Company and Mr. Darrell Bruckert of Union Oil Company during the refinery
tests is gratefully acknowledged.
viii
-------
SECTION 1
INTRODUCTION
This report covers the tests and evaluations conducted by Midwest Re-
search Institute (MRI) of proposed methods to replace the present Method
11 procedure (Federal Register. Vol. 39, March 8, 1974, pp. 9321-9323,
(see Appendix A). The testing was done for the Environmental Protection
Agency (EPA) under Contract No. 68-02-1098, "Standardization of Stationary
Source Emission Measurement Methods." Volume I of this report covers Task
6 of the contract which includes the search for a method that is free of
the mercaptan interference, method evaluation, and field testing of the
final method. Task 8 was a collaborative test of the proposed new Method
11 and is covered in Volumes II and III.
Method 11 is intended for use in the analysis of refinery fuel gas
streams for hydrogen sulfide (t^S). Under the current standard (Federal
Register^ March 8, 1974) limits have been placed on sulfur dioxide (802)
emissions from refinery process heaters and boilers. SC^ emissions are
controlled indirectly by limiting the amount of l^S in the fuel gas to
230 mg/dscm.
The March 8, 1974, Method 11 specifies alkaline cadmium sulfate as
the absorbent for l^S. An impinger filled with hydrogen peroxide is in-
cluded to eliminate S02« However, in some refineries significant amounts
of mereaptans are present in the fuel gases and the mercaptans are collected
along with the l^S. One mole of mercaptan is measured as 1/2 mole of
in the iodometric titration of the H2S collected.
-------
Task 6 began in the fall of 1974 with an examination of the literature
for possible alternate methods. A test facility was then constructed that
allowed for the addition of known amounts of I^S, S02, and methyl and ethyl
mercaptans to a natural gas stream. Several absorbing reagents were then
tested using cadmium or zinc solutions with sulfate, acetate, or formate
anions. The general strategy was to control the solution pH and thereby
obtain a high collection efficiency for I^S without also collecting the
mercaptans. The absorbent chosen for final use was 0.16 M cadmium sulfate
adjusted to a pH of 3.0. This absorbing solution was then tested for col-
lection efficiency and 14 procedure variables were evaluated in a ruggedness
test. The optimized procedure was then used at three refineries that had
a variety of fuel gas streams. A final procedure was then written that in-
corporated several changes that were determined from the results of the
field tests.
The following sections of this report examine the fuel-gas, test assem-
bly used by MRI in its laboratory tests, the various analysis methods tested,
the efficiency and ruggedness tests of the final method and the field test-
ing of the proposed, new Method 11 at three refineries.
-------
SECTION 2
LABORATORY TEST FACILITY
A stream of natural gas spiked with l^S was used to simulate a re-
finery fuel -gas stream for MRI's laboratory investigations. A schematic
of the system is shown in Figure !• The l^S concentration is determined
by the ratio of the natural gas meter flow to the flow rate of the pure
H2S gas being added. Since the t^S rotameter has a logarithmic taper,
the accuracy, which is 5%, is constant over the entire flow range. Since
the natural gas meter is calibrated to 1% accuracy, an t^S concentration
range of 40 to 5,000 mg/m^is available with an accuracy of 57o.
The manifold includes provisions for the addition of sulfur dioxide,
methyl mercaptan and ethyl mercaptan singly or in combination to check
interference effects. The S02 and CH-jSH are added to the test stream as
the pure gases. The C2H5SH is added by bubbling nitrogen through the
liquid mercaptan and controlling the rate of addition by controlling the
flow rate and partial pressure of the C2H5SH in the mixture. All critical
sections of the system are made from Teflon, SJ stainless steel, or glass.
The system also includes a provision for addition of other gases if requiredi
Excess gases are burnt outside the building to convert the sulfur compounds
to
To obtain thorough mixing of the l^S and the other gases, the two
spike gas streams enter the natural gas stream at the center of a 1-in.
0«D«, Teflon pipe. For greater stability, the l^S stream is also mixed
with a flow of 200 cc/min of dry nitrogen just before it enters the natural
gas stream.
a/ Trade name.
-------
Manometer Tap
Regulator Saftey Vent
to Atmosphere
Gas Cock
Natural
Gas »—
Supply
H2S Cylinder
Corrosion Resistant
Single Stage Regulator
Methyl Mercaptan
(Lecture Bottle)
Shut Off Valve (V) 1 Shut Off Valve
SO2 Cylinder
Corrosion Resistant
Single Stage Regulator
Shut Off Valve
(X) (Micrometer Valve
Rotometer
(.3 - lOOcc/min)
Low Pressure
Gas Regulator
(2.5 inches H2O)
Dry Gas
Meter
(Approx.
30-70
L./min)
(X) 1 Micrometer Valve
Rotometer
(.3 - lOOcc/min)
Micrometer Valve
Rotometer
(0- 700cc/min)
High Pressure
Nitrogen Cylinder
Two Stage High
Pressure Regulator
Shut Off Valve
Micrometer Valve
Midget Bubbler
Containing
Ethyl Mercaptan
Immersed in
Ice Bath
Rotometer
(0- 700cc/miri)
Sampling
Manifold
Flame Out
Saftey Valve
o
Burner and
Flue Stack
.(Area enclosed in dotted lines is composed entirely of Teflon with the exception of sampling valves which are stainless steel)
Figure 1 - H2S Sampling Manifold
-------
The construction of the diffuser is detailed in Figure 2. The sampling
manifold is a section of 1-in. 0«D», Teflon pipe with center-line taps at
8 -in. intervals.
After the system had been in operation for some time, the I^S rota-
meter began fouling. After packing the line leading to the rotameter with
glass wool, degreasing the micrometer valve, and using high-vacuum silicone
grease to lubricate the valve threads, the rotameter gave no more trouble.
Also, due to the highly offensive odors of the gases used and the parts per
billion odor threshholds of the sulfur compounds, the system had to be very
carefully sealed to avoid leakage to the room air. Thickwall Teflon tubing
was used to avoid permeation through the tubing walls, especially wherever
the gases are under pressure. To prevent the build up of objectionable or
dangerous gas concentrations two exhaust blowers were operated continuously
during testing. Even with 1,300 ft^ of air per min being exhausted, some
odor usually remained, but not enough to be a problem.
-------
Photo 1 - Top View Diffuser Components: Housing, End
Sections, Spiraler Tube, Teflon Screens, Retaining
Rings.
Photo 2 - External View of Diffuser.
m
A-r-7
Jlttl
VI
Exploded cross section of all-Teflon diffuser with inlet (A),
end section (B), spiraler tube with angled holes (C),
prescreen block with holes (D), five sets of fine mesh
Teflon screen and retaining blocks (E), end section (F),
exit (G) and diffuser housing (H). Double cross-hatched
end plates are stainless steel.
/////S////////S/S
Figure 2 - Schematic Drawing and Photographs of the Diffuser
-------
SECTION 3
EVALUATION OF ALTERNATIVE ANALYSIS PROCEDURES
A number of methods were initially examined as possible replacements
for the alkaline CdSO^ procedure. A number of other heavy metal salts have
been used for the analysis of l^S or mercaptans. Most of the existing methods
report the analysis of t^S or the analysis of mercaptans but seldom examine
the analysis of I^S in the presence of mercaptans.
Among the methods for analysis of t^S are: (a) reaction to form methy-
lene blue, measured photometrically, (b) oxidation to S02 with analysis
of the S02 produced, (c) potentiometric titration of l^S and mercaptans
using AgN03 as titrant, and (d) collection in various heavy metal solutions
followed usually by an iodometric titration. Mercaptans also can react with
carbonyl compounds to form mercaptals or the direct oxidation to the disul-
fide is possible.
No simple method of measuring the H2S reaction products independent
of the mercaptal or disulfide products could be found. The methylene blue
method is designed for trace analysis in the parts per billion range and
gives erratic results at the levels found in fuel gases. Conversion to
S02 before measurement would be a rather inconvenient procedure, since S02
is often present in significant amounts. The S02 would have to be measured
twice, before and after the l^S conversion.
The potentiometric method gives two separate breaks in the titration,
first for H2S and then for the mercaptans. However, the t^S must first be
trapped in sodium or potassium hydroxide to form the unstable, soluble
or K2S which requires an analysis immediately after collection. The poten-
tiometric titration also requires more specialized equipment than the io-
dometric methods and would respond to other redox reactions.
-------
Since the solubilities of the metal sulfides and mercaptides are pH
dependent, the main effort in the evaluation of alternate analysis pro-
cedures went into developing a buffered, metal-salt system that would col-
lect the H2S in high yields without collecting the mercaptans.
The first method tested was a cadmium acetate buffer solution that
used an antifoam agent to prevent carryover of the impinger contents. A
copy of this procedure is given in Appendix B. The initial tests of this
method by EPA showed very promising results. At a pH of about 4.2 quanti-
tative recovery of I^S was possible using only two impingers. Methyl mer-
captan began to be absorbed at a pH of 5 or more. The acetate solution did
foam considerably but the addition of an antifoaming agent prevented foam-
ing without interfering with the anaysis. Only the silicone-based, anti-
foam agents gave a stable solution, however, and then only if the emulsi-
fied form was used. Dow-Corning Antifoam-ES.' gave excellent results. (It
was available from supply houses in small quantities.) An additional ad-
vantage of using the Antifoam-B was that the cadmium sulfide precipitate
did not cake onto the walls of the impingers, but usually could be recovered
with a water rinse.
After the encouraging EPA results, MRI proceeded to measure the col-
lection efficiency and interference effects. By spiking the natural gas
with H2S, consistent results were obtained with a high collection efficiency!
Analysis results using the cadmium acetate system are shown in Table 1.
Using the basic procedure of Appendix B, collection efficiency of ^S re-
mains near 100% up to ^ 300 mg/dscm and falls to about 90% at 700 mg/dscm.
High levels of S02 have little or no effect. Mercaptans are collected with
an efficiency approximately equal to that for l^S, but only when l^S is
also present. Reducing the pH to about 3 has little effect. With 0.03 M
cadmium acetate at pH 3 the l^S collection efficiency is only about 5%
lower than the original 0.04 M, pH 4.2 solution. However, the mercaptans
are no longer collected with equal efficiency but instead the efficiency
decreases with increasing mercaptan/^S ratio to as little as 10% for a
10:1 ratio (mercaptan as its h^S equivalent) and reaches zero with no l^S
present. Under normal refinery conditions where the mercaptan content is
50 to 200% of the H2S concentration, from 100 to 30% collection is obtained.
Due to the problems involved with a cadmium acetate absorbing solution,
the evaluation was extended to include other metal salt systems. The results
of testing in the additional systems are summarized in Table 2. Parallel
testing was also done by EPA. The final conclusion was that 0.16 M GdSO^
at pH 3 showed the most promise with 0.04 M cadmium formate at pH 3.2 as
a second choice. The testing also indicated that Antifoam-B was still de-
sirable in the absorbing solution and there was an excellent chance that
the acid extraction of the impingers could be eliminated.
a/ Trade name.
-------
TABLE 1. CADMIUM ACETATE ABSORBENT RESULTS
No.
21
22
31
32
33
34
19
20
29
30
23
24
25
26
43
44
45
46
49
50
53
54
58
59
60
65
Sample—
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
.04
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
M,
EtSH
pH 4
pH 4
pH 4
pH 4
pH 4
pH 4
pH 4
pH 4
pH 4
pH 4
pH 4
pH 4
pH 4
pH 4
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
S02 = 1,700 ppm
S02 = 1,700 ppm
EtSH
EtSH
EtSH
EtSH
EtSH
EtSH
MeSH
MeSH
MeSH
pH 4
= 170
= 850 ppm
=850 ppm
=200 ppm
= 200 ppm
= 50 ppm
= 50 ppm
= 240 ppm
= 120 ppm
= 120 ppm
.2, S02 = 1,700 ppm
ppm, MeSH = 100 ppm
H2S Measured
(mg/DSCM)
6
5
95
94
198
182
283
281
348
349
489
432
657
643
383
371
955
963
518
522
428
434
521
452
444
573
H2S Calculated
(mg/DSCM)
0
0
84
84
196
196
281
281
387
387
552
552
728
728
394
394
400
400
400
400
398
398
399
379
379
385
% Recovery—
(91)
(91)
(94)
(94)
(98)
(100)
(89)
(96)
(94)
(97)
113
112
101
93
101
100
90
90
89
78
90
88
97
94
239
241
130
130
108
109
131
119
117
149
a/ MeSH = Methyl mercaptan, EtSH = ethyl mercaptan.
Jb/ Numbers in parentheses are the collection efficiencies obtained from the total of all ^S and mercap-
tans present. Since 1 mole of mercaptan titrates as 0.5 mole of ^S and since, at standard condi-
tions, 1 ppm H2S = 1.54 mg/DSCM, 1 ppm of mercaptan is equivalent to 0.77 mg/DSCM of H2S .
-------
TABLE 1 (Concluded)
H2S measured H2S calculated
No. Sample^/ (mg/DSGM) (mg/DSCM)
67
68
69
70
71
72
77
78
83
84
89
90
91
92
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.04 M,
.04 M,
.02 M,
.02 M,
.03 M,
.03 M,
.03 M,
.03 M,
.03 M,
EtSH
.03 M,
EtSH
.03 M,
EtSH
.03 M,
EtSH
.03 M,
EtSH
.03 M,
pH 3
pH 3
pH 3
pH 3
pH 3
pH 3
pH 3
pH 3
pH 3
= 400
pH 3
= 400
pH 3
= 450
pH 3
= 450
pH 3
= 500
pH 3
EtSH = 500
93
0
.03 M,
pH 3
EtSH = 750
94
0
.03 M,
pH 3
.3
.3
.0
".0
.0
.0
.0, MeSH
.0, MeSH
.0, MeSH
ppm
.0, MeSH
ppm
.0, MeSH
ppm
.0, MeSH
ppm
.0, MeSH
ppm
.0, MeSH
ppm
.0, MeSH
ppm
.0, MeSH
= 100
= 100
= 160
= 160
= 160
= 160
= 100
= 100
= 500
= 500
ppm
ppm
ppm,
ppm,
ppm,
ppm,
ppm,
ppm,
ppm,
ppm,
378
368
260
274
348
346
420
435
463
469
4
4
148
155
158
187
430
430
410
410
410
410
409
409
391
391
0
0
87
87
83
83
(86)
(90)
(56)
(57)
MM
MM
(27)
(28)
(15)
(18)
88
86
63
67
85
84
103
106
118
120
170
178
190
225
EtSH = 750 pprn
a./ MeSH = Methyl mercaptan, EtSH = ethyl mercaptan.
b/ Numbers in parentheses are the collection efficiencies obtained from the total of all ^S and mercap-
tans present. Since 1 mole of mercaptan titrates as 0.5 mole of H2S and since, at standard condi-
tions, 1 ppm H2S = 1»54 mg/DSGM, 1 ppm of mercaptan is equivalent to 0.77 mg/DSCM of H2S.
-------
TABLE 2. TEST RESULTS OF CdS04, Cd FORMATE, AND Zn ACETATE ABSORBING REAGENT SYSTEMS
No_._
101
102
107
108
165
167
169
171.
175
147
148
151
152
127
128
129
130
141
142
143
144
153
157
155
154
158
156
Sample^/
0.04 M CdS04, pH 5, 2 Impingers
0.04 M CdS04, pH 5, 3rd Impinger, 0.04 M CdS04, pH > ?k/
0.08 M CdS04, pH 5, 2 Impingers
0.08 M CdS04, pH 5, 3rd Impinger, 0.04 M, CdS04, pH > 7k/
0.16 M CdS04, pH 3, 3 Impingers, MeSH = 250 ppm
0.16 M CdS04, pH 3, 3 Impingers
0.16 M CdS04, pH 3, 3 Impingers, MeSH = 350 ppm
0.16 M CdS04, pH 3, 3 Impingers, MeSH = 350 ppm
0.16 M CdS04, pH 3, 3 Impingers
0.08 M CdS04, 3 Impingers
0.08 M CdS04, 3 Impingers
0.08 M CdS04, 3 Impingers, MeSH = 500 ppm
0.08 M CdS04, 3 Impingers, MeSH = 500 ppm
0.04 M Cd Formate, pH 3.2
0.04 M Cd Formate, pH 3.2
0.04 M Cd Formate, pH 3.2, MeSH = 350 ppm
0.04 M Cd Formate, pH 3.2, MeSH = 350 ppm
0.04 M Cd Formate, pH 3.2
0.04 M Cd Formate, pH 3.2
0.04 M Cd Formate, pH 3.2, MeSH = 230 ppm
0.04 M Cd Formate, pH 3.2, MeSH = 230 ppm
0.04 M Cd Formate, pH 3.2
0.04 M Cd Formate, pH 3.2
0.04 M Cd Formate, pH 3.2, MeSH = 450 ppm
0.08 M Zn Acetate
0.08 M Zn Acetate
0.08 M Zn Acetate, MeSH = 450 ppm
H2S Measured
(me/DSCM)
417
496
715
761
290
283
321
323
304
486
491
322
325
511
525
571
587
361
359
391
409
250
280
319
290
315
466
H2S Calculated
(ma/DSCM)
620
620
787
787
312
329
312
313
314
523
523
284
284
572
572
570
570
372
372
376
376
271
364
349
271
364
349
% Recovery
67
80
91
97
93
86
103
103
97
93
94
113
114
89
92
100
103
97
97
104
109
92
77
91
107
87
134
a/ MeSH = Methyl mercaptan.
b/ Concentrated NaOH added until formation of Cd(OH>2 precipitate.
-------
SECTION 4
TESTS FOR RUGGEDNESS AND COLLECTION EFFICIENCY
Three impingers containing 0,16 M cadmium sulfate absorbing solution
at pH 3.0 was chosen as the procedure for further development. A ruggedness
test was then designed and run to test the effect of 14 procedure variables.
Details of the ruggedness test design are given in Appendix C«
1 2/
A ruggedness test 3 f is an experimental design for evaluating a set
of variables in a minimal number of runs. For n variables a ruggedness
test would have n+1 runs. For design simplicity the number of runs is usu-
ally chosen to be a power of 2 with dummy variables added if necessary to yield
2X-1 variables. For each variable "high" and "low" conditions are assigned,
and each run consists of a different set of "high" and "low" conditions for
each variable. A complete test includes an equal number of "high" and "low"
condition runs for each variable. The statistical analysis of the results
factors together all "high" runs for each variable and compares them with
the "low" runs for that variable. The final result is a significance level
for each variable at the "high" and "low" conditions chosen.
The ruggedness test design is based upon the assumptions that all vari-
ables are independent of one another and that all variables not analyzed
"average out" for all runs. If either of these assumptions fail, the dummy
variables will become significant. An additional problem with a ruggedness
test is that the two conditions for each variable must be carefully chosen
to represent reasonable variations for each variable since the variable's
significance is a measure of the effect of changing that variable between
the two conditions.
I/ Stowe, R. A., and R. P. Mayer, Ind. and Eng. Chem.. 58:2, pp. 36-40,(1966).
2l Youden, W. J., Statistical Techniques for Collaborative Tests, Assoc.
of Official Analytical Chemists, Washington, D,C», pp. 64 (1973).
12
-------
The results of the ruggedness test are shown in Table 3. A separate
test for significance was made for the blank values and for the final re-
sults* In both cases, dummy variables were found to be significant. This
is partially due to second- or higher-order interaction of the variables.
Impinger tip diameter, flow rate and purge time are all dummy variables
for the blanks. The impinger solution pH is a significant variable for both
blanks and final results. Specifying a pH of 3.0 + 0.1 should control this
variable. CdSO^ concentration is also critical to both blanks and final re-
sults. Normal weighing errors and impurity levels should not cause trouble
in this variable. The aging effect on the blank should normally have no
effect since blanks must be measured daily. The effect of impinger tip to
bottom spacing on the final result and the effects on the blanks of reaction
time, presence of Antifoam-B, amount of HCl added to the 1^ and impinger ex-
traction were the subjects of further tests.
To check the effect of the bottom spacing of the impinger tip, trains
were run with all conditions identical except that one train had a spacing
of 2 to 4 mm and the other train had a 5 to 7 ran spacing. In two trials,
the 2 to 4 mm set gave 2 to 4% higher collection.
Tests were also made to determine the effects of reaction time and
amount of acid on the titration blank. In the first set, 45 ml of pH 3,
0.16 M CdS04 with 50 ml of 0.01 M l£ had varying amounts of 10% HCl added
and were titrated immediately. With no acid, 5 ml 10% HCl, and 50 ml of
10% HCl, the respective titrations were 30.16 ml, 30.07 ml, and 30.30 ml.
With a 30 min delay before titration, the respective titrations were 29.86
ml, 30.06 ml, and 30.34 ml. Thus, with no acid, part of the iodine was
consumed, but neither acid concentration showed a significant change with
time. The fact that the immediate titration of blanks containing 5 ml of
acid gave a lower value than without added acid indicates that the small
amount of IkSO^ in the adsorbing reagent is not sufficient to provide a
stoichiometric reaction. The increased titrant volumes with 50 ml of acid
reflect the acid-catalyzed air oxidation of iodide.
From the results of these tests, a possible alternate method of analy-
sis was formulated. By adding 5 ml of HCl and extracting the impingers with
only water, the major problem of extraction could be avoided, the analysis
greatly simplified, and analysis time shortened. To allow this change, 10
drops of Antifoam-B must be added in each liter of absorbing solution or
large amounts of CdS will remain on the impinger walls.
To test the modified method, a test of collection efficiency was made.
Adding about 300 mg/nr of ^S to the gas stream, each method of analysis
(water extraction, 5 ml of acid versus extraction with iodine containing
50 ml of acid; Antifoam-B used in both) was tested against the performance
13
-------
TABLE 3. PROCEDURE VARIABLES AND RESULTS OF RUGGEDNESS TEST
Variable
Low Level High Level
Significance Level'
Blank Result
a/
Temperature
Impinger tip to
bottom spacing
Impinger tip diameter
Impinger solution volume
Impinger solution pH
Sampling flow rate
Purge time
Reaction time before
titration
0°C
25°C
2-4 mm 5-7 mm
- (1.5)
- (0.5)k/ 95% (6.1)
1-1.02 rim 1.02-1.04 mm 95% (4.8)£/ - (0.3)
10 ml
2.5
20 ml
3.5
- (0.0) - (0.0)
90% (3.4) 90% (4.4)
0.8 je/min 1.5 4/min 99% (116)^ - (0.1)
10 min 20 min 99% (22)£/ - (0.5)
15 min 45 min 99% (9.7) - (1.2)
Impinger solution age
CdSO, concentration
Shaking of iodine flask
Ant i foam B
HC1 addition to I2
Extraction of impingers
Dummy
1 day
0.08 M
2 sec
None
5 ml
None
•
1 week
0.24 M
60 sec
10 drops/1
50 ml
Yes
-
99% (44)
99% (340)
- (0.5)
99% (31)
99% (375)
99% (640)
- (3)
- (0.7)
99% (24)
- (0.0)
- (0.0)
- (0.5)
- (1.6)
95% (5.9)
a/ Numbers in parentheses are the F-value results of ruggedness test.
b/ Dummy variable for blanks.
14
-------
of an identical train with NaOH added to the absorbing solution to create
an alkaline pH with some Gd(OH)2 present. The alkaline trains were ex-
tracted with a mixture of 50 ml of HCl and 50 ml of ~L~* Separate blanks
were made for each set of conditions. It was found that the alkaline cadmium
will absorb essentially all of the I^S in the first impinger. With 50 ml
of acid and iodine extraction, 94 and 98% of the t^S was collected relative
to the alkaline cadmium trains. With 5 ml of acid* and no iodine extraction,
99 and 96% was collected relative to the alkaline cadmium trains. Only a
slight yellow film was left in the impingers after the water rinse.
Further tests of collection efficiency for the modified method (0.16 M
CdSO^, pH 3, with Antifoam-B, water extraction, 5 ml of acid) using an
alkaline CdS04 reference showed 93% efficiency at 100 mg/m3 and 97% effi-
ciency at 400 mg/m3. The collection efficiency appears to be 96 + 2% up to
400 mg/m3 of H2S.
Checks were also made of the methyl mercaptan (Ct^SH) and ethyl mer-
captan (C2H5SH) interferences. The results are given in Table 4.
TABLE 4. MEASUREMENT OF METHYL AND ETHYL MERCAPTAN INTERFERENCES
Measured value CI^SH present C2H5SH present
(mg/m3 as H2S) (mg/m3 as H2S) (mg/m3 as H2S)
211
228
214
236
245
219
140
> 387
--
_-
'>' 300
80
--
197
>363
> 200
140
Note: H2S levels for all tests were 200 + 10 mg/m3.
The quantity of mercaptan present was measured using a train of alka-
line cadmium sulfate. The higher levels of mercaptans showed heavy precipi-
tates in the last impinger, so these are minimum values.
The results obtained from the ruggedness and efficiency tests were
used to rewrite the procedure in preparation for field trials at refineries•
A copy of this procedure is given in Appendix D.
* This amount was changed to 10 ml of acid in the final procedure to pro-
vide a better safety margin for dissolving the cadmium sulfide pre-
cipitate.
15
-------
SECTION 5
FIELD TESTING
Field tests of the proposed method were conducted by MRI in October
1975, to determine if the method functions properly on actual sources and
to refine the method in preparation for a collaborative test. Three refineries
were selected for the field trials which represented a wide range of sour
feedstocks and with a number of different types of sample sources.
The first refinery tested operated primarily on a sour West Texas feed-
stock* This site was also tentatively selected for the collaborative test.
The results of testing are summarized in Table 5. Parallel trains were run
during all tests.
TABLE 5. FIELD TEST RESULTS - WEST TEXAS FEEDSTOCK
Test No. Stream Date HoS measured (mg/m^)
1
2
3
4
5
6
Fuel gas treater
Fuel gas treater
Fuel gas treater
Fuel gas treater
Sulfur plant fuel
gas
Sulfur plant fuel
10/15/75
10/15/75
10/15/75
10/15/75
10/16/75
10/16/75
1,140
62
109
225
8
4
1,010
78
109
139
9
5
16
-------
The sampling point of the fuel gas treater was downstream from a
diethanolamine scrubber. The scrubber was not operating at maximum ef-
ficiency during the tests and was further upset by occasional input over-
loads. An existing sample tap was used that was located at a low point in
the pipe. A diagram of the sample conditioning system is shown in Figure
3. Significant amounts of condensate, primarily oily, sulfur-loaded amine,
collected in the sample lines and had to be drained frequently, foone of
the araine ever appeared in the impingers. The sulfur plant fuel gas was
one of the few streams sampled which was at a pressure low enough to not
require a pressure regulator in the sampling system. This was a dry stream
with barely detectable amounts of I^S. Test No. 6 was run for 60 min at
1 liter/min and the first cadmium sulfate impinger had a definite yellow
color, although no precipitate was evident.
For the west Texas tests, as well as the following ones, a gas chro-
matograph (GC) equipped with a flame photometric detector was taken to the
field sites for confirmation of the test results. A |3,P'-oxydipropionitrile
column was installed in the GC and separated the mercaptans from H2S. How-
ever, the detector had excessive drift during all tests and only qualita-
tive results were obtainable. Methyl and ethyl mercaptan were detected in
the fuel gas treater stream in moderate amounts. At the sulfur plant, the
levels were too low to obtain any definite information.
The second field test was conducted at a refinery which used a western
Alberta feedstock. Test results are shown in Table 6. Duplicate trains were
run here and the basic test procedure was the same as that used in the first
test.
17
-------
To GC
To Sample
Train
To Sample
Train
Line
Regulator
n
I I
Lj
IT
Cap
Drain
Valve
Figure 3 - Sample Conditioning System for Field Tests
18
-------
TABLE 6. FIELD TEST RESULTS - WESTERN ALBERTA FEEDSTOCK
Test No. Stream Date HoSmeasured (ing/m )
1
2
3
4
5
6
7
8
9
10
Fuel gas K»0. drum
Fuel gas K.O. drum
ME A outlet
MEA outlet
Natural gas makeup
Natural gas makeup
Platformer sep.
off -gas
Platformer sep*
of f -gas
Platformer stab.
overhead accum.
off -gas
Platformer stab.
10-22
10-22
10-22
10-22
10-22
10-22
10-23
10-23
10-23
10-23
1,520
1,600
212
258
30
18
6
7
22
27
1,520
1,670
210
253
29
34
7
3
17
22
The streams sampled for Tests Nos. 5 through 10 were dry with low
levels, in a methane/hydrogen mixture, except for Tests Nos. 9 and
10, which contained large amounts of 63 and 64 hydrocarbons that extin-
guished the flame in the GC detector. The fuel-gas knockout-drum samples
had appreciable quantities of water present and the MEA (monoethanolamine
scrubber) outlet contained both water and monoethanolamine condensate.
The method functioned well at this refinery with no unusual occurrences.
All streams had very little mercaptan present.
The third field test was at a refinery operated on imported feed-
stock, primarily from sour middle east sources. Plant personnel made tests
in parallel with MRI at this site. The plant personnel ran a single modi-
fied Method 11 train and a special train with a potentiometric analysis.
The potentiometric procedure allowed the measurement of the I^S and mer-
captan concentrations from a double inflection point titration curve. The
results of the testing are given in Table 7.
All of the streams sampled contained a 2:1 or 3:1 ratio of methyl
mercaptan to I^S. The first stream was dry, the remaining two streams
were wet with monoethanolamine condensate. The last stream also contained
some ethyl mercaptan. The refinery Method 11 results were limited by the
use of a 1.0 ft-Vrev dry gas meter which would never complete even one-half
of a revolution for a test. The second MRI result for Tests 5 and 6 was
probably in error due to a leak in the sampling train. This leak was not
19
-------
discovered until after testing was completed. The refinery Method 11 re-
sults tend to be higher than the other results, which may have been caused
by the oversized dry gas meter. The MRI results are in general agreement
with the refinery potentiometric results with a maximum difference of about
15%.
After the field tests the procedure write-up was revised in prepara-
tion for the collaborative test. The main changes dealt with the inclusion
of a leak check before each run, and a rearrangement of the sampling train
components to accommodate the normally positive pressure fuel gas streams.
A general tightening of specifications and procedures was also made. A
copy of the final revision, which was used for the collaborative test,
appears in Appendix E.
TABLE 7. FIELD TEST RESULTS - MIDDLE EAST SOUR FEEDSTOCK
iH?S Refinery Results (mg/m3)
Test
No.
1
2
3
4
5
6
MRI Results
Stream
Unit 43
Unit 43
Unit 17
Unit 17
Unit 12
Unit 12
Date
10-27
10-27
10-28
10-28
10-28
10-28
H2S measured
250
297
330
318
238
288
(mg/m3)
274
279
328
319
312
372
Method 11
321
327
376
382
305
336
Potentio-
metric
245
—
373
339
272
325
20
-------
APPENDIX A
METHOD 11 - DETERMINATION OF HYDROGEN SULFIDE EMISSIONS FROM
STATIONARY SOURCES
21
-------
1«0 Principle and Applicability
1.1 Principle
Hydrogen sulfide (t^S) is collected from the source in a series
of midget impingers and reacted with alkaline cadmium hydroxide (CdCOH^)
to form cadmium sulfide (CdS). The precipitated CdS is then dissolved in
hydrochloric acid and absorbed in a known volume of iodine solution. The
iodine consumed is a measure of l^S content of the gas. An impinger con-
taining hydrogen peroxide is included to remove SC>2 as an interfering
species.
1.2 Applicability
This method is applicable for the determination of hydrogen sul-
fide emissions from stationary sources only when specified by the test
procedures for determining compliance with the new source performance
standards.
2.0 Apparatus
2.1 Sampling Train
a/
2.1.1 Sampling line - Six to 7 mm (1/4 in.) Teflon— tubing to
connect sampling train to sampling valve, with provisions for heating to
prevent condensation. A pressure reduing valve prior to the Teflon sam-
pling line may be required depending on sampling stream pressure.
2.2.2 Impingers - Five midget impingers, each with 30 ml capac-
ity, or equivalent.
2.1.3 Ice bath container - To maintain absorbing solution at a
constant temperature.
2.1.4 Silica gel drying tube - To protect pump and dry gas me-
ter .
2.1.5 Needle valve, or equivalent - Stainless steel or other cor-
rosion resistant material, to adjust gas flow rate.
2.1.6 Pump - Leak free, diaphragm type, or equivalent, to trans-
port gas. (Not required if sampling stream under positive pressure.)
2.1.7 Dry gas meter - Sufficiently accurate to measure sample
volume to within 17<>.
2.1.8 Rate meter - Rotameter or equivalent, to measure a flow
rate of 0 to 3 liters per minute (0.1 ft^/min).
a/ Trade name.
22
-------
2.1.9 Graduated cylinder - 25 ml.
2.1.10 Barometer - To measure atmospheric pressure within +2.5 mm
(0.1 in.) Hg.
2.2 Sample Recovery
2.2.1 Sample container - 500 ml glass-stoppered iodine flask.
2.2.2 Pipette - 50 ml volumetric type.
2.2.3 Beakers - 250 ml.
2.2.4 Wash bottle - Glass.
2.3 Analysis
2.3.1 Flask - 500 ml glass-stoppered iodine flask.
2.3.2 Burett - One 50 ml.
2.3.3 Flask - 125 ml conical.
3.0 Reagents
3.1 Sampling
3.1.1 Absorbing solution - Cadmium hydroxide (Gd(OH)o) - Mix
4.3 g cadmium sulfate hydrate (3 CdSO^S^O) and 0.3 g of sodium hydroxide
(NaOH) in 1 liter of distilled water (H20). Mix well.
[NOTE: The cadmium hydroxide formed in this mixture will precipitate as
a white suspension. Therefore, this solution must be thoroughly mixed be-
fore using to ensure an even distribution of the cadmium hydroxide.J
3.1.2 Hydrogen peroxide, 3% - Dilute 30% hydrogen peroxide to 3%
as needed. Prepare fresh daily.
3.2 Sample Recovery
3.2.1 Hydrochloric acid solution (HCl), 10% by weight - Mix
230 ml of concentrated HCl (specific gravity 1.19) and 770 ml of distilled
H20.
3.2.2 Iodine solution, 0.1 N - Dissolve 24 g potassium iodide (Kl)
in 30 ml of distilled H20 in a 1 liter graduated cylinder. Weigh 12.7 g of
resublimed iodine (I2) in a weighing bottle and add to the potassium iodide
23
-------
solution. Shake the mixture until the iodine is completely dissolved. Slowly
dilute the solution to 1 liter with distilled 1^0, with swirling. Filter
the solution, if cloudy, and store in a brown glass-stoppered bottle.
3.2.3 Standard iodine solution, 0.01 N - Dilute 100 ml of the
0.1 N iodine solution in a volumetric flask to 1 liter with distilled
water. Standardize daily as follows: Pipette 25 ml of the 0.01 N iodine
solution into a 125 ml conical flask. Titrate with standard 0.01 N thio-
sulfate solution (see Section 3.3.2) until the solution is a light yellow.
Add a few drops of the starch solution and continue titrating until the
blue color just disappears. From the results of this titration, calculate
the exact normality of the iodine solution (see Section 5.1).
3.2.4 Distilled, deionized water.
3.3 Analysis
3.3.1 Sodium thiosulfate solution, standard 0.1 N - For each
liter of solution, dissolve 24.8 g of sodium thiosulfate (^28203 • 51^0)
in distilled water and add 0.01 g of anhydrous sodium carbonate (Na^CC^)
and 0.4 ml of chloroform (CHC^) to stabilize. Mix thoroughly by shaking
or by aerating with nitrogen for approximately 15 min, and store in a
glass-stoppered glass bottle. Standardize frequently as follows: Weigh
into a 500 ml volumetric flask about 2 g of potassium dichromate (t^C^Oy)
weighed to the nearest milligram and dilute to the 500 ml mark with dis-
tilled H20. Use dichromate which has been crystallized from distilled
water and oven-dried at 182 to 199°C (360 to 390°F>. Dissolve approximately
3 g of potassium iodide (KI) in 50 ml of distilled water in a glass-stoppered,
500 ml conical flask, then add 50 ml of 10% hydrochloric acid solution.
Pipette 50 ml of the dichromate solution into this mixture. Gently swirl
the solution once and allow it to stand in the dark for 5 min. Dilute the
solution with 100 to 200 ml of distilled water, washing down the sides of
the flask with part of the water. Swirl the solution slowly and titrate
with the thiosulfate solution until the solution is light yellow. Add 4 ml
of starch solution and continue with a slow titration with the thiosulfate
until the bright blue color has disappeared and only the pale green color
of the chromic ion remains. From this titration, calculate the exact nor-
mality of the sodium thiosulfate solution (see Section 5.2).
3.3.2 Sodium thiosulfate solution, standard 0.01 N - Pipette
100 ml of the standard 0.1 N thiosulfate solution into a volumetric flask
and dilute to 1 liter with distilled water.
3.3.3 Starch indicator solution - Suspend 10 g of soluble starch
in 100 ml of distilled water and add 15 g of potassium hydroxide pellets. ;>
Stir until dissolved, dilute with 900 ml of distilled water, and let stand
1 hr. Neutralize the alkali with concentrated hydrochloric acid, using an
24
-------
indicator paper similar to Alkacid—/ test ribbon, then add 2 ml of glacial
acetic acid as a preservative. Test for decomposition by titrating 4 ml of
starch solution in 200 ml of distilled water with O.Oi N iodine solution.
If more than 4 drops of the 0.01 N iodine solution are required to obtain
the blue color, make up a fresh starch solution.
4.0 Procedure
4.1 Sampling
4.1.1 Assemble the sampling train as shown in Figure A-l, con-
necting the five midget impingers in series. Place 15 ml of 37o hydrogen
peroxide in the first impinger. Place 15 ml of the absorbing solution in
each of the next three impingers, leaving the fifth dry. Place crushed ice
around the impingers. Add more ice during the run to keep the temperature
of the gases leaving the last impinger at about 20°G (70°F) or less.
4.1.2 Purge the connecting line between the sampling valve and
the first impinger. Connect the sample line to the train. Record the ini-
tial reading of the dry gas meter as shown in Table A-l.
4.1.3 Open the flow control valve and adjust the sampling rate
to 1.13 liters per minute (0.04 cfm). Read the meter temperature and re-
cord on Table A-l.
4.1.4 Continue sampling a minimum of 10 min. If the yellow color
of cadmium sulfide is visible in the third impinger, analysis should con-
firm that the applicable standard has been exceeded. At the end of the sam-
ples time, close the flow control valve and read the final meter volume and
temperature.
4.1.5 Disconnect the impinger train from the sampling line. Purge
the train with clean ambient air for 15 min to ensure that all I^S is re-
moved from the hydrogen peroxide. Cap the open ends and move to the sample
clean-up area.
4.2 Sample Recovery
4.2.1 Pipette 50 ml of 0.01 N iodine solution into a 250 ml beaker.
Add 50 ml of 10% HCl to the solution. Mix well.
4.2.2 Discard the contents of the hydrogen peroxide impinger.
Carefully transfer the contents of the remaining four impingers to a 500 ml
iodine flask.
a/ Trade name.
25
-------
SAMPLING VALVE
TEFLON SAMPLING LINE (HEATED)
MIDGET IMPINGERS
FUEL GAS
LINE
DRY GAS METER
SILICA GEL TUBE
VALVE
PUMP ( Not Required
if Lines Pressurized
RATE METER
Figure A-l - H2S Sampling Train
26
-------
TABLE A-l
FIELD DATA
Location Comments:
Test
Date
Operator
Barometric Pressure
Gas Volume Rotameter Meter
Clock Through Meter (Vm), Setting, jtfpm Temperature,
Time I (cu ft) (cfm) °C (°F)
27
-------
5.0 Calculations
5.1 Normality of the Standard Iodine Solution
_ NTVT
where:
NT = normality of iodine, g-eq/liter;
VT = volume of iodine used, ml;
Nf = normality of sodium thiosulfate, g-eq/liter; and
Vm = volume of sodium thiosulfate used, ml.
5.2 Normality of the Standard Thiosulfate Solution
NT = 2.04 H_
VT (A-2)
where:
W = weight of K Cr 0 used, g;
VT = volume of Na2S20~ used, ml;
NT = normality of standard thiosulfate solution, g-eq/liter;
and
2.04 = conversion factor.
(6 eq I2/mole K2Cr20?) (1,000 ml/liter)
(294.2 g K2Cr207/mole) (10 aliquot factor)
5 .3 Dry Gas Volume
Correct the sample volume measure by the dry gas meter to stan-
dard conditions [21°C (70°F) and 760 mm (29.92 in.)] Hg by using Equation
A-3.
Vm v _ / i _ / (A.3)
where:
Vm = volume at standard conditions of gas sample through
std
the dry gas meter, standard liters;
V = volume of gas sample through the dry gas meter (meter
conditions), liters;
solute temperature al
erage dry gas meter 1
= barometric pressure at the orifice meter, mm Hg; and
T , = absolute temperature at standard conditions, 294°K;
std
T = average dry gas meter temperature, K;
i
oar
P , = absolute pressure at standard conditions, 760 mm Hg.
std
28
-------
4.2.3 Rinse the four absorbing impingers and connecting glass-
ware with three portions of the acidified iodine solution. Use the entire
100 ml of acidified iodine for this purpose. Immediately after pouring the
acidified iodine into an impinger, stopper it and shake for a few moments
before transferring the rinse to the iodine flask. Do not transfer any rinse
portion from one impinger to another; transfer it directly to the iodine
flask. Once acidified iodine solution has been poured into any glassware
containing cadmium sulfide sample, the container must be tightly stoppered
at all times except when adding more solution, and this must be done as
quickly and carefully as possible. After adding any acidified iodine solu-
tion to the iodine flask, allow a few minutes for absorption of the I^S
into the iodine before adding any further rinses.
4.2.3 Titrate the blanks in the same manner as the samples.
4.2.4 Follow this rinse with two more rinses using distilled
water. Add the distilled water rinses to the iodine flask. Stopper the flask
and shake well. Allow about 30 min for absorption of the l^S into the iodine,
then complete the analysis titration.
[CAUTION: Keep the iodine flask stoppered except when adding sample or
titrant.]
4.2.5 Prepare a blank in an iodine flask using 45 ml of the ab-
sorbing solution, 50 ml of 0.01 N iodine solution, and 50 ml of 10% HCl.
Stopper the flask, shake well and analyze with the samples.
4.3 Analysis
[NOTE: This analysis titration should be conducted at the sampling location
in order to prevent loss of iodine from the sample. Titration should never
be made in direct sunlight.
4.3.1 Titrate the solution in the flask with 0.01 N sodium thio-
sulfate solution until the solution is light yellow. Add 4 ml of the starch
indicator solution and continue titrating until the blue color just disap-
pears.
29
-------
5.4 Concentration of
Calculate the concentration of I^S in the gas stream at standard
conditions using Equation A-4.
_ KCCVj-N-j- - VTNT) sample - (VjNj - VTNT) blank] "(A-4)
mstd
where (metric units):
CH q = concentration of lUS at standard conditions, mg/dscm;
^K = conversion factor = 17.0 x 103
(34.07 g/mole H2S) (1,000 liters/m3) (1,000 mg/g)
(1,000 ml/liter) (2H2S eq/mole)
V-r = volume of standard iodine solution, ml;
N_ = normality of standard iodine solution, g-eq/liter;
VT = volume of standard sodium thiosulfate solution, ml;
NT - normality of standard sodium thiosulfate solution,
g-eq/liter; and
V = dry gas volume at standard conditions, liters
mstd
6.0 References
6.1 Determination of Hydrogen Sulfide, Ammoniacal Cadmium Chloride
Method, API Method 772-54. In: Manual on Disposal of Refinery Wastes,
Vol. V: Sampling and Analysis of Waste Gases and Particulate Matter,
American Petroleum Institute, Washington, D.C., 1954.
6.2 Tentative Method for Determination of Hydrogen Sulfide and Mer-
captan Sulfur in Natural Gas, Natural Gas Processors Association, Tulsa,
Oklahoma, NGPA Publication NO. 2265-65, 1965.
30
-------
APPENDIX B
TENTATIVE METHOD FOR THE DETERMINATION OF HYDROGEN SULFIDE EMISSIONS
FROM STATIONARY SOURCES*/
CADMIUM ACETATE PROCEDURE
aj A tentative method is one which has been carefully drafted from avail-
able experimental information, reviewed editorially within the Meth-
ods Standardization and Performance Evaluation Branch, QAEML, and has
undergone extensive laboratory evaluation. The method is still under
investigation and, therefore, is subject to revision.
31
-------
1.0 Principle and Applicability
1.1 Principle
Hydrogen sulfide (H2S) is collected from a source in a series of
midget impingers and absorbed in buffered cadmium acetate solution to form
cadmium sulfide (CdS). The latter compound is then dissolved in hydrochloric
acid and measured iodometrically. An impinger containing hydrogen peroxide
is included to remove S02 as an interfering species.
1.2 Applicability
This method is applicable for the determination of hydrogen sul-
fide emissions from stationary sources only when specified by the test pro-
cedures for determining compliance with the new source performance standards.
2.0 Range and Sensitivity
3
The limit of detection is approximately 8 mg/m (6 ppm). The max-
imum of the range is 740 mg/nP (520 ppm). The lower limit of the range may
be extended by collecting a larger volume of gas sample; the upper limit
by increasing the concentration of the iodine solution.
3.0 Interferences
Any compound that reduces iodine or oxidizes iodide ion will in-
terfere in this procedure, provided it is collected in the cadmium acetate
impingers. Sulfur dioxide in concentrations of up to 0.1 mole percent is
eliminated by the peroxide solution. Thiols in concentrations of 0.2% and
carbon oxysulfide of 20% do not interfere. Certain carbonyl-containing
compounds react with iodine and produce recurring endpoints. However,
acetaldehyde and acetone at concentrations of 1 and 3%, respectively, do
not interfere.
Entrained hydrogen peroxide produces a negative interference
equivalent to 100% of that of an equimolar quantity of hydrogen sulfide.
Avoid the ejection of hydrogen peroxide into the cadmium acetate impingers.
\
4.0 Precision and Accuracy
Replicate analyses should not deviate by more than 570 relative
standard deviation. The accuracy of hydrogen sulfide measurements has been
established at 96 + 2% of the absolute value based on a known standard.
32
-------
5.0 Apparatus
5.1 Sampling Train
a/
5.1.1 Sampling line - Six to 7 mm (1/4 in.) Teflon— tubing to
connect sampling train to sampling valve, with provisions for heating to
prevent condensation. A pressure reduction valve prior to the Teflon sam-
pling line may be required depending on sampling stream pressure.
5.1.2 Impingers - Five midget impingers, each with 30 ml capacity.
5.1.3 Ice bath container - To maintain absorbing solution at a
low temperature.
5.1.4 Silica gel drying tube - To protect pump and dry gas meter.
5.1.5 Needle valve or equivalent - Stainless steel or other cor-
rosion resistant material to adjust gas flow rate.
5.1.6 Pump - Leak free, diaphragm-type, or equivalent, to trans-
port gas. (Not required if sampling stream is under positive pressure.)
5.1.7 Dry gas meter - Sufficiently accurate to measure sample
volume to within 1% and calibrated over the range of flow rates used in
sampling.
5.1.8 Flow meter - Rotameter or equivalent, to measure a 0.5 to
2.0 1pm (1 to 4 CFH) flow rate.
5.1.9 Graduated cylinder - 25 ml size.
5.1.10 Barometer - To measure atmospheric pressure to within
+ 2.5 mm (0.1 in.) Hg.
5.2 Sample Recovery
5.2.1 Sample container - Iodine flask, glass-stoppered. 500 ml
size.
5.2.2 Pipette - 50 ml volumetric type.
5.2.3 Beakers - 250 ml.
5.2.4 Wash bottle.
5.3 Analysis
5.3.1 Flask - 500 ml glass-stoppered iodine flask.
a/ Trade name. 33
-------
5.3.2 Burette - 50 ml.
5.3.3 Flask - 125 ml, Erlenmeyer.
6.0 Reagents
Unless otherwise indicated, it is intended that all reagents
conform to the specifications established by the Committee on Analytical
Reagents of the American Chemical Society, where such specifications are
available. Otherwise, use best available grade.
6.1 Sampling
6.1.1 Cadmium acetate absorbing solution - Dissolve 10.7 g of
Cd(C2H302)2 2H20 and 5.0 ml of glacial acetic acid in 1 liter of deionized
distilled water. Add several drops of a suitable antifoam agent (6.1.3).
6.1.2 Hydrogen peroxide, 3% - Dilute 30% hydrogen peroxide to 3%
as needed. Prepare fresh daily.
6.1.3 Antifoam agent - Fisher Antifoam ZSJ or Hodag Antifoam MG-803/
have been found effective in preventing foaming of the absorbing solution
during sampling.
6.1.4 Water - Deionized, distilled, to conform to ASTM specifica-
tions D1193-72, Type 3.
6.2 Sample Recovery
6.2.1 Hydrochloric acid solution (HCl), 10% by weight. Mix 230 ml
of concentrated HCl (specific gravity 1.19) and 770 ml of deionized, dis-
tilled water.
6.2.2 Iodine solution, 0.1 N - Dissolve 24 g of potassium iodide
(KI) in 30 ml of deionized, distilled water. Add 12.7 g of resublimed iodine
(T.^) to the potassium iodide solution. Shake the mixture until the iodine
is completely dissolved. Slowly dilute the solution to 1 liter with deionized,
distilled water, with swirling. Filter the solution if cloudy and store
in a brown glass reagent bottle.
6.2.3 Standard iodine solution, 0.01 N - Dilute 100 ml of the
0.1 N iodine solution to 1 liter with deionized, distilled water. Stan-
dardize daily as in Section 8.1 below:
a/ Trade name.
34
-------
6.3 Analysis
6.3.1 Sodium thiosulfate solution, standard 0.1 N - Dissolve
24.8 g of sodium thiosulfate (Na2So03 51^0) in 1 liter of deionized, dis-
tilled water and add 0.01 g of anhydrous sodium carbonate (^2(303) and
0.4 ml of chloroform (CHC^) to stabilize. Mix thoroughly by shaking or by
aerating with nitrogen for approximately 15 min, and store in a glass-
stoppered reagent bottle. Standardize as in Section 8.2 below:
6.3.2 Sodium thiosulfate solution, standard 0.01 N - Pipette
50 ml of the standard 0.1 N thiosulfate solution into a volumetric flask
and dilute to 500 ml with distilled water.
6.3.3 Starch indicator solution - Suspend 10 g of soluble starch
in 100 ml of deionized, distilled water and add 15 g of potassium hydrox-
ide (KOH) pellets. Stir until dissolved, dilute with 900 ml of deionized
distilled water and let stand for 1 hr. Neutralize the alkali with concen-
trated hydrochloric acid, using an indicator paper similar to AlkacidS/ test
ribbon, then add 2 ml of glacial acetic acid as a preservative.
[NOTE: Test starch indicator solution for decomposition by titrating
4 ml of starch solution in 200 ml of distilled water with 0.01 N iodine
solution. If more than 4 drops of the 0.01 N iodine solution are required
to obtain the blue color, a fresh solution must be prepared.]
7.0 Procedure
7.1 Sampling
7.1.1 Assemble the sampling train as shown in Figure B-l, connect-
ing the five midget impingers in series. Place 15 ml of 3% hydrogen perox-
ide solution in the first impinger. Leave the second impinger empty. Place
15 ml of the cadmium acetate absorbing solution in the third and fourth
impingers and leave the fifth impinger empty. Place impinger assembly in
ice bath container and add crushed ice around the impingers. Add more ice
during the run, if needed.
7.1.2 Purge the connecting line between the sampling valve and
the first impinger. Connect the sample line to the train. Record the ini-
tial reading of the dry gas meter as shown in Table B-l.
7.1.3 Open the flow control valve and adjust the sampling rate
to approximately 1 liter per minute (0.04 cfm). Read the meter temperature
and record on Table B-l.
7.1.4 Continue sampling a minimum of 10 min. At the end of the
sampling time, close the flow control valve and record the final volume
and temperature readings in Table B-l.
a/ Trade name. 35
-------
SAMPLING VALVE
•TEFLON SAMPLING LINE (HEATED)
MIDGET IMPINGERS
s3te^
r
SILICA GEL TUBE
CENTER
LINE
TAP
FUEL GAS
LINE
VALVE
DRY GAS METER
PUMP ( Not Required
if Lines Pressurized
RATE METER
Figure B-l - H2S Sampling Train
36
-------
TABLE B-l
FIELD DATA
Location
Test
Comment s:
Date
Operator
Barometric Pressure
Clock
Time
Gas Volume
Through Meter (Vm),
I (cu ft)
Rotameter
Setting, ipm
(cfm)
Meter
Temperature,
°C (°F)
37
-------
7.1.5 Disconnect the impinger train from the sampling line. Purge
the train with clean ambient air for 15 min to ensure that all l^S is re-
moved from the hydrogen peroxide. (Clean ambient air can be provided by
passing air through a charcoal filter.) Cap the open ends and remove to a
clean area away from sources of heat for sample cleanup. The area should
be well lighted, but not exposed to direct sunlight.
7.2 Sample Recovery
7.2.1 Discard the contents of the hydrogen peroxide impinger.
Carefully rinse the contents of the third, fourth, and fifth impingers into
a 500 ml iodine f,lask.
7.2.2 Pipette exactly 50 ml of 0.01 N iodine solution into a
250 ml beaker. Add 50 ml of 107. HCl to the solution. Mix well.
7.2.3 Extract the remaining cadmium sulfide from the third, fourth
and fifth impingers using the acidified iodine solution. Immediately after
pouring the acidified iodine into an impinger, stopper it and shake for a
few moments, then transfer the liquid to the iodine flask. Do not transfer
any rinse portion from one impinger to another; transfer it directly to
the iodine flask. Once acidified iodine solution has been poured into any
glassware containing cadmium sulfide, the container must be tightly stop-
pered at all times except when adding more solution, and this must be done
as quickly and carefully as possible. After adding any acidified iodine
solution to the iodine flask, allow a few minutes for absorption of the
H2S before adding any further rinses. Repeat the iodine extraction until
all cadmium sulfide is removed from the impingers. Extract that part of
the connecting glassware that contains visible cadmium sulfide.
7.2.4 Quantitatively rinse all of the iodine from the impingers,
connectors, and the beaker into the iodine flask using deionized distilled
water. Stopper the flask and shake well. Allow to stand about 30 min in
the dark for absorption of the H2S into the iodine, then complete the ti-
tration analysis as in Section 7.3.
[NOTE: CAUTION! Iodine evaporates from acidified iodine solutions, and
samples to which acidified iodine has been added may not be stored, but
must be analyzed in the time schedule stated above.]
7.2.5 Prepare a blank by adding 30 ml of cadmium acetate absorb-
ing solution to an iodine flask. Pipette exactly 50 ml of 0.01 iodine solu-
tion into a 250 ml beaker. Add 50 ml of 10% HCl. Follow the same impinger
extracting and quantitative rinsing procedure carried out in sample analy-
sis. Stopper the flask, shake well and titrate with the samples.
38
-------
7.3 Analysis
[NOTE: Titration analyses should be conducted at the sample clean-up
area in order to prevent loss of iodine from the sample. Titration should
never be made in direct sunlight.]
7.3.1 Using 0.01 N sodium thiosulfate solution, rapidly titrate
samples in iodine flasks using gentle mixing, until solution is light yel-
low. Add 4 ml of starch indicator solution and continue titrating slowly
until blue color just disappears. Record Vt, the volume of sodium thiosul-
fate solution used (ml).
7.3.2 Titrate the blanks in the same manner as the samples.
8.0 Calibration and Standards
8.1 Standardize the 0.01 N iodine solution daily as follows: pipette
25 ml of the iodine solution into a 125 ml Erlenmeyer flask. Titrate rap-
idly with standard 0.01 N thiosulfate solution until the solution is light
yellow, using gentle mixing. Add four drops of starch indicator solution
and continue titrating slowly until the blue color just disappears. Record
Vt, the volume of thiosulfate solution used. Repeat until replicate values
agree within 0.05 ml. Average the replicate titration values which agree
within 0.05 ml and calculate the exact normality of the iodine solution
using Equation A-l. Repeat the standardization daily.
8.2 Standardize the 0.1 N thiosulfate solution as follows: Crys-
tallize potassium dichromate (^C^Oy) from distilled water and oven-dry
at 180 to 200°C (300 to 390°F). Weigh to the nearest milligram 2 g of
potassium dichromate into a 500 ml volumetric flask, dissolve in deionized,
distilled water and dilute to exactly 500 ml. In a 500 ml iodine flask,
dissolve approximately 3 g of potassium iodide (KI) in 45 ml of deionized,
distilled water, then add 10 ml of 10% hydrochloric acid solution. Pipette
50 ml of the dichromate solution into this mixture. Gently swirl the solu-
tion once and allow it to stand in the dark for 5 min. Dilute the solution
with 100 to 200 ml of deionized distilled water, washing down the sides of
the flask with part of the water. Swirl the solution slowly and titrate
with the thiosulfate solution until the solution is light yellow. Add 4 ml
of starch indicator solution and continue titrating slowly until the bright
blue color has disappeared and only the pale green color of the chromic
ion remains. Record Vt, the volume of thiosulfate solution used. Replicate
titrations should agree within 0.05 ml. Average the replicate titrations
and calculate the exact normality of the sodium thiosulfate solution using
Equation A-2.
39
-------
[NOTE: Sodium thiosulfate solutions are affected by bacterial action,
by air oxidation and by decomposition with the precipitation of sulfur.
When properly prepared and handled, they may last for several weeks. Avoid
exposure to light. Check solution for cloudiness and presence of sediment,
and restandardize frequently.]
9.0 Calculations
Carry out calculations, retaining at least one extra decimal
figure beyond that of the acquired data. Round off figures after final
calculation. (Calculations are performed in accordance with the original
Method 11, Federal Register, March 8, 1974.)
40
-------
APPENDIX C
RUGGEDNESS TEST DATA
41
-------
The titration results were compared to the level calculated from the
respective flow rates of pure H2S and natural gas. This calculated value
varies by 2 to 5% from one run to another and may have caused false changes
for some variables*
When the CdS04 concentration was 0.24 M, 5 ml of HCl were added and
the impingers were extracted, a very large effect on the blank was found.
Unfortunately, these three variables were always in their worst levels at
the same time during the test, and the possible interactions are not separable
from the ruggedness test data.
Further tests were then made to determine the individual contributions
of these three variables. CdSC>4 concentration had no effect when it was
changed while holding HCl addition at 5 ml and extracting the impinger.
Changing the HCl addition alone made a change of about 0.30 ml of titrant.
Changing the extraction procedure made a shift of over 0.5 ml in the blank
values. Thus, it was the unfortunate coincidence of the 0.24 M CdSC>4 concen-
tration above coinciding with the worst case of the other two that led to
the large significance of the CdSC^,. concentration in the ruggedness test.
42
-------
TABLE C-l
TEST DESIGN MATRIX-
A.
B.
C.
D.
E.
F.
G.
H.
I-
J.
E.
U
H.
N.
O.
Variable
Temperature (°C)
Tip Clearance (nn)
Tip Diameter
Sol. Volune (ml)
pH
Flow Bate (//mln)
Purge Time (min)
Bun Time (min)
Sol. Age
MS04 Cone. (H)
Shaking (sec)
Antifoam (dropa/()
HC1 (ml)
Extraction
Dumy
1
25
5-7
1.02-1.04
10
3.5
0.8
20
45
day
o.oa
60
0
5
No
-
1
0
2-4
1.00-1.02
10
2.5
0.8
10
15
day
0.08
2
0
5
No
-
J
0
5-7
1.00-1.02
20
3.5
0.8
10
45
day
0.08
2
10
50
Yes
-
A
25
2-4
1.02-1.04
20
2.5
0.8
20
15
day
0.08
60
10
50
Yes
-
•5
25
2-4
1.00-1.02
10
3.5
1.5
20
45
day
0.24
2
10
50
No
-
Run
i
0
2-4
1.02-1.04
20
3.5
1.5
10
45
day
0.24
60
0
5
Yes
-
^er
2
25
5-7
1.00-1.02
20
2.5
1.5
20
15
day
0.24
2
0
5
Yes
-
&
0
5-7
1.02-1.04
10
2.5
1.5
10
15
day
0.24
60
10
50
Ho
-
3
0
5-7
1.02-1.04
20
3.5
0.8
20
15
week
0.24
2
0
50
No
-
IS
0
2-4
1.00-1.02
20
3.5
1.5
20
15
week
0.08
60
10
5
No
-
U
0
2-4
1.02-1.04
10
2.5
0.8
20
45
week
0.24
2
10
5
Yes
-
12
0
5-7
1.00-1.02
10
2.5
1.5
20
45
week
o.oa
60
0
50
Yes
-
"
25
2-4
1.00-1.02
20
2.5
0.8
10
45
week
0.24
60
0
50
No
-
14
25
5-7
1.02-1.04
20
2.5
1.5
10
45
week
0.08
2
10
5
No
-
Ii
25
5-7
1.00-1.02
10
3.5
0.8
10
15
week
0.24
60
10
5
Yes
.
Ifi
25
2-4
1.02-1.04
10
3.5
1.5
10
15
week
0.08
2
0
50
Yes
_
al Arranged in order of measurement. See Table 4 of main text for explanation of variables*
-------
TABLE C-2
RESULTS OF RUGGEDNESS TEST - BLANKS AND H2S MEASURED
Run
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Blanks
(ml of I2)
45.74
46.82
44.98
45.79
46.36
46.15
46.31
45.23
46.48
44.81
45.70
46.33
46.09
44.92
46.11
46.47
45.74
46.75
45.07
45.62
46.39
46.25
46.26
44.85
46.30
44.44
45.66
46.29
46.17
44.67
46.04
46.43
45.82
46.76
44.66
45.65
46.34
46.24
46.29
44.91
46.28
44.54
45.70
46.24
46.10
44.94
46.14
46.61
Theo. Blks.
(ml of I2)
45.84
46.58
46.48
46.03
46.24
46.24
46.48
46.03
46.03
46.16
45.84
46.24
46.16
46.48
45.84
46.58
Results Theo* Results
(mg/dscm)
171
205
266
240
264
195
267
280
255
261
194
230
244
279
281
168
175
177
272
252
256
194
270
282
305
268
196
246
255
285
286
187
(me/dscm)
329
318
320
324
325
322
329
332
324
321
326
322
318
331
328
306
44
-------
APPENDIX D
TENTATIVE METHOD FOR THE DETERMINATION OF HYDROGEN SULFIDE EMISSIONS
FROM STATIONARY SOURCES-'
pH 3*0 CADMIUM SULFATE PROCEDURE
a/ A tentative method is one which has been carefully drafted from
available experimental information, reviewed editorially within
the Methods Standardization and Performance Evaluation Branch,
QAEML, and has undergone extensive laboratory evaluation. The
method is still under investigation and, therefore, is subject
to revision.
45
-------
1.0 Principle and Applicability
1.1 Principle - Hydrogen sulfide (H«S) is collected from a source
in a series of midget impingers and absorbed in buffered cadmium sulfate
solution to form cadmium sulfide (CdS). The latter compound is then mea-
sured iodometrically. An impinger containing hydrogen peroxide is included
to remove SCL as an interfering species.
1.2 Applicability. This method is applicable for the determination
of hydrogen sulfide emissions from stationary sources only when specified
by the test procedures for determining compliance with the new source
performance standards.
2.0 Range and Sensitivity. The limit of detection is approximately
8 rag/in^ (6 ppm). The maximum of the range is 740 mg/m^ (520 ppm). The
lower limit of the range may be extended by collecting a larger volume
of gas samples; the upper limit by increasing the concentration of the
iodine solution.
3.0 Interferences. Any compound that reduces iodine or oxidizes iodide
ion will interfere in this procedure, provided it is collected in the
cadmium sulfate impingers. Sulfur dioxide in concentrations of up to 0.1
mole percent is eliminated by the peroxide solution. Mercaptans copreci-
pitate with hydrogen sulfide. Methyl and/or ethyl mercaptan produce a
maximum positive error of 25%. In the absence of l^S only traces of mer-
captan are collected. A mercaptan concentration equal to that of the H«S
present yields results that are approximately 5% high. Carbon oxysulfide
of 20% does not interfere. Certain carbonyl-containing compounds react
with iodine and produce recurring endpoints. However, acetaldehyde and
acetone at concentrations of 1 and 3%, respectively, do not interfere.
Entrained hydrogen peroxide produces a negative interference equiva-
lent to 100% of that of an equimolar quantity of hydrogen sulfide. Avoid
the ejection of hydrogen peroxide into the cadmium sulfate impingers.
4.0 Precision and Accuracy. Replicate analyses should not deviate by
more than 5% relative standard deviation. The collection efficiency of
hydrogen sulfide measurements has been established at 96 + 2% of the
absolute value based on known standards.
46
-------
5.0 Apparatus.
5.1 Sampling Train.
5.1.1 Sampling line - 6 to 7 mm (1/4 in.) Teflon8-' tubing to
connect sampling train to sampling valve, with provisions for heating
to prevent condensation. A pressure reduction valve prior to the Teflon
sampling line may be required depending on sampling stream pressure.
5.1.2 Impingers - Five midget impingers, each with 30 ml capa-
city. The internal diameter of the impinger tip must be 1.00 mm + 0.5 mm.
The impinger tip must be 4 to 6 mm from the bottom of the impinger.
5.1.3 Ice bath container - To maintain absorbing solution at a
temperature.
5.1.4 Silica gel drying tube - To protect pump and dry gas meter.
5.1.5 Needle valve or equivalent. Stainless steel or other
corrosion resistant material to adjust gas flow rate.
5.1.6 Pump - Leak free, diaphragm-type, or equivalent, to trans-
port gas. (Not required if sampling stream is under positive pressure.)
5.1.7 Dry gas meter - Sufficiently accurate to measure sample
volume to within 1% and calibrated over the range of flow rates used in
sampling.
5.1.8 Flow meter - Rotameter or equivalent, to measure a 0.5 to
2.0 liters/min (1 to 4 CFH) flow rate.
5.1.9 Graduated cylinder - 25 ml size.
5.1.10 Barometer - To measure atmospheric pressure to within
+ 2.5 mm (0.1 in.) Hg.
5.2 Sample Recovery.
5.2.1 Sample container - Iodine flask, glass-stoppered; 500 ml
size.
5.2.2 Pipette - 50 ml volumetric type.
ai/ Trade name.
47
-------
5.2.3 Graduated cylinders - One each 25 and 250 ml.
5.2.4 Flasks - 125 ml, Erlenmeyer.
5.2.5 Wash bottle.
5.2.6 Volumetric flasks - Three 1,000 ml.
5.3 Analysis.
5.3.1 Flask - 500 ml glass-stoppered iodine flask.
5.3.2 Burette - 50 ml.
5.3.3 Flask - 125 ml, Erlenmeyer.
5.3.4 Pipettes, volumetric - One each 15 and 25 ml; two each
50 and 100 ml.
5.3.5 Volumetric flasks - One 1,000 ml; two 500 ml.
5.3.6 Graduated cylinders - One each 10 and 100 ml.
6.0 Reagents. Unless otherwise indicated, it is intended that all re-
agents conform to the specifications established by the Committee on
Analytical Reagents of the American Chemical Society, where such speci-
fications are available. Otherwise, use best available grade.
6.1 Sampling.
6.1.1 Cadmium sulfate absorbing solution - Dissolve 41.0 g
of 3Cd SO^ • 8 H20 and 15.0 ml of 0.1 M sulfuric acid in 1 liter of de-
ionized distilled water. pH should be 3.0 + 0.1. Add 10 drops of Antifoam
6.1.2 Hydrogen peroxide, 3% - Dilute 30% hydrogen peroxide to
3% as needed. Prepare fresh daily.
6.1.3 Water - Deionized, distilled, to conform to ASTM speci-
fications D1193-72, Type 3.
6.2 Sample recovery.
a/ Trade name.
48
-------
6.2.1 Hydrochloric acid solution (HCl), 3 M - Add 240 ml of
concentrated HCl (specific gravity 1.19) to 500 ml of deionized, dis-
tilled water in a 1 liter volumetric flask. Dilute to 1 liter with de-
ionized water. Mix thoroughly.
6.2.2 Iodine solution, 0.1 N - Dissolve 24 g of potassium
iodide (KI) in 30 ml of deionized, distilled water. Add 12.7 g of re-
sublimed iodine (12) to the potassium iodide solution. Shake the mix-
ture until the iodine is completely dissolved. If possible, let stand
overnight in the dark. Slowly dilute the solution to 1 liter with de-
ionized, distilled water, with swirling. Filter the solution if cloudy
and store in a brown-glass reagent bottle.
6.2.3 Standard iodine solution, 0.01 N - Dilute 100 ml of the
0.1 N iodine solution to 1 liter with deionized, distilled water. Stan-
dardize daily as in Section 8.1 below.
6.3 Analysis.
6.3.1 Sodium thiosulfate solution, standard 0.1 N - Dissolve
24.8 g of sodium thiosulfate (Na^O o»5H20) in 1 liter of deionized,
distilled water and add 0.01 g of anhydrous sodium carbonate (
and 0.4 ml of chloroform (CHClg) to stabilize. Mix thoroughly by shaking
or by aerating with nitrogen for approximately ; 15 min, and store in a
glass-stoppered reagent bottle. Standardize as in Section 8.2 below.
6.3.2 Sodium thiosulfate solution, standard 0.01 N - Pipette
50 ml of the standard 0.1 N thiosulfate solution into a volumetric flask
and dilute to 500 ml with distilled water.
6.3.3 Starch indicator solution - Suspend 10 g of soluble
starch in 100 ml of deionized, distilled water and add 15 g of potassium
hydroxide (KOH) pellets. Stir until dissolved, dilute with 900 ml of
deionized distilled water and let stand for 1 hr. Neutralize the alkali
with concentrated hydrochloric acid, using an indicator paper similar to
Alkacid— ' test ribbon, then add 2 ml of glacial acetic acid as a preservative.
(Note 1: Test starch indicator solution for decomposition by titrating
4 ml of starch solution in 200 ml of distilled water containing
1 g potassium iodide with 0.01 N iodine solution. If more than
4 drops of the 0.01 N iodine solution are required to obtain .
the blue color, a fresh solution must be prepared.)
a/ Trade name.
49
-------
7.0 Procedure.
7.1 Sampling.
7.1.1 Assemble the sampling train as shown in Figure D-l,
connecting the five midget impingers in series. Place 15 ml of 3%
hydrogen peroxide solution in the first impinger. Leave the second
impinger empty. Place 15 ml of the cadmium sulfate absorbing solu-
tion in the third, fourth, and fifth impingers. Place impinger as-
sembly in ice bath container and add crushed ice around the impingers.
Add more ice during the run, if needed.
7.1.2 Purge the connecting line between the sampling valve
and the first impinger. Connect the sample line to the train. Record
the initial reading of the dry gas meter.
7.1.3 Open the flow control valve and adjust the sampling
rate to approximately 1 liter/min. Record the meter temperature.
7.1.4 Sample for 10 min. At the end of the sampling time,
close the flow control valve and record the final volume and temper-
ature readings.
7.1.5 Disconnect the impinger train from the sampling line.
Purge the train with clean ambient air for 15 min to ensure that all
H2S is removed from the hydrogen peroxide. (Clean ambient air can be
provided by passing air through a charcoal filter.) Cap the open ends
and remove to a clean area away from sources of heat for sample cleanup.
The area should be well lighted, but not exposed to direct sunlight.
7.2 Sample recovery.
7.2.1 Discard the contents of the hydrogen peroxide impinger.
Carefully rinse the contents of the third, fourth, and fifth impingers
into a 500 ml iodine flask.
(NOTE: The impingers normally have only a thin film of cadmium sulfide
remaining after a water rinse. If significant quantities of
yellow cadmium sulfide remain in the impingers, the alternate
recovery procedure must be used.)
50
-------
SAMPLING VALVE
^J
TEFLON SAMPLING LINE (HEATED)
MIDGET IMPINGERS
SILICA GEL TUBE
FUEL GAS
LINE
DRY GAS METER
VALVE
PUMP ( Not Required
if Lines Pressurized
RATE METER
Figure D-l - H_S Sampling Train
51
-------
7.2.2 Pipette exactly 50 ml of 0.01 N iodine solution into
a 125 ml Erlenmeyer flask. Add 10 ml of 3 M HCl to the solution. Quan-
titately rinse the acidified iodine into the iodine flask. Stopper the
flask immediately and shake briefly.
7.2.2 (Alternate) Extract the remaining cadmium sulfide from
the third, fourth, and fifth impingers using the acidified iodine solution.
Immediately after pouring the acidified iodine into an impinger, stopper
it and shake for a few moments, then transfer the liquid to the iodine
flask. Do not transfer any rinse portion from one impinger to another;
transfer it directly to the iodine flask. Once acidified iodine solution
has been poured into any glassware containing cadmium sulfide, the con-
tainer must be tightly stoppered at all times except when adding more
solution, and this must be done as quickly and carefully as possible.
After adding any acidified iodine solution to the iodine flask, allow a
few minutes for absorption of the HoS before adding any further rinses.
Repeat the iodine extraction until add cadmium sulfide is removed from
the impingers. Extract that part of the connecting glassware that con-
tains visible cadmium sulfide.
Quantitatively rinse all of the iodine from the impingers,
connectors, and the beaker into the iodine flask using deionized dis-
tilled water. Stopper the flask and shake well.
7.2.3 Allow to stand about 30 min in the dark for absorption
of the I^S into the iodine, then complete the titration analysis as in
Section 7.3
(NOTE: CAUTION! Iodine evaporates from acidified iodine solutions and
samples to which acidified iodine has been added may not be
stored, but must be analyzed in the time schedule stated above.)
52
-------
7.2.4 Prepare a blank by adding 45 ml of cadmium sulfate ab-
sorbing solution to an iodine flask. Pipette exactly 50 ml of 0.01 iodine
solution into a 125 ml Erlenmeyer flask. Add 10 ml of 3 M HCl. Follow the
same impinger extracting and quantitative rinsing procedure carried out
in sample analysis. Stopper the flask, shake well and titrate with the
samples.
(NOTE: If the alternate extraction procedure is used, the blank must be
handled following the alternate procedure.)
7.3 Analysis.
(NOTE: Titration analyses should be conducted at the sample cleanup
area in order to prevent loss of iodine from the sample.
Titration should never be made in direct sunlight.)
7.3.1 Using 0.01 N sodium thiosulfate solution, rapidly ti-
trate samples in iodine flasks using gentle mixing, until solution is
light yellow. Add 4 ml of starch indicator solution and continue ti-
trating slowly until blue color just disappears. Record Vt, the volume
of sodium thiosulfate solution used (ml).
7.3.2 Titrate the blanks in the same manner as the samples.
8.0 Calibration and Standards
8.1 Standardize the 0.01 N iodine solution daily as follows:
Pipette 25 ml of the iodine solution into a 125 ml Erlenmeyer flask.
Add 2 ml of 3 M HCl. Titrate rapidly with standard 0.01 N thiosulfate
solution until the solution is light yellow, using gentle mixing. Add
four drops of starch indicator solution and continue titrating slowly
until the blue color just disappears. Record Vt, the volume of thio-
sulfate solution used. Repeat until replicate values agree within 0.05
ml. Average the replicate titration values which agree within 0.05 ml
and calculate the exact normality of the iodine solution using equation
D-l. Repeat the standardization daily.
53
-------
8.2 Standardize the 0.1 N thiosulfate solution as follows:
Oven dry potassium dichromate (K2Cr207) at 180 to 200°C. Weigh to
the nearest milligram to grams of potassium dichromate into a 500
ml volumetric flask, dissolve in deionized, distilled water and
dilute to exactly 500 ml. In a 500 ml iodine flask, dissolve ap-
proximately 3 g of potassium iodide (KI) in 45 ml of deionized,
distilled water, then add 10 ml of 3 M hydrochloric acid solution.
Pipette 50 ml of the dichromate solution into this mixture. Gently
swirl the solution once and allow it to stand in the dark for 5 min.
Dilute the solution with 100 to 200 ml of deionized distilled water,
washing down the sides of the flask with part of the water.
9.0 Calculations
9.1 Normality of the Standard Iodine Solution.
= NTVT (D-l)
NI =
where:
N,. = normality of iodine, g-eq/liter;
Vj = volume of iodine used, ml;
Nj = normality of sodium thiosulfate, g-eq/liter; and
Vm = volume of sodium thiosulfate used, ml.
9.2 Normality of the Standard Thiosulfate Solution.
NT = 2.04 5L (D-2)
VT
where:
W = weight of K Cr 0 used, g;
Vip = volume of Na2S20o used, ml;
NT = normality of standard thiosulfate solution, g-eq/liter;
and
2.04 = conversion factor.
(6 eq I2/mole K2Cr207) (1,000 ml/liter)
(294.2 g K2Cr207/mole) (10 aliquot factor)
54
-------
9.3 Dry Gas Volume - Correct the sample volume measured by the dry
gas meter to standard conditions (21°C) and 760 mm Hg.
mstd m V T
\ m
v -v 3& *L (D-3)
where:
V_ = volume at standard conditions of gas sample through
s td
the dry gas meter, standard liters;
Vm = volume of gas sample through the dry gas meter (meter
conditions), liters;
T , = absolute temperature at standard conditions, 294°K;
T = average dry gas meter temperature, °K;
P, = barometric pressure at the orifice meter, mm Hg; and
P = absolute pressure at standard conditions, 760 mm Hg.
9.4 Concentration of ^S - Calculate the concentration of ^S in
the gas stream at standard conditions using equation:
^LV.TNT - VTNm) sample - (VTNT - VTNT) blank] . ..
Cu o = i-i i-i i_i L_t (D-4)
H0b „
mstd
where (metric units):
CH q = concentration of H^S at standard conditions, mg/dscm;
^K = conversion factor = 17.0 x 103
(34.07 g/mole H2S) (1,000 liters/m3) (1,000 mg/g)
(1,000 ml/liter) (2H2S eq/mole)
Vj = volume of standard iodine solution, ml;
N_ = normality of standard iodine solution, g-eq/liter;
VT = volume of standard sodium thiosulfate solution, ml;
Nip = normality of standard sodium thiosulfate solution,
g-eq/liter; and
V = dry gas volume at standard conditions, liters
mstd
55
-------
10.0 Stability. The absorbing solution is stable for at least
1 month. Sample recovery and analysis should begin within 1 hr of
sampling to minimize oxidation of the acidified cadmium sulfide.
Once iodine has been added to the sample the remainder of the
analysis procedure must be completed according to Sections 7.2.2,
7.2.3, and 7.3.
56
-------
APPENDIX E
TENTATIVE METHOD FOR THE DETERMINATION OF HYDROGEN SULFIDE EMISSIONS
FROM STATIONARY SOURCES*/
(FINAL VERSION USED FOR COLLABORATIVE TEST)
a/ A tentative method is one which has been carefully drafted from
available experimental information, review editorially within
the Quality Assurance Branch, EMSL, and has undergone extensive
laboratory evaluation. The method is still under investigation
and, therefore, is subject to revision*
57
-------
1.0 Principle and Applicability
1.1 Principle
Hydrogen sulfide (HoS) is collected from a source in a series of
midget impingers and absorbed in pH 3.0 cadmium sulfate solution to form
cadmium sulfide (CdS). The latter compound is then measured iodometrically.
An impinger containing hydrogen peroxide is included to remove S02 as an
interfering species.
1.2 Applicability
This method is applicable for the determination of hydrogen sul-
fide emissions from stationary sources only when specified by the test pro-
cedures for determining compliance with the new source performance stan-
dards.
2.0 Range and Sensitivity
O
The limit of detection is approximately 8 mg/m (6 ppm). The
maximum of the range is 740 mg/m-* (520 ppm).
3.0 Interferences
Any compound that reduces iodine or oxidizes iodide ion will in-
terfere in this procedure, provided it is collected in the cadmium-sulfate
impingers. Sulfur dioxide in concentrations of up to 0.1 mole percent is
eliminated by the peroxide solution. Mercaptans coprecipitate with hydrogen
sulfide. In the absence of l^S, only traces of mercaptan are collected. A
mercaptan concentration equal to that of the I^S present yields results
that are approximately 57o high. Carbon oxysulfide of 20% does not interfere.
Certain carbonyl-containing compounds react with iodine and produce recurr-
ing endpoints. However, acetaldehyde and acetone at concentrations of 1 and
3%, respectively, do not interfere.
Entrained hydrogen peroxide produces a negative interference
equivalent to 100% of that of an equimolar quantity of hydrogen sulfide.
Avoid the ejection of hydrogen peroxide into the cadmium sulfate impingers.
4.0 Precision and Accuracy
Replicate analyses should not deviate by more than 5% relative
standard deviation. The collection efficiency of hydrogen sulfide measure-
ments has been established at 96 + 2% of the absolute value based on known
standards.
58
-------
5.0 Apparatus
5.1 Sampling Train
5.1.1 Sampling line - Six to 7 mm (1/4 in.) Teflon^/ tubing to
connect sampling train to sampling valve. Depending on sampling stream
pressure, a pressure-reduction regulator may be required just prior to the
Teflon sampling line.
If significant amounts of water or amine are present in the
sample stream, a corrosion-resistant cold trap should be used immediately
after the sample tap. The trap should not be operated below 0°C to avoid
condensation of €3 or 64 hydrocarbons.
5.1.2 Impingers - Five midget impingers, each with 30 ml capacity.
The internal diameter of the impinger tip must be 1.00 mm + 0.05 mm. The
impinger tip must be positioned 4 to 6 mm from the bottom of the impinger.
5.1.3 Glass or Teflon connecting tubing for the impingers.
5.1.4 Ice bath container - To maintain absorbing solution at a
low temperature.
5.1.5 Silica gel drying tube - To protect pump and dry gas meter.
5.1.6 Sampling valve - Needle valve or equivalent to adjust gas
flow rate. Stainless steel or other corrosion-resistant material.
5.1.7 Dry gas meter - Sufficiently accurate to measure sample vol-
ume to within 170 and calibrated with a wet test meter over the range of flow
rates used in sampling. Gas volume for one dial revolution must not be more
than 10 liters. The gas meter should have a gas petcock or equivalent on the
outlet connector which can be closed during the leak test.
5.1.8 Flow meter - Rotameter or equivalent, to measure a 0.5 to
2.0 liters/min (1 to 4 CFH) flow rate.
5.1.9 Graduated cylinder - 25 ml size.
5.1.10 Barometer - To measure atmospheric pressure to within
+ 2.5 mm (0.1 in.) Hg.
5.1.11 U-Tube manometer - 0-30 cm. water column. For leak check
procedure.
a/ Trade name.
59
-------
5.1.12 Rubber squeeze bulb - To pressurize train for leak check.
5.1.13 Tee, pinchclamp, and connecting tubing - For leak check.
5.1.14 Vacuum pump - Required for air purge.
5.1.15 Needle valve or orifice - To set air purge flow to 1 liter/rain,
5.1.16 Tube packed with activated carbon - To filter air during
purge.
5.1.17 Volumetric flask - One 1,000 ml.
5.1.18 Volumetric pipette - One 15 ml.
5.2 Sample Recovery
5.2.1 Sample container - Iodine flask, glass-stoppered; 500 ml
size.
5.2.2 Pipette - 50 ml volumetric type.
5.2.3 Graduated cylinders - One each 25 and 250 ml.
5.2.4 Flasks - 125 ml, Erlenmeyer.
5.2.5 Wash bottle.
5.2.6 Volumetric flasks - Three 1,000 ml.
5.3 Analysis
5.3.1 Flask - 500 ml glass-stoppered iodine flask.
5.3.2 Burette - 50 ml.
5.3.3 Flask - 125 ml. Erlenmeyer.
5.3.4 Pipettes, volumetric - One 25 ml; two each 50 and 100 ml,
5.3.5 Volumetric flasks - One 1,000 ml; two 500 ml.
5.3.6 Graduated cylinders - One each 10 and 100 ml.
60
-------
6.0 Reagents
Unless otherwise indicated, it is intended that all reagents con-
form to the specifications established by the Committee on Analytical Re-
agents of the American Chemical Society, where such specifications are
available. Otherwise, use best available grade.
6.1 Sampling
6.1.1 Cadmium sulfate absorbing solution - Dissolve 41,0 g of
3CdS04'8 H20 and 15.0 ml of 0.1 M sulfuric acid in a 1-liter volumetric
flask that contains approximately 3/4 liter of deionized distilled water.
Dilute to volume with deionized water. Mix thoroughly. pH should be
3.0 + 0.1. Add 10 drops of Dow-Corning Antifoam B.— / Shake well before
use. If Antifoam B is not used, the alternate acidified iodine extraction
procedure must be used.
6.1.2 Hydrogen peroxide, 3% - Dilute 30% hydrogen peroxide to
37o as needed. Prepare fresh daily.
6.1.3 Water - Deionized, distilled, to conform to ASTM specifi-
cations D1193-72, Type 3.
6.2 Sample Recovery
6.2.1 Hydrochloric acid solution (HCl), 3 M - Add 240 ml of
concentrated HCl (specific gravity 1.19) to 500 ml of deionized, distilled
water in a 1-liter volumetric flask. Dilute to 1 liter with deionized
water. Mix thoroughly.
6.2.2 Iodine solution, 0.1 N - Dissolve 24 g of potassium
iodide (KI) in 30 ml of deionized, distilled water. Add 12.7 g of re-
sublimed iodine (12) to the potassium iodide solution. Shake the mixture
until the iodine is completely dissolved. If possible, let the solution
stand overnight in the dark. Slowly dilute the solution to 1 liter with
deionized, distilled water, with swirling. Filter the solution if it is
cloudy. Store solution in a brown-glass reagent bottle.
6.2.3 Standard iodine solution, 0.01 N - Pipette 100.0 ml of the
0.1 N iodine solution into 1-liter volumetric flask and dilute to volume
with dionized, distilled water. Standardize daily as in Section 8.1.
This solution must be protected from light. Reagent bottles and flasks
must be kept tightly stoppered.
a/ Trade name.
61
-------
6.3 Analysis
6.3.1 Sodium thiosulfate solution, standard 0.1 N - Dissolve
24.8 g of sodium thiosulfate pentahydrate (Na2S203'5H20) or 15.8 g of an-
hydrous sodium thiosulfate (Na2S203), in 1 liter of deionized, distilled
water and add 0.01 g of anhydrous sodium carbonate (Na2COo) and 0.4 ml of
chloroform (CHC^) to stabilize. Mix thoroughly by shaking or by aerating
with nitrogen for approximately 15 rain and store in a glass-stoppered, re-
agent bottle. Standardize as in Section 8.2 below.
6.3.2 Sodium thiosulfate solution, standard 0.01 N - Pipette
50.0 ml of the standard 0.1 N thiosulfate solution into a volumetric flask
and dilute to 500 ml with distilled water.
6.3.3 Starch indicator solution - Suspend 10 g of soluble starch
in 100 ml of deionized, distilled water and add 15 g of potassium hydroxide
(KOH) pellets. Stir until dissolved, dilute with 900 ml of deionized dis-
tilled water and let stand for 1 hour. Neutralize the alkali with concen-
trated hydrochloric acid, using an indicator paper similar to Alkacid—' test
ribbon, then add 2 ml of glacial acetic acid as a preservative.
(NOTE: Test starch indicator solution for decomposition by titrating
with 0.01 N iodine solution 4 ml of starch solution in 200 ml
of distilled water that contains 1-g potassium iodide. If
more than 4 drops of the 0.01 N iodine solution are required
to obtain the blue color, a fresh solution must be prepared.)
7.0 Procedure
7.1 Sampling
7.1.1 Assemble the sampling train as shown in Figure E-l, connect-
ing the five midget impingers in series. Place 15 ml of 3% hydrogen per-
oxide solution in the first impinger. Leave the second impinger empty.
Place 15 ml of the cadmium sulfate absorbing solution in the third, fourth,
and fifth impingers. Place the impinger assembly in an ice bath container
and place crushed ice around the impingers. Add more ice during the run,
if needed.
7.1.2 Connect the rubber bulb and manometer to first impinger,
as shown in Figure E-l. Close the petcock on the dry gas meter outlet. Pres-
surize the train to 30-cm. water pressure with the bulb and close off tubing
connected to rubber bulb. Train must hold a 30-cm. water pressure with not
more than a 1 cm. drop in pressure in a 1-min interval. Stopcock grease is
acceptable for sealing ground glass joints.
aj Trade name.
62
-------
Used for
Air Purge
SAMPLING VALVE
Used for
Leak Check
TEFLO^J SAMPLING LINE
•
•
/ MIDGET IMPINGERS
FUEL GAS
LINE
SILICA GEL TUBE
p— GAS PETCOCK
I
DRY GAS METER
RATE METER-
fl.
Used for
Air Purge
Figure E-l - ^S Sampling Train
63
-------
7.1.3 Purge the connecting line between the sampling valve and
the first impinger. Close valve and connect the sample line to the train.
Open the petcock on the dry gas meter outlet. Record the initial reading
of the dry gas meter.
7.1.4 Open the sampling valve and then adjust the valve to obtain
a rate of approximately 1 liter/min. Maintain a constant flow rate during
the test. Record the meter temperature.
7.1.5 Sample for at least 10 min. At the end of the sampling
time, close the sampling valve and record the final volume and temper-
ature readings.
7.1.6 Disconnect the impinger train from the sampling line. Con-
nect the charcoal tube and the pump, as shown in Figure E-l. Purge the train
with clean ambient air for 15 min to ensure that all l^S is removed from the
hydrogen peroxide. For sample recovery, cap the open ends and remove to a
clean area that is away from sources of heat. The area should be well
lighted, but not exposed to direct sunlight.
7.2 Sample Recovery
7.2.1 Discard the contents of the hydrogen peroxide impinger.
Carefully rinse the contents of the third, fourth, and fifth impingers
into a 500 ml iodine flask.
(NOTE: The impingers normally have only a thin film of cadmium sulfide
remaining after a water rinse. If Antifoam B was not used or
if significant quantities of yellow cadmium sulfide remain in
the impingers, the alternate recovery procedure must be used.)
7.2.2 Pipette exactly 50 ml of 0.01 N iodine solution into a
125-ml Erlenmeyer flask. Add 10 ml of 3 M HCl to the solution. Quanti-
tately rinse the acidified iodine into the iodine flask. Stopper the
flask immediately and shake briefly.
7.2.2 (Alternate) Extract the remaining cadmium sulfide from
the third, fourth, and fifth impingers using the acidified iodine solution.
Immediately after pouring the acidified iodine into an impinger, stopper it
and shake for a few moments, then transfer the liquid to the iodine flask.
Do not transfer any rinse portion from one impinger to another; transfer it
directly to the iodine flask. Once the acidified iodine solution has been
poured into any glassware containing cadmium sulfide, the container must be
tightly stoppered at all times except when adding more solution, and this
must be done as quickly and carefully as possible. After adding any acidi-
fied iodine solution to the iodine flask, allow a few minutes for absorp-
tion of the H2S before adding any further rinses. Repeat the iodine
64
-------
extraction until all cadmium sulfide is removed from the impingers. Ex-
tract that part of the connecting glassware that contains visible cadmium
sulfide.
Quantitatively rinse all of the iodine from the impingers,
connectors, and the beaker into the iodine flask using deionized, distilled
water. Stopper the flask and shake briefly.
7.2.3 Allow to stand about 30 min in the dark for absorption of
the HoS into the iodine, then complete the titration analysis as in Sec-
tion 7.3.
(NOTE: CAUTION! Iodine evaporates from acidified iodine solutions.
Samples to which acidified iodine have been added may not be
stored, but must be analyzed in the time schedule stated above
in 7.2.3.)
7.2.4 Prepare a blank by adding 45 ml of cadmium sulfate absorb-
ing solution to an iodine flask. Pipette exactly 50 ml of 0.01 iodine so-
lution into a 125-ml Erlenmeyer flask. Add 10 ml of 3 M HCl. Follow the
same impinger extracting and quantitative rinsing procedure carried out in
sample analysis. Stopper the flask, shake briefly, let stand 30 min in
the dark, and titrate with the samples.
(NOTE: The blank must be handled by exactly the same procedure as that
used for the samples.)
7.3 Analysis
(NOTE: Titration analyses should be conducted at the sample-cleanup area
in order to prevent loss of iodine from the sample. Titration
should never be made in direct sunlight.)
7.3.1 Using 0.01 N sodium thiosulfate solution, rapidly titrate
samples in iodine flasks using gentle mixing, until solution is light yel-
low. Add 4 ml of starch indicator solution and continue titrating slowly
until the blue color just disappears. Record Vfc, the volume of sodium thio-
sulfate solution used (ml).
7.3.2 Titrate the blanks in the same manner as the samples. Run
blanks each day until replicate values agree within 0.05 ml. Average the
replicate titration values which agree within 0.05 ml.
8.0 Calibration and Standards
8.1 Standardize the 0.01 N iodine solution daily as follows: Pipette
25 ml of the iodine solution into a 125-ml Erlenmeyer flask. Add 2 ml of
3 M HCl. Titrate rapidly with standard 0.01 N thiosulfate solution until
the solution is light yellow, using gentle mixing. Add four drops of starch
65
-------
indicator solution and continue titrating slowly until the blue color just
disappears. Record Vt, the volume of thiosulfate solution used (ml). Re-
peat until replicate values agree within 0.05 ml. Average the replicate
titration values which agree within 0.05 ml and calculate the exact normal-
ity of the iodine solution using equation E-l. Repeat the standardization
daily.
8.2 Standardize the 0.1 N thiosulfate solution as follows: Oven-dry
potassium dichromate (I^C^Oy) at 180 to 200°C. Weigh to the nearest milli-
gram, two grams of potassium dichromate into a 500 ml volumetric flask, dis-
solve in deionized, distilled water and dilute to exactly 500 ml. In a
500-ml iodine flask, dissolve approximately 3 g of potassium iodide (KI) in
45 ml of deionized, distilled water, then add 10 ml of 3 M hydrochloric acid
solution. Pipette 50 ml of the dichromate solution into this mixture. Gent-
ly swirl the solution once and allow it to stand in the dark for 5 min. Di-
lute the solution with 100 to 200 ml of deionized distilled water, washing
down the sides of the flask with part of the water. Titrate with 0.1 N.
thiosulfate until the solution is light yellow. Add 4 ml of starch indi-
cator and continue titrating slowly to a green end point. Record Vt, the
volume of thiosulfate solution used (ml). Repeat until replicate analyses
agree within 0.05 ml. Calculate the normality using eq. E-2. Repeat the
standardization each week.
9.0 Calculations
Carry out calculations retaining at least one extra decimal figure
beyond that of the acquired data. Round off results only after the final
calculation.
9.1 Normality of the Standard Iodine Solution.
(E-l)
where:
Nj = normality of iodine, g-eq/litcr;
Vj = volume of iodine used, ml;
Nj - normality of sodium thiosulfate, p-cq/litcr; ami
VT = volume of sodium thiosulfate tisod, ml.
9.2 Normality of the Standard Thiosulfate SoluU
on.
NT = 2.04 !=L (E-2)
VT
66
-------
where:
W = weight of K Cr'07 used, g;
VT = volume of Na^O.^ used, ml;
NT - normality of standard thiosulfate solution, t'.-<''l/llt
and
2.04 " conversion factor.
(6 eq l2/mole K2Cr,,Oy) (1,000 ml/liter)
(294.2 g K2Cr207/mole) (10 aliquot factor)
9.3 Dry Gas Volume - Correct the sample volume measim-d l>y M>
•as meter to standard conditions (21°C) and 7f>0 mm II)'..
Vm = V_ I£td } I ibar (E-3)
tt-A
f> LU
where:
V_ " volume at standard conditions of p.as s.-inipl
•"std
the dry pas meter, standard liter??;
ilumc of >',ns sample tl
conditions), liters;
V = volume of f,ns sample tlirouj-.li I he dry gas mein
T , = absolute temperature at standard condition;;, ."' i K ;
std
T = average dry gas meter temperature, K;
P, = barometric pressure at the orifice meter, mm lip; am!
P , - absolute pressure at standard conditions, 760 mm HR.
9.4 Concentration of I^S - Calculate the concentration of H0S in
the gas stream at standard conditions using equation:
_ Nj - VTNT) sample - (VjNj - VTNT) blank]
HS
2
mstd
where (metric units):
(L. s = concentration of H2S at standard conditions, mg/dscm;
^K = conversion factor = 17.0 x 10^
(34.07 g/mole H2S) (1,000 liters/m3) (1,000 mr,/)0
(1,000 ml/liter) (2H2S cq/mole)
67
-------
VT = volume of standard iodine solution, ml;
NT • normality of standard iodine solution, g-cq/liter;
VT B volume of standard sodium thiosulfatc solution, ml
NX c normality of standard sodium thiosulfate solution,
g-eq/liter; and
V • dry gas volume at standard conditions, litt-rs
mstd
10.0 Stability
The absorbing solution is stable for at least 1 month. Sample
recovery and analysis should begin within 1 hour of sampling to minimize
oxidation of the acidified cadmium sulfide. Once iodine has been added
to the sample, the remainder of the analysis procedure must be completed
according to Sections 7.2.2, 7.2.3, and 7.3.
68
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1. REPORT NO.
EPA 600/4-77-008a
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
STANDARDIZATION OF METHOD 11 AT A PETROLEUM REFINERY.
VOLUME I
5. REPORT DATE
January 1977
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
George W. Scheil and Michael C. Sharp
Midwest Research Institute
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Midwest Research Institute
425 Volker Boulevard
Kansas City, Missouri 64110
10. PROGRAM ELEMENT NO.
1HD621
11. CONTRACT/GRANT NO.
68-02-1098
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Method 11 (Federal Register. 39. pp. 9321-9323, March 8, 1974), "Determination of
Hydrogen Sulfide Emissions from Stationary Sources," is subject to serious mercaptan
interference. Several alternate absorbing reagents were evaluated, including several
salts of cadmium and zinc. The solution pH was adjusted to obtain a high collection
efficiency for H^S without also collecting mercaptans. The most selective absorbing
solution was 0.16 M cadmium sulfate at a pH of 3.0. The H~S collection efficiency
was 96 percent, and mercaptan concentration equal to the HpS gave results about 5 per-
cent high. The effect of 14 variables on the analysis were evaluated in a ruggedness
test. The optimized procedure was then field tested at three refineries under a
variety of conditions. The laboratory and field tests were then used to write a
final version of the procedure.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air pollution
Gases
Hydrogen sulfide
Measuring
Petroleum refineries
Thiols
Methods evaluation
Methods development
Stationary sources
13B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
69
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
-------
INSTRUCTIONS
i. REPORT NUMBER
Insert the EPA report number as it appears on the cover of the publication.
2. LEAVE BLANK
3. RECIPIENTS ACCESSION NUMBER
Reserved for use by each report recipient.
4. TITLE AND SUBTITLE
Title should indicate clearly and briefly the subject coverage of the report, and be displayed prominently. Set subtitle, if used, in smaller
type or otherwise subordinate it to main title. When a report is prepared in more than one volume, repeat the primary title, add volume
number and include subtitle for the specific title.
5. REPORT DATE
Each report shall carry a date indicating at least month and year. Indicate the basis on which it was selected (e.g., date of issue, date of
approval, date of preparation, etc.).
6. PERFORMING ORGANIZATION CODE
Leave blank.
7. AUTHOR(S)
Give name(s) in conventional order (John R. Doe, J. Robert Doe, etc.). List author's affiliation if it differs from the performing organi-
zation.
8. PERFORMING ORGANIZATION REPORT NUMBER
Insert if performing organization wishes to assign this number.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Give name, street, city, state, and ZIP code. List no more than two levels of an organizational hirearchy.
10. PROGRAM ELEMENT NUMBER
Use the program element number under which the report was prepared. Subordinate numbers may be included in parentheses.
11. CONTRACT/GRANT NUMBER
Insert contract or grant number under which report was prepared.
12. SPONSORING AGENCY NAME AND ADDRESS
Include ZIP code.
13. TYPE OF REPORT AND PERIOD COVERED
Indicate interim final, etc., and if applicable, dates covered.
14. SPONSORING AGENCY CODE
Leave blank.
15. SUPPLEMENTARY NOTES
Enter information not included elsewhere but useful, such as: Prepared in cooperation with, Translation of, Presented at conference of,
To be published in, Supersedes, Supplements, etc.
16. ABSTRACT
Include a brief (200 words or less) factual summary of the most significant information contained in the report. If the report contains a
significant bibliography or literature survey, mention it here.
17. KEY WORDS AND DOCUMENT ANALYSIS
(a) DESCRIPTORS - Select from the Thesaurus of Engineering and Scientific Terms the proper authorized terms that identify the major
• concept of the research and are sufficiently specific and precise to be used as index entries for cataloging.
(b) IDENTIFIERS AND OPEN-ENDED TERMS - Use identifiers for project names, code names, equipment designators, etc. Use open-
ended terms written in descriptor form for those subjects for which no descriptor exists.
(c) COSATI FIELD GROUP - Field and group assignments are to be taken from the 1965 COSATI Subject Category List. Since the ma-
jority of documents are multidisciplinary in nature, the Primary Field/Group assignment(s) will be specific discipline, area of human
endeavor, or type of physical object. The application(s) will be cross-referenced with secondary Field/Group assignments that will follow
the primary posting(s).
18. DISTRIBUTION STATEMENT
Denote releasability to the public or limitation for reasons other than security for example "Release Unlimited." Cite any availability to
the public, with address and price. /
19. &20. SECURITY CLASSIFICATION
DO NOT submit classified reports to the National Technical Information service.
21. NUMBER OF PAGES
Insert the total number of pages, including this one and unnumbered pages, but exclude distribution list, if any.
22. PRICE
Insert the rwicerSefeby Jhf ,Na.tional.Technical Information Service or the Government Printing Office, if known.
EPA Form 2220-1 (9-73) (Reverse)
------- |