EVALUATION OF MEASUREMENT METHODS
AND INSTRUMENTATION FOR ODOROUS
COMPOUNDS IN STATIONARY SOURCES
VOLUME I -
STATE OF THE ART
U.S. ENVIRONMENTAL PROTECTION AGENCY
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EVALUATION OF MEASUREMENT METHODS
AND INSTRUMENTATION
FOR ODOROUS COMPOUNDS
IN STATIONARY SOURCES
VOLUME I - STATE OF THE ART
by
H. J. Hall and R. H. Salvesen
Esso Research and Engineering Company
Government Research Laboratory
P.O. Box 8, Linden, New Jersey 07036
Contract No. 68-02-0219
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Research Triangle Park, North Carolina
July 1972
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The APTD (Air Pollution Technical Data) series of reports is issued by
the Environmental Protection Agency to report technical data of interest
to a limited number of readers. Copies of APTD reports are available
free of charge to Federal employees, current contractors and grantees,
and non-profit organizations - as supplies permit - from the Air Pollution
Technical Information Center, Environmental Protection Agency, Research
Triangle Park, North Carolina 27711 or may be obtained, for a nominal cost,
from the National Technical Information Service, 5285 Port Royal Road,
Springfield, Virginia 22151.
This report was furnished to the Environmental Protection Agency by
Esso Research and Engineering Company Government Research Laboratory,
Linden, New Jersey in fulfillment of Contract No. 68-02-0219. The
contents of this report are reproduced herein as received from the
Esso Research and Engineering Company. The opinions, findings, and
conclusions expressed are those of the author and not necessarily
those of the Environmental Protection Agency.
Publication No, APTD-1180
11
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TABLE OF CONTENTS
1. Introduction .......................... 1
2. Background ........................... 4
2.1 Odors Vs. Od .rants ..... .............. 4
2.1.1 Characteristic Odorants .............. 5
2.2 Problems in Emission Measurements ............. 7
2.2.1 Range and Sampling ................. 7
2.2.2 Sulfide Interferences ............... 8
2.2.3 Point Source and Diffuse Source Effects ...... 8
2.2.4 Effects of Odor Controls .............. 9
2.3 Coulometric Titrations for Total Reduced Sulfides ..... 10
2.3.1 Automatic Instrumentation ............. 10
2.3.2 Major Advantages and Disadvantages ......... 11
2.3.3 Types of Coulometric Cells ............. 12
2.4 Methods for Detailed Analysis ............... 14
2.4.1 Infrared and Mass Spectroscopy ........... 14
2. A. 2 Gas Chromatography ................. 15
2.5 Continuous Sensors .................... 15
3. Odorant Sources Considered ................... 17
3.1 Kraft Pulping ....................... 17
3.1.1 Sulfur Odorants Present .............. 17
3.1.2 Sources of Emissions ................ 17
3.1.3 Sulfur Disposal .................. 19
3.1.4 Measurement of Odorants .............. 19
3.1.5 Requirements for Monitoring ............ 21
3.2 Petroleum Refining/Petrochemical Operations ........ 21
3.2.1 Sulfur Odorants Present .............. 21
3.2.2 Sources of Emission ................ 22
3.2.3 Petrochemical Operations .............. 23
3.2.4 Sulfur Disposal .................. 23
3.2.5 Measurement of Sulfur Odorants ........... 26
3.2.6 Instrumentation for Monitoring ........... 28
ill
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TABLE OF CONTENTS (Continued)
3.3 Animal Waste Rendering Plants ............... 30
3.3.1 Odor ant Emissions ................. 30
3.3.2 Sources of Emission ................ 30
3.3.3 Methods of Measurement ............... 34
3.3.3.1 Odor Panels ................ 36
3.3.3.2 Wet Chemical Methods ........... 36
3.3.3.3 Instrument Methods ............ 37
3.3.3.4 Spectroscopy .... ........... 38
3.3.3.5 Gas Chromatography ............ 38
4. Specific Instrumentation for S Odo rants ........... 42
4.1 Preferred Commercial ................... 43
Coulometric Titration ................... 43
Gas Chromatography .................... 53
Tape Samplers ....................... 60
4.2 Commercial Alternates
Conduct imetry ....... . ......... « ..... 64
Ultraviolet ........................ 66
Color imetry ........................ 68
Electrochemical ...................... 72
4.3 Potential ..................... .... 73
Bioluminescence ........ . ............. 73
Chemiluminescence ........... . ......... 74
Fast Scan Infrared .................... 75
Fluorescence ............. . .......... 73
Infrared . . ....................... 81
Infrared Laser Radiation ................. 83
Metallic Silver Filters ............ .!!..! 84
Plasma Chromatograph .... ............... 86
BIBLIOGRAPHY 37
IV
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1. INTRODUCTION
This is a state-of-the-art review made to collect and evaluate
information on the instrumentation available to measure the quantities of
specific odorants in industrial plant emissions. Its object is to examine
the possibility of substituting a quantitative measurement of Q dorants for
the subjective measurement of odors as a guide for the control of odorous
emissions. This report completes Phase I of EPA Contract No. 68-02-0219
on "Evaluation of Measurement Methods and Instrumentation for Odorous
Compounds in Stationary Sources." Phase II of this program will consist
of the laboratory and field evaluation of instruments selected on the
basis of Phase I.
The instrumental measurement of odorants rather than odors is a
valid approach only when there is prior agreement as to what odorants
are primarily responsible for odor. No reliable correlations exist in the
general case between odor and the physical or chemical properties of
odorants, and the extent to which satisfactory correlations have been
made to date varies greatly from one industry to another. This is examined
here for three specific industries which have been the subject of major
odor complaints: kraft pulp mills, petroleum/petrochemical refineries, and
animal rendering plants.
The degree to which instrumentation is available for field use in
emission measurements can be related directly to the complexity of the
odorant mixture to be measured. The nature of the odorant mixture in
kraft mill emissions is well defined, and instrumentation to measure it is
commercially available. The situation in petroleum refineries is more com-
plex: a part of the odor problem is in stack emissions which can be
instrumented directly, but another part is due to small amounts of material
from diffuse sources which can only be measured at present by ambient
methods. The odor problem in animal rendering plants is even less well
defined: there is no agreement yet as to the identity of the specific
odorants most responsible for the odors observed, and instruments for their
detection and measurement are just now being developed.
The odorants emitted in kraft pulping consist primarily of four
reduced sulfides: t^S, methyl mercaptan, dimethyl sulfide, and dimethyl
disulfide. The I^S and methyl derivatives are considered equally objection-
able in odor complaints, and they are frequently measured together as
total reduced sulfide (TRS). They are present in varying proportions
in different streams, together with moderate amounts of S02 which is not
malodorous. The literature provides ample evidence that these four are
the key components both for odor emissions and for process changes to
control them. The much smaller amounts of higher sulfides which are
present have a secondary effect and they respond similarly to the methyl
homologs in odor controls.
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Petroleum/petrochemical refinery emissions also contain ^5 and
mercaptans, as key components. The problem of odorant measurements is
much different from kraft mills, however, since a primary object of
petroleum refining is the removal and disposal of large amounts of sulfur
present in the original feed stock. The refining process handles many
streams rich in H2S and other organic sulfides. These are converted to
non-odorous products, chiefly elemental sulfur and SC>2.
The principle emission point for residual sulfides in the refinery
is the burner stack of the sulfur plant. This normally consists chiefly
of SC>2 and other combustion gases. It may contain H2S or other sulfides
during periods of upset conditions. Small amounts of carbonyl sulfide are
also present, and they normally exceed the amount of l^S. The sulfur
plant in a modern refinery processes all collectible gas streams to remove
residual H2S and sulfides, before the gas is vented to the atmosphere.
The odorants emitted from small diffuse sources throughout the plant are more
varied in composition. Key components include I^S, alkyl and aromatic
mercaptans, all of which will be included in an ambient measurement of total
reduced sulfur. The massive amounts of S02 compared to reduced sulfur in
refinery emissions are a complicating factor, and the contribution of COS
requires further study.
The odorant picture for animal rendering plants is much less
clear. The composition of the odorants released is directly related to
the nature and quality of the material being processed. Odorants such as
trimethylamine which are highly characteristic of the emissions from a
plant processing feathers, hair, or fish meal are minor components or
missing in plants processing animal flesh. Other objectionable amines
such as skatole, putrescine and cadaverine are present only if the feed
to the plant is not properly washed, or if it contains badly decayed
flesh, which can be avoided. The odorants recognized as generally
characteristic of animal waste rendering include aliphatic aldehydes,
free fatty acids, ammonia, and variable amounts of amines and H.2S
depending on the specific feed stock. The laboratory instruments available
for the analysis of these recognized odorants are reviewed herein, to
indicate preferred approaches for a prototype for field use.
The continuous automatic instrumentation available for the direct
measurement of total reduced sulfide depends upon two types of sensors:
bromine coulometric titration, and the flame photometric detector.
Coulometric titration can be carried out continuously in a flowing stream,
or in a microcoulometer which accepts very small discrete samples such as
the fractions eluted from a gas chromatographic column. Both approaches
are very useful for differential measurements, but they are subject to
difficulties with zero stability which require frequent calibration if
absolute values are desired. Coulometric cells can also be based on titra-
tion with iodine or with silver ions, which respond to different portions
of the total sulfur present.
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Flame photometry responds equally to all sulfur atoms. It can
be used as a total measurement, or more desirably in a GC/FPD combination.
This permits a distinction between S types such as I^S, SC>2 , total S, or
some other selected component such as methyl mercaptan. Automatic
programmed equipment for such measurements is available.
Continuous measurements can also be made using lead acetate
tape samplers or similar automatic instruments which are sensitive only to
or to H2S and mercaptans as key components.
An alternate approach is to convert all sulfur compounds present
to SC>2, with or without a preliminary separation of the SC>2 initially
present, and use this as an analysis of sulfides in the sample. This
combination has been applied particularly with a conductivity cell or a
microcoulometer for the detection of S02- It could also be used with
any of the very large number of S02 detection systems available. The
analogous approach of catalytically or thermally converting all sulfur
compounds to I^S has also been used, particularly with the silver cell
microcoulometer or lead acetate tape as the sensor for H2S.
Wet chemical methods which consume reagents are considered
intrinsically less desirable for field measurements than the use of
electrical or optical sensors, but they are much more flexible when
analyses of varying composition are required. Most of the present standard
methods for product quality measurements in petroleum refining are based
on wet chemistry. Many of these measurements can be automated, if enough
samples are to be measured in a given time. Nevertheless, they have been
excluded as far as kraft mills and refineries are concerned in the
present review, which is aimed primarily at the evaluation of physical methods
of measurement. Automated wet chemistry may well be a preferred approach
to the analysis for odorants in animal rendering plants, where both
qualitative and quantitative base data are still required.
The review which follows presents background information in
Section 2 for the basic definitions of the problem of odorant emission
measurements, and the types of instrumentation available. Section 3 gives
details of the three industries considered as odorant sources. Section 4
summarizes the information on specific instruments which are commercially
preferred, on available alternates, or potential alternates where further
development is required.
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2. BACKGROUND
2.1 Odors vs. 0dorants
The measurement of odors is the one problem in air pollution
In which the subjective response of human sensors has continued to be
most important. At present, there are no known physical or chemical
properties of odorous materials which correlate with their odor, and the
only accepted method of measuring odors as such is a panel of human observers,
Odor is measured on a hedonistic scale, in terms of degrees
of pleasure or obnoxiousness. The usual scale has five units, from zero
or undetectable to intolerable or overpowering. This scale, like many
biological reactions, is related exponentially to the amount of the
stimulus, so that it is linear by orders of magnitude. A typical curvp
is that shown by Wright (26) for ethyl mercaptan, in Figure 1:
Figure 1
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ETHYL MERCAPTAN
MK1K>««AM« KK LITER
The relationship between odor intensity and odorant concentration is
considered as a classic example of the Weber-Fechner Equation (I):
P = K log S
where P = odor intensity, K = constant, S = odorant concentration. Values
of K for different materials range from 0.3 to 0.6; at 0.5, one unit on
the odor intensity scale corresponds to two orders of magnitude in
concentration.
The statistical reliability of odor panel measurements involving
several individuals is considered no better than + 1 unit on the intensity
scale. Recent data on a biological response to chemical stimulus have a
bearing on such measurements, from results obtained with a bio-luminescence
detector. This device measures the change in light emission of a luminescent
bacterial culture, on exposure to a chemical to which the particular strain
has been sensitized. This is a biological response which is free of subjective
influences. The detector can distinguish clearly between S02 concentrations of
0.2, 2.0 and 20 ppb (ICT^), with about two to three levels of discrimination
between each order of magnitude.
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The number of odor levels between odorant orders of magnitude
corresponds to the constant in the Weber-Fechner equation. The analytical
significance of this coefficient is that it takes a shift or change of
some -50% to +100% in a measured concentration to be biologically
detectable as a difference. This means that odorant measurements within
+_ 20 to 50% may be quite acceptable for odor correlations, even though
they would be considered marginal or worthless from the viewpoint of
conventional analytical chemistry.
If odorous compounds are to be measured for purposes of pollution
control, it is necessary to determine first what compounds to measure,
and where, and in what amounts. The determination of what to look for
is a major problem. It has been estimated that the human nose is sensitive
enough to determine concentrations of the range of 10^ molecules per ml.
of air, and the stated limit of detectability is continually going down
with improved methods of test. The odor threshold for H2S was stated as
0.13 ppm in 1930 (2), 20 ppb in 1962 (3), and 0.5 ppb in 1968 (4). The
total effect is usually due to a mixture of many odorants, at extremely
low concentrations. Dravnieks has estimated (5) that- the odors emanating
from a human being consist of from 150 to 500 different compounds or
groups of compounds, but that as few as 15 groups are enough to distinguish
types of humans such as Caucasian male, Caucasian female, and Asian Indian
(vegetarians). If only a limited number of compounds are to be measured
they must be chosen on the base of experience, or the statistical analysis
of large amounts of data which indicate that a useful correlation between
odor and odorant does exist. The odorant approach is valid only when
there is prior knowledge that the particular compound to be measured is
significant (45).
2.1.1 Characteristic Odorants^
One class of odorants for which the connection between odor
and chemical composition is clearly known are the volatile sulfides,
including H2S (rotten egg odor), the mercaptans (skunk odors), and the
organic sulfides which are the thioethers of the mercaptan thio-alcohols•
The human odor response is highest for methyl and ethyl mercaptan, a
little higher for ethyl (lower threshold), and in each case the odor
response is somewhat lower (higher threshold) for the sulfide than it
is for the corresponding mercaptan. These relationships are shown in
Figure 2.
Hydrogen sulfide, mercaptans and organic sulfides as a group
are easily recognized by their odor, and known to be present in the
uncontrolled emissions from pulp and paper mills and from petroleum
refineries. Further studies have shown that H2S and methyl mercaptan
and its derivatives are usually by far the major compounds of this series
present, and that they may be considered as key components for the
measurement of sulfides as a whole. The recognition that they are
important odorants has led to the development of automated industrial
chemical and instrumental methods for their measurement, which are
reviewed further herein.
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Figure 2
Variations In Odor Threshold with Number of C Atoms
in Several Series of Non-branched Homologs (5)
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NUMBER OF C ATOMS
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In many industries there is no such body of information as to
which specific odorants are most important, either in terms of quantity
or in terms of contribution to the odor effect. This is the case for
the odor emissions from animal waste rendering plants. The total odor
effect from these sources is strongly affected by the presence of
particulates or moisture droplets, which can adsorb enough odorant near
the source to carry a strong odor stimulus in individual particles to a
distance. Under these conditions, the usual relationships governing
dilution effects by atmospheric dispersion do not apply. Qualitative
data are available to indicate that aliphatic aldehydes, free fatty acids,
and alkyl amines are present as major odorants, but very little is known
as to their amounts, or what changes these amounts during plant operations.
In this situation, the collection of data on selected odorous materials
in terms of their amount and relationships to odor panel measurement
on the one hand and plant operating conditions on the other are a necessary
first step. Instrumentation suitable for measurements of the mixed
aldehydes, free acids and amines characteristic of animal waste rendering
odors is available, but only at the research level. It is still to be
assembled into a prototype and tested before it is available for use in
the field.
2.2 Problems in Emission Measurements
The measurement of odorants at the emission level rather than
at ambient dilutions presents special problems of sensor range, sampling
procedure, and interference effects. The specific nature of these problems
depends upon the source being measured.
2.2.1 Range and Sampling
In the case of kraft pulp mills, the total emission of l^S and
organic sulfides ranges from about 300 to 600 ppra in the older uncontrolled
operations, to less than 3 ppm in the best modern mills. This is commonly
referred to as total reduced sulfur (TRS). Regulations now in force or
set in various jurisdictions specify a total allowable sulfide emission
of 17.5 ppm. TRS measurements in the emission range have been standard
practice in the industry for purpose of process control, and the sensors
in commercial equipment are designed for this range (6)
The problem of sampling in kraft mill odorant measurements is
serious, and it has not been entirely solved. The stack gases which are
the principal emission source are hot, wet, and dirty, and subject to
rapid and wide fluctuations in concentration and amount. Major efforts
to improve this situation have been made by individual industries and
the industry's trade association NCASI (National Council for Air and
Stream Improvement). The standard Barton Instrument probe includes
integral filters and a timed blow-back cycle designed to minimize these
problems. All measuring instruments, however, are subject in some degree
to the complications caused by the inability or failure of the sampling
system to provide a clean gas sample for analysis. Thus, the ability
of a given instrument to handle or withstand poor samples is an important
characteristic for field evaluation tests (7).
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2.2.2 julfide Interferences
The reaction of SC^ as an oxidizing agent toward reduced sulfur
compounds and particularly toward I^S can cause serious interferences in
the emissions concentration range. This is a major problem in stack
sampling. The reaction is promoted by heat, moisture and reactive
particulate surfaces, all of which may be present. The result is to
form water and elemental sulfur which drop out in the sampling line, and
can easily clog the apparatus while vitiating the analysis.
The sulfur compounds of interest in kraft mill and petroleum
refinery emissions have many chemical and physical properties in common.
An instrument based such a non-fcpeciflc property will respond to any sulfide
present. With such an instrument, all other compounds in the group will
count as interferences when only one of them is of interest. This makes
it relatively easy to analyze for total sulfur, but correspondingly
difficult to measure say H-S alone, or total reduced sulfur in the
presence of large amounts of SO^-
The ability to discriminate between individual sulfur compounds
or types when the sensor responds to all depends on a preliminary separation
into fractions, which may then be separately analyzed by the same sensor to
measure their sulfur content. Separations of this type can be made by
a series of chemical absorption solutions (8), by a similar series of
dry absorption filters (9) or by gas chromatography (10) Any of these methods
can be applied to a sensor which does not discriminate between sulfur types,
such as a bromine coulometer or a flame photometric detector.
2.2.3 Point Source^and Diffuse Source Effects
While measurements at the emission levels of 1-100 ppm correspond
to standard industrial practice in kraft pulp mills, this is not true in
many other industries. In petroleum refineries, instrumentation for sulfide
measurements has been primarily at the percent level, for process streams
rich in H2S or sulfur-containing hydrocarbons, or at ambient levels near
or below 1-10 ppm for toxicity alarms and air pollution effects. No
instrumentation has been regularly applied to the measurement of odorous
emissions from animal rendering plants, and new proposals for such
measurements are just now appearing in the literature.
Emissions measurements apply only to effluents from a discrete
source such as a stack or vent line, while the total odor effect of a
plant may include many diffuse sources. Both are important in plants
such as a petroleum refinery, or animal waste rendering, where process
flow streams include odorants in high concentration. The odor effects
of many small leaks, each in low amount, can only be evaluated by ambient
measurements.
Ambient measurements are of more interest than emissions
measurements as far as odor thresholds and esthetic effects are concerned.
No direct health effects effects are expected below I ppm, however, in the
emissions range, even with materials as toxic as H2S (16).
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2.2.4 Effects of Odor Controls
Emissions measurements frequently apply to the analysis of
effluents before and after a treatment to reduce their amount. Odor
controls for this purpose may remove the odorant by oxidation or other
rhemical conversion, combined with dilution by ventilation in rrwfi~*A
areas or dispersal in open air, or by absorption or scrubbing. Chemical
conversion by oxidation may be effective only if the oxidation is complete,
resulting in final products which are either odorless or much less
odorous than their precursors (11, 12, 13, 14), Partial oxidation can
increase odor. Direct flame incinerators are used for air oxidation
employing temperatures of 1,100 to 1,500°F, while catalytical decomposition
systems operate at temperatures 500-800°F lower (11, 13, 14), Chemical
conversion by oxidizing agents such as ozone, permanganates, and chlorine
compounds does not result in complete oxidation>and it is important to
appraise the actual degree of odor reduction obtained. Proper incineration
is capable of reducing odor discharges by more than 99.99% in some instances,
and only rarely by less than 99% (12, 13). Control by absorbents is
practically synonymous with the use of activated carbon, and has usually
been found effective, though expensive if applied to large amounts of
odorant. In contrast to these results, the effectiveness of odor control
by time honored water-spray scrubbing techniques has been found to be
quite variable—from less than 50% in some installations to about 90-95%
at best (16)
Partial oxidation or oxidation/reduction reactions frequently
introduce new compounds into the odorant mixture. An important constituent
of this type is carbonyl sulfide. This appears in the stack gases from
a kraft mill when the recovery furnace is overloaded, and is a regular
constituent of the emissions from the Claus suxfur plants used instead
of burning for the disposal of refinery streams rich in I^S. The odor
response of COS can vary markedly from one individual to another, and it
is not included in the usual definition of TRS as H2S and total organic
sulfides. The response of a given instrument to COS is important either
way, since it may be included with H2S (by FPD), excluded (Barton or Philips)
or give a partial response (Dohrmann silver reductive cell). Further
research is required on the significance of this compound in the measurement
of odorants.
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2.3 Coulometric Titrations for Total Sulfide
2.3.1 Automatic Instrumentation
Automatic instrumentation for the measurement of organic sulfide
emissions was an industrial outgrowth of U.S. government research at the
end of World War II. The original problem was to detect and record very
minute concentrations of mustard gas in air. A highly sensitive coulometric
cell capable of making this measurement was based on the chemical oxidation
ot the organic sulfide with electrolytically generated bromine:
RSR + Br2 + H20 =* R2SO + 2H+ + 2Br~
The measurement can be made continuously on a flowing stream, in
terms of the bromine required Lo react with various forms of oxidizable
sulfur present in the sample. In the coulometric cell, the potentiotnetric
end-point and electrolytic generation are coupled through a feed-back
amplifying system. This controls the rate of reagent generation so that
it is at all times equal to the rate of reagent disappearance in the gas
titration. The current required to generate the bromine a function of the
sulfide concentration.
The commercial instrument developed on this basis by Austin at
the Consolidated Engineering Corp. in Pasadena was known as the Titrilog
(16). It was originally offered for the monitoring of natural gas odorants,
air pollution studies, and a variety of uses involving the detection of
hydrogen sulfide. The instrument has gone through several generations of
improvements, and is the predecessor of the Barton Titrator now available
as Models 286 and 400.
The coulometric cell proved to be very useful in the measurement
of odorous emissions in the pulp and paper industry, which consist primarily
of sulfur compounds oxidizable by bromine. Early demonstrations of its
success showed that the measurement of total reduced sulfur in these emis-
sions was a powerful tool to follow the results of process changes on the
amounts of odorous emission. Its speed of response and sensitivity were
used to advantage in the study of new methods of odor control, particularly
in Kraft mills. Improvements were made in the Barton Titrator to increase
its sensitivity and range to both lower and higher limits, so that the same
instrument can be used for direct measurements from 0.01 to 1000 ppm of
total reduced sulfur. This covers both the ambient and emission ranges.
Its use in Kraft mills has expanded rapidly in the last five years, using
improved ^methods of sampling and sample pretreatment developed by workers
at Crown Zellerbach (17) and Weyerhaeuser (8) in Washington, and in a series
of research and field projects sponsored by NCASI, the pulp and paper
industry's National Council for-Air and Stream Improvement.
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Bromine coulometry can be used to measure hydrogen sulfide,
sulfur dioxide, mercaptans, thioethers, organic disulfides and thiophenes.
This includes all of the organic sulfur compounds which are recognized as
characteristic odorants in Kraft mills, and the same compounds as character-
istic odorants in petroleum and petrochemical refining. It also includes
the two major inorganic sulfur pollutant gases, H2S and S02. Sulfur
trioxide, carbonyl sulfide and carbon disulfide are inorganic gases which
do not titrate with bromine.
Iodine coulometric cells have also been developed commercially by
Austin (a Barton prototype), and Dohrmann (oxidative microcoulometer).
Iodine titrates S02, H2S, and mercaptans, but does not react with other
organic sulfides or disulfides. Dohrmann oxidative cells of this
type are widely used. Theoretically, the difference between analyses with
an iodine cell and a bromine cell could be used to calculate the total of
these sulfides and disulfides, but this approach over-emphasizes small
differences between the two cells and it has not proved practical (18).
2.3.2 Major Advantages and Disadvantages
1. All reduced sulfur compounds react:
The fact that one instrument responds to such a variety of
hydrogen sulfide and reduced organic sulfur compounds has been a distinct
advantage since all of these compounds appear together, in varying
proportions, in the odorous emissions which are to be measured. However,
the lack of discrimination between different types of sulfur compounds is
also a disadvantage.
2. Conversion factors differ for different compounds.
The amount of halogen required for the titration is not the same
for different sulfur types, so that the conversion factor between cell
output and sulfide concentration varies with a varying ratio of sulfur
compound types. The exact course of this oxidation is not known in
detail, and it does not correspond stoichiometrically to any single react-
ion. The following reactions are typical (19):
S Compound Conversion Factors Observed
Theoretical Reaction with Bromine Mol. Wt. (x millivolts • ppm. IQx range)
S + 2HBr 34 0.86
CH3SH -I- 2Br2 + 2H2<> * CH.SO.H + 4HBf 46 1.3
2HBr 66 3.5
64 2*°
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The problem which this creates can be ignored by using the
factor for H2S and reporting the total calculated "as H2S". The value
thus obtained is called "total reduced sulfur". This is justified as a
simple method to get a useful result, because the compounds measured are
usually present together, and they are removed together by the usual
methods of control. If it is known, however, that another compound type
such as mercaptan predominates in a mixed stream, more accurate data may
be obtained by using its factor instead in the data conversion. For any
higher accuracy It is necessary to carry out a preliminary separation into
individual compounds or compound types, by subtractive chemical absorption
or otherwise, and measure each fraction using its appropriate conversion
factor. All three of these approaches are used.
3. Prefilter separations are not exact.
Unfortunately, the separation by sulfur compounds types which is
obtained by chemical absorption filters is only approximately quantitative.
Automatic equipment is available to make such measurements in a programmed
cycle, but it is not widely used except for research. The TRS measurement
is much simpler to make. Even though it is admittedly a compromise, it
is considered a reliable basis for the measurement of differences* to indicate
the direction and magnitude of changes in odor ant concentration as a result
of process changes in the plant.
4. Interaction effects are possible.
A further limitation of the coulometric cell in the discrimina-
tion of individual compounds or types in a mixed sample is the possibility
of secondary interaction effects on the stoichiometry of the oxidation
reaction, when there are marked changes in the ratio of sulfur types
present. When this occurs, the results obtained- in a mixed sample will
not exactly equal the sum of the results obtained on separate fractions.
2.3.3 Types of Coulometric Cells
Coulometry is based upon the principle of electrically generating
a selected titrant (ion or element) in a titration cell. This may be a
free halogen (bromine or iodine) in aqueous solution, as an oxidizing agent,
or a metal ion (silver) as a reducing agent. The electrolytic current re-
quired to generate the titrant as it Is consumed is a linear measure of
the concentration of reactable compounds in the gas sample. In practice,
the titration cell has two sets of electrodes—a generating pair and a
reference pair. The electrical relationship between these differs in
different types of cells.
1. In the Barton bromine cell and the Philips S02 Monitor bromine
cell a constant low level of titrant is continuously ijalntafned to produce a
"zero level" on the instrument. When reactable compounds enter the cell,
the available titrant is consumed. The associated feedback amplifier
responds to the change in sensed titrant level and generates sufficient
additional titrant to maintain the "zero level" concentration. In this
type of cell, the generation rate of free halogen as titrant Is governed
by a control circuit which senses an excess of halogen, at a level fixed
by the depolarization of and flow of current through the reference electrode.
In this case the generating current required to maintain that excess is
measured, and is proportional to the measured component.
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- 13 -
2. In a second type of titration, the cell is driven by a constant
current source. The consumption of free halogen prevents reaction at the
cathode and current flows instead through the reference electrodes. The
reference current is measured and is proportional to the decrease in halogen
concentration and thus to the concentration of reactable pollutant in the
sample. (Dohrmann Microcoulometer, Beckman 906A) .
3. In another type of cell, hydrogen is allowed to build up on the
electrodes. Current flow, limited by diffusion to the electrode surface,
is proportional directly to halogen concentration and inversely to the
concentration of reactable pollutant. (Atlas 1203).
The Barton Titrator Model 400 for pulp and paper plant use is a
modification of the earlier Titrilog (19), which adds an optional SC>2 filter
cycle to the basic total sulfur Model 286. A high degree of selectivity
in S02 removal in obtained by absorption in 3% aqueous potassium acid
phthalate. Total sulfur includes S02> and total reduced sulfur includes H2S,
mercaptan, sulfide, and disulfide. These sulfur compounds can be separated
by type if desired and measured separately, using an auxiliary system of
absorption filter cells which can be automated (Model 327). The Titrator
measures bromine oxidizable sulfur gases through the entire range from
10 ppb to 1000 ppm. This is the widest range for direct measurements of
H2$ and TRS of any instrument which has been available for purchase, and
the convenience of using the same instrument for both ambient and emission
measurements has been one factor in its acceptance in the industry.
Microcoulometric cells which operate on small discrete samples
rather on a flowing stream have become widely accepted during the past
two or three years as preferred methods for the research laboratory
determination of low concentrations of sulfur, in either Kraft mill gases
or petroleum products. Their major advantages are sensitivity and speed,
and the fact that they require only microliter amounts of liquid sample
or milliliter quantities of gas.
There are two principal types of microcoulometer cells. The
oxidative cell was originally developed as a specific gas chromatographic
detector, and linked directly to the column outlet through a combustion
unit which converts all S compounds to S02 for the titration. An alternate
is the reductive microtitration cell utilizing silver-silver chloride
electrodes, used for the coulometric analysis of hydrogen sulfide and
raercaptans (2jD) . The reductive cell will not respond to S02, or to alkyl
sulfides and disulfides. The reductive method is usually combined with a
preliminary hydrogenolysis by which the sulfur compounds present in the
sample are reduced to hydrogen sulfide, over a Pt/alumina catalyst in a
stream of hydrogen, and titrated with silver ions. The silver cell can
also be used for the determination of ammonia, or ammonia formed from
nitrogen compounds by catalytic reduction with hydrogen.
The microcoulometer, originally combined with a preliminary
decomposition by combustion to S02 or hydrogenolysis to H2S prior to
titration, may also be used to advantage for the direct titration of the
sulfur species which react. These are SC>2 in the oxidation mode, and
H2S or RSH in the reductive mode. t^S and RSH also react ia the oxida-
tive mode, but with less favorable conversion factors.
-------
- 14 -
Commercial models of the microcoulometer are marketed by the
Dohrmann Instrument Co. (now Envirotech Corp.)- The original model was
an iodine cell, and this has been used extensively in the petroleum industry.
Its effective range covers three orders of magnitudes, from about 0.2 to
1000 ppm of sulfur. The addition of sodium azide to the electrolyte over-
comes the interference effects of small amounts of chlorides or nitrogen
oxides (21), which are often responsible for short electrolyte life. The
original design of the iodine cell was modified and converted to bromine
coulometry by Adams (22) with improved sensitivity for ambient measurements
at concentrations down to 3 ppb of hydrogen sulfide. Both the iodine and
bromine cells are available from Dohrmann (Envirotech).
The zero adjustment in the Barton and Dohrmann cells is an approxi-
mation which is never exact, since it is a dynamic balance involving the
small amount of bromine gas physically swept out of the cell by the constant
flow of sample carrier gas, in the absence of reactive sulfur compounds in
the sample. The effect has been minimized in the Philips cell by changes
in cell geometry and improved mixing within the cell. This zero and the
cell readings above it also respond sensitively and promptly to any change
in the flow rate, pressure, or molecular weight of the gas flow through
the cell.
2.4 Methods for Detailed Analysis
2 ..4 ..1 IR and_ Mags Spectrosgopy
The determination of individual compounds in a complex odorous
plant emission is a laboratory research problem in which the most
sophisticated methods available can be employed. Basic studies of this
type have been made using both infrared and mass spectroscopy, and such
measurements are necessary to define the specific compounds which need to
be measured for purposes of monitoring. This includes both qualitative and
quantitative data on composition. In the general case of odorous compounds
it is necessary sooner or later to make a further correlation by data or
by analogy between the amount of a given odorant and its contribution to
total odor response. However, such a correlation, while it is required,
is not a part of the present project. Once the nature and concentration
range of the odorous components to be measured has been defined, a much
simpler method is desirable for field use to measure a selected group of
key componerttf.'
The complete analysis of individual components by infrared, mass
spectrometry or other sophisticated spectroscopic methods gives definitive
results, but these methods are time consuming, expensive, and not suited
for routine use in the field (6). The odorants to be measured by instru-
mentation for H2S and TRS in Kraft mills and in petroleum refining are
known, as the result of prior studies» and it is necessary to control
them all if complaints from obnoxious odors are to be avoided. The research
methods are still useful and used to great advantage for special purposes
such as the study of trace impurities or the mechanism of reactions, but
the large amount of additional information which they supply is neither
-accessary nor desirable for routine use in the monitoring of emissions.
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- 15 -
It is also possible to make simplified equipment using either
infrared or mass spectroscopy which is suitable for field use to measure
a single pollutant compound in air, but IR is not a good method for I^S
and the other odorants of interest are a complex mixture. While further
developments may appear along these lines, other approaches have turned
out to be simpler, to date.
2.4.2 Gas Chromatogr&
Gas chromatograp hy (GC) has been used to great advantage in the
analysis of odorous emissions (9). It was one of the early industrial uses
of this new technique, starting in 1957 with studies by the British Columbia
Research Council (23) and in parallel studies since 1958 by Adams and co-
workers at the University of Washington (24). The GC technique can be
used either for complete analysis or, by a proper choice of substrate and
elution procedures, it may be used for a short-cut analysis in which a
few compounds of particular interest are measured first. In a preferred
technique, the rest of the sample can then be back-flushed out of the column
and discarded, to restore the column to its original state for another run
in minimum elapsed time.
One limitation on the sensitivity and discrimination of the GC
technique was originally the type of sensor available to detect changes
in composition, for the minute amounts of material in the succeeding fractions
eluted from the column. The original analysis using thermal conductivity
cells which responded to about 500 ppm of sulfur compounds on direct
injection was improved by substituting the flame ionization detector (FID)
which responds to about 5 ppm of organic sulfide, and still further improved
by the flame photometric detector (FPD) which is sensitive to 3 ppm of
sulfur compound in the GC concentrates. The FPD responds equally to sulfur
in S(>2, sulf ide, or any sulfur compound which is combustible in a hydrogen-
rich flame. The combination of GC/FPD is just now becoming available in
commercial instruments which are offered as Bendix Model 8700 and Tracer
Model 250H, and Varian Aerograph Model 1490.
2.5 Continuous Sensors?
Over the past two decades, instrumentation researchers and
manufacturers have put most of their efforts into the measurement step
of the analytical process. Sensors that measure all sorts of properties,
for both identification and quantification, have been developed to a high
degree of analytical sophistication. Some of these sensors have high
sensitivity, low holdup, and rapid response, and are suited with little
or no modification to continuous analysis. Developments along these lines
have been summarized in detail by Blaedel (25). The methods listed in
Table 1 have been used or recommended for the continuous analysis of organic
sulfides or their conversion products, H2S or
-------
- 16 -
Table 1
Continuous Sensors for Sulfur Compounds
Electrical sensors Optical sensors
Conduetometrie Colorimetric (speetrophotometrlc,
visible region)
Coulometric titration: Bromine Fluorimetric
Iodine Infrared spectrophotometrie
Silver ion
Flame lonization detectors Turbidimetric
Polarographic Ultraviolet spectrophotometric
Potentiometric: specific ion electrode
Potentiometric titrations Mass spectrotnetric
Thermistor: thermal conductivity
The ability of an instrument to make continuous measurements rather
than cumulative measurements in the field is a desirable characteristic, and
it is essential when the readings obtained are to be related directly to
process controls. Continuous sensors of the types listed are discussed further
in Section 4 of the present report.
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- 17 -
3. ODORANT SOURCES CONSIDERED
3.1 Kraft Pulping
3.1.1 Sulfur Odorants Present
The characteristic odor for which kraft pulp mills are known
as a major source of air pollution is due to a mixture of reduced sulfur
compounds consisting largely of hydrogen sulfide, methyl mercaptan, and
its derivatives dimethyl sulfide and dimethyl disulfide. Very much
smaller amounts of higher sulfides are present (26). The methyl deriva-
tives predominate because of the chemical structure of wood, for the same
reason that methyl alcohol is formed in wood distillation.
The same four compounds appear in all of the gas streams pro-
duced in kraft pulping, in varying proportions. Terpene hydrocarbons are
also released in the treatment of soft woods and may contribute to odor,
but they are not considered as objectionable as the sulfides and mercaptans,
Sulfur dioxide appears in the stack gases from the recovery furnace and
the lime kiln, in an amount which is normally low or moderate compared to
total reduced sulfur.
The sulfur odorants emitted in the kraft process come from the
pulping reaction. They are not part of the feed to the process (wood)
or the product (pulp), but they are chemical products of the reaction,
and the sulfur which they contain is reusable in the process.
Sulfite pulping is an alternate to the kraft process which pro-
duces no H2S or organic sulfide emissions, only SC>2. Its use is limited
and decreasing, however, since it is employed primarily in reprocessing
plants and on a limited variety of woods which are not those most readily
available. The present review is based on kraft pulping.
3.1.2 Sources of Emission
The pulping process is a means of chemically dissolving the
lignin in wood away from cellulose fibers which are then made into paper.
The kraft pulping reagent is an aqueous solution of sodium sulfide and
hydroxide, A major feature of the process, shown schematically in
Figure 3, is its ability to recover most of the chemicals from the spent
treating liquor and re-use them for the next batch (26). Sodium sulfide
is continuously regenerated from the l^S and organic sulfides released
and recovered in the cycle.
The combined fresh and regenerated white liquor is mixed with
wood chips and cooked for 3 hours in one of a battery of large upright
digesters, with steam at a pressure of approximately 110 psig.
Digester gases are relieved periodically during the cooking period to
reduce the build-up of pressure within the system. At the end of the
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- 18 -
cooking, the bottom of the digester is suddenly opened and its contents
forced into a blow tank. Here the major part of the spent cooking liquor
containing dissolved lignin is drained off. The raw pulp is filtered free
of undissolved knots, washed, bleached, pressed, and dried ready for
further use.
Figure 3
ScheTT.atic Diagram of the Kraft Pulping Process
"FLIEF
$
WON
CH,SH.CMjSCMj.H,S
CONXNSABLLS
TURPEWTlNt
/
CONTAMINATED WATER
OONIAMPN'ATED WATER
AIR
OXIDATION
I STEAM,CONTAMINATED WATER,KjS, 6. CHj
13 X SOLIDS
Sf'E'iT AIR . CHjSCHj f
i
i
EVA
The spent black liquo*- from the blow tanks is concentrated to
50-60% solids by evaporation, and better results are realized by an
oxidation of this black liquor before the first stage of evaporation.
This reduces corrosion in the evaporators and decreases the loss of
-------
- 19 -
sulfides in the gases by converting them to partially or completely
oxidized compounds which are less volatile. It thereby conserves
reagent sulfur, while decreasing the emission of sulfur-containing
odorants into the atmosphere. The black liquor may be further con-
centrated in a direct contact evaporator, by heat exchange with the
recovery furnace flue gases. Much lower emissions can be realized
by replacing this direct contact evaporation with an indirect heat
exchange system for the final concentration, which avoids re-evaporating
odorants into the stack gases. Several designs of this type are available.
The concentrated black liquor is combustible because of its
lignin content. This is burned in the recovery furnace under lean air
conditions, so that the inorganic chemicals present are reduced to a
melted mixture which is mainly sodium sulfide and sodium carbonate.
This smelt is removed from the bottom of the furnace, dissolved to form
a green liquor, and the carbonate is reconverted to sodium hydroxide
by slaked lime in the causticizer tank. The spent mud from this tank
is sent to a lime kiln, where it is burned to regenerate calcium oxide
to complete the cycle.
3.1.3 Means of Sulfur Disposal
Sulfur containing gases collected from the digesters, blow
tanks, evaporators and miscellaneous washers and filters throughout the
plant are disposed of by burning in the lime kiln or the recovery furnace.
The control of emissions by this means requires a careful adjustment of
furnace loading and operating conditions to keep the system in balance.
A summary of the principal emission sources to be controlled and typical
analyses of their odorant composition is given in Table 2 (27).
3.1.4 Measurement of Odorants
The odor problems inherent in the kraft process were well
recognized by its developers in 1891, and technical papers evaluating
the problem began to appear around 1900 (26). Quantitative measurements
of the amounts of me reaptan, methyl sulfide, and dimethyl disulfide emitted
per ton of pulp were published as early as 1922 (28) , and the picture as
to what compounds are responsible has not changed since.
The early measurements of the amounts of these compounds were
made by conventional chemical means (29), usually colorimetric reactions
for H2S and the formation of mercury salts from mercaptans (mercaptan *
"mercurium cap tans "). The development of black liquor oxidation in
Scandinavian mills, shortly after World War II (30) , was a process for im-
proving the economics of kraft pulping by reducing the emissions of sulfur
odorants. It coincided with the development of the bromine coulometer as
a rapid and convenient automatic instrument for measuring total reduced sul-
fur (18). This gave a strong incentive for the production of a commercial
instrument to operate in the normal range of uncontrolled emissions, up
to about 1000 ppm.
-------
Table 2
Average and Range of Odorous Compounds
in Various Kraft Mill Emissions
Digester
Blow Gases
Odorant
Hydrogen Sulfide
Methyl Mercaptan
Dimethvl Sulfide
Ditnethvl Disulfide
Acetone
Methanol
Alpha-pinene
so2
Gas Flow
during tests
Av.
80
4400
5100
1100
350
1100
1350
170
Range
10-200
1300-8700
2300-7000
600-2200
100-600
500-2400
950-2200
CFM at 60 °F
Multiple
(PPM by Volume)
Effect Contact
Evaporators
Av.
9000
100 ,000
4000
5000
—
110
960
10 CFM
Range
3000-
30 ,000
50,000-
300,000
500-6000
—
—
50-160
300-1800
at 60°F
Evaporator
Av.
<10
45
18
35
60
1000
30
6,500
60
Range
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- 21 -
The Barton Titrator has been used widely as a process tool,
to follow the course of plant design and operating changes made to re-
duce the amount of sulfur lost as emissions. Initial models were
improved to provide multiple ranges in a single instrument, from ambient
through stack emissions (16) . The most serious problems encountered in
the field have been related to difficulties in sampling the gas stream
which is hot, wet, and dirty. Methods to handle this difficulty have
been developed by many workers (_7 ) , but the problem has not been completely
solved.
Apart from sampling problems, one disadvantage of the Barton has
been its inability to distinguish directly between any of the major
odorants present. This directed attention to gas chroma tography and
physical sensors to go wit1 it, to avoid the use of tedious and time-
consuming chemical filtrati -n systems for preliminary separation.
3.1.5 Requirements for Monitoring
Experience has shown that the complete analysis for individual
compounds and the changes in their concentration as a result of process
controls is primarily a problem for laboratory research. Once these
determinations have been made and suitably confirmed, there ^ ™ *£*-f
taae in making a complete analysis for routine monitoring. The number or
suth compounds which need to be measured is limited to a few key components,
whose changes are enough to indicate satisfactory or unsatisfactory opera-
tions in the system or source concerned.
Present indications are that the distinction between H^S, total
reduced S and So gives useful data for the control of kraft mill emissions,
and that this may be enough information for routine monitoring.
3.2 Petroleum Refining/Petrochemical Operations
3.2.1 Sulfur Odorants Present
Hydrogen sulfide and mercaptans are the major sulfur-containing
odorants in oil refinery emissions. Some of the I^S comes from crude oil,
and more of it is formed from other sulfur compounds during the refining
process. Alkyl mercaptans are present in crude oil in a wide range of
molecular weights, with relatively larger amounts of the lighter compounds
which have more noticeable odors ,
The alkyl mercaptans are readily decomposed to split out
by thermal cracking or catalytic treatment. This type of processing is
usually preferred in modern oil refining to the older processes of
chemically or catalytically converting the mercaptans to the corresponding
dialkyl sulfides or disulfides, which are less odorous. Sweetening pro-
cesses which double the molecular weight of the original sulfide are still
used in the deodorization of fuel oils, but they are no longer preferred
methods in the treatment of lighter distillates, partly because they de-
crease the yield of product in the original boiling racge.
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- 22 -
Aromatic mercaptans such as phenyl mercaptan are also present.
They are mostly formed by catalytic processes such as catalytic cracking,
where they may result from the ring-splitting of polycyclic S-containing
compounds such as benzothiophene. The amount of these aromatic mercaptans
produced is directly related to the ring sulfur content of the crude.
3.2.2 Sources of Einisjsions
Hydrogen sulfide comes from three major sources in a modern
refinery. A schematic processing plan is shown in Figure 4. I^S in the
original crude oil comes overhead with the wet gas from primary crude
distillation. Minor amounts are also released into the air space of
crude storage tanks (not shown), which can be vented to a gas collection
system to avoid odorous emissions. The second major source is the dilute
H2S-containing wet gas produced by a variety of thermal treatments which
include catalytic cracking, catalytic reforming, and thermal or fluid bed
coking. The wet gas from all of these sources, rich in light hydrocarbons,
is combined and sent to a gas plant for recovery. The gas in this plant
is scrubbed with a suitable solution, such as an ethanolamine, to remove
H2S and the low molecular weight mercaptans present. The desulfurized gas
and light hydrocarbons produced are available as finished products or they
may be used as fuel and as raw materials for further refining or petro-
chemical processes. The third major source is a rich stream of H2S in
hydrogen, ranging from about 15 to 70 mol %, produced by treating middle
distillate fractions with a limited amount of hydrogen for sulfur removal (31)
Figure 4
^Fu«l Got
Gotolmi
Crudt Oil
Crudi
R«tiduwm
-------
- 23 -
A listing of points recognized as potential sources of specific
emissions in the refinery is given in Table 4 (32).
Table 4
Potential Sources of
Specific Malodorous Emissions
Emission Refinery Sources
Hydrogen Sulfide Untreated gas stream leaks, vapor from crude
oil and raw distillates, process condensate
sewers; traces in treated gas streams.
Mercaptans Cracking units, caustic regeneration units,
some asphalt plants.
Organic Sulfides Movement and storage of the acid solutions
used in scrubbing organic sulfides and mixed
sulfur-nitrogen bases, if they are present,
from straight run or cracked distillates or
lubricating oil fractions.
Sulfur Dioxide Combustion of fuels containing sulfur, flares,
catalytic cracking unit regenerators, treating
units, decoking operations.
3.2.3 Petrochemical Operations
Petrochemical operations are based mainly on the chemical reactions
of olefins, aromatics, or other light hydrocarbons derived from petroleum.
These reactions are frequently sensitive to very small amounts of sulfur
compounds in the feed stocks. The processes used to desulfurize these
chemical intermediates are essentially those shown in Figure 2, involving
catalytic or thermal cracking, catalytic reforming, further hydrogen
treatment if required, and an amine extraction of the product to remove
the H2S and mercaptans present. The odorants present and the measurement
problems which they present are basically the same.
3.2.4 Means of Sulfur Disposal
The H2S from hydrotreating and the H2S/RSH concentrate from the
gas plant are too rich in H2S to be vented to the atmosphere as such. They
may be burned to S02, which gets rid of the toxicity problem but creates
an equal amount of S02 which is frequently undesirable. The preferred
method which is becoming standard practice is to send all of this H2S to
a Glaus process sulfur plant. A third of the ELS is burned to SC>2, and
the two gases are combined at a slightly elevated temperature to produce
elemental sulfur:
2HS + S0 >• 2H0 + 3 S°
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- 24 -
The small amounts of alkyl RSH present with this l^S are ordinarily
consumed in the sulfur plant. If they are present in unusually large
amounts, however, they may be recovered from the amine extract in the
gas plant by a simple distillation and re-refined to recover their hydro-
carbon content.
The vent gas from the sulfur plant contains chiefly combustion
gases, S02, carbonyl sulfide, carbon disulfide, and trace amounts of un-
converted organic sulfides. A typical composition is shown in Table 3.
This stream was originally vented to the atmosphere, after suitable dilu-
tion. It is usually incinerated first, which converts almost all of the
remaining sulfides present to S02 and dilutes the whole with combustion
air.
Table 3
Typical Tail Gas to and from
Sulfur Plant Incinerator
From Glaus Plant From Plant
to Incinerator, Vol. % Incinerator, Vol. %
S02 3.0 1.2
COS 0.25 0.008
CSj 0.25 <;10 ppm
H2S 200-1000 ppm <10 ppm
CO 2.0 0.6
C02 13.0 3.2
The stack gas from the sulfur plant incinerator and the vent
gas from the sulfur plant, if any, are thus the chief points of source
emissions in a modern refinery. This system provides sulfur disposal for
every collectable sulfur-containing gas in the refinery. A variety of
means may be employed to dispose of collectable odorants outside of the
sulfur plant, usually by burning or air oxidation (33).
Hydrogen sulfide and mercaptans may escape from process steam
condensates, drain liquids from the various processes, barometric condenser
pumps, sour volatile product tankage, and spent caustic solutions from
treating operations. The malodorous components in steam condensates can
be removed by stripping with air, flue gas or steam, and the malodorous
gases burned in a furnace. Drain liquids can be routed to a closed
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- 25 -
storage vessel and returned to the process. Barometric condensers are re-
placed by the more modern surface condensers; the non-condensables are
burned in process heaters or in a separate incinerator. Spent caustic can
be degasified, neutralized with flue gas or stripped before disposal»
Sulfides can also be removed from sour process water and spent caustic
solutions by air oxidation to thiosulfates and sulfates.
Another I^S problem may be caused when suddenly large quantities
of hydrogen sulfide must be burned in the flare. It is difficult to burn
these large quantities completely to SOo. The problem must be overcome by
redressing the upset causing the increased l^S production, usually by re-
ducing the charge to the hydro desulfurizers. This situation can be
minimized by suitably sizing the CLaus sulfur plant to accomodate expected
overloads. Concentrated organic sulfides are rendered harmless by conver-
sion to H2S in a hydro desulfurizer unit, or by combustion in a process
heater.
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- 26 -
3.2.5 Measurement of Sulfur Odorants
Analytical methods and procedures using wet chemistry for the
determination of sulfur-containing streams in the refinery have been highly
standardized. Referee methods formalized as ASTM Procedures by the American
Society for Testing Materials have been adopted throughout the industry,
and continuously annotated or revised to include the results of further
experience and comparative testing between laboratories. The commercial
use of sulfur specifications as a measure of product quality and relative
market value between competing manufacturers has given the strongest
incentive to the development of reliable methods.
The primary emphasis in these methods has been on the determination
of sulfur in the products. The analytical range of interest for liquid
fuels was originally in the percent range with stated limits of accuracy
of the order of + 0.1 for the Lamp Sulfur Method, which has been in use
for over fifty years. Sensitivity has been continually improved, for the
analysis of lighter fuels and gaseous hydrocarbon products ,anrl for the up-
grading of product quality to lower levels of sulfur content.
The old Lamp Sulfur Method ASTM D-90 oxidizes the sulfur in a
liquid hydrocarbon sample to sulfur dioxide in a wick-fed flame, and
gravimetrically determines its amount. The same principle of oxidation
to S02 and measurement as such is applied to light liquid hydrocarbons and
gases by burning in a pressure-fed flame (Wickbold, ASTM D-2785). Higher
sensitivity for very low sulfur contents can be achieved by turbidimetric
measurements after further oxidation and precipitation as BaSO^. The
general approach here is to oxidize all sulfur compounds present to S02,
and measure this as an indication of sulfur content. When the material
being analyzed is a hydrocarbon liquid or gas, there is no problem of
interference from SC>2 in the original sample.
Analyses for S02 as such have been developed primarily for the
monitoring of combustion stacks. The prior art and evaluation of instruments
for this purpose have been covered elsewhere and are not the object of the
present review. Particularly useful references include discussions by Palmer
and Rodes (34), Tokiwa (35), and the current EPA Project EHSD 71-23.
The oxidation of all S compounds to SC>2 as a preliminary step to
instrumental measurement was recommended by Thomas (36) using a conductimeteric
method, titrating the acidity developed after absorbing the 862 in dilute
hydrogep peroxide. The Thomas Autometer was used in industry but did not
widely displace the standard wet chemical methods, partly because of
problems in instrument maintenance. Preliminary oxidation to SC>2 has also
been combined with the Dohrmann Microcoulometer, as a research tool for the
measurement of very small samples. Analyses by this procedure have been
made in the field, but it has not yet been developed sufficiently for
routine use.
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- 27 -
The comparable principle of converting all S compounds present
to H2$ by catalytic hydrogenolysis and measurement as H2S has also been
applied to refinery products. This can be accomplished using a lead
acetate tape recorder, as commercialized by Houston Atlas, It can also
be done using the silver reductive micro coulometric cell offered for labora-
tory use by Dohrmann , based on developmental work by Burchf ield
The use of instrumental methods for sulfur determinations has
been slow to displace wet chemistry in refinery product analyses. This
is partly because the standard wet chemical methods have been so highly
developed, in a market situation where the direct competition between
manufacturers on product quality allows no leeway for the adoption of less
reliable or accurate procedures. Another factor has been the problem of
instrument maintenance, which is particularly important when there are
relatively few measurements over a period of time. It must also be
recognized that once the basic correlations between product quality and
operating conditions of temperature, pressure, flow rate and feed com-
position have been established for a given process, by research measure-
ments and pilot studies, very few complete analyses are required on any
plant stream except the feed and final product. Research type measure-
ments may be made once a year or once every few months, for a plant test
to confirm previous correlations, but this amount of use does not justify
automatic instrumentation.
Instrumentation for emissions control is a new emphasis, and
automatic instrumentation for this purpose is just now being developed.
An example is the exact control of the Glaus process to give minimum sulfur
emissions in the product gas. A general discussion of this system is
given in EPA pulbication AP-42, "Control Techniques for Sulfur Oxide
Pollutants." The critical point for analysis is the affect of variations
in t^S to S02 ratio on the maximum theoretical conversion to S in a given
plant. The effect is illustrated in Figure 5. Optimum conversion is
obtained at a mol ratio of exactly 2.0 and if this deviates by as much as
2.1 to 1.9, the maximum conversion obtainable decreases to an efficiency
of 96.8 to 98.3% conversion. This corresponds to an analytical accuracy
of + 5% in the reported value. Monitors developed for this measurement
include a non-dispersive UV, sensitive to both S02 and H2S. While this
difference in conversion level may have relatively little effect on the
tonnage of sulfur produced, it is critical for the amount of unconverted
material emitted from the plant.
-------
_ 28 -
Figure 5
Variation of I^S to S02 Ratio with Conversion and
Maximum Theoretical Conversion Possible at Specified Ratio
100.0
CONVERSION, %
3.2.6 Instrumentation for Monitoring
The sulfur odorants produced and removed in oil refining come
directly from the feed stock to the refinery. Unlike the Kraft pulping
process which seeks to conserve sulfur, the I^S and mercaptans produced
in oil refining must be disposed of in production quantities. They are
handled in the refinery as process streams at a relatively high concen-
tration, in the percent range or higher, and in systems which are com-
pletely closed because of the toxic hazards involved at these concentra-
tions.
Odorant controls operate by converting the sulfur compounds to
odorless or less odorous forms, primarily elemental sulfur or S02, and to
a limited extent to heavier sulfur compounds which can be tolerated in some
other petroleum product.
-------
- 29 -
Monitoring requirements are of two types: emission measurements
on the principal stack gases, and ambient measurements to determine the
cumulative effects of miscellaneous small leaks from odorous process streams.
Emission measurements are of most interest for H^S, since most other sulfides
are now converted to H2? as an intermediate step in their final disposal.
Mercaptan emissions are more likely from diffuse sources, monitored by ambient
measurements, than from the stack gases which are the major emission points.
-------
- 30 -
3.3 Animal Waste Rendering Plants
3.3.1 Odorant Emissions
Odor emissions from animal waste rendering (AWR) plants are
derived from the processing of inedible raw materials which are unsuitable
for other use. The odors associated with these operations have long been
recognized as a severe type of air pollution and one of the more frequent
causes of public complaint, but they have been most difficult to measure
or quantify. Recent research studies combining odor panels with physical
separations and the chemical or spectroscopic identification of constituents
have been able to identify specific malodorous compounds and types of com-
pounds as present in AWR emissions, but the data obtained by this technique
are only qualitative or semi-quantitative at best. Instruments to measure
the compounds identified are only in the conceptual stage or just now being
developed. Parts of this problem in odor measurement and instrumentation
therefor have thus been solved, but no total system for this purpose has
been set up and tested.
The odorants released in animal waste rendering are normal prod-
ucts of animal metabolism and the concentrations of these materials de-
tectable by smell are extremely low, of the order of parts per billion or
even less. This has been beyond the instrumental range and in some cases
it is still marginal at best. Concentrations at the source will be
correspondingly higher, in the range of parts per million.
The relationship between source concentrations and those de-
tectable at a distance from the plant are by no means linear, however, for
different compound types. The reasons for this are only partly known.
Aldehydes, for example, are relatively easily peroxidized in air to form
the physiologically reactive peracids, and the concentration of these
might remain constant or even increase with time and distance from the
source. It is entirely possible, although not yet fully established, that
it is this or some similar mechanism which explains why aldehydes are con-
sidered among the most persistent odorous compounds emitted.
3.3.2 The Sources of Emission
The animal rendering process consists of reducing animal tissue
from Inedible meat, bone scrap, fish and poultry wastes to solids, fats
and water. The products produced are tallow, grease, fertilizer and animal
feed. Whole b^lood may also be processed to give solid blood meal which
is also valuable as a fertilizer and in the manufacture of glue.
A typical continuous rendering process such as that shown in
Figure & consists of a receiving area for the animal wastes, which are con-
veyed to a cooker where water is removed, followed by additional cooking
to remove tallow,, other liquids and gases, drying, pressing of the solids
-------
- 31 -
Figure 6
Schematic Diagram of a Continuous Rendering Process
Receivinf Pit
Animal Pastes
I
1
LiqUi
>
Cookers *'
i "•
solids &
liquids
Parcolacoi; g
| va,
AA *
Solids
1
Solids
si/
'tallows Expo Her
(Hydraulic press)
i
f
Steam-hen ted HtiuitH
Separation
Tank
e
& . Contact i spray lv atm03phct
mnm ' condensers f\ scrubber! 7
' 1 ;]
ascs
pors
gases
^V — ^T1-, i
\—
Liquids to
JL^ lagoon
vapors
solids x j Hananer- v
"~^» mill 7
FinishcJ Product
Paclia^ed for sale
tallows
i
1'inished Product
Tallov; storage
Tank
-------
- 32 -
and grinding of the solids to form a finished product. Gases and vapor
from the cooker are condensed in a contact condenser. If an air dryer
is used, the vented drying air is passed first through a spray scrubber
before being vented to the atmosphere. The odorous effluent from such a
plant will consist mainly of vented gases and odoriferous liquids.
There are two main sources of odorants in animal rendering
plants and these are discussed briefly below:
1. Raw materials in transit and in storage: This source can emit
powerful odorants due to the natural and bacterial decomposi-
tion of tissue beginning with the death of the animal. Such
odors increase rapidly in intensity with time. To minimize
such odors, the handling time of the animal material is usually
kept to a minimum; however, it is sometimes difficult to avoid
putrefaction and enzymatic decomposition of these materials,
A variety of odorant materials may be formed in these biologi-
cal processes including hydrogen sulfide, volatile amines
such as methyl and ethyl amines, putrescine, cadaverine, and
skatole.
2. Odors arising from processing equipment: The equipment in-
volved consists mostly of boilers, dryers, blood spray dryers,
crackling bins, rendering kettles, mixers, holding tanks,
storage tanks, incinerators, and catch basins. The cooking
process is the main part of the rendering operation in which the
proteinaceous material is decomposed at a temperature exceeding
200°F. The effluent from the cooking process contains mostly
steam driven from the animal tissue, along with considerable
amount of many odorous compounds such as amines, fatty acids,
aldehydes, etc. The gases from the cooker are usually condensed
(95% condensable) and the remaining odorous uncondensable gases
are vented to the atmosphere or passed through an afterburner.
In some plants, an air dryer"is used to further concentrate the
solids, and the large volumes of air used and emitted can then
add to the odor problem. Typical levels of air are 10,000 CFM
per dryer. Attempts to clean up the exhaust air by condensation
or water scrubbing do not appreciably reduce the amount of
odorants contained in this air. Most plants do not incinerate
the dryer gas effluent.
Odor emissions from typical rendering plants have been identified
as to their sources and types of compounds. Odor concentrations and
emission rates have been determined by several workers (37^381, and are sum-?
marized in Table 4. It is evident from these data that there are wide
variations in odorants produced from similar equipment. It may be noted
there are also some differences in the types of compounds emitted, e.g.,
the mercaptans and sulfides are found mainly in the processing of feathers.
-------
Table 4
Odorants and Concentrations Emitted from Rendering Plants
Operations
Dry Cooking
Blood Cooking
Feather Cooking
& Drier
Source of Air Pollution
Noncondensibles in vapor
Vapor leaks from cooker
Dumping of hot fats
Noncondensibles in vapor
Vapor leaks from cooker
Product dumping
Product drying
Loading docks
Compound
Classes
Amines
AIdehydes
Fats
Fatty Acids
Same as
above
Aldehydes
Amines
Me reaptans
Sulfides
Fatty Acids
Fats
Odor Concentration
Odor Units/SCF^ '
Typical
Range Average
5000 to 50,000
500,000
10,000 to 100,000
1 million
600 to
25 ,-000
2,000
Exhaust Odor Erais-
Products, sion Rate
SCF/Ton Odor Unit/Ton
of Feed of Feed
20,000
38,000
77,000
1000 x
3800 x 10
153 x 10'
(1) Odor Unit
Odor Unit -
No. of volumes of odor free air required to dilute one volume of odorous air to the
minimum identifiable odor (MIO) level.
Odor Free Air Volume
MIO
-------
- 34 -
This is a somewhat oversimplified tabulation of the compounds released from
rendering plants,and actually the odorant materials are an extremely com-
plex mixture of organic compounds containing both odorous and nonodorous
components; however, many of the odorous compounds are obnoxious even at
very low concentrations.
Many efforts have been made over the years to identify the
odorous components in animal tissue as well as those emitted from render-
ing plants. Ronald (39) identified H2S, NH3, di- and triethylamine, and C02
in the condensate from dry rendering of flesh by wet chemical methods prior
to the advent of GC techniques. Chromatographic techniques were used in
1957 by Wood and Bender (40) to identify components extracted from ox muscle.
These workers separated the protein from the extract and identified 27
different materials by paper chromatography. Most recent work has con-
centrated on the identification of components by a variety of gas chroma-
tographic techniques. Studies at the IIT Research Institute (60) have shown
that decomposition of meat samples in the laboratory closely approximates the
odorant materials emitted from rendering plants. A number of the organic
components released have been identified by GC and mass spectroscopy and
characterized by odor, in addition to determining their odor threshold
level. The Kovats Index System was used to characterize their GC behavior.
Table 5 summarizes the major components identified and indicates the odor
threshold level and other pertinent information. The materials identified
in Table 5 are the more volatile emissions from rendering plants and these
are believed to be the most important in determining odor.. A number of
other less volatile materials have been separated and many of them have
been identified by similar analyses. These latter compounds consist mainly
of higher alcohols, aldehydes and acids; however, it is anticipated that
these heavier materials will make a smaller intrinsic contribution to odor
emissions, and that they would generally be trapped in the various con-
densers and scrubbing systems in the plant.
3.3.3 Methods of Measurement
As indicated in the above review, the volatile aldehydes and
organic acids appear to be major components in most AWR odorant emissions.
In plants where feathers, fish or decomposed materials are processed,
amines, mercaptans and I^S may make a significant contribution to odorant
emissions. For these latter compounds, automated analytical techniques
developed for the Kraft Mill or petroleum industries may be used. However,
there are no instruments available for automated measurement of aldehydes
or organic acids and these need to be developed.
-------
Table 5
Characterization and Identification of Major Odor Compounds
Commonly Found in Rendering Plant Emissions (60)
Kovats
Index
889
925
969
989
1046
1078
Concentration Range
(Expressed in Peak Area %
from GC Analysis) Odor Note
0.34
0.22
0.01
1.19
0.06
1.41
- 23.60
- 36.62
- 2.21
- 55.19
- 2.32
- 46.00
Aldehydic
Rancid
Butter
Aldehydic
Butter
Aldehydic
Odor Threshold
Identity ng/cc
n-Butanal
3-Methyl Propanal
2,3 Butane dione
n-Pentanal
Probably 2,3-Pentanedione
n-Hexanal
2,000
--
•» w
3,000
~
—
u>
Ui
-------
- 36 -
A wide variety of analytical research methods have been used
to determine the nature and composition of AWR odorant emissions. At
present, odor panels are the most widely used means of measuring these
objectionable odorants in the field. Generally, analytical techniques
are applied to odorous materials after they have been separated and
concentrated from the ambient air. Wet chemical methods, instrumental
methods and combinations of these techniques have been used and are
summarized below.
3.3.3.1 Odor Panels
While odor panels are used mainly to determine whether there is
an objectionable odor, they may also be used to determine qualitative and
semi-quantitative concentrations of odorants in the atmosphere. Trained
odor panels can detect certain specific types of odorants and may also
determine threshhold levels of odor with surprising accuracy. Examples of
the usefulness of odor panels in this regard have been given by Hemeon (42) .
This technique and others described by Sullivan (43) are generally based
on a dilution technique in which the original sample is diluted until it
can just be detected by the human evaluator. This vapor dilution technique
can be a static method, a continuous method,or a volatilization technique.
A number of instruments have been developed to assist in using these techniques
for both laboratory and field evaluation. The odor panel approach is excluded *
by definition in the present review.
3.3.3.2 Wet Chemical Methods
Aldehydes in air may be determined directly by a number of
colorimetric techniques and titration methods which are. suitable for
automated wet chemistry. These are generally for rather specific and
usually low molecular weight aldehydes, and with a number of these
methods, ketones also interfere. Methods which have been used are given
below:
1. MBTH (3-methyl-2-benzothiazolonehydrazone) solution in
sulfuric acid produces a blue cationlc dye that can be
measured at 628 n}ti(44). The sensitivity of this method
is 2 ppb.
2. A modified Schiff procedure using rosaniline and dichloro
sulfitomercurate may be used for low molecular weight
aldehydes with a reported sensitivity of .01 ppm (48)
3. NaHSO^ is used as a standard method (48) for the determina-
tion of low molecular weight aldehydes. The bisulfite
solution is adjusted to a pH of 9.6 + 1 with Na2S03 or
acetic acid as required which decomposes the bisulfite ion
equivalent to the aldehydes present in the sample. The
liberated bisulfite is then titrated with standard iodine.
The sensitivity of this method is about 1 ppm, and interfer-
ing compounds are methyl ketones.
-------
- 37 -
4. Formaldehyde may be determined using chromotropic acid or
the modified Schiff method and both give a sensitivity
of about .01 ppm. Polarographic methods have also been
evaluated but need further study
5. Acrolein forms a specific color compound with 4-hexyl-
resorcinol in ethanoltrichloroacetic acid solution to
yield a blue color product which can be measured spectro-
photometrically at 605 m/j. The sensitivity of this method
is about .005 ppm (44) .
Several methods have been developed for the direct determination
of organic acids which are . c generally applicable to acetic acid and
other specific low molecular weight organic acids. In one of these methods,
the acid is collected in a dilute solution of NaOH (57«) in an ice bath (48) .
The acid is then liberated with concentrated H2S04 to a pH of 2 to 3 and
extracted by refluxing with ether for 8 hours. The resultant extract is
then titrated with .IN NaOH. A second method is a color indicator method
based on Fleisher methyl purple which has been developed by Miller and
co-workers (47) . This is a sensitive method of detecting acetic acids
using a collection medium composed of 1:1 glycerol:water solution
containing a small amount of Dow Corning Antifoam A. This solution, con-
taining the indicator, is adjusted to a pH of about 6 and a color change
from Kelly green to purple occurs over a pH of about 1. Thus, by measur-
ing the volume of air required to change this color, it is possible to
calculate the concentration of acetic acid in air directly.
A method for the determination of ammonia and ammonium com-
pounds has been developed by California workers (fr.U) for use where their
concentration is generally very low. A series of impingers containing
water and 5% HC1 solution cooled with an ice bath is used for collections
of the nitrogen compounds. The solutions are then analyzed by either the
Kjeldahl method, or for more sensitive determinations, by the Nessler color
test method.
3.3.3.3 Instrument Methods
A few instrumental methods have been used for the direct
analysis of odorous materials including AWR emissions, but a preliminary
separation is usually required. Gas chromatographic techniques have
proven to be well suited for separation prior to the analysis of complex
mixed odorants. Such separations have been combined with various types
of detection equipment to differentiate and identify in detail the major
components of effluent gases. A brief review of methods used and their
suitability for analysis of rendering plant emissions follows:
-------
- 38 -
3.3.3.4 Spectroscopy
UV spectrophotometers are useful mainly for analysis of aromatic
compounds and since these are not indicated to be of major importance in
rendering plant emissions, these techniques may not be appropriate for
direct analysis. However, UV may be useful for the determination of
aromatic derivatives of odorant compounds, such as the DNPH derivatives
of aldehydes, either as a group or as individual compounds.
Infrared spectrometers have been used for both qualitative
and quantitative analysis of odorous emissions. IR techniques are often
used to complement the mass spectrometer, since the latter can differ-
entiate accurately between homologous series and structural isomers, but
it cannot distinguish geometrical isomers and identify functional groups,
which is often required. This latter capability is readily attainable
with IR spectrometers . Trief f and co-workers (58) tried to determine
aldehyde concentrations and other organics from rendering plant emissions
directly using the IR Spectrophotometer. However, they found that the
concentration of gases was too low to be detected directly by this in-
strument . Many colorimetric methods are available to identify aldehydes
as a group, and also specific aldehydes and these may be separately
determined using IR detectors. A good summary of the capability of
such methods is shown in Table 6 from the work of Stahl
The mass spectrometer is a powerful analytical tool which can
give a positive identification of many different types of compounds.
However, this instrument cannot analyze complex mixtures. Thus, odorous
materials, such as emissions from rendering plants, must be separated into
fairly simple mixtures of components before being subjected to analysis
on a mass spectrometer. This instrument is also very big and expensive
and is thus most suitable for research studies. An entirely new principle
which may be useful with polar compounds including many odorants is "drift
mass spectroscopy." This is a laboratory development in which, an ion (H+)
is reacted with the molecules and a detector then measures the shift of
the protonated species in an electric field.
In view of the requirements of the mass spectrometer, it is best
used in combination with some separation technique such as a chemical separa-
tion by compound type or a GC separation technique.
3.3.3.5 Gas Chromatographv
t
Many workers have evaluated the use of GC columns with and without
additional detectors for the analysis of odorant materials In air (45 . 46) .
Several detailed studies have also been made on odorants from rendering
plants. These techniques have been outlined briefly below with comments
on their limitations.
-------
- 39 -
Table 6
SUMMARY OF QUALITATIVE COLORIMETR1C DETERMINATION METHODS
1 •
Reaqent
Indole
Fuchsin (Schiff method)
4-Phenylazo-phenyl-
hydrazine sulfonic acid
2-Hydraz ino-benzothiazole
4- p-nitrobenzenediazoniunt
fluoborate
2-Hydraz ino-benzothiazole
(HBT)
3-Methyl-2-benzothiazolone
hydra zo n e ( MBTH )
(J-acid) 6-amino-l-
naphthol-3-sulfonic acid
Color
Orange to red
Violet to blue
Red to blue
Blue to green
Blue
Blue
Blue
Limits of Identification
in Microeratns
Aldehydes
~0.05-1
~1-30
0.2-0.4
0.2-200
0.01-3.0
0.1-80
0.01-11
Formaldehyde
0.2
1
0.25
0.2
0.01
0.1
0.03
Aero le in
0.2
0.3
-------
- 40 -
The advantages of gas chromatography for the detection of
odorants In the atmosphere was recognized in 1958 (49), and subsequent
experiments by Williams identified fifty-eight atmospheric pollutants
by this procedure (50). His list of compounds identified includes most
of those found in AWR emissions. Williams used a short stainless steel
column containing Chromosorb P partially deactivated with di-ni-butyl-
phthalate cooled to -80°C to collect the samples. The gas was then
desorbed from the column, dried, and injected into a Perkin-Elmer Model
154-D gas chromatograph fitted with flame ionization and electron capture
detectors. Williams also tested a specially treated molecular sieve
column heated to 150°C, or one containing sulfuric acid on an inert sub-
strate, as a means of further separating air pollutants before analysis
on the GC columns. Using various combinations of drying agents, sulfuric
acid, and molecular sieves, he was able to separate and identify hydro-
carbons, aldehydes, alcohols, organic acids, sulfides, disulfides, organic
nitro compounds, nitriles, thiols, ketones, and halogenated compounds in
the atmospheric samples tested.
Low molecular weight aldehydes have been studied in industrial
effluents by Levaggi and Feldstein (51) and in automotive exhaust by
Prater (52). Levaggi employed a Varian 1200 gas chromatography with a
hydrogen flame detector and a stainless steel column packed with 15%
Carbowax 20M on Chromosorb, followed by a 5" x 1/8" stainless steel column
containing UCON-dinonylphthalate on fire brick. This equipment enabled
them to detect C^ and higher aldehydes. Prater suggested the use of GC
equipment with a dual flame ionization detector and an OD-17 column for
analysis of the aldehydes collected in 2,4-DNPH. Using this equipment,
he was able to detect aldehydes from formaldehyde up to paratolualdehyde
in concentrations ranging from .03 to 5 ppm.
Several workers have used dual column GC techniques on air pollu-
tants and found they were not sensitive enough to identify all the odorant
materials which could be detected by human sensors. A study of air pollu-
tion from animal wastes by Burnett (53) u»ed a Varian Aerograph Model
1520B equipped with dual flame ionization detectors. He was able to
identify 8 or 9 compounds with good certainty but some odorous materials
detected by human evaluators did not show up as peaks on the GC plots.
Analysis of odorant materials in the atmosphere by Okita (54) identified
a number of amines, mercaptans and organic sulfides, but even with the
use of the GC with flame ionization detectors, he found the equipment was
not sensitive enough and he felt there was a need for electron capture and
electroconductivity detectors.
Dravnieks (55) has shown that routine GC techniques with to* i
stage detectors are sensitive enough to detect nanogram (10~9 gm) amounts
of individual substances. This amounts to 6 x 101 molecules for a typical
compound having a molecular weight of 100. Assuming that the limit of
detection of odorous materials is in the range of 10 molecules per cubic
centimeter of air, it is only necessary to concentrate the odorant materials
in air by a factor of 6,000. Such a concentration factor is readily obtain-
able using organics to absorb vapors, when the temperature is changed from
-------
- 41 -
ambient to about 200-250°C. Dravnieks has identified discriminators
which can be applied in gas chromatography for polar and non-polar
separations in animal-source materials. These include optically
active dipeptides for the dispersion of optical isoners, cobalt
stearate for the strong dispersion of primary and secondary amines by
complex formation, sorbitol or diglycerol for the hydrogen bonding of
polar groups, and Emulphor 0 for the dispersion of polar functional
groups or double bonds with respect to paraffinic hydrocarbons.
The complexity of odorant emissions from rendering plants and
other sources has led researchers to methods of further discriminating
the peaks obtained using GC columns and various detection techniques.
One cf the most widely used research techniques for the comparative
indexing of unknowns is the Kovats Index Sys tern (56) . This technique
combined with a split column GC provided with a so-called "sniff port"
has been used by Dravnieks and Trief f (57, 5_8 respectively). Using these
combined techniques it is possible to detect specific compounds as well
as odorant types and relate the peaks noted from the GC analysis to odor
panel response.
The most complete qualitative analysis which has been conducted
to date on rendering plant emissions combines GC techniques with mass
spectrometry (59). This involves either single or double column GC
equipment withThe effluent then being put through a mass spectrometer.
Using these techniques, Dravnieks, Burgwald (59, 60) and co-workers have
been able to identify a number of compounds by chemical type. In this
work, it was necessary to identify knowns by similar techniques and relate
them to the unknown emissions from the rendering plant. An indication or
positive identification of 30 different compounds was obtained. Such
techniques, involving the mass spectrometer, are excellent for detailed
identification of components but are not practical for control purposes.
Use of simpler GC columns and the detection equipment discussed
above shows promise for identifying specific odorant compounds or types from
rendering plant emissions and other odorants in the atmosphere. Such a
type analysis may be satisfactory for monitoring purposes, where the odorant
originates from a fairly uniform source. It must be recognized, however,
that in the general case a type measurement for total aldehydes, for
example, or total organic sulfur compounds, does not necessarily relate
to the concentrations of the individual compounds present as principal
odorants.
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- 42 -
4. SPECIFIC INSTRUMENTATION FOR S ODORANTS
This section contains brief summaries of the characteristics
of specific types of instruments which are considered as applicable to
the field measurement of sulfur compounds (and other odorants), and
literature sources for additional information. It is divided into three
sections; 1) preferred commercial instruments, which can measure several
(or all) types of sulfur odorants; 2) alternate instruments, commercially
available, which can measure at least H2? , the principal S odorant; and
3) potential instrumental approaches, which need to be developed further
before they can be properly evaluated. The capabilities of the instruments
described can be summarized briefly as follows:
4.1 Preferred Commerical H2S + RSH ^and others)
4.2 Commercial Alternate I^S (and others)
4.3 Potential R/D required
Information regarding the individual techniques discussed
in each of these sections is organized into a brief review of the operating
principle, commercially available equipment for this specific use, biblio-
graphic references (for operating principle, applications, data on uses or
comparisons, and specific instrument descriptions), stated advantages and
disadvantages, and conclusions or recommendations. The statements of advantage
and disadvantages listed are taken from the literature, with some editing, for
the purpose of this interim report. It must be recognized that such statements
are subject to change on evaluation, and not always mutually consistent.
Pertinent extracts of the manufacturer's operating, maintenance
or application manuals are appended for the commercially available instruments
in Section 4.1, to include statements of operating performance. The originals
of these manuals should be consulted for details.
This section of the interim report is a guide to source material
to be used in Contract 68-02-0219, for the "Evaluation of Measurement Methods
and Instrumentation for Adorous Compounds in Stationary Sources."
It is intended as a survey and not as a definitive review. The reader who is
interested in critical reviews of various portions of the background informatlo
available will find numerous publications of interest. Good analytical reviews
which cover the literature in detail on specific topics in the measurement of
odorous (sulfur) compounds have been published in 1943 by Thomas (36) , in
1952 by Bialkowsky (146), in 1963 by Kenline (26), in 1967 by Walther (91) >
in 1968 by Blosser (7), Thoen (8), Adams (9), and Leithe (147), in 1970 by
Hendrickson (6), Tokiwa (35), and Stevens (73), and in 1971 by Dravnieks (59)
and Austin (62) .
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- 43 -
noULOMETRIC TITRATION (S02> H2S, Mercaptans, Halogens and Nitrogen Compounds)
Principle of Operation
Four different types of coulometric (amperometric) units are
available namely bromine, iodine, silver and hydrogen cells. While the
principles are similar in each case, the chemistry and methods of analysis
are somewhat different for each type, as discussed below. The hydrogen cell
is not widely used in the industries of concern, and is not discussed here
in detail.
Bromine Cells (For SC^, H^S, Mercaptans)
A constant level of free bromine is generated by electrolysis
from a solution of KBr. Reaction with SCv decreases the free halogen
present and is detected by bromine sensors which signal the electrolysis
current to increase. The additional current required to maintain the
original bromine level is proportional to the S02 concentration according
to the following reactions:
2Br" - 2e
Bromine units respond to SO^, H«S, mercaptans (35) and all oxidizable
organic sulfides. If desired, EJS and other reduced sulfides can be
removed by passing the inlet gas over a heated (120°C) silver gauge, leaving
S02 to be measured alone, or S02 can be scrubbed out leaving only the sulfides.
Iodine Cells (S02, HjS and Mercaptans)
A constant level of free iodine is generated by electrolysis
from a solution of KI or Nal. Reaction with oxidizable sulfur compounds
reduces the amount of free iodine present. This reduction is detected by
polarizing electrodes. The titrant I-j" consumed is proportional to the
sulfur content of the sample as shown by the following reactions. All
sulfur compounds in the sample are first oxidized in a combustion tube, and
swept into the tit rat ion cell.
2H+
2e
Sodium azide (NaN3) is generally added to the iodide electrolyte
solution to minimize possible interference from chlorine and nitrogen con-
taining compounds in the sample stream.
-------
- 44 -
Silver Cell (H S, Mercaptans and Chlorine)
The concentration of silver ions is kept constant by electrolysis
from a solution of silver iodide. Sulfide or chloride present in the
sample reacts with the silver ions which are coulometrically replaced. The
total current required to replace the silver ions is a measure of the
sulfur or chloride present in the injected sample. Since this cell reacts
only with reduced sulfur and/or chloride the unit can be used to measure
reduced sulfur alone.
If oxidized compounds are present, total sulfur can be determined
by a preliminary pyrolysis in a reducing atmosphere to convert all sulfur
compounds to H~S. In this mode the hydrogen used in the reduction reaction
is humidified, to reduce coke formation and the formation of small amounts
of cyanide from any nitrogen compounds in the sample. To stabilize the
cell reaction, the electrolyte is saturated with a gas mixture of 10% NH-
in nitrogen.
This cell can also be operated to measure reduced sulfur and
chloride independently. To accomplish this a titration endpoint or "bias"
potential is chosen for S determination such that the chlorides will not
consume silver ions. For determination of chloride a higher "bias" potential
is used. Under these conditions neither material interferes with the other in
desired analysis.
Commercial Manufacturers
The Barton Titrator is a continuous-flow bromine microcoulometer
which can accept samples for direct measurement of lUS and TRS at emission
level concentrations. It is widely used in the pulp and paper industry.
The Philip S0_ Monitor can be used for continuous measurements of H^S and
RSH (but not other sulfides) at ambient concentrations. Commercial Dohrmann
microcoulometers are available as either bromine, iodine, or silver ion
cells. They are primarily research laboratory tools, for the measurement
of small discrete samples such as the fractions produced by gas chromatography.
Suppliers of such instruments are as follows:
Bromine Cells
ITT Barton Models 286 and 400
Dohrmann Models C-200 + 250B
Philips Electronic Model PW 9700
Iodine Cells
Atlas Electric Devices Model L 1202
Beckman Inst. Co. Model 906
Dohrmann Cell T-300-P
Silver Cell
Dohrmann Cell T-400-S
Hartmann + Braun A.G., Frankfurt-am-Main, GFR. Picoflux
-------
- 45 -
References
Barton Model 286
1. Principle of Operation: 61, 62, 63, £, 64, 65, 35, 66, 6J7
2. Applications: 61, 62, 63, 8_, 64, 65, 68, 66, 67, j>9_
3. Data: 6.L, 62_, 63., IB, 64_, 65_, 66_, £7, 69.
4. Specific Instrument Description: 61, 62, 63, 8^, 65, 66, 61_
Bromine Cells
1. Principle of Operation: 70_, 7^, 72_, 73>, 35_, 22_, 7^, 75, 66_,
76, ZZ» 78^
2. Applications: 70, 71., 72_, 7^, 22_, T±, J5, 66_, 76, 77^, J8, 79.
3. Data: 70, 71, 72_, 73_, 22_, 74., 75_, 66, 76, 77., 7^
4. Specific Instrument Description: 70^, 71, 72_, 22_, J5_, 66^
Iodine Cells
1. Principle of Operation: 71, 35. 75, 66, 1J.
2. Applications: 71. 75, 66, Ii8
3. Specific Instrument Description: 71, 75, 66. _18
Silver Cells
1. Principle of Operation: J30
2. Applications: 80
3. Data: 80
4. Specific Instrxanent Description: 80
-------
- 46 -
Discussion
Advantages
Barton Model 286
1. Reliable with a minimum of maintenance (weekly).
2. Gives rapid, continuous, direct measurement for SQ^.
3. Sensitivity to SO- in the range of 0.05 to 1.0 ppm (64)
ranges from + 0.05 to + 0.24 ppm respectively.
4. Sensitivity to ILS and mercaptans is 0.02 ppm (64_).
5. Well suited for long sample lines with monitor at a distance
from the source.
Others (Dohrmann, Philips)
1. Good sensitivity to H2? (10 ppb) and SO, (50 ppb): (Dohrmann, 22)
(2 ppfa) and(4 ppb): (Philips)
2. Rapid response time.
3. Relatively trouble free: Philips has internal (automatic)
7ero and calibration.
4. Accurate.
5. Interference from other gases in the ambient air generally minor.
6. Applicable to both liquid and gases (Dohrmann).
7. Suitable for determination of oxidized and reduced sulfur
compounds and compounds containing chlorine and nitrogen at
levels ranging from 0.1 ppm to several percent.
Disadvantages
Barton Model 286^
1. Minimum sensitivity 30 ppb (H S) (66).
2. When H_S cone, in gas is above 100 ppm over extended periods,
some elemental sulfur is deposited and may cause a sluggish
response (62).
3. Chlorine compounds Interfere.
Others
1. Dohrmann requires daily calibration by skilled technicians,
sensitive to temperature changes.
2. lodometric cells do not respond to organic sulfides or disulfides,
-------
3. Reducing compounds such as 0«, unsaturated compounds and NO
interfere in the iodometric cells, however, these may be
removed with appropriate absorbers (35).
4. Philips has limited range above ambient levels.
Conclusions
The Barton titrator is well suited for automatic monitoring of
S02, ^S, and total reduced sulfides over a fairly wide range of concentra-
tions. Interfering compounds can generally be eliminated. Maintenance
problems which can be troublesome in the field are due largely to the dif-
ficulties involved in providing a suitable sample stream.
Other coulometric titrators generally are just as sensitive as the
Barton and the technique can be adapted to monitoring a variety of compounds
including sulfides, chloride, phosphorous and nitrogen compounds. One of
the major drawbacks with the microcoulometer is the frequent (daily) calibra-
tion required, and the high degree of technical skills needed to get optimum
results.
Recomroendat ions
Evaluate the Barton instrument at plant sites for monitoring of
refinery as well as kraft mill emissions.
Evaluate the microcoulometer further as a possible referee method.
-------
- 48 -
BARTON
Model 400 Titrator
Flow Diagram
Titration Cell
General Specifications
Sensitivity
Hydrogen Sulfide 0.02 ppm
Mercaptans 0.02 ppm
Organic Sulfides 0.05 ppm
Sulfur Dioxide 0.05 ppm
Range 0-1000 H2S ppm (7 ranges)
Model 400 Outputs ... 0-100 ua, 0-10 mv or 0-100 mv
Function Controls On, Off, Total Sulfur, Total
Minus SO2, and Automatic Cycling
Power 115 v z-c, 60 Hz, less than 45 watts
Power Connection 6-feet, 3-conductor cable,
3-prong plug
Sample Flow Rate 200-600 ml per minu
(250 ml nominal recommende
Inlet Connections V4-inch tubing fittir
Outlet Connections V4- inch tubing fitth
Titration Module
Height 10 inch
Width 9 inch
Depth 22 inch
Recording Controller Module
Height , 141/2 inch
w'dth 87/e inct-
Depth 13y8 inct.
-------
DOHRMANN MICROCOULOMETER
JT ^
Figure 3. Comparison of titration celts
Oxidativc cell
(T-300-P) Iodine cell
Electrolyte:
0.05% potassium iodide
0.50% acetic odd
0.06% sodium azide
Sensor: Pt°
Reference:
Ptc—Triiodide Saturated
Anode: Pt°
Cathode: Pt°
Bias Voltage: 160 mV
Titration:
21° + SO, + H,O -*
SO, + 21- + 2H+
Generation: 2I~ -* 21° -f 2e~
Rcductive cell
(T-400-S) Silver cell
Electrolyte:
0.3M ammonium hydroxide
Q.1M sodium acetate
Sensor: Ag°
Reference:
H£°/HgO Saturated
Anode: Ag°
Cathode: Pt°
Bias Voltage: 110 mV
Titration:
2Ag* + S«- -* Ag,S
Generation:
Ag° -^ Ag^ + e~
Au^illary gas flow:
10% NH, in Ni at 40 cc/min
-------
5.3 Standardization
- 50 -
Oxidaiive cell Dohrmann
Iodine cell Application Note MC301
5.3.1 Not all of the sulfur in the samples comes through the furnace as titratable S02. In the strongly
oxidative conditions of the pyrolysis tube, some of the sulfur is also converted to S03 which does not react
with the titrant. Accordingly, system recovery should be verified every four hours (more often in critical
applications) by using the standards supplied with the MCTS-30 System or in the CEM-30 Chemical Kit
System recovery is typically 85% ± 10%.
7 RANGE AND PRECISION
T' following specifications are based upon an injected sample volume of 5 - 8 n\ at concentrations greater than
2 sm and 30 - 40 (J.\ at concentrations of 2 ppm or less. The amount of analyte per injection should not exceed
10,0( ng and the sample injection rate should not exceed 1 /ul/sec.
The following precision data is typical:
C ppm PRECISION (± ppm) RELATIVE PRECISION (± %)
0.1 0.05 50.0
0.5 0.07 14.0
1.0 0.10 10.0
10.0 0.50 5.0
100.0 3.20 3.2
500 and greater - 3.0
Reductive cell Application Note MC401
5.3 Standardization Silver cell
5.3.1 System recovery should be verified every four hours (more often in critical applications) by using the
standards supplied with the MCTS-40 System or in the CEM-40 Chemical Kit. System recovery is typically
100% ± 5%.
7 RANGE AND PRECISION
The following specifications are based upon an injected sample volume of 5 • 8 jul. The amount of analyte per in-
jection should not exceed 10,000 ng and the sample injection rate should not exceed 0.2/^l/sec. The following pre-
cision data is typical:
C ppm PRECISION (± ppm) RELATIVE PRECISION (±%)
1 0.5 50.0
10 0.8 8.0
100 3.5 3.5
500 and greater - 3.0
Above 10,000 ng of sulfur (eg. 1 JLI! of 10,000 ppm S) titration time becomes excessive which in turn degrades pre-
cision. Concentrations greater than 10,000 ppm can be measured by diluting the sample with a suitable solvent
C 'utions of up to 1000/1 will not significantly degrade the precision specifications cited above. Dilutions to the
100 ppm level provides a good compromise between analysis speed and precision as well as ease of sample handling
8 ACCURACY
System recovery is 100% ± 5% when the analyte concentration is calculated from instrumental data using Faraday's
Law. System accuracy will be equal to the sum of system precision and recovery. Accuracy can be significantly
improved when sample values are compared to those obtained with analyte standards. Accuracy cannot be better
than precision, however.
-------
- 51 -
PHILIPS SOg MONITOR, ~PW 9700
DESCRIPTION OF BLOCK DIAGRAM
The air is introduced through the sampler unit comprising two filters. The air is then lead
through a selectivity filter to the measuring cell. The measuring cell contains an aqueous solution
of KBr; Br? and H2SO.. The SO2 in the air reacts with free bromine in this measuring solution.
The bromine concentration is converted into a redox potential which is compared with a constant
voltage.
The difference between both voltages controls a current through two generating electrodes via
an amplifier. When the bromine concentration is decreased from a certain value, this system
regenerates bromine. This coulometric titration controls the bromine concentration in the
measuring solution at a constant level.
SAMPLER UNIT
l>w J71G
6LOCKDIAGRAM CHEMICAL UNIT
Fig. 2.1 Block diagram SO2 monitor (chemical part)
\
The current required to maintain this constant balance is directly proportional to the quantity
of bromine used and consequently to the quantity of SO2 lead through the measuring cell.
As a result of evaporation, some bromine will leave the cell, thus causing a small zero current.
Parts have been built into the monitor for measuring the size of this zero current automatically.
A resistance is fitted in series with the generating electrodes. This resistor converts the
generating current into the input voltage of the output amplifier.
-------
2. Mgasuring ranee,
3 3 - 52 -
3 mg/m SO (1.15 ppm SO2/nT air).
3 3
Other measuring ranges between 1.5 mg/m and 10 mg/m can be realised.
q
In measuring ranges below 0-1,5 mg/m the calibration signal falls out of scale.
0-20 mA into a resistance of 0-300 Q.
3. Response time
Approx. ij minutes (63 % of final value)
Approx. 3 • minutes (95 % of final value).
4. Accuracy (overall, absolute)
Better than 15 % of the measuring signal, Better than 26 pig/m3 SO- (=0, 01 ppm) if the SO0
3
concentrations are smaller than 183 /tg/m (= 0,07 ppm).
Provided calibration is performed once a day, for instance.
5. Reproduclbility
Better than 1 % of the measuring signal.
6. Detection limit
Smaller than 10 (Jg/m SO- (4 p.p.b.)
,tt
7. Size of zero current
3
Corresponding to a measuring signal smaller than 100 ngfm SO^
8. Drift of the zero signal
Smaller than 26 ^g/m3 SO0 (=0, 01 ppm) a day, non cumulative.
i
9. Influence of 10 %m.iins voltage variation
Negligible.
10. Climatologies! inflviRnce
Negligible.
11. Selectivity
The interference (I ), due to a substance X, is expressed by the relation I ^
x 100 %, in
which S = measuring signal due to 0,05 ppm of substance X and S = measuring signnl due to
0, 05 ppm SO. .
X Selectivity
N'02 < 5 %
O., < 1%
H2S < ] %
Methyl-mere aptan SB 180 %
Klhylene < 2 %
C12 < 2 %
NO < 1 %
Aldehydes < ] %
Henzene, chloroform < j %
-------
- 53 -
GAS CHROMATOGRAFHY + VARIOUS DETECTORS (SC>2, l^S, RSH, RjS, RSSR)
Gas samples may be separated in a chromatographic column and
the eluted components identified by a variety of detection methods. The
volatile sample is transported through the chromatographic column by an
inert gas (N2> He, A, etc.) and separated by preferential adsorption on
a finely dispersed column packing. The adsorbed materials are then removed
with an inert gas and the various components, which desorb at different
rates, may be separately identified and measured as they issue in the
carrier gas.
Many different types of column packing materials have been
evaluated (95., 81, T^, 94_, 86., 10., 74, 75_, 96,, 87, 97., 98, 89_, 90) but two
appear most promising for the separation of sulfur compounds: Triton X-305
coated on Chromosorb (99) and (100) polyphenylether coated on finely
devided Teflon (101). For the separation of amines, aldehydes, ketones,
alcohols and mixtures of these components, two GC columns in series contain-
ing Chromosorb 102 coated with Emulphor 0 in the first column and, either
sorbitol or diglycerol is the second column, were found to be efficient
by Dravnieks (69).
Following separation of the test sample into its individual
components or simpler mixtures by GC, these materials may then be
identified by a variety of detector techniques, such as those listed below.
Colorimetric
(Micro) Coulometric (M)CD
Electron Capture (EC)
Flame lonization (FID)
Flame Photometric (FPD)
Infrared Spectroscopy
Thermal Conductivity (TCD)
Ultraviolet Spectroscopy
Most of the above techniques are discussed elsewhere in this
report and only the FPD, FID, TC and EC detectors will be covered here.
FPD is a preferred method, highly sensitive and specific for sulfur in any
volatile form. FID responds to any organic sulfide, but not to S02 or l^S.
Thermal conductivity and electron capture are older methods, less sensitive
to sulfur and of limited use at present.
rtommercial Equipment
Gas chromatographic columns, packings, coating agents for various
packings and detectors are available from a wide variety of suppliers and a
complete Listing of all is beyond the scope of this report. Commercial
units combining GC/FPD which should be suitable for use in kraft pulp
mills or petroleum refineries are offered by Bendix, Tracor, and Varian
Aerograph. While these components are also available for monitoring
specific odorants in emissions from animal waste rendering or other sources,
no combinations have been offered or recommended as a package unit for this
purpose.
-------
- 54 -
References
GC + FPD
1. Principle of Operation: 81^, 82. J73, 8_3, 74_, 66_
2. Applications: 81, 82_, 73» il' 74, 84, 85_
3. Data: jft, 82, 13, J33, 74_, 85.
4. Specific Instrument Descriptions: JU, 82_, 73. 83, 74, 84_
GC + (M)CD
GC + TCD
GC + FID
GC + EC
1. Principle of Operation: 61., 71, 17, 86, 22_, 75^, 74_, 84_
2. Applications: jtt, 71, 17, 86, 64_, 22_, 75, 74, 84, 90
3. Data: 6^L, 71, 17_, 86, 74_, 75_, 90
4. Specific Instrument Descriptions: 61, 71, 17. 86, 74. _75»
84, 90
1. Principle of Operation: 17, 74, 91
2. Applications: 17, 64, 74, jtt
3. Data: _17, 74_, 9^
4. Specific Instrument Descriptions: 17, _74.
1. Principle of Operation: 17, 86, 22, 74
2. Applications: .T7, 86_, 64_, 22^, 92_, _7_i, 75, 93
3. Data: 1.7, &6, 64, 22^, lk_
4. Specific Instrument Descriptions: 17, 86, _74_
1. Principle of Operation: 74
2. Applications: 74, 93.
3. Data: 74
4. Specific Instrument Descriptions: 74
-------
- 55 -
Discussion
Advantage
GC + FPD
1. Capable of detecting S compounds at 2 ppb level (81) .
2. Can detect a wide variety of S compounds such as SC-2,
G1~C3SH> and higher molecular weight sulfides + disulfides (82)
3. Shows potential for use in monitoring (73, 84).
4. Interference from non-sulfur compounds is small (83), except
for carbon oxides or hydrocarbons at concentrations greatly in
excess of total sulfur.
GC + (M)CD
1. Best combination found for kraft pulp mill emissions, but not
completely satisfactory (22).
2. Minimum detection level of 0.05 ppm P02 and 0.02 ppra H^S (75).
3. Equal of similar in sensitivity to GC + EPD (61).
GC + TCP
1. Sensitive to S02, H2S and mercaptans.
GC + FID
1. Method for carbon number analysis in any homologous series.
2. Might be useful at high concentrations for S compounds (74).
3. Combined with a S detector it can be very useful and has high
sensitivity for hydrocarbons.
GC + EC
1. Good sensitivity to compounds containing one or more
functional groups.
2. Can serve as a complementary system with GC + FID.
-------
- 56 -
Disadvantages
GC + FPD
1. Massive amounts of CO, C02 or hydrocarbon interfere.
GC + MCD
GC + TCD
1. Dohrmann type iodine cell not suitable for routine process
analysis (22).
2. Requires standardization of the coulometric cell for each
type of compound eluted (22).
1, Sensitivity for the detection of H2S and CH-SH about 500 ppm
which is not suitable for direct analyses or process gases
(74, 91).
GC + FID
1. Not suitable for sulfur compound in the presence of hydrocarbons
since they are obscured by S free compounds, and the response
does not follow the "carbon number" rule as with aliphatic
hydrocarbons (94, 86, 22).
PC + EC
1. Not suitable for sulfur compounds.
2. Small sample capacity limits usefulness (36) because of
interference caused by ©2 (74).
3. Not sensitive to hydrocarbons.
Conclusions
GC instruments combined with an appropriate detector are extremely
sensitive and discriminating. Such combinations may be used for all known
gas mixtures, to Identify most individual compounds or to identify com-
pounds by type analysis. The most versatile combinations for the kraft and
petroleum Industries are:
1. GC plus flame photometric detectors (FPD).
2. GC plus microcoulometric detectors (M)CD.
The other techniques have some serious drawbacks.
-------
- 57 -
Re commendations
Continue evaluation of GC + FPD and GC + MOD systems for monitoring
emissions from kraft and petroleum industries. Need to evaluate present
initial production instruments for commercial use.
-------
I
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-------
- 59 -
The Bendix Environmental Chromatograph will meet or surpass the
following specifications if properly maintained and the specified operating
parameters are adhered to.
• Ranges: 0. 02 to 0-20 ppm on continuously adjustable attenuator
• Precision: *4% of full scale
• Minimum Detectable Limit: less than . 005 ppm H£S and 0. 01 ppm SC>2
• Noise Level: 0. 5% of full scale
• Zero Drift: Less than tl% per day and 2% per three days with automatic
zero before each component.
• Span Drift: Less than tl% per day and 2% per three days
• Interference Equivalent: Less than 0.01 ppm
• Electrometer: Linearized electrometer corrects the signal to provide output
directly proportional to sulfur concentration
• Linearity: Less than 2% of full scale
e Oven Temperature: Controlled to 0. 5°C
o Cycle Time: Five minutes
« Operational Period: More than three days unattended
e Output Signal: Trend outputs of 0-10 volts or 1-5, 4-20 or 10-50 made for
each component
• Readout: Chromatogram, bargraph and trend
• Power: 115V 60 hz
-------
- 60 -
TAPE SAMPLERS (H2S^
Principle of Operation
The reaction of water soluble compounds of heavy metals such as
Pb(Ac)2, HgCl2 or Cd(OH)2 etc. with H2S results in an insoluble sulfide
precipitate:
Pb(Ac)2 + H2S - > PbS + 2HAc
Cd(OH) + HS - > CdS + 2H0
Filter paper on other appropriate material may be impregnated with Pb(Ac)
or Cd(OH>2 and air drawn through the paper will cause a response to sulfide
compounds. Mercaptans may or may not react. Such papers may be supplied
as a tape for continuous monitoring of sulfide in air.
A number of schemes have been devised to automate tape samplers
and various means are available for determination of the concentration
level. One of the simplest methods is to read the color intensity or
amount of precipitate developed with some sort of spot evaluator (102).
Other methods involve dissolving the precipitate formed on the tape with
reagents such as NItyOH and measuring the intensity of the brown color
developed colorimetrically (102, 103) . The sulfide may also be dissovled
and measured colorimetrically by the methylene blue method (104) . In each
of these cases the sulfide concentration observed is correlated with a
standard ILS curve.
Modifications have been made by various researchers and equip-
ment suppliers to overcome the inherent problems such as light sensitivity
humidity control, and variations in tape response. The limits of detection
range from 0.5 to 100 ppb. Lead acetate detectors have a lower limit of
about 50-60ppb, Cd(OH)2 about 1-3 ppb and the HgCl2 type unit is sensitive
to 0.5 ppb.
Commercial Equipment
No instrument is available which gives a direct output or linear
readout proportional to sulfide concentration. Lead acetate tape samplers
according to several different principles are available.
Houston Atlas 825: continuous readout of exposed trace on moving
tape.
Houston Atlas 855: catalytically hydrogenates all sulfides to
H2S, fed to tape sampler.
RAG 5000: cumulative spot analysis on 5 minute cycle (or
multiples), each spot pre-corrected for tape zero.
Bendix Monocolor (Maihak) : continuous readout on moving tape,
zeroed against light absorbance of
unexposed tape.
-------
- 61 -
Simplified samplers are also available for use in field stations
with provision for separate tape readout in a control laboratory.
Calibration curves are generally provided with each instrument, but these
have been found to be inaccurate by a number of investigators.
References
1. Principle of Operation: ji8, £6_, 105, 103, 104, 106. 101
2. Applications: 88, 66, 105
3. Data: 88, 66, 105
4. Specific Instrument Description: 88, 66, 105
Discussion,
Advantages
1. Low cost.
2. Simple operation and maintenance.
3. Cd(OH)2 and HgCl2 detectors sensitive to very low
concent rat ions.
4. No interference with CH..SH, at lUS to CH-SH ratios
greater than 1.0.
Disadvantages
1. Lead sulfide impregnated tape sensitive to light and fades
with time, other materials such as Cd(OH>2 and Hgd-2 more
stable.
2. Lead sulfide not accurate at concentrations below 50 ppb.
3. Need to control humidity of gas stream.
4. Ozone and S02 cause fading of lead acetate tapes.
C!onclus ions
Tape samplers good for detection of I^S in air above 50 ppb
provided adequate precautions are taken to control humidity of gas and
to minimize fading problems.
Recommendations
Further development needed to fully automate the system and
improve accuracy.
-------
- 62 -
TAPE SAMPLERS
MonocolotMClOOl Maihak AC, Hamburg. (147)
sample cell;
reference cell;
lump;
photocell 1;
photocell 2;
paper tape impregnated with rciigrfnt;
box for papur lapc;
spool head for paper t'tj^;
indicating device.
The instrument operates according to the following principle: A paper tape
impregnated with the reagent (e.g., lead acetate for H2S) is successively Jr;i wn thrc;:^!;
two cells. One of these, the rr-fcrencc ccl!, is fiiicd with pure air, while tlie air sample
passing over the paper is blown into the sample cell. Bolh tells, which are
symmetrically arranged are illuminated by a common lamp. The light reflected from
both lape surfaces is respectively measured by two photocells. The current diflcroiKo
corresponds to the blackening of the paper caused by the foreign matter in the air
sample (e.g., H2S). The tape feed rate is 1 mm/tnin; since the diameter of the sample
cell is 12 mm, the paper is illuminated 12min and a mean value over this period is
measured. The throughput rate of the sample gas (c.g., lOOml/min) can be adjusted
by means of control valves and measured. The lowest measurement range for H2S
is 0-14 ppm.
A similar instrument, the AISI Automatic Smoke Sampler (Research Appliance
Co., Pittsburgh, USA), can also be used for determining H3S when a paper
impregnated with lead acetate is inserted.
Air MM
Revolving spool Motor for spool
Stated accuracy + 15% PS at 0,4 ppm, + 30% at 0.05 ppm,
higher concentrations measured by dynamic dilution.
-------
- 63 -
HOUSTON ATLAS, INC.
The Model 855 Analyzer is comprised of two components:
The PYROLYZER* for sample preparation and conversion of ad liquid hydrocarbons to yases and ai
sulfur compounds into hydrogen sulfide. The Model 825 H2S Analyzer for readout of sulfur content.
GENERAL SPECIFICATIONS
RESPONSE TIME:
RANGES:
LINEARITY:
SUPPLIES:
CONSTRUCTION:
93% in 30 minutes at 2 ppm full scale plus flow tubing resident time. More rapid
response at high sulfur levels.
As specified. 0-2 parts per million to 0-20% by weight sulfur. Normally
continuous reading, peak reading below 50 ppm.
± 3% of scale (+ 3% at 50% FS).
Hydrogen gas (sulfur free) at 1 SCFH required. Lecd acetate sensing tape. 5%
acetic acid solution.
Flow system stainless steel, 1/16 inch tubing. Available in explosion proof model.
RAC Model 5000
OPERATION
Filter paper tape is fed through the sampling nozzle where
air is drawn through tape by an oil-less vacuum pump at
approximately 0,25 cubic feet per minute. Pump rate (1.1
CFH) is controlled and set at 0.25 CFM (15CFH) by a flow
adjust valve.
Filtered exhaust air places slight positive pressure in sam-
pler's front area to prevent any contamination of tape
around sampling spot.
Tape, punched on two inch centers for positive indexing,
is moved automatically by timer which can be pre-set for
any sampling period from 5 minutes to 3 hours 20 minutes
in 5 minute increments. When sampling period ends, tape
is automatically indexed.
Samplers are easily adapted for sampling gases such as
hydrogen sulfide. A prefilter and humidity jar is attached to
air inlet and exhaust gases are passed through a soda and
lime tube to scrub out any hydrogen sulfide that may have
passed through the tape.
Direct reading range: 0.001 to 0.5 ppm
in 1 hour sample (x 12 iri 5 minutes)
higher levels by flow dilution.
Stated accuracy:
+ 15% of scale at 0.4 ppm
+ 30% of scale at 0.05 ppm
; ,-JT*»rt\ ** I*
2^. ~3
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-------
CONDUCTIMETRY
Principle of Operation
The air sample is absorbed in a dilute solution of sulfuric
acid (H2SO^) containing hydrogen peroxide (H202) . Any S02 in the sample
is converted to SO 3 and H2S04 according to the reaction below, thus
increasing the conductivity which is recorded as S02 concentration,
Most conductivity systems are equipped to measure conductance in solutions
between two platinum electrodes. Distilled or deionized water should be
used. Absorption of C02 is prevented and its interference reduced by using
enough I^SO^ to give an equivalent of 2X1Q-5N and enough H202 (3%) to bring
the absorbent to a strength of 3X10~% with respect to peroxide. Instru-
ments are calibrated against primary standards.
Commercial Equipment
Instruments from a number of suppliers are available as listed
below :
Beckman Instruments, Fullerton, Calif.; Models K78 and K1006
Inst. Development Corp; Reston Va. ; Models 903-1, 902-3
Kimoto Electric, Osaka, Japan; Model S-350N
Leeds and Northrup, North Wales, Pa.; Model 7860
Research Appliances
Hartmann-Braun = Intertech, Princeton, N.J.
Wo'sthoff (Mikrogas) - Calibrated Instruments, Ards ley, N.Y. ;
Model U3S
Davis Instruments, Charlottesville, Va.; Model 11-7000
Scott Aviation; Model 7010 RPA
Scientific Industries, Hempstead, N.Y.; Model 67
References
1. Principle of Operation: 63, 73, 35
2, Applications: 6_3, 107, ^73
3. Data: £3_, 107, _7_1
4. Specific Instrument Description: 63
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- 65 -
Discussion
Advantages
1. Very good performance in the range of 0.2 - 4 ppm with a
standard deviation of 0.01 - 0.9 ppm.
2. Specific when SCL is the principal acid gas oresent.
3. Interference due to NOX at concentrations generally found
in ambient atmosphere is not significant.
4, Used widely by many air pollution agencies.
Disadvantages
1. Errors can occur if interfering substances exceed 10% of S00
level. L
2. Interfering substances are not easy to monitor.
Conclusions
Most instruments are sensitive enough for general use with a
minimum of interference problems. The various instruments generally
correlate fairly well. Improvements are still being made for more
selective monitors, which will be reliable under varying conditions.
Re commen dat ions
Most instruments perform well but need frequent checking against
standards.
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- 66 -
ULTRAVIOLET SPECTROPHOTOMETRY (H2S, S02>
Principle of Operation
Direct measurement of S02 is possible in the ultraviolet (UV)
range since this gas absorbs strongly at about 285 nm. H2S may be con-
verted to S02 by oxidation, or converted to other derivatives which
ibsorb in this range. The effects of UV interferences can be minimized
by dual beam measurements at two wavelengths. Methods and equipment have
also been developed for the detection of H2S and SC>2 in the presence of
one another (108, 109).
In the method for detection of H2S and S02 simultaneously (109),
the sample gas is mixed with air, filtered and split into two streams.
One stream passes through an oxidation furnace to convert the H2S to S02
and the other stream, which is used as a reference, is passed through a
dummy furnace and exits unchanged. The two streams are analyzed for S02
and H2S content determined by difference. Systems can be arranged to
use the unchanged stream in a reference cell and compare the differences
in UV absorption electronically to give a direct reading proportional to
the HLS content of the sample gas. Such a system can measure S02 and/or
H2S in the range of 10-2500 ppm. In another system, H2S is absorbed on
a filter medium impregnated with Pb(Ac)2 and the PbS precipitate extracted
with organic solvent (CH3COOCH3, Ci^OH and HOAc) (no). The resulting brown
suspension is measured with a spectrophotometer at 350 nm. The amount of
H2S is determined by comparison to a standard curve. Reproducibility is
reportedly +15% (110) with very little humidity effect.
Commercial Equipment
The duPont Model 461 UV Spectrophotometer is available to
automatically determine S02 (and H2S). The major components for the oxida-
tion method including the sample handling system, have also been made by
Analytic Systems Co. to be used with their Series 600 UV analyzer, but not
on a commercial basis.
References
1. Principles of operation; 110, 111, 109
2. Applications: 110, 109
3. Data: 112, 110, 109
4. Specific instrument description: 110, 109
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- 67 -
Discussion
Advantages
1. Specific for S02> at high concentrations.
2. Reliable measurement over a wide concentration range.
3. The Pb(Ac)2 extraction method gives a collection efficiency of
greater than 90% and compares favorably with the
•methylene blue method (J12) .
Pis advantages
1. Dual measurement is more reliable for differences or
ratio measurements of l^S and SC^ than for absolute values.
2. Other reduced sulfides also oxidized to S02«
3. 862 and ozone interfere in the Pb(Ac)2 method but
can be removed by scrubbing for I^S only determinations.
4. The Pb(Ac>2 tape fades with time.
Conclusions
Satisfactory for field sampling, but other methods such as the
coulometric titrators, tape samplers and combined GC techniques generally
better where absolute values are required.
Recommendations
Not recommended for complex mixtures, useful where H S and S09
are the principal constituents to be determined. 2
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- 68 -
COLORIMETRY (S02, H2S, Mercaptans)
Principle of Operation
A sample of gas is bubbled through a solution which selectively
absorbs the component desired. The absorbed compound is than reacted with
specific reagents to form a characteristic color which is measured
spectroscopica]ly.
Separate methods have been developed for the determination of
S(>2 and sulfides (^S and mercaptans). Both types of gases may be detected
in the presence of the other by use of scrubbers to absorb the undesired
materials.
For the determination of SC>2 a dilute aqueous solution of sodium
tetrachlororaercurate is used for absorption to form nonvolatile techlorosulfito-
mercurate ion. This is reacted with formaldehyde and bleached pararosaniline
to form a red-purple color and measured at 560 nm. This is the modified
West-Gaeke method and has been tentatively adopted as a standard by the
NAPCA (114).
"Total reduced sulfides" including H2S and volatile mercaptans
may be determined colorimetrically by the methylene blue method which
involves absorption of the gas in an alkaline suspension of Cd(OH)2 to
form CdS. The precipitate is then reacted with a strongly acid solution
of N, N dimethyl-p-phenylenediamine and FeCl3 to give methylene blue, which
is measured spectrophotometrically at 500 nm. This procedure has been
adopted as a standard method for H0S (108).
£, ' '
Commercial Equipment
1. SO:? Analysis
Instrument manufacturers (Atlas, IDC, Monitor Labs, PSD, Technicon
and WACO) supply components to collect and analyze gases for S02. Selective
prefilters may be added depending upon the nature of the gas sample to be
analyzed. Automated analytical trains for this procedure are supplied by
Technicon and others in this country and by several manufacturers in
Germany, England, and Japan.
2. H?S Analysis
Instruments such as those noted above for S02 may be adapted for
H2S analysis.
References^
1. Principle of Operation:
For SO?: 6!3, 64., _73, 115. 35_, 116, 6_7, 114, 117
For H?S and Mercaptans: 64_, _73, 115, 92_, 118, 119, 120, 121
122, 116, 67
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- 69 -
2. Applications:
For S02: 63, 64, 73
For H2S and Mercaptans; 64, 115, 92, ^7
3. Data:
For S02: 63, _73, _35_
For H2S and Mercaptans; 73, 115, 92_, 123. 124, 108, 67,
4. Specific Instrument Description:
For 502: 63., 125. 99., 100
For H2S and Mercaptans: 115, 108
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- 70 -
Discussion
For SO?
Advant ages
1. Specific to S02.
2. Levels from 0.002 to 5 ppm can be detected,
3. Sensitivity in the range of 0.02 - 0.04 ppm or better
(in the 1 ppm range).
4. Correlates well with most other test methods.
5. Response time to changes in S02 concentration fairly rapid
( 15 min.)
6. Has been chosen as a tentative standard by EPA.
Disadvantages
1. Ozone, C12, HC1, NH3 and N02 interfere if more than 10% of
S02 concentration, by destroying some of the dye.
2. Requires careful reagent quality and temperature control.
For H2S
Advantages
3
1. Sensitive to 1-100 ppb at 10 mg/m .
2. Specific for H-S and reduced sulfides.
3. Standard deviation + 3.5%, recovery 80% or better.
4. Being used as a tentative standard for ambient H2S measurement,
Pis ady ant age s
1. Strong reducing agents (e.g., S02) inhibit color development.
2. Total reduced sulfides respond.
3. N02 above 0.3 ppm and 0. above 57 ppb interfere.
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- 71 -
4. Takes discrete samples, not a continuous method.
5. Economics are favorable only when a large number of similar
samples are to be measured in a short time.
Conclusions
Colorimetric methods for both SOo and t^S (and mercaptans) are
very satisfactory, but have not been developed yet to give direct, continuous
measurements,
Re commen dat ions
Further work is needed to develop fully automated, continuous,
rapid response techniques.
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- 72 -
ELECTROCHEMICAL
Principle of Operation
The pollutant gas diffuses through a selective membrane and
dissolves in the underlying electrolyte film and becomes adsorbed at a
sensing electrode where a charge transfer occurs. The flow of electrons
forms a current which is proportional to the partial pressure of the
pollutant. Such sensors are reported to be liquid-state devices that con-
tain surfaces onto which the pollutants are adsorbed. The adsorption is
followed by electron transfer either to or from the adsorbate. The cur-
rent flow is determined mainly by the rate at which the gas molecules
reach the catalytically active surface and by the valence change which
the adsorbed species undergo at this surface.
Presumably the catalytically active electrodes and the electrolyte
are enclosed in the sensor that is equipped on one surface with a semi-
pereable membrane. The membrane is exposed to the atmosphere being
monitored. The current generation by the sensor is permeation-controlled
by the transport of the pollutant gas through the membrane. The rate of
permeation is proportional to the pollutant concentration in the atmosphere.
The selectivity of the sensor is attained through the appropriate combination
of catalytically active electrodes and electrolyte.
Commercial Equipment
Prototype instruments are available by Dynasciences and by Enviro
Metrics, Inc. for SO or H S, but not for other sulfur-containing gases.
Discussion
Although the principle has been demonstrated, application of this
method is still under development. Test results to date indicate that
sensors in the emission concentration range (0-1000 ppm) are more reliable
than those offered for the ambient range (0.04-2.0 ppm).
References; (35)
-------
BIOLUMINESCENCE (H S, RSH)
Principle of Operation
This detection system involves the utilization of extremely
sensitive and highly reliable biosensors - living, light-emitting
(bioluminescent) organisms. The biosensor cartridge is placed in an
electro-mechanical system which is equipped with a photocell to monitor
the light generated by the bacteria. An air pump pulls the sample gas
across the surface of the biosensor whose response is monitored electronically
and displayed on a meter. Specific sensors must be selected to monitor
specific pollutants.
Commercial Equijjmenjb
Prototype units and sensors are available from RPC Corporation,
El Segundo, California.
Discussion
The supplier's information indicates a diverse capability by use
of individual strains of bacteria which respond selectively to different
chemicals. Sensitivity can be greatly improved by selective breeding of
bacterial strains and has been extended in some cases to concentrations
below 10~12 mol fraction. Certain biosensors are capable of responding
to classes of chemicals, but yet are capable of differentiating qualitatively
between members of that class. Sensitivity of specific cultures now
available permits detection of H^S at 70 ppb, S09 at 0.2 ppb, or NH0 at
0.001 ppb. L 3
Reference: 126
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- 74 -
CHEMILUMINESCENCE
Principle of Operation
NH3 Is converted to N02 by thermal conversion at above 300°C
and then reacted with ozone to produce nitric oxide
A
ANH3 + S02 —— > 6H2O + 4NO (1)
N0+03 > N02*+02 (2)
Chemiluminescence is produced by deactivation^of the N02*
NOo* > NOo + hV ( - 6300 A) (3)
*• ^ max r
Chemiluminescence detectors, based on a prototype unit developed
by Ford Research of Dearborn, which have been developed for the monitoring
of NOX in ambient air, may be used combined with a thermal preconverter to
oxidize the NH3. This equipment has a fast linear response and is sensitive
to concentrations of O.OOSppm (127). The equipment consists of a variable
temperature chamber containing catalytic surfaces in which the gas stream
and oxidant are reacted. Conventional.,ozone .generators with appropriate,
scrubbers to provide clean air may be used to furnish the atomic oxygen
for the conversion of NO to N02*.
N02, S02 and CO also react with atomic oxygen to produce
chemiluminescence. S02 and C0~ activated oxygen compounds emit at different
wavelengths (3500 A and 4350 A.) and may be distinguished from N0£* emissions.
To detect NH3 in the presence of NOjj the NH3 may be separated from the NO*
components and determined by difference using either a split gas stream or
separate analyses for total and total less NH3.
Commercial Equipment
Commercial units are available from Aerochem, Bendix, Scott Research,
REM and Thermo Electron.
References
Principle Of Operation: 127. 128, 129
Applications: 127. 130. 131
Data: 127, 129
Specific Instrument Descriptions: 127, 132
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- 75 -
Discussion
Advantages
1. CO and SC>2 cause no interference.
2. NOX can be readily distinguished by separating out NH3,
3* Rapid response (1 sec.)*
4. High reliability anticipated.
5. Reasonable cost.
6. Range of 0.002 -1000 ppm.
Disadvantages
,3:'- .. . •
1. Continuous evacuation to 1-3 torr required for reactor flow.
2. Other reduced H compounds interfere i.e., amines.
Conclusions
Not specific enough for NH3, other methods such as direct titra-
tion probably better suited, but combinations with NOX can be measured.
Recommendations 'r"
Satisfactory for use in combinations containing NOX and NH3. A
similar method might be possible for determination of S02*
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- 76 -
FAST SCAN INFRARED SPECTROMETER (S02)
Principle of Operation
A single-beam spectrophotometer with automatic repetitive
scanning in 5 or 12.5 seconds, of wavelengths in three divisions 2.5
to 4.5 microns; 4.4 to 8.0 microns and 7.9 to 14.5 microns with
interference filters is used, coupled with a high speed hot-stylus
oscillographic recorder. Bands in the spectrum from C02 and moisture
in the air are corrected by means of a background trace before and after
analysis. Spectra are obtained by simultaneously passing the pure gas
and dilution gas (He or N2) through the gas cell in a flow-through manner.
The small spectrum makes it essential that measurement of the band
absorbance is accurate. To assure this, part of the standard IR absor-
bance scale is redrawn, photographed, and reduced to the size of the
instrument spectra. A transparent plastic overlay is then placed over
the spectra and the absorbance of the individual band is measured. With
the aid of an illuminated magnifier, readings can be obtained with an
accuracy of +J0.05 to +0.1 and good reproducibility.
Commercial Equipment
Several fast-scan IR spectrophotometers are available such as the
Warner-Swasey (OCLI) and Beckman IR-102. A completely automated analyzer
system has not been produced.
References
1. Principle of operation: 133
2. Applications: 133
3. Data: 133
4. Specific instrument descriptions: 133
Discussion
Advantages
1. Gives a complete spectrum in 12.5 seconds or less.
2. The instruments can be made portable and may be used up
to temperatures of 300°C.
Disadvantages
1. Cannot be used in actual stack gas analysis.
2. Suited primarily as a research tool.
Conclusions
A good method for research studies with clean, dry gases.
Recommendations
Not practical for control studies.
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- 77 -
FLUORESCENCE (H2S)
Principle of Operation
Fluorescent liquids can be made which react with I^S and other
sulfur compounds resulting in a reduction of fluorescence. The change in
fluorescence may be related to the concentration of S compound absorbed.
The original procedure developed (73) utilized tetra-acetoxymercarifluorescein
(IMF) and a method has been suggested for its use in the determination of
H£S in the atmosphere (48). Recent improvements (47) include use of
fluorescein mercuric acetate (FMA) instead of (TMF) since the former is
commercially available.
Photofluorometers are available for measurement of the solution
fluorscence in conjunction with a paried optical filters (Corning Glass
No. 5113 and 2424). The method involves passing a known volume of air
through a specific volume of FMA solution in 0.01N NaOH. Fluorscence is
measured and compared with a standard calibration curve. A linear response
is obtained at H2S concentrations ranging from about 4-6 yg of I^S in
25 ml. of solution.
Commercial Equipment
None available, but photofluorometers are available such as the
Model 12C from Coleman Instruments, which could be built into a prototype
unit for monitoring ambient air or emissions.
References
1. Principle of Operation: 4J7, 4£, 73, 35_
2. Applications: 47. 48. 35_
3. Data: 47. 4j8
4. Specific Instrument Description: 47
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- 78 -
Discussion
Advantages
1. FMA reagent stable up to 16 days.
2. Method reliable and accurate to ± 1% in the range of 2-8 yg
of H£S.
Pisjtdvant age s
1. Mercaptans and disulfides also cause quenching of fluorescence
2. Effect is non-linear in multicomponent blends.
3. Solutions stable for only 16 days.
A. Acidic materials in air such as C02, S02 could affect reagent
if over SOOppm by volume in air.
Conclusions
Good for H2S in presence of C02 + SC^ at low air concentrations.
Mercaptans + disulfides may interfere.
Re commen dat ions
Consider for a prototype instrument.
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- 79 -
INFRARED SPECTROSCOPY (H2S, CI^SH, RSH, RSSR)
Infrared spectroscopy measures the energy absorption pattern
in the vibrational and rotational modes of organic molecules. This
characteristic can be utilized to measure organic compounds such as
mercaptans directly with the IR, or derivatives of H2S which are
prepared subsequent to collection. IR is not a good method for I^S itself
For direct measurement of gases, the material is collected in
a suitable container, and water generally removed prior to measurement
of I.R. absorption. Direct measurement has limited use due to the
complexity of most odorous emissions and a preliminary separation is
usually preferred. Combinations of IR with gas chromato graphic (GC)
separation techniques are discussed in the section on GC.
Commercial Equipment
IR spectrophotometers suitable for the detection of sulfides and
sulfur derivatives are available from Bausch and Lomb, Beckman, Perkin-Elraer,
and many other manufacturers.
References
1, Principles of operation: 137
2. Application: 137
3. Data: 13"7
4. Specific instrument description: 137
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- 80 -
Discussion
Advantages
1. Permits positive identification of components.
2. Interference effects are slight in most simple mixtures.
Pis advan t_ages
1. Separation techniques generally required prior to analysis
due to the complexity of ambient or emission gas samples.
2. Complete analysis is a research procedure, not for routine
use.
3. Not a good method for H-S , which has a. weak spectrum.
Conclusions
IR methods have limited application for direct measurements,
Re commendat ions
IR is a powerful tool when combined with an appropriate
separation technique and should be considered for identification tech-
niques in such systems.
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- 81 -
IR LASER RADIATION
Principle of Operation
Carbon dioxide or Iodine infrared lasers are attenuated when
passed through a sample gas and this change is related to the concentra-
tion of pollutants in the gas sample. The narrow spectral width of the
laser emission permits sensitive detection of pollutants. Three modes of
operating the laser probe are possible (1) using a folded beam laser,
(2) reflecting the laser beam from a retro-reflector, and (3) reflecting
the laser beam from natural targets.
Commercial Equipment
No commercial equipment is available although the laser components
are produced.
Discussion
Currently efforts are being made to build prototype units for
field testing. This technique shows promise because it permits remote
sensing, is not affected by atmospheric moisture, and minimizes interferences
among pollutants. it is anticipated S02 can be detected at 1.5 ppra using
a C02 laser.
Reference: (138)
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- 82 -
METALLIC SILVER FILTER MEMBRANE (H2S)
Principle of Operation
Metallic silver reacts with H2S and/or mercaptans to produce
silver sulfide by the following reaction:
(HO)
H2S + 2Ag + 1/202 —= >- Ag2S + H20
(H70)
2RSH + 2Ag + 1/202 —- >• AgSR + H20
The black silver sulfide formed changes the reflectance of the original
silver surface. This can be measured by a reflectometer and related to
sulfide content of the ambient gas. The reflectance of the initial surface
may be compared to a standard magnesium oxide surface as defined by the U.S.
Bureau of Standards. A membrane of metallic silver reacts quantitatively
with H2S or mercaptans causing a decrease in the reflectivity of the surface.
Each membrane is calibrated before use to the nearest 1/2 reflectance unit
using a reflectance meter equipped with a green tristimulus filter.
Commercial Equipment
No equipment is available for automatic determination of gaseous
sulfides by this method. Components are available for reflectance measure-
ments and air sampling, but a complete system has not been devised.
References
1. Principle of operation: 139, 140, 141. 142, 143
2. Applications: 139
3. Data: 139
4. Specific instrument descriptions: 139
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- 83 -
Pis cussion
Advantages
1. Sensitive to very low concentrations of lUS and RSR.
2. NOX, 03 or ultraviolet light do not interfere, as they
do with Pb(Ac>2, HgCl2 and other similar detectors.
3. Simple, low cost and rapid.
Disadvantages
1. Mercaptans interfere.
Conclusions
Needs further testing, since the method appears quite promising.
Re commendations^
For the detection of very low concentrations of mainly H.2S,
the metallic silver membrane seems appropriate for further development.
To detect high concentrations other methods probably better suited to
automation.
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- 84 -
PLASMA CHROMATOGRAPH (S02, RSH, RSSR)
Principle of Operation
Gases are detected by conversion to ion-molecules and separated
by drifting through an electical field toward a detector. The detector
output of ion current versus time presents a plasmagram of the reactant
ion and the different ion molecules formed. The plasmagram resembles a
chromatogram,with a millisecond time scale.
Commercial Equipment
None available.
Discussion
This technique enables measurement of the mass of an organic
molecule with an instrument that operates at atmospheric pressure. Thus,
it may be possible to use as a simpler instrument than the mass spectrometer
for detailed analyses. This instrument, with further development may
become a valuable laboratory tool.
References: 144» 145
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- 85 -
BIBLIOGRAPHY
(1) Duffee, R. A., JAPCA 18:472-4, July, 1968.
(2) Katz, S. H. and Talbert, E. J., U.S. Bur. Mines Tech. Paper 480 (1930).
(3) Ryazanov, V. A., Arch. Environ. Health ,5:480-94, 1962.
(4) Manufacturing Chemists Assoc. Research on Chemical Odors. Research report
from A. D. Little, Inc., October 1968.
(5) Dravnieks, A., "Theories of Olfaction", in Chemistry and Physiology of
Flavors, ed. H. W. Schultz, Avi Publishing Co., Westport, Conn. (1966).
(6) Hendrickson, E. R., Control of Atmospheric Emissions in the Wood Pulping
Industry, Vol. 3, Final Report of EPA Contract CPA 22-69-18, 1970.
NTIS No. PB 190,353.
(7) Blosser, R. 0. and Cooper, H.B.H., Jr., "Compendium of Methods for Measuring
Ambient Air Quality and Process Emissions", National Council for Air and
Stream Improvement, Technical Bulletin No. 38, New York, Dec. 1968.
(8) Thoen, G., DeHaas, G. G. and Austin, R. R., TAPPI j>l:246, 1968.
(9) Adams, D. F., Presentation at the Ninth Methods Conference in Air Pollution
and Industrial Hygiene Studies, Pasadena, California. "Analysis of
Malodorus Sulfur Containing Compounds" February 7-9, (1968).
(10) Stevens, R. K., O'Keeffe, A. E. and Ortman, G. C., Environ. Sci. & Tech. _3»
652 (1969).
(11) Turk, A., Heating, Piping, Air Cond. _39 207-10, 1968.
(12) Larsen, R. I., APCA Meeting New York, June 1969, Paper 69-210.
(13) Mills, J. L., Walsh, R. T., Luedtke, K. 0. and Smith, L. K., JAPCA JL3_:467-75,
1963.
(14) Benforado, D. M., Rotella, W. J. and Horton, D. L., JAPCA 19_: 105-5, 1969.
(15) Banks, 0. M., "Problems of Odor Measurement and Control", American
Petroleum Institute, New York, Oct. 1969.
(16) Landsberg, H. and Escher, E. E., Ind. Eng. Chem. 46_:1422-8, 1954.
(17) Walther, J. E. and Amberg, H. R., TAPPI 51:126A-29A (1968).
(18) Tarman, P. B., Andreen, B. H. and Kniebes, D. V., Chem. Eng. Progress 61(17):l-8
(1960). ~~
(19) Washburn, H. W. and Austin, R. R. in "Air Pollution", ed. McCabe,
Chapter 72, 576 McGraw Hill, New York, 1952.
(2°) Fredericks, E. M. and Harlow, G. A., Anal. Chem. 36:263, 1969.
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- 86 -
(21) McWilliams, I. G. and Dewar, R. A., Nature 181:760, 1958.
(22) Adams, D. F., Jensen, G. A., Steadman, J. P., Koppe, R. K. and
Robertson, T. J., Anal. Chem. _36:1094 (1966).
(23) British Columbia Research Council, "A Manual Describing a Method for
the Collection and Analysis of Pulp Mill Effluents", Vancouver, 1959.
(24) Adams, D. F. and Koppe, R. K., TAPPI ^1:366, 1958.
(25) Blaedel, W. J. and Laessig, R. H., "Automation of the Analytical Process
through Continuous Analysis", in Advances in Anal. Chem. and Instrumentation
2:69-168, J. Wiley, New York, 1966.
(26) Kenline, P. A. and Hales, J. M., "Air Pollution and the Kraft Pulping
Industry11,, PHS Publication 999-AP-4, 1963.
(27) Walther, J. E. and Atnberg, H. R., JAPCA 20(1):9-18, 1970.
(28) Schwalbe, C. G., Paper Trade J. 2i:52» 1922.
(29) Colombo, R., Corbetta, D., Pirotta, A. and Sartori, A., TAPPI ^0_ 490, 1957.
(30) Bergstrom, H. and Trobeck, K. G., Svensk Papper 48_:49-54, 1945;
see also U.S. Patent 2,406,581.
(31) Control Techniques for Sulfur Oxide Air Pollutants, NAPCA Publication
No. AP-52, Chapter 5.2.
(32) Air Pollution Control Assoc. Petroleum Committee TI-3, JAPCA ^ (1), 1964.
(33) Termeulen, M. A., "Air Pollution Control by Oil Refineries", First
International Clean Air Congress, London 1966, Paper IV-5.
(34) Palmer, H. F., Rodes, C. E. and Nelson, C. J., JAPCA JL9:778-86, 1969.
(35) Tokiwa, Y., "Sulfur Dioxide", paper at llth Methods Conference in Air
Pollution, Berkeley, Cal., April 1970.
(36) Thomas, M. D. and Cross, R. J., Ind. Eng. Chem. J20:645, 1928;
ibid. Anal. Ed 4_:253-6, 1932 and L5:287-90, 1943.
(37) Danielson, J. A., "Air Pollution Engineering Manual", Air Pollution
Control District, County of Los Angeles, U.S. Dept. of HEW (1967).
(38) Teller, A. J., APCA 13 No. 4 Pg. 148 (April 1963).
(39) Ronald, D., "Handbook on Offensive Trades", Wm. Hodge, London (1935).
(40) Wood, T. and Bender, A. E., "Analysis of Tissue Constituents - Commercial
Ox-Muscle Extract", 67 (1957).
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- 87 -
(41) Burchfield, H. P., Johnson, D. E., Rhoades, J. W., and Wheeler,
R. J., J. Gas Chromatog. _3:28, 1965.
(42) Hemeon, W.C.L., "Malodors - A Basis for Regulations", JAPCA, 2.1 (12) Pg. 770
(Dec. 1971).
(43) Sullivan, R. J., "Air Pollution Aspects of Odorous Compounds", Technical
Report by Environmental Systems, Bethesda, Md., (For Nat'l Air Pollution
Control Administration, USPHS).
(44) Stahl, Q. R., "Preliminary Air Pollution Survey of Aldehydes", U.S.
Dept. of HEW, Publ. Health Service, NAPCA, (Oct. 1969).
(45) Dravnieks, A., "Current Status of Odor Theories", Advances in Chemistry,
Series #56, Pg. 29 (1966) ACS.
(46) Dravnieks, A. and Lafford, P., "Possibilities of Predicting Odor Intensity
and Quality by Means of Chemical Analysis", Conf. on Odorous Pollutants,
The Karolinska Institute, Stockholm, (June, 1970).
(47) Miller, F., et al., "Determination of Acetic Acid in Air", Amer. Ind.
Hyg. Assoc., 1£> (1) Pg. 221 (Mar. 1955).
(48) Holmes, R. G., "Air Pollution Source Testing Manual", Los Angeles Air
Pollution Control District, Los Angeles County, Calif.
(49) Stahl, W. H., "Instrumental Methods Used in the Analysis of Odorants",
Proceedings of the 3rd Annual Symposium on Problems in Air Pollution,
Franklin Institute (Oct. 1958).
(50) Williams, I. H., "Gas Chromatographic Techniques for the Identification
of Low Concentrations of Atmospheric Pollutants", Anal. Chem. 3]_ (13)
Pg. 1723 (Dec. 1965).
(51) Levaggi, D. A. and Feldstein, M., "The Determination of Formaldehyde,
Acrolein and Low Molecular Weight Aldehydes in Industrial Emissions"
JAPCA 20. (5) Pg. 312 (May 1970); 19_ (1) Pg. 43-5 (Jan. 1969).
(52) Prater, T. J., "Exhaust Gas Carbonyl Measurements by the Gas Chromato-
graphic 2,4-Dinitrophenylhydrazine Method", Ford Motor Co., Dearborn,
Mich.
(53) Burnett, W. E., "Air Pollution from Animal Wastes", Environmental Science
and Technology 3_ (8) Pg. 744 (Aug. 1969).
(54) Okita, T., "Filter Method for the Determination of Trace Quantities of
Amines, Mercaptans and Organic Sulfldes in the Atmosphere", Atmospheric
Environment, Pergamon Press 1970 Vol. 4 Pgs. 93-102, Printed in Great
Britain.
(55) Dravnieks, A. and Krotoszynski, B. K., "Systematization of Analytical
and Odor Data on Odorous Air", from Symposium Bulletin, "Odors and
Odorants: The Engineering View", Amer. Soc. of Heating, Refrigerating
and Air Conditioning Engineers, Inc. (ASHRAE), (1968).
-------
- 88 -
(56) "The Kovats Retention Index System", Anal. Chem. _36 (8) Pg. 31A (1964).
(57) Dravnieks, A. and O'Donnell, Anne, "Principles and Some Techniques of
High-Resolution Headspace Analysis", J. Agr. Food Chem. JL9 (6) Pg. 1049
(1971).
(58) Trieff, N. M., et al., "Analysis of Industrial Odor Emissions", 19th
Pittsburg Conf. on Analytical Chemistry and Applied Spectroscopy, Inc.
Cleveland, Ohio (Mar. 1968).
(59) Dravnieks, A., "Odors: Their Nature, Measurement, and Control", IIT
Research Institute, Chicago, 111.
(60) Burgwald, T. A., "Identification of Chemical Constituents in Rendering
Industry Odor Emission", IIT Research Institute Report.
(61) Smith, D. 0. and Tauss, R. H., "Modification of a Coulometric Titrator
for the Monitoring of Gaseous Pulp Mill Effluents", S. Pulp Paper Mfg
33 #2, 32, 4-6 (1970).
(62) Austin, R. R., "Sampling and Analysis of Pulp Mill Gases for Sulfur
Compounds", TAPPI, 54 #6, 977-80 (1971).
(63) Palmer, H. F., Rodes, C. E. and Nelson, C. J., "Performance Characteristics
of Instrumental Methods for Monitoring Sulfur Dioxide II Field Evaluation",
JAPCA, 19_, #10, T18-86 (1969).
(64) Kesler, R. B., "Modern Methods of Monitoring Gaseous Pulp Mill Effluents
for Sulfur Compounds", Advan Automat Anal., Technicon Int. Congr.
2, 111-14 (1969).
(65) Austin, R. R., et al., "The Application of Couloraetric Titration to
Atmospheric H^S and S02 Measurements and to Hydrogen Reforming Measurements",
Ann u. ISA Conf. Proc. 2Q_, #3, 2.1-1-65 (1965).
(66) Bamesberger, W. L. and Adams, D. F., "Field Comparison of the Coulometric,
Colorimetric, and Lead Acetate Tape Analysis Methods for Sulfur Containing
Gases", TAPPI, 52, #7, 1302-1306 (1969).
(67) Garber, W. F., et al., Journal WPCF, 42. #5, 209-220 (1970).
(68) Thoen, G. N., et al., "Continuous Measurement of Sulfur Compounds and
Their Relationship to Operating Kraft Mill Black Liquor Furnaces",
TAPPI, 52, #8, 1485-87 (1969).
(69) Tretter, V. S., TAPPI, _52, #12, 2324-26 (1969).
(70) Adams, D. F., et al., "Analysis of Sulfur Containing Gases in the Ambient
Air Using Selective Pre-Filters and a Microcoulometric Detector",
JAPCA 18 #3, 145-8 (1968).
(71) Andree, B. H., et al., "Instrumental Methods of Analysis for Odorant
Compounds in Natural Gas", Inst. of Gas Technology, Tech. Report No. 7 (1963).
-------
- 89 -
(72) Nader, J. S. and Coffey, W. L., "Automatic Zero Drift Correction
of the Titrilog", Am. Ind Hyg Assoc. J 2l4_ (8), 563-5 (1963).
(73) Stevens, R. K., "Review of Analytical Methods for the Measurement of
Sulfur Compounds in the Atmosphere", llth Conf. on Methods in Air
Pollution and Industrial Hygiene Studies, Calif. State Dept. of Public
Health (1970).
(74) Adams, D. F., et al., "Analysis of Kraft-Mill, Sulfur Containing Gases
with GLC lonization Detectors", JAPCA !L5_, #1, 31-33 (1965).
(75) Adams, D. F. and Koppe, R. K., "Direct GLC Coulometric Analysis of
Kraft Mill Gases", JAPCA, 1J, #3, 161-65 (1967).
(76) Drushel, H. V., Preprints, Div. Petr. Chem. ACS, 14, #3, B232 (1969).
(77) Drushel, H. V., Analytical Letters, _3_, 353, (1970).
(78) Killer, F.C.A. and Underhill, K. E., Analyst, £5_, 505 (1970).
(79) Marsh, W. W., Jr., Analytical Letters, .3, 341 (1970),
(80) Engelhardt, H., Instr. Rev. Pg 98-99, (Feb. 1968).
(81) Stevens, R. K., et al., "Gas Chromatography of Reactive Sulfur Gases
in Air at PPB Level", EPA Publication.
(82) Mulik, J. D., et al., "An Analytical System Designed to Measure
Malodorous Compounds Related to Kraft Mill Activities" TAPPI Water
and Air Conf. Apr. 1971.
(83) Mulik, J. D., "Continuous Determination of Sulfur Dioxide with Flame
Photometric Detector, ibid (1970).
(84) McGinnity, et al., "Mobile Source Sampling Laboratory for the Pulp
and Paper Industry Presented at a Symposium on Methods for Measuring
and Evaluating Odorous Air Pollutants at the Source and in the Ambient
Air 6/1-5/70 Dept. of HEW, NAPCA, Durham, NC.
(85) Harrison, G.A.F. and Coyne, C. M., J. Chromatogr., 41, #3,4, 45.3-5 (1969).
(86) Brink, D. L., et al., "Analysis of Sulfur Containing and Sulfur Frea
Organic Products Formed in Kraft Black Liquor Pyrolysis", TAPPI 54,
#5, 714-20 (1971).
(87) Adams, D. F. and Koppe, R. K., TAPPI, 42, #7, 6Q1-6Q5 (1959).
(88) Siu, W., Levaggi, D. A., et al., "Modifications to an H2S Tape Sampler for
Increasing Sensitivity and Accuracy in H S Sampling", JAPCA, 21,
#10, 636-8, (Oct. 1971). z —
(89) Dravnieks, A., "Olfactory Information Information Processing and
Mechanisms", AGARD Symposium on Bionics, Brussels, Belgium, Sept. 1968.
-------
- 90 -
(90) Applebury, T. E. and Schaer, M. J., JAPCA, 20, #2, 83-6 (1970).
(91) Walther, J. E. and Amberg, H. R., "Continuous Monitoring of Kraft
Mill Stack Gases with a Process Gas Chromatograph", TAPPI, 50, #10,
108A-110A (1967).
(92) Adams, D. F., "Analysis of Malodorous Sulfur-Containing Gases", TAPPI
51, //I, 53-58 (1969).
(93) Craig, J. C., et. al., "Analysis of Organic Pollutants", Univ. of Calif.,
Project Clean Air, Res. Rep. 6^ Vll-115, Sept. 1, 1970.
(94) Feldstein, M., et. al., "Gas Chromatographic Determination of Mercaptans",
JAPCA 15, #5, Pg 215-17 (1965).
(95) Williams, I. H. and Murray, F. E., "Studies of the Gas Chromatographic
Analysis of Kraft Mill Sulfides Part I Collection and Analysis of
Gaseous Samples", Pulp Paper Mag Can 67_, #8, T347-52, (1966).
(96) Martin, R. L. , Anal. Chem., _38_, 1209 (1966).
(97) Adams, D. F., et. al., TAPPI, 43_, #6, 602-608 (1960).
(98) McKean, W. T., Jr., et. al., TAPPI, 48, #12, 699-704 (1965).
(99) "Environmental Measurements" (1965), PHS Publication No. 999-AP-15.
(100) Morgan, G. B., et. al., Automation in Analytical Chemistry, Technicon
Symposia 1966, Mediad, 1967, p 526-523.
(101) Jacobs, M. B., "The Analytical Chemistry of Industrial Poisons, Hazards
and Solvents", Interscience, N.Y. (1949).
(102) Pare, J. P., JAPCA JL6, #6, 325-7 (1966).
(103) Budd, J. and Bewick, H. A., Anal. Chem 2_3, 1536 (1952).
(104) Marbach, E. P. and Doty, D. M., J. Agr and Food Chem., 4_, 881 (1956).
(105) Hochheiser, S. and Elfers, L. A., "Automatic Sequential Sampling of
Atmospheric H^S by Chemisorption on Mercuric Chloride-Treated Paper Tape",
Environ. Sci. Technol. _4, #8, 672-6 (1970).
(106) Sensenbaugh, J. D. and Hemeon, W.C.L., Air Repair 4_, 1 (1954).
(107) Shikiya, J. M. and MacPhee, R. D., "Multi-Instrument Performance
Evaluation of Conductivity-Type Sulfur Dioxide Analyzers", JAPCA 19,
#12, 943-45 (1969).
(108) Intersociety Committee, Health Laboratory Sci, _7_, #4 (Oct. 1970).
(109) Risk, J. B. and Murray, F. E., Can. Pulp and Paper Ind., 1_7_ #10, 31-34 (1964)
-------
- 91 -
(110) Oklta, T., et. al., "Filter Method for the Measurement of Atmospheric
Hydrogen Sulfide", Environ. Sci. Technol 5_, #6, 532-4 (1971).
(Ill) Lodge, J. P., et. al., Amer Ind Hyg. Assoc. J,, 24, 380 (1963).
(112) Sanderson, H. P., et. al., "Limitations of the Lead Acetate Impregnated
Paper Tape Method for Hydrogen Sulfide", JAPCA 1£, #6, 328-30 (1966).
(113) High, M. D. and Horstman, S. W., "Field Experience in Measuring Hydrogen
Sulfide", Am Ind Hyg Assoc J. 2£, #4, 366-73 (1965).
(114) Intersociety Committee, Health Laboratory Sci. £, #4, (Oct. 1969).
(115) Adams, D. F., "Tentative Method of Analysis for Hydrogen Sulfide Content
of the Atmosphere", Health Lab Sci _7_, *3, 157-63 (1970).
(116) Bostrom, C. E. and Brosset, C., "A Method for Simultaneous Determination
of H2S and S02 in Flue Gases", in "Atmospheric Environment" Pergamon Press
Vol 2» p 407-16 (1969) Great Britain.
(117) Gaeke, G. C. and West, P. W., Anal Chem 28, 1816-19 (1956).
(118) Sliwinske, R. A. and Doty, D. M., Agr. Food Chem _6, 41 (1958).
(119) Jacobs, M. B., et. al., Anal. Chem. 29, 1349 (1957).
(120) Mecklenburg, W. and Rozenkranzer, R., A. Anorg Chem 86, 143 (1914).
(121) Almy, L. H., J Am Chem Soc., £7, 1381 (1925).
(122) Sheppard, S. E. and Hudson, J. H., Ind. Eng. Chem., Anal. Ed. 2_, 73 (1930).
(123) Moore, H., Helwig, H. H. and Graul, R. J., Ind. Hyg. J. 21, 466 (1960).
(124) Bamesberger, W. L. and Adams, D. F., Environ. Sci and Tech. _3_, 258 (1969).
(125) Stern, A. C. (Editor), "Air Pollution", Vol II (1968), Academic Press, N.Y.,
Chap. 17: "Analysis of Inorganic Gaseous Pollutants".
(126) Bulletin No. 101, RPC Corporation, El Segundo, Calif.
(127) Hodgeson, J. A., et. al., "Application of Chemiluminescence Detector for
the Measurement of Total Oxides of Nitrogen and Ammonia in the Atmosphere",
EPA Tech. Center.
(128) Hodgeson, J. A., et. al., Anal. Chem. 43, 1123 (1971).
(129) Parts, L. P., et. al., "Instrumentation for the Determination of Nitrogen
Oxides Content of Stationary Source Emissions", Interim Report Contract No.
EHSD 71-30 for Air Pollution Control Office of EPA, Durham, N.C.
(130) Fontijn, A. and Ronco, R. J., Aerochem Research Labs, Princeton, N.J.,
EPA, APCO Contract No. 70-79 (1971).
-------
- 92 -
(131) Ballard, L. F. and Decker, C., Research Triangle Institute, Research
Triangle Park, N.C., EPA Contract No. 70-101 (1971).
(132) Stedman, D. H., et. al., Publication Preprint, Ford Research, Dearborn,
Michigan.
(133) Comberiati, J. R., "Application of Rapid Spectrometry to Air Pollution
Research", Anal Chem 43, #11, 1497-9 (Sept. 1971).
(134) Wronski, M., Z. Anal Chem. 180, 185 (1961).
(135) Andrew, T. R. and Nichols, P.N.R., "The Determination of Hydrogen Sulfide
in the Atmosphere", Analyst 90 (1071) 367-70 (1965).
(136) Hardwick, B. A., et. al., "A Fluorometric Method for Determining Low
Concentrations of Hydrogen Sulfide in Air", Atmos. Environ 4^ #4, 379-85 (1970)
(137) Thoen, G. N. and Nicholson, D. C., "infrared Analysis of Kraft Pulping
Process Gases", TAPPI _53_, #2, 224-6 (1970).
(138) tianst, P. L. and Morreal, J. A., "Detection and Measurement of Air Pollutants
by Absorptions of Infrared Radiation", JAPCA, 18_, #11, 754-9 (1968).
(139!) Falgout, D. A. and Harding, C. I., "Determination of H2S Exposure by
Dynamic Sampling with Metallic Silver Filters", JAPCA 18_, #1, 15-20 (1968).
(140) Drott, J., Arkiv for Kemi, 15, 14 (1960).
(141) Sullivan, J. L., "An Investigation of Air Pollution Problems in the
South Auckland Area", R. E. Owens, Govt. Printer, Wellington, New Zealand.
(142) Lilienfield, S. and White, C. E., JACS .52_, 886 (1930).
(143) Ricca, P. M., "The Effect of Temperature and Humidity on the Odor
Threshold of Hydrogen Sulfide Gas", Masters' Thesis, Univ. of Florida.
(144) Karasek, F. W., "A Drift-Mass Spectrometer", Research Development
Pg. 26 (Dec. 1970).
(145) Karasek, F. W., Research Development 21_, 34 (1970).
(146) Bialkowsky, H. W., DeHaas, G. G., "Catalytic Oxidation Procedure for
Determining Sulfur Compounds in Kraft Mill Gases", Pulp and Paper Mag.
Canada 53 (11) 100-(1952).
(147) Leithe, W., "The Analysis of Air Pollutants" (Stuttgart 1968, Transl.
1970 by Ann Arbor-Humphrey Science Publishers, Inc.)
ftd.S. Govranunt Printing Office: 1972—746-763/4109 Region Ho. 4
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