EPA-650/2-74-024
March 1974
Environmental Protection Technology Series
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EPA-650/2-74-024
DEVELOPMENT OF SAMPLING
AND ANALYTICAL METHODS
OF LIME/LIMESTONE
WET SCRUBBING TESTS
by
K. Schwitzgebel, F. B. Meserole,
C. M. Thompson, J. L. Skloss, and M. A. McAnally
Radian Corporation
8500 Shoal Creek Boulevard
Austin, Texas 78766
Contract No. CPA 70-143
ROAP No. 21ACY-25
Program Element No. 1AB013
EPA Project Officer: Robert M. Statnick
Control Systems Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
March 1974
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This report has been reviewed by the Environmental Protection Agency
and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Agency,
nor does mention of trade names or commercial products constitute
endorsement or recommendation for use.
11
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ACKNOWLEDGEMENTS
The authors wish to acknowledge the assistance of
OAF personnel under whose guidance this program was carried out.
Mr. Julian Jones was ORD's Project Officer from the beginning
of the contract until December, 1971. Dr. Robert Statnick (ORD)
directed the program starting in January, 1972. We appreciate
the cooperative spirit of both project officers.
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ABSTRACT
This study was carried out to develop appropriate
sampling and analytical methods to be used at OAF's test
facility at Shawnee. The three problem areas encountered in
analyzing thermodynamically unstable slurry streams as encoun-
tered in lime/limestone based S02 wet scrubbing processes are
sampling, sample handling and chemical analysis. A positive
pressure filtration was found to minimize the mass transfer
phenomena during the filtration step to an acceptable level.
Quenching of the filtered liquid was chosen to avoid change in
sample composition. Two sets of analytical methods were
selected for application at Shawnee. The back-up methods are
based on atomic absorption and wet chemical procedures. The
rapid field methods are based on X-ray fluorescence, atomic
absorption, and wet chemical analyses.
The X-ray fluorescence spectrometer was automated by
interfacing it with a NOVA 1200 minicomputer. Additional
peripheral devices have the function of processing all raw data
The raw data are input to the system with a card reader, a
teletype, or a CRT. The final results are stored on a magnetic
tape. A hard copy is provided by a printer.
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TABLE OF CONTENTS
VOLUME I
PAGE
1.0 INTRODUCTION 1
2.0 PROBLEM DEFINITION 3
3.0 SAMPLING 8
4.0 SAMPLE HANDLING 11
• •
5.0 LIQUID PHASE CHARACTERIZATION 12
5.1 Wet Chemical Procedures 13
5.1.1 Chloride Determination 13
5.1.2 COS Determination 17
5.1.3 Sulfur Dioxide Determination 19
5.1.4 Total Sulfur Determination 19
5.1.5 Total Nitrogen 21
5.1.6 Determination of Nitrite and Nitrate .... 22
5.2 Atomic Absorption Procedures 23
5.2.1 Determination of Ca, Mg, K, and Na 26
5.2.2 Determination of Catalytically Effective
Trace Elements 27
5.3 X-Ray Fluorescence 28
5.3.1 Physical Phenomena 28
5.3.2 Description of Available Equipment 29
5.3.3 Preliminary Tests 29
5.3.4 Description of Sequential
Instrumentation 30
5.3.5 Matrix Interference Corrections 32
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5.3.6 Summary of Selected Values for Matrix
Interference Coefficients and
Associated Uncertainties 36
5.3.7 Calibration Procedures for X-Ray
Fluorescence Spectrometry 36
5.3.8 Mathematical Background for Computer
Calculation of Calibration Parameters ... 39
5.3.9 Fluorescence Counting Rate Measurements . 39
6.0 SOLID PHASE CHARACTERIZATION 41
6.1 Chemical Composition 41
6.2 Phase Identification 42
7.0 FIELD STUDIES 44
8.0 USE OF THE RAW DATA 53
9.0 DATA HANDLING SYSTEM 57
9.1 Laboratory Data Analysis Hardware 59
9.2 Laboratory Data Analysis Software ., 60
9.2.1 Executive System 60
9.2.2 Application Routines 61
9.2.3 Diagnostic Routines 61
10.0 SUMMARY 63
11.0 BIBLIOGRAPHY 67
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PAGE
VOLUME II
1.0 INTRODUCTION 1
2.0 PROCESS DESCRIPTION AND PROBLEM
DEFINITION 3
2.1 Shawnee Test Facility 4
2.2 Process Chemistry 7
2.3 Required Procedures 13
3.0 LIQUID PHASE ANALYSIS 15
3.1 Literature Review* 16
3.2 Experimental Evaluation of Atomic
Absorption Spectrophotometry* 179
3.3 Experimental Studies of X-Ray Fluorescence
Spectrometry* 251
3.4 Experimental Evaluation of Methods for
Individual Species* 314
3.5 Selected Referee Methods for Liquid
Phase Analyses* 421
3.6 Selected Field Methods and Data Analysis
System 485
4.0 SOLIDS CHARACTERIZATION 491
4.1 Phase Identification Using X-Ray
Diffraction 497
4.1.1 Theory of Powder Diffraction 497
4.1.2 Instrumentation 500
4.1.3 Compilation of X-Ray Powder Diffraction
Data 504
* Detailed contents of these sections are given at the front
of these sections.
vi
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PAGE
4.2 Methods to Measure Particle Size and
Surface Area 511
4.2.1 Phase Separation 512
4.2.2 Methods for Particle Size Determination . 513
4.2.3 Surface Area and Pore Size
Determination 526
4.3 Solids Dissolution and Analysis Methods . 533
4.3.1 Analysis for Calcium, Magnesium and
Total Sulfur 533
4.3.2 Analysis Method for the Determination of
Total Carbonate in Solids 540
4.3.3 Analysis for Sulfite 546
5.0 SAMPLING TECHNIQUES 548
5.1 Theory of Sampling Fluid Phase Streams .. 549
5.2 Recommended Procedure for Sampling and
Rapid Separation of Unstable Slurries ... 556
5.2.1 Pump 556
5.2.2 Filter Holder and Membrane 558
5.2.3 Sample Train 558
5.2.4 Procedure 559
5.3 Recommendations for Collecting Liquid
Samples and Fixing Unstable Solutions ... 560
5.3.1 Fixing Solution for Carbon Dioxide
Analysis 561
5.3.2 Fixing Solutions for Sulfite Analysis ... 564
5.3.3 Fixing Solutions for Calcium Analysis and
for Sulfate (Total Sulfur) Analysis 564
5.4 Field Sampling 566
Vll
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PAGE
6.0 FIELD TESTS OF SELECTED METHODS 567
6.1 GAP In-house Test Data Conditions 569
6.2 Tidd Plant Test Data 573
6.2.1 Process Description for the Tidd Plant
Scrubbing Unit 573
6.2.2 Sampling Procedures 577
6.2.3 Analytical Methods 579
6.2.4 Results 580
6.3 Key West Test Data 592
6.3.1 Pilot Unit and Test Conditions 592
6.3.2 Results of Chemical Analyses of the
Liquid Phase 596
6.3.3 X-Ray Diffraction Results 599
6.3.4 Results of the Chemical Analyses of Key
West Solids 609
6.4 Colbert Test Data 613
6.4.1 Pilot Unit and Test Conditions 613
6.4.2 Results of Chemical Analyses of the
Liquid Phase 617
6.4.3 X-Ray Diffraction Results 621
6.4.4 Results of the Chemical Analyses of
Colbert Solids 630
6.5 Shawnee Test Data 635
6.5.1 Pilot Unit and Test Conditions 635
6.5.2 Results of Chemical Analyses of the
Liquid Phase 637
6.5.3 X-Ray Diffraction Results 637
6c5.4 Results of the Chemical Analyses of
Shawnee Solids 647
viii
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PAGE
7.0 SUMMARY 650
8.0 BIBLIOGRAPHY 652
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PAGE
VOLUME III
1.0 INTRODUCTION
2.0 EXECUTIVE SYSTEM
3.0 APPLICATION SOFTWARE 10
3.1 X-Ray Operation 10
3.2 System Commands 27
4.0 DIAGNOSTIC TEST ROUTINES 69
5.0 DATA STORAGE AND INPUT 74
APPENDIX A - PROGRAM WRITE-UPS 105
APPENDIX B - PROGRAM LISTINGS 182
APPENDIX C - CONSIDERATIONS FOR SOLVING
X-RAY FLUORESCENCE MATRIX CORRECTIONS . 354
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1.0 INTRODUCTION
The Office of Research and Development has sponsored
several approaches for sulfur dioxide removal from flue gases
emitted by coal and oil-fired power stations in the past years.
One of the most advanced control strategies is S03 removal based
on lime/limestone wet scrubbing techniques. Since the summer
of 1972, three different scrubbing units were tested at Shawnee
a venturi scrubber, a turbulent contact absorber, and a marble
bed. The goal of these tests was to demonstrate the long term
reliability of these units and the extraction of engineering
design information such as:
vapor-liquid mass transfer characteristics
in the scrubbers,
solid-liquid mass transfer rates through-
out the system, and
scaling potential.
The mathematical description of these problem areas depends on
the knowledge of equilibrium partial pressures and important
activity products. These quantities can be calculated from the
chemical composition of the scrubber solutions obtained by
chemical analysis.
Radian was granted a contract in 1970 to select ap-
propriate referee and field chemical analysis methods to be
used at Shawnee. This final report consists of three volumes.
Volume I summarizes the major findings of the literature and
experimental results in broad terms. It starts with a short
process description and problem definition. The problem areas
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encountered in sampling and sample handling are then discussed.
Analytical methods selected for the liquid and solids analyses
are described in the following sections. The data collected
at TVA's Colbert Steam Plant are presented as an example of
methods testing in the field. The analytical results obtained
from the scrubber effluent are further processed to demonstrate
the extraction of equilibrium partial pressures and important
activity products necessary for process evaluation.
X-ray fluorescence proved to be a rapid and accurate
procedure for the determination of sulfur in aqueous scrubber
samples. Calcium, chlorine, and potassium are additional ele-
ments that are detectable by X-ray fluorescence. The X-ray
spectrometer was interfaced with a minicomputer and several
peripheral devices such as teletype, CRT, card reader, disk,
magnetic tape, etc., to automate the fluorescence analysis and
to facilitate the data handling problem associated with data
reduction.
Volume II is a detailed description of the literature
findings and experimental effort leading to the methods of
choice. Details of the automated X-ray fluorescence unit and
the data handling systems are presented in Volume III.
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2.0 PROBLEM DEFINITION
The basic equipment arrangement for limestone injec-
tion wet scrubbing (LIWS) processes is shown in Figure 2-1.
The three streams entering the system are flue gas, particulates
and make-up water. Three streams leaving the unit are cleaned
stack gas, solid waste products, and scrubbing liquor. The
composition of the incoming streams provides a means of predict-
ing the liquor composition on a qualitative basis. The important
species in the LIWS process are:
Group I Group II Group III
Calcium Sodium Trace elements
Sulfite Potassium Iron
Sulfate Magnesium Cobalt
Chloride Nickel
Nitrate Copper
Nitrite Manganese
Carbonate
The components listed in Group I are the most important.
They dominate the process by participating in the gas-liquid
and liquid-solid mass transfer steps. The species listed under
Group II contribute to the process performance in three ways.
First, they influence solubilities which are dependent on the
ionic strength of the solution. Second, they form ion pairs
with Group I compounds. Finally, they influence the driving
force for the mass transfer rates. The components in this group
form very soluble compounds with the exception of magnesium
hydroxide and calcium carbonate. In a closed loop operation
there is a buildup of the soluble compounds, since the only
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GAS SPECIES
FG, SG
I. S02
2. C02
3. NOX
A. HZ0
5. 02
6. CO
7. N2
FLUE GAS
FG
LIMESTONE
FLY ASH
SOLIDS
LA
t. CoO
2. MgO
3. CoS04
4. MgS04
5. CoS03
6. MgSOj
7. CoC03
8. MgC03
9. FLY ASH
10. SOLUBLE No
II. SOLUBLE Cl
STACK GAS
SG
I
VTiiTEfT
MAKEUP
WM
SCRUBBER
S
SCRUBBER FEED
SF
'Li
PROCESS
WATER
HOLD TANK
P
SCRUBBER
BOTTOMS
SB
SLURRY RECYCLE SR
SCRUBBER
EFFLUENT
HOLD TANK
E
CLARIFIER
LIQUID
CL
CLARIFIER
FEED _
CF
CLARIFIER
C
CLARIFIER
BOTTOMS
* CB
FILTER
F
FILTER
LIQUID
FL
FILTER
(BOTTOMS
FB
PROCESS SOLID SPECIES
(CF, SR, CB, FB.SF]
I. CoO
2. Co(OH)2
3. Co CO 3
4. CcS03 • xH20
5. CoSO-; • xH20
6. MgO
7. Mg(OH)2
8. MgC03-xH20
9. MgS03 • xH20
10. FLY ASH
PROCESS
LIQUID
SPECIES
SB.CF.SR, CB,
FB.CL.FL.SF
I.H*
2. OH~
3. HS03
4. SOf
5. SO?
6. HC03
7. COf
0. HSOJT
9. H2S03
10. H2C03
II. Co++
12. CoOHf
13. CoS03
14. CoCOj
15. CoHCOj
16. CoSO/,
17. CoKOj
10. NOj
19. Mg+ +
20. MgOH*
21. MgSO<»
22. MgHCOj
23. MgS03
24. MgCOj
25. No +
26. NoOH
27. NoC03
28. NollCOj
29. NoS04
30. NoNOj
31.cr
FIGURE 2-1 - WET SCRUBBING SCHEME
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stream in which they can leave the scrubbing unit is the liquor
adherent to the solids. This fact must be kept in mind when
selecting analytical methods. The procedures must give accurate
results in those cases where the soluble species build up to
a high level. The implications for the selection of methods
for sulfate and sulfite will be discussed later.
The third group is comprised of species leached from
the fly ash and impurities in the limestone. The concentration
of these elements is never very high, since it is limited by
the solubility of the hydroxides in the alkaline parts of the
scrubbing unit. Their importance is based on the fact that
they are catalysts for sulfite oxidation, even if present in
the parts per billion range.
The process simulations, performed under CPA Contract
No. 70-45, "Study of the Limestone Injection Wet Scrubbing
Process," gave a valuable basis for estimating anticipated con-
centration ranges. Estimation was necessary since no data on
a closed loop system operated over an extended period of time
were available at the time of analytical method development.
As a general rule, the higher the accuracy demand of
an analysis, the higher are its costs. This fact raises the
question as to the ultimate use of the analytical results. The
accuracy requirements for routine, day-to-day operation are less
stringent than the requirements for process analysis. One key
objective of the tests at Shawnee is the collection of engineer-
ing design information. From an engineering point of view the
following areas are of ultimate interest:
gas-liquid mass transfer rates in
the scrubber
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dissolution and precipitation rates
as function of liquor composition
scaling potential
The driving force term in the mass transfer equations
describing these rates is a function of the difference of the
actual process conditions and the equilibrium conditions of the
system. In other words, the rates are a function of the dif-
ference of two activity expressions. The closer the system
approaches equilibrium the more severely analytical errors will
influence rate correlations. For LIWS processes the analyses
of the species listed in Group 1 are, therefore, the most
important. Error propagation calculations showed that the error
in these analyses should not be greater than about 270. The
concentration of the species influencing the ionic strength
(Group II) must be known within about 470. The accuracy require-
ments for the trace elements effective as catalysts are still
less stringent. Twenty to fifty percent is considered to be
sufficient.
An example of how to calculate partial pressures and
important solubility (activity) products from chemical analysis
data is shown in Chapter VIII of this volume. These data are
necessary inputs to evaluate scrubber performance from a chemical
engineering point of view.
The analytical results are influenced by three steps:
solid-liquid separation
sample handling
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actual analysis
These problem areas will be discussed next
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3.0 SAMPLING
The scrubbing system can be divided into an acidic
and a basic part. The environment is acidic in the scrubber
itself and in the pipe between the scrubber and the effluent
hold tank. The solutions circulated in the rest of the system
are alkaline. For sampling purposes it should be noted that
the scrubbing slurry, especially in the acidic part of the
system, is not in thermodynamic equilibrium. The sorbent tends
to dissolve and sulfite and sulfate tend to precipitate. The
technique often used to sample this stream is collection of a
slurry sample in a beaker and filtration through a Buchner
funnel. This technique results in only semi-quantitative results
for the follow-on chemical analysis for three reasons:
1. Loss of acidic gases (SOS, C0a)
especially if a vacuum is used.
2. Solid-liquid mass transfer during
the sampling procedure.
3. Sulfite oxidation by air oxygen.
Because of these sources of error much of the pilot plant data
collected using this method must be considered to be qualitative
in nature and not suitable for the extraction of engineering
design information. In-line, positive pressure filtration was
the sampling method selected after field tests at several pilot
units (see Figure 3-1). The sampling apparatus consists of a
positive pressure pump, a membrane filter holder and lines and
valves to control sampling and purge rates. Flow rates used in
the tests were about 1300 ml/min. The residence time of the
slurry is about 2.3 seconds in the filter and approximately
seven seconds in the entire sampling equipment.
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Reagent Reservoirs
Process
Stream
-{Xh
Positive
Pressure Pump
Filter Holder
\
Purge to
Drain
Sample
Container
FIGURE 3-1 - TYPICAL SLURRY SAMPLING TRAIN
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The degree of mass transfer in the filter cake, which
is by nature a good contacting device, was checked by taking
consecutive samples and plotting the chemical analysis results
as a function of the filtered volume. Extrapolation to zero
volume of filtrate represents the true aqueous phase composition,
With the exception of carbonate, the amount of solids dissolved
or precipitated in the filter cake was within the experimental
error of the chemical analyses.
Loss of acidic gases is avoided by the positive pres-
sure filtration, and air oxidation of sulfite is prevented by
fixing the sample immediately.
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4.0 SAMPLE HANDLING
After filtration care mast be taken that the liquid
samples do not undergo further change. This is especially true
for the sulfite analysis. Sulfite losses can occur by:
Evaporation from acidic samples
Oxidation by air oxygen
Interaction with nitrites
All three sulfite losses can be avoided by quenching the sample
in a solution of pH = 6 with known iodine content (see Chapter
5.3.2 of Volume II). Nitrites can be formed by absorption of
NO and N02 from the flue gas. The degree of NO* absorption
was unknown at the time of method selection.
Carbonate losses from acidic liquid can be avoided
by quenching the sample in a solution of pH - 10. EDTA must
be added to the buffer in order to avoid calcium carbonate
precipitation at this pH (see Chapter 5.3.1 of Volume II).
Sulfate in the presence of sulfite is determined as
the difference between the total sulfur and the sulfite sulfur.
In order to avoid sulfite losses and sulfate precipitation, the
sample for total sulfur analysis is quenched in a H3 Og-water
solution. Hydrogen peroxide oxidizes the sulfite. Dilution
with distilled water prevents sulfate precipitation in the
sample bottle (see Chapter 5.3.3 of Volume II).
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5.0 .LIQUID PHASE CHARACTERIZATION
The literature was surveyed through 1970 for analytical
methods which might be applicable to the solutions of interest.
The sources consulted were:
1. Kolthoff and Elving, "Treatise on
Analytical Chemistry"
2. Biannual Reviews on Analytical
Chemistry
3. 1969 Book of ASTM Standards
4. FWPCA Methods for Chemical Analysis
of Water and Wastes
5. Chemical Abstracts
6. Pertinent Original Articles
The present chapter discusses the wet chemical
procedures for the determination of chloride, C03 in aqueous
solution, sulfite in aqueous solution, total sulfur as sulfate,
total nitrogen and for the analysis of nitrite and nitrate.
The methods chosen are applicable for highly concentrated
scrubber solution as encountered in closed loop operation.
Atomic absorption proved most suitable for the analysis
of calcium, magnesium, sodium, and potassium. The catalytically
active transition elements, iron, manganese, cobalt, nickel,
and copper, are determined after chelation with diethyl-dithio-
carbatnate and extraction into methyl isobuthyl-ketone.
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X-ray fluorescence proved to be an accurate and rapid
procedure for the determination of total sulfur, which is a
very critical analysis in limestone based wet scrubbing solutions
In addition, calcium, chlorine, and potassium in the aqueous
phase can be analyzed by this approach.
The methods selected are described in this chapter
in a succinct form. The results of the literature survey and
a detailed description of the interference studies performed
experimentally are presented in Volume II of this final report.
5.1 Wet Chemical Procedures
5.1.1 Chloride Determination
A summary of the relevant methods for determination
of chloride ion in aqueous solution, based on the literature
survey, is given in Table 3.1-6 of Volume II. The methods
covered in this table fall into one of the following broad
categories.
1. Gravimetric as silver chloride
2. Volumetric (visual end point)
3. Spectrophotometric
4. Nephelometry
5. Flame Photometry
6. Potentiometric measurements
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7. Amperometrie (current) measurements
8. Coulometric measurements
Most chloride determinations are based on the reaction
of chloride ion with either silver (I) or mercury (II). The
methods proposed by Volhard, the mercurimetric .titration for
chloride and the potentiometric method described by Shiner and
Smith (SH-014, FI-019) were tested in the laboratory. The
Volhard method was found to yield good results down to a chloride
concentration of 0.02 M (Volume II, page 315). The mercurimetric
procedure suffered interferences from iron ion found in some
pilot plant samples (Volume II, page 327).
The potentionmetric determination of chloride proved
to be the most satisfactory wet chemical procedure (Volume II,
page 319). A Fisher Automatic Titralyzer (Model 740) was used
to check this procedure. This is an automated potentiometric
titrator designed to do volumetric analyses fully automatically.
It incorporates into a single, integrated system an electrometer,
an automatic buret, a digital data recording system, and an
automatic sample changing device.
The potential between a metallic silver indicator
electrode and a silver-silver chloride reference electrode is
measured as a function of the amount of standard silver nitrate
solution added. The reaction of silver nitrate with chloride
ion may be represented in the following way.
Cl" + Ag+ -> AgCl (solid) (5-1)
The potential of the metallic silver electrode depends on the
amount of silver ion in solution.
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In practice the potential at the equivalence point
is determined by a manual titration or by addition of a known
amount of standard silver nitrate solution to a known amount
of a standard chloride solution. This known equivalence point
potential is then set as the end point potential on the Titra-
lyzer and all other titrations are stopped when this potential
,is reached.
Interferences
Bromide and iodide will be determined as equivalent
chloride concentrations. Ferricyanide causes high results and
must be removed. Chromate and dichromate interfere unless
reduced to the chromic state. Concentrations of ferric iron,
if substantially higher than the amount of chloride, will
interfere. Ferrous ion and phosphate do not interfere.
Results of Chloride Titrations
Accuracy and precision are excellent. The relative
error using artificial scrubber samples never exceeded .5% in
a series of 15 titrations.
This method for determining chloride was also applied
to field samples. For the Key West series of samples, triplicate
titrations were run for each sample. Recovery tended to run a
little low ranging from 98.2% to 99.8% for 22 samples.
For the Colbert Test Series one unspiked aliquot and
one spiked aliquot were run for each sample. The results of
the recovery studies are given in Table 5-1. Recoveries ranged
from 99.4% to 101.8% for 15 samples.
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TABLE 5-1
RECOVERY STUDIES
Sample Name
Scrubber Effluent
Scrubber Spray
F-12 Overflow
F-13 Recycle
Clarifier Overflow
Limestone Feed
Make Up Water
Scrubber Effluent
Scrubber Spray
F-12 Overflow
F-13 Recycle
Scrubber Effluent
Scrubber Spray
F-12 Overflow
F-13 Recycle
ON COLBERT CHLORIDE DETERMINATIONS
(1)
Titration
of
Unspiked
Aliquot
ml AgN03
2.22
.32
1.91
1.88
2.15
1.81
.05
2.38
.53
2.30
2.18
2.30
.49
4.86
4.56
(2)
Titration
of
Spiked
Aliquot
ml AgN03
7.26
5.32
6.92
6.95
7.12
6.82
5.06
7.44
5.50
7.32
7.19
7.36
5.49
9.90
9.65
Difference
(2)-(l)
5.04
5.00
5.01
5.07
4.97
5.01
5.01
5.06
4.97
5.02
5.01
5.06
5.00
5.04
5.09
Percent
Recovery
100.8
100.0
100.2
101.4
99.4
100.2
100.2
101.2
99.4
100.4
100.2
101.2
100.0
100.6
101.8
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The recoveries are all well within the accuracies
required for chloride determinations and indicate that no
serious interferences for this method of chloride determination
were found in these sets of field samples.
5.1.2 C0a Determination
The literature findings on methods used for measuring
COS content in liquid and solid samples are summarized in
Chapter 3.1.8 of Volume II. The procedures described can be
grouped into one of the following categories:
Volumetry
Colorimetry
Gravimetry
Evolution techniques
An instrument based on C02 evolution in an acid pool with sub-
sequent CO., detection by a nond isper sive infrared analyzer was
found to be suitable for C0a determinations in aqueous solutions
(Total Carbon System, Oceanography International). Interferences
caused by nitrates, nitrites, and sulfite could be overcome by
using a 10% KR, P04 solution in the reactor.
Accuracies of better than two percent were obtained
in analyzing synthetic scrubber solutions. Table 5-2 gives
supporting data. The analysis time per sample ranges from five
to six minutes.
-17-
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TABLE 5-2
Run
No.
1
2
3
4
i
»-•
T5
6
7
8
9
10
me
Injected
46.4
96.1
146
146
146
146
146
146
146
146
INFLUENCE
OF NITRITE, NITRATE AND SULFITE ON THE TOTAL
USING THE "TOTAL CARBON
NO;
mtration
ss/Liter
0.5
0.5
0.5
0.5
«__
0.5
___
0.5
NO;
Concentration
Moles/Liter
0.5
0.5
0.5
0.5
0.5
.0.5
so;
Concentration
Moles/Liter
0.05
0.05
0.05
0.05
0.05
0.05
SYSTEM" CQce
Actual C0a
Concentration
mg/Liter
100
100
100
100
100
100
C02 ANALYSIS
:anography International)
Experimental C03
Concentration Percent
- mg/Liter Error
102.0
100.6
100.2
102.0
100.5
101.0
0.0
0.0
0.0
0.4
- 2.0
- 0.6
- 0.2
- 2.0
- 0.5
- 1.0
0.0
0.0
0.0
- 0.4
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5.1.3 Sulfur Dioxide Determination
The literature finding concerning methods for
determination are summarized in Volume II, page 113. The
procedures are based on:
Polarography
Atomic absorption spectroscopy
Fluorescence
Visible and ultraviolet spectro-
photometry
Amperometry
The amperometric procedure was found to be the most straight-
forward approach. The sample is added to an excess iodine
solution buffered to pH = 6.0 - 6.2 to inhibit sulf ite-nitrite
and nitrite-iodine interaction (DE-029, SE-015). Iodine remain-
ing after stoichiometric S0a oxidation is titrated with standard
sodium arsenite solution. An amperometric dead stop method for
end point detection is used. The error is 2-4% in the presence
of 20 mrnoles nitrite.
5.1.4 Total Sulfur Determination
The methods described in the literature for the
determination of sulfate in aqueous solutions are summarized
in Volume II, Chapter 3.1.10.
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The published procedures can be divided into five
groups :
1. Gravimetric procedures
2. Direct titrimetric procedures
•
3. Indirect titrimetric methods
4. Colorimetric techniques
5. Acidimetric methods
The most elegant method is the titrimetric approach using thorin
as end point indicator (AM-002, MA-039, FR-003, FR-009). Un-
fortunately, this method is subject of severe anion interference
caused by the presence of phosphate, fluoride, nitrate, and
chloride.
The barium chloranilate spectrophotometric procedure
was extensively checked (BE-024, PR-007, FE-004). It is based
on the precipitation of barium sulfate upon interaction of
barium chloranilate with sulfate ion. The intensity of the
colored chloranilate is measured at 530 nm. This procedure is
amenable to automation (Volume II, page 366). Nitrate and
chloride showed interferences if present in high concentrations.
The method showed, in addition, pH-sensitivity and problems in
the removal of the very fine precipitate.
Barium sulfate precipitation and backtitration of
excess barium using EDTA and Eriochrome Black T as indicator
gave satisfactory results (Volume II, page 358). Interfering
3+ 3+
cations (Fe , Al , Ca and Mg) are removed using a cation
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exchange resin in the sodium form. A disadvantage of the
procedure is the long digestion time (KO-015, TH-007, SI-005,
SH-006).
The titrimetric procedure proposed by Dollman (DO-006)
was finally accepted (Volume II, page 383). A sample aliquot
is passed through a strong acid type ion exchange resin in the
hydrogen form. Sulfate and other anions are converted to the
corresponding acids. The column effluent is quantitatively
retained. All acids except H^ S04 and Hg P04 are volatilized
at 75°C. Titration with a standard base completes the deter-
mination. Phosphate, if present, interferes. It can be deter-
mined by the same technique by volatilizing the HgS04. The
sulfate value is then corrected. The accuracy of the method,
if carefully applied, is better than 17» (see Tables 3.4-13,
3.4-14, 3.4-15 of Volume II).
5.1.5 Total Nitrogen
The nitrogen containing compounds found in lime/
limestone based scrubbing solution can be quantitatively reduced
to ammonia in the presence of a metallic reducing agent (Volume
II, page 138). Devarda's alloy (50% Cu, 4570 Al, and 5% Zn) in
a strong NaOH solution was found to be satisfactory (EN-020,
KO-050, MU-020). The reduction cannot be performed in an acidic
medium due to hydrogen sulfide evolution. Ammonia is distilled
into hydrochloric acid. Excess HC1 is backtitrated.
The error determined in the presence of sulfite was
found to be smaller than 170 at nitrate levels of 100 to 160 mg
in the aliquot (Volume II, page 399).
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5.1.6 Determination of Nitrite and Nitrate
The literature findings for the quantitative analysis
of nitrites are presented in Volume II, Chapter 3.1.12. Table
3.1.11 shows examples of the principal types of methods which
can be used to determine nitrite in aqueous media. They can
be classified in the following categories:
* Ultraviolet
Manometric
Amperometric
Coulometric
Chemical
Procedures for nitrate determination are similarly
numerous. They encompass:
Nitration
Reduction
Ultraviolet
Electrochemical
Manometric
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Gravimetric
Other methods
Key examples are presented in Volume II, Table 3.1-12.
The simultaneous determination of nitrate and nitrite
proposed by Wetters and Uglum (WE-008) was found suitable for
analysis of scrubber solutions. The method is based on the
fact that both nitrate and nitrite absorb in the ultraviolet.
Nitrite has an absorbance maximum at 355 nm while nitrate shows
a maximum at 302 nm. Calcium, magnesium, sodium, potassium,
carbonate, sulfite, sulfate and chloride showed negligible
interference. Samples with nitrite concentrations of 100-1000
mg/£ can be determined with better than 3% accuracy using 1 cm
cells. Samples with nitrate concentrations of 20-500 mg/£ and
nitrite concentrations of 20-100 mg/1 can be determined with
better than 570 accuracy using 10 cm cells. Tables 5-3 and 5-4
give supporting data. The experimental results are described
in more detail in Volume II, page 400.
Nitrate concentrations at lower levels can be deter-
mined using the procedure by West and Ramachandran (WE-012).
This method is based on a reaction of nitrate with chromotropic
acid. The absorbance is measured at 410 nm. Beer's Law is
fulfilled for a nitrate concentration between 0 and 60 ppm.
Experimental details of the procedure are presented in Volume
II, page 416.
5.2 Atomic Absorption Procedures
The application of atomic absorption procedures for
the analysis of scrubber liquors is discussed in detail in
-23-
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TABLE 5-3
N3
4>
i
"355
.505
.505
.504
.202
.101
.052
"30 a
.763
.219
.225
.539
.614
.055
Simultaneous Determination of Nitrate and Nitrit.e
in pH 6 Simulated Filter Bottoms
Corrected A3oa
.561
.117
.024
.458
.574
.024
NO "-Added
Cmg/jO
1000
1000
1000
400
200
100
NO ~ Found
*mg/A)
1004
1004
1002
400
198
100
(1 cm cells)
% Error
-0.4
-0.4
-0.2
0.0
+1.0
0.0
NO ~ Added
(mg/j&)
5000
-1000
200
4000
5000
200
NO " Found
(~g/A)
4855
1000
200
3924
4965
200
7, Error
+2.9
0.0
0.0
+1.9
+0.7
0.0
-------
TABLE 5-4
i
NJ
Ln
^3 38
.505
.501
.499
.201
.100
.048
.025
^303
.762
.317
.223
.536
.609
.079
.388
Simultaneous
Determination of Nitrate and Nitrite in
pH 11.3 Simulated Filter Bottoms
Corrected A303
.560
.117
.0234
.456
.569
.060
.288
N0a" Added
(mg/jl)
1000
1000
1000
400
200
100
500
NO "Found
1010
1002
998
404
204
100
500
(1 cm Cells)
7. Error
-1.0
-0.2
+0.2
-1.0
-2.0
0.0
0.0
NO 3~ Added
(mg/jl)
5000
1000
200
4000
5000
500
2500
N03~ Found
(mg/l)
4870
1000
199
3974
4950
508
2483
7o Error
+2.6
0.0
+0.5
+0.7
+1.0
-1.7
+0.7
*A11 runs were made using delonized water as a reference and NaNOa and NaN03 as standards.
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Volume II, Section 3.2. This method was found suitable for
the analysis of calcium, magnesium, sodium, potassium, and
trace elements.
5.2.1 Determination of Ca, Mg. K, and Na
The experimental studies to define optimum concentra-
tion ranges and interferences encountered in lime/limestone
based wet scrubber solutions are described in detail on pages
181-233 of Volume II. A Perkin-Elmer Model 403 Atomic Absorption
instrument was used.
o
The calcium line at 4227 A was measured. Interferences,
mainly from sulfate, could be suppressed by using a 1% LaCl3,
57o HC1 solution in the final dilution step. The absorbance is
a linear function of calcium concentration in the range 0-7 mg/jl
Ca. The accuracy in synthetic scrubber solutions was found to
be about 2%.
o
Magnesium was measured at the 2852 A line. Interfer-
ences could also be suppressed by using a 170 LaCl3 , 570 HC1
solution in the final solution step. Absorbance is a linear
function of concentration in the 0-0.7 mg Mg/£ range. The error
in analyzing wet scrubbing solutions is approximately 270.
o
The absorbance of sodium at 5890 A is linear up to
a sodium concentration of about 1.5 mg/£. Interferences are
suppressed by 170 LaCl3 , 57o HC1, with the exception of potassium
interference. The standards should contain approximately the
same amount of potassium than the test solution for accurate
determinations. Accuracies using synthetic scrubber solutions
were found to be approximately 370.
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Sulfate, calcium, magnesium, and sodium were found
o
to interfere with the potassium determination at 7665 A. The
addition of 170 LaCl3 , 5% HC1 suppresses the interference partly.
The Mg, Ca, and Na content in the standard must be matched to
that in the sample. The optimum potassium concentration ranges
up to 6 mg/Ji. Errors in analyzing artificial scrubber solutions
using matched standards were approximately 4%.
5.2.2 Determination of Catalytically Effective Trace Elements
Cobalt, copper, iron, manganese, and nickel are reported
to catalyze sulfite oxidation by oxygen even if present in the
ppb range. These elements can be determined by atomic absorption
once they are extracted from the original phase. The elements
of interest are concentrated in the extraction step. In
addition, the instrument sensitivity is increased two to five-
fold (PE-037) when an organic, instead of an aqueous phase, is
aspirated into the atomic absorption spectrophotometer.
The system dithizone, 8-quinolinol and acetyl acetone
(chelating agent)-ethyl propionate (solvent) extracted Co, Cu,
Fe, and Ni but not Mn. It was abandoned in favor of methyl
isobutyl ketone (solvent) and diethyldithiocarbamate (chelating
agent) (JO-012).
Using this method cobalt, copper, iron, and manganese
can be determined at approximately the 10 ppb level to better
than ± 25%. Nickel can only be determined to 100 ppb with this
accuracy due to flame emission effects at the low wavelength
at which nickel is measured. Chapter 3.2.3 in Volume II gives
more details.
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5.3 X-Ray Fluorescence
The evaluation of the literature on methods to deter-
mine total sulfur (in the form of sulfate) revealed that no
rapid field method existed giving accuracies of better than 3%.
X-ray fluorescence spectrometry was investigated as a possible
means to determine sulfur rapidly and accurately. No literature
could be found describing the application of X-ray fluorescence
to the analysis of liquid samples of composition comparable to
samples taken from SOS removal processes. In addition to sulfur,
calcium, potassium, and chlorine may be determined rapidly using
X-ray fluorescence spectrometry.
This section of the report presents a brief discussion
of the physical basis for X-ray fluorescence spectrometry and
a description of the types of instrumentation available. This
section also contains the report of the experimental measure-
ment of relevant matrix interference coefficients and the mathe-
matical description of their application to calibration and
measurement procedures. Chapters 3.3 and 4.1 of Volume II dis-
cusses the application of X-ray fluorescence in more detail.
5.3.1 Physical Phenomena
If a material is bombarded with X-rays of sufficiently
high energy (short wavelength), the atoms of the material will
give off characteristic X-rays. The wavelength of the emitted
(fluorescent) X-rays will be characteristic of the kinds of
atoms (elements) in the material, and the intensity of a given
wavelength will indicate the concentration of that particular
element. Then by measuring the intensity of the fluorescent
X-radiation at different wavelengths it is possible to deter-
mine the elements present in a given material and their
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concentrations. Absorption of the fluorescent radiation by
the sample or secondary fluorescent effects are potential sources
of error and are discussed later.
5.3.2 Description of Available Equipment
In conventional X-ray fluorescence instruments, the
fluorescent radiation is dispersed so that the angle of
dispersion is dependent upon the wavelength. X-ray detectors
are used to determine the intensity of the radiation at each
angle. X-ray dispersion is usually accomplished by directing
the X-rays onto a crystal which acts in the same way as a
diffraction grating.
Energy dispersive X-ray fluorescence utilizes a semi-
conductor detector which responds linearly to the energy of
the incoming X-ray and a multichannel analyzer which sorts the
resulting voltage pulses according to height and counts the
number of pulses in each energy band to produce a complete
energy spectrum of the X-rays. Such systems do not have as
much resolution as wavelength dispersive instruments, and if
radioactive elements are used as sources of existing radiation,
they are not as sensitive to low concentrations of elements in
the sample. This type of instrument v?as not tested for Lhis
application.
5.3.3 Preliminary Tests
Wavelength dispersive instruments are available
which measure one element after another (sequential) or which
measure several elements simultaneously (multichannel).
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Instruments of both types were tested in the manufacturers'
laboratories using simulated scrubbing liquors. The multi-
channel instrument yielded more precise analyses for chlorine.
The sequential instrument yielded more precise analyses for
sulfur and calcium. The precision of potassium analyses was
comparable on the two instruments. Sulfur and calcium were
the elements for which the more accurate analyses were required;
therefore, the sequential instrument was chosen as being more
suitable for this particular application.
5.3.4 Description of Sequential Instrumentation
The spectrometer arrangement for the sequential X-ray
spectrometer chosen is shown in Figure 5-1. The sample to be
analyzed is irradiated from below; the excited characteristic
X-radiation is collimated by a Soller slit and reflected at the
analyzer crystal at various angles, depending on the wavelength
(Bragg reflection condition). The intensity of a spectral line
is measured by the proportional counters and the associated
electronics. The wavelength to be counted is set for each ele-
ment in a given sample in sequence. A given analyzing crystal
can cover only a finite wavelength range so for large wavelength
changes one crystal must be replaced by another. The angle
setting mechanism is continuously variable and by careful choice
of crystals a large- number of elements may be determined.
The system chosen was operated manually for deter-
mination of matrix interference coefficients (described below).
Before installation at Shawnee a minicomputer and data acquisition
system were interfaced with the X-ray fluorescence spectrometer
system so that operation of the spectrometer system was controlled
by the computer and data reduction was automatic.
-30-
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Primary X-ray Beam
(Continuum -f Anode Characteristic)
SampFc—_r
I ,
X-ray Tube
Wavelength Measured, X
Secondary Emission Lines
(Sample Characteristic)
Analysing Crystal-
Changer
Flov/
Proportional
Counter
-Scintillation
Counter
FIGURE 5-1 - BEAM PATH IN THE SEQUENTIAL X-RAY SPECTROMETER
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5.3.5 Matrix Interference Corrections
Quantitative X-ray fluorescence analysis, as with
most other analytical procedures, is subject to interferences.
The intensity of the fluorescent radiation of element i can be
reduced or increased by another element j present in the sample.
Reduction of intensity is caused by absorption effects and
increased intensity is observed if secondary excitation occurs.
In the analysis of S03 scrubbing liquors, absorption effects
are the dominant interfering phenomena and secondary excitation
effects can be neglected if they are present at all.
Figure 5-2 is a plot of counting rate versus concen-
tration of chlorine in the presence of varying amounts of sulfur
The error bars represent counting errors for individual measure-
ments. The equations for the lines were obtained using the non-
linear least squares program outlined later in this section.
The general equation relating concentrations of inter-
fering elements to the observed intensities may be written:
-Ik., c.
•i LJ J
Ni = ai + biC± exp J (5-2)
where the i subscripts refer to the element being measured and
the j subscripts to the interfering elements. The definitions
•
of the terms in this equation are listed below.
N. = the counting rate for fluorescent
radiation f$r the element i as cal-
culated from number of counts and
the time required to obtain those
counts (counts/sec). The counting
rate is the instrumental measure
of the intensity of the fluorescent
radiat ion.
-32-
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I
OJ
OJ
£000 -
/e>oo -
(600 -
O
O
u
CO
MOO -
IZOO -
11 ~!"~T~" . • | • •
•:;• • ; h •• : h;1; r; I;
.......... i ......
I '
.01 .02. .03 .04. .OS .06 .07 .OS>
FIGURE 5-2 - CONCENTRATION OF CHLORINE (MOLES PER LITER)
-------
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a. = the intercept of the calibration
line. It is the counting rate at
the setting for measuring element
i when no element i is present in
the sample (counts/sec).
b. = the slope of the calibration line
for element i when no interfering
elements are present
c. - the concentration of element i in
the sample measured (moles/liter).
k. . - matrix interference coefficient for
j as the interfering element when
element i is being measured (liters/
mole).
c. := The concentration of interfering
element j (moles/liter).
Reliable literature values for the matrix interference
coefficients (k..) were not available. Matrix interference
coefficients of importance in analyzing lime/limestone scrubber
liquors were determined as part of the in-house testing and
preparation of the sequential X-ray fluorescence system.
Matrix interference coefficients were determined using
solutions containing kno^n concentrations of interfering ele-
ments as well as known concentrations of the element being
measured. In the simplest case, three solutions were used which
had the following concentration specifications. One solution
would contain no element i. Measurement of the fluorescent
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intensity of this solution would determine a.. The other two
solutions would contain equal amounts of element i but different
amounts of element j, the interfering element. Practical con-
siderations (prevention of the formation of a precipitate or a
volatile species) dictated that in some cases more than one
interfering element had to be present. In practice.there were
never more than three interfering elements present. We now let
the subscript j stand for the element, the effect of which we
are trying to measure, and the subscripts i and p indicate oLher
interfering elements which may be in solution. If appropriate
substitutions are made into Equation (5-2) , the resulting
equations solved simultaneously and rearranged we obtain:
- c
C
-k. (c 0 - c i )
IP \ p2 pi/
^N.9 a.) "ije Vu£2 "£l/ ip \"P2 pi
k. - ^ ~ L (5-3)
J r- — r
Equation (5-3) is the basic equation used to calculate all the
values of k-. which were obtained by measurements on three
solutions.
Matrix interference coefficients were determined for
the four elements to be measured by X-ray fluorescence, sulfur,
chlorine, potassium, and calcium as element i. Interfering
elements were taken to be nitrogen, sodium, magnesium, sulfur,
chlorine, potassium, calcium. The self-interference of an
element (k..) was found to be zero in the concentration range
of interest. Typically, three determinations of each matrix
interference coefficient were made by the method outlined above
In order to obtain more accurate data for certain key
interactions and for those systems which for practical reasons
did not contain large excesses of the interfering element,
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several sets of data were taken using 10-16 known solutions.
The data for these solutions were correlated using a computer
to perform a non-linear least squares program which calculated
the coefficients a., b., and k.. (Equation 5-2) iteratively so
as to minimize the error between observed counting rates and
counting rates calculated using the coefficients and known con-
centrations. Mathematical details and computer printouts are
given in Section 3.3.4.4, Volume II of this report.
5.3.6 Summary of Selected Values for Matrix Interference
Coefficients and Associated Uncertainties
The selected values of k^. are listed in Table 5-5.
In cases where least squares values are available, they are
used. In some cases the average of two least squares calculations
was chosen. If sets of least squares data were not available,
then averages of the values obtained on sets of three solutions
were selected. These are the values which are used in the
Shawnee data handling computer program to calculate matrix
corrections.
Table 5-5 lists the errors to be expected for a
solution of a composition which might reasonably be found at
Shawnee. The sixth column lists the errors if matrix interference
corrections are neglected at all, and the last column the un-
certainties of the results caused by errors of the k. . ' s .
5.3.7 Calibration Procedures for X-Ray Fluorescence
Spectrometry
Referring back to Equation (5-2), we note that counting
rates that are measured, N., are related not only to the
-36-
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TABLE 5-5
SUMMARY OF ERRORS TO BE EXPECTED IN CONCENTRATION MEASUREMENTS IF MATRIX INTERFERENCES ARE IGNORED
AND OF UNCERTAINTIES IN CONCENTRATION MEASUREMENTS DUE TO UNCERTAINTY IN VALUES OF It.
Concentration
of Measured
Element Interfering Element 1
Measured 1 Element i iir.oles/liter)
Limestone
S
S
s
s
s
s
Totals
Cl
Cl
Cl
Cl
Cl
Cl
Totals
K
K
K
K
K
K
Totals
Ca
Ca
Ca
Ca
Ca
Ca
Totals
Sodium
System
N
Na
Mg
Cl
K
Ca
for Sulfur
N
Na
MS
S
K
Ca
for Chlorine
N
Na
Mg
S
Cl
Ca
for Potassiun
N
Na
Mg
S
Cl
K
for Calcium
Carbonate Svstem
.025
.025
.025
.025
.025
.025
.025
.025
.025
.025
.025
.025
.001
.001
.001
.001
.001
.001
.020
.020
.020
.020
.020
.020
X Relative
Error In
Concentration
Concentration .. , Measurement
of Interfering * " If Matrix
Element J or Klj Correction
(moles/liter) Used is Ignored
.002
.001
.017
.025
.001
.020
.002
.001
.017
.025
.001
.020
.002
.001
.017
.025
.025
.020
.002
.001
.017
.025
.025
.001
.03*
.05
.10*
.009*
.01
.1**
.02
.08
.11
.26*
.03
.2*
.03
.08
.11
.28
.26
.08
.03*
.08
.09*
.3**
.29**
.41
.008
.005
.17
.025
.001
.2
.4
.004
.008
.2
.65
.003
.4
1.3
.006
.008
.2
.8
.65
, .18
1.8
.006
.008
.15
.9
.72
.04
1.8
Uncertainty
In Value
of ku
.01
.01
.02
.005
.01
.1
.02
.01
.04
.01
.01
.2
.01
.02
.04
.01
.01
.04
.01
.01
.03
.2
.03
.06
1 Relative
Uncertainty In
Concentration
Measurement of
Element i Due
to Uncertainty
in kj.
.003
.001
.04
.01
.001
.2
.3
.004
.001
.008
.02
.001
.4
.4
.002
.002
.11
.03
.025
.08
.3
.002
.001
.05
.6"
.05
.006
.7
.015
.035
.05
.18
.01
.03
* Obtained by non-linear least squares calculation using at least 10 data points.(Tables 3.3-8 - 3.3-20)
** Average of 2 values obtained from non-linear least squares calculations on 2 sets of data points.
(Estimated concentrations for limestone runs were obtained from data for Colbert Steam Plant Pilot
Unit - October, 1971. The concentrations listed are approximately % the maximum concentration
found for a given element. Thus, a dilution of approximately 1:1 la assumed In line with the
standard procedure for obtaining type X samples.)
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concentration of the element for which the analysis is run, c-,
the concentration of interfering species, c., and the matrix
interference coefficient, k.., but also to a. and b. which are
respectively the intercept and slope of the calibration line.
These last two parameters are dependent not only on the settings
and characteristics of the entire X-ray excitation and measuring
system but also on the characteristics of the individual plastic
membrane used as a window on the bottom of the sample cup.
Measurements on sulfuric acid solutions using a set of
nine hostaphane membranes revealed significant variation from
one membrane to the next. The necessity of calibrating each
plastic membrane was established.
Calibration will also be required if any change is
made in the settings of the X-ray excitation and measuring
system. In normal field operation this is likely to occur when
the P-10 gas used in the flow proportional counter is changed
or in the instances of instrumental failure and subsequent
repairs.
The following calibration procedure is recommended.
For a given membrane all elements will be calibrated at once.
Two to four calibrating solutions each containing different
amounts of sulfur, chlorine, potassium, and calcium will be used
The counts obtained in analyzing deionized water determine a..
The minimum total number of calibration solutions is three so
that the calibration line may be calculated by the least squares
program outlined below. Five solutions including deionized
water are a practical number to establish the calibration
constants.
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5.3.8 Mathematical Background for Computer Calculation
of Calibration Parameters for XRF System
The computer program is designed to calculate the
intercept and slope of the best straight line as fitted by a
least squares calculation through three to five data points.
It is anticipated that each datum point will represent the
counting rate for a different concentration of the element under
consideration.
The program optimizes the intercept and slope in an
iterative manner by minimizing the difference between the
measured counting rates and those calculated from trial values
of a. and b. and the known concentrations. Matrix interference
corrections are made for the interfering elements in the calibrat'
ing solutions.
The mathematical basis for the program is given in
more detail in Section 3.3.5.1 of Volume II. Details of the
computer program are given in Volume III.
Detailed instructions for the preparation of suitable
calibrating solutions are given in Volume II, Section 3.6,
"Selected Field Methods and Data Analysis System."
5.3.9 Fluorescence Counting Rate Measurements
Referring again to Equation (5-2), we have listed the
values of k.. (in Table 5-5) and have outlined the method for
obtaining a. and b. from the calibration procedure. N. is
obtained directly from the output of the X-ray measuring system,
and if we can obtain values of c. we will be in a position to
calculate c-.
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The concentrations of interfering elements (the c.'s)
come from two different sources. The concentrations of nitro-
gen, sodium, and magnesium are determined by methods other than
X-ray fluorescence. These concentrations, when available, may
be put into the computer and the corrections calculated directly,
The concentrations of sulfur, chlorine, potassium, and calcium
will usually be determined by X-ray fluorescence and their con-
centrations must be calculated simultaneously by an interative
process. For computational purposes the interfering elements
are divided into two groups. The group j = 1 through J are
elements determined by XRF. The elements i = j+1 through L are
determined externally. The logarithm of Equation (5-2) is taken
and the above definitions used.
0n (—^~ j = ^ Ci - Z ^ij °j
ci
The s subscripts for N, a, and b refer to a particular sample
membrane .
The set of non-linear equations obtained when known
values are substituted into Equation (5-4) is solved iteratively
by assuming that the corrections are small to obtain initial
values, then defining an error function and minimizing it.
Mathematical details are given in Section 3.3.5.2 of Volume II.
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6.0 SOLID PHASE CHARACTERIZATION
The characterization of solids comprises two steps,
namely (1) determination of the chemical composition and (2)
crystalline phase identification. The first task is achieved
by chemical analysis after dissolution of the solids, the second
by use of X-ray diffraction. The problem area is discussed in
detail in Section 4.0 of Volume II on pages 491-547.
6.1 Chemical Composition
The components of interest in the solids include
calcium, magnesium, total sulfur, carbon dioxide, and sulfur
dioxide. Total sulfate is calculated as the difference of
total sulfur and sulfite sulfur.
Approximately 1 g of solid sample (dried at 75°C) is
dissolved in a hydrogen peroxide, hydrochloric acid solution.
The dissolution step is carried out in a stoppered flask to
avoid loss of SOS. Sulfate, sulfite, and carbonate dissolve
completely under these conditions. Sulfite sulfur is oxidized
to sulfate sulfur. The solution is brought to volume. Total
sulfate is determined by the ion exchange alkalimetric procedure
or by X-ray fluorescence. Calcium is determined by X-ray fluo-
rescence or atomic absorption. Atomic absorption is the method
of choice for magnesium.
Carbon dioxide in solids is determined by an evolution
technique (see Sections 3.4.4 and 4.3.2 of Volume II). C03 from
solids is liberated by acidifying the sample with sulfuric acid
in a closed system, which includes a carbon dioxide absorber,
a gas scrubber, an expansion baldder and a circulating pump.
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The carbon dioxide combines with barium hydroxide solution of
known normality content to form BaC03 precipitate. The excess
hydroxide is titrated with standard hydrochloric acid to the
phenolphthalein end point.
About 0.1 to 0.4 g of original sample is dissolved in
a buffered iodine solution for sulfite determination. Excess
iodine is back titrated with arsenite solution using the dead
stop technique for end point determination. The procedure is
described in more detail in Sections 3.5.4 and 4.3.3 of Volume
II.
6.2 Phase Identification
The crystalline phases contained in the solids are
identified by X-ray diffraction. The principle of X-ray dif-
fraction techniques are summarized in Section 4.1 of Volume II.
A finely ground powder is irradiated with monochromatic
X-radiation. The lattice planes of the fine crystals diffract
the X-rays in a discrete direction if the Bragg equation is
fulfilled.
nX = 2di • sin ei (6-1)
X = wavelength of the incident X-ray
o
beam (A)
n = order of the reflection
d. = distance between reflecting crystal
planes
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P.O. BOX 9948 • AUSTIN. TEXAS 78766 • TELEPHONE 512 • 454-4797
0. = reflection angle from crystal planes
of distance d.
The intensity of the diffracted radiation is a function of the
atomic structure of the crystalline phase which is reflected
in the atom form and structure factors. The set of lattice
spacings d. and the intensity of the diffracted lines is unique
for each distinct crystalline phase and is used for phase
identification of unknown material.
The instrumentation used to record the X-ray pattern
is either a powder camera (Debye-Scherrer method) or a goinometer,
Section 4.1.3 of Volume II shows the X-ray patterns
of the following phases potentially present in solids from lime/
limestone wet scrubbing processes.
1. CaO 9.
2. Ca(OH)s 10.
3. CaCQs (aragonite) 11.
4. CaC03 (calcite) 12.
5. CaS03-%HsO 13.
6. yCaS04 (soluble anhydride) 14.
7. pCaS04 (insoluble anhydride)15.
8. CaSO,-2HpO 16.
CaS04 -%HaO
MgO
Mg(OH)s
MgC03-3HsO
MgSOg -3^0
MgS03 • 6H^ 0
CaMg(C03)8 (dolomite)
SiOa (from fly ash)
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7.0 FIELD STUDIES
The sampling, sample handling, and analytical methods
described in previous sections were developed and tested by
analyzing data from several pilot units. Samples were collected
during
OAF in-house studies (Volume II, page 569),
pilot plant runs at the Tidd Plant in
Brilliant, Ohio (Volume II, page 573),
pilot plant runs at Key West (Volume II,
page 592),
pilot plant studies at TVA's Colbert
Steam Plant (Volume II, page 613),
pilot plant studies at Shawnee (Volume II,
page 635).
Representative results will be presented here for the pilot
studies at TVA's Colbert steam plant (see Volume II for the
other systems). The system arrangement at Colbert is shown in
Figure 7-1. Samples were taken and analyzed at the scrubber
effluent (Sample Point 2), scrubber spray (Sample Point 1),
effluent hold tank F-12 overflow (Sample Point 3), and the
process liquor tank F-13 (Sample Point 4). The results of the
liquid and solid phase analyses are shown in Tables 7-1 through
7-3 for the liquids and Tables 7-4 through 7-6 for the solids
analyses. The buildup of inerts is very small in this arrange-
ment since most of the fly ash was removed by the raw water
spray. The accuracy of the methods is reflected in the total
ionic imbalance.
-44-
-------
Venturi Rod
Scrubber
Raw Water Spra
Flue Gas
From Boiler
Water, Flyash
to Sewer
Flue Gas
to Stack
affluent Hold Tank Process Liquor Tank
(F 12, 500 gal) (F 13, 500 gal)
Limestone Solids
Limestone Slurry
Feed Tank
(120 gal)
©
Clarifier (3000 gal)
FIGURE 7-1 - TVA LIMESTONE WET SCRUBBER PILOT UNIT
-------
TABLE 7-1
Results of Liquid Sample
Colbert Plant. Run 1
Sample
Sample Point
Designation (See Fig. 2-1) K Na Ca
Scrubber Effluent #1
Scrubber Effluent #2
Scrubber Effluent #3
Scrubber Spray
F-12 Overflow #1
' F-12 Overflow #2
ON F-12 Overflow #3
F-13 Recycle #1
F-13 Recycle #2
F-13 Recycle #3
Clarifier Overflow #1
Clarifier Overflow #2
Clarifier Overflow #3
Lir.estone Feed
Raw Water
2
2
2
1
3
3
3
4
4
4
6
6
6
5
8
0.31 33.8
0.56 36.0
0.56 35.2
0.11 0.23 6.40
0.28 0.55 34.3
0.53 36.1
36.2
0.28 0.46 31.4
0.51 32.4
32.2
0.30 0.62 25.7
26.5
26.2
0.22 0.55 25.1
0.03 0.19 0.55
Mg
10.1
10.5
10.7
0.26
10.6
10.4
10.6
9.9
10.0
9.7
10.6
11.1
10.9
10.0
0.14
Sulfite
4-
Sulfate
47.7
48.8
49.4
9.25
47.0
46.9
48.3
43.2
44.2
44.0
32.4
33.9
33.4
31.1
0.0
Sul-
fite
15.4
15.9
16.2
7.0
13.3
13.3
12.7
14.0
14.1
14.0
3.5
3.3
3.3
1.2
Anal ysis
5-27-71
Sul-
fate
32.3
32.9
33.2
2.25
33.7
33.6
35.6
29.0
30.1
30.0
28.9
30.6
30.1
29.9
0.0
Imbalance
^ipos' Zi *
Total m^ Zi Temperature
C°* CL N N°a (^les) P" CF>
3.18
3.75 9.0 2.73 .614 -3.95 5.31 101
3.70
2.48 1.3 0.67 .036 +1.42 5.42 109
3.64
4.14 7.7 1.17 -2.72 5.55 101
4.86
3.75
4.80 7.7 1.43 .551 -2.66 5.57 98
4.25
3.61
5.95 8.5 1.90 .614 -2.12 6.13 89.5
4.55
2.75 7.3 2.10 .555 -2.89 6.94 95
0.66 0.20 0.30 .025
(Concentrations ara given In m moles per liter)
-------
TABLE 7-2
Results of Liquid
Sample Analysis
Colbert Plant . Run 2
Sample
Sample Point
Designation (See Fie. 2-
Scrubber Effluent #1
Scrubber Effluent 02
Scrubber Effluent 03
Scrubber Spray
F-12 Overflow 01
F-12 Overflow 02
F-12 Overflow #3
F-13 Recycle #1
F-13 Recycle 02
F-13 Recycle 03
2
2
2
1
3
3
3
4
4
4
., K Na Ca
0.29 0.48 35
35
0.48 36
0.16 0.27 7
0.28 0.47 31
0.48 32
32
0.30 0.48 30
30
30
.5
.3
.2
.10
.6
.9
.0
.3
.5
.2
Mg
12.3
12.3
12.5
0.34
11.8
12.1
11.9
11.9
11.9
11.9
Sulfite
Sulfate
47.4
48.0
48.5
8.92
42.3
43.6
43.2
40.0
39.6
39.7
Sul-
fite
12.2
12.2
11.8
6.2
10.1
10.1
10.1
6.70
6.40
6.50
5-28-7
Sul-
fate
35.
35.
36.
2.
32.
33.
33.
33.
33.
33.
2
8
7
72
2
5
1
3
2
2
1
C0a CL
3
3
3
1
3
5
4
3
3
4
.25
.98 9.6
.39
.42 2.1
.75
.25 9.2
.93
.41
.75 8.7
.02
Total
N
1.73
0.40
1.33
1.10
NO,
.690
.044
.678
.614
Imbalance
(m moles)
Tcirperature
-2.21 5.52 99
+2.36 3.38 104
-3.24 5.88 100
-0.66 5.68 100
Clarifler Overflow
0.95 .560
(Concentrations are given in m moles per liter)
-------
TABLE 7-3
00
I
Sample
Designation
Scrubber Effluent #1
Scrubber Effluent #2
Scrubber Effluent #3
Scrubber Spray
F-12 Overflow #1
F-12 Overflow #2
F-12 Overflow #3
F-13 Recycle #1
F-13 Recycle #2
F-13 Recycle #3
Sample
Point
(See Fie. 2-1)
2
2
2
1
3
3
3
4
4
4
K
0.28 0
0
0
0.12 0
0.30 0
0
0.29 0
0
0
Na
.49
.51
.52
.25
.49
.50
.49
.48
.48
Ca
31.6
34.1
32.5
6.9
31.2
30.3
30.8
29.7
29.9
30.1
Results
Colbert
Mg
12.2
12.5
12.4
0.27
12.7
12.6
12.9
12.4
12.7
12.6
of Llauid
Plant
Sample
. Run 3
Sulfite
•f
Sulfate
42
43
44
9
41
41
41
39
39
39
.4
.8
.1
.23
.1
.4
.7
.2
.0
.0
Sul-
fite
10.3
10.5
9.1
6.5
8.5
9.0
8.7
5.3
5.6
5.4
Analysis
5-28-71
Sul-
fate
32.1
33.3
35.0
2.73
32.6
32.4
33-0
33.9
33.4
33.6
CO,
3.07
4.55
5.16
1.45
4.75
4.95
5.75
3.23
3.93
3.93
CL
9.3
2.0
9.8
9.2
Total
N
3.50 .662
0.17
1.27 .723
1.23 .649
Imbalance
^W Zi "
mi , Zi
(n moles)
-2.69
+1.78
-1.87
-1.12
pH
5.67
3.19
5.77
5.96
Temperature
101
102
101
101
Clarifler Overflow
0.94 .588
(Concentrations are given in m moles per liter)
-------
TABLE 7-4
KelRht
Sanple of
Point Results of X-Ray Analyzed
Saffiple Designation (see FlR. 2.1) Analysis Sample ( YR)
Scrubber Effluent 2 I. CaCO, (C.Iclte)
2. CaSO. -2H.O (Cypsun) 982
3. CnSO,-VI,0
Scrubber Spray 1 1. CnCO, (Calclte)
3. Ca(Al,SI,0.) -4H.O 1003
(poss Ible)
6. S10. (possible)
r-12 Overflow 3 1. CaCO, (Cslclte)
2. CaSO. -211,0 (Gypsum) 993
4. CnSO,-\,H.O
(A l.o unidentified
compound) major peak
F-13 RecycU 4 1. CnCO, (Calclte)
2. CaSO.-2H,0 (Gypsum) 990
4. c«so,-yi.o
Clarlfler Overflow 6 1. CaCO, (Cnlclte)
2. CaSO.-JH.O (Gypaun) 342
4. CaSO.-l,H.O
Clarlfler Bottoei 7 1. CaCO, (Cslclte)
2. CaSO.-2H,0 (Cypmn) 1011
4. CaSO, • VI ,0
Lloe>tona F«ed 5 1. CaCO. (Calclte)
2. CaSO.-2H,0 (Cypaun) 984
4. CaSO.-^H.O
(Unidentified ccoponmta
present)
Results of Solid Sample Analyala
Colbert Flant Hun 1 5-27-71
Slurry Sulflta Sulfate +
Undltaolved Concentration and Sulflte +
Sollda (OR) (R/i) C« MR Sulfate Sulfate Sulflte Carbonate Ca + MR Carbonate Solids Compofl 1 t Ion
CnSO.-ljH.O 36.61
CaSO.-2H,0 18.41
29 143 7.97 0.50 3.91 1.07 2.84 4.09 8.47 8.00 MRCO, 4.21
CaCO, 40.61
Insoluble 3.01
Total 102.81
701 12.: 2.79 0.23 .10 0.01 0.09 2.89 3.02 2.99 MpCOJ " K91
CaCO. 26.91
Insoluble 69.11
Total 99.31
CaSO,-VH.O 23.01
20 99.6 8.»3 0.53 2.33 0.57 1.78 6.24 8.98 8.59 CaSO. -2H.O 9.81
MgCO , t» . J*
CaCO, 61.01
Insoluble 2.07.
Total 100.31
CaSO,-\H.O 30.21
33 59.4 | 07 0 52 3 36 1.02 2.34 5.20 8.59 8.56 CnSO.-2H.O 17.51
MpCO. 4.41
CnCO, 47.11
Insoluble 3.31
Total 102.51
CaSO,-HH.O 46.51
4 1-5 j in 0 19 5 36 1.76 J.60 1.40 7.59 7.76 CaSO..2H.O 30 31
MgCO, 1.61
CaCO. 20.41
Inaoluble 1.27.
Total 100.01
CaSO,-\H.O 15.11
71 — 8.18 0.35 1.96 0.79 1.17 6.55 8.53 8.50 CaSO..2H.O 13.61
MnCO, 3.01
CaCO, 62.21
Insoluble 7.01
Total 100.91
CaSO,-VH.O 14 si
26 1*1 j.g4 c.63 1.67 0.52 1.15 7.73 9.47 9.40 CaSO.-2H.O 9.01
HgCO. 5.31
C.CO. 71.71
Iniolubl* 3.01
Total 103.61
vO
I
-------
TABLE 7-5
Saople
Point
Saaole Designation (see riR. 2.1)
Scrubber Effluent 2 1.
2.
4.
Scrubber Spray 1 1
J.
6.
f-12 Overflew 3 1
2.
4.
f-13 R.cycla 4 1.
2.
4.
Weight Weight
of of
Reaults of X-Ray Analyzed Undlssolved
Analrsla Sample (maj Solids
CaCO. (Calclte)
C«SO.. 211.0 991 66
CaSO.-^H.O
CaCO. (Calclte)
Ca(Al.S1.0.)-4H.O 993 779
(poiilblr)
S10, (poislble)
CaCO. (Calclte)
CaSO.-2H.O 1007 41
• jn.o
CaCO. (Calclte)
CaS04-2H.O 987 47
CaSO.-VH.O
Results of Solid Sample Analrnli
Colbert Plant Run 2 5-28-71
AnalTaes of Acid Soluble Material Concentration In m moles Per Cram of Solid
Slurry Sulflte lulf't. t
COTC"5"tl°° r. -. 5..?^t. Sulfate Sulflt. Carbonate Ca t «R Carbonate Sollda Cor:po.ltlon
C.SO.-SH.O
CaSO.-2H.O
88.0 8.17 0.49 3.0* 1.02 2.04 J.43 8.66 8.49 MjCO,
Inaofuble
Total
CaSO.-ljH.O
1J.7 1.46 0.10 0.11 0.03 .08 1.44 1.56 1.55 CnSO, -2H.O
CaCO!
Insoluble
Total
CaSO.'Vl.O
B6.0 g.j9 o.4» J.79 1.02 1.77 5.47 8.77 8.26 CoSO.-ZH.O
CaCO.
Insoluble
Total
CaSO.-VH.O
»-° 8.09 0.49 3.30 1.22 2.08 J.JO 8.J8 ».6C M!|S;'2Hl°
CaCO
Inaofubla
Total
26.51
17.51
4.11
51.11
6.71
105.91
1.01
o'.si
13.51
94.21
22.81
17.51
4.01
55.01
4.11
10J.41
26.91
21.01
4.11
l»l 91
4.81
105.71
o
I
-------
TABLE 7-6
Weight Weight
Sonple of o!
Seerele PtlU"«Uon lit* Tin. 2.1) Analysis Sample (olO Solids
Scrubber Effluent 2 1. CaCO, (Calclte)
2. C«SO -2H 0 (Cypeua) 100] 33
4. CaSO,-SH.O
Scrubber Spr«» 1 1. CaCO (Calclte)
i. C.(A!.SI 0.)-4«,0 9»6 784
(po.slble)
6. S10. (poaslble)
F-12 Overflow 3 1. C.CO, (Calclte)
2. CaSO. -2HO 1006 42
4. -CaSO.-SH.O
r-13 R««7CU » 1. C«CO. (Celclte)
2. C«SO. -2H.O 1014 44
4. CeSO.-^H.O
Unidentified Ccnponent
Preeent In Significant
Result! of Solid Sample Analj£eie_
(o^tert Pl>m Ryn ] ;-2g-?l
Analveei of A-rld Soluble Katertal Concentration In ra nolea Per Crftm of Solid
Slurry Sulflt* Sulfate »
CB/I) Ce rU Sulfate Sulfite Sulflte Carbonate Ca + Ki Carbonate Solid. Co
CaSO.-iH.
CaSO. -2H,
85. 2 7.98 0.53 3.11 1.16 1.95 5.41 8.51 8.52 HgCO,
C.CO,
I naolubla
Totel
CeSO, -iH.
17.2 1.51 O.m .076 .006 0.07 1.57 1.61 1.63 C.SO. -2H,
MgCO,
CaCO
Insoluble
Total
CaSO.-fcH.
CaSO. -2H.
100 >.10 0.59 2.78 1.05 1.73 5.38 8.69 8.16 rujCO,
CaCO,
Insoluble
Totel
C.SO -^H,
CeSO. -2H.
87.9 7.63 0.51 3.4* 1.40 2.04 5.00 8.36 8.44 MgCO.
C.CO.
Inioluble
Total
n?os It Ion
0 25. 21
0 20.01
1.51
48.71
101.91
0 1.01
0 0.11
o.ai
14.41
78.61
94^91
0 22.31
0 18.11
5.01
53.21
102 !BI
0 26.31
0 24.11
4.31
44.11
10) '.It
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Radian Corporation
8500 SHOAL CREEK BLVD. • P.O. BOX 9948 • AUSTIN. TEXAS 78766 • TELEPHONE 51 2 • 451-4797
Imbalance = ^ K'^) - J'
pos L i i neg
m. = molar concentration of charged species
z. = charge number
The pH measurements and analytical results shown in
Tables 7-1 through 7-3 were used to calculate this imbalance.
The imbalance should ideally be zero for zero errors in the
analytical determinations. Another source of ionic imbalance
is the presence of species for which no analysis was made.
The results of the solid phase analyses are presented
in Tables 7-4 through 7-6. The concentrations of the solid
species add up to nearly 10070 with exception of the solids of
the scrubber spray which contain most of the fly ash. Compounds
leached from the fly ash for which no analysis was made may be
responsible for the low values found.
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Radian Corporation
8500 SHOAL CREEK BLVD. • P.O. BOX 9948 • AUSTIN. TEXAS 78766 • TELEPHONE 512 -454-4797
8.0 USE OF THE RAW DATA
It was mentioned earlier that the results of the
chemical analyses have no value per se. They gain their value
in the chemical engineering framework within which they are used.
Dominant points of interest are:
mass transfer characteristics in the
scrubber
solid-liquid mass transfer rates
scaling potential
Therefore, analytical results like those presented
in the previous chapter must be processed further. As an example,
the scaling tendency of the scrubber effluent of Run 3 given
in Table 7-3 will be determined. This task is solved by con-
sidering the ionic equilibria in the aqueous phase. The results
of the chemical analysis listed in Table 7-3, the pH value, and
the temperature were used as inputs for computer calculations.
This equilibrium program distributes the eight key species into
30 important complexes (see Table 8-1) and calculates the
equilibrium partial pressures of sulfur dioxide and carbon
dioxide. Individual activity coefficients are calculated using
an extended Davies equation. The resulting activities of the
individual ionic species for the scrubber effluent are listed
•in Table 8-1.
The activities of Ca , S03, and S04 are given as
7.25 x 10"3, 1.22 x 10"4, and 5.84 x 10"3, respectively. The
ratios of activity product to solubility product constant at
38°C for CaS03 -^HgO and CaS04-2HsO are 10.6 and 1.79, respectively
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BSOO SHOAL CREEK BLVD. • P.O. BOX 9948 • AUSTIN. TEXAS 78766 • TELEPHONE 512.454.4797
TABLE 8-1
DISTRIBUTION ACTIVITIES OF KEY SPECIES
10 June 1971 14:41:52.539
Temperature 38.340 Deg. C
INPUT MOLES
S02 = 1.00-02
C0a = 3.07-03
S03 -•= 3.34-02
!a,0 = 3.85-04
Component
H,,0
H+
OH"
HS03"
S03'~
S04~~
HC03~
C03~~
N03"
HS04"
H^S03
HaC03
Ca"^
CaOH+
N305 = 1.
HCL = 9.
AQUEOUS
Molality
2.6-06
1.6-08
6.8-03
3. 5-04
1.9-02
7.0-04
4.3-08
3.4-03
2.3-06
1.1-06
2.2-03
2.0-02
3.0-09
75-03 CaO = 3.27-02
30-03 HS0 = 5.55+01
SOLUTION EQUILIBRIA
Activity
2.1-05
1.2-08
5.2-03
1.2-04
5.8-03
5.4-04
1.5-08
2.4-03
1.8-06
1.1-06
2.3-03
7.2-03
2.3-09
MgO = 1.24-02
Activity
Coefficient
1.0-00
8.3-01
7.7-01
7.7-01
3.4-01
3.0-01
7.7-01
3.4-01
7.0-01
7.7-01
1.0+00
1.0+00
3.6-01
7.7-01
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Activity
Component
CaS03
CaC03
CaHCOg +
CaS04
CaN03 +
M ++
Mg
MgOH+
MgS03
MgHC03 +
MgS04
MgC03
Na+
NaOH
NaC03 "
NaHC03
NaS04 "
NaN03
CL"
Molality
2.6-03
2.0-07
1.0-04
10.0-03
7.0-05
8.0-03
2.1-08
3.3-04
1.9-05
4.1-03
1.2-07
7.4-04
1.9-12
2.3-10
1.7-07
2.5-05
5.5-07
9.3-03
Activity
2.6-03
2.0-07
7.8-05
1.0-02
5.4-05
2.8-03
1.6-08
3.3-04
1.5-05
4.1-03
1.2-07
5.8-04
1.9-12
1.8-10
1.8-07
1.9-05
5.6-07
7.1-03
Coefficient
1.0+00
1.0+00
7.7-01
1.0+00
7.7-01
3.5-01
7.7-01
1.0+00
7.7-01
1.0+00
1.0+00
7.8-01
1.0+00
7.7-01
1 . 0+00
7.7-01
1.0+00
7.6-01
PS03 = 1.46-06 ATM
PC03 = 9.37-02 ATM
Molecular Water = 9.99-01 KGS
Specified pH ••= 5.670
Ionic Strength = 1.08-01
Res. E. N. = -2.692-03
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asoo SHOAL CREEK BLVD. • P.O. BOX 99^8 • AUSTIN. TEXAS 78766 • TELEPHONE 512 .asa.4797
This shows that the solution is highly supersaturated with
respect to CaS03-%HaO and moderately supersaturated with
respect to CaS04 -2H20. These numbers will be of value in con-
junction with scaling studies to define scaling tendency.
Another number of importance for engineering cal-
culations is the partial pressure of S0a . From Table 8-1, it
is seen that Pcri in the scrubber effluent is 1.46 x 10 atm
O Ug
or about 1.5 ppm. This is a necessary input for SQS vapor-
liquid mass transfer calculations. In similar fashion other
activities can be calculated if required for the description
of solid-liquid mass transfer rates.
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9.0 DATA HANDLING SYSTEM
The Shawnee laboratory data analysis system is designed
to perform data storage, laboratory computations, and report
generation tasks associated with the laboratory operations. The
system is basically a card oriented system using marked-sense
card input to ease the problem of converting data to a machine
readable format. In addition, the system is designed to provide
automatic operation of an X-ray fluorescence spectrometer with
automatic calibration and matrix corrections performed upon
the results. The X-ray analysis results are entered automatically
without operator intervention. The system is represented diagram-
matically in Figure 9-1.
For each set of analyses defined by a time, sampling
point, sample type (i.e., line out, steady-state, or exception),
and run number, a data packet is created on disk to store all
raw data and computed results associated with that set of
analyses. After all data for that particular set of analyses
has been entered into the data processing system and all cal-
culations performed, the completed data packet is transferred by
the operator from the disk to magnetic tape and by means of the
line printer a hard copy is prepared. The data analysis system
may be commanded to prepare sample taking schedules and sample
analysis schedules.
Volume III of this report contains a detailed
description of the system, including complete operating instruc-
tions. The paragraphs below give a very brief description of
the hardware and software components of the system.
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8500 SHOAL CREEK BLVD. • P.O. BOX 9948 • AUSTIN. TEXAS 78766 • TELEPHONE 512-454-4797
FIGURE 9-1 - LABORATORY DATA ANALYSIS SYSTEM USED AT SHAWNEE
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8500 SHOAL CREEK BLVD. • P.O. BOX 9918 • AUSTIN. TEXAS 78766 • TELEPHONE 512 .454.4797
9.1 Laboratory Data Analysis Hardware
In addition to the X-ray fluorescence spectrometer,
the hardware system consists of the following major components:
Nova 1200 (20 K)/Jumbo Chassis
Fixed Head Disk (256 K)
Magnetic Tape Transport (9 track/800
BPI/10V reels/24 IPS)
Automata Marked Sense, Punched Card
Reader
ASR 33 Teletype
KSR 35 Teletype
Beehive CRT Terminal
Data Products Line Printer (80 column,
1100 LPM)
The fixed disk is used for storage of all data in
data handling programs. The Beehive CRT terminal is used as the
basic input/output device for the user of the data analysis sys-
tem. The ASR 33 Teletype is used as a backup to the CRT and to
supply the capability of the paper tape reader/punch. The KSR
35 (without paper tape feature) is included for the basic control
of the X-ray equipment. As mentioned previously, the system
input is basically card oriented using marked sense cards. The
magnetic tape transport provides the capability of storing data
on magnetic tapes for transfer to other sites as well as storage
of the basic data handling system, the disk operating system
with FORTRAN compiler, and diagnostic routines for the major
hardware components. The line printer provides a permanent hard
copy of all data.
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9.2 Laboratory Data Analysis Software
The software system can be divided logically into
three parts: (1) executive system, (2) application routines,
and (3) diagnostic routines.
9.2.1 Executive System
The executive system for the laboratory data handling
system is an extension of the vendor supplied disk operating
system. The system provides comprehensive file handling capabil-
ities and protection. The executive system allows the execution
of the laboratory data system as well as program generation and
development software including a FORTRAN compiler, editor, de-
bugger, etc. The executive system retrieves appropriate files
from disk storage as commanded from the user operating input
device.
The executive system provides the user a variety of
commands to perform the laboratory data handling. These include
data input, report generation, generation of magnetic tape files,
and automatic operation of the X-ray fluorescence spectrometer.
Upon receiving a data input command, the system reads the data,
retrieves the appropriate application programs, performs neces-
sary calibrations and computations, and stores the raw data as
well as the resultant computed values. The executive system
also performs bookkeeping functions such as scheduling samples
to be taken and scheduling the analysis of these samples.
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9.2.2 Application Routines
The laboratory application routines actually perform
the function as instructed by the executive system. The ap-
plication routines are initiated under user control; however,
the user is not required to insure that appropriate disk files
are input into the computer memory. Most application routines
are written in FORTRAN which allows easy modification if lab-
oratory computations are changed or if new procedures are
implemented in the laboratory.
9.2.3 Diagnostic Routines
This software package operates independently of the
previously mentioned packages. The primary function is for
trouble-shooting hardware failures to localize the equipment
that is malfunctioning, and for performing preventative main-
tenance. These routines guide the user through series of tests
on each peripheral device to check all phases of operation.
The test routines may be input from any of three input devices:
(1) the teletype paper tape reader, (2) the card reader, and
(3) the magnetic tape unit. This allows for diagnostic testing
even if one of the input units becomes inoperative. The print-
out for a typical set of analyses is given in Figure 9-2.
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RESULTS OF SAMPLE ANALYSES
I
SAMPLE It)
SAMPLE POINT
TEMPERATURE(C)
CONDUCTIVITY
PH
3616
FIELD
0,0
,0B00E 0
.000I3E 0
J RUN NUMBER
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10.0 SUMMARY
The chemical analysis of the key species in lime/
limestone based sulfur dioxide removal processes is the basis
for the engineering evaluation of the system performance. The
problem area encompasses five individual steps.
1) Sampling
2) Sample Handling
3) Sample Analysis
4) Data Processing
5) Data Evaluation
Figure 10-1 shows the methods selected to accomplish the
individual tasks.
The pH and the temperature of the slurry are measured
in situ. A positive pressure filtration system separates the
liquid from the solids. The solids content of the slurry is
calculated from the solid to liquid ratio.
The liquid is thermodynamically unstable and must be
quenched by appropriate techniques. An aliquot is diluted in
an aqueous hydrogen peroxide solution. Sulfite is oxidized
and sulfate precipitation is avoided by the dilution involved.
Total sulfur, calcium, chloride, potassium, sodium, magnesium,
and catalytically active trace constituents such as manganese,
cobalt, copper, iron, and nickel are determined in this sample
using the procedures as indicated by Figure 10-1.
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SAMPLING
QUENCHING
In Aqueous
Hydrogen Peroxide
X-RAY DIFFRACTION
DISSOLUTION
tn HCL,
H.,00 - Solution
DISSOLUTION
In Buffered Iodine
CO, - Evolution
in Closed System
SAMPLE HANDLING
TOTAL SULFUR h* '"" Exchnnr.e Titrlmctrlc
Proc. or X-Ray
CALCIUM
CHLORIDE
by Atomic Absorption or
X-Ray Fluorescence
by Polentlonctric Iteration or
POTASSIUM
by Atonic Absorption or
y
SODIUM by Atomic Absorption
MAGNESIUM by Atomic Absorption
TRACE-ELEMENTS by Atomic Absorption
SULFITE by BacktItratlon of Excess
Iodine
CARBONATE by CO, - Evolution and
Detection by NDIR
TOTAL NITROGEN by modified Kjeldahl
Procedure
NITRATE by Colorlmetry or UV
Spectrophotometry
NITRITE by UV Spcctrophotomccry
| SOLIDS CONTENT of Slurry
J pH an:
id TEMPERATURE
CRYSTALLINE PHASES of Major Consclcutcnts
TOTAL SULFUR by Ion Exchange Titrlir.etric
Procedure or X-Ray
Fluorescence
CALCIUM by Atonic Absorption or X-Ray
Fluoresccnce
MAGNESIUM by Atomic Absorption
INERTS In weight 7.
SULFITE sulfur by Backtlcracion of excess
Iodine
CARBONATE by CO, absorption In Ba(OH).
SAM-'LE ANALYSIS DATA PROCESSING
FIGURE 10-1: SCRUBBER SLURRY ANALYSIS SCHJEMZ
DATA EVALUATION
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A second aliquot is quenched directly in a buffered
iodine solution thus avoiding any sulfite losses. Excess iodine
is back-titrated using standard arsenite and a dead stop pro-
cedure for end point detection.
A sample to determine carbonate is quenched in an
alkaline EDTA solution. The EDTA prevents calcium carbonate
precipitation. The alkaline environment lowers the COS partial
pressure of the sample. The C0a determination involves evolution
from an acidified sample and determination by a nondispersive
infrared analyzer.
Total nitrogen, nitrate, and nitrite are determined
by a modified Kjeldahl procedure and by ultraviolet spectroscopy.
A colorimetric procedure based on the interaction of nitrate
with chromotropic acid is specific for nitrate.
The X-ray fluorescence unit was interfaced with a
minicomputer for rapid field measurements and data reduction.
Data not measured by X-ray fluorescence are entered into the
system through a card reader, a CRT or a teletype. The system
stores all the data on a magnetic tape. In this fashion they
can be read directly in a larger computer for chemical equilibrium
calculation. A hard copy of the data is provided by the printer.
The solid sample obtained in the filtration step is
processed in a similar fashion. Part of the crystals are finely
powdered. Subsequent X-ray diffraction determines the crystalline
phases of the major constituents.
The solid sample is dissolved prior to chemical analysis
Dilute hydrochloric acid containing hydrogen peroxide is used to
dissolve approximately 1 g solids. Total sulfur, calcium,
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8500 SHOAL CREEK BLVD. • P.O. BOX 9918 • AUSTIN. TEXAS 78766 • TELEPHONE 5! 2-454-4797
magnesium and weight percent inerts are determined in this
sample. The analytical methods are the same as those chosen for
liquid sample analysis.
Sulfite is determined on a solid sample dissolved in
a buffered iodine solution. Excess iodine is back-titrated
with arsenite solution and a dead stop technique for end point
detection.
The carbonate analysis is performed by dissolving a
solid sample in sulfuric acid in a closed system. The evolved
COS is absorbed in barium hydroxide solution. Excess barium
hydroxide is back-titrated to the phenolphthalein end point.
The data processing in the field is done by the minicomputer
and the peripheral devices.
The analysis scheme was checked and developed by
sampling and analysis of several pilot plants. They included
the GAP in-house test facility and pilot plants at the Tidd
Plant, Key West, Colbert Steam Plant, and at Shawnee.
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11.0 BIBLIOGRAPHY
AM-002 American Society for Testing and Materials, 1969
Book of. ASTM Standards, Part 23 : Water, Atmospheric
Analysis, Philadelphia, 1969.
BE-024 Bertolacini, R. J. and J. E. Barney, Anal. Chem. 29.,
281-83 (1957).
DE-029 DeBerry, David W., "Procedure for the Determination
of Total S03 in Aqueous Solutions," Radian Technical
Note 200-004-04, Radian Corporation, Austin, Texas,
May, 1970.
DO-006 Dollman, G. W. , Env. Sci. Tech. 2., 1027-29 (1968).
EN-020 Environmental Protection Agency, Water Quality Office,
Analytical Quality Control Lab., Methods for Chemical
Analysis of Water and Wastes, Washington, D.C., GPO,
1971.
FE-004 Federal Water Pollution Control Administration,
FWPCA Methods for Chemical Analysis of Water and
Wastes , U. S. Department of Interior, FWPCA,
Division of Water Quality Res., Anal. Qua 1. Contr.
Laboratory, Cincinnati, Ohio, November, 1969.
FI-019 Fisher Scientific Instruments Div., Bull. No. 68-2A,
Cat. No. 9-319-100, Pittsburgh, Pennsylvania.
FR-003 Fritz, J. S., S. S. Yamamura, Anal. Chem. 27, 1461-
64, 1955.
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Radian Corporation
8500 SHOAL CREEK BLVD. • P.O. BOX 9948 • AUSTIN. TEXAS 78766 • TELEPHONE 51 2 • 454-4797
FR-009 Fritz, J. S., M. Q. Freeland, Anal. Chem. 26., 1593-5,
(1954).
JO-012 Joyner, et al., Env. Sci. and Tech. I, 417 (1967).
KO-015 Kolthoff, I. M. and P. J. Elving, Treatise on Analytical
Chemistry, Part II, Vol. 7, Interscience Publishers,
N.Y., 1961.
KO-050 Kolthoff, I. M. and E. B. Sandell, Textbook of
Quantitative Inorganic Analysis, 3rd Ed. MacMillan,
N.Y., 1952.
MA-039 Macchi, G., B. Cescon and D.'Mameli-D1Errico, Archo
Oceanogr. Llmnol. 16, 163-71 (1969).
MU-020 Muller, Gerhard-Otfried, Praktikum der quantitativen
chemischen Analyse. Leipzig, S. Hirzel Verlag, 1957.
PE-037 Anal. Method for A. A. Spec., March 1971 supp.
PR-007 Prochazkova, L., Zeitschr. Anal. Chem. 182, 103-7
(1961).
SE-015 Seel, F. and E. Degener, Z. fur Anorg. und Allgem.
Chemie 284, 101-17 (1956).
SH-006 Shaw, W. M. , Anal. Chem. 3_0, 1682-9 (1958).
SH-014 Shiner, V. J. and Morris L. Smith, Anal. Chem. 28., 1043-
45 (1956).
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SSOO SHOAL CREEK BLVD. • P.O. BOX 9948 • AUSTIN. TEXAS 78766 • TELEPHONE 512 - 451-4797
SI-005 Sijderius, R., Anal. Chim. Acta 11, 28 (1954).
TH-007 Thompson, C. M., Radian Technical Note 200-004-13,
Sept. 4, 1970.
WE-008 Wetters, J. H. and K. L. Uglum, Anal. Chem. 42. (3),
335-40 (1970).
WE-012 West, Philip W. and T. P. Ramachandran, Anal. Chim.
Acta 35., 317-24 (1966).
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TECHNICAL REPORT DATA
(Please read Inunicliuns on llie reverse before completing)
1 REPORT NO.
EPA-650/2-74-024
2.
4. TITLE AND SUBTITLE
Development of Sampling and Analytical Methods
of Lime/Limestone Wet Scrubbing Tests
7.AUTHORis)K . schwitzgebel , F. B. Meserole, C. M.
Thompson, J. L.Skloss , and M. A. Me Anally
9. PERFORMING ORGANIZATION NAME AC
Radian Corporation
8500 Shoal Creek Blvd.
Austin, Texas 78766
JD ADDRESS
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
NERC-RTP, Control Systems Laboratory
Research Triangle Park, North Carolina 27711
3. RECIPIENT'S ACCESSION-NO.
Mir criT Ml
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
RAD-073-013
10. PROGRAM ELEMENT NO.
1AB013; ROAP 21ACY-25
11. CONTRACT/GRANT NO.
CPA 70-143
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
i6.ABSTRACTThe report' gives results of B. study to develop appropriate sampling and
analytical methods to be used at EPA's test facility at Shawnee. Three problem
areas developed in analyzing the thermodynamically unstable slurry streams
encountered in lime/limestone-based SO2 wet scrubbing processes: sampling,
sample handling, and chemical analysis. Positive-pressure filtration was found to
lower the mass transfer phenomena during the filtration step to an acceptable level.
Quenching of the filtered liquid was chosen to avoid changing sample composition.
Two sets of analytical methods were selected for application at Shawnee: the
back-up methods are based on atomic absorption and wet chemical procedures; and
the rapid field methods are based on X-ray fluorescence, atomic absorption, and
wet chemical analysis. The X-ray fluorescence spectrometer was automated by
interfacing it with a NOVA 1200 minicomputer. Additional peripheral devices have the
function of processing all raw data. The raw data are input to the system with a card
reader, a teletype, or a CRT. The final results are stored on a magnetic tape. A
hard copy is provided by a printer.
17.
a. DESCRIPTORS
KEY WORDS AND DOCUMENT ANALYSIS
b. IDENTIFIERS/OPEN ENDED TERMS
Air Pollution Sulfur Oxides Air Pollution Control
Sampling Desulfurization Stationary Sources
Analyzing Scrubbers Atomic Absorption
Slurries X-Ray Fluorescence
Calcium Oxides Automation
Limestone Spectrometers
13. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITY CLASS (This page)
Unclassified
c. COSATI Field/Group
13B
14B
7B
20F
7A
8G
21. NO. OF PAGES
22. PRICE
EPA Form 2220-1 (9-73)
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