Contract No, 68-02-0208
Report No. IITRI-C6241-7
ELECTRON PARAMAGNETIC RESONANCE (EPR) INVESTIGATION OF
LIMESTONES AND THEIR CALCINES AND CORRELATION WITH
REACTIVITY WITH ACID GASES
Prepared by
Nicholas A. Ashford and Frank H. Jarke
IIT Research Institute
10 West 35th Street
Chicago, I nois 60^ L6
18 February
Final Report for Period 23 June 1970 through 22 Januarv 1972
Prepared foi
ENVIRONMENTAL PROTECTION AGENCY
411 West Chapel Hill Street
Durham, North Carolina 27701
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MANAGEMENT SUMMARY
The investigations reported herein were performed in
the Physical Chemistry Section of the Chemistry Division of
IIT Research Institute. Dr. Nicholas A. Ashford, Research
Chemist, acted as project leader and was responsible for
the experimental design and interpretation. Mr. Frank H.
Jarke, Assistant Chemist, performed the experimental work
and assisted in the experimental design and interpretation.
Dr. Elliott Raisen, Manager of Physical Chemistry, was
responsible for general administration of the program.
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FOREWORD
This report No. IITRI-C6241-7 is the Final Technical
Report on IITRI Project C6241, Contract: No. 68-02-0208,
entitled "Electron Paramagnetic Resonance (EPR) Investiga-
tion of Limestones and Their Calcines and Correlation with
Reactivity with Acid Gases". This program is being conducted
by I IT Research Institute, 10 West 35th Street, Chicago,
Illinois for the Environmental Protection Agency, Durham,
North Carolina 27701, and covers the period from June 23, 1971
through January 22, 1972. The program monitor is Dr. Dennis
C. Drehtnel.
Respectfully submitted,
IIT RESEARCH INSTITUTE
Approved by:
X
Elliott Raisen
Manager
Physical Chemistry Research
NAA:FHJ:rta
Nicholas A. Ashford
Research Chemist
Physical Chemistry Research
_
Frank H. Jarke
Assistant Chemist
Physical Chemistry Research
11
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ABSTRACT
A research program was undertaken to investigate a
selected set of calcined and uncalcined carbonate rock samples
by electron paramagnetic resonance (EPR) spectroscopy in
order to (a) assist in the characterization of marls and
chalks to identify properties which account for their high
reactivity with SC^, (b) establish a semi-quantitative basis
for evaluating a crystalline order of limestones to predict
their reactivity with acid gases, (c) investigate the effect
of altering the calcination temperature on the crystalline
structure of calcines in order to identify those properties
which account for the varying reactivity and deadburning,
and (d) investigate the effects of slaking on the crystalline
parameters of calcines produced at different temperatures in
order to support wet limestone scrubbing process development„
_l i_
Using Mn as a probe of calcium carbonate crystallinitys
the fitting of Mn"1""1" EPR linewidth data to the S02 reactivity
and capacity data resulted in correlation coefficients of
r=0o55 and r=0.49 respectively„ No significant EPR linewidth
correlation was found for the reactivity and capacity of
calcined materials. However, in a calcined series in which
the calcination temperature was varied producing variations
in density, a good correlation of the EPR linewidths was
found with the density data, Hydration of calcined materials
J L
produces a hydrated site for the Mn which gives a different
I [
and distinguishable EPR spectrum than that for Mn in
unhydrated sites„ Quantitative measurement of the degree of
hydration was therefore possible.
111
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2
SUMMARY OF FINDINGS
1. The fitting of Mn*"1" EPR linewidth data to the SO,
reactivity and capacity data resulted in correlation coeffi-
cients of r=0.55 and r=0.49 respectively, for all the carbonate
samples except dolomites. From the qualitative observations that
within acarbonate type, the sharper and better-resolved
i I
Mn lines occur for the more reactive material, it: is
believed that better linewidth correlation might be found
within any carbonate type. Variations of the inherent
structure, of even a perfect lattice from carbonate type
to carbonate, type might account for a not-larger correlation
among all the. samples.
2. The effect of room temperature ultraviolet-irradiation
of Michigan Marl. (Typt; ].„ #2129) under high vacuum is signi-
ficant. Fe is promoted to Fe^^T without (presumably) a
change in the surface area or pore volume. The increase in
I i i
Fe is maintainable in air - i.e. stable. This suggests
that (permanent) decoration of the defect state, of the
carbonates may be possible in order to utilize photo-created
I i i i i
Fe as a measure of crystallinitys as well as Mn
3. In the Type 1 Iceland spar calcine, the low S09 capacity
anisotropic 1700°F calcine with a high degree of strain shows
I [ |
no Fe center while the higher-capacity isotropic 1800°F
calcine yields the Fe1'' center. Thus, while Fe**"*" seems to
iv
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be an indicator of S02 capacity, its role is by no means clear
at this time. However, there are two other EPR parameters
i i_
relating to impurity Mn ions which may indicate the degree
of crystallinity of the materials; transitions which are
quantum-mechanicslly forbidden and the fine structure. As
expected, the 1800°F calcine with the more perfect lattice
results in weaker forbidden transition intensitites and
stronger transitions corresponding to the fine structure.
4. In the 2061 calcine series, in which five different
temperatures were used to calcine the same carbonate material,
I L.
the Mn linewidths did prove to correlate well with the density
data. The SO,-, reactivity and capacity data did not correlate
I i
with the Mn linewidths either in this series or in any of
the calcines investigated. Reactivity, however, depends on
both the density and the initial crystallinity, the latter
J L
to which the Mn EPR is not sensitive.
5. The EPR results on the calcined samples after soaking
with water and drying indicate the presence of a second
j i_
site for Mn which is most probably the hydrated oxide
site. The near linear relationship of the EPR data for the
variable temperature Series 2061, 2062 and 2069 with the
results of the slaking test is independent evidence of the
assignment of the new EPR lines to Mn in hydrated sites.
The small shift observed for the field positions of the
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"second phase" is almost conclusive by itself.
6. Increasing the calcination temperature of the three
different series 2061, 2062 and 2069 results in an increase
i I I
in the Fe 9 except for the highest temperature in each
I | |
series - 3200°F. Since the Fe level in calcines seems
to be related to the calcination temperature as a general
\
phenomena3 it may be possible to utilize EPR to find the
\
optimum calcination temperature. Most of the iron is
probably present as Fe 9 which is not observed by EPR in
these materials.
VI
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TABLE OF CONTENTS
Page
Management Summary i
Abstract ii
Summary of Findings iii
I. INTRODUCTION 1
II. EXPERIMENTAL PROCEDURE- 6
A. Samples 6
B. EPR Procedure 6
C. Ultraviolet-Visible Irradiation 6
of Sample Type 11
D. Slaking Test 10
III. EXPERIMENTAL RESULTS 1.1
A. Carbonate Samples 11
B. Calcined Samples 15
IV. DISCUSSION OF RESULTS 25
A. Carbonate Samples 25
B. Calcined Samples 26
C. Slaking Test . 27
D. The Role of Fe in the Calcines 27
V, RECOMMENDATIONS AND CONCIUSIGNS 28
References 30
APPENDIX A
APPENDIX B
APPENDIX C
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LIST OF TABLES AND FIGURES
Table
I
II
III
IV
Figure
1
5
6
7
Carbonate Samples
Calcined Samples
Calcined Samples, Variable Temperature
Series
Regression Coefficients for EPR
Linewidths L to the Reaction Data
S02 Reactivity in Differential Test
Versus EPR Linewidth Parameter of
Selected Limestones. Correlation
Coefficient is 0.55.
Sorption Capacity., Fixed Bed,, Versus
EPR Linewidth Parameter of Selected
Limestones. Correlation Coefficient is
0.49
S02 Reactivity in Differential Test
Versus EPR Linewidth Parameter of
Selected Calcines
Sorption Capacity, Fixed Bed,, Versus
EPR Linewidth Parameter of Selected
Calcines
Density Versus EPR Linewidth for Series
2061 Calcines
Effect of Calcination Temperature on Fe
Center in Calcines
Page
7
8
9
12
1.3
Relationship of Mn ' EPR Signal Intensities
to the Slaking Test Data
14
1.7
18
19
20
24
Vlll
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ELECTRON PARAMAGNETIC RESONANCE (EPR) INVESTIGATION
OF LIMESTONES AND THEIR CALCINES AND
CORRELATION WITH REACTIVITY WITH ACID GASES
I. INTRODUCTION - PURPOSE AND SCOPE OF WORK
Abatement of atmospheric pollution by sulfur dioxide
or hydrogen sulfide has received particular attention with
emphasis based on reactions of the pollutants with limestone.
The limestone wet scrubbing process, limestone fluidized
bed combustors and coal gasification are currently under
intensive investigation and development. Limestones, dolomites
and their derivatives as naturally occurring substances show
a wide range of reaction rates as well as capacity for acid
gas sorption.
Mechanistic and kinetic studies were initiated on the
dry injection process. Borgwardt (Ref. 1,2) has shown that
limestone absorbs S02 by a mechanism involving at least two
consecutive steps; (1) dissociation of the calcium carbonate,(2)
followed by reaction of CaO with sulfur dioxide. He suggested
(Ref. 1) that some reaction takes place within the interior
structure of the solid and that the relative importance of
the internal reaction becomes greater as the particle size
decreases. He subsequently demonstrated (Ref. 2), that the
rate of sorption is limited by a first-order reaction which
occurs throughout the internal pore structure of small
particles. There is a strong influence of physical properties
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upon the sorption of SO^. Small pores and large surface
areas lead to high reaction rates while large pores lead to
high capacity. Stones of varying geological type yield
calcines of distinctly different physical properties which
show correspondingly large differences in both rate of
reaction and total capacity for S02 sorption (Ref. 2).
Ishida,et al (Ref. 3) have shown that there is an unreactTtjd .
core, the size of which may depend on the particle size
(and porosity) of the particle itself.
Murthi,et al (Ref. 4) have recently reported studies on
the SOj sorption capacity of limestones and dolomites as a
function of calcination time and temperature in the dry
injection process. The role of surface area, porosity, and
chemical composition on the sorbent capacity was discussed.
The effect of moisture and of the presence of iron oxide in
the samples was also reported.
Harvey (Ref. 5, 6) has carried out extensive studies of
the petrographic and mineralogical characteristics of carbonate
rocks related to sorption of sulfur oxides in flue gases~.
Detailed petrographic, mineralogical, and chemical analyses
of 26 carbonate rocks were made and compared with the capacity
(3-1/2 hr. reaction period) and differential reactivity
(120 sec. reaction period) of calcined specimens for sorption
of sulfur dioxide (802). Three petrographic and chemical
properties appear to be useful indexes of the S02 sorption
-------
capacity: the pore volume, the grain size, and the sodium
oxide content of the rocks. The larger the pore volume,
the greater was the sorption capacity of the rock. In
general, the finer the grain size of the rock, the higher was
the sorption capacity. Of the chemical elements analyzed,
only sodium showed a correlation trend with the SC^ test
data. The sodium present in the samples increased with
increasing sorption capacity. Unlike the sorption capacity
tests, the differential reactivity tests showed little or no
correlation with petrographic and chemical properties.
Relatively high SO^ reactivity was observed for chalks,
calcareous marls, and oolitic aragonite sand samples and is
believed due mainly to the high pore volume and fine grain
size of these carbonate rocks.
Drehmel (Ref. 7) reported studies of the chemical and
physical properties of three series of calcined carbonates
(two limestones and one dolomite) as they pertain to "dead-
burning" in the dry injection process. A high degree of
intercorrelation was found between sulfur dioxide reactivities,
surface area and pore volume.
Drehmel (Ref. 8) has recently compared carbonate rock
types as to their sulfur dioxide removal efficiencies in a
batch scrubber and found the best types to be marl and
chalk and the worst marble and magnesite. For calcined
limestone, the change in scrubbing efficiency with calcination
temperature was found to be due to the resulting
-------
change in surface area or pore volume. At higher temperatures
where surface area was lost, reactivity was lost. The
variation in scrubbing efficiency with different calcined
limestone types was found to be a function of both the
surface area and pore volume.
Much of the primary reactivity and capacity data
referred to in this report is also to be found in a recent
technical report issued by EPA (Ref. 9).
The purposes of the present investigation of a selected
set of limestone and calcine samples by electron paramagnetic
resonance (EPR) spectroscopy were to (a) assist in the
characterization of marls and chalks to identify properties
which account for their high reactivity, (b) establish a
semi-quantitative basis for evaluating a crystalline order of
limestones to predict their reactivity with acid gases,
(c) investigate the effect of altering the calcination
temperature on the crystalline structure of calcines in
order to identify these properties which account for the
varying reactivity and deadburning, and (d) investigate the
effects of slaking on the crystalline parameters of calcines
produced at different temperatures in order to support wet
limestone scrubbing process development.
The theory of electron paramagnetic resonance (EPR)
spectroscopy and its application to the characterization of
solid-state materials are provided in Appendix A.
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Pure CaCO~ exhibits no EPR absorption, unless the material
I I I i 1
is irradiated. However, both Mn and Fe occur naturally
in limestones as substitutional ions for Ga and thus act
as paramagnetic probes of the crystal structure. It is
these probes which provide the basis of the present investi-
gation.
It is interesting to note that scientists in India
I i
(Ref. 10) have suggested using the Mn concentration
determined by EPR techniques in calcium carbonate materials
as an aid to manganese ore prospecting and also as an index
for establishing the relative ages of samples belonging to
unclassified geological periods.
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II. EXPERIMENTAL PROCEDURE
A. Samples
The polycrystalline carbonates and calcines which were
examined are listed in Tables I, II and III.
B. EPR Procedure
The polycrystalline samples were placed in Varian 9.5 GHz
quartz sample tubes, Si 3 mm ID and the tubes evacuated to a
pressure less than 50 microns. The EPR spectra were obtained
at liquid nitrogen temperatures using a standard cold finger
dewar placed in the Varian Model V-4531 multipurpose cavity
operated at a microwave frequency of 2*9140 MHz. Superhetero-
dyne detection and 400 Hz field modulation were employed.
The spectra were recorded on a Varian X-Y recorder using
the magnetic field as a base. See Appendix A for a more
detailed discussion of EPR spectroscopy and its application
to solid-state materials.
C. Ultraviolet-Visible Irradiation of Sample Type 11
Ultraviolet-visible irradiation of the sample Type 11 in
a suprasil EPR tube under high vacuum (10 torr) was performed
utilizing unfiltered light from an Osram 500 watt point-
source lamp collimated with a four-inch diameter fused silica
lens (focal-length four inches). The lens was placed at
approximately twice the focal length from the lamp providing
a one-to-one magnification of the point-source arc whose
image was entirely contained within the polycrystalline
sample area. The irradiation was carried out for 63 hrs at
ambient temperatures outside the dewar and cavity. EPR
measurements at liquid nitrogen temperatures^ were carried
out immediately after the irradiation and again, one week later,
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TABLE I
CARBONATE SAMPLES*
IGS Type**
Type 1
Type 3
Type 4
Type 5
Type 6
Type 7
Type 8
Type 10
Type 1]***
Type 12
EPA Nomenclature
#2201
#2203
#2204
#2205
#2206
#2207
#2208
#1336
#2129
#2077
#2081
#2109
#2080
Size
150/170
150/170
150/170
150/170
150/170
Hand Ground
150/170
150/170
150/170
150/170
150/170
150/170
150/170
Description
Iceland spar, calcite
Limestone, coarse grained
high purity
Limestone, fine grained
high purity
Dolomite, reef type high
purity
Dolomite
Magnesite, fine grained
high purity
Aragonite
White crushed marble
Michigan marl
Austin chalk
Kansas chalk
New York marl
Northeastern Ohio marl
* Supplied by EPA and Described by Harvey
** Illinois Geological Survey nomenclature
*** Ultraviolet decoration performed
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TABLE II
CALCINED SAMPLES*
IGS EPA
Type Nomenclature
Type 1
Type 3
Type 4
Type 5
Type 6
Type 9
Type 10
Type 11
Type 12
#2201
#2203
#2204
#2205
#2206
#2209
#1336
#2129
#2077
#2081
#2109
#2080
Size
150/170
10/28
150/170
150/170
150/170
150/170
150/170
42/65
***
***
***
***
Calcination
Temperature
1700°F
1800°F**
1700°F
1700°F
1700°F
1700°F
1700°F
1700°F
1700°F
***
***
***
***
Description of the
Precuisor Carbonate
Iceland spar, cal-
cite
Limestone, coarse
grained, high purity
Limestone, fine
grained, high purity
Dolomite, reef type,
high purity
Dolomite
Dolomite
White crushed marble
Michigan marl
Austin chalk
Kansas chalk
New York marl
Northeastern marl
* All samples prepared by EPA (2 hours at temperature)
** Contaminated with light-green colored material
*** Data unknown
8
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TABLE III
CALCINED SAMPLES*, VARIABLE TEMPERATURE SERIES
EPA
Nomenclature
Size
Temperature,°F
Description
#2061
#2062
#2069
170/200 1700**
2000**
2300**
2600**
3200**
-170 1700**
2000**
2300
2600
3200**
-170 1700**
2000**
2300
3200**
Fredonia White Limestone
Cedar Bluff Limestone
James River Dolomite
* Supplied by EPA
** Slaking Test Performed
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The sample was then exposed to air at atmospheric pressure
for one hour and then repumped to 10" torr in order to
investigate the air-stability of the irradiation created
Fe44"1".
D. Slaking Test
Selected calcined samples listed in Table III were
placed on pyrex watch glasses and were investigated according
to the slaking test conceived by T. D. Womble of T.V.A. and
used by EPA. Since the samples had not been received from
EPA sealed from the air, they were preheated at 650°C for
three hours to dispel any absorption of atmospheric water.
After cooling to room temperature in a dessicator over
P2^5» water was added to the samples in the ratio 1 ml/g
sample or 5 ml/g sample and the samples then soaked for
times of 30, 60, or 120 minutes. The wet samples were then
dried in an oven at 240°C for two hours, after which they
were removed and again placed over Po°5 in a dessicator where
they cooled. They were then reexamined for EPR absorption
at liquid nitrogen temperatures.
10
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III. EXPERIMENTAL RESULTS
A. Carbonate Samples
1. EPR Spectra
The six main transitions characteristic (Ref. 11) of
Mn"1"1" are observed in all the carbonates except Type 7(magnesite) .
A well-resolved spectrum in Type 10 (marble) is shown in
Figure Bl of Appendix B*. Sample Type 11 (Michigan marl) exhibts more
poorly resolved Mn"1"*" transitions as is shown in Figure B2,
but also displays a center at g = 2.0029 which we attribute
to Fe"H~f(Ref. 12). The limestones, chalks and marls all
exhibit similar, but not identical, spectra with the g-value
for Mn4"* = 2.0048. Representative spectra are shown in
Appendix B. Aragonite and the dolomites exhibit slightly
different spectra, which are also showi\ in Appendix B.
I I I
The role of Fe in the carbonates was not fully investi-
gated, but it was observed in samples Type 1, 8 and 11.
2. EPR Linewidth Analysis and Correlation With
Chemical Reaction Data
The highfield "line" of the six Mn"1""*" transitions was
chosen for linewidth analysis since it was the best resolved.
The theory and discussion of linewidth analysis is given in
Appendix A.
* In the remainder of the text, Figures in Appendix B will
be designated Bn while Figures in the main text will be
designated by an integer n, as is the usual practice
11
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A least-squares linear regression analysis was done on
eight of the samples listed (Table I). The two dolomites
were not included in the fitting as their variance from the
set seemed to be significant and because the linewidths
may be affected by the presence of Kg"1"4" in the dolomite
structure.
Three different EPR parameters were chosen and each
fitted to the reactivity and capacity data of Table 14 of
Reference 6. The three parameters are designated L-^, L2
and LO and are discussed in Appendix A. The correlation
coefficients for the fitting of the linewidths to the
reactivity and capacity data are listed in Table IV. The
data for L, are presented in Figures 1 and 2. The dolomite
data -"D"-have been circled to indicate that they were not
used in the fitting.
TABLE IV
REGRESSION COEFFICIENTS FOR EPR LINEWIDTHS L
TO THE, REACTION DATA
Reaction data
reactivity
capacity
3.
0
0
Ll
.55
.49
Ultraviolet-Visible
0
0
L2
.20
.45
Irradiation of
0.
0.
L3
18
17
Sample Type
11
The EPR spectra of the material before and after
12
-------
25
20
o
o
o
CO
CO
o
V)
15
L
9
c
o
10
o
LU
or
M
•
L = LIMESTONE
D = DOLOMITE
S = MARBLE
C = CHALK
M = MARL
I 234567
LINEWIDTH PARAMETER, GAUSS
Figure I S02 REACTIVITY IN DIFFERENTIAL TESTS VERSUS EPR LINEWIDTH
PARAMETER OF SELECTED LIMESTONES. CORRELATION COEFFICIENT IS 0.55,
-------
25 i—
20
en
O
CM
O
•«s
Q_
•<
O
O
CO
15
M
O
10
L
O
L = LIMESTONE
D = DOLOMITE
S = MARBLE
C = CHALK
M = MA.RL
I 23456
LIKEVMDTH PARAMETER, GAUSS
Figure 2 SORPTION CAPACITY, FIXED BED, VERSUS EPR LINEWIDTH PARAMETER
OF SELECTED LIMESTONES. CORRELATION COEFFICIENT IS 0.49.
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63 hrs. irradiation at ambient temperatures are shown in
I I I
Figures B3 & B4,, respectively. The Fe is increased by
the irradiation and remained stable for more than a week
under high vacuum ( < 10" torr). Furthermore, the subse-
quent admission of air at atmospheric pressure to the
sample for one hour did not result in any reduction in
signal intensity.
B. Calcined Samples
1. EPR Spectra
I [
Six Mn transitions were observed in the calcines with
slightly different g-values (2.0069 for the calcites) and
splittings than are found in the carbonates. A typical
spectrum in the 1700°F calcine of Type 1 (Iceland Spar
Calcite) is shown in Figure B5. When Type 1 calcined at
!800°F_, a center at g = 2.0047, characteristic of Fe"f"i"i"
(Ref. 13) is also observed. (The sample also exhibits
another strong line,, believed to be an impurity). Aside
from the appearance of the Fe in the 1800°F calcine
along two other significant differences exist between the
two calcines. First, closer examination of the two minor
I I §
peaks flanking the place where Fe is observed shows that
the peaks are stronger in the 1700°F calcine (Figures B7 & B8)
Secondly, the structure underlying each of the six main M
peaks is stronger and better resolved in the 1800°F cal-
15
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cine. The fifth-highest main Mn line is shown in (Figures
B9 & BIO) Type 1 was the only material for which a 1700°F
and 1800°F calcine was available for investigation. However,
the other 1700°F calcines showed the main Mn transitions
and FeH ' was also observed in Type 3, 5, 6, 10 and 11.
2. EPR Linewidth Analysis
The linewidth of the low field Mn*4" transition were
measured for all the samples in Table II and in Figures 3 and
4 are plotted against the reactivity and capacity data of
Table 14 of Reference 6. No regression analysis was
attempted since the scatter is large, but the chalks did
appear to have rather large linewidths, indicative of their
'unconsolidated1 nature.
3. Variable Temperature Series
The Series 2061 was examined for Mn linewidth analysis
for the five different temperatures (See Table III). While
no correlation was apparent between the linewidths and the
reactivity or capacity data, a significant relationship was
found between the linewidth and the density data found in
Table B2-2A of Reference 9. The data is plotted in Figure 5.
The spectra of the 2061 series are shown in Figures Bll-15.
One striking feature of the series is the variation of
I I I
the Fe intensity as a function of temperature. The
signal heights of the Fe444" center normalized to those of the
Mn peak immediately downfield are plotted versus calcination
temperature in Figure 6. A qualitative feature of Series 2062
16
-------
25
20
01
15
CO
o
v>
10
o
•<
UI
oc.
• M
s
L = LIMESTONE
D = DOLOMITE
S - MAP.BLE
C = CHALK
M = MARL
LINEWIDTH PARAMETER, GAUSS
Figure 3 S02 REACTIVITY IN DIFFERENTIAL TEST VERSUS EPR LINEWIDTH
PARAMETER OF SELECTED CALCINES.
-------
25.
20
o
CM
15
M
•00
10
o
CO
— s s
c
L LIMESTONE
D DOLOMITE
S MARBLE
C CHALK
M MARL
1234?
LINEWIDTH PARAMETER. GAUSS
Figure 4 SORPTION CAPACITY, FIXED BED, VERSUS EPR LINEWIDTH
PARAMETER OF SELECTED LIMESTONES.
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3.50
3.UO
3.30
o
en
z
o
3.20
1700
>-
I—
co
z
o
3. 10
2300
3200
3.00
2.90
2600
I
2000
I
O.I 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 I.I 1.2 1.3 I.U
EPR LINEWIDTH, GAUSS
Figure 5 DENSITY VERSUS EPR LINEWIDTH FOR SERIES 2061 CALCINES.
19
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5.0
4.0
ce
| 3.0
CD
or
CO
LU
E 2.0
LU
1.0
0.0
A
O
D
O
A
8
A
i
SAMPLE NO.
O = 2061
A=2062
D = 2069
1700
2000 2300 2600
CALCINATION TEMPERATURE, °F
3200
Figure 6 EFFECT OF CALCINATION TEMPERATURE ON Fe~M~rCENTER IN CALCINES.
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aud 2069 are similar with the hard-burned sample (3200°F)
deviating significantly from a linear relationship.
The spectra of the Fe1'' centers in the 2061 and 2062
calcines are similar but differ from what is observed in the
2069 series. There appears to be (at least) one other center
I I I
overlapping the center identified as Fe substituted in the
I i
Ca lattice position.
4. Slaking Test
The samples showed a weight loss on preheating at 650°C
and a weight gain after soaking and drying. Different soaking
times and volumes were used for the series 2061, 2062 and
2069 and the changes in weights are shown in Tables C-I,
C-II and C-III of Appendix C. The results agree generally
with those of Drehmel (Ref. 7). The EPR spectra of the
dry 1700°F, 2000°F, 2600°F and 3200°F calcines in Series
2061 which had been soaked with 1 ml of water for 60 minutes
are shown in Figures B16-19. The spectra showed a "doubling"
I i
of the six Mn lines, indicating that a second site exists
I [
for Mn with hyperfine splittings larger by about 1.5% and
a down-fie Id shift in g-value. The behavior of the 2061
series was similar for other soaking times and volumes. The
other series, 2062 and 2069 behaved in a similar manner. Tte
spectra for a 5 ml, 120 min. soak for the 1700°F 2061 calcine
is shown in Figure B20. The g-value for Mn4"1", which entirely
21
-------
is the second site, is equal to 2.0077.
If, the second site is that associated with hydrated
CaO, then*
hydrated site signal intensity _ k ' actual % Wt. gain
non-hydrated site signal intensity theoretical 70 -
actual" % Wt, gain
Concentration of a center oc Signal Height
c = al
c' = a'l'
where c = concentration of non-hydrated CaO
c ' = concentration of hydrated CaO
_c ' _ 70 wt, gain _ ______^
c^+^z theoretical maximum 70
inverting
1 , c _ theoretical maximum %
c o wt. gain
c _ theoretical maximum 7o - °L wt. gain
cT1" 70 wto gain '
inverting,
c' _ 7o wt. gain _ _
c theoretical maximum 70 - 70 wt. gain
H = a £— = k £l
I T1" c c
Ij. _ k % wt. - _ _
I theoretical maximum 7o - 70 wt. gain
so that the plots of data taken from the spectra (signal
intensity) and the Tables C-I, C-II and C-III (slaking test)
22
-------
should provide independent evidence of whether or not the
second site is in fact hydrated CaO. The log-log plot of the
data for all experiments is provided in Figure 7, and the
slope is seen to be nearly equal to one. Due to overlap of
I I
the Mn transitions in the two sites, the observed devia-
tions are to be expected.
A cursory examination reveals that there does not
I I I
appear to be any large change in the Fe for the 2061 and
2062 series after slaking and drying. However, the 2069
centers increased greatly.
23
-------
IOOOO
1000
Iml
O - 30 mln
O- 60 mln
5ml
•- 30 mln
• -60 mln
A-l20min
A1700
IO.O
U
I
LJ
O
UJ
o
Xv
I
UJ
•x.
UJ
z
O
UJ
a:
o
V
I
1.0
|700
|700
'1700
Dl700
A1700
A 3200
O.I
2000
2600
320?
• • 3200
O3200
OX>I
000
III
i i I I ll
O.Ol
O.I
1.0
ACTUAL WEIGHT GAIN
10.0
100.0
1000.0
THEORETICAL- ACTUAL WEIGHT GAIN
Figure 7 RELATIONSHIP OF Mn
SLAKING TEST DATA.
*"1"
EPR SIGNAL INTENSITIES TO THE
-------
IV. DISCUSSION OF RESULTS
A. Carbonate Samples
The fitting of EPR linewidth data to the reactivity and
capacity data resulted in correlations which in the best
case (r = 0.55 and 0.49) were significant, though not as
high as we might have liked. It is interesting though, that
both the reactivity and capacity correlations were comparable.
The other two parameters chosed for regression analysis,
while poorer in result, might have been expected from
the less accurate determination of the linewidths in the
case of L2 and Lj, and from the possibility for overlap
effects for L3 as well. From the qualitative observations
that within a carbonate type, the sharper and better-resolved
I I
Mn lines occur for the more reactive material, it is
believed that better linewidth correlation might be found
within any carbonate type. Variations of the inherent
structure of even a perfect lattice from carbonate type to
carbonate type might account for a not- larger correlation
among all the samples.
The effect of ultraviolet-irradiation on Michigan Marl
(Type 11, #2129) under high vacuum is remarkable. Fe+4+ is
increased in intensity without (presumably) a change in the
surface area or pore volume. The increase in Fe44"1" is main-
tainable in air - i.e. stable. This implies that the decora-
tion of the defect structure of carbonates may be investigated
by the creation of Fe^ by the photo-oxidation of Fe^ and
could prove to be as valuable a probe of crystallinity as
the
25
-------
B. Calcined Samples
The two Type 1 Iceland Spar Calcines (1700°F and 1800°F)
exhibit considerably different external morphology and
capacity (Ref. 6). In the Type 1 Iceland spar material,
the low capacity anisotropic 1700°F calcine with a high
degree of strain shows no Fe''' center while the higher-
I I i
capacity isotropic 1800°F calcine yields the Fe center.
Thus while Fe''' seems to be an indicator of capacity, its
role is by no means clear at this time. However, there are
two other EPR parameters which do indicate the. degree of
crystallinety of the materials.
i i i
The two minor peaks flanking the Fe center are
essentially quantum-mechanically forbidden transitions
whose presence is enhanced by a departure from a cubic environ-
ment. Thus, as expected the minor peaks are more intense
in the 1700°F calcine.
Furthermore, the structure under the six main Mn^"1" lines
is what is known as "fine structure" in spectroscopic langu-
age and the better resolution and increase in intensity in
the 1800°F calcine is what is expeqted for a more perfect
lattice. It would have been valuable if more of such "pairs"
of radically different materials were available for study.
In the 2061 calcine series, the Mn4"4" linewidths did
prove to correlate well with the density data. The reactivity
and capacity data did not correlate with either the
26
-------
linewidths in the calcines of the various types of limestones, or
with the density data (Ref. 9). Perhaps, these observations
merely reflect that fact that reactivity depends on both the
density and the initial crystallinity, the latter to which
EPR is not sensitive.
C. Slaking Test
The EPR results on the calcined samples after soaking and
_L_|_
drying indicate the presence of a second site for Mn which is
most probably the hydrated oxide site. The relationship of the
EPR linewidth data to the slaking test data in Figure 7 is
independent evidence of the assignment of the new EPR lines to
I [^
Mn in hydrated sites. The small shift observed for the field
positions of the "second phase" is almost conclusive by itself.
D. The Role of Fe in the Calcines
I i i
Since the Fe level in the three (unsoaked) series
seems to be related to the calcination temperature (Figure 6),
it may be possible to utilize EPR to find the optimum calcination
temperature. Most of the iron is probably present as Fe"^",which
is not observed by EPR in these materials.
The appearance of another signal in the 2069 series may be
-i_,4-_i_ * i
due to Fe substituted in Mg sites. This may not have any
bearing on the reactivity of the calcine,however. What is
interesting in this series is the great increase in the
after soaking and drying. It is difficult to satisfactorily
rationalize.this observation.
27
-------
V. RECOMMENDATIONS AND CQNCIUSIGNS
The findings of the investigative effort are well
summarized at the beginning of this report and will not be
repeated here. However, it is clear that some questions
remained unanswered and further research may be expected to
be fruitful.
The correlation of EPR linewidths in all the carbonate
materials with reactivity and capacity (r = 0.55 and r = 0.49
respectively), does indicate that higher correlation may be
found within a carbonate type. Thus further investigations
of a large number of samples for each carbonate type may
prove to be of value.
The data show that in the 2061 temperature calcine
i i_
series, the Mn linewidths did correlate extremely well
with the density data, though not with reactivity or capacity.
An attempt to correlate the density data for calcines of all
I i
stone types ought to be done. Although the Mn EPR data
seem to be sensitive to the density determinant of reactivity,
I i i
and not to the initial crystallinity, photocreated Fe
might prove to be a surface defect and hence sensitive to
initial crystallinity. The role of iron in the limestones
and their calcines was barely emphasized compared to the
++ I I I
Mn probe, and we believe that Fe may turn out to be
j i_
valuable in ways that Mn is not as a probe. This is
indicated by the comparison of the 1700°F and 1800°F calcines
28
-------
of the Type 1 Iceland Spar material as well as by the
temperature series 2061S 2062 and 2069. Decoration of the
I I i I I
defect state by UV-irradiation producing Fe from Fe
ought to be pursued in both the limestones and their
calcines.
The sensitivity of the EPR spectra to the degree, of
hydration in the calcines points to a very important poten-
tial use of EPR for investigating chemical reactions in
these materials. One should be able to follow the convers-
ion of CaCOo to CaO to CaSO~ to CaSO, and each species should
give distinguishable EPR spectra in a mixture - even with
many reactions occurring simultaneously. Since EPR spectros-
copy is an instantaneous measurement (£29000 "experiments"
per second) kinetic studies can be done on solid-gas and
solid-liquid reactions, as well as liquid-gas reactions.
^
The EPR investigations of the chemistry of the limestone and
calcine materials with S0~ should prove to be a fruitful
area - in both dry injection and wet-scrubbing processes.
29
-------
REFERENCES
1. R. H. Borgwardt, Environmental Science and Technology
4, 59 (1970).
2. R. H. Borgwardt, "Isothermal Reactivity of Selected
Calcined Limestones with SOJ1, Paper presented at the
International Dry Limestone Injection Process Symposium,
Paducah, Kentucky, June 22-26, 1970.
3. M. Ishida, S. C. Wang, C. Y. Wen, "Study of Rate of S02
Absorption by an Agglomerated Single Sphere of Calcium
Dioxide Powder" - preprint of paper, Journal or Confe-
rence Source Unknown.
4. K. S. Murthi, D. Morrison, and R. K. Chan, Env. Sci. &
Tech., 5, 776 (1971).
5. R. D. Harvey, Interim Report to the National Air Pollution
Control Administration, Contract No. CPA-22-69-65,
June 22, 1970.
6. R. D. Harvey, Final Report, Contract No. CPA 22-69-65,
July 15, 1971.
7. D. C. Drehtnel, Am. Cer. Soc. Bull., 50, 666 (1971).
8. D. C. Drehmel, "Limestone Types for Flue Gas Scrubbing",
Paper presented at the Second International Lime/Lime-
stone Wet Scrubbing Symposium, New Orleans, Louisiana,
November 8-12, 1971.
9. R. H. Borgwardt, D. C. Drehmel, T. A. Kittelman, D. R.
Mayfield and J. S. Bowen, "Alkaline Additives for Sulfur
Dioxide Control". Air Pollution Technical Data
Document 0737.
10. P. K. Ghosh, M. Samaddar, S. C. Sinha, J. S. Tiwari and
A. C. Banerji, Technology 2, No. 4, 276 (1970).
11. C. Kikuchi and L. M. Matarrese, J. Chem. Phys. 33
601 (1960). y —'
12. S. A. Marshall and A. R. Reinberg, Phys. Rev. 132. 134 (1963).
13. A. J. Shuskus, Phys. Rev. 127. 1529 (1962).
30
-------
APPENDIX A
EPR THEORY AND APPLICATION TO THE CHARACTERIZATION
OF SOLID-STATE MATERIALS
-------
GENERAL THEORY
Systems with unpa i r e d^ e 1 e c t ro ns exhibit a paramagnetism
which serves to identify them on the application of electron
paramagnetic resonance (EPR) spectroscopy in a magnetic field.
This paramagnetism is due primarily to the spin angular
momentum of the unpaired electron (S = 1/2) which can be
quantized in a magnetic field such that the projection of the
spin angular momentum along the axis of quantization (along
the magnetic field) is S -= ± 1/2. For an isolated electron
in a magnetic field, the energy is described by the Hamiltonian
(1)
in which p is the Bohr magneton, S is the spin angular momentum,
H is the magnetic field and g is a second rank tensor. For an
electron, in the absence of other perturbations, the principal
values of the g tensor are equal so that )f = 9>-pH«H and two
magnetic levels are oossible for the electron:
S = + 1/2 .
^-^T
Energy
-------
Transitions may be induced between these two levels by the
application of radiofrequency energies (usually X = 3cm at
3500 Gauss) such that
= hv - glpl|H|
(2)
It is principally this energy absorption which gives rise to
EPR spectroscopy, In practice, the microwave source is held
constant and the magnetic field varied until absorption is
observed, contingent on the resonant condition in equation (2) .
Of course in real systems, we do not have an isolated,
perturbation-free electron. The unpaired electron may be
non-bonded, but in an anion vacancy in a crystal lattice; or
it may be an integral part of a molecular species such as
Mn*4", Fe44"*", H, N02, 02~, Ti+3, Zn+1, Ag+2, etc. An isolated
electron has no orbital angular momentum and g is a function
of spin only and equal to 2.0023, but once the electron is
constrained to move within a molecular or crystalline frame-
work, a finite orbital angular momentum can result, imparting
an additional paramagnetism to the electron such that g is
a function of both spin and orbital angular momentum. In real
systems g can vary more than 10% from the free electron value.
As examination of equation (2) will show, systems with different
g-values will give rise to spectra at different magnetic
fields. Another distinguishing feature is the interaction of
the unpaired electron with magnetic nuclei in the same species;
e.g. the unpaired electron interacts with the manganese nucleus
2-A
-------
in Mn4"1", with the nitrogen nucleus in N02, with protons in
H OH, C.H.-, and with C13 in natural abundance in organic
' ' D _> '
compounds.
When magnetic nuclei are present the energy is best
described by
tI (3)
in which I. is the nuclear spin of the ith nucleus and A^ is
the second rank hyperfine interaction tensor. The magnetic
nuclei in effect "split" the EPR transitions in characteristic
ways so that molecular structure determinations can be made.
For example the nuclear spin of magnanese is 5/2 and thus
1 _ L
each electron spin transition in Mn is split into six
components, giving a six line spectrum.
For a particular paramagnetic species there are definite
values for g and A. which distinguish not only the species
but also the symmetry of the species. For example it is
possible to distinguish 02~ on the surface of ZnO from 09~
in the crystal lattice.
EPR and optical spectroscopy serve to complement one
another in solid state studies. The curve under the EPR
absorption curve is proportional to both the concentration
and the total amount of absorbing centers, and hence EPR does
3-A
-------
not follow Beer's Law as is the case with optical absorption.
The EPR transition probability (related to the extinction
coefficient) is essentially the same for the unpaired electron,
regardless of the environment. Thus quantitative determination
of an unidentified paramagnetic species can be easily made by
comparison with a known standard. This is certainly not the
case with optical investigations. Furthermore, because the
magnetic environment of different species is different, the
transitions for each species are distinguishable in a mixture
of paramagnetic molecules which may not be the case for optical
investigations in which there can be considerable overlap of
absorption or reflection. The sensitivity of the method is
very high, 10 spins or molecules is the usual minimally
detectable limit for each species. For a usual sample size of
3 - n
1 cm s this represents 2 x 10 moles.
EPR is a non-destructive technique, a physical measure-
ment not affecting the concentration of nature of the
species. In optical investigations this may not be the case
since (especially ultra-violet) light can actually produce
additional absorbing centers. Thus the comparison of EPR
and optical investigations can serve to detect the effects
of optical irradiation on solid-state materials. In fact,
the effects of optical irradiation on solid-state material
can be determined by simultaneously observing the EPR and
optically irradiating the material in the same EPR sample
cell.
4-A
-------
Reflectance spectroscopy on poly-crystalline material
has been demonstrated to yield the absorption coefficient, but
the studies are sometimes complicated by scattering, internal
reflection, and particulate size effects. The problem of
optical centers on the surface, in contradistinction to the
bulk of the material, can be a complex one, one which EPR
studies may clarify since the technique is so sensitive to
small changes in magnetic environment and symmetry. EPR is
particularly useful in resolving optical spectra in which
there is a great deal of overlap of structurally similar or
dissimilar species.
The species in their natural states to which EPR
techniques may be applied are generally limited to natural
paramagnetic defects in solids, a few stable free-radicals
(such as NC^) , and compounds of transition metals and rare
earths. However, almost any solid material can be rendered
paramagnetic by several techniques: (1) ^-irradiation, which
is widely utilized to decorate the defect state of solid-state
material, (2) ultra-violet irradiation which can ionize snecies
to become paramagnetic, (3) thermal ionization for low energy
processes, (4) paramagnetic creation of a photo-excited
paramagnetic triplet state, and (5) doping the solid with
paramagnetic ions.
5-A
-------
LINEWIDTH ANALYSIS
The highfield "line" of the six MrT^ transitions was
chosen for linewidth analysis since it was the best resolved.
Under high resolution the "line" is rather complex and a
typical spectra (Type 3) is shown in Figure Al. The "line"
is the first derivative of the EPR absorption of a random
selection of crystallites - i.e. a powder spectra. The
EPR transitions in each "line" fall into two groups, each
characterized by a maximum absorption' which is understandable
in terms of (1) the way the transitions for the random
orientations vary in intensity at different directions in
the crystalline lattice and (2) the number of systems
absorbing at each orientation. The theory is complex,though
understood,and we will not repeat it here. Suffice it to
say, the two groups are observable in Figure Al and are
designated A arid B. The less perfect the lattice, the
broader the EPR absorption (and first derivative) of each
group will be.
Three different EPR parameters were chosen and each
fitted to the reactivity and capacity data of Table 14 of
Reference 6. The. three parameters are designated L, , L* and
L~ in Figure Al. L, and L« are, in effect, the horizontal
distance (in magnetic field) between second derivative
maximum and minimum points for the least-overlapped portion
of each of the absorption groups. L~ is a measure of the
horizontal distance (in field) between the maximum absorption
and the half-height. Both measures are usecl in linewidth analysis*
6-A
-------
Figure Al: EPR SPECTRA OF HIGH-FIELD
Mn"1"1" TRANSITION IN SAMPLE
TYPE 3, #2203.
7-A
-------
APPENDIX B
EPR SPECTRA
-------
I
ca
"mic = 91*0.3 MHz
73.7G-*j
Figure Bl: EPR AT »77°K OF SAMPLE 1336, WHITE CRUSHED MARBLE, MODULATION - 0.52G
-------
N3
I
03
Figure B2: EPR AT K 77°K OF SAMPLE 2129, MICHIGAN MARL, MODULATION - 0.52G
-------
U 87.2 G »|
= 2.0029
mic
= 9|i|l.t; MHz
Figure B3: EPR SPECTRUM AT ^77°K OF TYPE 11, #2129, BEFORE U.V.-IRRADIATION, MODULATION - 0.40G
-------
mjc= 9111.1 MHz
Figure B4: EPR SPECTRUM AT ^ 77°K OF TYPE 11, #2129, AFTER 63 HRS-
U.V.-IRRADIATION, MODULATION - 0.39G
-------
Ul
I
03
l'mic= 9110.5 MHz
Figure B5: EPR SPECTRUM AT & 77°K OF TYPE 1, #2201, 1700°F CALCINE, MODULATION - 0.40G
-------
I
W
Figure B6: EPR SPECTRUM AT #77°K OF TYPE 1, #2201, 1800°F CALCINE, MODULATION - 0.39G
-------
MHz
Figure B7: EPR SPECTRUM AT ~77°K OF TYPE 1, #2201,
1700°F CALCINE, MODULATION - 1.59G.
7-B
-------
= 9IU2.9 MHz
Figure B8: EPR SPECTRUM AT » 77°K OF TYPE 1, #2201,
1800°F CALCINE, MODULATION - 1.60G.
8-B
-------
7.5G.
>'(nic=9m0.5 MHz
Figure B9: EPR SPECTRUM AT »77°K OF TYPE 1, #2201,
1700°F CALCINE, MODULATION - 0.39G.
9-B
-------
MHz
7.5G.
Figure BIO: EPR SPECTRUM AT »77°K OF
TYPE 1, #2201, 1800°F
CALCINE, MODULATION -
0.40G.
10-B
-------
I
03
= 2.0046
73.7G-H
H
v . -
mic = 9110.3 MHz
Figure Bll: EPR AT »77°K OF SAMPLE #2061 CALCINED AT 1700°F, MODULATION - 0.52G
-------
NJ
03
73.7G-*|
-3 MHz
Figure B12: EPR AT «77°K OF SAMPLE #2061 CALCINED AT 2000°F, MODULATION - 0.52G
-------
u>
I
MHz
Figure B13: EPR AT «77°K OF SAMPLE #2061 CALCINED AT 2300°F, MODULATION - 0.52G
-------
-73.7G-*]
= 9l39.7 MHz
Figure B14: EPR AT ^77°K OF SAMPLE #2061 CALCINED AT 2600°F, MODULATION - 0.52G
-------
73.7G—I
^mic=9l38. I MHz
Figure B15: EPR AT ^77°K OF SAMPLE #2061 CALCINED AT 3200°F, MODULATION - 0.52G
-------
75.9G
Figure B16:
EPR SPECTRUM AT « 77°K OF 1700°F #2061 CALCINED, AFTER 1 ML,
60 MIN SLAKING TEST, MODULATION - 0.45G
-------
-J
Cd
Figure B17:
EPR SPECTRUM AT « 77°K OF 2000°F 2061 CALCINE, AFTER 1 ML,
60 MIN SLAKING TEST, MODULATION - 0.45G
-------
Figure B18:
EPR SPECTRUM AT »77°K OF 2600°F 2061 CALCINE, AFTER 1 ML,
60 MIN SLAKING TEST, MODULATION - 0.45G
-------
vo
I
OS
Figure B19:
EPR SPECTRUM AT »77°K OF 3200°F 2061 CALCINE, AFTER 1 ML,
60 MIN SLAKING TEST, MODULATION - 0.45G
-------
NJ
O
I
03
U—76.56 —»|
H
V
mic
= 91^3.6 MHz
Figure B20:
EPR AT »77°K OF 1700°F 2061 CALCINE AFTER 5 ML,
120 MIN SLAKING TEST, MODULATION - 0.40G
-------
N3
I—1
S3
Figure B-21 EPR AT^77°K OF SAMPLE 2203, LIMESTONE (COARSE), MODULATION - 0.52G
-------
fo
ro
i
C3
[-1 73.7 G-~)
"mic= 8I40-9 MHZ
Figure B-22 EPR AT«77°K OF SAMPLE 2077, AUSTIN CHALK, MODULATION - 0.52G
-------
N3
U>
I
MHz
Figure B-23 EPR AT «770K OF SAMPLE 2081, KANSAS CHALK, MODULATION - 0.52G
-------
= 9137-8 MHz
Figure B-24 EPR AT -^-77°K OF SAMPLE 2206, DOLOMITE, MODULATION - 0.52G
-------
Ul
I
tXJ
Figure B-25 EPR AT ^ 77°K OF SAMPLE 2208, ARAGONITE, MODULATION - 0.5.2G
-------
APPENDIX C
SLAKING TEST DATA
-------
TABLE C-I
o
SERIES 2061 (170/200) SLAKING TEST
(Percent Weight Gain For A 1 Gram Sample)
Calcination
Temperature
1700°F
2000°F
2300°F
2600°F
3200°F
% Wt. loss
on heating
at 650°C
6.5%
3.5
2.0
5.1
1.4
Soaking Volume
30Min 60Min
30.4 28.5
-
-
21.5
9.9 11.4
1ml
120Min
30.1
24.2
-
-
13.6
Soaking
30Min
32.8
-
-
-
14.2
Vo lume
60Min
32.8
-
-
-
15.9
5ml
120Min
32.4
-
-
-
22.8
-------
TABLE C-II
SERIES 2062 (-170 SIZING) SLAKING TEST
(Percent Weight Gain For A 1 Gram Sample)
Calcination
Temperature
% Wt. loss
on heating
at 650°C
Soaking Volume 1ml
60Min 120Min
1700°F
2000°F
2300°F
2600°F
3200°F
3.4%
8.3
3.9
3.4
1.6
28.1
27.0
22.6
21.4
12.6
28.7
28.2
14.7
2-C
-------
TABLE C-III
SERIES 2069 (-170 SIZING) SLAKING TEST
(Percent Weight Gain For A 1 Gram Sample)
Calcination
Temperature
% Wt. loss
on heating
at 650°C
Soaking Volume 1ml
60Min 120Min
1700°F
2000°F
2300°F
3200°F
3.3%
3.7
2.0
4.0
16.1
10.5
11.0
5.3
16.2
5.3
3-C
-------
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------- |