379 A/g/J /i0.7k~n<\
MODEL DEVELOPMENT FOR THE CATALYTIC/CALCINATION
OF CALCIUM CARBONATE
DISSERTATION
Presented to the Graduate Council of the
North Texas State University in Partial
Fulfillment of the Requirements
For the Degree of
DOCTOR OF PHILOSOPHY
By
Jin-Mo Huang
Denton, Texas
December, 1987 Huang, Jin-Mo, Model Development for the Catalytic
Calcination of Calcium Carbonate. Doctor of Philosophy
(Analytical Chemistry), December, 1987, 88 pp., 25 tables,
18 figures, bibliography, 60 titles.
Lime is one of the largest manufactured chemicals in the United States. The conversion of calcium carbonate into calcium oxide is an endothermic reaction and requires
approximately two to four times the theoretical quantity of energy predicted from thermodynamic analysis. With the skyrocketing costs of fossil fuels, how to decrease the energy consumption in the calcination process has become a very important problem in the lime industry.
In the present study, many chemicals including lithium carbonate, sodium carbonate, potassium carbonate, lithium chloride, magnesium chloride, and calcium chloride have been proved to be the catalysts to enhance the calcination rate of calcium carbonate. By mixing these chemicals with pure calcium carbonate, these additives can increase the calcination rate of calcium carbonate at constant temperatures; also, they can complete the calcination of calcium carbonate at relatively low temperatures. As a result, the energy required for the calcination of calcium carbonate can be decreased.
The present study has aimed at developing a physical model, which is called the extended shell model, to explain the results of the catalytic calcination. In this model, heat transfer and mass transfer are two main factors used to predict the calcination rate of calcium carbonate.
By using the extended shell model, not only the catalytic calcination but also the inhibitive calcination of calcium carbonate have been explained. TABLE OF CONTENTS
PAGE
LIST OF TABLES iv
LIST OF ILLUSTRATIONS vi Chapter
I. GENERAL INTRODUCTION 1
II. DETAILS OF THE RESEARCH 17
III. CATALYTIC EFFECT OF ALKALI CARBONATES ON
THE CALCINATION OF CALCIUM CARBONATE 48
IV. LITHIUM CARBONATE ENHANCEMENT OF THE
CALCINATION OF CALCIUM CARBONATE
PROPOSED EXTENDED SHELL MODEL 61
V. INHIBITION OF THE CALCINATION OF
CALCIUM CARBONATE 75
APPENDIX 83
BIBLIOGRAPHY 85
ill LIST OF TABLES
Table Page
I. Various Forms Of CaC03 20
II. Melting Temperatures Of Li2C03, Na2C03, K2C03> MgCO 3, And CaC03 26
III. Fluctuation Of Calcination Rates Of Pure CaC03 Due To Temperature Variation In Heating Chamber Of Lindberg Furnace At 800 °C 31
IV. Variance Of Calcination Rates Of Pure CaC03 At A Fixed Position In Heating Chamber Of Lindberg Furnace At 800 °C... 33
V. Calcination Rates Of Pure CaC03 (As Blank) From Eight Different Sample Runs From Lindberg Furnace At 800 °C 34
VI. .Calcination Rates Of Using Fused Salts As Catalysts From Lindberg Furnace At 800 °C 35
VII. Calcination Rates Of Using Some Chemicals As Catalysts From Lindberg Furnace At 800 oc 35
VIII. Calcination Rates Of Pure CaC03 At Different Temperatures From DTA-TGA Analyzer At 700 °C 38
IX. Some Catalytic Calcination Results From DTA-TGA Analyzer At 700 °C 41
X. Precision Of DTA-TGA Technique 42
XI. Transition Temperatures Of Some Chelating Agents 43 XII. Calcination Rates Of Alkali Carbonate- CaC03 Mixtures From Lindberg Furnace At 800 °C 51
XIII. Calcination Rates Of Alkali Carbonate- CaC03 Mixtures From DTA-TGA Analyzer At 700 °C . 52
IV LIST OF TABLES Continued
Table Page
XIV. Transition Temperatures Of Alkali Carbonate-CaC03 Mixtures From DTA Curve 55
XV. Calcination Rates Of Pure CaC03 And Pure Na2C03 From DTA-TGA Analyzer 57 XVI. Melting Temperatures Of Alkali Carbonates And Pure CaC03 58
XVII. Calcination Rates Of Usng Li2C03 As Catalyst From Lindberg Furnace At 800 oc 64
XVIII. Calcination Rates Of Using Li2C03 As Catalyst From DTA-TGA Analyzer At 700 °C 65
XIX. Transition Temperatures Of Li2C03-CaC03 Mixtures From DTA Curve 68
XX. Calcination Rates Of CaC03 At Different Temperatures From DTA-TGA Analyzer 71
XXI. Melting Temperatures Of MgCl2 And CaCl2.... 72
XXII. Calcination Rates Of 5% MgCl2 And 5% CaCl2 In CaC03 From DTA-TGA Analyzer At 700 °C 73
XXIII. Calcination Rates Of Additive-CaC03 Mixtures From DTA-TGA Analyzer At 700 °C 78
XXIV. Transition Temperatures Of Additive-CaC03 Mixtures From DTA Curve 79
XXV. Melting Temperatures Of Additives 80 LIST OF ILLUSTRATIONS
Figure Page
1. The structure of CaC03 1
2. Influence of C02 concentration and pressure on dissociation temperature of CaC03.... 3
3. Decomposition of a sphere of CaC03 (shell model) 5
4. A reflux reactor 12
5. Block diagram for the Norelco x-ray diffraction unit 22 6. X-ray diffraction pattern of fused material of Na2C03-CaC03 salt 28 7. X-ray diffraction pattern of unfused material of Na2C03-CaC03 salt 29 8. A fixed position in heating chamber of Lindberg furnace to produce reliable results 32
9. Typical thermogram used for the calculation of calcination rate 37
10. A typical thermogram used for the determination of transition temperature. 39
11. Calcination rates of pure CaC03 vs. temperatures from DTA-TGA analyzer 40
12. The extended shell model 46
13. Calcination rate vs. alkali carbonates from Lindberg furnace 53 14. Calcination rate vs. alkali carbonates from DTA-TGA analyzer at 700 °C 54 15. Transition temperature vs. alkali carbonate-calcium carbonate mixtures.... 56
vi LIST OF ILLUSTRATIONS Continued
Figure page
16. Calcination rate vs. Li2C03 concentration from Lindberg furnace at 800 °C 66
17. Calcination rate vs. Li2C03 concentration from DTA-TGA analyzer at 700 °C 67
18. Transition temperature vs. Li2C03 concentration 69
VII CHAPTER I
GENERAL INTRODUCTION
Theory of Calcination
Calcium carbonate (CaC03) has the structure shown in
Figure 1. During calcination or thermal decomposition of
CaC03 a carbon-to-oxygen bond and a calcium-to-oxygen bond
are broken. Carbon dioxide (C02) is evolved, and calcium
oxide (CaO) remains. Because there is only bond breakage,
and no bond formation, the calcination process is an
endothermic reaction.
\ / 9 \ /9 \ , Lc. \ L, \ o*^ o! O' / A >cax \ / <* \ / X 7 x /
Figure 1. The structure of CaC03
The measurements of the dissociation pressures of CaC03 have been made through a range of temperatures by Debray
(1), Le Chatelier (2), Brill (3), Pott (4), Zavriev (5), and
Riesenfeld (6). Riesenfeld showed that the possibility of formation of a solid solution of CaO in the CaC03 and vice
versa is practically excluded. It is, therefore, proved
that the dissociation of CaC03 proceeds according to the
following reaction only:
A N CaC03(s) ^ CaO(s) + C02(g)
Johnson (7) showed that for a number of heterogeneous
equilibria similar to the dissociation of CaC03, the
dissociation pressure is connected with the heat of
reaction, AH, and the dissociation temperature, T, by the
following equation:
AH log P = 4.576 T 4.576
J is the thermodynamically indeterminate constant.
Actually, the dissociation temperatures are not rigid values since they vary with the counteracting C02 pressure
and concentration, as shown in Figure 2 (8). If the temperature and pressure are in equilibrium, regardless of their values, dissociation is static. But if there is a minute change in one of these variables, such as a decrease in C02 pressure or concentration or an increase in temperature, dissociation immediately proceeds with evolution of C02 gas and the simultaneous formation of CaO. 760 690
^3 610 P | 532 E» O 454 CO E E 380 § 310 ifi £ 2281 a. 152 77
740 780 820 860 900 Temperature, *C
Ficfu^© 2. Influence of C02 concentration and pressure on dissociation temperature of CaC03. This means that if the dissociation pressure of CaC03 is
only 380 nun Hg, corresponding to 50% C02 concentration, then
the dissociation temperature is reduced to 848 °C. In all
cases there is a definite relationship between C02 pressure,
and dissociation temperature.
The dissociation always proceeds gradually from the
outside surface inward. Usually the depth of penetration
moves uniformly inward on all sides of the particle, like a
growing veneer or shell. That means that at a given instant
the central core is undecomposed CaC03 and the outer shell
is CaO. So, Furnas (9) and others have suggested the shell
model (Figure 3) for the decomposition of CaC03.
Theoretically, the calcination rate is determined by the
interrelationships between three major rate processes:
(1) Heat Transfer
Heat must first be transferred to the surface of the mass and then through the outer layer of CaO to the reaction
zone. Haslam and Smith (10) have treated the calcination as
a problem of the heat transfer alone.
(2) Mass Transfer
The C02 released at the reaction zone must escape through the outer shell of CaO. Consequently, at finite rates of decomposition the pressure at the reaction zone must be greater than that at the surface of the sphere. The increase in pressure requires an increase in the temperature HEAT IN
REACTION CARBON ZONE DIOXIDE OUT
Figure 3. Decomposition of a sphere of CaCO, (shell model). of the reaction zone to maintain decomposition. According
to Le Chatelier's principle, the quick removal of C02 will speed the calcination.
(3) Chemical Reaction
A considerable number of studies for the calcination of
CaC03 have been reported (11,12,13,14). According to their reports, the experimental results have usually been treated
as though chemical kinetics is the only rate-limiting step.
Actually, the reported data of the activation energy for the
reaction varied greatly, from 35.5 to 50.1 Kcal/mol
(12,13,14,15).
Statement of the Problem
Lime (CaO) is considered to be one of the oldest materials known to mankind. It is certain that the
Egyptians used lime and limestone in building the pyramids between 4000 and 2000 B.C. (8). Besides being used as building and agricultural material, lime is being used in a great number of industrial areas including (16): Metallurgy:
steel manufacturing
magnesium manufacturing
alumina manufacturing ore flotation
non-ferrous metals and smelting Chemicals:
insecticides and fungicides bleaches
dyes and dye stuffs
coke by-products
Water Treatment:
purification
coagulation
neutralization of acid water
silica removal
Sewage-Waste Treatment:
industrial trade wastes
steel and metal fabricating plants
chemical and explosives plants
acid mine drainage
paper and fibers
food plants
Ceramic products:
glass
refractories
whiteware pottery and vitrified enamel Building Materials:
calcium silicate brick
concrete products
insulation materials
miscellaneous building units 8
Protective Coating:
pigments
water paints
varnish
Food and Food products:
dairy industry
sugar industry
animal glue and gelatin industries baking industry
controlled atmospheric storage of fruits and vegetables Miscellaneous Uses:
petroleum
leather
rubber
soaps and fats
pulp and paper industry
In 1986, lime was ranked fifth (17) (about 15 million tons) in production among all chemicals produced in the
United States. If the annual totals of lime produced in the lime industry and that used in the cement industry (about 55 million tons) were combined, lime would be the largest produced manufactured chemical in the United States.
Commercial processes of manufacturing lime and cement are relatively simple in basic concept. Particulate materials are fed into a refractory lined furnace, mixed
with suitable fuels, and subjected to intense heat caused by
the combustion of the fuel. Provisions are made to optimize
exposure of the feeds to the thermal environment and the
system is an open one in order to permit escape of the
products of calcination lime, C02, and traces of moisture. This process used too much energy. When energy was
inexpensive and abundant, it was not unusual to employ excessive temperatures to hasten calcination and to promote the removal of C02 from the reaction bed.
The conversion of CaC03 into CaO is an endothermic reaction and theoretically necessitates 759 Kcal/Kg of CaO.
As burning proceeds, the hot gases pass upwards and heat the charge evenly, with the quicklime formed sinking gradually to the bottom. In practice the specific heat consumption under the best operating conditions is about 1120 Kcal/Kg of
CaO. Generally speaking, the commercial process uses two to four times the theoretical quantity of energy predicted from thermodynamic analysis.(18). With the escalating costs of fossil fuels, how to decrease the energy consumption has become a very important problem in the lime and in the cement industries. Also, operating the lime and cement kilns at lower temperatures will extend the life of kilns and reduce maintenance costs. 10
Literature Survey
The first technical explanation of the calcination of
limestone was by the British chemist, Joseph Black, in the
eighteenth century. Lavoisier, the French scientist,
elaborated and confirmed Black's theory a few years later
(8).
In 1956, Murray (19) experimented with salt additions
in the laboratory. Comparing both 10% sodium chloride
(NaCl) and sodium carbonate (Na2C03) solutions separately, limestone particles were soaked for 16 hours and then
calcined in a laboratory rotary kiln. He observed a definite trend of lower shrinkage. The limestones that were prone to high shrinkage contracted less; those with a low shrinkage tendency were unaffected. The efficacy of NaCl and Na2C03 solutions averaged out about equal; some limes were enhanced more by one or the other of those two salts.
Murray also observed that limestones containing the most sodium oxide (Na20) as an impurity generally exhibited less shrinkage than those stones with only a trace. Salt addition to some dolomites yielded even more profound changes, as determined by differential thermal analysis
(DTA), in comparing the same stone with and without salts.
In the 1960's, some lime manufacturers in several countries had experimented with small additions of sodium chloride (NaCl) to the limestone or to the fuel prior to 11
calcination (8). The salt was added either dry (0.2 to
1•0«) or the limestone was soaked in or doused with brine.
Contradictory results have been reported; some claim
benefits from improved lime quality and even in superior
fuel economy. The Japanese in particular have reported
encouraging results, some of which border on the incredible.
In the 1970"s, the dry process, which eliminates the
addition of water to make raw feed slurries and so
eliminates the large quantity of energy expended in removal
of water, has been developed in the lime industry. However,
this is only the physical and mechanical improvement.
In the late 1970*s, many researchers (20,21,22,23,24)
studied the decarboxylation of organic compounds by using
catalysts, enzymes, and combinations of both. They
emphasized that when the decarboxylation takes place in
acidic or basic media, the product and the mechanism would be different from that in a neutral environment. The decarboxylation of limestone yields a strong base, CaO.
This strong alkaline medium would inhibit the enzymatic effect.
The choice of polar solvents to enhance the calcination of CaC03 was mentioned in Safa's dissertation (18). This approach utilized a slurry of limestone in a reflux reactor using a variety of polar solvents. The reflux reactor for this research is shown in Figure 4. A barium chloride
(BaCl2) solution was used to react with C02 produced during 12
Thtroi Saftit? Trap
SoUttm
Catalyst Funnel InttrU Vast
Raatar/Scirrcr
Figure 4. A reflux reactor 13
the calcination process. The product formed, barium
carbonate (BaC03), can be easily detected by turbidimetry. The solvents used included tetrahydrofuran (THF),
dimethylsulfoxide (DMSO), acetone, acetonitrile, and
alcohol. It was believed that a suitable solvent medium for
the CaC03 with an appropriate catalyst could provide for the
C02 evolution by Lewis acid-base theory. However, this approach did not produce any significant results.
Other approaches applied in the calcination study were
crown ethers, which are known to have a cavity that will
hold the calcium ions, and it was believed that these
complexes might influence the calcination rate of CaC03. Some chelating agents, such as ethylenediaminetetraacetic acid (EDTA), disodium EDTA, nitrilotriacetic acid (NTA), hexamethylphosphoamide (HMPA), and Calgon, with strong complexing formation constants for calcium ions, could possibly influence the calcination rate of CaC03.
Except for the above approaches, according to Le
Chatelier's principle, the vacuum dissociation of CaC03 . might influence the calcination positively. Also, silica and alumina materials with high surface area might react with CaO, and positively influence the calcination of CaC03.
In general, no dramatic catalytic effect was observed with anY the approaches mentioned above. Although the lime industry produces one of the largest and most energy 14 intensive manufactured chemicals, there has been little published information relating to catalytic efforts to reduce the energy in the limestone calcination process to produce lime. In 1982/ the workers in our laboratory and in collaboration with Southwest Research Institute in San
Antonio, Texas, began to study CaC03 catalytic calcination. They have found that sodium salts of 12—molybdosilicic acid and 12-molybdophosphoric acid (25), alkali halides (26), and alkali carbonate-calcium carbonate salts (27) can enhance the calcination rate at constant temperatures. 15
Chapter References
1. Debray, Compt. Rend., 64, 603 (1967).
2. Le Chatelier, Id., 102, 1243 (1886).
3. Brill, Z. Anorg. Chem., 45, 275 (1905).
4. Pott, Dissertation, Freiburg in B., 1905.
5. Zavriev, Compt. Rend., 145, 428 (1907).
6. Johnson, J., J. Am. Chem. Soc., 32, 938 (1910).
7. Johnson, J., J. Am. Chem. Soc., 30, 1357 (1908).
8. Boynton, R.S., Chemistry and Technology of Lime and
Limestone, Interscience Publishers, 1966.
9. Furnas, C.C., Ind. En^. Chem., 23, 534 (1931).
10. Haslam, R.T., and Smith, V.C. Ind. Eng. Chem., 20, 170 (1928). — — 11. Wist, A.0., Thermal Anal. Proc. Int. Conf. 2, 170 (1969).
12. Britton, H.T.S., Gregg, S.J., and Winsor, G.W., Trans. Faraday Soc., 48, 63 (1952).
13. Kappel, H., and Huttig, G.F., Kolloid. Zs., 91, 117 (1940). — —
14. Slonim, C., Z. Elektrochem., 36, 439 (1930).
15. Splichal, J., Skramovoky, S., and Goll, J., Czech. Chem. Comm. , 9_, 302 (1937).
16• Chemical Lime Fact, Bulletin 214, Published by National Lime Association, Washington, D.C., 20016, 1973.
17. Chemical & Engineering News, April 13, 1987.
18. Safa, A.I., Catalytic Calcination of Calcium Carbonate, Ph.D. Dissertation, North Texas State University, August, 1985.
19. Murray, J.A., Research Report to National Lime Assn. on Summary of Fundamental Research on Lime, 1956. 16
20. Jordan, F., Kuo, D.J., and Monse, E.V., J. Amer. Chem, £• Amer- Chem. Soc., 100 (9), 2872 (1978). 21. Madson, M.A., and Feather, M.S., Carbohydr. Res., 70 (2), 307 (1979).
22. Mao, H.K., The Effect of Solvent and Ligand on the Metal Ion Catalyzed Oxalacetate Decarboxylation: An Equilibrium and Kinetics Study, Dissertation, Ohio State Univ., 1978.
23. Ohmura, I., Inagaki, C., Araki, H., and Tanaka,C., Japan J. Pharmacol., 28 (5), 747 (1978).
24. Rao, N.V., and Adams, E., J. Biol. Chem., 253 (18), 6327 (1978). ~ —
25 Safa, A.I., Daugherty, K.E., Mallow, W.A., and Dziuk, J.J., Thermochimica Acta, 78, 309 (1984)
26. Safa, A.I., Daugherty, K.E., Mallow, W.A., Mallow, J.J., and Funnell, J.E., ASTM J. Cem. Concr. Aggregates, 5, 21 (1983). '
27. Mallow, W.A., Dziuk, J.J., and Daugherty, K.E., Development of Low Energy Methods for the Production of Lime, Draft Final Report, Contract DE-AC03-82-CE40500, for the U.S. Department of Energy, December, 1984. CHAPTER II
DETAILS OF THE RESEARCH
Introduction
The project is a continuous one at our laboratory. The previous worker, Safa (1), prepared the fused salts of
alkali carbonate-calcium carbonate at approximately 1025 °C
and 1450 °C. After grinding the fused salts, he has tested them as the catalysts for the calcination of CaC03, and has found that the Na2C03-CaC03 (molar ratio=l:l) salt prepared at 1025 °C has the largest catalytic effect on the calcination reaction. From Safa's conclusion, the four possible Na2C03-CaC03 salts which include natrofairchildite
(Na2Ca(C03)2), shortite (Na2Ca2(C03)3), pirssonite
(Na2Ca(C03)2 2H20), and gaylussite (Na2Ca(C03)2 5H20) were taken into consideration. At the beginning, it was thought that one or some of these salts might be the so-called catalysts for the calcination reaction. Therefore, considerable time has been spent on the literature research
(Appendix) for determining their physical and chemical properties and means of preparation. Unfortunately, not much information related to these salts has been found.
Keeping the catalytic calcination of CaC03 in mind, several questions have been raised:
17 18
(1) Is it really necessary to put a lot of energy,
time, and money, in order to make the fused salts to enhance
the calcination of CaC03? At laboratory scale, it takes about 8 hours and 15 watts to prepare a fused salt of 6
grams.
(2) Is there a better catalyst than the fused salts?
(3) What kind of model can be developed to explain the
catalytic calcination of CaC03? In order to answer the
above questions, the Na2C03-CaC03 fused salts, including the molar ratioes of 1:1 and 1:2, were prepared and tested for
the calcination. Also, an x-ray diffraction technique has been used to try to identify the fused salts of
Na2C03-CaC03. After the Na2C03-CaC03 salt has been proven to be the catalyst for the calcination reaction, additional fused salts, including lithium carbonate-calcium carbonate
(Li2C03-CaC03), potassium carbonate-calcium carbonate
(K2C03-CaC03), and magnesium carbonate-calcium carbonate
(MgC03-CaC03) were prepared and tested for the calcination. Some other chemicals, including alkali carbonates, calcium chloride (CaCl2), magnesium chloride (MgCl2), lithium chloride (LiCl), and potassium chromate (K2Cr04) were also tested for the calcination.
The purpose of this project is to find better catalysts and to develop a physical model to explain the catalytic calcination. Some good catalysts will be discussed in 19
Chapter III, the relationship between the concentration of
Li2CO3 and the catalytic effect, and the physical model will be explained in Chapter IV. The inhibition effect on the
calcination of CaC03 based on the proposed physical model will be discussed in Chapter V. This chapter will cover the
information about the instruments used, possible catalysts
investigated in this research, the means to obtain reliable
results from Lindberg furnace studies, the development of
the extended shell model, and the unpublished data.
Experimental
Sample Preparation
Calcium carbonate (CaC03) is present in various forms. Calcite, Aragonite, and Vaterite are shown in Table I. The
CaC03 used in this research is calcite (Fisher certified grade). The other chemicals used in this research are lithium carbonate (Li2C03, MCB reagent grade), sodium carbonate (Na2C03, Fisher certified grade), potassium carbonate (K2C03, Fisher certified grade), rubidium carbonate (Rb2C03, Alfa reagent grade), cesium carbonate
(Cs2C03, Alfa reagent grade), lithium chloride (LiCl, Fisher certified grade), calcium chloride (CaCl2, Fisher certified grade), magnesium chloride (MgCl2, Fisher certified grade), and potassium chromate (K2Cr04, Fisher certified grade). 20
TABLE I
VARIOUS FORMS OF CaCO-
Form Crystal Melting Point (°C)
Calcite Rhombohedral 1339
Aragonite Orthorhombic Transfer to Calcite at 520 °C Vaterite Hexagonal
The preparation of fused salts was accomplished by-
weighing suitable amount of Li2C03, Na2C03, K2C03, and MgC03
in casseroles , then, suitable quantities of CaC03 were added to each casserole to synthesize the mixtures of 1:1
molar ratio. After that, the casseroles were placed in a
1025 °C Lindberg furnace for 20 minutes. The Lindberg
furnace was turned off for about two hours. Then, the
casseroles were taken out of the Lindberg furnace, and
cooled in a desiccator. After that, the fused salts were
ground into small particles by using porcelain and agate mortars. Finally, the ground salts were sieved through an
ASTM sieve of 45 micrometers in diameter. The salt particles which were smaller than 45 micrometers were collected and used for the experiments.
The additive-CaC03 mixtures were prepared by weighing certain quantities of additives into glass vials, and then a 21
fixed amount of CaC03 was added to the vials to make a certain weight ratio (ranging from 1:500 to 1:20). Finally, they were mixed manually to homogeneous mixtures.
X-Ray Diffraction A lead-shielded Philips (Norelco) x-ray diffraction analyzer (Figure 5), model 112045/3, with a sodium iodide detector in a Hammer manufactured goniometer, and a nickel filtered copper x-ray tube, Cu Kax, was used for obtaining the x-ray diffraction patterns. The conditions for running the instrument were 35 Kilovolts and 15 milliamperes. The samples were spread evenly and uniformly on glass slides with double-stick tape. The scanning range was from 20 of 5 to 65° at a rate of 2°-20 angle per minute and a chart speed of half inch per minute.
The Bragg equation (2) was used to calculate the d-spacing:
n x - 2 d SinQ where
n : the order of diffraction (=1) X : the wavelength for the radiation, using Cu tube, x = 1.541 A 0 : the angle of diffraction obtained as 20 from the diffraction pattern 22
• © © z pz
U M-O i
— r r* 1 er fti tUZJ •H CL < O u O ac £ mCt I—« I CL bi zH UCDJ 3 4J © oO •H in £ 0 3 M 3 G tP-O •H «H-P P«4 0 (ti M-4 •mH L 15 23
d : the distance between each set of atomic planes of
the crystal lattice
Usually, the x-ray diffraction patterns are used for the
structure determination. In this experiment, the x-ray diffraction patterns were used for comparisons.
Lindberg Furnace
A Lindberg electric furnace, model 51333, which contains 6 heating elements, 3 on top and 3 on bottom, with
a'heating range of 500 to 1500 °C, was used for the preparation of fused salts and the calcination studies. The size of the heating chamber of the Lindberg furnace is 42 cm x 18 cm x 16 cm.
According to Safa's experiment (3), the samples were placed in the Lindberg furnace at room temperature, then, the furnace was taken up to approximately 800 °C. and then allowed to cool. The time necessary to reach 800 °C was about 2 hours. The time necessary to cool back to room temperature was at least 5 hours. Besides spending too much time on running the samples, the results were not reliable.
Even more, it was impossible to compare the results of two different runs.
In this experiment, after testing the instrument for a while, an iron pan was utilized to bring a blank and four samples into Lindberg furnace at the same time. The samples to be run in the Lindberg furnace were weighed to 24
3.0000±0.0020 g into casseroles. A casserole of pure CaC03 (as blank) surrounded by four samples was arranged on the
iron pan. Then, the pan was placed into the Lindberg
furnace with the temperature setting at 800 ®C for 40
minutes. Subsequently, the samples were cooled in a
desiccator for 40 minutes and weighed. The calcination rate was expressed as:
weight loss(in mg) % calculation rate= sample weight(in mg) x time(in h)
The contracting test for the additives was run by weighing about 3.00 g of additives into casseroles, and the casseroles were placed in a Lindberg furnace at a certain temperature for one hour. After that, the additives in casseroles were thoroughly examined and compared.
Thermal Analyzer
The Mettler thermal analysis system was used in this research. The unit has six components:
1. Electronics cabinet with temperature control
2. Quartz furnace with a reflector
3. Cooling attachment
4. HE 20 thermoanalytical balance
5. BE 20 control unit
6. GA 16 multichannel recorder 25
The electronics cabinet displays the various
combinations of heating rate. Different combinations of heating rate, ranging from 1 to 125 °C per minute can be
chosen.
The quartz furnace has a heating range of 25 to 1000 °C with inlet and outlet connections, and a platinum/10%
rhodium-platinum thermocouple. The 8 mm in diameter, 20 mm high platinum/10% rhodium crucibles are seated on the top of
the thermocouple. One crucible holds the sample while the
other contains alumina as reference. Any interchange in position of these two crucibles will result in a reversing
the polarity and hence changing the exothermic and
endothermic peaks in the DTA curve, since it is a measure of
the change in temperature between the sample and the
reference.
The thermoanalytical balance uses the tare weight method and houses the cooling unit and the furnace on top of
it, and has 100 and 1000 mg full scale weighing ranges. Dry
air was circulated at the rate of 5 liters per hour.
The multi-channel recorder records simultaneously in different colors the TGA (weight) curve, DTA curve, and the
furnace temperature. It also has the adjustable chart speed ranging from 1 cm per hour to 60 cm per minute.
The conditions for running the DTA-TGA system included
a heating rate of 10 °C per minute, a chart speed of 10 cm 26
per hour, and a 2 mV range for the DTA, and a 100 mg range
for the TGA. The sample amount for each run was carefully
controlled at 90.0±0.5 mg.
Results and Discussion
The Observation of Fused Salt and the X-Ray Diffraction
Patterns of Na^CO-.-CaCO, Fused Salts
After the fused salts were cooled in the desiccator,
the phenomena of phase separation for the Li2C03-CaC03,
Na2C03-CaC03, and K2C03-CaC03 mixtures were observed. The
MgC03-CaC03 mixture was not fused at all. These phenomena
can be explained by the melting point argument. Table II
shows the pielting points (4) of Li2C03, Na2C03, K2C03,
TABLE II
MELTING TEMPERATURES OF Li2C03, Na2C03, K2C03, MgC03, AND CaC03
Compound Melting Point (°C)
Li2CO3 723
Na2C03 851
K2C03 891
MgC03 350 (decompose)
CaC03 1339 27
MgC03, and CaC03. Because the melting points of Li2C03,
NazC03, and K2C03 are lower than 1025 °C, they are melting at 1025 °C Lindberg furnace in 20 minutes. While the
melting points of MgC03 and CaC03 are higher than 1025 °C, they are not fused in 1025 °C Lindberg furnace.
For the so-called fused salts of Na2C03-CaC03, both of
1:1 and 1:2 molar ratios, the fused Na2C03 is light blue color and sticks on the walls of the casserole, the unfused
CaC03, seemingly wetted by the melted Na2C03, still remains on the bottom of the casserole. The two different phases of the so-called fused salt were taken off and ground into
small particles separately, then, their x-ray diffraction patterns were obtained using the Philips x-ray diffraction apparatus. Figure 6 and Figure 7 show the x-ray diffraction patterns for these two different phases. Apparently, they are different from each other. As for the light blue color of the melted phase, in order to prove that it is from the melted Na2C03, a casserole of pure Na2C03 is placed in the 1025 °C Lindberg furnace for 20 minutes. After cooling in a desiccator, the light blue melted material, sticking on the walls of casserole, is observed. 28
tJ 0) 1/2 2 M-l O CJ M Hl» 0 4-> 4-J &(d a 0 •H -P U • cd -P M H m fd m iq •H 13 n o >iO td cd M u 1 I X o« u • N St vo %nS 0 m m 3 o •H «H Fn fd •H M 0 -P (d 6 29
H3 0 £ M (D -P nS 04 a o •H 4-> O • fd 43 H H m td m w •H TJ ™ O >iU aJ ai M U l l n O U • N as £ 0) ^ m &3 o •H H pti flS •H a) 4flj3 S 30 From the above results, it seems that the temperature of 1025 °C is not high enough for preparing the fused salts of this kind. But, if the fused salts were prepared at temperature high enough to melt CaC03, the alkali content would be volatilized from the fused salt. With the loss of alkali metal in fused salt, it has been proven that the catalytic effect on the calcination of CaC03 will decrease (1). The Reliable Results from Lindberg Furnace The heating chamber of the Lindberg furnace is 42 cm x 18 cm x 16 cm. The samples placed in the heating chamber for each r.un only occupy a small portion of the relatively large chamber. So, the temperature variation in the chamber must be taken into account. In order to test the effect of the temperature variation of the chamber on the experimental results, a casserole of pure CaC03 surrounded by four other casseroles of pure CaC03 were put on an iron pan, and the pan was placed into the heating chamber of the Lindberg furnace for 40 minutes. A series of similar blank tests were conducted by placing the iron pan in the different positions of the heating chamber. Table III demonstrates the fluctuation of the calcination rate of pure CaC03 samples. This is the evidence that there is temperature unevenness within the heating chamber of the Lindberg furnace. 31 TABLE III FLUCTUATION OF CALCINATION RATES OF PURE CaC03 DUE TO TEMPERATURE VARIATION IN HEATING CHAMBER OF LINDBERG FURNACE AT 800 °C Run Calcination Rate Av. ± S.D. (%wt/h) (%wt/h) 1 28 .72, 28 .95, 29. 64, 32 .92, 31. 77 30. 40 ± 1 .85 2 28 .68, 29 .55, 30. 12, 33 .09, 32. 94 30. 79 ± 1 .91 3 32 .36, 30 .66, 30. 09, 27 .02, 26. 20 29. 27 ± 2 .58 4 31 .35, 29 .06, 29. 91, 29 .67, 27. 99 29. 60 ± 1 .23 After testing the temperature variation in the heating chamber of the Lindberg furnace many times, a fixed position located between 12 to 24 cm from the door of the furnace seems to have uniform temperature. By placing the casseroles of sample in this area (Figure 8), the reliable calcination results has been obtained. Table IV shows the results of the calcination rates for three consecutive runs by placing the iron pan at the fixed position of the heating chamber. From Table IV, the standard deviation of calcination rate in a run is quite small. Table V shows the calcination rates of pure CaC03 from eight different sample runs. The standard deviation is only 0.37 %wt/h which is 32 S o Q S u cro CN T JL. 18 cm Figure 8. A fixed position in heating chamber of Lindberg furnace to produce reliable results. 33 TABLE IV CALCINATION RATES OF PURE CaC03 AT A FIXED POSITION IN HEATING CHAMBER OF LINDBERG FURNACE AT 800 °C Run Calcination rate Av. ± S.D. (%wt/h) (%wt/h) 1 30.62, 29.90, 30.60, 29.50, 29.66 30.06 ± 0.52 2 29.36, 28.96, 29.70, 29.74, 29.78 29.51 ± 0.35 3 28.78, 28.29, 29.70, 29.73, 29.01 29.10 ± 0.62 acceptable. So, the Lindberg furnace is suitable for the calcination study. The advantage of using the Lindberg furnace is that four samples can be run at the same time. Although two separated phases were found from the preparation of the fused salts, the fused salt samples for testing the catalytic calcination were obtained by grinding both separated phases together. Then, 5 %wt of fused salt was added to pure CaC03. Table VI shows the data of calcination rate for the salts being used as catalysts. From the results in Table VI, the Li2C03-CaC03 salt enhances the calcination more than the Na2C03-CaC03 salt. For the catalysts being used for enhancing the calcination of CaC03, most of them contain the alkali metals. Consequently, the alkali carbonates have been used for the catalytic 34 TABLE V CALCINATION RATES OF PURE CaC03 (AS BLANK) FROM EIGHT DIFFERENT SAMPLE RUNS FROM LINDBERG FURNACE AT 800 °C Run Calcination Rate (%wt/h) 1 28.92 2 29.43 3 29.01 4 28.89 5 28.55 6 29.70 7 29.06 8 29.74 Av. ± S.D. 29.04 ± 0.37 calcination. The results for using alkali carbonates as catalysts are discussed in Chapter III and Chapter IV. Also, some other compounds are tested for enhancing the calcination of CaC03. Table VII shows some data of calcination rate from Lindberg furnace. From Table VII, LiCl and K2Cr04 can also be added to pure CaC03 to enhance its calcination rate. 35 TABLE VI CALCINATION RATES OF USING FUSED SALTS AS CATALYSTS FROM LINDBERG FURNACE AT 800 °C Mixture Calcination Rate (1:20) (%wt/h) Li2C03-CaC03 salt + CaC03 44 .44, 44 .67 C O o • C O Na2C03-CaC03 salt + CaC03 40 o 40 K2C03-CaC03 salt + CaC03 33 .31 MgC03-CaC03 salt + CaC03 28 .39 Pure CaC03 29 H O TABLE VII CALCINATION RATES OF USING SOME CHEMICALS AS CATALYSTS FROM LINDBERG FURNACE AT 800 °C Mixture Calcination Rate (i:20) (%wt/h) LiCl + CaC03 39.93, 39.88 K2Cr04 + CaC03 36.37 Pure CaC03 29.10 For the contracting test, most of the additives which have a positive catalytic effect on the calcination contract 36 from the walls of the casseroles after being heated in the Lindberg furnace at a temperature below their melting points. The additives, including Li2C03, LiCl, MgCl2, and CaCl2, which enhance the calcination more seem to contract more. The Results from DTA-TGA Thermal Analyzer Two different thermograms were obtained. One was obtained by programming to certain temperatures (often at 700 °C) then keeping the temperature constant for about 50 minutes. From the TGA curve of the thermogram, the calcination rate could be calculated. Figure 9 shows a typical thermogram for the calculation of calcination rate. From the TGA curve in Figure 9, the calcination rate is expressed as: Ma(in mg) - M2(in mg) % Calcination Rate = xlOO % W(in mg) x T(in h) where Mx and M2 are the readings in milligrams on the TGA curve. T is the time lapse from to M2. W is the sample weight. 37 III! [Mi Mi! o\« •H++ iili O c O o rH •H X 43 rtf !!'• H rrr a) 0* ! i! •p B 0 rci (d TTTT c 0 •H i ii a G 0) o CM •H 43 !.H! •H s •P i EH nl ll. X o Pi •H a tT> U g T 0 i—I c V3 aj •H c 3 U •H o\<> M tr» o s H 0) XI 43 H nS U •H a. * >i a> B 43 aS M CT\ d O a> -H M 43 3 nS tx> a •H -H Pm O »—i aS U 4-1 O --o-n 38 The other thermogram was obtained by running the instrument to 1000 °C. The transition temperature could then be found from the temperature which corresponds to the DTA peak. Figure 10 illustrates a typical thermogram in which the DTA peak corresponds to the temperature of calcining completion. Table VIII shows the calcination rate of pure CaC03 at different temperatures. Figure 11 is plotted from the data in Table VIII. From Figure 11, the calcination rate TABLE VIII CALCINATION RATES OF PURE CaC03 AT DIFFERENT TEMPERATURES FROM DTA-TGA ANALYZER AT 700 °C Temperature Calcination Rate (°C) (%wt/h) 600 0 .96 650 5 .46 680 15,.46 690 19..01 700 26.,3 9 39 £ O •H -P G •H s M 0 -P 0 Tf 0) JC -P M O TJ 0) W 3 tr> o S M 0 x: -p H 0 nj M O 3 •H -P si td >1 M Eh &0 S 0 O -P H C 0 o M •H 3 -P tr*-H •H W G flj 4-> O 40 25 20 CT g 15 £ R< 10 Z I s •«—»- 600 620 650 680 700 TEMPERATURE(°C) Figure 11. Calcination rate of pure CaC03 vs temperatures from DTA-TGA analyzer. 41 at the temperature below 600 °C is almost zero. Then, the calcination rate increases smoothly when the temperature increases. Under the operating conditions of DTA-TGA thermal analyzer, the slope of TGA curve of thermogram at 700 °C is the proper one (neither too high nor too low) for calculating the calcination rate. So,the temperature of 700 °C has been chosen for the measurement of catalytic calcination rate. Table IX shows some of the calcination TABLE IX SOME CATALYTIC CALCINATION RESULTS FROM DTA-TGA ANALYZER AT 700 °C Mixture Calcination Rate (1*20) (%wt/h) Li2C03-CaC03 + CaC03 35.52 LiCl + CaC03 32.25 MgC03 + CaC03 27.19 Pure CaC03 26.39 data from the DTA-TGA analyzer. From Table IX, LiCl and LiC03-CaC03 salt again have been confirmed as the catalysts for the calcination of CaC03. MgC03 seems to show no catalytic effect on the calcination reaction. 42 The DTA-TGA technique is very unique for determining transition temperature. But, it takes too much time (about 3 hours) to run a sample. Table X shows the precision of TABLE X PRECISION OF DTA-TGA TECHNIQUE Measurement Data Av. ± S.D. Calcination Rate 26.39, 26 .16 (%wt/h) 26.17, 26 .62 26.36 ± 0.23 Transition Temperature 837, 836, 838, (°c) 838 837.2 ± 1.0 the transition temperature measurement and the calcination rate measurement for the pure CaC03. The standard deviations are low. So, the DTA-TGA technique is very good for the study of the calcination of CaC03. The Development of the Extended Shell Model The decarboxylation of limestone is quite different from that of an organic compound. In the organic system, the reaction usually occurs in the liquid phase. In the liquid phase, the heat transfer must not be the problem. As for the calcination reaction, CaC03 decomposes before it melts. During the dissociation, gas and solid coexist. For the gas-solid reaction system, the heat transfer is always a 43 factor to be emphasized. So, the theory which can be used to explain the catalytic decarboxylation of organic compounds might not be suitable for the CaC03 system. The idea of using polar solvents to enhance the calcination in a reflux reactor, or using some of the chelating agents to form complexes with calcium ion to enhance the calcination is not applicable. Because the calcination of CaC03 starts at very high temperature (from Table VIII, the temperature must be higher than 600 °C), the solvents or the chelating agents will vaporize or decompose into inactive forms under the condition of high temperature. Table XI illustrates the transition temperatures (5) of some chelating agents. From Table XI, the chelating agents do TABLE XI TRANSITION TEMPERATURES OF SOME CHELATING AGENTS Chelating Agent Transition Temperature (°C) EDTA 240 (decompose) NTA 240 (decompose) HMPA 231 (boiling point) decompose at the temperature below 600 »C. So, the Lewis acid-base theory (from the point of polar solvents), and the 44 complexation-forming mechanism can not be applied to the catalytic calcination. From the thermogram shown in Figure 9, before the slope of the TGA curve being constant, there is gradual change of calcination rate. This is because of the time lag needed for the heat to transfer from the outer into the center of the sample. So, the heat transfer is very important. From Figure 2, the higher C02 pressure will cause CaC03 to dissociate at higher temperature. So, the the mass transfer of C02 must be an important factor for the calcination. The activation energy of the calcination of CaC03 has been reported ranging from 35.5 to 50.1 Kcal/mole (6,7,8,9). From Figure 11, the calcination rate of CaC03 increases exponentially as the temperature increases. But, the increasing of the calcination rate is still too low comparing to that predicted from thermodynamic rule which says that for every 10 °C increase in temperature, the reaction rate will double. It seems that the chemical reaction is not, relatively, an important factor. From the above discussion, it seems that profound chemical theories are not suitable to explain the catalytic calcination of CaC03. In our research, many additives have been proved to be the catalysts which can enhance the calcination reaction. It might be concluded that the catalytic calcination of CaC03 is not chemically specific 45 reaction. Therefore, a physical model called extended shell model has been developed to explain the catalytic calcination. Figure 12 illustrates the extended shell model. In this model, two physical phenomena, heat transfer and mass transfer, are the important factors for predicting the calcination rate of CaC03. According to this model, any additive which will promote the heat transfer and does not hinder the removal of C02 formed from the calcination will enhance the calcination of CaC03. The application of the extended shell model to approach the catalytic effect on the calcination of CaC03 will be discussed in Chapter IV and Chapter V. By using the extended shell model, the catalytic calcination can be explained well by the arguments of heat transfer and mass transfer. 46 0 z LU O< o < 5 111 a. S Chapter References 1. Safa, A.I., Catalytic Calcination of Calcium Carbonate, Ph.D. Dissertation, North Texas State University, August, 1985. 2. Mallow, W.A., Dziuk, J.J., and Daugherty, K.E., Development of Low Energy Methods for the Production of Lime, Draft Final Report, Contract DE-AC03-82-CE40500, for the U.S. Department of Energy, December, 1984. 3. Safa, A.I., Daugherty, K.E., Mallow, W.A., and Dziuk, J.J., Thermochimica Acta, 78, 309 (1984). 4. Weast, R.C., Handbook of Chemistry and Physics, Chemical Rubber Company Press, 60th ed., 1980. 5. Hawley, G.G., The Condensed Chemical Dictionary, 10th ed., 1984. 6. Britton, H.T.S., Gregg, S.J., and Winsor, G.W., Trans. Faraday Soc., 48, 63 (1952). 7. Kappel, H., and Hutting, G.F., Kolloid. Zs., 91, 117 (1940). 8. Slonim, C., Z. Elektrochem., 36, 439 (1930). 9. J. Splichal, St. Skramovoky, and J. Goll, Czech. Chem. Comm., 9, 302 (1937). CHAPTER III CATALYTIC EFFECT OF ALKALI CARBONATES ON THE CALCINATION OF CALCIUM CARBONATE Abstract Alkali carbonates (except for francium carbonate) have been tested to enhance the calcination of calcium carbonate (CaC03) using a Lindberg furnace and a differential thermal analysis-thermogravimetric analysis (DTA-TGA) system. The alkali carbonates were mixed with CaC03 (calcite) at a weight ratio of 1:20 and were studied at constant temperatures of 800 °C and 700 °C in a Lindberg furnace and a DTA-TGA analyzer respectively. The results of calcination rates (%wt/h) from the Lindberg furnace and DTA-TGA analyzer have shown similarly that lithium carbonate (Li2C03) is the best catalyst among the alkali carbonates. Introduction Calcination of calcium carbonate (CaC03) is thought to be one of the most basic reactions. It has been proven that the dissociation of CaC03 proceeds chemically by the following reaction (1): A CaC03(s) v > CaO(s) + C02(g) 48 49 Although the reaction is simple, commercial applications use two to four times the theoretical quantity of energy- predicted from thermodynamic analysis (2). Many researchers have attempted to reduce the energy consumption of this calcining process. The previous workers in our laboratory have tried many additive to enhance the calcination rate. They found that sodium salts of 12-molybdosilicic and 12-molybdophosphoric acid (2), alkali halides (3), and alkali carbonate-calcium carbonate fused salts (4) can enhance the calcination rate at constant temperatures. The common characteristic among these additives with positive catalytic effects, is that they all contain alkali metals. In order to avoid potential corrosion of alkali halides on manufacturing facilities and to prevent the tedious work for preparing the fused salts, alkali carbonates have been investigated as potential catalysts for the calcination of CaC03. Experimental The alkali carbonates used in this study were lithium carbonate (Li2C03, MCB reagent grade), sodium carbonate (Na2C03, Fisher certified grade), potassium carbonate (K2C03, Fisher certified grade), rubidium carbonate (Ru2C03, Alfa reagent grade), and cesium carbonate (Ce2C03, Alfa reagent grade). They were mixed manually to a homogeneous mixture with reagent grade CaC03 in a weight ratio of 1:20. 50 The samples to be run in a Lindberg furnace were weighed to 3.0000±0.0020 g into casseroles. A casserole of pure CaC03 (as a blank) surrounded by four samples was arranged on an iron pan. Then, the pan was placed into a Lindberg furnace with the temperature setting at 800 °C for 40 minutes. Subsequently, the samples were cooled in a desiccator for 40 minutes and weighed. The DTA-TGA system employed in this study is a Mettler thermal analyzer with a Mettler BE 20 balance controller and a Mettler HE 20 balance. The conditions for running the DTA-TGA included a heating rate of 10 °C/min, a chart speed of 10 cm/h, and a 2 mV range for the DTA. The reference material was alumina (Al203). The sample amount for each run was carefully controlled at 90.0±0.5 mg. Two different thermograms were obtained. One was obtained by programming the temperature to 700 °C then keeping it constant for about 50 minutes. From the TGA curve, the calcination rate could be calculated. The other thermogram was obtained by running the instrument to 1000 °C. The transition temperature could then be obtained from the DTA curve. The dissociation of CaC03 is independent of the geometry of the sample holder since the reaction is reversible (5), but the calcination rate does depend on the sample weight for each run. In order to take this factor into account, the calcination rate was expressed as: 51 weight loss(in mg) Calcination Rate = ______sample weight(in mg) x time(in h) The contracting test for additives was run by weighing about 3.00 g of additives into casseroles, and the casseroles were placed in a Lindberg furnace at 700 °C for one hour. After that, the additives in casseroles were thoroughly examined and compared. Results and Discussion Table XII summarizes the data of the calcination rate TABLE XII CALCINATION RATES OF ALKALI CARBONATE-CaC03 MIXTURES FROM LINDBERG FURNACE AT 800 °C Composition Calcination Rate Av. Calcination Rate (1:20) (%wt/h) (%wt/h) Li2CO3 + CaC03 41.72, 40.30 41.01 Na2C03 + CaC03 37.90, 39.64 38.77 K2C03 + CaC03 34.14 34.14 Rb2C03 + CaC03 32.97, 33.87 33.42 Cs2C03 + CaC03 31.62, 33.12 32.37 Pure CaC03 28.78, 28.29, 29.70, 29.73, 29.01 29.10 52 obtained from the Lindberg furnace setting at 800 °C for 40 minutes. Figure 13 is the diagram plotted from the data in Table XII. Table XIII summarizes the data of the TABLE XIII CALCINATION RATES OF ALKALI CARBONATE-CaCO3 MIXTURES FROM DTA-TGA ANALYZER AT 700 °C Composition Calcination Rate (1:20) (%wt/h) Li2C03 + CaC03 33.49 Na2C03 + CaC03 31.60 K2C03 + CaC03 27.84 Rb2C03 + CaC03 26.74 Cs2C03 + CaC03 28.66 Pure CaC03 26.39 calcination rate calculated from the TGA curve of DTA-TGA analyzer programmed to 700 °C. Figure 14 is the diagram plotted from the data in Table XIII. From Figure 13 and Figure 14, the consistency between these two different thermal methods is seen. Also, the highest catalytic effect of Li2C03 as compared to the other alkali carbonates on the calcination of CaC03 is observed. 53 AiPureCaCQj B:1Cs£X^ 42 CilRbpOj D:1K£C^ E:1 Na^Oj F:1 40 8 \u 38 36 34 - Q gj 32 O 30 28 B C D E ADD TO 20 CaCQj Figure 13. Calcination rate vs. alkali carbonates from Lindberg furnace. 54 APureCaOOj BilCsgX^ C:1 Rt^X^ D:1 36 E:1 Na£Cfc F:1 LipC^ 34 £ c£ 32 30 28 «! O 26 24 B C D E ADD TO 20 CaCOj Figure 14. Calcination rate vs alkal i rarhnnafoc from DTA-TGA analyzer. axKali carbonates 55 In the DTA-TGA thermogram, the transition temperature, the peak of DTA curve, corresponds to the temperature of calcining completion. Table XIV shows transition temperature for different alkali carbonate-calcium carbonate TABLE XIV TRANSITION TEMPERATURES OF ALKALI CARBONATE- CaC03 MIXTURES FROM DTA CURVE Composition Transition Temperature (1:20) (oc) Li2C03 + CaC03 813 Na2C03 + CaC03 817 K2C03 + CaC03 822 Rb2C03 + CaC03 834 Cs2C03 + CaC03 834 Pure CaC03 838 mixtures. From Figure 15, the alkali carbonates demonstrate the catalytic effect by completing the calcination of CaC03 at lower temperatures, and Li2C03 is the best catalyst among alkali carbonates. 56 ArPureCaCQj B:1G&PQ, C:1 Rb^Oj D:1 KfO^ E1 NE^XJJ F:1 810 820 830 840 850 B C D E ADD TO 20 CaCOj Figure 15. Transition temperature vs. alkali carbonate-calcium carbonate mixtures. 57 The slow calcination rates of pure Li2C03 and Na2C03 are shown in Table XV. This explains that the enhancement of calcination by adding alkali carbonates into pure CaC03 is not from the calcination of alkali carbonates. TABLE XV CALCINATION RATES OF PURE Li2C03 AND PURE Na2C03 FROM DTA-TGA ANALYZER Compound Calcination Rate (%wt/h) Li2C03 4.99 (at 700 °C) Na2C03 0.00 (at 700 °C) Na2C03 13.97 (at 1000 °C) Table XVI shows the melting temperatures of alkali carbonates and CaC03 (6). The melting points of alkali carbonates are relatively lower and around the dissociation temperature of CaC03. The catalytic effect of alkali carbonates might be explained by the heat transfer argument (7). When the sample particles are heated close to the melting temperature, they appear to have contracted together. This phenomenon has been proven by placing different alkali carbonates in a 700 °C Lindberg furnace for one hour, and Li2C03 contracts to the highest degree. The Li2C03 pulls away from the side walls of the casserole to a 58 TABLE XVI MELTING TEMPERATURES OF ALKALI CARBONATES AND PURE CaCO, Compound Melting Point (°C) Li2CO3 723 Na2C03 851 K2C03 891 Rb2C03 837 Cs2C03 610 (decompose) CaC03 1339 larger extent than any of the other alkali carbonates. Under this circumstance, the contacting surface area of the sample particles increase. As the contacting surface area of sample particles increases, the heat transfer among those particles is enhanced. As a result, the calcination rate is increased. The calcination of CaC03 is an endothermic reaction. The temperature needs to be raised to very high (From Table VIII, at least 600 °C) in order to keep the calcination going. It is apparent that the heat transfer plays an important role. If a material can promote the heat transfer among the CaC03 particles in any way, it might be used to enhance the calcination of CaC03. 59 Chapter References 1. Johnston, J., J. Am. Chem. Soc. 32, 938 (1910). 2. Safa, A.I., Daugherty, K.E., Mallow, W.A., and Dziuk, J.J., Thermochimica Acta, 78, 309 (1984). 3. Safa, A.I., Daugherty, K.E., Mallow, W.A., Dziuk,J.J., and Funnell, J.E., ASTM J. Cem., Concr. Aggregates, 5, 21 (1983). 4. Mallow, W.A., Dziuk, J.J., and Daugherty, K.E., Development of Low Energy Methods for the Production of Lime, Draft Final Report, Contract DE-AC03-82-CE40500, for the U.S. Department of Energy, December, 1984. 5. Wendlandt, W.W., Thermal Methods of Analysis, 2nd ed., Wiley-Interscience, New York, 1974. 6. Weast, R.C., Handbook of Chemistry and Physics, 60th ed., Chemical Rubber Company Press, 1980. 7. Haslam, R.T., and Smith, V.C., Ind. Eng. Chem., 20, 170 (1928). CHAPTER IV LITHIUM CARBONATE ENHANCEMENT OF THE CALCINATION OF CALCIUM CARBONATE PROPOSED EXTENDED SHELL MODEL Abstract Lithium Carbonate (Li2C03) has been tested to enhance the calcination of calcium carbonate (CaC03) using a Lindberg furnace and a differential analysis- thermogravimetric analysis (DTA-TGA) system. The Li2C03 was mixed with CaC03 (calcite) at weight ratios ranging from 1:500 to 1:20 and the mixtures were studied at constant temperatures of 800 °C and 700 °C in a Lindberg furnace and a DTA-TGA analyzer respectively. The results of calcination rates (%wt/h) from the Lindberg furnace and DTA-TGA analyzer have shown similarly that the Li2C03-CaC03 mixture of about 1:200 has the highest calcination rate. In order to explain the data, a physical model is proposed. This extended shell model has been tested by running 5% magnesium chloride-calcium carbonate (MgCl2-CaC03) and 5% calcium chloride-calcium carbonate (CaCl2-CaC03) samples. 60 61 Introduction In the previous paper (1), lithium carbonate (Li2C03) was proved to be the best catalyst among alkali carbonates for the calcination reaction: A CaC03(s) v > CaO(s) + C02(g) The increase in the calcination rate is due to the enhancement of heat transfer by adding alkali carbonates to calcium' carbonate (CaC03). It is apparent that the calcination reaction starts at the outside surface and proceeds towards the center of the sample. Furnas (2) and others have suggested the shell model (Figure 3) for the decomposition of CaC03. In this model, heat transfer and mass transfer (the removal of carbon dioxide) play the important roles. According to Satterfield and Feakes (3), the calcination rate is determined by the interrelationships between three major rate processes: (1) Heat Transfer It is clear that the heat must be transferred from the surface to the center of the sample. If the heat-transfer process can be enhanced, the calcination rate will be increased. 62 (2) Mass Transfer The carbon dioxide (C02) released from the reaction must escape through the outer shell of calcium oxide (CaO). The increase of C02 pressure requires an increase in the temperature of the reaction zone to maintain decomposition. Also, according to Le Chatelier's principle, the quick removal of C02 will promote the reaction to the right. (3) Chemical Reaction From the chemical kinetics point of view, the activation energy might be the rate limiting factor. If the activation energy of a reaction can be reduced, the reaction rate will be increased. The purpose of the present study was to determine the relation of Li2C03 concentration and its catalytic effect on the calcination of CaC03. Furthermore, a physical model was developed in order to explain the catalytic phenomenon found in this study. Experimental Lithium carbonate (MCB reagent grade) was mixed manually to a homogeneous mixture with reagent grade CaC03 in weight ratios ranging from 1:500 to 1:20. The samples to be run in a Lindberg furnace were weighed to 3.0000±0.0020 g into casseroles. A casserole of pure CaC03 (as blank) surrounded by four samples was arranged on an iron pan. Then, the pan was placed into a Lindberg furnace with 63 temperature setting at 800 °C for 40 minutes. After that the samples were cooled in a desiccator for 40 minutes and weighed. The DTA-TGA system in this study is a Mettler thermal analyzer with a Mettler BE 20 balance controller and a Mettler HE 20 balance. The conditions for running the DTA-TGA included a heating rate of 10 °C/min, a chart speed of 10 cm/h, and a 2 mV range for the DTA. The reference material was alumina. The sample amount for each run was carefully controlled at 90.0±0.5 mg. Two different thermograms were obtained. One was programmed to a temperature Of 700 °C, and then kept temperature constant for about 50 minutes. From the TGA curve the calcination rate was calculated. The other thermogram was obtained by running the instrument to 1000 °C, and the transition temperature was obtained from the DTA curve. The dissociation of CaC03 is independent of the geometry of the sample holder since the reaction is reversible (4), but the calcination rate does depend on the sample weight for each run. In order to take this factor into account, the calcination rate was expressed as: weight loss(in mg) % calcination rate = sample weight(in mg) x time(in h) 64 The contracting test for Li2C03 was run by weighing about 3.00 g of Li2C03 into casserole, and the casserole was placed in a Lindberg furnace at 700 <>C for one hour. After that, the Li2C03 sample in the casserole was thoroughly examined. Results and Discussion Table XVII summarizes the data of calcination rate obtained from the Lindberg furnace setting at 800 °C for TABLE XVII CALCINATION RATES OF USING Li2C03 AS CATALYST FROM LINDBERG FURNACE AT 800 °C %wt of Li2CO3 Calcination Rate Av. Calcination Rate to 100 % CaC03 (%wt/h) (%wt/h) 0.2 42.36, 42.48 42.42 0.3 44.24, 44.10 44.17 0.4 45.62, 44.25 44.94 0.6 44.79, 43.74 44.26 0.8 45.36, 44.24 44.80 1.0 43.46, 43.83 43.64 2.0 41.86 41.86 5.0 41.72, 40.30 41.01 Pure CaC03 28.78, 28.29, 29.70, 29.73, 29.01 29.10 65 40 minutes. Figure 16 is the diagram plotted from the data in Table XVII. Table XVIII summarizes the data of the calcination rate calculated from the TGA curve of the TABLE XVIII CALCINATION RATES OF USING Li2C03 AS CATALYST FROM DTA-TGA ANALYZER AT 700 °C %wt of Li2CO3 Calcination Rate to 100% CaC03 (%wt/h) 0.2 34.57 0.3 36.95 0.4 39.67 0.6 39.90 0.8 37.42 1.0 32.89 2.0 34.30 5.0 33.49 Pure CaC03 26.39 DTA-TGA analyzer programmed to 700 °C. Figure 17 is the diagram plotted from the data in Table XVIII. From Figure 16 and Figure 17, the consistency between these two different methods is seen. Also, the highest catalytic effect of 0.4 to 0.6% Li2C03 in CaC03 as compared to the other concentrations of Li2C03 in CaC03 on the calcination of CaC03 is observed. 66 1 2 3 %wt OF L^COj ADD TO 100% CaCOtj Figure 16. Calcination rate vs. Li2C03 concentration from Lindberg furnace at 800 °C. 67 -? 40 S 28 12 3 4 %wtOFL^DC^ ADD TO 100% CaCOj Figure 17. Calcination rate vs. Li2C03 concentration from DTA-TGA analyzer at 700 °C. 68 In the DTA-TGA thermogram, the transition temperature, the peak of DTA curve, corresponds to the temperature of calcining completion. Table XIX shows transition temperatures for different compositions of Li2C03-CaC03 TABLE XIX TRANSITION TEMPERATURE'ERATURES CO F Li2C03-CaC03 MIXTURES FROM DTA CURVE %wt of Li2C03 Transition Temperature to 100% CaC03 (oc) 0.1 815 0.2 780 0.4 773 0.6 788 1.0 793 2.0 795 5.0 813 Pure CaC03 838 mixtures. From Figure 18, Li2C03 demonstrates the catalytic effect by completing the calcination of CaC03 at lower temperatures. Furthermore, Li2C03 enhances the calcination 69 840 Ol 810 12 3 4 %wt OF Li^CC^ ADD TO 100% CaCQj Figure 18. Transition temperature vs. Li2C03 concentration. 70 rate approximately 50% at a low concentration of 0.4% in CaC03 by weight. Thus, the potential contamination of lithium metal in lime can be minimized in a commercial operation. In Satterfield and Feakes' work. (3), they found that the temperature at the center of the sample rose rapidly to a maximum, and then, after a small temperature drop, passed through a minimum. The temperature remained practically constant for the major part of the reaction time and it also remained substantially in excess of the equilibrium temperature through the run. This suggests that after the decomposition of the outer layer of the sample, the formation of CaO does hinder the heat transfer of the calcination process. This is because the thermal conductivity and the bulk density (3) of CaO are relatively lower than those of CaC03. The low thermal conductivity of CaO hinders the heat transfer from the outer to the inner portion of the sample. While the low bulk density of CaO means more void space among sample particles, the conduction of heat decreases. Also, Haslam and Smith (5) treated the decomposition of CaC03 as a heat transfer alone. It is clear that the heat transfer is a very important factor. Wist (6) pointed out that the reaction rate of the calcination of CaC03 is directly proportional to the difference between the C02 pressure before and after the 71 reaction zone. Therefore, the mass transfer has an important role as well. As for the activation energy of this reaction, the data reported are between 35.5 to 50.1 kcal/mol (7,8,9,10). The calcination rates from TGA curves at 700 °C and 800 °C (Table XX) tell us that the chemical reaction is not, relatively, an important factor, because from 700 to 800 °C, the calcination rate only increases about 6 times (theoretically the rate might increase 1024 times). That means the other factors, heat transfer and mass transfer, govern the calcination rate more than the chemical kinetics does TABLE XX CALCINATION RATES OF CaC03 AT 700 °c AND 800 °C Temperature Calcination Rate (°c) (%wt/h) 700 26.39 800 168.19 From the above discussion and the results of previous work in this laboratory (1), an extended shell model (Figure 12), which can explain the data from this work, by using the heat transfer and mass transfer argument, has been 72 developed. When Li2C03 is added to CaC03 and the mixture is heated to the temperature (700 °C) of calcination, the particles of Li2C03 begin to contract. This contraction increases the contacting surface area among the sample particles. When the amount of Li2C03 in the mixture is greater than 0.8%, the contraction is so great that the interstitial space among sample particles is small. This situation prevents the C02 from escaping freely. Thus, the pressure of C02 is increased. As a result, the calcination rate decreases. This is why the relationship between calcination rate and concentration of Li2C03 is mountain-shaped. In order to predict other possible catalysts for the calcination by using this extended shell model, magnesium chloride (MgCl2) and calcium chloride (CaCl2), both having melting temperatures (Table XXI) (11) close to the TABLE XXI MELTING TEMPERATURES OF MgCl2 AND CaCl2 Compound Melting Temperature (°C) MgCl2 714 CaCl2 782 73 calcining temperature of CaC03 and contracting at the temperature of 700 °C, were chosen. The calcination rates 5% MgClz and 5% CaCl2 in CaC03 are shown in Table XXII. Because MgCl2 contracted more than CaCl2 did after placing in a 700 °C Lindberg furnace for one hour, MgCl2 enhanced the calcination rate more than CaCl2 did. Other possible catalysts may be chosen to further refine this proposed extended shell model. TABLE XXII CALCINATION RATES OF 5% MgCl2 AND 5% CaCl2 IN CaC03 FROM DTA-TGA ANALYZER AT 700 °C Mixture Calcination Rate (1:20) (%wt/h) MgCl2 + CaC03 37.19 CaCl2 + CaC03 34.03 pure CaC03 26.39 74 Chapter References 1. Huang, J.M., and Daugherty, K.E., Thermochimica Acta, 115, 57 (1987). 2. Furnas, C.C., Ind. Eng. Chem., 23, 534 (1931). 3. Satterfield, C.N., and Feakes, F., A. I. Ch. E. Journal 5, 115 (1959). ~ ~ 4. Wendlandt, W.W., Thermal Methods of Analysis, Wiley-Interscience, New York, 2nd "ed. 1974. 5. Haslam, R.T., and Smith, V.C., Ind. Eng. Chem., 20, 170 (1928). — 6. Wist, A.0., Thermal Anal., Proc. Int. Conf., 2, 1095 (1969). 7. Britton, H.T.S., Gregg, S.J., and Winsor, G.W., Trans. Farady Soc., 48, 63 (1952). 8. Kappel, H., and Huttig, G.F., Kolloid. Zs., 91, 117 (1940). — 9. Slonim, C., Z. Elektrochem., 36, 439 (1930). 10. Splichal, J., St. Skramovoky, and J. Goll, Czech. Chem. Comm., 9, 302 (1937). 11. Weast, R.C., Handbook of Chemistry and Physics, Chemical Rubber Company Press, 60th ed., 1980. CHAPTER V INHIBITION OF THE CALCINATION OF CALCIUM CARBONATE Abstract Aluminum oxide (Al203), calcium oxide (CaO), vanadium pentoxide (V20s), and fly ash were respectively mixed with alcium carbonate (calcite, CaC03) at a weight ratio of 1:20 and the mixtures were studied at a constant temperature of 700 °C in a DTA-TGA analyzer. The results of calcination rate (%wt/h) have shown that Al203 and CaO do not have any effect on the calcination rate of CaC03, while V205 and fly ash inhibit the calcination rate of CaC03. An explanation is proposed. Introduction In a previous paper (1), the extended shell model has been developed to explain the calcination reaction of calcium carbonate (CaC03): A CaC03(s) ^ "* CaO(s) + C02(g) From this model, heat transfer and mass transfer are two main factors for predicting the calcination rate of CaC03. A previous study (2) showed that lithium carbonate (Li2CO3), with a melting point of 723 °C, was the best 75 76 catalyst among alkali carbonates to enhance the calcination of CaC03. In the present study, aluminum oxide(Al203), calcium oxide (CaO), and fly ash with a melting point higher than that of Li2C03, and vanadium oxide (V205) with a melting point lower than that of Li2C03, were chosen to mix with pure CaC03 in an effort to test the model (1). The mixtures were analyzed by DTA-TGA, and conclusions reached concerning the extended shell model. Experimental The additives used in this study were Al203 (certified grade from Fisher Scientific Company), CaO (certified grade from Scientific Company), V205 (chemical pure grade from Vanadium Corportation of America), and fly ash (obtained from Raba-Kistner Consultants, Incorporated, San Antonio, Texas). They were mixed each manually to a homogeneous mixture with reagent grade CaC03 in a weight ratio of 1:20. The DTA-TGA system employed in this study is a Mettler thermal analyzer with a Mettler BE 20 balance controller and a Mettler HE balance. The conditions for running the DTA-TGA included a heating rate of 10 °C/min, a chart speed of 10 cm/h, and a 2 mV range for the DTA. The sample amount for each run was carefully controlled at 90.0 ± 0.5 mg. Two different thermograms were obtained. One was obtained by programming the temperature to 700 °C then keeping it for about 50 minutes. From the TGA curve, the 77 calcination rate could be calculated. The calcination rate was expressed as: weight loss(in mg) % calcination rate — sample weight(in mg) x time(in h) The other thermogram was obtained by running the instrument to 1000 °C. The transition temperature could then be found from the DTA curve. The contracting test for additives was run by weighing about 3.00 g of each of the additives into casseroles, and the casseroles were placed in a Lindberg furnace at a certain temperature for one hour. After that, the additives in casseroles were thoroughly examined and compared. Results and Discussion Table XXIII summarizes the data of calcination rate calculated from the TGA curve of DTA-TGA analyzer programmed to 700 °C. All of the calcination rates of the mixtures are lower than that of pure CaC03. Because the weight ratio of each additive and pure CaC03 is 1:20, the effective weight of CaC03 in the mixture must be taken into account in order to do precise comparisons. The corrected average rate is obtained by multiplying the average calcination rate by a corrected factor of 21/20 for the effective weight of CaC03 in the mixture. From Table XXIII, it is apparent that Al203 78 TABLE XXIII CALCINATION RATES OF ADDITIVE-CaCO3 MIXTURES FROM DTA-TGA ANALYZER AT 700 °C Composition Calcination Av. Calcination Corrected (1:20) Rate Rate Av. Rate (%wt/h) (%wt/h) (%wt/h) A1203 + CaCo3 25.39, 25.50 25.44 26.71 CaO + CaC03 25.87, 25.70 25.78 27.07 V205 + CaC03 19.62, 20.48 20.05 21.05 Fly ash + CaC03 22.47, 21.67 22.07 23.17 Pure CaC03 26.16, 26.62 26.39 26.39 and CaO do not have the significantly catalytic or inhibitive effect on the calcination rate of CaC03, while V205 and fly ash demonstrate the inhibitive effect on the calcination rate of CaC03. In the DTA-TGA thermogram, the transition temperature, the peak of DTA curve, corresponds to the temperature of calcining completion. Table XXIV shows the transition temperatures of the mixtures. Again, Al203 and CaO do not change the transition temperature of CaC03, so they do not have any effect on the calcination rate of CaC03. Vanadium pentoxide (V20s) and fly ash demonstrate the inhibitive effect by completing the calcination of CaC03 at higher temperature. 79 TABLE XXIV TRANSITION TEMPERATURES OF ADDITIVE-CaCO MIXTURES FROM DTA CURVE 3 Composition Transition Temperature Av. Transition (1:20) (°C) Temperature (°C) Al20 3 839, 837, 838 838 CaO + CaC03 838, 839 838 V205 + CaC03 843, 842 842 Fly ash + CaC03 840, 841, 841 841 Pure CaC03 837, 838, 838 838 Table XXV shows the melting points of A1203, CaO, V205 (3), and fly ash (4). Because the melting points of Al203, CaO, and fly ash are relatively high, they are expected to be thermally inert at 700 °C. This has been proved by placing them in a 700 °C Lindberg furnace for one hour, and none of them shows significant contraction. Although the melting point of V205 is only 690 °C, it does not contract after heating in a 680 °C Lindberg furnace for one hour. It starts to melt at 690 °C and is completely liquefied at 700 °C. The extended shell model (1) can be used to explain the above calcining results. From the argument of heat transfer, Al203, CaO, V205, and fly ash do not contract 80 TABLE XXV MELTING TEMPERATURES OF ADDITIVES Additive Melting Temperature (°C)' Al203 2072 CaO 2614 V2Os 690 Fly ash = 1245 around the temperature of 700 °C , so, they can not enhance the heat transfer by increasing the contacting area among CaC03 particles. As a result, the calcination rate can not be increased by adding these additives to pure CaC03. With regard to the mass transfer, Al203 and CaO are thermally inert, they can neither promote nor hinder the escaping of carbon dioxide (C02) during the calcination of CaC03. But, this is not true for V20s and fly ash. Vanadium pentoxide melts at 690 °C and completely liquefies at 700 °C. The expanding liquid fills the interstitial space and hinder the C02 from escaping freely among the CaC03 particles. As a result, temperature of completing the calcination is higher than that of pure CaC03, and the calcination rate is lower than that of pure CaC03 at 700 =C. As for fly ash, although the major components of fly ash are metallic oxides with 81 very high melting points, but some constituents (5) with relatively low melting points are still existing, such as, produced from the calcination of CaC03. That is why fly ash shows inhibitive effect on the calcination of CaC03. This has been proved by running the calcination rate of P20s-CaC03 (1:20) mixture. The measured calcination rate is only 21.21 %wt/h which is lower than 26.39 %wt/h of pure CaCO,. 82 Chapter References 1. Huang, J.M., and Daugherty, K.E., Thermochimica Acta, 118, 135 (1987). 2. Huang, J.M., and DaugheDty, K.E., Thermochimica Acta, 115, 57 (1987). 3. Weast, R.C., Handbook of Chemistry and Physics, Chemical Rubber Company Press, 60th ed., 1980. 4. Huang, J.M., Fly Ash Fusion, Master Thesis, Department of Chemistry, New Mexico Highlands University, Las Vegas, New Mexico, 1984. 5. Roy, N.K., Murtha, M.J., and Burnet, G., Use of the Magnetic Fraction of Fly Ash as a Heavy Medium Material in Coal Washings," Proceedings, The Fifth International Ash Utilization Symposium, February 25-27, 1979. APPENDIX LITERATURE RESEARCH B 309 1j u185 11:05:05 User1089 $0.13 0.005 Hrs F i1e1* #0.05 Tymnet #0.1© Estimated Total Cost F i1e309:CA Search - 1972-1976 (Copr. 1984 by the Amer. Chem. Soc.) Set Items Description ? B 301 1ju185 11:05"24 User1089 #0.53 0.007 Hrs File309 #0.07 Tymnet #0.60 Est i mated Tota1 Cost Fi 3.e301: CHEMNAME (tm) 1967-Mar85 1,571,950 subs (Copr. DIAL0G Inf.Ser.Inc.1984) Set Items Description ? SS NYEREREITE OR NATROFAIRCHILDITE 1 1 NYEREREITE 2 0 NATRQFAIRCHILDITE 3 1 1 OR 2 ? T 1/2/1 1/2/1 CAS REGISTRY NUMBER: 51830-08-1 FORMULA: CH203.1/2Ca.Na CA NAME(S): HP~Nyererei t e < CaNa2(COS)2) (9CI) SYNONYMS: .Nyerereite ? S SHORTITE 4 1 SHORTITE ? T 4/2/1 4/2/1 CAS REGISTRY NUMBER: 24492-43-1 FORMULA: CH203.2/3Ca.2/3Na CA NAME(S): HP~Short i t e(Ca2Na2(C03)3) (9CI) HP=Shortite (SCI) 83 84 ? S PIRSSONITE 5 1 PIRSSONITE ? T 5/2/1 5/2/1 CAS REGISTRY NUMBER: J.G347-59-8 FORMULA: QH203.l/2Ca.H20.Na REPLACED CAS REGISTRY NUMBER ( S ) : CA NAME(S): HP=P i r ssort i t e < CaNa2 (COS) 2. 2H20) < 9CI ) HP=Pirssonits (8CI) ? S GAYLUSSITE 6 .1 GAYLUSSITE ? T 6/2/1 6/2/1 CAS REGISTRY NUMBER: 13814-92-1 I" ORMIJL A: (JH203. 1 / 2Ca. 5/2H20 „ Na CA NAME < S): HP=Gay 1 u.ssi t.e (CaNa2 (C03) 2. 5H20) (9CI ) H P = G a yIussite (8CI) ? LOGOFF 1j u185 11:06:54 User1089 $3. 77 0.026 HPS File301 4 Closer1 iptors $0.26 Tymnet #0.60 4 Types $4.63 Estimated Total Cost. LOGOFF 11:06:57 TYMNET: call cleared by request 85 BIBLIOGRAPHY Books Anderson, J.R., and Boudart, M., Catalysis, Science and Technology, New York, 1981. American Society for Testing and Materials, Annual Book of ASTM Standard, Philadephia, Part 41, E473, 1973. Bard, A.J., and Faulkner L.R., Electrical Methods, John Wiley & Sons, New York, 1980. Boynton, R.S., Chemistry and Technology of Lime and Limestone, Interscience Publishers, 1966. Gran, P.D., Thermoanalytical Methods of Investigation, Academic Press, New York, 1965. Ipatieff, V.N., Catalytic Reactions at High Pressures and Temperatures, The Macmillan Company, New York, 1936. Lea, F.M., The Chemistry of Cement and Concrete, Chemical Publishing Company, Inc., 1970. Levin, E.M., Robbins, C.R., and McMuroie, F., Phase Diagrams for Ceramicists, The American Ceramic Society, Inc., 1964. Masters, C., Homogeneous Transition-Metal Catalysis Chapman and Hall, New York, 1981. ~~ Articles Adamowicz, L. and Zielenkiewicz, W. Journal of Thermal Analysis, 26, 217 (1983). Adamowicz, L., Journal of Thermal Analysis, 22, 199 (1981). Anderson, H.C., Analytical Chemistry, 32, (12), 1593 (1960). Bark, L.S., Journal of Thermal Analysis, 21, 119 (1981). Brill, Z. Aanorg. Chem., 45, 275 (1905). Britton, H.T.S., Gregg, S.J., Winsor, G.W., Trans. Faraday Soc., 48, 63 (1952). 86 Collier, G.L., and Singleton, F., J. Appl. Chem., J. Appl Chem., 6, 5 (1956). Criado, J.M., and Ortega, A., Thermochimica Acta, 80, 123 (1984). Davis, H.M., and Smith, D.C., Industr. Engng. Chem., 15, 609 (1943). Debray, Compt. Rend., 64, 603 (1867). Egunov, V.P., Journal of Thermal Analysis, 30, 649 (1985). Freeman, E.S., and Edelman, D., Anal. Chem., 31, 624 (1959). Furnas, C.C., Ind. Eng. Chem., 23, 534 (1931). Gordon, S., and Campbell, C., Analytical Chemistry, 27 (7), 1102 (1955). Haslam, R.T., and Smith, V.C., Ind. Eng. Chem., 20, 170 (1928). Hedvall, J.A., and Heuberger, J., Z. Anorg. Chem., 1202, 181 (1922). Hedvall, J.A., and Heuberger, J., Z. Anorg. Chem., 140, 234 (1924). Hedvall, J.A., and Heuberger, J., Z. Anorg. Chem., 162, 110 (1927). Heide, K., and Eichhorn, Thermochimica Acta, 93, 238 (1985). Hooten, R.D., Pelletized Slag Cement: Hydraulic Potential and Autoclave Reactivity, Doctoral Dissertation, Department of Civil Engineering, McMaster University, Hamilton, Ontario, 1981. Hunter, H., Lee, W., and Sim, S.K., J. C. S. Chem. Comm., 1018 (1974). Hyatt, E.P., Cutler, I.B., and Wadsworth, M.E., J. Am. Ceram. Soc., 41, 70 (1958). Johnston, J., J. Am. Chem. Soc., 30, 1357 (1908). Johnston, J., J. Am. Chem. Soc., 32, 938 (1910). 87 Lukac, P., Tolgyessy, J., and Lapcik, V.L., Thermochimica Acta, 92, 429 (1985). Kapila, S.D., Pathak, K.K., and Bhatia, M.C., Journal of Thermal Analysis, 29, 1393 (1984). Kappel, H., and Hutting, G.F., Kolloid. Zs., 91, Kolloid. Zs., 91, 117 (1940). Kisinger, H.E., Analytical Chemistry, 29, (11) 1702 (1957). Le Chatelier, Id., 102 1243 (1886). Lombardi, G., Thermochimica Acta, 28, 1 (1979). Mallow, W.A., Dziuk, J.J., and Daugherty, K.E., Development of Low Energy Methods for Production of Lime, Draft Final Report, Contract DE-AC03-82-CE40500, for the U.S. Department of Energy, December, 1984. Mackenzie, R.C., The Analyst, 99, 900 (1974). Malyshev, V.P., Sshkodin, V.G., Kim, R.F., and Berezin, G.G., Thermochimica Acta, 92, 181 (1985). Meisel, T., and Seybold, K., CRC Critical Review in CRC Critical Review in Analytical Chemistry, 267 (1981). Meisel, T., Journal of Thermal Analysis., 29, 1379 (1984). Paulik, F., Paulik, J., and Arnold, M., Journal of Thermal Analysis, 29, 333 (1984). Pott, Dissertation, Freiburg in B., 1905. Redferm, J.P., Journal of Thermal Analysis, 27, 427 (1983). Ribas, J., Serra, M. , and Escuu, A., Thermochimica Acta, 91, 107 (1985). Safa, A.I., Daugherty, Mallow, W.A., and Dziuk, J.J., Thermochimica Acta, 78, 309 (1984). Safa, A.I., Daugherty, K.E., Mallow, W.A., and Dziuk, J.J., and Funnell, J.E., ASTM J. Cem., Concr. Aggregates, 5, 21 (1983). Savitzky, A., and Golay, J.E., Analytical Chemistry, 36 (8), 1627 (1964). 88 Sharpless, N.E., and Munday, J.S., Analytical Chemistry, 29 1619 (1957). Shearer, J.A., Johnson, I., and Turner, C.B., Ceramic Bulletin, 59, 521 (1980). Shevtherko, A.V., and Lopato, L.M., Thermochimica Acta, 93, 537 (1985). Smith, S.G., and Stevens, I.D.R., Journal of Chemical Education, 38 (11), 575 (1961). Wendlandt, W.W., Journal of Chemical Education, 38 (11), 571 (1961). Whitaker, S., Pigford, R.L., Indus, and Engineering Chemistry, 52 (2), 185 (1960). Wiederhott, E., and Heinemann, S., Thermochimica Acta, 94, 215 (1985). Wist, A.O., Therm. Anal., Proc. Int. Conf., 2, 1095 (1969). Wunderlich, B., Thermochimica Acta, 83, 35 (1985).