• Lithium Production from Spodumene
by
Ernest Mast
A Thesis submitted to the Faculty of Graduate Studies in partial fulfillment of the requirements of the degree of Master of Engineering. 1
Department of Mining and Metallurgical Engineering McGiII University, Montreal, Canada © Ernest Mast May 1989
" ... '
To the incomprehensible forces which started it all.
l ABSTRACT
A new metallo-thermie reduetion process designated "Meit - Leaeh - 1 Evaporation " is under development for the extraction of lithium and other Group lA and lIA metaIs. The metaI tn be recovered is leached out of the ore or concentrate by an excess of liquid metal reductant which is then vacuum refined to recover the metal as a sohd or hqUld condensate. The expenments performed contacted approxlmately one mole of Beta
spodumene, LiAlSI 0 6' with molten alummum-magneslUm. The molar ratio of 2 the alummum to spodumene was approxlmately 86 ta 1 and the molar ratio of magneslum ta spodumene was increased from zero ta ten. The experiments were perfonned In alumina cruclbles, under an argon atmosphere, at 900°C for mnety mmutes. MIXIng was provlded by mechanical stlITing.
Assays of lIthIum and sIlicon In the cast mgot confmned that lithm
and sihca I;ontamed 10 the spodumene were reduced and russolved mto the ex cess molten alummum reductant. As much as 60 % of the lIthlUm in the spodumene was recovered to the alummllm Ingot cast after the expenment. IncreaslOg the magneslUm to spodllmene ratIo improved the recovery of lithium ta the lOgot. This was as predlcted by a thermodynarruc mode!.
X -Ray dIffraction results detected spmel, MgA1 0 4 and Silicon in 2 1 the powder residlle for al! expenments. These compounds were formed by the following two-step reacuon process,
LI 2O-AI 20 3 ASiO 2 + ~ 3 Al = LI 2 O·AI 20 3 + 4Si + !3 Al 20 3 [1)
[2)
which produced the lithium and silicon dissolved In the cast ingot. A one-step reacnon nmy have occurred simultaneously at magnesium to spodumene ratlos greater than or equal to eight to one,
(3)
1 RÉSUMÉ
Un nouveau procédé de réductIOn thenno-métallique communément appelé 1 "Fusion - LIxiviation - Evaporauon" est sous développement pour r extraction du lIthium et d'autres métaux du groupe rA et lIA. Le métal à extraire est lixlvié à partIr du minéral ou du concentre par un excès de réducteur métallIque liqUide Ce dermer est cn~lIlte raffIné sous VIde pour recouvrer le métal d'Intérêt '>ous la forme d'un ~olide ou d'un liqUIde condensé.
Lc~ e~saI~ expénmentaux ImplIquaIent une réaction avec près d'une mole
de ~podllmène Bêta, LIJ'\.ISI 0 , ct un allIage d '.t1umInlllm -magnésIUm liquide. 2 6 Le rapport molaIre alumll1ll1m/~podumène étal! environ de 86 pour 1, tandis que
le rapport magnéslllm/spodumène vanalt ~ulvant un accroIssement de zéro à
dIX. Les expénences furent COndllItC~ en tenant compte de certains para-
mètres Importants teb que' de~ crcu~eb en alumme, une atmosphère d'argon et une température de 900°C dU! ant 90 mmutes avec agItatIOn mécanique.
L'analyse chImIque des IIngot~ d'aiummlllm a confirmée que l'oxide de
hthlllm et la ~Ilice contenu~ dans la ~podllmène ont été réduit et dissoÜ.1
dans l'excès d'al ummium hq lIlde. J ll~qll' à 60% du lithium présent dans la
~podumène a été recouvré dans le lIngot d'alumlmllm après l'expénence. L'augmentation du rapport magn6Ium/srodumène a démontrée une meilleure 1 extractlon du lIthIUm dans le lIngot. De plus, ce résultat a été prédit à l'aide d'un modèle thennodynamlque. Les résultat~ obtenus par dJffractIOn-X ont démontrés que le réSIdu
poudreux obtenu lors des expénences étan fonné de spmel, (MgAI 0 ) et de 2 4 ... J!lClUm. Ces composés ont été formés en deux étapes considérant les réactions suivantes,
! AIO [ 1) 3 2 3
(2)
lesquelles ont produites le lithlllm et le SIlIcium dISSOUS dans le lIngot. Par contre, une réaction consIdérant une seule étape peut avoir eu lieu pour un rapport magnéslllrn/spodumène plus grand ou égal à huit.
Li O·AI 0 AS10 + 9Mg = 2Ll + MgO Al 0 + 4Si + 8MgO. [3} 2 2 3 2 2 3
Il ,
ACKNOWLEDGEMENTS
1 would first like to express gratItude to my ~upervisor, Dr. Ralph Harris, who was most responsible for my declsion to undertake this endeavour. • His foresight, patience, encouragement and special talents were much appreciated.
The author IS indebted to members of Dr. Hams' group: Robert Selby, Zhou Wang, Liu Jin and especially Blrendra Jena [or their helpful
assistance 10 aU aspects of the proJect.
1 would hke to acknowledge the helpful suggestions from Professors James Toguri and Bert Wratth of the Umversiues of Toronto and Newcastle, respectively.
Thanks to aIl of the students, techmclans and professors in the Department for making the author's sray at McGill a most rewarding one.
The author wlshes to acknowledge The Tantalum Mining Company of Canada and especlally Mr. lohn Flemmg, for expressmg an mrert!st in thlS project, l providmg matenals and perfonrung chemlcal analyses.
Thanks to my office mates, Murray Brown, Welxing Wang and Sugundo for their companionship and acceptance of my temtonal expansion within the office.
1 would like to thank my famlly for therr support.
A spL.cial thank you to Carmen, my gIrlfriend, for being herself.
III TABLE OF CONTENTS
l, Page No.
ABSTRACT , , RESUME ii
ÂCK~OWLEDGEMENTS iii
T Â BLE 0 F CO :\1TENTS iv
LIST OF TABLES viii
LIST OF FIGURES x
CHAPTER 1: INTRODUCTION
1 1.1. MeIr-Leach-EvaporatIon 1 2.1. Charactenst!cs and Uses of Lithium Metal 1.2.2. LIthIUm Occurrence 4 1.2.3. LIthIUm Industry 5 1.2.4. LahlUm Extraction Technology 6 1.3. Alpha to Beta Spodumene Transition 8
CHAPTER 2: LITERATURE SURVEY
II.!. Metallo-Therrruc Reduction Processes 12 11.2. LIthium Production by Metallo-Thennic Reduction 12 II.3. Lime-Spodumene ReactIOns 13 IIA. Interfacial Phenomena 14 l
IV CHAPTER 3:THERMODYNAMIC ANALYSIS OF SPODUMENE REDUCTION • Ill. 1. Reducmg Agent 17 CHAPTER 4: LIME-SPODUMENE TESTS
IV.I. Introduction 22 IV.2. Apparatus and Reagents 22 IV.2. Procedure 23 IV.3. Results of Lime-Spodumene Tests 24 IV.4. DIScussion 26 IV.5. ConclusIOns, Lime-Spodumene Tests 28
CHAPTER 5: EX PERIMENT AL
V.l. Objectlve 29 V.2. Expenmental Vanables 29 V.3. Materials 29 V.4. Apparatus 30 V.5. Expenmental Procedure for Spodumene Reduction Tests 34 V.5.l. Expenmental Preparation 34 V.5.2. Experimental Procedure 34 V.6. Experimental Program 35
CHAPTER 6: RESULTS
VI. 1. Spodumene TransItion 37 VI.2. Visual Observations of Reduction Products 39 VI.3. XRD Analysls of Reduction Products 47 VI.4. Atomic AbsorptIon Analysis 49 VI.4.l. Samphng For Atomlc AbsorptIOn Analysis 50 VI.4.2. Atomic Absorption Analytlcal Methods 50 VI.4.3. Atomic AbsorptIOn Results 54 VI.5. Scanning Electron Microscope Analysis 58
v CHAPTER 7: EXAMPLE CALCULATIONS
VII.I. Detenmning Sample Concentrations From Absorbance Readings 60 VII.2. Sample Calculauons of Analytical Error 61
CHAPTER 8: DISClJSSION
VIn 1. Introduet:on VIII.2 1. Dlscus~lOn of Pre~cnt Experimental Progr:un 63 VIII.22. DIScu~slon of Expenmental Procedure 63 VIII.2.3.1. RelatIve Errors of Sample A~says 64 VIII.2.3.2. Companson of Assays wlth an Outslde Analysis VII!.3. Expenmental Modelmg 67 VII!.3.1. Detennination of Gas Purgmg Rate 67 VIII.3.2. Formation of Sohd S pecies 69 VInA. Mass Balances 70 VIII.5. The Effeet of MagnesIUm AdditIon on the 1 ReactIon Products Assays 73 VIII.6. Kmeties of the Spodumene Reduction System 86 VIII.7. DIscussIOn of XRD Results 88 VIII.8. Wetting Effect of Magne~lUm 88 VUL9. DISCUSSIon of Reaction Mechamsms 89 VIII.IO. DIscuSSIOn of Reaction Pathways 90 VIII.lO.1. Two-Step ReactIOn Pathway 90 VIII.lO.2. One-Step ReactIon Pathway 91 VIII.lt. Vacuum Refinmg of LithIUm from Aluminum 91 VIII. 12. Comparison of Expenmental Results with F* A *C*T CalculatIOns 93 VIII.I2.t. Introduction 93 VIII. 12.2. Companson of Thermodynamlc Model with Expenmental Results 93
1 VI CHAPTER 9: CONCLUSIONS AND FUTURE WORK
IX.l. ConclUSIOns 101 , IX.2. Future Work 102
CHAPTER 10: CONTRIBUTIONS 104
REFERENCES 105
APPENDICES
A: F*A*C*T Simulation of Alumino-Thermie Reduction of Spodumene 109 B: Phase Diagrams 116
1
• VII LIST OF TABLES
Page No. 1 Table 1.1. Physical Properues of Lithium 2 Table 1.2. LithIum Bearing MIneraIs 4 Table 1.3 Uses of lithIUm Metal In the V.S. (Short Tons) 5 Table 1 4 Operaung ConditIOns for LI Electrolysis Cell 8 Table 1 5. Cry~tal Structural Data for Alpha and Beta Spodumene 10 Table 2.l. Surface TenslOn~ for Selected Liquid Metals 15 Table 3.1. CharaeteristIcs of PO%Ible Reductants 18 Table 3.2. Standard Free Energy of Solution of Elements in LIqUld Al und thelr Ab~olute Entropies 19 Table 3 3. F* A *C*T Output of Spodumene ReductIon with Al-Ca Ar oyat 1173 K and l Atm. 20 Table 3.4. F* A *C*T Output of Spodumene Reduction with Al-Mg AUoy at 1173 K and 1 Atm. 20 Table 4.1. Spodumene Assays 22 Table 4.2. XRD ResuIts of LIme Spodumene Smters and ,, j Compounds Predlcted by F* A *C*T 26 Table 5.1. SpecIfications of Alummum (Weight%) 29 Table 5.2 Spodumene Reduction Expenments Performed 36 Table 6.1. Produets of Spodumene Reduction Expenments 40 Table 6.2. Settmgs for LI A.A. Analysis 51 Table 6.3 Settlngs for Mg A.A. Analysis 52 Table 6.4. Settmgs for Si A.A. Analysis 53 Table 6.5. A.A. Raw Data for a Set of Li Standards and Ingot Assays 55 Table 6.6. Assays of Condensate (Welght%) 55 Table 6.7. Assays of Flue Powder (Weight%) 56 Table 6.8. Assays of Resldue (Welght%) 56 Table 6.9. Assays of Ingot (Welght%) 57 Table 6 10 Assays of Drass (Weight%) 57 Table 6.11. LIthium Assays from Kmetic Samples 57 Table 6.12. SEM Assays of Partlcle m FigUIe 6.12, (Weight%) 59 Table 7.1. Results of Linear Regression 60 1
VIII Table 8.l. Average Relative Errors in Sample Concentrations 65 Table 8.2. Comparison of Analytical Results 66 Table 8.3. Mass Balance for Lithium 71 Table 8.4. Mass Balance for Magnesium 72 Table 8.5. Mass Balance for Silicon 72 • Table 8.6. Volatility CoefficIents of Various Solutes in Molten Aluminum 92
1
IX LIST OF FIGURES
Page No . .... Figure 1.1. The Acid Process for Lithium Carbonate Production from Spodumene 7 Figure 1.2. The Silica Tetrahedral 9 Flgure 1.3. Correlation Between Crystal Structure and the Strength of Tetrahedral Frameworks 10 Figure 2.1. The Contact Angle Between a Liquid and Solid 15 FIgure 2.2. Surface Tensions for Aluminum Alloys at 50°C 16 to 80° r; Above Llqmdus Temperature 16 Figure 3.1. Free Energy of Formation for Lithium and Potential Reductants 17 Figure 3.2. Thermodynrumc Simulation of the Lithium Extraction from Spodumene by Reduction with Al-Mg and Al-Ca Alloys 21 Figure 4.1. Apparatus used to Perform the Lime-Spodumene Experiments 23 Figure 4.2. Reaction Product from Lime-Spodumene Experiments l \ at Temperatures of 1050°C and Below 24 i Figure 4.3. Reaction Product from Lime-Spodumene Experiments at 1100°C 25 Figure 4.4. Reaction Product from Lime-Spodumene Experiments at 1150°C 25 Figure 5.1. Experimental Cap Assembly. 30 Figure 5.2. Experimental Apparatus used to Perform the Spodumene ReductIon Experiments 31 Figure 6.1. XRD Patterns of the Raw Materials in this Study and Various LIthium Aluminum Silicates 37 Figure 6.2. Cumulative Size Distnbution of Alpha Spodumene and Transformed Material 38 Figure 6.3 Microphotograph of the Received and Transformed Spodumene 39 Figure 6.4. Condensate 41 Figure 6.5. Fine Black Powder 42 Figure 6.6. Fine Black Powder Lost During an Experiment 43 ~.
X Figure 6.6. Fine Black Powder Lost During an Experiment 43 Figure 6.7. Powder Residue 44 Figure 6.8. Dross 45 • Figure 6.9. Metal Ingot 46 Figure 6.10 Material S'uck to Inside of the Crucible After an Experiment 47 Figure 6.11. SEM Microphotograph of Particle in the Powder Residue 59 Figure 8.1. The Analysis of Solid Formation in the Reduction of Spodumene for Two Reaction Paths 70 Figure 8.2. Lithium Welght% in the Ingot and Dross vs. the Magnesium to Spodumene Ratio 74 Figure 8.3. Lithium Concentration in the Residue and Very Fine Black Powder vs. Magnesium to Spodumene Molar Ratio 75 Figure 8.4. The Masses of the Powder Residue and J3 Spodumene Charge vs. the Magnesium to to Spodumene Ratio 75 ·1 Figure 8.5. Lithium Weight% ln the Condensate vs. the MagneSIUm to S podumene Ratio 76 Figure 8.6. Lithium Weight% In the Very Fine Black Powder vs. the Magnesium to Spodurnene Ratio 77 Figure 8.7. The Sllicon Welght% in the Dross and Ingot vs. the Magnesium to Spodumene Ratio 78 Figure 8.8. The Silicon Weight% ln the POVrder Residue vs. the MagneSIUm to Spodumene Ratio 79 Figure 8.9. Magnesium Concentrations in the Ingot and Dross vs. the MagnesIUm to S podumene Ratio 80 Figure 8.10. Magnesium Weight% in the Powder Residue and Very Fine Black Powder vs. the Magnesium to Spodumene Ratio 81 Figure 8.11. Lithium Extraction from the Powder Residue vs. the Magnesium to Spodumene Ratio 82 Figure 8.12. Lithium Recovery to the Metal Ingot vs. the Magnesium to Spodumene Ratio 83 t
XI Figure 8.13. Lithium Distribution in the Reaction Products for each Experiment 84 1 Figure 8.14. Silicon Distribution in the Reaction Products for each Experiment 85 Figure 8.15. MagnesIUm Distribution in the Reaction Products for each Experiment 86 Figure 8.16. Rate of Lithium Recovery to the Melt vs. Time for Various Experiments Performed in the Study 87 Figure 8.17. LithIUm Extraction from Spodumene from Experimental Results and F* A*C*T Calculations vs. the Magnesium to Spodumene Molar Ratio 94 Figure 8.18. Lithium ExtractIOn from Spodumene vs. Temperature 96 Figure 8.19. LithlUm Extractlon from Spodumene vs. the amount of excess liquid alummum 97 Figure 8.20. Lithium Extraction from Spodumene vs. Pressure at 900°C 98 FIgure 8.21. Pressure of 100% Lithium Extraction vs. Temperature 99 Figure 8.22. Magnesium's Effect on the Lithium Extraction 1 from Spodumene as Temperature Changes 100
, .'n
XII Il INTRODUCTION t 1.1. MELT-LEACH·EVAPORATION
In the Melt-Leach-Evaporation (MLE)(l) process for extracting Group lA and Group lIA metals, solid particulate ores or concentrates are contacted with an excess of molten meta!. The excess molten metaI extracts volatile, metal species into solution by reducing compounds of the species present in the ores or concentrates. The dissolved species are then vacuum refined from the excess moIten metaI. An advantage of MLE IS that it Improves the materials handling and production kinetics as compared to a powder process, such as Pidgeon type vacuum retons. By usmg an ex cess liqmd metaI reductant, the activlty of the recovered specles would be lowered by dilution in the ex cess molten metaI and thus more of the species would enter the solutIon. The extraction of lithium from spodumene (L1 Ü.AI 0 ·4Si0 ) by 2 2 3 2 moIten metallo-thermie reduction was the subject of thlS thesis and is a representative ex ample of metal extractIOn by MLE. The evaporation of the lithIUm from the excess molten metaI was not examined experimentally in this thesls.
1.2. LITHIUM
1.2.1. CHARACTERISTICS AND USES OF LITHIUM METAL
LIthium is the third element in the Periodie Table and it is the frrst of the alkali metals. Lithium was first discovered in 1817 by Arfwedson in Sweden(2) and the metal was first isolated in 1855. The fIfst commercial use occurred when the German finn, Metallgesellschaft A.G., used lithium as a hardener in a lead alloy(2). Sinee then, sClentists and engineers have envisioned many new uses for the metal, due to lünium's unique physical properties shown in Table 1.1.
1 (3) (4) Table 1.1. PHYSICAL PROPERTIES OF LITHIUM
PROPERTY VALUE REF.
-3 • DENSITY, gcm 0.534 3 MP, Oc 180.5 3 BP, Oc 1342 3 FIRST IONIZATION POTENTIAL kj/gmo1e 519 3 ELECTRON AFFINITY kj/gmole 52.3 3
CRYSTAL STRUCTURE BCC 3 SPECIFIC HEAT AT 25 oc, kj/kg Oc 3.55 3 SPECIFIC HEAT AT MP, kj/kg Oc 4.39 3 STANDARD POTENTIAL AT 0 oc, V -3.05 4 ELECTRO. CHEM. EQUIVALENCE A'hours/g 3.86 4
Lithium's density makes it the lightest of aU metals. Alone it can not be used as an structural engineering component due to its reactivity with air and water. However, it is a very effective alloymg element, especially with alurrunum. One weight percent lithium added to aluminum decreases the density
1 by three percent and increases the elastlc modulus by six percent. (5) Aircraft rnanufacturers and users ale excited about using lithiurn-aluminum alloys to mcrease the payload capacity, fuel economy, flight distance, and overall performance of th eu aireraft. These advantages will also be aVaIlable for other users of IIthlUm-aluminum alloys. Lithium's density combined wah lts very high electrochemical standard potenual and eleetrochemical equivalent make lIthium an exceptional anode material for energy ceUs. Many variatIOns of hthium cells exist depending on th{; cathode material and electrolyte used. Characteristics of lithium cells are:
1) ~lat discharge. Constant CUITent production with respect to voltage and irnpedance. 2) Longer shelf life. The lithium-manganese oXlde battery available commercially can be stored for ten years at room temperature and retain 85% of its capaclty. A zinc alkaline battery can be stored
2 for only 2-3 years(6). Storage for one year at 170°C is also possible for lithium ceUs. 3) Wider operating ternperatures. Lithium batteries with organic electrolytes can be operated at temperatures as low as -155°C. 4) Higher voltage. Hlgher cel! output reduces the number of ceUs in a battery pack by a factor of two wh en compared with regular zinc anode battenes 5) High energy density. The energy denslty of lithium batteries is 2-4 tIrnes higher than zinc alkalme battenes. 6) Vinually no self-discharge. This is due to the hennetic seaI of the battery case.
These characteristics translate to the speclalized use of lithium cells in cold chmates as portable energy sources and m components which are actlvated occasionally but perform VItal funetions, such as back-up power for an important installatIOn, Lithium use in batteries for radios, toys,
calculators, etc, etc.. IS mereasmg and a number of companies are deveIopmg this technology(7). Lithium has a very large temperature range between its normal melting and boiling points which, combmed wlth as large heat capacity, make lithium a potential high temperature heat transfer medium.
The use of lithIUm 10 fusion energy reactors as a blanket material is also anticipated. LithIUm reaets WIth the neutrons produced in the fusion plasma in the followmg manner:
LI + Neutron = He + Tritium {Ill
The large amounts of energy carried by the neutrons would he transferred to the excess lithium and then removed by a heat exchanger. Tritium is a fuel for the fusion process, so the lIthium blanket material has the benefit of regenerating a fuel. The future of lithium is very promlsing AIl reports are optinustic on the metal' s increased use and importance as the twenty fIfSt century approaches.
3 1.2.2. LITHIUM OCCURRENCE 1 Lithium IS widely distributed across the earth. It occurs in soils, clays, rocks and water bodies. The average lithium content of the earth' s crust is 20 ppm(8) The average concentration of lithIUm in seawater is 18 ppm(8). Presently two tyres of lithIUm deposits are economical as an ore; brines and pegmatite rocks. Eighty percent of the world's lithIUm reserves are present as brines. The major hthium-bearing bnne deposIts are sub-surface and include Salar de
Atacama(Chlle), Salar de Uyum(Bohvla) and In Silver Peak(Nevada). PegmatItes are coarse gramed Igneous rocks. The lithium-bearing mineraIs are shown in Table 1.2.
Table 1.2. Lithium Bearing Minerals
NAME FORMULA
SPODUMENE Li O-AL 0 45i0 LiALSi 0 2 2 3' 2' 2 6 EUCRYPTITE Li O'Al 0 '2Sio LiAlSiO 1 2 2 3 2, 4 PETALITE Li O-Al 0 '88io LiA1Si 0 2 2 3 2, 4 10 LEPIDOLITE COMPLEX Li MICA
Of these mineraIs spodumene is the most important. It has a theoretical lithia and lithium content of 8.03% and 3.75% respectiveIy. Major spodumene deposlts are Kmg's Mountam(North Carolina), The Greenbush property(Austraha) Bernlc Lake(Mamtoba), The Bitka Pegmatite(Zimbabwe) and The KItotolo deposlt(Zaire), WhlCh is the world's
largest. The mined ore contalOs usually 2.5-3.5% hthia and IS upgraded by froth flotation to a maximum of 7.5% lIthium oXIde. Other pOSSIble sources which are not economlcally feasible at present, are geothermal bnnes and hectonte clays of the Western United States(9). InformatIOn on lIthIUm reserves of the V.S.S.R. and China is not
available. (9)
4 1.2.3. LITHIUM INDUSTRY
The largest producing and consummg nation of lithium is the United States. Most of the production IS from North Carolina pegmatite ores by the Lithium Company of Amenea and the Foote Mmeral Company. These companies have agreements WIth South Amencan governments to co-deveJop the Chilean and Bolivlan brine resources. Despite pnor behefs that a lIthium shortage is immlflent(IO)(lI) the present estabhshed reserves are estlmated to be 7.6 million tons for pegmatites and 14.0 million tons for brines(9! The probable cumulatIve demand for the period of 1983-2000 IS 179,000 tons(\2) of contained lithium. The applicatIons of lithium are changmg with ume. The uses of lithium during the penod between 1978 and 2000 are shown in Table 1.3. A greater
percentage of the total lithium used is 1I1 metallic forro. This trend is expected to contmue as more lithium IS used in energy ceUs and aIloys.
Table 1.3. USES OF LITHIUM METAL IN THE U.S. (SHORT TONS)
197B (12) 19B3 (13) 2000 (13)
Total Use 3400 2200 5600 Use in Batteries 0 50 150 Use in Al-Li Alloys 0 a 750 % of Metal Use (%) 0 2.27 15.1
1.2.4. LITHIUM EXTRACTION TECHNOLOGY
The only commercial method of produclOg lithium metaI today is molten salt electrolysls of lithium chloride. ThIS process is applied to all lithium beanng raw matenaIs and, therefore, lIthium chloride is an essential mtennediate product m lIthium metaI production. Three methods eXIst to treat spodumene ore for the purpose of lithium extraction. They are 1) The Acid Process, 2) The Alkaline Process and 3) Ion Exchange.
The Acid Process IS the only method used commercially and a flow sheet
5 is shown in Figure 1.1. The spodumene concentrate is frrst converted from its a phase to its more reactive ~ phase by heating to approximately lOS0°C. 1 The ore is then leached with hot sulfuric aCld at 250°C. Hydrogen ions from the H S04 replace the lithium ions In the spodumene, thereby forming a Z soluble lithium sulfate and an Insoluble gangue. During purification, the aC1d solution 1S neutralized with ground limestone and filtered to eliminate 1ron and alumInum impurities. After a prehminary punfication step, hydrated lime is used to precipltate magneslUm and soda ash is used to preClpltate excess calcium. The solutlOn is then adjusted to a pH of 7 - 8 and concentrated by evaporatIon to 200 - 250 gIlitre of lithium sulfate pnor, to formation of lithium carbonate via Na C0 addition. The spent Z 3 solution contams about 15% of the original lIthium and must be recycled. Pnor ta 11 rejoining the process at the purification stage, it is cooled to O°C where sodium sulfate, WhlCh precipltates on cooling, IS separated and sold as a by-product.
1
6 SPODUMENE CONCENTRATE • l ex TD (3 CONVERS ION l
ACID ROASTING l
LEACHING ---~) SILICA AND TAILS l
PURIFICATION --~) Mg(OH) 2,caco l 3
CARBONATION ~(--- Na Co l 2 3
GLAUBER RECOVERY ~ SEPARATION l l
Li CO PRODUCT 2 31
CONVERSION TO LiCl l
MOLTEN SALT ELECTROLYSIS ~ Li METAL
Figure 1.1. The acid process for producing lithium carbonate which is converted ta lithium chloride for molten salt electrolysis to produce lithium metai.
An lflteresung feature of the flow sheet shawn in Figure 1.1 is that
lithium carbonate IS made pnor to the production of lithium chloride. Lithium carbonate is the most widely used lithium chemical, used in aluminum production, and it serves as the raw material for the production of all other lithium cherri.cals. If lIthium met al were to approach lithium carbonate in usage, the process could he easIly modlfied sa that the stream of lithium bearing liquor was transformed directly into Liel. Sorne of the parameters of the molten salt production of lithium are listed in Table 1.4. 1
7 a Table 1.4. OPERATING CONDITIONS FOR loi ELECTROLYSIS CE:i..L (15) (16)
Material LiCl
Electrolyte LiCl % 48-50 RCl % 65.8-50 Temperature Oc 450-460 Current Cell Current (A) 3500 Voltage (V) 4.86-8.19 Anode Graphite
Power Theoretical, (kWh/kg Li) 31. 5-39.2
Total Power, (kWh/kg Li) 140(16)
Analysis Li% 99.0
The result of this process is a lithium product with a market price of 1 $CDN 65.45 / kg(16) for a standard lithium ingot of commercial purity. One tonne of spodumene concentrate costs $Cdn 450. The concentrate has a contained lithium value of,
1000 kg/tonne x 0.0325 Li x $ 65.45/kg Li = $Cdn 2127/tonne [1.2)
The cost analysis shows that an effective extraction method could he profitable.
1.3. ALPHA TO BETA SPODUMENE TRANSITION
The reaetivity of the lithia species in the spodumene can he improved by its polymorphie transformatlOn from the stable alpha phase to the more open beta phase. The aIterauon of the crystal structure 1S not unique to the mineraI spodumene and occurs for many silicates, the most weil known are the five polymorphs of quartz: high and low quartz, tridymite, and high and low 1 8 cristabolite. ?olymorphism occurs when the ambient crystal structure is not the most stable phase at other temperatures and pressures. In practice, the transformation is found to occur at temperatures greater than 900°C. Above 930°C, the mechamsm IS by almost instantaneous nucleauon with umdlmenslOnal growth of the nuclel wh Ile below 930°C only nucleatlon occurs(17). The hlgher temperature is necessary to overcome the acuvatlon energy of the transformatlon, equal to 289 kj/mole above 930°C and 753 kJ/mole below 930°C(l8).
To better understand the effect of the a to ~ transformation an examination of sllicate chemistry is useful. The bUIlding block
of slhcate chemistry IS the Si0 tetrahedral, displayed In Figure 1.2. 4
c:;::..
Figure 1.2. The silica tetrahedral. Open circles represent oxygen atoms and full circle represents a silicon atom.
The silicon atom in the center is covalently bonded to four oxygt tl atoms and is known as a tetrahedral site (T). Large crystal nelworks are formed when tetrahedra share a common oxygen atom. Sorne of the Ideal structural requirements of silica are(18):
1) ideal bond length d(Si-O) = 1.605Â 2) strain-free SI-Q-Sl bond angles of 1400 3) good space filhng with as many bonds per unit volume (in order to 3 attain maximum free energy per umt volume): ideal V 15 • ox = A
The correlatIon between the stability of the tetrahedral frameworks and
crystal data is shown in Figure 1.3(19). 1
9 • • 14 --1---- ",~ ~,1" 12 ---~-- - I~r" LfoUCI TE ',- '0 /h- -.. ~--e__ T~iDYMITE ' 8 PAR:'CELSIAN/ --...;tt. \. ~' , \ ~ , b.T\..--. .~ "- \ - .111 J\" -...... "- \ \ 8 , f'm / c;1l, > 6 HEXACl LSIAN '-KEATITE FIgure 1.3. Correlation between the difference in oxygen density (6V ), ox l Si-Q-Si bond angles (t. T-Q-T) and relative stability of the tetrahedral frameworks and chains of silica and Al containing alkali and alkaline earth silicates. The frameworks and chains are less stable, the larger the distance from the point 6 V = 0 ox and ~ T-Q-T = O. Table 1.5(20) shows structural data for (l and Il spodumene. Table 1.5. CRYSTAL STRUCTURAL DATA FOR ALPHA AND BETA SPODUMENE T-O-T V OX 0: SPODUMENE 139.0 16.2 (3 SPODUMENE 149.4 21.7 1 10 Alpha spodumene's crystal structure is much closer to the ideal than 0 that of 13 spodumene: 1 for bond angle difference for Cl versus 9.40 for 13 and 3 3 I1V = 1.2 for Cl versus 6.7À for~. The !1T-G-T and I1V for ex spodumene 1 ~ ~ corresponds to the stable pyroxene structure which is a tmee dimensional framework. The data for f3 spodumene give it a keatite structure, a two dimensIOnal chain structure wll1ch may be easier to penetrate in the metallo-thermie reductlOn proeess. Another difference is that the alummum cations in the ~ spodumene occupy T sites while alpha spodumene does not have its aluminum cations in T SItes. The importance of this difference in the location of the aluminum atoms is that in the Cl phase, where less interstitial volume exists, more non-tetrahedral cations must be accommodated. In 13 spodumene, the lithium atoms have larger In ters tlti al volumes to fit into and no interstitial aluminum cations are present. The difference in the V and the crystal structure leads to a density ox difference between the polymorphs. Alpha spodurnene has a specifie gravit y of 3 3 3.150 glcm and 13 spodumene has a specifie gravit y of 2.400 g/cm (3) As a result ~ spodumene 15 23% less dense than Cl spodumene and a corresponding volume expansIOn occurs during the transiuon. :1 The converSIOn of spodumene to the 13 phase from the ex phase creates a more reactive raw material by: 1) Increasmg the volume of the material and thus increasing its surface area 2) Giving the lithia species more mobllity 10 the material. 3) Weakening the crystal structure of the material. Beta spodum':ne appears to be more amen able to metallo-thermie reduction than ex spodumene and the spodumene transition would be an effective pretreatment of spodumene for metallo-thermie reduction . • 11 ------ II. LITERATURE SURVEY 1 II.l. METALLO-THERMIC REDUCTION PROCESSES The most widely known metallo-thennic reduction proce'is is the Pidgeon Process for the production of magnesium(21). In this process. magnesium is produced from calcined dolomite by reduction with ferro silicon in a vacuum retort. The reaction is d~scribed by the equation: 2[CaO·MgO](s) + Si(s) = 2Mg(g) + 2CaO·Si0 (s) [2.1) 2 This process is one of the methods used to produce magnesium commercially. Alumino-thermIc reduction processes are used for the production of manganese, chromium(22)(23) and calcium(24). II.2. LITHIUM PRODUCTION BY METALLO·THERMIC REDUCTION ,. Kroll and Schlechten(25) were able to reduce lithIUm oxide, in the l presence of lime, with silicon, aluminum and magnesium as shown below: 2Li 0(5) + 2CaO(s) + Sics) = SiO ·2CaO(s) + 4Li(g) [2.2) 2 2 Li 0(s) + CaO(s) + xMg(s) = CaO + MgO + Li + (x-I)Mg [2.4) 2 Their experiments had recoveries of the order of 90%. They stated that lime was essential In ail the systems. except in the study using magnesium where the hme "had no chemlcal function" and the condensate contained magnesium Impuriues. Stauffer(26) carned this process one step further by reducing spodumene directly wnh ferrosllicon (FeSi/ Once again recoveries of the order of 90% were attained. It was noted that lime was an absolutely essential reagent for the process because of the way It "tied up" the alumina and sllica specles in spodumene and without lime, poor recoveries were obtamed. 1 12 i In both s('ts of experiments a combmation of reducing agent, lime and lithium raw material were combmed in varying concentrations into a 1 briquette. The briquettes were then placed in a vacuum retort and the condensate product was analyzed for lIthlUm. Pidgeon and MorriS(27) measured the vapor pressure of hthium in the hthium oxide-calcium oxide-sIlicon system They found that the vapour pressure increased with temperature between 972°C and l02SoC and was sufficient to commence commercial producuon(28). Fedorov and Sharma(28) examined the kinetics of the reduction of lithium aluminate by aluminum in vacuum; [2.5] by utilizing a method of continuous weighing. They concluded that a periocl of constant reaction rate existed and I.hat the kinetics varied considerably with temperature. AH the above studies and processes uulized powder reactants in a vacuum retort. The previous studies on hthium productIon were successful yet the process was never successfully mdustrialized. Reasons why the commercial process did not succeed were; - slow productIon rates due to the fact that only small briquettes could be used for fear that the Li vapours would not be released. - a smali demand for lithlUm metaI at the time. - poor metai vapour condensation technology. With a MLE process, large reactors could be constructed and the process could be developed mto a high yield, continuous one. The lithium may be able to be condensed as a liquid. II.3. LIME - SPODUMENE REACTIONS In the prevlOus studies of llthlUm production by metallo-thennic reduction of lIthium oxide and spodumene, calcium oXlde played an important role. In view of lime's Importance to a proposed process, this section examines the lite rature of spodumene-hme reactions. Various work has been done on the reaction of lime with lithium 13 materials(29.30.3l). In the most comprehensive study of Iime-spodumene sinters, Lainer and Nazirov(32), stated that the first stage of the reaction might 1 proceed according to the equation: Li a·AI ·4SiO + 8CaO = Li O·AI 0 + 4(2CaO.Si0 ) [2.6) 223a 2 2 23 2 and in a second stage excess lime would break up the lithium aluminate to form lithium oxide. In Chapter IV It was investigated whether a lime pretreatment would he used in the MLE process. II.4. INTERFACIAL PHENOMENA Solid oxides and molten metals are not materials which readily mix and are often described as non-wettmg. Wetting phenomena were Important in this study of the MLE process because the reactions involved were hetween sol id oxides and molten metal and if no wettmg occurred, no reaction wou Id QCcur. A measure of wetting between a liquid and solid can he described by the contact angle, e, shown in FIgt;re 2.1. 1 The contact angle can be expressed theoretically by Young's equation; cose = [2.7) where Y ' Y and Y represent the surface tension between solid and sv SL LV vapour, solid and liquid and liquid and vapour respectively. J 14 VAPOUR VAPOUR 8 1 Figure 2.1. The angle between the tangent of the liquid-gas interface and the solid plane 1S the contact angle, 8. In the above Figure, 8 is greater than 9 and as a result greater wetting 1 2 will occur at surface 1. Table 2.1 shows 'Y for selected molten metaIs and their solid phases • SL compared to 'Y of the same metals with their vapours. The table shows that '. LV if Y for metaI A IS much larger than 'Y for metaI B then Y for metal A LV LV SL will be larger that Y for metaI B. SL Table 2.1. SURFACE TENSIONS FOR SELECTF.D LIQUID METALS (34) (35) Metal '1 '1 SL LV Li 398 30 Na 191 20 Al 914 122 Ag 903 126 Using Equation 2.7, the contact angle, 8 for a spodumene particle in contact with either aluminum or an aluminum-magnesium alloy can he compared. • For bath liquid metals, 'Ysv would be equal. According to the relationship 15 between "(LV and Y established from Table 2.1, Equation 2.7 can he SL rewritten, 1 cose = (28) thus the contact angle would increase as y v decreases. L Figure 2.2 shows that the surface tension, "(LV' of aluminum decreases wnh magneslUm addItion. As a result the contact angle between an oxide particle and molten aluminum would decrease with magneslUm addition, improvlOg the wetting. -~~ Zn :-1 ï E u cCIl 1 1 2-'"' 700 J 1 c ~ , '"c 2! ~Sb~ 1 600 =-__ Il> u ""1'- 1 .2 ; 400~ __~ __~ ______b_'_~ 023 4 6 7 SI'llJle (,." %) Figure 2.2. Surface tensions for aluminum alloys at 50°C to 80°C above , liquidus temperature. (35) lfi 1 III. THERMODYNAMIC ANALYSIS OF SPODUMENE REDUCTION m.l. REDUCING AGENT The Ellingham Diagram in Figure 3.1 and the thermodynantic computer program F* A *C*T [Facility * for the Analysis * of ChemicaI * Thennodynamics](36) developed by Baie, Thompson and Pelton were used to choose the molten metal reductant. A list of the possible reductants and their characteristics is shown in Table 3.1. The characteristics of lithium are aIso given. -200 ,.-, W Ll ~ -4 00 0 ;r:::,,...... 51 1-) (Il Mg 1 ~ '-"h -600 co Al )- -120~ 00 1000 1500 2000 2500 ---- TEI1PERATURE (K) Figure 3.1. Free Energy of FOffilation for lithium and potentia! reductants. 1 17 Table 3.1. CHARACTERISTICS OF LITHIUM AND POSSIBLE RBDUCTANTS 1 PROPERTY MATERIAL Li Al Ca Mg Si MELTING POINTee 180 660 839 648 1410 BOILING POINToC 1342 2467 1484 1090 2355 CaST ($C/kg) (17) 65.45 2 9 7.0 3.6 1.3 The Ellingham diagram shows that aluminum and silicon are not suitable reducing agents at atmosphenc pressure. Only calcIUm and magnesium cou Id reduce lithium oXIde to fonn lIthium. However, neuher IS SUl table as a bulk. metal due to cost, reactivtty or vapour pressure. Alummum IS an Ideal bulk metal becallse of as low cost, SUl table melung pOInt and very high bOlhng pOInt, 1 e, a low vapour pressure. 10·\0Atm, at the anncipated operating temperature of approximately lOO entropIes(38) of the dissolved species. The data u<;ed IS ~hown ll1 Table 3.2. The data for calCIum was from estImates by Richardson(39). The procedure outlined in the F* A*C*T DA TAENTRY program was followed to create the dissolved specles. 1 18 Table 3.2. STANDARD FREJ!: ENRERGY OF SOLUTION OF ELEMENTS IN LIQUm Al 1 AND THEIR ABSOLUTE ENTROPIES METAL MO SO (kJ/MOLE) (J/MOLE) si 40,145.0 - 47.241T 18.82 Mg -14,551.9 - 1. 255T 32.51 Li -24,267.2 + 13.440T 28.03 Ca -43,513.6 41. 63 For the calculation, Inputs 3.1 and 3.2 below were used. These roughly approxiamated the expenmental trials described later. The value was varied from 0 to lOin increments of 1. Li D·AI 0 ·(SiD) + 85.5 Al + Mg [3.1) 2 2 3 2 4 Li D·AI 0 (SiD) + 85.5 Al + Ca (3.2] 2 2 3 2 4 The complete F* A *C*T output for the magnesium simulation is given in Appendix A. The results of the simulation are summarized in Tables 3.3 and 3.4 and Figure 3.2. When the value was zero. F*A*C*T predicted that the molten alummum would fully reduce the sllica species to form silicon. Ten point six percent of the llthium oxide in the spodumene was reduced to lithium and the remamder was converted to lnhium aluminate. Thus the task of a reducing agent would be to decrease the lithium aluminate predicted and fonn more pure lithlUm. Table 3.3 shows that the simulatIon predicted that the total number of moles of free lithium decreases, with calcium addition. Instead of reducmg the lIthium alum1I1are, the calcIUm was predicted to form the compound CaA1 When magneslUm IS added, more free lIthium is predicted 4 ta oceur. This IS due to magneslUm reduction of lithium aluminate to fonn spinel and lithium dissolved ln the molten met al. At ten moles of magnesium 70% recovery of the lithium was predlcted. If the amount of magnesium was increased above ten moles more lithium would be produced . • 19 Table 3.3. l'*A*C*T OUTPU'l' 01' SPODUMENE REDUCTION WI'rH JU-Ca ALLOY AT 1173 K AND l ATM. 1 MOLES PRODUCTS [LiJ Li (1) LiAIO (s) CaAl ( 1 ) Al 0 3 ( s) Si (~) A: ;' 4 2 0 0.140 0.079 1.781 - 2.81 3.99 1 0.134 0.075 1.790 l.0 2.81 3.99 2 0.128 0.072 1.797 2.0 2.81 3.99 3 0.122 0.071 1.809 3.0 2.79 3.99 4 o .ll7 0.066 1.818 4.0 2.79 3.99 5 0.111 0.062 1.827 5.0 2.78 3.99 6 0.105 0.059 1.836 6.0 2.78 3.99 7 0.099 0.056 1.845 7.0 2.77 3.99 8 0.093 0.052 1.854 8.0 2.76 3.99 9 0.087 0.049 1. 864 9.0 2.76 3.99 10 0.081 0.048 1.873 10.0 2.75 3.99 Table 3.4. F*A*C*T OUTPU'l' OF SPODUMENE REDUCTION MITH Al-Mg" ALLOY AT 1173 K AND l ATM. 1 20 , 80r-----~----~----~------~ 70 -.... • ...•.••••.• ~ •.•.••..•.••• ~. ~g Ca 60 -. -...... -...... [±J ...... -...... _...... z 50 · . . o t= · . u · . c( 40 ....•..•.•. ;. .•..••...... •.• ·····f···· ...... !...... cr ..... x w 30 ...... •. ; . .:J 20 - .. MOLES AEDUCTANT Figure 3.2. Thennodynamic simulation of the lithium extraction from spodumene by reduction with Al-Mg and Al-Ca alloys at 1173 K and 1 1 atm. The lithium extracted from the spodumene is plotted against the respective magne sium and calcium to spodumene molar ratios. , Figure 3.2 shows that magne sium is the superior reductant in this study. An aluminum-magnesium alloy was thus chosen as the reducing agent in the experimental program in this study. The drawback with magnesium as the alloying element is its vapour pressure, which is similar to lithium's and which would pose a contamination problem during lithium distillation and recovery. The similarity in vapour pressure may be resolved by fractional condensation or distillation using lithium's much lower melting point as compared with magnesium's. ISO°C versus 648 ° C. 1 21 IV. LIME· SPODUMENE TESTS 1 IV.1. INTRODUCTION Kroll and Schlechten(26) stated that lIme was chemically inactive in the reduction of lithIUm oxide by magnesium. However, Stauffer(28) found that lime was e!lsentIal 10 the reduction of spodumene by ferrosilicon. From this information a decIsIon whether to use a lIme pretreatment in this study can not be made. A senes of lime-spodumene tests were thus performed to determme if the lithium oXIde portion of the lime treated spodumene was significantly more amenable for reductIon than that in P spodumene. The results of the tests, thermodynamIc analysis and common sense were used to decide whether a lime pretreatment of the spodumene was necessary 10 thIS study. IV.2. APPARAT US & REAGENTS A muffle fumace was used to heat the fIre clay crucibles used to contain the reactant mixtures in the lime-spodumene tests. Temperature 1 measurements were obtained via type K thermocouples, placed in alumina sheaths and inserted into the center of the mIxtures. The apparatus is shown in Fi.;ure 4.1. The spodumene was a high grade concentrate obtamed from The Tantalum Mining Co. of Canada (Tanca), Bermc Lake, Mamtoba with the Tanco assays shown in Table 4.1. (t) Table 4.1. SPODUMENE ASSAYS (%) Li 0 Na 0 K 0 Fe 0 P 0 2 2 2 2 3 2 5 7.0-7.5 0.16 0.06-0.15 0.05 0.15-0.2 (t) Assay performed by Tanco. The lime was commercial grade obtamed from 10lichaud in Montréal, and was calcined at 600°C for one hour, a recornrnended calcining treatment(40). 1 22 1 TEMPERATURE RECORDER • /------JI :/1000 / ALUMINA SHEATH --.....~ THERMOCOUPLE-*~~-----~ MUFFLE J t FURNACE CRUCIBlE & MIXTURE Figure 4.1. Apparatus used to perform the lime-spodumene experiments. IV.2. PROCEDURE Two arbitrarily chosen mixtures of lime and spodumene containing 38.4 wt% and 68.7 wt% spodumene, respectively, were heated at temperatures of 900°C, 950°C, lOOO°C, 1050°C, l100°C and 1150°C for four ho urs in frre clay crucibles in a muffle furnace. The crucibles and contents were slowly cooled. The lime to spodumene molar ratios of the mixes were 4:1 and 10.5:1. respectively. The products of reaction were analyzed by X-Ray Diffraction (XRD). The raw data was obtained by a 37 minute scan between 10° and 100° and then • analyzed using the Phillips APD 1700(41) software analysis system . 23 IV.3. RESUL TS OF LIME·SPODUMENR TESTS 1 Three disunct reactlon products were dpparcnt aftcr cxpcriments at different temperatûrcs. Photograph!> arc !>hown ln FIgures 4:2 - 4.4. At 10S0oe and below, l grey powder, -;ltghtly affected by the a -> f3 expansIOn of the spodurncne, occurred for both IIme--;podumene mixes. For trials at } HXtC, a green, friable, 'lInter that had ex pandcd was ubtamcd. I\t 1150"C, a white, fused product was obtamed. -- --.------ Figure 4.2. ReactIon producl from lIme - <.,podumene experiments at temperatures of I050°C and below J 24 1 Figure 4.3. Reaction product from lIme - spodumene experiments at l100°C Figure 4.4. Reaction product from lime - spodumene experiments at 1150°C. 25 Table 4.2. XRD RESULTS OF LDŒ SPODmŒNE SIN'rERS AND COMPOUNDS 1 PREDICTF~ BY F*A*C*T T Oc RATIO IDENTIFIED PHASES B'*A*C*T 950 10.5:1 SPODUMENE LiAlO ,Ca SiO ,CaO 1 2 2 4 4: 1 LiAIO , CaSiO " 2 3 1000 10.5:1 LiAIO ,Ca SiO ,CaO 2 2 4 4:1 LiAIO , CaSiO " 2 J 1050 10.5: 1 LiAIO , Ca SiO , CaO " 2 2 4 4:1 LiAISi 0 LiAIO 2,CaSi0 3 8 3 1100 10.5:1 Ca Al SiO Ca SiO LiAIO ,Ca SiO ,CaO 2 2 7 2 4 2 2 4 4: 1 Ca Al SiO LiAIO , CaSiO 2 2 7 2 3 1150 10.5:1 NO SPECIES DETECTED LiAIO ,Ca SiO ,CaO ? 2 4 4:1 CaSiO LiAIO ,CaSiO 3 2 3 IV.4. DISCUSSION The goal of the lime - spodumene tests was to examine the results from the XRD and thennodynamic analysis and using those results, to detenrune the necessity of a lime pretreatrnent of the spodumene. At 1050°C or below, spodumene was detected for all products except for the 4: 1 molar ,~tio at 1050°C, where the lithium alumino silicate, LiAISi û , was delected by XRD. 3 g At temperatures at and greater than 1100°C, products containing calcium silicates and calcium aluITIlno sIlicates were Identified, indicating reaction between the lime and spodumene. At 1100°C these products were gehlenite (Ca Si AI0 ) and lamite (Ca Siû ). Both are greemsh in colour 2 2 7 2 4 and were the cause of the green colour of the products. For experiments run at 1150°C, the white minerai, wollastomte (CaSiO) 3 was detected by XRD. The EQUILIB program from F* A *C*T was used to predict the most thermodynamically stable producis of the lime-spodumene pretreatment. The 26 larnite (Ca Si0 ) and lime for the 10.5: 1 molar mix at all temperatures. For 2 4 the 4: 1 mix, lithium aluminate (LiAIO ) and wollastonite (CaSiO) were 2 3 predlcted. In additIOn F* A*C*T predicted that gehlenite (Ca Al SiO) would 2 2 7 have a high activuy in the system, but Ilot h!gh enough for it ta form. The XRD analysis venfled the F* A *C*T calculatIOns by detecting, gehlenite, larnite and wollastomte. The F* A *C*T prediction of lithium aluminate agreed with work by Nazlrov(33) The reactlOn products predlcted by F* A *C*T were the same for all temperatures. However, as mentioned above, three different experimental products were observed. This was due to the very slow kinetics at lower temperatures and the activatIOn energles necessary to commence reaction(18). No sImple method was available ta separate the lithium containing species from the calcium con tain mg specles in the products. Thus it threw into question the desirability of the hme-spodllm~ne sinter product over 13 spodumene as a feed material for molten metallo-thermie reduction. The sahent information is as follows: 1) The pretreatment did indeed break up the spodumene structure and free lithium oXIde species to either form the aluminate or remai!] as an oXIde. Neither of these specles were identificd in the XRD study. 2) The lime pretreatment diluted the lithium content in the material. 3) As weIl, the addItIOn of lime mtroduced calCIUm mto the system which was shown ln Chapter III ta have a negative effect on the thermodynamics of the system. 4) The thermodynamic study III Chapter III shows that the reduction of the spodumene with an aluminum-magnesium alloys is feasible without a lime pretreatmen 1. It was conc1uded that a lime pretreatment was not nescessary and furthennore that lime's importance in the powder experiments peIformed by Stauffer was due to the paSSIve oxide layer on the surface of the powder reductants. In those experiments, lime was necessary as a flux to decompose the oxide layer and expose free metal for reaction. Smce the reactions were perfonned 111 vacuum, no further oxidation, aside from the formation of reactIon products, occurred. With the MLE , process, molten metaIs, free of oxide surfaces, would be the reducing 27 agent, so the fluxing properties of lime would not be necessary. IV.5. CONCLUSIONS; LIME - SPODUMENE TESTS. The lime pretreatment of spodumene was not considered advantageous for the MLE process for the folJowing rcasons; 1) Dilution of lithIum ln feed matenal for reduction. 2) Thermodynamic feasibility of system wnhout lime. 3) No distinct disassoclation of the lithia species from alumina and silica. As a result, the reduction of spodumene was attempted without lime pretreatment in t/lIS study. 28 V. EXPERIMENTAL '1 V.I. OBJECTIVE The aim of the experimental program was to detenrune the effect of changing the magne sium concentration of an aluminum-magnesium molten reductant, on the recovery of lithium to the molten phase, via spodumene reduction at 1 Atm. and 1173 K. V.2. EXPERIMENT AL VARIABLES The process variables which were controlled during the experiments were: a) melt ternperature b) Ar gas fl ush rate c) stirring mechamsm and rate d) reaction time e) amount of excess molten aluminum The process variable which was altered was the amount of magnesium added to the system, calculated as the molar ratio of magnesium to spodumene. V.3. MATERIALS Three charge materials were used; a) high grade spodumene concentrate supplied by Tanco and converted in house to !3 spodumene. b) aluminum, commercial grade supphed by ALCOA, Pittsburgh, PennsylvanIa WIth the specifications shown in Table 5.1. Table 5.1. SPECIFICATIONS OF ALUMlNUM{t)WEIGH~% Si Fe C Mn Mg Zn Ti V 0.033 0.029 0.004 a .001 <0.001 0.005 0.004 0.012 1 (t) Assay perforrned by emission spectrometry at McGill UniverSIty. 29 c) magnesium, commercial grade supplied by Timminco, Haley, Ontario . • V.4. APP ARATUS The experimental apparatus used to perform the reduction experiments is shawn in Figures 5.I.and 5.2. 1 Figure 5.1. Experimental cap assembly. 1 30 1 DRIVE CHAN STIRRING DRIVE , MOTOR SHAFT SUPPORT --. L--I+----'------,--t-----t--'" IMPELLER SHAFT • ARGON INLET EXHAUST GAS CRUCBLE CAP ... INDUCTION FURNACE-~~[')( IMPELLER ALU~A CRUCI3LE IMPELLER DRIVE & SUPPORT VEHlCLE Figure 5.2. Schematic of experimental apparatus used to perfonn the spodumene reduction experiments. 1 31 Below is a descnption of the eqUlpment used . Induction Furnace: • 100 kW, Bradley Controls: tilting capabilities, removable crucibles, gas ventilation. Crucible: Bonded alumma, 28.8 cm hlgh , 12.8 cm in diameter, supplied by Engineering Ceramics, GIlberts, IllInois. Impeller: For Experiments 1-3: stainless steel blades, Il. 8 cm blade to blade diameter, 1.0 cm blade thlckness, II cm blade helght, welded onto 1.90 cm diameter shaft. For experiments 4-8: high temperature refractory cement bonded onto stainless steel mesh remforced blades, 11 8 cm blade to blade diameter, 1 cm blade thlckness, Il cm blade helght WIth a 2.54 cm shaft diameter Impeller shaft: Machined ta 1.58 cm diameter at top to fit into brass connector. Experiments 1-3: 1.90 cm diameter 36 cm height. Experiments 4-8: 2.54 diameter, 36 cm helght. Brass Connector: Hexagonal shaped, 2.54 cm from edge to edge, 1.58 cm hole driHed in underslde to accommodate impeller shaft, three 0.635 cm threaded holes for screws to sec ure Impeller shaft, threaded at top to accommodate dri ve shaft. Impeller Drive and Support Vehicle: Movable in any direction, ralsmg and lowering of steel angles attached to shaft suppon, ball beanng attachment of drive shaft to shaft support, two levels of storage. 32 , Thermocouple: Handheld Omega type K thennocouple probe with 30.48 cm long, with 1 0.3175 cm tip diameter coated in clay protection. Motor: Tigear two speed motor, sprocket and chain system used to drive shaft at 36 or 60 rpm. Gas: Liquid Air prepurified 99.998% Ar gas. Less than 10 ppm water vapour, less than 10 ppm oxygen. Flowmeter: Flowrate controlled by Gilmont flowmeter, size no. four, with a ball diameter of 0.9525 cm, ball mass of 1.142 g and ball density of 2.53 g cm-3 Sarnpler: 1 Steel crucible, 1.4 cm outer diameter, 1 cm inner diameter, Steel wire, 0.1 cm diameter, spot welded onto crucible side for lowering into the melt through viewport. Crucible Cap: Mild steel, 17.1 cm in di arne ter, 1.2 cm thick, a groove machined into underside provided a fit between cap and crucible, two 1.59 cm holes drilled through cap, one for gas exhaust and other for viewport / temperature measurement / sampling, one 1.59 cm threaded hole for Ar gas intake, 1.905 cm copper tubing leadmg from gas exhaust to ventilation system, 0.635 cm copper tube 181d over and soldered to surface with connec tors leading to pye hoses for water intake and ourlet. Experiments 1-3: 1.90 cm hole drilled in center, Experiments 4-8: 2.54 cm hole drilled in center. • 33 V.S. EXPERIMENTAL PROCEDURE FOR SPODUMENE REDUCTION TESTS 1 V.S.1. PREPARATION OF EXPERIMENTS Pnor ta the reducuon expenmcnts the a -> P trcatment of the spodumene was perfomled. The a'l recelved a '>padumcnc was heated at 1050°C for three hours in the muftle furnace in fIreclay cruclbles slmllar to the ones used in the lime-~padumene te~ts. When li new cfllclble was u~cd in the reduction experiments, the crucible was mstalled sa that 1tS nm was paralIel to the ground. This was done to ensure that the Impeller entered the cruclble at an angle of 90°. The cruclble was sUITounded by caarse slhca partleles whlch provided packmg and insulauan. The ~lhca was covered with cement to cantalO It during the casting of the reductlon expcnment products A spout was molded from the cement to provlde a channel ta imprave pounng. Pnor ta a reducuan expenment, the lmpeller was coated wlth an alumina cement and allawed ta dry for 24 hours. After WhlCh, it was heated to 90 for 5 haurs ta ehmmate mOl sture In the alumina paint and to strengthen the' 1 bonding of the pall1t. V.S.2. EXPERIMENTAL PROCEDURE Chargmg consisted of placing piece~ of pure alummum into the crucible. The power was set at 35 kW. and melung, WhlCh varied with the shape of the aluminum pleces, due ta dlfferenr efficlencles m energy uuhzanon, took about nmety minutes. Once molten, the temperature of the aluminum rose very quickly. At a temperature of 90 wnh tongs. Black oxide beheved to magne~lUm oXlde was vbible on the surface of the alummum as dlS~alutlon was occumng. This oXlde formatIon decreased the efflclency of the experirnent~ a~ 1t con~umed magnesium. Followmg magneslum addItIon, p ~podumene wa~ added to the top of the melt. The Impeller and cap were then attached to the cart and moved mto place and the water coahng and argon gas tlow were connected The Impeller wa~ lowered ,,Jowly mtn the melt, by the manual WInch, to T prevent thennal ~hock As the Impeller was lowered, Il was turned slowly by 34 hand to ensure that no contact of impeller and the crucible wall occurred (Le .• that the impeller was centered properly). The immersion of the cold impeller extracted a great deal of heat from the liquid metaI. Once the • temperature again reached 900°C, stirring and argon gas flow began. This marked the starting point of the reductlOn experiments. Temperature measurements samphng were taken every 20 minutes for one hour. The temperature was held at 900 ± 20°C. During a temperature measurement, the ir..1peller was stopped, the temperature rneasurernent hole uncovered and thf: thermocouple probe inserted into the melt. Sampling was performed every twenty minutes or at every second temperature measurement. The sampler was lowered mto the melt through the temperature measurement/samphng hole to obtam the samples. Ninety minutes after the beginning of the experiments stirring was stopped and the impeller and cart apparatus were removed. The melt was allowed to cool to approxlmately 750°C pnor to pouring the entire contents of the cruclble mto a mold. Sorne molten, VISCOUS materiaI remained inside the crucible and was scraped out of the crucible mto the mold. A thin metai skin was removed from the Impeller after each experiment and added to the products. The removal of thiS meta! stnpped the alumina 1 paint and sorne cement from the Impeller. As a result the impeller was touched up with cement and repamted prior to an experiment. 35 V.6. EXPERIMENTAL PROGRAM " The experimental program consisted of eight experiments listed in Table 5.2. Table 5.2. SPODUMENE REDUCTION EXPERIMENTS PERi'ORMED EXP. REACTANTS (g) MOLES REACTANTS Mg/SPOD Al Mg SPOD AL Mg SPOD mole ratio 1 2340.5 97.6 365.7 86.7 4.1 0.98 4.2 2 2291.0 0.0 343.8 84.8 0.0 0.92 0.0 3 2355.8 104.0 369.0 87.2 4.3 0.99 4.3 4 2410.3 47.6 368.6 89.3 2.0 0.99 2.0 5 2439.8 143.3 370.2 90.3 6.0 1. 00 6.0 6 2220.0 191. 9 361. 8 82.2 8.0 0.97 8.2 7 2280.5 220.6 342.1 84.5 9.2 0.92 10.0 8 2269.8 224.8 348.4 84.1 9.4 0.94 10.0 l 36 VI. RESULTS VI.t. SPODUMENE TRANSITION The transfonnation of alpha to beta spodumene during the treatment resulted in a volume expansIOn. The crucible contents were loosely packed prior to the treatment but afterwards they were densely packed together. In sorne cases the pressure from the expansion was so great that the crucible cracked. The XRD patterns of the a. spodumene and of the transfonned material are compared with the patterns of a. and f3 spodumene in Figure 6.1. ,10.:": 5.00 4.00 3.1313 A 2.01.3 1.130 1 JlI ,II Il 1 1 1 II. 1 Il .1 Il 1 Il 1 20.13 413.0 6e.13 80.0 10e.e 1~~:~ 1 Il B ~::~ 1 1 20.0~~ __~I~I __~I~I~IWI~I~I~I~I~,,~,1~1,~I~L~, ~.~,~,I~,L'~I~I~I~i'~I--~'~, ----~'----~I 2e.13 60.13 80.13 100.0 0.813 c e.be 1).413 1) .20 1 l, 1 1 h'-' l ~ l "II 20.0 40.13 813.13 1130.13 20.13 40.13 00.13 813.13 1013.13 Figure 6.1. XRD patterns of the material received from Tanco(A), Cl • spodumene(B), the transformed material(C) and ~ spodumene(D) . 37 The difference in the patterns between the ex spodumene and tl}e transfonned material and the resemblance between the patterns of the transfonned material and ~ spodumene indicated a successful pretreatment. The cumulative size distnbution of the feed material was altered by the treatment as shown in Figure 6.2 and nùcrophotographs of (l and ~ spodumene are shown in Figure 6.3. , 1 • 1 1 1 ,1 1 1" 1 90 · __ .. -:-· .. · .. t- .. _..... ~_ .... _~ .. __ ..... t-· .. - .. __ .. ~ ...... _~ .. -.- ALPHA 1 • 1 1 1 1 1 t , , 1 1 1 • • 1 1 l' 1 80 -... _~.-.-! .. __ ... ~ .... _-~ .. __ ..... ! -..!.----~ .. _... _~-_ .... 1 1 1 1 1 • 1 1 BETA , 1 1 .' 1 1 1 1 • 1 1 1 • 1 1 1 1 1 70 ._-.-:-._ ..•. _-_.~. __ .. ~ .. _- , .... .;.-.. -~.- .. -~.- .. 1 1 1 1 1 • 1 1 1 1 1 1 1 • 1 1 t • 1 1 1 1 1 1 1 1 1 1 1 1 1 1 60 ·····:···-·t···--l-····~- -·-t-····:·····,·····~···· 1 • 1 1 1 • 1 • fil 1 1 • 1 1 1 • 1 f l " 1 50 -_ .. --:- .... _·t· __ .. _~·_- --_.~_ •• --:- ..... _~ ... _-~.- ... 1 1 1 l' J 1 1 • l , \ • • , 1 1 1 1 1 • 1 • • 1 1 • 1 1 1 1 40 ----i'" .. ·-i- ...... ~ ...... -! ...... -:-- ... -~ ...... ~ .. - .. .. lit • 1 1 1 • • 1 1 1 1 • 1 1 l' 1 1 • • 1 1 l ,1 1 1 1 30 .. __ .. -; ...... r.... ; ...... ·'· ...... _... r· ... ·· ... r- .. _... ~--·_·r .. --- 1 1 1 1 1 1 1 fil 1 t 1 1 20 .....: ... ' ..•. ~-···~·····i·····:·····~·····~···· 1 1 1 1 • 1 • 1 1 1 l' , 1 1 1 l' 1 1 1 1 l' 1 10 .--- ·-··t .. ·_ .. ·~·· .. ·~· __ ··!····-:--··_~····_~·-·· lit , 1 1 1 l , 1 1 1 1 l '1 1 lit 1 0~-.~3~8~~+~5~8.~7=5~+~1~0~6.~1~50~+~2~1*?·~3~00~~ +38-58 +75-106 + 150-212 +300 SIZE FRACTION (MICROMETERS) Figure 6.2. The cumulative size distribution of the received alpha spodumene and of the transformed material. Although the sPodumene expanded during the rreatment, the fifty percent passing size of the transfonned material was finer due to cracking and subsequent breaking of the particles during the ex to ~ conversion. Sixteen point two percent of the ~ spodumene compared to only 10.8% of the (l spodumene was finer than the smallest size fraction, ·38 mIcrons. J 38 t Microphotographs of the as received (above left) and transformed spodumene. The a to ~ conversion altered the crystal structure of the material and the forcEs mvoived were great enough to cause cracks in the particles. VI.2. VISUAL OBSERVATIONS OF REDUCTION PRODUCTS Five different materials were identified at the end of an experiment. They were: ~a white condensate -a very fine black dust -a powder residue -a dross -a metai ingot. The material scraped out of the crucible at the end of an experiment and the metal skin on the impeller were included in the dross. Photographs of the products are shown in Figures 6.4 to 6.10. The masses of each of the products and the total mass recovered compared to the initial mass of reactants is presented in Table 6.1. 39 Table 6.1. PRODUCTS OF SPODUMENE REDUCTION EXPER~S PROOUCT MASS (g) REACTANT 1 EXP MASS (g) METAL POWDER FINE INGOT DROSS RESIDUE CONO. POWDER TOTAL 'lIDIFF 1 2803.8 881. 0 1336.3 415 A 1.12 3.00 2264.2 -19.0 2 2634.8 2062.5 90.4 415.9 0.00 0.00 2568.8 -2.5 3 2828.8 2099.1 157.9 477.1 1. 03 1. 05 2735.1 -3.3 4 2826.5 2098.1 133.7 433.8 0.00 Il. 80 2665.9 -5.7 5 2953.3 2110.1 225.0 455.7 0.35 5.93 2791 .1 -5.5 6 2782.7 2056.1 1/8.3 389.3 0.47 20.22 2624 .2 -5.4 7 2843.2 2299.7 117.1 361. 6 1. 35 4.82 2779.8 -2.2 8 2843.0 2201 0 160.9 467.2 0.08 8.28 2828.2 -0.5 The products were complex and the mass balance was complicated by material losses such as particle emissions from the crucible and adherence to the crucible walls. The % difference of input versus output masses, calculated as, (6.1) had an average value of -5.5% that was considered acceptable and indicates that by and large most of the reaction products were collected. Dunng the experiments, a white plume was eVldent emerging from the exhaust tube of the reactor. Numerous attempts were made to photograph this vapour, but were unsuccessful. Sorne vapour dId condense on the underslde of the cap and In the exhaust tubes, as shown In FIgure 6.4. The condensate's fineness, -75 microns, gave It a soft texture. Conden~ate was collected for each experiment by scrapmg the underslde of the cap and the mside of the tubes. No condensate was observed for Expenment 2, In which no magnesium was used. 40 • 1 Ftgure 6.4. Condensate • 41 1 Figure 6.5. Fme Black Powder A fine black powder, -75 mIcrons, wa~ produced during the reaction and portions were carrieà into the exhaust tubes by the argon flushing gas where it settled in the hOrIzontal portion of the tube. Dunng temperature measurements and visuai observatlons of the meh, ga~ e~çaped the reactor from the temperature measurement port and carned ~ome fine powder wuh it. The flts between the cap and cruclblc and betwcen the Impeller ~haft and cap were not hermetic, thus pen1llttmg the e~capç of the flue powder. FIgure 6.6 illustrates flue powder losses around the reactor. Varytng amounts of flue powder were collected from each expenment but the quanl1ues lost, prevented accurate determmallon of the total amount produced. -l2 • FIgure 6.6a, 6.6b. Fine black powder lost during an expenment The amount of fine black powder lost varied among tests. It was carried out of the reactor and onto the cap or furnace. FIgure 6.6a shows the losses around the crucible. FIgure 6.6b shows the losses on the cap. During temperature measurements particles would spout out of the reactor and onto the cap surface. These particles consisted mostly of fine powders but occasionally sorne small droplets of molten metal would emerge. The above examples represented expenments wlth extreme loses of fine black powder. t 43 • J Figure 6.7. Powder Residue The powder resldue contained unreacted 'ipodumene. sohd reactlon products of the reductIon. bits of impeller and n1JlllHe piCceS of alummum separated from the mam body of lIqUld mctal After the expenments, It was floatinglresting on the melt surface. It wa'i :--eparaled from the other products after the enure contents of the reactor wcre poun~d out lOto a mold. In the above FIgure of the powder rC'>ldue from Expenment 3, one can see whIte, unreacted spodumene particlcs, powdcr agglomerate~. brown powder a5sumed ta be a reaction product, and pICCC'l of metal. The powder resldue was a mélange of matenals of many dlffcrent "Ize'). ! 44 • :1 Figure 6.8. Dross The dross recovered was present on the rnelt surface and possibly along the crucible walls. It was cornposed of irregularly shaped rnetaI clumps with highly oXldized surfaces. Sorne dross had cavlties containing powder residue. AlI the dross had sorne powder attached to Its rough surface. Any powder that was shaken off the dross was added to the powder resldue but sorne rernamed in cavlties, as mclusions, or embedded m the surface. As shown ln Table 6.1, the masses of the dross vaned only slightly, except for Experiment 1, where 1338.3 g was formed as a result of impeller problems in that experirnent. , 45 • ------• Figure 6.9. Metal Ingot The metal ingot was the large~t contnbutor te the total mass of the products, except ln Expenment 1 A small arnount of powdcr resldue and sIllca Induction furnace packmg, which spllled dunng pouring, wa~ cmbedded into the lngot'~ ~urface. The tngot from Expenmcnt 2, ln WhlCh no magne'ilUm was added, was ~hiny. For expcnmcnt~ whcrc more magnesium was added, the ~urface of the Ingot wa~ dullcd due tu Incn;a~cd oXldatIon The above mgots were From Expenment 3 on the left and Expenmcnt 2 on the nght. The ingots were 2R cm long and 8 cm wlde. 1 46 • .~ ...r . • J ...... iI Figurt" 6 10. Marena] stuck to inside of the cruclble after an experiment Ar rhe end of each ex periment, a layer of material was attached to the wner surtac..:e of the crucible as shown m Figure 6.10. ft was impossible to remove lhls layer Slnce a new cruclble was not used for each experiment the buildup pre!>cnt after an expenmenr vaned. Figure 6.10 shows rhe buildup after Expenmcnts 7 and 8 VI.3. XRD ANAL YSIS OF REDUCTION PRODUCTS X Ray Diffraction (XRD) analysis of the non-metallic samples was perfonned to detennine the materials pre!>ent In these samples. The XRD analy!>is system was the same as was uscd for the the lime - spodumene experiments AIl the specles which were matchcd by the Philhps !>ystem are listed by name, compound formula and Idenntïcation number. Those that "scored high enough" ta be positively Identifïed by the analyzing software are noted by an a<;rensk * The powder resldue was analyzed and the followmg specles were identified: 1 47 Experiment 1: synthe tic spinel *, MgAl 0 (21-1152), silicon • (5-565), silicon z 4 (27-1042), aluminum (4-787), low quartz (33-1161), and synthellC iron (6·696). Experiment 2: spodumene * , LIAlSi 0 (35·797), aluminum (4-787), lithium 2 6 alumIno sIlicate, LIAI(SIO)z (31-706), and synthetic iron (6-696). Experiment 3: silicon * (5-565), :'Ihcon (27-1042), alummum (4-787), and synthetic spinel *,MgAI 0 (21-1152). 2 4 ?xperiment 4: spodumene * (35-797), lithium alumIno ~Ïiicate (35-794), LiAISI 0 g, FeAl ° (35-794), Mg~AI 0 (33-853), alummum 3 2 4 * ~ 2 4 (4-787), syntheuc spmel , MgAl 0 (21-1152), lithium alumino 2 4 silicate, LIA1(SiO )2 (31-706), ~yntheuc Iron (6-696). J Expenment 6: alummum * (4-787), synthe tiC penclase * , MgO(4-829), sIlIcon (5-565), slhcon *(27-1032), synthetlc Iron (6-696), lithium alummo silicate, LiAl(SiO) (31-706), synthetic spinel, 3 2 MgAl 0 (21-1152), spodumene (35-797) 1 2 4 Experiment 7: spodumene *(35-797), ~llicon (5-565), sIlicon (27-1042), aluminum (4-787), syntheuc penclase, MgO (4-829), synthetic Iron, (6-696), lithium alummo sIlicate, LiAI(Si0 )3 (31-706). 2 Expenment 8: The powder resldue greater [han 20 Mesh; ~Ilicon (5-565), silicon (27-1042), synthe tIC spmel *. MgAIO (21-1152), '" 2 4 synthetic penclase , MgO (4-X29) and aluminum (4-787). Powder resldue les~ th?.n 65 Mesh; silicon (5-565), ~lhcon (27-1042), The black powder wa~ analyzed for certam expenments and the following specles were Idenllfied. Expenment 4: aluminum * (4-787), ~Ihcon * (5-565), silicon (27-1042), "ynthetlc Iron (6-696). Experiment 5: aluminum * (4-787), sllicor, ( 5-565), silicon * (27-1042), synthetic spinel * . MgAl 0 4 (21-1152) and synthetic iron (6-696) 2 Experiment 6: synthe tic periclase *, MgO( 4-829), hercynite *,FeAl 0 (34-192). 2 4 The condensate was analyzed for Experiment 7 and the following species were Identified: syntheuc periclase *, MgO(4-829), aluminum (4-787), synthetic ITon, (6-696), The detection of the synthetic iron ln man y of the samples was caused by the iron backed sample holder WhlCh was lItiIized in the XRD apparatus. The detection of hercynite 10 th"! Expenment 6 black powder was due to It being an iron spinel and havmg a slmilar pattern to other species present. The XRD analysls showed that the powder resldue was a complex material. Il was composed of aluminum, spmel, slhcon, spodumene, lithIUm alumino silicates and pendase The flue powder was composed of aluminum, silicon and spinel. AIl these constituents were present In the powder resldue and may have been a part of the fme slzed pomon of the powder resldue, which was physlcally transported From the reaetor by gases The condensate was formed by the condensatIon and subsequent oXldation of magnesium. Some alumInum was det~cted but due to aluminum's low vapour pressure at 1173 K, 10- 10 Atm, it was unhkely that aluminum vapourized and condensed. VI.4. ATOMIC ABSORPTION ANAL YSIS Atomic Absorptlcln (A.A.) was the method of analysls used to perform numerous chemical assays ior sIlicon, magne~illm, and lithium. It is the most common and versatlle of the analytlcal methods for metaIs. It is a sensitIve analyucal method and elements WhlCh have enhancement or depression effects must be known Other factors WhlCh may ~ause ~punous results are dlfferences In the composItIon betwcen ~[andard~ and samples, known as matrix effects. As weIl, the VlSCO::,Ity of the so!u[Ion WIll affect the reading as it affects the aSplratlOn rate of the tlame_ \Vith the knowledge of the A.A. 1 charactensttcs for each element, one can dCCloe how to prepare standard and 49 sample solutions to obtam the best results. A technique u~ed to counter inecrferenccs from the elements in solution is ma~KJng the sample ~olu!Ions by the standard solutions. An example of masking l~ as follow~ A )olutJOn be1l1g .tnalY7ed for clement A contamed b amounts of element B known to affect the ab,>orbance of clement A. To ensure th:n accur dte re~ult~ were obtaIned, Ihe ~tandard~ were made ~o that they contaIned b amoune) of B a') weIl. ThiS wOllld "l11a~k" the pre~ence of element B In the ~olutIon and mInIn1lZe m effert on the raJculated concentratIon of A Ali reaCHon r/roducts of the reductlon expenments were analyzed for lithium. Analysl~ ù)r magne!->lUm and SIlIcon was done whenever It was thought necessary. VI.4.1. SAMPLING FOR ATOMIC ABSORPTION ANALYSIS The folloWIng :-.amphng method wa~ med to ohtaIn Ingot samples: Drilhngs were made at vanou:-. location,> on the mgot at vanous depths. The ~havmgs were mlxed together to accumulate a one gram sample. This was done to aVOId :-.egregatIon. For the dro<;~ ~amples. ~mall blt~ were eut off variou!> dro!>s c1umps to form a one gram ~ample. A representatlve ,>ample of the powder re!->idue wa!-> ohtained by separating the powder into observable groups by hand such as fu~ed or ~intered powders, Impeller bas and the rest, mas~Ing each part and then addltlg each component according to ItS mass fraction. The ~dmpling method for the flue powder and condemate was collection by ",craping or bru~hIng from thelr respectIve ~ource~. VI.4.2. ATOMIC ABSORPTION ANAL YTICAL METHODS Dross and Ingot Assays: One gram sample~ of Ingot and dro..,s '>.lmple') were dl,>~olved 1!1 a 40 ml aqua regla ~olutlon contaInIng 10 ml mtne aCld and 30 ml hydrochlonc acid. Ten mlliihter!-> of water wa~ added to the bcaker pnor to contactmg , the ~amples with the aCld In order le,>,>cn the VIOlence of the reacuon between ~ample~ and aCld The rcaCl10n hetween magne"'lum and hydrochloric 50 acid was extremely explosive. The acids were also added in stages as a precautionary procedure. The liquor was diluted to 250 ml with distilled • l water. For lithium analysis, the solutions were further diluted four times so that the solutions contained, Ig / 250 ml x 0.25 = O.lg / 100 ml (62) of sample, which can be converted to ppm by the following equation; 1 ppm = 0.001 g / 1000 ml [6.3J Therefore the solutions contained 1000 ppm of sample; the majority being aluminum. 42 For hthlUm analysls, aluminum causes depresslOn of the absorbancé ). Standards were made to mask the solutions sa that they contamed 1000 ppm aluminum as weIl. Another element present in large quantities was magnesium, which has no effect on lithium readings(43). SIlIcon was another element present 10 the Ingot and it tao has no effeet on lithium readings(43). The A.A. machme settmgs for ltthium are shown in Table 6.2. These settings were aiso used for the lithIUm analysis of the other experimental products. Table 6.2. SETTINGS FOR Li A.A. ANALYSIS PARAMETER SETTING CURRENT 8 mA VOLTAGE 460 V BANDWIDTH 0.5 nm WAVELENGTH 670.8 nm BURNER air-acetylene For magnesium analysis. the liquors produced for the lithium analysis were used as the stock solution and dlluted 100 times, which resulted in a background concentration of 10 ppm aluminum. Magnesium readings are 1 sensitive to depresslon effects by lithium, Silicon and aluminum. As weIl, 51 the acids used for dissolution have a large effect on the A.A. readings. The concentrations of the other elements were estimated and masking of the 1 solution by standards was attempted. The absorbance readings of the masked magnesium standards were erratIc and a proper calibration curve cOlild not be obtained. Thus masking was llllsuccessful. A dlfferent technique was utilized. A chemlcal agent, strontlum mtrate, was added at concentrations of 2000 ppm to the solutIons and standards for the purpose of canceling the effects of other the dlssolved elements(4Jl Thl~ was found to be successful. The analyucal parameters for the magne~lUrn analysls are shown In Table 6.3 Table 6.3. SETTINGS FOR Mg A.A. ANALYSIS P ARAMET ER VALUE CURRENT 4mA VOLTAGE 530 V BANDWIDTH 1 mn WAVELENGTH 285.2 nm BURNER air-acetylene 1 Silicon does not dissolve in aqua regla, th us new ingot and dross samples were dissolved 10 the following manner: A one-tenth of a gram samples from dnll shavmgs were added to polyethylene beakers contaming 10 ml of water and 15 ml of hydrochloric aCld. Flfteen mIihhters of hydrogen peroxlde were then added in small portions. After coohng, two milhliters of hydrofluonc aCld were ddded. The hqllor was fIltered and diluted to 100 ml with dlsullcd waler. The background concentration was; D.lg / 100 ml = 1000 ppm [64) Aluminum depresses the silicon readIngs as lt does lithium readings and the ~ame maskmg strategy used for the lIthium analysis was employed for the sihcon analysis. The A.A. settii1gs for the SIlicon analysls are shown in , Table 6.4. 52 Table 6.4. SETTINGS FOR Si A.A. ANALYSIS 1 PARAMETER VALUE CURRENT 12 mA VOLTAGE 530 V BANDWIDTH 0.32 nro WAVELENGTH 25L 6 nro BURNER air-nitrous oxide Condensate Assays: The condensate was analyzed quantitauvely by atomic absorption. An amount of approxlmately one gram was dlssolved in 15 ml of slightly heated mtrie acid. The condensate absorbance was compared to lithium standards. The standards contamed no magneslUm, SInce lt has a neglible effect on lIthium absorption as mentioned earlier. Black Powder Assays: 1 About one gram of black powder was dissolved into an aqua regia solution containing 5 ml HN0 and 15 ml HCl. Afterwards it was analyzed for 3 lithium and compared with pure lithium standards. A black residue remained. Powder Resldue Assays: The preferred method of analysls for oXlde powders is X-Ray Fluorescence (XRF) ThIs lS a x-ray spectrographic method. The sample is heated so that excitation of the atoms occur X-ray photons are emItted with an energy proportlonal to the utomie number Z of the element, detected and counted to determine the chemical composItion of the sample. However, lithIUm can not be analyzed for because its x-rays are too low 10 energy to pass through the berylhum wlOdC'w used between the chamber and the x-ray netec.tor. In XRF a platlOum cruClble is used to contain the sample. 'l'he powder residue contamed pure sl11con and pure aluminum WhlCh would react with and destroy a platmum cruclble. Therefore XRF was ehmlOated as an analytieal method and 1 A.A. was used ta assay the powders. 53 The resldue samples were sent to Tanco where they were analyzed for lithium, sodium, potassium, and aluminum. The liquors were sent back to McGill te be analyzed for silicon and magneslUm. For magnesium analysis, the liquors were diluted by 100 times and strontium nitrate was added to cancel effects of other elements. Analysis of the Tanco IIquor for sIlicon was impossIble due to the method used to the prepare the liquor. Thus, silicon analysls of the powder resldue was performed at MCGll1. A one gram sample of powder resldue was added to a polyethylene beaker. One hundred and fIfty mIllilItres of hydrochlonc acid and 50 ml of nitric acid were added to H. After the reacuon subslded, 30 ml of hydrofloric aCld was added to the solutIon. The beaker was heated to 90°C h~· placing it a water filled metal tray, heated by a hot plate. After reactIon ceased, the solution was cooled to 1000 ml and the volume was made up Wlth the addition of dlstIlled water The samples were compared against standards containing 40 ppm aluminum. VI.4.3. ATOMIC ABSORPTION RESUL TS T An example of data generated from a set of lithium standards with 1000 ppm aluminum is given in Table 6.5. The error was calculated as the standard devIation of the absorbançe re~dIngs and IS aiso shown in Taule 6.5. [65J 54 Table 6.5. A.A. RAW DATA FOR A SET Oi' Li STANDARDS AND INGOT ASSAYS 1 STANDARD ABSORBANCE (x) MEAN (x) ERROR (s) ppm Li 0.5 0.074 0.087 0.088 0.083 0.008 1.0 0.146 0.157 0.162 0.155 0.008 2.0 0.268 0.291 0.296 0.285 0.015 3.0 0.421 0.428 0.436 0.428 0.008 4.0 0.559 0.577 0.568 0.013 INGOT SAMPLE 1 0.167 0.232 0.240 0.213 0.040 2 0.002 0.003 0.003 0.003 0.001 3 0.073 0.070 0.072 0.218 0.002 4 0.217 0.221 0.217 O. 072 0.002 5 0.291 0.302 0.311 0.301 0.010 6 0.395 0.406 0.404 0.402 0.006 7 0.403 0.406 0.409 o .406 0.003 8 0.382 0.407 0.418 0.402 0.018 From the absorbance data the concentration and errors of the solutions 1 and samples were determ10ed utiliz10g the method outlined 10 the examplecalculauons in Chapter VII. The calculated weight perce - and the correspondmg relative errors of the products analyzed for are presented in Tables 6.6 - 6.10. The relative errors, L\C, are dlscussed 10 Section V iII.2 3. Table 6.6. ASSAYS OF CONDENSATE (WEIGHT~) Mg: SPOD MASS C fJ.c EXP Li L~ RATIO (g) (Wt%) 1 4.2 l.12 0.42 0.033 2 o .0 0.00 - - 3 4.3 1. 03 0.57 0.053 4 2.0 0.00 0.55 0.023 5 6.0 0.35 0.94 0.045 6 8.2 0.47 0.68 0.056 7 10.0 1.35 0.26 0.006 • 8 10.0 'L 08 0.20 O. 007 55 • Table 6.7. ASSAYS OF FLUE POWDER (WEIGHT %) Mg :SPOD MASS C 6c c I1C EXP ;.., l. Ll Mg Mg RATIO (g) (Wt%) (Wt%) 1 4.2 3.00 2 0.0 0.00 3 4.3 1. 05 4 2.0 11. 80 1.27 0.050 20.11 0.024 5 6.0 5.93 1.18 0.056 24.40 0.031 6 8.2 20.22 1.22 0.042 33.10 0.026 7 10.0 4.82 1.22 0.059 39.97 0.028 8 10.0 8.28 1. 12 0.034 35.45 0.028 Table 6.8. ASSAYS OF POWOER RESIDUE (WIGHT %) EXP Mg:SPOD MAS.s C C C C C 6C c 6C Ll A_ < 20 Na20 5 l Si Mg Mg RATIO (g) 1 (Wt%) (WU) 1 4.2 415.8 1. 56 33.2 0.08 0.18 8.48 1. 52 16.90 6.140 2 0.0 415.9 2.53 31. 6 0.11 0.21 15.28 1. 69 - - 3 4.3 477.1 1. 24 38.1 0.07 0.12 4.73 0.50 13 .26 1.260 4 2.0 433.8 1. 89 33.6 0.09 0.16 12.47 2.25 9.08 6.140 5 6.0 455.7 1. 07 45.7 0.10 0.13 4.88 0.59 16.84 1. 410 6 8 2 389.3 1. 06 37 2 0.09 0.16 7.28 0.80 20.00 1. 410 7 10.0 361.6 1. 08 32.7 0.11 0.30 9.36 0.76 122.20 - 8 10.0 467.2 0.83 41 2 0.08 0.12 6.41 0.57 19.48 1.260 1 56 Table 6.9. ASSAYS OF INGOT (WRIGHT %) EXP Mg: SPOD MASS C IJ.C C IJ.C C t:.C Li Li Mg Mg Si Si RATIO (g) 1 (Wt%) (Wt%) (Wt%) 1 4.2 881. 0 0.15 0.034 1 .39 0.159 3.31 0.59 2 0.0 2062.5 0.02 - - 2.72 0.34 3 4.3 2099.1 0.15 0.008 1 .50 0.220 3.82 0.60 4 2.0 2098.1 0.05 0.008 0 .51 0.178 1.54 0.43 5 6.0 2110.1 0.21 0.013 1 .57 0.164 2.32 0.16 6 8.2 2056.1 0.28 O. 011 4 .71 0.262 3.74 0.75 7 10.0 2299.7 0.29 0.008 4 .69 0.187 3.37 0.47 8 10.0 220l. 0 0.28 0.019 3 .84 0.201 3.03 0.54 Table 6.10. ASSAYS OF DROSS (WRIGHT %) EXP Mg:SPOD MASS C b.C C t:.C C IJ.C Li Li Mg Mg Si Si RATIO (g) (Wt%) (Wt%) (Wt%) 1 4.2 1336.3 0.12 0.007 1. 26 - 2.42 0.37 2 0.0 90.4 0.01 0.001 - - 1. 63 0.24 1 3 4.3 157.9 0.17 0.011 2.05 0.438 2.36 0.26 4 2.0 133.7 0.19 0.007 1.11 0.469 1. 93 0.33 5 6.0 225.0 0.24 0.001 2.59 0.800 1. 75 0.37 2.27 6 1 8.2 178.3 0.34 0.027 4.90 0.706 0.32 7 10.0 117.1 0.39 0.037 6.60 0.541 2.68 0.49 8 10.0 160.9 0.34 0.012 6.81 0.823 6.39 0.85 Table 6. 11. LITHIUM ASSAYS FROM KINETIC SAMPLES EXP Mg: SPOD Li ASSAY IN SAMPLE (Wt%) RATIO :::0 MIN 40 MIN 60 MIN 4 2.0 0.05 0.09 0.04 5 6.0 0.14 - 0.22 6 8.2 0.21 0.29 0.31 8 10.0 0.25 0.26 0.30 1 57 VI.S. SCANNING ELECTRON MICROSCOPE ANALYSIS • A JEOL JSM-T300 scanmng electron t1ucroscope (SEM) was used to analyze the powder resldue The goal of the SEvI cxamwatIon of the powder resldue was to locate eVldence of reacnon and the man 11er by WhlCh reacuon occurred between the spodumelle and molten reductant. Samples for SEM analysis were made by impregnating a re~l/l wlth the powder resldl!e and then aIlowmg the resm to set The reSll1 was pohshed on a 0.3 mIcron alumma wheel wlth the aim of exposmg a cros~-~ectIon of a reacted spodumene parucle. Prior to the SEM analysls, the sample was carbon coated ta aVOld electrical charging in the samplc chamba The SEM IS capü.ble of performmg chemlcal analysls in a manner similar ta the XRF umt descnbed m SectIon VI.4.2. The SEM analysis system has two major drawbacks concernmg the analysls of the powder residuc: 1) A berylhum wmdow IS used betweer the sample chamber and the x-ray detector and as a result lithium and oxygen can not be analyzed for because thelr charactensnc x-rays do not possess the energy to pass through the wmdow. 1 2) Wnhout oxygen detectlon, the analysls could not distll1gUlsh between pure metals and their oXldes, WhlCh would make the results s.peculative. Therefore, analysis results from the SEM were used quahtauvely and not quantltanvely. The SEM analysls used wa~ the SQ program of [he Tracor Northern(44) TN-5400 software analysls system. Figure 6.11 shows a reduced spodumene partlcle observed in the resiàue from Expenment 5 at an acceleratmg voltage of 10 kIlovolts. The pamcle was charactenzed by large and small cracks aIl over Hs surface and sorne of these cracks were contamed wIthm the outer edges of the particle. It~ chemlcal assay is shown in Table 6.12. , 58 F 1 n Inn U IUU Figure 6.11. SEM microphotograph of particle ln the powder residue. Magruficauon equals 2000x. 1 Table 6.12. SEM ASSAY 01' PARTICLI IN l'IGURE 6.12, WZIGHT% Si Mg Al 28.6 11.7 59.8 spodumene. The panicle showed no eVldence of the eXl~tence of a boundary layer between spodumene and molten reductant or a deposited reacùon product. This finding nu~es q uest10ns concerning the reaction mechanism which occllrred which are dealt with ln the discussion. 1 59 VII. EXAMPLE CALCULATIONS e VB.I. DETERMINING SAMPLE CONCENTRATIONS FROM ABSORBANCE READINGS Lotus 123(45) was used to perfonn a hnear regresslOn belween the concentration of the standard sr1utlons (X) and the corresponding absorbance readIng (Y). The regresslon output from the data of the standard solutions ln Table 6.5 IS shown In Table 7.1. Table 7. 1. RESULTS OF LlNEAR REGRESSION SLOPE (ml 0 .143 INTERCEPT (b) 0.0 R SQUARED 0.998 STANDARD ERROR OF SLOPE (Am) 0.002 STANDARD ERFOR OF y ESTlMATE (âY) 0.009 The regression !ine was forced through zero, the absorbance of a distilled 1 water solution. The value for r squared obtamed, 0.998, revealed an excellent fit of the data to the linear regresslOn. The standard error in the Y estimate is the standard error of the regresslon and was used to detennine the analytlcal error. A calIbratIon curve, EquatIon 7.1, was constructed from the regression results. The purpose of the cahbration curve IS to define a relatIonship between the absorbance readings of a species in solunon and the concentration of that species in solurion. Y=mX+b (71) where, y is the absorbance, counts m the slope of the regression line, counts.ppm·! X the concentration, ppm , b the intercept = O. 60 The concentration of the sample solutions was determined by moclifying Equation 7.1, 50 that, • x = Y/m (7.2) To calculate the sample assays from the measured A.A. concentrations, a series of calculatlOns were required, as shown below for the lithium concentratIOn in the ingot from Expenment 3. For the ingot in Expenment 3 the absorbance was 0.219, thus the lithium concentration of the solution was equal to, llsmg eqllation 7.2, 0.219 / 0.143 = 1.53 ppm or l.53 mg LI/lItre. (73) The solution was dlluted by a factor of four, therefore the original concentration of the liquor was, 4 x 1.53 mg Li / 1 = 6.12 mg Li / 1 (74) , the original solution' s volume was 250 ml, therefore if contained, 0.25 1 x 6.12 mg Li 1 1 = 1.53 mg Li (7 S) The solution was obtained by dissolving 1000 mg sample, therefore the lithium concentration of the onginal sample was, 1.53 mg Li / 1000 mg sample x 100 % = 0.153 wt % Li (761 VII.2. EXAMPLE CALCULATIONS OF ANALYTICAL ERROR Two factors contributed to the error of the sample assays: the error in the regression and the error from the absorbance readmgs. In the Lotu~ output, the error ln the regression curve is given as the standard error of the Y estimate, WhlCh was, for the Lotus output from Table 6.5, 0.009 umts of absorbance. ThIS can be converted to an error in concentratIOn by the folluwing equatlon, 1 61 [ !Y 1 [7.7) 1 where, .1C is the error in concentration due to the error in the Regression REG curve. S y is the standard error of the Y estImate from the regression. m is the slope of the calibration curve obtained from the regression. For the present example, l.e., the LI as say of the mgot in Experiment 3, the error m the lIthIum concentration from the regression curve was 0.0063 ppm. To determIne the error due to the sample absorbance readings, the error in the absorbance readmgs, calculated using Equatlon 6.6, replaces the error in the Y r-stimate In Equation 7.7. For Expenment 3, the ::-,tandard deviation of the readings was 0.002. This corresponded ta a concentratlon error of 0.014 ppm. The total error ln concentratIon, ~C, for the ingot sample in Experiment J 3 would then be, .1C = .1C + .1C A A.= 0.0063 + 0.00 14 = 0.0077 ppm Li [7.8) REG where.1C is the error In concentration fonn the regression and ~C is ~G AA the error in concentratlon of the absorbance readmgs. Replacmg the concentratIon of lithIUm In the onginal liquor, with the concentratlon error, .1C, calculated In Equation 7.4 and following Equations 7.5 and 7.6, the error ln weight % was calculated and found to be 0.008 wt %. This represents a relative error of, 0.008 [7.9) x 100 % = 5.28 % 0.153 in the lithium reading in the ingot from Experiment 3. The error incurred by mass and volume measurements was considered to be too small to have an effect on the weight % error. 1 62 VIII. DISCUSSION t Vill.l. INTRODUCTION The goals of the discussIOn are: 1) to crItique the experimental program, expenmental error and analytical errors encountered. 2) to examine the quanutatIve and qualitative results from the experiments and explalO their significance in terrns of the physical phenomena occumng ln the system. 3) to compare the quantitatIve results WIth those predicted thermodynamically. VIII.2.1. DISCUSSION OF PRESENT EXPERIMENTAL PROGRAM The goal of the experimental program was to de termine the effect of magnesium addItion on the lithium extraction from spodumene. This goal was achieved sausÎactonly but thL largest amount of magneslUm added, corresponding to a magneslUm to spodumene molar ratio of 10.1, was chosen 1 arbnrarily Thermodynamlc analysis showed that increased magneslUffi addition past a molar rauo of ten further mcreased lithtum extractIOn. Therefore tests at greater magneslUm concentrations could be useful. VIII.2.2. DISCUSSl..ON OF EXPERIMENTAL PROCEDURE Various expenmental errors were incurred dunng the study. They are brought to hght and thelr Impact on the findmgs are discussed in this section. The order and method In which the rcactants were charged was detenmned by the experimental apparatus. The Impe 11er could anly be inserted into the reactor when the metal reductant was malten and the cruclble cap could only be placed after the Impeller was inserted. Therefore, the melting of the reductant alloy was perforrned 10 mr and sorne oxidation of magneslUm and alummum accurred. A better method of commencmg t;te expenment would have been to heat aU three charge matenals sImultaneously. This could only be done ln a reactor wah the proper desIgn. , Temperature control was an important experirnental par1ITIeter in this 63 study. Later in this chapter, Figure 8.12 predicts the theoretiCal effect of temperature on lithium extractIon. The precIsion of ± 20°C would have affected the recovery but the temperature tluctuatlon abcve and below 90(tC would decrease the net effect on recovery White vapours were observed leavIng the apparatus which must have contaIncd ~ome hthlulTl SInce lIthIum was detected in the condensate. This lost hthlUm would not have been accounted for 10 a mass balance. A condensmg ,Ipparatm that collected ail of the vapours would have improved the InvestIgatlon on the condensate and retneved more lIthIUm. The separatIon of the powder resldue from the 1I1got, would have been improved upon If the powders were sklmmed or scraped from the metal surface prior to pounng the mgot TI1ls would have resulted 111 more homogeneous dross, Ingot and rC:'ldue ~amples. The atmosphere In the reaetor was argon. Usmg a noble gas was essentlal to the Sllccess of the experiments due to the highly oXldizing nature of alumInum, magne:'lUm and hthium The ~eal of the reacter Wlth the outslde atmosphere was not perfect and dunng temperature measurements, plugs were removed from the cruclble cap. The argon tlushmg gas created il positive pressure IOslde the reactor preventing atmospheric f 1 gases form entenng the system and oxidlzing the melt during 5ampling * and temperature measurements. In the present ~tlldy, there 15 ample eVldence that reduction of the spodumene by the mollen reductant occurred. A questIon which then arises IS why were the Impe 11er, whose surface was an alumma pamt, and the crucible, a ceramlC made from a slllÇa - alumma combmauon, not reduced. An explanation IS that oXlde formaLlOn OCCI .Ted at the Interface between the excess metal reductant and these objects. ThIS oxide would achleve a thickness whlch would prevent attack of the cruclble or Impeller. VIII.2.3. DISCUSSION OF ANALYTICAL ERROR VIII.2.3.1. RELATIVE ERRORS OF SAMPLE ASSAYS As mentioned earlier, the error In the alomlC absorption analysis arose from the eITors in the regresslOn curve and absorptIon readmgs. In this .. section, the error from each source IS analyzed ~eparately to see if any trends eXlSt. 64 The average relative errors of the sample concentrations from the regression and from the absorption readings are listed in Table 8.1. Table 8. 1 . AVERAGE RELATIVE ERRORS IN SAMPLE CONCENTRATIONS SAMPLE REGRESSION ERROR(%) ABSORBANCE ERROR(%) Li Mg Si Li Mg Si DROSS 3.4 7.6 4.5 3.8 5.3 8.2 RESIDUE - B.O 7.8 - 1.9 4.2 INGOT 4.3 7.2 7.2 4.6 1.7 13.5 BLACK POWDER 2.6 7.4 - 1.2 1.0 - CONDENSATE 1.3 - - 1.5 -- AVERAGE(%) 3.4 7.5 6.5 2.8 2.5 8.7 Table 8.1 shows that not aU elements are slmllar in therr A.A. characteristtcs in terms of regression and absorbance variance. Lithium was the bes[ element for regresSlOn analySlS. Its average relative error was 3.4%. Next best was silicon wnh an average relauve error of 6.5%. MagnesIUm analysls produced the worst regresslon having a relative error of 75%. The error arismg from the vanance of the absorbance readings was affected by the dnft in the absorbance readmgs over a period of time for a senes of readmgs. For ex ample, an absorbance reading for a sample solution and was IdentIcal to the absorbance for a standard solullon containing 1 ppm. After other solutions were analyzed the absorb:mce was retaken for the se two solutIOns. The rearlmgs were identlcal agam, but were 10% less than obtall.ed before. The precislOn of the machine has not changed but the vanance of the solutIOn readmgs has Increased. Thus the errors calculated due tG the VarIance of the absorbance are arufIcially high, as they do not compemate for the machme dnft The amount of dnftmg WhiCh occurred for each element varied. Silicon had severe driftmg, causmg an average relative error of 8.7%. As a result of the large absorbance dnft when analyzmg for SIlicon, it is recommended that the amount sampI es analyzed for sillcon m one sitting he restricted . • The relative error from the absorbance drift for lithium and magnesium were 65 2.8% and 2.5% respectively. For magneslUm, the absorbance error from the dross of Experiment 5 was 15.7%. If It was excluded the average relative absorbance error for the dross wou Id have been 2.7% and the average relative magnesium absorbance error wou Id have been 1.8%. VIII.2.3.2. COMPARISON OF ASSAYS WITH AN OUTSIDE ANALYSIS The results from an outside analysis performed at Centre Recherches des Minérales (CRM) are shown with the corresponding assays used in this work in Table 8.2. Table 8.2. COMPARISON OF ANALYTICAL RESULTS ANALYTICAL SAMPLE Wt % Li Wt % Si Wt % Al LAB EXP 5 POWDER RESIDUE CRM 0.84 - 16.8 EXP 5 POWDER RESIDUE TANCO 1. 07 - 45.7 EXP 6 1 METAL INGOT CRM 0.10 1. 54 - EXP 6 METAL INGOT McGILL 0.28 3.74 - Large differences exist between the results. However, the outside data are inconsistent with the mass balance for lithlUm performed in Section VIl.4. The total lithium accounted for at the end of the experiments was less than that contained in the spodumene. The CRM values were less than those used for the mass balance, therefore, if the y were to be substituted into the mass balance the lithium deficlency would Increase. However, the fact that the dlfference ln sorne values is so large is disturbing and unacco1mted for. For future researchers the followmg recommendations should he considered: -The Size of the sample should be as large as possIble but balanced agamst practicality ln terms of manageable solutions and safety, for , increasmg the amount of sample also increases the vIOlence of the reaction 66 with acid. -Segregation exists within the ingot and therefore the samples must be made by collected drillings and pie ces from as many different locations as possible. VIII.3. EXPERIMENT AL MODELINC This study, although lt dld not concentrate on the process phenomena occurring 10 the m :tallo-thermic reduction of spodumene, did rely on, and was affected by, vanous process phenomena. In this section, two process phenomena are exammed. VIn.3.1. DETERMINATION OF GAS PURGlNG RATE The mert argon atmosphere above the melt surface was essennal in preventmg oxidation of the moltell metaI. The rate of argon purging was determmed from the volume abave the melt surface and the rate of argon input. The volume of above the melt surface was calculated by subtracting the 1 volume of the molten alummum, spodumene and Impeller from the crucible volume. The volume of the magneslUm added was not tncluded and thus to compensate, the mass of alummum used in the calculatwn was increased to 2400 g. The intenor dlmenslOns of the crucibles were 28.8 cm high and 12.8 cm diameter. The cap overlapped the crucible by one centlmeter. Thus the effective volume of the reactor was: 2 2 3 (28.8 -1) cm x 1t 12.8 cm =: 3 577.4 cm [8.1] 4 The volume of the impeller was calculated by adding the volume of a) its blades coated in cement, b) the upper portIon of the shaft and c) the lower part of the shaft, coated in cement. The total impeller volume, assuming it operated two centimeters from the bottom of the cruclble was, 1 67 3 a) b lades 4 ( 4. 95 x 11. 0 x 1. 0) cm [8.2) 2 3 f b) metal shaft (27. 8 -2 -1 1) x 1t 1. 90 cm (8.3) 4 2 3 c) s haft coated in cement Il x 1t 6. 35 cm [8.4) 4 d) total 610.95 cm 3 An amount equal to one mole of spodumene was added to the reactor which had a volume of, î 3 v = 372 g + 2.6 ggcm- = 143 cm (85) however, in its loose fonn and restmg on top of the melt lt was estimated to have a poroslty of 50% making the effective volume of the powder 286 cm3, The volume of 2400 g of molten aluminum can be calculated from its densuy, given by the equation for molten aluminum(46l, 3 p = 2385 - (0.28 (T -933)) kg m- [8.6) at the operating Temperature of 1173 K the specifie gravity of the aluminum would be, 3 3 p = 2385 - (0.28(1173-933) = 2318 kg m = 2.32 g cm- [8.7) [hiS would make the volume of molten aluminum equal to, 3 3 2300 g + 2.32 g cm- = 1034.5 cm [88) Thus the total volume of the matenals in the reactor was 1 931.4 cm3, leaving 1 646 cm3 of free space. The average reSldence rime, 't, of the argon was, 1 68 3 v 1646 c m (8.9] 't = = = 32.9 s Q 50 cm 3·1s 1 where, v is the volume Q is the flow rate of gas. The equatIon for the gas purging of a system is, [Ct) dt = -exp [ -~ 1 [810J where, f(t) is the fractIon of gas purged form the system t is the rime in seconds 1: is the gas flow rate entenng the system in m S·l Solving Equation 8.10 by integrauon wnh respect to rime detenmnes that 83.8% of the gas would he purged every minute. 1 VIII.3.2. FORMATION OF SOLID SPECIES A possible, practical difficulty with this process IS the formation of solids during reactIon. FIgure 8.4, presented In SectIon VIII.5 shows that more solids were present as residue at the end of an experiment than the amount of spodumene added. In thiS sectIon, two reactlOn paths having one mole of ~podumene feact wah an excess (XS) of aluminum are examined: one where two moles of magnesium feact with the spodumene and the other without any magnesium, to detennine the theoreticdl amount of solids pfoduced. In each reaction path the spodumene IS r~duced 100% , 69 REACTION PATH 1: Li 0 Al 0 ·4SiO + XSAI +2Mg=2Li+2MgO·AI 0 + (XS-6)AI + 4Si + 3AI 0 223 2 23 23 MASS POWDER 1 N: S P ODUMENE = 372 g MASS POWDER OUT: MgO·AI 0 284 g 2 3 = S 1 LCON = x(112) g Al r03 = 306 gz DIFFERE 1\l CE = +218 + x(112) g REACTION PATH 2: Li 0 Al 0 4S iO + XSAI 2Ll + (XS-3)AI + 4Si + 4AIO 2 2 3 2 = 2 3 MASS POWDER IN: SPODUMENE = 372 g MAS S POWDER OUT: Al 2 °3 = 408 g S i = x(l12) g DIFFERENCE = +36 + x(112) g Figure 8.1. The analysis of solid formatIon m the reduction of spodumene for two reactlon paths. X is the percentage of sIlIcon that would enter the powder phase. Figure 8.1 shows that as the reactIon progresses more solids are forrned. This would result m a build up of solIds ln the reactor which wou Id have adverse effects on the proces.). For a contlnUOUS process, to counter the buildup of sohds, occaslonal mechanical removal of the solids would he necessary. The formatlon of solids IS greater when magnesium is added due to the formation of spmel. VIlI.4. MASS BALANCES In this study, three elements were very well suited to mass balance analysis: silicon and lithium in the spodumene and magnesium from 70 the additions. The total mass of an element eXIsung from an ex periment was calculated by multlplymg the assays of the products from Tables 6.6 - 6.10 by rheir respectIve masses from Table 6.1 The mass balances for lithIUm, magne~lllm and sIlIcon are shown ln Tables 8 3 - 8 5 re~peCtlvely. The s1l1eon and magneslUm Impuriues In the aluOlInum reaetant meral were neghglble, as shown In Table 5.1, and were Ilot mcorporated into the mass balance. Table 8 3. MASS BALANCE FOR LITHIUM MASS MASS % EXP IN(g) OUT (g) DIFF 1 12.36 9.40 -24.0 2 11.62 10.59 -8.9 3 12.47 9.41 -24.6 4 12.46 9.51 -23.7 5 12.51 9.93 -20.6 6 12.23 10.76 -12.0 7 11. 56 11.16 -3.6 1 8 11.78 10.68 -9.4 The average difference In the lithlUm mass balance 1S minus 15.8%. The sources of the lithIUm dIscrepancy cou Id have been, analyucal error and 10ss of lithlUm vapour It 15 possible that lIthIUm dIffusion due to a lithium concentratIon gradient between the molten alloy and the cruclble and impellcr occurred. LIthIUm has long been known as a destructIve material and it destI uys a sol id by Imbedding itself into the lattIce(47) which could have occuITed wlth the Impeller and the cruclble. During the expenmental program the cruclbles were changed occasionally due to cracks and matenal build-up. However, it was not recorded whether an experiment used a new crucIble or not. The lIthIUm mass balances appear to divlded mto two groups: (hose wah a lIthium deflclency between 20.6% and 24.6% and those wnh a lower Inillum deflclency between 3.6% and 12.0%. It would be very mterestmg to detenmne If a relauonshlp eXlsted between the lithIUm deficiency and the cruclble used. 1 l 71 Table 8.4. MASS BALANCE FOR MAGNl:SItJM 1 MASS MASS % EXP IN(g) OUT (g) DIFF '- 1 97.60 100.85 '3.3 2 0.0 0.0 - 3 104.00 99.01 -4.8 4 46.71 53.91 13.2 5 143.20 117.46 -18.0 6 191.90 190.57 -0.7 7 220.60 560.74 154.2 8 224.80 189.48 -15.7 The mean, absolute, difference in the magnesium mass balance excluding Experiment 7, where a spurious reading was obtained for the powder residue, was 9.3%. Magnesium losses occurred through volatilisation and the losses of fine magnesium oxide and spmel in the fine black powder. Table 8.5. MASS BALANCE FOR SILICON MASS MASS % EX!? IN(g) OUT(g) DIFF 1 110.44 97.41 -1l.8 2 103.83 121.16 16.7 3 111. 44 106.48 -4 4 4 111. 33 89.04 -20.0 5 111.80 75.03 -17.S 6 109.90 109.26 -0.0 7 103.31 114.50 10.8 8 105.22 106.98 1.7 The mean, absolute, difference in the silicon mass balance was 8.90%. Sources of the silicon could have been losses to the fine black powder and analytical error. 72 VIII.S. THE EFFECT OF MAGNESIUM ADDITION ON THE REACTION PRODUCTS ASSA YS The expenmental program vaned the magnesium additIon to the system and 10 this sectIon as effect on the lIthium, sIlIcon and magne sIUm assays in the products IS analyzed. The data used to plot the graphs In thls section was obtamed from the a~says presented In Section VI 4. Figure 8 2 ~hows that the hthium concentratlon ln the Ingot InGreased as the Mg:Spod molar ratIo was mcreased up to a ratio of 8'1. where It leveled off. Thus, as more magneslllm was added as a reductant, more lithium was released and dissolved mto the excess molten metal. When no molgnesium was used, very IIttle lIthium was determmed to be In the mgot, thus no reduction of lithla 10 ~ spodumene occurred. The weight % LI in the dross aiso mcreased steadtly. The hthlUm concentratlon was higher In the dross than in the mgot for SIX ot the eight expenments. ThiS was due to the formation of dross in areas of the reactar where the powder was m good contact with the molten metal, 1 e., on the surface of the melt and along the walis. " " 1 73 National Library Biblioth~que nationale of Canada du Canada Canadian Theses Service Service des th~ses canadiennes NOTICE AVIS THE QUALITY OF THIS MICROFICHE LA QUALITE DE CETTE MICROFICHE IS HEAVILY DEPENDENT UPON THE DEPEND GRANDEMENT DE LA QUALITE DE LA QUALITY OF THE THESIS SUBMITTED THESE SOUMISE AU MICROFILMAGE. FOR MICROFILMING. UNFORTUNATELY THE COLOURED MALHEUREUSEMENT, LES DIFFERENTES ILLUSTRATIONS OF THIS THESIS ILLUSTRATIONS EN COULEURS DE CETTE CAN ONLY YIELD DIFFERENT TONES THESE NE PEUVENT DONNER QUE DES OF GREY. TEINTES DE GRIS. 0.45,----,----,----r------.,.----,, , • 1 l , INGOT 0.40 .... o •••• ~ •••••• oo.~ •••••••• o~o •••••••• ~o •• o •••• l , , 1 1 • 1 1 __ ..lC. __ 1 1 1 1 1 • 1 1 a 35 .-...... ~- ..... -.. ~ .....•.. -~ ..... -.... ~ •....••.. DROSS . : : : : )( 1 1 1 1 1 1 1 1 l , , , 0.30 ••••••••• ~ •..•..• o.~ ••••.•••• ~ ••••••••• ~ •••••••.• :1 1: :1 :+1 l , 1 1 025 .••.••••• ; ..••..••• ; •.•..•.. 0"*'••••••. ~ ••••••••• " , " , 0.20 ·········t·········t········, , ,·········i·········, : : x : 1 0.15 ·· ...... ---f .. · .. ·...... · .. ' .. _-_ .... _~_ ...... _..... _~_ .... _...... :1 :x1 :1 :1 0.10 ...... "' ...... t...... _--t .... _· ...... ·_~ .. _.. ·_ ...... ~ ... _-_ ...... ~ :, :, :, 0.05 .... o'/f" ...... f-'" .... -~ ...... ~_ ...... / 1 1 1 1 l , 1 1 1 1 1 1 000n~-~?~_--~4~-~S~-~8~--~10 Mg SPODUMENE MOLAR RATiO Figure 8.2. Lithium welght % in the ingot and dross vs. the magnesium to spodumene ratio. The lithium concentration in the powder residue, Figure 8.3. decreased curvilinearly at a decreasing rate with the Mg:Spod ratio. The range was from 2.53% Li at a Mg:Spod ratio of 0: 1 to 1.06% LI at a ratio of 10: 1. The decrease in the amount of lithium in the residue could have been due to lithium extraction from the P spodumene or dIlution due to the formation of other oxides in the residue. Figure 8.4 shows that the latter was not the case. r1'he powder residue did have a greater mass than the charge mass of p spodumene as a result of incluslOn of metal panteles, alloy oXldauon and the production of reaction products such as, silicon and spinel. However, the difference was roughly constant and not enough to account for the decrease of the lithium in the powder residue. 1 74 3.0r---~----r----r---r--~ 1 . 2.5 ·····-···tr···----·t·····-·--~····--···~-··-····-· . · .· . · ·• 2.0 .. _---- ~.-.----._~.· .. _•. ----~.-._-----~--.------t · 1.5 ---_·_---t--_ .. _----t -.-----~ .. -._--~-~-_._ .. _-- 1 ·1 .1 1 ·: + ., ______• ______••·: ••• • ____ ~t-. __ ••• ____ 41 _____ •••• 1.0 1 1 1 1 , , · , 05 ·········t·········.·········i·········i·········· · 000~----~2----~4------~6~--~8----~10 Mg'SPODUMENE MOLAR RAT!O Figure 8.3. Lithium concentration in the residue vs. Mg:Spod ratio. ,. --+- ·: )( : > : :le CHARGE , ·: .: : )( ~ : :x : : 400 ...... ! ...... ".. : ...... i"''' ...... ~ x.... . RES lOUE ~1.+ ... : : : · :, 300 ····· .. ··t· .. ·· .... f···· .. · .. i······ .. ·~ .... · .... · ., , • ___ ••• __ • __ .... ____ • ___ .... __ ._ ...., ______4 ______•• 200 . · . · ·• 100 ...... --+ ...... +...... ~ .... -.... ~· ...... Mg SPOOUMENE MOLAR RATIO Figure 8.4. The masses of the powder residue and 13 spodumene charge vs. T the magnesium to spodumene ratio. 75 The lithium concentration in the condensate, Figure 8.5, increased to a peak of 0.94% at a Mg:Spod ratio of six and then decreased as more magnesium 1 was added to the system. The increase of lithium in the conàensate was believed to be due to increased liberation of lIthium from the spodumene as more magneslUm was added to the system. The decrease a....er a ratio of six was due to the lllcreased vapounzatIon and suosequent condensation of magneslUm, thereby dilutIng the lithium In the condensate. This data indlcates that the vapours nchest In lIthium were produced 10 Expemnent 5 which had a Mg:Spod ratio of six to one. 10----~----~--~----~----~---, , ., 0.8 ...... --_ .. -- .~ ...... _--:-_ ... _...... _..... : ...... , , 1 :+1 . ,.1 1 1 1 1 1 0.6 ------, ... -----r .. -- .. · .... t-- ...... :...... -t ...... • .. - + :+ ' , : l , , .,.. 1 1 1 1 1 ~ 1 ! : o4 _..... _.... _~ ...... ~ ...... _.. _.. ~_ .... _.. _-+_ .... _.... ~ .. _.... __ .. l , l , 1 1 1 1 l , 1 • 1 1 1 1 : : 1 1 1 : ,\+ 1 1 1 l , 0.2 ...... ~ ...... r ...... +...... -: ...... -t- ...... l \ , , 1 1 1 1 1 1 .1 ,1 ,1 1 :, .: :, , , , , , , 2 4 6 8 10 12 Mg SPODUMENE MOLAR RATIO Figure 8.5. Lithium weight % in the condensate vs. the magnesium to spodumene raùo. 76 The lithium conceptration in the fine black powder, Figure 8.6, remained constant at appoxiamately 1.2% Li, as the Mg:Spod ratio was increased from two to one to ten to one. This suggests that the lithium present in the • very fine black powder 15 unaffected by the amount of magnesium addition. 14r-----r---~------r_----r_--~ , , , 1.2 ·········f·········f·~~~~i'~--~'~'·+·~·.:..:·:.:.~··~·~ ...... +. 1 1 1 l , l , l , l , 1 1 1.0 .. _.. _--- .. ~.- -- .... _.. -f- -...... -~ .. _...... -- ~_ ... -_ ...... - 1 1 1 1 l , 1 1 1 1 1 1 1 l , 0.8 ·······_·t·_·· __ ···!···_ .... ···~·_·· .. _-_·~ .. ···_·_·· • 1 1 1 1 1 1 1 " 1 , 1 1 0.6 ·········I·········t········_~·_-_· __ ··~··· __ ·--- ,1 ,1 ,1 1 1 l , ,l , , 1 1 1 1 0.4 .-...... ~ .. __ ._-.. ~ .. __ .. _--.~._ .. ---_.~ ... __ .-.. 1 1 1 1 1 1 1 ,1 1 , o 2 • ____ ._~_. ____ ... _••• ______.. _-4 .. ___ ... ____ ~_. ______ 1 O.OO~-~2~----'4~--6~---8~----,J10 Mg'SPODUMENE MOLAR RATIO Figure 8.6. Lithium weight % in the very fine black powder vs. the magnesium to spodumene ratio. 1 77 ~------ The silicon com,\"!ntration in the ingot and dross, Figure 8.7, increased slightly with the increase in the Mg:Spod raùo. The presence of silicon in the in~ot when no magnesium was used, confirms that ah1Qrinum reduces the • silica in the ~ spodumene to fonn silicon. The silicon concentration of the dross sample from Experiment 8 (Mg:Spod ratio of 10:1) was extremely high and attests to the non-homogeneity of the dross. 7.0,----r---r---r---r-----.· ·: , l , 1 1 I~' INGOT 6.0 ...... ~- ..... -_.~ ...... ~ .... -.... ~-.-- .... . ·1 .1 .1 1 --X-.- ·1 .1 . DROSS 5.0 .-~ ... _--!-••••• -.-! .. --.-.. -~-- .. -----~-.--- .•.. ·1 1 .1 · . ·1 4.0 -_ •...... ~ •..... _.. !· .. __ .... _~ __ ...... _~b. ___ ... . : : + • :+ · ·1+ .:J 3.0 --.. =--~.----u--t-.:..::------I-- ••••. --~ : : : : ~ : :Xx + ~ :x ~ 2.0 ··_·_····r·····-··i·..--.... ···~-_· .. _··_·~·· __ ····· w ~ !- ~- - : * ! p +: : 1.0 --..... _.. -.... - _w. --_ .. !· .... _- _...... ~ ...... _..... _~ ...... __ ... ·1 1 · O.OO~-~2~--'4~-~6:---~8:-----:J10 Mg:SPODUMF.NE MOLAR RATIO Figure 8.7. The silicon weight % in the dross and ingot vs. the magnesium to spodumene ratio. 1 78 The silicon concentration in the powder residue, Figure 8.8, decreased with the increase in the Mg:Spod ratio and then leveled off. The range of the silicon concentrations was from 15.3% at a Mg:Spod ratio of zero to 4.7% at a Mg:Spod ratio of 4.3. The leveling of silicon concentration can be explained by either 1) no further reduction of the silica species in the spodumene occurred or 2) funher reduction of the silica with the silicon product remaining undlssolved in the molten reductant. The phase diagram of the aluminum-magnesium system shown in Appendix B shows that at 900°C a liquid solution exists until liquid metaI is 37 wt% silicon so therefore a saturated silIcon solution did not occur in the present study. However, it is possible that the silIcon remair,ed undissolved for unknown reasons. l , 1 16.0 1 JI' 1 1 • Uf • , 1 1 l , 1 1 14.0 - •• ,..•• ~ ••••..••• ~ ••• " ..... ~ ••••••.•• ~ •••••.••• 1 l , 1 120 •••••• • .f., ...... L1 ...... L• ...... L1 ...... j 1 1 1 1 1 1 1 1 1 : : ! J 10.0 ·········t· ······t······· .. ~·········~········· t 1 1 1 1 1 1 1 1 1 1 1 : 1+ : : 8.0 -_·····_-~·_-_··_·-t _.. _._.~-_ .. -.---~----_._-- , , , 1 1 1 1+ 1 : : 1 ----;'----:1 6.0 ·········.·········.·········i·········i········· 1 1 • 1 , 1 1 1 : : + + : fIl 1 4.0 ••• -_. __ .~._------~--_._- •. _~----_. __ .~----_ .... 1 1 1 1 1 1 1 1 l , 1 l , l , 2.0 -----··-··--·-··-··f-·----·--~--_·_----~--_·_··_· ,l , 1 1 1 O.OO!-----!:-2---4":----!:-6----=8--~10 Mg:SPODUMENE MOLAR RATIO Figure 8.8. Silicon weight % in the powder residue vs. the magne sium t.o spodumene ratio. 1 79 The magnesium concentration in the ingot and dross increased a!l more magnesium was added to the system as shown in Figure 8.9. The concentrations 1 are less than the weight % magnesium expected according to the stoichiometric amounts of the reactants. This is due to 10ss of magnesium from the alloy via oxidation, volatIlisation, and reaction. 7.0,-----r-----,r-----,,.------,----, INGOT ·• 1 .1 6.0 ...... ~ ...... ; .. -..... -~ ...... -.~ ...... -.,/ 1• .1 1 1 o DROSS o 5.0 ·_··_··_·f·········:· __ ·····_~····_·_--~1(····_~· 1 ::+ o 1 1 o 1 • 4.0 ·········~·········t···_····_~·_·····_-~_···· o 1 0 1 1 1 o 0 o 1 3.0 ·········t·········i·········i··· o 1 0 o ·o o 1 o 1 1 1 2.0 ·····_~·_· __ ··_-~_-·······1 o 0 :+ t : : s'< : : ~ 1 1 1 1.0 ••. __ ..~ ••. __ ••. _~ ..• _. __ ._~ .• __ •.. __ ~8_ •••• _ •• /./_ 1 1 1 /. 1 • 1 1 + 1 1 1 1 1 1 1 1 1 1 1 2 4 6 8 10 Mg:SPODUMENE MOLAR RATIO Figure 8.9. Magnesium concentrations in the ingot and dross vs. the magnesium to spodumene ratio. 80 The magnesium concentration in the powder residue increased as the Mg:Spod ratio incrcased as shown in Figure 8.10 . The magnesium concentration in the flue powder, also shawn in Figure • 8.10, increased with Mg:Spod ratios. The flue powders were thought to be composed of the finer sizes of the residue. At the hlgher Mg:Spod ratios, more fine magnesium particies were produced, such as magnesium oxide, and were carried away by the flushing gas. 45~--~r---~----~~----~--~ 1 1 1 1 • , t 40 .-_ .. _...... :. -.... -_..... :._. -... - .. _~- - .. -.. - .... - ~ ... --... -.... RES lOUE 1 1 1 f , 1 1 1 1 l , 1 ... ~ - -)( -. 1 • 1 1 / 35 ._ .... _.. __ ! .... _.. _.. !_ •••• _... _~_ ...... J ...... ::: .. _. 1 1 1 1 FLUE POW. • J' 1 ""1 X 1 1 , 1 30 ...... -. f"" -- .. _.. _.~ ...... ------~- .... -- .. -... ~_ .. -_ .... _.. .. ,1 , . ,. 25 ..... -.... _.!: ...... --_ .. !-: ---...... *J.. __ .. __ _._l : ...... __ .... : ~ : : 1 J" , 1 20 .•.....•.~ ~.'..•.. t········· ;"""'" ~-t- ••••••• , 1 1 1 ::+ ~ 15 -_ ...... ! .. _- .... --_.!..... -_._-~._--_ .. -_ .. !_--_ •• __ .. 1 • 1 t ,+, ,' 10 ...... •.•.•.....••....•..••.•.•.....•...•..•..: : + • : : 1 , . . 5 .. , .. , • 1 • 1 --,------T""------,------,··--···_·, , , . , 1 , .1 °O~----~2----~4----~6~----8~--~10 Mg'SPODUMENE MOLAR RATIO Figure 8.10. The magnesium weight % in the powder residue and very fme black powder versus the magnesium to spodumene ratio. 1 81 The lithium extraction from spodl1mene shown in Figure 8.11 was calculated as the difference in the mass of lit"lium between the charge, p spodurnene, and the powder resldue dlvlded by the charge mass of lithium in • the Il spodumene times one-hundred percent, Li C1' - LIRESIDUE) LiSPOD·lQO% [8.11) EXTRA = (Mass LiSPOD Mass + Mass It increased curvilinearly as the Mg:Spod ratio increased at decreasing rates. The largest lIthium extractIon was 67.2% and occurred at a Mg:Spod ratio of ten to one. 70r-----~----._----~----~----ï, ., , , , . , ..... 60 ••••••••• ~ ••••••••• ~ ••••• -••• :t'•••• ~ !,.. ..1 lit , UJ ,. Z • l , UJ '.! : + : ::i 50 - •••••...• -----•••• ~ ...... -...... ::l CI , 0 , , Q. CIl 40 -_··_····t-_·-'····i··_ .. ·····~···· __ ···~······ __ · : /: : : ~ -+ 1 1 1 1 lE l : : : z 1 Q 1- () :: ::/":":::r::: 1 :::1::::::::[1 1 ::: :::L::::::1 ~ 1 1 1 1 1 1 1 1 l- 1 1 1 1 X 1 1 1 1 UJ · ,. ..::; 10 _•• _..... ~_ ...... _•• _... _~ ...... __ .. _.. ~ ... __ • __ ... · ... · °O~------2~------~4-----.....~6------~8-----71'O Mg:SPODUMENE MOLAR RATIO Figure 8.11. Lithium extraction from the powder residue vs. the magnesium to spodumene ratio. , 82 The lithium recovery to the ingot, Figure 8.12, was calculated as the mass of lithium in the meta! ingot divided by the mass of lithium in the 1 spodumene charge rimes one-hundred percent, LiRECOVERY - (Wt% Li ' Mass + Mass Li ) . 100% [8.12) INGOT INGOT spoo The lithium recovery to the ingot increased as the Mg:Spod ratio increased. The maximum recovery attained was 58.1 % The lithIUm recoveries were less than the lIthium extraction from spodumene due to lithium occurrence 10 dross, flue powder and condensate as weIl as lithium losses to the vapour phase. The low recovery value at a Mg:Spod ratio of four to one was for Experiment 1 and was due to the small ingot obtained in that trial. 60~----r---~----~-----.----~ , ,1 50 .-. --- t··_··_·_-~· ~_ ···t--, -... ·_· .. __ ... · .-.- , ... .. -- .... , 1 , ,1 , . , 40 •••• _•.•• ~ ••••••... ~ ••••••••• ~ •• _. , ,. , 1 : : + , 1 , , , , , 1 30 ...... ~ ... _..... ~ .. _.. -- ..., __ .. -.... -.~, .... __ .. _.... , , , ,1 , , , , , 1 1 20 ------;------r·---- .. ---~-·------1 .. ·------1, ,1 ,\ , , ,l , ., , 10 •••••••• • .. ······it········~ .... ···_·~_· __ ·_--- +, ,1 ,1 1 , 1 , , 2 4 6 8 10 Mg SPODUMENE MOLAR RATIO Figure 8.12. Lithium recovery to the metal ingot vs. the magnesium to spodumene ratio . • 83 A summary of the mass balances and the lithium, sIlicon and magnesium distributIon to the reactIon products for each Expenment is shown In Figures 1 8.13 to 8 16 These FIgures show much lI1formatlOn that has already been presented ~arlter. but JO Li shghtly different manner, WhICh may aid the reader ln gra<'pll1g the relatiomhlps put forw;ud lf1 the prcvlOUS section. New eVH.lcncc prc~ented IS discus~ed for cach FIgure The ltthium ul~tnbutIon ln the rcactIon prouucts shows that the percentage of hthlllm pn..:<,cm ln the mgot II1crl'a~cd as the magneslUm to ~podumene ratIo wa~ ll1crca~cd. Conver~ely, the dIstnbutIOn shows that the lithium percentage of the powuer rcsldue decrca~ed as the magnesIUm to spodumene ratIo lncrea~ed. The htiullm dl~tnblltJon for the cxperiment with a rnagneslllrn to ~podurnene ratIo of zero ..,how~ that about ninety percent of the lithIUm rernamed ll1 the powdcr reslduc, attc~tmg to ,he small arnount of lithlllm redllctlon \VhICh occurred 111 thl~ cxpcnment. The amollnt of lIthIUm unaccollntcd for decreased as the magnesium to spodurnene ratio IOcreased for undetermined rcasons. 1100r------, T ! 1000 ~O DROSS 8 8)0 o ~ ~ 700 RES. ::E ;:J I ~ !:: 000 ...J BP :00 t727Zl t- 400 LOST ~ u el ])0 0. XlO 100 00 o 41 6.0 100 20 44 8.2 100 ~ M1.AR RAID Cf TEST Figure 8.13. Lithium distnbution in the reaction products for each experiment. T 84 The silicon percentage of the powder resldue decreased as the magnesium to spodumene ratio Increased. The silicon dIstribution in the other reaction products is inconslstent among the experiments. 12)0 1100 1000 8 000 œoss 0 ~ 000 ~ RES. ~ /1)0 U ...1 ~ 1I1 000 BP b :DO tZVZl f- LOST ~u 400 a.ffi 200 2)0 100 DO 0 41 6.0 100 20 44 B.2 100 ~ M::tAR RAID Cf TEST Figure 8.14. Silicon distribution in the reaction products for each experiment. 1 85 The dIstnbutIon for magnesium shows thut the percentage of magnesium in the powder residue decreased as the magne51Um to spodumene ratio was 1 lIlcreased ThIS meant that at the lower Mg:Spod ratios a greater percentage of the magneslUm wa~ utihzcd in the rcductlü/1 reactlOns and magnesium oxide products contalncd 111 the powdcr residuc weI c formcd The second bar from the nght was excluded from the analysls due to the spunous reading of the magneslUm concentration ln the powder rC~ldllc from Expcnrnent 7. 1:;:D0 ~~ 1100 N1)T 1000 0 w 0 ~O CROSS ~ ~~ :1 ffJO :J RES. lJl w 700 z ~ ü fDO ~ BP ~ :00 f7T//J 1- 400 LOST ~ u ffi .YJO a.. X>O 100 00 0 41 60 100 20 44 82 100 M:j:SPOOlJ.Uf M1..AR RA m Cf TEST Figure 8.15. MagnesIUm distribution in the reaction products for each experiment. VIII.6. KINETICS OF THE SPODUMENE REDUCTION SYSTEM The rates of spodumene reducnon were qualitatively determined from the plot of lithium recovery to the kinetic samples versus the sample time, Figure 8.16 The hthIUm recovery was calculated as the lithium assays of the klIletic sample dlvlded by the nommaI lIthIUm concentratIon, according to the amount of reactants, of the excess molten reductant, i.e., 86 [8.13) 1 (Mu s poo / MMELT ) High rates of lithium recovery occurred for the frrst twenty minutes of the experiments and then decreased considerably thereafter. Also, the rate of lithium recovery and amount of hthium recovered increased wnh mcreased magnesium to spodumene ratIOS. The latter finding IS consistent wah the results of the lithium recovery to the mgot samples, shown in Figure 8.12. ~~------~ • 2 ro ------$ ~ 6 60 ------;-- * 00 ------?iw ---+ -- 10 8 ~ ------a:w .:l ~ ------~------ o 10 20 30 40 50 60 TIME (MINUTES) Figure 8.16. Rate of lithium recovery ta the melt versus rime for various experiments performed in this study. The decrease in the rate may have been a result of the following, 1) Equilibrium was attained by the system. 2) A rate limitmg step has been reached. 3) Depletion of ~ spodumene ore. 4) Depletion of magneslUm reductant. 1 However, a discussion of these is beyond the scope of tbis thesis. 87 VIII.7. DISCUSSION OF XRD RESULTS The XRD re~ults gave m~lght lOto the rcactlons which occurred and aided In the detemlInJtlOn of the phy~lcal meCh,lnI~mS whlch took place. The XRD analysls \howcd that the powder w;ldue was a very complex matenal. Ir wa'i cornpo'icd of aIUmInllII1, \PlI1CI. \llIco/1, spodumene, hthium alumIno ~Iltcates and pencla~c The alummum l[l the re~ldue was cau\ed by the entrainment of alummum in the powder pha~e. The spmel was a reactlOn product from the redtlcl10n of alumina by magneslUm The pure ~lhLOn detected H1 the le~ldue was the product of the reductlon of slhca 111 the spodumene by aIU111ll111m or magnesillm. The ~podllrnene present 111 the resldue ll1dlcated that not a11 of the spodumene reacted. This may have bcen becau~c ,>orne of ex spodumene feed may not have undergone the ex -> ~ trJn~fonn,l!1on ,md was th us addcd as relatively mert ex spodumene. In faet, the lahlUm alllmmo ~llIcate spccles, 35-797 and 31-706, detected In the powder resldue have XRD patterns slmilar to ex spodumene. In the spodumene conversIon perfonncd, the concentrate expanded and packed ltself 1I1to a very dense matenal. It 15 po~slble that sorne 1 parncles were "crushed" by others and the resultmg compressIve forces deterred the transformatIon of certam crystals It IS recommended that future researchers perform spodumene converSIOns in vessels that allow the spodumene to expand freely. The magneslUm oXlde present In the resldue was fro-- the oxidation of magneslUm; during dissolution and by reductlon of the SPO(': : nene. The flue powder was composed of alllmmum, SIlIcon dfld spin el. AH the se constituents were present in the powder resldue and were beheved to have been a fine sized portion of the powder resldlle, WhlCh was physically transported from the reactor by the argon flll~ll1ng gas. The conden~ate was compo~ed of magne~lllm oXlde. It fonned via the vapourization of molten magnesIùm 111 the liqUld alloy and ils subsequent condensation and oxidation on the underslde of the cruclble cap. VIII.8. WETTING EFFECT OF MAGNESIUM It was thought that magnesium dissolved in aluminum would improve the wettmg between the molten alloy and the ~podurnene as explained in Section 88 II.4. III Experirnent 2, wl1ere no rnagnesium was used, silicon recoveries to the ingot, shown In Figure 8.7, were slrnIlar to those encountered ln the other tests. This meant that ~uffIclent wettmg occurred, wHhout magnesium. • to permit the rèaCtlon betwCé'1l rnolten alummum :md spodumene. Thus rnogneslllm 's Importance ln the other cxpenment<; was thennodynamlc. The kmetIc ~tudy of the IithlUm rccovery to the molten alloy showed that mcreased magneslum aùùltlon mcreaseo the rate of lIthium extraction. ThIS effect could be due to Improved wettIng caused by the magne<.;ium but a more plamlble explanation IS that the hthlUm extractIon W.lS [aster due to a higher magneslUm acnvlty, [hough the exact relatlonshlp 15 not known. VIII.9. DISCUSSION OF REACTION MECHANISMS The rcactIOn mechanü,m desenbes the physlcal nature of the reaction between the "podumene partlcles and the molten reductant The reaction mechamsm WhICh occurred 10 the present work IS In faet 15 beyond the scope of this thesls. Howevé'r 10 thlS ~ectlon, observatlons pertment to the reactlOn mechanism are mentloned and the questlons which they raise are dlscllssed: 1 1) There was ln absence of a layer of reachon products on the reacted partlcles' surface by SEM analysis: ThIs mcant that the reaction products dIssolved or were released into the molten reductant. Another possibjhty IS that the reaction products formed wnhm the spodumene and not just at the surface. 2) There was positIve identificanon of spmel and silIcon in the powder residue: This result more than any other indlcated that reduction of the spodumene occurred as these are products of spodumene reductlon. However, the presence of SIlicon in the powder also meant that the silicon did not dissolve in the excess reductant. This is an entlrely unexplained observatIOn 3) The kinetic study found that reactlOn occurred very rapidly in the frrst twenty minutes and then slowed considerably: , A very fast reactlon mechanism occurred. ThIS was invariably due to the 89 small size of the spodumene charge However. for a system dealing with solid crystals and molten meral, the rare \Vas hlgher thdn anticlpated. t 4) There were cracks and holes eVldent In the powdcr residue reaction particles: These phenomena may have re~ulted from In SItu reaction by diffusion of reductant atoms and the ~ub~equent dlffu\lOn ot the rcacHon products out of the cry~tal In!O the exce~s molten reductant JeavlIlg the holes. The cracks would have faCllltated the transport of atom<;. A fTloblle <;mall atom such as lithium would have a vcry l11gh dlffu~!On r .tte and thu~ the greater amount of lt produced \Vould enter the malien rcductant. Silicon, WhlCh would have a ~lower dlffu~lOn rate would only partly enter the molten phat>e. An oxide product, ~uch as '>plnel, would ::.tauon Ihelf Hl the cry!:>tal lanice and not enter the melt Tlm would explalO the: detcctlon of spmel and SIlicon in the powder resldue and the sIlIcon a~say of the metal mgot. VIII.lO. DISCUSSION OF REACTION PATHWAYS Pmpomtmg the reacnons whlch occur ln a system is an important task which ralses the level of understanding of a ::.y::.tem. Information obtained from the dlfferent modes of analysis were uuhzed to develop two proposed different reaction pathways ln thlS SectIon. VIII. 10. 1. TWO-STEP REACTION PATHWAY From the XRD results of the powder resldue and the silicon assay of the mgot from Expenment 2, where no magneslUffi was used, the reduction of the silica in the spodumene uy alummum must have occurred, 1.e., LI O·Al 0 ·4S10 + ~ Al = ~ Al 0 + 4Si + LI 0 Al 0 (8.14] 2. 23 23 323 223 This first step IS ln agreement with the F* A *CicT sImulation of the system and would have to have occurred by a hquid-solid reaction mechanism. In the second step, the magneslUm 111 the mol te!". alununum reduced the lithium alummate ta fonu splOel and lithlUm, 1 e., 1 90 Mg + Li O·AI 0 = 2Li + [81S) 2 2 3 It is not known which of the two reaCHons was rate lirniting, but as shown in the kinetlc study in Section VIII.6, the rate at WhlCh the majority of the lithIUm entered the alloy was very fast. VIII. 10.2. ONE-STEP REACTION PATHWAY In the one-step reacnon pathway the alumll1um does not participate 10 the reduction process, only the magneslUm reucts, due to a much hlgher rate of reaction with the spodumene by a gas-solid mechamsm than that for aluminum by a liqUld sohd mechanism. The one-step reaction pathway reqUIres a magnesIUm ta spodllmene ratIo of nine to one. MagnesIUm oxide or penclase(MgO) IS a reactlOn product fonned in the one-step pathway not formed In the two-step pathway. Penclase was detected 10 the powder rcsldue only for Expenmcnts f),7 and 8 where the magneslum ta ~podumene ratios of elght to one for Experiment 6 and ten to one for Expenments 7 and 8 were used. The free energy of rhls equatlon at 900°C, calculated by F*A*C*T, IS -865343 2 J wInch means chat the reacuon Will procede ta the right. At magnesillm ta spodumene ratIOS of SIX to one and Jess, lithium was produced by the two step reactlon pathway and at 11lgher magnesium to spodumene ratIOS lt IS beheved that both the one and two-step rcaction pathways contributed ta hthium formation. VIII. lI. VACUUM REFINING OF LITHIUM FROM ALUMINUM In this thesis, an assumptlon has been made that It is possIble to vacuum refine lIthIUm from alumInum In tlus sectIon, a brief explanation of vacuum refimng is glven and it is Investigated whether it IS thcoretically possIble ta of vacuum fefme InhlUm from aluI1l1l1um. Vacuum refInIng iS based on the dlfference !11 vapour pressure between two specles In a melt When the melt IS exposed ta vacuum, the species with , the hlgher vapour pressure, WIll preferentially evaporate from the species 91 which has the lower vapour pressure. A description of the ma~s transfer phenomena and the series of equations necessary to develop the cquauon which determmes whether solute elimination I~ possible via vacuum refimng IS beyond the ",cope of this thesis. · (48) (49) Exce Il ent re f erence~ arc OImayuga and Harn~ . The volanhty coeffICient, [8.17) where, y') 15 the actIVlty coefficlc.nt In the melt pO is the eqUlhbnum vapour pressure of pure species, (Pa) M is the molecular mass, kg kgmole"l l, b denote the solute i and solvent b, respectlvely. If a solute has a volauhty coeffiCient greater than one, then vacuum 1 refining of the solute is pOSSIble. Dimayuga (48) calculated the volaulity coeffiCIents for various elements ln liqUld aluminum and a few are listed In Table 8.6. Table 8.6. VOLATILITY COEFFICIENTS OF VARIOUS SOLUTES IN MOLTEN ALUMINUM 0 SOLUTE, i ri T = 973 K T '" 1173 K T = 1473 K 7 4 Li 0.40 1.3 X 10 5.1 x 10~ 2.1 x 10 8 6 5 Mg 0.7 1.5 x 10 4.2 x 10 1.2 x 10 9 7 4 Si 0.04 3.6 x 10- 7.0 x 10- 1.6 x 10- The results state that lithium and magnesium would both be eliminated by , vacuum refining white silicon would not. If spodumene reduction operation 92 utilized an aluminum-magnesium alloy then magnesium would volatîlize with the lithium and the two wou Id have to be separated. This could be achieved by: 1) havmg different condensation characteristics in the reactor for • fractlonal condensutlon or 2) separating the lIthium from the magnesiuITI in a bulk condensate by meltmg the condensate and utilizing lithium's lower melting point, 180°C vs. 648°C. VIII. 12. COMPARISON OF EX PERIMENT AL RESUL TS WITH F* A*C*T CALCULATIONS VIn.I2.!. INTRODUCTION The F*A*C*T analysis performed m Section IV.I had a great bearing on the design of the experimental pro gram. The experimental results were compared ta the F* A *C*T calculations here. The goal of the comparison was to determ'n~ if a slmllarity eXlsted between the lIthIUm extractIOn values and if so, then to use F* A *C*T to simulate the alumino-thennic reducrion of spodumene while varymg other thermodynamlc parameters such as temperature, pressure and amount of excess liquid aluffllnum. VIII.12.2. COMPARISON OF THERMODYNAMIC MODEL AND EXPERIMENTAL RESUL TS The graphs from Figures 8.11 and 3.2 are presented here again in Figure 8.17 in order to compare the expenrnental results to the thermodynamic predictIOns. Equation 8.11 was used to de termine lithium extraction and Input 3.1, showr, here again as Input 8.17, was used for the F* A *C*T calculations. Li 0 Al 0 ·(SiO) + 85.5 Al + Mg {S.17] 2 2 3 2 d FIgure 8.17 shows that g, 0d agreement existed between the lithium extraction obtamed expenmentally and ca1culated by F*A *C*T. At a magneslUm to spodumene ratIo of two to one, the lithium extraction in the experime'1t was much larger than the predlcted extraction by F* A *C*T. This may have been due to the less than perfeet mlxmg of aIl the reael.:tnts which , would have resulted 10 lor;alized, large, magnesium concentrations that would 93 have improved spodumene reduction. Another discrepancy is the flattening of the experimental curve at ". higher Mg:Spod ratIos. This was due to less than 100% efficiency of reaction, pos'ilbly due to the less th an 100% transformation of a. to ~ spodumene 80r-----~----~----~----~·----~ , + , ) 1 1 1 1 EXP. 70 ••• -.----~-.------.~-.- ••• ---~.- •• -----~-.---.--. lit IX ... )( : : : :+ i 1 1 1 1 1 1 l , FACT 60 ···-·---·r··-·---·-l·-··-·--·t·-··--·--~···--··-- 1 1 1 1 1 1 1 1 1 1 1 1 : : + * : 50 ·_··-····t-··_··_··t······-··~·········~······-·- : :+ : : 1 1 1 1 1 1 1 1 40 __ ._._ .•. ! .... __ ._.i .••.••••. ~ .•.....•• ~ •.••.. __ • : bcx i i + : : : 30 ·····-···i·········i·········i·········i········· , 1 1 1 1 t , 1 1 1 1 1 1 1 1 1 1 1 1 1 20 --.-----.~._------~_.------~--_._----~------_.\ 1 1 1 1 1 1 • 1 1 1 1 1 1 1 1 1 1 1 1 10 _w_ ...... -_ .. f- .. --- --_.~ ..... ----.- ~-·_--"---1----"---" ~ *1 :1 :1 :1 1 1 1 1 1 °0~----~2----~4----~6----~8----~10 Mg:SPODUMENE MOLAR RATIO Figure 8.17 Lithium extraction from expef"1mental work and F*A*C*T calcul~tions V~. the magne sIUm to spodumene molar ratio. Differences in a thermodynamlc simulatIon and experimental work will always exist because thermodynamic calculations are done for steady state, ideal systems which were not attained in this study due to: a) Argon flushing gas which camed lithium vapour out of the vessel, and lowered the amount of lithIUm ln solution, offsetting the equihbrium and pennitting more lithium to enter the molten metal. b) Imperfect ffilxing of the reactants. c) Unknown wetting characterisucs between the molten reductant and spodumene. 94 Other reasons for dlfferences between expenmental work and thermodynamic simulated results in metallurgical processes are: d) miscellaneous material losses. e) analytical error. f) The data used to create dlssolved specles is continually being updated and untIl data for dissolved species is obtained which is unrefutable, the thermodynamic predictions are not 100% accurate. Wilh aIl the posslbIlmes for drfferences and the complexity of the system, the close resemblance of the expenmental and computer modeled curves is nevertheless an outstanding achievement of this thesls and suggests that there is great value in using F*A*C*T as a sImulation tool for further study of thIS system. VIII.l2.3. F*A*C*T SIMULATION OF THE ALUMINO THERMIC REDUCTION OF SPODUMENE The addition of magne sium is a themlOdynamlc parameter in the reaction between spodumene and alumi.num. Other parameters are temperature, pressure and the amount of excess molh~n aluminum. U Sll1g the F* A*C*T EQUll..JB program the alumino-thennic reductlOn of ~lJodùITlene \l1~S ex~::nined while varying the above three parameters. The Input supplied to F"" A *C*T Jor the temperature change simulauon IS shown In Input 8.18. at a pressure of 1 Atm. and at temperatures ranging from 700°C to 1300°C by increments of lOOue. The Input ta F* A *C*T for the pressure sImulation also uses Input 8.18. The temperature was fixed at 900°C and the pressure was 10wered from 1 Atm. to lE-5 Atm by orders of magmtude. The simulation for the excess molten reductant used Equation 8.19 as the Input, Li O·AI 0 ·4SiO + Al [8.191 2 2 3 2 = 95 at a temperature of 900°C and a pressure of 1 Atm while increasing the number of moles of aluminum from 50 to 739. The results of the simulations are shown in Figures 8.18 - 8.22. The F*A *C.j.T sImulation of the lIthium extraction from the ore vs. temperature shown In Figure 8.18 Increased exponenually as the ternperature was increased. At a ternperature of 1582°C, 100% recovery was obtained. This would not be a reasonable operaung temperature. Alummum fuming would occur, causIng alumInum impurities in the condensate and there would be serious attack on the refractories used. 100r-----r----.-----,----~----~, , , , , 80 ...... -...... -_ .. .. __ .. _~ ___ ...... ~...... ___ .. • ·, .l , 1 1, ·l , , .l ., > ., cc 1 • 1 1 60 ·········t-··· .... ·t······.. ·i······ .. i······· .. ~ l , 1 1 1 : 1 : 8 l , LLJ ·1 •, l , cc l , • 1 .:i 40 -...... ---- .. - .. --...... !------... ~- .... _.. _... ~-_ .. _- ___ .. • 1 1 1 ~ " , ,." , 1 1 1 •, 1 , 20 ·· .. · .. ··f-··· .... ·t· ... -... ~- ... -.... ~ ... --.... l , 1 1 1 ~oo 800 1000 1200 1400 1600 TEMPERATUREOC Figure 8.18. Lithium extraction from spodumene vs. temperature, Input 8.18. 1 96 The lithium extraction linearly increased as the amount of excess aluminum was increased as shown in Figure 8.19. One·hundred percent recovery t occurred when the ratio of aluminum to spodumene was 739:1, corresponding to an alurninum to spodurnene mass ratio of 53.6: 1. , , , 80 ...... f...... -~ ...... r...... f...... 7" .... - 1 l" , l' 1 1 1 1 1 ,1 1 1 ,1 , , , , , , , . _..... :- ...... -}-_ .... --i---.... 60 ·····t······:·····, , , 1 1 , , ,1 l , , . , 1 , , , 1 ,1 , 1 1 1 1 40 ...... --.--- ...... , --- -_ ... -... -.. _.. ~, .. _.. _-~, .. __ .. _~, .. -- .. - ,• ,1 ,1 1 , ., ,1 , , . •, 1 1 1 1 l , ••: •••••• ~ _•• -- t - --_ ••:- •• - _.~ ••••• ~ ••• _. , l , : : ! , 1 1 , 1 1 , 1 • , l , 1 l , ., ,1 .1 MOLES AI Figure 8.19. Lithium extraction from spodumene vs. the amount of excess liquid aluminurn, Input 8.19 . • 97 1 Figure 8.20 shows that the lithium recovery did not increase as the pressure was 10wered until a value of 1.2E-03 Atm was reached, whence 100% recovery of the lithium occurred. The recovery in this simulation is to the • gas phase as lithium vapour is formed. This critical pressure cou Id be increased by mcreasmg the temperature of the system as shown in Figure 8.21. The addition of more liquid alummum was found to not have an effect on the pressure required for 100% recovery. 100~--~--~---T--~---'----'-~, , ., , 1 1 1 1 80 ------f- .. ·.. --~ --_·_·~ .. _----~·--- .. -f .. -- .. _.. ~_ .. _-_ ... 1 1 1 1 1 1 ,1 ,1 ,1 1 , , , l , , , 1 1 1 1 1 1 60 ···_ .. -t- .. ·_ .. ·~ -- .... -·: .. -·----~·-- .... -t----- .. 1- .. -- .. - 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ,l ," 1 , 1, lit , 1 40 ...... ---~ .... -- .. ~ -- .. --+- .... ---~.- ..... --: .. -- .. --~- .... -.. - l , 1 ,1 , ., 1 20 ····_·i······~ -·····i····--·~······i--····~·····- ,1 l, , J , , , ~~7--~·6~~.5~---~4--~-3~--.2~--.~1--~O LOG PRESSURE (ATM) Figure 8.20. Lithium extraction from the spodurnene vs. pressure at 900°C, Input 8.18. , 98 1.or------.,.-----r-----r-----, 1 1 1 1 1 1 1 0.0 ------:---1 ------~--1 ------~------1 1 1 1 1 1 1 -1.0 -- ...... -- ...... -• ..!-- .... ------! ------..... -~ ...... -... 1 1 1 1 1 1 - 1 • 1 1 1 1 1 1 1 ~ -2.0 --·-·--···-~···--·_····t---··--·····~·--··-····- 1 1 w 1 1 CI: 1 1 ::l 1 1 1 -30 ------__ J. __ ------~- ____ ------_~ ______en • 1 l , enw a: :1 :1 +1 Q. -4.0 ------:------1 Ti------~1 ------1 1 § 1 1 1 1 -5.0 ------*--1 ------;--1 --- --. --- -~1 ------1 1 • 1 1 1 1 1 1 -6.0 .. --.------~--_.------.!-1 1 ... -- .... -----~------.----1 1 1 1 1 -7·~0~0--~90::::0:----1:-=O~OO~--1.,....,''''=0."...O--.,.",11200 TEMPERATUREOC Figure 8.21. Pressure of 100% lithium extraction vs. temperature, Input 8.18. Magnesium addition to the system for each simulation would have the effect of decreasmg the required pressure, ternperature or molar amount of alurninum necessary to obtain 100% recovery. This is illustrated in Figure 8.22 for temperature. Input 8.17 was used with a constant pressure and the temperature was increased from 1025°C to 127SoC by increments of 50°C 1 99 ------ 90 , , OMg 80 ...... -~- ---.-- -~_ .. -- .... -!- .. -_ .. --.!. .... -- .. 1 t 1 t , 1 l , ,1 ,1 ,1 1 •• 2Mg t 4Mg itw > 6Mg 8w , B a: , .::; , , 8Mg 30 ••••••• ~ •••••••. ~ •• -. l , , , , 1 l , 1 20 _.- .. -... ~_ ...... ~ .... - ...... -i ...... · .... -+-- .... -.... t..... -...... 10Mg 1 1 1 1 1 t 1 1 1 1 1 1 1 1 • l' 1 10 .... · .. _.. ·i- .. _.. -- .... ~-- ' ---+_ ...... _~ .. _.. _ ...... 1 1 1COOO 1050 1100 1150 1200 1250 1300 TEMPERATURE C Figure 8.22. The effect of magnesmm to spodumene ratio on the lithium extraction from spodumene with temperature change. 1 The F* A*C*T analysis of the reduction of spodumene by aluminum under various thermodynamic conditions showed that 100% extraction of lithium from the spodumene is possible by either increasing the temperature, increasing the amount of excess molten alummum or by decreasing the pressure of the system. The amount by which one parameter has to be changed depends on the levels of the other two parameters and the magnesium concentration. This section demonstrated that complicated systems can be simulated and the options available can be narrowed down to the best candidates: without having to obtain and construct the different apparatus, perfonn a series of experiments and analyze the products. As a result enormous amounts of time, money and effort are saved. More importantly, this section also showed a good agreement in the percent lIthium extracted from spodumene obtained experimentally and from a , thermodynarnic simulation. 100 IX. CONCLUSIONS AND FUTURE WORK IX.l. CONCLUSIONS • The main fmding of this study was [hat magnesium addition to molten aluminum increases the lIthium extraction from ~ spodumene in a molten metallo-thelmlc reduction process. The effect of magnesium addition on the extraction of lIthium from spodumene was slmllar to calculanons made by a computer thennodynamlc program, F*A*C*T. The lithium producmg reactions at magnesium to spodumene ratios of less than eight to one occurred by a two-step process, Ll a·AI a ·4SiO + ~ Al = LI O·AI 0 + 4Si + ~ Al 0 [9.1) 22323 223 323 Li a·AI 0 + 9Mg 2Li + MgO·AIO [9.2) 2 2 3 = 2 3 In the first step the aluminum reduced the silica in the spodumene to form SIlicon, lIthIUm aluminate, and alumIna. In the second step '1 the magnesium reduced the lithium aluminate to fonn spmel and lithium. At magneslUm to spodumene ratios greater than or equal to eight to one a one-step reaction pathway occurred simultaneously, [9.3) whereby the magnesium reduced the spodumene to form lithium, spinel, silicon, and magnesium oXlde. The discovery that pure molten alummum was able co reduce the silica species in the spodumene indicated that sufficient wetting occurre.d between the spodumene and the molten aluminum for reaction to occur. Therefore magneslUm's role in the system was thermodynamic in nature. The presence of lithium in the condensed meraI vapours indicated that lithium was produced and volatilized. This suggests that at sufficiently low 1 pressures aIl the lithium present In the molten mgot could be voiatilized 101 from the ingot. This coneurs with the vacuum refining theory of lithium in aluminum. 1 F* A*C*T predlcted that one hundred percent extraction of lithium from spodumene can be obrained without magneslUm additIOn, by altenng the thermodynamlc parameters of the system, <;uch as, the amount of excess alummum, the pressure or temperature. The~e parameters could be varied Indivldually or m combmatlon to result m Ideal operatmg conditions. The rate of reaction was hlgh in the fmt twenty minutes of the experiments and in that time penod the majority of the lithIUm was extraeted from the spodumene PreVIOlls daIms that lime was an absolutely necessary reactant in the alumino-thermie reduction of spodumene does not apply to a MLE process. The conversion of a. to f3 spodumene IS a neeessity beeause it produces a more reactlve charge material with a larger surface area. IX.2. FUTURE WORK This first investigation on the metallo-thermie reduetion of spodumene was successful in achievmg 11S goals of a reducmg spodumene to produce a lIthIUm bearing molten ingot. There is great potenual for thiS process commercially, but more work is necessary for funher development. In this section projects and tasks that wou\d aId in the further development of this process are proposed below: The theory and the experimentation of the condensation of pure metal vapours, preferably to the liquid phase. These models wou Id b~ used in a lithium condensing apparatus in the alummo-therrTIlc reduction of spodumene. The surface chemistry of f3 spodumene and liqmd metals. The vacuum refinmg of lithIUm from molten alurninum. The kmetics of the reduction of spodumene by metallo-thennie reduetion. 102 The reaction mechanisms between liquid metais and oxide particles and • their effect on the kinetics. The process, ideally wouid not mclude magneslUm as a reactfu1t due to its simllar vapour pressure te lithium and its hlgh cost. Therefore an all important task would be the reduction of P spodumene by molten aluminum under conditions speclfied F* A *C*T at which 100% lithlUm extraction was predicted. A VItal task would be to desIgn and construct a reaetor suitable for future tests. The reactor wou Id have te: charge aH the matenals simultaneously In an mert atmosphere or vacuum, have intense mixing between the ore and the molten reductant, control of fme powder enusslOns, a method of powder removal from the molten metaI, materin.ls unreactIve with lithium, and an opnon for the development of a continuous process. ·1 • 103 • X. CONTRIBUTIONS • This work examined four original topies which were: 1) the production of lithium via the molten metallo-thermie reductlon of spodumene. 2) the production of lithium via metallo-thermlc reduction at at atmospheric pressure. 3) the reductIon of spodumene by molten metallo-thermie reduetion. 4) the reducuon of an oXlde ore by a molten alloy. The findings from this study were extremely useful and provided new information on the chemlstry and physlcal phenomena on MLE processes and more specifically on the spodumene, aluminum and magnesium system. The eneouragmg results mdlcate that the development of a process for lithium production from spodumene by molten metai reductlon is worth pursuing. 1 104 REFERENCES R. Harris, A.E. Wraith, and J. Togun, "Producing Volatile Metals", Canadlan Patent Application, Ser.No.: 539,058, June 8, 1987, USA Patent ApphcatlOn, Ser No .. 201,446, June 2, 1988 E.P. Corner" The LahIUm Industry Today If, Energy, 3 (1978) pp.237-240 3 Ricardo Bach, J.R. Wasson "LahIUm and Lithium Compounds",Kirk-Othmer EncyclopedIa of ChemIcal Technology, Vol. 14., New York, Wiley & Sons, 1981, pp.449-476. 4 D. LInden, ~attenes and Fuel Cells, McGraw Hill Book Co., Montréal, 1984, p.Il.6. 5 M. Hunt, " New FrontIers In Superhght Alloys ", Materia/s Eng., Aug (1988), pp 29-32. 6 T.R. Crompton, Sm:Jl Battenes- Pnmary Cells, The McMillan Press Ltd, Vol 2, London, 1986, p.147 7 DavId Lmden, Handbook of Battenes and Fuel Cells, McGraw Hill Book Co., Montréal, 1984, pp 11.1-11.87. SR Taylor, "Abundance of Chemical Elements .1 the Continental Crust: A New Table," Geochmllca et Cosmochemlca Acta 1 '164, Vol. 28, pp.1273-1285. 9 L. Crocker, R H Llen, "LIthIUm and as Recovery ~ :om Low-Grade Nevada Clays", US Bureau of Mines Bulletin 691,1987 10 J.O. Vine, "The LIthIUm Resource Emgma", LahIUm Resources and Requirements by the Year 2000, U.S G S. Prof. Paper 1005, 1976. Il J. Norton, "LIthIUm Resource E~timates - What Do They Mean?", Lithium Resources and Reqmrements by the Year 2000, D.S.O.S. Prof. Paper 1005, 1976. 12 J.E. Ferre l , "LithIUm", MIneral Facts and Problems, U.S, Bureau of Mines Bulletin 675, U S. Departmem of the Intenor, 1985, pp.461-470. 1 105 13 J. Searls, "Lithium", Mineral Facts and Problems, U.S. Bureau of Mines Bulletin 671, U.S. Department of the Intenor, 1980, pp.521-534. 14 A.T. Kuhn, Industrial Electrochemical Processes, Elsevier, London, V.K., 1971. 15 C.L. Mantell, Electrochemical Engineering, McGraw-Hill, London, U.K., 1960. 16 Mwing Journal, Vol. 312, No. 8002, Apnl 7, 1989, p.35. 17 l.L. Botto, S Cohen Arazl, T.G. Krenkel, (Fac. Cienc. Exactas. Univ. Nae. La Plata, La Plata, Argentma) Bol Soc Esp. Ceram. Vidrio, 15(1)(1976), pp.5-1O. 18 Friednch Liebau, Structural Chemistry of the SIlicates, Springer Verlag, New York, 1985, p.260. 19 Friedrich Liebau, Structural Chemistry of the Silicates, Springer Verlag, New York, 1985, p.265. 20 Friedrich Liebau, Structural Chemistry of the SIlicates, Springer Verlag, New York, 1985, p.254. 21 L.M. Pldgeon and W A. Alexander, "Thennal Production of Magnesium: Pilot Plant Studles on the Retort Ferrosllicon Process", Trans. AlA1E, 159. 1944, pp.315-352. 22 O. Kubaschewskl, C.B. A1cock, Metallurglcai Thennochemistry, 5th Ed., Pergamon Pre5~, Toronto, pp.212-214. 23 R.H. Parker, An Introduction to Chemical Metallurgy, Pergamon Press, Toronto, 1967, pp 272-273 24 Cl Kunesh, "Calcium and Calel um Alloys", KIrk Ot_b.!11cr Encyclopedia of Chemlcal Technol~, Vol. 14, New York. Wlley & Sons, 1981, pp.414-415. 25 W.J. Kroll, and A W. Schlechtcn, "Laboratory Preparation of LIthIUm Metal by Vacuum Metallurgy", Trans AIME, 182, 1948, pp.266-274. 26 R.A. Stauffer, "Vacuum Process for Preparation of LIthIUm Metal from Spodumene", Trans. AIME, 182, 1948, pp 275-285. , 106 27 W. Morris and L.M. Pidgeon, "The Vapor Pressure of Lithium in the Reduction of LIthium Oxide by Silicon," Can J. Chem., 36, 1958, 1 pp.910-914. 28 T.F. Fedorov and FI. Sharmal, "The Physico-Chemical Principles of the Vacuum ThermIte Reduction of LithIUm", The Uses of Vacuum in Meta11urgy, Oliver & Boyd, Edinburgh, U.K., 1964, pp.126-132. 29 Mlkulinski et aL "Kmet1cs and Condltlon~ of Condensation During the PreparatIOn of Alkali Metals by a Vacuum-Thermal Method", Redk. Shchelochnye Elem., Sb Dokl Vses Soveeclzch 2nd. NOvoslbirsk, 1964, pp.350-360. 30 A.S. Kozhevnikov, " Reduction of Lithium Oxide With Aluminum", ReJk. Shchelochnye Elem., Sb Dokl. Vses. Soveechch., 2nd. Novosibirsk, 1964, pp 343-349. 31 Mikulinski, A.S. and Efremkin, V.V., "Lithium Ores as Complex Raw Materials". Redk. Shchelochnye Elem, Sb. Dokl. Vses. Soveechch., 2nd. Novosibirsk, 1964, pp.339-342. 32 A.I. Lainer, A. Kh. Nazlrov, "Mineral Composition of Lime Spodumene Sinters", Izv. AkaJ. Nauk SSSR, Metal. 6(1966), pp.36-39. 33 E C. Allen, Llqmd Metals, Marcel Dekker, New York, 1973, p.161. 34 R.H. Ewmg, Phil A1ag. , Vol. 25, 1979. 35 A.M. Korol'kov, "Castmg Properties of Metals and Alloys", Consultants Bureau, 1960, p.37. 36 W.T. Thompson, A.D. Pelton and C.W. Baie, F*A*C*T~ Facility for the Analysls of Chemlcal Thennodynamics, (CRCT) Centre for Research in Computauona1 Thermochemistry, École Polytechnique, Montréal, 1988. 37 G.K. Slgworth, T.A. Engh, "Refming of Liquid Aiuminum - a Review of Important Chenucal Factors", Scandmavwn Journal of Mctallurgy, Il. 1982, pp.143-149. 38 CRC Handbook of Chemlstry and Physics, 6-tth Ed., CRC Press Ltd., Boca Raton, F1onda, p.d-46. 107 ...... i.2! .. ~;.2~C 39 Richardson, F.D., Physical Chemlstry of Melts in Metal~, Vol. l, Academie Press, New York, 1974, pp. 141-143. 40 1 R.S. Boy ton, "Chemistry and Technology of Lime and T. imestone", John Wiley & Sons Inc., Toronto, 1980, p.358. 41 Software for Automated Powder DIffractIOn, APD 1700, Operation Manual, Ist Ed. PhilIps Corp, The Netherlands, 1984. 42 G.F Bell, "The Analysis of Alummum Alloys by Means of Atomic Absorption Spectrophotometry", Atomlc Absorption Newsletter, Vol. 5, No. 73, 1966, pp.73-76. 43 1. Soters and R. Stux, "Atomic AbsorptIOn Methods Manual", Vol. 1, InstrumentatIon Lab Inc, Wilmington Ma., 1979. 44 Tracor Northern, 2551 West BeltIine, Mlddletop, Wis., 1985. 45 Lotus 123, Release ~, Lotus Development CorporatIon, Seattle Wash., 1985. 46 Peter Hayes, Process SelectIOn In ExtractIve Metallurgy, Hayes Publishmg Co., Brisbane, Aus., 1985, p.276. 47 M.A. Filyand, E.l. Semenova, Handbook 01 the Rare Elements, Edited by M.E. Alfeneff, Boston Technical Publishers, Cambridge Mass., 1968, p.162. 48 Dlmayuga, F., "Vacuum Refining of Molten Aluminum", Ph.D. Thesis, MCGIll University, 1980, pp.18-45. 49 Hams, R.L. , "Vacuum ~efimng of Molten Steel", Ph.D. Thesis, McGIll University, 1980, pp.14-38. 50 Olette, M., "Vacuum DistIllatIon of Mmor Elements from Liquid Ferrous AlIoys", Physical Chemlstry of Process Metallurgy : Part ~, Edited by G. St. Pierre, Interscience, N.Y., 1961, pp. 1065-1087. , 108 APPENDIX A t The F*A*C*T simulation of the addition of magnesium to the alumino-thermie reduction of spodumene is shown below. The product species identified with ' <---' were drawn from the private data ereated for the dissolved species in molten aluminum. The gaseous magnesium identified with a T was extrapolated from its normal temperature range, the value given would he the magnesiums's partial pressure over the 5 system. The eutoff concentration was set at 1 x 10. , species with a concentration or actlvity less than that were not listed. Mg:Spod ratio = 0 (LI20)*(AL203)*(SIl02)4 + 85.5 AL + MG = 80.318 ( 0.99720 Al + 0.17424E-02 Li <--- + 0.9796IE-03 Li) ( 1173.0, 1.00 ,SOLN 2) ,~, + 3.9939 Si ( 1173.0, 1.00 ,51, 1.0000 ) + 2.8124 A1203 ( 1173.0, 1.00 ,51, 1.0000 ) + 1.7814 LiAI02 ( 1173.0, 1.00 ,51, 1.0000 ) WHERE 'A' ON THE REACfANT SIDE IS O.OOOE+OO Mg:Spod ratio = 1 (LI20)*(AL203)*(SIl02)4 + 85.5 AL + MG = 81.055 ( 0.99467 Al + 0.20963E-02 Mg <--- + 0.17409E-02 Li <--- + 0.97878E-03 Li + 0.43586E-03 Mg) ( 1173.0, 1.00 ,SOLN 2) + 3.9939 Si ( 1173.0, 1.00 ,51, 1.0000 ) '1 109 + 1. 7796 LiAI02 ( 1173.0, LOO ,S 1, 1.0000 ) + 1.7540 Al203 ( 1173.0, l.OO ,S 1, 1.0000 ) + 0.79476 (MgO)(A1203) ( 1173.0, 1.00 ,S 1, l.0000 ) + O.OOOOOE+OO MgO ( 1173.0, 1.00 ,SI, 0.22977E-Ol) WHERE 'A' ON THE REACfANT SIDE IS 1.00 Mg:Spod ratio = 2 (LI20)*(AL203)*(SIl02)4 + 85.5 AL + <.A> MG = 81.723 ( 0.99467 Al + 0.20963E-02 Mg <--- + 0.17409E-02 Li <--- + 0.97878E-03 Li + 0.43586E-03 Mg) ( 1173.0, 1.00 ,SOLN 2) + 3.9938 Si ( 1173.0, 1.00 ,SI, 1.0000 ) 1 + 1.7931 (MgO)(AI203) ( 1173.0, 1.00 ,SI, 1.0000 ) + 1.7777 LiAI02 ( 1173.0, 1.00 ,SI, 1.0000 ) + 0.42409 Al203 ( 1173.0, 1.00 ,S 1, 1.0000 ) + 0.000002+00 MgO ( 1173.0, 1.00 ,S 1, 0.22977E-Ol) WHERE 'A' ON THE REACfANT SIDE IS 2.00 Mg:Spod ratio = 3 (LI20)*(AL203)*(SIl02)4 + 85.5 AL + MG = O.OOOOOE+OO (0.25912E-03 Mg T) ( 1173.0, 1.00 ,G ,O.284E-03) + 82.724 ( 0.98521 Al + O.78317E-02 Mg <--- l + 0.33649E-02 Li <--- 110 + 0.18919E-02 Li + 0.16284E-02 Mg) ( 1173.0, 1.00 ,SOLN 2) + 3.9937 Si ( 1173.0, 1.00 ,SI, 1.0000 ) + 2.2174 (MgO)(A1203) ( 1173.0, 1.00 ,SI, 1.0000 ) + 1.5651 LiAI02 ( 1173.0, 1.00 ,SI, 1.0000 ) + O.OOOOOE+OO Al203 ( 1173.0, 1.00 ,S 1, 0.37036 ) + O.OOOOOE+OO MgO ( 1173.0, 1.00 ,Sl, 0.62040E-Ol) + O.OOOOOE+OO Mg2Si ( 1173.0, 1.00 ,SI, O.63224E-03) WHERE 'A' ON THE REACfANT SIDE 1S 3.00 Mg:Spod ratio = 4 1 t (LI20)*(AL203)*(SIl02)4 + 85.5 AL + MG = O.OOOooE+OO ( 0.54874E-03 Mg T) ( 1173.0, 1.00 ,0 ,0.585E-03) + 83.827 ( 0.97224 Al + 0.16585E-0l Mg <--- + 0.48968E-02 Li <--- + 0.34485E-02 Mg + 0.27531E-02 Li) ( 1173.0, 1.00 ,SOLN 2) + 3.9937 Si ( 1173.0, 1.00 ,SI, 1.0000 ) + 2.3206 (MgO)(Al203) ( 1173.0, 1.00 ,SI, 1.0000 ) + 1.3587 LiAI02 ( 1173.0, 1.00 ,SI, 1.0000 ) + O.OOOOOE+OO Al203 ( 1173.0, 1.00 ,S 1, 0.20958 ) + O.OOOOOE+OO MgO l, ( 1173.0, 1.00 ,SI, 0.10964 ) 111 + O.OOOOOE+OO Mg2Si ( 1173.0, 1.00 ,S l, 0.28354E-02) 1 WHERE 'A' ON THE REA CfANT SIDE IS 4.00 Mg:Spod ratio = 5 (LI20)*(AL203)*(SIl02)4 + 85.5 AL + MG = O.OOOOOE+OO ( 0.83830E-03 Mg T) ( 1173.0, 1.00 ,G ,O.883E-03) + 84.908 ( 0.95986 Al + 0.25337E-0l Mg <--- + 0.60523E-02 Li <--- + 0.52681E-02 Mg + 0.34028E-02 Li) ( 1173.0, 1.00 ,SOLN 2) + 3.9936 Si ( 1173.0, 1.00 ,SI, 1.0000 ) + 2.4014 (MgO)(A1203) ( 1173.0, 1.00 ,SI, 1.0000 ) + 1.1972 LiAI02 1 ( 1173.0, 1.00 ,SI, 1.0000 ) + O.OOOOOE+OO MgO ( 1173.0, 1.00 ,SI, 0.15162 ) + O.OOOOOE+OO Al203 ( 1173.0, 1.00 ,SI, 0.15154 ) + O.OOOOOE+OO Mg2Si ( 1173.0, 1.00 ,SI, 0.66173E-02) WHERE 'A' ON THE REACfANT SIDE IS 5.00 Mg:Spod ratio = 6 (LI20)*(AL203)*(SIl02)4 + 85.5 AL + MG = O. OOOOOE +00 ( O.11244E-02 Mg T) ( 1173.0, 1.00 ,G ,0.118E-02) + 85.977 ( 0.94793 Al + 0.33983E-Ol Mg <--- + 0.70658E-02 Mg + 0.70094E-02 Li <--- , + 0.39409E-02 Li) 112 ( 1173.0, 1.00 ,SOLN 2) + 3.9935 Si ,1 ( 11'73.0, 1.00 ,SI, 1.0000 ) + 2.4707 (MgO)(A1203) ( 1173.0, 1.00 ,SI, 1.0000 ) + 1.0585 LiAI02 ( 1173.0, 1.00 ,SI, 1.0000 ) + O.OOOOOE+OO MgO ( 1173.0, 1.00 ,SI, 0.19015 ) + O. OOOOOE +00 Al203 ( 1173.0, 1.00 ,S 1, 0.12083 ) WHERE 'A' ON THE REACfANT SIDE IS 6.00 Mg:Spod ratio = 7 (LI20)*(AL203)*(SIl02)4 + 85.5 AL + MG = O.oooOOE+OO ( 0.14058E-02 Mg T) ( 1173.0, 1.00 ,G ,0.146E-02) + 87.039 ( 0.93616 Al '1 + 0.42489E-01 Mg <--- + 0.88344E-02 Mg + 0.78376E-02 Li <--- + 0.44065E-02 Li) ( 1173.0, 1.00 ,SOLN 2) + 3.9934 Si ( 1173.0, 1.00 ,SI, 1.0000 ) + 2.5329 (MgO)(A1203) ( 1173.0, 1.00 ,SI, 1.0000 ) + 0.93427 LiAI02 ( 1173.0, 1.00 ,SI, 1.0000 ) + O.OOOOOE+OO MgO ( 1173.0, 1.00 ,SI, 0.22622 ) + O.OOOOOE+OO A1203 ( 1173.0, 1.00 ,SI, 0.10157 ) WHERE 'A' ON THE REAC!' ANT SIDE 1S 7.00 113 Mg:Spod ratio = 8 (LI20)*(AL203)*(Sl102)4 + 85.5 AL + MG = O.OOOOOE+OO ( 0.16821 E-02 Mg T) ( 1173.0, 1.00 ,G ,0.174E-02) + 88.097 ( 0.92512 Al + 0.50840E-Ol Mg <--- + 0.10571E-Ol Mg + 0.85733E-02 Li <--- + 0.48202E-02 Li) ( 1173.0, 1.00 ,SOLN 2) + 3.9933 Si ( 1173.0, 1.00 ,SI, 1.0000 ) + 2.5900 (MgO)(A1203) ( 1173.0, 1.00 ,SI, 1.0000 ) + 0.82008 LiAI02 ( 1173.0, 1.00 ,SI, 1.0000 ) + O.OOOOOE+OO MgO ( 1173.0, 1.00 ,S 1, 0.26037 ) + O.OOOOOE+OO Al203 1 ( 1173.0, 1.00 ,SI, 0.88246E-Ol) + O.OOOOOE+OO Mg2Si ( 1173.0, 1.00 ,SI, 0.26643E-0l) WHERE 'A' ON THE REACfANT SillE IS 8.00 Mg:Spod ratio = 9 (LI20)*(AL203)*(SIl 02)4 + 85.5 AL + MG = O. OOOOOE +00 ( O.l9531E-02 Mg T) ( 1173.0, 1.00 ,0 ,0.202E-02) + 89.150 ( 0.91419 Al + 0.59030E-Ol Mg <--- + 0.1 2274E-01 Mg + 0.92381E-02 Li <--- + 0.51939E-02 Li) ( 1173.0, 1.00 ,SOLN 2) + 3.9933 Si ( 1173.0, l.oo ,S l, 1.0000 ) , + 2.6433 (MgO)(A1203) 114 ( 1173.0, 1.00 ,SI, 1.0000 ) + 0.71338 LiAI02 1 ( 1173.0, 1.00 ,SI, 1.0000 ) + O.OOOOOE+OO MgO ( 1173.0, 1.00 ,S l, 0.29298 ) + O.OOOOOE+OO A1203 ( 1173.0, 1.00 ,SI, 0.78426E-Ol) + O.OOOOOE+OO LiAI T ( 1173.0, 1.00 ,SI, 0.76319E-01) + O.OOOOOE+OO Mg2Si ( 1173.0, 1.00 ,SI, 0.35918E-01) WHERE 'A' ON THE REACfANT SIDE 1S 9.00 Mg:Spod ratio = 10 (LI20)*(AL203)*(SIl02)4 + 85.5 AL + <Â> MG = O. OOOOOE +00 ( O.22187E-02 Mg T) ( 1173.0, 1.00 ,G ,0.229E-02) t + 90.201 ( 0.90354 Al + O.67057E-Ol Mg <--- + O.13943E-Ol Mg + O.98462E-02 Li <--- + 0.55359E-02 Li) ( 1173.0, 1.00 ,SOLN 2) + 3.9932 Si ( 1173.0, 1.00 ,SI, 1.0000 ) + 2.6937 (MgO) (A1203) ( 1173.0, 1.00 ,SI, 1.0000 ) + 0.61253 LiAlO2 ( 1173.0, 1.00 ,SI, 1.0000 ) + O.OOOOOE+OO MgO ( 1173.0, 1.00 ,SI, 0.32427 ) + O.OOOOOE+OO Al203 ( 1173.0, 1.00 ,SI, 0.70858E-Ol) + O.OOOOOE+OO Mg2Si ( 1173.0, 1.00 ,S 1, 0.46352E-Ol) f WHERE 'A' ON THE REACT ANT SIDE IS lO.O 115 APPENDIX B In this study the reductant was a mixture of molten aluminum with dissolved magnesium, lithium and silicon. Figures B.I, B.2, and B.3 show the phase diagrams Welghl Percent MagneSium o 10 20 30 10 50 60 70 /l0 QI) 100 700r~...... ,.I-,...... -""T""'----"'~~-r-.l,.....~~~~...l.-~~~_T'""'l,--~~._ ...._ • 600 L 500 t.J 0 V 1.0 ....:1 l'd 400 1.0 1 V Co E v E- 300 200 10 20 30 40 50 60 70 1\0 GO 100 Al Atomlc Percent MagneSium \Ig Figure B.l. Aluminum-magnesium phase diagram T. Massalski, Ed., "Binary Alloy Phase Diagrams", ASME, Metals Park, , OhiD, 1985. 116 Welght Prrcent Lit hlurn 0 j 10 r 30 40 50 60 70 SO 100 1 r 1 1 ! ! I __ ~_ • 800 1 j 700 1 600 L U 0 Q) '- ~ .....=' t1:I '-Q) a. 400 8 Q) E- JOO 200 20 JO 40 50 60 70 eo 90 100 • AtOffilC Percent LithIUm LI Figure B.l. Aluminum-Lithium phase diagram 117 Welght Percent SIlicon 0 10 30 40 ~ 60 '0 80 90 1 I~ tt;J 1300 1100 :)'-- CJ :::"" .-J ~ 900 ().l ""C- E CJ E- 300+--~~,...... ~...... ,-~~~ , \ r ~·T"'"r ~~"'r ...... ,..""T"T"~"T" o 10 20 30 40 !50 60 70 ao 90 100 Al Atomlc Percent Silicon SI l Figure B.3. Aluminum-silicon phase diagram. 118 -l f>-l -1000 0: ~