ze ss te ch nik. Recycling. Development of a CaO-CaF. 2. -slag system for high ... Concentrate after mechanical processing, w%. 2-3. C. 1-2. 0.5-1. 13-16. 9-11.
Development of a CaO-CaF2-slag system for high rare earth contents
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Metallurgie
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T. Müller; B. Friedrich
Recycling
IME Process Metallurgy and Metal Recycling Aachen University, Germany Prof. Dr.-Ing. Bernd Friedrich
Source for Rare Earth: Battery Recycling Design
Types
Nickel-Metalhydride battery composition (wt-%) Ni
Co
La, Ce, Nd, Pr
36-42 3-4 8-10 Application today
Fe
H2+O2
plastic
22-25 15-17 3-4 Further application:
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TOYOTA MOTOR CORPORATION Prius,110,000 sold Hybrid Vehicles since 1998
Recycling
Flowsheet of the intended recycling process Ni-MH-batteries Can scrap Organic/separators
Mechanical processing NiMH –Ni(OH)2 – Ni – mass partly with carbon black and organics Flux
Melting RE-rich slag Return slag
Slag processing Pyromet. refining Ni-Co-alloy
Molten salt electrolysis Mischmetal
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Ni-MH battery production Recycling
Flowsheet of the intended recycling process Ni-MH-batteries Can scrap Organic/separators
Mechanical processing NiMH –Ni(OH)2 – Ni – mass partly with carbon black and organics Flux
Melting RE-rich slag Return slag
Slag processing Pyromet. refining Ni-Co-alloy
Molten salt electrolysis Mischmetal
Ni-MH battery production
Concentrate after mechanical processing, w% Co
La, Ce, Nd, Pr
Fe
Mn
C
45-50
9-11
13-16
0.5-1
1-2
2-3
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Ni
Recycling
Required slag properties
• Liquid at 1500 °C (melting point of NiCo-alloy) • Low evaporation pressure of slag components • Low viscosity • High density difference of slag and metal • High solubility for RE respectively poor solubility for Ni and Co
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• Suitable for slag processing
Recycling
Slag development (I) – First scan Result
No flux added
No phase separation
SiO2 - CaO - MgO
Sufficient, but difficult phase separation
SiO2 - CaO - Al2O3
Sufficient
CaF2 - CaO SiO2
From very good to unsuccessful depending on added amount Unsuccessful
CaCl2
No phase separation
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Slag system
Recycling
Slag development (II) – Lab-scale el. arc melting Experimental set up 1 graphite electrode (cathode) 2 copper electrode (anode) water cooled 3 refractory 4 water inlet 5 bag filter 6 spark shield
6 4
5 T... thermo couples
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water outlet
Recycling
Slag development (III) – Lab-scale el. arc melting Results Slag system CaF2 – CaO
Composition (wt%) NiMH/flux 13-35 CaO, 65-100 CaF2
45 SiO2, SiO2 - CaO – MgO 40 CaO, 15 MgO SiO2 - CaO - Al2O3
36-48 CaF2, 18-45 CaO, 36-38 Al2O3
Result
0.8-9
from insufficient to very good
3-9
from poor to very good
2.3-5.7
all insufficient
Due to unexpected results in repeated trials basic investigation of slag systems required: chni sste Proze
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Investigation of density, surface tension and viscosity Recycling
Density determination – Experimental procedure • No information about RE-influence on CaO-CaF2 systems were found • Decided to determine some basic properties • Lab-facilities for measurement of density, viscosity, surface tension, wetting angle available at IME • Start with density measurement using hydrostatic weighing method: Derived equation for measurements with different bobs:
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ma1, mm1, ma2, mm2: V1, V2:
Recycling
(ma1 - mm1 ) − (ma 2 - mm 2 ) ρm − ρa = 3 (V1 − V2 ) ⋅ (1 + ε )
Weights of 1. + 2. bob in air and in the melt Volumes of 1. + 2. bob
Density determination – Experimental setup Scale Balance Pt-Wire Pt-Rh wire Thermocouple to PC Mo bob Pt-Sphere
to PC
Frame Crucible Melt
Furnace Furnace Controller
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Transformer Recycling
Density determination – Results ρ min
ρ max Arithmetic mean Standard deviation
Trial 1 4.072 4.556 Trial 2 4.073 4.550 Trial 3 4.082 4.550
4.309 4.315 4.307 Trial 1
Trial 2
0.142 0.139 0.150 Trial 3
3
Propability density
2,5 2 1,5 1 0,5
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0 4,05 Recycling
4,10
4,15
4,20
4,25
4,30
4,35
4,40 -3
Density, g cm
4,45
4,50
4,55
4,60
Pilot plant tests – Experimental set-up
tapping operation
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• Charging velocity 100-200 kg/h • Average tapping weight 245 kg • Power during operation app.150 kW (max. 480) • Average tapping temperature 1680 °C Recycling
Pilot plant tests – Input composition Nr.
Material
Flux composition
SiO2 CaF2 Anode scrap 65 % Production scrap 65 % Spent batteries 65 % Pyrolysed spent batteries 65 % Pyrolysed spent batteries 65 % Pyrolysed spent batteries 65 % Mixture 65 % Mixture 65 % Polluted Mixture 65 %
1 2 3 4 5 6 7 8 9
CaO 35 % 35 % 35 % 35 % 35 % 35 % 35 % 35 % 35 %
Charge composition Flux Ni-MH 10 % 90 % 10 % 90 % 10 % 90 % 10 % 90 % 5% 95 % 5% 95 % 5% 95 % 5% 95 % 5% 95 %
Pouring temperature °C 1730 1660 1600 1675 1710 1730 1545 1720 1520
• Similar smelting behaviour of different scraps • Successful separation of NiCo and RE • Required flux amount reduced to 5 % • Both slag systems are suitable chni sste Proze
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• CaF2-CaO-system is easier to handle Recycling
Material preparation
Pellets
Powder
Pilot plant tests – Slag composition Nr.
Material
1 2 3 4 5 6 7 8 9
Anode scrap Production scrap Spent batteries Pyrolysed spent batteries Pyrolysed spent batteries Pyrolysed spent batteries Mixture Mixture Polluted Mixture
RE-Oxide
Ca
Mg
Fe
Al
Co
Ni
55.6 59.1 53.3 55.3 66.1 69.0 63.8 64.1 65.8
14.6 15.3 16.6 16.8 12.1 5.81 10.1 5.12 10.8
0.93 0.24 0.33 0.35 0.70 1.69 0.21 0.93 0.33
0.74 0.37 1.77 0.49 0.29 0.18 0.36 0.38 0.33
4.03 2.8 3.08 2.97 3.32 3.59 3.44 3.85 3.74
0.12 0.10 0.31 0.017 0.009 0.008 0.015 0.155 0.027
0.73 0.59 2.25 0.10 0.04 0.03 0.05 1.00 0.12
• RE content varies from 53 % to 69 % • Low Ni and Co content • Only part of Fe and Mn were slagged
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• Mg originated from furnace refractory
Recycling
Focus on CaF2-CaO-system
Mn
SiO2
F
0.31 8.95 1.17 8.83 0.70 8.95 0.94 7.29 0.34 4.18 0.16 10.8 1.93 4.81 0.37 10.8 1.27 5.10
Summary • Objective of the project is the development of a closedloop recycling process for NiMH batteries • Scan delivered possible suitable slag systems • In more than 50 Lab-scale trials two possible slag systems were determined (CaF2-CaO and CaO-SiO2)
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• Start of basic information investigation (density, surface tension, viscosity) • Pilot plant trials: Transfer from 5 kg to 300 kg successful conducted Next steps: • Further trials for densiy, surface tension and viscosity determination Recycling
Thank you for your attention Acknowledgements: The authors are thankful to the Federal Ministry of Education and Research (BMBF) for financial support of this project.
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IME Process Metallurgy and Metal Recycling Recycling
University of Technology , Aachen, Germany Prof. Dr.-Ing. Bernd Friedrich
