EMC Leipzig 2017
WEEE recycling – metal recycling from complex beneficiation fines
Anna Trentmann, B. Friedrich
IME Process Metallurgy and Metal Recycling, RWTH Aachen University Prof. Dr.-Ing. Dr. h.c. Bernd Friedrich
WEEE - a complex recycling source •
49.8 mio.t estimated for 2018 (worldwide UN)
•
Complex and inhomogeneous composition
•
• Glasses • Ceramics • Nonferrous metals • Critical metals • Precious metals • Plastics Enormous recycling potential
Fractions in mass.-% 4% electronics
10% other
19% plastics 21% Nonferrous metals
10% Glasses
36% Ferrous metals reference: Bundesverband Sekundärrohstoffe und Entsorgung e. V,
Recycling of electronic scrap - challenges Processing • Standard methods • Output of different fractions • Formation of waste fractions
Pyrometallurgy • Copper recycling route • Challenges because of high energy content • Difficult process control
Pyrolysis • Thermal decomposition under inert conditions • Subject of research • Formation of hazardous offgas
Processing of electronic scrap WEEE (Waste of Electrical and Electronic Equipment)
pre-crushing selective removal
pollutants composites recyclates
1. shredding
dust extraction
separation/ sorting
•
•
filter dust
2. shredding
separation/ classification
pollutants and residues reference: Rotter, Martens,
•
processing of electronic scrap produces metal-rich fractions Waste fractions e.g. filter dust and shredder light fraction Special treatment is necessary
recyclates
Potentials of waste fractions from WEEE recycling • Special treatment for waste fractions is needed because of high energy content • Input of waste fractions is limited (overheating, offgas) Focus on beneficiation fines: → 7.7 kg/t WEEE are generated → Worldwide: ~ 6000 t dust/year reference: Chancerel et al.
Potentials Carbon: • Exothermic reaction can be used to melt other waste fractions • Reduction potential
Metal content • Ag: 600 ppm, Au: 20 ppm, Cu: 6-12 % Development of autogenous pellets • • •
Reduction potential Autotherm Melting point
Research program for beneficiation fines Characterization • Chemical analysis • Continuous offgas investigation via FTIR analysis
Thermo-chemical modelling • Slag optimization • Calculation of oxygen amount • Presumed phase distribution
Conditioning • Homogenization and upgrading • Compaction
Melting process • Combustion of material with oxygen • Separation into slag and metal phase • Investigation about kinetics
Chemical Characterization
• • •
High energy content (organic carbon) Alumina content leads to a high melting slag Copper rich metal phase
Slag phase
Wt. %
Energy source
Metal phase
Al2O3
CaO
SiO2
MgO
FeO/Fe2O3
Cu
Fe
Zn
Au (ppm)
C
15.028.0
4.95.5
17.019.0
1.1
1.3
6.812.0
0.59 -2.2
2.82.9
311531
16.420.1
Offgas investigation via FTIR analysis
•
Process temperature up to 550°C, heating rate 300-700°C/h
•
continuous offgas analysis via FTIR spectroscopy (CO2, CO, CxHy, halogen…) and oxygen sensor
•
variation of atmosphere (inert/air/ gas mixture) possible
Pyrolysis of filter dust • Variation of heating rate, holding time and atmosphere °𝐶 °𝐶 • Change of heating rate from 300 up to 600 ℎ
ℎ
parameter • Use of inert and argon/oxygen mixture (1 Vol.% O2)
results
• • • •
formation of hydrocarbons starting at 200 °C 27 % weight loss Detection of styrene and hydrogen chloride Injection of argon/oxygen mixture leads to a higher amount of CO2 and reduces formation of hydrocarbons
Thermo-chemical models – slag optimization
•
Slag composition leads to a high melting point of 1559,65 °C
•
Variation of SiO2, CaO, Na2O, FeO amount to reduce the melting point
•
Addition of different amounts of sodium oxide lowers the melting point to 1298 °C
Calculation of oxygen amount 100 90
Metal yield in melt %
80 70
Cu
60
Fe
50
Ni Zn
40
Sn
30
Pb
20
C
10 0 0
10
20
30 40 oxygen in %
50
•
Carbon (plastic) as separate phase
•
Oxidation of Nickel over 50 % oxygen, oxidation of copper over 70 % oxygen
•
Optimum: 40 % oxygen – total combustion of carbon ( complete conversion)
60
70
Presumed phase distribution without slag additives 1300 °C phases in g / 100 g filter dust
70 60 50 40
total
30 other 20
total
CaO
FeO Sn
Al2O3 10
Cu
SiO2 0 Feststoffe Solid (s) (s)
Schlacke Slag (l) (l)
Metal Metall(l)(l)
•
12 % metal phase presumed composed of over 90 % copper
•
Liquid slag phase consisting of SiO2, Al2O3 and FeO/ Fe2O3
•
Solid mineral phase
•
Gas phase (CO, CO2, H2O)
Gas (g)
Presumed phase distribution with slag additives 1300 °C 120
other FeO
Phases in g / 100 g filter dust
100 CaO 80
60
Al2O3
40 total SiO2
20
Sn Cu 0
Gesamt
Feststoffe Solid (s) (s)
Schlacke Slag (l) (l)
Metall metal (l) (l)
Gas (g)
•
Variation of slag additives CaO, SiO2
•
Avoiding of high melting phases and spinels
•
All oxides components are soluble in liquid slag phase
Experimental work compaction
Rotating pelletizer plate
Experimental setup •
Oxygen input with a ceramic lance
•
Continuous temperature and Offgas measurement (CO, CO2)
•
Starting temperature minimum 900 °C
•
After complete combustion, holding time 1h (1300 °C)
•
Mixing of filter dust, additives and slag additives
•
Compaction to pellets under usage of binders (molasses)
•
Defined drying time under air
Influence of compaction on melting behaviour Melting behaviour of filter dust without additives: • • •
•
Variation of oxygen supply No homogenous melt formation possible High mass losses because of dust generation and high turbulences Only melt formation on the surface
Melting behaviour of optimized pellets: • • • •
• Definite separation slag and Copper content in slag < of 2 mass.% metal phase Copper content slag in metal phase: • Optimized shows good80-92 % settling properties for >95,6% metal Recovery rates for copper droplets Slag correspond with the • composition Complete combustion under FactSage modeling oxygen possible
Pellet behaviour Electronic balance
Investigation of • Relation between mass loss, temperature and time • Reaction progress inside pellet • Treatment of single pellets
Measured values •
•
Relations between mass loss and time •
10-90s
•
Continuous weight measurement
Temperature profile inside pellet •
•
furnace
Transition from total organic carbon (TOC) to inorganic carbon (TC) •
pellet
800-1200°C furnace temperature
Carbon analysis in core, shell
Results 10s
800°C
•
Weight loss 30-33 %
•
TOC decreases from 16.4 % to < 1 %
•
Formation of shell
•
90s to reach furnace temperature in shell
•
Weight loss increases with holding time and temperature
Summary and outlook conclusion
outlook •
Optimization of oxygen supply
•
Addition of copper-rich additives to control exothermal reactions
•
Trials with filter dust-pellets and other waste fraction in demo scale TBRC
•
Autothermal recycling of filter dust is possible
•
Total combustion of contained carbon in form of plastics under oxygen possible
•
Clear metal/ slag separation was observed
•
Pelletizing step is necessary
EMC Leipzig 2017
Thank you for your attention!
[email protected]
IME Process Metallurgy and Metal Recycling, RWTH Aachen University Prof. Dr.-Ing. Dr. h.c. Bernd Friedrich