WEEE recycling – metal recycling from complex

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Recycling of electronic scrap - challenges. Processing ... Copper recycling route. • Challenges .... 12 % metal phase presumed composed of over 90 % copper.
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



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