Zheng WANG University of Nottingham, Ningbo, China

Supervisor: Prof. Nick Miles, Dr Philip Hall

Particle Separation Techniques for WEEE Recycling

Background •  20-25 million tonnes WEEE

production worldwide per year. (Robinson, 2009)

•  More than 70% shipped to developing countries.

•  Environmental polluting recycling.

!

Pollute the Environment

Threat Human health

Discarded Resources

Material Concentration in UK WEEE stream

Aluminium 20-200 kg/t

Iron 100-420 kg/t

Copper 20-90 kg/t

Silver 21.41 g/t

Gold 6.45 g/t

Platinum Group Metals 2.14 g/t

Objectives: •  Environmental friendly

method for WEEE recycling.

•  Particle segregation to separate metallic fractions.

(WRAP, 2012)

Particle Separation Techniques Explored

Pneumatic separation •  Particle segregation induced

by pulsation of air. •  Principle: Stokes’ law and

terminal velocity

Vibratory separation •  Brazil nut effect: !

(Gupta and Yan, 2006)

A.  Bed at rest B.  Air pulsation and differential

acceleration C.  Hindered settling D.  Consolidation trickling

(Kudrolli, 2004)

Inverse density segregation: •  Dense particles have more

momentum, travel further. •  Bottom voids filled by lighter

particles. •  Inverse density segregation.

Pneumatic Separation - Sample Preparation

!!•  !!

!!

!!!!0%

5%

10%

15%

20%

25%

30%

Particle size (mm)

Mass percentage in each size fraction

•  Waste computer mother boards (lithium

batteries and heat sinks removed)

•  Shredding: CSF570 hammer mill (Fengli

Pulverization Equipment Co., Ltd), 10 mm

aperture size on the discharge plate

•  Sieving: particle size distribution

Pneumatic Separation – Pneumatic Jig

Pneumatic Separation Process

Bed height = 100mm, superficial velocity of air pulsation = 4m/s!

Light-to-dense fraction weight ratio: 1:6 – 1:9; throughput: 150kg/h!

Pneumatic Separation – Result

Before separation, density =2.27 g/cm3, metal content 34.6%

Dust collected in the dust extraction unit

Bottom fraction – metallic fraction density =2.34 g/cm3, metal content 45.1%

Top fraction – non-metallic fraction density =1.96 g/cm3, metal content 14.0%

Vertical Vibratory Separation •  Investigate vibration parameter for

separation of irregular shaped particles •  Cutting mill grinded copper (density =

8.76g/cm3) & polypropylene (density = 0.91g/cm3) particles, particle size less than 850µm

•  Volume Ratio (mimic metallic/non-metallic fractions): Light material : Dense material = 3:1. Dr. Helena Webster, 2009

10mm thin cell with slopped design

Dr. Muddasar Habib, 2010 T-shape cell design

Previous work with 90-125µm bronze and glass spheres

Copper particles Polypropylene particles

Vibratory Separator Separation chamber

Supporting frame

Vibration table

Pneumatic piston

Separation chamber

Vibration monitoring

Thin cell design for fast segregation, powered by pneumatic piston.

Vertical Vibratory Separation

Copper and polypropylene particles, less than 850µm!

Bed height = 40 mm, slope = 15°; Vibration : �=5, f=30�2Hz

Conclusion & Future work Pneumatic separation

•  Experiment with reduced particle size (better liberation of metal)

•  Multi-stage process to improve separation efficiency.

•  Scale up design, longer retention time to enhance the concentration effect.

Vibratory separation

•  Suitable vibration condition: bed height 30-50mm, vibration intensity Γ= 4-6, frequency ! = 30±5 Hz

•  Continuous separation experiment and examine the separation efficiency.

•  Particle segregation of three-phase system: copper, glass and polypropylene particles.

•  Separation of shredded printed wiring boards.

Scale up design, throughput 2 tone/hr.

THANK YOU!

Acknowledgement: This work was supported by Innovation Team of Ningbo

Science and Technology Bureau (2012B82011) International Technological Cooperation Project of

the Ministry of Science and Technology (2012DFG91920).