WRAP MDD018 WEEE Separation Kinetic Gravity Separator Trial ¢  The Kinetic Gravity Separator

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  • WRAP MDD018/23 WEEE separation techniques

    Delft University of Technology

    Kinetic Gravity Separator trial report

    Abstract This report details a trial conducted on the kinetic gravity separator at Delft University of Technology for WRAP project MDD018/23. The aim of the project was to trial innovative techniques to tackle some of the more difficult separations encountered by primary and secondary WEEE processors. Recovering fine copper from mixed WEEE is a notoriously difficult separation. Primary WEEE processors typically use eddy current separators to extract non-ferrous metals from shredded WEEE. These separators are unable to extract fine wire and smaller non-ferrous items such as screws and washers because these components are too small in cross-section to generate sufficient eddy current to create a separation force. To allow high grade plastic recycling all non-ferrous metals must be removed from the WEEE plastic fraction. Several techniques have been tested during this project to attempt to find a solution to the problem.

    The kinetic gravity separator is a piece of equipment which Dr Peter Rem and his team at Delft University have developed to separate materials based on the principle of shape and density. The separator exploits the different settling velocities of materials with different shape and density. A large scale pilot plant is available at Delft University where research into the relatively new technique is still in progress. However, one unit is currently in use in an industrial application. The kinetic gravity separator (KGS) at Sluiskil in the Netherlands has a capacity of 10 tonne per hour and separates aluminium and stone from heavy non- ferrous metals into three size ranges: 1-3mm, 3-8mm and 8-12mm. The machine uses conveyors to remove the material from the collection compartments.

    The aim of the trial was to test the machine’s ability to separate fine copper, metal and glass from plastic. Two different materials were tested:

     The first sample was a mixture of plastics and fine copper wires with small quantities of glass, wood, circuit boards, glass and other materials in the size range 8-12mm.

     The second material was a coarser mixture of plastic and copper along with other metals, stone and glass in the size range 10-15mm.

    Both materials were processed in the kinetic gravity separator and a successful separation was achieved. The copper and metals concentrated in the heavy fraction whilst the plastic concentrated in the middle and light fractions.

       

  • WRAP MDD018 WEEE Separation Techniques   

    Delft Kinetic Gravity Separator Trial Report       

    The results of the trial with the first sample gave a copper recovery of 83% with concentrations of 18% copper, 22% coated wire (assumed to contain 50% copper and 50% plastic) and 9% other metals in the heavy stream, a total metal content of 38%. The level of combustible plastic, rubber and wood in the heavy fraction, at around 43%, is still above the recommended value of 5%. Therefore the material would need to be processed further to reduce the combustible content to below the specification set by the copper smelters.

    The second trial recovered 95% of the copper into a heavy fraction with a total metal concentration of 76%. The concentration of combustible material in the heavy fraction was 8% which is close to the acceptance limit set by the smelters.

    The equipment is a prototype and some problems with the design of the product off-take system became apparent during the trial. It should be possible to resolve these issues in a production unit.

    If the equipment can be adjusted to cut the combustible content of the heavy product to below 5% and also achieve throughput of at least 1tonne/hr the payback time would be just over a year.

    Overall the technique demonstrated good recovery of non-ferrous metals and glass from plastic/ metal mixtures produced by secondary WEEE recycling plants and has the potential to become a practical WEEE separation technique.

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  • WRAP MDD018 WEEE Separation Techniques   

    Delft Kinetic Gravity Separator Trial Report       

    Table of Contents Abstract.......................................................................................................................... 1

    1.0 ......................................................................................... 5 Information on the trial

    1.1 ............................................................................ 5 Photograph of trial equipment

    1.2 ............................................................................. 7 Description of trial equipment

    1.3 .................................................................................................. 9 Trial objectives

    2.0 ....................................... 11 Trial number 1 - Recovering fine copper from plastic mix

    2.1 .................................................................................................. 11 Trial objective

    2.2 .................................................................................................. 11 Feed material

    2.3 ............................................................................................................. 11 Trial 1

    2.4 ........................................................................... 13 Photograph of result samples

    2.5 ............................................................................... 15 Analysis of results samples

    2.6 ........................................................................................ 17 Discussion of results

    2.6.1 Throughput ................................................................................................... 17

    2.7 ....................................................................................... 17 Conclusions from trial

    3.0 ................ 19 Trial Number 2 - Recovering heavy copper and metal from a plastic mix

    3.1 .................................................................................................. 19 Trial objective

    3.2 .................................................................................................. 19 Feed material

    3.3 ............................................................................................................. 20 Trial 2

    3.4 ....................................................................... 21 Photographs of product samples

    3.5 .............................................................................. 23 Analysis of product samples

    3.6 ........................................................................................ 25 Discussion of results

    3.6.1 .............................................................................................. 26 Throughput

    3.7 ....................................................................................... 26 Conclusions from trial

    4.0 ........................... 26 Economic assessment of the technique via a payback calculation

    4.0 ............................................................................. 29 Overall final conclusion of trial

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  • WRAP MDD018 WEEE Separation Techniques   

    Delft Kinetic Gravity Separator Trial Report       

    List of Figures Figure 1: Side view of kinetic gravity separator ................................................................. 6 Figure 2: Aerial view of kinetic gravity separator ............................................................... 6 Figure 3: Product off-take end of kinetic gravity separator ................................................. 6 Figure 4: Cut-away sketch of kinetic gravity separator....................................................... 7 Figure 5: Plan view showing the product off-take compartments relative the feed point ...... 8 Figure 6: Graph of the settling velocities for various particles............................................. 9 Figure 7: Photograph of Copper Rich Plastic Feed Material............................................... 11 Figure 8: Trial 1 heavy product fraction .......................................................................... 13 Figure 9: Trial 1 middle product fraction ......................................................................... 13 Figure 10: Trial 1 light product fraction........................................................................... 14 Figure 11: Schematic of the trial 1 results....................................................................... 16 Figure 12: Photograph of heavy copper plastic mix feed material ..................................... 19 Figure 13: Trial 2 heavy product fraction ........................................................................ 21 Figure 14: Trial 2 middle product fraction ....................................................................... 21 Figure 15: Trial 2 light product fraction........................................................................... 22 Figure 16: Trial 2 floaters product fraction ...................................................................... 22 Figure 17: Schematic of the trial 2 results....................................................................... 24

    List of Tables Table 1: Settling velocity and compartment information for the kinetic gravity separator ..... 8 Table 2: Results collected during trial 1 .......................................................................... 12 Table 3: Results of hand sorting of trial 1 samples ...

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