WRAP MDD018 WEEE Separation Techniques Kinetic Gravity Separator Trial Report.pdf · The Kinetic Gravity Separator (KGS) is a system developed by the recycling laboratory at Delft

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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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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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 .......................................................... 15 Table 4: Q and R separation efficiencies for trial 1 .......................................................... 17 Table 5: Results collected during trial 2 .......................................................................... 20 Table 6: Results of hand sorting of trial 2 samples .......................................................... 23 Table 7: Q and R separation efficiencies for trial 2 .......................................................... 25 Table 8: Economic assessment by a payback calculation.................................................. 27

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1.0 Information on the trial

Trial host: Recycling Laboratory at Delft University of Technology, Delft, The Netherlands.

Trial equipment: Kinetic Gravity Separator (KGS)

Trial date: 14th/15th January 2009

The Kinetic Gravity Separator (KGS) is a system developed by the recycling laboratory at Delft University during their research into recycling and separation techniques.

1.1 Photograph of trial equipment Figures 1-3 show views of the kinetic gravity separator. A detailed description of the system follows.

Product pipes

Additional

water supply

to entrain

Water

Pump

Feed hopper onto

vibrating feeder

Overflow chute

with screen (Not in

use)

Rotating inner

compartment

Product pipes

carrying

material to

dewatering

screens

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Figure 1: Side view of kinetic gravity separator

Figure 2: Aerial view of kinetic gravity separator

Figure 3: Product off-take end of kinetic gravity separator

Top up

water pipe

Vibrating

feeder

Rotating

vanes

Product

dewatering

screens

Product

chutes

Water

reservoir

Heavy

products

collection

bin

Light

product

collection

bin

Middle

products

collection

bin

6



1.2 Description of trial equipment This equipment exploits differences in the terminal falling velocities of particles in water to achieve a separation. It is capable of separating the feed material into more than two fractions and has been used by Delft University to separate light and heavy non-ferrous alloys in the size range 2-10mm along with various types of plastics. Material which floats in the separator is collected separately.

Figure 4: Cut-away sketch of kinetic gravity separator

Figure 1 shows the main vessel of the kinetic gravity separator. Material is fed from the feed hopper into the kinetic gravity separator itself by a vibratory feeder. The product removal pipes are visible in this photograph. These tended to block with heavy material during the trial unless they were shaken regularly.

Figure 2 shows the rotating vanes which form an integral part of the separator. They are approximately 20-30cm long, about 200cm deep and 5cm apart.

Figure 3 shows the dewatering screens and off-take chutes for the light, middle and heavy products. The material collects in bins at the bottom of the chutes and has to be removed by hand. The water from the de-watering screens is re-circulated to the water reservoir.

Figure 4 is a cut away sketch showing the inside of the unit and indicates which compartments different materials will land in.

The feed material is directed by the vibrating feeder into the slots created by the vanes, which act as isolated separating columns. Particles in each column fall through the water as the vanes rotate. Since the vanes rotate, particles with high settling velocities will fall into the collection compartments closer to the feed point, and those with low settling velocities will be carried further around. The table below compares the rotation rate of the separator to the settling velocities for each product off-take compartment.

Table 1 shows the range of settling velocities at the fastest rotation speed used in the trial of 6 seconds per rotation and the slowest rotation speed of 35 seconds per rotation. It also shows which compartments were used to separate the light, middle and heavy product

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fractions. Figure 5 shows a plan view of the product compartments relative to the feed point.

Compartment

Settling velocity at 6 seconds per

rotation (m/s)

Settling velocity at 35 seconds per

rotation (m/s)

Product Fraction

1 0.21 - 0.22 0.03 - 0.04 Light

2 >1 >0.2 Heavy

3 0.5 - 1 0.1 - 0.2 Middle

4 0.33 - 0.5 0.066 - 0.1 Middle

5 0.25 - 0.33 0.05 - 0.066 Middle

6 0.22 - 0.25 0.04 - 0.05 Light

Table 1: Settling velocity and compartment information for the kinetic gravity separator

Feed

1 2

6 3

5 4

Figure 5: Plan view showing the product off-take compartments relative the feed point

Typically the separator will be adjusted so that the heavy fraction contains mainly metals and stone/glass, the middle fraction will be lighter metals, plastics and possibly some stone/glass whilst the light fraction will contain plastic only.

The rotation speed of the separator is adjusted so that the slowest settling material lands in compartments 6 and 1. If the unit rotates too quickly the slow settling material will travel all the way round into the heavy fraction. If it rotates too slowly light fraction material will land in the middle fraction offtake compartments.

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Delft predicts that the separator should be able to process at least 1 tonne per hour of feed material. From previous trials they have learned that in order for the machine to separate effectively the maximum particle size should be no more than three times the minimum size and there should be a difference of at least 10% in the terminal velocities of the particles.

Prior to the trial at Delft tests were conducted on some of the mixed metal/plastic feed material at Axion’s laboratory in Salford. Figure 6 shows the settling velocities of various materials selected from the mixture. The majority of thick copper wires have a settling velocity above 0.25 m/s. There is an overlap of the settling velocities of the fine copper wires and the PVC coated copper wires in the range 0.1-0.2 m/s, so separating these into two fractions from each other may prove difficult. There is some overlap between the settling velocities of the fine copper wires, PVC wires and heavier plastic particles in the range 0.8-.12 m/s.

A separation using a settling velocity of around 0.08 m/s should produce a clean plastic fraction.

Figure 6: Graph of the settling velocities for various particles

The information on the settling velocities was used to adjust the settings of the kinetic gravity separator during the trial to obtain the most effective separation.

1.3 Trial objectives The main objective of the trial was to separate metal and if possible glass from other components of mixtures derived from mixed WEEE, and produce a saleable non-ferrous fraction. Copper smelters in Europe require a maximum of 5% combustible material in the non-ferrous fractions that they process. Non-combustible materials such as stone and glass

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can be present at much higher percentages because they do not interfere with the gas flows in the furnace. They fuse and become part of the slag.

1.4 Trial samples The following materials were chosen for the kinetic gravity separator trial, both of which are produced at Axion’s polymer processing plant in Salford.

a) Plastic/glass/copper mixture in the size range 8-12mm, derived from small WEEE separation; and

b) A copper/stone and plastic mixture derived from larger WEEE items. This consists of copper, plastic and stone in the size range 8-15mm. The copper in this fraction is much heavier and thicker than the copper found in the plastic copper mixture and hence should be easier to separate.

In both the samples the copper wires tend to be finer than the plastic/stone/glass and can be as small as 0.5mm (diameter) x 2mm (length).

1.5 Trial methodology For the two materials tested during the kinetic gravity separator trial the same methodology was followed. Prior to commencing the trial the samples of feed material were weighed and left to soak in water for one hour. This was to ensure that the plastic was fully wetted prior to adding it to the separator so that it would sink.

The test material was then processed through the machine. Changes were made to the rotation speed of the machine for each run in order to optimise the separations but the physical configuration of the machine remained the same during the trials.

Once all the feed material had been processed the product fractions were collected and weighed. The samples were bagged and labelled ready for return to Axion’s laboratory in Salford for analysis.

For both of the trials the same analytical technique was used. Samples of each of the product fractions were taken and hand sorted into the respective components: wood, plastic, rubber, copper wires, PVC coated wires, circuit boards, stone/glass, other metals and fines.

The product and reject separation efficiencies were calculated for each trial run.

For this trial the product separation efficiency, Q, is the probability that the target material (metal) is correctly separated into the heavy product stream.

The reject separation efficiency, R, is the probability that all other materials are correctly separated into the light or middling streams.

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2.0 Trial number 1 - Recovering fine copper from plastic mix

2.1 Trial objective The objective of the trial was to separate copper from other components of the feed and produce a saleable copper fraction containing less than 5% combustible material.

2.2 Feed material The feed material was copper rich plastic mixture containing fine copper wires and a mix of plastic types along with glass, PVC coated wires, rubber, wood, circuit boards and glass. Currently this material is sent to land fill because the copper content is too low for it to be commercially interesting. This material has a size range of 8- 12mm, and is illustrated in Figure 7.

Figure 7: Photograph of Copper Rich Plastic Feed Material

2.3 Trial 1 For this material the separator was operated at a rotation speed of 35 seconds per revolution, corresponding to settling velocities over 0.2m/s for the heavy fraction

After 6 minutes of operation the rotation time was increased to 37 seconds per revolution as too many wires were landing in the middle fraction. Table 2 shows the initial results which were collected at the end of the trial. The gain in weight is due to the absorption of water by the material.

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12

Trial 1

Material

Cooper

rich

plastic

Rotation sec/rev 35

1 full

2 full

3 full

4 full

5 full

6 1/2 open

Feed kg 5.81

Start

time12:11

End

time12:18

Throughput kg/hr 49.8

Heavies 0.77

Middle 5.42

Lights 0.42

Floaters 0

Total kg 6.61

Gain/Loss kg 0.81

Outlet position

Product fraction

weights

Table 2: Results collected during trial 11

The photographs in the following section show the product fractions. Figure 8 shows the heavy product fraction where the copper and PVC wires concentrated. Figure 9 shows the middle product fraction which mainly consists of plastic. The light product fraction is shown in Figure 10 and there is some wood visible along with plastic.

1 Rotation time was increased during the trial from 35 seconds per revolution to 37 second per revolution after

6 minutes.



2.4 Photograph of result samples

Figure 8: Trial 1 heavy product fraction

Figure 9: Trial 1 middle product fraction

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14

Figure 10: Trial 1 light product fraction



2.

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5 Analysis of results samples Samples of the heavy, middle and light fractions were taken for hand sorting to determine the composition of each fraction, with the results in Table 3.

Trial Material Fraction

Weight of

hand sorted

sample

kg g g % g % g % g % g % g % g % g % g % g

Heavy 0.77 770 0.7 0% 33.2 18% 5.8 3% 34.6 18% 42.2 22% 29.7 16% 1.4 1% 24.5 13% 17.6 9% 189.7

Middle 5.42 5420 14.4 6% 183.5 74% 5.7 2% 1.0 0.4% 9.0 4% 3.0 1% 3.5 1% 28.3 11% 0.1 0% 248.5

Light 0.42 420 2.7 1% 113.3 57% 9.8 5% 3.0 2% 4.5 2% 4.1 2% 2.8 1% 47.9 24% 9.6 5% 197.7

Total 6.61

1

Copper

Rich

Plastic

Total

Weight of

Fraction

Composition

Wood Plastic RubberCopper

wirePVC wires

Stone/

Glass

Circuit

BoardsFines

Other

metals

Table 3: Results of hand sorting of trial 1 samples



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Lights kg %

Total 0.42 7%

Wood 0.01 1%

Plastic 0.24 57%

Trial 1 Rubber 0.02 5%

Copper wires 0.01 2%

PVC wires 0.01 2%

Stone/Glass 0.01 2%

Feed kg % PCB's 0.01 1% Middle kg %

Total 5.81 100 Other metals 0.02 5% Total 5.42 93%

Wood 0.32 6% Fines 0.10 24% Wood 0.31 6%

Plastic 4.38 75% Plastic 4.00 74%

Rubber 0.17 3% Rubber 0.12 2%

Copper wires 0.17 3% Copper wires 0.02 0.4%

PVC wires 0.38 6% PVC wires 0.20 4%

Stone/Glass 0.19 3% Heavy kg % Stone/Glass 0.07 1%

PCB's 0.09 2% Total 0.77 13% PCB's 0.08 1%

Other metals 0.09 2% Wood 0.00 0.4% Other metals 0.00 0%

Fines 0.82 14% Gain 0.8kg Plastic 0.13 18% Fines 0.62 11%

Throughput 50 kg/hr Rubber 0.02 3%


PVC wires 0.17 22%

Stone/Glass 0.12 16%

PCB's 0.01 1%

Other metals 0.07 9%

Fines 0.10 13%

KGS

Trial 1

Copper Rich Plastic

Figure 11: Schematic of the trial 1 results



6%

3%

Q 6

R 9

Table 4: Q and R separation efficiencies for trial 1

2.6 Discussion of results Figure 11 shows the mass balance for the trial. This was calculated from the total weights collected during the trial and the compositions measured by hand sorting samples of each of the products.

The light and middle fractions consisted mainly of unidentifiable fines and plastic with only 18% of the copper lost from the feed in these fractions. The heavy fraction is a mixture of plastic, copper wires, PVC wires, stone/glass, other metals and fines.

Previous work by Axion has shown that the coated wire fraction typically contains 50% copper by weight. The hand sort categories that are treated as the target metal fraction in the analysis of sorting efficiency are therefore ‘copper’, ‘coated wire’ (assuming 50% of this is metal) and ‘other metal’.

The concentration of metal in the heavy fraction, at 38%, is an increase from the feed concentration of 8%. The heavy material is still unlikely to be attractive to copper smelters at this metal concentration. Furthermore, the concentration of plastic, wire coating, rubber and wood in the heavy fraction is 32%, which is well above the target of 5% combustible material required by the smelters. Of this 32%, 11% is contributed by the plastic component coated wire and is therefore impossible to separate from the copper without further size reduction. The heavy fraction may need to be reworked by a different process in order to reduce the combustible concentration below 5%.

Table 4 shows the Q and R separation efficiencies. The product separation efficiency, Q, for metals is good at 83%.

The reject separation efficiency, R, is 93%. This needs to be higher because too much combustible material ended up in the heavy fraction.

2.6.1 Throughput The throughput measured during the trial was 50kg/hr. This throughput is too low to be commercially viable. It appeared that the settling separation itself was not overloaded but that the throughput of the machine was limited by the ability of the product off-take system to convey heavy material away without blocking. The system uses water jets with venturis to entrain the material as it lands at the base of the separator and convey it in flexible pipes up to the dewatering sieves. When the feed to the machine was increased above about 50Kg/hr the pipes carrying heavy material started to block with particles.

2.7 Conclusions from trial The machine achieved a reasonable separation of copper from the plastic with 66% of the metals recovered to the heavy fraction. However, the heavy fraction contained only 38% metals and the combustible component exceeded the 5% limit expected by copper smelters.

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This material contained a high proportion of relatively thin coated copper wire particles. Around half of these were separated into the middle fraction rather than the heavies.

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

3.1 Trial objective The main objective of the trial is to use the kinetic gravity separator to separate metals from other components of mixtures derived from mixed WEEE, and produce a saleable metal fraction.

3.2 Feed material The feed material for trial 2 was a mixture of heavy copper, other metals and plastic which was coarser than the trial 1 material, and is illustrated in Figure 12 below. This material was derived from large WEEE items and was collected at a different stage in Axion’s WEEE separation process than the first trial sample.

Figure 12: Photograph of heavy copper plastic mix feed material

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3.3 Trial 2 For this material, the kinetic gravity separator was operated with a faster rotation speed of 22 seconds per revolution. This is because the particle size of the feed material was larger than the previous trial so the settling velocities would be higher.

Table 5 shows the initial results collected at the end of the trial. The gain in weight is due to absorption of water by the samples.

Trial 2

Material

Heavy

cooper

plastic mix

Rotation sec/rev 22

1 full

2 full

3 full

4 full

5 full

6 1/2 open

Feed kg 7.1

Start

time14:20

End

time14:26

Throughput kg/hr 71 Comments

Heavies 4.76

very good

copper

& glass

Middle 2.08

plastic & few

pieces

of cable

Lights 0.47 plastic only

Floaters 0.5

Total kg 7.81

Gain/Loss kg 0.71

Outlet position

Product fraction

weights

Table 5: Results collected during trial 2

A large quantity of thick copper wires can be seen in the heavy product fraction in Figure 13. Figure 14 shows the middle product fraction and there are pieces of PCV coated wire visible but no exposed copper wires. The majority of the fraction is plastic. The light product fraction is shown in Figure 15 and there are some PVC coated wires visible again along with the plastic. Figure 16 is the floating fraction which is plastic and wood.

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3.4 Photographs of product samples

Figure 13: Trial 2 heavy product fraction

Figure 14: Trial 2 middle product fraction

21



22

Figure 15: Trial 2 light product fraction

Figure 16: Trial 2 floaters product fraction



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3.5 Analysis of product samples The results of the hand sorting of the samples from the product fractions is shown in Table 8.

Trial Material Fraction

Weight of

sample for

hand

sorting

kg g g % g % g % g % g % g % g % g % g

Heavy 4.76 4760 0.0 0% 36.2 6% 1.0 0.2% 204.8 32% 19.4 3% 110.4 17% 0.4 0.1% 277.3 43% 649.5

Middle 2.08 2080 0.4 0.1% 187.2 70% 3.5 1% 23.0 9% 17.6 7% 31.6 12% 3.9 1% 0.9 0.3% 268.1

Light 0.47 470 2.3 1% 235.8 96% 0.0 0% 4.2 2% 3.6 1% 0.1 0.0% 0.0 0% 0.8 0.3% 246.8

Floaters 0.5 500 10.0 8% 109 91% 0.9 1% 0.0 0 0.1 0.1% 0.0 0% 0.0 0% 0.0 0% 120.0

Total 7.81

2

Heavy

Copper

Plastic

Mix

Total

Weight

of Fraction

Wood Plastic

Composition

RubberCopper

wirePVC wires

Stone/

Glass

Circuit

Boards

Other

metals

Table 6: Results of hand sorting of trial 2 samples



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Floaters kg %

Total 0.5 7%

Wood 0.04 8%

Plastic 0.45 91%

Rubber 0.00 1% Lights kg %

PVC Wires 0.00 0.1% Total 0.47 7%

Wood 0.00 1%

Plastic 0.45 96%

Feed kg % Rubber 0.00 0%

Total 7.10 100 Copper wires 0.01 2%

Wood 0.05 1% PVC wires 0.01 1%

Plastic 2.62 45% Stone/Glass 0.00 0.04%

Rubber 0.04 1% PCB's 0.00 0.0% Middle kg %

Copper wires 1.69 29% Other metals 0.00 0.3% Total 2.08 29%

PVC wires 0.29 5% Wood 0.00 0.1%

Stone/Glass 1.05 18% Plastic 1.45 70%

PCB's 0.03 1% Rubber 0.03 1%

Other metals 2.04 35% Copper wires 0.18 9%

Gain 0.71kg PVC wires 0.14 7%

Throughput 70 kg/hr Stone/Glass 0.25 12%

Heavy kg % PCB's 0.03 1%

Total 4.76 67% Other metals 0.01 0.3%

Wood 0.00 0%

Plastic 0.27 6%

Rubber 0.01 0.2%


PVC wires 0.14 3%

Stone/Glass 0.81 17%

PCB's 0.00 0.1%

Other metals 2.05 43%

KGS

Trial 2

Heavy Plastic Copper Mix

Figure 17: Schematic of the trial 2 results



Copper only Copper and other metals

Q 89% 93% R 39% 64% Table 7: Q and R separation efficiencies for trial 2

3.6 Discussion of results The results from the hand sorting have been scaled up to the mass of material used in the trial and are given in Figure 17 shows the mass balance for the trial. This was calculated from the total weights collected during the trial and the compositions measured by hand sorting samples of each of the products.

The floating fraction contained 91% plastic and 8% wood. The lights fraction contained 96% plastic but also contained 2% fine copper wires. The middle fraction contained plastic, copper wires, PVC wires and stone/glass. 89% of the copper and 93% of all the metals in the feed were recovered in the heavy fraction.

The heavy fraction contained copper wires, other metals and a small quantity of stone/glass. The copper concentration was 32% and the total metal concentration was 75%. The content of combustible materials was 8%. By adjusting settings, such as the rotation speed, to ensure more copper and metal is collected in the heavy fraction and more plastic rejected in the middle fraction it is likely that the plastic composition could be reduced below the target of 5%.

Table 7 shows the Q and R separation efficiencies for this trial.

The table shows two separation efficiencies in each case; one for the copper fraction alone and one for all the metals in the feed material.

The coated wire fraction is assumed to contain 50% plastic and 50% metal.

The product separation efficiency, Q, is the probability that either copper alone or all metals are correctly separated into the heavy product fraction.

The reject separation efficiency, R, is the probability that either all non copper materials or all non-metals are correctly separated into the floaters, light or middle fractions.

For copper alone the product separation efficiency, Q, is 89% which good. The product separation efficiency for all metals is even better at 93%, because the material contained a high proportion of compact non-wire metal fragments which settled rapidly and were easily captured in the heavy fraction.

The reject separation efficiency, R, was 39% for copper alone because the feed contained a large proportion of other heavy materials (metals, glass and stone) which joined the copper in the heavy fraction.

The reject separation efficiency, R, for all metals was higher at 64%. It was reduced by the high proportion of stone and glass in the feed, which mostly collected in the heavy fraction.

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Note that some of the other metals may be of little value to the copper smelters so could be treated as a contaminant.

3.6.1 Throughput The throughput measured for this material was approximately 70kg/hr. This is too low to be acceptable for industrial/commercial use. However, again the constraint appeared to be the product off-take system rather than the settling velocity separation itself.

3.7 Conclusions from trial The trial objective, to separate a saleable metal fraction containing less than 5% combustible material was almost achieved. A metal recovery of 93% (89% for copper) was achieved. The combustible concentration in the heavy fraction was 8% which is close to the target of 5%. If minor adjustments were made to the settings of the machine to fine tune the separation it is likely that the specification could be achieved.

4.0 Economic assessment of the technique via a payback calculation As the machine showed technical potential, an assessment of the economic feasibility of the separation was made using a simple pay back calculation, shown in Table 8.

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Trial Delft

Equipment Kinetic Gravity Separator

Capacity te/hr 1

Cost of unit £ 200000

Basis of operation hr/yr 3000

Overall Equipment Effectiveness OEE % 70%

Plant Input te/yr 2100

Operating Costs

Water

Consumption kg/hr 100

Cost (assuming £2/te) £/hr 0.20

Power

Consumption kW 15

Cost (assuming 10p/kW hr) £/hr 1.5

Water and Power costs £/te of feed 1.70

Water and Power costs £/yr 3570

Labour costs (assuming £15/hr job cost) 45000

Annual process licence costs to Delft 10000

Total Operating Costs 58570

Revenue

Assuming 15% of feed is separated as product

Product extracted te/yr 315

Assuming only 70% of product is useful metal

with a value of £1000/te

Value of product £/te 700

£/yr 220500

Margin £/yr 161930

Payback time months 15

Table 8: Economic assessment by a payback calculation

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This assessment assumes a 2m diameter unit with the capacity of 1 tonne per hour and a build cost for the unit of £100,000 and an installed cost of £200,000.

The basis for operation of 12 hours per day, 5 days a week, 50 weeks a year is assumed, giving 3000 hours of operation per year.

The water usage has been based on the assumption that 10% of the fresh water is lost per tonne of material sent to landfill. Therefore the fresh water required is 100kg/hr, with an assumed water cost of £2 per tonne.

The power cost estimate assumes demand of 15kW for the rotor drive and water pumping with a power cost of 10p/kW hr.

The calculation assumes a overall equipment effectiveness (OEE) for the separator system of 70% where the OEE is defined as follows:

hoursrun available

hoursrun actual ty availabili

production specificaton of % ratequality

t throughpurated

t throughpuactual ratecapacity

tyavailabili x ratequality x ratecapacity OEE

Total job cost for 1 operator is estimated to be £45000 per year.

It is assumed that a technology license from Delft University is required to operate the machine, estimated at £10,000 per year.

The revenue estimate is based on the amount of non-ferrous metal extracted. An overall recovery of 15% metal rich material from the feed has been estimated, with a useful metal content of 70%.

These assumptions produce an estimated operating margin of £161,930/yr. This gives a payback time of 15 months for the estimated installed equipment cost of £200,000.

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4.0 Overall final conclusion of trial The results of the kinetic gravity separator trial were promising, particularly for the larger sized feed material.

The results for the second trial were better than for the first trial as more metal was recovered at a higher concentration.

For the first sample of material the trial objective was only part met. The machine recovered 66% of the metal to the heavy fraction. However, the heavy fraction contained only 38% metal and the combustibles exceeded the 5% limit, which meant that the product did not meet the target specification.

In trial 2 a metal recovery of 93% at a concentration of 76% was achieved. The plastic concentration in the heavy fraction was 8% which was much closer to the target of 5%. If minor adjustments were made to the settings of the machine to fine tune the separation it is thought that the specification could be achieved.

Throughput of the trial machine was too low to be commercially viable because the product collection system tended to block at very low throughputs. A production version of the machine would require a redesign of this system. It appeared during the trial that the settling velocity separation section itself could handle a throughput of at least 1te/hr.

Documents

WRAP MDD018 WEEE Separation Techniques Kinetic Gravity Separator Trial Report.pdf · The Kinetic Gravity Separator (KGS) is a system developed by the recycling laboratory at Delft