WRAP MDD018 WEEE Separation techniques NIR Trial Report final.pdf · WRAP MDD018/23 WEEE Separation...

WRAP MDD018/23 WEEE Separation techniques

Titech NIR sorting trial report

Abstract This is a report on a trial conducted for WRAP project MDD018. 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. The separation of mixed plastic fractions produced during WEEE recycling can be difficult. Various techniques have been tested in this project to establish if a new solution can be found.

Titech has recently developed an ultra high resolution Near Infrared (NIR) sorter for hard plastics which is available for testing at their facility in Germany. The machine uses NIR sensing technology to identify and separate materials. NIR machines are commonly used in the recycling industry to sort plastic containers.

The trial aimed to test four separation objectives:

1. Identify and separate a mixed plastic stream by polymer type; 2. Identify and remove contaminants from a mixed plastic stream; 3. Investigate the effect of particle size distribution on the efficiency of the sort; and 4. Determine the limits of detection of the machine.

Four different samples of material were tested; each selected to correspond with the aims described above.

1. Sample of mixed styrenic plastic from WEEE containing mainly polystyrene (PS) and acrylonitrile butadiene styrene (ABS), known as Axion grade PS11;

2. Sample of mixed styrenic plastic from WEEE containing a wide range of minor polymer types, known as Axion grade PS07;

3. Specially made mixture of PS and polypropylene (PP), classified into size fractions; and

4. Black PS plaques containing different levels of black masterbatch pigment. The separation of ABS and PS was quite successful and produced product fractions containing 85% ABS and 80% PS. Ideally the compositions need to be above 95% for the product to be saleable. It is possible that this could be achieved with a second pass of the material through the machine.

The particle size trial concluded that the larger particle fractions produced better separation efficiencies but no lower limit for particle size was determined as the sub 6mm material still separated successfully.

WRAP MDD018 WEEE Separation Techniques

Titech Near Infra Red Sorter Trial Report

The test to remove contaminants was partially successful in that the contaminant level was reduced from 10% to 7% but this was not enough to eliminate the polymer compatibility and melt filtration problems that these contaminants create.

The blackness detection limit of the machine was determined.

The economic assessment of the machine assumed that ABS and PS in PS11 material could be separated into fractions of 95% purity. It indicated a payback time of around 28 months which could be economically viable.

Overall the machine performed well. The trial results show that it has potential for use within the WEEE recycling industry but needs further work for the technique to produce saleable products from mixed waste plastic generated by WEEE recycling.

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

Information on the trial ................................................................................................... 8

1.1 Description of trial equipment............................................................................. 8

1.2 Photograph of trial equipment .......................................................................... 10

1.3 Trial objectives ................................................................................................ 11

1.4 Sample material............................................................................................... 11

1.5 Trial methodology............................................................................................ 12

1.6 Summary of the individual trials........................................................................ 13

Trial 1: Identification and ejection by polymer type from a mixed plastic stream ............... 14

1.7 Trial objective.................................................................................................. 14

1.8 Feed material .................................................................................................. 14

1.9 Trial 1 Sort 1 ................................................................................................... 14

1.9.1 Photographs of product samples ................................................................ 15

1.9.2 Conclusions from trial ................................................................................ 16

1.10 Trial 1 Sort 2 ................................................................................................... 16

1.10.1 Photograph of result samples..................................................................... 16

1.10.2 Analysis of results samples ........................................................................ 17

1.10.3 Discussion of results.................................................................................. 18


1.11 Trial 1 Sort 3 ................................................................................................... 20


1.11.2 Analysis of results samples ........................................................................ 21



1.12 Trial 1 Sort 4 ................................................................................................... 23


1.12.2 Analysis of product samples....................................................................... 24



1.13 Trial 1 Sort 5 ................................................................................................... 26



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1.14 Trial 1 Sort 6 ................................................................................................... 29




1.14.4 Physical Properties Tests ........................................................................... 33


1.15 Trial 1 Sort 7 ................................................................................................... 35




1.15.4 Physical Property Tests.............................................................................. 38


1.16 Overall conclusions from Trial 1 ........................................................................ 39

Trial 2: Effect of particle size on efficiency of the sort using a PS/PE mixture .................... 40

1.17 Trial objective.................................................................................................. 40

1.18 Feed material .................................................................................................. 40

1.19 Trials conducted on material............................................................................. 40

1.20 Trial 2 Sort 1 ................................................................................................... 41





1.21 Trial 2 Sort 2 ................................................................................................... 43





1.22 Trial 2 Sort 3 ................................................................................................... 45





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1.23 Overall conclusions on trial 2 ............................................................................ 47

Trial 3: Removal of contaminants from mixed plastic (PS07) ............................................ 48

1.24 Trial objective.................................................................................................. 48

1.25 Feed material .................................................................................................. 48

1.26 Trial 3 Sort 1 ................................................................................................... 49


1.27 Trial 3 Sort 2 ................................................................................................... 50


1.28 Analysis of product samples.............................................................................. 51

1.29 Discussion of results ........................................................................................ 54

1.30 Conclusions from Trial 3 ................................................................................... 55

Trial 4: Level of blackness detection tests ....................................................................... 56

1.31 Trial objective.................................................................................................. 56

1.32 Feed material .................................................................................................. 56

1.33 Trial results ..................................................................................................... 56

1.34 Discussion of results ........................................................................................ 58

1.35 Conclusions from Trial 4 ................................................................................... 59

6.0 Economic assessment of the machine................................................................... 60

Overall final conclusion of trials ...................................................................................... 62

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List of Figures Figure 1: Schematic of the Titech NIR Sorter (courtesy of Titech) ...................................... 9 Figure 2: Photograph of Titech NIR sorter ...................................................................... 10 Figure 3: Feed material for Trial 1 - PS11 ....................................................................... 14 Figure 4: Trial 1 Sort 1 Eject Fraction - Visible material.................................................... 15 Figure 5: Trial 1 Sort 1 Reject fraction - Non visible material............................................ 15 Figure 6: Trial 1 Sort 2 Eject fraction - Visible material .................................................... 16 Figure 7: Trial 1 Sort 2 Reject fraction - Non visible material............................................ 17 Figure 8: Schematic of Trial 1 Sort 2 Results................................................................... 18 Figure 9: Trial 1 Sort 3 Eject fraction - ABS material ........................................................ 20 Figure 10: Trial 1 Sort 3 Reject fraction - non ABS material.............................................. 20 Figure 11: Schematic of Trial 1 Sort 3 Results ................................................................. 21 Figure 12: Trial 1 Sort 4 Eject fraction - PS material ........................................................ 23 Figure 13: Trial 1 Sort 4 Reject fraction - non PS material................................................ 23 Figure 14: Schematic of Trial 1 Sort 4 Results ................................................................. 24 Figure 15: Trial 1 Sort 5 Eject Fraction - non ABS and PS material.................................... 26 Figure 16: Trial 1 Sort 5 Reject fraction - ABS and PS...................................................... 27 Figure 17: Schematic of Trial 1 Sort 5 Results ................................................................. 27 Figure 18: Composition from Titech NIR machine for reject fraction of trial 1 sort 5 .......... 28 Figure 19: Trial 1 Sort 6 Eject Fraction - ABS material ..................................................... 30 Figure 20: Trial 1 Sort 6 Reject fraction - PS material ...................................................... 30 Figure 21: Schematic of Trial 1 Sort 6 Results ................................................................. 31 Figure 22: Composition of the eject fraction by the NIR machine from trial 1 sort 6 .......... 32 Figure 23: Trial 1 Sort 7 Eject fraction - ABS material ...................................................... 35 Figure 24: Trial 1 Sort 7 Reject fraction - PS material ...................................................... 35 Figure 25: Schematic of Trial 1 Sort 7 Results ................................................................. 36 Figure 26: NIR determined composition for the trial 1 sort 7 eject.................................... 37 Figure 27: Trial 2 Sort 1 Eject fraction - PE material ........................................................ 41 Figure 28: Trial 2 Sort 1 Reject fraction - PS material ...................................................... 41 Figure 29: Schematic of Trial 2 Sort 1 Results ................................................................. 42 Figure 30: Trial 2 Sort 2 Eject fraction - PE material ........................................................ 43 Figure 31: Trial 2 Sort 2 Reject fraction - PS material ...................................................... 44 Figure 32: Schematic of Trial 2 Sort 2 Results ................................................................. 44 Figure 33: Trial 2 Sort 3 Eject fraction - PE material ........................................................ 45 Figure 34: Trial 2 Sort 3 Reject fraction - PS material ...................................................... 45 Figure 35: Schematic of Trial 2 Sort 3 Results ................................................................. 46 Figure 36: Trial 3 feed material - PS07 ........................................................................... 48 Figure 37: Trial 3 Sort 1 Eject material - Contaminants.................................................... 49 Figure 38: Trial 3 Sort 1 Reject fraction - non contaminants............................................. 49 Figure 39: Trial 3 Sort 2 Eject fraction - PP and PE fraction.............................................. 50 Figure 40: Trial 3 Sort 2 Reject fraction - contaminant free material ................................. 50 Figure 41: Schematic of Trial 3 Sort 1 and Sort 2 Results................................................. 53

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Figure 42: Photograph of black plaques visible to Titech NIR machine.............................. 56 Figure 43: Photograph of handpicked particles visible to Titech NR machine ..................... 57 Figure 44: Photograph of black plaques not visible to the Titech NIR machine .................. 57 Figure 45: Photograph of handpicked particles not visible to the Titech NIR machine ........ 58

List of Tables Table 1: Summary of Trials............................................................................................ 13 Table 2: Results of FTIR analysis for Trial 1 Sort 2 .......................................................... 17 Table 3: Results of FTIR analysis of Trial 1 Sort 3 ........................................................... 21 Table 4: Q and R separation efficiencies for Trial 1 Sort 3................................................ 21 Table 5: Results of the FTIR analysis for Trial 1 Sort 4 .................................................... 24 Table 6: Q and R separation efficiencies for trial 1 sort 4 ................................................. 25 Table 7: Results of the FTIR analysis for Trial1 Sort 5 ..................................................... 27 Table 8: Q and R separation efficiencies for Trial 1 Sort 5................................................ 28 Table 9: Results for the FTIR analysis for Trial 1 Sort 6 ................................................... 31 Table 10: Q and R separation efficiencies for Trial 1 Sort 6 .............................................. 32 Table 11: Physical properties data for Axpoly PS11........................................................ 33 ®

Table 12: Results of physical properties tests for Trial 1 Sort 6 ........................................ 33 Table 13: Results of FTIR analysis for Trial1 Sort 7 ......................................................... 36 Table 14: Q and R separation efficiencies for Trial 1 Sort 7 .............................................. 37 Table 15: Physical properties data for Axpoly PS11........................................................ 38 ®

Table 16: Results of physical properties tests for Trial 1 Sort 7 ........................................ 38 Table 17: Summary of Trial 1 results.............................................................................. 39 Table 18: Results of analysis of Trial 2 Sort 1 fractions .................................................... 42 Table 19: Q and R separation efficiencies for Trial 2 Sort 1 .............................................. 42 Table 20: Results of analysis on Trial 2 Sort 2 fractions ................................................... 44 Table 21: Q and R separation efficiencies for Trial 2 Sort 2 .............................................. 44 Table 22: Results of analysis on Trial 2 Sort 3 fractions ................................................... 46 Table 23: Q and R separation efficiencies for Trial 2 Sort 3 .............................................. 46 Table 24: Comparison of Q and R values for Trial 2......................................................... 47 Table 25: Results of FTIR analysis for Trial 3 samples ..................................................... 51 Table 26: Q and R separation efficiencies for Trial 3........................................................ 54 Table 27: Colour analysis values for black plaques .......................................................... 58 Table 28: Economic Assessment by a payback calculation................................................ 61

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1. Information on the trial Trial host: Titech GmbH, test conducted at facility at Mulheim-Karlich, Germany

Trial equipment: Ultra High Resolution Near Infra Red Sorter (PolySort® Ultra-High Resolution UHR with an Ultra-High-Resolution 34/6.25 valve block)

Trial date: 25th November 2008

1.1 Description of trial equipment The Titech equipment uses an NIR sensor to detect the characteristic infrared spectrum of light reflected by an illuminated object. The NIR spectrum of each material is unique and can be used to identify specific materials and then separate them.

Axion Recycling has previously conducted trials using near infrared (NIR) sorting with Titech and others using conventional sorting machines. The results were unconvincing for two reasons:

Resolution of the detection and ejection devices was too low to allow accurate detection of the much smaller particles required for effective sorting of WEEE at throughputs which are commercially viable. Packaging items have typical dimensions in the range 100-200mm, while effective sorting of WEEE polymers requires particles to be reduced to the 5-30mm size range; and

Many WEEE polymers are dark coloured or black. The high absorption of these materials in the NIR spectral range means that conventional packaging sorters tend to miss many of the target particles in WEEE. Packaging materials are generally transparent or light coloured, making it much easier to generate an accurate spectrum and therefore achieve effective separation.

However Titech has developed their new NIR machine with ‘ultra high’ resolution specifically to process WEEE polymers.

Titech has a range of NIR sorting machines. The standard PolySort unit works on particle sizes greater than 20mm x 20mm whilst the basic unit, PolySort Basic, deals with particles larger than 45mm x 45mm. The high resolution sorting system, PolySort HR, can sort objects with a minimum size of approximately 13mm x 13mm. This system has been trialled previously by Axion Recycling with poor results on mixed WEEE polymers. The ultra high resolution sorting system, PolySort UHR, was used for this trial. It is designed to sort objects as small as 8mm x 8mm. A schematic of the sorter is shown in Figure 2.

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Figure 1: Schematic of the Titech NIR Sorter (courtesy of Titech)

The system works by scanning the material as it travels along a conveyor belt. The PolySort UHR uses a fast near infrared analyser along with a computer-controlled air jet ejection system. Material is identified across the entire width of the conveyor belt. The type of material, position and projected area of every single object on the belt is determined by the machine. A computer then rapidly processes the information and controls a series of air jets situated at the end of the conveyor belt. The air jets are activated accordingly to remove the identified material from the main product stream. The projected area determines which air jets need to be activated and only those which the object will pass over are used. The duration for which the air jet is active corresponds to the overall projected length of the object.

Two product streams are formed, the reject material which flows off the conveyor and the eject material which is removed by the air jets. The system normally works with a feed conveyor belt speed of approximately 2.5 – 3.0 m/sec. For all the trials in this report the belt speed was 3 m/s.

The system is operated entirely by a computer with an LCD screen display from which the system can be controlled. Most settings and functions can be changed via the screen such as the belt speed, material selected for ejection.

The only manual operation which is required is the positioning of the splitter plate. After a short time of operation the optimum position for the splitter plate can be determined and hence adjustment of it is generally required.

It is claimed by Titech, that the NIR sorter can distinguish between most polymer types including polycarbonate (PC), polyamide (PA), Polymethyl methacrylate (PMMA), polyoxymethylene (POM), polycarbonate acrylonitrile butadiene styrene (PCABS)

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polypropylene (PP) and polyethylene (PE). However, the infrared spectra for PS and ABS are very similar, so this has previously made it very difficult to separate these two polymer types. Titech claim that the new machine can identify and distinguish between ABS and PS so a separation should be possible.

1.2 Photograph of trial equipment Figure 2 is a photograph of Titech’s test facility at Mulheim-Karlich.

Valve block

of air jets

Splitter Plate

Reject Fraction

Eject Fraction

NIR Control Panel

Start of feed conveyor

Conveyor BeltFeed

Figure 2: Photograph of Titech NIR sorter

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1.3 Trial objectives Four objectives were tested during the trial as follows:

a) To investigate the effect of particle size distribution on the efficiency of the sort. The aim of this trial was to quantify how well the machine can perform when separating polymers in different size fractions. It was important to keep the trial fairly simple in order to ensure that it was only the size distribution being assessed and not, for example, the colour of the particles. From the results of the trial it should be possible to determine whether screening the material before passing it through the NIR sorter yields a better separation. It should also quantify the minimum size limit for efficient identification.

b) Test the level of darkness of particles which the NIR detector can identify for a range of different polymer types. This trial aimed to determine the level of darkness at which the machine could no longer identify black particles and hence give an indication of how much dark material within a sample the machine may be unable to detect.

c) Identification and ejection by polymer type from a mixture. This trial aimed to test how well the machine could identify and eject specific contaminant polymers, such as nylon, silicone rubber, polycarbonates, polymethylmethacrylate (PMMA) and filled PP. Having removed these, the final aim was to separate PS and ABS from each other.

d) Identification and ejection of minor impurities including nylon, silicone rubber, polycarbonate and PMMA. The objective for this trial was to see if the machine could remove contaminant polymers which are present in small concentrations in WEEE plastic without significant loss of the bulk product.

1.4 Sample material The material used for the trial was prepared as follows, with the samples below corresponding to the objectives above:

a) 3 x 30kg samples (all white material) split into three fractions: 1) Sub 6mm 90% PS / 10% PE 2) 6-12mm 90% PS / 10% PE 3) Unscreened 90% PS / 10% PE

Sample preparation procedure: Firstly white fridge material (PS01) containing mainly PS was granulated and sieved at 6mm. White PE (virgin material) was also granulated and sieved at 6mm. The white PE was then added to the sub 6mm and over 6mm fractions of PS01 to give a 10% composition of PE in the samples, (a1) and (a2). A sample of unscreened PS material was also spiked with 10% PE, (a3).

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b) 9 x black sample plaques of PS were prepared in Axion’s lab by extrusion and injection moulding - samples were prepared by the addition of 0.5% to 5% black masterbatch to virgin PS in 0.5% increments.

c) 250kg of Axion grade PS11 was separated from mixed small WEEE (for PS/ABS separation after contaminant polymer removal).

d) 250kg of Axion grade PS07 was separated from mixed small WEEE (for contaminant polymer removal).

1.5 Trial methodology As the objectives for each of the individual trials were different this required different machine set ups for each run. Details are given in each trial section of this report. No alterations were made to the belt speed during the trial.

For each trial the sample was processed through the machine. The eject and reject fractions were collected, re bagged, labelled and returned to Salford for post trial analysis.

Two analysis techniques were used on the samples. For the mixed plastic products (trial 1 and 3) a Fourier Transform mid Infra Red spectrometer (FTIR) machine was used to identify the different polymer types present in a sample.

For trial 2 a sink-float test in water was used to separate the PS and PE.

The black plaques were colour analysed to determine the blackness levels.

The Q and R separation efficiency convention was applied to each of the sorts to assess the efficiency of the sort.

The product separation efficiency, Q, is the probability that the desired product is correctly sorted into the product stream.

The reject separation efficiency, R, is the probability that the secondary product is correctly sorted into the secondary product stream.

In the case of an NIR sorter if the material being ejected is the product then the product fraction is the eject and the reject fraction is the secondary product stream. For all the sorts in this trial the aim was to eject a specific material so the product fraction was the eject stream.

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1.6 Summary of the individual trials Table 1 shows a summary of the trials indicating the feed material, the eject material and the reject material.

Trial Feed Eject Reject Trial

Objectives

Material Material Material

T1 S1 PS11 Visible Non-visible a T1 S2 PS11 Visible Non-visible a T1 S3 T1 S2 Eject ABS All other a T1 S4 T1 S2 Eject PS All other a T1 S5 T1 S2 Eject non ABS/PS ABS/PS a T1 S6 T1 S5 Reject ABS (aggressive) PS a T1 S7 T1 S5 Reject ABS (less aggressive) PS a

T2 S1 sub 6mm PS/PE (90:10) PE PS b

T2 S2 Unscreened PS/PE (90:10) PE PS b

T2 S3 + 6mm PS/PE (90:10) PE PS b

T3 S1 PS07 PMMA, PC, POM, PA, PVC, PBT/PET All other c

T3 S2 T3 S1 Reject PP, PE All other c

Table 1: Summary of Trials

The following sections of the report detail each of the individual sorts.

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Trial 1: Identification and ejection by polymer type from a mixed plastic stream

1.7 Trial objective

The trial objective was to identify and eject specific polymer types such as nylon, silicone rubber, polycarbonates, PMMA and PP from a mixed polymer mixture. Having removed these, the material was reworked to separate PS from ABS.

1.8 Feed material The feed material for this trial was a styrenic plastic fraction from Axion’s WEEE processing plant in Salford (known as PS11).

Figure 3: Feed material for Trial 1 - PS11

1.9 Trial 1 Sort 1 Initially the feed material was loaded into the test unit via the conveyor and set to re-circulate around the unit. The machine was configured to positively sort on everything it could identify so all particles identifiable by the NIR detectors were ejected. During the recirculation it was noted that the test material was becoming contaminated with debris left in the unit from the previous trial. The debris mainly consisted of wood and could pose problems if the sorted material was to be extruded at a later date during the post trial analysis. Therefore the test material was re-circulated to pick up as much debris as possible

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before being collected in the receiving bins. The two product streams from this sort were put to one side and were not processed further.

1.9.1 Photographs of product samples

Figure 4: Trial 1 Sort 1 Eject Fraction - Visible material

Figure 5: Trial 1 Sort 1 Reject fraction - Non visible material

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1.9.2 Conclusions from trial Because the material became contaminated no analysis was completed on these samples. It should however be noted from the two photographs that the eject fraction is mainly coloured/light grey particles and the reject fraction is black/dark grey particles. This is the expected result from this separation.

1.10 Trial 1 Sort 2 PS11 was added to the test unit which was configured to eject all identifiable particles. The aim was to quantify the proportion of the feed mix which was capable of being NIR sorted and to prepare the feed for subsequent sorts.

1.10.1 Photograph of result samples

Figure 6: Trial 1 Sort 2 Eject fraction - Visible material

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Figure 7: Trial 1 Sort 2 Reject fraction - Non visible material It can be seen from Figure 6 and 7 that the coloured and light grey material is in the eject fraction whilst the black and dark grey particles are in the reject fraction. This is because the machine could not identify the dark particles.

1.10.2 Analysis of results samples All of the eject material from this sort was processed in the later sorts and therefore there was none available for analysis. A sample of the reject material was kept and this has been analysed to determine the polymers present in the unidentifiable fraction.

The result of the analysis is shown below.

FractionWeight of

Fraction

Weight of

FTIR sample

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

T1 S2 Eject 63.91

T1 S2 Reject 59.66 40.9 48% 39.2 46% 0.6 1% 0.6 1% 1.6 2% 0.9 1% 0.7 1% 84.5

No Sample

COMPONENTS PRESENT

ABS PS PP PE PC/PCABS PVC PA

Table 2: Results of FTIR analysis for Trial 1 Sort 2

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TRIAL 1 SORT 2 Eject Visible Polymers

PS11 ‐ Ejecting all visible material kg %

Total 63.91 52%

ABS 27.64 43%

PS 33.61 53%

PP 0.80 1%

Feed PE 0.27 0%

kg % PC/PCABS 1.45 2%

Total 123.57 100% PVC 0.00 0%

ABS 56.52 46% PA 0.11 0%

PS 61.29 50%

PP 1.22 1% Reject

PE 0.69 1% Non Visible Polymers

PC/PCABS 2.58 2% 0.44 t/h/m kg %

PVC 0.64 1% Total 59.66 48%

PA 0.61 0% ABS 28.88 48%

PS 27.68 46%

PP 0.42 1%

PE 0.42 1%

PC/PCABS 1.13 2%

PVC 0.64 1%

PA 0.49 1%

Trial 1 Sort 2

Figure 8: Schematic of Trial 1 Sort 2 Results

1.10.3 Discussion of results Figure 8 is a mass balance for the trial, with the eject composition back calculated from subsequent trials, and the feed composition back calculated by mass balance. The split between visible and non visible particles was approximately equal (52%/48%). Neither of the fractions produced by the visible/non visible separation is of any use as a final product because they both contain too many different polymer types.

There was no point in doing further processing with the non visible material as the machine had already rejected it as unidentifiable. The sort was beneficial in that it removed the bulk of the non visible material from the feed material, and the machine should be able to identify all of the material in subsequent sorts.

The throughput of the trial was measured at 0.44 tonnes per hour per metre of belt width. This is below the expected capacity of 1 tonne per hour/m belt width. However as the throughput is directly proportional to the belt width, a 2m wide sorter would be able to process 0.88 tonne per hour.

It is not possible to determine Q and R separation efficiencies for this sort. This is because it is not possible to analyse the material produced to say whether it should be visible to the machine or not.

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1.10.4 Conclusions from trial The machine was able to perform a separation between visible (light or coloured) material and non visible (black). Visual assessment of the samples shows that it appears to have worked and produced a visible fraction suitable for subsequent trials.

Only about 50% of the feed material was detectable by the NIR sorter. The reject fraction and accept/eject fractions had almost exactly the same compositions as each other and the feed. This means that for a production unit a visible/ non visible separation step would be required prior to NIR sorting to separate ABS and PS. Otherwise the 50% non visible particles (which contain roughly 50:50 ABS: PS) would contaminate the reject stream with around 25% of the target eject material.

Ejecting 50% visible particles from a feed stream in a pre-separation step could be done by a lower cost colour chip sorter from a supplier such as Sortex or Buhler but would still be expensive in terms of equipment cost and air consumption.

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1.11 Trial 1 Sort 3 A portion of the visible ejected material from trial 1 sort 2 was sent through the test unit, configured to eject all ABS material with everything else retained in the reject fraction.


Figure 9: Trial 1 Sort 3 Eject fraction - ABS material

Figure 10: Trial 1 Sort 3 Reject fraction - non ABS material

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1.11.2 Analysis of results samples Material from the eject and reject streams was analysed by FTIR to determine the composition of the fractions.

Fraction Weight of

Fraction

Weight of

FTIR sample

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

T1 S3 Eject 3.38 64.9 75% 19.5 23% 0.5 1% 1.1 1% 0.5 1% 0 0% 0 0% 86.5

T1 S3 Reject 10.27 31.1 35% 54.5 61% 1.9 2% 0 0% 1.2 1% 0 0% 0.4 0.4% 89.1

COMPONENTS PRESENT


Table 3: Results of FTIR analysis of Trial 1 Sort 3

TRIAL 1 SORT 3

T1 S2 Eject ‐ Ejecting ABS Eject ABS

kg %

Total 3.38 25%

ABS 2.54 75%

PS 0.76 23%

Feed PP 0.02 1%

kg % PE 0.04 1%

Total 13.65 100% PC/PCABS 0.02 1%

ABS 6.12 45% PVC 0.00 0%

PS 7.04 52% PA 0.00 0%

PP 0.24 2%

PE 0.04 0%

PC/PCABS 0.16 1% 0.45 t/h/m Reject All other material

PVC 0.00 0% kg %

PA 0.05 0% Total 10.27 75%

ABS 3.58 35%

PS 6.28 61%

PP 0.22 2%

PE 0.00 0%

PC/PCABS 0.14 1%

PVC 0.00 0%

PA 0.05 0%

Trial 1 Sort 3


T1 S3

Q 41%

R 89%

Table 4: Q and R separation efficiencies for Trial 1 Sort 3

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1.11.3 Discussion of results The aim of sort 3 was to separate ABS from the visible material. Figure 11 is a mass balance for trial 1 sort 3. The eject fraction was 25% of the feed, and contained 75% ABS, which is too low for sale as an ABS product. The throughput was measured at 0.45 tonnes per hour per metre of belt.

The separation efficiencies of this sort were calculated.

In this case the product separation efficiency, Q, is the probability that ABS is correctly removed in the eject stream.

The reject separation efficiency, R, is the probability that everything else ends up correctly in the reject stream.

For this sort the product separation efficiency, Q, is low at 41% but the reject separation efficiency, R, is high at 89%. This means that less than half of the ABS will be correctly separated from the feed into the eject fraction. The loss of non-ABS material into the eject fraction is only 11%.

1.11.4 Conclusions from trial The Titech NIR sorting machine can identify ABS from a mixed waste plastic stream, but can only recover 41% of the ABS in the feed, with a product composition of 75% ABS. This is not sufficient for the ABS product to be commercially attractive.

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1.12 Trial 1 Sort 4 A portion of the visible ejected material from trial 1 sort 2 was sent through the test unit, configured to eject all PS material with everything else retained in the reject fraction.


Figure 12: Trial 1 Sort 4 Eject fraction - PS material

Figure 13: Trial 1 Sort 4 Reject fraction - non PS material

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1.12.2 Analysis of product samples FTIR analysis was conducted on the eject and reject fractions to determine their compositions.

Fraction

Weight of

Fraction

Weight of

FTIR sample

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

T1 S4 Eject 3.54 11.8 16% 62.5 82% 0.1 0.1% 0.1 0.1% 1.3 2% 0 0% 0 0% 75.8

T1 S4 Reject 11.03 40.4 49% 35.0 42% 2.5 3% 1.6 2% 3.0 4% 0 0% 0.4 0.5% 82.9

COMPONENTS PRESENT


Table 5: Results of the FTIR analysis for Trial 1 Sort 4

TRIAL 1 SORT 4

T1 S2 Eject ‐ Ejecting PS Eject PS

kg %

Total 3.54 24%

ABS 0.55 16%

PS 2.92 82%

Feed PP 0.00 0%

kg % PE 0.00 0.1%

Total 14.57 100% PC/PCABS 0.06 2%

ABS 5.93 41% PVC 0.00 0%

PS 7.58 52% PA 0.00 0%

PP 0.34 2%

PC/PCABS 0.46 3% 0.46 t/h/m

PVC 0.00 0% Reject All other material

PA 0.05 0.4% kg %

Total 11.03 76%

ABS 5.38 49%

PS 4.66 42%

PP 0.33 3%

PE 0.21 2%

PC/PCABS 0.40 4%

PVC 0.00 0%

PA 0.05 0.5%

Trial 1 Sort 4


T1 S4

Q 39%

R 91%

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Table 6: Q and R separation efficiencies for trial 1 sort 4

1.12.3 Discussion of results Figure 14 shows a mass balance for trial 1 sort 4. The eject fraction was 24% of the feed. It contained over 80% PS. This is still too low because a saleable high grade PS product needs to contain at least 95% PS to avoid compatibility issues with the contaminant polymers. The composition of the reject fraction is nearly a 50:50 split of ABS and PS.

The feed composition in Figure 14 is back calculated from the eject and reject compositions. The back calculated compositions for the feed to sorts 3 and 4 are very similar. This demonstrates that the compositional analysis of the product fractions is accurate.

The throughput was measured at 0.46t/h per metre belt width.

The product separation efficiency, Q, is low at 39% but the reject separation efficiency, R, is high at 91%. This means that less than half of the PS will be recovered from the feed in the eject fraction whilst the loss of other material in the eject fraction is 9%.

1.12.4 Conclusions from trial The Titech NIR sorting machine can identify PS from a mixed waste plastic stream, but recovered only 39% of the PS in the feed, with a product composition of 80% PS.

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1.13 Trial 1 Sort 5 A portion of the visible ejected material from trial 1 sort 2 was sent through the test unit, configured to eject all non ABS and PS material. The aim of this was to remove any of the contaminants in the PS11 material and leave a saleable fraction containing only ABS and PS.

The NIR machine was also used to take a compositional analysis of the sample whilst it was on the belt. At this point there were few black particles present which meant that the composition would be fairly accurate.


Figure 15: Trial 1 Sort 5 Eject Fraction - non ABS and PS material

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Figure 16: Trial 1 Sort 5 Reject fraction - ABS and PS

1.13.2 Analysis of product samples A FTIR analysis was conducted to determine the composition of the eject fraction. However, the entire reject sample was processed in sorts 6 and 7, leaving none available for analysis.

FractionWeight of

Fraction

Weight of

FTIR sample

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

T1 S5 Eject 4.65 55.0 76% 11.7 16% 3 3% 0 0% 3.0 4% 0 0% 0 0.6% 72.6

T1 S5 Reject 28.63 No Sample

COMPONENTS PRESENT


Table 7: Results of the FTIR analysis for Trial1 Sort 5

Figure 17 gives the mass balance for trial 1 sort 5. The reject composition has been back calculated from the feed compositions for trial 1 sort 6 and trial 1 sort 7. The sort 5 feed composition has then been back calculated from the eject analysis and the back calculated reject composition.

TRIAL 1 SORT 5 Eject non ABS/PS

T1 S2 Eject ‐ Ejecting non ABS/PS kg %

Total 4.65 14%

ABS 3.52 76%

PS 0.75 16%

PP 0.16 3%

Feed PE 0.00 0%

kg % PC/PCABS 0.19 4%

Total 33.28 100% PVC 0.00 0%

ABS 14.55 44% PA 0.00 0%

PS 17.72 53%

PP 0.19 1%

PE 0.00 0% Reject ABS/PS

PC/PCABS 0.78 2% 0.37 t/h/m kg %

PVC 0.00 0% Total 28.63 86%

PA 0.01 0.02% ABS 11.03 39%

PS 16.97 59%

PP 0.03 0.1%

PE 0.00 0%

PC/PCABS 0.59 2%

PVC 0.00 0%

PA 0.01 0.03%

Trial 1 Sort 5


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Figure 18 shows the computer screen shot of the composition of the sort 5 reject fraction as determined by the NIR detectors.

Figure 18: Composition from Titech NIR machine for reject fraction of trial 1 sort 5

T1 S5

Q 36%

R 87%


1.13.3 Discussion of results The back calculated composition of the sort 5 reject can be compared to the composition determined by the NIR detectors. The NIR machine gave a composition of approximately 45% ABS and 50% PS. The back calculated composition is 39% ABS and 59% PS. The difference between the values is probably because the black particles (which can be seen in Figure 16) were not detected by the NIR machine but could be analysed by the FTIR spectrometer.

The sort recovered 86% of the material to the reject stream and only 14% to the eject fraction. The reject stream has a styrenics composition of 98%, 39% ABS and 59% PS. In this ratio the product should be saleable as a lower grade styrene product but if the ABS and PS can be split into fractions containing over 95% of each polymer the value for the fractions will be significantly greater.

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The throughput was 0.37t/h per metre belt width.

The Q and R separation efficiencies are similar to the previous sorts.

The product separation efficiency, Q, is the probability that anything other than ABS and PS was correctly ejected.

The reject separation efficiency, R, is the probability that ABS and PS was correctly sorted into the reject fraction.

At 36% the Q for correct removal of contaminants is poor, but the 87% reject separation efficiency, R, means the majority of the ABS and PS was recovered correctly in the reject fraction.

1.13.4 Conclusions from trial There was some removal of contaminants during the trial and the reject fraction was an improvement on the feed composition with only 2% contamination remaining compared to 3% in the feed.

The sorter was much better at detecting PP than PC/ABS, which has a similar NIR spectrum to ABS.

If the reject fraction containing 39% ABS, 59% PS and 1% PC/ABS is saleable then the separation is potentially worthwhile.

1.14 Trial 1 Sort 6 Using the reject fraction from trial 1 sort 5 (mainly ABS and PS) a positive sort for ABS was performed. The system was set up to aggressively eject as much ABS as possible. This may result in mis-sorting of PS to the eject fraction.

It was decided to sort for ABS rather than PS as this would reduce the problem of remaining unidentifiable black particles in the feed. In Titech’s experience these are commonly PS so it is better to send PS to the reject fraction. Note that the compositional analysis for the first sort showed that for this feed material the proportions of PS and ABS in the unidentifiable fraction are nearly equal.

29




Figure 19: Trial 1 Sort 6 Eject Fraction - ABS material

Figure 20: Trial 1 Sort 6 Reject fraction - PS material

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1.14.2 Analysis of product samples Both the eject and reject fractions were sampled and analysed by FTIR to determine the composition.

FractionWeight of

Fraction

Weight of

FTIR sample

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

T1 S6 Eject 5.13 63.0 85% 8.7 12% 0 0% 0 0% 2 3% 0 0% 0 0% 73.7

T1 S6 Reject 12.73 17.5 18% 79.1 80% 0 0% 0 0% 2.8 3% 0 0% 0 0% 99.4

COMPONENTS PRESENT


Table 9: Results for the FTIR analysis for Trial 1 Sort 6

TRIAL 1 SORT 6

T1 S5 Reject ‐ Ejecting ABS Eject ABS

kg %

Total 5.13 29%

ABS 4.39 85%

PS 0.61 12%

Feed PP 0.0 0%

kg % PE 0.00 0%

Total 17.86 100% PC/PCABS 0.14 3%

ABS 6.63 37% PVC 0.00 0%

PS 10.74 60% PA 0.00 0%

PP 0.00 0%

PE 0.00 0%

PC/PCABS 0.50 3% 0.37 t/h/m Reject PS

PVC 0.00 0% kg %

PA 0.00 0% Total 12.73 71%

ABS 2.24 18%

PS 10.13 80%

PP 0.00 0%

PE 0.00 0%

PC/PCABS 0.36 3%

PVC 0.00 0%

PA 0.00 0%

Trial 1 Sort 6


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Figure 22 shows the composition of the eject fraction as determined by the NIR machine.

Figure 22: Composition of the eject fraction by the NIR machine from Trial 1 Sort 6

T1 S6

Q 66%

R 94%


1.14.3 Discussion of results Figure 21 shows the mass balance for trial 1 sort 6. Around 30% of the feed material was ejected and the eject fraction contained 85% ABS.

The composition measured by FTIR analysis can be compared to the composition determined by the NIR machine. The FTIR result at 85% ABS is close to the NIR result of 80%, giving confidence in the results. The reject contained 80% PS. Both these percentages need to be in the region of 95%, in order to be able to sell these fractions for compounding to high grade PS and ABS products. With a second pass through the NIR machine it may be possible to achieve the required compositions.


For this trial the product separation efficiency, Q, is the probability that ABS is correctly sorted into the eject fraction.

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The reject separation efficiency, R, is the probability that PS is correctly sorted into the reject stream.

In this case Q is 66% and R is 94%. These values mean the separation is fairly efficient although a higher Q value would be preferred as this would mean more ABS was recovered.

1.14.4 Physical Properties Tests Both the eject and reject fractions from sort 6 tested at Axion’s polymer laboratory in Salford. The aim was to compare the physical properties of the separated ABS-rich and PS-rich fractions against the physical properties of the original material, PS11, to assess if the separations done by the Titech NIR machine had improved the quality of the material.

The tests conducted were:

Melt Flow Index;

Impact Strength;

Tensile Strength;

Elongation at yield; and

Elongation at break.

Sample MFI Density

Impact

Strength

(notched)

Tensile

Strength

Elong @

Yield

Elong @

Break

Pellet

QualityColour

Surface

FinishDelaminating

kj/m2 Mpa % %

Axpoly

PS116.7 1.032 10.1 31 3.8 15.7 Good Dark grey Smooth Yes

Table 11: Physical properties data for Axpoly® PS11

Sample Content MFIImpact

Strength

Tensile

Strength

Elong @

Yield

Elong @

Break Comments

kj/m2 Mpa % %

T1 S6

Eject85% ABS 3.3 12 37.3 4.1 10.1

Shows signs of delamination so higher

impact strength is probably explained by this

rather than improved polymer properties.

T1 S6

Reject80% PS 5.6 10.7 28.7 3.5 9.4 Brittle compared to other AXPOLY resins

Table 12: Results of physical properties tests for Trial 1 Sort 6

Error! Reference source not found. shows the physical properties of a typical batch of Axpoly PS11, the original starting material for the trial. Error! Reference source not found. shows the results for the two samples produced during sort 6. The ABS-rich eject fraction has a higher

33



impact and tensile strength than the original material and a higher elongation at yield but lower elongation at break.

Delamination was observed in the ABS-rich eject fraction when it was moulded into test bars. This indicates that the mix of polymer types in this fraction is not compatible. This may also explain the relatively high impact strength measured for this sample.

Apart from higher impact strength all the test results for the PS-rich reject fraction were lower than the starting material.

Elongation at break is typically 25% for a good styrenic polymer. Elongation at break for both the eject and reject fractions was well below this.

Ideally the ABS or PS content needs to be at least 95% for a saleable polymer with better physical properties than the mixed material, Axpoly PS11.

1.14.5 Conclusions from trial The machine was able to identify and separate the ABS and PS from each other to produce fractions with over 80% of the respective polymer present.

However the poor physical property results indicate that although relatively clean polymer fractions can be produced, they would require further separation to be saleable as single polymer types with physical properties close to the equivalent virgin material.

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1.15 Trial 1 Sort 7 This was a repeat of trial 1 sort 6 but with the system configured to sort less aggressively for ABS. The less aggressive sort should produce an ABS fraction with a higher ABS composition as less of the other material should be ejected.


Figure 23: Trial 1 Sort 7 Eject fraction - ABS material


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1.15.2 Analysis of product samples The composition of the eject and reject fractions was determined by FTIR analysis.

Fraction

Weight of

Fraction

FTIR

sample

weight

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

T1 S7 Eject 2.57 75.5 87% 10.2 12% 0 0% 0 0% 1.0 1% 0 0% 0 0% 86.7

T1 S7 Reject 7.74 24.3 26% 69.2 73% 0.4 0% 0 0% 0.6 1% 0 0% 0.1 0.1% 94.6

COMPONENTS PRESENT


Table 13: Results of FTIR analysis for Trial1 Sort 7

TRIAL 1 SORT 7

T1 S5 Reject ‐ Ejecting ABS

Eject ABS

kg %

Total 2.57 25%

ABS 2.24 87%

Feed PS 0.30 12%

kg % PP 0.00 0%

Total 10.31 100% PE 0.00 0%

ABS 4.23 41% PC/PCABS 0.03 1%

PS 5.96 58% PVC 0.00 0%

PP 0.03 0% PA 0.00 0%

PE 0.00 0%

PC/PCABS 0.08 1% 0.37 t/h/m

PVC 0.00 0% Reject PS

PA 0.01 0% kg %

Total 7.74 75%

ABS 1.99 26%

PS 5.66 73%

PP 0.03 0%

PE 0.00 0%

PC/PCABS 0.05 1%

PVC 0.00 0.0%

PA 0.01 0.1%

Trial 1 Sort 7


36



Figure 26: NIR determined composition for the Trial 1 Sort 7 eject

The composition of the ABS fraction was higher with the less aggressive sort.

T1 S7

Q 53%

R 95%


1.15.3 Discussion of results Figure 25 shows the mass balance for trial 1 sort 7. 25% of the feed material was ejected and it had 87% ABS content.

The composition measured by FTIR analysis can be compared to that determined by the NIR machine. The FTIR result at 87% ABS is very close to the NIR measurement of 88%, giving confidence in the results. The reject fraction contained 73% PS.

The ABS and PS compositions need to be higher, in the region of 95%, in order to be able to sell these fractions for compounding. With a second pass through the NIR machine it may be possible to achieve the required compositions.


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In this case the product separation efficiency, Q, is the probability that ABS is correctly sorted into the eject fraction.

The reject separation efficiency, R, is the probability that PS is correctly sorted into the reject stream.

In this case Q is 53% and R is 95%. These values mean the separation is fairly efficient although a higher Q value would be preferred as this would mean more ABS was recovered.

Therefore in order to obtain a higher purity ABS fraction the machine should be configured to run less aggressively, but this reduces the probability that the material is correctly sorted. A more aggressive sort increases the probability of the material being sorted but decreases the purity so a balance between the two is required.

1.15.4 Physical Property Tests The tests conducted on the material from sort 6 were repeated on the material from sort 7.

Sample MFI Density

Impact

Strength

(notched)

Tensile

Strength

Elong @

Yield

Elong @

Break

Pellet

QualityColour

Surface

FinishDelaminating

kj/m2 Mpa % %

Axpoly

PS116.7 1.032 10.1 31 3.8 15.7 Good Dark grey Smooth Yes

Table 15: Physical properties data for Axpoly® PS11

Sample Content MFIImpact

Strength

Tensile

Strength

Elong @

Yield

Elong @

Break Comments

kj/m2 Mpa % %

T1 S7

Eject87% ABS 3.1 23.9 38.7 4.6 19.8

Badly delaminated high impact strength

figure is because of this.

T1 S7

Reject75% PS 5.6 10.1 30.0 3.3 14.5 Brittle although less brittle than T1 S6

Table 16: Results of physical properties tests for Trial 1 Sort 7

Table 15 shows the physical properties of a typical batch of PS11, the original starting material for the trial whilst Table 16 shows results for the two samples produced during sort 7.

The results indicate that the ABS-rich eject fraction has a higher impact, tensile strength, elongation at yield and elongation at break than the PS11 starting material. However the material delaminated when extruded which is still a problem but the results show improvement in the right direction.

Test results for the PS-rich reject fraction were lower than for the PS11 starting material. Ideally the ABS or PS content needs to be at least 95% for a good saleable polymer.

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1.15.5 Conclusions from trial A separation of ABS from PS is possible and the machine is able to identify between the two polymers. It is capable of producing an ABS-rich fraction containing 87% ABS and a PS-rich fraction containing 73% PS.

The physical property testing shows that the concentration of ABS and PS in the product fractions is not high enough for the product fractions to be saleable as single polymer products with properties close to equivalent virgin material.

1.16 Overall conclusions from Trial 1 Table 17 shows a summary of the trial 1 sorts.

Sort Eject Q R Throughput

tonnes/m/hr % ABS % PS % ABS % PS

3 ABS 41% 89% 0.45 75 23 35 61

4 PS 39% 91% 0.46 16 82 49 42

5 non ABS/PS 36% 87% 0.36 76 16 39 59

6 aggressive ABS 66% 94% 0.37 85 12 18 80

7 less aggressive ABS 53% 95% 0.37 87 12 26 73

Eject Reject

Table 17: Summary of Trial 1 results

The results show that it is possible to use an NIR sorter to produce an ABS-rich fraction with 85% purity and PS-rich fractions with 80% purity. However physical properties testing of the samples show that these samples are not yet in a saleable form as single polylmers.

Ideally the ABS and PS compositions need to be at leat 95%. A second pass of the fraction through the separator may be able to achieve this but it was not possible to test this during the trials.

The separation efficiencies vary somewhat but may be commerically acceptable. The throughput is also quite low but a 2m wide machine would be able to process just under 1 tonne per hour, which may be viable if the product value can be upgraded sufficiently.

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Trial 2: Effect of particle size on efficiency of the sort using a PS/PE mixture

1.17 Trial objective

The aim of the second trial was to investigate the effect of particle size on the efficiency of the sort in order to quantify how well the machine performs with different particle size fractions. The trial was kept simple to ensure that the effect of particle size was assessed and not, for example, material colour. From the results of the trial it should be possible to determine whether screening the material before passing it through the NIR sorter yields a better separation. It should also identify the minimum size limit for efficient polymer identification and ejection.

1.18 Feed material 3 x 30kg samples (all white material):

1) Sub 6mm 90% PS / 10% PE; 2) 6-12mm 90% PS / 10% PE; and 3) Unscreened 90% PS / 10% PE.

1.19 Trials conducted on material The samples were processed through the machine one at a time.

The machine was set up identically for all three samples to ensure that it was the size classification which was affecting the sort and nothing else. The NIR was configured to positively eject the PE in order to create a pure PE eject fraction. The two fractions were simply collected in the receiving bins and weighed.

For all three sorts the eject fractions were small so the whole samples were used for the analysis but a sub sample of the larger reject fraction was analysed in each case.

A sink float test in water was performed on the samples after the trial. The PE floated whilst the PS sank. The PE was skimmed off and both fractions were dried and weighed.

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1.20 Trial 2 Sort 1 The first sort was conducted on the sub 6mm fraction. It was anticipated that this material might not separate very well as it is smaller than the recommended range for the machine.


Figure 27: Trial 2 Sort 1 Eject fraction - PE material


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1.20.2 Analysis of product samples All of the eject and reject fractions were kept for post trial analysis. The results of the sink float tests are shown in Table 18.

TRIAL 2 SAMPLESample

Weight

g g % g % g

T2 S1 Eject 1210 154 13% 1056 87% 1210

T2 S1 Reject 27740 3074 95% 149 5% 3223

sub 6mm PS/PE

(90:10)

Fraction

WeightAnalysis of Fraction

PS PE

Table 18: Results of analysis of Trial 2 Sort 1 fractions

TRIAL 2 SORT 1

sub 6mm PS/PE (90:10) ‐ Ejecting PE

Eject ‐ PE kg

Total 1.21 4%

PS 0.16 13%

PE 1.05 87%

Feed kg

Total 30.0 100%

PS 27.0 90% Reject ‐ PS kg

PE 3.0 10% 0.21 t/h/m Total 27.74 92%

loss 1.1 kg PS 26.35 95%

4% PE 1.39 5%

Trial 2 Sort 1


TRIAL 2 Q R

sub 6mm PS/PE (90:10) 35% 98%


1.20.3 Discussion of results Figure 29 is a mass balance for the sort. It shows that 92% of the PS in the feed was recovered in the reject fraction, and that the level of PE contamination was reduced from 10% to 5%. The eject fraction contained 87% PE.

For this sort the product separation efficiency, Q, is the probability of the PE being correctly sorted into the eject fraction.

The reject separation efficiency, R, is the probability of the PS being correctly sorted into the reject fraction.

42



The Q value of 35% is low which indicates that only a small amount of the PE was removed.

1.20.4 Conclusions from trial A separation was achieved, removing approximately 35% of the PE contamination with a loss of less than 2% of the PS present in the feed. The feed material for this trial was all below 6mm. This is smaller than the 8mm minimum size recommended by Titech for this machine.

1.21 Trial 2 Sort 2 The final sort was conducted on the over 6mm fraction.



43




1.21.2 Analysis of product samples The same analysis was completed on the two fractions as for the previous sort.


Weight

kg g g % g % g

T2 S2 Eject 1.6 1630 79.6 5% 1535.8 95% 1615

T2 S2 Reject 27.4 27440 3061.8 95% 172.8 5% 3235

+ 6mm PS/PE

(90:10)

Fraction Weight Analysis of Fraction

PS PE

Table 20: Results of analysis on Trial 2 Sort 2 fractions

The purity of the eject fraction for sort 3 is the highest of the three sorts.

+6mm PS/PE (90:10) ‐ Ejecting PE

Eject ‐ PE kg

Total 1.63 5%

PS 0.08 5%

PE 1.55 95%

Feed kg

Total 30 100%


PE 3.00 10% 0.26 t/h/m Total 27.44 91%

loss 0.93 kg PS 26.07 95%

3% PE 1.37 5%

Trial 2 Sort 2


TRIAL 2 Q R

+ 6mm PS/PE (90:10) 52% 96%



The product separation efficiency, Q, was 52% and the reject separation efficiency was 96%.

1.21.4 Conclusions from trial A separation was achieved, removing approximately 50% of the PE contamination with a loss of less than 1% of the PS present in the feed.

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1.22 Trial 2 Sort 3 This sort was conducted on the mixed (unscreened) fraction.




45



1.22.2 Analysis of product samples Table 23 shows the results of the sink float tests.


Weight

kg g g % g % g

T2 S3 Eject 1.1 1100 105.1 10% 995.6 90% 1101

T2 S3 Reject 28.39 28390 1776.3 95% 101.5 5% 1878

Unscreened

PS/PE

Fraction Weight Analysis of Fraction

PS PE

Table 22: Results of analysis on Trial 2 Sort 3 fractions

TRIAL 2 SORT 3

Unscreened PS/PE (90:10) ‐ Ejecting PE

Eject ‐ PE kg

Total 1.10 4%

PS 0.11 10%

PE 0.99 90%

Feed kg

Total 30.0 100%


PE 3.0 10% 0.27 t/h/m/ Total 28.39 95%

loss 0.51kg PS 26.97 95%

2% PE 1.42 5%

Trial 2 Sort 3


Table 23 shows the Q and R separation efficiencies for trial 2 sort 3.

TRIAL 2 Q R

Unscreened PS/PE 33% 99%



The product separation efficiency, Q, was 33% and the reject separation efficiency was 99%.

1.22.4 Conclusions from trial A separation was achieved, removing approximately 33% of the PE contamination with a loss of less than 1% of the PS present in the feed.

46



1.23 Overall conclusions on trial 2 Table 24 shows the Q and R separation efficiencies for the three sorts. It appears that screening the material at 6mm to remove fines will increase the probability of the PE being correctly sorted into the eject fraction, but will incur slightly larger losses of PS. The particle size has little effect on the recovery of PS to the reject stream.

TRIAL 2 Q R

sub 6mm PS/PE (90:10) 35% 98%

+ 6mm PS/PE (90:10) 52% 96%

Unscreened PS/PE 33% 99%

Table 24: Comparison of Q and R values for Trial 2

Overall it can be said that the machine worked best on the greater than 6mm material so size classifying the feed produces better results. The sub 6mm material still worked surprisingly well even though it was below the minimum particle size specified by Titech for the machine.

As this sub 6mm fraction still worked well no minimum particle size for the machine was determined. This is positive because these are the particle sizes commonly created during WEEE processing.

47



Trial 3: Removal of contaminants from mixed plastic (PS07)

1.24 Trial objective The aim of the trial was to identify and eject minor impurities including nylon, silicone rubber, polycarbonate and PMMA from a stream of mixed plastic.

1.25 Feed material The feed material for this trial was a plastic mixture from small WEEE, known as Axplas PS07, produced at Axion’s recycling plant in Salford, typically in the size range 5-12mm.

Figure 36: Trial 3 feed material - PS07

The PS07 feed material was processed once by the machine to eject a first set of contaminants (PMMA, PC, POM, PA, PVC, PBT/PET). The reject from the first sort, now with some of the contaminants removed, was then processed again to remove a second set of contaminants (PP and PE).

The analysis, discussion of results and conclusions are combined after both trial descriptions.

48



1.26 Trial 3 Sort 1 The machine was configured to positively eject PMMA, PC, POM, PA, PVC, PBT/PET.


Figure 37: Trial 3 Sort 1 Eject material - Contaminants

Figure 38: Trial 3 Sort 1 Reject fraction - non contaminants

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1.27 Trial 3 Sort 2 The reject fraction from trial 3 sort 1 was then processed with a positive sort for PP and PE.


Figure 39: Trial 3 Sort 2 Eject fraction - PP and PE fraction

Figure 40: Trial 3 Sort 2 Reject fraction - contaminant free material

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1.28 Analysis of product samples A sub sample of each of the trial 3 fractions underwent FTIR analysis to determine the composition of each fraction. Table 25 shows these results.

TRIAL SAMPLEFraction

weight

Weight of

sample

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

3 PS07 Feed 61.31 27.0 37% 38.8 54% 1.0 1% 1.2 1.7% 4.1 6% 0.3 0.4% 72.4

T3 S1 Eject 1.81 24.7 33% 31.0 41% 0.8 1% 0.0 0% 19.1 25% 0.0 0.0% 75.6

T3 S1 Reject 59.5 27.0 35% 39.0 51% 3.7 5% 1.2 2% 3.9 5% 1.3 1.7% 76.1

T3 S2 Eject 0.48 11.9 28% 5.0 12% 19.0 44% 6.3 15% 0.5 1% 0.0 0.0% 42.7

T3 S2 Reject 59.02 29.2 41% 37.1 52% 1.0 1% 0.0 0% 3.2 4% 1.5 2.1% 72.0

COMPONENTS PRESENT

ABS PS PP PE PC/PCABS PA

Table 25: Results of FTIR analysis for Trial 3 samples

51



52



Trial 3 ‐ PS07 ‐ Ejecting contaminants Eject PMMA, PC, PCABS,

POM, PA, PVC, PET

kg %

Total 1.81 3%

ABS 0.59 33%

Feed kg % PS 0.74 41%

Total 61.31 100% PP 0.02 1%

ABS 24.45 40% PE 0.00 0%

PS 30.94 50% PC/PCABS 0.46 25% Eject PP, PE

PP 1.05 2% 0.41 t/h/m PA 0.00 0% kg %

PE 0.07 0.1% Total 0.48 1%

PC/PCABS 3.06 5% ABS 0.13 28%

PA 1.22 2% Reject PS, ABS, PE, PP PS 0.06 12%

kg % PP 0.21 44%

Total 59.5 97% PE 0.07 15%

ABS 23.86 40% Feed PC/PCABS 0.01 1%

PS 30.20 51% 59.0 kg PA 0.00 0%

PP 1.03 2% 0.41 t/h/m

PE 0.07 0.1%

PC/PCABS 2.61 4%

PA 1.22 2% Reject PS, ABS,

kg %

Sample 0.5 kg Total 58.5 99%

ABS 23.73 41%

PS 30.14 52%

PP 0.81 1%

PE 0.00 0%

PC/PCABS 2.60 4%

PA 1.22 2%

Trial 3 Sort 1

Trial 3 Sort 2

Figure 41: Schematic of Trial 3 Sort 1 and Sort 2 Results

53



Q R

Sort 1 11% 98%

Sort 2 26% 99.6%

Overall 14% 97%

Table 26: Q and R separation efficiencies for Trial 3

1.29 Discussion of results This trial aimed to test the machine’s ability to remove contaminants from a bulk stream of plastic. The level of contaminants within the sample was under 10%. This means the machine had to fire on a very small number of particles which can increases the risk of mis-sorting by ejecting product particles along with the contaminants.

The main contaminant present in the feed was PCABS, which was reduced from 5% to 4% by the first sort. The second sort removed all of the PE and 20% of the PP present. The contaminant PA was not removed by either sort. The losses of ABS and PS by the two sorts were less than 3%.

The composition of the sort 2 reject fraction was better than the feed in that some of the contaminants had been removed but there was further scope for the separation to be improved.

The PS07 material which formed the feed for this trial is sold as a product for low grade moulding applications at present. Removing the minor contaminants will improve its moulding performance and should allow a higher price to be obtained.

Error! Reference source not found. shows the Q and R separation efficiencies for sort 1, sort 2 and then an overall value.

For sort 1 the product separation efficiency, Q, is the probability of the contaminants, in this case only PA and PCABS, being correctly sorted into the eject stream.

The reject separation efficiency, R, is the probability of everything else being sorted correctly into the reject stream.

For sort 1 Q was very low at 11% and R was 98%.

For sort 2 Q is the probability of PE and PP being correctly sorted into the eject fraction, whilst R is the probability of ABS and PS being correctly sorted into the reject fraction. In this case Q and R were 26% and 99.6% respectively.

The overall Q is the probability of all the contaminants being correctly removed in the eject stream, whilst the overall R is the probability of the other components (PS and ABS) being sorted into the reject stream. The overall Q was 14% and the overall R was 97%.

54



For both sorts the product separation efficiency, Q, was very low. Only a small proportion of the contaminants were correctly sorted into the eject fraction.

This may be because the amount of contaminant in the feed was low and the machine found it difficult to identify these contaminants among the bulk material.

The R values are high which means that majority of the material for the reject is correctly sorted.

1.30 Conclusions from Trial 3 Contamination of minor polymer components in the feed was reduced from just below 10% to 7%. The loss of ABS and PS with the contaminants was minimal. The separation improved the feed material but there was scope to remove more contaminants in order to upgrade the product further.

55



Trial 4: Level of blackness detection tests

1.31 Trial objective The objective of this trial was to determine the point at which the machine could no longer identify black particles.

1.32 Feed material A set of black test plaques were specially made up for the trial. The plaques were made from virgin PS and covered the range from 0.5% black masterbatch to 5% black masterbatch in 0.5% increments giving a total of nine different shades.

1.33 Trial results The PS plaque with 1.0% black masterbatch was visible to the machine but the PS01 plaque with 1.5% black masterbatch was not visible. The test was conducted a number of times and the results were consistent.

The PS plaque containing 1.5% masterbatch was scratched on the back to see if this had any effect but it was still undetected.

Therefore the limit of detection by the NIR sorter is 1.0% black masterbatch in PS.

Particles of varying degrees of black were also handpicked from the bulk PS07 material and sent through the machine. The following figures indicate what was visible and not visible to the machine.

Figure 42: Photograph of black plaques visible to Titech NIR machine

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Figure 43: Photograph of handpicked particles visible to Titech NR machine

Figure 44: Photograph of black plaques not visible to the Titech NIR machine

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Figure 45: Photograph of handpicked particles not visible to the Titech NIR machine

1.34 Discussion of results The 1.0% and 1.5% black plaques which were used during the trial were colour analysed, along with a set which covered the range between 1% and 1.5% on 0.1% increments. The 1% black master batch plaque was the standard reference value against which the other plaques between 1.1% and 1.5% were tested.

The plaques were analysed with a spectrophotometer by Colloids Limited, the masterbatch manufacturers.

The results of the colour analysis are shown in Table 27.

DL*

1.1% -0.88

1.2% -1.44

1.3% -1.51

1.4% -1.57

1.5% -5.49

Table 27: Colour analysis values for black plaques

The DL* value refers to the difference in lightness value of the material compared to the reference sample. A negative value means the material is darker than the standard reference value whilst a positive value means the material is lighter than the standard reference value.

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Therefore the 1.5% plaque is 5.49 colour units darker than the 1% plaque. There is a noticeable jump from 1.4% to 1.5% so the machine may be able to detect up to 1.4% but these plaques were not available for testing during the trial.

1.35 Conclusions from Trial 4 The NIR Titech machine is able to detect black PS particles containing 1% masterbatch but not 1.5% masterbatch, where the 1.5% plaque is 5.48 colour units darker than the 1% plaque.

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6.0 Economic assessment of the machine As the machine demonstrated technical potential an assessment of the economic potential of the machine was conducted via a simple payback calculation.

Note that further test work would be required on the TiTech NIR separator to demonstrate that 95% purity can be achieved in this way.

Specific assumptions for the TiTech machine used in this calculation are:

2m belt width for a capacity of 1te/hr with two machines required to deliver sorting in three passes (a total of 6,700te/yr of sorting);

Plant operating 24 hours per day, 5 days per week, 6,000 hours per year; Power consumption about 70Kw, mostly for compressed air to supply the ejection

jets; Mixed feed plastic value £200/te; Separated 95% PS and ABS fractions valued at £400/te; Overall recovery of about 40% high value material from the feed (600te each of 95%

PS and ABS from 3,000te of feed); Reject fractions retain the same value as the feed as they will still contain a high

proportion of black styrenic material; Overall equipment efficiency (OEE) of 70%, giving 4,200 effective running hours per

year; Labour cost of £15/operating hour (full job cost of a single operator); and Power cost £10p/KWhr.

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Pay back calculation

Trial Titech

Equipment

NIR Sorter (2 units

required for feed)

Capacity te/hr 1

Cost of plant £ 500000

Overall Equipment Effectiveness OEE % 70%

Basis of operation hr/yr 6000

Plant Input te/yr 4200

Operating Costs

Power

Consumption for 2 units kW 70

Cost (assuming 10p/kW hr) £/hr 7

Power costs £/te of feed 7.00

Power costs £/yr 29400

Labour costs 90000

Total Operating Costs 119400

Revenue

all feed becomes one

of the product fractions

High grade product extracted (40%) te/yr 1680Value upgrade for high

grade PS and ABS

fractions from £200 to

£400/te

Value of product £/te 200

£/yr 336000

Margin £/yr 216600

Payback time (months) 28

Table 28: Economic Assessment by a payback calculation

The economic assessment shows that it would take about 28 months for an investment in two machines to pay itself back, provided the visible ABS and PS fractions can be upgraded to at least 95% purity with multiple passes through the system.

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Overall final conclusion of trials Overall the trial was successful in that all of the objectives were tested.

Trial 1 indicated that a bulk separation of ABS and PS from WEEE plastics with a Titech ultra high resolution NIR sorter is possible. The results show that it is possible to separate an ABS fraction with 85% purity and a PS fraction with 80% purity. However physical property testing of the samples show that these materials are not yet saleable as single polymer materials. Ideally the ABS and PS compositions need to be at least 95%. A second pass of the ABS-rich and PS-rich fractions through the machine may be able to achieve this.

Trial 2 investigated the effect of particle size on the efficiency of the sort. The results confirmed that particle size does have some effect on the efficiency of the sort. It appears that screening the material at 6mm to remove fines will increase the probability of the PE being correctly sorted into the eject fraction, but will incur slightly larger losses of PS. The particle size had little effect on the recovery of the PS to the reject stream. The sub 6mm material still worked surprising well even though it was believed that it might be below the minimum particle size the machine could process.

Contamination by minor polymer components in the PS07 feed material was only reduced from just below 10% to 7% so this trial was not entirely successful. The loss of ABS and PS with the contaminants was minimal. The separation improved the feed material but there was scope for removal of more contaminants.

The NIR Titech machine is able to detect black PS particles containing 1% masterbatch but not 1.5% masterbatch, where the 1.5% plaque is 5.48 colour units darker than the 1% plaque.

Most of the Q and R separation efficiencies were acceptable. However the throughput was less than expected, at less than 500Kg per hour per metre of belt width. A 2m wide machine would be able to process just under 1 tonne per hour. The commercial viability of the machine was determined by a payback calculation for the separation of ABS and PS from mixed styrenic WEEE polymers, assuming that 95% purity could be achieved for the ABS-rich and PS-rich fractions with a second pass of each fraction through the separator. On this basis the projected payback time is 28 months, which should be commercially viable.

The Titech NIR sorter has a number of advantages as a technique for polymer separation. It is a dry separation which simplifies product handling. The system can be reprogrammed to target a wide range of separations which makes it very flexible.

A fundamental weakness of NIR sorting for WEEE polymers is that even the Titech machine, which was able to detect significantly darker particles than the RTT machine that was also tested in this project, was unable to detect about 50% of the particles in the feed because they were too dark in colour.

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