WO2012143692A2

WO2012143692A2 - Processing system and method

Info

Publication number: WO2012143692A2
Application number: PCT/GB2012/000377
Authority: WO
Inventors: Andreas Christel
Original assignee: Buhler Sortex Ltd
Priority date: 2011-04-20
Filing date: 2012-04-20
Publication date: 2012-10-26
Also published as: GB2492942A; GB201106955D0; WO2012143692A3

Abstract

A processing system for and method of recovering a desired material from a source of particulate material containing contaminated material, the system comprising : a heat treatment unit for heat treating a supply of particulate material, some of which is contaminated, in accordance with a heating regime, wherein the heating regime provides for an optically-detectable change in a physical characteristic of one or more materials other than the desired material; and a sorting unit which receives the particulate material, while still in the heated condition, from the heat treatment unit, and separates contaminated particles from particles of the desired material by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the desired material.

Description

PROCESSING SYSTEM AND METHOD

The present invention relates to a processing system and method, in particular a processing system and method for recovering clean plastics/polymeric material from a source of contaminated plastics/polymeric material, and producing clean, finished plastic/polymeric product therefrom.

The present invention has particular application to the processing of polyester particles, especially PET particles, where contaminants, such as PVC particles, PET particles including glue residues and polyamide blends/multi-layers, are removed from clean PET particles, and the clean PET particles are processed into clean, finished PET product.

The present invention does, however, have application in relation to the processing of any materials which allows for optical discrimination of contaminants, which include ceramics and metals.

As regards polymeric materials, the present invention has particular application to thermoplastics and especially polycondensates, such as polyesters, including polyethylene terephthalate (PET), polybutyl terephthalate (PBT) and polyethylene napthalate (PEN), and polyamides, including PA6, PA66 and PA6T.

The present invention also has application to bio-based polymers, such as starch-based plastics, including thermoplastic starch, cellulose-based plastics, including cellulose esters, aliphatic polyesters, including polyhydroxyalkanoate (PHA), e.g. poly-3-hydroxybutyrate (PHB), polyhydroxyvalerate (PHV) and polyhydroxyhexanoate (PHH), polylactic acid (PLA), PA 11, bio-derived polyethylene and genetically-modified bio-plastics.

In one aspect the present invention provides a processing system for recovering a desired material from a source of particulate material containing contaminated material, the system comprising : a heat treatment unit for heat treating a supply of particulate material, some of which is contaminated, in accordance with a heating regime, wherein the heating regime provides for an optically-detectable change in a physical characteristic of one or more materials other than the desired material; and a sorting unit which receives the particulate material, while still in the heated condition, from the heat treatment unit, and separates contaminated particles from particles of the desired material by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the desired material.

In another aspect the present invention provides a sorting unit for recovering a desired material from a source of heated particulate material which contains contaminated material, the sorting unit comprising : a tray which receives a bulk flow of heated particulate material; a vibrator which vibrates the tray to provide a particulate flow of individually-spaced particulate material; a camera for individually imaging particles within the particulate flow; an ejector assembly comprising a plurality of ejectors, each being individually selectively actuatable to eject a particle from within the particulate flow into a waste particulate flow; and a controller for actuating the ejectors of the ejector assembly in response to a detected optical characteristic of the particles.

In a further aspect the present invention provides a sorting unit for recovering a desired material from a source of heated particulate material which contains contaminated material, the sorting unit comprising : a camera for individually imaging particles within a particulate flow; an ejector assembly for ejecting selected particles from within the particulate flow into a waste particulate flow; and an electromagnetic radiation generator, such as an infra-red (IR), near infra-red (NIR) or microwave generator, for applying electromagnetic radiation to the received particulate material, and upstream of the camera.

In another aspect the present invention provides a sorting unit for recovering a desired material from a source of heated particulate material which contains contaminated material, the sorting unit comprising : a camera for individually imaging particles within a particulate flow; an ejector assembly for ejecting selected particles from within the particulate flow into a waste particulate flow; and an enclosed chamber which acts to retain the heat of received particulate material during transit through the sorting unit, and/or a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment.

In still another aspect the present invention provides a method of recovering a desired material from a source of particulate material containing contaminated material, the method comprising the steps of: heat treating a supply of particulate material, some of which is contaminated, in accordance with a heating regime to provide at least for an optically-detectable change in a physical characteristic of one or more materials other than the desired material; providing the particulate material to a sorting unit; and separating, at the sorting unit, while the particulate material is still in the heated condition, contaminated particles from particles of the desired material by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the desired material.

In yet another aspect the present invention provides a method of recovering a desired material from a source of particulate material containing contaminated material, the method comprising the steps of: applying electromagnetic radiation, such as an infra-red (IR), near infra-red (NIR) or microwave, to a received particulate material prior to imaging; imaging particles within a particulate flow of the particulate material; and ejecting selected particles from within the particulate flow into a waste particulate flow by identification of an optically-detectable change in a physical characteristic of the one or more materials other than the desired material.

In still yet another aspect the present invention provides a method of recovering a desired material from a source of particulate material containing contaminated material, the method comprising the steps of: transferring heated particulate material through a sorting unit, which comprises an enclosed chamber which acts to retain the heat of received particulate material during transit through the sorting unit, and/or a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment; imaging particles within a particulate flow of the particulate material; and ejecting selected particles from within the particulate flow into a waste particulate flow by identification of an optically-detectable change in a physical characteristic of the one or more materials other than the desired material.

In yet another aspect the present invention provides a processing system for providing one or more desired materials from one or more sources, optionally streams, of particulate material, optionally containing contaminated material, the system comprising : at least one heat treatment unit for heat treating one or more sources of particulate material, some of which may be contaminated, in accordance with a heating regime, wherein the heating regime provides or could provide for an optically-detectable change in a physical characteristic of one or more materials other than the one or more desired materials; and at least one sorting unit which receives the particulate material, while still in the heated condition, from the at least one heat treatment unit, and (1) separates contaminated particles from particles of the one or more desired materials by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the one or more desired materials, or (2) provides at least two separate sources of particulate materials, at least one of which comprises substantially one desired material or a blend of one or more desired materials.

In a still yet further aspect the present invention provides a method of providing one or more desired materials from one or more sources, optionally streams, of particulate material, optionally containing contaminated material, the method comprising the steps of: heat treating one or more sources of particulate material, some of which may be contaminated, in accordance with a heating regime using at least one heat treatment unit, wherein the heating regime provides or could provide for an optically-detectable change in a P T/GB2012/000377

5 physical characteristic of one or more materials other than the one or more desired materials; and sorting the particulate material, while still in the heated condition, as received from the at least one heat treatment unit using at least one sorting unit; and separating contaminated particles from particles of the one or more desired materials by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the one or more desired materials, or providing at least two separate sources of particulate materials, at least one of which comprises substantially one desired material or a blend of one or more desired materials.

The present invention also extends to a melt of clean, desired material as produced by the above-described methods.

The present invention further extends to a finished product of clean, desired material as produced by the above-described methods.

Preferred embodiments of the present invention will now be described hereinbelow by way of example only with reference to the accompanying drawings, in which:

Figure 1 illustrates a processing system in accordance with a first embodiment of the present invention;

Figure 2 illustrates the sorting apparatus of the processing system of Figure 1;

Figure 3 illustrates a modified sorting apparatus for the processing system of Figure 1; and

Figure 4 illustrates a processing system in accordance with a second embodiment of the present invention.

Figures 1 and 2 illustrate a processing system in accordance with a first embodiment of the present invention. The processing system comprises a heat treatment unit 3 for heat treating a supply of plastics particles, in this embodiment PET flakes contaminated with contaminants, such as PVC flakes, PET flakes including residues, e.g. glue residues, and polyamide blends/multi-layers.

In preferred embodiments the plastics particles can comprise flakes, pellets or grains.

In this embodiment the heat treatment unit 3 comprises a reactor 5 in which the plastics particles are heated at a predetermined elevated temperature below the melting point (Tm) of the plastics particles for a predetermined period of time, and optionally at a predetermined pressure. In other embodiments the reactor 5 could be operated to heat the plastics particles to a plurality of different temperatures for predetermined periods of time, optionally at a plurality of different pressures.

In one embodiment the heating achieved by a hot gaseous medium, examples including air or nitrogen, which is optionally provided as a hot gas stream through the reactor 5.

This heating regime is selected to provide for one or more of (i) drying of the plastics particles, where the plastics particles are typically prior subjected to a hot wash in water, (ii) removal of contaminants, typically by evaporation of volatile substances, such as impurities from recycled material and any residual solvents, monomers, dimers, oligomers and cleavage products, (iii) crystallization of the desired plastics particles, and (iv) solid-state polycondensation (SSP) of the desired plastics particles, and also to provide for an optically-detectable change in a physical characteristic of plastics particles other than those which are desired.

By virtue of providing for an optically-detectable change in a physical characteristic of plastics particles other than those which are desired, the present invention allows for optical sorting of the contaminated plastics particles, as will be discussed in more detail below.

In this embodiment the heating regime provides for a visual change in one or more contaminants, such as a change in color.

In this embodiment the plastics particles are heated to a temperature of at least 100 C, and preferably to a temperature above the glass transition temperature (Tg).

In preferred embodiments the plastics particles are heated to a temperature of at least 150 C, preferably at least 200 C, and more preferably at least 225 C.

In one embodiment the plastics particles are heated to a temperature of less than 250 C, with the upper bound being the melting temperature (Tm).

In embodiments where the plastics material to be discriminated is glue, a heating regime of 170 C for 30 mins could be employed.

In embodiments where the plastics material to be discriminated is PVC, a heating regime of 180 C for 30 mins could be employed.

In embodiments where the plastics material to be discriminated is PA6, a heating regime of 200 C for 30 mins could be employed.

In one embodiment the reactor 5 can contain a medium, such as a gas, which provides for or promotes the optically-detectable change in plastics particles other than the desired plastics particles. For example, the medium could be a reactive medium which reacts with contaminants and plastics materials other than the plastics material of interest, to produce the optically-detectable change. The processing system further comprises a sorting unit 11 which receives the plastic particles, while still in the heated condition, from the heat treatment unit 3 and separates contaminated plastics particles and plastics particles of other than the plastics materials of interest from the desired, clean plastic particles.

In this embodiment the sorting unit 11 comprises a tray 14 which receives a bulk flow of hot plastics particles, here via a hopper 17 supplied by the heat treatment unit 3, and a vibrator 15 which vibrates the tray 14 to provide a particle flow F of individually-spaced plastics particles, a camera unit 19, here a line camera extending across a width of the particle flow F as delivered from the tray 14, for individually imaging the plastics particles within the particle flow F, an ejector assembly 21, here a pneumatic assembly comprising a plurality of pneumatic ejectors 23 located at spaced intervals across the width of the particle flow F, each being individually actuatable to eject a plastics particle from within the particle flow F into a waste particle flow F' when thereadjacent, and a controller 25 for actuating the ejectors 23 of the ejector assembly 21 in response to a detected optical characteristic of the plastics particles.

In this embodiment the sorting unit 11 is a color sorting unit, and the controller 25 is configured to separate plastics particles having a predetermined color characteristic, here by actuating respective ones of the pneumatic ejectors 23 in response to detection of plastics particles having a predetermined color characteristic.

In a preferred embodiment the controller 25 is configured to identify plastics particles to be separated when having one or more visible wavelength components, corresponding to one or more colors.

In an alternative embodiment the controller 25 could be configured to identify plastics particles to be separated when having one or more wavelength components outside the visible spectrum, such as infra-red (IR), including near infra-red (NIR), or microwave radiation.

In another alternative embodiment the sorting unit 11 could include an electromagnetic radiation generator, such as an infra-red (IR), including near infra-red (NIR), or microwave generator, for applying electromagnetic radiation to the received plastics particles, and upstream of the camera unit 19.

For some materials, which exhibit preferential absorption of electromagnetic radiation, the application of electromagnetic radiation to the received plastics particles can provide for additional or more selective discrimination or contaminated particles.

In this embodiment the sorting unit 11 includes an enclosed chamber 26, here an insulated enclosure, which acts to retain the heat of the heated plastic particles, and thereby prevent significant cooling of the plastics particles during transit to post-processing apparatus. In one embodiment the chamber 26 could be heated, such as to maintain the plastics particles at a predetermined temperature.

In this embodiment the sorting unit 11 includes a thermal jacket 27, here a water-cooled jacket, which houses the vibrator 15, the camera 19, the pneumatic assembly 21 and the controller 25, and any associated circuitry, such as to isolate these components from the high-temperature thermal environment. In an alternative embodiment the thermal jacket 27 could comprise an insulated enclosure.

The processing system further comprises a finishing unit 31 which receives the sorted, clean plastic particles from the sorting unit 11, still in a heated condition, and processes the plastic particles into finished product. T B2012/000377

10

In this embodiment the finishing unit 31 comprises an extruder 33 to an infeed of which the clean plastic particles are delivered from the sorting unit 11, here via a hopper 35, and a finisher 37 for providing finished product.

In this embodiment the extruder 33 is configured to melt, condition and homogenize the received plastic particles into a molten form suitable for the required finishing process. In one embodiment, in conditioning the plastics material, a required degree or dryness and/or polymerization is achieved.

In preferred embodiments the finisher 37 can comprise a sheet line for producing sheet or film, a pelletizer for producing pellets, or a pre-former for producing pre-forms, for example, bottle pre-forms.

Example

The present invention will now be described with reference to the following non-limiting Example.

In this Example, PVC samples (Numbers 1 to 6) were tested to identify suitable heating temperatures and times for achieving an optically-detectable change in the reactor 5. The results are as follows.

As will be noted, for PVC materials, a temperature of 140 C can achieve sufficient discoloration over an extended period, and a temperature of 200 C can also achieve the required discoloration over shorter periods. However, a temperature of 230 C for an extended period is too great, in causing melting. Figure 3 illustrates a sorting unit 11 as a modification of the sorting unit 11 of the above-described embodiment. In this embodiment the thermal jacket 27 isolates the vibrator 15 from other components of the sorting unit 11 and is ventilated to atmosphere. The vibrator 15, as a consequence of its function, can tend to run hot, and this embodiment prevents this heat from being transferred to the other components of the sorting unit 11.

Figure 4 illustrates a sorting apparatus in accordance with a second embodiment of the present invention.

The sorting apparatus of this embodiment is a modification of the above- described embodiment, and, in order to avoid unnecessary duplication of description, only the differences will be described in detail with like parts being designated by like reference signs.

In this embodiment the sorting apparatus comprises first and second heat treatment units 3a, b, which receive respective ones of first and second streams A, B of plastics particles.

In one embodiment at least one of the streams A, B comprises a mixed stream of at least two different types of plastics materials, here PET flakes. In this embodiment the streams A, B each comprise a mixed stream of at least two different types of plastics materials.

In this embodiment one of the streams A, B comprises a first fraction of one kind of plastics material, such as 5-95%, by weight or volume, for example, of clear PET flakes, and a second fraction of another kind of plastics material, for example, of green PET flakes, and the other of the streams A, B comprises a first fraction of the other kind of plastics material, such as 5-95%, by weight or volume, and a second fraction of the one kind of plastics material. 12 000377

12

In this embodiment the sorting apparatus comprises first and second sorting units 11a, b, which receive the respective streams A, B of plastic particles from the heat treatment units 3a, b, and first and second finishing units 31a, b which receive first and second sorted streams of plastic particles as sorted by the sorting units 11a, b.

In this embodiment the first sorting unit 11a is configured to sort the received stream A, such that plastics particles of the one kind are delivered to the first finishing unit 31a and plastics particles of at least one other kind are delivered to the second finishing unit 31b, and the second sorting unit lib is configured to sort the received stream B, such that plastics particles of the one kind are delivered to the first finishing unit 31a and plastic particles of at least one other kind are delivered to the second finishing unit 31b.

In this embodiment the plastics particles as delivered to the first finishing unit 31a have less than 0.1%, by weight or volume, of the at least one other plastics material.

In this embodiment contaminated plastics particles of the one kind which change color during heat treatment are delivered to the second finishing unit 31b.

In an alternative embodiment contaminated plastics particles of the one or other kind, which change color during heat treatment, could be delivered to a further finishing unit (not illustrated) or as a waste product flow.

In one embodiment the first stream A comprises a mixture of clear and green PET flakes, here a major fraction of clear PET flakes, and the second stream B comprises a mixture of green and clear PET flakes, here a major fraction of green PET flakes, and the operation of the sorting units 11a, b is such that a sorted stream of clear PET flakes, with substantially no contaminants, is delivered to the first finishing unit 31a, and a sorted stream of green PET flakes, with other plastics materials, including contaminated clear PET flakes, where appropriate, is delivered to the second finishing unit 31b.

Finally, it will be understood that the present invention has been described in its preferred embodiments and can be modified in many different ways without departing from the scope of the invention as defined by the appended claims.

For example, in one modification, the second-described embodiment could include only one heat treatment unit 3 and one sorting unit 11, with the first and second streams A, B of plastic materials being delivered to the one heat treatment unit 3, sorted by the one sorting unit 11, and the sorted streams being delivered to the respective ones of the first and second finishing units 31a, b.

treating a supply of particulate material, some of which is contaminated, in accordance with a heating regime, wherein the heating regime provides for an optically-detectable change in a physical characteristic of one or more materials other than the desired material; and a sorting unit which receives the particulate material, while still in the heated condition, from the heat treatment unit, and separates contaminated particles from particles of the desired material by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the desired material.

17 physical characteristic of one or more materials other than the one or more desired materials; and sorting the particulate material, while still in the heated condition, as received from the at least one heat treatment unit using at least one sorting unit; and separating contaminated particles from particles of the one or more desired materials by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the one or more desired materials, or providing at least two separate sources of particulate materials, at least one of which comprises substantially one desired material or a blend of one or more desired materials.

22

Example

24

1. A processing system for recovering a desired material from a source of particulate material containing contaminated material, the system comprising :

a heat treatment unit for heat treating a supply of particulate material, some of which is contaminated, in accordance with a heating regime, wherein the heating regime provides for an optically-detectable change in a physical characteristic of one or more materials other than the desired material; and

a sorting unit which receives the particulate material, while still in the heated condition, from the heat treatment unit, and separates contaminated particles from particles of the desired material by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the desired material.

2. The system of claim 1, wherein the heat treatment unit heats the particulate material to a predetermined elevated temperature, and optionally at a predetermined pressure.

3. The system of claim 2, wherein the heat treatment unit heats the particulate material to a plurality of different temperatures for predetermined periods of time, and optionally at a plurality of different pressures.

4. The system of any of claims 1 to 3, wherein the heating is achieved by a hot gaseous medium, such as of air or nitrogen, which is optionally provided as a hot gas stream.

5. The system of any of claims 1 to 4, wherein the optically-detectable change is a visual change, optionally a change in color. The system of any of claims 1 to 5, wherein the particles comprise flakes, pellets or grains. The system of any of claims 1 to 6, wherein the heat treatment unit comprises a chamber which contains a medium, such as a gas, which provides for or promotes the optically-detectable change in materials other than the desired material. The system of claim 7, wherein the medium is a reactive medium which reacts with materials other than the desired material to produce the optically-detectable change. The system of any of claims 1 to 8, wherein the sorting unit comprises a tray which receives a bulk flow of heated particulate material from the heat treatment unit, a vibrator which vibrates the tray to provide a particulate flow of individually-spaced particulate material, a camera for individually imaging particles within the particulate flow, an ejector assembly comprising a plurality of ejectors, each being individually selectively actuatable to eject particles from within the particulate flow into a waste particulate flow, and a controller for actuating the ejectors of the ejector assembly in response to a detected optical characteristic of the particles. The system of claim 9, wherein the sorting unit is a color sorting unit, and the controller is configured to separate particles having a predetermined color characteristic. The system of claim 10, wherein the .controller is configured to identify particles to be separated when having one or more visible wavelength components, corresponding to one or more colors. The system of claim 9, wherein the controller is configured to identify particles to be separated when having one or more wavelength components outside the visible spectrum, such as infra-red (IR), near infra-red (NIR) or microwave radiation. The system of any of claims 1 to 12, wherein the sorting unit includes an electromagnetic radiation generator, such as an infra-red (IR), near infra-red (NIR) or microwave generator, for applying electromagnetic radiation to the received particulate material, and upstream of the camera. The system of any of claims 1 to 13, wherein the sorting unit includes an enclosed chamber which acts to retain the heat of the heated particulate material during transit to post-processing apparatus. The system of claim 14, wherein the chamber is heated so as to maintain the particulate material at a predetermined temperature. The system of any of claims 1 to 15, wherein the sorting unit includes a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment. The system of any of claims 1 to 6, further comprising:

a finishing unit which receives the sorted, clean particulate material from the sorting unit, while still in a heated condition, and processes the particulate material into finished product. The system of claim 17, wherein the finishing unit comprises an extruder to an infeed of which the clean particulate material is delivered from the sorting unit, and a finisher for providing finished product. The system of claim 18, wherein the extruder is configured to melt, condition and homogenize the received particulate material into a molten form suitable for a required finishing process. The system of any of claims 17 to 19, wherein the temperature of the particulate material at an inlet of the sorting unit is not more than 30 C, optionally more than 20 C, optionally more than 10 C, lower than the temperature of the particulate material at an outlet of the sorting unit. The system of any of claims 1 to 20, wherein the particulate material is a plastics/polymeric material. The system of claim 21, wherein the heating regime is selected to provide for one or more of (i) drying of the particulate material, (ii) removal of contaminants, optionally by evaporation of volatile substances, such as impurities from recycled material and any residual solvents, monomers, dimers, oligomers and cleavage products, (iii) crystallization of the desired material, and (iv) solid-state polycondensation (SSP) of the desired material. The system of claim 21 or 22, wherein the particulate material is heated to a temperature of at least 100 C, and optionally to a temperature above the glass transition temperature (Tg) of the desired material. The system of claim 23, wherein the particulate material is heated to a temperature of at least 150 C, optionally at least 200 C, and optionally at least 225 C. The system of any of claims 21 to 24, wherein the particulate material is heated to a temperature lower than the melting temperature (Tm) of the particulate material, optionally less than 250 C, optionally less than 225 C, and optionally less than 200 C. The system of any of claims 21 to 25, wherein the desired material is a polyester, such as PET, and the material to be discriminated is PVC, glue and/or PA. B2012/000377

30 A sorting unit for recovering a desired material from a source of heated particulate material which contains contaminated material, the sorting unit comprising:

a tray which receives a bulk flow of heated particulate material;

a vibrator which vibrates the tray to provide a particulate flow of individually-spaced particulate material;

a camera for individually imaging particles within the particulate flow; an ejector assembly comprising a plurality of ejectors, each being individually selectively actuatable to eject a particle from within the particulate flow into a waste particulate flow; and

a controller for actuating the ejectors of the ejector assembly in response to a detected optical characteristic of the particles. The sorting unit of claim 27, wherein the sorting unit is a color sorting unit, and the controller is configured to separate particles having a predetermined color characteristic. The sorting unit of claim 28, wherein the controller is configured to identify particles to be separated when having one or more visible wavelength components, corresponding to one or more colors. The sorting unit of claim 27, wherein the controller is configured to identify particles to be separated when having one or more wavelength components outside the visible spectrum, such as infra-red (IR), near infra-red (NIR) or microwave radiation. The sorting unit of any of claims 27 to 30, wherein the sorting unit includes an electromagnetic radiation generator, such as an infra-red (IR), near infra-red (NIR) or microwave generator, for applying electromagnetic radiation to the received particulate material, and upstream of the camera. The sorting unit of any of claims 27 to 31, wherein the sorting unit includes an enclosed chamber which acts to retain the heat of received particulate mater)a\ during transit through the sorting unit. The sorting unit of claim 32, wherein the chamber is heated so as to maintain the particulate material at a predetermined temperature. The sorting unit of any of claims 27 to 33, wherein the sorting unit includes a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment. The sorting unit of any of claims 27 to 34, wherein the particulate material is a plastics/polymeric material . The sorting unit of claim 35, wherein the desired material is a polyester, such as PET, and the material to be discriminated is PVC, glue and/or PA. The sorting unit of any of claims 27 to 36, wherein the temperature of the particulate material at an inlet of the sorting unit is not more than 30 C, optionally more than 20 C, optionally more than 10 C, lower than the temperature of the particulate material at an outlet of the sorting unit. A sorting unit for recovering a desired material from a source of heated particulate material which contains contaminated material, the sorting unit comprising :

a camera for individually imaging particles within a particulate flow; an ejector assembly for ejecting selected particles from within the particulate flow into a waste particulate flow; and

an electromagnetic radiation generator, such as an infra-red (IR), near infra-red (NIR) or microwave generator, for applying electromagnetic radiation to the received particulate material, and upstream of the camera.

A sorting unit for recovering a desired material from a source of heated particulate material which contains contaminated material, the sorting unit comprising :

an enclosed chamber which acts to retain the heat of received particulate material during transit through the sorting unit, and/or a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment. The sorting unit of claim 39, wherein the chamber is heated so as to maintain the particulate material at a predetermined temperature. The sorting unit of claim 39 or 40, wherein the temperature of the particulate material at an inlet of the sorting unit is not more than 30 C, optionally more than 20 C, optionally more than 10 C, lower than the temperature of the particulate material at an outlet of the sorting unit. A method of recovering a desired material from a source of particulate material containing contaminated material, the method comprising the steps of:

heat treating a supply of particulate material, some of which is contaminated, in accordance with a heating regime to provide at least for an optically-detectable change in a physical characteristic of one or more materials other than the desired material;

providing the particulate material to a sorting unit; and

separating, at the sorting unit, while the particulate material is still in the heated condition, contaminated particles from particles of the desired material by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the desired material. The method of claim 42, wherein the particulate material is heated to a predetermined elevated temperature, and optionally at a predetermined pressure. The method of claim 43, wherein the particulate material is heated to a plurality of different temperatures for predetermined periods of time, and optionally at a plurality of different pressures. The method of any of claims 42 to 44, wherein the heating is achieved by a hot gaseous medium, such as of air or nitrogen, which is optionally provided as a hot gas stream. The method of any of claims 42 to 45, wherein the optically-detectable change is a visual change, optionally a change in color. The method of any of claims 42 to 46, wherein the particles comprise flakes, pellets or grains. The method of any of claims 42 to 46, wherein the particulate material is heated in a chamber which contains a medium, such as a gas, which provides for or promotes the optically-detectable change in materials other than the desired material. The method of claim 48, wherein the medium is a reactive medium which reacts with materials other than the desired material to produce the optically-detectable change. The method of any of claims 42 to 49, wherein the sorting unit comprises a tray which receives a bulk flow of heated particulate material, and the separating step comprises the step of:

vibrating the tray to provide a particulate flow of individually-spaced particulate material;

individually imaging particles within the particulate flow; and

ejecting particles from within the particulate flow into a waste particulate flow in response to a detected optical characteristic of the particles. The method of claim 50, wherein the sorting unit is a color sorting unit, and particles are separated having a predetermined color characteristic. The method of claim 51, wherein particles are separated when having one or more visible wavelength components, corresponding to one or more colors. The method of claim 50, wherein particles are separated when having one or more wavelength components outside the visible spectrum, such as infra-red (IR), near infra-red (NIR) or microwave radiation. The method of any of claims 42 to 53, further comprising the step of: applying electromagnetic radiation, such as an infra-red (IR), near infrared (NIR) or microwave, to the received particulate material prior to imaging. The method of any of claims 42 to 54, wherein the sorting unit includes an enclosed chamber which acts to retain the heat of the heated particulate material during transit to post-processing apparatus.

The method of claim 55, wherein the chamber is heated so as to maintain the particulate material at a predetermined temperature. The method of any of claims 42 to 56, wherein the sorting unit includes a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment. The method of any of claims 46 to 57, further comprising the step of: providing the sorted, clean particulate material from the sorting unit to a finishing unit; and

processing the particulate material, while still in a heated condition, at the finishing unit into finished product. The method of claim 58, wherein the finishing unit comprises an extruder to an infeed of which the clean particulate material is delivered from the sorting unit, and a finisher for providing finished product. The method of claim 59, wherein the extruder is configured to melt, condition and homogenize the received particulate material into a molten form suitable for a required finishing process. The method of any of claims 42 to 50, wherein the clean, sorted particulate material has a temperature of not more than 30 C, optionally not more than 20 C, optionally not more than 10 C, lower than the temperature of the particulate material as supplied to the sorting unit. The method of any of claims 42 to 61, wherein the particulate material is a plastics/polymeric material. The method of claim 62, wherein the heating regime is selected to provide for one or more of (i) drying of the particulate material, (ii) removal of contaminants, optionally by evaporation of volatile substances, such as impurities from recycled material and any residual solvents, monomers, dimers, oligomers and cleavage products, (iii) crystallization of the desired material, and (iv) solid-state polycondensation (SSP) of the desired material. The method of claim 62 or 63, wherein the particulate material is heated to a temperature of at least 100 C, and optionally to a temperature above the glass transition temperature (Tg) of the desired material. The method of claim 64, wherein the particulate material is heated to a temperature of at least 150 C, optionally at least 200 C, and optionally at least 225 C. The method of any of claims 62 to 65, wherein the particulate material is heated to a temperature lower than the melting temperature (Tm) of the particulate material, optionally less than 250 C, optionally less than 225 C, and optionally less than 200 C. The method of any of claims 62 to 66, wherein the desired material is a polyester, such as PET, and the material to be discriminated is PVC, glue and/or PA. A method of recovering a desired material from a source of particulate material containing contaminated material, the method comprising the steps of:

applying electromagnetic radiation, such as an infra-red (I ), near infrared (NIR) or microwave, to a received particulate material prior to imaging;

imaging particles within a particulate flow of the particulate material; and

ejecting selected particles from within the particulate flow into a waste particulate flow by identification of an optically-detectable change in a physical characteristic of the one or more materials other than the desired material. A method of recovering a desired material from a source of particulate material containing contaminated material, the method comprising the steps of:

transferring heated particulate material through a sorting unit, which comprises an enclosed chamber which acts to retain the heat of received particulate material during transit through the sorting unit, and/or a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment;

imaging particles within a particulate flow of the particulate material; and

ejecting selected particles from within the particulate flow into a waste particulate flow by identification of an optically-detectable change in a physical characteristic of the one or more materials other than the desired material. The method of claim 69, wherein the chamber is heated so as to maintain the particulate material at a predetermined temperature. The method of claim 69 or 70, wherein the temperature of the particulate material at an inlet of the sorting unit is not more than 30 C, optionally more than 20 C, optionally more than 10 C, lower than the temperature of the particulate material at an outlet of the sorting unit. A melt of clean, desired material as produced by the method of any of claims 42 to 71. A finished product of clean, desired material as produced by the method of any of claims 42 to 71. A processing system for providing one or more desired materials from one or more sources, optionally streams, of particulate material, optionally containing contaminated material, the system comprising: at least one heat treatment unit for heat treating one or more sources of particulate material, some of which may be contaminated, in accordance with a heating regime, wherein the heating regime provides or could provide for an optically-detectable change in a physical characteristic of one or more materials other than the one or more desired materials; and

at least one sorting unit which receives the particulate material, while still in the heated condition, from the at least one heat treatment unit, and (1) separates contaminated particles from particles of the one or more desired materials by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the one or more desired materials, or (2) provides at least two separate sources of particulate materials, at least one of which comprises substantially one desired material or a blend of one or more desired materials. The system of claim 74, wherein the sorting apparatus comprises first and second heat treatment units, which receive respective ones of first and second sources of particulate material. The system of claim 75, wherein at least one of the sources comprises a mixed source of at least two different types of particulate materials, optionally each of the sources comprises a mixed source of at least two different types of particulate materials. The system of claim 76, wherein one of the sources comprises a first fraction of one kind of particulate material, optionally containing 5-95%, by weight or volume, and a second fraction of another kind of particulate material, and the other of the sources comprises a first fraction of the other kind of particulate material, optionally containing 5- 95%, by weight or volume, and a second fraction of the one kind of particulate material. The system of any of claims 74 to 77, comprising first and second sorting units, which receive the respective sources of particulate material from the heat treatment units, and first and second finishing units, which receive first and second sorted streams of particulate material as sorted by the sorting units. The system of claim 78, wherein the first sorting unit is configured to sort the source received thereby, such that particulate material of the one kind is delivered to the first finishing unit and particulate material of at least one other kind is delivered to the second finishing unit, and the second sorting unit is configured to sort the source received thereby, such that particulate material of the one kind is delivered to the first finishing unit and particulate material of at least one other kind is delivered to the second finishing unit. The system of any of claims 74 to 77, comprising first and second finishing units, which receive first and second sorted streams of particulate material as sorted by one or more sorting units. The system of any of claims 78 to 80, wherein the particulate material as delivered to the first finishing unit has less than 0.1%, by weight or volume, of the at least one other particulate material. The system of any of claims 78 to 81, wherein contaminated particulate material of the one kind, which changes color during heat treatment, is delivered to the second finishing unit. The system of any of claims 78 to 82, wherein contaminated particulate material of the one or other kind, which changes color during heat treatment, is delivered (1) to a further finishing unit or (2) as a waste product flow. The system of any of claims 74 to 83, wherein the particulate material comprises plastics material, optionally PET flakes. The system of claim 84, wherein the first source comprises a mixture of one color, optionally clear, and other color, optionally green, PET flakes, optionally a major fraction of the one color PET flakes, and the second source comprises a mixture of the other color and the one color PET flakes, optionally a major fraction of the other color PET flakes, and the operation of the at least one sorting unit is such that a sorted stream of the one color PET flakes, with substantially no contaminants, is delivered to the first finishing unit, and a sorted stream of the other color PET flakes, with other color PET flakes and contaminated clear PET flakes, where appropriate, is delivered to the second finishing unit. A method of providing one or more desired materials from one or more sources, optionally streams, of particulate material, optionally containing contaminated material, the method comprising the steps of: heat treating one or more sources of particulate material, some of which may be contaminated, in accordance with a heating regime using at least one heat treatment unit, wherein the heating regime provides or could provide for an optically-detectable change in a physical characteristic of one or more materials other than the one or more desired materials; and

sorting the particulate material, while still in the heated condition, as received from the at least one heat treatment unit using at least one sorting unit; and

separating contaminated particles from particles of the one or more desired materials by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the one or more desired materials, or providing at least two separate sources of particulate materials, at least one of which comprises substantially one desired material or a blend of one or more desired materials.

Claims

5. The system of any of claims 1 to 4, wherein the optically-detectable change is a visual change, optionally a change in color.

6. The system of any of claims 1 to 5, wherein the particles comprise flakes, pellets or grains.

7. The system of any of claims 1 to 6, wherein the heat treatment unit comprises a chamber which contains a medium, such as a gas, which provides for or promotes the optically-detectable change in materials other than the desired material.

8. The system of claim 7, wherein the medium is a reactive medium which reacts with materials other than the desired material to produce the optically-detectable change.

9. The system of any of claims 1 to 8, wherein the sorting unit comprises a tray which receives a bulk flow of heated particulate material from the heat treatment unit, a vibrator which vibrates the tray to provide a particulate flow of individually-spaced particulate material, a camera for individually imaging particles within the particulate flow, an ejector assembly comprising a plurality of ejectors, each being individually selectively actuatable to eject particles from within the particulate flow into a waste particulate flow, and a controller for actuating the ejectors of the ejector assembly in response to a detected optical characteristic of the particles.

10. The system of claim 9, wherein the sorting unit is a color sorting unit, and the controller is configured to separate particles having a predetermined color characteristic.

11. The system of claim 10, wherein the .controller is configured to identify particles to be separated when having one or more visible wavelength components, corresponding to one or more colors.

12. The system of claim 9, wherein the controller is configured to identify particles to be separated when having one or more wavelength components outside the visible spectrum, such as infra-red (IR), near infra-red (NIR) or microwave radiation.

13. The system of any of claims 1 to 12, wherein the sorting unit includes an electromagnetic radiation generator, such as an infra-red (IR), near infra-red (NIR) or microwave generator, for applying electromagnetic radiation to the received particulate material, and upstream of the camera.

14. The system of any of claims 1 to 13, wherein the sorting unit includes an enclosed chamber which acts to retain the heat of the heated particulate material during transit to post-processing apparatus.

15. The system of claim 14, wherein the chamber is heated so as to maintain the particulate material at a predetermined temperature.

16. The system of any of claims 1 to 15, wherein the sorting unit includes a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment.

17. The system of any of claims 1 to 6, further comprising:

a finishing unit which receives the sorted, clean particulate material from the sorting unit, while still in a heated condition, and processes the particulate material into finished product.

18. The system of claim 17, wherein the finishing unit comprises an extruder to an infeed of which the clean particulate material is delivered from the sorting unit, and a finisher for providing finished product.

19. The system of claim 18, wherein the extruder is configured to melt, condition and homogenize the received particulate material into a molten form suitable for a required finishing process.

20. The system of any of claims 17 to 19, wherein the temperature of the particulate material at an inlet of the sorting unit is not more than 30 C, optionally more than 20 C, optionally more than 10 C, lower than the temperature of the particulate material at an outlet of the sorting unit.

21. The system of any of claims 1 to 20, wherein the particulate material is a plastics/polymeric material.

22. The system of claim 21, wherein the heating regime is selected to provide for one or more of (i) drying of the particulate material, (ii) removal of contaminants, optionally by evaporation of volatile substances, such as impurities from recycled material and any residual solvents, monomers, dimers, oligomers and cleavage products, (iii) crystallization of the desired material, and (iv) solid-state polycondensation (SSP) of the desired material.

23. The system of claim 21 or 22, wherein the particulate material is heated to a temperature of at least 100 C, and optionally to a temperature above the glass transition temperature (Tg) of the desired material.

24. The system of claim 23, wherein the particulate material is heated to a temperature of at least 150 C, optionally at least 200 C, and optionally at least 225 C.

25. The system of any of claims 21 to 24, wherein the particulate material is heated to a temperature lower than the melting temperature (Tm) of the particulate material, optionally less than 250 C, optionally less than 225 C, and optionally less than 200 C.

26. The system of any of claims 21 to 25, wherein the desired material is a polyester, such as PET, and the material to be discriminated is PVC, glue and/or PA.

27. A sorting unit for recovering a desired material from a source of heated particulate material which contains contaminated material, the sorting unit comprising:

a tray which receives a bulk flow of heated particulate material;

a controller for actuating the ejectors of the ejector assembly in response to a detected optical characteristic of the particles.

28. The sorting unit of claim 27, wherein the sorting unit is a color sorting unit, and the controller is configured to separate particles having a predetermined color characteristic.

29. The sorting unit of claim 28, wherein the controller is configured to identify particles to be separated when having one or more visible wavelength components, corresponding to one or more colors.

30. The sorting unit of claim 27, wherein the controller is configured to identify particles to be separated when having one or more wavelength components outside the visible spectrum, such as infra-red (IR), near infra-red (NIR) or microwave radiation.

31. The sorting unit of any of claims 27 to 30, wherein the sorting unit includes an electromagnetic radiation generator, such as an infra-red (IR), near infra-red (NIR) or microwave generator, for applying electromagnetic radiation to the received particulate material, and upstream of the camera.

32. The sorting unit of any of claims 27 to 31, wherein the sorting unit includes an enclosed chamber which acts to retain the heat of received particulate mater)a\ during transit through the sorting unit.

33. The sorting unit of claim 32, wherein the chamber is heated so as to maintain the particulate material at a predetermined temperature.

34. The sorting unit of any of claims 27 to 33, wherein the sorting unit includes a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment.

35. The sorting unit of any of claims 27 to 34, wherein the particulate material is a plastics/polymeric material .

36. The sorting unit of claim 35, wherein the desired material is a polyester, such as PET, and the material to be discriminated is PVC, glue and/or PA.

37. The sorting unit of any of claims 27 to 36, wherein the temperature of the particulate material at an inlet of the sorting unit is not more than 30 C, optionally more than 20 C, optionally more than 10 C, lower than the temperature of the particulate material at an outlet of the sorting unit.

38. A sorting unit for recovering a desired material from a source of heated particulate material which contains contaminated material, the sorting unit comprising :

an enclosed chamber which acts to retain the heat of received particulate material during transit through the sorting unit, and/or a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment.

40. The sorting unit of claim 39, wherein the chamber is heated so as to maintain the particulate material at a predetermined temperature.

41. The sorting unit of claim 39 or 40, wherein the temperature of the particulate material at an inlet of the sorting unit is not more than 30 C, optionally more than 20 C, optionally more than 10 C, lower than the temperature of the particulate material at an outlet of the sorting unit.

42. A method of recovering a desired material from a source of particulate material containing contaminated material, the method comprising the steps of:

providing the particulate material to a sorting unit; and

separating, at the sorting unit, while the particulate material is still in the heated condition, contaminated particles from particles of the desired material by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the desired material.

43. The method of claim 42, wherein the particulate material is heated to a predetermined elevated temperature, and optionally at a predetermined pressure.

44. The method of claim 43, wherein the particulate material is heated to a plurality of different temperatures for predetermined periods of time, and optionally at a plurality of different pressures.

45. The method of any of claims 42 to 44, wherein the heating is achieved by a hot gaseous medium, such as of air or nitrogen, which is optionally provided as a hot gas stream.

46. The method of any of claims 42 to 45, wherein the optically-detectable change is a visual change, optionally a change in color.

47. The method of any of claims 42 to 46, wherein the particles comprise flakes, pellets or grains.

48. The method of any of claims 42 to 46, wherein the particulate material is heated in a chamber which contains a medium, such as a gas, which provides for or promotes the optically-detectable change in materials other than the desired material.

49. The method of claim 48, wherein the medium is a reactive medium which reacts with materials other than the desired material to produce the optically-detectable change.

50. The method of any of claims 42 to 49, wherein the sorting unit comprises a tray which receives a bulk flow of heated particulate material, and the separating step comprises the step of:

individually imaging particles within the particulate flow; and

ejecting particles from within the particulate flow into a waste particulate flow in response to a detected optical characteristic of the particles.

51. The method of claim 50, wherein the sorting unit is a color sorting unit, and particles are separated having a predetermined color characteristic.

52. The method of claim 51, wherein particles are separated when having one or more visible wavelength components, corresponding to one or more colors.

53. The method of claim 50, wherein particles are separated when having one or more wavelength components outside the visible spectrum, such as infra-red (IR), near infra-red (NIR) or microwave radiation.

54. The method of any of claims 42 to 53, further comprising the step of: applying electromagnetic radiation, such as an infra-red (IR), near infrared (NIR) or microwave, to the received particulate material prior to imaging.

55. The method of any of claims 42 to 54, wherein the sorting unit includes an enclosed chamber which acts to retain the heat of the heated particulate material during transit to post-processing apparatus.

56. The method of claim 55, wherein the chamber is heated so as to maintain the particulate material at a predetermined temperature.

57. The method of any of claims 42 to 56, wherein the sorting unit includes a thermal jacket, optionally a water-cooled jacket or an insulated enclosure, which isolates components of the sorting unit from the thermal environment.

58. The method of any of claims 46 to 57, further comprising the step of: providing the sorted, clean particulate material from the sorting unit to a finishing unit; and

processing the particulate material, while still in a heated condition, at the finishing unit into finished product.

59. The method of claim 58, wherein the finishing unit comprises an extruder to an infeed of which the clean particulate material is delivered from the sorting unit, and a finisher for providing finished product.

60. The method of claim 59, wherein the extruder is configured to melt, condition and homogenize the received particulate material into a molten form suitable for a required finishing process.

61. The method of any of claims 42 to 50, wherein the clean, sorted particulate material has a temperature of not more than 30 C, optionally not more than 20 C, optionally not more than 10 C, lower than the temperature of the particulate material as supplied to the sorting unit.

62. The method of any of claims 42 to 61, wherein the particulate material is a plastics/polymeric material.

63. The method of claim 62, wherein the heating regime is selected to provide for one or more of (i) drying of the particulate material, (ii) removal of contaminants, optionally by evaporation of volatile substances, such as impurities from recycled material and any residual solvents, monomers, dimers, oligomers and cleavage products, (iii) crystallization of the desired material, and (iv) solid-state polycondensation (SSP) of the desired material.

64. The method of claim 62 or 63, wherein the particulate material is heated to a temperature of at least 100 C, and optionally to a temperature above the glass transition temperature (Tg) of the desired material.

65. The method of claim 64, wherein the particulate material is heated to a temperature of at least 150 C, optionally at least 200 C, and optionally at least 225 C.

66. The method of any of claims 62 to 65, wherein the particulate material is heated to a temperature lower than the melting temperature (Tm) of the particulate material, optionally less than 250 C, optionally less than 225 C, and optionally less than 200 C.

67. The method of any of claims 62 to 66, wherein the desired material is a polyester, such as PET, and the material to be discriminated is PVC, glue and/or PA.

68. A method of recovering a desired material from a source of particulate material containing contaminated material, the method comprising the steps of:

imaging particles within a particulate flow of the particulate material; and

ejecting selected particles from within the particulate flow into a waste particulate flow by identification of an optically-detectable change in a physical characteristic of the one or more materials other than the desired material.

69. A method of recovering a desired material from a source of particulate material containing contaminated material, the method comprising the steps of:

imaging particles within a particulate flow of the particulate material; and

70. The method of claim 69, wherein the chamber is heated so as to maintain the particulate material at a predetermined temperature.

71. The method of claim 69 or 70, wherein the temperature of the particulate material at an inlet of the sorting unit is not more than 30 C, optionally more than 20 C, optionally more than 10 C, lower than the temperature of the particulate material at an outlet of the sorting unit.

72. A melt of clean, desired material as produced by the method of any of claims 42 to 71.

73. A finished product of clean, desired material as produced by the method of any of claims 42 to 71.

74. A processing system for providing one or more desired materials from one or more sources, optionally streams, of particulate material, optionally containing contaminated material, the system comprising: at least one heat treatment unit for heat treating one or more sources of particulate material, some of which may be contaminated, in accordance with a heating regime, wherein the heating regime provides or could provide for an optically-detectable change in a physical characteristic of one or more materials other than the one or more desired materials; and

at least one sorting unit which receives the particulate material, while still in the heated condition, from the at least one heat treatment unit, and (1) separates contaminated particles from particles of the one or more desired materials by identification of the optically-detectable change in the physical characteristic of the one or more materials other than the one or more desired materials, or (2) provides at least two separate sources of particulate materials, at least one of which comprises substantially one desired material or a blend of one or more desired materials.

75. The system of claim 74, wherein the sorting apparatus comprises first and second heat treatment units, which receive respective ones of first and second sources of particulate material.

76. The system of claim 75, wherein at least one of the sources comprises a mixed source of at least two different types of particulate materials, optionally each of the sources comprises a mixed source of at least two different types of particulate materials.

77. The system of claim 76, wherein one of the sources comprises a first fraction of one kind of particulate material, optionally containing 5-95%, by weight or volume, and a second fraction of another kind of particulate material, and the other of the sources comprises a first fraction of the other kind of particulate material, optionally containing 5- 95%, by weight or volume, and a second fraction of the one kind of particulate material.

78. The system of any of claims 74 to 77, comprising first and second sorting units, which receive the respective sources of particulate material from the heat treatment units, and first and second finishing units, which receive first and second sorted streams of particulate material as sorted by the sorting units.

79. The system of claim 78, wherein the first sorting unit is configured to sort the source received thereby, such that particulate material of the one kind is delivered to the first finishing unit and particulate material of at least one other kind is delivered to the second finishing unit, and the second sorting unit is configured to sort the source received thereby, such that particulate material of the one kind is delivered to the first finishing unit and particulate material of at least one other kind is delivered to the second finishing unit.

80. The system of any of claims 74 to 77, comprising first and second finishing units, which receive first and second sorted streams of particulate material as sorted by one or more sorting units.

81. The system of any of claims 78 to 80, wherein the particulate material as delivered to the first finishing unit has less than 0.1%, by weight or volume, of the at least one other particulate material.

82. The system of any of claims 78 to 81, wherein contaminated particulate material of the one kind, which changes color during heat treatment, is delivered to the second finishing unit.

83. The system of any of claims 78 to 82, wherein contaminated particulate material of the one or other kind, which changes color during heat treatment, is delivered (1) to a further finishing unit or (2) as a waste product flow.

84. The system of any of claims 74 to 83, wherein the particulate material comprises plastics material, optionally PET flakes.

85. The system of claim 84, wherein the first source comprises a mixture of one color, optionally clear, and other color, optionally green, PET flakes, optionally a major fraction of the one color PET flakes, and the second source comprises a mixture of the other color and the one color PET flakes, optionally a major fraction of the other color PET flakes, and the operation of the at least one sorting unit is such that a sorted stream of the one color PET flakes, with substantially no contaminants, is delivered to the first finishing unit, and a sorted stream of the other color PET flakes, with other color PET flakes and contaminated clear PET flakes, where appropriate, is delivered to the second finishing unit.

86. A method of providing one or more desired materials from one or more sources, optionally streams, of particulate material, optionally containing contaminated material, the method comprising the steps of: heat treating one or more sources of particulate material, some of which may be contaminated, in accordance with a heating regime using at least one heat treatment unit, wherein the heating regime provides or could provide for an optically-detectable change in a physical characteristic of one or more materials other than the one or more desired materials; and