Title

Process and system for the recycling of composite plastic materials, mixed and pure waste plastics Field

This invention relates to the recycling of composite plastics, e.g., metal coated plastics including batteries, carbon fibre and glass fibre plastics, mixed plastics and pure plastics by pyrolysis. Background

Plastics are derived from hydrocarbon oil; they are generally not biodegradable, but they can be converted back into synthetic oil with pyrolysis. Pyrolysis breaks down the plastic macromolecules into smaller ones, e.g. into synthetic fuel. Pyrolysis is a thermal decomposition process operating at around 350 to 500°C in the absence of oxygen and, typically, at ambient pressures. The three products from plastic waste pyrolysis are 90 wt% synthetic oil, 8 wt% gas, and 2 wt% solid. The gas is a mixture of light organics (methane, propane etc.) and may produce heat for the process. The synthetic oil can be upgraded to transport fuel, e.g. diesel or used as a basic chemical or both. Aluminium laminated (AL) packaging meets many of the packaging requirements of the food and pharmaceutical industries. AL packaging is inert, lightweight, tough and the aluminium layer with a thickness of 6-150 pm provides a life-long barrier against aroma loss and protects the product against ingress of moisture, air, microorganisms, UV light and other spoiling agents, resulting in extending shelf life. Because of these important advantages, AL packaging has had annual growth rates of 10-15%, and in 2015 about 190,000 tonnes of aluminium were consumed for its production in Europe.

The one disadvantage of AL packaging is that it is considered unrecyclable. WO 2005/061098 A1 discloses a microwave pyrolysis process to treat composite waste materials such as AL waste. The pyrolysis reactor comprises two chambers, one after the other, and both equipped with a rotary stirrer. Both chambers contain a bed of particulate microwave absorbing material such as carbon. The stirrers are configured to fluidise the mixture such that the upper surface of the fluidised mixture has a radial profile that biases laminate or delaminated metal (aluminium) floating on the fluidised mixture to migrate outwards. Intimate contact between the particles of microwave absorbing material (e.g., carbon) and the laminate ensures efficient heat transfer to the organic material over all surfaces. The delaminated metal is concentrated at the top of the second chamber and can be recovered from the reactor. After exiting the reactor, the delaminated metal is separated from the particulate microwave material using suitable separation techniques, e.g., sieving. Disadvantages of this process include that a microwave reactor with two stirrers is potentially expensive from a capital point of view. Moreover, microwave treatment in itself may be expensive as it is relatively high tech compared to low-cost waste material.

The PCT patent application WO 97/00268 discloses a process in which solid plastic material is pyrolyzed on molten lead. An auger partially immersed in the lead bath carries the floating pieces along the molten lead bath. Lead is problematic from an environmental and health perspective. The products will contain some lead, which may result in problems selling them. Moreover, the auger is partially immersed in the molten lead and is, hence, subjected to the molten lead reducing its lifespan. The US patent 5,085,738 also uses molten lead to pyrolyse organic waste material such as tyres or plastics. The pyrolysis chamber is elongated and inclined so that material introduced in a lower portion migrates through the molten lead to a higher portion of the chamber. This may result in a difficult to control process as the vapour fraction would also have to “bubble” through the molten lead. Moreover, the waste has to be dry as otherwise, a steam explosion may result. And as mentioned above lead is problematic from an environmental and health perspective. The products will contain some lead, which may result in problems selling them.

The PCT patent application WO 2010/034076 A1 discloses a system to pyrolyses whole tyres in a molten alloy of zinc and aluminium. The tyres are placed in a chamber, which is subsequently filled with molten which is pumped from a holding container underneath. The waste tyres have to be dry as otherwise, a steam explosion may result. Furthermore, molten zinc is very corrosive when it is moving. Moreover, the door preventing the molten zinc from leaking out of the chamber is subjected directly to the molten zinc and, hence, very expensive. Finally, the movements of the tyres in and out of the chamber require mechanical movements which will be difficult to implement at these temperatures and are, hence, expensive.

The US patent US 2009/0014311 A1 discloses an apparatus for treating waste material by pyrolysis in molten metal. A rotating conveyor pushes the waste at least portion-wise beneath the molten metal ensuring rapid heat transfer and hence pyrolysis. There are a number of problems with this apparatus. First, the waste has to be dry as otherwise, a steam explosion may result. Second, the conveyor pushing the waste beneath the molten metal is subjected to severe corrosion by the molten zinc limiting its lifespan or making it very expensive. The US patent US 2017/0218164 A1 discloses a fibreglass plastic pyrolysis process executed in a carbon dioxide environment to recover the organic (resin) and inorganic (glass fibre) portions separately. Subsequently to the pyrolysis process, the fibreglass is treated in a combustion process to remove carbon still adhering to the glass fibres. The pyrolysis process is executed in a conventional rotary kiln. Flowever, rotary kilns have already been shown to be too inefficient for large scale applications. Moreover, the combination of pyrolysis and combustion makes for a potentially expensive process for a low-cost feedstock.

The European patent EP 2 233 547 B1 discloses a waste plastic pyrolysis process comprising of an extruder and a screw tyre reactor. The extruder melts the plastic by a combination of mechanical friction and external heating. The molten plastic is added to the screw reactor for pyrolysis. Inert substances such as ball bearings and catalysts may also be added. The ball bearings or other inert substances to improve heat transfer and the catalysts to improve the reaction conditions in general. The catalyst may have various functions: (1) reduce the operating temperature of the process, (2) increase the efficiency of fuel fractions, (3) accelerate the pyrolysis process or (4) initiate it after bringing the plastic to a certain temperature. A catalyst, however, may be expensive compared to the waste product and is, therefore, not desirable.

The PCT patent application WO 2018/000050 A1 discloses a batch process that adds a certain amount of molten plastic from a feeding screw to a stirred vertical batch pyrolysis reactor. The molten plastic remaining in the feeding screw provides a process seal. The char will be transferred in batch mode to a fluidised bed burner, which heat output may provide the heat for the entire process. Disadvantages of this relatively complex process include that it is a batch process and that the molten plastic remaining in the feeding screw may decompose, resulting in overpressures and corrosion of the screw.

The PCT patent application WO 2014/032843 A1 discloses a system for the recycling of whole tyres, coarsely cut tyres, large plastic pieces, plastic composites such as hoses or combinations of above into gases, liquids and solids by direct heating in a pyrolysis liquid such as molten salt or molten metal. The pyrolysis system is constructed such that the segregation of the light (e.g., recovered carbon black) and heavy materials (e.g., steel) occurs within the pyrolysis chamber in a sink-float separation facilitated by the molten salt or metal. In the case of tyre recycling, the resulting carbon black separates to the top of the molten zinc. The carbon black is removed from the molten zinc with the pyrolysis vapours. The carbon black is segregated from the vapours by a cyclone. Diesel or other oils, steel, carbon black and synthesis gas are recovered. The process is, however, not specifically designed to recycle materials such as composite, mixed or pure plastics or steel free shredded tyres lacking the means of removing the recovered materials from the zinc surface. Moreover, a U-shaped chamber structure is not necessary as none of the materials will sink in the molten zinc and hence a simpler and more cost- effective solution can be designed.

The US patent US 2020/0299590 A1 discloses a pyrolysis system for the production of synthetic crude oil from unconventional oil sources such as oil sands or oil shale. This system is, however, not specifically designed to treat materials such as composite, mixed or pure plastics lacking the means of removing the recovered materials from the zinc surface. Moreover, the system is not designed to deal with long-chain products such as waxes.

The PCT patent application WO 2014/167139 A2 discloses a system for the recycling of printed circuit boards (PCBs) and similar materials by pyrolysis; specifically, by direct heat contact of the PCBs in molten salt. The separation of the light and heavy materials occurs within the separation chamber. This process avoids the inefficient procedure of sorting the batteries to type, size or both and also avoids shredding and pulverisation associated with many other processes. Further disclosed is a U-shaped pyrolysis chamber with a sloped bottom. There are a number of problems with this patent if dealing with plastics or plastic composites. First, the char, ash or carbon solids would contaminate the salt, which would have to be replaced intermittently generating additional operating costs. Second, the solids products will be contaminated with salt, which removal will be expensive, if not impossible, reducing its resale value.

The PCT application WO 2015/0777080 A1 and the US patent US 8,616,475 B1 disclose a process for the recovery of aluminium, copper and the cathode material containing lithium and cobalt from waste lithium-ion batteries. The batteries are crushed either in a water spray or under an inert (nitrogen) atmosphere to prevent ignition of the solvents and producing a slurry. This slurry is screened for the coarser solids to recover copper and aluminium. The slurry is filtered, obtaining a filter cake. This filter cake is heated in air to 400- 840°C to destroy the binder and any plastic pieces left.

The US patent 2012/0024687 A1 disclose a method to separate a boiling component, for example, a hydrocarbon solvent, from a mixture in an induction heated screw conveyor. Such a system, however, does not work well for larger waste materials such as batteries or carbon fibre pieces.

The US patent 2018/0301769 A1 discloses a process for processing used batteries, in particular, used lithium batteries. The batteries are comminuted under a shielding gas, e.g., nitrogen, which is extracted. The comminuted material is fed into a drying device equipped with a mixer, which dries the material under vacuum until the electrolyte content in the comminuted material so low that an electrochemical reaction is impossible. Such a process, however, always carries the risk of ignition of solvents within the comminuting apparatus and, moreover, comminution mixes all materials making recovery of individual materials, e.g. the metals, more challenging.

The US patent 2005/0241943 A1 discloses a process which first treats the batteries to a temperature of 150°C for at least 1 hour before shredding and sieving and then treating the resulting mass further at a temperature of up to 500°C for one hour before another sieving step and further processes to recycle lithium. This is a complicated multi-step process, and a simpler process that had fewer steps and avoided the need for shredding would be desirable.

The US patent 6,143,940 discloses a process for making a heavy wax composition by operating a sub-atmospheric pyrolysis reactor. The US patent 11 ,091 ,700 B2 entitled "Process for the preparation of a C20 to Ceo wax from the selective thermal decomposition of plastic polyolefin polymer" discloses another pyrolysis process for making a wax from plastics by operating a sub- atmospheric pyrolysis reactor. However, such sub-atmospheric or vacuum processes are expensive to operate and may be risky from a safety point of view as air might be sucked into the process.

The UK patent application GB 2388842 A discloses a continuous process converting plastics (polyolefins) into lube oils or waxes. The plastic is added to the pyrolysis reactor molten, and at least a portion of the vapours are treated in a catalytic isomerisation dewaxing unit. It is, however, expensive to melt the plastic prior to pyrolysis and not necessary if a molten metal reactor is used. The UK patent application GB 2473528 A discloses a plastic (polyolefins) to wax process using microwaves. As already discussed above, microwave reactors have disadvantages over other reactors; for example, microwave treatment may be expensive as it is relatively high tech compared to low-cost waste material.

It is an object of the present invention to solve at least one of the above mentioned problems.

Summary This invention, as defined by the appended claims, proposes to pyrolyse AL packaging by direct heat transfer with molten metal, e.g., molten zinc resulting in a very fast process as the theoretically fastest heat transfer is achieved, i.e. , direct heat transfer. In other words, no other plastic waste pyrolysis process could be faster. Target materials are aluminium, the pyrolysis oil or wax gained from plastic pyrolysis, and the pyrolysis gases, which may be burned for heat or the generation of electricity or both.

The present invention solves the problems described above. As a result, the invention provides an economical method for the recycling of valuable metals, and for obtaining pyrolysis wax and oil and pyrolysis gases from waste composite plastics, mixed plastics and pure plastics and similar plastics waste materials. It is noted that other plastic wastes may also be recycled.

From various plastic pyrolysis experiments performed on a molten metal pilot plant, it is clear that a molten metal reactor is particularly suitable for converting polyolefins into waxes.

According to a first aspect of the present invention there is provided a pyrolysis system for recycling feedstock composed of plastic-metal composites such as food packaging materials, for example, Tetra Pak® or aluminium-laminated plastics, glass and carbon fibre reinforced plastics, mixed plastics, automobile shredder residue (ASR), batteries, biomass, plastic containing biomass, shredded tyres, or single waste plastic streams, for example, polyolefins, the system comprising: a charging device for continuous or discontinuous charging said feedstock onto a stationary pyrolysis liquid maintained in a molten state at temperatures between 160 and 650°C in an oxygen devoid atmosphere and operating pressures above atmospheric within a pyrolysis chamber; at least one pyrolysis vapour removal line to remove the vapour product from said pyrolysis chamber; and at least one solid product removal device for removing the solid product from the surface of said pyrolysis liquid and, subsequently, from said pyrolysis chamber.

In this system each solid product removal device may comprise a continuous discharge screw, a discontinuous rake, a continuous outlet rotary valve, a continuous outlet conveyor or combinations thereof. So the solid product may be removed continuously or intermittently.

The system may also comprise at least one screw mechanism or at least one rake overhead conveyor to move said feedstock along the surface of said pyrolysis liquid towards the inlet of said solid product removal device without said screw mechanism or said rake overhead conveyor contacting said pyrolysis liquid.

The system may comprise multiple said screw mechanisms or multiple said solid product removal devices or multiple said pyrolysis vapour removal lines or variations thereof.

The pyrolysis liquid may be a molten non-ferrous metal or alloy consisting of at least one of zinc, tin, indium, lead, aluminium and copper. Molten zinc may for example be used. Where multiple said pyrolysis vapour removal lines are installed to remove said product vapours from said pyrolysis chamber, they may be located at similar distances from where the charging device feeds into said pyrolysis chamber. The system may also comprise an impingement plate located above said pyrolysis liquid and below the outlet from the charging device into said pyrolysis chamber. The charging device may be a screw feeder.

The pyrolysis chamber may be equipped with one or more weirs. However the chamber desirably has a flat base plate, so the depth of the molten metal is uniform.

The molten metal may be heated by a plurality of heat sources such as burners, below the base plate, at different locations. It is desirable to ensure that the temperature does not vary significantly across the surface of the molten metal. This can be achieved by monitoring the temperature of the molten metal at a plurality of spaced-apart locations, and controlling the heat sources in response to those temperature measurements. For example, the temperature may be controlled in this way to ensure it varies by no more than 5°C, and preferably no more than 2°C, across the width of the pyrolysis chamber. It will be appreciated that the good thermal conductivity of the molten metal and natural convection within the molten metal both help to ensure substantially uniform temperature across the surface. According to a second aspect of the present invention, there is provided with a process for producing waxes from a feedstock composed of plastic-metal composites such as food packaging materials, for example, Tetra Pak® or aluminium-laminated plastics, glass and carbon fibre reinforced plastics, mixed plastics, automobile shredder residue (ASR), batteries, biomass, plastic containing biomass, shredded tyres, or single waste plastic streams, for example, polyolefins, the process comprising the steps of: a) continuously or discontinuously charging said feedstock onto a stationary pyrolysis liquid maintained in a molten state at a temperature between 160 to 650°C in an oxygen devoid atmosphere and at an operating pressure above atmospheric within a pyrolysis chamber; b) continuously or discontinuously removing the vapour product via at least one pyrolysis vapour removal line from said pyrolysis chamber while maintaining an operating pressure above atmospheric within said pyrolysis chamber; c) continuously or discontinuously removing the solid products from the surface of said pyrolysis liquid via at least one solid product removal device and, subsequently, from said pyrolysis chamber; and d) continuously or discontinuously condensing the vapour product to produce waxes. The aforesaid process may instead be performed to produce compounds suitable for use as fuel or lubricants from the feedstock. In this case the vapour product is condensed to produce waxes and oils, and these condensed waxes and oils are utilised as compounds suitable for use as fuel or lubricants. The vapours may for example be passed through a plurality of condensors at different temperatures, and the liquid phase produced by each condenser separated from the remaining vapours. For example, a condenser that cools the vapour to between 150°C and 80°C will produce a liquid phase that is a wax at ambient temperature, while a condenser that cools the vapour to between 30°C and 15°C will produce a liquid phase that is an oil at ambient temperature.

In this case, the process may further comprise separating the condensed waxes from the condensed oils; returning the condensed waxes onto said pyrolysis liquid in the pyrolysis chamber; and utilising the condensed oils as compounds suitable for use as fuel or lubricants. Alternatively, after separating the condensed waxes from the condensed oils, the condensed waxes may be utilised as a desired product. According to one aspect of the invention there is provided a system for recycling feedstock composed of one or more materials such as printed circuit boards (PCBs), batteries, plastic containing biomass, plastic-metal composites such as food packaging materials, for example Tetra Pak® or aluminium-laminated plastics, glass fibre and carbon fibre reinforced plastics, compact disks (CDs, DVDs), lithium-ion batteries, automobile shredder residue (ASR), mixed plastics, single waste plastic streams such as polypropylene, the system comprising: means for charging said feedstock by charging device, said charging device adapted to remove air from said feedstock; means for charging said feedstock from said charging device into pyrolysis chamber comprising of a pyrolysis liquid, which is held at a desired temperature range, which is a stationary fluid, and comprises of a continuous, fluidic surface, on which said feedstock separates into a vapour and a solid product; means for removing said vapour product via pyrolysis vapour removal line from said pyrolysis chamber; and/or means for; means for removing said solid product via solid product removal device from the surface of said pyrolysis liquid.

According to another aspect of the invention there is provided a method for recycling feedstock composed of one or more materials such as printed circuit boards (PCBs), batteries, plastic containing biomass, plastic-metal composites such as food packaging materials, for example Tetra Pak® or aluminium- laminated plastics, glass fibre and carbon fibre reinforced plastics, compact disks (CDs, DVDs), lithium-ion batteries, automobile shredder residue (ASR), mixed plastics, but also single waste plastic streams such as polypropylene, the system comprising: charging said feedstock by charging device, said charging device adapted to remove air from said feedstock; charging said feedstock from said charging device into pyrolysis chamber comprising of a pyrolysis liquid (17), which is held at a desired temperature, which is a stationary fluid, and comprises of a continuous, fluidic (molten) surface, on which said feedstock separates into a vapour and a solid product; removing said vapour product via pyrolysis vapour removal line from said pyrolysis chamber; and/or means for; removing said solid product via solid product removal device from the surface of said pyrolysis liquid.

Brief Description of the Drawings

The characteristics and advantageous characteristics of the present invention are detailed in this section based on the accompanying drawings in three non- restrictive feedstock examples: (1) aluminium laminated (AL) plastic, (2) mixed plastics and (3) glass or carbon fibre composite plastics with reference to the attached drawings wherein:

Fig. 1 is a cross-sectional view of one embodiment of the continuous conveyor charging mechanism to pyrolysis chamber 15.

Fig. 2 is a partial cross-sectional view of one embodiment of a charging mechanism to pyrolysis chamber 15 using a lock system.

Fig. 3 is a partial cross-sectional view of one embodiment of pyrolysis chamber 15 filled with molten metal as pyrolysis liquid 17 and conveyor 7 providing waste plastics from the side to pyrolysis chamber 15.

Fig. 4 is a partial cross-sectional view of one embodiment of pyrolysis chamber 15 with a number of screw feeder(s) 28 on the side of pyrolysis chamber 15.

Fig. 5 is a cross-sectional view of section A-A (Fig. 8), showing two options as to how feedstock 3 may be distributed within pyrolysis chamber 15.

Fig. 6 is a partial cross-sectional view of one embodiment of pyrolysis chamber 15 where screw feeder 28 is located on top of pyrolysis chamber 15 and pyrolysis vapour removal line(s) 22 located on the four sides of pyrolysis chamber 15.

Fig. 7 is a cross-sectional view of section A-A as indicated in Fig. 6; also shown is the direction of travel of feedstock 3 by arrows 4 to four pyrolysis vapour removal line(s) 22 located in each corner of pyrolysis chamber 15 above the surface of pyrolysis oil liquid 17.

Fig. 8 is a partial cross-sectional view of one embodiment of pyrolysis chamber 15 filled with molten metal as pyrolysis liquid 17 and where screw feeder 28 is located on the side of pyrolysis chamber 15 above the surface of pyrolysis liquid 17; also shown are two weirs 31 in series.

Fig. 9 is a cross-sectional view of one embodiment of pyrolysis chamber 15 filled with molten metal as pyrolysis liquid 17, where the feedstock 3 is fed into to pyrolysis chamber 15 by screw feeder 28 and where the solid pyrolysis products are removed from pyrolysis chamber 15 by discharge screw 33. Fig. 9 also shows multiple pyrolysis vapour removal line(s) 22.

Fig. 10 is a cross-sectional drawing of section A-A (Fig. 7) and section X-X (Fig. 9), showing a different embodiment of the pyrolysis chamber 15 capable of treating two different feedstocks at the same time.

Fig. 11 is a partial cross-sectional view of one embodiment of pyrolysis chamber 15, where feedstock 3 is provided by hopper 27, fed into pyrolysis chamber 15 via inlet rotary valve 40, transported through the pyrolysis chamber 15 by screw mechanism 46 and exiting the pyrolysis chamber 15 via outlet rotary valve 48 into product hopper 35.

Fig. 12 is a partial cross-section view of one embodiment of pyrolysis chamber 15, where feedstock 3 is provided by hopper 31, fed into pyrolysis chamber 15 via inlet rotary valve 40, directly onto pyrolysis liquid 17. The treated material may exist the pyrolysis chamber 15 by various routes detailed in figures 13, 14 Fig. 13 is a partial cross-section view of one embodiment of pyrolysis chamber 15 with rake overhead conveyor 45 providing the means to move the feedstock within pyrolysis chamber 21 in the direction of travel of feedstock 4 towards the outlet and the discharge screw 33. Fig. 14 is a partial cross-section view of one embodiment of pyrolysis chamber 15 with rake overhead conveyor 45 providing the means to move the feedstock within pyrolysis chamber 21 in the direction of travel of feedstock 4 towards the outlet directly into product hopper 33.

Fig. 15 is a partial cross-section view of one embodiment of pyrolysis chamber 15 with rake 43 providing the means to move the feedstock within pyrolysis chamber 21 into the direction of the exit of pyrolysis chamber 15, i.e. , towards outlet rotary valve 48 and product hopper 35.

Fig. 16 is a partial cross-section view of one embodiment of pyrolysis chamber 15 with rake 43 providing the means to move the feedstock within pyrolysis chamber 21 into the direction of the exit of pyrolysis chamber 15, i.e., towards outlet conveyor 49, which is routed through liquid seal fluid 5.

Note that for clarity, not all features of the invention are shown on all drawings.

Drawings Legend

I. Charging device; here: Continuous charging mechanism 2. Liquid seal fluid supply

3. Feedstock

4. Direction of travel of feedstock

5. Liquid seal fluid

6. Liquid seal fluid drain 7. Feedstock conveyor

8. Lock inlet door

9. Inert gas inlet, e.g., nitrogen

10. Charging device; here: Lock

I I . Line to vacuum pump 12. Vacuum pump

13. Vacuum pump exhaust

14. Pyrolysis chamber top wall

15. Pyrolysis chamber 16. Lock outlet door

17. Pyrolysis liquid

18. Burners

19. Pyrolysis chamber sidewall

20. Pyrolysis chamber bottom wall 21. Feedstock within pyrolysis chamber

22. Pyrolysis vapour removal line

23. Condenser system

24. Fan

25. Non-condensable line 26. Pyrolysis oil

27. Feedstock hopper

28. Charging device; here: Screw feeder

29. Screw of screw feeder

30. Screw feeder motor 31. Weir

32. Screw of discharge mechanism

33. Solid product removal device; here: Discharge screw

34. Discharge motor

35. Product hopper 36. Flange for screw feeder

37. Separation wall

38. Guiding slope

39. Impingement plate

40. Charging device; here: Inlet rotary valve 41. Drain

42. Separation plate

43. Solid product removal device; here: Rake 44. Rake motor mechanism

45. Rake overhead conveyor

46. Screw mechanism

47. Screw mechanism motor 48. Solid product removal device; here: Outlet rotary valve

49. Solid product removal device; here: Outlet conveyor

50. Pyrolysis oil return line

Detailed Description In the following, four examples are presented of how the invention treats (1) Aluminium laminated (AL) plastic, (2) Mixed plastics, (3) Glass or carbon fibre composite plastics with zinc as the molten metal and (4) AL and mixed plastics.

For the examples, the pyrolysis liquid 17 is a molten metal, specifically molten zinc. Zinc, tin or alloys thereof are most desirable. Zinc melts at 419°C, boils at 905°C and is a relatively low-cost material and harmless in comparison to many other metals. Tin is also desirable as it melts at 231.9°C and boils at 2,602°C. The molten metal is the heat transfer medium only and is not consumed by the process. Using indium as the molten metal operating temperatures as low as 156.6°C (melting point of indium) may be achieved. Although in practice the actual operating point will be about 5-10°C higher. In practice an alloy may instead be used, for example of zinc and/or tin and/or indium. In this example the pyrolysis liquid 17 is molten zinc, held at 450°C by burners 18.

In the figures, the same constitutional elements or components are represented by the same reference numerals as given in the drawing legend above. Example 1: Aluminium laminated (AL) plastic

The objective of AL plastic treatment with the present invention is to recycle the waste AL plastic and to recover pyrolysis oil and aluminium metal.

Arrow 4 indicates the direction of travel feedstock 3 takes through the process. In one embodiment, waste AL plastic or feedstock 3 is fed by screw feeder 28 to pyrolysis chamber 15 (Fig. 8). Feedstock 3 with a particle size suitable for screw feeder 28 is added to feedstock hopper 27, and screw feeder 28 adds feedstock 3 to pyrolysis chamber 15. Screw feeder 28 operates in such a fashion that air cannot enter pyrolysis chamber 15 via screw feeder 28. Weirs 31 (two weirs 31 are shown in series in Fig. 8) may assist in freeing the aluminium and may be added to the pyrolysis chamber 15. Weir 31 may be tapered to assist in getting the solids over weir 31. (Although referred to as weirs 31 , the arrangement is such that only the solid materials floating on the surface of the pyrolysis liquid 17 pass over the weir 31, not the pyrolysis liquid 17 itself.) The recovered aluminium is pushed by the continuous feed material 3 over weir(s) 31 and drops towards the inlet section of discharge screw 33, which transports the aluminium into product hopper 35. Discharge screw 33 operates in such a fashion that air cannot enter pyrolysis chamber 15 via discharge screw 33. The pyrolysis vapours are removed from pyrolysis chamber 15 via pyrolysis vapour removal line 22 at one or more locations (Fig. 8 shows an embodiment with one vapour removal line 22). The vapours are condensed by condenser system 23 to pyrolysis oil 26 or pyrolysis wax. As previously mentioned, there may instead be a plurality of condensor systems 23 arranged in series to treat vapours. For example there may be a first condensor system 23 to cool vapours to between 80°C and 120°C to produce a condensate that is a wax at room temperature; and a second condensor system 23 to cool the vapours from the first condensor system 23 to below 30°C to produce a condensate that is an oil at room temperature. The suction or driving force for the vapour removal is provided by fan 24. The fan 24 is controlled in response to measurements of the pressure within the pyrolysis chamber 15, to ensure that the pressure above the pyrolysis liquid 17 within the pyrolysis chamber 15 remains somewhat above ambient pressure, for example the pressure not exceeding 800 mbarg, and preferably not exceeding 100 mbarg. The non-condensable 25, i.e. , methane, propane may be sent to the burner or heaters 18 to provide or to minimise the energy requirements of the pyrolysis process or may be used to generate electricity or both. Due to the high operating temperature of pyrolysis liquid 17 (typically between 350 and 600°C, and preferably 450°C), the AL plastics of feedstock 3 decompose (pyrolyse) into organic and inorganic vapours, char and metal. Any water present in feedstock 3 evaporates. The solids (generated by the pyrolysis reaction of the plastic waste) float on the molten zinc as its density is lower than that of molten zinc. Moreover, aluminium freed from the plastic will float on the molten zinc (if the zinc is saturated with aluminium).

In another embodiment, the waste AL plastic or feedstock 3 (Fig. 9) is fed by screw feeder 28 to pyrolysis chamber 15 and removed by discharge screw 33. The recovered aluminium is pushed by feed material 3 towards the inlet section of discharge screw 33, which transports the recovered aluminium into product hopper 35. The pyrolysis vapours are removed from pyrolysis chamber 15 via pyrolysis vapour removal line 22 at one or more locations (Fig. 9 shows three pyrolysis vapour removal line(s) 22). The vapours are condensed by condenser system 23 to pyrolysis oil 26. The suction or driving force for the vapour removal is provided by fan 24. The non-condensable vapours/gases 25, e.g., methane, propane, may be sent to the burner or heaters 18 to provide or to minimise the energy requirements of the pyrolysis process or may be used to generate electricity or both.

Drain 41 shown in Fig. 9 may be added to pyrolysis chamber 15 to conveniently remove pyrolysis liquid 17 if desired.

Example 2: Mixed and pure plastics

The objective of mixed plastic treatment with the present invention is to recycle the mixed plastic and to recover pyrolysis oil. In many respects the system and process are the same as discussed above.

In one embodiment, mixed plastics pieces or feedstock 3 are placed onto feedstock conveyor 7 (Fig. 1). The waste plastic is moved via feedstock conveyor 7 through the liquid seal fluid 5, which provides an air-tight seal to the previously inerted pyrolysis chamber 15 (Fig. 3). Liquid seal fluid 5 (Fig. 1) could either be water-based or an organic liquid. In another embodiment, waste mixed plastic waste or feedstock 3 may be added via lock 10 (Fig. 2) to pyrolysis chamber 15. Feedstock 3 is placed onto conveyor 7, moved into lock 10, door 8 is closed, and lock 10 is inerted with nitrogen 9 or another inert gas. Vacuum pump 12 may be used to remove air (gas) between nitrogen additions. Once inerted, lock outlet door 16 may be opened, and feedstock 3 may be added by conveyor 7 onto pyrolysis liquid 17 present in pyrolysis chamber 15 (Fig. 3) intermittently. Gliding slope 38 may be added to avoid splashing of the pyrolysis liquid 17 when feedstock 3 is added. Due to the high operating temperature of pyrolysis liquid 17 (typically between 350 and 600°C), the mixed plastics or feedstock 3 decompose (pyrolyse) into organic and inorganic vapours, char and other components. Any water present in feedstock 3 evaporates. The solids (char or carbon generated by the pyrolysis reaction of the plastic waste) float on the molten zinc as their density is lower than that of molten zinc. The pyrolysis vapours are removed from pyrolysis chamber 15 via pyrolysis vapour removal line 22. The pyrolysis vapours are condensed by condenser system 23 to pyrolysis wax or oil 26. Fan 24 provides the required suction for the pyrolysis vapour and pyrolysis solids removal operation. The non-condensables line 25 carries the pyrolysis gases or the non-condensables such as methane, propane and other gases, which may be sent to burner(s) 18 to heat the pyrolysis process making it self-sustaining or the gases may be used to generate electricity or both.

In another embodiment, mixed plastic waste or feedstock 3 is added from the top of pyrolysis chamber 15 (Fig. 6) onto the middle of pyrolysis chamber 15 - i.e. , at substantially equal distances from the pyrolysis vapour removal lines 22 (Fig. 7). An impingement plate 39 may be added to pyrolysis chamber 15 to avoid molten metal splashes within pyrolysis chamber 15 caused by the waste plastic addition. The pyrolysis vapours are removed simultaneously from pyrolysis chamber 15 via the pyrolysis vapour removal lines 22. The pyrolysis vapours are condensed by condenser system 23 to pyrolysis wax or oil 25. Fan 24 provides the required suction for the pyrolysis vapour and pyrolysis solids removal operation. The non-condensables line 25 carries the pyrolysis gases or the non-condensables such as methane, propane and other gases, which may be sent to burner(s) 18 to heat the pyrolysis process making it self-sustaining or the gases may be used to generate electricity or both.

In another embodiment (Fig. 4), one or more screw feeder(s) 28 and associated equipment are located on the side of pyrolysis chamber 15. The removal of the pyrolysis vapours from pyrolysis chamber 15 is accomplished by pyrolysis vapour removal line(s) 22. The pyrolysis vapours are condensed by condenser system 23 to pyrolysis oil 25. Fan 24 provides the required suction for the vapour and solids removal operation. The non-condensables 25 include methane, propane and other gases, which may be sent to burner(s) 18 to heat the pyrolysis process making it self-sustaining, or the non-condensable gases may be used to generate electricity or for other uses or combinations thereof.

In another embodiment (Fig. 5, option A or option B), pyrolysis chamber 15 is split into lanes or sections by one or more separation wall(s) 37. Separation wall 37 ensures that feedstock 3 within pyrolysis chamber 15 moves along the surface of pyrolysis liquid 17 in a defined manner. Fig. 5 shows two different options. In option A every lane is fed by a dedicated screw feeder 28. The pyrolysis vapours are removed by a dedicated pyrolysis vapour removal line 22 located at the end of the line. In option B, one screw feeder 28 feeds more than one lane, each of which is equipped with one pyrolysis vapour removal line 22. A pyrolysis oil return line 50 may be added to recycle part or all of the pyrolysis oil 26 to pyrolysis chamber 15 for cracking.

Drain 41 shown in Fig. 4 and Fig. 9 may be added to pyrolysis chamber 15 to conveniently remove pyrolysis liquid 17 if desired.

It has been found by experiments on a pilot-scale plant that plastic (polypropylene) pyrolysis on molten metal resulted in essentially the same products in terms of yields and quality as the products obtained from laboratory experiments using grams of plastic (polypropylene) (as for instance published by S. Flonus et al. , Pyrolysis gases produced from individual and mixed PE, PP, PS, PVC, and PET - Part I: Production and physical properties, Fuel, 221, (2018), 346-360). This is due to three reasons (1) rapid heat transfer from the molten metal to the plastic, (2) a minimum temperature gradient across the molten metal and (3) the ease of scale-up of a surface-bound reaction, for which doubling the surface area doubles the throughput. Example 3: Glass or carbon fibre composite plastics

The objective of mixed plastic treatment with the present invention is to recycle the glass or carbon fibre composite plastic material and to recover glass or carbon fibre and pyrolysis oil. The glass and carbon fibres float on the molten metal, whereas the resin pyrolyses. The operation of glass and carbon fibre composite plastic treatment is analogous to the treatment of AL plastic and mixed plastic, so the system and process are substantially the same as discussed above. Operating the pyrolysis chamber 15 at 450°C, as discussed above, ensures that the glass fibres, where present, do not melt, but float on the surface of the pyrolysis liquid 17.

Example 4: AL and plastic waste

The objective of simultaneously treating AL plastic and plastic waste with the present invention is to recycle the waste AL plastic and waste plastic and to recover pyrolysis oil and aluminium metal. In many respects the system and process are the same as discussed above.

An embodiment to treat two different types of waste plastics, e.g., mixed and AL plastics in one pyrolysis chamber 15, is shown in Fig. 10. On the left side of separation wall 37 is the mixed plastic recycling plant (shown in more detail by Fig. 7 and associated description), whereas on the right-hand side of separation wall 37 is the AL plastic recycling plant (shown by Fig. 9, section X-X, and associated description). Many more configurations are possible. The separation plate 47 may extend from the top to the bottom of pyrolysis chamber 15, but other configurations are possible.

Example 5: Lithium-ion pouch batteries The objective of treating lithium-ion pouch batteries with the present invention is to recycle the aluminium foil, the copper, and the active cathode material containing lithium-ion compound and, depending on the battery chemistry, a cobalt compound. In many respects the system and process are the same as discussed above. An embodiment to treat lithium-ion pouch batteries in one pyrolysis chamber 15 is shown in Fig. 11. Whole lithium-ion pouch batteries are provided, for example, by hopper 3 and are fed into pyrolysis chamber 15 via inlet rotary valve 40; there is no need to discharge the batteries first. The batteries are moved in the direction of travel of feedstock 4 by screw mechanism 46 to exit pyrolysis chamber 15 via outlet rotary valve 48.

In another embodiment to treat lithium-ion pouch batteries, the batteries enter pyrolysis chamber 15 from feedstock hopper 3 via inlet rotary valve 40 directly onto pyrolysis liquid 17 as shown in Fig. 12.

In another embodiment to treat lithium-ion pouch batteries, the batteries are moved along the direction of travel of feedstock 4 with the assistance of rake overhead conveyor 45 to exit pyrolysis chamber 15 via discharge screw 33, as shown in Fig. 13.

In another embodiment to treat lithium-ion pouch batteries, the batteries are moved along the direction of travel of feedstock 4 with the assistance of rake overhead conveyor 45 to exit pyrolysis chamber 15 into product hopper 35, as shown in Fig. 14.

In another embodiment to treat lithium-ion pouch batteries, the batteries are moved along the direction of travel of feedstock 4 with the assistance of rake 43 to exit pyrolysis chamber 15 via outlet rotary valve 48 into product hopper 35, as shown in Fig. 15.

In yet another embodiment to treat lithium-ion pouch batteries, the batteries are moved along the direction of travel of feedstock 4 with the assistance of rake 43 to exit pyrolysis chamber 15 via outlet conveyor 49, which is routed through liquid seal fluid 5, as shown in Fig. 16.

The advantage of recycling lithium-ion batteries with this system is that the batteries do not have to be discharged or opened before treatment. Instead, whole, non-discharged batteries are treated. Moreover, glue, plastics and solvents present in the batteries are pyrolysed, leaving behind only valuable materials such as copper, aluminium, lithium and cobalt compounds.

A desirable characteristic of the present invention is that non-condensable gases such as methane or propane may be routed to the burners minimising the energy requirements of the process. Another desirable characteristic of the present invention is that the pyrolysis vapours may be condensed to pyrolysis oil, pyrolysis waxes or both, for example by providing a plurality of condensor systems in series; there might for example be four condensor systems in series arranged to produce liquid phases at 150°C, at 80°C, at 45°C and at 20°C. Another desirable characteristic of the present invention is that the pyrolysis process is fast as the heat transfer is by direct heating of the waste material by molten metal or molten salt. This is due to the fact that waste plastic is not a good heat conductor and, therefore, bringing plastics to reaction temperature may take a long time in conventional rotary kilns. Another desirable characteristic of the present invention is that the pyrolysis process is readily scalable, as doubling the surface area of the pyrolysis liquid doubles throughput.

Another desirable characteristic of the present invention is that surface crusts, which frequently form on the surfaces of fixed wall pyrolysis reactors, are avoided as the pyrolysis liquid is a liquid, i.e. , not a solid wall. Moreover, molten zinc repels carbon, glass and carbon fibre materials.

Another desirable characteristic of the present invention is the ability of pyrolysis to treat mixed plastics, i.e., a waste stream composed of different types of plastics. This is important, as it is difficult to obtain a plastic waste stream from municipal waste composed of one type of plastic only. Moreover, pyrolysis can also treat plastics contaminated with foreign materials, e.g., plastic packaging with food residues, paper, ink and other contaminants.

In the specification the terms "comprise, comprises, comprised and comprising" or any variation thereof and the terms include, includes, included and including" or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation and vice versa.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.

Definitions

The term "composite plastics" ("composite" for short) refers to a material made from two or more constituent materials (one of which is plastic) with significantly different physical or chemical properties that, when combined, produce a material with characteristics different from the individual components. The individual components remain separate and distinct within the finished structure, differentiating composites from mixtures. This composite material may be stronger, lighter, or less expensive compared to the original materials. Here, however, composite material also refers to batteries, especially lithium-ion batteries.

"Aluminium laminated plastics" refers to a composite plastic typically used for food or pharmaceutical packaging, in which at least one layer of aluminium foil is used. "Glass fibre plastics" or "Carbon fibre plastics" also known as Fibre-Reinforced Polymer (FRP) composites, refers to a polymer matrix that is reinforced with an engineered, man-made or natural fibre (like glass, carbon or aramid) or other reinforcing material. "Mixed plastics" refers to a waste plastic stream composed of various types of plastics mixed, e.g., polyethylene (PE), polypropylene (PP), low-density polyethylene (LDPE), high-density polyethylene (FIDPE), polyvinyl chloride (PVC), polystyrene (PS), etc.

"Pure plastics" refers to a waste plastic stream composed of a single type of plastic such as PE, PP, LDPE, HDPE, PVC or PS.

"Polyolefin" refers to a waste plastic stream composed of polymers produced from a simple olefin (also called an alkene with the general formula CnFhn) as a monomer — for example, PE, PP, LDPE, HDPE as pure or mixed streams.