Hydrothermal Treatment of Materials

This application claims priority from Australian Provisional Patent Application No. 2022900901, filed on 6 Apr. 2022, the entire contents of which are incorporated herein by reference.

The present invention relates generally to the field of hydrothermal treatment, and more specifically to devices and methods for the production of chemicals, oils and/or gases from polymeric feedstock materials. In certain embodiments, the present invention provides for the hydrothermal conversion of synthetic polymers such as, for example, plastic, into energy-rich oils and/or high-grade chemicals. However, it will be appreciated that the invention is not limited to these particular fields of use.

The following discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of the common general knowledge in the field.

Pollution arising from discarded polymeric waste, and in particular waste arising from synthetic polymeric materials, has become a serious environmental issue on a global scale. For example, humans have produced over 8 billion tonnes of plastic since 1950. Of this only approximately 10% was recycled, over 50% went into landfill, and much of the remaining waste was incinerated or ended up in the ocean. Between 4.8 and 12.7 million metric tonnes of plastic are estimated to enter the ocean on an annual basis. In being largely derived from fossil fuels, it is well-documented that waste plastics contribute significantly to climate change, by emitting greenhouse gases at each stage of their life cycle, from extraction to end-of-life. There are also significant impacts on marine-life and various other adverse environmental factors arising from the continued expansion of worldwide synthetic polymeric material production.

In addition to the challenges of synthetic waste disposal, the global energy crisis continues to gain momentum. Non-renewable fossil fuels required for transportation and other key activities are being consumed at an unsustainably high rate all over the world. The production of alternative fuel sources from the depolymerisation of materials such as plastic waste offers a means of addressing the challenges of plastic waste management and the increasing demand for energy in parallel.

Considerable research and funding continues to be invested in technologies aimed at converting synthetic polymer waste materials such as plastics into fuels, chemicals and other valuable products. Of these, thermochemical processes such as pyrolysis, gasification, and liquefaction have emerged as promising technologies.

Hydrothermal treatment is one type of thermochemical process used for the conversion of synthetic polymers into hydrocarbon liquids and oils. In this process, polymeric materials are treated in the presence of water at highly elevated temperature and pressure to depolymerise the feedstock into shorter chain hydrocarbons which are closer to the original material used to originally manufacture the synthetic polymers. However, a number of challenges remain in adapting hydrothermal technology to the treatment of synthetic polymeric feedstocks that remain highly viscous under elevated temperature and pressures (e.g. plastics). For example, a two-phase flow can occur, comprising plastic flow and a separate flow of steam, meaning that the steam can only crack the limited surface of the plastic flow with which it is in contact. Complicating matters, is that cracked oils and water can then gradually penetrate the main plastic melt flow. The presence of two-phase flow (separate gas and liquid streams) during the initial reaction phase can be disadvantageous due to the additional time it takes for the water to fully penetrate and crack the viscous melt flow of feedstock into an oil stream.

A need thus exists for improved methods and devices for the hydrothermal treatment of polymeric materials, for example, by facilitating more thorough and/or more rapid mixing of water with viscous polymeric material feedstocks under elevated temperature and pressure.

It is an object of the present invention to overcome or ameliorate one or more the disadvantages of the prior art, or at least to provide a useful alternative.

The present invention addresses at least one of the difficulties of the prior art, and in particular those difficulties associated with the application of existing hydrothermal systems to the treatment polymeric feedstock material, and in particular to the treatment of viscous polymeric feedstock material under elevated temperature and pressure.

A first aspect of the present invention provides a method for converting feedstock comprising synthetic polymers into a product, comprising:

A second aspect of the present invention provides a method for converting feedstock comprising synthetic polymers into a product, comprising:

In some embodiments of the first and second aspects, the heated and pressurised water is injected across a full or partial cross section of the melt stream.

In other embodiments of the first and second aspects, the heated and pressurised water is injected across multiple cross sections of the melt stream. At least two of the multiple cross sections may be oriented at different angles relative to each other.

In other embodiments of the first and second aspects, the injection device comprises two injection pipes each spanning either a full or partial cross section of the melt stream, and oriented at different angles within the melt stream relative to each other. The injection pipes may be oriented within the melt stream perpendicular to each other, or, within 5°, within 10°, within 20°, within 30°, or within 40°, of perpendicular to each other. Either or both injection pipes may comprise a sparge pipe.

A third aspect of the present invention provides a method for converting feedstock comprising synthetic polymers into a product, comprising:

In some embodiments of the first and third aspects, the mixing device comprises three, four, five, or six of the lattice modules, each lattice module rotated at an angle relative to adjacent lattice module(s).

In some embodiments of the first and third aspects, the mixing device comprises a first lattice module rotated between 20° and 90°, 40° and 90°, 60° and 90°, or 80° and 90° relative to a second adjacent lattice module.

In other embodiments of the first and third aspects, the mixing device comprises a first lattice module rotated perpendicular or substantially perpendicular relative to a second adjacent lattice module.

In other embodiments of the first and third aspects, the first and/or second lattice modules comprise a sequential series of adjacently positioned lattice sheets, wherein each individual lattice sheet of the series is rotated less than: 50°, 40°, 30°, 20°, 10° or 5°; relative to other adjacent lattice sheet(s) within the series, or is not rotated relative other adjacent lattice sheet(s) within the series. The series may comprise 2, 3, 4, 5, 6 or more individual lattice sheets rotated less than 50°, 40°, 30°, 20°, 10° or 5° relative adjacent lattice sheet(s), or not rotated relative to adjacent lattice sheet(s). The lattice sheets may comprise square, circular, oval, hexagonal and/or octagonal shaped lattice units. The adjacently positioned lattice sheets may be in direct contact or separated by spacer component(s).

In still other embodiments of the first and third aspects, the injecting of heated and pressurised water into the melt stream is from apertures of an injection device, wherein the apertures are located internally of the melt stream.

In additional embodiments of the first and third aspects, the water is supercritical immediately prior to the injecting into the melt stream.

In further embodiments of the first and third aspects, the heated and pressurised water is injected across a full or partial cross section of the melt stream.

In further embodiments of the first and third aspects, the heated and pressurised water is injected across multiple cross sections of the melt stream. At least two of the multiple cross sections may be oriented at different angles relative to each other.

In still further embodiments of the first and third aspects, the injection device comprises two injection pipes each spanning either a full or partial cross section of the melt stream, and oriented at different angles within the melt stream relative to each other. The injection pipes may be oriented within the melt stream perpendicular to each other, or, within 5°, within 10°, within 20°, within 30°, or within 40°, of perpendicular to each other. Either or both injection pipes may comprise a sparge pipe.

In some embodiments of the first, second and third aspects, the mixing device comprises only one type of static mixer.

In some embodiments of the first, second and third aspects, the melt stream comprises: polyethylene (PE), Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), Polypropylene (PP), Polyester, Poly(ethylene terephthalate) (PET), poly(lactic acid) PLA, Poly(vinyl chloride) (PVC), Polystyrene (PS), Polyamide, Nylon, Nylon 6, Nylon 66, Acrylonitrile-Butadiene-Styrene (ABS), Poly(Ethylene vinyl alcohol) (E/VAL), Poly(Melamine formaldehyde) (MF), Poly(Phenol-formaldehyde) (PF), Epoxies, Polyacetal, (Acetal), Polyacrylates (Acrylic), Polyacrylonitrile (PAN), Polyamide-imide (PAI), Polyaryletherketone (PAEK), Polybutadiene (PBD), Polybutylene (PB), Polycarbonate (PC), Polydicyclopentadiene (PDCP), Polyketone (PK), polycondensate, Polyetheretherketone (PEEK), Polyetherimide (PEI), Polyethersulfone (PES), Polyethylenechlorinates, (PEC), Polyimide, (PI), Polymethylpentene (PMP), Poly(phenylene Oxide) (PPO), Polyphenylene Sulfide (PPS), Polyphthalamide, (PTA), Polysulfone (PSU), Polyurethane, (PU), Poly(vinylidene chloride) (PVDC), Poly(tetrafluoroethylene) (PTFE), Poly(fluoroxy alkane) (PFA), Poly(siloxanes), silicone, thermoplastic, plastic, or mixtures thereof.

In some embodiments of the first, second and third aspects, during the treatment, the water and the melt stream combined comprises at least at least 30 wt %, at least 35 wt %, at least 40 wt %, at least 45 wt %, at least 50 wt %, at least 60 wt %, at least 70 wt %, at least 80 wt %, at least 90 wt %, at least 95 wt %, or at least 98 wt % of the polymeric material.

In other embodiments of the first, second and third aspects, during the treatment, the water and the melt stream combined comprises at least at least 30 wt %, a minimum of 40 wt % of the polymeric material and up to 60 wt % of the water.

In some embodiments of the first, second and third aspects, the melt stream is generated using an extruder.

In some embodiments of the first, second and third aspects, prior to injecting the heated and pressurised water, the melt stream is at a temperature of between 200° C. and 350° C. and at a pressure of between 100 bar and 300 bar, or at a temperature of between 250° C. and 300° C. and at a pressure of between 230 bar and 280 bar.

In other embodiments of the first, second and third aspects, the water is at a temperature of between of between 300° C. and 700° C. immediately prior to the injecting into the melt stream. The water may be at a pressure of 100 and 300 bar immediately prior to the injecting into the melt stream.

In still other embodiments of the first, second and third aspects, the water is supercritical and at a temperature of between 500° C. and 700° C. and at a pressure of 100 to 300 bar, or a temperature of between 550° C. and 650° C. and at a pressure of 100 to 300 bar immediately prior to the injecting into the melt stream.

In other embodiments of the first, second and third aspects, the water has a viscosity of between 1×10Pa·s and 0.1 Pa·s immediately prior to the injecting into the melt stream.

In other embodiments of the first, second and third aspects, the injecting of the heated and pressurised water from apertures of the injection device into the melt stream is conducted while the melt stream is at a flow rate of between 1,000 kg/hr and 15,000 kg/hr and/or a viscosity of between 10 Pa·s and 1,000 Pa·s, a flow rate of between 3,000 kg/hr and 12,000 kg/hr and/or a viscosity of between 100 Pa·s and 1,000 Pa·s, a flow rate of between 5,000 kg/hr and 10,000 kg/hr, and/or a viscosity of between 400 Pa·s and 800 Pa·s.

In further embodiments of the first, second and third aspects, the reaction mixture enters and/or exits the mixing device at a temperature between 200° C. and 550° C. and at a pressure of 100 to 300 bar, at a temperature between 300° C. and 550° C. and at a pressure of 100 to 300 bar, at a temperature between 350° C. and 550° C. and at a pressure of 100 to 300 bar, or at a temperature of between 400° C. and 500° C. and at a pressure of 100 to 300 bar. The reaction mixture may enter and/or exit the mixing device at a flow rate of above 2,000 kg/hr or a viscosity of above 100 Pa·s. The flow rate may be less than 15,000 kg/hr. The flow rate may be between 2,000 kg/hr and 15,000 kg/hr. The viscosity may be less than 1,000 Pa·s. The viscosity may be between 100 Pa·s to 1,000 Pa·s.

In further embodiments of the first, second and third aspects, the method comprises further heating of the reaction mixture after it exits the mixing device. The further heating may be conducted using an indirect heater located downstream of the mixing device and to a pressure let down device.

In further embodiments of the first, second and third aspects, said further treating of the reaction mixture at a reaction temperature and pressure is: at a temperature of between 300° C. and 500° C. and at a pressure between 100 bar and 350 bar, at a temperature between 373° C. and 500° C. and at a pressure between 220 bar and 350 bar, at a temperature between 400° C. and 500° C. and at a pressure between 220 bar and 350 bar, or at a temperature between 420° C. and 480° C. and at a pressure between 220 bar and 300 bar.

In still further embodiments of the first, second and third aspects, the method is performed under conditions of continuous flow.

In some embodiments of the first, second and third aspects, the synthetic material comprises or consists of plastic, or a mixture of different plastics.

A fourth aspect of the present invention provides a reactor apparatus comprising:

A fifth aspect of the present invention provides a reactor apparatus comprising a device for injecting heated and pressurised water into a melt stream of polymeric material flowing through a vessel of the reactor apparatus, wherein the device comprises a component spanning all or a portion of a cross section of the vessel, the component comprising apertures for injection of the heated and pressurised water internally of the melt stream.

In one embodiment of the fourth and fifth aspects, the device comprises a plurality of the components spanning all or a portion of a cross section of the vessel. At least two of the components may be oriented at different angles relative to each other. At least two of the components may be oriented within the melt stream perpendicular to each other, or, within 5°, within 10°, within 20°, within 30°, or within 40°, of perpendicular to each other.

In one embodiment of the fourth and fifth aspects, any said component comprises a sparge pipe.

In another embodiment of the fourth and fifth aspects, the melt stream is at a flow rate of between 1,000 kg/hr and 15,000 kg/hr and/or a viscosity of between 10 Pa·s and 1,000 Pa·s, a flow rate of between 3,000 kg/hr and 12,000 kg/hr and/or a viscosity of between 100 Pa·s and 1,000 Pa·s, a flow rate of between 5,000 kg/hr and 10,000 kg/hr, and/or a viscosity of between 400 Pa·s and 800 Pa·s.

In another embodiment of the fourth and fifth aspects, the vessel further comprises the melt stream of polymeric material. The melt stream of polymeric material may comprise plastic.

A sixth aspect of the present invention provides a reactor apparatus comprising a mixer device located downstream of a device for injecting heated and pressurised water into a melt stream of polymeric material, wherein the mixer device:

In one embodiment of the fifth and seventh aspects, the mixing device comprises three, four, five, or six of the lattice modules, each lattice module rotated at an angle relative to adjacent lattice module(s).

In one embodiment of the fifth and seventh aspects, the mixing device comprises a first lattice module rotated between 20° and 90°, 40° and 90°, 60° and 90°, or 80° and 90° relative to a second adjacent lattice module.

In an additional embodiment of the fourth and sixth aspects, the mixing device comprises a first lattice module rotated perpendicular or substantially perpendicular relative to a second adjacent lattice module.