Related applications

This application claims the priority of UK patent application number 2106334.2 filed on 4 May 2021.

Field of the Invention

The present invention relates to a reactor for the generation of hydrocarbon and hydrogen- rich gas products by thermochemical treatment, a modular system comprising such a reactor and a process for the generation of a hydrocarbon product by thermochemical treatment.

Background of the Invention

The thermochemical treatment of feedstock materials to prepare more valuable products is well known and used in various industrial processes. One known example of a thermochemical process is pyrolysis. Another known thermochemical process is gasification, which uses limited quantities of air or oxygen to convert biomass or other carbonaceous materials into valuable gaseous products including hydrogen. In general such processes use heat treatment of solid feedstock materials within a reactor to convert the solid feedstock into the desired more valuable product.

The pyrolysis of materials for the generation of a hydrocarbon product within a fluidised bed is known. For example, combustible hydrocarbon products for use as fuels may be prepared by pyrolysis. Pyrolysis is the process of thermal destruction of hydrocarbons (e.g. polyolefins) in an oxygen-free environment at temperatures of 400-900 °C, for example 500- 900 °C, and small excess pressure. Pyrolysis may be used to obtain low molecular weight monomers from naphtha, but may also be used to break down more complex materials, including polymers and biomass, for the generation of combustible hydrocarbons.

Such processes are desirable because they provide a means to produce a valuable product from a less valuable material, such as a waste material. Waste plastic has become particularly problematic over recent years and the limitations of conventional plastics recycling have become increasingly evident. Therefore, additional processes which make use of waste plastics materials are desirable to reduce the quantity of waste plastic going to landfill or polluting the environment.

Biomass is another waste material which may be usefully subjected to thermochemical treatment such as pyrolysis to provide valuable products. The pyrolysis of polymers is known to generate a heterogeneous hydrocarbon mixture which tends to include molecules of a wide range of molecular weights, including short chain gaseous hydrocarbons and long chain waxes. Wax by-products cause operational problems by plugging product lines and condenser tubes, while residual carbon may deactivate catalysts. Furthermore, solid or gaseous by-products reduce the overall yield of the intended liquid hydrocarbon product. The broad spectrum of product weights means that utilisation of the products on an industrial scale is difficult and extensive downstream catalytic upgrading tends to be necessary in order to obtain a drop-in fuel product, making the process inefficient.

US 3,901,951 B1 describes a process which converts waste plastic into a useful product comprising a mixture of liquid hydrocarbons. Waste plastics are melted and then fed into a reactor where they come into contact with a particulate solid heat medium to effect pyrolysis of the melt. The molten plastic is fed into a fluidised bed of the heat medium. After pyrolysis within the fluidised bed of heat medium, the product is extracted in gaseous form and condensed to form a mixture of liquid hydrocarbons.

There are a number of problems associated with known fluidised bed pyrolysis processes such as that in US 3,901 ,951 B1. One problem is that the quality of the product of these processes tends to be poor, containing high levels of impurities such as heavier hydrocarbons, sulphur or chloride components and oxygenated compounds which make the product unsuitable for use in certain applications without first going through further energy intensive and expensive refinement steps.

Another problem with the type of reactor and process described in US 3,901,951 B1 is the nature of the fluidised bed. Plastics materials have a very high calorific value of greater than 30 MJ/kg, making direct contact with oxygen (for gasification, for example) highly problematic. Plastics and biomass also contain a high proportion of volatile matter which is flashed rapidly from the bed, such that reforming reactions occur predominantly in the zone directly above the bed rather than within the bed itself, while heavier residual waxes from plastics tend to cover the particles within the bed, causing aggregation of the particles which leads to localised defluidised regions within the bed. These defluidised regions cause incipient agglomeration within the fluidised bed, leading to difficulty of solid circulation and bed collapse. In addition, industrial scale fluidised beds tend to have large gas bubbles with irregular fluidisation (slugging) and significant gas by-pass, reducing the efficiency of the process and hindering both heat transfer and mass transfer. Furthermore, in many known processes, solid feedstock is fed directly into the hot bed. The high temperature at the entry point into the reactor causes incipient melting of feedstock in the delivery system which can lead to blockage of the feed tube or mechanical failure of the delivery system. It may also cause the feedstock to be fed into the bed in large slugs, inhibiting the proper dispersion and mixing of the feedstock within the thermal reactor which causes the formation of large agglomerates and concomitant defluidisation of the bed. The process in US 3,901,951 B1 feeds plastic into the reactor in molten form, however this increases the energy cost of the process by requiring plastic to be pre-melted and stored in molten form, and also does not address the issue of plastic being fed into the reactor bed in large slugs and the resultant defluidisation. Furthermore, such melt preparation is only applicable to plastics feedstock and cannot be applied more broadly to e.g. biomass.

In addition, to achieve the pyrolysis of the waxes and other heavy fractions from the solid feedstock, very high temperatures are required within the reactor, but this comes at the cost of reduced liquid oil yield, high gas by-product volumes and low energy efficiency.

The application of a catalyst in a thermal degradation process within a thermochemical reactor would help provide products in the desired range of carbon atom number and facilitate lower operating temperatures. However in situ catalysis, i.e. direct contact between catalysts and waste feedstock in the same reactor, is practically difficult and noticeably results in poor conversion rates and fast catalyst deactivation.

The present invention has been developed to address the above-mentioned problems.

There is a need for thermochemical reactors and processes able to produce a hydrocarbon product (including, for example, liquid combustible hydrocarbon fuel product or chemical feedstock suitable for plastics manufacturing) of high quality with reduced content of by products and impurities, in a process which is efficient and scalable. There is also a need for such processes which can deal with contaminated feedstock, for example waste consumer plastic, and biomass-plastics mixtures. The reactor of the invention and the corresponding process for the production of hydrocarbons produces a much cleaner hydrocarbon product which is of a grade suitable for many applications with only straightforward standard subsequent refinement being necessary, for example to generate a drop-in fuel product. The result is a product of improved quality, simplification of the process, reducing the cost of the process, along with improved flexibility and control. Summary of the Invention

A first aspect of the invention is a reactor for the generation of hydrocarbon products by thermochemical treatment, comprising a feeding means for the addition of feedstock material to the reactor; an outlet for the extraction of hydrocarbon products from the reactor; a devolatilization zone; and a cracking zone; wherein the devolatilization zone comprises a first gas distribution base plate for the generation of a fluidised bed of material in the devolatilization zone, the cracking zone comprises a second gas distribution base plate for the generation of a fluidised bed of material in the cracking zone, and the devolatilization zone is in fluid communication with the cracking zone through a plurality of apertures within the second gas distribution base plate permitting the passage of gas from the devolatilization zone into the cracking zone.

The reactor of the invention includes a plurality of gas distribution plates which provide the means to establish a corresponding plurality of fluidised beds of material during the thermochemical process in which pyrolysis and/or cracking processes may take place. The multiple fluidised beds in the present reactor provide surprising advantages over the single bed reactors used in existing processes. The inventors have found that by providing a first gas distribution base plate for the generation of a fluidised bed of material in the devolatilization zone, and a second gas distribution base plate for the generation of a fluidised bed of material in the cracking zone, improved mixing of the fluidised beds is achieved. This is due to the reduction in size of each individual bed made possible by dividing the beds into discrete beds supported on separate gas distribution plates. The smaller size of each bed reduces slugging by facilitating the creation of relatively small fluidised regions forming the discontinuous phase within the fluidised bed. This not only enhances the available surface area for mass and heat transport, but also avoids gas bypass, maximising gas-solid contact, and increasing the degree of cross mixing within the bed, further enhancing the heat and mass transfer fluxes.

Furthermore, the presence of multiple gas distribution base plates permits the feeding of separate gas supplies to each fluidised bed within the reactor. The first gas distribution base plate comprises a gas feed which supplies fluidising gas to the fluidised bed of material in the devolatilization zone and the second gas distribution base plate comprises a plurality of apertures permitting the passage of gas from the devolatilization zone into the cracking zone, thereby fluidising the bed of material supported on the second gas distribution base plate. This improves control of temperature profile and the degree of reducing conditions, and hence improves the overall thermal performance of the unit.

Providing fluid communication between the pyrolysis and cracking zones of the reactor through apertures in the second gas distribution base plate means that products from the devolatilization zone pass as vapours through the second gas distribution base plate into the fluidized bed of material in the cracking zone, where they are further refined, such that the reactor provides a product of a higher grade than is possible with existing thermochemical reactors.

A second aspect of the invention is a modular reactor system comprising a reactor according to the first aspect and one or more additional reactor system modules each independently selected from: a feedstock material separation module upstream of the reactor; a feedstock material size reduction module upstream of the reactor; a feedstock material drying module upstream of the reactor; a hydrocarbon product filter module downstream of the reactor; a hydrocarbon product condensation module downstream of the reactor; a catalyst regeneration module; an electrolyser module; and a hydrocarbon product reforming module downstream of the reactor.

Such a modular system or modular plant provides a flexible process for the thermochemical treatment of feedstock to produce hydrocarbons. It enables a single system to carry out the complete synthesis of a product, for example a fuel product, starting from crude waste material feedstock such as waste plastics material. It also enables the reclamation of heat and by-products from one module and their use in one or more further modules, thereby improving the efficiency of the overall process and reducing environmental impact.

A third aspect of the invention provides a process for the generation of a hydrocarbon product by thermochemical treatment, comprising

(a) feeding a feedstock material into a reactor, wherein the reactor comprises: a feeding means for the addition of the feedstock material to the reactor; an outlet for the extraction of the hydrocarbon product from the reactor; a devolatilization zone; a cracking zone; a first gas distribution base plate for the generation of a fluidised bed of material in the devolatilization zone, a second gas distribution base plate for the generation of a fluidised bed of material in the cracking zone, and the devolatilization zone is in fluid communication with the cracking zone through a plurality of apertures within the second gas distribution base plate permitting the passage of fluids from the devolatilization zone into the cracking zone;

(b) subjecting the feedstock material to thermochemical treatment within a fluidised bed of material supported on the first gas distribution base plate in the devolatilization zone, wherein the bed of material is fluidised by feeding a fluidising gas through the first gas distribution base plate; and

(c) cracking or fragmentation of the intermediate product formed from the thermochemical treatment of the feedstock material, within a fluidised bed of material supported on the second gas distribution base plate in the cracking zone, wherein the bed of material in the cracking zone is fluidised by the passage of the intermediate product through the second gas distribution base plate.

In some embodiments the process is carried out using a reactor according to the first aspect.

Such a process provides the advantages described above. In particular, improved mixing of the fluidised beds is achieved due to the reduction in size of each individual bed made possible by dividing the beds into separate beds supported on separate gas distribution plates.

Pyrolysis products from the devolatilization zone pass as vapours through the second gas distribution base plate into the fluidized bed of material in the cracking zone, where they are further refined, such that the process provides a product of a higher grade than is possible with existing reactors.

Brief Description of the Drawings

Figure 1 is a schematic cross-section of a reactor according to the invention.

Figure 2 is a schematic cross-section of a reactor system according to the invention including a thermochemical reactor and a catalyst regeneration module.

Figure 3 is a process flow diagram based on one example of a modular reactor system according to the invention. Figure 4 is a process flow diagram based on an alternative example of a modular reactor system according to the invention.

Detailed Description

Preferred and/or optional features of the invention will now be set out. Any aspect of the invention may be combined with any other aspect of the invention unless the context demands otherwise. Any of the preferred and/or optional features of any aspect may be combined, either singly or in combination, with any aspect of the invention unless the context demands otherwise.

Definitions

The term “combustible hydrocarbon products” as used herein refers to any hydrocarbon product which may be used as the fuel in a combustion reaction. Examples of combustible hydrocarbon products are those products useful in the production of fuel for vehicles or aircraft. Combustible hydrocarbon products include combustible hydrocarbon products which are liquid under standard conditions of temperature and pressure. In some cases the combustible hydrocarbon products are C _6-50 hydrocarbon products, for example C _9-19 or C _5-19 hydrocarbon products. In some cases the combustible hydrocarbon products are hydrocarbon products useful in the production of jet aircraft fuel, for example “drop-in” fuel products which may be used as an alternative to existing fuels without the need for any engine or infrastructure modification.

The combustible hydrocarbon products may alternatively find use as chemical feedstock in downstream processes, rather than as a fuel for combustion. For example, they could be used to replace current naphtha feedstock in steam crackers without the need for further treatment of the hydrocarbon or modification of the steam cracker.

The term “feedstock material” as used herein encompasses any material which the skilled person understands could be converted by thermochemical treatment into a hydrocarbon product, e.g. combustible hydrocarbon product. Feedstock materials for the present invention may include a wide range of plastics materials (polymers) and include both virgin and waste plastics materials. Feedstock materials may include biomass. Feedstock materials may comprise a single type of material or may comprise a mixture of different types of material. Polymer feedstock materials may comprise a single type of polymer or a mixture of different types of polymer. The term “devolatilization zone” as used herein refers to the internal volume of the reactor in which primarily initial pyrolysis and devolatilization processes occur, i.e. the thermal destruction of hydrocarbons (for example feedstock material and/or downstream intermediate products) to produce lighter intermediate products which pass into the cracking zone. The fluidised bed of material in the devolatilization zone may be a low superficial velocity fluidised bed of material.

The term “cracking zone” as used herein refers to the internal volume of the reactor in which primarily cracking and fragmentation processes of long chain hydrocarbons (e.g. tars and waxes) occur, i.e. the thermal and/or catalytic reaction of hydrocarbons to form products of reduced molecular weight. The cracking zone lies downstream of the devolatilization zone within the reactor (in the context of hydrocarbon processing) and the products from the devolatilization zone pass into the cracking zone. The cracking zone may alternatively be referred to as the “depolymerisation zone”, since primarily depolymerisation processes occur in that zone. The fluidised bed of material in the devolatilization zone may be a high superficial velocity fluidised bed of material.

The term “gas distribution base plate” as used herein refers to a component well-known to the skilled person which functions to support a fluidised bed of particulate material.

Generally, a gas distribution base plate provides physical support for the material of a fluidised bed while also providing the means for fluidisation of the bed, usually through the supply of a gas to the bed.

A first aspect of the invention is a reactor for the generation of hydrocarbon products by thermochemical treatment, comprising a feeding means for the addition of feedstock material to the reactor; an outlet for the extraction of hydrocarbon products from the reactor; a devolatilization zone; and a cracking zone; wherein the devolatilization zone comprises a first gas distribution base plate for the generation of a fluidised bed of material in the devolatilization zone, the cracking zone comprises a second gas distribution base plate for the generation of a fluidised bed of material in the cracking zone, and the devolatilization zone is in fluid communication with the cracking zone through a plurality of apertures within the second gas distribution base plate permitting the passage of gas from the devolatilization zone into the cracking zone. In some embodiments, the reactor is for the generation of hydrocarbon products by pyrolysis of one or more polymers. In some embodiments, the reactor is for the generation of hydrocarbon products by the thermochemical treatment or degradation of one or more polymers. In some embodiments, the reactor is for the generation of combustible hydrocarbon products by pyrolysis of one or more polymers. In some embodiments, the one or more polymers are in the form of solid plastics material, for example virgin plastic or waste plastic.

In some embodiments, the reactor is for the gasification of a carbonaceous feedstock material to provide a gaseous product, for example the gasification of biomass feedstock.

The skilled person will understand that the reactor may be suitable for many types of thermochemical process including but not limited to pyrolysis and gasification, and that the particular process carried out will depend upon the nature of the feedstock and product, and the reaction conditions used.

The hydrocarbon products produced by the reactor are not limited and will depend on the feedstock used and the process conditions. In some embodiments, the hydrocarbons are combustible hydrocarbons, for example hydrocarbons comprising C9-19 hydrocarbons. In general, the present reactor is able to prepare a combustible hydrocarbon product of higher grade, i.e. including a greater proportion of useful fractions and a lower proportion of heavier fractions and impurities.

In some embodiments, the hydrocarbon product comprises predominantly C ₆ or lighter hydrocarbons. In some embodiments, the hydrocarbon product comprises one or more types of olefin. In some embodiments, the hydrocarbon product comprises ethylene (C2 olefin) and propylene (C3 olefin). In some embodiments, the hydrocarbon product comprises ethylene (C2 olefin). Such products may find use in e.g. the manufacture of plastics materials.

In some embodiments, the hydrocarbon product comprises C5-10 hydrocarbons. Such products may find use as naphtha.

In some embodiments, the hydrocarbon product comprises one or more of propane, butane and pentane. In some embodiments, the hydrocarbon product comprises a mixture of two or more of propane. Such products may find use as LPG. In some embodiments, the hydrocarbon product comprises hydrocarbons with chain lengths in the range Ce-ie. Such products may find use as jet fuel.

The exact product distribution will depend on e.g. the reaction conditions during the thermochemical treatment, and the skilled person will be able to modify the conditions to tailor the composition of the product. For example, it is well-known that increasing the temperature in a thermochemical process leads to a higher level of cracking of hydrocarbons resulting in a higher proportion of light-chain hydrocarbons (e.g. C ₂ -C ₄ ) in the product.

The number of gas distribution base plates within the reactor may not be limited to the first and second gas distribution base plates. The performance of the reactor may be further improved by including one or more further gas distribution base plates to further divide the fluidised bed of material into separate independently supported portions.

In some embodiments, the cracking zone comprises one or more further gas distribution base plates for the generation of a second fluidised bed of material in the cracking zone. In this way the cracking or fragmentation processes performed in the cracking zone occur across two separate fluidised beds, providing improved mixing of the beds, reducing gas- bypass even further and therefore further enhancing the heat and mass transfer.

The further gas distribution base plate may comprise a plurality of apertures permitting the passage of gas from a first section of the cracking zone into a second section of the cracking zone. The further gas distribution base plate may support a bed of particulate material within the second section of the cracking zone which is fluidised by the gas passing through the further gas distribution base plate.

In some embodiments the reactor comprises an elongate structure wherein the first gas distribution base plate and the second gas distribution base plate are spaced from each other along the length of the reactor. The first gas distribution base plate may comprise a gas feed which provides fluidising gas for the generation of a fluidised bed of material in the devolatilization zone supported upon the first gas distribution base plate. In some embodiments, the first gas distribution base plate comprises a plurality of apertures through which the fluidising gas is fed. The fluidising gas supplied to the first gas distribution base plate may comprise nitrogen. The fluidising gas supplied to the first gas distribution base plate may comprise a mixture of nitrogen and hydrogen. The fluidising gas supplied to the first gas distribution base plate may comprise one or more of steam, CO ₂ , nitrogen and hydrogen. The fluidising gas supplied to the first gas distribution base plate may comprise recycled gas (including gaseous hydrocarbons) from elsewhere in the process.

In some embodiments, the fluidising gas comprises or consists of CO2. In some embodiments, the fluidising gas comprises CO2 in combination with one or more further gases. In some embodiments, the fluidising gas comprises CO2 in combination with one or more of H2 and steam. The use of CO2 within the fluidising gas may be preferred as the CO2 will become incorporated into the hydrocarbon product, thereby providing a means for carbon capture and utilisation. This reduces the carbon footprint of the reactor and provides a way to convert CO2 into valuable hydrocarbon products.

In some embodiments, the reactor comprises means for feeding a fluidising gas to the first gas distribution base plate. The reactor may also comprise means for pre-heating the fluidising gas prior to feeding into the first gas distribution base plate. In some embodiments the reactor comprises means to recycle at least a proportion of product gas from the process and feed at least some of this gas to the first gas distribution base plate.

In some embodiments, the first gas distribution base plate forms part of a wall of the reactor, such that the fluidised bed of material in the devolatilization zone is supported upon an internal surface of the reactor wall, for example the base of the reactor.

In some embodiments, the devolatilization zone is configured to operate at a temperature of at least 350 °C during operation of the reactor, for example at least 360 °C, at least 370 °C, at least 380 °C, at least 390 °C or at least 400 °C. In some embodiments, the devolatilization zone is configured to operate at a temperature of up to 600 °C during operation of the reactor, for example up to 550 °C, up to 500 °C, up to 490 °C, up to 480 °C, up to 470 °C, up to 460 °C or up to 450 °C. Temperatures in excess of these would increase the risk of incipient melting and agglomeration issues.

In some embodiments, the devolatilization zone is configured to operate at a temperature of 400 to 450 °C during operation of the reactor. The reactor may comprise a means to supply heat to the devolatilization zone to ensure the correct temperature for pyrolysis is achieved.

In some embodiments a heater external to the reactor is provided adjacent the devolatilization zone. The means to supply heat is not limited but examples include a heat exchanger or an electric or gas heating mantle. The reactor comprises a feeding means for the addition of feedstock material to the reactor. In some embodiments, the feeding means comprises a feedstock inlet located within an internal wall of the reactor between the first gas distribution base plate and the second gas distribution base plate.

In some embodiments, the feedstock inlet is located at a distance from the first gas distribution base such that feedstock material is fed into the reactor within a particle-free zone, above the surface of a fluidised bed of material in the devolatilization zone. In this way, feedstock material is fed into a region above the surface of the fluidised bed rather than into the bed itself. This avoids the problems caused by direct feeding into the bed. The temperature above the bed is lower than the temperature within the bed, such that the inlet is less likely to become blocked by molten feedstock material (e.g. molten plastic). It is also easier to feed the feedstock into the reactor as smaller discrete particles rather than the large slugs which form upon feeding directly into the bed, such that distribution of the feedstock within the bed is improved.

In some embodiments, the feeding means comprises a feedstock inlet located within an internal wall of the reactor and a cooling element upstream of the feedstock inlet to cool the feedstock material before entry into the reactor. Cooling the feedstock material in this way, particularly when the feedstock material comprises a solid material such as a solid plastics material, reduces the risk of the feedstock material melting and blocking the inlet. The cooling element is not limited but in some embodiments may comprise a water-cooled element. In some embodiments the cooing element surrounds a feed tube through which the feedstock passes before entry into the reactor.

In some embodiments the feeding means comprises a hopper for the introduction of feedstock material and a feed conduit for conveying the feedstock material from the hopper to the feedstock inlet and into the reactor. In some embodiments, vacuum conveying or inert pneumatic conveying is used to convey the feedstock material within the feed conduit. This further reduces the risk of mechanical blockage which would be inherent in alternative feeding mechanisms such as a screw feeder.

In some embodiments the processes performed within the reactor will be operated at pressures above atmospheric pressure, for example at around 10 bar, to enable effective refining of the product within the reactor and more compact reactor units. However, such pressurised operation requires the presence of mechanical airlocks and lock hoppers to facilitate feeding of the feedstock under pressure. Although such measures are generally known to the skilled person, for the present process it has been found that the nature of the feedstock, which may include gritty or sticky materials, may lead to problems with the maintenance of such components.

To address such problems, the feeding means of the reactor may comprise means for feeding the feedstock material into the reactor as a spray of pressurised liquid. For example, when the feedstock material comprises plastics material, the feeding means may be configured to spray molten plastic into the reactor under pressure. In this way, any problems associated with the mechanical feeding of solid material in a high pressure environment are avoided. In such embodiments the reactor may further comprise a unit for the preparation of liquid feedstock, for example liquid polymer. The unit may be configured to provide superheating of the feedstock material until a high fluidity feedstock material is provided, which is subsequently fed into the reactor under pressure as a spray. The use of a spray ensures good dispersion of the feedstock material into the fluidised bed within the reactor.

The devolatilization zone of the reactor is an internal region or volume of the reactor where initial pyrolysis and devolatilization of the feedstock material to thermally degrade the material takes place. This may involve the thermal degradation of the feedstock to produce more volatile intermediate products which pass into the cracking zone and/or the removal of existing volatile material from the feedstock before its passage into the cracking zone. In some embodiments the devolatilization zone is the volume defined by the first gas distribution base plate, the second gas distribution base plate and a portion of the surface of the internal wall of the reactor. For example, the devolatilization zone may extend from the first gas distribution base plate at the bottom or base of the reactor to the second gas distribution base plate at a location vertically distant from the first gas distribution base plate. A first portion of the devolatilization zone, for example a lower portion, may contain the fluidised bed of material during use of the reactor for pyrolysis. A second portion of the devolatilization zone, for example an upper portion above the first, lower portion, in some cases does not contain any of the solid material which makes up the fluidised bed, or contains a negligible amount of such material.

Ash contaminants are collected in the bottom of the devolatilization zone, thus avoiding contamination of above fluidised bed levels. These contaminants may be periodically extracted and removed from the system without the need to shut down the reactor.

In some embodiments, an additive is present in the devolatilization zone, wherein the additive is adapted to remove one or more contaminants from the feedstock. In some embodiments, the additive comprises CaO. CaO will act to absorb sulfur and chlorine contaminants from the feedstock within the devolatilization zone, forming calcium sulfate and/or calcium chloride product which can then be easily removed from the reactor. In some embodiments, the particle size of the additive, e.g. CaO, is larger than the particle size of the fluidised bed of material within the devolatilization zone, facilitating the removal of the Ca- based additive from the reactor after absorption of the contaminants. In some embodiments, the density of the additive, e.g. CaO, is larger than the density of the fluidised bed of material within the devolatilization zone, facilitating the removal of the Ca-based additive from the reactor after absorption of the contaminants.

The reactor comprises a cracking zone which comprises a second gas distribution base plate for the generation of a fluidised bed of material in the cracking zone. The second gas distribution base plate therefore separates the devolatilization zone from the cracking zone. The devolatilization zone is in fluid communication with the cracking zone through a plurality of apertures within the second gas distribution base plate permitting the passage of gas from the devolatilization zone into the cracking zone. Thus the intermediate products formed in the devolatilization zone by initial pyrolysis of the feedstock material are vaporised within the devolatilization zone and pass through the apertures in the second gas distribution base plate, into the cracking zone. Such vaporised intermediate products thereby provide a source of fluidising gas to form a fluidised bed of particulate material supported upon the second gas distribution base plate during use of the reactor. This fluidised bed of material facilitates the fragmentation and cracking of the intermediate products into further refined downstream products within the cracking zone. As explained above, the cracking zone may comprise one or more further gas distribution base plates in addition to the second gas distribution base plate, thereby dividing the fluidised bed within the cracking zone into two or more discrete fluidised beds, each supported on a separate gas distribution base plate.

In some embodiments, the cracking zone is configured to operate at a temperature of at least 450 °C during operation of the reactor, for example at least 460 °C, at least 470 °C, at least 480 °C, at least 490 °C or at least 500 °C. In some embodiments, the cracking zone is configured to operate at a temperature of up to 900 °C during operation of the reactor, for example up to 800 °C, up to 700 °C, up to 690 °C, up to 680 °C, up to 670 °C, up to 660 °C or up to 650 °C.

In some embodiments, the cracking zone is configured to operate at a temperature of 500 to 650 °C during operation of the reactor. The heat to facilitate this temperature of operation may be provided by heating means located outside the reactor, or alternatively may be provided by the circulation of heated solid particulate material into the cracking zone from elsewhere in the reactor, as discussed in more detail below. For example, as discussed below, regenerated heated catalyst particles may be fed into the cracking zone from a catalyst regeneration unit in communication with the cracking zone.

The plurality of apertures within the second gas distribution base plate may comprise apertures of a sufficiently small size to prevent the passage of the solid particulate materials which make up the fluidised bed through the apertures during use of the reactor. In general, the size of particles in the bed is decided based on fluidisation principles, as would be understood by the skilled person, to ensure smooth fluidisation and good mixing.

The size of the apertures within the second gas distribution base plate may be selected to ensure adequate pressure drop across the second gas distribution base plate and to avoid particle weeping (backflow of particles from the fluisidsed bed through the second gas distribution base plate).

In some embodiments, the second gas distribution base plate further comprises an overflow aperture for the passage of solid materials from the cracking zone into the devolatilization zone. Such an overflow aperture or overflow chute permits the circulation of solid materials within the reactor in a direction opposite to the direction of flow of gases through the gas distribution base plates. This permits solid materials, such as spent catalyst materials, to eventually pass into the devolatilization zone from where they may be extracted into a catalyst regeneration unit, as explained in more detail below. It will be understood that this aperture or chute will be of a larger size than the gas distribution apertures to allow the solid material to pass through.

In alternative embodiments it may be preferred to provide gas distribution base plates which lack any overflow aperture or other means which would facilitate backflow of the material within the fluidised beds. This may be preferred for example where different catalysts are used in each fluidised bed and cross-contamination of the beds with catalysts from other beds is undesirable.

When one or more further gas distribution base plates are provided in the cracking zone, in addition to the second gas distribution base plate, these one or more further gas distribution base plates may also each comprise an overflow aperture for the passage of solid materials through said base plate into the preceding section of the cracking zone. For example, when the cracking zone comprises the second gas distribution base plate and a further gas distribution base plate which divides the cracking zone into a first section and a second section, the further gas distribution base plate may comprise an overflow aperture or overflow chute permitting the overflow of solid particulate material from the second section into the first section.

In some embodiments, the reactor further comprising a refining zone, wherein the refining zone comprises a third gas distribution base plate for the generation of a fluidised bed of material in the refining zone, wherein the refining zone is in fluid communication with the cracking zone through a plurality of apertures within the third gas distribution base plate permitting the passage of fluids from the cracking zone into the refining zone.

The third gas distribution base plate therefore separates the cracking zone from the refining zone. The cracking zone is in fluid communication with the refining zone through a plurality of apertures within the third gas distribution base plate permitting the passage of gas from the cracking zone into the refining zone. Thus the intermediate products formed in the cracking zone by the cracking of the vapours passed into the cracking zone from the devolatilization zone in turn pass through the apertures in the third gas distribution base plate, into the refining zone. Such vaporised intermediate products thereby provide a source of fluidising gas to form a fluidised bed of particulate material supported upon the third gas distribution base plate during use of the reactor. This fluidised bed of material facilitates the refining of the intermediate products into further refined downstream products within the refining zone.

The purpose of the refining zone is to reduce the presence of aromatics and heavy hydrocarbons by hydrogenating the compounds passing into the refining zone from the cracking zone. Furthermore, this catalytic zone would be able to convert the obtained short chain olefins generated in the cracking zone to C5-C19 hydrocarbons rich in paraffins, as an effect of hydrogen transfer reactions. This is preferably facilitated by the presence of one or more suitable catalysts in the bed of material within the refining zone. Furthermore the refining zone may also include one or more oligomerisation catalysts to “reassemble” any short chain products resulting from excessive cracking in the cracking zone, such as C2 hydrocarbons, into longer linear chain hydrocarbons, where this is desirable.

The refining zone therefore further improves the quality of the product of the pyrolysis process and ameliorates the need for separate downstream refining, hydrotreatment, reforming or oligomerisation processes. In this way, the products from the reactor are able to serve as high grade “drop-in” fuel, or chemical feedstock products, i.e. functional alternatives to existing fuels usable in existing engines or steam crackers without the need for modification. The reactor is particularly effective in providing drop-in fuels and chemical feedstock in the C5-19 hydrocarbon range.

In some embodiments, the third gas distribution base plate prevents the passage of solid particulate material from the fluidised bed of material in the refining zone into the cracking zone. In some cases, this is achieved by ensuring that the third gas distribution base plate does not contain any overflow aperture or overflow chute such as the ones described above which permit the flow of solids within the cracking zone, or between the cracking zone and the devolatilization zone. Since the refining zone may contain a catalyst specific to the refining process, it is beneficial to prevent the circulation of this catalyst into the other zones of the reactor.

In some embodiments, the refining zone is configured to operate at a temperature of at least 350 °C during operation of the reactor, for example at least 360 °C, at least 370 °C, at least 380 °C, at least 390 °C or at least 400 °C. In some embodiments, the refining zone is configured to operate at a temperature of up to 500 °C during operation of the reactor, for example up to 490 °C, up to 480 °C, up to 470 °C, up to 460 °C or up to 450 °C.

The temperature used will depend to some extent on the catalyst used in the refining zone and the skilled person will be able to select an appropriate temperature.

In some embodiments, the refining zone is configured to operate at a temperature of 400 to 450 °C during operation of the reactor. The heat to facilitate this temperature of operation may be provided by heating means located outside the reactor, or alternatively may be provided by the circulation of vapours into the cracking zone from elsewhere in the reactor (e.g. the cracking zone). In some embodiments the cracking zone is configured to operate at a temperature higher than that of the refining zone, and the temperature of the refining zone is maintained by the passage of hot vapour products from the cracking zone into the refining zone.

In some embodiments, the reactor comprises means for feeding a hydrotreating gas comprising H2 to the third gas distribution base plate. The presence of hydrotreating conditions within the refining zone facilitates refining of the products, for example to reduce the amount of aromatic or oxygenated hydrocarbons or other impurities in the product. The hydrocarbon product, e.g. combustible hydrocarbon product, after leaving the refining zone will be drawn off from the main reactor and taken for further processing steps including condensation. The reactor may comprise means to remove solid particulate material, such as entrained solid particulate material, from the gaseous product stream prior to condensation of the product. Such solid removal means will remove any unwanted solid materials including solid additives used in the process such as sulfur/chloride absorbents. In this way the levels of sulfur and chloride in the product stream may be reduced to very low levels.

In some embodiments, the reactor comprises one or more cyclones for the removal of particulate matter from the gaseous product stream. In some embodiments, the reactor comprises one or more filters, such as ceramic filters, for the removal of particulate matter from the gaseous product stream. In some embodiments, the reactor further comprises a guard polishing bed downstream of the solid removal means to reduce the level of impurities in the product stream even further, for example to the ppb level, improving the quality of the hydrocarbon product.

In some embodiments a condensing unit is placed downstream of the reactor. The condensing unit exposes the hydrocarbon product to temperatures sufficiently low to condense the product, for example temperatures of 150 °C or lower. Any remaining uncondensed gas (including e.g. H2, N2 and light hydrocarbons such as ChU and C2-C3 hydrocarbons) may be recycled for use as at least part of the fluidising gas fed to one or more gas distribution base plates within the reactor.

In some embodiments, the reactor further comprises a catalyst regeneration zone connected to the devolatilization zone to receive solid catalyst material from the devolatilization zone for regeneration.

In some embodiments, the reactor comprises means for feeding a combustion gas comprising O2 to the catalyst regeneration zone. In some embodiments the combustion gas is air.

A second aspect of the invention is a modular reactor system comprising a reactor according to the first aspect and one or more additional reactor system modules each independently selected from: a feedstock material separation module upstream of the reactor; a feedstock material size reduction module upstream of the reactor; a feedstock material drying module upstream of the reactor; a hydrocarbon product filter module downstream of the reactor; a hydrocarbon product condensation module downstream of the reactor; a catalyst regeneration module; an electrolyser module; and a hydrocarbon product reforming module downstream of the reactor.

The feedstock material separation module separates a feedstock stream to remove material which may be less suitable for processing in the reactor, thereby improving the efficiency of the process and the quality of the product. For example, for the pyrolysis of polymer materials it may be beneficial to reduce the proportion of PVC and PET polymer within the feedstock. This ensures that the product contains fewer impurities such as sulfur or chlorine which may result from the presence of these polymers in the feedstock. It may also be beneficial to remove materials from the feedstock which are easily recycled by standard polymer recycling methods, increasing the proportion of difficult-to-recycle polymers in the feedstock stream thereby providing an even more useful process for the disposal of waste plastic. For example, the feedstock material separation module may remove recyclable polymer materials from the feedstock stream thereby increasing the proportion of materials such as thin film polymer materials, polymer materials contaminated with food or liquids, and weathered polymer materials.

Nevertheless, in some embodiments the process of the invention is able to handle feedstock with a relatively high content of PVC and/or PET which would not be possible for more conventional pyrolysis processes. In particular, amounts of PVC and/or PET in the feedstock may be up to 1 wt%, up to 3 wt% or up to 5 wt% when an additive is present within the devolatilization zone adapted to remove sulfur and chlorine contaminants from the feedstock.

Alternatively or additionally, the feedstock material separation module may remove one or more non-polymeric materials from the feedstock, such as metals and/or ceramics.

The feedstock material size reduction module processes the feedstock material stream to reduce the size of individual pieces or particles of material within the feedstock to facilitate feeding into the reactor and distribution within the fluidised bed.

The feedstock material drying module removes water from the feedstock material. The amount of water present in the feedstock after drying may be up to 30 wt%, for example up to 25 wt% or up to 20 wt%. In some embodiments the amount of water present in the feedstock after drying is from 10 to 30 wt%, for example from 10 to 25 wt% or from 10 to 20 wt%.

The hydrocarbon product filter module filters the gaseous hydrocarbon product stream to remove one or more impurities, for example one or more solid material impurities. In some embodiments the hydrocarbon product filter module comprises one or more cyclones for the removal of solid particulate material from the product stream. In some embodiments hydrocarbon product filter module comprises one or more filters for the removal of solid particulate material from the product stream. In some embodiments, some or all of the removed solid particulate material may be recirculated to an upstream module of the reactor system. The one or more filters may comprise one or more ceramic filters. In some embodiments the one or more filters may comprise a sorbent material for the removal of one or more impurities from the product stream. The hydrocarbon product filter module may comprise a polishing filter, for example a guard polishing bed, for further reduction of the level of solids or impurities within the product stream.

The hydrocarbon product condensation module condenses the gaseous hydrocarbon product to provide a liquid hydrocarbon product. The hydrocarbon product condensation module may comprise a condenser unit configured to operate at a temperature sufficiently low to condense at least a portion of the hydrocarbon product leaving the reactor into a liquid product. In some embodiments the temperature is 150 °C or less. The exact temperature will depend on the boiling point of the product and the skilled person can choose a suitable temperature for condensation accordingly.

The catalyst regeneration module provides a means to regenerate spent or carbon-coated catalyst from the reaction, and/or provide the material used in the fluidised beds with heat. The reactor may comprise a means for feeding spent fluidised bed material (e.g. catalyst) to the catalyst regeneration module and a means for receiving regenerated and/or heated catalyst from the catalyst regeneration module. In some embodiments, the reactor comprises an outlet within the devolatilization zone of the reactor which collects spent catalyst which is then conveyed to the catalyst regeneration module, for example through a suitable conduit.

The high temperatures within the devolatilization zone necessary for pyrolysis cause the build-up of solid carbon residues (char) on the fluidised bed material and coking of catalyst in the bed, which becomes deactivated as a result. These pyrolysis residues including deactivated catalyst may be fed to the catalyst regeneration module. In some embodiments the catalyst regeneration module comprises a gas distribution base plate for the generation of a fluidised bed, for example a fast fluidised bed, of residue material in the catalyst regeneration module. The catalyst regeneration module may also comprise means for feeding a hydrogen, steam or oxygen-containing gas to the gas distribution base plate to fluidise the residue material, and means for heating the residue material to a temperature sufficient to achieve combustion of the carbon residues and regeneration of the catalyst.

The catalyst regeneration module may also comprise means to extract regenerated catalyst and feed it back to the reactor. For example, the catalyst regeneration module may comprise one or more cyclones to extract regenerated catalyst. The catalyst regeneration module may comprise one or more loop seal tubes to feed the regenerated catalyst back to the reactor at any level.

In some embodiments the reactor comprises an inlet for feeding regenerated catalyst from the catalyst regeneration module. The inlet may be located at a suitable position on the internal wall of the reactor. In some embodiments, the inlet is located within the cracking zone, such that regenerated catalyst enters a fluidised bed of material supported upon a gas distribution base plate within the cracking zone, for example the second gas distribution base plate or a further gas distribution base plate within the cracking zone. Such an inlet allows the process in the reactor to operate autothermally, i.e. without any external heat source being necessary, because the heat provided by the high-temperature regenerated catalyst material entering the reactor through the inlet is sufficient for the cracking reactions to proceed.

In embodiments where circulation of fluidised bed material is not permitted (e.g. because there are no overflow chutes through the gas distribution base plates, separate inlets for feeding regenerated catalyst from the catalyst regeneration module may be provided within each reactor zone. For example, a first inlet may be provided in the devolatilization zone and a second inlet in the cracking zone.

In embodiments where different zones of the reactor include different catalysts and mixing of the catalysts is undesirable, the modular system may comprise several catalyst regeneration modules specific to each respective type of catalyst, which are each adapted to feed the regenerated catalyst back into the correct reactor zone. The electrolyser module provides a source of H2 from electrolysis. In is advantageous to product H2 in this way in a module located within the same system as the reactor so that the gas can be easily transported to and used by the reactor as a fluidising gas and/or hydrotreating gas.

In some embodiments the electrolyser module, when present, is operated using a renewable source of electricity. In some embodiments the electricity used to power the electrolyser module is derived entirely from one or more renewable sources.

The hydrocarbon product reforming module performs a reforming process on the hydrocarbon product from the reactor, for example to generate more hydrogen when required (e.g. for use in the fluidising gas or the hydrotreating gas). The (steam or dry) reforming of hydrocarbons is a known process well-understood by the skilled person.

In some embodiments, some or all of the non-condensed fraction from the hydrocarbon product reforming module (e.g. H2 and/or C1-4 hydrocarbons) may be recycled to the catalyst regeneration module and combusted to increase the heat production.

The modular reactor system may comprise a flash stage for the removal of residual heavier hydrocarbons from the hydrocarbon product where this is desirable. In some embodiments the flash stage comprises means to recirculate the collected heavier hydrocarbons back to the devolatilization zone of the reactor, thereby improving the efficiency of the reactor system and avoiding waste material.

In some embodiments, the modular reactor system comprises a gas engine for the combustion of gaseous by-products such as light hydrocarbons (C1-C4). Such a gas engine may be used to generate electricity, which may in turn be used to run an electrolyser to provide hydrogen gas for the process (e.g. for use in the fluidising gas or the hydrotreating gas).

A third aspect of the invention provides a process for the generation of a hydrocarbon product, comprising

(a) feeding a feedstock material into a reactor, wherein the reactor comprises: a feeding means for the addition of the feedstock material to the reactor; an outlet for the extraction of the hydrocarbon product from the reactor; a devolatilization zone; a cracking zone; a first gas distribution base plate for the generation of a fluidised bed of material in the devolatilization zone, a second gas distribution base plate for the generation of a fluidised bed of material in the cracking zone, and the devolatilization zone is in fluid communication with the cracking zone through a plurality of apertures within the second gas distribution base plate permitting the passage of fluids from the devolatilization zone into the cracking zone;

(b) thermochemically treating the feedstock material within a fluidised bed of material supported on the first gas distribution base plate in the devolatilization zone, wherein the bed of material is fluidised by feeding a fluidising gas through the first gas distribution base plate; and

(c) cracking the intermediate product formed from the pyrolysis of the feedstock material, within a fluidised bed of material supported on the second gas distribution base plate in the cracking zone, wherein the bed of material in the cracking zone is fluidised by the passage of the intermediate product through the second gas distribution base plate.

All of the options and preferences set out above in relation to the first and second aspects of the invention apply equally to the third aspect.

In some embodiments the process of the third aspect of the invention is carried out in a reactor according to the first aspect of the invention.

In some embodiments, the feedstock material comprises one or more polymers.

In some embodiments, the one or more polymers are each independently selected from polypropylene, polyethylene and polystyrene. These plastics are commonly used in consumer products and may be difficult to recycle if they are contaminated, for example contaminated with food or cosmetic materials. Examples of polyethylene include HDPE, MDPE, LDPE and LLDPE. The reactor is able to process such waste consumer plastics materials, including contaminated materials. As a result, the environmental impact of the process is low because the feedstock comes from a source of waste material which would otherwise go to landfill or incineration.

In some embodiments, the feedstock material comprises waste material, for example waste polymer material. This may be consumer waste, such as used polymer packaging, or industrial waste. The physical form of the polymer feedstock is not limited and may be a moulded product or a film, including laminate films. In some cases the plastics material fed to the reactor is the product of a size-reduction process on larger plastics materials, for example shredding or grinding.

In some embodiments, the feedstock material comprises carbonaceuous material. In some embodiments, the feedstock material comprises waste carbonaceuous material. In some embodiments, the feedstock material comprises biomass.

The process of the invention is not only useful for the thermochemical treatment of plastics feedstock; it may also be used to treat carbonaceous feedstock such as biomass to generate a useful syngas or hydrocarbon product. In some embodiments the feedstock comprises a mixture of plastics material and carbonaceous material, e.g. a mixture of plastics material and biomass. In this way the process is useful in the treatment of soiled plastics materials which would otherwise be incinerated or go to landfill.

Since biomass contains oxygen, in embodiments where the feedstock comprises biomass it may be necessary to include a step of removing oxygen from the hydrocarbon product after the product has formed. Such oxygen removal processes are known to the skilled person.

In some embodiments the process comprises a feedstock drying step before feeding the feedstock material to the reactor. In some embodiments, the drying is performed using residual heat from other modules of the plant, e.g. flue gases from the catalyst regeneration module or gas engine. The amount of water present in the feedstock after drying may be up to 30 wt%, for example from 1 wt% to 30 wt%, from 1 wt% to 25 wt%, from 1 wt% to 20 wt% or from 1 wt% to 10 wt%.

In some embodiments the process comprises a feedstock material size reduction step before feeding the feedstock material to the reactor. In some embodiments, the size reduction is achieved by mechanical shredders.

In some embodiments, the feedstock material is processed until the average particle size of the material is 2-50 mm, for example from 2-40 mm, from 2-30 mm, from 2-20 mm, from 2- 10 mm or from 2-5 mm.

In some embodiments, feeding the feedstock material into the reactor comprises feeding the feedstock material above the upper surface of the fluidised bed of material in the devolatilization zone. In this way, feeding directly into the fluidised bed is avoided, reducing the risk of inhomogeneous distribution of the feedstock material within the bed and providing a lower temperature at the entry point of the feedstock material into the reactor, avoiding the melting of feedstock material and concomitant blockage of the feedstock inlet. In some embodiments, the feedstock material enters the reactor through a feedstock inlet located within an internal wall of the reactor between the first gas distribution base plate and the second gas distribution base plate.

In some embodiments, the process further comprises cooling the feedstock material before entry into the reactor. This further reduces the likelihood of feedstock material melting before it has fully entered the reactor (e.g. when the feedstock comprises meltable material such as plastics), which would carry the risk of blockage of the inlet. Cooling may be achieved using a cooling element upstream of the feedstock inlet to cool the feedstock material before entry into the reactor, as described above under the first aspect.

The process may comprise feeding the feedstock material into the reactor by vacuum conveying or inert pneumatic conveying. These feeding methods reduce the risk of blockage of the feeding equipment.

In some embodiments, the process comprises spraying the feedstock into the reactor in liquid form (when the feedstock is able to be converted into liquid form, e.g. by melting when the feedstock comprises plastics material). In such cases, the process may comprise a step of liquefying the feedstock material prior to spraying into the reactor, for example by superheating the feedstock material to provide a high fluidity feedstock, for example liquid polymer.

The pyrolysis may be performed under a pressure of from 100 kPa to 1000 kPa

In some embodiments, the temperature of the fluidised bed of pyrolysis catalyst in the devolatilization zone is from 400 to 450 °C

In some embodiments, the temperature of the fluidised bed of catalyst in the cracking zone is from 500 to 650 °C.

In some embodiments, the fluidising gas fed through the first gas distribution base plate comprises one or more of steam, CO2, N2 and H2. In some embodiments, the fluidising gas fed through the first gas distribution base plate comprises one or more of N ₂ and H ₂ .

In some embodiments, the fluidising gas comprises or consists of CO ₂ . In some embodiments, the fluidising gas comprises CO ₂ in combination with one or more further gases. In some embodiments, the fluidising gas comprises CO ₂ in combination with one or more of H ₂ and steam. The use of CO ₂ within the fluidising gas may be preferred as part of the CO ₂ will become incorporated into the hydrocarbon product, thereby providing a means for carbon capture and utilisation. This reduces the carbon footprint of the process and provides a way to convert CO ₂ into valuable hydrocarbon products.

In some embodiments the fluidising gas fed through the first gas distribution base plate comprises one or more gases recycled from elsewhere in the process. For example, residual light hydrocarbons in the product such as CFU or C2-C3 hydrocarbons may be recycled.

In some embodiments, the process further comprises refining the product formed by cracking of the intermediate product to provide a refined product, wherein the refining takes place in a refining zone, wherein the refining zone comprises a third gas distribution base plate for the generation of a fluidised bed of material in the refining zone, wherein the refining zone is in fluid communication with the cracking zone through a plurality of apertures within the third gas distribution base plate permitting the passage of fluids from the cracking zone into the refining zone.

In some embodiments, the process further comprises feeding a hydrotreating gas comprising H ₂ to the third gas distribution base plate.

Some traditional thermochemical reactions use an inert solid material in a fluidised bed, such as sand, and rely on the high temperatures alone to achieve thermal degradation and pyrolysis of the polymer. However in such reactions very high temperatures are necessary in order to pyrolyse heavier wax fractions. Since employing such high temperatures would come at the cost of low liquid product yield due to the increased gas product volume, and the use of high temperatures increases the process cost and lowers efficiency, the traditional way to process these waxy materials is to remove them from the bed and break them down in a different reactor. This adds complexity and expense to the process. It is therefore preferred that the process of the invention employs fluidised beds of material comprising a catalyst, for the thermochemical treatment and subsequent cracking (and optional refining). This increases the quality of the product due to a higher degree of cracking of the heavier fractions, and eliminates the need to remove and treat waxes in a separate reactor.

Nevertheless, the process may also be performed such that one or more of the fluidised beds do not contain any catalyst. In such cases the multi-compartment nature of the process still provides a much more efficient process.

The material used in the fluidised beds may be inert, for example when the process is a non- catalytic pyrolysis process or other non-catalytic process.

Preferably the fluidised bed in the devolatilization zone is made up of either an inert or a catalytic material; the fluidised bed in the cracking zone is made up of either an inert or a catalytic material; and the fluidised bed in the refining zone (when present) is made up of a catalytic material.

In some embodiments, the fluidised bed in the devolatilization zone comprises a first catalyst. In some embodiments, the fluidised bed in the cracking zone comprises a second catalyst. In some embodiments, the fluidised bed in the refining zone (when present) comprises a third catalyst.

In some embodiments, the fluidised bed in the devolatilization zone comprises a first catalyst, the fluidised bed in the cracking zone comprises a second catalyst and the fluidised bed in the refining zone (when present) comprises a third catalyst. The catalysts in the different zones may be the same or different. The presence of multiple fluidised beds within the reactor enables the use of different catalysts in any two or more beds, thereby increasing the flexibility of the process and enabling the selection of a catalyst for each bed which is tailored to the function and conditions of that bed.

The material making up the fluidised bed in the devolatilization zone may comprise or consist of an inert material, i.e. a material having no catalytic activity towards the reactants within the devolatilization zone. For example, the material making up the fluidised bed in the devolatilization zone may comprise or consist of sand. In some embodiments the material making up the fluidised bed in the devolatilization zone comprises a pyrolysis catalyst. In some embodiments the amount of pyrolysis catalyst is at least 10 wt% of the total mass of material in the fluidised bed. In some embodiments the amount of pyrolysis catalyst is up to 50 wt% of the total mass of material in the fluidised bed. In some embodiments the amount of pyrolysis catalyst is from 10 wt% to 50 wt% of the total mass of material in the fluidised bed.

In some embodiments the material making up the fluidised bed in the devolatilization zone comprises an additive adapted to remove one or more contaminants from the feedstock. In some embodiments the additive is adapted to remove one or more of sulfur and chlorine contaminants from the feedstock within the devolatilization zone. In some embodiments, the additive comprises CaO. In some embodiments, the additive comprises particulate CaO. In some embodiments, the particle size of the additive, e.g. CaO, is larger than the particle size of the fluidised bed of material within the devolatilization zone, facilitating the removal of the CaO additive from the reactor after absorption of the contaminants. In some embodiments, the density of the additive, e.g. CaO, is larger than the density of the fluidised bed of material within the devolatilization zone, facilitating the removal of the CaO additive from the reactor after absorption of the contaminants. In some embodiments the amount of additive is at least 10 wt% of the total mass of material in the fluidised bed. In some embodiments the amount of additive is up to 50 wt% of the total mass of material in the fluidised bed. In some embodiments the amount of additive is from 10 wt% to 50 wt% of the total mass of material in the fluidised bed.

The balance of the material making up the fluidised bed in the devolatilization zone may be an inert material such as sand.

The pyrolysis catalyst within the fluidised bed in the devolatilization zone may comprise any catalyst suitable for facilitating the pyrolysis of the feedstock material, for example the pyrolysis of polymers. The function of the pyrolysis catalyst is ensuring rapid maxing and good gas-solid contact, carrying the thermal inertia required for feedstock pyrolysis and increasing the rate of reaction. Catalytic action may be promoted by the presence of acidic sites on the particles and hydrogen in the gas phase. Thus in some embodiments, the fluidising gas comprises H2. Non-limiting options for suitable pyrolysis catalyst include fluid catalytic cracking (FCC) catalysts, zeolite (e.g. beta, USY, ZSM-5, REY, clinoptilolite, MCM- 41, SAPO-34, YZ or NZ), olivine, dolomite and CaO. The size of the pyrolysis catalyst particles is chosen to ensure adequate fluidisation and catalytic activity. The particles will typically have a D _v 50 particle size within the range 500 to 1500 pm, where D _v 50 is defined as the particle diameter in microns which splits the volume distribution in half, with half of the volume of particles below this size and half above.

Particle sizes may be measured using a laser diffraction method such as ASTM D4464-15 under the Mie scattering theory.

As explained above, when the material in the fluidised bed in the devolatilization zone includes catalysts and/or additives for contaminant removal, these may have a particle size and/or density different to the remaining material, to facilitate separation and removal of the catalysts and/or additives from the bottom of the reactor.

The material making up the fluidised bed in the cracking zone may comprise or consist of an inert material, i.e. a material having no catalytic activity towards the reactants within the cracking zone. For example, the material making up the fluidised bed in the cracking zone may comprise or consist of sand.

In some embodiments the material making up the fluidised bed in the cracking zone comprises a catalytic material. In some embodiments the amount of catalytic material is at least 10 wt% of the total mass of material in the fluidised bed. In some embodiments the amount of catalytic material is up to 50 wt% of the total mass of material in the fluidised bed. In some embodiments the amount of catalytic material is from 10 wt% to 50 wt% of the total mass of material in the fluidised bed. The balance may be an inert material such as sand.

In some embodiments, the catalyst used within a fluidised bed in the cracking zone is the same catalyst as used as the pyrolysis catalyst. In some embodiments, the catalyst used within a fluidised bed in the cracking zone is selected from the same catalysts mentioned above for the pyrolysis catalyst (but may be the same as or different from the specific catalyst used as the pyrolysis catalyst).

When the process includes the step of refining the product formed by cracking of the intermediate product to provide a refined product, a catalyst may be present within a fluidised bed in the refining zone. The catalyst may differ from the catalyst used in the devolatilization zone. The catalyst may differ from the catalyst used in the cracking zone. The catalyst may differ from the catalyst used in the devolatilization zone and differ from the catalyst used in the cracking zone. The catalyst in the refining zone should facilitate hydrogenation to reduce the presence of aromatic compounds and heavy hydrocarbons in the product. The catalyst may be a hydrogenation catalyst. In some embodiments the catalyst comprises a transition metal-containing catalyst. In some embodiments the catalyst is a noble metal catalyst or a carbon-based catalyst. Suitable catalysts include those already mentioned above for the pyrolysis catalyst. Other suitable catalysts for cracking include activated carbon, nickel-containing catalysts (e.g. raney nickel), iron-containing catalysts, palladium-containing catalysts and platinum-containing catalysts.

In some embodiments the material making up the fluidised bed in the refining zone consists of a catalytic material, i.e. 100 wt% of the material in the fluidised bed of the refining zone is catalytic material.

The size of the refining catalyst particles is chosen to ensure adequate fluidisation and catalytic activity. In general, the particles in the fluidised bed in the refining zone will be smaller than those in the pyrolysis or cracking zones to ensure smooth fluidisation and excellent gas-solid contact. The smaller particle size generates a different fluidization behaviour, such that the gas-solid phase within the bed in the refining zone is more homogenous ensuring better performance of the refining process. The particles will typically have a D _v 50 particle size within the range 60 to 200 pm, where D _v 50 is defined as the particle diameter in microns which splits the volume distribution in half, with half of the volume of particles below this size and half above. Particle sizes may be measured using a laser diffraction method such as ASTM D4464-15 under the Mie scattering theory.

In some embodiments, the process further comprises the regeneration of catalyst within a regeneration zone and feeding of regenerated catalyst back into one or more of the devolatilization zone and cracking zone of the reactor. The regeneration of catalyst may comprise feeding spent catalyst from the reactor into a catalyst regeneration module and regenerating the catalyst by combustion or steam/hydrogen regeneration. The catalyst regeneration may comprise forming a fluidised bed, for example a fast fluidised bed, of catalyst material in the regeneration module, flowing an oxygen-containing gas (such as air) through the fluidised bed and performing combustion to remove solid carbon residues from the catalyst. In some embodiments this is done while increasing temperature of the catalyst. The catalyst regeneration may comprise forming a fast fluidised bed of catalyst material in the regeneration module, flowing a steam or hydrogen-containing gas through the fluidised bed and performing regeneration to remove solid carbon residues from the catalyst and/or reducing the active metal sites (if present). The regenerated catalyst may then be extracted from the bed and fed back to the reactor, for example using a cyclone. In some embodiments, the regenerated catalyst is fed back to the cracking zone of the reactor. In some embodiments, the hydrocarbon product comprises a combustible hydrocarbon product. In some embodiments, the hydrocarbon product comprises a product which is a suitable substitute for one or more types of liquid fuel or chemical feedstock products, for example naphtha, kerosene or gasoline.

In some embodiments, the hydrocarbon product comprises C5-C19, such as C9-C19 hydrocarbons.

In some embodiments, the hydrocarbon product comprises ³50 wt% n-paraffins (i.e. n- alkanes), for example from 50-90 wt%, from 50-80 wt% or from 50-70 wt% n-paraffins. In some embodiments, the hydrocarbon product comprises ³50 wt% C9-19 n-paraffins, for example from 50-90 wt%, from 50-80 wt% or from 50-70 wt% C9-19 n-paraffins.

In some embodiments, the hydrocarbon product comprises from 20-30 wt% i-paraffins (i.e. branched-chain alkanes). In some embodiments, the hydrocarbon product comprises from 20-30 wt% C9-19 i-paraffins.

The hydrocarbon product may comprise less than 15 wt% aromatic compounds. The hydrocarbon product may comprise less than 15 wt% aromatic compounds and less than 10 wt% combined content of naphtha and olefins.

In some embodiments the hydrocarbon product contains substantially no oxygenated compounds.

The density of the hydrocarbon product at 15 °C is typically from 780 to 845 g cm ³ . The boiling point is typically £ 280 °C. The energy density is typically 40-41 MJ/kg.

In some embodiments, the process comprises filtering the hydrocarbon product which leaves the cracking zone (or, when present, the refining zone). This may comprise passing the product through one or more filters to remove one or more impurities, for example one or more solid material impurities. The one or more filters may comprise one or more ceramic filters. In some embodiments the one or more filters may comprise a sorbent material for the removal of one or more impurities from the product stream. In some embodiments one or more cyclones are used for the removal of solid particulate material from the product stream. The process may comprise polishing the product stream for further removal of impurities and solid material.

The process may comprise a step of condensing the vapour product from the reactor to provide a liquid hydrocarbon product, e.g. liquid combustible hydrocarbon product.

The process may comprise feeding hydrogen gas to the reactor, for example feeding a fluidising gas comprising hydrogen gas to the reactor. As explained above, the hydrogen gas helps improve the performance of the catalysts in the cracking and devolatilization zones. As such, in some embodiments the fluidising gas fed to the fluidised bed in the devolatilization zone may comprise hydrogen. In some embodiments the fluidising gas fed to one or more of the fluidised beds in the cracking zone may comprise hydrogen. Hydrogen also facilitates hydrotreatment in the refining zone. So, when the refining zone is present in the reactor, the fluidising gas fed to one or more of the fluidised beds in the refining zone may comprise hydrogen.

In some embodiments the process comprises generating hydrogen through electrolysis and feeding at least some of the generated hydrogen into the reactor in the manner described above. This is the preferred option when an excess of renewable power is available. When this is not the case (e.g. wind or solar power supply is insufficient or unavailable) the required hydrogen may be produced internally from the reforming module. This makes the process very efficient, cost effective and with low carbon footprint.

Hydrogen produced by an electrolyser can be used to refine the hydrocarbon product to a certain level in the refining zone. However, the process also generates its own hydrogen, available in part in the remaining non-condensable gas after removal of the liquid hydrocarbons from the products, or generated from the reforming of the gases which have to be recirculated. As such the process is able to work continuously even if a discontinuous power source (e.g. solar or wind powered electrolyser) is used, and without any expensive and challenging hydrogen storage facility. This provides a very reliable process with a power grid balancing ability.

In some embodiments the process comprises flashing the hydrocarbon product in a flash stage to separate residual heavy hydrocarbons from the product. The process may also comprise feeding at least a portion of the residual heavy hydrocarbons back to the devolatilization zone of the reactor. In some embodiments the process further comprises reforming the hydrocarbon product. Such reforming processes are known the skilled person and improve the efficiency of the process by reducing waste streams. Such reforming processes are also used to generate hydrogen (as an alternative to, or in addition to, electrolysis) which may then be fed back to the process for use in the fluidising gas.

A schematic cross-section of a reactor system according to the invention is shown in Figure 1. The reactor 2 is of a generally tubular geometry with the main axis of the tube aligned vertically. The reactor has a wall 30 defining an internal volume 31 in which the thermochemical treatment process (e.g. pyrolysis) takes place. The reactor volume includes a devolatilization zone 32 and a cracking zone 33.

The base of the reactor includes a gas distribution base plate 34 in the devolatilization zone 32 which includes a plurality of apertures through which a fluidising gas may pass into the internal volume of the reactor. A fluidised bed of solid particulate material 35 is supported on the gas distribution base plate 34. The passage of gas through the apertures in the gas distribution base plate 34 causes fluidisation of the bed of material 35 supported thereon.

The cracking zone 33 includes two gas distribution base plates 36, 37, each defining a plurality of apertures through which gas may pass. Each of the two gas distribution base plates 36, 37 support a fluidised bed of solid particulate material 38, 39.

The two zones are in fluid communication with one another through the apertures in the gas distribution base plates 36, 37. The apertures in the gas distribution base plates prevent the passage of particles of solid material from the fluidised bed. The reactor contains vertical chutes 40, 41 which bypass the gas distribution base plates 36, 37 to permit the flow of solid material downwards through the gas distribution base plates 36, 37. The inlets 42, 43 of the vertical chutes 40, 41 are distanced from the gas distribution base plates 36, 37 such that a fluidised bed may remain supported upon the gas distribution base plates until the height of the bed exceeds the location of the inlet 42, 43, at which point solid particulate material will pass by overflow into the chute and downwards into the next zone of the reactor.

The fluidised beds of solid particulate material 35, 38 and 39 each comprise a particulate catalyst material. Examples of suitable particulate catalyst materials include fluid catalytic cracking (FCC) catalysts, zeolite (e.g. HZSM-5, SAPO-34, YZ or NZ), olivine, dolomite and CaO. The reactor includes a feedstock material inlet 44 positioned in the reactor wall at the end of a feeding conduit 45 along which solid feedstock material passes. The feeding conduit 45 is wrapped in a cooling jacket 46 cooled by a flow of water. A hopper 47 feeds feedstock material into the conduit 45 for feeding to the reactor by a pneumatic feeding mechanism. Feedstock material enters the hopper after being processed by size reduction (shredding) and drying in a size reduction module and a drying module (not shown). The feedstock material inlet 44 is located between the fluidised bed of solid particulate material 35 in the devolatilization zone and the fluidised bed of solid particulate material 38 in the cracking zone, such that feedstock material fed into the reactor falls into the fluidised bed of solid particulate material 35 in the devolatilization zone. The feedstock material inlet 44 is distanced sufficiently from the gas distribution base plate 34 in the devolatilization zone 32 such that it lies above the upper surface of the fluidised bed of solid particulate material 35 in the devolatilization zone.

The reactor includes a product outlet 48 through which gaseous hydrocarbon products pass out of the reactor from the cracking zone 33. The gaseous hydrocarbon products may then be treated in filtration and condenser modules (not shown).

A heating element 49 external to the reactor provides heat to the reactor contents. Note that this heating element is absent in some embodiments where heat is provided by the recirculation of regenerated catalyst material from a catalyst regeneration module (described in more detail below).

Before performing the thermochemical treatment in the reactor, suitable solid particulate catalysts are added to the reactor to form beds upon each gas distribution base plate. The fluidised bed of solid particulate material 35 in the devolatilization zone is heated to a temperature of 400-450 °C using the heating element 49, and feedstock material is fed into the reactor through the feedstock material inlet 44. The feedstock material falls into the fluidised bed 35 by gravity and is rapidly pyrolysed by the heat and action of the catalyst.

The vapours generated by the pyrolysis in the bed 35 are carried upwards through the apertures in the gas distribution base plate 36 and into the fluidised bed of solid particulate material 38 in the cracking zone (the movement of vapours through the various perforated gas distribution plates in Figure 2 is denoted by upwardly directed arrows).

The vapours are subjected to cracking within the fluidised bed of solid particulate material 38 in the cracking zone to further refine the product, before being passed into the second fluidised bed of solid particulate material 39 in the cracking zone for further refining. Both beds 38, 39 are heated to temperatures within the range 500-650 °C, the heat for which is provided by the recirculation of hot regenerated catalyst from the catalyst regeneration module into the cracking zone.

The vapours from the second fluidised bed of solid particulate material 39 in the cracking zone then pass out of product outlet 48 and on to further optional processing modules such as a condenser module (not shown).

A schematic cross-section of a reactor system according to the invention is shown in Figure 2. The reactor system 1 includes a reactor 10 and a catalyst regeneration module 20. The reactor 10 is of a generally tubular geometry with the main axis of the tube aligned vertically. The reactor has a wall 11 defining an internal volume 12 in which the thermochemical treatment process takes place. The reactor volume includes a devolatilization zone 121 , a cracking zone 122 and a refining zone 123.

The base of the reactor includes a gas distribution base plate 124 in the devolatilization zone 121 which includes a plurality of apertures through which a fluidising gas may pass into the internal volume of the reactor. A fluidised bed of solid particulate material 125 is supported on the gas distribution base plate 124. The passage of gas through the apertures in the gas distribution base plate 124 causes fluidisation of the bed of material supported thereon.

The cracking zone 122 includes two gas distribution base plates 126, 127, each defining a plurality of apertures through which gas may pass. Each of the two gas distribution base plates 126, 127 support a fluidised bed of solid particulate material 128, 129.

The refining zone 123 includes a gas distribution base plate 130 which includes a plurality of apertures through which a fluidising gas may pass into the refining zone. A fluidised bed of solid particulate material 131 is supported on the gas distribution base plate 130. The passage of gas through the apertures in the gas distribution base plate 130 causes fluidisation of the bed of material supported thereon.

All three zones are in fluid communication with one another through the apertures in the gas distribution base plates 126, 127 and 130. The apertures in the gas distribution base plates prevent the passage of particles of solid material from the fluidised bed. The reactor contains vertical chutes 132, 133 which bypass the gas distribution base plates 126, 127 to permit the flow of solid material downwards through the gas distribution base plates 126,

127. The inlets 134, 135 of the vertical chutes 132, 133 are distanced from the gas distribution base plates 126, 127 such that a fluidised bed may remain supported upon the gas distribution base plates until the height of the bed exceeds the location of the inlet 134, 135, at which point solid particulate material will pass by overflow into the chute and downwards into the next zone of the reactor.

The fluidised beds of solid particulate material 125, 128 and 129 each comprise a particulate catalyst material. Examples of suitable particulate catalyst materials include fluid catalytic cracking (FCC) catalysts, zeolite (e.g. e.g. beta, USY, ZSM-5, REY, clinoptilolite, MCM-41, SAPO-34, YZ or NZ ), olivine, dolomite and CaO.

The fluidised bed of solid particulate material 131 in the refining zone 123 comprises a particulate catalyst material. Examples of suitable particulate catalyst materials include those already mentioned above for the pyrolysis catalyst. Other suitable catalysts for cracking include activated carbon, nickel-containing catalysts (e.g. raney nickel), iron- containing catalysts, palladium-containing catalysts and platinum-containing catalysts.

The reactor includes a feedstock material inlet 136 positioned in the reactor wall at the end of a feeding conduit 137 along which solid feedstock material passes. The feeding conduit 137 is wrapped in a cooling jacket 138 cooled by a flow of water. A hopper 139 feeds feedstock material into the conduit 137 for feeding to the reactor by a pneumatic feeding mechanism. Feedstock material enters the hopper after being processed by size reduction (shredding) and drying in a size reduction module and a drying module (not shown). The feedstock material inlet 136 is located between the fluidised bed of solid particulate material 125 in the devolatilization zone and the fluidised bed of solid particulate material 128 in the cracking zone, such that feedstock material fed into the reactor falls into the fluidised bed of solid particulate material 125 in the devolatilization zone. The feedstock material inlet 136 is distanced sufficiently from the gas distribution base plate 124 in the devolatilization zone 121 such that it lies above the upper surface of the fluidised bed of solid particulate material 125 in the devolatilization zone.

The reactor includes a product outlet 140 through which gaseous hydrocarbon products pass out of the reactor from the refining zone 123. The gaseous hydrocarbon products are then treated in filtration and condenser modules (not shown).

A heating element 13 external to the reactor 10 adjacent the devolatilization zone provides heat to the devolatilization zone. Note that this heating element is absent in some embodiments where heat is provided by the recirculation of regenerated catalyst material from a catalyst regeneration module.

The reactor system 1 also includes a catalyst regeneration module 20. The catalyst regeneration module 20 is connected to the reactor 10 via a spent catalyst conduit 21 through which spent catalyst which has become coked and deactivated during the reaction passes from the devolatilization zone into the catalyst regeneration module 20.

The catalyst regeneration module 20 includes a gas distribution base plate 22 which includes a plurality of apertures through which a fluidising gas may pass into the refining zone. A fluidised bed of solid particulate material 23 is supported on the gas distribution base plate 22. The passage of gas through the apertures in the gas distribution base plate 22 causes fluidisation of the bed of material supported thereon.

The catalyst regeneration module 20 includes an outlet 24 through which regenerated catalyst passes back into the reactor 10.

Before performing the thermochemical treatment in the reactor, suitable solid particulate catalysts are added to the reactor to form beds upon each gas distribution base plate. The fluidised bed of solid particulate material 125 in the devolatilization zone is heated to a temperature of 400-450 °C using the heating element 13, and feedstock material is fed into the reactor through the feedstock material inlet 136. The feedstock material falls into the fluidised bed 125 by gravity and is rapidly pyrolysed by the heat and action of the catalyst. The vapours generated by the pyrolysis in the bed 125 are carried upwards through the apertures in the gas distribution base plate 126 and into the fluidised bed of solid particulate material 128 in the cracking zone (the movement of vapours through the various perforated gas distribution plates in Figures 2 and 3 is denoted by upwardly directed arrows).

The vapours are subjected to cracking within the fluidised bed of solid particulate material 128 in the cracking zone to further refine the product, before being passed into the second fluidised bed of solid particulate material 129 in the cracking zone for further refining. Both beds 128, 129 are heated to temperatures within the range 500-650 °C, the heat for which is provided by the recirculation of hot regenerated catalyst from the catalyst regeneration module into the cracking zone.

The vapours from the second fluidised bed of solid particulate material 129 in the cracking zone then pass through apertures in the gas distribution base plate 130 in the refining zone 123 and into the fluidised bed of solid particulate material 131 for refining by hydrotreating. Hydrotreating gas is fed into the fluidised bed of solid particulate material 131 alongside the vapours from the cracking zone.

After refining in the fluidised bed of solid particulate material 131 the product vapours pass out of product outlet 140 and on to further optional processing modules such as a condenser module (not shown).

Solid carbon residues (char) and coked catalyst from the fluidised bed 125 are extracted from the devolatilization zone into the catalyst regeneration module 20 through the spent catalyst conduit 21. In the catalyst regeneration module 20 the spent catalyst is combusted or steam/hydro treated to remove the carbon before being extracted using a cyclone and fed back into the cracking zone of the reactor 10. CO2 and H2O off-gas leaves the reactor via an outlet at this point.

Figure 3 shows a schematic diagram of a modular reactor system layout according to the invention. The reactor system includes multiple modules including a thermochemical reactor. The system includes a reformer module which provides a source of H2 gas to form part of the fluidising gas to the reactor.

Figure 4 shows a schematic diagram of an alternative modular reactor system layout according to the invention. This is similar to the system shown in Figure 3, except that an electrolyser module is present for the electrolysis of water to form H2 gas, which is then used to form part of the fluidising gas to the reactor. The electrolyser is powered by electricity generated either from renewable sources.

Examples

Pyrolysis was carried out in a lab-scale pilot unit including a reactor having the structure shown schematically in Figure 1.

The reactor had the capability to be used as both a thermal and catalytic pyrolysis, using different feedstocks such as plastic and biomass materials. FCC (fluid catalytic cracking) catalysts were added in the reactor with the feedstock. The FCC catalyst used was High mesoporosity (pore volume in the 100-600 A range) powder available commercially from UOP or JM. The reactor could hold up to 20 L of feedstock and the maximum working safe temperature of up to 600°C could be achieved. Nitrogen was used as the primary carrier gas fed to the reactor to provide an inert atmosphere and to carry the product gases through the reactor. A small quantity (approx..

10 vol% of the total fluidising gas volume) of hydrogen was also added to the fluidising gas to test the possibility of refining the oil directly inside the unit. A continuous condensation system was used which employed a water bath to ensure the condensation temperature was kept below 30°C, and to ensure the maximum condensation of vapour to liquid oil. The produced liquid oil was collected from the oil collection tank, and further characterization was carried out to determine its chemical composition and characteristics for other potential applications. Plastic waste was used as the feedstock in the catalytic pyrolysis process. The plastic was collected from consumer waste points and included grocery bags, disposable juice cups and plates, and drinking water bottles, which consist of polyethylene (PE), polypropylene (PP) polystyrene (PS), and polyethylene terephthalate (PET) plastics, respectively. The selection of these plastic materials was made based on the fact that they are the primary source of plastic waste generated in locations such as airports. To obtain a homogenous mixture, all the waste samples were crushed into smaller pieces of around 2-5 mm.

Four different streams (A-D) of composite polymer materials were used as feedstock. The compositions of these streams are shown in Table 1:

Table 1

Two pure plastic streams A-B were separated from specific mechanical recycling facility waste streams. Mixed plastic waste streams C and D were obtained from generic airport terminal waste. Both fractions differ mainly in the content of biomass (food residues), polystyrene, metal films and other inorganic fillers.

The rate of feedstock supply to the reactor was 250 g/h, with 5000 g of catalyst pre-loaded in the bed.

The zeolite component, sourced from Catal, had a molar S1O2 : AI2O3 ratio of 50 and the surface area of the calcined blend was 580 m ² /g. The batch was first treated with 200 ml of distilled water and allowed to soak for 25 hrs before filtering off and drying at 50 °C. The dried granules were then treated with 200 mL of a 10 % wt. solution of Citric acid and stirred for 3 hrs before filtering off, washing 1x with distilled water and drying at 50 °C. The batch was finally calcined at 480 °C for 2 hrs to produce a high acid strength H+ZSM-5 material.

The FCC, also sourced form Catal, was used as the catalyst in the devolatilization zone whereas the zeolite was used as catalyst in the cracking zone.

Both catalysts were crushed into powder (<200 pm) in a ball-milling machine, before being modified as described above and then added to the reactor. The product oil was characterized using gas chromatography coupled with mass spectrophotometry (GC-MS), while the gas composition was continuously monitored using Fourier transform infrared spectroscopy (FT-IR). The chemical composition of oil was studied using a GC-MS with FI detector. A capillary GC 30 m long and 0.25 mm wide column coated with a 0.25 pm thick film of 5% phenyl-methylpolysiloxane (HP-5) was used. The oven was set at 50 °C for 2 min and then increased up to 290 °C using a 5°C/min heating rate. The temperature of the ion source and transfer line were kept at 230 °C, and 300 °C respectively and splitless injection was applied at 290 °C. The internal mass spectral data library was used to identify the chromatographic peaks, and the peak percentages were assessed for their total ion chromatogram (TIC) peak area.

The experiments were carried out at 450°C, using a heating rate of 10°C/min and run duration of approximately 5 hours (steady state-operation) per sample. Steady state was achieved after approximately 2 hours from start-up.

The obtained yield of each pyrolysis product was calculated based on weight, after the completion of each experiment. Characterization of the liquid oil product was carried out to investigate the effect of feedstock composition on the quality of liquid oil produced.

The GC-MS analysis of the oil sample obtained from the four streams A-D was carried out to verify the exact composition of the oil and is summarized in Table 2. The components present in all oil samples are mostly aliphatic hydrocarbons (alkane and alkenes) with carbon number C9-C19.

Table 2

The amount of gas formed in the pyrolysis reached values between 35 (stream D) and 41% (stream C).

On an industrial scale, less gas would be formed than in the laboratory fluidized bed process because the residence time of the gases in the lab fluidized bed is three-to-four times longer. The main components of the gaseous fraction of the product were methane, ethylene, ethane and propene. Carbon monoxide and carbon dioxide were formed from the presence of paper and polyethylene terephthalate (PET) contaminants in the mixed plastics.

The main fraction of the product was a liquid oil in an amount of up to 51 wt% of the product (stream D). The long residence time of the gases in the lab-scale fluidised bed favours secondary reactions which lead to the formation of a greater amount of aromatics such as toluene and styrene.

To increase the proportion of C9-C12 fraction in the product from mixed plastics feedstock streams, it is necessary to reduce the residence time of the product gases in the fluidized bed zone to reduce the amount of secondary reactions taking place. As a result the product gas exiting the reactor should ideally not be circulated and used as fluidizing gas when C9- C12 hydrocarbons are the desired product. A better solution would be to use hydrogen or nitrogen as fluidizing gas. Under these conditions, more than 50 wt% of C9-C12 can be obtained.