NZ566448A - Conversion of plastics to hydrocarbon-based materials - Google Patents

Abstract

Disclosed is a method of converting a feedstock such as plastic into hydrocarbon-based materials, including the steps of: a) mixing liquid with the feedstock in a mixing chamber to form a feedstock/liquid mixture, b) heating the feedstock/liquid mixture in the mixing chamber to produce a free-flowing mixture, and c) heating the free-flowing mixture under vacuum conditions in a reaction chamber to produce a first hydrocarbon-based product in the form of a vapour; and a second hydrocarbon-based product in the form of a solid/liquid residue, characterised in that the temperature in step c) is kept below 280 degrees C.

Description

PATENTS FORM NO, 5 Fee No. 4: $250.00 Ref: 128854/62 RD PATENTS ACT 1953 COMPLETE SPECIFICATION After Provisional No: 566448 Dated: 4 March 2008 CONVERSION PROCESS WE RMR GROUP LIMITED, a New Zealand company having its registered office at 22 Roderick Place, Hamilton 3210, New Zealand; do hereby declare this invention to be described in the following statement: James & Wells Ref: 128854/62 RD 566448 CONVERSION PROCESS technical field The invention relates to a conversion process. In particular it relates to a process for conversion of plastic and rubber materials into hydrocarbon products.

Background Art Products made of plastics and rubber materials are used extensively around the world. These products inevitably end up as waste materials which create a major disposal problem. Storing the materials in a landfill is typically not a good solution due to the sheer volume of material and to the very long time required for these materials to break down.

One solution has been to incinerate the plastic and rubber waste material. However, a major issue with this method is that dioxins and other environmentally undesirable products are commonly produced during the incineration process. Increasingly regulations are being put in place to limit atmospheric release of such compounds. This has resulted in the need to remove dioxins and other pollutants prior to release into the environment which adds substantially to the cost of processing the waste.

Dioxins are among the most toxic chemicals known today and have been linked with the incidence of cancer. Dioxins are very stable in the atmosphere, remaining active for many years after release into the environment. Very minute amounts of dioxins are widely considered to cause negative effects on the environment and on human health. As a result, many government agencies around the world have introduced strict regulations covering the release of dioxins and monitoring of the release process. For example many developed countries have adopted a maximum exhaust concentration of dioxins of about 0.1 ng TEQ/m3 2 James & Wells Ref: 128854/62 RD 566448 It is well known in the art that dioxins are typically formed according to the de Novo reaction in which inorganic chlorine, carbon, hydrogen and oxygen are the starting components. All of these materials are commonly found in waste plastics and rubber products. Chlorine may be found in plastics materials, particularly in products incorporating PVC and in plastic pesticide containers. Carbon, generally in an amorphous form, is commonly produced during incomplete combustion as soot, fly ash or carbon black. These small carbon particles can provide both a carbon source and act as a catalyst for the reaction. Carbon black is used extensively in the formation of tyres, a major component of waste rubber products.

As well as the above basic ingredients, the reaction can also be catalysed by the present of metals such as copper, iron, zinc, aluminium and chromium. All of these are likely to be found in plastics and rubber products, often as a component of a label or as a supplementary part of the product.

It is apparent therefore that when waste plastics and rubber materials are incinerated all the ingredients and conditions for production of dioxins are present. When such a mixture is heated to over about 200°C dioxins start to form, with production peaking between 280°C to 450°C.

As a result conventional incineration processes produce relatively large quantities of dioxins which must be removed from exhaust gases prior to release into the atmosphere. This can add significantly to the cost of the conversion process.

Apart from incineration of waste, for many years waste plastics and rubber material have been converted, with various degrees of success, into liquid fuel using various well known methods. Demand for this type of conversion process has been largely driven by rising world oil prices.

However, a problem with all of these processes is that the waste material is derived 3 566448 from diverse sources, so that generally when collected there is a wide variety of different products mixed together. This, combined with the different composition for each type of waste material or product, makes it very difficult to produce fuel that can meet the increasingly stringent vehicle fuel standards.

As a result, existing methods and systems to convert waste plastics (for example) into light fuel require careful pre-selection and sorting of the various types of waste plastic products. This not only increases process running costs but also places restrictions on the steady supply of raw material for the process, as only the pre-sefected products can be used. It also leaves the problem of disposal of the remaining products.

Furthermore, present methods used to polymerise waste plastics, such as thermal pyrolysis and catalytic cracking, all require the use of temperatures over 300°C in order to melt and gasify the raw material and to produce the desired vapour for conversion to fuel.

During the conversion of plastics and rubber materials to fuel, dioxins in significant amounts will be formed at temperatures above around 250°C unless PVC or other forms of chlorine containing materials, as well as carbon particles, can be limited or removed completely from the waste products. At present this is not practical or economical.

United States Patent No.s 5,753,086 and 6,861,568 (a divisional application of 5,753,086), both to Guffey et al., disclose a process for waste plastic recycling. The method of Guffey et al. involves mixing waste plastic with oil prior to heating. The method disclosed by Guffey et al is focussed on production and control of free radical precursors during the conversion process. The authors assert that free radical precursors may exist as part of the waste plastic feedstock or may be separately 4 4 James & Wells Ref: 128854/62 RD 566448 added as a further solid component or as part of the diluents.

The authors of US '568 consider that the break down is due to free radical chain depolymerisation reactions which break up the synthetic polymer structures. As a consequence their method requires monitoring of the free radical concentration at all 5 times and adjustment of the free radical component in the solution. This involves additional monitoring and can involve pre-selection of the kinds of plastic used in the feedstock, all of which adds to the cost of the process.

Most importantly, however, the method of US Patent No.s 5,753,086 and 6,861,568 involves heating the mixture to at least around 350 °C, at which temperature 10 significant amounts of dioxins can be produced. There is no discussion within these patents of any method to control or reduce the production of dioxins.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

It is a further object of the present invention to address the problem of dioxin 15 production during conversion of plastics and rubber materials to hydrocarbon-based products.

All references, including any patents or patent applications cited in this specification 4(a) _ j mi /nun j James & Wells Ref: 128854/62 RD 566448 are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

Disclosure of Invention According to one aspect of the present invention there is provided a method of converting a feedstock into hydrocarbon-based materials, including the steps of a) mixing fluid with the feedstock in a mixing chamber to form a feedstock/fluid mixture; and b) heating the feedstock /fluid mixture in the mixing chamber to produce a free-flowing mixture; and c) heating the free-flowing mixture under vacuum conditions in a reaction James SWells Ref: 128854/62 RD 566448 chamber to produce a first hydrocarbon-based product in the form of a vapour and a second hydrocarbon-based product in the form of a solid/liquid residue, the method characterised in that temperature in step c) is kept below 280° C.

In a preferred embodiment the feedstock includes plastics and rubber material.

In some embodiments a feedstock may also include various oils, such as lubricant oil, motor oil.

The feedstock for the present invention may use unsorted plastics and rubber products, but could include other products. Typically the plastics products may be waste materials, such as discarded containers, bags, plastic waste from factories and other products. The rubber may be largely sourced from used tyres.

As the plastics and rubber products do not need to be sorted, there is a significant advantage over prior art methods where the feedstock must be carefully sorted and only a relatively small proportion of the available material can be used, adding significantly to the cost of the prior art processes.

In alternative embodiments the feedstock may be plastics material only or rubber material only. However, in each case there is no requirement to sort the plastics or rubber products prior to processing.

A feedstock of plastics or rubber materials will typically be a collection of discrete pieces. Heating such a mixture evenly, without creating localised hot spots, poses significant problems. In the method of the present invention a fluid is mixed with the feedstock to transfer heat among the various pieces of the feedstock. It is important therefore that the fluid used is a good thermal conductor.

In a preferred embodiment the fluid includes oil. 6 James & Wells Ref: 128854/62 RD 566448 A fluid may preferably include heavy oil, although lubricant oil and used diesel may also be used. These may be sourced from used oil, for example from vehicles or industrial waste. Oils are typically good thermal conductors.

Reference to heavy oil throughout this specification should be understood to mean oil having a specific gravity in excess of 0.933.

Preferably the amount of fluid added may be sufficient to cover the feedstock in the mixing chamber.

Large pieces of plastic and rubber in the feedstock may be cut into smaller pieces prior to mixing. Preferably the pieces in the feedstock may have a dimension of around 1cm to 20cm. This may assist with the softening and melting to form a free-flowing mixture in step b), thus reducing the cost. However, the only real limitation on size of the pieces of feedstock is that they must fit through the inlet into the mixing chamber.

In a preferred embodiment the maximum temperature in step b) is in the range from about 80° C to about 240° C.

The specific maximum temperature required depends on the nature of the feedstock mixture. However, this range of temperatures is generally sufficient to melt most plastics and rubber materials and to form a free-flowing mixture.

In general a free-flowing mixture may have a viscosity from 1000cP to 6000cP which may be sufficient to enable the mixture to flow freely through a pipe, as for example to transfer the free flowing liquid from the mixing chamber into the reaction chamber through a connecting pipe.

Preferably the feedstock/fluid mixture may be stirred during heating in step b) to reduce any localised temperature fluctuations. This may limit the formation of local 7 James & Wells Ref: 128854/62 RD 566448 hot spots that can lead to production of carbon black and/or dioxins.

The covering of fluid may also be effective in ensuring equilibration of the temperature throughout the feedstock/fluid mixture. In particular, the presence of fluid around the feedstock may prevent hot spots from occurring, for example as could occur when a sharp edge of plastics or rubber material is exposed. In such cases the temperature locally may exceed the desired temperature, leading to unwanted production of carbon black (and other carbon products) as well as dioxins.

Furthermore, the fluid may act as a trap for any dust and free carbon particles, such as carbon black, that may be produced and to retain, in suspension, any solid residue remaining during step c). The reduction in dust and free carbon particles may limit the production of dioxins.

In the conversion process of the present invention the maximum temperature that the mixture is heated to in step c) is in the range 180° C to 280° C.

The advantage of keeping the temperature in this range is that the maximum temperature is kept below the temperature at which significant amounts of dioxin are produced.

In a preferred embodiment the pressure in the reaction chamber during step c) is in the range from about 30 mmHg to about 550 mmHg (about 4 kPa to about 73 kPa).

An advantage of reducing the pressure below atmospheric pressure is that the boiling point of the free-flowing mixture is reduced. This means that there is an increase in the amount of vapour given off with respect to that given off at atmospheric pressure. As the vapour contains the volatile gases that form one of the desired products, this increase in yield, while keeping the temperature relatively low, is a considerable advantage. 8 James & Wells Ref: 128854/62 RD 566448 The pressure used in the reaction chamber during step c) may be related to the chlorine content of the feedstock. This in turn may be related to the amount of PVC and other chlorine containing products in the feedstock. Generally a higher chlorine content of the feedstock requires a lower pressure in the reaction chamber in order to limit the production of dioxins by lowering the boiling point to a value below that where significant amounts of dioxin may be formed.

Using pressures in the range from about 30 to 550 mmHg in the reaction chamber may provide a sufficient lowering of the boiling point of the free-flowing mixture to ensure the desired conversion to vapour from different types of feedstock.

In a preferred embodiment a variety of catalysts and de-chlorination agents are introduced in step c). The catalysts may assist the process of breaking down long chain molecules to produce oil vapour. The de-chlorination agents, which may be alkali based (as are well known in the art) may be used to reduce or remove chlorine from within the reaction chamber, thus limiting the production of dioxins.

The chlorine content in most commercial PVC products, which account for less than 20% of waste plastic materials, may vary from 63% to 69 % by mass. The specific catalysts used may be adjusted depending on the nature of the feedstock used and on the desired final product (particularly the first hydrocarbon-based product).

In a preferred embodiment the variety of catalysts added in step c) include catalytic compounds to crack the long-chain polymers at temperatures below about 280° C.

A key feature of the present invention is the way in which a number of factors are used to reduce the production of dioxins during heating of the free-flowing mixture of feedstock and fluids in step c). These factors include: • limitation of the maximum temperature to a temperature below 280° C, and preferably to around 250° C, where production of dioxins is significantly lower 9 James & Wells Ref: 128854/62 RD 566448 than at temperatures over around 300° C; • the action of the fluid in trapping any free carbon particles; • removal of chlorine from within the reaction chamber through the use of dechlorination agents.

Therefore, a significant advantage of the present invention is that the conversion process is designed to limit the production of dioxins throughout the process, rather than producing dioxins and then trying to eliminate them, as is common in prior art processes.

The first hydrocarbon-based product produced in the reaction chamber during step c) is in the form of a hot vapour.

In a preferred embodiment the method includes the further step of d) condensing the vapour from the reaction chamber in a condenser to produce a first liquid hydrocarbon-based product and an uncondensed residue gas mixture, The main purpose of the condenser in the present method is to condense the vapour into a liquid form. For this purpose a simple, single stage condenser may be used. The first liquid hydrocarbon based product contains liquid with carbon chain length range from C9 to C24.

The uses of the first liquid hydrocarbon-based product may depend on the specific details of the conversion process used, such as the maximum temperature in the reaction chamber and the nature of any catalysts used. However, in general the first liquid hydrocarbon-based product may be a suitable starting material, essentially free of dioxins and other undesirable materials, for refining into fuel by any of the well known refining methods. Other uses may include (without limitation) a base for paint James & Wells Ref: 128854/62 RD 566448 and paint thinners, as rust inhibiters and waterproof coatings,.

In some embodiments of the present invention the conversion process includes the further step of e) passing the vapour from the reaction chamber through a catalytic converter to produce a reformed vapour prior to condensing the reformed vapour as in step d).

The catalytic converter may include a variety of catalysts to modify the hydrocarbon polymer molecular structure and to remove chlorine and sulphur from the vapour. Again, the specific catalysts employed may depend on the nature of the feedstock (and hence the constituents of the vapour produced from it) as well as the intended use for products derived from it.

Step e) is optional, its use depending on the desired nature of the first hydrocarbon product produced in step d). For example, if the first hydrocarbon product at step d) is to be fuel oil, then particular catalysts may be used in step e) to provide an oil vapour having carbon chains more closely in-line with a mixed grade of diesel and kerosene liquid. The vapour may later be further refined into usable furnace fuel oil (for example).

In a preferred embodiment the pressure in the condenser during step d) is in the order of normal atmospheric pressure.

As it is not an objective of the present method to produce fuel, at least not directly, there is no need to pressurise the condenser. This provides a cost advantage as non-pressurised condensers typically involve a lower capital cost, thus reducing the cost of the conversion equipment as well as the operating costs.

In a preferred embodiment the method includes the further steps of 11 James & Wells Ref: 128854/62 RD 566448 f) passing the un-condensed residue gas mixture from the condenser through a filter to remove particulate material and produce filtered gas; and g) burning the filtered gas in a gas burner at a temperature of about 900° C to produce high temperature gas.

These steps are used to remove any remaining particulate material and to break down any remaining dioxins or other unwanted chemicals in the un-condensed gas mixture.

In a preferred embodiment the method includes the further step of h) using the high temperature gas to heat the reaction chamber during step c)- This utilises the heat from the gas burner in step g) as an input into heating the free-flowing mixture in the reaction chamber during step c), thus saving energy costs.

In a preferred embodiment the method includes the further step of i) passing an exhaust gas from the reaction chamber through a filter system to remove unwanted chemicals from the exhaust gas prior to venting the gas into the environment.

In particular the unwanted chemicals include any remaining dioxins.

In some embodiments the filter system may include a nano-titanium dioxide mesh filter illuminated by UV light, and a chemical catalyst neutralisation filter. In general, a specialised filter system may be chosen, typically from those well known in the art, to meet the specific requirements for removing dioxins and unwanted chemicals from the exhaust gases from the reaction chamber.

In a preferred embodiment the second hydrocarbon-based product includes solid 12 James & Wells Ref: 128854/62 RD 566448 hydrocarbon material and heavy oil residue. Solid hydrocarbon material may, or may not contain carbon black, metals, and fine dust particles.

Under the conditions in the reaction chamber during step c) there will be a residue from the free-flowing mixture, being what remains after the volatile gases have been removed. Typically this residue will include solids, such as the carbon black trapped in the fluid, as well as heavy oils from the fluid.

In a preferred embodiment the method includes the further steps of j) drawing off the second hydrocarbon-based product from the reaction chamber into a reservoir; and k) separating the second hydrocarbon-based product into a heavy oil residue and a solid hydrocarbon material in a separator.

The solid hydrocarbon material may be used commercially as a valuable base product, for example in the production of asphalt and modified asphalt products as used in road paving, and as a source for carbon black (which is used extensively in many industries such as tyre manufacture and printing).

In a preferred embodiment the method includes the further step of I) using the heavy oil residue from the separator as preheated fluid in step b).

Recycling the preheated heavy oil residue back into step b) provides a valuable additional source of fluid and heat into the mixing chamber. This may save operating costs, as less heat is used in step b) as well as recycling the heavy oil residue.

The present invention provides a number of advantages over the prior art, including: • A significant reduction in the amount of dioxins and other environmentally 13 James & Wells Ref: 128854/62 RD 566448 undesirable materials produced during the conversion process in comparison to prior art methods. This can be achieved by limiting the maximum temperature in the reaction chamber to less than about 280° C, together with removal of chlorine within the reaction chamber and trapping of carbon particles within the fluid mixture; • Lower conversion costs as the lower dioxin levels require less cost to remove from the exhaust gas prior to release into the environment; • Lower conversion costs as the feedstock can be a general mixture of plastics and rubber materials which do not require sorting; • Versatility of final product, particularly of the first hydrocarbon product in vapour form, as the conditions (temperatures, catalysts used, pressures etc) of the conversion method may be varied to produce different end products.

Brief Description of Drawings Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a schematic representation of the steps of the conversion method according to one embodiment of the present invention.

Best Modes for Carrying out the Invention In step a) of the method, feedstock in the form of waste plastic and/or roughly cut scrap rubber, typically in the form of tyres, is feed through the feedstock holder (1) into a mixing chamber (2). The feedstock is mixed with fluids in the form of various types of used oil products including lubricant oil and heavy oil is stirred to mix the feedstock and fluid together. 14 James & Wells Ref: 128854/62 RD 566448 In step b) the feedstock/fluid mixture in the mixing chamber (2) is heated at a constant rate to a temperature between 80°C and 240°C until the mixture is in a free-flowing state. The maximum temperature during this process is that required to reduce the feedstock/fluid mixture into a free flowing state and will depend on the nature of the feedstock.

In step (c) the free-flowing feedstock/fluid mixture is transferred into the reaction chamber (4) as indicated by arrow (3). The free-flowing mixture is stirred and heated at less than atmospheric pressure to a maximum temperature in the range from 180°C to 280°C. Preferably the temperature maximum is controlled under 250°C to reduce formation of dioxins in significant quantities.

Various catalysts are added at different stages of the heating process to assist cracking of large hydrocarbon molecules at various temperature ranges to produce oil vapour.

De-chlorination agents are also added at various stages and temperatures to remove chlorine. The applicants have found that with 80% of chlorine removed, dioxins in the final exhaust will be well within the maximum allowed 0.1 ng TEQ/m3 level.

Laboratory tests carried out by the applicants have found that alkali based dechlorination agents can remove around 80% of chlorine in 3 hours at 250° C. Figure 2 shows a typical graph of percentage reduction in chlorine over 3 hours as a function of temperature (in degrees Celsius). The applicants have found that removal of 90% of chlorine is achievable at longer times, or higher temperature range.

Figure 3 shows a typical graph of the time taken using de-chlorination agents to remove about 80% of the chlorine as a function of temperature.

James & Wells Ref: 128854/62 RD 566448 The level of fluid within the reaction chamber (4) during step (c) is maintained at a level such that coking of the feedstock due to overheating is limited, and such that any dust particles, such as carbon black, are absorbed within the free flowing liquid mixture.

The step (c) produces a first hydrocarbon-based product in the form of a vapour and a second hydrocarbon-based product.

In step (d) the vapour from the reaction chamber (4) is transferred into a condenser (8) where it is condensed under atmospheric pressure to produce a second hydrocarbon-based product and an uncondensed residue gas mixture.

In this embodiment the vapour from the reaction chamber (4) is passed through a catalytic converter (6) to produce a reformed vapour prior to entering the condenser (8) as outlined in step (e).

In step (f) the un-condensed residue gas mixture from the condenser (8) to a filter (14), as indicated by arrow (13) in Figure 1. The uncondensed residue gas mixture is filtered and cooled in the filter (14).

In step (g) the cooled, filtered and dried incondensable gases are transferred to a gas burner (16) as indicated by arrow (15). The un-condensed gases are burnt at a high temperature, typically about 900°C to break down any residual dioxins.

Excess heat from the gas burner (16) is transferred to the reaction chamber (4) where it is used as a heat source for step (c) as described in step (h).

In step (i) exhaust gases from the reaction chamber (4) are passed through a first filter (24) containing oxidised metal filters, where the metal filter can include titanium, vanadium, and tungsten. The exhaust gases are exposed to UV light and/or an electric field to break down residual dioxins. 16 James & Wells Ref: 128854/62 RD 566448 The gas is then passed through a second filter in which various chemical catalysts are used to purify the exhaust gas and to neutralise any remaining dioxins or other harmful gases before discharging the clean exhaust into the atmosphere as indicated by arrow (26).

In step (j) the second hydrocarbon-based product is drawn off from the reaction chamber (4) into a reservoir (19). The first hydrocarbon-based product includes residue solid material including dirt, carbon and fluid (primarily heavy oil).

In step (k) the second hydrocarbon-based product is separated into a heavy oil residue and a solid hydrocarbon material. The solid hydrocarbon material is transferred into a further reservoir (22) as indicated by arrow (21) in Figure 1. The solid hydrocarbon material contained in reservoir (22) may be suitable for use as a base for the production of asphalt and as a source of carbon black (among other things).

In step (i) the heavy oil residue from reservoir (19), in preheated form, is introduced back into the mixing chamber (2) as indicated by arrow (20). The heavy oil residue for plastic feedstock is likely to be in the temperature range of about 80 °C to about 240 °C.

.Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof of the appended claims. 17 James & Wells Ref: 128854/62 RD 566448

Claims (21)

WHAT WE CLAIM IS:

1. A method of converting a feedstock into hydrocarbon-based materials, including the steps of: a) mixing liquid with the feedstock in a mixing chamber to form a feedstock/liquid mixture; and b) heating the feedstock/liquid mixture in the mixing chamber to produce a free-flowing mixture; and c) heating the free-flowing mixture under vacuum conditions in a reaction chamber to produce: a first hydrocarbon-based product in the form of a vapour; and a second hydrocarbon-based product in the form of a solid/liquid residue, characterised in that the temperature in step c) is kept below 280° C.

2. A method of converting a feedstock into hydrocarbon-based materials as claimed in claim 1 wherein the feedstock includes plastics material.

3. A method of converting a feedstock into hydrocarbon-based materials as claimed in either claim 1 or claim 2 wherein the feedstock includes rubber material.

4. A method of converting a feedstock into hydrocarbon-based materials as claimed in any one of claims 1 to 3 wherein the liquid includes oil.

5. A method of converting a feedstock into hydrocarbon-based materials as claimed in any one of claims 1 to 4 wherein the second hydrocarbon-based 18 James & Wells Ref: 128854/62 RD product includes solid hydrocarbon material. 566448 7. 8. 9. 10. 11.

A method of converting a feedstock into hydrocarbon-based materials as claimed in any one of claims 1 to 5 wherein the second hydrocarbon-based product includes heavy oil residue.

A method of converting a feedstock into hydrocarbon-based materials as claimed in any one of claims 1 to 6 wherein the maximum temperature that the mixture is heated to in step b) is in the range from 80° C to 240° C.

A method of converting a feedstock into hydrocarbon-based materials as claimed in any one of claims 1 to 7 wherein the pressure in the reaction chamber during step c) is in the range from 30 mmHg to 550 mmHg (4 kPa to 73 kPa).

A method of converting a feedstock into hydrocarbon-based materials as claimed in any one of claims 1 to 8 wherein catalysts and de-chlorination agents are introduced in step c) to reduce the chlorine content within the reaction chamber.

A method of converting a feedstock into hydrocarbon-based materials as claimed in claim 9 wherein the catalysts added in step c) include catalytic compounds to crack the long-chain polymers at temperatures below 280° C.

A method of converting a feedstock into hydrocarbon-based materials as claimed in any one of claims 1 to 10 including the step of d) condensing the vapour from the reaction chamber in a condenser to produce a first liquid hydrocarbon-based product and an uncondensed residue gas mixture.

A method of converting a feedstock into hydrocarbon-based materials as James & Wells Ref. 128854/62 RD 566448 14. 15. 16. claimed in claim 11 including the step of e) passing the vapour from the reaction chamber through a catalytic converter to produce a reformed vapour prior to condensing the reformed vapour as in step d).

A method of converting a feedstock into hydrocarbon-based materials as claimed in either one of claims 11 or 12 wherein the pressure in the condenser during step d) is normal atmospheric pressure.

A method of converting a feedstock into hydrocarbon-based materials as claimed in any one of claims 11 to 13 including the step of f) passing the un-condensed residue gas mixture from the condenser through a filter to remove particulate material and produce filtered gas.

A method of converting a feedstock into hydrocarbon-based materials as claimed in claim 14 including the step of g) burning the filtered gas in a gas burner at a temperature up to 900° C to produce high temperature gas.

A method of converting a feedstock into hydrocarbon-based materials as claimed in claim 15 including the step of h) using the high temperature gas to heat the reaction chamber during step c).

A method of converting a feedstock into hydrocarbon-based materials as claimed in claim 16 including the step of i) passing an exhaust gas from the reaction chamber through a filter system to remove unwanted chemicals from the exhaust gas prior to 20 James & Wells Ref: 128854/62 RD 566448 venting the gas into the environment.

18. A method of converting a feedstock into hydrocarbon-based materials as claimed in claim 17 including the step of j) drawing off the second hydrocarbon-based product from the reaction chamber into a reservoir.

19. A method of converting a feedstock into hydrocarbon-based materials as claimed in claim 18 including the step of k) separating the second hydrocarbon-based product into a heavy oil residue and a solid hydrocarbon material in a separator.

20. A method of converting a feedstock into hydrocarbon-based materials as claimed in claim 19 including the step of I) using the heavy oil residue from the separator as preheated fluid in step

21. A method of converting a feedstock into hydrocarbon-based materials as herein described with reference to and as illustrated by the accompanying Disclosure of Invention and Best Modes for Carrying out the Invention sections of the description and drawings. b). 21