EP1948723A1

EP1948723A1 - Batch depolymerisation of hydrocarbon material

Info

Publication number: EP1948723A1
Application number: EP06812968A
Authority: EP
Inventors: Christer Forsgren; Hitomi Yoshiguchi; Sune Andreason
Original assignee: Stena Miljoteknik AB
Current assignee: Stena Miljoteknik AB
Priority date: 2005-11-02
Filing date: 2006-11-02
Publication date: 2008-07-30
Also published as: EP1948723A4; WO2007053088A1; SE0502436L

Abstract

The invention relates to a method and an apparatus/system for batch depolymerisation of hydrocarbon material. Hydrocarbon material (18) is loaded into a support means (17) which is placed into an outer container (10), the opening of which is sealed by a outer container lid (12). The support means (17) is designed so as to retain waste material. The hydrocarbon material (18) is heated with microwave or high-frequency radiation, to cause depolymerisation of the hydrocarbon material, while exhaust gases are allowed to escape from the outer container (10) via a gas outlet (13). After depolymerisation, the radiation is turned off, the support means (17) containing waste material is removed from the outer container (10) and the process may be repeated. Two or more outer containers (10) may be connected in parallel to a gas purification device (26) and be started up non-simultaneously, so as to produce a substantially continuous flow of gas through the gas purification device.

Description

BATCH DEPOLYMERISATION OF HYDROCARBON MATERIAL

TECHNICAL FIELD

The present invention relates to processing of hydrocarbon material, particularly in the fields of waste disposal and recycling. The invention relates to a method and an apparatus/system for depolymerisation of hydrocarbon material.

BACKGROUND OF THE INVENTION

Recycling and disposal of waste is an extensive activity due to the increasing amount of waste material produced in modern society. Stricter environmental legislation has lead to a requirement for improved techniques and apparatus for disposal of waste. Disposal of hydrocarbon waste poses a particular problem, as part of this waste is not biodegradable and/or is difficult to recycle. Simple combustion of some of such waste may form toxic gases, e.g. hydrogen chloride from the combustion of PVC or sulfurous gases from the combustion of vehicle tyres.

Conventional depolymerisation techniques are built on pyrolysis and use burners, i.e. convection and radiant heat, to heat the polymeric material. This technique has the disadvantage that the pyrolysis and the escape of exhaust gases are uneven and that they are difficult to control.

WO 88/08871 describes a method for destruction of plastics waste using microwaves. The waste is itself not susceptible to heating by microwave radiation, so it is placed in contact with carbonaceous material while being subjected to the microwave radiation.

EP 0 522 231 discloses a method and apparatus for treating infectious medical wastes (i.e. sterilisation). Microwave radiation is used to evaporate water present in the waste, and the waste is sterilised by the circulation of hot air. The temperature is held at a level at which substantial incineration and production of exhaust gases is avoided.

WO 05/073344 describes a microwave system for the resolution of waste rubber. The apparatus comprises a basket-type insert. The residue from the microwave process falls through the basket and is collected in a separate pan. There still exists a need for new techniques and systems for the depolymerisation of hydrocarbon material, which rationalizes the handling of the waste material and the byproducts. It should further be possible to process the exhaust gases produced at the depolymerisation process for further use for example for energy production. In particular, the system and process should be designed so as to tolerate the corrosive gases which are a by-product of such a depolymerisation.

SUMMARY OF THE INVENTION

The object of the present invention is to offer a solution to the above problem and to provide a method, apparatus and system for rational depolymerisation of hydrocarbon material on an industrial scale.

In its most general form, the present invention describes a method for depolymerisation of hydrocarbon material, said method comprising the steps of: a. providing a outer container, said outer container having an opening and a outer container lid for sealing said opening; b. loading hydrocarbon material into a support means; c. placing the support meanscontaining said hydrocarbon material into said outer container; d. sealing the opening of the outer container with said outer container lid; e. heating the hydrocarbon material with microwave or high-frequency radiation, to cause depolymerisation of the hydrocarbon material. f. allowing exhaust gases to escape from the outer container via a gas outlet; g. turning off the radiation; h. removing the support means from the outer container;

and repeating steps b.-h.

More specifically, the method according to the invention comprises the steps of: a. providing a outer container, said outer container having an opening and a outer container lid for sealing said opening; b. loading hydrocarbon material into a support means, said support means being designed so as to retain waste material; c. placing the support means containing said hydrocarbon material into said outer container; d. sealing the opening of the outer container with said outer container lid; e. heating the hydrocarbon material with microwave or high-frequency radiation, to cause depolymerisation of the hydrocarbon material. f. allowing exhaust gases to escape from the outer container via a gas outlet; g. turning off the radiation; h. removing the support means and the retained waste material from the outer container;

Optionally, steps b. - h. of this method may be repeated.

According to one embodiment of the method, in which the support means comprises an inner container, the method further comprises the step of sealing the inner container with an inner container lid, after hydrocarbon material has been loaded into said inner container. Particulate residue may be removed from the inner container by means of a vacuum cleaner, preferably after said inner container has been removed from the outer container. Preferably, the inner container is allowed to cool before particulate residue is removed. Solids such as metals may be removed by turning the support means upside- down. The inner container may be subjected to mechanical agitation before and/or while removing particulate residue.

The method may further comprise the step of providing a microwave or high-frequency radiation-absorbing substance which becomes warm upon irradiation without substantially altering form, in said support means or in said outer container. The microwave or high- frequency radiation-absorbing substance may be mixed with the hydrocarbon material or it may be contained in a separate receptacle. Additionally, the method may further comprise the step of providing an alkaline substance in the outer container or in said support means, in order to neutralize acid substances that may be formed. Additionally, the method may further comprise a step where a catalyst is added to the hydrocarbon material or is placed in the outer container or outer container lid to improve the quality of the gasoil produced.

The method according to the invention may also comprise the step of flushing the outer container with an inert gas before heating the hydrocarbon material, so that oxygen gas (which may cause uncontrolled combustion) is removed from the container. According to one aspect of this method, the exhaust gas which is produced by depolymerisation and which escapes from the outer container via gas outlet is fed into a gas purification apparatus.

Suitably, during microwave or high-frequency radiation irradiation, the gas in the outer container is maintained at a pressure above atmospheric pressure.

Preferably, said outer container comprises means for supply of microwave radiation or high-frequency radiation, said means for supply of microwave radiation or high-frequency radiation being shielded from the hydrocarbon material by a gas-impermeable, microwave-permeable material. Additionally, the gas-impermeable, microwave-permeable material may comprise an inner wall of the outer container.

In one embodiment, the present invention concerns a method for depolymerisation of hydrocarbon material, said method comprising the steps of: a. providing at least two outer containers, each of said outer containers having an opening and an outer container lid for sealing said opening ; b. connecting the outer containers in parallel to a gas purification apparatus; c. carrying out depolymerisation of hydrocarbon material in each of the at least two outer containers, said depolymerisation comprising steps b. - h. as described above, wherein depolymerisation is started non-simultaneously in said at least two outer containers, so that a substantially continuous flow of gas passes through the gas purification apparatus.

Suitably, the depolymerisation is carried out in such a way that the means for supply of microwave radiation or high-frequency radiation is shielded from the hydrocarbon material by a gas-impermeable, microwave-permeable material, and the depolymerisation is controlled so that the flow of gas through the gas purification apparatus is substantially constant.

According to this method, in which each support means comprises an inner container, the method may further comprise the step of sealing the inner container with an inner container lid, after hydrocarbon material has been loaded into said inner container. The method may then comprise the step of removing particulate residue from each inner container by means of a vacuum cleaner, preferably after said inner container has been removed from the outer container. Preferably, each inner container is allowed to cool before particulate residue is removed. Each inner container may be subjected to mechanical agitation before and/or while removing particulate residue.

In general terms, the present invention further concerns a system for depolymerisation of hydrocarbon material, comprising an array of at least two outer containers, each of said outer containers having an opening and an outer container lid for sealing said opening, each outer container or outer container lid being provided with a gas outlet and means for supply of microwave radiation or high-frequency radiation, each outer container being provided with a support means for receiving hydrocarbon material said outer containers being arranged in parallel such that the gas outlet of each outer container leads to the same gas purification apparatus.

More specifically, the system is used in the field of waste disposal and recycling, and the support means is designed so as to retain waste material,

Preferably, the outer container or outer container lid comprises a gas-impermeable, microwave-permeable material which is arranged so that said means for supply of microwave radiation or high-frequency radiation is shielded from the hydrocarbon material by the gas-impermeable, microwave-permeable material.

In the system as described above, each outer container or outer container lid may be further provided with a pressure valve, and a gas inlet for the supply of inert gas to the container. According to one aspect of this system, the support means can be removed from the outer container. According to one embodiment, the support means of the system comprises an inner container. In one variation, each of said outer containers further contains a receptacle for receiving a microwave or high-frequency radiation-absorbing substance.

The system may comprise a gas flow control unit adapted to detect the flow of exhaust gases escaping from the at least two outer containers, said gas flow control unit being arranged to control the means for supply of microwave radiation or high-frequency radiation to each outer container in response to the flow of exhaust gases. The gas flow control unit may be arranged so as to control the means for supply of microwave radiation or high-frequency radiation to each outer container so that a substantially continuous flow of exhaust gases is produced.

The present invention also relates to the use of a system as described herein for the depolymerisation of hydrocarbon material.

The present invention further refers to an apparatus for depolymerisation of hydrocarbon material in the field of waste disposal and recycling, said apparatus comprising an outer container, said outer container having an opening and an outer container lid for sealing said opening; said outer container or said outer container lid being provided with a gas outlet and means for supply of microwave or high-frequency radiation, said outer container being provided with a removable support means for receiving hydrocarbon material. Suitably, said support means is designed so as to retain waste material.

According to this embodiment, the outer container or the outer container lid may further comprise a gas inlet, and/or a pressure valve.

The gas outlet of the apparatus preferably leads to a gas purification apparatus. This gas purification apparatus suitably comprises a gas condenser. The outer container or the outer container lid may be provided with a further outlet for measurement of gas properties. According to one aspect of this embodiment, the outer container is provided with means which enables material to be emptied from the container. Suitably, the means for supply of microwave or high-frequency radiation is located in the walls or the floor of the outer container. The outer container or outer container lid may comprises a gas- impermeable, microwave-permeable material which is arranged so that said means for supply of microwave radiation or high-frequency radiation is shielded from the hydrocarbon material by the gas-impermeable, microwave-permeable material.

The present invention also relates to the use of an apparatus as described herein for the depolymerisation of hydrocarbon material.

DEFINITIONS

Depolymerisation

Depolymerisation is essentially the reverse process of polymerisation - large polymeric molecules are broken down into small molecules. For instance, a polymer having a molecular weight of a few thousand Daltons can be broken down into components having a molecular weight of e.g. less than 100 Daltons. These small molecules are usually given off in the form of gas or liquid, and can be used as fuel or raw material. Depolymerisation avoids wasting a material which is derived from a non-renewable resource (oil) and avoids the environmental problems inherent in conventional disposal methods (land-fill or burning).

Hydrocarbon material

According to this invention, the term "hydrocarbon materia!' encompasses a wide range of materials. Particular hydrocarbon materials which can be processed by the present invention include the following material types:

- synthetic polymers (e.g. polyalkenes, polyesters, polyamides, polystyrenes, polyurethanes, PVC, PTFE, nylon, etc.) natural polymers (e.g. rayon, natural rubber, textiles) - organic materials (e.g. wood, vegetable and animal matter, leather, fat, proteins, cellulose) liquid hydrocarbon materials (e.g. oils, sludge waste material).

Preferred hydrocarbon materials for processing according to the present invention are synthetic polymers. The hydrocarbon material may be a mixture of the above materials, or may be a mixture with other materials such as metals, ceramics, fillers, glass or other inorganic materials. Separation of the materials before submitting them to the process of the present invention is not necessary, as non-hydrocarbon materials will be relatively unaffected by the microwave or high-frequency radiation. Non-hydrocarbon materials such as metals or ceramics can be separated at the end of the process.

Microwave and high-frequency radiation

While microwaves generated at a frequency of 2.45 GHz are the most commonly used for heating purposes, other high-frequency radiation may be used for the purpose of the present invention. With "high-frequency" is meant frequencies mainly in the 1 MHz to 30 GHz range.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view of an apparatus for depolymerisation of hydrocarbon material. Figure 2 is a schematic view of an alternative apparatus for depolymerisation of hydrocarbon material.

Figure 3 shows a system for depolymerisation of hydrocarbon material comprising three apparatuses. Figure 4 shows an alternative embodiment adapted for depolymerisation of vehicle tyres Figure 5 illustrates the method for depolymerisation of hydrocarbon material.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 shows schematically an apparatus for depolymerisation of hydrocarbon material. The apparatus comprises an outer container 10, which is made from a heat-resistant material such as stainless steel or ceramics. The outer container 10 has an opening 11 and an outer container lid 12 for sealing said opening 11. The outer container lid 12 should seal the opening 11 sufficiently tightly so that gas, microwaves or high-frequency radiation and fine particulate matter cannot escape from the outer container 10.

The outer container 10 or outer container lid 12 is provided with a gas outlet 13. During depolymerisation, exhaust gases of the waste material evaporate and escape from the outer container 10 via this outlet 13. It is advantageous that the gas outlet 13 has a wide bore, as shown in Fig 1 , so that microwave radiation can diffuse into the outlet 13. For 2.45GHz microwaves, this means that the bore of the gas outlet 13 should be greater than 12.5cm in diameter. The fact that the microwaves can diffuse into the gas outlet 13 means that the outlet is kept at a temperature similar to that of the outer container and condensation of any components of the exhaust gases which condense at a relatively low temperature in the outlet 13 is avoided.

The outer container 10 or outer container lid 12 is further provided with means for supply 14,15 of microwave or high-frequency radiation. The means for supply of microwave or high-frequency radiation may be a wave guide 14 connected to a magnetron 15 which generates microwave or high-frequency radiation, said magnetron 15 being located outside the outer container 10. Microwave radiation is illustrated by the zigzag arrow in Fig. 1. In this case the microwaves or high-frequency radiation are preferably distributed by a rotating reflector (not shown) located adjacent the wave guide on the inside of the outer container lid 12 (alternatively the outer container 10). In an alternative embodiment the magnetron 15 is located on the outside of the outer container 10 or the outer container lid 12. Additionally, materials which reflect microwave or high-frequency radiation can be included in the outer container 10 to aid the distribution of radiation. A control unit 16 is provided for controlling the generation of microwaves or high-frequency radiation from the magnetron 15.

The container 10 is further provided with a support means 17 for receiving hydrocarbon material 18. The support means 17 for holding the hydrocarbon material 18 can be removed from the outer container 10, so that rapid and efficient recharging of the hydrocarbon material can be carried out. The support means 17 may rest on projections in the walls of the outer container 10, or on the floor of the outer container 10. Alternatively, the support means 17 may be suspended from the outer container lid 12. The support means 17 is preferably made of a material which reflects microwaves or high- frequency radiation.

In Figure 1 the support means 17 is in the form of an inner container 17' which may receive hydrocarbon material in any physical shape. This support means/inner container

17/17' may have a number of holes through which microwaves or high-frequency radiation can pass, however, the support means 17 should be designed so as to retain waste material. This allows waste material to be more readily packed into the support means

17, and means that all waste material is retained in the support means 17 after depolymerisation and bad odours are minimised.

The inner container 17' may be sealed with an inner container lid 12', after hydrocarbon material 18 has been loaded into said inner container 17'. If the inner container lid 12' is sealed before radiation is applied, the inner container lid 12' should be transparent to the radiation in question, e.g. a ceramic or glass lid. Escape of gas from the inner container 17' should not be hindered by the inner container lid 12'.

In a preferred embodiment, the means for supply of microwave radiation or high- frequency radiation 14,15 is shielded from the hydrocarbon material 18 by a gas- impermeable, microwave-permeable material 30. This may take the form of a window of such material which completely isolates the magnetron 15 from the gases which are a byproduct of the depolymerisation process (see Fig, 1). In such a way, damage to the radiation supply is reduced. The gas-impermeable, microwave-permeable material 30 is preferably arranged in the outer container 10 or the outer container lid 12. In an alternative embodiment (as shown in Figure 2) the gas-impermeable, microwave- permeable material 30 comprises an inner wall of the outer container 10, i.e. the outer container has a lining of the gas-impermeable, microwave-permeable material 30. The means for supply of microwave radiation or high-frequency radiation 14,15 projects through the walls of the outer container, but is protected from the corrosive gases in the container by the gas-impermeable, microwave-permeable material 30 which lines the outer container.

Suitable gas-impermeable, microwave-permeable materials 30 are ceramics, polymers and quartz glasses.

Furthermore, it is preferred that the apparatus comprises a plurality of means for supply of microwave radiation or high-frequency radiation 14,15 (see Fig. 2), i.e. at least 2, such as e.g. 3, 4 5, 6 or more means 14,15. To obtain the best balance between complexity of the apparatus and supply of a sufficient level of radiation within the apparatus, the apparatus preferably comprises six means for supply of microwave radiation or high-frequency radiation 14,15. In this way, smaller commercially-available radiation sources such as those in household microwave ovens can be used, leading to significant cost savings and ease of replacement in case of component failure. Using a plurality of radiation sources can provide the same depolymerising effect as one farge radiation source. Each means for supply of microwave radiation or high-frequency radiation 14,15 can be controlled by separate control units 16, or a single control unit 16 may be used to control a plurality of means 14,15 (as per Figure 2).

To further minimise damage to the means for supply of microwave or high-frequency radiation 14, 15, it is preferred that said means is located in the walls or the floor of the outer container 10, as per Figure 2. In this way, gases rising from the depolymerisation process will flow upwards and avoid the radiation sources.

Figure 4 shows an alternative support means 17 which is in the form of hooks or a rod fastened with a clinch-wire which holds the hydrocarbon material 18 to be depolymerised. The latter option is particularly suitable when vehicle tyres are to be depolymerised. In this case, the support means 17 includes a tray 19 which collects the products of depolymerisation. It is possible to mix or add a microwave or high-frequency radiation-absorbing substance, like elemental carbon, with the hydrocarbon material 18 in the support means 17 or in the outer container 10. This absorbs radiation and becomes hot, increasing the effectiveness of the depolymerisation process. As above, materials which reflect microwave or high- frequency radiation can be included in the support means 17 to aid the distribution of radiation.

The outer container 10 or the outer container lid 12 may further comprise a gas inlet 21.

The gas inlet 21 provides the possibility to flush the system with inert gas, as described below. Suitably, the gas outlet 13 leads to a gas purification apparatus 26. The gas purification apparatus 26 may comprise a gas condenser where gases are cooled to form liquids, and the resulting liquids and gases are separated. Alternatively or additionally, the gas produced by depolymerisation is broken down in a catalytic converter.

Furthermore, condensable components of the gas produced by depolymerisation may be purified by gravimetric separation. In the embodiment shown in Figure 1, gases leave the gas purification apparatus 26 as shown by arrow A, while liquids leave the gas purification apparatus 26 as shown by arrow B.

The outer container 10 or the outer container lid 12 may also comprise a pressure valve 23. This allows the pressure within the outer container 10 to be regulated, and acts as a safety measure if the pressure becomes too high. As described below, it is desirable that the outer container 10 is maintained at a pressure above atmospheric pressure.

The outer container 10 or the outer container lid 12 of the apparatus according to the invention may be provided with a further outlet 24 for measurement of gas properties. Measurement of gas properties may be carried out by a computer 25, and the gas properties investigated include, e.g. composition, moisture content or flammability.

The outer container 10 may be provided with means which enables material to be emptied from the container. This may simply require that the outer container 10 can be upturned, so that material can be emptied from the outer container. Alternatively, the outer container may be fitted with a second opening and door (not illustrated) through which material can be emptied. Figures 5a-d illustrate a method for depolymerisation of hydrocarbon material according to the present invention. A heat-resistant outer container 10 with an outer container lid 12 and a support means 17 for supporting hydrocarbon material 18 are provided as described above.

Hydrocarbon material 18 is loaded into the support means 17 (an inner container 17' in Fig 4a-d) and the support means 17 is placed into the outer container 10 (Figure 4a). The support means 17 is designed so as to retain waste material. In the case where the support means 17 comprises an inner container 17', it is desirable to seal the inner container 17' with an inner container lid 12', after hydrocarbon material 18 has been loaded into said inner container 17'. Particulate residue is then prevented from leaving the inner container 17'. Depending on the type of hydrocarbon material that is treated, an inner container 17' having a thin metal wall could be used. Escape of gas from the inner container 17' should not be hindered by the inner container lid 12'.

When the support means 17 has been placed in the outer container, the outer container lid 12 is placed on the container, which may be achieved by moving the outer container 10 sideways under a fixed outer container lid 12 and subsequently lifting it up against the outer container lid 12, sealing the opening of the outer container 10. A microwave or high-frequency radiation-absorbing substance may be present in the support means 17 as described above.

The presence of oxygen in the outer container 10 increases the risk of combustion rather than depolymerisation. A hazardous mixture of heat, flammable gases and oxygen may be obtained. In addition, depolymerisation in the presence of oxygen can lead to toxic byproducts. Oxygen may be present in the atmosphere, or may be produced upon irradiation of the hydrocarbon material. To reduce the amount of oxygen in the container (or eliminate it altogether) the outer container 10 may be flushed with an inert gas through gas inlet 21 before the hydrocarbon material 18 is heated. Suitable inert gases include carbon dioxide, nitrogen, noble gases or mixtures thereof.

The hydrocarbon material is then irradiated by microwaves (as illustrated by the zigzag arrow), suitably with a frequency of 2.45 GHz. Alternatively other high-frequency heating at other frequencies may be used. With "high-frequency" is meant frequencies mainly in the 1 MHz to 30 GHz range. During irradiation, the temperature within the container lies in the range 300-500⁰C, and preferred pressures within the container lie between 1 and 1.5 bar absolute pressure.

The temperature of the surface of the material thereby increases, and starts to char and thereby absorb microwaves or high-frequency radiation.

Heating of halogenated polymers (e.g. PVC, PTFE) to high temperatures releases acidic gases (HCI or HF). To overcome the corrosive effect of such gases, an alkaline substance may also be provided in the outer container 10 or the support means 17. Suitable alkaline substances are alkali hydroxides like sodium hydroxide, calcium oxides, hydroxides or carbonates.

Furthermore, during microwave irradiation, the interior of the outer container 10 is preferably maintained at a pressure above atmospheric pressure, so as to minimise leakage of atmospheric oxygen into the container. The depolymerisation step is illustrated in Figure 4b.

Exhaust gas produced by depolymerisation - which typically comprise water vapour and both condensable and non-condensable gases - may leave the container 10 and be fed into a gas purification apparatus 26 via gas outlet 13. Here, condensable components of the gas produced by depolymerisation may be condensed in a gas-condensing apparatus. Primarily water is condensed, but hydrocarbons are also transformed from gas to liquid in the later stages of the gas-condensing equipment. The liquid obtained from condensation is preferably purified by gravimetric separation. The warm air from the outer container 10 can be used to dry/pre-heat materials which are to be depolymerised.

In order to remove acidic components in the gas, these are absorbed in water with a pH appropriate for the gas. The non-condensable gas is dried to minimize the water content and, if required, carbon dioxide is also removed so as to obtain a combustible gas with properties suitable for energy production.

When depolymerisation is complete the radiation is turned off. Complete depolymerisation in the outer container 10 is indicated by the temperature, carbon monoxide content etc. falling. The magnetron is turned off and cold air may be introduced in order to cool the apparatus to <60°C. The support means 17 and the retained waste material are removed from the outer container 10 and the apparatus is ready to be used again with a fresh batch of hydrocarbon material 18. Optionally, a new support means 17 which has been filled with hydrocarbon material may be placed into the container and a new treatment sequence starts.

The residue remaining in the support means 17 after irradiation is usually fine particulate matter, plus any non-hydrocarbon material (inorganic material) such as metal, ceramic, elemental carbon or glass. The metals can be suitably separated with magnetism, for recycling and the carbon can be put to good use, inter alia as an absorbent. The residue may also comprise elemental carbon, if this is used as the microwave or high-frequency radiation-absorbing substance.

After depolymerisation, the inner container 17' is removed from the outer container 10 and a new inner container 17' filled with hydrocarbon material put into the outer container 10. Fine particulate matter is thus prevented from escaping into the surroundings, and the problems associated with dust and odour are minimised. Particulate residue can be removed from the inner container 17' by means of a vacuum cleaner 27 (Fig. 4d). Preferably, the inner container 17' is removed from the outer container 10 before particulate material is removed by the vacuum cleaner. Preferably, the inner container 17' is cooled down to room temperature before it is emptied.

If an inner container lid 12' was not placed on the inner container 17' before depolymerisation, this may be carried out after turning off the radiation but before removing the support means 17 from the outer container 10.

To improve the vacuuming process, the inner container 17¹ can be subjected to mechanical agitation before and/or while removing particulate residue. This dislodges the residue. Mechanical agitation can be performed by subjecting the support means 17 to physical forces or displacement. As a preferred alternative, mechanical agitation can be performed by subjecting the support means 17 to short, rapid changes in pressure, causing the gas in the support means 17 to expand and contract rapidly.

If supplied to a combustion-based power station, the gases which are purified as described above can produce the electricity required to drive the magnetron, which in turn generates the microwaves or high-frequency radiation. If the gas produced by depolymerisation is not to be used as a fuel, it may be broken down in a catalytic converter to produce heat. Alternatively the purified condensed oil or gasoil may be a fuel for electricity production.

The method according to this embodiment allows simple operation, short turnaround times and lower investment costs than continuous pyrolysis.

Figure 3 illustrates a system for depolymerisation of hydrocarbon material 18. The system comprises an array at least two (three in Figure 3) outer containers 10, each of said containers having an opening 11 and an outer container lid 12 for sealing said opening 11 as described above. Each outer container 10 or outer container lid 12 is provided with a gas outlet 13 and means for supply of microwave or high-frequency radiation 14, 15. A magnetron 15 may alternatively be provided inside the outer container 10 or outer container lid 12. Each outer container 10 is also provided with a support means 17 for supporting hydrocarbon material 18 and which is designed so as to retain waste material. The outer containers 10 are arranged in parallel such that the gas outlet 13 of each container leads to the same gas purification apparatus 26.

It is pointed out that while this embodiment shows three outer containers 10 connected in parallel to the gas purification apparatus 26, any number from two outer containers may be provided. Preferably the number of outer containers 10 is between two and six.

Each outer container 10 or outer container lid 12 may be provided with the same kind of components as described above in connection with Figures 1 and 2. In particular, it is advantageous that the outer container 10 or outer container lid 12 comprises a gas- impermeable, microwave-permeable material 30 which is arranged so that the means for supply of microwave radiation or high-frequency radiation 14,15 is shielded from the hydrocarbon material 18 by the gas-impermeable, microwave-permeable material.

Preferably the support means 17 can, in this embodiment, be removed from said outer container 10, so that rapid and efficient recharging of the hydrocarbon material can be carried out. However in an alternative embodiment, charging and recharging of the container is provided in other ways. The gas purification apparatus 26 in this system may comprise a gas condenser, a catalytic converter and/or means for gravimetric separation, as described for the apparatus in Figs. 1 and 2.

Depolymerisation of hydrocarbon material is carried out in each of the at least two outer containers 10 as described in the method steps above. It is preferred that depolymerisation is started up non-simultaneously in at least two outer containers 10, in order to produce a substantially continuous flow of gas passing through the gas purification apparatus 26.

Typically three or four parallel localised outer containers 10 are started up at equally as many different times, so as to minimise the momentary load on the gas purification equipment 26, and to obtain a more continuous production of combustible gas. No depolymerisation of the material, and thereby no production of combustible gas, occurs until the temperature in the outer container reaches 100⁰C and all the water vaporises. During depolymerisation, the pressure in each outer container is regulated, so that a weak overpressure is obtained, which counteracts any air leaking into the container.

The most suitable number of outer containers depends on the type of hydrocarbon material which is to be treated, but is preferably between two and six. In smaller plants, two outer containers may be used and operated alternately. In a large plant with material that evaporates rapidly, it may be possible to run as many as six outer containers in parallel. The advantage with many outer containers is that the production of gas is more constant and gas processing and cleaning is then simpler. Using the gas for electricity production is also easier in this case. If - for example - six outer containers are used, at any given time, four can be carrying out depolymerisation, a fifth can be being loaded with hydrocarbon material and a sixth can be being cleaned.

In a preferred aspect of this particular method, the depolymerisation is controlled so that the flow of gas through the gas purification apparatus 26 is substantially constant. This is easily carried out, as stopping the microwave radiation immediately removes the heating source and depolymerisation quickly stops. This is in contrast to non-microwave based processes, in which stopping depolymerisation requires a slow cooling process. Thus, an increase in the flow of gas through the gas purification apparatus 26 can be obtained by increasing the power of the microwave radiation, and vice versa. A gas flow control unit 28 can be used to monitor the flow of gas through the gas purification apparatus 26 and to send signals to the control units 16 controlling the magnetrons 15 for each outer container 10 to adjust the power of the microwave or high-frequency radiation accordingly.

The present invention also relates to the use of an apparatus and a system as described herein for the depolymerisation of hydrocarbon material.

In one aspect of the invention the apparatus is built as a mobile device, which for example may stand on a truck platform or in a frame that is lifted off from a truck, in which the other equipment for depolymerisation operations is located.

The scope of the present invention should not be limited by the description and embodiments described herein, but rather by the limitations set out in the appended claims.

Claims

1. A method for depolymerisation of hydrocarbon material (18) in the field of waste disposal and recycling, said method comprising the steps of: a. providing a outer container (10), said outer container having an opening (11) and a outer container lid (12) for sealing said opening; b. loading hydrocarbon material (18) into a support means (17), said support means (17) being designed so as to retain waste material; c. placing the support means (17) containing said hydrocarbon material into said outer container (10); d. sealing the opening (11) of the outer container (10) with said outer container lid (12); e. heating the hydrocarbon material (18) with microwave or high-frequency radiation, to cause depolymerisation of the hydrocarbon material. f. allowing exhaust gases to escape from the outer container (10) via a gas outlet (13); g. turning off the radiation; h. removing the support means (17) and the retained waste material from the outer container (10);

2. A method according to claim 1, wherein the support means (17) comprises an inner container (17'), characterised in that it further comprises the step of sealing the inner container (17') with an inner container lid (12'), after hydrocarbon material (18) has been loaded into said inner container (17').

3. A method according to claim 2, characterised in that it further comprises the step of removing particulate residue from the inner container (17') by means of a vacuum cleaner (27), preferably after said inner container (17') has been removed from the outer container (10).

4. A method according to claim 3, characterised in that the inner container (17') is allowed to cool before particulate residue is removed.

5. A method according to claim 3 or 4, characterised in that the inner container (17') is subjected to mechanical agitation before and/or while removing particulate residue.

6. A method according to any of claims 1-5, characterised in that it further comprises the step of providing a microwave or high-frequency radiation-absorbing substance which becomes warm upon irradiation without substantially altering form, in said support means (17), alternatively in said outer container (10).

7. A method according to any of claims 1-6, characterised in that it further comprises the step of providing an alkaline substance in said outer container (10) or said support means (17).

8. A method according to any of claims 1-7, characterised in that it further comprises the step of flushing the outer container (10) with an inert gas before heating the hydrocarbon material (18).

9. A method according to any of claims 1-8, characterised in that exhaust gas which is produced by depolymerisation and which escapes from the outer container (10) via a gas outlet (13) is fed into a gas purification apparatus (26).

10. A method according to any of claims 1-9, characterised in that, during microwave irradiation, the outer container (10) is maintained at a pressure above atmospheric pressure.

11. A method according to any of claims 1-10, characterised in that said outer container comprises means for supply of microwave radiation or high-frequency radiation (14, 15), said means for supply of microwave radiation or high-frequency radiation being shielded from the hydrocarbon material by a gas-impermeable, microwave-permeable material (30).

12. A method according to claim 11 , characterised in that the gas-impermeable, microwave-permeable material (30) comprises an inner wall of the outer container

(10).

13. A method for depolymerisation of hydrocarbon material (18) as claimed in any of claims 1-12, said method comprising the steps of: a. providing at least two outer containers (10), each of said outer containers having an opening (11) and an outer container lid (12) for sealing said opening ; b. connecting the outer containers (10) in parallel to a gas purification apparatus (26); c. carrying out depolymerisation of hydrocarbon material in each of the at least two outer containers, said depolymerisation comprising steps b. - h. as described in claim 1 wherein depolymerisation is started non-simultaneously in said at least two outer containers (10), so that a substantially continuous flow of gas passes through the gas purification apparatus (26).

14. A method according to claim 13, wherein the depolymerisation is carried out in such a way that the means for supply of microwave radiation or high-frequency radiation (14, 15) is shielded from the hydrocarbon material (18) by a gas- impermeable, microwave-permeable material (30).

15. A method according to claim 13 or 14, wherein the depolymerisation process is controlled so that the flow of gas through the gas purification apparatus (26) is substantially constant.

16. A method according to claims 13-15, wherein each support means (17) comprises an inner container (17'), characterised in that it further comprises the step of sealing each inner container (17') with an inner container lid (12'), after hydrocarbon material (18) has been loaded into said inner container (17').

17. A method according to claim 16, characterised in that it further comprises the step of removing particulate residue from each inner container (17') by means of a vacuum cleaner (27), preferably after said inner container (17') has been removed from the outer container (10).

18. A method according to claim 16, characterised in that each inner container (17') is allowed to cool before particulate residue is removed.

19. A method according to claim 17 or 18, characterised in that each inner container (17¹) is subjected to mechanical agitation before and/or while removing particulate residue.

20. A system for depolymerisation of hydrocarbon material (18) in the field of waste disposal and recycling, comprising an array of at least two outer containers (10), each of said outer containers having an opening (11) and an outer container lid (12) for sealing said opening, each outer container (10) or outer container lid (12) being provided with a gas outlet (13) and means for supply of microwave radiation or high-frequency radiation (14, 15), each outer container being provided with a support means (17) for receiving hydrocarbon material (18), said support means (17) being designed so as to retain waste material, said outer containers (10) being arranged in parallel such that the gas outlet (13) of each outer container (10) leads to the same gas purification apparatus (26).

21. A system according to claim 20, characterised in that said outer container (10) or outer container lid (12) comprises a gas-impermeable, microwave-permeable material (30) which is arranged so that said means for supply of microwave radiation or high-frequency radiation (14,15) is shielded from the hydrocarbon material (18) by the gas-impermeable, microwave-permeable material (30).

22. A system according to claim 20 or 21 , characterised in that each outer container (10) or outer container lid (12) is further provided with a pressure valve (22).

23. A system according to any of claims 20-22, characterised in that each outer container (10) or outer container lid (12) is further provided with a gas inlet (21).

24. A system according to any of claims 20-23, characterised in that the support means (17) can be removed from said outer container (10).

25. A system according to any of claims 20-24, characterised in that the support means (17) comprises an inner container (17').

26. A system according to any of claims 20-25, characterised in that a gas flow control unit (28) is provided to detect the flow of exhaust gases escaping from the at least two outer containers (10), said gas flow control unit being arranged to control the means for supply of microwave radiation or high-frequency radiation (14, 15) to each outer container in response to the flow of exhaust gases.

27. A system according to claim 26, characterised in that said gas flow control unit (28) is arranged so as to control the means for supply of microwave radiation or high-frequency radiation (14, 15) to each outer container (10) so that a substantially continuous flow of exhaust gases is produced.

28. Use of a system according to any of claims 20-27 for the depolymerisation of hydrocarbon material (18).

29. Apparatus for depolymerisation of hydrocarbon material (18) in the field of waste disposal and recycling, said apparatus comprising an outer container (10), said outer container having an opening (11) and an outer container lid (12) for sealing said opening; said outer container (10) or said outer container lid (12) being provided with a gas outlet (13) and means for supply of microwave or high- frequency radiation (14, 15), said outer container (10) being provided with a removable support means (17) for receiving hydrocarbon material (18) characterised in that said support means (17) is designed so as to retain waste material.

30. Apparatus according to claim 29, characterised in that the outer container (10) or the outer container lid (12) further comprises a gas inlet (21).

31. Apparatus according to any of claims 29-30, characterised in that the outer container (10) or the outer container lid (12) further comprises a pressure valve (22).

32. Apparatus according to any of claims 29-31, characterised in that the gas outlet (13) leads to a gas purification apparatus (26).

33. Apparatus according to any of claims 29-32, characterised in that the outer container (10) or the outer container lid (12) is provided with a further outlet (24) for measurement of gas properties.

34. Apparatus according to any of claims 29-33, characterised in that the outer container (10) is provided with means which enables material to be emptied from the outer container.

35. Apparatus according to any of claims 29-34, wherein the support means (17) comprises an inner container (17').

36. Apparatus according to any of claims 29-35, wherein the means for supply of microwave or high-frequency radiation (14, 15) is located in the walls or the floor of the outer container (10).

37. Apparatus according to any of claims 29-36, characterised in that said outer container (10) or outer container lid (12) comprises a gas-impermeable, microwave-permeable material (30) which is arranged so that said means for supply of microwave radiation or high-frequency radiation (14,15) is shielded from the hydrocarbon material (18) by the gas-impermeable, microwave-permeable material (30).

38. Use of an apparatus as claimed in any of claims 29-37 for the depolymerisation of hydrocarbon material.