WO2004072163A1

WO2004072163A1 - A method and a device for continuous conversion of polyolefinic plastics wastes

Info

Publication number: WO2004072163A1
Application number: PCT/PL2003/000032
Authority: WO
Inventors: Zbigniew Tokarz; Marek Stelmachowski
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-02-17
Filing date: 2003-04-02
Publication date: 2004-08-26
Anticipated expiration: 2005-08-17
Also published as: PL199825B1; AU2003303917A1; EP1594916A1; PL358774A1

Abstract

The present invention concerns a method for continuous conversion of plastics wastes, comprising continuous loading the charge, plastifying it, bringing it to the liquid state and converting it catalytically, characterized in that the whole process, from charge loading to collecting of the gaseous product and removing impurities, is conducted in a single stage and in a single internal vessel (1a), of an integrated, melting - heat exchanging - reactor devise with a vertical arrangement, wherein plastified and liquefied charge forms a uniform block of the charge mass moving downwards gravitationally. The present invention concerns also a device for continuous conversion of plastics wastes, characterized in that it constitutes a modular, integrated, melting box - heat exchanger - reactor device with a vertical arrangement, for a single stage conducting of the whole process of thermo-catalytic conversion of plastic wastes, from the charge loading to collecting of gaseous product and removing impurities, in a single internal vessel (1a).

Description

A METHOD AND A DEVICE FOR CONTINUOUS CONVERSION OF POLYOLEFINIC PLASTICS WASTES

Field of the invention

The present invention concerns a method for continuous conversion of polyolefinic plastics wastes such as for example polyethylene or polypropylene, to the form of liquid mixture of non-saturated and saturated hydrocarbons, constituting the high quality paraffin. In particular the present invention relates to the single-stage industrial scale process for the continuous thermo-catalytic conversion of highly contaminated polyolefinic plastics wastes in a single vessel. The present invention relates also to a device to realize the said method.

Background of the invention

The problem of effectively utilizing polyolefinic wastes has become very urgent recently and many documents relate to this field.

The Polish patent application P 336,773 teaches a method for conversion of plastics wastes comprising thermic or catalytic cracking of plastics wastes in the presence of the waste catalysts from fluidal catalytic cracking or natural aluminosilicates in the reactor, wherein gaseous or liquid products of cracking are directed to an evaporator directly after cracking, where they are mixed with hydrogen, evaporated and sent to a hydrogenation reactor. In the reactor the olefines contained in the hydrogen-hydrocarbons mixture a rehydrogenated in the presence of typical hydrogenation catalysts such as palladium or platinum, tungsten-nickel and molybdenum-nickel on solid carriers.

Additionally, the Polish patent application P 314,409 presents a method for recycling waste thermoplastic materials, in particular polyolefines, polystyrene, polycarbonates, saturated polyesters, polyacetals, polyphenylene oxide, polyacrylic esters, polyvinyl chloride and their copolymers and thermopolymers and their mixtures. It comprises melting comminuted and mechanically cleaned waste thermoplastic materials, containing at least 20% by weight polyolefines (or with addition of polyolefines), preferably polyethylene or polypropylene, with high-molecular compounds of 2-oxazoline, preferably methylmaleate of ricynyl-2-oxazoline and organic superoxides. If the mixture of waste thermoplastic materials does not contain any polyolefines it can be recycled in a two-stage process. In the first stage polyolefines are melted with high-molecular compounds of 2- oxazoline, preferably methylmaleate of ricynyl-2-oxazoline and organic superoxides. In the second stage so treated polyolefines are melted with comminuted and mechanically cleaned waste thermoplastic materials.

Also the Polish patent application P 339,821 discloses a method for manufacturing aliphatic hydrocarbons from a preselected mixture of waste plastics, particularly from unreusable packaging. This method for manufacturing aliphatic hydrocarbons in a thermic decomposition reaction comprises heating the mixed mass of waste thermoplastic materials, preferably after separating its lighter than water fraction and (possibly) the preliminary cleaning, to the temp. 320-400 °C at the pressure 0.008-3.5 MPa and subsequently distillating it under the same conditions. The obtained product can be separated and purified by known methods.

There are also other relevant documents.

The US 4,108,730 patent (Chen et al.) describes a process for converting relatively ash-free solid polymeric wastes to more valuable liquid, solid, and gaseous products which comprises mixing rubber and/or plastic wastes at high temperatures in a refractory petroleum stream and catalytically cracking the mixture. A disclosed set up comprises : a shredder, a grinder, a metals separation unit, a mixer/dissolver, a reactor, a catalyst regenerator and a distillation vessel.

The international publication WO 01/05908 (Xing) relates to a process for producing gasoline and diesel from waste plastics and/or heavy oil and comprises the steps of a) a mixing waste plastics and/or heavy oil with a first catalyst in a pyrolysis reactor at high temperature to carry out a pyrolysis and a first catalytic cracking; and (b) introducing the products in step (a) into a fixed bed to perform a second catalytic cracking with a second catalyst. The process -f-urther comprises the step (c) recycling the first catalyst in the reaction.

The European Patent Specification EP) 276081 (Saito et al.) discloses a process for preparing a normally liquid hydrocarbon product which comprises thermally cracking a plastics material in the molten liquid phase and catalytically convertion the vaporous product thereby generated by contact at 200-350 ° C with a zeolite having a constraint index between 1 and 12.

Additionally US 4,942,022 (Kasai et al.) a catalytic reactor includes a reactor vessel, a catalyst bed and at least two heat exchangers. The catalyst bed and heat exchangers are arranged coaxially with the central axis of a reactor vessel and substantially at the same height. Besides, the Polish patent PL 99,486 describes the device for conversion of plastics wastes comprising a boiler for melting the waste, a reactor, provided with a mixer and a supply pomp, for the thermic decomposition of the waste and product storage tank having a cooler and a burner, wherein the device is also equipped with the cooling tank to cool the product directed to the burner.

The realized processes for the conversion of plastics wastes have the process of catalytic conversion carried out exclusively in the reactor. Such processes require maintaining high pressure and using large quantities of catalyst. The charge treated by those processes requires preliminary comminution, purification, phase separation, addition of hydrogen or mixing with depolymerization facilitation agents. The chemical plant hardware is exposed to strongly corrosive agents. Most of the disclosed methods have never been executed in the form of industrial scale production, as witnessed by the laboratory scale examples given in the publications. The disclosed catalytic methods require costly catalysts and do not allow for the direct conversion into high grade mixture of non-saturated and saturated hydrocarbons.

Besides, the known devices for the conversion of plastics wastes do not have an integrated modular construction nor are they suitable for conducting the whole process of the conversion of plastics wastes on the industrial scale (small or medium) in a single reaction vessel. The known devices are susceptible to corrosion. They are usually very complex and require many auxiliary tanks, pumps, heaters etc. for each active apparatus in the plant.

It is an aim of the present invention to provide a method for continuous conversion of polyolefinic plastics wastes, and a device to realize the said method, without the above mentioned drawbacks. In particular, it is the aim of the present invention to provide the said method and the said device specially for the industrially scaled, ecological and cheap continuous conversion of polyolefinic wastes directly into the mixture of non-saturated and saturated hydrocarbons in a single modular reaction vessel.

The summary of the invention

These objects are achieved by a method for continuous conversion of plastics wastes, comprising continuous loading the charge, plastifying it, bringing it to the liquid state and converting it catalytically, as expressed in claim 1, characterized in that the whole process, from charge loading to collecting the gaseous product and removing impurities, is conducted in a single stage and in a single internal vessel of an integrated, melting box- heat exchanger - reactor device with a vertical arrangement, wherein plastified and liquefied charge forms a uniform block of the charge mass moving downwards gravitationally.

A device for continuous conversion of plastics wastes, as expressed in claim 14, characterized in that it constitutes a modular integrated melting box - heat exchanger - reactor device with a vertical arrangement, for a single stage conducting of the whole process of thermo-catalytic conversion of plastics wastes, from the charge loading to collecting the gaseous product and removing impurities in a single internal vessel.

Advantageous features have been presented in the sub claims 2-13 and 15-34 accordingly dependent on independent claims 1 and 14.

Brief description of the drawings

The present invention will be described in detail in advantageous embodiments with reference to the attached diagrammatic drawings, where Fig.l shows the front section view of the present device and Fig.2 shows the cross-section view of the present device.

Detailed description of the invention

As shown in Fig.l and Fig.2, the charge is placed in the chute 20 of the loading press 21 and then, through the connection 19, in the transport conduit 18 connected to the melting box 10 of the internal vessel la. The charge material is compacted and formed in the way enabling its transporting into the device with the simultaneous removal, from it, of air and water.

The transport conduit 18 after having been filled with the compressed charge material ensures the sufficient sealing for the hydrocarbon vapours. The melting box 10 passes through the heating chamber 17 of the charge intake, where its walls are heated to the temperature of, preferably, 120 °C. The charge material is then supplied to the space between the head 11 a^d the Il-nd stage pipe heat exchanger chamber unit 14. In this space it is heated and partially dissolved by the hydrocarbon vapours filling the whole interior of the device. The surface of the pipes of the Il-nd stage pipe heat exchanger chamber unit 14 is heated by means of the combustion gasses to the temperature of, preferably, 420 °C. Owing to the presence of the pipes, the heated and partially melted charge material is divided into a number of narrow streams with the width of, preferably, 50 to 70 mm. After this division the charge material is moved towards the pipes of the I-st stage pipe heat exchanger chamber unit L5 by means of the forces of gravitation and the press pushing. Both the I-st and the Il-nd stage of the charge material melting comprise, preferably, two rows each of horizontal pipes with an external diameter, preferably, 120 to 140 mm and the wall thickness, preferably, 3 to 4 mm. The temperature of the pipes of the I-st stage pipe heat exchanger chamber unit 15 is, preferably, 440 to 490 °C. The distances between the pipes at this stage are also, preferably, 50 to 70 mm. Advantageously the pipes belonging to the consecutive rows in the exchanger are shifted in relation to the pipes of previous rows so that the axis of symmetry of each shifted pipe is placed exactly in the middle of the distance between the two pipes placed above it.

The charge material after passing through both chambers of the heat exchanger, under the influence of the gravitational forces, falls into the reactor chamber 8. The bi-convex bottom 32 of the reactor chamber 8 is constructed out of two 120 degrees cylindrical sections with the diameter of, preferably, 600 mm and the length 1200 mm, which are made of the nickel alloy HAYNES HR-120 with the thickness of, preferably, 10 mm and are separated with the stiffener partition 29.

In the axes of symmetry of the cylindrical sections of the bottom 32 there are mounted agitators 22 driven by the separate moto-reductor 24 each and they rotate with the constant speed of 15 to 20 rpm. The stability of the bottom temperature and the steady collection of heat from its surface is ensured by a layer of liquid metal 33 with the temperature of melting, preferably, 270 to 300 °C. The thickness of metal layer in the hollows of the sections of the bottom 32 is, preferably, no more than 50 to 70 mm. After processing of the plastics wastes the gaseous product is collected by means of the conduit 35.

The removal of impurities introduced into the device together with the charge material is enabled by two cleaning units each comprising the impurities feeder 30, displaceable partition 31, the screw conveyer with its housing 25 for removing the impurities from the reactor chamber 8, connecting lock 26 and impurities receptable 28. The screw conveyer with its housing 25 is driven by the hand crank 27. The heat, necessary to carry out the process in the heat exchanger chambers 14, _15 and the reactor chamber 8, is provided by the system comprising a burner fed for example with the generator gas obtained out of the bio-mass gas generator.

In the disccussed example of embodiment a local brand combustion gas generator (designated AZS-automatic wood combustion unit) with the power output of lOOkW was used, having the combustion chamber 2 with the roof 4 constituting a heat equalizing baffle. The roof 4 contains the bores 3, preferably 16 to 20 of them, with a diameter, preferably 80 to 100mm. The combustion gases pass through the bores 3 from the combustion chamber 2 to the heat distributing chamber 5, which is supporting the module of the reactor chamber 8. The combustion gases, after giving away some of their heat to the interior of the reactor chamber 8, move by means of the passage 7 to the heat exchanger giving away their heat in the heat exchanger pipe chamber units 14 and 15. Then they heat the melting box 10 placed in the heating chamber 17 before getting into the chimney conduit 12. The flow regulating throttle 9 enables maintaining the required pipe surface temperatures. The process thermal stability and limiting the heat losses are provided by the heating unit housing 1, thermal side isolation 6 and thermal top isolation 13. Cleaning of the module of the heat exchanger and the module of the reactor chamber 8 are eanbled and provided by the system of clamps 16. Removal of the clamps 16 enables separating the head H from the module of the heat exchanger and the module of the heat exchanger from the module of the reactor chamber 8.

The housing of the reactor chamber 8 is constructed in the form of a cuboid with dimensions 2670x1250x1120mm. Its sides are made of heat- and acid-resistant steel H25N20S2 with the thickness, preferably, 8 to 10mm. The rigidity of this construction is provided by the external skeleton 34 in the form of a grid made of steel sheet H20N12S2, with the thickness, preferably, of 8 to 10mm and the dimensions 130x130x100mm.

The module of the heat exchanger is constructed similarly to the module of the reactor chamber 8 housing and is in the form of a cuboid with dimensions 1450x1250x940mm and walls made of steel sheet H20N12S2, with the thickness, preferably, of 8mm. The rigidity of this construction is provided by the external skeleton 23 in the form of a grid made of steel sheet 18G2A, with the thickness of 8mm and the dimensions 130x130x100mm. The transport conduit 18 of the charge inlet has got the rectangular cross-section with dimensions, preferably, 200x400mm and the length 500 to 700mm. It ends with the connection 19 and is made of steel sheet 1H18N9T, with the thickness, preferably, of 8mm. The connection 19 leads to the loading press 2 feeding the charge to the present device.

Claims

1. A method for continuous conversion of plastics wastes, comprising continuous loading the charge, plastifying it, bringing it to the liquid state and converting it catalytically, characterized in that the whole process, from charge loading to collecting the gaseous product and removing impurities, is conducted in a single stage and in a single internal vessel (la), of an integrated, melting box - heat exchanger - reactor device with a vertical arrangement, wherein plastified and liquefied charge forms a uniform block of the charge mass moving downwards gravitationally.

2. A method according to claim 1, characterized in that the charge is loaded under pressure into the transport conduit (18) situated under the head (IT) of the internal vessel (la).

3. A method according to claim 2, characterized in that the charge from the transport conduit (18) is moved through the melting box (10) to the Il-nd stage pipe heat exchanger chamber unit (14) with the pipe surface temperature, praferably, about 420 °C.

4. A method according to claim 3, characterized in that the charge in the Il-nd stage pipe heat exchanger chamber unit (14) separates into a number of narrow streams.

5. A method according to claim 4, characterized in that the charge from the Il-nd stage pipe heat exchanger chamber unit (14) is gravitationally and under the pressure transported to the I-st stage pipe heat exchanger chamber unit (15) with the pipe surface temperature, praferably, 440 to 490 °C.

6. A method according to claim 5, characterized in that the charge after passing the I-st stage pipe heat exchanger chamber unit (15) gravitationally (free) falls into the reactor chamber ( 8).

7. A method according to claim 6, characterized in that the charge in the reactor chamber (8) gets into contact with the layer of liquid metal (33).

8. A method according to claim 7, characterized in that the layer of liquid metal (33) consists of an alloy with the temperature of melting 270 to 300 °C.

9. A method according to claim 1, characterized in that a catalyst in the form of a carrier with aluminium oxide, formed on its surface in the high-temperature process, is added to the charge.

10. A method according to claim 1, characterized in that the internal vessel (la) of the integrated, melting box- heat exchanger - reactor device is heated from all its sides, by means of heat carrier, in a controlled way.

11. A method according to claim 10, characterized in that the intensity of heating is controlled by means of the flow regulating throttle (9).

12. A method according to claim 1, characterized in that the liquefied charge is intensively mixed in the bottom area of the internal vessel (la) by means of the two multi-rotor horizontal agitators (22).

13. A method according to claim 1, characterized in that impurities are periodically removed by means of a screw conveyer system direstly to the placed mobile impurities receptable (28).

14. A device for continuous conversion of plastics wastes, characterized in that it constitutes a modular, integrated, melting box - heat exchanger - reactor device with a vertical arrangement, for a single stage conducting of the whole process of thermo- catalytic conversion of plastics wastes, from the charge loading to collecting the gaseous product and removing impurities, in a single internal vessel (la).

15. A device according to claim 14, characterized in that it comprises the heating unit and the internal vessel (la) surrounded by the heat distributing system and thermal isolation.

16. A device according to claim 15, characterized in that the heating unit comprises the combustion chamber (2) with the roof (4) containing the bores (3), separating it from the heat distributing chamber (5) situated under the bottom of the internal vessel (la).

17. A device according to claim 16, characterized in that the bores (3) counting, preferably, 16 to 20, are arranged symmetrically in a number of rows and are, preferably, 80 to 100mm in diameter.

18. A device according to claim 16, characterized in that the combustion chamber (2) and the heat distributing chamber (5) are surrounded by the isolating ceramic heating unit housing (1).

19. A device according to claim 15, characterized in that the internal vessel (la) is of modular construction and comprises, counting from the top, the module of the head (11) and the transport conduit (18), the integrated module of the Il-nd stage pipe heat exchanger chamber unit (14) and the I-st stage pipe heat exchanger chamber unit (15) and the module of the reactor chamber (8).

20. A device according to claim 18, characterized in that the consecutive modules of the internal vessel (la) are connected by means of the system of fixing clamps (16).

21. A device according ,to claim 18, characterized in that the module of the head (11) and the transport conduit (18) is provided with the melting box (10) and the transport conduit (18) is connected by means of the connection (19) with the loading press (21).

22. A device according to claim 20, characterized in that the loading press (21) constitutes a two-stroke pneumatic press.

23. A device according to claim 18, characterized in that the integrated module of the Il- nd stage pipe heat exchanger chamber unit (14) and the I-st stage pipe heat exchanger chamber unit (15) includes the external skeleton (23) in the form of a reinforcing grid.

24. A device according to claim 18, characterized in that the integrated module of the Il- nd stage pipe heat exchanger chamber unit (14) and the I-st stage pipe heat exchanger chamber unit (15) includes the set of the Il-nd stage pipes and the set of the I-st stage pipes.

25. A device according to claim 24, characterized in that both the integrated module of the Il-nd stage pipe heat exchanger chamber unit (14) and the I-st stage pipe heat exchanger chamber unit (15) include at least two rows each of horizontal, parallel and equidistant pipes, wherein the. distances between pipes are, preferably, 50 to 70mm, pipe external diameters are, preferably, 120 to 140mm and the thickness of pipe walls is, preferably, 3 to 4mm.

26. A device according to claim 24, characterized in that the pipes in the consecutive rows, both in the Il-nd stage pipe heat exchanger chamber unit (14) and in the I-st stage pipe heat exchanger chamber unit (15), are shifted so that the axes of symmetry of the pipes in the consecutive row are placed symmetrically in the centers of the distances between the pipes of the previous row.

27. A device according to claim 18, characterized in that the module of the reactor chamber (8) includes the external skeleton (34) i the form of a reinforcing grid.

28. A device according to claim 18, characterized in that the module of the reactor chamber (8) includes the bi-convex bottom (32) in the form of two 120 degrees cylindrical sections with the stiffener separator (29) between them, wherein the bottom (32) is made, preferably, of nickel alloy sheet, with the thickness, preferably, at least 10mm.

29. A device according to claim 28, characterized in that in the axes of the cylindrical sections of the bi-convex bottom (32) there are placed horizontal, multi-rotor, padle agitators (22), preferably driven by means of a separate moto-reductor each.

30. A device according to claim 18, characterized in that the module of the reactor chamber (8) includes two cleaning units situated at its sides.

31. A device according to claim 30, characterized in that each of the cleaning units includes the impurities feeder (30), the displaceable partition (31), the screw conveyer with its housing (25) and the connecting lock (26).

32. A device according to claim 30, characterized in that the connecting lock (26) forms a connection between the cleaning unit and the placed mobile impurities receptable (28).

33. A device according to claim 30, characterized in that each of the cleaning units includes the hand crank (27).

34. A device according to claim 15, characterized in that the heat distributing system comprises the main combustion gases passage (7), the flow regulating throttle (9), the heating chamber (17) situated around the internal vessel (la) and the chimney conduit

02).