WO2023078965A1

WO2023078965A1 - Device for continuous feeding of a system for pyrolysis of plastics materials

Info

Publication number: WO2023078965A1
Application number: PCT/EP2022/080606
Authority: WO
Inventors: Christofer COSTES
Original assignee: Earthwake Entreprise
Priority date: 2021-11-04
Filing date: 2022-11-03
Publication date: 2023-05-11
Also published as: FR3128718A1

Abstract

The invention relates to a system for producing fuel by pyrolysis from crushed plastics materials, comprising a reactor fed with molten plastics materials by a feed device (1b), and a distillation column, the feed device (1b) being heated by the circulation of a heat-transfer fluid. The distillation column is in communication with the feed device (1b) via an inlet duct (18b) which recovers the waxes produced during distillation in the distillation column in order to circulate them as a heat-transfer fluid in said feed device (1b).

Description

CONTINUOUS FEED DEVICE FOR A PLASTICS PYROLYSIS SYSTEM

The present invention relates to a device for continuously supplying a system for the treatment by pyrolysis of plastic materials, with a view to their transformation into fuel and in particular into diesel.

Many devices are known for treating plastic materials by pyrolysis, but these devices have the disadvantage of being complex to implement and of having relatively low yields.

There is also known, through application FR 3095450 in the name of the EARTH WAKE Association, a system for treating plastic materials in which the latter undergo degradation by pyrolysis and, depending on the particular conditions of this treatment, this process makes it possible to to achieve hitherto unequaled yields since, starting for example from 100 kg of polyethylene waste, it makes it possible to produce 70 kg of diesel, 15 kg of gasoline and a quantity of methane sufficient to provide the energy necessary for the operation of this system.

We understand that it is interesting to operate such a system continuously.

A first difficulty stems from the fact that a continuous supply must imperatively be done without any admission of air into the reactor of the system in operation, under penalty of risking the explosion of the latter.

A second difficulty stems from the fact that it is also imperative that the vapors cannot leave the reactor, otherwise they risk igniting.

The object of the present invention is to provide a means making it possible to ensure continuous operation of this type of supply device, without any admission of air into the reactor or any exit of vapors from the latter.

The subject of the present invention is thus a device for supplying elements of molten plastic materials to a reactor of a system for producing fuel by pyrolysis of these plastic materials using a distillation column, this device being traversed by a heat transfer fluid, this fluid being constituted by the waxes supplied by the distillation column.

Wax will be understood in the present text to mean the product forming the heavy fraction at the bottom of the distillation column.

According to various implementations, possibly combined: the supply device comprises a set of two coaxial metal tubes, namely an outer tube and an inner tube which form between them a circulation volume closed off at its two ends, the device feed comprises a central and coaxial tube which is arranged inside the inner tube, the plastic elements are admitted at one end, called the proximal end, and circulate in the volume between the inner tube and the central tube to leaving through the opposite end, called the distal end, the proximal end of the circulation volume is in communication with the distal end of the internal volume of the central tube by a conduit at least partly external, the proximal end of the internal volume of the central tube is in communication with the outside via an outlet duct, the supply device comprises a wax inlet duct in communication with the distal end of the circulation volume.

In one embodiment of the invention, the aforesaid outlet duct extends partly inside the central tube.

In one embodiment of the invention, the duct for putting the proximal end of the circulation volume into communication with the distal end of the internal volume of the central tube passes through the central tube, substantially in its middle, as well as the outer and inner tubes to extend axially in the latter towards its distal end and to be interrupted at a short distance from a bottom thereof.

In another mode of implementation, the conduit for putting the proximal end of the circulation volume into communication with the distal end of the internal volume of the central tube passes through, substantially at its distal end, the outer and inner tubes to open into the bottom, or distal end, of the central tube.

In some implementations, the feed device comprises an axial conveying screw, the proximal end of which is fed with crushed plastic materials, and which is driven in rotation by a motor equipped with means for managing its speed of rotation, and which supplies crushed plastics to the volume between the inner tube and the central tube.

According to various implementations, the diameter of the outer tube is between 80 mm and 200 mm and is preferably close to 170 mm.

According to various implementations, the diameter of the internal tube is between 50 mm and 160 mm and is preferably close to 140 mm.

According to various implementations, the diameter of the central tube is between 20 mm and 100 mm and is preferably close to 60 mm.

Advantageously, the exchange surface between the walls conveying the heat transfer fluid and the plastic materials to be melted is between 0.4 m ² and 1.5 m ² and is preferably close to 1 m ² .

Advantageously, a helical turn is arranged over the entire height of the annular space between the outer tube and the inner tube, this turn being contiguous with the outer surface of said tubes.

In one embodiment, the distal end of the feed device is provided with a valve.

The present invention also relates to a system for producing fuel by pyrolysis from crushed plastic materials, comprising a distillation column associated with a reactor and a device for supplying said reactor with said crushed plastic materials, comprising melting means of the latter as described above, said fusion means comprising a circuit conveying a heat transfer fluid consisting of waxes recovered at the outlet of the lower stage of the distillation column.

Advantageously, this fuel production system comprises means for loading the supply device comprising means for crushing the plastic materials and blowing means in said feed device for crushed plastic materials.

There will be described below, by way of non-limiting example, embodiments of the present invention, with reference to the appended drawing in which:

- Figure 1 is a schematic principle view of an installation for the production of fuel by pyrolysis of plastic materials comprising a supply device according to the invention,

- Figure 2 is a vertical and diametral sectional view of a first mode of implementation of the supply device according to the invention,

- Figure 3 is a schematic view of the installation according to Figure 1, supplemented by means of grinding plastic materials,

- Figure 4 is a vertical and diametrical sectional view of a second mode of implementation of the power supply device according to the invention,

- Figure 5 is a vertical and diametrical sectional view of a third mode of implementation of the supply device according to the invention,

- Figure 6 is a perspective view of the feeder shown in Figure 5.

There is shown in Figure 1 a block diagram of a supply device 1 according to the invention, in the context of its essential use, namely the continuous supply of molten plastics without supply of oxygen from a reactor 3 belonging to a system ensuring the transformation by pyrolysis of said plastic materials into fuels, and in particular into diesel.

In this diagram, the supply device 1 is arranged close to a reactor 3 to which it delivers ground plastic materials in the molten state, this reactor 3 being heated at its lower part by a gas ramp 4 which is capable of bringing its internal temperature to a value necessary to ensure the pyrolysis of the plastic materials introduced, in particular of the order of 450° C. This reactor 3 ensures the operation of a distillation column 5, from which the distillates are recovered in the form of gas oil, gasoline and methane. The base of the distillation column 5 is joined to the base of the feed device 1 by an inlet pipe 7 which recovers the "wax" produced during the distillation in the column 5 and which are usually returned to the latter after have been cooled, this arrangement being explained below. In addition, a second conduit 9 recovers the reflux of the waxes at the bottom of column 5, to return them to reactor 3.

The feed device 1 receives at its upper part, in a hopper 10, plastic materials in crushed or crushed form and delivers them to its lower part to the reactor 3 after having been heated, so that they are admitted into the reactor. 3 in a pasty molten form, this feeding of the reactor 3 taking place under the effect of their sheer weight.

As shown in Figure 2, the feed device 1 comprises several concentric vertical tubes. First of all, a pair of tubes close to each other, namely an outer tube 11 with a diameter D of around 170 mm and an inner tube 12 with a diameter d of the order of 140 mm. These two tubes 11, 12 are closed at their upper part and terminate at their lower part in a double convergent 13, with a taper of the order of 40%, which is also closed at its base, so that the volume between the outer 11 and inner 12 tubes forms a circulation volume V, making it possible to ensure the passage of a heat transfer liquid as described below.

The two tubes 11, 12 terminate at their upper part in a flange 14 which makes it possible to connect them to a device supplying plastic chips, in particular the hopper 10, as explained below, and the two tubes 1 1, 12 end at their lower part with a flange 16, which makes it possible to connect the outlet of the supply device 1 to the reactor 3.

The volume between the two tubes 11, 12 which form the double convergent 13 is in communication with a horizontal pipe 18 provided with a connection flange 20 which allows it to be connected, via the pipe 7, to the output of the waxes of the distillation column 5. It is thus understood that the waxes penetrate, as heat transfer fluid, into the circulation volume V between the outer tubes 11 and inner 12.

The feed device 1 also comprises an axial tube 22 which extends over the entire length of the two tubes 11, 12, i.e. from the upper flange 14 to a distance close to the lower outlet, substantially up to mid -height of the double convergent 13, the axial tube 22 terminating in a convergent 23 and being closed at its upper part by a shutter 24 and at its lower part by a bottom 25.

In order to allow passage of the heat transfer fluid inside the circulation volume V defined by the two tubes 11, 12, the upper part of said circulation volume V is connected to a conduit 26 external to the supply device 1, and of smaller diameter than the tube 22. This conduit 26 descends substantially to mid-height of said tube 22, then crosses the latter as well as the two tubes 11, 12 to extend axially downwards at the inside the tube 22, up to near its bottom 25.

Furthermore, another axial duct 28 of the same diameter as the duct 26 originates at the upper part of the tube 22, descends inside the latter and emerges horizontally from the supply device 1, substantially in the middle of the latter, after having passed through the tube 22 and the two tubes 11, 12. This outlet duct 28 ends in a flange 30 which makes it possible to connect it via a duct 32 to the distillation column 5, with the interposition of an exchanger 8 making it possible to optionally complete the cooling of the waxes.

In the mode of implementation presently described, the supply of plastic chips to the supply device 1 is ensured, as shown schematically in FIG. 3, by a crusher 34 into which the plastic material elements are introduced. to be treated, such as for example bottles, which is associated with a propulsion device, such as for example a fan 36, which propels the plastic chips, via a pipe 38, into the hopper 10 whose outlet is in communication with the inlet of the supply device 1 via its connection flange 14. A vent 40 is provided, to relieve the system of pressure in the event of overpressure generated by the fan 36.

Under these conditions, the operation of the supply device 1 is established as described below.

The plastic chips are admitted by the so-called proximal end of the device via the hopper 10, into the space of annular cross-section between the internal tube 12 and the axial tube 22 where they are heated both on the internal surface of the inner tube 12 and on the outer surface of the axial tube 22. These two surfaces thus constitute the exchange surfaces of the supply device 1, as explained below. The plastic materials are melted during the crossing of the device 1 and leave the latter by its so-called distal end, i.e. by the double convergent 13, from which they are delivered to the reactor 3.

The waxes coming from the distillation column 5, which constitute the heat transfer fluid, are introduced through the conduit 18 and circulate in the circulation volume V between the walls of the outer tubes 11 and inner 12, to exit at the top of this volume V through the duct 26 from which they are directed by the latter inside the first axial tube 22, to leave the duct 26 and go up in the axial tube 22 to the top of the latter where they enter the second axial conduit 28 and come out of the supply device 1 at the level of the flange 30, to return to the distillation column 5 after having passed through the exchanger 8 intended to cool them to a temperature preferably between 220° C. and 300° C. and in particular of the order of 270° C. The circuit traveled by the waxes inside the supply device 1 is shown in Figure 2 by arrows in solid lines, while the path traveled by the plastics is shown by arrows in dotted bold lines.

The use of waxes as a heat transfer fluid is particularly advantageous from the point of view of energy saving because, on the one hand, a heat transfer fluid is thus used which does not need to be heated, since it leaves the distillation column 5 at a temperature sufficient to melt the plastic materials and, on the other hand, the used waxes which should in any case be cooled before returning to the distillation column 5 are cooled here, at least in part, due to the amount of heat they gave up to ensure the heating and melting of plastics.

It has been observed by the applicant that by using the waxes as heat transfer fluid and by providing the supply device 1 with an exchange surface of 1 m ² , the latter was able to supply the reactor 3 a quantity of plastics in the molten state of the order of 40 kg per hour.

In one embodiment, the annular space between the outer tube 11 and the inner tube 12 receives a helical turn, not shown in the drawing, which extends from top to bottom of this space and which connects the facing surfaces of these two tubes 11, 12. This turn makes it possible to force the coolant to take a helical path, which has the effect of improving heat exchange between the heat transfer fluid and the inner wall 12 and the axial tube 22 with which it is in contact and which heat the plastics.

This helical turn will be fixed to the inner wall of the outer tube 11 and the outer wall of the inner tube 12 in particular by welding means. The cross section of this turn may be circular or, preferably, rectangular.

Furthermore, in order to avoid heat losses between the outer tube 11 and the outside of the supply device 1, the outer wall of the outer tube 11 as well as the outer pipe 13 can advantageously be insulated. For reasons of clarity of the drawing, this insulation is not shown in the figures.

As shown in Figures 1 and 3, the outlet of the molten plastic which is introduced into the reactor 3 can be closed in its distal part by a valve 21, which allows, when stopping the system, to keep the sealing of the reactor 3 by preventing the entry of air into it and also preventing the exit of the vapors from this reactor 3.

The present invention is particularly advantageous in that it makes it possible to deliver the molten plastic material to the reactor 3 of a set for transforming plastic materials into fuel as shown schematically in FIG. 1, without on the one hand there is a supply of oxygen in the reactor 3, risking causing its explosion, and without on the other hand there being an exit of the vapors from this same reactor 3, which could ignite on contact with the ambiant air.

Indeed, if we consider the path of the plastic materials from the proximal end of the supply device 1 (i.e. the top of the latter in the present example) towards the distal end of the latter (i.e. the bottom in the present example), it can be seen that at the level of the hopper 10 the plastic materials are in the state of chips, therefore in a state where air is admitted between the latter and that, gradually when one goes down in it, these plastic materials leave their rigid state to pass gradually to the molten state. Under these conditions, it is understood that when these plastic materials pass into a molten state, the remaining air bubbles will be expelled to the top of the mixture and then to the outside of the feed device.

The present mode of implementation is more interesting in that the ducts 18 and 28 through which the waxes enter and leave the device respectively by crossing the path taken by the plastic materials are respectively far from the inlet and the outlet of the device, which makes it possible to avoid the formation of blocking plugs at these levels.

There is shown in Figure 4 a second example of implementation of a continuous power supply device according to the invention.

In this example, the elements performing the same function as in the first example have retained the same numerical references, with the addition of an index a.

Like the previous one, this supply device 1a is vertical in operation and comprises two coaxial tubes 11a, 12a, terminating at their base in a double convergent 13a and which are closed at their upper part and at their lower part of so as to form a circulation volume Va. This circulation volume Va is in communication with a duct 18a, through which the waxes ensuring the heating of the device are admitted. It also comprises an axial inner tube 22a, which extends substantially over the entire length of the two tubes 11a, 12a, i.e. from the proximal end of the device to its distal end, and which is closed at its upper part.

This tube 22a opens at its base onto a duct 26a, which crosses the two tubes 11a, 12a horizontally to extend outside the device as far as the upper or proximal part of the latter where it opens in the circulation volume Va.

As in the previous example, the plastic materials are admitted to the upper or proximal part of the device, in the hopper 10a, and descend by gravity into the space of annular cross-section between the two tubes 22a, 12a.

The heating waxes which are admitted through the conduit 18a enter the circulation volume Va and go up in the latter to exit at the top through the conduit 26a, and move therein towards the base of the axial tube 22a in which they ascend to exit through conduit 28a and return to the distillation column through conduit 32.

In this mode of implementation, it is understood that the plastic materials are here subjected to a heating gradient increasing from top to bottom. Such an embodiment is advantageous in that it is easier and faster to construct. There is shown in Figures 5 and 6 a third embodiment of the present invention, in which the feed of the crushed plastics is no longer done by gravity.

In this example, the elements providing the same function as in the previous examples have retained the same numerical references, with the addition of an index b.

The device 1b with a horizontal longitudinal axis comprises two coaxial tubes 11b, 12b ending in a double convergent 13b, and forming between them a circulation volume Vb.

The device 1b also comprises an axial tube 22b, closed at both ends, which extends substantially from the middle of the convergent 13b to about half the length of the two tubes 11b, 12b.

The device 1b also comprises a conduit 26b and a conduit 28b, which are arranged functionally as well as the respective conduits 26, 28 of the first example.

As mentioned above, in this mode of implementation, the supply of plastic chips is not done by gravity, but mechanically. To do this, the flange 14b disposed at the inlet of the two tubes 11b, 12b is connected to a flange 44 of a tubular body 46 containing an endless conveying screw 48, disposed on an axis 50 which is driven in rotation by a motor 52 whose speed of rotation is controlled by servo means 54. The entry of the plastic materials into the body 46 takes place at the proximal end of the device, through a hopper 10b, and their exit takes place at its distal end by the convergent 13b.

This device 1b, as well as that described with regard to FIG. 4, may comprise in the space of annular cross-section between its outer wall 11b and its inner wall 12b a helical turn, making it possible to promote the heat exchanges.

Such an embodiment is advantageous in that it makes it possible to take into account the quality of the plastic materials that it admits. Thus, depending on the hardness of the latter, the device makes it possible to adjust and control the speed with which they move inside it, by adjusting the speed of rotation of the conveying screw 48 using servo means 54. Thus, for materials resistant plastics, a lower rotation speed should be set than for less resistant plastics.

Moreover, in this mode of implementation, the power supply device is more easily accommodated when its place of installation is limited in the direction of the height, which is in particular the case when it is desired, for example, to place it in a container.

Claims

CLAIMS System for producing fuel by pyrolysis from crushed plastics, of the type comprising a reactor (3) supplied with molten plastics by a supply device (1, 1a, 1b), and a distillation column ( 5), the supply device (1, 1 a, 1 b) being heated by the circulation of a heat transfer fluid, characterized in that the distillation column (5) is in communication with the supply device (1 , 1 a, 1 b) via an inlet duct (7, 18, 18a, 18b) which recovers the waxes produced during the distillation in the distillation column (5) to circulate them as heat transfer fluid in said power supply device (1, 1 a, 1 b). Fuel production system according to claim 1, characterized in that it comprises means for loading the supply device (1) comprising means for crushing (34) the plastic materials and blowing means (36) for the materials plastics crushed in said supply device (1). Supply device for a system according to one of Claims 1 or 2, characterized in that: it comprises a set of two coaxial metal tubes, namely an outer tube (1 1 , 1 1 a, 1 1 b) and a internal tube (12, 12a, 12b) which form between them a circulation volume (V, Va, Vb) closed at its two ends, it comprises a central and coaxial tube (22, 22a, 22b) which is arranged at the inside the inner tube (12, 12a, 12b), the plastic materials are admitted at one end, called the proximal end, and circulate in the volume between the inner tube (12, 12a, 12b) and the central tube (22, 22a , 22b) to exit through the opposite end, called the distal end, the proximal end of the circulation volume (V, Va, Vt>) is in communication with the distal end of the internal volume of the central tube (22, 22a, 22b) by a conduit (26, 26a, 26b) at least external part, the proximal end of the internal volume of the central tube (22, 22a, 22b) is in communication with the outside via an outlet duct (28, 28a, 28b), it comprises a wax inlet duct ( 18, 18a, 18b) in communication with the distal end of the circulation volume (V, Va, Vt>). Feeding device according to Claim 3, characterized in that the aforesaid outlet duct (28, 28b) extends partly inside the central tube (22, 22b). Feeding device according to one of Claims 3 or 4, characterized in that the conduit (26) for placing the proximal end of the circulation volume (V) in communication with the distal end of the internal volume of the central tube (22) crosses the latter substantially in the middle, as well as the outer (1 1) and inner (12) tubes, to extend axially in the latter towards its distal end and to be interrupted at a short distance from a bottom (25) of it. Feeding device according to Claim 3, characterized in that the conduit (26a) for placing the proximal end of the circulation volume (Va) in communication with the distal end of the internal volume of the central tube (22a) passes through, substantially at its distal end the outer tubes (1 1 a) and inner (12a) to open into the bottom, or distal end, of the central tube (22a). Feeding device according to one of Claims 3 or 4, characterized in that it comprises an axial conveying screw (48), the proximal end of which is fed with ground plastics and which is driven in rotation by a motor ( 52) equipped with means (54) for managing its speed of rotation, and which circulates the crushed plastic materials in the volume between the inner tube (12b) and the central tube (22b). Feeding device according to any one of Claims 3 to 7, characterized in that the diameter of the outer tube (1 1 , 11 a, 11 b) is between 80 mm and 200 mm and is preferably close to 170 mm. 14 . Feeding device according to any one of Claims 3 to 8, characterized in that the diameter of the internal tube (12, 12a, 12b) is between 50 mm and 160 mm and is preferably close to 140 mm. 0. Feeding device according to any one of claims 3 to 9, characterized in that the diameter of the central tube (22, 22a, 22b) is between 20 mm and 100 mm and is preferably close to 60 mm. 1. Supply device according to any one of claims 3 to 10, characterized in that the exchange surface between the walls of the tubes (1 1b, 12b) conveying the heat transfer fluid and the plastics to be melted is comprised between 0.4 m ² and 1.5 m ² and is preferably close to 1 m ² . 2. Feeding device according to any one of claims 3 to 1 1, characterized in that a helical turn is arranged over the entire height of the annular space between the outer tube (1 1, 1 1 a, 1 1 b) and the inner tube (12, 12a, 12b), this turn being contiguous with the outer surface of said tubes. 3. Feeding device according to any one of claims 3 to 12, characterized in that its distal end is provided with a valve (21).