Process for separating metals from composite laminated bodies

Abstract

 The process comprises the gradual heating of the composite laminar materials to a temperature which is sufficient to remove the non-metal materials but which is lower than the melting temperature of the metal material of the support, the extraction of the gases produced by the removal of those non-metal materials and the continuous recovery, at the end of the thermal treatment stage, of the resulting metal residues which are conveyed to the outside in order to be cooled and processed for re-use. The apparatus comprises a rotary treatment chamber having means for introducing the materials from one end and having means for bringing about the rotation of the chamber, the chamber having at one end a duct for the discharge of the gases generated and at the other end a duct for the continuous evacuation of the metal residues.

Description

[0001] The present invention discloses a process for separating metals from composite laminated bodies, especially bodies of the laminar type that are used for the manufacture of containers of various types and that comprise a metal sheet combined with a sheet of plastics material, cellulose material, textile material or other types of covering.

[0002] Such composite laminated materials are widely used in many fields of industry in order to manufacture containers in which various products, such as foodstuffs, pharmaceuticals, etc., are marketed. A major problem currently posed by that type of container is its recycling since, being of a kind made of a large number of materials based on a metal laminate and other covering material, at least on one of its faces, it is difficult to achieve correct recycling using materials of said laminates, and the result is the generation of large amounts of non-usable waste.

[0003] The present invention discloses a process and an apparatus permitting recycling of said type of material by separation of the metal by removing the remainder of the constituent material, such as a laminate of plastics material.

[0004] In order to achieve those aims, the process forming the subject-matter of the present invention is based on subjecting the laminar bodies of metal and, for example, plastics composite material to a controlled temperature which is higher than the vaporisation temperature of the plastics material covering the metal support but lower than the melting temperature of the metal. The thermal treatment is effected with the exclusion of air or with an amount of air lower than that required for combustion of the gasified plastics, that is to say, lower than the flame propagation point in the gases from the plastics material. Preferably, the thermal treatment is carried out by displacing the composite materials along a heating chamber, producing a gradual pyrolysis effect until the metal support, which is recovered later as scrap metal, has been completely released.

[0005] The process is applied preferably to metal laminar waste having a layer of plastics, with the exception of PVC. The maximum thickness of the layer of metal, especially aluminium, is some 40 microns.

[0006] If the starting material is a laminate formed by a metal, for example, aluminium, and a layer of a cellulose material, for example, paper, the layer of paper will be burnt in the thermal treatment stage, giving rise to a small residue of ash.

[0007] In the case of the removal of layers of plastics material, the pyrolysis thereof gives rise to process discharge gases that have a considerable calorific potential and that can therefore be used in the most suitable form in the industrial installation itself.

[0008] The apparatus for carrying out the process forming the subject-matter of the present invention basically comprises a rotary combustion chamber to which the residues to be recovered from the composite materials of metal and a covering of a plastics or cellulose type are conveyed, the recovery elements being displaced continuously and at a reduced rate along the chamber, which is subjected to heating over its entire length by means of a surrounding jacket heated inside an oven-type chamber of refractory material by the combustion of gas or other fuels. The displacement of the materials along the heating chamber is preferably effected by the gentle inclination and the rotation thereof, which enables them to be displaced by gravity. The metal residues slightly puddled by the action of heat and mechanical action are moved along the chamber for heating to an elevated temperature, lower than the melting temperature, by means of a duct provided with a conveyor, and are then cooled and optionally used as scrap metal. The chamber has an inlet at its end for the materials to be recovered which arrive from a system of two hoppers which operate in parallel and which are in communication with the inlet duct by means of corresponding valves. An outlet tube for the gases generated, which can be used for their high energy content, is arranged coaxially, preferably at the same inlet end.

[0009] The treatment chamber is supported inside the surrounding heating chamber at various points along its outer surface, with the provision of roller bearings produced from materials resistant to relatively high temperatures.

[0010] The process provides for the production of a partial vacuum in the chamber at the beginning of the process in order to extract as much air, and therefore oxygen, as possible in order to avoid the risk of fire, above all at the beginning of the process. Alternatively, it would be possible to scavenge the treatment chamber by means of an inert gas, for example, nitrogen, above all at the beginning of the process. When the process has already started, the generation of large quantities of gases by the pyrolysis of the plastics material will involve the automatic formation of non-combustible mixtures.

[0011] An extractor is preferably provided at the gas outlet, which extractor increases the draught inside the chamber and combines with a reduced air intake at the outlet for the recovered metal elements in order thus to improve the scavenging of the thermal treatment chamber.

[0012] In order to aid understanding, some drawings of a preferred embodiment of the present invention are appended by way of non-limiting explanatory example.

Figure 1 is a complete diagrammatic section through a recovery installation according to the present invention.

Figure 2 is a sectional detail of the chamber of the installation of Figure 1.

Figures 3 and 4 are, respectively, details of the mounting of the chamber and of the conveyor for the extraction of recovered metal elements.

[0013] As shown in the Figures, the apparatus forming the subject-matter of the present invention comprises a surrounding external chamber of refractory material 1 which accommodates a heating chamber 2 which receives the heating gases of the combustion in the interior 3 of the chamber 1, which combustion is produced by gas or another type of fuel, by way of an inlet and burners represented diagrammatically by the numeral 4. The inside of the heating chamber 2 accommodates the rotary treatment chamber 5 operated by the end shaft 6 by means of a suitable drive system (not shown). The unit composed of the rotary chamber 5 and the surrounding heating chamber 2 is arranged so that it slopes slightly from the inlet end or face 7 to the opposite end 8 of the chamber 1, permitting a slow displacement of the residues to be recovered, which have been introduced via the duct 9 and come from one or two hoppers 10 and 11 which operate in parallel and which are controlled by the respective valves 12 and 13. An outlet duct 14 which opens out in the rotary combustion chamber 5 enables the gases recovered from the plastics material, which can be exploited for their calorific potential, to escape to the outside.

[0014] The metal residues at the end of the treatment in the chamber 5 are evacuated via the outlet duct 15 which is arranged with a given inclination in order to promote the discharge of the materials by gravity, although that duct likewise comprises an internal conveyor 16, which is preferably in the form of a helicoidal element. A duct 17 arranged in parallel with the outlet duct 15 and along the outer surface thereof permits the conveyance of the gases generated in that region towards the end region of the chamber 2, conveying them finally to the outlet 14.

[0015] The temperature to which the residues to be recovered are subjected inside the recovery chamber 5 is sufficient to produce pyrolysis of the plastics material but insufficient to cause the metal in question to melt, for example, some 400°C. In the portion corresponding to the outlet duct 15, the temperature can be higher than that of the combustion gases which are introduced into the chamber 3, being as much as some 500 - 600°C.

[0016] In order better to ensure the operation of the rotary chamber 5, a plurality of support points are provided, such as those indicated in Figures 1 and 2 by the numerals 18, 19, 20 and 21, Figure 3 showing a detail of one of those supports with, at the inside, the roller bearing 22 which is produced from a temperature-resistant material and which reduces the friction of the rotary chamber inside the surrounding heating chamber.

[0017] The combustion gases inside the chamber 3 are discharged to the outside via the gas outlet 23 which comprises an extractor 24 for improving the draught.

[0018] Optionally, an auxiliary pipe 25 may be provided for the introduction of an inert gas which permits scavenging of the gases formed during pyrolysis, thus promoting pyrolysis, and which can also be used for the initial scavenging of the treatment chamber.

[0019] As will be appreciated, both ends of the rotary chamber are provided with the necessary sealing means, both those which are necessary for the tubes for the introduction of the materials to be recovered and that corresponding to the drive shaft 6.

[0020] Although the diagrammatic drawings are not very detailed, it will be appreciated that the apparatus forming the subject-matter of the present invention permits control of the process parameters, for example, temperatures, gas compositions and speeds and, above all, it will have safety detectors preventing critical temperatures from being exceeded, situations of possible gas explosion, etc.

Claims

1. Process for separating metals from composite laminated bodies of the type formed by a metal support and a removable covering, characterised in that the composite laminar materials are gradually heated to a temperature which is sufficient to remove, by pyrolysis, the non-metal materials but which is lower than the melting temperature of the metal material of the support, the gases produced by the removal of the non-metal materials being extracted and the resulting metal residues being recovered continuously at the end of the thermal treatment stage and conveyed to the outside in order to be cooled and processed for re-use.

2. Process according to claim 1, characterised in that, when the non-metal materials accompanying the basic metal are plastics materials, the treatment is carried out at a temperature capable of producing pyrolysis of the plastics materials, in an atmosphere depleted of oxygen in order to impede their combustion, permitting the later use of the generated gases for exploiting their calorific potential.

3. Process according to the preceding claims, characterised in that, in an initial stage prior to the treatment of the composite laminar materials to be recovered, the oxygen content of the treatment chamber is reduced in order to prevent the formation of explosive mixtures.

4. Process according to claim 3, characterised in that the reduction of the oxygen content is effected by forming a partial vacuum in the chamber.

5. Process according to claim 3, characterised in that the reduction of the oxygen content is effected by scavenging with an inert gas.

6. Apparatus for carrying out the process of the preceding claims, characterised in that it comprises a cylindrical rotary treatment chamber having means for introducing the composite laminar materials to be recovered from one end and having means for bringing about the rotation of the chamber on its axis, the chamber having, at the end for the introduction of the materials to be recovered, a duct for the discharge of the generated gases and being connected at the opposite end to a duct for the continuous evacuation of the metal residues recovered.

7. Apparatus according to claim 6, characterised in that the treatment chamber is contained in the interior of a fixed heating chamber which receives the action of the heating means and which has various points for supporting the rotary chamber along its outer surface, with roller bearings resistant to elevated temperatures.

8. Apparatus according to claim 6, characterised in that the heating means are constituted preferably by the combustion gases of a liquid or gaseous fuel of which the combustion is effected in a chamber having refractory properties and surrounding the heating chamber of the apparatus.

9. Apparatus according to claim 6, characterised in that the duct for the continuous discharge of the recovered metal residues has a helicoidal extraction conveyor and extends through the interior of the heating chamber, the residue discharge duct having an upper duct for collecting any gases generated in order to convey them to the end of the treatment chamber so that they can be recovered.

10. Apparatus according to claim 6, characterised in that the introduction of materials to be recovered is effected by means of a system of one or more hoppers arranged in parallel which supply the inlet duct to the treatment chamber and which are provided with control valves for bringing about the optional operation of one or other thereof.

11. Apparatus according to claim 6, characterised in that the discharge duct for the recovery gases has an extractor for improving the extraction draught for the gases.

12. Apparatus according to claims 6 to 9, characterised by the provision of a reduced inlet passageway for air at the end of the discharge duct for the recovered metal materials in order to permit the formation of a stream of inlet air which improves the scavenging of the treatment chamber but the amount of which is not sufficient to create an explosive mixture with the gases generated.

Drawing