TECHNICAL FIELD The present invention relates to a system and method for separating metal from paint waste.

BACKGROUND OF THE INVENTION

Metal paint cans are still widely used compared to plastic ones. However, currently, separating the metal from the paint waste is challenging. As the metal is often left more or less unseparated from the paint waste, the metal is reused to a modest, or even negligible, extent.

Still, in many places, the paint cans are only cleaned manually, by scraping the cans. This process does not clean the metal and, therefore, its reuse continues to be challenging. The paint waste is currently taken to a high-temperature incineration process, and, because there is no operable method available for separating the metal, the metal cans are usually taken to the same incineration process, along with the paint waste. It is possible to separate metal residues from the ash by screening but, after the incineration process, the recovery rate of metal is still low. A few metal recycling systems and methods are known from the prior art. WO08010621 Al, for example, discloses a system and method for recycling metal cans. However, this solution utilizes magnetic conveyors and washing tanks containing solvents for separating the metal. The process is a multi-step, space- consuming and expensive process to be carried out for separating metal from paint waste.

DE4325104 Al discloses another method of separating metal from paint waste. In this method, the paint cans are frozen down to -90 degrees Celsius and the metal is removed by impact on the paint cans. Thereafter, magnetic devices are used for separating the metal. This method is laborious and time-consuming, especially because the metal cans must first be frozen down to a low temperature. SUMMARY OF THE INVENTION

The invention aims at alleviating the above-mentioned problems related to separating metal from paint waste. An objective of the invention is separate metal from paint waste in a way allowing the metal to be reused. The objective of the invention is achieved by a system and method for separating metal from paint waste according to an aspect.

The system of the invention is characterized in what is set forth in the characterizing part of the independent claim 1.

The method of the invention is characterized in what is set forth in the characteriz- ing part of the independent claim 12.

Preferred embodiments of the invention are also described in the dependent claims.

According to an aspect of the invention, the system for separating metal from paint waste according to the present invention comprises

-a crusher for crushing the metal, -at least one rotating drum for mixing the waste, and

-a vapor phase in which vapor is arranged in at least one rotating drum so that the metal being treated is exposed to vapor.

According to an embodiment of the invention, the system comprises a number of consecutive rotating drums, the drums being separated from each other by partition walls, and, in these rotating drums, the crushed metal is arranged to move, from the preceding drum to the next drum, through an inlet provided in the partition walls. According to an embodiment of the invention, the partition walls are provided between the rotating drums, and, the partition walls are provided with feeding chutes for moving the crushed metal to the next drum. The partition walls may be integrat- ed with the drum in order to cause the partition wall and the chute to rotate together with the drum. The feeding chutes may be fitted in the partition walls in such a way that, as the drum rotates, the chute receives metal so that the metal moves from the preceding drum to the next drum. The feeding chutes may be easily replaceable so that the amount of moving metal is easily adjusted. A wider chute moves a larger amount of metal from the preceding drum to the next drum at once. According to an embodiment of the invention, the system comprises a rinsing phase for bringing a rinsing fluid into contact with the rotating drum, the rinsing phase being after the vapor phase.

According to an embodiment of the invention, the system comprises a drying phase for drying the metal being treated by the rotating dmm, the drying phase being after the rinsing phase.

According to an embodiment of the invention, conveyor screws are provided on the bottom of the system to convey the separated paint away from the system. In some embodiments, the system comprises V-shaped bottom pools to collect the separated paint. The conveyor screws may be provided on the bottom of the pools for conveying the paint away from the system.

According to an embodiment of the invention, the vapor phase comprises at least three drums one after another. In some embodiments, a single drum or two drums may be used. In some embodiments, more than three, such as four or five, drums may be used one after another. In some embodiments, nozzles direct the vapor close to the surface of the drum so that the vapor is directed to the metal being treated.

According to another aspect of the invention, the method of the present invention for separating metal from paint waste comprises at least the steps of

-crushing metal, -mixing waste in drums, and

-directing vapor to the metal.

According to an embodiment of the invention, the method comprises a step of rinsing the metal.

According to an embodiment of the invention, the method comprises a step of dry- ing the metal.

According to an embodiment of the invention, the method comprises a step of conveying away and/or recovering the separated paint.

The utility of the system and method according to the invention is based on a number of issues. The separated metal may be highly free from the separated paint waste. The separated metal may be of high quality, and, therefore, the reuse of the metal may be possible. The reuse of metal may increase considerably with the present invention. The present invention may provide a cost-effective system and method for separating metal from paint waste. The present invention may also provide a compact separation process which may be implemented, when needed, in various locations. The compact structure of the present invention may allow it to be easily moved from place to place. When placed in a sea container, the system may be easily transferred/moved by a suitable crane and/or transport vehicle.

In this application, the expression "a number of refers to any positive integer starting from one (1), such as one, two or three. The expression "a plurality of, in turn, refers to any integer starting from two (2).

In this application, the expression "paint waste" refers to waste containing at least paint and waste metal.

BRIEF DESCRIPTION OF THE FIGURES In the following, preferred embodiments of the invention will be described in more detail with reference to the accompanying figures wherein

Figure 1 is an exemplary view of a system according to an embodiment of the present invention,

Figure 2 is an exemplary view of rotating drums according to an embodiment of the present invention,

Figures 3a to 3c are exemplary views of a partition wall and a feeding chute according to an embodiment of the present invention,

Figure 4 is an exemplary view of an inlet formed by a drum and a partition wall, according to an embodiment of the present invention, Figure 5 is an exemplary view of a system according to another embodiment of the present invention, and

Figure 6 is a flow chart of a method according to an embodiment of the present invention. MORE DETAILED DESCRIPTION OF THE FIGURES

Figure 1 shows a system 100 for separating metal from paint waste according to an embodiment of the present invention. The system comprises a first conveyor 102 for conveying the material to be treated, such as metal paint cans, to a crusher 104. For instance, the crusher 104 may comprise two toothed crushers 106a, 106b for crushing the material to be treated.

A second conveyor 108 is provided below the crusher for moving the material to rotating drums 110a to HOe. The moving direction of the material is designated by an arrow 111a. The conveyor 108 is perforated in order to allow the paint separated from the material being treated to flow down to the bottom of the system. The flow of the separated paint down to the bottom of the system is designated by an arrow 113a. Conveyor screws 112a, 112b are provided on the bottom for moving the separated paint to the ends of the system. The first conveyor screw 112a and the second conveyor screw 112b are adapted to convey the separated paint to the front end of the system (arrow 113b) and to the rear end of the system (arrow 113b), respectively. Collection bins for the paint can be provided at the ends of the screw conveyors, for example.

The three first rotating drums 110a, 110b, 110c of the system 100 comprise a vapor phase 114. Preferably, vapor is supplied to the surfaces of the rotating drums so that the material rotating in the drums is exposed to the vapor. Preferably, the vapor may be water vapor, for example. For example, small nozzles may be used for supplying the vapor, allowing the vapor to be directed close to the surfaces of the drums. The vapor may be generated by a vapor generator, for example. In some embodiments, vapor generators of approximately 10 to 20 kW may be used. In some embodi- ments, more effective vapor generators, such as 200 kW vapor generators, may be used. A more effective vapor generator allows the metal being treated to be freed from paint faster/more effectively. Lighter vapor generators give a good outcome as well, when directing the vapor to the metal being treated. The rotating drums may comprise apertures/holes, through which the vapor acts on the metal being treated. The paint that comes off the metal being treated may also flow through the apertures/holes out of the drums. The diameter of the holes may be 15 mm, 20 mm or 25 mm, for example.

The fourth rotating drum 1 lOd of the system 100 comprises a rinsing step. A rinsing pool 116 is arranged below the rotating drum HOd so that the fluid of the rinsing pool is in contact with the drum. Water, oil in water or alkaline water may be used as the washing fluid, for example. The fifth rotating drum HOe of the system 100 comprises a drying step. The drying step may merely comprise the rotating drum 1 lOe, or, air may be fed/blown into the drum, for example. The air may be supplied by a suitable fan and/or blower, for example. After the drying step, the treat- ed/washed metal is moved onto a collection platform 118. The moving direction of the material being treated is designated by an arrow 11 lb.

The rotating drums 110a to HOe preferably form a single continuous unit divided into sections by the partition walls 120a to 120d. The partition walls 120a to 120d and the feeding chutes 122a to 122d are provided between the rotating drums 110a to 1 lOe for moving the material from the preceding drum to the next drum. The last drum HOe is also provided with a feeding chute 122e for moving the metal to the next step. The feeding chutes can be easily replaceable in order to allow the rate at which the material being treated is moved from one step another to be adjusted. Wider/larger chutes move a larger amount of material at a time. The system 100 can be placed in a sea container 124, for example. The sea container 124 can be an ISO-standard container, such as a 20 foot sea container. In some embodiments, the conveyor 108 and the collection platform 118 are located outside the container.

The diameter of the rotating drums 110a to 1 lOe of the vapor step is preferably 1 to 2 m, more preferably 1.2 to 1.8 m and most preferably 1.4 to 1.6 m. The diameter of the drum HOd of the rinsing step is preferably 1.5 to 2.5 m, more preferably 1.7 to 2.3 m and most preferably 1.9 to 2.1 m. The diameter of the drum HOe of the drying step is preferably 0.8 to 1.8 m, more preferably 1 to 1.6 m and most preferably 1.2 to 1.4 m. The combined width of the rotating drums 110a to HOe is preferably 3.4 to 5.8 m, more preferably 3.8 to 5.4 m and most preferably 4.2 to 5 m.

Referring to Figure 2, the rotating drums 110a to HOe may comprise tooth-like tumbling discs 226 for mixing the material being treated in order to prevent the material from packing together. The tumbling discs may run around the entire periphery of the drum or consist of tumbling disc sections on the periphery of the drum. The tumbling discs may also comprise indentations, for example.

Figures 3a to 3c show the partition walls 220a to 220c and the feeding chutes 222a to 222c thereof. Figure 3a is an oblique rear view of the partition wall 220a and the feeding chute 222a. Figure 3b is a front view of the partition wall 220b and the feeding chute 222b. Figure 3c, in turn, is a lateral view of the partition wall 220c and the feeding chute 222c. The chute picks up the metal being treated while the partition wall and the chute rotate along with the drum. The feeding chute moves the metal to next drum/step through an inlet.

Figure 4 shows an inlet formed by a drum and a partition wall. As an example, the drum inlet 228 can be slightly bigger than the partition wall inlet 230.

Figure 5 shows a system 300 according to another embodiment of the present invention, comprising four rotating drums 310a to 310d. The first drum 310a comprises a vapor phase. The drum 310a is provided with holes/apertures through which the vapor can act on the metal being treated and through which the separated paint can flow out of the drum. Preferably, the vapor is directed close to the surface of the drum in order to subject the metal being treated to the vapor through the holes/apertures. The second and third drums 310b, 310c comprise a rinsing step, with a rinsing pool 316 below the drums, the drums being in contact with the rinsing fluid. The drums 310a, 310b are provided with holes/apertures through which the rinsing fluid can act on the metal being treated and through which apertures/holes the paint can flow out of the drums. The fourth drum 310d comprises a drying phase in which the material being treated is dried by the rotational movement of the drum. The fourth drum is also provided with apertures/holes allowing the fluid to flow out of the drum. Besides, the drying phase may comprise an air blow into the drum and/or after the drum. Two screw conveyors 312a, 312b are arranged on the bottom of the system 300 for conveying the paint waste away from the system. The paint waste is deposited on the bottom of the rinsing pool to be conveyed away therefrom by the second screw conveyor 312b.

Figure 6 is a flow chart of a method 500 of separating metal from paint waste ac- cording to an embodiment of the invention.

In step 502, all of the preparatory measures of the method are carried out. This step may comprise assembling and installing the system for operation, for example. This step may also comprise placing the system in a sea container, for example.

In step 504, the metal to be treated is crushed. This step may comprise supplying paint cans to the crusher, for example.

In step 506, the waste being treated is mixed in the drums. This step may comprise conveying the metal from the crusher to the rotating drums by a conveyor, for example. In step 508, vapor is directed to the metal being treated. This step may comprise generating vapor, such as water vapor, by a vapor generator. The vapor can be directed to the surfaces of the rotating drums by nozzles, for example, to allow the vapor act on the metal being treated through apertures provided in the drums. In step 510, the metal is rinsed. This step may comprise a washing pool, for example, the washing pool being in contact with the rotating drum in order to subject the metal being treated to a rinsing fluid.

In step 512, the metal is dried. This step may comprise a rotating drum that dries the metal. Besides, this step may comprise supplying air to the rotating drum, for ex- ample. After step 512, the treated metal can be collected onto a collection platform, for example, to be passed on therefrom.

In step 514, the paint is conveyed further on and/or recovered. This step may comprise conveying the separated paint away from the system and into collection bins, by the screw conveyors. Step 516 illustrates the end of the present method.

Steps 510, 512 and 514 are denoted by dashed lines because these steps are not necessarily carried out in each embodiment. In some embodiments, after the vapor step, that is, step 508, the metal is already completely separated from the paint waste. In some embodiments, however, the metal can also be rinsed (step 510) and/or dried (step 512). The separated paint can be conveyed by screw conveyors and/or collected into collection bins, for example (step 514). Alternatively, in some embodiments, the paint can be directly collected into bottom pools, for example.

The scope of the invention is defined by the accompanying claims. However, it is obvious to a person skilled in the art that the details of the different features of the invention may vary to some extent within the overall inventive idea, depending on the embodiment. The present invention relates to separating metal from paint waste, but, it will be understood by the person skilled in the art that the present system and method also can be applied for separating some other material, such as plastics, from paint waste or some other similar liquid/paste-like waste.