JPH04333531A - Method for recovering metal from mixed waste of metal and plastic - Google Patents

Abstract

PURPOSE:To recover only a metallic piece in good condition by mixing the crushed metallic piece and plastic piece, burning the mixture in a rotary kiln and then removing the carbonized material. CONSTITUTION:The mixed waste of metals such as aluminum, iron and copper and plastics is crushed and passed through a screen with the diameter of the opening controlled to about 30-50mm. The undersize is separated into the metallic piece and plastic piece by gravity concentration, etc. The metallic piece and plastic piece are supplied to a rotary kiln in the weight ratio of about 4:1. The mixture is burned at about 300-500 deg.C. The metallic piece and the carbonized plastic discharged from the kiln are screened by a screen, the carbonized material is screened off, and the metallic piece is recovered. The recovered metallic piece is treated by a magnetic separator to sort out iron, and the other metallic pieces are manually sorted out.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of burning mixed waste of metal and plastic to convert the plastic into carbide and recover the metal.

0002

BACKGROUND OF THE INVENTION Conventional methods for treating mixed metal and plastic waste include incinerating it in an incinerator, or burying it in a landfill in the same way as household waste.

0003

[Problem to be Solved by the Invention] In the former method of treating mixed waste of metal and plastic, the incinerator quickly burns due to the high temperature generated when the plastic is incinerated in the incinerator. There were problems such as damage and the metals in the mixed waste melting due to the high temperature and adhering to the inner walls of the incinerator. Furthermore, there is a problem in that the metals (Fe, Al, Cu, etc.) melted in the incinerator become alloys with little utility value. In addition, in the latter conventional treatment method, the mixed waste of metal and plastic is directly landfilled, which is bulky and does not corrode, and there is also the problem that the metal is not recovered and is not used effectively.

[0004] This invention solves these problems that conventional methods of treating mixed waste of metal and plastic have, and makes it possible to effectively recover limited resources without oxidizing or dissolving the metal, and to use an incinerator. The purpose is to completely burn the plastic and turn it into char, and the small char (ash) can be disposed of in an industrial waste site, such as a landfill.

[0005]

[Means for Solving the Problems] This invention involves burning a mixture of metal pieces crushed to a predetermined size or less and plastic pieces at a weight ratio of about 4:1 in a rotary kiln at a predetermined temperature. After that, the carbide is removed and the metal is recovered.

[0006]

[Operation] By burning metal pieces and plastic pieces that have been crushed to below a predetermined size in a rotary kiln at a predetermined temperature, the plastic pieces are well burned and become carbide with small bulk, and the metal pieces are oxidized. Very little is done and no melting is done, carbide is removed and only high quality metal pieces are recovered.

[0007]

[Embodiment] Next, one embodiment of the method of recovering metal from mixed waste of metal and plastic according to the present invention will be described. A mixed waste of metals such as aluminum (Al), iron (Fe), and copper (Cu) and plastics is crushed by a crusher, and the holes of the crusher are 50 m long by a screen with a diameter of 50 mm.
Only irregularly shaped metal and plastic pieces with a size of less than m are allowed to pass through.

[0008] The metal pieces and plastic pieces that have passed through the screen are conveyed to a specific gravity sorter by a belt conveyor.
A specific gravity separator separates metal pieces and plastic pieces. The separated metal pieces are stored on a conveyor in a metal piece storage tank. Further, the separated plastic pieces are classified by air-fed cyclone, and the plastic pieces are stored in a plastic piece storage tank.

[0009] From the storage tank for metal pieces and the storage tank for plastic pieces, metal pieces and plastic pieces are supplied to the rotary kiln at a weight ratio of about 4:1 by respective screw conveyors. Inside the rotary kiln, the burner first raises the temperature of the plastic pieces to the flash point, but the temperature at which the plastic pieces self-combust varies depending on the type of plastic pieces, but is usually around 30°C.
The temperature range is from 0°C to about 500°C. The plastic debris that self-combusts in the rotary kiln becomes a smooth burnt-out char, and this char and metal debris are discharged from the outlet of the rotary kiln. The metal chips and carbide discharged from the rotary kiln are conveyed by a screw conveyor to a sieve machine, where the carbide is sieved and the metal chips are recovered. The recovered metal pieces are separated into iron by a magnetic separator, and other metal pieces are sorted out by humans.

[0010] The self-combusted plastic pieces are pulverized in advance from a large plastic container and film to a size that can pass through a screen with a diameter of about 50 mm, and the metal pieces are crushed into plastic pieces in a rotating rotary kiln. Since it plays the role of a raking blade (louver), it breaks up the aggregate of plastic pieces and supplies oxygen smoothly.In order to make the plastic pieces self-combust well, the plastic pieces are made of sticky unburned carbon (carbide).
It does not turn into charcoal, but instead becomes a smooth carbide (ash). At the same time, the metal strips are only heated from about 300°C to about 500°C, and the oxygen is oxidized because it is consumed by self-combustion of the plastic pieces, so the metal pieces are not oxidized or melted, and the aluminum (Al) , iron (Fe), copper (Cu)
Each product is discharged from the rotary kiln outlet as a single unit. In this way, about 30
The internal temperature of the rotary kiln is kept almost constant since the metal pieces and carbide heated from 0°C to about 500°C are discharged.

[0011] In order to maintain good self-combustion and atmospheric temperature, it is better to adjust the amount of plastic pieces and metal pieces fed into the rotary kiln depending on the type of plastic (or type of metal pieces). It is even better to adjust the rotation speed and inclination of the rotary kiln. In addition, the size of the metal and plastic pieces is such that each piece has a diameter of about 30 mm, because the metal and plastic pieces are easy to mix together, and the plastic pieces tend to self-combust.
A size that allows it to pass through a screen of about 50 mm to about 50 mm is preferable.

0012

[Effects of the Invention] This invention crushes mixed waste of metal and plastic to a predetermined size or less, separates the waste, and then mixes the metal pieces and plastic pieces in a predetermined weight ratio. Since this method recovers metals by burning them at a predetermined temperature in a rotary kiln and removing carbides, the metals can be recovered in good condition without being oxidized or melted, and it is also an effective way to use limited resources. Can be reused. The heat generated by the self-combustion of the plastic strips is absorbed by the metal strips and reaches a predetermined temperature (
Since the temperature does not exceed 300° C. to 500° C., the rotary kiln, which is a combustion furnace, is not damaged. Furthermore, in the rotary kiln, the metal pieces scrape up the plastic pieces and act as blades, breaking the plastic pieces apart and supplying oxygen smoothly, allowing the plastic pieces to completely self-combust and turn into complete carbide ( By burying such a small-volume, complete charred material in an industrial waste site, such as a landfill, the landfill can be used effectively over a long period of time.

Claims (1)

[Claims] Claim 1: Mixed waste of metal and plastic is crushed to a size that can pass through a screen with a diameter of about 30 mm to 50 mm, and then metal pieces and plastic pieces are separated, and metal pieces and plastic pieces are separated. Weight ratio of plastic strips to 4
A method for recovering metals from a mixed waste of metals and plastics, which comprises burning a mixture in a ratio of 1 to 1 in a rotary kiln at about 300°C to about 500°C to remove carbides from metal pieces.