JP2553811B2 - How to recycle iron scrap - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling iron scrap from iron scraps such as steel beverage cans and tin plates by removing the substance currently plated on the scraps. In particular, the present invention relates to a method for recovering iron scrap as a steelmaking raw material by removing tin from the tin-plated iron scrap.

[0002]

2. Description of the Related Art In order to recycle iron scrap such as steel beverage cans as a steelmaking raw material, it is necessary to separate and remove paints, synthetic resins, plating layers, etc. adhering thereto. . In particular, unless the tin plating adhering to the iron scrap is surely removed, high quality steel cannot be regenerated.

For this reason, various iron scrap recycling methods have been conventionally proposed, and among them, there is a method of removing tin plating by an electrolytic method. However, although this method has high tin separation efficiency, it requires a large amount of electric power and is not practical.

On the other hand, as a method for removing tin plating from iron scrap, there are methods disclosed in, for example, Japanese Patent Laid-Open Nos. 2-182842 and 2-97624. These methods involve heating tin-plated iron scrap with a detinning agent under reduced pressure to form a tin compound and separating the tin compound from the iron scrap. In this method, it is necessary to set the processing conditions such as performing the processing in a closed container under reduced pressure, and since a destining agent such as sulfur is used, it is necessary to perform post-processing such as recovery thereof There is.

An object of the present invention is to propose a method capable of efficiently regenerating iron scrap by removing paint, plating, etc. adhering thereto, particularly tin plating, from iron scrap with a simple treatment process. To do.

[0006]

In order to solve the above problems, in the iron scrap recycling method of the present invention, the recycling is performed by the following procedure.

First, iron scraps such as used iron beverage cans are crushed to a predetermined size. Usually, it is a scaly strip having a size of about 5 to 50 mm.

[0008] The iron scrap pieces thus obtained are
By heating in the rotary kiln, combustible substances such as synthetic resin and paint that adhere to the kiln are burned to form carbides. Normally,
As the tin plating formed on the iron scrap melts
Within the range of about 350 degrees Celsius to about 850 degrees Celsius
Although it is heated to a temperature , since the lid of an iron beverage can or the like is made of aluminum, it is heated to a temperature at which the aluminum can lid melts.

After that, the heated iron scrap pieces are cooled. That is, the iron scrap piece heated in the rotary kiln is cooled to 350 degrees Celsius until it is discharged from the rotary kiln to solidify aluminum while the tin content is melted and the surface of the iron scrap piece is melted. An oxide film is formed on. That is, at about 350 degrees Celsius
Since the tin content remains molten in the rotary kiln,
The tin moves in the rotary kiln and the surface of the scrap iron is
Exposed. Therefore, it is difficult for tin to reattach to iron scrap.
It is possible to form an oxide film on the surface of iron scrap
I can .

In solidified aluminum and molten state
Exhaust scrap iron from a rotary kiln with some tin.
After taking out, the iron scrap piece on which the oxide film is formed is hit with a rotary hammer or the like to separate the oxide film from the iron scrap piece.

Finally, from the scrap iron scrap, the peeled oxide film, carbide, solidified aluminum , and tin are removed.
Separate and collect only scrap iron.

The synthetic resin, paint, tin plating and the like are separated from the iron scrap by the treatment process of the present invention.
However, by repeatedly performing this treatment step on the same iron scrap, it is possible to recover the iron scrap with less impurities. In particular, tin can be reduced in content to the extent that it can be used as a steelmaking raw material by repeating the treatment process of the present invention several times.

In the method of the present invention, the oxide film is peeled off by using a rotary hammer, and the iron scrap pieces are recovered in a granulated state by repeating each step for the same iron scrap. It can be used as an iron ball for shot blasting.

[0014]

EXAMPLE A method for recycling a used iron beverage can according to the present invention will be described below with reference to FIG.

In the method of this embodiment, first, a used iron beverage can is crushed by the crusher 1 into scale-like iron fine pieces. The crushed iron strip is dropped through the screen 1a arranged at the bottom of the crusher 1. Screen 1 of this example
a is a mesh with a diameter of 30 mm, and only iron fine particles smaller than this drop.

The iron strips that have dropped on the screen 1a are air-fed to the cyclone 3 by the blower 2, and the high speed rotation in the cyclone 3 separates impurities such as dust and sand adhering to the iron strips. At the same time, fine powder such as paint having a particle size of 100 μm or less and vaporized water vapor remaining and remaining in the iron strips are absorbed by the back filter 4 and removed.

Next, impurities such as dust and sand separated from the iron strips discharged from the cyclone 3 are removed from the iron strips and the iron strips are fed into the tank 7 by air.

Next, the iron strips stored in the tank 7 are
It is supplied to the heat treatment machine 8 at a predetermined supply rate by a screen conveyor. The heat treatment machine 8 is a high temperature heat resistant special rotary kiln in this example, and the iron strips are heated to about 720 degrees Celsius while being conveyed through the inside toward the discharge side. By being heated to a burning state in this way, the synthetic resin, paint, compound, etc. adhering to the iron strips self-combust into carbides. Further, the strips of the aluminum can lid mixed with the iron strips are melted and separated from the iron strips.

After that, the iron strip heated to the scorching state is gradually cooled as it is transported to the discharge side of the heat treatment machine 8 and is discharged to the outside. In this example, it is cooled down to around 350 degrees Celsius. In this cooling step, a film containing about 50% of iron oxide is formed on the surface of the iron strip. Also, the aluminum pieces that have been melted and separated solidify again.

The iron strip with the oxide film thus formed is carried into a rotary hammer 9 which is an impact granulator. In this, fixed impact plate and rotary impact body are arranged,
By these, the iron strip is hit and the oxide film on the surface is peeled off. While passing through the inside of the rotary hammer 9, the iron strip is formed into a spherical shape, and the peeled oxide film,
Separated from carbide and solidified aluminum pieces.

Through the above steps, spherical iron from which impurities have been removed is recovered from the used iron beverage can.

Here, in order to reduce the content of tin contained in the recovered iron, the above steps may be repeated for the recovered iron. According to tests by the present inventors,
When one cycle of the above treatment was carried out using a 28% tin-plated iron beverage can, it was confirmed that about half of the tin had been removed. Subsequently, when the above treatment was repeated, it was confirmed that the content of tin in the iron recovered after the completion of 3 cycles was about 0.05% or less.

It was also confirmed that the iron recovered by repeating the method of this example has a spherical shape, which can be directly used as an iron ball for shot blasting.

Here, in the method of this example, in order to efficiently form the oxide film on the iron strip, the temperature inside the rotary kiln is increased, excess air is supplied, the cooling time is lengthened, etc. The conditions may be set appropriately. Alternatively, a long louver of the rotary kiln may be adopted to promote the supply of air to the burning iron strip. The heating temperature in the rotary kiln, the residence time of the iron strips therein, the cooling rate of the heated iron strips, etc. are not uniquely set, but the supply ratio of the iron strips to the rotary kiln, Based on the capacity of the rotary kiln, etc., it should be set to optimum conditions individually.

Further, according to the method of this embodiment, not only tin but also zinc, chromium, nickel contained in iron scrap,
Of course, impurities such as solder, lead, and copper can also be separated and removed. Further, it goes without saying that the iron scrap targeted by the method of the present example is not limited to a used iron beverage can and may be another iron scrap.

[0026]

As described above, in the method of the present invention, iron scrap pieces obtained by crushing iron scrap such as used iron beverage cans into a predetermined size are heated and adhered thereto. Combustible materials such as synthetic resins and paints are burned, and heated iron scrap pieces are cooled to form an oxide film on the surface, and the oxide film is struck to remove the oxide film from the surface. Therefore, according to the method of the present invention, iron scrap can be regenerated by a simple processing step. Further, according to the method of the present invention, by repeating the same treatment step for the same iron scrap, it is possible to recover a steelmaking raw material containing a small amount of impurities such as tin.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a method of recycling a used iron beverage can according to the present invention.

[Explanation of symbols]

 1 ... Crusher 1a ... Screen 3 ... Cyclone 7 ... Tank 8 ... Rotary kiln 9 ... Rotary hammer

Claims (4)

(57) [Claims] 1. A crushing step of crushing iron scrap including iron beverage cans having a tin layer and aluminum pieces to a predetermined size, and a synthetic resin and a paint adhered to the crushed iron scrap pieces in a rotary kiln. When burning combustible materials such as
First, the tin layer and the aluminum pieces are melted.
The heating process and heated iron scrap pieces are discharged from the rotary kiln.
Aluminum in the molten state solidifies before
The scrap iron is cooled until
By moving the molten tin inside the run,
Exposing the surface of the lap piece and oxidizing it to the surface of the iron scrap piece
Cooling process to form a film, along with solidified aluminum and molten tin
After discharging scrap iron from the rotary kiln,
Striking scrap pieces to remove oxide film from iron surface
Peeling process and oxidized skin peeled from scrap iron by the peeling process
Membranes, carbides produced by combustion of the combustibles, iron scrap
Aluminum and iron scrap pieces detached from the scrap pieces
Separation and removal of tin desorbed from iron from iron scrap pieces
A method for recycling iron scrap, comprising the steps of : 2. The method for recycling iron scrap according to claim 1, wherein the steps are repeated for the same iron scrap. 3. The iron scrap piece heated in the cooling step according to claim 1, is cooled to around 350 degrees Celsius in the cooling step, and the peeling step is performed by an impact granulator to granulate the iron scrap piece. A method for recycling iron scrap, which is characterized in that 4. The method for reclaiming iron scrap according to claim 3, wherein iron balls for shot blasting are formed by repeating the above steps for the same iron scrap.