JP2007021444A - Recycling method of shredder dust and raw material for steelmaking - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively utilize resins, which are sorted from shredder dust and processed, as a heat source of an electric furnace for steelmaking when shredder dust is thrown in the electric furnace for steelmaking and reused as the heat source of the electric furnace for steelmaking. <P>SOLUTION: Resins are sorted from shredder dust and the sorted resins are processed to recover the processed resins as a melt-solidified material. Such a raw material/fuel body 60 is molded that the periphery of the recovered melt-solidified material 48 is covered with an iron piece 62 so that the surface of the recovered melt-solidified material 48 is not exposed. The molded raw material/fuel body 60 is thrown in the electric furnace. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for reusing shredder dust that is generated when shredded automobiles and waste home appliances are shredded with a shredder. Specifically, the present invention relates to a technique for reusing a resin selected and processed from shredder dust as a heat source for a steelmaking electric furnace.

Shredder dust contains a large amount of plastics, rubbers, and fibers (hereinafter referred to as resins), and it is considered to reuse these resins. As a technique for reusing waste made of resins, for example, a technique described in Patent Document 1 is known.
In the technique of Patent Document 1, a metal product waste mainly made of an iron-based metal material and a resin product waste mainly made of a tire waste and a synthetic resin material are made into a scrap scrap press at a predetermined ratio. Into a rectangular parallelepiped shape. The steelmaking raw fuel body formed into a rectangular parallelepiped shape is suspended by an electromagnet and put into a bucket, and then put into a steelmaking electric furnace. Of the raw material for steelmaking, the metal product waste becomes an iron source, and the tire waste and the resin product waste are reused as fuel for an electric furnace for steelmaking.
Japanese Patent Laid-Open No. 10-30112

  However, in the raw material for steelmaking according to the prior art, resins and irons are randomly mixed, and the resins are exposed on the surface thereof. For this reason, when a conventional raw material for steelmaking is put into an electric furnace, the resins exposed on the surface are instantaneously exposed to a high temperature. Moreover, since resin and iron are mixed at random, the contact area of resin and iron is large, and the thermal decomposition rate of resin is large. For these reasons, when a conventional steelmaking raw fuel element is put into an electric furnace, the resin of the steelmaking raw fuel element burns rapidly, and a large amount of combustion gas is generated in a short time. Since a large amount of combustion gas generated in a short time is discharged from the electric furnace as exhaust gas as it is, there is a problem that the resin for the steelmaking raw fuel is not effectively used as a heat source for the electric furnace.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a technique that can effectively use resins selected and processed from shredder dust as a heat source of a steelmaking electric furnace. .

The method of reusing shredder dust of the present invention created in order to solve the above-mentioned problems is a method of throwing shredder dust into an electric furnace for steel making and reusing it as a heat source for an electric furnace for steel making. A process of selecting and processing and collecting the resins, a process of forming a raw fuel body whose periphery is covered with iron pieces so that the recovered resins are not exposed from the surface, and a molded raw fuel body And putting it into an electric furnace.
In this method, resins selected and processed from shredder dust are not exposed on the surface of the raw fuel body. For this reason, even if the raw fuel body is put into the electric furnace, the resin of the raw fuel body is not instantly exposed to the high temperature atmosphere in the electric furnace. Moreover, since resin is hardened and arranged inside the iron piece, the contact area between the resin and the iron piece is reduced, and the thermal decomposition rate of the resin is suppressed. For these reasons, the combustion of the resins proceeds gently, the generation of a large amount of combustion gas is suppressed in a short time, and it can be effectively used as a heat source for an electric furnace for steel making.

In the molding step, it is preferable to press-mold the resin and the iron piece so that the resin is not exposed from the surface. By press-molding the resins and iron pieces, the amount of resin per raw fuel body can be increased.
The recovered resins are preferably melted and solidified by being heated and compressed before the molding step. By melting and solidifying the resins, the amount of resin per raw fuel body can be increased. Moreover, by melting and solidifying the resins, the burning rate of the resins can be further suppressed, and the resin can be used more effectively as a heat source for the steelmaking electric furnace.

The present invention also provides a novel raw material for steelmaking that can be suitably used as a heat source for an electric furnace for steelmaking. That is, the steelmaking raw fuel body of the present application is a steelmaking raw fuel body produced by press-molding resins selected and processed from shredder dust and iron pieces recovered from iron-based waste. The iron piece covers the periphery of the resin, and the resin is not exposed from the surface.
Even in this steelmaking raw fuel body, since the resins are not in contact with the surface of the raw fuel body, the combustion rate is low, and the steelmaking raw fuel body can be effectively used as a heat source for the steelmaking electric furnace.
In addition, it is preferable that the iron piece which covers the circumference | surroundings of resin is sufficiently thin with respect to the dimension of a raw fuel body. By setting it as such a structure, the resin amount per raw fuel body can be increased. The resins are preferably melted and solidified by heat compression.

  Moreover, it is preferable that resin is formed in multiple layers by the iron piece distribute | arranged to the inside. By dividing the resin, which is solidified inside the iron piece, into a plurality of layers (solids) by the iron piece, the combustion rate of the resin can be controlled more easily.

Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings. First, a shredder plant that processes scrap automobiles and waste home appliances and a recycling plant that recycles shredder dust (hereinafter also referred to as ASR) generated in the shredder plant will be described. FIG. 1 is a diagram showing the overall configuration of a shredder plant and a recycling plant.
In the shredder plant 10, first, a scrap car to be delivered is roughly cut with a pre-shredder 12, and the cut scrap car is put into a shredder body 14. The thrown-out automobiles and the like that are input are further finely cut by the shredder body 14.
The cut matter discharged from the shredder main body 14 is separated into a heavy object and a light object by the wind power classification 16. What is made light by the wind separation 16 is collected by the cyclone and becomes shredder dust 24. In addition, dust contained in the air discharged from the shredder body 14 is also collected by a cyclone or the like to become shredder dust 24.
What is made heavy by the wind separation 16 is further separated into one of iron scrap 20, non-ferrous metal 22 and shredder dust 24 by a magnetic separator 18. The iron scrap 20 and the non-ferrous metal 22 separated in the shredder plant 10 are reused as resources, while the shredder dust 24 is reused in the recycling plant 26.

In the recycling plant 26, first, the shredder dust 24 is applied to the rotary sieve 28. Falling objects falling from the rotary sieve 28 are separated into glass 30 and light weight objects by air separation. A lightweight thing is thrown into the melt solidification machine 46 mentioned later.
The shredder dust 24 remaining on the rotary sieve 28 is crushed by a crusher 32. The shredder dust 24 crushed by the crusher 32 is separated into aluminum 34, iron 37, and resins by non-ferrous sorting 36. Resins separated by the non-ferrous fractionation 36 are further pulverized by a pulverizer 38. The shredder dust 24 pulverized by the pulverizer 38 is sorted into copper 42 and granular resins 44 by air separation and specific gravity separation, and the other resins are put into the melt-solidifier 46.
The melt-solidifier 46 heats and compresses the shredder dust 24 that has been charged to produce a melt-solidified product 48. As the melting and solidifying machine 46, for example, the one described in Japanese Patent Application Laid-Open No. 2003-21139 can also be used. That is, the melting and solidifying machine 46 can include a casing, two screws arranged in the casing, and a heating unit. The two screws rotate in opposite directions while engaging each other. When the shredder dust 24 is introduced into one end of the casing, the introduced shredder dust 24 is conveyed while being compressed in the casing by the rotation of the screw. The shredder dust 24 conveyed in the casing is heated by the heating means, whereby the thermoplastic resin contained in the shredder dust is melted, and the melted solid product 48 is produced.

In this embodiment, the raw fuel body 60 of the electric furnace for steel making is manufactured using the melt-solidified material 48 manufactured by the recycling plant 26 mentioned above. FIG. 3 is a perspective view of the raw fuel body 60, and FIG. 4 is a cross-sectional view of the raw fuel body 60.
As shown in FIGS. 3 and 4, the raw fuel body 60 includes a resin part 64 formed of the melted solidified product 48 and an iron scrap part 62 that covers the outer periphery of the resin part 64. The iron scrap part 62 is comprised with the iron piece etc. which were collect | recovered from the iron-type waste. As is apparent from the drawing, the raw fuel body 60 is formed in a rectangular parallelepiped shape, and the surface thereof is covered with the iron scrap portion 62. For this reason, the resin part 64 is not exposed to the surface of the raw fuel body 60.
3 and 4, the iron scrap portion 62 is shown as a single iron plate, but actually, the iron scrap portion 62 is formed from a plurality of iron pieces. For this reason, the thickness and shape of the iron scrap portion 62 differ depending on the location. However, the thickness of the iron scrap part 62 with respect to the dimension of the raw fuel body 60 is sufficiently small.
Further, as shown in FIG. 5, in the raw fuel body 60, an iron scrap portion 62 a can be formed in the resin portion 64, and the resin portion 64 can have a two-layer structure. By making the resin part 64 have a two-layer structure, the combustion state after charging the electric furnace can be controlled more finely.

The raw fuel body 60 is manufactured by mixing the molten solidified material 48 and iron pieces (for example, plate-shaped iron scrap) at a ratio of 5: 5 to 2: 8 (weight ratio) and press-molding it into a rectangular parallelepiped shape with a baler machine. To do. At this time, an iron piece is spread and leveled, and then the melted solid 48 is placed and press-molded. As a result, the melted solid 48 is not exposed on the surface, and only the iron piece is exposed on the surface.
In addition, although a loose plate can be used for the iron piece, it is preferable to use a large plate. By using a large plate, the molten solidified product 48 is hardly exposed to the surface. The melted solid 48 may be packed in a sandbag or the like and put into a baler machine, but may be put into pieces separately. When the melted and solidified product 48 is thrown apart, the melted and solidified product 48 may be piled up at one place, but it is preferable that the melted and solidified product 48 is spread evenly. By uniformly spreading the melt-solidified product 48, the melt-solidified product 48 becomes difficult to be exposed on the surface.

  The raw fuel body 60 described above can be used as a heating source and a carburizing source for electric furnace steelmaking. Electric furnace steelmaking refers to the process of recycling iron scrap into steel. FIG. 2 schematically shows the configuration of an electric furnace used for electric furnace steelmaking. As shown in FIG. 2, the electric furnace 50 includes a furnace body 51 that is open at the top and a lid 53 that closes the top of the furnace body 51. An electrode 52 is attached to the lid 53. The electrode 52 can be moved back and forth in the electric furnace 50.

Here, an example of the operation pattern of electric furnace steelmaking will be briefly described. In the electric furnace steelmaking process, iron scrap is first adsorbed by a lifting magnet and put into a charging bucket. The lid 53 of the electric furnace 50 is opened, and then the iron scrap charged in the charging bucket is transported together with the charging bucket to the furnace body 51, and the iron scrap is loaded into the furnace body 51 from above the furnace body 51. Enter (first dress). The lid 53 of the furnace body 51 is closed, an arc is generated from the electrode rod 52, and the iron scrap in the electric furnace 50 is melted by the arc (first melting period).
When the iron scrap in the electric furnace 50 is melted to some extent, the scrap is put into the electric furnace 50 in the same procedure as the initial wearing (additional). An arc is generated again from the electrode rod 52, and the scrap in the electric furnace 50 is melted by the arc (second melting period). Finally, forming is performed to raise the temperature of the molten steel 56 in the electric furnace 50, and then the molten steel 56 in the electric furnace 50 is removed.

The raw fuel body 60 described above can be charged into the electric furnace 50 at the initial stage of the electric furnace steelmaking process, or can be charged into the electric furnace 50 at the stage of additional loading. When charging the electric furnace 50 in the initial loading stage, the raw fuel body 60 can be charged in any of the lower part, the center, or the upper part of the furnace body 51. That is, even if charged in the lower part of the furnace, the resin part 64 (solidified resin 48) of the raw fuel body 60 is gently pyrolyzed and burned as will be described later, so there is no risk of bumping.
In addition, the raw fuel body 60 has an iron scrap portion 62 arranged on the outer side thereof, and is attracted by a lifting magnet and charged into a charging bucket like the iron scrap, and is charged into the electric furnace 50.

The raw fuel body 60 charged in the electric furnace 50 is heated in the electric furnace 50, the iron scrap part 62 is melted to become a raw material of steel, and the resin part 64 is combusted. The resin part 64 is surrounded by the iron scrap part 62 from the initial stage to the middle stage when the iron scrap starts to melt, and the combustion rate of the resin part 64 is suppressed by the low oxygen atmosphere in the iron scrap part 62. Moreover, since the resin part 64 is solidified and exists in the iron scrap part 62, a contact area with the surrounding iron piece (iron scrap part 62) becomes small, and the thermal decomposition rate becomes slow. By these, the combustion of the resin part 64 proceeds gently, and combustion gas is not generated abruptly. For this reason, the combustion heat of the resin part 64 heats to iron scrap effectively. Moreover, since the amount of combustion gas does not increase rapidly, the exhaust gas can be treated with a small exhaust gas treatment facility.
Furthermore, since the solidified resin 48 is solidified inside the raw fuel body 60, the thermal decomposition rate is slow, and the solidified resin 48 remains until the end of melting of the iron scrap. For this reason, combustion gas of the resin solidified material 48 is generated at the end of melting, and the molten slag is formed by the combustion gas and the arc is stabilized (that is, the metal vapor partial pressure in the electric furnace 50 is reduced and the arc is stabilized. ).
Further, the resin portion 64 of the raw fuel body 60 contains carbon. Usually, in the electric furnace steelmaking process, it is said that about 5% is good as the carbon concentration necessary for raising the temperature of the iron scrap (refer to JP-A-9-143533). The carbon concentration in the iron scrap charged in the electric furnace 50 is about 0.2%, and in the case of a thin plate, it is about 0.05%. For this reason, the fixed carbon of the resin portion 64 of the raw fuel body 60 functions as a carburizing material, and the amount of carbon source (such as coke powder) blown into the electric furnace 50 can be reduced.
In addition, the volatile matter of the resin part of the raw fuel body 60 is used as a heat source, and the ash remains as steelmaking slag. This steelmaking slag can be used for roadbed materials and the like.

As is clear from the above description, in this embodiment, the resins and plastics recovered from the shredder dust are melted and solidified, and the raw fuel body 60 is manufactured using the melted and solidified product 48. The raw fuel body 60 has iron scrap disposed on the surface thereof, and no molten solidified product is exposed on the surface. For this reason, rapid combustion of the resin part 64 of the raw fuel body 60 is suppressed, and the resin part 64 of the raw fuel body burns slowly. When the resin part 64 burns slowly, the combustion heat of the resin part 64 can be effectively used for raising the temperature of the iron scrap.
In addition, since the resin part 64 burns slowly, the temperature in the electric furnace 50 does not rise rapidly, so that the electric furnace 50 can be prevented from being damaged.

  Next, examples of the present invention will be described. In an embodiment of the present invention, a raw fuel body was manufactured using shredder dust of a scrap car, and the raw fuel body was used in a steelmaking process. Table 1 shows the properties of the shredder dust (ASR) used in the examples, the granular resins 44 obtained from the shredder dust (ASR), and the melt-solidified product 48.

The raw solid fuel body 60 was manufactured by mixing the melt-solidified material 48 shown in Table 1 and press waste (iron pieces) at a ratio (weight ratio) of 4: 6 and press-molding it into a rectangular parallelepiped with a baler machine. The shape of the raw fuel body 60 was 600 mm × 500 mm × 500 mm, and its bulk specific gravity was about 2.6 t / m ³ . In the following table, the raw fuel body 60 is described as “Experimental material 2”.
Further, granular resins 44 shown in Table 1 and iron scrap (Dalai dust) were mixed at a weight ratio of 3 to 7, and melted and solidified by a melt-solidifying machine 46 to produce a raw fuel body. The shape of the raw fuel body was Φ130 mm × 150 to 200 mm, and the bulk specific gravity was about 2.5 t / m ³ . In the following table, this raw fuel body is described as “Experimental material 1”.
Furthermore, as a comparative example, a waste car that was primarily dismantled was produced as it was. In the table below, it is described as “waste car”.

  In the electric furnace 50, iron scrap, which is the main raw material, was charged in a bucket by initial charging and additional charging. The experimental materials (raw fuel body 60, raw fuel body, and scrap automobile materials) were charged at the same time as iron scrap at the time of initial charging. The total amount of experimental materials and iron scrap was about 95t (of which 3t was experimental material), and the amount of input was about 59t of iron scrap. The experiment time is 2-3 minutes for the first charge, 20 minutes for the first melting period, 2-3 minutes for the additional charge, 20 minutes for the second melting period, 20 minutes for the heating, and 5 minutes for the steel output. there were.

  First, in order to determine the charging position of the experimental material, the charging position (lower part, center, upper part) of the experimental material 1 is changed, the state of the flame in the electric furnace 50 immediately after charging is observed, and the electric power immediately after charging is observed. The upper temperature of the furnace 50 was measured. The measurement results are shown in Table 2.

In the table, regarding the occurrence of visual flame, the evaluation was made as follows: 1: the same as usual, 2: somewhat more flame, 3: more flame. Moreover, regarding the electric furnace upper part temperature immediately after charging, it was evaluated that 1: the same as usual, 2: the temperature was slightly high, and 3: the temperature was high.
As apparent from Table 2, when the charging position of the experimental material was set to the upper part of the initial part, a flame was generated and the temperature of the upper part of the electric furnace also increased. On the other hand, no flame was generated and no increase in temperature was observed regardless of whether the experimental material was placed at the lower part of the initial part or the center of the initial part. However, since the lower part of the initial wear is preferable from the viewpoint of workability, the following measurement was performed by inserting the lower part of the initial wear.

Table 3 shows the heat balance when the experimental material 1, the experimental material 2, and the scrapped automobile are charged into the electric furnace 50 and the steel making process is performed. Moreover, the heat balance in normal operation is shown as a comparative example.
As is clear from Table 3, the “waste car” had the highest exhaust gas temperature and the largest amount of heat carried by the exhaust gas. Assuming that the overall heat receiving efficiency is the retained heat of the molten steel / subtotal, the heat receiving efficiency deteriorates in the order of normal operation, experimental material 2, experimental material 1, and scrapped vehicle.

Further, the heat receiving efficiency of the resin in the experimental material was evaluated as heat receiving efficiency = (material heat amount−heat loss 1−heat loss 2) ÷ material heat amount.
Here, heat loss 1 is {in the case using the resin material (heat removed from the cooling water + heat removed from the exhaust gas)} − {in normal operation (heat removed from the cooling water + heat removed from the exhaust gas)} Loss 2 = CO concentration increase in this case compared to normal operation was defined as calorie conversion— {in normal operation (heat removed from cooling water + heat removed from exhaust gas)}.
Table 4 shows the evaluation results of the heat receiving efficiency of the resin in the experimental material. The unit of each numerical value in Table 4 is Mcal / Mt.

  As can be seen from Table 4, when the “waste car” was used, the combustion heat from the resin did not reach the iron scrap, while when the experimental materials 1 and 2 were used, the resin burned. Heat is applied to iron scrap. This is thought to be because, in the experimental materials 1 and 2, since the resin component is melted and solidified and gently fueled, the combustion heat stably heats the iron scrap.

  Table 5 shows the evaluation results of the carburizing effect. In the experimental materials 1 and 2, the basic unit of the carburized material was low, and it was confirmed that the experimental materials 1 and 2 functioned as the carburized material. In addition, it was confirmed that the basic unit of the carburized material was high in the “waste car” and this material did not function as a carburized material.

The preferred embodiments of the present invention have been described in detail above. However, these are merely examples, and the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. it can.
It should be noted that the technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

The figure which shows the whole structure of the shredder plant and recycling plant of this embodiment. Sectional view schematically showing the configuration of the electric furnace Perspective view of raw fuel Cross section of raw fuel Cross-sectional view of a raw fuel element according to a modification

Explanation of symbols

10. Shredder plant 26 Recycle plant 44 Granular resin 48 Melted solid 60 Raw material

Claims (6)

It is a method of putting shredder dust into a steelmaking electric furnace and reusing it as a heat source for a steelmaking electric furnace.
A process of selecting, processing and collecting resins from shredder dust,
Molding the raw fuel body in which the periphery of the resin is covered with iron pieces so that the recovered resin is not exposed from the surface;
A method of reusing shredder dust, comprising: charging a molded raw fuel body into an electric furnace.   The method for reusing shredder dust according to claim 1, wherein in the molding step, the resin and the iron piece are press-molded so that the resin is not exposed from the surface.   The method for reusing shredder dust according to claim 1 or 2, wherein the recovered resins are heated and compressed and melted and solidified before the molding step. It is a raw material for steelmaking manufactured by press-molding resins sorted and processed from shredder dust and iron pieces recovered from iron-based waste.
A steelmaking raw fuel element characterized in that an iron piece covers the periphery of a resin and the resin is not exposed from the surface.   The raw fuel body for steelmaking according to claim 4, wherein the resins are divided into a plurality of lumps by iron pieces disposed therein.   6. The raw fuel body for steel making according to claim 4 or 5, wherein the resins are melted and solidified by being heated and compressed.

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