JP4593443B2 - Recycling method of shredder dust - Google Patents

Description

  The present invention relates to a method for recycling shredder dust, and more particularly to a method for effectively using shredder dust as an additive such as a carburizing material and auxiliary fuel in a steelmaking and steelmaking furnace.

  Shredder dust (SR) is a general term for crushing waste remaining after crushing waste after removing useful parts that can be reused from used automobiles, home appliances, etc., and collecting valuable metals. Shredder dust consists mainly of organic substances (combustible materials) such as resin, fiber, urethane, rubber, and other miscellaneous lightweight mixtures that contain inorganic substances such as glass, earth, and uncollected metals (usually a bulk specific gravity of about 0.2-0. 4).

  Conventionally, most of shredder dust has been disposed of in landfills as it is or after volume reduction. However, there are limits to the disposal site, and it is desirable to effectively use shredder dust from the viewpoint of recycling and environmental protection. As one of them, it is known to use shredder dust as an alternative to coke or coal used as a carburizing material or auxiliary material in an electric furnace for steelmaking.

  If shredder dust is put into the furnace as it is, the combustion speed is too fast and the combustion reaction is concentrated at once. As a result, the exhaust gas temperature rises due to the combustion heat, or the rate at which the CO gas is exhausted outside the furnace (such as a dust collector) without being completely burned increases, and the heat generated by the shredder dust heats the iron scrap and molten steel. In some cases, the amount of energy required for melting the scrap may be increased due to the introduction of the shredder dust. In addition, there was a problem that excessive load was applied to the equipment, for example, the flame soared at the time of charging and the temperature rose rapidly.

For this reason, shredder dust has been reduced and solidified for use, and it has also been proposed to adjust the combustion rate by molding large and small solidified products and mixing them (for example, And Patent Documents 1-2).
However, these methods are still not sufficient in terms of effective use of shredder dust. In addition, when conditions such as the scale, type, and operation method of the furnace to which the volume-reduced solids are introduced change, the optimum burning speed of the shredder dust often varies, and each time such a change in conditions occurs, If an attempt is made to adjust the burning rate by changing the size of the solidified product, a new volume-reducing solidification facility is required. Further, in order to reduce the burning rate by volume reduction solidification, it is necessary to increase the size of the solidified product, but there is a limit to this.
JP 2001-116226 A JP 2002-192137 A

  The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to make it possible to use shredder dust as an additive such as a carburizing material or auxiliary material in a steelmaking and steelmaking furnace, and to easily increase the burning rate. It is to provide a method for recycling shredder dust that can be adjusted.

As a result of intensive studies by the present inventors in order to achieve the above-mentioned problems, it is possible to easily adjust the combustion rate by mixing reduced slag with shredder dust and reducing the volume, and in steelmaking and steelmaking furnaces. The present invention was completed by finding that it can be used effectively.
That is, in the method for recycling shredder dust according to the present invention, the shredder dust containing combustible material contains at least one selected from reducing slag and converter slag as a combustion rate control agent in a content of 3 to 60% by mass. It mixes so that it may become, and this is volume-reduced and it is used as an additive of the furnace for iron manufacture and steelmaking .
In the method of the present invention, it is preferable that the bulk specific gravity of the volume-reduced product is 0.8 to 1.5.

  According to the present invention, by mixing the combustion rate control agent with the shredder dust, the combustion rate can be easily adjusted using the existing volume reduction solidification equipment, and the shredder dust is added to the furnace additive for iron making and steel making. Can be used as effective. Further, reduced slag has been difficult to reuse in the past, but according to the present invention, the reduced slag can be effectively utilized as a combustion rate inhibitor and can be reused by making it into oxidized slag.

When processing shredder dust into steelmaking and steelmaking furnaces, the carbon content of organic matter contained in shredder dust can be used as a carburizing material, and the amount of heat generated by the combustion of organic matter is effective for melting iron scrap, etc. Although it is desirable to use it, in order to use the carbon content of organic matter as a carburizing material and to effectively use the amount of heat held by the shredder dust, the burning rate of the shredder dust in the furnace must be set appropriately. It is important to adjust.
In the present invention, the combustion rate of the shredder dust is adjusted by mixing the shredder dust with a combustion rate control agent.

  The control agent is preferably mixed with the shredder dust so as to be 3 to 60% by mass with respect to the entire mixture of the shredder dust and the inhibitor. If the amount of the control agent is too small, the shredder dust burning rate suppression effect will not be exhibited, the carbon content of the organic matter in the shredder dust cannot be converted into a carburized material, and the heat generated by the shredder dust input cannot be used effectively for melting iron scrap, etc. . On the other hand, when there is too much control agent, the ratio of shredder dust will become too small, and the processing efficiency of shredder dust will worsen. Moreover, since the amount of organic substances in the volume-reduced product is insufficient, the combustion efficiency and the heat receiving efficiency are reduced.

The control agent is preferably powdery or granular. In particular, the powder has good miscibility with the shredder dust and has a high combustion rate control effect.
As the control agent, those that do not cause an exothermic reaction in the furnace and do not adversely affect iron and steel making, and can be preferably used as hatching materials or desulfurization materials if possible. In the present invention, reduced slag and converter slag can be mentioned, and particularly reduced slag can be preferably used.

Although reduced slag is slag generated at the time of reductive refining in an electric furnace, since it contains CaO as a main component, it has expansion and collapse properties and its reuse is not progressing. Converter slag is a component system similar to reduced slag and has the same problems. In the present invention, reduced slag or the like can be used as a control agent. When the shredder dust volume-reduction product mixed with reduced slag is used during electric furnace oxidation refining, the reduced slag is regenerated as oxidized slag. Oxidized slag has a lower CaO ratio and higher quality stability than reduced slag, so it can be reused almost 100% as aggregate for asphalt or aggregate for concrete.
Therefore, the present invention is useful not only as shredder dust but also as one method for reusing reduced slag. Moreover, since reducing slag contains many CaO, the reduction effect of the lime used at the time of oxidation refining can also be anticipated.

After mixing the control agent with the shredder dust, the volume is reduced by an ordinary method such as pressurization. In volume reduction, you may heat as needed. By reducing the volume, the surface area is reduced and the bulk specific gravity is increased, so that the combustion rate is further suppressed.
The bulk specific gravity of the volume-reduced product is usually 0.8 to 1.5, preferably 1.0 to 1.5, more preferably 1.2 to 1.4. The size and shape of the volume-reduced product are not particularly limited.

The shredder dust volume-reduced product of the present invention thus obtained can be used as an additive for a steelmaking / steelmaking furnace. In particular, it can be suitably used as a carburizing material or auxiliary material in an electric furnace for steel making.
In the present invention, it is possible to reduce shredder dust using existing volume-reducing solidification equipment by appropriately selecting the type and ratio of the control agent according to various conditions such as the furnace to which shredder dust is to be introduced and the operation method thereof. The combustion rate of the contents can be adjusted easily.
Hereinafter, the present invention will be further described with specific examples, but the present invention is not limited thereto.

Reduced to shredder dust (80 mm sieve, bulk specific gravity of about 0.3, organic matter content of about 60%) after further removal of valuable metals from crushed materials such as scrapped automobiles and waste home appliances after removing useful parts The slag was mixed and reduced in volume by pressure extrusion to produce an additive (bulk specific gravity: about 1.3) having a diameter of about 11 cm and a length of about 20 cm.
The obtained additive was put into an electric furnace (EF) together with iron scrap, and the relationship between the amount of input heat and the amount of exhaust heat when melting by a normal operation method was investigated.

FIG. 1 shows the relationship between the input heat amount and the exhaust heat amount when the reduction slag mixing ratio is 30% by mass (Test Example 1).
In FIG. 1, the input heat amount is the retained heat amount (Mcal) of the input additive per 1 Mt of input iron scrap. The amount of heat discharged is the amount of heat (Mcal / Mt · input iron scrap) discharged outside the furnace without being used in the electric furnace. The input heat amount = exhaust heat amount line is a line in which the input heat amount is not used at all, that is, the heat receiving efficiency = 0. It means that the smaller the amount of exhausted heat with respect to the amount of input heat (the smaller the slope of the straight line), the higher the heat receiving efficiency of the additive material.

  As can be seen from FIG. 1, when the solidified product of Test Example 1 was used, the utilization rate of the input heat amount was about 40%. On the other hand, when the volume reduction and solidification was not performed only with the shredder dust (Comparative Example 1), the input heat amount was discharged with little use. Even when only the shredder dust was reduced and solidified without using a control agent, the utilization rate of the input heat amount was low.

Table 1 below is a result of comparing the exhaust gas composition of the electric furnace between (a) volume reduction solidification without adding a control agent and (b) volume reduction solidification by adding a control agent. . It can be seen that by blending the control agent, not only the exhaust gas temperature was lowered, but also the CO gas concentration was lowered. Since CO is an unburned gas, this result shows that the reaction indicated by CO + 1 / 2O ₂ = CO ₂ occurs more in the electric furnace when the control agent is used, and the retained energy of the additive is calculated as the amount of heat. It shows that it can be used effectively.

(Table 1)
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Test level Exhaust gas temperature (° C) CO ₂ (%) CO (%) O ₂ (%)
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(A) No inhibitor added 1,011 7.2 11.2 5.2
(B) Inhibitor formulation * 969 9.8 8.5 4.6
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* Inhibitor compounding ratio: 30% by mass

It is a figure which shows the relationship of the amount of exhaust heat with respect to the amount of input heat | fever when only the additive material (test example 1) obtained by the manufacturing method of this invention or only shredder dust (comparative example 1) is thrown into the electric furnace.

Claims (2)

The shredder dust containing combustible material is mixed with at least one selected from reducing slag and converter slag as a burning rate control agent so that the content is 3 to 60% by mass, and this is reduced in volume to produce steel. A method for recycling shredder dust, which is used as an additive for a steelmaking furnace. 2. The method for recycling shredder dust according to claim 1 , wherein the bulk specific gravity of the volume-reduced product is 0.8 to 1.5.

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