JP2002241830A - Method for producing molten metal as steelmaking raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing molten metal with which a waste tire is easily charged regardless of at an initial charging time or at an additional charging time, and the using efficiency of the waste tire is improved by improving a method for utilizing the waste tire to the production of the molten metal as a steelmaking raw material in the steelmaking in an electric furnace. SOLUTION: When the molten metal is obtained by charging an iron source including scrap and an auxiliary raw material into the electric furnace and melting the iron source mainly with the heat of an arc, the raw materials finely divided the cut tire e.g. the waste tire as a part of the auxiliary raw material are used and a steel cord in the waste tire is added into the iron source, and a carbon content is utilized as a heat source and a carburizing agent, and sulfur content is dissolved into the molten metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a steelmaking process using an electric furnace, in which waste tires are used as a part of raw materials to improve the unit energy consumption and the unit consumption of reducing agents. The present invention relates to a method for producing a molten metal as a raw material for steelmaking.

[0002]

2. Description of the Related Art Electric furnace steelmaking begins with the operation of melting an iron source such as scrap by arc heating. In order to reduce energy costs, the furnace is heated with a heavy oil burner or blown with pulverized coal. Is being done. Oxygen blowing is also performed with the intention of decarburizing and raising the temperature of the molten steel.

On the other hand, the increase in the number of automobiles in recent years has produced a large amount of tire waste, and its reuse and disposal have become a serious problem in terms of effective use of resources and the environment. As a method of recycling waste tires, powder rubber is obtained by freeze grinding and cutting, and this is put into a mold together with a vulcanizing agent,
Attempts have been made to mold by heating, but since the powder rubber has poor moldability, there is a complaint that only a simple product such as a sheet can be obtained.

[0004] In the end, waste tires are the simplest way of use as fuel, so they are put into, for example, cement production and iron making furnaces. The applicant has also developed a metal melting method that uses waste fuel as a fuel by disposing of waste tires as they are in the electric furnace, that is, in a discarded form (hereinafter referred to as “round tires”) when melting metals. (JP-A-2000-185322).

In this metal melting method, since a round tire is directly charged into an electric furnace, the round tire may be bulky, so that there is a limit to the amount of iron source and waste tire that can be charged at one time. Therefore, the number of inputs will be increased, but this will reduce the efficiency of the operation. The larger the round tire,
The ignitability is not good either. Therefore, the introduction of round tires into the electric furnace is awkward at the time of initial installation, but at the time of retrofitting, there is still some difficulty.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the method of using waste tires for the production of molten metal as a raw material for steelmaking in electric furnace steelmaking, and to use the tires at the time of initial loading or additional loading. An object of the present invention is to provide a method for producing a molten metal that is easy and has improved use efficiency of waste tires.

[0007]

According to the method of the present invention for producing a molten metal as a raw material for steelmaking, the method according to the present invention is characterized in that in a steelmaking operation, an iron source such as scrap and an auxiliary material are charged into an electric furnace, and When melting the iron source by the heat of the arc to obtain molten metal, a round tire is finely divided (hereinafter referred to as “cut tire”) as a part of the auxiliary material, and the steel cord in the waste tire is replaced by the iron source. In addition, the carbon is used as a heat source and a carburizing agent, and the sulfur is dissolved in a molten metal. These workflows are:
As shown in FIG.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing molten metal according to the present invention includes various operations normally performed in electric furnace steelmaking, that is, in addition to arc heating, heating by a heavy oil burner, replenishment of thermal energy by blowing pulverized coal, and the like. Operations that can be performed in the field of this technology can optionally be accompanied.
Performing insufflation of oxygen or oxygenated air is also included in the normal operation herein.

As shown in FIG. 1, the cut tire is preferably mixed with scrap in advance, charged in a clamshell, and then charged into an electric furnace. Since the cut tire is finely divided, the cut tire has no bulkiness and is easily mixed with scrap or the like, and thus can be uniformly distributed in the furnace.

[0010] The term "subdivision" means that one round tire is cut to such an extent that the advantages of the cut tire described above can be enjoyed. More specifically, ordinary-sized automobiles (passenger cars and ordinary cars) are cut. Truck), preferably cut into 12 or more sections by radial cutting lines,
Or less than that. Waste tires of special things such as waste tires of large dump trucks need to be subdivided into 12 or more, while even round tires,
Small or thin tires such as motorcycle and bicycle tires do not necessarily need to be subdivided into twelve.

[0011] In the production of molten metal in preparation for the steelmaking operation, how much waste tires can be put into an electric furnace and treated can be considered as 3 to 40 waste tires per ton of scrap.
The range is 0 kg. If the input amount of waste tires is less than 3 kg per ton of scrap, it is of little significance to dispose in an electric furnace. On the other hand, 400 kg of waste tire is the limit of the amount that can be processed in actual operation. From the viewpoint of stable operation, about 70 kg is the practical upper limit.

[0012] When considered as a raw material for steelmaking, waste tires are well-known for their components, and the dispersion of components according to the type of tire is not so large.
It can be said that the raw materials are easy to use. The following data (% by weight) is given as a representative example of the components of a radial tire for a passenger car.

Fe: 7% C: 83% S: 2% Zn: 1% Needless to say, Fe is a main component of the steel cord,
It enters the melt and is collected and reused. C includes carbon black and carbon rubber. The latter is mostly volatile, and the volatiles immediately burn in the furnace and generate heat. Those that did not volatilize, along with carbon black, partially burn, and some contribute to reduction or carburization. In any case, it is useful for reducing the amount of electric energy, heavy oil or pulverized coal used.

S is a component of a rubber vulcanizing agent, which is mostly dissolved in molten steel in an electric furnace and exists in that state.
This means that the amount of SOx released into exhaust gas when waste tires are burned in an electric furnace for steelmaking is significantly smaller than when simply burned, and the burden of exhaust gas treatment is reduced. It has the benefit of being low.

S present in the molten steel can be removed by reducing slag refining in a later step if necessary.
In sulfur free-cutting steel and the like, it can be used as an essential component. In the above-mentioned waste tire throughput, the amount of S transferred into the molten steel is 0.1% at most per ton of molten steel, considering S coming from other sources. Since ordinary sulfur free-cutting steel contains S: 0.3%, it is often necessary to further supplement S, but in any case, the present invention is advantageously implemented when manufacturing sulfur free-cutting steel. It is.

[0016] Zn is a component contained in metal soap added at the time of molding rubber, but is reduced to metal and volatilized at the temperature of electric furnace steelmaking to form an oxide, which is collected in a dust collector. You.

[0017] Once collected, waste tires are quickly subdivided into cut tires, which is advantageous from the viewpoint that storage space can be saved by eliminating bulkiness. If the round tires are stacked as they are, water may accumulate inside the tires, causing a bad smell or providing a place where pests are generated. Therefore, it is desirable to cut the tires to prevent them. Increasing the bulk density also has the advantage that handling can be facilitated and transport costs can be reduced when transporting from the processing company to the site of use.

[0018]

EXAMPLES Scraps were melted in an aerial three-phase AC arc furnace with a nominal capacity of 70 tons. A cut tire obtained by dividing a waste tire of a normal passenger car into 12 pieces by a radial cutting line was supplied to an arc furnace at a rate of 20 kg / ton scrap according to the process shown in FIG. Oxygen blowing was performed along with the energization.
The unit of electricity and unit of oxygen required to obtain the same amount of molten metal are used in normal (ie, no waste tire loading) operation,
In addition, the following data were obtained in comparison with the case where a round tire was loaded.

Waste tire loading Amount of power consumption Amount of oxygen consumption (kg / ton scrap) (Index) (Index) Normal operation -100 100 Round tire 20 80 165 Cut tire 20 76 165 The power consumption is round tire mounting. Was improved by 20%, but by switching to cut tires,
A 4% improvement was seen. This improvement represents a further 20% advance, more than offsetting the disadvantage of increasing the oxygen intensity.

FIG. 2 shows the tendency of reduction in the power consumption when the waste tire loading is increased to 70 kg / ton scrap.

[0021]

According to the present invention, an iron source such as scrap and an auxiliary material are charged into an electric furnace, and the iron source is melted mainly by the heat of an arc to obtain a molten metal used as a steelmaking material. Using cut tires as a part,
The steel cord in the waste tire is used as a heat source and carburizing agent in addition to the iron source, while the sulfur content is dissolved in the molten metal to reduce the power consumption and fuel consumption, and to treat the waste tire. In addition to enjoying the benefits of the technology proposed earlier, the new benefits of further improving the unit power consumption can be obtained as compared to the case where round tires are used as they are.

[0022] The improvement of handleability by using cut tires is achieved by mixing waste tires with raw material scraps.
It allows the mixture to be handled in a clamshell for melting furnace input, which offers significant operational convenience. Fragmentation also makes it easier to ignite waste tires in the furnace, improves heating efficiency, helps transfer sulfur into the molten metal, and reduces the amount of SOx contained in exhaust gas. I do.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flow of a method for producing a molten metal as a raw material for steelmaking using cut tires (waste tires finely divided) according to the present invention.

FIG. 2 is a graph showing data of the example of the present invention, showing the relationship between the amount of waste tire charged and the power consumption reduction effect.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akishige Ichikawa 39 Motomoto-cho, Tokai-shi, Aichi F-term in Chita Plant of Daido Steel Co., Ltd. (Reference) 4K014 CB00 CB01 CB05 CB09 CC01 CD18

Claims (6)

[Claims] 1. In a steelmaking operation, an iron source and auxiliary materials such as scrap are charged into an electric furnace, and waste iron is used as a part of the auxiliary materials when melting the iron source mainly by the heat of an arc to obtain molten metal. Using the subdivision of
A method for producing a molten metal as a raw material for steelmaking, wherein a steel cord in a waste tire is used as a heat source and a carburizing agent, and a sulfur component is dissolved in the molten metal in addition to an iron source. 2. The method for producing a molten metal according to claim 1, wherein heating by a heavy oil burner and / or oxygen blowing is performed in addition to the arc heating. 3. The method for producing molten metal according to claim 1, wherein the finely divided waste tire is preliminarily mixed with scrap, charged in a clamshell, and put into an electric furnace for execution. 4. The method for producing a molten metal according to claim 1, wherein the finely divided waste tire is obtained by cutting the waste of automobile tires into twelve or more equal parts. 5. The method for producing molten metal according to claim 1, wherein the amount of waste tire charged is in the range of 3 to 400 kg of waste tire per ton of scrap. 6. The method for producing molten metal according to claim 1, wherein the produced molten metal is used for producing sulfur free-cutting steel.