JP2980481B2 - Operation method of double arc furnace equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double arc furnace equipment for effectively utilizing the calorific value of exhaust gas by alternately repeating melting and preheating in two arc furnaces used for melting metal materials, refining molten metal, etc. Related to the operation method.

[0002]

2. Description of the Related Art Arc furnaces used for melting metal materials, refining molten metal, etc. mainly use electric energy, and the energy required for melting and refining scrap is 130 to 130%. 150% of energy was input, and 30 to 50% was discharged without being used. Most of this is the sensible heat of the exhaust gas discharged from the arc furnace,
Successful utilization of the sensible heat of the exhaust gas was an important issue for the operation of the arc furnace.

For this reason, as a means for effectively utilizing the sensible heat of the exhaust gas, a preheating tank provided separately from the arc furnace as in Japanese Patent Publication No. 59-52359 is provided. A system has been proposed. This system enabled recovery of the sensible heat of some exhaust gas, but the length of the duct that led the exhaust gas to the preheating tank became longer, and the duct was water-cooled to maintain strength, and the exhaust gas reached the preheating tank At that time, the temperature of the exhaust gas decreased, and it was not possible to efficiently recover the sensible heat of the exhaust gas. In addition, if the scrap to which oil or the like is attached is preheated with exhaust gas of 800 ° C. or less, a odor or white smoke is generated, which is not preferable in terms of environmental measures.

[0004] In order to solve these problems and problems, the preheating of the scrap is carried out with a high-temperature exhaust gas of 800 ° C or more,
A double arc furnace has been known as a technique for completely thermally decomposing odors and white smoke generated by oil and the like attached to scraps. In this method, two arc furnaces are operated alternately with melting and preheating alternately, and high-temperature exhaust gas from the arc furnace during melting operation is introduced into the other arc furnace to perform high-temperature preheating of scrap.

A technique related to this method is disclosed in
Japanese Patent Application Laid-Open Nos. -80489, 62-136514 and 63-169777 propose improved techniques. Japanese Patent Application Laid-Open No. 62-80489 proposes a technique in which a movable electrode is used in common for two arc furnaces due to the problem of installation space of the equipment.
In Japanese Patent No. 6514 and Japanese Patent Application Laid-Open No. 63-169777, the exhaust gas circuit is switched by a valve operation through a combustion chamber provided between two arc furnaces in order to improve high-temperature preheating efficiency, and exhaust gas is introduced into the lower part of the arc furnace. Technology for arranging ducts to the mouth, simplification of equipment and reduction of energy loss 2
A method has been proposed in which each of the base arc furnaces has its own movable electrode.

The inventors of the present invention have disclosed a technique for solving the technical problems associated with these proposed techniques, that is, problems such as deterioration of the basic unit of the electrode, poor reliability of the switching valve, and blockage of the connecting duct of the two furnaces. It is proposed in Japanese Patent Publication No. 3-262546. This technology is to provide a sealing device that blocks the movable electrode on the preheating side from the air, connect the connecting duct between the two furnaces, eliminate the switching valve, and make the connecting duct inclined to eliminate the blockage by the duct. .

[0007]

However, there are still the following problems in the improvement technique of such a double arc furnace.

[0008] Scraps are filled into the arc furnace by a basket or the like, and the scrap of one charge to be processed in the arc furnace may be batch-loaded into the arc furnace in two or three parts. General. This is due to the difference in bulk density between the scrap and the molten steel.If the entire amount of scrap for one charge is charged into the arc furnace once, the furnace volume required is ten times the volume of the molten steel to be processed for one charge. This is because the equipment becomes very large and poses a problem. In the case of a double arc furnace, only the scrap charged into the preheating furnace is a high-temperature exhaust gas discharged from the melting furnace and is to be preheated. The technology that 40% to 50% of the scrap cannot be preheated, and from the viewpoint of effectively preheating the scrap by the exhaust gas, the technology of recovering the sensible heat of the exhaust gas by the scrap preheating is still insufficient. There are issues.

An object of the present invention is to solve the above technical problem, and an object of the present invention is to increase the amount of scrap preheated by exhaust gas from a melting furnace with respect to the total amount of scrap processed in one charge in a double arc furnace. In other words, it is an object of the present invention to provide a method of operating a multiple arc furnace capable of increasing the preheating target scrap rate and minimizing electric energy required for melting and refining scrap.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for operating a double-arc furnace using two furnaces alternately for melting and preheating.
On the furnace side, high temperature exhaust gas discharged from the other furnace is charged with scrap with molten steel left in the furnace used for preheating.
And melt the scrap by blowing an inert gas such as nitrogen or oxygen into the furnace from the bottom or side of the furnace.
Then, a new scrap is additionally charged into a new furnace space formed above.

Further, two furnaces are used alternately for melting and preheating.
In the operation of multiple arc furnace equipment
Into the preheating furnace and discharge it from the other furnace.
A new furnace space created above by introducing high-temperature exhaust gas and burning the fuel such as combustible gas, heavy oil, and kerosene using the burner provided on the side of the furnace body to melt the scrap
And a new scrap is additionally charged .

Further, two furnaces are alternately used for melting and preheating.
In the operation of multiple arc furnace equipment
With the molten steel remaining in the furnace used for preheating,
High temperature exhaust gas charged with clap and discharged from the other furnace
Combustion is introduced to scan, see write blow an inert gas or oxygen, such as nitrogen from the furnace bottom to the side into the furnace, and combustible gas by burners provided in the furnace body side portion, heavy oil, fuel such as kerosene To dissolve the scraps
New scrap inside the new furnace space.
And features.

[0013]

In the double arc furnace according to the present invention, on the preheating furnace side of the scrap, high-temperature exhaust gas discharged from the other furnace during the melting of the scrap is introduced to preheat the scrap, and at the same time, the scrap is placed at the bottom or side of the furnace body. The blowing device blows an inert gas such as nitrogen or oxygen. At this time, since a part of the molten steel was left in the furnace and the first scrap in an amount corresponding to the furnace body volume was charged and preheating was started, the scrap immersed in the molten steel was made of nitrogen or the like. By vigorously stirring the molten steel by blowing inert gas or oxygen, melting is promoted in the furnace even during preheating.

When the scrap in the preheating furnace is melted, a large space is created in the furnace due to the difference in the bulk specific gravity between the scrap and the molten steel, so that the scrap can be appropriately charged in that space. For this reason, it is possible to increase the preheating target scrap rate.

[0015] As a second method, on the preheating furnace side of the scrap, high-temperature exhaust gas discharged from the other furnace during melting of the scrap is introduced to preheat the scrap, and at the same time, the combustible gas is burned by a burner provided on the side of the furnace body. In some cases, fuel such as heavy oil or kerosene may be burned. At this time, the scrap in the preheating furnace is preheated to a temperature higher than the temperature exceeding the softening point of the scrap by both the high temperature exhaust gas discharged from the other furnace and the combustion gas of the fuel.

When the scrap is softened, the bulk specific gravity of the scrap increases, so that a large space is created in the upper part of the furnace body, and it is possible to appropriately add the scrap into the space. For this reason, it is possible to increase the preheating target scrap rate.

As a third method, the first method and the second method may be used in combination. At this time, the scrap immersed in the molten steel by the scrap in the preheating furnace is melted by vigorously stirring the molten steel by blowing in an inert gas such as nitrogen or oxygen, and the scrap not immersed in the molten steel. Is preheated to a temperature higher than the temperature exceeding the softening point of scrap by both the high temperature exhaust gas discharged from the other furnace and the combustion gas of the fuel. However, due to the melting of the scrap immersed in the molten steel and the increase in the bulk specific gravity due to the softening of the scrap not immersed in the molten steel, only one of the first method or the second method is adopted. As a result, a larger space is created in the furnace, the amount of scrap that can be additionally charged into the space can be increased, and the rate of scrap to be preheated can be maximized. Alternatively, the furnace capacity for obtaining the same preheating-target scrap rate as in the case of employing only one of the first method and the second method is small.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. Although FIG. 1 shows a vertical sectional view of a DC arc furnace as an example, it goes without saying that the present invention is also applied to an AC arc furnace.

In FIG. 1, furnaces A and B are a pair of two arc furnaces. The furnace body 1 is lined with a refractory 2 and a water-cooled panel 3, and the upper part of the furnace body 1 is open at the upper part. The furnace lid 4 which can be set to the above is disposed. A furnace bottom electrode 5 is arranged on the furnace bottom part, and generates an arc between the furnace bottom electrode 5 and the upper movable electrode 6. In addition, a tuyere 7 for blowing an inert gas such as nitrogen or oxygen into the furnace is provided at the bottom of the furnace.

In FIG. 1, the furnace A on the right shows a state of melting and the furnace B on the left shows a state of preheating, but in the furnace B, a scrap 9 to be melted next is filled in the furnace while the molten steel 8 is partially left. A high-temperature exhaust gas generated in the furnace A is connected to the furnace lid 4 by a duct 10.
To the furnace B to preheat the scrap inside. At this time, the furnace B is being preheated, but at the same time, an inert gas such as nitrogen or oxygen is blown into the furnace from the tuyere 7 installed at the furnace bottom to stir the molten steel 8.
The scrap 9 immersed therein will be melted in the preheating B furnace. The melting of the scrap 9 causes the initial upper end 11 of the scrap in the furnace B to descend during the preheating, and reaches the upper end 12 of the scrap after a predetermined preheating time has elapsed. When the inside of the furnace changes to this state, a level difference exists between the upper end of the scrap 11 and the upper end of the scrap 12 as a space in the upper part of the furnace main body 1, and the scrap is transferred to the furnace B during preheating by the position of the initial upper end of the scrap 11. It is possible to additionally charge up to this point, and it is possible to increase the rate of scrap to be preheated using high-temperature exhaust gas generated in the furnace A. FIG. 3 is a longitudinal sectional view of a second embodiment according to the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. Although FIG. 3 shows a DC arc furnace as an example similarly to FIG. 1, it goes without saying that the present invention is also applied to an AC arc furnace.

In FIG. 3, a burner 13 for burning a fuel such as combustible gas, heavy oil, kerosene or the like is provided on the side of the furnace body.

In FIG. 3, the furnace A on the right shows melting and the furnace B on the left shows preheating. In the furnace B, scrap 9 to be melted next is filled. FIG. 3 shows a diagram in which the furnace 9 is filled with the scrap 9 to be melted next while the molten steel 8 is partially left in the furnace B, but the scrap 9 may be filled without the molten steel 8. . The high-temperature exhaust gas generated in the furnace A is sent to the furnace B through a duct 10 connected to the furnace cover 4 to preheat the internal scrap. At this time, the furnace B is being preheated by the exhaust gas generated in the furnace A. At the same time, the burner 13 installed on the side of the furnace body burns fuel such as combustible gas, heavy oil, and kerosene to reduce the energy of the combustion gas. The scrap 9 is used for preheating the scrap 9
Is preheated to a higher temperature than in the case where only the exhaust gas generated in the furnace A is preheated. The scrap 9 is softened by being preheated to a high temperature, and the upper end 11 of the scrap in the initial furnace in the furnace B descends during the preheating, and goes down to the upper end 12 of the scrap after a lapse of a predetermined preheating time. When the inside of the furnace changes to this state, there is a level difference between the upper end 11 of the scrap and the upper end 12 of the scrap as a space in the upper part of the furnace body 1, and the scrap is transferred to the furnace B during preheating at the position of the upper end 11 of the initial scrap. It is possible to additionally charge up to this point, and it is possible to increase the rate of scrap to be preheated using high-temperature exhaust gas generated in the furnace A.

FIG. 4 is a longitudinal sectional view of a third embodiment according to the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. Although FIG. 4 shows a DC arc furnace as an example similarly to FIG. 1, it goes without saying that the present invention is also applied to an AC arc furnace.

In FIG. 4, a tuyere 7 for blowing an inert gas such as nitrogen or oxygen into the furnace at the bottom of the furnace, and a burner 13 for burning a fuel such as combustible gas, heavy oil or kerosene are provided on the side of the furnace body. . At this time, melting of the scrap immersed in the molten steel by the scrap in the preheating furnace is promoted by vigorously stirring the molten steel by blowing an inert gas such as nitrogen or oxygen as described in the first embodiment. The scrap not immersed in the molten steel is heated to a temperature higher than the temperature exceeding the softening point of the scrap by both the high temperature exhaust gas discharged from the other furnace and the combustion gas of the fuel as described in the second embodiment. It will be preheated. However, due to the melting of the scrap immersed in the molten steel and the increase in the bulk specific gravity due to the softening of the scrap not immersed in the molten steel,
A larger space is created in the furnace as compared with the case where only one of the methods of the embodiment and the second embodiment is adopted, so that the amount of scrap that can be additionally charged into that space can be increased, and the rate of scrap to be preheated is maximized. It becomes possible to. Alternatively, the furnace capacity for obtaining the same preheating-target scrap rate as in the case of employing only one of the first and second embodiments can be reduced. FIG. 2 shows an operation pattern when the operation method of the first embodiment according to the present invention is performed, taking as an example the case where scrap is charged into an arc furnace three times. The same applies to the embodiment. In this case, the second scrap is charged during preheating, and the preheating target scrap in the conventional double arc furnace is only the first scrap, so the preheating target scrap rate is 0.5 to 0.6.
On the other hand, in the present invention, the preheated scrap rate is 0.7 to
It can be increased to 0.8. The increase in the scrap rate to be preheated acts to reduce the power consumption, and together with the high-temperature preheating of the double arc furnace, the power consumption can be reduced by 20 to 30 kwh / t.

[0025]

As described above, according to the present invention, the rate of scrap to be preheated in a double arc furnace can be increased as compared with the prior art, and the effective use of sensible heat of exhaust gas can be improved. This greatly contributes to the improvement of productivity by shortening the melting time and the reduction of production cost by reducing the power consumption per unit of energy.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of an arc furnace according to the present invention.

FIG. 2 is a pattern diagram of an operation according to the present invention.

FIG. 3 is a longitudinal sectional view showing a second embodiment of the arc furnace of the present invention.

FIG. 4 is a longitudinal sectional view showing a third embodiment of the arc furnace of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Furnace main body 2 ... Refractory 3 ... Water-cooled panel 4 ... Furnace lid 5 ... Furnace bottom electrode 6 ... Movable electrode 7 ... Tuyere 8 ... Molten steel 11 ... Initial scrap upper end 12 ... Scrap upper end after a fixed preheating time 13 ... burner

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁶ , DB name) F27D 17/00 101 F27D 13/00 F27B 3/00-3/28

Claims (3)

(57) [Claims] 1. A operating method of a double arc furnace equipment using furnace 2 groups dissolved and preheating alternately, pre scrap
On the heating furnace side, scrap is charged with the molten steel left in the furnace used for preheating, and the high-temperature exhaust gas discharged from the other furnace is discharged.
Introduce inert gas such as nitrogen or oxygen into the furnace from the bottom or side of the furnace to melt the scrap.
A method for operating a double-arc furnace facility, comprising adding new scrap to a new furnace space formed at the top . 2. A method for operating a double-arc furnace facility in which two furnaces are alternately used for melting and preheating, wherein a method for scrap
He was charged with scrap thermal furnace side, and is discharged from the other of the furnace
High-temperature exhaust gas is introduced, and combustible gas, heavy oil, kerosene, and other fuels are burned by a burner provided on the side of the furnace body.
Melts scraps and creates a new furnace space at the top
A method for operating a double arc furnace facility, comprising adding additional scrap. 3. A method for operating a double-arc furnace equipment in which two furnaces are alternately used for melting and preheating, wherein a method for scrap
The scrap is charged with the molten steel left in the furnace used for preheating on the heating furnace side, and the high-temperature exhaust gas discharged from the other furnace is discharged.
At the same time , an inert gas or oxygen such as nitrogen is blown into the furnace from the bottom or side of the furnace body, and a burner provided on the side of the furnace body burns combustible gas, heavy oil, kerosene, and other fuels to reduce scrap. New melted and formed on top
A method for operating a double-arc furnace facility, characterized in that new scrap is additionally charged into a space inside the furnace.