JPH06185879A - Method for operating complex type arc furnace facility - Google Patents

Abstract

PURPOSE:To increase a rate of scrap to be preheated and make an electrical power as small as possible by a method wherein some scraps are loaded while molten steel being left in a furnace for use in performing a preheating operation, either inert gas such as nitrogen or oxygen is blown into the furnace from a lower part of the furnace body or its side part and then additional scraps are loaded into the furnace in the midway of the preheating operation. CONSTITUTION:Scraps 9 to be melted in subsequent operation are loaded in a furnace B while molten steel 8 being partially left in it. Waste gas of high temperature generated at a furnace A is fed to the furnace B through a duct 10 connected to a furnace lid 4 and preheated there. Concurrently, either inert gas such as nitrogen or oxygen is blown into the furnace at a tuyere 7 arranged at a furnace bottom part so as to agitate the molten metal 8. Scrap upper end 11 at the initial time within the furnace B descends under an influence of melting of the scrap 9 during its preheating operation. At the upper part of the furnace main body 1 is produced a spacing by a level difference between the scrap upper ends 11 and 12, resulting in that the scrap can be added and loaded into the furnace B during the preheating operation. With such an arrangement as above, it becomes possible to increase a rate of scrap to be preheated under utilization of waste gas of high temperature generated at the furnace A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a double arc furnace facility for alternately utilizing melting and preheating in two arc furnaces used for melting metal materials and refining molten metal to effectively utilize the heat quantity of exhaust gas. Regarding the operating method of.

[0002]

2. Description of the Related Art An arc furnace used for melting a metal material, refining a molten metal, etc. mainly uses electric energy. 150% of energy was input and 30 to 50% was discharged without being utilized. Most of this is the sensible heat of the exhaust gas discharged from the arc furnace,
Success or failure of effective utilization of the sensible heat of the exhaust gas was an important issue for the operation of the arc furnace.

Therefore, as a means for effectively utilizing the sensible heat of the exhaust gas, a preheating tank provided separately from the arc furnace is provided as in Japanese Patent Publication No. 59-52359, and scrap preheating for preheating the scrap with the exhaust gas is performed here. A system has been proposed. With this system, it was possible to recover the sensible heat of part of the exhaust gas, but the length of the duct that guides the exhaust gas to the preheating tank becomes longer, and the duct is water-cooled to maintain its strength, and the exhaust gas reaches the preheating tank. At that time, the temperature of the exhaust gas was lowered, and the sensible heat of the exhaust gas could not be efficiently collected. Further, when scraps such as oil adhered are preheated with exhaust gas of 800 ° C. or less, a phenomenon of producing odor or white smoke occurs, which is not preferable in terms of environmental measures.

In order to solve these problems and problems, the scrap is preheated with high temperature exhaust gas of 800 ° C. or higher,
A double arc furnace is known as a technology for completely thermally decomposing odors and white smoke generated by oil adhering to scrap. This is a system in which two arc furnaces are alternately operated for melting and preheating, and high-temperature exhaust gas from the arc furnace during the melting operation is introduced into the other arc furnace to preheat scrap at high temperature.

As a technique related to this system, Japanese Patent Laid-Open No. 62-62
Improvement techniques have been proposed in Japanese Unexamined Patent Publication No. -80489, Japanese Unexamined Patent Publication No. 62-136514 and Japanese Unexamined Patent Publication No. 63-169477. JP-A-62-80489 proposes a technique in which a movable electrode is shared by two arc furnaces due to the problem of equipment installation space, and JP-A-62-13.
In Japanese Patent No. 6514 and Japanese Patent Laid-Open No. 63-169477, in order to improve the high-temperature preheating efficiency, the exhaust gas circuit is switched by a valve operation via a combustion chamber provided between two arc furnaces to introduce the exhaust gas in the lower part of the arc furnace. From the viewpoint of technology to arrange ducts to the mouth, simplification of equipment, and reduction of energy loss 2
A system has been proposed in which each of the base arc furnaces has its own movable electrode.

The inventors propose a technique for solving the technical problems associated with these proposed techniques, that is, problems such as deterioration of the electrode unit consumption, poor reliability of the switching valve, and blockage of the connecting duct of the two furnaces. It is proposed in Japanese Patent Laid-Open No. 3-262547. This technology is to install a sealing device that shuts off the movable electrode on the preheating side from the air, connect the connecting duct between the two furnaces to eliminate the switching valve, and tilt the connecting duct to eliminate the blockage by the duct. .

[0007]

However, even in the technique for improving such a double-type arc furnace, there are still the following problems.

The arc furnace is filled with scraps by a basket or the like, but one charge of scrap to be processed in the arc furnace may be divided into a few times and charged into the arc furnace in a batch system. It is common. This is because the difference in bulk density between scrap and molten steel means that if the entire amount of scrap for one charge is charged into the arc furnace at one time, the volume of the molten steel to be processed per charge will be ten times the volume of the furnace. This is because the equipment becomes very large and poses a problem. In the case of a dual arc furnace, only the scrap charged into the preheating furnace is the high-temperature exhaust gas discharged from the melting furnace and is subject to preheating, so it is additionally charged in the current two or three times charging method of scrap. Since 40 to 50% of the scrap cannot be preheated, from the viewpoint of effectively preheating the scrap with the exhaust gas, the technology that the sensible heat of the exhaust gas is still insufficient in the scrap preheat recovery technology There are challenges.

The present invention is intended to solve the above technical problem, and its object is to increase the amount of scrap preheated by the exhaust gas from the melting furnace with respect to the total amount of scrap processed in one charge in a double-arc arc furnace. That is, it is to provide a method of operating a double-arc arc furnace that can increase the rate of scrap to be preheated and minimize the power energy required for melting and refining scrap.

[0010]

In order to achieve the above object, the present invention is a method of operating a double arc furnace facility in which two furnaces are alternately used for melting and preheating. Molten steel is used in the furnace used for preheating. It is characterized in that scrap is charged in the state where it remains, and inert gas such as nitrogen or oxygen is blown into the furnace from the bottom or side of the furnace body to additionally charge scrap during preheating.

Instead of blowing an inert gas such as nitrogen or oxygen from the bottom or side of the furnace body, a burner provided on the side of the furnace body is used to burn fuel such as combustible gas, heavy oil, or kerosene. Characterize.

Further, in addition to blowing an inert gas such as nitrogen or oxygen from the lower portion or side portion of the furnace body, a burner provided on the side portion of the furnace body burns combustible gas, fuel oil, kerosene or other fuel. It is characterized by

[0013]

In the dual arc furnace of the present invention, the scrap preheating furnace side is provided with high-temperature exhaust gas discharged from the other furnace during melting of scrap to preheat the scrap and at the same time, is installed in the lower part or side part of the furnace body. An inert gas such as nitrogen or oxygen is blown by the blowing device. At this time, a portion of the molten steel is left in the furnace and the first scrap is charged in an amount corresponding to the capacity of the furnace body to start preheating. By injecting an inert gas or oxygen to stir the molten steel strongly, the 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 bulk specific gravity between the scrap and the molten steel, and the scrap can be additionally charged into the space as appropriate. Therefore, it is possible to increase the preheating target scrap rate.

As a second method, on the scrap preheating furnace side, high temperature exhaust gas discharged from the other furnace during scrap melting is introduced to preheat the scrap and, at the same time, a combustible gas is burned by a burner provided on the side of the furnace body. May burn fuel such as heavy oil and kerosene. At this time, the scrap in the preheating furnace is preheated to a temperature higher than the softening point of the scrap by the high temperature exhaust gas discharged from the other furnace and the combustion gas of the fuel.

When the scrap is softened, the bulk density of the scrap is increased, and a large space is generated in the upper part of the furnace body, and it is possible to additionally charge the scrap into the space. Therefore, it is possible to increase the preheating target scrap rate.

As the 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 promoted to dissolve by vigorous stirring of the molten steel by injecting an inert gas such as nitrogen or oxygen, and the scrap not immersed in the molten steel Will be preheated to a temperature higher than the softening point of the scrap by both the hot exhaust gas discharged from the other furnace and the combustion gas of the fuel. However, when only one of the first method and the second method is adopted due to the increase in bulk specific gravity due to the melting of scrap immersed in molten steel and the softening of scrap not immersed in molten steel. As compared with the above, a larger space is created in the furnace, the amount of scrap that can be additionally charged in that space can be increased, and the preheating target scrap rate can be maximized. Alternatively, the capacity of the furnace body for obtaining a preheating target scrap rate equivalent to that in the case where only one of the first method and the second method is adopted may be 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, a furnace body 1 is lined with a refractory 2 and a water cooling panel 3, and the upper part of the furnace body 1 is in an open state. A furnace lid 4 which can be A furnace bottom electrode 5 is arranged in the furnace bottom portion, and an arc is generated between the furnace bottom electrode 5 and the movable electrode 6 above. A tuyere 7 for blowing an inert gas such as nitrogen or oxygen into the furnace is installed on the bottom of the furnace.

In FIG. 1, the furnace A on the right shows the state of melting and the furnace B on the left shows the state of preheating. In the furnace B, the scrap 9 to be melted next is filled in the furnace with a part of the molten steel 8 left. Duct 10 that connects high-temperature exhaust gas generated in furnace A to furnace lid 4
It is sent to the B furnace through the 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 bottom of the furnace to stir the molten steel 8.
The scrap 9 immersed therein will be melted in the B furnace during preheating. Due to the melting of the scrap 9, the initial scrap upper end 11 in the B furnace descends during preheating, and reaches the scrap upper end 12 after the elapse of a certain preheating time. When the inside of the furnace is changed to this state, a level difference between the scrap upper end 11 and the scrap upper end 12 exists as a space in the upper part of the furnace main body 1, and the scrap is placed in the B furnace during preheating at the initial scrap upper end 11 position. It is possible to additionally charge up to, and it is possible to increase the preheating target scrap rate using the high temperature exhaust gas generated in the A furnace. FIG. 3 is a vertical sectional view of a second embodiment according to the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof is omitted. Note that FIG. 3 also shows a DC arc furnace as an example like FIG. 1, but it goes without saying that it is also applied to an AC arc furnace.

In FIG. 3, a burner 13 for burning fuel such as combustible gas, heavy oil, kerosene, etc. is installed 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, but the furnace B is filled with scrap 9 to be melted next. Although FIG. 3 shows a diagram in which the molten steel 8 is partially left in the furnace B, and the scrap 9 to be melted next is filled in the furnace, it does not matter if the scrap 9 is filled without the molten steel 8. . The high-temperature exhaust gas generated in the furnace A is sent to the furnace B through the duct 10 connected to the furnace lid 4 to preheat the internal scrap. At this time, the furnace B is being preheated by the exhaust gas generated in the furnace A, but at the same time, the burner 13 installed on the side of the furnace burns combustible gas, heavy oil, kerosene and other fuels, and the energy of these combustion gases is changed. Scrap 9 is used to preheat scrap 9.
Will be preheated to a higher temperature than in the case where only the exhaust gas generated in the furnace A is preheated. This scrap 9 is softened by being preheated to a high temperature, and the initial scrap upper end 11 in the B furnace descends during preheating and descends to the scrap upper end 12 after a certain preheating time. When the inside of the furnace is changed to this state, a level difference between the scrap upper end 11 and the scrap upper end 12 exists as a space in the upper part of the furnace main body 1, and the scrap is placed in the B furnace during preheating at the initial scrap upper end 11 position. It is possible to additionally charge up to, and it is possible to increase the preheating target scrap rate using the high temperature exhaust gas generated in the A furnace.

FIG. 4 is a vertical sectional view of a third embodiment according to the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof is omitted. Although FIG. 4 also shows a DC arc furnace as an example as in FIG. 1, it goes without saying that it 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 is installed on the bottom of the furnace, and a burner 13 for burning a fuel such as flammable gas, heavy oil, or kerosene is installed on the side of the furnace body. . At this time, the scrap immersed in the molten steel by the scrap in the preheating furnace is promoted to be melted by strongly stirring the molten steel by blowing in an inert gas such as nitrogen or oxygen as described in the first embodiment. Further, the scrap not immersed in the molten steel is heated to a temperature higher than the softening point of the scrap due to 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, the melting of scraps immersed in molten steel and the increase in bulk specific gravity due to the softening of scraps not immersed in molten steel lead to
As compared with the case where only one of the methods of the embodiment and the second embodiment is adopted, a larger space is created in the furnace, the amount of sack lap that can be additionally charged in the space can be increased, and the preheating target scrap rate can be maximized. It becomes possible to Alternatively, the capacity of the furnace body for obtaining the same preheating target scrap rate as in the case where only one of the methods of the first and second embodiments is adopted 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 of charging scrap into an arc furnace three times. The same applies to the case of the embodiment. In this case, the second scrap is charged during the 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 preheating target scrap rate is 0.7 to
It is possible to increase to 0.8. This increase in the scrap rate to be preheated acts on the reduction of the electric power consumption rate, and in combination with the high temperature preheating of the double-arc furnace, the electric power consumption rate of 20 to 30 kwh / t can be reduced.

[0025]

As described above, according to the present invention, the preheating target scrap rate in the double arc furnace can be increased as compared with the prior art, and the effective utilization 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 such as the reduction of power consumption per unit of energy.

[Brief description of drawings]

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

[Explanation of symbols]

 1 ... Furnace main body 2 ... Refractory material 3 ... Water cooling panel 4 ... Furnace lid 5 ... Furnace bottom electrode 6 ... Movable electrode 7 ... Tuyere 8 ... Molten steel 11 ... Initial scrap top end 12 ... Scrap top end after a certain preheating time 13 ... burner

Claims (3)

[Claims] 1. A method of operating a double arc furnace facility, wherein two furnaces are alternately used for melting and preheating. In the furnace used for preheating, scrap is charged with molten steel left, and the lower part or side of the furnace body. A method of operating a double arc furnace facility, characterized in that an inert gas such as nitrogen or oxygen is blown into the furnace from the section, and additional scrap is charged during preheating. 2. In a method of operating a double arc furnace facility in which two furnaces are alternately used for melting and preheating, scrap is charged into the furnace used for preheating, and a combustible gas is burned by a burner provided on the side of the furnace body. A method of operating a double-type arc furnace facility, which comprises burning fuel such as heavy oil and kerosene, and additionally charging scrap during preheating. 3. In a method of operating a double arc furnace facility in which two furnaces are alternately used for melting and preheating, scrap is charged in the furnace used for preheating while leaving molten steel, and the lower part or side of the furnace body is charged. Inert gas such as nitrogen or oxygen is blown into the furnace from the section, and fuel such as flammable gas, heavy oil, kerosene is burned by the burner provided on the side of the furnace body, and scrap is additionally charged during preheating. Characteristic double arc furnace equipment operation method.