JPH10237529A - Operation of arc furnace equipment, and arc furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the high efficiency in energy, to reduce the melting time, and to reduce the electric power unit requirement by contributing the sensible heat of an exhaust gas and the secondary combustion heat generated in burning CO gas to preheat the scrap in an extremely effective manner in an operating method of an arc furnace equipment to preheat the main raw material by introducing the hot exhaust gas to be generated from the arc furnace during the melting and refining operation into other arc furnace in which the main raw material is charged in the arc furnace equipment provided with a plurality of furnace bodies. SOLUTION: The CO gas to be generated in an arc furnace is discharged while the outside air is prevented from being mixed by closing a slag hole 10 in the arc furnace during the melting and refining operation. In other arc furnaces, the CO gas is introduced into the furnace without any combustion tower 7, and a gas containing oxygen is fed from a tuyere 14 provided on a furnace body side wall to perform the secondary combustion, and the main raw material is preheated by the sensible heat and the combustion heat of CO gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc furnace facility for preheating the main raw material by introducing high temperature exhaust gas generated from an arc furnace during a melting and refining operation to another arc furnace charged with a main raw material. Regarding the operation method, in particular, by utilizing the secondary combustion heat as well as the sensible heat of the exhaust gas for preheating, it is possible to shorten the melting and refining time and reduce the power consumption. To be proposed together with an advantageous arc furnace.

[0002]

2. Description of the Related Art Among electric energy supplied to an arc furnace, most of the electric energy which is not used for melting, refining, etc. is discharged from the arc furnace as sensible heat of exhaust gas. It is important in the operation of an arc furnace from the viewpoint of improving energy efficiency.

[0003] Therefore, there is known a method for reducing the electric power required for dissolving the solid main material by preheating the main material to be melted such as scrap by utilizing the sensible heat of the exhaust gas discharged from the arc furnace. Have been. As a preheating method, a so-called scrap preheater is provided in which a preheating tank is provided separately from a furnace body of an arc furnace, and the main raw material is carried into the preheating tank together with a bucket, and exhaust gas from the arc furnace is introduced to perform preheating. Scrap Pre-Heater (hereinafter referred to as SPH)) and two arc furnaces (hereinafter referred to as TWIN furnaces) connected by ducts, and the exhaust gas generated from one of the arc furnaces performing melting and refining operations. When the preheating is performed by passing the main raw material to the other arc furnace previously charged through the detoxification in the combustion tower through the duct, and when performing the melting and refining operation in the other arc furnace, There is a method in which melting, refining, and preheating are alternately repeated, such as preheating in one of the arc furnaces (for example, "Recent Progress in Arc Furnace Steelmaking (Third Edition)" edited by the Iron and Steel Institute of Japan (1993)) , p.23
1). By adopting these preheating methods, 20 to 25 kWh / t in the SPH method and 30 kW in the TWIN furnace compared to the case without preheating
It is reported that h / t reduction in power consumption was achieved.

[0004]

However, the above-mentioned SPH method has problems such as generation of offensive odor and white smoke and deformation of the scrap bucket. There was a limit to heat recovery. Moreover, in the TWIN furnace, since the above-mentioned problems such as generation of bad smell, white smoke, and deformation of the scrap bucket do not occur, the preheating temperature can be relatively increased, but the power of 5 to 10 kWh / t which is higher than that of the SPH method is required. It is only reduced. This is because even when the gas temperature is high when it is generated from the molten steel in the arc furnace during the melting and refining operation, it is mixed with room temperature air sucked from the discharge hole of the arc furnace or the inlet collecting pipe of the combustion tower. It is considered that the temperature of the exhaust gas was lowered at the time of introduction into the preheating furnace due to mixing. In other words, the CO gas generated from the arc furnace during melting and refining is subjected to secondary combustion by the oxygen in the sucked and mixed air and generates heat. However, compared with the amount of CO gas generated from the arc furnace, the suction air If the amount is large, the exhaust gas temperature will rather decrease. Also, even if the amount of sucked air is small and a high exhaust gas temperature is obtained, the sensible heat is exchanged with the cooling water of the combustion tower, and as a result the utilization rate for scrap preheating is small. It is.

A method for effectively utilizing the secondary combustion heat of the CO gas generated in the arc furnace for scrap preheating is disclosed in Japanese Patent Publication No. 63-1366. In this method, exhaust gas generated from a melting furnace is guided to a preheating furnace without passing through a combustion tower, and oxygen-containing gas is blown into the preheating furnace, whereby the exhaust gas is secondarily burned in the preheating furnace to perform scrap preheating. Is the way. However, even with this method, no remarkable power reduction effect was obtained for the following reasons. This is because most of the CO gas generated from molten steel in the arc furnace during melting and refining operations has already completed secondary combustion by air sucked from the waste holes provided in the furnace body, This is because the proportion of CO gas that is secondarily burned in the furnace is small. Incidentally, according to the results of the inventors' sampling of the gas in the arc furnace and investigation of the composition, the CO concentration in the gas in the furnace was only about 20% at most.

Accordingly, the present invention advantageously solves the above-mentioned problems, and makes the sensible heat provided by the exhaust gas and the secondary combustion heat generated by the combustion of the CO gas as effective as possible for the preheating of the scrap, thereby increasing the energy consumption. It is an object of the present invention to propose a method of operating an arc furnace facility which can improve the efficiency, thereby shorten the melting operation time and reduce the power consumption unit, together with its advantageous arc furnace.

[0007]

SUMMARY OF THE INVENTION According to the present invention, in an arc furnace facility having a plurality of furnace bodies, high-temperature exhaust gas generated from an arc furnace during melting and refining operations is led to another arc furnace charged with a main raw material. This is a method of operating arc furnace equipment that preheats the main raw material. In an arc furnace during melting and refining operations, the exhaust port is closed to prevent the intrusion of outside air while discharging CO gas generated in the furnace. In other arc furnaces, the above-mentioned CO gas is guided into the furnace without passing through the combustion tower, and an oxygen-containing gas is supplied from a tuyere provided on the furnace body side wall to perform secondary combustion, thereby reducing the main raw material. This is an operation method of an arc furnace facility characterized by preheating by sensible heat of CO gas and heat of combustion.

Further, the present invention is an arc furnace characterized by comprising means for opening and closing a discharge port corresponding to a melting, refining period, and a preheating period, and a tuyere for blowing oxygen-containing gas on a side wall.

[0009]

According to the method for operating the arc furnace equipment of the present invention, in the arc furnace during the melting and refining operation,
It is generated inside the furnace while closing the exhaust port and preventing outside air from entering.
By discharging CO gas, air can be sucked into the furnace and the concentration of CO gas can be reduced, and secondary combustion in the melting furnace can be prevented as much as possible. The secondary combustion of CO gas can be used sufficiently for preheating the main raw material.

In another arc furnace for preheating the main raw material, the CO gas is introduced into the furnace without passing through a combustion tower, and an oxygen-containing gas is supplied from a tuyere provided on a side wall of the furnace body. The CO gas generated from the arc furnace during melting and refining operations is introduced into the preheating furnace without performing secondary combustion at the combustion tower stage, and preheated by the oxygen-containing gas supplied from the tuyere of the preheating furnace. Since the secondary combustion takes place in the arc furnace, the secondary combustion in the furnace effectively contributes to the preheating of the main raw material.

Further, the arc furnace of the present invention is provided with an opening / closing means of a discharge port corresponding to a melting, refining period and a preheating period, and a tuyere for blowing an oxygen-containing gas into a side wall. During the preheating operation, the exhaust port is closed to prevent outside air from being mixed into the furnace, and during preheating operation, oxygen-containing gas is introduced into the furnace from tuyeres provided on the side walls. By supplying, the secondary combustion in the furnace can be sufficiently performed, and contributes to the preheating of the charged main raw material.

Hereinafter, the present invention will be specifically described with reference to the drawings. FIG. 1 shows an embodiment of an arc furnace facility suitable for using the arc furnace operating method of the present invention. FIG. 1A is a plan view, and FIG. 1B is a front view. In the figure, reference numerals 1 and 2 denote furnace bodies of an arc furnace. In this example, two bodies are made into a set, and preheating, melting, and refining of a main raw material are alternately performed.

Exhaust gas discharge holes are formed in the furnace lid 3 of each arc furnace, and an exhaust gas discharge duct 4 is connected to the discharge holes. The exhaust gas discharge duct 4 branches downstream, and one of the exhaust gas discharge ducts 4 communicates with the upper part of the tapping hole 5 of another furnace body.
And the other is connected to the combustion tower 7. An exhaust fan 8 is provided downstream of the combustion tower via a duct to suck the exhaust gas after the secondary combustion for preheating and to completely burn the unburned gas.

A plurality of valves, for example, a butterfly valve 9 are disposed in the exhaust gas discharge duct 4 and the exhaust gas introduction duct 6, and the flow of the exhaust gas can be controlled by opening and closing the butterfly valve 9. That is, butterfly valves are provided between the exhaust gas discharge duct 4 and the combustion tower 7, between the exhaust gas discharge duct 4 and the exhaust gas introduction duct 6, and between the exhaust gas introduction duct 6 and the upper part of the tapping hole. The operation controls the exhaust gas flow path.

On the other hand, the arc furnaces 1 and 2 are arc furnaces having the same structure (AC arc furnace in the illustrated example) and have the following features. The slag door 10 that opens and closes the waste port has a structure that can maintain airtightness in the furnace.
The slag door is closed, and operation is performed in a state where outside air does not flow into the furnace. Specific means for maintaining the airtightness in the furnace include, for example, opening and closing of a slag door (generally in a vertical direction).
There is a method in which a slag door is brought into close contact with the furnace body when the slag door is closed by adding a drive mechanism in the furnace radial direction by a hydraulic cylinder or the like in addition to the mechanism, thereby eliminating the clearance between the slag door and the furnace body. Thus, in an arc furnace during melting and refining operations, exhaust gas is discharged without causing inconvenience such as mixing of outside air with CO gas generated during melting and refining operations and burning in the furnace during melting and refining operations. It can be guided to a duct, and thus effectively contributes to secondary combustion in a preheating furnace.

Since the melting and refining operation is performed with the slag door closed as described above, a countermeasure is taken by not discharging the sludge during the operation but discharging the steel after tapping. Therefore, it is desirable that the tilting equipment of the arc furnace has a furnace tilting angle that enables waste after tapping. Furnace lid 3
The gap between the exhaust gas discharge hole 11 and the exhaust gas discharge duct 4 and the gap between the exhaust gas inlet (not shown) provided above the tapping hole 5 and the exhaust gas duct 6 can be moved up and down, respectively. The skirt 12 keeps airtight.

Further, from the waste side of the furnace lid 3, an acid feed lance 13 is provided.
And the furnace wall is provided with an oxygen supply tuyere 14 for secondary combustion.

Hereinafter, the operation method according to the present invention will be described with reference to the embodiment shown in FIG. 1. In this embodiment, an example used for preheating, melting and refining scrap in steelmaking will be described. Considering the case where the arc furnace 1 is operated as a furnace for melting and refining operations (hereinafter also referred to as a melting furnace) and the arc furnace 2 is operated as a furnace for preheating (hereinafter also referred to as a preheating furnace), the arc furnace 1 is considered. An arc is generated inside the furnace, and oxygen is supplied from the acid supply lance 12 to dissolve the scrap and refine the molten steel. On the other hand, the other arc furnace 2
Then, it stands by with the scrap loaded.

At this time, the gas generated from the arc furnace 1 is
By opening and closing the butterfly valve 9 in the duct, the gas is introduced into the arc furnace 2 from the exhaust gas discharge duct 4 through the exhaust gas introduction duct 6 in the flow path indicated by the arrow in FIG. At this time, the CO in the exhaust gas introduced by the oxygen supplied from the oxygen supply tuyere 13 for the secondary combustion of the arc furnace 2 causes the following exothermic reaction in the furnace of the arc furnace 2, so that the gas temperature increases. I do. CO
+1/2 O ₂ = CO ₂ ΔH ° = -393.5 kJ / mol (at 298 K) The gas thus introduced into the arc furnace 2 and subjected to secondary combustion is as follows:
The gas is discharged through the exhaust gas discharge duct 4 and the combustion tower 7 through the gap between the loaded scrap and the scrap, and at this time, the scrap in the arc furnace 2 is preheated by heat exchange with the scrap. Will be

When the tapping of the arc furnace 1 is completed, the arc furnace 2 starts the melting and refining by supplying an electric current to the arc and feeding an acid. Due to the introduction of the exhaust gas from the arc furnace 1 and the preheating effect of the scrap by the secondary combustion in the arc furnace 2, the melting time of the scrap by the arc conduction in the arc furnace 2 is shortened. As a result, the electric energy required for the arc conduction Is reduced. In addition, the exhaust gas generated from the arc furnace 2 is opposite to the above-described route, and the arc furnace 1 in which scrap is charged is used.
To preheat the scrap in the arc furnace 1.

According to the present invention, unlike the prior art, since the operation time from the start of energization to the start of tapping of the melting furnace is to close the discharge port and operate in a closed state, the CO concentration in the preheating furnace is high. In addition, it is possible to introduce a high-temperature gas and perform secondary combustion. Therefore, the sensible heat and the secondary combustion heat of the exhaust gas can be used most effectively for scrap preheating. Further, since the scrap preheating is performed in the arc furnace, there is no problem such as generation of offensive odor or white smoke and deformation of the scrap bucket.

[0022]

EXAMPLE The operation according to the present invention was carried out using a 100 t twin AC arc furnace having the equipment shown in FIG. The operation was carried out in the following procedure, with the main raw material being 70t scrap and 30t hot metal. First, the first scrap 70 in arc furnace 1
Insert t and energize for 10 minutes to drill the scrap. During this time, the butterfly valve 9 in the exhaust gas discharge duct 4 and the exhaust gas introduction duct 6 is set so that the exhaust gas from the arc furnace 1 is directly sucked from the exhaust gas discharge duct 4 to the combustion tower 7. Also, while boring scraps in the arc furnace 1, the initially loaded scrap 70t is charged into the arc furnace 2 and is on standby. When the scrap boring for 10 minutes in the arc furnace 1 is completed, the exhaust gas of the arc furnace 1 is discharged to the arc furnace 2
The butterfly valve 9 in the exhaust gas discharge duct 4 and the exhaust gas introduction duct 6 is switched so that the gas can be introduced into the exhaust gas exhaust duct 4 and the exhaust gas introduction duct 6. Subsequently, 30 tons of hot metal was added to the arc furnace 1, and the arc energization and acid lance were performed.
The acid is fed (80 Nm ³ / min) from 13 to dissolve and refine the scrap. During this time, acid was fed to the arc furnace 2 from the secondary combustion oxygen supply tuyere 13, and the exhaust gas introduced from the arc furnace 1 was secondarily burned. The flow rate of oxygen for secondary combustion in the arc furnace 2 is 60 Nm ³ / mi until the arc furnace 1 is burnt down.
n, and 30 Nm ³ / min after burn-through.

When the temperature and components of the molten steel in the arc furnace 1 reach the target values and start tapping, the arc furnace 2 is energized and boring scrap. Thereafter, the operation was continued using the arc furnace 1 and the arc furnace 2 alternately by the method described above. In this operation, the operation was always performed in a state where the waste hole was closed except when the waste was discharged after tapping.

As a comparative example, the operation was carried out by the method of the present invention without the scrap preheating. That is, only the arc furnace 1 was operated, and the exhaust gas from the arc furnace 1 was directly sucked into the combustion tower 7 from the exhaust gas discharge duct 4. Other operating conditions were the same as in the above example, after boring a 70t initial scrap (10 minutes), 30t of hot metal was added, electricity was supplied and acid was supplied from an acid lance (80Nm ³ / min). For melting and refining. Further, as a comparative example, operation was performed under the same conditions as in the example, except that melting and refining were performed in a state where the waste hole was opened.

The results of these operations are summarized in Table 1. The average value of the Tap to Tap time in the present invention was remarkably shortened as compared with the comparative example, and the power consumption was also reduced. From these results, it is apparent that the present invention makes it possible to preheat the scrap with higher thermal efficiency than the conventional method, thereby shortening the steel making time and reducing the power consumption.

[0026]

[Table 1]

[0027]

As described above, according to the present invention, the exhaust gas generated from the arc furnace (melting furnace) for melting and refining in a closed state is supplied to the arc furnace (preheating furnace) directly charged with the main raw material. By blowing oxygen into the preheating furnace,
By preheating the main raw material by secondary-combustion of the CO gas in the exhaust gas, it is possible to preheat the scrap with high thermal efficiency, thereby shortening the steelmaking time and reducing the power consumption.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of an arc furnace facility using the operation method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arc furnace furnace body 2 Arc furnace furnace body 3 Furnace cover 4 Exhaust gas discharge duct 5 Tapping hole 6 Exhaust gas introduction duct 7 Combustion tower 8 Exhaust fan 9 Butterfly valve 10 Slug door 11 Exhaust gas exhaust hole 12 Skirt 13 Acid lance 14 Secondary combustion Oxygen supply tuyere

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Nakato Sanka 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. 1-chome (without address) Inside Kawasaki Steel Corporation Mizushima Works

Claims (2)

[Claims] 1. A high-temperature exhaust gas generated from an arc furnace during a melting and refining operation in an arc furnace facility having a plurality of furnace bodies is led to another arc furnace charged with a main material, and the main material is preheated. This is a method of operating the arc furnace equipment. In the arc furnace during melting and refining operations, the discharge port is closed to discharge CO gas generated inside the furnace while preventing outside air from being mixed. The above-mentioned CO gas is introduced into the furnace without passing through the combustion tower, and an oxygen-containing gas is supplied from a tuyere provided on the furnace body side wall to perform secondary combustion, and the main raw material is produced by CO gas sensible heat and combustion heat. A method for operating an arc furnace facility, comprising preheating. 2. An arc furnace comprising: a discharge port opening / closing means corresponding to a melting, refining period, and a preheating period, and an oxygen-containing gas blowing tuyere provided on a side wall.