JP3596691B2 - Method and apparatus for supplying secondary combustion air in electric furnace - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method and an apparatus for supplying secondary combustion air in an electric furnace, and more particularly to a method and an apparatus for supplying secondary combustion air in an electric furnace having a scrap preheating tank above the electric furnace. .
[0002]
[Prior art]
The electric furnace melts and refines the scrap put in the electric furnace by a very high arc heat of 1,400 ° C. to 1,700 ° C. generated from an electrode arranged on the upper lid of the electric furnace. . When the scrap is melted in the electric furnace, a scrap preheating layer is provided on the downstream side of the exhaust gas supply duct provided in the upper lid of the electric furnace in order to utilize the thermal energy of the combustion exhaust gas generated in the electric furnace. Preheating is performed by the combustion exhaust gas generated in the electric furnace in the process of storing the scrap in the layer, and the preheated scrap is put into the electric furnace through the exhaust gas supply duct and melted. In addition, when melting scrap in an electric furnace, usually, carbon and oxygen are blown through a lance arranged in the upper lid of the electric furnace to generate heat by reacting the carbon and oxygen, and the heat dissolves the scrap. It has been promoted to reduce electricity usage.
[0003]
Carbon is also used to adjust the carbon content of the steel, and the supply of excess oxygen causes the steel to be oxidized, so the amount of oxygen supplied is less than that required for complete combustion. Therefore, since the exhaust gas contains carbon monoxide, it was burned outside the electric furnace. Further, a combustion device for that purpose has to be provided at the exhaust gas outlet of the electric furnace.
[0004]
[Problems to be solved by the invention]
In recent years, it has been considered to introduce air into an electric furnace to perform secondary combustion in the electric furnace.
However, if only air is introduced for secondary combustion in the electric furnace, mixing with air in the electric furnace does not work well, and unburned exhaust gas may be released to the outside without secondary combustion. Was.
[0005]
The present invention has been made in view of the above problems, and provides a method and an apparatus for supplying secondary combustion air in an electric furnace in which unburned exhaust gas generated in the electric furnace is prevented from being blown out of the electric furnace. It is an object.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a first invention of the present invention provides a scrap preheating tank which is disposed on an upper lid of an electric furnace between two electrodes which are arranged apart from each other, and which is disposed above the electric furnace. When scrap is melted in an electric furnace having an exhaust gas supply duct for supplying exhaust gas generated in the electric furnace, air is discharged from at least two air nozzles in the electric furnace toward a lower part of the center of the exhaust gas supply duct. And the secondary combustion of unburned exhaust gas generated in the electric furnace near the lower part of the exhaust gas supply duct.
[0007]
According to a second aspect of the present invention, the exhaust gas generated in the electric furnace is disposed in a scrap preheating tank disposed between the two electrodes disposed apart from each other on the upper lid of the electric furnace and disposed above the electric furnace. An exhaust gas delivery duct for delivery;
An air supply pipe connected to the blower for supplying air into the electric furnace,
At least two air nozzles forming a connection portion of the air supply pipe with the electric furnace, and the air nozzle is attached so as to supply the air downward from the center of the exhaust gas supply duct. .
[0008]
According to a third aspect of the present invention, the air nozzle feeds the air by swirling the air therein.
[0009]
[Action]
According to the above-described method and apparatus for supplying secondary combustion air in the electric furnace of the present invention, air is supplied into the electric furnace from at least two air nozzles toward the lower portion of the center of the exhaust gas supply duct, and the exhaust gas is supplied. Secondary combustion of the unburned exhaust gas generated in the electric furnace near the lower part of the supply duct makes the vicinity of the inlet of the exhaust gas to the exhaust gas supply duct the secondary combustion area, and the unburned exhaust gas generated in the electric furnace Does not blow out of the electric furnace.
[0010]
【Example】
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
1 to 6 show an embodiment of the present invention. FIG. 1 is a schematic diagram of a secondary combustion air supply device in an electric furnace, FIG. 2 is an enlarged view of a main part of FIG. 1, and FIG. FIG. 4 is a view showing another embodiment of FIG. 3, FIG. 5 is an enlarged view of an air nozzle, and FIG. 6 is an enlarged view of another embodiment of an air nozzle.
[0011]
In FIG. 1, reference numeral 1 denotes an electric furnace, and 1a denotes an upper cover provided on an upper part of the electric furnace 1. Reference numeral 2 denotes two electrodes arranged on the upper lid 1a apart from each other. Although not shown, a corresponding opposite electrode is provided at the bottom of the electric furnace 1. Reference numeral 3 denotes a lance arranged on the upper lid 1a. Further, an exhaust gas supply duct 4 is disposed on the upper lid 1a, and a scrap preheating tank 5 is disposed downstream of the exhaust gas supply duct 4. An air supply pipe 7 has one end connected to the blower 6 and the other end connected to the air nozzle 8, and is connected to the electric furnace 1 via the air nozzle 8. 9 is an air flow fed from the air nozzle 8. Reference numeral 10 denotes molten steel, and reference numeral 11 denotes slag generated when the scrap is melted, and floats on the molten steel 10. Numeral 12 denotes a scrap stored in the upper part of the exhaust gas supply duct 4 and in the scrap preheating tank 5 and preheated by the exhaust gas, and numeral 13 denotes an arc generated from the electrode 2. Reference numerals 14 and 14a denote pushers which are used to feed the scrap 12 from the scrap preheating tank 5 into the electric furnace 1 through the exhaust gas supply duct 4.
[0012]
3 and 4 show the arrangement of the air nozzles 8 and the flow of the air supplied from the air nozzles 8 in the electric furnace. As shown in FIG. 4, the air nozzle 8 may be at two positions A and B or three at positions A, B and C among positions indicated by arrows A, B and C as shown in FIG. Four. Further, the electric furnace 1 has a diaper shape, but is not necessarily limited to the diaper shape, and may be a round shape or a polygon shape.
[0013]
The air nozzle 8 may be a cylindrical one as shown in FIG. 5 or a bifurcated one having a tangential inlet in the cylinder as shown in FIG. The bifurcated air nozzle 8 is configured to swirl inside the air nozzle 8 to supply air before the air is supplied to the electric furnace 1. By doing so, the air becomes the swirling flow 9a, the air flow spreads at the nozzle outlet, and the secondary combustion is performed better.
[0014]
Next, the operation of the above embodiment will be described.
When the scrap 12 is melted, the scrap 12 is put into the electric furnace 1, electricity is supplied to the electrode 2, an arc 13 is generated, and carbon and oxygen are blown through the lance 3 to react the carbon and oxygen to generate heat. . In this reaction, as described above, since CO is contained in incomplete combustion, air is sent to perform secondary combustion. At this time, the thermal energy of the exhaust gas generated in the electric furnace 1 is supplied to the scrap preheating tank 5 through the exhaust gas supply duct 4 provided in the upper lid 1a of the electric furnace 1, and the scrap stored in the scrap preheating tank 5 12 used for preheating. In the secondary combustion, the blower 6 is operated, and air is supplied from two to four air nozzles 8 through the air supply pipe 7 toward the lower part of the center of the exhaust gas supply duct 4 so that the exhaust gas supply duct 4 is operated. , The unburned exhaust gas generated in the electric furnace 1 does not flow out of the exhaust gas supply duct 4.
[0015]
The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the technical idea described in the claims.
[0016]
【The invention's effect】
As described above, the method and apparatus for supplying secondary combustion air in the electric furnace of the present invention introduces air into the electric furnace for secondary combustion of CO gas, mixes the air into the electric furnace, and lowers the gas below the exhaust gas supply duct. Since the secondary combustion is performed in the vicinity, it is possible to prevent the unburned exhaust gas containing CO generated in the electric furnace from flowing through the inside of the electric furnace. This makes it possible to eliminate the need for any additional equipment and to achieve more effective use of thermal energy.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a secondary combustion air supply device in an electric furnace of the present invention.
FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is a view taken in the direction of arrows III-III in FIG. 2;
FIG. 4 is a view showing another embodiment of FIG. 3;
FIG. 5 is an enlarged view of an air nozzle.
FIG. 6 is an enlarged view of another embodiment of the air nozzle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electric furnace 1a Furnace top 2 Electrode 3 Lance 4 Exhaust gas supply duct 5 Scrap preheating tank 6 Blower 7 Air supply pipe 8 Air nozzle 9 Air flow 9a Air swirl flow 10 Molten steel 11 Slag 12 Scrap 13 Arc 14, 14a Pusher

Claims (3)

The electric furnace was placed on the upper lid of the electric furnace whose plane shape was symmetrical, and was placed at the approximate center of the upper lid , sandwiched between two electrodes arranged symmetrically apart from each other, and disposed above the electric furnace. When scrap is melted in an electric furnace having an exhaust gas supply duct for supplying exhaust gas generated in the electric furnace to the scrap preheating tank, at least two air nozzles are provided in the electric furnace below the center of the exhaust gas supply duct. The air is supplied obliquely downward toward the electrode and not hitting the electrodes, and near the lower part of the exhaust gas supply duct, unburned exhaust gas generated in the electric furnace is subjected to secondary combustion while preventing blow- by A method for supplying secondary combustion air in an electric furnace. A scrap disposed between the two electrodes arranged symmetrically apart from each other on the upper lid of an electric furnace having a symmetrical planar shape , disposed substantially at the center of the upper lid, and disposed above the electric furnace. An exhaust gas supply duct for supplying exhaust gas generated in the electric furnace to the preheating tank, an air supply pipe connected to the blower to supply air into the electric furnace, and an electric furnace peripheral wall of the air supply pipe. And at least two air nozzles forming a connecting portion of the air nozzle. The air nozzles supply the air obliquely downward from the peripheral wall of the electric furnace toward the center of the exhaust gas supply duct and downward so as not to hit the electrodes. A secondary combustion air supply device for an electric furnace, wherein the secondary combustion air supply device is installed so as to prevent blow-through of unburned exhaust gas . 3. The secondary combustion air supply device for an electric furnace according to claim 2, wherein the air nozzle is configured to swirl and supply the air therein.

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