JPH08311525A - Method for melting steel scrap and melting furnace - Google Patents

Abstract

PURPOSE: To provide a method and a melting furnace for melting steel scrap which can prevent the insertion of a metal into a burner tuyere at the time of stopping gas supply, by preventing the remaining of non-melting scrap in the melting furnace and using the tuyeres for burner and for stirring jointly. CONSTITUTION: In the method for melting the steel scrap with an electric furnace or a top-bottom combined blowing refining furnace 1, while conducting an electrode of supplying oxygen, the steel scrap is melted, and gas for stirring is blown from at least one tuyere 5 arranged at the furnace bottom to stir the molten iron. While injecting carbonaceous material and oxygen-containing gas through the burner 7 arranged at the furnace bottom separated from the tuyere 5, the steel scrap is melted, and after melting a part of the steel scrap, the gas for stirring is blown from the burner 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel scrap melting method and a melting furnace.

[0002]

2. Description of the Related Art Conventionally, an upper-bottom blowing converter or an upper-bottom blowing melting furnace is used to charge steel scrap and carbonaceous material from the upper side of the furnace with residual or charged or a small amount of hot metal as a seed hot water, and then blow-blown. The steel scrap melting method, in which steel scrap is melted by the heat obtained by burning the carbonaceous material with an acid to increase the amount of hot metal in the furnace, and the molten metal is discharged after reaching a predetermined amount of hot metal, uses electricity from the steel scrap. Therefore, as a new hot metal production method, for example, "Recent Advances in Arc Furnace Steelmaking" (issued on June 21, 1986) by the Iron and Steel Institute of Japan, KS Converter It is widely practiced as in technology and Japanese Patent Laid-Open No. 2-141511 by the applicants. At the time of tapping, a part of the hot metal in the converter is allowed to remain, and this residual hot metal is often used as the seed hot water for the next charge.

However, in this steel scrap melting method, the main purpose of the oxygen gas blown through the lance from above is to generate heat by burning combustible gas components such as carbonaceous material and generated CO to supply the melting heat of scrap. The bottom blowing gas has the purpose of stirring the molten iron bath in addition to the auxiliary role of heat supply. That is, the bottom blowing gas is supplied to promote the transfer of heat generated on the surface of the molten iron bath to the entire molten iron bath, and the conventional bottom blowing tuyere is intended for stirring the slag-molten iron bath. Is the actual situation.

[0004]

However, in the above-described top-bottom blowing composite blowing, the agitation by the bottom-blowing gas may impede the burning rate of carbonaceous material and oxygen, and the amount of the bottom-bottom gas (agitation In many cases, some of the hot metal left in the furnace cannot be used as the seed water for the next charge because of the unmelted residue of the scrap in the furnace, and some measures to prevent the unmelted residue. It was Therefore, as one countermeasure against the method of removing the unmelted scrap and leaving no seed water, for example, a method of adding a separate burner may be considered, but the burner at the bottom of the furnace becomes unnecessary after melting the scrap and gas from the burner tuyere When the supply is stopped, molten iron is inserted into the burner tuyere, solidifies and is blocked, and there is a problem that it cannot be used with the next charge. Also, the burner from above or from the side may interfere with the oxygen top blowing lance and may not necessarily assist the heat supply, or may melt the top blowing lance, and the unmelted residue is present in the lower part of the molten iron bath. Because it does, there is not much effect.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the conventional problems of melting steel scrap as described above, prevents the unmelted scrap from remaining in the melting furnace, and uses a blade for both burner and stirring. The present invention provides a method for melting steel scrap and a melting furnace for the same, which can prevent the insertion of metal into the burner tuyere when the gas supply is stopped. The gist of the invention is (1) In a method of melting steel scrap in an electric furnace or a top-bottom blowing smelting furnace, at least 1 which is provided on the bottom of the furnace is used to melt steel scrap while energizing electrodes or feeding oxygen.
A stirring gas is blown from two tuyere to stir the molten iron, and the steel scrap is melted while a carbon material and an oxygen-containing gas are blown by a burner provided separately from the tuyere to the furnace bottom, and a part of the steel scrap is removed. After melting, a method for melting steel scrap is characterized in that a stirring gas is blown from the burner.

(2) Instead of the burner provided at the bottom of the furnace,
A steel scrap according to (1), characterized in that the steel scrap is melted by blowing a carbonaceous material and an oxygen-containing gas with a burner provided on the furnace wall, and a stirring gas is blown from the burner after melting the steel scrap. Dissolution method. (3) Nitrogen, argon, oxygen, CO as a stirring gas
_{2. The} method for melting steel scrap according to (1) or (2), wherein one or more of CO, LPG and LPG is blown.

(4) The method for melting steel scrap according to any one of (1) to (3), characterized in that only the steel scrap is melted without a seed bath. (5) In a steel scrap melting furnace having an electrode, a furnace bottom has two or more stirring gas blowing tuyere, and a single pipe or double pipe is provided in the furnace bottom or the furnace wall portion corresponding to the tuyere. A melting furnace for steel scrap, characterized in that it has at least one burner consisting of multiple tubes or more tubes or two or more kinds of aggregated thin tubes.

[0008]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a vertical sectional view of a melting furnace for steel scrap by an upper-bottom blowing converter according to the present invention. The melting furnace 1 is lined with a refractory material 2, for example, a converter, and is provided with an oxygen top blowing lance 6. Oxygen gas is blown onto the molten slag 4 on the molten iron 3 from the oxygen top blowing lance 6. Charcoal materials such as coal and coke and scrap are charged from above the furnace onto the molten slag 4 in the furnace. In order to transfer the heat of combustion of these carbon materials and top-blown oxygen from the molten slag layer to the molten iron bath therebelow, for example, N ₂ , Ar, CO, CO ₂ , O
_2. Gases such as LPG are blown in to stir the slag layer and molten iron.

On the other hand, while the carbonaceous material and the oxygen-containing gas are blown by a burner 7 provided separately from the bottom blowing tuyere 5, a part of the unmelted steel scrap existing in the lower portion of the molten iron bath is melted, and at the end of the melting operation, From this burner 7, bottom blown tuyere 5
Similarly to the above, the stirring gas is blown in. That is, it is different from the bottom blowing tuyere 5 provided for blowing gas for stirring the molten iron bath, and is another furnace bottom tuyere between the bottom blowing tuyere 5 and the bottom blowing tuyere 5. A burner 7 is provided, and oxygen and carbonaceous materials such as pulverized coal and kerosene are blown from the burner 7 to be a melting and heating burner.
After melting the steel scrap directly above and around the burner 7, the function as a melting heat supply burner is no longer necessary. Therefore, the injection of fuel such as oxygen and carbonaceous material from the burner tuyere is stopped, and at the same time, the gas species is changed. If changed and used as a stirring gas blowing tuyere, molten iron will not be plugged into the burner tuyere and clogged. Also, only the bottom blowing tuyere 5 for stirring the molten iron bath is used together with the melting burner.
Kerosene or oxygen and carbonaceous materials are blown in the initial stage of melting by using more than one kind of collecting thin tube tuyere, and after the melting, it is possible to switch to a stirring gas (for example, nitrogen) or CO gas.

FIG. 2 is a vertical sectional view of a horizontal blowing melting furnace showing another embodiment according to the present invention. As shown in FIG. 2, instead of the burner provided at the bottom of the furnace, the side wall burner 8 provided at the position where the furnace wall exists, particularly the slag layer or the position corresponding to the molten iron bath during operation, contains carbonaceous materials and oxygen. While the gas is being blown, the steel scrap existing near the inner wall of the furnace is melted, and after the steel scrap is melted, the side blowing burner 8 is changed to a stirring gas and blown. _{That, N 2, Ar, CO 2} , CO, O 2, blown LPG 1 or more kinds of the stirring gas.

FIG. 3 is a vertical sectional view of an electric furnace showing another embodiment according to the present invention. As shown in FIG. 3, one electrode 10 is provided in the central portion of the upper part of the electric furnace 9 capable of bottom blowing, and the scrap is melted by energizing this electrode 10. Further, a bottom blowing burner 7 is provided near the center of the furnace body of the furnace bottom 11, and three bottom blowing tuyeres 5 are provided around it.
A water cooling panel 12 is lined inside the furnace wall so that gas is blown from the bottom blowing tuyere 5 into the molten iron bath 3 inside the furnace body 9 and communicated with an external stirring gas supply source (not shown). are doing. On the other hand, a bottom blowing burner 7 provided near the center of the furnace bottom is a burner for melting and heating by blowing oxygen and carbonaceous materials such as pulverized coal and kerosene. After melting steel scrap existing near the bottom of the molten iron bath lower furnace wall at a position far from the lower end of the electrode in the furnace, or after the molten iron bath in the furnace is full, the role as a burner is not required as described above. Therefore, the gas species are changed and the stirring gas is blown from the burner tuyere.

FIG. 4 is a sectional view showing an example of the structure of the burner according to the present invention. As shown in FIG. 4, fuel 14 such as carbonaceous material and kerosene and nitrogen 13 are used as fuel from the center of the burner.
The mixed gas body 17 is composed of a burner structure in which oxygen 15 flows on the outer circumference and LPG 16 for cooling flows on the outer circumference. With this burner, for example, kerosene or oxygen and carbonaceous materials are blown in the initial stage of melting, and after the scrap is melted, the fuel blowing section is stopped and changed to a stirring gas such as nitrogen gas and blown.

[0013]

EXAMPLE A burner consisting of multiple tubes shown in FIG. 4 was used to blow 1 Nm ³ / min of nitrogen, 1 kg / min of pulverized coal and 1 Nm ³ / min of oxygen to melt a part of the steel scrap in the melting furnace. The blowing of pulverized coal and oxygen of the bottom-blown burner was stopped and nitrogen was replaced with 4 Nm ³ / mi.
The mixture was blown in and stirred. As a result, there is no metal adhesion to the burner tuyere due to the stoppage of pulverized coal and oxygen, and there is no unmelted scrap remaining, and the melting effect is improved, and the melting energy cost is 20% lower than the conventional method.
It has been reduced by%. On the other hand, as a comparative example, in the case of an electric furnace, a burner arranged on the furnace shoulder was provided separately from the electrodes, and a bottom blown tuyere for gas stirring was provided to prevent scrap unmelted residue. As a result, when the amount of bottom-blown gas is increased, the molten iron bath cools and the unmelted scrap remains unsolved. The burner has no effect on the unmelted scrap in the lower part of the furnace, and the melting energy cost is only improved by 2%. .

[0014]

As described above, by implementing the melting furnace of the present invention, there is no scrap unmelted residue, and
Only the steel scrap can be melted without using the seed water, and furthermore, it is extremely inexpensive in terms of equipment and can be operated at low cost.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a steel scrap melting furnace by an upper-bottom blowing converter according to the present invention,

FIG. 2 is a vertical sectional view of a horizontal blowing melting furnace showing another embodiment according to the present invention,

FIG. 3 is a longitudinal sectional view of an electric furnace showing another embodiment according to the present invention,

FIG. 4 is a cross-sectional view showing an example of the structure of the burner according to the present invention.

[Explanation of symbols]

 1 Melting Furnace 2 Refractory 3 Molten Iron 4 Molten Slag 5 Bottom Blowing Tuyer 6 Oxygen Top Blowing Lance 7 Burner 8 Side Blowing Burner 9 Electric Furnace 10 Electrode 11 Furnace Bottom 12 Water Cooling Panel 13 Nitrogen 14 Fuel 15 Oxygen 16 LPG for Cooling

Claims (5)

[Claims] 1. A method of melting steel scrap in an electric furnace or a top-bottomed refining furnace, wherein the steel scrap is melted while an electrode is energized or while acid is fed, and stirring is performed from at least one tuyere provided in the furnace bottom. Gas is blown to stir the molten iron, and the steel scrap is melted while blowing carbonaceous material and oxygen-containing gas by a burner provided on the furnace bottom separately from the tuyere, and after melting a part of the steel scrap, the burner is used A method for melting steel scrap, characterized by blowing a stirring gas. 2. The steel scrap is melted while a carbonaceous material and an oxygen-containing gas are being blown by a burner installed in the furnace wall instead of the burner installed in the furnace bottom, and after the steel scrap is melted, stirring is performed from the burner. The method for melting steel scrap according to claim 1, wherein gas is blown into the steel scrap. 3. The method for melting steel scrap according to claim 1, wherein one or more of nitrogen, argon, oxygen, CO ₂ , CO and LPG is blown in as the stirring gas. 4. The method for melting steel scrap according to claim 1, wherein only the steel scrap is melted without a seed water. 5. A melting furnace for steel scrap having electrodes, comprising two or more tuyere for blowing a stirring gas at the bottom of the furnace, and a single pipe at the bottom or the wall of the furnace corresponding to the tuyere, Two
A melting furnace for steel scrap, comprising at least one burner consisting of multiple tubes of heavy tubes or more or two or more kinds of aggregated thin tubes.