JPH08291311A - Steel scrap melting method excellent in heat conductive efficiency - Google Patents

Abstract

PURPOSE: To transfer the heat at a firing point on the upper surface of a slag to a metal by the shortest distance and the shortest time, by combining a top-blowing lance with plural steps of side-blowing tuyeres in a refining furnace at the optimum condition and developing circulating flow in the slag from the center point of the furnace to a furnace wall side. CONSTITUTION: In a top-blowing or a top-bottom combined blowing converter 1, carbonaceous material as heat source is charged and oxygen is blown onto the molten slag 4 from the top-blowing lance 6 to melt a steel scrap with the combustion heat of this carbonaceous material. Further, in the side-blowing tuyeres 5, 7 arranged in two steps in the furnace wall, the gaseous oxygen from the tuyeres 5 at the upper side is blown in an almost horizontal direction, and the gaseous oxygen from the tuyeres 7 at the lower side is blown into the slag layer toward the tuyeres 5 at the upper side while increasing gas flow rate. Further, inert gas, etc., are blown in from bottom blowing tuyeres 2 to stir the molten iron 3. By this method, the slag 4 is turned from the furnace wall side of the slag surface layer to the center side to develop the circulating flow, and the heat of the firing point obtd. from the top-blowing lance 6 is transferred to the molten iron 3 and the heat conductive efficiency is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting steel scrap by side blowing and top blowing or top bottom blowing in which blowing gas is blown into a slag layer from tuyere provided on the furnace wall side. is there.

[0002]

2. Description of the Related Art In recent years, it has become a technical subject to efficiently produce molten metal by recycling solid metal raw materials such as scrap due to resource and environmental problems. There are various kinds of metal scraps, but as a method for obtaining molten iron by using steel scrap, which has a large amount of generation, conventionally, most has been carried out in an electric furnace. However, in the case of an electric furnace, a large amount of electric power is consumed for scrap melting and refining, so it is not preferable as a cost increase in a country such as Japan where the electric power price is extremely high. Therefore, as a method of melting and refining scrap economically without using an electric furnace,
A method for melting and refining scrap using inexpensive carbonaceous materials has been studied by utilizing the surplus production capacity of a converter having a high acid transfer capacity.

Under such circumstances, generally, the existing upper-bottom blown composite blowing furnace is used to suppress the increase in equipment and to ignite the seeds charged in the furnace together with the scrap. After that, a method of melting and refining while charging carbonaceous material as a heat source from above the furnace at the time of blowing from the top and bottom has been proposed. Further, as a lateral blowing converter blowing method for laterally blowing a gas into a slag layer, Japanese Patent Laid-Open No. 57-60009, Japanese Patent Laid-Open No. 2-166212, and Japanese Patent Publication No. 6-99.
Japanese Patent Publication No. 735 and Japanese Patent Publication No. 6-99736 are known. Japanese Patent Publication No. 61-51605 is known as a converter blowing method in which horizontal blowing tuyere is provided in two stages.
That is, in JP-A-57-60009, an appropriate number of upper tuyeres and lower tuyere are provided at intervals above and below the portion of the converter side of the furnace to be immersed in the hot metal, and blowing is started. Sometimes the flow rate of the blowing gas supplied to the upper tuyere is set to be larger than that of the blowing gas supplied to the lower tuyere, and the gas flow rate supplied to the lower tuyere during the blowing is the gas flow rate supplied to the upper flow rate. It is a lateral blowing converter blowing method in which the gas flow rates of the upper tuyeres and the lower tuyere are changed so that the flow rate is larger than that, and the blowing is completed in that state until the blowing is completed.

Further, Japanese Patent Laid-Open No. 2-166212 is a method capable of predicting sloping accurately and with a sufficient time margin in smelting reduction in which a side blowing tuyere is provided as a stirring gas in a slag layer. . In addition,
No. 99735 discloses that a carbon monoxide gas that is generated in a molten metal in a smelting furnace and floats in the slag is combusted by injecting an oxidizing gas into the slag while inclining the slag, and the slag that burns and rises in temperature is swirled. Then, when adding the heat of the slag to the molten metal, it is a method of injecting an oxidizing gas under given conditions. Japanese Patent Publication No. 6-99736 discloses a method of burning carbon monoxide in a slag layer. When the high-temperature combustion heat is transferred to the molten metal by stirring and circulating the slag layer, the inclination angle with respect to the horizontal direction is point-symmetrical with respect to the furnace core and provided on the furnace wall corresponding to the range of the slag layer. There is a method in which the oxidizing gas is blown from the upward tuyere in the range of 0 to 60 ° and the downward tuyere in the range of −60 ° to 0 with respect to the horizontal direction.

In Japanese Patent Publication No. 61-51605, an appropriate number of upper and lower tuyeres are provided at intervals above and below the portion of the side of the converter to be immersed in molten iron, and blown. At the start of smelting, the flow rate of the blowing gas supplied to the upper tuyere is set to be larger than that of the blowing gas supplied to the lower tuyere,
Change the gas flow rate of the upper tuyere and the lower tuyere so that the gas flow rate supplied to the lower tuyere is higher than the gas flow rate supplied to the upper flow rate during the blowing, and in that state until the end of blowing The method is a side-blown converter blowing method, which is a side-blown converter blowing method in which blowing gas is blown into molten iron from tuyere provided on the side of the furnace.

[0006]

However, the above-mentioned Japanese Patent Application Laid-Open No. 57-60009 and Japanese Patent Publication No. 61-51.
Japanese Patent No. 605 has two stages of upper and lower tuyeres provided in the hot metal of the converter, and is not intended to stir the slag.
Further, Japanese Patent Laid-Open No. 166212/1990 provides a side blowing tuyere, but it is a smelting reduction, and the stirring of the slag is not intended at all as in the above. In addition, Japanese Patent Publication No. 6-9973
In Japanese Patent Publication No. 5 and Japanese Patent Publication No. 6-99736, the slag is swirled and the heat of the slag is added to the molten metal, which is the same as the present invention. However, in stirring the slag, Japanese Patent Publication No. 6-99735 is used. According to the publication, as shown in FIG. 2, the slag is agitated by a horizontal rotary flow over the entire furnace, and
Flowing to the furnace wall. In addition, Japanese Patent Publication 6-997
The same is true of Japanese Patent No. 36, in which a horizontal rotary flow is performed in the entire furnace as shown in FIG. In such a horizontal rotating flow, the heat conduction from the fire point (heat generation place) on the slag upper surface to the molten metal under the slag is not the shortest distance nor the shortest time, and the space from the slag upper surface is not moving during the horizontal movement of the slag. Alternatively, there is a problem that heat is likely to be radiated and radiated to the refractory wall.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and combines the upper blowing lance and at least two stages of side blowing tuyeres under optimum conditions so that the upper slag layer is removed from the furnace wall. At the center of the furnace, the lower slag layer causes a vertical circulation flow that moves in the direction from the center of the furnace to the furnace wall, and upward in the contact area with the furnace wall. It is to provide a method for melting steel scrap that transfers heat to metal in time. The gist of the invention is (1) In a method of melting steel scrap while generating slag by introducing carbonaceous material in a top-blown or bottom-blown refining furnace, at least two stages are provided in the vertical direction of the furnace wall. With the side blowing tuyeres, gas is blown into the slag layer from the lower tuyeres toward the upper tuyeres while increasing the gas flow rate, and the slag is rotated from the slag surface layer furnace wall side to the slag surface layer center side. A method for melting steel scrap with excellent heat deposition efficiency, characterized by: (2) Instead of increasing the gas flow rate from the lower tuyere to the upper tuyere, when the horizontal blowing tuyers provided in the vertical direction of the furnace wall have three or more stages, The method for melting steel scrap with excellent heat deposition efficiency described in (1) is characterized in that the gas flow rate blown from a part of the tuyere is the same.

[0008]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a side sectional view of a scrap melting furnace using at least two stages of side blowing tuyere according to the present invention. As shown in FIG. 1, a converter furnace body 1 is lined with a refractory material, and is provided with an oxygen-down blowing tuyere 2 and an oxygen-up blowing lance 6 in, for example, an upper-bottom blowing converter. Oxygen gas is blown onto the molten slag 4 on the molten ferrous metal 3 from the oxygen top blowing lance 6. Carbon materials such as coal and coke and scrap are charged from above and charged on the molten slag 4 in the furnace.
In order to effectively convey the combustion generated gas of these carbon materials to the molten slag, bottom blowing gas such as N ₂ , CO, C from the furnace bottom is used.
Good heat transfer is carried out by stirring the slag with O ₂ , O ₂ , LPG, an inert gas, etc. and stirring and mixing the slag and molten iron.

On the other hand, the upper part of the furnace wall immersed in the slag is installed.
Single-stage side-blown tuyere 5 for blowing oxygen for secondary combustion
Is 0.01% gas within the range of 0 to 1/2 from the surface layer of the slag.
Nm ³/Min/Slagton-2000.0Nm³/ M
Horizontally blown in the range of in / slag tons, lower side blow
The tuyere 7 is installed in the range below the half position of the slag layer.
Kick Interaction with the gas blown from the oxygen top blowing lance 6
Causes the upper side of the slag to rise from the slag layer around the furnace wall C
While collecting O gas at the fire point, center the space gas from the furnace wall
By moving the slag surface layer to the slag surface layer furnace wall side
The slag is rotated vertically toward the center of the surface layer. Well
Also, the gas from the lower tuyere is forcibly centered on the lower slag layer.
To the furnace wall. In this way, whether the slag surface layer wall side
By rotating the slag up and down to the center of the slag surface
The shortest distance to the molten iron below the flash point directly below the top blowing lance.
The heat transfer efficiency can be improved by separating and transmitting in the shortest time.
You can Moreover, this slag rotation is shown in the figure
If the rotation is opposite to the arrow, the heat generated at the fire point will
This is because radiation is dissipated and heat is lost.

Further, it is oxygen gas that is blown from above the converter through the oxygen top blowing lance. This oxygen gas is a high-purity oxygen-containing gas, and is pure oxygen gas or 7
A mixture of a relatively low-purity oxygen gas or pure oxygen gas containing 0% or more oxygen and a diluent gas such as air or nitrogen, and having an oxygen concentration of 70% or more. Oxygen gas is generated by burning combustible gas components such as carbonaceous material and generated CO, and supplies heat of melting to scrap. On the other hand, the bottom-blown gas has the effect of stirring the melt and is necessary for the progress of heat transfer. As the bottom blowing gas, O ₂ , N ₂ , C
A mixed gas of one or more kinds of O, CO ₂ , argon, LPG and the like is used.

FIG. 2 is a side sectional view of a scrap melting furnace using a three-stage side blowing tuyere according to another embodiment of the present invention. As shown in FIG. 2, the horizontal blown tuyere 5 at the first stage from the top is immersed in the range of 0 to 1/2 from the surface layer of the slag, and 2 from the top.
The horizontal blowing tuyeres 7 of the first stage are arranged at a position 1/2 from the slag layer, and the lateral blowing tuyeres 8 of the third stage from the top are blown diagonally upward, and a part of the adjacent vertical direction. The gas flow rates blown from the tuyere are the same. For example, the first stage tuyeres should be large and the gas flow rates from the second and third stage tuyeres should be the same small flow rates, or the gas flow rates of the first and second stage tuyeres should be large and the gas flow rates from the third stage tuyeres should be large. Is to reduce. In this way, the side blowing tuyere is controlled, and the slag 4 is efficiently rotated vertically from the slag surface layer furnace wall side to the slag surface layer center side by the interaction with the upper blowing lance. The upper oblique blowing angle θ of the lateral blowing lance is 0 <θ ≦ 90 ° with respect to the horizontal, and preferably 30 <θ ≦ 75 °.

[0012]

[Example] Oxygen gas was applied to the slag layer surface from the top blowing lance by 1
Blowing at 000 Nm ³ / hr, the upper tuyere position was set to 50 mm from the surface layer of the slag using the two-stage lateral blowing tuyere.
Further, the tuyere position of the lower stage was arranged at a position of 50 mm from the lower layer of the slag. Pure oxygen was blown into each at 100 Nm ³ / hr. While burning the carbonaceous material and oxygen in the slag layer, the surface layer of the slag moves toward the central axis of the furnace and reaches the fire point.
Similar to 0 °, the gathered flows collided and moved to the lower side of the slag layer, and heat could be transferred to the molten iron metal just below the fire point. As a result, the heat deposition efficiency became 100%. On the other hand, as a comparative example, the result of performing the upper blowing lance and the horizontal blowing into the molten ferrous metal shows that the molten ferrous metal can be stirred well, but the heat deposition efficiency remains 90% at the secondary combustion rate of 50%. Did not show any improvement.

[0013]

As described above, according to the present invention, the amount of gas is changed and blown from at least two stages of horizontal blowing tuyere to move the gas from the furnace wall to the center point of the furnace in the upper layer of the slag layer, and the slag. The lower layer is in the direction of the furnace wall, and the slag swirl that causes an up-and-down circulation flow that moves upward at the contact portion with the furnace wall allows the combustion heat to be applied to the molten metal with high efficiency,
This is an industrially excellent effect in that the reaction efficiency in scrap melting that requires a large amount of heat can be increased.

[Brief description of drawings]

FIG. 1 is a top-bottom blow converter of at least 2 according to the present invention.
Side sectional view of a scrap melting furnace using horizontal blowing tuyeres,

FIG. 2 is a side sectional view of a scrap melting furnace using a three-stage side blowing tuyere according to another embodiment of the present invention.

[Explanation of symbols]

 1 Converter furnace body 2 Oxygen-blown tuyeres 3 Molten iron metal 4 Molten slag 5 1st-stage side-blown tuyeres 6 Oxygen top-blown lance 7 2nd-stage laterally-blown tuyeres 8 3rd-stage horizontally-blown tuyeres

Claims (2)

[Claims] 1. In a method for melting steel scrap while introducing carbonaceous material in a top-blown or top-bottom-blown refining furnace to generate slag, a horizontal blowing tuyer provided at least two stages vertically in the furnace wall From the side tuyere to the upper tuyere, gas is blown into the slag layer while increasing the gas flow rate, and the slag is rotated from the slag surface layer furnace wall side to the slag surface layer center side. Excellent steel scrap melting method. 2. A horizontal blowing tuyer provided in the vertical direction of the furnace wall is 3
In the case of a step or more, instead of increasing the gas flow rate from the lower tuyere to the upper tuyere, the gas flow rate blown from a part of the adjacent vertical tuyere is the same. The method for melting steel scrap according to claim 1, which is excellent in heat deposition efficiency.