JPS62188711A - Melt reduction steel making method - Google Patents

Abstract

PURPOSE:To uniformly transfer the combustion heat of CO generated from a molten iron to the molten iron in the stage of producing the molten from iron ore with an oxygen top blown converter by blowing the oxygen from plural nozzles provided under the molten iron surface toward the direction inclined in the axial direction of the converter. CONSTITUTION:The molten iron 2 is thrown into the oxygen top blown converter 1 and gaseous O2 is ejected from an upper lance 3; at the same time, the iron ore and coal which is a reducing agent are thrown into the converter to reduce the iron ore to the molten iron. The gaseous O2 is injected from the plural nozzles 4a-4n provided under the molten iron bath surface 2a in the direction inclined from the central axis of the converter 1. The CO-contg. gas generated by the decarburization reaction of the molten iron 2 is burned in a secondary combustion zone 6 by the O2 from the lance 3 and the generated heat is transferred to the liquid drops 5 of the molten slag and molten iron formed by the oxygen ejected from nozzles 4a-4n to heat the molten iron 2. Since the nozzles 4a-4n are inclined, the flying distance of the liquid drops of the molten slag and molten iron is long and the heat of the secondary combustion zone 6 is efficiently transferred to the molten iron 2, by which the thermal efficiency is improved and the amt. of coal to be used can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a smelting reduction steelmaking method for directly producing molten iron from iron ore, and in particular to a method for reducing iron ore with high efficiency.

[Conventional technology]

A typical conventional method for obtaining steel from iron ore is a method that combines a blast furnace method and a converter method. This method is a so-called indirect method in which iron ore is reduced in a blast furnace to obtain pig iron, and then this pig iron is decarburized in a converter to obtain steel.

However, this indirect method has the same problems as the current law.

■ The coke used in blast furnaces uses strong coking coal, but as the demand for strong coking coal increases worldwide, there are concerns about the availability of strong coking coal, and at the same time prices are rising. be.

■ A coke oven is required to produce coke, and fuel costs are high.

■ To increase efficiency, expensive sintering equipment is required to sinter the iron ore charged into the blast furnace.

For this reason, proposals for improving the indirect method have been made, and at the same time, several efforts are being made to develop a direct smelting reduction method that does not use a blast furnace as a steelmaking method to replace the indirect method.

However, the direct smelting reduction method uses a preliminary reduction furnace to prevent an increase in coal consumption.
It is necessary to incorporate a process for producing reduced iron such as the method (method), and the equipment cost is high, so it has not been put into practical use at this stage.

Furthermore, the direct smelting reduction method for producing steel by directly reducing iron ore without using a preliminary reduction furnace has the following metallurgical problems.

For example, an iron bath is formed in the furnace using a converter, iron ore is put into this iron bath and reduced, and the gradually increasing amount of iron bath is extracted continuously or intermittently to produce steel. In this case, a reducing agent is required to reduce the iron ore, and when using an iron bath as a reducing agent, the iron bath must have a high reducing potential.

However, common sense suggests that the steel bath to be extracted has a carbon content [C] of less than 1%, and has a lower reduction potential than a blast furnace bath with a carbon content [C] of about 4%. Even if the iron ore placed in the iron ore is melted on an iron bath, the Ka value is not immediately restored. For this reason, various methods have been attempted to obtain direct melting from iron ore by charging iron ore and coal into an oxygen converter.

[Problem that the invention seeks to solve]

In either case, the method of charging iron ore and coal into an oxygen converter to obtain molten steel directly from the iron ore has the problem that it is economically far inferior to reducing hot metal using a blast furnace.

This is because CO gas generated by the decarburization reaction C+O→CO in the soft wire in the oxygen converter reacts with the oxygen jet from the lance above the surface of the iron bath, resulting in secondary combustion of CO+10 and →CO1. This is because the heat generated by this secondary combustion does not heat up the iron bath and is dissipated as gas.

There is also the problem that the heat generated by this secondary combustion damages the furnace refractories.

This invention was made to solve the above problems, and it provides a smelting reduction steelmaking method that can stably and economically obtain steel directly from iron ore by reducing iron ore with high efficiency. The purpose is to make suggestions.

[Means for solving problems]

In the smelting reduction steelmaking method according to the present invention, a plurality of gas blowing nozzles are provided on the side wall of the converter directly below the surface of the iron bath in the converter, and the gas blowing nozzles are installed in a direction inclined with respect to the axial direction of the converter. By blowing more oxygen into the iron bath, causing the slag and iron bath droplets to fly toward the lance's flash point, and simultaneously rotating the iron bath and ensuring a long flying distance, molten steel or hot metal can be removed from the iron ore thrown onto the iron bath. This is a direct manufacturing method.

[For production]

In this invention, the slag and iron bath droplets are blown over a long distance into the secondary combustion zone near the lance ignition point using oxygen blown into the iron bath from a plurality of gas blowing nozzles, thereby causing secondary combustion with the droplets. The generated heat is absorbed and transferred into the iron bath, and at the same time the iron bath is rotated by blown oxygen, thereby uniformly transmitting the generated heat into the iron bath.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a plan view. In the figure, 1 is a converter, 2 is an iron bath in the converter 1, and 6 is an iron bath inserted into the converter 1. Lances 4a to 4n for blowing high-pressure oxygen into the two surfaces of the iron bath are gas blowing nozzles provided in plural on the side wall of the converter just below the iron bath surface 2JL. These gas injection nozzles: k4a to 4n are connected to the converter 2 as shown in FIG.
It is provided in a direction inclined with respect to the axial direction.

An iron bath 2 is charged into the converter 1 constructed as described above, and iron ore and coal are continuously charged while blowing oxygen from the lance 6 onto the surface of the iron bath 2, so that molten steel or hot metal is produced directly from the iron ore. Manufacture. At this time, oxygen is injected into the iron bath 2 from a plurality of gas blowing nozzles 4a to 4n, and part of the slag (not shown) on the iron bath 2 and the hot water surface 2a is turned into droplets 5, and the lance 3 is ignited. Fly in the direction of point 6a.

In the converter 1, the primary combustion reaction of CO104CO is actively carried out by the oxygen blown in from the lance 6 and the coal thrown in.
This CO gas is used to reduce iron ore.

On the other hand, the oxygen jet from the lance 6 causes CO gas to flow into the secondary combustion zone 6 above the hot water level 2a as Co+HO,→C0102
The next combustion is being carried out. The droplets 5 of the slag and iron bath generated by the oxygen blown into the secondary combustion zone 6 through the gas blowing nozzles 4a to 4n are blown away in a swirling manner, and the droplets 5 are distributed almost uniformly in the secondary combustion zone 6. At the same time, the heat generated by the secondary combustion is efficiently absorbed by the droplets 5, and the droplets 5 efficiently heat the iron bath 2.

The iron bath 2, which has received secondary combustion heat by the droplets 5, is given a rotational motion with respect to the furnace axis and a vertical rotational motion by the oxygen blown in from the gas blowing nozzles 4a to 4n, so that the iron bath 2 receives the primary combustion heat and the secondary combustion heat. The heat generated by the next combustion is transferred to the iron bath 2.
It can be transmitted evenly inside.

〔Concrete example〕

First, an iron bath 2 whose carbon content (C) was adjusted to 3% is placed in the converter 1 shown in FIG. combustion zone 6
When oxygen is blown into the gas blowing nozzles 4a to 4n
Figure 6 shows the results of examining the carbon content 11 (C) and coal consumption rate (kFi/1o11 iron) of iron bath 2 when no oxygen is blown into the bath.

In FIG. 3, A is the change in the coal consumption rate when oxygen is blown from the gas injection nozzles 4a to 4n, and B is the change in the coal consumption rate when oxygen is not blown from the gas injection nozzles 4a to 4n.

As is clear from Fig. 6, the carbon content (C
), the coal consumption rate was significantly reduced in the case where oxygen was injected from the gas blowing nozzles 4a to 4n, compared to the case where oxygen was not injected. This is caused by the oxygen blown into the secondary combustion zone 6 by gas blowing nozzles 4&~4n.
When the carbon content cc) in the droplets 5 blown away is high, CO and gas in the secondary combustion zone 6 are reduced by the carbon in the droplets 5, but the carbon content [C] in the iron liquid decreases. However, as the carbon content (C) in the droplet 5 decreases, the droplet 5 only absorbs the heat of the secondary combustion zone 6, and this liquid ? 1. i!
This is thought to be because the iron bath 2 can be heated by i5.

Therefore, by blowing oxygen from the gas blowing nozzles 4a to 4n and applying a flow of droplets 5 to the secondary combustion zone 6, the distribution of the droplets 5 in the secondary combustion zone 6 is made almost uniform.
It is possible to improve secondary combustion heat absorption by the droplets 5.

In the above embodiment, the gas blowing nozzles 41 to 4n are
As shown in the figure, we have explained the case where the K gas blowing nozzle 4 Even if t4b is provided, it is possible to impart a vortex to the droplet 5 as in the above embodiment, and at the same time, it is also possible to impart rotational motion to the iron bath 2.

〔Effect of the invention〕

As explained above, this invention uses oxygen blown in from a plurality of gas blowing nozzles to give the vortex of the slag and iron bath to the secondary combustion zone. In addition, since the oxygen blown into the iron bath imparts @ rotational motion to the iron bath, the temperature distribution in the iron bath can be made uniform, and the heat transfer efficiency of the iron bath can be improved. Therefore, coal intensity (kg/lo
n iron) can be greatly reduced, and iron ore can be reduced economically. Furthermore, since the heat generated by the secondary combustion is efficiently transferred to the iron bath, damage to the furnace refractories due to the secondary combustion can be prevented.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a plan view of the above embodiment, and Fig. 6 is a carbon-containing ff1 (C
] (%) and coal unit consumption (yu/l o n iron) characteristic diagram,
FIG. 4 is a plan view of another embodiment. 1; converter, 2; iron bath, 2a; hot water surface, 3; lance, 4a~
4n; gas injection nozzle; 5; droplet; 6; secondary combustion zone.

Claims (1)

[Claims] In the direct smelting reduction steelmaking method in which molten steel or hot metal is produced from iron ore using an oxygen converter that blows oxygen from a lance, a gas injection nozzle installed in a direction inclined to the axial direction of the converter is used to blow the iron inside the converter. A smelting reduction characterized in that a plurality of gas blowing nozzles are provided on the side wall of the converter just below the bath water surface, and oxygen is blown from the gas blowing nozzles to blow the slag and iron bath droplets toward the lance flash point, while simultaneously rotating the iron bath. Steel manufacturing method.