JPS5881909A - Steel making process - Google Patents

Abstract

PURPOSE:To recover a mass of useful gas by existing gas-furnace and to increase the adaptability for scrap ratio and reduced iron ratio etc. by a method in which scrap and reduced iron etc. are charged into the molten iron and are melted in the gasifying method for coal and then are refined. CONSTITUTION:Suitable amount of molten iron 1 is stored in a furnace 2, and carbon-material C such as coal, coke, pitch and heavy oil etc. and oxygen are blown into said molten iron by a non-immersed top blowing lance 3 and are gasified. The gases (CO, CO2, H2) generated in the furnace are recovered by way of a skirt 6 and a hood 7. Then, when the temperature in the furnace is elevated by gasifying reaction, the metallic source S such as scrap and/or reduced iron etc. are thrown into the iron bath from a charging port 4. The metallic source S is rapidly melted in the iron bath by receiving heat, and simultaneously it reacts to a mass of carbon melted in the iron bath, thereby reducing metallic oxides. The predetermined amount of metallic source is charged, and then the carbon-material C and oxygen blown into the furnace is stopped. After the slag is removed from the iron bath, flux is added from the charging port 4, and desulphurization and oxidizing refining are performed.

Description

Detailed Description of the Invention The present invention uses a method of gasifying carbonaceous materials such as coal, coke, and pitch into a high-temperature molten iron bath to melt metal sources such as scrap and/or reduced iron. The present invention relates to a method for melting steel.

Methods for melting and refining metal sources such as scrap and/or reduced iron using a converter include: ■ After melting and refining scrap in a converter, molten steel is produced using the LF method, which is one of the ladle refining methods. A method to raise the temperature to a predetermined value, ■KMS method, which uses a pure oxygen bottom-blowing converter to inject fuel into the scrap to preheat the scrap, and then pours and refines it; ■Secondary combustion (Co
- ARBED method that measures heat transfer to the bath by Co, );
■A converter-charcoal blowing method is known, in which a carbon source such as coal is charged and refined.

However, the LF method (2) has the disadvantage that the electric power cost and the refractory cost are large, and the equipment cost is also high because it requires a device to seal the ladle and heat the molten steel. The KMS method in (■) requires high fuel costs because it preheats the scrap (and has the disadvantage that the temperature cannot be raised during refining after pouring.AR in (■)
The BED method has drawbacks such as poor transfer rate of heat generated by secondary combustion to the bath and inability to recover CO gas.

In LD carburizing and blowing, the composition of the produced gas deteriorates (C0w increases) due to the introduction of a C source, and the gasification efficiency is also poor due to C scattering. ), and no desulfurization equipment has been installed, which poses a pollution problem in that 8% of the gas is not removed, leading to environmental pollution.Furthermore, the target α℃] is not being met due to lumpy C sources floating in the bath. It had the drawback of being unstable.

In view of the above-mentioned current situation, the inventors investigated a refining method that could more economically melt scrap and at the same time efficiently recover clean gas. We focused on the fact that a large amount of heat is generated when carbonaceous materials are gasified, and that a large amount of carbon is always dissolved in molten iron. discovered a method to melt and refine metal sources.

That is, in this invention, a considerable amount of molten iron is stored in a melting furnace, and carbonaceous substances such as coal, coke, pitch, and heavy oil are blown into the molten iron bath together with oxygen to gasify it.
This is a steelmaking method characterized by putting a metal source such as scrap and/or reduced iron into an iron bath, melting it, and then refining it.

Iron bath gasification of coal, etc. is a method that uses molten iron to provide the heat necessary for gas and sulfurization reactions, and carbonaceous materials such as coal and coke are placed in a gasifier that stores high-temperature molten iron. This is a method of gasifying by blowing together with a gasifying agent (oxygen, water vapor, etc.).

That is, when coal, etc. is blown into a molten iron bath together with a gasifying agent, H3 is generated due to the decomposition reaction of the carbonaceous material such as coal in the iron bath.
Gas formation and C dissolution occur. The C dissolved in the iron bath reacts with the oxygen that is blown in at the same time and becomes CO gas.
At this time, a large amount of heat is generated and the temperature of the molten iron rises. In normal gasification methods, steam is injected as a coolant to prevent the iron bath temperature from rising more than necessary, but in this invention, a metal source such as scrap and/or reduced iron is injected instead of steam. , melted with hot molten iron. When metal sources such as scrap and/or reduced iron are input during gasification operations, they rapidly receive heat and melt in the high-temperature iron bath, and at the same time, semi-reduced metals dissolve in large quantities dissolved in the iron bath. Reaction with carbon causes a reduction reaction, and the reduced metal dissolves in the iron bath to become crude gold or pig iron.

In this invention, the crude gold iron or pig iron thus produced is refined in the same gasification furnace to melt steel. In this case, the slag in the furnace is removed prior to refining, then a slag-forming agent is added and the hot metal is desulfurized, and then oxygen blowing is carried out, or the slag in the furnace is separated after oxygen blowing. A method such as performing a desulfurization treatment afterwards is used.

According to this invention method, the existing gasifier can be used as is, so the equipment cost is low, and a large amount of useful gas can be recovered, and there is flexibility in terms of percentage, scrap ratio and/or reduced iron ratio, etc. is also large.

Next, an example of equipment for carrying out the method of this invention will be explained based on the drawings.

Basically, as shown in Figure 1, a melting furnace (2) that stores S molten iron (1), a carbonaceous material such as coal or coke (6), and a gasifying agent such as oxygen (0) are injected. Non-immersion top blowing lance (S)
, Scrap inlet (4)% OHw installed on the furnace side wall
Bottom blowing nozzle (for blowing stirring gas CG such as COH)
6), produced gas recovery skirt (・) and hood (7)
) and a solvent inlet (8).

As shown in Fig. 2, a lance for blowing coal, oxygen, etc., has one, for example, a central hole (al) and a porous hole (a) around it.
), and carbonaceous materials such as coal are introduced through the central hole (al).
A four-hole lance having a structure in which oxygen is blown out from each hole (a,) can be used.

Further, metal sources such as scrap and/or reduced iron may be introduced through the solvent inlet (8).

When steel is melted using the above device, a considerable amount of molten iron (temperature of approximately 1200 to 1400°C) is stored in a melting furnace, and carbon such as coal is poured into the molten iron bath from a non-immersed top blowing lance (3). Gaseous material (C) and oxygen (0) are blown into the furnace.The gas (Co, Cow%Ha) generated in the furnace is passed through the skirt f8).
and is collected via the hood (7). After that, when the temperature of the iron bath in the furnace rises to 1500°C or higher due to the heat generated by the gasification reaction, scraps and/or metal sources (S) such as reduced iron are poured into the iron bath from the scrap input port (4). put it in. The metal sources such as scrap and/or reduced iron fed into the furnace rapidly receive heat and melt in the iron bath, and at the same time, the semi-reduced metals react with a large amount of carbon dissolved in the iron bath. Reduction of metal oxide progresses.

After inputting a specified metal source such as scrap and/or reduced iron, the injection of carbonaceous material and oxygen is stopped,
Usually, slag removal is carried out, and a slag-forming agent is added from the solvent inlet (8) or the scrap inlet (4) to perform desulfurization treatment. After desulfurization, slag is removed and oxidation refining is performed.

In addition, after melting metal sources such as scrap and/or reduced iron, the steel is tapped into a ladle, etc., and after desulfurization treatment is performed therein, the slag is removed, and the steel is transferred to the melting furnace (2) or another converter. Methods include pouring iron and performing oxidation refining, or after melting metal sources such as scrap and/or reduced iron, continuing oxidation refining, decarburization, and dephosphorization, followed by desulfurization treatment in a furnace or in a ladle after tapping. method etc. may be used.

In addition, in the gasification of carbonaceous substances such as coal, there are methods in which (C) is blown from a bottom blowing nozzle (6) and oxygen (0) is blown from a non-immersed top blowing lance (3). It goes without saying that a method of blowing both oxygen (0) and oxygen (0) from a bottom blowing nozzle may also be used.

Examples of the present invention will be described below.

Hot metal at 1,300°C was stored, and using a non-immersed top-blown four-hole lance, coal powder and oxygen having the composition shown in Table 2 were heated at 2,500 kti/Hr and 1,350 Ntd/Ilr, respectively.
Infused. At the same time, six cans of mixed gas (each 100 Nm/Hr) were blown in as stirring gas from a bottom blowing nozzle at the bottom of the furnace.

Next, when the iron bath temperature reached 1560"C, we started to feed in the scraps. The amount of scrap to be fed was increased or decreased while watching the changes in the iron bath temperature, but on average it was about
o O Pass/Hr input. Further, the solvent was appropriately added so that the basicity of the slag was about 1.5 to 2.0. After 3.9 hours had elapsed after the start of scrap input, the supply of coal and oxygen was stopped, and the furnace was tilted to remove slag.
Then, a slag-forming agent (FeSi 2s, 200 # lime, 30 # fluorite) was added, and rinsing was performed using bottom blowing gas and Ar for 5 minutes to desulfurize.

The bottom-blown Ar gas flow rate during this period was zoONm'/Hr. After desulfurization, the slag was removed again and refining was performed. The oxygen at that time was 2200 Nrrl/H1 bottom blowing Os/CoI
(8 cups) was blown at 100/100 Nvl/Hr, respectively. Additionally, 600 kg of lime and 9+ of fluorite were added as a solvent to decarburize and dephosphorize.

Table 3 shows the composition and temperature changes of the hot metal and molten steel in this example, and Table 4 shows the composition of the resulting gas.

As is clear from Tables 2 and 3, scrap could be melted and refined by the method of the present invention, and at the same time, gas that could serve as a useful energy source was also obtained.

Table 3: Composition and temperature changes of hot metal and molten steel (96) Table 4: Schematic diagram showing the composition (%) of gas produced during gasification, No. 2
The figure is a schematic diagram showing an example of a top blowing lance in the same equipment.

1... Molten iron, 2... Melting furnace, 3... Top blowing lance, 4... Scrap inlet, 5... Bottom blowing nozzle, 6
...Scar for gas recovery), 7...Hood for gas recovery, 8...Solvent inlet, C-...Carbonaceous material, 0...
- Gasifying agent, G... Stirring gas, S... Metal source such as scrap or/and reduced iron.

Applicant: Sumitomo Metal Industries, Ltd. Agent push ・1) Good winter゛ζ1,1-1+ Figure 1 Figure 2 Continuation of page 1 0 shots Akira Mitsuru Fukuda 1-3- Marunouchi, Chiyoda-ku, Tokyo 3, Oaza Hikari, Kashima-cho, Kashima-gun, Ibaraki Prefecture Manufactured by Kashima, Sumitomo Metal Industries, Ltd. Inside scrap metal 0 shots clear person Toru Matsuo Inside the research institute 0 shots Akira Masuda Inside the research institute

Claims (1)

[Claims] A considerable amount of molten iron is stored in a melting furnace, and coal,
Carbonaceous substances such as coke, pitch, and heavy oil are blown in with oxygen to gasify them, and at the same time metal sources such as scrap and/or reduced iron are introduced into an iron bath and dissolved.
A steel manufacturing method characterized by refining.