KR100901758B1 - High Speed Desulfurizing Method using Oxygen Injection on Slag - Google Patents

Abstract

The present invention relates to a desulfurization method that lowers the sulfur content and reduces the amount of slag generated.

In the high-speed desulfurization method of molten steel according to the present invention, the step of injecting oxygen to the upper surface of the slag through the upper nozzle provided on the top of the ladle and the step of injecting oxygen to the slag through the immersion nozzle provided inside the slag And during the desulfurization through the oxygen injection and performing a low odor of argon gas or nitrogen gas, and stirring the molten steel and slag, the upper nozzle is sprayed with oxygen at a flow rate of 20 Nm ³ / hr or less slag and oxygen and It is characterized by preventing molten steel from directly reacting and desulfurizing sulfur contained in the slag.

Molten steel, slag, oxygen injection, desulfurization, steelmaking

Description

High Speed Desulfurizing Method using Oxygen Injection on Slag}             

1 is a schematic diagram of a high-speed desulfurization method of molten steel through the slag upper oxygen injection according to the present invention.

Figure 2 is a graph showing the change in the content of sulfur contained in the slag over time by the high-speed desulfurization method of molten steel through the slag upper oxygen injection in accordance with the present invention.

Figure 3 is a graph showing the change of sulfur content in the molten steel with or without oxygen injection by the high-speed desulfurization method of molten steel through the slag upper oxygen injection according to the present invention.

Description of the main symbols in the drawings

1: ladle 2: molten steel 3: slag

4: Immersion nozzle 5: Upper nozzle 6: Low odor gas

The present invention relates to a desulfurization method for lowering the concentration of sulfur contained in molten steel in steelmaking, and more particularly, to a high-speed desulfurization method of molten steel by lowering the sulfur content and reducing the amount of slag generated.

Sulfur contained in the steel in the steel manufacturing process is an element that adversely affects the steel, such as causing cracks in the steel, causing red brittleness. In particular, defects such as rupture of petroleum transport pipes, oil well pipes, and cracks in the welded areas are mainly caused by sulfides drawn in the rolling direction such as manganese sulfide (MnS). Steel grades try to keep the sulfur content low. Therefore, it is a basic goal of steel operation to manufacture clean sulfur containing less sulfur through proper desulfurization in steelmaking.

In such a steelmaking process, desulfurization agents for reducing the content of sulfur are quicklime (CaO), fluorspar (CaF2), carbide (CaC2) and the like are used, the reaction formula of the quicklime is a typical desulfurization agent is as follows.

Formula (1): (CaO) _slag → (Ca ²⁺ ) _slag + (O ^2- ) _slag

Formula (2): (Ca ²⁺ ) _slag + (O ^2- ) _slag + [S ^2- ] _{molten steel} → (Ca ²⁺ ) + (S ^2- ) _slag + 1/2 O ₂

Calcium injected into the slag is decomposed by the reaction of Formula (1), and reacted with sulfur in molten steel and removed into slag as shown in Formula (2).

At this time, the equilibrium constant (K) of the desulfurization reaction of Equation (2) can be expressed as Equation (3) below.

Equation (3):

In order to promote the desulfurization reaction by increasing the equilibrium constant, the concentration of sulfur contained in the slag is kept low to keep the activity in the slag small, and at the same time, the oxygen concentration in the slag is kept low.

Conventionally, in order to keep the concentration of sulfur in the slag low, the amount of slag is increased by using a commercial amount of quicklime (CaO) more than a predetermined amount, and a method of lowering the concentration of sulfur is relatively used. However, the above method not only increases the cost of treating waste by increasing the amount of slag, which is a waste of the steelmaking process, but also increases the amount of quicklime used to lower the concentration of sulfur, thereby increasing the cost. to be.

The present invention has been invented to solve the above problems, an object of the present invention is to provide a high-speed desulfurization method of molten steel through oxygen injection of slag to reduce the content of sulfur and reduce the amount of slag without the use of additional quicklime in the steelmaking process.

The high-speed desulfurization method of the molten steel of the present invention for achieving the above object is the step of injecting oxygen to the upper surface of the slag through the upper nozzle provided on the top of the ladle and through the immersion nozzle provided inside the slag Injecting oxygen into the slag and desulfurization through the oxygen injection, and performing stirring of argon gas or nitrogen gas to stir the molten steel and the slag, wherein the upper nozzle flows up to 20 Nm ³ / hr into slag. By spraying the oxygen to prevent the oxygen and molten steel to react directly, it characterized in that the sulfur contained in the slag desulfurization.

Hereinafter, a high-speed desulfurization method of molten steel through slag upper oxygen injection of the present invention will be described in detail.

According to another embodiment of the present invention, a method for rapidly desulfurizing molten steel through oxygen injection of slag is provided with an upper nozzle 5 on the upper part of the ladle 1 in addition to the immersion nozzle 4, into the slag 3 through the immersion nozzle 4. At the same time as oxygen is supplied, oxygen is injected to the upper surface of the slag 3 through the upper nozzle 5.

By injecting oxygen into the upper surface of the slag 3, the same desulfurization effect can be obtained using a smaller amount of desulfurization agent than in the conventional method, and the time required for desulfurization can also be shortened.

Such methods may be embodied as matching the equipment as shown in Fig. 1, wherein the desulfurizing agent fed to the calcium oxide (CaO), calcium fluoride (CaF _2), carbide (CaC _2), etc., the desulfurizing reaction of the formula (4) The sulfur component contained in the molten steel 2 is absorbed into the slag 3 in the form of calcium sulfide (CaS).

Formula (4): (CaS) _slag + X / 2 O ₂ → (CaO) _slag + SO _{x (gas)}

Calcium sulfide (CaS) produced by the desulfurization reaction of the molten steel (2) reacts with oxygen injected into the slag (3) through the upper nozzle (5), desulfurized in the form of SO _x and vaporized into the atmosphere, slag In (3), new quicklime (CaO) is produced and used again as a desulfurization agent to remove sulfur in molten steel.

When oxygen is injected into the slag 3 from the beginning of the desulfurization reaction of the molten steel in which the calcium sulfide starts to form in the slag 3, the desulfurization rate can be improved and the molten steel having a low sulfur content even with a small amount of desulfurization agent is used. You can get it.

At this time, the amount of oxygen injected into the upper slag is limited to a flow rate of 20 Nm ³ / hr or less so that oxygen and molten steel do not directly react. If the injection amount of oxygen increases, the molten steel reacts directly with the oxygen to increase the oxygen concentration in the molten steel, and the oxygen concentration of the slag 3 which is in equilibrium with the oxygen in the molten steel increases, thereby increasing the sulfur content of the molten steel. Causes pickup.

During the desulfurization of the slag 3 using oxygen injection, the slag in contact with oxygen is produced by stirring the argon gas or the nitrogen gas at a flow rate of 5 to 10 Nm ³ / hr and stirring the molten steel 2 and the slag 3. As the amount of (3) is increased, vaporization desulfurization is promoted, and the desulfurization rate is increased.

When the desulfurization reaction is completed in order to confirm the vaporization desulfurization reaction by spraying oxygen on the slag 3, the slag 3 is sprayed with oxygen at a flow rate of 10 to 15 Nm ³ / hr, and the slag (3) The change in the amount of oxygen contained in) is measured and shown in [Table 1] and FIG. Here, the amount of injected oxygen was adjusted within the range of 10 to 15 Nm ³ / hr in order to prevent the oxygen and the molten steel (2) from directly reacting, in proportion to the thickness of the slag (3) above the molten steel (2) The amount of oxygen was adjusted.

Table 1 shows the content of sulfur contained in the slag (3) component and molten steel (2) according to the steel number, Figure 2 is the sulfur content in the slag (3) according to the time to supply oxygen to the slag (3) The change was shown.

River Slag component (%) Molten steel [S] (%) T-Fe-MnO CaO Al ₂ O ₃ SiO ₂ (S) A 0.8 62.4 35.8 1.8 1.1 0.0041 B 0.5 60.5 38.2 1.3 1.2 0.0032 C 0.6 60.8 35.8 3.4 1.0 0.0049

[Table 1] Slag Components and Sulfur Contents in Different Steels

The content of sulfur in the slag (3) after the dehydration was 1.10% on average, but SO _x is generated by injecting oxygen on the slag (3), and the sulfur content gradually decreases and 4 minutes after the oxygen is injected. The sulfur content in the slag 3 decreased by 0.43% on average.

In order to calculate the reaction rate of desulfurization by spraying oxygen on the slag (3), sulfur content and slag (3) composition in molten steel (2) before desulfurization reaction were respectively measured for steels as shown in [Table 2].

River Slag component (%) Molten steel [S] (%) T-Fe + MnO CaO Al ₂ O ₃ SiO ₂ (S) D 1.6 59.9 37.3 2.8 1.0 0.0150 E 2.1 62.4 36.0 1.6 1.1 0.0148

 The sulfur content in the molten steel (2) with respect to the oxygen injection time was investigated and the results are shown in FIG.

Here, 200 kg of alumina was added for deoxidation of molten steel (2), and 650 kg of quicklime (CaO) was added for desulfurization, and the slag thickness was 200 mmf. It was made. On the other hand, the D steel plate was injected with oxygen at a flow rate of 12 Nm ³ / hr on the slag 3, the oxygen was not injected to the E steel plate.

As a result of investigating the change of sulfur content in molten steel (2) according to desulfurization time for two steel buns under the same condition before desulfurization treatment, it can be seen that the desulfurization rate is significantly improved in the D steel bun subjected to the slag (3) oxygen injection. have.

The high-speed desulfurization method of molten steel through the slag upper oxygen injection of the present invention having the configuration and action as described above can be expected the following effects.

By spraying oxygen on the slag of the molten steel, the sulfur contained in the slag is desulfurized and vaporized, and the desulfurizing agent is reduced, thereby lowering the content of sulfur contained in the molten steel and reducing the amount of the desulfurizing agent used.

Claims (1)

In the method of desulfurizing molten steel of the ladle to lower the sulfur content in the molten steel, Spraying oxygen on an upper surface of the slag through an upper nozzle provided on an upper portion of the ladle; Injecting oxygen into the slag through an immersion nozzle provided inside the slag; In the desulfurization through the oxygen injection step of performing a low odor of argon gas or nitrogen gas to stir molten steel and slag; and The upper nozzle is a high-speed desulfurization method of molten steel, characterized in that the injection of oxygen at a flow rate of 20 Nm ³ / hr or less slag to prevent the oxygen and molten steel directly reacts, and to desulfurize sulfur contained in the slag.

Images