JPH07157816A - Method for refining moltenmetal - Google Patents

Abstract

PURPOSE:To improve the reaction efficiency of powdery material for refining by arranging plural blowing nozzles toward the direction crossed to the axis in a lance for blowing the powdery material and dispersing the powdery material for refining with carrier gas having different pressure from each nozzle into molten metal. CONSTITUTION:Desulfurizing agent in tanks 1a, 1b is discharged into guide pipes 4a, 4b, respectively and the carrier gas is fed to pressure adjusting valves 12, 13 through the guide pipe 4 and the carrier gas for high pressure blowing is introduced into the guide pipe 4a and the carrier gas for low pressure blowing is introduced into the guide pipe 4b. Successively, the desulfurizing agent in the guide pipes 4a, 4b is fed into the inner pipe 6a and the outer pipe 6b in the blowing lance 6 through flexible hoses 5a, 5b with the high pressure gas and the low pressure gas, respectively and blown into molten iron 8 in a ladle 10 from each blowing nozzle 14, 15 extended to the horizontal direction. As the pressure of the blowing carrier gas from the blowing nozzles 14, 15 are different, the horizontally arrival distances L2, L3 of the desulfurizing agent can be adjusted and the desulfurizing agent can uniformly be dispersed into the molten iron 8.

Description

Detailed Description of the Invention

[0001]

[Industrial application] S,
Although a large amount of impurity elements such as P are contained, since such impurity elements greatly affect the refining efficiency and the quality of steel in the next steelmaking process, in general, such impurities are removed prior to the steelmaking process. Pretreatment of hot metal is performed.

Further, even after temporary refining such as converter refining, secondary refining is carried out if necessary for the purpose of removing S and reducing O in steel. The present invention relates to a molten metal refining method suitable for use in the pretreatment and secondary refining of molten pig iron as described above, and particularly by improving the reaction efficiency of the refining powder, the reduction of the refining powder unit consumption At the same time, it aims to improve productivity.

[0003]

2. Description of the Related Art As one of the methods for pretreatment of molten pig iron and secondary refining of molten steel, a refining powder is blown into a molten metal together with a carrier gas by using a powder blowing lance, and bubbles containing the powder are contained. There is a so-called injection method in which desulfurization and the like are performed by causing a gas-liquid reaction in the process of rising in the molten metal.

Generally, in the injection system, a blowing lance is used to blow the refining powder into the molten metal. For example, in hot metal desulfurization, as shown in FIG. 4, the desulfurizing agent in the blowing tank 1 opens the powder cut-out valve 2 and is supplied to the conduit 4. At the same time, a carrier gas such as N ₂ is sent to the conduit 4 through the flow control valve 3 and is blown together with the desulfurizing agent through the blowing hose 6 into the hot metal 8 in the ladle 10 through the blowing lance 6.

The blowing lance 6 is provided with a gas passage 22 at the center of the shaft. The gas passage 22 is formed by two holes (some of which are single holes) formed in a direction intersecting with the axis. It communicates with the nozzle 7. The desulfurizing agent blown into the hot metal 8 from the blowing nozzle 7 at the tip of the blowing lance 6 is desulfurized by the gas-liquid reaction while floating with the bubbles 11 of the carrier gas.

Since the pressure of the carrier gas is constant while the desulfurizing agent is being blown together with the carrier gas using the blowing lance 6 as described above, the bubble reaching distance L that is blown horizontally from the two-hole blowing nozzle 7 is reached. ₁ is almost constant. Further, since the position of the blowing nozzle 7 does not change, the bubbles 11 floating in the hot metal 8 continue to float at the same position in the hot metal 8 and in a limited range together with the desulfurizing agent.

Therefore, the hot metal 8 in the ladle 10 has a wide area where the desulfurizing agent is not directly supplied. In particular, since the amount of stirring of the hot metal 8 in the ladle 10 by the carrier gas blown together with the desulfurizing agent is small at the beginning of the blowing from the blowing lance 6, the desulfurizing agent floats up unreacted and is adsorbed on the slag 9. large. The desulfurizing agent is supplied to the whole from the stage where the stirring of the hot metal 8 by the carrier gas reaches the whole, but until that time, the concentration of the desulfurizing agent in the hot metal 8 is not uniform, and the reaction efficiency is not improved. There was room.

In order to improve the reaction efficiency of the refining powder, Japanese Patent Application Laid-Open No. 58-34126 discloses a blowing stirrer which is provided at the tip of a rotating stirrer while rotating the blowing lance about its axis. A method is disclosed in which a flux or the like is blown from an injection nozzle using an inert gas as a carrier gas to degas molten steel and remove inclusions. Further, in Japanese Examined Patent Publication No. 63-26169, while refining powder is blown from a blowing lance, a molten steel flow velocity of 0.8 m / s or more is obtained by a rotating or moving magnetic field and a dipping stirrer in the lower molten steel in the ladle. There is disclosed a method for cleaning molten steel by using the above method.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention JP-A-58-34126
By rotating the blowing lance about the axis as disclosed in Japanese Patent Publication No. JP-A-2004-242242, the bubbles generated when the refining powder is blown together with the carrier gas are sheared and refined, and the refining powder is also used. Can be made uniform in the circumferential direction. Therefore, the reaction interfacial area is increased and the reaction efficiency of the refining powder can be improved. However, since the bubble reaching distance L ₁ blown horizontally from the blowing nozzle into the molten metal is constant, There is a problem that the refining powder is dispersed locally in the horizontal direction and becomes uneven.

Further, the prior art disclosed in the above Japanese Patent Publication No. 63-26169 can improve the reaction efficiency of the refined powder blown by the stirring effect of the molten metal in which the moving magnetic field and the immersion stirrer are combined. . However, this device has a complicated structure and is disadvantageous in terms of equipment cost and maintenance. The present invention advantageously solves the above problems of the prior art and effectively improves the efficiency of the refining reaction by blowing the refining powder, thereby reducing the basic unit of the refining powder and producing molten metal. It is an object of the present invention to provide a method for refining molten metal capable of achieving improved properties.

[0011]

In order to achieve the above object, the present invention according to claim 1 immerses a powder blowing lance in a molten metal, and a refining powder is injected from a blowing nozzle at the tip of the lance. In the method for refining molten metal in which the impurity element is blown into the molten metal by using a carrier gas, the powder injection lance is provided with at least two injection nozzles in a direction intersecting with the axis of the powder injection lance. A refining powder is provided from each of the blowing nozzles, and the refining powder is dispersed in the molten metal by using carrier gases having different blowing pressures and then blown.

The present invention according to claim 2 is the method for refining molten metal according to claim 1, characterized in that the powder injection lance is rotated about its axis.

[0013]

Operation: Refining powder is blown from at least two blowing nozzles arranged in the direction intersecting with the axis of the powder blowing lance, and the molten metal is melted by using carrier gases having different pressures. Since the air is blown in, it is possible to adjust the bubble arrival distance in the molten metal blown out horizontally from the blow nozzle. As a result, it is possible to widen the dispersion range of the refining powder in the horizontal direction in the molten metal.

By rotating the powder blowing lance itself about its axis, it is possible to widen the dispersion range of the refining powder in the circumferential direction in the molten metal. A case where the configuration of the present invention is applied to desulfurization equipment will be described with reference to FIG. The desulfurizing agents (CaO, Na ₂ CO ₃ , Mg, etc.) in 1a and 1b of the two injection tanks are powder cutoff valves 2 respectively.
a and 2b are opened and supplied to the conduits 4a and 4b. At the same time N
The carrier gas such as ₂ is branched from the conduit 4 through the conduit 4.
The pressure control valves 12 and 13 are respectively provided at a and b. Here, for example, when the pressure control valve 12 is used for high pressure injection and the pressure control valve 13 is used for low pressure injection and the carrier gas is adjusted to a predetermined pressure, the desulfurizing agent supplied to the two conduits 4a and 4b is flexible together with the carrier gas. It reaches the blowing lance 6 through the hoses 5a and 5b. The blowing lance 6 is supported by an elevating device 21 via a support arm 20, and the elevating device 21 moves up and down along an elevating post 17 to move the blowing lance 6 into the hot metal 8 in the ladle 10. It is possible to adjust the immersion depth.

The blowing lance 6 immersed in the hot metal 8 in the ladle 10 has a concentric two-piece structure consisting of an inner pipe 6a and an outer pipe 6b, as shown in FIGS. 2 (a) and 2 (b). The inner pipe 6a and the outer pipe 6b are reinforced by using the reinforcing ribs 16. At the lower end of the inner pipe 6a, a high-pressure side blowing nozzle 14 is arranged horizontally at one position, and at the lower end of the outer pipe 6b, a low-pressure side blowing nozzle 15 is provided. It is arranged at one place in the horizontal direction slightly above. Furthermore, the inner pipe 6a
Is connected to the high pressure side flexible hose 5a, and the outer tube 6b is connected to the low pressure side flexible hose 5a.
connected to b. The part of the blowing nozzle 6 exposed to high temperature is covered with a refractory material 6c.

Therefore, the flexible hose 5a on the high pressure side
The desulfurizing agent supplied to the inner pipe 6a from the inside passes through the inner pipe 6a together with the carrier gas, and then is blown out from the single blowing nozzle 14 into the hot metal 8 in the ladle 10. Further, the desulfurizing agent supplied from the low pressure side flexible hose 5b to the outer pipe 6b passes through the outer pipe 6b together with the carrier gas, and then is blown out from the single blowing nozzle 15 into the hot metal 8 in the ladle 10.

The blowing pressures of the carrier gas blown from the blowing nozzles 14 and 15 are different, and in the case shown in FIG. 1, the blowing pressure P ₁ from the blowing nozzle 14 is larger than the blowing pressure P ₂ from the blowing nozzle 15. Since P ₁ > P ₂ is also high, the distance that the desulfurizing agent reaches in the horizontal direction with the carrier gas is different.
That is, assuming that the horizontal reach from the high-pressure side blow nozzle 14 is L ₂ and the horizontal reach from the low-pressure side blow nozzle 15 is L ₃ (L ₂ > L ₃ > 0), each blow nozzle. The horizontal momentum of the desulfurizing agent and the carrier gas is almost lost from 14 and 15 at the points L ₂ and L ₃ in the horizontal direction, and the floating starts.

The desulfurizing agent and carrier gas blown from the respective blowing nozzles 14 and 15 are adjusted so that the horizontal reaching distances L ₂ and L ₃ are adjusted so that the carrier gases are not mixed with each other during the floating. Can be uniformly dispersed.
For example, in the hot metal desulfurization treatment, it is possible to reduce the unreacted region due to the sulfur transfer rate control in the hot metal 8 and to improve the reaction efficiency of the desulfurizing agent.

The bubble reaching distance L _H from the blowing nozzles 14 and 15 can be obtained by using the following relational expression. _{L H = 3.7 · d n F} r 1/3 F r = ρ g · ν O 2 / g (ρ l -ρ g) · d n d n: Nozzle diameter F _r: Flute Number [rho _l: liquid density [rho _g : Gas Density ν _O : Gas Velocity FIG. 3 shows a configuration of the present invention of a type in which a blow lance 6 having a double pipe structure composed of an inner pipe 6a and an outer pipe 6b is rotated about an axis.

In this case, the blowing lance 6 is supported by the support arm 20.
The gear 19a mounted on the blow-in lance 6 is supported above the bearing 22 and meshes with the gear 19b connected to the electric motor 18 with a reduction gear. When the electric motor 18 is rotated, the blowing lance 6 is rotated at a predetermined rotation speed via the gears 19a and 19b. In this case, as shown in FIG. 3, the high-pressure side blowing nozzle 14 and the low-pressure side blowing nozzle 14 which communicate with the inner pipe 6a and the outer pipe 6b of the blowing nozzle 6, respectively.
15 are arranged one by one. You may arrange | position two pieces symmetrically as needed.

In the configuration shown in FIG. 3, the pressure of the carrier gas blown out from the high-pressure side blowing nozzle 14 and the low-pressure side blowing nozzle 15 is different as in the case of FIG. 1, so that the respective blowing nozzles are different. L _{2 in} the horizontal direction from 14, 15
Horizontal momentum of the desulfurizing agent and a carrier gas at a point of L ₃ is almost lost and starts floating. This horizontal reach L
₂ , the desulfurizing agent blown into the hot metal 8 is dispersed in the horizontal direction by adjusting L ₃ and L ₃
Is rotated about the axis to achieve dispersion in the circumferential direction, thereby expanding the dispersion region of the desulfurizing agent and the carrier gas in the hot metal 8.

[0022]

【Example】

Example 1 After hot metal dephosphorization (iron oxide, CaO) treatment with a tope car, the molten iron with a C content of 4.5% by weight and a temperature of 1300 ° C. discharged to a ladle was subjected to high pressure and low pressure using the refining apparatus shown in FIG. Desulfurization treatment with CaO and Mg was performed by using a one-hole side injection lance.

Other conditions are as follows. Ladle capacity: 200 t, inner diameter 4 m Hot metal depth: 2.94 m Distance from bath surface to high-pressure side injection lance: 2.1 m Distance from bath surface to low-pressure side injection lance: 2.0 m Lance diameter: 30 cm High pressure Side carrier gas injection pressure: 20 kg / cm ² Horizontal direction reach L ₂ : 0.3 m Low pressure side carrier gas injection pressure: 10 kg / cm ² Horizontal direction reach L ₃ : 0.15 m Desulfurizing agent injection speed: 100 kg / min Example 2 Using the same refining apparatus as shown in FIG.
While rotating the high-pressure side and low-pressure side one-hole blow lances
Desulfurization treatment was performed with CaO and MgO.

Other conditions were the same as those in the above-mentioned embodiment except that the lance rotation speed was 6 rpm. The desulfurization treatment of hot metal according to Examples 1 and 2 of the present invention and the conventional example shown in FIG. 4 was performed under the same conditions of the carrier gas amount and the desulfurizing agent blowing rate. S before the hot metal treatment and S after the hot metal treatment
And the like are shown in Table 1 in comparison.

[0025]

[Table 1]

As shown in Table 1, according to the present invention, when the S concentration before treatment and the S concentration after treatment are at the same level, the treatment time is shortened by 2 to 3 minutes as compared with the conventional case, and desulfurization is performed. The reaction efficiency (index) of the agent was significantly improved from 1.0 to 2.8 and 2.9, and good results were obtained. In addition, in the embodiment of the present invention, the case where it is applied to the desulfurization treatment equipment is described, but the present invention is not limited to this,
It can be applied to various gas blowing equipments for blowing refining powder.

[0027]

INDUSTRIAL APPLICABILITY According to the present invention, when the powder is blown into the molten metal, the refining powder is supplied to the hot metal from a high-pressure blowing nozzle, a low-pressure blowing nozzle, and a nozzle having a different blowing pressure to melt the molten metal. It is possible to supply the refining powder in a wide range in the molten metal in a uniform concentration by making the horizontal reaching distance of the refining powder in the metal from the blowing nozzle different. This can improve the reaction efficiency of the refining powder,
A reduction in the amount of refining powder used and a reduction in processing time are achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of an apparatus according to the present invention.

FIG. 2 shows a powder injection lance according to the present invention, (a)
Is a side view, and (b) is a cross-sectional view showing AA arrow of (a).

FIG. 3 is a cross-sectional view showing another configuration of the device according to the present invention.

FIG. 4 is a cross-sectional view showing a configuration of a device according to a conventional example.

[Explanation of symbols]

 1 Blow Tank 2 Powder Cutoff Valve 3 Flow Control Valve 4 Conduit 5 Flexible Hose 6 Blow Lance 7 Blow Nozzle 8 Hot Metal 9 Slag 10 Ladle 11 Floating Carrier Gas and Powder 12 Pressure Control Valve (for High Pressure) 13 Pressure control valve (for low pressure) 14 Blow nozzle (for high pressure) 15 Blow nozzle (for low pressure) 16 Reinforcing rib 17 Lifting post 18 Motor with reduction gear 19 Rotating gear 20 Support arm 21 Lifting device 22 Bearing

Claims (2)

[Claims] 1. A molten metal for immersing a powder blowing lance in a molten metal, and blowing a refining powder from a blowing nozzle at the tip of the lance into the molten metal by using a carrier gas to remove impurity elements. In the refining method, the powder blowing lance is provided with blowing nozzles at least at two positions in a direction intersecting with the axis thereof, and carriers for blowing the refining powder from the respective blowing nozzles have different pressures. A refining method for molten metal, which comprises using gas to disperse and blow in molten metal. 2. The method for refining molten metal according to claim 1, wherein the powder blowing lance is rotated about its axis.