JP3238016B2 - Hot metal pretreatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has an open bottom part.
When immersing the lower part of the immersion free board, which is a container evacuated from the upper part, into a hot metal pot and inserting a lance from the center of the immersion free board to perform hot metal de-P treatment, the de-P reaction efficiency is lower than the conventional level. The present invention relates to a pretreatment method for hot metal characterized by preventing overflow of slag accumulated between a immersion free board and a hot metal pot during the de-P treatment while maintaining the same.

[0002]

2. Description of the Related Art Hot metal is processed by blowing a processing material from a lance.
The lance discharge from the reaction mode
Reaction zone near nozzle, slag-metal interface reaction zone
From the reaction area near the discharge nozzle of the lance.
Slag-metal interface reaction area
The region is divided into a transient reaction region. The conventional technology focuses only on the transit reaction of the de-P treatment, and the inner diameter of the lower tank is the maximum reachable distance in the horizontal direction considering the transit reaction due to the spread of the jet of oxygen and the processing material discharged from the lance, An immersion freeboard lower tank that is larger by about 500 mm than the diameter obtained by adding the diameter of the lance has been employed. Therefore, the intermediate tank has a structure having substantially the same inner diameter as the lower tank because of the simplicity of preparation of the processing tank and the ease of detaching and attaching the tanks.

[0003]

SUMMARY OF THE INVENTION
It has the following issues. Since the volume between the hot metal pot and the lower part of the immersion free board becomes smaller, the de-P slag accumulated between the hot metal pot and the lower part of the immersion free board during the de-P treatment overflows from the hot metal pot, so Problems such as processing equipment trouble due to slag, reduction in acid feed rate for avoiding overflow of de-P slag, and increase in frequency of cleaning of overflowed de-P slag occurred, resulting in reduced productivity.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its gist is to form an upper tank, an intermediate tank, and a lower tank in hot metal in a hot metal pot. Immerse the lower part of the immersion freeboard, insert a lance into the hot metal bath from the center of the immersion freeboard, and inject oxygen and treatment material to remove the hot metal from the intermediate bath. Near the lance discharge nozzle
From the reaction zone at the side to the reaction zone at the slag-metal interface
In consideration of the spread of the oxygen discharged from the lance and the jet of the processing material in the transit reaction, which is the reaction of the above, the diameter obtained by adding the diameter of the lance to the maximum reach in the lateral direction is made larger than the diameter obtained by the inner diameter of the lower tank. Is characterized by the use of an immersion-free board, which is obtained by adding the diameter of the lance to the maximum reach in the horizontal direction, taking into account the transit reaction due to the spread of the oxygen discharged from the lance and the jet of the processing material. Hot metal pretreatment method.

[0005]

FIG . 3 shows a freeboard (upper tank) immersed in a hot metal ladle 2.
7a, intermediate tank 7b, lower tank 7c)
FIG. In the figure, 1 is hot metal, 3 is lance,
4 is a discharge nozzle, 5 is a processing material (mixing of gas and powder)
Object) and 6 are slag. FIG. 2 shows a discharge nozzle diameter of 27 m.
This figure shows the spread state of the powder and gas discharged from the treatment material blowing lance when oxygen is supplied at a flow rate of 3600 Nm ³ / hr from a lance having four discharge nozzles at m. The powder is CaO and dust, C
It blows you a nitrogen gas as a carrier at a rate of aF ₂ 900kg / min. Discharge powder is 60cm from lance discharge port
It begins to spread upward from a position farther away, and the spread is converged at about 95 cm. This allows the lower tank 7
The inner diameter of c is preferably a diameter having a value substantially equal to the maximum spread position of the powder in order to keep the volume between the hot metal pot 2 and the outer diameter of the lower part of the immersion free board as large as possible. On the other hand, the intermediate tank 7b
In the above, considering the reaction surface of the treatment material, a wider reaction interface is more advantageous for the reaction, so the inner diameter is preferably as large as possible. From such a viewpoint, it is preferable to increase the inner diameter of the intermediate tank within an allowable range in the hot metal pot.

The present invention was made on the basis of this finding, the upper tank 7a, the intermediate tank during the hot metal in the hot metal pot in 2
7b , the lower part of the immersion freeboard consisting of the lower tank 7c is immersed, the lance 3 is inserted into the hot metal bath from the center of the immersion freeboard, oxygen and the processing material are injected, and P
In determining the diameter of the immersion free board when performing the treatment, the inner diameter of the intermediate tank 7b which affects the permanent reaction between the top slag and the metal is determined by the transit reaction due to the spread of the oxygen discharged from the lance and the jet of the treatment material. The diameter obtained by adding the diameter of the lance to the maximum lateral distance considered was made larger than the diameter obtained, and the inner diameter of the lower tank 7c took into account the transient reaction due to the spread of the oxygen discharged from the lance 3 and the jet of the processing material. , Obtained by adding the lance diameter A (FIG. 3) to the maximum lateral distance.

[0007]

EXAMPLES Table 1 shows the specifications of the immersion free board used in the examples and the conventional examples. FIG. 1 shows the deoxidation efficiency of the present invention and the conventional example in comparison, and it can be seen that the oxygen efficiency of the present invention is excellent in terms of the average value.

[0008]

[Table 1]

Further, as is clear from Table 1, the gap between the lower tank of the immersion freeboard and the lining of the hot metal pot was expanded by 250 mm as compared with the conventional one, and the de-P slag deposited in the hot metal pot did not overflow from the pot. .

[0010]

According to the present invention, it is possible to prevent the slag from overflowing during the de-P treatment while maintaining the conventional de-P reaction efficiency at the conventional level. Has reduced the frequency of removing P-slag and has improved the productivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between CaO / O and deoxygenation efficiency.

FIG. 2 is a diagram showing a trajectory of powder and gas discharged from a lance.

Fig. 3 Hot metal immersed in immersion freeboard in hot metal ladle
Schematic diagram explaining processing

[Description of Signs ] 1 hot metal 2 hot metal ladle 3 lance 4 discharge nozzle 5 treatment material 6 slag 7a upper tank of immersion free board 7b intermediate tank of immersion free board 7c lower tank of immersion free board

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shinji Matsuo Oita, Oita, Oita, 1st section, Nishinosu Oita Works Nippon Steel Corporation (72) Inventor Teranishi, Seiko 1st section, Oita, Oita, Oaza, 1F Steel Works Co., Ltd. Oita Works (58) Fields surveyed (Int. Cl. ⁷ , DB name) C21C 1/02

Claims (1)

(57) [Claims] 1. A immersion freeboard comprising an upper tank, an intermediate tank, and a lower tank is immersed in hot metal in a hot metal ladle, and a lance is inserted into the hot metal bath from a central portion of the immersion freeboard. upon by injecting treatment material performs de-P treatment of molten pig iron, the intermediate tank inner diameter of the immersion freeboard is Reims ejection
Slag-metal interface reaction zone from the reaction zone near the discharge nozzle
It was calculated by adding the lance diameter to the maximum lateral distance, taking into account the oxygen discharged from the balance and the spread of the jet of the processing material in the transit reaction, which is the reaction during the reaction up to the zone . The inner diameter of the lower tank was determined by adding the diameter of the lance to the maximum lateral distance, taking into account the transit reaction due to the spread of the jet of oxygen and processing material discharged from the lance, and the diameter of the lance. And a hot metal pretreatment method characterized by using an immersion free board.