JPH02200714A - Pretreatment of molten pig iron - Google Patents

Abstract

PURPOSE:To easily melt and remove pig iron stuck and solidified on the throat of a furnace for pretreating molten pig iron by prerefining molten pig iron in the furnace provided with a bottom blowing tuyere and a top blowing lance by desiliconization and dephosphorization with oxygen and by blowing oxygen on the stuck and solidified pig iron from the top blowing lance. CONSTITUTION:Molten pig iron 5 discharged from a blast furnace is poured into a pretreating furnace 1 provided with a bottom blowing tuyere 4 and a top blowing lance 3 and gaseous O2 is blown from the tuyere 4 and the lance 3 to oxidize Si and P in the molten pig iron 5 and to remove them as SiO2 and P2O5. Since the molten pig iron 5 splashes, sticks and solidifies on the upper opening of the furnace 1 during the desiliconization and dephosphorization, the lance 3 is slowly pulled up while feeding gaseous oxygen from the lance 3 after the pretreatment and the stuck and solidified pig iron is melted and perfectly removed by blowing gaseous oxygen on the pig iron.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a preliminary treatment method for melting and removing ingots adhering to a furnace during preliminary treatment of hot metal for desiliconization, dephosphorization, and the like.

[Conventional technology]

Hot metal pre-treatment (1JN) furnaces have lower post-treatment temperatures than converters, so they have disadvantageous conditions for base metal adhesion, and various removal methods have been proposed in the past.

JP-A-55-51041.3 proposes a method for removing ingots attached to metal refining vessel L-1 and a lance nozzle used to carry out this method. It uses a special lance, and after the refining process,
- First, the lance for processing is pulled out, and then a lance dedicated to removing the metal is inserted to melt the metal.

Jikai Showa 5 again? -168126, 54-97796
The publication proposes a lance for melting ingots adhering to the converter mouth and a nozzle for melting ingots adhering to the converter mouth, both of which are equipped with an oxygen flow divider for melting the ingots attached to the converter blowing lance. The structure is such that it is not possible to fuse the base metal while blowing oxygen after the completion of blowing.

[Problem to be solved by the invention]

Togoro and each of the above-mentioned techniques is a method in which a special lance for the metal is inserted after the processing is completed and oxygen is blown into the metal.
The lance preparation time is required, which lowers the metal surface temperature, and even when oxygen is blown, the metal does not ignite, resulting in poor metal cutting efficiency, and in some cases, it may become impossible to remove the metal.

The present invention solves the above-mentioned problems and provides a preliminary treatment method that uses a preliminary treatment lance and efficiently removes ingots by 1/8 inch.

[Means to solve the problem]

The present invention is a hot metal pretreatment method characterized in that, at the final stage of the hot metal pretreatment, a lance supplying gaseous oxygen is raised without stopping the oxygen supply to melt the furnace mouth ingot.

(Function) The present invention does not continue to blow oxygen even after preliminary treatments such as desiliconization and dephosphorization are completed, but rather raises the lance or stops the process midway if necessary to remove CO gas generated from inside the furnace. Next combustion is carried out to maintain the area near the furnace mouth at a predetermined temperature, and oxygen is directly blown onto the metal to dissolve and remove the adhered metal.

Normally, pretreatment has a lower treatment end temperature of about 1280°C to 1360°C compared to reactions using two converters, etc.
Although it is disadvantageous for metal removal, it promotes secondary combustion of the CO gas generated by continuing to blow oxygen even after the treatment is finished, and makes it easier to dissolve and remove the metal by raising the temperature. It is.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic side sectional view showing an example of a pretreatment furnace. 1
2 is a furnace body, 2 is an exhaust gas duct, and the furnace body 1 is provided with a lance 3 for top blowing and a tuyere 4 for bottom blowing.
Preliminary blowing treatment is carried out by supplying acid from lance 39 and tuyere 4.

After the pretreatment reaction is completed, the lance 3 is raised without stopping the oxygen supply, and the CO gas generated from the hot metal 5 is secondaryly combusted. This combustion causes the temperature inside the furnace to rise, so
When performing secondary combustion, consider the rise in temperature from the target temperature after the completion of pretreatment, set it slightly lower, and calculate the auxiliary materials and oxygen consumption required for desiliconization and dephosphorization. and process it.

This secondary combustion heat raises the temperature of the base metal, and furthermore, oxygen is directly blown onto the base metal to melt and remove it.

FIG. 2 (8) is a cross-sectional view showing an example of the detailed structure of the tip outlet of the lance 3 suitable for performing this metal removal.
Figure (B) is a plan view seen from the bottom of Figure 2 (A).

Near the center of the tip of the lance, there are four main holes 3a for supplying oxygen for preliminary treatment, and on the outside thereof four sub holes 3b, which are smaller in diameter than the main holes 3a, are arranged. The number of main holes 3a and sub-holes 3b is determined appropriately depending on the scale of the furnace, etc., but the sub-holes 3b should have an opening cross-sectional area ratio of 30% or more of the main hole 3a, and the inclination angle α with respect to the vertical direction should be 20° or more. It is desirable that there be.

As an example of construction by the method of the present invention, lances with 4 main holes of 20φ and 4 secondary holes of 17φ are used, the distance between the lance surfaces is maintained at 2 to 5 m, and the oxygen flow rate is 1.500 ON/h. As a result of blowing oxygen with 11270 Nrrf of practical acid for 5 minutes at
The temperature rose to 10°C, and approximately 3 tons of metal was dissolved and removed.

〔Effect of the invention〕

As explained above, according to the pretreatment method of the present invention, the ingot metal at the furnace mouth is melted and removed by continuing to feed oxygen without lowering the temperature inside the furnace after the completion of the pretreatment. In addition, the fuel source and oxygen consumption rate for metal removal can be reduced. Furthermore, preparation time such as removal of ingots after preliminary treatment is unnecessary, and the time for preliminary treatment can be shortened, thereby improving productivity in the steel manufacturing process.

[Brief explanation of the drawing]

Figure 1 is a schematic side sectional view showing an example of a Hayabi processing furnace, Figure 2 (
Δ) is a sectional view showing an example of the air outlet at the tip of the lance;
Figure (B) is a plan view of the second time (A) seen from the bottom. ■... Furnace body, 2... Exhaust gas duct, (3... Lance, 3a... Main hole, 3b... Sub-hole, 4... Bottom blower D, 5... ?8 Pig Agent Patent Attorney Masamitsu Akisawa and 1 person Figure 2

Claims (1)

[Claims] A method for preliminary treatment of hot metal, characterized in that at the end of the preliminary treatment of hot metal, a lance supplying gaseous oxygen is raised without stopping the oxygen supply to melt the metal at the furnace mouth.