JPS62161906A - Pretreatment of molten pig iron in tapping spout of blast furnace - Google Patents

Abstract

PURPOSE:To prevent the temp. of molten pig iron from falling and to attain efficient pretreatment of the molten pig iron by retreating the molten pig iron discharged from a blast furnace in the pig-bed of the furnace. CONSTITUTION:Molten pig iron and slag discharged from the tap hole 1 of a blast furnace reach a skimmer 3 through a larger runner 2 and the molten pig iron is separated from the slag by the skimmer 3 and flows in a torpedo car 6 through a medium runner 4 and an inclined trough 5. The slag is discharged through a slag runner 7 before the skimmer 3. At this time, a treating agent in a blow tank 9 is blown on a flow of molten pig iron from a blow lance 8 at a position within the range of at least 1/3 of the length of the large runner 2 between the tap hole 1 and the skimmer 3 on the tap hole side.

Description

[Detailed description of the invention] [Industrial application field] The present invention desiliconizes hot metal tapped from a blast furnace.

This invention relates to a method in which hot metal is pretreated in a blast furnace tap trough by adding dephosphorization and desulfurization agents.

[Prior Art] As is well known, pre-treatment of hot metal includes desiliconization, dephosphorization, and desulfurization. For example, desiliconization involves injecting an oxidizing agent into the hot metal before pouring it into the steelmaking furnace to oxidize and remove some of the Si in the hot metal. Slopping can be prevented. Conventionally, the method of spraying or blowing the above-mentioned desiliconizing agent etc. into the pig iron mixing car has been commonly carried out. However, according to these methods, desiliconization slag and the like get mixed into the pig iron mixing car, resulting in severe wear and tear on the refractories. In order to prevent this, if refractories with high corrosion resistance are used, the thermal conductivity increases and the temperature drop of the hot metal increases, which becomes a problem. Therefore, a method has been proposed in which a treatment agent is added to the cast bed of a blast furnace where the hot metal temperature is higher. Examples of such technology include Japanese Patent Application Laid-open No. 5
As shown in Japanese Patent No. 7-143414, there is a method of creating a steep drop in the flow of molten iron flowing through a blast furnace casthouse gutter and adding a hot metal pretreatment agent.

[Problems to be Solved by the Invention] In conventionally proposed methods for treating hot metal in and after the hot metal trough of a casthouse, the slag after treatment is not separated and is transferred to the subsequent process while being mixed. Furthermore, it is necessary to separate again, and even if skinmer separation, dragger separation, etc. are performed after the inner gutter, it is necessary to construct new equipment, which has the disadvantage of increasing costs.

The object of the present invention is to advantageously solve these difficulties by adding a treatment agent in the gutter of the casthouse and separating the slab from the blast furnace slag using an existing skinmer at the same time.

[Means for Solving the Problems] The present invention provides that, when pre-treating hot metal in a blast furnace taphole, on the taphole side of the taphole, at least 1/3 of the length of the taphole between the taphole and the skinmer is provided. This is a method for pre-treatment of hot metal in a blast furnace tap trough, which is characterized by adding a treatment agent at a step.

[Function] The function of the present invention will be explained below. FIG. 1 is an overall explanatory diagram of the present invention. That is, the hot metal slag discharged from the taphole 1 passes through the large gutter 2 and is separated into a slab and hot metal by the skimmer 3, and the hot metal flows into the pig iron mixer car 6 via the inner gutter 4 and the tilting gutter 5. The slag is discharged through a slag trough 7 in front of the skimmer 3. Normally, the length of the large trough is designed so that while the tap slag discharged from the taphole 1 reaches the skimmer 3, the slag is separated into the upper part and the hot metal is separated into the lower part due to the difference in specific gravity. The present inventors determined at what point on this large gutter the treatment agent should be added to complete the reaction, and the slag produced by the treatment agent would separate from the hot metal, float to the top, and flow into the slag gutter in front of the skinmer 3. As a result of experiments, it was found that the distance for discharge from No. 7 was within 1/3 of the tap hole. That is, if the treatment agent is added at this position, the conventional slag treatment in the post-process is completely unnecessary.

When adding a treatment agent, it is most effective if a method that directly reacts with the hot metal is used. There are 5 ways to do this
For example, as shown in Fig. 1, the spraying agent may be added through a lance 8, or as shown in Fig. 2, the treatment agent may be injected into the hot metal through a refractory lance 10 using a blow tank 9, or as shown in Fig. 3. In particular, the treatment agent can be easily and effectively added to the hot metal slag discharged from the taphole 1 by cutting it out from the hopper 11 and properly introducing it into the discharge stream.

[Example] In a 4.0OOrn' blast furnace, with a large trough length of 12 m and a distance of 1 m from the tap hole, as shown in Fig. 1, a desiliconizing agent was applied to the hot metal slag discharged from the tap hole 1. 3m
The sintered powder having a particle size of less than m was conveyed by compressed air using a blow tank 9, and was sprayed into the flow from the tip of a lance 8 with the spread angle and linear flow rate adjusted. Sintered powder, which is a desiliconizing agent, has various basic units (
5 to 30 kg/ton of hot metal). The compressed air was adjusted to between 50 and 400 Nrd/hr in consideration of gas transport.

While blast furnace slag generates 300 kg/ton of hot metal, desiliconization slag generates about 10 to 30 kg/ton of hot metal.The basicity of blast furnace slag decreases by a small amount, and due to the heat of reaction, there is no decrease in slab temperature, which occurs simultaneously with desiliconization. Desulfurization was also possible. This seems to be because the desulfurization ability of the blast furnace slab was effectively utilized by strong stirring under atmospheric pressure. Figure 4 is a desiliconization efficiency diagram, and the desiliconization efficiency is also as shown in the curve of the figure in this example compared to the conventional addition treatment after the inner gutter shown by the curve of the comparative example as shown in Figure 4. , the molten pig iron temperature was improved by about 50°C. Also, after desiliconization 0.15X10
A hot metal quality of 2% or less was obtained.

In this embodiment, desiliconization treatment has been described, but it goes without saying that the present invention can also be applied to dephosphorization, desulfurization, etc.

[Effects] As described above, according to the present invention, a drop in molten iron temperature can be prevented by performing preliminary treatment of hot metal tapped from a blast furnace in a cast bed, and furthermore, slag treatment in a subsequent process can be omitted. This invention is useful for steel manufacturing because it has the effect of enabling high-efficiency hot metal pretreatment at low cost.

[Brief explanation of drawings]

FIG. 1 is an overall diagram of the present invention, FIGS. 2 and 3 are explanatory diagrams of an example of a processing agent addition method, and FIG. 4 is a desiliconization efficiency diagram in an example. 1... Tap hole, 2... Large gutter, 3... Skinmer, 4... Middle gutter, 5... Tilt gutter, 6... Pig mixer car, 7... Slag gutter, 8.・Spraying is done by lance,
9... Blow tank, 10... Refractory lance,
11... Hopper No. 2 Fig. 33 Fig. 〇-Example No. 4 Amendment to the drawing procedure July 29, 1985 Display of the Director General of the Port Authority Pre-processing power of hot metal in pig iron sluices Relationship with the person holding the Pope New patent applicant 2-6-3 Otemachi, Chiyoda-ku, Tokyo (Name)
(665) Takeshi, Representative of Nippon Steel Corporation 1) Toyo Burial Address: Mr. 5, 4-24-3, Shinbashi, Minato-ku, Tokyo 105, Date of amendment order Voluntary -゛6,
Subject of amendment (a) Column for detailed explanation of the invention in the specification (b) Column for brief explanation of drawings in the specification (c) Figure 5 and 7 of the drawings, contents of amendment (a) Page 6 of the specification The sections from line 3 to line 5 on page 6 will be corrected as shown in Attachment (A). (b) The entire text of the brief description of the drawings section of the specification shall be amended as shown in Attachment (b). (c) Add Figure 5. Attachment (a) In another example, three
In the same manner as in the above example, limestone with a particle size of 1+nm or less and sintered powder were added as a desiliconizing and desulfurizing agent at a weight ratio of 9 (
Limestone): 1 (sintered powder) was prepared and sprayed. Desulfurization could be carried out at the same time as desiliconization without reducing the slag temperature. This seems to be because the blast furnace slag is strongly stirred by the gas generated by the decomposition of calcium carbonate, and the quicklime content produced at this time and the desulfurization ability of the blast furnace slag, which originally exists under atmospheric pressure, are effectively utilized. Furthermore, the reaction progressed due to the sintered powder added at the same time, and desiliconization was also possible. Figure 5 is a desulfurization efficiency diagram, and as shown in Figure 5, the desulfurization efficiency is also higher as shown in the curve in this example compared to the conventional addition treatment after the inner gutter shown by the curve in the comparative example. I was able to process it. Attachment (b) 4. Brief explanation of the drawings Figure 1 is an overall view of the present invention, Figures 2 and 3 are explanatory diagrams of an example of the method of adding a treatment agent, and Figure 4 is the desiliconization efficiency in an example. FIG. 5 is a desulfurization efficiency diagram in an example. 1... Taphole, 2... Big gutter, 3... Skinmer,
4... Middle gutter, 5... Tilting gutter, 6... Mixed iron car, 7.
... Slag gutter, 8... Lance for spraying, 9... Blow tank, 10... Refractory lance, 11... Hopper. Figure 5

Claims (1)

[Claims] A blast furnace characterized in that, in the preliminary treatment of hot metal tapped from a blast furnace, a treatment agent is sprayed and added to the molten iron flow within at least 1/3 of the taphole length between the taphole and the skinmer. Preliminary treatment method for hot metal in the tap runner.