JPH0819448B2 - Hot metal desiliconizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is directed to the bath surface of molten pig iron that falls on a slant gutter provided in the vicinity of an end of a tap pipe installed in a blast furnace casting floor. The present invention relates to a hot metal desiliconizing agent for performing desiliconization treatment.

(Prior Art) In the hot metal pretreatment, a desiliconizing agent composed mainly of iron oxide is sprinkled on the hot metal in the tap iron installed in the blast furnace casting floor, and desiliconization is performed in the flowing process. Japanese Patent Application Laid-Open No. 59-1430, in which a desiliconizing agent is spray-added to the hot metal in an inclined gutter provided close to the end of a tap pipe.
The projection method disclosed in No. 10 is known.
In the former spraying method, in order to ensure the reaction between the sprayed desiliconizing agent and the hot metal, the spraying is performed upstream of the tap iron gutter, and during the downflow process and at the drop position from the tap iron gutter end to the inclined gutter. Desiliconization reaction occurs in the process of stirring and mixing with energy. The latter projection method is generally performed in an inclined gutter at the end of the tap gutter, and the projection is performed at the position where the molten pig iron that falls into the inclined gutter causes the desiliconization reaction.

In Japanese Patent Laid-Open No. 59-25913, in a spraying method, a gutter lid in which a pressing lower surface projecting inwardly and downwardly of the hot metal spout is located at a level between the upper surface of the desiliconizing agent layer formed on the hot metal surface and the hot metal surface. A continuous desiliconization method of hot metal is disclosed, which is placed in a gutter, and the desiliconizing agent is pressed below the surface of the hot metal by the pressing wall of the gutter lid to perform contact stirring of the desiliconizing agent and the hot metal. Sho 61-3364 discloses a hot metal desiliconizer that improves the desiliconization efficiency by identifying the particle size composition of the desiliconizer that is desiliconized during passage through tapping gutters and that produces a desiliconized slag with good slag discharge properties. Has been done.

(Problems to be Solved by the Invention) In the conventional hot metal desiliconization treatment by the spraying method and the blasting method, a diameter reducing agent having a particle diameter of 1 mm or less is generally used. Since these desiliconizers are conditioned by grinding,
As the particle size distribution, the one having a small ratio of 100 μm or less is used. Therefore, when performing hot metal desiliconization, the reaction speed with the hot metal is slow because the particle size is large, and the reaction mainly takes place in the hot metal carrying device introduced from the inclined gutter. As a result, unreacted iron oxide increased in the desiliconization slag in the hot metal carrier, causing slag foaming, and the addition of the anti-foaming agent was unavoidable to reduce the hot metal filling amount. Also, since slag foaming occurs, the upper limit of the amount of desiliconizing agent input is limited, and even if an attempt is made to control the amount of desiliconizing agent input according to the amount of Si component in the hot metal, if the amount of Si component is high, Due to the limitation, only a limited amount of Si component was desiliconized, and the oxygen component escaped as iron oxide into the slag, so a high level of reaction efficiency could not be expected. Furthermore, if slag foaming occurs in the hot metal carrier, it is impossible to control the level of the molten metal surface required when performing the dephosphorization treatment in the next step.

The method of pushing the desiliconizing agent under the hot metal in the hot metal gutter in the spraying method of JP-A-59-25913 has a problem in that slag foaming occurs at the pushing position, and the method of the method of JP-A-61-3364 does not work. The method of specifying the grain size composition of the silicifying agent has a problem in that the cost is increased due to grain size. The same applies to the projection method.
If the particle size is large, the hot metal after projection is discharged into the hot metal carrier, and forming occurs in the carrier, which tends to direct fine particles, resulting in an increase in cost.

(Means for Solving Problems) The present invention aims to provide a hot metal desiliconizing agent in which the problems of the prior art are eliminated and improved, and a hot metal desiliconizing agent according to the claims is provided. By doing so, the above object can be achieved. That is, it is a hot metal desiliconizing agent for performing desiliconization treatment by projecting on the bath surface of the hot metal that falls through the tapping gutter and into the inclined gutter, and the coarse particles of 3 mm or less to 100 μm or more
From a mixture consisting of ~ 30% by weight of iron oxide with the balance being fine particles of 100 μm or less, and fine particles collected from blast furnace casting floor dust collection and steel factory building dust collection. The present invention relates to a hot metal desiliconizing agent characterized in that

 Next, the present invention will be described in detail.

INDUSTRIAL APPLICABILITY The present invention is used in the desiliconization treatment by the projection method in which the hot metal desiliconizing agent is projected onto the bath surface of the hot metal that drops into the inclined gutter provided in the vicinity of the tapping gutter end installed in the blast furnace casting floor. When the particle size of the desiliconizing agent is 100 μm or less, the desiliconizing reaction efficiency reaches about 70%, but it is difficult to increase the efficiency more than that. The reason for this is that when the particle size of the desiliconizer is small, the reactivity is good, but the mass of each particle is small, and the bulk specific gravity of the particle aggregate powder is also light at 1.2 to 1.5, so the specific gravity is about 7 It is considered that the reaction efficiency is low as a result.

Therefore, the present inventor considered not only the fine-powder desiliconizing agent but also the coarse-grain desiliconizing agent to be mixed therewith. According to this method, the coarse particles obtain sufficient energy by the projection to reach the underside of the bath surface, and at the same time, the fine particle desiliconizing agent also penetrates. By carrying out such a method, that is, by using different raw materials for the fine-grain desiliconizing agent and the coarse-grain desiliconizing agent, the desiliconizing reaction efficiency can be increased far above 70%. Furthermore, there is no need to dry the fine-grain desiliconizing agent iron oxide when pneumatically transporting dust particles with a particle size of 100 μm or less based on the average particle size collected in the blast furnace casting floor dust collection and steel factory building dust collection. Using dust collection dust that is a waste, as coarse iron oxide, it can be obtained as a sieve without crushing 0.1
Powdered ore containing 70% of ~ 3mm or average particle size 200μ
By using sand iron of about m, the cost can be reduced and the desiliconization efficiency can be increased, thus completing the present invention.

Fig. 1 shows the ratio of the coarse iron oxide particles exceeding 100 μm to the iron oxide particles of 100 μm or less collected in the blast furnace casting floor dust collector and steel factory building dust collector as a desiliconizing agent on the horizontal axis. (%) And the relationship between the silicidation reaction efficiency (%) indicated by ×-× on the vertical axis and the amount of pig iron (tons / T / c) in the hot metal carrier due to the effect of slag forming indicated by ○-○ It is the figure which illustrated.

From Fig. 1, if 5% or more of coarse grain desiliconizing agent is mixed with fine grain dust which is fine grain desiliconizing agent, the coarse grain penetrates well into the hot metal. Used, the desiliconization reaction efficiency (%) was 70% or more. This effect is up to about 0% of the compounding ratio, and if it is mixed more than this, the effect of coarse particles having a slow reaction efficiency begins to appear, the amount of slag forming in the hot metal carrier increases, and the amount of pig iron received decreases.

Therefore, the proportion of the coarse-particle desiliconizing agent iron oxide having a particle size of 100 μm or less and being mixed with the fine-particle desiliconizing agent iron oxide dust collection particles exceeding 100 μm needs to be 5% to 30%.

 Next, the present invention will be described with reference to examples.

(Example) A case where a desiliconizing agent having a particle size of 0.1 to 1 mm, which has been conventionally used, is used as a desiliconizing agent for performing desiliconizing treatment on a bath surface of a hot metal falling on an inclined gutter by a projection method. Fine particles of the invention: 80% dust collection dust with a particle size of 60 μm, average particle size as a coarse particle
The characteristics of the case where a diameter reducing agent containing 20% of sand iron of 200 μm was used were comparatively investigated.

Fig. 2 is a graph showing the relationship between the coarse particle content (% by weight) and the slag foaming occurrence rate. When it exceeds 30%, the slag foaming occurrence rate rises sharply, so the coarse particle content rate is 30%.
Must be less than or equal to%.

Figure 3 shows the basic unit of desiliconizing agent (kg / tp), that is, the amount of desiliconizing agent projected and the reaction efficiency (%) when the Si content in the hot metal is 0.30%.
And a diagram showing the relationship with the hot metal filling rate (%) in the hot metal carrier, in which ○ indicates the reaction efficiency, × indicates the hot metal filling rate, the solid line indicates the conventional desiliconizing agent, and the broken line indicates the desiliconizing agent according to the present invention. The results are shown. The hot metal filling rate is shown as 100% without desiliconization. The reaction efficiencies of both the conventional agent and the agent of the present invention decrease as the projection amount of the desiliconizing agent increases, but the agent of the present invention has higher reaction efficiency than the conventional agent, and the agent of the present invention improves the efficiency by about 20%. . In addition, as the amount of projection increases, slag foaming is induced in the hot metal carrier by the unreacted agent, and as a result, the filling rate decreases, but the agent of the present invention maintains a high filling rate. The result shows that the filling rate is increased by about 15% as compared with the conventional agent. Therefore, the maximum input amount can be increased by 5 kg / tp.

Fig. 4 is a diagram showing the correspondence between the freeboard value (m), that is, the distance from the mouth to the surface of the molten metal in the hot metal carrier, between the ironmaking side (pouring side) and the steelmaking side that is the recipient. The mark indicates the conventional desiliconizing agent, and the cross indicates the desiliconizing agent of the present invention. The invented agents show a good agreement between the freeboard values of both, but the conventional agent has a large value on the steelmaking side, and this difference indicates that the occurrence rate of slag foaming in the hot metal carrier is high. ing. From this, it is unavoidable that the filling rate of the hot metal of the conventional agent is lowered. Therefore, the use of the agent of the present invention improves the control accuracy of the bath surface level.

From the above results, the use of the desiliconizing agent according to the present invention reduces slag foaming, and
We achieved the results of 20% improvement, hot metal filling rate improvement of 15%, improvement of bath surface level control accuracy, and increase of the maximum input amount by 5 kg / tp.

In addition, the fine-grained desiliconizer iron oxide uses dust collected from the blast furnace casting floor dust collection and steel factory building dust collection, and coarse iron oxide that does not require pulverization and sand iron is mixed. By doing so, it is possible to reduce the pretreatment cost of crushing and sorting and mixing, and to treat waste (dust), which enables low-cost treatment.

(Effects of the Invention) According to the present invention, as a desiliconizing agent for performing desiliconizing treatment on the bath surface by the projection method, the hot metal falling on the slant gutter provided at the end of the tapping girder is used as a desiliconizing agent in a blast furnace casting floor and a steel factory building. 100 collected
By using a desiliconizing agent which is mainly composed of fine iron oxide particles of dust less than μm and which is mixed with coarse iron oxide particles of 3 mm or less to 100 μm or more in the range of 5 to 30% in the total amount of the mixture, By reducing the occurrence rate of slag foaming, it is possible to improve desiliconization reaction efficiency, improve the hot metal filling rate, increase the upper limit of the amount of desiliconizing agent added, improve the bath surface level control accuracy, and achieve low cost treatment. .

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the coarse particle composition ratio of the desiliconizing agent according to the present invention, the reaction efficiency and the amount of pig iron, and FIG. 2 is the relationship between the coarse particle composition ratio of the desiliconizing agent and the slag foaming occurrence rate. Fig. 3 is a diagram showing the relationship between the basic unit used by the present invention and the conventional desiliconizing agent, the reaction efficiency, and the hot metal filling rate, and Fig. 4 is the ironmaking side and the steelmaking side of the agent of the present invention and the conventional agent. It is a figure which shows the relationship of a freeboard value.

Claims (1)

[Claims] 1. A hot metal desiliconizing agent for performing desiliconization by projecting on a bath surface of hot metal that falls through a tapping gutter and falls into an inclined gutter, and is 3 mm to 100 mm.
The coarse particles of μm are composed of 5 to 30% by weight of iron oxide, and the balance is
A hot metal desiliconizer characterized by comprising a mixture composed of blast furnace cast bed dust collection as fine particles of 100 μm or less and fine particle collection dust collected by steel factory building dust collection.