JP2000290715A - Method for desiliconizing molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the siliconizing efficiency and also, to restrain the generation of a slag foaming at the desiliconizing treatment by receiving molten iron from a molten iron runner for blast furnace through a tilting trough in a molten iron receiving vessel and injecting a desiliconizing agent together with gas directly to the dropping stream. SOLUTION: When a molten iron 4 is received into the molten iron receiving vessel 2 from the molten iron runner for blast furnace through the tilting trough, the desiliconizing agent 6 together with the carrier gas 5 are directly injected into the molten iron stream 3 from an injecting lance 1. At this time, since the desiliconized slag foaming is not generated, the siliconized slag 7 does not overflow from the vessels. The desiliconizing agent 6 is not especially restricted by using a solid oxygen supplying agent and this adding quantity is desirably about 5-20 kg/T-pig and the average grain diameter is made to about 4-1 mm from the view point of the restraint of foaming and the maintaining of desiliconizing efficiency in the molten iron receiving vessel 2. As the carrier gas 5, Ar gas or N2 gas is desirably used and the injecting pressure is made to 1.0-30 kgf/cm2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for desiliconizing molten iron in which a desiliconizing agent is supplied when molten iron is received from a blast furnace molten iron gutter through a slanting gutter into a receiving vessel.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of reducing the amount of slag generated in a steelmaking stage and reducing refining costs, it has been desired to reduce Si in hot metal at a stage prior to steelmaking. For this reason, a desiliconizing agent (also called a de-Si agent) is usually added to the hot metal prior to steelmaking.
To remove Si.

[0003] As a conventional method for performing a de-Si treatment, a cast-bed de-Si method in which a de-Si agent is introduced into hot metal flowing through a tapping gutter provided in a blast furnace, or after receiving iron into a pig receiving vessel. There are injection methods in which the de-Si agent is blown into the hot metal together with the carrier gas, and placement methods in which the Si-removal agent is placed in a pig iron container before receiving the iron, etc. Technology.

[0004] However, in the desiliconization method in which the desiliconizing agent is introduced into the hot metal as described above, the desiliconizing agent is placed on the hot metal and reacted with the hot metal, but the contact between the hot metal and the desiliconizing agent is insufficient. Therefore, the reaction with the hot metal was insufficient and sufficient desiliconization efficiency could not be obtained. In addition, the unreacted iron oxide in the desiliconized slag reacted with the carbon in the hot metal, forming occurred, and the amount of hot metal in the receiving vessel was limited.

To solve such a problem, for example, Japanese Unexamined Patent Publication No. 57-92116 discloses a method in which addition of a desiliconizing agent is performed in a gutter. Each method has been proposed in which the injection of a desiliconizing agent is used in combination.

[0006]

However, in the case of using the above-mentioned prior art, in the case of the former, the refractory of the gutter is damaged by reacting with the desiliconizing agent, and the frequency of repair is increased. In this case, a special treatment facility is required, and it takes time to perform a sufficient desiliconization treatment, and there is a problem in distribution.

[0007] Therefore, an object of the present invention is to develop a method which can use the conventional equipment as it is and can realize the Si removal treatment in a short time with a simple operation.

[0008]

Means for Solving the Problems In order to achieve such a problem,
First, the improvement of the de-Si agent, the improvement of the method of introducing the de-Si agent,
Furthermore, an approach to improving the pretreatment of the hot metal and the like is conceivable, but the present inventors have focused exclusively on the improvement of the method of introducing the Si-removing agent.

The problems of the prior art relating to this point are that a large amount of the Si-removing agent is added in a short period of time, resulting in insufficient slagging of the Si-removing agent. It is conceivable to solidify as it is.

Therefore, in an environment where small quantities can be introduced at a high speed in a small amount, even if a large quantity is introduced in a short time, it is considered that slagification proceeds rapidly. If so, it is conceivable that the possibility that the Si-removing agent solidifies without being reacted is reduced.

[0011] Then, a place where such an environment exists in the path from the tapping gutter to the pig receiving vessel was searched for, but such an environment did not exist. The present inventors have further studied and searched for a place where such an environment can be most easily realized. As a result, while the conventional technology puts the de-Si agent in the receiving vessel as an insertion method, the de-Si agent is supplied to the falling flow when pouring from the inclined gutter into the receiving vessel. At this time, if the carrier gas is injected together with the carrier gas, the small amount can be introduced at a high speed, and once the carrier gas is blown into the hot metal, it acts as a stirring gas. An environment that can be realized can be realized.

On the basis of such knowledge, the present inventors have actually introduced a de-Si agent together with a carrier gas into the falling flow of hot metal from the inclined pouring trough to the pig iron receiving vessel. It was confirmed that the desiliconization rate was improved, and desiliconization slag forming was not observed, and it was confirmed that the desiliconization treatment was completed in a short time, thus completing the present invention.

Accordingly, the present invention relates to a method for desiliconizing hot metal in which a hot metal is supplied from a blast furnace hot metal gutter via a slanting gutter to a receiving vessel by way of a slanting gutter. It is a method for desiliconizing hot metal, which is sprayed together with the molten iron.

[0014]

Next, an embodiment of the present invention will be described together with its operation and effect. According to the present invention, a de-Si agent is added together with a carrier gas to the falling flow of hot metal from the inclined gutter to the pig iron receiving vessel, thereby improving the de-siliconization efficiency and preventing de-silicon slag forming. be able to.

FIG. 1 is a schematic explanatory view of a method for charging a Si-removing agent according to the present invention. As shown in FIG. When the hot metal 4 is received in the hot metal receiving vessel 2 through the step (i), the desiliconizing agent 6 is directly blown from the charging lance 1 together with the carrier gas 5 onto the hot metal flow 3. At this time, since the desiliconized slag forming is not observed unlike the conventional case, the desiliconized slag 7 does not overflow from the inside of the pig receiving vessel 2.

The Si-removing agent used in the present invention is not particularly limited as long as it is a solid oxygen supplying agent, and a conventional Si-removing agent can be used as it is. And from the viewpoint of maintaining the Si removal efficiency, preferably at most 20 kg / T-pig, more preferably 5 to 20 kg / T-pig.
It is Kg / T-pig. Further, in the case of the present invention, it is preferable to use particles having a diameter of 4 mm or less, for example, in order to be accompanied by a carrier gas. Preferred de-Si agents have an average particle size of 4-1 mm. If it is more than 4 mm, the reactivity may be poor. On the other hand, if it is too fine, it scatters and deteriorates the working environment.

Examples of the type of the Si-removing agent include pickling scale, mill scale, sintered ore, iron sand and the like. If necessary, a slag adjusting agent may be added simultaneously. The carrier gas does not but Ar gas or N ₂ gas is preferably limited thereto. In the case of the present invention, the blowing pressure is sufficient as long as it can accompany the falling flow, for example, 1.0 kgf / cm ² or more, and there is no particular limitation. , About 1.0 to 30 kgf / cm ² . If the blowing pressure is too small, its effect cannot be distinguished from the holding method, so it should be 1.0 kgf / cm ² or more.

The Si-removing agent added to the falling flow as described above is diffused throughout the hot metal by the stirring energy of the carrier gas and the stirring energy of the falling flow. Since it is already almost uniformly dispersed when it is put into the falling flow,
In the pig iron receiving vessel, the Si-removing agent is quickly diffused throughout the hot metal,
The contact efficiency between the hot metal and the desiliconizing agent can be increased to improve the desiliconization efficiency.

After the pouring into the pig receiving vessel is completed, the lance is immersed in the pig receiving vessel, bubbling with Ar gas or N ₂ gas or the like is performed to stir the hot metal, and the injection removal S step is performed. It is also possible to carry out and remove the Si treatment at the same time.

Further, when dispensing hot metal from an iron receiving container such as a mixed iron car to a ladle, a Si-removing agent may be further added together with the carrier gas in the same manner. Next, embodiments of the present invention will be described together with their effects.

[0021]

EXAMPLES The operating conditions in this example were as follows. Initial hot metal composition: Si: 0.5 to 0.7% Desiliconizing agent: Sintered fine ore Injected carrier gas Air: 500 to 1000Nm ³ / h Table 1 shows the composition of typical desiliconizing agents that can be used in the present invention. Show.

Table 2 summarizes the results of the method of the present invention and the conventional method. In the case of the present invention, not only is the amount of desiliconization significantly improved, but also the desiliconization reaction efficiency of the desiliconizing agent reaches 80 to 100%, indicating that slag forming can be substantially prevented.

As shown in FIG. 2, when the desiliconizing agent is introduced by using the desiliconizing agent introducing device of the present invention, it is possible to improve the desiliconizing efficiency and to suppress the occurrence of slag forming during the desiliconizing treatment. became.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

As described above, according to the present invention, when the hot metal is received from the blast furnace hot metal gutter into the receiving iron container via the inclined pouring gutter,
By directly blowing the desiliconizing agent together with the gas onto the falling flow of the hot metal, it is possible to improve the desiliconization efficiency and suppress the forming of the desiliconization slag.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an operation of charging a desiliconizing agent into a hot metal stream according to the present invention.

FIG. 2 is a graph showing the results of Examples.

[Explanation of symbols]

 1: Input lance, 2: Iron receiving container 3: Desiliconized slag, 4: Hot metal

Claims (1)

[Claims] 1. A method for removing silicon from a blast furnace hot metal gutter through a tilting gutter into a pig iron receiving vessel, wherein the hot metal is supplied with a desiliconizing agent. Characterized method of desiliconizing hot metal.