KR19980051233A - Desorbent for blast furnace pretreatment and its manufacturing method - Google Patents

Abstract

An object of the present invention is to provide a degreasing agent used in the molten iron preliminary treatment during the steelmaking process and a manufacturing method thereof.

In the present invention to achieve the above object by weight, CaO: 46-52%, SiO ₂ : 4-7%, Al ₂ O ₃ : 41-46% comprising a degreasing agent and a secondary refining The technical subject matter of the method which can be easily manufactured using slag is made.

Description

Desorbent for blast furnace pretreatment and its manufacturing method

The present invention relates to a degreasing agent used in the steelmaking process of the steel industry and a method for manufacturing the same, and more particularly to a degreasing agent for the purpose of desulfurization in the blast furnace pretreatment and a method for producing a desorbent using secondary refining slag. will be.

Generally, the molten iron from the blast furnace contains about 200 ppm of sulfur. This sulfur must be removed because it will ultimately adversely affect the quality of the river. Therefore, a significant portion of steelmaking technology has been made regarding the removal of sulfur.

Sulfur is removed in several steps in the steelmaking process. First of all, the sulfur contained in the charter preliminary treatment process after removal from the blast furnace is removed, and the secondary composition is adjusted to the desired composition by reflowing through steel stirring or powder blowing. In other words, sulfur has a very strong affinity with an alkali metal or alkaline earth metal element because of its strong property to exist as a divalent anion when the oxygen partial pressure is low. Therefore, in terms of cost and reactivity in the steelmaking process, conventionally, sulfur is removed by using a lime-based desorbent during preliminary molten metal treatment. The following equations are used for the removal of sulfur.

CaO + [S] = CaS

CaC2 + 0 = Ca0 + 2 [C]

As can be seen from the above, the conventional degassing agent mainly used for the removal of sulfur has used a lot of quicklime or calcium carbide. Since the degreasing agent mainly has a high melting point, the slag existing in the upper part of Torpedo Car after dehydration is mainly solid slag, and thus, the material movement of sulfur is quite difficult. In addition, most of the sulfur is removed from the blast furnace after the molten iron preliminary treatment process, conventionally a significant amount of lime-based desorbent is added to remove the sulfur, which leads to an increase in the degassing cost. On the other hand, it is difficult to produce molten steel with the desired composition only by this desulfurization, so the slag with a high rate of quicklime is formed in the secondary refining process, increasing the contact area between slag and molten steel through steel stirring and performing dehydration or calcium The contained powder was blown in and molten steel was deflowed.

In the sulfur removal process in the secondary refining process, the sulfur concentration in the slag is not so high because the sulfur content in the molten steel is not high. This process is expressed as follows.

(% S): Sulfur content in slag

[% S]: Sulfur content in molten steel

Ks: reaction equilibrium constant between desorbent and sulfur

aO ^2- : activity of oxygen ion in slag

aO: activity of oxygen in molten steel

fS ^2- : activity coefficient of sulfur ions in slag

fS: activity coefficient of sulfur ions in molten steel

Looking at the above, all values other than the reaction equilibrium constant Ks are constant values when the temperature and molten steel composition are constant. Therefore, it can be regarded that it exists in a certain ratio assuming that conditions different from sulfur contained in slag and sulfur contained in molten steel are constant. In this aspect, the sulfur content in the molten iron after the blast furnace is very high compared to the secondary refining process, so the sulfur in the molten iron slag can also be high. Table 1 shows the comparison of the sulfur content of slag and molten iron in the molten iron preliminary treatment process and the sulfur content of slag and molten iron in the secondary refining process.

As shown in Table 1, the sulfur content in the molten iron slag is considerably higher than the sulfur content in the secondary refining slag, and it can be seen that the secondary refining slag still has a considerable amount of dewatering capacity after dewatering. However, since the secondary refining slag is simply discarded by pouring it into the slag container after continuous casting, a considerable amount of loss is expected in terms of environment and manufacturing cost.

Accordingly, the present invention provides a desorbent for blast furnace pretreatment capable of lowering the slag and reducing the amount of slag, while exhibiting dehydration efficiency at an equivalent or higher level as compared with the conventional blast furnace pretreatment desorbent. The purpose is.

Another object of the present invention is to provide a method for preparing a blast furnace pretreatment desorbent using secondary refining slag that is simply discarded.

1 is a ternary state diagram for explaining the dehydrating agent composition region of the present invention

2 is a ternary state diagram for explaining a composition region of secondary refining slag.

The present invention for achieving the above object is a degreasing agent for removing sulfur in the molten iron during pretreatment of the molten iron from the blast furnace, in weight%, CaO: 46-52%, SiO ₂ : 4-7%, Al ₂ The present invention relates to a blast furnace pretreatment desorbent composed of O ₃ : 41-46%, T.Fe: 5% or less, and other unavoidable components. In addition, the present invention is a method for producing a desulfurizing agent to remove the sulfur in the molten iron during pretreatment of the molten iron from the blast furnace, after the slag slag generated by refining the pretreated molten iron in the slag, slag to the slag The present invention relates to a method for preparing a blast furnace pretreatment desulfurizer in which alumina-based waste smoke and ton: 160 ± 10 kg, metal Al: 80 ± 7 kg and quicklime: 60 ± 5 kg are added per ton.

Hereinafter, the desorbing agent of the present invention will be described in detail.

As the conventional degassing agent used for preliminary molten metal treatment, quicklime or calcium carbide has a very high melting point and is present in the solid phase at the molten iron cloud. Makes it difficult. Therefore, the sorbent for blast furnace pretreatment of the present invention is characterized in that it has a melting point as low as possible in order to suppress the formation of a solid film. That is, the desorbent of the present invention, as shown in the CaO-A1 ₂ O ₃ -SiO ₂ ternary state diagram of FIG. 1, has a composition region having a low melting point to facilitate the movement of sulfur material. To this end, the desorbing agent of the present invention is preferably limited to 46-52 wt% of CaO, 4-7 wt% of SiO ₂ , and 41-46 wt% of Al ₂ O ₃ .

Such a desulfurizing agent can be prepared with quicklime, silica powder or alumina powder, but preferably ladle slag generated during secondary refining. Hereinafter, a preferred embodiment of preparing the desorbent of the present invention will be described.

First, Table 2 shows an example of the composition for the secondary refining slag used as the raw material of the desorbent of the present invention.

Looking at the components of the slag shown in Table 2, the slag is mainly in the liquid phase region in the secondary refining process, as shown in the ternary state diagram shown in Figure 2, while in the molten iron preliminary treatment process is present in the solid phase region biased toward the liquid region Able to know. In addition, the slag contained in the secondary refining slag is about 0.25%, it can be seen that very low compared to the sulfur content of the molten iron preliminary slag of Table 1. Therefore, the secondary refining slag can be used as a desulfurizing agent for the molten iron preliminary treatment simply by lowering the melting point. That is, for this purpose, it is necessary to move the composition of the secondary refining slag to the desorbent composition region of the present invention as shown in FIG. 1, in the present invention, alumina waste lead, metal aluminum and quicklime are added to the secondary refining slag. The additives act to lower the melting point of the secondary refining slag, and when blown into the molten iron, the solid film formed as a result of the dehydration reaction is lowered to facilitate the movement of sulfur.

The method for producing the desorbent of the present invention can be made by adding a secondary refining slag to the slag container in which alumina-based waste smoke is added. However, since this method has a bad effect of lowering the temperature of the entire slag due to the waste heat and the specific heat of CaO, it is preferable to inject aluminum together to achieve thermal compensation of the slag. In other words, the additives are added to the slag in the hot state immediately after the second refining, after the ladle slag is excluded. For example, the heat of oxidation of aluminum is 7400㎉ / kg, and the heat generated by adding about 80 ± 5kg of aluminum can be used to provide the heat compensation necessary for the input of waste lead and CaO. Since the average specific heat of CaO is about 982cal / K-kg, the amount of heat to raise 1kg of Ca0 to about 1600 ℃ is about 1571㎉. In addition, the average heat of alumina, the main component of waste smoke, is about 130OcaI / K-kg, so the heat required to increase the temperature to 1600 ℃ is about 2080㎉. Therefore, the heat required to raise 160kg waste smoke and 60kg Ca0 to 1600 ℃ is about 427060㎉ and the heat of oxidation of 80kg aluminum is about 592000㎉, so there is no problem of heat supply for heating and melting of the flux. In addition, it is more preferable to oxidize aluminum by injecting oxygen on the container after the addition of aluminum in order to help the oxidation of the aluminum and to promote a rapid reaction.

The alumina waste smoke used in the present invention includes a ladle wall, etc., and such waste smoke usually contains 93% or more of Al ₂ O ₃ . On the other hand, the desulfurizing agent prepared using the secondary refining slag may be crushed after being collected in the slag container, blown through the lance or collected in the slag container, or may be added to the charter transportation container without change in its formation.

Hereinafter, the present invention will be described in detail through examples.

(Example)

The desorbent of the present invention prepared by using the secondary refining slag was blown using a deflow lance in the same manner as the existing dehydration treatment in the molten iron preliminary treatment process. In addition, both desorbents were directly added to the molten iron and the stirring was increased to increase the contact area between the molten iron and the desorbent to promote the deflow reaction. However, in the case of using the deflow lance, the desorbent prepared for blowing in the form of bunte through the lance was used.

The comparison between the case of using the deflow lance and the method of directly introducing the desorbent to the molten iron is shown in Table 3 below.

As shown in Table 3 above, it can be seen that the efficiency of the dehydration reaction is better when the desulfurization lance is directly added than when the dehydrating agent is directly added. However, in the case of using degassing lance, the flux must be crushed to an appropriate particle size, which can lead to an increase in the cost, and a considerable degree of degassing effect can be expected even when degassing by directly introducing the desorbent into the molten iron. Therefore, the direct introduction of the desorbent to the upper part of the molten iron can be said to be effective for the molten iron deflow.

On the other hand, it can be seen that when comparing the desulfurization efficiency with CaO, which is one of the fluxes used as the existing degreasing agent, the equivalent deflowing effect is shown.

As described above, the desulfurizing agent for the pretreatment of the present invention is capable of lowering the slag to lower the melting point of the slag, so that the material movement of the sulfur in the slag is smooth, so that the same or more desulfurization efficiency can be obtained even at a small dosage compared to the conventional desulfurizing agent. In addition, the desulfurizing agent of the present invention can be simply produced using the secondary refining slag, which can be said that the industrial value is very large.

Claims (3)

In the degreasing agent which removes sulfur in the molten iron during pretreatment of the molten iron from the blast furnace, in weight%, CaO: 46-52%, SiO ₂ : 4-7%, A1 ₂ O ₃ : 41-46%, T.Fe: 5% or less, and degreasing agent for blast furnace pretreatment, characterized in that it is composed of other unavoidable components In the method of manufacturing a desulfurizing agent which removes sulfur in the molten iron during pretreatment of the molten iron from the blast furnace, after the ladle slag generated by the re-refining of the molten iron in the pretreatment, the alumina waste smoke per slag ton : 160 ± 10kg, Metal Al: 80 ± 7kg and quicklime: 60 ± 5kg The method according to claim 2, wherein the waste smoke is a ladle wall containing 93% or more of Al ₂ O ₃ .