JP2017193733A - Desiliconization treatment method - Google Patents

Abstract

[Problem] To improve the efficiency of the desiliconization reaction in a high [Si] concentration region where the [Si] concentration in the hot metal after the treatment is 0.2 mass% or more in the preliminary desiliconization treatment performed in the first stage of hot metal pretreatment, that is, To stably lower the post-treatment [Si] concentration without increasing the desiliconizing agent unit consumption or prolonging the treatment time, and to lower the FeO concentration of the post-siliconizing slag without excessively increasing its amount. , and suppression of slag foaming that occurs during desiliconization. % SiO2) is 0.5 to 1.5 and slag before desiliconization treatment is used, and solid acid is blown, gaseous acid is blown or blown. In addition, the amount of slag before desiliconization is set to 1 kg/t or more and 15 kg/t or less, and a CaO solvent is added in terms of pure CaO content of 0.5 kg/t-iron or more during desiliconization. [Selection drawing] Fig. 3

Description

    The present invention relates to a silicon removal treatment method in hot metal preliminary treatment.

  Conventionally, there is a steelworks that manufactures hot metal from iron ore in a blast furnace and steel from the hot metal. As described in Patent Document 1, in such an integrated steelworks, work for removing impurities is performed. For example, in order to remove carbon, silicon, and phosphorus, which are impurities, oxidative refining is performed to supply oxygen combined with these elements. The removal of impurities from hot metal performed prior to decarburization using a refining furnace represented by a converter is now called hot metal pretreatment.

JP-A-62-170409

  Hot metal desiliconization, which is one of the hot metal pretreatments, is performed at the blast furnace discharge and transfer container prior to the decarburization process in order to improve the efficiency of oxidative refining and reduce the amount of solvent and slag generated. It has been common practice to perform silicidation. The reason is that if the [Si] concentration in the hot metal fluctuates greatly, it becomes a variable factor of phosphorus and sulfur when performing dephosphorization that is oxidative refining in the subsequent process and desulfurization that is reductive refining. Further, this is because an increase in the amount of solvent used, an accompanying increase in discharged slag, and a productivity hindrance due to an extended processing time occur. Therefore, when the variation of [Si] concentration in hot metal is large due to restrictions on iron ore raw materials, hot metal desiliconization is important in avoiding the variation.

  In particular, the hot metal [Si] concentration should be allowed to fluctuate to a high level in order to obtain operating margin in a blast furnace that produces hot metal to cope with inferior resources, while the [Si] concentration of hot metal It is desirable that the fluctuation of is as low as acceptable in the subsequent process. In addition, the demand for low phosphatization and low sulfidation of steel products has increased, and so-called pre-desiliconization treatment before dephosphorization and desulfurization of hot metal has become increasingly necessary.

  By the way, heat is generated in the desiliconization reaction in which hot metal [Si] is oxidized and removed. In addition to enjoying the maximum benefit of being able to apply heat generated by this desiliconization reaction to hot metal, lowering the desiliconizer basic unit, avoiding the loss of iron due to inclusion of iron oxide in the slag, etc. In view of this point, it is required to effectively use the oxygen source supplied for the oxidation reaction for desiliconization.

In addition, it is known that slag containing SiO ₂ generated by an oxidation reaction is formed by a decarburization reaction that occurs simultaneously with desiliconization. Depending on the smelting vessel at the time of desiliconization, the slag overflowing due to this slag forming may become an impediment to improving the processing speed. For this reason, the technique which avoids the obstruction factor has been calculated | required, maintaining the preferable desiliconization conditions (Desiliconization rate of 40% or more, in process slag (% FeO) <= 30 mass%). Conventionally, the mainstream is to lower the [Si] concentration in the hot metal to less than 0.2 mass% by continuing the dephosphorization reaction after the desiliconization reaction. When the [Si] concentration in the hot metal was less than 0.2 mass%, the systematic study of slag before treatment was not made because the addition method and amount of oxidizer was dominant in the desiliconization reaction. .

  In the pre-desiliconization process performed in the first stage of the hot metal pretreatment, the present invention improves the efficiency of the desiliconization reaction in a high [Si] concentration region in which the [Si] concentration in the molten iron becomes 0.2 mass% or more, That is, without increasing the desiliconizing unit basic unit and extending the treatment time, the [Si] concentration after treatment is stably lowered, and the slag after desiliconization treatment is reduced to a low FeO concentration without excessively increasing the amount. That is, it is possible to suppress the formation of slag generated during the desiliconization process.

The present invention made to solve the above problems employs the following means. First, the first means is a desiliconization treatment method in a concentration range of hot metal [% Si] of 0.2 mass% or more, in which solid acid is blown, gas acid is blown or blown (% CaO) In the desiliconization method using slag before desiliconization with / (% SiO ₂ ) of 0.5 to 1.5, the amount of slag before desiliconization is 1 kg / t or more and 15 kg / t or less, and the CaO medium is used during desiliconization. The addition of 0.5 kg / t-iron or more of the solvent in terms of pure CaO.

  The first means is to divide and / or separate the CaO culture medium added during the treatment at a time when the treatment time ratio t / t0 is 0.1 or more and 0.9 or less when the desiliconization treatment elapsed time t and the desiliconization treatment time t0. It is preferable to use the second means of continuous addition.

  The first or second means is preferably a third means for stirring the molten iron and the desiliconized slag after the addition of the desiliconizing agent with a carrier gas of solid acid.

In the first means, the molten iron [% Si] concentration range of not lower than 0.2 mass%, blowing of Katasan performs spraying or blowing of hexane, the (% CaO) / (% SiO 2) 0.5~ The amount of 1.5 slag before desiliconization treatment is set to 1 kg / t or more and 15 kg / t or less, and a CaO solvent is added in a pure CaO content of 0.5 kg / t-iron or more during the desiliconization treatment. This makes it possible to achieve a desiliconization rate of 40.0% or more and a slag component after desiliconization to (% FeO) ≦ 30.0 mass% without causing desiliconization slag forming during desiliconization. Therefore, the efficiency of the desiliconization process in the high Si concentration range where the hot metal [% Si] is 0.2 mass% or more, that is, the improvement of the desiliconization oxygen efficiency and the suppression of slag foaming, thereby reducing the processing time. Can be provided. In addition, the desired desiliconization rate can be obtained in the high Si concentration range, and the desired [% Si] concentration can be obtained after the treatment, so that the operating margin of the hot metal pretreatment process can be secured, and the hot metal desulfurization reaction in the subsequent stage. In addition, the hot metal dephosphorization reaction can be made more efficient and the unit of the culture medium source can be reduced.

  The second means is to divide and / or divide the CaO culture medium added during the treatment at a time when the treatment time ratio t / t0 when the desiliconization treatment elapsed time t and the desiliconization treatment time t0 are 0.1 or more and 0.9 or less. It is added continuously. Therefore, it is possible to enjoy the advantage of desiliconization reaction efficiency while enjoying the CaO source addition effect. In addition, it is more advantageous for dissolution and reaction in desiliconized slag than to add a solvent as a CaO source at a time.

   The third means is to stir the slag after the hot metal and the desiliconization treatment with the carrier gas of the solid acid after the addition of the desiliconizing agent. Therefore, the carrier gas can be used not only for the transport of the solid acid but also for the stirring of the slag after the hot metal and desiliconization treatment.

It is a figure which shows the relationship between the amount of slag before a desiliconization process, its basicity, and the amount of desiliconization after a process. It is a figure which shows the relationship between the amount of slag before a desiliconization process, and a forming index. It is a figure which shows the relationship between CaO pure content addition amount and the amount of silicon removal after a process.

In the following, first, the concept of the present invention will be shown, and then examples will be described. Desiliconization reaction and SiO ₂ was oxidized by adding demineralized珪剤as the oxidizing agent to the molten iron to [Si] in molten iron, which is a reaction to absorb the SiO ₂ to desiliconization slag. A necessary condition for efficiently proceeding with the desiliconization reaction is to allow the desiliconization slag to absorb SiO ₂ as a reaction product while reacting [Si] in the hot metal with the oxidizing agent. Here, the desiliconization slag is a slag related to a desiliconization reaction, and means a slag accompanying the desiliconization treatment and the hot metal before and after the desiliconization treatment. The desiliconization treatment means an operation of adding a desiliconization agent and stirring the molten iron and the desiliconization slag. In the present invention, the desiliconization slag before the desiliconization treatment is treated as slag before the desiliconization treatment, and after the treatment. Use slag after desiliconization.

By the way, in order to efficiently perform the desiliconization treatment, it is important that a desiliconization slag capable of absorbing the SiO ₂ coexists on the interface where the reaction occurs. This is because the oxidant causes a so-called decarburization reaction that reacts with [C] in the hot metal to form CO gas unless it coexists. This means that the oxidizing agent is consumed in the decarburization reaction, so that the desiliconization oxygen efficiency is lowered and the desiliconizer basic unit is increased. Furthermore, CO gas generated by the decarburization reaction causes so-called slag foaming, which is present as bubbles in the surrounding desiliconized slag. Therefore, the desiliconization slag plays an important role in improving the efficiency of the desiliconization reaction while avoiding the decarburization reaction.

The desiliconizing agent is an oxidizing agent that oxidizes [Si] in the hot metal to form SiO ₂ . This is roughly divided into a solid oxygen source and a gaseous oxygen source. For high-efficiency desiliconization, it is necessary to supply a gaseous oxygen source and a solid oxygen source containing oxygen corresponding to the desiliconization amount Δ [Si]. Therefore, generally, these oxidizing agents are used in combination.

The solid oxygen source is mainly composed of iron oxide that acts as an oxidizing agent for [Si] in the hot metal, and is also called solid acid. The solid acid is a solid containing at least 50 mass% of FeO or Fe ₂ O ₃ which is iron oxide. Some of them contain less than 20 mass% of a component such as CaO because the reactivity increases when dissolved quickly at the hot metal temperature. Industrially, iron ore, steelmaking dust with a lot of iron oxide, ironmaking sludge, sintered ore and sintered dust when producing it are also used.

  The gaseous oxygen source is mainly composed of oxygen and is also called gaseous acid. The gas acid is an oxidizing gas that can be desiliconized, and specifically includes oxygen, carbon dioxide, and a mixed gas containing the same.

  Using these, the efficiency of the desiliconization reaction in the high [Si] concentration range, that is, the [Si] concentration after treatment can be stably lowered without increasing the desiliconizer basic unit or extending the treatment time, We considered the need to reduce the FeO concentration without excessively increasing the amount of slag after silicidation and to suppress the formation of slag that occurs during the desiliconization treatment, and considered the following points to be noted.

In order to suppress the slag forming during the desiliconization process, (1) “To prevent the decarburization reaction that accompanies the desiliconization reaction, the reaction product SiO ₂ is absorbed so as to be absorbed by the desiliconization slag. “To make it basic”, (2) “To make a desiliconization reaction through a slag composition region with high FeO concentration that is hard to form”, (3) “To make the slag amount before desiliconization treatment more than a predetermined amount. , “Maintaining slag basicity in the middle of the treatment to obtain a high FeO concentration” is required.

  In addition, in order to reduce the FeO concentration without excessively increasing the amount of slag after desiliconization, (4) “Make the amount of slag before desiliconization equal to or less than a predetermined amount”, (5) “Desiliconizer at the end of treatment. Among them, it is required to restrict the supply of solid acid containing FeO, and (6) “to make the FeO concentration in the desiliconized slag at the end of the treatment be a condition that contributes to the desiliconization reaction”.

  Considering (3) and (4) here, it is considered that there is a suitable range for the amount of slag before desiliconization. Also, considering (1), (2), (5) and (6), the slag basicity is changed from high basicity to low basicity, and the FeO concentration in slag is increased from high concentration as the processing time progresses. We have come up with the idea that it is appropriate to change to a low concentration while maintaining the preferred range for each period.

  Based on the above, in order to stably reduce the [Si] concentration after treatment without increasing the desiliconizer basic unit or extending the treatment time, considering the conditions (1) to (6), (7 ) It is necessary to add and react within the processing time the amount of desiliconizing agent consisting of gas acid and solid acid necessary for the amount of desiliconization Δ [Si] (mass%).

By intensively studying the conditions of (7), using the processing time ratio t / t ₀ obtained by dividing the processing time t (min) by the desiliconizing agent addition time t ₀ (min), the addition timing of the desiliconization agent is determined. I came to think that I could make it clear. As a means for realizing (1), (2), (5) and (6), CaO, which is a factor that adjusts the basicity using the treatment time ratio t / t ₀ and changes the FeO activity in the slag. It was thought that the addition amount and timing of the solvent containing CaO and CaO could be specified.

Here, the slag will be described in detail. The desiliconization slag absorbs the reaction product SiO ₂ and completes the desiliconization reaction. The desiliconization slag, de珪剤containing an oxidizing agent, medium solvents to assist their action, reaction products such as SiO _2, and consists of desiliconization pretreatment slag, the desiliconization processed slag after desiliconization treatment .

  Slag before desiliconization is derived from carry-over from blast furnace slag, derived from deposits associated with transport containers that are used repeatedly, or derived from refractories of transport containers that are worn before and during processing In addition, it is composed of a desiliconizing agent being processed and an auxiliary solvent solvent.

Blast furnace slag is slag associated with hot metal at the time of tapping. Its main components consist of CaO, SiO ₂ and small amounts of Al ₂ O ₃ , MgO, TiO ₂ , MnO, S and unavoidable impurities. The blast furnace slag is partially removed at the stage of brewing or the like because the contained S may return to the hot metal. On the other hand, when the hot metal surface of the hot metal transport container is left to cover the hot metal surface, there is an effect such as suppression of hot metal temperature decrease due to radiant heat and suppression of dust generation. In addition, since the hot metal transport container is repeatedly used, there is slag adhered and remaining on the inner wall of the container during the previous desiliconization. The main component is close to the blast furnace slag, but differs depending on the transport situation and the removal condition at that time.

  The slag before the desiliconization treatment includes the amount of elution from the refractory material of the transport container during transport from after receiving. Furthermore, in the transport container before the desiliconization treatment, there is also a medium solvent that is added and dissolved as an iron source such as scrap or shaped iron at the time of receiving, or is added as a dissolution aid for the iron source. Part of the oxide of the iron source and the auxiliary solvent solvent are brought into contact with and dissolved in the refractory in the transport container on the hot metal in the transport container to become a part of the slag before desiliconization.

Next, a study process for numerical values applied to the present invention will be described. In order to investigate the effect of the amount of slag before desiliconization treatment on the desiliconization behavior, 220 ton of hot metal having a [Si] concentration of about 0.6 mass% was desiliconized using a torpedo car that is one of the hot metal transfer containers. The model calculation based on the actual operation results was performed. The desiliconization condition is that the component of slag before desiliconization treatment is CaO-SiO ₂ system, desiliconization agent containing 10% CaO as solid acid, 60% FeO and 30% Fe ₂ O ₃ is 15kg / t- Assuming that iron is injected and oxygen gas is blown at 0.5 Nm3 / t-iron as a gaseous acid, the amount of slag before desiliconization and the CaO / SiO ₂ ratio in the slag before desiliconization are the hot metal after desiliconization △ The effect on [% Si] was estimated. This hot metal Δ [% Si] represents the difference between the [% Si] concentration before the desiliconization treatment and the [% Si] concentration after the desiliconization treatment. Moreover, the CaO / SiO ₂ ratio is one that is commonly used as an indicator of the basicity of the slag. The CaO / SiO ₂ ratio of the slag before desiliconization is affected by the blast furnace slag, and the range is about 0.5 to 1.5. Therefore, the three levels of 1.0, 1.1, and 1.3 that are frequently used are set. The result is shown in FIG.

As shown in FIG. 1, the amount of slag before desiliconization treatment is shown to increase the amount of SiO ₂ that is a reaction product by securing a certain amount, so that the hot metal Δ [% Si] is increased. It was found that the amount and composition of slag before treatment were influential factors. However, it was also found that the effect tends to saturate at 15 kg / t. Considering the increase in the amount of slag after desiliconization treatment, it was found that if the slag amount before desiliconization has an upper limit of about 15 kg / t or less, desiliconization reaction efficiency will be improved in a high [Si] concentration region.

Next, regarding the relationship between slag forming, which is an obstacle to implementing the desired desiliconization rate in desiliconization, and the amount of slag before desiliconization, 220 ton of hot metal having a [Si] concentration of about 0.6 mass% is added to the torpedo car. The model calculation based on the actual operation results when desiliconization was performed was examined. Desiliconization conditions, 10% of CaO as Katasan, the FeO 60%, de珪剤containing 30% of Fe ₂ O ₃ as well as injection of 15 kg / t-iron, the oxygen gas as hexane 0.5Nm3 / t-iron is sprayed. At this time, the slag forming height is normalized by the forming height when the slag is formed to the hot metal inlet of the torpedo car, and the slag before desiliconization treatment in which the CaO / SiO ₂ ratio in the slag is 1.0 to 1.3 The quantity relationship was examined. The result is shown in FIG.

  If the amount of slag before desiliconization is large, the forming height increases because the amount of slag itself is large. When the amount of slag before desiliconization exceeded 15 kg / t-iron, the forming index exceeded 1, and the slag overflowed from the hot metal inlet, forming a state with forming. On the other hand, if there is little slag before a desiliconization process, a decarburization reaction will also increase by a desiliconization agent, and slag will form during a desiliconization process. It was found that when the slag before desiliconization was less than 1 kg / t-iron, the forming index exceeded 1 in the forming index. Therefore, in order to perform high-efficiency desiliconization in a high [Si] concentration region, it was found that the amount of slag before desiliconization is 1 kg / t-iron or more and 15 kg / t-iron or less.

On the other hand, as shown in FIG. 1, when the amount of slag before desiliconization is small, the hot metal Δ [% Si] is low. When this is analyzed, the reason is that the addition of a desiliconizing agent during the treatment promotes desiliconization by increasing the FeO concentration in the slag, while the CaO / SiO ₂ ratio during the treatment decreases and the desiliconization is reduced. The knowledge that it was influenced that it was controlled was acquired. Based on this knowledge, the idea of adding a CaO source during the desiliconization process to increase the CaO / SiO ₂ ratio was to increase the desiliconization amount even with the same desiliconizing agent addition amount.

Therefore, the effect of CaO source addition during desiliconization on hot metal desiliconization was examined by model calculation. The hot metal Δ [% Si] in the case where the hot metal contained in the torpedo car with a weight of 220 t and the [Si] concentration was about 0.6 mass% was subjected to desiliconization treatment was determined. Its desiliconization conditions, desiliconization pretreatment slag amount 2~4kg / t-iron, 10% of CaO as Katasan, the FeO 60%, de珪剤containing 30% of Fe ₂ O ₃ 15kg / t -Iron was injected and oxygen gas as a gaseous acid was sprayed at 0.5 Nm3 / t-iron for 10 minutes. As the CaO source addition, the relationship between the CaO pure addition amount in the CaO source and the molten iron Δ [% Si] was determined. Here, as a CaO source, CaO grains composed of 95 mass% CaO and inevitable impurities were used. The addition time is between 2 minutes and 7 minutes from the start of the treatment. The result is shown in FIG.

  Even with the same desiliconizing agent addition rate and processing time, the effect of increasing the hot metal △ [% Si] becomes obvious when the CaO source CaO pure addition amount becomes 0.5 (kg / t-iron) or more by adding the CaO source. did. Therefore, the necessary amount of CaO added is 0.5 (kg / t-iron) or more as the CaO source CaO pure content. As shown in the figure, the effect was saturated at 6 (kg / t-iron) in terms of the amount of pure CaO added. Further, since the use of a large amount of a solvent leads to an increase in production cost, the addition of the CaO source is preferably 6 kg / t-iron or less in terms of the pure CaO addition amount.

  By the way, when a CaO source is added during the desiliconization process, the composition of the slag during the desiliconization process may change depending on the timing and method of addition, and this may affect the desiliconization reaction and slag forming. It was. Therefore, if it was assumed that the desiliconizing agent was continuously added with solid acid and gas acid, it was considered that the addition timing could also be specified. In other words, when the addition time is extremely late or when the amount of slag before desiliconization is small, it is thought that desiliconization slag partially becomes a solid phase and becomes an inhibitor of desiliconization reaction. It was.

  Therefore, the standardization of silicon removal treatment was considered. The amount of oxygen in the desiliconizing agent is generally expressed as oxygen supply rate Vo2 (Nm3 / min) in terms of gaseous oxygen. If the solid acid and gas acid origin are expressed as Vo2_s (Nm3 / min) and Vo2_g (Nm3 / min), respectively, the sum is obtained.

  If the target hot metal [Delta] [% Si] aim is determined, the desiliconization processing time to (min) can be determined via the coefficient α for converting the unit to the oxygen supply rate multiplied by the desiliconization oxygen efficiency η.

  Therefore, the desiliconization elapsed time t (min) can be made dimensionless by dividing by the desiliconization processing time to (min). It was found that the CaO source addition time in the present invention depends on the addition time when expressed by this treatment time ratio t / to. If the CaO source is added continuously like powder supply, the desiliconization reaction efficiency can be improved by ensuring the desiliconization rate, hot metal △ [% Si], and avoiding forming. It was found that it could be increased.

The importance of the CaO source addition time will be further described. If the amount of CaO source is excessively large relative to the desiliconized slag, FeO in the slag is diluted, and the effect of promoting desiliconization may be reduced. Furthermore, adding a CaO source during the treatment leads to not excessively increasing the SiO ₂ concentration and the FeO concentration in the latter half of the treatment. If the SiO ₂ concentration is not excessively high, the viscosity of the slag is stabilized at a low level, and slag forming is less likely to occur. Further, if the FeO concentration is not excessively increased, the generation of CO bubbles due to the decarburization reaction caused by slag is suppressed, and this also makes slag forming difficult to occur.

  In order to enjoy the advantage of desiliconization reaction efficiency while enjoying the CaO source addition effect, it is preferable to set the addition time and period at 0.1 to 0.9 at a treatment time ratio t / to. The reason for this is that if the addition is started at less than 0.1, even if the slag before desiliconization is limited to 15 kg / t-iron or less, the desiliconization reaction due to partial solidification of the desiliconized slag is still caused by the addition of the CaO source. This is because inhibition occurs. That is, when the addition is started at less than 0.1, problems such as getting on the slag before the desiliconization treatment whose surface is solidified or adhering to the refractory of the transfer container may occur, as in the case of adding the CaO source before the desiliconization treatment. . On the other hand, if the treatment time ratio exceeds 0.9 and the addition of the CaO source does not contribute to the efficiency of the desiliconization reaction, the undissolved CaO source remains and the increase in the desiliconization slag and the desiliconization slag In some cases, recycling may be hindered.

  In order to enjoy the advantage of desiliconization reaction efficiency by the method of controlling the amount of slag before desiliconization slag treatment and adding the CaO source, it is necessary to continue the addition of hot metal and desiliconization slag beyond the desiliconization agent addition time to Is also effective. That is, making CaO source addition effective and reacting unreacted oxygen in the desiliconizing agent and FeO in the slag. Although this stirring method may be a conventional method, for example, a method of supplying with a carrier gas using a solid acid injection apparatus which is a premise of the present invention is also conceivable. However, since the extension of the processing time itself is not desirable, the processing time ratio t / to is 1.2 or less, more preferably 1.1 or less.

It is desirable to add the solvent as a CaO source in a divided and / or continuous manner. This is because the SiO ₂ concentration in the desiliconization slag gradually increases during the desiliconization treatment, and the amount of slag increases while the FeO concentration varies depending on the supply rate of the desiliconization agent and the desiliconization rate. This is because it is more advantageous for dissolution and reaction in desiliconized slag than to add a solvent as a CaO source at a time. In particular, hot metal transport containers represented by torpedo cars are not expected to vigorously stir hot metal and coexisting slag, and when it is desired to increase the amount of CaO source added, the addition method is divided and / or continuous. I think it is desirable to do so.

By applying the present invention to the desiliconization treatment in the high Si concentration region which is the object of the present invention, the (% FeO) concentration in the slag after the desiliconization treatment can be reduced to 30 mass% or less. In addition, the density | concentration (% FeO) in slag after a desiliconization process is the mass% of FeO in the slag after a desiliconization process. Generally, the lower the concentration (% FeO) in the slag after desiliconization treatment, the better the desiliconization oxygen efficiency, and it can be considered that the efficient desiliconization treatment was completed. If the concentration of slag (% FeO) in the slag after desiliconization treatment exceeds 30 mass%, it is considered that this slag still has a degree of oxidation that can be desiliconized, and the iron yield decreases for that concentration. That's right. Therefore, Desiliconization processed slag (% FeO) concentration is preferably as low, as the threshold of manifestation of the effect of the present invention, lower than CaO and SiO ₂ concentration is a major constituent of desiliconization processed slag Therefore, 30 mass% or less at which the component activity was sufficiently reduced was taken.

A torpedo car was used as a hot metal transfer container, and the present invention was carried out in a method of performing a desiliconization process on a hot metal amount of 220 t and a temperature of 1360 ° C. to 1440 ° C. The treatment conditions were set such that the hot metal having a [Si] concentration in the hot metal before desiliconization of about 0.59 mass% to 0.61 mass% and the target hot metal Δ [% Si] was about 0.23 mass% or more. Its desiliconization conditions, 10% of CaO as Katasan, the FeO 60%, while injection of 15 kg / t-iron in a total amount of powdery de珪剤containing 30% of Fe ₂ O _3, as hexane The treatment was performed by blowing oxygen gas at 0.5 Nm3 / t-iron. Nitrogen gas was used as the carrier gas for the solid acid. As the CaO source addition, CaO grains composed of 95 mass% CaO and inevitable impurities were used. The amount of slag before treatment was estimated using the torpedo car inner wall shape from the slag thickness and the hot metal surface before treatment.

Table 1 shows the amount of slag before treatment, the presence / absence of CaO source addition, and the addition amount based on the above conditions. The (% CaO) / (% SiO2) ratio of the slag before desiliconization treatment was in the range of 1.0 to 1.3 except for the numbers 4 and 5. The desiliconizing agent addition time to is expressed by the addition period of the desiliconizing agent, and was about 10 minutes. Examples of CaO source addition not described in the column of CaO source addition rate are batch or two-part addition methods. In the case of batch addition, the addition time at the processing time ratio t / t ₀ described in the column of addition 1 is described. In the case of two divisions, the addition amount was equally divided, and the addition time at the treatment time ratio t / t ₀ described in the columns of addition 1 and addition 2 was described. When the treatment time ratio t / t ₀ was less than 0.1 and a CaO source was added, some of the CaO grains added as a CaO source remained in the refractory on the inner wall of the torpedo car after the desiliconization treatment, and the conditions were not met. Therefore, it was not included in the examples. When it is described as continuous in the column of the addition method of the CaO source and a number is described in the column of the CaO source addition rate, it is continuous addition, and the processing start time and the processing end time are respectively displayed in the column of the processing time ratio t / t _0. Described.

  The slag forming that occurs during the desiliconization process is judged visually, and the standard is large when the desiliconized slag clearly overflows from the exit of the torpedo car, but when the forming is recognized but does not overflow from the exit The case where the forming was observed but the forming port was not reached was minute, and the case where the slag forming was not recognized was regarded as none.

The agitation after the desiliconization treatment, described the processing time in the processing time ratio t / t ₀ for if implemented. Since the Si concentration after desiliconization is also affected by the Si concentration before desiliconization, the difference between [% Si] concentration before desiliconization and [% Si] concentration after desiliconization Si]. The silicon removal rate was expressed as a percentage of Δ [% Si] / [% Si]. The denominator of this equation is the [% Si] concentration before desiliconization.

As an effect of the present invention, slag forming during desiliconization treatment, desiliconization rate after desiliconization treatment, and FeO concentration in slag after desiliconization treatment were evaluated. The slag forming can be small, fine and none, good and large, and is visually confirmed as described above. The silicon removal rate after the silicon removal treatment was good at 40.0% or more, and less than 40.0%. If this is 40.0% or more, it is recognized that the hot metal △ [% Si], which is the amount of silicon removal, can be secured to about 0.24 mass% or more, which is about 5% higher than the target silicon removal amount. is there. Moreover, about the density | concentration (% FeO) in slag after a desiliconization process, 30 mass% or less was good, and it exceeded 30 mass%. This is because the FeO concentration is low and the activity is low as compared with the CaO and SiO ₂ concentrations, which are the main constituent components of the slag after desiliconization, as described above.

  No. 1 is an example in which the amount of slag before desiliconization treatment is 3.0 kg / t-iron, and a CaO source is added at a treatment time ratio t / t0 of 0.2 and 1.0 kg / t-iron. The slag forming was small, the desiliconization rate after desiliconization treatment was 40.0% or more, and the concentration in slag (% FeO) after desiliconization treatment was 30.0 mass% or less.

  No. 2 is an example in which the amount of slag before desiliconization treatment is 5.0 kg / t-iron, and a CaO source is added at a treatment time ratio t / t0 of 0.95 and 5.0 kg / t-iron. The slag forming was small, the desiliconization rate after desiliconization treatment was 40.0% or more, and the concentration in slag (% FeO) after desiliconization treatment was 30.0 mass% or less.

  No. 3 is an example in which the amount of slag before desiliconization treatment is 3.0 kg / t-iron, and 2.0 kg / t-iron is added to the CaO source when the treatment time ratio t / t0 is 0.3. The slag forming was small, the desiliconization rate after desiliconization treatment was 40.0% or more, and the concentration in slag (% FeO) after desiliconization treatment was 30.0 mass% or less.

No. 4, desiliconization pretreatment slag amount 2.0 kg / t-iron, as (% CaO) / (% SiO 2) ratio of desiliconization pretreatment slag 0.55, a CaO source processing time ratio t / t0 0.3 In this example, 2.0 kg / t-iron was added at the same time. The slag forming was small, the desiliconization rate after desiliconization treatment was 40.0% or more, and the concentration in slag (% FeO) after desiliconization treatment was 30.0 mass% or less.

No. 5, desiliconization pretreatment slag amount 10.0 kg / t-iron, as (% CaO) / (% SiO 2) ratio of desiliconization pretreatment slag 1.43, a CaO source processing time ratio t / t0 0.6 In this example, 2.0 kg / t-iron was added at the same time. The slag forming was small, the desiliconization rate after desiliconization treatment was 40.0% or more, and the concentration in slag (% FeO) after desiliconization treatment was 30.0 mass% or less.

  In No. 6, the amount of slag before desiliconization was 4.0 kg / t-iron, the CaO source was divided into two, and a total of 2.0 kg / t-iron was added when the treatment time ratio t / t0 was 0.2 and 0.3 It is an example. There was no slag forming, the desiliconization rate after desiliconization treatment was 40.0% or more, and the concentration (% FeO) in the slag after desiliconization treatment was 30.0 mass% or less.

  No. 7 is an example in which the amount of slag before desiliconization is 4.0 kg / t-iron, and 4.5 kg / t-iron is added to the CaO source when the treatment time ratio t / t0 is 0.5. The slag forming was minimal, the desiliconization rate after desiliconization treatment was 40.0% or more, and the concentration in slag (% FeO) after desiliconization treatment was 30.0 mass% or less.

  In No. 8, the amount of slag before desiliconization was 4.0 kg / t-iron, the CaO source was divided into two, and a total of 5.7 kg / t-iron was added when the treatment time ratio t / t0 was 0.3 and 0.5 It is an example. There was no slag forming, the desiliconization rate after desiliconization treatment was 40.0% or more, and the concentration (% FeO) in the slag after desiliconization treatment was 30.0 mass% or less.

  No. 9 is an example in which the amount of slag before desiliconization treatment is 3.0 kg / t-iron, and the CaO source is continuously added at 1.0 kg / t-iron during the treatment time ratio t / t0 of 0.1 to 0.5. . Slag forming was very small. The desiliconization rate after desiliconization treatment was 40.0% or more, and the (% FeO) concentration in slag after desiliconization treatment was 30.0 mass% or less.

  No. 10 is an example in which the amount of slag before desiliconization is 3.0 kg / t-iron, and 2.0 kg / t-iron is continuously added to the CaO source during a period of the treatment time ratio t / t0 of 0.2 to 0.4. . Slag forming was very small. The desiliconization rate after desiliconization treatment was 40.0% or more, and the (% FeO) concentration in slag after desiliconization treatment was 30.0 mass% or less.

  No. 11 is an example in which 4.0 kg / t-iron was added continuously during a period of a treatment time ratio t / t0 of 0.1 to 0.5 with a slag amount before desiliconization of 3.0 kg / t-iron and a CaO source continuously. . The slag forming is very small, the desiliconization rate after desiliconization treatment is 40.0% or more, the concentration in slag (% FeO) after desiliconization treatment is 30.0 mass% or less, and 4.5 kg / t-iron of the CaO source. Even compared with the batch addition number 6, the desiliconization rate after the desiliconization treatment was high, and the concentration (% FeO) in the slag after the desiliconization treatment was low.

  No. 12 is an example in which the amount of slag before desiliconization treatment is 3.0 kg / t-iron, and the CaO source is continuously added at a treatment time ratio t / t0 of 5.6 kg / t-iron during a period of 0.2 to 0.6. . Slag forming was very small. The desiliconization rate after desiliconization treatment was 40.0% or more, and the (% FeO) concentration in slag after desiliconization treatment was 30.0 mass% or less.

  No. 13 is that the amount of slag before desiliconization is 4.0 kg / t-iron, and the CaO source is continuously added at 2.8 kg / t-iron during the treatment time ratio t / t0 of 0.1 to 0.8. In this example, the mixture was stirred with nitrogen gas until the treatment time ratio t / t0 was 1.15 after the addition of the agent. The slag forming is very small, the desiliconization rate after desiliconization treatment is 40.0% or more, the concentration in slag (% FeO) after desiliconization treatment is 30.0 mass% or less, and 3.0 kg / t-iron of the CaO source. Even compared with the number 4 of divided addition, the silicon removal rate after the silicon removal treatment was high, and the concentration (% FeO) in the slag after the silicon removal treatment was low.

  No. 14 is a comparative example in which the slag amount before desiliconization treatment was 0.4 kg / t-iron, and no CaO source was added. The slag forming was large, the desiliconization rate after desiliconization treatment was less than 40.0%, and the (% FeO) concentration in the slag after desiliconization treatment was more than 30.0 mass%.

  No. 15 is a comparative example in which the slag amount before desiliconization treatment was 18.0 kg / t-iron and no CaO source was added. The slag forming was large, the desiliconization rate after desiliconization treatment was less than 40.0%, and the (% FeO) concentration in the slag after desiliconization treatment was more than 30.0 mass%.

  No. 16 is a comparative example in which the slag amount before desiliconization treatment was 1.2 kg / t-iron, and no CaO source was added. Although the slag forming was small, the desiliconization rate after the desiliconization treatment was less than 40.0%, and the concentration (% FeO) in the slag after the desiliconization treatment was more than 30.0 mass%.

  No. 17 is a comparative example in which the amount of slag before desiliconization treatment is 2.4 kg / t-iron, and a CaO source is added at 0.4 kg / t-iron when the treatment time ratio t / t0 is 0.8. Although the slag forming was small, the concentration (% FeO) in the slag after desiliconization treatment exceeded 30.0 mass%, and the desiliconization rate after desiliconization treatment was less than 40.0%.

  The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be applied without departing from the spirit of the present invention.

Claims (3)

Hot metal [% Si] is a desiliconization processing method in 0.2 mass% or more concentration range, with use of (% CaO) / Desiliconization pretreatment slag (% SiO ₂₎ is 0.5 to 1.5, blowing of Katasan In addition, in the desiliconization treatment method in which gas acid is blown or blown, the amount of slag before desiliconization treatment is set to 1 kg / t or more and 15 kg / t or less, and the CaO medium solvent is added to a pure CaO content during desiliconization treatment. A desiliconization method characterized by adding kg / t-iron or more.   When the treatment time ratio t / t0 is 0.1 or more and 0.9 or less when the desiliconization treatment elapsed time t and desiliconization treatment time t0 are set, the CaO medium solvent added during the treatment is divided and / or continuously added. The desiliconization processing method according to claim 1.   3. The desiliconization method according to claim 1, wherein after the addition of the desiliconization agent, the molten iron and the slag after the desiliconization treatment are stirred with a carrier gas of solid acid.