JP2018016853A - Method for melting iron-containing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further reduce carbon dust while maintaining operability.SOLUTION: In an iron-containing material melting method according to the present invention, by using a melting furnace having a top blowing lance and a bottom blowing tuyere and lined with a basic refractory containing magnesium oxide as a main component, an iron-containing material is supplied into the melting furnace containing molten iron, a carbon material is blown from the bottom blowing tuyere into the molten iron and at the same time oxygen is supplied from the top blowing lance or both of the top blowing lance and the bottom blowing tuyere into the molten iron, whereby the iron-containing material is molten. The temperature of the molten iron in a melting step is maintained at 1,250°C or higher and 1,400°C or lower, the amount of used auxiliary material is controlled so that the components of the slag in the melting furnace at the time of completion of the melting provide a basicity of 1.4 or more and 2.0 or less and MgO content of 5 mass% or more and 30 mass% or less. The Mn-containing raw material is added to the molten iron to set the liquid phase rate of the slag during the melting to 50% or more and less than 80%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for melting an iron-containing material.

  In recent years, many attempts have been made to develop a technique for producing molten iron without using a blast furnace or an electric furnace. One of such techniques is a technique for melting iron-containing cold material by burning carbonaceous materials. In this technology, a converter-type melting furnace is used to dissolve iron-containing cold materials such as scrap, sponge iron, pellets, solid pig iron, iron ore, etc., using the combustion energy of coal, coke, etc. Molten iron is produced.

  As an example of such a method for melting iron-containing cold material, as disclosed in the following Patent Document 1, using a converter having an upper blowing lance and a bottom blowing tuyere, melting a certain amount or more of high carbon Supplying iron-containing cold material into the converter where iron (hereinafter also referred to as “seed bath”) is present, while blowing powdered carbonaceous material (pulverized coal), oxygen, cooling gas, etc. from the bottom blowing tuyere, There is a method in which oxygen is blown from an upper blowing lance to dissolve the iron-containing cold material.

Japanese Patent No. 3764543

  Here, in the melting method of the iron-containing cold material as disclosed in Patent Document 1, the carbon material is blown into the seed hot water from the bottom blowing tuyere, but a part of the blown carbon material is a furnace. It blows out and becomes carbon dust. When such a large amount of carbon dust is generated, an increase in the basic unit of carbon material is caused. Therefore, a technique capable of reducing carbon dust while maintaining operability is desired.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a method for melting an iron-containing material capable of further reducing carbon dust while maintaining operability. There is to do.

In order to solve the above problems, the gist of the present invention is as follows.
[1] Using a melting furnace having a top lance and bottom blowing tuyeres and lined with a basic refractory composed mainly of magnesium oxide, supplying iron-containing material into the melting furnace where molten iron exists In addition, the carbon material is blown into the molten iron from the bottom blowing tuyere and oxygen is supplied from the upper blowing lance or the upper blowing lance and the bottom blowing tuyere to dissolve the iron-containing material. In the melting method of the iron-containing material to be performed, the temperature of the molten iron in the melting process is maintained at 1250 ° C. or higher and 1400 ° C. or lower, and the slag component in the melting furnace at the end of melting is basicity: 1.4 or higher. The amount of the auxiliary raw material used is controlled to be 0 or less, MgO: 5% by mass or more and 30% by mass or less, and the Mn-containing raw material is added to the molten iron. Dissolution of iron-containing materials with a phase ratio of 50% or more and less than 80% Law.
[2] The method for melting an iron-containing material according to [1], wherein the Mn-containing raw material is added so that the MnO content in the slag is greater than 0% by mass and 20% by mass or less.
[3] The method for melting an iron-containing material according to [1] or [2], wherein the Mn-containing raw material is added so that the MnO content in the slag is greater than 0% by mass and 10% by mass or less.
[4] The iron-containing material according to any one of [1] to [3], wherein the Mn-containing raw material is added so that the MnO content in the slag is 4% by mass or more and 10% by mass or less. Dissolution method.
[5] T. in the slag at the end of dissolution. Fe is 0.5% by mass or more and 6% by mass or less, and Al ₂ O ₃ in the slag at the end of the dissolution is 5% by mass or more and 30% by mass or less. [1] to [4] The method for melting an iron-containing material according to any one of the above.

  As described above, according to the present invention, it is possible to further reduce carbon dust while maintaining operability.

It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity and MnO addition amount of slag. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, MgO content, and MnO addition amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, MgO content, and MnO addition amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, MgO content, and MnO addition amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, MgO content, and MnO addition amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, MgO content, and MnO addition amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, MgO content, and MnO addition amount. Basicity of the slag is a graph showing a state of a change in the liquid phase ratio when changing the content of Al ₂ O ₃ and MnO amount. Basicity of the slag is a graph showing a state of a change in the liquid phase ratio when changing the content of Al ₂ O ₃ and MnO amount. Basicity of the slag is a graph showing a state of a change in the liquid phase ratio when changing the content of Al ₂ O ₃ and MnO amount. Basicity of the slag is a graph showing a state of a change in the liquid phase ratio when changing the content of Al ₂ O ₃ and MnO amount. Basicity of the slag is a graph showing a state of a change in the liquid phase ratio when changing the content of Al ₂ O ₃ and MnO amount. Basicity of the slag is a graph showing a state of a change in the liquid phase ratio when changing the content of Al ₂ O ₃ and MnO amount. Basicity of the slag is a graph showing a state of a change in the liquid phase ratio when changing the content of Al ₂ O ₃ and MnO amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, FeO content, and MnO addition amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, FeO content, and MnO addition amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, FeO content, and MnO addition amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, FeO content, and MnO addition amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, FeO content, and MnO addition amount. It is the graph which showed the mode of the change of the liquid phase rate at the time of changing the basicity of slag, FeO content, and MnO addition amount.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(Reaction mechanism in melting furnace)
Prior to describing the method for melting an iron-containing material according to an embodiment of the present invention, first, a reaction mechanism in a melting furnace will be briefly described.
In the converter type melting furnace used in the method of melting iron-containing materials, a high amount (for example, about 4.3%) of molten iron (seed hot water) is present in a certain amount in the melting furnace. Iron-containing material is charged from the top of the furnace, and charcoal is blown from the bottom of the furnace. In addition, when an oxygen jet blown from the upper blow lance inserted from the furnace collides with the molten iron surface, a hot spot is formed on the molten iron surface near the collision position, and on the molten iron surface around the fire point. A slag layer is generated in At this time, as shown in Table 1 below, (1) in the slag layer, combustion of carbonaceous materials (CO gas generation), reduction of iron oxide (CO gas generation), and combustion of CO gas (CO ₂ generation) (2) In the furnace space around the top blowing lance, CO gas combustion (generation of CO ₂ ) due to the CO gas generated in the fire point or slag layer being entrained in the oxygen jet, Reduction of CO ₂ gas (solution loss) by the carbon material scattered inside occurs.

  Here, as previously mentioned, a part of the blown carbon material blows out of the furnace and becomes carbon dust. When such a large amount of carbon dust is generated, an increase in the basic unit of the carbonaceous material is caused. Therefore, it is important to reduce the carbon dust while maintaining operability.

  In order to reduce the carbon dust, as can be seen from the generation process of the carbon dust as described above, the carbon material that blows through the molten iron may be reduced. In order to prevent the carbonaceous material from blowing through from the surface of the molten iron into the furnace space, the slag layer formed in the upper layer of the molten iron is melted so that the molten slag covers the molten iron (hot metal). do it. From this point of view, the present inventor has found that carbon dust can be reduced by lowering the melting point of slag formed in the furnace.

  Here, the present inventor has earnestly studied a method for lowering the melting point of slag, and has obtained the following knowledge.

As a method for lowering the melting point of slag, first, a method for reducing the basicity of slag (ratio of CaO content to SiO ₂ content) and the amount of MgO added as an auxiliary material are reduced. And a method.

  However, when the basicity of slag is lowered, the desulfurization efficiency of molten iron is greatly reduced. Here, when sulfur (S) is contained in raw fuel such as dust and carbonaceous material, if the desulfurization efficiency is reduced, S is concentrated in the hot metal. When S which is a surface adsorbing element is concentrated, dissolution (carbonization) of carbon (C) contained in the carbonaceous material into hot metal is inhibited, and the C concentration of hot metal is lowered. If the C concentration of the hot metal is reduced, the amount of metal attached to the top blowing lance or the like may increase or the hot metal may solidify. In addition, the inner wall of a melting furnace such as a converter is often lined with a basic refractory composed mainly of magnesium oxide (MgO), but the decrease in basicity increases the saturation solubility of MgO. Then, MgO in the refractory is melted into the hot metal, and refractory wear is promoted. From this point of view, it was concluded that reducing the basicity of slag is not desirable.

  Moreover, in order to suppress the wear of the refractory lined on the inner wall of the furnace, generally, MgO is added as an auxiliary material, and the MgO concentration in the slag is adjusted to an appropriate value. Therefore, if the amount of MgO added as an auxiliary material is reduced, wear of the refractory is promoted, which is not preferable.

  From the above knowledge, as a result of further investigation on a method that can realize the melting point of slag without causing deterioration in operability, as described in detail below, manganese oxide (MnO) is added to slag. The idea was to add.

(Study on MnO addition)
Based on the above studies, the present inventor has conceived of reducing the melting point of slag by adding MnO to slag. By adding MnO to the slag, it becomes possible to suppress the formation of merwinite (Ca ₃ MgSi ₂ O ₈ ), which is a high melting point mineral phase, and as a result, the melting point can be greatly reduced. Thus, the liquid phase rate of the slag can be increased.

  As a result of the molten slag covering the hot metal, it becomes possible to suppress the blowout of the carbonaceous material such as pulverized coal supplied from the bottom blowing tuyeres to the outside of the furnace. Units can be reduced. In addition, by suppressing the blow-through of the carbon material, the floating of the excess carbon material (pulverized coal) in the in-furnace gas phase is reduced. As explained earlier, in the furnace space, floating charcoal caused a solution loss reaction, but by reducing the floating charcoal, the solution loss reaction is less likely to occur, and it is possible to increase the heat receiving efficiency. It becomes. As a result, it is possible to reduce the oxygen intensity.

  Also, since MnO is a substance that acts to increase the optical basicity of slag, the addition of MnO can increase sulfide capacity, which is an index of slag desulfurization efficiency, and lower slag. It is possible to achieve both melting point and desulfurization efficiency.

  Next, the present inventor actually verified how much the slag should be melted, and the liquid phase ratio of the slag being dissolved (the ratio of the volume of the slag in the liquid phase to the total volume of the slag) ). As a result, it was conceived that the liquid phase ratio of the slag during dissolution should be 50% or more and less than 80%. By controlling the liquid phase rate of the slag during melting to 50% or more and less than 80%, it is possible to suppress the deterioration of the yield and the operability due to the occurrence of slopping while suppressing the blowout of the carbonaceous material to the outside of the furnace. It becomes possible. When the liquid phase rate of slag is less than 50%, it is difficult to suppress the blowout of the carbonaceous material to the outside of the furnace, and it is difficult to reduce C dust, which is not preferable. On the other hand, when the liquid phase rate of slag exceeds 80%, there is a concern about yield deterioration and operability deterioration due to the occurrence of slopping, which is not preferable.

  Here, in the melting treatment of the iron-containing material to which attention is paid in the present embodiment, from the viewpoint of suppressing the wear of the basic refractory mainly composed of MgO lined in the converter type melting furnace, the temperature of the molten iron is In general, it is generally controlled to a value as low as possible. Since the melting point (liquidus temperature) of the hot metal containing 4% by mass of carbon is about 1200 ° C., it is preferable to maintain the temperature of molten iron at 1250 ° C. or higher and 1400 ° C. or lower during the melting process of the iron-containing material. By setting the temperature of the molten iron to 1250 ° C. or higher and 1400 ° C. or lower, it becomes possible to melt the iron-containing material while suppressing wear of the refractory.

  Based on the above findings, the present inventor uses FactSage, a commercially available thermodynamic calculation application, to determine the liquid phase composition and solid phase composition when the slag having the composition described below reaches equilibrium. Calculations were made to simulate the liquid phase rate of the slag.

In this simulation, based on the above knowledge, 1300 ° C. is set as the average temperature of the molten iron during the melting treatment, MgO: 12 mass%, Al ₂ O ₃ : 12 mass%, FeO: 2 mass%, basicity (CaO % By mass / SiO ₂ % by mass, hereinafter abbreviated as “C / S”.): Based on slag having a composition of 0.8 to 2.4, the amount of MnO added is in the range of 0% by mass to 30% by mass. The liquid phase rate of the slag was calculated by changing the value.

The obtained results are shown in FIG. In FIG. 1, the horizontal axis represents basicity (C / S), and the vertical axis represents the obtained liquid phase ratio. As apparent from FIG. 1, as the amount of MnO added increases from 0% by mass to 20% by mass, the liquid phase ratio of the slag increases, and when the amount of MnO added exceeds 20% by mass. It can be seen that the liquid phase ratio decreases. The reason why the liquid phase ratio decreases when the amount of MnO added exceeds 20% by mass is considered as follows. That is, referring to the ternary phase diagram of CaO—SiO ₂ —MnO, if the basicity is constant, the melting point decreases by increasing MnO, and there is a minimum melting point. Recognize. Until the minimum value of the melting point is reached, the melting point decreases as MnO is added, so the liquid phase ratio increases. Thereafter, when MnO is added exceeding the minimum value, a solid phase with CaO or MgO is easily precipitated and the melting point is increased, so that the liquid phase ratio is lowered again.

  Here, as shown in FIG. 1, when the basicity (C / S) is less than 1.4, the liquid phase ratio is sufficiently high without adding MnO, and the importance of adding MnO becomes low. Further, in the actual operation, when the basicity (C / S) is 2.0 or more, the hatching is poor and the equilibrium cannot be approached and the liquid phase ratio is very low. In such a state, the melting point decrease due to the addition of MnO is considered to be inefficient. Therefore, it was determined that the range of basicity (C / S) meaningful for adding MnO is 1.4 or more and 2.0 or less.

  From FIG. 1, while maintaining the basicity (C / S) at 1.4 or more and 2.0 or less, MnO so that the content of MnO in the slag at the end of dissolution is 0 mass% or more and 20 mass% or less. It can be seen that a liquid phase ratio of 50% or more can be realized by adding. Here, when MnO is added too much, the liquid phase of the slag is promoted too much, and the wear of the refractory in the furnace due to the flow of the slag may become remarkable. In view of the cost of adding MnO, the amount of MnO added is preferably as small as possible. Therefore, in the following, further simulation was performed focusing on the case where the amount of MnO added was 10% by mass or less.

First, the present inventor explains how the liquid phase rate of slag changes with the addition of MnO when the content of MgO added to suppress wear of the refractory is changed. A similar application was used for verification. In this verification, 1300 ° C. is set as the average temperature of the molten iron during the dissolution treatment, MgO: 5% by mass to 30% by mass, Al ₂ O ₃ : 12% by mass, FeO: 2% by mass, basicity (C / S): Assuming a slag having a composition of 0.8 to 2.4, the liquid phase ratio of the slag was calculated by changing the amount of MnO added in the range of 0% by mass to 10% by mass.

  The obtained results are shown in FIGS. 2A to 2F. As is clear from FIGS. 2A to 2F, when the MgO content is in the range of 5 to 30% by mass, the liquidity ratio is 50 in the range of basicity (C / S) of 1.4 to 2.0. It can be seen that there is an added amount of MnO that can achieve more than%. Such an increase in the liquid phase ratio is thought to be because MnO greatly reduced the melting point of slag by suppressing the formation of merwinite, which is a high melting point mineral phase. On the other hand, when the content of MgO is increased, the liquid phase ratio tends to decrease. Such a tendency of the liquid phase ratio occurs because the content of MgO increases beyond the saturation solubility. As described above, although it is desired to increase the content of MgO from the viewpoint of protecting the refractory, it is desirable that the content of MgO is low from the viewpoint of increasing the liquid phase ratio. In addition, when the content of MgO exceeds 30% by mass in actual operation, the hatching is poor and the equilibrium cannot be approached. Even when 10% by mass of MnO is added, MgO is added more than necessary. As a result, a large amount of undissolved MgO was present, and it was found that a liquid phase ratio of 50% could not be realized. From such a result, it was found that it is preferable to add an auxiliary material so that MgO is contained in an amount of 5% by mass to 30% by mass in the slag at the end of dissolution.

Next, the present inventor verified how the liquid phase ratio of slag changes by adding MnO when the content of Al ₂ O ₃ is changed, using the same application as described above. Went. In this verification, 1300 ° C. is set as the average temperature of molten iron during the dissolution treatment, MgO: 12% by mass, Al ₂ O ₃ : 0% by mass to 30% by mass, FeO: 2% by mass, basicity (C / S): Assuming a slag having a composition of 0.8 to 2.4, the liquid phase ratio of the slag was calculated by changing the amount of MnO added in the range of 0% by mass to 10% by mass.

The obtained results are shown in FIGS. 3A to 3G. First, as apparent from FIG. 3A, when the content of Al ₂ O ₃ is 0% by mass, the liquid phase ratio of slag is extremely small, and even when MnO is added, the liquid phase ratio is reduced. It turns out that it is difficult to increase sufficiently. Moreover, as apparent from FIGS. 3B to 3G, in the range where the content of Al ₂ O ₃ is 5 to 30% by mass, the basicity (C / S) is in the range of 1.4 to 2.0. It can be seen that there is an added amount of MnO capable of realizing a liquid phase ratio of 50% or more. Depending on the basicity, there is an optimum value for the content of Al ₂ O ₃ that maximizes the liquid phase rate. For example, when the basicity is 1.6, the content of Al ₂ O ₃ is 15% by mass, and there is an optimum value that maximizes the liquid phase ratio. In addition, when the content of Al ₂ O ₃ exceeds 30% by mass in actual operation, the liquid phase ratio cannot be approached due to poor hatching, and even when 10% by mass of MnO is added. 50% cannot be realized. From such a result, it was found that it is preferable to add an auxiliary material so that Al ₂ O ₃ is contained in an amount of 5% by mass or more and 30% by mass or less in the slag at the end of dissolution.

Subsequently, when the content of FeO is changed, the present inventor has verified how the liquid phase ratio of slag is changed by the addition of MnO using the same application as described above. . In this verification, 1300 ° C. is set as the average temperature of molten iron during the dissolution treatment, MgO: 12% by mass, Al ₂ O ₃ : 12% by mass, FeO: 0% by mass to 10% by mass, basicity (C / S): Assuming a slag having a composition of 0.8 to 2.4, the liquid phase ratio of the slag was calculated by changing the amount of MnO added in the range of 0% by mass to 10% by mass.

  The obtained results are shown in FIGS. 4A to 4F. As is apparent from FIGS. 4A to 4F, the basicity (C / S) is 1 when the FeO content is in the range of 0 to 10% by mass, which is actually set in a general iron-containing material dissolution treatment. It can be seen that there is an added amount of MnO that can realize a liquid phase ratio of 50% or more in the range of .4 to 2.0. Accordingly, the content of FeO is not particularly limited as long as it is a range set by a general iron-containing material dissolution treatment operation. By adding MnO, the liquid phase ratio is 50% or more. It turned out to be feasible.

The simulation results shown in FIGS. 2A to 4F show that the content of a certain component (MgO, Al ₂ O ₃ , FeO) in the slag composition is changed and the content of the remaining components is fixed, and then MnO It verified about the increase in the liquid phase rate by addition of. Based on this knowledge, the basicity (C / S) and the content of MgO are comprehensively controlled (more preferably, the basicity (C / S) and the content of MgO and Al ₂ O ₃ are controlled. By controlling the total amount), it is possible to realize a state where the liquid phase rate of the slag is 50% or more.

(About iron-containing material melting method)
Next, the iron-containing material melting method according to the present embodiment, which has been conceived based on the knowledge described above, will be described in detail.
The iron-containing material melting method according to the present embodiment uses a converter type melting furnace having a top lance and a bottom blowing tuyere and lined with a basic refractory mainly composed of magnesium oxide. Supply iron-containing material into the melting furnace where iron (seed bath) is present, blow carbon material into the molten iron from the bottom blowing tuyere, and oxygen from the top blowing lance or the top blowing lance and bottom blowing tuyere Is supplied to dissolve the iron-containing material.

  Here, the converter-type melting furnace to which the iron-containing material melting method according to the present embodiment is applied is not particularly limited, and a basic refractory mainly composed of MgO (for example, MgO-C). A known melting furnace can be used as long as the brick is lined.

  The iron-containing material supplied into the seed bath is not particularly limited, and known iron-containing cold materials such as scrap, sponge iron, pellets, reduced iron, solid pig iron, iron ore, etc. can be used as appropriate. It is.

  Also, the carbon material to be blown into the seed hot water is not particularly limited, and it is possible to appropriately use a powdered material containing carbon such as coal, coke, graphite, etc. or pulverized coal. is there.

  Furthermore, the amount of oxygen blown from the top blowing lance or the bottom blowing tuyere is not particularly limited, and may be set as appropriate according to the capacity of the hot metal to be produced.

  In the iron-containing material melting method according to the present embodiment, the temperature of the molten iron in the melting process is maintained at 1250 ° C. or higher and 1400 ° C. or lower. By setting the temperature of the molten iron in the melting process to 1250 ° C. or more and 1400 ° C. or less, the iron-containing material can be melted while suppressing the wear of the refractory as described above. When the temperature of the molten iron is less than 1250 ° C., it is difficult to melt the supplied iron-containing material, which is not preferable. On the other hand, if the temperature of the molten iron exceeds 1400 ° C., wear of the refractory lined in the melting furnace is promoted, which is not preferable. The temperature of the molten iron is preferably 1250 ° C. or higher and 1350 ° C. or lower, and more preferably 1280 ° C. or higher and 1320 ° C. or lower.

  Moreover, in the melting method of the iron-containing material according to the present embodiment, the components of the slag in the converter at the end of melting are basicity (C / S): 1.4 or more and 2.0 or less, MgO: 5% by mass or more The amount of auxiliary raw material used is controlled so that it is in the range of 30% by mass or less, and the Mn-containing raw material is added to the molten iron, so that the liquid phase ratio of the slag during melting becomes 50% or more and less than 80%. Like that.

  Basicity (C / S): 1.4 or more and 2.0 or less, MgO: The amount of auxiliary materials used is controlled to be in the range of 5 to 30% by mass, and Mn is contained in the molten iron By adding the raw materials so that the liquid phase ratio of the slag during dissolution is 50% or more and less than 80%, as described above, while maintaining operability and desulfurization efficiency, carbon dust can be reduced. It becomes possible to plan.

  Here, the liquid phase ratio of the slag during melting is preferably 55% or more and 75% or less, and more preferably 60% or more and 70% or less.

  Further, when the basicity (C / S) and the content of MgO are out of the above ranges, as described above, even if MnO is added, the liquid phase ratio of the slag during dissolution is 50%. % Or less and less than 80%, which is not preferable. The basicity (C / S) is preferably 1.4 or more and 1.8 or less, and more preferably 1.4 or more and 1.6 or less. The content of MgO is preferably 5% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 15% by mass or less.

Furthermore, in the method for melting an iron-containing material according to the present embodiment, it is preferable that Al ₂ O ₃ is 5% by mass or more and 30% by mass or less as a slag component in the converter at the end of melting. By controlling the amount of auxiliary raw material used so that the content of Al ₂ O ₃ at the end of dissolution is in the above range, it is possible to more reliably reduce carbon dust while maintaining operability and desulfurization efficiency. It becomes possible. The content of Al ₂ O ₃ is preferably 5% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 15% by mass or less.

  Moreover, in the melting method of the iron-containing material according to the present embodiment, as a slag component in the converter at the end of melting, T.I. Fe may be contained in an amount of 0.5% by mass or more and 6% by mass or less.

  In addition, the auxiliary material added in order to implement | achieve the above slag compositions is not specifically limited, It is possible to utilize well-known auxiliary materials, such as quick lime, limestone, dolomite, and fluorite. is there. What is necessary is just to determine the usage-amount of each auxiliary | assistant raw material so that the above slag compositions may be implement | achieved using a well-known auxiliary | assistant raw material.

Further, Mn-containing raw material is added to the molten iron, as long as it contains Mn, it is possible to use any material, Mn oxide as Mn ore (MnO ₂₎ What is contained by the form (manganese oxide containing material) may be used, and what contains Mn by forms other than an oxide may be used. Even when a Mn-containing raw material containing Mn in a form other than an oxide is used, Mn in the Mn-containing raw material is oxidized during processing to function as MnO.

  Here, the Mn-containing raw material as described above is preferably added so that the MnO content in the slag in the converter at the end of melting is greater than 0% by mass and 20% by mass or less. More preferably, the MnO content is more than 0% by mass and 10% by mass or less, and it is further added that the MnO content at the end of dissolution is 4% by mass or more and 10% by mass or less. preferable. By setting the amount of the Mn-containing raw material to the above value, the melting point of the slag can be lowered, and carbon dust can be reduced while maintaining operability and desulfurization efficiency.

  Next, the method for melting an iron-containing material according to the present invention will be specifically described with reference to Examples and Comparative Examples. In addition, the Example shown below is an example of the melting method of the iron-containing material which concerns on this invention to the last, Comprising: The melting method of the iron-containing material which concerns on this invention is not limited to the following example.

  In the following experimental examples, a melting test was performed using a 160-ton converter-type melting furnace. The seed containing hot water having a carbon content of about 4.0% by mass to 4.3% by mass was charged with an iron-containing raw material from above the furnace and dissolved. At this time, reduced iron was used as the main iron-containing material. Reduced iron uses dust generated from melting furnaces, converters, blast furnaces, etc. as the main raw material, and after mixing carbon material containing C as a reducing agent with the main raw material, It was obtained by melting and reducing the granulated material in a reduction furnace. Moreover, although granulation was performed using the twin roll type briquette machine, pellet granulation by a rolling method may be used. The reduction furnace used was a rotary bed furnace having a furnace diameter of 20 m, and the reduction temperature was controlled to 1300 to 1400 ° C. with an LNG burner. The metallization rate of iron in the reduced iron was 88 to 93%.

In the melting test in the converter type melting furnace, oxygen was supplied at 25000 Nm ³ / h from the top blowing lance. In addition, carbon material is supplied from the bottom blowing tuyere using N ₂ gas as a carrier gas so that the temperature after melting can be maintained at 1390 ° C. to 1410 ° C. and the C concentration of molten iron can be maintained at 4.0% by mass to 4.3% by mass. Went. As the carbon material, pulverized coal was used. In the dissolution test, the hot metal temperature in the middle stage of dissolution was about 1300 ° C.

In order to adjust the amount of slag discharged after completion of melting and to adjust the components of slag generated from carbonaceous materials and reduced iron, slag was added with lime to adjust the basicity of slag (CaO / SiO ₂ ). At each level shown below, approximately the same amount of reduced iron, charcoal, and dolomite were added to adjust the MgO content and Al ₂ O ₃ content. As a result, the MgO content was in the range of 5% by mass to 30% by mass, and the Al ₂ O ₃ content was in the range of 10% by mass to 14% by mass. Moreover, Mn ore was used as a Mn containing raw material, and it added so that it might become a predetermined density | concentration.

  In the following experimental examples, the amount of dust contained was determined for each level by collecting the water in the dust collecting trough at intervals of 5 minutes during the treatment, evaporating the water and taking out the residue. Then, the C concentration in the dust was measured by analysis by a combustion method, and the amount of C dust generated was evaluated. More specifically, the amount of C dust generated in Comparative Example 1 shown below was set to 1, and the amount of C dust generated at each level was indexed. The desulfurization efficiency was evaluated by dividing the S concentration of hot metal at the end of dissolution by the hot metal S concentration of Comparative Example 1. Moreover, the thing which stopped the acid-feeding speed | velocity | rate by slopping was defined as "slipping generation | occurrence | production", and it evaluated as occurrence frequency. The liquid phase rate of slag was evaluated by the thermodynamic calculation software FactSage.

  The obtained results are summarized in Table 2 below.

  When the basicity (C / S) is 1.4, in Example 1 and Example 2, as a result of increasing the MnO concentration and controlling the liquid phase ratio to 50% or more and less than 80%, C dust generation amount is The S concentration also decreased due to the promotion of desulfurization. On the other hand, in Comparative Examples 1 to 3, it can be seen that the liquid phase ratio is low and the amount of C dust generated is not sufficiently reduced. In Comparative Example 4, although good results were obtained for both the amount of C dust generated and the S concentration, the liquid phase ratio was as high as 80%, so that slopping occurred and the operation could not be continued. .

  In Examples 1 to 5, the basicity (C / S) was controlled to 1.4 to 2.0, and the liquid phase ratio was controlled to 50% or more and less than 80%. In addition, the S concentration decreased due to the promotion of desulfurization. On the other hand, in Comparative Example 5 and Comparative Example 6, since the basicity (C / S) was lowered to 1.0, it can be seen that the desulfurization index increases regardless of the MnO concentration. In addition, when the basicity (C / S) was 2.1 as in Comparative Example 7, no decrease in the amount of C dust was observed despite the high calculated liquid phase rate. This is presumably because slag having a low liquidus rate was generated because it was not able to approach equilibrium due to poor hatching.

In Example 6 to Example 10, as a result of controlling the MgO concentration to 5 to 20%, the amount of C dust generated decreased, and the S concentration decreased due to the promotion of desulfurization. This is because the formation of merwinite (Ca ₃ MgSi ₂ O ₈ ) was suppressed by increasing the MnO concentration. On the other hand, in Comparative Example 8, as a result of controlling the MgO concentration to exceed 30%, it can be seen that the amount of C dust generated is not sufficiently reduced.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

Claims (5)

Using a melting furnace having a top lance and bottom blowing tuyere, lined with a basic refractory composed mainly of magnesium oxide, supplying iron-containing material into the melting furnace where molten iron exists, An iron-containing material that melts the iron-containing material by blowing carbonaceous material into the molten iron from the bottom blowing tuyere and supplying oxygen from the upper blowing lance or the upper blowing lance and the bottom blowing tuyere In the dissolution method of
The temperature of the molten iron in the melting process is maintained at 1250 ° C. or higher and 1400 ° C. or lower, and the components of the slag in the melting furnace at the end of melting are basicity: 1.4 or higher and 2.0 or lower, MgO: 5% by mass The amount of the auxiliary raw material used is controlled so as to be in the range of 30% by mass or less, and the Mn-containing raw material is added to the molten iron, so that the liquid phase ratio of the slag during melting is 50% or more and 80%. The melting method of the iron-containing material to be less than.   The method for melting an iron-containing material according to claim 1, wherein the Mn-containing raw material is added so that the MnO content in the slag is 0 mass% and 20 mass% or less.   The method for melting an iron-containing material according to claim 1 or 2, wherein the Mn-containing raw material is added so that the MnO content in the slag is 0 mass% and 10 mass% or less.   The method for melting an iron-containing material according to any one of claims 1 to 3, wherein the Mn-containing raw material is added so that the MnO content in the slag is 4 mass% or more and 10 mass% or less. T. in the slag at the end of dissolution. Fe is less than 0.5 mass% to 6 mass%, _Al 2 _{O 3} of the slag in the melting end is 30 mass% or more 5% by weight, any of claims 1 to 4 The method for melting iron-containing material according to claim 1.

Images