JP6729073B2 - Reduction/dissolution method of iron raw material containing iron oxide - Google Patents

Description

The present invention relates to a method for reducing and dissolving iron oxide-containing iron raw material. Specifically, iron oxide raw materials such as iron ore and dust are heated and pre-reduced in a preliminary reduction furnace such as a shaft furnace or a rotary hearth furnace to obtain iron oxide-containing iron raw materials, and then the iron oxide-containing iron raw materials The present invention relates to a method for reducing/melting iron raw material containing iron oxide, which is charged into a DC arc furnace to reduce/melt.

In the direct reduction ironmaking method for producing reduced iron from iron ore and dust generated from iron mills, shaft furnaces, rotary kilns, rotary hearth furnaces, fluidized bed furnaces, etc. are used for reducing furnace types, and natural gas is used for reducing agents. , Coal, etc. are used. Various iron-making processes based on these combinations have been proposed and industrialized.

Among these direct reduction ironmaking processes, iron oxide produced by a method in which a reducing furnace type uses a natural gas as a reducing agent in a shaft furnace, or a reducing furnace type uses a rotary hearth furnace in which coal is used as a reducing agent. As a method for producing hot metal using the contained iron raw material, a method of producing hot metal by melting an iron oxide-containing iron raw material having a high reduction rate using an arc furnace is currently the most mainstream.

However, in order to produce iron oxide-containing iron raw materials with a high reduction rate, a large amount of reducing agent is used, and a residence time is required until the reduction reaction of iron oxide is almost completed. Is difficult in terms of cost and productivity. Therefore, instead of producing iron oxide-containing iron raw materials with a high reduction rate in these direct reduction furnaces, the direct reduction furnace is used as a preliminary reduction furnace, and an oxidation with a relatively low reduction rate is performed by performing preliminary reduction in the preliminary reduction furnace. A method of producing hot metal by reducing and melting an iron-containing iron raw material using an arc furnace or a melting converter has been adopted. On page 66 of Patent Document 1, a mixture raw material (pellet or powder mixture raw material) containing semi-reduced iron pre-reduced in a rotary hearth furnace (RHF) is charged in a submerged arc furnace (SRF), It is stated that a final refining with the aim of final reduction and dissolution is carried out. In the SRF, oxygen gas and coal are supplied, and hot metal and recovered gas are obtained. It should be noted that in the SRF, it is necessary to charge seed hot water such as hot metal when the furnace is started up, but this is not necessary in the steady operation state due to the presence of the iron bath in the furnace. In Patent Document 2, the carbonaceous material is internally agglomerated in the dust generated in the converter to agglomerate, and is heated at a high temperature in a preliminary reduction furnace to preliminarily reduce the internal carbonaceous material as a reducing material. As a part, a method of supplying the molten steel to a dedicated melting furnace in which seed hot water is present and reusing it is disclosed.

In the method for producing hot metal by introducing the iron oxide-containing iron raw material produced by preliminary reduction into the arc furnace in which the seed water is present to reduce and dissolve it, the iron oxide-containing iron raw material that was introduced is somehow devised. Unless it is applied, the specific gravity is small, so it is reduced and dissolved while floating on the hot metal surface. Further, since the iron oxide-containing iron raw material contains slag components such as CaO and SiO ₂ , the slag floats on the hot metal surface as the melting progresses, and the raw material charged from the furnace is trapped in the slag and comes into contact with the hot metal. Since it inhibits, it does not dissolve, leading to a decrease in iron yield. In order to accelerate the dissolution and reduction of the iron oxide-containing iron raw material that has been input, the input iron oxide-containing iron raw material is reduced by using the high temperature part as much as possible and being entangled in the hot metal by controlling bottom-blown stirring. A method of dissolving may be mentioned.

Various proposals have hitherto been made on a method of introducing an oxide raw material into a high temperature region of an arc of a DC arc furnace or an AC electric furnace and applying bottom-blown stirring to reduce and/or dissolve it.

For example, Patent Document 3 describes an invention of a smelting reduction method for metal oxides in a three-phase AC electric furnace. In the three-phase AC electric furnace, the invention supplies powdery metal raw material ore, for example, chromium ore to an arc forming region, melts the metal raw material ore by arc heat, and further, gas is supplied to the bottom of the electric furnace. The present invention relates to an electric furnace refining method characterized in that a gas is blown into a molten metal in an electric furnace by arranging a blowing nozzle, but it relates to a method for reducing chromium ore, in which a reducing agent in slag and a raw material ore are contacted. The distinction between the effect of improving the reduction reaction due to and the effect of improving the reduction reaction due to contact between the molten metal and the raw material ore is unclear. Further, as in the present invention, the conditions for smelting and reducing an iron oxide-containing iron raw material using a DC arc furnace are not specifically described.

Patent Document 4 discloses a method of supplying a carbon-containing fuel and an oxygen-containing gas in a steelmaking arc furnace and supplying oxygen by a nozzle arranged at the bottom of the arc furnace. It is described that an ore, a pre-reduced ore, etc. are blown through a hollow electrode using an arc furnace having three electrodes to give bottom-blown stirring when a metal melt is produced. No mention is made of the positional relationship of the blowing nozzles or the yield of the input material.

International Publication No. 01/018256 JP-A-2000-45012 JP-A-1-294815 JP-A-63-125611

In the method for producing hot metal, the iron raw material containing iron oxide produced by pre-reduction is put into an arc furnace in which a seed water is present to reduce and melt it. Even if the method of introducing the iron oxide-containing iron raw material while blowing gas into the mixture with stirring is adopted, the iron oxide-containing iron raw material having a small specific gravity cannot be retained in the high-temperature molten metal surface below the upper electrode, and However, the effect of improving the iron yield was not sufficient because it could not be rolled up in the hot metal and sufficiently mixed with the hot metal.

The present invention is an iron oxide-containing iron raw material that is heated and reduced in a pre-reduction furnace such as a rotary hearth furnace to produce iron oxide-containing iron raw material, which is then fed into a DC arc furnace to reduce and melt. It is an object of the present invention to provide a method for reducing and dissolving iron oxide-containing iron raw material having a high iron yield in the method for reducing and dissolving iron.

In the pre-reduction, it may be considered to produce iron oxide-containing iron raw material with a low reduction rate by granulation. On the other hand, iron oxide-containing iron raw material with a low reduction rate has a low crushing strength and granules are partially There is a problem of powdering. When iron oxide-containing iron raw material is reduced/dissolved to produce hot metal, it is desirable to use the cheapest raw material to improve the iron yield, but for that purpose, powdered iron oxide-containing iron raw material is reduced/dissolved. Will be required. However, when the powdered iron oxide-containing iron raw material is gravity-fed from the top of the arc furnace, a part of the iron raw material is absorbed by the exhaust duct, which reduces the iron yield.

The present invention provides a method for reducing/dissolving iron oxide-containing iron raw material having a high iron yield when reducing/melting in a DC arc furnace using a powdery or granular iron oxide-containing iron raw material produced by preliminary reduction. Also for the purpose.

The gist of the present invention is as follows.
(1) In a method of introducing an iron oxide-containing iron raw material from a furnace into a direct-current arc furnace in which seed hot metal is present, and reducing and melting by contact between the arc heat and the hot metal hot seed,
The iron oxide-containing iron raw material has a metallization ratio of iron of 45% or more and 95% or less and contains an oxide other than iron oxide in an amount of 4 to 20% by mass.
The DC arc furnace comprises one upper electrode, one furnace bottom electrode and three or more bottom blowing tuyeres, the radius in the melting furnace is R, and the bottom blowing tuyeres are from the center of the furnace bottom electrode. R is the distance to the center of the bottom blown tuyere, and the bottom blown tuyere is installed at a position that satisfies the following equation (1),
The number r of bottom blown tuyere is N, and the distance r from the center of the furnace bottom electrode to the center of each bottom blown tuyere is within 0.8 to 1.2 times the average value of the distance r, The angle formed by the bottom blown tuyere with the center of the furnace bottom electrode is in the range of 300°/N to 430°/N,
A method for reducing/dissolving an iron oxide-containing iron raw material, characterized in that the iron oxide-containing iron raw material is charged immediately below the upper electrode while performing bottom blowing stirring of the hot metal by a gas blown from the bottom blowing tuyere.
0.2≦r/R≦0.8 (1 )
(2 ) Part or all of the iron oxide-containing iron raw material to be introduced into the DC arc furnace with the upper electrode hollow, is a small-diameter iron oxide-containing iron raw material having a maximum particle size of 5 mm or less. The method for reducing/dissolving an iron oxide-containing iron raw material according to (1 ) above, wherein the raw material is charged into a DC arc furnace via the hollowed upper electrode.

According to the present invention, in a DC arc furnace having a bottom blown tuyere for bottom blowing a gas, a specific number determined by the number of bottom blown tuyere and the distance between the center of the bottom electrode and the center of the bottom blown tuyere By introducing the iron oxide-containing iron raw material directly below the upper electrode while performing bottom-blown stirring in the condition range, the iron oxide-containing iron raw material introduced from the furnace moves from the high temperature surface center to the side wall side. In addition, it is possible to prevent the iron oxide-containing iron raw material from being reduced and dissolved at a high iron yield by suppressing the occurrence of iron oxides, and being caught in the hot metal at the center of the molten metal surface to promote the reduction reaction of iron oxide in the raw material and the dissolution of metallic iron. It will be possible.

Further, according to the present invention, a small-diameter iron oxide-containing iron raw material having a particle diameter of 5 mm or less is charged into a DC arc furnace via a hollow upper electrode, so that even a small-diameter iron oxide-containing iron raw material is sent to an exhaust duct. It is possible to put into the hot metal surface directly under the electrode without increasing the suction loss, and it is possible to reduce and dissolve the iron raw material containing iron oxide with a high iron yield.

It is a figure which shows an example of the reduction / dissolution method of the iron oxide containing iron raw material in this invention. It is a figure which shows an example of the positional relationship of a furnace bottom electrode and a bottom blown tuyere when the number of bottom blown tuyere is two. It is a figure which shows an example of the positional relationship between a furnace bottom electrode and a bottom blown tuyere when the number of bottom blown tuyere is three. The index (r/R) of the bottom blown tuyere arrangement and the% T.S. in slag when the number of bottom blown tuyere is 2, 3, and 4, respectively. It is a figure which shows the relationship with Fe.

The object is a method of introducing an iron oxide-containing iron raw material into the arc furnace in which the molten hot metal of the seed is present from the top of the furnace, and reducing and melting by contact between the arc heat and the molten hot metal of the hot seed. The heat required for the reduction reaction of iron oxide and carbon that is a reducing agent can be sufficiently supplied, and by introducing the raw material into the hot metal surface portion just below the upper electrode, which is at a high temperature, oxidation with high iron yield can be achieved. Provided is a reduction/dissolution method of iron-containing iron raw material.

The present invention applies a DC arc furnace as the arc furnace. A mode for carrying out the invention will be described in detail with reference to FIG. FIG. 1 is a diagram showing an example of the hot metal production method using the iron oxide-containing iron raw material of the present invention. In FIG. 1, 1 is a DC arc furnace, 2 is an upper electrode, 3 is a material feed hole on the furnace, 4 is an arc, 5 is a furnace bottom electrode, 6 is a bottom blowing tuyere, and 12 is a refractory material. Although a hollow electrode is used as the upper electrode 2 in FIG. 1, a solid electrode may be used as the upper electrode 2.

The iron oxide-containing iron raw material is added to the inside of the DC arc furnace by using the furnace raw material charging hole 3 (charging chute), or when the hollow upper electrode 2 is used as shown in FIG. Together with the chute, it is added into the DC arc furnace via the internal passage of the hollow upper electrode 2. Since it is advantageous to use the high-temperature molten metal surface portion directly below the upper electrode 2 for the reduction/dissolution of the iron oxide-containing iron raw material, when adding from the charging chute, the high-temperature molten metal surface portion is added aiming at the high-temperature molten metal surface portion. At this time, it is somewhat difficult to adjust the addition position, and a part of the powdery portion of the raw material is sucked into the exhaust duct 15, so that the addition yield to the surface of the hot metal becomes low. In this respect, it is preferable to introduce the powdery raw material through the internal passage of the hollow upper electrode 2 because the powdery material can be easily introduced into the high temperature portion of the hot metal 11 without being sucked into the exhaust duct. ..

Furthermore, the iron oxide-containing iron raw material added to the high-temperature molten metal surface tends to float on the molten metal surface because it has a smaller specific gravity than the hot metal, move to the furnace wall surface side, and accumulate there. As described above, the bottom blowing tuyere 6 is appropriately arranged and a suitable amount of bottom blowing gas is blown into the hot metal 11, so that the movement toward the furnace wall surface side can be suppressed. This is because, by staying in the hot-water surface for as long as possible, the contact time between the hot metal at high temperature and the iron oxide-containing iron raw material becomes long, and the reduction and dissolution of the iron oxide-containing iron raw material are promoted.
Further, by appropriately using the bottom-blown gas, the interfacial area in which the hot metal and the iron oxide-containing iron raw material are mixed and stirred and the carbon in the hot metal and the iron oxide in the iron oxide-containing iron raw material react are increased. A downflow is formed in the central part of the hot metal bath surface, which makes it possible to promote that the iron oxide-containing iron raw material is rolled into the hot metal.

The iron oxide-containing iron raw material to be melted/reduced in the present invention has an iron metallization rate of 45% or more and 95% or less. The metallization rate (%) of iron means “metallic iron/total iron content (mass %)×100” in the iron oxide-containing iron raw material.

As described above, according to the present invention, iron oxide raw materials such as iron ore and dust are heated and pre-reduced in a preliminary reduction furnace such as a shaft furnace or a rotary hearth furnace to obtain iron oxide-containing iron raw materials, The present invention relates to a method for reducing/melting an iron oxide-containing iron raw material in which an iron raw material is put into a direct current arc furnace in which hot metal of seed is present and reduced/melted. Using the CO gas generated when reducing the raw material by using carbon as a reducing agent in the direct current arc furnace as the preliminary reducing agent in the preliminary reducing furnace can significantly reduce or eliminate the use amount of natural gas. This is preferable because a new process that is not directly related to the molten steel manufacturing process such as a gas generation furnace can be made unnecessary.

If the iron metallization rate of the iron oxide-containing iron raw material produced by pre-reduction is 45% or more, use the entire amount of CO gas generated in the DC arc furnace as CO gas for reduction in the pre-reduction furnace. In addition, it is possible to suppress the increase of the carbonaceous material unit and to suppress the increase of the necessary reduction heat in the DC arc furnace without preventing the reduction efficiency of the entire body from decreasing, and to prevent the increase of the power unit consumption. On the other hand, when reducing mainly CO gas without using natural gas in a preliminary reduction furnace such as a shaft furnace, it is difficult to produce reduced iron with a reduction rate of more than 95%. The upper limit of the metallization rate of iron was set to 95%.

The iron oxide in the iron oxide-containing iron raw material is reduced by using carbon contained in the hot metal of the seed bath as a reducing agent. As a result, the carbon concentration in the hot metal seed is reduced, and it is necessary to supply a carbon source. The iron oxide-containing iron raw material may contain a carbon-containing substance as a reducing agent that contributes to reduction in an arc furnace. Further, the additional carbon source may be supplied by charging a carbon-containing substance into a DC arc furnace, separately from the iron oxide-containing iron raw material.

The iron oxide-containing iron raw material contains 4 to 20 mass% of oxides other than iron oxide. Specific examples of the oxide include CaO, SiO ₂ , Al ₂ O ₃ and MgO. These oxides are slag components. The slag component in the raw material is not melted because the slag 13 floats on the hot metal surface as the melting progresses, and the raw material charged from the furnace is trapped by the slag 13 and hinders the contact with the hot metal 11, thus reducing the iron yield. Invite. Therefore, the upper limit of the slag component in the raw material is set to 20 % by mass. On the other hand, the iron oxide-containing iron raw material is used as a sinter or pellet in order to heat and pre-reduce the iron oxide-containing iron raw material such as iron ore and dust in a preliminary reduction furnace. For that purpose, it is usual to contain at least 4 mass% of the above-mentioned oxides, so the lower limit of the slag component in the raw material is set to 4 mass %.

Since the iron oxide-containing iron raw material to be charged into the hot metal of the DC arc furnace contains iron oxide and oxides other than iron oxide as described above, its specific gravity is smaller than that of the hot metal, so that the iron material floats on the surface of the hot metal when charged. For this reason, the iron oxide-containing iron raw material that is fed tends to drift toward the furnace wall side while floating on the surface of the hot metal while being pushed by new raw materials that are fed one after another.

Therefore, as shown in FIG. 1, a plurality of bottom blowing tuyeres 6 are arranged so as to surround the high-temperature molten metal surface portion just below the upper electrode so as to prevent the bottom blowing tuyeres 6 from bottoming so as not to approach the furnace wall side. The idea was to make the blowing gas flow properly. These bottom-blown gases form a flow toward the center at the surface of the molten metal and promote the downward flow formation at the center of the surface of the molten metal, and further agitate the hot metal and the iron oxide-containing iron raw material on the hot metal to stir the material in the raw material. The effect of increasing the reaction interface area between iron oxide and carbon in the hot metal and promoting reduction/dissolution is expected.

Then, in the method of reducing and melting the iron oxide-containing iron raw material from the furnace into a direct-current arc furnace (see FIG. 1) in which the molten hot metal is present, and contacting with the molten hot metal at the high temperature portion just below the upper electrode, A bottom blown tuyere 6 was provided on the bottom of the DC arc furnace 1, and the number of bottom blown tuyere 6 and the installation location were variously changed to investigate the influence of the bottom blown condition on the iron yield of reduction/melting. The number of bottom blowing tuyeres 6 was set to 2, 3, and 4, and they were arranged rotationally symmetrically about the furnace bottom electrode center 14 (see FIGS. 2 and 3). Then, the radius in the melting furnace was R, and the distance from the furnace bottom electrode center 14 to the center of the bottom blowing tuyere 6 was r, and r/R was changed to investigate the effect on iron yield. However, as an index showing the iron yield,% T. Fe was adopted.

In this study, iron oxide-containing iron raw material pre-reduced in a shaft furnace was used. The composition of the iron oxide-containing iron raw material was as shown in Table 1. The metallization ratio of iron is 91.5%, and the content of oxides other than iron oxide is 6.1% by mass. The equipment specifications and operating conditions of the DC arc furnace 1 are as shown in Table 2, and are equipped with a bottom blown tuyere 6. The DC arc furnace is charged with 50 tons of molten pig iron hot metal having a temperature of 1380 to 1415° C. and a C concentration of 4.2 to 4.3% by mass, and a maximum particle diameter of 5 mm or less from the hollow upper electrode 2 at 500 kg/min. 30 t of small-sized iron oxide-containing iron raw material, and 20 t of massive iron oxide-containing iron raw material having a particle size larger than 5 mm from the furnace raw material input hole 3, a total of 50 t of iron oxide-containing raw material directly under the upper electrode in the furnace A reduction and dissolution were performed while aiming at the high temperature part of No. 1 by gravity dropping for 60 minutes. The carbon in the hot metal of the seed bath was consumed as the reduction proceeded, and the carbon concentration decreased. Therefore, in order to supplement the consumed carbon, soil graphite was sequentially charged into the furnace as a carbon-containing substance. After the completion of the dissolution, the dissolved amount of 50 ton was poured into a pan, and the above-mentioned work was repeated to reduce and dissolve the iron oxide-containing iron raw material. In addition, the slag generated by the reduction/melting after the hot metal was tapped was used as a% T. A sample was taken to investigate Fe and then discharged into a slag discharge pan.

In this investigation, the distance from the furnace bottom electrode center 14 to the center of the bottom blown tuyere 6 is three levels of r=1.0, 2.5, 4.0 m when the number of tuyere is two, When the number of tuyere is 3, r=0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5m, 9 levels, When the number of tuyere is 4, it is changed at one level of r=3.5 m, and the ratio r/R of the radius R in the melting furnace and the distance r from the furnace bottom electrode center 14 to the center of the bottom blowing tuyeres 6 is The effect on iron yield was investigated. In the investigation according to the present invention, as an index of iron yield,% T. Fe was adopted. The results are collectively shown in Table 3 and FIG. 4 together with the index r/R.

When the number of bottom blowing tuyeres is two, as shown by the black squares in FIG. 4, at any of the three levels of r/R=0.2, 0.5, and 0.8, the change in r/R Slag medium T. No change in Fe was observed and %T. Fe was as high as 13% or more. That is, the reduction reaction of iron oxide in the raw material did not proceed sufficiently, and the iron yield was in a low state.

When the number of bottom tuyere is 3, as shown by the black circles in FIG. 4, r/R=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0. Among the nine levels of 7, 0.8, and 0.9, a downward convex tendency is seen with r/R=0.5 as the minimum value, and in particular, in the range of the following formula (1), the% T.S. A high iron yield of 9% or less of Fe was realized. Even when the number of bottom-blown tuyers is four and the formula (1) is satisfied, the %T. Fe has achieved a high Fe yield of 5%.
0.2≦r/R≦0.8-(1)

The number of bottom blown tuyere and r/R described above are respectively% T.S. From the effect on Fe, bottom blowing has the effect of improving the iron yield. It is thought that this is because the reduction/dissolution occurs with high efficiency because it contacts with the hot metal without being captured by the. If so, the flow of hot metal collected from the peripheral part toward the central part of the hot metal surface where the iron oxide-containing iron raw material is charged is generated, and the flow of the hot metal gathered from the peripheral part is downward flow in the central part. It should be advantageous to carry out bottom-blown stirring so as to cause the occurrence of iron.

As described above, when the number of bottom blowing tuyere was two, the iron yield remained low regardless of r/R. This means that not only the flow to the central part of the hot metal surface but also the flow to the furnace wall side away from the central part of the hot metal surface are likely to occur with only the two bottom blowing tuyeres 6, so that the flow is injected into the central part of the hot metal surface. It is presumed that the iron raw material containing iron oxide flows to the furnace wall side and is not caught in the hot metal. On the other hand, when the number of bottom blowing tuyeres was 3 or more, there was a preferable range for r/R, and a high iron yield could be realized within the preferable range. When stirring with three or more bottom blowing tuyeres, the surface flow to the central part of the hot metal surface occurs due to the interference of the flow from each tuyere, and the raw material floating on the hot metal surface is caught in the molten iron at the central part, so the slag % T. This is consistent with the low Fe content. Further, when the gas flow from the bottom blown tuyere is too close to the central part of the hot metal surface, the raw material is pushed up by the flow from below the gas, and as a result, the raw material is dissipated without being entrained in the hot metal. On the other hand, if the gas flow from the bottom blowing tuyer is too far to the center of the hot metal surface, the gas flow will be attenuated without reaching the raw material in the center of the hot metal surface, and as a result, the raw material will be input without being entrained in the hot metal. It will be retained in the position where it was made. When r/R is within the preferable range of the formula (1), as shown above, the surface flow to the central part of the hot metal surface is caused by the interference of the flow from each tuyere by stirring with three or more bottom-blown tuyere. The raw material that is generated and floats on the hot metal surface is caught in the molten iron at the center. This means that the% T.S. Except for the case where Fe is convex downward and the gas flow from the bottom blowing tuyere is r/R=0.1 near the center of the hot metal surface and r/R=0.9 far from the hot metal surface center. %T. in slag This is consistent with the fact that Fe was low, that is, the iron yield was good. A suitable effect is obtained even with four bottom blowing tuyeres, and an effect equal to or more than the above is expected even with five or more tuyere. On the other hand, there is a concern that the furnace bottom electrode may be worn due to an increase in stirring force with an increase in the number of bottom blowing tuyeres, so the number of bottom blowing tuyeres is preferably three or four. Further, the above-described effects of the present invention can be further enjoyed when r/R=0.3 to 0.7.

In the present invention, nitrogen gas, argon gas, oxygen-containing gas or the like can be used as the gas species blown from the bottom blowing tuyere 6. In the case of nitrogen gas or argon gas, the bottom blowing tuyere 6 can be a single tube tuyere. When blowing an oxygen-containing gas, for example, pure oxygen, it is preferable to use a double tube tuyere, to flow the oxygen-containing gas from the inside of the inner tube and to flow the cooling gas from the space between the inner tube and the outer tube. The amount of gas blown from the bottom blowing tuyere may be about ³ to 15 Nm ³ /h in terms of the flow rate per ton of hot metal blown from one tuyere. If this flow rate is too low, the effect of promoting reduction/dissolution by bottom blowing will not be apparent, while if it is too high, the effect will saturate, and the bottom tuyeres will be worn out severely, improving overall operation. Because it will not be.

As the bottom blowing tuyeres 6 of the present invention, at least three bottom blowing tuyeres 6 are provided, the radius in the melting furnace is R, and the distance from the furnace bottom electrode center 14 to the center of the bottom blowing tuyeres 6 is As the r, the bottom blown tuyere 6 may be installed at a position satisfying the expression (1). More preferably, the number of bottom blowing tuyeres 6 is N, and the distance r from the furnace bottom electrode center 14 to the center of each bottom blowing tuyere 6 is 0.8 to 1.2 times the average value of the distance r. The angle formed by the adjacent bottom blowing tuyeres 6 with the furnace bottom electrode center 14 is preferably within the range of 300°/N to 430°/N. By setting the arrangement of the bottom blown tuyere 6 within the above range, it is possible to prevent uneven distribution of the bottom blown tuyere 6 and form a good stirring flow. Most preferably, the bottom blowing tuyeres 6 are arranged to be rotationally symmetrical with respect to the furnace bottom electrode center 14.

When manufacturing the iron oxide-containing iron raw material to be fed into the DC arc furnace in the preliminary reduction furnace, it is possible to granulate and produce the iron oxide-containing iron raw material with a low reduction rate. The contained iron raw material has a low crushing strength, and there is a problem that the granulated material is partially pulverized. When iron oxide-containing iron raw material is reduced/dissolved to produce hot metal, it is desirable to use the cheapest raw material to improve the iron yield, but for that purpose, powdered iron oxide-containing iron raw material is reduced/dissolved. Will be required. However, when a powdery iron oxide-containing iron raw material is gravity-fed from the top of the arc furnace, part of the iron raw material is absorbed by the exhaust duct, so that the iron yield is reduced.

In the present invention, preferably, as shown in FIG. 1, a powdery iron oxide-containing iron raw material is charged into the DC arc furnace 1 through the hollow upper electrode 2 and the furnace upper material charging hole 3 and reduced/melted by arc heat. In the hot metal production method, a small iron oxide-containing iron raw material having a maximum particle size of 5 mm or less is supplied from a hollow upper electrode 2 of a DC arc furnace, and carbon powder in the hot metal and heat are contained in the iron oxide powder at a high temperature portion just below the upper electrode. Reduces and dissolves iron raw materials. When a small-diameter iron oxide-containing iron raw material is charged through the furnace raw material charging hole 3, at least a part of it is absorbed by the exhaust duct 15 before reaching the hot metal surface, but by charging through the hollow upper electrode 2, The raw material emitted from the outlet of the hollow upper electrode 2 passes through the high-temperature arc and immediately reaches the hot metal 11, so that there is no absorption loss in the exhaust duct 15. Further, since the raw material is added from the upper electrode 2 to the high-temperature molten metal surface portion immediately below it, it is inevitably added to the highest temperature portion, which is convenient. It is to be noted that the massive iron oxide-containing iron raw material having a particle diameter of more than 5 mm may be aimed at from the furnace raw material charging hole 3 to a high temperature portion just below the upper electrode.

The iron oxide-containing iron raw material is manufactured in a preliminary reduction furnace such as a shaft furnace or a rotary hearth furnace. The type of raw material for the preliminary reduction is not particularly limited, and various types can be used. Among them, for example, sinter ore in which agglomerated iron ore (lump ore) and powdered iron ore (including iron-containing dust such as steelmaking dust) are agglomerated, and powdered iron ore (iron-containing dust Pellets agglomerated) are preferred.

1 DC Arc Furnace 2 Upper Electrode 3 Top Material Feeding Hole 4 Arc 5 Furnace Bottom Electrode 6 Bottom Blowing Tuyer 11 Hot Metal 12 Refractory 13 Slag 14 Furnace Bottom Electrode Center 15 Exhaust Duct

Claims (2)

Iron oxide-containing iron raw material, from the furnace into the direct current arc furnace where the hot metal seed is present, in the method of reducing and melting by contact with the arc heat and hot metal hot seed,
The iron oxide-containing iron raw material has a metallization ratio of iron of 45% or more and 95% or less and contains an oxide other than iron oxide in an amount of 4 to 20% by mass.
The DC arc furnace comprises one upper electrode, one furnace bottom electrode and three or more bottom blowing tuyeres, the radius in the melting furnace is R, and the bottom blowing tuyeres are from the center of the furnace bottom electrode. With the distance to the center of r being r, for all the bottom blown tuyere , the bottom blown tuyere is installed at a position that satisfies the following formula (1),
The number r of bottom blown tuyere is N, and the distance r from the center of the furnace bottom electrode to the center of each bottom blown tuyere is within 0.8 to 1.2 times the average value of the distance r, The angle formed by the bottom blown tuyere with the center of the furnace bottom electrode is in the range of 300°/N to 430°/N,
A method for reducing/dissolving an iron oxide-containing iron raw material, characterized in that the iron oxide-containing iron raw material is charged directly below the upper electrode while performing bottom blowing stirring of the hot metal by a gas blown from the bottom blowing tuyere.
0.2≦r/R≦0.8 (1) Part or all of the iron oxide-containing iron raw material to be introduced into the DC arc furnace with the upper electrode hollow is a small-diameter iron oxide-containing iron raw material having a maximum particle size of 5 mm or less. The method for reducing/dissolving an iron oxide-containing iron raw material according to claim 1, wherein the iron raw material containing iron oxide is charged into a DC arc furnace via the hollowed upper electrode.

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