JP2008291332A - Method for producing molten iron using vertical-type scrap-melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably perform the operation without developing such problems as to increase the blasting pressure and drop the molten iron tapping temperature and slag temperature, when the molten iron is produced by using dust-agglomerate as a part of the charging material into a vertical-type scrap-melting furnace. <P>SOLUTION: In the method for producing the molten iron by charging iron-based scrap, the dust-agglomerate for agglomerating the dust containing metallic oxide, and coke into the vertical-type scrap-melting furnace and blasting hot blast from a plurality of tuyeres arranged at the lower part of the furnace; the operation is performed so that a typical length R(m) of the dust-agglomerate charged into the vertical-type scrap-melting furnace and the molten iron producing speed W(t/m<SP>2</SP>×hr), satisfy formula (1), 0.018≤R≤0.090-0.00333×W, or desirably, formula (2), 0.018≤R≤0.065-0.00233×W. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention uses a vertical scrap melting furnace to agglomerate dust containing metal oxide as part of the furnace charge in a method for producing hot metal by melting iron scrap by the combustion heat of coke. The present invention relates to a hot metal manufacturing method using a dust agglomerated product.

Conventionally, a process for melting iron-based scrap using a vertical melting furnace is known (for example, Patent Document 1). In this process, iron-based scrap and coke are charged from the top of the vertical melting furnace. Hot metal is blown from a plurality of tuyere (blower tuyere) provided at the lower part of the furnace, and iron scrap is melted by the combustion heat of coke to obtain hot metal.
In general, iron-based scrap contains a considerable amount of zinc derived from a galvanized material and the like, and in the above process, zinc contained in the iron-based scrap is heated in the process of descending in the furnace to become metal vapor. The zinc metal vapor rises along with the gas flow in the furnace, and when it reaches the vicinity of the top of the furnace where the temperature is low, it is oxidized to become fine zinc oxide and discharged together with the furnace exhaust gas as a part of dust. For this reason, about 20-30 mass% of zinc is contained in the dust recovered from the furnace exhaust gas.

Zinc contained in such dust needs to be reused as a resource, but in order to use zinc-containing dust as a raw material for refining zinc as it is, a zinc concentration of at least about 50 mass% is required. Therefore, the dust having the zinc concentration recovered by the above process needs a special treatment for concentrating zinc in order to use it as a zinc raw material for refining, and the processing cost is high.
To solve this problem, the zinc-containing dust generated in the vertical melting furnace for iron making is agglomerated, and this dust agglomerated material is recycled and charged in the vertical melting furnace, so that the secondary dust (into the furnace) is obtained. There is known a method in which zinc is concentrated in dust that is generated when a dust agglomerated material is charged and operated (see, for example, Patent Document 2).
JP-A-56-156709 Japanese Patent Laid-Open No. 55-125211

However, as a result of the study by the present inventors, in the process of recycling the dust agglomerate in the vertical melting furnace as described above, the gas blowing performance is hindered and the blowing pressure is increased, and the output temperature and slag temperature are increased. It has been found that problems such as lowering of slag and slag discharge due to lowering of slag temperature are likely to occur, and stable operation cannot always be performed.
Therefore, the object of the present invention is to increase the blast pressure, lower the tapping temperature and the slag temperature, etc. in the method of producing hot metal using dust agglomerates as part of the furnace charge in a vertical scrap melting furnace. An object of the present invention is to provide a hot metal production method capable of performing stable operation without causing problems.

As a result of repeated studies to solve the above-mentioned problems, the inventors of the present invention, in the process of manufacturing hot metal by charging dust agglomerates as part of the furnace charge into a vertical scrap melting furnace, It is important to optimize the particle size of the dust agglomerate according to the speed, and the above problems are caused by the inappropriate particle size of the dust agglomerate used. There was found.
The present invention has been made based on such findings, and the gist thereof is as follows.
[1] In a vertical scrap melting furnace, iron scrap from the top of the furnace, dust agglomerates agglomerated dust containing metal oxide, and coke are charged, and a plurality of A method for producing hot metal by blowing hot air from a tuyere,
Operation is performed so that the representative length R (m) of the dust agglomerate charged into the vertical scrap melting furnace and the hot metal production rate W (t / m ² · hr) satisfy the following formula (1): A hot metal production method using a vertical scrap melting furnace.
0.018 ≦ R ≦ 0.090−0.00333 × W (1)
However, the representative length R of the dust agglomerated material: the shortest distance from an arbitrary point inside the dust agglomerated material to the surface of the agglomerated material is obtained. This distance is obtained at all points inside the dust agglomerate, and the maximum value is taken as the representative length R of the dust agglomerate.

[2] In the production method of [1] above, the representative length R (m) of the dust agglomerate charged into the vertical scrap melting furnace and the hot metal production rate W (t / m ² · hr) are as follows (2 ) A hot metal production method using a vertical scrap melting furnace characterized in that the operation is performed so as to satisfy the formula.
0.018 ≦ R ≦ 0.065−0.00233 × W (2)
[3] In the manufacturing method according to [1] or [2] above, as the dust agglomerate charged into the vertical scrap melting furnace, the zinc-containing dust generated in the vertical scrap melting furnace or dust containing the same is agglomerated. A method for producing hot metal using a vertical scrap melting furnace, characterized by using an agglomerated dust agglomerated material.
[4] In the production method according to any one of [1] to [3] above, the dust agglomerated product is compression molded from a moisture-added raw material mixture mainly composed of a dust containing a metal oxide and a hydraulic binder. After that, a hot metal manufacturing method using a vertical scrap melting furnace, which is a hydrated and hardened dust agglomerate.

  According to the hot metal production method of the present invention, when producing hot metal using a dust agglomerate as part of the furnace charge in a vertical scrap melting furnace, the increase of the blowing pressure, the hot metal temperature and the slag temperature Stable operation can be performed without causing problems such as lowering.

In the vertical scrap melting furnace, the present invention is a steel scrap, a dust agglomerate obtained by agglomerating dust containing metal oxide from the top of the furnace, a plurality of coke and charged at the bottom of the furnace. This is a method for producing hot metal by blowing hot air from the tuyere and melting iron scrap with the combustion heat of coke.
FIG. 1 schematically shows an example of a vertical scrap melting furnace, where 1 is a raw material charging portion provided at the top of the furnace, and 2 is a plurality of tuyere provided at appropriate intervals in the circumferential direction of the lower portion of the furnace ( 3 is a hot air pipe for supplying hot air to the tuyere 2, 4 is an exhaust gas outlet, and 5 is an outlet. Although there is no essential limitation on the size of the melting furnace or the like, the furnace inner diameter at the tuyere position is usually about 2 to 4 m and the furnace height is 6 to 6 as a size that is substantially operable or advantageous in operation. It is about 10m.

In such a vertical scrap melting furnace, raw materials such as iron scrap, dust agglomerates, and coke are charged into the furnace from the raw material charging section 1 at the top of the furnace. Hot air is blown from the plurality of tuyere 2, and iron-based scrap or the like is melted by the heat of the combustion gas of coke. The produced hot metal is taken out of the furnace through the outlet 5 at the bottom of the furnace.
Iron-based scrap and coke, which are the main raw materials, may be charged into the furnace simultaneously or alternately. In addition to iron-based scrap, dust agglomerates and coke, for example, pig iron, reduced iron, agglomerates of other dust and sludges, iron sources such as iron ore, charcoal materials such as charcoal and anthracite You may enter.
The dust agglomerated material used in the present invention may be a dust agglomerated material obtained by agglomerating dust containing a metal oxide such as iron oxide or zinc oxide. A particularly preferable dust agglomerated product will be described in detail later.

In the present invention, the representative length R (m) of the dust agglomerate charged into the vertical scrap melting furnace and the hot metal production rate W (t / m ² · hr) are expressed by the following formula (1), preferably the following (2 ) To produce hot metal.
0.018 ≦ R ≦ 0.090−0.00333 × W (1)
0.018 ≦ R ≦ 0.065−0.00233 × W (2)
Here, the representative length R of the dust agglomerate is defined as follows. That is, the shortest distance from any point inside the dust agglomerate to the agglomerate surface is determined. This distance is obtained at all points inside the dust agglomerate, and the maximum value is taken as the representative length R of the dust agglomerate. 2 (a) to 2 (c) show the representative length R of dust agglomerates having various shapes. For example, if the dust agglomerate is a sphere, the radius of the sphere becomes the representative length R. In the case of an elliptic sphere, ½ of the minor axis is the representative length R. In the present invention, the particle size of the dust agglomerated material is defined by such a representative length R when the center of the dust agglomerated material in which R is defined enters the furnace into the furnace. This is because it is the most difficult part of the temperature to rise.

  Generally, dust generated in the iron making process contains a large amount of metal oxides (oxides such as Fe and Zn). When the dust agglomerate obtained by agglomerating dust containing such metal oxide is charged into a vertical scrap melting furnace and appropriately heated in the furnace, iron oxide among the metal oxides Reacts with carbon in the dust and is reduced, and when heated, the temperature rises and melts to form molten iron. After the zinc oxide is reduced and vaporized, it is re-oxidized in the air stream to form fine zinc oxide, which is discharged from the top of the furnace as part of the dust accompanying the furnace exhaust gas.

  However, if the particle size of the dust agglomerated material is too large, the temperature rise inside the dust agglomerated material is delayed, and the metal oxide is dissolved without being sufficiently reduced. The dissolved metal oxide is melted and reduced while dripping inside the furnace in a state of being dissolved in a slag shape. Since zinc oxide is more easily reduced than iron oxide, it is usually sufficiently reduced. On the other hand, the smelting reduction of iron oxide is not enough to complete the reduction under the conditions of the vertical scrap melting furnace, especially when there is too much iron oxide in the initial slag, it is not fully reduced, The FeO concentration in the slag increases. Thus, the situation where the FeO concentration in the slag at the time of tapping is high means that the amount of smelting reduction at the lower part of the furnace is large, and since this reaction is endothermic, the tapping temperature and the slag temperature are lowered, Slag discharge is also difficult. Therefore, in the operation of the vertical scrap melting furnace, from the viewpoint of suppressing the increase in the FeO concentration in the slag by sufficiently increasing the temperature up to the inside of the dust agglomerated charged material, so that the reduction proceeds. It is preferable to limit the particle size of the dust agglomerated material (provide an upper limit).

  As described above, if the particle size of the dust agglomerated material is too large, the temperature rise inside the dust agglomerated material is delayed, and the metal oxide is dissolved without being sufficiently reduced. As a result, when the dust agglomerated material is melted, more slag is generated than the metal (metal iron) as the amount of the melt. In general, slag has a higher viscosity than metal and has a higher hold-up amount in the furnace. For this reason, if there is much slag generation amount, the quantity which fills the coke space | gap in a furnace lower part will increase, gas permeability will be inhibited, and ventilation pressure will rise. When the blowing pressure rises, not only the blower power rises, but the gas in the furnace tends to drift and the gas utilization rate decreases, and as a result, the tapping temperature and slag temperature fall. Therefore, in the operation of the vertical scrap melting furnace, the temperature rises sufficiently to the inside of the charged dust agglomerate → the reduction proceeds so that the amount of slag generated is suppressed and the gas permeability in the furnace is secured. Also from the viewpoint, it is preferable to limit the particle size of the dust agglomerates to be charged (set an upper limit).

Here, the rise in the internal temperature of the dust agglomerate is also affected by the residence time of the dust agglomerate in the furnace. That is, if the residence time of the dust agglomerated material in the furnace is long, the temperature is sufficiently increased to the inside even if it is a large agglomerated dust agglomerated material and is sufficiently reduced to the inside of the agglomerate. Naturally, if the residence time of the dust agglomerate in the furnace is short, the opposite result is obtained. The residence time of the dust agglomerate in the furnace is inversely proportional to the hot metal production rate, and therefore the upper limit of the preferred range of the particle size of the dust agglomerate varies with the hot metal production rate.
On the other hand, if the particle size of the dust agglomerated material is too small, the dust agglomerated material blocks the coke layer voids formed by coke charged at the same time, impedes the flow of the gas in the furnace, and the blowing pressure increases. As described above, when the air blowing pressure increases, not only the blower power increases, but the gas in the furnace tends to drift and the gas utilization rate decreases, and as a result, the tapping temperature and slag temperature decrease. . Therefore, in the operation of the vertical scrap melting furnace, the particle size of the dust agglomerate to be charged is limited from the viewpoint that the dust agglomerate blocks the coke layer gap and does not hinder the flow of gas in the furnace ( It is preferable to provide a lower limit.

In a vertical scrap melting furnace (furnace diameter 2.1 m, number of tuyere 6) as shown in FIG. 1, iron agglomerate was charged together with iron-based scrap and coke to produce hot metal. At that time, the representative length R of the dust agglomerate to be used is changed under different three levels of hot metal production rate, and the relationship between the representative length R of the dust agglomerate, the FeO concentration in the slag, and the blowing pressure I investigated. The results are shown in FIGS. FIG. 3 shows an operation example of hot metal production speed W: 4 t / m ² · hr, FIG. 4 shows an operation example of hot metal production speed W: 8 t / m ² · hr, and FIG. 5 shows hot metal production speed W: 12 t / m ² · hr. Each of the operation examples is shown.

The used dust agglomerated material is agglomerated zinc-containing dust recovered from the exhaust gas of the vertical scrap melting furnace. The raw material consisting of zinc-containing dust: 90 mass%, Portland cement: 10 mass%, After adding water 1.4 times the mass of the container and mixing it thoroughly with a mixer, it is compression-molded into a rectangular parallelepiped shape (100 mm x 100 mm x 60 mm) by a vibration molding method. It is an agglomerated product.
The iron source charged in the furnace was iron scrap: 60 mass% and pig iron: 40 mass%. Similarly, the coke was 50 mass% when the particle size was 190 mm and 50 mass% when the particle size was 65 mm. Hot air at 550 ° C. was blown from the tuyere, and the blown air volume was adjusted so that the hot metal production rate was the target. Further, oxygen enrichment (normal temperature, oxygen enrichment rate 3%) was performed on the hot air. The operation was carried out for 14 to 16 hours including start-up and blow-down, and data obtained when operating continuously for 5 hours or more under the same operation conditions was used.

  According to FIGS. 3 to 5, regardless of the hot metal production speed W, the blowing pressure is significantly increased when the representative length R of the dust agglomerated material is less than 0.018 m. This is presumably because the dust agglomerated material blocked the coke layer voids and prevented the flow of the gas in the furnace because the particle size of the dust agglomerated material was too small. Therefore, the representative length R of the dust agglomerated product needs to be 0.018 m or more.

On the other hand, the following results are obtained for the upper limit side of the representative length R of the dust agglomerates. That is, in the operation example of the hot metal production rate W: 4 t / m ² · hr shown in FIG. 3, when the representative length R of the dust agglomerated product exceeds 0.0767 m, the FeO concentration in the slag increases rapidly. Further, even if the representative length R of the dust agglomerated material is 0.0767 m or less, the blowing pressure slightly increases when it exceeds 0.0557 m. Moreover, in the operation example of the hot metal production speed W: 8 t / m ² · hr shown in FIG. 4, when the representative length R of the dust agglomerate exceeds 0.0634 m, the FeO concentration in the slag increases rapidly. Moreover, even if the representative length R of the dust agglomerated material is 0.0634 m or less, the blowing pressure slightly increases when it exceeds 0.0464 m. Furthermore, in the operation example of the hot metal production rate W: 12 t / m ² · hr shown in FIG. 5, when the representative length R of the dust agglomerate exceeds 0.0500 m, the FeO concentration in the slag increases rapidly. Moreover, even if the representative length R of the dust agglomerated material is 0.0500 m or less, the blowing pressure slightly increases when it exceeds 0.0370 m.

  Among the above results, when the representative length R of the dust agglomerate exceeds a certain level, the concentration of FeO in the slag increased rapidly because the particle size of the dust agglomerate was too large, It is thought that this is because the reduction of the hot metal was not delayed, and the reduction was delayed. The larger the hot metal production rate, the shorter the residence time of the dust agglomerate in the furnace. Therefore, the higher the hot metal production rate (FIG. 3 → FIG. 5), It is considered that the upper limit value of the representative length R of the dust agglomerated product that can maintain the FeO concentration in the slag within an appropriate range is small.

  In addition, when the representative length R of the dust agglomerated material exceeds a certain level, the blowing pressure slightly increased because the particle size of the dust agglomerated material was too large, and the temperature did not rise sufficiently to the inside of the agglomerate, The reduction was delayed, and as a result, the amount of slag was increased and the gas permeability was hindered.The higher the hot metal production rate, the shorter the residence time of the dust agglomerate in the furnace, and the higher the hot metal production rate. The upper limit of the representative length R of the dust agglomerated product that can maintain the blowing pressure in the optimum range is considered to be smaller (FIG. 3 → FIG. 5).

FIG. 6 is based on the results of FIGS. 3 to 5, the representative length R of the dust agglomerate is 0.018 m or more, and the FeO concentration in the slag is within an appropriate range in relation to the hot metal production rate W. The range of the typical length R of the dust agglomerated material that can be maintained is shown in order to suppress the deterioration of the blowing pressure due to the particle size of the dust agglomerated material being too small, and the FeO concentration in the slag is appropriate. In order to maintain the range, the representative length R (m) of the dust agglomerate charged in the vertical scrap melting furnace and the hot metal production rate W (t / m ² · hr) satisfy the following formula (1): It can be seen that the operation should be carried out.
0.018 ≦ R ≦ 0.090−0.00333 × W (1)

7 is based on the results of FIGS. 3 to 5, and the representative length R of the dust agglomerate is 0.018 m or more, and the blowing pressure is maintained in a preferable range in relation to the hot metal production speed W. The range of the representative length R of the dust agglomerated material that can be produced is shown in order, the deterioration of the blowing pressure due to the particle size of the dust agglomerated material being too small is suppressed, and the FeO concentration in the slag is within the appropriate range In order to suppress the increase in the blowing pressure due to the particle size of the dust agglomerate being too large, the representative length R (m) of the dust agglomerate charged into the vertical scrap melting furnace and the hot metal production It can be seen that the operation may be performed so that the speed W (t / m ² · hr) satisfies the following expression (2).
0.018 ≦ R ≦ 0.065−0.00233 × W (2)
Although there is no particular limitation on the hot metal production speed W, even if the hot metal production speed W is operated too low, the processing amount of the dust agglomerate is reduced and the substantial meaning is lost. On the other hand, if the hot metal production speed W is too high, there will be problems such as poor melting of the scrap and deterioration of the hot metal quality. Therefore, generally, the hot metal production rate W is preferably in the range of about ³ to 12 t / m ² · hr as shown in FIGS.

Next, a particularly preferred embodiment of the present invention will be described.
As described above, in order to use the zinc-containing dust generated in the vertical scrap melting furnace as it is as a zinc raw material for refining, it is necessary to have a sufficiently high zinc concentration (at least about 50 mass%), In order to increase the zinc concentration of the zinc-containing dust, the zinc-containing dust generated in the vertical scrap melting furnace is agglomerated, and this dust agglomerate is recycled and charged in the vertical scrap melting furnace. It is effective to concentrate zinc in the dust that is produced when the dust agglomerated material is charged and operate and collect the dust with an increased zinc concentration.
Therefore, in the present invention, the dust agglomerate charged into the vertical scrap melting furnace is preferably an agglomeration of zinc-containing dust generated in the vertical scrap melting furnace or dust containing the same. Then, the dust agglomerated material is charged into a vertical scrap melting furnace for operation, and zinc-containing dust enriched with zinc is recovered from the furnace exhaust gas during the operation.

  Usually, the dust to be agglomerated is dust containing less than 50 mass% of zinc. If the zinc content of the dust is 50 mass% or more, it can be said that the zinc is sufficiently high in concentration, and directly passes through the agglomeration and recycle charging in a vertical scrap melting furnace to concentrate the zinc. Sending to the zinc refining process is more advantageous in terms of cost and environmental impact. The zinc-containing dust to be agglomerated may be composed only of dust generated in a vertical scrap melting furnace as long as it contains less than 50 mass% of zinc, or against dust generated in a vertical scrap melting furnace. Other dusts, for example, converter dusts may be mixed.

  In the process of recycling the dust agglomerated material containing agglomerated zinc-containing dust into the vertical scrap melting furnace, in order to recover secondary dust with as high a zinc concentration as possible, high-strength dust that is difficult to be pulverized in the furnace It is effective to use an agglomerated product. This is because dust agglomerates become dust when pulverized in the furnace. Therefore, if the dust agglomerates in the furnace are prevented from being pulverized, the amount of zinc in the secondary dust is constant but the amount of dust other than zinc is constant. This is because the zinc concentration in the secondary dust increases. However, the dust containing a large amount of zinc oxide is difficult to obtain a high-strength agglomerate because the zinc oxide itself is fine and has a narrow particle size distribution, and the bulk density is low (usually a bulk density of 0.8 or less). Moldability is also poor.

Accordingly, the method for producing the dust agglomerated material is arbitrary, but from the viewpoint of stably producing the dust agglomerated material having as high a strength as possible, it is preferably produced by the following compression molding method.
That is, in the compression molding method, an appropriate amount of water is added to and mixed with a raw material mainly composed of zinc-containing dust and a hydraulic binder, and then compression molding is performed. To do. As the hydraulic binder, Portland cement is generally used. In addition, for example, blast furnace cement, granulated blast furnace slag powder, quicklime, alumina cement, and the like may be used, and one or more of these hydraulic binders may be used. Can be used. In addition, hydraulic binders containing sulfur such as gypsum (calcium sulfate) increase the sulfur concentration in the hot metal, which is not so preferable, but there is a margin in the process of removing sulfur as an impurity from the hot metal. May be used in some cases. Moreover, you may use a hardening accelerator as needed for adjustment of a cure rate.

Usually, the blending amount of the hydraulic binder in the raw material is 4 to 15 mass%, preferably about 7 to 12 mass%, and the water content is about 10 to 20 parts by mass with respect to 100 parts by mass of the raw material. It is.
Moreover, you may mix | blend suitably the granular material other than zinc containing dust and a hydraulic binder as a raw material. For example, in order to give an appropriate particle size distribution to the raw material and improve the moldability, it is possible to increase the particle size of particles (for example, particles containing iron oxides such as sintered sieve powder). Can be blended.

  The raw material to which moisture has been added is sufficiently mixed with a mixer (for example, a mixer equipped with stirring blades) and then compression molded. This compression molding process can be performed by any method such as molding using a mold, extrusion molding, roll press molding, etc. However, since zinc-containing dust is a powder with extremely poor moldability, it can be appropriately compressed and molded. From the viewpoint of obtaining a molded product having stable and stable quality, molding using a mold is preferable, and vibration molding in which compression molding is performed while vibrating the mold is particularly preferable. This vibration molding is suitable for packing a zinc-containing dust having a small bulk density into a mold at high density. The shape of the molded product is arbitrary, but it is preferable that there are few corners in order to suppress pulverization when charged into the furnace as much as possible.

  Since the molded product obtained by compression molding the raw material is hydrated and cured with a hydraulic binder, it is cured for a certain period. The curing method and period may be arbitrary. For example, after performing primary curing with steam, secondary curing in the atmosphere may be performed. The curing period is preferably as short as possible from the aspects of curing space and productivity, but may be appropriately selected according to the required strength after curing. In general, one week or more is preferable. If the curing period is long, the amount of the molded product to be stored increases. Therefore, when a sufficient storage space cannot be secured, it is preferable to use a curing accelerator or the like to shorten the period.

When the above zinc-containing dust agglomerates are charged into a vertical scrap melting furnace and operated, zinc is concentrated in the dust in the furnace exhaust gas of the furnace and used as it is as a zinc raw material for refining. Secondary dust having a high zinc concentration can be recovered.
Zinc-containing dust agglomerates may be charged into the furnace at any time, but if a large amount is charged in a short period of time, the concentration of zinc in the dust can be promoted, and dust with a high zinc concentration can be recovered. it can. For this reason, a dust agglomerate produced from zinc-containing dust generated during other operation periods (a period during which no dust agglomerate is charged) is provided throughout the operation period. It is preferable to concentrate the charging during the charging period and recover secondary dust having a high zinc concentration from the furnace exhaust gas during the charging period.

Note that the dust agglomerate contained in the furnace interior is pulverized and scattered in the furnace exhaust gas, except that the zinc content becomes metal vapor and eventually becomes a part of the dust, and the iron content dissolves and the molten metal becomes molten. It becomes a part, and most of the remainder (for example, SiO ₂ , Al ₂ O _3, etc.) dissolves and becomes a part of the slag. And since the high-intensity dust agglomerates as described above are difficult to be pulverized in the furnace (low scattering rate), the amount of dust generated is reduced as a result, and the zinc concentration in the dust is increased accordingly. become.

In a vertical scrap melting furnace (furnace diameter 2.1 m, number of tuyere 6) as shown in FIG. 1, iron agglomerate was charged together with iron-based scrap and coke to produce hot metal.
The used dust agglomerated material is agglomerated zinc-containing dust recovered from the exhaust gas of the vertical scrap melting furnace. The raw material consisting of zinc-containing dust: 90 mass%, Portland cement: 10 mass%, After adding water 1.4 times the mass of the container and mixing it thoroughly with a mixer, it is compression-molded into a rectangular parallelepiped shape (100 mm x 100 mm x 60 mm) by a vibration molding method. It is an agglomerated product.

  The iron source charged in the furnace was iron scrap: 60 mass% and pig iron: 40 mass%. Similarly, the coke was 50 mass% when the particle size was 190 mm and 50 mass% when the particle size was 65 mm. Hot air at 550 ° C. was blown from the tuyere, and the blown air volume was adjusted so that the hot metal production rate was the target. Further, oxygen enrichment (normal temperature, oxygen enrichment rate 3%) was performed on the hot air. The operation was carried out for 14 to 16 hours including start-up and blowing down, and data obtained when operating continuously for 5 hours or more under the same operation conditions was used.

Table 1 shows the representative length R of the dust agglomerates used in each Example, the operating conditions and operating results of the vertical scrap melting furnace, and the like. According to this, in the inventive example, the FeO concentration in the slag is as low as 0.11 to 0.23 mass%, and the blowing pressure is also as low as 1120 to 1380 mmH ₂ O. On the other hand, in Comparative Examples 4 to 6 in which the representative length R of the dust agglomerate exceeds the upper limit of the expression (1) of the present invention, the FeO concentration in the slag is 1.6 mass% or more, and the furnace The hot metal temperature (steaming temperature) is below 1510 ° C. due to the increase of direct reaction in the bed. Further, in Comparative Examples 1 to 3 in which the representative length R of the dust agglomerate is lower than the lower limit of the formula (1) of the present invention, the blowing pressure is 1800 mmH ₂ O or more, the gas flow is deteriorated, and the gas utilization rate is increased. It is falling. Moreover, the hot metal temperature is also decreasing with the decrease in the gas utilization rate.
Of the invention examples, those in which the representative length R of the dust agglomerate exceeds the upper limit of the formula (2) (Invention Examples 4, 5, 9, 10, 13, 14) have a slightly higher blowing pressure (1320 to 1202). 1380 mmH ₂ O), and the gas utilization factor and the hot metal temperature are slightly lower.

Explanatory drawing schematically showing an example of vertical scrap melting furnace Explanatory drawing showing representative length R of dust agglomerates Typical length R and slag of dust agglomerate when molten agglomerate is charged into a vertical scrap melting furnace together with iron scrap and coke, and hot metal is produced at a hot metal production rate of 4 t / m ² · hr. Showing the relationship between the FeO concentration and the blowing pressure Typical length R and slag of dust agglomerated material when iron agglomerate and iron agglomerated material are charged into a vertical scrap melting furnace and hot metal is produced at a hot metal production rate of 8 t / m ² · hr. Showing the relationship between the FeO concentration and the blowing pressure Typical length R and slag of dust agglomerates when molten agglomerate is charged together with iron scrap and coke into a vertical scrap melting furnace and hot metal is produced at a hot metal production rate of 12 t / m ² · hr. Showing the relationship between the FeO concentration and the blowing pressure Based on the results of FIGS. 3 to 5, the dust agglomerate has a representative length R of 0.018 m or more and can maintain the FeO concentration in the slag within an appropriate range in relation to the hot metal production rate W. Graph showing the range of the representative length R of the compound Based on the results shown in FIGS. 3 to 5, the dust agglomerated material has a representative length R of 0.018 m or more and can maintain the blowing pressure within the optimum range in relation to the hot metal production speed W. Graph showing the range of the representative length R

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw material charging part 2 Tuyere 3 Hot air pipe 4 Exhaust gas outlet 5 Outlet

Claims (4)

In a vertical scrap melting furnace, iron scrap from the top of the furnace, dust agglomerates agglomerated dust containing metal oxides, and coke are charged from a plurality of tuyere provided at the bottom of the furnace. A method for producing hot metal by blowing hot air,
Operation is performed so that the representative length R (m) of the dust agglomerate charged into the vertical scrap melting furnace and the hot metal production rate W (t / m ² · hr) satisfy the following formula (1): A hot metal production method using a vertical scrap melting furnace.
0.018 ≦ R ≦ 0.090−0.00333 × W (1)
However, the representative length R of the dust agglomerated material: the shortest distance from an arbitrary point inside the dust agglomerated material to the surface of the agglomerated material is obtained. This distance is obtained at all points inside the dust agglomerate, and the maximum value is taken as the representative length R of the dust agglomerate. Operation is performed so that the representative length R (m) of the dust agglomerate charged into the vertical scrap melting furnace and the hot metal production rate W (t / m ² · hr) satisfy the following formula (2): The hot metal manufacturing method using the vertical scrap melting furnace of Claim 1 characterized by the above-mentioned.
0.018 ≦ R ≦ 0.065−0.00233 × W (2)   The dust agglomerate charged in the vertical scrap melting furnace is a zinc agglomerated product obtained by agglomerating zinc-containing dust generated in the vertical scrap melting furnace or dust containing the same. A hot metal production method using the vertical scrap melting furnace according to 1 or 2.   The dust agglomerated product is a dust agglomerated product mainly composed of a dust containing a metal oxide and a hydraulic binder, compression-molded with a moisture-added raw material mixture, and then hydrated and hardened. A hot metal production method using the vertical scrap melting furnace according to claim 1.

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