JP2003247032A - Operation method of smelting reduction furnace - Google Patents

Abstract

(57) Abstract: A tuyere for blowing high-temperature oxygen-enriched air is provided at least in two upper and lower stages in a packed bed of a carbon-based solid reducing agent, and at least an upper stage of the tuyere contains a powdery metal oxide. The present invention relates to a method for operating a smelting reduction furnace for injecting a raw material to produce a chromium-containing molten metal. SOLUTION: A powdery chromium ore is mixed with a metal oxide powder containing a metal component of the above-mentioned molten metal to form a chromium-containing massive raw material. Charge from the furnace top. Preferably, the molten metal is hot metal obtained by melting iron, and the metal oxide powder is a powder containing iron oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a smelting reduction furnace for producing a molten metal by smelting and reducing a powdery raw material containing a metal oxide, and particularly to a method for producing a chromium-containing molten metal. Is. In the following, iron, which is a typical metal, will be described as an example, and a case of producing a chromium-containing hot metal as a molten metal will be described. However, it is similarly applicable to the production of other chromium-containing molten metals. Needless to say.

[0002]

2. Description of the Related Art Conventionally, an electric furnace has been generally used to obtain chromium-containing hot metal by using chromium ore as a part or all of a chromium source. However, since the ratio of electric energy consumption to the manufacturing cost is extremely high, there is a problem that the electric consumption greatly affects the product price.

As a means for solving this, Patent Document 1 discloses a method using a vertical furnace type smelting reduction furnace as means for smelting and reducing a powdery and granular metal oxide-containing raw material to recover metal. Has been done. In this method, the powdery or granular raw material is blown into the vertical furnace together with the hot air from at least the upper tuyere of the upper and lower tuyeres that are installed in the lower part of the furnace and are filled into the furnace. The carbonized material is burned and melt-reduced.

In this method, since the carbonaceous material filled between the upper and lower tuyere can burn to form a high temperature region, the chrome ore is also easily melted, and while the packed bed is dripped thereafter, the solid carbon packed bed is used. It is directly reduced. Therefore, it is possible to easily recover the chromium-containing hot metal in a molten state by using the chromium ore that is difficult to reduce. As a means for further increasing the chromium concentration by the above method, for example, in Patent Document 2,
A method is disclosed in which powdered chromium ore is blown from the tuyere and at the same time, high carbon Fe-Cr is charged as a chromium source from the upper part of the furnace.

In this method, the high carbon Fe-Cr charged from the upper part of the furnace is easily melted in the upper raceway, and the chromium source such as powdered chrome ore blown from the tuyere is the upper and lower tuyere. Since it is reduced in the high temperature region formed in between, the hot metal having a high chromium concentration can be easily manufactured.

[0006]

[Patent Document 1] Japanese Patent Publication No. 02-42884

[Patent Document 2] JP-A-60-162718

[Patent Document 3] Japanese Patent Laid-Open No. 2001-316731

[0007]

[Problems to be Solved by the Invention] However, high carbon
Since Fe-Cr is manufactured by using electric power, it is expensive and it is difficult to adjust the particle size to a size that can be charged. Therefore, there is a problem in that mass production of massive high-carbon Fe-Cr cannot be used, and mass production at low cost cannot be performed. In addition, instead of charging the high carbon Fe-Cr from the furnace top, it is also possible to charge massive chromium ore from the furnace top. However, chrome ores are generally minerals having spinel type crystals, most of which have a melting point of 2000 ° C. or higher, and have a property of being difficult to reduce. Therefore, by simply charging massive chromium ore from the top of the furnace, heat utilization is expected because the temperature of the chromium ore and the reduction of Fe contained in the chromium ore slightly progress in the shaft part. However, it seems that the reduction of chrome ore hardly progresses until it falls to the high temperature part near the upper tuyeres and melting begins. Therefore, charging of massive chromium ore from the furnace top was not performed.

[0008] However, if it is possible to charge massive chromium ore from the furnace top, the productivity of the smelting reduction furnace targeted by the present invention may be improved, which is considered desirable. INDUSTRIAL APPLICABILITY The present invention provides a method capable of charging massive chromium ore from the furnace top, and capable of inexpensively producing high chromium hot metal in a smelting reduction furnace, and enables stable operation of the smelting reduction furnace. is there.

[0009]

[Means for Solving the Problems] It is considered that charging the massive chrome ore as it is from the top of the smelting reduction furnace can hardly be expected due to the properties of the chrome ore such as the difficulty of reducing. On the other hand, if powdered chrome ore can be charged from the furnace top, it can be expected to promote gas reduction at the shaft, but if powdered chrome ore is directly charged from the furnace top, it will rise in the furnace. It will be discharged as dust from the furnace top along with the internal gas. Therefore, it is difficult to directly charge the powdery chrome ore from the furnace top.

Therefore, the present inventors have conceived a method of agglomerating powdery chromium ore and charging it from the furnace top. Then, from various experiments, it was found that mixing and agglomerating powdered chrome ore with an oxide containing iron oxide for agglomeration has an effect of promoting reduction and melting of chrome ore in the shaft. . That is, the present invention provides at least two upper and lower stages of tuyere for blowing high-temperature oxygen-enriched air into a packed bed of a carbon-based solid reducing agent, and blowing a granular metal oxide-containing raw material from at least the upper stage of the tuyere. A method for operating a smelting reduction furnace for producing molten metal, comprising a chromium-containing massive raw material as an agglomerated ore containing a powdery chromium ore and a metal oxide powder containing a metal component of the molten metal. The above problem is solved by a method for operating a smelting reduction furnace, which is characterized in that the chrome-containing bulk raw material is formed and charged from the top of the smelting reduction furnace to produce a chromium-containing molten metal.

In the present invention, the molten metal is hot metal obtained by melting iron, and the metal oxide powder containing the metal component of the molten metal is powder containing metallic iron and iron oxide. That is preferable. Further, the present invention, in forming the chromium-containing lump raw material, the chromium ore and 70 mass% or less of the chromium ore relative to the dry mass of the mixture of the metal oxide powder containing the metal component of the molten metal. And 10% by mass or more of the metal component, and the dry mass
It is preferable to form the chromium-containing lumpy raw material by setting the water content to 40 parts by mass or less with respect to 100 parts by mass.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The theoretical background of the present invention and the preferred embodiments of the present invention will be described below. The present inventor has found that, in a smelting reduction furnace having at least two upper and lower tuyeres for injecting high temperature oxygen-enriched air into a packed bed of a carbon-based solid reducing agent, it is possible to easily smelt and reduce powdery chromium ore. Therefore, it was thought that smelting reduction would be possible even in a vertical furnace if the lumped powdered chromium ore was charged from the top of the furnace. Usually, for agglomeration of powder,
It costs a lot of money. So, using ironmaking dust,
The method of agglomerating powdery chrome ore was investigated.

The points of agglomeration include three points: strength after agglomeration, melt-reducing property of agglomerate, and time required for agglomeration. Study was carried out. As a method of agglomerating powdery oxide, Patent Document 3
Discloses a method in which 10% metallic iron is mixed with iron-making dust and agglomeration is carried out by utilizing the oxidation exothermic reaction of the metallic iron. This method has an advantage that the cost is low because it does not require a binder or special equipment, but it has a problem that it takes about 3 weeks to agglomerate. Then, the method of adding water was considered as a method of shortening this. This is expected to increase the agglomeration rate due to the heat generated by the exothermic reaction when water reacts with metallic iron. As an experiment, 50% of ironmaking dust containing about 40% of metallic iron in 50% of chromium ore having the composition shown in Table 1 described later is used.
After blending, the amount of water added was changed and the time until agglomeration was measured. To determine the completion of agglomeration, the content of metallic iron in the sample was measured and the value was set to 1.5% or less.
The results are shown in FIG. 6, and it was confirmed that the agglomeration time was shortened when the water content was 10 to 40%. When water content exceeding 40% was added, the agglomeration time became longer, which is considered to be because it took time for the water content to evaporate and dry.

Next, with the water content kept constant at 30%, chrome ore and ironmaking dust were mixed at various ratios to agglomerate. It was found from previous knowledge that if the crushing strength of the agglomerate is 400 N / cm ² or more, pulverization at the time of being conveyed by a belt conveyor can be suppressed, so this value was made the target value. Figure 7 shows an example of crush strength measurement results for agglomerates. If the metal content is 10% or more, the target crush strength is 4
It was confirmed that 00N / cm ² could be secured.

FIG. 2 shows an evaluation test of the meltability of this agglomerate.
It carried out using the load softening test device shown in. This test device reproduces the temperature, the load due to deposits, and the gas composition while the raw material charged from the upper part of the furnace descends in the furnace, and is used to investigate the smelting reduction behavior of the charged material at the shaft part. It is valid.

In the evaluation test, first, the crucible 10 was charged with an agglomerate 15 formed by mixing a binder (which also functions as a flux) and powdered chromium ore in a state in which the coke layer 14 was sandwiched between the upper and lower parts. To do. And from below, C
O: 45%, N ₂ : 55%, with a constant composition of gas, is heated by the heater 12 to measure the dropping behavior of the charging materials (14 and 15), level change, composition change of exhaust gas, etc. It was

FIG. 3 is a graph showing the relationship between the chromium ore ratio and the residue (excluding coke) on the plate. On the other hand, FIG. 4 is a graph showing the relationship between the chromium ore ratio and the amount of the substance dropped below the plate. As is clear from FIGS. 3 and 4, the mass ratio of the powdery chrome ore and the oxide containing iron oxide is
With 60:40 as the boundary, the one with a large amount of oxides including iron oxide,
The residue on the perforated plate becomes small and the reduction melting of the chromium ore proceeds.

This is because there is an oxide containing iron oxide, so when molten iron produced by reduction of this oxide is dropped,
It is considered that this is because it comes into contact with the chromium-containing iron having a high chromium content generated on the surface of the chromium ore, is assimilated, and is dropped together. On the other hand, in the case of the agglomerated raw material obtained by agglomerating only the chromium ore, even if a metal is produced on the surface of the chromium ore due to the reduction, the concentration of chromium is high, so that the melting point and viscosity of the metal become high and the metal does not drop easily. That is, the generated metal stays on the surface of the chrome ore, which hinders the contact between the reducing gas and the chrome ore in the surroundings. As a result, the reduction of the chrome ore is delayed and the metal drops almost completely. .

As described above, by mixing the powdery chrome ore and the oxide containing iron oxide together and agglomerating, the dropping of the metal produced from the chrome ore in the furnace is promoted, and the smelting reduction furnace The reduction of chromium ore in the shaft part is promoted. The powdery chromium ore of the present invention is
It means a particle size of less than 5 mm, such as under a sieve when chrome ore is classified with a 5 mm sieve. When powdered chrome ore with a particle size of less than 5 mm is charged from the furnace top, the particle size difference with other packings such as coke becomes large, which may cause segregation of chrome ore and clogging of the packed bed. Therefore, according to the present invention, such a problem can be avoided by mixing with the metal oxide powder to obtain a chromium-containing lump raw material.

The present invention is based on such a technical idea. If powdered chromium ore is agglomerated with a water content of 40% or less, a metallic iron content of 10% or more, and a chromium ore content of 60% or less, It is possible to produce a chromium-containing lumpy raw material that can be charged from the top of a vertical smelting reduction furnace without any problem, and as a result, it is possible to produce high chromium pig iron at low cost. Hereinafter, the content of the present invention will be described in detail based on examples.

[0021]

Example 1 Agglomeration of chromium ore powder Agglomeration was carried out by mixing chromium ore powder having the composition shown in Table 1 and powdered iron dust.

[0022]

[Table 1]

The amount of raw material used is 240 t of powdered iron dust,
Chromium ore of 360t and moisture of 180t was mixed and kneaded, and then spread in a yard as a bed with a height of about 300mm. After 2 weeks, a part of the sample was collected and analyzed, and the ratio of metallic iron was 1.1%. Therefore, the whole amount was crushed with a shovel car and sieved with a 5 mm sieve. 53 for lumps of 5 mm or more
It was 0t. Further, the crush strength of the sample was measured and found to be 600 N / cm ^{2 on} average for 10 samples, and it was confirmed that there was no problem in terms of strength and yield. (Example 2) A smelting reduction furnace with a production amount of 200 t / day is used, and a chrome agglomerate having the composition shown in Table 1 is mixed with steelmaking dust to form an agglomerate from the furnace top. The invention was carried out.

Here, the oxide raw material blown from the tuyere is
Steel dust generated from the converter of a steelmaking plant is dried, and contains metal oxides such as iron oxide and chromium oxide. Other operating conditions are air flow of 230 m ³ (standard condition) / min
, Oxygen enrichment 40m ³ (standard condition) / min, blast temperature 850
C., the raw material blowing rate was 11 t / hr, and the raw material charging rate from the furnace top was 2.5 t / hr. The rate of raw material injection from the tuyere when the agglomerate was not charged from the furnace top was 13.5 t / hr.
And operated so that the total amount of treated dust was constant.

Transitions of the chromium concentration in the metal tapped from the taphole and in the slag are shown in FIGS. 5 (a) and 5 (b), respectively. Until the third day, the conventional operation without charging the agglomerate was performed from the furnace top, and the operation of the present invention was performed thereafter. From the transition of the figure, it can be seen that the chromium concentration in the metal increased by about 5% at the start of the furnace top charging. This value was predicted from the amount of chromium input. on the other hand,
Since there is no change in the chromium concentration in the slag,
It can be confirmed that the chromium ore charged from the furnace top has been sufficiently reduced. In addition, there was no problem in operation and we were able to continue stable operation throughout the period.

[0026]

According to the present invention, the production of a metal containing high concentration of chromium in a (vertical) smelting reduction furnace can be carried out more easily and at a lower cost.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a smelting reduction furnace to which an operating method of the present invention is applied.

FIG. 2 is a schematic diagram of a load softening device used for verification of the present invention.

FIG. 3 is a graph showing a relationship between a chromium ore ratio and an amount of residual substance on a plate in an experiment using a load softening device.

FIG. 4 is a graph showing a relationship between a chromium ore ratio and an amount of dropped substance in an experiment using a load softening device.

FIG. 5 is a graph showing transitions of (a) chromium concentration in metal and (b) chromium concentration in slag in a smelting reduction furnace.

FIG. 6 is a graph showing the relationship between the number of days required for agglomeration and the water addition rate.

FIG. 7 is a graph showing the relationship between the metallic iron compounding ratio in the mixed raw material and the crush strength.

[Explanation of symbols]

1 furnace body (vertical smelting reduction furnace) 2 Solid reducing material (carbon material) 3 upper tuyeres 4 Lower tier 5 blower 6 hot air generator 7 Raw material injection device 8 Top charging device 9 Outlet 10 crucibles 11 Pressing piston 12 heater 13th plate 14 Coke layer 15 agglomerates 16 drops

Continued front page    (72) Inventor Soichiro Watanabe             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. F-term (reference) 4K001 AA08 BA05 CA17 CA18 DA01                       FA14 GA01 GB03 HA01                 4K045 AA01 AA02 BA01 GB11 GB12                       GC09

Claims (3)

[Claims] 1. A tuyere for blowing high-temperature oxygen-enriched air is provided in at least two upper and lower stages in a packed bed of a carbon-based solid reducing agent,
A method for operating a smelting reduction furnace for producing a molten metal by injecting a powdery metal oxide-containing raw material from at least the upper stage of the tuyere, which comprises a powdery chromium ore and a metal containing a metal component of the molten metal. A chromium-containing lump raw material is formed as an agglomerated ore containing an oxide powder, and the chrome-containing lump raw material is charged from the furnace top of the smelting reduction furnace to produce a chrome-containing molten metal. Method of operating smelting reduction furnace. 2. The molten metal is hot metal obtained by melting iron, and the metal oxide powder containing the metal component of the molten metal is powder containing metal iron and iron oxide. The method for operating the smelting reduction furnace according to claim 1. 3. When forming a chromium-containing lump raw material,
Chromium ore, and 70% by mass or less of the chromium ore, and 10% by mass or more of the metal component, based on the dry mass of the mixture of the metal oxide powder containing the metal component of the molten metal, and the drying. The method for operating a smelting reduction furnace according to claim 1 or 2, wherein the chromium-containing lump raw material is formed with a water content of 40 parts by mass or less with respect to 100 parts by mass.