JPH10310810A - Smelting process in smelting reduction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smelting process in smelting reduction method which drastically reduces the smelting cost in comparison with the conventional method, at the time of producing a stainless steel base iron in the smelting process in the smelting reduction method. SOLUTION: In the smelting process in the smelting reduction method obtaining molten metal containing the main component of ore by adding carbon- containing material and the ore into the molten metal held in a converter type metallurgical reaction vessel 1 and also, blowing oxygen and 13 on the molten metal surface, dusts 6, 7 generated and recovered during smelting, are mixed with the ore, and again added into the molten metal through a lance. Then, as the ore, the Cr ore 18 is desirable to be used and this process is effective tecnique to produce the stainless steel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molten metal by a smelting reduction smelting method using a converter type reaction vessel. Used as a source of carbon and metal for smelting
This is a technique for inexpensively melting and reducing r ore and Mn ore.

[0002]

2. Description of the Related Art To manufacture stainless steel, a combination process of an electric furnace and AOD (argon-oxygen decarburization) or a process using a converter has been conventionally employed. However, recently, when a stainless steel is melted by a converter process, an Fe-Cr alloy, a pre-reduced Cr
Inexpensive C without using expensive Cr source such as pellets
Technologies have been developed that use r ore directly. It is called a smelting reduction smelting method, in which a Cr-ore ore and a carbon-containing substance as a reducing agent are added to a molten metal in a metallurgical reaction vessel (hereinafter, referred to as a reaction vessel), and then the Cr-ore is added to the molten metal. Is melt-reduced and dissolved in a molten metal to produce a stainless steel mother liquor. This process is currently being put to practical use through many studies on concrete implementation.

For example, Japanese Patent Application Laid-Open No. Hei 7-300609 discloses a method for adding powdery Cr ore to a molten metal by using a long opening from the upper opening (furnace opening) of a converter. It was proposed to be introduced through a cylindrical body (hereinafter referred to as a lance). The advantage of this method is that the powdery ore is dropped through a long lance, the falling speed of the powdery ore increases, and the rising ore of exhaust gas generated at the time of smelting causes the ore before the ore particles reach the molten metal. In addition, it is possible to prevent the particles from being scattered and being taken away by the exhaust gas, and to ensure a high Cr addition yield.

[0004] However, this method also has the following problems. (1) To reduce Cr ore, as a carbon-containing substance,
Generally, coke and anthracite are used, but in order to effectively reduce the coke, it is necessary to always keep these carbon-containing substances in the slag existing on the molten metal. In other words, a large amount of carbon material is required, and the cost is enormous. (2) The carbonaceous material powder staying in the slag is scattered while staying in the slag, escapes from the converter together with the exhaust gas, and is collected by the dust collector, but has a high C content ( Usually, 30 to 50% by weight) generates a large amount of dust.

[0005] As a method for reusing dust having a high C content, a smelting reduction smelting method using a reduction furnace such as an electric furnace or a rotary kiln (Japanese Patent Laid-Open No. 61-37727), or briquetting is used. Agglomeration treatment (see, for example, JP-A-59-215414) is conceivable.
Neither method has been put to practical use because the processing cost is high.

[0006] The mother liquor produced by the smelting reduction smelting method is then decarburized and refined in a normal converter to stainless steel. Further, the collected unused dust amounts to 200 kg / t or more per charge.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present invention provides a smelting reduction smelting method in which a so-called smelting reduction smelting method is used to manufacture a stainless steel mother liquor at a significantly lower smelting cost. It is intended to provide.

[0008]

Means for Solving the Problems In order to achieve the above object, the inventor has focused on recycling the collected dust. However, at the stage of actual execution, the dust becomes hopper,
The lance was clogged, preventing smooth operation. After diligent research into the cause, we found that dust oxidized by moisture during transportation and adhered and solidified to various devices, and worked diligently to realize it, including countermeasures, and completed the present invention described below. Was.

That is, according to the present invention, a carbon-containing substance and an ore are added to a molten metal held in a converter-type metallurgical reaction vessel, and oxygen gas is blown onto the molten metal surface so that a main component metal of the ore is removed. In a smelting reduction smelting method for obtaining a molten metal containing smelting, the dust generated and recovered during the smelting is mixed with the ore, and added to the molten metal again via a lance, the smelting reduction smelting method comprising: It is.

[0010] Further, the present invention provides a method for producing a molten metal obtained by the above-mentioned smelting reduction smelting, which is subsequently decarburized and refined in another converter-type metallurgical reaction vessel. A smelting reduction smelting method characterized by mixing with the ore together with the dust generated and recovered in the above. Further, the present invention provides a smelting reduction smelting method characterized in that a mixing ratio of the dust and ore determined by the following formula (1) is 0.5 or less, or a mixture of the dust and ore is dried. And a smelting reduction refining method characterized in that the mixture is dried to a moisture content of 2% by weight or less.

Α = dust weight / (ore weight + dust weight) (1) In addition, in the present invention, the dust is obtained by converting exhaust gas from a converter-type metallurgical reaction vessel into a slurry by water treatment, The particle size distribution of the dust is 100% or less by the rectification separation of 20% by weight.
A smelting reduction smelting method characterized by the following.

[0012] In addition, the present invention relates to the present invention,
The present invention also provides a smelting reduction smelting method characterized by making ore or mainly using anthracite as the carbon-containing substance. According to the present invention, dust having a high C content generated during smelting reduction smelting is mainly used for recycling, so that dust can be recycled without increasing carbonaceous material costs, and smelting costs are reduced. Become cheap. That is,
Since the ore containing the metal oxide can be reduced by recycling the dust, the metal yield in the entire system of the smelting reduction apparatus is improved. Conventionally, when recycling dust, measures such as agglomeration with the carbon material have been taken. However, in the present invention, the dust can be recycled. Further, since the apparatus for this is simple and not large-scale, the equipment cost can be reduced.

[0013]

FIG. 1 shows an example of equipment for performing a smelting reduction smelting method according to the present invention. It uses a converter 1 as a reaction vessel, in which, for example, in the case of stainless steel smelting, hot metal dephosphorized in a pretreatment and scrap are charged in advance, and charged into the molten metal surface from above the converter. In a state where the temperature is raised to a predetermined temperature by spraying the carbon material and oxygen 13, the molten metal 14 is held. The acid supply is performed by supplying oxygen gas 13 from a so-called upper blowing lance 15 disposed above the converter 1,
It is performed by spraying the surface of the molten metal 14 at a high speed. In the present invention, dust generated during smelting reduction smelting by such an apparatus is collected by a dust collection system shown in the lower right of FIG. 1 and recycled for the same or next smelting reduction smelting. . Hereinafter, the embodiment will be described.
This will be described in more detail.

First, the dust collecting system shown in FIG. 1 sprays water on the exhaust gas from the converter 1 in a dust collecting device 12 to collect dust contained in the exhaust gas. At that time, the water that has collected the dust (hereinafter, referred to as dust collection water) flows through the pipe 16 as slurry. In particular, among dusts generated in the smelting reduction smelting, those in which the retained carbon material in the slag is scattered are relatively coarse particles, and thus are collected as coarse dust 6 through the coarse particle separator 3. . Here, the coarse particle separator 3 is a device for retaining collected water and sedimenting dust by gravity.
On the other hand, the fine dust is put into the thickener 8 together with the drainage 17 of the coarse separator 3, concentrated, extracted from the lower part of the thickener 8, further concentrated in the concentration tank 11, and then extracted from the lower part. And is discharged as fine dust 7. One example of the particle size and chemical composition of the coarse dust 6 and the fine dust 7 is shown in Tables 1 and 2. In addition, among the collected coarse dust 6 and fine dust 7, the coarse dust 6 is particularly suitable for the processing target in the present invention. That dust 6
Has a particle size distribution of 100 μm
m or less is preferably 20% by weight or less. The reason is that, as shown in FIG.
This is because the iron content is high and coagulation occurs when water is contained and clogs with a hopper or the like. Therefore, it is desirable that the content of dust having a size of 100 μm or less be as low as possible. However, the coarse particle separator 3 sediments a part of the dust by gravity based on the specific gravity and the particle diameter of the dust and sorts the dust, so that iron-containing dust of 100 μm or less is generated at all. If not, coarse dust having a low specific gravity also flows into the thickener at the same time, and the amount of dust 6 suitable for recycling into the furnace through the lance according to the present invention is greatly reduced.

Then, when the conditions under which dust clogging occurs in a hopper and the like were further examined in detail, as described later,
Under drying conditions of 2% by weight or less of moisture, 100 μm
It has been found that if the content of the following dust is set to 20% by weight or less, the problem of clogging can be avoided.

[0016]

[Table 1]

[0017]

[Table 2]

Next, the collected dust 6 is mixed with the powdered ore 11. Since a known mixer 4 may be used for this mixing, the description is omitted. In the present invention, the mixing ratio (weight ratio) of dust and ore is not particularly limited. However, when Cr ore is specifically used,
Dust: Cr ore = about 2: 5 is preferred. The reason is that the bulk specific gravity of dust is as low as 0.8 to 1.0, while the bulk specific gravity of Cr ore is about 2.5, and when the mixing ratio of dust is increased, the specific gravity of the mixture 20 increases. Become smaller.
At the same time, even if the mixture 20 is blown into the converter 1 through the addition lance 5, the scattering rate increases. According to the inventor's investigation, when the mixing ratio α of dust and ore determined by the following equation (1) is 0.5 or more, the scattering rate increases to 5% or more.

Α = dust weight / (ore weight + dust weight) (1) At this time, the specific gravity of the dust is about 1.5, and from the viewpoint of lowering the scattering rate, the specific gravity of the dust is 1.5. It is desired to operate with the above mixing ratio. Since the specific gravity at the time of mixing is represented by equation (2), the mixing ratio suitable for operation is determined by the specific gravity of the ore (A) and the dust (B) to be mixed.

[0020]

(Equation 1)

Here, ρ _A , ρ _B ; specific gravity of powders A and B α, β; weight mixing ratio of powders A and B Therefore, in the present invention, the mixing ratio of the dust ( (Weight ratio) α is desirably 0.5 or less.

In the present invention, the molten metal in the converter 1 is added to the molten metal in the converter 1 via an addition lance 5 provided separately from the one for the acid supply above the converter 1. It has been found that the water content of the powder needs to be maintained within a certain range. That is, if the moisture content is set to 0.5% or less, it becomes possible to blow in a state where there is little problem of clogging regardless of the particle size of the dust. However, since the raw material has high moisture in rainy weather, it is difficult to dry the raw material until the moisture becomes less than 0.5% by weight. Also, the energy cost required for drying increases. Therefore, the particle size of 100 μm or less is reduced to 20% by weight or less, and at the same time, the drying is performed until the water content becomes 2% by weight or less.

Here, the reason why the clogging disappears when the water content is 2% by weight or less was examined by various test methods (not described) for the characteristics of the mixture considered to be related to the clogging. As shown in FIG. It was revealed that the angle of repose, the degree of compression, the cohesiveness, and the fluidity were affected by moisture, and that the characteristics all changed at about 2% by weight of moisture. In the present invention, the water content is set to 2% by weight or less based on the result of the investigation. If the water content exceeds that value, the blowing characteristic from the addition lance 5 deteriorates because the dust contains metallic iron, and an oxidation reaction occurs between the moisture and the metallic iron, and an oxide reaction occurs. Is considered to be fixed to the lance wall. The means for drying is not particularly limited. For example, a rotary kiln is one of suitable means. This is because by mixing ore and dust into the kiln, mixing is promoted simultaneously with drying.

Further, in the present invention, dust generated by decarburization refining other than smelting reduction refining is also used. The molten stainless steel obtained in the practice of the present invention is charged into an upper-bottom blowing converter and is decarburized and refined into stainless steel by a normal method.At this time, from the exhaust gas of the converter, This is because the same dust as that shown in Tables 1 and 2 is collected, although the amount is small. Therefore, this dust is recovered, mixed with ore, dried by the same method as described above, and is recycled.

In addition, in the present invention, a mixture of dust and ore 2
The method of adding 0 to the molten metal 14 from the addition lance 5 is as follows.
The mixture 20 may be dropped by its own weight, or may be sprayed on a molten metal surface using a carrier gas. In actual addition, a place where the ascending flow rate of the generated gas in the furnace is relatively small is found in advance by experiments and model calculations, and the tip of the addition lance 5 is positioned there to supply the mixture 20. . FIG. 3 is a diagram for explaining this. The molten metal 14 is held in the converter 1, and oxygen gas 13 is blown from an oxygen upper blowing lance 15, and the mixture 20
The mixture 20 is added from the addition lance 5 of the above. At this time,
The rising gas flow 19 of the gas generated in the furnace has a distribution as schematically shown in FIG. 3, and the mixture 20 is preferably supplied to a position where the flow velocity of the rising gas flow 19 is small. This allows
It is possible to achieve an addition yield comparable to a case where the mixture is formed into a lump and charged from a furnace chute. In addition, since the input amount during refining can be controlled by using the addition lance 5, there is little disturbance to the reaction in the furnace due to the input of dust, and stable operation is possible. Further, in the present invention, since there is no restriction on the specific components, the entire amount of generated dust can be recycled.

The carbon material used in the smelting reduction furnace is not particularly limited, but anthracite is suitable for smelting reduction in order to promote reduction, and anthracite is refined in slag, The carbonaceous material is suitable for the present invention because it is scattered as dust in the exhaust gas.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Dust contained in exhaust gas from a converter 1 is collected by a dust collector 12 shown in FIG. 1, and the dust is mixed with a Cr ore 18 to mix the dust and ore determined by the above formula (1). The smelting reduction smelting with a rate α of 0.5 or less was performed. First, in the raw material yard, the powdery Cr ore and the dust collected from the dust collector 12 are alternately placed on a pallet using an excavator.
It was loaded so as to have a ratio of 0.3 to 0.4. The dust used was the coarse particles shown in Table 1. The pallet on which the mixture was placed was transported from a raw material yard to an underground driving bunker, and the mixture was charged into a rotary kiln and dried. After being kept in the kiln for about 20 minutes, the water content of the mixture (powder) taken out was measured. The water content after drying was 0.3 to 0.7% by weight in fine weather and 1% in rainy weather.
It was about 1.9% by weight.

Next, the mixture whose water content was reduced to 2% by weight or less by the drying was used for smelting reduction smelting under the following conditions. The smelting reduction furnace is a converter type reaction vessel capable of blowing gas upward and downward, and has an addition lance 5 for the mixture. At this time, the flow rate of the top-blown oxygen gas was 550 Nm ³ /
And the bottom blown gas is oxygen: 50 Nm ³ from the furnace bottom tuyere.
/ Min, nitrogen: a mixed gas of 20 Nm ³ / min. At the time of melting SUS304, the iron source was 200kg /
At the time of melting SUS430, after charging 40 kg / t of scrap into the furnace in advance, the molten iron was reduced to 120 to 150 t.
I am charging. Also, during blowing, after confirming that the molten iron temperature became 1550-1570 ° C in the sub-lance,
The mixture is allowed to flow from 1000 to 1500
It was supplied at a rate of kg / min. At the same time, 70% of anthracite (Vietnamese, VM5.8%, HGI35)
It was charged into the furnace at a rate of 0 to 1000 kg / min. As the height of the lance, the O ₂ supply lance is 3.5 to 3.5 m above the molten iron surface.
4m, the lance 5 for adding the mixture is 3.5 to 5m from the molten iron surface
It is.

A large number of such refining operations are carried out, and the operation results are represented collectively in FIG. The data shown by the black circles in FIG. 4 is the embodiment of the present invention, while the data shown by the white circles is the Cr ore 18
This is the yield in the conventional example in which only 100% is added. FIG.
Thus, there is almost no difference between the embodiment (black circles) of the present invention and the yield (white circles) in which the Cr ore alone (100%), which has been conventionally used in the process, is charged. Obtained. In addition, the same investigation was performed on the yield of the carbonaceous material (C component 30%) in the dust, and it was found that the yield was equivalent to that of the carbonaceous material used in the process.

Subsequently, the molten metal obtained by the smelting reduction refining method according to the present invention is subjected to SUS using another converter.
304 and other stainless steels. As a result, conventionally unused dust can be recycled, and the recovery of Cr and Fe in the smelting reduction furnace has been improved by 4% and 5%, respectively, by recovering the metal content in the dust. Furthermore, the reduction yield of Cr ore is 3-4%.
Improved. Although the reason is not clear, it is considered that C in the dust had a favorable effect on the promotion of the reduction of the Cr ore by blowing the dust together with the Cr ore. As described above, conventionally, when recycling dust, a carbon material for dust reduction was required. However, according to the present invention, this carbon material has become unnecessary.

Using the same operating method as above, α = 0.6 to
A smelting reduction operation of 0.7 was also performed, and the operation results were similarly arranged in FIG. 4 by the addition yield of the Cr component. As a result, although the result is better than that of the conventional Cr ore, α =
The yield is slightly lower than in the case of 0.3 to 0.4. Also, the amount of scattering into dust increased at the same time, and it is considered that the scattering rate was increased by increasing α.

Subsequently, the mixture was operated under conditions of α = 0.3 to 0.4 while the mixture was dried with a rotary kiln during heavy rain. The water content after drying varies greatly from 1.5 to 2.5 wt% due to fluctuations in the raw material water content before the introduction. The results of this operation were not different from the results mentioned above,
Clogging in the lance and clogging in the hopper before the conveyor
Occurred about once a day. Therefore, after the mixture was blown in the operation for 4 to 5 charges, only the Cr ore was blown, and the operation for eliminating clogging with a lance or the like was performed for 1 to 2 charges. Although the operation could be continued by repeating such a thing, the total mixing ratio of dust was necessarily low.

Further, in order to further increase the amount of dust recycling, an operation for changing the particle size of the dust to be recycled was performed. Specifically, the residence time was extended by reducing the amount of water in the coarse particle separator 3 in FIG. 1, and the ratio of fine dust to total dust was increased. Table 3 shows an example of the particle size of the coarse dust at this time.

[0034]

[Table 3]

As shown in Table 3, the ratio of dust having a size of 100 μm or less is about 30% by weight. At this time, the clogging was expected to be larger than the conventional knowledge,
The amount of hot air in the kiln was increased to enhance drying. As a result, the moisture on the dry outlet side was 0.6 to 1.0 wt%. In addition, when the weather was rainy and the moisture on the exit side of the dryer was likely to be high, the mixing of dust was stopped. Although the Cr yield is shown in FIG. 4, it was as good as that of the above example. However, there was a tendency that the amount of scattering slightly increased and the generation of dust increased.

Although the above embodiment is directed to the case of smelting reduction refining for producing a mother molten steel before producing stainless steel, the present invention is not limited to this and can be used for refining, for example, high Mn steel.

[0037]

As described above, according to the present invention, dust having a high content of C and Cr generated in smelting reduction smelting can be recycled. As a result, smelting reduction smelting can be performed at a lower cost than in the past, and the price of stainless steel manufactured by using this method can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of equipment for implementing a smelting reduction smelting method according to the present invention.

FIG. 2 is a diagram showing a relationship between moisture of a dust and ore mixture and clogging of an addition lance.

FIG. 3 is a diagram illustrating an appropriate position of an addition lance in a converter.

FIG. 4 is a view showing a Cr addition yield in smelting reduction refining.

FIG. 5 is a diagram showing the influence of moisture on various characteristics of a powder mixture, (a) is the angle of repose of the powder mixture, (b) is the degree of compression, (c) is cohesive, and (d) is It shows the effect on liquidity.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Converter (metallurgical reaction vessel) 2 Dust recovery system 3 Coarse particle separator 4 Mixer (mixer) 5 Addition lance 6 Coarse particle dust 7 Fine particle dust 8 Thickener 9 Exhaust gas recovery system 10 Water tank 11 Concentration tank 12 Dust collector 13 Oxygen gas (oxygen) 14 Molten metal (Molten metal) 15 Top blowing lance 16 Piping 17 Drainage 18 Ore (Cr ore) 19 Updraft 20 Mixed powder (mixture)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiko Kimura 1 Kawasaki-cho, Chuo-ku, Chiba Kawasaki Steel Co., Ltd. (72) Inventor Koji Aida 1 Kawasaki-cho, Chuo-ku, Chiba Kawasaki Steel Technical Research In-house (72) Inventor Nozomi Tamura 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Corporation Chiba Works (72) Inventor Satoshi Saito 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Corporation Chiba Works, Ltd. (72) Inventor Hiroyasu Morioka 1 Kawasakicho, Chuo-ku, Chiba City Kawasaki Steel Corporation Chiba Works

Claims (9)

[Claims] 1. A carbon-containing substance and an ore are added to a molten metal held in a converter-type metallurgical reaction vessel, and an oxygen gas is blown onto a surface of the molten metal, whereby a molten metal containing a main component metal of the ore is removed. In the smelting reduction smelting method to be obtained, dust generated and collected during the smelting is mixed with the ore and added to the molten metal via a lance again. 2. Dust generated and recovered during the decarburization and refining of the molten metal obtained by the smelting reduction smelting in another converter type metallurgical reactor, and generated and recovered by the smelting reduction smelting. The smelting reduction smelting method according to claim 1, wherein the smelting reduction smelting is performed by mixing with the ore together with the produced dust. 3. The smelting reduction smelting method according to claim 1, wherein a mixing ratio of the dust and the ore determined by the following equation (1) is 0.5 or less. α = Dust weight / (ore weight + dust weight) ... (1) 4. The smelting reduction smelting method according to claim 1, wherein the mixture of the dust and the ore is dried. 5. The smelting reduction refining method according to claim 4, wherein the drying of the mixture is performed until the moisture content is 2% by weight or less. 6. The dust according to claim 1, wherein the exhaust gas from the converter type metallurgical reaction vessel is slurried by water treatment and rectified and separated from the slurry. The smelting reduction smelting method according to 1. 7. The smelting reduction smelting method according to claim 6, wherein the particle size distribution of the dust is reduced to 100% by weight or less by the rectification separation to 20% by weight or less. 8. The smelting reduction refining method according to claim 1, wherein the ore is a Cr ore. 9. The smelting reduction smelting method according to claim 1, wherein the carbon-containing substance is mainly anthracite.