JP3146066B2 - Method and apparatus for smelting reduction of steelmaking dust - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steelmaking dust recovered from the exhaust gas of a converter and a pickling scale recovered from a pickling process after rolling steel (hereinafter these are collectively referred to as steelmaking dust). The present invention relates to a smelting reduction method and an apparatus therefor.

[0002]

2. Description of the Related Art It has been known that steelmaking dust recovered from exhaust gas from a converter is melt-reduced in an electric furnace or the like for effective use. For example, there is a Seedaberg method in which steelmaking dust is briquetted and processed using Joule heat using an electric furnace of a self-firing electrode. This technique has a problem that the operation is not stable because briquettes are suspended on the shelves and gas is blown up, so that the sealed type cannot be used, so that there is no gas recovery advantage and the processing cost is high. As a DC arc furnace method, there is also known a technique in which steelmaking dust is dried and pulverized and treated using an arc in an electric furnace using a hollow electrode, but the dust loss is large, the gas recovery amount is small, and the cost is also low. Be up.

On the other hand, there is a technique for melting and reducing powdery ore using a vertical furnace, which is characterized by low power consumption, easy gas recovery and low dust loss. For example, in the Japanese Patent Publication No. 59-18452, the present applicant blows molten pre-reduced powder ore together with flux from a tuyere of a vertical smelting reduction furnace having a coke packed bed and a two-stage tuyere. We provide technology for reduction. Also,
As a similar technique, a method of recovering nonvolatile metal from dust containing metal oxide by providing a tuyere with plasma in a vertical furnace having a coke packed bed is disclosed in Japanese Patent Publication No. 60-555.
No. 74 discloses this. This technology uses a shaft furnace type smelting reduction furnace and blows fine ore from the tuyere into the coke packed bed using a plasma tuyere, and is said to be able to recover gas and operate on a commercial basis. However, the life of the plasma torch is as short as 240 hours,
There is also a problem that a large amount of electric power is used.

Further, a vertical furnace having a coke packed bed is provided with a two-stage tuyere, and powdery chromium ore and slag-making material are blown from the tuyere, and at the same time, a metal source, a carbon material and a slag-making material are blown from the furnace top. A method for producing chromium-containing hot metal into which slag is charged is disclosed in Japanese Patent Publication No. 1-59.
327, which is a technique in which tuyere blowing is used in combination with a cupola image. A similar technique is disclosed in
-54007, JP-A-1-294812,
JP-A-1-247535, JP-A-1-208842
No. 5, JP-A-1-240628, JP-A-2-40628
It is also disclosed in Japanese Patent No. 282433.

[0005]

However, there is known a technique in which steelmaking dust is blown from the tuyere of a vertical smelting reduction furnace having a coke packed bed and having two-stage tuyere, and only this is melted and reduced. Not. Steelmaking dust recovered from the exhaust gas from the converter and pickling scale recovered from the pickling process after rolling the steel are irregular particles with very fine particle size, and are recovered in a slurry state. Therefore, appropriate pretreatment is required.

In particular, fine powder in a gas generated when refining stainless steel or the like in a converter is very fine particles, and therefore must be wet-recovered in a slurry state. Such converter exhaust gas contains a lot of active ingredients, but in order to dry and recover this and efficiently melt-reduce it, technology development such as appropriate raw material adjustment, stable operation of the smelting reduction furnace, effective use of heat, etc. , And these organically integrated combinations only allow industrial-scale processing.

An object of the present invention is to provide a method for efficiently melting and reducing steelmaking dust recovered from the waste gas of a converter, pickling scale generated from a pickling process after rolling steel, and the like. Aim. The present invention basically belongs to a technology in which a raw material is blown from a tuyere of a coke packed bed vertical furnace and melt-reduced.

[0008]

According to the present invention, a steelmaking dust is granulated into physically aggregated spherical fine powder having an average particle size of about 60 μm, and the physically aggregated spherical fine powder is uniformly mixed with a flux fine powder. A method for smelting and reducing steelmaking dust, characterized in that molten steel is produced by blowing into the furnace from the upper tuyere of a packed bed two-stage tuyere vertical smelting reduction furnace and melting and reducing the steelmaking dust. Here, the physically agglomerated fine powder is a fine powder in which a single particle is simply aggregated physically to form an aggregate, and when it is exposed to a high-temperature atmosphere or the like, it is decomposed into the original particles and instantly dissolved. Say fine powder. Dust slurry collected from the exhaust gas of a converter for refining chromium steel is used as steelmaking dust, concentrated and spray-dried to produce physically aggregated spherical fine powder, which can be melt-reduced with high efficiency.

The apparatus of the present invention capable of suitably carrying out the present invention includes: (a) an apparatus for producing a physically aggregated spherical fine powder by spray-drying a converter dust wet-type dust collecting dust slurry; Mixing device for uniform mixing with flux fines. (C) Two-stage tuyere vertical smelting reduction furnace with coke packed bed. (D) Recuperator that burns exhaust gas from this furnace and uses tuyere blowing air as hot air. (E) Recuperator This is a smelting reduction device for steelmaking dust, which is provided with an exhaust heat utilization device that uses exhaust gas for spray drying.

[0010]

The steelmaking dust recovered from the exhaust gas from the converter has an average particle size of about 1 μm. In addition, the fluidity is poor because the granules have an irregular and complicated shape. It is collected in a slurry state. In the present invention, in the step of drying the steelmaking dust, the steelmaking dust is formed into a physically aggregated spherical fine powder simultaneously with the drying.

In the present invention, physical aggregation refers to maintaining a physically aggregated sphere by simply drying water from a spherical state due to the surface tension of a spray slurry without using a binder or the like. To tell. In such a physically agglomerated spherical fine powder, the agglomerated particles return to the original fine particle state in a high-temperature reducing atmosphere in front of the tuyere (raceway) of the smelting reduction furnace, and are instantaneously dissolved. The physically aggregated spherical fine powder of the present invention has an average particle size of about 60 μm.

The physically aggregated spherical fine powder can be obtained by spray-drying a slurry of fine powder having an appropriate concentration by a centrifugal spray dryer. That is, the device of the present invention that can suitably carry out the present invention is
The dust slurry can be appropriately adjusted in concentration and centrifugally spray-dried to produce a physically aggregated spherical fine powder.

Physically aggregated particles have good fluidity and are easy to handle. When such physically agglomerated particles are blown into the high-temperature raceway formed in the smelting reduction furnace, they are disintegrated and instantaneously melted as extremely small particles in the original particle state. It is reduced in a very short time in a reducing atmosphere. The reduction reaction in a smelting reduction furnace is mainly performed by direct reduction with coke. Therefore, the exhaust gas discharged from the smelting reduction furnace is a gas with extremely high CO. A recuperator that burns this gas and uses the tuyere blowing air as hot air is arranged to recover heat. In this case, the exhaust gas of the recuperator is used for spray drying.
Further, the exhaust gas may be directly used for spray drying. In any case, heat is utilized efficiently and comprehensively.

[0014]

1 is an overall flow sheet showing a method for smelting and reducing steelmaking dust according to an embodiment of the present invention. The examples can be roughly divided into (A) a raw material adjustment step of appropriately adjusting steelmaking dust to be blown into a coke packed bed smelting reduction furnace, (B) a smelting reduction step by a smelting reduction furnace, and (C) gas recovery and effective use. Gas recovery and heat utilization processes. Hereinafter, these will be described in detail. (A) Raw Material Adjusting Step FIG. 2 shows the details of the part A in FIG.

[0015] The dust 1 collected from the converter is collected in a storage tank 3 by a wedge wire screen except for foreign matter.
Then, it is sent to the centrifugal dehydrator 4 by a pump to be dehydrated, and then stored in the slurry storage tank 7. The rolled slurry 2 recovered from the pickling process after the rolling of the steel strip is adjusted to a slurry having an appropriate concentration through a repulp process 5 and stored in a slurry storage tank 7. The slurry whose concentration has been adjusted is sent to a spray dryer 10 through a pipe 9 by a pump 8. The slurry sent to the spray dryer 10 is dried and granulated by centrifugal spray drying. The hot gas of the burner 11 of the spray dryer uses the exhaust gas of the smelting reduction furnace.

FIG. 8 shows an example of the particle size distribution of dust and the particle size distribution of the particles formed in the spray dryer 10. In FIG. 8, a histogram 100 shows the particle size distribution of OG dust, and a curve 101 is a cumulative curve thereof. Particle size range 14μm ~ 0.2μm, average particle size about 1μ
m. The particle size distribution of particles 104 dried and granulated by centrifugal spray drying is represented by histogram 102 and cumulative curve 10.
3, the particle size range is 176 μm to 16 μm,
It becomes granular particles having an average particle size of about 60 μm. FIG. 7 shows the particles granulated simultaneously with the drying. FIG. 7 shows one of the particles 104 after drying and granulation in the spray dryer 10.
FIG. The dust is fine particles having a particle size of about 1 μm, and the granulated particles 104 have a particle size of about 60 μm.
Spherical particles. Such particles are physically aggregated particles that do not contain a binder and are highly crushable and have a water content of 1%.
Contains only the following. These particles have a substantially spherical shape, are very easy to handle, and can be blown with hot air from the tuyere of the smelting reduction furnace without causing clogging or the like in a transport pipe or a hopper. In addition, it has the property of being easily broken into original particles, quickly melted and reduced in the raceway in the furnace.

The particles collected at the bottom of the spray dryer 10 or the bottom of the gas separator 12 are collected in a storage tank 14.
On the other hand, dry dust 15 such as dust powder having a particle size of 2 mm or less is accumulated in the storage tank 17. Further, steel slag is stored in the storage tank 18. From these storage tanks 14, 17, and 18, rotary feeders 19 and 20 and screw feeders 2 are provided.
A predetermined amount is cut out using 1, foreign matter is removed by a screen 22, and is loaded into a weighing / equalizing hopper 23. The weighing / equalizing hopper 23 weighs these various powders and mixes them in a gas stream to adjust the blowing material. The mixing ratio of the slag is adjusted so that the basicity of the slag discharged from the furnace is 1.4 ± 0.1. The weighing / equalizing hopper 23 is the next lift tank 24
And supply the blowing material while equalizing the pressure. Lift tank 24
Is fluidized and blown together with a carrier gas into a tuyere of a smelting reduction furnace, and blown into the furnace through a lance. (B) Smelting Reduction Step In the vertical smelting reduction furnace 31, coke 34 is supplied from the furnace top via a furnace top hopper 33 to form a coke packed bed 34 in the furnace. The vertical smelting reduction furnace 31 converts the high-temperature air or the oxygen-enriched air 65 sent from the hot air generator into a pipe 38,
The gas is blown into the furnace from the upper and lower tuyeres 35 and 36 through the upper and lower stages 39 to form a raceway in the furnace by coke combustion. The raw material blown from the upper tuyere 35 via the lance 40 is melted and reduced in the raceway.
The smelted and reduced metal descends in the furnace and is discharged from a discharge port at the bottom of the furnace.

FIG. 5 shows the reaction mechanism in the smelting reduction furnace when the blowing material is blown from the upper tuyere 35.
FIG. 5 is a schematic partial cross-sectional view of the furnace illustrating a state in the furnace near the upper tuyere 35 and the lower tuyere 36 of the vertical furnace. FIG.
The various shapes depicted in are described in FIG. ▲ Fe ₂ O ₃ (S) State at the beginning of thermal dissociation ■ Fe ₃ O ₄ (L) State at the end of thermal dissociation

[0019]

[Outside 1]

The inside of the furnace is a packed bed of coke 34 drawn with hexagonal marks. Lance 4 inserted in upper tuyere 35
From 0, the raw material of the powder is supplied and is blown into the furnace together with the hot air blown from the tuyere 35 through the pipe 38. The still solid Fe ₂ O ₃ (S) has begun thermal dissociation, and the liquefied Fe ₃ O ₄ (L) is undergoing thermal dissociation. These are blown into a high-temperature raceway in front of the tuyere and melted to form molten FeO (melt), which is further reduced to reduced Fe (L) (molten state), and coke 34
Between layers.

The two-stage tuyere smelting reduction proceeds in a cylindrical region between the upper and lower tuyeres whose end face is a raceway cross section.
The powdery raw material blown from the upper tuyere 35 dissolves during flight and adheres to the coke surface. Coke in the vicinity of the raceway is swirling while holding the melt, and the blown raw material is assimilated into the melt. Since the blowing main material of the present invention is physically agglomerated particles having high crushability, it is easily melted in the raceway when blown into the furnace of the smelting reduction furnace through the lance 40 from the upper tuyere. FIG. 9 shows the relationship between the reduction reaction rate and the temperature. FIG. 10 shows the distribution of the gas temperature Tg with respect to the distance from the tuyere tip to the inside of the furnace, and
The results of calculating the temperature rising process of the raw material blown from the tuyere using the particle diameter as a parameter are shown. The temperature Ts of the particles in the inner wall of the raceway according to the particle size d _0, of Ts = 818 ° C. particle size d ₀ = 100 [mu] m when Ts = 294 ° C. particle size d ₀ = 250 [mu] m when the particle diameter d ₀ = 1000 .mu.m When Ts = 1398 ° C. When the particle diameter d ₀ = 50 μm, Ts = 1854 ° C. 9 and 10, in the smelting reduction using the steelmaking dust of the present invention, the temperature of the blown material blown from the tuyere rises almost instantaneously and is almost completely reduced while descending to the position of the lower tuyere. In this way, the smelting reduction of the present invention enables the smelting reduction of steelmaking dust efficiently.

Gas is discharged from the top of the smelting reduction furnace.
This gas 42 is a gas containing CO as a main component. Effective use of this gas is also important in the technology of the present invention. (C) Gas Recovery and Heat Utilization Process FIG. 4 is a process diagram of a process for utilizing the gas discharged from the smelting reduction furnace.

Exhaust gas 50 discharged from a vertical smelting reduction furnace
Is a gas containing CO as a main component. Characteristics of tuyere injected gas
CO-rich gas whose nitrogen content is determined by the condition
You. For example, CO: 50%, N_Two : 47%, H_Two : 3%,
Heat generation 1480 kcal / Nm ^Three Exhaust gas. Piping
51, the dry dust collector 52 and the wet dust collector 57
Is collected in the gas holder 60 and the energy source
Collect and use. Part 61 is the recuperator 6
2 for the burner 63 and the smelting reduction vertical furnace blades
The blow-in gas 64 is heated to produce hot air 65. Also,
Is used for the hot air generator of the spray dryer 10 described above. Les
Exhaust gas from the cuperator 62 is also sprayed through the pipe 66.
It is mixed with the hot air of the dryer 10 and used.

According to the embodiment, the internal volume is 300 m.
^3, blade talkative: 4 pcs × 2 stages, air volume: 350 Nm ³ / m
The smelting reduction furnace was used to perform smelting reduction of dust in the converter. Coke ratio: 1120 kg / t, furnace top gas amount:
It was possible to operate smoothly with 35,000 Nm ³ / h, furnace gas temperature: 750 ° C., metal production: 180 T / day, and slag discharge: 90 T / day.

FIGS. 11 to 13 are charts showing the operation results. The horizontal axis indicates the number of taps, and the vertical axis indicates the molten metal temperature (HMT), the amount of tapping / slag, and the amount of slag (FeO).
Is shown. In the embodiment, each element is stable.

[0026]

According to the present invention, fine and irregular particles such as steelmaking dust recovered from the exhaust gas from a converter and pickling scale recovered from a pickling process after rolling steel are used. ,
By subjecting the steelmaking dust collected in a slurry state to appropriate pretreatment, the steelmaking dust can be blown from the tuyere of a vertical smelting reduction furnace provided with a coke packed bed to perform highly efficient smelting reduction.

[Brief description of the drawings]

FIG. 1 is an overall flow sheet illustrating a method for smelting and reducing steelmaking dust according to an example.

FIG. 2 is a flow sheet of a pretreatment step for smelting reduction of steelmaking dust.

FIG. 3 is a flow sheet showing smelting reduction of steelmaking dust.

FIG. 4 is a flow sheet showing a heat recovery step of the smelting reduction method.

FIG. 5 is a schematic reaction diagram of a smelting reduction furnace.

FIG. 6 is an explanatory diagram of symbols in a schematic reaction explanatory diagram of the smelting reduction furnace.

FIG. 7 is a schematic perspective view of physically aggregated particles.

FIG. 8 is a graph showing the particle size distribution of steelmaking dust and the particle size distribution of the physically aggregated particles of the present invention.

FIG. 9 is a graph showing the relationship between temperature and reduction reaction rate.

FIG. 10 is a graph showing a process of raising the temperature of a raw material blown from a tuyere in a raceway.

FIG. 11 is a chart showing a molten metal temperature for each tap according to the example.

FIG. 12 is a chart showing tapping / slagging amounts for each tap according to the embodiment.

FIG. 13 shows (FeO) in slag for each tap in Example.
FIG.

[Explanation of symbols]

Reference Signs List 1 Converter exhaust gas wet dust collection dust 2 Rolling slurry 3 Storage tank 4 Centrifugal dehydrator 5 Repulp process 7 Slurry storage tank 6, 8 Pump 9 Piping 10 Spray dryer 11 Burner 12 Gas separator 13 Air flow transport pipe 14 Storage tank 15 Dry dust 16 Decarburization Slag 17 Storage tank 18 Storage tank 19, 20 Rotary feeder 21 Screw feeder 22 Screen 23 Measuring / equalizing hopper 24 Lift tank 31 Vertical smelting reduction furnace 32 Coke charging conveyor 33 Furnace top hopper 34 Coke packed bed 35 Upper tuyere 36 Lower tuyere 38, 39 Piping 40 Lance 42 Gas 50 Exhaust gas 51 Piping 52 Dry dust collector 57 Wet dust collector 60 Gas holder 61 Some gases 62 Recuperator 63 Burner 64 Cold air 65 Hot air 66 Piping

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tsuneo Aihara 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Corp. Inside Chiba Works (72) Inventor Yoichi Watanabe 1-1-1 Kawasaki-cho, Chuo-ku, Chiba Kawasaki Steel Corp. Inside Chiba Works (72) Inventor Tsuneya Hasegawa 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Works Ltd. Inside Chiba Works (56) References JP-A-5-311253 (JP, A) JP-A-5-9529 ( JP, A) JP-A-5-271735 (JP, A) JP-B-7-26160 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21B 11/00-13/00 C22B 1/14 C22B 5/10

Claims (3)

(57) [Claims] 1. A steelmaking dust is granulated into physically aggregated spherical fine powder having an average particle diameter of about 60 μm, and the physically aggregated spherical fine powder is uniformly mixed with a flux fine powder. A method for smelting and reducing steelmaking dust, comprising blowing molten steel from the upper tuyere of the smelting reduction furnace into the furnace to melt and reduce the steelmaking dust to produce hot metal. 2. The method for smelting and reducing steelmaking dust according to claim 1, wherein the converter exhaust gas wet dust collected dust slurry is concentrated and spray-dried to produce physically aggregated spherical fine powder. 3. An apparatus for producing a physically aggregated spherical fine powder by spray-drying a converter exhaust gas wet dust dust slurry, a mixing apparatus for uniformly mixing the spherical fine powder with a flux fine powder, and a two-stage tuyere vertical coke packed bed. A smelting reduction furnace, a recuperator that burns exhaust gas from the furnace to generate tuyere blowing air as hot air, and an exhaust heat utilization device that uses the exhaust gas from the recuperator for spray drying. Smelting reduction equipment for steelmaking dust.