JP2001271107A - Method for treating iron manufacturing dust in vertical smelting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of piled powder in a furnace caused by solid material mainly composed of carbon contained in iron manufacturing dust blown from an upper step tuyere into a coke packed layer in a vertical smelting furnace. SOLUTION: The solid mainly composed of carbon in the iron manufacturing dust blown from the upper step tuyere 1A is supplied by controlling the grain diameter to be not larger than the upper limit grain diameter by which the grains are ascended together with exhaust gas in a furnace top space formed on the packing layer 3 of the verticals melting furnace 1 and able to be exhausted out of the furnace top. The piling of the powdery carbon solid in the packing layer 3 of the vertical smelting furnace 1 is prevented and the gas ventilation in the furnace is improved and since the gas is smoothly exhausted out of the furnace accompanied with the ascended exhaust gas in a space of the furnace top formed on the stock line of the packing layer 3, the good operation is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a vertical melting furnace having two upper and lower tuyeres, forming a packed layer of carbonaceous solid reducing material in the furnace and supplying iron-making dust from the upper tuyeres. The present invention relates to a method for treating iron-making dust by a vertical melting furnace.

[0002]

2. Description of the Related Art Self-generated scrap generated in the steel making process of steelworks has a clear nature and contains a small amount of impurities, so that most of the scrap is recycled to a converter or the like as an iron source in a generating plant. On the other hand, secondary processing scrap or waste scrap separated and collected in the process of secondary processing of steel products and final products contains a large amount of surface-treated steel sheets and special steel scraps, so their characteristics are low. It is unclear and contains many impurities. Many of these are usually refined in electric furnaces and reused.

[0003] Electric furnace dust generated when refining scrap in an electric furnace contains about several percent of elements, such as chromium, cadmium, and lead, which are eluted when landfilled and disposed and cause environmental pollution. Therefore, as a technology for inexpensively fixing harmful metals such as chromium, cadmium and lead to recover and recycle valuable metals such as zinc and iron, a method using a vertical melting furnace with two upper and lower tuyeres is known. Are known.

For example, Japanese Patent Application Laid-Open No. 8-325646 discloses that a packed bed of a carbonaceous solid reducing material is formed in a vertical melting furnace having two upper and lower tuyeres and at least electric furnace dust is discharged from the upper tuyeres. Blowing, reducing and evaporating zinc contained in the electric furnace dust, and collecting the zinc by cooling the exhaust gas containing the evaporated zinc outside the furnace, thereby recovering zinc. Is disclosed.

In addition to the electric furnace dust, steelmaking dust, converter dust, blast furnace dust, and sludge (hereinafter referred to as metal oxide dust mainly generated in steel works,
Attempts have also been made to inject sludge (simply called steelmaking dust) and recover it as molten metal.

[0006]

Some iron-making dusts contain a large amount (about 20% by mass) of carbon powder. When such ironmaking dust is supplied from the upper tuyere of the vertical melting furnace, this carbon powder can be used as an auxiliary fuel, which is advantageous for maintaining the inside of the vertical melting furnace at a high temperature. Therefore, in accordance with the method for treating electric furnace dust using a vertical melting furnace disclosed in Japanese Patent Application Laid-Open No. 8-325646, ironmaking dust containing about 20% by mass of carbon powder is supplied from the upper tuyere of the vertical melting furnace. Tried to do.

[0007] As a result, sedimentary powder which is considered to be caused by iron-making dust powder is formed in the massive carbonaceous solid reducing material packed bed filled in the vertical melting furnace, and this sedimentary powder impairs air permeability in the furnace. It was confirmed that. As a result of industrial analysis by sampling the deposited powder formed in the furnace,
As shown in Table 1, the main component was found to be a carbon-based solid.

[0008]

[Table 1]

[0009] In order to elucidate the cause of the formation of the sedimentary powder, the particle size distribution of the carbon-based solids contained in the used steelmaking dust, the sedimentary powder inside the furnace of the vertical melting furnace and the powder discharged outside the furnace was investigated. As a result, from the particle size (mm) of the carbon-based solid particles and the mass ratio (mass%), each particle size distribution as shown in FIG. 2 was obtained, and the particle size of the carbon-based solid in the powder deposited in the furnace was obtained. Has a particle size larger than that of other steelmaking dusts and powders discharged outside the furnace. Thus, when ironmaking dust containing carbon powder is supplied into the furnace from the upper tuyere, carbon-based solids present in the ironmaking dust having a large particle size remain in the furnace and form sedimentary powder. It was estimated that.

According to the present invention, when ironmaking dust containing a carbon-based solid is supplied from at least the upper tuyere of a vertical melting furnace,
The purpose of the present invention is to prevent the formation of sedimentary powder due to a carbon-based solid having a large particle diameter in ironmaking dust in a carbonaceous solid reducing material packed bed in a vertical melting furnace.

[0011]

Means for Solving the Problems In order to achieve the above object, the present inventor has conducted intensive studies and has studied the terminal velocity of carbon-based solid particles in a furnace top space formed on a packed bed of a vertical melting furnace. It was found that the maximum particle size of the carbon-based solid that can be discharged from the furnace top together with the exhaust gas to the outside of the furnace without staying in the furnace can be estimated based on the above, and the present invention has been completed.

In order to achieve the above object, the present invention uses a vertical melting furnace having two upper and lower tuyeres, in which a packed bed made of massive carbonaceous solid reducing material is formed, and at least an upper stage is formed. In the method for treating iron-making dust by a vertical melting furnace for supplying iron-making dust from tuyeres, the particle size of the powdery carbon-based solid contained in the iron-making dust is formed on a packed bed of the vertical melting furnace. This is a method for treating iron-making dust in a vertical melting furnace, characterized in that the inside of the furnace top space is raised along with the exhaust gas and supplied to the furnace at a particle size equal to or less than an upper limit particle size that can be discharged from the furnace top to the outside of the furnace.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the configuration of a vertical melting furnace suitable for treating ironmaking dust according to the present invention. FIG.
The specifications of the vertical melting furnace 1 are as follows: furnace inner diameter: 1.2 mφ, furnace height: 8.0 m, number of tuyeres: upper three, lower three, tuyere diameter: 1
00 mm. In the vertical melting furnace 1, a packed bed 3 is formed by supplying coke having an average particle size of 15 mm as a massive carbonaceous solid reducing material from a carbonaceous material hopper 2. Ironmaking dust having a chemical composition as shown in Table 2 containing a powdery carbon-based solid at about 15 to 20% by mass includes smelting of limestone and silica stone added for the purpose of adjusting the viscosity and melting point of slag. The molten material is previously mixed at a predetermined ratio, and is blown into the furnace from the powder blowing device 4 through the upper tuyere 1A of the vertical melting furnace 1.

[0014]

[Table 2]

The blast air is heated to about 800 to 1000 ° C.
Hot air is blown into the furnace from the upper tuyere 1A and the lower tuyere 1B through a blower tube. At that time, an appropriate amount of oxygen gas is supplied into the hot air as needed, and coke is burned in the vertical melting furnace 1. The iron oxide dust blown from the upper tuyere 1A by the combustion heat and the reducing gas at that time. Is melted.

In this case, under the operating conditions shown in Table 3, the unburned carbon-based solids in the iron-making dust blown through the upper tuyere 1A pass upward through the packed bed 3 of coke. Rises in the furnace top space formed on the stock line with the exhaust gas.

[0017]

[Table 3]

Metal oxides (Fe, Cr, Ni,
(Including Zn, Pd, etc.) is the upper tuyere 1A due to the combustion heat of coke
The melt produced by melting in the tuyere tip raceway descends the packed layer 3 toward the lower tuyere 1B, and in the process, the lower tuyere
While being reduced in countercurrent contact with the reducing gas generated at the tuyere of 1B, the gas is brought into contact with the coke of the packed bed 3 during the dropping and is separated into molten metal (hot metal) 14 and slag 15. The molten metal 14 finally collected in the hearth is discharged from the tap hole 6 and the slag 15 is discharged from the slag port 7, and at this time, Cr and the like are fixed in the molten metal 14 and made harmless. .

[0019] Zn oxide contained in the iron-making dust blown into the vertical melting furnace 1 from the upper tuyere 1A is reduced to Zn vapor, passes through the coke packed bed 3, and passes through the space at the furnace top together with the exhaust gas. It is discharged to the exhaust gas duct 10. Since the amount of Zn in the iron-making dust is very small (see Table 2), the Zn treatment is performed in accordance with the later-described treatment of an electric furnace dust with a large amount of Zn, and therefore the description thereof is omitted here.

When ironmaking dust containing a carbon-based solid is blown into the furnace from the upper tuyere 1A to perform smelting, the carbon-based solid as shown in Table 1 is mainly contained in the packed bed 3 as described above. The air permeability in the furnace is reduced by the deposited powder. We thought that all carbon-based solids would be consumed by combustion and reactions in the furnace,
It was found that there was unreacted one. As shown in FIG. 2, the carbon-based solids in the iron-making dust have a particle size of approximately 1.4 mm or less as shown by a two-dot chain line, and the mass ratio (mass%) of the fine particles is very high. The rest is 0.5m particle size
Those smaller than m have a gentle particle size distribution slightly larger than those larger. As shown by the solid line, the carbon-based solids in the powder deposited in the furnace have a particle size distribution within a range of 1.4 mm or less, and have a mountain-shaped distribution with a peak of 0.8 mm in particle size. The solid is 0.6 m
The peaks below 0.2 m indicate a mountain-shaped distribution with a peak at 0.2 mm and biased to the smaller particle size side.

As described above, the particle diameter of the carbonaceous solid deposited in the furnace has a distribution larger than the particle diameter of the carbonaceous solid of the ironmaking dust and the powder discharged outside the furnace. Under the operating conditions shown in Table 3 above, the terminal speed at which the carbon-based solid particles rising along with the exhaust gas in the furnace top space formed on the packed bed 3 of the vertical melting furnace 1 can be discharged from the furnace top to the outside of the furnace. _Ut is given by the following equation (1)
Calculated according to, it was also calculated respectively according to the equation the maximum particle diameter D _t of the terminal velocity U _t possible discharged from the furnace top out of the furnace a carbonaceous solid particles (2).

U _t = √ (2m (ρP-ρg) g / (C ・ ρ ・ ρg ・ A))…… （１ (1) D _t = [2 〔(2m (ρP-Pg) g / (π · C · ρP · ρg)) ] / U _t ...... (2) where, m: particle mass (kg / pieces), ρP: particle density (kg / m
³ ), ρg: gas density (kg / m ³ ), g: gravitational acceleration (m / se
c ² ), A: particle cross-sectional area (m ² ), Re: number of Reynolds nozzles (−), C: resistance coefficient (−), C value: Re ≦ 5.7
6/24 / Re, 5.76 <Re ≦ 517/10 / Re ^0.5 , 517 <
Re was 0.44.

As a result of the calculation, the terminal speed U _t = 1.47 m / se
c, the particle upper limit particle diameter D _t was 0.0006 m. Terminal speed U
Between the upper diameter D _t of _t and the carbon-based solid particles correlates almost direct proportion as shown in FIG. 3, the carbon-based solid particles as an upper limit particle diameter D _t of carbonaceous solid particles is increased The terminal speed _Ut increases. That is, the terminal velocity U _t of carbonaceous solid particles is calculated based on the equation (1), in the operating conditions shown in Table 3, as shown in FIG. 3, gas furnace top space velocity U _g = 1.47m / sec, and using this value,
The upper limit particle diameter of the carbon-based solid particles that can be discharged from the furnace top to the outside of the furnace calculated based on the above equation (2) is D _t = 0.6 mm.

Therefore, when the carbon-based solid blown from the upper tuyere 1A exceeds the upper limit particle diameter D _t = 0.6 mm, it cannot smoothly pass through the packed bed 3 and accumulates in the furnace. It becomes difficult to stay in the space and be discharged out of the furnace. Under these conditions, the carbon-based solids in the iron-making dust were sized to reliably discharge the carbon-based solid particles from the furnace top to the outside at a gas velocity U _g of the furnace top space of 1.47 m / sec.
We decided to use it below 0.6mm.

Ironmaking dust containing a carbon-based solid having a particle size of 0.6 mm or less has a smelting material composed of limestone and silica added in a predetermined ratio in advance to adjust the viscosity and melting point of slag. Under the operating conditions shown in Table 3, the operation of blowing the powder from the powder blowing device 4 into the furnace through the upper tuyere 1A of the vertical melting furnace 1 was performed. Upper tuyere 1A of vertical melting furnace 1
This prevents powdery carbon-based solids present in the iron-making dust blown from accumulating in the packed bed 3. The gas permeability in the furnace is reduced by improving the gas permeability in the furnace, and the carbon-based material having a particle size of 0.6 mm or less accompanying the exhaust gas rising in the furnace top space formed on the stock line of the packed bed 3 is reduced. The solid was smoothly discharged out of the furnace together with the exhaust gas from the furnace top without staying in the furnace.

The carbonaceous solids present in the steelmaking dust blown from the upper tuyere 1A serve as auxiliary fuel and serve as an auxiliary fuel.
It generates heat by burning due to the hot air blown from it, and the radiant heat promotes the heating of the steelmaking dust. Further, this heat amount is used as an auxiliary heat amount of coke that falls downward from the upper tuyere 1A, and promotes the reduction of iron oxide of iron-making dust and also serves as a substitute for coke in the packed bed 3, so that the coke ratio is reduced. You.

The operation of injecting ironmaking dust from the upper tuyere 1A is performed smoothly, and the temperature of the hot metal rises due to a rise in the temperature of the packed bed 3, so that the hot metal 14 and the slag 15 are removed from the taphole 6 and the slag. It was possible to discharge stably from the mouth 7. As shown by the solid line in FIG. 4, according to the method of the present invention, the pressure loss in the furnace (ΔP / V, ΔP / V,
Here, ΔP: pressure difference, V: volume) were reduced. The pressure loss in the furnace is ΔP / V = 3.11 and the standard deviation δ in the conventional method.
= 0.116, whereas in the method of the present invention, ΔP / V =
2.75, standard deviation δ = 0.030. As a result, it has become possible to continue stable operation of the vertical melting furnace in which deposition of carbon-based solids in the furnace is not observed.

The operation of the vertical melting furnace using electric furnace dust is basically the same as the case of using the ironmaking dust. As shown in Table 4, electric furnace dust contains a large amount of Zn at the level of 30% by mass, so in the treatment of electric furnace dust with a vertical melting furnace, the treatment of Zn contained in the exhaust gas is strictly performed. Will be

[0029]

[Table 4]

As shown in FIG. 1, oxidation contained in the electric furnace dust blown into the vertical melting furnace 1 from the upper tuyere 1A.
Zn is reduced to Zn vapor, passes through the coke packed bed 3, and is discharged from the space at the furnace top together with the exhaust gas to the exhaust gas duct 10. In the upper part of the vertical melting furnace 1, a secondary combustion lance 5 is provided.
Are arranged, and by burning exhaust gas, 600
Maintained at ~ 1000 ° C.

Exhaust gas containing dust mainly containing Zn (including carbon and ash) discharged from the upper part of the vertical melting furnace 1 is discharged from the secondary gas provided in the middle and at the end of the exhaust gas duct 10. The fuel is burned by oxygen or air supplied from the combustion burners 8 and 9, and the temperature is ensured to prevent ZnO from adhering to the inner surface of the duct as Zn vapor and to increase the concentration of Zn in the dust to increase the cooling tank 11. To be introduced.

The exhaust gas is cooled in the cooling tank 11 by spraying water from a water spray nozzle 12 for supplying ring water, and the high Zn concentration-containing dust contained in the exhaust gas is collected in a slurry liquid 13. The exhaust gas cooled in the cooling tank 11 is led to an exhaust gas system, and the dust settled at the bottom of the cooling tank 11 is transported to a slurry processing system as slurry dust by suspension with cooling water.

In the present invention, it is possible to treat as a mixture of ironmaking dust and electric furnace dust, and it is also possible to treat various dusts including powdered carbon-based solids. Further, a carbon-based solid such as pulverized coal can be used as an auxiliary fuel. In any case, necessary to the particle size of the powdery carbonaceous solid containing the furnace top space less elevated diameter outside the furnace to be discharged upper limit particle from the furnace top D _t with the exhaust gas Is as described above.

If necessary, in addition to the upper tuyere, a carbon-based solid serving as an auxiliary fuel may be blown from the lower tuyere 1B in the same manner, and the particle size may be adjusted here. It is similar to the case of tuyeres.

[0035]

As described above, according to the present invention, at least the particle size of the powdery carbon-based solid contained in the ironmaking dust supplied from the upper tuyere is reduced on the packed bed of the vertical melting furnace. Since the inside of the furnace top space that is formed rises together with the exhaust gas and is supplied with a particle size equal to or less than the upper limit particle size that can be discharged from the furnace top to the outside of the furnace, powdery powder is contained in the packed bed of massive carbon material filled in the vertical melting furnace. The deposition of carbon-based solids can be prevented, and the air permeability in the furnace is improved. Good because the carbon-based solids accompanying the exhaust gas rising in the furnace top space formed on the stock line of the packed bed are smoothly discharged out of the furnace together with the exhaust gas from the furnace top without staying in the furnace. Operation is achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a vertical melting furnace for injecting steelmaking dust according to the present invention together with an auxiliary device.

FIG. 2 is a graph showing a comparison of the particle size distributions of the in-furnace powder, out-of-furnace powder and iron-making dust according to the conventional method, and the dust used in the method of the present invention.

FIG. 3 is a graph showing a relationship between a gas velocity U _{g in a} furnace top space and an upper limit particle diameter D _t of carbon-based solid particles.

FIG. 4 is a graph showing a comparison of a time transition of a furnace pressure loss (ΔP / V) between a conventional method in which ironmaking dust is directly blown and a method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vertical melting furnace 1A Upper tuyere 1b Lower tuyere 2 Carbon material hopper 3 Packing bed 4 Powder injection device 5 Secondary combustion lance 6 Tap hole 7 Slag outlet 8, 9 Secondary combustion burner 10 Exhaust gas duct 11 Cooling Tank 12 Water spray nozzle 13 Slurry liquid 14 Molten metal 15 Slag

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Uchiyama 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. 4K001 AA10 BA14 DA05 EA03 GA06 GB01 GB03 HA01 4K002 AA10 AB01 AB04 AC06 AD05 BA09 4K012 CA05 CA10

Claims (1)

[Claims] 1. A vertical melting furnace having two upper and lower tuyeres, in which a packed layer made of massive carbonaceous solid reducing material is formed, and at least ironmaking dust is supplied from at least the upper tuyeres. In the method of treating iron-making dust by a mold melting furnace, the particle size of the powdery carbon-based solid contained in the iron-making dust is accompanied by the exhaust gas in the furnace top space formed on the packed bed of the vertical melting furnace. A method for treating iron-making dust in a vertical melting furnace, wherein the iron-making dust is supplied with a particle diameter of not more than an upper limit particle size that can be raised and discharged from the furnace top to the outside of the furnace.