JP2803501B2 - Recovery method of zinc in 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 method for recovering zinc in dust, and more particularly to a method for efficiently recovering zinc in dust generated from an ironworks.

[0002]

2. Description of the Related Art From steelworks that produce iron using iron ore and scrap as raw materials, blast furnace slag as a cement raw material and converter slag that can be used as a landfill material and a roadbed material are produced as by-products. can get. Furthermore, blast furnace dust or converter dust containing a large amount of iron is generated from an ironworks. In the steel mill, after separating the zinc component from these dusts, it is mixed with the iron ore raw material, or the dust is mixed with the sintering raw material little by little to reduce the zinc concentration, and then used as a blast furnace raw material. We are trying to recycle dust.

[0003] However, there is a problem that the increase and accumulation of zinc components which hinder the recycling of dust cannot be avoided. The main sources of zinc brought into the steel mill are iron ore and galvanized steel as scrap.

At present, a considerable amount of scrap is being accumulated in countries that consume large amounts of iron. In the future, from the viewpoint of promoting the recycling of resources against the background of global environmental problems, steelworks must further increase the amount of scrap used. Must be increased. Therefore, it is expected that the amount of zinc brought into the steelworks will surely increase.

[0005] In the total amount of dust generated from steelworks,
The proportion of blast furnace dust and converter dust reaches more than 60%. The main components of blast furnace dust are carbon and iron oxide,
The main component of the converter dust is iron oxide, and the zinc content of each is 0.1 to 3.0 wt.%.

Particularly important when recycling dust as a raw material for a blast furnace is to strictly control the amount of zinc returned to the blast furnace. At present, the amount of zinc entering the blast furnace is controlled to 0.1 kg or less per ton of pig iron.

The reason why the amount of zinc entering the blast furnace is strictly controlled is as follows. That is, the zinc component in the blast furnace raw material is reduced in the blast furnace to metal zinc. The melting point of metallic zinc is 420 ° C and the boiling point is 920 ° C, but the temperature in the height direction of the blast furnace is 200 °
It is distributed in the range from ℃ to the hot metal (molten pig iron) temperature of 1500 ℃. The zinc metal melts at 420 ° C. in the blast furnace, evaporates at 920 ° C., and rises in the blast furnace together with the reducing gas in the furnace. A part of this metal zinc vapor is discharged outside the furnace together with the blast furnace gas, and another part is
During the process of rising to 420 ° C, it adheres to the furnace wall in liquid or solid form. In this manner, the metallic zinc circulates vertically in the vicinity of the position of 420 ° C. to 920 ° C. in the blast furnace, and as a result, the adhesion to the furnace wall proceeds. The metal zinc that adheres to the furnace wall and grows worsens the air permeability inside the furnace,
The furnace malfunctions. For the above reasons, the amount of zinc entering the blast furnace is strictly controlled.

[0008] As described above, dust is recycled in steel works. However, when the zinc concentration in dust increases as the amount of scrap used increases, zinc components are separated and recovered from dust. May not be able to cope with the dezincing treatment, or the use as a sintering raw material may be restricted. For this reason, the amount of dust that cannot be processed increases and dust recycling does not proceed. Therefore, efficient recovery of zinc in dust is a very important issue for smooth recycling of dust.

Japanese Patent Application Laid-Open No. 58-144437 discloses, as a prior art, a method for recovering zinc in dust as described below. The prior art will be described below with reference to the drawings.

FIG. 4 is a process chart showing the prior art. In FIG. 4, 1 is a dust hopper containing zinc-containing dust 2 mainly composed of iron oxide, 3 is a mixed iron wheel storing hot metal 4, 5 is an upper blowing lance, and 6 is a dust hopper 1 A gas blow-in pipe for transporting dust 2 for transporting dust 2 for transporting dust and the like, such as oxygen and / or air;
7 is a dust transport pipe connected between the upper blowing lance 5 and the gas blowing pipe 6, 8 is a hood attached to the opening of the mixed iron wheel 3, 9 is a wet separation device, and an inlet 9A. Is supplied from the outlet 9B, the water level is constantly maintained, and the gas in the apparatus is recovered from the discharge pipe 9C. 10 is a duct connected between the hood 8 and the wet separation device 9 and 11 is a duct 10
Is a suction fan installed in the middle of the process.

The dust 2 in the dust hopper 1 is blown into the hot metal 4 in the mixed iron wheel 3 by the gas blown from the gas blowing pipe 6 through the dust transport pipe 7 and the upper blowing lance 5. In this way, the iron oxide in the dust 2 blown into the hot metal 4 together with the gas and the zinc oxide deposited on the surface of the iron oxide are reduced by the carbon in the hot metal 4 and a part of the iron is reduced. Is dissolved in the hot metal 4, while the vaporized zinc enters the wet separation device 9 through the hood 8 and the duct 10 together with the iron not melted in the hot metal 4 by the suction fan 11. Thus, the wet separation device 9
The iron and zinc that have entered are re-oxidized here, and are separated as oxides, respectively, by the difference in specific gravity.
In the container 12, and zinc oxide lighter in specific gravity than iron oxide,
Each is separately collected in the container 13.

[0012]

However, the above-mentioned prior art has the following problems. That is, in order to blow the dust 2 into the hot metal 4 from the upper blowing lance 5,
Use a large amount of gas. By blowing the dust 2 in the state of fine powder into the hot metal 4 together with the gas in this way, bubbles mixed with dust are generated in the hot metal 4. When the bubbles containing the dust float on the liquid surface of the hot metal 4 and burst, the dust in the bubbles floats on the hot metal 4. In this way, the dust floating on the hot metal 4 is collected from the discharge pipe 9C without being dissolved in the hot metal. Therefore, zinc recovery efficiency is poor.

Accordingly, an object of the present invention is to increase the amount of iron oxide in dust recovered as iron, and as a result, it is possible to increase the concentration of reduced and vaporized zinc,
Another object of the present invention is to provide a method for recovering zinc in dust, which can promote a desiliconization reaction by iron oxide in hot metal.

[0014]

According to the present invention, a zinc-containing dust containing iron oxide as a main component is charged into hot metal in a hot metal pot, and the iron oxide in the dust is reduced in the hot metal,
It recovered in the hot metal, and the zinc oxide in the dust reduction, vaporized, thus consists in recovering zinc vaporized as a zinc oxide, in the method for recovering zinc in the dust, cold the dust Pellet or call
It is characterized in that it is granulated into dobriquettes and this granulated dust is charged into the hot metal pot simultaneously with the hot metal.

[0015]

According to the method for recovering zinc in dust of the present invention, instead of blowing zinc-containing dust containing iron oxide as a main component into hot metal from an upper blowing lance, the dust is necessary for handling cold pellets or briquettes. Granulated into agglomerates having sufficiently high strength, such granulated dust is poured into a hot metal ladle at the same time as hot metal, compared to the prior art in which powder dust is blown into hot metal, the following: It has the following advantages.

By injecting the granulated dust into the hot metal without using a carrier gas, there is little possibility that the dust jumps out of the hot metal as in the prior art. By introducing the granulated dust into the hot metal at the same time as the hot metal, the effect of dispersing the granulated dust into the hot metal is enhanced. When the dust is granulated into cold pellets, the moisture contained in the cold pellets, which is derived from the hydrate formed at the time of pellet formation, turns into steam by contact with the hot metal and expands in volume. Thereby, the cold pellets are finely and uniformly pulverized and dispersed in the hot metal. Therefore, the effect of dispersing the dust in the hot metal is further enhanced. This effect is similar for cold briquettes
It is.

As described above, by simultaneously adding the granulated dust and the hot metal to the hot metal pot, the effect of dispersing the dust in the hot metal is enhanced, and the contact efficiency between the iron oxide in the dust and the hot metal is increased. As a result, the desiliconization reaction, dephosphorization reaction, and reduction reaction by the iron oxide in the hot metal are promoted, so that the dissolution of iron in the dust is promoted. As a result, the amount of dust collected after being charged into the hot metal is reduced as compared with the prior art. However, almost the whole amount is reduced by the carbon in the hot metal and the carbonaceous reducing agent in the granulated dust in the original dust,
As a whole, the zinc concentration in the dust collected from the hot metal pot is higher than in the prior art, since the content of zinc which evaporates, is reoxidized in the gas phase and is recovered does not change.

If the collected dust is re-granulated and the re-granulated dust is repeatedly charged into the hot metal pot in the same manner as described above, the zinc concentration in the dust is further increased.

[0019]

Next, the method for recovering zinc in dust according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a process diagram of an embodiment of the method for recovering zinc in dust according to the present invention. In FIG. 1, 14 is
Dust hopper divided into first to fourth hoppers, 15
Is a converter dust stored in the first dust hopper 14A; 16 is a binder hopper storing Portland cement A and granulated blast furnace slag B as a binder; 17 is a mixer; 18 is a pan pelletizer; Is a rapid curing machine, 20 is a dryer, 21 is a cold pellet hopper, 22 is a hot metal pot into which cold pellets 23 and hot metal 24 are simultaneously injected, and 25 is a dust collecting duct installed above the hot metal pot 22. And 26 are dust collectors to which the dust collection duct 25 is connected, 27
Is a blower, and 28 is a dust distributor.

The converter dust 15 stored in the first hopper 14A is sent to the mixer 17 together with the binder in the binder hopper 16 to be mixed. The mixture of the dust 15 thus obtained and the binder is supplied to a pelletizer.
It is sent to 18 and granulated into pellets having an average particle size of 15 mm or less. The pellets granulated in this way are used in a rapid curing machine.
19 for 10 hours in a steam atmosphere of 120 ° C or more,
It is steam-cured and then heated to a temperature of 150 ° C. or more by the dryer 20 and dried.

The cold pellets 23 thus prepared are stored in a cold pellet hopper 21 and are poured into a hot metal pot 22 at the same time as the hot metal 24 in an appropriate amount. Cold pellets 23 injected simultaneously with hot metal 24
Has a lower specific gravity than the hot metal 24,
It is caught in the flow and is sufficiently dispersed in the hot metal 24. When the cold pellets 23 are dispersed in the hot metal 24, the water contained in the cold pellets 23 as crystallization water becomes steam.
As a result , the cold pellets 23 are finely and uniformly pulverized and dispersed in the hot metal 24.
This phenomenon occurs in cold briquettes as well.
You.

The iron oxide in the converter dust 15 reacts with silicon in the hot metal and is reduced to iron. Silicon is oxidized to SiO ₂ . This SiO ₂ forms a stable compound with blast furnace slag or cement CaO added as a binder to the cold pellets 23 and floats on the hot metal in the hot metal pot 22 as slag. Iron oxide is also reduced by the carbon in the molten iron and is recovered in the hot metal as iron. Zinc oxide is reduced and evaporated by the carbon in the molten iron, and oxidized in the air to form fine zinc oxide particles of 10 μm or less. At this time, the evaporated iron and powdered cold pellets are floating in the air, and are collected together with the zinc oxide particles from the dust collection duct 25 into the dust collector 26.

Although the zinc concentration in the dust collected by the dust collector 26 is higher than the zinc concentration in the cold pellets 21 before being charged, the zinc concentration in the dust is further increased by the dust collector 26 in order to further increase the zinc concentration in the dust. The collected dust is again stored in the second hopper 14B via the distributor 28, and the same operation as described above is repeated. Thereby, the first hopper
The zinc concentration in the dust increases in the order of 14A, the second hopper 14B, the third hopper 14C, and the fourth hopper 14D. Then, the zinc concentration in the dust finally collected in the hopper 14E from the dust collector 26 becomes 58%, which is much more concentrated than the zinc concentration of the original converter dust of 0.1 to 3%. FIG.
Figure 2 shows the transition of zinc concentration. As is clear from FIG.
It can be seen that the zinc concentration in the dust increases each time it is reused. FIG. 3 shows the desiliconization effect. 10 tons of cold pellets 21 are put into a hot metal pot 22 simultaneously with 250 tons of hot metal 24. As a result, as is apparent from FIG.
It can be seen that the silicon concentration in the hot metal decreases, and that there is an excellent silicon removal effect.

[0025]

As described above, according to the present invention, zinc-containing dust mainly composed of iron oxide generated from an ironworks is granulated into agglomerates, and the granulated dust is put into a hot metal pot. By charging the hot metal at the same time, the dust is not collected before coming into contact with the hot metal, and the contact between the finely divided dust and the hot metal is maintained, so that high-concentration zinc can be recovered, In addition, various useful effects are provided, such as the ability to promote the desiliconization reaction by iron oxide in the hot metal.

[Brief description of the drawings]

FIG. 1 is a process chart of an embodiment of a method for recovering zinc in dust according to the present invention.

FIG. 2 is a graph showing changes in zinc concentration.

FIG. 3 is a graph showing a silicon removal effect.

FIG. 4 is a process diagram showing a method for recovering zinc in dust in the prior art.

[Explanation of symbols]

 1: Dust hopper, 2: Dust, 3: Mixed iron wheel, 4: Hot metal, 5: Top blowing lance, 6: Gas injection pipe, 7: Dust transport pipe, 8: Hood, 9: Wet separator, 10: Duct , 11: suction fan, 12: container, 13: container, 14: dust hopper, 15: converter dust, 16: binder hopper, 17: mixer, 18: pan pelletizer, 19: curing machine, 20: dryer, 21: Cold pellet hopper, 22: Hot metal pot, 23: Cold pellet, 24: Hot metal, 25: Dust collection duct, 26: Dust collector, 27: Blower, 28: Distributor.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-3504 (JP, A) JP-A-58-144437 (JP, A) JP-A-50-62117 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C22B 1/00-61/00

Claims (2)

(57) [Claims] 1. A zinc-containing dust containing iron oxide as a main component is introduced into hot metal in a hot metal ladle, iron oxide in the dust is reduced in the hot metal, collected in the hot metal, and the dust is recovered. reducing the zinc oxide in, vaporized, thus consists in recovering zinc vaporized as zinc oxide, in the method for recovering zinc in the dust, cold the dust
A method for recovering zinc in dust, comprising granulating into pellets or cold briquettes, and charging the granulated dust into the hot metal pot simultaneously with hot metal. 2. The dust generated by charging the granulated dust into the hot metal ladle is again cooled into cold pellets.
2. The method for recovering zinc in dust according to claim 1, wherein the method comprises the steps of: granulating the powder into a cold briquette; and repeatedly charging the re-granulated dust into the hot metal pot simultaneously with the hot metal.