JP7750320B2 - Treatment method for ironmaking dust - Google Patents

Description

The present invention relates to a method for treating ironmaking dust.

Dust (steel dust) generated during steelmaking processes such as the blast furnace and converter processes primarily contains iron, so efforts have long been made to recycle it by returning it to the steelmaking process.

However, due to the zinc contained in steelmaking dust along with the iron, the amount of dust that can be recycled is limited by the zinc content. This is because zinc forms deposits inside blast furnaces and has a negative impact on blast furnace operation. Therefore, in order to promote the recycling of steelmaking dust, it is necessary to remove the zinc from the dust.

Furthermore, due to growing demands for _CO2 reduction in the steelmaking process, the use of scrap iron has increased in recent years. Because scrap iron is coated with zinc, the amount of zinc contained in converter dust is expected to increase in the future.

There are a wide variety of methods for separating zinc from steel dust, but one widely used method is the hydrocyclone method, which can separate zinc using simple equipment. Since the zinc in steel dust is mainly in the form of fine particles, this method separates and recovers zinc by using centrifugal force to sift (classify) the steel dust into coarse and fine particles.

With the aim of further increasing the efficiency of zinc separation, Patent Document 1, for example, proposes a method in which slurry-like wet blast furnace dust is subjected to ultrasonic treatment and then passed through a wet cyclone, with the upper recovered material being mainly zinc, and the lower recovered material being subjected to wet cyclone treatment and magnetic separation again, thereby separating the material into mainly zinc, mainly iron, and mainly carbon.

JP 2013-023720 A

The zinc recovery method described in Patent Document 1 requires multiple wet classification stages to separate zinc, making the process cumbersome. Furthermore, dilution is required before the second-stage wet classification stage, and there is a concern that the expected zinc separation performance may not be achieved unless an appropriate dilution concentration is set based on the results of the first-stage classification stage. Furthermore, there is a concern that zinc physically or chemically bound to the surface of magnetic metallic iron (M.Fe) or ferrous oxide (FeO) particles may migrate to the iron-based recovered product along with M.Fe or FeO during magnetic separation, reducing the zinc separation efficiency.

The object of the present invention is to propose a method for treating ironmaking dust that can easily and inexpensively separate the zinc contained in ironmaking dust.

The inventors conducted extensive research into ways to solve the above problems. As a result, they discovered that it was extremely effective to first mix blast furnace dust and converter dust, and then wet classify the mixed dust into fine and coarse dust particles, which led to the completion of the present invention.

The gist and configuration of the present invention are as follows.
[1] A dust mixing step of mixing a converter dust slurry containing converter dust and a blast furnace dust slurry containing blast furnace dust to form a mixed dust slurry;
a wet classification step of separating the mixed dust slurry into a coarse dust slurry containing coarse dust with a low zinc content and a fine dust slurry containing fine dust with a high zinc content;
a fine dust concentrating step of concentrating the separated fine dust slurry to form a concentrated fine dust slurry;
a coarse dust dilution step of mixing the separated coarse dust slurry with water to dilute it to form a diluted coarse dust slurry;
a fine dust dehydration step of dehydrating the concentrated fine dust slurry to obtain a dehydrated fine dust cake;
a coarse dust dewatering step of dewatering the diluted coarse dust slurry to obtain a coarse dust dewatered cake;
A method for treating ironmaking dust, comprising:

[2] The method for treating iron manufacturing dust described in [1], wherein the dust mixing step is carried out so that the total Fe (T.Fe) concentration of the resulting mixed dust slurry is 25% by mass or more and 60% by mass or less.

[3] The method for treating ironmaking dust described in [1] or [2], wherein the dust mixing step is carried out so that the concentration of the resulting mixed dust slurry is 5% by mass or more and 40% by mass or less.

[4] The method for treating iron manufacturing dust described in any one of [1] to [3] above, wherein the wet classification step is carried out using a wet cyclone.

[5] The method for treating ironmaking dust described in any one of [1] to [4], wherein the fine dust concentration step is carried out so that the concentration of the resulting concentrated fine dust slurry is 10% by mass or more and 50% by mass or less.

[6] The method for treating ironmaking dust described in any one of [1] to [5], wherein the coarse dust dilution step is carried out so that the concentration of the resulting diluted coarse dust slurry is 10% by mass or more and 50% by mass or less.

[7] The method for treating iron manufacturing dust described in any one of [1] to [6], wherein the water used in the coarse dust dilution process is water produced in the fine dust concentration process.

[8] The method for treating iron manufacturing dust described in any one of claims [1] to [7], wherein the fine dust dewatering step is carried out so that the moisture content of the resulting fine dust dewatered cake is 35% by mass or less.

[9] The method for treating iron manufacturing dust described in any one of claims [1] to [8], wherein the coarse dust dewatering step is carried out so that the moisture content of the resulting coarse dust dewatered cake is 35% by mass or less.

[10] A method for treating ironmaking dust described in any one of [1] to [9] above, in which the coarse dust dewatered cake obtained in the coarse dust dewatering step is fed into a sintering machine, a rotary hearth furnace, or a rotary kiln, and reused as an iron source.

[11] A method for treating iron manufacturing dust according to any one of [1] to [9], wherein the coarse dust dewatered cake obtained in the coarse dust dewatering step is mixed with at least a portion of the fine dust dewatered cake obtained in the fine dust dewatering step to form a mixed dewatered cake, and the mixed dewatered cake is fed into a sintering machine, a rotary hearth furnace, or a rotary kiln to be reused as an iron source.

This invention makes it possible to separate zinc contained in steelmaking dust easily and at low cost.

FIG. 1 is a flowchart showing a preferred example of a method for treating iron manufacturing dust according to the present invention. 1 is a graph showing the correlation between the T.Fe concentration of the mixed dust slurry and the mass ratio of blast furnace dust to converter dust. 1 is a diagram showing the correlation between the T.Fe concentration of a mixed dust slurry and the T.Fe concentration of a coarse dust slurry. FIG. 10 is a flowchart showing another preferred example of a method for treating iron manufacturing dust according to the present invention. FIG. 10 is a flowchart showing yet another preferred example of a method for treating iron manufacturing dust according to the present invention. FIG. 1 is a flowchart showing a method for treating iron manufacturing dust used in a comparative example.

(Method for treating ironmaking dust)
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. Figure 1 shows a flowchart of a preferred example of a method for treating iron manufacturing dust according to the present invention. The method for treating steelmaking dust according to the present invention includes a dust mixing step (Step S1) of mixing a converter dust slurry containing converter dust with a blast furnace dust slurry containing blast furnace dust to form a mixed dust slurry; a wet classification step (Step S2) of separating the mixed dust slurry into a coarse dust slurry containing coarse dust with little zinc and a fine dust slurry containing fine dust with a lot of zinc; a fine dust concentration step (Step S3) of concentrating the separated fine dust slurry to form a concentrated fine dust slurry; a coarse dust dilution step (Step S4) of mixing the separated coarse dust slurry with water to dilute it to form a diluted coarse dust slurry; a fine dust dewatering step (Step S5) of dewatering the concentrated fine dust slurry to form a dewatered fine dust cake; and a coarse dust dewatering step (Step S6) of dewatering the diluted coarse dust slurry to form a dewatered coarse dust cake.

The inventors conducted extensive research into a simple, low-cost method for separating zinc from steelmaking dust. Blast furnace dust and converter dust are typically recovered as slurries using scrubbers or similar devices. The inventors passed a blast furnace dust slurry containing only blast furnace dust, a mixed dust slurry containing a mixture of blast furnace dust and converter dust, and a converter dust slurry containing only converter dust through a hydrocyclone to separate the particles into a fine dust slurry containing zinc-rich fine dust and a fine dust slurry containing zinc-poor coarse dust, and investigated their behavior.

The results showed that when only blast furnace dust slurry was circulated, and when a mixed dust slurry of blast furnace dust and converter dust was circulated, zinc concentrated in the fine dust slurry, whereas when only converter dust slurry was circulated, zinc hardly concentrated in the fine dust slurry. This is thought to be because the particle size of the iron-based particles contained in the converter dust slurry is similar to the particle size of zinc. Furthermore, the iron concentration in the coarse dust slurries was highest in the converter dust slurry, followed by the mixed dust slurry containing blast furnace dust and converter dust, and then the blast furnace dust slurry.

Furthermore, analysis of metallic iron (hereinafter referred to as "M.Fe") concentrations before and after cyclone classification revealed that, as shown in Table 1, the M.Fe concentration in the coarse dust slurry increased at all levels compared to before passing through the cyclone, with M.Fe particularly concentrating in the coarse particles. Furthermore, calculation of the ratio of M.Fe to total Fe (hereinafter referred to as "T.Fe") revealed that the ratio of M.Fe to T.Fe in the coarse dust increased compared to before passing through the cyclone. This suggests that a reduction in the reducing agent ratio (the amount of coke and auxiliary fuel used) can be expected when the dust is returned to the blast furnace as an iron source, improving its value as an iron source. In other words, it was found that in order to achieve both zinc separation and the recycling benefits as an iron source, it is necessary to mix blast furnace dust slurry and converter dust slurry to prepare a mixed dust slurry and pass the resulting mixed dust slurry through a hydrocyclone.

However, because the concentrations of blast furnace dust slurry and converter dust slurry vary depending on operating conditions, it is difficult to maintain a constant mixing ratio through simple flow rate control, etc. However, research by the inventors has revealed that, as shown in Figure 2, there is a certain correlation between the T.Fe concentration of the mixed dust slurry and the mass ratio of blast furnace dust to converter dust (blast furnace dust/converter dust). Taking this correlation into consideration, the mixing ratio of the blast furnace dust slurry and the converter dust slurry was adjusted and introduced into a hydrocyclone. It was found that zinc can be efficiently separated by adjusting the T.Fe concentration of the resulting mixed dust slurry to be 25% by mass or more and 60% by mass or less, more preferably 30% by mass or more and 55% by mass or less.

In this way, the inventors discovered that zinc can be separated easily and at low cost by mixing blast furnace dust slurry and converter dust slurry to form a mixed dust slurry and then wet classifying the resulting mixed dust slurry, thereby completing the present invention. Each step is described below.

<Dust mixing process>
First, in step S1, a converter dust slurry containing converter dust and a blast furnace dust slurry containing blast furnace dust are mixed to prepare a mixed dust slurry (dust mixing step).

The mixing ratio of the blast furnace dust slurry and the converter dust slurry is preferably determined by the T.Fe concentration of the mixed dust slurry, rather than by the mass or volume ratio of these dust slurries. This is because the T.Fe concentrations of these dusts vary depending on the operating conditions of the blast furnace and converter. This process is preferably performed so that the T.Fe concentration of the resulting mixed dust slurry is 60% by mass or less. This is because if the T.Fe concentration of the mixed dust slurry exceeds 60% by mass, the proportion of converter dust is expected to be high, reducing the particle size difference between zinc and iron-based particles and decreasing the classification efficiency. From the perspective of classification efficiency, this process is more preferably performed so that the T.Fe concentration of the mixed dust slurry is 55% by mass or less. However, if the T.Fe concentration of the mixed dust slurry is reduced too much, the difference in specific gravity between zinc and other elements will decrease, resulting in a decrease in the classification efficiency of the subsequent hydrocyclone. Furthermore, as shown in Figure 3, if the T.Fe concentration of the mixed dust slurry is reduced too much, the T.Fe concentration of the resulting coarse dust slurry will also decrease, raising concerns about its value as an iron source. Therefore, this step is preferably carried out so that the T.Fe concentration of the mixed dust slurry is 25% by mass or more, and more preferably 30% by mass or more.

In addition, taking into consideration the subsequent wet classification process, this process is preferably carried out so that the concentration of the resulting mixed dust slurry is 5% by mass or more and 40% by mass or less. It is more preferable to carry out this process so that the T.Fe concentration is 60% by mass or less and the concentration of the mixed dust slurry is 5% by mass or more and 40% by mass or less. In this specification, "concentration of the mixed dust slurry" refers to the ratio of the mass of the mixed dust (solid content) to the total mass of the mixed dust slurry.

The method for mixing the converter dust slurry and the blast furnace dust slurry is not particularly limited, but it is preferable to use a general mixing tank and mixer to mix the blast furnace dust slurry and the converter dust slurry as uniformly as possible.

<Wet classification process>
Next, in step S2, the mixed dust slurry is separated into a coarse dust slurry containing coarse dust with a low zinc content and a fine dust slurry containing fine dust with a high zinc content (wet classification step).

In this process, the mixed dust slurry is separated (by particle size classification) into a coarse dust (low-zinc dust) slurry and a fine dust (high-zinc dust) slurry. In this invention, "coarse dust" refers to dust with a particle size of 20 μm or more, and "fine dust" refers to dust with a particle size of less than 20 μm.

Particle size classification can be performed using sieves or by taking advantage of differences in the settling or movement speed of particles in a fluid (fluid classification). Fluid classification can be broadly divided into methods that use gravity and methods that use centrifugal force. There are no particular restrictions on the classification method, but fluid classification, especially wet cyclones that use centrifugal force, is preferred.

As will be explained later, zinc exists as fine particles of about a few microns in size. When classifying using a sieve, zinc can be selectively recovered if the sieve openings are a few microns in size. However, because the sieve openings are so fine, they tend to clog, making stable processing difficult.

Gravity-based methods use differences in settling speed to separate the particles. However, if you try to separate the entire amount of mixed dust using gravity settling, you will need a huge settling tank, and the classification accuracy will be insufficient.

In contrast, hydrocyclones have the advantage of being able to classify large amounts of slurry using small-scale equipment. Furthermore, the particle size of the particles can be estimated using the equation described in, for example, Plitt, L. R.: A mathematical model of the hydrocyclone classifier, CIM Bulletin (1976), pp. 114-123. In other words, by appropriately setting the cyclone's lower outlet diameter, inlet flow rate, slurry concentration, etc., using the equation described in the above literature as a reference, hydrocyclones have the advantage of being able to easily control the classification performance. For these reasons, it is preferable to use a hydrocyclone for this process.

There are no particular restrictions on the concentration of the mixed dust slurry supplied to the wet cyclone, but if the concentration is too low, the number of cyclones required will increase, reducing equipment efficiency. Conversely, if the concentration of the mixed dust slurry is too high, it may lead to equipment problems such as blockages. Therefore, as mentioned above, it is preferable to adjust the concentration of the mixed dust slurry to between 5% and 40% by mass before supplying it to the wet cyclone. The concentration of the mixed dust slurry to be adjusted to within the range of between 5% and 40% by mass is preferably determined by referring to the formula in Non-Patent Document 1, etc.

When the mixed dust slurry passes through a hydrocyclone, particles with a larger specific gravity and particle size are closer to the wall of the hydrocyclone, while particles with a smaller specific gravity and particle size are closer to the center. The fine particles with a small specific gravity present in the center ride the upward flow within the hydrocyclone and are recovered from the top of the hydrocyclone as a fine dust slurry containing fine dust. In contrast, the coarse particles with a large specific gravity present on the wall side of the hydrocyclone ride the downward flow within the hydrocyclone and are recovered as a coarse dust slurry containing coarse dust.

Zinc volatilized in blast furnaces and converters generally exists as fine particles of a few microns in size, and its specific gravity tends to be lower than that of iron. As a result, fine dust contains more zinc than coarse dust. In contrast, iron, especially metallic iron, has a higher specific gravity than zinc, so it tends to migrate in greater amounts to the coarse dust side. In other words, coarse dust has a lower zinc concentration than blast furnace dust before passing through the hydrocyclone, making it possible to reuse it as a raw material for steelmaking.

<Fine dust concentration process>
Subsequently, in step S3, the separated fine dust slurry is concentrated to form concentrated fine dust slurry (fine dust concentration step).

Fine dust slurry has a lower concentration than the mixed dust slurry before wet classification, and if it is transferred to a dehydrator in the subsequent fine dust dehydration process without being concentrated, the dehydration efficiency will be poor. Therefore, the fine dust slurry is concentrated to increase its concentration before being transported to the fine dust dehydration process. This process is carried out by discharging a certain amount of water from the fine dust slurry.

There are no particular limitations on the concentration method, but one example is concentration using a settling tank. Specifically, the fine dust slurry is introduced into a settling tank to allow the fine dust to settle, the resulting supernatant water is discharged via overflow, and the solid fine dust is extracted from the bottom of the tank, thereby increasing the concentration.

Regarding the concentration of the concentrated fine dust slurry, which is the fine dust slurry after concentration, if the concentration is too high, handling becomes difficult. Therefore, this process is preferably carried out so that the concentration of the resulting concentrated fine dust slurry is 10% by mass or more and 50% by mass or less, and more preferably 20% by mass or more and 40% by mass or less. In this specification, "concentration of concentrated fine dust slurry" refers to the ratio of the mass of fine dust (solids) to the total mass of the concentrated fine dust slurry.

<Coarse dust dilution process>
In parallel with step S3, in step S4, the separated coarse-particle dust slurry is mixed with water to dilute it, thereby forming a diluted coarse-particle dust slurry (coarse-particle dust dilution step).

In contrast to fine dust slurry, coarse dust slurry has a very high slurry concentration, which can cause problems such as equipment blockages during the transportation process. Therefore, in this process, the coarse dust slurry is diluted to a concentration that is easy to handle.

If the concentration of the diluted coarse dust slurry, which is the coarse dust slurry after dilution, is too low, the efficiency of subsequent dewatering will be poor. Therefore, this process is preferably carried out so that the concentration of the resulting diluted coarse dust slurry is 10% by mass or more and 50% by mass or less, and more preferably 20% by mass or more and 40% or less. In this specification, "concentration of diluted coarse dust slurry" refers to the ratio of the mass of coarse dust (solids) to the total mass of the diluted coarse dust slurry.

The water used for dilution may be new industrial water, etc., but from the perspective of saving water resources, it is preferable to use the water generated when concentrating the fine dust slurry. For example, as shown in Figure 4, it is even more preferable to use the supernatant water generated when concentrating the fine dust slurry in a settling tank. When diluting, it is preferable to stir the coarse dust slurry and water in a stirring tank until they become homogeneous.

The fine dust concentration process in step S3 and the coarse dust dilution process in step S4 may be carried out simultaneously in parallel as described above, or one of the processes may be carried out first and the other after.

<Fine dust dehydration process>
After step S3, in step S5, the concentrated fine dust slurry is dehydrated to obtain a dehydrated fine dust cake (fine dust dehydration step).

In this process, the water content of the concentrated fine dust slurry is reduced by mechanically removing the water from the slurry, yielding a residue of dehydrated fine dust cake. There are no particular restrictions on the method for dehydrating the concentrated fine dust slurry, but methods that can be used include a filter press, which squeezes out the water from the slurry by squeezing, and centrifugal dehydration, which separates the slurry into water and solids using centrifugal force and then drains the water to dehydrate it.

If the moisture content of the dehydrated fine dust cake obtained in this process is high, the dust will adhere to the bucket of the transport vehicle, etc., resulting in a poor yield. Therefore, this process is preferably carried out so that the moisture content of the dehydrated fine dust cake is 35% by mass or less. Conversely, if the moisture content is lowered too much, fine powder may fly around during transport. Therefore, this process is preferably carried out so that the moisture content of the dehydrated fine dust cake is 10% by mass or more.

<Coarse dust dehydration process>
After step S4, in step S6, the diluted coarse dust slurry is dewatered to obtain a dewatered coarse dust cake (coarse dust dewatering step).

In this process, the water in the diluted coarse dust slurry is mechanically removed to reduce the moisture content of the slurry, yielding a residue, a dewatered coarse dust cake. As with the concentrated fine dust slurry, the dewatering method for the diluted coarse dust slurry is not limited, and methods such as filter press and centrifugal dewatering can be used. The moisture content of the dewatered coarse dust cake is the same as that of the dewatered fine dust cake. Therefore, this process is preferably carried out so that the moisture content of the dewatered coarse dust cake is 35% by mass or less. It is also preferable to carry out this process so that the moisture content of the dewatered coarse dust cake is 10% by mass or more.

The zinc concentration in the coarse dust is reduced compared to before classification. Therefore, the coarse dust dewatered cake obtained in the coarse dust dewatering process can be fed into a sintering machine, rotary hearth furnace, or rotary kiln in step S7 and reused as an iron source.

Alternatively, if there is a surplus in the blast furnace's zinc charging upper limit, as shown in Figure 5, the coarse dust dewatered cake obtained in the coarse dust dewatering process can be mixed with at least a portion of the fine dust dewatered cake obtained in the fine dust dewatering process until the zinc charging upper limit is reached to form a mixed dust dewatered cake, which can then be fed into a sinter machine, rotary hearth furnace, or rotary kiln and reused as an iron source. By performing this operation, it is possible to increase the amount of dust recycled compared to when only coarse dust is reused.

The following describes examples of the present invention, but the present invention is not limited to these examples.

Example 1
According to the flow chart shown in FIG. 1 , a blast furnace dust slurry and a converter dust slurry were mixed so that the total iron (T.Fe) concentration was 55% by mass or less (dust mixing step). The resulting mixed dust slurry was then passed through a wet cyclone and separated into a fine dust slurry and a coarse dust slurry (wet classification step). The resulting fine dust slurry was concentrated in a settling tank (fine dust concentration step) and then dehydrated using a filter press to obtain a fine dust dehydrated cake (fine dust dehydration step). Meanwhile, the coarse dust was diluted with industrial water (coarse dust dilution step) and then dehydrated using a filter press in the same manner as the fine dust to obtain a coarse dust dehydrated cake (coarse dust dehydration step). Portions of the resulting fine dust dehydrated cake and coarse dust dehydrated cake were sampled, and the total Zn (T.Zn) and T.Fe concentrations were measured.

Table 2 shows the T.Zn and T.Fe concentrations, M.Fe concentration, slurry concentration, and moisture content of the dehydrated cake of the mixed dust slurry and the coarse dust slurry and fine dust slurry obtained after the wet classification process. Table 2 also shows the Zn removal rate calculated using the following formula from the T.Zn concentration. The "Zn removal rate" defined here refers to the proportion of Zn that migrates to the fine dust slurry when the Zn contained in the mixed dust is taken as 100.

As shown in Table 2, 61.8% of the Zn contained in the mixed dust slurry was removed.

Table 2 also shows the percentage of M.Fe contained in T.Fe calculated from the T.Fe concentration and M.Fe concentration using the following formula:

As shown in Table 2, the ratio of M.Fe to T.Fe in the coarse dust was found to be higher than that before passing through the cyclone (mixed dust slurry). In other words, it was found that a reduction in the reducing agent ratio (amount of coke and auxiliary fuel used) can be expected when the coarse dust is returned to the blast furnace as an iron source.

Example 2
The steelmaking dust was treated in the same manner as in Example 1. However, the treatment was carried out according to the flow shown in Figure 4, and the supernatant water generated in the fine dust concentration step was used as part of the water used to dilute the coarse dust slurry in the coarse dust dilution step. All other conditions were the same as in Example 1.

Table 3 shows the concentration of each slurry, total zinc concentration, total iron concentration, mineral iron concentration, and zinc removal rate, as well as the moisture content of each dehydrated cake and the proportion of mineral iron in total iron.

Table 4 also shows the results of a comparison between the amount of industrial water used in the coarse dust dilution process in Example 1 and Example 2.

As shown in Table 3, the method following the flow shown in Figure 4 also achieved a high Zn removal rate of 71.0%. Furthermore, as in Example 1, the ratio of M.Fe to T.Fe in the coarse dust was higher than that before passing through the cyclone (mixed dust slurry). Furthermore, as shown in Table 4, the amount of industrial water used to dilute the coarse dust was reduced by approximately 30%, demonstrating that treating dust according to the flow shown in Figure 4 also makes it possible to reduce the amount of industrial water used.

Example 3
The steelmaking dust was treated in the same manner as in Example 1. However, the process was carried out according to the flow shown in Figure 5, and the supernatant water generated in the fine dust concentration process was used as part of the water used to dilute the coarse dust slurry in the coarse dust dilution process. The obtained coarse dust dewatered cake was entirely sintered and recycled as an iron source to the blast furnace. Meanwhile, the obtained fine dust dewatered cake was mixed with coarse dust until the upper limit of zinc charging in the blast furnace was reached, and then charged into the blast furnace. All other conditions were the same as in Example 1.

Table 5 shows a comparison of the amount of dust recycled. Note that the amount of dust recycled is shown as a relative value, with Examples 1 and 2 set to 1.

As shown in Table 5, by following the flow shown in Figure 5, the amount of dust recycled can be increased by 1.4 times.

(Comparative Example)
The steelmaking dust was treated in the same manner as in Example 1. However, the treatment was carried out according to the flow shown in Figure 6, except that the dust mixing step was not carried out, and the blast furnace dust slurry and the converter dust slurry were separately transported to the wet classification step and passed through the wet cyclone. All other conditions were the same as in Example 1.

Table 6 shows the concentration, total zinc concentration, total iron concentration, zinc removal rate, and moisture content of each dehydrated cake for blast furnace dust slurries. Table 7 shows the concentration, total zinc concentration, total iron concentration, magnesium iron concentration, zinc removal rate, moisture content of each dehydrated cake for converter dust slurries, and the ratio of magnesium iron to total iron.

As shown in Table 6, the Zn removal rate for the blast furnace dust slurry was high at 70.5%. On the other hand, as shown in Table 7, the Zn removal rate for the converter dust slurry was found to be low at 47.5%. This is thought to be because the difference in particle size between Zn and Fe in the converter dust slurry is small, resulting in the Zn and Fe being mixed and classified.

On the other hand, because the original M.Fe concentration of blast furnace dust slurry is low, although M.Fe is somewhat concentrated in the coarse dust, the concentration is low at 0.3%, and it has become clear that its value as an Fe source is hardly improved compared to before it was passed through the cyclone.

In this way, this invention makes it possible to separate zinc from blast furnace dust and converter dust simply and at low cost.

This invention allows zinc contained in steelmaking dust to be separated easily and at low cost, making it useful in the steelmaking industry.

Claims (10)

a dust mixing step of mixing a converter dust slurry containing converter dust and a blast furnace dust slurry containing blast furnace dust to form a mixed dust slurry;
a wet classification step of separating the mixed dust slurry into a coarse dust slurry containing coarse dust with a low zinc content and a fine dust slurry containing fine dust with a high zinc content;
a fine dust concentrating step of concentrating the separated fine dust slurry to form a concentrated fine dust slurry;
a coarse dust dilution step of mixing the separated coarse dust slurry with water to dilute it to form a diluted coarse dust slurry;
a fine dust dehydration step of dehydrating the concentrated fine dust slurry to obtain a dehydrated fine dust cake;
a coarse dust dewatering step of dewatering the diluted coarse dust slurry to obtain a coarse dust dewatered cake;
Including,
A method for treating iron-making dust , characterized in that the dust mixing step is carried out so that the total Fe (T.Fe) concentration of the resulting mixed dust slurry is 25 mass % or more and 60 mass % or less . 2. The method for treating iron manufacturing dust according to claim 1 , wherein the dust mixing step is carried out so that the concentration of the resulting mixed dust slurry is 5% by mass or more and 40% by mass or less. The method for treating ironmaking dust described in claim 1 or 2, wherein the wet classification process is carried out using a wet cyclone. The method for treating ironmaking dust described in claim 1 or 2, wherein the fine dust concentration process is carried out so that the concentration of the resulting concentrated fine dust slurry is 10% by mass or more and 50% by mass or less. The method for treating ironmaking dust described in claim 1 or 2, wherein the coarse dust dilution process is carried out so that the concentration of the resulting diluted coarse dust slurry is 10% by mass or more and 50% by mass or less. The method for treating iron manufacturing dust described in claim 1 or 2, wherein the water used in the coarse dust dilution process is water produced in the fine dust concentration process. The method for treating iron manufacturing dust described in claim 1 or 2, wherein the fine dust dewatering process is carried out so that the moisture content of the resulting fine dust dewatered cake is 35% by mass or less. The method for treating iron manufacturing dust described in claim 1 or 2, wherein the coarse dust dewatering process is carried out so that the moisture content of the resulting coarse dust dewatered cake is 35% by mass or less. The method for treating ironmaking dust according to claim 1 or 2, wherein the coarse dust dewatered cake obtained in the coarse dust dewatering step is fed into a sintering machine, a rotary hearth furnace, or a rotary kiln and reused as an iron source. 3. The method for treating iron manufacturing dust according to claim 1, wherein the coarse dust dewatered cake obtained in the coarse dust dewatering step is mixed with at least a portion of the fine dust dewatered cake obtained in the fine dust dewatering step to form a mixed dewatered cake, and the mixed dewatered cake is fed into a sintering machine, a rotary hearth furnace, or a rotary kiln to be reused as an iron source.