JP2009191305A - Method for effectively utilizing iron content and zinc content in secondary dust generated from reduction furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for practically recovering a zinc with which in the case of recovering the zinc from secondary dust generated in a reduction furnace for reducing sub-production materials, such as iron and zinc-containing dust, slurry, etc., generated from an iron-making process, a zinc concentration ratio and also, a zinc recovering ratio are raised. <P>SOLUTION: This method is separated into the portion for using a zinc raw material containing much zinc fine particles and the portion for using the iron-making material containing much iron particles, by passing through the following two processes; a first process, in which after turning to slurry having 8-10 pH to the secondary dust generated in the reduction furnace, the fine particles of much zinc content stuck on the large particles of much iron content, are exfoliated under micro state with the treatment method, such as supersonic cleaning; and a second process, in which the portion containing much fine particles of much zinc content and the portion containing much iron particles, generated in the first process, are separated with the means, such as a wetting type magnetic separation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for effectively utilizing zinc-containing dust generated in an iron-making process and iron in a slurry, and more particularly, effective utilization of iron and zinc in secondary dust generated from a reduction furnace for dezincing zinc-containing dust and slurry. Regarding usage.

  A reduction furnace such as a rotary hearth type reduction furnace or a rotary kiln is used for the reduction treatment for effectively recovering the zinc-containing dust generated in the iron making process and the iron content in the slurry.

  In these reduction furnaces, when a raw material containing zinc oxide such as converter dust is reduced, dust containing a large amount of zinc is recovered from the exhaust gas. For example, dust containing 20 to 50% by mass of zinc and 10 to 25% by mass of total iron is recovered from a rotary kiln type reduction furnace. Further, in the rotary hearth type reducing furnace, since the iron-containing material is less scattered, the dust from the reducing furnace has a high zinc ratio, and the dust containing 30 to 60% by mass of zinc and 2 to 15% by mass of total iron is recovered. Is done.

  From this zinc-containing secondary dust, metallic zinc and zinc carbonate are produced. However, since this zinc-containing secondary dust contains a large amount of impurities other than zinc and has a low zinc concentration, there is a problem that costs for producing zinc product raw materials and metal zinc raw materials are high.

  In order to solve this problem, Patent Document 1 discloses a concentration method for removing impurities to increase the purity of zinc. This is a mixture of zinc-containing dust generated from a reduction furnace such as a rotary hearth type reduction furnace or rotary kiln that reduces zinc-containing reducing metal oxide and water to form a slurry. This is a method of separating into a zinc-concentrated powder slurry and a zinc-poor powder slurry by a wet separation device such as a hydrocyclone by utilizing the difference in particle diameter and specific gravity of the body.

  Patent Document 2 discloses, as an example of a method for removing impurities and zinc concentration in zinc-containing secondary dust generated from a reduction furnace, zinc-containing secondary dust generated when iron-making dust is reduced and fired with water. After repulping and eluting soluble salts, wet magnetic separation is performed to separate magnetic deposits, and then the pulp is solid-liquid separated to recover and separate zinc-containing nonmagnetic substances and halogen compounds.

  In addition, many methods have been proposed for concentrating or removing zinc from dust generated from a blast furnace instead of zinc-containing secondary dust generated from a reduction furnace.

  For example, Patent Document 3 discloses a blast furnace gas ash treatment method in which a slurry is introduced into a slurry blast furnace gas ash and then irradiated with ultrasonic waves to separate a slurry with a high zinc content and a slurry with a low zinc content. Is disclosed.

  Further, in Patent Document 4, a dispersant is added to slurry blast furnace dust, and then irradiated with ultrasonic waves, and the dust particles contained in the slurry are dispersed and led to a wet cyclone using negative pressure. A method of treating blast furnace dust that separates into a high slurry and a low slurry is disclosed.

  Furthermore, in Patent Document 5, high-pressure water is injected into a container through a nozzle, and air sucked into the high-pressure water from the nozzle is taken into the injection water, and water and air are injected into the container in two fluids. A step of generating a flow, and adding the slurry-like blast furnace dust to the two-fluid jet in the container, and by the stirring force of the two-fluid jet, the zinc content adhering to the particles of the blast furnace dust A method for dezincing blast furnace dust having a step of exfoliating a high part from particles is disclosed.

  Furthermore, Patent Document 6 does not specify the type of furnace that generates dust, and as a method of improving the recovery rate of zinc, for example, turning the central axis sideways and rotating around the central axis, Into a rotating drum that reciprocates in two directions perpendicular to the central axis, dust with Zn attached is continuously thrown in and sent in the central axis direction of the rotating drum, and the dust continuously discharged from the rotating drum is wet cyclone. Shows a dust treatment method in which continuous classification treatment is performed.

  Patent Document 7 discloses a zinc carbonate production process by an ammonium carbonate dissolution method to which the present invention can be applied.

  In the above-mentioned Patent Document 2, it is shown that water is repulped in order to elute soluble salts of zinc-containing secondary dust generated from a reduction furnace. In order to suppress it, the pH is adjusted. As shown in Non-Patent Document 1, this is based on the general knowledge of chemistry that since zinc is an amphoteric metal, the pH is about 9 to 10 and the amount of elution into the aqueous solution is minimized.

Further, Non-Patent Document 2 shows a method of calculating the design 50% classified particle diameter d ₅₀ * [unit micrometer] of the hydrocyclone used in Patent Document 1 and the like.
JP-A-2005-21841 JP-A-55-104434 JP 52-002807 JP-A-53-081479 JP 10-317018 A JP-A-5-132724 Patent No. 737379 Edited by Pollution Prevention Technology and Regulations Editorial Committee, “New Pollution Prevention Technology and Regulations [Water Quality] 2006”, published by Japan Industrial Environment Management Association Chemical Engineering Association; Chemical Engineering Handbook 4th Edition, 1964, Maruzen

  However, the method of recovering zinc from the secondary dust generated from the reduction furnace described in Patent Document 1 is (Zn mass% in the zinc recovery slurry in the dry state / Zn mass% of the slurry before treatment in the dry state). ), The zinc concentration rate is 1.3 to 1.9 times. However, the zinc recovery rate indicating how much zinc can be separated and recovered from the total amount of zinc contained in the secondary dust is not shown. The applicant conducted a supplementary test in the same manner as in Patent Document 1, and the zinc recovery rate was around 60%. This zinc recovery rate is lower than the actual value of 70 to 90% of the zinc recovery rate by the zinc recovery method from blast furnace dust described in Patent Literature 3, Patent Literature 4 and Patent Literature 5.

  Thus, when the zinc recovery rate is low, the total amount of charged zinc increases when the iron-rich residue is used again in the reduction furnace. As a result, the zinc content of the reduced iron, which is the main product of the reduction furnace, is high. In the case of use in a blast furnace, the total amount of zinc brought in increases. As a result, in order to reduce the zinc level of reduced iron, the entire residue cannot be used in the reduction furnace, the iron source cannot be used effectively, and when the obtained reduced iron is used in the blast furnace, the amount used Will be subject to restrictions.

  Also in Patent Document 2, according to the description of the examples, the zinc recovery rate is 63%, which is lower than the Zn recovery rate of 70 to 90% which is a normal zinc recovery method for blast furnace dust.

  Furthermore, as in the case of Patent Document 6, several techniques for separating zinc and iron have been proposed for Zn-attached dust in general not limited to blast furnace dust, but with a high Zn content value such as 20 to 60%, In addition, there is no known technique that can be substantially applied to the dezincification of reducing furnace dust having a salt component adhering to 10 to 20%.

  The object of the present invention is to recover zinc from secondary dust having a high zinc content and salt content generated in a reduction furnace that reduces by-products such as iron and zinc-containing dust and sludge generated in the iron making process. Another object of the present invention is to provide a practical zinc recovery method capable of increasing the zinc recovery rate together with the zinc concentration rate.

  The present invention has been completed on the basis of microstructural analysis of dust to improve zinc recovery of zinc-containing secondary dust generated in a reduction furnace that reduces iron and zinc-containing by-products generated in the iron making process. .

  FIG. 1 is an SEM photograph of so-called reducing furnace secondary dust generated in a reducing furnace.

  FIG. 2 schematically shows the microstructure of the reduction furnace secondary dust schematically shown from SEM photographs, quantitative analysis results, and the like. As shown in the figure, the microstructure of the reducing furnace secondary dust has a very fine structure of 1 μm or less on base particles having a size of several μ to several tens μ mainly composed of Fe as a metal element. The structure is such that non-dissolved particles mainly composed of Zn are adhered, and further, salts such as potassium, calcium, sodium, and chlorine are adhered to the surface.

  Table 1 shows a comparison between the microstructure of the reducing furnace secondary dust and the microstructure of the blast furnace dust. As shown in the table, the composition and size of blast furnace dust and reducing furnace dust are significantly different. That is, the secondary dust of the reducing furnace has a much larger amount of zinc fine particles attached than the blast furnace dust, and the size of the attached particles is very fine, 1 μm or less.

  Table 2 shows an analysis example of secondary dust in the reduction furnace. As shown in the table, salt components such as potassium, calcium, sodium and chlorine are contained together with zinc fine particles in a total amount of about 10 to 20%, most of which are as shown in the schematic diagram of FIG. It adheres to the surface together with the zinc fine particles, and it is more difficult to separate particles mainly composed of fine Zn from the base particles than blast furnace dust.

  In addition, it is also difficult to separate the portion where the particles mainly composed of Fe and the portion where particles mainly composed of Zn are collected into macro, because the particles mainly composed of Zn are very fine. There is.

  The basic method relating to the effective utilization method of the iron and zinc contents of the secondary dust generated from the reduction furnace according to the present invention is the two methods generated in the reduction furnace that reduces iron and zinc-containing by-products generated from the iron making process. The first dust is made into a slurry suspended in a liquid, and the first step of microscopically peeling fine particles having a high zinc content from large particles having a high iron content, a portion containing the zinc fine particles and iron The second step of separating the portion containing a large amount of particles in a macro form and the portion containing a large amount of separated zinc fine particles as a raw material for zinc, or the portion containing a large amount of separated iron particles as a raw material for iron making The third step is to sequentially perform the three steps.

  In the present invention, “separate in a micro state” and “separate in a macro state” mean the following matters, respectively.

  That is, “microscopic peeling” means that the secondary dust generated in the reduction furnace has the microstructure shown in FIG. 2 as described above, and in this microstructure, the main component is Fe content as a metal element. From the base particles, the particles mainly composed of very fine Zn are physically peeled off in such a micro-structure. The zinc fine particles can be removed from the aggregate of iron particles in a micro state by any method as long as the micro state can be substantially peeled off. However, mechanical strong stirring using a stirring blade or the like and a dispersing agent are used in combination. It is performed by stirring and ultrasonic cleaning.

  In addition, “separate in a macro form” means that an aggregate of particles mainly composed of Zn separated from a micro part and a base particle composed mainly of Fe are physically separated in a macro state. It is to be. In the present invention, a wet magnetic separation method, a hydrocyclone method, a flotation method, and other separation methods can be applied as the means for separating in a macro form.

  Confirmation and evaluation of the microscopic delamination status, that is, microscopic delamination of fine particles with high zinc content from large particles with high iron content, as well as direct observation by SEM etc. Evaluation by particle size distribution investigation and reverse evaluation from the macroscopic separation result in the second step are also possible. Any method that can be substantially evaluated can be used.

  The present invention has the following effects.

  Increasing the total amount of zinc recovered from the reduction furnace secondary dust increases the effective use of zinc, contributing to effective use of resources and cost reduction.

  As a result of the improvement of the Zn recovery rate compared to the conventional method, the zinc content on the residual iron content side after zinc recovery is reduced. As a result, the residual iron content can be easily reused even under restrictions on the total amount of zinc brought into the blast furnace. Similarly, effective utilization of resources and cost reduction can be obtained.

  Based on the present invention, the initial treatment of the secondary dust from the reduction furnace is performed by suspending the secondary dust generated from the reduction furnace in fresh water or pH-adjusted water and adjusting the pH to 8 to 10 to obtain a slurry. Thus, the first process and the second process are performed. At that time, if necessary to maintain the pH, an alkaline agent such as soda ash or sodium hydroxide is also added. The mixing ratio at the time of slurrying is about 3 to 35 dust weights with respect to the liquid weight 100, and preferably the dust weight is within the range of 5 to 15 with respect to the liquid weight 100. Even if these blending ratios are deviated, it cannot be treated, but on the side where the dust weight is small, that is, the dilution side, the apparatus becomes large and the equipment cost becomes high. On the side where the dust is heavy, that is, on the thick side, the salt washing efficiency and the ultrasonic irradiation efficiency are lowered, and handling such as uniformizing and transferring the slurry becomes difficult. In addition, the efficiency of macro separation is reduced during magnetic separation.

In the exfoliation of the microscopic zinc fine particles from the iron particle aggregate shown in FIG. 2, which is the first step of the present invention, as a mechanical strong stirring means, washing is performed for 2 hours while stirring at a stirring energy density of 12 w / m ^3. Table 3 shows SEM observation results for a large number of base particles. From Table 3, it can be seen that the separation of the fine particles in the case of strong stirring is progressing as compared with the case of mere slurrying.

  Similarly, the means for irradiating the slurry with ultrasonic waves for peeling the microscopic zinc fine particles from the iron particle aggregate is most preferable from the viewpoints of efficiency and effect, and the processing cost. Specifically, dust is put into a liquid to form a slurry, and further, ultrasonic waves are irradiated in a state of being sufficiently stirred and suspended.

  In particular, the frequency of the ultrasonic wave is preferably 160 KHz or less. Although the lower limit side is not particularly defined, since the lower limit side of the ultrasonic transmitters and transmitters that are usually marketed is about 20 to 25 KHz, it is substantially higher than this. There is no significant difference up to 160 KHz. However, the effect is significantly reduced at 750 KHz. Therefore, it can be said that a preferable result can be obtained up to 160 KHz.

  The treatment time for ultrasonic cleaning is preferably about 0.5 to 10 minutes, and more preferably about 1.6 to 10 minutes. If it is too short, peeling will be insufficient, and if it is shorter than 0.5 minutes, the effect will be drastically reduced. The effect is improved up to about 10 minutes, but the effect is hardly improved even if the treatment is performed longer than 10 minutes, and there is no industrial value.

 The use of a dispersing agent such as sodium hexametaphosphate in combination with this ultrasonic cleaning does not require a significant difference from the case where it is not used, and it is not necessary to use it at a high cost. On the other hand, in the case of using an organic dispersant as a raw material for basic zinc carbonate, a portion containing a large amount of fine zinc particles may cause a problem of slightly remaining organic components depending on the use of the basic zinc carbonate. Therefore, it is preferable not to use it.

  Thus, regarding zinc peeling of the secondary dust of the reduction furnace which concerns on this invention, it becomes conditions different from the ultrasonic treatment conditions said to be suitable for the treatment of blast furnace dust. This is because the target dust components and properties are different as shown in Table 1.

  The pH of the slurry in the second step in which the ultrasonic treatment in the first exfoliation step and the subsequent macroscopic separation and concentration are made to be in the range of 8 to 10 can be achieved after exfoliation or exfoliation of zinc fine particles by ultrasonic waves. It does not adversely affect the macroscopic zinc concentration and contributes to the improvement of the Zn recovery rate.

  FIG. 3 shows the amount of elution into an aqueous solution in relation to the pH of various metals. Since zinc is an amphoteric metal, the amount of elution into the aqueous solution is minimized at a pH of about 9-10. In the pH range where the amount of elution is the lowest, pH adjustment is performed on reducing furnace dust that contains a large amount of components such as Na, K, and Cl, soda ash, sodium hydroxide, potassium hydroxide, and the like, which are representative alkalis. In this case, Na ions and K ions in the liquid increase, which may slow the dissolution rate of Na and K. Together with them, Zn fine particles adhering around large Fe particles are ultrasonically cleaned. When it peels off, it becomes a disadvantageous direction.

  In response to these concerns, the inventor of the present invention, as a result of actual processing as in the examples described later, suppressed the dissolution loss without being affected by the microscopic separation and macroscopic separation behavior as follows. It was discovered that the zinc recovery rate was improved. That is, even in a slurry whose pH is adjusted to a range of about 9 to 10, compared to a slurry in which pH is not adjusted, the microscopic peeling effect by ultrasonic cleaning or the like, and the resulting macroscopic zinc by wet magnetic separation or the like We found that the effect of separation was not affected.

  FIG. 4 shows the relationship between the pH value of the reducing furnace secondary dust slurry and the Zn concentration in the liquid. As shown in the figure, if the pH is 8 or more on the lower limit side of the pH adjustment range, the Zn dissolution concentration is sufficient. In the case of a slurry of secondary dust generated in a reducing furnace, there is a slight deviation from the theoretical value, but if the pH is 8 or more, the amount of Zn dissolved in the slurry solution is less than 10 ppm, and the pH when pH adjustment is not performed However, the amount of dissolution loss is on the order of 1/100 when compared with the Zn dissolution amount of 100 to 1000 ppm or more at around 7. The range over 10 on the high pH side is still good in terms of the amount of dissolution and prevention of loss, but the amount of the pH-adjusting alkaline agent increases logarithmically and is not economically preferable. For this reason, in practice, the upper limit of the pH is 10. From an economical point of view, the pH is preferably 9 or less. However, the reducing furnace secondary dust containing a large amount of impurity components is unlikely to change in pH and is difficult to control with an alkaline agent. The lower limit of about 8 to 2.0 width is the minimum required.

  In the present invention, the application of wet magnetic separation as a means for separating the portion containing a large amount of zinc fine particles and the portion containing a large amount of iron particles in the second step into a macro form is a simple and reliable separation effect, that is, zinc Since a concentration effect is obtained, this is one of the most preferable methods. In addition, the application of magnetic separation in a state where the slurry is sufficiently stirred and suspended is a wet magnetic force as long as it is premised on securing the magnetic separation time according to the area of the magnetized part depending on the type and type of the magnetic separation machine used. There are no particular restrictions on the sorting conditions and the magnetic sorter type. In the implementation, it is not necessary to use a strong magnetic field, and about 0.1 to 0.2 Tesla is sufficient.

  Hydrocyclone is also a suitable macro-type separation method as the second step. Separation of zinc and iron by hydrocyclone is better after separation after micro-peeling treatment such as ultrasonic treatment, compared to the case where the slurry is subjected to hydrocyclone separation without micro-peeling. Is obtained. As the hydrocyclone to be used, it is not particularly necessary to use a hydrocyclone utilizing negative pressure or a hydrocyclone having a magnetic field, and a normal hydrocyclone whose upper and lower discharge sides are open to the atmosphere is sufficient.

However, in consideration of the particle size of the zinc particles peeled from the secondary dust of the reduction furnace, a hydrocyclone designed to have a 50% classified particle size d ₅₀ * [micrometer] calculated by the following formula of 10 μm or less is used. More preferably.

  Further, the type of the reduction furnace to which the present invention is applied may be a rotary hearth type reduction furnace, a rotary kiln type reduction furnace, or other types of furnaces as long as the dezincification phenomenon occurs in the furnace. However, in the rotary hearth type reduction furnace, the dezincification rate from iron in the furnace is as high as 80 to 97%, and as a result, the zinc content in the secondary dust is also high. Play. In other words, a rotary hearth type reduction furnace is suitable as a form of the reduction furnace to which the present invention is applied.

  In the present invention, when a portion containing a large amount of zinc fine particles is used as a raw material for a zinc carbonate production process as described in, for example, Japanese Patent No. 737379 after the first and second steps, the same product production capacity However, the scale of the manufacturing facility is reduced. This is because the size of the reaction apparatus used for cleaning, dissolution, purification, etc. can be reduced by significantly increasing the raw material Zn concentration. Further, the production cost is reduced by reducing the amount of residues such as Fe removed by purification. In other words, the present invention uses a method for producing high-purity zinc carbonate that crystallizes high-purity zinc carbonate from a Zn-containing raw material by an ammonium carbonate dissolution method as a method for using a portion containing a large amount of zinc fine particles as a zinc raw material. It is a way to make better use of the effects of.

  However, the effective use as a zinc source of the portion containing a large amount of zinc fine particles after the second step of the present invention is not necessarily limited to the zinc carbonate production process, and the production of recycled zinc ingots in non-ferrous smelting manufacturers Any method such as raw material may be used.

  Further, after the second step of the present invention, as an effective utilization method of the portion containing a large amount of iron particles obtained, any step of the iron making process, for example, may be directly returned to the blast furnace or converter after drying. However, since some zinc still remains, it is preferable to recycle and use it in a reduction furnace having a large dezincing function from the whole iron making process.

  Hereinafter, more specific modes of the present invention will be described based on examples.

  FIG. 5 illustrates a processing flow according to the first embodiment. In the figure, the dust for the treatment according to the present invention is obtained after the secondary dust is slurried and the first step of exfoliating the zinc fine particles from the iron particle aggregate in a micro shape is performed by ultrasonic cleaning treatment. Wet magnetic separation was performed on the resulting slurry, which was peeled microscopically, in order to perform macroscopic separation for separating a portion containing a large amount of zinc particles and a portion containing a large amount of iron particles.

  Table 4 shows the composition and working conditions of the dust used in Example 1 and the Comparative Example. As the dust, four types of dust having the composition of iron and zinc shown in Table 4 were used. Both are secondary dusts captured by a dry dust collector when treated in a rotary hearth type reducing furnace in order to convert dust sludge generated from the iron making process into reduced iron and return it to the iron making process.

  After these dusts were slurried with pH-adjusted water, both dusts were subjected to both the level of ultrasonic treatment as the first step and the level of no ultrasonic treatment for comparison. As for the level at which ultrasonic cleaning was performed, the treatment time was set to 10 minutes, and the frequency was set to 5 levels from 28 KHz to 750 KHz as shown in Table 4.

  In the second step, all wet magnetic separation was performed using a filter type wet magnetic separation apparatus using an electromagnet. As shown in Table 4, two levels of magnetic force, a strong magnetic force of about 0.3 Tesla and a weak magnetic force of about 0.1 Tesla, were provided.

  The magnetized side and the non-magnetized side (residual side) after magnetic separation were dehydrated and dried, respectively, and then analyzed.

  6 and 7 show the respective enrichment rates of Zn and Fe after wet magnetic separation in both cases with and without ultrasonic cleaning. 6 shows the Zn concentration ratio on the non-magnetization side (Zn mass% of the zinc recovery side slurry (dry) / Zn mass% of the slurry before treatment (dry)), and FIG. It shows Fe mass% (dry) of the iron recovery side slurry / Fe mass% (dry) of the slurry before treatment.

  Further, FIG. 8 shows the non-magnetization-side Zn recovery rate (Zn recovery-side slurry-containing Zn mass (dry) / pre-treatment slurry-containing Zn mass (dry)). The Zn concentration rate on the non-magnetization side did not change much depending on the presence or absence of ultrasonic cleaning, but the Zn recovery rate on the non-magnetization side was greatly improved by performing ultrasonic cleaning, depending on the dust composition. Zinc could be recovered at an amount ratio of 90% or more. In addition, the ultrasonic cleaning greatly improved the concentration of iron on the magnetized side in dusts with low iron content. That is, it can be seen that preferable results were obtained for use again in the reduction furnace as an iron source.

  As shown in FIGS. 6 to 8, in the ultrasonic cleaning treatment conditions, only the level of the frequency of 750 KHz did not show the effect of the ultrasonic cleaning, whereas those cleaned at a frequency of 160 KHz or less are all effective. Admitted.

  Moreover, when the ultrasonic irradiation was performed, good zinc-iron separation results were obtained regardless of the strength of the magnetic force. That is, if the microscopic peeling in the first step is performed well, it is judged that the wet magnetic separation in the second step is sufficient with a magnetic force of about 0.1 Tesla.

  The processing flow is the same as in the first embodiment. In the case of pH adjustment, the pH was adjusted to 8 to 10 by adding an aqueous sodium hydroxide solution while measuring the pH when suspending the dust.

  Both with and without pH adjustment were subjected to ultrasonic treatment at the frequencies shown in Table 5, followed by wet magnetic separation. The magnetic separation method and the strength of the magnetic force are the same as in the first embodiment.

  FIG. 9 and FIG. 10 show whether the pH and the Zn and Fe contents of the non-magnetization-side collected material after ultrasonic treatment / wet magnetic separation shown in Table 5 and the Zn and Fe contents of the magnetized-side collected material are adjusted for pH. It shows by comparison of each. Moreover, FIG. 11 is a figure which shows the comparison of the presence or absence of pH adjustment of the zinc recovery rate by the side of non-magnetization.

  From FIG. 9 and FIG. 10, the component values (mass% in dry state) of the non-magnetized side and the magnetized side after magnetic separation are significantly more than the experimental / analysis error due to the presence or absence of pH adjustment in each dust. It was judged that there was no difference. There was no feared phenomenon that the dissolution behavior of potassium, calcium, sodium, chlorine, etc. was different between fresh water and alkaline water of pH 8-10, and as a result, the micro-peeling behavior of zinc fine particles by ultrasonic cleaning was different. Moreover, as shown in FIG. 11, the zinc recovery rate to the non-magnetization side of magnetic separation was improved by 2 to 5%, and it was more preferable to adjust the pH. Further, similar to the result of Example 1, it was determined that there was no difference due to the strength of the magnetic separation.

  As shown in FIG. 12, an example is shown in which a hydrocyclone is used as a macro zinc separation / concentration method after micro separation by ultrasonic cleaning.

  The reduction furnace secondary dust having a composition of 15% Zn-30% Fe was separated by hydrocyclone both when irradiated with ultrasonic waves of 44 KHz and when not irradiated. The hydrocyclone used is a normal type cyclone that does not use negative pressure as in Patent Document 1. In the hydrocyclone, a small particle size portion containing a large amount of zinc was discharged on the upper discharge side, and a relatively large particle size portion containing a large amount of iron was discharged on the lower side. FIG. 13 shows the upper discharge side zinc concentration rate, and FIG. 14 shows the upper discharge side zinc recovery rate. As shown in the figure, the preferred values were obtained when the ultrasonic irradiation was performed. As a result, in the case of micro zinc fine particle peeling by ultrasonic irradiation, it has been found that the macro zinc concentration method in the second step is effective even when hydrocyclone is used.

  Table 6 shows a comparison of Zn values of the reduced pellets as reducing furnace products operated for 5 days in each of the conventional method, the comparative method, and the present invention method. The reduction furnace is a rotary hearth type reduction furnace.

  Sampling and analysis of raw materials and reduced pellets were performed once every three shifts per day.

  The conventional method is based on the processing flow shown in FIG. 15, and does not effectively use the iron content of the reducing furnace secondary dust, but outsources the secondary dust to the outside. Of course, since the secondary dust was not recycled at all, the Zn value of the reduction furnace product was low. The control upper limit of 0.15% for the Zn value could not exceed 1 shift.

  The comparative method is a method in which zinc is separated by the method described in Patent Document 1, and the lower emission is recycled to the reduction furnace. FIG. 16 shows the processing flow. As mentioned above, the treatment with only hydrocyclone has a low zinc recovery rate. As a result, a large amount of zinc was recharged together with the iron that was recycled to the reduction furnace. The upper management limit of 0.15% was exceeded in 7 shifts. As a result, the reduction pellets of each shift had to be compounded when used in a blast furnace.

  The embodiment of the present invention is based on the processing flow shown in FIG. After the secondary dust was slurried, the magnetized material separated by a wet magnetic separator after ultrasonic cleaning was recharged in a reduction furnace. The slurry concentration was 12%, washing was performed with ultrasonic waves having a frequency of 28 KHz, and macro separation was performed with a drum-type wet magnetic separator.

  Although the zinc value of the reduced pellets was higher than that of the conventional method, even one shift did not exceed the control upper limit of 0.15%.

  The upper discharge side substance or the non-magnetization side substance according to the present invention in the comparative example was used as a raw material for the zinc carbonate production process by the ammonium carbonate dissolution method disclosed in Patent Document 7. In either case, the amount of purified residue generated during the production of zinc carbonate was less than when secondary dust was used directly as a raw material without any treatment. Among them, the method of the present invention had less residue generation unit.

It is a photograph which shows the SEM (Scanning Electron Microscope) observation result of a reduction furnace secondary dust. It is a schematic diagram which shows the structure of the reduction furnace dust by a SEM observation result. It is an example of the graph which shows the solubility of metal ion, and pH. It is a graph which shows the actual value of pH value of slurry of a reduction furnace secondary dust, and Zn concentration in liquid. It is a figure which shows the processing flow of Example 1 and Example 2. FIG. 4 is a graph showing the Zn concentration ratio on the non-magnetically adhered side of Example 1. 3 is a graph showing the Fe concentration ratio on the magnetic adhesion side of Example 1. 2 is a graph showing the Zn recovery rate on the non-magnetization side of Example 1. It is a graph which shows the comparison by the presence or absence of pH adjustment of the non-magnetization side component after the ultrasonic treatment of Example 2, and magnetic selection. It is a graph which shows the comparison by the presence or absence of pH adjustment of the adhesion side component after the ultrasonic treatment and magnetic separation of Example 2. It is a graph which shows the result comparison by the presence or absence of pH adjustment of the non-magnetization side Zn collection | recovery rate after the ultrasonic treatment of Example 2, and magnetic selection. FIG. 10 is a diagram illustrating a processing flow of Example 3. It is a graph which shows the Zn concentration rate by the side of discharge on the cyclone of Example 3. It is a graph which shows the Zn recovery rate of the discharge side on a cyclone of Example 3. It is a figure which shows the processing flow of the conventional method with respect to Example 4. FIG. FIG. 10 is a diagram showing a processing flow of a comparison method of Example 4. It is a figure which shows the processing flow of this invention method of Example 4. FIG.

Claims (9)

  Secondary dust generated from a reduction furnace that reduces iron and zinc-containing by-products generated from the iron making process is made into a slurry suspended in a liquid, and fine particles with high zinc content are converted from large particles with high iron content. The first step of peeling microscopically, the second step of separating the portion containing a large amount of zinc fine particles and the portion containing a large amount of iron particles into a macro shape, and the portion containing a large amount of separated zinc fine particles as a zinc raw material Effective utilization method of iron content and zinc content of secondary dust generated from a reduction furnace that sequentially performs three steps of the third step to be used.   Secondary dust generated from a reduction furnace that reduces iron and zinc-containing by-products generated from the iron making process is made into a slurry suspended in a liquid, and fine particles with high zinc content are converted from large particles with high iron content. The first step of peeling microscopically, the second step of separating the portion containing a large amount of zinc fine particles and the portion containing a large amount of iron particles into a macro shape, and the portion containing a large amount of separated iron particles as an iron production raw material Effective utilization method of iron content and zinc content of secondary dust generated from a reduction furnace that sequentially performs three steps of the third step to be used.   In the first step, the slurry is suspended in a liquid and the means for separating microparticles with a high zinc content from microparticles with a high iron content in a microscopic form is mechanically stirred using a stirring blade. The method for effectively using the iron and zinc contents of the secondary dust generated from the reduction furnace according to claim 1, wherein the washing is agitated washing using a dispersant and ultrasonic washing together.   The effective use method of the iron and zinc-containing iron-making process by-product of Claim 3 whose frequency of the ultrasonic wave irradiated in ultrasonic cleaning is 160 KHz or less.   3. The method according to claim 1 or 2, wherein in the second step, the means for separating the portion containing a large amount of zinc fine particles and the portion containing a large amount of iron particles into a macro shape is any one of a wet magnetic separation method, a hydrocyclone method, and a flotation process. Effective utilization method of iron content and zinc content of secondary dust generated from the reduction furnace described in 1.   The method for effectively utilizing the iron and zinc contents of the secondary dust generated from the reduction furnace according to claim 1 or 2, wherein the pH range of the slurry in the first step and the second step is 8 or more and 10 or less.   The method for effectively utilizing the iron and zinc contents of secondary dust generated from the reduction furnace according to claim 1, wherein the reduction furnace is a rotary hearth type reduction furnace.   The third step of using a portion containing a large amount of separated zinc fine particles as a zinc raw material is a method for producing high-purity zinc carbonate that crystallizes high-purity zinc carbonate from a Zn-containing raw material by an ammonium carbonate dissolution method Item 2. An effective utilization method of iron and zinc in secondary dust generated from the reduction furnace according to item 1.   The method of using a portion containing a large amount of separated iron particles is a method of effectively reusing iron as a raw material for iron making by charging the iron into a reduction furnace, and the iron content of secondary dust generated from the reduction furnace according to claim 2. And effective use of zinc content.