JP2010001524A - Method of making zinc content in dust in iron manufacturing low - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of making zinc content in dust in iron manufacturing low, in which processes are made efficient while using a magnetic separation method, and which is economically excellent. <P>SOLUTION: The method for making the zinc content in the dust in the iron manufacturing low, includes: a zinc elution process in which a leaching solution is added to the dust in iron manufacturing containing iron and zinc to make it primary slurry and the zinc contained in the dust in iron manufacturing is dissolved; a magnetic separation process in which the primary dust is separated into a low-zinc content magnetized material and a secondary slurry containing high zinc content non-magnetized material by using the magnetic separation method; and an iron making raw material recovering process in which the separated low-zinc content magnetized material is recovered as the iron making raw material by dehydrating and washing it. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for reducing zinc in iron-making dust, and more particularly, to a method for reducing zinc in iron-making dust such as blast furnace dust, converter dust, or electric furnace dust using a magnetic separation method.

  Ironmaking dust such as blast furnace dust, converter dust, or electric furnace dust contains iron, zinc, carbon, and the like, and is desired to be reused as an ironmaking raw material. In the blast furnace / converter method, various types of dust are used as part of the sintering raw material and reused as blast furnace raw material. However, when dust with a high zinc content is thrown into the blast furnace, zinc erodes the furnace wall bricks. Reuse of steelmaking dust was restricted because it could hinder blast furnace operation.

  In order to solve the above problem, a technique for reducing zinc in the ironmaking dust, that is, a technique for separating zinc from the ironmaking dust is required, and a typical example of such a technique is a so-called dry method. This dry method is a method of separating and recovering zinc from ironmaking dust by reducing ironmaking dust at high temperature and volatilizing zinc as metal vapor, and is used for the treatment of electric furnace dust with a high zinc content. ing. However, such a method requires a large-scale apparatus such as a high-temperature reduction apparatus and requires a large amount of energy for the heating / reduction process. When used for steelmaking dust such as furnace dust, there is a problem that it is not economically realized because the amount of zinc recovered is small.

  Further, as another zinc separation technique from the iron-making dust, which is different from the dry method, a so-called wet method can be mentioned. As a method for recovering zinc by this wet method, for example, as disclosed in Patent Document 1, an elution step of elution of zinc by contacting the iron dust with an acid, and neutralization of neutralizing the eluate with an alkali And a method for recovering zinc having a separation step for solid-liquid separation of the effluent of this neutralization step, and as disclosed in Patent Document 2, the iron dust is treated in an ammonia solution to remove zinc. After selectively dissolving as an ammonia complex ion, the solution is distilled to recover basic zinc carbonate crystals, and ammonia vapor is directly blown into the basic zinc carbonate solution together with carbon dioxide gas to adjust its ammonium carbonate concentration. A method for increasing zinc recovery is mentioned.

JP 7-216470 A JP-A-6-107415

  However, although both of the zinc recovery methods of Patent Document 1 and Patent Document 2 can selectively dissolve zinc by controlling the pH of the acid, the zinc recovery method of Patent Document 1 At the same time, iron is also dissolved, so there is a problem of cost that the amount of alkali necessary for neutralization increases, and a problem of complicated processes that require multi-stage neutralization to separate zinc and iron precipitates. there were. Furthermore, the zinc recovery method of Patent Document 2 is not economically effective in the case of processing ironmaking dust in which the energy required for crystallization of basic zinc carbonate crystals is large and the zinc content is about several percent. There was a problem.

  An object of the present invention is to provide a method for reducing the zinc content of iron-making dust that has an efficient process and is economical.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention used a magnetic slurry for a primary slurry obtained by adding a leachate to ironmaking dust, and using a magnetic separation method, It has been found that it can be recovered as an iron-making raw material by separating it into a secondary slurry containing a magnetic deposit and dehydrating and washing the separated low-zinc magnetic deposit.

The present invention has been made based on such knowledge, and the gist of the present invention is as follows.
(1) A leaching solution is added to iron-making dust containing iron and zinc to form a primary slurry, and a zinc elution step for dissolving zinc contained in the iron-making dust and the primary slurry are reduced using a magnetic separation method. A magnetic separation step for separating a zincated magnetic product into a secondary slurry containing a high-zincated non-magnetic product, and steelmaking recovered as an ironmaking raw material by dehydrating and washing the separated low-zincated magnetic product. A method for reducing zinc in steelmaking dust, comprising a raw material recovery step.

  (2) The zinc recovery step of recovering zinc-containing dust by precipitating zinc contained in the highly zincated non-magnetized product in the secondary slurry and separating it into solid and liquid, as described in (1) above A method for reducing zinc in steelmaking dust.

  (3) The method for reducing zinc content in ironmaking dust according to (1) or (2), wherein the leachate is sulfuric acid and / or ammonium sulfate.

  (4) The method for reducing zinc content in ironmaking dust according to (1), (2) or (3), wherein the leachate is added so that the pH of the primary slurry is 3 to 10.

  According to the present invention, a leachate is added to iron-making dust containing iron and zinc to form a primary slurry, and the zinc elution step for dissolving zinc contained in the iron-making dust and the primary slurry are magnetically separated. In addition, a magnetic separation step for separating the low-zincified magnetic product into a secondary slurry containing a high-zincified non-magnetic product, and by dehydrating and washing the separated low-zincified magnetic product, By providing the steelmaking raw material recovery process to be recovered, it is possible to provide an efficient and economical method for reducing the zinc content of steelmaking dust. It became possible to recycle.

  Next, an embodiment of the method for reducing zinc content in iron-making dust according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a method for reducing zinc in iron-making dust according to the present invention.

  The method for reducing zinc content in ironmaking dust according to the present invention comprises a zinc elution step, a magnetic separation step, and an ironmaking raw material recovery step. Below, detailed description of each process is given.

(Zinc elution process)
In the zinc elution step of the present invention, as shown in FIG. 1, a leachate 11 is added to iron-making dust 10 containing iron and zinc to form a primary slurry 12, and zinc contained in the iron-making dust 10 is dissolved. The addition of the leachate 11 is preferably performed in the leach tank 13.

  In general, dust treated in an existing dust treatment facility is concentrated to a moisture content of about 70 to 85%, and then subjected to a solid-liquid separation process using a filter press dehydrator or the like, so that the moisture content is about 30 to 40%. It is stored as dehydrated dust. Such iron-made dust forms primary particles of about several μm, but secondary particles having an average particle diameter of several tens of μm to several mm are formed through the above-described dehydration process. At this time, the magnetic material and non-magnetic material in the iron-making dust aggregate or loosely solidify, so that in the subsequent magnetic separation process, the non-magnetic material caught in the magnetic material is magnetically separated as a magnetic deposit. There is a risk of being. Therefore, it is preferable to use the dust having a moisture content of about 70 to 85% before the dehydration is performed for the iron-making dust 10 of the present invention.

The present invention provides a zinc leaching step before the magnetic separation step, thereby dissolving the surface of the particles forming the secondary particles under a mild condition and improving the separation between the magnetic substance and the non-magnetic substance. Can do. Further, examples of the iron-making dust 10 include blast furnace dust, converter dust, electric furnace dust, and the like, and converter dust is used in that ZnO.Fe ₂ O ₃ which is a complex oxide having magnetism is small. It is preferable to use it.

  The leachate 11 may be any one that can dissolve zinc, but hydrochloric acid is not preferable because the furnace may be damaged when the recovered iron-making raw material is reused. On the other hand, sulfuric acid and / or ammonium sulfate can be used as the leachate 11 because there is no risk of damage to the furnace and it is easily obtained because it is by-produced in the steelworks. The composition of the sulfuric acid and / or ammonium sulfate can be arbitrarily set, and for the purpose of reducing processing costs, as described above, the ammonium sulfate produced as a by-product at the ironworks or the waste sulfuric acid used as an acid detergent is used. It is particularly preferable to use it.

  The leachate 11 is preferably added so that the pH of the primary slurry 12 is 3-10. When the pH is set to 3 or more, the dissolution of iron contained in the iron-making dust 10 is not promoted, and the iron concentration in the low-zincified magnetic material separated in the subsequent magnetic separation step is not reduced. In addition, since the iron concentration in the secondary slurry containing the highly galvanized non-magnetized material decreases, when the zinc precipitation step is performed thereafter, the zinc precipitation agent added for zinc precipitation must react with dissolved iron. There is no risk of increasing the required amount of the zinc depositing agent. In addition, when a large amount of zinc in the iron-making dust is present as zinc oxide, the zinc oxide is dissolved by forming a zinc-ammonia complex ion in the presence of ammonia in the pH range of 8 to 10, and the pH is In the case of 10 or less, the formed zinc ammonia complex ion does not dissociate. Therefore, a fine precipitate of zinc hydroxide is not generated, and the separation efficiency of zinc in the subsequent magnetic separation process is improved. Furthermore, it is more preferable that the pH is 5 to 6 from the viewpoint of achieving both treatment effect and economy.

  The concentration of the leachate 11 can be arbitrarily set, but is preferably as high as possible from the viewpoint of reducing the amount of water used. When ammonium sulfate is used as the leachate 11 and the pH is adjusted to 3 to 10 and zinc in the ironmaking dust 10 is dissolved as zinc ammonia complex ions, the concentration of the ammonium sulfate is about 3 mol per liter of the leach tank. It is preferable that At this time, the concentration of the ammonium sulfate depends on the zinc concentration in the ironmaking dust 10.

  Although the reaction time, reaction temperature, and stirring conditions of the iron-making dust 10 and the leachate 11 can be arbitrarily set, ammonium sulfate is used as the leachate 11, the pH is adjusted to 3 to 10, and the iron-making dust 10 When zinc contained therein is dissolved as zinc-ammonia complex ions, it is preferable to make the reaction time as long as possible, the reaction temperature as high as possible, and strong stirring conditions in order to improve the elution rate of zinc. When sulfuric acid is used as the leachate 11, the reaction time is preferably 10 to 60 minutes. When the reaction time is 10 minutes or longer, the dispersibility of the particles is good and the separation efficiency of the magnetic separation step is improved. Moreover, when the reaction time is 60 minutes or less, there is no possibility that iron in the iron making dust 10 is dissolved by the added sulfuric acid.

(Magnetic separation process)
In the magnetic separation process of the present invention, as shown in FIG. 1, the primary slurry 12 is separated from the low-zincified magnetic product 14 and the secondary slurry 15 containing the high-zincated non-magnetic material using a magnetic separation method. To separate. The magnetic separation step is preferably performed using a magnetic force sorting device 16.

  Examples of the magnetic sorting device 16 include a non-magnetic drum that rotates at a predetermined speed in one direction, a feeding device for feeding the primary slurry to a predetermined location on the non-magnetic drum, A magnet that is fixedly arranged inside the magnetic drum and magnetically adheres the low-zincized magnetic product of the primary slurry that has been charged to the non-magnetic drum in a predetermined circumferential range. There is a wet magnetic separator.

When the iron in the primary slurry 12 contains a large amount of ferromagnetic materials such as metallic iron and iron oxide (FeO), the primary slurry 12 is separated by a low magnetic force sorting device (for example, 0.1 to 0.3 T). The low-zincized magnetized material 14 is separated from the material. On the other hand, when the iron in the primary slurry 12 contains a lot of weak magnetic materials such as ferric trioxide (Fe ₂ O ₃ ), a high magnetic force sorting device (for example, 0.3 to 1.0 T) The low-zincized magnetic deposit 14 is separated from the primary slurry 12. In any case, what is not separated by the magnetic separator 16 becomes the secondary slurry 15 containing highly zincated non-magnetized substances such as zinc, zinc oxide particles, and metal zinc particles.

(Steel manufacturing process)
In the iron making raw material recovery step of the present invention, as shown in FIG. 1, the separated low zincated magnetic material 14 is recovered as an iron making raw material 17 by dehydration and washing. The dehydration is preferably performed using a dehydrator 18. The dehydrating device 18 can be arbitrarily selected. From the viewpoint of reducing the water content of the low-zincated magnetic product 14, a filter press dehydrator having a function of cleaning the low-zincated magnetic material 14 in the dehydrating device can be used. It is preferable to use it.

(Zinc recovery process)
It is preferable that the method for reducing zinc content in the steelmaking dust according to the present invention further includes a zinc recovery step. In the zinc recovery step of the present invention, as shown in FIG. 1, the zinc-containing dust 19 is recovered by precipitating dissolved zinc contained in the non-magnetized material in the secondary slurry 15 and performing solid-liquid separation. To do. The zinc deposition is preferably performed by adding a zinc deposition agent 21 to the secondary slurry 15 in the zinc deposition tank 20.

  The zinc depositing agent 21 is optionally selected from alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal sulfides, alkali metal hydrosulfides, etc., depending on the method of treating the recovered zinc. Although it can be selected, it is preferable to use an alkali metal hydrosulfide, particularly sodium hydrosulfide, in view of the solid-liquid separability of the generated precipitate. In other words, alkali metal hydroxides and alkaline earth metal hydroxides have poor solid-liquid separation properties due to the occurrence of bulky precipitation, and a zinc precipitation agent is added to an alkali having a pH of about 8-9. This is because the drug cost is necessary. On the other hand, alkali metal sulfides and alkali metal hydrosulfides also have the merit that chemical costs can be reduced because zinc sulfide is precipitated from a low pH.

  When an alkali metal sulfide or an alkali metal hydrosulfide is used as the zinc deposition agent 21, the soluble zinc in the secondary slurry 15 is precipitated as zinc sulfide, and the zinc-containing dust 19 is separated by the solid-liquid separator 22. And the recovered leachate 23 can be separated. The recovered leachate 23 is transferred to a water treatment facility and discharged after water treatment, or when the concentration is sufficiently high, it can be mixed with the leachate 11 and repeatedly used.

  FIG. 1 shows an example of a typical embodiment, and the present invention is not limited to this embodiment.

Example 1
After adding ammonium sulfate to iron-making dust (converter dust) having the composition shown in Table 1 so as to be 0.1 mol / l as sulfuric acid, a sulfuric acid solution (sulfuric acid: water = 1: 1) (62% by mass as sulfuric acid) was added. In addition, the pH was adjusted to 5 and stirred for 30 minutes. The primary slurry thus obtained is magnetically separated into a low-zinc magnetized product and a secondary slurry containing a high-zincized non-magnetized product, and the obtained low-zinc magnetized product is dehydrated and washed with water. The steelmaking raw material recovered in this way was analyzed.

  A sodium hydrosulfide solution (45% by mass) was added to the secondary slurry to produce zinc sulfide and iron sulfide precipitates, and then the zinc-containing dust recovered by centrifugation was analyzed.

  Table 2 shows the composition of the iron-making raw material and the zinc-containing dust of Example 1.

(Comparative Example 1)
A sulfuric acid solution (sulfuric acid: water = 1: 1) (62% by mass as sulfuric acid) was added to ironmaking dust (converter dust) having the composition shown in Table 1 above to adjust the pH to 1, followed by stirring for 30 minutes. The slurry thus obtained was subjected to solid-liquid separation, and the dust collected as a solid was washed with water and analyzed for dust. The composition of the recovered dust is shown in Table 3.

  From Table 2 and Table 3, the iron recovery rate of the iron making dust to the iron making raw material in Example 1 according to the present invention is 70%, and the zinc concentration in the iron making raw material is 0.3% by mass, which can be used as the iron making raw material. The zinc concentration could be reduced to the extent. Moreover, the zinc recovery rate to the zinc-containing dust was 80%, and most could be recovered to the zinc-containing dust. Compared with Example 1, the zinc concentration of the recovered dust in Comparative Example 1 is significantly high at 0.8% by mass, and it can be seen that Example 1 according to the present invention can greatly reduce the iron-making dust. .

  According to the present invention, a leachate is added to iron-making dust containing iron and zinc to form a primary slurry, and the zinc elution step for dissolving zinc contained in the iron-making dust and the primary slurry are magnetically separated. In addition, a magnetic separation step for separating the low-zincified magnetic product into a secondary slurry containing a high-zincified non-magnetic product, and by dehydrating and washing the separated low-zincified magnetic product, By providing the steelmaking raw material recovery process to be recovered, it is possible to provide an efficient and economical method for reducing the zinc content of steelmaking dust. It became possible to recycle.

It is a schematic diagram of the zinc reduction method of the iron-making dust according to embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Iron dust 11 Leaching liquid 12 Primary slurry 13 Leaching tank 14 Low zincation magnetic deposit 15 Secondary slurry 16 Magnetic separator 17 Ironmaking raw material 18 Dehydration apparatus 19 Zinc containing dust 20 Zinc precipitation tank 21 Zinc precipitation chemical 22 Solid-liquid separation apparatus 23 Recovery leachate

Claims (4)

A zinc elution step of adding a leachate to iron-making dust containing iron and zinc to form a primary slurry, and dissolving zinc contained in the iron-making dust,
A magnetic separation step of separating the primary slurry into a low-zincized magnetic product and a secondary slurry containing a high-zincified non-magnetic product using a magnetic separation method;
A method of reducing the zinc content of ironmaking dust, comprising: a step of recovering the separated zincated magnetized product as an ironmaking material recovery by dehydrating and washing.   The low iron-making dust according to claim 1, further comprising a zinc recovery step of recovering zinc-containing dust by precipitating zinc contained in the highly zincated non-magnetized product in the secondary slurry and separating it into solid and liquid. Zincing method.   The method for reducing zinc in iron-making dust according to claim 1 or 2, wherein the leachate is sulfuric acid and / or ammonium sulfate.   The said leachate is a method for reducing zinc in iron-making dust according to claim 1, 2 or 3, wherein the primary slurry is added so that the pH of the primary slurry is 3-10.

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